Sample records for anchored amphiphilic polymers

  1. Lipopolysaccharide Neutralization by Cationic-Amphiphilic Polymers through Pseudoaggregate Formation. (United States)

    Uppu, Divakara S S M; Haldar, Jayanta


    Synthetic polymers incorporating the cationic charge and hydrophobicity to mimic the function of antimicrobial peptides (AMPs) have been developed. These cationic-amphiphilic polymers bind to bacterial membranes that generally contain negatively charged phospholipids and cause membrane disintegration resulting in cell death; however, cationic-amphiphilic antibacterial polymers with endotoxin neutralization properties, to the best of our knowledge, have not been reported. Bacterial endotoxins such as lipopolysaccharide (LPS) cause sepsis that is responsible for a great amount of mortality worldwide. These cationic-amphiphilic polymers can also bind to negatively charged and hydrophobic LPS and cause detoxification. Hence, we envisaged that cationic-amphiphilic polymers can have both antibacterial as well as LPS binding properties. Here we report synthetic amphiphilic polymers with both antibacterial as well as endotoxin neutralizing properties. Levels of proinflammatory cytokines in human monocytes caused by LPS stimulation were inhibited by >80% when coincubated with these polymers. These reductions were found to be dependent on concentration and, more importantly, on the side-chain chemical structure due to variations in the hydrophobicity profiles of these polymers. These cationic-amphiphilic polymers bind and cause LPS neutralization and detoxification. Investigations of polymer interaction with LPS using fluorescence spectroscopy and dynamic light scattering (DLS) showed that these polymers bind but neither dissociate nor promote LPS aggregation. We show that polymer binding to LPS leads to sort of a pseudoaggregate formation resulting in LPS neutralization/detoxification. These findings provide an unusual mechanism of LPS neutralization using novel synthetic cationic-amphiphilic polymers.

  2. Amphiphilic vinyl polymers effectively prolong liposome circulation time in vivo. (United States)

    Torchilin, V P; Shtilman, M I; Trubetskoy, V S; Whiteman, K; Milstein, A M


    Newly synthesized amphiphilic polyacrylamide and poly(vinyl pyrrolidone), single terminus-modified with long-chain fatty acyl groups, are able to incorporate into the liposomal membrane, and similar to poly(ethylene glycol) prolong liposome circulation in vivo and decrease liposome accumulation in the liver. Protective efficacy of modified polymers increases with the increase in the length of acyl moiety and decreases for higher molecular weight polymers. The data on amphiphilic polymer-modified liposome biodistribution are presented.

  3. New synthetic amphiphilic polymers for steric protection of liposomes in vivo. (United States)

    Torchilin, V P; Trubetskoy, V S; Whiteman, K R; Caliceti, P; Ferruti, P; Veronese, F M


    Carboxy group-terminated synthetic polymers--branched poly(ethylene glycol), poly(acryloylmorpholine), and poly(vinylpyrrolidone)--were made amphiphilic by derivatization with phosphatidyl ethanolamine via the terminal carboxy group and then incorporated into lecithin-cholesterol liposomes prepared by the detergent dialysis method. Following the biodistribution of liposomes in mice, all three polymers were shown to be effective steric protectors for liposomes and were able to sharply increase liposome circulation times in a concentration-dependent manner. The accumulation of liposomes in the liver decreases. The effects observed are similar to those found for liposomes modified with linear poly(ethylene glycol). At low polymer concentration, amphiphilic branched poly(ethylene glycol) seems to be the most effective liposome protector, most probably, because at the same molar content of anchoring groups, each attachment point carries two polymeric chains and doubles the quantity of liposome-grafted polymer comparing to linear poly(ethylene glycol).

  4. Revealing Amphiphilic Nanodornains of Anti-Biofouling Polymer Coatings

    Energy Technology Data Exchange (ETDEWEB)

    Amadei, CA; Yang, R; Chiesa, M; Gleason, KK; Santos, S


    Undesired bacterial adhesion and biofilm formation on wetted surfaces leads to significant economic and environmental costs in various industries. Amphiphilic coatings with molecular hydrophilic and hydrophobic patches can mitigate such biofouling effectively in an environmentally friendly manner. The coatings are synthesized by copolymerizing (Hydroxyethyl)methacrylate and perfluorodecylacrylate via initiated chemical vapor deposition (iCVD). In previous studies, the size of the patches was estimated to be similar to 1.4-1.75 nm by fitting protein adsorption data to a theoretical model. However, no direct observations of the molecular heterogeneity exist and therefore the origin of the fouling resistance of amphiphilic coatings remains unclear. Here, the amphiphilic nature is investigated by amplitude modulation atomic force microscopy (AM-AFM). High-resolution images obtained by penetrating and oscillating the AFM tip under the naturally present water layer with sub-nanometer amplitudes reveal, for the first time, the existence of amphiphilic nanodomains (1-2 nm(2)). Compositional heterogeneity at the nanoscale is further corroborated by a statistical analysis on the data obtained with dynamic AM-AFM force spectroscopy. Variations in the long range attractive forces, responsible for water affinity, are also identified. These nanoscopic results on the polymers wettability are also confirmed by contact angle measurements (i.e., static and dynamic). The unprecedented ability to visualize the amphiphilic nanodomains as well as sub-nanometer crystalline structures provides strong evidence for the existence of previously postulated nanostructures, and sheds light on the underlying antifouling mechanism of amphiphilic chemistry.

  5. Surfactant Behavior of Amphiphilic Polymer-Tethered Nanoparticles. (United States)

    Zhang, Yue; Zhao, Hanying


    In recent years, an emerging research area has been the surfactant behavior of polymer-tethered nanoparticles. In this feature article, we have provided a general introduction to the synthesis, self-assembly, and interfacial activity of polymer-tethered inorganic nanoparticles, polymer-tethered organic nanoparticles, and polymer-tethered natural nanoparticles. In addition, applications of the polymer-tethered nanoparticles in colloidal and materials science are briefly reviewed. All research demonstrates that amphiphilic polymer-tethered nanoparticles exhibit surfactant behavior and can be used as elemental building blocks for the fabrication of advanced structures by the self-assembly approach. The polymer-tethered nanoparticles provide new opportunities to engineer materials and biomaterials possessing specific functionality and physical properties.

  6. Dendronized multifunctional amphiphilic polymers as efficient nanocarriers for biomedical applications. (United States)

    Kumari, Meena; Gupta, Shilpi; Achazi, Katharina; Böttcher, Christoph; Khandare, Jayant; Sharma, Sunil K; Haag, Rainer


    To gain insight into the factors that affect stability and transport efficiency under dilution conditions, dendronized and hyperbranched multifunctional amphiphilic polymers are synthesized by following the "grafting to" approach using varied amounts of propargylated alkyl chain with perfect and hyperbranched polyglycerol dendrons on the base copolymer of PEG (Mn: 1000 g mol(-1)) diethylester and 2-azidopropane-1,3-diol following the "bio-catalytic method" and "click approach". The dendronized and hyperbranched polymeric systems form supramolecular aggregates and exhibit an efficient transport potential for the model dye "Nile red" in the low μm range in the core-shell-type architecture provided with distinct amphiphilicity as required for encapsulation. Cytotoxicity studies show the polymeric systems to be non-toxic over a wide concentration range. The cellular internalization of Nile-red-encapsulated supramolecular micellar structures is also studied using cellular fluorescence micro-scopy and fluorescence-activated cell sorting (FACS) measurements. A comparison of the data for the dendronized polymers (PEG Mn: 600/1000 g mol(-1)) with the respective low-molecular-weight amphiphile reveal that these polymeric systems are excellent nanotransporters.

  7. Preparation of plasmonic vesicles from amphiphilic gold nanocrystals grafted with polymer brushes (United States)

    Song, Jibin; Huang, Peng; Chen, Xiaoyuan


    Gold nanovesicles contain multiple nanocrystals within a polymeric coating. The strong plasmonic coupling between adjacent nanoparticles in their vesicular shell makes ultrasensitive biosensing and bioimaging possible. In our laboratory, multifunctional plasmonic vesicles are assembled from amphiphilic gold nanocrystals (such as gold nanoparticles and gold nanorods) coated with mixed hydrophilic and hydrophobic polymer brushes or amphiphilic diblock co-polymer brushes. To fulfill the different requirements of biomedical applications, different polymers that are either pH=responsive, photoactive or biodegradable can be used to form the hydrophobic brush, while the hydrophilicity is maintained by polyethylene glycol (PEG). This protocol covers the preparation, surface functionalization and self-assembly of amphiphilic gold nanocrystals grafted covalently with polymer brushes. The protocol can be completed within 2 d. The preparation of amphiphilic gold nanocrystals, coated with amphiphilic diblock polymer brushes using a ‘grafting to’ method or mixed hydrophilic and hydrophobic polymer brushes using tandem ‘grafting to’ and ‘grafting from’ methods, is described. We also provide detailed procedures for the preparation and characterization of pH-responsive plasmonic gold nanovesicles from amphiphilic gold nanocrystals using a film-rehydration method that can be completed within ~3 d. PMID:27763624

  8. Anti-biofouling properties of amphiphilic phosphorylcholine polymer films. (United States)

    Li, Yan; Liu, Cheng-Mei; Yang, Jin-Ying; Gao, Ya-Hui; Li, Xue-Song; Que, Guo-He; Lu, J R


    Surfaces of amphiphilic phosphorylcholine polymer (PC1036) prepared by spin-coating were characterized by spectroscopic ellipsometry, water contact angle and atomic force microscopy. The antifouling properties of the PC1036 films to marine benthic diatom Nitzschia closterium MMDL533 were also investigated. The results showed that the dry PC1036 film promoted the adhesion of N. closterium MMDL533 because the hydrophobic lauryl groups were present in the film surface. The 2 h-swelled PC1036 films had excellent anti-fouling properties with extremely low attachment densities and retention densities no matter what the annealing temperature was. The thickness of the coated films lower than 147 Å had a profound effect on the film anti-fouling properties. Otherwise, when the film thickness was higher than that value, there was no more improvement of diatom cell reduction observed. The annealing temperature had only a little effect on the film resistant to diatom adhesion, which might be attributed to two factors including the PC group packing densities in the outer PC layer and the equilibrated water volume fraction in the 2 h-swelled PC1036 films.

  9. Intra-chain organisation of hydrophobic residues controls inter-chain aggregation rates of amphiphilic polymers

    CERN Document Server

    Varilly, Patrick; Kirkegaard, Julius B; Knowles, Tuomas P J; Chandler, David


    Aggregation of amphiphiles through the action of hydrophobic interactions is a common feature in soft condensed matter systems and is of particular importance in the context of biophysics as it underlies both the generation of functional biological machinery as well as the formation of pathological misassembled states of proteins. Here we explore the aggregation behaviour of amphiphilic polymers using lattice Monte-Carlo calculations and show that the distribution of hydrophobic residues within the polymer sequence determines the facility with which dry/wet interfaces can be created and that such interfaces drive the aggregation process.

