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Sample records for absorbent hydrogels based

  1. Synthesis and Characterization of Super absorbent Hydrogels Based on Natural Polymers Using Ionizing Radiations

    Radiation processing technology is a useful tool for modification of polymer material including grafting of monomer onto polymer. In this study, novel super absorbent hydrogels was prepared with biodegradable and eco-friendly properties by graft copolymerization of chitosan and different synthetic monomers (AAc, DEAEMA, HEMA, HPMA and HEA) using gamma irradiation to examine the potential use of these hydrogels in the controlled drug release systems. The different chitosan hydrogels were characterized using FTIR spectroscopy, scanning electron microscopy and thermal analysis techniques. The effects of the preparation conditions on the gelation process of the synthesized copolymer were investigated. The influence of variables such as feed concentration, irradiation dose, composition ratio, ph and temperature on the swelling of the prepared hydrogels was also examined. The water absorbency of these hydrogels in various ph and salt solutions was studied. The swelling kinetics of the prepared hydrogels and in vitro release dynamics of model drug (Chlortetracycline hydrochloride) from these hydrogels has been studied for the evaluation of swelling mechanism and drug release mechanism from the hydrogels. The adsorption and in vitro release profiles of Chlortetracycline HCl from the prepared gels were also estimated in different ph buffers. The amount of drug released from CS/ (AAc-DEAEMA) hydrogels was higher than that released from other modified CS/AAc hydrogels. This preliminary investigation of chitosan based hydrogels showed that they may be exploited to expand the utilization of these systems in drug delivery applications

  2. Hydrogel based occlusion systems

    Stam, F.A.; Jackson, N.; Dubruel, P.; Adesanya, K.; Embrechts, A.; Mendes, E.; Neves, H.P.; Herijgers, P.; Verbrugghe, Y.; Shacham, Y; Engel, L.; Krylov, V.

    2013-01-01

    A hydrogel based occlusion system, a method for occluding vessels, appendages or aneurysms, and a method for hydrogel synthesis are disclosed. The hydrogel based occlusion system includes a hydrogel having a shrunken and a swollen state and a delivery tool configured to deliver the hydrogel to a target occlusion location. The hydrogel is configured to permanently occlude the target occlusion location in the swollen state. The hydrogel may be an electro-activated hydrogel (EAH) which could be ...

  3. Hydrogel based occlusion systems

    Stam, F.A.; Jackson, N.; Dubruel, P.; Adesanya, K.; Embrechts, A.; Mendes, E.; Neves, H.P.; Herijgers, P.; Verbrugghe, Y.; Shacham, Y.; Engel, L.; Krylov, V.

    2013-01-01

    A hydrogel based occlusion system, a method for occluding vessels, appendages or aneurysms, and a method for hydrogel synthesis are disclosed. The hydrogel based occlusion system includes a hydrogel having a shrunken and a swollen state and a delivery tool configured to deliver the hydrogel to a tar

  4. Super absorbent hydrogel composites as water retentive in soil

    Super absorbent hydrogels (SAP) were synthesized at room temperature, by the use of potassium persulfate as initiator, N,N'-methylene bis acrylamide (MBA) as crosslinking agent, and N,N,N',N'- tetramethylethylenediamine. Gels at the same conditions were prepared with 10% of minerals (bentonite or dolomite). The materials of bentonite series were obtained from acrylamide followed by hydrolysis with NaOH. The gels of dolomite series were prepared from the two co-monomers (acrylamide and acrylate). All SAPs were characterized by elemental microanalysis, FTIR, x-ray diffraction, SEM, and by swelling measurements in water. An intercalated composite was obtained with bentonite hydrogel. After hydrolysis an exfoliated nanocomposite was formed. The dolomite mineral was dispersed in the polymeric matrix. The swelling degrees of the SAPs with mineral were higher than those gels without it. This degree was 1,000 times the dry gel weight. Taking into account the amount of water needed to the process, the gel with dolomite is the most promising as soil conditioner. (author)

  5. Synthesis and characterization of super absorbent poly (acrylamide-co-potassium acrylate) hydrogels by radiation technique

    A series of super absorbent hydrogels were prepared from acrylamide (AAm) and potassium acrylate (KA) by gamma irradiation technique at room temperature. The solution containing potassium acrylate 15% and different concentrations of AAm (10-16%) were irradiated by gamma rays (20-40 kGy). The hydrogels produced by irradiation were characterized by fourier transform infra red spectroscopy (FT-IR). The gel fraction, kinetics of swelling and the equilibrium degree of swelling (EDS) were studied. Under irradiation dose of 20 kGy and concentration of AAM 10 %), poly(AAm-co-KA) hydrogel with high gel fraction (99.08%) and very high EDS (420 g/g) were obtained. The capacity of hydrogel to adsorb metal ion Cu2+and Fe3+were investigated. It is shown than 10 minutes the hydrogel could adsorb Cu2+ ion up to 95 %, and Fe3+ ion up to 55 % in 80 minutes. This hydrogel has a potential to be used for soil conditioning and ion metal absorbent. (author)

  6. Soy-Based Hydrogels for Biomedical Applications

    Soy based hydrogels were prepared by ring-opening polymerization of epoxidized soybean oil, flowing hydrolysis of formed polymer. The hydrogels were evaluated loading and release water-soluble anticancer drug doxorubin (Dox). The results suggested that this new system may offer great potential to ...

  7. Biocatalytic synthesis of highly ordered degradable dextran-based hydrogels

    Ferreira, Lino; Gil, Maria H.; Cabrita, António M. S.; Dordick, Jonathan S.

    2005-01-01

    We have prepared unique macroporous and ordered dextran-based hydrogels using a single-step biocatalytic transesterification reaction between dextran and divinyladipate in neat dimethylsulfoxide. These hydrogels show a unimodal distribution of interconnected pores with average diameters from 0.4 to 2.0 [mu]m depending on the degree of substitution. In addition, the hydrogels show a higher elastic modulus for a given swelling ratio than chemically synthesized dextran-based hydrogels. In vivo s...

  8. Alginate based hydrogel as a potential biopolymeric carrier for drug delivery and cell delivery systems: present status and applications.

    Giri, Tapan Kumar; Thakur, Deepa; Alexander, Amit; Ajazuddin; Badwaik, Hemant; Tripathi, Dulal Krishna

    2012-11-01

    Alginate is a non-toxic, biocompatible and biodegradable natural polymer with a number of peculiar physicochemical properties for which it has wide applications in drug delivery and cell delivery systems. Hydrogel formation can be obtained by interactions of anionic alginates with multivalent inorganic cations by simple ionotropic gelation method. Hydrophilic polymeric network of three dimensional cross linked structures of hydrogels absorb substantial amount of water or biological fluids. Among the numerous biomaterials used for hydrogel formation alginate has been and will continue to be one of the most important biomaterial. Therefore, in view of the vast literature support, we focus in this review on alginate - based hydrogel as drug delivery and cell delivery carriers for biomedical applications. Various properties of alginates, their hydrogels and also various techniques used for preparing alginate hydrogels have been reviewed. PMID:22998675

  9. Hydrogel-based piezoresistive biochemical microsensors

    Guenther, Margarita; Schulz, Volker; Gerlach, Gerald; Wallmersperger, Thomas; Solzbacher, Florian; Magda, Jules J.; Tathireddy, Prashant; Lin, Genyao; Orthner, Michael P.

    2010-04-01

    This work is motivated by a demand for inexpensive, robust and reliable biochemical sensors with high signal reproducibility and long-term-stable sensitivity, especially for medical applications. Micro-fabricated sensors can provide continuous monitoring and on-line control of analyte concentrations in ambient aqueous solutions. The piezoresistive biochemical sensor containing a special biocompatible polymer (hydrogel) with a sharp volume phase transition in the neutral physiological pH range near 7.4 can detect a specific analyte, for example glucose. Thereby the hydrogel-based biochemical sensors are useful for the diagnosis and monitoring of diabetes. The response of the glucosesensitive hydrogel was studied at different regimes of the glucose concentration change and of the solution supply. Sensor response time and accuracy with which a sensor can track gradual changes in glucose was estimated. Additionally, the influence of various recommended sterilization methods on the gel swelling properties and on the mechano-electrical transducer of the pH-sensors has been evaluated in order to choose the most optimal sterilization method for the implantable sensors. It has been shown that there is no negative effect of gamma irradiation with a dose of 25.7 kGy on the hydrogel sensitivity. In order to achieve an optimum between sensor signal amplitude and sensor response time, corresponding calibration and measurement procedures have been proposed and evaluated for the chemical sensors.

  10. Preparation of bacterial cellulose based hydrogels and their viscoelastic behavior

    Shah, Rushita; Vyroubal, Radek; Fei, Haojei; Saha, Nabanita; Kitano, Takeshi; Saha, Petr

    2015-04-01

    Bacterial cellulose (BC) based hydrogels have been prepared in blended with carboxymethylcellulose and polyvinyl pyrrolidone by using heat treatment. The properties of BC-CMC and BC-PVP hydrogels were compared with pure BC, CMC and PVP hydrogels. These hydrogels were investigated by measuring their structural, morphological and viscoelastic properties. Through the morphological images, alignment of the porous flake like structures could be seen clearly within the inter-polymeric network of the hydrogels. Also, the detail structure analysis of the polymers blended during the hydrogel formation confirms their interactions with each other were studied. Further, the viscoelastic behavior of all the hydrogels in terms of elastic and viscous property was studied. It is observed that at 1% strain, including CMC and PVP hydrogels, all the BC based hydrogels exhibited the linear trend throughout. Also the elastic nature of the material remains high compared to viscous nature. Moreover, the changes could be noticed in case of blended polymer based hydrogels. The values of complex viscosity (η*) decreases with increase in angular frequency within the range of ω = 0.1-100 rad.s-1.

  11. Piezoresistive Chemical Sensors Based on Functionalized Hydrogels

    Margarita Guenther

    2014-06-01

    Full Text Available Thin films of analyte-specific hydrogels were combined with microfabricated piezoresistive pressure transducers to obtain chemomechanical sensors that can serve as selective biochemical sensors for a continuous monitoring of metabolites. The gel swelling pressure has been monitored in simulated physiological solutions by means of the output signal of piezoresistive sensors. The interference by fructose, human serum albumin, pH, and ionic concentration on glucose sensing was studied. With the help of a database containing the calibration curves of the hydrogel-based sensors at different values of pH and ionic strength, the corrected values of pH and glucose concentration were determined using a novel calibration algorithm.

  12. Dually cross-linked single network poly(acrylic acid) hydrogels with superior mechanical properties and water absorbency.

    Zhong, Ming; Liu, Yi-Tao; Liu, Xiao-Ying; Shi, Fu-Kuan; Zhang, Li-Qin; Zhu, Mei-Fang; Xie, Xu-Ming

    2016-06-28

    Poly(acrylic acid) (PAA) hydrogels with superior mechanical properties, based on a single network structure with dual cross-linking, are prepared by one-pot free radical polymerization. The network structure of the PAA hydrogels is composed of dual cross-linking: a dynamic and reversible ionic cross-linking among the PAA chains enabled by Fe(3+) ions, and a sparse covalent cross-linking enabled by a covalent cross-linker (Bis). Under deformation, the covalently cross-linked PAA chains remain intact to maintain their original configuration, while the Fe(3+)-enabled ionic cross-linking among the PAA chains is broken to dissipate energy and then recombined. It is found that the mechanical properties of the PAA hydrogels are significantly influenced by the contents of covalent cross-linkers, Fe(3+) ions and water, which can be adjusted within a substantial range and thus broaden the applications of the hydrogels. Meanwhile, the PAA hydrogels have excellent recoverability based on the dynamic and reversible ionic cross-linking enabled by Fe(3+) ions. Moreover, the swelling capacity of the PAA hydrogels is as high as 1800 times in deionized water due to the synergistic effects of ionic and covalent cross-linkings. The combination of balanced mechanical properties, efficient recoverability, high swelling capacity and facile preparation provides a new method to obtain high-performance hydrogels. PMID:27230478

  13. Force-compensated hydrogel-based pH sensor

    Deng, Kangfa; Gerlach, Gerald; Guenther, Margarita

    2015-04-01

    This paper presents the design, simulation, assembly and testing of a force-compensated hydrogel-based pH sensor. In the conventional deflection method, a piezoresistive pressure sensor is used as a chemical-mechanical-electronic transducer to measure the volume change of a pH-sensitive hydrogel. In this compensation method, the pH-sensitive hydrogel keeps its volume constant during the whole measuring process, independent of applied pH value. In order to maintain a balanced state, an additional thermal actuator is integrated into the close-loop sensor system with higher precision and faster dynamic response. Poly (N-isopropylacrylamide) (PNIPAAm) with 5 mol% monomer 3-acrylamido propionic acid (AAmPA) is used as the temperature-sensitive hydrogel, while poly (vinyl alcohol) with poly (acrylic acid) (PAA) serves as the pH-sensitive hydrogel. A thermal simulation is introduced to assess the temperature distribution of the whole microsystem, especially the temperature influence on both hydrogels. Following tests are detailed to verify the working functions of a sensor based on pH-sensitive hydrogel and an actuator based on temperature-sensitive hydrogel. A miniaturized prototype is assembled and investigated in deionized water: the response time amounts to about 25 min, just half of that one of a sensor based on the conventional deflection method. The results confirm the applicability of t he compensation method to the hydrogel-based sensors.

  14. Hyaluronic Acid Based Hydrogels for Regenerative Medicine Applications

    2015-01-01

    Hyaluronic acid (HA) hydrogels, obtained by cross-linking HA molecules with divinyl sulfone (DVS) based on a simple, reproducible, and safe process that does not employ any organic solvents, were developed. Owing to an innovative preparation method the resulting homogeneous hydrogels do not contain any detectable residual cross-linking agent and are easier to inject through a fine needle. HA hydrogels were characterized in terms of degradation and biological properties, viscoelasticity, injec...

  15. Biodegradable HEMA-based hydrogels with enhanced mechanical properties.

    Moghadam, Mohamadreza Nassajian; Pioletti, Dominique P

    2016-08-01

    Hydrogels are widely used in the biomedical field. Their main purposes are either to deliver biological active agents or to temporarily fill a defect until they degrade and are followed by new host tissue formation. However, for this latter application, biodegradable hydrogels are usually not capable to sustain any significant load. The development of biodegradable hydrogels presenting load-bearing capabilities would open new possibilities to utilize this class of material in the biomedical field. In this work, an original formulation of biodegradable photo-crosslinked hydrogels based on hydroxyethyl methacrylate (HEMA) is presented. The hydrogels consist of short-length poly(2-hydroxyethyl methacrylate) (PHEMA) chains in a star shape structure, obtained by introducing a tetra-functional chain transfer agent in the backbone of the hydrogels. They are cross-linked with a biodegradable N,O-dimethacryloyl hydroxylamine (DMHA) molecule sensitive to hydrolytic cleavage. We characterized the degradation properties of these hydrogels submitted to mechanical loadings. We showed that the developed hydrogels undergo long-term degradation and specially meet the two essential requirements of a biodegradable hydrogel suitable for load bearing applications: enhanced mechanical properties and low molecular weight degradation products. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1161-1169, 2016. PMID:26061346

  16. Synthesis and Swelling Properties of Thermosensitive Hydrogels based on Terpolymerization

    Cai Hua NI; Xian Yu ZENG; He HUANG

    2005-01-01

    Novel thermosensitive hydrogels based on polymerization of N-isopropyl acrylamide,Sodium acrylate, and diacetone acrylamide were synthesized. The swelling ratio and dynamic swelling were investigated. The results indicated that the hydrogels exhibited high water uptake and themosensitivity. The swelling properties and volume phase transition temperature could be adjusted by contents of the comonomers in the gels.

  17. Metallic glass nanofibers in future hydrogel-based scaffolds.

    Sadeghian, Ramin Banan; Ahadian, Samad; Yaginuma, Shin; Ramón-Azcón, Javier; Liang, Xiaobin; Nakajima, Ken; Shiku, Hitoshi; Matsue, Tomokazu; Nakayama, Koji S; Khademhosseini, Ali

    2014-01-01

    Electrically conductive reinforced hydrogels offer a wide range of applications as three-dimensional scaffolds in tissue engineering. We report electrical and mechanical characterization of methacrylated gelatin (GelMA) hydrogel, containing palladium-based metallic glass nanofibers (MGNF). Also we show that the fibers are biocompatible and C2C12 myoblasts in particular, planted into the hybrid hydrogel, tend to attach to and elongate along the fibers. The MGNFs in this work were created by gas atomization. Ravel of fibers were embedded in the GelMA prepolymer in two different concentrations (0.5 and 1.0 mg/ml), and then the ensemble was cured under UV light, forming the hybrid hydrogel. The conductivity of the hybrid hydrogel was proportional to the fiber concentration. PMID:25571184

  18. Planar Metamaterial Absorber Based on Lumped Elements

    GU Chao; QU Shao-Bo; PEI Zhi-Bin; ZHOU Hang; XU Zhuo; BAI Peng; PENG Wei-Dong; LIN Bao-Qin

    2010-01-01

    @@ We present the design of a planar metamaterial absorber based on lumped elements,which shows a wide-band polarization-insensitive and wide-angle strong absorption.This absorber consists of metal electric resonators,the dielectric substrate,the metal film and lumped elements.The simulated absorbances under two different loss conditions indicate that high absorbance in the absorption band is mainly due to lumped resistances.The simulated absorbances under three different load conditions indicate that the local resonance circuit(lumped resistance and capacitance)could boost up the resonance of the whole RLC circuit.The simulated voltage in lumped elements indicates that the transformation efficiency from electromagnetic energy to electric energy in the absorption band is high,and electric energy is subsequently consumed by lumped resistances.This absorber may have potential applications in many military fields.

  19. Flexible hydrogel-based functional composite materials

    Song, Jie; Saiz, Eduardo; Bertozzi, Carolyn R; Tomasia, Antoni P

    2013-10-08

    A composite having a flexible hydrogel polymer formed by mixing an organic phase with an inorganic composition, the organic phase selected from the group consisting of a hydrogel monomer, a crosslinker, a radical initiator, and/or a solvent. A polymerization mixture is formed and polymerized into a desired shape and size.

  20. Bioresponsive systems based on polygalacturonate containing hydrogels.

    Schneider, Konstantin P; Rollett, Alexandra; Wehrschuetz-Sigl, Eva; Hasmann, Andrea; Zankel, Armin; Muehlebach, Andreas; Kaufmann, Franz; Guebitz, Georg M

    2011-04-01

    Polysaccharide acid (PSA) based devices (consisting of alginic acid and polygalacturonic acid) were investigated for the detection of contaminating microorganisms. PSA-CaCl(2) hydrogel systems were compared to systems involving covalent cross-linking of PSA with glycidylmethacrylate (PSA-GMA) which was confirmed with Fourier Transformed Infrared (FTIR) analysis. Incubation of PSA-CaCl(2) and PSA-GMA beads loaded with Alizarin as a model ingredient with trigger enzymes (polygalacturonases or pectate lyases) or bacteria lead to a smoothening of the surface and exposure of Alizarin according to Environmental Scanning Electron Microscopy (ESEM) analysis. Enzyme triggered release of Alizarin was demonstrated for a commercial enzyme preparation from Aspergillus niger and with purified polygalacturonase and pectate lyase from S. rolfsii and B. pumilus, respectively. In contrast to the PSA-CaCl(2) beads, cross-linking (PSA-GMA beads) restricted the release of Alizarin in absence of enzymes. There was a linear relation between release of Alizarin (5-348 μM) and enzyme activity in a range of 0-300 U ml(-1) dosed. In addition to enzymes, both PSA-CaCl(2) and PSA-GMA beads were incubated with Bacillus subtilis and Yersinia entercolitica as model contaminating microorganism. After 72 h, a release between 10 μM and 57 μM Alizarin was detected. For protection of the hydrogels, an enzymatically modified PET membrane was covalently attached onto the surface. This lead to a slower release and improve long term storage stability based on less than 1% release of dye after 21 days. Additionally, this allowed simple detection by visual inspection of the device due to a colour change of the white membrane to orange upon enzyme triggered release of the dye. PMID:22112943

  1. Radiation synthesis and characterization of super absorbent hydrogels for controlled release of some agrochemicals

    Superabsorbent copolymers of carboxymethyl cellulose/polyacrylamide (CMC/PAM) and carboxymethyl celullose/polyacrylamide/silica (CMC/PAM/Si) were synthesized using a γ-irradiation technique. The effects of irradiation dose, content of CMC, AM, and Si on swelling percentage of the produced hydrogels were evaluated. It was found that the maximum swelling percent increased dramatically up to 12,000 % at pH 12 with increasing content of silica up to 5 % in the CMC/PAM/Si composite hydrogel. The prepared copolymers were characterized by FTIR, and SEM techniques. In order to evaluate their controlled release potentials, different hydrogels were loaded with potassium nitrate (KNO3), and the release of the KNO3 was studied and evaluated at various pH values. (author)

  2. Mussel-mimetic protein-based adhesive hydrogel.

    Kim, Bum Jin; Oh, Dongyeop X; Kim, Sangsik; Seo, Jeong Hyun; Hwang, Dong Soo; Masic, Admir; Han, Dong Keun; Cha, Hyung Joon

    2014-05-12

    Hydrogel systems based on cross-linked polymeric materials which could provide both adhesion and cohesion in wet environment have been considered as a promising formulation of tissue adhesives. Inspired by marine mussel adhesion, many researchers have tried to exploit the 3,4-dihydroxyphenylalanine (DOPA) molecule as a cross-linking mediator of synthetic polymer-based hydrogels which is known to be able to achieve cohesive hardening as well as adhesive bonding with diverse surfaces. Beside DOPA residue, composition of other amino acid residues and structure of mussel adhesive proteins (MAPs) have also been considered important elements for mussel adhesion. Herein, we represent a novel protein-based hydrogel system using DOPA-containing recombinant MAP. Gelation can be achieved using both oxdiation-induced DOPA quinone-mediated covalent and Fe(3+)-mediated coordinative noncovalent cross-linking. Fe(3+)-mediated hydrogels show deformable and self-healing viscoelastic behavior in rheological analysis, which is also well-reflected in bulk adhesion strength measurement. Quinone-mediated hydrogel has higher cohesive strength and can provide sufficient gelation time for easier handling. Collectively, our newly developed MAP hydrogel can potentially be used as tissue adhesive and sealant for future applications. PMID:24650082

  3. Multi-responsive hydrogel based on lotus root starch.

    Zhu, Baodong; Ma, Dongzhuo; Wang, Jian; Zhang, Jianwei; Zhang, Shuang

    2016-08-01

    The lotus root starch-based hydrogel was synthesized by free radical copolymerization. Fourier Transform Infrared Spectroscopy (FTIR) demonstrated that the formation of target product. X-ray diffraction (XRD) analysis showed the change of the starch's crystallization. The morphology and pore structure of the hydrogel were evaluated by Field Emission Scanning Electron Microscope (FESEM) and Biomicroscope. Thermogravimetric analysis revealed the better thermal stability of hydrogel. Furthermore, the swelling in CaCl2 and AlCl3 solutions/temperature (25°C-65°C) displayed the "overshooting effect" swelling-deswelling phenomenon with prolonging the swelling time. The hydrogel can rapidly response to various pH value as well. PMID:27177459

  4. Perfectly matched layer based multilayer absorbers

    Stefaniuk, Tomasz; Stolarek, Marcin; Pastuszczak, Anna; Wróbel, Piotr; Wieciech, Bartosz; Antosiewicz, Tomasz J.; Kotyński, Rafał

    2015-05-01

    Broadband layered absorbers are analysed theoretically and experimentally. A genetic algorithm is used to opti- mize broadband and wide-angle of incidence metal-dielectric layered absorbers. An approximate representation of the perfectly matched layer with a spatially varied absorption strength is discussed. The PML is realised as a stack of uniform and isotropic metamaterial layers with permittivieties and permeabilities given from the effective medium theory. This approximate representation of PML is based on the effective medium theory and we call it an effective medium PML (EM-PML).1 We compare the re ection properties of the layered absorbers to that of a PML material and demonstrate that after neglecting gain and magnetic properties, the absorber remains functional.

  5. Hyaluronic Acid Based Hydrogels for Regenerative Medicine Applications

    Assunta Borzacchiello

    2015-01-01

    Full Text Available Hyaluronic acid (HA hydrogels, obtained by cross-linking HA molecules with divinyl sulfone (DVS based on a simple, reproducible, and safe process that does not employ any organic solvents, were developed. Owing to an innovative preparation method the resulting homogeneous hydrogels do not contain any detectable residual cross-linking agent and are easier to inject through a fine needle. HA hydrogels were characterized in terms of degradation and biological properties, viscoelasticity, injectability, and network structural parameters. They exhibit a rheological behaviour typical of strong gels and show improved viscoelastic properties by increasing HA concentration and decreasing HA/DVS weight ratio. Furthermore, it was demonstrated that processes such as sterilization and extrusion through clinical needles do not imply significant alteration of viscoelastic properties. Both SANS and rheological tests indicated that the cross-links appear to compact the network, resulting in a reduction of the mesh size by increasing the cross-linker amount. In vitro degradation tests of the HA hydrogels demonstrated that these new hydrogels show a good stability against enzymatic degradation, which increases by increasing HA concentration and decreasing HA/DVS weight ratio. Finally, the hydrogels show a good biocompatibility confirmed by in vitro tests.

  6. Super absorbent hydrogel composites as water retentive in soil; Hidrogeis compositos superabsorventes como retentores de agua no solo

    Magalhaes, Antonio Savio G. [Faculdade de Educacao de Itapipoca, Curso de Quimica, UECE, Itapipoca, Ceara (Brazil); Almeida Neto, Manuel P. [Instituto Federal de Educacao, Ciencia e Tecnologia do RN - IFRN, Caico, RN (Brazil); Bezerra, Maslandia N.; Feitosa, Judith P.A., E-mail: judith@dqoi.ufc.br [Departamento de Quimica Organica e Inorganica, UFC, Fortaleza, Ceara (Brazil)

    2011-07-01

    Super absorbent hydrogels (SAP) were synthesized at room temperature, by the use of potassium persulfate as initiator, N,N'-methylene bis acrylamide (MBA) as crosslinking agent, and N,N,N',N'- tetramethylethylenediamine. Gels at the same conditions were prepared with 10% of minerals (bentonite or dolomite). The materials of bentonite series were obtained from acrylamide followed by hydrolysis with NaOH. The gels of dolomite series were prepared from the two co-monomers (acrylamide and acrylate). All SAPs were characterized by elemental microanalysis, FTIR, x-ray diffraction, SEM, and by swelling measurements in water. An intercalated composite was obtained with bentonite hydrogel. After hydrolysis an exfoliated nanocomposite was formed. The dolomite mineral was dispersed in the polymeric matrix. The swelling degrees of the SAPs with mineral were higher than those gels without it. This degree was 1,000 times the dry gel weight. Taking into account the amount of water needed to the process, the gel with dolomite is the most promising as soil conditioner. (author)

  7. Hydrogel-based supports: design and synthesis

    Horák, Daniel; Hlídková, Helena

    Oakville : Apple Academic Press Inc, 2014 - (Liu, L.; Ballada, A.), s. 1-18 ISBN 978-1-926895-86-4 R&D Projects: GA ČR GAP304/11/0731 Institutional support: RVO:61389013 Keywords : hydrogel * 2-hydroxyethyl methacrylate * porosity Subject RIV: FH - Neurology http://www.appleacademicpress.com/title.php?id=9781926895864

  8. Circular polarization sensitive absorbers based on graphene

    Yang, Kunpeng; Wang, Min; Pu, Mingbo; Wu, Xiaoyu; Gao, Hui; Hu, Chenggang; Luo, Xiangang

    2016-01-01

    It is well known that the polarization of a linearly polarized (LP) light would rotate after passing through a single layer graphene under the bias of a perpendicular magnetostatic field. Here we show that a corresponding phase shift could be expected for circularly polarized (CP) light, which can be engineered to design the circular polarization sensitive devices. We theoretically validate that an ultrathin graphene-based absorber with the thickness about λ/76 can be obtained, which shows efficient absorption >90% within incident angles of ±80°. The angle-independent phase shift produced by the graphene is responsible for the nearly omnidirectional absorber. Furthermore, a broadband absorber in frequencies ranging from 2.343 to 5.885 THz with absorption over 90% is designed by engineering the dispersion of graphene. PMID:27034257

  9. Self-Healing Hydrogels Based on Carboxymethyl Chitosan and Acryloyl-6-aminocaproic Acid

    Jiufang Duan

    2015-01-01

    Once cracks have formed within hydrogel materials, the integrity of the structure is signifcantly compromised, regardless of the application. Here, we demonstrate cross-linked CMCS hydrogels can be engineered to exhibit self-healing under mild conditions. CMCS hydrogels based on CMCS and acryloyl-6-aminocaproic acid (A6ACA) were synthesized by free radical aqueous copolymerization using ammonium persulfate as initiator. A series of hydrogels was synthesized varying the percentage of A6ACA. T...

  10. Hydrogel based drug carriers for controlled release of hydrophobic drugs and proteins

    Ke Peng,

    2011-01-01

    The aim of this study is to prepare in situ forming hydrogels based on biocompatible polymers for the controlled release of hydrophobic drug and proteins. In order to load hydrophobic drug to the hydrophilic hydrogel matrix, beta-cyclodextrin and human serum albumin was introduced to the hydrogel ne

  11. Interpenetrating polymer network hydrogels based on polysaccharides for biomedical applications

    Pescosolido, L.

    2011-01-01

    The main theme of this thesis is the development and the characterization of interpenetrating polymer network hydrogels (IPNs) based on biodegradable and biocompatible polysaccharides, in particular alginate, hyaluronic acid and dextran. The suitability of these novel systems as pharmaceutical and b

  12. On-Demand Dissolution of a Dendritic Hydrogel-based Dressing for Second-Degree Burn Wounds through Thiol-Thioester Exchange Reaction.

    Konieczynska, Marlena D; Villa-Camacho, Juan C; Ghobril, Cynthia; Perez-Viloria, Miguel; Tevis, Kristie M; Blessing, William A; Nazarian, Ara; Rodriguez, Edward K; Grinstaff, Mark W

    2016-08-16

    An adhesive yet easily removable burn wound dressing represents a breakthrough in second-degree burn wound care. Current second-degree burn wound dressings absorb wound exudate, reduce bacterial infections, and maintain a moist environment for healing, but are surgically or mechanically debrided from the wound, causing additional trauma to the newly formed tissues. We have developed an on-demand dissolvable dendritic thioester hydrogel burn dressing for second-degree burn care. The hydrogel is composed of a lysine-based dendron and a PEG-based crosslinker, which are synthesized in high yields. The hydrogel burn dressing covers the wound and acts as a barrier to bacterial infection in an in vivo second-degree burn wound model. A unique feature of the hydrogel is its capability to be dissolved on-demand, via a thiol-thioester exchange reaction, allowing for a facile burn dressing removal. PMID:27410669

  13. Synthesis of poly (acrylamide-co-metacrylic acid) hydrogels By means of gamma irradiation techniques: influence of Absorbed dose on the swelling process

    In this report gamma radiation techniques were performed a double function of proceeding the processes of polymerization and crosslinking with the advantage of avoid the uses of chemicals crosslinks. The influence of absorbed dose on the swelling ratio as a function of pH have been presented. For these hydrogels, swelling studies indicated that swelling decrease with the increase of the absorbed dose from 10 to 50 kGy. It was confirmed that at the firsts stages (100-150 min) the diffusion studies were in accordance with Fickian behavior and the diffusion coefficients were obtained, whereas the latest stages were in good agreement with second-order diffusion kinetics proposed by Schott 1 .These news hydrogels exhibit a higher degree of swelling, a factor that, a priori, assures high biocompatibility because it increases the similarity with living tissues

  14. Highly swelling hydrogels from ordered galactose-based polyacrylates.

    Martin, B D; Linhardt, R J; Dordick, J S

    1998-01-01

    High swelling galactose-based hydrogels have been prepared using a chemoenzymatic procedure. Regioselective acylation of beta-O-methyl-galactopyranoside in nearly anhydrous pyridine with lipase from Pseudomonas cepacia yields the 6-acryloyl derivative (Compound I). Further lipase-catalysed acylation of the monoacrylate derivative in nearly anhydrous acetone yielded 2,6-diacryloyl-beta-O-methyl galactopyranoside (Compound II) that can act as a cross-linker with a structure similar to that of the sugar-based monomer. The high selectivity of enzyme catalysis yielded apparently highly regular hydrogel networks with swelling ratios at equilibrium ranging from 170 to 1100. elastic moduli ranging from 0.005 to 0.088 MPa and calculated mesh sizes ranging from 1160 to 6600 A. These values are far higher than conventional uncharged or lightly charged hydrogels at similar elastic moduli. Gel swelling was fast, with 75% of the equilibrium swelling value reached in a fractional time of 0.17. Non-selective chemical acryloylation of beta-O-methyl galactopyranoside followed by polymerization yielded a far lower-swelling hydrogel than that obtained using selective enzyme catalysis. These results indicate that the highly regular polymer structure achieved by regioselective enzyme-catalysed acylation yields relatively strong and highly swellable materials. Sugar-based hydrogels, such as those described herein, may find particular use as biomaterials because of their high water content, homogeneity, stability and expected non-toxicity. A wide range of pore sizes can be attained, suggesting that they may also be especially useful as matrices for enzyme immobilization and controlled delivery of biological macromolecules. PMID:9678852

  15. Injectable biopolymer based hydrogels for drug delivery applications.

    Atta, Sadia; Khaliq, Shaista; Islam, Atif; Javeria, Irtaza; Jamil, Tahir; Athar, Muhammad Makshoof; Shafiq, Muhammad Imtiaz; Ghaffar, Abdul

    2015-09-01

    Biopolymer based pH-sensitive hydrogels were prepared using chitosan (CS) with polyethylene glycol (PEG) of different molecular weights in the presence of silane crosslinker. The incorporated components remain undissolved in different swelling media as they are connected by siloxane linkage which was confirmed by Fourier transform infrared spectroscopy. The swelling in water was enhanced by the addition of higher molecular weight PEG. The swelling behaviour of the hydrogels against pH showed high swelling in acidic and basic pH, whereas, low swelling was examined at pH 6 and 7. This characteristic pH responsive behaviour at neutral pH made them suitable for injectable controlled drug delivery. The controlled release analysis of Cefixime (CFX) (model drug) loaded CS/PEG hydrogel exhibited that the entire drug was released in 30 min in simulated gastric fluid (SGF) while in simulated intestinal fluid (SIF), 85% of drug was released in controlled manner within 80 min. This inferred that the developed hydrogels can be an attractive biomaterial for injectable drug delivery with physiological pH and other biomedical applications. PMID:26118484

  16. Effect of discarded keratin-based biocomposite hydrogels on the wound healing process in vivo

    Park, Mira [Department of Organic Materials & Fiber Engineering, Chonbuk National University, Jeonju 561–756 (Korea, Republic of); Shin, Hye Kyoung [Department of Chemistry, Inha University, 100 Inharo, Incheon 402–751 (Korea, Republic of); Kim, Byoung-Suhk [Department of BIN fusion technology, Chonbuk National University, Jeonju 561–756 (Korea, Republic of); Kim, Myung Jin; Kim, In-Shik [Department of Veterinary Anatomy, College of Veterinary Medicine and Bio-safety Research institute, Chonbuk National University, Jeonju 561–756 (Korea, Republic of); Park, Byung-Yong, E-mail: parkb@jbnu.ac.kr [Department of Veterinary Anatomy, College of Veterinary Medicine and Bio-safety Research institute, Chonbuk National University, Jeonju 561–756 (Korea, Republic of); Kim, Hak-Yong, E-mail: khy@jbnu.ac.kr [Department of BIN fusion technology, Chonbuk National University, Jeonju 561–756 (Korea, Republic of)

    2015-10-01

    Biocompatible keratin-based hydrogels prepared by electron beam irradiation (EBI) were examined in wound healing. As the EBI dose increased to 60 kGy, the tensile strength of the hydrogels increased, while the percentage of elongation of the hydrogels decreased. After 7 days, the dehydrated wool-based hydrogels show the highest mechanical properties (the % elongation of 1341 and the tensile strength of 6030 g/cm{sup 2} at an EBI dose of 30 kGy). Excision wound models were used to evaluate the effects of human hair-based hydrogels and wool-based hydrogels on various phases of healing. On post-wounding days 7 and 14, wounds treated with either human hair-based or wool-based hydrogels were greatly reduced in size compared to wounds that received other treatments, although the hydrocolloid wound dressing-treated wound also showed a pronounced reduction in size compared to an open wound as measured by a histological assay. On the 14th postoperative day, the cellular appearances were similar in the hydrocolloid wound dressing and wool-based hydrogel-treated wounds, and collagen fibers were substituted with fibroblasts and mixed with fibroblasts in the dermis. Furthermore, the wound treated with a human hair-based hydrogel showed almost complete epithelial regeneration, with the maturation of immature connective tissue and hair follicles and formation of a sebaceous gland. - Highlights: • Biocompatible keratin-based hydrogels were examined for wound healing process. • Human hair-based hydrogel is superior to wool-based hydrogel in wound healing. • Discarded keratin-based hydrogels are expected more eco-friendly therapeutic agents.

  17. Effect of discarded keratin-based biocomposite hydrogels on the wound healing process in vivo

    Biocompatible keratin-based hydrogels prepared by electron beam irradiation (EBI) were examined in wound healing. As the EBI dose increased to 60 kGy, the tensile strength of the hydrogels increased, while the percentage of elongation of the hydrogels decreased. After 7 days, the dehydrated wool-based hydrogels show the highest mechanical properties (the % elongation of 1341 and the tensile strength of 6030 g/cm2 at an EBI dose of 30 kGy). Excision wound models were used to evaluate the effects of human hair-based hydrogels and wool-based hydrogels on various phases of healing. On post-wounding days 7 and 14, wounds treated with either human hair-based or wool-based hydrogels were greatly reduced in size compared to wounds that received other treatments, although the hydrocolloid wound dressing-treated wound also showed a pronounced reduction in size compared to an open wound as measured by a histological assay. On the 14th postoperative day, the cellular appearances were similar in the hydrocolloid wound dressing and wool-based hydrogel-treated wounds, and collagen fibers were substituted with fibroblasts and mixed with fibroblasts in the dermis. Furthermore, the wound treated with a human hair-based hydrogel showed almost complete epithelial regeneration, with the maturation of immature connective tissue and hair follicles and formation of a sebaceous gland. - Highlights: • Biocompatible keratin-based hydrogels were examined for wound healing process. • Human hair-based hydrogel is superior to wool-based hydrogel in wound healing. • Discarded keratin-based hydrogels are expected more eco-friendly therapeutic agents

  18. Metamaterial perfect absorber based hot electron photodetection.

    Li, Wei; Valentine, Jason

    2014-06-11

    While the nonradiative decay of surface plasmons was once thought to be only a parasitic process that limits the performance of plasmonic devices, it has recently been shown that it can be harnessed in the form of hot electrons for use in photocatalysis, photovoltaics, and photodetectors. Unfortunately, the quantum efficiency of hot electron devices remains low due to poor electron injection and in some cases low optical absorption. Here, we demonstrate how metamaterial perfect absorbers can be used to achieve near-unity optical absorption using ultrathin plasmonic nanostructures with thicknesses of 15 nm, smaller than the hot electron diffusion length. By integrating the metamaterial with a silicon substrate, we experimentally demonstrate a broadband and omnidirectional hot electron photodetector with a photoresponsivity that is among the highest yet reported. We also show how the spectral bandwidth and polarization-sensitivity can be manipulated through engineering the geometry of the metamaterial unit cell. These perfect absorber photodetectors could open a pathway for enhancing hot electron based photovoltaic, sensing, and photocatalysis systems. PMID:24837991

  19. Corundum-based transparent infrared absorbers

    Schwingenschlögl, Udo

    2009-10-01

    Hypothetical corundum-based compounds are studied by electronic structure calculations. One quarter of the Al atoms in Al2O3 is replaced by a 3d transition metal from the M = Ti, ..., Zn (d1, ..., d9) series. Structure optimisations are performed for all the M-Al2O3 compounds and the electronic states are evaluated. Due to the M substitutes, narrow partially filled bands are formed at the Fermi energy. Beyond, for M = Ni and M = Cu the optical properties of Al2O3 in the visible range are conserved, while for M = Ti, ..., Co the systems form high accuracy optical filters. Since the compounds absorb the infrared radiation, the M = Ni and M = Cu systems are good candidates for heat-protective coatings. © 2009 Elsevier B.V. All rights reserved.

  20. Shock Absorbing Function Study on Denucleated Intervertebral Disc with or without Hydrogel Injection through Static and Dynamic Biomechanical Tests In Vitro

    Zhiyu Zhou

    2014-01-01

    Full Text Available Hydrogel injection has been recently proposed as a novel therapy for disc degenerative diseases, with the potential to restore the spine motion and the intervertebral disc height. However, it remains unknown whether the new technique could also maintain the shock absorbing property of the treated intervertebral disc. In this study, 18 porcine lumbar bone-disc-bone specimens were collected and randomly divided into three groups: the normal with intact intervertebral discs, the mimic for the injection of disulfide cross-linked hyaluronan hydrogels following discectomy, and the control disc with discectomy only. In the static compression test, specimens in the mimic group exhibited displacements similar to those in the normal discs, whereas the control group showed a significantly larger displacement range in the first two steps (P<0.05. With the frequency increasing, all specimens generally displayed an increasing storage modulus, decreasing loss modulus, and tanδ. At any frequency point, the control group exhibited the largest value in all the three parameters among three groups while the normal group was the lowest, with the mimic group being mostly close to the normal group. Therefore, the hydrogel injection into the intervertebral discs greatly restored their shock absorbing function, suggesting that the technique could serve as an effective approach to maintaining biomechanical properties of the degenerative intervertebral disc.

  1. Development of polyvinyl pyrrolidone (PVP) based hydrogel as cooling fever plester induced by electron beam irradiation

    The development of PVP based hydrogel as cooling fever plester using electron, beam irradiation technique has been done. The hydrogel was prepared by irradiating mixtures of PVP, PVA and another ingredients with various compositions (formula I, II, III and IV) at dose of 20 to 40 kGy. Several parameters of hydrogel such as physical properties, gel fraction, water content, tackiness and reduction time of water temperature from 40°C to 37°C were evaluated. The results showed that at irradiation dose of 20 kGy, hydrogel formula I had un appropriate physical characteristics such as brittle, the surface of hydrogel was watery and leave residues when it is applied to the skin. While hydrogel formula IV was rigid, unelastic and brittle. At 20 kGy irradiation dose, hydrogel formula II and III showed physical characteristics such as a bit brittle. At 30 kGy, it was shown appropriate physical characteristics such as no residu leave on skin, tough, the surface of hydrogel was not watery and gave pleasant feeling when it applied on the skin. But at 40 kGy, it was abit rigit. Gel fraction increase with increasing of dose from 20 to 30 kGy, further more the increase in dose was not give significant increase of gel fraction. At 20 kGy of irradiation dose, gel fraction was 83 - 87% and it was becomes 83 - 98% for irradiation dose of 30 to 40 kGy. Water content of hydrogel was depend on polymer concentration in hydrogel. It decreased by increasing of polymer concentration and it was not affected by irradiation dose. Hydrogel had water content around 73 - 84%. The tackiness of hydrogel formula II and III irradiated by 30 to 40 kGy was 8,3 - 8,9 gf. It was in proportion to tackiness of commercial hydrogel Bye Bye Fever. The ability of hydrogels in reducing water temperature from 40°C to 37°C showed that hydrogel formula I was the fastest among formulas used, that is 11 minutes. While it was 12 minutes for hydrogel formula II and III and in proportion with commercial hydrogel Bye

  2. Development and study of hydrogel-based microvalves for lab-on-a-chip systems

    Li, Ang

    2012-01-01

    Stimuli-responsive hydrogels such as poly(N-isopropylacrylamdie) (PNIPAAm) are excellent materials for microvalves due to their biocompatibility and high energy conversion efficiency. Hydrogel-based microvalves are simple to fabricate and operate compared to other actuation schemes. While many other hydrogel-based valves have been developed by other researchers, the valves presented here differ in the use of polymers as the basis for all microvalve components for increased flexibility. Thi...

  3. Microemulsion-based hydrogel formulation for transdermal delivery of dexamethasone

    Chandra Amrish

    2009-01-01

    Full Text Available The purpose of this study was to construct a microemulsion-based hydrogel formulation for the transdermal delivery of dexamethasone. Almond oil, olive oil, linseed oil, and nutmeg oil were screened as the oil phase. A microemulsion-based system was chosen due to its good solubilizing capacity and skin permeation capabilities. The pseudoternary phase diagrams for microemulsion regions were constructed using various oils, egg lecithin as the surfactant, isopropyl alcohol (IPA as the cosurfactant, and distilled water as the aqueous phase. Microemulsion gel formulations were prepared using Carbopol and filled into a reservoir-type transdermal system. The ability of various microemulsion formulations to deliver dexamethasone through the rat skin was evaluated in vitro using Keshary Chien diffusion cells. In order to enhance permeation, the skin was treated with an abrading gel (apricot seed powder in hydrogel base. The in vitro permeation data showed that microemulsions increased the permeation rate of dexamethasone compared with the control. The optimum formulation consisting of 0.1% dexamethasone, 10% olive oil, 70% egg lecithin:IPA (2:1, and water showed a permeation rate of 54.9 µg/cm 2 /h. The studied microemulsion-based hydrogel was stable toward centrifugation test and was nonirritating to the skin. The pharmacodynamic studies indicated that microemulsion based on nutmeg oil demonstrated a significantly ( P < 0.05 higher anti-inflammatory potential. The nutmeg oil-based transdermal microemulsion gel system demonstrated 73.6% inhibition in rat paw edema. Thus, microemulsion-based transdermal systems are a promising formulation for dermal delivery of dexamethasone.

  4. Evaporation-based microfluidic production of oil-free cell-containing hydrogel particles

    Fan, Rong; Naqvi, Kubra; Patel, Krishna; Sun, Jun; Wan, Jiandi

    2015-01-01

    We demonstrate an evaporation-based microfluidic strategy to produce oil-free cell containing hydrogel particles. Perfluoro-n-pentane, which is used as the continuous oil phase to generate cell-containing hydrogel (Extracel) particles, is removed at an elevated temperature. Human colon cancer cells (HCT116) encapsulated in the hydrogel particles show higher viability than cells encapsulated in particles that are produced via a non-evaporative oil phase. In addition, single HCT116 cells can be...

  5. Elastin Based Cell-laden Injectable Hydrogels with Tunable Gelation, Mechanical and Biodegradation Properties

    Fathi, Ali; Mithieux, Suzanne M.; Wei, Hua; Chrzanowski, Wojciech; Valtchev, Peter; Anthony S. Weiss; Dehghani, Fariba

    2014-01-01

    Injectable hydrogels made from extracellular matrix proteins such as elastin show great promise for various biomedical applications. Use of cytotoxic reagents, fixed gelling behavior, and lack of mechanical strength in these hydrogels are the main associated drawbacks. The aim of this study was to develop highly cytocompatible and injectable elastin-based hydrogels with alterable gelation characteristics, favorable mechanical properties and structural stability for load bearing applications. ...

  6. Synthesis and Properties of IPN Hydrogels Based on Konjac Glucomannan and Poly(acrylic acid)

    Bing LIU; Zhi Lan LIU; Ren Xi ZHUO

    2006-01-01

    Novel interpenetrating polymer network (IPN) hydrogels based on konjac glucomannan (KGM) and poly(acrylic acid) (PAA) were prepared by polymerization and cross-linking of acrylic acid (AA) in the pre-fabricated KGM gel. The IPN gel was analyzed by FT-IR. The studies on the equilibrium swelling ratio of IPN hydrogels revealed their sensitive response to environmental pH value. The results of in vitro degradation showed that the IPN hydrogels retain the enzymatic degradation character of KGM.

  7. Multi-functions of hydrogel with bilayer-based lamellar structure

    Haque, Md. Anamul; Gong, Jian Ping

    2013-01-01

    A novel hybrid hydrogel has been developed by combining bilayer-based lamellar structure of a self-assembled polymer surfactant and polymer network of conventional hydrogel system. A wide range of lamellar structure from micro-domain up to macro-domain (cm-scale) has been successfully generated in the hydrogel. Flat, infinitely large, and perfectly aligned lamellar macro-domain was formed by applying mechanical shear to the gel forming precursor solution containing monomer, cross-linker, and ...

  8. Rheological Characterization of Cataplasm Bases Composed of Cross-Linked Partially Neutralized Polyacrylate Hydrogel

    Wang, Jian; Zhang, Hongqin; An, Dianyun; Yu, Jian; Li, Wei; Shen, Teng; Wang, Jianxin

    2014-01-01

    Viscoelasticity is a useful parameter for characterizing the intrinsic properties of the cross-linked polyacrylate hydrogel used in cataplasm bases. The aim of this study was to investigate the effects of various formulation parameters on the rheological characteristics of polyacrylate hydrogel. The hydrogel layers were formed using a partially neutralized polyacrylate (Viscomate™), which contained acrylic acid and sodium acrylate in different copolymerization ratios, as the cross-linked gel ...

  9. Preparation of Graphene Oxide-Based Hydrogels as Efficient Dye Adsorbents for Wastewater Treatment

    Guo, Haiying; Jiao, Tifeng; Zhang, Qingrui; Guo, Wenfeng; Peng, Qiuming; Yan, Xuehai

    2015-06-01

    Graphene oxide (GO) sheets exhibit superior adsorption capacity for removing organic dye pollutants from an aqueous environment. In this paper, the facile preparation of GO/polyethylenimine (PEI) hydrogels as efficient dye adsorbents has been reported. The GO/PEI hydrogels were achieved through both hydrogen bonding and electrostatic interactions between amine-rich PEI and GO sheets. For both methylene blue (MB) and rhodamine B (RhB), the as-prepared hydrogels exhibit removal rates within about 4 h in accordance with the pseudo-second-order model. The dye adsorption capacity of the hydrogel is mainly attributed to the GO sheets, whereas the PEI was incorporated to facilitate the gelation process of GO sheets. More importantly, the dye-adsorbed hydrogels can be conveniently separated from an aqueous environment, suggesting potential large-scale applications of the GO-based hydrogels for organic dye removal and wastewater treatment.

  10. A hydrogel-based enzyme-loaded polymersome reactor

    Hoog, de Hans-Peter; Arends, Isabel W.C.E.; Rowan, Alan E.; Cornelissen, Jeroen J.L.M.; Nolte, Roeland J.M.

    2010-01-01

    In this study we report the immobilization of enzyme-containing polymersomes into a macromolecular hydrogel. Whereas free enzyme shows progressive leakage from the hydrogel in a period of days, leakage of the polymersome-protected enzyme is virtually absent. The preparation of the hydrogel occurs un

  11. Physical Cross-Linking Starch-Based Zwitterionic Hydrogel Exhibiting Excellent Biocompatibility, Protein Resistance, and Biodegradability.

    Ye, Lei; Zhang, Yabin; Wang, Qiangsong; Zhou, Xin; Yang, Boguang; Ji, Feng; Dong, Dianyu; Gao, Lina; Cui, Yuanlu; Yao, Fanglian

    2016-06-22

    In this work, a novel starch-based zwitterionic copolymer, starch-graft-poly(sulfobetaine methacrylate) (ST-g-PSBMA), was synthesized via Atom Transfer Radical Polymerization. Starch, which formed the main chain, can be degraded completely in vivo, and the pendent segments of PSBMA endowed the copolymer with excellent protein resistance properties. This ST-g-PSBMA copolymer could self-assemble into a physical hydrogel in normal saline, and studies of the formation mechanism indicated that the generation of the physical hydrogel was driven by electrostatic interactions between PSBMA segments. The obtained hydrogels were subjected to detailed analysis by scanning electron microscopy, swelling ratio, protein resistance, and rheology tests. Toxicity and hemolysis analysis demonstrated that the ST-g-PSBMA hydrogels possess excellent biocompatibility and hemocompatibility. Moreover, the cytokine secretion assays (IL-6, TNF-α, and NO) confirmed that ST-g-PSBMA hydrogels had low potential to trigger the activation of macrophages and were suitable for in vivo biomedical applications. On the basis of these in vitro results, the ST-g-PSBMA hydrogels were implanted in SD rats. The tissue responses to hydrogel implantation and the hydrogel degradation in vivo were determined by histological analysis (Hematoxylin and eosin, Van Gieson, and Masson's Trichrome stains). The results presented in this study demonstrate that the physical cross-linking, starch-based zwitterionic hydrogels possess excellent protein resistance, low macrophage-activation properties, and good biocompatibility, and they are a promising candidate for an in vivo biomedical application platform. PMID:27249052

  12. Injectable in situ forming xylitol-PEG-based hydrogels for cell encapsulation and delivery.

    Selvam, Shivaram; Pithapuram, Madhav V; Victor, Sunita P; Muthu, Jayabalan

    2015-02-01

    Injectable in situ crosslinking hydrogels offer unique advantages over conventional prefabricated hydrogel methodologies. Herein, we synthesize poly(xylitol-co-maleate-co-PEG) (pXMP) macromers and evaluate their performance as injectable cell carriers for tissue engineering applications. The designed pXMP elastomers were non-toxic and water-soluble with viscosity values permissible for subcutaneous injectable systems. pXMP-based hydrogels prepared via free radical polymerization with acrylic acid as crosslinker possessed high crosslink density and exhibited a broad range of compressive moduli that could match the natural mechanical environment of various native tissues. The hydrogels displayed controlled degradability and exhibited gradual increase in matrix porosity upon degradation. The hydrophobic hydrogel surfaces preferentially adsorbed albumin and promoted cell adhesion and growth in vitro. Actin staining on cells cultured on thin hydrogel films revealed subconfluent cell monolayers composed of strong, adherent cells. Furthermore, fabricated 3D pXMP cell-hydrogel constructs promoted cell survival and proliferation in vitro. Cumulatively, our results demonstrate that injectable xylitol-PEG-based hydrogels possess excellent physical characteristics and exhibit exceptional cytocompatibility in vitro. Consequently, they show great promise as injectable hydrogel systems for in situ tissue repair and regeneration. PMID:25543981

  13. Radiation synthesis and characterization of gelatine category hydrogel

    The hydrogels based on gelatine cross-linked with sodium carboxymethyl cellulose (CMC-Na) and polyvinylpyrrolidone (PVP) were synthesized through 60Co γ ray irradiation, and the swelling ability, pH-sensitivity, gelatine fraction and the absorbing ability of Cr were measured by the Soxhlet extraction device, Uv-vis spectrophotometer and atomic absorption spectrometer, respectively. The result indicates that it is easy to synthesize hydrogels of gelatine/CMC-Na/PVP with monomer mass proportions of 4 : 1 : 2, 4 : 1 : 5 and 2 : 1 : 5 at the absorbed doses of 15, 25, 35 and 45 kGy at the dose rate of 83 Gy/min, respectively. It shows that the swelling behavior of hydrogels becomes different when either the monomer proportion of raw materials or the absorbed doses vary. The swelling ratio (SR) of hydrogels can be up to 56 at pH=7, while the minimal value is 7 at pH=1, which indicates that the SR of hydrogel is sensitive to pH. The hydrogel of PVP will not be degraded after many years, but the hydrogels of gelatine/CMC-Na/PVP will be degraded within one month. It indicates that the degradation of hydrogels can be accelerated as the nature polymer can be degraded into the hydrogels. The adsorptive capacity of Cr(Ⅵ) is up to 0.539 g/g. (authors)

  14. Composite hydrogel based on surface modified mesoporous silica and poly[(2-acryloyloxy)ethyl trimethylammonium chloride

    Torres, Cecilia C. [Department of Organic Chemistry, Faculty of Chemical Science, University of Concepción (Chile); Urbano, Bruno F., E-mail: burbano@udec.cl [Department of Polymer Chemistry, Faculty of Chemical Science, University of Concepción (Chile); Campos, Cristian H. [Department of Organic Chemistry, Faculty of Chemical Science, University of Concepción (Chile); Rivas, Bernabé L. [Department of Polymer Chemistry, Faculty of Chemical Science, University of Concepción (Chile); Reyes, Patricio [Department of Physical Chemistry, Faculty of Chemical Science, University of Concepción (Chile)

    2015-02-15

    This work focused on the synthesis, characterization and water absorbency of a composite hydrogel based on poly[(2-acryloyloxy)ethyl trimethylammonium chloride] and mesoporous silica, MCM-41. The MCM-41 was synthesized and later surface functionalized with triethoxyvinylsilane (VTES) and 3-trimethoxysilylpropylmethacrylate (TMSPM) by a post-grafting procedure. The composite hydrogels were obtained by in-situ polymerization using a mixture of monomer, crosslinker and initiator in the presence of functionalized MCM-41. Diverse characterization techniques were used at the different stages of synthesis, namely, FT-IR, TEM, SEM, DRX, {sup 29}Si and {sup 13}C solid state NMR, and N{sub 2} adsorption isotherms at 77 K. Finally, the water uptake performance of the composites was tested as a function of time, mesoporous silica loading and coupling agent used at the functionalization. The composites using non-functionalized MCM-41 reached the highest water uptake, whereas those composite with MCM-41 TMSPM exhibited the lowest sorption. - Highlights: • Hydrophilic crosslinked polymer-mesoporous silica was obtained. • Mesoporous silica MCM-41 was synthesized and functionalized with organosilane. • Functionalization of MCM-41 affects the water uptake of composite. • Mesoporous silica is covalently bound to the polymer acting as crosslinked point.

  15. A review of cermet-based spectrally selective solar absorbers

    Cao, Feng; McEnaney, Kenneth; Chen, Gang; Ren, Zhifeng

    2013-01-01

    Spectrally selective solar absorbers harvest solar energy in the form of heat. Solar absorbers using cermet-based coatings demonstrate a high absorptance of the solar spectrum and a low emittance in the infrared (IR) regime. Extensive work has been done to optimize cermet-based solar absorbers to achieve high performance by exploring different cermet (ceramic–metal composite) materials and film configurations through different preparation techniques such as electrodeposition, sputtering, puls...

  16. IPN hydrogel nanocomposites based on agarose and ZnO with antifouling and bactericidal properties.

    Wang, Jingjing; Hu, Hongkai; Yang, Zhonglin; Wei, Jun; Li, Juan

    2016-04-01

    Nanocomposite hydrogels with interpenetrating polymer network (IPN) structure based on poly(ethylene glycol) methyl ether methacrylate modified ZnO (ZnO-PEGMA) and 4-azidobenzoic agarose (AG-N3) were prepared by a one-pot strategy under UV irradiation. The hydrogels exhibited a highly macroporous spongelike structure, and the pore size decreased with the increase of the ZnO-PEGMA content. Due to the entanglement and favorable interactions between the two crosslinked networks, the IPN hydrogels exhibited excellent mechanical strength and light transmittance. The maximum compressive and tensile strengths of the IPN hydrogels reached 24.8 and 1.98MPa respectively. The transparent IPN hydrogels transmitted more than 85% of visible light at all wavelengths (400-800nm). The IPN hydrogels exhibited anti-adhesive property towards Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), and the bactericidal activity increased with the ZnO-PEGMA content. The incorporation of ZnO-PEGMA did not reduce the biocompatibility of the IPN hydrogels and all the IPN nanocomposites showed negligible cytotoxicity. The present study not only provided a facile method for preparing hydrogel nanocomposites with IPN structure but also developed a new hydrogel material which might be an excellent candidate for wound dressings. PMID:26838864

  17. Development and characterization of hydrogels based on natural polysaccharides: Policaju and chitosan

    Soares, Paulo A.G. [Departamento de Bioquímica, Universidade Federal de Pernambuco (UFPE), Av. Prof. Moraes Rego, s/n, Cidade Universitária, 50670-420 Recife, PE (Brazil); Laboratório de Imunopatologia Keizo Asami-LIKA, Universidade Federal de Pernambuco (UFPE), Av. Prof. Moraes Rego, s/n, Cidade Universitária, 50670-901 Recife, PE (Brazil); Bourbon, Ana I.; Vicente, António A. [Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho (UMINHO), Campus de Gualtar, 4710-057 Braga (Portugal); Andrade, Cesar A.S. [Departamento de Bioquímica, Universidade Federal de Pernambuco (UFPE), Av. Prof. Moraes Rego, s/n, Cidade Universitária, 50670-420 Recife, PE (Brazil); Barros, Wilson [Departamento de Física, Universidade Federal de Pernambuco (UFPE), Av. Prof. Moraes Rego, s/n, Cidade Universitária, 50670-420 Recife, PE (Brazil); Correia, Maria T.S. [Departamento de Bioquímica, Universidade Federal de Pernambuco (UFPE), Av. Prof. Moraes Rego, s/n, Cidade Universitária, 50670-420 Recife, PE (Brazil); Pessoa, Adalberto [Faculdade de Ciências Farmacêuticas, Universidade de São Paulo (USP), Av. Lineu Prestes, 580, Butantã, 05508-000 São Paulo, SP (Brazil); and others

    2014-09-01

    The development of hydrogels based on natural polysaccharides was investigated by preparing mixtures of policaju/chitosan at weight ratios of 1:4 and 2:3. Utilizing dynamic light scattering (DLS) techniques for these mixtures, an increase on the hydrodynamic particle radius was observed varying their pH from 3.0 to 12.0. Furthermore, a reduction of ζ-potential was also observed for the same pH interval. Following rounds of drying/hydration cycles at a specific pH value, hydrogel matrices were formed. The pore size distribution of these formed hydrogels was examined using scanning electron microscopy. Further FT-IR analyses confirmed a physical interaction between the polysaccharides policaju and chitosan. Swelling experiments revealed water uptake values, after 24 h of immersion in water, close to 270% for 1:4, and 320% for 2:3 hydrogels. Finally, rheological measurements were then conducted in order to confirm hydrogel viscoelastic features. These results indicate a promising road to biomaterials fabrication and biomedical applications. - Highlights: • POLI–CHI hydrogels were obtained by direct injection and extrusion. • POLI–CHI hydrated hydrogels have 4.2 times their dry weight. • Due to the high water absorption POLI–CHI hydrogels are extremely soft. • POLI–CHI hydrogels can be used in cosmetic and medical industry.

  18. Development and characterization of hydrogels based on natural polysaccharides: Policaju and chitosan

    The development of hydrogels based on natural polysaccharides was investigated by preparing mixtures of policaju/chitosan at weight ratios of 1:4 and 2:3. Utilizing dynamic light scattering (DLS) techniques for these mixtures, an increase on the hydrodynamic particle radius was observed varying their pH from 3.0 to 12.0. Furthermore, a reduction of ζ-potential was also observed for the same pH interval. Following rounds of drying/hydration cycles at a specific pH value, hydrogel matrices were formed. The pore size distribution of these formed hydrogels was examined using scanning electron microscopy. Further FT-IR analyses confirmed a physical interaction between the polysaccharides policaju and chitosan. Swelling experiments revealed water uptake values, after 24 h of immersion in water, close to 270% for 1:4, and 320% for 2:3 hydrogels. Finally, rheological measurements were then conducted in order to confirm hydrogel viscoelastic features. These results indicate a promising road to biomaterials fabrication and biomedical applications. - Highlights: • POLI–CHI hydrogels were obtained by direct injection and extrusion. • POLI–CHI hydrated hydrogels have 4.2 times their dry weight. • Due to the high water absorption POLI–CHI hydrogels are extremely soft. • POLI–CHI hydrogels can be used in cosmetic and medical industry

  19. Hydrogel-based reinforcement of 3D bioprinted constructs.

    Melchels, Ferry P W; Blokzijl, Maarten M; Levato, Riccardo; Peiffer, Quentin C; Ruijter, Mylène de; Hennink, Wim E; Vermonden, Tina; Malda, Jos

    2016-01-01

    Progress within the field of biofabrication is hindered by a lack of suitable hydrogel formulations. Here, we present a novel approach based on a hybrid printing technique to create cellularized 3D printed constructs. The hybrid bioprinting strategy combines a reinforcing gel for mechanical support with a bioink to provide a cytocompatible environment. In comparison with thermoplastics such as [Formula: see text]-polycaprolactone, the hydrogel-based reinforcing gel platform enables printing at cell-friendly temperatures, targets the bioprinting of softer tissues and allows for improved control over degradation kinetics. We prepared amphiphilic macromonomers based on poloxamer that form hydrolysable, covalently cross-linked polymer networks. Dissolved at a concentration of 28.6%w/w in water, it functions as reinforcing gel, while a 5%w/w gelatin-methacryloyl based gel is utilized as bioink. This strategy allows for the creation of complex structures, where the bioink provides a cytocompatible environment for encapsulated cells. Cell viability of equine chondrocytes encapsulated within printed constructs remained largely unaffected by the printing process. The versatility of the system is further demonstrated by the ability to tune the stiffness of printed constructs between 138 and 263 kPa, as well as to tailor the degradation kinetics of the reinforcing gel from several weeks up to more than a year. PMID:27431861

  20. Characterization of Network Structure of Polyacrylamide Based Hydrogels Prepared By Radiation Induced Polymerization

    In this study network structure of polyacrylamide based hydrogels prepared by radiation induced polymerization has been investigated. Polyacrylamide based hydrogels in the rod form were prepared by copolymerization of acrylamide(AAm) with hydroxyl ethyl methacrylate(HEMA) and methyl acrylamide(MAAm) in the presence of cross-linking agent and water by gamma rays at ambient temperature. Molecular weight between cross-links and effective cross-link density of hydrogels were calculated from swelling as well as shear modulus data obtained from compression tests. The results have shown that simple compression analyses can be used for the determination of effective cross-link density of hydrogels without any need to some polymer-solvent based parameters as in the case of swelling based determinations. Diffusion of water into hydrogels was examined by analyzing water absorption kinetics and the effect of network, structure on the diffusion type and coefficient was discussed

  1. Bacterial cellulose based hydrogel (BC-g-AA) and preliminary result of swelling behavior

    In this study, hydrogel based on Bacterial cellulose (BC) or local known as Nata de Coco, which grafted with monomer: Acrylic acid (AA) is synthesis by using gamma radiation technique. These hydrogel (BC-g-AA) has unique characteristic whereby responsive to pH buffer solution

  2. Preparation and characterization of hydrogels based on clay and synthetic polymers formed by electron beam irradiation

    Hydrophilic hydrogels were prepared by electron irradiation based on different ratios of poly (viny alcohol) and acrylamide monomer (AM). The hydrogels were compounded with different contents of sodium montmorillonite clay (MMT) or organo-montmorillonite clay. The composites were characterized by (XRD) spectroscopy and thermogravimetric analysis (TGA). The effect of temperature and ph on the degree of swelling of composites was also studies.

  3. Bacterial cellulose based hydrogel (BC-g-AA) and preliminary result of swelling behavior

    Hakam, Adil; Lazim, Azwan Mat [UKM-MIMOS Laboratory, School of Chemical Sciences and Food Technology, National University of Malaysia (UKM) (Malaysia); Abdul Rahman, I. Irman [Laboratory of Gamma Radiation Instrument, Science Nuclear Program, School of Applied Physics, National University of Malaysia (UKM) (Malaysia)

    2013-11-27

    In this study, hydrogel based on Bacterial cellulose (BC) or local known as Nata de Coco, which grafted with monomer: Acrylic acid (AA) is synthesis by using gamma radiation technique. These hydrogel (BC-g-AA) has unique characteristic whereby responsive to pH buffer solution.

  4. Bacterial cellulose based hydrogel (BC-g-AA) and preliminary result of swelling behavior

    Hakam, Adil; Lazim, Azwan Mat; Abdul Rahman, I. Irman

    2013-11-01

    In this study, hydrogel based on Bacterial cellulose (BC) or local known as Nata de Coco, which grafted with monomer: Acrylic acid (AA) is synthesis by using gamma radiation technique. These hydrogel (BC-g-AA) has unique characteristic whereby responsive to pH buffer solution.

  5. Gelatin- and starch-based hydrogels. Part A: Hydrogel development, characterization and coating.

    Van Nieuwenhove, Ine; Salamon, Achim; Peters, Kirsten; Graulus, Geert-Jan; Martins, José C; Frankel, Daniel; Kersemans, Ken; De Vos, Filip; Van Vlierberghe, Sandra; Dubruel, Peter

    2016-11-01

    The present work aims at constructing the ideal scaffold matrix of which the physico-chemical properties can be altered according to the targeted tissue regeneration application. Ideally, this scaffold should resemble the natural extracellular matrix (ECM) as close as possible both in terms of chemical composition and mechanical properties. Therefore, hydrogel films were developed consisting of methacrylamide-modified gelatin and starch-pentenoate building blocks because the ECM can be considered as a crosslinked hydrogel network consisting of both polysaccharides and structural, signaling and cell-adhesive proteins. For the gelatin hydrogels, three different substitution degrees were evaluated including 31%, 72% and 95%. A substitution degree of 32% was applied for the starch-pentenoate building block. Pure gelatin hydrogels films as well as interpenetrating networks with gelatin and starch were developed. Subsequently, these films were characterized using gel fraction and swelling experiments, high resolution-magic angle spinning (1)H NMR spectroscopy, rheology, infrared mapping and atomic force microscopy. The results indicate that both the mechanical properties and the swelling extent of the developed hydrogel films can be controlled by varying the chemical composition and the degree of substitution of the methacrylamide-modified gelatin applied. The storage moduli of the developed materials ranged between 14 and 63kPa. Phase separation was observed for the IPNs for which separated starch domains could be distinguished located in the surrounding gelatin matrix. Furthermore, we evaluated the affinity of aggrecan for gelatin by atomic force microscopy and radiolabeling experiments. We found that aggrecan can be applied as a bioactive coating for gelatin hydrogels by a straightforward physisorption procedure. Thus, we achieved distinct fine-tuning of the physico-chemical properties of these hydrogels which render them promising candidates for tissue engineering

  6. Colorimetric logic response based on aptamer functionalized colloidal crystal hydrogels

    Ye, Baofen; Wang, Huan; Ding, Haibo; Zhao, Yuanjin; Pu, Yuepu; Gu, Zhongze

    2015-04-01

    A novel colorimetric logic system based on the aptamer-cross-linked colloidal crystal hydrogel (CCH) was developed. With the input stimuli of Hg2+ and Ag+, the CCH displayed shrinking response and colour change corresponding to the logical ``OR'' and ``AND'' gate. The visualization of the logic output signals is realized.A novel colorimetric logic system based on the aptamer-cross-linked colloidal crystal hydrogel (CCH) was developed. With the input stimuli of Hg2+ and Ag+, the CCH displayed shrinking response and colour change corresponding to the logical ``OR'' and ``AND'' gate. The visualization of the logic output signals is realized. Electronic supplementary information (ESI) available: I. Experimental section. II. Photograph of the aptamer functionalized CCH in the presence of different targets. III. The specificity of the aptamer functionalized CCH. IV. Relationship between the input ion concentration and the reflection wavelength blue shift. V. The logic swelling kinetics of CCH. See DOI: 10.1039/c5nr00586h

  7. Hydrogel-Based Nanocomposites and Mesenchymal Stem Cells: A Promising Synergistic Strategy for Neurodegenerative Disorders Therapy

    Diego Albani

    2013-01-01

    Full Text Available Hydrogel-based materials are widely employed in the biomedical field. With regard to central nervous system (CNS neurodegenerative disorders, the design of injectable nanocomposite hydrogels for in situ drug or cell release represents an interesting and minimally invasive solution that might play a key role in the development of successful treatments. In particular, biocompatible and biodegradable hydrogels can be designed as specific injectable tools and loaded with nanoparticles (NPs, to improve and to tailor their viscoelastic properties upon injection and release profile. An intriguing application is hydrogel loading with mesenchymal stem cells (MSCs that are a very promising therapeutic tool for neurodegenerative or traumatic disorders of the CNS. This multidisciplinary review will focus on the basic concepts to design acellular and cell-loaded materials with specific and tunable rheological and functional properties. The use of hydrogel-based nanocomposites and mesenchymal stem cells as a synergistic strategy for nervous tissue applications will be then discussed.

