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Sample records for ca-deficient hydroxyapatite whiskers

  1. Whiskers and fibers of hydroxyapatite; Whiskers e fibras de hidroxiapatita

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    Cardoso, G.B.C.; Motisuke, M.; Zavaglia, C.A.C., E-mail: guicardoso@fem.unicamp.b [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Fac. de Engenharia Mecanica. Dept. de Engenharia de Materiais; Arruda, A.C.F. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Fac. de Engenharia Mecanica. Dept. de Engenharia de Petroleo

    2009-07-01

    Hydroxyapatite is a bioactive ceramic, which acts in tissue engineering by attracting bone cells. Occasionally it can be used as a biocompatible reinforcement. The mechanical role of this biomaterial can be defined depending of some characteristics analyzed by scanning electron microscope and X ray power diffraction. It can be classified in whiskers and fibers; each one has their own properties, which were discussed in this work. For its use as reinforcement it is necessary matrix with specific characteristics. (author)

  2. Formation mechanism of Ca-deficient hydroxyapatite coating on Mg–Zn–Ca alloy for orthopaedic implant

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    Wang, Huanxin [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); College of Materials and Chemical Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002 (China); Zhu, Shijie; Wang, Liguo; Feng, Yashan; Ma, Xun [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); Guan, Shaokang, E-mail: skguan@zzuedu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China)

    2014-07-01

    A biodegradable Ca-deficient hydroxyapatite (Ca-def HA) coating has been directly prepared on Mg–Zn–Ca alloy by pulse electrodeposition to improve its corrosion resistance and biocompatibility. However, the formation mechanism of such a Ca-def HA coating on magnesium substrate is still not clear. In this study, the microstructure evolution of the coating was characterized using x-ray diffractometer, x-ray photoelectron spectroscopy and scanning electron microscopy. Thermodynamic and kinetic studies of the precipitation of hydroxyapatite (HA), octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) in the used electrolyte were also carried out. Theoretical analyses illustrate that the precipitation of HA, OCP and DCPD are all possible when the electrolyte pH is higher than 6 at 80 °C, and that the higher the pH value, the more favorable is the formation of HA. Nevertheless, there is mainly poor crystalline Ca-def HA on the substrate when pulse electrodeposition lasts for 5 min, and its crystallinity increases with duration time The direct formation of the Ca-def HA coating on Mg–Zn–Ca alloy is closely dependent on the phase composition and microstructure of the substrate, the deposition parameters and Mg{sup 2+} ions substitution in HA structure.

  3. SYNTHESIS AND STRUCTURAL CHARACTERISTICS OF MAGNESIUM AND ZINC DOPED HYDROXYAPATITE WHISKERS

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    Hongquan Zhang

    2017-07-01

    Full Text Available Mg and Zn doped hydroxyapatite whiskers were successfully prepared by hydrothermal homogeneous precipitation using amide additives. The morphology and structure of the products were characterized using SEM, XRD, and FTIR. It was shown that all samples prepared using ˂ 10 % mol L-1 Mg or Zn ions were identified as HA. Further increasing their concentration gave rise to the appearance of the second phase. The Mg or Zn doped HA whiskers had a length of 60 - 110 mm and aspect ratio of 30 - 50, when the concentration of Mg or Zn ions were ˂ 5mol%. Substitution of Mg or Zn impaired the crystallization of HA whiskers and led to changes in the morphology, lattice parameters and XRD peaks diffraction position, which demonstrated that Mg or/and Zn ions were incorporated into the unit cell of HA, rather than just absorption on the surface of the whiskers.

  4. Hydroxyapatite Whisker Reinforced 63s Glass Scaffolds for Bone Tissue Engineering

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    Cijun Shuai

    2015-01-01

    Full Text Available Bioactive glass (BG is widely used for bone tissue engineering. However, poor mechanical properties are the major shortcomings. In the study, hydroxyapatite nanowhisker (HANw was used as a reinforcement to improve the mechanical properties. 63s glass/HANw scaffolds were successfully fabricated by selective laser sintering (SLS. It was found that the optimal compressive strength and fracture toughness were achieved when 10 wt.% HANw was added. This led to 36% increase in compressive strength and 83% increase in fracture toughness, respectively, compared with pure 63s glass scaffolds. Different reinforcement mechanisms were analyzed based on the microstructure investigation. Whisker bridging and whisker pulling-out were efficient in absorbing crack propagating energy, resulting in the improvement of the mechanical properties. Moreover, bioactivity and biocompatibility of the scaffolds were evaluated in vitro. The results showed that composite scaffolds with 10 wt.% HANw exhibited good apatite-forming ability and cellular affinity.

  5. Effect of surface treatment of hydroxyapatite whiskers on the mechanical properties of bis-GMA-based composites

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    Zhang Hongquan; Zhang Ming, E-mail: htmzhang@polyu.edu.h [Department of Health Technology and Informatics, Hong Kong Polytechnic University (Hong Kong)

    2010-10-01

    The mechanical properties of bis-GMA-based composites filled with hydroxyapatite (HA) particles or whiskers are characterized in this paper. The inherent properties of reinforcements, the bonding strength of the filler-matrix interface and their dispersibility in a polymer matrix were intimately associated with the mechanical performance of the composites. Silanization of both particles and whiskers effectively improved the bonding of the filler-matrix interface, their dispersibility in matrix monomers and filler loading. The particle- and whisker-filled composites showed highly significant differences in both flexural strength and fracture toughness. HA whiskers prepared by hydrothermal homogeneous precipitation had superior dispersibility and wettability in the polymer matrix; no aggregation and entanglement were found in both the products before and after silanization and the resin composites. These features conferred the whiskers having good interface bonding with the polymer matrix and superior reinforcing and toughening effects. For the particulate filler, the addition of HA led to a decrease in the flexural strength for both silane-treated and untreated fillers. Cracks propagated easily through the micropores and voids in the HA aggregates, leading to lower flexural strength and low toughness. However, silanization of HA did not show obvious effects on the elastic modulus of the composites.

  6. In Vitro Corrosion and Cytocompatibility Properties of Nano-Whisker Hydroxyapatite Coating on Magnesium Alloy for Bone Tissue Engineering Applications

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    Huawei Yang

    2015-03-01

    Full Text Available We report here the successful fabrication of nano-whisker hydroxyapatite (nHA coatings on Mg alloy by using a simple one-step hydrothermal process in aqueous solution. The nHA coating shows uniform structure and high crystallinity. Results indicate that nHA coating is promising for improving the in vitro corrosion and cytocompatibility properties of Mg-based implants and devices for bone tissue engineering. In addition, the simple hydrothermal deposition method used in the current study is also applicable to substrates with complex shapes or surface geometries.

  7. The influence of silicon substitution on the properties of spherical- and whisker-like biphasic α-calcium-phosphate/hydroxyapatite particles.

    Science.gov (United States)

    Jokic, B; Mitric, M; Popovic, M; Sima, L; Petrescu, S M; Petrovic, R; Janackovic, Dj

    2011-10-01

    In this work, the influence of the morphology of hydroxyapatite particles on silicon substitution through hydrothermal synthesis performed under the same conditions was investigated. Spherical- and whisker-like hydroxyapatite particles were obtained starting from calcium-nitrate, sodium dihydrogen phosphate, disodium-ethylenediaminetetraacetic acid and urea (used only for the synthesis of whisker-like particles) dissolved in aqueous solutions. Silicon was introduced into the solution using tetraethylorthosilicate. X-ray diffraction, infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy indicate that silicon doping induce different phase compositions and bioactivity of spherical- and whisker-like hydroxyapatite particles obtained under the same hydrothermal conditions. Silicon-substituted, spherical hydroxyapatites particles showed greater phase transformation to silicon-substituted α- calcium-phosphate compared with whiskers-like hydroxyapatite particles synthesized with the same amount of added silicon. Metabolic activity assay performed with SaOs2 osteosarcoma cells showed better biocompatibility of annealed biphasic spherical-like particles compared with annealed whiskerlike particles while dried spherical-like particles induce high cytotoxicity effect.

  8. A Preliminary Evaluation of Lyophilized Gelatin Sponges, Enhanced with Platelet-Rich Plasma, Hydroxyapatite and Chitin Whiskers for Bone Regeneration

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    Andrew J. Spence

    2013-04-01

    Full Text Available The purpose of this study was to perform a number of preliminary in vitro evaluations on an array of modified gelatin gel sponge scaffolds for use in a bone graft application. The gelatin gels were modified through the addition of a number of components which each possess unique properties conducive to the creation and regeneration of bone: a preparation rich in growth factors (PRGF, a bioactive, lyophilized form of platelet-rich plasma, hydroxyapatite, and chitin whiskers. Platelet-rich plasma therapy is an emerging practice that has proven effective in a number of clinical applications, including enhancing bone repair through improved deposition of new bony matrix and angiogenesis. As such, the inclusion of PRGF in our gelatin scaffolds was intended to significantly enhance scaffold bioactivity, while the addition of hydroxyapatite and chitin whiskers were anticipated to increase scaffold strength. Additionally, the gelatin sponges, which readily dissolve in aqueous solutions, were subjected to 1-Ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC cross-linking, either during or post-gelation, to control their rate of degradation. Scaffolds were evaluated in vitro with respect to compressive strength, mass loss/degradation, protein release, and cellular interaction, with results demonstrating the potential of the gelatin gel sponge scaffold for use in the regeneration of bone.

  9. Effect of hydroxyapatite spheres, whiskers, and nanoparticles on mechanical properties of a model BisGMA/TEGDMA composite initially and after storage.

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    Lezaja, Maja; Veljovic, Djordje N; Jokic, Bojan M; Cvijovic-Alagic, Ivana; Zrilic, Milorad M; Miletic, Vesna

    2013-11-01

    This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (SphSi), whiskers (Wh), silicon-doped whiskers (WhSi), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and SphSi groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites. Copyright © 2013 Wiley Periodicals, Inc.

  10. Preparation, in vitro degradability, cytotoxicity, and in vivo biocompatibility of porous hydroxyapatite whisker-reinforced poly(L-lactide) biocomposite scaffolds.

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    Xie, Lu; Yu, Haiyang; Yang, Weizhong; Zhu, Zhuoli; Yue, Li

    2016-01-01

    Biodegradable and bioactive scaffolds with interconnected macroporous structures, suitable biodegradability, adequate mechanical property, and excellent biocompatibility have drawn increasing attention in bone tissue engineering. Hence, in this work, porous hydroxyapatite whisker-reinforced poly(L-lactide) (HA-w/PLLA) composite scaffolds with different ratios of HA and PLLA were successfully developed through compression molding and particle leaching. The microstructure, in vitro mineralization, cytocompatibility, hemocompatibility, and in vivo biocompatibility of the porous HA-w/PLLA were investigated for the first time. The SEM results revealed that these HA-w/PLLA scaffolds possessed interconnected pore structures. Compared with porous HA powder-reinforced PLLA (HA-p/PLLA) scaffolds, HA-w/PLLA scaffolds exhibited better mechanical property and in vitro bioactivity, as more formation of bone-like apatite layers were induced on these scaffolds after mineralization in SBF. Importantly, in vitro cytotoxicity displayed that porous HA-w/PLLA scaffold with HA/PLLA ratio of 1:1 (HA-w1/PLLA1) produced no deleterious effect on human mesenchymal stem cells (hMSCs), and cells performed elevated cell proliferation, indicating a good cytocompatibility. Simultaneously, well-behaved hemocompatibility and favorable in vivo biocompatibility determined from acute toxicity test and histological evaluation were also found in the porous HA-w1/PLLA1 scaffold. These findings may provide new prospects for utilizing the porous HA whisker-based biodegradable scaffolds in bone repair, replacement, and augmentation applications.

  11. Modeling tin whisker growth.

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    Weinberger, Christopher Robert

    2013-08-01

    Tin, lead, and lead-tin solders are the most commonly used solders due to their low melting temperatures. However, due to the toxicity problems, lead must now be removed from solder materials. This has lead to the re-emergence of the issue of tin whisker growth. Tin whiskers are a microelectronic packaging issue because they can lead to shorts if they grow to sufficient length. However, the cause of tin whisker growth is still not well understood and there is lack of robust methods to determine when and if whiskering will be a problem. This report summarizes some of the leading theories on whisker growth and attempts to provide some ideas towards establishing the role microstructure plays in whisker growth.

  12. Synthetische diamant-whisker

    Science.gov (United States)

    Derjaguin, B. V.; Fedoseev, D. V.

    1994-04-01

    РефератUnter speziellen Bedingungen wachsen auf Metallen und auch Nichtmetallen sehr dünne einkristalline Fäden auf, die man als Whisker bezeichnet. Diese Einkristalle zeigen höchst bemerkenswerte Eigenschaften. Uns ist es gelungen, Diamant-Whisker aufwachsen zu lassen unter Bedingungen, bei denen der Diamant eine metastabile Form von Kohlenstoff darstellt (1, 2). Möglicherweise läβt sich daraus ein Verfahren der epitaktischen Diamantsynthese entwickeln.

  13. Box-and-Whisker Plots.

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    Larsen, Russell D.

    1985-01-01

    Box-and-whisker plots (which give rapid visualization of batches of data) can be effectively used to present diverse collections of data used in traditional first-year chemistry courses. Construction of box-and-whisker plots and their use with bond energy data and data on heats of formation and solution are discussed. (JN)

  14. The advantages of a tapered whisker.

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    Christopher M Williams

    Full Text Available The role of facial vibrissae (whiskers in the behavior of terrestrial mammals is principally as a supplement or substitute for short-distance vision. Each whisker in the array functions as a mechanical transducer, conveying forces applied along the shaft to mechanoreceptors in the follicle at the whisker base. Subsequent processing of mechanoreceptor output in the trigeminal nucleus and somatosensory cortex allows high accuracy discriminations of object distance, direction, and surface texture. The whiskers of terrestrial mammals are tapered and approximately circular in cross section. We characterize the taper of whiskers in nine mammal species, measure the mechanical deflection of isolated felid whiskers, and discuss the mechanics of a single whisker under static and oscillatory deflections. We argue that a tapered whisker provides some advantages for tactile perception (as compared to a hypothetical untapered whisker, and that this may explain why the taper has been preserved during the evolution of terrestrial mammals.

  15. Mitigating tin whisker risks theory and practice

    CERN Document Server

    Handwerker, Carol A; Bath, Jasbir

    2016-01-01

    Discusses the growth mechanisms of tin whiskers and the effective mitigation strategies necessary to reduce whisker growth risks. This book covers key tin whisker topics, ranging from fundamental science to practical mitigation strategies. The text begins with a review of the characteristic properties of local microstructures around whisker and hillock grains to identify why these particular grains and locations become predisposed to forming whiskers and hillocks. The book discusses the basic properties of tin-based alloy finishes and the effects of various alloying elements on whisker formation, with a focus on potential mechanisms for whisker suppression or enhancement for each element. Tin whisker risk mitigation strategies for each tier of the supply chain for high reliability electronic systems are also described.

  16. Material factors influencing metallic whisker growth

    Science.gov (United States)

    Rodekohr, Chad L.

    Whiskering refers to the formation of slender, long, metallic filaments, much thinner than a human hair, that grow on a metallic thin film surface. They are readily observed for pure and alloyed zinc (Zn), silver (Ag), cadmium (Cd), indium (In), and tin (Sn) surfaces. The longest reported whisker length is 4.5 mm long but most high-aspect ratio whiskers range from 1-500 mum. The focus of this research is upon Sn whiskers. Sn whiskers pose serious reliability problems for the electronics industry and are known to be the source of failure in a wide range of electronic devices, such as nuclear power facilities, heart pacemakers, commercial satellites, aviation radar, telecommunication equipment, and desktop computers. The problem with whiskering has been recently exacerbated by the worldwide shift to lead (Pb) free electronics and the continuing reduction in electrical contact pitches. A thorough understanding of the growth mechanism of Sn whiskers is urgently needed. Currently, there is no universally accepted model that explains the broad range of observations on whiskering. The goals of this research are: (1) to develop a more detailed understanding of the physical mechanisms leading to the initiation and growth of Sn whiskers and (2) to outline reasonable mitigation strategies that could be followed to reduce or eliminate the problem of Sn whiskers. The major contributions of this work are: (1) A reliable method for growing Sn whiskers with predictable incubation times has been developed and tested. (2) A surface oxide is not necessary for whisker growth. (3) Intermetallic compounds (IMC) are not necessary for whisker growth. (4) Smoother, not rougher, substrate surfaces promote whisker growth. (5) Whiskers grow under both compressive and tensile thin film stress states. (6) Whisker growth increases with externally applied compression and tension forces. (7) Sn whiskers are composed of pure Sn except for the expected thin, native Sn oxide on their surface. (8) For

  17. Method for manufacturing whisker preforms and composites

    Science.gov (United States)

    Lessing, P.A.

    1995-11-07

    A process is disclosed for manufacturing Si{sub 3}N{sub 4}/SiAlON whiskers by mixing silicon carbide powder with aluminum nitride powder, adding impurities such as calcium oxide or potassium chloride to control whisker characteristics, forming the mixture in a boron nitrogen mold of desired shaped and hot isostatically pressing the formed mixture in a nitrogen environment to produce whiskers comprised substantially of SiAlON at the nucleating end of the whisker and Si{sub 3}N{sub 4} at the other end of the whisker. In one embodiment, reinforced composites are formed by impregnating the Si{sub 3}N{sub 4}/SiAlON whisker preform with a matrix material such as resin binders, liquid metals, intermetallics or ceramic materials.

  18. Temperature Effect on Hydroxyapatite Preparation by Co-precipitation Method under Carbamide Influence

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    Luo Jing

    2015-01-01

    Full Text Available Hydroxyapatite crystal was prepared by homogeneous co-precipitation method using a mixture of Calcium nitrate and diammonium phosphate as raw materials and carbamide as the buffering agent. To analyzed the influence of temperature on hydroxyapatite crystal morphology, the phase composition, crystal morphology and growth orientation were characterized by X-ray diffraction, scanning electron microscope and infrared spectrum respectively. The results show that when the reaction temperature increase from 70 °C to 95 °C, the phases composition of crystal transform from the two phases of tricalcium phosphate and eight calcium phosphate to hydroxyapatite single crystal; the morphology of the hydroxyapatite crystals transforms from nodular whisker to perfectly and compactly acicular whisker.

  19. Silicon Whisker and Carbon Nanofiber Composite Anode

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    Ma, Junqing (Inventor); Newman, Aron (Inventor); Lennhoff, John (Inventor)

    2015-01-01

    A carbon nanofiber can have a surface and include at least one crystalline whisker extending from the surface of the carbon nanofiber. A battery anode composition can be formed from a plurality of carbon nanofibers each including a plurality of crystalline whiskers.

  20. Whisker Formation On Galvanic Tin Surface Layer

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    Radanyi A.L.

    2015-06-01

    Full Text Available The present work reports the effect of substrate composition, thickness of the tin electroplate and its morphology on pressure-induced tin whisker formation. Pure tin deposits of different thickness were obtained on a copper and brass substrates using methane sulfonic industrial bath. The deposits were compressed by a steel bearing ball forming imprint on the surface. The microstructure of tin whiskers obtained at the boundary of each imprint, their length and number were studied using both light and scanning electron microscopy. It was shown that the most intensive formation and growth of whiskers was observed in the first two hours. In general, brass substrate was shown to be more prone to whisker formation than copper independently of the tin coating thickness. The results have been compared with industrial bright tin finish on control unit socket leads and proposals have been made as to modification of the production process in order to minimize the risk of whiskering.

  1. The probabilistic distribution of metal whisker lengths

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    Niraula, D., E-mail: Dipesh.Niraula@rockets.utoledo.edu; Karpov, V. G., E-mail: victor.karpov@utoledo.edu [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States)

    2015-11-28

    Significant reliability concerns in multiple industries are related to metal whiskers, which are random high aspect ratio filaments growing on metal surfaces and causing shorts in electronic packages. We derive a closed form expression for the probabilistic distribution of metal whisker lengths. Our consideration is based on the electrostatic theory of metal whiskers, according to which whisker growth is interrupted when its tip enters a random local “dead region” of a weak electric field. Here, we use the approximation neglecting the possibility of thermally activated escapes from the “dead regions,” which is later justified. We predict a one-parameter distribution with a peak at a length that depends on the metal surface charge density and surface tension. In the intermediate range, it fits well the log-normal distribution used in the experimental studies, although it decays more rapidly in the range of very long whiskers. In addition, our theory quantitatively explains how the typical whisker concentration is much lower than that of surface grains. Finally, it predicts the stop-and-go phenomenon for some of the whiskers growth.

  2. Monoclinic hydroxyapatite.

    Science.gov (United States)

    Elliott, J C; Mackie, P E; Young, R A

    1973-06-08

    The existence of a monoclinic phase of hydroxyapatite, Ca(2)(PO(4))(4)OH, has been confirmed, by single-crystal structure analysis (weighted "reliability" factor = 3.9 percent on |F|(2)). The structure has space group P21/b, a = 9.4214(8) angstroms, b = 2a, c = 6.8814(7) angstroms, and gamma = 120 degrees , and is analogous to that of chlorapatite. The distortions from the hexagonal structure with which the monoclinic structure is pseudosymmetric are similar to those in chlorapatite, including enlargement of that triangular array of oxygen atoms in which the chlorine ion or, in hydroxyapatite, the hydroxyl hydrogen ion is approximately centered. The hydroxyapatite specimen was prepared by the conversion of a single crystal of chlorapatite in steam at 1200 degrees C, was mimetically twinned, and was approximately 37 percent monoclinic.

  3. Texture coding in the rat whisker system: slip-stick versus differential resonance

    National Research Council Canada - National Science Library

    Wolfe, Jason; Hill, Dan N; Pahlavan, Sohrab; Drew, Patrick J; Kleinfeld, David; Feldman, Daniel E

    2008-01-01

    .... In the resonance model, whisker motion across different textures excites mechanical resonance in distinct subsets of whiskers, due to variation across whiskers in resonance frequency, which varies with whisker length...

  4. Contact Whiskers for Millimeter Wave Diodes

    Science.gov (United States)

    Kerr, A. R.; Grange, J. A.; Lichtenberger, J. A.

    1978-01-01

    Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.

  5. Whisker Formation on SAC305 Soldered Assemblies

    Science.gov (United States)

    Meschter, S.; Snugovsky, P.; Bagheri, Z.; Kosiba, E.; Romansky, M.; Kennedy, J.; Snugovsky, L.; Perovic, D.

    2014-11-01

    This article describes the results of a whisker formation study on SAC305 assemblies, evaluating the effects of lead-frame materials and cleanliness in different environments: low-stress simulated power cycling (50-85°C thermal cycling), thermal shock (-55°C to 85°C), and high temperature/high humidity (85°C/85% RH). Cleaned and contaminated small outline transistors, large leaded quad flat packs (QFP), plastic leaded chip carrier packages, and solder balls with and without rare earth elements (REE) were soldered to custom designed test boards with Sn3Ag0.5Cu (SAC305) solder. After assembly, all the boards were cleaned, and half of them were recontaminated (1.56 µg/cm2 Cl-). Whisker length, diameter, and density were measured. Detailed metallurgical analysis on components before assembly and on solder joints before and after testing was performed. It was found that whiskers grow from solder joint fillets, where the thickness is less than 25 µm, unless REE was present. The influence of lead-frame and solder ball material, microstructure, cleanliness, and environment on whisker characteristics is discussed. This article provides detailed metallurgical observations and select whisker length data obtained during this multiyear testing program.

  6. Whisker encoding of mechanical events during active tactile exploration

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    Yves eBoubenec

    2012-11-01

    Full Text Available Rats use their whiskers to extract a wealth of information about their immediate environment, such as the shape, position or texture of an object. The information is conveyed to mechanoreceptors located within the whisker follicle in the form of a sequence of whisker deflections induced by the whisker/object contact interaction. How the whiskers filter and shape the mechanical information and effectively participate in the coding of tactile features remains an open question to date. In the present article, a biomechanical model was developed that provides predictions of the whisker dynamics during active tactile exploration, amenable to quantitative experimental comparison. This model is based on a decomposition of the whisker profile into a slow, quasi-static sequence and rapid resonant small-scale vibrations. It was applied to the typical situation of a rat whisking across an object. Having derived the quasi-static sequence of whisker deformation, the resonant properties of the whisker were analyzed, taking into account the boundary conditions imposed by the whisker/surface contact. We then focused on two elementary mechanical events that are expected to trigger neural responses, namely (i the whisker/object first contact and (ii the whisker detachment from the object. Both events were found to trigger a deflection wave propagating upward to the mystacial pad at constant velocity of 3-5m/s. This yielded a characteristic mechanical signature at the whisker base, in the form of a large peak of negative curvature occurring 4ms after the event was triggered. The dependence in amplitude and lag of this mechanical signal with the main contextual parameters (such as radial or angular distance was investigated. The model was validated experimentally by comparing its predictions to high-speed video recordings of shock-induced whisker deflections performed on anesthetized rats. The consequences of these results on possible tactile encoding schemes are

  7. Biopolymer nanocomposite films reinforced with nanocellulose whiskers

    Science.gov (United States)

    Amit Saxena; Marcus Foston; Mohamad Kassaee; Thomas J. Elder; Arthur J. Ragauskas

    2011-01-01

    A xylan nanocomposite film with improved strength and barrier properties was prepared by a solution casting using nanocellulose whiskers as a reinforcing agent. The 13C cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) analysis of the spectral data obtained for the NCW/xylan nanocomposite films indicated the signal intensity originating...

  8. Properties of Doped GaSb Whiskers at Low Temperatures

    Science.gov (United States)

    Khytruk, Igor; Druzhinin, Anatoly; Ostrovskii, Igor; Khoverko, Yuriy; Liakh-Kaguy, Natalia; Rogacki, Krzysztof

    2017-02-01

    Temperature dependencies of GaSb whiskers' resistance doped with Te to concentration of 1.7 × 1018 cm-3 were measured in temperature range 1.5-300 K. At 4.2 K temperature, a sharp drop in the whisker resistance was found. The observed effect is likely connected with the contribution of two processes such as the electron localization in the whiskers and transition in superconducting state at temperature below 4.2 K. The whisker magnetoconductance is considered in the framework of weak antilocalization (WAL) model and connected with subsurface layers of the whiskers. The Shubnikov-de Haas (SdH) oscillatory effect is observed in high-quality n-type GaSb whiskers with tellurium doping concentration near the metal-insulator transition (MIT) for both longitudinal and transverse magnetoresistance.

  9. Innovation Incubator: Whisker Labs Technical Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Sparn, Bethany F. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Frank, Stephen M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Earle, Lieko [National Renewable Energy Lab. (NREL), Golden, CO (United States); Scheib, Jennifer G. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-08-01

    The Wells Fargo Innovation Incubator (IN2) is a program to foster and accelerate startup companies with commercial building energy-efficiency and demand management technologies. The program is funded by the Wells Fargo Foundation and co-administered by the National Renewable Energy Laboratory (NREL). Whisker Labs, an Oakland, California-based company, was one of four awardees in the first IN2 cohort and was invited to participate in the program because of its novel electrical power sensing technology for circuit breakers. The stick-on Whisker meters install directly on the front face of the circuit breakers in an electrical panel using adhesive, eliminating the need to open the panel and install current transducers (CTs) on the circuit wiring.

  10. A model of toughening effects in whisker-reinforced composites

    Energy Technology Data Exchange (ETDEWEB)

    Hoagland, R.G. (Washington State Univ., Pullman, WA (United States). Dept. of Mechanical and Materials Engineering); Henager, C.H. Jr. (Pacific Northwest Lab., Richland, WA (United States))

    1991-01-01

    A numerical approach is presented that lends itself to modeling the screening or antiscreening effects due solely to modulus differences of a discrete array of whiskers in an elastic matrix. The method is applied to single whiskers, and to examining the issue of whisker orientation of the toughness of ceramic composites. The model results indicate that crack-tip shielding due to modulus defect interactions occurs when the reinforcement has a higher modulus than the matrix material, and that anti-shielding occurs for the opposite case. Results for a single whisker located at the crack-tip (maximum effect) indicate that the crack-tip stress intensity is reduced by about 10% when a modulus ratio of four is assumed. Calculations performed with whisker arrays demonstrate pronounced effects of whisker orientation on the crack-tip screening, being larger for whiskers oriented perpendicular to the crack plane, as expected. Ordered whisker arrays produce larger and more uniform screening than do random whisker arrays. 16 refs., 10 figs.

  11. Comparative Evaluation of Fluoride Recharge Ability of Conventional and Hydroxyapatite Modified Glass Ionomer Cement with Daily Low Fluoride Exposure- An Invitro Study.

    Science.gov (United States)

    Panigrahi, Antarmayee; Sudeep, S; Sharma, Shalini; Mohanty, Susant

    2016-02-01

    Glass ionomer cement (GIC) has best suited paediatric dentists and is well recognised in the preventive era of dentistry. However its use is affected by its inferior mechanical properties. Hydroxyapatite whiskers have been lately introduced as strengthening additive without affecting its fluoride releasing property, but literature lacks data related to its effect on recharging ability of glass ionomer cement. To evaluate and compare fluoride release from hydroxyapatite incorporated glass ionomer cement following recharging with low fluoride dentifrices. An 8% Hydroxyapatite whiskers were added to Conventional Glass ionomer powder and 40 specimens each of conventional and Hydroxyapatite Glass ionomer cement were prepared using customised Teflon mould (5mm x 2mm) and were suspended in deionised water. Recharging of aged specimens was done using low fluoridated dentifrices containing 500ppm fluoride, twice daily and water was replenished every 24 hours. Fluoride release was analysed daily for 7 days and then weekly till 21 days using Sension 4 pH/ion selective electrode. Data thus obtained was statistically analysed by descriptive analysis followed by repeated measures ANOVA. Significant (pglass ionomer was found to be similar to conventional glass ionomer cement. Within the limitations of this study it can be evinced that fluoride rechargability and re-release remains unaffected by the addition of hydroxyapatite whiskers and hence proves to be more acceptable additive to glass ionomer cement to improve its mechanical properties widening its arena of usage by clinicians.

  12. Nanoreinforced biocompatible hydrogels from wood hemicelluloses and cellulose whiskers

    Science.gov (United States)

    Muzaffer Ahmet Karaaslan; Mandla A. Tshabalala; Daniel J. Yelle; Gisela Buschle-Diller

    2011-01-01

    Nanoreinforced hydrogels with a unique network structure were prepared from wood cellulose whiskers coated with chemically modified wood hemicelluloses. The hemicelluloses were modified with 2-hydroxyethylmethacrylate prior to adsorption onto the cellulose whiskers in aqueous medium. Synthesis of the hydrogels was accomplished by in situ radical polymerization of the...

  13. Quantifying the Effect of Stress on Sn Whisker Nucleation Kinetics

    Science.gov (United States)

    Chason, Eric; Vasquez, Justin; Pei, Fei; Jain, Nupur; Hitt, Andrew

    2018-01-01

    Although Sn whiskers have been studied extensively, there is still a need to understand the driving forces behind whisker nucleation and growth. Many studies point to the role of stress, but confirming this requires a quantitative comparison between controlled stress and the resulting whisker evolution. Recent experimental studies applied stress to a Sn layer via thermal cycling and simultaneously monitored the evolution of the temperature, stress and number of nuclei. In this work, we analyze these nucleation kinetics in terms of classical nucleation theory to relate the observed behavior to underlying mechanisms including a stress dependent activation energy and a temperature and stress-dependent whisker growth rate. Non-linear least squares fitting of the data taken at different temperatures and strain rates to the model shows that the results can be understood in terms of stress decreasing the barrier for whisker nucleation.

  14. Organization of sensory feature selectivity in the whisker system.

    Science.gov (United States)

    Bale, Michael R; Maravall, Miguel

    2017-09-14

    Our sensory receptors are faced with an onslaught of different environmental inputs. Each sensory event or encounter with an object involves a distinct combination of physical energy sources impinging upon receptors. In the rodent whisker system, each primary afferent neuron located in the trigeminal ganglion innervates and responds to a single whisker and encodes a distinct set of physical stimulus properties - features - corresponding to changes in whisker angle and shape and the consequent forces acting on the whisker follicle. Here we review the nature of the features encoded by successive stages of processing along the whisker pathway. At each stage different neurons respond to distinct features, such that the population as a whole represents diverse properties. Different neuronal types also have distinct feature selectivity. Thus, neurons at the same stage of processing and responding to the same whisker nevertheless play different roles in representing objects contacted by the whisker. This diversity, combined with the precise timing and high reliability of responses, enables populations at each stage to represent a wide range of stimuli. Cortical neurons respond to more complex stimulus properties - such as correlated motion across whiskers - than those at early subcortical stages. Temporal integration along the pathway is comparatively weak: neurons up to barrel cortex (BC) are sensitive mainly to fast (tens of milliseconds) fluctuations in whisker motion. The topographic organization of whisker sensitivity is paralleled by systematic organization of neuronal selectivity to certain other physical features, but selectivity to touch and to dynamic stimulus properties is distributed in "salt-and-pepper" fashion. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  15. Preparation of Aragonite Whiskers by Dolomite

    Directory of Open Access Journals (Sweden)

    Xu W.R

    2017-01-01

    Full Text Available Aragonite CaCO3 with complicated morphologies needle-like structrues have been successfully synthesized through dolomite as raw materials by the decomposition of urea. The phase of the aragonite whiskers were characterized by X-ray diffraction and Fourier transform infrared, the structrue of the samples was characterized by scanning electron microscope and the effects of different ratio of materials were studied. The result show that the concentration of urea was found to have an effect on the morphology of aragonite crystals. All the prepared crystals were almost aragonite and there was no phase under varied experiment conditions.

  16. Anatomical pathways involved in generating and sensing rhythmic whisker movements.

    Science.gov (United States)

    Bosman, Laurens W J; Houweling, Arthur R; Owens, Cullen B; Tanke, Nouk; Shevchouk, Olesya T; Rahmati, Negah; Teunissen, Wouter H T; Ju, Chiheng; Gong, Wei; Koekkoek, Sebastiaan K E; De Zeeuw, Chris I

    2011-01-01

    The rodent whisker system is widely used as a model system for investigating sensorimotor integration, neural mechanisms of complex cognitive tasks, neural development, and robotics. The whisker pathways to the barrel cortex have received considerable attention. However, many subcortical structures are paramount to the whisker system. They contribute to important processes, like filtering out salient features, integration with other senses, and adaptation of the whisker system to the general behavioral state of the animal. We present here an overview of the brain regions and their connections involved in the whisker system. We do not only describe the anatomy and functional roles of the cerebral cortex, but also those of subcortical structures like the striatum, superior colliculus, cerebellum, pontomedullary reticular formation, zona incerta, and anterior pretectal nucleus as well as those of level setting systems like the cholinergic, histaminergic, serotonergic, and noradrenergic pathways. We conclude by discussing how these brain regions may affect each other and how they together may control the precise timing of whisker movements and coordinate whisker perception.

  17. Automated Tracking of Whiskers in Videos of Head Fixed Rodents

    Science.gov (United States)

    Clack, Nathan G.; O'Connor, Daniel H.; Huber, Daniel; Petreanu, Leopoldo; Hires, Andrew; Peron, Simon; Svoboda, Karel; Myers, Eugene W.

    2012-01-01

    We have developed software for fully automated tracking of vibrissae (whiskers) in high-speed videos (>500 Hz) of head-fixed, behaving rodents trimmed to a single row of whiskers. Performance was assessed against a manually curated dataset consisting of 1.32 million video frames comprising 4.5 million whisker traces. The current implementation detects whiskers with a recall of 99.998% and identifies individual whiskers with 99.997% accuracy. The average processing rate for these images was 8 Mpx/s/cpu (2.6 GHz Intel Core2, 2 GB RAM). This translates to 35 processed frames per second for a 640 px×352 px video of 4 whiskers. The speed and accuracy achieved enables quantitative behavioral studies where the analysis of millions of video frames is required. We used the software to analyze the evolving whisking strategies as mice learned a whisker-based detection task over the course of 6 days (8148 trials, 25 million frames) and measure the forces at the sensory follicle that most underlie haptic perception. PMID:22792058

  18. Automated tracking of whiskers in videos of head fixed rodents.

    Science.gov (United States)

    Clack, Nathan G; O'Connor, Daniel H; Huber, Daniel; Petreanu, Leopoldo; Hires, Andrew; Peron, Simon; Svoboda, Karel; Myers, Eugene W

    2012-01-01

    We have developed software for fully automated tracking of vibrissae (whiskers) in high-speed videos (>500 Hz) of head-fixed, behaving rodents trimmed to a single row of whiskers. Performance was assessed against a manually curated dataset consisting of 1.32 million video frames comprising 4.5 million whisker traces. The current implementation detects whiskers with a recall of 99.998% and identifies individual whiskers with 99.997% accuracy. The average processing rate for these images was 8 Mpx/s/cpu (2.6 GHz Intel Core2, 2 GB RAM). This translates to 35 processed frames per second for a 640 px×352 px video of 4 whiskers. The speed and accuracy achieved enables quantitative behavioral studies where the analysis of millions of video frames is required. We used the software to analyze the evolving whisking strategies as mice learned a whisker-based detection task over the course of 6 days (8148 trials, 25 million frames) and measure the forces at the sensory follicle that most underlie haptic perception.

  19. Texture coding in the rat whisker system: slip-stick versus differential resonance.

    Directory of Open Access Journals (Sweden)

    Jason Wolfe

    2008-08-01

    Full Text Available Rats discriminate surface textures using their whiskers (vibrissae, but how whiskers extract texture information, and how this information is encoded by the brain, are not known. In the resonance model, whisker motion across different textures excites mechanical resonance in distinct subsets of whiskers, due to variation across whiskers in resonance frequency, which varies with whisker length. Texture information is therefore encoded by the spatial pattern of activated whiskers. In the competing kinetic signature model, different textures excite resonance equally across whiskers, and instead, texture is encoded by characteristic, nonuniform temporal patterns of whisker motion. We tested these models by measuring whisker motion in awake, behaving rats whisking in air and onto sandpaper surfaces. Resonant motion was prominent during whisking in air, with fundamental frequencies ranging from approximately 35 Hz for the long Delta whisker to approximately 110 Hz for the shorter D3 whisker. Resonant vibrations also occurred while whisking against textures, but the amplitude of resonance within single whiskers was independent of texture, contradicting the resonance model. Rather, whiskers resonated transiently during discrete, high-velocity, and high-acceleration slip-stick events, which occurred prominently during whisking on surfaces. The rate and magnitude of slip-stick events varied systematically with texture. These results suggest that texture is encoded not by differential resonant motion across whiskers, but by the magnitude and temporal pattern of slip-stick motion. These findings predict a temporal code for texture in neural spike trains.

  20. Bio-Inspired PVDF-Based, Mouse Whisker Mimicking, Tactile Sensor

    Directory of Open Access Journals (Sweden)

    Mohsin Islam Tiwana

    2016-10-01

    Full Text Available The design and fabrication of a Polyvinylidene fluoride (PVDF based, mouse (or rodent whisker mimicking, tactile sensor is presented. Unlike previous designs reported in the literature, this sensor mimics the mouse whisker not only mechanically, but it also makes macro movements just like a real mouse whisker in a natural environment. We have developed a mathematical model and performed finite element analysis using COMSOL, in order to optimise the whisker to have the same natural frequency as that of a biological whisker. Similarly, we have developed a control system that enables the whisker mimicking sensor to vibrate at variable frequencies and conducted practical experiments to validate the response of the sensor. The natural frequency of the whisker can be designed anywhere between 35 and 110 Hz, the same as a biological whisker, by choosing different materials and physical dimensions. The control system of this sensor enables the whisker to vibrate between 5 and 236 Hz.

  1. Research on SiC Whisker Prepared by H-PSO

    Directory of Open Access Journals (Sweden)

    WANG Yao

    2017-10-01

    Full Text Available SiC whiskers were prepared on the matrix of graphite by using high hydrogenous silicone oil(PSO as raw material. The effect of surface conditions of graphite and heating temperature on the growth of SiC whisker was mainly studied in this paper. The main factor which affects the nucleation and growth of SiC whisker is the heating temperature, with the heating temperature rising, the production of SiC whisker increases. The surface condition of graphite matrix also influences the growth of SiC whisker. With the nucleation points provided by graphite matrix defects increasing, the production of SiC whisker incleases and SiC whisker starts to overlap with each other. The formation process of SiC whisker includes two steps:nucleation and growth. SiC whisker nucleates at low temperature and grows at high temperature, which follows the VLS (vapor-liquid-solid growth mechanism.

  2. Silicon Whisker and Carbon Nanofiber Composite Anode Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Physical Sciences Inc. (PSI) has successfully developed a silicon whisker and carbon nanofiber composite anode for lithium ion batteries on a Phase I program. PSI...

  3. Whisker Formation Induced by Component and Assembly Ionic Contamination

    Science.gov (United States)

    Snugovsky, Polina; Meschter, Stephan; Bagheri, Zohreh; Kosiba, Eva; Romansky, Marianne; Kennedy, Jeffrey

    2012-02-01

    This paper describes the results of an intensive whisker formation study on Pb-free assemblies with different levels of cleanliness. Thirteen types of as-received surface-mount and pin-through-hole components were cleaned and intentionally contaminated with solutions containing chloride, sulfate, bromide, and nitrate. Then the parts were assembled on double-sided boards that were also cleaned or intentionally contaminated with three fluxes having different halide contents. The assemblies were subjected to high-temperature/high-humidity testing (85°C/85% RH). Periodic examination found that contamination triggered whisker formation on both exposed tin and solder fillets. Whisker occurrence and parameters depending on the type and level of contamination are discussed. Cross-sections were used to assess the metallurgical aspects of whisker formation and the microstructural changes occurring during corrosion.

  4. Silicon Whisker and Carbon Nanofiber Composite Anode Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Physical Sciences Inc. (PSI) proposes to develop a silicon whisker and carbon nanofiber composite anode for lithium ion batteries on a Phase I program. This anode...

  5. Low-temperature strain gauges based on silicon whiskers

    Directory of Open Access Journals (Sweden)

    Druzhinin A. A.

    2008-08-01

    Full Text Available To create low-temperature strain gauges based on p-type silicon whiskers tensoresistive characteristics of these crystals in 4,2—300 K temperature range were studied. On the basis of p-type Si whiskers with different resistivity the strain gauges for different materials operating at cryogenic temperatures with extremely high gauge factor at 4,2 K were developed, as well as strain gauges operating at liquid helium temperatures in high magnetic fields.

  6. A solid-state NMR investigation of the structure of nanocrystalline hydroxyapatite.

    Science.gov (United States)

    Jäger, Christian; Welzel, Thea; Meyer-Zaika, Wolfgang; Epple, Matthias

    2006-06-01

    Nanocrystalline hydroxyapatite (HAp) prepared by a precipitation route was investigated. The X-ray diffraction (XRD) powder patterns of the elongated nanocrystals with a typical diameter of about 10 nm and length of 30-50 nm (by transmission electron microscopy (TEM)) revealed the presence of HAp with significantly broadened XRD reflections. However, Ca deficiency was found, as the Ca/P ratio was 1.5 only (so-called calcium-deficient hydroxyapatite (CDHA)), and not 1.67. This Ca deficiency of nanocrystalline HAp is explained using NMR. It is shown unambiguously that (i) the nanocrystals consist of a crystalline core and a (disordered) surface region with a relative phosphate content of about 1:1, (ii) the crystalline core is HAp, and (iii) the surface region is dominated by hydrogen phosphate anions (with no hydroxyapatite-like structural motif) and structural water (hydrate). From the relative phosphate content and taking into account the crystal shape, the thickness of the surface layer along the main crystal axis could be estimated to be about 1 nm, and the average chemical composition of the surface layer has been determined. Finally, a Ca/P ratio of 1.52 was estimated from the NMR data that compares well with the value of 1.51 from chemical analysis. The important consequences are that the surface of nanocrystalline HAp has nothing in common with the bulk composition and that the chemistry of such materials (e.g. the binding of protein molecules to phosphate surfaces) must be reconsidered. 2006 John Wiley & Sons, Ltd.

  7. A novel biomimetic whisker technology based on fiber Bragg grating and its application

    Science.gov (United States)

    Zhao, Chenlu; Jiang, Qi; Li, Yibin

    2017-09-01

    The paper describes a novel, biomimetic whisker-based sensing technology following the basic design of the facial whiskers of animals such as rats and mice. The sensor consists of a 3× 2 whisker array on each side of a robot. In experiments with the artificial whiskers, the motor drives rotating whiskers, and the center wavelength of a fiber Bragg grating pasted on the whisker will shift when the whisker touches an obstacle. The distance will be obtained by processing the wavelength shift data with algorithms. Then the shape recognition can be realized by postprocessing the distance data. The experimental results prove that the whisker array is capable of accurately gathering the distance and shape information of an object.

  8. Preparation of Polyaniline-Doped Fullerene Whiskers

    Directory of Open Access Journals (Sweden)

    Bingzhe Wang

    2013-01-01

    Full Text Available Fullerene C60 whiskers (FWs doped with polyaniline emeraldine base (PANI-EB were synthesized by mixing PANI-EB/N-methyl pyrrolidone (NMP colloid and FWs suspension based on the nature of the electron acceptor of C60 and electron donor of PANI-EB. Scanning electron microscopy (SEM, Fourier transform infrared (FT-IR, and ultraviolet-visible (UV-Vis spectra characterized the morphology and molecular structure of the FWs doped with PANI-EB. SEM observation showed that the smooth surface of FWs was changed to worm-like surface morphology after being doped with PANI-EB. The UV-Vis spectra suggested that charge-transfer (CT complex of C60 and PANI-EB was formed as PANI-EBδ+-C60δ-. PANI-EB-doped FWs might be useful as a new type of antibacterial and self-cleaning agent as well as multifunctional material to improve the human health and living environment.

  9. Interlayer tunneling spectroscopy of mixed-phase BSCCO superconducting whiskers

    Science.gov (United States)

    Kizilaslan, O.; Truccato, M.; Simsek, Y.; Aksan, M. A.; Koval, Y.; Müller, P.

    2016-06-01

    In this work, we present a study on the interlayer tunneling spectroscopy (ITS) of mixed-phase BiSrCaCuO (BSCCO) superconducting whiskers. The tunneling experiments were carried out on the artificial cross-whisker (twist angle of 90°) junctions. A multiple superconducting energy gap in the cross-whisker junctions was observed, which is attributed to the presence of different doping levels of two Bi2Sr2CaCu2O8+δ phases (Bi-2212), rather than two different phases, in the BSCCO whiskers, namely Bi2Sr2CaCu2O8+δ and Bi2Sr2Ca2Cu3O8+δ (Bi-2212 and Bi-2223). The temperature dependence of the energy gaps was discussed in the framework of the BCS T-dependence. On the other hand, the carrier concentration of the cross-whisker junction was changed by the carrier injection process. The effects of the carrier injection on the critical current, I c, and the ITS of intrinsic Josephson junctions were investigated in details.

  10. Whisker movements evoked by stimulation of single motor neurons in the facial nucleus of the rat

    NARCIS (Netherlands)

    L.J. Herfst (Lucas); M. Brecht (Michael)

    2008-01-01

    textabstractThe lateral facial nucleus is the sole output structure whose neuronal activity leads to whisker movements. To understand how single facial nucleus neurons contribute to whisker movement we combined single-cell stimulation and high-precision whisker tracking. Half of the 44 stimulated

  11. Strengthening and toughening of poly(L-lactide) composites by surface modified MgO whiskers

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Wei [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Luo, Binghong, E-mail: tluobh@jnu.edu.cn [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Qin, Xiaopeng; Li, Cairong [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Liu, Mingxian; Ding, Shan [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Zhou, Changren, E-mail: tcrz9@jnu.edu.cn [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China)

    2015-03-30

    Highlights: • The grafted PLLA chain on the surface of g-MgO whisker was ruled out by FTIR spectroscopy and TG/DTG analyses. • The excellent dispersion of g-MgO whiskers and the strong interfacial adhesion of g-MgO whiskers/PLLA composite were proved by FSEM. • Comparing to MgO particles and MgO whiskers, fibrous-like g-MgO whiskers are the most effective reinforcing and toughening fillers for PLLA. - Abstract: To improve both the strength and toughness of poly(L-lactide) (PLLA), fibrous-like MgO whiskers with diameters of 0.15–1 μm and lengths of 15–110 μm were prepared, and subsequently surface modified with L-lactide to obtain grafted MgO whiskers (g-MgO whiskers). The structures and properties of MgO whiskers and g-MgO whiskers were studied. Then, a series of MgO whiskers/PLLA and g-MgO whiskers/PLLA composites were prepared by solution casting method, for comparison, MgO particles/PLLA composite was prepared too. The resulting composites were evaluated in terms of hydrophilicity, crystallinity, dispersion of whiskers, interfacial adhesion and mechanical performance by means of polarized optical microscopy (POM), contact angle measurement, field emission scanning electron microscope (FSEM), transmission electron microscopy (TEM) and tensile testing. The results revealed that the crystallization rate and hydrophilicity of PLLA were improved by the introduction of MgO whiskers and g-MgO whiskers. The g-MgO whiskers can disperse more uniformly in and show stronger interfacial adhesion with the matrix than MgO whiskers as a result of the surface modification. Due to the bridge effect of the whiskers and the excellent interfacial adhesion between g-MgO whiskers and PLLA, g-MgO whiskers/PLLA composites exhibited remarkably higher strength, modulus and toughness compared to the pristine PLLA, MgO particles/PLLA and MgO whiskers/PLLA composites.

  12. Whisker-reinforced ceramic composites for heat engine components

    Science.gov (United States)

    Duffy, Stephen F.

    1988-01-01

    Much work was undertaken to develop techniques of incorporating SiC whiskers into either a Si3N4 or SiC matrix. The result was the fabrication of ceramic composites with ever-increasing fracture toughness and strength. To complement this research effort, the fracture behavior of whisker-reinforced ceramics is studied so as to develop methodologies for the analysis of structural components fabricated from this toughened material. The results, outlined herein, focus on the following areas: the use of micromechanics to predict thermoelastic properties, theoretical aspects of fracture behavior, and reliability analysis.

  13. Investigation into ramie whisker reinforced arylated soy protein composites

    CSIR Research Space (South Africa)

    Kumar, R

    2010-03-01

    Full Text Available bonding, and dispersion of the whiskers in the matrix [11-14]. Ramie is a plant fiber that has been used since ancient times and is commonly known as China grass. Ramie fibers are widely cultivated plant of industrial importance. We have shown... Reinforced Arylated Soy Protein Composites Rakesh Kumar1,2*, Lina Zhang2 1CSIR MSM, Port Elizabeth 6000, South Africa 2Department of Chemistry, Wuhan University, Wuhan 430072, China Abstract Whiskers were prepared from ramie fibers and were...

  14. DC Characterisation of C60 Whiskers and Nanowhiskers

    DEFF Research Database (Denmark)

    Larsson, Michael; Kjelstrup-Hansen, Jakob; Lucyszyn, Stepan

    2007-01-01

    on C60 whiskers and nanowhiskers with diameters in the range 650 nm to 1.3 mm are reported for the first time. Samples are attached to pre-patterned planar and raised electrodes using FIB-deposited tungsten. A low resistivity of 3 Wcm is measured in air, on a C60 whisker having a diameter of 650 nm......-invasive electrical connections with samples. Preliminary results of such trials are presented, indicating it to be a feasible alternative to the use of deposited electrodes....

  15. Synthesis and growth mechanisms of ZrC whiskers fabricated by a VLS process

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dongju [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of). Nuclear Materials Development Division; Song, Sung Ho [Kongju National Univ., Chungnam (Korea, Republic of). Division of Advanced Materials Engineering

    2017-08-15

    The mechanisms of nano-sized ZrC whisker formation by a vapor-liquid-solid process (VLS) are investigated, which produces a very high purity, single crystal whisker. Rectangular ZrC whiskers with a cross-sectional diameter of 100-200 nm and lengths up to tens of microns are formed under the catalytic effect of nickel. The ZrC whiskers are characterized using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. ZrC whiskers can be used as a potential reinforcing and strengthening phase for ceramic composites.

  16. Hydroxyapatite synthesis using EDTA

    Science.gov (United States)

    Kang, Nak Heon; Kim, Soon Je; Song, Seung Han; Choi, Sang mun; Choi, Sik Young; Kim, Youn Jung

    2013-01-01

    Bone comprises structure of body and is consisted of inorganic substances. It exists in an organic structure in the body. Even though it is firm and has self healing mechanism, it can be damaged by trauma, cancer, or bone diseases. Allograft can be an alternative solution for autologous bone graft. Hydroxyapatite(Ca10(PO4)6(OH)2), an excellent candidate for allograft, can be applied to bone defect area. There are several methods to produce hydroxyapatite, however economical cost and time consuming make the production difficult. In this study we synthesized the hydroxyapatite with Ethyenediamine tetraacetic acid. Freeze Dried Bone Allograft(Hans Biomed) was used to be a control group. Synthesized hydroxyapatite was a rod shape, white powdery type substance with 2 ~ 5 μm length and 0.5 ~ 1 μm width. X-ray diffraction showed the highest sharp peak at 32° and high peaks at 25.8°, 39.8°, 46.8°, 49.5°, and 64.0° indicating a similar substance to the freeze Dried Bone Allograft. 3 days after the cell growth of synthesized hydroxyapatite showed 1.5 fold more than the Bone Allograft. Cellular and media alkaline phosphate activity increased similar to the bone alloagraft. In this study we came up with a new method to produce the hydroxyapatite. It is a convenient method that can be held in room temperature and low pressure. Also the the product can be manufactured in large quantity. It can be also transformed into scaffold structure which will perform a stronger configuration. The manufacturing method will help the bony defect patients and make future medical products. PMID:23714942

  17. The effect of whisker movement on radial distance estimation: a case study in comparative robotics

    Directory of Open Access Journals (Sweden)

    Mathew H Evans

    2013-01-01

    Full Text Available Whisker movement has been shown to be under active control in certain specialist animals such as rats and mice. Though this whisker movement is well characterised, the role and effect of this movement on subsequent sensing is poorly understood. One method for investigating this phenomena is to generate artificial whisker deflections with robotic hardware under different movement conditions. A limitation of this approach is that assumptions must be made in the design of any artificial whisker actuators, which will impose certain restrictions on the whisker-object interaction. In this paper we present three robotic whisker platforms, each with different mechanical whisker properties and actuation mechanisms. A feature-based classifier is used to simultaneously discriminate radial distance to contact and contact speed for the first time. We show that whisker-object contact speed predictably affects deflection magnitudes, invariant of whisker material or whisker movement trajectory. We propose that rodent whisker control allows the animal to improve sensing accuracy by regulating contact speed induced touch-to-touch variability.

  18. The effect of whisker movement on radial distance estimation: a case study in comparative robotics.

    Science.gov (United States)

    Evans, Mathew H; Fox, Charles W; Lepora, Nathan F; Pearson, Martin J; Sullivan, J Charles; Prescott, Tony J

    2012-01-01

    Whisker movement has been shown to be under active control in certain specialist animals such as rats and mice. Though this whisker movement is well characterized, the role and effect of this movement on subsequent sensing is poorly understood. One method for investigating this phenomena is to generate artificial whisker deflections with robotic hardware under different movement conditions. A limitation of this approach is that assumptions must be made in the design of any artificial whisker actuators, which will impose certain restrictions on the whisker-object interaction. In this paper we present three robotic whisker platforms, each with different mechanical whisker properties and actuation mechanisms. A feature-based classifier is used to simultaneously discriminate radial distance to contact and contact speed for the first time. We show that whisker-object contact speed predictably affects deflection magnitudes, invariant of whisker material or whisker movement trajectory. We propose that rodent whisker control allows the animal to improve sensing accuracy by regulating contact speed induced touch-to-touch variability.

  19. Vortex Shedding in the Wake Induced by a Real Elephant Seal Whisker

    Science.gov (United States)

    Turk, Jodi; Omilion, Alexis; Zhang, Wei; Kim, Jeong-Jae; Kim, Jeong-Ju; Choi, Woo-Rak; Lee, Sang-Joon

    2017-11-01

    Biomimicry has been adopted to create innovative solutions in a vast range of applications. One such application is the design of seal-whisker-inspired flow sensors for autonomous underwater vehicles (AUVs). In dark, cramped, and unstable terrain AUVs are not able to maneuver using visual and sonar-based navigation. Hence, it is critical to use underwater flow sensors to accurately detect minute disturbances in the surroundings. Certain seal whiskers exhibit a unique undulating three-dimensional morphology that can reduce vortex induced vibrations (VIVs) if the major axis of the whisker cross-section is aligned to the inflow. This allows the seal to precisely track prey fish upstream using solely their whiskers. The current study aims to understand the effect of a real seal whisker's morphology on the vortex shedding behavior. Despite extensive studies of wake induced by scaled whisker-like models, the vortex shedding in the wake of a real seal whisker is not well understood. A series of experiments are conducted with a high-speed Particle Imaging Velocimetry (PIV) system in a water channel to examine the vortex shedding downstream from a smooth whisker and an undulating whisker at a Reynolds number of a few hundred. Results of the vortex shedding induced by real seal whiskers can provide insights on developing high-sensitivity underwater flow sensors for AUVs and other whisker-inspired structures.

  20. Facile Synthesis of Electroconductive AZO@TiO2 Whiskers and Their Application in Textiles

    Directory of Open Access Journals (Sweden)

    Hui Ma

    2016-01-01

    Full Text Available The electroconductive AZO@TiO2 whiskers have been successfully prepared via coating Al doped ZnO onto TiO2 whisker. The orthogonal tests were employed to optimize the synthetic conditions. The crystallographic structure and the morphology of the AZO@TiO2 whiskers and the polypropylene nonwoven fabrics modified with AZO@TiO2 whiskers were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope, four-probe meter, and electrometer. The results showed the AZO@TiO2 whiskers exhibited good electroconductive performance. Moreover, the polypropylene nonwoven fabrics modified with AZO@TiO2 whiskers revealed excellent antistatic performance indicating wide application of AZO@TiO2 whiskers in the antistatic textiles.

  1. Understanding and predicting metallic whisker growth and its effects on reliability : LDRD final report.

    Energy Technology Data Exchange (ETDEWEB)

    Michael, Joseph Richard; Grant, Richard P.; Rodriguez, Mark Andrew; Pillars, Jamin; Susan, Donald Francis; McKenzie, Bonnie Beth; Yelton, William Graham

    2012-01-01

    Tin (Sn) whiskers are conductive Sn filaments that grow from Sn-plated surfaces, such as surface finishes on electronic packages. The phenomenon of Sn whiskering has become a concern in recent years due to requirements for lead (Pb)-free soldering and surface finishes in commercial electronics. Pure Sn finishes are more prone to whisker growth than their Sn-Pb counterparts and high profile failures due to whisker formation (causing short circuits) in space applications have been documented. At Sandia, Sn whiskers are of interest due to increased use of Pb-free commercial off-the-shelf (COTS) parts and possible future requirements for Pb-free solders and surface finishes in high-reliability microelectronics. Lead-free solders and surface finishes are currently being used or considered for several Sandia applications. Despite the long history of Sn whisker research and the recently renewed interest in this topic, a comprehensive understanding of whisker growth remains elusive. This report describes recent research on characterization of Sn whiskers with the aim of understanding the underlying whisker growth mechanism(s). The report is divided into four sections and an Appendix. In Section 1, the Sn plating process is summarized. Specifically, the Sn plating parameters that were successful in producing samples with whiskers will be reviewed. In Section 2, the scanning electron microscopy (SEM) of Sn whiskers and time-lapse SEM studies of whisker growth will be discussed. This discussion includes the characterization of straight as well as kinked whiskers. In Section 3, a detailed discussion is given of SEM/EBSD (electron backscatter diffraction) techniques developed to determine the crystallography of Sn whiskers. In Section 4, these SEM/EBSD methods are employed to determine the crystallography of Sn whiskers, with a statistically significant number of whiskers analyzed. This is the largest study of Sn whisker crystallography ever reported. This section includes a

  2. Method of making in-situ whisker reinforced glass ceramic

    Science.gov (United States)

    Brown, Jesse J.; Hirschfeld, Deidre A.; Lee, K. H.

    1993-02-16

    A heat processing procedure is used to create reinforcing whiskers of TiO.sub.2 in glass-ceramic materials in the LAS and MAS family. The heat processing procedure has particular application in creating TiO.sub.2 in-situ in a modified .beta.-eucryptite system.

  3. Chemical precursors to zinc sulfide: ZnS whisker synthesis

    Science.gov (United States)

    Guiton, T. A.; Czekaj, C. L.; Rau, M. S.; Geoffroy, G. L.; Pantano, C. G.

    1988-07-01

    Currently, Chemical Vapor Deposition (CVD) derived zinc sulfide is one of the most widely used infrared optical window materials. Unfortunately, for numerous applications it does not possess optimum mechanical properties. To fabricate infrared transmitting ZnS/ZnS composites requires the development of high aspect ratio, micron sized ZnS whiskers. Although larger ZnS single crystals and whiskers have been made by a variety of high temperature routes, alternative routes have been sought for greater ZnS whisker morphology control. Low temperature organometallic routes are attractive for this purpose. The precursor compound used in this study is the known pentameric species (EtZn(SBut))5. One of the most successful routes involves the reaction of (EtZn(SBU sup t))5 with hydrogen sulfide at ambient or sub-ambient temperature to yield a precipitate which is subsequently heated under flowing H2S at 500 C to yield a mixture of sub-micron particles and single-crystal ZnS whiskers. Transmission electron micrographs of the (EtZn(SBU sup t))5 products indicate that the ZnS morphology is critically dependent on the rate of H2S reaction. Corresponding X-ray/electron diffraction, electron microscopy, elemental analysis, NMR and infrared spectroscopies have been conducted. A summary of the chemical methods, product characterization results, and proposed synthesis mechanisms are presented.

  4. Isoniazid loaded gelatin-cellulose whiskers nanoparticles for ...

    Indian Academy of Sciences (India)

    Natural polymers like gelatin have been used as a potential drug carrier for controlled delivery applications due to their various advantages over synthetic polymers. Cellulose Whiskers (CWs) have the capacity to form strong hydrogen bonds which help in controlling the release of drug and also provide goodstrength to the ...

  5. Isoniazid loaded gelatin-cellulose whiskers nanoparticles for ...

    Indian Academy of Sciences (India)

    Abstract. Natural polymers like gelatin have been used as a potential drug carrier for controlled delivery applications due to their various advantages over synthetic polymers. Cellulose Whiskers (CWs) have the capacity to form strong hydrogen bonds which help in controlling the release of drug and also provide good.

  6. Manual Whisker Annotator (MWA: A Modular Open-Source Tool

    Directory of Open Access Journals (Sweden)

    Brett M. Hewitt

    2016-04-01

    Full Text Available Rodents are key to generating translational data for healthcare research. Behavioural analyses, in particular, are integral to the non-invasive monitoring of rodent health and welfare. Finding quantitative behavioural measures mitigates stress, allowing for the animal behave freely while also enabling the same animal to be studied over the time-course of its life. Locomotion and whisking are both such quantitative behavioural measures, and have been found to be significantly impacted in rodent models of neurodegenerative disease. While automatic trackers of whiskers and locomotion exist, a manual tracker is required to validate these approaches, and also to annotate complex videos where these automatic versions fail. Manually annotating whiskers for research purposes is a long and tedious task and current software does little to provide an intuitive and simple interface to carry out this task. This led to the creation of the Manual Whisker Annotator (MWA. MWA is an open source, portable whisker annotation tool developed for the Windows platform. Not only does MWA make the process much quicker, it also provides added statistical tools to analyse the data. MWA was developed in C# and WPF using the .NET framework, and could be used in any situation where annotating or tracking multiple targets is desired.

  7. Box-and-Whisker Plots Applied to Food Chemistry

    Science.gov (United States)

    Ferreira, Joao E. V.; Miranda, Ricardo M.; Figueiredo, Antonio F.; Barbosa, Jardel P.; Brasil, Edykarlos M.

    2016-01-01

    Box-and-whisker plots or simply boxplots are powerful graphical representations that give an overview of a data set. In this work five different examples illustrate the applications of boxplots in food chemistry. The examples involve relative sweetness of sugars and sugar alcohols with respect to sucrose, the potassium content of fruits and…

  8. Magnetic susceptibility and magnetoresistance of neutron-irradiated doped SI whiskers

    Energy Technology Data Exchange (ETDEWEB)

    Druzhinin, A.A., E-mail: druzh@polynet.lviv.ua [Lviv Polytechnic National University, S. Bandera Str., 12, Lviv 79013 (Ukraine); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw (Poland); Ostrovskii, I.P.; Khoverko, Yu.M. [Lviv Polytechnic National University, S. Bandera Str., 12, Lviv 79013 (Ukraine); International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw (Poland); Rogacki, K. [International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw (Poland); Litovchenko, P.G.; Pavlovska, N.T. [Institute of Nuclear Researches, NAS of Ukraine, 47, Prospect Nauky, 03028 Kyiv (Ukraine); Pavlovskyy, Yu.V.; Ugrin, Yu.O. [Ivan Franko Drohobych State Pedagogical University, 24, Franko str., 82100 Drohobych (Ukraine)

    2015-11-01

    The effect of 8.6·10{sup 17} n/cm{sup 2} fast neutron irradiation on the magnetic susceptibility and magnetoresistance of Si whiskers with impurity concentration near metal–insulator transition (MIT) has been studied. Neutron irradiated specimens with boron concentration away of MIT are mainly diamagnetic with a small amount of paramagnetic centers originated from dangling bonds on the whisker surface. It has been established that at temperatures near 4.2 K, a significant contribution to the conductivity is made by light charge carriers of low concentration but with high mobility. The as grown whiskers with impurity concentration correspondent to MIT showed hysteresis loops in magnetization at temperature of liquid helium. Besides hysteresis loops in magnetoresistance was observed for whiskers under compression stress at low temperature up to 7 K. The possible reason of the effect can be magnetic interaction between impurities centers in subsurface region of the whisker with the orbital moment of dangle bounds in the whisker core–shell interstices. - Highlights: • Neutron irradiation influence on magnetic susceptibility of Si whiskers is studied. • Neutron irradiated Si whiskers with boron concentration away of MIT are diamagnetic. • Whiskers in the vicinity to MIT showed hysteresis loops in magnetoresistance. • Whiskers in the vicinity to MIT showed hysteresis loops in magnetic susceptibility.

  9. Reverse micelle mediated synthesis, processing, mechanical and biological characterization of hydroxyapatite nanopowders for bone graft application

    Science.gov (United States)

    Banerjee, Ashis

    Hydroxyapatite (HA) is the most widely used bioceramic material in bone graft applications because of its compositional similarity with natural bone. However, synthetic HA does not show similar mechanical and biological properties to the inorganic component of bone. Properties of ceramic material depend on starting materials, processing techniques, densification and microstructure of the final product. The objective of this research was to process HA whisker reinforced HA composite using HA nanopowders and whiskers. HA nanopowders with different length scale and morphology were synthesized by reverse micelle system using NP5 and NP12 as surfactants and cyclohexane as organic solvent. The lowest average aspect ratio was 1.357+/-0.39 with average particle size of 66 nm and the highest average aspect ratio was 7.277+/-3.227 with average length of 150 nm and width of 20 nm, were synthesized. Micron sized HA whiskers with aspect ratio between 20 and 50, average particle length of 15 mum and width of 400 nm was synthesized using urea as a precipitating agent. Desired microstructure was obtained after sintering with spherical HA nanopowder and whiskers along with dopants. Addition of whiskers decreased density of the sintered compacts. However, at 10 wt% whisker content sample showed microhardness and fracture toughness of 3.6 GPa and 1.5 MPa.m1/2, respectively, and a compressive strength of 80 MPa was obtained. Mineralization study in simulated body fluid (SBF) showed formation of apatite layer on the dense HA compacts indicating a good tendency of bond formation with natural bone. Cytotoxicity results showed excellent cell attachment on the HA surface. In the Appendices, 3 journal articles have been attached which describe synthesis, processing and characterization of undoped and doped PZT nanopowders. Free standing and agglomerated PZT nanopowders were synthesized by the sucrose templated method and the citrate nitrate autocombustion method. Particle size in the range

  10. Hydroxyapatite coatings for biomedical applications

    CERN Document Server

    Zhang, Sam

    2013-01-01

    Hydroxyapatite coatings are of great importance in the biological and biomedical coatings fields, especially in the current era of nanotechnology and bioapplications. With a bonelike structure that promotes osseointegration, hydroxyapatite coating can be applied to otherwise bioinactive implants to make their surface bioactive, thus achieving faster healing and recovery. In addition to applications in orthopedic and dental implants, this coating can also be used in drug delivery. Hydroxyapatite Coatings for Biomedical Applications explores developments in the processing and property characteri

  11. A radial map of multi-whisker correlation selectivity in the rat barrel cortex.

    Science.gov (United States)

    Estebanez, Luc; Bertherat, Julien; Shulz, Daniel E; Bourdieu, Laurent; Léger, Jean-François

    2016-11-21

    In the barrel cortex, several features of single-whisker stimuli are organized in functional maps. The barrel cortex also encodes spatio-temporal correlation patterns of multi-whisker inputs, but so far the cortical mapping of neurons tuned to such input statistics is unknown. Here we report that layer 2/3 of the rat barrel cortex contains an additional functional map based on neuronal tuning to correlated versus uncorrelated multi-whisker stimuli: neuron responses to uncorrelated multi-whisker stimulation are strongest above barrel centres, whereas neuron responses to correlated and anti-correlated multi-whisker stimulation peak above the barrel-septal borders, forming rings of multi-whisker synchrony-preferring cells.

  12. Whisker-Like Formations in Sn-3.0Ag-Pb Alloys

    Directory of Open Access Journals (Sweden)

    Koncz-Horváth D.

    2017-06-01

    Full Text Available In this study, different types of whisker-like formations of Sn-3.0Ag based alloy were presented. In the experimental process the amount of Pb element was changed between 1000 and 2000 ppm, and the furnace atmosphere and cooling rate were also modified. The novelty of this work was that whisker-like formations in macro scale size were experienced after an exothermic reaction. The whiskers of larger sizes than general provided opportunities to investigate the microstructure and the concentration nearby the whiskers. In addition, the whisker-like formations from Sn-Ag based bulk material did not only consist of pure tin but tin and silver phases. The whisker-like growth appeared in several forms including hillock, spire and nodule shaped formations in accordance with parameters. It was observed that the compound phases were clustered in many cases mainly at hillocks.

  13. Cadmium immobilization by hydroxyapatite

    Directory of Open Access Journals (Sweden)

    Smičiklas Ivana D.

    2003-01-01

    Full Text Available The contamination of air, soil and water by cadmium is a great environmental problem. If cadmium occurs in nature in ionic form, soluble in water, it easily enters into the food chain. Hydroxyapatite (HAP, Ca-o(POAe(OH2 is a sparingly soluble salt and an excellent matrix for the removal of heavy metals from solutions. Considerable research attention has been paid to the bond between Cc/2+ ions and synthetic hydroxyapatite of known composition. The sorption mechanism is complex. The dominant process is ion exchange, but surface adsorption, surface complexation and coprecipitation can also contribute to the overall mechanism. The sorption capacity depends on the characteristics of hydroxyapatite itself and on the experimental conditions. Under optimum conditions a maximum capacity of 0.8 mol Cd2+/mol HAP can be achieved. HAP is a potential sorbent for the remediation of contaminated water and soil, for industrial waste treatment, and it is also referenced as a material that can be used as a barrier around waste depositories.