  10. Amphiphilic semi-interpenetrating polymer networks using pulverized rubber (United States)

    Shahidi, Nima

    Scrap rubber materials provide a significant challenge to either reuse or safe disposal. Every year, millions of tires are discarded to landfills in the United States, consuming a staggering amount of land space, creating a high risk for large fires, breeding mosquitoes that spread diseases, and wasting the planet's natural resources. This situation cannot be sustained. The challenge of reusing scrap rubber materials is mainly due to the crosslinked structure of vulcanized rubber that prevent them from melting and further processing for reuse. The most feasible recycling approach is believed to be a process in which the vulcanized rubber is first pulverized into a fine powder and then incorporated into new products. The production of fine rubber particles is generally accomplished through the use of a cryogenic process that is costly. Therefore, development of a cost effective technology that utilizes a large quantity of the scrap rubber materials to produce high value added materials is an essential element in maintaining a sustainable solution to rubber recycling. In this research, a cost effective pulverization process, solid state shear extrusion (SSSE), was modified and used for continuous pulverization of the rubber into fine particles. In the modified SSSE process, pulverization takes place at high compressive shear forces and a controlled temperature. Furthermore, an innovative particle modification process was developed to enhance the chemical structure and surface properties of the rubber particles for manufacturing of high value added products. Modification of rubber particles was accomplished through the polymerization of a hydrophilic monomer mixture within the intermolecular structure of the hydrophobic rubber particles. The resulting composite particles are considered as amphiphilic particulate phase semi-interpenetrating polymer networks (PPSIPNs). The modified rubber particles are water dispersible and suitable for use in a variety of aqueous media

  11. Versatile antifouling polyethersulfone filtration membranes modified via surface grafting of zwitterionic polymers from a reactive amphiphilic copolymer additive. (United States)

    Zhao, Yi-Fan; Zhang, Pei-Bin; Sun, Jian; Liu, Cui-Jing; Yi, Zhuan; Zhu, Li-Ping; Xu, You-Yi


    Here we describe the development of versatile antifouling polyethersulfone (PES) filtration membranes modified via surface grafting of zwitterionic polymers from a reactive amphiphilic copolymer additive. Amphiphilic polyethersulfone-block-poly(2-hydroxyethyl methacrylate) (PES-b-PHEMA) was beforehand designed and used as the blending additive of PES membranes prepared by phase inversion technique. The surface enriched PHEMA blocks on membrane surface acted as an anchor to immobilize the initiating site. Poly(sulfobetaine methacrylate) (PSBMA) were subsequently grafted onto the PES blend membranes by surface-initiated atom transfer radical polymerization (SI-ATRP). The analysis of surface chemistry confirmed the successful grafting of zwitterionic PSBMA brushes on PES membrane surface. The resulted PES-g-PSBMA membranes were capable of separating proteins from protein solution and oil from oil/water emulsion efficiently. Furthermore, the modified membranes showed high hydrophilicity and strongly antifouling properties due to the incorporation of well-defined PSBMA layer. In addition, the PES-g-PSBMA membranes exhibited excellent blood compatibility and durability during the washing process. The developed antifouling PES membranes are versatile and can find their applications in protein filtration, blood purification and oil/water separation, etc.


    Institute of Scientific and Technical Information of China (English)

    LIU Hanfan; MAO Guoping


    A well-dispersed metallic palladium catalyst modified by polymer-anchored thioether ligands was used for the hydrogenation of cyclopentadiene to cyclopentene with high activity and selectivity in ambient condition. The evidences to show the modification of catalytic properties by polymer anchored ligands were given.

  13. Novel Amphiphilic Polymer Gel Electrolytes Based on PEG-b-GMA-co-MMA

    Institute of Scientific and Technical Information of China (English)


    1 Results Gel polymer electrolytes for lithium battery have been widely investigated recently because of their high ion conductivity at room temperature. We synthesized and characterized novel gel electrolytes based on amphiphilic copolymethacrylates containing different lengths of ethylene oxide (EO) chain as ionophilic units and methyl methacrylate (MMA) chain as ionophobic units[1]. Their electrochemical properties were also measured.1H NMR and FTIR analysis results elucidated that PEG-b-glycidyl met...

  14. Hydration-Induced Phase Separation in Amphiphilic Polymer Matrices and its Influence on Voclosporin Release

    Energy Technology Data Exchange (ETDEWEB)

    Khan, I. John [The State Univ. of New Jersey, Piscataway, NJ (United States); Murthy, N. Sanjeeva [The State Univ. of New Jersey, Piscataway, NJ (United States); Kohn, Joachim [The State Univ. of New Jersey, Piscataway, NJ (United States)


    Voclosporin is a highly potent, new cyclosporine -- a derivative that is currently in Phase 3 clinical trials in the USA as a potential treatment for inflammatory diseases of the eye. Voclosporin represents a number of very sparingly soluble drugs that are difficult to administer. It was selected as a model drug that is dispersed within amphiphilic polymer matrices, and investigated the changing morphology of the matrices using neutron and x-ray scattering during voclosporin release and polymer resorption. The hydrophobic segments of the amphiphilic polymer chain are comprised of desaminotyrosyl-tyrosine ethyl ester (DTE) and desaminotyrosyl-tyrosine (DT), and the hydrophilic component is poly(ethylene glycol) (PEG). Water uptake in these matrices resulted in the phase separation of hydrophobic and hydrophilic domains that are a few hundred Angstroms apart. These water-driven morphological changes influenced the release profile of voclosporin and facilitated a burst-free release from the polymer. No such morphological reorganization was observed in poly(lactide-co-glycolide) (PLGA), which exhibits an extended lag period, followed by a burst-like release of voclosporin when the polymer was degraded. An understanding of the effect of polymer composition on the hydration behavior is central to understanding and controlling the phase behavior and resorption characteristics of the matrix for achieving long-term controlled release of hydrophobic drugs such as voclosporin.

  15. Amphiphilic block copolymers as efficiency boosters in microemulsions a SANS investigation of the role of polymers

    CERN Document Server

    Endo, H; Mihailescu, M; Monkenbusch, M; Gompper, G; Richter, D; Jakobs, B; Sottmann, T; Strey, R


    The effect of amphiphilic block copolymers on ternary microemulsions (water, oil and non-ionic surfactant) is investigated. Small amounts of PEP-PEO block copolymer lead to a dramatic expansion of the one-phase region where water and oil can be solubilized by the mediation of surfactant molecules. Small-angle neutron-scattering experiments employing a high-precision two-dimensional contrast-variation technique demonstrate that the polymer is distributed uniformly on the surfactant membrane, where it modifies the membrane curvature elasticity. Furthermore, a new approach to determine the bending rigidity of an amphiphilic membrane is proposed, which is precise enough to measure the logarithmic scale dependence of the bending rigidity and its universal prefactor in bicontinuous microemulsions. (orig.)

  16. The Effect of Nano-Morphology Modification Using an Amphiphilic Polymer on the Proton Conductivity of Composite Membrane for a Polymer Membrane-Based Fuel Cell. (United States)

    Roh, Sung-Hee; Rho, Seon-Gyun; Kim, Sang-Chai; Kim, Ju-Young; Jung, Ho-Young


    The effect of morphology modification using an amphiphilic polymer on the proton conductivity of composite membrane for a polymer membrane-based fuel cell was investigated. The proton conductivity of each composite membrane was analyzed by the electrochemical impedance spectroscopy (EIS). The morphological change was confirmed by scanning electron microscope (SEM). In the composite membrane, the proton conductive component was sulfonated poly(ether ether ketone) (sPEEK), while the nonconductive component was poly(vinylidenedifluoride) and the amphiphilic polymer as a compatibilizer was urethane acrylate non-ionomer (UAN). UAN as a compatibilizer improved the interfacial stability between sPEEK and PVdF polymers, even though two polymers were apparently immiscible. The homogeneous distribution of sPEEK and PVdF domains in the composite membrane was obtained with the introduction of UAN due to the amphiphilicity. Therefore, it was found that the proton conductivity of the composite membrane increased with the incorporation of UAN as a compatibilizer.


    Institute of Scientific and Technical Information of China (English)

    Jing Li; Fei-peng Wu; Er-jian Wang


    A novel associating polymer P(AEBA) was synthesized by radical polymerization of the cationic amphiphilic monomer, 4-(2-(acryloyloxy)ethoxy)benzyl tri-ethyl ammonium bromide (AEBA), in aqueous solutions. P(AEBA) displays a strong tendency for self-association in aqueous solutions and is sensitive to the external stimulation such as added salt. The associative properties and morphologies of P(AEBA) were studied by fluorescnece probe technique, viscometry and TEM. In dilute salt-free solutions P(AEBA) behaves as polyelectrolyte, while its behavior is similar to that of the polysoap as salt added. Accompanying increasing polymer concentration, polymer aggregation conformation changes from an extended necklace-like structure to a compact globular aggregate corresponding to the viscosity reduction.

  18. Screening nylon-3 polymers, a new class of cationic amphiphiles, for siRNA delivery. (United States)

    Nadithe, Venkatareddy; Liu, Runhui; Killinger, Bryan A; Movassaghian, Sara; Kim, Na Hyung; Moszczynska, Anna B; Masters, Kristyn S; Gellman, Samuel H; Merkel, Olivia M


    Amphiphilic nucleic acid carriers have attracted strong interest. Three groups of nylon-3 copolymers (poly-β-peptides) possessing different cationic/hydrophobic content were evaluated as siRNA delivery agents in this study. Their ability to condense siRNA was determined in SYBR Gold assays. Their cytotoxicity was tested by MTT assays, their efficiency of delivering Alexa Fluor-488-labeled siRNA intracellularly in the presence and absence of uptake inhibitors was assessed by flow cytometry, and their transfection efficacies were studied by luciferase knockdown in a cell line stably expressing luciferase (H1299/Luc). Endosomal release was determined by confocal laser scanning microscopy and colocalization with lysotracker. All polymers efficiently condensed siRNA at nitrogen-to-phosphate (N/P) ratios of 5 or lower, as reflected in hydrodynamic diameters smaller than that at N/P 1. Although several formulations had negative zeta potentials at N/P 1, G2C and G2D polyplexes yielded >80% uptake in H1299/Luc cells, as determined by flow cytometry. Luciferase knockdown (20-65%) was observed after transfection with polyplexes made of the high molecular weight polymers that were the most hydrophobic. The ability of nylon-3 polymers to deliver siRNA intracellularly even at negative zeta potential implies that they mediate transport across cell membranes based on their amphiphilicity. The cellular uptake route was determined to strongly depend on the presence of cholesterol in the cell membrane. These polymers are, therefore, very promising for siRNA delivery at reduced surface charge and toxicity. Our study identified nylon-3 formulations at low N/P ratios for effective gene knockdown, indicating that nylon-3 polymers are a new, promising type of gene delivery agent.

  19. Anchoring Strength of Thin Aligned-Polymer Films Formed by Liquid Crystalline Monomer (United States)

    Murashige, Takeshi; Fujikake, Hideo; Ikehata, Seiichiro; Sato, Fumio


    We have evaluated the polar anchoring strength of a thin molecule-aligned polymer film formed by a liquid crystalline monomer. The polymer film was obtained by photopolymerization of the monomer oriented by a rubbed polyimide alignment layer in a chamber filled with N2 gas. We fabricated a nematic liquid crystal cell using the thin aligned-polymer films as alignment layers, and then evaluated the anchoring strength of the polymer by measuring the optical retardation curve of the cell driven by voltages. The experimental result showed that the anchoring strength was one order of magnitude lower than that of a conventional rubbed polyimide alignment layer, and decreased with increasing the cure temperature of the monomer film.