  8. Self-Healing Hydrogels Based on Carboxymethyl Chitosan and Acryloyl-6-aminocaproic Acid

    Jiufang Duan

    2015-01-01

    Full Text Available Once cracks have formed within hydrogel materials, the integrity of the structure is signifcantly compromised, regardless of the application. Here, we demonstrate cross-linked CMCS hydrogels can be engineered to exhibit self-healing under mild conditions. CMCS hydrogels based on CMCS and acryloyl-6-aminocaproic acid (A6ACA were synthesized by free radical aqueous copolymerization using ammonium persulfate as initiator. A series of hydrogels was synthesized varying the percentage of A6ACA. The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR techniques and their morphologies were investigated by scanning electron microscope (SEM images. When the proportion of A6ACA was increased, the compressive strength, stress, and strain of hydrogels were increased. The cross-linked hydrogel based on CMCS that can autonomously heal between cut surfaces after 1 h was formed under mild conditions. The increase of A6ACA content in the hydrogels will lead to increased mechanical properties and mechanical healing efficiencies for highly cross-linked polymeric networks. Hydrogen bond is the main reason for self-healing ability, and the covalent cross-linkss and noncovalent cross-links both bear loads in the hyrogel. Polymers with the ability to self-repair after sustaining damage could extend the lifetime of materials used in many applications.

  9. Design of multiband metamaterial absorber based on artificial magnetic conductor

    Dang, Kezheng; He, Zijian; Li, Zhigang; Miao, Lei; Liu, Hao

    2015-10-01

    We present a general method to design multiband absorber by replacing the ground plane in a conventional metamaterial absorber with an artificial magnetic conductor. Due to its unique property of in-phase reflection at some specific frequency, the artificial magnetic conductor is used to introduce new absorption in the operation band. Meanwhile, out of the in-phase reflection band, the original absorbing capability of the absorber is reserved. To demonstrate it, we design a metamaterial absorber comprising three layers which are grids patterned resistive frequency selective surface, dielectric layer and the ground plane respectively. With an appropriate design, the absorber performs an absorbing peak at about 10 GHz. Then, we utilize a single band artificial magnetic conductor at 6.25 GHz and a dual-band one at 6.27 GHz and 8.17 GHz, which are both lossy and comprised of patches array varying in periodic size with a thickness of 0.6 mm, to replace the ground plane in the metamaterial absorber separately. The reflectivity of these multiband absorbers are simulated, and experiments are carried out later. Experimental results agree well with the simulations. All results verified that the method presented at the beginning is effective. The results show that additional absorptions exist at the frequencies where microwaves are nearly reflected in phase on the artificial magnetic conductor. Meanwhile the original absorbing capability of the metamaterial absorber has been preserved mostly. Based on the artificial magnetic conductor, the multiband absorber performs better with an increasing absorption bandwidth from 8.5 GHz to 10 GHz compared to the metamaterial absorber.

  10. Recommended method for measurement of absorbency of superabsorbent polymers in cement-based materials

    Esteves, Luis Pedro

    2015-01-01

    The application of superabsorbent polymers in concrete technology is now becoming a reality in several places in the world. Independently of the specific technical application involving any of the hydrogels, the design of cement-based materials requires that the knowledge on the absorbency of...... superabsorbent polymers in cementitious environments is well determined. It is vital that a generalized agreement over which method should be utilized with this regard is obtained, so large-scale industrial applications can be developed with sufficient quality and safeguards. There ought to be a standard method...... so that the properties of concrete with superabsorbent polymers can be better controlled in practice. In this paper, a technique that can be potentially used as a standard method is developed. The method is based on a measurement technique validated through an international standard procedure...

  11. A new water absorbable mechanical Epidermal skin equivalent: the combination of hydrophobic PDMS and hydrophilic PVA hydrogel.

    Morales-Hurtado, M; Zeng, X; Gonzalez-Rodriguez, P; Ten Elshof, J E; van der Heide, E

    2015-06-01

    Research on human skin interactions with healthcare and lifestyle products is a topic continuously attracting scientific studies over the past years. It is possible to evaluate skin mechanical properties based on human or animal experimentation, yet in addition to possible ethical issues, these samples are hard to obtain, expensive and give rise to highly variable results. Therefore, the design of a skin equivalent is essential. This paper describes the design and characterization of a new Epidermal Skin Equivalent (ESE). The material resembles the properties of epidermis and is a first approach to mimic the mechanical properties of the human skin structure, variable with the length scale. The ESE is based on a mixture of Polydimethyl Siloxane (PDMS) and Polyvinyl Alcohol (PVA) hydrogel cross-linked with Glutaraldehyde (GA). It was chemically characterized by XPS and FTIR measurements and its cross section was observed by macroscopy and cryoSEM. Confocal Microscope analysis on the surface of the ESE showed an arithmetic roughness (Ra) between 14-16 μm and contact angle (CA) values between 50-60°, both of which are close to the values of in vivo human skins reported in the literature. The Equilibrium Water Content (ECW) was around 33.8% and Thermo Gravimetric Analysis (TGA) confirmed the composition of the ESE samples. Moreover, the mechanical performance was determined by indentation tests and Dynamo Thermo Mechanical Analysis (DTMA) shear measurements. The indentation results were in good agreement with that of the target epidermis reported in the literature with an elastic modulus between 0.1-1.5 MPa and it showed dependency on the water content. According to the DTMA measurements, the ESE exhibits a viscoelastic behavior, with a shear modulus between 1-2.5MPa variable with temperature, frequency and the hydration of the samples. PMID:25840121

  12. Dual band metamaterial perfect absorber based on artificial dielectric "molecules".

    Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-01-01

    Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of these dual band metamaterial absorbers proposed were based on resonances of metal patterns. Here, we numerically and experimentally demonstrate a dual band metamaterial perfect absorber composed of artificial dielectric "molecules" with high symmetry. The artificial dielectric "molecule" consists of four "atoms" of two different sizes corresponding to two absorption bands with near unity absorptivity. Numerical and experimental absorptivity verify that the dual-band metamaterial absorber is polarization insensitive and can operate in wide-angle incidence. PMID:27406699

  13. Preparation and characterization of keratin-based biocomposite hydrogels prepared by electron beam irradiation

    Park, Mira; Kim, Byoung-Suhk [Department of Organic Materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Shin, Hye Kyoung [Department of Chemistry, Inha University, 100 Inharo, Incheon 402-751 (Korea, Republic of); Park, Soo-Jin, E-mail: sjpark@inha.ac.kr [Department of Chemistry, Inha University, 100 Inharo, Incheon 402-751 (Korea, Republic of); Kim, Hak-Yong, E-mail: khy@jbnu.ac.kr [Department of Organic Materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2013-12-01

    The biocompatible and highly porous keratin-based hydrogels were prepared using electron beam irradiation (EBI). The conditions for keratin-based hydrogel formation were investigated depending on several conditions, including the presence of poly(vinyl alcohol) (PVA), concentration of keratin solution, EBI dose, and poly(ethylene imine) (PEI) additives. The pure keratin (human hair and wool) aqueous solution was not gelled by EBI, while the aqueous keratin solutions blended with PVA were gelled at an EBI dose of more than 90 kGy. Furthermore, in the presence of PEI, the aqueous keratin solution blended with PVA could be gelled at a considerably lower EBI dose, even at 10 kGy. This finding suggests that the PEI additives significantly influence the rate of gelation and that PEIs function as an accelerator during gelation. The resulting keratin-based hydrogels were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), gel fraction, degree of swelling, gel strength, and kinetics of swelling analyses. - Highlights: • The biocompatible and highly porous keratin-based hydrogels were prepared using EBI. • The conditions for keratin-based hydrogel formation were examined. • PEI would play an accelerator role in the formation of keratin-based hydrogels. • The resulting keratin-based hydrogels are expected to be more environmentally friendly.

  14. Graphene metamaterials based tunable terahertz absorber: effective surface conductivity approach

    Andryieuski, Andrei; Lavrinenko, Andrei

    2013-01-01

    In this paper we present the efficient design of functional thin-film metamaterial devices with the effective surface conductivity approach. As an example, we demonstrate a graphene based perfect absorber. After formulating the requirements to the perfect absorber in terms of surface conductivity...

  15. Self-Healing Supramolecular Self-Assembled Hydrogels Based on Poly(L-glutamic acid).

    Li, Guifei; Wu, Jie; Wang, Bo; Yan, Shifeng; Zhang, Kunxi; Ding, Jianxun; Yin, Jingbo

    2015-11-01

    Self-healing polymeric hydrogels have the capability to recover their structures and functionalities upon injury, which are extremely attractive in emerging biomedical applications. This research reports a new kind of self-healing polypeptide hydrogels based on self-assembly between cholesterol (Chol)-modified triblock poly(L-glutamic acid)-block-poly(ethylene glycol)-block-poly(L-glutamic acid) ((PLGA-b-PEG-b-PLGA)-g-Chol) and β-cyclodextrin (β-CD)-modified poly(L-glutamic acid) (PLGA-g-β-CD). The hydrogel formation relied on the host and guest linkage between β-CD and Chol. This study demonstrates the influences of polymer concentration and β-CD/Chol molar ratio on viscoelastic behavior of the hydrogels. The results showed that storage modulus was highest at polymer concentration of 15% w/v and β-CD/Chol molar ratio of 1:1. The effect of the PLGA molecular weight in (PLGA-b-PEG-b-PLGA)-g-Chol on viscoelastic behavior, mechanical properties and in vitro degradation of the supramolecular hydrogels was also studied. The hydrogels showed outstanding self-healing capability and good cytocompatibility. The multilayer structure was constructed using hydrogels with self-healing ability. The developed hydrogels provide a fascinating glimpse for the applications in tissue engineering. PMID:26414083

  16. Synthesis and Characterization of Cellulose-Based Hydrogels to Be Used as Gel Electrolytes

    Maria Assunta Navarra

    2015-11-01

    Full Text Available Cellulose-based hydrogels, obtained by tuned, low-cost synthetic routes, are proposed as convenient gel electrolyte membranes. Hydrogels have been prepared from different types of cellulose by optimized solubilization and crosslinking steps. The obtained gel membranes have been characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical tests in order to investigate the crosslinking occurrence and modifications of cellulose resulting from the synthetic process, morphology of the hydrogels, their thermal stability, and viscoelastic-extensional properties, respectively. Hydrogels liquid uptake capability and ionic conductivity, derived from absorption of aqueous electrolytic solutions, have been evaluated, to assess the successful applicability of the proposed membranes as gel electrolytes for electrochemical devices. To this purpose, the redox behavior of electroactive species entrapped into the hydrogels has been investigated by cyclic voltammetry tests, revealing very high reversibility and ion diffusivity.

  17. Synthesis of Borohydride and Catalytic Dehydrogenation by Hydrogel Based Catalyst

    Boynuegri, Tugba Akkas; Karabulut, Ahmet F.; Guru, Metin

    2016-08-01

    This paper deals with the synthesis of calcium borohydride (Ca(BH4)2) as hydrogen storage material. Calcium chloride salt (CaCl2), magnesium hydride (MgH2), and boron oxide (B2O3) were used as reactants in the mechanochemical synthesis of Ca(BH4)2. The mechanochemical reaction was carried out by means of Spex type ball milling without applying high pressure and temperature. Parametric studies have been established at different reaction times and for different amounts of reactants at a constant ball to powder ratio (BPR) 4:1. The best combination was determined by Fourier Transform Infrared (FT-IR) analysis. According to the FT-IR analysis, reaction time, the first reaction parameter, was found as 1600 min. After the reaction time was fixed at 1600 min, the difference of the B-H peak areas was dependent on the amount of reactant MgH2 that was investigated. The amount of the reactant (MgH2), the second reaction parameter, was measured to be 2.85 times more than the stoichiometric amount of MgH2. According to our previous studies, BPR was selected as 4:1 for all experiments. Samples were prepared in a glove box under argon atmosphere but the time that elapsed for FT-IR analysis highly affected B-H bonds. B-H peak areas clearly decreased with time because of negative effect of ambient atmosphere. A catalyst was prepared by absorbing cobalt fluoride (CoF2) in poly (acrylamide-co-acrylic acid) hydrogel matrices type and its catalytic dehydrogenation performance that has been characterized by the catalytic reaction of sodium borohydride's known hydrogen capacity in an alkaline medium. The metal amount of hydrogel catalyst was determined as 135.82 mg Co by Atomic Absorption Spectroscopy (AAS). The specific dehydrogenation capacity of the Co active compound in the catalyst thanks to catalytic dehydrogenation of commercial sodium borohydride was measured as 1.66 mL H2/mg Co.

  18. Formulation and characterization of poloxamine-based hydrogels as tissue sealants.

    Cho, Eunhee; Lee, Jeoung Soo; Webb, Ken

    2012-07-01

    In situ cross linkable polyethylene glycol (PEG)-based polymers play an increasing role in surgical practice as sealants that provide a barrier to fluid/gas leakage and adhesion formation. This study investigated the gelation behavior and physical properties of hydrogels formed from homogeneous and blended solutions of two acrylated poloxamines (Tetronics® T1107 and T904) of various molecular weights and hydrophilic/lipophilic balances relative to a PEG control. Hydrogels were formed by reverse thermal gelation at physiological temperature (T1107-containing formulations) and covalent crosslinking by Michael-type addition with dithiothreitol. All poloxamine-based hydrogels exhibited thermosensitive behavior and achieved significantly reduced swelling, increased tensile properties and increased tissue bond strength relative to the PEG hydrogel at physiological temperature. Swelling and tensile properties of all poloxamine-based hydrogels were significantly greater at 37°C relative to 4°C, suggesting that their improved physical properties derive from cooperative crosslinking by both noncovalent and covalent mechanisms. Poloxamine-based hydrogels were cytocompatible and underwent hydrolytic degradation over 2-5weeks, depending on their T1107/T904 composition. In conclusion, select poloxamine-based hydrogels possess a number of properties potentially beneficial to tissue sealant applications, including a substantial increase in viscosity between room/physiological temperatures, resistance to cell adhesion and maintenance of a stable volume during equilibration. PMID:22406506

  19. Macroporous hydrogels based on 2-hydroxyethyl methacrylate. Part 3. Hydrogels as carriers for immobilization of proteins

    Michálek, Jiří; Přádný, Martin; Artyukhov, A.; Šlouf, Miroslav; Smetana Jr., K.

    2005-01-01

    Roč. 16, č. 8 (2005), s. 783-786. ISSN 0957-4530 R&D Projects: GA ČR GA203/01/0737; GA AV ČR IBS4050005; GA MŠk LN00A065 Keywords : macroporous hydrogels * hydroxyethyl methacrylate * crosslinked copolymers Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.248, year: 2005

  20. Drug release into hydrogel-based subcutaneous surrogates studied by UV imaging

    Ye, Fengbin; Larsen, Susan Weng; Yaghmur, Anan; Jensen, Henrik; Larsen, Claus Selch; Ostergaard, Jesper

    2012-01-01

    triglyceride (MCT) into 0.5% (w/v) agarose or 25% (w/v) F127-based hydrogels was investigated by monitoring the concentration profiles of the drug in the gels. The effect of pH on piroxicam distribution and diffusion coefficients was studied. For both hydrogel systems, the diffusion of piroxicam in the gels...... of piroxicam upon the injection of aqueous or MCT solutions into an agarose-based hydrogel were investigated by UV imaging. The spatial distribution of piroxicam around the injection site in the gel matrix was monitored in real-time. The disappearance profiles of piroxicam from the injected aqueous...

  1. Xylan-based temperature/pH sensitive hydrogels for drug controlled release.

    Gao, Cundian; Ren, Junli; Zhao, Cui; Kong, Weiqing; Dai, Qingqing; Chen, Qifeng; Liu, Chuanfu; Sun, Runcang

    2016-10-20

    Xylan-based temperature/pH sensitive hydrogels were prepared by the crosslinking copolymerization of xylan with N-isopropylacrylamide (NIPAm) and acrylic acid (AA) using N,Ń-methylenebis-acrylamide (MBA) as a cross-linker and 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator via ultraviolet irradiation. The influence of the NIPAm, AA and MBA amount on properties of xylan-based hydrogels was discussed. The morphology and interactions of hydrogels were characterized by SEM and FTIR. The lower critical solution temperature (LCST) of hydrogels was investigated by DSC. The results indicated that the LCST of hydrogels emerged at around 34°C and increased with increasing the AA content. The drug encapsulation efficiency of as-prepared hydrogels reached to 97.60% and the cumulative release rate of acetylsalicylic acid was 90.12% and 26.35% in the intestinal and gastric fluid, respectively. Xylan-based hydrogels were proved to be biocompatible with NIH3T3 cell by MTT assay and showed the promising application as drug carriers for the intestinal-targeted oral drug delivery. PMID:27474557

  2. Characterization of pH-sensitive Poly (acrylic acid-co-N-vinyl-2-pyrrolidone) Hydrogels Prepared by Gamma Radiation

    YANG Ming-cheng; HE Su-qin; LIU Wen-tao; SONG Hong-yan; ZHU Cheng-shen

    2007-01-01

    The pH-sensitive copolymer hydrogels were prepared with the monomers of acrylic acid and N-vinyl-2-pyrrolidone based on gamma radiation technique. The morphology of the hydrogels was monitored by using scanning electron microscope. The influence of absorbed dose, monomer compasition and concentration on the swelling ratio (SR) of the hydrogels were investigated in detail. The effect of pH and temperature of the swelling medium on the swelling behavior of the hydrogels were also examined. The results show that the SR of the copolymer hydrogels decreases with the monomer concentration and absorbed dose increasing. The copolymer hydrogels show a better pH-sensitive behavior. In alkaline solution, the SR of the hydrogels is much higher than in acid solution.

  3. A Hydrogel-Based Epirubicin Delivery System for Intravesical Chemotherapy

    Ching-Wen Liu

    2016-06-01

    Full Text Available This study aimed to examine the efficacy of epirubicin-loaded gelatin hydrogel (EPI-H in the treatment of superficial urothelium carcinoma. Hydrogel was prepared by Schiff base-crosslinking of gelatin with glutaraldehyde. EPI-H exhibited high entrapment efficiency (59.87% ± 0.51%. EPI-H also increased epirubicin accumulation in AY-27 cells when compared with the effect of aqueous solutions of epirubicin (EPI-AQ; respective epirubicin-positive cell counts were 69.0% ± 7.6% and 38.3% ± 5.8%. EPI-H also exhibited greater cytotoxicity against AY-27 cells than that of EPI-AQ; IC50 values were 13.1 ± 1.1 and 7.5 ± 0.3 μg/mL, respectively. Cystometrograms showed that EPI-H reduced peak micturition, threshold pressures, and micturition duration, and that it increased bladder compliance more so than EPI-AQ. EPI-H enhanced epirubicin penetration into basal cells of urothelium in vivo, whereas EPI-AQ did so only to the umbrella cells. EPI-H inhibited tumor growth upon intravesical instillation to tumor-bearing bladder of F344 rats, inducing higher levels of caspase-3 expression than that observed with EPI-AQ treatment; the number of caspase-3 positive cells in treated urothelium carcinoma was 13.9% ± 4.0% (EPI-AQ and 34.1% ± 1.0%, (EPI-H. EPI-H has value as an improved means to administer epirubicin in intravesical instillation treatments for bladder cancer.

  4. Economic benefit of a polyacrylate-based hydrogel compared to an amorphous hydrogel in wound bed preparation of venous leg ulcers

    Kaspar D

    2015-04-01

    Full Text Available Daniela Kaspar,1 Jörg Linder,1 Petra Zöllner,1 Ulrich Simon,2 Hans Smola1,31Medical Competence Centre, Paul Hartmann AG, Heidenheim, Germany; 2Scientific Computing Centre, Ulm University, Ulm, Germany; 3Department of Dermatology, University of Cologne, Cologne, GermanyObjective: To assess the cost-effectiveness of a polyacrylate (PA-based hydrogel compared to an amorphous hydrogel in wound bed preparation for venous leg ulcers.Method: A cost-effectiveness analysis was undertaken alongside a multicenter, randomized controlled trial performed in France. A total of 75 patients with venous leg ulcers extensively covered with fibrin and necrotic tissue were randomized to a PA-containing hydrogel or an amorphous hydrogel. Wounds were treated for 14 days and costs were estimated from the German payer's perspective. Medical costs included study treatment, wound treatment supply, and labor time. The clinical benefit was expressed as the number of patients with wounds >50% covered with granulation tissue within 14 days. The incremental cost-effectiveness ratio (ICER was expressed as the additional cost spent with >50% granulation tissue per day per patient within 14 days of leg ulcer care.Results: Because of individual pricing of wound dressings in hospitals, cost data were derived from the outpatient sector. A total of 33 patients were treated using the PA-based hydrogel and 37 patients using the amorphous hydrogel. The estimated total direct costs per patient and per 14 days of therapy were €306 for both treatment groups. However, with the PA-based hydrogel, 2.5 additional days with wounds covered >50% with granulation tissues were gained within 14 days of leg ulcer care compared to the comparator. The ICER was €0 per additional day spent with >50% granulation tissue.Conclusion: Although there were a greater number of dressing changes in the PA-based hydrogel treatment, the total treatment cost for 14 days of leg ulcer care was the same for both

  5. A high efficacy antimicrobial acrylate based hydrogels with incorporated copper for wound healing application

    Vuković, Jovana S.; Babić, Marija M.; Antić, Katarina M.; Miljković, Miona G.; Perić-Grujić, Aleksandra A.; Filipović, Jovanka M.; Tomić, Simonida Lj., E-mail: simonida@tmf.bg.ac.rs

    2015-08-15

    In this study, three series of hydrogels based on 2-hydroxyethyl acrylate and itaconic acid, unloaded, with incorporated copper(II) ions and reduced copper, were successfully prepared, characterized and evaluated as novel wound healing materials. Fourier transform infrared spectroscopy (FTIR) confirmed the expected structure of obtained hydrogels. Scanning electron microscopy (SEM) revealed porous morphology of unloaded hydrogels, and the morphological modifications in case of loaded hydrogels. Thermal characteristics were examined by differential scanning calorimetry (DSC) and the glass transition temperatures were observed in range of 12–50 °C. Swelling study was conducted in wide range of pHs at 37 °C, confirming pH sensitive behaviour for all three series of hydrogels. The in vitro copper release was investigated and the experimental data were analysed using several models in order to elucidate the transport mechanism. The antimicrobial assay revealed excellent antimicrobial activity, over 99% against Escherichia coli, Staphylococcus aureus and Candida albicans, as well as good correlation with the copper release experiments. In accordance with potential application, water vapour transmission rate, oxygen penetration, dispersion characteristics, fluid retention were observed and the suitability of the hydrogels for wound healing application was discussed. - Graphical abstract: Display Omitted - Highlights: • Design and evaluation of novel pH responsive hydrogel series. • Structural, morphological, thermal characterization and controlled copper release. • Antibacterial activity against Escherichia coli and Staphylococcus aureus over 99%. • Antifungal activity against Candida albicans over 99%. • In vitro evaluation studies revealed great potential for wound healing application.

  6. A drug delivery hydrogel system based on activin B for Parkinson's disease.

    Li, Juan; Darabi, Mohammadali; Gu, Jingjing; Shi, Junbin; Xue, Jinhua; Huang, Lu; Liu, Yutong; Zhang, Lei; Liu, N; Zhong, Wen; Zhang, Lin; Xing, Malcolm; Zhang, Lu

    2016-09-01

    Parkinson's disease (PD) is one of the most common neurodegenerative diseases. Activins are members of the superfamily of transforming growth factors and have many potential neuroprotective effects. Herein, at the first place, we verified activin B's neuroprotective role in a PD model, and revealed that activin B's fast release has limited function in the PD therapy. To this end, we developed a multi-functional crosslinker based thermosensitive injectable hydrogels to deliver activin B, and stereotactically injected the activin B-loaded hydrogel into the striatum of a mouse model of PD. The histological evaluation showed that activin B can be detected even 5 weeks post-surgery in PD mice implanted with activin B-loaded hydrogels, and activin B-loaded hydrogels can significantly increase the density of tyrosine hydroxylase positive (TH(+)) nerve fibers and reduce inflammatory responses. The behavioral evaluation demonstrated that activin B-loaded hydrogels significantly improved the performance of the mice in the PD model. Meanwhile, we found that hydrogels can slightly induce the activation of microglia cells and astrocytes, while cannot induce apoptosis in the striatum. Overall, our data demonstrated that the developed activin B-loaded hydrogels provide sustained release of activin B for over 5 weeks and contribute to substantial cellular protection and behavioral improvement, suggesting their potential as a therapeutic strategy for PD. PMID:27322960

  7. A high efficacy antimicrobial acrylate based hydrogels with incorporated copper for wound healing application

    In this study, three series of hydrogels based on 2-hydroxyethyl acrylate and itaconic acid, unloaded, with incorporated copper(II) ions and reduced copper, were successfully prepared, characterized and evaluated as novel wound healing materials. Fourier transform infrared spectroscopy (FTIR) confirmed the expected structure of obtained hydrogels. Scanning electron microscopy (SEM) revealed porous morphology of unloaded hydrogels, and the morphological modifications in case of loaded hydrogels. Thermal characteristics were examined by differential scanning calorimetry (DSC) and the glass transition temperatures were observed in range of 12–50 °C. Swelling study was conducted in wide range of pHs at 37 °C, confirming pH sensitive behaviour for all three series of hydrogels. The in vitro copper release was investigated and the experimental data were analysed using several models in order to elucidate the transport mechanism. The antimicrobial assay revealed excellent antimicrobial activity, over 99% against Escherichia coli, Staphylococcus aureus and Candida albicans, as well as good correlation with the copper release experiments. In accordance with potential application, water vapour transmission rate, oxygen penetration, dispersion characteristics, fluid retention were observed and the suitability of the hydrogels for wound healing application was discussed. - Graphical abstract: Display Omitted - Highlights: • Design and evaluation of novel pH responsive hydrogel series. • Structural, morphological, thermal characterization and controlled copper release. • Antibacterial activity against Escherichia coli and Staphylococcus aureus over 99%. • Antifungal activity against Candida albicans over 99%. • In vitro evaluation studies revealed great potential for wound healing application

  8. Hydrogel-Based Platforms for the Regeneration of Osteochondral Tissue and Intervertebral Disc

    Luigi Ambrosio

    2012-09-01

    Full Text Available Hydrogels currently represent a powerful solution to promote the regeneration of soft and hard tissues. Primarily, they assure efficient bio-molecular interactions with cells, also regulating their basic functions, guiding the spatially and temporally complex multi-cellular processes of tissue formation, and ultimately facilitating the restoration of structure and function of damaged or dysfunctional tissues. In order to overcome basic drawbacks of traditional synthesized hydrogels, many recent strategies have been implemented to realize multi-component hydrogels based on natural and/or synthetic materials with tailored chemistries and different degradation kinetics. Here, a critical review of main strategies has been proposed based on the use of hydrogels-based devices for the regeneration of complex tissues, i.e., osteo-chondral tissues and intervertebral disc.

  9. Infrared perfect absorber based on nanowire metamaterial cavities

    He, Yingran; Jiao, Xiangyang; He, Sailing; Gao, Jie; Yang, Xiaodong

    2012-01-01

    An infrared perfect absorber based on gold nanowire metamaterial cavities array on a gold ground plane is designed. The metamaterial made of gold nanowires embedded in alumina host exhibits an effective permittivity with strong anisotropy, which supports cavity resonant modes of both electric dipole and magnetic dipole. The impedance of the cavity modes matches the incident plane wave in free space, leading to nearly perfect light absorption. The incident optical energy is efficiently converted into heat so that the local temperature of the absorber will increase. Simulation results show that the designed metamaterial absorber is polarization-insensitive and nearly omnidirectional for the incident angle.

  10. The design of conductimetric biosensors based on environmentally responsive hydrogels

    Lesho, Matthew Jerome

    Responsive hydrogels are hydrophilic, crosslinked polymers that undergo large changes in hydration in response to environmental stimuli such as changing temperature, pH, electric field, and ionic strength. Accompanying this change in hydration are changes in material properties of the hydrogel, which has led to their application in controlled drug delivery, separations, and as superabsorbants. The present study investigated the hydration-dependent electrical conductivity of a pH-responsive hydrogel and its application as a transduction layer for microfabricated, conductimetric pH and glucose sensors. The investigation was divided into four parts. First, the material properties of a copolymer of 2-hydroxyethyl methacrylate (HEMA) and N,N-dimethylaminoethyl methacrylate (DMA), crosslinked with tetraethylene glycol diacrylate (TEGDA), were examined with respect to its ability to detect changes in pH. It was determined that the electrical conductivity of the hydrogel was a sensitive measure of hydration and was a function of pH, hydrogel composition, buffer concentration, buffer identity, and ionic strength. Second, a method was developed for reproducibly depositing thin (1-25 mum), adherent hydrogel layers by photolithographic patterning techniques. Third, sensors were developed that utilized planar interdigitated electrode arrays to probe the change in electrical conductivity of hydrogel membranes. The sensitivity, response time, operating range and lifetime of pH sensors were functions of pH, hydrogel composition, buffer concentration, buffer identity, and ionic strength. Glucose sensors were developed by incorporating glucose oxidase into the pH-responsive hydrogel and measuring the decrease in pH that accompanies the enzymatic generation of protons. Finally, a model was formulated to relate the measured sensor responses to the measured material properties. Information from model simulations was incorporated into the design of next-generation sensors.

  11. Fabrication of Amino Acid Based Silver Nanocomposite Hydrogels from PVA-Poly(Acrylamide-co-Acryloyl phenylalanine) and Their Antimicrobial Studies

    Cha, Hyeongrae; Babu, V. Ramesh; Rao, K. S. V. Krishna; Kim, Yonghyun; Mei, Surong; Lee, Yongill; Joo, Woo Hong [Changwon National Univ., Changwon (Korea, Republic of)

    2012-10-15

    New silver nanoparticle (AgNP)-loaded amino acid based hydrogels were synthesized successfully from poly (vinyl alcohol) (PVA) and poly(acryl amide-co-acryloyl phenyl alanine) (PAA) by redox polymerization. The formation of AgNP in hydrogels was confirmed by using a UV-Vis spectrophotometer and XRD. The structure and morphology of silver nanocomposite hydrogels were studied by using a scanning electron microscopy (SEM), which demonstrated scattered nanoparticles, ca. 10-20 nm. Thermogravimetric analysis revealed large differences of weight loss (i. e., 48%) between the prestine hydrogel and silver nanocomposite. The antibacterial studies of AgNP-loaded PAA (Ag-PAA) hydrogels was evaluated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. These Ag-PAA hydrogels showed significant activities against all the test bacteria. Newly developed hydrogels could be used for medical applications, such as artificial burn dressings.

  12. Facile synthesis of magnetic-/pH-responsive hydrogel beads based on Fe3O4 nanoparticles and chitosan hydrogel as MTX carriers for controlled drug release.

    Wu, Juan; Jiang, Wei; Tian, Renbing; Shen, Yewen; Jiang, Wei

    2016-10-01

    In the present study, methotrexate (MTX)-encapsulated magnetic-/pH-responsive hydrogel beads based on Fe3O4 nanoparticles and chitosan were successfully prepared through a one-step gelation process, which is a very facile, economic and environmentally friendly route. The developed hydrogel beads exhibited homogeneous porous structure and super-paramagnetic responsibility. MTX can be successfully encapsulated into magnetic chitosan hydrogel beads, and the drug encapsulation efficiency (%) and encapsulation content (%) were 93.8 and 6.28%, respectively. In addition, the drug release studies in vitro indicated that the MTX-encapsulated magnetic chitosan hydrogel beads had excellent pH-sensitivity, 90.6% MTX was released from the magnetic chitosan hydrogel beads within 48 h at pH 4.0. WST-1 assays in human liver hepatocellular carcinoma cells (HepG2) demonstrated that the MTX-encapsulated magnetic chitosan hydrogel beads had good cytocompatibility and high anti-tumor activity. Therefore, our results revealed that the MTX-encapsulated magnetic chitosan hydrogel beads would be a competitive candidate for controlled drug release in the area of targeted cancer therapy in the near future. PMID:27464586

  13. An in situ forming biodegradable hydrogel-based embolic agent for interventional therapies.

    Weng, Lihui; Rostambeigi, Nassir; Zantek, Nicole D; Rostamzadeh, Parinaz; Bravo, Mike; Carey, John; Golzarian, Jafar

    2013-09-01

    We present here the characteristics of an in situ forming hydrogel prepared from carboxymethyl chitosan and oxidized carboxymethyl cellulose for interventional therapies. Gelation, owing to the formation of Schiff bases, occurred both with and without the presence of a radiographic contrast agent. The hydrogel exhibited a highly porous internal structure (pore diameter 17±4 μm), no cytotoxicity to human umbilical vein endothelial cells, hemocompatibility with human blood, and degradability in lysozyme solutions. Drug release from hydrogels loaded with a sclerosant, tetracycline, was measured at pH 7.4, 6 and 2 at 37°C. The results showed that tetracycline was more stable under acidic conditions, with a lower release rate observed at pH 6. An anticancer drug, doxorubicin, was loaded into the hydrogel and a cumulative release of 30% was observed over 78 h in phosphate-buffered saline at 37°C. Injection of the hydrogel precursor through a 5-F catheter into a fusiform aneurysm model was feasible, leading to complete filling of the aneurysmal sac, which was visualized by fluoroscopy. The levels of occlusion by hydrogel precursors (1.8% and 2.1%) and calibrated microspheres (100-300 μm) in a rabbit renal model were compared. Embolization with hydrogel precursors was performed without clogging and the hydrogel achieved effective occlusion in more distal arteries than calibrated microspheres. In conclusion, this hydrogel possesses promising characteristics potentially beneficial for a wide range of vascular intervention procedures that involve embolization and drug delivery. PMID:23791672

  14. Design of integration-ready metasurface-based infrared absorbers

    Ogando, Karim, E-mail: karim@cab.cnea.gov.ar; Pastoriza, Hernán [Laboratorio de Bajas Temperaturas, Instituto Balseiro and Centro Atómico Bariloche, Bariloche 8400 (Argentina)

    2015-07-28

    We introduce an integration ready design of metamaterial infrared absorber, highly compatible with many kinds of fabrication processes. We present the results of an exhaustive experimental characterization, including an analysis of the effects of single meta-atom geometrical parameters and collective arrangement. We confront the results with the theoretical interpretations proposed in the literature. Based on the results, we develop a set of practical design rules for metamaterial absorbers in the infrared region.

  15. Design of integration-ready metasurface-based infrared absorbers

    We introduce an integration ready design of metamaterial infrared absorber, highly compatible with many kinds of fabrication processes. We present the results of an exhaustive experimental characterization, including an analysis of the effects of single meta-atom geometrical parameters and collective arrangement. We confront the results with the theoretical interpretations proposed in the literature. Based on the results, we develop a set of practical design rules for metamaterial absorbers in the infrared region

  16. Elastin based cell-laden injectable hydrogels with tunable gelation, mechanical and biodegradation properties.

    Fathi, Ali; Mithieux, Suzanne M; Wei, Hua; Chrzanowski, Wojciech; Valtchev, Peter; Weiss, Anthony S; Dehghani, Fariba

    2014-07-01

    Injectable hydrogels made from extracellular matrix proteins such as elastin show great promise for various biomedical applications. Use of cytotoxic reagents, fixed gelling behavior, and lack of mechanical strength in these hydrogels are the main associated drawbacks. The aim of this study was to develop highly cytocompatible and injectable elastin-based hydrogels with alterable gelation characteristics, favorable mechanical properties and structural stability for load bearing applications. A thermoresponsive copolymer, poly(N-isopropylacrylamide-co-polylactide-2-hydroxyethyl methacrylate-co-oligo(ethylene glycol)monomethyl ether methacrylate, was functionalized with succinimide ester groups by incorporating N-acryloxysuccinimide monomer. These ester groups were exploited to covalently bond this polymer, denoted as PNPHO, to different proteins with primary amine groups such as α-elastin in aqueous media. The incorporation of elastin through covalent bond formation with PNPHO promotes the structural stability, mechanical properties and live cell proliferation within the structure of hydrogels. Our results demonstrated that elastin-co-PNPHO solutions were injectable through fine gauge needles and converted to hydrogels in situ at 37 °C in the absence of any crosslinking reagent. By altering PNPHO content, the gelling time of these hydrogels can be finely tuned within the range of 2-15 min to ensure compatibility with surgical requirements. In addition, these hydrogels exhibited compression moduli in the range of 40-145 kPa, which are substantially higher than those of previously developed elastin-based hydrogels. These hydrogels were highly stable in the physiological environment with the evidence of 10 wt% mass loss in 30 days of incubation in a simulated environment. This class of hydrogels is in vivo bioabsorbable due to the gradual increase of the lower critical solution temperature of the copolymer to above 37 °C due to the cleavage of polylactide from

  17. Light-guiding hydrogels for cell-based sensing and optogenetic synthesis in vivo

    Choi, Myunghwan; Choi, Jin Woo; Kim, Seonghoon; Nizamoglu, Sedat; Hahn, Sei Kwang; Yun, Seok Hyun

    2013-12-01

    Polymer hydrogels are widely used as cell scaffolds for biomedical applications. Although the biochemical and biophysical properties of hydrogels have been investigated extensively, little attention has been paid to their potential photonic functionalities. Here, we report cell-integrated polyethylene glycol-based hydrogels for in vivo optical-sensing and therapy applications. Hydrogel patches containing cells were implanted in awake, freely moving mice for several days and shown to offer long-term transparency, biocompatibility, cell viability and light-guiding properties (loss of improved glucose homeostasis. Furthermore, real-time optical readout of encapsulated heat-shock-protein-coupled fluorescent reporter cells made it possible to measure the nanotoxicity of cadmium-based bare and shelled quantum dots (CdTe; CdSe/ZnS) in vivo.

  18. Experiments with hydrogel pearls

    Pavlin, Jerneja

    2015-01-01

    Hydrogels are very attractive materials since they can absorb large quantities of water. They also have very interesting optical properties which can be easily shown. The experiments with hydrogel pearls related to the absorption of water, density, optical properties and influence of pH are presented in the contribution.

  19. Potential of Cellulose-Based Superabsorbent Hydrogels as Water Reservoir in Agriculture

    Demitri, C.; F. Scalera; M. Madaghiele; A. Sannino; Maffezzoli, A.

    2013-01-01

    The present work deals with the development of a biodegradable superabsorbent hydrogel, based on cellulose derivatives, for the optimization of water resources in agriculture, horticulture and, more in general, for instilling a wiser and savvier approach to water consumption. The sorption capability of the proposed hydrogel was firstly assessed, with specific regard to two variables that might play a key role in the soil environment, that is, ionic strength and pH. Moreover, a preliminary eva...

  20. Biocompatibility Evaluation of a New Hydrogel Dressing Based on Polyvinylpyrrolidone/Polyethylene Glycol

    Esmaeil Biazar; Ziba Roveimiab; Gholamreza Shahhosseini; Mohammadreza Khataminezhad; Mandana Zafari; Ali Majdi

    2012-01-01

    The composition of the dressings is based on polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and agar. The electron beam irradiation technique has been used to prepare hydrogel wound dressings. The in vitro biocompatibility of the hydrogel was investigated by check samples (hydrocolloid Comfeel), antibacterial test (Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia Coli k12), anti fungal test (Candida Albicans) and cytotoxicity test (Fibroblast L929...

  1. New starch-based thermoplastic hydrogels for use as bone cements or drug-delivery carriers

    C.S. Pereira; Vásquez, Blanca; A.M. Cunha; Reis, R.L.; San Román, J.

    1998-01-01

    The development of new biodegradable hydrogels, based on corn starch/cellulose acetate blends, produced by free-radical polymerization with methyl methacrylate monomer (MMA) and/or an acrylic acid monomer (AA), is reported. The polymerization was initiated by a redox system consisting of a benzoyl peroxide and 4-dimethlyaminobenzyl alcohol at low temperature. These hydrogels may constitute an alternative to the materials currently used as bone cements or drug-delivery carriers. Swelling studi...

  2. Gamma ray-induced synthesis of hyaluronic acid/chondroitin sulfate-based hydrogels for biomedical applications

    Hyaluronic acid (HA)/chondroitin sulfate (CS)/poly(acrylic acid) (PAAc) hydrogel systems were synthesized by gamma-ray irradiation without the use of additional initiators or crosslinking agents to achieve a biocompatible hydrogel system for skin tissue engineering. HA and CS derivatives with polymerizable residues were synthesized. Then, the hydrogels composed of glycosaminoglycans, HA, CS, and a synthetic ionic polymer, PAAc, were prepared using gamma-ray irradiation through simultaneous free radical copolymerization and crosslinking. The physicochemical properties of the HA/CS/PAAc hydrogels having various compositions were investigated to evaluate their feasibility as artificial skin substitutes. The gel fractions of the HA/CS/PAAc hydrogels increased in absorbed doses up to 15 kGy, and they exhibited 91–93% gel fractions under 15 kGy radiation. All of the HA/CS/PAAc hydrogels exhibited relatively high water contents of over 90% and reached an equilibrium swelling state within 24 h. The enzymatic degradation kinetics of the HA/CS/PAAc hydrogels depended on both the concentration of the hyaluronidase solution and the ratio of HA/CS/PAAc. The in vitro drug release profiles of the HA/CS/PAAc hydrogels were significantly influenced by the interaction between the ionic groups in the hydrogels and the ionic drug molecules as well as the swelling of the hydrogels. From the cytotoxicity results of human keratinocyte (HaCaT) cells cultured with extracts of the HA/CS/PAAc hydrogels, all of the HA/CS/PAAc hydrogel samples tested showed relatively high cell viabilities of more than 82%, and did not induce any significant adverse effects on cell viability. - Highlights: • HA/CS/PAAc hydrogels were synthesized by gamma-ray irradiation. • HA/CS/PAAc hydrogels exhibited 91–93% gel fractions under 15 kGy radiation. • All of the HA/CS/PAAc hydrogels exhibited high water contents of over 90%. • The hydrogel samples showed relatively high cell viabilities of more than

  3. Metamaterial-based perfect absorber: polarization insensitivity and broadband

    We report the design and simulation of a microwave metamaterials-based perfect absorber using a simple and highly symmetric structure. The basic structure consists of three functional layers: the middle is a dielectric, the back is a metallic plane and the front is a ring of metal. The influence of structural parameters on the absorbance and absorption frequency were investigated. The results show an exceptional absorption performance of near unity around 16 GHz. In addition, the absorption is insensitive to the polarization of the incident beam due to the highly symmetric structure. Finally, four and nine rings with different sizes are arranged appropriately in a unit cell in order to construct a broadband absorber. A polarization-insensitive absorbance of above 90% is achieved over a bandwidth of 15%. (papers)

  4. Dynamics in poly vinyl alcohol (PVA) based hydrogel: Neutron scattering study

    Results of quasielastic neutron scattering measurements carried out on Poly Vinyl Alcohol (PVA) based hydrogels are reported here. PVA hydrogels are formed using Borax as a cross-linking agent in D2O solvent. This synthetic polymer can be used for obtaining the hydrogels with potential use in the field of biomaterials. The aim of this paper is to study the dynamics of polymer chain in the hydrogel since it is known that polymer mobility influences the kinetics of loading and release of drugs. It is found that the dynamics of hydrogen atoms in the polymer chain could be described by a model where the diffusion of hydrogen atoms is limited within a spherical volume of radius 3.3 Å. Average diffusivity estimated from the behavior of quasielastic width is found to be 1.2 × 10−5 cm2/sec

  5. Crosslinked hydrogels based on biological macromolecules with potential use in skin tissue engineering.

    Vulpe, Raluca; Popa, Marcel; Picton, Luc; Balan, Vera; Dulong, Virginie; Butnaru, Maria; Verestiuc, Liliana

    2016-03-01

    Zero-length crosslinked hydrogels have been synthesized by covalent linking of three natural polymers (collagen, hyaluronic acid and sericin), in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. The hydrogels have been investigated by FT-IR spectroscopy, microcalorimetry, in vitro swelling, enzymatic degradation, and in vitro cell viability studies. The obtained crosslinked hydrogels showed a macroporous structure, high swelling degree and in vitro enzymatic resistance compared to uncrosslinked collagen. The in vitro cell viability studies performed on normal human dermal fibroblasts assessed the sericin proliferation properties indicating a potential use of the hydrogels based on collagen, hyaluronic acid and sericin in skin tissue engineering. PMID:26704998

  6. Dynamics in poly vinyl alcohol (PVA) based hydrogel: Neutron scattering study

    Prabhudesai, S. A., E-mail: swapnil@barc.gov.in; Mitra, S.; Mukhopadhyay, R. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 40085 (India); Lawrence, Mathias B. [Department of Physics, St. Xavier’s College, Mapusa, Goa 403507 (India); Desa, J. A. E. [Department of Physics, Goa University, Taleigao Plateau, Goa 403206 (India)

    2015-06-24

    Results of quasielastic neutron scattering measurements carried out on Poly Vinyl Alcohol (PVA) based hydrogels are reported here. PVA hydrogels are formed using Borax as a cross-linking agent in D{sub 2}O solvent. This synthetic polymer can be used for obtaining the hydrogels with potential use in the field of biomaterials. The aim of this paper is to study the dynamics of polymer chain in the hydrogel since it is known that polymer mobility influences the kinetics of loading and release of drugs. It is found that the dynamics of hydrogen atoms in the polymer chain could be described by a model where the diffusion of hydrogen atoms is limited within a spherical volume of radius 3.3 Å. Average diffusivity estimated from the behavior of quasielastic width is found to be 1.2 × 10{sup −5} cm{sup 2}/sec.

  7. Self-assembled peptide-based hydrogels as scaffolds for anchorage-dependent cells.

    Zhou, Mi; Smith, Andrew M; Das, Apurba K; Hodson, Nigel W; Collins, Richard F; Ulijn, Rein V; Gough, Julie E

    2009-05-01

    We report here the design of a biomimetic nanofibrous hydrogel as a 3D-scaffold for anchorage-dependent cells. The peptide-based bioactive hydrogel is formed through molecular self-assembly and the building blocks are a mixture of two aromatic short peptide derivatives: Fmoc-FF (Fluorenylmethoxycarbonyl-diphenylalanine) and Fmoc-RGD (arginine-glycine-aspartate) as the simplest self-assembling moieties reported so far for the construction of small-molecule-based bioactive hydrogels. This hydrogel provides a highly hydrated, stiff and nanofibrous hydrogel network that uniquely presents bioactive ligands at the fibre surface; therefore it mimics certain essential features of the extracellular matrix. The RGD sequence as part of the Fmoc-RGD building block plays a dual role of a structural component and a biological ligand. Spectroscopic and imaging analysis using CD, FTIR, fluorescence, TEM and AFM confirmed that FF and RGD peptide sequences self-assemble into beta-sheets interlocked by pi-pi stacking of the Fmoc groups. This generates the cylindrical nanofibres interwoven within the hydrogel with the presence of RGDs in tunable densities on the fibre surfaces. This rapid gelling material was observed to promote adhesion of encapsulated dermal fibroblasts through specific RGD-integrin binding, with subsequent cell spreading and proliferation; therefore it may offer an economical model scaffold to 3D-culture other anchorage-dependent cells for in-vitro tissue regeneration. PMID:19201459

  8. Nanocomposite hydrogels based on water soluble polymer and montmorillonite-Na+

    Fatiha Reguieg

    2015-09-01

    Full Text Available A series of composites hydrogels based on Poly (1,3-dioxolane (PDXL,water soluble polymer, were synthesized directly in water by free-radical homopolymerization of a,w-methacryloyloxy PDXL macromonomers using hydrophilic sodium Montmorillonite clay: Maghnite-Na+ (Mag-Na+ and potassium persulfate as an initiator. These materials were characterized by X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FT-IR, thermogravimetric analysis (ATG and their equilibrium swelling behavior in water and were compared with those of pure hydrogels prepared without Mag-Na+. X-ray diffraction and Infrared spectroscopy confirmed insertion of clay into polymer. The thermal decomposition temperature of the hydrogels based on maghnite-Na+ was found to be higher than of pure hydrogels. At the same time, the influence of the macromonomer precursor molar mass value, its concentration and the quantities of Mag-Na+, on the values of the volume degree of equilibrium swelling were studied. The results showed that the volume degree of equilibrium swelling was investigated as a function of the clay content. However, whether the concentration of macromonomer precursor increased, the volume or weight degree of equilibrium swelling of hydrogels all decreased. The addition of Mag-Na+ particles changed the crosslinking density of hydrogels.

  9. Protein composition alters in vivo resorption of PEG-based hydrogels as monitored by contrast-enhanced MRI.

    Berdichevski, Alexandra; Shachaf, Yonatan; Wechsler, Roni; Seliktar, Dror

    2015-02-01

    We report on the use of magnetic resonance imaging (MRI)-based non-invasive monitoring to document the role of protein adjuvants in hydrogel implant integration in vivo. Polyethylene glycol (PEG) hydrogels were formed with different protein constituents, including albumin, fibrinogen and gelatin. The hydrogels were designed to exhibit similar material properties, including modulus, swelling and hydrolytic degradation kinetics. The in vivo resorption properties of these PEG-based hydrogels, which contained a tethered gadolinium contrast agent, were characterized by MRI and histology, and compared to their in vitro characteristics. MRI data revealed that PEG-Albumin implants remained completely intact throughout the experiments, PEG-Fibrinogen implants lost about 10% of their volume and PEG-Gelatin implants underwent prominent swelling and returned to their initial volume by day 25. Fully synthetic PEG-diacrylate (PEG-DA) control hydrogels lost about half of their volume after 25 days in vivo. Transverse MRI cross-sections of the implants revealed distinct mechanisms of the hydrogel's biodegradation: PEG-Fibrinogen and PEG-Albumin underwent surface erosion, whereas PEG-Gelatin and PEG-DA hydrogels mainly underwent bulk degradation. Histological findings substantiated the MRI data and demonstrated significant cellular response towards PEG-DA and PEG-Gelatin scaffolds with relatively low reaction towards PEG-Fibrinogen and PEG-Albumin hydrogels. These findings demonstrate that PEG-protein hydrogels can degrade via a different mechanism than PEG hydrogels, and that this difference can be linked to a reduced foreign body response. PMID:25542788

  10. A Dendritic Thioester Hydrogel Based on Thiol-Thioester Exchange as a Dissolvable Sealant System for Wound Closure

    Ghobril, Cynthia; Charoen, Kristie; Rodriguez, Edward K.; Nazarian, Ara; Grinstaff, Mark W.

    2013-01-01

    A dissolvable dendritic thioester hydrogel based on thiol-thioester exchange for wound closure is reported. The hydrogel sealant adheres strongly to tissues, closes an ex vivo vein puncture, and withstands high pressures placed on a wound. The hydrogel sealant can be completely washed off upon exposure to thiolates based on thiol-thioester exchange and allow gradual wound re-exposure during definitive surgical care.

  11. Novel silicone hydrogel based on PDMS and PEGMA for contact lens application.

    Lin, Chien-Hong; Yeh, Yi-Hsing; Lin, Wen-Ching; Yang, Ming-Chien

    2014-11-01

    A silicone-based hydrogel was synthesized from poly(dimethylsiloxane) dialkanol (PDMS), isophorone diisocyanate (IPDI), 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEGMA). The hydrophilicity of the resulting block copolymer was adjustable by manipulating the ratio of PDMS and PEGMA. The results showed that higher PEGMA content led to a lower water contact angle, higher water content, lower elastic modulus and higher glucose permeability. At a PEGMA content of 20%, the protein adsorption decreased to 23% and 18% for lysozyme and human serum albumin (HSA), respectively, of those of the control (PDMS-PU). This indicated that the PDMS-PU-PEGMA hydrogels exhibited an ability to resist protein adsorption. The oxygen permeability (Dk) was 92 barrers for the hydrogel with 20% PEGMA. Furthermore, these hydrogels were non-cytotoxic according to an in vitro L929 fibroblast assay. Overall, the results demonstrated that the PDMS-PU-PEGMA hydrogels exhibited not only relatively high oxygen permeability and relative optical transparency, but also hydrophilicity and anti-protein adsorption; therefore, they would be applicable as a contact lens material. Furthermore, this study demonstrated a new approach to controlling the performance of silicone hydrogels. PMID:25465755

  12. SYNTHESIS AND CHARACTERIZATION OF AMPHOTERIC HYDROGELS BASED ON N-CARBOXYETHYLCHITOSAN

    Yan Li; Qiang Yin; Ming-yu Deng; Jun-jie Cui; Bo Jiang

    2009-01-01

    New amphoteric hydrogels based on carboxyethylchitosans (CECH) with various degrees of substitution (DS) were prepared using different amounts of epichlorohydrin (ECH) as the crosslinking agent. The equilibrium swelling ratio (SW) was determined as functions of pH and salt concentration. The hydrogels show typical amphoteric character responding to pH change of the external medium. At isoelectric point (IEP), the hydrogels shrink. The DS value has important effect on the swelling properties of the hydrogels. When the DS of N-carboxyethylchitosan increases from 0.32 to 0.72, the equilibrium swelling ratio (SW) of the hydrogel changes from 76 to 290 at pH 7.3 and from 117 to 499 at pH 11.3. A marked volume decrease was observed in hydrogels with increasing salt concentration in the surrounding solution. The viscoelastic properties of the hydrogeis were studied by oscillatory shear measurements under small-deformation conditions. The elastic modulus G' of all the samples has no dependence on frequency and is one order of magnitude larger than the loss modulus G", corresponding to a strong gel behavior.

  13. Gelatin-Methacryloyl Hydrogels: Towards Biofabrication-Based Tissue Repair.

    Klotz, Barbara J; Gawlitta, Debby; Rosenberg, Antoine J W P; Malda, Jos; Melchels, Ferry P W

    2016-05-01

    Research over the past decade on the cell-biomaterial interface has shifted to the third dimension. Besides mimicking the native extracellular environment by 3D cell culture, hydrogels offer the possibility to generate well-defined 3D biofabricated tissue analogs. In this context, gelatin-methacryloyl (gelMA) hydrogels have recently gained increased attention. This interest is sparked by the combination of the inherent bioactivity of gelatin and the physicochemical tailorability of photo-crosslinkable hydrogels. GelMA is a versatile matrix that can be used to engineer tissue analogs ranging from vasculature to cartilage and bone. Convergence of biological and biofabrication approaches is necessary to progress from merely proving cell functionality or construct shape fidelity towards regenerating tissues. GelMA has a critical pioneering role in this process and could be used to accelerate the development of clinically relevant applications. PMID:26867787

  14. Characterization of a Functional Hydrogel Layer on a Silicon-Based Grating Waveguide for a Biochemical Sensor

    Hong, Yoo-Seung; Kim, Jongseong; Sung, Hyuk-Kee

    2016-01-01

    We numerically demonstrated the characteristics of a functional hydrogel layer on a silicon-based grating waveguide for a simple, cost-effective refractive index (RI) biochemical sensor. The RI of the functional hydrogel layer changes when a specific biochemical interaction occurs between the hydrogel-linked receptors and injected ligand molecules. The transmission spectral profile of the grating waveguide shifts depends on the amount of RI change caused by the functional layer. Our character...

  15. Chitosan-based hydrogel for dye removal from aqueous solutions: Optimization of the preparation procedure

    Gioiella, Lucia; Altobelli, Rosaria; de Luna, Martina Salzano; Filippone, Giovanni

    2016-05-01

    The efficacy of chitosan-based hydrogels in the removal of dyes from aqueous solutions has been investigated as a function of different parameters. Hydrogels were obtained by gelation of chitosan with a non-toxic gelling agent based on an aqueous basic solution. The preparation procedure has been optimized in terms of chitosan concentration in the starting solution, gelling agent concentration and chitosan-to-gelling agent ratio. The goal is to properly select the material- and process-related parameters in order to optimize the performances of the chitosan-based dye adsorbent. First, the influence of such factors on the gelling process has been studied from a kinetic point of view. Then, the effects on the adsorption capacity and kinetics of the chitosan hydrogels obtained in different conditions have been investigated. A common food dye (Indigo Carmine) has been used for this purpose. Noticeably, although the disk-shaped hydrogels are in the bulk form, their adsorption capacity is comparable to that reported in the literature for films and beads. In addition, the bulk samples can be easily separated from the liquid phase after the adsorption process, which is highly attractive from a practical point of view. Compression tests reveal that the samples do not breakup even after relatively large compressive strains. The obtained results suggest that the fine tuning of the process parameters allows the production of mechanical resistant and highly adsorbing chitosan-based hydrogels.

  16. Polyethylene glycol (PEG)-Poly(N-isopropylacrylamide) (PNIPAAm) based thermosensitive injectable hydrogels for biomedical applications.

    Alexander, Amit; Ajazuddin; Khan, Junaid; Saraf, Swarnlata; Saraf, Shailendra

    2014-11-01

    Protein and peptide delivery by the use of stimuli triggered polymers remains to be the area of interest among the scientist and innovators. In-situ forming gel for the parenteral route in the form of hydrogel and implants are being utilized for various biomedical applications. The formulation of gel depends upon factors such as temperature modulation, pH changes, the presence of ions and ultra-violet irradiation, from which drug is released in a sustained and controlled manner. Among various stimuli triggered factors, thermoresponsive is the most potential one for the delivery of protein and peptides. Poly(ethylene glycol) (PEG) based copolymers play a crucial role as a biomedical material for biomedical applications, because of its biocompatibility, biodegradability, thermosensitivity and easy controlled characters. This review, stresses on the physicochemical property, stability and compositions prospects of smart thermoresponsive polymer specifically, PEG/Poly(N-isopropylacrylamide) (PNIPAAm) based thermoresponsive injectable hydrogels, recently utilized for biomedical applications. PEG-PNIPAAm based hydrogel exhibits good gelling mechanical strength and minimizes the initial burst effect of the drug. In addition, upon changing the composition and proportion of the copolymer molecular weight and ratio, the gelling time can be reduced to a great extent providing better sol-gel transition. The hydrogel formed by the same is able to release the drug over a long duration of time, meanwhile is also biocompatible and biodegradable. Manuscript will give the new researchers an idea about the potential and benefits of PNIPAAm based thermoresponsive hydrogels for the biomedical application. PMID:25092423

  17. Epidermal growth factor loaded heparin-based hydrogel sheet for skin wound healing.

    Goh, MeeiChyn; Hwang, Youngmin; Tae, Giyoong

    2016-08-20

    A heparin-based hydrogel sheet composed of thiolated heparin and diacrylated poly (ethylene glycol) was prepared via photo polymerization and human epidermal growth factor (hEGF) were loaded into it for the purpose of wound healing. It showed a sustained release profile of hEGF in vitro. In order to evaluate its function on wound healing in vivo, full thickness wounds were created on the dorsal surface of mice. Application of hEGF loaded heparin-based hydrogel sheet accelerated the wound closure compared to the non-treated control group, hEGF solution, and hEGF loaded PEG hydrogel sheet. Histological and immunohistological examinations also demonstrated an advanced granulation tissue formation, capillary formation, and epithelialization in wounds treated by hEGF loaded heparin-based hydrogel compared to other groups, and no biocompatibility issue was observed. In conclusion, the delivery of hEGF using the heparin-based hydrogel could accelerate the skin wound healing process. PMID:27178931

  18. Investigation on a hydrogel based passive thermal management system for lithium ion batteries

    An appropriate operating temperature range is critical for the overall performance and safety of lithium-ion batteries. Considering the excellent performance of water in heat dissipation in industrial applications, in this paper, a water based PAAS (sodium polyacrylate) hydrogel thermal management system has been proposed to handle the heat surge during the operation of a Li-ion battery pack. A thermal model with constant heat generation rate is employed to simulate the high current discharge process (i.e., 10 A) on a 4S1P battery pack, which shows a good consistence with the corresponding experimental results. Further experiments on 4S1P and 5S1P battery packs validate the effectiveness of the hydrogel thermal management system in lowering the temperature increase rate of battery packs at different discharge rates and minimizing the temperature difference inside battery packs during operation, thereby enhancing the stability and safety in continuous charge and discharge process and decreasing the capacity fading rate during life cycle tests. This novel hydrogel based cooling system also possesses the characteristics of high energy efficiency, easy manufacturing process, compactness, and low cost. - Highlights: • A hydrogel thermal management system (TMS) is proposed for Li-ion battery. • It is found that the heat from internal resistance predominates at high discharge rate. • Effectiveness of hydrogel in controlling cell temperature is proved. • Battery equipped with hydrogel TMS is safer at continuous high rate cycle test. • The capacity fading rate of battery pack decreases when hydrogel TMS is implemented

  19. Optical Projection Tomography Technique for Image Texture and Mass Transport Studies in Hydrogels Based on Gellan Gum.

    Soto, Ana M; Koivisto, Janne T; Parraga, Jenny E; Silva-Correia, Joana; Oliveira, Joaquim M; Reis, Rui L; Kellomäki, Minna; Hyttinen, Jari; Figueiras, Edite

    2016-05-24

    The microstructure and permeability are crucial factors for the development of hydrogels for tissue engineering, since they influence cell nutrition, penetration, and proliferation. The currently available imaging methods able to characterize hydrogels have many limitations. They often require sample drying and other destructive processing, which can change hydrogel structure, or they have limited imaging penetration depth. In this work, we show for the first time an alternative nondestructive method, based on optical projection tomography (OPT) imaging, to characterize hydrated hydrogels without the need of sample processing. As proof of concept, we used gellan gum (GG) hydrogels obtained by several cross-linking methods. Transmission mode OPT was used to analyze image microtextures, and emission mode OPT to study mass transport. Differences in hydrogel structure related to different types of cross-linking and between modified and native GG were found through the acquired Haralick's image texture features followed by multiple discriminant analysis (MDA). In mass transport studies, the mobility of FITC-dextran (MW 20, 150, 2000 kDa) was analyzed through the macroscopic hydrogel. The FITC-dextran velocities were found to be inversely proportional to the size of the dextran as expected. Furthermore, the threshold size in which the transport is affected by the hydrogel mesh was found to be 150 kDa (Stokes' radii between 69 and 95 Å). On the other hand, the mass transport study allowed us to define an index of homogeneity to assess the cross-linking distribution, structure inside the hydrogel, and repeatability of hydrogel production. As a conclusion, we showed that the set of OPT imaging based material characterization methods presented here are useful for screening many characteristics of hydrogel compositions in relatively short time in an inexpensive manner, providing tools for improving the process of designing hydrogels for tissue engineering and drugs

  20. Morphology maps of ice-templated hydrogels based on chitosan

    Dinu, M. V.; Přádný, Martin; Dragan, E. S.; Michálek, Jiří

    Iasi : Faculty of Physics, Alexandru Ioan Cuza University, 2012. s. 115. [International Conference on Physics of Advanced Materials /9./ - ICPAM-9. 20.09.2012-23.09.2012, Iasi] R&D Projects: GA ČR GAP108/12/1538 Institutional support: RVO:61389013 Keywords : chitosan * porous hydrogel * 2-hydroxyethyl methacrylate Subject RIV: CD - Macromolecular Chemistry

  1. Achievements in design and synthesis of hydrogel-based supports

    Horák, Daniel; Hlídková, Helena

    Waretown : Apple Academic Press, 2014 - (Klodzinska, E.), s. 161-179 ISBN 978-1-77188-045-9 R&D Projects: GA ČR GAP304/11/0731 Institutional support: RVO:61389013 Keywords : 2-hydroxyethyl methacrylate * hydrogel * porosity Subject RIV: FH - Neurology http://www.crcnetbase.com/doi/abs/10.1201/b17786-16

  2. Formulation and Evaluation of Topical Hydrogel Patch Containing Amide Type Local Anaesthetic Agent

    Jayrajsinh Sarvaiya

    2012-09-01

    Full Text Available Hydrogel based drug delivery systems provides significant effect in designing sustained release topical dosage forms. Topical patch containing drug in hydrogel type polymer matrix provides not only targeted drug flux through the skin but also provides cooling effect on application site. Topical hydrogel patch containing lidocaine was prepared by using sodium poly acrylate as bioadhesive polymer. Effect of brij 30 and transcutol was also evaluated on topical flux of lidocaine base from hydrogel patch. Transcutol (10% w/w provides sufficient drug release in contrast to brij 30(4%w/w in prepared hydrogel patches. Maintenance of uniformity of weight is one of the critical task in preparation of hydrogel patch as polymers used are highly water absorbent. Excess amount of penetration enhancers leads to alter adhesive property of bioadhesive patch so formulation was optimized with Sodium polyacrylate (7%w/w as the desired concentration for necessary bioadhesiveness and zinc oxide as cross linking agent.

  3. Hydrogels Constructed from Engineered Proteins.

    Li, Hongbin; Kong, Na; Laver, Bryce; Liu, Junqiu

    2016-02-24

    Due to their various potential biomedical applications, hydrogels based on engineered proteins have attracted considerable interest. Benefitting from significant progress in recombinant DNA technology and protein engineering/design techniques, the field of protein hydrogels has made amazing progress. The latest progress of hydrogels constructed from engineered recombinant proteins are presented, mainly focused on biorecognition-driven physical hydrogels as well as chemically crosslinked hydrogels. The various bio-recognition based physical crosslinking strategies are discussed, as well as chemical crosslinking chemistries used to engineer protein hydrogels, and protein hydrogels' various biomedical applications. The future perspectives of this fast evolving field of biomaterials are also discussed. PMID:26707834

  4. Development and characterization of a new hydrogel based on galactomannan and κ-carrageenan.

    Soares, Paulo A G; de Seixas, José R P C; Albuquerque, Priscilla B S; Santos, Gustavo R C; Mourão, Paulo A S; Barros, Wilson; Correia, Maria T S; Carneiro-da-Cunha, Maria G

    2015-12-10

    A new hydrogel based on two natural polysaccharides was prepared in aqueous medium with 1.7% (w/v) galactomannan (from Cassia grandis seeds) and different concentrations of κ-carrageenan (0.3, 0.4 and 0.5%w/v), CaCl2 (0.0, 0.1 and 0.2M) and pH (5.0, 5.5 and 6.0), using a full factorial design based on rheological parameters. The best formulation was obtained with 1.7% (w/v) galactomannan and 0.5% (w/v) κ-carrageenan, containing 0.2M CaCl2 at pH 5.0. Nuclear magnetic resonance and scanning electron microscopy where used in order to characterize the hydrogel formulation. A shelf life study was carried out with this formulation along 90 days-period of storage at 4 °C, evaluating pH, color, microbial contamination and rheology. This hydrogel showed no significant changes in pH, no microbial contamination and became more translucent along the aging. Analyses by nuclear magnetic resonance and rheology showed a larger organization of the polysaccharides in the hydrogel matrix. The results demonstrated that this hydrogel was stable with possible applications in medical and cosmetic fields. PMID:26428171

  5. ABSORBENT MATERIALS BASED ON KRAFT PULP: PREPARATION AND MATERIAL CHARACTERIZATION

    Fredrik Wernersson Brodin,

    2012-02-01

    Full Text Available Today, petroleum-based superabsorbents are widely used, but interest in renewable alternatives is on the rise. This study presents two wood-based absorbent materials suitable for various absorption applications as an alternative to petroleum-based products. Never-dried bleached kraft pulp was treated with TEMPO-oxidation, and new carboxylate and aldehyde groups were introduced. It was found that the aldehyde groups contributed to the wet integrity of the absorbent materials, possibly by the formation of hemiacetal bonds. After oxidation, the pulp fibers were gradually disintegrated, and size analysis showed that the disintegration rate was enhanced by an increase in the charge of the oxidant. Freeze drying produced a porous foam with a large surface area that enabled a rapid absorption rate as well as a reasonably high absorption capacity even for absorption under load. Air drying formed a compact film with a slow absorption rate but with a high final capacity for absorption.

  6. The fate of free radicals in a cellulose based hydrogel: detection by electron paramagnetic resonance spectroscopy.

    Basumallick, Lipika; Ji, J Andrea; Naber, Nariman; Wang, Y John

    2009-07-01

    Cellulose derivatives are commonly used as gelling agents in topical and ophthalmic drug formulations. During the course of manufacturing, cellulose derivatives are believed to generate free radicals. These free radicals may degrade the gelling agent, leading to lower viscosity. Free radicals also may react with the active ingredient in the product. The formation of radicals in a 3% hydrogel of hypromellose (hydroxypropyl methylcellulose) was monitored by electron paramagnetic resonance (EPR) spectroscopy and spin trapping techniques. Radicals were trapped with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and quantitated by comparing the EPR intensity with 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (TEMPOL), a stable free radical. Typically, the hydrogels showed an initial increase in the radical concentration within 2 days after autoclaving, followed by a drop in radical concentration in 7 days. EDTA prevented the formation of free radicals in the hypromellose (HPMC) hydrogel, suggesting the involvement of metal ions in the generation of free radicals. The oxidizing potential of the hydrogel was estimated by measuring the rate at which methionine (a model for the protein active pharmaceutical ingredient) was degraded, and was consistent with the amount of radicals present in the gel. This study is the first report investigating the application of EPR spectroscopy in detecting and estimating free radical concentration in cellulose based hydrogels. PMID:19090570

  7. Poly(ethylene glycol)-based thiol-ene hydrogel coatings: curing chemistry, aqueous stability, and potential marine antifouling applications

    Lundberg, P.; Bruin, A.; Klijnstra, J.W.; Nyström, A.M.; Johansson, M.; Malkoch, M.; Hult, A.

    2010-01-01

    Photocured thiol-ene hydrogel coatings based on poly(ethylene glycol) (PEG) were investigated for marine antifouling purposes. By varying the PEG length, vinylic end-group, and thiol cross-linker, a library of hydrogel coatings with different structural composition was efficiently accomplished, with

  8. Acoustic metasurface-based perfect absorber with deep subwavelength thickness

    Li, Yong; Assouar, Badreddine M.

    2016-02-01

    Conventional acoustic absorbers are used to have a structure with a thickness comparable to the working wavelength, resulting in major obstacles in real applications in low frequency range. We present a metasurface-based perfect absorber capable of achieving the total absorption of acoustic wave in an extremely low frequency region. The metasurface possessing a deep subwavelength thickness down to a feature size of ˜ λ / 223 is composed of a perforated plate and a coiled coplanar air chamber. Simulations based on fully coupled acoustic with thermodynamic equations and theoretical impedance analysis are utilized to reveal the underlying physics and the acoustic performances, showing an excellent agreement. Our realization should have an high impact on amount of applications due to the extremely thin thickness, easy fabrication, and high efficiency of the proposed structure.

  9. The effect of modified polysialic acid based hydrogels on the adhesion and viability of primary neurons and glial cells.

    Haile, Yohannes; Berski, Silke; Dräger, Gerald; Nobre, Andrè; Stummeyer, Katharina; Gerardy-Schahn, Rita; Grothe, Claudia

    2008-04-01

    In this study we present the enzymatic and biological analysis of polysialic acid (polySia) based hydrogel in terms of its degradation and cytocompatibility. PolySia based hydrogel is completely degradable by endosialidase enzyme which may avoid second surgery after tissue recovery. Viability assay showed that soluble components of polySia hydrogel did not cause any toxic effect on cultured Schwann cells. Moreover, green fluorescence protein transfected neonatal and adult Schwann cells, neural stem cells and dorsal root ganglionic cells (unlabelled) were seeded on polySia hydrogel modified with poly-L-lysine (Pll), poly-L-ornithine-laminin (porn-laminin) or collagen. Water soluble tetrazolium salt assay revealed that modification of the hydrogel significantly improved cell adhesion and viability. These results infer that polySia based scaffolds in combination with cell adhesion molecules and cells genetically modified to express growth factors would potentially be promising alternative in reconstructive therapeutic strategies. PMID:18255143

  10. Novel biosensing platform based on self-assembled supramolecular hydrogel.

    Ma, Dong; Zhang, Li-Ming

    2013-07-01

    The supramolecular hydrogel self-assembled from α-cyclodextrin (α-CD) and an amphiphilic triblock copolymer was used for the first time as a biosensing platform by the in-situ incorporation of horseradish peroxidase and polyaniline (PANI) nanoparticles. It was found that the used triblock copolymer could disperse well PANI nanoparticles in aqueous system and then interact with α-CD in the presence of horseradish peroxidase for the formation of supramolecular hydrogel composite. The content of PANI nanoparticles was found to affect the gelation time and gel strength. The circular dichroism analyses showed that the entrapped horseradish peroxidase could retain its native conformation. By electrochemical experiments, the incorporated PANI nanoparticles were confirmed to improve the current response and enzymatic activity, and the fabricated biosensor was found to provide a fast amperometric response to hydrogen peroxide. PMID:23623078

  11. Self-Healing Supramolecular Hydrogels Based on Reversible Physical Interactions

    Satu Strandman

    2016-04-01

    Full Text Available Dynamic and reversible polymer networks capable of self-healing, i.e., restoring their mechanical properties after deformation and failure, are gaining increasing research interest, as there is a continuous need towards extending the lifetime and improving the safety and performance of materials particularly in biomedical applications. Hydrogels are versatile materials that may allow self-healing through a variety of covalent and non-covalent bonding strategies. The structural recovery of physical gels has long been a topic of interest in soft materials physics and various supramolecular interactions can induce this kind of recovery. This review highlights the non-covalent strategies of building self-repairing hydrogels and the characterization of their mechanical properties. Potential applications and future prospects of these materials are also discussed.