  14. Mystacial Whisker Layout and Musculature in the Guinea Pig (Cavia porcellus): A Social, Diurnal Mammal.

    Science.gov (United States)

    Grant, Robyn A; Delaunay, Mariane G; Haidarliu, Sebastian

    2017-03-01

    All mammals (apart from apes and humans) have whiskers that make use of a similar muscle arrangement. Whisker specialists, such as rats and mice, tend to be nocturnal and arboreal, relying on their whisker sense of touch to guide exploration around tree canopies at night. As such, nocturnal arboreal rodents have many whiskers that are organised into a grid-like pattern, and moved using a complex array of muscles. Indeed, most arboreal, nocturnal mammals tend to have specialised whiskers that are longer and arranged in a dense, regular grid, compared with terrestrial, diurnal mammals. The guinea pig diverged early from murid rodents (around 75 million years ago), and are ground-dwelling, diurnal animals. It would be predicted that, as a terrestrial mammal, they may have less whiskers and a reduced muscle architecture compared to arboreal, nocturnal rodents. We examined the mystacial whisker layout, musculature and movement capacity of Guinea pig (Cavia porcellus) whiskers and found that they did indeed have a disorganized whisker layout, with a fortification around the eye area. In addition, there was a reduction in musculature, especially in the intrinsic muscles. Despite guinea pigs not cyclically moving their whiskers, the mystacial musculature was still very similar to that of murid rodents. We suggest that the conserved presence of whisker layout and musculature, even in visual mammals such as primates and guinea pigs, may indicate that whiskers still play an important role in these animals, including protecting the eyes and being involved in tactile social behaviors. Anat Rec, 300:527-536, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  15. Surface modification of magnesium hydroxide sulfate hydrate whiskers using a silane coupling agent by dry process

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Donghai, E-mail: zhudonghai-2001@163.com [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, 810008 (China); Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Chinese Academy of Sciences, Xining, 810008 (China); Nai, Xueying [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, 810008 (China); Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Chinese Academy of Sciences, Xining, 810008 (China); Lan, Shengjie; Bian, Shaoju [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, 810008 (China); Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Chinese Academy of Sciences, Xining, 810008 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Liu, Xin [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, 810008 (China); Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Chinese Academy of Sciences, Xining, 810008 (China); Li, Wu, E-mail: driverlaoli@163.com [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, 810008 (China); Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Chinese Academy of Sciences, Xining, 810008 (China)

    2016-12-30

    Highlights: • Dry process was adopted to modify the surface of MHSH whiskers using silane. • Si−O−Mg bonds were formed directly by the reaction between Si−OC{sub 2}H{sub 5} and −OH of MHSH. • Dispersibility and compatibility of modified whiskers greatly improved in organic phase. • Thermal stability of whiskers was enhanced after modified. - Abstract: In order to improve the compatibility of magnesium hydroxide sulfate hydrate (MHSH) whiskers with polymers, the surface of MHSH whiskers was modified using vinyltriethoxysilane (VTES) by dry process. The possible mechanism of the surface modification and the interfacial interactions between MHSH whiskers and VTES, as well as the effect of surface modification, were studied. Scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) analyses showed that the agglomerations were effectively separated and a thin layer was formed on the surface of the whiskers after modification. Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses showed that the VTES molecules were bound to the surface of MHSH whiskers after modification. Chemical bonds (Si−O−Mg) were formed by the reaction between Si−OC{sub 2}H{sub 5} or Si−OH and the hydroxyl group of MHSH whiskers. The effect of surface modification was evaluated by sedimentation tests, contact angle measurements and thermogravimetric analysis (TGA). The results showed that the surface of MHSH whiskers was transformed from hydrophilic to hydrophobic, and the dispersibility and the compatibility of MHSH whiskers were significantly improved in the organic phase. Additionally, the thermal stability of the VTES-modified MHSH whiskers was improved significantly.

  16. An Empirical Model for Estimating the Probability of Electrical Short Circuits from Tin Whiskers. Part 2

    Science.gov (United States)

    Courey, Karim; Wright, Clara; Asfour, Shihab; Onar, Arzu; Bayliss, Jon; Ludwig, Larry

    2009-01-01

    In this experiment, an empirical model to quantify the probability of occurrence of an electrical short circuit from tin whiskers as a function of voltage was developed. This empirical model can be used to improve existing risk simulation models. FIB and TEM images of a tin whisker confirm the rare polycrystalline structure on one of the three whiskers studied. FIB cross-section of the card guides verified that the tin finish was bright tin.

  17. The vortex glass to liquid transition in Bi2212 whisker

    Science.gov (United States)

    Zheng, P.; Zhou, Y. Q.; Chen, Z. J.; Luo, S.; Wang, W. H.; He, Y. S.; Duo, J.

    1999-05-01

    Through scaling the dc I- V isotherms of Bi2212 whisker in magnetic field H‖ c, the vortex glass-liquid transition is found in Bi2212 whisker whereas it does not appear in Bi2212 crystal slab [R. Behr, J. Kotzler, G. Nakielski, M. Baumann, M. Kaufmann, J. Kowalewski, Physica C 235 (1994) 2669]. The critical exponents are ν=0.5, z=4.0. We found that the critical exponents are influenced by the planar defects of the sample. The result was compared to those of single crystals and films [Behr et al., 1994; H. Yamasaki, K. Endo, S. Kosaka, M. Umeda, S. Yoshida, K. Kajimura, Phys. Rev. B 50 (17) (1994) 12959].

  18. Whisker growth on Sn thin film accelerated under gamma-ray induced electric field

    Science.gov (United States)

    Killefer, Morgan; Borra, Vamsi; Al-Bayati, Ahmed; Georgiev, Daniel G.; Karpov, Victor G.; Ishmael Parsai, E.; Shvydka, Diana

    2017-10-01

    We report on the growth of tin metal whiskers significantly accelerated under non-destructive gamma-ray irradiation. Sn thin film, evaporated on glass substrate, was subjected to a total of 60 h of irradiation. The irradiated samples demonstrated enhanced whisker development, in both densities and lengths, resulting in an acceleration factor of  ∼50. We attribute the observed enhancement to gamma-ray induced electrostatic fields, affecting whisker kinetics. These fields are due to the substrate charging under gamma-rays. We propose that gamma-ray irradiation can be a much needed tool for accelerated testing of whisker propensity.

  19. Surface modification of magnesium hydroxide sulfate hydrate whiskers using a silane coupling agent by dry process

    Science.gov (United States)

    Zhu, Donghai; Nai, Xueying; Lan, Shengjie; Bian, Shaoju; Liu, Xin; Li, Wu

    2016-12-01

    In order to improve the compatibility of magnesium hydroxide sulfate hydrate (MHSH) whiskers with polymers, the surface of MHSH whiskers was modified using vinyltriethoxysilane (VTES) by dry process. The possible mechanism of the surface modification and the interfacial interactions between MHSH whiskers and VTES, as well as the effect of surface modification, were studied. Scanning electronic microscopy (SEM), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) analyses showed that the agglomerations were effectively separated and a thin layer was formed on the surface of the whiskers after modification. Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses showed that the VTES molecules were bound to the surface of MHSH whiskers after modification. Chemical bonds (Sisbnd Osbnd Mg) were formed by the reaction between Sisbnd OC2H5 or Sisbnd OH and the hydroxyl group of MHSH whiskers. The effect of surface modification was evaluated by sedimentation tests, contact angle measurements and thermogravimetric analysis (TGA). The results showed that the surface of MHSH whiskers was transformed from hydrophilic to hydrophobic, and the dispersibility and the compatibility of MHSH whiskers were significantly improved in the organic phase. Additionally, the thermal stability of the VTES-modified MHSH whiskers was improved significantly.

  20. The application and research status of tin whisker formation in electric usage

    Science.gov (United States)

    Zhao, Heng; Liu, Qing-bin; Lan, Yuan-pei; Wang, Hua; Yao, Da-wei

    2017-05-01

    `Hair Like' crystalline structure grows from most pure tin or zinc finishes. Usually, the diameter of tin whisker is up to 10 mm and the length of tin whisker is typically 1 µm. In detail, the questions for tin whisker formation are classified into 6 categories: 1. Residual stress with in the tin plating; 2. Intermetallic Formation; 3. Externally Applied Compressive Stress; 4. Bending and Stretching; 5. Scratches and Nicks; 6. Coefficient of Thermal Expansion Mismatches. The result shows that, whisker formation could causes electrical short circuit (High current of whisker melting), debris contamination (Sensitive Optical and Micro Electrical Mechanical System) and metal vapor (Vaporize Damage). Thus, it is suggested that environmental tests and standards (Whisker Shape, Temperature, Pressure, Moisture, Thermal Cycling, and Electrical Field) are required for suppressing whisker formation. Nowadays, the new standards committee of Europe Union acts RoHS (Restriction of certain Hazardous Substances) and WEEE (Waste Electrical and Electronic Equipment) to restrict Pb usage. Thus, new compounds adding to alloys to suppress whiskers are required in electronic application area. In summary, the tin whisker formation is largely influenced by compositions and precipitations.

  1. Bioinspired active whisker sensor for robotic vibrissal tactile sensing

    Science.gov (United States)

    Ju, Feng; Ling, Shih-Fu

    2014-12-01

    A whisker transducer (WT) inspired by rat’s vibrissal tactile perception is proposed based on a transduction matrix model characterizing the electro-mechanical transduction process in both forward and backward directions. It is capable of acting as an actuator to sweep the whisker and simultaneously as a sensor to sense the force, motion, and mechanical impedance at whisker tip. Its validity is confirmed by numerical simulation using a finite element model. A prototype is then fabricated and its transduction matrix is determined by parameter identification. The calibrated WT can accurately sense mechanical impedance which is directly related to stiffness, mass and damping. Subsequent vibrissal tactile sensing of sandpaper texture reveals that the real part of mechanical impedance sensed by WT is correlated with sandpaper roughness. Texture discrimination is successfully achieved by inputting the real part to a k-means clustering algorithm. The mechanical impedance sensing ability as well as other features of the WT such as simultaneous-actuation-and-sensing makes it a good solution to robotic tactile sensing.

  2. The Formation of Graphite Whiskers in the Primitive Solar Nebula

    Science.gov (United States)

    Nuth, Joseph A., III; Kimura, Yuki; Lucas, Christopher; Ferguson, Frank; Johnson, Natasha M.

    2010-02-01

    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from protostellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H2, CO, and N2 reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H2, CO, and N2 at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.

  3. The Formation of Graphite Whiskers in the Primitive Solar Nebula

    Science.gov (United States)

    Nuth, Joseph A., III; Kimura, Yuki; Lucas, Christopher; Ferguson, Frank; Johnson, Natasha M.

    2010-01-01

    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from proto stellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H2, CO, and N2 reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H2, CO, and N2 at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.

  4. Synthesis of whiskers of SiC microwave assisted; Sintesis de whiskers de SiC asistida por microondas

    Energy Technology Data Exchange (ETDEWEB)

    Garza-Mendez, F. J.; Vanegas, A. J.; Vazquez, B. A.; Garza-Paz, J.

    2013-06-01

    We developed a new process for the synthesis of SiC whiskers assisted by microwaves; this is based on the mixture of silica xerogels and graphite powder. As energy source were used microwaves of 2.45 GHz and 1.0 kW of power RMS. On the other hand, mesoporous silica was synthesized via sol-gel, the precursors used were TEOS/H{sub 2}O and ethanol. Through analysis of the BET is determined the value of average pore size (3.0 nm) and the surface area (1090 m2/g).By mean of X-Ray diffraction it was demonstrated that the silica obtained is an amorphous solid and, the powders obtained in the microwave synthesis are {beta}-SiC. Synthesized SiC powders were observed using a SEM in secondary electron mode, it was observed that this powders consists of SiC whiskers. The effect of microwaves on the synthesis of whiskers of SiC is discussed in the present work. (Author) 19 refs.

  5. Modeling the emergence of whisker direction maps in rat barrel cortex.

    Directory of Open Access Journals (Sweden)

    Stuart P Wilson

    Full Text Available Based on measuring responses to rat whiskers as they are mechanically stimulated, one recent study suggests that barrel-related areas in layer 2/3 rat primary somatosensory cortex (S1 contain a pinwheel map of whisker motion directions. Because this map is reminiscent of topographic organization for visual direction in primary visual cortex (V1 of higher mammals, we asked whether the S1 pinwheels could be explained by an input-driven developmental process as is often suggested for V1. We developed a computational model to capture how whisker stimuli are conveyed to supragranular S1, and simulate lateral cortical interactions using an established self-organizing algorithm. Inputs to the model each represent the deflection of a subset of 25 whiskers as they are contacted by a moving stimulus object. The subset of deflected whiskers corresponds with the shape of the stimulus, and the deflection direction corresponds with the movement direction of the stimulus. If these two features of the inputs are correlated during the training of the model, a somatotopically aligned map of direction emerges for each whisker in S1. Predictions of the model that are immediately testable include (1 that somatotopic pinwheel maps of whisker direction exist in adult layer 2/3 barrel cortex for every large whisker on the rat's face, even peripheral whiskers; and (2 in the adult, neurons with similar directional tuning are interconnected by a network of horizontal connections, spanning distances of many whisker representations. We also propose specific experiments for testing the predictions of the model by manipulating patterns of whisker inputs experienced during early development. The results suggest that similar intracortical mechanisms guide the development of primate V1 and rat S1.

  6. Contributions of Stress and Oxidation on the Formation of Whiskers in Pb-free Solders

    Science.gov (United States)

    2016-01-29

    environmental legislation continues to increase the life-cycle cost of lead in electronics, the instances of whisker driven failures in these devices...Department of Defense Strategic Environmental Research and Development Program (SERDP). The publication of this report does not indicate... environmental factors influencing formation of tin whiskers on electrodeposited lead free, tin coatings over copper (or copper containing) substrates is the

  7. Eliminating Whisker Growth by Indium Addition in Electroplated Sn on Copper Substrate

    Science.gov (United States)

    Das Mahapatra, S.; Majumdar, B. S.; Dutta, I.; Bhassyvasantha, S.

    2017-07-01

    Whisker growth from Sn coatings is a reliability concern in electronic packages, until recently mitigated by Pb addition. Recently, it was demonstrated that doping with In dramatically reduces whisker growth in 1 μm thick Sn. Here, we present the results of In-doping on whisker growth from 3 μm and 6 μm thick Sn-films and explore the reasons behind this mitigation, and compare the results with a baseline sample of pure Sn and a control sample of tri-layer Sn-In-Sn, all subjected to identical thermal treatments. It is shown that In addition completely stops whisker growth from electroplated Sn. The impact of In addition on the film microstructure and the role of the surface oxide coating are investigated. Previous work had shown that while In addition reduces grain boundary diffusivity, it does not fully account for the observed dramatic reduction of whisker growth. In this work, it is shown by Auger electron spectroscopy and x-ray photoelectron spectroscopy that In is incorporated in the surface-oxide. Since whisker-growth is contingent on the presence of a tenacious surface-oxide, this suggests that the alteration of the oxide properties may be responsible for the observed reduction in whisker growth. Finite element modeling is utilized to demonstrate that a reduction of the elastic modulus of the surface oxide would reduce the driving force of Sn whisker growth, thus proffering a rationale for the effect of In incorporation.

  8. Preparation and characterization of keratin-K2Ti6O13 whisker ...

    African Journals Online (AJOL)

    USER

    2010-05-10

    May 10, 2010 ... application of the keratin material as a biomaterial. In this article, it was firstly proposed that potassium hexatitanate (K2Ti6O13) whiskers be used to reinforce keratin film. The effects of coupling agent, whisker content, distribution and orientation on properties of composite were investigated by microscope ...

  9. Hydroxyapatite for keratoprosthesis biointegration.

    Science.gov (United States)

    Wang, Liqiang; Jeong, Kyung Jae; Chiang, Homer H; Zurakowski, David; Behlau, Irmgard; Chodosh, James; Dohlman, Claes H; Langer, Robert; Kohane, Daniel S

    2011-09-22

    Integration of keratoprosthesis with the surrounding cornea is very important in preventing bacterial invasion, which may cause ocular injury. Here the authors investigated whether hydroxyapatite (HAp) coating can improve keratoprosthesis (KPro) biointegration, using polymethyl methacrylate (PMMA)--the principal component of the Boston KPro--as a model polymer. HAp coatings were induced on PMMA discs after treatment with concentrated NaOH and coating with poly-dopamine (PDA) or polydopamine and then with 11-mercaptoundecanoic acid (11-MUA). Coatings were characterized chemically (Fourier transform infrared spectroscopy [FTIR], energy dispersive X-ray spectroscopy [EDX]) and morphologically (SEM) and were used as substrates for keratocyte growth in vitro. Cylinders of coated PMMA were implanted in porcine corneas ex vivo for 2 weeks, and the force required to pull them out was measured. The inflammatory reaction to coated discs was assessed in the rabbit cornea in vivo. FTIR of the coatings showed absorption bands characteristic of phosphate groups, and EDX showed that the Ca/P ratios were close to those of HAp. By SEM, each method resulted in morphologically distinct HAp films; the 11-MUA group had the most uniform coating. The hydroxyapatite coatings caused comparable enhancement of keratocyte proliferation compared with unmodified PMMA surfaces. HAp coating significantly increased the force and work required to pull PMMA cylinders out of porcine corneas ex vivo. HAp coating of implants reduced the inflammatory response around the PMMA implants in vivo. These results are encouraging for the potential of HAp-coated surfaces for use in keratoprostheses.

  10. Contributions of stress and oxidation on the formation of whiskers in Pb-free solders

    Energy Technology Data Exchange (ETDEWEB)

    Duncan, A. J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hoffman, E. N. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-01-01

    Understanding the environmental factors influencing formation of tin whiskers on electrodeposited lead free, tin coatings over copper (or copper containing) substrates is the topic of this study . An interim report* summarized initial observations as to the role of stress and oxide formation on whisker growth. From the initial results, two main areas were chosen to be the focus of additional research: the demonstration of effects of elastic stress state in the nucleation of whiskers and the confirmation of the effect of oxygen content in the formation of whiskers. Different levels of elastic stress were induced with the incorporation of a custom designed fixture that loaded the sample in a four-point bending configuration and were maintained in an environmental chamber under conditions deemed favorable for whisker growth. The effects of oxygen content were studied by aging substrates in gas vials of varying absolute pressure and different oxygen partial pressure.

  11. Rat whisker motor cortex is subdivided into sensory-input and motor-output areas

    Directory of Open Access Journals (Sweden)

    Jared B Smith

    2013-01-01

    Full Text Available Rodent whisking is an exploratory behavior that can be modified by sensory feedback. Consistent with this, many whisker-sensitive cortical regions project to agranular motor (MI cortex, but the relative topography of these afferent projections has not been established. Intracranial microstimulation (ICMS evokes whisker movements that are used to map the functional organization of MI, but no study has compared the whisker-related inputs to MI with the ICMS sites that evoke whisker movements. To elucidate this relationship, anterograde tracers were placed in posterior parietal cortex (PPC and in the primary (SI and secondary (SII somatosensory cortical areas so that their labeled projections to MI could be analyzed with respect to ICMS sites that evoke whisker movements. Projections from SI and SII terminate in a narrow zone that marks the transition between the medial (AGm and lateral agranular (AGl cortical areas, but PPC projects more medially and terminates in AGm proper. Paired recordings of MI neurons indicate that the region between AGm and AGl is highly responsive to whisker deflections, but neurons in AGm display negligible responses to whisker stimulation. By contrast, AGm microstimulation is more effective in evoking whisker movements than microstimulation of the transitional region between AGm and AGl. The AGm region was also found to contain a larger concentration of corticotectal neurons, which could convey whisker-related information to the facial nucleus. These results indicate that rat whisker motor cortex is comprised of at least two functionally distinct subregions: a sensory processing zone in the transitional region between AGm and AGl, and a motor output region located more medially in AGm proper.

  12. Strain gradient plasticity effects in whisker-reinforced metals

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof

    2002-01-01

    A metal reinforced by fibers in the micron range is studied using the strain gradient plasticity theory of Fleck and Hutchinson (2001). Cell-model analyzes are used to study the influence of the material length parameters numerically. Different higher order boundary conditions are considered...... at the fiber-matrix interface. The results are presented as overall stress-strain curves for the whisker-reinforced metal, and also contour plots of effective plastic strain are shown. The strain gradient plasticity theory predicts a significant stiffening effect when compared to conventional models...

  13. The effects of temperature and humidity on the growth of tin whisker and hillock from Sn5Nd alloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, Cai-Fu [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Liu, Zhi-Quan, E-mail: zqliu@imr.ac.cn [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Shang, Jian-Ku [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2013-02-15

    Highlights: Black-Right-Pointing-Pointer Tin whiskers and hillocks grow from Sn5Nd alloy due to oxidation. Black-Right-Pointing-Pointer Temperature and humidity can affect the oxidation and the growth diversities. Black-Right-Pointing-Pointer Growth models of whiskers and hillocks were proposed upon microstructural study. Black-Right-Pointing-Pointer The proposed models can explain the characteristics of whiskers and hillocks. - Abstract: The effects of exposure time, temperature and humidity on the growth of tin whisker and hillock from Sn5Nd alloy were investigated via scanning electron microscopy. It was found that tin whiskers grew from NdSn{sub 3} compound, while hillocks grew from the tin matrix around the NdSn{sub 3} compound, which was induced by the oxidation of NdSn{sub 3} compound by oxygen and water vapor in the ambient. More tin whiskers and/or hillocks were extruded from the substrate with longer exposure time, higher temperature and higher humidity. This resulted in the formation of various morphologies of tin extrusions at different storage conditions, including thread-like, spiral, flute-like, claw-like, sprout-like, chrysanthemum-like and rod-like whiskers, as well as hillocks. Tin whisker was extruded from the crack of the surface Nd(OH){sub 3} layer which serves as the mold of tin whisker growth. And the proposed growth models of tin whisker and hillock on Sn-Nd alloy can explain the diversity of the whisker morphology.

  14. Tin Whisker Electrical Short Circuit Characteristics. Part 2

    Science.gov (United States)

    Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Lawrence L.; Wright, Maria C.

    2009-01-01

    Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish.

  15. Crystalline instability of Bi-2212 superconducting whiskers near room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cagliero, Stefano; Khan, Mohammad Mizanur Rahman [Torino Universita, ' NIS' Centre of Excellence, Dip. Chimica Generale e Chimica Organica, and CNISM UdR, Turin (Italy); Torino Universita, ' NIS' Centre of Excellence, Dip. Fisica Sperimentale, and CNISM UdR, Turin (Italy); Agostino, Angelo [Torino Universita, ' NIS' Centre of Excellence, Dip. Chimica Generale e Chimica Organica, and CNISM UdR, Turin (Italy); Truccato, Marco [Torino Universita, ' NIS' Centre of Excellence, Dip. Fisica Sperimentale, and CNISM UdR, Turin (Italy); Orsini, Francesco; Marinone, Massimo; Poletti, Giulio [Universita degli Studi di Milano, Istituto di Fisiologia Generale e Chimica Biologica, Milan (Italy); CNR-INFM-S3 NRC, Modena (Italy); Lascialfari, Alessandro [Universita degli Studi di Milano, Istituto di Fisiologia Generale e Chimica Biologica, Milan (Italy); CNR-INFM-S3 NRC, Modena (Italy); Universita degli Studi di Pavia, INFM-CNR c/o Dipartimento di Fisica A. Volta, Pavia (Italy)

    2009-05-15

    We report new evidences for the thermodynamic instability of whisker crystals in the Bi-Sr-Ca-Cu-O (BSCCO) system. Annealing treatments at 90 C have been performed on two sets of samples, which were monitored by means of X-rays diffraction (XRD) and atomic force microscopy (AFM) measurements, respectively. Two main crystalline domains of Bi{sub 2}Sr{sub 2}CuCa{sub 2}O{sub 8+x} (Bi-2212) were identified in the samples by the XRD data, which underwent an evident crystalline segregation after about 60 hours. Very fast dynamics of the surface modifications was also described by the AFM monitoring. Two typologies of surface structures formed after about 3 annealing hours: continuous arrays of dome shaped bodies were observed along the edges of the whiskers, while in the central regions a dense texture of flat bodies was found. These modifications are described in terms of the formation of simple oxide clusters involving a degradation of the internal layers. (orig.)

  16. Growth of whiskers from Sn surfaces: Driving forces and growth mechanisms

    Science.gov (United States)

    Chason, Eric; Jadhav, Nitin; Pei, Fei; Buchovecky, Eric; Bower, Allan

    2013-05-01

    Sn whiskers are thin filaments that grow spontaneously out of the surface of coatings on Cu and have become a critical reliability problem in Pb-free electronics. In this review, we focus on what creates the driving force for whiskers (or more rounded “hillocks”), and what determines where on the surface they will form. Experimental studies are reviewed that quantify the relationship between the Cu-Sn intermetallic (IMC) formation, stress in the layer and whisker/hillock density. Measurements of the mechanical properties show how stress relaxation in the Sn layer is intimately related to how much stress develops due to the IMC formation. Real-time scanning electron microscope (SEM)/focused ion beam (FIB) studies are described that illustrate the whisker/hillock growth process in detail. Whiskers are found to grow out of a single grain on the surface with little lateral growth while hillock growth is accompanied by extensive grain growth and crystallite rotation. Electron-backscattering detection (EBSD) shows the grain structure around where the whiskers/hillocks form, indicating that whiskers can grow out of pre-existing grains and do not require the nucleation of new grains. This has led to a picture in which stress builds up due to IMC growth and causes whiskers/hillocks to form at “weak grains”, i.e., grains that have a stress relaxation mechanism that becomes active at a lower stress than its neighbors. FEA (finite element analysis) calculations are used to simulate the evolving stress and whisker growth for several different mechanisms that may lead to “weak” grains.

  17. Toxicity in vitro of some silicon carbides and silicon nitrides: whiskers and powders.

    Science.gov (United States)

    Svensson, I; Artursson, E; Leanderson, P; Berglind, R; Lindgren, F

    1997-03-01

    The objectives of this work were to investigate the toxicity of silicon carbide whiskers and powders and silicon nitride whiskers and powders and to compare their toxicity with the toxicity of crocidolite. The effects studied were inhibition of the cloning efficiency of V79 cells, formation of DNA strand breaks by means of a nick translation assay, formation of oxygen radicals in three different assays, and the ability to stimulate neutrophils to produce hydroxyl radicals. All materials showed concentration-dependent inhibition of the cloning efficiency of V79 cells. The inhibition by the most toxic whiskers was in the same order of magnitude as that of crocidolite. Milled whiskers and powders were less toxic than the whiskers. There was a high DNA breaking potential for crocidolite and four of the silicon carbide whiskers and a rather low one for the other materials. Formation of hydroxyl radicals was found for crocidolite and one of the silicon carbide whiskers. In the neutrophil activation test, there was a great variation in the different materials' abilities to activate neutrophils. There was also a good correlation between chemiluminescence and H2O2 formation. The highest activation was found in neutrophils exposed to two of the silicon carbide whiskers and one milled whisker. The conclusion of the investigation is that some of the ceramic materials studied had damaging biological effects comparable to or greater than those of crocidolite. The results from the investigation clearly imply that caution is needed in the introduction of new ceramic fiber materials, so that the correct precautions and protective devices are used in order to avoid harm to the personnel handling the material.

  18. Variability of hydroxyapatite preparations.

    Science.gov (United States)

    Young, R A; Holcomb, D W

    1982-01-01

    Hydroxyapatite synthesized by various "standard" ways exhibits marked differences with preparation method. Specimens were prepared with two precipitation methods, a reflux method, a hydrothermal method, a high-temperature (1000 degrees C) solid-state reaction method, and by conversion of chlorapatite at 1000 degrees C. They were compared in detail by use of several techniques, the major ones being x-ray diffraction including Rietveld structure refinements, quantitative i.r. analyses, and deuteration kinetics studies. At least some of the specimens differed with respect to each of the approximately 14 properties measured. The major lattice parameter differences could be largely accounted for by structurally incorporated H2O, CO2-3, and + O2- for 2(OH)-. Deuterizability was used as an indicator of ease of diffusion along the X-ion channels, a property that may be related to dissolution kinetics. The differently prepared specimens differed in deuterizability by at least two orders of magnitude. The high-temperature preparations, which were monoclinic, deuterated little at 110 degrees C, even in 1000 h. The precipitated and reflux specimens deuterated readily. There were general indications of correlation between ease of diffusion and features providing passing sites for the diffusing species, e.g., OH- disorder, vacancies, and distortions in the walls of the X-ion channels (mostly by CO3 for PO4), and possibly OH- vacancies. Correlation of structural H2O, present in the aqueous preparations, with ease of diffusion is still ambiguous.

  19. Encoding of Whisker Vibration by Rat Barrel Cortex Neurons: Implications for Texture Discrimination

    National Research Council Canada - National Science Library

    Arabzadeh, Ehsan; Petersen, Rasmus S; Diamond, Mathew E

    2003-01-01

    .... What is the representation of texture in rat somatosensory cortex? We hypothesize that as rats "whisk" over a surface, the spatial frequency of a grooved or pebbled texture is converted to a temporal frequency of whisker vibration...

  20. Biology of nesting crested, least, and whiskered auklets at Buldir Island, Alaska

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — During avifaunal investigations at Buldir Island 1974-1976, some aspects of the biology of Crested, Least, and Whiskered Auklets were investigated in a colony where...

  1. Study of ferromagnetism in Mn-doped ZnO whisker arrays

    Indian Academy of Sciences (India)

    WINTEC

    -doped ZnO whiskers. magnetizations exist up to 300 K. This magnetization difference can be attributed to the following: For FC sample at room temperature, the ferromagnetic ordering appears obviously under the magnetic field of 1T. When.

  2. Fused traditional and geometric morphometrics demonstrate pinniped whisker diversity.

    Directory of Open Access Journals (Sweden)

    Carly C Ginter

    Full Text Available Vibrissae (whiskers are important components of the mammalian tactile sensory system, and primarily function as detectors of vibrotactile information from the environment. Pinnipeds possess the largest vibrissae among mammals and their vibrissal hair shafts demonstrate a diversity of shapes. The vibrissae of most phocid seals exhibit a beaded morphology with repeating sequences of crests and troughs along their length. However, there are few detailed analyses of pinniped vibrissal morphology, and these are limited to a few species. Therefore, we comparatively characterized differences in vibrissal hair shaft morphologies among phocid species with a beaded profile, phocid species with a smooth profile, and otariids with a smooth profile using traditional and geometric morphometric methods. Traditional morphometric measurements (peak-to-peak distance, crest width, trough width and total length were collected using digital photographs. Elliptic Fourier analysis (geometric morphometrics was used to quantify the outlines of whole vibrissae. The traditional and geometric morphometric datasets were subsequently combined by mathematically scaling each to true rank, followed by a single eigendecomposition. Quadratic discriminant function analysis demonstrated that 79.3, 97.8 and 100% of individuals could be correctly classified to their species based on vibrissal shape variables in the traditional, geometric and combined morphometric analyses, respectively. Phocids with beaded vibrissae, phocids with smooth vibrissae, and otariids each occupied distinct morphospace in the geometric morphometric and combined data analyses. Otariids split into two groups in the geometric morphometric analysis and gray seals appeared intermediate between beaded- and smooth-whiskered species in the traditional and combined analyses. Vibrissal hair shafts modulate the transduction of environmental stimuli to the mechanoreceptors in the follicle-sinus complex (F-SC, which

  3. Neonatal whisker trimming causes long-lasting changes in structure and function of the somatosensory system.

    Science.gov (United States)

    Lee, Li-Jen; Chen, Wan-Jung; Chuang, Ya-Wen; Wang, Yu-Chun

    2009-10-01

    The significance of very early experience in the maturation of whisker-to-barrel system comes primarily from neonatal whisker or infraorbital nerve lesion studies conducted prior to the formation of cortical barrels. However, the surgical procedures damage the sensory pathway; it is difficult to examine the consequence after the recovery of sensory deprivation. To address this issue, we performed a neonatal whisker-cut (WC) paradigm and examined their behavioral performance during P30 to P35. With fully regrown whiskers, the rats that had whisker cut from the date of birth (P0) to postnatal day (P) 3 (WC 0-3) exhibited shorter crossable distance in the gap-crossing test. However, the rats had whisker cut at P3 only (WC 3) behaved normally in this test, suggesting the critical period for the development of whisker-specific tactile function is P0-P3, agreed with previous findings demonstrated by lesion methods. In the WC 0-3 rats, the cortical areas in the layer IV somatosensory region in relation to the trimmed whiskers were enlarged and the spiny stellate neurons within had larger dendritic span and greater spine density. Furthermore, more long and multiple-head spines were found in these rats. With abnormal structure and function in the somatosensory system, the WC 0-3 rats showed higher explorative activity and more frequent social interactions. Our results have demonstrated that the early tactile deprivation, similar to early visual deprivation, perturbed the developmental program of the brain and affected later behaviors in various aspects.

  4. Effects of Chitin Whiskers on Physical Properties and Osteoblast Culture of Alginate Based Nanocomposite Hydrogels.

    Science.gov (United States)

    Huang, Yao; Yao, Mengyu; Zheng, Xing; Liang, Xichao; Su, Xiaojuan; Zhang, Yu; Lu, Ang; Zhang, Lina

    2015-11-09

    Novel nanocomposite hydrogels composed of polyelectrolytes alginate and chitin whiskers with biocompatibility were successfully fabricated based on the pH-induced charge shifting behavior of chitin whiskers. The chitin whiskers with mean length and width of 300 and 20 nm were uniformly dispersed in negatively charged sodium alginate aqueous solution, leading to the formation of the homogeneous nanocomposite hydrogels. The experimental results indicated that their mechanical properties were significantly improved compared to alginate hydrogel and the swelling trends were inhibited as a result of the strong electrostatic interactions between the chitin whiskers and alginate. The nanocomposite hydrogels exhibited certain crystallinity and hierarchical structure with nanoscale chitin whiskers, similar to the structure of the native extracellular matrix. Moreover, the nanocomposite hydrogels were successfully applied as bone scaffolds for MC3T3-E1 osteoblast cells, showing their excellent biocompatibility and low cytotoxicity. The results of fluorescent micrographs and scanning electronic microscope (SEM) images revealed that the addition of chitin whiskers into the nanocomposite hydrogels markedly promoted the cell adhesion and proliferation of the osteoblast cells. The biocompatible nanocomposite hydrogels have potential application in bone tissue engineering.

  5. Contributions of Stress And Oxidation on the Formation of Whiskers in Pb-Free Solders

    Energy Technology Data Exchange (ETDEWEB)

    Duncan, Andrew J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL). Materials Science & Technology; Hoffman, Elizabeth N. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2014-03-25

    This report summarizes the research activities of WP-1754. The study focusses on the environmental factors influencing formation of lead free whiskers on electrodeposited tin coatings over copper (or copper containing) substrates. Much of the initial results are summarized in an interim report. From the initial results, two main areas were chosen to be the focus of additional research: the demonstration of effects of elastic stress state in the nucleation of whiskers and the confirmation of the effect of oxygen/nitrogen ratio in the formation of whiskers. Different levels of elastic stress were induced with the incorporation of a custom designed fixture that loaded the substrates in a four-point bending configuration and were maintained in an environmental chamber under conditions deemed favorable for whisker growth. The results show that induced elastic stress slightly increased the concentration of nucleation sites of whiskers. The effects of oxygen content were studied by aging substrates in gas vials of varying absolute pressure and different oxygen/nitrogen ratios. The concentration of whiskers were measured and appear to be sensitive to absolute pressure but are not sensitive to oxygen content (as previously observed).

  6. Growth of cadmium oxide whiskers on cadmium sulphide single crystals with copper as growth activator

    Energy Technology Data Exchange (ETDEWEB)

    Koparanova, N.; Simov, S. (Bylgarska Akademiya na Naukite, Sofia. Inst. po Fizika na Tvyrdoto Tyalo); Genchev, D. (Bylgarska Akademiya na Naukite, Sofia. Inst. za Yadrena Izsledvaniya i Yadrena Energetika); Metchenov, G. (Research Inst. of Criminalistics and Criminology, Sofia (Bulgaria))

    1985-02-01

    Some results on the growth and morphology of cadmium oxide whiskers, obtained on cadmium sulphide single crystals with copper as a growth activator, are presented in this work. Cadmium oxide whiskers have been obtained on brace 112-bar0 brace faces of cadmium sulphide plates with a copper layer deposited in advance. The whiskers grew during the annealing of the plates in a weak stream of technically pure argon at temperatures 670 to 730 deg C for 15 min to 3.5 h. Details about the procedure have been given elsewhere. The composition and morphology of the whiskers have been studied by an X-ray microanalyser JEOL 35 DDS and a scanning electron microscope JEOL, JSM 35. The optical microscopic observations have shown that after annealing, a gray-black granular layer is formed on the cadmium sulphide single crystals and this layer can easily be separated from the crystal substrate. Under the granular layer the crystal is heavily damaged. The whiskers grow on the granular layer and they are coloured yellow-brown or red-brown. The maximum whisker length attains several hundreds of micrometres and in some cases up to 1 mm or more.

  7. Prenatal Ethanol Exposure and Whisker Clipping Disrupt Ultrasonic Vocalizations and Play Behavior in Adolescent Rats

    Science.gov (United States)

    Waddell, Jaylyn; Yang, Tianqi; Ho, Eric; Wellmann, Kristen A.; Mooney, Sandra M.

    2016-01-01

    Prenatal ethanol exposure can result in social deficits in humans and animals, including altered social interaction and poor communication. Rats exposed to ethanol prenatally show reduced play fighting, and a combination of prenatal ethanol exposure and neonatal whisker clipping further reduces play fighting compared with ethanol exposure alone. In this study, we explored whether expression of hedonic ultrasonic vocalizations (USVs) correlated with the number of playful attacks by ethanol-exposed rats, rats subjected to postnatal sensory deprivation by whisker clipping or both compared to control animals. In normally developing rats, hedonic USVs precede such interactions and correlate with the number of play interactions exhibited in dyads. Pregnant Long-Evans rats were fed an ethanol-containing liquid diet or a control diet. After birth, male and female pups from each litter were randomly assigned to the whisker-clipped or non-whisker-clipped condition. Animals underwent a social interaction test with a normally developing play partner during early or late-adolescence. USVs were recorded during play. Prenatal ethanol exposure reduced both play and hedonic USVs in early adolescence compared to control rats and persistently reduced social play. Interestingly, ethanol exposure, whisker clipping and the combination abolished the significant correlation between hedonic USVs and social play detected in control rats in early adolescence. This relationship remained disrupted in late adolescence only in rats subjected to both prenatal ethanol and whisker clipping. Thus, both insults more persistently disrupted the relationship between social communication and social play. PMID:27690116

  8. Prenatal Ethanol Exposure and Whisker Clipping Disrupt Ultrasonic Vocalizations and Play Behavior in Adolescent Rats

    Directory of Open Access Journals (Sweden)

    Jaylyn Waddell

    2016-09-01

    Full Text Available Prenatal ethanol exposure can result in social deficits in humans and animals, including altered social interaction and poor communication. Rats exposed to ethanol prenatally show reduced play fighting, and a combination of prenatal ethanol exposure and neonatal whisker clipping further reduces play fighting compared with ethanol exposure alone. In this study, we explored whether expression of hedonic ultrasonic vocalizations (USVs correlated with the number of playful attacks by ethanol-exposed rats, rats subjected to postnatal sensory deprivation by whisker clipping or both compared to control animals. In normally developing rats, hedonic USVs precede such interactions and correlate with the number of play interactions exhibited in dyads. Pregnant Long-Evans rats were fed an ethanol-containing liquid diet or a control diet. After birth, male and female pups from each litter were randomly assigned to the whisker-clipped or non-whisker-clipped condition. Animals underwent a social interaction test with a normally developing play partner during early or late-adolescence. USVs were recorded during play. Prenatal ethanol exposure reduced both play and hedonic USVs in early adolescence compared to control rats and persistently reduced social play. Interestingly, ethanol exposure, whisker clipping and the combination abolished the significant correlation between hedonic USVs and social play detected in control rats in early adolescence. This relationship remained disrupted in late adolescence only in rats subjected to both prenatal ethanol and whisker clipping. Thus, both insults more persistently disrupted the relationship between social communication and social play.

  9. Investigation of Whisker Growth from Alkaline Non-cyanide Zinc Electrodeposits

    Science.gov (United States)

    Wu, L.; Ashworth, M. A.; Wilcox, G. D.

    2017-02-01

    Electroplated zinc finishes have been widely used in the packaging of electronic products for many years as a result of their excellent corrosion resistance and relatively low cost. However, the spontaneous formation of whiskers on zinc electroplated components, which are capable of resulting in electrical shorting or other damaging effects, can be highly problematic for the reliability of long-life electrical and electronic equipment. This work investigated the mechanism for whisker growth from zinc electrodeposited mild steel substrates. The incubation time for whisker growth from the surface of nodules on the surface of the electrodeposit was considerably reduced compared with that from the planar deposit surface. Recrystallisation of the as-deposited columnar structure was observed at the whisker root. This result is consistent with some recent whisker growth models based on recrystallisation. There was no evidence of iron-zinc (Fe-Zn) intermetallic formation at the iron/zinc (Fe/Zn) interface or within the zinc coating beneath the whiskers.

  10. Kinetics and thermodynamics studies on the BMP-2 adsorption onto hydroxyapatite surface with different multi-morphological features

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Zhiwei; Huangfu, Changxin; Wang, Yanying; Ge, Hongwei; Yao, Yao; Zou, Ping; Wang, Guangtu [College of Science, Sichuan Agricultural University, Ya' an 625014 (China); He, Hua [Institute of Animal Genetics and Breeding, Sichuan Agricultural University, Wenjiang, Sichuan 611130 (China); Rao, Hanbing, E-mail: rhbscu@gmail.com [College of Science, Sichuan Agricultural University, Ya' an 625014 (China)

    2015-07-01

    The effect of the surface topography on protein adsorption process is of great significance for designing hydroxyapatite (HA) ceramic material surfaces. In this work, three different topographies of HA materials HA-sheet, HA-rod, and HA-whisker were synthesized and testified by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Brunauer–Emmett–Teller (BET) and a field emission scanning electron microscopy (FE-SEM). We have systematically investigated the adsorption kinetics and thermodynamics of bone morphogenetic proteins (BMP-2) on the three different topography surfaces of HA, respectively. The results showed that the maximum adsorption capacities of HA-sheet, HA-rod and HA-whisker were (219.96 ± 10.18), (247.13 ± 12.35), and (354.67 ± 17.73) μg · g{sup −1}, respectively. Kinetic parameters, rate constants, equilibrium adsorption capacities and related correlation coefficients, for each kinetic model were calculated as well as discussed. It demonstrated that the adsorption of BMP-2 onto HA could be described by the pseudo second-order equation. Adsorption of BMP-2 onto HA followed the Langmuir isotherm. It confirmed that compared with other samples HA-whisker had more adsorption sites for its high specific surface area which could provide more opportunities for protein molecules. The adsorption processes were endothermic (ΔH > 0), spontaneous (ΔG < 0) and entropy increasing (ΔS > 0). A possible adsorption mechanism has been proposed. In addition, the BMP-2 could be adsorbed to the surface which existed slight conformational changes by FT-IR. - Highlights: • A novel protein adsorption studies based on sheet, rod and whisker of HA were designed. • Kinetic and thermodynamics parameters of BMP-2 and HA bonded materials were evaluated. • Surface topographies of the HA effect BMP-2 adsorption • The HA-whisker material had excellent adsorption performance for protein enrichment. • The electrostatic interaction is responsible for the

  11. Selection of head and whisker coordination strategies during goal-oriented active touch.

    Science.gov (United States)

    Schroeder, Joseph B; Ritt, Jason T

    2016-04-01

    In the rodent whisker system, a key model for neural processing and behavioral choices during active sensing, whisker motion is increasingly recognized as only part of a broader motor repertoire employed by rodents during active touch. In particular, recent studies suggest whisker and head motions are tightly coordinated. However, conditions governing the selection and temporal organization of such coordinated sensing strategies remain poorly understood. We videographically reconstructed head and whisker motions of freely moving mice searching for a randomly located rewarded aperture, focusing on trials in which animals appeared to rapidly "correct" their trajectory under tactile guidance. Mice orienting after unilateral contact repositioned their whiskers similarly to previously reported head-turning asymmetry. However, whisker repositioning preceded head turn onsets and was not bilaterally symmetric. Moreover, mice selectively employed a strategy we term contact maintenance, with whisking modulated to counteract head motion and facilitate repeated contacts on subsequent whisks. Significantly, contact maintenance was not observed following initial contact with an aperture boundary, when the mouse needed to make a large corrective head motion to the front of the aperture, but only following contact by the same whisker field with the opposite aperture boundary, when the mouse needed to precisely align its head with the reward spout. Together these results suggest that mice can select from a diverse range of sensing strategies incorporating both knowledge of the task and whisk-by-whisk sensory information and, moreover, suggest the existence of high level control (not solely reflexive) of sensing motions coordinated between multiple body parts. Copyright © 2016 the American Physiological Society.

  12. Lithium-doped hydroxyapatite nano-composites: Synthesis, characterization, gamma attenuation coefficient and dielectric properties

    Science.gov (United States)

    Badran, H.; Yahia, I. S.; Hamdy, Mohamed S.; Awwad, N. S.

    2017-01-01

    Lithium-hydroxyapatite (0, 1, 5, 10, 20, 30 and 40 wt% Li-HAp) nano-composites were synthesized by sol-gel technique followed by microwave-hydrothermal treatment. The composites were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) and Raman techniques. Gamma attenuation coefficient and the dielectric properties for all composites were investigated. The crystallinity degree of Li-doped HAp was higher than that of un-doped HAp. Gamma attenuation coefficient values increased from 0.562 cm-1 for 0 wt% Li-HAp to 2.190 cm-1 for 40 wt% Li-HAp. The alternating current conductivity increased with increasing frequency. The concentration of Li affect the values of dielectric constant where Li doped HAp of low dielectric constant can have an advantage for healing in bone fractures. The calcium to phosphorus ratio decreased from 1.43 to 1.37 with the addition of lithium indicating the Ca deficiency in the studied composites. Our findings lead to the conclusion that Li-HAp is a new nano-composite useful for medical applications and could be doped with gamma shield materials.

  13. Controlling of dielectric parameters of insulating hydroxyapatite by simulated body fluid.

    Science.gov (United States)

    Kaygili, Omer; Keser, Serhat; Ates, Tankut; Tatar, Cengiz; Yakuphanoglu, Fahrettin

    2015-01-01

    Hydroxyapatite (HAp) samples were synthesized under various amounts of citric acid using the sol-gel method. Before and after immersion in simulated body fluid (SBF) for 14 and 28 days, the structural properties of HAp samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy with energy dispersive X-ray (EDX) spectroscopy and dielectric measurements. The crystallite size (D) was found to be in the range of 25.17-33.06 nm with the crystallinity percent (XC%) of 69.53-86.09. The lattice parameters of a and c were calculated to be in the ranges of 9.373-9.434 Å and 6.828-6.896 Å, respectively. The morphology of the as-synthesized samples was changed with the amount of citric acid and soaking period in SBF. The Ca/P molar ratios indicated a decrease with increasing immersion time, and Ca-deficiency was observed. The relative permittivity (ε') and dielectric loss (ε″) were significantly affected by citric acid content and soaking period in SBF. It was seen that the alternating current conductivity (σac) increased with increasing frequency and the σac values changed with increasing soaking period and amount of citric acid. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Labile Zn ions on octacalcium phosphate-derived Zn-containing hydroxyapatite surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Honda, Yoshitomo; Anada, Takahisa; Morimoto, Shinji [Division of Craniofacial Function Engineering (CFE), Tohoku University Graduate School of Dentistry, Sendai (Japan); Suzuki, Osamu, E-mail: suzuki-o@m.tohoku.ac.jp [Division of Craniofacial Function Engineering (CFE), Tohoku University Graduate School of Dentistry, Sendai (Japan)

    2013-05-15

    We previously synthesized and characterized zinc-containing octacalcium phosphate (OCP) and its hydrolyzed Ca-deficient hydroxyapatite (HA). In the present report, we attempted to define the state of Zn in the OCP-derived Zn-calcium phosphates (CaPs) in relation to the presence of specific amino acids. Zn-containing OCPs were prepared in solutions that included Zn ions up to a concentration of 3.5 mM, and their hydrolyzates [hydrolyzed (hy)-Zn-CaP] were obtained in hot water. The materials were characterized by x-ray diffraction and scanning electron microscopy. The concentration of Ca and Zn ions at room temperature was determined by analyzing the supernatant after incubating the materials in α-minimal essential medium (α-MEM) and HEPES buffer including cysteine, histidine, lysine, aspartic acid, and glutamic acid. Zn ions were more dissolved in α-MEM than HEPES buffer in the absence of amino acids. The inclusion of the amino acids enhanced Zn dissolution by several hundred fold, even in HEPES buffer. Among the amino acids, both cysteine and histidine enhanced the release of Zn. The effect was particularly remarkable with cysteine even in the presence of the other amino acids tested. These results indicate that Zn ions are present as a surface labile pool, which tends to be preferentially desorbed by cysteine, a ubiquitous molecule present in serum.

  15. Nanofiber generation of hydroxyapatite and fluor-hydroxyapatite bioceramics.

    Science.gov (United States)

    Kim, Hae-Won; Kim, Hyoun-Ee

    2006-05-01

    In this study, we produced hydroxyapatite (HA) and fluor-hydroxyapatite (FHA) bioceramics as a novel geometrical form, the nanoscale fiber, for the biomedical applications. Based on the sol-gel precursors of the apatites, an electrospinning technique was introduced to generate nanoscale fibers. The diameter of the fibers was exploited in the range of a few micrometers to hundreds of nanometers (1.55 microm-240 nm) by means of adjusting the concentration of the sols. Through the fluoridation of apatite, the solubility of the fiber was tailored and the fluorine ions were well released from the FHA. The HA and FHA nanofibers produced in this study are considered to find potential applications in the biomaterials and tissue engineering fields. (c) 2005 Wiley Periodicals, Inc.

  16. A kind of carbon whiskers in new structure and morphology

    Institute of Scientific and Technical Information of China (English)

    DONG; Jian

    2001-01-01

    [1]Endo, M., Saito, R., Dresselhaus, M. S. et al. From carbon fibers to nanotubes, in Carbon Nanotubes Preparations and Properties (ed. Ebbesen, T. W.), New York: CRC Press Inc., 1997, 54-66.[2]Baker, R. T. K., Baker, M. A., Harris, P. S. et al., Nucleation and growth of carbon deposits from the nickel catalyzed de-composition of acetylene, J.Catal., 1972, 26(7): 51.[3]Audier, M., Coulon, M., Kinetic and microscopic aspects of catalytic carbon growth, Carbon, 1985, 23(3): 317.[4]Oberlin, A., Endo, M., Koyama, T., High resolution microscope observations of graphitized carbon fibers, Carbon, 1976, 14(1): 133.[5]Bacon, R., Growth, structure, and properties of graphite whiskers, Journal of Applied Physics, 1960, 31(2): 283.[6]Murayama, H., Maeda, M., A novel form of filamentous graphite, Nature, 1990, 345(28): 791.[7]Pimpinelli, A., Villain, J., Physics of Crystal Growth, New York: Cambridge University Press, 1998, 62-64.[8]Minkoff, I., Solidification and Cast Structure, Chichester: Wiley, 1986, 42-47.[9]Pierson, H. O., Handbook of Carbon, Graphite, Diamond, and Fullerenes: Properties, Processing, and Applications, Park Ridge: Noyes Publications, 1993, 151.[10]Bennema, P., Spiral growth and surface roughing: Developments since Burton, Cabrera and Frank, Journal of Crystal Growth, 1984, 69(2): 182.

  17. Isolation of whiskers from natural sources and their dispersed in a non-aqueous medium

    Directory of Open Access Journals (Sweden)

    Mauro Vestena

    Full Text Available Abstract Whiskers have been used as a nanomaterial dispersed in polymer matrices to modify the microscopic and macroscopic properties of the polymer. These nanomaterials can be isolated from cellulose, one of the most abundant natural renewable sources of biodegradable polymer. In this study, whiskers were isolated from sugarcane bagasse and corn cob straw fibers. Initially, the cellulose fiber was treated through an alkaline/oxidative process followed by acid hydrolysis. Dimethylformamide and dimethyl sulfoxide were used to replace the aqueous medium for the dispersion of the whiskers. For the solvent exchange, dimethylformamide or dimethyl sulfoxide was added to the aqueous dispersion and the water was then removed by fractional distillation. FTIR, TGA, XRD, TEM, Zeta and DLS techniques were used to evaluate the efficiency of the isolation process as well as the morphology and dimensions of the whiskers. The dimensions of the whiskers are comparable with values reported in the literature, maintaining the uniformity and homogeneity in both aqueous and non-aqueous solvents.

  18. Preparation of mullite whiskers reinforced SiC/Al2O3 composites by microwave sintering

    Directory of Open Access Journals (Sweden)

    Wei Li

    2016-12-01

    Full Text Available Mullite whiskers reinforced SiC/Al2O3 composites were prepared by microwave sintering in a microwave chamber with TE666 resonant mode. Original SiC particles were coated with SiO2 using sol-gel processing and mixed with Al2O3 particles. Mullite was formed in the reaction between SiO2 and Al2O3. The isostatically pressed cylindrical pellets were sintered from 1350 °C to 1600 °C for 30 min. Physical and chemical responses were investigated by detecting changes in reflected power during the microwave sintering process. XRD was carried out to characterize the samples and showed that mullite could be formed at 1200 °C. Bridging of mullite whiskers between Al2O3 and SiC particles was observed by SEM and is due to a so-called local hot spot effect, which was the unique feature for microwave sintering. The optimized microwave sintering temperature was 1500 °C corresponding to the maximum amount of mullite whiskers within SiC/Al2O3 composites. The high electro-magnetic field enhanced the decomposition of mullite at higher temperatures above 1550 °C. The mechanical properties of mullite whiskers reinforced SiC/Al2O3 composites are much better than the SiC/Al2O3 composites without mullite whiskers.

  19. Terrestrial whisker growth experiments which anticipate some special effects of a space station environment

    Science.gov (United States)

    Hobbs, H. H.

    1983-01-01

    The effects of the absence of gravitationally driven thermal convection on the growth of whiskers by chemical reduction of metal salts was studied. It was possible to accomplish nearly complete suppression of such convection. Suppression of the convection does indeed effect the growth but in subtle, not necessarily detrimental ways: none of the changes observed were such as to hamper efforts to produce whiskers in space. Copper whiskers grown from cuprous iodide respond most positively to the suppression of convection; therefore, they are strongly recommended for tests in the space environment. Cobalt whiskers grown from cobaltous bromide show the greatest independence from conditions of convection and applied electric fields of any material studied; therefore, this medium is highly recommended. A strong pulse of electric field forces the whiskers to stick to the growth vessel top plate, this facilitates study or "harvesting'. On the space station it is recommended that the growth vessels be mounted outside the laboratory and joined with the station by means of double vacuum valves and gas service lines.

  20. Peculiarities of magnetoresistance in InSb whiskers at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Druzhinin, A., E-mail: druzh@polynet.lviv.ua [Lviv Polytechnic National University, Bandera Str., 12, 79013 Lviv (Ukraine); International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw (Poland); Ostrovskii, I.; Khoverko, Yu. [Lviv Polytechnic National University, Bandera Str., 12, 79013 Lviv (Ukraine); International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw (Poland); Liakh-Kaguy, N.; Khytruk, I. [Lviv Polytechnic National University, Bandera Str., 12, 79013 Lviv (Ukraine); Rogacki, K. [International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, Wroclaw (Poland)

    2015-12-15

    Highlights: • Magnetoresistance in InSb whiskers with impurity concentration near MIT is studied. • SdH oscillations of transverse and longitudinal magnetoresistance are examined. • Mechanisms of electron scattering are determined • Main crystal parameters of InSb whiskers are determined. - Abstract: The study of the magnetoresistance in InSb whiskers with an impurity concentration in the vicinity to the metal-insulator phase transition, at low temperature range 4.2–77 K, and in fields, with induction up to 14 T, was conducted. The presence of Shubnikov-de Haas oscillations in both transverse and longitudinal magnetoresistance was observed. The following parameters of InSb whiskers were defined: period of oscillations 0.1 T{sup −1}, cyclotron effective mass of electrons m{sub c} ≈ 0.14m{sub o,} concentration of charge carriers 2.3 × 10{sup 17} cm{sup −3}, g-factor g{sup *} ≈ 30 and Dingle temperature T{sub D} = 14.5 K. To determine the nature of crystal defects, the electron scattering processes on the short-range potential, caused by interaction with polar and nonpolar optical phonons, piezoelectric and acoustic phonons, static strain centers and ionized impurities in n-InSb whiskers, with defect concentration 2.9 × 10{sup 17} cm{sup −3}, are considered. The temperature dependences of electron mobility in the range 4.2–500 K were calculated.

  1. Isolation of whiskers from natural sources and their dispersed in a non-aqueous medium

    Energy Technology Data Exchange (ETDEWEB)

    Vestena, Mauro; Gross, Idejan Padilha; Pires, Alfredo Tiburcio Nunes; Muller, Carmen Maria Olivera, E-mail: mauro@utfpr.edu.br [Universidade Federal Santa Catarina (UFSC), Florianopolis, SC (Brazil)

    2016-10-15

    Whiskers have been used as a nano material dispersed in polymer matrices to modify the microscopic and macroscopic properties of the polymer. These nanomaterials can be isolated from cellulose, one of the most abundant natural renewable sources of biodegradable polymer. In this study, whiskers were isolated from sugarcane bagasse and corn cob straw fibers. Initially, the cellulose fiber was treated through an alkaline/oxidative process followed by acid hydrolysis. Dimethylformamide and dimethyl sulfoxide were used to replace the aqueous medium for the dispersion of the whiskers. For the solvent exchange, dimethylformamide or dimethyl sulfoxide was added to the aqueous dispersion and the water was then removed by fractional distillation. FTIR, TGA, XRD, TEM, Zeta and DLS techniques were used to evaluate the efficiency of the isolation process as well as the morphology and dimensions of the whiskers. The dimensions of the whiskers are comparable with values reported in the literature, maintaining the uniformity and homogeneity in both aqueous and non-aqueous solvents. (author)

  2. Tactile soft-sparse mean fluid-flow imaging with a robotic whisker array.

    Science.gov (United States)

    Tuna, Cagdas; Jones, Douglas L; Kamalabadi, Farzad

    2015-08-04

    An array of whiskers is critical to many mammals to survive in their environment. However, current engineered systems generally employ vision, radar or sonar to explore the surroundings, not having sufficiently benefited from tactile perception. Inspired by the whisking animals, we present here a novel tomography-based tactile fluid-flow imaging technique for the reconstruction of surroundings with an artificial whisker array. The moment sensed at the whisker base is the weighted integral of the drag force per length, which is proportional to the relative velocity squared on a whisker segment. We demonstrate that the 2D cross-sectional mean fluid-flow velocity-field can be successfully mapped out by collecting moment measurements at different angular positions with the whisker array. We use a regularized version of the FOCal underdetermined system solver algorithm with a smoothness constraint to obtain soft-sparse static estimates of the 2D cross-sectional velocity-squared distribution. This new proposed approach has the strong potential to be an alternative environmental sensing technology, particularly in dark or murky environments.

  3. Synthesis of CaSiO{sub 3} Whiskers by alkaline salt flux for biomaterials reinforcement; Sintese de 'Whiskers' de CaSiO{sub 3} em fluxo salino para o reforco de biomateriais

    Energy Technology Data Exchange (ETDEWEB)

    Motisuke, M., E-mail: motisuke@unifesp.br [Universidade Federal de Sao Paulo (UNIFESP), Sao Jose dos Campos, SP (Brazil). Instituto de Ciencia e Tecnologia; Bertran, C.A. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Instituto de Quimica

    2011-07-01

    Ceramic materials reinforcement by whiskers has been employed for a long time in a variety of industrial applications. Nevertheless, the materials by which these whiskers are commonly made of (carbide and silicon nitride) do not allow their use in the biomaterials field due to the high toxicity related to these materials. Then, it is of interest to synthesize ceramic whiskers which could reinforce biocompatible ceramic and polymeric biomaterials without harming the patients' health. In this manner, the aim of this work is to propose a synthetic route to produce whiskers of CaSiO{sub 3} (wollastonite): a biocompatible, bioactive and resorbable biomaterial. It was employed the molten salt synthesis at 900°C to grow wollastonite crystals which were characterized by X ray diffraction and scanning electron microscopy. The proposed method was efficient for growing whiskers with aspect ratio ranging 10. (author)

  4. Cementless Hydroxyapatite Coated Hip Prostheses

    Science.gov (United States)

    Herrera, Antonio; Mateo, Jesús; Gil-Albarova, Jorge; Lobo-Escolar, Antonio; Ibarz, Elena; Gabarre, Sergio; Más, Yolanda

    2015-01-01

    More than twenty years ago, hydroxyapatite (HA), calcium phosphate ceramics, was introduced as a coating for cementless hip prostheses. The choice of this ceramic is due to its composition being similar to organic apatite bone crystals. This ceramic is biocompatible, bioactive, and osteoconductive. These qualities facilitate the primary stability and osseointegration of implants. Our surgical experience includes the implantation of more than 4,000 cementless hydroxyapatite coated hip prostheses since 1990. The models implanted are coated with HA in the acetabulum and in the metaphyseal area of the stem. The results corresponding to survival and stability of implants were very satisfactory in the long-term. From our experience, HA-coated hip implants are a reliable alternative which can achieve long term survival, provided that certain requirements are met: good design selection, sound choice of bearing surfaces based on patient life expectancy, meticulous surgical technique, and indications based on adequate bone quality. PMID:25802848

  5. Cementless Hydroxyapatite Coated Hip Prostheses

    Directory of Open Access Journals (Sweden)

    Antonio Herrera

    2015-01-01

    Full Text Available More than twenty years ago, hydroxyapatite (HA, calcium phosphate ceramics, was introduced as a coating for cementless hip prostheses. The choice of this ceramic is due to its composition being similar to organic apatite bone crystals. This ceramic is biocompatible, bioactive, and osteoconductive. These qualities facilitate the primary stability and osseointegration of implants. Our surgical experience includes the implantation of more than 4,000 cementless hydroxyapatite coated hip prostheses since 1990. The models implanted are coated with HA in the acetabulum and in the metaphyseal area of the stem. The results corresponding to survival and stability of implants were very satisfactory in the long-term. From our experience, HA-coated hip implants are a reliable alternative which can achieve long term survival, provided that certain requirements are met: good design selection, sound choice of bearing surfaces based on patient life expectancy, meticulous surgical technique, and indications based on adequate bone quality.

  6. Box, Line, and Midgap Plots: Effects of Display Characteristics on the Accuracy and Bias of Estimates of Whisker Length.

    Science.gov (United States)

    Stock, William A.; Behrens, John T.

    1991-01-01

    The accuracy and bias of estimates of whisker length based on box, line, and midgap plots were examined. For each type of graph, 20 different undergraduates (n=60) viewed 48 single-plot graphs. Whisker-length estimates for box and line plots were more accurate and less biased than those for midgap plots. (TJH)

  7. Tapered ZnO Whiskers: {hkil}-Specific Mosaic Twinning VLS Growth from a Partially Molten Bottom Source

    Directory of Open Access Journals (Sweden)

    Chen Shuei-Yuan

    2009-01-01

    Full Text Available Abstract Zn particulates overlaid with wurtzite (W-type ZnO condensates having nearly orthogonal and facets were found to self-catalyze unusual tapered W-ZnO whiskers upon isothermal atmospheric annealing, i.e., thermal oxidation, at 600 °C. Analytical electron microscopic observations indicated that such whiskers formed tapered slabs having mosaic and twinned domains. The tapered whiskers can be rationalized by an alternative vapor–liquid–solid growth, i.e., {hkil}-specific coalescence twinning growth from the ZnO condensates taking advantage of a partially molten bottom source of Zn and the adsorption of atoms at the whisker tips and ledges under the influence of capillarity effect. The tapered whiskers having strong photoluminescence at 391 nm and with a considerable flexibility could have potential applications.

  8. Visual Map Shifts based on Whisker-Guided Cues in the Young Mouse Visual Cortex

    Directory of Open Access Journals (Sweden)

    Kohei Yoshitake

    2013-12-01

    Full Text Available Mice navigate nearby space using their vision and whiskers, and young mice learn to integrate these heterogeneous inputs in perceptual space. We found that cortical responses were depressed in the primary visual cortex of young mice after wearing a monocular prism. This depression was uniformly observed in the primary visual cortex and was eliminated by whisker trimming or lesions in the posterior parietal cortex. Compensatory visual map shifts of responses elicited via the eye that had worn the prism were also observed. As a result, cortical responses elicited via each eye were clearly separated when a visual stimulus was placed in front of the mice. A comparison of response areas before and after prism wearing indicated that the map shifts were produced by depression with spatial eccentricity. Visual map shifts based on whisker-guided cues may serve as a model for investigating the cellular and molecular mechanisms underlying higher sensory integration in the mammalian brain.

  9. Whisker-mediated transformation of peanut with chitinase gene enhances resistance to leaf spot disease

    Directory of Open Access Journals (Sweden)

    Mahmood ul Hassan

    2016-07-01

    Full Text Available Peanut (Arachis hypogaea is an important legume and oilseed crop, native to South America and grown in all tropical and temperate regions of the world. A simplified and rapid direct gene delivery system in peanut was developed by vortexing silicon carbide whiskers with callus and with plasmid harboring chitinase and hygromcin genes. The effects of callus age and whisker quantity on transformation efficiency were evaluated. Transformation efficiency (6.88% was highest when 200 mg of whiskers were used with 5 µg plasmid for 2 g of 20-day-old callus. Hygromcin-resistant calli were regenerated to complete plants which produced seeds normally. Transgene insertion and number of transgene copieswere confirmed by PCR and southern blot analyses, respectively. Transgene expression was evaluated by a pathogenecity test and RT-PCR analysis. In transgenic events, the resistance level to leaf spot disease was far higher than in control plants.

  10. Variation in plumage, molt, and morphology of the Whiskered Auklet (Aethia pygmaea) in Alaska

    Science.gov (United States)

    Pitocchelli, Jay; Piatt, John F.; Carter, Harry R.

    2003-01-01

    We studied molt and size variation in Whiskered Auklets collected at sea in August from the Aleutian Islands in 1992 and 1993. We evaluated size differences from external and skeletal measurements. Adults were molting extensively in August, indicating that molt began in July. Primaries 1-5 had been completely replaced, while primaries 6-8 were in various stages of replacement, and primaries 9 and 10 were old in most birds. We also found that juveniles were not molting. This pattern is similar to other species of small auklets where breeding and molt in adults overlap, but juveniles do not molt until the following summer. This suggests that Whiskered Auklets are subjected to similar ecological constraints as other auklets. We provide the first skeletal measurements of Whiskered Auklets and some new external measurements. Results of statistical analyses indicate that there is no sexual dimorphism in adults. A small sample of juveniles suggests that they are similar in size to adults.

  11. Stability to irradiation of SiGe whisker crystals used for sensors of physical values

    Directory of Open Access Journals (Sweden)

    Druzhinin A. A.

    2011-04-01

    Full Text Available An influence of g-irradiation (Co60 with doze up to 1—1018 сm–2 and magnetic field with induction up to 14 T on conduction of 1–xGex (х = 0,03 whisker crystals with resistivity of 0,08—0,025 Оhm·сm in temperature range 4,2—300 K have been studied. It is shown that whisker crystals resistance faintly varies under irradiation with doze 2·1017 сm–2, while their magnetoresistance substantially changes. The strain sensors stable to irradiation action operating in high magnetic fields on the base of the whiskers have been designed.

  12. The 'whisker sign' as an indicator of ochronosis in skeletal scintigraphy

    Energy Technology Data Exchange (ETDEWEB)

    Paul, R.; Ylinen, S.L. (Turku Univ. (Finland). Dept. of Nuclear Medicine)

    1991-03-01

    A patient with alkaptonuria and ochronotic arthrosis was imaged twice with ({sup 99m}Tc-DPD) - once during a bout of arthritic knee pain and once when symptom-free. There was a marked accumulation of radioactivity in the large joints. During the episode of arthritis the knee joints had a higher uptake than when the patient was without symptoms. The intervertebral discs showed a high uptake which extended laterally from the axial vertebral column; the finding gave an impression of whiskers, and this 'whisker sign' may be characteristic of ochronosis. (orig.).

  13. Synthesis of nanocrystalline fluorinated hydroxyapatite by ...

    Indian Academy of Sciences (India)

    Synthetic hydroxyapatite, (Ca10(PO4)6(OH)2, HA), is an important material used for orthopedic and dental implant applications. The biological hydroxyapatite in the human bone and tooth is of nanosize and differs in composition from the stoichiometric HA by the presence of other ions such as carbonate, magnesium, ...

  14. An organometallic route to micron-sized whiskers of zinc sulfide

    Science.gov (United States)

    Czekaj, C. L.; Rau, M. S.; Geoffroy, G. L.; Guiton, T. A.; Pantano, C. G.

    1988-06-01

    A number of technologies require the development of high performance optical materials that also meet stringent specifications of optical transparency and thermal, chemical, and mechanical properties. For example, an infrared transmitting window material should have low thermal expansion, high melting and decomposition temperatures, chemical inertness to hydrolysis and oxidation, and high fracture toughness. One of the most attractive materials for many infrared optical applications is Zinc sulfide, but this material, as presently fabricated, does not process the required mechanical properties. One approach to improving the mechanical properties of a material is to form a self-similar composite, in this case, ZnS whiskers in polycrystalline ZnS matrix. To fabricate IR transmitting ZnS/ZnS composites, it would be necessary to use micron-sized whiskers of ZnS that have length to width ratios (aspect ratios) greater than 10. No present methodology exists for the convenient, large-scale preparation of such whiskers, although larger single crystals and whiskers of ZnS have been made by a variety of high temperature (less than 900 C), generally vapor-phase, routes.

  15. Adjustable tunneling barrier in bi-based high-Tc cross-whisker junctions

    Science.gov (United States)

    Kizilaslan, O.; Simsek, Y.; Aksan, M. A.; Koval, Y.; Yakinci, M. E.; Müller, P.

    2015-02-01

    We present a study of cross-whisker junctions with electronically modified tunneling barriers. Cross-whisker junctions were successfully prepared by annealing two crossed Bi-based whisker bars at temperatures of around 840 °C. In addition to the artificially produced junction at the interface, intrinsic Josephson junctions in the respective bars of the cross were observed. The artificial junction exhibited reproducible and almost ideal junction characteristics. The tunneling barrier/interface properties were controlled by carrier injection in c-axis direction. Using this process, we were able to reduce the tunneling resistance from 408 Ω to 30 Ω. At the same time, the critical current did rise by a factor of 4. Subsequently, the critical current was doubled while the tunneling resistance stayed constant. We interpret this observation in terms of the counter-play between transparency of the barrier and the carrier concentration of the electrodes. In this sense, we can consider the current injection procedure as an electronic gluing process of the two cross-junction whisker bars.

  16. Parallel pathways from whisker and visual sensory cortices to distinct frontal regions of mouse neocortex.

    Science.gov (United States)

    Sreenivasan, Varun; Kyriakatos, Alexandros; Mateo, Celine; Jaeger, Dieter; Petersen, Carl C H

    2017-07-01

    The spatial organization of mouse frontal cortex is poorly understood. Here, we used voltage-sensitive dye to image electrical activity in the dorsal cortex of awake head-restrained mice. Whisker-deflection evoked the earliest sensory response in a localized region of primary somatosensory cortex and visual stimulation evoked the earliest responses in a localized region of primary visual cortex. Over the next milliseconds, the initial sensory response spread within the respective primary sensory cortex and into the surrounding higher order sensory cortices. In addition, secondary hotspots in the frontal cortex were evoked by whisker and visual stimulation, with the frontal hotspot for whisker deflection being more anterior and lateral compared to the frontal hotspot evoked by visual stimulation. Investigating axonal projections, we found that the somatosensory whisker cortex and the visual cortex directly innervated frontal cortex, with visual cortex axons innervating a region medial and posterior to the innervation from somatosensory cortex, consistent with the location of sensory responses in frontal cortex. In turn, the axonal outputs of these two frontal cortical areas innervate distinct regions of striatum, superior colliculus, and brainstem. Sensory input, therefore, appears to map onto modality-specific regions of frontal cortex, perhaps participating in distinct sensorimotor transformations, and directing distinct motor outputs.

  17. Estimating the Probability of Electrical Short Circuits from Tin Whiskers. Part 2

    Science.gov (United States)

    Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Larry L.; Wright, Maria C.

    2009-01-01

    To comply with lead-free legislation, many manufacturers have converted from tin-lead to pure tin finishes of electronic components. However, pure tin finishes have a greater propensity to grow tin whiskers than tin-lead finishes. Since tin whiskers present an electrical short circuit hazard in electronic components, simulations have been developed to quantify the risk of said short circuits occurring. Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that had an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage.

  18. 3D printed biomimetic whisker-based sensor with co-planar capacitive sensing

    NARCIS (Netherlands)

    Delamare, John; Sanders, Remco G.P.; Krijnen, Gijsbertus J.M.

    2016-01-01

    This paper describes the development of a whisker sensor for tactile purposes and which is fabricated by 3D printing. Read-out consists of a capacitive measurement of a co-planar capacitance which is affected by a dielectric that is driven into the electric field of the capacitance. The current

  19. Estimating the Probability of Electrical Short Circuits from Tin Whiskers. Part 2

    Science.gov (United States)

    Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Larry L.; Wright, Maria C.

    2010-01-01

    To comply with lead-free legislation, many manufacturers have converted from tin-lead to pure tin finishes of electronic components. However, pure tin finishes have a greater propensity to grow tin whiskers than tin-lead finishes. Since tin whiskers present an electrical short circuit hazard in electronic components, simulations have been developed to quantify the risk of said short circuits occurring. Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that had an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish .

  20. Rat whisker movement after facial nerve lesion: Evidence for autonomic contraction of skeletal muscle.

    NARCIS (Netherlands)

    Heaton, J.T.; Sheu, S.H.; Hohman, M.H.; Knox, C.J.; Weinberg, J.S.; Kleiss, I.J.; Hadlock, T.A.

    2014-01-01

    Vibrissal whisking is often employed to track facial nerve regeneration in rats; however, we have observed similar degrees of whisking recovery after facial nerve transection with or without repair. We hypothesized that the source of non-facial nerve-mediated whisker movement after chronic

  1. Validation of the Dynamic Recrystallization (DRX) Mechanism for Whisker and Hillock Growth on Sn Thin Films

    Science.gov (United States)

    Vianco, P. T.; Neilsen, M. K.; Rejent, J. A.; Grant, R. P.

    2015-10-01

    A study was performed to validate a first-principles model for whisker and hillock formation based on the cyclic dynamic recrystallization (DRX) mechanism in conjunction with long-range diffusion. The test specimens were evaporated Sn films on Si having thicknesses of 0.25 μm, 0.50 μm, 1.0 μm, 2.0 μm, and 4.9 μm. Air annealing was performed at 35°C, 60°C, 100°C, 120°C, or 150°C over a time duration of 9 days. The stresses, anelastic strains, and strain rates in the Sn films were predicted by a computational model based upon the constitutive properties of 95.5Sn-3.9Ag-0.6Cu (wt.%) as a surrogate for pure Sn. The cyclic DRX mechanism and, in particular, whether long whiskers or hillocks were formed, was validated by comparing the empirical data against the three hierarchal requirements: (1) DRX to occur at all: ɛc = A D o m Z n , (2) DRX to be cyclic: D o tensile stress-driven diffusion mechanism, confirmed the pervasiveness of long-range diffusion so that it did not control whisker or hillock formation other than a small loss of activity by reduced thermal activation at lower temperatures. A first-principles DRX model paves the way to develop like mitigation strategies against long whisker growth.

  2. High-temperature pressure sensors with strain gauges based on silicon whiskers

    OpenAIRE

    Druzhinin A. A.; Kutrakov A. P.; Maryamova I. I.

    2012-01-01

    Studies aimed at the creating of piezoresistive pressure sensors based on silicon whiskers, operating at high temperatures were carried out. Using the glass adhesive for strain gauges mounting on spring elements of covar alloy gave the possibility to elevate the sensor’s operating temperature range. Several modifications of pressure sensors based on the proposed strain-unit design were developed.

  3. High-temperature pressure sensors with strain gauges based on silicon whiskers

    Directory of Open Access Journals (Sweden)

    Druzhinin A. A.

    2012-12-01

    Full Text Available Studies aimed at the creating of piezoresistive pressure sensors based on silicon whiskers, operating at high temperatures were carried out. Using the glass adhesive for strain gauges mounting on spring elements of covar alloy gave the possibility to elevate the sensor’s operating temperature range. Several modifications of pressure sensors based on the proposed strain-unit design were developed.

  4. Ostrich eggshell as calcium source for the synthesis of hydroxyapatite and hydroxyapatite partially substituted with zinc

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, J.R.M.; Louro, L.H.L.; Costa, A.M.; Silva, M.H. Prado da [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil); Campos, J.B. de, E-mail: josericardo@r-crio.com, E-mail: louro@ime.eb.br, E-mail: andrea@r-crio.com, E-mail: brantjose@gmail.com, E-mail: marceloprado@ime.eb.br [Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil)

    2016-10-15

    In the present study, hydroxyapatite and Zn-substituted hydroxyapatite powders were synthesized using ostrich eggshell as a calcium source. The samples were analyzed by scanning electron microscopy with field emission gun, and X-ray diffraction (XRD) to identify the present phases, and X-ray fluorescence spectroscopy for quantitative chemical analysis of the synthesized and heat treated powders. The Fourier transform infrared spectroscopy technique was used before and after heat treatments at 700, 900 and 1100 °C in order to identify the functional groups present, as an additional technique to the XRD analysis. The results presented in this study represent a promising method for synthesis of hydroxyapatite and hydroxyapatite partially substituted with zinc, since the results showed no undesirable phases or impurities in the produced powders. It was observed that Zn-substituted hydroxyapatite showed higher thermal stability, when compared to pure hydroxyapatite. (author)

  5. Substituted Hydroxyapatites with Antibacterial Properties

    Directory of Open Access Journals (Sweden)

    Joanna Kolmas

    2014-01-01

    Full Text Available Reconstructive surgery is presently struggling with the problem of infections located within implantation biomaterials. Of course, the best antibacterial protection is antibiotic therapy. However, oral antibiotic therapy is sometimes ineffective, while administering an antibiotic at the location of infection is often associated with an unfavourable ratio of dosage efficiency and toxic effect. Thus, the present study aims to find a new factor which may improve antibacterial activity while also presenting low toxicity to the human cells. Such factors are usually implemented along with the implant itself and may be an integral part of it. Many recent studies have focused on inorganic factors, such as metal nanoparticles, salts, and metal oxides. The advantages of inorganic factors include the ease with which they can be combined with ceramic and polymeric biomaterials. The following review focuses on hydroxyapatites substituted with ions with antibacterial properties. It considers materials that have already been applied in regenerative medicine (e.g., hydroxyapatites with silver ions and those that are only at the preliminary stage of research and which could potentially be used in implantology or dentistry. We present methods for the synthesis of modified apatites and the antibacterial mechanisms of various ions as well as their antibacterial efficiency.

  6. Enhanced osteoconductivity of sodium-substituted hydroxyapatite by system instability.

    Science.gov (United States)

    Sang Cho, Jung; Um, Seung-Hoon; Su Yoo, Dong; Chung, Yong-Chae; Hye Chung, Shin; Lee, Jeong-Cheol; Rhee, Sang-Hoon

    2014-07-01

    The effect of substituting sodium for calcium on enhanced osteoconductivity of hydroxyapatite was newly investigated. Sodium-substituted hydroxyapatite was synthesized by reacting calcium hydroxide and phosphoric acid with sodium nitrate followed by sintering. As a control, pure hydroxyapatite was prepared under identical conditions, but without the addition of sodium nitrate. Substitution of calcium with sodium in hydroxyapatite produced the structural vacancies for carbonate ion from phosphate site and hydrogen ion from hydroxide site of hydroxyapatite after sintering. The total system energy of sodium-substituted hydroxyapatite with structural defects calculated by ab initio methods based on quantum mechanics was much higher than that of hydroxyapatite, suggesting that the sodium-substituted hydroxyapatite was energetically less stable compared with hydroxyapatite. Indeed, sodium-substituted hydroxyapatite exhibited higher dissolution behavior of constituent elements of hydroxyapatite in simulated body fluid (SBF) and Tris-buffered deionized water compared with hydroxyapatite, which directly affected low-crystalline hydroxyl-carbonate apatite forming capacity by increasing the degree of apatite supersaturation in SBF. Actually, sodium-substituted hydroxyapatite exhibited markedly improved low-crystalline hydroxyl-carbonate apatite forming capacity in SBF and noticeably higher osteoconductivity 4 weeks after implantation in calvarial defects of New Zealand white rabbits compared with hydroxyapatite. In addition, there were no statistically significant differences between hydroxyapatite and sodium-substituted hydroxyapatite on cytotoxicity as determined by BCA assay. Taken together, these results indicate that sodium-substituted hydroxyapatite with structural defects has promising potential for use as a bone grafting material due to its enhanced osteoconductivity compared with hydroxyapatite. © 2013 Wiley Periodicals, Inc.

  7. Synthetic hydroxyapatites doped with Zn(II) studied by X-ray diffraction, infrared, Raman and thermal analysis

    Science.gov (United States)

    Guerra-López, José R.; Echeverría, Gustavo A.; Güida, Jorge A.; Viña, Raúl; Punte, Graciela

    2015-06-01

    Calcium hydroxyapatite (CaHap) formation when different amounts of Zn(II) are present in the mother solution has been investigated by atomic absorption, infrared and Raman spectroscopies, X-ray diffraction and thermal analysis (DTA and TG). The studied samples have been synthesized at T=95 °C and pH 9 in air. The analysis of the results have shown that the pure CaHap sample crystallizes in the monoclinic form P21/b. Concentrations up to 20% of Zn(II) in the mother solution, equivalent to smaller concentrations in solid (up to 9.1% in wt), favor the formation of the hexagonal apatite, P63/m, while Zn(II) concentrations higher than 20% in solution help an amorphous phase development where vibrational spectra indicated coexistence of two phases: an apatite and ZnNH4PO4·H2O. Infrared data of thermal treated samples endorse that HPO42- ion had not been incorporated in Zn(II) doped samples during the synthesis process. Present results also allow to conclude that Zn(II) cation exhibits a preference to occupy the Ca2 site of the apatite structure and induces water adsorption and a small quantity of CO32- cation incorporation, leading to formation of a less crystalline Ca deficient apatite.

  8. ZnO whiskers and belts in chestnut husk-like structures: synthesis and proof of chemomechanical transduction.

    Science.gov (United States)

    Alessandri, Ivano; Bergese, Paolo; Depero, Laura E

    2009-02-01

    The preparation of chestnut husk-like ZnO starting from Zn powders is described, pointing out the role of ZnO(1-x) seeds in the self-catalytic liquid-solid growth process. The final architecture is made up of ZnO whiskers stemming from ZnO platelets which are self-assembled into spheroidal agglomerates. Whiskers can be converted into belts by using polyvinylpyrrolidone and configurations exhibiting whiskers and belts on the same husk are obtained through a sequential growth procedure. Polystyrene microspheres are employed in Raman microscopy proof of concept experiments to demonstrate the potential of ZnO whiskers in transduction of chemomechanical interactions, which opens promising perspectives for in-vivo bioapplications.

  9. Fabrication and properties of aluminum silicate fibrous materials with in situ synthesized K2Ti6O13 whiskers

    Science.gov (United States)

    Liu, Hao; Wei, Nan; Wang, Zhou-fu; Wang, Xi-tang; Ma, Yan

    2017-11-01

    To improve their mechanical and thermal insulation properties, aluminum silicate fibrous materials with in situ synthesized K2Ti6O13 whiskers were prepared by firing a mixture of short aluminum silicate fibers and gel powders obtained from a sol-gel process. During the preparation process, the fiber surface was coated with K2Ti6O13 whiskers after the fibers were subjected to a heat treatment carried out at various temperatures. The effects of process parameters on the microstructure, compressive strength, and thermal conductivity were analyzed systematically. The results show that higher treatment temperatures and longer treatment durations promoted the development of K2Ti6O13 whiskers on the surface of aluminum silicate fibers; in addition, the intersection structure between whiskers modulated the morphology and volume of the multi-aperture structure among fibers, substantially increasing the fibers' compressive strength and reducing their heat conduction and convective heat transfer at high temperatures.

  10. Neural Computation via Neural Geometry: A Place Code for Inter-whisker Timing in the Barrel Cortex?

    Science.gov (United States)

    Wilson, Stuart P.; Bednar, James A.; Prescott, Tony J.; Mitchinson, Ben

    2011-01-01

    The place theory proposed by Jeffress (1948) is still the dominant model of how the brain represents the movement of sensory stimuli between sensory receptors. According to the place theory, delays in signalling between neurons, dependent on the distances between them, compensate for time differences in the stimulation of sensory receptors. Hence the location of neurons, activated by the coincident arrival of multiple signals, reports the stimulus movement velocity. Despite its generality, most evidence for the place theory has been provided by studies of the auditory system of auditory specialists like the barn owl, but in the study of mammalian auditory systems the evidence is inconclusive. We ask to what extent the somatosensory systems of tactile specialists like rats and mice use distance dependent delays between neurons to compute the motion of tactile stimuli between the facial whiskers (or ‘vibrissae’). We present a model in which synaptic inputs evoked by whisker deflections arrive at neurons in layer 2/3 (L2/3) somatosensory ‘barrel’ cortex at different times. The timing of synaptic inputs to each neuron depends on its location relative to sources of input in layer 4 (L4) that represent stimulation of each whisker. Constrained by the geometry and timing of projections from L4 to L2/3, the model can account for a range of experimentally measured responses to two-whisker stimuli. Consistent with that data, responses of model neurons located between the barrels to paired stimulation of two whiskers are greater than the sum of the responses to either whisker input alone. The model predicts that for neurons located closer to either barrel these supralinear responses are tuned for longer inter-whisker stimulation intervals, yielding a topographic map for the inter-whisker deflection interval across the surface of L2/3. This map constitutes a neural place code for the relative timing of sensory stimuli. PMID:22022245

  11. Neural computation via neural geometry: a place code for inter-whisker timing in the barrel cortex?

    Directory of Open Access Journals (Sweden)

    Stuart P Wilson

    2011-10-01

    Full Text Available The place theory proposed by Jeffress (1948 is still the dominant model of how the brain represents the movement of sensory stimuli between sensory receptors. According to the place theory, delays in signalling between neurons, dependent on the distances between them, compensate for time differences in the stimulation of sensory receptors. Hence the location of neurons, activated by the coincident arrival of multiple signals, reports the stimulus movement velocity. Despite its generality, most evidence for the place theory has been provided by studies of the auditory system of auditory specialists like the barn owl, but in the study of mammalian auditory systems the evidence is inconclusive. We ask to what extent the somatosensory systems of tactile specialists like rats and mice use distance dependent delays between neurons to compute the motion of tactile stimuli between the facial whiskers (or 'vibrissae'. We present a model in which synaptic inputs evoked by whisker deflections arrive at neurons in layer 2/3 (L2/3 somatosensory 'barrel' cortex at different times. The timing of synaptic inputs to each neuron depends on its location relative to sources of input in layer 4 (L4 that represent stimulation of each whisker. Constrained by the geometry and timing of projections from L4 to L2/3, the model can account for a range of experimentally measured responses to two-whisker stimuli. Consistent with that data, responses of model neurons located between the barrels to paired stimulation of two whiskers are greater than the sum of the responses to either whisker input alone. The model predicts that for neurons located closer to either barrel these supralinear responses are tuned for longer inter-whisker stimulation intervals, yielding a topographic map for the inter-whisker deflection interval across the surface of L2/3. This map constitutes a neural place code for the relative timing of sensory stimuli.

  12. Response properties of whisker-associated primary afferent neurons following infraorbital nerve transection with microsurgical repair in adult rats

    OpenAIRE

    Xiao, Bo; Zanoun, Rami R.; Carvell, George E.; Simons, Daniel J.; Washington, Kia M.

    2016-01-01

    The rodent whisker/trigeminal system, characterized by high spatial and temporal resolution, provides an experimental model for developing new therapies for improving sensory functions of damaged peripheral nerves. Here, we use controlled whisker stimulation and single-unit recordings of trigeminal ganglion cells to examine in detail the nature and time course of functional recovery of mechanoreceptive afferents following nerve transection with microsurgical repair of the infraorbital nerve (...

  13. Neonatal Whisker Trimming Impairs Fear/Anxiety-Related Emotional Systems of the Amygdala and Social Behaviors in Adult Mice.

    Directory of Open Access Journals (Sweden)

    Hitomi Soumiya

    Full Text Available Abnormalities in tactile perception, such as sensory defensiveness, are common features in autism spectrum disorder (ASD. While not a diagnostic criterion for ASD, deficits in tactile perception contribute to the observed lack of social communication skills. However, the influence of tactile perception deficits on the development of social behaviors remains uncertain, as do the effects on neuronal circuits related to the emotional regulation of social interactions. In neonatal rodents, whiskers are the most important tactile apparatus, so bilateral whisker trimming is used as a model of early tactile deprivation. To address the influence of tactile deprivation on adult behavior, we performed bilateral whisker trimming in mice for 10 days after birth (BWT10 mice and examined social behaviors, tactile discrimination, and c-Fos expression, a marker of neural activation, in adults after full whisker regrowth. Adult BWT10 mice exhibited significantly shorter crossable distances in the gap-crossing test than age-matched controls, indicating persistent deficits in whisker-dependent tactile perception. In contrast to controls, BWT10 mice exhibited no preference for the social compartment containing a conspecific in the three-chamber test. Furthermore, the development of amygdala circuitry was severely affected in BWT10 mice. Based on the c-Fos expression pattern, hyperactivity was found in BWT10 amygdala circuits for processing fear/anxiety-related responses to height stress but not in circuits for processing reward stimuli during whisker-dependent cued learning. These results demonstrate that neonatal whisker trimming and concomitant whisker-dependent tactile discrimination impairment severely disturbs the development of amygdala-dependent emotional regulation.

  14. Síntesis de whiskers de SiC asistida por microondas

    Directory of Open Access Journals (Sweden)

    Garza-Méndez, F. J.

    2013-06-01

    Full Text Available We developed a new process for the synthesis of SiC whiskers assisted by microwaves; this is based on the mixture of silica xerogels and graphite powder. As energy source were used microwaves of 2.45 GHz and 1.0 kW of power RMS. On the other hand, mesoporous silica was synthesized via sol-gel, the precursors used were TEOS/H2O and ethanol. Throughanalysis of the BET is determined the value of averageporesize (3.0 nm and the surface area (1090 m2/g.By mean of X-Ray diffraction it was demonstrated that the silica obtained is an amorphous solid and, the powders obtained in the microwave synthesis are β-SiC. Synthesized SiC powders were observed using a SEM in secondary electron mode, it was observed that this powders consists of SiC whiskers. The effect of microwaves on the synthesis of whiskers of SiC is discussed in the present work.Se desarrolló un nuevo proceso para la síntesis de whiskers de SiC asistida por microondas, basada en la mezcla de xerogeles de sílice y grafito en polvo. Como fuente de energía se emplearon microondas de 2.45 GHz y 1.5 kW de potencia. La sílice mesoporosa se sintetizó vía sol-gel, los precursores usados para esta síntesis fueron TEOS/H2O y etanol. A través del análisis BET se determinó el valor de tamaño de poro promedio (3.0 nm y el área superficial (1090 m2/g. Mediante difracción de rayos-x método de polvos se demostró que la sílice sintetizada es amorfa y que los polvos obtenidos en el microondas corresponden a β-SiC. Para determinar la morfología de los whiskers de SiC se analizó por MEB en el modo de electrones secundarios. El efecto de las microondas en la síntesis de whiskers de SiC se discute en el presente trabajo.

  15. Long-Term Extensive Ectopic Hair Growth on the Spinal Cord of Mice from Transplanted Whisker Follicles.

    Directory of Open Access Journals (Sweden)

    Wenluo Cao

    Full Text Available We have previously demonstrated that hair follicles contain nestin-expressing pluripotent stem cells that can effect nerve and spinal cord repair upon transplantation. In the present study, isolated whisker follicles from nestin-driven green fluorescent protein (ND-GFP mice were histocultured on Gelfoam for 3 weeks for the purpose of transplantation to the spinal cord to heal an induced injury. The hair shaft was cut off from Gelfoam-histocultured whisker follicles, and the remaining part of the whisker follicles containing GFP-nestin expressing pluripotent stem cells were transplanted into the injured spinal cord of nude mice, along with the Gelfoam. After 90 days, the mice were sacrificed and the spinal cord lesion was observed to have healed. ND-GFP expression was intense at the healed area of the spinal cord, as observed by fluorescence microscopy, demonstrating that the hair follicle stem cells were involved in healing the spinal cord. Unexpectedly, the transplanted whisker follicles sprouted out remarkably long hair shafts in the spinal cord during the 90 days after transplantation of Gelfoam whisker histocultures to the injured spine. The pigmented hair fibers, grown from the transplanted whisker histocultures, curved and enclosed the spinal cord. The unanticipated results demonstrate the great potential of hair growth after transplantation of Gelfoam hair follicle histocultures, even at an ectopic site.

  16. High-affinity integration of hydroxyapatite nanoparticles with chemically modified silk fibroin

    Energy Technology Data Exchange (ETDEWEB)

    Wang Li; Li Chunzhong [East China University of Science and Technology, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering (China)], E-mail: czli@ecust.edu.cn; Senna, Mamoru [Keio University, Department of Applied Chemistry, Faculty of Science and Technology (Japan)

    2007-10-15

    Hydroxyapatite (HA)-based nanocomposites were prepared by a co-precipitation method with silk fibroin (SF) serving as organic matrix. Silk fibroin was chemically modified with an alkali solution or an enzyme attempting to improve the interface between the mineral and the organic matrix. The influences of the alkali and enzyme pretreatments on microstructure and physicochemical properties of HA-SF composite were examined and compared. The results reveal that both the two kinds of pretreatments facilitate the formation of highly ordered three-dimensional porous network throughout the composites, increase the microhardness of the composite, and promote the preferential growth of HA crystallites along c-axis. Among all the as-prepared samples, the composite containing the enzyme pretreated SF shows desirable hierarchical microstructure with higher degree of organization and more uniform pore size distribution. Due to the enzyme pretreatment, HA crystallites undergo obvious changes in morphology from rod-like to whisker-like and in crystal growth towards more apparent epitaxy along c-axis. The alkali pretreatment induces the stronger chemical interactions between HA and SF and thus to strengthen the inorganic-organic interfacial adhesion. The newly developed HA-SF composites are expected to be attractive biomedical materials for bone repair and remodeling.

  17. Controlling of dielectric parameters of insulating hydroxyapatite by simulated body fluid

    Energy Technology Data Exchange (ETDEWEB)

    Kaygili, Omer, E-mail: okaygili@firat.edu.tr [Department of Physics, Faculty of Science, Firat University, Elazig (Turkey); Keser, Serhat [Department of Chemistry, Faculty of Science, Firat University, Elazig (Turkey); Ates, Tankut; Tatar, Cengiz; Yakuphanoglu, Fahrettin [Department of Physics, Faculty of Science, Firat University, Elazig (Turkey)

    2015-01-01

    Hydroxyapatite (HAp) samples were synthesized under various amounts of citric acid using the sol–gel method. Before and after immersion in simulated body fluid (SBF) for 14 and 28 days, the structural properties of HAp samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy with energy dispersive X-ray (EDX) spectroscopy and dielectric measurements. The crystallite size (D) was found to be in the range of 25.17–33.06 nm with the crystallinity percent (X{sub C}%) of 69.53–86.09. The lattice parameters of a and c were calculated to be in the ranges of 9.373–9.434 Å and 6.828–6.896 Å, respectively. The morphology of the as-synthesized samples was changed with the amount of citric acid and soaking period in SBF. The Ca/P molar ratios indicated a decrease with increasing immersion time, and Ca-deficiency was observed. The relative permittivity (ε′) and dielectric loss (ε″) were significantly affected by citric acid content and soaking period in SBF. It was seen that the alternating current conductivity (σ{sub ac}) increased with increasing frequency and the σ{sub ac} values changed with increasing soaking period and amount of citric acid. - Highlights: • The crystallite size is in the range of 25.17–33.06 nm. • The Ca/P molar ratio showed a decrease with increasing immersion time. • Citric acid content and soaking period in SBF affect the relative permittivity. • The alternating current conductivity increased with increasing frequency.

  18. TEM study of the morphology of Mn2+ -doped calcium hydroxyapatite and beta-tricalcium phosphate.

    Science.gov (United States)

    Mayer, I; Cuisinier, F J G; Gdalya, S; Popov, I

    2008-02-01

    Mn-doped carbonated hydroxyapatites (HA) were prepared by precipitation method. Ca-deficient HA samples were obtained by this method with the characteristic hexagonal apatite structure. Scanning transmission electron microscopy (STEM) of two HA samples with two different Mn content has shown that their morphology depends on their Mn content. In case of relatively low (0.73%) Mn content (HAMn1), platelet crystals about micron size and needle-like crystals up to 100 nm were observed, while with 1.23% Mn (HAMn2) crystals were smaller, needle-like and with sizes up to 400 nm only. Mn-doped TCP samples were prepared by two methods. In one case it was obtained by direct solid-state reaction with the characteristic rhombohedral structure of beta-TCP and with composition of Ca(2.7)Mn(0.3)(PO(4))(2). TEM pictures of crystals of this sample were tens of micron and submicron size with visible faces. Crystals of beta-TCP obtained by high temperature partial transformation of sample HAMn2 to beta-TCP were found by TEM to be smaller, micron sized, drop-like shaped, sensitive to beam radiation. These results indicate that the morphology of Mn doped beta-tricalcium phosphate samples depends on the method of their preparation. Morphological properties of HA and TCP are discussed and it is suggested that the smaller and less perfect HA crystals with the higher Mn-content as well as the less perfect TCP crystals obtained by transformation of HA to TCP might be of more biocompatible character.

  19. Characterisation, corrosion resistance and in vitro bioactivity of manganese-doped hydroxyapatite films electrodeposited on titanium.

    Science.gov (United States)

    Huang, Yong; Ding, Qiongqiong; Han, Shuguang; Yan, Yajing; Pang, Xiaofeng

    2013-08-01

    This work elucidated the corrosion resistance and in vitro bioactivity of electroplated manganese-doped hydroxyapatite (MnHAp) film on NaOH-treated titanium (Ti). The NaOH treatment process was performed on Ti surface to enhance the adhesion of the MnHAp coating on Ti. Scanning electron microscopy images showed that the MnHAp coating had needle-like apatite crystals, and the approximately 10 μm thick layer was denser than HAp. Energy-dispersive X-ray spectroscopy analysis revealed that the MnHAp crystals were Ca-deficient and the Mn/P molar ratio was 0.048. X-ray diffraction confirmed the presence of single-phase MnHAp, which was aligned vertically to the substrate. Fourier transform infrared spectroscopy indicated the presence of phosphate bands ranging from 500 to 650 and 900 to 1,100 cm(-1), and a hydroxyl band at 3,571 cm(-1), which was characteristic of HAp. Bond strength test revealed that adhesion for the MnHAp coating was more enhanced than that of the HAp coating. Potentiodynamic polarisation test showed that the MnHAp-coated surface exhibited superior corrosion resistance over the HAp single-coated surface. Bioactivity test conducted by immersing the coatings in simulated body fluid showed that MnHAp coating can rapidly induce bone-like apatite nucleation and growth. Osteoblast cellular tests revealed that the MnHAp coating was better at improving the in vitro biocompatibility of Ti than the HAp coating.

  20. Functionalization of Calcium Sulfate/Bioglass Scaffolds with Zinc Oxide Whisker.

    Science.gov (United States)

    Shuai, Cijun; Zhou, Jianhua; Gao, Dan; Gao, Chengde; Feng, Pei; Peng, Shuping

    2016-03-18

    There are urgent demands for satisfactory antibacterial activity and mechanical properties of bone scaffolds. In this study, zinc oxide whisker (ZnOw) was introduced into calcium sulfate/bioglass scaffolds. Antimicrobial behavior was analyzed using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The results showed that the scaffolds presented a strong antibacterial activity after introducing ZnOw, due to the antibacterial factors released from the degradation of ZnO. Moreover, ZnOw was also found to have a distinct reinforcing effect on mechanical properties. This was ascribed to whisker pull-out, crack bridging, crack deflection, crack branching and other toughening mechanisms. In addition, the cell culture experiments showed that the scaffolds with ZnOw had a good biocompatibility.

  1. Functionalization of Calcium Sulfate/Bioglass Scaffolds with Zinc Oxide Whisker

    Directory of Open Access Journals (Sweden)

    Cijun Shuai

    2016-03-01

    Full Text Available There are urgent demands for satisfactory antibacterial activity and mechanical properties of bone scaffolds. In this study, zinc oxide whisker (ZnOw was introduced into calcium sulfate/bioglass scaffolds. Antimicrobial behavior was analyzed using Escherichia coli (E. coli and Staphylococcus aureus (S. aureus. The results showed that the scaffolds presented a strong antibacterial activity after introducing ZnOw, due to the antibacterial factors released from the degradation of ZnO. Moreover, ZnOw was also found to have a distinct reinforcing effect on mechanical properties. This was ascribed to whisker pull-out, crack bridging, crack deflection, crack branching and other toughening mechanisms. In addition, the cell culture experiments showed that the scaffolds with ZnOw had a good biocompatibility.

  2. Cryptic mammalian species: a new species of whiskered bat (Myotis alcathoe n. sp.) in Europe

    Science.gov (United States)

    von Helversen, O.; Heller, K.-G.; Mayer, F.; Nemeth, A.; Volleth, M.; Gombkötö, P.

    2001-05-01

    The analysis of morphological, behavioural and genetic characters of whiskered bats revealed a new European bat species within the family Vespertilionidae. We describe the morphology, karyology, genetic similarity, ecology and distribution of Myotis alcathoe n. sp. It closely resembles Myotis mystacinus, Myotis brandtii and Myotis ikonnikovi in morphology, but all four species show clear genetic differences in two mitochondrial genes (ND1 and 12S rRNA). Myotis alcathoe n. sp. is the smallest species among the European whiskered bats and uses the highest-frequency echolocation calls of all the European Myotis species. It prefers to hunt in small valleys with deciduous trees and flowing water, which is an endangered habitat. Records from Greece and Hungary indicate a distribution range in south-eastern Europe.

  3. Synthesis and Characterization of Hydroxyapatite/Fullerenol Nanocomposites.

    Science.gov (United States)

    Djordjevic, Aleksandar; Ignjatovic, Nenad; Seke, Mariana; Jovic, Danica; Uskokovic, Dragan; Rakocevic, Zlatko

    2015-02-01

    Fullerenols are polyhydroxylated, water soluble derivatives of fullerene C60, with potential application in medicine as diagnostic agents, antioxidants or nano drug carriers. This paper describes synthesis and physical characterization of a new nanocomposite hydroxyapatite/fullerenol. Surface of the nanocomposite hydroxyapatite/fullerenol is inhomogeneous with the diameter of the particles in the range from 100 nm to 350 nm. The ζ potential of this nanocomposite is ten times lower when compared to hydroxyapatite. Surface phosphate groups of hydroxyapatite are prone to forming hydrogen bonds, when in close contact with hydroxyl groups, which could lead to formation of hydrogen bonds between hydroxyapatite and hydroxyl groups of fullerenol. The surface of hydroxyapatite particles (-2.5 mV) was modified by fullerenol particles, as confirmed by the obtained ζ potential value of the nanocomposite biomaterial hydroxyapatite/fullerenol (-25.0 mV). Keywords: Hydroxyapatite, Fullerenol, Nanocomposite, Surface Analysis.

  4. The Effect of Zirconia in Hydroxyapatite on Staphylococcus epidermidis Growth

    Directory of Open Access Journals (Sweden)

    Widowati Siswomihardjo

    2012-01-01

    . Conclusion. The addition of zirconia into hydroxyapatite affected the growth of S. epidermidis. Hydroxyapatite with 20% zirconia proved to be an effective concentration to inhibit the growth of S. epidermidis colony.

  5. Rat Whisker Movement after Facial Nerve Lesion: Evidence for Autonomic Contraction of Skeletal Muscle

    OpenAIRE

    Heaton, James T.; Sheu, Shu-Hsien; Hohman, Marc H.; Knox, Christopher J.; Weinberg, Julie S.; Kleiss, Ingrid J.; Hadlock, Tessa A.

    2014-01-01

    Vibrissal whisking is often employed to track facial nerve regeneration in rats; however, we have observed similar degrees of whisking recovery after facial nerve transection with or without repair. We hypothesized that the source of non-facial nerve-mediated whisker movement after chronic denervation was from autonomic, cholinergic axons traveling within the infraorbital branch of the trigeminal nerve (ION). Rats underwent unilateral facial nerve transection with repair (N=7) or resection wi...

  6. Room temperature properties of electrical contacts to alumina composites containing silicon carbide whiskers

    Science.gov (United States)

    Bertram, Brian D.; Gerhardt, Rosario A.

    2009-04-01

    The electrical properties of contacts to hot-pressed alumina composites having variable volume fractions of SiC whiskers (Vw) were investigated with impedance spectroscopy and current-mode atomic force microscopy at room temperature. Three different contact materials were studied: sputtered Pt, sputtered Ag, and conductive Ag paint. Electrode properties were characterized while fresh due to instability over long times (˜100 h). For percolated samples with Vw≥0.10, the electrical response of the electrodes is manifested in the complex impedance plane by a semicircle whose properties are rooted in Schottky barrier blocking at metal contacts to surface whiskers participating in percolated linkages. This process was modeled with a parallel resistor-capacitor (RcCc) equivalent circuit having a relaxation frequency ωc. The dependences of the specific contact resistance (ρs) and specific capacitance (Cs) on Vw were in agreement with the microlevel interpretation above. The three contact materials exhibited significantly different properties, indicating sensitivities to metal work function and metal-whisker interfacing. Both Rc and ωc have exponential dependences on dc bias (Vdc) which are related through the equivalent circuit model. The strengths of these exponentials and the degree of nonlinearity in I-Vdc curves increase with the fraction of Vdc dropping at the electrodes. The dependence of Cs on Vdc also indicated symmetrical Schottky blocking and was used to estimate charge carrier concentration in the whiskers as 1017-1019 cm-3 and a barrier height of 0.2-1.6 eV for sputtered Ag.

  7. The peripheral and central changes resulting from cutting or crushing the afferent nerve supply to the whiskers.

    Science.gov (United States)

    Waite, P M; Cragg, B G

    1982-01-22

    In neonatal rats, crushing or cutting the infraorbital nerve, the sensory nerve supply to the whiskers, has been found to prevent cortical barrel formation. However, both procedures are followed by regeneration of one-third to one-half of the nerve fibres and reinnervation of the whiskers. By counting fibres in individual whisker follicle nerves, it has been shown that 29-67% (mean 45%) of the myelinated fibres regenerate to the whiskers after a crush compared to 24-56% (mean 39%) after a cut. Further differences between the crush and cut lesions were indicated by studies on the time course of regeneration. Counts of the regenerating fibres at various ages as well as recordings of cortical evoked potentials in normal, nerve-crushed and nerve-cut animals showed that recovery was 3-4 days earlier in the nerve-crushed, compared with the nerve-cut animals. In normal and nerve-crushed animals the evoked potential was first detectable 2-3 days after birth while the response after nerve cut could not be recorded until day 7. Even after 60 days the amplitude of responses on both crushed and cut pathways was only about one-third of normal, while the latency was prolonged (normal 5.8 +/- 0.25 ms, crush 6.5 +/- 0.26 ms, cut 7.7 +/- 0.67 ms). Central changes occurring as a result of nerve cut or crush have been studied by microelectrode recordings from the trigeminal nucleus (the first synaptic level) and the somatosensory cortex. These also indicate clearly the greater severity of the cut lesion. Thus, in crushed animals, all levels of the trigeminal nucleus as well as the cortex show only minor modifications. The whiskers occupy the same total area and responses from all whiskers are present at their normal sites. However, after nerve cut, the responses from both the trigeminal nucleus and cortex show clear abnormalities. The total whisker area is reduced with a concomitant expansion of responses from the nose, check, lower jaw, and whiskers by the eye and ear. In addition

  8. Zinc oxide crystal whiskers as a novel sorbent for solid-phase extraction of flavonoids.

    Science.gov (United States)

    Wang, Licheng; Shangguan, Yangnan; Hou, Xiudan; Jia, Yong; Liu, Shujuan; Sun, Yingxin; Guo, Yong

    2017-08-15

    As a novel solid-phase extraction material, zinc oxide crystal whiskers were used to extract flavonoid compounds and showed good extraction abilities. X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy and surface area/pore volume characterized the sorbent. The zinc oxide was packed into a solid-phase extraction micro-column and its extraction ability was evaluated by four model flavonoid compounds. The sample loading and elution parameters were optimized and the zinc oxide based analytical method for flavonoids was established. It showed that the method has wide linearities from 1 to 150μg/L and low limits of detection at 0.25μg/L. The relative standard deviations of a single column repeatability and column to column reproducibility were less than 6.8% and 10.6%. Several real samples were analyzed by the established method and satisfactory results were obtained. The interactions between flavonoids and zinc oxide were calculated and proved to be from the Van der Waals' forces between the 4p and 5d orbitals from zinc atom and the neighboring π orbitals from flavonoid phenyl groups. Moreover, the zinc oxide crystal whiskers showed good stability and could be reused more than 50 times under the operation conditions. This work proves that the zinc oxide crystal whiskers are a good candidate for flavonoids enrichment. Copyright © 2017. Published by Elsevier B.V.

  9. Characteristics of porous zirconia coated with hydroxyapatite as ...

    Indian Academy of Sciences (India)

    Since hydroxyapatite has excellent biocompatibility and bone bonding ability, porous hydroxyapatite ceramics have been intensively studied. However, porous hydroxyapatite bodies are mechanically weak and brittle, which makes shaping and implantation difficult. One way to solve this problem is to introduce a strong ...

  10. Support for the slip hypothesis from whisker-related tactile perception of rats in a noisy environment

    Science.gov (United States)

    Waiblinger, Christian; Brugger, Dominik; Whitmire, Clarissa J.; Stanley, Garrett B.; Schwarz, Cornelius

    2015-01-01

    Rodents use active whisker movements to explore their environment. The “slip hypothesis” of whisker-related tactile perception entails that short-lived kinematic events (abrupt whisker movements, called “slips”, due to bioelastic whisker properties that occur during active touch of textures) carry the decisive texture information. Supporting this hypothesis, previous studies have shown that slip amplitude and frequency occur in a texture-dependent way. Further, experiments employing passive pulsatile whisker deflections revealed that perceptual performance based on pulse kinematics (i.e., signatures that resemble slips) is far superior to the one based on time-integrated variables like frequency and intensity. So far, pulsatile stimuli were employed in a noise free environment. However, the realistic scenario involves background noise (e.g., evoked by rubbing across the texture). Therefore, if slips are used for tactile perception, the tactile neuronal system would need to differentiate slip-evoked spikes from those evoked by noise. To test the animals under these more realistic conditions, we presented passive whisker-deflections to head-fixed trained rats, consisting of “slip-like” events (waveforms mimicking slips occurring with touch of real textures) embedded into background noise. Varying the (i) shapes (ramp or pulse); (ii) kinematics (amplitude, velocity, etc.); and (iii) the probabilities of occurrence of slip-like events, we observed that rats could readily detect slip-like events of different shapes against noisy background. Psychophysical curves revealed that the difference of slip event and noise amplitude determined perception, while increased probability of occurrence (frequency) had barely any effect. These results strongly support the notion that encoding of kinematics dominantly determines whisker-related tactile perception while the computation of frequency or intensity plays a minor role. PMID:26528148

  11. Support for the slip hypothesis from whisker-related tactile perception of rats in a noisy environment

    Directory of Open Access Journals (Sweden)

    Christian eWaiblinger

    2015-10-01

    Full Text Available Rodents use active whisker movements to explore their environment. The ‘slip hypothesis’ of whisker-related tactile perception entails that short-lived kinematic events (abrupt whisker movements, called ‘slips’, due to bioelastic whisker properties that occur during active touch of textures carry the decisive texture information. Supporting this hypothesis, previous studies have shown that slip amplitude and frequency occur in a texture dependent way. Further, experiments employing passive pulsatile whisker deflections revealed that perceptual performance based on pulse kinematics (i.e. signatures that resemble slips is far superior to the one based on time-integrated variables like frequency and intensity. So far, pulsatile stimuli were employed in a noise free environment. However, the realistic scenario involves background noise (e.g. evoked by rubbing across the texture. Therefore, if slips are used for tactile perception, the tactile neuronal system would need to differentiate slip-evoked spikes from those evoked by noise. To test the animals under these more realistic conditions, we presented passive whisker-deflections to head-fixed trained rats, consisting of 'slip-like' events (waveforms mimicking slips occurring with touch of real textures embedded into background noise. Varying the i shapes (ramp or pulse, ii kinematics (amplitude, velocity, etc., and iii the probabilities of occurrence of slip-like events, we observed that rats could readily detect slip-like events of different shapes against noisy background. Psychophysical curves revealed that the difference of slip event and noise amplitude determined perception, while increased probability of occurrence (frequency had barely any effect. These results strongly support the notion that encoding of kinematics dominantly determines whisker-related tactile perception while the computation of frequency or intensity plays a minor role.

  12. Síntese de "whiskers" de CaSiO3 em fluxo salino para elaboração de biomateriais Synthesis of CaSiO3 "whiskers" in alkaline salt flux for biomaterials reinforcement

    Directory of Open Access Journals (Sweden)

    M. Motisuke

    2012-12-01

    Full Text Available Há tempos empregam-se "whiskers" cerâmicos como reforço de materiais nas mais diversas aplicações, porém os materiais com os quais estes são comumente fabricados (carbeto e nitreto de silício não permitem a sua utilização no campo dos biomateriais devido sua elevada toxicidade. Assim, torna-se interessante sintetizar "whiskers" biocompatíveis capazes de reforçar biomateriais cerâmicos e poliméricos sem prejudicar a saúde dos pacientes. Dessa forma, este trabalho tem como objetivo desenvolver e determinar os parâmetros limitantes de uma nova rota de síntese por fusão de sais de "whiskers" de CaSiO3, uma biocerâmica biocompatível, bioativa e reabsorvível. Este método é simples, barato e permite a produção em larga escala. Utilizou-se um fluxo de NaCl/KCl a 900 ºC para sintetizar "whiskers" de wollastonita, que foram caracterizados por difração de raios X e microscopia eletrônica de varredura. O método proposto mostrou-se eficiente, entretanto os tempos de patamar empregados não foram suficientes para garantir 100% de rendimento da reação de formação de CaSiO3, ocorrendo a formação de cristobalita.Materials reinforcement by ceramic whiskers has been employed for a long time in a variety of industrial applications. Nevertheless, the materials by which these whiskers are commonly made of (carbide and silicon nitride do not allow their use in biomaterials field due to their high toxicity. Then, it is of interest to synthesize ceramic whiskers which could reinforce biocompatible ceramic and polymeric biomaterials without harming the patients' health. In this manner, the aim of this work is to propose and analyze the limiting process variables of a new synthetic route to produce whiskers of CaSiO3 (wollastonite: a biocompatible, bioactive and readsorbable biomaterial. It was employed the molten salt synthesis at 900 ºC to grow wollastonite crystals which were characterized by X-ray diffraction and scanning electron

  13. Spontaneous loosening of hydroxyapatite peg sleeves.

    Science.gov (United States)

    Jordan, D R

    2001-11-01

    To report a new complication associated with pegging hydroxyapatite orbital implants: spontaneous loosening of the sleeve. Retrospective noncomparative case series. Four patients ranging in age from 38 to 60 years participated. Four patients are described who successfully received hydroxyapatite orbital implants with motility peg and sleeve systems. In each case spontaneous loosening of the sleeve developed. Clinical and surgical outcomes were assessed. Three patients had the peg and sleeve removed followed by repair of the peg hole, and one patient had placement of a larger diameter peg and sleeve system. All patients did well. Problems have been reported when motility coupling pegs are used with hydroxyapatite orbital implants. Spontaneous loosening of the sleeve is another potential complication to discuss with the patient considering an implant peg.

  14. Ostrich eggshell as calcium source for the synthesis of hydroxyapatite and hydroxyapatite partially substituted with zinc

    OpenAIRE

    Ferreira,J. R. M.; Louro,L. H. L.; Costa, A. M.; Campos, J. B; Silva,M. H. Prado da

    2016-01-01

    Abstract In the present study, hydroxyapatite and Zn-substituted hydroxyapatite powders were synthesized using ostrich eggshell as a calcium source. The samples were analyzed by scanning electron microscopy with field emission gun, and X-ray diffraction (XRD) to identify the present phases, and X-ray fluorescence spectroscopy for quantitative chemical analysis of the synthesized and heat treated powders. The Fourier transform infrared spectroscopy technique was used before and after heat trea...

  15. Effect of biopolymers on structure of hydroxyapatite and interfacial interactions in biomimetically synthesized hydroxyapatite/biopolymer nanocomposites.

    Science.gov (United States)

    Verma, Devendra; Katti, Kalpana S; Katti, Dinesh R

    2008-06-01

    The interfacial interaction and effect of biopolymer on crystal structure of hydroxyapatite in biomimetically synthesized nanocomposites, chitosan/hydroxyapatite (ChiHAP50), polygalacturonic acid/hydroxyapatite (PgAHAP50), and chitosan/polygalacturonic acid/hydroxyapatite (ChiPgAHAP50) have been investigated using atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, and Rietveld analysis. AFM phase images show nano-sized hydroxyapatite particles uniformly distributed in biopolymer. FTIR spectra indicate that chitosan interacts with hydroxyapatite through NH(3)(+) groups, whereas in polygalacturonic acid/hydroxyapatite, dissociated carboxylate groups (COO(-)) form unidentate chelate with calcium atoms. A change in lattice parameters of hydroxyapatite in all nanocomposites is observed using Rietveld analysis. The increase in lattice parameters was most prominent along c-axis in ChiHAP50 and ChiPgAHAP50 nanocomposites, which was 0.388% and 0.319%, respectively. Comparison between particle sizes of hydroxyapatite, determined from AFM and Rietveld analysis, indicates presence of amorphous phase in hydroxyapatite particles, which is believed to be present at the interface of hydroxyapatite and biopolymer.

  16. Thickness of hydroxyapatite nanocrystal controls mechanical properties of the collagen-hydroxyapatite interface.

    Science.gov (United States)

    Qin, Zhao; Gautieri, Alfonso; Nair, Arun K; Inbar, Hadass; Buehler, Markus J

    2012-01-31

    Collagen-hydroxyapatite interfaces compose an important building block of bone structures. While it is known that the nanoscale structure of this elementary building block can affect the mechanical properties of bone, a systematic understanding of the effect of the geometry on the mechanical properties of this interface between protein and mineral is lacking. Here we study the effect of geometry, different crystal surfaces, and hydration on the mechanical properties of collagen-hydroxyapatite interfaces from an atomistic perspective, and discuss underlying deformation mechanisms. We find that the presence of hydroxyapatite significantly enhances the tensile modulus and strength compared with a tropocollagen molecule alone. The stiffening effect is strongly dependent on the thickness of the mineral crystal until a plateau is reached at 2 nm crystal thickness. We observe no significant differences due to the mineral surface (Ca surface vs OH surface) or due to the presence of water. Our result shows that the hydroxyapatite crystal with its thickness confined to the nanometer size efficiently increases the tensile modulus and strength of the collagen-hydroxyapatite composite, agreeing well with experimental observations that consistently show the existence of extremely thin mineral flakes in various types of bones. We also show that the collagen-hydroxyapatite interface can be modeled with an elastic network model which, based on the results of atomistic simulations, provides a good estimate of the surface energy and other mechanical features. © 2011 American Chemical Society

  17. Large-Scale Growth of Tubular Aragonite Whiskers through a MgCl2-Assisted Hydrothermal Process

    Directory of Open Access Journals (Sweden)

    Changyin Dong

    2011-08-01

    Full Text Available In this paper, we have developed a facile MgCl2-assissted hydrothermal synthesis route to grow tubular aragonite whiskers on a large scale. The products have been characterized by powder X-ray diffraction (XRD, optical microscopy, and scanning electronic microscopy (SEM. The results show the as-grown product is pure tubular aragonite crystalline whiskers with a diameter of 5–10 mm and a length of 100–200 mm, respectively. The concentration of Mg2+ plays an important role in determining the quality and purity of the products. Furthermore, the method can be extended to fabricate CaSO4 fibers. The high quality of the product and the mild conditions used mean that the present route has good prospects for the growth of inorganic crystalline whiskers.

  18. An Empirical Model for Estimating the Probability of Electrical Short Circuits from Tin Whiskers-Part I

    Science.gov (United States)

    Courey, Karim; Wright, Clara; Asfour, Shihab; Bayliss, Jon; Ludwig, Larry

    2008-01-01

    Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has a currently unknown probability associated with it. Due to contact resistance, electrical shorts may not occur at lower voltage levels. In this experiment, we study the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From this data, we can estimate the probability of an electrical short, as a function of voltage, given that a free tin whisker has bridged two adjacent exposed electrical conductors. In addition, three tin whiskers grown from the same Space Shuttle Orbiter card guide used in the aforementioned experiment were cross sectioned and studied using a focused ion beam (FIB).

  19. Continuous microwave flow synthesis of mesoporous hydroxyapatite.

    Science.gov (United States)

    Akram, Muhammad; Alshemary, Ammar Z; Goh, Yi-Fan; Wan Ibrahim, Wan Aini; Lintang, Hendrik O; Hussain, Rafaqat

    2015-11-01

    We have successfully used continuous microwave flow synthesis (CMFS) technique for the template free synthesis of mesoporous hydroxyapatite. The continuous microwave flow reactor consisted of a modified 2.45GHz household microwave, peristaltic pumps and a Teflon coil. This cost effective and efficient system was exploited to produce semi-crystalline phase pure nano-sized hydroxyapatite. Effect of microwave power, retention time and the concentration of reactants on the phase purity, degree of crystallinity and surface area of the final product was studied in detail. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to study the phase purity and composition of the product, while transmission electron microscopy (TEM) was used to study the effect of process parameters on the morphology of hydroxyapatite. The TEM analysis confirmed the formation of spherical particles at low microwave power; however the morphology of the particles changed to mesoporous needle and rod-like structure upon exposing the reaction mixture to higher microwave power and longer retention time inside the microwave. The in-vitro ion dissolution behavior of the as synthesized hydroxyapatite was studied by determining the amount of Ca(2+) ion released in SBF solution. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Hydroxyapatite, a biomaterial: Its chemical synthesis ...

    Indian Academy of Sciences (India)

    Hydroxyapatite, a biomaterial: Its chemical synthesis, characterization and study of biocompatibility prepared from shell of garden snail,. Helix aspersa. ANJUVAN SINGH. Department of Biotechnology and Biosciences, Lovely Professional University, Phagwara 144 411, India. MS received 10 February 2010; revised 20 July ...

  1. Preparation of microstructured hydroxyapatite microspheres using ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Hydroxyapatite (HAP) microspheres with peculiar spheres-in-sphere morphology were prepared by using oil-in-water emulsions and solvent evaporation technique. Ethylene vinyl acetate co-polymer (EVA) was used as the binder material. Preparation of HAP/EVA microspheres was followed by the thermal de-.

  2. Fabrication and characterization of porous hydroxyapatite ocular ...

    Indian Academy of Sciences (India)

    Unknown

    areas of medicine (Aoki et al 1987; Grote 1987; Shin et al 1992) also. The use of hydroxyapatite as an ocular .... the experimental error, throughout the whole process of fabrication. The median particle size of HAp powder used ... per medication and resolution took place within the 12th post-operative day (figures 9 a–d).

  3. Preparation of microstructured hydroxyapatite microspheres using ...

    Indian Academy of Sciences (India)

    Each microsphere of 100–1000 m was in turn composed of spherical hydroxyapatite granules of 2–15 m size which were obtained by spray drying the precipitated HAP. The parameters such as percentage of initial HAP loading, type of stabilizer, concentration of stabilizer, stirring speed and temperature of microsphere ...

  4. Multidimensional characterisation of biomechanical structures by combining Atomic Force Microscopy and Focused Ion Beam: A study of the rat whisker.

    Science.gov (United States)

    Adineh, Vahid Reza; Liu, Boyin; Rajan, Ramesh; Yan, Wenyi; Fu, Jing

    2015-07-01

    Understanding the heterogeneity of biological structures, particularly at the micro/nano scale can offer insights valuable for multidisciplinary research in tissue engineering and biomimicry designs. Here we propose to combine nanocharacterisation tools, particularly Focused Ion Beam (FIB) and Atomic Force Microscopy (AFM) for three dimensional mapping of mechanical modulus and chemical signatures. The prototype platform is applied to image and investigate the fundamental mechanics of the rat face whiskers, a high-acuity sensor used to gain detailed information about the world. Grazing angle FIB milling was first applied to expose the interior cross section of the rat whisker sample, followed by a "lift-out" method to retrieve and position the target sample for further analyses. AFM force spectroscopy measurements revealed a non-uniform pattern of elastic modulus across the cross section, with a range from 0.8GPa to 13.5GPa. The highest elastic modulus was found at the outer cuticle region of the whisker, and values gradually decreased towards the interior cortex and medulla regions. Elemental mapping with EDS confirmed that the interior of the rat whisker is dominated by C, O, N, S, Cl and K, with a significant change of elemental distribution close to the exterior cuticle region. Based on these data, a novel comprehensive three dimensional (3D) elastic modulus model was constructed, and stress distributions under realistic conditions were investigated with Finite Element Analysis (FEA). The simulations could well account for the passive whisker deflections, with calculated resonant frequency as well as force-deflection for the whiskers being in good agreement with reported experimental data. Limitations and further applications are discussed for the proposed FIB/AFM approach, which holds good promise as a unique platform to gain insights on various heterogeneous biomaterials and biomechanical systems. Copyright © 2015 Acta Materialia Inc. Published by Elsevier

  5. Probability distributions of whisker-surface contact: quantifying elements of the rat vibrissotactile natural scene.

    Science.gov (United States)

    Hobbs, Jennifer A; Towal, R Blythe; Hartmann, Mitra J Z

    2015-08-01

    Analysis of natural scene statistics has been a powerful approach for understanding neural coding in the auditory and visual systems. In the field of somatosensation, it has been more challenging to quantify the natural tactile scene, in part because somatosensory signals are so tightly linked to the animal's movements. The present work takes a step towards quantifying the natural tactile scene for the rat vibrissal system by simulating rat whisking motions to systematically investigate the probabilities of whisker-object contact in naturalistic environments. The simulations permit an exhaustive search through the complete space of possible contact patterns, thereby allowing for the characterization of the patterns that would most likely occur during long sequences of natural exploratory behavior. We specifically quantified the probabilities of 'concomitant contact', that is, given that a particular whisker makes contact with a surface during a whisk, what is the probability that each of the other whiskers will also make contact with the surface during that whisk? Probabilities of concomitant contact were quantified in simulations that assumed increasingly naturalistic conditions: first, the space of all possible head poses; second, the space of behaviorally preferred head poses as measured experimentally; and third, common head poses in environments such as cages and burrows. As environments became more naturalistic, the probability distributions shifted from exhibiting a 'row-wise' structure to a more diagonal structure. Results also reveal that the rat appears to use motor strategies (e.g. head pitches) that generate contact patterns that are particularly well suited to extract information in the presence of uncertainty. © 2015. Published by The Company of Biologists Ltd.

  6. Rat whisker movement after facial nerve lesion: evidence for autonomic contraction of skeletal muscle.

    Science.gov (United States)

    Heaton, James T; Sheu, Shu Hsien; Hohman, Marc H; Knox, Christopher J; Weinberg, Julie S; Kleiss, Ingrid J; Hadlock, Tessa A

    2014-04-18

    Vibrissal whisking is often employed to track facial nerve regeneration in rats; however, we have observed similar degrees of whisking recovery after facial nerve transection with or without repair. We hypothesized that the source of non-facial nerve-mediated whisker movement after chronic denervation was from autonomic, cholinergic axons traveling within the infraorbital branch of the trigeminal nerve (ION). Rats underwent unilateral facial nerve transection with repair (N=7) or resection without repair (N=11). Post-operative whisking amplitude was measured weekly across 10weeks, and during intraoperative stimulation of the ION and facial nerves at ⩾18weeks. Whisking was also measured after subsequent ION transection (N=6) or pharmacologic blocking of the autonomic ganglia using hexamethonium (N=3), and after snout cooling intended to elicit a vasodilation reflex (N=3). Whisking recovered more quickly and with greater amplitude in rats that underwent facial nerve repair compared to resection (Pnerve-mediated whisking was elicited by electrical stimulation of the ION, temporarily diminished following hexamethonium injection, abolished by transection of the ION, and rapidly and significantly (Precovery period (indicative of reinnervation), but re-appeared in the resected rats after undergoing ION transection (indicative of motor denervation). Cholinergic, parasympathetic axons traveling within the ION innervate whisker pad vasculature, and immunohistochemistry for vasoactive intestinal peptide revealed these axons branching extensively over whisker pad muscles and contacting neuromuscular junctions after facial nerve resection. This study provides the first behavioral and anatomical evidence of spontaneous autonomic innervation of skeletal muscle after motor nerve lesion, which not only has implications for interpreting facial nerve reinnervation results, but also calls into question whether autonomic-mediated innervation of striated muscle occurs naturally in

  7. Adsorption of benzoxaboroles on hydroxyapatite phases.

    Science.gov (United States)

    Pizzoccaro, Marie-Alix; Nikel, Ondrej; Sene, Saad; Philippe, Coralie; Mutin, P Hubert; Bégu, Sylvie; Vashishth, Deepak; Laurencin, Danielle

    2016-09-01

    Benzoxaboroles are a family of molecules that are finding an increasing number of applications in the biomedical field, particularly as a "privileged scaffold" for the design of new drugs. Here, for the first time, we determine the interaction of these molecules with hydroxyapatites, in view of establishing (i) how benzoxaborole drugs may adsorb onto biological apatites, as this could impact on their bioavailability, and (ii) how apatite-based materials can be used for their formulation. Studies on the adsorption of the benzoxaborole motif (C7H7BO2, referred to as BBzx) on two different apatite phases were thus performed, using a ceramic hydroxyapatite (HAceram) and a nanocrystalline hydroxyapatite (HAnano), the latter having a structure and composition more similar to the one found in bone mineral. In both cases, the grafting kinetics and mechanism were studied, and demonstration of the surface attachment of the benzoxaborole under the form of a tetrahedral benzoxaborolate anion was established using (11)B solid state NMR (including (11)B-(31)P correlation experiments). Irrespective of the apatite used, the grafting density of the benzoxaborolates was found to be low, and more generally, these anions demonstrated a poor affinity for apatite surfaces, notably in comparison with other anions commonly found in biological media, such as carboxylates and (organo)phosphates. The study was then extended to the adsorption of a molecule with antimicrobial and antifungal properties (3-piperazine-bis(benzoxaborole)), showing, on a more general perspective, how hydroxyapatites can be used for the development of novel formulations of benzoxaborole drugs. Benzoxaboroles are an emerging family of molecules which have attracted much attention in the biomedical field, notably for the design of new drugs. However, the way in which these molecules, once introduced in the body, may interact with bone mineral is still unknown, and the possibility of associating benzoxaboroles to

  8. A Calculation of Elastic Flexural Vibrations of Whisker Crystals Irradiated with Nanosecond Electron Beams

    Science.gov (United States)

    Chebodayev, M. I.

    2017-10-01

    Within the framework of the linear thermal elasticity theory a dynamic thermoelastic bending of a whisker crystal is considered under conditions of its irradiation with a high-current electron beam of nanosecond duration. It is shown that the characteristic time of leveling the temperature of superthin pin-type rod nonuniformely heated over its thickness is comparable with the period of the fundamental wave of flexural vibrations. This gives rise to a considerable decrease in the bending amplitude, which is concurrent with the heat conduction processes.

  9. Preparation and characterization of selenite substituted hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jun; Wang, Yanhua; Zhou, Lei [Advance Biomaterials and Tissue Engineering Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang, Shengmin, E-mail: caltary@gmail.com [Advance Biomaterials and Tissue Engineering Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); China-Korea Center for Biomaterials and Nano-biotechnology, Life Science Building, 1037 Luoyu Road, Wuhan 430074 (China)

    2013-01-01

    Selenite-substituted hydroxyapatite (Se-HA) with different Se/P ratios was synthesized by a co-precipitation method, using sodium selenite (Na{sub 2}SeO{sub 3}) as a Se source. Selenium has been incorporated into the hydroxyapatite lattice by partially replacing phosphate (PO{sub 4}{sup 3-}) groups with selenite (SeO{sub 3}{sup 2-}) groups. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) techniques reveal that substitutions of phosphate groups by selenite groups cause lower carbonate groups occupying at phosphate sites and change the lattice parameters of hydroxyapatite. The powders obtained are nano-crystalline hydroxyapatite when the Se/P ratios are not more than 0.1. The particle shape of Se-HA has not been altered compared with selenite-free hydroxyapatite but Se-incorporation reduces the crystallite size. The crystallinity was reduced as the Se/P ratios increased until amorphous phase (Se/P = 0.3) appeared in the Se-HA powder obtained, and then another crystal phase presented as calcium selenite hydrate (Se/P = 10). In addition, the sintering tests show that the Se-HA powders with the Se/P ratio of 0.1 have thermal stability at 900 Degree-Sign C for 2 h; hence they have great potential in the fabrication of bone repair scaffolds. - Highlights: Black-Right-Pointing-Pointer We investigate the Se/P ratio for the synthesis of selenium substituted HA. Black-Right-Pointing-Pointer Nano-crystalline HA structure is remained when Se/P ratio is below 0.1. Black-Right-Pointing-Pointer Calcium selenite hydrate forms when Se/P ratio is beyond 10. Black-Right-Pointing-Pointer Selenite substituted HA powders (Se/P < 0.1) are stable at 900 Degree-Sign C for 2 h.

  10. [Hydroxyapatite for experimental laryngotracheal reconstruction].

    Science.gov (United States)

    Qin, Y; Yu, M; Han, D

    2001-08-01

    The porous hydroxyapatite (HA) tubiform prosthesis was employed for reconstruction of large circumferential defect of the larynx and cervical trachea. The biocompatibility, bioactivity and biofunctionality of the HA prosthesis were evaluated, and the feasibility for laryngotracheal reconstruction was discussed. Twelve healthy canines were used to establish the experimental models, a large portion of cricoid cartilage and upper ten-ring segment of cervical trachea were resected and substituted with a corresponding 5 cm HA prosthesis by end-to-end anastomosis. Six months later, the eight survival canines were sacrificed and the HA prostheses with surrounding tissues were removed. They were observed in decalcified sections by optical microscopy and scanning electron microscopy. Two canines died in the immediate postoperative period with unknown reason and another two deaths were attributed to obstruction caused by the complete dislocation of the HA prostheses owing to rupture of the sutures within three weeks after operation. Eight canines survived up to six months. The implanted HA prostheses were tolerated in all cases without any rejection and dislocation or shift. An excellent airway was obtained and no signs of dyspnea and suffocation were found though there were hypergranulation and scar formation occurred at the site of anastomosis. Morphologic examination revealed that collagen fibers, new vessels and plenty of cells penetrated deeply into the pores of HA, and occupying the outer two third of HA wall. HA prostheses were surrounded by connective tissues and anchored firmly to the neighboring tissues, including the ends of the cricoid and tracheal cartilage by ingrowths of cartilaginous tissue into the macropores of the HA. However, the luminal surface of HA prosthesis was not covered at all section levels by respiratory mucosa. The implantation of the porous HA tubiform prosthesis can maintain the normal respiratory function of the experimental canines, but the

  11. Comparative evaluation of fluoride release from hydroxyapatite incorporated and conventional glass ionomer cement: an in vitro study.

    Science.gov (United States)

    Tiwari, S; Nandlal, B

    2012-01-01

    Glass ionomers are most commonly used esthetic restorative material, but has inferior mechanical properties. The search to improve its mechanical properties led to the use of hydroxyapatite (HA) whiskers as strengthening material for glass ionomer cement but its effect on fluoride release is still not clear. To evaluate and compare the fluoride release from HA incorporated glass ionomer and conventional glass ionomer cement (CGIC). This in vitro study comprised of total forty sample. Twenty Specimens of each HA incorporated glass ionomer and conventional glass ionomer were fabricated. Specimens were suspended individually in 25 mL of distilled water in a 50 mL plastic container and stored at 37°C. Distilled water was renewed every 24 h for 21 days. Fluoride release of sample was measured every 24 h for 7 days and weekly from 7 th day to 21 st day using Sension4 pH/ion selective electrode/mV meter. Descriptive statistics, Repeated Measure analysis of variance, Paired Sample t-test, Independent Sample t-test, scheffe post hoc test. There was a significant decrease in the mean fluoride release from day 1 to day 21 for both the groups hydroxyapatite glass ionomer cement and conventional glass ionomer cement ([HA-GIC] and CGIC). Though, the mean values of HA-GIC were slightly lower than C GIC, there was no statistically significant difference in the mean fluoride release between HA-GIC and CGIC throughout the experimental period. Within the limitations of this experimental design, definitive conclusions cannot be drawn and further investigations at a molecular level are needed to evaluate the trend of fluoride release from this material.

  12. Structural and biological evaluation of lignin addition to simple and silver-doped hydroxyapatite thin films synthesized by matrix-assisted pulsed laser evaporation.

    Science.gov (United States)

    Janković, A; Eraković, S; Ristoscu, C; Mihailescu Serban, N; Duta, L; Visan, A; Stan, G E; Popa, A C; Husanu, M A; Luculescu, C R; Srdić, V V; Janaćković, Dj; Mišković-Stanković, V; Bleotu, C; Chifiriuc, M C; Mihailescu, I N

    2015-01-01

    We report on thin film deposition by matrix-assisted pulsed laser evaporation of simple hydroxyapatite (HA) or silver (Ag) doped HA combined with the natural biopolymer organosolv lignin (Lig) (Ag:HA-Lig). Solid cryogenic target of aqueous dispersions of Ag:HA-Lig composite and its counterpart without silver (HA-Lig) were prepared for evaporation using a KrF* excimer laser source. The expulsed material was assembled onto TiO2/Ti substrata or silicon wafers and subjected to physical-chemical investigations. Smooth, uniform films adherent to substratum were observed. The chemical analyses confirmed the presence of the HA components, but also evidenced traces of Ag and Lig. Deposited HA was Ca deficient, which is indicative of a film with increased solubility. Recorded X-ray Diffraction patterns were characteristic for amorphous films. Lig presence in thin films was undoubtedly proved by both X-ray Photoelectron and Fourier Transform Infra-Red Spectroscopy analyses. The microbiological evaluation showed that the newly assembled surfaces exhibited an inhibitory activity both on the initial steps of biofilm forming, and on mature bacterial and fungal biofilm development. The intensity of the anti-biofilm activity was positively influenced by the presence of the Lig and/or Ag, in the case of Staphylococcus aureus, Pseudomonas aeruginosa and Candida famata biofilms. The obtained surfaces exhibited a low cytotoxicity toward human mesenchymal stem cells, being therefore promising candidates for fabricating implantable biomaterials with increased biocompatibility and resistance to microbial colonization and further biofilm development.

  13. Ferroelectric Polarization in Nanocrystalline Hydroxyapatite Thin Films on Silicon

    Science.gov (United States)

    Lang, S. B.; Tofail, S. A. M.; Kholkin, A. L.; Wojtaś, M.; Gregor, M.; Gandhi, A. A.; Wang, Y.; Bauer, S.; Krause, M.; Plecenik, A.

    2013-01-01

    Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and pyroelectricity. While a spontaneous polarization in hydroxyapatite has been predicted since 2005, the reversibility of this polarization (i.e. ferroelectricity) requires experimental evidence. Here we use piezoresponse force microscopy to demonstrate that nanocrystalline hydroxyapatite indeed exhibits ferroelectricity: a reversal of polarization under an electrical field. This finding will strengthen investigations on the role of electrical polarization in biomineralization and bone-density related diseases. As hydroxyapatite is one of the most common biocompatible materials, our findings will also stimulate systematic exploration of lead and rare-metal free ferroelectric devices for potential applications in areas as diverse as in vivo and ex vivo energy harvesting, biosensing and electronics. PMID:23884324

  14. Zirconia toughened SiC whisker reinforced alumina composites small business innovation research

    Science.gov (United States)

    Loutfy, R. O.; Stuffle, K. L.; Withers, J. C.; Lee, C. T.

    1987-01-01

    The objective of this phase 1 project was to develop a ceramic composite with superior fracture toughness and high strength, based on combining two toughness inducing materials: zirconia for transformation toughening and SiC whiskers for reinforcement, in a controlled microstructure alumina matrix. The controlled matrix microstructure is obtained by controlling the nucleation frequency of the alumina gel with seeds (submicron alpha-alumina). The results demonstrate the technical feasibility of producing superior binary composites (Al2O3-ZrO2) and tertiary composites (Al2O3-ZrO2-SiC). Thirty-two composites were prepared, consolidated, and fracture toughness tested. Statistical analysis of the results showed that: (1) the SiC type is the key statistically significant factor for increased toughness; (2) sol-gel processing with a-alumina seed had a statistically significant effect on increasing toughness of the binary and tertiary composites compared to the corresponding mixed powder processing; and (3) ZrO2 content within the range investigated had a minor effect. Binary composites with an average critical fracture toughness of 6.6MPam sup 1/2, were obtained. Tertiary composites with critical fracture toughness in the range of 9.3 to 10.1 MPam sup 1/2 were obtained. Results indicate that these composites are superior to zirconia toughened alumina and SiC whisker reinforced alumina ceramic composites produced by conventional techniques with similar composition from published data.

  15. Toward "strong" green nanocomposites: polyvinyl alcohol reinforced with extremely oriented cellulose whiskers.

    Science.gov (United States)

    Jalal Uddin, Ahmed; Araki, Jun; Gotoh, Yasuo

    2011-03-14

    To exploit the maximum potential of cellulose whiskers (CWs), we report here for the first time the successful fabrication of nanocomposites reinforced with highly oriented CWs in a polymer matrix. The nanocomposites were prepared using polyvinyl alcohol (PVA) and a colloidal suspension of cotton-derived CWs. The macroscopically homogeneous PVA-CW suspensions were extruded into cold methanol to form gel fibers followed by a hot drawing. Compared to the neat PVA fiber, the as-spun fiber containing a small amount of CWs (5 wt % of solid PVA) showed higher drawability, leading to an extremely high orientation of CWs with the matrix PVA. The stress-transfer mechanism, a prime determining factor for high mechanical properties of nanocomposites, was studied by X-ray diffraction. The stress on the incorporated CWs was monitored by applying an in situ nondestructive load to the composite fibers. The applied stress to the whole sample was found to be effectively transferred to the CWs inside the composites, suggesting strong interfacial bonding between the filler and the matrix. Effective stress transfer to the oriented whiskers resulted in outstanding enhancement in mechanical properties of the nanocomposites.

  16. Mechanical properties and biocompatibility of the sputtered Ti doped hydroxyapatite.

    Science.gov (United States)

    Vladescu, A; Padmanabhan, S C; Ak Azem, F; Braic, M; Titorencu, I; Birlik, I; Morris, M A; Braic, V

    2016-10-01

    The hydroxyapatite enriched with Ti were prepared as possible candidates for biomedical applications especially for implantable devices that are in direct contact to the bone. The hydroxyapatites with different Ti content were prepared by RF magnetron sputtering on Ti-6Al-4V alloy using pure hydroxyapatite and TiO2 targets. The content of Ti was modified by changing the RF power fed on TiO2 target. The XPS and FTIR analyses revealed the presence of hydroxyapatite structure. The hardness and elastic modulus of the hydroxyapatite were increased by Ti addition. After 5 days of culture, the cell viability of the Ti-6Al-4V was enhanced by depositing with undoped or doped hydroxyapatite. The Ti additions led to an increase in cell viability of hydroxyapatite, after 5 days of culture. The electron microscopy showed the presence of more cells on the surface of Ti-enriched hydroxyapatite than those observed on the surface of the uncoated alloys or undoped hydroxyapatite. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Prussian Blue Modified Solid Carbon Nanorod Whisker Paste Composite Electrodes: Evaluation towards the Electroanalytical Sensing of H2O2

    Directory of Open Access Journals (Sweden)

    Carolin Siimenson

    2012-01-01

    Full Text Available Metallic impurity free solid carbon nanorod “Whiskers” (SCNR Whiskers, a derivative of carbon nanotubes, are explored in the fabrication of a Prussian Blue composite electrode and critically evaluated towards the mediated electroanalytical sensing of H2O2. The sensitivity and detection limits for H2O2 on the paste electrodes containing 20% (w/w Prussian Blue, mineral oil, and carbon nanorod whiskers were explored and found to be 120 mA/(M cm2 and 4.1 μM, respectively, over the concentration range 0.01 to 0.10 mM. Charge transfer constant for the 20% Prussian Blue containing SCNR Whiskers paste electrode was calculated, for the reduction of Prussian Blue to Prussian White, to reveal a value of 1.8±0.2 1/s (α=0.43, N=3. Surprisingly, our studies indicate that these metallic impurity-free SCNR Whiskers, in this configuration, behave electrochemically similar to that of an electrode constructed from graphite.

  18. Developing an Empirical Model for Estimating the Probability of Electrical Short Circuits from Tin Whiskers. Part 2

    Science.gov (United States)

    Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Larry L.; Wright, Maria C.

    2009-01-01

    To comply with lead-free legislation, many manufacturers have converted from tin-lead to pure tin finishes of electronic components. However, pure tin finishes have a greater propensity to grow tin whiskers than tin-lead finishes. Since tin whiskers present an electrical short circuit hazard in electronic components, simulations have been developed to quantify the risk of said short circuits occurring. Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that had an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish.