  20. Mesomorphous structure change by tail chain number in ionic liquid crystalline complexes of linear polymer and amphiphiles

    Institute of Scientific and Technical Information of China (English)

    Zhi Yu Cheng; Bi Ye Ren; Shu Ying He; Xin Xing Liu; Zhen Tong


    Three polymer-amphiphile complexes were prepared by combining poly(allylamine hydrochloride) (PAH) with the potassium salt of mono-, di-, and trisubstituted benzoic acid dendrons (4-octyloxybenzoic acid, 3,5-dioctyloxybenzoic acid, and 3,4,5-trioctyloxybenzoic acid). The solid structure and properties were monitored with FT-IR, XRD, TG, DSC, and polarized optical microscope (POM). Difference in the tail chain number of the dendritic amphiphile induced two different mesomorphous structures: lamella for the mono-, disubstituted dendron containing complexes and hexagonal column for the trisubstituted dendron containing complexes. These corresponded to the ionic thermotropic liquid crystal SmA and φh phases, respectively. This finding is significant for design of functional nanostructures based on the ionic complexation of polymers and amphiphiles.

  1. Mussel-Inspired Anchoring of Polymer Loops That Provide Superior Surface Lubrication and Antifouling Properties. (United States)

    Kang, Taegon; Banquy, Xavier; Heo, Jinhwa; Lim, Chanoong; Lynd, Nathaniel A; Lundberg, Pontus; Oh, Dongyeop X; Lee, Han-Koo; Hong, Yong-Ki; Hwang, Dong Soo; Waite, John Herbert; Israelachvili, Jacob N; Hawker, Craig J


    We describe robustly anchored triblock copolymers that adopt loop conformations on surfaces and endow them with unprecedented lubricating and antifouling properties. The triblocks have two end blocks with catechol-anchoring groups and a looping poly(ethylene oxide) (PEO) midblock. The loops mediate strong steric repulsion between two mica surfaces. When sheared at constant speeds of ∼2.5 μm/s, the surfaces exhibit an extremely low friction coefficient of ∼0.002-0.004 without any signs of damage up to pressures of ∼2-3 MPa that are close to most biological bearing systems. Moreover, the polymer loops enhance inhibition of cell adhesion and proliferation compared to polymers in the random coil or brush conformations. These results demonstrate that strongly anchored polymer loops are effective for high lubrication and low cell adhesion and represent a promising candidate for the development of specialized high-performance biomedical coatings.

  2. Polypeptoids from N -Substituted Glycine N -Carboxyanhydrides: Hydrophilic, Hydrophobic, and Amphiphilic Polymers with Poisson Distribution

    KAUST Repository

    Fetsch, Corinna


    Preparation of defined and functional polymers has been one of the hottest topics in polymer science and drug delivery in the recent decade. Also, research on (bio)degradable polymers gains more and more interest, in particular at the interface of these two disciplines. However, in the majority of cases, combination of definition, functionality and degradability, is problematic. Here we present the preparation and characterization (MALDI-ToF MS, NMR, GPC) of nonionic hydrophilic, hydrophobic, and amphiphilic N-substituted polyglycines (polypeptoids), which are expected to be main-chain degradable and are able to disperse a hydrophobic model compound in aqueous media. Polymerization kinetics suggest that the polymerization is well controlled with strictly linear pseudo first-order kinetic plots to high monomer consumption. Moreover, molar mass distributions of products are Poisson-type and molar mass can be controlled by the monomer to initiator ratio. The presented polymer platform is nonionic, backbone degradable, and synthetically highly flexible and may therefore be valuable for a broad range of applications, in particular as a biomaterial. © 2011 American Chemical Society.

  3. Self-assembly of metal--polymer analogues of amphiphilic triblock copolymers (United States)

    Nie, Zhihong; Fava, Daniele; Kumacheva, Eugenia; Zou, Shan; Walker, Gilbert; Rubinstein, Michael


    We proposed a block copolymer approach to the self-assembly of inorganic nanrods terminated with polymer molecules at both ends. We organized metal nanorods in structures with varying geometries by using a striking analogy between amphiphilic ABA triblock copolymers and the hydrophilic nanorods tetheredwith hydrophobic polymer chains at both ends. The self-assembly was tunable and reversible and it was achieved solely by changing the solvent quality for the constituent blocks. The distance between adjacent nanorods along chains can be tuned by varying the composition of mixture solvents or the molecular weight of polymer blocks, which allows us precisely control the plasmonic band of self-assembled structures. A systematic study of the self-assembly as a function of solvent composition and the molecular weight of the polymer blocks allowed us to construct a diagram that maps the assembled structures. This approach provides a new route to the organization of anisotropic nanoparticles by using the strategies that are established for the self-assembly of block copolymers.

  4. Formation and properties of surface-anchored polymer assemblies with tunable physico-chemical characteristics (United States)

    Wu, Tao

    We describe two new methodologies leading to the formation of novel surface-anchored polymer assemblies on solid substrates. While the main goal is to understand the fundamentals pertaining to the preparation and properties of the surface-bound polymer assemblies (including neutral and chargeable polymers), several examples also are mentioned throughout the Thesis that point out to practical applications of such structures. The first method is based on generating assemblies comprising anchored polymers with a gradual variation of grafting densities on solid substrates. These structures are prepared by first covering the substrate with a molecular gradient of the polymerization initiator, followed by polymerization from these substrate-bound initiator centers ("grafting from"). We apply this technique to prepare grafting density gradients of poly(acryl amide) (PAAm) and poly(acrylic acid) (PAA) on silica-covered substrates. We show that using the grafting density gradient geometry, the characteristics of surface-anchored polymers in both the low grafting density ("mushroom") regime as well as the high grafting density ("brush") regime can be accessed conveniently on a single sample. We use a battery of experimental methods, including Fourier transform infrared spectroscopy (FTIR), Near-edge absorption fine structure spectroscopy (NEXAFS), contact angle, ellipsometry, to study the characteristics of the surface-bound polymer layers. We also probe the scaling laws of neutral polymer as a function of grafting density, and for weak polyelectrolyte, in addition to the grafting density, we study the affect of solution ionic strength and pH values. In the second novel method, which we coined as "mechanically assisted polymer assembly" (MAPA), we form surface anchored polymers by "grafting from" polymerization initiators deposited on elastic surfaces that have been previously extended uniaxially by a certain length increment, Deltax. Upon releasing the strain in the

  5. High-performance Polymer Membranes with Multi-functional Amphiphilic Micelles for CO2 Capture. (United States)

    Kim, Sang Jin; Jeon, Harim; Kim, Dong Jun; Kim, Jong Hak


    Herein, we report a high performance polymer membrane with simultaneously large improvements in the CO2 permeability and CO2/N2 selectivity. These improvements are obtained by incorporation of a multi-functional amphiphilic comb copolymer micelle, that is, poly(dimethylsiloxane)-g-poly(oxyethylene methacrylate) (PDMS-g-POEM), into a poly(amide-b-ethylene oxide) (Pebax) matrix. Both CO2 and N2 permeabilities continuously increased with PDMS-g-POEM content, whereas the CO2/N2 selectivity increased up to 40 wt % of PDMS-g-POEM, which enabled the maximum performance to approach the upper bound limit (2008). The membranes with PDMS-g-POEM exhibited greater CO2 permeability and CO2/N2 selectivity than those with a zeolitic imidazolate framework (ZIF-8), a well-known expensive inorganic filler, indicating the effectiveness of PDMS-g-POEM micelles for CO2 capture.

  6. Recent advances in amphiphilic polymers for simultaneous delivery of hydrophobic and hydrophilic drugs. (United States)

    Martin, Chloe; Aibani, Noorjahan; Callan, John F; Callan, Bridgeen


    Nanomedicine has evolved with the use of biological compounds such as proteins, peptides and DNA. These hydrophilic and often highly charged compounds require a delivery system to allow effective transport and release at the site of action. These new biological therapeutics have not replaced the more traditional smaller molecule, but instead are working synergistically to the benefit of the end user. To that end, drug delivery systems are now required to encapsulate both larger hydrophilic compounds as well as the smaller and generally more hydrophobic compound. This review highlights the emerging role in drug delivery of amphiphilic polymers that by their very nature can associate with compounds of differing physicochemical properties, in particular the role of micelles, polymersomes and nanocapsules.

  7. Novel functional materials from renewable lipids: Amphiphilic antimicrobial polymers and latent heat thermal energy storage (United States)

    Floros, Michael Christopher

    Vegetable oils represent an ideal and renewable feedstock for the synthesis of a variety of functional materials. However, without financial incentive or unique applications motivating a switch, commercial products continue to be manufactured from petrochemical resources. Two different families of high value, functional materials synthesized from vegetable oils were studied. These materials demonstrate superior and unique performance to comparable petrochemical analogues currently on the market. In the first approach, 3 amphiphilic thermoplastic polytriazoles with differing lipophilic segment lengths were synthesized in a polymerization process without solvents or catalysts. Investigation of monomer structure influence on the resultant functional behaviour of these polymers found distinctive odd/even behaviour reliant on the number of carbon atoms in the monomers. Higher concentrations of triazole groups, due to shorter CH2 chains in the monomeric dialkynes, resulted in more brittle polymers, displaying higher tensile strengths but reduced elongation to break characteristics. These polymers had similar properties to commercial petroleum derived thermoplastics. One polymer demonstrated self-assembled surface microstructuring, and displayed hydrophobic properties. Antimicrobial efficacy of the polymers were tested by applying concentrated bacterial solutions to the surfaces, and near complete inhibition was demonstrated after 4 hours. Scanning electron microscope images of killed bacteria showed extensive membrane damage, consistent with the observed impact of other amphiphilic compounds in literature. These polytriazoles are suited for applications in medical devices and implants, where major concerns over antibiotic resistance are prevalent. In the second approach, a series of symmetric, saturated diester phase change materials (PCMs) were also synthesized with superior latent heat values compared to commercial petrochemical analogues. These diesters exhibit

  8. Polymer-hybridized liposomes anchored with alkyl grafted poly(asparagine). (United States)

    Park, Sung-Il; Lee, Eun-Ok; Kim, Jin Woong; Kim, Youn Joon; Han, Sang Hoon; Kim, Jong-Duk


    Polymer-hybridized liposomes (PHLs) of saturated lecithin were formed by association of poly(asparagines) grafted with alkyl chains (PAsn-g-Cn). The thermal, physical, and surface properties of the polymer-hybridized liposomes were examined with varying polymer concentration, alkyl chain length (C(8), C(12), C(18), C(22)), and degree of substitution (DS) in the polymer. The inclusion of the polymer raised the membrane fluidity of liposomes. By the incorporation of small amount of polymer, the membrane rigidity of liposomes dropped sharply and then increased close to the original level as the polymer concentrations increased in the cases of PAsn-g-C(18) and PAsn-g-C(22). Also, the membrane rigidity and stability of PHLs increased with alkyl chain length at the same polymer concentration. The surface charge of PHL associated with PAsn-g-C(22) was changed by DS of alkyl chains. The polymer bearing long alkyl chains (C(12), C(18), C(22)) formed PHLs well at low polymer concentration and the number of disk-shaped polymer-lipid mixed micelles increased with polymer concentration. The anchored polymers induced shifts in gel-to-liquid crystal transition temperature (Tc) of the vesicles and Tc varied with polymer concentration, alkyl chain length, and DS of the polymer.