  12. Novel hydrogel-based preparation-free EEG electrode.

    Alba, Nicolas Alexander; Sclabassi, Robert J; Sun, Mingui; Cui, Xinyan Tracy

    2010-08-01

    The largest obstacles to signal transduction for electroencephalography (EEG) recording are the hair and the epidermal stratum corneum of the skin. In typical clinical situations, hair is parted or removed, and the stratum corneum is either abraded or punctured using invasive penetration devices. These steps increase preparation time, discomfort, and the risk of infection. Cross-linked sodium polyacrylate gel swelled with electrolyte was explored as a possible skin contact element for a prototype preparation-free EEG electrode. As a superabsorbent hydrogel, polyacrylate can swell with electrolyte solution to a degree far beyond typical contemporary electrode materials, delivering a strong hydrating effect to the skin surface. This hydrating power allows the material to increase the effective skin contact surface area through wetting, and noninvasively decrease or bypass the highly resistive barrier of the stratum corneum, allowing for reduced impedance and improved electrode performance. For the purposes of the tests performed in this study, the polyacrylate was prepared both as a solid elastic gel and as a flowable paste designed to penetrate dense scalp hair. The gel can hold 99.2% DI water or 91% electrolyte solution, and the water content remains high after 29 h of air exposure. The electrical impedance of the gel electrode on unprepared human forearm is significantly lower than a number of commercial ECG and EEG electrodes. This low impedance was maintained for at least 8 h (the longest time period measured). When a paste form of the electrode was applied directly onto scalp hair, the impedance was found to be lower than that measured with commercially available EEG paste applied in the same manner. Time-frequency transformation analysis of frontal lobe EEG recordings indicated comparable frequency response between the polyacrylate-based electrode on unprepared skin and the commercial EEG electrode on abraded skin. Evoked potential recordings demonstrated

  13. Self-Healing Supramolecular Hydrogels Based on Reversible Physical Interactions

    Satu Strandman; Zhu, X.X

    2016-01-01

    Dynamic and reversible polymer networks capable of self-healing, i.e., restoring their mechanical properties after deformation and failure, are gaining increasing research interest, as there is a continuous need towards extending the lifetime and improving the safety and performance of materials particularly in biomedical applications. Hydrogels are versatile materials that may allow self-healing through a variety of covalent and non-covalent bonding strategies. The structural recovery of phy...

  14. New hydrogels based on maleilated collagen with potential applications in tissue engineering

    New hydrogels based on maleic anhydride (MA) modified collagen were prepared with the aim of overcoming the high degradation rate displayed by collagen that is not otherwise chemically crosslinked. Semi-interpenetrated matrices were obtained by free radical polymerization of maleilated collagen (CM) and 2-hydroxyethyl methacrylate (HEMA) in the presence of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) as initiating system. The resulting matrices (CMH) had a sharp decrease in degradation, when compared to pure collagen. FTIR and H1 NMR spectroscopies were used to confirm the incorporation of MA on the collagen peptide chains. The final composition of CMH was found to be strongly dependent by the concentration of maleilated collagen. The morphology of the hydrogels was studied by Scanning electron microscopy (SEM) and the macro-gel structure was confirmed. Water uptake of the synthetised hydrogels is influenced by both composition and the porosity of the matrices.

  15. Study on swelling behaviour of hydrogel based on acrylic acid and pectin from dragon fruit

    Abdullah, Mohd Fadzlanor; Lazim, Azwani Mat

    2014-09-01

    Biocompatible hydrogel based on acrylic acid (AA) and pectin was synthesized using gamma irradiation technique. AA was grafted onto pectin backbone that was extracted from dragon fruit under pH 3.5 and extracts and ethanol ratios (ER) 1:0.5. The optimum hydrogel system with high swelling capacity was obtained by varying the dose of radiation and ratio of pectin:AA. FTIR-ATR spectroscopy was used to verify the interaction while thermal properties were analyzed by TGA and DSC. Swelling studies was carried out in aqueous solutions with different pH values as to determine the pH sensitivity. The results show that the hydrogel with a ratio of 2:3 (pectin:AA) and 30 kGy radiation dose has the highest swelling properties at pH of 10.

  16. Improving the performance of electrochemical microsensors based on enzymes entrapped in a redox hydrogel

    Microsensors based on carbon fiber microelectrodes coated with enzyme-entrapping redox hydrogels facilitate the in vivo detection of substances of interest within the central nervous system, including hydrogen peroxide, glucose, choline and glutamate. The hydrogel, formed by cross-linking a redox polymer, entraps the enzymes and mediates electron transfer between the enzymes and the electrode. It is important that the enzymes are entrapped in their enzymatically active state. Should entrapment cause enzyme denaturation, the sensitivity and the selectivity of the sensor may be compromised. Synthesis of the redox polymer according to published procedures may yield a product that precipitates when added to aqueous enzyme solutions. Casting hydrogels from solutions that contain the precipitate produces microsensors with low sensitivity and selectivity, suggesting that the precipitation disrupts the structure of the enzymes. Herein, we show that a surfactant, sodium dodecyl sulfate (SDS), can prevent the precipitation and improve the sensitivity and selectivity of the sensors

  17. New hydrogels based on maleilated collagen with potential applications in tissue engineering

    Potorac, Simona; Popa, Marcel [' Gheorghe Asachi' Technical University, Faculty of Chemical Engineering and Environmental Protection, Department of Natural and Synthetic Polymers, 71 Dimitrie Mangeron, 700050 Iasi (Romania); Maier, Vasilica [' Gheorghe Asachi' Technical University, Faculty of Textile, Leather and Industrial Management, Department of Chemical Technology of Leather and Substitutes, 71 Dimitrie Mangeron, 700050, Iasi (Romania); Lisa, Gabriela [' Gheorghe Asachi' Technical University, Faculty of Chemical Engineering and Environmental Protection, Department of Natural and Synthetic Polymers, 71 Dimitrie Mangeron, 700050 Iasi (Romania); Verestiuc, Liliana, E-mail: liliana.verestiuc@bioinginerie.ro [' Gr.T.Popa' University of Medicine and Pharmacy, Faculty of Medical Bioengineering, Department of Biological Sciences, 9-13 Kogalniceanu Street, 700454, Iasi (Romania)

    2012-02-01

    New hydrogels based on maleic anhydride (MA) modified collagen were prepared with the aim of overcoming the high degradation rate displayed by collagen that is not otherwise chemically crosslinked. Semi-interpenetrated matrices were obtained by free radical polymerization of maleilated collagen (CM) and 2-hydroxyethyl methacrylate (HEMA) in the presence of ammonium persulfate (APS) and N,N,N Prime ,N Prime -tetramethylethylenediamine (TEMED) as initiating system. The resulting matrices (CMH) had a sharp decrease in degradation, when compared to pure collagen. FTIR and H{sup 1} NMR spectroscopies were used to confirm the incorporation of MA on the collagen peptide chains. The final composition of CMH was found to be strongly dependent by the concentration of maleilated collagen. The morphology of the hydrogels was studied by Scanning electron microscopy (SEM) and the macro-gel structure was confirmed. Water uptake of the synthetised hydrogels is influenced by both composition and the porosity of the matrices.

  18. Characterization of a Functional Hydrogel Layer on a Silicon-Based Grating Waveguide for a Biochemical Sensor

    Hong, Yoo-Seung; Kim, Jongseong; Sung, Hyuk-Kee

    2016-01-01

    We numerically demonstrated the characteristics of a functional hydrogel layer on a silicon-based grating waveguide for a simple, cost-effective refractive index (RI) biochemical sensor. The RI of the functional hydrogel layer changes when a specific biochemical interaction occurs between the hydrogel-linked receptors and injected ligand molecules. The transmission spectral profile of the grating waveguide shifts depends on the amount of RI change caused by the functional layer. Our characterization includes the effective RI change caused by the thickness, functional volume ratio, and functional strength of the hydrogel layer. The results confirm the feasibility of, and set design rules for, hydrogel-assisted silicon-based grating waveguides. PMID:27322286

  19. Single-photon absorber based on strongly interacting Rydberg atoms

    Tresp, Christoph; Mirgorodskiy, Ivan; Gorniaczyk, Hannes; Paris-Mandoki, Asaf; Hofferberth, Sebastian

    2016-01-01

    Removing exactly one photon from an arbitrary input pulse is an elementary operation in quantum optics and enables applications in quantum information processing and quantum simulation. Here we demonstrate a deterministic single-photon absorber based on the saturation of an optically thick free-space medium by a single photon due to Rydberg blockade. Single-photon subtraction adds a new component to the Rydberg quantum optics toolbox, which already contains photonic logic building-blocks such as single-photon sources, switches, transistors, and conditional $\\pi$-phase shifts. Our approach is scalable to multiple cascaded absorbers, essential for preparation of non-classical light states for quantum information and metrology applications, and, in combination with the single-photon transistor, high-fidelity number-resolved photon detection.

  20. A Hydrogel-Based Hybrid Theranostic Contact Lens for Fungal Keratitis.

    Huang, Jian-Fei; Zhong, Jing; Chen, Guo-Pu; Lin, Zuan-Tao; Deng, Yuqing; Liu, Yong-Lin; Cao, Piao-Yang; Wang, Bowen; Wei, Yantao; Wu, Tianfu; Yuan, Jin; Jiang, Gang-Biao

    2016-07-26

    Fungal keratitis, a severe ocular disease, is one of the leading causes of ocular morbidity and blindness, yet it is often neglected, especially in developing countries. Therapeutic efficacy of traditional treatment such as eye drops is very limited due to poor bioavailability, whereas intraocular injection might cause serious side effects. Herein, we designed and fabricated a hybrid hydrogel-based contact lens which comprises quaternized chitosan (HTCC), silver nanoparticles, and graphene oxide (GO) with a combination of antibacterial and antifungal functions. The hydrogel is cross-linked through electrostatic interactions between GO and HTCC, resulting in strong mechanical properties. Voriconazole (Vor), an antifungal drug, can be loaded onto GO which retains the drug and promotes its sustained release from the hydrogel-based contact lenses. The contact lenses also exhibited good antimicrobial functions in view of glycidyltrimethylammonium chloride and silver nanoparticles. The results from in vitro and in vivo experiments demonstrate that contact lenses loaded with Vor have excellent efficacy in antifungal activity in vitro and could significantly enhance the therapeutic effects on a fungus-infected mouse model. The results indicate that this hydrogel contact lenses-based drug delivery system might be a promising therapeutic approach for a rapid and effective treatment of fungal keratitis. PMID:27244244

  1. Stimulus-responsive hydrogels based on associative polymers

    Hietala, Sami; Hvilsted, Søren; Jankova Atanasova, Katja;

    2008-01-01

    associative behaviour with stimuli-responsiveness. Suitable stimuli include for example temperature, pH, ionic strength or variation of polymer or additive concentration. Developments in the controlled radical polymerization methods has enabled versatile modification of polymer structures, which in tum...... enables design of novel associating polymers. Two different stimuli-responsive hydrogel systems will be discussed. Poly(N-isopropylacrylamide) (PNIPAM) has attracted attention due to its sharp and reversible transition behavior and well-defined demixing temperature in aqueous medium. This however only...

  2. Reduced Graphene Oxide-Based Silver Nanoparticle-Containing Composite Hydrogel as Highly Efficient Dye Catalysts for Wastewater Treatment

    Tifeng Jiao; Haiying Guo; Qingrui Zhang; Qiuming Peng; Yongfu Tang; Xuehai Yan; Bingbing Li

    2015-01-01

    New reduced graphene oxide-based silver nanoparticle-containing composite hydrogels were successfully prepared in situ through the simultaneous reduction of GO and noble metal precursors within the GO gel matrix. The as-formed hydrogels are composed of a network structure of cross-linked nanosheets. The reported method is based on the in situ co-reduction of GO and silver acetate within the hydrogel matrix to form RGO-based composite gel. The stabilization of silver nanoparticles was also ach...

  3. Hydrogel-laden paper scaffold system for origami-based tissue engineering.

    Kim, Su-Hwan; Lee, Hak Rae; Yu, Seung Jung; Han, Min-Eui; Lee, Doh Young; Kim, Soo Yeon; Ahn, Hee-Jin; Han, Mi-Jung; Lee, Tae-Ik; Kim, Taek-Soo; Kwon, Seong Keun; Im, Sung Gap; Hwang, Nathaniel S

    2015-12-15

    In this study, we present a method for assembling biofunctionalized paper into a multiform structured scaffold system for reliable tissue regeneration using an origami-based approach. The surface of a paper was conformally modified with a poly(styrene-co-maleic anhydride) layer via initiated chemical vapor deposition followed by the immobilization of poly-l-lysine (PLL) and deposition of Ca(2+). This procedure ensures the formation of alginate hydrogel on the paper due to Ca(2+) diffusion. Furthermore, strong adhesion of the alginate hydrogel on the paper onto the paper substrate was achieved due to an electrostatic interaction between the alginate and PLL. The developed scaffold system was versatile and allowed area-selective cell seeding. Also, the hydrogel-laden paper could be folded freely into 3D tissue-like structures using a simple origami-based method. The cylindrically constructed paper scaffold system with chondrocytes was applied into a three-ring defect trachea in rabbits. The transplanted engineered tissues replaced the native trachea without stenosis after 4 wks. As for the custom-built scaffold system, the hydrogel-laden paper system will provide a robust and facile method for the formation of tissues mimicking native tissue constructs. PMID:26621717

  4. A versatile fluorescent biosensor based on target-responsive graphene oxide hydrogel for antibiotic detection.

    Tan, Bing; Zhao, Huimin; Du, Lei; Gan, Xiaorong; Quan, Xie

    2016-09-15

    A fluorescent sensing platform based on graphene oxide (GO) hydrogel was developed through a fast and facile gelation, immersion and fluorescence determination process, in which the adenosine and aptamer worked as the co-crosslinkers to connect the GO sheets and then form the three-dimensional (3D) macrostructures. The as-prepared hydrogel showed high mechanical strength and thermal stability. The optimal hydrogel had a linear response for oxytetracycline (OTC) of 25-1000μg/L and a limit of quantitation (LOQ) of 25μg/L. Moreover, together with the high affinity of the aptamer for its target, this assay exhibited excellent sensitivity and selectivity. According to its design principle, the as-designed hydrogel was also tested to possess the generic detection function for other molecules by simply replacing its recognition element, which is expected to lay a foundation to realize the assembly of functionalized hierarchical graphene-based materials for practical applications in analytical field. PMID:27132000

  5. Graphene-based perfect optical absorbers harnessing guided mode resonances

    Grande, M; Stomeo, T; Bianco, G V; de Ceglia, D; Akozbek, N; Petruzzelli, V; Bruno, G; De Vittorio, M; Scalora, M; Orazio, A D

    2015-01-01

    We numerically and experimentally investigate graphene-based optical absorbers that exploit guided mode resonances (GMRs) achieving perfect absorption over a bandwidth of few nanometers (over the visible and near-infrared ranges) with a 40-fold increase of the monolayer graphene absorption. We analyze the influence of the geometrical parameters on the absorption rate and the angular response for oblique incidence. Finally, we experimentally verify the theoretical predictions in a one-dimensional, dielectric grating and placing it near either a metallic or a dielectric mirror.

  6. Porphyrin Based Near Infrared-Absorbing Materials for Organic Photovoltaics

    Zhong, Qiwen

    The conservation and transformation of energy is essential to the survival of mankind, and thus concerns every modern society. Solar energy, as an everlasting source of energy, holds one of the key solutions to some of the most urgent problems the world now faces, such as global warming and the oil crisis. Advances in technologies utilizing clean, abundant solar energy, could be the steering wheel of our societies. Solar cells, one of the major advances in converting solar energy into electricity, are now capturing people's interest all over the globe. While solar cells have been commercially available for many years, the manufacturing of solar cells is quite expensive, limiting their broad based implementation. The cost of solar cell based electricity is 15-50 cents per kilowatt hour (¢/kwh), depending on the type of solar cell, compared to 0.7 ¢/kwh for fossil fuel based electricity. Clearly, decreasing the cost of electricity from solar cells is critical for their wide spread deployment. This will require a decrease in the cost of light absorbing materials and material processing used in fabricating the cells. Organic photovoltaics (OPVs) utilize organic materials such as polymers and small molecules. These devices have the advantage of being flexible and lower cost than conventional solar cells built from inorganic semiconductors (e.g. silicon). The low cost of OPVs is tied to lower materials and fabrication costs of organic cells. However, the current power conversion efficiencies of OPVs are still below 15%, while convention crystalline Si cells have efficiencies of 20-25%. A key limitation in OPVs today is their inability to utilize the near infrared (NIR) portion of the solar spectrum. This part of the spectrum comprises nearly half of the energy in sunlight that could be used to make electricity. The first and foremost step in conversion solar energy conversion is the absorption of light, which nature has provided us optimal model of, which is

  7. Genotoxicity and molecular response of silver nanoparticle (NP-based hydrogel

    Xu Liming

    2012-05-01

    Full Text Available Abstract Background Since silver-nanoparticles (NPs possess an antibacterial activity, they were commonly used in medical products and devices, food storage materials, cosmetics, various health care products, and industrial products. Various silver-NP based medical devices are available for clinical uses, such as silver-NP based dressing and silver-NP based hydrogel (silver-NP-hydrogel for medical applications. Although the previous data have suggested silver-NPs induced toxicity in vivo and in vitro, there is lack information about the mechanisms of biological response and potential toxicity of silver-NP-hydrogel. Methods In this study, the genotoxicity of silver-NP-hydrogel was assayed using cytokinesis-block micronucleus (CBMN. The molecular response was studied using DNA microarray and GO pathway analysis. Results and discussion The results of global gene expression analysis in HeLa cells showed that thousands of genes were up- or down-regulated at 48 h of silver-NP-hydrogel exposure. Further GO pathway analysis suggested that fourteen theoretical activating signaling pathways were attributed to up-regulated genes; and three signal pathways were attributed to down-regulated genes. It was discussed that the cells protect themselves against silver NP-mediated toxicity through up-regulating metallothionein genes and anti-oxidative stress genes. The changes in DNA damage, apoptosis and mitosis pathway were closely related to silver-NP-induced cytotoxicity and chromosome damage. The down-regulation of CDC14A via mitosis pathway might play a role in potential genotoxicity induced by silver-NPs. Conclusions The silver-NP-hydrogel induced micronuclei formation in cellular level and broad spectrum molecular responses in gene expression level. The results of signal pathway analysis suggested that the balances between anti-ROS response and DNA damage, chromosome instability, mitosis inhibition might play important roles in silver-NP induced toxicity

  8. Thermo-responsive hydrogels from cellulose-based polyelectrolytes and catanionic vesicles for biomedical application.

    Milcovich, Gesmi; Antunes, Filipe; Golob, Samuel; Farra, Rossella; Grassi, Mario; Voinovich, Dario; Grassi, Gabriele; Asaro, Fioretta

    2016-07-01

    In this study, negatively charged catanionic vesicles/hydrophobically modified hydroxyethylcellulose polymers thermo-responsive hydrogels have been fabricated. Vesicular aggregates were found to act as multifunctional junctions for networking of modified-cellulose water solutions. The contributions of the electrostatic and hydrophobic interactions were evaluated by changing either vesicles composition or the polymer hydrophobic substitution. Thermal-induced size and lamellarity of hydrogel-enclosed vesicles were detected, with further polygonal shape changes induced by cellulose-based polymer addition. The thermal transition was also found to tune hydrogel mechanical behaviour. The network formation was further assessed through molecular insights, which allow to determine the arrangement of the polymer chains on the vesicles' surface. The examined systems exhibited interesting thermo-responsive characteristics. Thus, vesicularly cross-linked hydrogels herein presented can offer a wide variety of applications, i.e. in biomedical field, as multi-drug delivery systems, thanks to their ability to provide for different environments to guest molecules, comprising bulk water, vesicles' interior and bilayers, sites on polymeric chains. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1668-1679, 2016. PMID:26939864

  9. A protein-based hydrogel for in vitro expansion of mesenchymal stem cells.

    Jingyu Wang

    Full Text Available Hydrogels are widely used as scaffolds in tissue engineering because they can provide excellent environments for bioactive components including growth factors and cells. We reported in this study on a physical hydrogel formed by a specific protein-peptide interaction, which could be used for the three dimensional (3D cell culture of murine mesenchymal stem cells (mMSC. The mMSC kept dividing during the 7-day culture period and the metabolic-active cell number at day 7 was 359% more than that at day 1. This kind of physical hydrogel could be converted to a homogeneous solution by firstly adding an equal volume of culture medium and then pipeting for several times. Therefore, mMSC post culture could be easily separated from cell-gel constructs. We believed that the protein-based hydrogel system in this study could be developed into a promising scaffold for in vitro expansion of stem cells and cell therapy. This work would be in the general interests of researchers in the fields of biomaterials and supramolecular chemistry.

  10. Formulation Changes Affect Material Properties and Cell Behavior in HA-Based Hydrogels

    Thomas Lawyer

    2012-01-01

    Full Text Available To develop and optimize new scaffold materials for tissue engineering applications, it is important to understand how changes to the scaffold affect the cells that will interact with that scaffold. In this study, we used a hyaluronic acid- (HA- based hydrogel as a synthetic extracellular matrix, containing modified HA (CMHA-S, modified gelatin (Gtn-S, and a crosslinker (PEGda. By varying the concentrations of these components, we were able to change the gelation time, enzymatic degradation, and compressive modulus of the hydrogel. These changes also affected fibroblast spreading within the hydrogels and differentially affected the proliferation and metabolic activity of fibroblasts and mesenchymal stem cells (MSCs. In particular, PEGda concentration had the greatest influence on gelation time, compressive modulus, and cell spreading. MSCs appeared to require a longer period of adjustment to the new microenvironment of the hydrogels than fibroblasts. Fibroblasts were able to proliferate in all formulations over the course of two weeks, but MSCs did not. Metabolic activity changed for each cell type during the two weeks depending on the formulation. These results highlight the importance of determining the effect of matrix composition changes on a particular cell type of interest in order to optimize the formulation for a given application.

  11. Development of a sodium alginate-based organic/inorganic superabsorbent composite hydrogel for adsorption of methylene blue.

    Thakur, Sourbh; Pandey, Sadanand; Arotiba, Omotayo A

    2016-11-20

    Batch adsorption experiments were carried out for the removal of methylene blue (MB) cationic dye from aqueous solution using organic/inorganic hydrogel nanocomposite of titania incorporated sodium alginate crosslinked polyacrylic acid (SA-cl-poly(AA)-TiO2). The hydrogel was prepared by graft copolymerization of acrylic acid (AA) onto sodium alginate (SA) biopolymer in the presence of a crosslinking agent, a free radical initiator and TiO2 nanoparticles. The hydrogel exhibited a high swelling capacity of 412.98g/g. The factors influencing adsorption capacity of the absorbents such as pH of the dye solutions, initial concentration of the dye, amount of absorbents, and temperature were investigated and used to propose a possible mechanism of adsorption. The adsorption process concurs with a pseudo-second-order kinetics and with Langmuir isotherm equation. A very high adsorption capacity (Qmax=2257.36 (mg/g)) and a correlation coefficient of 0.998 calculated from isotherm equations show the high efficiency of the absorbent and thus expected to be a good candidate as an absorbent for water treatment. PMID:27561469

  12. [The study of quality characteristics of the hydrogel ointments and films based on copolymers divinyl esters of diethylene glycol].

    Bakirova, R E; Tazhbaeva, E M; Muravleva, L E; Fazylov, S D; Akhmetova, S B

    2014-12-01

    The possibility of using a hydrogel based on divinyl ether co- and terpolymer of diethylene glycol as the backbone polymer for incorporating water-soluble medicinal substances was examined. The character of the influence of emulsifiers, plasticizers, high-boiling liquids and bioactive substances is defined within the changes of physical-chemical properties of obtained hydrogels. The obtained polyelectrolyte hydrogels by their homogeneity, dehydration and rheological characteristics may be of concern in function of matrices to create external prolonged-action dosage forms. PMID:25617104

  13. Removal of Cu{sup 2+} and Pb{sup 2+} ions using CMC based thermoresponsive nanocomposite hydrogel

    Oezkahraman, Bengi [Faculty of Engineering, Chemical Engineering Department, Hitit University, Corum (Turkey); Acar, Isil; Emik, Serkan [Faculty of Engineering, Chemical Engineering Department, Istanbul University, Avcilar-Istanbul (Turkey)

    2011-07-15

    In this study, carboxymethylcellulose (CMC) based thermoresponsive nanocomposite hydrogel was synthesized for the removal of Cu{sup 2+} and Pb{sup 2+} ions from aqueous solutions. To prepare nanocomposite hydrogel, graft copolymerization of N-isopropyl acrylamide (NIPAm) and acrylic acid (AA) onto CMC was carried out in Na-montmorillonite (MMT)/water suspension media and ammonium persulfate (APS) used as initiator. The chemical structures of hydrogels were characterized by Fourier transform infrared (FT-IR) and X-ray diffraction spectroscopy (XRD). Lower critical solution temperature (LCST), pH responsivity, swelling, and deswelling properties of the hydrogels were also examined. In addition competitive and non-competitive removal of Cu{sup 2+} and Pb{sup 2+} studies were carried out. According to heavy metal sorption studies results, removal capacities of nanocomposite hydrogel for both metal ions were found to be higher than those of pure hydrogel. The analyzed adsorption data showed that the adsorption process of Cu{sup 2+} and Pb{sup 2+} could be explained by pseudo-second order kinetic model. Moreover, according to competitive sorption studies, it is found to be that both hydrogels are more selective to Cu{sup 2+} ion rather than Pb{sup 2+}. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. A multiband perfect absorber based on hyperbolic metamaterials.

    Sreekanth, Kandammathe Valiyaveedu; ElKabbash, Mohamed; Alapan, Yunus; Rashed, Alireza R; Gurkan, Umut A; Strangi, Giuseppe

    2016-01-01

    In recent years, considerable research efforts have been focused on near-perfect and perfect light absorption using metamaterials spanning frequency ranges from microwaves to visible frequencies. This relatively young field is currently facing many challenges that hampers its possible practical applications. In this paper, we present grating coupled-hyperbolic metamaterials (GC-HMM) as multiband perfect absorber that can offer extremely high flexibility in engineering the properties of electromagnetic absorption. The fabricated GC-HMMs exhibit several highly desirable features for technological applications such as polarization independence, wide angle range, broad- and narrow- band modes, multiband perfect and near perfect absorption in the visible to near-IR and mid-IR spectral range. In addition, we report a direct application of the presented system as an absorption based plasmonic sensor with a record figure of merit for this class of sensors. PMID:27188789

  15. Extracellular matrix formation in self-assembled minimalistic bioactive hydrogels based on aromatic peptide amphiphiles

    ZHOU, MI; Ulijn, Rein V.; Gough, Julie E

    2014-01-01

    The hitherto inconsistency in clinical performance for engineered skin drives the current development of novel cell-scaffolding materials; one challenge is to only extract essential characteristics from the complex native ECM (extracellular matrix) and incorporate them into a scaffold with minimal complexity to support normal cell functions. This study involved small-molecule-based bioactive hydrogels produced by the co-assembly of two aromatic peptide amphiphiles: Fmoc-FF (Fluorenylmethoxyca...

  16. Development of novel microemulsion-based hydrogel for topical delivery of sinomenium

    Gui, Shuangyin; Pan, Enyuan; Liu, Peng; Lu, Chuanhua; Peng, Daiyin

    2011-01-01

    The objective of the present investigation was to develop and evaluate microemulsion-based hydrogel (MBH) for the topical delivery of sinomenium. The solubility of sinomenium in oils and surfactants was evaluated to identify components of the microemulsion, the pseudo-ternary phase diagrams were developed to identify the area of microemulsion existence and obtain the optimization Km (the weight ratio of surfactant to cosurfactant). The transdermal ability of various microemulsion formulations...

  17. Effect of particle size and charge on the network properties of microsphere-based hydrogels

    van Tomme, S.R.; van Nostrum, C.F.; Dijkstra, M.; de Smedt, S.C.; Hennink, W.E.

    2008-01-01

    This work describes the tailorability of the network properties of self-assembling hydrogels, based on ionic crosslinking between dextran microspheres. Copolymerization of hydroxyethyl methacrylate-derivatized dextran (dex-HEMA), emulsified in an aqueous poly(ethylene glycol) (PEG) solution, with methacrylic acid (MAA) or dimethylaminoethyl methacrylate (DMAEMA) resulted in negatively or positively charged microspheres, respectively, at physiological pH. The monomer/HEMA ratio ranged between ...

  18. Impedimetric quantification of cells encapsulated in hydrogel cultured in a paper-based microchamber.

    Lei, Kin Fong; Huang, Chia-Hao; Tsang, Ngan-Ming

    2016-01-15

    Recently, 3D cell culture technique was proposed to provide a more physiologically-meaningful environment for cell-based assays. With the development of microfluidics technology, cellular response can be quantified by impedance measurement technique in a real-time and non-invasive manner. However, handling of these microfluidic systems requires a trained engineering personnel and the operation is not compatible to traditional biological research laboratories. In this work, we incorporated the impedance measurement technique to paper-based 3D cell culture model and demonstrated non-invasive quantification of cells encapsulated in hydrogel during the culture course. A cellulose filter paper was patterned with an array of circular microchambers. Cells were encapsulated in hydrogel and loaded to the microchambers for culturing cells in 3D environment. At the preset schedule during the culture course, the paper was placed on a glass substrate with measurement electrodes for the impedance measurement. Cells in each microchamber was represented by impedance magnitude and cell proliferation could be studied over time. Also, conventional bio-assay was performed to further confirm the feasibility of the impedimetric quantification of cells encapsulated in hydrogel cultured in the paper-based microchamber. This technique provides a convenient, fast, and non-invasive approach to monitor cells cultured in 3D environment. It has potential to be developed for routine 3D cell culture protocol in biological research laboratories. PMID:26592655

  19. REVIEW: CHITOSAN BASED HYDROGEL POLYMERIC BEADS – AS DRUG DELIVERY SYSTEM

    Manjusha Rani

    2010-11-01

    Full Text Available Chitosan obtained by alkaline deacetylation of chitin is a non-toxic, biocompatible, and biodegradable natural polymer. Chitosan-based hydrogel polymeric beads have been extensively studied as micro- or nano-particulate carriers in the pharmaceutical and medical fields, where they have shown promise for drug delivery as a result of their controlled and sustained release properties, as well as biocompatibility with tissue and cells. To introduce desired properties and enlarge the scope of the potential applications of chitosan, graft copolymerization with natural or synthetic polymers on it has been carried out, and also, various chitosan derivatives have been utilized to form beads. The desired kinetics, duration, and rate of drug release up to therapeutical level from polymeric beads are limited by specific conditions such as beads material and their composition, bead preparation method, amount of drug loading, drug solubility, and drug polymer interaction. The present review summarizes most of the available reports about compositional and structural effects of chitosan-based hydrogel polymeric beads on swelling, drug loading, and releasing properties. From the studies reviewed it is concluded that chitosan-based hydrogel polymeric beads are promising drug delivery systems.

  20. Small-angle neutron scattering from polymer hydrogels with memory effect for medicine immobilization

    Hydrogels synthesized based on cross-linked copolymers of 2-hydroxyethyl methacrylate and functional monomers (acrylic acid or dimethylaminoethyl methacrylate), having a memory effect with respect to target medicine (cefazolin), have been investigated by small-angle neutron scattering. The hydrogels are found to have a two-level structural organization: large (up to 100 nm) aggregates filled with network cells (4–7 nm in size). The structural differences in the anionic, cationic, and amphiphilic hydrogels and the relationship between their structure and the ability of hydrogels to absorb moisture are shown. A relationship between the memory effect during cefazolin immobilization and the internal structure of hydrogels, depending on their composition and type of functional groups, is established.

  1. Synthesis of new greener biopolymer chitosan based hydrogel and its application for separation of 152Eu and 137Cs

    A chitosan based hydrogel has been synthesised followed by its characterization by IR, swelling study and TGA. The hydrogel was used for separation of long-lived radionuclides such as 152Eu and 137Cs using solid liquid extraction (SLX) technique. Separation of 152Eu and 137Cs was carried out using various concentration of HCl (10-5 to 1 M) against 0.1 g of hydrogel as solid phase. At typical experimental condition maximum adsorption of 152Eu into the solid phase was 87% without any contamination of 137Cs. In desorption study of solid phase containing 152Eu, about 72% of 152Eu was extracted into liquid phase from solid hydrogel phase in a single run. (author)

  2. Effect of Sodium Salicylate on the Viscoelastic Properties and Stability of Polyacrylate-Based Hydrogels for Medical Applications

    Zuzana Kolarova Raskova

    2016-01-01

    Full Text Available Investigation was made into the effect exerted by the presence of sodium salicylate (0–2 wt.%, in Carbomer-based hydrogel systems, on processing conditions, rheological and antimicrobial properties in tests against Gram-positive (Staphylococcus aureus and Gram-negative (Escherichia coli bacterial strains, and examples of yeast (Candida albicans and mould (Aspergillus niger. In addition, the work presents an examination of long-term stability by means of aging over one year the given hydrogels at 8°C and 25°C. The results show that 0.5 wt.% NaSal demonstrated a noticeable effect on the hydrogel neutralization process, viscosity, and antimicrobial properties against all of the tested microorganisms. The long-term stability studies revealed that hydrogels can maintain antimicrobial activity as well as viscosity to a degree that would be sufficient for practical use.

  3. Phase transitions of macromolecular microsphere composite hydrogels based on the stochastic Cahn–Hilliard equation

    We use the stochastic Cahn–Hilliard equation to simulate the phase transitions of the macromolecular microsphere composite (MMC) hydrogels under a random disturbance. Based on the Flory–Huggins lattice model and the Boltzmann entropy theorem, we develop a reticular free energy suit for the network structure of MMC hydrogels. Taking the random factor into account, with the time-dependent Ginzburg-Landau (TDGL) mesoscopic simulation method, we set up a stochastic Cahn–Hilliard equation, designated herein as the MMC-TDGL equation. The stochastic term in the equation is constructed appropriately to satisfy the fluctuation-dissipation theorem and is discretized on a spatial grid for the simulation. A semi-implicit difference scheme is adopted to numerically solve the MMC-TDGL equation. Some numerical experiments are performed with different parameters. The results are consistent with the physical phenomenon, which verifies the good simulation of the stochastic term

  4. “A novel highly stable and injectable hydrogel based on a conformationally restricted ultrashort peptide”

    Thota, Chaitanya Kumar; Yadav, Nitin; Chauhan, Virander Singh

    2016-01-01

    Nanostructures including hydrogels based on peptides containing non protein amino acids are being considered as platform for drug delivery because of their inherent biocompatibility and additional proteolytic stability. Here we describe instantaneous self-assembly of a conformationally restricted dipeptide, LeuΔPhe, containing an α,β-dehydrophenylalanine residue into a highly stable and mechanically strong hydrogel, under mild physiological aqueous conditions. The gel successfully entrapped several hydrophobic and hydrophilic drug molecules and released them in a controlled manner. LeuΔPhe was highly biocompatible and easily injectable. Administration of an antineoplastic drug entrapped in the gel in tumor bearing mice significantly controlled growth of tumors. These characteristics make LeuΔPhe an attractive candidate for further development as a delivery platform for various biomedical applications. PMID:27507432

  5. Hyaluronan delivery by polymer demixing in polysaccharide-based hydrogels and membranes for biomedical applications.

    Travan, Andrea; Scognamiglio, Francesca; Borgogna, Massimiliano; Marsich, Eleonora; Donati, Ivan; Tarusha, Lorena; Grassi, Mario; Paoletti, Sergio

    2016-10-01

    Alginate-based membranes containing hyaluronic acid (HA) were manufactured by freeze-drying calcium-reticulated hydrogels. The study of the distribution of the two macromolecules within the hydrogel enabled to highlight a polymer demixing mechanism that tends to segregate HA in the external parts of the constructs. Resistance and pliability of the membranes were tuned, while release and degradation studies enabled to quantify the diffusion of both polysaccharides in physiological solution and to measure the viable lifetime of the membranes. Biological studies in vitro proved that the liquid extracts from the HA-containing membranes stimulate wound healing and that fibroblasts are able to colonize the membranes. Overall, such novel alginate-HA membranes represent a promising solution for several medical needs, in particular for wound treatment, giving the possibility to provide an in situ administration of HA from a resorbable device. PMID:27312652

  6. Phase transitions of macromolecular microsphere composite hydrogels based on the stochastic Cahn–Hilliard equation

    Li, Xiao, E-mail: lixiao1228@163.com; Ji, Guanghua, E-mail: ghji@bnu.edu.cn; Zhang, Hui, E-mail: hzhang@bnu.edu.cn

    2015-02-15

    We use the stochastic Cahn–Hilliard equation to simulate the phase transitions of the macromolecular microsphere composite (MMC) hydrogels under a random disturbance. Based on the Flory–Huggins lattice model and the Boltzmann entropy theorem, we develop a reticular free energy suit for the network structure of MMC hydrogels. Taking the random factor into account, with the time-dependent Ginzburg-Landau (TDGL) mesoscopic simulation method, we set up a stochastic Cahn–Hilliard equation, designated herein as the MMC-TDGL equation. The stochastic term in the equation is constructed appropriately to satisfy the fluctuation-dissipation theorem and is discretized on a spatial grid for the simulation. A semi-implicit difference scheme is adopted to numerically solve the MMC-TDGL equation. Some numerical experiments are performed with different parameters. The results are consistent with the physical phenomenon, which verifies the good simulation of the stochastic term.

  7. Absorbance characterization of microsphere-based ion-selective optodes

    Ye Nan [Department of Chemistry, Purdue University, West Lafayette, IN 47907 (United States); Wygladacz, Katarzyna [Department of Chemistry, Purdue University, West Lafayette, IN 47907 (United States); Bakker, Eric [Department of Chemistry, Purdue University, West Lafayette, IN 47907 (United States)]. E-mail: bakkere@purdue.edu

    2007-07-23

    Ionophore-based microsphere sensors are characterized here in transmission mode. These sensors contain a lipophilic ionophore for the analyte cation, a chromoionophore for recognizing H{sup +}, and a lipophilic cation-exchanger. They function on the basis of an ion-exchange equilibration step where an increased concentration of analyte ion leads to increased level of extraction into the bulk of the microsphere, expelling protons in return and deprotonating the chromoionophore. Since the path length is variable across the microsphere, such bead-based sensors are normally characterized in fluorescence mode. In this paper, the response of the sensing microspheres is calculated from the ratio of transmitted light intensities at the absorbance peak maxima of the protonated and unprotonated forms of the chromoionophore. At a fixed position of the particle, the resulting responses are found to be independent of light scattering, incident light intensity and the shape or size of the microsphere. The responses of potassium-selective microspheres obtained by this method agree quantitatively with corresponding fluorescence-based data.

  8. Nanographene-Based Saturable Absorbers for Ultrafast Fiber Lasers

    Hsin-Hui Kuo

    2014-01-01

    Full Text Available The generation of femtosecond pulse laser in the erbium-doped fiber laser system is presented by integrating of the nanographene-based saturable absorbers (SAs. A simplified method of dispersed nanographene-based SAs side-polished fiber device with controllable polished length and depth was also developed. The dependence of geometry of a graphene-deposited side-polished fiber device on optical nonlinear characteristics and on the performance of the MLFL was screened. We found that the 10 mm polished length with 1.68 dB insertion loss had the highest modulation depth (MD of 1.2%. A stable MLFL with graphene-based SAs employing the optimized side-polished fiber device showed a pulse width, a 3 dB bandwidth, a time-bandwidth product (TBP, a repetition rate, and pulse energy of 523 fs, 5.4 nm, 0.347, 16.7 MHz, and 0.18 nJ, respectively, at fundamental soliton-like operation. The femtosecond pulse laser is achieved by evanescent field coupling through graphene-deposited side-polished fiber devices in the laser cavity. This study demonstrates that the polished depth is the key fabrication geometric parameter affecting the overall optical performance and better results exist within the certain polished range.

  9. Versatile hydrogel-based nanocrystal microreactors towards uniform fluorescent photonic crystal supraballs

    Zhang, Jing; Tian, Yu; Ling, Lu-Ting; Yin, Su-Na; Wang, Cai-Feng; Chen, Su, E-mail: chensu-njut@163.com, E-mail: chensu@njtech.edu.cn [Nanjing Tech University, State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering (China)

    2014-12-15

    Versatile hydrogel-based nanocrystal (NC) microreactors were designed in this work for the construction of uniform fluorescence colloidal photonic crystal (CPC) supraballs. The hydrogel-based microspheres with sizes ranging from 150 to 300 nm were prepared by seeded copolymerization of acrylic acid and 2-hydroxyethyl methacrylate with micrometer-sized PS seed particles. As an independent NC microreactor, the as-synthesized hydrogel microsphere can effectively capture the guest cadmium ions due to the abundant carboxyl groups inside. Followed by the introduction of chalcogenides, in situ generation of higher-uptake NCs with sizes less than 5 nm was finally realized. Additionally, with the aid of the microfluidic device, the as-obtained NC–latex hybrids can be further self-assembled to bi-functional CPC supraballs bearing brilliant structural colors and uniform fluorescence. This research offers an alternative way to finely bind CPCs with NCs, which will facilitate progress in fields of self-assembled functional colloids and photonic materials.

  10. Improved skin delivery of voriconazole with a nanostructured lipid carrier-based hydrogel formulation.

    Song, Seh Hyon; Lee, Kyung Min; Kang, Jong Boo; Lee, Sang Gon; Kang, Myung Joo; Choi, Young Wook

    2014-01-01

    In order to develop topical preparations of voriconazole (VRC) for the treatment of mycotic infections of the skin, a nanostructured lipid carrier-based hydrogel (NLC-gel) formulation was developed and its physical characteristics, in vitro skin permeation, and retention profiles were examined. A VRC-loaded NLC dispersion, consisting of Precirol ATO 5, Labrafil 1944 CS, and Tween 80, was prepared by high-pressure homogenization and embedded into Carbopol 940 hydrogel. The lipid nanoparticles in the hydrogel were approximately 210 nm in size, with a spherical shape and zeta potential of -30 mV. In a skin permeation study using a Franz diffusion cell mounted with depilated mouse skin, the NLC-gel was superior to conventional cream and microemulsion-based gel formulations, showing 2.8- and 1.7-fold greater flux values, respectively. In addition, the NLC-gel led to markedly greater accumulation of VRC in deeper skin layers as compared with the reference formulations. In conclusion, the novel topical formulation reported here represents an alternative treatment for skin infections such as candidiasis, with less potential for systemic adverse effects than oral therapy. PMID:25087631

  11. Versatile hydrogel-based nanocrystal microreactors towards uniform fluorescent photonic crystal supraballs

    Versatile hydrogel-based nanocrystal (NC) microreactors were designed in this work for the construction of uniform fluorescence colloidal photonic crystal (CPC) supraballs. The hydrogel-based microspheres with sizes ranging from 150 to 300 nm were prepared by seeded copolymerization of acrylic acid and 2-hydroxyethyl methacrylate with micrometer-sized PS seed particles. As an independent NC microreactor, the as-synthesized hydrogel microsphere can effectively capture the guest cadmium ions due to the abundant carboxyl groups inside. Followed by the introduction of chalcogenides, in situ generation of higher-uptake NCs with sizes less than 5 nm was finally realized. Additionally, with the aid of the microfluidic device, the as-obtained NC–latex hybrids can be further self-assembled to bi-functional CPC supraballs bearing brilliant structural colors and uniform fluorescence. This research offers an alternative way to finely bind CPCs with NCs, which will facilitate progress in fields of self-assembled functional colloids and photonic materials

  12. Chitosan-Based Thermosensitive Hydrogel for Controlled Drug Delivery to the Temporomandibular Joint.

    Talaat, Wael M; Haider, Mohamed; Kawas, Sausan Al; Kandil, Nadia G; Harding, David R K

    2016-05-01

    Intra-articular injections of hyaluronic acid (HA) and corticosteroids have been extensively used in treating temporomandibular disorders. However, rapid clearance from the site of injection is a major concern that is commonly managed by frequent dosing, which is not without complications. This study aimed to determine the suitability of thermosensitive chitosan-based hydrogels for intra-articular controlled release of drugs in the rabbit temporomandibular joint (TMJ). A series of hydrogels were prepared using different chitosan (Ch) to β-glycerophosphate (β-GP) ratios. The gelation time, swelling ratio, the shape, and surface morphology of the prepared gels were investigated to select the formulation with optimum characteristics. The left TMJ in 13 adult male New Zealand white rabbits was injected with 0.2 mL of Chitosan/β-glycerophosphate/HA while the right TMJ was injected with 0.2 mL of control solution of HA. Hyaluronic acid concentrations in experimental and control groups were measured using Hyaluronan Quantikine Enzyme-Linked Immunosorbent Assay Kit. In vitro characterization showed that both the Ch:β-GP ratio and incorporation of HA had a significant effect on gelation time, degree of swelling, and surface morphology of the hydrogels. No morphological changes were observed in the joints in both groups. The mean concentration of HA in the experimental joints after 7 days (1339.79 ± 244.98 μg/g) was significantly higher than that in the control (474.52 ± 79.36 μg/g). In conclusion, the chitosan-based thermosensitive hydrogel can be considered as a promising controlled drug release system to the TMJ in a rabbit model that would potentially overcome many of the current limitations of intra-articular formulations. PMID:27100649

  13. The biocompatibility of PluronicF127 fibrinogen-based hydrogels.

    Shachaf, Yonatan; Gonen-Wadmany, Maya; Seliktar, Dror

    2010-04-01

    Our research is focused on the design of hydrogel biomaterials that can be used for 3-D cell encapsulation and tissue engineering. In this study, our goal was to engineer a temperature-responsive biomaterial to possess bioactive properties using polymer and protein chemistry, and at the same time provide the biomaterial with susceptibility to cell-mediated remodeling. Toward this goal, we developed a biomimetic material that can harness the bioactive properties of fibrinogen and the unique structural properties of PluronicF127. PluronicF127 is a synthetic block copolymer that exhibits reverse thermal gelation (RTG) in response to small changes in ambient temperature. We conjugated fibrinogen to Pluronic)F127 to create a biosynthetic precursor with tunable physicochemical properties based on the relationship between the two constituents. A hydrogel matrix was formed from the fibrinogen-F127 adducts by free-radical polymerization using light activation (photo-polymerization). These materials displayed a reversible temperature-induced physical sol-gel transition and an irreversible light-activated chemical cross-linking. The susceptibility of this hydrogel biomaterial to protease degradation and consequent cell-mediated remodeling was controlled by the PluronicF127 constituent. The protein-based material also conveyed inductive signals to cells through bioactive sites on the fibrinogen backbone, as well as through structural properties such as the matrix modulus. We apply these materials as a tissue engineering hydrogel scaffold for 3-D in vitro culture of dermal fibroblasts in order to gain a better understanding of how the material bioactivity and matrix properties can independently affect cell morphology and remodeling. PMID:20092890

  14. In vivo bioengineered ovarian tumors based on collagen, matrigel, alginate and agarose hydrogels: a comparative study

    Scaffold-based tumor engineering is rapidly evolving the study of cancer progression. However, the effects of scaffolds and environment on tumor formation have seldom been investigated. In this study, four types of injectable hydrogels, namely, collagen type I, Matrigel, alginate and agarose gels, were loaded with human ovarian cancer SKOV3 cells and then injected into nude mice subcutaneously. The growth of the tumors in vitro was also investigated. After four weeks, the specimens were harvested and analyzed. We found that tumor formation by SKOV3 cells was best supported by collagen, followed by Matrigel, alginate, control (without scaffold) and agarose in vivo. The collagen I group exhibited a larger tumor volume with increased neovascularization and increased necrosis compared with the other materials. Further, increased MMP activity, upregulated expression of laminin and fibronectin and higher levels of HIF-1α and VEGF-A in the collagen group revealed that the engineered tumor is closer to human ovarian carcinoma. In order, collagen, Matrigel, alginate, control (without scaffold) and agarose exhibited decreases in tumor formation. All evidence indicated that the in vivo engineered tumor is scaffold-dependent. Bioactive hydrogels are superior to inert hydrogels at promoting tumor regeneration. In particular, biomimetic hydrogels are advantageous because they provide a microenvironment that mimics the ECM of natural tumors. On the other hand, typical features of cancer cells and the expression of genes related to cancer malignancy were far less similar to the natural tumor in vitro, which indicated the importance of culture environment in vivo. Superior to the in vitro culture, nude mice can be considered satisfactory in vivo ‘bioreactors’ for the screening of favorable cell vehicles for tumor engineering in vitro. (paper)

  15. pH- and Metal Ion- Sensitive Hydrogels based on N-[2-(dimethylaminoethylacrylamide

    Leena Nebhani

    2016-06-01

    Full Text Available Smart hydrogels are promising materials for actuators and sensors, as they can respond to small changes in their environment with a large property change. Hydrogels can respond to a variety of stimuli, for example temperature, pH, metal ions, etc. In this article, the synthesis and characterization of polyampholyte hydrogels based on open chain ligands showing pH and metal ion sensitivity are described. Copolymer and terpolymer gels using different mixtures of monomers i.e., N-[2-(dimethylaminoethylacrylamide] (DMAEAAm, N,N-dimethylacrylamide (DMAAm, acrylic acid (AA and 2-acrylamido-2-methyl-1-propanesulphonic acid (AMPS, have been synthesized. The effect of copolymer composition, i.e., the ratio and amount of ionic monomers and the degree of crosslinking on the swelling characteristics, was evaluated as a function of pH. On this basis, metal ion sensitivity measurements were performed at selected pH values. The metal ion sensitivity was measured by varying the concentration of Cu2+, Zn2+ and Ag+ ions under acidic pH conditions.

  16. Self-Healing and Thermoresponsive Dual-Cross-Linked Alginate Hydrogels Based on Supramolecular Inclusion Complexes.

    Miao, Tianxin; Fenn, Spencer L; Charron, Patrick N; Oldinski, Rachael A

    2015-12-14

    β-Cyclodextrin (β-CD), with a lipophilic inner cavity and hydrophilic outer surface, interacts with a large variety of nonpolar guest molecules to form noncovalent inclusion complexes. Conjugation of β-CD onto biomacromolecules can form physically cross-linked hydrogel networks upon mixing with a guest molecule. Herein, the development and characterization of self-healing, thermoresponsive hydrogels, based on host-guest inclusion complexes between alginate-graft-β-CD and Pluronic F108 (poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)), are described. The mechanics, flow characteristics, and thermal response were contingent on the polymer concentration and the host-guest molar ratio. Transient and reversible physical cross-linking between host and guest polymers governed self-assembly, allowing flow to occur under shear stress and facilitating complete recovery of the material's properties within a few seconds of unloading. The mechanical properties of the dual-cross-linked, multi-stimuli-responsive hydrogels were tuned as high as 30 kPa at body temperature and are advantageous for biomedical applications such as drug delivery and cell transplantation. PMID:26509214

  17. Thermal behavior of water in the selected starch- and cellulose-based polymeric hydrogels.

    Faroongsarng, Damrongsak; Sukonrat, Patchara

    2008-03-20

    In a polymer-water matrix, freezable water is depressed due to either porosity confinement or interaction. The aim of the study was to examine water crystallization/melting depression by sub-ambient differential scanning calorimetry. The selected starch- and cellulose-based polymers including pre-gelatinized starch (PS), sodium alginate, sodium starch glycolate, hydroxypropylmethyl cellulose (HPMC), sodium carboxymethyl cellulose, and croscarmellose sodium were employed. The pre-treated with ambient humidity (85-100% relative humidity, at 30.0+/-0.2 degrees C for 10 days) and with excess water (hydrogels) samples were subjected to between 25 and -150 degrees C cooling-heating cycle at 5.00 degrees C/min rate. The volume fractions of hydrogels were measured by light scattering technique. It was observed that all polymers but PS and HPMC with ambient humidity presented freezable water in two distinct fractions namely bound water where crystallizing/melting temperature was depressed and bulk water. The water transition in samples with various contents exhibited the pattern as a polymer solution, thus rather than confinement, the depression was due to interaction. The volume fraction-melting temperature data derived from endotherms of hydrogels were successfully fitted to Flory's model (r(2): 0.934-0.999). The Flory's interaction parameters (chi(1)) were found to vary between 0.520 and 0.847. In addition, the smaller the value of chi(1), the larger melting was depressed, i.e., stronger affinity for water. PMID:18061379

  18. Energy Recovery from Solutions with Different Salinities Based on Swelling and Shrinking of Hydrogels

    Zhu, Xiuping

    2014-06-17

    Several technologies, including pressure-retarded osmosis (PRO), reverse electrodialysis (RED), and capacitive mixing (CapMix), are being developed to recover energy from salinity gradients. Here, we present a new approach to capture salinity gradient energy based on the expansion and contraction properties of poly(acrylic acid) hydrogels. These materials swell in fresh water and shrink in salt water, and thus the expansion can be used to capture energy through mechanical processes. In tests with 0.36 g of hydrogel particles 300 to 600 μm in diameter, 124 mJ of energy was recovered in 1 h (salinity ratio of 100, external load of 210 g, water flow rate of 1 mL/min). Although these energy recovery rates were relatively lower than those typically obtained using PRO, RED, or CapMix, the costs of hydrogels are much lower than those of membranes used in PRO and RED. In addition, fouling might be more easily controlled as the particles can be easily removed from the reactor for cleaning. Further development of the technology and testing of a wider range of conditions should lead to improved energy recoveries and performance. © 2014 American Chemical Society.

  19. Rheological characterization of cataplasm bases composed of cross-linked partially neutralized polyacrylate hydrogel.

    Wang, Jian; Zhang, Hongqin; An, Dianyun; Yu, Jian; Li, Wei; Shen, Teng; Wang, Jianxin

    2014-10-01

    Viscoelasticity is a useful parameter for characterizing the intrinsic properties of the cross-linked polyacrylate hydrogel used in cataplasm bases. The aim of this study was to investigate the effects of various formulation parameters on the rheological characteristics of polyacrylate hydrogel. The hydrogel layers were formed using a partially neutralized polyacrylate (Viscomate(™)), which contained acrylic acid and sodium acrylate in different copolymerization ratios, as the cross-linked gel framework. Dihydroxyaluminum aminoacetate (DAAA), which produces aluminum ions, was used as the cross-linking agent. Rheological analyses were performed using a "stress amplitude sweep" and a "frequency sweep". The results showed that greater amounts of acrylic acid in the structure of Viscomate as well as higher concentrations of DAAA and Viscomate led to an increase in the elastic modulus (G'). However, greater amounts of acrylic acid in the structure of Viscomate and higher concentrations of DAAA had an opposite on the viscous modulus (G″); this might be owing to higher steric hindrance. The results of this study can serve as guidelines for the optimization of formulations for cataplasms. PMID:24865937

  20. [The effect of various types of Carbopol and different neutralizing bases on pharmaceutical availability of morphine hydrochloride from hydrogel preparations].

    Samczewska, Grazyna

    2009-01-01

    In the second half of the 20th century a heterogenic group of opioid receptors was discovered and identified in the central nervous system and in peripheral tissues. However, micro-type opioid receptors, responsible for analgesic effect of endogenic and egzogenic opioids, were not found on majority of peripheral neurons. They appear in skin or mucous membranes with active inflammatory or neoplastic process due to intensive migration to peripheral nerve efferent fibres. These discoveries made it possible to apply opioid analgesics topically (ointments, hydrogels) on pathologically changed skin or mucous membranes. This study presents the results of tests on two batches of hydrogel preparations produced according to own prescription on the base of acrylic acid polymers (Carbopol Ultrez 10 and Carbopol 980 NF). The polymer carboxyl groups were neutralized with different bases: sodium hydroxide, potasium hydroxide, triethanolamine, sodium tetraborate. The obtained hydrogel preparations were subjected to rheological tests. Extensibility was determined by extensometric method, whereas viscosity, yield stress and thixotropy were determined with the use of cone-plate digital rheometer. The activity of hydrogels hydrogen ions (pH) and the rate of their loss of volatile components at human body temperature were also tested. Using modified Mutimer apparatus morphine hydrochloride (MCl) diffusion was performed from the surface of the produced hydrogels through model stratum corneum (Tomofan) to acceptor fluid (water). The quantity of the released therapeutic agent in time function was determined by spectrophotometric method. The carried out studies have demonstrated that the produced hydrogels are non-Newtonian, viscoelastic, thixotropic systems of similar yield stress. The obtained results do not allow to determine unequivocally the effect of MCl, the kind of Carbopol and cross-linking base on hydrogel viscosity. The inversely proportional dependence between hydrogel

  1. Enzyme responsive GAG-based natural-synthetic hybrid hydrogel for tunable growth factor delivery and stem cell differentiation.

    Anjum, Fraz; Lienemann, Philipp S; Metzger, Stéphanie; Biernaskie, Jeff; Kallos, Michael S; Ehrbar, Martin

    2016-05-01

    We describe an enzymatically formed chondroitin sulfate (CS) and poly(ethylene glycol) (PEG) based hybrid hydrogel system, which by tuning the architecture and composition of modular building blocks, allows the application-specific tailoring of growth factor delivery and cellular responses. CS, a negatively charged sulfate-rich glycosaminoglycan of the extracellular matrix (ECM), known for its growth factor binding and stem cell regulatory functions, is used as a starting material for the engineering of this biomimetic materials platform. The functionalization of CS with transglutaminase factor XIII specific substrate sequences is utilized to allow cross-linking of CS with previously described fibrin-mimetic TG-PEG hydrogel precursors. We show that the hydrogel network properties can be tuned by varying the degree of functionalization of CS as well as the ratio and concentrations of PEG and CS precursors. Taking advantage of TG-PEG hydrogel, compatible tagged bio-functional building blocks, including RGD peptides or matrix metalloproteinase sensitive domains, can be incorporated on demand allowing the three-dimensional culture and expansion of human bone marrow mesenchymal stem cells (BM-MSCs). The binding of bone morphogenetic protein-2 (BMP-2) in a CS concentration dependent manner and the BMP-2 release mediated osteogenic differentiation of BM-MSCs indicate the potential of CS-PEG hybrid hydrogels to promote regeneration of bone tissue. Their modular design allows facile incorporation of additional signaling elements, rendering CS-PEG hydrogels a highly flexible platform with potential for multiple biomedical applications. PMID:26914701

  2. Polymer-conjugated albumin and fibrinogen composite hydrogels as cell scaffolds designed for affinity-based drug delivery.

    Oss-Ronen, Liat; Seliktar, Dror

    2011-01-01

    Serum albumin was conjugated to poly-(ethylene glycol) (PEG) and cross-linked to form mono-PEGylated albumin hydrogels. These hydrogels were used as a basis for drug carrying tissue engineering scaffold materials, based on the natural affinity of various drugs and compounds for the tethered albumin in the polymer network. The results of the drug release validation experiments showed that the release kinetics of the drugs from the mono-PEGylated albumin hydrogels were controlled by the molecular weight (MW) of PEG conjugated to the albumin protein, the drug MW and its inherent affinity for albumin. Composite hydrogels containing both mono-PEGylated albumin and PEGylated fibrinogen were used specifically for three-dimensional (3D) cell culture scaffolds, with inherent bioactivity, proteolytic biodegradability and controlled drug release properties. The specific characteristics of these complex hydrogels were governed by the ratio between the concentrations of each protein, the addition of free PEG diacrylate (PEG DA) molecules to the hydrogel matrix and the MW of the PEG conjugated to each protein. Comprehensive characterization of the drug release and degradation properties, as well as 3D cell culture experiments using these composite materials, demonstrated the effectiveness of this combined approach in creating a tissue engineering scaffold material with controlled drug release features. PMID:20643230

  3. Reduced Graphene Oxide-Based Silver Nanoparticle-Containing Composite Hydrogel as Highly Efficient Dye Catalysts for Wastewater Treatment

    Jiao, Tifeng; Guo, Haiying; Zhang, Qingrui; Peng, Qiuming; Tang, Yongfu; Yan, Xuehai; Li, Bingbing

    2015-07-01

    New reduced graphene oxide-based silver nanoparticle-containing composite hydrogels were successfully prepared in situ through the simultaneous reduction of GO and noble metal precursors within the GO gel matrix. The as-formed hydrogels are composed of a network structure of cross-linked nanosheets. The reported method is based on the in situ co-reduction of GO and silver acetate within the hydrogel matrix to form RGO-based composite gel. The stabilization of silver nanoparticles was also achieved simultaneously within the gel composite system. The as-formed silver nanoparticles were found to be homogeneously and uniformly dispersed on the surface of the RGO nanosheets within the composite gel. More importantly, this RGO-based silver nanoparticle-containing composite hydrogel matrix acts as a potential catalyst for removing organic dye pollutants from an aqueous environment. Interestingly, the as-prepared catalytic composite matrix structure can be conveniently separated from an aqueous environment after the reaction, suggesting the potentially large-scale applications of the reduced graphene oxide-based nanoparticle-containing composite hydrogels for organic dye removal and wastewater treatment.

  4. Rapid Synthesis of Superabsorbent Smart-Swelling Bacterial Cellulose/Acrylamide-Based Hydrogels for Drug Delivery

    Manisha Pandey

    2013-01-01

    Full Text Available This study evaluated the effect of solubilized and dispersed bacterial cellulose (BC on the physicochemical characteristics and drug release profile of hydrogels synthesized using biopolymers. Superabsorbent hydrogels were synthesized by graft polymerization of acrylamide on BC solubilized in an NaOH/urea solvent system and on dispersed BC by using N,N′-methylenebisacrylamide as a crosslinker under microwave irradiation. Fourier transform infrared spectroscopy analysis of the resulting hydrogels confirmed the grafting, and an X-ray diffraction pattern showed a decrease in the crystallinity of BC after the grafting process. The hydrogels exhibited pH and ionic responsive swelling behavior, with hydrogels prepared using solubilized BC (SH having higher swelling ratios. Furthermore, compared to the hydrogels synthesized using dispersed BC, the hydrogels synthesized using solubilized BC showed higher porosity, drug loading efficiency, and release. These results suggest the superiority of the hydrogels prepared using solubilized BC and that they should be explored further for oral drug delivery.

  5. Enhancement mechanism of the additional absorbent on the absorption of the absorbing composite using a type-based mixing rule

    Xu, Yonggang; Yuan, Liming; Zhang, Deyuan

    2016-04-01

    A silicone rubber composite filled with carbonyl iron particles and four different carbonous materials (carbon black, graphite, carbon fiber or multi-walled carbon nanotubes) was prepared using a two-roller mixture. The complex permittivity and permeability were measured using a vector network analyzer at the frequency of 2-18 GHz. Then a type-based mixing rule based on the dielectric absorbent and magnetic absorbent was proposed to reveal the enhancing mechanism on the permittivity and permeability. The enforcement effect lies in the decreased percolation threshold and the changing pending parameter as the carbonous materials were added. The reflection loss (RL) result showed the added carbonous materials enhanced the absorption in the lower frequency range, the RL decrement value being about 2 dB at 4-5 GHz with a thickness of 1 mm. All the added carbonous materials reinforced the shielding effectiveness (SE) of the composites. The maximum increment value of the SE was about 3.23 dB at 0.5 mm and 4.65 dB at 1 mm, respectively. The added carbonous materials could be effective additives for enforcing the absorption and shielding property of the absorbers.

  6. Modulation of Huh7.5 spheroid formation and functionality using modified PEG-based hydrogels of different stiffness.

    Lee, Bae Hoon; Kim, Myung Hee; Lee, Jae Ho; Seliktar, Dror; Cho, Nam-Joon; Tan, Lay Poh

    2015-01-01

    Physical cues, such as cell microenvironment stiffness, are known to be important factors in modulating cellular behaviors such as differentiation, viability, and proliferation. Apart from being able to trigger these effects, mechanical stiffness tuning is a very convenient approach that could be implemented readily into smart scaffold designs. In this study, fibrinogen-modified poly(ethylene glycol)-diacrylate (PEG-DA) based hydrogels with tunable mechanical properties were synthesized and applied to control the spheroid formation and liver-like function of encapsulated Huh7.5 cells in an engineered, three-dimensional liver tissue model. By controlling hydrogel stiffness (0.1-6 kPa) as a cue for mechanotransduction representing different stiffness of a normal liver and a diseased cirrhotic liver, spheroids ranging from 50 to 200 μm were formed over a three week time-span. Hydrogels with better compliance (i.e. lower stiffness) promoted formation of larger spheroids. The highest rates of cell proliferation, albumin secretion, and CYP450 expression were all observed for spheroids in less stiff hydrogels like a normal liver in a healthy state. We also identified that the hydrogel modification by incorporation of PEGylated-fibrinogen within the hydrogel matrix enhanced cell survival and functionality possibly owing to more binding of autocrine fibronectin. Taken together, our findings establish guidelines to control the formation of Huh7.5 cell spheroids in modified PEGDA based hydrogels. These spheroids may serve as models for applications such as screening of pharmacological drug candidates. PMID:25692976

  7. Modulation of Huh7.5 spheroid formation and functionality using modified PEG-based hydrogels of different stiffness.

    Bae Hoon Lee

    Full Text Available Physical cues, such as cell microenvironment stiffness, are known to be important factors in modulating cellular behaviors such as differentiation, viability, and proliferation. Apart from being able to trigger these effects, mechanical stiffness tuning is a very convenient approach that could be implemented readily into smart scaffold designs. In this study, fibrinogen-modified poly(ethylene glycol-diacrylate (PEG-DA based hydrogels with tunable mechanical properties were synthesized and applied to control the spheroid formation and liver-like function of encapsulated Huh7.5 cells in an engineered, three-dimensional liver tissue model. By controlling hydrogel stiffness (0.1-6 kPa as a cue for mechanotransduction representing different stiffness of a normal liver and a diseased cirrhotic liver, spheroids ranging from 50 to 200 μm were formed over a three week time-span. Hydrogels with better compliance (i.e. lower stiffness promoted formation of larger spheroids. The highest rates of cell proliferation, albumin secretion, and CYP450 expression were all observed for spheroids in less stiff hydrogels like a normal liver in a healthy state. We also identified that the hydrogel modification by incorporation of PEGylated-fibrinogen within the hydrogel matrix enhanced cell survival and functionality possibly owing to more binding of autocrine fibronectin. Taken together, our findings establish guidelines to control the formation of Huh7.5 cell spheroids in modified PEGDA based hydrogels. These spheroids may serve as models for applications such as screening of pharmacological drug candidates.

  8. Highly effective metal vapor absorbents based on carbon nanotubes

    Liu, Zongwen; Gao, Yihua; Bando, Yoshio

    2002-12-01

    It was shown that, when filled with gallium, carbon nanotubes can absorb copper vapor with extraordinarily high efficiency. The copper vapor generated from the supporting copper grid upon heating to 800 °C in an electron microscope under a pressure of 1.0×10-5 Pa quickly deposited into the carbon nanotubes and formed an alloy with gallium where the vapor pressure is up to 500 times higher (5×10-3 Pa). These filled carbon nanotubes may be used as highly sensitive toxic or radioactive metal vapor absorbents since gallium also tends to form alloys with metals like mercury and uranium.

  9. Polymer hydrogels as optimized delivery systems

    Batista, Jorge G.S.; Varca, Gustavo H.C.; Ferraz, Caroline C.; Garrido, Gabriela P.; Diniz, Bruna M.; Carvalho, Vinicius S.; Lugao, Ademar B., E-mail: jorgegabriel@usp.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2013-07-01

    Hydrogels are formed by polymers capable of absorbing large quantities of water. They consist of one or more three-dimensionally structured polymer networks formed by macromolecular chains linked by covalent bonds-crosslinks - and physical interactions. The application of hydrogels, has been widely studied. Biodegradable synthetic or natural polymers such as chitosan, starch and poly-lactic-co-glycolic acid, have properties that allow the development of biodegradable systems for drug and nutraceutics delivery. This study aimed to develop polymeric hydrogels based on polyvinyl alcohol, polyacrylamide and polyvinylpyrrolidone using ionizing radiation in order to develop hydrogels for improved loading and release of compounds. Polymer solutions were solubilized in water and poured into thermoformed packages. After sealing, the material was subjected to γ-irradiation at 25kGy. The samples were assayed by means of mechanical properties, gel fraction and swelling degree. Nanostructure characterization was performed using Flory's equation to determine crosslinking density. The systems developed showed swelling degree and adequate mechanical resistance. The nanostructure evaluation showed different results for each system demonstrating the need of choosing the polymer based on the specific properties of each material. (author)

  10. Sensors of absorbed dose of ionizing radiation based on mosfet

    Perevertaylo V. L.

    2010-01-01

    The requirements to technology and design of p-channel and n-channel MOS transistors with a thick oxide layer designed for use in the capacity of integral dosimeters of absorbed dose of ionizing radiation are defined. The technology of radiation-sensitive MOS transistors with a thick oxide in the p-channel and n-channel version is created.

  11. Hyaluronic acid based hydrogel system for soft tissue regeneration and drug delivery

    Jha, Amit Kumar

    We have developed hyaluronic acid (HA)-based, biomimetic hydrogel matrices that are hierarchically structured, mechanically robust and biologically active. Specifically, HA-based hydrogel particles (HGPs) with controlled sizes, defined porosity, and improved stability were synthesized using different inverse emulsion systems and crosslinking chemistries. The resultant particles either contained residual functional groups or were rendered reactive by subsequent chemical modifications. HA-based doubly crosslinked networks (DXNs) were synthesized via covalent crosslinking of HA HGPs with soluble HA macromers carrying mutually reactive functional groups. These hybrid matrices are hierarchical in nature, consisting of densely crosslinked HGPs integrated in a loosely connected secondary matrix. Their mechanical properties and degradation kinetics can be readily tuned by varying the particle size, functional group density, intra- and interparticle crosslinking. To improve the biological functions of HA HGPs, perlecan domain I (PlnDI), a basement membrane proteoglycan that has strong affinity for various heparin binding growth factors (HBGFs), was successfully conjugated to the particles through the core protein via a flexible poly(ethylene glycol) (PEG) linker. The immobilized PlnDI maintains its ability to bind bone morphogenetic proteins (BMP-2) and modulates its in vitro release. A similar, sustained release of BMP-2 was achieved by encapsulating BMP-2-loaded HGPs within a photocrosslinked HA matrix. When encapsulated in HA DXNs, primary bovine chondrocytes were able to maintain their phenotype, proliferate readily and produce abundant glycosaminoglycan. Finally, cell-adhesive HA DXNs were fabricated by encapsulating gelatin-decorated HA HGPs in a secondary HA matrix. Human MSCs were shown to adhere to the composite matrix through the focal adhesion sites clustered on particle surface. The cell-adhesive composite matrices supported hMSC proliferation and migration into

  12. Effects of bound versus soluble pentosan polysulphate in PEG/HA-based hydrogels tailored for intervertebral disc regeneration.