  19. Hydroxyapatite Fibers: A Review of Synthesis Methods

    Science.gov (United States)

    Qi, Mei-Li; He, Kun; Huang, Zhen-Nan; Shahbazian-Yassar, Reza; Xiao, Gui-Yong; Lu, Yu-Peng; Shokuhfar, Tolou

    2017-08-01

    Hydroxyapatite (HA) exhibits excellent biocompatibility, bioactivity, osteoconductivity, non-toxicity and so on, making it a perfect candidate for biomedical applications. However, HA is not qualified to be used in load-bearing sites due to its poor flexural strength and fracture toughness. Design, synthesis and application of fibrous HA is a promising strategy to overcome the inherent brittleness. This review provides a brief description of HA and hydroxyapatite fiber (HAF), then introduces different synthesis methods of HAF and highlights the inherent merits and drawbacks involved in each method. Finally, the future perspectives in this active research area are given. The purpose of this review is to acquaint the reader with this promising new field of biomaterials research and with emphasis on recent techniques to obtain continuous, uniform and long HAF.

  20. Biomineralization of nanoscale single crystal hydroxyapatite.

    Science.gov (United States)

    Omokanwaye, Tiffany; Wilson, Otto C; Gugssa, Ayelle; Anderson, Winston

    2015-11-01

    The chemical and physical characteristics of nanocrystalline hydroxyapatite particles which formed during the subcutaneous implantation of crab shell in Sprague-Dawley rats were studied using selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The initial SAED characterization evidence indicated the presence of an amorphous calcium phosphate phase. The electron dense nanophase particles which formed in the wound healing zone displayed broad diffuse rings which usually indicate a low crystalline order or amorphous phase. High resolution transmission electron microscopy (HRTEM) revealed that these mineralized regions contained discrete single crystal particles less than 5nm in size. Micrographs taken at successively higher magnifications revealed very small nanoparticles with a hexagonal arrangement of ion channels with characteristic spacing of 0.54nm and 0.23nm. This study revealed that single crystal hydroxyapatite nanoparticles consisting of only a few unit cells formed via a biomineralization directed process. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Evolving application of biomimetic nanostructured hydroxyapatite

    Directory of Open Access Journals (Sweden)

    Norberto Roveri

    2010-11-01

    Full Text Available Norberto Roveri, Michele IafiscoLaboratory of Environmental and Biological Structural Chemistry (LEBSC, Dipartimento di Chimica ‘G. Ciamician’, Alma Mater Studiorum, Università di Bologna, Bologna, ItalyAbstract: By mimicking Nature, we can design and synthesize inorganic smart materials that are reactive to biological tissues. These smart materials can be utilized to design innovative third-generation biomaterials, which are able to not only optimize their interaction with biological tissues and environment, but also mimic biogenic materials in their functionalities. The biomedical applications involve increasing the biomimetic levels from chemical composition, structural organization, morphology, mechanical behavior, nanostructure, and bulk and surface chemical–physical properties until the surface becomes bioreactive and stimulates cellular materials. The chemical–physical characteristics of biogenic hydroxyapatites from bone and tooth have been described, in order to point out the elective sides, which are important to reproduce the design of a new biomimetic synthetic hydroxyapatite. This review outlines the evolving applications of biomimetic synthetic calcium phosphates, details the main characteristics of bone and tooth, where the calcium phosphates are present, and discusses the chemical–physical characteristics of biomimetic calcium phosphates, methods of synthesizing them, and some of their biomedical applications.Keywords: hydroxyapatite, nanocrystals, biomimetism, biomaterials, drug delivery, remineralization

  2. Biomineralization of nanoscale single crystal hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Omokanwaye, Tiffany [Catholic University of America, BONE/CRAB Lab, Department of Biomedical Engineering, Washington, DC 20064 (United States); Wilson, Otto C., E-mail: wilsono@cua.edu [Catholic University of America, BONE/CRAB Lab, Department of Biomedical Engineering, Washington, DC 20064 (United States); Gugssa, Ayelle; Anderson, Winston [Howard University, Department of Biology, Washington, DC (United States)

    2015-11-01

    The chemical and physical characteristics of nanocrystalline hydroxyapatite particles which formed during the subcutaneous implantation of crab shell in Sprague–Dawley rats were studied using selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The initial SAED characterization evidence indicated the presence of an amorphous calcium phosphate phase. The electron dense nanophase particles which formed in the wound healing zone displayed broad diffuse rings which usually indicate a low crystalline order or amorphous phase. High resolution transmission electron microscopy (HRTEM) revealed that these mineralized regions contained discrete single crystal particles less than 5 nm in size. Micrographs taken at successively higher magnifications revealed very small nanoparticles with a hexagonal arrangement of ion channels with characteristic spacing of 0.54 nm and 0.23 nm. This study revealed that single crystal hydroxyapatite nanoparticles consisting of only a few unit cells formed via a biomineralization directed process. - Highlights: • Nanocrystalline particles were formed during in vivo implantation of crab shell using a rat model. • High resolution TEM revealed that nanoparticles were single crystals and less than 5 nm in size. • The relative distance between spots matches the expected values for hydroxyapatite.

  3. Synthesis, Electromagnetic and Wave-Absorbing Properties of a FeNi Alloy Nano-Whisker/Particle Mixture

    Science.gov (United States)

    Zhou, Jia; Zhu, Zheng-Hou; Xiong, Chao

    2017-11-01

    A Fe20Ni80 alloy nano-whisker/particle mixture was synthesized by a hydrazine hydrate reduction method at 60°C. Electromagnetic parameters of the alloy nano-whisker/particle mixture after a 0.3-T magnetic treatment were measured in the 1.0-8.0 GHz range using an E5063A vector network analyzer. The results showed that the real part (ɛ') of the complex permittivity of the Fe20Ni80 alloy nano-whisker/particle mixture in the 1.0-8.0 GHz range was between 23 and 18, and the imaginary part (ɛ″) was approximately 4. The real part (μ') of the complex permeability in 1.0-5.0 GHz range decreased greatly with increasing frequency, from a maximum of 2.5 to a minimum of 1. The imaginary part (μ″) presented a parabolic shape change; when the frequency was 4.0 GHz, there was a maximum of 1.5. After the 0.3-T magnetic treatment, both the real part (ɛ') and the imaginary part (ɛ″) of the complex permittivity decreased: the real part (μ') of the complex permeability increased sharply, and the imaginary part (μ″) decreased slightly. The dissipation factor (tgδ) of the Fe20Ni80 alloy nano-whisker/particle mixture in the 4.0-7.0 GHz range was approximately 1.0, which shows it has excellent wave-absorbing properties. The thickness of interference-absorbing was approximately 11 mm at 1.0 GHz; it decreased with increasing frequency. The thickness of interference-absorbing was 2.5-2 mm in the 4.0-8.0 GHz range, which shows that the Fe20Ni80 alloy nano-whisker/particle mixture has good interference-absorbing properties when the thickness is 2 mm.

  4. Synthesis, Electromagnetic and Wave-Absorbing Properties of a FeNi Alloy Nano-Whisker/Particle Mixture

    Science.gov (United States)

    Zhou, Jia; Zhu, Zheng-Hou; Xiong, Chao

    2018-02-01

    A Fe20Ni80 alloy nano-whisker/particle mixture was synthesized by a hydrazine hydrate reduction method at 60°C. Electromagnetic parameters of the alloy nano-whisker/particle mixture after a 0.3-T magnetic treatment were measured in the 1.0-8.0 GHz range using an E5063A vector network analyzer. The results showed that the real part ( ɛ') of the complex permittivity of the Fe20Ni80 alloy nano-whisker/particle mixture in the 1.0-8.0 GHz range was between 23 and 18, and the imaginary part ( ɛ″) was approximately 4. The real part ( μ') of the complex permeability in 1.0-5.0 GHz range decreased greatly with increasing frequency, from a maximum of 2.5 to a minimum of 1. The imaginary part ( μ″) presented a parabolic shape change; when the frequency was 4.0 GHz, there was a maximum of 1.5. After the 0.3-T magnetic treatment, both the real part ( ɛ') and the imaginary part ( ɛ″) of the complex permittivity decreased: the real part ( μ') of the complex permeability increased sharply, and the imaginary part ( μ″) decreased slightly. The dissipation factor ( tgδ) of the Fe20Ni80 alloy nano-whisker/particle mixture in the 4.0-7.0 GHz range was approximately 1.0, which shows it has excellent wave-absorbing properties. The thickness of interference-absorbing was approximately 11 mm at 1.0 GHz; it decreased with increasing frequency. The thickness of interference-absorbing was 2.5-2 mm in the 4.0-8.0 GHz range, which shows that the Fe20Ni80 alloy nano-whisker/particle mixture has good interference-absorbing properties when the thickness is 2 mm.

  5. Response properties of whisker-associated primary afferent neurons following infraorbital nerve transection with microsurgical repair in adult rats.

    Science.gov (United States)

    Xiao, Bo; Zanoun, Rami R; Carvell, George E; Simons, Daniel J; Washington, Kia M

    2016-03-01

    The rodent whisker/trigeminal system, characterized by high spatial and temporal resolution, provides an experimental model for developing new therapies for improving sensory functions of damaged peripheral nerves. Here, we use controlled whisker stimulation and single-unit recordings of trigeminal ganglion cells to examine in detail the nature and time course of functional recovery of mechanoreceptive afferents following nerve transection with microsurgical repair of the infraorbital nerve (ION) branch of the trigeminal nerve in adult rats. Response measures include rapid vs. slow adaptation, firing rate, interspike intervals, latency, and angular (directional) tuning. Whisker-evoked responses, readily observable by 3 wk post-transection, recover progressively for at least the next 5 wk. All cells in transected animals, as in control cases, responded to deflections of single whiskers only, but topography within the ganglion was clearly disrupted. The time course and extent of recovery of quantitative response measures were receptor dependent. Cells displaying slowly adapting (SA) properties recovered more quickly than rapidly adapting (RA) populations, and for some response measures-notably evoked firing rates-closely approached or attained control levels by 8 wk post-transection. Angular tuning of RA cells was slightly better than control units, whereas SA tuning did not differ from control values. Nerve conduction times and refractory periods, examined separately using electrical stimulation of the ION, were slower than normal in all transected animals and poorly reflected recovery of whisker-evoked response latencies and interspike intervals. Results underscore the need for multiple therapeutic strategies that target different aspects of functional restitution following peripheral nerve injury. Copyright © 2016 the American Physiological Society.

  6. Complications associated with pegging hydroxyapatite orbital implants.

    Science.gov (United States)

    Jordan, D R; Chan, S; Mawn, L; Gilberg, S; Dean, T; Brownstein, S; Hill, V E

    1999-03-01

    Prior studies of hydroxyapatite orbital implant complications have primarily focused on complications of the implant itself with only occasional mention of the complications associated with the peg system. This in part may be because of a low rate of pegging and, thus, a small sample size to evaluate. Therefore, a full range of complications that can occur with pegging has not been presented. The objective of this study was to determine the complications associated with pegging and to discuss ways to manage them. Retrospective, noncomparative case series. The authors analyzed all of the complications associated with pegging 165 of a possible 275 hydroxyapatite implants implanted by 2 surgeons over 7 years. The following data were recorded: type of surgery performed, size of implant used, type of hydroxyapatite used, peg system used, time of pegging, follow-up duration, problems encountered, and treatment. Sixty-two (37.5%) of the 165 patients who had pegged implants were found to have problems with their pegs. Twenty-one (33.8%) of the 62 patients with peg problems had more than 1 peg-related problem. Complications associated with pegging included discharge (37%; 23 of 62), pyogenic granulomas (30.6%; 19 of 62), peg falling out (29%; 18 of 62), poor transfer of movement (11.2%; 7 of 62), clicking (11.2%; 7 of 62), conjunctiva overgrowing peg (4.8%; 3 of 62), poor-fitting sleeve (4.8%; 3 of 62), part of sleeve shaft visible (4.8%; 3 of 62), peg drilled on an angle (4.8%; 3 of 62), hydroxyapatite visible around peg hole (3.2%; 2 of 62), peg drilled off-center (3.2%; 2 of 62), popping peg (3.2%; 2 of 62), and excess movement of peg (3.2%; 2 of 62). The most serious complication occurring in two individuals (3.2%) was implant infection requiring implant removal. There are several potential complications that can occur after pegging the hydroxyapatite implant. These problems are generally of a minor nature but often require additional patient visits that would not

  7. Hydroxyapatite does not improve the outcome of a bipolar hemiarthroplasty.

    NARCIS (Netherlands)

    Meijerink, H.J.; Gardeniers, J.W.M.; Buma, P.; Lemmens, J.A.M.; Schreurs, B.W.

    2004-01-01

    In a one-surgeon study the clinical and radiographic results of 30 cementless bipolar hip prostheses in 24 patients younger than 55 years were evaluated. Eleven noncoated prostheses (Noncoated Group) and 19 hydroxyapatite-coated prostheses (Hydroxyapatite Group) were compared after a mean followup

  8. Hydroxyapatite-coated uncemented implants and peri-implant infection

    NARCIS (Netherlands)

    Oosterbos, Cornelis Johannes Maria

    2004-01-01

    One of the major complications of joint replacement surgery is a peri-implant infection. A hip prosthesis coated with hydroxyapatite, a calcium phosphate (found in human bone), may offer protection in this respect. In a series of patients who were treated with a hydroxyapatite-coated hip prosthesis

  9. In vitro corrosion investigations of plasma-sprayed hydroxyapatite ...

    Indian Academy of Sciences (India)

    The present paper discusses various issues associated with biological corrosion of uncoated and plasma-sprayed hydroxyapatite (HA)-coated 316L SS and studies the effect of contents of calcium phosphate (CaP) on corrosion behaviour of hydroxyapatite (HA) coatings in simulated body fluid (Ringer's solution).

  10. Development of hydroxyapatite bone cement for controlled drug ...

    Indian Academy of Sciences (India)

    The purpose of this work was to study the preparation and characterization of drug–hydroxyapatite cement. The hydroxyapatite (HA) cement has been synthesized by using tricalcium phosphate, calcium carbonate and dicalcium phosphate anhydrous with sodium hydrogen phosphate as liquid phase. The effect of added ...

  11. Fine structure study on low concentration zinc substituted hydroxyapatite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Wei [Advanced Biomaterials and Tissue Engineering Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Ma, Jun, E-mail: caltary@gmail.com [Advanced Biomaterials and Tissue Engineering Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wang, Jianglin [Advanced Biomaterials and Tissue Engineering Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang, Shengmin, E-mail: smzhang@mail.hust.edu.cn [Advanced Biomaterials and Tissue Engineering Center, Huazhong University of Science and Technology, Wuhan 430074 (China); China-Korea Center for Biomaterials and Nano-biotechnology, Life Science Building, 1037 Luoyu Road, Wuhan 430074 (China); Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2012-12-01

    The fine structure of zinc substituted hydroxyapatite was studied using experimental analysis and first-principles calculations. The synthetic hydroxyapatite nanoparticles containing low Zn concentration show rod-like morphology. The crystallite sizes and unit-cell volumes tended to decrease with the increased Zn concentration according to X-ray diffraction patterns. The Zn K-edge X-ray absorption spectra and fitting results suggest that the hydroxyapatite doped with 0.1 mole% zinc is different in the zinc coordination environments compared with that containing more zinc. The density function theory calculations were performed on zinc substituted hydroxyapatite. Two mechanisms included replacing calcium by zinc and inserting zinc along the hydroxyl column and were investigated, and the related substitution energies were calculated separately. It is found that the substitution energies are negative and lowest for inserting zinc between the two oxygen atoms along the hydroxyl column (c-axis). Combined with the spectral analysis, it is suggested that the inserting mechanism is favored for low concentration zinc substituted hydroxyapatite. Highlights: Black-Right-Pointing-Pointer We investigate the fine structure of hydroxyapatite with low content of Zn. Black-Right-Pointing-Pointer XANES spectra are similar but a little different at low zinc content. Black-Right-Pointing-Pointer Zinc ions influence hydroxyapatite crystal formation and lattice parameters. Black-Right-Pointing-Pointer Formation energies are calculated according to plane-wave density function theory. Black-Right-Pointing-Pointer Low content of zinc prefers to locate at hydroxyl column in hydroxyapatite lattice.

  12. In vitro corrosion investigations of plasma-sprayed hydroxyapatite ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. The present paper discusses various issues associated with biological corrosion of uncoated and plasma-sprayed hydroxyapatite (HA)-coated 316L SS and studies the effect of contents of calcium phosphate. (CaP) on corrosion behaviour of hydroxyapatite (HA) coatings in simulated body fluid (Ringer's solution).

  13. MICROSCOPIC ASPECT AND MECHANICS OF CREEP-FATIGUE FAILURE IN SiC WHISKER REINFORCED ALUMINUM BASE COMPOSITE AT HIGH TEMPERATURE

    National Research Council Canada - National Science Library

    OKAZAKI, Masakazu; TASHIRO, Hiromichi; MIZUTANI, Junnosuke

    1997-01-01

    The microscopic aspect of creep-fatigue failure process in a 6061 aluminum alloy composite reinforced with SiC whiskers, SiCw/6061, was studied at high temperature, with specific attention being paid...

  14. Macroscopic quantum coherence in charge density wave whisker NbSe{sub 3} under strain

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, P.; Chen, Z.J.; Jiang, Q.; Jin, D. [Physics Institute, Laboratory of Ultra-Low Temperature Physics, Chinese Academy of Sciences, Beijing (China)

    2000-07-03

    The magnetoresistance oscillation of the charge density wave (CDW) material NbSe{sub 3} whisker has been studied under strain at different temperatures (4.2 K, 30 K, 40 K). With a constant measuring current, the magnetoresistance (MR) curves oscillate at 30 K while they are smooth at 4.2 K and become a series of zigzag curves at 40 K. These oscillation periods are {delta}H, rather than {delta}(1/H ). It is found that either increasing the temperature to 40 K, or straining the sample to a displacement as large as {epsilon}=3.1%, makes the regular oscillations disappear. By analysing the data, we found our results can be interpreted as the quantum coherence effect of a moving CDW. (author)

  15. The posterior parietal cortex as integrative hub for whisker sensorimotor information.

    Science.gov (United States)

    Mohan, Hemanth; de Haan, Roel; Mansvelder, Huibert D; de Kock, Christiaan P J

    2018-01-01

    Our daily life consists of a continuous interplay between incoming sensory information and outgoing motor plans. Particularly during goal-directed behavior and active exploration of the sensory environment, brain circuits are merging sensory and motor signals. This is referred to as sensorimotor integration and is relevant for locomotion, vision or tactile exploration. The somatosensory (tactile) system is an attractive modality to study sensorimotor integration in health and disease, motivated by the need for revolutionary technology that builds upon conceptual understanding of sensorimotor integration, such as brain-machine-interfaces and neuro-prosthetics. In this perspective, we focus on the rat whisker system and put forward the posterior parietal cortex as a potential circuit where sensorimotor integration could occur during active somatosensation. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  16. Whisker: a client-server high-performance multimedia research control system.

    Science.gov (United States)

    Cardinal, Rudolf N; Aitken, Michael R F

    2010-11-01

    We describe an original client-server approach to behavioral research control and the Whisker system, a specific implementation of this design. The server process controls several types of hardware, including digital input/output devices, multiple graphical monitors and touchscreens, keyboards, mice, and sound cards. It provides a way to access this hardware for client programs, communicating with them via a simple text-based network protocol based on the standard Internet protocol. Clients to implement behavioral tasks may be written in any network-capable programming language. Applications to date have been in experimental psychology and behavioral and cognitive neuroscience, using rodents, humans, nonhuman primates, dogs, pigs, and birds. This system is flexible and reliable, although there are potential disadvantages in terms of complexity. Its design, features, and performance are described.

  17. Study on the mechanism of surface modification of magnesium oxysulfate whisker

    Energy Technology Data Exchange (ETDEWEB)

    Dang, Li [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Nai, Xueying; Zhu, Donghai [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008 (China); Jing, Yanwei [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Xin; Dong, Yaping [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008 (China); Li, Wu, E-mail: driverlaoli@163.com [Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008 (China)

    2014-10-30

    Graphical abstract: - Highlights: • Physisorbed lauric acid was ruled out by FT-IR spectroscopy. • The inexistence of physisorbed magnesium laurate was proved by DSC analyses. • {sup 13}C NMR further verified the formation of COO–Mg< bonds on the surface of MOSw. • “Acid-base neutralization” was proved by the pH meter monitoring synchronously. • The type of surface modification of MOSw was proved to be chemical adsorption only. - Abstract: Hydrophobic-lipophilic magnesium oxysulfate whisker (MOSw) was prepared by surface modification with lauric acid and the surface morphology of MOSw was examined with field emission scanning electron microscope (FESEM). X-ray powder diffraction (XRD) was used to characterize the crystalline degree of MOSw and modified MOSw (MOSw-LA). Both FESEM and XRD suggested that modification occurred on the surface of MOSw exclusively. The inexistence of physisorbed lauric acid was proved by Fouier transform infrared (FT-IR) spectroscopy. Thermogravimetric analyses ruled out the possibility that magnesium laurate (LA-Mg) physisorbed on the surface of MOSw-LA. Solid state {sup 13}C nuclear magnetic resonance ({sup 13}C NMR) further verified the formation of COO–Mg< bonds based on the significant changes of chemical shift and decrease in intensity. Hence, we confirmed that the type of surface modification of MOSw with lauric acid was chemical adsorption taken place between lauric acid and Mg<. In order to study the dynamic state approach of this reaction, a pH meter was employed to monitor the reaction process synchronously, and then we proposed a reaction mechanism which was similar to the “acid-base neutralization”. This research provides a detailed explanation for a kind of surface modification, which may be further used in the performance of whisker/polymer matrix composites.

  18. Polishing and whitening properties of toothpaste containing hydroxyapatite.

    Science.gov (United States)

    Niwa, M; Sato, T; Li, W; Aoki, H; Aoki, H; Daisaku, T

    2001-03-01

    Toothpastes containing hydroxyapatite (HA-toothpaste) have demonstrated efficacy in preventing caries, treating hypersensitivity and curing periodontal diseases, however, their effects on whitening teeth have not been investigated. In this study, the polishing and whitening properties of hydroxyapatite contained toothpastes were evaluated in a combined experimental and clinical study. The polishing properties were evaluated in artificial teeth by polishing with different toothpastes, while the brightening and whitening properties were examined in volunteers using two colorimeters with two specially made fiberscopes. The results revealed that the addition of hydroxyapatite to toothpaste did not alter its polishing properties, while it did result in a marked increase in tooth-whiting. It was also found that the brightening and whitening properties increased as the amount of hydroxyapatite in the toothpaste increased. It is concluded that toothpaste containing hydroxyapatite are effective at whitening tooth and that whitening was not due to their polishing effect on tooth surface. Copyright 2001 Kluwer Academic Publishers

  19. Synthesis of nanocrystalline hydroxyapatite by using precipitation method

    Energy Technology Data Exchange (ETDEWEB)

    Mobasherpour, I. [Ceramics Department, Materials and Energy Research Center, P.O. Box 31787-316, Tehran (Iran, Islamic Republic of)]. E-mail: I_Mabasherpour@merc.ac.ir; Heshajin, M. Soulati [Biomaterials Engineering Department, Amir Kabir University of Tehran, Tehran (Iran, Islamic Republic of); Kazemzadeh, A. [Ceramics Department, Materials and Energy Research Center, P.O. Box 31787-316, Tehran (Iran, Islamic Republic of); Zakeri, M. [Materials Engineering Department, Islamic Azad University of Saveh, Saveh (Iran, Islamic Republic of)

    2007-03-14

    In this investigation, hydroxyapatite powder has been synthesized from the calcium nitrate hydrated and di-ammonium hydrogen phosphate solution by precipitation method and heat treatment of hydroxyapatite powders. In order to study the structural evolution, the Fourier transform infrared spectroscopy (FTIR), the X-ray diffraction (XRD) and simultaneous thermal analysis (STA) were used. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to estimate the particle size of the powder and observe the morphology and agglomeration state of the powder. Results show that hydroxyapatite nanocrystalline can successfully be produced by precipitation technique from raw materials. Hydroxyapatite grain gradually increased in size when temperature increased from 100 to 1200 {sup o}C, and the hydroxyapatite hexagonal-dipyramidal phase was not transformed to the other calcium phosphates phases up to 1200 {sup o}C.

  20. Hydroxyapatite nanoparticles: electrospinning and calcination of hydroxyapatite/polyvinyl butyral nanofibers and growth kinetics

    NARCIS (Netherlands)

    Zakaria, S.M.; Zein, S.H. Sharif; Othman, M.R.; Jansen, J.A.

    2013-01-01

    Electrospinning of hydroxyapatite (HA)/polyvinyl butyral solution resulted in the formation of fibers with average diameter of 937-1440 nm. These fibers were converted into HA nanoparticles with size <100 nm after undergoing calcination treatment at 600 degrees C. The diameter of the fiber was

  1. Synergistically toughening effect of SiC whiskers and nanoparticles in Al2O3-based composite ceramic cutting tool material

    Science.gov (United States)

    Liu, Xuefei; Liu, Hanlian; Huang, Chuanzhen; Wang, Limei; Zou, Bin; Zhao, Bin

    2016-09-01

    In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiCnp advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vol% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730±95 MPa and fracture toughness is 5.6±0.6 MPa·m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.

  2. Unusual facet cyst containing struvite and hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Grantham, M.; Richmond, B. [Dept. of Musculoskeletal Radiology, Cleveland Clinic Foundation, OH (United States)

    2001-01-01

    This case report describes a patient with severe back pain and radiculopathy. She was found to have a facet cyst within the lumbar spine that appeared to contain calcium on MRI and CT. Upon aspiration the cyst was found to contain calcium ammonium phosphate (struvite) and calcium phosphate (hydroxyapatite). Ammonia production in the presence of urease-producing bacteria is responsible for the production of struvite in the human body. We postulate that there was a prior infection of the facet with urease-producing bacteria, thus accounting for the production of the struvite within the facet cyst. (orig.)

  3. Sterilisation effect study on granular hydroxyapatite (HA).

    Science.gov (United States)

    Saidu, M F; Mashita, M; Khadijah, K; Fazan, F; Khalid, K A

    2004-05-01

    Hydroxyapatite is a calcium phosphate bioceramic that has been shown by many authors to be biocompatible with bioactive properties. It is widely accepted as the best synthetic material available for surgical use as a bone graft substitute. HA granules produced by AMREC-SIRIM from local materials underwent 5 types of sterilisation techniques with different ageing periods. Samples were tested for chemical and phase composition and microbial contamination before and after being sterilised. From the microbiological tests done, none of the unsterilised positive control yielded a positive culture. Results from X-Ray diffraction studies found that all the sterilisation techniques did not chemically degrade or structurally change the HA granules significantly.

  4. Synthesis of hydroxyapatite from biogenic wastes

    Directory of Open Access Journals (Sweden)

    Teerawat Laonapakul

    2015-09-01

    Full Text Available Hydroxyapatite (HAp is a major component of human bone, teeth and hard tissue. It is one of only a few bioactive materials. Since HAp is the most widely used ceramic biomaterial, various techniques have been developed to synthesize HAp. In recent years, the use of natural biogenic structures and materials for medical proposes has been motivated by limitations in producing synthetic materials. This article mainly focuses on the use of biogenic wastes to prepare HAp. These include bio-wastes, marine corals, eggshells, seashells and bio-membranes. In the present review, useful information about HAp preparation methodologies has been summarized for further research and development.

  5. Bi-2212 and Y123 highly curved single-crystal-like objects: whiskers, bows and ring-like structures

    Science.gov (United States)

    Badica, Petre; Agostino, Angelo; Mizanur Rahman Khan, Mohammad; Cagliero, Stefano; Plapcianu, Carmen; Pastero, Linda; Truccato, Marco; Hayasaka, Yuichiro; Jakob, Gerhard

    2012-10-01

    High-temperature superconducting objects of Bi2Sr2CaCu2O8 and Y Ba2Cu3O7 highly curved in the ab-plane, such as curved/kinked whiskers, bows and ring-like structures, were obtained within a solid-liquid-solid (SLS) grass-like growth mechanism. As-grown objects are crystals with three-dimensional epitaxy similar to conventional single crystals: they can be viewed as crystal parts ‘cut’ from a conventional rectangular crystal. Between our curved objects and conventional crystals, whiskers or thin films there are some differences in the superconducting properties induced only by the shape factors and no new physics is observed. Some details of the growth mechanism are discussed, emphasizing curved-line formation.

  6. Study of hydroxyapatite behaviour during sintering of 316L steel

    Directory of Open Access Journals (Sweden)

    A. Szewczyk-Nykiel

    2010-07-01

    Full Text Available 316L stainless steel – hydroxyapatite composite biomaterials with different hydroxyapatite weight fraction in the composite wereinvestigated. Hydroxyapatite (HAp – Ca10(PO46(OH2 is well known biomaterial. HAp reveals excellent chemical and biological affinitywith bony tissues. On the other hand hydroxyapatite shows low mechanical properties. The combination of very good biocompatibility of hydroxyapatite and high mechanical properties of stainless steel seems to be a good solution. In presented research natural originhydroxyapatite and 316L austenitic stainless steel were used. In this work, metal-ceramics composites were fabricated by the powdermetallurgy technology (involving pressing and sintering process. Sintering was carried out at 1250oC in hydrogen atmosphere. Thedensity, porosity and hardness were investigated. Metallographic microscope and SEM were carried out in order to investigate themicrostructure. The horizontal NETZSCH DIL 402E dilatometer was used to evaluate the dimensional changes and phenomena occurringduring sintering. The research displayed that physical properties of sintered 316L-HAp composites decrease with increase ofhydroxyapatite content. Microstructure of investigated composites consists of austenitic and probably inclusions of hydroxyapatite andheterogeneous eutectic occurring on the grain boundaries. It was shown that amount of hydroxyapatite in the powder mixtures influencethe dimensional changes occurring during sintering.

  7. Hydroxyapatite-silver nanoparticles coatings on porous polyurethane scaffold.

    Science.gov (United States)

    Ciobanu, Gabriela; Ilisei, Simona; Luca, Constantin

    2014-02-01

    The present paper is focused on a study regarding the possibility of obtaining hydroxyapatite-silver nanoparticle coatings on porous polyurethane scaffold. The method applied is based on a combined strategy involving hydroxyapatite biomimetic deposition on polyurethane surface using a Supersaturated Calcification Solution (SCS), combined with silver ions reduction and in-situ crystallization processes on hydroxyapatite-polyurethane surface by sample immersing in AgNO3 solution. The morphology, composition and phase structure of the prepared samples were characterized by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements. The data obtained show that a layer of hydroxyapatite was deposited on porous polyurethane support and the silver nanoparticles (average size 34.71 nm) were dispersed among and even on the hydroxyapatite crystals. Hydroxyapatite/polyurethane surface acts as a reducer and a stabilizing agent for silver ions. The surface plasmon resonance peak in UV-Vis absorption spectra showed an absorption maximum at 415 nm, indicating formation of silver nanoparticles. The hydroxyapatite-silver polyurethane scaffolds were tested against Staphylococcus aureus and Escherichia coli and the obtained data were indicative of good antibacterial properties of the materials. © 2013.

  8. Electrochemical Processes for the Formation of Hydroxyapatite Powders

    Directory of Open Access Journals (Sweden)

    Adrian Nur

    2014-10-01

    Full Text Available Electrochemical synthesis of hydroxyapatite particles was performed from a homogeneous solution of Na2H2EDTA.2H2O, KH2PO4 and CaCl2 without stirring to investigate the mechanism of hydroxyapa-tite formation. We found that OH- ions generated by water reduction at the cathode play an important role in the formation of hydroxyapatite particles. The OH- ions induce the liberation of Ca2+ ions and the dissociation of phosphoric acid, which serve as the reactants for the formation of hydroxyapatite particles. Two layers with a clear boundary were formed during electrolysis. The upper layer comprises the produced particles and the lower layer is a homogeneous solution. The produced particles were held in the region between the electrodes mainly due to the electrostatic interactions of charged particles in an electric field. The hydroxyapatite particles are agglomerates consisting of spherical particles. Aging the suspension for 24 h after electrolysis leads to the transformation of hydroxyapatite to brushite. Thus, if producing hydroxyapatite is desired, the particles should be continuously removed from the system. This method appears to be promising as a continuous process to produce hydroxyapatite parti-cles using an electrochemical method. © 2014 BCREC UNDIP. All rights reservedReceived: 10th April 2014; Revised: 25th May 2014; Accepted: 27th June 2014How to Cite: Nur, A., Setyawan, H., Widjaja, A., Lenggoro, I.W. (2014. Electrochemical Processes for the Formation of Hydroxyapatite Powders. Bulletin of Chemical Reaction Engineering & Catalysis, 9 (3: 168-175. (doi:10.9767/bcrec.9.3.6686.168-175Permalink/DOI: http://dx.doi.org/10.9767/bcrec.9.3.6686.168-175

  9. Whiskers amiss, a new vibrissae and hair mutation near the Krt1 cluster on mouse chromosome 11.

    Science.gov (United States)

    Taylor, L A; Harris, M J; Juriloff, D M

    2000-04-01

    Whiskers amiss (wam) is a new spontaneous recessive mutation in the SELH/Bc strain of mice that causes a phenotype of askew, sometimes kinked or curled, breakable whiskers and disheveled-appearing body hair, apparently owing to disoriented guard hairs. Heterozygotes on three genetic backgrounds are indistinguishable from normal. Using informative SSLPs in the F2 generation after crosses to two normal strains, we have mapped wam to the region of the type I keratin cluster on Chromosome (Chr) 11, within an approximately 6-cM segment according to the current Mouse Genome Database (MGD) map position of flanking SSLPs. Although several other hair mutations also map to the Krt1 region (Re, Rim3, Bdai, Bsk), none has a hair and whisker phenotype similar to that of wam, and, because all are transmitted as dominants, interpretable complementation tests could not be done. Scabbing and tissue loss occur on the rims of the pinnae and tail tip in some aging wam homozygotes, suggesting that wam may be an animal model of a genetic ectodermal disorder. The SELH/Bc strain background appears to have an unusually high rate of spontaneous mutation; wam is the sixth mutation to be described.

  10. Evolving application of biomimetic nanostructured hydroxyapatite.

    Science.gov (United States)

    Roveri, Norberto; Iafisco, Michele

    2010-11-09

    By mimicking Nature, we can design and synthesize inorganic smart materials that are reactive to biological tissues. These smart materials can be utilized to design innovative third-generation biomaterials, which are able to not only optimize their interaction with biological tissues and environment, but also mimic biogenic materials in their functionalities. The biomedical applications involve increasing the biomimetic levels from chemical composition, structural organization, morphology, mechanical behavior, nanostructure, and bulk and surface chemical-physical properties until the surface becomes bioreactive and stimulates cellular materials. The chemical-physical characteristics of biogenic hydroxyapatites from bone and tooth have been described, in order to point out the elective sides, which are important to reproduce the design of a new biomimetic synthetic hydroxyapatite. This review outlines the evolving applications of biomimetic synthetic calcium phosphates, details the main characteristics of bone and tooth, where the calcium phosphates are present, and discusses the chemical-physical characteristics of biomimetic calcium phosphates, methods of synthesizing them, and some of their biomedical applications.

  11. Histologic analysis of a retrieved hydroxyapatite-coated femoral prosthesis

    DEFF Research Database (Denmark)

    Søballe, K; Gotfredsen, K; Brockstedt-Rasmussen, H

    1991-01-01

    A hydroxyapatite-coated hip hemi-prosthesis was retrieved from a 98-year-old osteoporotic woman 12 weeks after implantation. Histologic analysis revealed bone and fibrous tissue almost evenly distributed around the surface of the implant circumference. Quantitative histologic analysis showed...... that 48% of the hydroxyapatite surface was covered by bone. Fibrous tissue covered 30% of the prosthetic surface, and 20% of the surface had no tissue coverage. Scanning electron microscopy showed direct contact without any clear boundary between the newly formed bone and the hydroxyapatite ceramic....

  12. Cytotoxicity of hydroxyapatite, fluorapatite and fluor-hydroxyapatite: a comparative in vitro study.

    Science.gov (United States)

    Theiszova, M; Jantova, S; Letasiova, S; Palou, M; Cipak, L

    2008-01-01

    The purpose of this study was to evaluate the cytotoxicity of two formulations of hydroxyapatite (HA), namely fluorapatite (FA) and fluor-hydroxyapatite (FHA). HA is used as carrier material for antibiotics or anticancer drugs during treatment of bone metastasis. Negative control, represented by HA, was included for comparative purposes. Leukemia cells were used as a model cell line, and the effect of eluates of tested biomaterials on cell proliferation/viability and mechanism of antiproliferative activity were assessed. Study design attempted to reveal the toxicity of tested biomaterials with an emphasis to decide if tested biomaterials have promise for further studies in vivo. Results showed that eluates of FA and FHA inhibit the growth of leukemia cells and induce programmed cell death through mitochondrial/caspase-9/caspase-3-dependent pathway. Due to these differences compare to HA, it is concluded that FA and FHA have promise for evaluation of their behaviour in vivo.

  13. Carbonate Hydroxyapatite and Silicon-Substituted Carbonate Hydroxyapatite: Synthesis, Mechanical Properties, and Solubility Evaluations

    Directory of Open Access Journals (Sweden)

    L. T. Bang

    2014-01-01

    Full Text Available The present study investigates the chemical composition, solubility, and physical and mechanical properties of carbonate hydroxyapatite (CO3Ap and silicon-substituted carbonate hydroxyapatite (Si-CO3Ap which have been prepared by a simple precipitation method. X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, X-ray fluorescence (XRF spectroscopy, and inductively coupled plasma (ICP techniques were used to characterize the formation of CO3Ap and Si-CO3Ap. The results revealed that the silicate (SiO44- and carbonate (CO32- ions competed to occupy the phosphate (PO43- site and also entered simultaneously into the hydroxyapatite structure. The Si-substituted CO3Ap reduced the powder crystallinity and promoted ion release which resulted in a better solubility compared to that of Si-free CO3Ap. The mean particle size of Si-CO3Ap was much finer than that of CO3Ap. At 750°C heat-treatment temperature, the diametral tensile strengths (DTS of Si-CO3Ap and CO3Ap were about 10.8±0.3 and 11.8±0.4 MPa, respectively.

  14. Macroporous hydroxyapatite bioceramics by solid freeform fabrication: towards custom implants

    CSIR Research Space (South Africa)

    Richter, PW

    1999-08-01

    Full Text Available structure that would be impossible to make by conventional manufacturing methods. Application of this technology to the manufacture of macro porous hydroxyapatite bio ceramics for bone substitute applications is discussed. A new design is described...

  15. Physical characterization of hydroxyapatite porous scaffolds for tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, S., E-mail: smsilva@ineb.up.pt [INEB - Instituto de Engenharia Biomedica, Divisao de Biomateriais, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto (Portugal); Universidade do Porto, Faculdade de Engenharia, Departamento de Engenharia Metalurgica e Materiais, Porto (Portugal); Rodriguez, M.A.; Pena, P.; De Aza, A.H.; De Aza, S. [Instituto de Ceramica y Vidrio, CSIC, 28049-Cantoblanco, Madrid (Spain); Ferraz, M.P. [INEB - Instituto de Engenharia Biomedica, Divisao de Biomateriais, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto (Portugal); Faculdade de Ciencias da Saude da Universidade Fernando Pessoa, Rua Carlos da Maia, 296, 4200-150 Porto (Portugal); Monteiro, F.J. [INEB - Instituto de Engenharia Biomedica, Divisao de Biomateriais, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto (Portugal); Universidade do Porto, Faculdade de Engenharia, Departamento de Engenharia Metalurgica e Materiais, Porto (Portugal)

    2009-06-01

    The present study refers to the preparation and characterization of porous hydroxyapatite scaffolds to be used as matrices for bone regeneration or as specific release vehicles. Ceramics are widely used for bone tissue engineering purposes and in this study, hydroxyapatite porous scaffolds were produced using the polymer replication method. Polyurethane sponges were used as templates and impregnated with a ceramic slurry at different ratios, and sintered at 1300 deg. C following a specific thermal cycle. The characteristics of the hydroxyapatite porous scaffolds and respective powder used as starting material, were investigated by using scanning electron microscopy, particle size distribution, X-ray diffraction, Fourier transformed infrared spectroscopy and compressive mechanical testing techniques. It was possible to produce highly porous hydroxyapatite scaffolds presenting micro and macropores and pore interconnectivity.

  16. Synthesis of mesoporous nano-hydroxyapatite by using zwitterions surfactant

    Science.gov (United States)

    Mesoporous nano-hydroxyapatite (mn-HAP) was successfully synthesized via a novel micelle-templating method using lauryl dimethylaminoacetic acid as zwitterionic surfactant. The systematic use of such a surfactant in combination with microwave energy inputenables the precise contr...

  17. Antifungal Applications of Ag-Decorated Hydroxyapatite Nanoparticles

    OpenAIRE

    Zamperini, C. A.; André, R. S.; Longo, V. M.; Mima, E. G.; Vergani, C. E.; Machado, A. L.; Varela, J. A.; Longo, E.

    2013-01-01

    Pure hydroxyapatite (HA) and hydroxyapatite decorated with silver (HA@Ag) nanoparticles were synthesized and characterized. The antifungal effect of HA@Ag nanoparticles in a distilled water solution was evaluated against Candida albicans. The origin of the antifungal activity of the HA@Ag is also discussed. The results obtained showed that the HA nanorod morphology remained the same with Ag ions decorations on the HA structure which were deposited in the form of nanospheres. Interaction where...

  18. Hydroxyapatite-coated uncemented implants and peri-implant infection

    OpenAIRE

    Oosterbos, Cornelis Johannes Maria

    2004-01-01

    One of the major complications of joint replacement surgery is a peri-implant infection. A hip prosthesis coated with hydroxyapatite, a calcium phosphate (found in human bone), may offer protection in this respect. In a series of patients who were treated with a hydroxyapatite-coated hip prosthesis for their osteoarthritis, excellent clinical performance and radiographic appearance were found after 5 and 10 years. Radiographically there were signs of osseointegration of the proximal part of t...

  19. A novel electrospun silk fibroin/hydroxyapatite hybrid nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Ming, Jinfa, E-mail: jinfa.ming@gmail.com [National Engineering Laboratory for Modern Silk, Soochow University, Suzhou 215123 (China); College of Textile and Clothing Engineering, Soochow University, Suzhou 215021 (China); Zuo, Baoqi, E-mail: bqzuo@suda.edu.cn [National Engineering Laboratory for Modern Silk, Soochow University, Suzhou 215123 (China); College of Textile and Clothing Engineering, Soochow University, Suzhou 215021 (China)

    2012-11-15

    A novel electrospinning of silk fibroin/hydroxyapatite hybrid nanofibers with different composition ratios was performed with methanoic acid as a spinning solvent. The silk fibroin/hydroxyapatite hybrids containing up to 30% hydroxyapatite nanoparticles could be electrospun into the continuous fibrous structure. The electrospun silk fibroin/hydroxyapatite hybrid nanofibers showed bigger diameter and wider diameter distribution than pure silk fibroin nanofibers, and the average diameter gradually increased from 95 to 582 nm. At the same time, the secondary structure of silk fibroin/hydroxyapatite nanofibers was characterized by X-ray diffraction, Fourier transform infrared analysis, and DSC measurement. Comparing with the pure silk fibroin nanofibers, the crystal structure of silk fibroin was mainly amorphous structure in the hybrid nanofibers. X-ray diffraction results demonstrated the hydroxyapatite crystalline nature remained as evidenced from the diffraction planes (002), (211), (300), and (202) of the hydroxyapatite crystallites, which was also confirmed by Fourier transform infrared analysis. The thermal behavior of hybrid nanofibers exhibited the endothermic peak of moisture evaporation ranging from 86 to 113 Degree-Sign C, and the degradation peak at 286 Degree-Sign C appeared. The SF/HAp nanofibers mats containing 30% HAp nanoparticles showed higher breaking tenacity and extension at break for 1.1688 {+-} 0.0398 MPa and 6.55 {+-} 1.95%, respectively. Therefore, the electrospun silk fibroin/hydroxyapatite hybrid nanofibers should be provided potentially useful options for the fabrication of biomaterial scaffolds for bone tissue engineering. -- Highlights: Black-Right-Pointing-Pointer The novel SF/HAp nanofibers were directly prepared by electrospinning method. Black-Right-Pointing-Pointer The nanofiber diameter had significant related to the content of HAp. Black-Right-Pointing-Pointer The crystal structure of silk fibroin was mainly amorphous structure in

  20. Thermal Sensitive Shape Memory Behavior of Epoxy Composites Reinforced with Silicon Carbide Whiskers

    Directory of Open Access Journals (Sweden)

    Yongkun Wang

    2017-01-01

    Full Text Available A novel shape memory polymer composite was fabricated by introducing various amounts of silicon carbide whiskers (SiCws into a shape memory epoxy. The relationship between the thermomechanical properties of the system and structural changes were investigated via dynamic mechanical analysis, scanning electron microscopy, and bending tests. The results show that the bend strength of composites can improve by 64.1% when SiCw content reaches 12 wt %. The shape transition temperatures of SiCw/epoxy composites decreased slightly with the increase in SiCw content, but it was noted that all of the composites showed excellent shape memory properties. The shape fixity ratio increased as SiCw content increased (>99%, and the shape recovery ratio slightly decreased as SiCw content increased (>95%. All of the composites nearly recovered to their original shape within 2 min (not 100%, and the shape recovery speed significantly improved at a higher temperature. It is anticipated that tagging products will be used in the aerospace industry.

  1. Phase-slip centers in superconducting whiskers of Pb with small concentrations of In and Bi

    Science.gov (United States)

    Damaschke, B.; Tidecks, R.

    1990-05-01

    The current-induced transition from the superconducting to the normal state in whiskers from Pb, Pb-In and Pb-Bi has been investigated. Very close to the critical temperature T c0 the voltage-current (V-I) characteristics show linear portions that are not separated by voltage jumps. For lower temperatures a voltage-step structure occurs. The temperature region over which the step structure extends is shifted towards T c0 for decreasing mean free path l of the conduction electrons. The differential resistance of the first linear part of the characteristics in most cases does not depend on temperature like the related normal-like length that is proportional to l1/2 in agreement with the phase-slip model of Skocpol, Beasley, and Tinkham. Very close to T c0 the time-averaged supercurrent still flowing above the critical current is about the critical current itself. The shape and the characteristic properties of the V I characteristics are compared with theoretical predictions.

  2. Magnetoresistance of proton irradiated Si0.97Ge0.03 whiskers

    Directory of Open Access Journals (Sweden)

    Nadezhda T. Pavlovskaya

    2016-09-01

    The effects of proton irradiation and high magnetic fields on the magnetoresistance of Si1-xGex (x = 0,03 whiskers in the 4.2–300 K temperature range has been studied. A slight decrease in the electrical resistance of the crystals in the 4.2–40 K temperature range during irradiation with small proton doses and a significant increase in their resistance in the entire investigated temperature range for a dose of 1×1017 p+/cm2 have been found. The ionization energy of the impurity atoms in different magnetic fields has been calculated. It has been revealed that the energy level of the impurity depends on the magnetic field but slightly which in turn indicates a independence of the concentration of holes on the magnetic field. It has been shown that a significant magnetoresistance at all studied temperatures was due to the magnetic field-caused decrease in the mobility of free carriers (holes. It has been found that the concentration of holes depends on magnetic field but a little. Conclusion has been made about a negligible expansion of the band gap in magnetic fields of up to 8 T.

  3. Stability of Neural Firing in the Trigeminal Nuclei under Mechanical Whisker Stimulation

    Directory of Open Access Journals (Sweden)

    Valeri A. Makarov

    2010-01-01

    Full Text Available Sensory information handling is an essentially nonstationary process even under a periodic stimulation. We show how the time evolution of ridges in the wavelet spectrum of spike trains can be used for quantification of the dynamical stability of the neuronal responses to a stimulus. We employ this method to study neuronal responses in trigeminal nuclei of the rat provoked by tactile whisker stimulation. Neurons from principalis (Pr5 and interpolaris (Sp5i show the maximal stability at the intermediate (50 ms stimulus duration, whereas Sp5o cells “prefer” shorter (10 ms stimulation. We also show that neurons in all three nuclei can perform as stimulus frequency filters. The response stability of about 33% of cells exhibits low-pass frequency dynamics. About 57% of cells have band-pass dynamics with the optimal frequency at 5 Hz for Pr5 and Sp5i, and 4 Hz for Sp5o, and the remaining 10% show no prominent dependence on the stimulus frequency. This suggests that the neural coding scheme in trigeminal nuclei is not fixed, but instead it adapts to the stimulus characteristics.

  4. Elements of solid state electronics based on soi-structures and si whiskers for cryogenic temperatures

    Directory of Open Access Journals (Sweden)

    Druzhinin A. A.

    2014-12-01

    Full Text Available The paper presents the study results of electrical properties of polycrystalline silicon films in silicon-on-insulator structures and Si whiskers in the temperature range of 4,2—70 K obtained by impedance measurements in the frequency range from 10 Hz to 250 kHz and the possibility of their use in solid-state electronics, functioning at cryogenic temperatures. Characteristics of samples obtained with impedance measurements allow to predict certain specifications of reactive elements of solid state electronics based on polycrystalline and single crystalline silicon, operable at low temperatures. Using the established dependencies, separate elements in the form of solid-state electronics capacitive and inductive elements as well as a combined system in an oscillatory circuit, operable at cryogenic temperatures, have been suggested. The features of developed system depend on the structure of samples and their doping level, which allows to change the required parameters of the elements of solid state electronics in a wide range.

  5. Whisker Deprivation Drives Two Phases of Inhibitory Synapse Weakening in Layer 4 of Rat Somatosensory Cortex.

    Directory of Open Access Journals (Sweden)

    Melanie A Gainey

    Full Text Available Inhibitory synapse development in sensory neocortex is experience-dependent, with sustained sensory deprivation yielding fewer and weaker inhibitory synapses. Whether this represents arrest of synapse maturation, or a more complex set of processes, is unclear. To test this, we measured the dynamics of inhibitory synapse development in layer 4 of rat somatosensory cortex (S1 during continuous whisker deprivation from postnatal day 7, and in age-matched controls. In deprived columns, spontaneous miniature inhibitory postsynaptic currents (mIPSCs and evoked IPSCs developed normally until P15, when IPSC amplitude transiently decreased, recovering by P16 despite ongoing deprivation. IPSCs remained normal until P22, when a second, sustained phase of weakening began. Delaying deprivation onset by 5 days prevented the P15 weakening. Both early and late phase weakening involved measurable reduction in IPSC amplitude relative to prior time points. Thus, deprivation appears to drive two distinct phases of active IPSC weakening, rather than simple arrest of synapse maturation.

  6. Facile synthesis of Cu/tetrapod-like ZnO whisker compounds with enhanced photocatalytic properties

    Science.gov (United States)

    Liu, Hong; Liu, Huarong; Fan, Ximei

    2017-09-01

    Cu/tetrapod-like ZnO whisker (T-ZnOw) compounds were successfully synthesized using N2H4 \\cdot H2O as a reducing agent by a simple reduction method without any insert gas at room temperature. The crystal phase composition and morphology of the as-prepared samples were investigated by XRD, SEM and FESEM tests. The photocatalytic property of the as-prepared samples was detected by the degradation of methyl orange (MO) aqueous solution under UV irradiation. It can be found that Cu nanoparticles (CuNPs) dispersed on the surface of T-ZnOw increased with the increasing of Cu/Zn molar ratios (Cu/Zn MRs), and an octahedral structure of CuNPs was obtained when the sample was prepared with less than and equal to 7.30% Cu/Zn MR, but tended to a spherical or nanorod structure of CuNPs densely arranged on the surface of T-ZnOw, which is prepared by Cu/Zn MRs up to 22.00%. All the compounds exhibited excellent photocatalytic activity in decomposing of MO than T-ZnOw, the photocatalytic property of the samples increased with the increasing of Cu/Zn MRs up to 7.30%, while it decreases when further increasing the Cu/Zn MRs. The Schottky barrier of the Cu/T-ZnOw compound can effectively capture photoinduced electrons from the interface and enhanced the photocatalytic property of T-ZnOw.

  7. Defect induced asymmetric pit formation on hydroxyapatite.

    Science.gov (United States)

    Kwon, Ki-Young; Wang, Eddie; Chung, Alice; Chang, Neil; Saiz, Eduardo; Choe, Uh-Joo; Koobatian, Maxwell; Lee, Seung-Wuk

    2008-10-07

    Defect sites on bone minerals play a critical role in bone remodeling processes. We investigated single crystal hydroxyapatite (100) surfaces bearing crystal defects under acidic dissolution conditions using real-time in situ atomic force microscopy. At defect sites, surface structure-dependent asymmetric hexagonal etch pits were formed, which dominated the overall dissolution rate. Meanwhile, dissolution from the flat terraces proceeded by stochastic formation of flat bottom etch pits. The resulting pit shapes were intrinsically dictated by the HAP crystal structure. Computational modeling also predicted different step energies associated with different facets of the asymmetric etch pits. Our microscopic observations of HAP dissolution are significant for understanding the effects of local surface structure on the bone mineral remodeling process and provide useful insights for the design of novel therapies for treating osteoporosis and dental caries.

  8. Processing of hydroxyapatite obtained by combustion synthesis

    Directory of Open Access Journals (Sweden)

    M. Canillas

    2017-09-01

    Full Text Available One of the reasons of implants failure are the stress forces appearing in the material–tissue interface due to the differences between their mechanical properties. For this reason, similar mechanical properties to the surrounding tissue are desirable. The synthesis of hydroxyapatite by solution combustion method and its processing have been studied in order to obtain fully dense ceramic bodies with improved mechanical strength. Combustion synthesis provides nanostructured powders characterized by a high surface area to facilitate the following sintering. Moreover, synthesis was conducted in aqueous and oxidizing media. Oxidizing media improve homogenization and increase the energy released during combustion. It gives rise to particles whose morphology and size suggest lower surface energies compared with aqueous media. The obtained powders were sintered by using a controlled sintering rate schedule. Lower surfaces energies minimize the shrinkage during sintering and relative densities measurements and diametral compression test confirm improved densification and consequently mechanical properties.

  9. Novel doped hydroxyapatite thin films obtained by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Duta, L. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, 409 Atomistilor Street, Magurele (Romania); Oktar, F.N. [Department of Bioengineering, Faculty of Engineering, Marmara University, Goztepe, Istanbul 34722 (Turkey); Department of Medical Imaging Technics, Vocational School of Health Services, Marmara University, Uskudar, Istanbul 34668 (Turkey); Nanotechnology and Biomaterials Application and Research Centre, Marmara University, Istanbul (Turkey); Stan, G.E. [National Institute of Materials Physics, 105 Bis Atomistilor Street, Magurele (Romania); Popescu-Pelin, G.; Serban, N.; Luculescu, C. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, 409 Atomistilor Street, Magurele (Romania); Mihailescu, I.N., E-mail: ion.mihailescu@inflpr.ro [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, 409 Atomistilor Street, Magurele (Romania)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer HA coatings synthesized by pulsed laser deposition. Black-Right-Pointing-Pointer Comparative study of commercial vs. animal origin materials. Black-Right-Pointing-Pointer HA coatings of animal origin were rougher and more adherent to substrates. Black-Right-Pointing-Pointer Animal origin films can be considered as promising candidates for implant coatings. - Abstract: We report on the synthesis of novel ovine and bovine derived hydroxyapatite thin films on titanium substrates by pulsed laser deposition for a new generation of implants. The calcination treatment applied to produce the hydroxyapatite powders from ovine/bovine bones was intended to induce crystallization and to prohibit the transmission of diseases. The deposited films were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. Pull-off adherence and profilometry measurements were also carried out. X-ray diffraction ascertained the polycrystalline hydroxyapatite nature of the powders and films. Fourier transform infrared spectroscopy evidenced the vibrational bands characteristic to a hydroxyapatite material slightly carbonated. The micrographs of the films showed a uniform distribution of spheroidal particulates with a mean diameter of {approx}2 {mu}m. Pull-off measurements demonstrated excellent bonding strength values between the hydroxyapatite films and the titanium substrates. Because of their physical-chemical properties and low cost fabrication from renewable resources, we think that these new coating materials could be considered as a prospective competitor to synthetic hydroxyapatite used for implantology applications.

  10. Novel doped hydroxyapatite thin films obtained by pulsed laser deposition

    Science.gov (United States)

    Duta, L.; Oktar, F. N.; Stan, G. E.; Popescu-Pelin, G.; Serban, N.; Luculescu, C.; Mihailescu, I. N.

    2013-01-01

    We report on the synthesis of novel ovine and bovine derived hydroxyapatite thin films on titanium substrates by pulsed laser deposition for a new generation of implants. The calcination treatment applied to produce the hydroxyapatite powders from ovine/bovine bones was intended to induce crystallization and to prohibit the transmission of diseases. The deposited films were characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. Pull-off adherence and profilometry measurements were also carried out. X-ray diffraction ascertained the polycrystalline hydroxyapatite nature of the powders and films. Fourier transform infrared spectroscopy evidenced the vibrational bands characteristic to a hydroxyapatite material slightly carbonated. The micrographs of the films showed a uniform distribution of spheroidal particulates with a mean diameter of ∼2 μm. Pull-off measurements demonstrated excellent bonding strength values between the hydroxyapatite films and the titanium substrates. Because of their physical-chemical properties and low cost fabrication from renewable resources, we think that these new coating materials could be considered as a prospective competitor to synthetic hydroxyapatite used for implantology applications.

  11. Formation of Biomimetic Hydroxyapatite Coating on Titanium Plates

    Directory of Open Access Journals (Sweden)

    Ievgen Volodymyrovych PYLYPCHUK

    2014-09-01

    Full Text Available Hydroxyapatite (HA has long been used as a coating material in the implant industry for orthopedic implant applications. HA is the natural inorganic constituent of bone and teeth. By coating titanium (base material of implant engineering because of its lightness and durability with hydroxyapatite, we can provide higher biocompatibility of titanium implants, according to HA ability to form a direct biochemical bond with living tissues. This article reports a biomimetic approach for coating hydroxyapatite with titanium A method of modifying the surface of titanium by organic modifiers (for creating functional groups on the surface, followed by formation "self-assembled" layer of biomimetic hydroxyapatite in simulated body fluid (SBF. FTIR and XPS confirmed the formation of hydroxyapatite coatings on titanium surface. Comparative study of the formation of HA on the surface of titanium plates modified by different functional groups: Ti(≡OH, Ti/(≡Si-OH and Ti/(≡COOH is conducted. It was found that the closest to natural stoichiometric hydroxyapatite Ca/P ratio was obtained on Ti/(≡COOH samples. DOI: http://dx.doi.org/10.5755/j01.ms.20.3.4974

  12. Suspension thermal spraying of hydroxyapatite: microstructure and in vitro behaviour.

    Science.gov (United States)

    Bolelli, Giovanni; Bellucci, Devis; Cannillo, Valeria; Lusvarghi, Luca; Sola, Antonella; Stiegler, Nico; Müller, Philipp; Killinger, Andreas; Gadow, Rainer; Altomare, Lina; De Nardo, Luigi

    2014-01-01

    In cementless fixation of metallic prostheses, bony ingrowth onto the implant surface is often promoted by osteoconductive plasma-sprayed hydroxyapatite coatings. The present work explores the use of the innovative High Velocity Suspension Flame Spraying (HVSFS) process to coat Ti substrates with thin homogeneous hydroxyapatite coatings. The HVSFS hydroxyapatite coatings studied were dense, 27-37μm thick, with some transverse microcracks. Lamellae were sintered together and nearly unidentifiable, unlike conventional plasma-sprayed hydroxyapatite. Crystallinities of 10%-70% were obtained, depending on the deposition parameters and the use of a TiO2 bond coat. The average hardness of layers with low (hydroxyapatite, with a Weibull modulus of ≈3.3. During soaking in simulated body fluid, glassy coatings were progressively resorbed and replaced by a new, precipitated hydroxyapatite layer, whereas coatings with 70% crystallinity were stable up to 14days of immersion. The interpretation of the precipitation behaviour was also assisted by surface charge assessments, performed through Z-potential measurements. During in vitro tests, HA coatings showed no cytotoxicity towards the SAOS-2 osteoblast cell line, and surface cell proliferation was comparable with proliferation on reference polystyrene culture plates. © 2013.

  13. Hydroxyapatite Growth Inhibition Effect of Pellicle Statherin Peptides.

    Science.gov (United States)

    Xiao, Y; Karttunen, M; Jalkanen, J; Mussi, M C M; Liao, Y; Grohe, B; Lagugné-Labarthet, F; Siqueira, W L

    2015-08-01

    In our recent studies, we have shown that in vivo-acquired enamel pellicle is a sophisticated biological structure containing a significant portion of naturally occurring salivary peptides. From a functional aspect, the identification of peptides in the acquired enamel pellicle is of interest because many salivary proteins exhibit functional domains that maintain the activities of the native protein. Among the in vivo-acquired enamel pellicle peptides that have been newly identified, 5 peptides are derived from statherin. Here, we assessed the ability of these statherin pellicle peptides to inhibit hydroxyapatite crystal growth. In addition, atomistic molecular dynamics (MD) simulations were performed to better understand the underlying physical mechanisms of hydroxyapatite growth inhibition. A microplate colorimetric assay was used to quantify hydroxyapatite growth. Statherin protein, 5 statherin-derived peptides, and a peptide lacking phosphate at residues 2 and 3 were analyzed. Statherin peptide phosphorylated on residues 2 and 3 indicated a significant inhibitory effect when compared with the 5 other peptides (P hydroxyapatite for phosphopeptides, whereas unphosphorylated peptides interacted weakly with the hydroxyapatite. Our data suggest that the presence of a covalently linked phosphate group (at residues 2 and 3) in statherin peptides modulates the effect of hydroxyapatite growth inhibition. This study provides a mechanism to account for the composition and function of acquired enamel pellicle statherin peptides that will contribute as a base for the development of biologically stable and functional synthetic peptides for therapeutic use against dental caries and/or periodontal disease. © International & American Associations for Dental Research 2015.

  14. Rapid growth of hydroxyapatite nanoparticles using ultrasonic irradiation.

    Science.gov (United States)

    Rouhani, Parvaneh; Taghavinia, Nima; Rouhani, Shohre

    2010-06-01

    A rapid, environmental friendly and low-cost method to prepare hydroxyapatite nanoparticles is proposed. In this method, hydroxyapatite is produced in a sonicated pseudo-body solution. The sonication time was found effective in the formation of the crystalline phase of nanoparticles. In our experimental condition, 15 min sonication resulted in the most pure hydroxyapatite phase. Also it was shown that growth temperature is a crucial factor and hydroxyapatite crystallizes only at 37 degrees C. The particles formed by sonication were generally smaller and more spherical than those obtained without sonication. Sonication increased the hydroxyapatite crystal growth rate up to 5.5 times compared to non-sonication condition. The comparison between the specific surface area of hydroxyapatite nanoparticles obtained by sonication and without sonication demonstrated that sonication increased the specific surface area from 63 m(2)/g to 107 m(2)/g and decreased the size of nanoparticles from 30 nm to 18 nm. Analysis on the pore structure demonstrated that the fractal structures obtained with and without sonication were considerably different. (c) 2010 Elsevier B.V. All rights reserved.

  15. Neurons in the barrel cortex turn into processing whisker and odor signals: a cellular mechanism for the storage and retrieval of associative signals

    Directory of Open Access Journals (Sweden)

    Dangui eWang

    2015-08-01

    Full Text Available Associative learning and memory are essential to logical thinking and cognition. How the neurons are recruited as associative memory cells to encode multiple input signals for their associated storage and distinguishable retrieval remains unclear. We studied this issue in the barrel cortex by in vivo two-photon calcium imaging, electrophysiology and neural tracing in our mouse model that the simultaneous whisker and olfaction stimulations led to odorant-induced whisker motion. After this cross-modal reflex arose, the barrel and piriform cortices connected. More than 40% of barrel cortical neurons became to encode odor signal alongside whisker signal. Some of these neurons expressed distinct activity patterns in response to acquired odor signal and innate whisker signal, and others encoded similar pattern in response to these signals. In the meantime, certain barrel cortical astrocytes encoded odorant and whisker signals. After associative learning, the neurons and astrocytes in the sensory cortices are able to store the newly learnt signal (cross-modal memory besides the innate signal (native-modal memory. Such associative memory cells distinguish the differences of these signals by programming different codes and signify the historical associations of these signals by similar codes in information retrievals.

  16. Ethanolic extract of Astragali radix and Salviae radix prohibits oxidative brain injury by psycho-emotional stress in whisker removal rat model.

    Directory of Open Access Journals (Sweden)

    Hyeong-Geug Kim

    Full Text Available Myelophil, an ethanolic extract of Astragali Radix and Salviae Radix, has been clinically used to treat chronic fatigue and stress related disorders in South Korea. In this study, we investigated the protective effects of Myelophil on a whisker removal-induced psycho-emotional stress model. SD rats were subjected to whisker removal after oral administration of Myelophil or ascorbic acid for consecutive 4 days. Whisker removal considerably increased total reactive oxygen species in serum levels as well as cerebral cortex and hippocampal regions in brain tissues. Lipidperoxidation levels were also increased in the cerebral cortex, hippocampus regions, and brain tissue injuries as shown in histopathology and immunohistochemistry. However, Myelophil significantly ameliorated these alterations, and depletion of glutathione contents in both cerebral cortex and hippocampus regions respectively. Serum levels of corticosterone and adrenaline were notably altered after whisker removal stress, whereas these abnormalities were significantly normalized by pre-treatment with Myelophil. The NF-κB was notably activated in both cerebral cortex and hippocampus after whisker removal stress, while it was efficiently blocked by pre-treatment with Myelophil. Myelophil also significantly normalizes alterations of tumor necrosis factor-α, interleukin (IL-1β, IL-6 and interferon-γ in both gene expressions and protein levels. These results suggest that Myelophil has protective effects on brain damages in psycho-emotional stress, and the underlying mechanisms involve regulation of inflammatory proteins, especially NF-κB modulation.

  17. Bone regeneration based on nano-hydroxyapatite and hydroxyapatite/chitosan nanocomposites: an in vitro and in vivo comparative study

    Science.gov (United States)

    Tavakol, S.; Nikpour, M. R.; Amani, A.; Soltani, M.; Rabiee, S. M.; Rezayat, S. M.; Chen, P.; Jahanshahi, M.

    2013-01-01

    Surface morphology, surface wettability, and size distribution of biomaterials affect their in vitro and in vivo bone regeneration potential. Since nano-hydroxyapatite has a great chemical and structural similarity to natural bone and dental tissues, incorporated biomaterial of such products could improve bioactivity and bone bonding ability. In this research, nano-hydroxyapatite (23 ± 0.09 nm) and its composites with variety of chitosan content [2, 4, and 6 g (45 ± 0.19, 32 ± 0.12, and 28 ± 0.12 nm, respectively)] were prepared via an in situ hybridization route. Size distribution of the particles, protein adsorption, and calcium deposition of powders by the osteoblast cells, gene expression and percentage of new bone formation area were investigated. The highest degree of bone regeneration potential was observed in nano-hydroxyapatite powder, while the bone regeneration was lowest in nano-hydroxyapatite with 6 g of chitosan. Regarding these data, suitable size distribution next to size distribution of hydroxyapatite in bone, smaller size, higher wettability, lower surface roughness of the nano-hydroxyapatite particles and homogeneity in surface resulted in higher protein adsorption, cell differentiation and percentage of bone formation area. Results obtained from in vivo and in vitro tests confirmed the role of surface morphology, surface wettability, mean size and size distribution of biomaterial besides surface chemistry as a temporary bone substitute.

  18. Bone regeneration based on nano-hydroxyapatite and hydroxyapatite/chitosan nanocomposites: an in vitro and in vivo comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Tavakol, S. [Tehran University of Medical Sciences, Department of Medical Nanotechnology, School of Advanced Technologies in Medicine (Iran, Islamic Republic of); Nikpour, M. R. [Babol University of Technology, Nanotechnology Research Institute, Nanobiotechnology Research Group (Iran, Islamic Republic of); Amani, A. [Tehran University of Medical Sciences, Department of Medical Nanotechnology, School of Advanced Technologies in Medicine (Iran, Islamic Republic of); Soltani, M. [University of Waterloo, Department of Chemical Engineering, Waterloo Institute for Nanotechnology (Canada); Rabiee, S. M. [Babol University of Technology, Nanotechnology Research Institute, Nanobiotechnology Research Group (Iran, Islamic Republic of); Rezayat, S. M. [Tehran University of Medical Sciences, Department of Medical Nanotechnology, School of Advanced Technologies in Medicine (Iran, Islamic Republic of); Chen, P., E-mail: p4chen@uwaterloo.ca [University of Waterloo, Department of Chemical Engineering, Waterloo Institute for Nanotechnology (Canada); Jahanshahi, M., E-mail: mjahan@nit.ac.ir [Babol University of Technology, Nanotechnology Research Institute, Nanobiotechnology Research Group (Iran, Islamic Republic of)

    2013-01-15

    Surface morphology, surface wettability, and size distribution of biomaterials affect their in vitro and in vivo bone regeneration potential. Since nano-hydroxyapatite has a great chemical and structural similarity to natural bone and dental tissues, incorporated biomaterial of such products could improve bioactivity and bone bonding ability. In this research, nano-hydroxyapatite (23 {+-} 0.09 nm) and its composites with variety of chitosan content [2, 4, and 6 g (45 {+-} 0.19, 32 {+-} 0.12, and 28 {+-} 0.12 nm, respectively)] were prepared via an in situ hybridization route. Size distribution of the particles, protein adsorption, and calcium deposition of powders by the osteoblast cells, gene expression and percentage of new bone formation area were investigated. The highest degree of bone regeneration potential was observed in nano-hydroxyapatite powder, while the bone regeneration was lowest in nano-hydroxyapatite with 6 g of chitosan. Regarding these data, suitable size distribution next to size distribution of hydroxyapatite in bone, smaller size, higher wettability, lower surface roughness of the nano-hydroxyapatite particles and homogeneity in surface resulted in higher protein adsorption, cell differentiation and percentage of bone formation area. Results obtained from in vivo and in vitro tests confirmed the role of surface morphology, surface wettability, mean size and size distribution of biomaterial besides surface chemistry as a temporary bone substitute.

  19. Post-translational modification of osteopontin: Effects on in vitro hydroxyapatite formation and growth

    DEFF Research Database (Denmark)

    Boskey, Adele L.; Christensen, Brian Søndergaard; Taleb, Hayat

    2012-01-01

    The manuscript tests the hypothesis that posttranslational modification of the SIBLING family of proteins in general and osteopontin in particular modify the abilities of these proteins to regulate in vitro hydroxyapatite (HA) formation. Osteopontin has diverse effects on hydroxyapatite (HA...

  20. [Cytotoxicity of the strontium-substituted hydroxyapatite evaluated by MTT colorimetry].

    Science.gov (United States)

    Fu, Y; Chen, D; Zhang, J

    2001-09-01

    This study was conducted to evaluate the cytotoxicity of strontium-substituted hydroxyapatite by methyl thiazolyl tetrazolium (MTT) colorimetry. We used the MTT method to assay the cytotoxicity of the strontium-substituted hydroxyapatite containing different strontium concentrations (1%, 5%, 10%, 100% Sr2+) and the pure hydroxyapatite. The results showed that the cytotoxicity scores of the different materials were grade 0 or grade 1. These led us to the conclusion that strontium-substituted hydroxyapatite has good biocompatibility.