  9. Optimum design of amphiphilic polymers bearing hydrophobic groups for both cell surface ligand presentation and intercellular cross-linking. (United States)

    Takeo, Masafumi; Li, Cuicui; Matsuda, Masayoshi; Nagai, Hiroko; Hatanaka, Wataru; Yamamoto, Tatsuhiro; Kishimura, Akihiro; Mori, Takeshi; Katayama, Yoshiki


    Amphiphilic polymers bearing hydrophobic alkyl groups are expected to be applicable for both ligand presentation on the cell surface and intercellular crosslinking. To explore the optimum design for each application, we synthesized eight different acyl-modified dextrans with varying molecular weight, alkyl length, and alkyl modification degree. We found that the behenate-modified polymers retained on the cell surface longer than the palmitate-modified ones. Since the polymers were also modified with biotin, streptavidin can be presented on the cell surface through biotin-streptavidin recognition. The duration of streptavidin on the cell surface is longer in the behenate-modified polymer than the palmitate-modified one. As for the intercellular crosslinking, the palmitate-modified polymers were more efficient than the behenate-modified polymers. The findings in this research will be helpful to design the acyl-modified polymers for the cell surface engineering.

  10. Enthalpy of interaction and binding isotherms of non-ionic surfactants onto micellar amphiphilic polymers (amphipols). (United States)

    Diab, C; Winnik, F M; Tribet, C


    The interactions in water between short amphiphilic macromomolecules, known as amphipols, and three neutral surfactants (detergents), dodecylmaltoside (DM), n-octylthioglucoside (OTG), and n-octyltetraethyleneoxide (C8E4), have been assessed by static and dynamic light-scattering (SLS and DLS), capillary electrophoresis (CE), and isothermal titration calorimetry (ITC). The amphipols selected are random copolymers of the hydrophobic n-octylacrylamide (25-30 mol %), a charged hydrophilic monomer, either acrylic acid ( approximately 35 mol %) or a phosphorylcholine-modified acrylamide (40-70 mol %), and, optionally, N-isopropylacrylamide (30-40 mol %). In water, the copolymers form micelles of small size (hydrodynamic radius: approximately 5 nm). Neutral surfactants, below their critical micellar concentration (cmc), form mixed micelles with the amphipols irrespective of the chemical structure of the detergent or the polymer. The fraction of detergent in the surfactant/polymer complexes increases significantly (cooperatively) as the surfactant concentration nears the cmc. The ITC data, together with data gathered by CE, were fitted via a regular mixing model, which allowed us to predict the detergent concentration in equilibrium with complexes and the heat evolved upon transfer of detergent from water into a mixed surfactant/polymer complex. The enthalpy of transfer was found to be almost equal to the enthalpy of micellization, and the regular mixing model points to a near-ideal mixing behavior for all systems. Amphipols are promising tools in biochemistry where they are used, together with neutral surfactants, for the stabilization and handling of proteins. This study provides guidelines for the optimization of current protein purification protocols and for the formulations of surfactant/polymer systems used in pharmaceutics, cosmetics, and foodstuffs.

  11. Amphiphilic comb-like polymer for harvest of conductive nano-cellulose. (United States)

    Choi, Jaeyoo; Park, Subeom; Cheng, Jie; Park, Minsung; Hyun, Jinho


    In this study, electrically conductive bacterial cellulose (BC) was prepared by culturing Gluconacetobacter xylinus in a carbon nanotube (CNT)-dispersed medium. The CNTs were dispersed by adopting a non-covalent approach in the presence of non-ionic amphiphilic comb-like polymer (CLP). Specifically, the hydrophobic backbone of CLP was chemophysically attached to the surface of the CNTs and the hydrophilic side chains were released freely toward the medium in an aqueous environment. CLP-modified CNTs were stable and did not show any noticeable sediment, even after centrifugation at 15,000 rpm for 30 min. Notably, the dispersion solution of CLP-modified CNTs was stable at room temperature for several months because the long-range entropic repulsion among polymer-decorated tubes acted as a barrier to aggregation. The morphology of the BC membrane was studied by field-emission scanning electron microscopy. The presence of CLP bound to the CNT surface was characterized by Fourier transform infrared spectroscopy and the conductivity of the CNT-incorporated BC membrane was measured by four-probe measurements.

  12. Supramolecular amphiphiles. (United States)

    Zhang, Xi; Wang, Chao


    Supramolecular amphiphiles (SA), also named superamphiphiles, refer to amphiphiles that are formed by non-covalent interactions. This tutorial review focuses on the molecular architectures of SAs, including diversified topologies such as single chain, double chain, bolaform, gemini and rotaxane types. Non-covalent syntheses that have been employed to fabricate SAs are driven by hydrogen bonding, electrostatic attraction, host-guest recognition, charge transfer interaction, metal coordination and so on. It should be noted that SAs can be either small organic molecules or polymers. SAs allow for tuning of their amphiphilicity in a reversible fashion, leading to controlled self-assembly and disassembly. This line of research has been enriching traditional colloid chemistry and current supramolecular chemistry, and the application of SAs in the field of functional supramolecular materials is keenly anticipated.

  13. Smectic Layer Deformation of Ferroelectric Liquid Crystal Sandwiched between Polymer Walls with Anchoring Effects (United States)

    Murashige, Takeshi; Fujikake, Hideo; Ikehata, Seiichiro; Sato, Fumio


    We studied smectic layer structures of ferroelectric liquid crystal (FLC) formed in elongated small spaces surrounded by molecule-aligned polymer walls and rubbed polyimide alignment layers. The polymer walls, which are parallel to the rubbing direction and vertical to the alignment layers, were formed by the photopolymerization of an aligned monomer under patterned ultraviolet light irradiation. From the observation of the alignment textures of the FLC between the polymer walls with a polarizing microscope, it was found that the smectic layer structure was changed from vertical plane bending alignment (chevron structure), as observed with a conventional surface-stabilized FLC, into horizontal plane bending, as the interval between the polymer walls decreased. It is thought that the smectic layer structure is governed by the competition between the anchoring effects of the alignment polyimide layers and the molecule-aligned polymer walls.

  14. Glycoconjugated amphiphilic polymers via click-chemistry for the encapsulation of quantum dots. (United States)

    Schmidtke, Christian; Kreuziger, Anna-Marlena; Alpers, Dirk; Jacobsen, Anna; Leshch, Yevgeniy; Eggers, Robin; Kloust, Hauke; Tran, Huong; Ostermann, Johannes; Schotten, Theo; Thiem, Joachim; Thimm, Julian; Weller, Horst


    Herein, we present a strategy for the glycoconjugation of nanoparticles (NPs), with a special focus on fluorescent quantum dots (QDs), recently described by us as "preassembly" approach. Therein, prior to the encapsulation of diverse nanoparticles by an amphiphilic poly(isoprene)-b-poly(ethylene glycol) diblock copolymer (PI-b-PEG), the terminal PEG appendage was modified by covalently attaching a carbohydrate moiety using Huisgen-type click-chemistry. Successful functionalization was proven by NMR spectroscopy. The terminally glycoconjugated polymers were subsequently used for the encapsulation of QDs in a phase transfer process, which fully preserved fluorescence properties. Binding of these nanoconstructs to the lectin Concanavalin A (Con A) was studied via surface plasmon resonance (SPR). Depending on the carbohydrate moiety, namely, D-manno-heptulose, D-glucose, D-galactose, 2-deoxy-2-{[methylamino)carbonyl]amino}-D-glucopyranose ("des(nitroso)-streptozotocin"), or D-maltose, the glycoconjugated QDs showed enhanced affinity constants due to multivalent binding effects. None of the constructs showed toxicity from 0.001 to 1 μM (particle concentration) using standard WST and LDH assays on A549 cells.

  15. Micellar and structural stability of nanoscale amphiphilic polymers: Implications for anti-atherosclerotic bioactivity. (United States)

    Zhang, Yingyue; Li, Qi; Welsh, William J; Moghe, Prabhas V; Uhrich, Kathryn E


    Atherosclerosis, a leading cause of mortality in developed countries, is characterized by the buildup of oxidized low-density lipoprotein (oxLDL) within the vascular intima, unregulated oxLDL uptake by macrophages, and ensuing formation of arterial plaque. Amphiphilic polymers (AMPs) comprised of a branched hydrophobic domain and a hydrophilic poly(ethylene glycol) (PEG) tail have shown promising anti-atherogenic effects through direct inhibition of oxLDL uptake by macrophages. In this study, five AMPs with controlled variations were evaluated for their micellar and structural stability in the presence of serum and lipase, respectively, to develop underlying structure-atheroprotective activity relations. In parallel, molecular dynamics simulations were performed to explore the AMP conformational preferences within an aqueous environment. Notably, AMPs with ether linkages between the hydrophobic arms and sugar backbones demonstrated enhanced degradation stability and storage stability, and also elicited enhanced anti-atherogenic bioactivity. Additionally, AMPs with increased hydrophobicity elicited increased atheroprotective bioactivity in the presence of serum. These studies provide key insights for designing more serum-stable polymeric micelles as prospective cardiovascular nanotherapies.

  16. Investigations on diffusion limitations of biocatalyzed reactions in amphiphilic polymer conetworks in organic solvents. (United States)

    Schoenfeld, Ina; Dech, Stephan; Ryabenky, Benjamin; Daniel, Bastian; Glowacki, Britta; Ladisch, Reinhild; Tiller, Joerg C


    The use of enzymes as biocatalysts in organic media is an important issue in modern white biotechnology. However, their low activity and stability in those media often limits their full-scale application. Amphiphilic polymer conetworks (APCNs) have been shown to greatly activate entrapped enzymes in organic solvents. Since these nanostructured materials are not porous, the bioactivity of the conetworks is strongly limited by diffusion of substrate and product. The present manuscript describes two different APCNs as nanostructured microparticles, which showed greatly increased activities of entrapped enzymes compared to those of the already activating membranes and larger particles. We demonstrated this on the example of APCN particles based on PHEA-l-PDMS loaded with α-Chymotrypsin, which resulted in an up to 28,000-fold higher activity of the enzyme compared to the enzyme powder. Furthermore, lipase from Rhizomucor miehei entrapped in particles based on PHEA-l-PEtOx was tested in n-heptane, chloroform, and substrate. Specific activities in smaller particles were 10- to 100-fold higher in comparison to the native enzyme. The carrier activity of PHEA-l-PEtOx microparticles was tenfold higher with some 25-50-fold lower enzyme content compared to a commercial product.

  17. Controlling Phase Separation of Tough Interpenetrating Polymer Networks via Addition of Amphiphilic Block Copolymers (United States)

    Rohde, Brian; Krishnamoorti, Ramanan; Robertson, Megan

    Interpenetrating polymer networks (IPNs) offer a unique way to combine the mechanical properties of two thermoset systems. Often used to create a material that possesses both high toughness and tensile properties, here we use polydicyclopentadiene, cured via ring opening metathesis polymerization, to contribute high toughness and diglycidyl ether of bisphenol A cured via anhydride chemistry to contribute high tensile strength and modulus. As the uncompatibilized system reacts in the presence of one another, mesoscopic phase separation occurs and dictates the overall efficacy of combining mechanical properties. To control phase separation and drive the system towards more mechanically robust nanostructed IPNs, amphiphilic block copolymers of polybutadiene- b-polyethylene oxide, where one block possesses strong affinity to polyDCPD and the other the DGEBA, were added to the system. Here we present a systematic study of the influence of block copolymer composition in the overall blend on degree of phase separation and morphology using a combination of small-angle x-ray scattering (SAXS) and scanning electron microscopy (SEM) techniques. The resultant mechanical properties are then explored in an effort to link mechanical properties to blend morphology.