    Frith, Jessica E; Menzies, Donna J; Cameron, Andrew R; Ghosh, P; Whitehead, Darryl L; Gronthos, S; Zannettino, Andrew C W; Cooper-White, Justin J

    2014-01-01

    Previous reports in the literature investigating chondrogenesis in mesenchymal progenitor cell (MPC) cultures have confirmed the chondro-inductive potential of pentosan polysulphate (PPS), a highly sulphated semi-synthetic polysaccharide, when added as a soluble component to culture media under standard aggregate-assay conditions or to poly(ethylene glycol)/hyaluronic acid (PEG/HA)-based hydrogels, even in the absence of inductive factors (e.g. TGFβ). In this present study, we aimed to assess whether a 'bound' PPS would have greater activity and availability over a soluble PPS, as a media additive or when incorporated into PEG/HA-based hydrogels. We achieved this by covalently pre-binding the PPS to the HA component of the gel (forming a new molecule, HA-PPS). We firstly investigated the activity of HA-PPS compared to free PPS, when added as a soluble factor to culture media. Cell proliferation, as determined by CCK8 and EdU assay, was decreased in the presence of either bound or free PPS whilst chondrogenic differentiation, as determined by DMMB assay and histology, was enhanced. In all cases, the effect of the bound PPS (HA-PPS) was more potent than that of the unbound form. These results alone suggest wider applications for this new molecule, either as a culture supplement or as a coating for scaffolds targeted at chondrogenic differentiation or maturation. We then investigated the incorporation of HA-PPS into a PEG/HA-based hydrogel system, by simply substituting some of the HA for HA-PPS. Rheological testing confirmed that incorporation of either HA-PPS or PPS did not significantly affect gelation kinetics, final hydrogel modulus or degradation rate but had a small, but significant, effect on swelling. When encapsulated in the hydrogels, MPCs retained good viability and rapidly adopted a rounded morphology. Histological analysis of both GAG and collagen deposition after 21 days showed that the incorporation of the bound-PPS into the hydrogel resulted in

  13. Hydrogel-based ultra-moisturizing cream formulation for skin hydration and enhanced dermal drug delivery.

    Lee, Sang Gon; Kim, Sung Rae; Cho, Hye In; Kang, Mean Hyung; Yeom, Dong Woo; Lee, Seo Hyun; Lee, Sangkil; Choi, Young Wook

    2014-01-01

    To develop an external vehicle for skin hydration and enhanced dermal drug delivery, a hydrogel-based ultra-moisturizing cream (HUMC) was successfully formulated with carbopol 934P, urea, Tinocare GL, grape seed oil, and other excipients. The HUMC showed plastic flow behavior due to a gel structure with a cream base. Different types of drug-free vehicles such as a hydrogel, conventional cream (CC), and three HUMCs were prepared and subjected to an in vivo skin hydration test on a hairless mouse using a corneometer. Hydration effect (∆AU) was in the order of HUMC2>HUMC1 ≥ CC>HUMC3>hydrogel. Using nile red (NR) and 5-carboxyfluorescein (5-CF) as lipophilic and hydrophilic fluorescent probes, respectively, in vitro skin permeation and accumulation studies were conducted using Franz diffusion cells. The values of steady-state flux (Jss, ng/h/cm(2)) were obtained: 74.8 (CC), 145.6 (HUMC1), and 161.9 (HUMC2) for NR delivery; 6.8 (CC), 8.3 (HUMC1), and 10.9 (HUMC2) for 5-CF delivery. The amounts retained in the skin at 12 h (Qr, ng/cm(2)) were determined: 86.4 (CC) and 102.0 (HUMC2) for NR; and 70.1 (CC) and 195.6 (HUMC2) for 5-CF. Confocal microscopy was used to visualize the distribution of the fluorescent probes. NR tended to be localized into the deeper part of the skin with adipose tissue whereas 5-CF localized in the upper layer of the skin. Thus we propose that HUMC2 is an efficacious vehicle for skin hydration and enhances dermal delivery of lipophilic and hydrophilic drugs. PMID:25273390

  14. Evaluation of a mPEG-polyester-based hydrogel as cell carrier for chondrocytes.

    Peng, Sydney; Yang, Shu-Rui; Ko, Chao-Yin; Peng, Yu-Shiang; Chu, I-Ming

    2013-11-01

    Temperature-sensitive hydrogels are attractive alternatives to porous cell-seeded scaffolds and is minimally invasive through simple injection and in situ gelling. In this study, we compared the performance of two types of temperature-sensitive hydrogels on chondrocytes encapsulation for the use of tissue engineering of cartilage. The two hydrogels are composed of methoxy poly(ethylene glycol)- poly(lactic-co-valerolactone) (mPEG-PVLA), and methoxy poly(ethylene glycol)-poly(lactic- co-glycolide) (mPEG-PLGA). Osmolarity and pH were optimized through the manipulation of polymer concentration and dispersion medium. Chondrocytes proliferation in mPEG-PVLA hydrogels was observed as well as accumulation of GAGs and collagen. On the other hand, chondrocytes encapsulated in mPEG-PLGA hydrogels showed low viability and chondrogenesis. Also, mPEG-PVLA hydrogel, which is more hydrophobic, retained physical integrity after 14 days while mPEG-PLGA hydrogel underwent full degradation due to faster hydrolysis rate and more pronounced acidic self-catalyzed degradation. The mPEG-PVLA hydrogel can be furthered tuned by manipulation of molecular weights to obtain hydrogels with different swelling and degradation characteristics, which may be useful as producing a selection of hydrogels compatible with different cell types. Taken together, these results demonstrate that mPEG-PVLA hydrogels are promising to serve as three-dimensional cell carriers for chondrocytes and potentially applicable in cartilage tissue engineering. PMID:24039062

  15. SOLAR ABSORBING COOLING SYSTEMS BASED ON MULTISTAGE HEAT-MASS-TRANSFER DEVICES

    Doroshenko A.V.; Ludnitsky K.V.

    2014-01-01

    The article presents the worked out schematics for the alternative refrigeration systems and of air-conditioning systems, based on the use of absorbing cycle and of the sunny energy for the regeneration (renewals) of absorbent solution. We use here the cascade principle of construction of all heat-mass-transfer apparatus with variation of both the temperature level and the growth of absorbent concentration on the cascade stages. The heat-mass-transfer equipment as a part of the drying and coo...

  16. SOLAR REFRIGERATION SYSTEMS BASED ON THE ABSORBER WITH INTERNAL EVAPORATIVE COOLING

    Дорошенко, O.В.; Людницький, К.В.

    2015-01-01

    The paper presents the developed schematics for alternative refrigeration systems and air conditioning systems based on the use of heat-absorption cycle and solar energy for regeneration (recovery) of the absorbent solution. Cascade principle of construction of the drying and cooling circuits with absorbent concentration increasing on the steps of the cascade is used. The absorber with internal evaporative cooling that eliminates a separate evaporative cooler, typically comprised after the co...

  17. Adsorption of crude oil from aqueous solution by hydrogel of chitosan based polyacrylamide prepared by radiation induced graft polymerization

    The adsorption of crude oil (initial concentration 0.5-30 g/L) from aqueous solution using hydrogel of chitosan based polyacrylamide (PAM) prepared by radiation induced graft polymerization has been investigated. The prepared hydrogel was characterized by FTIR and SEM micrographs. The experiments were carried out as a function of different initial concentrations of oil residue, acrylamide concentration, contact time and pH to determine the optimum condition for the adsorption of residue oil from aqueous solution and sea water. The results obtained showed that the hydrogel prepared at concentration of 40% acrylamide (AAm) and at a radiation dose of 5 kGy has high removal efficiency of crude oil 2.3 g/g at pH 3. Equilibrium studies have been carried out to determine the capacity of the hydrogel for adsorption of crude oil, Langmuir and Freundlich adsorption models were applied to describe the experimental isotherms and isotherms constants. Equilibrium data were found to fit very well with both Freundlich and Langmuir models. Also the adsorption of oil onto the hydrogel behaves as a pseudo-second-order kinetic models rather than the pseudo-first-order kinetic model.

  18. Self-healable mussel-mimetic nanocomposite hydrogel based on catechol-containing polyaspartamide and graphene oxide.

    Wang, Bo; Jeon, Young Sil; Park, Ho Seok; Kim, Ji-Heung

    2016-12-01

    Stimuli-responsive and self-healing materials have a wide range of potential uses, and some significant research has focused on cross-linking of hydrogel materials by means of reversible coordination bonding. The resulting materials, however, tend to have poor mechanical properties with pronounced weakness and brittleness. In this work, we present a novel mussel-inspired graphene oxide(GO)-containing hydrogel based on modified polyaspartamide with γ-amino butyric acid (GABA), 3.4-dihydroxyphenethylamine (DOPA), and ethanolamine (EA), termed PolyAspAm(GABA/DOPA/EA). Here both GO nanosheets and boric acid (H3BO3) act as cross-linkers, interacting with polar functional groups of the PolyAspAm(GABA/DOPA/EA). Compared to PolyAspAm(GABA/DOPA/EA)/B(3+) gel without GO, the same containing 5wt% of GO yielded a 10-fold increase in both the storage and loss moduli, as well as 134% and 104% increases in the tensile and compressive strengths, respectively. In addition, the GO-containing polyaspartamide hydrogel exhibited rapid and autonomous self-healing property. Two types of bonding, boron-catechol coordination and strong hydrogen bonding interactions between PolyAspAm side chains and GO nanosheets, would impart the enhanced mechanical strength and good reversible gelation behavior upon pH stimulation to the hydrogel, making this biocompatible hydrogel a promising soft matter for biomedical applications. PMID:27612701

  19. Microwave metamaterial absorber based on multiple square ring structures

    Weicheng Zhou

    2015-11-01

    Full Text Available In this paper, we report the design, analysis, and simulation of quintuple-band metamaterial absorber (MMA in the microwave region. The absorber is constructed of a delicate periodic patterned structures and a metallic background plane, separated by a dielectric substrate. By manipulating the periodic patterned structures, high absorption can be obtained at five specific resonance frequencies. Moreover, the significantly high absorptions of quintuple-peaks are persistent with polarization independence, and the influence of angle of incidence for both TE and TM modes was also elucidated. For explaining the absorption mechanism of proposed structures, the electric and magnetic field distributions and resistance matching principal were given. Importantly, the design idea has the ability to be extended to other frequencies, like terahertz, infrared and optical frequencies.

  20. Sensors of absorbed dose of ionizing radiation based on mosfet

    Perevertaylo V. L.

    2010-10-01

    Full Text Available The requirements to technology and design of p-channel and n-channel MOS transistors with a thick oxide layer designed for use in the capacity of integral dosimeters of absorbed dose of ionizing radiation are defined. The technology of radiation-sensitive MOS transistors with a thick oxide in the p-channel and n-channel version is created.

  1. Strong and Robust Polyaniline-Based Supramolecular Hydrogels for Flexible Supercapacitors.

    Li, Wanwan; Gao, Fengxian; Wang, Xiaoqian; Zhang, Ning; Ma, Mingming

    2016-08-01

    We report a supramolecular strategy to prepare conductive hydrogels with outstanding mechanical and electrochemical properties, which are utilized for flexible solid-state supercapacitors (SCs) with high performance. The supramolecular assembly of polyaniline and polyvinyl alcohol through dynamic boronate bond yields the polyaniline-polyvinyl alcohol hydrogel (PPH), which shows remarkable tensile strength (5.3 MPa) and electrochemical capacitance (928 F g(-1) ). The flexible solid-state supercapacitor based on PPH provides a large capacitance (306 mF cm(-2) and 153 F g(-1) ) and a high energy density of 13.6 Wh kg(-1) , superior to other flexible supercapacitors. The robustness of the PPH-based supercapacitor is demonstrated by the 100 % capacitance retention after 1000 mechanical folding cycles, and the 90 % capacitance retention after 1000 galvanostatic charge-discharge cycles. The high activity and robustness enable the PPH-based supercapacitor as a promising power device for flexible electronics. PMID:27328742

  2. New absorbent material acoustic based on kenaf’s fibre

    Ramis, J.

    2010-09-01

    Full Text Available Acoustic Standards in the building are responsible for, companies and individuals, propose new acoustic materials for the sound isolation. This paper presents a new sound-absorbent material, it is based on natural fibres, particularly fibres of kenaf. It also proposes an empirical model for this material, this models depends on the frequency. There are accepted models from the scientific community about mineral wool, glass wool, rock wool, foam or polyester fibre. Several of these models are empirical. They are obtained from the equation adjustments about the acoustic impedance and propagation constant behaviour, depending upon the flow resistivity, fibre’s diameter and density. There are even standards like UNE-EN 12354-6 where these models are accepted under certain limitations like the fundamental basis as in the materials’ acoustics behaviour prediction. From the various tests conducted in the laboratory, empirical equations are proposed for this new acoustic material. In addition, there has been a first approach to validate this model in combination with a micro-structural model, based on the steps taken by Bies-Hansen (1, which allows us to obtain the value of the resistance to flow.

    El carácter marcadamente prestacional de las normativas acústicas en la edificación abre el camino a la propuesta, por parte de empresas y particulares, de nuevos materiales acústicos susceptibles de ser utilizados en el ámbito de la acústica de la edificación. Éste es el caso que nos ocupa en el presente trabajo en el que se presenta un nuevo material acústico absorbente basado en fibras vegetales, concretamente el kenaf. Además se propone un modelo empírico de modelización del comportamiento absorbente de varias composiciones de este material en función de la frecuencia. Existen modelos de diferentes lanas minerales, lanas de roca, lanas de vidrio, espumas o lanas de poliéster. Algunos de estos modelos —llamados empíricos— se

  3. A Wide-Band Metamaterial Absorber Based on Loaded Magnetic Resonators

    GU Chao; QU Shao-Bo; PEI Zhi-Bin; MA Hua; XU Zhuo; BAI Peng; PENG Wei-Dong; LIN Bao-Qin

    2011-01-01

    @@ A wide-band polarization-insensitive and wide-angle metamaterial absorber based on loaded magnetic resonators is presented.The unit cell of this absorber consists of a magnetic resonator loaded with lumped resistances, a dielectric substrate and a back metal film.Theoretical and simulated results show that this absorber has a wide- band strong absorption for the incident wave from 3.87 GHz to 21.09 GHz.Simulated absorbance values under loading and unloading conditions indicate that electrocircuit's resonances are more stable than electromagnetic resonances and thus can be used to realize wide-band absorption.Simulated absorbance values under different polarization angles and different angles of incidence indicate that this absorber is polarization-insensitive and wide-angle.It may have potential applications in military fields.

  4. Designed biodegradable hydrogel structures prepared by stereolithography using poly(ethylene glycol)/poly(D,L-lactide)-based resins.

    Seck, Tetsu M; Melchels, Ferry P W; Feijen, Jan; Grijpma, Dirk W

    2010-11-20

    Designed three-dimensional biodegradable poly(ethylene glycol)/poly(D,L-lactide) hydrogel structures were prepared for the first time by stereolithography at high resolutions. A photo-polymerisable aqueous resin comprising PDLLA-PEG-PDLLA-based macromer, visible light photo-initiator, dye and inhibitor in DMSO/water was used to build the structures. Porous and non-porous hydrogels with well-defined architectures and good mechanical properties were prepared. Porous hydrogel structures with a gyroid pore network architecture showed narrow pore size distributions, excellent pore interconnectivity and good mechanical properties. The structures showed good cell seeding characteristics, and human mesenchymal stem cells adhered and proliferated well on these materials. PMID:20659509

  5. Raman-based imaging uncovers the effects of alginate hydrogel implants in spinal cord injury

    Galli, Roberta; Tamosaityte, Sandra; Koch, Maria; Sitoci-Ficici, Kerim H.; Later, Robert; Uckermann, Ortrud; Beiermeister, Rudolf; Gelinsky, Michael; Schackert, Gabriele; Kirsch, Matthias; Koch, Edmund; Steiner, Gerald

    2015-07-01

    The treatment of spinal cord injury by using implants that provide a permissive environment for axonal growth is in the focus of the research for regenerative therapies. Here, Raman-based label-free techniques were applied for the characterization of morphochemical properties of surgically induced spinal cord injury in the rat that received an implant of soft unfunctionalized alginate hydrogel. Raman microspectroscopy followed by chemometrics allowed mapping the different degenerative areas, while multimodal multiphoton microscopy (e.g. the combination of coherent anti-Stokes Raman scattering (CARS), endogenous two-photon fluorescence and second harmonic generation on the same platform) enabled to address the morphochemistry of the tissue at cellular level. The regions of injury, characterized by demyelination and scarring, were retrieved and the distribution of key tissue components was evaluated by Raman mapping. The alginate hydrogel was detected in the lesion up to six months after implantation and had positive effects on the nervous tissue. For instance, multimodal multiphoton microscopy complemented the results of Raman mapping, providing the micromorphology of lipid-rich tissue structures by CARS and enabling to discern lipid-rich regions that contained myelinated axons from degenerative regions characterized by myelin fragmentation and presence of foam cells. These findings demonstrate that Raman-based imaging methods provide useful information for the evaluation of alginate implant effects and have therefore the potential to contribute to new strategies for monitoring degenerative and regenerative processes induced in SCI, thereby improving the effectiveness of therapies.

  6. Water-in-Water Emulsion Based Synthesis of Hydrogel Nanospheres with Tunable Release Kinetics

    Aydın, Derya; Kızılel, Seda

    2016-06-01

    Poly(ethylene glycol) (PEG) micro/nanospheres have several unique advantages as polymer based drug delivery systems (DDS) such as tunable size, large surface area to volume ratio, and colloidal stability. Emulsification is one of the widely used methods for facile synthesis of micro/nanospheres. Two-phase aqueous system based on polymer-polymer immiscibility is a novel approach for preparation of water-in-water (w/w) emulsions. This method is promising for the synthesis of PEG micro/nanospheres for biological systems, since the emulsion is aqueous and do not require organic solvents or surfactants. Here, we report the synthesis of nano-scale PEG hydrogel particles using w/w emulsions using phase separation of dextran and PEG prepolymer. Dynamic light scattering (DLS) and scaning electron microscopy (SEM) results demonstrated that nano-scale hydrogel spheres could be obtained with this approach. We investigated the release kinetics of a model drug, pregabalin (PGB) from PEG nanospheres and demonstrated the influence of polymerization conditions on loading and release of the drug as well as the morphology and size distribution of PEG nanospheres. The experimental drug release data was fitted to a stretched exponential function which suggested high correlation with experimental results to predict half-time and drug release rates from the model equation. The biocompatibility of nanospheres on human dermal fibroblasts using cell-survival assay suggested that PEG nanospheres with altered concentrations are non-toxic, and can be considered for controlled drug/molecule delivery.

  7. A highly sensitive, low-cost, wearable pressure sensor based on conductive hydrogel spheres

    Tai, Yanlong

    2015-01-01

    Wearable pressure sensing solutions have promising future for practical applications in health monitoring and human/machine interfaces. Here, a highly sensitive, low-cost, wearable pressure sensor based on conductive single-walled carbon nanotube (SWCNT)/alginate hydrogel spheres is reported. Conductive and piezoresistive spheres are embedded between conductive electrodes (indium tin oxide-coated polyethylene terephthalate films) and subjected to environmental pressure. The detection mechanism is based on the piezoresistivity of the SWCNT/alginate conductive spheres and on the sphere-electrode contact. Step-by-step, we optimized the design parameters to maximize the sensitivity of the sensor. The optimized hydrogel sensor exhibited a satisfactory sensitivity (0.176 ΔR/R0/kPa-1) and a low detectable limit (10 Pa). Moreover, a brief response time (a few milliseconds) and successful repeatability were also demonstrated. Finally, the efficiency of this strategy was verified through a series of practical tests such as monitoring human wrist pulse, detecting throat muscle motion or identifying the location and the distribution of an external pressure using an array sensor (4 × 4). © 2015 The Royal Society of Chemistry.

  8. 21 CFR 878.4022 - Hydrogel wound dressing and burn dressing.

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Hydrogel wound dressing and burn dressing. 878... Hydrogel wound dressing and burn dressing. (a) Identification. A hydrogel wound dressing is a sterile or... percent) and capable of absorbing exudate. This classification does not include a hydrogel wound...

  9. PRAGMATIC HYDROGELS

    Patil S.A.; Rane B.R.; Bakliwal S.R.; Pawar S.P.

    2011-01-01

    Man has always been plagued with many ailments and diseases. The field of pharmaceutical science has today become more invaluable in helping to keep us healthy and prevent disease. The availability of large molecular weight protein and peptide-based drugs due to the recent advances has given us a new ways to treat a number of diseases. I wish to present new and promising techniques for the production of drug and protein delivery formulations that have been developed that is Hydrogel. These ar...

  10. Self-Healing and Thermo-Responsive Dual-Crosslinked Alginate Hydrogels based on Supramolecular Inclusion Complexes

    Miao, Tianxin; Fenn, Spencer L.; Charron, Patrick N.; Oldinski, Rachael A.

    2015-01-01

    β-cyclodextrin (β-CD), with a lipophilic inner cavity and hydrophilic outer surface, interacts with a large variety of non-polar guest molecules to form non-covalent inclusion complexes. Conjugation of β-CD onto biomacromolecules can form physically-crosslinked hydrogel networks upon mixing with a guest molecule. Herein describes the development and characterization of self-healing, thermo-responsive hydrogels, based on host-guest inclusion complexes between alginate-graft-β-CD and Pluronic® ...

  11. Optical absorbers based on strong interference in ultra-thin films

    Kats, Mikhail A

    2016-01-01

    Optical absorbers find uses in a wide array of applications across the electromagnetic spectrum, including photovoltaic and photochemical cells, photodetectors, optical filters, stealth technology, and thermal light sources. Recent efforts have sought to reduce the footprint of optical absorbers, conventionally based on graded structures or Fabry-Perot-type cavities, by using the emerging concepts of plasmonics, metamaterials, and metasurfaces. Unfortunately, these new absorber designs require patterning on subwavelength length scales, and are therefore impractical for many large-scale optical and optoelectronic devices. In this article, we summarize recent progress in the development of optical absorbers based on lossy films with thicknesses significantly smaller than the incident optical wavelength. These structures have a small footprint and require no nanoscale patterning. We outline the theoretical foundation of these absorbers based on "ultra-thin-film interference", including the concepts of loss-induc...

  12. Improve Cloud Temperature of Radiation Prepared Hydrogels Based on Poly(N-Isopropylacrylamide) by Addition of N,N-Dimethylacrylamide Monomer

    The poly(N-isopropylacrylamide) (PNIPAM) based hydrogels are typical thermosensitive material, which can be successfully synthesized from aqueous solution of NIPAM by radiation polymerization and cross-linking. Adding of N,N dimethylacrylamide (DMA) a hydrophilic monomer into the solution of reactant before irradiation much improved the cloud temperature of the created hydrogels. The phase transition temperature as well as swelling degree of hydrogel based on PNIPAM-DMA copolymer also depended on the ratio of DMA. Chemical structure of hydrogel P(NIPAM-co-DMA) were verified by proton spectroscopy (1H-NMR). The themosensivity of hydrogels was also investigated and the results showed that the low cloud temperature (Tp) is around of 37-40 oC. (author)

  13. Nanoslit-microcavity-based narrow band absorber for sensing applications.

    Lu, Xiaoyuan; Zhang, Lingxuan; Zhang, Tongyi

    2015-08-10

    We propose an ultranarrow bandwidth perfect infrared absorber consisting of a metal periodic structured surface with nanoslits, a spacer dielectric, and a metal back plate. Its bandwidth and aborption are respectively about 8 nm and 95%. The thickness of the nanobars and the spacer, and the width of the nanoslits are primary factors determining the absorption performance. This structure not only has narrow bandwidth but also can obtain the giant electric field enhancement in the tiny volume of the nanoslits. Operated as a refractive index sensor, this structure has figure of merit as high as 25. It has potential in biomedical and sensing applications. PMID:26367923

  14. Dextran based highly conductive hydrogel polysulfide electrolyte for efficient quasi-solid-state quantum dot-sensitized solar cells

    Highlights: ► Dextran based hydrogel is first used to prepare quasi-solid-state polysulfide electrolyte for quantum dot-sensitized solar cells. ► The ion conductivity of hydrogel electrolyte shows almost the same value as the liquid electrolyte. ► The liquid state at elevated temperature of hydrogel electrolyte allows for a good contact between electrolyte and CdS/CdSe co-sensitized TiO2 photoanode. ► The hydrogel electrolyte based cell exhibits slightly lower power conversion efficiency than that of liquid electrolyte based cell. ► The dynamic electron transfer mechanism in hydrogel electrolyte based cell is examined in detail by EIS and CIMPS/IMVS. -- Abstract: Highly conductive hydrogel polysulfide electrolyte is first fabricated using dextran as gelator and used as quasi-solid-state electrolyte for quantum dot-sensitized solar cells (QDSSCs). The hydrogel electrolyte with gelator concentration of 15 wt% shows almost the same conductivity as the liquid one. Moreover, its liquid state at elevated temperature allow for the well penetration into the pores in electrodeposited CdS/CdSe co-sensitized TiO2 photoanode. This gel electrolyte based QDSSC exhibits power conversion efficiency (η) of 3.23% under AG 1.5 G one sun (100 mW cm−2) illumination, slightly lower than that of liquid electrolyte based cell (3.69%). The dynamic electron transfer mechanism of the gel and liquid electrolyte based QDSSC are examined by electrochemical impedance spectroscopy (EIS) and controlled intensity modulated photocurrent/photovoltage spectroscopy (CIMPS/IMVS). It is found that the electron transport in gel electrolyte based cell is much faster than the liquid electrolyte based cell but it tends to recombine more easily than the latter. However, these differences fade away with increasing the light intensity, showing declining electron collection efficiency at higher light intensity illumination. As a result, a conversion efficiency of 4.58% is obtained for the gel

  15. Smart Hydrogel-Based Valves Inspired by the Stomata in Plants.

    Gargava, Ankit; Arya, Chandamany; Raghavan, Srinivasa R

    2016-07-20

    We report the design of hydrogels that can act as "smart" valves or membranes. Each hydrogel is engineered with a pore (about 1 cm long and chemistry of this gel. For example, if the active gel is made from N-isopropylacrylamide (NIPA), the actuation of the pore depends on the temperature of water relative to 32 °C, which is the lower-critical solution temperature (LCST) of NIPA. The concentric design of our hybrid provides directionality to the volumetric transition of the active gel, i.e., it ensures that the pore opens as the active gel shrinks. In turn, contact with hot water (T > 32 °C) opens the pore and allows the water to pass through the gel. Conversely, the pore remains closed when the water is cold (T < 32 °C). The gel thereby acts as a "smart" valve that is able to regulate the flow of solvent depending on its properties. We have extended the concept to other stimuli that can cause gel-swelling transitions including solvent composition, pH, and light. Additionally, when two different gel-based valves are arranged in series, the assembly acts as a logical "AND" gate, i.e., water flows through the valve-combination only if it simultaneously satisfies two distinct conditions (such as its pH being below a critical value and its temperature being above a critical value). PMID:27400459

  16. In situ gelling polyvalerolactone-based thermosensitive hydrogel for sustained drug delivery.

    Mishra, Gyan P; Kinser, Reid; Wierzbicki, Igor H; Alany, Raid G; Alani, Adam W G

    2014-10-01

    Biodegradable poly(ethyleneglycol)-poly(valerolactone)-poly(ethyleneglycol) [PEG-PVL-PEG] copolymers were synthesized through ring opening polymerization of δ-valerolactone (VL) followed by the coupling of monomethoxy poly(ethyleneglycol-poly(valerolactone) (mPEG-PVL) with hexamethylene diisocyanate (HDI). The copolymers were characterized by (1)H NMR, FT-IR, and GPC. Block copolymers of PEG and PVL with different VL/PEG molar ratios were successfully synthesized. One of the copolymers (Copolymer 2, PEG550-PVL6768-PEG550) displayed a sol-gel transition at a physiological temperature based on the test tube inverting method and rheological studies. The thermogelling copolymer demonstrated a characteristic crystalline peak for PVL block as determined by DSC and XRD analysis. In vitro release from the copolymer hydrogel matrix indicated that dexamethasone (DEX), a hydrophobic model drug, released comparatively slower than 5-fluoruracil (5-FU), a hydrophilic model drug, due to the potential partitioning of DEX into the PVL core. 5-FU in vitro release from copolymer 2 was 86% in 22 h, whereas only 14% of DEX was released in 24h. Cell viability studies confirmed that hydrogels composed of block copolymers are biocompatible. Copolymer 2 showed more than 80% relative cell viability at all concentrations, including concentrations greater than 200 fold CMC. In vivo gel formation studies indicate that gel integrity was maintained for 7 days upon subcutaneous injection into mice. These results indicate that PEG-PVL-PEG copolymers are suitable for drug delivery applications. PMID:24931340

  17. Extracellular matrix formation in self-assembled minimalistic bioactive hydrogels based on aromatic peptide amphiphiles.

    Zhou, Mi; Ulijn, Rein V; Gough, Julie E

    2014-01-01

    The hitherto inconsistency in clinical performance for engineered skin drives the current development of novel cell-scaffolding materials; one challenge is to only extract essential characteristics from the complex native ECM (extracellular matrix) and incorporate them into a scaffold with minimal complexity to support normal cell functions. This study involved small-molecule-based bioactive hydrogels produced by the co-assembly of two aromatic peptide amphiphiles: Fmoc-FF (Fluorenylmethoxycarbonyl-diphenylalanine) and Fmoc-RGD (arginine-glycine-aspartic acid). Three-dimensionally cultured human dermal fibroblasts deposited dense ECM networks including fibronectin and collagen I within the hydrogels in a 14-day culture. The fibroblasts organized the fibrous ECM and contracted the gel without differentiating into myofibroblasts. The stiffness of the cell-gel constructs increased dramatically due to ECM formation and gel contraction. This created an economical biomimetic model-scaffold to further understand skin reconstruction in vitro and supplied a design pathway to create versatile cell-scaffolds with varied bioactivities and simplicity. PMID:24812581

  18. Triptolide-loaded microemulsion-based hydrogels: physical properties and percutaneous permeability

    Lihua Chen

    2013-05-01

    Full Text Available Triptolide is a diterpenoid compound that inhibits the inflammation of rheumatoid arthritis (RA. However, the use of triptolide is limited due to its strong gastrointestinal toxicity. The purpose of this work was to develop a transdermal delivery system for triptolide to reduce this toxicity. A microemulsion-based hydrogel (MBH was prepared from the combination of Gemseal 40-oleic acid as oil phase, Tween 80-labrasol as surfactant, anhydrous ethanol as co-surfactant, water as aqueous phase and Poloxamer 407 as hydrogel matrix. Rheological measurements, environmental scanning electron microscopy (ESEM and transdermal experiments in vitro were used to characterize triptolide-loaded and blank MBH preparations. The effects of Poloxamer 407 and triptolide on the rheological properties and microstructures of the MBH were determined. Transparent and homogeneous MBH could only be formed when the concentration of Poloxamer 407 in the selected O/W microemulsion was in the range of 14.0–16.0% (w/w. When the concentration of Poloxamer 407 increased, the rheological properties such as the yield stresses (σy, storage and loss moduli (G′, G″ of the formulations increased, and the network structures became more compact. The addition of triptolide did not change the interconnected network structures of the MBH preparations. MBH preparations afford a better sustained release profile when compared to microemulsions, a finding confirmed by an in vitro permeation test in mice. MBH appears to be a promising vehicle for transdermal delivery of triptolide.

  19. Synthesis and properties of collagen-g-poly(sodium acrylate-co-2-hydroxyethylacrylate superabsorbent hydrogels

    M. Sadeghi

    2013-06-01

    Full Text Available Novel biopolymer-based superabsorbent hydrogels were prepared by grafting crosslinked poly(acrylic acid-co-2-hydroxyethyl acrylate (PAA-co-PHEA chains onto collagen backbones through a free radical polymerization method. The graft copolymerization reaction was carried out in a homogeneous medium and in the presence of ammonium persulfate (APS as initiator and N,N '-methylene bisacrylamide (MBA as crosslinker. A proposed mechanism for collagen-g-(PAA-co-PHEA formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy and TGA thermal analysis. Moreover, the morphology of the samples was examined by scanning electron microscopy (SEM. The effect of concentration of MBA as well as AA/HEA weight ratio on the swelling capacity of the hydrogel was also studied. Furthermore, the water absorbency of hydrogels was measured in solutions with pH ranging 1 to 13. The collagen-based hydrogel exhibited a pH-responsive character, so that a swelling-deswelling pulsatile behavior was recorded at pHs 2 and 8. Preliminary swelling and deswelling behaviors of the hydrogels were also studied. Additionally, the hydrogels exhibited salt-sensitivity and cation exchange properties.

  20. Preparation and physico-chemical properties of hydrogels from carboxymethyl cassava starch crosslinked with citric acid

    Boonkham, Sasikan; Sangseethong, Kunruedee; Chatakanon, Pathama; Niamnuy, Chalida; Nakasaki, Kiyohiko; Sriroth, Klanarong

    2014-06-01

    Recently, environmentally friendly hydrogels prepared from renewable bio-based resources have drawn significant attention from both industrial and academic sectors. In this study, chemically crosslinked hydrogels have been developed from cassava starch which is a bio-based polymer using a non-toxic citric acid as a crosslinking agent. Cassava starch was first modified by carboxymethylation to improve its water absorbency property. The carboxymethyl cassava starch (CMCS) obtained was then crosslinked with citric acid at different concentrations and reaction times. The gel fraction of hydrogels increased progressively with increasing citric acid concentration. Free swelling capacity of hydrogels in de-ionized water, saline solution and buffers at various pHs as well as absorption under load were investigated. The results revealed that swelling behavior and mechanical characteristic of hydrogels depended on the citric acid concentration used in reaction. Increasing citric acid concentration resulted in hydrogels with stronger network but lower swelling and absorption capacity. The cassava starch hydrogels developed were sensitive to ionic strength and pH of surrounding medium, showing much reduced swelling capacity in saline salt solution and acidic buffers.

  1. Smart hydrogel-functionalized textile system with moisture management property for skin application

    Wang, Xiaowen; Hu, Huawen; Yang, Zongyue; He, Liang; Kong, Yeeyee; Fei, Bin; Xin, John H.

    2014-12-01

    In this study, a functional textile-based material for topical skin application was fabricated by coating a thermoresponsive hydrogel onto one side of absorbent nonwoven fabric. The thermoresponsive hydrogel was synthesized easily through coupling of poly (ethylene glycol) (PEG) and poly (ɛ-caprolactone) (PCL) with hexamethylene diisocyanate (HMDI) as a chemical linker. The chemical structure of the as-prepared triblock copolymer hydrogel was unraveled by FTIR and 1H NMR analysis. The hydrogel showed a temperature-triggered sol-gel transition behavior and high potential for use as drug controlled release. When the surrounding temperature was close to the skin temperature of around 34 °C, it became a moisture management system where the liquids including sweat, blood, and other body fluids can be transported unidirectionally from one fabric side with the hydrophobic hydrogel coating to the untreated opposite side. This thereby showed that the thermoresponsive hydrogel-coated textile materials had a function to keep topical skin area clean, breathable, and comfortable, thus suggesting a great potential and significance for long-term skin treatment application. The structure and surface morphology of the thermoresponsive hydrogel, in vitro drug release behavior, and the mechanism of unidirectional water transport were investigated in detail. Our success in preparation of the functional textile composites will pave the way for development of various polymer- or textile-based functional materials that are applicable in the real world.

  2. Smart hydrogel-functionalized textile system with moisture management property for skin application

    In this study, a functional textile-based material for topical skin application was fabricated by coating a thermoresponsive hydrogel onto one side of absorbent nonwoven fabric. The thermoresponsive hydrogel was synthesized easily through coupling of poly (ethylene glycol) (PEG) and poly (ϵ-caprolactone) (PCL) with hexamethylene diisocyanate (HMDI) as a chemical linker. The chemical structure of the as-prepared triblock copolymer hydrogel was unraveled by FTIR and 1H NMR analysis. The hydrogel showed a temperature-triggered sol-gel transition behavior and high potential for use as drug controlled release. When the surrounding temperature was close to the skin temperature of around 34 °C, it became a moisture management system where the liquids including sweat, blood, and other body fluids can be transported unidirectionally from one fabric side with the hydrophobic hydrogel coating to the untreated opposite side. This thereby showed that the thermoresponsive hydrogel-coated textile materials had a function to keep topical skin area clean, breathable, and comfortable, thus suggesting a great potential and significance for long-term skin treatment application. The structure and surface morphology of the thermoresponsive hydrogel, in vitro drug release behavior, and the mechanism of unidirectional water transport were investigated in detail. Our success in preparation of the functional textile composites will pave the way for development of various polymer- or textile-based functional materials that are applicable in the real world. (paper)

  3. Perfect absorbers for electromagnetic wave, based on metamaterials

    Yoo, Young Joon; Kim, Young Ju; Lee, YoungPak

    2015-10-01

    Metamaterials (MMs), which are not existing in nature, but artificially-engineered materials for controlling electromagnetic wave. MMs have attracted more and more research attentions, since they have shown greatly novel properties such as left-handed behavior, negative refractive index, classical analog of electromagnetically-induced transparency, and extraordinary transmission. Among MMs, MM perfect absorbers (MMPAs), which are useful to enhance the efficiency in capturing solar energy and applied to various application areas, have been rapidly developed. In general, the structure of MMPAs is very simple, which consist of three layers: patterned conductor layer, which is used for minimizing the reflection by impedance matching, dielectric layer and continuous conductor layer for blocking the transmission. In addition, the unit-cell size of general MM absorbers is only 1/3-1/5 of the working wavelength of incident electromagnetic wave. Nevertheless, the properties of general MMPAs are in problems of the absorption only at specific frequency, the narrow absorption band, the polarization sensitivity and so on. In this review paper, the introduction of recent researches in the field of MMPAs operating in different frequency ranges is presented. Moreover, the researches on the improved electromagnetic properties are discussed, which comprise multi-band, broadband, tunable, polarization-insensitive, and wide-incident-angle MMPAs. The perspectives and the future works for the further investigations and the various real applications of MMPAs are also presented.

  4. Injectable Hydrogel Composite Based Gelatin-PEG and Biphasic Calcium Phosphate Nanoparticles for Bone Regeneration

    Van, Thuy Duong; Tran, Ngoc Quyen; Nguyen, Dai Hai; Nguyen, Cuu Khoa; Tran, Dai Lam; Nguyen, Phuong Thi

    2016-05-01

    Gelatin hydrogels have recently attracted much attention for tissue regeneration because of their biocompatibility. In this study, we introduce poly-ethylene glycol (PEG)—grafted gelatin containing tyramine moieties which have been utilized for in situ enzyme-mediated hydrogel preparation. The hydrogel can be used to load nanoparticles of biphasic calcium phosphate, a mixture of hydroxyapatite and β-tricalcium phosphate, and forming injectable bio-composites. Proton nuclear magnetic resonance (1H NMR) spectra indicated that tyramine-functionalized polyethylene glycol-nitrophenyl carbonate ester was conjugated to the gelatin. The hydrogel composite was rapidly formed in situ (within a few seconds) in the presence of horseradish peroxidase and hydrogen peroxide. In vitro experiments with bio-mineralization on the hydrogel composite surfaces was well-observed after 2 weeks soaking in simulated body fluid solution. The obtained results indicated that the hydrogel composite could be a potential injectable material for bone regeneration.

  5. Designed biodegradable hydrogel structures prepared by stereolithography using poly(ethylene glycol)/poly(D,L-lactide)-based resins

    Seck, Tetsu M.; Melchels, Ferry P. W.; Feijen, Jan; Grijpma, Dirk W.

    2010-01-01

    Designed three-dimensional biodegradable poly(ethylene glycol)/poly(D,L-lactide) hydrogel structures were prepared for the first time by stereolithography at high resolutions. A photo-polymerisable aqueous resin comprising PDLLA-PEG-PDLLA-based macromer, visible light photo-initiator, dye and inhibi

  6. Preparation and In Vitro Evaluation of a Stomach Specific Drug Delivery System based on Superporous Hydrogel Composite

    Chavda, H.V.; Patel, C. N.

    2011-01-01

    This study discusses efforts made to design drug-delivery system based on superporous hydrogel composite for sustained delivery of ranitidine hydrochloride. The characterization studies involve measurement of apparent density, porosity, swelling studies, mechanical strength studies, and scanning electron microscopy. Scanning electron microscopic images clearly showed the formation of interconnected pores, capillary channels, and the cross-linked sodium carboxymethylcellulose molecules around ...

  7. Photoluminescence-based quality control for thin film absorber layers of photovoltaic devices

    Repins, Ingrid L.; Kuciauskas, Darius

    2015-07-07

    A time-resolved photoluminescence-based system providing quality control during manufacture of thin film absorber layers for photovoltaic devices. The system includes a laser generating excitation beams and an optical fiber with an end used both for directing each excitation beam onto a thin film absorber layer and for collecting photoluminescence from the absorber layer. The system includes a processor determining a quality control parameter such as minority carrier lifetime of the thin film absorber layer based on the collected photoluminescence. In some implementations, the laser is a low power, pulsed diode laser having photon energy at least great enough to excite electron hole pairs in the thin film absorber layer. The scattered light may be filterable from the collected photoluminescence, and the system may include a dichroic beam splitter and a filter that transmit the photoluminescence and remove scattered laser light prior to delivery to a photodetector and a digital oscilloscope.

  8. Gelam (Melaleuca spp.) Honey-Based Hydrogel as Burn Wound Dressing

    Rozaini Mohd Zohdi; Zuki Abu Bakar Zakaria; Norimah Yusof; Noordin Mohamed Mustapha; Muhammad Nazrul Hakim Abdullah

    2012-01-01

    A novel cross-linked honey hydrogel dressing was developed by incorporating Malaysian honey into hydrogel dressing formulation, cross-linked and sterilized using electron beam irradiation (25 kGy). In this study, the physical properties of the prepared honey hydrogel and its wound healing efficacy on deep partial thickness burn wounds in rats were assessed. Skin samples were taken at 7, 14, 21, and 28 days after burn for histopathological and molecular evaluations. Application of honey hydrog...

  9. Hydrogel based sensor arrays (2 × 2) with perforated piezoresistive diaphragms for metabolic monitoring (in vitro)

    Orthner, M. P.; Lin, G.; Avula, M.; Buetefisch, S.; Magda, J.; Rieth, L. W.; Solzbacher, F.

    2010-01-01

    This report details the first experimental results from novel hydrogel sensor array (2 × 2) which incorporates analyte diffusion pores into a piezoresistive diaphragm for the detection of hydrogel swelling pressures and hence chemical concentrations. The sensor assembly was comprised of three components, the active four sensors, HPMA/DMA/TEGDMA (hydroxypropyl methacrylate (HPMA), N,N-dimethylaminoethyl methacrylate (DMA) and crosslinker tetra-ethyleneglycol dimethacrylate (TEGDMA)) hydrogel, ...

  10. Preparation of Graphene Oxide-Based Hydrogels as Efficient Dye Adsorbents for Wastewater Treatment

    Guo, Haiying; Jiao, Tifeng; Zhang, Qingrui; Guo, Wenfeng; Peng, Qiuming; Yan, Xuehai

    2015-01-01

    Graphene oxide (GO) sheets exhibit superior adsorption capacity for removing organic dye pollutants from an aqueous environment. In this paper, the facile preparation of GO/polyethylenimine (PEI) hydrogels as efficient dye adsorbents has been reported. The GO/PEI hydrogels were achieved through both hydrogen bonding and electrostatic interactions between amine-rich PEI and GO sheets. For both methylene blue (MB) and rhodamine B (RhB), the as-prepared hydrogels exhibit removal rates within abo...

  11. Reducing the Oxidation Level of Dextran Aldehyde in a Chitosan/Dextran-Based Surgical Hydrogel Increases Biocompatibility and Decreases Antimicrobial Efficacy

    Maggie Chan

    2015-06-01

    Full Text Available A highly oxidized form of a chitosan/dextran-based hydrogel (CD-100 containing 80% oxidized dextran aldehyde (DA-100 was developed as a post-operative aid, and found to significantly prevent adhesion formation in endoscopic sinus surgery (ESS. However, the CD-100 hydrogel showed moderate in vitro cytotoxicity to mammalian cell lines, with the DA-100 found to be the cytotoxic component. In order to extend the use of the hydrogel to abdominal surgeries, reformulation using a lower oxidized DA (DA-25 was pursued. The aim of the present study was to compare the antimicrobial efficacy, in vitro biocompatibility and wound healing capacity of the highly oxidized CD-100 hydrogel with the CD-25 hydrogel. Antimicrobial studies were performed against a range of clinically relevant abdominal microorganisms using the micro-broth dilution method. Biocompatibility testing using human dermal fibroblasts was assessed via a tetrazolium reduction assay (MTT and a wound healing model. In contrast to the original DA-100 formulation, DA-25 was found to be non-cytotoxic, and showed no overall impairment of cell migration, with wound closure occurring at 72 h. However, the lower oxidation level negatively affected the antimicrobial efficacy of the hydrogel (CD-25. Although the CD-25 hydrogel’s antimicrobial efficacy and anti-fibroblast activity is decreased when compared to the original CD-100 hydrogel formulation, previous in vivo studies show that the CD-25 hydrogel remains an effective, biocompatible barrier agent in the prevention of postoperative adhesions.

  12. Nanometer-scale ionic reservoir based on ion-responsive hydrogels

    Kazakov, Sergey V.; Kaholek, Marian; Levon, Kalle

    2002-07-01

    The applicability of the concept of ionic reservoir for the description of hydrogel behavior was demonstrated by potentiometric titration of poly(N-isopropylacrylamide-co-1- vinylimidazole) hydrogel suspension. Four different regions of pH-changes of the microgel suspensions were identified on the titration curve in comparison with pure water. Particularly, at 10.5>pH>6.5 a hydrogel accumulates or releases H+ and Cl- ions without significant swelling/deswelling whereas at 6.5>pH>4 the storage of the ions occurs both due to their binding with ionizable groups on polymer network and due to strong swelling. The mechanical response of hydrogel (swelling/deswelling) is assumed to be a faster process than the electrochemical response (equilibration of ion concentrations interior and exterior to the hydrogel). The size of hydrogel spheres should be diminished to fasten an ionic reservoir response of the hydrogel. A novel protocol for preparation of polymer hydrogel spherical particles on a nanometer scale (nanogels) has been developed. Temperature- and pH-sensitive nanogels were detected and characterized by the dynamic light scattering technique and atomic force microscopy. Ptoentiometric titration of the obtained nanogels shows that the decrease in the ionic reservoir size gains the efficiency and, presumably, the rate of the electrochemical response. These findings indicate the necessity of time-resolved pH-measurements of the hydrogel suspensions for the characterization of the rate of the solute diffusion through the gel/water surface.

  13. Graphene Based Terahertz Absorber Designed With Effective Surface Conductivity Approach

    Andryieuski, Andrei; Pizzocchero, Filippo; Booth, Tim;

    flexible and ultrastrong mechanically, transparent for optical radiation, with high electrical conductivity that can be tuned by electrochemical potential. Structured graphene layers constitute metamaterials that can provide tunable and very unusual electromagnetic properties. In this contribution we......Young field of terahertz (THz) science and technology demands new materials and devices, such as filters, modulators, polarization converters and absorbers. Graphene, a recently discovered single-atom-thick material, provides exciting properties for functional terahertz applications. Graphene is...... present the description of graphene metamaterial properties through the effective surface conductivity. Such description is very convenient, as it simplifies the design of THz devices, and very natural, since surface conductivity can be measured directly in experiment. We show how to extract the effective...

  14. Absorbable hydrogel spacer use in men undergoing prostate cancer radiotherapy: 12 month toxicity and proctoscopy results of a prospective multicenter phase II trial

    Radiation therapy is one of the recommended treatment options for localized prostate cancer. In randomized trials, dose escalation was correlated with better biochemical control but also with higher rectal toxicity. A prospective multicenter phase II study was carried out to evaluate the safety, clinical and dosimetric effects of the hydrogel prostate-rectum spacer. Here we present the 12 months toxicity results of this trial. Fifty two patients with localized prostate cancer received a transperineal PEG hydrogel injection between the prostate and rectum, and then received IMRT to a dose of 78 Gy. Gastrointestinal and genitourinary toxicity were recorded during treatment and at 3, 6 and 12 months following irradiation by using the RTOG/EORTC criteria. Additionally, proctoscopy was performed 12 months after treatment and the results were scored using the Vienna Rectoscopy Scale (VRS). Of the patients treated 39.6% and 12.5% experienced acute Grade 1 and Grade 2 GI toxicity, respectively. There was no Grade 3 or Grade 4 acute GI toxicity experienced in the study. Only 4.3% showed late Grade 1 GI toxicity, and there was no late Grade 2 or greater GI toxicity experienced in the study. A total of 41.7%, 35.4% and 2.1% of the men experienced acute Grade 1, Grade 2 and Grade 3 GU toxicity, respectively. There was no Grade 4 acute GU toxicity experienced in the study. Late Grade 1 and Grade 2 GU toxicity was experienced in 17.0% and 2.1% of the patients, respectively. There was no late Grade 3 or greater GU toxicity experienced in the study. Seventy one percent of the patients had a VRS score of 0, and one patient (2%) had Grade 3 teleangiectasia. There was no evidence of ulceration, stricture or necrosis at 12 months. The use of PEG spacer gel is a safe and effective method to spare the rectum from higher dose and toxicity

  15. Hydrogel-based encapsulation of biological, functional tissue: fundamentals, technologies and applications

    Zimmermann, H.; Ehrhart, F.; Zimmermann, D.; Müller, K.; Katsen-Globa, A.; Behringer, M.; Feilen, P. J.; Gessner, P.; Zimmermann, G.; Shirley, S. G.; Weber, M. M.; Metze, J.; Zimmermann, U.

    2007-12-01

    Replacing dysfunctional endocrine cells or tissues (e.g. islets, parathyroid tissue) by functional, foreign material without using immunosuppressives could soon become reality. Immunological reactions are avoided by encapsulating cells/tissues in hydrogel (e.g. alginate) microcapsules, preventing interaction of the enclosed material with the host’s immune system while permitting the unhindered passage of nutrients, oxygen and secreted therapeutic factors. Detailed investigations of the physical, physico-chemical and immunological parameters of alginate-based microcapsules have led recently to the development of a novel class of cell-entrapping microcapsules that meet the demands of biocompatibility, long-term integrity and function. This together with the development of ‘good medical practice’ microfluidic chip technology and of advanced cryopreservation technology for generation and storage of immunoisolated transplants will bring cell-based therapy to clinics and the market.

  16. Phantoms for diffuse optical imaging based on totally absorbing objects, part 2: experimental implementation

    Martelli, Fabrizio; Ninni, Paola Di; Zaccanti, Giovanni; Contini, Davide; Spinelli, Lorenzo; Torricelli, Alessandro; Cubeddu, Rinaldo; Wabnitz, Heidrun; Mazurenka, Mikhail; Macdonald, Rainer; Sassaroli, Angelo; Pifferi, Antonio

    2014-07-01

    We present the experimental implementation and validation of a phantom for diffuse optical imaging based on totally absorbing objects for which, in the previous paper [J. Biomed. Opt. 18(6), 066014, (2013)], we have provided the basic theory. Totally absorbing objects have been manufactured as black polyvinyl chloride (PVC) cylinders and the phantom is a water dilution of intralipid-20% as the diffusive medium and India ink as the absorber, filled into a black scattering cell made of PVC. By means of time-domain measurements and of Monte Carlo simulations, we have shown the reliability, the accuracy, and the robustness of such a phantom in mimicking typical absorbing perturbations of diffuse optical imaging. In particular, we show that such a phantom can be used to generate any absorption perturbation by changing the volume and position of the totally absorbing inclusion.

  17. Property-based design: optimization and characterization of polyvinyl alcohol (PVA) hydrogel and PVA-matrix composite for artificial cornea.

    Jiang, Hong; Zuo, Yi; Zhang, Li; Li, Jidong; Zhang, Aiming; Li, Yubao; Yang, Xiaochao

    2014-03-01

    Each approach for artificial cornea design is toward the same goal: to develop a material that best mimics the important properties of natural cornea. Accordingly, the selection and optimization of corneal substitute should be based on their physicochemical properties. In this study, three types of polyvinyl alcohol (PVA) hydrogels with different polymerization degree (PVA1799, PVA2499 and PVA2699) were prepared by freeze-thawing techniques. After characterization in terms of transparency, water content, water contact angle, mechanical property, root-mean-square roughness and protein adsorption behavior, the optimized PVA2499 hydrogel with similar properties of natural cornea was selected as a matrix material for artificial cornea. Based on this, a biomimetic artificial cornea was fabricated with core-and-skirt structure: a transparent PVA hydrogel core, surrounding by a ringed PVA-matrix composite skirt that composed of graphite, Fe-doped nano hydroxyapatite (n-Fe-HA) and PVA hydrogel. Different ratio of graphite/n-Fe-HA can tune the skirt color from dark brown to light brown, which well simulates the iris color of Oriental eyes. Moreover, morphologic and mechanical examination showed that an integrated core-and-skirt artificial cornea was formed from an interpenetrating polymer network, no phase separation appeared on the interface between the core and the skirt. PMID:24464723

  18. Development, characterization, and applications of self-assembling, photocrosslinkable collagen-based hydrogels

    Gaudet, Ian Daniel

    Development of functional soft-tissue engineered constructs for use in regenerative medicine is currently limited by homogeneity within scaffolds that fails to recapitulate the complex architecture that supports normal function in healthy tissues. Additionally, recent breakthroughs in our understanding the biomechanical cell-matrix interface have provided insight into the role of substrate compliance during development and in the pathophysiological environment. This thesis is the result of investigation into using type-I collagen as a base material for creating dynamic, self-assembling, mechanically and biochemically tunable 3D hydrogel scaffolds into which instructive cellular cues can be imparted anisotropically via the directed application of light. This overarching goal was approached by (1) evaluating extant methods for photonically manipulating type I collagen mechanical properties, which led us to the conclusion that published methods were inadequate for our purposes. Following this realization, we (2) developed a novel process for derivatizing free amines on collagen amino acid residues to reactive methacrylamide moieties, allowing robust spatiotemporal control of mechanical properties through photocrosslinking with long-wave UV light and the water-soluble photoinitiator Irgacure 2959. Thorough characterization of this material, collagen methacrylamide (CMA), provided the basis for multiple applications in the field of soft tissue engineering. Additionally, (3) CMA was used in conjunction with synthetic photopolymers in an effort to create a hybrid natural/synthetic hydrogel material. CMA was also (4) employed as a dynamic hydrogel scaffold which we showed could be used to culture a number of neurogenic stem and progenitor cell types with a focus on using photomodulation to impart instructive heterogeneity to the mechanical and biochemical microenvironment. Finally, (5) we used a computational modeling approach to explain interesting yet poorly understood

  19. Characterization and swelling-deswelling properties of wheat straw cellulose based semi-IPNs hydrogel.

    Liu, Jia; Li, Qian; Su, Yuan; Yue, Qinyan; Gao, Baoyu

    2014-07-17

    A novel wheat straw cellulose-g-poly(potassium acrylate)/polyvinyl alcohol (WSC-g-PKA/PVA) semi-interpenetrating polymer networks (semi-IPNs) hydrogel was prepared by polymerizing wheat straw and an aqueous solution of acrylic acid (AA), and further semi-interpenetrating with PVA occurred during the chemosynthesis. The swelling and deswelling properties of WSC-g-PKA/PVA semi-IPNs hydrogel and WSC-g-PKA hydrogel were studied and compared in various pH solutions, salt solutions, temperatures, particle sizes and ionic strength. The results indicated that both hydrogels had the largest swelling capacity at pH=6, and the effect of ions on the swelling of hydrogels was in the order: Na(+)>K(+)>Mg(2+)>Ca(2+). The Schott's pseudo second order model can be effectively used to evaluate swelling kinetics of hydrogels. Moreover, the semi-IPNs hydrogel had improved swelling-deswelling properties compared with that of WSC-g-PKA hydrogel. PMID:24702940

  20. Thermo-Responsive Hydrogels Based on Branched Poly(L-lactide)-poly(ethylene glycol) Copolymers

    Velthoen, Ingrid W.; Tijsma, Edze J.; Dijkstra, Pieter J.; Feijen, Jan

    2008-01-01

    Branched poly(L-lactide)-poly(ethylene glycol) (PLLA-PEG) block copolymers were synthesized from trifunctional PLLA and amine functionalized methoxy poly(ethylene glycol)s. The copolymers in water formed hydrogels that showed thermo-responsive behavior. The hydrogels underwent a gel to sol transitio

  1. Development of carboxymethyl cellulose-based hydrogel and nanosilver composite as antimicrobial agents for UTI pathogens.

    Alshehri, Saad M; Aldalbahi, Ali; Al-Hajji, Abdullah Baker; Chaudhary, Anis Ahmad; Panhuis, Marc In Het; Alhokbany, Norah; Ahamad, Tansir

    2016-03-15

    Silver nanoparticles (AgNPs) containing hydrogel composite were first synthesized by preparing a new hydrogel from carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and the cross-linker ethylene glycol diglycidyl ether (EGDE), followed by the incorporation of AgNPs by microwave radiation. The resulting neat hydrogels and AgNPs-hydrogel composites were characterized using spectral, thermal, microscopic analysis and X-ray diffraction (XRD) analyses. The SEM and TEM results demonstrated that the synthesized AgNPs were spherical with diameters ranging from 8 to 14nm. In addition, the XRD analysis confirmed the nanocrystalline phase of silver with face-centered cubic (FCC) crystal structure. Energy dispersive spectroscopy (EDS) analysis of the AgNPs confirmed the presence of an elemental silver signal, and no peaks of any other impurities were detected. Additionally, the antibacterial activities of the neat hydrogel and AgNPs-hydrogel composites were measured by Kirby-Bauer method against urinary tract infection (UTI) pathogens. The rheology measurement revealed that the values of storage modulus (G') were higher than that of loss modulus (G″). The AgNPs-hydrogel composites exhibited higher antibacterial activity against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus vulgaris, Staphylococcus aureus and Proteus mirabilis compared to the corresponding neat hydrogel. PMID:26794757

  2. Preparation of dual-sensitive graft copolymer hydrogel based on N-maleoyl-chitosan and poly(N-isopropylacrylamide) by electron beam radiation

    Jinchen Fan; Jie Chen; Liming Yang; Han Lin; Fangqi Cao

    2009-10-01

    Organic solvent-soluble N-maleoyl-chitosan (NMCS) was synthesized by reaction of chitosan with maleic anhydride (MAH) in N,N-dimethylformamide (DMF). N-maleoyl-chitosan-graft-poly(N-isopropylacrylamide) (NMCS-g-PNIPAAm) copolymer hydrogel was prepared via free radical polymerization by electron beam (EB) irradiation. The copolymer obtained was analysed by FT–IR, XRD and thermal gravimetric analysis (TGA). It was found that the grafting yield and grafting efficiency increased with increasing radiation absorbed dose and monomer amount, and then decreased. The swelling ratio of the copolymer hydrogel was low at pH 4–5, and LCST of the hydrogel was around 32°C.

  3. Radiation preparation and characterization of pH-sensitive hydrogel of acrylic acid/cyclodextrin based copolymer

    A β-cyclodextrin (β-CD) based monomer (MAH-β-CD) containing vinyl and carboxyl functional groups was synthesized by reaction of β-CD with maleic anhydride (MAH). A novel hydrogel, poly(AAc-co-MAH-β-CD) with pH and ionic strength sensitivities, was prepared by irradiating the aqueous solution mixture of acrylic acid (AAc) and MAH-β-CD with electron beam. The effect of the feed ratio of the components and irradiation dose on the swelling and deswelling properties of the hydrogel was studied, respectively, the effect of pH and ionic strength on the swelling ratio was determined. Experimental results showed that these copolymer hydrogels did not show any noticeable change in swelling ratio at lower pH range (pH 1-3). However they showed an abrupt increase in swelling ratio at the range of pH 3-6, due to the ionization of carboxyl groups. Fourier transform infrared (FT-IR) spectrometer was applied in the attenuated total reflectance (ATR) mode for analyzing the structure change of the hydrogels after the treatment of different pH buffer solutions. (author)

  4. Influence of polymer network parameters of tragacanth gum-based pH responsive hydrogels on drug delivery.

    Singh, Baljit; Sharma, Vikrant

    2014-01-30

    The present article deals with design of tragacanth gum-based pH responsive hydrogel drug delivery systems. The characterization of hydrogels has been carried out by SEMs, EDAX, FTIR, (13)C NMR, XRD, TGA/DTA/DTG and swelling studies. The correlation between reaction conditions and structural parameters of polymer networks such as polymer volume fraction in the swollen state (ϕ), Flory-Huggins interaction parameter (χ), molecular weight of the polymer chain between two neighboring cross links (M¯c), crosslink density (ρ) and mesh size (ξ) has been determined. The different kinetic models such as zero order, first order, Higuchi square root law, Korsmeyer-Peppas model and Hixson-Crowell cube root model were applied and it has been observed that release profile of amoxicillin best followed the first order model for the release of drug from the polymer matrix. The swelling of the hydrogels and release of drug from the drug loaded hydrogels occurred through non-Fickian diffusion mechanism in pH 7.4 solution. PMID:24299858

  5. WOOD HEMICELLULOSE/CHITOSAN-BASED SEMI-INTERPENETRATING NETWORK HYDROGELS: MECHANICAL, SWELLING AND CONTROLLED DRUG RELEASE PROPERTIES

    Muzaffer Ahmet Karaaslan

    2010-04-01

    Full Text Available The cell wall of most plant biomass from forest and agricultural resources consists of three major polymers, cellulose, hemicellulose, and lignin. Of these, hemicelluloses have gained increasing attention as sustainable raw materials. In this study, novel pH-sensitive semi-IPN hydrogels based on hemicelluloses and chitosan were prepared using glutaraldehyde as the crosslinking agent. The hemicellulose isolated from aspen was analyzed for sugar content by HPLC, and its molecular weight distribution was determined by high performance size exclusion chromatography. Results revealed that hemicellulose had a broad molecular weight distribution with a fair amount of polymeric units, together with xylose, arabinose, and glucose. The effects of hemicellulose content on mechanical properties and swelling behavior of hydrogels were investigated. The semi-IPNs hydrogel structure was confirmed by FT-IR, X-ray study, and the ninhydrin assay method. X-ray analysis showed that higher hemicellulose contents yielded higher crystallinity. Mechanical properties were mainly dependent on the crosslink density and average molecular weight between crosslinks. Swelling ratios increased with increasing hemicellulose content and were high at low pH values due to repulsion between similarly charged groups. In vitro release study of a model drug showed that these semi-IPN hydrogels could be used for controlled drug delivery into gastric fluid.

  6. Magnetic hydrogel beads based on PVA/sodium alginate/laponite RD and studying their BSA adsorption.

    Mahdavinia, Gholam Reza; Mousanezhad, Sedigheh; Hosseinzadeh, Hamed; Darvishi, Farshad; Sabzi, Mohammad

    2016-08-20

    In this study double physically crosslinked magnetic hydrogel beads were developed by a simple method including solution mixing of sodium alginate and poly(vinyl alcohol) (PVA) containing magnetic laponite RD (Rapid Dispersion). Sodium alginate and PVA were physically crosslinked by Ca(2+) and freezing-thawing cycles, respectively. Magnetic laponite RD nanoparticles were incorporated into the system to create magnetic response and strengthen the hydrogels. All hybrids double physically crosslinked hydrogel beads were stable under different pH values without any disintegration. Furthermore, adsorption of bovine serum albumin (BSA) on the hydrogel beads was investigated on the subject of pH, ion strength, initial BSA concentration, and temperature. Nanocomposite beads exhibited maximum adsorption capacity for BSA at pH=4.5. The experimental adsorption isotherm data were well followed Langmuir model and based on this model the maximum adsorption capacity was obtained 127.3mgg(-1) at 308K. Thermodynamic parameters revealed spontaneous and monolayer adsorption of BSA on magnetic nanocomposites beads. PMID:27178944

  7. Design, Simulation and Experimental Characteristics of Hydrogel-based Piezoresistive pH Sensors

    Trinh, Thong Quang; Sorber, Jorge; Gerlach, Gerald

    This paper presents the investigations of a novel type of piezoresistive pH sensors exploiting the chemo-mechanical energy conversion due to hydrogel swelling. pH-sensitive poly(vinyl alcohol)-poly(acrylic acid) (PVA-PAA) hydrogel is used for this aim. The pH sensor has been designed including a commercial piezoresistive pressure sensor chip, a hydrogel layer, and a rigid grid. Behaviour of pH sensor under swelling of polymer hydrogel has been simulated using finite element method (ANSYS). The sensor simulations have been performed using the experimental material parameters of PVA-PAA hydrogel. The sensor characteristics including the silicon diaphragm deflection and output voltage have been measured. There were good relative agreements between simulations and experimental results.

  8. Modified maltodextrin-based hydrogel as a potential device for magnetic bio material

    A magnetic hydrogel was synthesized by a cross-linking/co-polymerization reaction of modified malto-dextrin and acrylamide in the presence of magnetite nanoparticles and persulfate as an initiator. The characterization of the formed hydrogel was accomplished by means of Fourier transform infrared spectroscopy (FT-IR), Moessbauer spectroscopy (MS), X-ray diffraction (XRD), and swelling rate (WR). The FT-IR analysis revealed that the malto-dextrin modification and the gelling process were efficient. From the MS and XRD analyses, it was concluded that the magnetite nanoparticles were efficiently embedded into the hydrogel structure and that the crystalline planes were different from those of the start material. WR decreased with the use of increasing amounts of magnetite in the hydrogel synthesis. In this sense, the electrostatic interactions decreased for increasing amounts of magnetite because the Fe3+ ions neutralized the negative charges of the hydrogel structure. (author)

  9. Multi-responsive supramolecular hydrogels based on merocyanine-peptide conjugates.

    Wang, Wei; Hu, Jing; Zheng, Mengmeng; Zheng, Li; Wang, Huan; Zhang, Yan

    2015-12-21

    Stimuli-responsive hydrogels are "smart" materials with diverse applications. We now report short peptide conjugates with merocyanine (MC) that are able to form stimuli-responsive hydrogels. Systematic investigation reveals that merocyanine is a highly effective promoter for the self-assembly of its oligopeptide conjugates. Hydrogels formed by MC-peptide conjugates showed responses towards light and heat, and their sol-gel phase transition could be manipulated by the reverse photochromism of the corresponding spiropyran moiety. Impressively, a MCI-RGD conjugate formed a supramolecular hydrogel with responses to multiple stimuli, including visible light irradiation, pH change and the presence of Ca(2+) ions. An erasable photo-lithograph on the MCI-RGD hydrogel was demonstrated using visible light to write and heat-and-cool treatment to erase for multiple rounds without significant loss of sensitivity. PMID:26456175

  10. Direct absorbed dose to water determination based on water calorimetry in scanning proton beam delivery

    Purpose: The aim of this manuscript is to describe the direct measurement of absolute absorbed dose to water in a scanned proton radiotherapy beam using a water calorimeter primary standard. Methods: The McGill water calorimeter, which has been validated in photon and electron beams as well as in HDR 192Ir brachytherapy, was used to measure the absorbed dose to water in double scattering and scanning proton irradiations. The measurements were made at the Massachusetts General Hospital proton radiotherapy facility. The correction factors in water calorimetry were numerically calculated and various parameters affecting their magnitude and uncertainty were studied. The absorbed dose to water was compared to that obtained using an Exradin T1 Chamber based on the IAEA TRS-398 protocol. Results: The overall 1-sigma uncertainty on absorbed dose to water amounts to 0.4% and 0.6% in scattered and scanned proton water calorimetry, respectively. This compares to an overall uncertainty of 1.9% for currently accepted IAEA TRS-398 reference absorbed dose measurement protocol. The absorbed dose from water calorimetry agrees with the results from TRS-398 well to within 1-sigma uncertainty. Conclusions: This work demonstrates that a primary absorbed dose standard based on water calorimetry is feasible in scattered and scanned proton beams.

  11. The release dynamics of model drugs from the psyllium and N-hydroxymethylacrylamide based hydrogels.

    Singh, Baljit; Chauhan, G S; Sharma, D K; Kant, Anil; Gupta, I; Chauhan, Nirmala

    2006-11-15

    In order to utilize the psyllium husk, a medicinally important natural polysaccharide, for developing the novel hydrogels for the controlled drug delivery device, we have prepared psyllium and N-hydroxymethylacrylamide based polymeric networks by using N,N'-methylenebisacrylamide (N,N'-MBAAm) as crosslinker. The polymeric networks thus formed were characterized with scanning electron micrography (SEM), FTIR and thermogravimetric analysis (TGA) techniques to study various structural aspects of the networks and also with the swelling response of the polymeric networks as a function of time, temperature, pH and [NaCl]. Equilibrium swelling has been observed to depend on both structural aspects of the polymers and environmental factors. Maximum P(s) 748.3 was observed at 13.0 x 10(-3)mol/L of [N,N'-MBAAm] in 0.5M NaOH solution. The release dynamics of model drugs (salicylic acid and tetracycline hydrochloride) from hydrogels has also been discussed, for the evaluation of the release mechanism and diffusion coefficients. The effect of pH on the release pattern of tetracycline has been studied by varying the pH of the release medium. In release medium of pH 7.4 buffer the release pattern of tetracycline drastically changes to the extent that mechanism of drug diffusion shifted from non-Fickian diffusion to Fickian diffusion. It has been observed that diffusion exponent "n" have 0.71, 0.67 and 0.52 values and gel characteristic constant 'k' have 1.552 x 10(-2), 2.291 x 10(-2) and 5.309 x 10(-2) values in distilled water, pH 2.2 buffer and pH 7.4 buffer, respectively, for tetracycline release. In solution of pH 7.4 buffer, the rate of polymer chain relaxation was more as compare to the rate of drug diffusion from these hydrogels and it follows Fick's law of diffusion. The value of the initial diffusion coefficient for the release of tetracycline hydrochloride was higher than the value of late time diffusion coefficient in each release medium indicating that in the start

  12. Synthesis, characterization and application in biomedicine of a novel chondroitin sulfate based hydrogel and bioadhesive

    Strehin, Iossif

    Clinically, there exists a need for adhesive biomaterials. There is room to improve upon what is currently on the market as it is either too toxic, lacks the required adhesive strength and/or lacks the desired degradation properties. The general goals of this thesis all focused on designing a biomaterial which would improve upon these shortcomings while at the same time allow for modifications to meet the needs for the specific application of interest. To accomplish this task, it was important to choose the appropriate composition and crosslinking chemistry which will allow the most flexibility. Chondroitin sulfate (CS) was chosen as the principle component of the hydrogel because it is a ubiquitous glycosaminoglycan (GAG) found in almost all tissues in the body. Many variants of CS exist with each one possessing unique biological activity allowing for tight control over these properties of the material. To modulate cell migration through the adhesive, polyethylene glycol (PEG) or blood was used as the second constituent. The former made the scaffold act as a cell barrier while the ladder could be used in varying concentrations to modulate cell adhesion and migration into the biomaterial. Also, the CS and blood components are both biodegradable and degradation can be controlled using various methods. While the constituents were chosen to allow flexibility in the biological activity and cell migration into the scaffold, the crosslinking chemistry was chosen to allow control over the mechanical properties as well as to increase tissue adhesion. By functionalizing the carboxyl groups of the GAG with N-hydroxysuccinimide (NHS), the resulting chondroitin sulfate succinimidyl succinate (CS-NHS) molecule could react with primary amines on polymers to form a hydrogel as well as the primary amines on proteins comprising tissue to anchor the hydrogel to the tissue. The material has been characterized and optimized for several applications. The applications described here

  13. Dysprosium and hafnium base absorbers for advanced WWER control rods

    Dysprosium titanate is an attractive control rod material for thermal neutron nuclear reactors such as WWER and RBMK. Its main advantages are almost non-swelling, no out-gassing under neutron irradiation, quit high neutron efficiency, a high melting point (∼ 1870 deg. C), non-interaction with the cladding at temperatures above 1000 deg. C, simple fabrication. nonradioactive waste and easy to reprocess. The dysprosium titanate control rods have worked without operating problems in the reactor MIR during 17 years and in WWER-1000 4 years. After post-irradiation examinations, this long-life control rod type was recommended for using in the nuclear reactors. Dysprosium hafnate is a promising absorber ceramic material. The research results confirmed that it has a large radiation damage resistance. The examination results of hafnium dummies (GFE-1) irradiated in BOR-60 are presented. The maximum accumulated neutron fluence was 3.4 x 1022cm-2 (E>0.1 MeV) and the temperature range was 340 to 360 deg. C. Due to high radiation growth (3-4 %) and the absence of an axial gap between the dummy and the upper capsule tip the dummies were bent. The irradiated dummies have high mechanical properties. Other aspects of the expected hafnium irradiation behaviour and the use of hafnium in control rods are discussed. This report presents some experimental data on Dy2O3·TiO2, Hf, Dy2O3·HfO2 and possibilities of their use in WWER control rods. (author)

  14. Research Progress in Cellulose-based Absorbent Material%纤维素系吸水材料的研究现状及发展前景

    高桂林; 沈葵忠; 房桂干; 邓拥军; 李萍; 金莉; 别士霞

    2012-01-01

    This review addressed recent progress in cellulose-based absorbent materials preparation and application Firstly, absorbent material produced directly from native cellulose (including bacterial cellulose) via cellulose dissolution are introduced. Secondly, cellulose highly absorbing polymer based on its derivatives which were obtained by physical as well as chemical cross-linking strategies was discussed. Thirdly, composite prepared by using cellulose in conjunction with other polymers through blending, formation of polyelectrolyte complexes, and interpenetrating polymer networks (IPNs) technology was addressed . Finally, cellulose-inorganic hybrid hydrogel prepared by embedding inorganic nano-partieles in cellulose matrices was described. In addition,the prospect of cellulosic absorbent materials and some problems still needed to be solved were summarized.%本文回顾了近年来纤维素系吸水材料的制备方法及其应用,具体介绍了纤维素系吸水材料的几种主要制备方法:一是直接对天然纤维素进行处理来制备;第二是利用纤维素衍生物通过物理或化学交联的方法制备;第三是将纤维素与其他聚合物进行反应形成复合树脂或聚电解质配合物,还可以采用互穿聚合网络技术进行处理;另外将无机纳米粒子嵌入纤维素矩阵中也可以制备纤维素-无机混合凝胶树脂。最后还对纤维素系高吸水材料的发展前景以及仍需解决的问题进行了总结。

  15. Sorption of zinc by novel pH-sensitive hydrogels based on chitosan, itaconic acid and methacrylic acid

    Milosavljevic, Nedeljko B.; Ristic, Mirjana D.; Peric-Grujic, Aleksandra A.; Filipovic, Jovanka M. [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade (Serbia); Strbac, Svetlana B. [ICTM-Institute of Electrochemistry, University of Belgrade, P.O.B. 815, 11001 Belgrade (Serbia); Rakocevic, Zlatko Lj. [INS Vinca, Laboratory for Atomic Physics, University of Belgrade, P.O.B. 522, Mike Alasa 12-14, 11001 Belgrade (Serbia); Kalagasidis Krusic, Melina T., E-mail: meli@tmf.bg.ac.rs [Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade (Serbia)

    2011-08-30

    Highlights: {yields} A removal of Zn{sup 2+} ions by pH-sensitive Ch/IA/MAA hydrogel from aqueous solutions was studied. {yields} SEM/EDX analysis and AFM surface topography indicate that sorption takes place on the surface of the hydrogel and in the bulk. {yields} FTIR spectra of the Ch/IA/MAA hydrogel, free and Zn-loaded, indicate that -NH{sub 2}, -OH and -COOH groups are involved in the sorption process. {yields} The negative values of free energy and enthalpy indicated that the adsorption is spontaneous and exothermic one. {yields} The adsorption capacities did not show any significant decrease after the third reuse cycle. - Abstract: Novel pH-sensitive hydrogels based on chitosan, itaconic acid and methacrylic acid were applied as adsorbents for the removal of Zn{sup 2+} ions from aqueous solution. In batch tests, the influence of solution pH, contact time, initial metal ion concentration and temperature was examined. The sorption was found pH dependent, pH 5.5 being the optimum value. The adsorption process was well described by the pseudo-second order kinetic. The hydrogels were characterized by spectral (Fourier transform infrared-FTIR) and structural (SEM/EDX and atomic force microscopy-AFM) analyses. The surface topography changes were observed by atomic force microscopy, while the changes in surface composition were detected using phase imaging AFM. The negative values of free energy and enthalpy indicated that the adsorption is spontaneous and exothermic one. The best fitting isotherms were Langmuir and Redlich-Peterson and it was found that both linear and nonlinear methods were appropriate for obtaining the isotherm parameters. However, the increase of temperature leads to higher adsorption capacity, since swelling degree increased with temperature.