  1. Whiskers de fibra de sisal obtidos sob diferentes condições de hidrólise ácida: efeito do tempo e da temperatura de extração Whiskers from sisal fibers obtained under different acid hydrolysis conditions: effect of time and temperature of extraction

    Directory of Open Access Journals (Sweden)

    Kelcilene B. R. Teodoro

    2011-01-01

    Full Text Available Neste trabalho, os efeitos de diferentes condições de tempo e temperatura usados para a preparação de whiskers de sisal foram investigados com o objetivo de se determinar a influência destes parâmetros experimentais na morfologia, cristalinidade e estabilidade térmica dos materiais preparados. A obtenção dos whiskers deu-se após o pré-branqueamento da fibra de sisal com solução alcalina de peróxido de hidrogênio. A fibra branqueada foi submetida ao processo de hidrólise com solução de ácido sulfúrico 60% (m/m sob três diferentes condições de temperatura e tempos de extração: 45 °C e 60 minutos (WS45_60; 45 °C e 75 minutos (WS45_75 e 60 °C e 30 minutos (WS60_30. Os whiskers foram caracterizados quanto à morfologia por microscopia eletrônica de transmissão (MET, quanto à cristalinidade (DRX, carga superficial (potencial zeta , teor de enxofre (análise elementar e quanto à estabilidade térmica por termogravimetria (TGA. Os resultados mostraram que os whiskers de sisal apresentaram comprimento e diâmetro médios e 210 nm e 5 nm respectivamente. Devido à alta aglomeração dos whiskers, diferenças relativas às características dimensionais não puderam ser determinadas. Os resultados obtidos revelaram uma forte dependência da cristalinidade final dos whiskers com a temperatura e tempo de extração. O uso de temperatura mais alta (60 °C associado a um menor tempo de extração (30 minutos resulta em whiskers com boa estabilidade térmica (235 °C, maior cristalinidade e sem o comprometimento da estrutura cristalina da celulose.In this work, the effects of different conditions of time and temperature, used for the preparation of whiskers from sisal, were investigated to determine the influence of experimental parameters on morphology, crystallinity and thermal stability of materials prepared. The whiskers were obtained after the bleaching of sisal raw fiber with a solution of hydrogen peroxide alkaline. The

  2. A new strategy for TiO2 whiskers mediated multi-mode cancer treatment

    Science.gov (United States)

    Xu, Peipei; Wang, Ruju; Ouyang, Jian; Chen, Bing

    2015-02-01

    Traditional Chinese medicine (TCM) which functions as chemotherapeutic or adjuvantly chemotherapeutic agents has been drawing a great many eyeballs for its easy obtain and significant antitumor effects accompanied with less toxic and side effects. PDT (photodynamic therapy) utilizes the fact that certain compounds coined as photosensitizers, when exposed to light of a specific wavelength, are capable of generating cytotoxic reactive oxygen species (ROS) such as hydroxyl radical, hydrogen peroxide, and superoxide to kill cancer cells. Combinations of cancer therapeutic modalities are studied to improve the efficacy of treatment. This study aimed to explore a new strategy of coupling of titanium dioxide whiskers (TiO2 Ws) with the anticancer drug gambogic acid (GA) in photodynamic therapy. The nanocomposites were coined as GA-TiO2. The combination of TiO2 Ws with GA induced a remarkable enhancement in antitumor activity estimated by MTT assay, nuclear DAPI staining, and flow cytometry. Furthermore, the possible signaling pathway was explored by reverse transcription polymerase chain reaction (RT-PCR) and Western blot assay. These results identify TiO2 Ws of good biocompatibility and photocatalytic activity. In human leukemia cells (K562 cells), TiO2 Ws could obviously increase the intracellular concentration of GA and enhance its potential antitumor efficiency, suggesting that TiO2 Ws could act as an efficient drug delivery carrier targeting GA to carcinoma cells. Moreover, photodynamic GA-TiO2 nanocomposites could induce an evident reinforcement in antitumor activity with UV illumination. These results reveal that such modality combinations put forward a promising proposal in cancer therapy.

  3. Morphological and Cell Growth Assessment in Near Dense Hydroxyapatite Scaffold

    Directory of Open Access Journals (Sweden)

    Florencia Edith Wiria

    2013-01-01

    Full Text Available This paper reports the preliminary results on the morphology of low porosity hydroxyapatite scaffold and its compatibility as a substrate for osteoblast cells. Although having low porosity, the hydroxyapatite scaffold was found to be capable of sustaining cell growth and thus assisting bone ingrowth. Due to the low porosity nature, the scaffold provides higher strength and therefore more suitable for applications with load-bearing requirements such as spinal spacer. The hydroxyapatite scaffolds are prepared via powder processing techniques, using a combination of wet mixing, powder compaction, and sintering processes. The scaffold porosity is estimated via image analysis and micro-CT, which detect porosity level of approximately 16% and pore size of 13 μm. Cell culture investigation demonstrates that the hydroxyapatite substrate is able to provide favourable cell attachment and collagen matrix production, as compared to the commonly used cell culture control substrates. These results indicate that despite the low porosity in the hydroxyapatite scaffolds, they do not hinder being a preferred substrate to provide conducive environment osteoblast cell growth.

  4. Cobalt doped proangiogenic hydroxyapatite for bone tissue engineering application.

    Science.gov (United States)

    Kulanthaivel, Senthilguru; Roy, Bibhas; Agarwal, Tarun; Giri, Supratim; Pramanik, Krishna; Pal, Kunal; Ray, Sirsendu S; Maiti, Tapas K; Banerjee, Indranil

    2016-01-01

    The present study delineates the synthesis and characterization of cobalt doped proangiogenic-osteogenic hydroxyapatite. Hydroxyapatite samples, doped with varying concentrations of bivalent cobalt (Co(2+)) were prepared by the ammoniacal precipitation method and the extent of doping was measured by ICP-OES. The crystalline structure of the doped hydroxyapatite samples was confirmed by XRD and FTIR studies. Analysis pertaining to the effect of doped hydroxyapatite on cell cycle progression and proliferation of MG-63 cells revealed that the doping of cobalt supported the cell viability and proliferation up to a threshold limit. Furthermore, such level of doping also induced differentiation of the bone cells, which was evident from the higher expression of differentiation markers (Runx2 and Osterix) and better nodule formation (SEM study). Western blot analysis in conjugation with ELISA study confirmed that the doped HAp samples significantly increased the expression of HIF-1α and VEGF in MG-63 cells. The analysis described here confirms the proangiogenic-osteogenic properties of the cobalt doped hydroxyapatite and indicates its potential application in bone tissue engineering. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Bisphosphonates enhance bacterial adhesion and biofilm formation on bone hydroxyapatite.

    Science.gov (United States)

    Kos, Marcin; Junka, Adam; Smutnicka, Danuta; Szymczyk, Patrycja; Gluza, Karolina; Bartoszewicz, Marzenna

    2015-07-01

    Because of the suspicion that bisphosphonates enhance bacterial colonization, this study evaluated adhesion and biofilm formation by Streptococcus mutans 25175, Staphylococcus aureus 6538, and Pseudomonas aeruginosa 14454 reference strains on hydroxyapatite coated with clodronate, pamidronate, or zoledronate. Bacterial strains were cultured on bisphosphonate-coated and noncoated hydroxyapatite discs. After incubation, nonadhered bacteria were removed by centrifugation. Biofilm formation was confirmed by scanning electron microscopy. Bacterial colonization was estimated using quantitative cultures compared by means with Kruskal-Wallis and post-hoc Student-Newman-Keuls tests. Modeling of the interactions between bisphosphonates and hydroxyapatite was performed using the Density Functional Theory method. Bacterial colonization of the hydroxyapatite discs was significantly higher for all tested strains in the presence of bisphosphonates vs. Adherence in the presence of pamidronate was higher than with other bisphosphonates. Density Functional Theory analysis showed that the protonated amine group of pamidronate, which are not present in clodronate or zoledronate, forms two additional hydrogen bonds with hydroxyapatite. Moreover, the reactive cationic amino group of pamidronate may attract bacteria by direct electrostatic interaction. Increased bacterial adhesion and biofilm formation can promote osteomyelitis, cause failure of dental implants or bisphosphonate-coated joint prostheses, and complicate bone surgery in patients on bisphosphonates. Copyright © 2015 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

  6. New Bismuth-Substituted Hydroxyapatite Nanoparticles for Bone Tissue Engineering

    Science.gov (United States)

    Ciobanu, Gabriela; Bargan, Ana Maria; Luca, Constantin

    2015-11-01

    New bismuth-substituted hydroxyapatite [Ca10- x Bi x (PO4)6(OH)2 where x = 0-2.5] nanoparticles were synthesized by the co-precipitation method from aqueous solutions. The structural properties of the samples were analyzed by scanning electron microscopy coupled with x-ray analysis, x-ray powder diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller surface area analysis. The results confirm that bismuth ions have been incorporated into the hydroxyapatite lattice. The prepared nanocrystalline powders consisted of hydroxyapatite as single phase with hexagonal structure, crystal sizes smaller than 60 nm and (Bi + Ca)/P atomic ratio of around 1.67. The hydroxyapatite samples doped with Bi have mesoporous textures with pores size of around 2 nm and specific surface area in the range of 12-25 m2/g. The Bi-substituted hydroxyapatite powders are more effective against Gram-negative Escherichia coli bacteria than Gram-positive Staphylococcus aureus bacteria.

  7. A process for the development of strontium hydroxyapatite

    Science.gov (United States)

    Zahra, N.; Fayyaz, M.; Iqbal, W.; Irfan, M.; Alam, S.

    2014-06-01

    A procedure for the preparation of Strontium Hydroxyapatite is adapted to produce high purity and better homogeneity ceramic with good Crystallinity. The strontium substituted bone cement has potential for use in orthopedic surgeries. Ionic Strontium (Sr) in humans shares the same physiological pathway as calcium and can be deposited in the mineral structure of the bone. In the present study, a novel concept of preparing Sr-contained Hydroxyapatite bone cement by using a precipitation method is proposed to get an ideal biomaterial that possesses potential degradability and more excellent pharmacological effect. Chemical analysis, Fourier Transform Infra Red analysis and Thermogravimetric/ Differential Scanning Calorimetric studies were conducted on prepared Strontium Hydroxyapatite sample to characterize the incorporation of 15% Sr2+ into the crystal lattice of Hydroxyapatite. Strontium was quantitatively incorporated into Hydroxyapatite where its substitution for calcium provoked a linear shift of the infrared absorption bands of the hydroxyl and phosphate groups. Thus, the formation of Sr-HAp was confirmed by Chemical Analysis, FT-IR and TGA/DSC results.

  8. Biodegradable magnesium-hydroxyapatite metal matrix composites.

    Science.gov (United States)

    Witte, Frank; Feyerabend, Frank; Maier, Petra; Fischer, Jens; Störmer, Michael; Blawert, Carsten; Dietzel, Wolfgang; Hort, Norbert

    2007-04-01

    Recent studies indicate that there is a high demand to design magnesium alloys with adjustable corrosion rates and suitable mechanical properties. An approach to this challenge might be the application of metal matrix composite (MMC) based on magnesium alloys. In this study, a MMC made of magnesium alloy AZ91D as a matrix and hydroxyapatite (HA) particles as reinforcements have been investigated in vitro for mechanical, corrosive and cytocompatible properties. The mechanical properties of the MMC-HA were adjustable by the choice of HA particle size and distribution. Corrosion tests revealed that HA particles stabilised the corrosion rate and exhibited more uniform corrosion attack in artificial sea water and cell solutions. The phase identification showed that all samples contained hcp-Mg, Mg(17)Al(12), and HA before and after immersion. After immersion in artificial sea water CaCO3 was found on MMC-HA surfaces, while no formation of CaCO3 was found after immersion in cell solutions with and without proteins. Co-cultivation of MMC-HA with human bone derived cells (HBDC), cells of an osteoblasts lineage (MG-63) and cells of a macrophage lineage (RAW264.7) revealed that RAW264.7, MG-63 and HBDC adhere, proliferate and survive on the corroding surfaces of MMC-HA. In summary, biodegradable MMC-HA are cytocompatible biomaterials with adjustable mechanical and corrosive properties.

  9. Chemical characterization of some substituted hydroxyapatites

    Directory of Open Access Journals (Sweden)

    Ibrahim Doreya

    2011-11-01

    Full Text Available Abstract Synthetic multi-substituted hydroxyapatite nano powders containing silicon and or carbonate prepared by a wet chemical method. The process parameters are set up to allow the simultaneous substitution of carbonate and silicon ions in the place of phosphorus. The chemical and structural characterizations of the prepared powders are determined with the aid of; XRF, ICP, XRD and FTIR. The results show that, the ion substitution in the crystal lattice of HA caused a change in the unit cell dimensions and affected the degree of crystallization of the produced powders. The apatite formation abilityy of the prepared discs from the synthesized powders is determined by immersing in SBF solution for different periods. The degree of ion release was determined in the obtained solutions. The examined surface of the immersed discs under SEM and analyzed by CDS showed a more dense HA layer than those of un-substituted ones. The HA with the substituted silicon and carbonate ions, showed the highest solubility with greater rate of ion release, compared with carbonate-free powder. All prepared powders took sodium ion from the SBF solution during immersion, which was not recorded before.

  10. Chemical characterization of some substituted hydroxyapatites.

    Science.gov (United States)

    Ibrahim, Doreya Mohamed; Mostafa, Amany A; Korowash, Sara Ibrahim

    2011-11-28

    Synthetic multi-substituted hydroxyapatite nano powders containing silicon and or carbonate prepared by a wet chemical method. The process parameters are set up to allow the simultaneous substitution of carbonate and silicon ions in the place of phosphorus. The chemical and structural characterizations of the prepared powders are determined with the aid of; XRF, ICP, XRD and FTIR. The results show that, the ion substitution in the crystal lattice of HA caused a change in the unit cell dimensions and affected the degree of crystallization of the produced powders. The apatite formation abilityy of the prepared discs from the synthesized powders is determined by immersing in SBF solution for different periods. The degree of ion release was determined in the obtained solutions. The examined surface of the immersed discs under SEM and analyzed by CDS showed a more dense HA layer than those of un-substituted ones. The HA with the substituted silicon and carbonate ions, showed the highest solubility with greater rate of ion release, compared with carbonate-free powder. All prepared powders took sodium ion from the SBF solution during immersion, which was not recorded before.

  11. [Induced synthesis of hydroxyapatite by Aspergillus niger].

    Science.gov (United States)

    He, Fei; Lian, Bin; Liu, Shirong; Gong, Guohong

    2011-03-01

    The research objective is to induce hydroxyapatite (HAP) synthesis by using fungus. We used the PDA (Potato Dextrose Agar Medium) liquid medium containing different concentrations of Na2HPO4 and CaCO3 to study the way Aspergillus niger synthesize HAP, to observe the induced mineral crystal structure and to analyze the induced mineral type with transmission electron microscopy (TEM) and X-ray diffraction (XRD). The main results are as follows: (1) A. niger can induce HAP synthesis in PDA liquid medium with the proper concentration of Na2HPO4 and CaCO3. (2) The reaction of A. niger inducing HAP synthesis depends on the time of the response system. Longer time is more advantageous in producing HAP. The main reason for A. niger inducing HAP crystals formation are as follows: fungal metabolism produces the acidic substances to dissolve CaCO, and the growth mycelia absorbing Ca2+ lead to Ca2+ enriched on the surface, to promote the production of secondary mineral apatite and further transform into HAP in the mycelia spheres. A. niger can inducing HAP crystals formation in PDA liquid medium containing Na2HPO4 and CaCO3. Considering the importance of HAP in bio-medicine materials and its costly prices, our method for HAP bio-induction is of the temperate response condition, simple preparation craft, and lower cost, which has the potential application prospect.

  12. Electron paramagnetic resonance dosimetry using synthetic hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kwon; Kim, Hwi Young; Ye, Sung Joon [Seoul National University, Seoul (Korea, Republic of); Hirata, Hiroshi [Hokkaido University, Sapporo (Japan); Park, Jong Min [Seoul National University Hospital, Seoul (Korea, Republic of)

    2014-11-15

    The victims exposed doses under 3.5-4.0 Gy have chance to survive if treated urgently. To determine the priority of treatment among a large number of victims, the triage – distinguishing patients who need an urgent treatment from who may not be urgent – is necessary based on radiation biodosimetry. A current gold standard for radiation biodosimetry is the chromosomal assay using human lymphocytes. But this method requires too much time and skilled labors to cover the mass victims in radiation emergencies. Electron paramagnetic resonance (EPR) has been known for its capability of quantifying radicals in matters. EPR dosimetry is based on the measurement of stable radiation-induced radicals in tooth enamel. Hydroxyapatite (HAP) (Ca10(PO4)6(OH)2) contained in tooth enamel is a major probe for radiation dose reconstruction. This HAP dosimetry study was performed using a novel EPR spectrometer in Hokkaido University, Japan. The EPR dose-response curve was made using HAP samples. The blind test using 250 cGy samples showed the feasibility of EPR dosimetry for the triage purpose.

  13. A novel biomagnetic nanoparticle based on hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Wu, H-C [Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan (China); Wang, T-W [Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan (China); Sun, J-S [Institute of Biomedical Engineering, National Yang-Ming University, Taipei, Taiwan (China); Wang, W-H [Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan (China); Lin, F-H [Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, Taipei, Taiwan (China)

    2007-04-25

    In the present study, magnetic HAP was synthesized at different ratios of Fe:Ca (X{sub Fe/Ca}) by the co-precipitation method. We have evaluated the present essential properties including the crystal structure and cell parameters by XRD, lattice arrangement by HR-TEM, composition analysis by ICP-MS, and functional groups by FTIR. The morphology and magnetization were investigated by SEM and AFM and SQUID, respectively. The in vitro biocompatibility was also investigated with a lactate dehydrogenase assay. The results showed that the crystal and molecular structure of the synthesized magnetic-HAP nanoparticle remained unaltered without collapse with the addition of iron ions. The lattice constants of m-HAP were similar to reference JCPDS card no. 9-432. The magnetization of m-HAP nanoparticles increased with increasing X{sub Fe/Ca} and possessed the superparamagnetic property with size distribution around 20 nm. The hydroxyapatite-based magnetic nanoparticles were also examined with good biocompatibility. With the appropriate physico-chemical and biological properties, the magnetic-HAP nanoparticles would have great potential to be applied in biomedical applications.

  14. A novel biomagnetic nanoparticle based on hydroxyapatite

    Science.gov (United States)

    Wu, Hsi-Chin; Wang, Tzu-Wei; Sun, Jui-Sheng; Wang, Wen-Hsi; Lin, Feng-Huei

    2007-04-01

    In the present study, magnetic HAP was synthesized at different ratios of Fe:Ca (XFe/Ca) by the co-precipitation method. We have evaluated the present essential properties including the crystal structure and cell parameters by XRD, lattice arrangement by HR-TEM, composition analysis by ICP-MS, and functional groups by FTIR. The morphology and magnetization were investigated by SEM and AFM and SQUID, respectively. The in vitro biocompatibility was also investigated with a lactate dehydrogenase assay. The results showed that the crystal and molecular structure of the synthesized magnetic-HAP nanoparticle remained unaltered without collapse with the addition of iron ions. The lattice constants of m-HAP were similar to reference JCPDS card no. 9-432. The magnetization of m-HAP nanoparticles increased with increasing XFe/Ca and possessed the superparamagnetic property with size distribution around 20 nm. The hydroxyapatite-based magnetic nanoparticles were also examined with good biocompatibility. With the appropriate physico-chemical and biological properties, the magnetic-HAP nanoparticles would have great potential to be applied in biomedical applications.

  15. Synthesis of hydroxyapatite nanotubes for biomedical applications.

    Science.gov (United States)

    Chandanshive, Balasaheb B; Rai, Priyanka; Rossi, Andre L; Ersen, Ovidiu; Khushalani, Deepa

    2013-07-01

    Single phase, stoichiometrically pure, hollow nanotubes of hydroxyapatite have been synthesized and single-particle analysis has been performed to successfully prove the sole formation of Ca10(PO4)6(OH)2 phase. The facile synthesis involves a sol-gel process under neutral conditions in the presence of a sacrifical anodic alumina template. The structures formed are hollow nanotubes that have been characterized by XRD, SEM, TEM, SAED, EELS, EDS and BET measurements. The diameter of the resulting tubes is in the range of 140-350 nm, length is on the order of a few microns and the wall thickness of the tubes was found to be ca. 30 nm. Moreover these tubes had a large BET surface area of 115 m(2)/g and were found to be biocompatible. They displayed inertness in the presence of NIH 3T3 mouse fibroblast cells as dictated by an MTT assay. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Novel Development of Phosphate Treated Porous Hydroxyapatite

    Science.gov (United States)

    Doi, Kazuya; Abe, Yasuhiko; Kobatake, Reiko; Okazaki, Yohei; Oki, Yoshifumi; Naito, Yoshihito; Prananingrum, Widyasri; Tsuga, Kazuhiro

    2017-01-01

    Phosphoric acid-etching treatment to the hydroxyapatite (HA) surface can modify the solubility calcium structure. The aim of the present study was to develop phosphate treated porous HA, and the characteristic structures and stimulation abilities of bone formation were evaluated to determine its suitability as a new type of bone graft material. Although the phosphoric acid-etching treatment did not alter the three-dimensional structure, a micrometer-scale rough surface topography was created on the porous HA surface. Compared to porous HA, the porosity of phosphate treated porous HA was slightly higher and the mechanical strength was lower. Two weeks after placement of the cylindrical porous or phosphate treated porous HA in a rabbit femur, newly formed bone was detected in both groups. At the central portion of the bone defect area, substantial bone formation was detected in the phosphate treated porous HA group, with a significantly higher bone formation ratio than detected in the porous HA group. These results indicate that phosphate treated porous HA has a superior surface topography and bone formation abilities in vivo owing to the capacity for both osteoconduction and stimulation abilities of bone formation conferred by phosphoric acid etching.

  17. Porous hydroxyapatite for artificial bone applications

    Directory of Open Access Journals (Sweden)

    I. Sopyan et al

    2007-01-01

    Full Text Available Hydroxyapatite (HA has been used clinically for many years. It has good biocompatibility in bone contact as its chemical composition is similar to that of bone material. Porous HA ceramics have found enormous use in biomedical applications including bone tissue regeneration, cell proliferation, and drug delivery. In bone tissue engineering it has been applied as filling material for bone defects and augmentation, artificial bone graft material, and prosthesis revision surgery. Its high surface area leads to excellent osteoconductivity and resorbability providing fast bone ingrowth. Porous HA can be produced by a number of methods including conversion of natural bones, ceramic foaming technique, polymeric sponge method, gel casting of foams, starch consolidation, microwave processing, slip casting, and electrophoretic deposition technique. Some of these methods have been combined to fabricate porous HA with improved properties. These combination methods have yielded some promising results. This paper discusses briefly fundamental aspects of porous HA for artificial bone applications as well as various techniques used to prepare porous HA. Some of our recent results on development of porous HA will be presented as well.

  18. A system for delivering mechanical stimulation and robot-assisted therapy to the rat whisker pad during facial nerve regeneration.

    Science.gov (United States)

    Heaton, James T; Knox, Christopher J; Malo, Juan S; Kobler, James B; Hadlock, Tessa A

    2013-11-01

    Functional recovery is typically poor after facial nerve transection and surgical repair. In rats, whisking amplitude remains greatly diminished after facial nerve regeneration, but can recover more completely if the whiskers are periodically mechanically stimulated during recovery. Here we present a robotic "whisk assist" system for mechanically driving whisker movement after facial nerve injury. Movement patterns were either preprogrammed to reflect natural amplitudes and frequencies, or movements of the contralateral (healthy) side of the face were detected and used to control real-time mirror-like motion on the denervated side. In a pilot study, 20 rats were divided into nine groups and administered one of eight different whisk assist driving patterns (or control) for 5-20 minutes, five days per week, across eight weeks of recovery after unilateral facial nerve cut and suture repair. All rats tolerated the mechanical stimulation well. Seven of the eight treatment groups recovered average whisking amplitudes that exceeded controls, although small group sizes precluded statistical confirmation of group differences. The potential to substantially improve facial nerve recovery through mechanical stimulation has important clinical implications, and we have developed a system to control the pattern and dose of stimulation in the rat facial nerve model.

  19. [Effect of amount of silane coupling agent on flexural strength of dental composite resins reinforced with aluminium borate whisker].

    Science.gov (United States)

    Zhu, Ming-yi; Zhang, Xiu-yin

    2015-06-01

    To evaluate the effect of amount of silane coupling agent on flexural strength of dental composite resins reinforced with aluminium borate whisker (ABW). ABW was surface-treated with 0%, 1%, 2%, 3% and 4% silan coupling agent (γ-MPS), and mixed with resin matrix to synthesize 5 groups of composite resins. After heat-cured at 120 degrees centigrade for 1 h, specimens were tested in three-point flexure to measure strength according to ISO-4049. One specimen was selected randomly from each group and observed under scanning electron microscope (SEM). The data was analyzed with SAS 9.2 software package. The flexural strength (117.93±11.9 Mpa) of the group treated with 2% silane coupling agent was the highest, and significantly different from that of the other 4 groups (α=0.01). The amount of silane coupling agent has impact on the flexural strength of dental composite resins reinforced with whiskers; The flexual strength will be reduced whenever the amount is higher or lower than the threshold. Supported by Research Fund of Science and Technology Committee of Shanghai Municipality (08DZ2271100).

  20. A system for studying facial nerve function in rats through simultaneous bilateral monitoring of eyelid and whisker movements.

    Science.gov (United States)

    Heaton, James T; Kowaleski, Jeffrey M; Bermejo, Roberto; Zeigler, H Philip; Ahlgren, David J; Hadlock, Tessa A

    2008-06-30

    The occurrence of inappropriate co-contraction (synkinesis) of facially innervated muscles in humans is a common sequela of facial nerve injury and recovery. We have developed a system for studying facial nerve function and synkinesis in restrained rats using non-contact opto-electronic techniques that enable simultaneous bilateral monitoring of eyelid and whisker movements. Whisking is monitored in high spatio-temporal resolution using laser micrometers, and eyelid movements are detected using infrared diode and phototransistor pairs that respond to the increased reflection when the eyelids cover the cornea. To validate the system, 8 rats were tested with multiple 5-min sessions that included corneal air puffs to elicit blink and scented air flows to elicit robust whisking. Four rats then received unilateral facial nerve section and were tested at weeks 3-6. Whisking and eye blink behavior occurred both spontaneously and under stimulus control, with no detectable difference from published whisking data. Proximal facial nerve section caused an immediate ipsilateral loss of whisking and eye blink response, but some ocular closures emerged due to retractor bulbi muscle function. The independence observed between whisker and eyelid control indicates that this system may provide a powerful tool for identifying abnormal co-activation of facial zones resulting from aberrant axonal regeneration.

  1. The functional upregulation of piriform cortex is associated with cross-modal plasticity in loss of whisker tactile inputs.

    Directory of Open Access Journals (Sweden)

    Bing Ye

    Full Text Available Cross-modal plasticity is characterized as the hypersensitivity of remaining modalities after a sensory function is lost in rodents, which ensures their awareness to environmental changes. Cellular and molecular mechanisms underlying cross-modal sensory plasticity remain unclear. We aim to study the role of different types of neurons in cross-modal plasticity.In addition to behavioral tasks in mice, whole-cell recordings at the excitatory and inhibitory neurons, and their two-photon imaging, were conducted in piriform cortex. We produced a mouse model of cross-modal sensory plasticity that olfactory function was upregulated by trimming whiskers to deprive their sensory inputs. In the meantime of olfactory hypersensitivity, pyramidal neurons and excitatory synapses were functionally upregulated, as well as GABAergic cells and inhibitory synapses were downregulated in piriform cortex from the mice of cross-modal sensory plasticity, compared with controls. A crosswire connection between barrel cortex and piriform cortex was established in cross-modal plasticity.An upregulation of pyramidal neurons and a downregulation of GABAergic neurons strengthen the activities of neuronal networks in piriform cortex, which may be responsible for olfactory hypersensitivity after a loss of whisker tactile input. This finding provides the clues for developing therapeutic strategies to promote sensory recovery and substitution.

  2. Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles

    Science.gov (United States)

    Ciobanu, Carmen Steluta; Iconaru, Simona Liliana; Chifiriuc, Mariana Carmen; Costescu, Adrian; Le Coustumer, Philippe; Predoi, Daniela

    2013-01-01

    The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca10−xAgx(PO4)6(OH)2 nanoparticles (Ag:HAp-NPs) for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures. PMID:23509801

  3. Mechanical properties of hydroxyapatite single crystals from nanoindentation data

    Science.gov (United States)

    Zamiri, A.; De, S.

    2011-01-01

    In this paper we compute elasto-plastic properties of hydroxyapatite single crystals from nanindentation data using a two-step algorithm. In the first step the yield stress is obtained using hardness and Young’s modulus data, followed by the computation of the flow parameters. The computational approach is first validated with data from existing literature. It is observed that hydroxyapatite single crystals exhibit anisotropic mechanical response with a lower yield stress along the [1010] crystallographic direction compared to the [0001] direction. Both work hardening rate and work hardening exponent are found to be higher for indentation along the [0001] crystallographic direction. The stress-strain curves extracted here could be used for developing constitutive models for hydroxyapatite single crystals. PMID:21262492

  4. Study of thermal effects of silicate-containing hydroxyapatites

    Science.gov (United States)

    Golovanova, O. A.; Zaits, A. V.; Berdinskaya, N. V.; Mylnikova, T. S.

    2016-02-01

    The possibility of modifications of hydroxyapatite silicate ions, from the extracellular fluid prototype solution under near-physiological conditions has been studied. Formation of silicon-structured hydroxyapatite with different extent of substitution of phosphate groups in the silicate group has been established through chemical and X-ray diffraction analyses, FTIR spectroscopy and optical microscopy. The results obtained are in agreement and suggest the possibility of substitution of phosphate groups for silicate groups in the hydroxyapatite structure when introducing different sources of silica, tetraethoxysilane and sodium silicate, in the reaction mixture. Growth in the amount of silicon in Si-HA results in the increase in the thermal stability of the samples. The greatest mass loss occurs at temperatures in the range of 25-400 0C that is caused by the removal of the crystallization and adsorption water and volatile impurities. It is shown that the modified apatites are of imperfect structure and crystallize in a nanocrystalline state.

  5. Synthesis and Antimicrobial Activity of Silver-Doped Hydroxyapatite Nanoparticles

    Directory of Open Access Journals (Sweden)

    Carmen Steluta Ciobanu

    2013-01-01

    Full Text Available The synthesis of nanosized particles of Ag-doped hydroxyapatite with antibacterial properties is of great interest for the development of new biomedical applications. The aim of this study was the evaluation of Ca10−xAgx(PO46(OH2 nanoparticles (Ag:HAp-NPs for their antibacterial and antifungal activity. Resistance to antimicrobial agents by pathogenic bacteria has emerged in the recent years and became a major health problem. Here, we report a method for synthesizing Ag doped nanocrystalline hydroxyapatite. A silver-doped nanocrystalline hydroxyapatite was synthesized at 100°C in deionised water. Also, in this paper Ag:HAp-NPs are evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our compounds are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures.

  6. [Study on the defluoridation of drinking water with synthetic hydroxyapatite].

    Science.gov (United States)

    Ying, B; Li, X; Cong, Z

    2001-11-01

    Synthetic hydroxyapatite was used as a material for the defluoridation of drinking water. The defluoridation capacity, regeneration the capability of defluoridator and the corresponding parameters of defluoridation and regeneration have been studied with batch and column test. The results showed that the defluoridation capacity of synthetic hydroxyapatite on F- was 3.7-4.3 mg/g in batch test, 5.6 mg/g for break through (1.0 mg/L is considered as the break through point) in column test, and 10.7 mg/g for saturation in column test. The efficiency of regeneration was 46%-64% for saturated hydroxyapatite with surface-coating method.

  7. The precursors effects on biomimetic hydroxyapatite ceramic powders.

    Science.gov (United States)

    Yoruç, Afife Binnaz Hazar; Aydınoğlu, Aysu

    2017-06-01

    In this study, effects of the starting material on chemical, physical, and biological properties of biomimetic hydroxyapatite ceramic powders (BHA) were investigated. Characterization and chemical analysis of BHA powders were performed by using XRD, FT-IR, and ICP-AES. Microstructural features such as size and morphology of the resulting BHA powders were characterized by using BET, nano particle sizer, pycnometer, and SEM. Additionally, biological properties of the BHA ceramic powders were also investigated by using water-soluble tetrazolium salts test (WST-1). According to the chemical analysis of BHA ceramic powders, chemical structures of ceramics which are prepared under different conditions and by using different starting materials show differences. Ceramic powders which are produced at 80°C are mainly composed of hydroxyapatite, dental hydroxyapatite (contain Na and Mg elements in addition to Ca), and calcium phosphate sulfide. However, these structures are altered at high temperatures such as 900°C depending on the features of starting materials and form various calcium phosphate ceramics and/or their mixtures such as Na-Mg-hydroxyapatite, hydroxyapatite, Mg-Whitlockit, and chloroapatite. In vitro cytotoxicity studies showed that amorphous ceramics produced at 80°C and ceramics containing chloroapatite structure as main or secondary phases were found to be extremely cytotoxic. Furthermore, cell culture studies showed that highly crystalline pure hydroxyapatite structures were extremely cytotoxic due to their high crystallinity values. Consequently, the current study indicates that the selection of starting materials which can be used in the production of calcium phosphate ceramics is very important. It is possible to produce calcium phosphate ceramics which have sufficient biocompatibility at physiological pH values and by using appropriate starting materials. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Production of zinc substituted hydroxyapatite using various precipitation routes.

    Science.gov (United States)

    Shepherd, David; Best, Serena M

    2013-04-01

    Substituted hydroxyapatites have been investigated for use as bone grafts and have been investigated for many years. Zinc is of interest due to its potential to reduce bone resorption and antibacterial properties. However, it has proven problematic to substitute biologically significant levels of zinc into the crystal structure through wet chemical routes, whilst retaining the high temperature phase stability required for processing. The aim of this study is to investigate two different precipitation routes used to synthesize zinc substituted hydroxyapatite and to explore the effects of ammonia used in the reactions on the levels of zinc substituted into the crystal lattice. It was found that considerable amounts of ammonia are required to maintain a pH sufficiently high for the production of stoichiometric hydroxyapatite using a reaction between calcium nitrate, zinc nitrate and ammonium phosphate. X-ray fluorescence analysis showed that a significant proportion of the zinc added did not substitute into the hydroxyapatite lattice. Fourier transform infrared spectroscopy revealed the existence of a zinc-ammonia complex that, it is proposed, inhibits zinc substitution for calcium. It was found that by reacting orthophosphoric acid with calcium nitrate and zinc nitrate, the volume of ammonia required in the reaction was reduced and higher levels of zinc substitution were achieved, with up to 0.58 wt% incorporated into the hydroxyapatite lattice. The resulting products were found to be stoichiometric hydroxyapatite and did not appear to contain any extraneous calcium phosphate phases after heat treatment up to 1100 °C. X-ray diffraction and Rietveld analysis revealed that the effect of substituting zinc into the HA lattice was to decrease the a-lattice parameter whilst increasing the c-lattice. Transmission electron microscopy also showed that the incorporation of zinc reduced both the length and width of the precipitated crystals.

  9. Cobalt doped proangiogenic hydroxyapatite for bone tissue engineering application

    Energy Technology Data Exchange (ETDEWEB)

    Kulanthaivel, Senthilguru [Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India); Roy, Bibhas [Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302 (India); Agarwal, Tarun [Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India); Giri, Supratim [Department of Chemistry, National Institute of Technology, Rourkela, Odisha 769008 (India); Pramanik, Krishna; Pal, Kunal; Ray, Sirsendu S. [Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India); Maiti, Tapas K. [Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302 (India); Banerjee, Indranil, E-mail: indraniliit@gmail.com [Department of Biotechnology and Medical Engineering, National Institute of Technology, Rourkela, Odisha 769008 (India)

    2016-01-01

    ABSTRACT: The present study delineates the synthesis and characterization of cobalt doped proangiogenic–osteogenic hydroxyapatite. Hydroxyapatite samples, doped with varying concentrations of bivalent cobalt (Co{sup 2+}) were prepared by the ammoniacal precipitation method and the extent of doping was measured by ICP–OES. The crystalline structure of the doped hydroxyapatite samples was confirmed by XRD and FTIR studies. Analysis pertaining to the effect of doped hydroxyapatite on cell cycle progression and proliferation of MG-63 cells revealed that the doping of cobalt supported the cell viability and proliferation up to a threshold limit. Furthermore, such level of doping also induced differentiation of the bone cells, which was evident from the higher expression of differentiation markers (Runx2 and Osterix) and better nodule formation (SEM study). Western blot analysis in conjugation with ELISA study confirmed that the doped HAp samples significantly increased the expression of HIF-1α and VEGF in MG-63 cells. The analysis described here confirms the proangiogenic–osteogenic properties of the cobalt doped hydroxyapatite and indicates its potential application in bone tissue engineering. - Highlights: • Cobalt (Co{sup +2}) doped hydroxyapatite (Co-HAp) can be prepared by the wet chemical method. • The concentration of Co{sup +2} influences the physico-chemical properties of HAp. • Co-HAp was found to be biocompatible and osteogenic. • Co-HAp enhanced cellular VEGF secretion through HIF-1α stabilization. • The optimum biological performance of Co-HAp was achieved for 0.33% (w/w) Co{sup +2} doping.

  10. Waste utilization for the controlled synthesis of nanosized hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Nayar, Suprabha, E-mail: Suprabha.nayar@gmail.com [National Metallurgical Laboratory, Jamshedpur (India); Guha, Avijit [National Metallurgical Laboratory, Jamshedpur (India)

    2009-05-05

    This work uses biomolecules in waste and medicinally important materials for the synthesis of hydroxyapatite nanoparticles. Orange and potato peel, eggshell, papaya leaf and calendula flower extracts have varied biomolecules, which exert a significant, control on the in situ synthesis of nanosized hydroxyapatite particles. The biomimetic synthesis of inorganic particles using known matrices is already well established, however, there are only a few reports using compound extracts. The synthesized nanocomposite has been characterized using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy studies. Role of varied biomolecules in controlled inorganic synthesis may have tremendous technological impact.

  11. Synthesis of Biocompatible Hydroxyapatite Using Chitosan Oligosaccharide as a Template

    Directory of Open Access Journals (Sweden)

    Jinyu Wang

    2015-11-01

    Full Text Available In this study, a novel biocompatible hydroxyapatite (HA was synthesized by using chitosan oligosaccharide (COS as a template. These HA samples were studied by Fourier transform infrared (FTIR spectroscopy, X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, and transmission electron microscopy (TEM. The biocompatibility of HA samples was evaluated via cell viability, cell morphology and alkaline phosphatase staining of MG-63 cell lines. The results show that HA synthesized in the presence of COS was favorable to proliferation and osteogenic differentiation of MG-63 cells. These hydroxyapatites are potentially attractive biomaterials for bone tissue engineering applications.

  12. Spontaneous growth of whiskers from an interlayer of Mo sub 2 C beneath a diamond particle deposited in a combustion-flame

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Katsuyuki; Komatsu, Shojiro; Ishigaki, Takamasa; Matsumoto, Seiichiro; Moriyoshi, Yusuke (National Inst. for Research in Inorganic Materials, Tsukuba, Ibaraki (Japan))

    1992-02-01

    When diamond particles deposited on a molybdenum substrate in a C{sub 2}H{sub -}O{sub 2} combustion-flame were kept for one year in the ambient atmosphere at room temperature, spontaneous whisker growth from an interlayer of Mo{sub 2}C beneath the diamond particles took place. The whiskers were clarified by electron probe micro-analysis (EPMA) and transmission electron microscopy (TEM) in a polycrystal composed of MoO{sub 2}, MoOC, and Mo{sub 2}C. The growth mechanism of them is discussed from two different points of view as follows: One is that the oxidation of an interlayer of Mo{sub 2}C beneath a diamond particle effectively reduces the surface free energy between the interlayer and diamond particle; consequently, the whisker can grow by using a screw dislocation. The other is that the internal stress existing between a diamond particle and an Mo{sub 2}C interlayer provides a very reactive zone where the growth of whisker takes place through the oxidation of Mo{sub 2}C. (orig.).

  13. Molecular mechanics of tropocollagen-hydroxyapatite biomaterials

    Science.gov (United States)

    Dubey, Devendra Kumar

    Hard biomaterials such as bone, dentin, and nacre show remarkable mechanical performance and serve as inspiration for development of next generation of composite materials with high strength and toughness. Such materials have primarily an organic phase (e.g. tropocollagen (TC) or chitin) and a mineral phase (e.g. hydroxyapatite (HAP) or aragonite) arranged in a staggered arrangement at nanoscopic length scales. Interfacial interactions between the organic phases and the mineral phases and structural effects arising due to the staggered and hierarchical arrangements are identified to be the two most important determinants for high mechanical performance of such biomaterials. Effects of these determinants in such biomaterials are further intertwined with factors such as loading configuration, chemical environment, mineral crystal shape, and residue sequences in polymer chains. Atomistic modeling is a desired approach to investigate such sub nanoscale issues as experimental techniques for investigations at such small scale are still in nascent stage. For this purpose, explicit three dimensional (3D) molecular dynamics (MD) and ab initio MD simulations of quasi-static mechanical deformations of idealized Tropocollagen-Hydroxyapatite (TC-HAP) biomaterials with distinct interfacial arrangements and different loading configurations are performed. Focus is on developing insights into the molecular level mechanics of TC-HAP biomaterials at fundamental lengthscale with emphasis on interface phenomenon. Idealized TC-HAP atomistic models are analyzed for their mechanical strength and fracture failure behavior from the viewpoint of interfacial interactions between TC and HAP and associated molecular mechanisms. In particular, study focuses on developing an understanding of factors such as role of interfacial structural arrangement, hierarchical structure design, influence of water, effect of changes in HAP crystal shape, and mutations in TC molecule on the mechanical strength

  14. Hydroxyapatite nanoparticles: electrospinning and calcination of hydroxyapatite/polyvinyl butyral nanofibers and growth kinetics.

    Science.gov (United States)

    Zakaria, Siti Maisurah; Sharif Zein, Sharif Hussein; Othman, Mohd Roslee; Jansen, John A

    2013-07-01

    Electrospinning of hydroxyapatite (HA)/polyvinyl butyral solution resulted in the formation of fibers with average diameter of 937-1440 nm. These fibers were converted into HA nanoparticles with size <100 nm after undergoing calcination treatment at 600°C. The diameter of the fiber was found to be influenced by applied voltage and spinning distance. The injection flowrate did not affect the diameter significantly. The electrospinning method successfully reduced the commercial HA particle size in the range of 400-1100 nm into <100 nm. The dispersion of the finally calcined HA nanoparticles was improved significantly after anionic sodium dodecyl sulfate surfactant was introduced. The experimental data of HA growth kinetics were subjected to the integral method of analysis, and the rate law of the reaction was found to follow the first order reaction. Copyright © 2012 Wiley Periodicals, Inc.

  15. Effect of fuel characteristics on synthesis of calcium hydroxyapatite ...

    Indian Academy of Sciences (India)

    The effect of fuel characteristics on the processing of nano sized calcium hydroxyapatite (HA) fine powders by the solution combustion technique is reported. Urea, glycine and glucose were used as fuels in this study. By using different combinations of urea and glycine fuels and occasional addition of small amounts of ...

  16. Superior sealing effect of hydroxyapatite in porous-coated implants

    DEFF Research Database (Denmark)

    Rahbek, Ole; Kold, Søren Vedding; Bendix, Knud

    2005-01-01

    Migration of wear debris to the periprosthetic bone is a major cause of osteolysis and implant failure. Both closed-pore porous coatings and hydroxyapatite (HA) coatings have been claimed to prevent the migration of wear debris. We investigated whether HA could augment the sealing effect of a por...

  17. Synthesis of hydroxyapatite nanopowders by sol–gel emulsion

    Indian Academy of Sciences (India)

    Hydroxyapatite nanopowders were synthesized by a sol–gel emulsion technique by varying the concentration of a non-ionic surfactant in the organic phases (oil phase) of water-in-oil (w/o) emulsion. Calcium acetate dissolved in distilled water and phosphorous pentoxide dissolved in 2-butanol were used as starting ...

  18. Development of hydroxyapatite-based nanomaterials to enhance ...

    African Journals Online (AJOL)

    ... cells in tissue engineering microspheres. The outcome of this study may have a major impact on the development of novel nanomaterials for bone tissue engineering. Keywords: Chitosan/gelatin-hydroxyapatite, Osteoblast, Osteoinduction, Bone tissue engineering, Nanomaterials, Microspheres, Calcium nodule formation ...

  19. Bone growth response with porous hydroxyapatite granules in a ...

    Indian Academy of Sciences (India)

    This study evaluated the tissue reaction to porous hydroxyapatite (HA) granules in a critical sized tibial-defect of New Zealand white rabbits for a period of 2, 6, 12 and 24 weeks. Physicochemical characterizations of the granules were done using transmission electron microscopy, scanning electron microscopy, X-ray ...

  20. Amino acid-assisted synthesis of strontium hydroxyapatite bone ...

    Indian Academy of Sciences (India)

    present paper reports about the successful synthesis of stron- tium hydroxyapatite bone cement that could be widely used in orthopaedic applications to anchor implants to existing bone, reconstruct bone and deliver bioactive agents to the body by using glycine as template and freezing at 2. ◦. C. The main advantage of this ...

  1. Development of hydroxyapatite from Setiu coral via hydrothermal method

    Science.gov (United States)

    Adnen, Noor Asliza Ismail; Halim, Nur Aini Abd; Nor, Mohd Al Amin Muhamad

    2017-09-01

    Coral and converted coralline hydroxyapatites (CHAp) have been widely used in biomedical application as orbital implant and bone graft substitute. In this study, the effect of calcination temperature towards properties of hydroxyapatite were investigated. Three different species of corals which commonly found in Setiu, Terengganu was identified based on coral skeleton and its mean pore diameter was analysed using SEM image analyzer. Corals sample undergo hydrothermal process at calcination temperatures range from 200°C to 240°C with addition of di-ammonium hydrogen phosphate as mineralizer. Three species of corals was identified as Platygyra Lamellina sp., Leptoria Phrygia sp. and Pocillopora Damicornis sp. The mean pore diameter of Setiu corals are 0.751mm, 0.495mm and 0.313mm for Platygyra Lamellina sp., Leptoria Phrygia sp. and Pocillopora Damicornis sp., respectively. The XRD diffractograms showed that the raw corals was sucessfully converted to hydroxyapatite (HA) with presence of minor impurities for all type of corals. Calcination temperature of 240°C was found the best temperature to convert coral to coralline hydroxyapatite. Based on this finding, coral species found in Setiu, Terengganu has great potential to be used as bone graft substitutes.

  2. Facilitated transport of copper with hydroxyapatite nanoparticles in saturated sand

    Science.gov (United States)

    Saturated packed column experiments were conducted to investigate the facilitated transport of Cu with hydroxyapatite nanoparticles (nHAP) at different pore water velocities (0.22-2.2 cm min–1), solution pH (6.2-9.0), and fraction of Fe oxide coating on grain surfaces (', 0-0.36). The facilitated tr...

  3. Fabrication of hydroxyapatite from fish bones waste using reflux method

    Science.gov (United States)

    Cahyanto, A.; Kosasih, E.; Aripin, D.; Hasratiningsih, Z.

    2017-02-01

    The aim of this present study was to investigate the fabrication of hydroxyapatites, which were synthesized from fish bone wastes using reflux method. The fish bone wastes collected from the restaurant were brushed and boiled at 100°C for 10 minutes to remove debris and fat. After drying, the fish bones were crushed, and ball milled into a fine powder. The fish bone wastes were then processed by refluxing using KOH and H3PO4 solutions. The samples were calcined at 900°C and characterized by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectrometry (FT-IR). The XRD pattern of samples after treatment revealed that the peak of hydroxyapatite was observed and the bands of OH- and PO4 3- were observed by FT-IR. The scanning electron microscope evaluation of sample showed the entangled crystal and porous structure of hydroxyapatite. In conclusion, the hydroxyapatite was successfully synthesized from fish bone wastes using reflux method.

  4. Sphingoid bases inhibit acid-induced demineralization of hydroxyapatite

    NARCIS (Netherlands)

    Valentijn-Benz, M.; van 't Hof, W.; Bikker, F.J.; Nazmi, K.; Brand, H.S.; Sotres, J.; Lindh, L.; Arnebrant, T.; Veerman, E.C.I.

    2015-01-01

    Calcium hydroxyapatite (HAp), the main constituent of dental enamel, is inherently susceptible to the etching and dissolving action of acids, resulting in tooth decay such as dental caries and dental erosion. Since the prevalence of erosive wear is gradually increasing, there is urgent need for

  5. Amino acid-assisted synthesis of strontium hydroxyapatite bone ...

    Indian Academy of Sciences (India)

    Strontium was quantitatively incorporated into hydroxyapatite where its substitution for calcium provoked a linear shift of the infrared absorption bands of the hydroxyl and phosphate groups. The strontium substituted bone cement has potential for use in orthopaedic surgeries. The present study shows that the addition of ...

  6. Cerium doped hydroxyapatite nanoparticles synthesized by coprecipitation method

    Directory of Open Access Journals (Sweden)

    Ciobanu Carmen Steluta

    2016-01-01

    Full Text Available The present work reports a simple coprecipitation adapted method for the synthesis of stable Ce substituted to Ca hydroxyapatite (HAp nanoparticles. The structural and morphological properties of Ce doped hydroxyapatite (Ce:HAp were characterized by X-ray diffraction (XRD, Transmission Electron Microscopy (TEM, Scanning Electron Microscopy (SEM and Energy Dispersive X-ray analysis (EDAX. The optical properties of Ce doped hydroxyapatite were also investigated using Fourier Transform Infrared (FTIR spectroscopy, FT Raman spectroscopy and photoluminescence analysis. The results of the XRD studies revealed the progressive increase in the a- and c-axes with increasing of Ce concentrations. In the FTIR studies of Ce:HAp powders a similar structure to hydroxyapatite was observed. IR and Raman wavenumbers and the peak strength of the bands associated to the P-O and O-H bonds decreases progressively with the increase of Ce concentration. All the emission maxima could be attributed to the 5d-4f transitions of Ce ions. The displacement of maximum emission bands with the increase of Cerium in the samples is in agreement with the results obtained by XRD studies. The Ce:HAp samples with xCe =0.03 and 0.05 exhibited significant antibacterial activity against Staphylococcus aureus ATCC 6538 and E. coli 714 bacterial strains compared to Ce:HAp samples with xCe =0 (pure HAp and 0.01.

  7. Bone-Like Hydroxyapatite Formation in Human Blood

    Science.gov (United States)

    Titov, Anatoly T.; Larionov, Peter M.; Ivanova, Alexandra S.; Zaikovskii, Vladimir I.; Chernyavskiy, Mikhail A.

    2016-01-01

    The purpose of this study was to prove the mechanism of mineralization, when hydroxyapatite (HAP) is formed in blood plasma. These observations were substantiated by in vitro simulation of HAP crystallization in the plasma of healthy adults in a controllable quasi-physiological environment (T = 37°C, pH = 7.4) and at concentrations of dissolved Ca…

  8. Characteristics of porous zirconia coated with hydroxyapatite as ...

    Indian Academy of Sciences (India)

    TECS

    Sci., Vol. 30, No. 4, August 2007, pp. 309–314. © Indian Academy of Sciences. 309. Characteristics of porous zirconia coated with hydroxyapatite as human bones. V V NARULKAR*, S PRAKASH and K CHANDRA. Metallurgical and Materials Engineering Department, Indian Institute of Technology, Roorkee 247 667, India.

  9. Complications of motility peg placement for porous hydroxyapatite orbital implants.

    Science.gov (United States)

    Lin, C-J; Liao, S-L; Jou, J-R; Kao, S C S; Hou, P-K; Chen, M-S

    2002-04-01

    To evaluate the complications associated with pegging of porous hydroxyapatite orbital implants. Complications associated with pegging were retrospectively reviewed from the charts of 100 of 133 patients with hydroxyapatite implantation from 1993 to 2000. 48 (48%) of the 100 hydroxyapatite implanted patients who had undergone pegging were found to have problems with their pegs, including discharge (45.8%), peg falling out (20.8%), pyogenic granulomas (16.7%), popping peg (14.6%), hydroxyapatite visible around peg hole (8.3%), part of peg shaft visible (6.2%), peg drilled off centre (6.2%), peg drilled at an angle (4.2%), and excess movement of peg (4.2%). The standard peg fell out statistically more often than the peg and sleeve system (Yates's corrected chi(2), p=0.038). There was a trend towards complications of the peg with use of a standard peg (versus sleeved peg) (p=0.226). There are several potential complications of pegging. Most complications are minor and can be managed successfully.

  10. Periodontal regeneration with stem cells-seeded collagen-hydroxyapatite scaffold.

    Science.gov (United States)

    Liu, Zeping; Yin, Xing; Ye, Qingsong; He, Wulin; Ge, Mengke; Zhou, Xiaofu; Hu, Jing; Zou, Shujuan

    2016-07-01

    Re-establishing compromised periodontium to its original structure, properties and function is demanding, but also challenging, for successful orthodontic treatment. In this study, the periodontal regeneration capability of collagen-hydroxyapatite scaffolds, seeded with bone marrow stem cells, was investigated in a canine labial alveolar bone defect model. Bone marrow stem cells were isolated, expanded and characterized. Porous collagen-hydroxyapatite scaffold and cross-linked collagen-hydroxyapatite scaffold were prepared. Attachment, migration, proliferation and morphology of bone marrow stem cells, co-cultured with porous collagen-hydroxyapatite or cross-linked collagen-hydroxyapatite, were evaluated in vitro. The periodontal regeneration capability of collagen-hydroxyapatite scaffold with or without bone marrow stem cells was tested in six beagle dogs, with each dog carrying one sham-operated site as healthy control, and three labial alveolar bone defects untreated to allow natural healing, treated with bone marrow stem cells - collagen-hydroxyapatite scaffold implant or collagen-hydroxyapatite scaffold implant, respectively. Animals were euthanized at 3 and 6 months (3 animals per group) after implantation and the resected maxillary and mandibular segments were examined using micro-computed tomography scan, H&E staining, Masson's staining and histometric evaluation. Bone marrow stem cells were successfully isolated and demonstrated self-renewal and multi-potency in vitro. The porous collagen-hydroxyapatite and cross-linked collagen-hydroxyapatite had average pore sizes of 415 ± 20 µm and 203 ± 18 µm and porosity of 69 ± 0.5% and 50 ± 0.2%, respectively. The attachment, proliferation and migration of bone marrow stem cells were satisfactory on both porous collagen-hydroxyapatite and cross-linked collagen-hydroxyapatite scaffolds. Implantation of bone marrow stem cells - collagen-hydroxyapatite or collagen-hydroxyapatite scaffold in

  11. Urea-Hydroxyapatite Nanohybrids for Slow Release of Nitrogen.

    Science.gov (United States)

    Kottegoda, Nilwala; Sandaruwan, Chanaka; Priyadarshana, Gayan; Siriwardhana, Asitha; Rathnayake, Upendra A; Berugoda Arachchige, Danushka Madushanka; Kumarasinghe, Asurusinghe R; Dahanayake, Damayanthi; Karunaratne, Veranja; Amaratunga, Gehan A J

    2017-02-28

    While slow release of chemicals has been widely applied for drug delivery, little work has been done on using this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by in situ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.

  12. SnO2-core/SiOx-shell coaxial whiskers with a needle-like morphology

    Science.gov (United States)

    Kim, Hyoun Woo; Kim, Hyo Sung; Kebede, Mesfin Abayneh; Na, Han Gil; Yang, Ju Chan

    2010-02-01

    Needle-shaped structures of tin oxide (SnO2) were coated with a shell layer of SiOx via a sputtering method. The diameters of the SiOx-coated structures gradually became thinner, leading to the formation of sharp tips. The whiskers consisted of a crystalline SnO2 core surrounded by an amorphous SiOx shell. The photoluminescence (PL) spectrum with a Gaussian fitting exhibited yellow-green and orange light emission bands, and the overall shape and intensity of the PL spectrum were not changed by the SiOxcoating. The results of this study suggest that sputtering can be employed to achieve the layered growth of shell layers on a variety of nanostructures.

  13. Hydroxyapatite nanorods: soft-template synthesis, characterization and preliminary in vitro tests.

    Science.gov (United States)

    Nguyen, Nga Kim; Leoni, Matteo; Maniglio, Devid; Migliaresi, Claudio

    2013-07-01

    Synthetic hydroxyapatite nanorods are excellent candidates for bone tissue engineering applications. In this study, hydroxyapatite nanorods resembling bone minerals were produced by using soft-template method with cetyltrimethylammonium bromide. Composite hydroxyapatite/poly(D, L)lactic acid films were prepared to evaluate the prepared hydroxyapatite nanorods in terms of cell affinity. Preliminary in vitro experiments showed that aspect ratio and film surface roughness play a vital role in controlling adhesion and proliferation of human osteoblast cell line MG 63. The hydroxyapatite nanorods with aspect ratios in the range of 5.94-7 were found to possess distinctive properties, with the corresponding hydroxyapatite/poly(D, L)lactic acid films promoting cellular confluence and a fast formation of collagen fibers as early as after 7 days of culture.

  14. Binding properties of streptococcal glucosyltransferases for hydroxyapatite, saliva-coated hydroxyapatite, and bacterial surfaces.

    Science.gov (United States)

    Vacca-Smith, A M; Bowen, W H

    1998-02-01

    The binding specificities of Streptococcus glucosyltransferase (Gtf) B, C and D for hydroxyapatite (HA), saliva-coated hydroxyapatite (SHA), and bacterial surfaces were examined. For HA beads the following values were obtained: (K = affinity; N = number of binding sites) GtfB, K = 46 x 10(5) ml/mumol, N = 0.65 x 10(-6) mumol/m2; GtfC, K = 86 x 10(5) ml/mumol, N = 4.42 x 10(-6) mumol/m2.; GtfD, K = 100 x 10(5) ml/mumol, N = 0.83 x 10(-6) mumol/m2. For SHA beads, the following values were obtained: GtfB, K = 14.7 x 10(5) ml/mumol, N = 1.03 x 10(-6) mumol/m2; GtfC, K = 21.3 x 10(5) ml/mumol, N = 3.66 x 10(-6) mumol/m2; GtfD, K = 1.73 x 10(5) ml/mumol, N = 8.88 x 10(-6) mumol/m2. The binding of GtfB to SHA beads was reduced in the presence of parotid saliva, but the binding of GtfC and D was unaffected. The binding of GtfB to SHA in the presence of parotid saliva supplemented with GtfC and D was reduced when compared with its binding to SHA in the presence of parotid saliva alone. In contrast, te binding of GtfC and SHA was unaffected when parotid saliva was supplemented with the other Gtf enzymes. GtfB bound to several bacterial strains (Strep, mutans GS-5, Actinomyces viscosus OMZ105E and Lactobacillus casei 4646) in an active form, while GtfC and D did not bind to bacterial surfaces. It is concluded that of the three Gtf enzymes, GtfC has the highest affinity for HA and SHA surfaces and can adsorb on the the SHA surface in the presence of the other two enzymes. GtfD also binds to SHA in the presence of the other enzymes but has a very low affinity for the surface. GtfB does not bind to SHA in the presence of the other Gtf enzymes but binds avidly to bacterial surfaces in an active form. Therefore, GtfC most probably binds to apatitic surfaces, while GtfB binds to bacterial surfaces.

  15. Gel-derived bioglass as a compound of hydroxyapatite composites

    Energy Technology Data Exchange (ETDEWEB)

    Cholewa-Kowalska, Katarzyna; Kokoszka, Justyna; Laczka, Maria [Department of Glass Technology and Amorphous Coatings, Faculty of Materials Science and Ceramics, AGH University of Science and Technology, Krakow (Poland); Niedzwiedzki, Lukasz [Department of Health Sciences and Clinics of Ortopaedics and Traumatology, Institute of Physicotherapy, Collegium Medicum, Jagiellonian University, Krakow (Poland); Madej, Wojciech; Osyczka, Anna M, E-mail: j.kokoszka@poczta.f [Department of Cytology and Histology, Faculty of Biology and Earth Sciences, Institute of Zoology, Jagiellonian University, Krakow (Poland)

    2009-10-15

    Despite the excellent biocompatibility of hydroxyapatite and bioglass, their clinical applications are limited to non-load-bearing implants and implant coatings due to their low mechanical properties. We have developed two different composites made of hydroxyapatite (HA) and gel-derived bioglasses designated S2 (80 mol% SiO{sub 2}-16 mol% CaO-4 mol% P{sub 2}O{sub 5}) or A2 (40 mol% SiO{sub 2}-54 mol% CaO-6 mol% P{sub 2}O{sub 5}). We show that the combination of hydroxyapatite with either bioglass results in better composite bioactivity and biocompatibility compared to HA alone. We used a commercially available hydroxyapatite that was sintered with varying additions (10%, 50%) of A2 or S2 bioglass. Scanning electron microscopy and x-ray diffraction were used to characterize the microstructure and phases of the composites. The elastic properties of bioglass/HA composites were analyzed with the use of the pulse ultrasonic technique. The bioactivity (surface activity) of the composites was assessed by determining the changes of surface morphology and composition after soaking in simulated body fluid (SBF) for 7 and 14 days. The biocompatibility of the obtained composites was then assessed in vitro using adult human bone marrow stromal cells. Cells were seeded on the material surfaces at a density of 10{sup 4} cells cm{sup -2} and cultured for 7 days in non-differentiating and osteogenic conditions. The number of live cells was estimated in both standard and osteogenic cultures, followed by alkaline phosphatase (ALP) activity assay in osteogenic cultures. We determined that 10 wt% addition of A2 (E = 12.24 GPa) and 50 wt% addition of S2 (E = 16.96 GPa) to the HA base results in higher Young's modulus of the composites compared to pure hydroxyapatite (E = 9.03 GPa). The rate of Ca-P rich layer formation is higher for bioglass/HA composites containing A2 bioglass compared to the composites containing S2 bioglass. Evaluation of cell growth on the bioglass

  16. Gel-derived bioglass as a compound of hydroxyapatite composites.

    Science.gov (United States)

    Cholewa-Kowalska, Katarzyna; Kokoszka, Justyna; Laczka, Maria; Niedźwiedzki, Lukasz; Madej, Wojciech; Osyczka, Anna M

    2009-10-01

    Despite the excellent biocompatibility of hydroxyapatite and bioglass, their clinical applications are limited to non-load-bearing implants and implant coatings due to their low mechanical properties. We have developed two different composites made of hydroxyapatite (HA) and gel-derived bioglasses designated S2 (80 mol% SiO(2)-16 mol% CaO-4 mol% P(2)O(5)) or A2 (40 mol% SiO(2)-54 mol% CaO-6 mol% P(2)O(5)). We show that the combination of hydroxyapatite with either bioglass results in better composite bioactivity and biocompatibility compared to HA alone. We used a commercially available hydroxyapatite that was sintered with varying additions (10%, 50%) of A2 or S2 bioglass. Scanning electron microscopy and x-ray diffraction were used to characterize the microstructure and phases of the composites. The elastic properties of bioglass/HA composites were analyzed with the use of the pulse ultrasonic technique. The bioactivity (surface activity) of the composites was assessed by determining the changes of surface morphology and composition after soaking in simulated body fluid (SBF) for 7 and 14 days. The biocompatibility of the obtained composites was then assessed in vitro using adult human bone marrow stromal cells. Cells were seeded on the material surfaces at a density of 10(4) cells cm(-2) and cultured for 7 days in non-differentiating and osteogenic conditions. The number of live cells was estimated in both standard and osteogenic cultures, followed by alkaline phosphatase (ALP) activity assay in osteogenic cultures. We determined that 10 wt% addition of A2 (E = 12.24 GPa) and 50 wt% addition of S2 (E = 16.96 GPa) to the HA base results in higher Young's modulus of the composites compared to pure hydroxyapatite (E = 9.03 GPa). The rate of Ca-P rich layer formation is higher for bioglass/HA composites containing A2 bioglass compared to the composites containing S2 bioglass. Evaluation of cell growth on the bioglass/HA composites showed that the incorporation of

  17. Effect of Cell-seeded Hydroxyapatite Scaffolds on Rabbit Radius Bone Regeneration

    Science.gov (United States)

    2013-06-22

    Effect of cell-seeded hydroxyapatite scaffolds on rabbit radius bone regeneration C. R. Rathbone,1 T. Guda,1,2 B. M. Singleton,2 D. S. Oh,2,3 M. R...Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.a.34834 Abstract: Highly porous hydroxyapatite (HA) scaffolds were developed as bone graft substitutes...Periodicals, Inc. J Biomed Mater Res Part A: 102A: 1458– 1466, 2014. Key Words: hydroxyapatite , rabbit radius, mesenchymal stem cells, bone, callus

  18. Comparison of characteristics of hydroxyapatite powders synthesized from cuttlefish bone via precipitation and ball milling techniques

    Science.gov (United States)

    Faksawat, K.; Kaewwiset, W.; Limsuwan, P.; Naemchanthara, K.

    2017-09-01

    The aim of this work was to compare characteristics of hydroxyapatite synthesized by precipitation and ball milling techniques. The cuttlefish bone powder was a precursor in calcium source and the di ammonium hydrogen orthophosphate powders was a precursor in phosphate source. The hydroxyapatite was synthesized by the both techniques such as precipitation and ball milling techniques. The phase formation, chemical structure and morphology of the both hydroxyapatite powders have been examined by X-ray diffractometer (XRD), Fourier transform infrared spectroscope (FTIR) and field emission scanning electron microscope (FESEM), respectively. The results show that the hydroxyapatite synthesized by precipitation technique formed hydroxyapatite phase slower than the hydroxyapatite synthesized by ball milling technique. The FTIR results show the chemical structures of sample in both techniques are similar. The morphology of the hydroxyapatite from the both techniques were sphere like shapes and particle size was about in nano scale. The average particle size of the hydroxyapatite by ball milling technique was less than those synthesized by precipitation technique. This experiment indicated that the ball milling technique take time less than the precipitation technique in hydroxyapatite synthesis.

  19. Hydroxyapatite/poly(epsilon-caprolactone) double coating on magnesium for enhanced corrosion resistance and coating flexibility.

    Science.gov (United States)

    Jo, Ji-Hoon; Li, Yuanlong; Kim, Sae-Mi; Kim, Hyoun-Ee; Koh, Young-Hag

    2013-11-01

    Hydroxyapatite was deposited on pure magnesium (Mg) with a flexible poly(ε-caprolactone) interlayer to reduce the corrosion rate of Mg and enhance coating flexibility. The poly(ε-caprolactone) interlayer was uniformly coated on Mg by a spraying method, followed by hydroxyapatite deposition on the poly(ε-caprolactone) using an aerosol deposition method. In scanning electron microscopy observations, inorganic/organic composite-like structure was observed between the hydroxyapatite and poly(ε-caprolactone) layers, resulting from the collisions of hydroxyapatite particles into the poly(ε-caprolactone) matrix at the initial stage of the aerosol deposition. The corrosion resistance of the coated Mg was examined using potentiodynamic polarization tests. The hydroxyapatite/poly(ε-caprolactone) double coating remarkably improved the corrosion resistance of Mg in Hank's solution. In the in vitro cell tests, the coated Mg showed better cell adhesion compared with the bare Mg due to the reduced corrosion rate and enhanced biocompatibility. The stability and flexibility of hydroxyapatite/poly(ε-caprolactone) double coating was investigated by scanning electron microscopy inspections after the coated Mg was deformed. The hydroxyapatite coating on the poly(ε-caprolactone) interlayer revealed enhanced coating stability and flexibility without cracking or delamination during bending and stretching compared with the hydroxyapatite single coating. These results demonstrated that the hydroxyapatite/poly(ε-caprolactone) double coating significantly improved the surface corrosion resistance of Mg and enhanced coating flexibility for use of Mg as a biodegradable implant.

  20. Development of lattice-inserted 5-Fluorouracil-hydroxyapatite nanoparticles as a chemotherapeutic delivery system.

    Science.gov (United States)

    Tseng, Ching-Li; Chen, Jung-Chih; Wu, Yu-Chun; Fang, Hsu-Wei; Lin, Feng-Huei; Tang, Tzu-Piao

    2015-10-01

    Developing an effective vehicle for cancer treatment, hydroxyapatite nanoparticles were fabricated for drug delivery. When 5-Fluorouracil, a major chemoagent, is combined with hydroxyapatite nanocarriers by interclay insertion, the modified hydroxyapatite nanoparticles have superior lysosomal degradation profiles, which could be leveraged as controlled drug release. The decomposition of the hydroxyapatite nanocarriers facilitates the release of 5-Fluorouracil into the cytoplasm causing cell death. Hydroxyapatite nanoparticles with/without 5-Fluorouracil were synthesized and analyzed in this study. Their crystallization properties and chemical composition were examined by X-ray diffraction and Fourier transforms infrared spectroscopy. The 5-Fluorouracil release rate was determined by UV spectroscopy. The biocompatibility of hydroxyapatite-5-Fluorouracil extraction solution was assessed using 3T3 cells via a WST-8 assay. The effect of hydroxyapatite-5-Fluorouracil particles which directly work on the human lung adenocarcinoma (A549) cells was evaluated by a lactate dehydrogenase assay via contact cultivation. A 5-Fluorouracil-absorbed hydroxyapatite particles were also tested. Overall, hydroxyapatite-5-Fluorouracils were prepared using a co-precipitation method wherein 5-Fluorouracil was intercalated in the hydroxyapatite lattice as determined by X-ray diffraction. Energy dispersive scanning examination showed the 5-Fluorouracil content was higher in hydroxyapatite-5-Fluorouracil than in a prepared absorption formulation. With 5-Fluorouracil insertion in the lattice, the widths of the a and c axial constants of the hydroxyapatite crystal increased. The extraction solution of hydroxyapatite-5-Fluorouracil was nontoxic to 3T3 cells, in which 5-Fluorouracil was not released in a neutral phosphate buffer solution. In contrast, at a lower pH value (2.5), 5-Fluorouracil was released by the acidic decomposition of hydroxyapatite. Finally, the results of the lactate

  1. Evolution of the calcium hydroxyapatite crystal structure under plasma deposition and subsequent reducing treatment

    Science.gov (United States)

    Shamrai, V. F.; Karpikhin, A. E.; Sirotinkin, V. P.; Kalita, V. I.; Komlev, D. I.

    2014-03-01

    The structure of hydroxyapatite plasma coatings on a titanium substrate has been investigated by the X-ray Rietveld method. The hydroxyapatite crystal structure in plasma-deposited samples is characterized by strong distortions of its main element (tetrahedral PO4 cluster) and coordination calcium polyhedra, as well as calcium deficit in the Ca2 site; however, these features do not change the main motif of the hydroxyapatite structure. The bond distortions in PO4 clusters are estimated by the Bauer method. It is shown that hydrothermal treatment leads to the almost complete recovery of the hydroxyapatite structure.

  2. In-situ synchrotron micro-diffraction study of surface, interface, grain structure, and strain/stress evolution during Sn whisker/hillock formation

    Energy Technology Data Exchange (ETDEWEB)

    Pei, Fei; Bower, Allan F.; Chason, Eric [School of Engineering, Brown University, Providence, Rhode Island 02912 (United States); Jadhav, Nitin [IBM, Hopewell Junction, New York 12533 (United States); Buchovecky, Eric [Saint-Gobain, Northboro R& D Center, Northborough, Massachusetts 01532 (United States); Liu, Wenjun; Tischler, Jonathan Z.; Xu, Ruqing [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Ice, Gene E. [Oak Ridge National Lab, Oak Ridge, Tennessee 37831 (United States)

    2016-03-14

    We have performed X-ray synchrotron micro-diffraction measurements to study the processes controlling the formation of hillocks and whiskers in Sn layers on Cu. The studies were done in real-time on Sn layers that were electro-deposited immediately before the X-ray measurements were started. This enabled a region of the sample to be monitored from the as-deposited state until after a hillock feature formed. In addition to measuring the grain orientation and deviatoric strain (via Laue diffraction), the X-ray fluorescence was monitored to quantify the evolution of the Sn surface morphology and the formation of intermetallic compound (IMC) at the Sn-Cu interface. The results capture the simultaneous growth of the feature and the corresponding film stress, grain orientation, and IMC formation. The observations are compared with proposed mechanisms for whisker/hillock growth and nucleation.