  18. Synthesis of biodegradable amphiphilic Y-shaped block co-polymers via ring-opening polymerization for drug delivery. (United States)

    Jia, Lin; Yan, Lifeng; Li, Yang


    A series of novel Y-shaped biodegradable block co-polymers of poly(ε-caprolactone) (PCL) and poly(ethyl ethylene phosphate) (PEEP) (PCL-(PEEP)2) were synthesized via ring-opening polymerization (ROP) of EEP with bis-hydroxy-functional ROP initiator (init-PCL-(OH)2). The init-PCL-(OH)2 was synthesized by ROP of CL using 4-hydroxybutyl acrylate (HBA) as initiator and L-tartaric acid as catalyst in bulk, and subsequently the resulting vinyl-terminated PCL was end-capped by acetyl chloride, followed by Michael addition using excess diethanolamine. The Y-shaped co-polymers and their intermediates were characterized by (1)H-, (13)C-, (31)P-NMR, FT-IR and gel-permeation chromatography. The results indicated that the molecular weight of the Y-shaped co-polymers increased with the increasing of the molar ratios of EEP to init-PCL-(OH)2 in the feed, while the PCL chain length was kept constant. The amphiphilic block co-polymers could self-assemble into micelles in aqueous solution, which was demonstrated by dynamic light scattering, (1)H-NMR and atomic force microscopy. A study of controlled release of indomethacin indicated that the amphiphilic block co-polymers could potentially provide novel vehicles for drug delivery.

  19. Formation of polymer vesicles by amphiphilic fluorosiloxane graft copolymers in solution

    Institute of Scientific and Technical Information of China (English)

    Rui Gang Hou; Ling Min Yi; He Ming Lin; Jia Wei Li; Chuan Xia Huang


    Amphiphilic fluorosiloxane graft copolymers with a poly(dimethylsiloxane) (PDMS) backbone, a hydrophobic fluorosiloxane side-chain and three hydrophilic polyether side-chains were synthesized by hydrosilation reaction in this work. The micellization of amphiphilic graft copolymers in the water/ethanol solvent system was investigated, and vesicles with different size were formed after the self-assembly system was aged for different time.

  20. Platform Approach to Produce Polymer Nanoparticles with Modular Functionality from Amphiphilic Block Copolymer Stabilizers (United States)


    functionality, an amphiphilic BCP scaffold was devised to serve as an emulsion polymerization stabilizer. The PS-b-P(EO-co-AGE) BCP contained a PS...synthesized via emulsion polymerization using an amphiphilic block copolymer (BCP) surfactant. The polystyrene-block-poly(ethylene oxide-co-allyl...glycidyl ether) BCPs with various lengths and functional monomer incorporation were synthesized using anionic polymerization . Modification of the allyl

  1. Light transmission of polymer-dispersed liquid crystal layer composed of droplets with inhomogeneous surface anchoring (United States)

    Loiko, V. A.; Zyryanov, V. Ya.; Konkolovich, A. V.; Miskevich, A. A.


    We have developed a model and realized an algorithm for the calculation of the coefficient of coherent (direct) transmission of light through a layer of liquid crystal (LC) droplets in a polymer matrix. The model is based on the Hulst anomalous diffraction approximation for describing the scattering by an individual particle and the Foldy-Twersky approximation for a coherent field. It allows one to investigate polymer dispersed LC (PDLC) materials with homogeneous and inhomogeneous interphase surface anchoring on the droplet surface. In order to calculate the configuration of the field of the local director in the droplet, the relaxation method of solving the problem of minimization of the free energy volume density has been used. We have verified the model by comparison with experiment under the inverse regime of the ionic modification of the LC-polymer interphase boundary. The model makes it possible to solve problems of optimization of the optical response of PDLC films in relation to their thickness and optical characteristics of the polymer matrix, sizes, polydispersity, concentration, and anisometry parameters of droplets. Based on this model, we have proposed a technique for estimating the size of LC droplets from the data on the dependence of the transmission coefficient on the applied voltage.

  2. Self-consistent field theoretic simulations of amphiphilic triblock copolymer solutions: Polymer concentration and chain length effects

    Directory of Open Access Journals (Sweden)

    X.-G. Han


    Full Text Available Using the self-consistent field lattice model, polymer concentration φP and chain length N (keeping the length ratio of hydrophobic to hydrophilic blocks constant the effects on temperature-dependent behavior of micelles are studied, in amphiphilic symmetric ABA triblock copolymer solutions. When chain length is increased, at fixed φP, micelles occur at higher temperature. The variations of average volume fraction of stickers φcos and the lattice site numbers Ncols at the micellar cores with temperature are dependent on N and φP, which demonstrates that the aggregation of micelles depends on N and φP. Moreover, when φP is increased, firstly a peak appears on the curve of specific heat CV for unimer-micelle transition, and then in addition a primary peak, the secondary peak, which results from the remicellization, is observed on the curve of CV. For a long chain, in intermediate and high concentration regimes, the shape of specific heat peak markedly changes, and the peak tends to be a more broad peak. Finally, the aggregation behavior of micelles is explained by the aggregation way of amphiphilic triblock copolymer. The obtained results are helpful in understanding the micellar aggregation process.

  3. Characterization of Fe3O4/P(St-MPEO) Amphiphilic Magnetic Polymer Microspheres

    Institute of Scientific and Technical Information of China (English)


    Amphiphilic magnetic microspheres consisting of styrene and poly(ethylene oxide) macromonomer(MPEO) were prepared by dispersion copolymerization in the presence of Fe3O4 magnetic fluid in an ethanol/water medium. The sizes of the magnetic microspheres and their distribution were characterized by means of scanning electron microscopy(SEM). The surface morphology and the average surface roughness of the microspheres were investigated by virtue of atomic force microscopy(AFM). It was found that the microspheres exhibit microscopic phase-separate and the mean square surface roughness of the microspheres increases with increasing MPEO used in the copolymerization. The amphiphilic magnetic microspheres containing 0.4-3.5 mg/g hydroxyl groups could be prepared from MPEO with different concentrations and styrene.


    Institute of Scientific and Technical Information of China (English)

    Takeaki Miyamoto; Masahiko Minoda; Yoshinobu Tsujii


    Vinyl ether (VE)-based amphiphilic block copolymers with D-glucose residues as hydrophilic pendants were synthesized by CH3CH(OiBu)Cl/ZnI2-initiated sequential living cationic copolymerization of 3-O-(vinyloxy)ethyl-1, 2:5, 6-di-O-isopropylidene-D-glucofuranose (IGVE) and isobutyl VE (IBVE) and subsequent deprotection. The precursor block copolymers had a narrow molecular weight distribution(Mw/Mn~1.1) and a controlled segmental composition. The solubility characteristics of the amphiphilic copolymer depended strongly on composition. Their solvent-cast thin films were examined, under a transmission electron microscope, and could be seen to exhibit various microphase-separated surface morphologies such as spheres, cylinders, and lamellae, depending on composition. The amphiphilic copolymers with the appropriate segmental composition were found to form a stable monolayer at the airwater interface, which was successfully transferred onto a substrate by the Langmuir-Blodgett (LB)technique. The layered structure of the built-up LB films was controlled by blending the homopolymer.

  5. Molecular Differentiated Initiator Reactivity in the Synthesis of Poly(caprolactone-Based Hydrophobic Homopolymer and Amphiphilic Core Corona Star Polymers

    Directory of Open Access Journals (Sweden)

    Eileen Deng


    Full Text Available Macromolecules that possess three-dimensional, branched molecular structures are of great interest because they exhibit significantly differentiated application performance compared to conventional linear (straight chain polymers. This paper reports the synthesis of 3- and 4-arm star branched polymers via ring opening polymerisation (ROP utilising multi-functional hydroxyl initiators and Sn(Oct2 as precatalyst. The structures produced include mono-functional hydrophobic and multi-functional amphiphilic core corona stars. The characteristics of the synthetic process were shown to be principally dependent upon the physical/dielectric properties of the initiators used. ROP’s using initiators that were more available to become directly involved with the Sn(Oct2 in the “in-situ” formation of the true catalytic species were observed to require shorter reaction times. Use of microwave heating (MWH in homopolymer star synthesis reduced reaction times compared to conventional heating (CH equivalents, this was attributed to an increased rate of “in-situ” catalyst formation. However, in amphiphilic core corona star formation, the MWH polymerisations exhibited slower propagation rates than CH equivalents. This was attributed to macro-structuring within the reaction medium, which reduced the potential for reaction. It was concluded that CH experiments were less affected by this macro-structuring because it was disrupted by the thermal currents/gradients caused by the conductive/convective heating mechanisms. These gradients are much reduced/absent with MWH because it selectively heats specific species simultaneously throughout the entire volume of the reaction medium. These partitioning problems were overcome by introducing additional quantities of the species that had been determined to selectively heat.

  6. Spatially confined polymer chains: implications of chromatin fibre flexibility and peripheral anchoring on telomere telomere interaction (United States)

    Gehlen, L. R.; Rosa, A.; Klenin, K.; Langowski, J.; Gasser, S. M.; Bystricky, K.


    We simulate the extension of spatially confined chromatin fibres modelled as polymer chains and examine the effect of the flexibility of the fibre and its degree of freedom. The developed formalism was used to analyse experimental data of telomere-telomere distances in living yeast cells in the absence of confining factors as identified by the proteins Sir4 and yKu70. Our analysis indicates that intrinsic properties of the chromatin fibre, in particular its elastic properties and flexibility, can influence the juxtaposition of the telomeric ends of chromosomes. However, measurements in intact yeast cells showed that the telomeres of chromosomes 3 and 6 come even closer together than the parameters of constraint imposed on the simulations would predict. This juxtaposition was specific to telomeres on one contiguous chromosome and overrode a tendency for separation that is imposed by anchoring.

  7. A 'Plug and Play' Method to Create Water-dispersible Nanoassemblies Containing an Amphiphilic Polymer, Organic Dyes and Upconverting Nanoparticles. (United States)

    Arafeh, Khaled M; Asadirad, Amir M; Li, Jason Woodson; Wilson, Danielle; Wu, Tuoqi; Branda, Neil R


    In this protocol, we first describe a procedure to synthesize lanthanide doped upconverting nanoparticles (UCNPs). We then demonstrate how to generate amphiphilic polymers in situ, and describe a protocol to encapsulate the prepared UCNPs and different organic dye molecules (porphyrins and diarylethenes) using polymer shells to form stable water-dispersible nanoassemblies. The nanoassembly samples containing both the UCNPs and the diarylethene organic dyes have interesting photochemical and photophysical properties. Upon 365 nm UV irradiation, the diarylethene group undergoes a visual color change. When the samples are irradiated with visible light of another specific wavelength, the color fades and the samples return to the initial colorless state. The samples also emit visible light from the UCNPs upon irradiation with 980 nm near-infrared light. The emission intensity of the samples can be tuned through alternate irradiation with UV and visible light. Modulation of fluorescence can be performed for many cycles without observable degradation of the samples. This versatile encapsulation procedure allows for the transfer of hydrophobic molecules and nanoparticles from an organic solvent to an aqueous medium. The polymer helps to maintain a lipid-like microenvironment for the organic molecules to aid in preservation of their photochemical behavior in water. Thus this method is ideal to prepare water-dispersible photoresponsive systems. The use of near-infrared light to activate upconverting nanoparticles allows for lower energy light to be used to activate photoreactions instead of more harmful ultraviolet light.

  8. Characterization of novel soybean-oil-based thermosensitive amphiphilic polymers for drug delivery applications (United States)

    Characterization, aggregation behavior, physical properties and drug-polymer interaction of novel soybean oil-based polymers i.e., hydrolyzed polymers of (epoxidized) soybean oil (HPESO), were studied. The surface tension method was used to determine the critical micelle concentration (CMC). CMC w...