  16. Sorption of zinc by novel pH-sensitive hydrogels based on chitosan, itaconic acid and methacrylic acid

    Highlights: → A removal of Zn2+ ions by pH-sensitive Ch/IA/MAA hydrogel from aqueous solutions was studied. → SEM/EDX analysis and AFM surface topography indicate that sorption takes place on the surface of the hydrogel and in the bulk. → FTIR spectra of the Ch/IA/MAA hydrogel, free and Zn-loaded, indicate that -NH2, -OH and -COOH groups are involved in the sorption process. → The negative values of free energy and enthalpy indicated that the adsorption is spontaneous and exothermic one. → The adsorption capacities did not show any significant decrease after the third reuse cycle. - Abstract: Novel pH-sensitive hydrogels based on chitosan, itaconic acid and methacrylic acid were applied as adsorbents for the removal of Zn2+ ions from aqueous solution. In batch tests, the influence of solution pH, contact time, initial metal ion concentration and temperature was examined. The sorption was found pH dependent, pH 5.5 being the optimum value. The adsorption process was well described by the pseudo-second order kinetic. The hydrogels were characterized by spectral (Fourier transform infrared-FTIR) and structural (SEM/EDX and atomic force microscopy-AFM) analyses. The surface topography changes were observed by atomic force microscopy, while the changes in surface composition were detected using phase imaging AFM. The negative values of free energy and enthalpy indicated that the adsorption is spontaneous and exothermic one. The best fitting isotherms were Langmuir and Redlich-Peterson and it was found that both linear and nonlinear methods were appropriate for obtaining the isotherm parameters. However, the increase of temperature leads to higher adsorption capacity, since swelling degree increased with temperature.

  17. Alginate-Collagen Fibril Composite Hydrogel

    Mahmoud Baniasadi

    2015-02-01

    Full Text Available We report on the synthesis and the mechanical characterization of an alginate-collagen fibril composite hydrogel. Native type I collagen fibrils were used to synthesize the fibrous composite hydrogel. We characterized the mechanical properties of the fabricated fibrous hydrogel using tensile testing; rheometry and atomic force microscope (AFM-based nanoindentation experiments. The results show that addition of type I collagen fibrils improves the rheological and indentation properties of the hydrogel.

  18. Synthesis, Characterization, and Acute Oral Toxicity Evaluation of pH-Sensitive Hydrogel Based on MPEG, Poly( ε -caprolactone), and Itaconic Acid

    Liwei Tan; Xu Xu; Jia Song; Feng Luo; Zhiyong Qian

    2013-01-01

    A kind of chemically cross-linked pH-sensitive hydrogels based on methoxyl poly(ethylene glycol)-poly(caprolactone)-acryloyl chloride (MPEG-PCL-AC, PECA), poly(ethylene glycol) methyl ether methacrylate (MPEGMA, MEG), N,N-methylenebisacrylamide (BIS), and itaconic acid (IA) were prepared without using any organic solvent by heat-initiated free radical method. The obtained macromonomers and hydrogels were characterized by 1H NMR and FT-IR, respectively. Morphology study of hydrogels was also i...

  19. New antifouling silica hydrogel.

    Beltrán-Osuna, Ángela A; Cao, Bin; Cheng, Gang; Jana, Sadhan C; Espe, Matthew P; Lama, Bimala

    2012-06-26

    In this work, a new antifouling silica hydrogel was developed for potential biomedical applications. A zwitterionic polymer, poly(carboxybetaine methacrylate) (pCBMA), was produced via atom-transfer radical polymerization and was appended to the hydrogel network in a two-step acid-base-catalyzed sol-gel process. The pCBMA silica aerogels were obtained by drying the hydrogels under supercritical conditions using CO(2). To understand the effect of pCBMA on the gel structure, pCBMA silica aerogels with different pCBMA contents were characterized using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectroscopy, and the surface area from Brauner-Emmet-Teller (BET) measurements. The antifouling property of pCBMA silica hydrogel to resist protein (fibrinogen) adsorption was measured using enzyme-linked immunosorbent assay (ELISA). SEM images revealed that the particle size and porosity of the silica network decreased at low pCBMA content and increased at above 33 wt % of the polymer. The presence of pCBMA increased the surface area of the material by 91% at a polymer content of 25 wt %. NMR results confirmed that pCBMA was incorporated completely into the silica structure at a polymer content below 20 wt %. A protein adsorption test revealed a reduction in fibrinogen adsorption by 83% at 25 wt % pCBMA content in the hydrogel compared to the fibrinogen adsorption in the unmodified silica hydrogel. PMID:22607091

  20. Smart nanocomposite hydrogels based on azo crosslinked graphene oxide for oral colon-specific drug delivery

    Hou, Lin; Shi, Yuyang; Jiang, Guixiang; Liu, Wei; Han, Huili; Feng, Qianhua; Ren, Junxiao; Yuan, Yujie; Wang, Yongchao; Shi, Jinjin; Zhang, Zhenzhong

    2016-08-01

    A safe and efficient nanocomposite hydrogel for colon cancer drug delivery was synthesized using pH-sensitive and biocompatible graphene oxide (GO) containing azoaromatic crosslinks as well as poly (vinyl alcohol) (PVA) (GO–N=N–GO/PVA composite hydrogels). Curcumin (CUR), an anti-cancer drug, was encapsulated successfully into the hydrogel through a freezing and thawing process. Fourier transform infrared spectroscopy, scanning electron microscopy and Raman spectroscopy were performed to confirm the formation and morphological properties of the nanocomposite hydrogel. The hydrogels exhibited good swelling properties in a pH-sensitive manner. Drug release studies under conditions mimicking stomach to colon transit have shown that the drug was protected from being released completely into the physiological environment of the stomach and small intestine. In vivo imaging analysis, pharmacokinetics and a distribution of the gastrointestinal tract experiment were systematically studied and evaluated as colon-specific drug delivery systems. All the results demonstrated that GO–N=N–GO/PVA composite hydrogels could protect CUR well while passing through the stomach and small intestine to the proximal colon, and enhance the colon-targeting ability and residence time in the colon site. Therefore, CUR loaded GO–N=N–GO/PVA composite hydrogels might potentially provide a theoretical basis for the treatment of colon cancer with high efficiency and low toxicity.

  1. A Thixotropic Polyglycerol Sebacate-Based Supramolecular Hydrogel as an Injectable Drug Delivery Matrix

    Hongye Ye

    2016-04-01

    Full Text Available We have developed a “self-healing” polyglycerol sebacate—polyethylene glycol methyl ether methacrylate (PGS-PEGMEMA/α-Cyclodextrin (αCD hydrogel which could be sheared into a liquid during injection and has the potential to quickly “heal” itself back into gel post-injection. This hydrogel was shown to be biocompatible and biodegradable and therefore appropriate for use in vivo. Furthermore, the storage and loss moduli of the hydrogels could be tuned (by varying the concentration of αCD between a fraction of a kPa to a few 100 kPa, a range that coincides with the moduli of cells and human soft tissues. This property would allow for this hydrogel to be used in vivo with maximal mechanical compatibility with human soft tissues. In vitro experiments showed that the hydrogel demonstrated a linear mass erosion profile and a biphasic drug (doxorubicin release profile: Phase I was primarily driven by diffusion and Phase II was driven by hydrogel erosion. The diffusion mechanism was modeled with the First Order equation and the erosion mechanism with the Hopfenberg equation. This established fitting model could be used to predict releases with other drugs and estimate the composition of the hydrogel required to achieve a desired release rate.

  2. A Peptide-Based Mechano-sensitive, Proteolytically Stable Hydrogel with Remarkable Antibacterial Properties.

    Baral, Abhishek; Roy, Subhasish; Ghosh, Srabanti; Hermida-Merino, Daniel; Hamley, Ian W; Banerjee, Arindam

    2016-02-23

    A long-chain amino acid containing dipeptide has been found to form a hydrogel in phosphate buffer whose pH ranges from 6.0 to 8.8. The hydrogel formed at pH 7.46 has been characterized by small-angle X-ray scattering (SAXS), wide-angle powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM) imaging and rheological analyses. The microscopic imaging studies suggest the formation of a nanofibrillar three-dimensional (3D) network for the hydrogel. As observed visually and confirmed rheologically, the hydrogel at pH 7.46 exhibits thixotropy. This thixotropic property can be exploited to inject the peptide. Furthermore, the hydrogel exhibits remarkable antibacterial activity against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, which are responsible for many common diseases. The hydrogel has practical applicability due to its biocompatibility with human red blood cells and human fibroblast cells. Interestingly, this hydrogel shows high resistance toward proteolytic enzymes, making it a new potential antimicrobial agent for future applications. It has also been observed that a small change in molecular structure of the gelator peptide not only turns the gelator into a nongelator molecule under similar conditions, but it also has a significant negative impact on its bactericidal character. PMID:26818698

  3. Oral delivery of insulin using pH-sensitive hydrogels based on polyvinyl alcohol grafted with acrylic acid/methacrylic acid by radiation

    The pH-responsive hydrogels were studied as a drug carrier for the protection of insulin from the acidic environment of the stomach before releasing in the small intestine. Hydrogels based on poly(vinyl alcohol) networks grafted with acrylic acid or methacrylic acid were prepared via a two-step process. Poly(vinyl alcohol) hydrogels were prepared by gamma ray irradiation (50 kGy) and then followed by grafting either acrylic acid or methacrylic acid onto this poly(vinyl alcohol) hydrogels with subsequent irradiation (5-20 kGy). These graft hydrogels showed pH-sensitive swelling behavior. These hydrogels were used as carrier for the controlled release of insulin. The in vitro release of insulin was observed for the insulin-loaded hydrogels in a simulated intestinal fluid (pH 6.8) but not in a simulated gastric fluid (pH 1.2). The release behavior of insulin in vivo in a rat model confirmed the effectiveness of the oral delivery of insulin to control the level of glucose

  4. Smart poly(oligo(propylene glycol) methacrylate) hydrogel prepared by gamma radiation

    Suljovrujic, E., E-mail: edin@vinca.rs; Micic, M.

    2015-01-01

    Highlights: • Radiation induced synthesis of POPGMA hydrogel is reported for the first time. • High sol–gel conversion was observed even for small absorbed doses. • POPGMA hydrogel exhibits a volume phase transition temperature (VPTT) around 15 °C. • POPGMA homopolymeric hydrogel has good cell viability and low haemolytic activity. • OPGMA based hydrogels promise to be interesting for various applications. - Abstract: The synthesis of poly(oligo(propylene glycol) methacrylate) (POPGMA) from functionalised oligo(propylene glycol) methacrylate (OPGMA) monomers by gamma radiation-induced radical polymerisation is reported for the first time; POPGMA homopolymeric hydrogel with oligo(propylene glycol) (OPG) pendant chains, as a non-linear PPGMA-analogue, was synthesised from an monomer–solvent (OPGMA{sub 375}–water/ethanol) mixture at different irradiation doses (5, 10, 25, and 40 kGy). Determination of the gel fraction was conducted after synthesis. The swelling properties of the POPGMA hydrogel were preliminarily investigated over wide pH (2.2–9.0) and temperature (4–70 °C) ranges. Additional characterisation of structure and properties was conducted by UV–vis and Fourier transform infrared (FTIR) spectroscopy as well as by differential scanning calorimetry (DSC). In order to evaluate the potential for biomedical applications, biocompatibility (cytocompatibility and haemolytic activity) studies were performed as well. Sol–gel conversion was relatively high for all irradiation doses, indicating radiation-induced synthesis as a good method for fabricating this hydrogel. Thermoresponsiveness and variations in swelling capacity as a result of thermosensitive OPG pendant chains with a lower critical solution temperature (LCST) were mainly observed below room temperature; thus, the volume phase transition temperature (VPTT) of POPGMA homopolymeric hydrogel is about 15 °C. Furthermore, POPGMA has satisfactory biocompatibility. The results indicate

  5. Structural analysis of dextrins and characterization of dextrin-based biomedical hydrogels.

    Silva, Dina M; Nunes, Cláudia; Pereira, Isabel; Moreira, Ana S P; Domingues, Maria Rosário M; Coimbra, Manuel A; Gama, Francisco M

    2014-12-19

    The characterization of several commercial dextrins and the analysis of the potential of dextrin derived hydrogels for biomedical applications were performed in this work. The structural characterization of dextrins allowed the determination of the polymerization and branching degrees, which ranged from 6 to 17 glucose residues and 2 to 13%, respectively. Tackidex, a medical grade dextrin was choosen for further characterization. The combination of hydrogel with a dextrin nanogel and urinary bladder matrix was achieved without compromising the mechanical properties or microstructure. The encapsulation of cells, preserving its viability, confirms the biocompatibility of the injectable hydrogels, which have therefore great potential for biomedical applications. PMID:25263914

  6. Interpenetrating Polymer Network Hydrogels Based on Gelatin and PVA by Biocompatible Approaches: Synthesis and Characterization

    Eltjani-Eltahir Hago

    2013-01-01

    Full Text Available In this work, a new approach was introduced to prepare interpenetrating polymer network PVA/GE hydrogels by cross-linking of various concentration gelatin in the presence of transglutaminase enzyme by using the freezing-thawing cycles technique. The effects of freezing-thawing cycles on the properties of morphological characterization, gel fraction, swelling, mechanical, and MTT assay were investigated. The IPN PVA/GE hydrogels showed excellent physical and mechanical Properties. MTT assay data and the fibroblasts culture also showed excellent biocompatibility and good proliferation. This indicates that the IPN hydrogels are stable enough for various biomedical applications.

  7. A high-performance broadband terahertz absorber based on sawtooth-shape doped-silicon

    Du, Liang-Hui; Li, Jiang; Zhai, Zhao-Hui; Meng, Kun; Liu, Qiao; Zhong, Sen-Cheng; Zhou, Ping-Wei; Zhu, Li-Guo; Li, Ze-Ren; Peng, Qi-Xian

    2016-05-01

    Perfect absorbers with broadband absorption of terahertz (THz) radiation are promising for applications in imaging and detection to enhance the contrast and sensitivity, as well as to provide concealment. Different from previous two-dimensional structures, here we put forward a new type of THz absorber based on sawtooth-shape doped-silicon with near-unit absorption across a broad spectral range. Absorbance over 99% is observed numerically from 1.2 to 3 THz by optimizing the geometric parameters of the sawtooth structure. Our absorbers can operate over a wide range of incident angle and are polarization insensitive. The underlying mechanisms due to the combination of an air-cavity mode and mode-matching resonance on the air-sawtooth interface are analyzed in terms of the field patterns and electromagnetic power loss features.

  8. Recent trends in pH/thermo-responsive self-assembling hydrogels: from polyions to peptide-based polymeric gelators.

    Chassenieux, Christophe; Tsitsilianis, Constantinos

    2016-02-01

    In this article, we highlight some recent developments in "smart" physical hydrogels achieved by self-assembling of block type macromolecules. More precisely we focus on two interesting types of gelators namely conventional ionic (or ionogenic) block copolymers and peptide-based polymers having as a common feature their responsiveness to pH and/or temperature which are the main triggers used for potential biomedical applications. Taking advantage of the immense skills of conventional block copolymer hydrogelators, namely macromolecular design, self-assembling mechanism, gel rheological properties, responsiveness to various triggers and innovative applications, the development of novel self-assembling gelators, integrating the new knowledge emerging from the peptide-based systems, opens new horizons towards bio-inspired technologies. PMID:26781351

  9. Swelling and Drug Release Properties of Starch Based Copolymer Hydrogel Prepared By Ionizing Radiation

    ph-sensitive hydrogels composed of starch /acrylic acid were prepared by means of gamma-radiation induced graft copolymerization and crosslinking. The effects of the preparation conditions such as the feed solution concentration and composition and irradiation dose on the gelation process of the synthesized copolymer were investigated. The effects of ph and ionic strength on the equilibrium of swelling for the prepared hydrogels were studied. The swelling behavior of the starch/acrylic acid copolymer hydrogels was examined by studying the effect of the hydrogel composition on the time- and ph-dependent swelling. In order to estimate the ability of the prepared copolymer to be used as a colon-specific drug carrier, the release of ketoprofen was monitored as a function of time at ph 1 and ph 7

  10. WOOD HEMICELLULOSE/CHITOSAN-BASED SEMI-INTERPENETRATING NETWORK HYDROGELS: MECHANICAL, SWELLING AND CONTROLLED DRUG RELEASE PROPERTIES

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

    2010-01-01

    The cell wall of most plant biomass from forest and agricultural resources consists of three major polymers, cellulose, hemicellulose, and lignin. Of these, hemicelluloses have gained increasing attention as sustainable raw materials. In this study, novel pH-sensitive semi-IPN hydrogels based on hemicelluloses and chitosan were prepared using glutaraldehyde as the crosslinking agent. The hemicellulose isolated from aspen was analyzed for sugar content by HPLC, and its molecular weight distrib...

  11. Effect of Sodium Salicylate on the Viscoelastic Properties and Stability of Polyacrylate-Based Hydrogels for Medical Applications

    Zuzana Kolarova Raskova; Martina Hrabalikova; Vladimir Sedlarik

    2016-01-01

    Investigation was made into the effect exerted by the presence of sodium salicylate (0-2 wt.%), in Carbomer-based hydrogel systems, on processing conditions, rheological and antimicrobial properties in tests against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacterial strains, and examples of yeast (Candida albicans) and mould (Aspergillus niger). In addition, the work presents an examination of long-term stability by means of aging over one year the given hydr...

  12. Graphene-based extremely wide-angle tunable metamaterial absorber

    Linder, Jacob

    2016-01-01

    We investigate the absorption properties of graphene-based anisotropic metamaterial structures where the metamaterial layer possesses an electromagnetic response corresponding to a near-zero permittivity. We find that through analytical and numerical studies, near perfect absorption arises over an unusually broad range of beam incidence angles. Due to the presence of graphene, the absorption is tunable via a gate voltage, providing dynamic control of the energy transmission. We show that this strongly enhanced absorption arises due to a coupling between light and a fast wave-mode propagating along the graphene/metamaterial hybrid.

  13. Design of a Drug-Delivery System Based On Polyacrylamide Hydrogels. Evaluation of Structural Properties

    Ferreira, L; Vidal, M. M.; Gil, M. H.

    2001-01-01

    It is well known that hydrogels can be suitable for biomedical, agricultural, and industrial applications. In particular, they have been widely used for the preparation of drug-delivery systems. The preparation and characterization of such a system should be useful for introducing students to these materials. This paper describes the preparation of polyacrylamide hydrogels having different crosslinking densities from the view of optimizing this system for acetylsalicylic acid (aspirin) releas...

  14. Characterization of Lactate Sensors Based on Lactate Oxidase and Palladium Benzoporphyrin Immobilized in Hydrogels

    Liam P. Andrus; Rachel Unruh; Wisniewski, Natalie A; McShane, Michael J.

    2015-01-01

    An optical biosensor for lactate detection is described. By encapsulating enzyme-phosphor sensing molecules within permeable hydrogel materials, lactate-sensitive emission lifetimes were achieved. The relative amount of monomer was varied to compare three homo- and co-polymer materials: poly(2-hydroxyethyl methacrylate) (pHEMA) and two copolymers of pHEMA and poly(acrylamide) (pAam). Diffusion analysis demonstrated the ability to control lactate transport by varying the hydrogel composition,...

  15. Structural analysis of dextrins and characterization of dextrin-based biomedical hydrogels

    Silva, Dina M.; Nunes, Cláudia; Pereira, Isabel Sofia Melo; Moreira, Ana S. P.; Domingues, M. R. M.; Coimbra, Manuel A.; Gama, F. M.

    2014-01-01

    The characterization of several commercial dextrins and the analysis of the potential of dextrin derived hydrogels for biomedical applications were performed in this work. The structural characterization of dextrins allowed the determination of the polymerization and branching degrees, which ranged from 6 to 17 glucose residues and 2 to 13%, respectively. Tackidex, a medical grade dextrin was choosen for further characterization. The combination of hydrogel with a dextrin nanogel and urinary ...

  16. Polyglycerol Based Hydrogels for the Immobilization of Catalytically Active Enzymes and as Scaffolds for Cells

    Dey, Pradip

    2015-01-01

    Im Rahmen dieser Doktorarbeit wurden Hydrogele basierend auf dendritischem Polyglycerol (dPG) entwickelt, welche unter Verwendung verschiedener Vernetzungsreaktionen, wie z. B. durch Amidverknüpfung oder durch ringspannungsvermittelte Azid-Alkin Cycloaddition (strain promoted azide alkyne cycloaddition, SPAAC), hergestellt wurden. Das Anwendungsspektrum dieser Hydrogele reicht von der Entwicklung enzymbasierter Biosensoren bis hin zu Trägermaterialien für Knorpelzellen. Enzymbasierte Bios...

  17. Stiffness and Adhesivity Control Aortic Valve Interstitial Cell Behavior within Hyaluronic Acid Based Hydrogels

    Duan, Bin; Hockaday, Laura A.; Kapetanovic, Edi; Kang, Kevin H.; Butcher, Jonathan T.

    2013-01-01

    Bioactive and biodegradable hydrogels that mimic the extracellular matrix and regulate valve interstitial cells (VIC) behavior are of great interest as three dimensional (3D) model systems for understanding mechanisms of valvular heart disease pathogenesis in vitro and the basis for regenerative templates for tissue engineering. However, the role of stiffness and adhesivity of hydrogels in VIC behavior remains poorly understood. This study reports synthesis of oxidized and methacrylated hyalu...

  18. Thermal tuning of infrared resonant absorbers based on hybrid gold-VO2 nanostructures

    Resonant absorbers based on plasmonic materials, metamaterials, and thin films enable spectrally selective absorption filters, where absorption is maximized at the resonance wavelength. By controlling the geometrical parameters of nano/microstructures and materials' refractive indices, resonant absorbers are designed to operate at wide range of wavelengths for applications including absorption filters, thermal emitters, thermophotovoltaic devices, and sensors. However, once resonant absorbers are fabricated, it is rather challenging to control and tune the spectral absorption response. Here, we propose and demonstrate thermally tunable infrared resonant absorbers using hybrid gold-vanadium dioxide (VO2) nanostructure arrays. Absorption intensity is tuned from 90% to 20% and 96% to 32% using hybrid gold-VO2 nanowire and nanodisc arrays, respectively, by heating up the absorbers above the phase transition temperature of VO2 (68 °C). Phase change materials such as VO2 deliver useful means of altering optical properties as a function of temperature. Absorbers with tunable spectral response can find applications in sensor and detector applications, in which external stimulus such as heat, electrical signal, or light results in a change in the absorption spectrum and intensity

  19. Microwave absorption properties of double-layer absorber based on carbonyl iron/barium hexaferrite composites

    Ren, Xiaohu; Fan, Huiqing; Cheng, Yankui

    2016-05-01

    The microwave absorption properties of BaCo0.4Zn1.6Fe16O27 ferrite and carbonyl iron powder with single-layer and double-layer composite absorbers were investigated based on the electromagnetic transmission line theory in the frequency range from 1 to 14 GHz. XRD was used to characterize the structure of prepared absorbing particles. SEM was used to examine the micromorphology of the particles and composites. The complex permittivity and permeability of composites were measured by using a vector network analyzer. The reflection loss of the single-layer and double-layer absorbers with different thicknesses and orders was investigated. The results show that double-layer absorbers have better microwave absorption properties than single-layer absorbers. The microwave absorption properties of the double-layer structure are influenced by the coupling interactions between the matching and absorption layers. As the pure ferrite used as matching layer and the composite of BF-5CI used as absorption, the minimum RL of absorber can achieve to -55.4 dB and the bandwidth of RL <-10 dB ranged from 5.6 to 10.8 GHz when the thicknesses of matching layer and absorption layer were 0.9 and 1.4 mm, respectively.

  20. A Shape-Memory DNA-Based Hydrogel Exhibiting Two Internal Memories.

    Hu, Yuwei; Guo, Weiwei; Kahn, Jason S; Aleman-Garcia, Miguel Angel; Willner, Itamar

    2016-03-18

    The synthesis of a shape-memory acrylamide-DNA hydrogel that includes two internal memories is introduced. The hydrogel is stabilized, at pH 7.0, by two different pH-responsive oligonucleotide crosslinking units. At pH 10.0, one of the T-A⋅T triplex DNA bridging units is dissociated, resulting in the dissociation of the hydrogel into a shapeless quasi-liquid state that includes the other oligonucleotide bridges as internal memory. Similarly, at pH 5.0, the second type of bridges is separated, through the formation of C-G⋅C(+) triplex units to yield the shapeless quasi-liquid state that includes the other oligonucleotide bridges as internal memory. By reversible pH triggering of the hydrogel between the values 10.0⇔7.0⇔5.0, the two internal memories cycle the material across shaped hydrogel and shapeless quasi-liquid states. The two memories enable the pH-dictated formation of two different hydrogel structures. PMID:26915713

  1. Cytocompatibility of chitosan -based thermosensitive hydrogel to human periodontal ligament cell

    PAN Jian-feng; Ji Qiu-xia; Lv Bing-hua; Li Chang-chun; Wu Hong; Li Dan-dan; Li-Hui

    2015-01-01

    Objective:To investigate the ef ect of thermosensitive chitosan /β-glycerophosphate (CS /β-GP)hydrogel on proliferation of human periodontal ligament cel s (HPDLCs). Methods:CS /β-GP were prepared into a thermosensitive hydrogel and its three -dimensional structure was observed under electron microscope.HPDLCs harvested and cultured in vitro were co -cultured with the thermosensitive CS /β-GP hydrogel.Growth of the cel s in the hydrogel was observed with HE staining,and the ef ect of the extract on proliferation of HPDLCs was exam-ined by CCK -8 assay.Results:Observations of SEMand HE staining showed that the thermosensitive CS /β-GP hydrogel was large in pore size and appropriate for cel growth.Dif erent levels of CS /α,β-GP extracts could promote proliferation of HPDLCs.Conclusion:Thermosensitive CS /β-GP hydrogel can promote proliferation of HPDLCs and be a good carrier for periodontal tis-sue engineering because of its thermosensitivity.

  2. Self-assembled, photoluminescent peptide hydrogel as a versatile platform for enzyme-based optical biosensors.

    Kim, Jae Hong; Lim, Seong Yoon; Nam, Dong Heon; Ryu, Jungki; Ku, Sook Hee; Park, Chan Beum

    2011-01-15

    A self-assembled peptide hydrogel consisting of Fmoc-diphenylalanine has been employed as a biosensing platform through the encapsulation of enzyme bioreceptors (e.g., glucose oxidase or horseradish peroxidase) and fluorescent reporters (e.g., CdTe and CdSe quantum dots). Enzymes and quantum dots (QDs) were physically immobilized within the hydrogel matrix in situ in a single step by simply mixing aqueous solution containing QDs and enzymes with monomeric peptide (Fmoc-diphenylalanine) solution. By using atomic force microscopy and scanning transmission electron microscopy, we observed that the self-assembled peptide hydrogel had a three-dimensional network of nanofibers (with a diameter of approximately 70-90 nm) that physically hybridized with QDs and encapsulated enzyme bioreceptors with a minimal leakage. We successfully applied the peptide hydrogel to the detection of analytes such as glucose and toxic phenolic compounds by using a photoluminescence quenching of the hybridized QDs. The Michaelis-Menten constant (K(M)) of the photoluminescent peptide hydrogel was found to be 3.12 mM (GOx for glucose) and 0.82 mM (HRP for hydroquinone), respectively, which were much lower than those of conventional gel materials. These results suggest that the peptide hydrogel is an alternative optical biosensing platform with practical advantages such as simple fabrication via self-assembly, efficient diffusion of target analytes, and high encapsulation efficiencies for fluorescent reporters and bioreceptors. PMID:20171868

  3. Enantiomorphous Periodic Mesoporous Organosilica-Based Nanocomposite Hydrogel Scaffolds for Cell Adhesion and Cell Enrichment.

    Kehr, Nermin Seda

    2016-03-14

    The chemical functionalization of nanomaterials with bioactive molecules has been used as an effective tool to mimic extracellular matrix (ECM) and to study the cell-material interaction in tissue engineering applications. In this respect, this study demonstrates the use of enantiomerically functionalized periodic mesoporous organosilicas (PMO) for the generation of new multifunctional 3D nanocomposite (NC) hydrogels to control the affinity of cells to the hydrogel surfaces and so to control the enrichment of cells and simultaneous drug delivery in 3D network. The functionalization of PMO with enantiomers of bioactive molecules, preparation of their nanocomposite hydrogels, and the stereoselective interaction of them with selected cell types are described. The results show that the affinity of cells to the respective NC hydrogel scaffolds is affected by the nature of the biomolecule and its enantiomers, which is more pronounced in serum containing media. The differentiation of enantiomorphous NC hydrogels by cells is used to enrich one cell type from a mixture of two cells. Finally, PMO are utilized as nanocontainers to release two different dye molecules as a proof of principle for multidrug delivery in 3D NC hydrogel scaffolds. PMID:26811946

  4. Optimization and translation of MSC-based hyaluronic acid hydrogels for cartilage repair

    Erickson, Isaac E.

    2011-12-01

    Traumatic injury and disease disrupt the ability of cartilage to carry joint stresses and, without an innate regenerative response, often lead to degenerative changes towards the premature development of osteoarthritis. Surgical interventions have yet to restore long-term mechanical function. Towards this end, tissue engineering has been explored for the de novo formation of engineered cartilage as a biologic approach to cartilage repair. Research utilizing autologous chondrocytes has been promising, but clinical limitations in their yield have motivated research into the potential of mesenchymal stem cells (MSCs) as an alternative cell source. MSCs are multipotent cells that can differentiate towards a chondrocyte phenotype in a number of biomaterials, but no combination has successfully recapitulated the native mechanical function of healthy articular cartilage. The broad objective of this thesis was to establish an MSC-based tissue engineering approach worthy of clinical translation. Hydrogels are a common class of biomaterial used for cartilage tissue engineering and our initial work demonstrated the potential of a photo-polymerizable hyaluronic acid (HA) hydrogel to promote MSC chondrogenesis and improved construct maturation by optimizing macromer and MSC seeding density. The beneficial effects of dynamic compressive loading, high MSC density, and continuous mixing (orbital shaker) resulted in equilibrium modulus values over 1 MPa, well in range of native tissue. While compressive properties are crucial, clinical translation also demands that constructs stably integrate within a defect. We utilized a push-out testing modality to assess the in vitro integration of HA constructs within artificial cartilage defects. We established the necessity for in vitro pre-maturation of constructs before repair to achieve greater integration strength and compressive properties in situ. Combining high MSC density and gentle mixing resulted in integration strength over 500 k

  5. A thermo-responsive and photo-polymerizable chondroitin sulfate-based hydrogel for 3D printing applications.

    Abbadessa, A; Blokzijl, M M; Mouser, V H M; Marica, P; Malda, J; Hennink, W E; Vermonden, T

    2016-09-20

    The aim of this study was to design a hydrogel system based on methacrylated chondroitin sulfate (CSMA) and a thermo-sensitive poly(N-(2-hydroxypropyl) methacrylamide-mono/dilactate)-polyethylene glycol triblock copolymer (M15P10) as a suitable material for additive manufacturing of scaffolds. CSMA was synthesized by reaction of chondroitin sulfate with glycidyl methacrylate (GMA) in dimethylsulfoxide at 50°C and its degree of methacrylation was tunable up to 48.5%, by changing reaction time and GMA feed. Unlike polymer solutions composed of CSMA alone (20% w/w), mixtures based on 2% w/w of CSMA and 18% of M15P10 showed strain-softening, thermo-sensitive and shear-thinning properties more pronounced than those found for polymer solutions based on M15P10 alone. Additionally, they displayed a yield stress of 19.2±7.0Pa. The 3D printing of this hydrogel resulted in the generation of constructs with tailorable porosity and good handling properties. Finally, embedded chondrogenic cells remained viable and proliferating over a culture period of 6days. The hydrogel described herein represents a promising biomaterial for cartilage 3D printing applications. PMID:27261741

  6. Radiation preparation and characterization of temperature- and pH-sensitive hydrogel of N-isopropylacrylamide/β-cyclodextrin copolymer

    A hydrogel copolymer of N-isopropylacrylamide/β-cyclodextrin was prepared by radiation copoly- merization method. β-cyclodextrin (β-CD) based monomer (MAH-β-CD) containing vinyl and carboxyl functional groups was synthesized by modification of β-CD with maleic anhydride (MAH). And then the mixture aqueous solution of NIPAAm and MAH-β-CD was irradiated by electron beams with BIS as cross-linking agent for sample of poly (NIPAAm-co-MAH-β-CD) hydrogel. The effects of temperature, pH and ionic strength on swelling ratio of the hydrogel were determined meanwhile the effect of irradiation absorbed doses on its swelling and deswelling properties was also described. Experimental results show that the copolymer hydrogel possesses temperature, pH and ionic strength sensitive functions. (authors)

  7. Tungsten band edge absorber/emitter based on a monolayer of ceramic microspheres.

    Dyachenko, P N; do Rosário, J J; Leib, E W; Petrov, A Yu; Störmer, M; Weller, H; Vossmeyer, T; Schneider, G A; Eich, M

    2015-09-21

    We report on a band edge absorber/emitter design for high-temperature applications based on an unstructured tungsten substrate and a monolayer of ceramic microspheres. The absorber was fabricated as a monolayer of ZrO(2) microparticles on a tungsten layer with a HfO(2) nanocoating. The band edge of the absorption is based on critically coupled microsphere resonances. It can be tuned from visible to near-infrared range by varying the diameter of the microparticles. The absorption properties were found to be stable up to 1000°C. PMID:26406752

  8. Graphene based tunable fractal Hilbert curve array broadband radar absorbing screen for radar cross section reduction

    Xianjun Huang; Zhirun Hu; Peiguo Liu

    2014-01-01

    This paper proposes a new type of graphene based tunable radar absorbing screen. The absorbing screen consists of Hilbert curve metal strip array and chemical vapour deposition (CVD) graphene sheet. The graphene based screen is not only tunable when the chemical potential of the graphene changes, but also has broadband effective absorption. The absorption bandwidth is from 8.9GHz to 18.1GHz, ie., relative bandwidth of more than 68%, at chemical potential of 0eV, which is significantly wider t...

  9. Thermosensitive chitosan-based hydrogel as a topical ocular drug delivery system of latanoprost for glaucoma treatment.

    Cheng, Yung-Hsin; Tsai, Tung-Hu; Jhan, Yong-Yu; Chiu, Allen Wen-Hsiang; Tsai, Kun-Ling; Chien, Chian-Shiu; Chiou, Shih-Hwa; Liu, Catherine Jui-Lin

    2016-06-25

    Ocular hypertension is a major risk factor for the development and progression of glaucoma. Frequent and long-term application of latanoprost often causes undesirable local side effects, which are a major cause of therapeutic failure due to loss of persistence in using this glaucoma medical therapy. In the present study, we developed a thermosensitive chitosan-based hydrogel as a topical eye drop formulation for the sustained release of latanoprost to control ocular hypertension. The developed formulation without preservatives may improve compliance and possibly even efficacy. The results of this study support its biocompatibility and sustained-release profile both in vitro and in vivo. After topical application of latanoprost-loaded hydrogel, triamcinolone acetonide-induced elevated intraocular pressure was significantly decreased within 7 days and remained at a normal level for the following 21 days in rabbit eyes. This newly developed chitosan-based hydrogel may provide a non-invasive alternative to traditional anti-glaucoma eye drops for glaucoma treatment. PMID:27083831

  10. Multiscale approach for the construction of equilibrated all-atom models of a poly(ethylene glycol)-based hydrogel.

    Li, Xianfeng; Murthy, N Sanjeeva; Becker, Matthew L; Latour, Robert A

    2016-06-01

    A multiscale modeling approach is presented for the efficient construction of an equilibrated all-atom model of a cross-linked poly(ethylene glycol) (PEG)-based hydrogel using the all-atom polymer consistent force field (PCFF). The final equilibrated all-atom model was built with a systematic simulation toolset consisting of three consecutive parts: (1) building a global cross-linked PEG-chain network at experimentally determined cross-link density using an on-lattice Monte Carlo method based on the bond fluctuation model, (2) recovering the local molecular structure of the network by transitioning from the lattice model to an off-lattice coarse-grained (CG) model parameterized from PCFF, followed by equilibration using high performance molecular dynamics methods, and (3) recovering the atomistic structure of the network by reverse mapping from the equilibrated CG structure, hydrating the structure with explicitly represented water, followed by final equilibration using PCFF parameterization. The developed three-stage modeling approach has application to a wide range of other complex macromolecular hydrogel systems, including the integration of peptide, protein, and/or drug molecules as side-chains within the hydrogel network for the incorporation of bioactivity for tissue engineering, regenerative medicine, and drug delivery applications. PMID:27013229

  11. Fibrin Hydrogel Based Bone Substitute Tethered with BMP-2 and BMP-2/7 Heterodimers

    Lindsay S. Karfeld-Sulzer

    2015-03-01

    Full Text Available Current clinically used delivery methods for bone morphogenetic proteins (BMPs are collagen based and require large concentrations that can lead to dangerous side effects. Fibrin hydrogels can serve as osteoinductive bone substitute materials in non-load bearing bone defects in combination with BMPs. Two strategies to even further optimize such a fibrin based system include employing more potent BMP heterodimers and engineering growth factors that can be covalently tethered to and slowly released from a fibrin matrix. Here we present an engineered BMP-2/BMP-7 heterodimer where an N-terminal transglutaminase substrate domain in the BMP-2 portion provides covalent attachment to fibrin together with a central plasmin substrate domain, a cleavage site for local release of the attached BMP-2/BMP-7 heterodimer under the influence of cell-activated plasmin. In vitro and in vivo results revealed that the engineered BMP-2/BMP-7 heterodimer induces significantly more alkaline phosphatase activity in pluripotent cells and bone formation in a rat calvarial model than the engineered BMP-2 homodimer. Therefore, the engineered BMP-2/BMP-7 heterodimer could be used to reduce the amount of BMP needed for clinical effect.

  12. A reduced-boron OPR1000 core based on the BigT burnable absorber

    Yu, Hwan Yeal; Yahya, Mohd-Syukri; Kim, Yong Hee [Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon (Korea, Republic of)

    2016-04-15

    Reducing critical boron concentration in a commercial pressurized water reactor core offers many advantages in view of safety and economics. This paper presents a preliminary investigation of a reduced-boron pressurized water reactor core to achieve a clearly negative moderator temperature coefficient at hot zero power using the newly-proposed 'Burnable absorber-Integrated Guide Thimble' (BigT) absorbers. The reference core is based on a commercial OPR1000 equilibrium configuration. The reduced-boron ORP1000 configuration was determined by simply replacing commercial gadolinia-based burnable absorbers with the optimized BigT-loaded design. The equilibrium cores in this study were directly searched via repetitive Monte Carlo depletion calculations until convergence. The results demonstrate that, with the same fuel management scheme as in the reference core, application of the BigT absorbers can effectively reduce the critical boron concentration at the beginning of cycle by about 65 ppm. More crucially, the analyses indicate promising potential of the reduced-boron OPR1000 core with the BigT absorbers, as its moderator temperature coefficient at the beginning of cycle is clearly more negative and all other vital neutronic parameters are within practical safety limits. All simulations were completed using the Monte Carlo Serpent code with the ENDF/B-VII.0 library.

  13. Antibiotic loaded carboxymethylcellulose/MCM-41 nanocomposite hydrogel films as potential wound dressing.

    Namazi, Hassan; Rakhshaei, Rasul; Hamishehkar, Hamed; Kafil, Hossein Samadi

    2016-04-01

    Existing wound dressings have disadvantages such as lack of antibacterial activity, insufficient oxygen and water vapor permeability, and poor mechanical properties. Hydrogel-based wound dressings swell several times their dry volume and would be helpful to absorb wound exudates and afford a cooling sensation and a moisture environment. To overcome these hassles, a novel antibiotic-eluting nanocomposite hydrogel was designed via incorporation of mesoporous silica MCM-41 as a nano drug carrier into carboxymethylcellulose hydrogel. Tetracycline and methylene blue as antibacterial agents were loaded to the system and showed different release profiles. The prepared nanocomposite hydrogel was characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), UV-vis spectroscopy, and scanning electron microscopy (SEM). The prepared nanocomposite hydrogels exhibited an enhanced in vitro swelling, erosion, water vapor and oxygen permeability, and antimicrobial activity. This could effectively increase the time intervals needed to exchange the bandage. The obtained data strongly encourage the use of these nanocomposite hydrogels as wound dressing material. PMID:26740467

  14. Synthesis and characterization of zinc chloride containing poly(acrylic acid) hydrogel by gamma irradiation

    In this study, the characterization of zinc chloride incorporated into a poly(acrylic acid) (PAAc) hydrogel prepared by gamma-ray irradiation was investigated. Zinc chloride powder with different concentrations was dissolved in the PAAc solution, and it was crosslinked with gamma-ray irradiation. The effects of various parameters such as zinc ion concentration and irradiation doses on characteristics of the hydrogel formed were investigated in detail for obtaining an antibacterial wound dressing. In addition, the gel content, pH-sensitive (pH 4 or 7) swelling ratio, and UV–vis absorption spectra of the zinc particles in the hydrogels were characterized. Moreover, antibacterial properties of these new materials against Staphylococcus aureus and Escherichia coli strains were observed on solid growth media. The antibacterial tests indicated that the zinc chloride containing PAAc hydrogels have good antibacterial activity. - Highlights: • The characterization of zinc chloride containing PAA hydrogel was investigated. • The gel content increased with an increase in absorbed dose up to 75 kGy. • Finally, the zinc chloride based hydrogels have an antibacterial activity

  15. Preparation and characterization of superporous hydrogels as gastroretentive drug delivery system for rosiglitazone maleate

    N Vishal Gupta

    2010-09-01

    Full Text Available "n  "nBackground and the purpose of the study: Many drugs which have narrow therapeutic window and are absorbed mainly in stomach have been developed as gastroretentive delivery system. Rosiglitazone maleate, an anti-diabetic, is highly unstable at basic pH and is extensively absorbed from the stomach. Hence there is a need to develop a gastroretentive system. In this study a superporous hydrogel was developed as a gastroretentive drug delivery system. "nMethods: Chitosan/poly(vinyl alcohol interpenetrating polymer network type superporous hydrogels were prepared using a gas foaming method employing glyoxal as the crosslinking agent for Rosiglitazone maleate. Sodium bicarbonate was applied as a foaming agent to introduce the porous structure. Swelling behaviors of superporous hydrogel in acidic solution were studied to investigate their applications for gastric retention device. The optimum preparation condition of superporous hydrogels was obtained from the gelation kinetics. FT-IR, scanning electron microscopy, porosity and swelling ratio studies were used to characterize these polymers. In vitro drug release studies were also carried out. "nResults: The introduction of a small amount of Poly(Vinyl Alcohol enhanced the mechanical strength but slightly reduced the swelling ratio. The prepared superporous hydrogels were highly sensitive to pH of swelling media, and showed reversible swelling and de-swelling behaviors maintaining their mechanical stability. The degradation kinetics in simulated gastric fluid showed that it had biodegradability. Swelling was dependent on the amount of chitosan and crosslinker. The drug release from superporous hydrogels was sustained for 6 hrs. Major Conclusion: The studies showed that chitosan-based superporous hydrogels could be used as a gastroretentive drug delivery system for rosiglitazone maleate in view of their swelling and prolonged drug release characteristics in acidic pH.

  16. MESO-STRUCTURED POLYMERIC HYDROGELS

    Zhen-zhong Yang; Jian-hua Rong; Dan Li

    2003-01-01

    Meso-structured (opal and inverse opal) polymeric hydrogels of varied morphology and composition were prepared by using two methods: post-modification of the template-synthesized structured polymers and templatepolymerization of functional monomers. A polyacrylic acid based inverse opal hydrogel was chosen to demonstrate its fast pH response by changing color, which is important in designing tunable photonic crystals. Template effects of the hydrogels on controlling structure of the template-synthesized inorganic materials were discussed. The catalytic effect of acid groups inthe templates was emphasized for a preferential formation of TiO2 in the region containing acid groups, which allowed duplicating inorganic colloidal crystals from colloidal crystal hydrogels (or macroporous products from macroporous hydrogels) via one step duplication.

  17. MESO—STRUCTURED POLYMERIC HYDROGELS

    Zhen-zhongYang; Jian-huaRong; DanLi

    2003-01-01

    Meso-structured(opal and inverse opal) polymeric hydrogels of varied morphology and composition were prepared by using two methods:post-modification of the template-synthesized structured polymers and templatepolymerization of functional monomers.A polyacrylic acid based inverse opal hydrogel was chosen to demonstrate its fast pH response by changing color,which is important in designing tunable photonic crystals.Template effects of the hydrogels on controlling structure of the template-synthesized inorganic materials were discussed.The catalytic effect of acid groups in the templates was emphasized for a preferential formation of TiO2 in the region containing acid groups,which allowed duplicating inorganic colloidal crystals from colloidal crystal hydrogels (or macroporous products from macroporous hydrogels) via one step duplication.

  18. A Polyvinyl Alcohol-Polyaniline Based Electro-Conductive Hydrogel for Controlled Stimuli-Actuable Release of Indomethacin

    Pradeep Kumar

    2011-01-01

    Full Text Available Electro-conductive hydrogels based on poly(vinyl alcohol, crosslinked with diethyl acetamidomalonate as the hydrogel component, were engineered using polyaniline as the inherently conductive component, and fabricated in the form of cylindrical devices to confer electro-actuable release of the model drug indomethacin. The hydrogels were characterized for their physicochemical and physicomechanical properties. Cyclic voltammetry was employed for electro-activity and conductivity analysis. Drug entrapment efficiency ranged from 65–70%. “ON-OFF” switchable drug release was obtained by periodically applying-removing-reapplying an electric potential ranging from 0.3–5.0 V for 60 seconds at hourly intervals and the cumulative drug release obtained ranged from 4.7–25.2% after four release cycles respectively. The electro-stimulated release of indomethacin was associated with the degree of crosslinking, the polymeric ratio and drug content. A Box-Behnken experimental design was constructed employing 1.2 V as the baseline potential difference. The devices demonstrated superior swellability and high diffusivity of indomethacin, in addition to high electrical conductivity with “ON-OFF” drug release kinetics via electrical switching. In order to investigate the electro-actuable release of indomethacin, molecular mechanics simulations using AMBER-force field were performed on systems containing water molecules and the poly(vinyl alcohol-polyaniline composite under the influence of an external electric field. Various interaction energies were monitored to visualize the effect of the external electric field on the erosion of polyaniline from the co-polymeric matrix. This strategy allows the electro-conductive hydrogels to be suitably applied for controlled, local and electro-actuable drug release while sustaining a mild operating environment.

  19. Silver-containing antimicrobial membrane based on chitosan-TPP hydrogel for the treatment of wounds.

    Sacco, Pasquale; Travan, Andrea; Borgogna, Massimiliano; Paoletti, Sergio; Marsich, Eleonora

    2015-03-01

    Treatment of non-healing wounds represents hitherto a severe dilemma because of their failure to heal caused by repeated tissue insults, bacteria contamination and altered physiological condition. This leads to face huge costs for the healthcare worldwide. To this end, the development of innovative biomaterials capable of preventing bacterial infection, of draining exudates and of favoring wound healing is very challenging. In this study, we exploit a novel technique based on the slow diffusion of tripolyphosphate for the preparation of macroscopic chitosan hydrogels to obtain soft pliable membranes which include antimicrobial silver nanoparticles (AgNPs) stabilized by a lactose-modified chitosan (Chitlac). UV-Vis and TEM analyses demonstrated the time stability and the uniform distribution of AgNPs in the gelling mixture, while swelling studies indicated the hydrophilic behavior of membrane. A thorough investigation on bactericidal properties of the material pointed out the synergistic activity of chitosan and AgNPs to reduce the growth of S. aureus, E. coli, S. epidermidis, P. aeruginosa strains and to break apart mature biofilms. Finally, biocompatibility assays on keratinocytes and fibroblasts did not prove any harmful effects on the viability of cells. This novel technique enables the production of bioactive membranes with great potential for the treatment of non-healing wounds. PMID:25693676

  20. A novel biodegradable β-cyclodextrin-based hydrogel for the removal of heavy metal ions.

    Huang, Zhanhua; Wu, Qinglin; Liu, Shouxin; Liu, Tian; Zhang, Bin

    2013-09-12

    A novel biodegradable β-cyclodextrin-based gel (CAM) was prepared and applied to the removal of Cd(2+), Pb(2+) and Cu(2+) ions from aqueous solutions. CAM hydrogel has a typical three-dimensional network structure, and showed excellent capability for the removal of heavy metal ions. The effect of different experimental parameters, such as initial pH, adsorbent dosage and initial metal ion concentration, were investigated. The adsorption isotherm data fitted well to the Freundlich model. The adsorption capacity was in the order Pb(2+)>Cu(2+)>Cd(2+) under the same experimental conditions. The maximum adsorption capacities for the metal ions in terms of mg/g of dry gel were 210.6 for Pb(2+), 116.41 for Cu(2+), and 98.88 for Cd(2+). The biodegradation efficiency of the resin reached 79.4% for Gloeophyllum trabeum. The high adsorption capacity and kinetics results indicate that CAM can be used as an alternative adsorbent to remove heavy metals from aqueous solution. PMID:23911476

  1. Evaluation of different methods to prepare superabsorbent hydrogels based on deacetylated gellan.

    de Souza, Flavio Silva; de Mello Ferreira, Ivana Lourenço; da Silva Costa, Marcos Antonio; de Lima, Ana Luiza Ferreira; da Costa, Marcia Parente Melo; da Silva, Gustavo Monteiro

    2016-09-01

    This study stands out for analyzing distinct ways of preparing hydrogels from deacetylated gellan gum that have high swelling capacity and good thermal resistance. We carried out a thorough investigation, applying various combinations of different experimental parameters. Two preparation methods were evaluated, in which the pH was adjusted before or after thermal treatment of the gellan solution, with subsequent addition of the crosslinking agent, to assess the influence of preparation method on the conformation of the gellan chains regarding formation of double helices. The pH range tested varied from acid (2, 3 or 4) to basic (8, 9 or 10). Gellan solution was prepared in different concentrations. Both pure gellan and hydrogel samples were characterized by Fourier-transform infrared spectroscopy and thermogravimetry. Pure gellan was also characterized by atomic absorption spectroscopy. The swelling degree of the hydrogels was analyzed. The results showed that all the hydrogels had high swelling capacity (>400%), so they can be considered superabsorbent materials. Hydrogels prepared with acid pH in general had lower thermal resistance than samples prepared in alkaline pH, regardless of the preparation method. Samples prepared with alkaline pH tended to have initial decomposition temperature similar to that of pure gellan. PMID:27185144

  2. In situ supramolecular hydrogel based on hyaluronic acid and dextran derivatives as cell scaffold.

    Chen, Jing-Xiao; Cao, Lu-Juan; Shi, Yu; Wang, Ping; Chen, Jing-Hua

    2016-09-01

    In this study, hyaluronic acid-β-cyclodextrin conjugate (HA-CD) and dextran-2-naphthylacetic acid conjugate (Dex-NAA) were synthesized as two gelators. The degrees of substitution (DS) of these two gelators were determined to be 15.5 and 7.4%, respectively. Taking advantages of the strong and selective host-guest interaction between β-CD and 2-NAA, the mixture of two gelators could form supramolecular hydrogel in situ. Moreover, the pore size, gelation time, swelling ratio as well as modulus of the hydrogel could be adjusted by simply varying the contents of HA-CD and Dex-NAA. NIH/3T3 cells that entrapped in hydrogel grew well as compared with that cultured in plates, indicating a favorable cytocompatibility of the hydrogel. Collectively, the results demonstrated that the HA-Dex hydrogel could potentially be applied in tissue engineering as cell scaffold. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2263-2270, 2016. PMID:27087451

  3. Development of PAN-based absorbers for treating waste problems at U.S. DOE facilities

    Sebesta, F.; John, J.; Motl, A. [Czech Technical Univ., Prague (Czech Republic). Dept. of Nuclear Chemistry; Watson, J.S. [Oak Ridge National Lab., TN (United States)

    1995-12-31

    Polyacrylonitrile (PAN) can be used to bind together very small particles of absorbers into porous aggregates that can be used conveniently in packed columns. While binding the small particles together, the PAN allows substantial diffusion and even flow through the aggregates to give high effective mass transfer rates. Although PAN has been used or proposed for several applications, its capabilities for use with the US Department of Energy (DOE) radioactive wastes have not been determined. This paper summaries studies at the Czech Technical University on the stability of PAN-based absorbers under the radiation, chemical, and physical conditions needed for DOE wastes and assessments of their potential performance with selected US wastes.

  4. Sound-absorbing slabs and structures based on granular materials (bound and unbound). [energy absorbing efficiency of porous material

    Petre-Lazar, S.; Popeea, G.

    1974-01-01

    Sound absorbing slabs and structures made up of bound or unbound granular materials are considered and how to manufacture these elements at the building site. The raw material is a single grain powder (sand, expanded blast furnace slag, etc.) that imparts to the end products an apparent porosity of 25-45% and an energy dissipation within the structure leading to absorption coefficients that can be compared with those of mineral wool and urethane.

  5. Sensitive absorbance measurement method based on laser multi-wave mixing

    Wu, Zhiqiang; Liu, Jinying; Tong, william G.

    1994-12-01

    A sensitive absorbance measurement based on nonlinear laser degenerate four-wave mixing is demonstrated for cadmium. The cadmium ions react with dithizone to form a cadium complex which is then extracted in carbon tetrachloride and analyzed. A relatively low-power argon ion laser line at 514.5 nm is used as the excitation light source. This nonlinear laser method offers many useful features including efficient and simple optical signal detection (signal is a collimated coherent beam), excellent detection sensitivity for absorbance, and efficient use of low laser power levels, small laser probe volumes and short analyte path legnths (e.g., <0.5 mm). A detection limit of 7 fg or 0.05 ng/ml for cadmium, corresponding to an absorbance detection limit of 1.8 × 10 -6 AU is reported using a flowing analyte cell at room temperature.

  6. High-performance terahertz wave absorbers made of silicon-based metamaterials

    Yin, Sheng; Zhu, Jianfei; Jiang, Wei; Yuan, Jun; Yin, Ge; Ma, Yungui, E-mail: yungui@zju.edu.cn [State Key Lab of Modern Optical Instrumentation, Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310058 (China); Xu, Wendao; Xie, Lijuan; Ying, Yibin [College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058 (China)

    2015-08-17

    Electromagnetic (EM) wave absorbers with high efficiency in different frequency bands have been extensively investigated for various applications. In this paper, we propose an ultra-broadband and polarization-insensitive terahertz metamaterial absorber based on a patterned lossy silicon substrate. Experimentally, a large absorption efficiency more than 95% in a frequency range of 0.9–2.5 THz was obtained up to a wave incident angle as large as 70°. Much broader absorption bandwidth and excellent oblique incidence absorption performance are numerically demonstrated. The underlying mechanisms due to the combination of a waveguide cavity mode and impedance-matched diffraction are analyzed in terms of the field patterns and the scattering features. The monolithic THz absorber proposed here may find important applications in EM energy harvesting systems such as THz barometer or biosensor.

  7. Fabrication of chalcopyrite light-absorbing layers based on nanoparticle and nanowire networks

    Ren, Yuhang; Luo, Paifeng; Gao, Bo; Cevher, Zehra; Sun, Chivin

    2013-03-01

    We report on a method of preparing chalcopyrite, CuInGaSe2 (CIGS) light-absorbing layers using low cost air stable ink based on semiconductor nanoparticle and nanowires. The nanoparticles and nanowires are prepared from metal salts such as metal chloride and acetate at room temperature without inert gas protection. A uniform and non-aggregation CIGS precursor layer is fabricated with the formation of nanoparticle and nanowire networks utilizing ultrasonic spaying technique. We obtain a high quality CIGS absorber by cleaning the residue salts and carbon agents at an increased temperature and through selenizing the pretreated CIGS precursors. Our results offer an opportunity for the low-cost deposition of chalcopyrite absorber materials at large scale with high throughput. This work was partially sponsored by Sun Harmonics Ltd. and by NYSTAR through the Photonics Center for Applied Technology at the City University of New York.

  8. SOLAR ABSORBING COOLING SYSTEMS BASED ON MULTISTAGE HEAT-MASS-TRANSFER DEVICES

    Doroshenko A.V.

    2014-08-01

    Full Text Available The article presents the worked out schematics for the alternative refrigeration systems and of air-conditioning systems, based on the use of absorbing cycle and of the sunny energy for the regeneration (renewals of absorbent solution. We use here the cascade principle of construction of all heat-mass-transfer apparatus with variation of both the temperature level and the growth of absorbent concentration on the cascade stages. The heat-mass-transfer equipment as a part of the drying and cooling units is standardized and is executed by means of multistage monoblock compositions from poly-meric materials. The preliminary analysis of possibilities of the sunny systems in application to the tasks of cooling of environment and air-conditioning systems is carried out.

  9. A polarization insensitive and broadband metamaterial absorber based on three-dimensional structure

    Tang, Jingyao; Xiao, Zhongyin; Xu, Kaikai; Liu, Dejun

    2016-08-01

    In this paper, we propose a three-dimensional metamaterial absorber based on tailored resistive film patch array. The numerical results show that a broadband abs orption more than 90% can be achieved from 58.6 to 91.4 GHz for either transverse electric or magnetic polarization wave at normal incidence. And the E-field, surface current and power loss density distributions in the absorber are investigated to explain the physical mechanism of high absorption. In addition, the absorption efficiency of oblique incidence is also elucidated. According to the analysis of the E-field and power loss density distributions, we explain the absorption differences between TE and TM mode at oblique incidence. The proposed metamaterial absorber will pave the way for practical applications, such as sensing, imaging and stealth technology. Importantly, the design idea has the ability to be extended to terahertz, infrared and optical region.

  10. Precise tailoring of tyramine-based hyaluronan hydrogel properties using DMTMM conjugation.

    Loebel, Claudia; D'Este, Matteo; Alini, Mauro; Zenobi-Wong, Marcy; Eglin, David

    2015-01-22

    Injectable tyramine modified hyaluronic acid (HA-Tyr) hydrogels which are bio-orthogonally cross-linked with horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) are excellent candidate biomaterials for drug delivery, regenerative medicine and tissue engineering. Ligation of tyramine to HA has been reported using the very well established N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) chemistry. Here we demonstrate the applicability of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) as an alternative coupling agent to synthesize HA-Tyr conjugates. The optimized derivatization process allows accurate control of the degree of substituted Tyr on hyaluronan (DSmol). Hence, viscoelastic properties, in vitro swelling and enzymatic digestion profiles of the crosslinked hydrogels can be precisely tuned via DSmol. Our study demonstrates the advantages of DMTMM conjugation as a powerful tool to synthesize HA-Tyr hydrogels with properties exactly tailored for biomedical applications. PMID:25439901

  11. Hemostatic potential of natural/synthetic polymer based hydrogels crosslinked by gamma radiation

    Barba, Bin Jeremiah D.; Tranquilan-Aranilla, Charito; Abad, Lucille V.

    2016-01-01

    Various raw materials and hydrogels prepared from their combination were assessed for hemostatic capability using swine whole blood clotting analysis. Initial screening showed efficient coagulative properties from κ-carrageenan and its carboxymethylated form, and α-chitosan, even compared to commercial products like QuikClot Zeolite Powder. Blending natural and synthetic polymers formed into hydrogels using gamma radiation produced materials with improved properties. KC and CMKC hydrogels were found to have the lowest blood clotting index in granulated form and had the higher capacity for platelet adhesion in foamed form compared to GelFoam. Possible mechanisms involved in the evident thrombogenicity of the materials include adsorption of platelets and related proteins that aid in platelet activation (primary hemostasis), absorption of water to concentrate protein factors that control the coagulation cascade, contact activation by its negatively charged surface and the formation of gel-blood clots.

  12. Enhanced skin delivery of aceclofenac via hydrogel-based solid lipid nanoparticles.

    Raj, Rakesh; Mongia, Pooja; Ram, Alpana; Jain, N K

    2016-09-01

    The aim of the present study was to develop solid lipid nanoparticles (SLN) and formulate a hydrogel for enhanced topical delivery of aceclofenac (ACF). The SLN were prepared by the ultrasonic emulsification method and optimized on the basis of stirring speed and lipid content. The optimized formulation was characterized for particle size (189 ± 9.2 nm), polydispersity index (PDI) (0.162 ± 0.02), zeta potential (-32.51 ± 0.12 mV), entrapment efficiency (86.51 ± 2.46%), surface morphology, differential scanning calorimetry (DSC) and X-ray diffraction (XRD). In vivo performance of ACF-loaded SLN hydrogel showed prolonged inhibition of edema, as compared to that observed using plain ACF hydrogel, after 24 h. The results demonstrated that the ACF-SLN formulation for skin targeting could be a promising carrier for topical delivery of ACF. PMID:25919063

  13. Synthesis and properties of P(NIPA-co-NVP)-clay hydrogel by radiation polymerization

    Polymeric hydrogels are unique materials that can absorb and retain large amounts of water. The cross-linking of polymer chain makes them insoluble, soft and elastic. They are stimuli-responsive, displaying phase transitions in response to small changes in temperature, pH, electric field and light. The temperature-sensitive hydrogels have potential applications in gel-based separation processes and in biomedicine, e.g., preparation of drug delivery systems and separation of cells. Thermo-sensitive character of poly (N-isopropylacrylamide) (NIPAm) hydrogels shrinking or swelling below or above lower critical solution temperature (LCST) has widely been investigated in recent years. However, some of their potential applications are hindered by their low mechanical strength, low swelling ratio, bad biocompatibility and low purity, owing to the use of catalysts or additives in chemosynthesis. Liang synthesized clay/PNIPAm composite hydrogel to improve its mechanical strength. In this work, hydrogels of P (NIPA-co-NVP)-Clay were synthesized by 60Co γ-ray irradiation. Different thermo-sensitive hydrogels were made under different experimental conditions such as dose, dose rate, monomer concentration, monomer ratio and content of clay. X-ray diffraction shows that the layer distance of Na-clay is changed from 1.6nm to 2.7nm because Na-clay pieces can be intercalated or exfoliated by HTMAB, and P(NIPA-co-NVP) -clay pieces is 3.4nm. The swelling property tests show that the LCST of PNIPA is 32 degree C, the LCST of P(NIPA-co-NVP) is higher than PNIPA. With the increase of NVP content, LCST is higher. As the ratio of NIPA/NVP is 95/5, hydrogel shows the best swelling property and LCST is 37 degree C. LCST of P(NIPA-co-NVP)-clay Hydrogel is not changed, but the strength and swelling properties are better. (authors)

  14. Facile preparation of photodegradable hydrogels by photopolymerization

    Ki, Chang Seok; Shih, Han; Lin, Chien-Chi

    2013-01-01

    Photodegradable hydrogels have emerged as a powerful material platform for studying and directing cell behaviors, as well as for delivering drugs. The premise of this technique is to use a cytocompatible light source to cleave linkers within a hydrogel, thus causing reduction of matrix stiffness or liberation of matrix-tethered biomolecules in a spatial-temporally controlled manner. The most commonly used photodegradable units are molecules containing nitrobenzyl moieties that absorb light in...

  15. High resolution characterization of responsive hydrogels for biomedical application

    Gao, Ming

    2013-01-01

    Hydrogels are 3D polymer network that, differing from conventional solids, can eliminate or absorb water and as a consequence undergo changes in volume, mechanical properties. Various properties of the hydrogels can be altered as a consequence of their response to external stimuli. Thus, hydrogels are considered important materials for a variety of applications in medical technology.Here it will introduce the application of interferometric readout platform for determination of swelling proper...

  16. Viral infection of human progenitor and liver-derived cells encapsulated in three-dimensional PEG-based hydrogel

    Cho, Nam-Joon; Elazar, Menashe; Xiong, Anming; Glenn, Jeffrey S [Department of Medicine, Division of Gastroenterology and Hepatology, Stanford University School of Medicine, CCSR Building Room 3115A, 269 Campus Drive, Stanford, CA 94305 (United States); Lee, Wonjae [Mechanical Engineering, Stanford University, Stanford, CA 94305 (United States); Chiao, Eric; Baker, Julie [Department of Genetics, Stanford University School of Medicine, Stanford, CA 94305 (United States); Frank, Curtis W, E-mail: jeffrey.glenn@stanford.ed, E-mail: curt.frank@stanford.ed [Department of Chemical Engineering, Stanford University, Stanford, CA 94305 (United States)

    2009-02-15

    We have studied the encapsulation of human progenitor cells into 3D PEG hydrogels. Replication-incompetent lentivirus promoter reporter vectors were found to efficiently detect the in vivo expression of human hepatic genes in hydrogel-encapsulated liver progenitor cells. Similarly, hydrogel-encapsulated cells could be efficiently infected with hepatitis C virus, and progeny infectious virus could be recovered from the media supernatants of the hydrogels. Provocatively, the diameters of these virus particles range from {approx}50 to 100 nm, while the calculated mesh size of the 8 k hydrogel is 44.6 +- 1.7 A. To reconcile how viral particles can penetrate the hydrogels to infect the encapsulated cells, we propose that microfractures/defects of the hydrogel result in a functional pore size of up to 20 fold greater than predicted by theoretical mesh calculations. These results suggest a new model of hydrogel structure, and have exciting implications for tissue engineering and hepatitis virus studies. (communication)

  17. Synthesis and characterization of chitosan-graft-poly(acrylic acid)/rice husk ash hydrogels composites; Sintese e caracterizacao de hidrogeis compositos de cinza da casca de arroz e quitosana enxertada com poli(acido acrilico)

    Rodrigues, Francisco H.A. [Universidade Estadual Vale do Acarau - UVA, Sobral, CE (Brazil); Lopes, Gabriel V.; Pereira, Antonio G.B.; Fajardo, Andre R.; Muniz, Edvani C. [Universidade Estadual de Maringa - UEM, PR (Brazil)

    2011-07-01

    According to environmental concerns, super absorbent hydrogel composites were synthesized based on rice husk ash (RHA), an industrial waste, and Chitosan-graft-poly(acrylic acid). The WAXS and FTIR data confirmed the syntheses of hydrogel composites. The effect of crystalline or amorphous RHA on water uptake was investigated. It was found that the RHA in crystalline form induces higher water capacity (W{sub eq}) of composites hydrogels due to the fact that the intra-interactions among silanol groups on RHA make available new sites in the polymer matrix, which could interact to water. (author)

  18. Graphene based tunable fractal Hilbert curve array broadband radar absorbing screen for radar cross section reduction

    This paper proposes a new type of graphene based tunable radar absorbing screen. The absorbing screen consists of Hilbert curve metal strip array and chemical vapour deposition (CVD) graphene sheet. The graphene based screen is not only tunable when the chemical potential of the graphene changes, but also has broadband effective absorption. The absorption bandwidth is from 8.9GHz to 18.1GHz, ie., relative bandwidth of more than 68%, at chemical potential of 0eV, which is significantly wider than that if the graphene sheet had not been employed. As the chemical potential varies from 0 to 0.4eV, the central frequency of the screen can be tuned from 13.5GHz to 19.0GHz. In the proposed structure, Hilbert curve metal strip array was designed to provide multiple narrow band resonances, whereas the graphene sheet directly underneath the metal strip array provides tunability and averagely required surface resistance so to significantly extend the screen operation bandwidth by providing broadband impedance matching and absorption. In addition, the thickness of the screen has been optimized to achieve nearly the minimum thickness limitation for a nonmagnetic absorber. The working principle of this absorbing screen is studied in details, and performance under various incident angles is presented. This work extends applications of graphene into tunable microwave radar cross section (RCS) reduction applications

  19. Graphene based tunable fractal Hilbert curve array broadband radar absorbing screen for radar cross section reduction

    Xianjun Huang

    2014-11-01

    Full Text Available This paper proposes a new type of graphene based tunable radar absorbing screen. The absorbing screen consists of Hilbert curve metal strip array and chemical vapour deposition (CVD graphene sheet. The graphene based screen is not only tunable when the chemical potential of the graphene changes, but also has broadband effective absorption. The absorption bandwidth is from 8.9GHz to 18.1GHz, ie., relative bandwidth of more than 68%, at chemical potential of 0eV, which is significantly wider than that if the graphene sheet had not been employed. As the chemical potential varies from 0 to 0.4eV, the central frequency of the screen can be tuned from 13.5GHz to 19.0GHz. In the proposed structure, Hilbert curve metal strip array was designed to provide multiple narrow band resonances, whereas the graphene sheet directly underneath the metal strip array provides tunability and averagely required surface resistance so to significantly extend the screen operation bandwidth by providing broadband impedance matching and absorption. In addition, the thickness of the screen has been optimized to achieve nearly the minimum thickness limitation for a nonmagnetic absorber. The working principle of this absorbing screen is studied in details, and performance under various incident angles is presented. This work extends applications of graphene into tunable microwave radar cross section (RCS reduction applications.