  3. Extraction and characterization of cellulose nano whiskers from balsa wood; Extracao e caracterizacao de nanocristais de celulose obtidos da madeira balsa

    Energy Technology Data Exchange (ETDEWEB)

    Morelli, Carolina L.; Bretas, Rosario E.S., E-mail: bretas@ufscar.br [Universidade Federal de Sao Carlos - UFSCar, Sao Carlos, SP (Brazil); Marconcini, Jose M. [Embrapa Instrumentacao, Sao Carlos, SP (Brazil); Pereira, Fabiano V. [Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG (Brazil); Branciforti, Marcia C. [Universidade de Sao Paulo - USP, Sao Carlos, SP (Brazil)

    2011-07-01

    In this study cellulose nano whiskers were obtained from balsa wood. For this purpose, fibers of balsa wood were subjected to hydrolysis reactions for lignin and hemi cellulose digestion and acquisition of nano-scale cellulose. Cellulose nano crystals obtained had medium length and thickness of 176 nm and 7 nm respectively. Infrared spectroscopy and x-ray diffraction showed that the process used for extracting nano whiskers could digest nearly all the lignin and hemi cellulose from the balsa fiber and still preserve the aspect ratio and crystallinity, satisfactory enough for future application in polymer nano composites. Thermogravimetry showed that the onset temperature of thermal degradation of cellulose nano crystals (226 degree C) was higher than the temperature of the balsa fiber (215 degree C), allowing its use in molding processes with many polymers from the molten state.(author)

  4. Growth of single phase Bi sub 2 Sr sub 2 CaCu sub 2 O sub x whiskers using optimized starting compositions for glassy precursors

    CERN Document Server

    Sugimata, E; Kume, E; Sakai, S

    2003-01-01

    Single phase Bi sub 2 Sr sub 2 CaCu sub 2 O sub x whiskers were grown by optimized starting compositions for glassy precursors. The most optimal starting composition ratio and the composition after the whisker growth were found to be Bi : Sr : Ca : Al = 0.96 : 1.10 : 0.37 : 1.21 : 0.61 and Bi sub 2 sub . sub 2 sub 5 Sr sub 2 sub . sub 0 sub 9 Ca sub 0 sub . sub 8 sub 7 Cu sub 2 sub . sub 0 sub 0 O sub x , respectively. From the results of R-T characteristics, it was determined that there was no intergrowth of the Bi sub 2 Sr sub 2 Ca sub 2 Cu sub 3 O sub x phase. (author)

  5. Novel multiform morphologies of hydroxyapatite: Synthesis and growth mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Mary, I. Reeta [Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641046 (India); Department of Physics, Government Arts College, Coimbatore 641018 (India); Sonia, S.; Viji, S.; Mangalaraj, D.; Viswanathan, C. [Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641046 (India); Ponpandian, N., E-mail: ponpandian@buc.edu.in [Department of Nanoscience and Technology, Bharathiar University, Coimbatore 641046 (India)

    2016-01-15

    Graphical abstract: - Highlights: • Novel multiform morphologies of hydroxyapatite from nanoscale building blocks. • Facile hydro/solvothermal method under mild reaction conditions without the necessity of post-annealing treatment. • Growth mechanism by Ostwald ripening and self-assembly processes. - Abstract: Morphological evolution of materials becomes a prodigious challenge due to their key role in defining their functional properties and desired applications. Herein, we report the synthesis of hydroxyapatite (HAp) microstructures with multiform morphologies, such as spheres, cubes, hexagonal rods and nested bundles constructed from their respective nanoscale building blocks via a simple cost effective hydro/solvothermal method. A possible formation mechanism of diverse morphologies of HAp has been presented. Structural analysis based on X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy confirms the purity of the HAp microstructures. The multiform morphologies of HAp were corroborated by using Field emission scanning electron microscope (FESEM).

  6. Antifungal Applications of Ag-Decorated Hydroxyapatite Nanoparticles

    Directory of Open Access Journals (Sweden)

    C. A. Zamperini

    2013-01-01

    Full Text Available Pure hydroxyapatite (HA and hydroxyapatite decorated with silver (HA@Ag nanoparticles were synthesized and characterized. The antifungal effect of HA@Ag nanoparticles in a distilled water solution was evaluated against Candida albicans. The origin of the antifungal activity of the HA@Ag is also discussed. The results obtained showed that the HA nanorod morphology remained the same with Ag ions decorations on the HA structure which were deposited in the form of nanospheres. Interaction where occurred between the structure and its defect density variation in the interfacial HA@Ag and intrafacial HA region with the fungal medium resulted in antifungal activity. The reaction mechanisms involved oxygen and water adsorption which formed an active complex cluster. The decomposition and desorption of the final products as well as the electron/hole recombination process have an important role in fungicidal effects.

  7. Effect of Iron Additives on the Microstructure of Hydroxyapatite

    Directory of Open Access Journals (Sweden)

    G. A. Gamal

    2013-12-01

    Full Text Available In this article, some Fe (III doped hydroxyapatite samples (FeHAp were prepared using the wet chemical method. The prepared samples were characterized via the use of X-ray diffraction (XRD and scanning electron microscopy (SEM. Detailed structural analysis were done by Scherrer and Williamson–Hall plot methods to detect the effect of iron on the structure of hydroxyapatite (HAp. XRD patterns showed that all samples were single phased HAp. Relations between the Fe content and the deformation of the lattice parameters, dislocation density, grain size, microstrain, crystallinity were investigated. The presence of iron in the HAp lattice is found to decrease both the crystal size and the dislocation density. Further results are presented and discussed.

  8. Hydroxyapatite coating on silicon nitride surfaces using the biomimetic method

    Directory of Open Access Journals (Sweden)

    Cecilia Chaves Guedes e Silva

    2008-03-01

    Full Text Available Silicon nitride based ceramics are promising candidates for biomedical applications due to their chemical and dimensional stability associated to suitable mechanical strength and relatively high fracture toughness. However, the bioinert characteristics of these ceramics limit their application to situations where the formation of chemical bonds between the material and the tissue are not essential. A way to broaden the application field of these ceramics in medicine is promoting their bioactivity by means of a hydroxyapatite coating. Therefore, in this paper, samples of silicon nitride were coated with apatite using the biomimetic method. The treated silicon nitride surface was characterized by diffuse reflectance infrared Fourier transformed, X ray diffraction and scanning electron microscopy. The results showed that a layer of hydroxyapatite could be deposited by this method on silicon nitride samples surface.

  9. Biological activity of lactoferrin-functionalized biomimetic hydroxyapatite nanocrystals.

    Science.gov (United States)

    Nocerino, Nunzia; Fulgione, Andrea; Iannaccone, Marco; Tomasetta, Laura; Ianniello, Flora; Martora, Francesca; Lelli, Marco; Roveri, Norberto; Capuano, Federico; Capparelli, Rosanna

    2014-01-01

    The emergence of bacterial strains resistant to antibiotics is a general public health problem. Progress in developing new molecules with antimicrobial properties has been made. In this study, we evaluated the biological activity of a hybrid nanocomposite composed of synthetic biomimetic hydroxyapatite surface-functionalized by lactoferrin (LF-HA). We evaluated the antimicrobial, anti-inflammatory, and antioxidant properties of LF-HA and found that the composite was active against both Gram-positive and Gram-negative bacteria, and that it modulated proinflammatory and anti-inflammatory responses and enhanced antioxidant properties as compared with LF alone. These results indicate the possibility of using LF-HA as an antimicrobial system and biomimetic hydroxyapatite as a candidate for innovative biomedical applications.

  10. The effect of RGD peptides on osseointegration of hydroxyapatite biomaterials

    OpenAIRE

    Hennessy, KM; Clem, WC; Phipps, MC; Sawyer, AA; Shaikh, FM; Bellis, SL

    2008-01-01

    Given that hydroxyapatite (HA) biomaterials are highly efficient at adsorbing proadhesive proteins, we questioned whether functionalizing HA with RGD peptides would have any benefit. In this study, we implanted uncoated or RGD-coated HA disks into rat tibiae for 30 minutes to allow endogenous protein adsorption, and then evaluated mesenchymal stem cell (MSC) interactions with the retrieved disks. These experiments revealed that RGD, when presented in combination with adsorbed tibial proteins ...

  11. Assessment of microarchitecture and crystal structure of hydroxyapatite in osteoporosis

    OpenAIRE

    Zairin Noor; Sumitro, Sutiman B.; Mohammad Hidayat; Agus Hadian Rahim; Ahmad Taufiq

    2011-01-01

    Osteoporosis is characterized by lower bone mineral density (BMD) and microarchitectural degeneration, which tends to increase bone fragility and fracture risk. Bone microstructure depends on interactions between the mineral atoms, which may perform substitution or incorporation into bone crystals, and may dynamically take over the function of calcium or may become a complementary part. The mineral atoms may also become a composite in the hydroxyapatite crystals. The aim of this study was to ...

  12. Production of zinc substituted hydroxyapatite using various precipitation routes

    OpenAIRE

    Shepherd, David; Best, Serena M.

    2013-01-01

    Substituted hydroxyapatites have been investigated for use as bone grafts have been investigated for many years. Zinc is of interest due to it’s potential to reduce bone resorption and antibacterial properties. However, it has proven problematic to substitute biologically significant levels of zinc into the crystal structure through wet chemical routes, whilst retaining the high temperature phase stability required for processing. The aim of this study is to investigate two different precipit...

  13. Subtractive manufacturing of customized hydroxyapatite scaffolds for bone regeneration

    Czech Academy of Sciences Publication Activity Database

    Trunec, M.; Chlup, Zdeněk

    2017-01-01

    Roč. 43, č. 14 (2017), s. 11265-11273 ISSN 0272-8842 R&D Projects: GA MŠk(CZ) LQ1601 Institutional support: RVO:68081723 Keywords : tissue engineering applications * in-vivo * porous hydroxyapatite * phosphate bioceramics * suspensions * ceramics * laser * optimization * osteogenesis * deposition * Milling (A) * Porosity (B) * Apatite (D) * Biopmedical properties (E) * Scaffold Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.986, year: 2016

  14. STUDY ON HYDROXYAPATITE COATING ON BIOMATERIALS BY PLASMA SPRAY METHOD

    OpenAIRE

    Dr. Hanumantharaju H. G; Dr. H.K.Shivanand; Prashanth K. P; K. Suresh Kumar; S. P. Jagadish

    2012-01-01

    In plasma spray coating process the hydroxyapatite powder particles are melted in a high temperature plasma flame and propelled towards the substrate material thus forming a coating. The thin hydroxyapatitecoatings have shown better adhesion to substrates and are more stable in the biological environment because they have more uniform structure and composition. Samples are tested for Scanning Electron Microscopy analysis, to find the uniform coating and bonding strength. From the XRD analysis...

  15. Thermal effects of carbonated hydroxyapatite modified by glycine and albumin

    OpenAIRE

    Gerk, S. A.; Golovanova, O. A.; Kuimova, Marina Valerievna

    2017-01-01

    In this work calcium phosphate powders were obtained by precipitation method from simulated solutions of synovial fluid containing glycine and albumin. X-ray diffraction and IR spectroscopy determined that all samples are single-phase and are presented by carbonate containing hydroxyapatite (CHA). The thermograms of solid phases of CHA were obtained and analyzed; five stages of transformation in the temperature range of 25-1000°C were marked. It is shown that in this temperature range dehydra...

  16. Repairing the hole in hydroxyapatite orbital implants following peg removal.

    Science.gov (United States)

    Jordan, D R

    2000-01-01

    Pegging hydroxyapatite implants may lead to improved prosthetic eye movement but may also be associated with complications that may occasionally require peg removal. Removing the peg and leaving the peg hole to spontaneously granulate in, is one technique to deal with the remaining implant hole. The author describes a simple technique to fill the peg hole that provides a smooth implant-conjunctival-prosthesis interface and may potentially allow repegging.

  17. Associations of unilateral whisker and olfactory signals induce synapse formation and memory cell recruitment in bilateral barrel cortices: cellular mechanism for unilateral training toward bilateral memory

    Directory of Open Access Journals (Sweden)

    Zilong Gao

    2016-12-01

    Full Text Available Somatosensory signals and operative skills learned by unilateral limbs can be retrieved bilaterally. In terms of cellular mechanism underlying this unilateral learning toward bilateral memory, we hypothesized that associative memory cells in bilateral cortices and synapse innervations between them were produced. In the examination of this hypothesis, we have observed that paired unilateral whisker and odor stimulations led to odorant-induced whisker motions in bilateral sides, which were attenuated by inhibiting the activity of barrel cortices. In the mice that showed bilateral cross-modal responses, the neurons in both sides of barrel cortices became to encode this new odor signal alongside the innate whisker signal. Axon projections and synapse formations from the barrel cortex, which was co-activated with the piriform cortex, toward its contralateral barrel cortex were upregulated. Glutamatergic synaptic transmission in bilateral barrel cortices was upregulated and GABAergic synaptic transmission was downregulated. The associative activations of the sensory cortices facilitate new axon projection, glutamatergic synapse formation and GABAergic synapse downregulation, which drive the neurons to be recruited as associative memory cells in the bilateral cortices. Our data reveals the productions of associative memory cells and synapse innervations in bilateral sensory cortices for unilateral training toward bilateral memory.

  18. Reconstruction of intracortical whisker-evoked local field potential from electrocorticogram using a model trained for spontaneous activity in the rat barrel cortex.

    Science.gov (United States)

    Watanabe, Hidenori; Sakatani, Tomoya; Suzuki, Takafumi; Sato, Masa-Aki; Nishimura, Yukio; Nambu, Atsushi; Kawato, Mitsuo; Isa, Tadashi

    2014-10-01

    Electrocorticogram (ECoG) has provided neural information from the cortical surfaces, is widely used in clinical applications, and expected to be useful for brain-machine interfaces. Recent studies have defined the relationship between neural activity in deep layers of the cerebral cortex and ECoG. However, it is still unclear whether this relationship is shared across different brain states. In this study, spontaneous activity and whisker-evoked responses in the barrel cortex of anesthetized rats were recorded with a 32-channel ECoG electrode array and 32-channel linear silicon probe electrodes, respectively. Spontaneous local field potentials (LFPs) at various depths could be reconstructed with high accuracy (R>0.9) by a linear weighted summation of spontaneous ECoG. Current source density analysis revealed that the reconstructed LFPs correctly represented laminar profiles of current sinks and sources as well as the raw LFP. Moreover, when we applied the spontaneous activity model to reconstruction of LFP from the whisker-related ECoG, high accuracy of reconstruction could be obtained (R>0.9). Our results suggest that the ECoG carried rich information about synaptic currents in the deep layers of the cortex, and the same reconstruction model can be applied to estimate both spontaneous activity and whisker-evoked responses. Copyright © 2014 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

  19. Gelatine-Hydroxyapatite Nano-composites for Orthopaedic Applications

    Science.gov (United States)

    Vidyarthi, U.; Zhdan, P.; Gravanis, C.; Lekakou, C.

    2008-09-01

    This study focuses on the preparation and testing of hydroxyapatite-gelatine nano-composite gels via a sol-gel route and in situ formation of hydroxyapatite (HA) type salts. Four types of gels and foams were prepared with Ca/P molar ratio of 0.43 and 0.86 and hydroxyapatite/gelatine weight ratio of 0.50 and 0.70. Cross-linking of gelatine chains was carried out in 1% glutaraldehyde and dynamic mechanical torsion tests were used to measure the viscoelastic properties of the gels and foams, optimize the cross-linking time and assess their mechanical performance. Optical and atomic force microscopy were used to investigate the micro- and nano-structure of the produced composites: in these studies, it was confirmed that the gels were nano-composites with a nano-structure very similar to that of bone and several similarities in the microstructural features. The best foams incorporated dual pore size distribution.

  20. Calcium Deficient Hydroxyapatite for Medical Application Prepared by Hydrothermal Method

    Science.gov (United States)

    Ioku, Koji; Kamitakahara, Masanobu; Ikeda, Tohru

    2010-11-01

    Hydrothermal processing plays a key role in the synthesis of biomaterials with excellent biocompatibility in the physiological environment. Especially, calcium phosphates are paid to much attention for the regenerative medicine. Two kinds of porous materials of hydroxyapatite with 70% porosity were prepared. One of them is a newly developed calcium-deficient hydroxyapatite composed of rod-shaped particles of about 20 μm in length synthesized hydrothermally (HHA) and the other one is the stoichiometric hydroxyapatite (SHA) prepared by the conventional sintering method. These materials were used for animal implantation tests to compare these biological responses. In the rabbit femur, implanted HHA was slowly resorbed and then most of the implanted HHA was resorbed after 72 weeks. The implanted SHA was unresorbed throughout the experimental period. The volume of newly formed bone and the number of osteoclasts in the implanted region were significantly larger in HHA than in SHA after 24 weeks. Results in the present research suggested that the activity of osteoclasts correlated to the bone forming activity of osteoblasts. The method to synthesize biodegradable pure calcium-deficient HA is expected to provide adequate biodegradability and bone replaceability.

  1. Influence of ferrous iron incorporation on the structure of hydroxyapatite.

    Science.gov (United States)

    Morrissey, R; Rodríguez-Lorenzo, L M; Gross, K A

    2005-05-01

    Iron is a vital element of cellular function within the body. High concentrations of iron can be found in the kidneys and the circulatory system. In bones and teeth it is present as a trace element. The use of iron-based compounds in combination with hydroxyapatite offers a new alternative for prosthetic devices. This work investigates the synthesis and processing of iron containing apatites as a possible new type of ceramic for biomedical devices. Stoichiometric and calcium deficient iron containing apatites were synthesized by a wet chemical reaction with di-ammonium-hydrogen-phosphate, calcium nitrate and a ferrous iron nitrate solution. A secondary phase of tri-calcium-phosphate (TCP) was observed after heat treatment of iron containing, calcium deficient, hydroxyapatite. The apatite structure was maintained after heat treatment of stoichiometric apatite, synthesized in the presence of iron. Sintering in air produced oxidation of Fe2+ to Fe3+, resulting in the formation of hematite as a secondary phase. The introduction of iron into the synthesis of hydroxyapatite causes: (i) an increase of the a-lattice parameter after synthesis and heat treatment in air; (ii) an increase in the c-lattice parameter after sintering in air.

  2. In vitro electromagnetically stimulated SAOS-2 osteoblasts inside porous hydroxyapatite

    Science.gov (United States)

    Fassina, Lorenzo; Saino, Enrica; Sbarra, Maria Sonia; Visai, Livia; De Angelis, Maria Gabriella Cusella; Magenes, Giovanni; Benazzo, Francesco

    2009-01-01

    One of the key challenges in reconstructive bone surgery is to provide living constructs that possess the ability to integrate in the surrounding tissue. Bone graft substitutes, such as autografts, allografts, xenografts, and biomaterials have been widely used to heal critical-size long bone defects due to trauma, tumor resection, congenital deformity, and tissue degeneration. In particular, porous hydroxyapatite is widely used in reconstructive bone surgery owing to its biocompatibility. In addition, the in vitro modification of hydroxyapatite with osteogenic signals enhances the tissue regeneration in vivo, suggesting that the biomaterial modification could play an important role in tissue engineering. In this study we have followed a biomimetic strategy where electromagnetically stimulated SAOS-2 human osteoblasts proliferated and built their extracellular matrix inside a porous hydroxyapatite scaffold. The electromagnetic stimulus had the following parameters: intensity of the magnetic field equal to 2 mT, amplitude of the induced electric tension equal to 5 mV, frequency of 75 Hz, and pulse duration of 1.3 ms. In comparison with control conditions, the electromagnetic stimulus increased the cell proliferation and the surface coating with bone proteins (decorin, osteocalcin, osteopontin, type-I collagen, and type-III collagen). The physical stimulus aimed at obtaining a better modification of the biomaterial internal surface in terms of cell colonization and coating with bone matrix. PMID:19827111

  3. Effect of thermal decomposition of hydroxyapatite on the thermoluminescent response

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval C, K. J.; Zarate M, J.; Lemus R, J. [Universidad Michoacana de San Nicolas de Hidalgo, Instituto de Investigaciones Metalurgicas, Ciudad Universitaria, Edificio U, 58060 Morelia, Michoacan (Mexico); Rivera M, T., E-mail: karlasandovalc@gmail.com [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico)

    2014-08-15

    In this work, a study on the thermoluminescence (Tl) induced by gamma radiation in synthetic hydroxyapatite (Hap) annealed at different temperatures obtained by the precipitation method is presented. Synthesis of hydroxyapatite Hap was carried out starting from inorganic precursors [Ca(NO{sub 3}){sub 2}·4H{sub 2}O and (NH{sub 4}){sub 2}HPO{sub 4}]. The precipitate was filtered, washed, dried and then the powder was calcined at different temperatures until the Hap decomposition. The structural and morphological characterization was carried out using both X-ray diffraction (XRD) and scanning electron microscopy (Sem) techniques. Thermoluminescent (Tl) properties of Hap powders were irradiated at different gamma radiation doses. According to X ray diffraction patterns, the tricalcium diphosphate phase (Tcp) appear when the Hap was calcined at 900 grades C. Tl glow curve showed two peaks located at around 200 and 300 grades C, respectively. Tl response as a function of gamma radiation dose was in a wide range from 25 to 100 Gy. The fading of the Tl response at 134 days after irradiation was measured. Experimental results showed that the synthetic hydroxyapatite obtained by precipitation technique may have dosimetric applications when is annealed at temperature of 900 grades C, where the Tcp phase appears and contributes to Tl response, which opens the possibility of using this biomaterials in the area of dosimetry, as they are generally used for biomedical implants. (author)

  4. Controlled synthesis and thermal stability of hydroxyapatite hierarchical microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Ruixue [College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Chen, Kezheng, E-mail: dxb@sdu.edu.cn [College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China); Liao, Zhongmiao; Meng, Nan [College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042 (China)

    2013-03-15

    Highlights: ► Hydroxyapatite hierarchical microstructures have been synthesized by a facile method. ► The morphology and size of the building units of 3D structures can be controlled. ► The hydroxyapatite with 3D structure is morphologically and structurally stable up to 800 °C. - Abstract: Hydroxyapatite (HAp) hierarchical microstructures with novel 3D morphology were prepared through a template- and surfactant-free hydrothermal homogeneous precipitation method. Field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the morphology and composition of the synthesized products. Interestingly, the obtained HAp with 3D structure is composed of one-dimensional (1D) nanorods or two-dimensional (2D) nanoribbons, and the length and morphology of these building blocks can be controlled through controlling the pH of the reaction. The building blocks are single crystalline and have different preferential orientation growth under different pH conditions. At low pH values, octacalcium phosphate (OCP) phase formed first and then transformed into HAp phase due to the increased pH value caused by the decomposition of urea. The investigation on the thermal stability reveals that the prepared HAp hierarchical microstructures are morphologically and structurally stable up to 800 °C.

  5. Osteoblast response to nanocrystalline calcium hydroxyapatite depends on carbonate content.

    Science.gov (United States)

    Adams, Brandy R; Mostafa, Amany; Schwartz, Zvi; Boyan, Barbara D

    2014-09-01

    Normal bone mineral is a carbonated-apatite, but there are limited data on the effect of mineral containing carbonate on cell response. We characterized surface chemical compositions of three experimental carbonated hydroxyapatite (CO3(2-) HA) substrates and investigated their effect on osteoblast differentiation. Carbonate was incorporated into the hydroxyapatite powders while phosphate and hydroxyl groups were shown to be reduced by analyzing the chemical composition of the substrate surfaces. CO3(2-) HA powders with increasing carbonate concentrations designated as C1 (3.88%), C2 (4.85%), and C3 (5.82%) were molded, pressed, and fired into 14 mm discs. We observed that calcium phosphate ratios increased monotonically with increasing carbonate content, whereas differentiation of MG63 cells decreased. CO3(2-) HA surfaces also affected factor production. Addition of carbonate caused a 70% reduction in osteoprotegerin (OPG) compared to cultures on pure HA, but the effect of carbonate was not dose-dependent. Low carbonate content reduced VEGF-A by 80%, but higher levels of carbonate reversed this effect in a concentration dependent manner, with the C3 VEFG-A levels approximately twice that of C1 levels. These observations collectively indicate that bone cells are sensitive to carbonate content in bone mineral and the effects of carbonate substitution vary with the outcome being measured. Overall, this study provides a preliminary understanding of how carbonate substitution within hydroxyapatite modulates cellular behavior. © 2013 Wiley Periodicals, Inc.

  6. Eggshell-Derived Hydroxyapatite: A New Era in Bone Regeneration.

    Science.gov (United States)

    Kattimani, Vivekanand; Lingamaneni, Krishna Prasad; Chakravarthi, Pandi Srinivas; Kumar, T S Sampath; Siddharthan, Arjunan

    2016-01-01

    Defects of maxillofacial skeleton lead to personal (functional and aesthetic), social and behavioral problems; which make the person to isolate from the main stream of society. So, bone regeneration is the need for proper structure, function, and aesthetics following cyst enucleation, trauma, and tumor ablative surgery; which helps for overall health of the individual. The preliminary study is planned to evaluate and compare the efficacy of eggshell-derived hydroxyapatite (EHA) and synthetic hydroxyapatite (SHA) following cystectomy. Microwave-processed calcium deficient EHA and commercially available SHA are used for grafting. Total 20 patients enrolled in this study, consisting 10 in each group between 20 and 45 years of age. All the patients were evaluated for bone regeneration at first, second, third, and sixth month's interval, postsurgically, using radiovisiograph and clinical parameters. The bone formation characteristics vary at second month when compared to SHA. This difference may be because of the kinetics involved in the regeneration pattern. The pattern of bone healing was trabecular after third month, indicating complete bone formation. The study showed constant raise of density and remained same at the end of study period. Both EHA and SHA graft materials are equally efficient in early bone regeneration. Within the limitations of this study the EHA showed promising results. Which indicates the eggshell waste-bio mineral is worthwhile raw material for the production of HA and is a Go Green procedure. Eggshell-derived hydroxyapatite is economic, compared with SHA.

  7. Clinical observation of modified hydroxyapatite implant in scleral shell

    Directory of Open Access Journals (Sweden)

    Qing-Wei Du

    2014-10-01

    Full Text Available AIM: To evaluate the clinical effects of modified hydroxyapatite implant in scleral shell.METHODS:Thirty-four cases were performed eye evisceration, autogenous sclera shell anterior and posterior petaloid shape with posterior sclera fenestration, hydroxyapatite artificial eyeballs were implanted at stage I, and conjunctival wound, orbital activity and other complications were observed after surgery.RESULTS: The follow-up was 6~12mo. There was no patients with implant exposure, sclera dissolution, conjunctival wound dehiscence, conjunctival sac constriction noted. All the patients got good activity of artificial globe, and the active range of side motion of the HA was 10°~15°.The artificial eyes looked symmetrical, and the eyes socket were full.CONCLUSION: The modified hydroxyapatite implant in scleral shell can maintain the normal anatomy of the orbital tissue, and also can get full eyes socket and good activity, It was an easy and simple surgery which could obtain satisfactory clinical effect and less complications.

  8. [Three methods with functions of modification on aluminum borate whisker and with influence on flexural properties of dental composite resins].

    Science.gov (United States)

    Yuan, Yanbo; Zhang, Wenyun; Chen, Qinghua; Li, Xingxing; Xiao, Yuhong

    2012-04-01

    The present paper is aimed to discuss the influence of three different ways on modification of aluminum borate whiskers (AlBw) and on flexural properties of dental composite resins. In Group A, AlBw and silicon dioxide (SiO2) nanoparticles were thermally fused directly under certain processes. In Group B, Si-O network was formed on the surface of AlBw via the sol-gel process of tetraethoxysilane, then thermally fused with SiO2 nanoparticles to form AlBw-SiO2 compound as inorganic fillers. In Group C, SiO2 nanoparticles were repaired by sol-gel method of tetraethoxysilane under certain processes, and were deposited in the surface of AlBw. The mixtures were fused with high temperature sintering method. The effects of the surface morphology of AlBw with different ways were characterized by TEM and SEM. Then the mixtures were polymerized with resin matrix after surface siliconization and their flexural strength and Young's modulus were determined. SEM was used to examine specimen fracture surfaces. The results showed that the flexural properties of dental composite resins were significantly improved after whiskers were modified. Different methods produce different effects. Flexural strength of the Group A is (95.28 +/- 4.53) MPa. The results of TEM and SEM revealed that the aggregation was obvious between AlBw and SiO2 nanoparticles. Flexural strength of the Group B was (123.14 +/- 17.37) MPa. The results of TEM and SEM revealed that the dispersity was improved but SiO2 nanoparticles also reunited. AlBw were modified with nanometer-size SiO2 particles which were prepared by sol-gel method based on tetraethyl orthosioate (TEOS), the flexural properties of a new type of dental composite resins was (130.29 +/- 8.38) MPa. The results of TEM and SEM revealed that better dispersion between AlBw and SiO2 nanoparticles occurred. The SiO2 nanoparticles were fused and attached onto the surface of AlBw uniformly.

  9. Synthesis and release of trace elements from hollow and porous hydroxyapatite spheres.

    Science.gov (United States)

    Xia, Wei; Grandfield, Kathryn; Schwenke, Almut; Engqvist, Håkan

    2011-07-29

    It is known that organic species regulate fabrication of hierarchical biological forms via solution methods. However, in this study, we observed that the presence of inorganic ions plays an important role in the formation and regulation of biological spherical hydroxyapatite formation. We present a mineralization method to prepare ion-doped hydroxyapatite spheres with a hierarchical structure that is free of organic surfactants and biological additives. Porous and hollow strontium-doped hydroxyapatite spheres were synthesized via controlling the concentration of strontium ions in a calcium and phosphate buffer solution. Similarly, fluoride and silicon-doped hydroxyapatite spheres were synthesized. While spherical particle formation was attainable at low and high temperature for Sr-doped hydroxyapatite, it was only possible at high temperature in the F/Si-doped system. The presence of inorganic ions not only plays an important role in the formation and regulation of biological spherical hydroxyapatite, but also could introduce pharmaceutical effects as a result of trace element release. Such ion release results showed a sustained release with pH responsive behavior, and significantly influenced the hydroxyapatite re-precipitation. These ion-doped hydroxyapatite spheres with hollow and porous structure could have promising applications as bone/tooth materials, drug delivery systems, and chromatography supports.

  10. Characterization and inhibitive study of gel-grown hydroxyapatite crystals at physiological temperature

    Science.gov (United States)

    Parekh, Bharat; Joshi, Mihir; Vaidya, Ashok

    2008-04-01

    Hydroxyapatite is very useful for various biomedical applications, due to its chemical similarity with mineralized bone of human. Hydroxyapatite is also responsible for arthropathy (joint disease). In the present study, the growth of hydroxyapatite crystals was carried out by using single-diffusion gel growth technique in silica hydro gel media, at physiological temperature. The growth of hydroxyapatite crystals under slow and controlled environment in gel medium can be simulated in a simple manner to the growth in human body. The crystals, formed in the Liesegang rings, were characterized by powder XRD, FTIR and dielectric study. The diffusion study is also carried out for the hydroxyapatite crystals using the moving boundary model. The inhibitive influence of various Ayurvedic medicinal plant extracts such as Boswellia serrata gum resin , Tribulus terrestris fruits, Rotula aquatica roots, Boerhaavia diffusa roots and Commiphora wightii, on the growth of hydroxyapatite was studied. Roots of R. aquatica and B. diffusa show some inhibition of the hydroxyapatite crystals in vitro. This preclinical study will be helpful to design the therapy for prevention of hydroxyapatite-based ailments.

  11. Synthesis and release of trace elements from hollow and porous hydroxyapatite spheres

    Science.gov (United States)

    Xia, Wei; Grandfield, Kathryn; Schwenke, Almut; Engqvist, Håkan

    2011-07-01

    It is known that organic species regulate fabrication of hierarchical biological forms via solution methods. However, in this study, we observed that the presence of inorganic ions plays an important role in the formation and regulation of biological spherical hydroxyapatite formation. We present a mineralization method to prepare ion-doped hydroxyapatite spheres with a hierarchical structure that is free of organic surfactants and biological additives. Porous and hollow strontium-doped hydroxyapatite spheres were synthesized via controlling the concentration of strontium ions in a calcium and phosphate buffer solution. Similarly, fluoride and silicon-doped hydroxyapatite spheres were synthesized. While spherical particle formation was attainable at low and high temperature for Sr-doped hydroxyapatite, it was only possible at high temperature in the F/Si-doped system. The presence of inorganic ions not only plays an important role in the formation and regulation of biological spherical hydroxyapatite, but also could introduce pharmaceutical effects as a result of trace element release. Such ion release results showed a sustained release with pH responsive behavior, and significantly influenced the hydroxyapatite re-precipitation. These ion-doped hydroxyapatite spheres with hollow and porous structure could have promising applications as bone/tooth materials, drug delivery systems, and chromatography supports.

  12. FORMATION OF CHLOROPYROMORPHITE IN A LEAD-CONTAMINATED SOIL AMENDED WITH HYDROXYAPATITE

    Science.gov (United States)

    To evaluate conversion of soil Pb to pyromorphite, a Pb contaminated soil collected adjacent to a historical smelter was reacted with hydroxyapatite in a traditional incubation experiment and in a dialysis system in which the soil and hydroxyapatite solids were separated by a dia...

  13. Nanophase hydroxyapatite as a biomaterial in advanced hard tissue engineering: a review

    NARCIS (Netherlands)

    Zakaria, S.M.; Zein, S.H. Sharif; Othman, M.R.; Yang, F.; Jansen, J.A.

    2013-01-01

    Hydroxyapatite is a biocompatible material that is extensively used in the replacement and regeneration of bone material. In nature, nanostructured hydroxyapatite is the main component present in hard body tissues. Hence, the state of the art in nanotechnology can be exploited to synthesize

  14. [In Situ Polymerization and Characterization of Hydroxyapatite/polyurethane Implanted Material].

    Science.gov (United States)

    Gu, Muqing; Xiao, Fengjuan; Liang, Ye; Yue, Lin; Li, Song; Li, Lanlan; Feng, Feifei

    2015-08-01

    In order to improve the interfacial bonding strength of hydroxyapatite/polyurethane implanted material and dispersion of hydroxyapatite in the polyurethane matrix, we in the present study synthesized nano-hydroxyapatite/polyurethane composites by in situ polymerization. We then characterized and analyzed the fracture morphology, thermal stability, glass transition temperature and mechanical properties. We seeded MG63 cells on composites to evaluate the cytocompatibility of the composites. In situ polymerization could improve the interfacial bonding strength, ameliorate dispersion of hydroxyapatite in the properties of the composites. After adding 20 wt% hydroxyapatite into the polyurethane, the thermal stability was improved and the glass transition temperatures were increased. The tensile strength and maximum elongation were 6.83 MPa and 861.17%, respectively. Compared with those of pure polyurethane the tensile strength and maximum elongation increased by 236.45% and 143.30%, respectively. The composites were helpful for cell adhesion and proliferation in cultivation.

  15. Physicochemical Analysis of the Polydimethylsiloxane Interlayer Influence on a Hydroxyapatite Doped with Silver Coating

    Directory of Open Access Journals (Sweden)

    C. L. Popa

    2015-01-01

    Full Text Available We investigate by different complementary methods the processes occurring when a polydimethylsiloxane film is used as interlayer for a silver doped hydroxyapatite coating. The X-ray diffraction and Fourier Transform Infrared Spectroscopy measurements show that the hydroxyapatite doped with silver is in a crystalline form and some SiO44- ions formation takes place at the surface and in the bulk of the new hydroxyapatite doped with silver/polydimethylsiloxane composite layer. The possibility of SiO44- ions incorporation in the structure of silver doped hydroxyapatite by the mechanism of SiO44-/PO43- ions substitution is analysed. The new formed silver doped hydroxyapatite/polydimethylsiloxane composite layer is compact, homogeneous, with no cracks as it was shown by Scanning Electron Microscopy and Glow Discharge Optical Emission Spectrometry.

  16. Influence of Starting Powders on Hydroxyapatite Coatings Fabricated by Room Temperature Spraying Method.

    Science.gov (United States)

    Seo, Dong Seok; Lee, Jong Kook; Hwang, Kyu Hong; Hahn, Byung Dong; Yoon, Seog Young

    2015-08-01

    Three types of raw materials were used for the fabrication of hydroxyapatite coatings by using the room temperature spraying method and their influence on the microstructure and in vitro characteristics were investigated. Starting hydroxyapatite powders for coatings on titanium substrate were prepared by a heat treatment at 1100 °C for 2 h of bovine bone, bone ash, and commercial hydroxyapatite powders. The phase compositions and Ca/P ratios of the three hydroxyapatite coatings were similar to those of the raw materials without decomposition or formation of a new phase. All hydroxyapatite coatings showed a honeycomb structure, but their surface microstructures revealed different features in regards to surface morphology and roughness, based on the staring materials. All coatings consisted of nano-sized grains and had dense microstructure. Inferred from in vitro experiments in pure water, all coatings have a good dissolution-resistance and biostability in water.

  17. C-Axis-Oriented Hydroxyapatite Film Grown Using ZnO Buffer Layer

    Science.gov (United States)

    Sakoishi, Yasuhiro; Iguchi, Ryo; Nishikawa, Hiroaki; Hontsu, Shigeki; Hayami, Takashi; Kusunoki, Masanobu

    2013-11-01

    A method of fabricating c-axis-oriented hydroxyapatite film on a quartz crystal microbalance (QCM) sensor was investigated. ZnO was used as a template to obtain a hexagonal hydroxyapatite crystal of uniaxial orientation. The ZnO was grown as a c-axis film on a Au/quartz with the surface structure of a QCM sensor. Under optimized conditions, hydroxyapatite was deposited by pulsed laser deposition. X-ray diffraction showed the hydroxyapatite film to be oriented along the c-axis. Because Au and ZnO are applied to many devices, the anisotropic properties of hydroxyapatite may be incorporated into these devices as well as QCM sensors.

  18. Is hydroxyapatite a reliable fixation option in unicompartmental knee arthroplasty? A 5- to 13-year experience with the hydroxyapatite-coated unix prosthesis.

    Science.gov (United States)

    Epinette, Jean-Alain; Manley, Michael T

    2008-10-01

    Hydroxyapatite-coated unicompartmental knee arthroplasty (UKA) is a debatable approach to unicompartmental knee arthritis because UKA isoften viewed as a short-term solution, at best, fora condition that will eventually require a total knee arthroplasty (TKA). Unicompartmental knee arthroplasty is a more technically demanding procedure than TKA, and appropriate patient selection, careful surgical technique, and correct choice of implant geometry are all critical components to its success. A fundamental issue surrounding UKA is whether hydroxyapatite-coated unicompartmental components can provide a long-term solution to unicondylar arthritis. We address this issue in the current study, which is based on a prospective series of 125 hydroxyapatite-coated Unix knee prostheses implanted consecutively between 1994 and 2002, with a 5-year minimum follow-up and a 13-year maximum follow-up. The results of our study indicate that uncemented hydroxyapatite-coated UKA can be successful in the long term.

  19. Product technology and market assessment for silicon carbide whisker reinforced alumina heat-exchanger tubes. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Loutfy, R.O.; Withers, J.C. [Materials and Electrochemical Research Corp., Tucson, AZ (United States); Chakravarti, D. [Arizona Univ., Tucson, AZ (United States)

    1993-10-01

    This report describes a study designed to develop an assessment of key performance features, desirable technical specifications and market potential for silicon carbide whisker-reinforced alumina (henceforth SCWRA) tubes for heat exchanger applications in a number of industries. The results of the first stage of a Delphi study conducted in the US market are presented. The second phase of the study is in progress. The first stage results suggest that there is a small market for SCWRA tubes in heat exchanger applications. The market is expected to grow steadily during the 1990`s. With appropriate performance specifications and competitive pricing, growth should come from (a) new applications that permit recovery in cases that were previously infeasible and (b) selective, partial substitution and replacement of current ceramics and metal/ceramic composites in existing applications. We identify key performance factors and detailed specifications needed in six designated industries (primary metals, fabricated metals, chemicals, glass, utility and incinerators). Reliability, durability and low maintenance costs emerge as critical performance factors across these industries. The data show that although ceramics are recognized as having better properties, enhancing reliability and durability and thus improving maintenance cost performance is a key priority. Such improvements, reflected in the objectives for SCWRA tubes, should facilitate adoption in both new and existing applications. At this time, we are unable to assess market size directly. However, expert judgment provided indices tracking the projected market for heat exchanger tubes from 1990 to 2005.

  20. Comparative evaluation of bovine derived hydroxyapatite and synthetic hydroxyapatite graft in bone regeneration of human maxillary cystic defects: A clinico-radiological study

    OpenAIRE

    Kattimani, Vivekanand. S; Srinivas P Chakravarthi; Naga Neelima Devi, K.; Meka S Sridhar; L Krishna Prasad

    2014-01-01

    Introduction: Bone grafts are frequently used in the treatment of bone defects. Bone harvesting can cause postoperative complications and sometimes does not provide a sufficient quantity of bone. Therefore, synthetic biomaterials have been investigated as an alternative to autogenous bone grafts. Aim and Objectives: The aim of this study was to evaluate and compare bovine derived hydroxyapatite (BHA) and synthetic hydroxyapatite (SHA) graft material as bone graft substitute in maxillary c...

  1. Novel bioresorbable strontium hydroxyapatite membrane for guided bone regeneration.

    Science.gov (United States)

    Hao, J; Acharya, A; Chen, K; Chou, J; Kasugai, S; Lang, N P

    2015-01-01

    Membrane materials have been widely used for guided bone regeneration (GBR). However, due to bio-functional limitation of the current membranes, the ideal resorbable membrane that can stimulate bone regeneration has yet to be developed. This study seeks to investigate the effects of a strontium hydroxyapatite (SrHA)-containing membrane for GBR. Strontium hydroxyapatite powder was synthesized and mixed with gelatin solution to the final concentration of 10 mg/ml (Sr10) and 20 mg/ml (Sr20). Approximately 100-μm-thick membranes were fabricated, and the mechanical properties and strontium ion release pattern were analyzed. Rat bone marrow stromal cell (BMSC) responses were investigated in vitro. Bilaterial rat calvarial defects were used in vivo to compare the SrHA membranes against commercially available collagen membranes and evaluated radiologically and histologically. Strontium hydroxyapatite membranes exhibited higher elasticity and strength than the collagen membrane, and slow strontium ion release was also confirmed. No BMSC cytotoxicity was found on the SrHA membranes, and the alkaline phosphatase positively stained area was significantly greater than the collagen membrane at earlier time point. At 4 weeks, both micro-CT and histological analyses revealed that the Sr20 group yielded significantly greater bone formation. The SrHA-containing membrane developed in this study was found to be a biocompatible material that can stimulate BMSC differentiation as well as bone regeneration and maturation in rat calvarial defects at early time point compared with collagen membrane. The best result was observed in Sr20 group, which can be potentially effective for GBR. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Preparation and characterization of antimicrobial nano-hydroxyapatite composites

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Juhong [The Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Ministry of Education, College of Materials and Textiles, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Chu, Xiaobing [The First Affiliated Hospital, Zhejiang Chinese Medicine University, Hangzhou 310006 (China); Cai, Yurong [The Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Ministry of Education, College of Materials and Textiles, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Tong, Peijian [The First Affiliated Hospital, Zhejiang Chinese Medicine University, Hangzhou 310006 (China); Yao, Juming, E-mail: yaoj@zstu.edu.cn [The Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Ministry of Education, College of Materials and Textiles, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

    2014-04-01

    Deep infection of prosthesis is one of the most frequent complications after joint replacement. One of the most effective ways is to introduce directly some antibiotics in the local site of the surgery. In the present study, an antimicrobial composite has been fabricated using nano-hydroxyapatite particles as carriers for the antimicrobial drug of vancomycin hydrochloride (VAN) and the mixture of oxidation sodium alginate (OSA) and gelatin (GT) as a sticky matrix. Samples have been characterized using X-ray diffraction instrument (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and Fourier transform infrared (FTIR) spectra, Brunauer–Emmett–Teller (BET) methods, the rotational rheometer and the texture analyzer. The release of VAN from nano-hydroxyapatite (nHAP) particles was detected by the ultraviolet–visible (UV–vis) spectrophotometer and then bactericidal property of the composite was evaluated using the Staphylococcus aureus (S. aureus) as a bacterial model. Experimental results showed that the composite possessed an adhesive property derived from the gel of OSA and GT, which implied that the composite could bond directly to the fracture surface of bones in surgery. Furthermore, VAN was loaded efficiently on the surface of nHAP particles and could be released slowly from these particles, which endowed the composite with an obvious and continuous antimicrobial performance. The sticky and antimicrobial composite may has a potential application in arthroplasty to overcome deep infection in a simple and direct manner. - Highlights: • A sticky and antimicrobial composite has been designed to overcome deep infection. • The composite was composed of antibiotic, antibiotic carrier and a viscous matrix. • The sticky matrix was obtained by blending of oxidation sodium alginate and gelatin. • Hydroxyapatite nanoparticle could be used as carrier to control release of antibiotic.

  3. Risedronate/zinc-hydroxyapatite based nanomedicine for osteoporosis

    Energy Technology Data Exchange (ETDEWEB)

    Khajuria, Deepak Kumar, E-mail: deepak_kumarkhajuria@yahoo.co.in [Laboratory for Integrative Multiscale Engineering Materials and Systems, Department of Aerospace Engineering, Indian Institute of Science, Bangalore 560012 (India); Department of Pharmacology, Al-Ameen College of Pharmacy, Bangalore 560027 (India); Disha, Choudhary [Department of Pharmacology, Al-Ameen College of Pharmacy, Bangalore 560027 (India); Vasireddi, Ramakrishna [Laboratory for Integrative Multiscale Engineering Materials and Systems, Department of Aerospace Engineering, Indian Institute of Science, Bangalore 560012 (India); Razdan, Rema [Department of Pharmacology, Al-Ameen College of Pharmacy, Bangalore 560027 (India); Mahapatra, D. Roy [Laboratory for Integrative Multiscale Engineering Materials and Systems, Department of Aerospace Engineering, Indian Institute of Science, Bangalore 560012 (India)

    2016-06-01

    Targeting of superior osteogenic drugs to bone is an ideal approach for treatment of osteoporosis. Here, we investigated the potential of using risedronate/zinc-hydroxyapatite (ZnHA) nanoparticles based formulation in a rat model of experimental osteoporosis. Risedronate, a targeting moiety that has a strong affinity for bone, was loaded to ZnHA nanoparticles by adsorption method. Prepared risedronate/ZnHA drug formulation was characterized by field-emission scanning electron microscopy, X-ray diffraction analysis and fourier transform infrared spectroscopy. In vivo performance of the prepared risedronate/ZnHA nanoparticles was tested in an experimental model of postmenopausal osteoporosis. Therapy with risedronate/ZnHA drug formulation prevented increase in serum levels of bone-specific alkaline phosphatase and tartrate-resistant acid phosphatase 5b better than risedronate/HA or risedronate. With respect to improvement in the mechanical strength of the femoral mid-shaft and correction of increase in urine calcium and creatinine levels, the therapy with risedronate/ZnHA drug formulation was more effective than risedronate/HA or risedronate therapy. Moreover, risedronate/ZnHA drug therapy preserved the cortical and trabecular bone microarchitecture better than risedronate/HA or risedronate therapy. Furthermore, risedronate/ZnHA drug formulation showed higher values of calcium/phosphorous ratio and zinc content. The results strongly implicate that risedronate/ZnHA drug formulation has a therapeutic advantage over risedronate or risedronate/HA therapy for the treatment of osteoporosis. - Highlights: • Risedronate functionalized zinc-hydroxyapatite nanoparticles were prepared. • Risedronate was used as a carrier to deliver zinc-hydroxyapatite nanoparticles to bones. • Application of risedronate/ZnHA drug formulation in osteoporosis is described.

  4. Introducing the fluorine doped natural hydroxyapatite-titania nanobiocomposite ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Karamian, Ebrahim [Advanced Materials Research Center, Faculty of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad (Iran, Islamic Republic of); Abdellahi, Majid, E-mail: M.Abdellahi@Pa.iut.ac.ir [Advanced Materials Research Center, Faculty of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad (Iran, Islamic Republic of); Khandan, Amirsalar [Young Researchers and Elite Club, Khomeinishahr Branch, Islamic Azad University, Isfahan (Iran, Islamic Republic of); Abdellah, Sana [Advanced Materials Research Center, Faculty of Materials Engineering, Najafabad Branch, Islamic Azad University, Najafabad (Iran, Islamic Republic of)

    2016-09-15

    In the present research, natural hydroxyapatite (NHA) was synthesized from bovine bones and then fluorine was doped into the NHA matrix to produce fluorine doped NHA (FNHA; natural fluor-hydroxyapatite) in optimum conditions. At the end an FNHA-TiO{sub 2} nanobiocomposite ceramic with excellent biocompatibility and good chemical stability was synthesized through a mechanochemical route and a subsequent two step sintering (TSS) process. Thermal gravimetric analysis (TGA), Differential scanning calorimetry (DSC), X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), inductive coupled plasma (ICP), and energy-dispersive X-ray spectroscopy (EDX) were used as the means for gathering and analysis of the results. According to the obtained results, TiO{sub 2} can prevent early decomposition of FNHA by the formation of the CaTiO{sub 3} phases and hence strengthen the interactions between the apatite particles which results in the increase of the mechanical properties. Besides, TiO{sub 2} provides more Si−OH nucleation sites for the formation of the apatite layers and hence more bioactivity. - Highlights: • This work begins with preparing natural hydroxyapatite from bovine bones via a simple method. • With increasing the TiO{sub 2} content reinforced in FNHA matrix, the compaction increases. • TiO{sub 2} can prevent early decomposition of FNHA by the formation of CaTiO{sub 3} phase. • TiO{sub 2} can strengthen the interactions between the apatite particles and increase of compaction. • With increasing TiO{sub 2} content, the Si−OH nucleation sites increases lead to more bioactivity.

  5. Complications of pegged and non-pegged hydroxyapatite orbital implants.

    Science.gov (United States)

    Fahim, Daniel K; Frueh, Bartley R; Musch, David C; Nelson, Christine C

    2007-01-01

    The purpose of this study is twofold: to assess the incidence and implications of complications unique to placing a freestanding polycarbonate peg in patients with hydroxyapatite implants and to compare the incidence of complications in these patients with the incidence in patients with non-pegged hydroxyapatite implants. This is a retrospective clinical case series of 103 patients who underwent hydroxyapatite implant insertion at our institution. The incidence of postoperative complications in patients who underwent freestanding polycarbonate pegging procedures (n = 21) and those who had not (n = 82) were compared. One postoperative complication - infection - occurred in a significantly higher percentage of patients in the pegged group (42.9%, 9/21) compared with the non-pegged group (19.5%, 16/82), (p = 0.037). Fifteen of the 21 patients (71.4%) in the pegged group experienced complications unique to freestanding polycarbonate pegging. Overall, 95.2% (20/21) of patients in the pegged group experienced a complication compared with 58.5% (48/82) of patients in the non-pegged group, (p = 0.001). In addition, there was an average of 3.1 (66/21) complications per patient in the pegged group compared with an average of 1.9 (106/82) complications per patient in the non-pegged group (p = 0.010). Patients who received a freestanding polycarbonate pegged implant had a high risk of experiencing complications unique to pegging, and therefore a significantly higher rate of complications overall when compared with patients whose implant was not pegged. In addition, patients who received a pegged implant had a higher incidence of infection. However, most patients retained their pegs despite complications.

  6. Hydroxyapatite-Functionalized Graphene: A New Hybrid Nanomaterial

    Directory of Open Access Journals (Sweden)

    C. Rodríguez-González

    2014-01-01

    Full Text Available Graphene oxide sheets (GO were functionalized with hydroxyapatite nanoparticles (nHAp through a simple and effective hydrothermal treatment and a novel physicochemical process. Microstructure and crystallinity were investigated by Fourier transform infrared spectroscopy (FT-IR, Raman spectroscopy, X-ray diffraction (XRD, ultraviolet-visible (UV-Vis absorption spectroscopy, and thermogravimetric analysis (TGA. Transmission electron microscopy (TEM and scanning electron microscopy (SEM were performed to characterize the morphology of the functionalized material. The resulting novel materials combine the biocompatibility of the nHAp with the strength and physical properties of the graphene.

  7. Microwave annealing for preparation of crystalline hydroxyapatite thin films

    CSIR Research Space (South Africa)

    Adams

    2006-11-01

    Full Text Available Microwave annealing for preparation of crystalline hydroxyapatite thin films Daniel Adams Æ Gerald F. Malgas Æ R. D. Smith Æ S. P. Massia Æ T. L. Alford Æ J. W. Mayer Received: 18 October 2004 / Accepted: 22 December 2005 / Published online: 8 October... stream_source_info Adams_2006.pdf.txt stream_content_type text/plain stream_size 34761 Content-Encoding UTF-8 stream_name Adams_2006.pdf.txt Content-Type text/plain; charset=UTF-8 Abstract A sol was spun on single...

  8. Crystal Structure and Carbonate Species into Structure of Hydroxyapatite

    OpenAIRE

    元上, 康孝; 管野, 亨; 小林, 正義; 赤澤, 敏之; MOTOGAMI, Yasutaka; KANNO, Tohru; Kobayashi, Masayoshi; Akazawa, Toshiyuki

    1998-01-01

    The morphology of hydroxyapatite (HAp) had a significant effect on carbonates incorporated into HAp structures. A cattle bone-originated HAp (r-HAp) had two carbonates, OH-substituted and P04- substituted, and chemically synthesized HAp (s-HAp) had only the latter carbonate. This difference was ascribed to the increased calcium deficiency of r-HAp. Partial substitution of Sr for Ca caused expansion of the P-O bond and subjected the HAp structure to stress. This stress decreased the decomposit...

  9. Bioactivity And Bone Formation In Silicon-Substituted Hydroxyapatite

    Directory of Open Access Journals (Sweden)

    Ulvan Ozad

    2012-06-01

    Full Text Available Bioactivity and successful bone formation in silicon-substituted hydroxyapatite bone grafts were investigated by using scanning electron microscopy and electron dispersive x-ray spectroscopy. Areas of bone formation have been detected in scanning electron microscopy; and, arranged lamellar collagen has been observed. 20.8% average carbon content rise has been detected between bone graft and the produced bone; and, this has been confirmed to be a gradual increase throughout the interphase. Obvious bone formation and maturation were observed in the samples. Carbon content gradually increased from bone graft to the bone formed, confirming formation of new bone and dissociation of silicon-substituted bone graft.

  10. Ion-exchange properties of strontium hydroxyapatite under acidic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Shigeru; Nishioka, Hitoshi; Moriga, Toshihiro; Hayashi, Hiromu [Univ. of Tokushima, Minamijosanjima (Japan). Dept. of Chemical Science and Technology; Moffat, J.B. [Univ. of Waterloo, Ontario (Canada)

    1998-09-01

    The ion exchange of strontium hydroxyapatite (SrHAp) with Pb{sup 2+} has been investigated under acidic conditions at 293 K. The addition of various acids to the exchanging solution enhanced the exchange capacity in the order HCl > HBr > HF > HNO{sub 3} > no acid, corresponding to the formation of halogen apatites with the former three acids or hydrogen phosphate with HNO{sub 3}. Since the ion-exchange capacity of SrHAp under nonacidic conditions is higher than that of chlorapatite, the aforementioned observations can be attributed to the participation of the protons introduced by the acids.z

  11. Hybrid organic-inorganic materials based on hydroxyapatite structure

    Energy Technology Data Exchange (ETDEWEB)

    Moussa, Sana Ben; Bachouâ, Hassen [U.R. Matériaux et synthèse organique UR17ES31, Institut Préparatoire aux Etudes d’Ingénieur de Monastir, Université de Monastir, 5019 Monastir (Tunisia); Gruselle, Michel, E-mail: michel.gruselle@upmc.fr [Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8232, Institut Parisien de Chimie Moléculaire, F-75005 Paris (France); Beaunier, Patricia [Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 7197, Laboratoire de Réactivité de Surface, F-75005 Paris (France); Flambard, Alexandrine [Sorbonne Université, UPMC Univ Paris 06, CNRS, UMR 8232, Institut Parisien de Chimie Moléculaire, F-75005 Paris (France); Badraoui, Béchir [U.R. Matériaux et synthèse organique UR17ES31, Institut Préparatoire aux Etudes d’Ingénieur de Monastir, Université de Monastir, 5019 Monastir (Tunisia)

    2017-04-15

    The present article details the formation of calcium hydroxyapatite synthesized by the hydrothermal way, in presence of glycine or sarcosine. The presence of these amino-acids during the synthetic processes reduces the crystalline growthing through the formation of hybrid organic-inorganic species The crystallite sizes are decreasing and the morphology is modified with the increase of the amino-acid concentration. - Graphical abstract: Formation of Ca carboxylate salt leading to the grafting of glycine and sarcosine on the Ca=Hap surface (R= H, CH3).

  12. Hydroxyapatite-binding peptides for bone growth and inhibition

    Science.gov (United States)

    Bertozzi, Carolyn R [Berkeley, CA; Song, Jie [Shrewsbury, MA; Lee, Seung-Wuk [Walnut Creek, CA

    2011-09-20

    Hydroxyapatite (HA)-binding peptides are selected using combinatorial phage library display. Pseudo-repetitive consensus amino acid sequences possessing periodic hydroxyl side chains in every two or three amino acid sequences are obtained. These sequences resemble the (Gly-Pro-Hyp).sub.x repeat of human type I collagen, a major component of extracellular matrices of natural bone. A consistent presence of basic amino acid residues is also observed. The peptides are synthesized by the solid-phase synthetic method and then used for template-driven HA-mineralization. Microscopy reveal that the peptides template the growth of polycrystalline HA crystals .about.40 nm in size.

  13. Comparison of murine fibroblast cell response to fluor-hydroxyapatite composite, fluorapatite and hydroxyapatite by eluate assay.

    Science.gov (United States)

    Jantová, Sona; Letasiová, Silvia; Theiszová, Marica; Palou, M

    2009-03-01

    Fluorapatite (FA) is one of the inorganic constituents of bone or teeth used for hard tissue repairs and replacements. Fluor-hydroxyapatite (FHA) is a new synthetic composite that contains the same molecular concentration of OH(-) groups and F(-) ions. The aim of this experiment was to evaluate the cellular responses of murine fibroblast NIH-3T3 cells in vitro to solid solutions of FHA and FA and to compare them with the effect of hydroxyapatite (HA). We studied 24, 48 and 72 h effects of biomaterials on cell morphology, proliferation and cell cycle of NIH-3T3 cells by eluate assay. Furthermore, we examined the ability of FHA, FA and HA to induce cell death and DNA damage. Our cytotoxic/antiproliferative studies indicated that any of tested biomaterials did not cause the total inhibition of cell division. Biomaterials induced different antiproliferative effects increasing in the order HA < FHA < FA which were time- and concentration-dependent. None of the tested biomaterials induced necrotic/apoptotic death of NIH-3T3 cells. On the other hand, after 72 h we found that FHA and FA induced G0/G1 arrest of NIH-3T3 cells, while HA did not affect any cell cycle phases. Comet assay showed that while HA demonstrated weaker genotoxicity, DNA damage induced by FHA and FA caused G0/G1 arrest of NIH-3T3 cells. Fluoridation of hydroxyapatite and different FHA and FA structure caused different cell response of NIH-3T3 cells to biomaterials.

  14. Surface fractal dimensions and textural properties of mesoporous alkaline-earth hydroxyapatites

    Energy Technology Data Exchange (ETDEWEB)

    Vilchis-Granados, J. [Instituto Nacional de Investigaciones Nucleares, Departamento de Química, A.P. 18-1027, Col. Escandón, Delegación Miguel Hidalgo, C.P. 11801, México, DF (Mexico); Universidad Autónoma del Estado de México, Facultad de Química, Av. Paseo Colón esquina con Paseo Tollocan s/n Toluca, México (Mexico); Granados-Correa, F., E-mail: francisco.granados@inin.gob.mx [Instituto Nacional de Investigaciones Nucleares, Departamento de Química, A.P. 18-1027, Col. Escandón, Delegación Miguel Hidalgo, C.P. 11801, México, DF (Mexico); Barrera-Díaz, C.E. [Universidad Autónoma del Estado de México, Facultad de Química, Av. Paseo Colón esquina con Paseo Tollocan s/n Toluca, México (Mexico)

    2013-08-15

    This work examines the surface fractal dimensions (D{sub f}) and textural properties of three different alkaline-earth hydroxyapatites. Calcium, strontium and barium hydroxyapatite compounds were successfully synthesized via chemical precipitation method and characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, Fourier transform infrared spectroscopy, and N{sub 2}-physisorption measurements. Surface fractal dimensions were determined using single N{sub 2}-adsorption/desorption isotherms method to quantify the irregular surface of as-prepared compounds. The obtained materials were also characterized through their surface hydroxyl group content, determined by the mass titration method. It was found that the D{sub f} values for the three materials covered the range of 0.77 ± 0.04–2.33 ± 0.11; these results indicated that the materials tend to have smooth surfaces, except the irregular surface of barium hydroxyapatite. Moreover, regarding the synthesized calcium hydroxyapatite exhibited better textural properties compared with the synthesized strontium and barium hydroxyapatites for adsorbent purposes. However, barium hydroxyapatite shows irregular surface, indicating a high population of active sites across the surface, in comparison with the others studied hydroxyapatites. Finally, the results showed a linear correlation between the surface hydroxyl group content at the external surface of materials and their surface fractal dimensions.

  15. [Study on the antibacterial activity of four kinds of nano-hydroxyapatite composites against Enterococcus faecalis].

    Science.gov (United States)

    Liu, Yi; Zhou, Rongjing; Wu, Hongkun

    2015-06-01

    This study aims to compare and determine a kind of nano-hydroxyapatite composite material with good antibacterial efficacy on Enterococcusfaecalis (E. faecalis) in vitro. We investigated the antimicrobial activity of four kinds of nano-hydroxyapatite composites, namely, silver/hydroxyapatite composite nanoparticles (Ag/nHA), yttrium/hydroxyapatite composite nanoparticles (Yi/nHA), cerium/hydroxyapatite composite nanoparticles (Ce/nHA), and hydroxyapatite nanoparticles (nHA), against E. faecalis in vitro using the agar diffusion and broth dilution method by measuring the growth inhibition zone and the minimum inhibitory concentration (MIC), respectively. The agar diffusion test results showed that Ag/nHA displayed an obvious growth inhibition zone, whereas Yi/nHA, Ce/nHA, and nHA showed no influence on E. faecalis. The MIC value of Ag/nHA was 1.0 g.L-1, and the three other materials had no effect on E.faecalis even at the high concentration of 32.0 g.L-1. Ag/nHA display a potential antimicrobial efficacy to planktonic E.faecalis. Whereas, the three other kinds of nano-hydroxyapatite composites (Yi/nHA, Ce/nHA, nHA) show no influence.

  16. In vitro and in vivo evaluation of silicated hydroxyapatite and impact of insulin adsorption.

    Science.gov (United States)

    Lasgorceix, M; Costa, A M; Mavropoulos, E; Sader, M; Calasans, M; Tanaka, M N; Rossi, A; Damia, C; Chotard-Ghodsnia, R; Champion, E

    2014-10-01

    This study evaluates the biological behaviour, in vitro and in vivo, of silicated hydroxyapatite with and without insulin adsorbed on the material surface. Insulin was successfully adsorbed on hydroxyapatite and silicated hydroxyapatite bioceramics. The modification of the protein secondary structure after the adsorption was investigated by means of infrared and circular dichroism spectroscopic methods. Both results were in agreement and indicated that the adsorption process was likely to change the secondary structure of the insulin from a majority of α-helix to a β-sheet form. The biocompatibility of both materials, with and without adsorbed insulin on their surface, was demonstrated in vitro by indirect and direct assays. A good viability of the cells was found and no proliferation effect was observed regardless of the material composition and of the presence or absence of insulin. Dense granules of each material were implanted subcutaneously in mice for 1, 3 and 9 weeks. At 9 weeks of implantation, a higher inflammatory response was observed for silicated hydroxyapatite than for pure hydroxyapatite but no significant effect of adsorbed insulin was detected. Though the presence of silicon in hydroxyapatite did not improve the biological behaviour, the silicon substituted hydroxyapatite remained highly viable.

  17. An improved biofunction of titanium for keratoprosthesis by hydroxyapatite-coating.

    Science.gov (United States)

    Dong, Ying; Yang, Jingxin; Wang, Liqiang; Ma, Xiao; Huang, Yifei; Qiu, Zhiye; Cui, Fuzhai

    2014-03-01

    Titanium framework keratoprosthesis has been commonly used in the severe corneal blindness, but the tissue melting occurred frequently around titanium. Since hydroxyapatite has been approved to possess a good tissue integration characteristic, nanostructured hydroxyapatite was coated on the surface of titanium through the aerosol deposition method. In this study, nanostructured hydroxyapatite coating was characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy, and auger electronic spectrometer. Biological evaluations were performed with rabbit cornea fibroblast in vitro and an animal model in vivo. The outcomes showed the coating had a grain-like surface topography and a good atomic mixed area with substrate. The rabbit cornea fibroblasts appeared a good adhesion on the surface of nanostructured hydroxyapatite in vitro. In the animal model, nanostructured hydroxyapatite-titanium implants were stably retained in the rabbit cornea, and by contrast, the corneal stroma became thinner anterior to the implants in the control. Therefore, our findings proved that nanostructured hydroxyapatite-titanium could not only provide an improved bond for substrate but also enhance the tissue integration with implants in host. As a promising material, nanostructured hydroxyapatite-titanium-based keratoprosthesis prepared by the aerosol deposition method could be utilized for the corneal blindness treatment.

  18. Alendronate functionalized mesoporous hydroxyapatite nanoparticles for drug delivery

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dongdong, E-mail: lidongchem@sina.cn [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China); Zhu, Yuntao; Liang, Zhiqiang [State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012 (China)

    2013-06-01

    Highlights: ► The synthesized mesoporous hydroxyapatite has nanostructure and bioactivity. ► The materials have high surface area and amino group. ► The materials show higher drug loading and slower release rate than pure HAP. - Abstract: Mesoporous nanosized hydroxyapatite (HAP) functionalized by alendronate (ALN) was synthesized using cationic surfactant CTAB as template. The structural, morphological and textural properties were fully characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and N{sub 2} adsorption/desorption. Then the obtained materials were performed as drug delivery carriers using ibuprofen (IBU) as a model drug to investigate their drug storage/release properties in simulated body fluid (SBF). The materials showed relatively slower release rate compared with HAP due to the ionic interaction between -NH{sub 3}{sup +} on the matrix and -COO{sup −}belongs to IBU. The system provides a new concept for improving the drug loading or slowing down the release rate.

  19. Strontium and zoledronate hydroxyapatites graded composite coatings for bone prostheses.

    Science.gov (United States)

    Boanini, Elisa; Torricelli, Paola; Sima, Felix; Axente, Emanuel; Fini, Milena; Mihailescu, Ion N; Bigi, Adriana

    2015-06-15

    Both strontium and zoledronate (ZOL) are known to be useful for the treatment of bone diseases associated to the loss of bone substance. In this work, we applied an innovative technique, Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE), to deposit gradient thin films with variable compositions of Sr-substituted hydroxyapatite (SrHA) and ZOL modified hydroxyapatite (ZOLHA) on Titanium substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. The coatings display good crystallinity and granular morphology, which do not vary with composition. Osteoblast-like MG63 cells and human osteoclasts were co-cultured on the thin films up to 21 days. The results show that Sr counteracts the negative effect of relatively high concentration of ZOL on osteoblast viability, whereas both Sr and ZOL enhance extracellular matrix deposition. In particular, ZOL promotes type I collagen production, whereas Sr increases the production of alkaline phosphatase. Moreover, ZOL exerts a greater effect than Sr on osteoprotegerin/RANKL ratio and, as a consequence, on the reduction of osteoclast proliferation and activity. The deposition method allows to modulate the composition of the thin films and hence the promotion of bone growth and the inhibition of bone resorption. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Hydroxyapatite Nanopowder Synthesis with a Programmed Resorption Rate

    Directory of Open Access Journals (Sweden)

    Dariusz Smoleń

    2012-01-01

    Full Text Available A microwave, solvothermal synthesis of hydroxyapatite (HAp nanopowder with a programmed material resorption rate was developed. The aqueous reaction solution was heated by a microwave radiation field with high energy density. The measurements included powder X-ray diffraction (PXRD and the density, specific surface area (SSA, and chemical composition as specified by the inductively coupled plasma optical emission spectrometry technique (ICP-OES. The morphology and structure were investigated using scanning electron microscopy (SEM and transmission electron microscopy (TEM. A degradation test in accordance with norm ISO 10993-4 was conducted. The developed method enables control of the average grain size and chemical composition of the obtained HAp nanoparticles by regulating the microwave radiation time. As a consequence, it allows programming of the material degradation rate and makes possible an adjustment of the material activity in a human body to meet individual resorption rate needs. The authors synthesized a pure, fully crystalline hexagonal hydroxyapatite nanopowder with a specific surface area from 60 to almost 240 m2/g, a Ca/P molar ratio in the range of 1.57–1.67, and an average grain size from 6 nm to over 30 nm. A 28-day degradation test indicated that the material solubility ranged from 4 to 20 mg/dm3.

  1. Effect of hydroxyapatite-based biomaterials on human osteoblast phenotype.

    Science.gov (United States)

    Trombelli, L; Penolazzi, L; Torreggiani, E; Farina, R; Lambertini, E; Vecchiatini, R; Piva, R

    2010-03-01

    The present study evaluated human primary osteoblasts and two different osteoblast-like cell lines behaviour when cultured in presence of different hydroxyapatite-based (HA) biomaterials (SINTlife-FIN-CERAMICA S.p.a., Faenza, Italy; Bio-Oss, Geistlich Biomaterials, Woulhusen, Switzerland; Biostite-GABA Vebas, San Giuliano Milanese, MI, Italy), focusing attention on the effect of HA/Biostite in terms of modulation of osteoblastic differentiation. Analysis were about adhesion, proliferation and mineralization activity. Runt-related transcription factor 2 (Runx2), Estrogen Receptor alpha (ERalfa) expression and alkaline phosphatase activity (ALP) were measured as osteoblastic differentiation markers. Determination of viable cells was done with MTT colorimetric assay. Scanning electron microscopy (SEM) analysis was performed on biomaterial-treated cells. All hydroxyapatite-based biomaterials didn't affect cells morphology and viability, whereas only presence of HA/Biostite improved cells adhesion, growth and differentiation. Adhesion and spreading of the primary cells on HA/Biostite were the same showed by two different osteoblast-like cell lines. These results have important implications for both tissue-engineered bone grafts and enhancement of HA implants performance, to develop new teeth's supporting structure therapies and replacement.

  2. Monodisperse selenium-substituted hydroxyapatite: Controllable synthesis and biocompatibility.

    Science.gov (United States)

    Sun, Jianpeng; Zheng, Xiaoyan; Li, Hui; Fan, Daidi; Song, Zhanping; Ma, Haixia; Hua, Xiufu; Hui, Junfeng

    2017-04-01

    Hydroxyapatite (HA) is the major inorganic component of natural bone tissue. As an essential trace element, selenium involves in antioxidation and anticancer of human body. So far, ion-doped hydroxyapatites (HAs) are widely investigated owing to their great applications in field of biomaterial, biological labeling. In this paper, series of monodisperse HA doped with SeO32- (SeHA) was successfully synthesized based on the liquid-solid-solution (LSS) strategy. The obtained samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive spectrometer (EDS). The results indicated that the SeO32- doping level of the Se/(P+Se) molar ratio of 0-0.4 can be requisitely controlled, and the morphology of SeHA nanoparticles varied from nanorods to nanoneedles with increasing Se/(P+Se) molar ratio. Significantly, the as-synthesized SeHA nanocrystals exhibit a low cytotoxicity for osteoblastic cells, showing exciting potentials for application in artificial scaffold materials inhibiting of tumor growth in bone. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Synthesis of Nano Hydroxyapatite: Application in Drug Delivery of Sulfasalazine

    Directory of Open Access Journals (Sweden)

    D. Moslemi

    2015-10-01

    Full Text Available In this work we synthesized Nano hydroxyapatite (HAp  by Sol-gel method, Then we functionalized hydroxyapatite nanoparticle by use of  3-Aminopropyl trimethoxysilane (APTMS , to improve the loading and control release of sulfasalazine drug bonded to APTMS. The drug release patterns from Sulfasalazine loaded HAp nanoparticles at pH value 8 For 6h, Sulfasalazine loaded functionalized HAp nanoparticles (Sulfasalazine loaded HAp-APTMS at pH value 8 as in the intestine for 48h. Moreover, the functionalized HAp showed relatively slower release rate of sulfasalazine compare with non functionalized HAp. because the strong ionic interaction between NH2 group in sulfasalazine in HAp-APTMS. On other side, the functionalized HAp loaded more drug than pure HAp. The synthesized nanoparticles and functionalized HAp characterized by Scanning Electron Microscopy (SEM, X-ray Diffraction (XRD, Fourier transform infrared (FT-IR and  UV/Vis analysis techniques. Then the obtained material was studied in the simulated body fluid (SBF to this investigated storage and release properties.