  9. Amphiphilic comblike polymers enhance the colloidal stability of Fe(3)O(4) nanoparticles. (United States)

    Kim, Myeongjin; Jung, Jaeyeon; Lee, Jonghwan; Na, Kyunga; Park, Subeom; Hyun, Jinho


    Stable colloidal dispersions of magnetite (Fe(3)O(4)) nanoparticles (MNPs) were obtained with the inclusion of an amphiphilic comblike polyethylene glycol derivative (CL-PEG) as an amphiphilic polymeric surfactant. Both the size and morphology of the resulting CL-PEG-modified MNPs could be controlled and were characterized by transmission electron microscopy (TEM). The interaction between MNPs and CL-PEG was confirmed by the presence of characteristic infrared absorption peaks, and the colloidal stability of the nanoparticle dispersion in water was evaluated by long-term observation of the dispersion using UV-visible spectroscopy. SQUID measurements confirmed the magnetization of CL-PEG-modified MNPs. The zeta potential of the CL-PEG-modified MNPs showed a dramatic conversion from positive to negative in response to the pH of the surrounding aqueous medium due to the presence of carboxyl groups at the surface. These carboxyl groups can be used to functionalize the MNPs with biomolecules for biotechnological applications. However, regardless of surface electrostatics, the flexible, hydrophilic side chains of CL-PEG-modified MNPs prevented the approach of adjacent nanoparticles, thereby resisting aggregation and resulting in a stable aqueous colloid. The cytotoxicity of MNPs and CL-PEG-modified MNPs was evaluated by a MTT assay.

  10. Polymer micelles with hydrophobic core and ionic amphiphilic corona. 1. Statistical distribution of charged and nonpolar units in corona. (United States)

    Lysenko, Evgeny A; Kulebyakina, Alevtina I; Chelushkin, Pavel S; Rumyantsev, Artem M; Kramarenko, Elena Yu; Zezin, Alexander B


    Polymer micelles with hydrophobic polystyrene (PS) core and ionic amphiphilic corona from charged N-ethyl-4-vinylpyridinium bromide (EVP) and uncharged 4-vinylpyridine (4VP) units spontaneously self-assembled from PS-block-poly(4VP-stat-EVP) macromolecules in mixed dimethylformamide/methanol/water solvent. The fraction of statistically distributed EVP units in corona-forming block is β = [EVP]/([EVP]+[4VP]) = 0.3-1. Micelles were transferred into water via dialysis technique, and pH was adjusted to 9, where 4VP is insoluble. Structural characteristics of micelles were investigated both experimentally and theoretically as a function of corona composition β. Methods of dynamic and static light scattering, electrophoretic mobility measurements, sedimentation velocity, transmission electron microscopy, and UV spectrophotometry were applied. All micelles possessed spherical morphology. The aggregation number, structure, and electrophoretic mobility of micelles changed in a jumplike manner near β ~ 0.6-0.75. Below and above this region, micelle characteristics were constant or insignificantly changed upon β. Theoretical dependencies for micelle aggregation number, corona dimensions, and fraction of small counterions outside corona versus β were derived via minimization the micelle free energy, taking into account surface, volume, electrostatic, and elastic contributions of chain units and translational entropy of mobile counterions. Theoretical estimations also point onto a sharp structural transition at a certain corona composition. The abrupt reorganization of micelle structure at β ~ 0.6-0.75 entails dramatic changes in micelle dispersion stability in the presence of NaCl or in the presence of oppositely charged polymeric (sodium polymethacrylate) or amphiphilic (sodium dodecyl sulfate) complexing agents.

  11. Real-Time Monitoring of Chemical and Topological Rearrangements in Solidifying Amphiphilic Polymer Co-Networks: Understanding Surface Demixing. (United States)

    Guzman, Gustavo; Nugay, Turgut; Kennedy, Joseph P; Cakmak, Mukerrem


    Amphiphilic polymer co-networks provide a unique route to integrating contrasting attributes of otherwise immiscible components within a bicontinuous percolating morphology and are anticipated to be valuable for applications such as biocatalysis, sensing of metabolites, and dual dialysis membranes. These co-networks are in essence chemically forced blends and have been shown to selectively phase-separate at surfaces during film formation. Here, we demonstrate that surface demixing at the air-film interface in solidifying polymer co-networks is not a unidirectional process; instead, a combination of kinetic and thermodynamic interactions leads to dynamic molecular rearrangement during solidification. Time-resolved gravimetry, low contact angles, and negative out-of-plane birefringence provided strong experimental evidence of the transitory trapping of thermodynamically unfavorable hydrophilic moieties at the air-film interface due to fast asymmetric solvent depletion. We also find that slow-drying hydrophobic elements progressively substitute hydrophilic domains at the surface as the surface energy is minimized. These findings are broadly applicable to common-solvent bicontinuous systems and open the door for process-controlled performance improvements in diverse applications. Similar observations could potentially be coupled with controlled polymerization rates to maximize the intermingling of bicontinuous phases at surfaces, thus generating true three-dimensional, bicontinuous, and undisturbed percolation pathways throughout the material.

  12. BRCAA1 antibody- and Her2 antibody-conjugated amphiphilic polymer engineered CdSe/ZnS quantum dots for targeted imaging of gastric cancer (United States)

    Li, Chao; Ji, Yang; Wang, Can; Liang, Shujing; Pan, Fei; Zhang, Chunlei; Chen, Feng; Fu, Hualin; Wang, Kan; Cui, Daxiang


    Successful development of safe and highly effective nanoprobes for targeted imaging of in vivo early gastric cancer is a great challenge. Herein, we choose the CdSe/ZnS (core-shell) quantum dots (QDs) as prototypical materials, synthesized one kind of a new amphiphilic polymer including dentate-like alkyl chains and multiple carboxyl groups, and then used the prepared amphiphilic polymer to modify QDs. The resultant amphiphilic polymer engineered QDs (PQDs) were conjugated with BRCAA1 and Her2 monoclonal antibody, and prepared BRCAA1 antibody- and Her2 antibody-conjugated QDs were used for in vitro MGC803 cell labeling and in vivo targeted imaging of gastric cancer cells. Results showed that the PQDs exhibited good water solubility, strong photoluminescence (PL) intensity, and good biocompatibility. BRCAA1 antibody- and Her2 antibody-conjugated QD nanoprobes successfully realized targeted imaging of in vivo gastric cancer MGC803 cells. In conclusion, BRCAA1 antibody- and Her2 antibody-conjugated PQDs have great potential in applications such as single cell labeling and in vivo tracking, and targeted imaging and therapeutic effects' evaluation of in vivo early gastric cancer cells in the near future.

  13. Use of hybrid composite particles prepared using alkoxysilane-functionalized amphiphilic polymer precursors for simultaneous removal of various pollutants from water. (United States)

    Cho, Seulki; Kim, Nahae; Lee, Soonjae; Lee, Hoseok; Lee, Sang-Hyup; Kim, Juyoung; Choi, Jae-Woo


    In this study, we present new inorganic-organic hybrid particles and their possible application as an adsorbent for simultaneous removal of hydrophobic and hydrophilic pollutants from water. These hybrid particles were prepared using tailor-made alkoxysilane-functionalized amphiphilic polymer precursors (M-APAS), which have amphiphilic polymers and reactive alkoxysilane groups attached to the same backbone. Through a single conventional sol-gel process, the polymerization of M-APAS and the chemical conjugation of M-APAS onto silica nanoparticles was simultaneous, resulting in the formation of hybrid particles (M-APAS-SiO2) comprised of hyperbranch-like amphiphilic polymers bonded onto silica nanoparticles with a relatively high grafting efficiency. A test for the adsorption of water-soluble dye (organe-16) and water insoluble dye (solvent blue-35) onto the hybrid particles was performed to evaluate the possibility of adsorbing hydrophilic and hydrophobic compound within the same particle. The hybrid particle was also evaluated as an adsorbent for the removal of contaminated water containing various pollutants by wastewater treatment test. The hybrid particle could remove phenolic compounds from wastewater and the azo dye reactive orange-16 from aqueous solutions, and it was easily separated from the treated wastewater because of the different densities involved. These results demonstrate that the hybrid particles are a promising sorbent for hydrophilic and/or hydrophobic pollutants in water.

  14. Effects of amphiphilic chitosan-g-poly(ε-caprolactone) polymer additives on paclitaxel release from drug eluting implants

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Weibin [Department of General Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092 (China); Gu, Chunhua [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Jiang, Han [Department of General Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200092 (China); Zhang, Mengru [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Lang, Meidong, E-mail: [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)


    Bioresorbable polymer stents have been proposed as promising medical implants to avoid long-term safety concerns and other potential issues caused by traditional materials. As an important member, poly(ε-caprolactone) (PCL) was used as the implant matrix with different drug loadings. To better regulate drug release rate, the hydrophilicity of PCL was adjusted by addition of amphiphilic graft copolymers, chitosan-g-poly(ε-caprolactone) (CP). The in vitro release results indicated that the improvement of bulk hydrophilicity could accelerate drug release better than that of surface coating. The optimum additive amount was 25% with CP9. Further study showed that the effect of aspirin molecules displayed no obvious difference to that of CP macromolecules on drug release rate. Moreover, these release profiles were fitted with mathematical models. The similarities were evaluated with similarity factors. Scanning electron microscopy (SEM) images displayed surface/cross-section morphologies of pure PCL and modified implants before and after release. - Highlights: • The improvement of bulk hydrophilicity better accelerated drug release. • The higher weight ratio of CP implants had, the faster the drug released. • The shorter PCL chain in CP graft coploymers, the faster the drug released. • The optimum additive amount was 25% with CP9. • Drug release profile conformed to controllable Fick diffusional release mechanism.

  15. Hydrophobically modified inulin as an amphiphilic carbohydrate polymer for micellar delivery of paclitaxel for intravenous route. (United States)

    Muley, Pratik; Kumar, Sunny; El Kourati, Fadoua; Kesharwani, Siddharth S; Tummala, Hemachand


    Micellization offers several advantages for the delivery of water insoluble drugs including a nanoparticulate 'core-shell' delivery system for drug targeting. Recently, hydrophobically modified polysaccharides (HMPs) are gaining recognition as micelle forming polymers to encapsulate hydrophobic drugs. In this manuscript, for the first time, we have evaluated the self-assembling properties of a lauryl carbamate derivative of the poly-fructose natural polymer inulin (Inutec SP1(®) (INT)) to form paclitaxel (PTX) loaded micelles. INT self-assembled into well-defined micellar structures in aqueous environment with a low critical micellar concentration of 27.8 μg/ml. INT micelles exhibited excellent hemocompatibility and low toxicity to cultured cells. PTX loaded INT micelles exhibited a mean size of 256.37 ± 10.45 nm with excellent drug encapsulation efficiency (95.66 ± 2.25%) and loading (8.69 ± 0.22%). PTX loaded micelles also displayed sustained release of PTX and enhanced anti-cancer efficacy in-vitro in mouse melanoma cells (B16F10) compared to Taxol formulation with Cremophor EL as solvent. In addition, PTX loaded INT micelles exhibited comparable in-vivo antitumor activity in B16F10 allograft mouse model at half the dose of Taxol. In conclusion, INT offers safe, inexpensive and natural alternative to widely used PEG-modified polymers for the formulation of micellar delivery systems for paclitaxel.