  20. Graphene based tunable fractal Hilbert curve array broadband radar absorbing screen for radar cross section reduction

    Huang, Xianjun, E-mail: xianjun.huang@manchester.ac.uk [School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); College of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China); Hu, Zhirun [School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); Liu, Peiguo [College of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-11-15

    This paper proposes a new type of graphene based tunable radar absorbing screen. The absorbing screen consists of Hilbert curve metal strip array and chemical vapour deposition (CVD) graphene sheet. The graphene based screen is not only tunable when the chemical potential of the graphene changes, but also has broadband effective absorption. The absorption bandwidth is from 8.9GHz to 18.1GHz, ie., relative bandwidth of more than 68%, at chemical potential of 0eV, which is significantly wider than that if the graphene sheet had not been employed. As the chemical potential varies from 0 to 0.4eV, the central frequency of the screen can be tuned from 13.5GHz to 19.0GHz. In the proposed structure, Hilbert curve metal strip array was designed to provide multiple narrow band resonances, whereas the graphene sheet directly underneath the metal strip array provides tunability and averagely required surface resistance so to significantly extend the screen operation bandwidth by providing broadband impedance matching and absorption. In addition, the thickness of the screen has been optimized to achieve nearly the minimum thickness limitation for a nonmagnetic absorber. The working principle of this absorbing screen is studied in details, and performance under various incident angles is presented. This work extends applications of graphene into tunable microwave radar cross section (RCS) reduction applications.

  1. A new injectable biphasic hydrogel based on partially hydrolyzed polyacrylamide and nano hydroxyapatite, crosslinked with chromium acetate, as scaffold for cartilage regeneration

    Koushki, N.; Tavassoli, H.; Katbab, A. A.; Katbab, P.; Bonakdar, S.

    2015-05-01

    Polymer scaffolds are applied in the field of tissue engineering as three dimensional structures to organize cells and present stimuli to direct generation of a desired damaged tissue. In situ gelling scaffolds have attracted great attentions, as they are structurally similar to the extra cellular matrix (ECM). In the present work, attempts have been made to design and fabricate a new injectable and crosslinkable biphasic hydrogel based on partially hydrolyzed polyacrylamide (HPAM), chromium acetate as crosslink agent and nanocrystalline hydroxyapatite (nHAp) as reinforcing and bioactive agent for repair and regeneration of damaged cartilage. The distinct characteristic of HPAM is the presence of carboxylate anion groups on its backbone which allows to engineer the structure of the hydrogel for the desired bioactivity with appropriate cells differentiation towards both soft and hard (bone) tissues. The synthesized hydrogel exhibited bifunctional behavior which was derived by its biphasic structure in which one phase was loaded with nano hydroxyapatite to provide integration capability by subchondral bones and fix the hydrogel at cartilage defect without a need for suturing. The other phase differentiates the rabbit adipogenic mesenchymal stem cells (MSCs) towards soft tissue. Rheomechanical spectrometry (RMS) was employed to study the kinetic of the gelation including induction time and rate, as well as to measure the ultimate elastic modulus of the optimum crosslinked hydrogel. Surface tension measurement was also performed to tailor the surface characteristics of the gels. In vitro culturing of the cells inside the crosslinked hydrogel revealed high viability and high differentiation of the encapsulated rabbit stem cells, providing that the chromium acetate level was kept below 0.2 wt%. Based on the obtained results, the designed and fabricated biphasic hydrogel exhibited high potential as carrier for the stem cells for cartilage tissue engineering application

  2. Ice-templated hydrogels based on chitosan with tailored porous morphology

    Dinu, M. V.; Přádný, Martin; Dragan, E. S.; Michálek, Jiří

    2013-01-01

    Roč. 94, č. 1 (2013), s. 170-178. ISSN 0144-8617 R&D Projects: GA ČR GAP108/12/1538 Institutional support: RVO:61389013 Keywords : chitosan * ice-templated hydrogels * morphology Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.916, year: 2013

  3. Characterization of Lactate Sensors Based on Lactate Oxidase and Palladium Benzoporphyrin Immobilized in Hydrogels.

    Andrus, Liam P; Unruh, Rachel; Wisniewski, Natalie A; McShane, Michael J

    2015-01-01

    An optical biosensor for lactate detection is described. By encapsulating enzyme-phosphor sensing molecules within permeable hydrogel materials, lactate-sensitive emission lifetimes were achieved. The relative amount of monomer was varied to compare three homo- and co-polymer materials: poly(2-hydroxyethyl methacrylate) (pHEMA) and two copolymers of pHEMA and poly(acrylamide) (pAam). Diffusion analysis demonstrated the ability to control lactate transport by varying the hydrogel composition, while having a minimal effect on oxygen diffusion. Sensors displayed the desired dose-variable response to lactate challenges, highlighting the tunable, diffusion-controlled nature of the sensing platform. Short-term repeated exposure tests revealed enhanced stability for sensors comprising hydrogels with acrylamide additives; after an initial "break-in" period, signal retention was 100% for 15 repeated cycles. Finally, because this study describes the modification of a previously developed glucose sensor for lactate analysis, it demonstrates the potential for mix-and-match enzyme-phosphor-hydrogel sensing for use in future multi-analyte sensors. PMID:26198251

  4. Immunocompatibility of gelatin-based hydrogels supporting ex vivo gene therapy

    Šírová, Milada; Pakanová, Veronika; Rossmann, Pavel; Kovář, Lubomír; van Vlierberghe, S.; Dubruel, P.; Schacht, E. H.; Říhová, Blanka

    2009-01-01

    Roč. 39, - (2009), s. 545-545. ISSN 0014-2980. [European Congress of Immunology /2./. 13.09.2009-16.09.2009, Berlin] Institutional research plan: CEZ:AV0Z50200510 Keywords : gelatin B hydrogel * gene therapy Subject RIV: EC - Immunology

  5. Characterization of Lactate Sensors Based on Lactate Oxidase and Palladium Benzoporphyrin Immobilized in Hydrogels

    Liam P. Andrus

    2015-07-01

    Full Text Available An optical biosensor for lactate detection is described. By encapsulating enzyme-phosphor sensing molecules within permeable hydrogel materials, lactate-sensitive emission lifetimes were achieved. The relative amount of monomer was varied to compare three homo- and co-polymer materials: poly(2-hydroxyethyl methacrylate (pHEMA and two copolymers of pHEMA and poly(acrylamide (pAam. Diffusion analysis demonstrated the ability to control lactate transport by varying the hydrogel composition, while having a minimal effect on oxygen diffusion. Sensors displayed the desired dose-variable response to lactate challenges, highlighting the tunable, diffusion-controlled nature of the sensing platform. Short-term repeated exposure tests revealed enhanced stability for sensors comprising hydrogels with acrylamide additives; after an initial “break-in” period, signal retention was 100% for 15 repeated cycles. Finally, because this study describes the modification of a previously developed glucose sensor for lactate analysis, it demonstrates the potential for mix-and-match enzyme-phosphor-hydrogel sensing for use in future multi-analyte sensors.

  6. Fabrication and development of artificial osteochondral constructs based on cancellous bone/hydrogel hybrid scaffold.

    Song, Kedong; Li, Liying; Yan, Xinyu; Zhang, Yu; Li, Ruipeng; Wang, Yiwei; Wang, Ling; Wang, Hong; Liu, Tianqing

    2016-06-01

    Using tissue engineering techniques, an artificial osteochondral construct was successfully fabricated to treat large osteochondral defects. In this study, porcine cancellous bones and chitosan/gelatin hydrogel scaffolds were used as substitutes to mimic bone and cartilage, respectively. The porosity and distribution of pore size in porcine bone was measured and the degradation ratio and swelling ratio for chitosan/gelatin hydrogel scaffolds was also determined in vitro. Surface morphology was analyzed with the scanning electron microscope (SEM). The physicochemical properties and the composition were tested by using an infrared instrument. A double layer composite scaffold was constructed via seeding adipose-derived stem cells (ADSCs) induced to chondrocytes and osteoblasts, followed by inoculation in cancellous bones and hydrogel scaffolds. Cell proliferation was assessed through Dead/Live staining and cellular activity was analyzed with IpWin5 software. Cell growth, adhesion and formation of extracellular matrix in composite scaffolds blank cancellous bones or hydrogel scaffolds were also analyzed. SEM analysis revealed a super porous internal structure of cancellous bone scaffolds and pore size was measured at an average of 410 ± 59 μm while porosity was recorded at 70.6 ± 1.7 %. In the hydrogel scaffold, the average pore size was measured at 117 ± 21 μm and the porosity and swelling rate were recorded at 83.4 ± 0.8 % and 362.0 ± 2.4 %, respectively. Furthermore, the remaining hydrogel weighed 80.76 ± 1.6 % of the original dry weight after hydration in PBS for 6 weeks. In summary, the cancellous bone and hydrogel composite scaffold is a promising biomaterial which shows an essential physical performance and strength with excellent osteochondral tissue interaction in situ. ADSCs are a suitable cell source for osteochondral composite reconstruction. Moreover, the bi-layered scaffold significantly enhanced cell proliferation compared to

  7. A Study of the Anechoic Performance of Rice Husk-Based, Geometrically Tapered, Hollow Absorbers

    Muhammad Nadeem Iqbal

    2014-01-01

    Full Text Available Although solid, geometrically tapered microwave absorbers are preferred due to their better performance, they are bulky and must have a thickness on the order of λ or more. The goal of this study was to design lightweight absorbers that can reduce the electromagnetic reflections to less than −10 dB. We used a very simple approach; two waste materials, that is, rice husks and tire dust in powder form, were used to fabricate two independent samples. We measured and used their dielectric properties to determine and compare the propagation constants and quarter-wave thickness. The quarter-wave thickness for the tire dust was 3 mm less than that of the rice husk material, but we preferred the rice-husk material. This preference was based on the fact that our goal was to achieve minimum backward reflections, and the rice-husk material, with its low dielectric constant, high loss factor, large attenuation per unit length, and ease of fabrication, provided a better opportunity to achieve that goal. The performance of the absorbers was found to be better (lower than −20 dB, and comparison of the results proved that the hollow design with 58% less weight was a good alternative to the use of solid absorbers.

  8. Design of separately tunable terahertz two-peak absorber based on graphene

    Zhang, Longhui; Hu, Fangrong; Xu, Xinlong; Wang, Yue'e.; Guo, Enze

    2016-06-01

    A separately tunable terahertz (THz) two-peak absorber based on graphene is presented. From bottom to top, the absorber contains four layers, i.e., gold reflector, graphene patch array, polyimide and metal split-ring resonator (SRR) array layer. The controlling voltage is applied between the reflector and two separated surface electrodes to tune the Fermi level of graphene. As a result, these two absorption peaks can be separately tuned by the controlling voltages. The finite integral technique (FIT) is used to study the absorption theory and modulation mechanism. The simulation results show that the absorption of low-frequency and that of high-frequency are 95.5% and 90.0%, respectively. And the maximum modulation depths of them are about 49% and 71%, respectively. Moreover, the absorber is insensitive to polarization and still has good absorption at large angle. The separately tunable THz two-peak absorber offers a new way for the development of frequency selective detectors working in the range of microwave, THz and infrared.

  9. Integration of an interferometric IR absorber into an epoxy membrane based CO2 detector

    Measurements of carbon dioxide levels in the environment are commonly performed by using non-dispersive infrared technology (NDIR). Thermopile detectors are often used in NDIR systems because of their non-cooling advantages. The infrared absorber has a major influence on the detector responsivity. In this paper, the fabrication of a SU-8 epoxy membrane based Al/Bi thermopile detector and the integration of an interferometric infrared absorber structure of wavelength around 4 μm into the detector is reported. The membrane of thermopile detector has been utilized as a dielectric medium in an interferometric absorption structure. By doing so, a reduction in both thermal conductance and capacitance is achieved. In the fabrication of the thermopile, metal evaporation and lift off process had been used for the deposition of serially interconnected Al/Bi thermocouples. Serial resistance of fabricated thermopile was measured as 220 kΩ. The response of fabricated thermopile detector was measured using a visible to infrared source of radiation flux 3.23 mW mm−2. The radiation incident on the detector was limited using a band pass filter of wavelength 4.26 μm in front of the detector. A responsivity of 27.86 V mm2 W−1 at room temperature was achieved using this setup. The fabricated detector was compared to a reference detector with a broad band absorber. From the comparison it was concluded that the integrated interferometric absorber is functioning correctly

  10. Fast screening of ketamine in biological samples based on molecularly imprinted photonic hydrogels

    Meng, Liang [Department of Forensic Science, People' s Public Security University of China, Beijing (China); Meng, Pinjia, E-mail: mengpinjia@163.com [Department of Forensic Science, People' s Public Security University of China, Beijing (China); Zhang, Qingqing; Wang, Yanji [Department of Forensic Science, People' s Public Security University of China, Beijing (China)

    2013-04-10

    Graphical abstract: A novel label-free colorimetric chemosensor: with the increase in the concentration of ketamine, the Bragg diffraction peak of MIPHs gradually shifted to the longer wavelength region. Accompanying the peak shift, the color change of MIPHs was also observed obviously: from green to red. Highlights: ► We developed the label-free colorimetric MIPHs for handy and fast screening of ketamine. ► The obvious color change of MIPHs was observed upon ketamine. ► The MIPHs exhibited good sensing abilities in an aqueous environment. ► The sensing mechanisms of the water-compatible MIPHs were investigated. ► The MIPHs were employed to screening ketamine in real biological samples. -- Abstract: A novel label-free colorimetric chemosensor was developed for handy and fast screening of ketamine with high sensitivity and specificity based on molecularly imprinted photonic hydrogels (MIPHs) that combined the colloidal-crystal with molecular imprinting technique. The unique inverse opal arrays with a thin polymer wall in which the imprinted nanocavities of ketamine moleculars distributed allowed high sensitive, quick responsive, specific detection of the target analyte, and good regenerating ability in an aqueous environment. Due to the hierarchical inverse opal structural characteristics, the specific ketamine molecular recognition process can induce obvious swelling of the MIPHs to be directly transferred into visually perceptible optical signal (change in color) which can be detected by the naked eye through Bragg diffractive shifts of ordered macroporous arrays. In order to enhance the recognition ability in aqueous environments, the MIPHs were designed as water-compatible and synthesized in a water–methanol system. The molecular recognition mechanisms were investigated. The proposed MIPHs were successfully employed to screen trace level ketamine in human urine and saliva samples, exhibiting high sensitivity, rapid response, and specificity in the

  11. Fast screening of ketamine in biological samples based on molecularly imprinted photonic hydrogels

    Graphical abstract: A novel label-free colorimetric chemosensor: with the increase in the concentration of ketamine, the Bragg diffraction peak of MIPHs gradually shifted to the longer wavelength region. Accompanying the peak shift, the color change of MIPHs was also observed obviously: from green to red. Highlights: ► We developed the label-free colorimetric MIPHs for handy and fast screening of ketamine. ► The obvious color change of MIPHs was observed upon ketamine. ► The MIPHs exhibited good sensing abilities in an aqueous environment. ► The sensing mechanisms of the water-compatible MIPHs were investigated. ► The MIPHs were employed to screening ketamine in real biological samples. -- Abstract: A novel label-free colorimetric chemosensor was developed for handy and fast screening of ketamine with high sensitivity and specificity based on molecularly imprinted photonic hydrogels (MIPHs) that combined the colloidal-crystal with molecular imprinting technique. The unique inverse opal arrays with a thin polymer wall in which the imprinted nanocavities of ketamine moleculars distributed allowed high sensitive, quick responsive, specific detection of the target analyte, and good regenerating ability in an aqueous environment. Due to the hierarchical inverse opal structural characteristics, the specific ketamine molecular recognition process can induce obvious swelling of the MIPHs to be directly transferred into visually perceptible optical signal (change in color) which can be detected by the naked eye through Bragg diffractive shifts of ordered macroporous arrays. In order to enhance the recognition ability in aqueous environments, the MIPHs were designed as water-compatible and synthesized in a water–methanol system. The molecular recognition mechanisms were investigated. The proposed MIPHs were successfully employed to screen trace level ketamine in human urine and saliva samples, exhibiting high sensitivity, rapid response, and specificity in the

  12. The Norwegian system for implementing the IAEA code of practice based on absorbed dose to water

    The Norwegian Radiation Protection Authority (NRPA) SSDL recommended in 2000 the use of absorbed dose to water as the quality for calibration and code of practice in radiotherapy. The absorbed dose to water standard traceable to BIPM was established in Norway in 1995. The international code of practice, IAEA TRS 398 was under preparation. As a part of the implementation of the new dosimetry system the SSDL went to radiotherapy departments in Norway in 2001. The aim of the visit was to: Prepare and support the users in the implementation of TRS 398 by teaching, discussions and measurements on-site; Gain experience for NRPA in the practical implementation of TRS 398 and perform comparisons between TRS 277 and TRS 398 for different beam qualities; Report experience from implementation of TRS 398 to IAEA. The NRPA 30x30x30 cm3 water phantom is equal to the BIPM calibration phantom. This was used for the photon measurements in 16 different beams. NRPA used three chambers: NE 2571, NE 2611 and PR06C for the photon measurements. As a quality control the set-up was compared with the Finnish site-visit equipment at University Hospital of Helsinki, and the measured absorbed dose to water agreed within 0.6%. The Finnish SSDL calibrated the Norwegian chambers and the absorbed dose to water calibration factors given by the two SSDLs for the three chambers agreed within 0.3%. The local clinical dosimetry in Norway was based on TRS 277. For the site-visit the absorbed dose to water was determined by NRPA using own equipment including the three chambers and the hospitals reference chamber. The hospital determined the dose the same evening using their local equipment. For the 16 photon beams the deviations between the two absorbed dose to water determinations for TRS 277 were in the range -1,7% to +4.0%. The uncertainty in the measurements was 1% (k=1). The deviation was explained in local implementation of TRS 277, the use of plastic phantoms, no resent calibration of thermometers

  13. Adjustable low frequency and broadband metamaterial absorber based on magnetic rubber plate and cross resonator

    Cheng, Yongzhi; Nie, Yan; Wang, Xian; Gong, Rongzhou

    2014-02-01

    In this paper, the magnetic rubber plate absorber (MRPA) and metamaterial absorber (MA) based on MRP substrate were proposed and studied numerically and experimentally. Based on the characteristic of L-C resonances, experimental results show that the MA composed of cross resonator (CR) embedded single layer MRP could be adjustable easily by changing the wire length and width of CR structure and MRP thickness. Finally, experimental results show that the MA composed of CR-embedded two layers MRP with the total thickness of 2.42 mm exhibit a -10 dB absorption bandwidth from 1.65 GHz to 3.7 GHz, which is 1.86 times wider than the same thickness MRPA.

  14. Intensity tunable infrared broadband absorbers based on VO2 phase transition using planar layered thin films

    Kocer, Hasan; Butun, Serkan; Palacios, Edgar; Liu, Zizhuo; Tongay, Sefaattin; Fu, Deyi; Wang, Kevin; Wu, Junqiao; Aydin, Koray

    2015-08-01

    Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Here, we demonstrate a simple, lithography-free approach for obtaining a resonant and dynamically tunable broadband absorber based on vanadium dioxide (VO2) phase transition. Using planar layered thin film structures, where top layer is chosen to be an ultrathin (20 nm) VO2 film, we demonstrate broadband IR light absorption tuning (from ~90% to ~30% in measured absorption) over the entire mid-wavelength infrared spectrum. Our numerical and experimental results indicate that the bandwidth of the absorption bands can be controlled by changing the dielectric spacer layer thickness. Broadband tunable absorbers can find applications in absorption filters, thermal emitters, thermophotovoltaics and sensing.

  15. Knitted radar absorbing materials (RAM) based on nickel-cobalt magnetic materials

    Teber, Ahmet; Unver, Ibrahim; Kavas, Huseyin; Aktas, Bekir; Bansal, Rajeev

    2016-05-01

    There has been a long-standing interest in the development of flexible, lightweight, thin, and reconfigurable radar absorbing materials (RAM) for military applications such as camouflaging ground-based hardware against airborne radar observation. The use of polymeric Polyacrylonitrile (PAN) fabrics as a host matrix for magnetic metal nano-particles (either at the yarn-stage or after weaving the fabric) for shielding and absorbing applications has been described in the literature. In our experimental investigation, the relative concentrations of Nickel and Cobalt as well as the coating time are varied with a view to optimizing the microwave absorption characteristics of the resulting PAN-based composite material in the radar-frequency bands (X, Ku, and K). It is found that the PAN samples with the shortest coating time have the best return losses (under -20 dB return loss over a moderate bandwidth).

  16. C2-Symmetric Benzene-based Low Molecular Weight Hydrogel Modified Electrode for Highly Sensitive Detection of Copper Ions

    In this paper, a new type of low molecular weight gelators (LMWGs), C2-symmetric benzene-based hydrogel (C2-BHG) with a 1,4-dimine benzene was self-assembled on glassy carbon electrode (GCE) and mica surface based on the hydrogen bond or hydrophobic interaction. Atomic force microscopy (AFM) characterization demonstrated the formation process of the C2-BHG hydrogel layer from particles to clusters, and finally to interconnected fiber network gel. The C2-BHG hydrogel layer resulted in the increase of the hydrophilicity of GCE surface. The C2-BHG modified GCEs (C2-BHG/GCE) with different assembly time were studied by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of Fe(CN)64−/3− redox probe. The rich amide and hydroxyl groups in the gel film make the C2-BHG/GCE suitable as ultrasensitive sensor for the detection of Cu(II) ions by stripping voltammetry with the limit of detection of 5×10−10 g/L (S/N>3). Under the optimal conditions, the two linear ranges of Cu(II) ions were found to be 1×10−9∼1×10−7 g/L and 1×10−7∼1×10−4 g/L. The strong coordination interaction of C2-BHG with Cu(II) ions was confirmed by UV-Visible characterization. This new type of C2-BHG modified electrode was promising for highly sensitive Cu(II) ions sensor application due to high stability and excellent selectivity of the analytical signal

  17. In vivo and in vitro cellular response to PEG-based hydrogels for wound repair

    Waldeck, Heather

    Biomaterials are continuously being explored as a means to support, improve, or influence wound healing processes. Understanding the determining factors controlling the host response to biomaterials is crucial in developing strategies to employ materials for biomedical uses. In order to evaluate the host response to poly(ethylene glycol) (PEG)-based hydrogels, both in vivo and in vitro studies were performed to determine its efficacy as a dermal wound treatment and to investigate the mechanisms controlling cell-material interaction, respectively. The results of an in vivo study using a full thickness wound in a rat model demonstrated that both soluble and immobilized bioactive factors could be incorporated into a PEG-based semi-interpenetrating network (sIPN) to enhance the rate and the quality of dermal wound healing. To gain a better understanding of the results observed in vivo, in vitro studies were then conducted to examine the dynamics and mechanisms of the cell-material interaction. Degradation of the sIPN was explored as an influential factor in both mediating cellular response and controlling solute transport from the material. As degradation through gelatin dissolution could be influenced by simple alterations to the material formulation, these results provide facile guidelines to control the delivery of high molecular weight compounds. Further investigation of the cellular response to PEG-based biomaterials focused on key factors influencing cell-material interaction. Specifically, the role of the beta1 integrin subunit and several serum proteins (TGF-aalpha, IL-1beta and PDGF-BB) in mediating cellular response was explored. As cell-material interactions are based on commonly occurring interfaces between cells and molecules of the native extracellular environment, these studies provided insight into the mechanisms controlling the observed cellular response. Finally, the inflammatory response of primary monocytes to biomaterials was examined. Monocytes

  18. Cell Growth and Desorption on the Surface of Temperature-sensitive Semi-IPNs Hydrogels Based on Silk Sericin

    LI Xuewei; ZHANG Qingsong; CHEN Li; ZHANG Rui; GUO Gang

    2012-01-01

    Semi-interpenetrating (semi-IPNs) hydrogels containing biocompatible silk sericin (SS)and poly(N-isopropylacrylamide)(PNIPAM) were prepared as novel cellular matrices.Their maximum swelling degree and basic characteristics for biomedical applications such as mouse fibroblasts (L929) cell proliferation and desorption were investigated.The results showed that the incorporation of high hydrophilic SS into PNIPAM hydrogel increased the maximum swelling degree of the semi-IPNs hydrogels,and the adhesion and growth of the L929 on semi-IPNs hydrogels were at least comparable to,or even better than,that on conventional PNIPAM hydrogel.In addition,L929 cells were found to detach from the hydrogels surface naturally by controlling environmental temperature.These results suggest great potential of semi-IPNs hydrogels in tissue engineering.

  19. Stimuli-Sensitive Hydrogel Based on N-Isopropylacrylamide and Itaconic Acid for Entrapment and Controlled Release of Candida rugosa Lipase under Mild Conditions

    Nikola Milašinović

    2014-01-01

    Full Text Available Stimuli responsive pH- and temperature-sensitive hydrogel drug delivery systems, as those based on N-isopropylacrylamide (NiPAAm and itaconic acid (IA, have been attracting much of the attention of the scientific community nowadays, especially in the field of drug release. By adjusting comonomer composition, the matrix is enabled to protect the incorporated protein in the highly acidic environment of upper gastrointestinal tract and deliver it in the neutral or slightly basic region of the lower intestine. The protein/poly(NiPAAm-co-IA hydrogels were synthetized by free radical crosslinking copolymerization and were characterized concerning their swelling capability, mechanical properties, and morphology. The pore structure and sizes up to 1.90 nm allowed good entrapment of lipase molecules. Model protein, lipase from Candida rugosa, was entrapped within hydrogels upon mild conditions that provided its protection from harmful environmental influences. The efficiency of the lipase entrapment reached 96.7%, and was dependent on the initial concentration of lipase solution. The swelling of the obtained hydrogels in simulated pH and temperature of gastrointestinal tract, the lipase entrapment efficiency, and its release profiles from hydrogels were investigated as well.

  20. Influence of the ionic character of a drug on its release rate from hydrogels based on 2-hydroxyethylmethacrylate and acrylamide synthesized by photopolymerization

    M. L. Gomez

    2012-03-01

    Full Text Available The influence of the ionic character of a specific drug on its release rate from a hydrogel based on 2-hydroxyethylmethacrylate (HEMA and acrylamide (AAm is analyzed. The hydrogel was synthesized by photopolymerization employing visible light, safranine O (Saf, as sensitizer, and a silsesquioxane functionalized with amine and methacrylate groups (SFMA, as co-initiator and crosslinker. Safranine O (Saf was employed as a model of a cationic drug and the anionic form of resorufin (Rf as a model of an anionic drug. Saf exhibited a larger affinity with functional groups of the hydrogel than that of Rf. This produced a lower loading and a faster release rate of Rf with respect to Saf. Besides, the release rate of Rf followed a Fickian behavior, while that of Saf exhibited a non-Fickian behavior. By hydrolyzing the hydrogel at pH = 13, amide groups supplied by AAm were irreversibly converted into carboxylic acid groups. Higher loadings and slower release rates of Saf from the hydrolyzed hydrogels were observed, making them particularly suitable for the slow drug-delivery of cationic drugs.

  1. 半纤维素功能材料——水凝胶%Progress in Functional Materials-Hydrogel Based on Hemicellulose

    任俊莉; 彭新文; 孙润仓; 伍红

    2011-01-01

    Recently the preparation of functional biomaterials-hydrogel based on hemicelluloses biomass has obtained a special attention, and the product has exhibited important market prospects and application potential. Compared with synthetic polymer hydrogel, hemicellulo-ses-based hydrogel shows significant advantages, such as environmentally friendly property, bio-compatibility, non-toxicity and biodegrad-ability and so on, which is expected to be used in drug delivery, biosensors, and tissue engineering and other areas. According to the cross-linked type, the methods to prepare hydrogel are divided into physical crosslinking and chemical crosslinking. This paper summarized the research progress of hemicelluloses-based hydrogel materials and the commercial application potential, and pointed out the problems existed and the future development direction in the research of hemicelluloses-based hydrogel.%与各种高分子合成的水凝胶相比,半纤维素基水凝胶具有难以比拟的优势,如环境友好性、生物兼容性、无毒及可降解性等.文中从制备方法角度归纳和总结了木质纤维半纤维素基水凝胶材料近年来的研究进展以及潜在的商业应用前景,并指出了半纤维素基水凝胶在研究中存在的问题及发展方向.

  2. Functionalization, preparation and use of cell-laden gelatin methacryloyl-based hydrogels as modular tissue culture platforms.

    Loessner, Daniela; Meinert, Christoph; Kaemmerer, Elke; Martine, Laure C; Yue, Kan; Levett, Peter A; Klein, Travis J; Melchels, Ferry P W; Khademhosseini, Ali; Hutmacher, Dietmar W

    2016-04-01

    Progress in advancing a system-level understanding of the complexity of human tissue development and regeneration is hampered by a lack of biological model systems that recapitulate key aspects of these processes in a physiological context. Hence, growing demand by cell biologists for organ-specific extracellular mimics has led to the development of a plethora of 3D cell culture assays based on natural and synthetic matrices. We developed a physiological microenvironment of semisynthetic origin, called gelatin methacryloyl (GelMA)-based hydrogels, which combine the biocompatibility of natural matrices with the reproducibility, stability and modularity of synthetic biomaterials. We describe here a step-by-step protocol for the preparation of the GelMA polymer, which takes 1-2 weeks to complete, and which can be used to prepare hydrogel-based 3D cell culture models for cancer and stem cell research, as well as for tissue engineering applications. We also describe quality control and validation procedures, including how to assess the degree of GelMA functionalization and mechanical properties, to ensure reproducibility in experimental and animal studies. PMID:26985572

  3. Poly(ethylene glycol)-poly(lactic-co-glycolic acid) based thermosensitive injectable hydrogels for biomedical applications.

    Alexander, Amit; Ajazuddin; Khan, Junaid; Saraf, Swarnlata; Saraf, Shailendra

    2013-12-28

    Stimuli triggered polymers provide a variety of applications related with the biomedical fields. Among various stimuli triggered mechanisms, thermoresponsive mechanisms have been extensively investigated, as they are relatively more convenient and effective stimuli for biomedical applications. In a contemporary approach for achieving the sustained action of proteins, peptides and bioactives, injectable depots and implants have always remained the thrust areas of research. In the same series, Poloxamer based thermogelling copolymers have their own limitations regarding biodegradability. Thus, there is a need to have an alternative biomaterial for the formulation of injectable hydrogel, which must remain biocompatible along with safety and efficacy. In the same context, poly(ethylene glycol) (PEG) based copolymers play a crucial role as a biomedical material for biomedical applications, because of their biocompatibility, biodegradability, thermosensitivity and easy controlled characters. This review stresses on the physicochemical property, stability and composition prospects of smart PEG/poly(lactic-co-glycolic acid) (PLGA) based thermoresponsive injectable hydrogels, recently utilized for biomedical applications. The manuscript also highlights the synthesis scheme and stability characteristics of these copolymers, which will surely help the researchers working in the same area. We have also emphasized the applied use of these smart copolymers along with their formulation problems, which could help in understanding the possible modifications related with these, to overcome their inherent associated limitations. PMID:24144918

  4. Porous Hydrogels

    Přádný, Martin; Michálek, Jiří; Širc, Jakub

    New York: Nova Science Publishers, 2009 - (Acosta, J.; Camacho, A.), s. 57-74 ISBN 978-1-60741-401-8 R&D Projects: GA AV ČR 1QS400500558; GA MŠk 1M0538 Institutional research plan: CEZ:AV0Z40500505 Keywords : hydrogels * porous * tissue engineering Subject RIV: CD - Macromolecular Chemistry

  5. Estimation of absorbed organ doses and effective dose based on body mass index in digital radiography

    With the introduction of digital radiography, patients undergoing radiographic procedures are subject to being overexposed to radiation. Therefore, it is necessary to estimate the absorbed organ dose and the effective dose, which are significant for patient health, along with body type. During chest radiographic examinations conducted in 899 patients for screening, the absorbed dose of the 13 major organs, the average whole-body dose, and two effective doses weighted by factors published in ICRP 60 and ICRP 103 were calculated on the basis of patient information such as height, weight and examination condition, including kilovolt potential, focus-skin distance and entrance surface dose (ESD), using a PC-based Monte Carlo program simulation. It was found that dose per unit ESD had a tendency to decrease with body mass index (BMI). In particular, the absorbed dose for most organs was larger at high voltages (140 kVp) than at low voltages (120 kVp, 100 kVp). In addition, the effective dose which was based on ICRP 60 and ICRP 103 also represented the same tendency in respect of BMI and tube voltage. (authors)

  6. Optimization of a bolometer detector for ITER based on Pt absorber on SiN membrane.

    Meister, H; Eich, T; Endstrasser, N; Giannone, L; Kannamüller, M; Kling, A; Koll, J; Trautmann, T; Detemple, P; Schmitt, S

    2010-10-01

    Any plasma diagnostic in ITER must be able to operate at temperatures in excess of 200 °C and neutron loads corresponding to 0.1 dpa over its lifetime. To achieve this aim for the bolometer diagnostic, a miniaturized metal resistor bolometer detector based on Pt absorbers galvanically deposited on SiN membranes is being developed. The first two generations of detectors featured up to 4.5 μm thick absorbers. Results from laboratory tests are presented characterizing the dependence of their calibration constants under thermal loads up to 450 °C. Several detectors have been tested in ASDEX Upgrade providing reliable data but also pointing out the need for further optimization. A laser trimming procedure has been implemented to reduce the mismatch in meander resistances below 1% for one detector and the thermal drifts from this mismatch. PMID:21061487

  7. Optimization of a bolometer detector for ITER based on Pt absorber on SiN membrane

    Any plasma diagnostic in ITER must be able to operate at temperatures in excess of 200 deg. C and neutron loads corresponding to 0.1 dpa over its lifetime. To achieve this aim for the bolometer diagnostic, a miniaturized metal resistor bolometer detector based on Pt absorbers galvanically deposited on SiN membranes is being developed. The first two generations of detectors featured up to 4.5 μm thick absorbers. Results from laboratory tests are presented characterizing the dependence of their calibration constants under thermal loads up to 450 deg. C. Several detectors have been tested in ASDEX Upgrade providing reliable data but also pointing out the need for further optimization. A laser trimming procedure has been implemented to reduce the mismatch in meander resistances below 1% for one detector and the thermal drifts from this mismatch.

  8. A new method of seawater desalination via acrylic acid based hydrogels: Synthesis, characterisation, and experimental realisation

    Höpfner, Johannes

    2014-01-01

    The scarcity of potable water is a great challenge. It may be resolved by the desalination of seawater. In this work, the possibilities of a new desalination technique using polymeric hydrogels as a separation medium for water and salt is explored. The bound charges in such a polymeric network prevent salt from entering it - under pressure the desalinated water is released from the gel. It is demonstrated that the method is viable and the influence of various process parameters investigated.

  9. Highly robust chitosan hydrogels via a fast, simple and biocompatible dual crosslinking-based process

    Costa, A.M.S.; Mano, J. F.

    2015-01-01

    Load-bearing soft tissues such as cartilage, blood vessels and muscles are able to withstand a remarkable compressive stress of several MPa without fracturing. Interestingly, most of these structural tissues are mainly composed of water and in this regard, hydrogels, as highly hydrated 3D-crosslinked polymeric networks, constitute a promising class of materials to repair lesions on these tissues. Although several approaches can be employed to shape the mechanical properties of artificial hydr...

  10. Colloidal gas aphron foams: A novel approach to a hydrogel based tissue engineered myocardial patch

    Johnson, Elizabeth Edna

    Cardiovascular disease currently affects an estimated 58 million Americans and is the leading cause of death in the US. Over 2.3 million Americans are currently living with heart failure a leading cause of which is acute myocardial infarction, during which a part of the heart muscle is damaged beyond repair. There is a great need to develop treatments for damaged heart tissue. One potential therapy involves replacement of nonfunctioning scar tissue with a patch of healthy, functioning tissue. A tissue engineered cardiac patch would be ideal for such an application. Tissue engineering techniques require the use of porous scaffolds, which serve as a 3-D template for initial cell attachment and grow-th leading to tissue formation. The scaffold must also have mechanical properties closely matching those of the tissues at the site of implantation. Our research presents a new approach to meet these design requirements. A unique interaction between poly(vinyl alcohol) and amino acids has been discovered by our lab, resulting in the production of novel gels. These unique synthetic hydrogels along with one natural hydrogel, alginate (derived from brown seaweed), have been coupled with a new approach to tissue scaffold fabrication using solid colloidal gas aphrons (CGAs). CGAs are colloidal foams containing uniform bubbles with diameters on the order of micrometers. Upon solidification the GCAs form a porous, 3-D network suitable for a tissue scaffold. The project encompasses four specific aims: (I) characterize hydrogel formation mechanism, (II) use colloidal gas aphrons to produce hydrogel scaffolds, (III) chemically and physically characterize scaffold materials and (IV) optimize and evaluate scaffold biocompatibility.

  11. Encoding Cell-Instructive Cues to PEG-Based Hydrogels via Triple Helical Peptide Assembly

    Stahl, Patrick J.; Yu, S. Michael

    2012-01-01

    Effective synthetic tissue engineering scaffolds mimic the structure and composition of natural extracellular matrix (ECM) to promote optimal cellular adhesion, proliferation, and differentiation. Among many proteins of the ECM, collagen and fibronectin are known to play a key role in the scaffold’s structural integrity as well as its ability to support cell adhesion. Here, we present photocrosslinked poly(ethylene glycol) diacrylate (PEGDA) hydrogels displaying collagen mimetic peptides (CMP...

  12. Pharmacokinetics and pharmacodynamics evaluation of a thermosensitive chitosan based hydrogel containing liposomal doxorubicin.

    Ren, Shuangxia; Dai, Yu; Li, Cuiyun; Qiu, Zhixia; Wang, Xin; Tian, Fengjie; Zhou, Sufeng; Liu, Qi; Xing, Han; Lu, Yang; Chen, Xijing; Li, Ning

    2016-09-20

    In situ gelling thermosensitive hydrogel formulation has been reported to effectively sustain the release of macromolecules for a long time. However, the low-molecular-weight hydrophilic drugs, such as doxorubicin (DOX), are not suitable for intratumoral injection because the release will complete within one day. In this study, liposomal doxorubicin (LipDOX) was added into the hydrogel to form a novel thermosensitive formulation which prolonged the sustained release of DOX. DOX+C/GP (doxorubicin in chitosan/β-glycerophosphate) was prepared to compare with LipDOX+C/GP (liposomal doxorubicin in chitosan/β-glycerophosphate hydrogel). The particle size of DOX-loaded liposome was 94.2nm and the encapsulation efficiency of DOX was near 98%. In vitro release experiments, the release of DOX in both DOX+C/GP group and LipDOX+C/GP group increased along with the increasing pH of buffers. However, the LipDOX+C/GP group with lower initial burst release had a much longer releasing duration than DOX+C/GP group (21days vs. 24h). In vitro and in vivo antitumor experiments demonstrated that LipDOX+C/GP group had better antineoplastic effect and less toxicity than DOX+C/GP group. Pharmacokinetics study showed LipDOX+C/GP exhibited a higher AUC0-t and longer MRT than DOX+C/GP in blood and tumor, which indicated that LipDOX+C/GP obtained an enhanced antitumor activity compared with DOX+C/GP. In addition, the lower distribution index (the ratio of AUC of normal tissue/AUC of tumor tissue) of the LipDOX+C/GP implied it had lower toxicity to normal tissues than DOX+C/GP. Therefore, the novel thermosensitive hydrogel formulation was potential for clinical application in cancer treatment. PMID:27388491

  13. Metallo-supramolecular hydrogels based on copolymers bearing terpyridine side-chain ligands

    Jochum, Florian Daniel; Brassinne, Jérémy; Fustin, Charles-André; Gohy, Jean-François

    2013-01-01

    A well-defined amphiphilic poly(triethyleneglycol methylether methacrylate)-block-polystyrene (PTEGMAb-PS) block copolymer with terpyridine groups randomly distributed within the water-soluble block has been sequentially synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Its self-assembly into micellar structures was analyzed in dilute aqueous solution by dynamic light scattering measurements (DLS). Metallo-supramolecular hydrogels were obtained after the a...

  14. Bio-inspired two-dimensional nanofluidic generators based on a layered graphene hydrogel membrane.

    Guo, Wei; Cheng, Chi; Wu, Yanzhe; Jiang, Yanan; Gao, Jun; Li, Dan; Jiang, Lei

    2013-11-13

    An electrogenetic layered graphene hydrogel membrane (GHM) possesses ultra-large interlayer spacing of about 10 nm, forming charged 2D nanocapillaries between graphene sheets that selectively permeate counter-ions and exclude co-ions. When an electrolyte flow goes through the GHM, it functions as an integrated 2D nanofluidic generator converting hydraulic motion into electricity. The maximum streaming conductance density approaches 16.8 μA cm(-2) bar(-1) . PMID:23900945

  15. Tuned resonant mass or inerter-based absorbers: unified calibration with quasi-dynamic flexibility and inertia correction

    Krenk, Steen; Høgsberg, Jan Becker

    2016-01-01

    A common format is developed for a mass and an inerter-based resonant vibration absorber device, operating on the absolute motion and the relative motion at the location of the device, respectively. When using a resonant absorber a specific mode is targeted, but in the calibration of the device i...

  16. Functionalized graphene oxide-based thermosensitive hydrogel for magnetic hyperthermia therapy on tumors

    Zhu, Xiali; Zhang, Huijuan; Huang, Heqing; Zhang, Yingjie; Hou, Lin; Zhang, Zhenzhong

    2015-09-01

    A novel locally injectable, biodegradable, and thermo-sensitive hydrogel made from chitosan and β-glycerophosphate salt was prepared. It incorporated polyethylenimine (PEI)-modified super-paramagnetic graphene oxide (GO/IONP/PEI) as a form of minimally invasive treatment of cancer lesions by magnetically induced local hyperthermia. Doxorubicin (DOX) was mixed into the hydrogel which was pre-loaded on GO/IONP/PEI to create a drug delivery system DOX-GO/IONP/PEI-gel. In addition to the evaluation of in vitro and in vivo antitumor activities, the physicochemical properties, magnetic properties and DOX release profile of the DOX-GO/IONP/PEI-gel were determined. The aqueous solution of the hydrogel showed a sol-gel transition behavior depending on temperature changes. Magnetization loops indicated the super-paramagnetic properties of GO/IONP/PEI. Compared with free DOX, DOX-GO/IONP/PEI could efficiently pass through cell membranes, leading to more apoptosis and demonstrating higher antitumor efficacy on MCF-7 cells in vitro. Furthermore, DOX-GO/IONP/PEI-gel intratumorally injected (i.t.) showed high antitumor efficacy on tumor-bearing mice in vivo, with no obvious toxicity. The antitumor efficacy was higher when combined with an alternating magnetic field (AMF), showing that DOX-GO/IONP/PEI-gel under AMF has great potential for cancer magnetic hyperthermia therapy.

  17. Glycosaminoglycan-based hydrogels to modulate heterocellular communication in in vitro angiogenesis models

    Chwalek, Karolina; Tsurkan, Mikhail V.; Freudenberg, Uwe; Werner, Carsten

    2014-03-01

    Angiogenesis, the outgrowth of blood vessels, is crucial in development, disease and regeneration. Studying angiogenesis in vitro remains challenging because the capillary morphogenesis of endothelial cells (ECs) is controlled by multiple exogenous signals. Therefore, a set of in situ-forming starPEG-heparin hydrogels was used to identify matrix parameters and cellular interactions that best support EC morphogenesis. We showed that a particular type of soft, matrix metalloproteinase-degradable hydrogel containing covalently bound integrin ligands and reversibly conjugated pro-angiogenic growth factors could boost the development of highly branched, interconnected, and lumenized endothelial capillary networks. Using these effective matrix conditions, 3D heterocellular interactions of ECs with different mural cells were demonstrated that enabled EC network modulation and maintenance of stable vascular capillaries over periods of about one month in vitro. The approach was also shown to permit in vitro tumor vascularization experiments with unprecedented levels of control over both ECs and tumor cells. In total, the introduced 3D hydrogel co-culture system could offer unique options for dissecting and adjusting biochemical, biophysical, and cell-cell triggers in tissue-related vascularization models.

  18. Alginate-Collagen Fibril Composite Hydrogel

    Mahmoud Baniasadi; Majid Minary-Jolandan

    2015-01-01

    We report on the synthesis and the mechanical characterization of an alginate-collagen fibril composite hydrogel. Native type I collagen fibrils were used to synthesize the fibrous composite hydrogel. We characterized the mechanical properties of the fabricated fibrous hydrogel using tensile testing; rheometry and atomic force microscope (AFM)-based nanoindentation experiments. The results show that addition of type I collagen fibrils improves the rheological and indentation properties of th...

  19. Preparation and In vitro evaluation of a stomach specific drug delivery system based on superporous hydrogel composite

    H V Chavda

    2011-01-01

    Full Text Available This study discusses efforts made to design drug-delivery system based on superporous hydrogel composite for sustained delivery of ranitidine hydrochloride. The characterization studies involve measurement of apparent density, porosity, swelling studies, mechanical strength studies, and scanning electron microscopy. Scanning electron microscopic images clearly showed the formation of interconnected pores, capillary channels, and the cross-linked sodium carboxymethylcellulose molecules around the peripheries of pores. The prepared system floated and delivered the ranitidine hydrochloride for about 17 h. The release profile of ranitidine hydrochloride was studies by changing the retardant polymer in the system. To ascertain the drug release kinetics, the dissolution profiles were fitted to different mathematical models that include zero-order, first-order, Higuchi, Hixson-Crowell, Korsmeyer-Peppas, Weibull, and Hopfenberg models. The in vitro dissolution from system was explained by Korsmeyer-Peppas model. The diffusion exponent values in Korsmeyer-Peppas model range between 0.48±0.01 and 0.70±0.01, which appears to indicate an anomalous non-Fickian transport. It is concluded that the proposed mechanically stable floating drug-delivery system based on superporous hydrogel composite containing sodium carboxymethylcellulose as a composite material is promising for stomach specific delivery of ranitidine hydrochloride.

  20. Influence of the absorber dimensions on wavefront shaping based on volumetric optoacoustic feedback

    Dean-Ben, X L; Ozbek, A; Razansky, D

    2015-01-01

    The recently demonstrated control over light distribution through turbid media based on real-time three-dimensional optoacoustic feedback has offered promising prospects to interferometrically focus light within scattering objects. Nevertheless, the focusing capacity of the feedback-based approach is strongly conditioned by the number of effectively resolvable optical modes (speckles). In this letter, we experimentally tested the light intensity enhancement achieved with optoacoustic feedback measurements from different sizes of absorbing microparticles. The importance of the obtained results is discussed in the context of potential signal enhancement at deep locations within a scattering medium where the effective speckle sizes approach the minimum values dictated by optical diffraction.

  1. Reduction of graphene oxide/alginate composite hydrogels for enhanced adsorption of hydrophobic compounds

    Kim, Semin; Yoo, Youngjae; Kim, Hanbit; Lee, Eunju; Lee, Jae Young

    2015-10-01

    Carbon-based materials, consisting of graphene oxide (GO) or reduced GO (rGO), possess unique abilities to interact with various molecules. In particular, rGO materials hold great promise for adsorption and delivery applications of hydrophobic molecules. However, conventional production and/or usage of rGO in aqueous solution often causes severe aggregation due to its low water solubility and thus difficulties in handling and applications. In our study, to prevent the severe aggregation of GO during reduction and to achieve a high adsorption capacity with hydrophobic compounds, GO/alginate composite hydrogels were first prepared and then reduced in an aqueous ascorbic acid solution at 37 °C. Adsorption studies with a model hydrophobic substance, rhodamine B, revealed that the reduced composite hydrogels are more highly absorbent than the unreduced hydrogels. In addition, the adsorption properties of the composite hydrogels, which are consequences of hydrophobic and ionic interactions, could be modulated by controlling the degree of reduction for the adsorption of different molecules. The composite hydrogels embedding rGO can be very useful in applications related to drug delivery, waste treatment, and biosensing.

  2. Injectable and Self-Healing Dynamic Hydrogels Based on Metal(I)-Thiolate/Disulfide Exchange as Biomaterials with Tunable Mechanical Properties.

    Casuso, Pablo; Odriozola, Ibon; Pérez-San Vicente, Adrián; Loinaz, Iraida; Cabañero, Germán; Grande, Hans-Jürgen; Dupin, Damien

    2015-11-01

    Despite numerous strategies involving dynamic covalent bonds to produce self-healing hydrogels with similar frequency-dependent stiffness to native tissues, it remains challenging to use biologically relevant thiol/disulfide exchange to confer such properties to polymeric networks. Herein, we report a new method based on Metal(I) [Au(I) or Ag(I)] capping to protect thiolates from aerial oxidation without preventing thiolate/disulfide exchange. Dynamic hydrogels were readily prepared by injecting simultaneously aqueous solutions of commercially available HAuCl4 and 4-arm thiol-terminated polyethylene glycol [(PEGSH)4], resulting in a network containing a mixture of Au(I)-thiolate (Au-S) and disulfide bonds (SS). While the dynamic properties of the hydrogel were closely dependent on the pH, the mechanical properties could be easily tuned by adjusting (PEGSH)4 concentration and amount of Au-S, as judged by dynamic rheology studies. Permanent Au-S/SS exchange at physiological pH conferred self-healing behavior and frequency-dependent stiffness to the hydrogel. In addition, in vitro studies confirmed that Au-based dynamic material was not cytotoxic to human dermal fibroblasts, demonstrating its potential use as a medical device. Dynamic hydrogels obtained using Ag(I) ions demonstrated that the exchange reaction was not affected by the nature of the Metal(I) capping. Finally, this efficient thiolate capping strategy offers a simple way to produce injectable and self-healing dynamic hydrogels from virtually any thiol-containing polymers. PMID:26418440

  3. Experimental study on simultaneous desulfurization and denitrification based on highly active absorbent

    2006-01-01

    Simultaneous removal of SO2 and NO from flue gas by the highly active absorbent prepared from fly ash, lime and a few oxidizing manganese compound additive was studied using a flue gas circulating fluidized bed (CFB) under different experimental conditions. The effects influencing the removal effiencies were discussed. The optimal flue gas temperature, flue gas humidity, gas velocity of CFB and Ca/(S+N) molar ratio with this process were approximately 110℃, 6%, 1.8 m/s and 1.05, respectively. Removal efficiencies of 92.3% for SO2 and 60.88% for NO were obtained under the optimal experimental conditions. While the spent absorbent appeared in the form of dry powder, the mechanism of removal for SO2 and NO based on the highly active absorbent was investigated by a scanning electron microscope (SEM), a X-ray energy spectrometer and the chemical analysis methods. The valuable references can be provided for industrial application by the process. The foreground of application will be vast in China and in the world.

  4. Computational design for a wide-angle cermet-based solar selective absorber for high temperature applications

    The purpose of this study is to computationally design a wide-angle cermet-based solar selective absorber for high temperature applications by using a characteristic matrix method and a genetic algorithm. The present study investigates a solar selective absorber with tungsten–silica (W–SiO2) cermet. Multilayer structures of 1, 2, 3, and 4 layers and a wide range of metal volume fractions are optimized. The predicted radiative properties show good solar performance, i.e., thermal emittances, especially beyond 2 μm, are quite low, in contrast, solar absorptance levels are successfully high with wide angular range, so that solar photons are effectively absorbed and infrared radiative heat loss can be decreased. -- Highlights: • Electromagnetic simulation of radiative properties by characteristic matrix method. • Optimization for multilayered W–SiO2 cermet-based absorber by a Genetic Algorithm. • We propose a successfully high solar performance of solar selective absorber

  5. Capacitance properties and structure of electroconducting hydrogels based on copoly(aniline - p-phenylenediamine) and polyacrylamide

    Smirnov, Michael A.; Sokolova, Maria P.; Bobrova, Natalya V.; Kasatkin, Igor A.; Lahderanta, Erkki; Elyashevich, Galina K.

    2016-02-01

    Electroconducting hydrogels (EH) based on copoly(aniline - p-phenylenediamine) grafted to the polyacrylamide for the application as pseudo-supercapacitor's electrodes have been prepared. The influence of preparation conditions on the structure and capacitance properties of the systems were investigated: we determined the optimal amount of p-phenylenediamine to obtain the network of swollen interconnected nanofibrils inside the hydrogel which provides the formation of continuous conducting phase. Structure and morphology of the prepared samples were investigated with UV-VIS spectroscopy, scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD). The maximal value of capacitance was 364 F g-1 at 0.2 A g-1. It was shown that the EH samples demonstrate the retention of 50% of their capacity at high current density 16 A g-1. Cycle-life measurements show evidence that capacitance of EH electrodes after 1000 cycles is higher than its initial value for all prepared samples. Changes of the copolymer structure during swelling in water have been studied with WAXD.

  6. Encapsulation of lactase (β-galactosidase) into κ-carrageenan-based hydrogel beads: Impact of environmental conditions on enzyme activity.

    Zhang, Zipei; Zhang, Ruojie; Chen, Long; McClements, David Julian

    2016-06-01

    Encapsulation of enzymes in hydrogel beads may improve their utilization and activity in foods. In this study, the potential of carrageenan hydrogel beads for encapsulating β-galactosidase was investigated. Hydrogel beads were fabricated by injecting an aqueous solution, containing β-galactosidase (26 U) and carrageenan (1 wt%), into a hardening solution (5% potassium chloride). Around 63% of the β-galactosidase was initially encapsulated in the hydrogel beads. Encapsulated β-galactosidase had a higher activity than that of the free enzyme over a range of pH and thermal conditions, which was attributed to the stabilization of the enzyme structure by K(+) ions within the carrageenan beads. Release of the enzyme from the beads was observed during storage in aqueous solutions, which was attributed to the relatively large pore size of the hydrogel matrix. Our results suggest that carrageenan hydrogel beads may be useful encapsulation systems, but further work is needed to inhibit enzyme leakage. PMID:26830562

  7. In situ Gelation of Monodisperse Alginate Hydrogel in Microfluidic Channel Based on Mass Transfer of Calcium Ions

    A microfluidic method for the in situ production of monodispersed alginate hydrogels using biocompatible polymer gelation by crosslinker mass transfer is described. Gelation of the hydrogel was achieved in situ by the dispersed calcium ion in the microfluidic device. The capillary number (Ca) and the flow rate of the disperse phase which are important operating parameters mainly influenced the formation of three distinctive flow regions, such as dripping, jetting, and unstable dripping. Under the formation of dripping region, monodispersed alginate hydrogels having a narrow size distribution (C.V=2.71%) were produced in the microfluidic device and the size of the hydrogels, ranging from 30 to 60 µm, could be easily controlled by varying the flow rate, viscosity, and interfacial tension. This simple microfluidic method for the production of monodisperse alginate hydrogels shows strong potential for use in delivery systems of foods, cosmetics, inks, and drugs, and spherical alginate hydrogels which have biocompatibility will be applied to cell transplantation

  8. In situ Gelation of Monodisperse Alginate Hydrogel in Microfluidic Channel Based on Mass Transfer of Calcium Ions

    Song, YoungShin; Lee, Chang-Soo [Chungnam National University, Daejeon (Korea, Republic of)

    2014-10-15

    A microfluidic method for the in situ production of monodispersed alginate hydrogels using biocompatible polymer gelation by crosslinker mass transfer is described. Gelation of the hydrogel was achieved in situ by the dispersed calcium ion in the microfluidic device. The capillary number (Ca) and the flow rate of the disperse phase which are important operating parameters mainly influenced the formation of three distinctive flow regions, such as dripping, jetting, and unstable dripping. Under the formation of dripping region, monodispersed alginate hydrogels having a narrow size distribution (C.V=2.71%) were produced in the microfluidic device and the size of the hydrogels, ranging from 30 to 60 µm, could be easily controlled by varying the flow rate, viscosity, and interfacial tension. This simple microfluidic method for the production of monodisperse alginate hydrogels shows strong potential for use in delivery systems of foods, cosmetics, inks, and drugs, and spherical alginate hydrogels which have biocompatibility will be applied to cell transplantation.

  9. Enhanced performance of VOx-based bolometer using patterned gold black absorber

    Smith, Evan M.; Panjwani, Deep; Ginn, James; Warren, Andrew; Long, Christopher; Figuieredo, Pedro; Smith, Christian; Perlstein, Joshua; Walter, Nick; Hirschmugl, Carol; Peale, Robert E.; Shelton, David J.

    2015-06-01

    Patterned highly absorbing gold black film has been selectively deposited on the active surfaces of a vanadium-oxide-based infrared bolometer array. Patterning by metal lift-off relies on protection of the fragile gold black with an evaporated oxide, which preserves gold black's near unity absorption. This patterned gold black also survives the dry-etch removal of the sacrificial polyimide used to fabricate the air-bridge bolometers. Infrared responsivity is substantially improved by the gold black coating without significantly increasing noise. The increase in the time constant caused by the additional mass of gold black is a modest 14%.

  10. Hydrogel Walkers with Electro-Driven Motility for Cargo Transport

    Chao Yang; Wei Wang; Chen Yao; Rui Xie; Xiao-Jie Ju; Zhuang Liu; Liang-Yin Chu

    2015-01-01

    In this study, soft hydrogel walkers with electro-driven motility for cargo transport have been developed via a facile mould-assisted strategy. The hydrogel walkers consisting of polyanionic poly(2-acrylamido-2-methylpropanesulfonic acid-co-acrylamide) exhibit an arc looper-like shape with two “legs” for walking. The hydrogel walkers can reversibly bend and stretch via repeated “on/off” electro-triggers in electrolyte solution. Based on such bending/stretching behaviors, the hydrogel walkers ...

  11. Multifunctional Solar Systems Based On Two-Stage Regeneration Absorbent Solution

    Doroshenko A.V.

    2015-04-01

    Full Text Available The concepts of multifunctional dehumidification solar systems, heat supply, cooling, and air conditioning based on the open absorption cycle with direct absorbent regeneration developed. The solar systems based on preliminary drainage of current of air and subsequent evaporated cooling. The solar system using evaporative coolers both types (direct and indirect. The principle of two-stage regeneration of absorbent used in the solar systems, it used as the basis of liquid and gas-liquid solar collectors. The main principle solutions are designed for the new generation of gas-liquid solar collectors. Analysis of the heat losses in the gas-liquid solar collectors, due to the mechanism of convection and radiation is made. Optimal cost of gas and liquid, as well as the basic dimensions and configuration of the working channel of the solar collector identified. Heat and mass transfer devices, belonging to the evaporative cooling system based on the interaction between the film and the gas stream and the liquid therein. Multichannel structure of the polymeric materials used to create the tip. Evaporative coolers of water and air both types (direct and indirect are used in the cooling of the solar systems. Preliminary analysis of the possibilities of multifunctional solar absorption systems made reference to problems of cooling media and air conditioning on the basis of experimental data the authors. Designed solar systems feature low power consumption and environmental friendliness.

  12. Femtosecond laser micromachining of waveguides in silicone-based hydrogel polymers.

    Ding, Li; Blackwell, Richard I; Künzler, Jay F; Knox, Wayne H

    2008-06-10

    By tightly focusing 27 fs laser pulses from a Ti:sapphire oscillator with 1.3 nJ pulse energy at 93 MHz repetition rate, we are able to fabricate optical waveguides inside hydrogel polymers containing approximately 36% water by weight. A tapered lensed fiber is used to couple laser light at a wavelength of 632.8 nm into these waveguides within a water environment. Strong waveguiding is observed due to large refractive index changes. A large waveguide propagation loss is found, and we show that this is caused by surface roughness which can be reduced by optimizing the waveguides. PMID:18545281

  13. Oxygen and ionic transport in hydrogel and silicone-hydrogel contact lens materials : an experimental and theoretical study

    Pozuelo, Javier; Compañ Moreno, Vicente; González Méijome, J.M.; González, María; Mollá Romano, Sergio

    2014-01-01

    The transport of oxygen, water and naked ions of Na+ and Cl− across two kind of hydrogels materials, made of a conventional hydrogel (Hy) based on hydroxyethyl methacrylate (pHEMA) and a silicone hydrogel (Si-Hy) material containing siloxane moieties, was compared between Molecular Dynamics Simulations (MDS) and experimental measurements. Computer-assisted simulations were carried out for wet hydrogels at 310 K and equilibrium water uptake in the range from 10% to 40%. Our results show that i...

  14. Macroporous hydrogels based on 2-hydroxyethyl methacrylate. Part 6: 3D hydrogels with positive and negative surface charges and polyelectrolyte complexes in spinal cord injury repair

    Hejčl, Aleš; Lesný, Petr; Přádný, Martin; Šedý, Jiří; Zámečník, J.; Jendelová, Pavla; Michálek, Jiří; Syková, Eva

    2009-01-01

    Roč. 20, č. 7 (2009), s. 1571-1577. ISSN 0957-4530 R&D Projects: GA AV ČR IAA500390902 Grant ostatní: GA MŠk(CZ) 1M0538; GA MZd(CZ) 1A8697; EC FP6 project RESCUE(XE) LSHB-CT-2005-518233 Institutional research plan: CEZ:AV0Z50390703; CEZ:AV0Z40500505 Keywords : transplantation * biomaterials * macroporous hydrogels Subject RIV: FH - Neurology Impact factor: 1.955, year: 2009

  15. High power L-band mode-locked fiber laser based on topological insulator saturable absorber.

    Meng, Yichang; Semaan, Georges; Salhi, Mohamed; Niang, Alioune; Guesmi, Khmaies; Luo, Zhi-Chao; Sanchez, Francois

    2015-09-01

    We demonstrate a passive mode-locked Er:Yb doped double-clad fiber laser using a microfiber-based topological insulator (Bi(2)Se(3)) saturable absorber (TISA). By optimizing the cavity loss and output coupling ratio, the mode-locked fiber laser can operate in L-band with high average output power. With the highest pump power of 5 W, 91st harmonic mode locking of soliton bunches with average output power of 308 mW was obtained. This is the first report that the TISA based erbium-doped fiber laser operating above 1.6 μm and is also the highest output power yet reported in TISA based passive mode-locked fiber laser. PMID:26368409

  16. Microfiber-based gold nanorods as saturable absorber for femtosecond pulse generation in a fiber laser

    We reported on the femtosecond pulse generation from an erbium-doped fiber (EDF) laser by using microfiber-based gold nanorods (GNRs) as saturable absorber (SA). By virtue of the geometric characteristic of microfiber-based GNRs, the optical damage threshold of GNRs-SA could be greatly enhanced. The microfiber-based GNRs-SA shows a modulation depth of 4.9% and a nonsaturable loss of 21.1%. With the proposed GNRs-SA, the fiber laser emitted a mode-locked pulse train with duration of ∼887 fs. The obtained results demonstrated that the GNRs deposited microfiber could indeed serve as a high-performance SA towards the practical applications in the field of ultrafast photonics.

  17. Optimal semi-active vibration absorber for harmonic excitation based on controlled semi-active damper

    The semi-active vibration absorber (SVA) based on controlled semi-active damper is formulated to realize the behaviour of the passive undamped vibration absorber tuned to the actual harmonic disturbing frequency. It is shown that the controlled stiffness force, which is emulated by the semi-active damper to realize the precise real-time frequency tuning of the SVA, is unpreventably combined with the generation of undesirable damping in the semi-active damper whereby the SVA does not behave as targeted. The semi-active stiffness force is therefore optimized for minimum primary structure response. The results point out that the optimal semi-active stiffness force reduces the undesirable energy dissipation in the SVA at the expenses of slight imprecise frequency tuning. Based on these findings, a real-time applicable suboptimal SVA is formulated that also takes the relative motion constraint of real mass dampers into account. The results demonstrate that the performance of the suboptimal SVA is closer to that of the active solution than that of the passive mass damper. (paper)

  18. Controlled-surface-wettability-based fabrication of hydrogel substrates with matrix tethering density variations

    Rahman, Md. Mahmudur; Lee, Donghee; Bhagirath, Divya; Zhao, Xiangshan; Band, Vimla; Ryu, Sangjin

    2014-03-01

    It is widely accepted that cells behave differently responding to the stiffness of extracellular matrix (ECM). Such observations were made by culturing cells on hydrogel substrates of tunable stiffness. However, it was recently proposed that cells actually sense how strongly they are tethered to ECM, not the local stiffness of ECM. To investigate the hypothesis, we develop constant-stiffness hydrogel substrates with varying matrix tethering density (the number of anchoring sites between the gel and the ECM protein molecules). We fabricate polyacrylamide gel of static stiffness and conjugate ECM proteins to the gel using a cross-linker. When treating the gel with the cross-linker, we control positioning of cross-linker solutions with different concentrations using superhydrophobic barriers on glass, functionalize the gel by pressing it to the aligned cross-linker solutions, and conjugate an ECM protein of constant concentration to the gel. We expect that the gel will be functionalized to different degrees depending on the concentration distribution of the cross-linker and thus the gel will have variations of matrix tethering density even with constant ECM protein concentration. We acknowledge support from Bioengineering for Human Health grant of UNL-UNMC.

  19. Insights into the coassembly of hydrogelators and surfactants based on aromatic peptide amphiphiles.

    Fleming, Scott; Debnath, Sisir; Frederix, Pim W J M; Hunt, Neil T; Ulijn, Rein V

    2014-04-14

    The coassembly of small molecules is a useful means of increasing the complexity and functionality of their resultant supramolecular constructs in a modular fashion. In this study, we explore the assembly and coassembly of serine surfactants and tyrosine-leucine hydrogelators, capped at the N-termini with either fluorenyl-9-methoxycarbonyl (Fmoc) or pyrene. These systems all exhibit self-assembly behavior, which is influenced by aromatic stacking interactions, while the hydrogelators also exhibit β-sheet-type arrangements, which reinforce their supramolecular structures. We provide evidence for three distinct supramolecular coassembly models; cooperative, disruptive, and orthogonal. The coassembly mode adopted depends on whether the individual constituents (I) are sufficiently different, such that effective segregation and orthogonal assembly occurs; (II) adhere to a communal mode of self-assembly; or (III) act to compromise the assembly of one another via incorporation and disruption. We find that a greater scope for controllable coassembly exists within orthogonal systems; which show minimal relative changes in the native gelator's supramolecular structure by Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), and fluorescence spectroscopy. This is indicative of the segregation of orthogonal coassembly constituents into distinct domains, where surfactant chemical functionality is presented at the surface of the gelator's supramolecular fibers. Overall, this work provides new insights into the design of modular coassembly systems, which have the potential to augment the chemical and physical properties of existing gelator systems. PMID:24568678

  20. Influence of clay particles on microfluidic-based preparation of hydrogel composite microsphere

    Hong, Joung Sook

    2016-05-01

    For the successful fabrication of a hydrogel composite microsphere, this study aimed to investigate the influence of clay particles on microsphere formation in a microfluidic device which has flow focusing and a 4.5:1 contraction channel. A poly alginic acid solution (2.0 wt.%) with clay particles was used as the dispersed phase to generate drops in an oil medium, which then merged with drops of a CaCl2 solution for gelation. Drop generations were observed with different flow rates and particles types. When the flow rate increased, drop generation was enhanced and drop size decreased by the build-up of more favorable hydrodynamic flow conditions to detach the droplets. The addition of a small amount of particles insignificantly changed the drop generation behavior even though it reduced interfacial tension and increased the viscosity of the solution. Instead, clays particles significantly affected hydro-gelation depending on the hydrophobicity of particles, which produced further heterogeneity in the shape and size of microsphere.

  1. Fabrication and characterization of cross-linkable hydrogel particles based on hyaluronic acid: potential application in vocal fold regeneration.

    Sahiner, Nurettin; Jha, Amit K; Nguyen, David; Jia, Xinqiao

    2008-01-01

    There is a critical need to engineer hyaluronic acid (HA)-based hydrogels with prolonged in vivo residence time, temporal release of therapeutics and matching viscoelasticity for use in vocal fold tissue engineering. We have previously demonstrated the synthesis and characterization of HA-based soft hydrogel particles (HGP) and particle cross-linked networks as injectable materials to treat vocal fold scarring. In this paper, we report a more versatile technique for preparing cross-linkable HA HGP with reduced sizes. HA HGP were synthesized via chemical cross-linking with divinyl sulfone using a sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelle system in the presence of 1-heptanol. These HGP were rendered cross-linkable by introducing aldehyde groups via sodium periodate oxidation (oxHGP). The presence of aldehyde groups was confirmed by multi-photon confocal microscope upon fluorescence staining using cascade blue hydrazide. The aldehyde groups were used as reactive handles for covalent cross-linking with HA that has been previously modified with adipic acid dihydrazide (HADH). The resulting doubly cross-linked networks (DXN) are highly pliable and do not break until approx. 200-300% strain. The measured elastic modulus of the DXN is around 500 Pa, while the dynamic viscosity decreases linearly with frequency in log- log scale. The mechanical characteristics of DXN are similar to that of vocal fold lamina propria. In vitro cell-proliferation assays showed that the cross-linkable HA HGP did not adversely affect the proliferation of the cultured fibroblasts as assessed by MTT assay. A low-molecular-weight model drug, rhodamine 6G (R6G), was loaded into oxHGP, and its release was monitored using UV-Vis spectroscopy. R6G-loaded oxHGP maintained their ability to form DXN when mixed with the HAADH solution. Approximately 84% of entrapped R6G was liberated from oxHGP at a rate of 0.24%/min in the first 6 h. When encapsulated in the DXN, R6G was

  2. Preliminary study of MoS2 based saturable absorber used for crystal based mode locking laser system

    Tang, C Y; Tao, L-l.; Long, H.; Zeng, L-H.; Huang, C. C.; Hewak, D.W.; Tsang, Y.H.

    2015-01-01

    Due to the extremely high pulse peak power produced by ultrafast laser and its potential applications for precious material processing and cutting e.g. sapphire wafer surface processing for mobile phone display technology, it has attracted great interests from the laser photonic industry. Apart from Semiconductor Saturable Absorber Mirror (SESAM), the carbon based materials e.g. carbon nano tube or graphene and graphene oxide materials have demonstrated mode locking successfully by using diff...

  3. Removal of paraquat pesticide from aqueous solutions using a novel adsorbent material based on polyacrylamide and methylcellulose hydrogels

    This research studied the characteristics of poly(acrylamide) and methylcellulose (PAAm-MC) hydrogels as a novel adsorbent material for removal of pesticide paraquat, from aqueous solution, with potential applications in curbing environmental risk from such herbicides. PAAm-MC hydrogels with differe...

  4. Silicone-based tough hydrogels with high resilience, fast self-recovery, and self-healing properties.

    Si, Liqi; Zheng, Xiaowen; Nie, Jun; Yin, Ruixue; Hua, Yujie; Zhu, Xiaoqun

    2016-06-28

    Tough hydrogels are prepared from two monomers via photopolymerization of hydroxyethyl acrylate and sol-gel of methyltrimethoxysilane. Constitution and water content could be tuned easily because of the good water solubility of both monomers and two non-interfering polymerization processes. The hydrogels exhibit excellent integrated performance with toughness, high resilience, fast self-recovery, and self-healing. PMID:27257636

  5. Poly(N-isopropylacrylamide)–clay based hydrogels controlled by the initiating conditions: evolution of structure and gel formation

    Strachota, Beata; Matějka, Libor; Zhigunov, Alexander; Konefal, Rafal; Spěváček, Jiří; Dybal, Jiří; Puffr, Rudolf

    2015-01-01

    Roč. 11, č. 48 (2015), s. 9291-9306. ISSN 1744-683X R&D Projects: GA ČR(CZ) GAP108/12/1459; GA ČR(CZ) GA13-23392S Institutional support: RVO:61389013 Keywords : thermoresponsive hydrogel * hybrid nanocomposite * polymer clay hydrogel Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.029, year: 2014

  6. Biocompatible and bioadhesive hydrogels based on 2-hydroxyethyl methacrylate, monofunctional poly(alkylene glycols and itaconic acid

    Mićić Maja M.