  4. Biocompatible nano-gallium/hydroxyapatite nanocomposite with antimicrobial activity.

    Science.gov (United States)

    Kurtjak, Mario; Vukomanović, Marija; Kramer, Lovro; Suvorov, Danilo

    2016-11-01

    Intensive research in the area of medical nanotechnology, especially to cope with the bacterial resistance against conventional antibiotics, has shown strong antimicrobial action of metallic and metal-oxide nanomaterials towards a wide variety of bacteria. However, the important remaining problem is that nanomaterials with highest antibacterial activity generally express also a high level of cytotoxicity for mammalian cells. Here we present gallium nanoparticles as a new solution to this problem. We developed a nanocomposite from bioactive hydroxyapatite nanorods (84 wt %) and antibacterial nanospheres of elemental gallium (16 wt %) with mode diameter of 22 ± 11 nm. In direct comparison, such nanocomposite with gallium nanoparticles exhibited better antibacterial properties against Pseudomonas aeruginosa and lower in-vitro cytotoxicity for human lung fibroblasts IMR-90 and mouse fibroblasts L929 (efficient antibacterial action and low toxicity from 0.1 to 1 g/L) than the nanocomposite of hydroxyapatite and silver nanoparticles (efficient antibacterial action and low toxicity from 0.2 to 0.25 g/L). This is the first report of a biomaterial composite with gallium nanoparticles. The observed strong antibacterial properties and low cytotoxicity make the investigated material promising for the prevention of implantation-induced infections that are frequently caused by P. aeruginosa.

  5. Properties of pulsed laser deposited fluorinated hydroxyapatite films on titanium

    Energy Technology Data Exchange (ETDEWEB)

    Rau, J.V., E-mail: giulietta.rau@ism.cnr.it [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Smirnov, V.V. [A.A. Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Leninsky Prospect 49, 119991 Moscow (Russian Federation); Laureti, S. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via Salaria km 29.300, 00016 Monterotondo Scalo (RM) (Italy); Generosi, A. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Varvaro, G. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via Salaria km 29.300, 00016 Monterotondo Scalo (RM) (Italy); Fosca, M. [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Ferro, D.; Cesaro, S. Nunziante [Istituto per lo Studio dei Materiali Nanostrutturati, Consiglio Nazionale delle Ricerche, Piazzale Aldo Moro 5, 00185 Rome (Italy); Albertini, V. Rossi [Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche, Via del Fosso del Cavaliere 100, 00133 Rome (Italy); Barinov, S.M. [A.A. Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Leninsky Prospect 49, 119991 Moscow (Russian Federation)

    2010-09-15

    Fluorinated hydroxyapatite coated titanium was investigated for application as implant coating for bone substitute materials in orthopaedics and dentistry. Pulsed laser deposition technique was used for films preparation. Fluorinated hydroxyapatite target composition, Ca{sub 10}(PO{sub 4}){sub 6}F{sub 1.37}(OH){sub 0.63}, was maintained at 2 J/cm{sup 2} of laser fluence and 500-600 {sup o}C of the substrate temperature. Prepared films had a compact microstructure, composed of spherical micrometric-size aggregates. The average surface roughness resulted to be of 3 nm for the film grown at 500 {sup o}C and of 10 nm for that grown at 600 {sup o}C, showing that the temperature increase did not favour the growth of a more fine granulated surface. The films were polycrystalline with no preferential growth orientation. The films grown at 500-600 {sup o}C were about 8 {mu}m thick and possessed a hardness of 12-13 GPa. Lower or higher substrate temperature provides the possibility to obtain coatings with different fine texture and roughness, thus tayloring them for various applications.

  6. Assessment of microarchitecture and crystal structure of hydroxyapatite in osteoporosis

    Directory of Open Access Journals (Sweden)

    Zairin Noor

    2016-02-01

    Full Text Available Osteoporosis is characterized by lower bone mineral density (BMD and microarchitectural degeneration, which tends to increase bone fragility and fracture risk. Bone microstructure depends on interactions between the mineral atoms, which may perform substitution or incorporation into bone crystals, and may dynamically take over the function of calcium or may become a complementary part. The mineral atoms may also become a composite in the hydroxyapatite crystals. The aim of this study was to find an association between the bone microstructure and hydoxyapatite crystal structure in osteoporosis, in comparison to normal bone. The subjects of this study were surgery patients at the Department of Orthopedics of Ulin General Hospital in Banjarmasin and other centers. Inclusion criteria consisted of the presence of fracture of trabecular bone, normal or osteoporotic BMD values, and no past history of chronic disease. Bone was obtained from fracture patients during surgery. The characteristics of the hydroxyapatite crystals were analyzed by X-ray diffraction (XRD and the microarchitecture by scanning electron microscopy (SEM. SEM showed degeneration of the microarchitecture of osteoporotic bone, in comparison with normal bone. On XRD there was a peak of hydoxyapatite crystals only and no other crystal phases. Diffraction patterns showed a larger crystal size in osteoporotic bone as compared to normal bone, indicating higher porosity. It may be concluded that there is a difference in crystal size and morphologic distribution of hydoxyapatite in osteoporotic bone, determining bone microarchitecture.

  7. Assessment of microarchitecture and crystal structure of hydroxyapatite in osteoporosis

    Directory of Open Access Journals (Sweden)

    Zairin Noor

    2011-04-01

    Full Text Available Osteoporosis is characterized by lower bone mineral density (BMD and microarchitectural degeneration, which tends to increase bone fragility and fracture risk. Bone microstructure depends on interactions between the mineral atoms, which may perform substitution or incorporation into bone crystals, and may dynamically take over the function of calcium or may become a complementary part. The mineral atoms may also become a composite in the hydroxyapatite crystals. The aim of this study was to find an association between the bone microstructure and hydoxyapatite crystal structure in osteoporosis, in comparison to normal bone. The subjects of this study were surgery patients at the Department of Orthopedics of Ulin General Hospital in Banjarmasin and other centers. Inclusion criteria consisted of the presence of fracture of trabecular bone, normal or osteoporotic BMD values, and no past history of chronic disease. Bone was obtained from fracture patients during surgery. The characteristics of the hydroxyapatite crystals were analyzed by X-ray diffraction (XRD and the microarchitecture by scanning electron microscopy (SEM. SEM showed degeneration of the microarchitecture of osteoporotic bone, in comparison with normal bone. On XRD there was a peak of hydoxyapatite crystals only and no other crystal phases. Diffraction patterns showed a larger crystal size in osteoporotic bone as compared to normal bone, indicating higher porosity. It may be concluded that there is a difference in crystal size and morphologic distribution of hydoxyapatite in osteoporotic bone, determining bone microarchitecture.

  8. Biopolymers for Medical Applications: Polyglycerol Sebacate (PGS) doped Hydroxyapatite (HA)

    Science.gov (United States)

    Teruel, Maria; Kuthirummal, Narayanan; Levi, Nicole; Wake College Team

    2011-04-01

    In the investigation to engineer the ideal scaffolding device for cleft palate repair, polyglycerol sebacate (PGS) doped with hydroxyapatite (HA) were chosen for their elastomeric and biodegradable properties, as well as their cost-effective synthesis. Hydroxyapatite was integrated into the PGS to form a composite with high porosity and improved mechanical properties yielding a good substrate for cell attachment during the repair process. FT-IR scans were performed to characterize the composite polymer. Differential Scanning Calorimetry (DSC) was utilized to identify an acceptable glass transition temperature (Tg), between -18 and - 21°C. At this Tg, it was determined that the material was sufficiently polymerized to a point where it was durable yet pliable enough to use for cleft palate devices. In the synthesis of PGS 3% and 5% HA, a Tg of - 20.10°C and - 21.72°C, respectively, was achieved and further analytical tests were then performed on the polymers. Methods of analysis included X-Ray Diffraction and Tensile Strength Testing. Acknowledgements to the Research Department of Plastic and Reconstructive Surgery, Wake Forest University and College of Charleston.

  9. SCAFFOLD DARI BOVINE HYDROXYAPATITE DENGAN POLY VYNIALCHOHOL COATING

    Directory of Open Access Journals (Sweden)

    Alva Edy Tontowi, Punto Dewo, Endang Tri Wahyuni, dan Joko Triyono

    2012-06-01

    Full Text Available In Indonesia, it is about 40% patients with hard tissue defect due to ostheoporosis, cancer or accidents and therest are defect since they have born.For many years, efforts for recovering have been done by transplantation orimplantation methods.Transplantation is more appropriate butit is not sustain because of limited donor, whileimplantation using synthetic materials such as bioceramics scaffoldis expensive due to import and the scaffold iseasier to break which does not match to the medical requirements.The research therefore has been addressed to thisissue. Local bovine hydroxyapatite (bHAscaffold has been used as thebase material and poly vynilalchohol (PVAas a coating material.The bHA scaffold was prepared by cutting a fresh bovine bone in the size of 5mmx5mmx5mmand boil it in a distilled water to remove its organic material. It was then heated up at 900 oC for 2 hours infurnace to obtain bovine hydroxyapatite scaffold (bHA. Coating process has been carried out by dip coating of thebHAscaffold in PVA solution.

  10. Molecular Recognition at the Protein-Hydroxyapatite Interface

    Energy Technology Data Exchange (ETDEWEB)

    Stayton, Partick S.; Drobny, G. P.; Shaw, Wendy J.; Long, Joanna R.; Gilbert, Michelle R.

    2003-09-01

    Proteins found in mineralized tissues act as nature's crystal engineers, where they play a key role in promoting or inhibiting the growth of minerals, such as hydroxyapitite (bones/teeth) and calcium oxalate (kidney stones). Despite their importance in hard-tissue formation and remodeling, and in pathological processes such as stone formation and arterial calcification, there is little known of the protein structure-function relationships that govern hard-tissue engineering. Here we review early studies that have utilized solid-state NMR (ssNMR) techniques to provide in situ secondary-structure determination of statherin and statherin peptides on their biologically relevant hydroxyapatite (HAP) surfaces. In addition to direct structural study, molecular dynamics studies have provided considerable insight into the protein-binding footprint on hydroxyapatite. The molecular insight provided by these studies has also led to the design of biomimetic fusion peptides that utilize nature's crystal-recognition mechanism to display accessible and dynamic bioactive sequences from the HAP surface. These peptides selectively engage adhesion receptors and direct specific outside-in signaling pathway activation in osteoblast-like cells.

  11. Antibacterial coatings of fluoridated hydroxyapatite for percutaneous implants.

    Science.gov (United States)

    Ge, Xiang; Leng, Yang; Bao, Chongyun; Xu, Sherry Li; Wang, Renke; Ren, Fuzeng

    2010-11-01

    Percutaneous orthopedic and dental implants require not only good adhesion with bone but also the ability to attach and form seals with connective tissues and the skin. To solve the skin-seal problem of such implants, an electrochemical deposition method was used to modify the surfaces of metallic implants to improve their antibacterial ability and skin seals around them. A dense and uniform fluoridated calcium phosphate coating with a thickness of about 200 nm was deposited on an acid-etched pure titanium substrate by controlling the current density and reaction duration of the electrochemical process. The as-deposited amorphous fluoridated calcium phosphate transformed to fluoridated hydroxyapatite (FHA) after heat treatment at 600°C in a water vapor environment for 3 h. Both single crystal diffraction patterns and high-resolution transmission electron microscope (HRTEM) images confirmed the phase of the fluoridated calcium phosphate after the heat treatment. The antibacterial activities of FHA coatings were tested against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Porphyromonas gingivalis (P. gingivalis) with the film attachment method. The antibacterial activity of FHA coating is much higher than that of pure hydroxyapatite (HA) coating and acid-etched pure titanium surface. The promising features of FHA coating make it suitable for orthopedic and dental applications.

  12. Attachment and Proliferation of Osteoblasts on Lithium-Hydroxyapatite Composites

    Directory of Open Access Journals (Sweden)

    Ana Paula M. Shainberg

    2012-01-01

    Full Text Available The biocompatibility and bioactivity properties of hydroxyapatites (HAs modified through lithium addition were investigated. Hydroxyapatites obtained from bovine bone were mixed with lithium carbonate (Li, in the proportions of 0.25, 0.50, 1.00, and 2.00% wt, and sintered at 900°, 1000°, 1100°, 1200°, and 1300°C, creating LiHA samples. The osteoblast culture behavior was assessed in the presence of these LiHA compositions. The cellular interactions were analyzed by evaluating the viability and cellular proliferation, ALP production and collagen secretion. The cytotoxic potential was investigated through measurement of apoptosis and necrosis induction. The process of cellular attachment in the presence of the product of dissolution of LiHA, was evaluated trough fluorescence analysis. The physical characteristics of these materials and their cellular interactions were examined with SEM and EDS. The results of this study indicate that the LiHA ceramics are biocompatible and have variable bioactivities, which can be tailored by different combinations of the concentration of lithium carbonate and the sintering temperature. Our findings suggest that LiHA 0.25% wt, sintered at 1300°C, combines the necessary physical and structural qualities with favorable biocompatibility characteristics, achieving a bioactivity that seems to be adequate for use as a bone implant material.

  13. Cytotoxic evaluation of hydroxyapatite-filled and silica/hydroxyapatite-filled acrylate-based restorative composite resins: An in vitro study.

    Science.gov (United States)

    Chadda, Harshita; Naveen, Sangeetha Vasudevaraj; Mohan, Saktiswaren; Satapathy, Bhabani K; Ray, Alok R; Kamarul, Tunku

    2016-07-01

    Although the physical and mechanical properties of hydroxyapatite-filled dental restorative composite resins have been examined, the biocompatibility of these materials has not been studied in detail. The purpose of this in vitro study was to analyze the toxicity of acrylate-based restorative composite resins filled with hydroxyapatite and a silica/hydroxyapatite combination. Five different restorative materials based on bisphenol A-glycidyl methacrylate (bis-GMA) and tri-ethylene glycol dimethacrylate (TEGDMA) were developed: unfilled (H0), hydroxyapatite-filled (H30, H50), and silica/hydroxyapatite-filled (SH30, SH50) composite resins. These were tested for in vitro cytotoxicity by using human bone marrow mesenchymal stromal cells. Surface morphology, elemental composition, and functional groups were determined by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), and Fourier-transformed infrared spectroscopy (FTIR). The spectra normalization, baseline corrections, and peak integration were carried out by OPUS v4.0 software. Both in vitro cytotoxicity results and SEM analysis indicated that the composite resins developed were nontoxic and supported cell adherence. Elemental analysis with EDX revealed the presence of carbon, oxygen, calcium, silicon, and gold, while the presence of methacrylate, hydroxyl, and methylene functional groups was confirmed through FTIR analysis. The characterization and compatibility studies showed that these hydroxyapatite-filled and silica/hydroxyapatite-filled bis-GMA/TEGDMA-based restorative composite resins are nontoxic to human bone marrow mesenchymal stromal cells and show a favorable biologic response, making them potential biomaterials. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  14. Ceramic Technology Project database: September 1990 summary report. [SiC, SiN, whisker-reinforced SiN, ZrO-toughened aluminas, zirconias, joints

    Energy Technology Data Exchange (ETDEWEB)

    Keyes, B.L.P.

    1992-06-01

    Data generated within the Ceramic Technology Project (CTP) represent a valuable resource for both research and industry. The CTP database was created to provide easy access to this information in electronic and hardcopy forms by using a computerized database and by issuing periodic hardcopy reports on the database contents. This report is the sixth in a series of semiannual database summaries and covers recent additions to the database, including joined brazed specimen test data. It covers 1 SiC, 34 SiN, 10 whisker-reinforced SiN, 2 zirconia-toughened aluminas, 8 zirconias, and 34 joints.

  15. Lipid peroxidation modifies the picture of membranes from the "Fluid Mosaic Model" to the "Lipid Whisker Model".

    Science.gov (United States)

    Catalá, Angel

    2012-01-01

    The "Fluid Mosaic Model", described by Singer and Nicolson, explain both how a cell membrane preserves a critical barrier function while it concomitantly facilitates rapid lateral diffusion of proteins and lipids within the planar membrane surface. However, the lipid components of biological plasma membranes are not regularly distributed. They are thought to contain "rafts" - nano-domains enriched in sphingolipids and cholesterol that are distinct from surrounding membranes of unsaturated phospholipids. Cholesterol and fatty acids adjust the transport and diffusion of molecular oxygen in membranes. The presence of cholesterol and saturated phospholipids decreases oxygen permeability across the membrane. Alpha-tocopherol, the main antioxidant in biological membranes, partition into domains that are enriched in polyunsaturated phospholipids increasing the concentration of the vitamin in the place where it is most required. On the basis of these observations, it is possible to assume that non-raft domains enriched in phospholipids containing PUFAs and vitamin E will be more accessible by molecular oxygen than lipid raft domains enriched in sphingolipids and cholesterol. This situation will render some nano-domains more sensitive to lipid peroxidation than others. Phospholipid oxidation products are very likely to alter the properties of biological membranes, because their polarity and shape may differ considerably from the structures of their parent molecules. Addition of a polar oxygen atom to several peroxidized fatty acids reorients the acyl chain whereby it no longer remains buried within the membrane interior, but rather projects into the aqueous environment "Lipid Whisker Model". This exceptional conformational change facilitates direct physical access of the oxidized fatty acid moiety to cell surface scavenger receptors. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  16. Calcium Sulfate Hemihydrate Whiskers Obtained from Flue Gas Desulfurization Gypsum and Used for the Adsorption Removal of Lead

    Directory of Open Access Journals (Sweden)

    Xiaoshu Wang

    2017-09-01

    Full Text Available Abstract: As a recycled material, flue gas desulfurization gypsum has been used to prepare calcium sulfate hemihydrate whisker (CSHW through hydrothermal synthesis for several decades. However, the subsequent utilization of this resultant material has not yet received considerable attention. In the present research, CSHW was successfully synthesized at a certain region, and was used for the adsorption of lead ions from aqueous solutions, thereby broadening the research field for the practical application of CSHW. Its adsorption capacity was significantly influenced by various parameters, particularly, the pH level and initial lead concentration. The pH value highly affected the hydrolysis degree of lead ions and dominated the adsorption of lead. The equilibrium isotherms under two different temperatures were simulated using Langmuir, Freundlich, and Temkin models. Both Langmuir and Temkin models showed a good fit to the data. Combined with the well-fitted pseudo-second-order model, the adsorption mechanism was thought to be a chemisorption process that was enforced by the ion exchange reaction. In addition, the specific crystal structure of CSHW revealed that ion exchange reaction occurred on the (010 and (100 facets due to their preferential growth and negatively charged property. The residual solid phase after adsorption was collected and detected using X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. Results revealed that PbSO4 was formed on the surface of CSHW. The alkaline condition introduced the tribasic lead sulfate, and thus reduced the stability of the adsorption system.

  17. Obtention of the hydroxyapatite from continuous reactor; Obtencion de hidroxiapatito en un reactor continuo

    Energy Technology Data Exchange (ETDEWEB)

    Torrent Burgues, J.; Corcho Campos, M.A. [Universidad Politecnica de Catalunya (Spain); Gomez Morales, J.; Rodriguez Clemente, R. [Instituto de Ciencia de Materiales de Barcelona. CSIC. (Spain)

    1998-07-01

    Since hydroxyapatite is the principal inorganic component of bones and teeth, so there is a great demand in odontology and traumatology, the obtention of this crystalline product in a synthetic way using a continuous system has been studied. A product characterization has been done, showing an hydroxyapatite of good crystallinity, and the process yield has also been studied, showing yields up to 75% and production rates between 0.4 and 1.4 g/L min. Hydroxyapatite is composed by agglomerates where individual crystals have needle-like morphology. (Author) 7 refs.

  18. Tailoring the Microstructure of Sol–Gel Derived Hydroxyapatite/Zirconia Nanocrystalline Composites

    Directory of Open Access Journals (Sweden)

    Vasconcelos HC

    2011-01-01

    Full Text Available Abstract In this study, we tailor the microstructure of hydroxyapatite/zirconia nanocrystalline composites by optimizing processing parameters, namely, introducing an atmosphere of water vapor during sintering in order to control the thermal stability of hydroxyapatite, and a modified sol–gel process that yields to an excellent intergranular distribution of zirconia phase dispersed intergranularly within the hydroxyapatite matrix. In terms of mechanical behavior, SEM images of fissure deflection and the presence of monoclinic ZrO2 content on cracked surface indicate that both toughening mechanisms, stress-induced tetragonal to monoclinic phase transformation and deflection, are active for toughness enhancement.

  19. Variation of crystal structure of hydroxyapatite in calcium phosphate cement by the substitution of strontium ions.

    Science.gov (United States)

    Wang, Xiupeng; Ye, Jiandong

    2008-03-01

    New routes were used to introduce strontium into calcium phosphate cement in the present article. The study showed that by mixing 50 wt% amorphous calcium phosphate + amorphous strontium phosphate and 50 wt% dicalcium phosphate dihydrate, hydroxyapatite and Sr-hydroxyapatite precipitated separately in the hydrated cement; whereas, by mixing 50 wt% Sr- amorphous calcium phosphate and 50 wt% dicalcium phosphate dihydrate, strontium can be doped into hydroxyapatite lattice and increase the lattice dimensions and lattice volume. The strontium substituted calcium phosphate cement has potential for use in orthopedic surgeries.

  20. Effect of osteogenesis imperfecta mutations in tropocollagen molecule on strength of biomimetic tropocollagen-hydroxyapatite nanocomposites

    Science.gov (United States)

    Dubey, Devendra K.; Tomar, Vikas

    2010-01-01

    Osteogenesis Imperfecta (OI) is a genetic disorder that affects cellular synthesis of Type-I collagen fibrils and causes extreme bone fragility. This study reports the effects of OI mutations in Tropocollagen (TC) molecules on strength of model Tropocollagen-Hydroxyapatite biomaterials with two different mineral [hydroxyapatite (HAP)] distributions using three dimensional atomistic simulations. Results show that the effect of TC mutations on the strength of TC-HAP biomaterials is insignificant. Instead, change in mineral distribution showed significant impact on the overall strength of TC-HAP biomaterials. Study suggests that TC mutations manifest themselves by changing the mineral distribution during hydroxyapatite growth and nucleation period.

  1. [Manufacture of hydroxyapatite as a defluoridator and the mechanism of defluoridation for drinking water].

    Science.gov (United States)

    Li, Xinyun; Zheng, Dawei; Ying, Bo

    2002-04-01

    Hydroxyapatite as a defluoridator for drinking water is characterized by a large capacity of defluoridation, and easy and simple operation in application. The quality of drinking water is not changed, the sorbent is easy to be regenerated, and the second pollution does not occur after the treatment of drinking water with the sorbent. Hydroxyapatite method has advantage over the methods such as actived alumina, bone char and electrodialysis commonly used in defluorination of drinking water. It is for this reason that the components, structural feature, synthesis and application of hydroxyapatite and its mechanism of defluoridation are summarized in this paper.

  2. Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method: dissolution behaviour and biological properties after crystallisation.

    Science.gov (United States)

    Tredwin, Christopher J; Young, Anne M; Abou Neel, Ensanya A; Georgiou, George; Knowles, Jonathan C

    2014-01-01

    Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) were synthesised by the sol-gel method as possible implant coating or bone-grafting materials. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride were incorporated for the preparation of the FHA and FA sol-gels. After heating and powdering the sol-gels, dissolution behaviour was assessed using ion chromatography to measure Ca(2+) and PO4 (3-) ion release. Biological behaviour was assessed using cellular proliferation with human osteosarcoma cells and alamarBlue™ assay. Statistical analysis was performed with a two way analysis of variance and post hoc testing with a Bonferroni correction. Increasing fluoride substitution into an apatite structure decreased the dissolution rate. Increasing the firing temperature of the HA, FHA and FA sol-gels up to 1,000 °C decreased the dissolution rate. There was significantly higher cellular proliferation on highly substituted FHA and FA than on HA or Titanium. The properties of an implant coating or bone grafting material can be tailored to meet specific requirements by altering the amount of fluoride that is incorporated into the original apatite structure. The dissolution behaviour can further be altered by the temperature at which the sol-gel is fired.

  3. Mechanical Properties of Chitosan-Starch Composite Filled Hydroxyapatite Micro- and Nanopowders

    Directory of Open Access Journals (Sweden)

    Jafar Ai

    2011-01-01

    Full Text Available Hydroxyapatite is a biocompatible ceramic and reinforcing material for bone implantations. In this study, Starch-chitosan hydrogel was produced using the oxidation of starch solution and subsequently cross-linked with chitosan via reductive alkylation method (weight ratio (starch/chitosan: 0.38. The hydroxyapatite micropowders and nanopowders synthesized by sol-gel method (10, 20, 30, 40 %W were composited to hydrogels and were investigated by mechanical analysis. The results of SEM images and Zetasizer experiments for synthesized nanopowders showed an average size of 100 nm. The nanoparticles distributed as uniform in the chitosan-starch film. The tensile modulus increased for composites containing hydroxyapatite nano-(size particle: 100 nanometer powders than composites containing micro-(size particle: 100 micrometer powders. The swelling percentage decreased for samples containing hydroxyapatite nanopowder than the micropowders. These nanocomposites could be applied for hard-tissue engineering.

  4. Topographic measurements of eyelids and orbit in enucleated eyes with hydroxyapatite integrated implant versus PMMA implant

    National Research Council Canada - National Science Library

    Gradinaru, S; Totir, M; Iancu, R; Leasu, C; Pricopie, S; Yasin, S; Ciuluvica, R; Ungureanu, E

    2014-01-01

    ... (Group A comprising of twenty patients had the coralline hydroxyapatite implant -Integrated Ocular Implants, USA and Group B comprising of twenty-three received non-integrated PMMA ocular implants...

  5. The microstructural and in vitro characteristics of hydroxyapatite coating fabricated using Nd-YAG laser

    CSIR Research Space (South Africa)

    Tlotleng, Monnamme

    2015-03-01

    Full Text Available Hydroxyapatite (HAP) is the most researched calcium phosphate material in the field of biomaterials to be used for bone re-engineering applications; given its attractive properties. Plasma spraying is the best available industrial method that can...

  6. Preparation and characterization of an iron oxide-hydroxyapatite nanocomposite for potential bone cancer therapy.

    Science.gov (United States)

    Sneha, Murugesan; Sundaram, Nachiappan Meenakshi

    2015-01-01

    Recently, multifunctional magnetic nanostructures have been found to have potential applications in biomedical and tissue engineering. Iron oxide nanoparticles are biocompatible and have distinctive magnetic properties that allow their use in vivo for drug delivery and hyperthermia, and as T2 contrast agents for magnetic resonance imaging. Hydroxyapatite is used frequently due to its well-known biocompatibility, bioactivity, and lack of toxicity, so a combination of iron oxide and hydroxyapatite materials could be useful because hydroxyapatite has better bone-bonding ability. In this study, we prepared nanocomposites of iron oxide and hydroxyapatite and analyzed their physicochemical properties. The results suggest that these composites have superparamagnetic as well as biocompatible properties. This type of material architecture would be well suited for bone cancer therapy and other biomedical applications.

  7. Simple and Rapid Synthesis of Magnetite/Hydroxyapatite Composites for Hyperthermia Treatments via a Mechanochemical Route

    Science.gov (United States)

    Iwasaki, Tomohiro; Nakatsuka, Ryo; Murase, Kenya; Takata, Hiroshige; Nakamura, Hideya; Watano, Satoru

    2013-01-01

    This paper presents a simple method for the rapid synthesis of magnetite/hydroxyapatite composite particles. In this method, superparamagnetic magnetite nanoparticles are first synthesized by coprecipitation using ferrous chloride and ferric chloride. Immediately following the synthesis, carbonate-substituted (B-type) hydroxyapatite particles are mechanochemically synthesized by wet milling dicalcium phosphate dihydrate and calcium carbonate in a dispersed suspension of magnetite nanoparticles, during which the magnetite nanoparticles are incorporated into the hydroxyapatite matrix. We observed that the resultant magnetite/hydroxyapatite composites possessed a homogeneous dispersion of magnetite nanoparticles, characterized by an absence of large aggregates. When this material was subjected to an alternating magnetic field, the heat generated increased with increasing magnetite concentration. For a magnetite concentration of 30 mass%, a temperature increase greater than 20 K was achieved in less than 50 s. These results suggest that our composites exhibit good hyperthermia properties and are promising candidates for hyperthermia treatments. PMID:23629669

  8. Incorporation of different antibiotics into carbonated hydroxyapatite coatings on titanium implants, release and antibiotic efficacy

    NARCIS (Netherlands)

    Stigter, M.; Bezemer, J.M.; de Groot, K.; Layrolle, P.

    2004-01-01

    Carbonated hydroxyapatite (CHA) coatings were applied onto titanium implants by using a biomimetic precipitation method. Different antibiotics were incorporated into the CHA coatings and their release and efficacy against bacteria growth were studied in vitro. The following antibiotics were used

  9. Preparation and characterization of nano-hydroxyapatite/chitosan/konjac glucomannan composite

    NARCIS (Netherlands)

    Zhou, G.; Li, Yubao; Zhang, L.; Zuo, Y.; Jansen, J.A.

    2007-01-01

    Nano-hydroxyapatite (n-HA)/chitosan (CS)/konjac glucomannan (KGM) composite was prepared by coprecipitation method and investigated by thermal gravitivity/differentiate thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, inductively coupled plasma emission spectroscopy,

  10. Hydroxyapatite and Carbonated Apatite as Models for the Dissolution Behavior of Human Dental Enamel

    National Research Council Canada - National Science Library

    Budz, J.A; Lore, M; Nancollas, G.H

    1987-01-01

    ... to understand the mechanism of dental caries. In the present study, kinetic comparisons of the dissolution of hydroxyapatite, carbonated apatite, and ground human dental enamel have been made in order that the appropriateness of these synthetic...

  11. Hydroxyapatite scaffolds infiltrated with thermally crosslinked polycaprolactone fumarate and polycaprolactone itaconate

    NARCIS (Netherlands)

    Sharifi, Shahriar; Shafieyan, Yousef; Mirzadeh, Hamid; Bagheri-Khoulenjani, Shadab; Rabiee, Sayed Mahmood; Imani, Mohammad; Atai, Mohammad; Shokrgozar, Mohammad Ali; Hatampoor, Ali

    In this work, two unsaturated derivatives of polycaprolactone (PCL), polycaprolactone fumarate (PCLF), and polycaprolactone itaconate (PCLI), have been synthesized and used as an infiltrating polymer to improve the mechanical properties of brittle hydroxyapatite (HA) scaffolds. PCLF and PCLI were

  12. [Optimizing the synthesis of hydroxyapatite as a method for the defluoridation of drinking water].

    Science.gov (United States)

    Ying, B; Li, X; Zheng, D; Gao, J

    2001-07-01

    As the cheaper raw materials for the synthesis of hydroxyapatite as a defluoridator, calcium hydroxide and phosphoric acid are used. Hydroxyapatite is made by a hydro-synthesis method, and optimum conditions are determined by batch test for defluoridation with respect to the consumption of phosphoric acid, reaction time and acid-washed product. The results showed that the defluoridation capacity of the synthetic hydroxyapatite for break through (F- 1.0 mg/L is considered as the break through point) was F- 5.6 mg/g in column test, and F- 10.7 mg/g for saturation in column test. After optimization of the synthesis method, the defluoridation capacity of hydroxyapatite is much higher than activated alumina and bone charcoal, which are used currently.

  13. Separation of lanthanides through hydroxyapatite; Separacion de lantanidos mediante hidroxiapatita

    Energy Technology Data Exchange (ETDEWEB)

    Garcia M, F.G

    2006-07-01

    With the objective of obtaining from an independent way to each one of the lanthanides {sup 151} Pm, {sup 161} Tb, {sup 166} Ho and {sup 177} Lu free of carrier and with high specific activities starting from the indirect irradiation via, it intends in this work to determine the viability of separation of the couples Nd/Pm, Dy/Ho, Gd/Tb and Yb/Lu, by means of ion exchange column chromatography, using hydroxyapatite (HAp) and fluorite like absorbent material in complexing media. It is important to mention that have registered separation studies among lanthanides of the heavy group with those of the slight group, using the same mass and, in comparison with this work, quantities different from the father were used and of the son, also, that the separation studies were carried out among neighboring lanthanides. In this investigation, it was determined the effect that its have the complexing media: KSCN, sodium tartrate, sodium citrate, EDTA and aluminon, their pH and concentration, in the adsorption of the lanthanides in both minerals, in order to determine the chromatographic conditions for separation of the couples Nd/Pm, Dy/Ho, Gd/Tb and Yb/Lu. The work consists of five chapters, in the first one they are presented a theoretical introduction of the characteristics more important of the lanthanides, the hydroxyapatite and the fluorite; in the second, it is deepened in the ion exchange, as well as the two techniques (XRD and High Vacuum Electron Microscopy) to make the characterization of LnCI{sub 3} (Ln = Nd, Gd, Dy or Yb) synthesized. The third chapter, it describes the methodology continued in our experimental work; in the room, its are presented the obtained results of the static and dynamic method to determine the viability of separation of neighboring lanthanides; and finally, the five chapter shows the conclusions. In this study, it is concludes that the separation among neighboring lanthanides cannot be carried out in the minerals and used media; because

  14. Antibacterial effects of silver-doped hydroxyapatite thin films sputter deposited on titanium

    Energy Technology Data Exchange (ETDEWEB)

    Trujillo, Nathan A. [Dept. of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523-1374 (United States); School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523-1376 (United States); Oldinski, Rachael A. [College of Engineering and Mathematical Science, University of Vermont, Burlington, VT 05405 (United States); Dept. of Bioengineering, University of Washington, Seattle, WA 98195-5061 (United States); Ma, Hongyan; Bryers, James D. [Dept. of Bioengineering, University of Washington, Seattle, WA 98195-5061 (United States); Williams, John D. [Dept. of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523-1374 (United States); Popat, Ketul C., E-mail: Ketul.Popat@colostate.edu [Dept. of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523-1374 (United States); School of Biomedical Engineering, Colorado State University, Fort Collins, CO 80523-1376 (United States)

    2012-12-01

    Since many orthopedic implants fail as a result of loosening, wear, and inflammation caused by repeated loading on the joints, coatings such as hydroxyapatite (HAp) on titanium with a unique topography have been shown to improve the interface between the implant and the natural tissue. Another serious problem with long-term or ideally permanent implants is infection. It is important to prevent initial bacterial colonization as existing colonies have the potential to become encased in an extracellular matrix polymer (biofilm) that is resistant to antibacterial agents. In this study, plasma-based ion implantation was used to examine the effects of pre-etching on plain titanium. Topographical changes to the titanium samples were examined and compared via scanning electron microscopy. Hydroxyapatite and silver-doped hydroxyapatite thin films were then sputter deposited on titanium substrates etched at - 700 eV. For silver-doped films, two concentrations of silver ({approx} 0.5 wt.% and {approx} 1.5 wt.%) were used. Silver concentrations in the film were determined using energy dispersive X-ray spectroscopy. Hydroxyapatite film thicknesses were determined by measuring the surface profile using contact profilometry. Staphylococcus epidermidis and Pseudomonas aeruginosa adhesion studies were performed on plain titanium, titanium coated with hydroxyapatite, titanium coated with {approx} 0.5 wt.% silver-doped hydroxyapatite, and titanium coated with {approx} 1.5 wt.% silver-doped hydroxyapatite. Results indicate that less bacteria adhered to surfaces containing hydroxyapatite and silver; further, as the hydroxyapatite films delaminated, silver ions were released which killed bacteria in suspension. - Highlights: Black-Right-Pointing-Pointer We have developed a combination of plasma-based ion implantation and ion beam sputter deposition technique. Black-Right-Pointing-Pointer Silver-doped hydroxyapatite thin films on titanium were developed. Black-Right-Pointing-Pointer The

  15. Crucial effect of SiC particles on in situ synthesized mullite whisker reinforced Al2O3-SiC composite during microwave sintering

    Directory of Open Access Journals (Sweden)

    Meng Wei

    2017-06-01

    Full Text Available Mullite whisker reinforced Al2O3-SiC composites were in situ synthesized by microwave sintering at 1500°C for 30min. The influence of SiC particle size on heating process and properties of Al2O3-SiC composite were investigated. The XRD and SEM techniques were carried out to characterize the samples. The thermal shock resistance and flexural strength of the samples were examined through water quenching and three-point bending methods, respectively. It was found that the bridging of mullite whisker appeared between Al2O3 and SiC particles which enhanced the thermal shock resistance. A so-called local hot spot effect was proposed dependent on the coupling of SiC particles with microwave, which was the unique feature of microwave sintering. The maximal thermal shock resistance and flexural strength were obtained for the samples with SiC particle size of ~5μm.

  16. Effects of fluoridation of porcine hydroxyapatite on osteoblastic activity of human MG63 cells

    OpenAIRE

    Li, Zhipeng; Huang, Baoxin; Mai, Sui; Wu, Xiayi; Zhang, Hanqing; Qiao, Wei; Luo, Xin; Chen, Zhuofan

    2015-01-01

    Biological hydroxyapatite, derived from animal bones, is the most widely used bone substitute in orthopedic and dental treatments. Fluorine is the trace element involved in bone remodeling and has been confirmed to promote osteogenesis when administered at the appropriate dose. To take advantage of this knowledge, fluorinated porcine hydroxyapatite (FPHA) incorporating increasing levels of fluoride was derived from cancellous porcine bone through straightforward chemical and thermal treatment...

  17. The Role of Hydroxyl Channel in Defining Selected Physicochemical Peculiarities Exhibited by Hydroxyapatite

    OpenAIRE

    Uskoković, Vuk

    2015-01-01

    Mysteries surrounding the most important mineral for the vertebrate biology, hydroxyapatite, are many. Perhaps the Greek root of its name, απαταo, meaning ‘to deceive’ and given to its mineral form by the early gem collectors who confused it with more precious stones, is still applicable today, though in a different connotation, descriptive of a number of physicochemical peculiarities exhibited by it. Comparable to water as the epitome of peculiarities in the realm of liquids, hydroxyapatite ...

  18. Surface Structure Study of Crystal Hydroxy-Apatite from Fluorosis Enamels

    OpenAIRE

    Abdillah Imron Nasution; Harun Asyiq Gunawan; Sri Angky Soekanto

    2013-01-01

    Fluorosis is a condition due to ingestion of excessive amounts of fluor which can cause the change in tooth structure and strength. However, there is still lack of explanation on the surface structure of crystal hydroxyapatite that influences the microscopic characteristic of fluorosis enamel. Objectives: To investigate the surface structure of crystal hydroxy-apatite in fluorosis enamel. Materials and Methods: Determination of fluor concentration and the surface structure of normal and fluor...

  19. Comparison of hydroxyapatite and dental enamel for testing shear bond strengths.

    Science.gov (United States)

    Imthiaz, Nishat; Georgiou, George; Moles, David R; Jones, Steven P

    2008-05-01

    To investigate the feasibility of using artificial hydroxyapatite as a future biomimetic laboratory substitute for human enamel in orthodontic bond strength testing by comparing the shear bond strengths and nature of failure of brackets bonded to samples of hydroxyapatite and enamel. One hundred and fifty hydroxyapatite discs were prepared by compression at 20 tons and fired in a furnace at 1300 degrees C. One hundred and five enamel samples were prepared from the buccal and palatal/lingual surfaces of healthy premolars extracted for orthodontic purposes. Orthodontic brackets were bonded to each sample and these were subjected to shear bond strength testing using a custom-made jig mounted in an Instron Universal Testing Machine. The force value at bond failure was obtained, together with the nature of failure which was assessed using the Adhesive Remnant Index. The mean shear bond strength for the enamel samples was 16.62 MPa (95 per cent CI: 15.26, 17.98) and for the hydroxyapatite samples 20.83 MPa (95 per cent CI: 19.68, 21.98). The difference between the two samples was statistically significant (p enamel samples scored 2 or 3, while 49 per cent of the hydroxyapatite samples scored 0 or 1. Hydroxyapatite was an effective biomimetic substrate for bond strength testing with a mean shear bond strength value (20.83 MPa) at the upper end of the normal range attributed to enamel (15-20 MPa). Although the difference between the shear bond strengths for hydroxyapatite and enamel was statistically significant, hydroxyapatite could be used as an alternative to enamel for comparative laboratory studies until a closer alternative is found. This would eliminate the need for extracted teeth to be collected. However, it should be used with caution for quantitative studies where true bond strengths are to be investigated.

  20. LIBS analysis of hydroxyapatite extracted from bovine bone for Ca/P ratio measurements

    Science.gov (United States)

    Tariq, Usman; Haider, Zuhaib; Hussain, Rafaqat; Tufail, Kashif; Ali, Jalil

    2017-03-01

    Hydroxyapatite has been extensively used as a potential biocompatible ceramic in many orhtopedic applications. Hydroxyapatite is one of the members of calcium phosphate family and been used extensively as a bone substitute. The mechanical properties of hydroxyapatite itself, ceramics and bone cements prepared from hydroxyapatite vary greatly with slight variation in its Ca/P ratio. At present EDX, XRD, XRF and ICP-OES are being used for the determination of Ca/P ratio in hydroxyapatite. These techniques require special sample preparation, may also use toxic chemicals and usually are not very fast in giving the measurements. We report LIBS as a rapid alternative technique for calculation of Ca/P ratio in hydroxyapatite extracted from bovine bone (BHA). Ca/P ratio in laboratory prepared HA is calculated using LIBS and the results are validated against EDX results Ca/P ratio of the hydroxyapatite was calculated as 1.54±0.19 using LIBS while 1.63±0.03 using EDX. Ca/P ratio calculated by LIBS and EDX and showed comparable results with a difference of 5.5%. Moreover, plasma temperature and the ratio of the calcium (ion) line to calcium (atomic) line did not show significant variation in plasma conditions during measurements. The present study has demonstrated that LIBS can also be used for the determination of Ca/P ratio of hydroxyapatite and other calcium phosphates. At the request of all authors of the paper, and with the agreement of the Proceedings Editor, an updated version of this article was published on 24 May 2017.

  1. Surface modification of zinc-containing hydroxyapatite by tartaric acid

    Science.gov (United States)

    Turki, Thouraya; Othmani, Masseoud; Bac, Christophe Goze; Rachdi, Férid; Bouzouita, Khaled

    2013-11-01

    The surface of Zn-substituted hydroxyapatites (Ca(10-x)Znx(PO4)6(OH)2, with 0 ≤ x ≤ 2, CaxZnxHA) modified by tartaric acid was investigated by various techniques. XRD powder patterns revealed that synthesized samples were single phase of HA with broadened XRD reflections. FTIR and (13C, 1H and 31P) MAS NMR measurements confirmed the grafting of the tartaric acid on the apatite surface. Chemical analysis showed that for ZnHA the grafted acid amount increases with the increase of the acid concentration in the starting solutions, while for HA, it remained constant, indicating more reactivity for ZnHA surface. A mechanism of surface modification is proposed based on the obtained results.

  2. Hydroxyapatite-phosphonoformic acid hybrid compounds prepared by hydrothermal method

    Science.gov (United States)

    Turki, Thouraya; Othmani, Masseoud; Bantignies, Jean-Louis; Bouzouita, Khaled

    2014-01-01

    Hydroxyapatites were prepared in the presence of different amounts of phosphonoformic acid (PFA) via the hydrothermal method. The obtained powders were characterized through chemical analysis, XRD, IR, 31P MAS-NMR, TEM, and TG-TDA. The XRD showed that the PFA did not affect the apatite composition. Indeed, only a reduction of the crystallite size was noted. After grafting of PFA, the IR spectroscopy revealed the appearance of new bands belonging to HPO42- and carboxylate groups of the apatite and organic moiety, respectively. Moreover, the 31P MAS-NMR spectra exhibited a peak with a low intensity assigned to the terminal phosphonate group of the organic moiety in addition to that of the apatite. Based on these results, a reaction mechanism involving the surface hydroxyl groups (tbnd Casbnd OH) of the apatite and the carboxyl group of the acid was proposed.

  3. Synthesis and Antimicrobial Activity of a Silver-Hydroxyapatite Nanocomposite

    Directory of Open Access Journals (Sweden)

    Marcos Díaz

    2009-01-01

    Full Text Available A silver-hydroxyapatite nanocomposite has been obtained by a colloidal chemical route and subsequent reduction process in H2/Ar atmosphere at 350∘C. This material has been characterized by TEM, XRD, and UV-Visible spectroscopy, showing the silver nanoparticles (∼65 nm supported onto the HA particles (∼130 nm surface without a high degree of agglomeration. The bactericidal effect against common Gram-positive and Gram-negative bacteria has been also investigated. The results indicated a high antimicrobial activity for Staphylococcus aureus, Pneumococcus and Escherichia coli, so this material can be a promising antimicrobial biomaterial for implant and reconstructive surgery applications.

  4. Vibrational Investigations of Silver-Doped Hydroxyapatite with Antibacterial Properties

    Directory of Open Access Journals (Sweden)

    Carmen Steluta Ciobanu

    2013-01-01

    Full Text Available Silver-doped hydroxyapatite (Ag:HAp was obtained by coprecipitation method. Transmission electron microscopy (TEM, infrared, and Raman analysis confirmed the development of Ag:HAp with good crystal structure. Transmission electron microscopy analysis showed an uniform ellipsoidal morphology with particles from 5 nm to 15 nm. The main vibrational bands characteristic to HAp were identified. The bands assigned to phosphate vibrational group were highlighted in infrared and Raman spectra. The most intense peak Raman spectrum is the narrow band observed at 960 cm−1. In this article Ag:HAp-NPs were also evaluated for their antimicrobial activities against gram-positive, gram-negative, and fungal strains. The specific antimicrobial activity revealed by the qualitative assay demonstrates that our compounds are interacting differently with the microbial targets.

  5. Biodegradable and Biocompatible Systems Based on Hydroxyapatite Nanoparticles

    Directory of Open Access Journals (Sweden)

    Pau Turon

    2017-01-01

    Full Text Available Composites of hydroxyapatite (HAp are widely employed in biomedical applications due to their biocompatibility, bioactivity and osteoconductivity properties. In fact, the development of industrially scalable hybrids at low cost and high efficiency has a great impact, for example, on bone tissue engineering applications and even as drug delivery systems. New nanocomposites constituted by HAp nanoparticles and synthetic or natural polymers with biodegradable and biocompatible characteristics have constantly been developed and extensive works have been published concerning their applications. The present review is mainly focused on both the capability of HAp nanoparticles to encapsulate diverse compounds as well as the preparation methods of scaffolds incorporating HAp. Attention has also been paid to the recent developments on antimicrobial scaffolds, bioactive membranes, magnetic scaffolds, in vivo imaging systems, hydrogels and coatings that made use of HAp nanoparticles.

  6. Nano pores evolution in hydroxyapatite microsphere during spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Lin C.

    2011-01-01

    Full Text Available Micron-spherical granules of hydroxyapatite (HAp nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  7. Sulfobetaine as a zwitterionic mediator for 3D hydroxyapatite mineralization

    Science.gov (United States)

    Liu, Pingsheng; Song, Jie

    2013-01-01

    Both positively and negatively charged residues play pivotal roles in recruiting precursor ions or ion clusters, and lowering interfacial energy in natural biomineralization process. Synergistic utilization of opposite charges, however, has rarely been implemented in the design of cytocompatible synthetic scaffolds promoting hydroxyapatite (HA)-mineralization and osteointegration. We report the use of cytocompatible zwitterionic sulfobetaine ligands to enable 3-dimensional in vitro mineralization of HA across covalently crosslinked hydrogels. The overall charge-neutral zwitterionic hydrogel effectively recruited oppositely charged precursor ions while overcame excessive swelling exhibited by anionic and cationic hydrogels under physiological conditions, resulting in denser and structurally well-integrated mineralized composites. Further controls over the size, content, and spatial distribution of the mineral domains within the zwitterionic hydrogel are accomplished by facile adjustments of hydrogel crosslinking densities and the supersaturation rate governing heterogeneous mineral nucleation and growth. These findings should inspire many creative uses of zwitterionic polymers and polymer coatings for skeletal tissue repair and regeneration. PMID:23332320

  8. Incorporation of 140-lanthanum into bones, teeth and hydroxyapatite.

    Science.gov (United States)

    Fernandez-Gavarron, F; Huque, T; Rabinowitz, J L; Brand, J G

    1988-03-01

    The incorporation of lanthanum in the form of 140-lanthanum onto the surface of teeth, bone and synthetic hydroxyapatite was investigated. A small amount of lanthanum was taken up by the surface of all of the materials studied regardless of their origin. The depth of penetration into bone and teeth was dependent upon lanthanum concentration and time of incubation and, in these experiments, ranged from an estimated 5 to 15 microns. An exchange of lanthanum for calcium in the apatite matrix may be responsible for increased resistance of the hard tissues to acid dissolution. The effects of pH, temperature, time and concentration of the lanthanum solutions on this incorporation were investigated. Possible clinical uses of this effect are discussed.

  9. Silk fibroin/hydroxyapatite composites for bone tissue engineering.

    Science.gov (United States)

    Farokhi, Mehdi; Mottaghitalab, Fatemeh; Samani, Saeed; Shokrgozar, Mohammad Ali; Kundu, Subhas C; Reis, Rui L; Fatahi, Yousef; Kaplan, David L

    2017-10-07

    Silk fibroin (SF) is a natural fibrous polymer with strong potential for many biomedical applications. SF has attracted interest in the field of bone tissue engineering due to its extraordinary characteristics in terms of elasticity, flexibility, biocompatibility and biodegradability. However, low osteogenic capacity has limited applications for SF in the orthopedic arena unless suitably functionalized. Hydroxyapatite (HAp) is a well-established bioceramic with biocompatibility and appropriate for constructing orthopedic and dental substitutes. However, HAp ceramics tend to be brittle which can restrict applications in the repair of load-bearing tissues such as bones. Therefore, blending SF and HAp combines the useful properties of both materials as bone constructs for tissue engineering, the subject of this review. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Surface modification of zinc-containing hydroxyapatite by tartaric acid

    Energy Technology Data Exchange (ETDEWEB)

    Turki, Thouraya; Othmani, Masseoud [Laboratoire de Physico-Chimie des Matériaux, Faculté des Sciences de Monastir, 5019 Monastir (Tunisia); Bac, Christophe Goze [Laboratoire Charles Coulomb, UMR 5221 CNRS/UM2, Université Montpellier 2, Place E. Bataillon, 34095 Montpellier (France); Rachdi, Férid, E-mail: Ferid.Rachdi@univ-montp2.fr [Laboratoire Charles Coulomb, UMR 5221 CNRS/UM2, Université Montpellier 2, Place E. Bataillon, 34095 Montpellier (France); Bouzouita, Khaled [Institut Préparatoire aux Etudes d’Ingénieur de Monastir (Tunisia)

    2013-11-01

    The surface of Zn-substituted hydroxyapatites (Ca{sub (10−x)}Zn{sub x}(PO{sub 4}){sub 6}(OH){sub 2}, with 0 ≤ x ≤ 2, Ca{sub x}Zn{sub x}HA) modified by tartaric acid was investigated by various techniques. XRD powder patterns revealed that synthesized samples were single phase of HA with broadened XRD reflections. FTIR and ({sup 13}C, {sup 1}H and {sup 31}P) MAS NMR measurements confirmed the grafting of the tartaric acid on the apatite surface. Chemical analysis showed that for ZnHA the grafted acid amount increases with the increase of the acid concentration in the starting solutions, while for HA, it remained constant, indicating more reactivity for ZnHA surface. A mechanism of surface modification is proposed based on the obtained results.

  11. Hydroxyapatite-reinforced polymer biocomposites for synthetic bone substitutes

    Science.gov (United States)

    Roeder, Ryan K.; Converse, Gabriel L.; Kane, Robert J.; Yue, Weimin

    2008-03-01

    Hydroxyapatite (HA)-reinforced polymer biocomposites offer a robust system to engineer synthetic bone substitutes with tailored mechanical, biological, and surgical functions. The basic design rationale has been to reinforce a tough, biocompatible polymer matrix with a bioactive HA filler. A large number of studies have investigated modifications to the biocomposite structure and composition, aimed at improving the mechanical properties, often through modified or novel processing methods. In this article, the effects of the polymer composition and molecular orientation; the HA/polymer interface; and the HA-reinforcement content, morphology, preferred orientation, and size are reviewed with respect to mechanical properties, drawing frequent comparisons between various HA-reinforced polymer composites and bone tissue.

  12. Biomimetic hydroxyapatite particulate nanofiber modified silicon: in vitro bioactivity.

    Science.gov (United States)

    Aryal, Santosh; Bajgai, Madhab Prasad; Khil, Myung Seob; Kang, Hyung-Sub; Kim, Hak Yong

    2009-02-01

    A novel particulate nanofibrous hydroxyapatite (HA), which mimics the bone matrix, is presented as a surface functional material to modify silicon wafers by the electrospinning method. The HA precursors were treated with viscous polymer solution, and then electrospun under controlled conditions. After successive calcinations, the powder X-ray diffraction patterns of the samples revealed reflection toward the (300) HA plane that is linear with temperature. This prominent reflection suggests the crystallographic purity of the HA. Biocompatibility, cell proliferation, and microstructure were examined using AFM and FE-SEM. Morphology showed cell spreading and penetration instead of cell aggregation. The surface roughness as well as adhesion force was calculated using contact mode AFM. The results show that the composite matrix holds promise for use as a bone implant material.

  13. Adsorption of low-molecular-weight sodium polyacrylate on hydroxyapatite.

    Science.gov (United States)

    Misra, D N

    1993-10-01

    Adsorption of low-molecular-weight sodium polyacrylate from aqueous solution onto synthetic hydroxyapatite was studied at room temperature so that the mechanism of adhesion of polyacrylate cements to tooth mineral could be elucidated. The adsorption isotherm of sodium polyacrylate was Langmuirian in shape and was thus qualitatively different from that of polyacrylic acid (Misra, 1991), which exhibited an adsorption maximum. The self-association of the molecules that probably causes the maximum to occur with polyacrylic acid was effectively absent for the relatively well-ionized, electrostatically repelling polyacrylate ions of the salt. With the adsorption of acrylate ions, the concentration of phosphate ions increased monotonically, while the concentration of calcium ions showed a minimum. The adsorption of sodium polyacrylate was irreversible, as it was for polyacrylic acid.

  14. Fibrous growth of strontium substituted hydroxyapatite and its drug release

    Energy Technology Data Exchange (ETDEWEB)

    Suganthi, R.V.; Elayaraja, K.; Joshy, M.I. Ahymah; Chandra, V. Sarath [Crystal Growth Centre, Anna University, Chennai 600 025 (India); Girija, E.K. [Department of Physics, Periyar University, Salem 636 011 (India); Kalkura, S. Narayana, E-mail: kalkura@yahoo.com [Crystal Growth Centre, Anna University, Chennai 600 025 (India)

    2011-04-08

    The effect of strontium on the crystallization of helical ribbon of hydroxyapatite (HAp) was investigated by single diffusion technique in silica gel matrix at 27 deg. C and physiological pH. Fibers of HAp were obtained on addition of strontium. The length of the HAp fibers, were found to decrease as the strontium substitution increases. The presence of strontium ion increased the crystallinity as well as crystallite size of HAp. The strontium substituted HAp (Sr-HAp) has similar stoichiometry to that of biological apatite. Sr-HAp was found to have increased surface area (35%) compared to control. Further, strontium substitution leads to an enhancement of in vitro bioactivity. The cumulative in-vitro amoxicillin drug release in phosphate buffer solution (PBS, pH 7.2) showed a prolonged release profile for Sr-HAp.

  15. Synthesis and structure of cerium-substituted hydroxyapatite.

    Science.gov (United States)

    Feng, Zude; Liao, Yingmin; Ye, Meng

    2005-05-01

    The aim of this study was to explore the effect of cerium ions on the formation and structure of hydroxyapatite (HAP). All particles, prepared by hydrothermal method, were synthesized at varied X(Ce) = Ce/(Ca + Ce) (from 0 to 10%) with the atomic ratio (Ce + Ca)/P fixed at 1.67. Their morphology, composition and crystal structure were characterized by TEM, EPMA, XRD and FTIR. The results showed that in this composition range the apatite structure is maintained, Ce3+ ions could enter the crystal lattice of apatite and substitute Ca2+ ions. The doping of Ce3+ ions resulted in the decrease of the crystallite size with increase in X(Ce). The HAP particles without doping were short rods having a diameter from 10 to 20 nm and a length from 30 to 50 nm. They grew into long needles upon increasing X(Ce).

  16. Review of ferroelectric hydroxyapatite and its application to biomedicine

    Science.gov (United States)

    Lang, Sidney B.

    2016-08-01

    Hydroxyapatite (HA) is a major component of bone in humans and animals. Until about 10 years ago, it was considered to have a centrosymmetric crystal structure and could not contribute to the well-known piezoelectric effect in bone. This review describes the theoretical and experimental studies that showed that HA does have a non-centrosymmetric structure. Recent experiments have shown that HA exhibits piezoelectricity, pyroelectricity, and ferroelectricity. It has been made in the form of thick films and as space-charge electrets. It has an important biomedical application as an implant for bone cell attachment and growth. This paper is contributed in honor of the 80th birthday of my long-time friend and colleague, Bozena Hilczer.

  17. Preparation of nanometer-scale rod array of hydroxyapatite crystal.

    Science.gov (United States)

    Hayakawa, Satoshi; Li, Yaqi; Tsuru, Kanji; Osaka, Akiyoshi; Fujii, Eiji; Kawabata, Koji

    2009-07-01

    Fabrication of nano- or micro-structured scaffolds to mimic structural and three-dimensional details of natural bone or teeth has been the subject of much interest, and this study proposes a new strategy for self-assembling one-dimensional hydroxyapatite (HAp) nanorods into organized superstructures. A nanometer-scale rod array of HAp having preferred orientation to the c-axis was successfully prepared simply by soaking calcium-containing silicate glass substrates in Na(2)HPO(4) aqueous solution at 80 degrees C for various periods. Those HAp rods grew perpendicularly to the glass surface, and the crystallites covered the glass surface uniformly, resulting in a "dental enamel-like" rod array structure consisting of "pine-leaf-like" structure units.

  18. Dynamics of CTAB in hybrid CTAB-hydroxyapatite system

    Energy Technology Data Exchange (ETDEWEB)

    Dubey, P., E-mail: purushd@barc.gov.in; Sharma, V. K.; Mitra, S.; Mukhopadhyay, R. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai, 40085 (India); Verma, G.; Hassan, P. A. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai, 40085 (India); Johnson, M. [Institut Laue-Langevin, BP 156, 6, rue Jules Horowitz, 38042 Grenoble Cedex 9 (France)

    2016-05-23

    Synthetic hydroxyapatite (HAp) is an important material in biomedical engineering due to its excellent biocompatibility and bioactivity. Here we report dynamics of cetyltrimethylammonium bromide (CTAB) in HAp composite, prepared by co-precipitation method, as studied by quasielastic neutron scattering (QENS) technique. It is found that the observed dynamics involved two time scales associated with fast torsional motion and segmental motion of the CTAB monomers. In addition to segmental motion of the hydrogen atoms, few undergo torsional motion as well. Torsional dynamics was described by a 2-fold jump diffusion model. The segmental dynamics of CTAB has been described assumimg the hydrogen atoms undergoing diffusion inside a sphere of confined volume. While the diffusivity is found to increase with temperature, the spherical volumes within which the hydrogen atoms are undergoing diffusion remain almost unchanged.

  19. Hydroxyapatites: Key Structural Questions and Answers from Dynamic Nuclear Polarization.

    Science.gov (United States)

    Leroy, César; Aussenac, Fabien; Bonhomme-Coury, Laure; Osaka, Akiyoshi; Hayakawa, Satoshi; Babonneau, Florence; Coelho-Diogo, Cristina; Bonhomme, Christian

    2017-10-03

    We demonstrate that NMR/DNP (Dynamic Nuclear Polarization) allows an unprecedented description of carbonate substituted hydroxyapatite (CHAp). Key structural questions related to order/disorder and clustering of carbonates are tackled using distance sensitive DNP experiments using 13 C- 13 C recoupling. Such experiments are easily implemented due to unprecedented DNP gain (orders of magnitude). DNP is efficiently mediated by quasi one-dimensional spin diffusion through the hydroxyl columns present in the CHAp structure (thought of as "highways" for spin diffusion). For spherical nanoparticles and ϕ dynamics and line shape resolution). Finally, all 2D DNP experiments can be interpreted in terms of domains exhibiting well identified types of substitution: local order and carbonate clustering are clearly favored.

  20. Degradation of 17α-methyltestosterone by hydroxyapatite catalyst

    Directory of Open Access Journals (Sweden)

    Daniela Langaro Savaris

    2018-02-01

    Full Text Available Fish farming is becoming a highly profitable economic activity and the rearing of fingerlings involves the practice of sex reversal for the production of species (male using the hormone 17α-methyltestosterone (MT. This study analyzed the methodology for degradation of the hormone through solar and ultraviolet radiation using hydroxyapatite (HAP as heterogeneous catalyst, synthesized by two different methods, with and without doping with nickel and copper. The results showed that MT hormone is degraded by ultraviolet or solar radiation, and accelerated in the presence of the HAP catalyst. In the presence of Fe (III in the medium, the degradation rate of the hormone decreases. The method of HAP synthesis influences the degradation efficiency.

  1. Thermal effects of carbonated hydroxyapatite modified by glycine and albumin

    Science.gov (United States)

    Gerk, S. A.; Golovanova, O. A.; Kuimova, M. V.

    2017-01-01

    In this work calcium phosphate powders were obtained by precipitation method from simulated solutions of synovial fluid containing glycine and albumin. X-ray diffraction and IR spectroscopy determined that all samples are single-phase and are presented by carbonate containing hydroxyapatite (CHA). The thermograms of solid phases of CHA were obtained and analyzed; five stages of transformation in the temperature range of 25-1000°C were marked. It is shown that in this temperature range dehydration, decarboxylation and thermal degradation of amino acid and protein connected to the surface of solid phase occur. The tendency of temperature lowering of the decomposition of powders synthesized from a medium containing organic substances was determined. Results demonstrate a direct dependence between the concentration of the amino acid in a model solution and its content in the solid phase.

  2. Mesenchymal stem cell ingrowth and differentiation on coralline hydroxyapatite scaffolds

    DEFF Research Database (Denmark)

    Mygind, Tina; Stiehler, Maik; Baatrup, Anette

    2007-01-01

    Culture of osteogenic cells on a porous scaffold could offer a new solution to bone grafting using autologous human mesenchymal stem cells (hMSC) from the patient. We compared coralline hydroxyapatite scaffolds with pore sizes of 200 and 500 microm for expansion and differentiation of hMSCs. We...... polymerase chain reaction for 10 osteogenic markers. The 500-microm scaffolds had increased proliferation rates and accommodated a higher number of cells (shown by DNA content, scanning electron microscopy and fluorescence microscopy). Thus the porosity of a 3D microporous biomaterial may be used to steer h......MSC in a particular direction. We found that dynamic spinner flask cultivation of hMSC/scaffold constructs resulted in increased proliferation, differentiation and distribution of cells in scaffolds. Therefore, spinner flask cultivation is an easy-to-use inexpensive system for cultivating hMSCs on small...

  3. Thin hydroxyapatite surface layers on titanium produced by ion implantation

    CERN Document Server

    Baumann, H; Bilger, G; Jones, D; Symietz, I

    2002-01-01

    In medicine metallic implants are widely used as hip replacement protheses or artificial teeth. The biocompatibility is in all cases the most important requirement. Hydroxyapatite (HAp) is frequently used as coating on metallic implants because of its high acceptance by the human body. In this paper a process is described by which a HAp surface layer is produced by ion implantation with a continuous transition to the bulk material. Calcium and phosphorus ions are successively implanted into titanium under different vacuum conditions by backfilling oxygen into the implantation chamber. Afterwards the implanted samples are thermally treated. The elemental composition inside the implanted region was determined by nuclear analysis methods as (alpha,alpha) backscattering and the resonant nuclear reaction sup 1 H( sup 1 sup 5 N,alpha gamma) sup 1 sup 2 C. The results of X-ray photoelectron spectroscopy indicate the formation of HAp. In addition a first biocompatibility test was performed to compare the growing of m...

  4. Synthesis of antimicrobial monophase silver-doped hydroxyapatite nanopowders for bone tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Stanic, Vojislav, E-mail: voyo@vinca.rs [Vinca Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Janackovic, Djordje; Dimitrijevic, Suzana [Faculty of Technology and Metallurgy, University of Belgrade, 11000 Belgrade (Serbia); Tanaskovic, Sladjana B. [Faculty of Pharmacy, University of Belgrade, 11000 Belgrade (Serbia); Mitric, Miodrag; Pavlovic, Mirjana S. [Vinca Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Krstic, Aleksandra [Institute for Medical Research, University of Belgrade, 11000 Belgrade (Serbia); Jovanovic, Dragoljub [Faculty of Veterinary Medicine, University of Belgrade, 11000 Belgrade (Serbia); Raicevic, Slavica [Vinca Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia)

    2011-02-15

    Monophase silver-doped hydroxyapatite (Ag{sub x}Ca{sub 10-x}(PO{sub 4}){sub 6}(OH){sub 2}; 0.002 {<=} x {<=} 0.04) nanoparticles were prepared using a neutralization method and investigated with respect to potential medical applications. This method consists of dissolving Ag{sub 2}O in solution of H{sub 3}PO{sub 4}, and the slow addition to suspension of Ca(OH){sub 2} was applied for the purpose of homogenous distribution of silver ions. Characterization studies from XRD, TEM and FTIR spectra showed that obtained crystals are monophase hydroxyapatites and that particles of all samples are of nano size, with average length of 70 nm and about 15-25 nm in diameter. Antimicrobial studies have demonstrated that all silver-doped hydroxyapatite samples exhibit excellent antimicrobial activity in vitro against the following pathogens: Staphylococcus aureus, Escherichia coli and Candida albicans. The hydroxyapatite sample with the highest content of silver has shown the highest antimicrobial activity; killed all cells of E. coli and brought to more than 99% reduction in viable counts of S. aureus and C. albicans. The atomic force microscopic studies illustrate that silver-doped hydroxyapatite sample causes considerable morphological changes of microorganism cells which might be the cause of cells' death. Hemolysis ratios of the silver-doped hydroxyapatite samples were below 3%, indicating good blood compatibility and that are promising as biomaterials.

  5. Novel silk fibroin films prepared by formic acid/hydroxyapatite dissolution method.

    Science.gov (United States)

    Ming, Jinfa; Liu, Zhi; Bie, Shiyu; Zhang, Feng; Zuo, Baoqi

    2014-04-01

    Bombyx mori silk fibroin from the silkworm was firstly found to be soluble in formic acid/hydroxyapatite system. The rheological behavior of silk fibroin solution was significantly influenced by HAp contents in dissolved solution. At the same time, silk fibroin nanofibers were observed in dissolved solution with 103.6±20.4nm in diameter. Moreover, the structure behavior of SF films prepared by formic acid/hydroxyapatite dissolution method was examined. The secondary structure of silk fibroin films was attributed to silk II structure (β-sheet), indicating that the hydroxyapatite contents in dissolved solution were not significantly affected by the structure of silk fibroin. The X-ray diffraction results exhibited obviously hydroxyapatite crystalline nature existing in silk fibroin films; however, when the hydroxyapatite content was 5.0wt.% in dissolved solution, some hydroxyapatite crystals were converted to calcium hydrogen phosphate dehydrate in silk fibroin dissolution process. This result was also confirmed by Fourier transform infrared analysis and DSC measurement. In addition, silk fibroin films prepared by this dissolution method had higher breaking strength and extension at break. Based on these analyses, an understanding of novel SF dissolution method may provide an additional tool for designing and synthesizing advanced materials with more complex structures, which should be helpful in different fields, including biomaterial applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. In Vitro Evaluation of Nanoscale Hydroxyapatite-Based Bone Reconstructive Materials with Antimicrobial Properties.

    Science.gov (United States)

    Ajduković, Zorica R; Mihajilov-Krstev, Tatjana M; Ignjatović, Nenad L; Stojanović, Zoran; Mladenović-Antić, Snezana B; Kocić, Branislava D; Najman, Stevo; Petrović, Nenad D; Uskoković, Dragan P

    2016-02-01

    In the field of oral implantology the loss of bone tissue prevents adequate patient care, and calls for the use of synthetic biomaterials with properties that resemble natural bone. Special attention is paid to the risk of infection after the implantation of these materials. Studies have suggested that some nanocontructs containing metal ions have antimicrobial properties. The aim of this study was to examine the antimicrobial and hemolytic activity of cobalt-substituted hydroxyapatite nanoparticles, compared to hydroxyapatite and hydroxyapatite/poly-lactide-co-glycolide. The antibacterial effects of these powders were tested against two pathogenic bacterial strains: Escherichia coi (ATCC 25922) and Staphylococcus aureus (ATCC 25923), using the disc diffusion method and the quantitative antimicrobial test in a liquid medium. The quantitative antimicrobial test showed that all of the tested biomaterials have some antibacterial properties. The effects of both tests were more prominent in case of S. aureus than in E coli. A higher percentage of cobalt in the crystal structure of cobalt-substituted hydroxyapatite nanoparticles led to an increased antimicrobial activity. All of the presented biomaterial samples were found to be non-hemolytic. Having in mind that the tested of cobalt-substituted hydroxyapatite (Ca/Co-HAp) material in given concentrations shows good hemocompatibility and antimicrobial effects, along with its previously studied biological properties, the conclusion can be reached that it is a potential candidate that could substitute calcium hydroxyapatite as the material of choice for use in bone tissue engineering and clinical practices in orthopedic, oral and maxillofacial surgery.

  7. Interactions between dodecyl phosphates and hydroxyapatite or tooth enamel: relevance to inhibition of dental erosion.

    Science.gov (United States)

    Jones, Siân B; Barbour, Michele E; Shellis, R Peter; Rees, Gareth D

    2014-05-01

    Tooth surface modification is a potential method of preventing dental erosion, a form of excessive tooth wear facilitated by softening of tooth surfaces through the direct action of acids, mainly of dietary origin. We have previously shown that dodecyl phosphates (DPs) effectively inhibit dissolution of native surfaces of hydroxyapatite (the type mineral for dental enamel) and show good substantivity. However, adsorbed saliva also inhibits dissolution and DPs did not augment this effect, which suggests that DPs and saliva interact at the hydroxyapatite surface. In the present study the adsorption and desorption of potassium and sodium dodecyl phosphates or sodium dodecyl sulphate (SDS) to hydroxyapatite and human tooth enamel powder, both native and pre-treated with saliva, were studied by high performance liquid chromatography-mass Spectrometry. Thermo gravimetric analysis was used to analyse residual saliva and surfactant on the substrates. Both DPs showed a higher affinity than SDS for both hydroxyapatite and enamel, and little DP was desorbed by washing with water. SDS was readily desorbed from hydroxyapatite, suggesting that the phosphate head group is essential for strong binding to this substrate. However, SDS was not desorbed from enamel, so that this substrate has surface properties different from those of hydroxyapatite. The presence of a salivary coating had little or no effect on adsorption of the DPs, but treatment with DPs partly desorbed saliva; this could account for the failure of DPs to increase the dissolution inhibition due to adsorbed saliva. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Biocompatibility of hydroxyapatite scaffolds processed by lithography-based additive manufacturing.

    Science.gov (United States)

    Tesavibul, Passakorn; Chantaweroad, Surapol; Laohaprapanon, Apinya; Channasanon, Somruethai; Uppanan, Paweena; Tanodekaew, Siriporn; Chalermkarnnon, Prasert; Sitthiseripratip, Kriskrai

    2015-01-01

    The fabrication of hydroxyapatite scaffolds for bone tissue engineering applications by using lithography-based additive manufacturing techniques has been introduced due to the abilities to control porous structures with suitable resolutions. In this research, the use of hydroxyapatite cellular structures, which are processed by lithography-based additive manufacturing machine, as a bone tissue engineering scaffold was investigated. The utilization of digital light processing system for additive manufacturing machine in laboratory scale was performed in order to fabricate the hydroxyapatite scaffold, of which biocompatibilities were eventually evaluated by direct contact and cell-culturing tests. In addition, the density and compressive strength of the scaffolds were also characterized. The results show that the hydroxyapatite scaffold at 77% of porosity with 91% of theoretical density and 0.36 MPa of the compressive strength are able to be processed. In comparison with a conventionally sintered hydroxyapatite, the scaffold did not present any cytotoxic signs while the viability of cells at 95.1% was reported. After 14 days of cell-culturing tests, the scaffold was able to be attached by pre-osteoblasts (MC3T3-E1) leading to cell proliferation and differentiation. The hydroxyapatite scaffold for bone tissue engineering was able to be processed by the lithography-based additive manufacturing machine while the biocompatibilities were also confirmed.