  16. Strain Measurement Using Embedded Fiber Bragg Grating Sensors Inside an Anchored Carbon Fiber Polymer Reinforcement Prestressing Rod for Structural Monitoring

    DEFF Research Database (Denmark)

    Kerrouche, Abdelfateh; Boyle, William J.O.; Sun, Tong


    Results are reported from a study carried out using a series of Bragg grating based optical fiber sensors written into a very short length (60mm) optical fiber net work and integrated into carbon fiber polymer reinforcement (CFPR) rod. Such rods are used as reinforcements in concrete structures...... from the calibrated force applied by the pulling machine and from a conventional resistive strain gauge mounted on the rod itself is obtained. Calculations from strain to shear stress show a relatively uniform stress distribution along the bar anchor used. The results give confidence to results from...... various methods of insitu monitoring of strains on such CFRP rods when used in different engineering structures....

  17. Effects of anchored flexible polymers on mechanical properties of model biomembranes

    CERN Document Server

    Wu, Hao; 10.1063/1.4794653


    We have studied biomembranes with grafted polymer chains using a coarse-grained membrane simulation, where a meshless membrane model is combined with polymer chains. We focus on the polymer-induced entropic effects on mechanical properties of membranes. The spontaneous curvature and bending rigidity of the membranes increase with increasing polymer density. Our simulation results agree with the previous theoretical predictions.

  18. Zwitterionic peptide anchored to conducting polymer PEDOT for the development of antifouling and ultrasensitive electrochemical DNA sensor. (United States)

    Wang, Guixiang; Han, Rui; Su, Xiaoli; Li, Yinan; Xu, Guiyun; Luo, Xiliang


    Zwitterionic peptides were anchored to a conducting polymer of citrate doped poly(3,4-ethylenedioxythiophene) (PEDOT) via the nickel cation coordination, and the obtained peptide modified PEDOT, with excellent antifouling ability and good conductivity, was further used for the immobilization of a DNA probe to construct an electrochemical biosensor for the breast cancer marker BRCA1. The DNA biosensor was highly sensitive (with detection limit of 0.03fM) and selective, and it was able to detect BRCA1 in 5% (v/v) human plasma with satisfying accuracy and low fouling. The marriage of antifouling and biocompatible peptides with conducting polymers opened a new avenue to construct electrochemical biosensors capable of assaying targets in complex biological media with high sensitivity and without biofouling.

  19. Neutron reflectivity of supported membranes incorporating terminally anchored polymers: Protrusions vs. blisters

    DEFF Research Database (Denmark)

    Fragneto, Giovanna; Halperin, Avraham; Klösgen-Buchkremer, Beate Maria;


    was characterized by w 1/2 , the width at half-height of the scattering length density profile. The inner headgroup layer was essentially unperturbed while w 1/2 of the outer layer increased significantly. This suggests that the anchored PEG chains give rise to headgroup protrusions rather than to blister...

  20. Co-Delivery of Imiquimod and Plasmid DNA via an Amphiphilic pH-Responsive Star Polymer that Forms Unimolecular Micelles in Water

    Directory of Open Access Journals (Sweden)

    Wenjing Lin


    Full Text Available Dual functional unimolecular micelles based on a pH-responsive amphiphilic star polymer β-CD-(PLA-b-PDMAEMA-b-PEtOxMA21 have been developed for the co-delivery of imiquimod and plasmid DNA to dendritic cells. The star polymer with well-defined triblock arms was synthesized by combining activator regenerated by electron-transfer atom-transfer radical polymerization with ring-opening polymerization. Dissipative particle dynamics simulation showed that core-mesophere-shell-type unimolecular micelles could be formed. Imiquimod-loaded micelles had a drug loading of 1.6 wt % and a larger average size (28 nm than blank micelles (19 nm. The release of imiquimod in vitro was accelerated at the mildly acidic endolysosomal pH (5.0 in comparison to physiologic pH (7.4. Compared with blank micelles, a higher N:P ratio was required for imiquimod-loaded micelles to fully condense DNA into micelleplexes averaging 200–400 nm in size. In comparison to blank micelleplexes, imiquimod-loaded micelleplexes of the same N:P ratio displayed similar or slightly higher efficiency of gene transfection in a mouse dendritic cell line (DC2.4 without cytotoxicity. These results suggest that such pH-responsive unimolecular micelles formed by the well-defined amphiphilic star polymer may serve as promising nano-scale carriers for combined delivery of hydrophobic immunostimulatory drugs (such as imiquimod and plasmid DNA with potential application in gene-based immunotherapy.

  1. Amphiphilic dendronized homopolymers

    Institute of Scientific and Technical Information of China (English)


    A series of second generation of amphiphilic dendronized homopolymers are efficiently synthesized,and their thermoresponsiveness in aqueous solutions and secondary structures in methanol solutions are described.These polymers are constructed in each repeat unit with various generations of hydrophobic 4-aminoproline and hydrophilic oligoethylene glycol (OEG)-based dendrons,and their over-all hydrophilicity is tuned by varying these dendron generations.Polymers with or without the first generation of proline dendron show good water solubility at room temperature,but exhibit typical thermoresponsive behaviors at elevated temperatures as characterized by turbidity measurements using UV-vis spectroscopy,while the polymer with the secondary generation of proline dendron is not soluble in water.All polymers show ordered secondary structures as evidenced by the optical rotation and circular dichroism experiments.Finally,assembly of these amphiphilic homopolymers into porous films via breath figure (BF) technique is described,and polymer structures are found to show significant influence on the morphology of porous film.

  2. pH-induced vesicle-to-micelle transition in amphiphilic diblock copolymer: investigation by energy transfer between in situ formed polymer embedded gold nanoparticles and fluorescent dye. (United States)

    Maiti, Chiranjit; Banerjee, Rakesh; Maiti, Saikat; Dhara, Dibakar


    The ability to regulate the formation of nanostructures through self-assembly of amphiphilic block copolymers is of immense significance in the field of biology and medicine. In this work, a new block copolymer synthesized by using reversible addition-fragmentation chain transfer (RAFT) polymerization technique from poly(ethylene glycol) monomethyl ether acrylate (PEGMA) and Boc-l-tryptophan acryloyloxyethyl ester (Boc-l-trp-HEA) was found to spontaneously form pH-responsive water-soluble nanostructures after removal of the Boc group. While polymer vesicles or polymerosomes were formed at physiological pH, the micelles were formed at acidic pH (transition. Formation of these nanostructures was confirmed by different characterization techniques, viz. transmission electron microscopy, dynamic light scattering, and steady-state fluorescence measurements. Further, these vesicles were successfully utilized to reduce HAuCl4 and stabilize the resulting gold nanoparticles (AuNPs). These AuNPs, confined within the hydrophobic shell of the vesicles, could participate in energy transfer process with fluorescent dye molecules encapsulated in the core of the vesicles, thus forming a nanometal surface energy transfer (NSET) pair. Subsequently, following the efficiency of energy transfer between this pair, it was possible to monitor the process of transition from vesicles to micelles. Thus, in this work, we have successfully demonstrated that NSET can be used to follow the transition between nanostructures formed by amphiphilic block copolymers.

  3. Nanopore gating with an anchored polymer in a switching electrolyte bias (United States)

    Wells, Craig C.; Jou, Ining A.; Melnikov, Dmitriy V.; Gracheva, Maria E.


    In this work, we theoretically study the interaction between a solid state membrane equipped with a nanopore and a tethered, negatively charged polymer chain subjected to a time-dependent applied electrolyte bias. In order to describe the movement of the chain in the biomolecule-membrane system immersed in an electrolyte solution, Brownian dynamics is used. We show that we can control the polymer's equilibrium position with various applied electrolyte biases: for a sufficiently positive bias, the chain extends inside the pore, and the removal of the bias causes the polymer to leave the pore. Corresponding to a driven process, we find that the time it takes for a biomolecular chain to enter and extend into a nanopore in a positive bias almost increases linearly with chain length while the amount of time it takes for a polymer chain to escape the nanopore is mainly governed by diffusion.

  4. Preparation of pH-sensitive amphiphilic block star polymers, their self-assembling characteristics and release behavior on encapsulated molecules

    KAUST Repository

    Song, Xiaowan


    Poly(ethylene glycol) (PEG), a polymer with excellent biocompatibility, was widely used to form nanoparticles for drug delivery applications. In this paper, based on PEG, a series of pH-sensitive amphiphilic block star polymers of poly(ethylene glycol)-block-poly(ethoxy ethyl glycidyl ether) (PEG-b-PEEGE) with different hydrophobic length were synthesized by living anionic ring-opening polymerization method. The products were characterized using 1H NMR and gel permeation chromatography. These copolymers could self-assemble in aqueous solution to form micellar structure with controlled morphologies. Transmission electron microscopy showed that the nanoparticles are spherical or rodlike with different hydrophilic mass fractions. The pH response of polymeric aggregates from PEG-b-PEEGE was detected by fluorescence probe technique at different pH. A pH-dependent release behavior was observed and pH-responsiveness of PEG-b-PEEGE was affected by the hydrophobic block length. These results demonstrated that star-shaped polymers (PEG-b-PEEGE) are attractive candidates as anticancer drug delivery carriers. © 2016 Springer-Verlag Berlin Heidelberg

  5. Novel polymer anchored Cr(III) Schiff base complexes: Synthesis, characterization and antimicrobial properties (United States)

    Selvi, Canan; Nartop, Dilek


    New polymer-bound Schiff bases and Cr(III) complexes have been synthesized by the reaction of 4-benzyloxybenzaldehyde, polymer-bound with 2-aminophenol, 2-amino-4-chlorophenol and 2-amino-4-methylphenol. The structure of polymeric-Schiff bases and their Cr(III) complexes have been characterized by elemental analyses, magnetic measurements, IR, UV-Vis, TG-DTA and 1H-NMR. All these compounds have also been investigated for antibacterial activity by the well-diffusion method against Staphylococcus aureus (RSKK-07035), Shigella dysenteria type 10 (RSKK 1036), Listeria monocytogenes 4b(ATCC 19115, Escherichia coli (ATCC 1230), Salmonella typhi H (NCTC 901.8394), Staphylococcus epidermis (ATCC 12228), Brucella abortus (RSKK-03026), Micrococcs luteus (ATCC 93419, Bacillus cereus sp., Pseudomonas putida sp. and for antifungal activity against Candida albicans (Y-1200-NIH).