    2007-01-01

    Full Text Available New types of hydrogels were prepared by the radical copolymerization of 2-hydroxyethyl methacrylate, itaconic acid and four different poly(alkylene glycol (methacrylate components (Bisomers in a water/ethanol mixture as solvent. The polymers swell in water at 25°C to yield homogeneous transparent hydrogels. All the hydrogels displayed pH sensitive behavior in buffers of the pH range from 2.20 to 7.40, under conditions similar to those of biological fluids. The presence of these two comonomers, which were added to HEMA, increased the swelling degree of the hydrogels and gave gels with better elasticity. The hydrogels were thermally stable in the vicinity of the physiological temperature (37°C. The copolymer containing pure poly(ethylene glycol acrylate units generally had the best properties. The tests performed on the hydrogels confirmed that they were neither hemolytic nor cytotoxic. The copolymer samples showed better cell viability and less hemolytic activity than the PHEMA sample, confirming the assumption that poly(alkylene glycols improve the biocompatibility of hydrogels. Due to their swelling and mechanical characteristics, as well as the very good biocompatibility and bioadhesive properties, poly(Bisomer/HEMA/IA hydrogels are promising for utilization in the field of biomedicals, especially for the controlled release of drugs.

  7. The Preparation and Properties of Thermosensitive Hydrogels Based on Chitosan Grafted N-isopropylacrylamide via γ-Radiation

    Hong CAI; Jing ZHANG; Zheng Pu ZHANG; Yan Geng ZHANG; Bing Lin HE

    2004-01-01

    Thermosensitive hydrogels were prepared by graft polymerization of chitosan and N-isopropylacrylamide via 60Co γ-radiation. The effects of monomer concentration and total irradiation dose on percent grafting and grafting efficiency were studied. The thermosensitivity and swelling properties of the hydrogels were investigated.

  8. Physical properties of hemoglobin-poly(acrylamide) hydrogel-based oxygen carriers: effect of reaction pH.

    Patton, Jaqunda N; Palmer, Andre F

    2006-02-28

    This work examines the physical properties of bovine hemoglobin (BHb) chemically cross-linked to a pH responsive polymer (poly(acrylamide)) with the goal of taking advantage of the polymer's pH sensitivity to generate low-P50 oxygen carriers for application in physiological conditions characterized by deviations from normal pH. BHb-hydrogel-based oxygen carriers encapsulating 10-16 g/dL BHb displayed P50s liposomes (i.e. Hb-LGs) and change conformations between the R and T states. The magnitude of the zeta potential of Hb-LGs and Hb-NHPs was shown to be within the range of stored red blood cells and within the range of limited flocculation. Taken together, this work describes the preparation and characterization of oxygen carriers with increased oxygen affinities compared to those of red blood cells. PMID:16489809

  9. Adsorption of methyl violet from aqueous solution using gum xanthan/Fe3O4 based nanocomposite hydrogel.

    Mittal, H; Kumar, Vaneet; Saruchi; Ray, Suprakas Sinha

    2016-08-01

    This research paper reports the utilization of gum xanthan-grafted-polyacrylic acid and Fe3O4 magnetic nanoparticles based nanocomposite hydrogel (NCH) for the highly effective adsorption of methyl violet (MV) from aqueous solution. Synthesized NCH was characterized using various techniques, such as FTIR, XRD, SEM-EDS, TEM and BET. Adsorption behavior of NCH was studied for the adsorption of MV and it was found to remove 99% dye from the solution. Adsorption process followed Langmuir isotherm model (qe=642mg/g) and pseudo-second-order kinetics model. Thermodynamic studies suggested that the adsorption process was endothermic and spontaneous. Moreover, the adsorbent was successfully utilized for successive five cycles of adsorption-desorption. PMID:27106587

  10. Interaction of human plasma proteins with thin gelatin-based hydrogel films: a QCM-D and ToF-SIMS study.

    Schönwälder, Sina M S; Bally, Florence; Heinke, Lars; Azucena, Carlos; Bulut, Özgül D; Heißler, Stefan; Kirschhöfer, Frank; Gebauer, Tim P; Neffe, Axel T; Lendlein, Andreas; Brenner-Weiß, Gerald; Lahann, Jörg; Welle, Alexander; Overhage, Jörg; Wöll, Christof

    2014-07-14

    In the fields of surgery and regenerative medicine, it is crucial to understand the interactions of proteins with the biomaterials used as implants. Protein adsorption directly influences cell-material interactions in vivo and, as a result, regulates, for example, cell adhesion on the surface of the implant. Therefore, the development of suitable analytical techniques together with well-defined model systems allowing for the detection, characterization, and quantification of protein adsorbates is essential. In this study, a protocol for the deposition of highly stable, thin gelatin-based films on various substrates has been developed. The hydrogel films were characterized morphologically and chemically. Due to the obtained low thickness of the hydrogel layer, this setup allowed for a quantitative study on the interaction of human proteins (albumin and fibrinogen) with the hydrogel by Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). This technique enables the determination of adsorbant mass and changes in the shear modulus of the hydrogel layer upon adsorption of human proteins. Furthermore, Secondary Ion Mass Spectrometry and principal component analysis was applied to monitor the changed composition of the topmost adsorbate layer. This approach opens interesting perspectives for a sensitive screening of viscoelastic biomaterials that could be used for regenerative medicine. PMID:24956040

  11. Mechanical and structural response of a hybrid hydrogel based on chitosan and poly(vinyl alcohol) cross-linked with epichlorohydrin for potential use in tissue engineering.

    Garnica-Palafox, I M; Sánchez-Arévalo, F M; Velasquillo, C; García-Carvajal, Z Y; García-López, J; Ortega-Sánchez, C; Ibarra, C; Luna-Bárcenas, G; Solís-Arrieta, L

    2014-01-01

    The development and characterization of a hybrid hydrogel based on chitosan (CS) and poly(vinyl alcohol) (PVA) chemically cross-linked with epichlorohydrin (ECH) is presented. The mechanical response of these hydrogels was evaluated by uniaxial tensile tests; in addition, their structural properties such as average molecular weight between cross-link points (Mcrl), mesh size (DN), and volume fraction (v(s)) were determined. This was done using the equivalent polymer network theory in combination with the obtained results from tensile and swelling tests. The films showed Young's modulus values of 11 ± 2 MPa and 9 ± 1 MPa for none irradiated and ultraviolet (UV) irradiated hydrogels, respectively. The cell viability was assessed using Calcein AM and Ethidium homodimer-1 assay and environmental scanning electron microscopy. The 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan thiazolyl blue formazan (MTT Formazan assay) results did not show cytotoxic effects; this was in good agreement with nuclear magnetic resonance and fourier transform infrared spectroscopies; their results did not show traces of ECH. This indicated that after the crosslinking process, there was no free ECH; furthermore, any possibility of ECH release in the construct during cell culture was discarded. The CS-PVA-ECH hybrid hydrogel allowed cell growth and extracellular matrix formation and showed adequate mechanical, structural, and biological properties for potential use in tissue engineering applications. PMID:24007370

  12. Topical Anti-Nuclear Factor-Kappa B Small Interfering RNA with Functional Peptides Containing Sericin-Based Hydrogel for Atopic Dermatitis

    Takanori Kanazawa

    2015-09-01

    Full Text Available The small interfering RNA (siRNA is suggested to offer a novel means of treating atopic dermatitis (AD because it allows the specific silencing of genes related to AD pathogenesis. In our previous study, we found that siRNA targeted against RelA, an important nuclear factor-kappa B (NF-κB subdomain, with functional peptides, showed therapeutic effects in a mouse model of AD. In the present study, to develop a topical skin application against AD, we prepared a hydrogel containing anti-RelA siRNA and functional peptides and determined the intradermal permeation and the anti-AD effects in an AD mouse model. We selected the silk protein, sericin (SC, which is a versatile biocompatible biomaterial to prepare hydrogel as an aqueous gel base. We found that the siRNA was more widely delivered to the site of application in AD-induced ear skin of mice after topical application via the hydrogel containing functional peptides than via the preparation without functional peptides. In addition, the ear thickness and clinical skin severity of the AD-induced mice treated with hydrogel containing anti-RelA siRNA with functional peptides improved more than that of mice treated with the preparation formulated with negative siRNA.

  13. Topical Anti-Nuclear Factor-Kappa B Small Interfering RNA with Functional Peptides Containing Sericin-Based Hydrogel for Atopic Dermatitis.

    Kanazawa, Takanori; Shizawa, Yuki; Takeuchi, Mayu; Tamano, Kuniko; Ibaraki, Hisako; Seta, Yasuo; Takashima, Yuki; Okada, Hiroaki

    2015-01-01

    The small interfering RNA (siRNA) is suggested to offer a novel means of treating atopic dermatitis (AD) because it allows the specific silencing of genes related to AD pathogenesis. In our previous study, we found that siRNA targeted against RelA, an important nuclear factor-kappa B (NF-κB) subdomain, with functional peptides, showed therapeutic effects in a mouse model of AD. In the present study, to develop a topical skin application against AD, we prepared a hydrogel containing anti-RelA siRNA and functional peptides and determined the intradermal permeation and the anti-AD effects in an AD mouse model. We selected the silk protein, sericin (SC), which is a versatile biocompatible biomaterial to prepare hydrogel as an aqueous gel base. We found that the siRNA was more widely delivered to the site of application in AD-induced ear skin of mice after topical application via the hydrogel containing functional peptides than via the preparation without functional peptides. In addition, the ear thickness and clinical skin severity of the AD-induced mice treated with hydrogel containing anti-RelA siRNA with functional peptides improved more than that of mice treated with the preparation formulated with negative siRNA. PMID:26371030

  14. Design of Stable and Powerful Nanobiocatalysts, Based on Enzyme Laccase Immobilized on Self-Assembled 3D Graphene/Polymer Composite Hydrogels.

    Ormategui, Nerea; Veloso, Antonio; Leal, Gracia Patricia; Rodriguez-Couto, Susana; Tomovska, Radmila

    2015-07-01

    Graphene-based materials appear as a suitable answer to the demand for novel nanostructured materials for effective nanobiocatalytic systems design. In this work, a design of stable and efficient nanobiocatalysts made of enzyme laccase immobilized on composite hydrogels [reduced graphene oxide (rGO)/polymer] is presented. The composite hydrogel supports were synthesized by self-assembly of graphene oxide nanoplatelets in the frame of a polymer latex matrix, where the polymer nanoparticles were adsorbed onto the GO surface, creating hybrid nanoplatelets. These hybrids self-assembled when ascorbic acid was added as a GO reducing agent and formed three-dimensional porous structures, greatly swollen with water, e.g., the composite hydrogels. The hydrogels were used as a support for covalent immobilization of the laccase. The performance of the nanobiocatalysts was tested in the oxidative degradation of the recalcitrant synthetic dye Remazol Brilliant Blue R in aqueous solutions. The biocatalysts showed strong dye discoloration ability and high stability as they preserved their catalytic action in four successive batches of dye degradation. The presented biocatalysts offer possibilities for overcoming the main disadvantages of the enzyme catalysts (fragile nature, high cost, and high loading of the enzyme), which would lead to a step forward toward their industrial application. PMID:26075472

  15. Radiation synthesis of low swelling acrylamide based hydrogels and determination of average molecular weight between cross-links

    A comparative analysis of determination of cross-link density (νe) of hydrogels by using swelling tests and mechanical measurements has been made. Poly(acrylamide/methacrylamide) P(AAm/MAAm) and poly(acrylamide/hydroxyethyl methacrylate) P(AAm/HEMA) hydrogels were prepared by using gamma rays and used as model hydrogel systems. The uniaxial compression test was applied to cylindrical gel samples in the swollen state at pH 7. Stress-strain curves of hydrogels were evaluated to calculate the shear modulus values. The average molecular weight between cross-links (M-barc) and νe obtained from mechanical measurements were significantly different than the values obtained from swelling experiments. Large differences were attributed to the uncertainty on the value of the χ parameter used in the Flory-Rehner equation. ±1% change in this parameter doubled or reduced the M-barc value of hydrogel to half value

  16. Development of FeCoB/Graphene Oxide based microwave absorbing materials for X-Band region

    This work explored the microwave absorption capability of Graphene Oxide and Graphene Oxide coated with FeCoB for stealth technology. Epoxy based microwave absorbing materials were prepared with 30% loading of Graphene Oxide, FeCoB alloy and Graphene Oxide coated with FeCoB. Graphene Oxide and FeCoB were synthesized by Hummer's and Co-precipitation methods, respectively. The filler particles were characterized by FESEM, XRD and Vibrating Sample Magnetometer techniques. Permittivity, permeability and reflection loss values of the composite absorbers were measured with vector network analyzer which showed a reflection loss value of −7.86 dB, at 10.72 GHz, for single layered Graphene Oxide/Epoxy based microwave absorbers which can be correlated to the absorption of about 83.97% of the incident microwave energy. Reflection loss value of FeCoB/Epoxy based microwave absorber showed −13.30 dB at 11.67 GHz, which corresponded to maximum absorption of 93.8%. However, reflection loss values of Graphene Oxide coated with FeCoB/Epoxy based single-layer absorber increased to −22.24 dB at 12.4 GHz which corresponds to an absorption of 99% of the incident microwave energy. - Highlights: • FeCoB coated Graphene Oxide (GO) was synthesized by co-precipitation method. • GO, FeCoB and GO@FeCoB based microwave absorbers were developed with Epoxy matrix. • GO and FeCoB/Epoxy absorbers showed −7.86 & −13.30 dB reflection loss, respectively. • Maximum Reflection loss of −22.24 dB was achieved with GO@FeCoB/Epoxy absorber

  17. Multi-Analyte Biosensing -- The Integration of Sensing Elements into a Photolithographically Constructed Hydrogel Based Biosensor Platform

    Schmid, Matthew John

    The genome sequencing programs have identified hundreds of thousands of genetic and proteomic targets for which there are presently no ascribed functions. The challenge for researchers now is to characterize them, as well as identify and characterize their natural variants. Historically, this has meant studying each individual target separately. However, due to the recent development of multi-analyte microarray devices, these characterizations can be performed in a combinatorial manner in which a single experiment provides information on thousands of targets at a time. In the past decade, microarray technology has settled in on two major designs. The first entails spotting individual receptor types onto a functionalized glass substrate. This is a simple and inexpensive process; however, due to the limited resolution of the mechanical devices used to do the spotting, the densities of these arrays are relatively low. Moreover, receptor preparation requires substantial time and effort. The second variety of microarray uses photolithographic techniques adapted from the semi-conductor industry to chemically synthesize the receptor elements in situ on the sensing surface. Because lithographic patterning is spatially very precise, these arrays achieve very high densities, with as many as one million features per square centimeter. Although these arrays obviate the necessity for laborious "off chip" probe preparation, they are expensive to produce and are limited to two types of receptors (oligonucleotides and peptides). This dissertation presents the development work performed on a hydrogel-based biosensor platform which provides a high density and low cost alternative to the two aforementioned designs. The array features are fabricated lithographically from a liquid pre-polymer doped with biologically active sensing elements at sizes as small as 50microm. Each of the feature types is uniquely shaped, which enables the features to be mass-produced in batches, pooled

  18. T-style keratoprosthesis based on surface-modified poly (2-hydroxyethyl methacrylate) hydrogel for cornea repairs

    Xiang, Jun [Department of Ophthalmology, Eye & ENT Hospital, Shanghai Medical College, Fudan University (China); Key Laboratory of Myopia, Ministry of Health, Fudan University (China); Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University (China); Sun, Jianguo [Research Center, Eye & ENT Hospital, Shanghai Medical College, Fudan University (China); Key Laboratory of Myopia, Ministry of Health, Fudan University (China); Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University (China); State Key Laboratory of Molecular Engineering of Polymers, Fudan University (China); Hong, Jiaxu [Department of Ophthalmology, Eye & ENT Hospital, Shanghai Medical College, Fudan University (China); Key Laboratory of Myopia, Ministry of Health, Fudan University (China); Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University (China); Wang, Wentao [Research Center, Eye & ENT Hospital, Shanghai Medical College, Fudan University (China); Key Laboratory of Myopia, Ministry of Health, Fudan University (China); Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University (China); Wei, Anji [Department of Ophthalmology, Eye & ENT Hospital, Shanghai Medical College, Fudan University (China); Key Laboratory of Myopia, Ministry of Health, Fudan University (China); Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University (China); Le, Qihua [Research Center, Eye & ENT Hospital, Shanghai Medical College, Fudan University (China); Key Laboratory of Myopia, Ministry of Health, Fudan University (China); Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University (China); Xu, Jianjiang, E-mail: jianjiang-xu@163.com [Department of Ophthalmology, Eye & ENT Hospital, Shanghai Medical College, Fudan University (China); Key Laboratory of Myopia, Ministry of Health, Fudan University (China); Shanghai Key Laboratory of Visual Impairment and Restoration, Fudan University (China)

    2015-05-01

    Corneal disease is a common cause of blindness, and keratoplasty is considered as an effective treatment method. However, there is a severe shortage of donor corneas worldwide. This paper presents a novel T-style design of a keratoprosthesis and its preparation methods, in which a mechanically and structurally effective artificial cornea is made based on a poly(2-hydroxyethyl methacrylate) hydrogel. The porous skirt was modified with hyaluronic acid and cationized gelatin, and the bottom of the optical column was coated with poly(ethylene glycol). The physical properties of the T-style Kpro were analyzed using ultraviolet and visible spectrophotometry and electron scanning microscopy. The surface chemical properties were characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface modification in the spongy skirt promoted cell adhesion and produced a firm bond between the corneal tissue and the implant device, while the surface modification in the optic column resisted cell adhesion and prevented retroprosthetic membrane formation. Through improved surgical techniques, the novel T-style keratoprosthesis provides enough mechanical stability to facilitate long-term biointegration with the host environment. In vivo implantation experiments showed that the T-style keratoprosthesis is a promising cornea alternative for patients with severe limbal stem cell deficiency and corneal opacity. - Highlights: • T-style keratoprosthesis was designed and prepared based on a PHEMA hydrogel. • Selective surface modifications effectively regulated cells' selective adhesion. • T-style keratoprosthesis provides enough mechanical stability to facilitate long-term biointegration with host tissues.

  19. T-style keratoprosthesis based on surface-modified poly (2-hydroxyethyl methacrylate) hydrogel for cornea repairs

    Corneal disease is a common cause of blindness, and keratoplasty is considered as an effective treatment method. However, there is a severe shortage of donor corneas worldwide. This paper presents a novel T-style design of a keratoprosthesis and its preparation methods, in which a mechanically and structurally effective artificial cornea is made based on a poly(2-hydroxyethyl methacrylate) hydrogel. The porous skirt was modified with hyaluronic acid and cationized gelatin, and the bottom of the optical column was coated with poly(ethylene glycol). The physical properties of the T-style Kpro were analyzed using ultraviolet and visible spectrophotometry and electron scanning microscopy. The surface chemical properties were characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The surface modification in the spongy skirt promoted cell adhesion and produced a firm bond between the corneal tissue and the implant device, while the surface modification in the optic column resisted cell adhesion and prevented retroprosthetic membrane formation. Through improved surgical techniques, the novel T-style keratoprosthesis provides enough mechanical stability to facilitate long-term biointegration with the host environment. In vivo implantation experiments showed that the T-style keratoprosthesis is a promising cornea alternative for patients with severe limbal stem cell deficiency and corneal opacity. - Highlights: • T-style keratoprosthesis was designed and prepared based on a PHEMA hydrogel. • Selective surface modifications effectively regulated cells' selective adhesion. • T-style keratoprosthesis provides enough mechanical stability to facilitate long-term biointegration with host tissues

  20. Circuit model for graphene-based absorber at low-terahertz frequencies

    A general circuit model is presented to study the absorption of electromagnetic waves by a graphene-based structure at low-terahertz frequencies. The absorber consists of a monolayer graphene which is printed on the uneven dielectric slabs, with a metallic ground plane placed at the bottom interface. The approach is based on the simple and accurate analytical models for metal strips or patches. Compared with the full-wave electromagnetic simulator software, the proposed method shows high efficiency and the results obtained from the suggested method agree well with those from the full-wave simulations for a normal and oblique incidence. It is very helpful to design novel graphene plasmonic devices in the future. (paper)

  1. Application of Charpy Impact Absorbed Energy to the Safety Assessment Based on SINTAP

    2006-01-01

    The European Structural Integrity Assessment Procedure(SINTAP) was applied to the assessment of welded joints of the APl 5L X65 pipeline steel with an assumed embedded flaw and surface flaw at the weld toe. At default level( level 0), the assessment point was established by estimating fracture toughness value KIc conservatively from Charpy energy test data. At the same time, the analysis level 1 (basic level)was applied based on the fracture toughness CTOD. Then the two assessment levels were compared. The assessment results show that all assessment points are located within the failure lines of analysis levels 0 and 1. So the welded joint of the pipeline is safe. It can be concluded that the assessment based on Charpy absorbed energy is practicable when other fracture toughness data are not available, or cannot be easily obtained. The results are conservative.

  2. Physiologically based pharmacokinetic modeling of inhaled radon to calculate absorbed doses in mice, rats, and humans

    This is the first report to provide radiation doses, arising from inhalation of radon itself, in mice and rats. To quantify absorbed doses to organs and tissues in mice, rats, and humans, we computed the behavior of inhaled radon in their bodies on the basis of a physiologically based pharmacokinetic (PBPK) model. It was assumed that radon dissolved in blood entering the gas exchange compartment is transported to any tissue by the blood circulation to be instantaneously distributed according to a tissue/blood partition coefficient. The calculated concentrations of radon in the adipose tissue and red bone marrow following its inhalation were much higher than those in the others, because of the higher partition coefficients. Compared with a previous experimental data for rats and model calculation for humans, the present calculation was proved to be valid. Absorbed dose rates to organs and tissues were estimated to be within the range of 0.04-1.4 nGy (Bqm-3)-1 day-1 for all the species. Although the dose rates are not so high, it may be better to pay attention to the dose to the red bone marrow from the perspective of radiation protection. For more accurate dose assessment, it is necessary to update tissue/blood partition coefficients of radon that strongly govern the result of the PBPK modeling. (author)

  3. Fabrication and characterization of dysprosia and alumina based inert matrix neutron absorbers

    Among the elements of the lanthanides series, dysprosium has interesting nuclear properties. Its high thermal neutron absorption cross-section makes it a good neutron absorber. The best ceramic compound apt for nuclear use is its oxide, the disprosia (Dy2O3). In order to fabricate neutron absorbers diluted in an inert matrix, it is relevant to study the preparation of a ceramic compound based on alumina (Al2O3) and disprosia. In this work, we characterize a particular composition (44,5wt% Dy2O3, 55,5wt% Al2O3) by determining the geometrical density, microstructure and phase formation. The chosen composition corresponds to the lowest temperature eutectic of the alumina-disprosia system, allowing the sintering to proceed at 1700 oC in air. Comparing the data of the green and sinterized pellets, the relative shrinking is of about 17 %, in the same proportion both for diameter and length. The corresponding volumetric reduction is of about 43 %, indicating an increase of the relative geometric density of ∼ 70 %. X-ray diffraction analysis shows the existence of two phases corresponding to the lower eutectic: Dy3Al5O12 and Al2O3. The calculated theoretical density is ∼ 5.2 g/cm3. Consequently, the relative density of the pellets is 92 %, indicating the feasibility for the fabrication of the proposed material. In a near future, samples will be irradiated to evaluate their behavior for nuclear use.

  4. Supramolecular Packing Controls H₂ Photocatalysis in Chromophore Amphiphile Hydrogels.

    Weingarten, Adam S; Kazantsev, Roman V; Palmer, Liam C; Fairfield, Daniel J; Koltonow, Andrew R; Stupp, Samuel I

    2015-12-01

    Light harvesting supramolecular assemblies are potentially useful structures as components of solar-to-fuel conversion materials. The development of these functional constructs requires an understanding of optimal packing modes for chromophores. We investigated here assembly in water and the photocatalytic function of perylene monoimide chromophore amphiphiles with different alkyl linker lengths separating their hydrophobic core and the hydrophilic carboxylate headgroup. We found that these chromophore amphiphiles (CAs) self-assemble into charged nanostructures of increasing aspect ratio as the linker length is increased. The addition of salt to screen the charged nanostructures induced the formation of hydrogels and led to internal crystallization within some of the nanostructures. For linker lengths up to seven methylenes, the CAs were found to pack into 2D crystalline unit cells within ribbon-shaped nanostructures, whereas the nine methylene CAs assembled into long nanofibers without crystalline molecular packing. At the same time, the different molecular packing arrangements after charge screening led to different absorbance spectra, despite the identical electronic properties of all PMI amphiphiles. While the crystalline CAs formed electronically coupled H-aggregates, only CAs with intermediate linker lengths showed evidence of high intermolecular orbital overlap. Photocatalytic hydrogen production using a nickel-based catalyst was observed in all hydrogels, with the highest turnovers observed for CA gels having intermediate linker lengths. We conclude that the improved photocatalytic performance of the hydrogels formed by supramolecular assemblies of the intermediate linker CA molecules likely arises from improved exciton splitting efficiencies due to their higher orbital overlap. PMID:26593389

  5. Macroporous chitosan hydrogels: Effects of sulfur on the loading and release behaviour of amino acid-based compounds.

    Elviri, Lisa; Asadzadeh, Maliheh; Cucinelli, Roberta; Bianchera, Annalisa; Bettini, Ruggero

    2015-11-01

    Chitosan is a biodegradable, biocompatible polymer of natural origin widely applied to the preparation of functional hydrogels suitable for controlled release of drugs, peptides and proteins. Non-covalent interactions, expecially ionic interactions, are the main driver of the loading and release behaviour of amino acids or peptides from chitosan hydrogels. With the aim to improve the understanding of the mechanisms governing the behaviour of chitosan hydrogels on peptide uptake and delivery, in this paper the attention was focused on the role played by sulfur on the interactions of chitosan hydrogels with sulfur-containing amino acids (AA) and peptides. Hence, loading and release experiments on cysteine, cystine and glutathione (SH containing amino acid, dipeptide and tripeptide, respectively) as well as on glycine and valine as apolar amino acids were carried out. For these puroses, chitosan hydrogels were prepared in an easy and reproducible manner by a freeze-gelation process on a poly-L-lysine coated support. The hydrogel surface pore size, uniformity and distribution were tested. Optimal results (D50 = 26 ± 4 μm) were obtained by using the poly-L-lysine positively-charged surface. The loading results gathered evidenced that the sulfur-containing molecules presented an increased absorption both in terms of rate and extent by chitosan hydrogels with respect to nonpolar amino acids, mainly due to ionic and hydrogen bond interactions. ATR-FTIR analysis carried out on chitosan hydrogels, with and without the AA related compounds to study putative interactions, supported these apparent sulfur-dependent results. Finally, chitosan hydrogels displayed excellent retention capabilities (AA release <5%) for all AA, strongly supporting the use of chitosan hydrogels as matrix for controlled drug release. PMID:26256323

  6. Synthesis and properties of hectorite/poly(AM/IA) nanocomposite hydrogels with high gel strength

    Lan Wang; Wenzhong Cheng; Tao Wan; Ziwen Hu; Min Xu; Ruixiang Li; Chuzhang Zou

    2015-01-01

    A novel hectorite/poly(AM/IA)nanocomposite hydrogel was synthesized by inverse microemulsion polymerization. The influence of hectorite amount on water absorbency rate, gel strength and shearresistance was investigated. Dynamic viscoelasticity behaviour of the nanocomposite hydrogels was also studied. The nanocomposite hydrogels showed suitable water absorbency and shear-resistance, high gel strength, solid-like behaviour in the whole oscillation frequency region and enhanced viscoelastic behaviours under high stress. TEM indicated that the as-synthesized hydrogel particles were regular and spherical in shape with an average particle size of 43 nm in the range of 30-65 nm.

  7. Preparation of pH-sensitive poly(ethylene oxide) hydrogels grafted by γ-ray irradiation and their applications for drug delivery system

    Hydrogels are three-dimensional networks of hydrophilic polymers held together by crosslinks of covalent bonds or ionic bonds and secondary forces in the form of hydrogen bonds or hydrophobic interactions. Environmentally sensitive hydrogels have an enormous potential for various applications. Either pH-sensitive and/or temperature- sensitive hydrogels can be used for a site-specific controlled drug delivery. Especially, pH-sensitive hydrogels have been most frequently used to develop controlled release formulations for oral administration. All the pH-sensitive hydrogels contain pendent acidic, for example carboxylic and sulfonic acids, or basic, for example ammonium salts, groups that either accept or release protons in response to changes in environmental pH[3-5]. These ionic hydrogels are the swollen polymer networks which show sudden or gradual changes in their dynamic and equilibrium swelling behavior as a result of changing the external pH. In these gels, ionization occurs when the pH of the environment is above the pKa of the ionizable group . As the degree of ionization increases (pH increase in the system), the number of fixed charges increases, resulting in increased electrostatic repulsions between the chains. Irradiation, especially if combined with simultaneous sterilization of the product, is a very convenient tool for the synthesis of hydrogels. Radiation processing has many advantages over other conventional methods. For initiation processes, radiation differs from chemical initiation. In radiation processing, no catalysts or additives are needed to initiate the reaction. The advantages of the radiation methods are that they are relatively simple, and moreover, the degree of crosslinking, which strongly determines the extent of swelling in hydrogels, can be controlled easily by varying the absorbed dose. Therefore, these methods are found to be very useful in preparing hydrogels for medical applications, where even a small contamination is

  8. Acoustic perfect absorber based on metasurface with deep sub-wavelength thickness (Conference Presentation)

    Assouar, Badreddine; Li, Yong

    2016-04-01

    The concept of the coiling up space, based on which artificial structures could exhibit extreme acoustic properties, such as high refractive index, double negativity, near-zero index, etc., have been investigated intensively recently due to the fascinating underlying physics and diverse potential applications [1-3]. One of the most important functionality is the ability to shrink bulky structures into deep sub-wavelength scale. It is therefore intuitive to prospect that the concept of coiling up space, if could be extended into the perforated system, will benefit to significantly reduce the total thickness while keeping total absorption. Conventional acoustic absorbers require a structure with a thickness comparable to the working wavelength, resulting major obstacles in real applications in low frequency range. We present a metasurface-based perfect absorber capable of achieving the total absorption of acoustic wave in extremely low frequency region. The metasurface possessing a deep sub-wavelength thickness down to a feature size of ~ lambda/223 is composed of a perforated plate and a coiled coplanar air chamber. Simulations based on fully coupled acoustic with thermodynamic equations and theoretical impedance analysis are utilized to reveal the underlying physics and the acoustic performances, showing an excellent agreement. Our realization should have high impact on amount of applications due to the extremely thin thickness, easy fabrication and high efficiency of the proposed structure. References 1. Z. Liang and J. Li, Phys. Rev. Lett. 108, 114301 (2012). 2. Y. Li, B. Liang, X. Tao, X. F. Zhu, X. Y. Zou, and J. C. Cheng, Appl. Phys. Lett. 101, 233508 (2012). 3. Y. Xie, W. Wang, H. Chen, A. Konneker, B. I. Popa, and S. A. Cummer, Nat. Commun. 5, 5553 (2014).

  9. New biodegradable dextran-based hydrogels for protein delivery: Synthesis and characterization.

    Pacelli, Settimio; Paolicelli, Patrizia; Casadei, Maria Antonietta

    2015-08-01

    A new derivative of dextran grafted with polyethylene glycol methacrylate through a carbonate bond (DEX-PEG-MA) has been synthesized and characterized. The photo-crosslinking reaction of DEX-PEG-MA allowed the obtainment of biodegradable networks tested for their mechanical and release properties. The new hydrogels were compared with those made of dextran methacrylate (DEX-MA), often employed as drug delivery systems of small molecules. The inclusion of PEG as a spacer created additional interactions among the polymeric chains improving the extreme fragility and lack of hardness typical of gels made of DEX-MA. Moreover, the different behavior in terms of swelling and degradability of the networks was able to affect the release of a model macromolecule over time, making DEX-PEG-MA matrices suitable candidates for the delivery of high molecular weight peptides. Interestingly, the combination of the two dextran derivatives showed intermediate ability to modulate the release of high molecular weight macromolecules. PMID:25933541

  10. Development of a Biosensor for Environmental Monitoring Based on Microalgae Immobilized in Silica Hydrogels

    Claude Durrieu

    2012-12-01

    Full Text Available A new biosensor was designed for the assessment of aquatic environment quality. Three microalgae were used as toxicity bioindicators: Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. These microalgae were immobilized in alginate and silica hydrogels in a two step procedure. After studying the growth rate of entrapped cells, chlorophyll fluorescence was measured after exposure to (3-(3,4-dichlorophenyl-1,1-dimethylurea (DCMU and various concentrations of the common herbicide atrazine. Microalgae are very sensitive to herbicides and detection of fluorescence enhancement with very good efficiency was realized. The best detection limit was 0.1 µM, obtained with the strain C. reinhardtii after 40 minutes of exposure.

  11. Development of a biosensor for environmental monitoring based on microalgae immobilized in silica hydrogels.

    Ferro, Yannis; Perullini, Mercedes; Jobbagy, Matias; Bilmes, Sara A; Durrieu, Claude

    2012-01-01

    A new biosensor was designed for the assessment of aquatic environment quality. Three microalgae were used as toxicity bioindicators: Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. These microalgae were immobilized in alginate and silica hydrogels in a two step procedure. After studying the growth rate of entrapped cells, chlorophyll fluorescence was measured after exposure to (3-(3,4-dichlorophenyl)-1,1-dimethylurea) (DCMU) and various concentrations of the common herbicide atrazine. Microalgae are very sensitive to herbicides and detection of fluorescence enhancement with very good efficiency was realized. The best detection limit was 0.1 µM, obtained with the strain C. reinhardtii after 40 minutes of exposure. PMID:23223083

  12. Development of Bioadhesive Chitosan Superporous Hydrogel Composite Particles Based Intestinal Drug Delivery System

    Hitesh Chavda

    2013-01-01

    Full Text Available Bioadhesive superporous hydrogel composite (SPHC particles were developed for an intestinal delivery of metoprolol succinate and characterized for density, porosity, swelling, morphology, and bioadhesion studies. Chitosan and HPMC were used as bioadhesive and release retardant polymers, respectively. A 32 full factorial design was applied to optimize the concentration of chitosan and HPMC. The drug loaded bioadhesive SPHC particles were filled in capsule, and the capsule was coated with cellulose acetate phthalate and evaluated for drug content, in vitro drug release, and stability studies. To ascertain the drug release kinetics, the drug release profiles were fitted for mathematical models. The prepared system remains bioadhesive up to eight hours in intestine and showed Hixson-Crowell release with anomalous nonfickian type of drug transport. The application of SPHC polymer particles as a biomaterial carrier opens a new insight into bioadhesive drug delivery system and could be a future platform for other molecules for intestinal delivery.

  13. An evaluation of the design and performance for a new neutron absorber based on an artificial rare-earth compound

    Highlights: • A design of neutron absorber using artificial rare earth compound (radioactive wastes) was proposed for the criticality control of spent fuel storage. • The performance of the neutron absorber was evaluated in terms of the: (1) criticality control ability under compositions of various artificial rare earth compounds (2) stability for a long period of time (3) physical and chemical durability. • It can contribute to an increase in the efficient disposal of radioactive waste, as well as the providing economic benefits. - Abstract: In this study, a neutron absorber based on an artificial rare earth compound, which is a radioactive waste generated from pyro-process, is proposed for use in spent fuel storages. To secure the stable control of criticality with physical and chemical durability, a neutron absorber was designed and fabricated using borosilicate glass and a rare earth compound. The performance of the developed neutron absorber was evaluated in terms of the: (1) criticality controllability with various artificial rare earth compositions, (2) stability after neutron irradiation generated from the spent fuel, (3) radioactivity of the neutron absorber, and (4) physical and chemical properties. Our results show that the neutron absorber can successfully control the criticality regardless of the artificial rare earth composition. Also, we demonstrate that the neutron absorber can be utilized without any additional radiation shielding of the spent fuel storages for a long period of time (more than 100 years). In addition, analysis shows that the absorber has sufficient physical and chemical strength for use in spent fuel storage. We expect that this study will help to minimize the number of radioactive waste storage sites as well as reduce the disposal costs

  14. Gum karaya based hydrogel nanocomposites for the effective removal of cationic dyes from aqueous solutions

    Mittal, Hemant; Maity, Arjun; Ray, Suprakas Sinha

    2016-02-01

    Biodegradable hydrogel nanocomposites (HNC) of gum karaya (GK) grafted with poly(acrylic acid) (PAA) incorporated silicon carbide nanoparticles (SiC NPs) were synthesized using the in situ graft copolymerization method and tested for the adsorption of cationic dyes from aqueous solution. The structure and morphology of the HNC were characterized using different spectroscopic and microscopic techniques. The results showed that the surface area and porosity of the hydrogel polymer significantly increased after nanocomposite formation with SiC NPs. The HNC was employed for the removal of cationic dyes, i.e., malachite green (MG) and rhodamine B (RhB) from the aqueous solution. The HNC was found to remove 91% (MG) and 86% (RhB) of dyes with a polymer dose of 0.5 and 0.6 g l-1 in neutral medium, respectively. The adsorption process was found to be highly pH dependent and followed the pseudo-second-order rate model. The adsorption isotherm data fitted well with the Langmuir adsorption isotherm with a maximum adsorption capacity of 757.57 and 497.51 mg g-1 for MG and RhB, respectively. Furthermore, the HNC was demonstrated as a versatile adsorbent for the removal of both cationic and anionic dyes from the simulated wastewater. The HNC showed excellent regeneration capacity and was successfully used for the three cycles of adsorption-desorption. In summary, the HNC has shown its potential as an environment friendly and efficient adsorbent for the adsorption of cationic dyes from contaminated water.

  15. In vivo bioluminescence imaging for viable human neural stem cells incorporated within in situ gelatin hydrogels

    Hwang, Do Won; Park, Kyung Min; Shim, Hye-kyung; Jin, Yeona; Oh, Hyun Jeong; Oh, So Won; Lee, Song; Youn, Hyewon; Joung, Yoon Ki; Lee, Hong J.; Kim, Seung U.; Park, Ki Dong; Lee, Dong Soo

    2014-01-01

    Background Three-dimensional (3D) hydrogel-based stem cell therapies contribute to enhanced therapeutic efficacy in treating diseases, and determining the optimal mechanical strength of the hydrogel in vivo is important for therapeutic success. We evaluated the proliferation of human neural stem cells incorporated within in situ-forming hydrogels and compared the effect of hydrogels with different elastic properties in cell/hydrogel-xenografted mice. Methods The gelatin-polyethylene glycol-ty...

  16. Stimuli-Responsive Super Absorbent Copolymers for Industrial Waste Treatment

    Two hydrogels were prepared by gamma radiation copolymerization. The first hydrogel was based on different ratios of acrylic acid (AAc) and methacrylic acid (MAc) monomers, whereas the second was based on different ratios of poly (vinyl alcohol) and poly (ethylene glycol) (PVA/PEG). The hydrogels were characterized by IR spectroscopy and thermogravimetric analysis (TGA). The effect of temperature and pH on the degree of swelling of both hydrogels was also studied. The dye uptake of basic and direct dyestuffs was studied for the hydrogel based on AAc/MAc. Moreover, the metal uptake was studied for the hydrogel based on PVA/PEG. The results showed that the gel fraction of AAc is relatively higher than MAc, while, the gel fraction of AAc/MAc hydrogels decreased slightly with increasing the ratio of MAc monomer in the initial solution. The thermal study showed that PAAc hydrogel displayed higher thermal stability than PMAc and AAc/MAc hydrogels, over the studied compositions. However, the thermal study showed that PVA/PEG hydrogels displayed higher thermal stability than PVA over the studied compositions. The results showed that PAAc hydrogel reached equilibrium swelling state in water after four hours, whereas PMAc and AAc/MAc hydrogels reached the equilibrium after seven hours. It was found that the swelling of

  17. Nanostructured composites based on carbon nanotubes and epoxy resin for use as radar absorbing materials

    Silva, Valdirene Aparecida [Instituto Tecnologico de Aeronautica (ITA), Sao Jose dos Campos, SP (Brazil); Folgueras, Luiza de Castro; Candido, Geraldo Mauricio; Paula, Adriano Luiz de; Rezende, Mirabel Cerqueira, E-mail: mirabelmcr@iae.cta.br [Instituto de Aeronautica e Espaco (IAE), Sao Jose dos Campos, SP (Brazil). Div. de Materiais; Costa, Michelle Leali [Universidade Estadual Paulista Julio de Mesquita Filho (DMT/UNESP), Guaratingueta, SP (Brazil). Dept. de Materiais e Tecnologia

    2013-07-01

    Nanostructured polymer composites have opened up new perspectives for multifunctional materials. In particular, carbon nanotubes (CNTs) present potential applications in order to improve mechanical and electrical performance in composites with aerospace application. The combination of epoxy resin with multi walled carbon nanotubes results in a new functional material with enhanced electromagnetic properties. The objective of this work was the processing of radar absorbing materials based on formulations containing different quantities of carbon nanotubes in an epoxy resin matrix. To reach this objective the adequate concentration of CNTs in the resin matrix was determined. The processed structures were characterized by scanning electron microscopy, rheology, thermal and reflectivity in the frequency range of 8.2 to 12.4 GHz analyses. The microwave attenuation was up to 99.7%, using only 0.5% (w/w) of CNT, showing that these materials present advantages in performance associated with low additive concentrations (author)

  18. L-band passively harmonic mode-locked fiber laser based on a graphene saturable absorber

    We have proposed and demonstrated an L-band passively harmonic mode-locked fiber laser based on a graphene saturable absorber (SA). By adjusting the pump power and the polarization controller, we have experimentally observed L-band fundamental and harmonic mode-locked optical pulses. The fundamental optical pulse has the duration of 1.3 ps, and the maximum average output power of 13.16 mW at the incident pump power of 98.8 mW. The order of the harmonic mode-locked optical pulses can be changed over the range from the second to the fourth. From the experimental results, we deduced that the likely origin of the harmonic mode-locked self-stabilization was the result of global and local soliton interactions induced by the unstability continuous wave (CW) components

  19. Narrow band absorber based on a dielectric nanodisk array on silver film

    Callewaert, F.; Chen, S.; Butun, S.; Aydin, K.

    2016-07-01

    The simulations of normally incident visible light absorption in a periodic array of dielectric nanodisks on the top of a silver film are presented. Electromagnetic simulations indicate narrow resonances with absorption intensities as large as 95%. The absorption enhancement due to the periodic array can be as high as a factor of 30 compared to an equivalent dielectric film on top of a silver mirror. A parametric study shows that the resonance characteristics and the number of modes can be easily tuned and controlled by the refractive index and the geometric parameters of the nanodisks. In particular, the structure can be tuned to have either a single or two absorption peaks. The characteristics of the two main resonance peaks are described in detail using the simulated electric field profiles and the dispersion relation. Proposed narrowband absorber design utilizing continuous metal films and nanostructured dielectric arrays could be used for narrow-band absorption filters, refractive-index based biosensing applications and thermal emitters.

  20. Phase based stiffness tuning algorithm for a magnetorheological elastomer dynamic vibration absorber

    This paper presents a phase based stiffness tuning algorithm to overcome the uncertainty of the relation between the magnetic current and the natural frequency for magnetorheological elastomer (MRE) dynamic vibration absorbers (DVA) caused by the nonlinearity of the MRE. The phase difference of the relative acceleration of the DVA mass and the absolute acceleration of the primary system was used to check whether the natural frequency of the DVA is adjusted to the excitation frequency. The magnetic current was controlled by the phase difference, which made the proposed algorithm not rely on the model of the MRE DVA. Both the simulation and the experiment demonstrate that the proposed algorithm is efficient for MRE DVA in rapidly tracking the excitation frequency. (paper)

  1. Thermoresponsive and bioactive poly(vinyl ether)-based hydrogels synthesized by radiation copolymerization and photochemical immobilization

    A thermoresponsive hydrogel was synthesized by radiation copolymerization of ethylene glycol vinyl ether (EGVE) and butyl vinyl ether (BVE) in the presence of cross-linking agent diethylene glycol divinyl ether. The gel was modified by a cell adhesion factor RGD by photochemical immobilization technique. While the unmodified hydrogel shows fully hydrated form at low temperatures (+4 oC) and it extensively dehydrates at 37 oC, the biomodified hydrogel still kept its thermoresponsive character after immobilization. The effectiveness of immobilization was checked with FTIR-ATR and XPS. The use of bioactive thermoresponsive hydrogels in cell culture applications was investigated. For this purpose, cell culture experiments were realized by L929 mouse fibroblasts. Cell attachment experiments revealed the effect of immobilized RGD with higher values of cell attachment (∼85%), which were obtained especially in the absence of serum. The thermoresponsive character of the hydrogel was useful for the application of low-temperature treatment in order to recover the attached viable cells from the surface of the hydrogel without using trypsin. When the culture temperature was decreased from 37 to 10 deg. C for 30 min ∼80% of the cells were detached from the hydrogel surface

  2. Tough and multi-responsive hydrogel based on the hemicellulose from the spent liquor of viscose process.

    Du, Jian; Li, Bin; Li, Chao; Zhang, Yuedong; Yu, Guang; Wang, Haisong; Mu, Xindong

    2016-07-01

    The hemicellulose isolated from the spent liquor of a viscose process was successfully utilized to prepare hydrogels by the graft copolymerization of acrylic acid (AA) with hemicellulose. The hemicellulose and prepared hydrogel were characterized by Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance ((13)C NMR). Under the optimum preparation conditions, the highest compressive strength and strain at break of the resultant hydrogel were 105.1±12.9kPa and 34.8%, respectively. Furthermore, the maximum equilibrium swelling degree of prepared hydrogel was 192. Also, the hydrogel could rapidly respond to pH, salt and ethanol. Taken together, the prepared hydrogels had great mechanical and multi-responsive properties. Thus, the prepared hydrogels had a great potential application in drug release, water treatment and cell immobilization. In addition, the utilization of alkaline extracted hemicellulose from the viscose fiber factory has huge market potential and economic benefits. PMID:27064089

  3. Recent developments of smart electromagnetic absorbers based polymer-composites at gigahertz frequencies

    Idris, Fadzidah Mohd.; Hashim, Mansor; Abbas, Zulkifly; Ismail, Ismayadi; Nazlan, Rodziah; Ibrahim, Idza Riati

    2016-05-01

    The rapid increase in electromagnetic interference has received a serious attention from researchers who responded by producing a variety of radar absorbing materials especially at high gigahertz frequencies. Ongoing investigation is being carried out in order to find the best absorbing materials which can fulfill the requirements for smart absorbing materials which are lightweight, broad bandwidth absorption, stronger absorption etc. Thus, to improve the absorbing capability, several important parameters need to be taken into consideration such as filler type, loading level, type of polymer matrix, physical thickness, grain sizes, layers and bandwidth. Therefore, this article introduces the electromagnetic wave absorption mechanisms and then reveals and reviews those parameters that enhance the absorption performance.

  4. Radiation processing of sago hydrogel thin film

    Research study in the production of sago hydrogel sheet for wound dressings application by radiation process using high-energy electron beam machine (3 MeV) has been well established at MINT. However, producing thin film sago hydrogel is another potential usage of this sago hydrogel. The research activity is to look upon the possibility of utilize low-energy electron beam, Curetron (200 keV) for this purpose. The studies are concentrate on the radiation parameters such as beam current, voltage and dosage, thickness of sago hydrogel and density of polyvinyl alcohol solution for comparison purpose. The studies reveal that crosslinking of sago hydrogel depend on thickness of the material exposed to electron beam i.e. thin sample gives higher degree of crosslink compared to thicker sample, at specific dosage and beam current. Above 0.5 mm thickness, the sago hydrogel cannot be crosslinked by low energy electron beam. The results also show that for Curetron 8 mA is the optimum beam current for effective crosslinking process of sago hydrogel. The penetration of electron beam by Curetron depends on density, based on the gel fraction of PVA crosslink where 20% PVA has higher gel fraction than 25% PVA at specific dosage and thickness of sample. From the study using high-energy electron beam machine (3 MeV), the degree of crosslink reduced with increasing thickness of sago hydrogel for the voltage less than 0.75 MeV. (author)

  5. Swelling properties of cassava starch grafted with poly (potassium acrylate-co-acrylamide) superabsorbent hydrogel prepared by ionizing radiation

    Barleany, Dhena Ria, E-mail: dbarleany@yahoo.com; Ulfiyani, Fida; Istiqomah, Shafina; Rahmayetty [Department of Chemical Engineering, University of Sultan Ageng Tirtayasa, Cilegon, Banten (Indonesia); Heriyanto, Heri; Erizal [Centre for Application of Isotopes and Radiation, Jakarta (Indonesia)

    2015-12-29

    Natural and synthetic hydrophylic polymers can be phisically or chemically cross-linked in order to produce hydrogels. Starch based hydrogels grafted with copolymers from acrylic acid or acrylamide have become very popular for water absorbent application. Superabsorbent hydrogels made from Cassava starch grafted with poly (potassium acrylate-co-acrylamide) were prepared by using of ϒ-irradiation method. Various important parameters such as irradiation doses, monomer to Cassava starch ratio and acrylamide content were investigated. The addition of 7,5 % w w{sup −1} acrylamide into the reaction mixture generated a starch graft copolymer with a water absorption in distilled water as high as 460 g g{sup −1} of its dried weight. The effectivity of hydrogel as superabsorbent for aqueous solutions of NaCl and urea was evaluated. The obtained hydrogel showed the maximum absorptions of 317 g g{sup −1} and 523 g g{sup −1} for NaCl and urea solution, respectively (relative to its own dry weight). The structure of the graft copolymer was analyzed by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM)

  6. Swelling properties of cassava starch grafted with poly (potassium acrylate-co-acrylamide) superabsorbent hydrogel prepared by ionizing radiation

    Natural and synthetic hydrophylic polymers can be phisically or chemically cross-linked in order to produce hydrogels. Starch based hydrogels grafted with copolymers from acrylic acid or acrylamide have become very popular for water absorbent application. Superabsorbent hydrogels made from Cassava starch grafted with poly (potassium acrylate-co-acrylamide) were prepared by using of ϒ-irradiation method. Various important parameters such as irradiation doses, monomer to Cassava starch ratio and acrylamide content were investigated. The addition of 7,5 % w w−1 acrylamide into the reaction mixture generated a starch graft copolymer with a water absorption in distilled water as high as 460 g g−1 of its dried weight. The effectivity of hydrogel as superabsorbent for aqueous solutions of NaCl and urea was evaluated. The obtained hydrogel showed the maximum absorptions of 317 g g−1 and 523 g g−1 for NaCl and urea solution, respectively (relative to its own dry weight). The structure of the graft copolymer was analyzed by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM)

  7. Swelling properties of cassava starch grafted with poly (potassium acrylate-co-acrylamide) superabsorbent hydrogel prepared by ionizing radiation

    Barleany, Dhena Ria; Ulfiyani, Fida; Istiqomah, Shafina; Heriyanto, Heri; Rahmayetty, Erizal

    2015-12-01

    Natural and synthetic hydrophylic polymers can be phisically or chemically cross-linked in order to produce hydrogels. Starch based hydrogels grafted with copolymers from acrylic acid or acrylamide have become very popular for water absorbent application. Superabsorbent hydrogels made from Cassava starch grafted with poly (potassium acrylate-co-acrylamide) were prepared by using of ϒ-irradiation method. Various important parameters such as irradiation doses, monomer to Cassava starch ratio and acrylamide content were investigated. The addition of 7,5 % w w-1 acrylamide into the reaction mixture generated a starch graft copolymer with a water absorption in distilled water as high as 460 g g-1 of its dried weight. The effectivity of hydrogel as superabsorbent for aqueous solutions of NaCl and urea was evaluated. The obtained hydrogel showed the maximum absorptions of 317 g g-1 and 523 g g-1 for NaCl and urea solution, respectively (relative to its own dry weight). The structure of the graft copolymer was analyzed by using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM).

  8. IPN hydrogels based on PNIPAAm and PVA-Ma networks: characterization through measure of LCST, swelling ratio and mechanical properties - doi: 10.4025/actascitechnol.v34i2.15019

    Adriana Cristina Wenceslau

    2012-03-01

    Full Text Available IPN hydrogels based on chemically modified poly(vinyl alcohol (or PVA-Ma, with different degrees of substitution (DS, and poly(N-isopropylacrylamide (or PNIPAAm were obtained and characterized through measures of LCST, swelling ratio and mechanical properties. Linear PVA-Ma with several DS were obtained through the chemical reaction of PVA with glycidyl methacrylate (GMA. The DS of various PVA-Ma were determined through 1H NMR spectroscopy. Two steps were used for preparation the PVA-Ma/PNIPAAm membrane hydrogels. In the first step the PVA-Ma hydrogels (using PVA-Ma with different DS were prepared by reaction of double bonds on PVA-Ma, using the persulfate/TEMED system. Using a photoreaction pathway in the second step, PNIPAAm network was prepared within the parent PVA-Ma network at different PVA-Ma/NIPAAm ratios. The studies show that degree of swelling ratio (SR of PVA-Ma/PNIPAAm IPN hydrogels is dependent of temperature. The LCST for each IPN-hydrogel was determined by measuring the intensity of light transmitted through the hydrogel. The LCST of the IPN hydrogels ranged from 34.6 to 38.1oC. The elastic modules of swollen IPN hydrogels increased from 25 to 35oC but decreased by further warming to 45oC. The LCST, swelling ratio and mechanical properties of PVA-Ma/PNIPAAm IPN hydrogels can be tailored by tuning the PVA-Ma/NIPAAm ratio.

  9. Evaluation of absorbed doses in voxel-based and simplified models for small animals

    Internal dosimetry in non-human biota is desirable from the viewpoint of radiation protection of the environment. The International Commission on Radiological Protection (ICRP) proposed Reference Animals and Plants using simplified models, such as ellipsoids and spheres and calculated absorbed fractions (AFs) for whole bodies. In this study, photon and electron AFs in whole bodies of voxel-based rat and frog models have been calculated and compared with AFs in the reference models. It was found that the voxel-based and the reference frog (or rat) models can be consistent for the whole-body AFs within a discrepancy of 25 %, as the source was uniformly distributed in the whole body. The specific absorbed fractions (SAFs) and S values were also evaluated in whole bodies and all organs of the voxel-based frog and rat models as the source was distributed in the whole body or skeleton. The results demonstrated that the whole-body SAFs reflect SAFs of all individual organs as the source was uniformly distributed per mass within the whole body by about 30 % uncertainties with exceptions for body contour (up to -40 %) for both electrons and photons due to enhanced radiation leakages, and for the skeleton for photons only (up to +185 %) due to differences in the mass attenuation coefficients. For nuclides such as 90Y and 90Sr, which were concentrated in the skeleton, there were large differences between S values in the whole body and those in individual organs, however the whole-body S values for the reference models with the whole body as the source were remarkably similar to those for the voxel-based models with the skeleton as the source, within about 4 and 0.3 %, respectively. It can be stated that whole-body SAFs or S values in simplified models without internal organs are not sufficient for accurate internal dosimetry because they do not reflect SAFs or S values of all individual organs as the source was not distributed uniformly in whole body. Thus, voxel-based models

  10. Low temperature y-ray spectrometers based on bulk superconducting and dielectric absorber crystals

    Netel, H

    1999-11-19

    Many areas of research rely on the detection of radiation, in the form of single photons or particles. By measuring the photons or particles coming from an object a lot can be learned about the object under study. In some cases there is a simple need to know the number of photons coming from the source. In cases like this a simple counter, like a Geiger-Mueller survey meter, will suffice. In other cases one want to know the spectral distribution of the photons coming from the source. In cases like that a spectrometer is needed that can distinguish between photons with different energies, like a diffraction or transmission grating. The work presented in this thesis focused on the development of a new generation broad band spectrometer that has a high energy resolving power, combined with a high absorption efficiency for photon energies above 10 keV and up to 500 keV. The spectrometers we are developing are based on low-temperature sensors, like superconducting tunnel junctions or transition edge sensors, that are coupled to bulk absorber crystals. We use the low-temperature sensors because they can offer a significant improvement in energy resolving power, compared to conventional spectrometers. We couple the low-temperature sensors to bulk absorber crystals to increase the absorption efficiency. In this chapter I introduce different types of radiation detectors and spectrometers and areas where they are being used. I also discuss the history and motivation of low-temperature spectrometers and show some of the impressive results that have been achieved in this field over the last few years. Finally I discuss the outline of this thesis.

  11. Preparation and characterization of ceramic neutron absorbers based on dysprosia and gadolinia

    Among the elements of the lanthanide series, dysprosium and gadolinium have interesting nuclear properties. Due to their high thermal neutron absorption cross-section they are good neutron absorbers. The only compounds suitable for nuclear use are their oxides, dysprosia (Dy2O3) and gadolinia (Gd2O3). To fabricate neutron absorbers diluted in an inert matrix, e.g. alumina (Al2O3), it is relevant to study the preparation of a ceramic compound based on alumina (Al2O3) and dysprosia or gadolinia. In this work, we characterize four different nominal compositions with high contents of gadolinia and dysprosia: (a) (45 wt% Dy2O3, 55 wt% Al2O3), (b) (93 wt% Dy2O3, 7 wt% Al2O3), (c) (50 wt% Gd2O3, 50 wt% Al2O3) and (d) (90 wt% Gd2O3, 10 wt% Al2O3). These compositions were selected as their stoichiometry correspond to the eutectic phases found in the respective phase diagrams, so as to attain sinterization at lower temperatures of approximately 1700oC in air. The investigated parameters are the geometrical density of the pellets, the microstructure and the phases observed using x-ray diffraction. Contraction of the pellets was obtained by measuring the volumetric change between the green and the sintered samples. It was observed that the relative contraction was the same both in thickness and diameter. We discuss the eutectic phase formation and densification observed for the different compositions (author)

  12. An Evaluation on the Criticality Control Ability of a Neutron Absorber based on Artificial Rare Earth Compounds in PLUS7 and WH17x17 Spent Fuel Storage

    Storages have been designed to minimize space due to increasing storage efficiency. Therefore, the neutron absorbers are generally used for the design of dense spent fuel storages. In a previous study, a neutron absorber based on artificial rare earth compounds with a conceptual design was proposed for efficient and economic disposal of spent nuclear fuel. In this study, the design criteria of the neutron absorber are established by performance evaluations of the neutron absorber. In this study, a design criterion of the neutron absorber based on the artificial rare earth compound was established by the sensitivity analysis of the design parameters. The sensitivity estimations were pursued as the material composition, geometrical feature, heterogeneous conditions, and the arrangement of the absorber. The results show that the neutron absorber has an enough margin of the criticality control when the absorber is manufactured by the minimum requirements

  13. An Evaluation on the Criticality Control Ability of a Neutron Absorber based on Artificial Rare Earth Compounds in PLUS7 and WH17x17 Spent Fuel Storage

    Kim, Jae Hyun; Yim, Che Wook; Shin, Chang Ho; Kim, Song Hyun [Hanyang Univ., Seoul (Korea, Republic of); Choe, Jung Hun; Cho, In Hak; Kim, Jong Kyung; Park, Hwan Seo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Hyun Seo; Kim, Jung Ho; Kim, Yoon Ho [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2014-10-15

    Storages have been designed to minimize space due to increasing storage efficiency. Therefore, the neutron absorbers are generally used for the design of dense spent fuel storages. In a previous study, a neutron absorber based on artificial rare earth compounds with a conceptual design was proposed for efficient and economic disposal of spent nuclear fuel. In this study, the design criteria of the neutron absorber are established by performance evaluations of the neutron absorber. In this study, a design criterion of the neutron absorber based on the artificial rare earth compound was established by the sensitivity analysis of the design parameters. The sensitivity estimations were pursued as the material composition, geometrical feature, heterogeneous conditions, and the arrangement of the absorber. The results show that the neutron absorber has an enough margin of the criticality control when the absorber is manufactured by the minimum requirements.

  14. Progress on preparation of xanthan gum based hydrogels%黄原胶水凝胶制备的研究进展

    廖家娥; 刘根起; 杨小利; 史长明

    2012-01-01

    黄原胶水凝胶具有亲水性强、无毒、可降解及生物相容性好等优点,常作超吸水性树脂、药物载体和微胶囊.对黄原胶水凝胶的制备方法进行了综述,并对其发展进行展望.%Xanthan gum based hydrogels have fine performance of hydrophilicity.nontoxidty.biodegradability and biocompatibilit,which can be used for superabsorbant resin,medicine carrier and microcapsules.The preparation techniques of xanthan gum based hydrogels were reviewed and the future of their applications was also forecasted.

  15. Novel Hydrogels from Renewable Resources

    Karaaslan, Muzafer Ahmet

    2011-12-01

    The cell wall of most plant biomass from forest and agricultural resources consists of three major polymers, cellulose, hemicellulose and lignin. Of these, hemicelluloses have gained increasing attention as sustainable raw materials. In the first part of this study, novel pH-sensitive semi-IPN hydrogels based on hemicelluloses and chitosan were prepared using glutaraldehyde as the crosslinking agent. The hemicellulose isolated from aspen was analyzed for sugar content by HPLC, and its molecular weight distribution was determined by high performance size exclusion chromatography. Results revealed that hemicellulose had a broad molecular weight distribution with a fair amount of polymeric units, together with xylose, arabinose and glucose. The effect of hemicellulose content on mechanical properties and swelling behavior of hydrogels were investigated. The semi-IPNs hydrogel structure was confirmed by FT-IR, X-ray study and ninhydrin assay method. X-ray analysis showed that higher hemicellulose contents yielded higher crystallinity. Mechanical properties were mainly dependent on the crosslink density and average molecular weight between crosslinks. Swelling ratios increased with increasing hemicellulose content and were high at low pH values due to repulsion between similarly charged groups. In vitro release study of a model drug showed that these semi-IPN hydrogels could be used for controlled drug delivery into gastric fluid. The aim of the second part of this study was to control the crosslink density and the mechanical properties of hemicellulose/chitosan semi-IPN hydrogels by changing the crosslinking sequence. It has been hypothesized that by performing the crosslinking step before introducing hemicellulose, covalent crosslinking of chitosan would not be hindered and therefore more and/or shorter crosslinks could be formed. Furthermore, additional secondary interactions and crystalline domains introduced through hemicellulose could be favorable in terms of

  16. Microfluidic Distance Readout Sweet Hydrogel Integrated Paper-Based Analytical Device (μDiSH-PAD) for Visual Quantitative Point-of-Care Testing.

    Wei, Xiaofeng; Tian, Tian; Jia, Shasha; Zhu, Zhi; Ma, Yanli; Sun, Jianjun; Lin, Zhenyu; Yang, Chaoyong James

    2016-02-16

    A disposable, equipment-free, versatile point-of-care testing platform, microfluidic distance readout sweet hydrogel integrated paper-based analytical device (μDiSH-PAD), was developed for portable quantitative detection of different types of targets. The platform relies on a target-responsive aptamer cross-linked hydrogel for target recognition, cascade enzymatic reactions for signal amplification, and microfluidic paper-based analytic devices (μPADs) for visual distance-based quantitative readout. A "sweet" hydrogel with trapped glucoamylase (GA) was synthesized using an aptamer as a cross-linker. When target is present in the sample, the "sweet" hydrogel collapses and releases enzyme GA into the sample, generating glucose by amylolysis. A hydrophilic channel on the μPADs is modified with glucose oxidase (GOx) and colorless 3,3'-diaminobenzidine (DAB) as the substrate. When glucose travels along the channel by capillary action, it is converted to H2O2 by GOx. In addition, DAB is converted into brown insoluble poly-3,3'-diaminobenzidine [poly(DAB)] by horseradish peroxidase, producing a visible brown bar, whose length is positively correlated to the concentration of targets. The distance-based visual quantitative platform can detect cocaine in urine with high selectivity, sensitivity, and accuracy. Because the target-induced cascade reaction is triggered by aptamer/target recognition, this method is widely suitable for different kinds of targets. With the advantages of low cost, ease of operation, general applicability, and disposability with quantitative readout, the μDiSH-PAD holds great potential for portable detection of trace targets in environmental monitoring, security inspection, personalized healthcare, and clinical diagnostics. PMID:26765320

  17. Biodegradable In Situ Gel-Forming Controlled Drug Delivery System Based on Thermosensitive Poly(ε-caprolactone)-Poly(ethylene glycol)-Poly(ε-caprolactone) Hydrogel

    Elham Khodaverdi; Ali Golmohammadian; Seyed Ahmad Mohajeri; Gholamhossein Zohuri; Farnaz Sadat Mirzazadeh Tekie; Farzin Hadizadeh

    2012-01-01

    Traditional drug delivery systems which are based on multiple dosing regimens usually pose many disadvantages such as poor compliance of patients and drug plasma level variation. To overcome the obstacles of traditional drug formulations, novel drug delivery system PCL-PEG-PCL hydrogels have been purposed in this study. Copolymers were synthesized by rapid microwave-assisted and conventional synthesis methods. Polymer characterizations were done using gel permeation chromatography and 1H-NMR....

  18. Investigation of biopolymer-based hydrogels as green and heterogeneous catalysts in C-C bond formation

    Kühbeck, Dennis

    2015-01-01

    The present dissertation evaluates the efficacy of different polysaccharides (e.g. chitosan, alginate and kappa-carrageenan) and proteins (e.g. gelatin, collagen, silk fibroin) as possible catalysts for a variety of C-C bond formation reactions. These biopolymers can be obtained in different forms (e.g. hydrogels, mesoporous materials). Among different forms hydrogels are one of the most interesting since they could act as biphasic and heterogeneous systems in chemical transformations and fa...

  19. Vitronectin-Based, Biomimetic Encapsulating Hydrogel Scaffolds Support Adipogenesis of Adipose Stem Cells.

    Clevenger, Tracy N; Hinman, Cassidy R; Ashley Rubin, Rebekah K; Smither, Kate; Burke, Daniel J; Hawker, Craig J; Messina, Darin; Van Epps, Dennis; Clegg, Dennis O

    2016-04-01

    Soft tissue defects are relatively common, yet currently used reconstructive treatments have varying success rates, and serious potential complications such as unpredictable volume loss and reabsorption. Human adipose-derived stem cells (ASCs), isolated from liposuction aspirate have great potential for use in soft tissue regeneration, especially when combined with a supportive scaffold. To design scaffolds that promote differentiation of these cells down an adipogenic lineage, we characterized changes in the surrounding extracellular environment during adipogenic differentiation. We found expression changes in both extracellular matrix proteins, including increases in expression of collagen-IV and vitronectin, as well as changes in the integrin expression profile, with an increase in expression of integrins such as αVβ5 and α1β1. These integrins are known to specifically interact with vitronectin and collagen-IV, respectively, through binding to an Arg-Gly-Asp (RGD) sequence. When three different short RGD-containing peptides were incorporated into three-dimensional (3D) hydrogel cultures, it was found that an RGD-containing peptide derived from vitronectin provided strong initial attachment, maintained the desired morphology, and created optimal conditions for in vitro 3D adipogenic differentiation of ASCs. These results describe a simple, nontoxic encapsulating scaffold, capable of supporting the survival and desired differentiation of ASCs for the treatment of soft tissue defects. PMID:26956095

  20. Poly-γ-Glutamic Acid Nanoparticles Based Visible Light-Curable Hydrogel for Biomedical Application

    József Bakó

    2016-01-01

    Full Text Available Nanoparticles and hydrogels have gained notable attention as promising potential for fabrication of scaffolds and delivering materials. Visible light-curable systems can allow for the possibility of in situ fabrication and have the advantage of optimal applicability. In this study nanogel was created from methacrylated poly-gamma-glutamic acid nanoparticles by visible (dental blue light photopolymerization. The average size of the particles was 80 nm by DLS, and the NMR spectra showed that the methacrylation rate was 10%. Polymerization time was 3 minutes, and a stable nanogel with a swelling rate of 110% was formed. The mechanical parameters of the prepared structure (compression stress 0.73 MPa, and Young’s modulus 0.93 MPa can be as strong as necessary in a real situation, for example, in the mouth. A retaining effect of the nanogel was found for ampicillin, and the biocompatibility of this system was tested by Alamar Blue proliferation assay, while the cell morphology was examined by fluorescence and laser scanning confocal microscopy. In conclusion, the nanogel can be used for drug delivery, or it can be suitable for a control factor in different systems.

  1. Research Progress on Patented Technology of Xnthan Gum Based Hydrogels%黄原胶水凝胶的专利技术的研究进展

    王光新; 王岩; 蔡培培; 张红城

    2015-01-01

    Xanthan gum based hydrogels have fine performance of hydrophilicity, nontoxicity, biodegradability and biocompatibilit, which can be used for superabsorbant resin, medicine carrier and microcapsules.The method technique of xanthan gum based hydrogels was the main object of study of domestic researchers.According to time, the preparation techniques of xanthan gum based hydrogels was reviewed by combining with domestic and foreign patent applications, and the future of their applications on artificial muscles, micro-machinery and bionic equipment was also forecasted.%黄原胶水凝胶具有亲水性强、无毒、可降解及生物相容性好等优点,常作超吸水性树脂、药物载体和微胶囊。黄原胶水凝胶的制备方法成为了国内研究者的主要研究对象。以时间为主线,结合国内外对该产品的专利申请,梳理黄原胶水凝胶制备方法的发展脉络,并对其在人工肌肉、微机械以及仿生器材发展做了展望。

  2. The effect of calcium chloride concentration on alginate/Fmoc-diphenylalanine hydrogel networks.

    Çelik, Ekin; Bayram, Cem; Akçapınar, Rümeysa; Türk, Mustafa; Denkbaş, Emir Baki

    2016-09-01

    Peptide based hydrogels gained a vast interest in the tissue engineering studies thanks to great superiorities such as biocompatibility, supramolecular organization without any need of additional crosslinker, injectability and tunable nature. Fmoc-diphenylalanine (FmocFF) is one of the earliest and widely used example of these small molecule gelators that have been utilized in biomedical studies. However, Fmoc-peptides are not feasible for long term use due to low stability and weak mechanical properties at neutral pH. In this study, Fmoc-FF dipeptides were mechanically enhanced by incorporation of alginate, a biocompatible and absorbable polysaccharide. The binary hydrogel is obtained via molecular self-assembly of FmocFF dipeptide in alginate solution followed by ionic crosslinking of alginate moieties with varying concentrations of calcium chloride. Hydrogel characterization was evaluated in terms of morphology, viscoelastic moduli and diffusional phenomena and the structures were tested as 3D scaffolds for bovine chondrocytes. In vitro evaluation of scaffolds lasted up to 14days and cell viability, sulphated glycosaminoglycan (sGAG) levels, collagen type II synthesis were determined. Our results showed that alginate incorporation into FmocFF hydrogels leads to better mechanical properties and higher stability with good biocompatibility. PMID:27207058

  3. Ionizing radiation in the field of hydrogels used for agriculture and medicine

    The hydrogels, such as homopolymers of acrylamide (AHH type), co-polymers of acrylamide-sodium acrylate (ANACH type) and homopolymers of sodium acrylate (NAHH type), obtained by gamma ray and accelerated electron beam are presented. The effects of the solution chemical composition, swelling medium nature, radiation absorbed dose and radiation absorbed dose rate upon the swelling degree and mechanical strength of these hydrogel types are discussed. Distilled water, physiological serum and 4 N NaCl aqueous solution were used as swelling medium. Radiation absorbed dose has an important effect upon the swelling degree of AHH and ANACH types especially when distilled water is used as swelling medium while the NAHH swelling degree presents a small dependence versus absorbed dose for all swelling medium types. Usually, the swelling degree for all hydrogel types decreases versus absorbed dose and absorbed dose rate and exhibits the higher values for distilled water as swelling medium. The hydrogels mechanical strength exhibits a maximum value versus absorbed dose. The best values for mechanical strength depend on hydrogel type and swelling medium. The used range for absorbed dose was from 2 kGy to 16 kGy. Our types of hydrogels were developed for some applications such as in agriculture (AHH and ANACH types) to maintain soil humidity and in medicine as absorption material for dressing (NAHH types). (author)

  4. Graphene-based Recyclable Photo-Absorbers for High-Efficiency Seawater Desalination.

    Wang, Xiangqing; Ou, Gang; Wang, Ning; Wu, Hui

    2016-04-13

    Today's scientific advances in water desalination dramatically increase our ability to transform seawater into fresh water. As an important source of renewable energy, solar power holds great potential to drive the desalination of seawater. Previously, solar assisted evaporation systems usually relied on highly concentrated sunlight or were not suitable to treat seawater or wastewater, severely limiting the large scale application of solar evaporation technology. Thus, a new strategy is urgently required in order to overcome these problems. In this study, we developed a solar thermal evaporation system based on reduced graphene oxide (rGO) decorated with magnetic nanoparticles (MNPs). Because this material can absorb over 95% of sunlight, we achieved high evaporation efficiency up to 70% under only 1 kW m(-2) irradiation. Moreover, it could be separated from seawater under the action of magnetic force by decorated with MNPs. Thus, this system provides an advantage of recyclability, which can significantly reduce the material consumptions. Additionally, by using photoabsorbing bulk or layer materials, the deposition of solutes offen occurs in pores of materials during seawater desalination, leading to the decrease of efficiency. However, this problem can be easily solved by using MNPs, which suggests this system can be used in not only pure water system but also high-salinity wastewater system. This study shows good prospects of graphene-based materials for seawater desalination and high-salinity wastewater treatment. PMID:27019007

  5. Novel Chromatic Technique Based on Optical Absorbance in Characterizing Mineral Hydraulic Oil Degradation

    C. V. Ossia

    2012-01-01

    Full Text Available A low cost, compact, real-time, and quick measurement optical device based on the absorbance of white light, which comprised of photodiodes in a 3-element color-sensor, feedback diodes, water and temperature sensing element, and so on, was developed and tested in low absorption mineral oil. The device, a deviation from conventional electrical, mechanical, and electrochemical techniques, uses color ratio (CR and total contamination index (TCI parameters based on transmitted light intensity in RGB wavelengths for oil condition monitoring. Test results showed that CR corroborated CIE chromaticity (- Coordinates and increased with oil degradation unlike Saturation and Hue . CR was found to be independent of the particulate contaminants of oil, but dependent on chemical degradation. TCI depended on both chemical degradation and particulate contaminants in oil, being most sensitive in the blue wavelength range and least in the green. Furthermore, results agreed with those of viscometry, total acid number (TAN, and UV-VIS photospectrometry. CR and TCI gave clearer indication of oil degradation than key monitoring parameters like TAN and were found to be effective criteria for characterizing the degradation of hydraulic mineral oils.