  9. Investigation on the effect of collagen and vitamins on biomimetic hydroxyapatite coating formation on titanium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ciobanu, Gabriela, E-mail: gciobanu03@yahoo.co.uk [“Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, Prof. dr. docent Dimitrie Mangeron Rd., no. 63, zip: 700050, Iasi (Romania); Ciobanu, Octavian [“Grigore T. Popa” University of Medicine and Pharmacy, Faculty of Medical Bioengineering, Universitatii Str., no. 16, zip: 700115, Iasi (Romania)

    2013-04-01

    This study uses an in vitro experimental approach to investigate the roles of collagen and vitamins in regulating the deposition of hydroxyapatite layer on the pure titanium surface. Titanium implants were coated with a hydroxyapatite layer under biomimetic conditions by using a supersaturated calcification solution (SCS), modified by adding vitamins A and D{sub 3}, and collagen. The hydroxyapatite deposits on titanium were investigated by means of scanning electron microscopy (SEM) coupled with X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy. The results obtained have shown that hydroxyapatite coatings were produced in vitro under vitamins and collagen influence. - Highlights: ► Hydroxyapatite was grown on Ti using a modified supersaturated calcification solution (M-SCS). ► Vitamins (A and D3) and collagen in M-SCS have a significant effect on apatite precipitation. ► M-SCS stimulates a biomimetic apatite deposition with 0.5–1 μm thickness in a short time. ► Hydroxyapatite crystallites have thin plate morphologies and size below 1 μm.

  10. Interaction of some essential amino acids with synthesized poorly crystalline hydroxyapatite

    Directory of Open Access Journals (Sweden)

    A. El Rhilassi

    2016-09-01

    Full Text Available This study focused on the release of two essential amino acids, l-lysine and dl-leucine, previously adsorbed onto poorly crystalline hydroxyapatite of Ca/P = 1.59, synthesis by precipitation methods. The composition of the calcium-deficient hydroxyapatite (CDHA is chemically and structurally similar to the bone mineral. Their surface reactivity is indeed linked to the existence of hydrated surface particles (HPO42- and Ca2+. The adsorption kinetics is very fast while the release kinetics is relatively slow. The adsorption rate reached approximately 70%, but the release rate did not exceed 12%. The chemical composition of solution has an influence on the release processes. The presence of phosphate ions favored the release of amino acids, while the calcium ions inhibited it. Also, the release process is slightly influenced by Ra (ml/mg ratio and incubation temperature of the medium. The charged –COO− and NH3+ of amino acids are the strongest groups that interact with the surface of hydroxyapatite, the adsorption is mainly due to the electrostatic interaction between the groups –COO− of amino acids and calcium Ca2+ ions of the hydroxyapatite. dl-Leucine (non-polar and l-Lysine (polar–basic interact with the hydroxyapatite surface in the zwitterionic and cationic forms, respectively. The study of interactions between amino acids and hydroxyapatite is carried out in vitro by using UV–vis and infrared spectroscopy IR techniques.

  11. Improving the mechanical properties of nano-hydroxyapatite

    Science.gov (United States)

    Khanal, Suraj Prasad

    Hydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and polymerized epsilon-caprolactam (nylon) is studied. The fracture toughness, tensile strength, Young's modulus, stiffness and fracture energy were studied for a series of HAp samples with CfSWCNT concentrations varying from 0 to 1.5 wt. % without, and with nylon addition. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were used to characterize the samples. The fracture toughness and tensile test was performed under the standard protocol of ASTM D5045 and ASTM D638-02a respectively. Reproducible maximum values of (3.60 +/- 0.3) MPa.m1/2 for fracture toughness and 65.38 MPa for tensile strength were measured for samples containing 1 wt. % CfSWCNT and nylon. The Young's modulus, stiffness and fracture energy of the samples are 10.65 GPa, 1482.12 N/mm, and 644 J/m2 respectively. These values are comparable to those of the cortical bone. Further increase of the CfSWCNT content results to a decreased fracture toughness and tensile strength and formation of a secondary phase.

  12. Microwave assisted synthesis of nano sized sulphate doped hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Alshemary, Ammar Z.; Goh, Yi-Fan; Akram, Muhammad; Razali, Ili Rabihah [Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor Darul Ta’zim (Malaysia); Abdul Kadir, Mohammed Rafiq [Medical Implant Technology Group, Faculty of Biomedical Engineering and Health Science, Universiti Teknologi Malaysia,81310 UTM Skudai, Johor Darul Ta’zim (Malaysia); Hussain, Rafaqat, E-mail: rafaqat@kimia.fs.utm.my [Ibnu Sina Institute for Fundamental Science Studies, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor DarulTa’zim (Malaysia)

    2013-06-01

    Highlights: ► Phase pure nano-sized sulphur doped hydroxyapatite has been synthesized. ► TEM analysis confirmed formation of needle shaped structure. ► Lattice parameters and cell volume increased with increase in sulphate doping. ► Crystallite size decreased as sulphate content inside the structure increased. ► Degree of crystallinity decreased with increase in sulphate substitution. - Abstract: Inorganic sulphate is required by all mammalian cells to function properly, it is the fourth most abundant anion in the human plasma. Sulphate ions are the major source of sulphur which is considered an important element for sustenance of life as it is present in the essential amino and is required by cells to function properly. In this study we have successfully substituted sulphate ions (SO{sub 4}{sup 2−}) into hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6−x}(SO{sub 4}){sub x}(OH){sub 2−x}) lattice via ion exchange process with phosphate group. Concentration of SO{sub 4}{sup 2−} ions was varied between X = 0.05–0.5, using (Ca (NO{sub 3}){sub 2}·4H{sub 2}O), ((NH{sub 4}){sub 2}HPO{sub 4}) and (Na{sub 2}SO{sub 4}) as starting materials. X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), showed that the substitution of SO{sub 4}{sup 2−} ions into the lattice resulted in peak broadening and reduced peak height due to the amorphous nature and reduced crystallinity of the resulting HA powder. Transmission electron microscopy (TEM) and field emission electron microscopy (FESEM) analysis confirmed the formation of needle shaped particles of 41 nm size with homogenous and uniform distribution of element within the HA structure.

  13. Adsorption and bioactivity studies of albumin onto hydroxyapatite surface.

    Science.gov (United States)

    Mavropoulos, Elena; Costa, Andréa M; Costa, Lilian T; Achete, Carlos A; Mello, Alexandre; Granjeiro, José M; Rossi, Alexandre M

    2011-03-01

    Bovine serum albumin (BSA) may have an inhibitory or promoter effect on hydroxyapatite (HA) nucleation when apatite is precipitated in a medium containing the protein. In this study we evaluated the influence of BSA on the precipitation of calcium phosphate phases (CP) from simulated body fluid (SBF) when the protein was previously bounded to HA surface. The kinetics of BSA immobilization onto hydroxyapatite surface was performed in different buffers and protein concentrations in order to adjust experimental conditions in which BSA was tightly linked to HA surface for long periods in SBF solution. It was shown that for BSA concentration higher than 0.1mg/mL the adsorption to HA surface followed Langmuir-Freundlich mechanisms, which confirmed the existence of cooperative protein-protein interactions on HA surface. Fourier Transformed Infrared Attenuated Total Reflectance Microscopy (FTIRM-ATR) evidenced changes in BSA conformational state in favor of less-ordered structure. Analyses from high resolution grazing incident X-ray diffraction using synchrotron radiation (GIXRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed that a poorly crystalline calcium phosphate was precipitated on the surface of HA discs coated with BSA, after the immersion in SBF for 4 days. The new bioactive layer had morphological characteristics similar to the one formed on the HA surface without protein. It was identified as a carbonated apatite with preferential crystal growth along apatite 002 direction. The GIXRD results also revealed that BSA layer bound to the surface inhibited the HA dissolution leading to a reduction on the formation of new calcium phosphate phase. 2010 Elsevier B.V. All rights reserved.

  14. Can mesenchymal stem cell survive in hydroxyapatite sulphate?

    Directory of Open Access Journals (Sweden)

    Erica Kholinne

    2012-02-01

    Full Text Available Background: Many studies have reported the role of Mesenchymal Stem Cells (MSC in treating fractures. In case with bone defect, fracture healing needs not only osteogenic but also osteoconductive component (scaffold. Hydroxyapatite calcium sulphate (HA-CaSO4 being widely used as bone void filler, may serve as scaffold for MSC. However, the effect of this scaffold to the viability of MSC has not been evaluated before.Methods: MSC were isolated from the iliac marrow of a Giant Flamish rabbit, and expanded in DMEM using histogradient density. After one week, they were sub-cultured in a 25cc TC flask (passage 1 and have the medium replaced every 3 days. During the subculture, we embedded a HA-CaSO4 pellet into the flask. The cells were evaluated under inverted microscope at a weekly interval.Results: At the first week, MSC are difficult to be identified in microscope due to the large number of HA-CaSO4 crystals. By the third week however MSC have grown and the HA-CaSO4 crystals can readily be washed off by medium replacement. By the fourth weeks, MSC can be still seen on microscope.Conclusion: HA-CaSO4 could serve as a good scaffold due to its pellet shape and easily absorbed, thus providing revascularization which is essential for bone healing.In addition, HA-CaSO4 does not interfere with MSC survival. (Med J Indones 2012;21:8-12Keywords: Fracture healing, Hydroxyapatite Calcium Sulphate (HA-CaSO4, Mesenchymal Stem Cells (MSC

  15. Adsorption of {sup 188}Re complexes with aminomethylenephosphonate on hydroxyapatite

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, Kazuyuki; Matsuoka, Hiromitsu; Izumo, Mishiroku [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2001-12-01

    The adsorption properties of newly developed {sup 188}Re complexes with aminomethylenephosphonate (amp) (EDTMP-Ethylenediamine-N, N, N', N'-tetrakis (methylenephosphonic acid), EDBMP - Ethylenediamine-N, N'-bis (methylenephosphonic acid) and NTMP - Nitrilotris (methylenephosphonic acid)) on hydroxyapatite was investigated. The adsorption of {sup 188}Re complexes was strongly affected by pH and ionic strength in a solution. The adsorption coefficient (ml/g), which is defined by the ratio of the concentration of the complex per unit weight of the hydroxyapatite to the concentration in unit volume of the solution, increased with decreasing pH and ionic strength. These observations suggest that one of the causes of the adsorption of {sup 188}Re-amp is considered to be the electrostatic forces between the negative {sup 188}Re-amp complex and the positive HAP surface. The adsorption affinity of the {sup 188}Re-amp complex for HAP increased in the order of {sup 188}Re-EDBMP<{sup 188}Re-NTMP<{sup 188}Re-EDTMP. Furthermore, the adsorption coefficient of carrier-free {sup 188}Re-EDTMP was larger than that of carrier-added one under the same conditions. From a detailed comparison of the effect of the Re carrier concentration on the adsorption coefficient of {sup 188}Re-EDTMP with its structural analysis by HPLC, we concluded that the Re carrier effect on the adsorption coefficient was caused by the different distribution of the components in the {sup 188}Re-EDTMP mixture between the carrier-free and the carrier-added complex. (author)

  16. Prediction of microwave absorption properties of tetrapod-needle zinc oxide whisker radar absorbing material without prior knowledge

    Science.gov (United States)

    Zhao, Yu-Chen; Wang, Jie; Liu, Jiang-Fan; Song, Zhong-Guo; Xi, Xiao-Li

    2017-07-01

    The radar absorbing material (RAM) containing a tetrapod-needle zinc oxide whisker (T-ZnOw) has been proved to have good efficiency of microwave absorption. However, the available theoretical models, which are intended to predict the microwave absorbing properties of such an interesting composite, still cannot work well without some prior knowledge, like the measured effective electromagnetic parameters of the prepared T-ZnOw composite. Hence, we propose a novel predictive method here to calculate the reflectivity of T-ZnOw RAM without prior knowledge. In this method, the absorbing ability of this kind of material is divided into three main aspects: the unstructured background, the conductive network, and the nanostructured particle. Then, the attenuation properties of these three parts are represented, respectively, by three different approaches: the equivalent spherical particle and the static strong fluctuation theory, the equivalent circuit model obtained from the complex impedance spectra technology, and the combination of four different microscopic electromagnetic responses. The operational calculation scheme can be obtained by integrating these three absorption effects into the existing theoretical attenuation model. The reasonable agreement between the theoretical and experimental data of a T-ZnON/SiO2 composite in the range of 8-14 GHz shows that the proposed scheme can predict the microwave absorption properties of the T-ZnOw RAM. Furthermore, a detailed analysis of these three mechanisms indicates that, on the one hand, the background plays a dominant role in determining the real part of the effective permittivity of the T-ZnOw composite while the network and the particle are the decisive factors of its material loss; on the other hand, an zero-phase impedance, i.e., a pure resistance, with appropriate resonance characteristic might be a rational physical description of the attenuation property of the conductive network, but it is difficult to realize

  17. Influence of hydroxyapatite on maghemite-to-hematite phase transfer of FeO{sub x}-hydroxyapatite composite

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Kunfeng; Liu Xin; Jin Changzi; Yu Fuhai [Chinese Academy of Sciences, State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics (China); Rykov, Alexandre [Chinese Academy of Sciences, Moessbauer Effect Data Center, Dalian Institute of Chemical Physics (China); Wang Junhu, E-mail: wangjh@dicp.ac.cn; Zhang Tao, E-mail: taozhang@dicp.ac.cn [Chinese Academy of Sciences, State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics (China)

    2013-04-15

    FeO{sub x}-hydroxyapatite (FeO{sub x}-HAP) composites with different FeO{sub x} contents were prepared, and compared with pure FeO{sub x}, the FeO{sub x}-HAP composites exhibit strongly magnetic behavior in an external magnetic field even after 600 Degree-Sign C calcination. The combination of {sup 57}Fe Moessbauer and Fe K-edge XAFS indicates that HAP can stabilize the size and crystal phase of {gamma}-Fe{sub 2}O{sub 3} during heat treatment. Even after 600 Degree-Sign C calcination, the interaction imposed by HAP could produce large amounts of distorted octahedral coordination Fe sites in the interior lattice and then result in strong magnetism. The thermally stable {gamma}-Fe{sub 2}O{sub 3}-HAP composites may provide a new opportunity for developing efficient supported crystal-dependent catalysts.

  18. TSDC and impedance spectroscopy measurements on hydroxyapatite, β-tricalcium phosphate and hydroxyapatite/β-tricalcium phosphate biphasic bioceramics

    Science.gov (United States)

    Prezas, P. R.; Melo, B. M. G.; Costa, L. C.; Valente, M. A.; Lança, M. C.; Ventura, J. M. G.; Pinto, L. F. V.; Graça, M. P. F.

    2017-12-01

    Bone grafting and surgical interventions related with orthopaedic disorders consist in a big business, generating large revenues worldwide every year. There is a need to replace the biomaterials that currently still dominate this market, i.e., autografts and allografts, due to their disadvantages, such as limited availability, need for additional surgeries and diseases transmission possibilities. The most promising replacement materials are biomaterials with bioactive properties, such as the calcium phosphate-based bioceramics group. The bioactivity of these materials, i.e., the rate at which they promote the growth and directly bond with the new host biological bone, can be enhanced through their electrical polarization. In the present work, the electrical polarization features of pure hydroxyapatite (Hap), pure β-tricalcium phosphate (β-TCP) and biphasic hydroxyapatite/β-tricalcium phosphate composites (HTCP) were analyzed by measuring thermally stimulated depolarization currents (TSDC). The samples were thermoelectrically polarized at 500 °C under a DC electric field with a magnitude of 5 kV/cm. The biphasic samples were also polarized under electric fields with different magnitudes: 2, 3, 4 and 5 kV/cm. Additionally, the depolarization processes detected in the TSDC measurements were correlated with dielectric relaxation processes observed in impedance spectroscopy (IS) measurements. The results indicate that the β-TCP crystalline phase has a considerable higher ability to store electrical charge compared with the Hap phase. This indicates that it has a suitable composition and structure for ionic conduction and establishment of a large electric charge density, providing great potential for orthopaedic applications.

  19. In vitro effects of fluor-hydroxyapatite, fluorapatite and hydroxyapatite on colony formation, DNA damage and mutagenicity.

    Science.gov (United States)

    Jantová, S; Theiszová, M; Letasiová, S; Birosová, L; Palou, T M

    2008-04-30

    The number of biomaterials used in biomedical applications has rapidly increased in the past two decades. Fluorapatite (FA) is one of the inorganic constituents of bone or teeth used for hard-tissue repairs and replacements. Fluor-hydroxyapatite (FHA) is a new synthetically prepared composite that in its structure contains the same molecular concentration of OH(-) groups and F(-) ions. The aim of this experimental investigation was to evaluate cytotoxic, genotoxic and mutagenic effects of FHA and FA eluates on Chinese hamster V79 cells and to compare them with the effects of hydroxyapatite (HA) eluate. Cytotoxicity of the biomaterials tested was evaluated by use of the cell colony-formation assay and by direct counting of the cells in each colony. Genotoxicity was assessed by single-cell gel electrophoresis (comet assay) and mutagenicity was evaluated by the Hprt gene-mutation assay and in bacterial mutagenicity tests using Salmonella typhimurium TA100. The results show that the highest test concentrations of the biomaterials (100% and 75% eluates) induced very weak inhibition of colony growth (about 10%). On the other hand, the reduction of cell number per colony induced by these concentrations was in the range from 43% to 31%. The comet assay showed that biomaterials induced DNA breaks, which increased with increasing test concentrations in the order HA

  20. Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method: bonding to titanium and scanning electron microscopy.

    Science.gov (United States)

    Tredwin, Christopher J; Georgiou, George; Kim, Hae-Won; Knowles, Jonathan C

    2013-05-01

    Hydroxyapatite (HA), fluor-hydroxyapatite (FHA) with varying levels of fluoride ion substitution and fluorapatite (FA) production has been characterised and optimised by the sol-gel method and the dissolution and biological properties of these materials were investigated. It was the objective of this study to investigate the potential bond strength and interaction of these materials with titanium. HA, FHA and FA were synthesised by a sol-gel method. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of the FHA and FA sol-gels. Using a spin coating technique the sol-gels were coated onto commercially pure titanium disks and crystallised at various temperatures. Using scanning electron microscopy (SEM) and elemental analysis, the surface characteristics, coating thickness and interaction of the Ti substrate and coating were investigated. The bond strengths of the coating to the Ti were investigated using an Instron Universal Load Testing Machine. Statistical analysis was performed with a two-way analysis of variance and post hoc testing with a Bonferroni correction. (1) Coating speed inversely influenced the coating thickness. (2) Increasing fluoride ion substitution and heating temperature significantly increased bond strength and (3) increasing fluoride ion substitution increased the coating thickness. FHA and FA synthesised using the sol-gel technique may offer a superior alternative to coating titanium implants with HA and plasma spraying. HA, FHA and FA materials synthesised by the sol-gel method may also have a use as bone grafting materials. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  1. Hydroxyapatite, fluor-hydroxyapatite and fluorapatite produced via the sol-gel method. Optimisation, characterisation and rheology.

    Science.gov (United States)

    Tredwin, Christopher J; Young, Anne M; Georgiou, George; Shin, Song-Hee; Kim, Hae-Won; Knowles, Jonathan C

    2013-02-01

    Currently, most titanium implant coatings are made using hydroxyapatite and a plasma spraying technique. There are however limitations associated with plasma spraying processes including poor adherence, high porosity and cost. An alternative method utilising the sol-gel technique offers many potential advantages but is currently lacking research data for this application. It was the objective of this study to characterise and optimise the production of Hydroxyapatite (HA), fluorhydroxyapatite (FHA) and fluorapatite (FA) using a sol-gel technique and assess the rheological properties of these materials. HA, FHA and FA were synthesised by a sol-gel method. Calcium nitrate and triethylphosphite were used as precursors under an ethanol-water based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of the sol-gel derived FHA and FA. Optimisation of the chemistry and subsequent characterisation of the sol-gel derived materials was carried out using X-ray Diffraction (XRD) and Differential Thermal Analysis (DTA). Rheology of the sol-gels was investigated using a viscometer and contact angle measurement. A protocol was established that allowed synthesis of HA, FHA and FA that were at least 99% phase pure. The more fluoride incorporated into the apatite structure; the lower the crystallisation temperature, the smaller the unit cell size (changes in the a-axis), the higher the viscosity and contact angle of the sol-gel derived apatite. A technique has been developed for the production of HA, FHA and FA by the sol-gel technique. Increasing fluoride substitution in the apatite structure alters the potential coating properties. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

  2. Effect of Hydroxyapatite on Bone Integration in a Rabbit Tibial Defect Model

    Science.gov (United States)

    Sohn, Sung-Keun; Kim, Kyung-Taek; Kim, Chul-Hong; Ahn, Hee-Bae; Rho, Mee-Sook; Jeong, Min-Ho; Sun, Sang-Kyu

    2010-01-01

    Background The aim of the present study was to prepare hydroxyapatite (HA) and then characterize its effect on bone integration in a rabbit tibial defect model. The bone formation with different designs of HA was compared and the bony integration of several graft materials was investigated qualitatively by radiologic and histologic study. Methods Ten rabbits were included in this study; two holes were drilled bilaterally across the near cortex and the four holes in each rabbit were divided into four treatment groups (HAP, hydroxyapatite powder; HAC, hydroxyapatite cylinder; HA/TCP, hydroxyapatite/tri-calcium phosphate cylinder, and titanium cylinder). The volume of bone ingrowth and the change of bone mineral density were statistically calculated by computed tomography five times for each treatment group at 0, 2, 4, 6, and 8 weeks after grafting. Histologic analysis was performed at 8 weeks after grafting. Results The HAP group showed the most pronounced effect on the bone ingrowth surface area, which seen at 4, 6, and 8 weeks after graft (p 0.05). On histological examination, the HAP group revealed well-recovered cortical bone, but the bone was irregularly thickened and haphazardly admixed with powder. The HAC group showed similar histological features to those of the HA/TCP group; the cortical surface of the newly developed bone was smooth and the bone matrix on the surface of the cylinder was regularly arranged. Conclusions We concluded that both the hydroxyapatite powder and cylinder models investigated in our study may be suitable as a bone substitute in the rabbit tibial defect model, but their characteristic properties are quite different. In contrast to hydroxyapatite powder, which showed better results for the bone ingrowth surface, the hydroxyapatite cylinder showed better results for the sustained morphology. PMID:20514266

  3. Development of dental composites with reactive fillers that promote precipitation of antibacterial-hydroxyapatite layers.

    Science.gov (United States)

    Aljabo, Anas; Abou Neel, Ensanya A; Knowles, Jonathan C; Young, Anne M

    2016-03-01

    The study aim was to develop light-curable, high strength dental composites that would release calcium phosphate and chlorhexidine (CHX) but additionally promote surface hydroxyapatite/CHX co-precipitation in simulated body fluid (SBF). 80 wt.% urethane dimethacrylate based liquid was mixed with glass fillers containing 10 wt.% CHX and 0, 10, 20 or 40 wt.% reactive mono- and tricalcium phosphate (CaP). Surface hydroxyapatite layer thickness/coverage from SEM images, Ca/Si ratio from EDX and hydroxyapatite Raman peak intensities were all proportional to both time in SBF and CaP wt.% in the filler. Hydroxyapatite was, however, difficult to detect by XRD until 4 weeks. XRD peak width and SEM images suggested this was due to the very small size (~10 nm) of the hydroxyapatite crystallites. Precipitate mass at 12 weeks was 22 wt.% of the sample CaP total mass irrespective of CaP wt.% and up to 7 wt.% of the specimen. Early diffusion controlled CHX release, assessed by UV spectrometry, was proportional to CaP and twice as fast in water compared with SBF. After 1 week, CHX continued to diffuse into water but in SBF, became entrapped within the precipitating hydroxyapatite layer. At 12 weeks CHX formed 5 to 15% of the HA layer with 10 to 40 wt.% CaP respectively. Despite linear decline of strength and modulus in 4 weeks from 160 to 101 MPa and 4 to 2.4 GPa, respectively, upon raising CaP content, all values were still within the range expected for commercial composites. The high strength, hydroxyapatite precipitation and surface antibacterial accumulation should reduce tooth restoration failure due to fracture, aid demineralised dentine repair and prevent subsurface carious disease respectively. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  4. Reassigning the most stable surface of hydroxyapatite to the water resistant hydroxyl terminated (010) surface

    Science.gov (United States)

    Zeglinski, Jacek; Nolan, Michael; Thompson, Damien; Tofail, Syed A. M.

    2014-05-01

    Understanding the surface stability and crystal growth morphology of hydroxyapatite is important to comprehend bone growth and repair processes and to engineer protein adsorption, cellular adhesion and biomineralization on calcium phosphate based bone grafts and implant coatings. It has generally been assumed from electronic structure calculations that the most stable hydroxyapatite surface is the (001) surface, terminated just above hydroxyl ions perpendicular to the {001} crystal plane. However, this is inconsistent with the known preferential growth direction of hydroxyapatite crystals and previous experimental work which indicates that, contrary to currently accepted theoretical predictions, it is actually the (010) surface that is preferentially exposed. The surface structure of the (010) face is still debated and needs reconciliation. In this work, we use a large set of density functional theory calculations to model the interaction of water with hydroxyapatite surfaces and probe the surface stability and resistance to hydrolytic remodeling of a range of surface faces including the (001) surface and the phosphate-exposed, calcium-exposed, and hydroxyl-exposed terminations of the (010) surface. For the (001) surface and the phosphate-exposed (010) surface, dissociative water adsorption is favorable. In contrast, the hydroxyl-terminated (010) surface will not split water and only molecular adsorption of water is possible. Our calculations show, overall, that the hydroxyl-terminated (010) surface is the most stable and thus should be the predominant form of the hydroxyapatite surface exposed in experiments. This finding reconciles discrepancies between the currently proposed surface terminations of hydroxyapatite and the experimentally observed crystal growth direction and surface stability, which may aid efforts to accelerate biomineralization and better control bone-repair processes on hydroxyapatite surfaces.

  5. Characterization and formation of hydroxyapatite on Ti6Al4V coated by plasma electrolytic oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Durdu, Salih; Deniz, Oemer Faruk; Kutbay, Is Latin-Small-Letter-Dotless-I l [Department of Materials Science and Engineering, Gebze Institute of Technology, Gebze, Kocaeli 41400 (Turkey); Usta, Metin, E-mail: ustam@gyte.edu.tr [Department of Materials Science and Engineering, Gebze Institute of Technology, Gebze, Kocaeli 41400 (Turkey)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer Ti6Al4V alloys were coated by PEO in calcium acetate and {beta}-calcium glycerophosphate. Black-Right-Pointing-Pointer Hydroxyapatite and calcium apatite based phases were directly formed on Ti6Al4V. Black-Right-Pointing-Pointer Hydroxyapatite coatings were characterized systematically for different times. Black-Right-Pointing-Pointer After 5 min, hydroxyapatite and calcium based phases begin to form on the coating. Black-Right-Pointing-Pointer HAp on the coating is amorphous due to the rapid solidification during PEO. - Abstract: In this study, Ti6Al4V alloy was coated in the solution consisting of calcium acetate (CA) and {beta}-calcium glycerophosphate ({beta}-Ca-GP) by plasma electrolytic oxidation (PEO) to produce hydroxyapatite and calcium apatite-based composite used as of bioactive and biocompatible materials in biomedical applications. The phase structures, surface morphologies, functional groups of molecules, chemical compositions of the surfaces and the binding energies of atoms in the coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Anatase, rutile, calcium oxide, titanium phosphide, whitlockite, tri-calcium phosphate (TCP), perovskite calcium titanate and hydroxyapatite phases on the coating were detected by XRD analysis. The surface of coatings produced by PEO method has a porous structure. The amount of amorphous hydroxyapatite is the highest value for the coating produced at 5 min in XPS and ATR-FTIR results, whereas the amount of crystalline hydroxyapatite has the highest value for coating produced at 120 min in XRD results.

  6. Sliding wear of self-mated Al2O3-SiC whisker-reinforced composites at 23-1200 C

    Science.gov (United States)

    Farmer, S. C.; Dellacorte, C.; Book, P. O.

    1993-01-01

    Microstructural changes occurring during sliding wear of self-mated Al2O3 SiC whisker-reinforced composites were studied using optical, scanning electron microscopy and transmission electron microscopy. Pin-on-disc specimens were slid in air at 2.7 m/s sliding velocity under a 26.5 N load for 1 h. Wear tests were conducted at 23, 600, 800 and 1200 C. Mild wear with a wear factor of 2.4 x 10 exp -7 - 1.5 x 10 exp -6 cu mm /N per m was experienced at all test temperatures. The composite showed evidence of wear by fatigue mechanisms at 800 C and below. Tribochemical reaction (SiC oxidation and reaction of SiO2 and Al2O3) leads to intergranular failure at 1200 C. Distinct microstructural differences existing at each test temperature are reported.

  7. Sliding wear of self-mated Al2O3-SiC whisker reinforced composites at 23-1200 C

    Science.gov (United States)

    Farmer, Serene C.; Book, Patricia O.; Dellacorte, Christopher

    1991-01-01

    Microstructural changes occurring during sliding wear of self-mated Al2O3-SiC whisker reinforced composites were studied using optical, scanning electron microscopy, and transmission electron microscopy. Pin-on-disk specimens were slid in air at 2.7 m/sec sliding velocity under a 26.5 N load for 1 hr. Wear tests were conducted at 23, 600, 800, and 1200 C. Mild wear with a wear factor of 2.4 times 10(exp -7) to 1.5 times 10(exp -6) cu mm/Nm was experienced at all test temperatures. The composite shows evidence of wear by fatigue mechanisms at 800 C and below. Tribochemical reaction (SiC oxidation and reaction of SiO2 and Al2O3) leads to intergranular failure at 1200 C. Distinct microstructural differences existing at each test temperature are reported.

  8. Towards the synthesis of hydroxyapatite/protein scaffolds with controlled porosities: bulk and interfacial shear rheology of a hydroxyapatite suspension with protein additives.

    Science.gov (United States)

    Maas, Michael; Bodnar, Pedro Marcus; Hess, Ulrike; Treccani, Laura; Rezwan, Kurosch

    2013-10-01

    The synthesis of porous hydroxyapatite scaffolds is essential for biomedical applications such as bone tissue engineering and replacement. One way to induce macroporosity, which is needed to support bone in-growth, is to use protein additives as foaming agents. Another reason to use protein additives is the potential to introduce a specific biofunctionality to the synthesized scaffolds. In this work, we study the rheological properties of a hydroxyapatite suspension system with additions of the proteins bovine serum albumin (BSA), lysozyme (LSZ) and fibrinogen (FIB). Both the rheology of the bulk phase as well as the interfacial shear rheology are studied. The bulk rheological data provides important information on the setting behavior of the thixotropic suspension, which we find to be faster with the addition of FIB and LSZ and much slower with BSA. Foam bubble stabilization mechanisms can be rationalized via interfacial shear rheology and we show that it depends on the growth of interfacial films at the suspension/air interface. These interfacial films support the stabilization of bubbles within the ceramic matrix and thereby introduce macropores. Due to the weak interaction of the protein molecules with the hydroxyapatite particles of the suspension, we find that BSA forms the most stable interfacial films, followed by FIB. LSZ strongly interacts with the hydroxyapatite particles and thus only forms thin films with very low elastic moduli. In summary, our study provides fundamental rheological insights which are essential for tailoring hydroxyapatite/protein suspensions in order to synthesize scaffolds with controlled porosities. Copyright © 2013 Elsevier Inc. All rights reserved.

  9. Comparison of the x-ray attenuation properties of breast calcifications, aluminium, hydroxyapatite and calcium oxalate.

    Science.gov (United States)

    Warren, L M; Mackenzie, A; Dance, D R; Young, K C

    2013-04-07

    Aluminium is often used as a substitute material for calcifications in phantom measurements in mammography. Additionally, calcium oxalate, hydroxyapatite and aluminium are used in simulation studies. This assumes that these materials have similar attenuation properties to calcification, and this assumption is examined in this work. Sliced mastectomy samples containing calcification were imaged at ×5 magnification using a digital specimen cabinet. Images of the individual calcifications were extracted, and the diameter and contrast of each calculated. The thicknesses of aluminium required to achieve the same contrast as each calcification when imaged under the same conditions were calculated using measurements of the contrast of aluminium foils. As hydroxyapatite and calcium oxalate are also used to simulate calcifications, the equivalent aluminium thicknesses of these materials were also calculated using tabulated attenuation coefficients. On average the equivalent aluminium thickness was 0.85 times the calcification diameter. For calcium oxalate and hydroxyapatite, the equivalent aluminium thicknesses were 1.01 and 2.19 times the thickness of these materials respectively. Aluminium and calcium oxalate are suitable substitute materials for calcifications. Hydroxyapatite is much more attenuating than the calcifications and aluminium. Using solid hydroxyapatite as a substitute for calcification of the same size would lead to excessive contrast in the mammographic image.

  10. [Influence of different mixing fluids on mechanical and micromorphological in vitro qualities of hydroxyapatite cement].

    Science.gov (United States)

    Nitsch, A; Patyk, A; Schwartz, P; Merten, H-A

    2005-03-01

    In reconstructive craniofacial surgery a new synthetic hydroxyapatite cement has been used in the last few years. Tetra- and dicalcium phosphates react with either slow setting aqua bidest. or with faster setting sodium monophosphate solution to hydroxyapatite. The aim of this study was to investigate the two mixing fluids of hydroxyapatite for resulting micromorphology, pressure strength, and interactions with fibroblasts. Pressure strength tests of hydroxyapatite cement test samples (n=80) were performed after a setting time of 3 and 24 h. The micromorphology of surfaces of the resulting particles was assessed under an electron microscope. In cell cultures L-929 and HEp2 cells were incubated with test samples and cell growth was assessed by light and electron microscopy. The test samples mixed with sodium monophosphate solution showed statistically significantly higher values of pressure strength. The resulting pressure strength depended on respective mixing fluids, setting time, and pressure of application. In general, test samples mixed with sodium monophosphate solution showed a more load-stable, homogeneous anorganic matrix whereas test samples mixed with aqua bidest. had a porous microarchitecture which was more fragile. In cell culture the porous structure showed disintegration in cell culture medium. To what extent the two mixing liquids of hydroxyapatite cement influence the resorption and bony substitution has to be shown in further studies.

  11. BMP2-loaded hollow hydroxyapatite microspheres exhibit enhanced osteoinduction and osteogenicity in large bone defects.

    Science.gov (United States)

    Xiong, Long; Zeng, Jianhua; Yao, Aihua; Tu, Qiquan; Li, Jingtang; Yan, Liang; Tang, Zhiming

    2015-01-01

    The regeneration of large bone defects is an osteoinductive, osteoconductive, and osteogenic process that often requires a bone graft for support. Limitations associated with naturally autogenic or allogenic bone grafts have demonstrated the need for synthetic substitutes. The present study investigates the feasibility of using novel hollow hydroxyapatite microspheres as an osteoconductive matrix and a carrier for controlled local delivery of bone morphogenetic protein 2 (BMP2), a potent osteogenic inducer of bone regeneration. Hollow hydroxyapatite microspheres (100±25 μm) with a core (60±18 μm) and a mesoporous shell (180±42 m(2)/g surface area) were prepared by a glass conversion technique and loaded with recombinant human BMP2 (1 μg/mg). There was a gentle burst release of BMP2 from microspheres into the surrounding phosphate-buffered saline in vitro within the initial 48 hours, and continued at a low rate for over 40 days. In comparison with hollow hydroxyapatite microspheres without BMP2 or soluble BMP2 without a carrier, BMP2-loaded hollow hydroxyapatite microspheres had a significantly enhanced capacity to reconstitute radial bone defects in rabbit, as shown by increased serum alkaline phosphatase; quick and complete new bone formation within 12 weeks; and great biomechanical flexural strength. These results indicate that BMP2-loaded hollow hydroxyapatite microspheres could be a potential new option for bone graft substitutes in bone regeneration.

  12. Evaluation of Hydroxyapatite-Forsterite Glass Composite Nanopowder Prepared via Sol-Gel Method

    Science.gov (United States)

    Mazrooei Sebdani, Maryam; Fathi, Mohammadhossein

    In spite of attractive bioactivity of bioactive ceramics i.e. hydroxyapatite and bioactive glasses, their poor mechanical properties have restricted their clinical applications. To overcome these limitations, an alternative approach suggested is preparation a composite including these bioactive ceramics with others. It is expected that a ceramic reinforcement with reduced grain size below 100 nm promotes theirs. The aim of this work was fabrication and characterization of hydroxyapatite-forsterite-bioglass composite nanopowder. Novel hydroxyapatite-forsterite-bioglass composite nanopowder was synthesized by incorporation of the forsterite and bioactive glass in hydroxyapatite matrix via a sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fourier transform infrared (FTIR) spectroscopy techniques were utilized in order to evaluate the phase composition, agglomerates size distribution, morphology and particle size and functional groups of synthesized. The effects of sintering temperature and time were also investigated. Results showed that the appropriate temperature for calcination was 600°C and the particle size of composite nanopowder was about 60-70nm. The decomposition of hydroxyapatite was increased with the increase of the sintering temperature and sintering time. Obtained results indicate that prepared composite nanopowder could be a good candidate for medical applications.

  13. Fabrication and Microstructure of Hydroxyapatite Coatings on Zirconia by Room Temperature Spray Process.

    Science.gov (United States)

    Seo, Dong Seok; Chae, Hak Cheol; Lee, Jong Kook

    2015-08-01

    Hydroxyapatite coatings were fabricated on zirconia substrates by a room temperature spray process and were investigated with regards to their microstructure, composition and dissolution in water. An initial hydroxyapatite powder was prepared by heat treatment of bovine-bone derived powder at 1100 °C for 2 h, while dense zirconia substrates were fabricated by pressing 3Y-TZP powder and sintering it at 1350 °C for 2 h. Room temperature spray coating was performed using a slit nozzle in a low pressure-chamber with a controlled coating time. The phase composition of the resultant hydroxyapatite coatings was similar to that of the starting powder, however, the grain size of the hydroxyapatite particles was reduced to about 100 nm due to their formation by particle impaction and fracture. All areas of the coating had a similar morphology, consisting of reticulated structure with a high surface roughness. The hydroxyapatite coating layer exhibited biostability in a stimulated body fluid, with no severe dissolution being observed during in vitro experimentation.

  14. Open-Porous Hydroxyapatite Scaffolds for Three-Dimensional Culture of Human Adult Liver Cells

    Science.gov (United States)

    Schmelzer, Eva; Over, Patrick; Nettleship, Ian; Gerlach, Joerg C.

    2016-01-01

    Liver cell culture within three-dimensional structures provides an improved culture system for various applications in basic research, pharmacological screening, and implantable or extracorporeal liver support. Biodegradable calcium-based scaffolds in such systems could enhance liver cell functionality by providing endothelial and hepatic cell support through locally elevated calcium levels, increased surface area for cell attachment, and allowing three-dimensional tissue restructuring. Open-porous hydroxyapatite scaffolds were fabricated and seeded with primary adult human liver cells, which were embedded within or without gels of extracellular matrix protein collagen-1 or hyaluronan. Metabolic functions were assessed after 5, 15, and 28 days. Longer-term cultures exhibited highest cell numbers and liver specific gene expression when cultured on hydroxyapatite scaffolds in collagen-1. Endothelial gene expression was induced in cells cultured on scaffolds without extracellular matrix proteins. Hydroxyapatite induced gene expression for cytokeratin-19 when cells were cultured in collagen-1 gel while culture in hyaluronan increased cytokeratin-19 gene expression independent of the use of scaffold in long-term culture. The implementation of hydroxyapatite composites with extracellular matrices affected liver cell cultures and cell differentiation depending on the type of matrix protein and the presence of a scaffold. The hydroxyapatite scaffolds enable scale-up of hepatic three-dimensional culture models for regenerative medicine applications. PMID:27403430

  15. Microstructural Improvement of Hydroxyapatite-ZrO2 Composite Ceramics via Thermal Precipitation Techniques.

    Science.gov (United States)

    Sangmala, A.; Limsuwan, P.; Kaewwiset, W.; Naemchanthara, K.

    2017-09-01

    Hydroxyapatite-ZrO2 composite ceramic were synthesized using a thermal precipitation techniques. The chemical precursors were prepared from di-ammonium hydrogen orthophosphate, calcium oxide (CaO) derived from chicken eggshell, zirconium dioxide (ZrO2) and distilled water. The mixture were heated at the various temperatures from 100 to 700 °C in the furnace with an incremental temperature of 100 °C. The ZrO2 contents in the composite ceramic were varied from 0 to 15 percent weight of CaO. The prepared composites were then annealed at 300, 600 and 700 °C for 4 h in air. The crystal structure, function group and morphology of all samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and universal testing machine (UTM), respectively. The results indicated that the undoped-ZrO2 samples hydroxyapatite phase with a hexagonal structure. However, the hydroxyapatite was transformed to the tri-calcium phosphate after thermal treatment at 700 °C. For the doped-ZrO2 samples, the hydroxyapatite and ZrO2 phases were found. Moreover, the result showed that the compressive strength of hydroxyapatite-ZrO2 composite ceramic increased with increasing the ZrO2 content.

  16. Nano-hydroxyapatite and its applications in preventive, restorative and regenerative dentistry: a review of literature.

    Science.gov (United States)

    Pepla, Erlind; Besharat, Lait Kostantinos; Palaia, Gaspare; Tenore, Gianluca; Migliau, Guido

    2014-07-01

    This study aims to critically summarize the literature about nano-hydroxyapatite. The purpose of this work is to analyze the benefits of using nano-hydroxyapatite in dentistry, especially for its preventive, restorative and regenerative applications. We also provide an overview of new dental materials, still experimental, which contain the nano-hydroxyapatite in its nano-crystalline form. Hydroxyapatite is one of the most studied biomaterials in the medical field for its proven biocompatibility and for being the main constituent of the mineral part of bone and teeth. In terms of restorative and preventive dentistry, nano-hydroxyapatite has significant remineralizing effects on initial enamel lesions, certainly superior to conventional fluoride, and good results on the sensitivity of the teeth. The nano-HA has also been used as an additive material, in order to improve already existing and widely used dental materials, in the restorative field (experimental addition to conventional glass ionomer cements, that has led to significant improvements in their mechanical properties). Because of its unique properties, such as the ability to chemically bond to bone, to not induce toxicity or inflammation and to stimulate bone growth through a direct action on osteoblasts, nano-HA has been widely used in periodontology and in oral and maxillofacial surgery. Its use in oral implantology, however, is a widely used practice established for years, as this substance has excellent osteoinductive capacity and improves bone-to-implant integration.

  17. Nanocrystalline hydroxyapatite enriched in selenite and manganese ions: physicochemical and antibacterial properties

    Science.gov (United States)

    Kolmas, Joanna; Groszyk, Ewa; Piotrowska, Urszula

    2015-07-01

    In this work, we used the co-precipitation method to synthesize hydroxyapatite (Mn-SeO3-HA) containing both selenium IV (approximately 3.60 wt.%) and manganese II (approximately 0.29 wt.%). Pure hydroxyapatite (HA), hydroxyapatite-containing manganese (II) ions (Mn-HA), and hydroxyapatite-containing selenite ions alone (SeO3-HA), prepared with the same method, were used as reference materials. The structures and physicochemical properties of all the obtained samples were investigated. PXRD studies showed that the obtained materials were homogeneous and consisted of apatite phase. Introducing selenites into the hydroxyapatite crystals considerably affects the size and degree of ordering. Experiments with transmission electron microscopy (TEM) showed that Mn-SeO3-HA crystals are very small, needle-like, and tend to form agglomerates. Fourier transform infrared spectroscopy (FT-IR) and solid-state nuclear magnetic resonance (ssNMR) were used to analyze the structure of the obtained material. Preliminary microbiological tests showed that the material demonstrated antibacterial activity against Staphylococcus aureus, yet such properties were not confirmed regarding Escherichia coli. PACS codes: 61, 76, 81

  18. Effect of Metal Ions of Chlorapatites on the Topotaxial Replacement by Hydroxyapatite under Hydrothermal Conditions

    Science.gov (United States)

    Rendón-Angeles, J. C.; Yanagisawa, K.; Ishizawa, N.; Oishi, S.

    2000-11-01

    The effect of the metal ions in the chlorapatite structure on the topotaxial conversion to the hydroxyapatite structure was investigated, using three different types of chlorapatite single crystals, calcium, strontium, and barium chlorapatite. The topotaxial conversion to the hydroxyapatite structure was conducted under hydrothermal conditions at a range of temperature from 300 to 800°C for intervals between 3 and 96 h in concentrated KOH solutions. The Cl- ion exchange in the calcium and strontium chlorapatite crystals was completed at 500 and 700°C in a 6.25 M KOH solution, respectively, which resulted in the formation of hydroxyapatite structure. The transformed crystals retained their original shape and dimensions due to the topotaxial transformation. In contrast, the rate of the topotaxial conversion was further reduced on the barium chlorapatite crystals that contain metal ions with large size such as Ba. These crystals were only partially converted to hydroxyapatite even at 800°C in 10 M KOH solution. Under these conditions, a dissolution of ion species of the topotaxially converted barium hydroxyapatite layer was observed, which resulted in the precipitation of new crystals on the surface of the remaining barium chlorapatite crystals. The structure of the new crystals was matched with the hexagonal apatite structure, but a great amount of K was incorporated in the structure.

  19. Alternate Spray-coating for the Direct Fabrication of Hydroxyapatite Films without Crystal Growth Step in Solution.

    Science.gov (United States)

    Watanabe, Satoshi; Kashiwagi, Rei; Matsumoto, Mutsuyoshi

    2017-03-01

    We discuss an alternate spray-coating technique for the direct fabrication of hydroxyapatite films using metal masks, suction-type spray nozzles and two calcification solutions of calcium hydroxide and phosphoric acid aqueous solutions. Hydroxyapatite films were formed only on the hydrophobic surface of the substrates. Scanning electron microscopy and energy dispersive X-ray spectroscopy showed that the spray-coated films consisted of hydroxyapatite nanoparticles. The Ca/P ratio was estimated to be about 1.26. X-ray diffraction patterns of the spray-coated films almost coincided with those of the hydroxyapatite powders, showing that the spray-coated films consisted of hydroxyapatite nanoparticles. Dot arrays of hydroxyapatite films at a diameter of 100 μm were formed by tuning the concentrations of calcium hydroxide and phosphoric acid aqueous solutions. This technique allows for the direct fabrication of the hydroxyapatite films without crystal growth process in hydroxyapatite precursors, the scaffolds of crystal growth such as biocompatibility SiO2-CaO glasses, or electrophoresis processes. By using this technique, large-area ceramic films with biocompatibility will be micropatterned with minimized material consumption, short fabrication time, and reduced equipment investments.

  20. Highly efficient one-pot three-component synthesis of naphthopyran derivatives in water catalyzed by hydroxyapatite

    Science.gov (United States)

    An expeditious and efficient protocol for the synthesis of naphthopyrans has been developed that proceeds via one-pot three-component sequential reaction in water catalyzed by hydroxyapatite or sodium-modified-hydroxyapatite. The title compounds have been obtained in high yield a...

  1. Novel synthesis strategy for composite hydrogel of collagen/hydroxyapatite-microsphere originating from conversion of CaCO3 templates.

    Science.gov (United States)

    Wei, Qingrong; Lu, Jian; Wang, Qiaoying; Fan, Hongsong; Zhang, Xingdong

    2015-03-20

    Inspired by coralline-derived hydroxyapatite, we designed a methodological route to synthesize carbonated-hydroxyapatite microspheres from the conversion of CaCO3 spherulite templates within a collagen matrix under mild conditions and thus constructed the composite hydrogel of collagen/hydroxyapatite-microspheres. Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) were employed to confirm the successful generation of the carbonated hydroxyapatite phase originating from CaCO3, and the ratios of calcium to phosphate were tracked over time. Variations in the weight portion of the components in the hybrid gels before and after the phase transformation of the CaCO3 templates were identified via thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) shows these composite hydrogels have a unique multiscale microstructure consisting of a collagen nanofibril network and hydroxyapatite microspheres. The relationship between the hydroxyapatite nanocrystals and the collagen fibrils was revealed by transmission electron microscopy (TEM) in detail, and the selected area electron diffraction (SAED) pattern further confirmed the results of the XRD analyses which show the typical low crystallinity of the generated hydroxyapatite. This smart synthesis strategy achieved the simultaneous construction of microscale hydroxyapatite particles and collagen fibrillar hydrogel, and appears to provide a novel route to explore an advanced functional hydrogel materials with promising potentials for applications in bone tissue engineering and reconstruction medicine.

  2. The Kinetics of Ampicillin Release from Hydroxyapatite for Bones Regeneration

    Directory of Open Access Journals (Sweden)

    Giovanilton Ferreira da Silva

    2009-01-01

    Full Text Available Semisynthetic beta-lactam antibiotics are among the most used pharmaceuticals. Their use in veterinary and human medicine is in continuous expansion. There is a growing need for developing bioactive implants. Advantages of implantable drug delivery tools can include high release efficiency, precise dose control, low toxicity, and allow to overcome disadvantages connected with conventional methods. In this respect, hydroxyapatite (HA is an elective material. It enables to produce architectures similar to those of real bones. Here we studied a kinetic model to describe ampicillin release from HA. In the course of adsorption experiment, ampicillin was dissolved, maintained at 30∘C and shaken at 60 strokes/minute. Samples were withdrawn periodically for analysis and then returned to the mixture. Adsorbed amounts were measured by the difference of the concentration of the antibiotics before and after adsorption using UV adsorption at 225 nm. The aim of this work was to evaluate its application as ampicillin delivery carrier.

  3. Gene expression profile study on osteoinductive effect of natural hydroxyapatite.

    Science.gov (United States)

    Lü, Xiaoying; Wang, Jiandan; Li, Bin; Zhang, Zhiwei; Zhao, Lifeng

    2014-08-01

    The aim of this study was to investigate the osteoinductive effect of natural hydroxyapatite (NHA). NHA was extracted from pig bones and prepared into disk-like samples. Then, proliferation of mouse bone mesenchymal stem cells (MSCs) cultured on NHA was assessed by the methylthiazoltetrazolium (MTT) assay. Furthermore, microarray technology was applied to obtain the gene expression profiles of MSCs cultured on NHA at 24, 48, and 72 h. The gene expression profile was then comprehensively analyzed by clustering, Gene Ontology (GO), Gene Microarray Pathway Profiler (GenMAPP) and Ingenuity Pathway Analysis (IPA). According to the results of microarray experiment, 8992 differentially expressed genes were obtained. 90 differential expressed genes related to HA osteogenic differentiation were determined by GO analysis. These genes included not only 6 genes related to HA osteogenic differentiation as mentioned in the literatures but also newly discovered 84 genes. Some important signaling pathways (TGF-β, MAPK, Wnt, etc.) were influenced by these genes. Gene interaction networks were obtained by IPA software, in which the scoring values of two networks were highest, and their main functions were related to cell development. The comprehensive analysis of these results indicate that NHA regulate some crucial genes (e.g., Bmp2, Spp1) and then activate some pathways such as TGF-β signaling pathway, and ultimately osteogenic differentiation was induced. © 2013 Wiley Periodicals, Inc.

  4. Biomedical nanocomposites of hydroxyapatite/polycaprolactone obtained by surfactant mediation.

    Science.gov (United States)

    Kim, Hae-Won

    2007-10-01

    The composite approach to combining bioactive ceramic and degradable polymer is a promising strategy in the development of bone regenerative matrices. Moreover, in the fabrication of composites, the nanoscale organization of each component should improve the level of structural integration as well as the resultant mechanical and biological properties. The aim of this study was to develop a novel nanocomposite system consisting of hydroxyapatite (HA) and poly(epsilon-caprolactone) (PCL), wherein the HA nanoparticles were uniformly dispersed within the PCL matrix. The strategy was based on applying an amphiphilic surfactant, oleic acid in this case, between the HA and PCL. Oleic acid, which belongs to the fatty acid family and is generally noncytotoxic at the levels used in this study, is believed to mediate the interaction between the hydrophilic HA and hydrophobic PCL. With the mediation of oleic acid, the HA nanoparticles were distributed uniformly within the PCL matrix on the nanoscale (distributed particle size of less than 1 microm), which is in marked contrast to the conventionally mixed HA-PCL composite, in which the HA particles were severely agglomerated. The developed nanocomposite had significantly higher mechanical strength than did the conventional composite and the pure PCL. Moreover, the osteoblastic cells showed a better proliferation behavior on the nanocomposite than on the conventional composite. This HA-PCL nanocomposite mediated by oleic acid is expected to be useful in the bone regeneration field. Moreover, this methodology is applicable to the nanocomposite processing of other biomedical materials.

  5. Bacterial Cellulose-Hydroxyapatite Nanocomposites for Bone Regeneration

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    S. Saska

    2011-01-01

    Full Text Available The aim of this study was to develop and to evaluate the biological properties of bacterial cellulose-hydroxyapatite (BC-HA nanocomposite membranes for bone regeneration. Nanocomposites were prepared from bacterial cellulose membranes sequentially incubated in solutions of CaCl2 followed by Na2HPO4. BC-HA membranes were evaluated in noncritical bone defects in rat tibiae at 1, 4, and 16 weeks. Thermogravimetric analyses showed that the amount of the mineral phase was 40%–50% of the total weight. Spectroscopy, electronic microscopy/energy dispersive X-ray analyses, and X-ray diffraction showed formation of HA crystals on BC nanofibres. Low crystallinity HA crystals presented Ca/P a molar ratio of 1.5 (calcium-deficient HA, similar to physiological bone. Fourier transformed infrared spectroscopy analysis showed bands assigned to phosphate and carbonate ions. In vivo tests showed no inflammatory reaction after 1 week. After 4 weeks, defects were observed to be completely filled in by new bone tissue. The BC-HA membranes were effective for bone regeneration.

  6. The effect of RGD peptides on osseointegration of hydroxyapatite biomaterials

    Science.gov (United States)

    Hennessy, KM; Clem, WC; Phipps, MC; Sawyer, AA; Shaikh, FM; Bellis, SL

    2008-01-01

    Given that hydroxyapatite (HA) biomaterials are highly efficient at adsorbing proadhesive proteins, we questioned whether functionalizing HA with RGD peptides would have any benefit. In this study, we implanted uncoated or RGD-coated HA disks into rat tibiae for 30 minutes to allow endogenous protein adsorption, and then evaluated mesenchymal stem cell (MSC) interactions with the retrieved disks. These experiments revealed that RGD, when presented in combination with adsorbed tibial proteins (including fibronectin, vitronectin and fibrinogen), has a markedly detrimental effect on MSC adhesion and survival. Moreover, analyses of HA disks implanted for 5 days showed that RGD significantly inhibits total bone formation as well as the amount of new bone directly contacting the implant perimeter. Thus, RGD, which is widely believed to promote cell/biomaterial interactions, has a negative effect on HA implant performance. Collectively these results suggest that, for biomaterials that are highly interactive with the tissue microenvironment, the ultimate effects of RGD will depend upon how signaling from this peptide integrates with endogenous processes such as protein adsorption. PMID:18440064

  7. Anisotropic diffusion of water molecules in hydroxyapatite nanopores

    Science.gov (United States)

    Prakash, Muthuramalingam; Lemaire, Thibault; Caruel, Matthieu; Lewerenz, Marius; de Leeuw, Nora H.; Di Tommaso, Devis; Naili, Salah

    2017-07-01

    New insights into the dynamical properties of water in hydroxyapatite (HAP) nanopores, a model system for the fluid flow within nanosize spaces inside the collagen-apatite structure of bone, were obtained from molecular dynamics simulations of liquid water confined between two parallel HAP surfaces of different sizes (20 Å ≤ H ≤ 240 Å). Calculations were conducted using a core-shell interatomic potential for HAP together with the extended simple point charge model for water. This force field gives an activation energy for water diffusion within HAP nanopores that is in excellent agreement with available experimental data. The dynamical properties of water within the HAP nanopores were quantified in terms of the second-order water diffusion tensor. Results indicate that water diffuses anisotropically within the HAP nanopores, with the solvent molecules moving parallel to the surface twice as fast as the perpendicular direction. This unusual dynamic behaviour is linked to the strong polarizing effect of calcium ions, and the synergic interactions between the water molecules in the first hydration layer of HAP with the calcium, hydroxyl, and phosphate ions, which facilitates the flow of water molecules in the directions parallel to the HAP surface.

  8. Sodium-carbonate co-substituted hydroxyapatite ceramics

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    Zoltan Z. Zyman

    2013-12-01

    Full Text Available Powders of sodium-carbonate co-substituted hydroxyapatite, having sodium content in the range of 0.25–1.5 wt.% with a 0.25 wt.% step, were prepared by a precipitation-solid state reaction route. Compacts of the powders were sintered in a CO2 flow (4 mL/min at 1100 °C for 2 h. The sintered ceramics contained sodium and carbonate ions in the ranges of 0–1.5 wt.% and 1.3–6 wt.%, respectively, which are typical impurity concentrations in biological apatite. A relationship between sodium and carbonate contents and the type of carbonate substitution was found. The total carbonate content progressively increased with the sodium content. The obtained ceramics showed an AB-type carbonate substitution. However, the substitution became more B-type as the sodium content increased. As a result, the carbonation was almost B-type (94 % for the highest sodium content (1.5 wt.%.

  9. Fabrication of oriented hydroxyapatite film by RF magnetron sputtering

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    Hirata, Keishiro; Kubota, Takafumi; Koyama, Daisuke; Takayanagi, Shinji; Matsukawa, Mami

    2017-08-01

    Hydroxyapatite (HAp) is compatible with bone tissue and is used mainly as a bone prosthetic material, especially as the coating of implants. Oriented HAp film is expected to be a high-quality epitaxial scaffold of the neonatal bone. To fabricate highly oriented HAp thin films via the conventional plasma process, we deposited the HAp film on a Ti coated silica glass substrate using RF magnetron sputtering in low substrate temperature conditions. The X-ray diffraction pattern of the film sample consisted of an intense (002) peak, corresponding to the highly oriented HAp. The (002) peak in XRD diagrams can be attributed either to the monoclinic phase or the hexagonal phase. Pole figure analysis showed that the (002) plane grew parallel to the surface of the substrate, without inclination. Transmission Electron Microscope analysis also showed the fabrication of aligned HAp crystallites. The selected area diffraction patterns indicated the existence of monoclinic phase. The existence of hexagonal phase could not be judged. These results indicate the uniaxial films fabricated by this technique enable to be the epitaxial scaffold of the neonatal bone. This scaffold can be expected to promote connection with the surrounding bone tissue and recovery of the dynamic characteristics of the bone.

  10. Transformation of brushite to hydroxyapatite and effects of alginate additives

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    Ucar, Seniz; Bjørnøy, Sindre H.; Bassett, David C.; Strand, Berit L.; Sikorski, Pawel; Andreassen, Jens-Petter

    2017-06-01

    Phase transformations are important processes during mineral formation in both in vivo and in vitro model systems and macromolecules are influential in regulating the mineralization processes. Calcium phosphate mineralized alginate hydrogels are potential candidates for hard tissue engineering applications and transformation of the resorbable calcium phosphate phases to apatitic bone mineral in vivo enhances the success of these composite materials. Here, the transformation of brushite to hydroxyapatite (HA) and the effects of alginate additives on this process are studied by the investigation of supersaturation profiles with HA-seeded and unseeded experiments. This experimental design allows for detailed kinetic interpretation of the transformation reactions and deduction of information on the nucleation stage of HA by evaluating the results of seeded and unseeded experiments together. In the experimental conditions of this work, transformation was controlled by HA growth until the point of near complete brushite dissolution where the growth and dissolution rates were balanced. The presence of alginate additives at low concentration were not highly influential on transformation rates during the growth dominated region but their retardant effect became more pronounced as the dissolution and growth rates reached an equilibrium where both reactions were effective on transformation kinetics. Decoupling of seeded and unseeded transformation experiments suggested that alginate additives retard HA nucleation and this was most evident in the presence of G-block oligomers.

  11. Human serum protein adsorption onto synthesis nano-hydroxyapatite.

    Science.gov (United States)

    Mohsen-Nia, M; Massah Bidgoli, M; Behrashi, M; Mohsen Nia, A

    2012-02-01

    Adsorption of human serum proteins (Albumin and total protein) onto high purity synthesis nano-hydroxyapatite (HA), Ca₁₀(PO₄)₆(OH)₂, has been studied in a wide temperature range by UV-visible spectrophotometer. Adsorption isotherm is basically important to describe how solutes interact with adsorbent, and is critical in optimizing the use of adsorbent. In the present study, the experimental results were fitted to the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (DR) models to obtain the characteristic parameters of each model and square of the correlation coefficients (R²). According to the results, the DR isotherm model had the best agreement with the experimental data. The effect of temperature on adsorption of human serum proteins (HSP) onto the synthesized nano-HA was studied. The experimental results indicated that temperature increase generally causes an increase in the adsorption of HSP onto the nano-HA. This is basically due to the effect of temperature on the HSP activity and its diffusion rate on HA surfaces.

  12. Unique functions of hydroxyapatite with mutans streptococci adherence.

    Science.gov (United States)

    Arakawa, Tadayoshi; Fujimaru, Takeshi; Ishizak, Tsutomu; Takeuchi, Hiroaki; Kageyama, Masato; Ikemi, Takuji; Hanada, Nobuhiro; Watanabe, Haruo; Senpuku, Hidenobu

    2010-01-01

    Hydroxyapatite (HA) is used as a construction material for artificial supplementation of enamel tooth surfaces to improve oral hygiene. This study examined in vitro HA interactions with mutans streptococci (MS) and bacterial adherence to small (nanosize) crystal form of HA beads having a protean hexagonal structure. The adsorption and physical effects of HA employed in vivo is also described. [3H-thymidine]-labeled streptococci were incubated with HA noncoated or coated with salivary components or salivary agglutinin peptide (SRCRP2), a receptor for streptococcal surface proteins. Bacterial adhesion activities on HA were measured by uptake of [3H-thymidine]. Application of HA paste in an individual tray was tried on the tooth surface, and its effects on the colony ratio of MS/total streptococci (TS) in saliva were analyzed by culture technique. The adhesion assay showed that the binding of streptococci to HA was inhibited by coating with salivary components, whereas coating with SRCRP2 had nearly no influence on binding with or without Ca+. Further, treatment with HA decreased the adherence of Streptococci mutans to roughened enamel surfaces by one-third. In vivo application of a HA dentifrice to individual teeth demonstrated that the colony number ratio of MS/TS slowly decreased. MS adhesion to HA was restricted by both salivary components, except for SRCRP2, and the physical effects of HA; in addition, the material itself has a unique effect for removing MS from the oral cavity.

  13. The biotoxicity of hydroxyapatite nanoparticles to the plant growth.

    Science.gov (United States)

    Jiang, Hao; Liu, Jin-Ku; Wang, Jian-Dong; Lu, Yi; Zhang, Min; Yang, Xiao-Hong; Hong, Dan-Jing

    2014-04-15

    In the present study, hydroxyapatite (HAP) nanoparticles of different particle sizes with high crystallinity and similiar structure were prepared by hydrothermal method. The crystal structure and particle size were characterized by X-ray diffraction pattern (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. Mung bean sprouts were first used as experimental models. Instead of by MTT assay, the cytoxicity of HAP nanoparticles were proved and evaluated by measuring the hypocotyle length of mung bean sprouts in the culture media. The result showed that the inhibition effect to the growth of mung bean sprouts enhanced when HAP nanoparticles existed. Culture media of HAP nanoparticles with different concentrations and particle sizes was prepared to investigate the level of inhibition effect to the growth of mung bean sprouts. The result found that hypocotyl length of mung bean sprouts were the shortest cultured in 5mg/mL culture media in which the HAP nanoparticles were prepared by hydrothermal method for 24h. It was concluded the inhibition effect depended on the amount of intracellular HAP nanoparticles. The nanostructure and Ca(2+) concentration were considered as the main factors to cause cell apoptosis which was the reason of inhibition. The study provided a preliminary perspective about biotoxicity of HAP nanomaterials to the plant growth. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Biomimetic growth of hydroxyapatite on phosphorylated electrospun cellulose nanofibers.

    Science.gov (United States)

    Li, Kaina; Wang, Jiangnan; Liu, Xinqing; Xiong, Xiaopeng; Liu, Haiqing

    2012-11-06

    In biomimicking the formation of collagen fiber/hydroxyapatite (HAp) in natural bone, electrospun cellulose nanofiber (CelluNF)/HAp composites were synthesized in simulated body fluid (SBF). Their morphology and structure were characterized by SEM, TEM, XRD and XPS. CelluNFs showed low bioactivity in inducing the growth of HAp. In order to improve this ability, CelluNFs were slightly phosphorylated with a degree of substitution of phosphate group of 0.28. The modified CelluNFs were highly effective in guiding the HAp growth along the fibers. The HAp crystal size in the composites was ca. 24 nm, and the lattice spacing of (211) plane was 2.83 Å. It was found that the HAps in the composites were calcium deficient. The CelluNF/HAp composites are highly porous materials with micro-, meso-, and macro-pores. A mechanism for the HAp growth on CelluNFs was presented. Such CelluNF/HAp composites can be potentially useful in the field of bone tissue engineering. Copyright © 2012 Elsevier Ltd. All rights reserved.

  15. Synthesis and characterization of cadmium-calcium hydroxyapatite solid solutions

    Science.gov (United States)

    Zhao, Xin; Zhu, Yi-nian; Dai, Liu-qin

    2014-06-01

    A series of cadmium-calcium hydroxyapatite solid solutions was prepared by an aqueous precipitation method. By various means, the characterizations confirmed the formation of continuous solid solutions over all ranges of Cd/(Cd+Ca) atomic ratio. In the results, both lattice parameters a and c display slight deviations from Vegard's rule when the Cd/(Cd+Ca) atomic ratio is greater than 0.6. The particles change from smaller acicular to larger hexagonal columnar crystals as the Cd/(Cd+Ca) atomic ratio increases from 0-0.60 to 0.60-1.00. The area of the phosphate peak for symmetric P-O stretching decreases with the increase in Cd/(Cd+Ca) atomic ratio, and the peak disappears when the Cd/(Cd+Ca) atomic ratio is greater than 0.6; the two phosphate peaks of P-O stretching gradually merge together for the Cd/(Cd+Ca) atomic ratio near 0.60. These variations can be explained by a slight tendency of larger Cd ions to occupy M(2) sites and smaller Ca ions to prefer M(1) sites in the structure.

  16. Role of osteopontin in modulation of hydroxyapatite formation.

    Science.gov (United States)

    Hunter, Graeme K

    2013-10-01

    The presence of osteopontin (OPN) at high levels in both mineralized tissues such as bone and ectopic calcifications such as atherosclerotic plaque presents a conundrum: is OPN a promoter or inhibitor of hydroxyapatite (HA) formation? In vitro studies show that OPN adsorbs tightly to HA and is a potent inhibitor of crystal growth. Although the mechanism of the OPN-HA interaction is not fully understood, it is probably electrostatic in nature. Phosphorylation enhances OPN's ability to adsorb to and inhibit the growth of HA crystals, although other anionic groups also contribute to these properties. Recent findings suggest that OPN is an intrinsically unordered protein and that its lack of folded structure facilitates the protein's adsorption by allowing multiple binding geometries and the sequential formation of ionic bonds with Ca(2+) ions of the crystal surface. By analogy with other biominerals, it is likely that adsorption of OPN to HA results in "pinning" of growth steps. The abundance of OPN at sites of ectopic calcification reflects upregulation of the protein in response to crystal formation or even in response to elevated phosphate levels. Therefore, it appears that OPN is one of a group of proteins that function to prevent crystal formation in soft tissues. The role of OPN in bone mineralization, if any, is less clear. However, it is possible that it modulates HA formation, either by preventing crystal growth in "inappropriate" areas such as the osteoid seam or by regulating crystal growth habit (size and shape).

  17. Biomechanical evaluation of different hydroxyapatite coatings on titanium for keratoprosthesis

    Science.gov (United States)

    Dong, Ying; Qiu, Zhiye; Liu, Xiaoyu; Wang, Liqiang; Yang, Jingxin; Huang, Yifei; Cui, Fuzhai

    2015-09-01

    Stable tissue integration is important to keratoprosthesis (KPro). The aim of this study was to evaluate the tissue bonding ability of hydroxyapatite (HAp)-coated titanium KPro. The samples were divided into three groups: test groups (IBAD group and AD group) and Ti control. The coated samples had a HAp layer created by ion beam assisted deposition (IBAD) or aerosol deposition (AD). The surface characteristics were analyzed with SEM, AFM, and XRD. The samples were surgically inserted into the muscles of rabbits. Eight weeks after healing, the attachment to the tissue was tested with a universal test device. The three samples exhibited distinctive surface morphology. The force to remove the HAp implants from the muscles was significantly greater than that of Ti group ( P < 0.01), with the AD samples requiring the greatest force ( P < 0.01). After removal, SEM showed that the tissue was firmly attached to the surface of AD samples. Photomicrographs of the peri-implant muscles showed a layer of aligned fibrous tissue without severe inflammation. The AD samples had more fibroblasts. Results indicate that because of enhanced mechanical adhesion of soft tissue to the implants, HAp-coated Ti by AD is a suitable KPro skirt material.

  18. Surgical pitfalls with custom-made porous hydroxyapatite cranial implants

    Directory of Open Access Journals (Sweden)

    Bruno Zanotti

    2015-03-01

    Full Text Available Aim: Cranioplasty implants are used primarily in cases of surgical cranial decompression following pathological elevations of intracranial pressure. Available bone substitutes include porous hydroxyapatite (HA and polymethylmethacrylate. Whichever material is used, however, prosthetic cranial implants are susceptible to intra- and postsurgical complications and even failure. The aim of this study was to investigate such occurrences in HA cranioplasty implants, seeking not only to determine the likely causes (whether correlated or not with the device itself but also, where possible, to suggest countermeasures. Methods: We analyzed information regarding failures or complications reported in postmarketing surveillance and clinical studies of patients treated worldwide with custom-made HA cranial implants (Custom Bone Service Fin-Ceramica Faenza, Italy in the period 1997-2013. Results: The two most common complications were implant fractures (84 cases, 2.9% of the total fitted and infections (51 cases, 1.77%. Conclusion: Although cranioplasties are superficial and not difficult types of surgery, and use of custom-made implants are often considered the "easy" option from a surgical perspective, these procedures are nonetheless plagued by potential pitfalls. If performed well they yield more than satisfactory results from the points of view of both the patient and surgeon, but lack of appropriate care can open the door to numerous potential sources of failure, which can compromise-even irreparably-the ability to heal.

  19. Selective laser sintering of hydroxyapatite/poly-epsilon-caprolactone scaffolds.

    Science.gov (United States)

    Eosoly, Szilvia; Brabazon, Dermot; Lohfeld, Stefan; Looney, Lisa

    2010-07-01

    Selective laser sintering (SLS) enables the fabrication of complex geometries with the intricate and controllable internal architecture required in the field of tissue engineering. In this study hydroxyapatite and poly-epsilon-caprolactone, considered suitable for hard tissue engineering purposes, were used in a weight ratio of 30:70. The quality of the fabricated parts is influenced by various process parameters. Among them Four parameters, namely laser fill power, outline laser power, scan spacing and part orientation, were identified as important. These parameters were investigated according to a central composite design and a model of the effects of these parameters on the accuracy and mechanical properties of the fabricated parts was developed. The dimensions of the fabricated parts were strongly dependent on the manufacturing direction and scan spacing. Repeatability analysis shows that the fabricated features can be well reproduced. However, there were deviations from the nominal dimensions, with the features being larger than those designed. The compressive modulus and yield strength of the fabricated microstructures with a designed relative density of 0.33 varied between 0.6 and 2.3 and 0.1 and 0.6 MPa, respectively. The mechanical behavior was strongly dependent on the manufacturing direction. Copyright 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  20. Physicochemical properties of nanocomposite: Hydroxyapatite in reduced graphene oxide.

    Science.gov (United States)

    Rajesh, A; Mangamma, G; Sairam, T N; Subramanian, S; Kalavathi, S; Kamruddin, M; Dash, S

    2017-07-01

    Graphene oxide (GO) based nanocomposites have gained considerable attention in the field of material science due to their excellent physicochemical and biological properties. Incorporation of nanomaterials into GO sheets prevents the formation of π-π stacking bond thereby giving rise to composites that show the improved properties compared to their individual counterparts. In this work, reduced graphene oxide (rGO) - hydroxyapatite (HAP) nanocomposites were synthesized by ultrasonic method. Increasing the c/a ratio of HAP in the diffraction pattern of rGO/HAP nanocomposites indicates the c-axis oriented grown HAP nanorods interacting with rGO layers. Shift in wavenumber (15cm-1) and increase of full width at half maximum (45cm-1) of G band in Raman spectra of the rGO/HAP nanocomposites are observed and attributed to the tensile strain induced due to the intercalated HAP nanorods between the rGO layers. Atomic force microscopy (AFM) and phase imaging studies revealed the intercalation of HAP nanorod with diameter 30nm and length 110-120nm in rGO sheets was clearly perceived along with improved elasticity compared to pristine HAP. 13C-NMR results proved the synergistic interaction between both components in rGO/HAP nanocomposite. The novel properties observed and the microscopic mechanism responsible for this are a result of the structural modification in rGO layers brought about by the intercalation of HAP nanorods. Copyright © 2017. Published by Elsevier B.V.