  6. Microfiber-based few-layer black phosphorus saturable absorber for ultra-fast fiber laser

    Luo, Zhi-Chao; Guo, Zhi-Nan; Jiang, Xiao-Fang; Luo, Ai-Ping; Zhao, Chu-Jun; Yu, Xue-Feng; Xu, Wen-Cheng; Zhang, Han

    2015-01-01

    Few-layer black phosphorus (BP), as the most alluring graphene analogue owing to its similar structure as graphene and thickness dependent direct band-gap, has now triggered a new wave of research on two-dimensional (2D) materials based photonics and optoelectronics. However, a major obstacle of practical applications for few-layer BPs comes from their instabilities of laser-induced optical damage. Herein, we demonstrate that, few-layer BPs, fabricated through the liquid exfoliation approach, can be developed as a new and practical saturable absorber (SA) by depositing few-layer BPs with microfiber. The saturable absorption property of few-layer BPs had been verified through an open-aperture z-scan measurement at the telecommunication band and the microfiber-based BP device had been found to show a saturable average power of ~4.5 mW and a modulation depth of 10.9%, which is further confirmed through a balanced twin detection measurement. By further integrating this optical SA device into an erbium-doped fiber...

  7. Experimental design of mixture applied to study PVP hydrogels properties crosslinked by ionizing radiation

    Hydrogels are three dimensional hydrophilic crosslinked polymeric networks that have capacity to swell by absorbing water or biological fluids without dissolve. Hydrogels have been widely used in different application fields from agriculture, industry and in biomedicine. The properties of a hydrogel are extremely important in selecting which materials are suitable for a specific application. So mixtures can offer hydrogels with different properties to different applications. The PVP hydrogels were prepared by gamma radiation of an aqueous polymer solution and crosslinked by gamma ray, an effective and simple method for hydrogel formation that offers some advantages over the other techniques. In this work, a mixture experimental design was used to study the relationship between polymer cross-linking and swelling properties of PVP hydrogels with PEG as plasticizer and agar as gellifier. The gel fraction was measured for every mixture specified for the experiment D-optimal designs. (author)

  8. Europium fluoride based luminescent materials: From hydrogels to porous cryogels, and crystalline NaEuF{sub 4} and EuF{sub 3} micro/nanostructures

    Wang, Hongkang; Wang, Yu; Zhang, Jie [Department of Physics and Materials Science and Centre for Functional Photonics, City University of Hong Kong, Hong Kong Special Administrative Region (Hong Kong); Gaponik, Nikolai [Physical Chemistry/Electrochemistry TU Dresden, Bergstr. 66b, 01062 Dresden (Germany); Rogach, Andrey L., E-mail: andrey.rogach@cityu.edu.hk [Department of Physics and Materials Science and Centre for Functional Photonics, City University of Hong Kong, Hong Kong Special Administrative Region (Hong Kong)

    2014-01-15

    Highlights: • Europium fluoride based hydrogels and cryogels are reported. • Emission of Eu{sup 3+} ions is dependent on their existing states and the adopted fluorides (NaF or NH{sub 4}F). • The amorphous NaF- and NH{sub 4}F-mediated cryogels show the strongest emission intensity. -- Abstract: Europium fluoride based hydrogels, porous cryogels, and crystalline NaEuF{sub 4} and EuF{sub 3} nanostructures were prepared by wet chemical route at room temperature by using NaF or NH{sub 4}F as the reactants and gelation agents, in the absence of any other additives. The phase, morphology and thus resultant photoluminescence properties of luminescent products are demonstrated on the basis of the formation and evolution of europium fluoride complexes (EuF{sub 6}{sup 3−}). The characteristic emission of Eu{sup 3+} ions is strongly dependent on their existing states and also the adopted fluorides (both cations and anions of NaF or NH{sub 4}F). The amorphous NaF- and NH{sub 4}F-mediated cryogels with highly porous structure and uniform distribution of optically active Eu{sup 3+} ions show much (one or two order) stronger luminescence intensity than their corresponding hydrogels and crystalline NaEuF{sub 4} and EuF{sub 3} nanostructures.

  9. A novel gene delivery composite system based on biodegradable folate-poly (ester amine) polymer and thermosensitive hydrogel for sustained gene release

    Yang, Yi; Zhao, Hang; Jia, Yanpeng; Guo, Qingfa; Qu, Ying; Su, Jing; Lu, Xiaoling; Zhao, Yongxiang; Qian, Zhiyong

    2016-02-01

    Local anti-oncogene delivery providing high local concentration of gene, increasing antitumor effect and decreasing systemic side effects is currently attracting interest in cancer therapy. In this paper, a novel local sustained anti-oncogene delivery system, PECE thermoresponsive hydrogel containing folate-poly (ester amine) (FA-PEA) polymer/DNA (tumor suppressor) complexes, is demonstrated. First, a tumor-targeted biodegradable folate-poly (ester amine) (FA-PEA) polymer based on low-molecular-weight polyethyleneimine (PEI) was synthesized and characterized, and the application for targeted gene delivery was investigated. The polymer had slight cytotoxicity and high transfection efficiency in vitro compared with PEI 25k, which indicated that FA-PEA was a potential vector for targeted gene delivery. Meanwhile, we successfully prepared a thermoresponsive PECE hydrogel composite containing FA-PEA/DNA complexes which could contain the genes and slowly release the genes into cells. We concluded the folate-poly (ester amine) (FA-PEA) polymer would be useful for targeted gene delivery, and the novel gene delivery composite based on biodegradable folate-poly (ester amine) polymer and thermosensitive PECE hydrogel showed potential for sustained gene release.

  10. Mechanical Behavior of Tough Hydrogels for Structural Applications

    Illeperuma, Widusha Ruwangi Kaushalya

    novel applications. This thesis aims to investigate the broader applications, well beyond those investigated so far. We show fiber reinforced tough hydrogels can dissipate a significant amount of energy at a tunable level of stress, making them suitable for energy absorbing applications such as inner layer of helmets. We develop inexpensive fire-retarding materials using tough hydrogels that provide superior protection from burn injuries. We also study hydrogels as actuators that can be used in soft robotics. Hydrogels contain mostly water and they freeze when the temperature drops below 00C and lose its functions. We demonstrate a new class of hydrogels that do not freeze and hydrogels that partially freeze below water freezing temperature. Partially freezing hydrogels are ideal for cooling applications such as gel packs and non-freezing hydrogels are useful in all the structural applications at low temperatures. This thesis will enable the use of inexpensive hydrogels in a new class of non-traditional structural applications where the mechanical behavior of the hydrogel is of prime importance.

  11. Poly(N-isopropylacrylamide Hydrogels for Storage and Delivery of Reagents to Paper-Based Analytical Devices

    Haydn T. Mitchell

    2015-07-01

    Full Text Available The thermally responsive hydrogel N,N'-methylenebisacrylamide-cross-linked poly(N-isopropylacrylamide (PNIPAM was developed and evaluated as a reagent storage and delivery system for microfluidic paper-based analytical devices (microPADs. PNIPAM was shown to successfully deliver multiple solutions to microPADs in specific sequences or simultaneously in laminar-flow configuration and was found to be suitable for delivering four classes of reagents to the devices: Small molecules, enzymes, antibodies and DNA. PNIPAM was also able to successfully deliver a series of standard glucose solutions to microPADs equipped to perform a colorimetric glucose assay. The results of these tests were used to produce an external calibration curve, which in turn was used to determine the concentration of glucose in sample solutions. Finally, PNIPAM was used to store the enzyme horseradish peroxidase for 35 days under ambient conditions with no significant loss of activity. The combination of PNIPAM and microPADs may allow for more complex assays to be performed on paper-based devices, facilitate the preparation of external calibration curves in the field, and extend the shelf life of microPADs by stabilizing reagents in an easy-to-use format.

  12. Design and performance simulation of a segmented-absorber based muon detection system for high energy heavy ion collision experiments

    Ahmad, S. [University of Kashmir, Srinagar (India); Bhaduri, P.P. [Variable Energy Cyclotron Centre, Kolkata (India); Jahan, H. [Aligarh Muslim University, Aligarh (India); Senger, A. [GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt (Germany); Adak, R.; Samanta, S. [Bose Institute, Kolkata (India); Prakash, A. [Banaras Hindu University, Varanasi (India); Dey, K. [Gauhati University, Guwahati (India); Lebedev, A. [Institute für Kernphysik, Goethe Universität Frankfurt, Frankfurt (Germany); Kryshen, E. [Petersburg Nuclear Physics Institute (PNPI) NRC Kurchatov Institute, Gatchina (Russian Federation); Chattopadhyay, S., E-mail: sub@vecc.gov.in [Variable Energy Cyclotron Centre, Kolkata (India); Senger, P. [GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt (Germany); Bhattacharjee, B. [Gauhati University, Guwahati (India); Ghosh, S.K.; Raha, S. [Bose Institute, Kolkata (India); Irfan, M.; Ahmad, N. [Aligarh Muslim University, Aligarh (India); Farooq, M. [University of Kashmir, Srinagar (India); Singh, B. [Banaras Hindu University, Varanasi (India)

    2015-03-01

    A muon detection system (MUCH) based on a novel concept using a segmented and instrumented absorber has been designed for high-energy heavy-ion collision experiments. The system consists of 6 hadron absorber blocks and 6 tracking detector triplets. Behind each absorber block a detector triplet is located which measures the tracks of charged particles traversing the absorber. The performance of such a system has been simulated for the CBM experiment at FAIR (Germany) that is scheduled to start taking data in heavy ion collisions in the beam energy range of 6–45 A GeV from 2019. The muon detection system is mounted downstream to a Silicon Tracking System (STS) that is located in a large aperture dipole magnet which provides momentum information of the charged particle tracks. The reconstructed tracks from the STS are to be matched to the hits measured by the muon detector triplets behind the absorber segments. This method allows the identification of muon tracks over a broad range of momenta including tracks of soft muons which do not pass through all the absorber layers. Pairs of oppositely charged muons identified by MUCH could therefore be combined to measure the invariant masses in a wide range starting from low mass vector mesons (LMVM) up to charmonia. The properties of the absorber (material, thickness, position) and of the tracking chambers (granularity, geometry) have been varied in simulations of heavy-ion collision events generated with the UrQMD generator and propagated through the setup using the GEANT3, the particle transport code. The tracks are reconstructed by a Cellular Automaton algorithm followed by a Kalman Filter. The simulations demonstrate that low mass vector mesons and charmonia can be clearly identified in central Au+Au collisions at beam energies provided by the international Facility for Antiproton and Ion Research (FAIR)

  13. Design and performance simulation of a segmented-absorber based muon detection system for high energy heavy ion collision experiments

    A muon detection system (MUCH) based on a novel concept using a segmented and instrumented absorber has been designed for high-energy heavy-ion collision experiments. The system consists of 6 hadron absorber blocks and 6 tracking detector triplets. Behind each absorber block a detector triplet is located which measures the tracks of charged particles traversing the absorber. The performance of such a system has been simulated for the CBM experiment at FAIR (Germany) that is scheduled to start taking data in heavy ion collisions in the beam energy range of 6–45 A GeV from 2019. The muon detection system is mounted downstream to a Silicon Tracking System (STS) that is located in a large aperture dipole magnet which provides momentum information of the charged particle tracks. The reconstructed tracks from the STS are to be matched to the hits measured by the muon detector triplets behind the absorber segments. This method allows the identification of muon tracks over a broad range of momenta including tracks of soft muons which do not pass through all the absorber layers. Pairs of oppositely charged muons identified by MUCH could therefore be combined to measure the invariant masses in a wide range starting from low mass vector mesons (LMVM) up to charmonia. The properties of the absorber (material, thickness, position) and of the tracking chambers (granularity, geometry) have been varied in simulations of heavy-ion collision events generated with the UrQMD generator and propagated through the setup using the GEANT3, the particle transport code. The tracks are reconstructed by a Cellular Automaton algorithm followed by a Kalman Filter. The simulations demonstrate that low mass vector mesons and charmonia can be clearly identified in central Au+Au collisions at beam energies provided by the international Facility for Antiproton and Ion Research (FAIR)

  14. Broadband, Polarization-insensitive and Wide-angle Optical Absorber based on Fractal Plasmonics

    Eshaghian, Ali; Chizari, Ata; Mehrany, Khashayar

    2016-01-01

    In this paper, a plasmonic absorber consisting of a metal-dielectric-metal stack with a top layer of Sierpinski nanocarpet is theoretically investigated. Such compact absorber depicts broadband angle-independent behavior over a wide optical wavelength range ($400-700$ nm) and a broad range of angles of light incidence ($0-80^{\\circ}$). Including several feature sizes, such fractal-like structure shows widely strong extinction ($85-99$\\%) response for either transverse electric or magnetic polarization states under normal incidence. Underlying mechanisms of absorbance due to excited surface plasmon modes as well as electric/magnetic dipole resonances are well revealed by investigating electric field, magnetic field and current distributions. The proposed absorber opens a path to realize high-performance ultrathin light trapping devices.

  15. Enzyme-catalysed assembly of DNA hydrogel

    Um, Soong Ho; Lee, Jong Bum; Park, Nokyoung; Kwon, Sang Yeon; Umbach, Christopher C.; Luo, Dan

    2006-10-01

    DNA is a remarkable polymer that can be manipulated by a large number of molecular tools including enzymes. A variety of geometric objects, periodic arrays and nanoscale devices have been constructed. Previously we synthesized dendrimer-like DNA and DNA nanobarcodes from branched DNA via ligases. Here we report the construction of a hydrogel entirely from branched DNA that are three-dimensional and can be crosslinked in nature. These DNA hydrogels were biocompatible, biodegradable, inexpensive to fabricate and easily moulded into desired shapes and sizes. The distinct difference of the DNA hydrogel to other bio-inspired hydrogels (including peptide-based, alginate-based and DNA (linear)-polyacrylamide hydrogels) is that the crosslinking is realized via efficient, ligase-mediated reactions. The advantage is that the gelling processes are achieved under physiological conditions and the encapsulations are accomplished in situ-drugs including proteins and even live mammalian cells can be encapsulated in the liquid phase eliminating the drug-loading step and also avoiding denaturing conditions. Fine tuning of these hydrogels is easily accomplished by adjusting the initial concentrations and types of branched DNA monomers, thus allowing the hydrogels to be tailored for specific applications such as controlled drug delivery, tissue engineering, 3D cell culture, cell transplant therapy and other biomedical applications.

  16. An Improved Polymer-Based Hydrogel for Decontamination of Hard Assets

    Strippable coatings have been employed with mixed degrees of ease and efficacy over the last two decades. A new, zero-prep, non-toxic, minimum-odor hydrogel was tested on various material surfaces contaminated with uranium. The gel dries to a durable coating that provides improved ease of removal as compared to other coatings. The gel showed favorable performance on flat and textured surfaces containing grooves, pits, and joints with decontamination factors (DF) up to 50 for surfaces with high levels of alpha contamination. Of particular note was the ability of the gel to penetrate into joints and crevices and maintain its cohesiveness upon removal. The gel was applied on a typical fiber expansion joint in a concrete floor with initial activity of 24,400 cpm/100 cm2. After removal, the residual contamination level was 480 cpm/100 cm2, for a DF of 50 after a single application (98% removal). Materials tested included coated concrete, floor joint filler, painted steel stairs, unpainted wood, oxidized steel, and urethane glass. Loose and fixed surface contamination levels were determined to further evaluate the gel for removal of fixed contamination. Masking tape was applied to surfaces adjacent to the test surfaces which improved the dried gel removal. Loose contamination fractions were determined to be negligible, with tape DF values in the 1 to 1.07 range, i.e., essentially no loose contamination. These results indicated that the majority of contamination removed by the gel with high DFs was not simply loose particulate, but fixed in the surface. Some lower DFs were attributed to 90% humidity conditions, damp porous concrete, and incomplete cure time. Testing is planned to further evaluate high-humidity conditions and improved curing. (authors)

  17. Phenylboronic Acid Appended Pyrene-Based Low-Molecular-Weight Injectable Hydrogel: Glucose-Stimulated Insulin Release.

    Mandal, Deep; Mandal, Subhra Kanti; Ghosh, Moumita; Das, Prasanta Kumar

    2015-08-17

    A pyrene-containing phenylboronic acid (PBA) functionalized low-molecular-weight hydrogelator was synthesized with the aim to develop glucose-sensitive insulin release. The gelator showed the solvent imbibing ability in aqueous buffer solutions of pH values, ranging from 8-12, whereas the sodium salt of the gelator formed a hydrogel at physiological pH 7.4 with a minimum gelation concentration (MGC) of 5 mg mL(-1) . The aggregation behavior of this thermoreversible hydrogel was studied by using microscopic and spectroscopic techniques, including transmission electron microscopy, FTIR, UV/Vis, luminescence, and CD spectroscopy. These investigations revealed that hydrogen bonding, π-π stacking, and van der Waals interactions are the key factors for the self-assembled gelation. The diol-sensitive PBA part and the pyrene unit in the gelator were judiciously used in fluorimetric sensing of minute amounts of glucose at physiological pH. The morphological change of the gel due to addition of glucose was investigated by scanning electron microscopy, which denoted the glucose-responsive swelling of the hydrogel. A rheological study indicated the loss of the rigidity of the native gel in the presence of glucose. Hence, the glucose-induced swelling of the hydrogel was exploited in the controlled release of insulin from the hydrogel. The insulin-loaded hydrogel showed thixotropic self-recovery property, which hoisted it as an injectable soft composite. Encouragingly, the gelator was found to be compatible with HeLa cells. PMID:26184777

  18. Development of evanescent wave absorbance-based fibre-optic biosensor

    T Kundu; V V R Sai; R Dutta; S Titas; P Kumar; S Mukherjee

    2010-12-01

    Development of chemical and biochemical sensors is the current need of the society. In this report, we present our investigation on the development of a label-free fibre-optic biosensor based on evanescent wave absorbance to detect the presence of analytes such as bacteria, virus and some clinically important proteins. A simple UV-LED (280 nm) and photodetector combination along with a fibre probe was used for developing cost-effective, user-friendly and field applicable device. To improve the sensitivity of the detection technique, the probe design was modified and the U-bent probe was fabricated by simple procedure. Further, to overcome the problems for using UV light source in the fibre, the localized surface plasmon resonance of noble metal nanoparticles at visible wavelength was exploited as a sensing medium for the biochemical reactions. Our systematic studies in this regard presented in this communication may bring the excitement for developing the waterborne pathogen detection device for house-hold as well as field applications.

  19. Synthesis and properties of polyamide-Ag2S composite based solar energy absorber surfaces

    Krylova, Valentina; Baltrusaitis, Jonas

    2013-10-01

    Silver sulfide (Ag2S), an efficient solar light absorber, was synthesized using a modified chemical bath deposition (CBD) method and polyamide 6 (PA) as a host material via solution phase reaction between AgNO3 and Na2S2O3. X-ray diffraction (XRD) data showed a single, α-Ag2S (acanthite), crystalline phase present while surface and bulk chemical analyses, performed using X-ray photoelectron (XPS) and energy dispersive (EDS) spectroscopies, showed 2:1 Ag:S ratio. Direct and indirect bandgaps obtained from Tauc plots were 1.3 and 2.3 eV, respectively. Detailed surface chemical analysis showed the presence of three distinct sulfur species with majority component due to the Ag2S chemical bonds and minority components due to two types of oxygen-sulfur bonds. Conductivity of the resulting composite material was shown to change with the reaction time thus enabling to obtain controlled conductivity composite material. The synthesis method presented is based on the low solubility of Ag2S and is potentially green, no by-product producing, as all Ag2S nucleated outside the host material can be recycled into the process via dissolving it in HNO3.

  20. Synthesis and properties of polyamide–Ag{sub 2}S composite based solar energy absorber surfaces

    Krylova, Valentina, E-mail: valentina.krylova@ktu.lt [Department of Inorganic Chemistry, Kaunas University of Technology, Radvilenu st. 19, LT-50254 Kaunas (Lithuania); Baltrusaitis, Jonas, E-mail: j.baltrusaitis@utwente.nl [PhotoCatalytic Synthesis Group, MESA Institute for Nanotechnology, Faculty of Science and Technology, University of Twente, Meander 229, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2013-10-01

    Silver sulfide (Ag{sub 2}S), an efficient solar light absorber, was synthesized using a modified chemical bath deposition (CBD) method and polyamide 6 (PA) as a host material via solution phase reaction between AgNO{sub 3} and Na{sub 2}S{sub 2}O{sub 3}. X-ray diffraction (XRD) data showed a single, α-Ag{sub 2}S (acanthite), crystalline phase present while surface and bulk chemical analyses, performed using X-ray photoelectron (XPS) and energy dispersive (EDS) spectroscopies, showed 2:1 Ag:S ratio. Direct and indirect bandgaps obtained from Tauc plots were 1.3 and 2.3 eV, respectively. Detailed surface chemical analysis showed the presence of three distinct sulfur species with majority component due to the Ag{sub 2}S chemical bonds and minority components due to two types of oxygen–sulfur bonds. Conductivity of the resulting composite material was shown to change with the reaction time thus enabling to obtain controlled conductivity composite material. The synthesis method presented is based on the low solubility of Ag{sub 2}S and is potentially green, no by-product producing, as all Ag{sub 2}S nucleated outside the host material can be recycled into the process via dissolving it in HNO{sub 3}.

  1. Establishment of calorimetry based absorbed dose standard for newly installed Elekta Synergy accelerator at ARPANSA

    both quasi-adiabatic and quasi-isothermal modes. In the quasi-isothermal mode initially all the three bodies of the calorimeter (core, jacket and shield) are raised in temperatures with constant heating rates calculated based on the dose-rate obtained through the quasi-adiabatic mode. At the end of the heating period the radiation beam is brought on and the heaters switched off. Similarly at the end of the radiation run the heaters are switched on again to continue heating. The switching off/on of the heaters with radiation beam on/off is being done through a specially designed electronic circuit triggered by the output pulses from the monitor chamber.This has helped in reducing the uncertainties and improving the consistency of repeated measurements. Conversion of graphite absorbed dose to water absorbed dose is done through calorimetry, measurements of ionisation current in a graphite-walled chamber in a graphite phantom similar to the calorimeter and chamber measurements in a water tank all at the same distance. The conversion makes use of Monte-Carlo calculated doses in the graphite and water. Gap correction for the calorimeter is calculated using EGSnrc and the correction factor for radial non-uniformity is evaluated through beam profile measurements moving a thimble chamber mounted in a graphite phantom similar in construction to the calorimeter. As part of a bilateral intercomparison of accelerator measurements a graphite walled chamber was taken to NPL, U.K and was calibrated in their photon beams. The NPL-calibrated chamber was calibrated at ARPANSA against the IAEA calorimeter and the results of this intercomparison are presented here

  2. Magnetic actuated pH-responsive hydrogel-based soft micro-robot for targeted drug delivery

    Li, Hao; Go, Gwangjun; Ko, Seong Yong; Park, Jong-Oh; Park, Sukho

    2016-02-01

    For drug delivery in cancer therapy, various stimuli-responsive hydrogel-based micro-devices have been studied with great interest. Here, we present a new concept for a hybrid actuated soft microrobot targeted drug delivery. The proposed soft microrobot consists of a hydrogel bilayer structure of 2-hydroxyethyl methacrylate (PHEMA) and poly (ethylene glycol) acrylate (PEGDA) with iron (II, III) oxide particles (Fe3O4). The PHEMA layer as a pH-responsive gel is used for a trapping and unfolding motion of the soft microrobot in pH-varying solution, and the PEGDA-with-Fe3O4 layer is employed for the locomotion of the soft microrobot in the magnetic field. The bilayer soft microrobot was fabricated by a conventional photolithography procedure and its characteristics were analyzed and presented. To evaluate the trapping performance and the motility of the soft microrobot, test solutions with different pH values and an electromagnetic actuation (EMA) system were used. First, the soft microrobot showed its full trapping motion at about pH 9.58 and its unfolding motion at about pH 2.6. Second, the soft microrobot showed a moving velocity of about 600 μm s-1 through the generated magnetic field of the EMA system. Finally, we fabricated the real anti-cancer drug microbeads (PCL-DTX) and executed the cytotoxicity test using the mammary carcinoma cells (4T1). The viability of the 4T1 cells treated with the proposed microrobot and the PCL-DTX microbeads decreased to 70.25 ± 1.52%. The result demonstrated that the soft microrobot can be moved to a target position by the EMA system and can release a small amount of beads by the pH variation and the robot exhibited no toxicity to the cells. In the future, we expect that the proposed soft microrobot can be applied to a new tumor-therapeutic tool that can move to a target tumor and release anti-tumor drugs.

  3. A dynamically tunable terahertz metamaterial absorber based on an electrostatic MEMS actuator and electrical dipole resonator array

    Hu, Fangrong; Xu, Ningning; Wang, Weiming; Wang, Yue'e.; Zhang, Wentao; Han, Jiaguang; Zhang, Weili

    2016-02-01

    We experimentally demonstrate a dynamically tunable terahertz (THz) metamaterial absorber based on an electrostatic microelectromechanical systems (MEMS) actuator and electrical dipole resonator array. The absorption of the THz wave is mainly a result of the electrical dipole resonance, which shows a tunable performance on demand. By preforming the finite integral technique, we discovered that the central absorption frequency and the amplitude can be simultaneously tuned by the applied voltage U. Characterized by a white light interferometer and a THz time domain spectroscopy system, our THz absorber is measured to show a modulation of the central frequency and the amplitude to about 10% and 20%, respectively. The experimental results show good agreement with the simulation. This dynamically tunable absorber has potential applications on THz filters, modulators and controllers.

  4. Polysulfone based non-CA resists for 193 nm immersion lithography: Effect of increasing polymer absorbance on sensitivity

    The use of norbornene-based polysulfones as non-chemically amplified resists (non-CARs) for 193 nm immersion lithography was explored. Allylbenzene was incorporated into the polymer backbone to increase the absorbance of the polymers. The effect of polymer absorbance on sensitivity to 193 nm radiation was investigated. Polymer films on silicon wafers have been irradiated with 193 nm photons in the absence of a photo-acid generator. Chemical contrast curves (film thickness versus dose plots prior to solvent development) and contrast curves (film thickness versus dose plots after solvent development) were obtained by spectroscopic ellipsometry. The results show that E0 values could be reduced significantly by increasing the absorbance of the polymer.

  5. Electromagnetic behavior of radar absorbing materials based on Ca hexaferrite modified with Co-Ti ions and doped with La

    Valdirene Aparecida da Silva

    2009-06-01

    Full Text Available Radar Absorbing Materials (RAM are compounds that absorb incidental electromagnetic radiation in tuned frequencies and dissipate it as heat. Its preparation involves the adequate processing of polymeric matrices filled with compounds that act as radar absorbing centers in the microwave range. This work shows the electromagnetic evaluation of RAM based on CoTi and La doped Ca hexaferrite. Vibrating Sample Magnetization analyses show that ion substitution promoted low values for the parameters of saturation magnetization (123.65 Am2/kg and coercive field (0.07 T indicating ferrite softening. RAM samples obtained using different hexaferrite concentrations (40-80 per cent, w/w show variations in complex permeability and permittivity parameters and also in the performance of incidental radiation attenuation. Microwave attenuation values between 40 and 98 per cent were obtained.

  6. Determination of human absorbed dose of cocktail of 153Sm/177Lu-EDTMP, based on biodistribution data in rats

    The aim of this work was to estimate the absorbed dose due to compositional radiopharmaceutical of 153Sm/177Lu-EDTMP in human organs based on biodistribution data of rats by using OLINDA/EXM software. The absorbed dose was determined by the Radiation Dose Assessment Resource (RADAR) formulation after calculating cumulated activities in each organ. The results show that the organs that received the highest absorbed dose were the bone surface and red marrow (1.51 and 7.99 mGy/ MBq for 153Sm, and 1.98 and 10.76 mGy/MBq for 177Lu, respectively). According to the results, using of cocktail of 153Sm/177Lu-EDTMP has considerable characteristics as compared to 153Sm-EDTMP and 177Lu-EDTMP alone. (author)

  7. A dynamically tunable terahertz metamaterial absorber based on an electrostatic MEMS actuator and electrical dipole resonator array

    We experimentally demonstrate a dynamically tunable terahertz (THz) metamaterial absorber based on an electrostatic microelectromechanical systems (MEMS) actuator and electrical dipole resonator array. The absorption of the THz wave is mainly a result of the electrical dipole resonance, which shows a tunable performance on demand. By preforming the finite integral technique, we discovered that the central absorption frequency and the amplitude can be simultaneously tuned by the applied voltage U. Characterized by a white light interferometer and a THz time domain spectroscopy system, our THz absorber is measured to show a modulation of the central frequency and the amplitude to about 10% and 20%, respectively. The experimental results show good agreement with the simulation. This dynamically tunable absorber has potential applications on THz filters, modulators and controllers. (paper)

  8. Effect of cold storage on collagen-based hydrogels for the three-dimensional culture of adipose-derived stem cells

    Collagen gels have been extensively used as three-dimensional (3D) cell culture systems. To enhance their mechanical properties, the manufacture of collagen-based gels with agarose has been proposed. However, little is known about the stability of these gels under cold storage conditions. The consequences of cold storage on biological tissues for clinical applications are known to be significant; yet, they have not been considered on hydrogels used for in vitro experiments. This work studies the effect of extended cold storage on the stability of collagen and collagen-agarose hydrogels using rheometry and scanning electron microscopy. In addition, cell-matrix interactions of adipose-derived stem cells (ADSC) have been studied using these gels. Results show that both the storage modulus (G′) and loss modulus (G″) of pure collagen gels gradually decrease with extended cold storage along the 30 days of the study, while G′ and G″ increase in collagen-agarose gels under the same conditions. Moreover, significant changes in both moduli of collagen-agarose gels were only found after 30 days of cold storage, while in the case of collagen gels significant changes were already detected after 7 days. Finally, a reduction in the ability of ADSC to remodel the gel after prolonged cold storage was observed. To the best of our knowledge, this is the first work proving that cold storage of hydrogels prior to cell culture might have a significant impact on their mechanical properties and cell–matrix interactions. (paper)

  9. Enhancement in bioavailability of ketorolac tromethamine via intranasal in situ hydrogel based on poloxamer 407 and carrageenan.

    Li, Chenxi; Li, Chunyan; Liu, Zheshuo; Li, Qiuhong; Yan, Xueying; Liu, Yu; Lu, Weiyue

    2014-10-20

    The objective of this study was to construct a new in situ gel system based on the combination of poloxamer 407 and carrageenan (carrageenan-poloxamer 407 hydrogel, CPH) for intranasal delivery of ketorolac tromethamine. CPH showed potassium ion concentration - dependent erosion characteristics which ensured slow erosion in aqueous environment containing potassium ion at the physiological level. Loading with ketorolac tromethamine influenced erosion, drug release and thermosensitive properties of CPH. CPH containing 15% ketorolac tromethamine showed suitable gelation temperature (near 35°C) and in vitro sustained release profiles. Pharmacokinetic study of intranasal CPH containing 15% ketorolac tromethamine in rats demonstrated enhanced absolute bioavailability (68.8 ± 23.3%) and prolonged mean residence time (8.8 ± 3.5h) in comparison with the intranasal solution group (24.8 ± 13.8%, 3.9 ± 0.6h). Nasal ciliotoxicity evaluation on an in situ toad palate model preliminarily showed the safety of CPH for intranasal use. All results suggested the potential of CPH as a new sustained - release platform for the intranasal delivery of ketorolac tromethamine. PMID:25138250

  10. Cation transfer across a hydrogel/organic phase: Effect of cation size, hydrophobicity and acid-base properties

    Juarez, Ana V. [Departamento de Quimica Organica, IMBIV, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Yudi, Lidia M. [Departamento de Fisico Quimica, INFIQC, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Alvarez Igarzabal, Cecilia [Departamento de Quimica Organica, IMBIV, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina); Strumia, Miriam C., E-mail: mcs@fcq.unc.edu.a [Departamento de Quimica Organica, IMBIV, Facultad de Ciencias Quimicas, Universidad Nacional de Cordoba, Ciudad Universitaria, 5000 Cordoba (Argentina)

    2010-02-28

    The transfers of tetraethylammonium (TEA{sup +}) and protonated triflupromazine (HTFP{sup +}) through a hydrogel/liquid interface (g/o) and a liquid/liquid interface (w/o) were compared using cyclic voltammetry. After the two phases were put in contact, the behavior of each molecule was analyzed at different pH values and at different time points. The gel induces hydrophobic and electrostatic interactions with TEA{sup +} and HTFP{sup +}, shifting the peak potentials to more positive values. The diffusion coefficients, D, in both phases (g and w) at different pH values were calculated. In the case of TEA{sup +}, the D value remains constant in both systems. However, the D value of HTFP{sup +} is lower in the gel phase than in the liquid phase. HTFP{sup +} is transferred from the aqueous phase to the organic phase via a direct mechanism that involves coupled acid-base and partition processes. At the g/o interface, the coupled chemical reactions of HTFP{sup +} were inhibited by the drug/gel interaction. The results demonstrate that the g/o system could be used as a model to study the controlled release of charged drugs.

  11. In vitro and in vivo evaluation of a hydrogel-based prototype transdermal patch system of alfuzosin hydrochloride.

    Nair, Anroop B; Vaka, Siva Ram Kiran; Gupta, Sumit; Repka, Michael A; Murthy, S Narasimha

    2012-01-01

    The first-line therapy for moderate to severe benign prostatic hyperplasia is the oral therapy by alfuzosin hydrochloride. Unfortunately, the oral therapy of alfuzosin is associated with several route-specific systemic side-effects. The current study was aimed to develop a prototype transdermal patch system for alfuzosin using a hydrogel polymer and optimize the drug delivery through the skin for systemic therapy. The prospective of different chemical enhancers (polyethylene glycol (PEG 400), isopropyl myristate, propylene glycol, menthol and L-methionine; 5% w/v) and iontophoresis (0.3 mA/cm(2)) in the alfuzosin delivery across the full thickness rat skin was assessed in vitro. In vivo iontophoretic studies were carried out using selected patch system (PEG 400) for a period of 6 h in Sprague-Dawley rats. Passive permeation studies indicated that the incorporation of chemical agents have moderate effect (~4- to 7-fold) on the alfuzosin skin permeability and reduced the lag time. Combined approach of iontophoresis with chemical enhancers significantly augmented the drug transport (~ 43- to 72-fold). In vivo pharmacokinetic parameters revealed that the iontophoresis (transdermal patch with PEG 400) significantly enhanced the C(max) (~ 3-fold) and AUC(0-α) (~ 4-fold), when compared to control. The current study concludes that the application of iontophoresis (0.3 mA/cm(2)) using the newly developed agaorse-based prototype patch with PEG 400 could be utilized for the successful delivery of alfuzosin by transdermal route. PMID:20958130

  12. Influence of natural and synthetic crosslinking reagents on the structural and mechanical properties of chitosan-based hybrid hydrogels.

    Garnica-Palafox, I M; Sánchez-Arévalo, F M

    2016-10-20

    The objective of this work was to correlate the physical and chemical properties of chitosan/poly(vinyl alcohol)/genipin (CS/PVA/GEN) and chitosan/poly(vinyl alcohol)/glutaraldehyde (CS/PVA/GA) hydrogels with their structural and mechanical responses. In addition, their molecular structures were determined and confirmed using FTIR spectroscopy. The results indicated that the hybrid hydrogels crosslinked with genipin showed similar crystallinity, thermal properties, elongation ratio and structural parameters as those crosslinked with glutaraldehyde. However, it was found that the elastic moduli of the two hybrid hydrogels were slightly different: 2.82±0.33MPa and 2.08±0.11MPa for GA and GEN, respectively. Although the hybrid hydrogels crosslinked with GEN presented a lower elastic modulus, the main advantage is that GEN is five to ten thousand times less cytotoxic than GA. This means that the structural and mechanical properties of hybrid hydrogels crosslinked with GEN can easily be tuned and could have potential applications in the tissue engineering, regenerative medicine, food, agriculture and environmental industries. PMID:27474657

  13. Development of highly biocompatible Gelatin & i-Carrageenan based composite hydrogels: In depth physiochemical analysis for biomedical applications.

    Padhi, Jyostna Rani; Nayak, Debasis; Nanda, Arpita; Rauta, Pradipta Ranjan; Ashe, Sarbani; Nayak, Bismita

    2016-11-20

    In present investigation, gelatin and iota-carrageenan (CG) were used for the fabrication of composite hydrogels in different formulations (G1-G6). The hydrogels were characterized through optical, scanning electron and confocal microscopy to visualize their internal morphology. X-ray diffraction and ATR- FTIR spectroscopy were used for analyzing the chemical interaction between gelatin and CG. The hydrogels were found to be hemocompatible with high mucoadhesive and swelling properties. The standard drug ciprofloxacin was incorporated within the hydrogels and its interaction with the polymers was monitored through XRD and ATR-FTIR spectroscopy. In physiological pH 7.4, the G4 formulation showed a linear release profile. The antimicrobial activity was tested against nosocomial strains of Bacillus sp, Vibrio sp, Pseudomonas sp and Escherichia coli which showed a zone of inhibition between 8.5-20.7mm against the marketed Ciplox ointment. The cytocompatibility of the prepared hydrogels were investigated using normal HaCaT and HEK293 cell lines which showed their negligible cytotoxicity. PMID:27561499

  14. Self-Assembled DNA Hydrogel Based on Enzymatically Polymerized DNA for Protein Encapsulation and Enzyme/DNAzyme Hybrid Cascade Reaction.

    Xiang, Binbin; He, Kaiyu; Zhu, Rong; Liu, Zhuoliang; Zeng, Shu; Huang, Yan; Nie, Zhou; Yao, Shouzhuo

    2016-09-01

    DNA hydrogel is a promising biomaterial for biological and medical applications due to its native biocompatibility and biodegradability. Herein, we provide a novel, versatile, and cost-effective approach for self-assembly of DNA hydrogel using the enzymatically polymerized DNA building blocks. The X-shaped DNA motif was elongated by terminal deoxynucleotidyl transferase (TdT) to form the building blocks, and hybridization between dual building blocks via their complementary TdT-polymerized DNA tails led to gel formation. TdT polymerization dramatically reduced the required amount of original DNA motifs, and the hybridization-mediated cross-linking of building blocks endows the gel with high mechanical strength. The DNA hydrogel can be applied for encapsulation and controllable release of protein cargos (for instance, green fluorescent protein) due to its enzymatic responsive properties. Moreover, this versatile strategy was extended to construct a functional DNAzyme hydrogel by integrating the peroxidase-mimicking DNAzyme into DNA motifs. Furthermore, a hybrid cascade enzymatic reaction system was constructed by coencapsulating glucose oxidase and β-galactosidase into DNAzyme hydrogel. This efficient cascade reaction provides not only a potential method for glucose/lactose detection by naked eye but also a promising modular platform for constructing a multiple enzyme or enzyme/DNAzyme hybrid system. PMID:27526861

  15. RF-interrogatable hydrogel-actuated biosensor

    Hoel, Z; Wang, A W; Darrow, C B; Lee, A P; McConaghy, C F; Krulevitch, P; Gilman, A; Satcher, J H; Lane, S M

    2000-01-10

    The authors present a novel micromachined sensor that couples a swellable hydrogel with capacitive detection. The hydrogel swells in response to analyte concentration, exerting contact pressure on a deformable conducting membrane. Results are presented for characterization of a PHEMA hydrogel swelling in response to a calcium nitrate solution. Pressure-deflection measurements are performed on NiTi-based membranes. Hydrogel-actuated deflections of the membranes are measured. These measurements are correlated to determine the pressure generating characteristics of the hydrogel. Membrane deflection techniques have not previously been employed for hydrogel characterization. The PHEMA sample exhibited greatest sensitivity in the pH range of 6.0--6.5 and performed an average of 2.8 Joules of work per m{sup 3} per pH unit in response to ambient conditions over the pH range 3.5--6.5. The membrane deflections correspond to capacitive shifts of about 4 pF per pH unit for a capacitive transducer with initial gap of 100 {micro}m, capacitor plate area of 18.5 mm{sup 2} , and initial hydrogel volume of 11 {micro}L.

  16. An Interplay between Electrostatic and Polar Interactions in Peptide Hydrogels

    Joyner, Katherine; Taraban, Marc B; Feng, Yue; Yu, Y. Bruce

    2013-01-01

    Inherent chemical programmability available in peptide-based hydrogels has allowed diversity in the development of these materials for use in biomedical applications. Within the 20 natural amino acids, a range of chemical moieties are present. Here we used a mixing-induced self-assembly of two oppositely charged peptide modules to form a peptide-based hydrogel. To investigate electrostatic and polar interactions on the hydrogel, we replace amino acids from the negatively charged acidic glutam...

  17. Short-pulsed laser transport in absorbing and scattering media: time-based versus frequency-based approaches

    Optical tomography (OT) is a promising non-intrusive characterization technique of absorbing and scattering media that uses transmitted and/or reflected signals of samples irradiated with visible or near-infrared light. The quality of OT techniques is directly related to the accuracy of their forward models due to the use of inversion algorithms. In this paper, forward models for transient OT approaches are investigated. The system under study involves a one-dimensional absorbing and scattering medium illuminated by a short laser pulse; this problem is solved using a discrete ordinates-finite volume (DO-FV) method in both time and frequency domain. Previous works have shown that time-domain approaches coupled with first order spatial interpolation schemes cannot represent the physics of the problem adequately as transmitted fluxes emerge before the minimal physical time required to leave the medium. In this work, the Van Leer and Superbee flux limiters, combined with the second order Lax-Wendroff scheme, are used in an attempt to prevent this. Results show that despite significant improvement, flux limiters fail to completely eliminate the physically unrealistic behaviour. On the other hand, results for transmittance obtained from the frequency-based method are accurate, without physically unrealistic behaviours at early time periods. The frequency-dependent approach is however computationally expensive, since it requires approximately five times more computational time than its temporal counterpart when used as a forward model for transient OT. On the other hand, the great advantages of the frequency-based approach is that limited windows of temporal signals can be calculated efficiently (in transient OT), and it can also be used as a forward model for steady-state, frequency-based and transient OT techniques

  18. Radiation Synthesis of Stimuli-Responsive Hydrogels and Their Interactions with Poly(acrylic acid) and Ionic Surfactants

    Thermo-responsible hydrogels, which undergo a volume phase transition in an aqueous environment induced by a change in temperature, are the most interesting class of stimuli-responsive polymers. Some of them can be successfully used in biomedical fields as controlled drug delivery systems, in tissue engineering, food industry, etc. Most of these responsive hydrogels were obtained by three-dimensional polymerization of amphiphilic monomers such as N-isopropylacrylamide, vinyl methyl ether and N-vinylcaprolactame, which have hydrophilic and hydrophobic fragments in their structure simultaneously. We use another approach for synthesis of thermo-sensitive polymers of linear and cross-linked structure. This approach includes copolymerization of monomers having significant difference in hydrophobic/hydrophilic balance of their structure. It allows to regulate the ratio between hydrophilic and hydrophobic fragments of synthesized polymer macrochains in the wide range. The possibility for preparation of such thermo-sensitive hydrogels have been demonstrated by γ-radiation copolymerization of hydrophilic (vinyl ether of ethyleneglycol, 2-hydroxyethylacrylate, N-vinylpyrrolidone) and relatively hydrophobic monomers (vinyl butyl ether, vinyl isobutyl ether, hydroxyethylmethacrylate, butylacrylate, methylacrylate). It should be noted that homopolymers based on all above-mentioned monomers have no thermo-sensitive properties. However their copolymerization results in polymers able to undergo volume phase transitions upon increase of temperature. It was shown also the thermo-responsive swelling behavior of such hydrogels can be effectively regulated by varying of their composition and by complex formation with various poly(acids) and ionic surfactants. In particular, more hydrophobic hydrogels were found to absorb the surfactant more effectively because of hydrophobic nature of interaction. Significant increase in swelling ratio was observed for all hydrogels, especially for

  19. Preparation, characterization and protein sorption of photo-crosslinked cell membrane-mimicking chitosan-based hydrogels.

    Zhao, Yunfei; Ma, Liubo; Zeng, Rong; Tu, Mei; Zhao, Jianhao

    2016-10-20

    Photocrosslinkable biomimetic chitosan derivative, glycidyl methacrylate-phosphorylcholine-chitosan (PCCs-GMA) was synthesized through the combination of Atherton-Todd reaction for coupling phosphorylcholine and ring opening reaction of epoxides for attaching GMA, and confirmed by (1)H and (31)P NMR and Fourier transform infrared (FTIR) spectroscopy. The photo-crosslinking reaction of PCCs-GMA with different degree of substitution (DS) of GMA allowed the formation of biomimetic hydrogels with tunable mechanical and swelling properties. Cold crystallization behaviors ascribed to their restrained freezing bound water were investigated using differential scanning calorimetry (DSC). The rheological and swelling behaviors, hemolysis as well as protein sorption of PCCs-GMA hydrogels were investigated in terms of the DS of GMA, using fibrinogen, bovine serum albumin and lysozyme as model proteins. Low irreversible protein sorption and non hemolytic results indicated that photo-crosslinked PCCs-GMA hydrogels may offer a promising candidate material with resistance to protein fouling in biomedical applications. PMID:27474563

  20. Synthesis of Hydrogel Based on Nata De Coco and Acrylic Acid as Co-Monomer Using Free Radical Polymerization Method

    Nata de Coco or known as bacterial cellulose is produced by Acetobacter xylinum where it is more stable than plant cellulose. Moreover, it also provides outstanding advantages to be developed as an environmental responsive hydrogels. In this study the bacterial cellulose-g-acrylic acid hydrogel was synthesized by using a free radical polymerization method. Ammonium persulfate (APS) was used to initiate the reaction, while N,N'-methylene bis acrylamide has been used as the crosslinking agent. In order to test the hydrogel respond, swelling tests were made at different pH. Furthermore, ATR-FTIR analysis was used to determine the interactions between bacterial cellulose and acrylic acid. Finally, the determination of glass transition (Tg) was made by using DSC. (author)

  1. Tunable omnidirectional absorber and mode splitter based on semiconductor photonic crystal

    In this paper, the properties of one-dimensional (1D) photonic crystals (PCs) composed of the semiconductor (GaAs) and dielectric layers are theoretically investigated by the transfer matrix method (TMM). The absorption of semiconductor layers is investigated theoretically. Due to the magneto-optical Voigt effect, the dielectric constant of the semiconductor is modified differently in different modes and frequency ranges. If the frequency range of the incident wave is larger than the plasma frequency, TE and TM modes of the incident wave will be absorbed in a wide incident angle. TM wave will be absorbed but TE wave will be reflected while the frequency range is less than the plasma frequency. The absorption of semiconductor can also be tuned by varying the external magnetic field. The proposed PCs have a reconfigurable application to design a tunable omnidirectional absorber and mode splitter at same time

  2. Norwegian system for implementing the IAEA code of practice based on absorbed dose to water

    In 2001 the Nordic secondary standards dosimetry laboratories (SSDLs) recommended the use of absorbed dose to water as the quantity for the calibration standard and code of practice in radiotherapy.The code of practice adopted was IAEA Technical Reports Series No. 398. The Norwegian system for implementation includes the 60Co calibration of SSDL and hospital dosimeters in terms of absorbed dose to water at the Norwegian SSDL and on-site visits to every clinic teaching the new code and performing dose measurements. Comparisons of the Norwegian Radiation Protection Authority 60Co absorbed dose to water calibration at the Finnish SSDL with the French primary standards dosimetry laboratory showed agreement within 0.4%.The on-site visit measuring system compared with the Finnish on-site equipment agreed within 0.6%.The on-site visits were welcomed, and demonstrated the need for external dosimetry audits to improve the local implementation of the code of practice. (author)

  3. Tunable omnidirectional absorber and mode splitter based on semiconductor photonic crystal

    Ding, Guo-Wen [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Liu, Shao-Bin, E-mail: lsb@nuaa.edu.cn [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Zhang, Hai-Feng [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Nanjing Artillery Academy, Nanjing 211132 (China); Kong, Xiang-Kun; Li, Hai-Ming [Key Laboratory of Radar Imaging and Microwave Photonics (Nanjing Univ. Aeronaut. Astronaut.), Ministry of Education, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

    2015-07-15

    In this paper, the properties of one-dimensional (1D) photonic crystals (PCs) composed of the semiconductor (GaAs) and dielectric layers are theoretically investigated by the transfer matrix method (TMM). The absorption of semiconductor layers is investigated theoretically. Due to the magneto-optical Voigt effect, the dielectric constant of the semiconductor is modified differently in different modes and frequency ranges. If the frequency range of the incident wave is larger than the plasma frequency, TE and TM modes of the incident wave will be absorbed in a wide incident angle. TM wave will be absorbed but TE wave will be reflected while the frequency range is less than the plasma frequency. The absorption of semiconductor can also be tuned by varying the external magnetic field. The proposed PCs have a reconfigurable application to design a tunable omnidirectional absorber and mode splitter at same time.

  4. Understanding and predicting the behaviour of silver base neutron absorbers under irradiations

    The effect of neutron irradiation induced transmutations on the swelling of AgInCd (AIC) alloys used as neutron absorber in the control rods of Pressurized Water Reactors has been studied both experimentally and theoretically. Effective atomic volumes have been determined in synthetic AgCdInSn alloys with various compositions and containing fcc and hc phases, representative of irradiated AIC (Sn is a transmutation product). Swelling is shown to result first from the transmutation of Ag into Cd and of In into Sn, both with larger effective volume than the mother atom, and second from grain boundaries precipitation of s still less dense hc phase when solid solubility of transmuted products is exceeded. For both fcc and hc phases, we have determined profiles at the temperatures in the vicinity of the operating temperature. Unusual characteristics of second phase growth at grain boundaries induced by transmutations are identified on a simple binary alloy model: kinetics is controlled by irradiation temperature which scales diffusivities and flux which scales transmutation rates, as well as by the grain size in the underlying matrix. To address the AgInCdSn alloys, a novel technique is proposed to model diffusion in multicomponent alloys. It is based on a linearization of a simple atomistic model. With a single set of parameters, for each phase, our model well reproduces our interdiffusion measurements in quaternary alloys as well as existing interdiffusion experiments in binary alloys. Finally this diffusion model implemented with a moving interface algorithm is used to model the growth of the second phase induced by transmutation in the AIC under irradiation. (authors)

  5. Formulation based on artificial neural network of thermodynamic properties of ozone friendly refrigerant/absorbent couples

    This paper presents a new approach based on artificial neural networks (ANNs) to determine the properties of liquid and two phase boiling and condensing of two alternative refrigerant/absorbent couples (methanol/LiBr and methanol/LiCl). These couples do not cause ozone depletion and use in the absorption thermal systems (ATSs). ANNs are able to learn the key information patterns within multidimensional information domain. ANNs operate such as a 'black box' model, requiring no detailed information about the system. On the other hand, they learn the relationship between the input and the output. In order to train the neural network, limited experimental measurements were used as training data and test data. In this study, in input layer, there are temperatures in the range of 298-498 K, pressures (0.1-40 MPa) and concentrations of 2%, 7%, 12% of the couples; specific volume is in output layer. The back-propagation learning algorithm with three different variants, namely scaled conjugate gradient (SCG), Pola-Ribiere conjugate gradient (CGP), and Levenberg-Marquardt (LM), and logistic sigmoid transfer function were used in the network so that the best approach can find. The most suitable algorithm and neuron number in the hidden layer are found as SCG with 8 neurons. For this number level, after the training, it is found that maximum error is less than 3%, average error is about 1% and R2 value are 99.999%. As seen from the results obtained the thermodynamic equations for each pair by using the weights of network have been obviously predicted within acceptable errors. This paper shows that values predicted with ANN can be used to define the thermodynamic properties instead of approximate and complex analytic equations

  6. Bendable, ultra-black absorber based on a graphite nanocone nanowire composite structure.

    Sun, Yaoran; Evans, Julian; Ding, Fei; Liu, Nan; Liu, Wen; Zhang, Yuan; He, Sailing

    2015-07-27

    A bendable ultra-black material consisting of graphite nanocones and nanowires is fabricated through a simple plasma etching process. The optical properties of the absorber are characterized in the wavelength range of 400-2000 nm with average specular reflectance 0.05 ± 0.03% at normal incidence and the material thickness is only around 5 μm. The reflectance of the absorber remains low at large incident angles and is relatively independent of polarization. Simulations confirm the cooperative effect of the nanowires and nanocones leading to an ultra-black thin carbon material. PMID:26367669

  7. A Study of the Anechoic Performance of Rice Husk-Based, Geometrically Tapered, Hollow Absorbers

    Muhammad Nadeem Iqbal; Mohd. Fareq Malek; Yeng Seng Lee; Liyana Zahid; Muhammad Shafiq Mezan

    2014-01-01

    Although solid, geometrically tapered microwave absorbers are preferred due to their better performance, they are bulky and must have a thickness on the order of λ or more. The goal of this study was to design lightweight absorbers that can reduce the electromagnetic reflections to less than −10 dB. We used a very simple approach; two waste materials, that is, rice husks and tire dust in powder form, were used to fabricate two independent samples. We measured and used their dielectric propert...

  8. Numerical and theoretical analysis on the absorption properties of metasurface-based terahertz absorbers with different thicknesses.

    Wu, Kaimin; Huang, Yongjun; Wanghuang, Tenglong; Chen, Weijian; Wen, Guangjun

    2015-01-10

    In this paper, we numerically and theoretically discuss the novel absorption properties of a conventional metasurface-based terahertz (THz) electromagnetic (EM) absorber with different dielectric thicknesses. Two absorption modes are presented in the considered frequency band due to the increased dielectric thickness, and both modes can achieve near-unity absorptions when the dielectric layers reach additional nλ(d)/2 (n=1, 2) thicknesses, where λ(d) is the operating wavelength at the peak absorption in the dielectric slabs. The surface currents between the metasurface resonators and ground plane are not associated any longer, different from the conventional thin absorbers. Moreover, the EM wave energies are completely absorbed by the metasurface resonators and dielectric layer, and the main function of ground plane is to reflect the incident EM waves back to the resonators. The discussed novel absorption properties are analyzed and explained by classical EM theory and interference theory after numerical demonstrations. These findings can broaden the potential applications of the metasurface-based absorbers in the THz frequency range for different requirements. PMID:25967629

  9. Biodegradable water-absorbent synthesized from bacterial poly (amino acid)s

    Biodegradable hydrogels prepared by γ-irradiation from microbial poly (amino acid)s have been studied. pH-Sensitive hydrogels were prepared by means of γ-irradiation of poly(γ-glutamic acid) (PGA) produced by Bacillus subtilis and poly(ε-lysine) (PL) produced by Streptomyces albulus in aqueous solutions. When a dosage of γ-irradiation was 19 kGy or more and a concentration of PGA in water was 2 wt% or more, transparent hydrogels could be produced. In the case of 19 kGy, the produced hydrogel was very weak, however, the specific water content (wt. of absorbed water/wt. of dry hydrogel) of this PGA hydrogel was approximately 3,500. The specific water content was decreased to 200 increasing in the γ-irradiation dose over 100 kGy. Under acid conditions or on addition of electrolytes, PGA hydrogels shrinked. PGA hydrogel was pH-sensitive and changed the volume of the hydrogel depend on the value of pH outside hydrogel in the swelling medium. This PGA hydrogel was hydrodegradable and biodegradable. New novel purifier reagent (coagulant), made from PGA hydrogels, for contaminated turbid water was found and developed by Japanese venture company. Very small amount of this coagulant (only 1 ppm in turbid water) can work for purification of turbid water. PL aqueous solution also can change to hydrogel by γ-irradiation. The specific water content of PL hydrogel was range from 20 to 160 depend on the preparation conditions. Under acid conditions, the PL hydrogel swelled due to the ionic repulsion of the protonated amino groups in the PL molecules. The rate of enzymatic degradation of the respective PL hydrogels by a neutral protease was much faster than the rate of simple hydrolytic degradation. (author)

  10. Carbon Nanotube-hybridized Supramolecular Hydrogel Based on PEG-b-PDMAEMA /α-cyclodextrin%Carbon Nanotube-hybridized Supramolecular Hydrogel Based on PEG-b-PDMAEMA /α-cyclodextrin

    吴智明; 吴文文; 李玉金; 赵昕

    2011-01-01

    Well-dispersed multi-walled cabon nanotubes (MWCNTs) were successfully incorporated into a supramolecular hydrogel through combining dual roles of poly (ethylene glycol)-block-poly [(2-dimethylamino) ethyl methacrylate] (PEG-b-PDMAEMA) copolymer in disper

  11. Magnetic Resonance Imaging-Based Radiation-Absorbed Dose Estimation of 166Ho Microspheres in Liver Radioembolization

    Purpose: To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional 166Ho activity distribution to estimate radiation-absorbed dose distributions in 166Ho-loaded poly (L-lactic acid) microsphere (166Ho-PLLA-MS) liver radioembolization. Methods and Materials: MRI, computed tomography (CT), and single photon emission CT (SPECT) experiments were conducted on an anthropomorphic gel phantom with tumor-simulating gel samples and on an excised human tumor-bearing liver, both containing known amounts of 166Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the 166Ho activity distribution, derived from quantitative MRI data, with a 166Ho dose point-kernel generated by MCNP (Monte Carlo N-Particle transport code) and from Medical Internal Radiation Dose Pamphlet 17. MRI-based radiation-absorbed dose distributions were qualitatively compared with CT and autoradiography images and quantitatively compared with SPECT-based dose distributions. Both MRI- and SPECT-based activity estimations were validated against dose calibrator measurements. Results: Evaluation on an anthropomorphic phantom showed that MRI enables accurate assessment of local 166Ho-PLLA-MS mass and activity distributions, as supported by a regression coefficient of 1.05 and a correlation coefficient of 0.99, relating local MRI-based mass and activity calculations to reference values obtained with a dose calibrator. Estimated MRI-based radiation-absorbed dose distributions of 166Ho-PLLA-MS in an ex vivo human liver visually showed high correspondence to SPECT-based radiation-absorbed dose distributions. Quantitative analysis revealed that the differences in local and total amounts of 166Ho-PLLA-MS estimated by MRI, SPECT, and the dose calibrator were within 10%. Excellent agreement was observed between MRI- and SPECT-based dose–volume histograms. Conclusions: Quantitative MRI was demonstrated

  12. Magnetic Resonance Imaging-Based Radiation-Absorbed Dose Estimation of {sup 166}Ho Microspheres in Liver Radioembolization

    Seevinck, Peter R., E-mail: p.seevinck@umcutrecht.nl [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Maat, Gerrit H. van de [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Wit, Tim C. de [Department of Nuclear Medicine, Amsterdam Medical Centre, Amsterdam (Netherlands); Vente, Maarten A.D.; Nijsen, Johannes F.W. [Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht (Netherlands); Bakker, Chris J.G. [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht (Netherlands)

    2012-07-01

    Purpose: To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional {sup 166}Ho activity distribution to estimate radiation-absorbed dose distributions in {sup 166}Ho-loaded poly (L-lactic acid) microsphere ({sup 166}Ho-PLLA-MS) liver radioembolization. Methods and Materials: MRI, computed tomography (CT), and single photon emission CT (SPECT) experiments were conducted on an anthropomorphic gel phantom with tumor-simulating gel samples and on an excised human tumor-bearing liver, both containing known amounts of {sup 166}Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the {sup 166}Ho activity distribution, derived from quantitative MRI data, with a {sup 166}Ho dose point-kernel generated by MCNP (Monte Carlo N-Particle transport code) and from Medical Internal Radiation Dose Pamphlet 17. MRI-based radiation-absorbed dose distributions were qualitatively compared with CT and autoradiography images and quantitatively compared with SPECT-based dose distributions. Both MRI- and SPECT-based activity estimations were validated against dose calibrator measurements. Results: Evaluation on an anthropomorphic phantom showed that MRI enables accurate assessment of local {sup 166}Ho-PLLA-MS mass and activity distributions, as supported by a regression coefficient of 1.05 and a correlation coefficient of 0.99, relating local MRI-based mass and activity calculations to reference values obtained with a dose calibrator. Estimated MRI-based radiation-absorbed dose distributions of {sup 166}Ho-PLLA-MS in an ex vivo human liver visually showed high correspondence to SPECT-based radiation-absorbed dose distributions. Quantitative analysis revealed that the differences in local and total amounts of {sup 166}Ho-PLLA-MS estimated by MRI, SPECT, and the dose calibrator were within 10%. Excellent agreement was observed between MRI- and SPECT-based dose

  13. Synthesis and properties of polyamide–Ag2S composite based solar energy absorber surfaces

    Krylovaa, Valentina; Baltrusaitis, Jonas

    2013-01-01

    Silver sulfide (Ag2S), an efficient solar light absorber, was synthesized using a modified chemical bath deposition (CBD) method and polyamide 6 (PA) as a host material via solution phase reaction between AgNO3 and Na2S2O3. X-ray diffraction (XRD) data showed a single, α-Ag2S (acanthite), crystallin

  14. Investigation of Non-Vacuum Deposition Techniques in Fabrication of Chalcogenide-Based Solar Cell Absorbers

    Alsaggaf, Ahmed

    2015-07-01

    The environmental challenges are increasing, and so is the need for renewable energy. For photovoltaic applications, thin film Cu(In,Ga)(S,Se)2 (CIGS) and CuIn(S,Se)2 (CIS) solar cells are attractive with conversion efficiencies of more than 20%. However, the high-efficiency cells are fabricated using vacuum technologies such as sputtering or thermal co-evaporation, which are very costly and unfeasible at industrial level. The fabrication involves the uses of highly toxic gases such as H2Se, adding complexity to the fabrication process. The work described here focused on non-vacuum deposition methods such as printing. Special attention has been given to printing designed in a moving Roll-to-Roll (R2R) fashion. The results show potential of such technology to replace the vacuum processes. Conversion efficiencies for such non-vacuum deposition of Cu(In,Ga)(S,Se)2 solar cells have exceeded 15% using hazardous chemicals such as hydrazine, which is unsuitable for industrial scale up. In an effort to simplify the process, non-toxic suspensions of Cu(In,Ga)S2 molecular-based precursors achieved efficiencies of ~7-15%. Attempts to further simplify the selenization step, deposition of CuIn(S,Se)2 particulate solutions without the Ga doping and non-toxic suspensions of Cu(In,Ga)Se2 quaternary precursors achieved efficiencies (~1-8%). The contribution of this research was to provide a new method to monitor printed structures through spectral-domain optical coherence tomography SD-OCT in a moving fashion simulating R2R process design at speeds up to 1.05 m/min. The research clarified morphological and compositional impacts of Nd:YAG laser heat-treatment on Cu(In,Ga)Se2 absorber layer to simplify the annealing step in non-vacuum environment compatible to R2R. Finally, the research further simplified development methods for CIGS solar cells based on suspensions of quaternary Cu(In,Ga)Se2 precursors and ternary CuInS2 precursors. The methods consisted of post deposition reactive

  15. Estimated human absorbed dose of 177Lu–BPAMD based on mice data: Comparison with 177Lu–EDTMP

    In this work, the absorbed dose of human organs for 177Lu–BPAMD was evaluated based on biodistribution studies into the Syrian mice by RADAR method and was compared with 177Lu–EDTMP as the only clinically used Lu-177 bone-seeking agent. The highest absorbed dose for both 177Lu–BPAMD and 177Lu–EDTMP is observed on the bone surface with 8.007 and 4.802 mSv/MBq. Generally, 177Lu–BPAMD has considerable characteristics compared with 177Lu–EDTMP and can be considered as a promising agent for the bone pain palliation therapy. - Highlights: • 177Lu–BPAMD complex was prepared in high radiochemical purity (>93%, ITLC). • The highest absorbed dose for 177Lu–BPAMD is observed in the bone (8.007 mSv/MBq). • All tissues receive insignificant absorbed dose in comparison with bone tissue. • 177Lu–BPAMD has considerable characteristics compared to 177Lu–EDTMP. • 177Lu–BPAMD can be considered as a promising agent for bone pain palliation therapy

  16. Gamma radiation synthesis of comb-type graft hydrogels based on poly(acrylic acid) and 4-vinylpyridine

    A pH-sensitive comb-type hydrogel was obtained by gamma radiation polymerization and crosslinking of acrylic acid (AAc) in solution. The pH-sensitive 4-vinylpyridine (4VP) was then grafted to the poly acrylic acid (PAAc) hydrogel using gamma radiation from a 60Co source. The comb type graft polymers obtained (net-PAAc)-g-4VP has been studied through determination of graft yield and swelling behavior. The critical pH value was found to be 5.6. The apparent mechanical properties appear to be qualitatively better than hydrogels of PAAc upon swelling. The new comb-type system presents faster swelling response (30 h) than the polyacrylic acid hydrogel (50 h). The increase in dose rate from 7.3 to 11.3 kGy h-1, increase the radiation grafting percentage of 4VP in the system. Comb-type polymers were also characterized by DSC, TGA and FTIR-ATR. (author)

  17. One-pot synthesis of isocyanate-multifunctionalized polyisobutylene and its related applications. Novel polyisobutylene-based hydrogels

    Toman, Luděk; Janata, Miroslav; Vlček, Petr; Látalová, Petra; Sikora, Antonín; Pleštil, Josef; Michálek, Jiří; Masař, Bohumil

    Goa : International Union of Pure and Applied Chemistry, 2005. s. 95. [International Symposium on Ionic Polymerization. 23.10.2005-28.10.2005, Goa ] R&D Projects: GA ČR GA203/04/1050 Keywords : polyisobutylene * hydrogels * amphiphilic networks Subject RIV: CD - Macromolecular Chemistry

  18. Designing tragacanth gum based sterile hydrogel by radiation method for use in drug delivery and wound dressing applications.

    Singh, Baljit; Varshney, Lalit; Francis, Sanju; Rajneesh

    2016-07-01

    Present article discusses synthesis and characterization of the sterile and pure hydrogel wound dressings which were prepared through radiation method by using polyvinyl alcohol (PVA), tragacanth gum (TG) and sodium alginate (SA). The polymer films were characterized by SEM, Cryo-SEM, FTIR, solid state C(13) NMR and XRD, TGA, and DSC. Some important biological properties such as O2 permeability, water vapor transmission rate, microbial permeability, haemolysis, thrombogenic behavior, antioxidant activity, bio-adhesion and mechanical properties were also studied. The hydrogel film showed thrombogenicity (82.43±1.54%), haemolysis (0.83±0.09%), oxygen permeability (6.433±0.058mg/L) and water vapor permeability (197.39±25.34g/m(2)/day). Hydrogel films were found biocompatible and impermeable to microbes. The release of antibiotic drug moxifloxacin occurred through non-Fickian mechanism and release profile was best fitted in Hixson-Crowell model for drug release. Overall, these results indicate the suitability of these hydrogels in wound dressing applications. PMID:27020943

  19. Dual-functional transdermal drug delivery system with controllable drug loading based on thermosensitive poloxamer hydrogel for atopic dermatitis treatment

    Wang, Wenyi; Wat, Elaine; Hui, Patrick C. L.; Chan, Ben; Ng, Frency S. F.; Kan, Chi-Wai; Wang, Xiaowen; Hu, Huawen; Wong, Eric C. W.; Lau, Clara B. S.; Leung, Ping-Chung

    2016-04-01

    The treatment of atopic dermatitis (AD) has long been viewed as a problematic issue by the medical profession. Although a wide variety of complementary therapies have been introduced, they fail to combine the skin moisturizing and drug supply for AD patients. This study reports the development of a thermo-sensitive Poloxamer 407/Carboxymethyl cellulose sodium (P407/CMCs) composite hydrogel formulation with twin functions of moisture and drug supply for AD treatment. It was found that the presence of CMCs can appreciably improve the physical properties of P407 hydrogel, which makes it more suitable for tailored drug loading. The fabricated P407/CMCs composite hydrogel was also characterized in terms of surface morphology by field emission scanning electron microscopy (FE-SEM), rheological properties by a rheometer, release profile in vitro by dialysis method and cytotoxicity test. More importantly, the findings from transdermal drug delivery behavior revealed that P407/CMCs showed desirable percutaneous performance. Additionally, analysis of cytotoxicity test suggested that P407/CMCs composite hydrogel is a high-security therapy for clinical trials and thus exhibits a promising way to treat AD with skin moisturizing and medication.

  20. Injectable self-gelling composites for bone tissue engineering based on gellan gum hydrogel enriched with different bioglasses

    Douglas, T.E.L.; Piwowarczyk, W.; Pamula, E.; Lišková, Jana; Schaubroeck, D.; Leeuwenburgh, S. C. G.; Brackman, G.; Balcaen, L.; Detsch, R.; Declercq, H.; Cholewa-Kowalska, K.; Dokupil, A.; Cuijpers, V.M.J.I.; Vanhaecke, F.; Cornelissen, R.; Coenye, T.; Boccaccini, A. R.; Dubruel, P.

    2014-01-01

    Roč. 9, č. 4 (2014), 045014. ISSN 1748-6041 R&D Projects: GA MŠk(CZ) EE2.3.30.0025; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:67985823 Keywords : hydrogel * bone tissue engineering * gellan gum * bioglass Subject RIV: EI - Biotechnology ; Bionics Impact factor: 3.697, year: 2014