  6. Anchoring-Induced Texture & Shear Banding of Nematic Polymers in Shear Cells (United States)


    varying orientation tensor ellipsoid at several locations between the plates. The Doi- Hess kinetic theory is developed to study the dynamics of LCP...profile is evident in one of the snapshots, a phenomenon seen by Sebastian Heidenreich in related studies and in full kinetic flow-nematic simulations of...kinetic phase diagram for nematic polymers, Rheol. Acta., 43 (2004), 17–37. [20] M.G. Forest, Q. Wang and R. Zhou, The flow-phase diagram of Doi- Hess

  7. Synthesis and In Vitro Cancer Cell Targeting of Folate-Functionalized Biodegradable Amphiphilic Dendrimer-Like Star Polymers

    NARCIS (Netherlands)

    Cao, Weiqiang; Zhou, Jing; Wang, Yong; Zhu, Lei


    By coupling a well-defined PLLA star polymer with six carboxylic acid-terminated polyester dendrons based on 2,2-bis(hydroxymethyl)propionic acid, a biodegradable dendrimer-like star polymer (DLSP) with multiple carboxylic acid groups at the outer surface was successfully synthesized. Conjugation of

  8. Bio-inspired Construction of Advanced Fuel Cell Cathode with Pt Anchored in Ordered Hybrid Polymer Matrix (United States)

    Xia, Zhangxun; Wang, Suli; Jiang, Luhua; Sun, Hai; Liu, Shuang; Fu, Xudong; Zhang, Bingsen; Sheng Su, Dang; Wang, Jianqiang; Sun, Gongquan


    The significant use of platinum for catalyzing the cathodic oxygen reduction reactions (ORRs) has hampered the widespread use of polymer electrolyte membrane fuel cells (PEMFCs). The construction of well-defined electrode architecture in nanoscale with enhanced utilization and catalytic performance of Pt might be a promising approach to address such barrier. Inspired by the highly efficient catalytic processes in enzymes with active centers embedded in charge transport pathways, here we demonstrate for the first time a design that allocates platinum nanoparticles (Pt NPs) at the boundaries with dual-functions of conducting both electrons by aid of polypyrrole and protons via Nafion® ionomer within hierarchical nanoarrays. By mimicking enzymes functionally, an impressive ORR activity and stability is achieved. Using this brand new electrode architecture as the cathode and the anode of a PEMFC, a high mass specific power density of 5.23 W mg−1Pt is achieved, with remarkable durability. These improvements are ascribed to not only the electron decoration and the anchoring effects from the Nafion® ionomer decorated PPy substrate to the supported Pt NPs, but also the fast charge and mass transport facilitated by the electron and proton pathways within the electrode architecture. PMID:26537781

  9. Amphiphilic polymer-mediated formation of laponite-based nanohybrids with robust stability and pH sensitivity for anticancer drug delivery. (United States)

    Wang, Guoying; Maciel, Dina; Wu, Yilun; Rodrigues, João; Shi, Xiangyang; Yuan, Yuan; Liu, Changsheng; Tomás, Helena; Li, Yulin


    The development of pH-sensitive drug delivery nanosystems that present a low drug release at the physiological pH and are able to increase the extent of the release at a lower pH value (like those existent in the interstitial space of solid tumors (pH 6.5) and in the intracellular endolysosomal compartments (pH 5.0)) is very important for an efficient and safe cancer therapy. Laponite (LP) is a synthetic silicate nanoparticle with a nanodisk structure (25 nm in diameter and 0.92 nm in thickness) and negative-charged surface, which can be used for the encapsulation of doxorubicin (DOX, a cationic drug) through electrostatic interactions and exhibit good pH sensitivity in drug delivery. However, the colloidal instability of LP still limits its potential clinical applications. In this study, we demonstrate an elegant strategy to develop stable Laponite-based nanohybrids through the functionalization of its surface with an amphiphile PEG-PLA copolymer by a self-assembly process. The hydrophobic block of PEG-PLA acts as an anchor that binds to the surface of drug-loaded LP nanodisks, maintaining the core structure, whereas the hydrophilic PEG part serves as a protective stealth shell that improves the whole stability of the nanohybrids under physiological conditions. The resulting nanocarriers can effectively load the DOX drug (the encapsulation efficiency is 85%), and display a pH-enhanced drug release behavior in a sustained way. In vitro biological evaluation indicated that the DOX-loaded nanocarriers can be effectively internalized by CAL-72 cells (an osteosarcoma cell line), and exhibit a remarkable higher anticancer cytotoxicity than free DOX. The merits of Laponite/PEG-PLA nanohybrids, such as good cytocompatibility, excellent physiological stability, sustained pH-responsive release properties, and improved anticancer activity, make them a promising platform for the delivery of other therapeutic agents beyond DOX.

  10. Polymer Physics Prize Lecture: Self-assemblies of Giant Molecular Shape Amphiphiles as a New Platform for Engineering Structures with Sub-Nanometer Feature Sizes (United States)

    Cheng, Stephen Z. D.


    Utilizing nano-building blocks rather than atoms to construct and engineer new structures is a fresh approach to design and develop functional materials for the purpose of transferring and amplifying microscopic functionality to macroscopic materials' property. As one of the important elements of these nano-building blocks, giant molecular shape amphiphiles (GMSAs) provide a latest platform for generating self-assembled ordered structures at nanometer scale, which are stabilized by collective physical bonds (such as collective hydrogen bonding). In this talk, two topics will be focused on. First, composed of functionalized hydrophilic molecular nanoparticles as the heads with rigid shape and fixed volume, and tethered polymer chains as the tails (such as giant molecular surfactants and lipids and other topologies), these GMSAs of various architectures can self-assemble into highly diversified, thermodynamically stable microstructures at sub-10 nm length scale in the bulk, thin film and solution states. Second, GMSAs could also be constructed solely from nanoparticles interconnected via different numbers of the rigid linkages in specific symmetry, simulating the overall shapes of small molecules but with sizes that are one-order of magnitude larger in length and three-order of magnitude larger in volume. Giant crystal structures can then be obtained from this class of ``giant molecules'' via supramolecular crystallization. These findings are not only scientifically intriguing in understanding the physical principles underlying their self-assembly, but also technologically relevant in industrial applications.

  11. Going beyond the classical amphiphilicity paradigm: the self-assembly of completely hydrophobic polymers into free-standing sheets and hollow nanostructures in solvents of variable quality. (United States)

    Huang, Huanting; Liao, Yin; Bu, Weifeng; Wang, Wenjie; Sun, Jing Zhi


    Self-assembly is well-known to occur in amphiphiles, and the totally hydrophobic ones are never reported to self-assemble. In this work we report for the first time that the latter can self-assemble into free-standing sheets and hollow spheres in toluene/methanol mixed solvents by modulating the solvent quality. The homopolymers studied in this work are polystyrene (PS), polyphenylacetylene (PPA), and poly(3-hexyl thiophene) (P3HT), representing polymers with different rigidity. All the three form a homogenous solution in toluene, but self-assembly occurs in the toluene/methanol mixed solvents. Micrometer sized free-standing sheets were formed for PS, PPA, and P3HT at methanol volume fractions being 43%, 50%, and 67%, respectively, and hollow spheres were observed for PPA at higher methanol fractions of 75 and 90%. Under the latter solvent conditions, PS forms solid spheres, yet ill-defined aggregates and free-standing sheets coexist in the case of P3HT. This non-solvent induced self-assembly was explained by a delicate balance of two "opposing forces": van der Waals attractive and entropic repulsive forces generated between the segments of these homopolymers within a single chain, between two chains, and among more chains in the solvents of worsened quality.

  12. Doxorubicin-loaded aromatic imine-contained amphiphilic branched star polymer micelles: synthesis, self-assembly, and drug delivery

    Directory of Open Access Journals (Sweden)

    Qiu L


    Full Text Available Liang Qiu, Chun-Yan Hong, Cai-Yuan Pan Chinese Academy of Sciences Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei, Anhui, People’s Republic of China Abstract: Redox- and pH-sensitive branched star polymers (BSPs, BP(DMAEMA-co-MAEBA-co-DTDMA(PMAIGPns, have been successively prepared by two steps of reversible addition–fragmentation chain transfer (RAFT polymerization. The first step is RAFT polymerization of 2-(N,N-dimethylaminoethylmethacrylate (DMAEMA and p-(methacryloxyethoxybenzaldehyde (MAEBA in the presence of divinyl monomer, 2,2'-dithiodiethoxyl dimethacrylate (DTDMA. The resultant branched polymers were used as a macro-RAFT agent in the subsequent RAFT polymerization. After hydrolysis of the BSPs to form BP(DMAEMA-co-MAEBA-co-DTDMA(PMAGPns (BSP-H, the anticancer drug doxorubicin (DOX was covalently linked to branched polymer chains by reaction of primary amine of DOX and aldehyde groups in the polymer chains. Their compositions, structures, molecular weights, and molecular weight distributions were respectively characterized by nuclear magnetic resonance spectra and gel permeation chromatography measurements. The DOX-loaded micelles were fabricated by self-assembly of DOX-containing BSPs in water, which were characterized by transmission electron microscopy and dynamic light scattering. Aromatic imine linkage is stable in neutral water, but is acid-labile; controlled release of DOX from the BSP-H-DOX micelles was realized at pH values of 5 and 6, and at higher acidic solution, fast release of DOX was observed. In vitro cytotoxicity experiment results revealed low cytotoxicity of the BSPs and release of DOX from micelles in HepG2 and HeLa cells. Confocal laser fluorescence microscopy observations showed that DOX-loaded micelles have specific interaction with HepG2 cells. Thus, this type of BSP micelle is an efficient drug delivery system

  13. Facile Determination of Molecular Structure Trends in Amphiphilic Core Corona Star Polymer Synthesis via Dielectric Property Measurement. (United States)

    Hild, Frederic; Nguyen, Nam T; Deng, Eileen; Katrib, Juliano; Dimitrakis, Georgios; Lau, Phei-Li; Irvine, Derek J


    The use of dielectric property measurements to define specific trends in the molecular structures of poly(caprolactone) containing star polymers and/or the interbatch repeatability of the synthetic procedures used to generate them is demonstrated. The magnitude of the dielectric property value is shown to accurately reflect: (a) the number of functional groups within a series of materials with similar molecular size when no additional intermolecular order is present in the medium, (b) the polymer molecular size for a series of materials containing a fixed core material and so functional group number, and/or (c) the batch to batch repeatability of the synthesis method. The dielectric measurements are validated by comparison to spectroscopic/chromatographic data.

  14. Stretching and imaging of single DNA chains on a hydrophobic polymer surface made of amphiphilic alternating comb-copolymer. (United States)

    Liu, Rongrong; Wong, Sheau Tyug; Lau, Peggy Pei Zhi; Tomczak, Nikodem


    Functionalization of amine derivatized glass slides with a poly(maleic anhydride)-based comb-copolymer to facilitate stretching, aligning, and imaging of individual dsDNA chains is presented. The polymer-coated surface is hydrophobic due to the presence of the long alkyl side chains along the polymer backbone. The surface is also characterized by low roughness and a globular morphology. Stretched and aligned bacteriophage λ-DNA chains were obtained using a robust method based on stretching by a receding water meniscus at pH 7.8 without the need for small droplet volumes or precoating the surface with additional layers of (bio)molecules. Although the dye to DNA base pairs ratio did not influence substantially the stretching length distributions, a clear peak at stretching lengths close to the contour length of the dsDNA is visible at larger staining ratios.

  15. Trapping of defect point to improve response time via controlled azimuthal anchoring in a vertically aligned liquid crystal cell with polymer wall

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Gyun; Kim, Sung Min; Kim, Youn Sik; Lee, Hee Kyu; Lee, Seung Hee [Polymer BIN Fusion Research Center, School of Advanced Materials Engineering, Chonbuk National University, Chonju, Chonbuk 561-756 (Korea, Republic of); Lyu, Jae-Jin; Kim, Kyeong Hyeon [AMLCD Division, Samsung Electronics, Kiheung, Kyunggi-Do 449-711 (Korea, Republic of); Lu, Ruibo; Wu, Shin-Tson [College of Optics and Photonics, University of Central Florida, Orlando FL 32816 (United States)], E-mail:


    Conventional multi-domain vertically aligned liquid crystal (LC) cells have defect points due to the collision of LC directors during the formation of multiple domains. In addition, the location of defects changes with time resulting in a slow response time. This paper proposes a robust vertically aligned LC cell, where the LCs are locked by polymer walls, and the azimuthal anchoring on the surface of the alignment layer is controlled by the polymerization of a UV curable reactive mesogen monomer. As a result, the defect points are trapped at a single position, resulting in a greatly improved response time.

  16. A comparative study on the effects of amphiphilic and hydrophilic polymers on the release profiles of a poorly water-soluble drug. (United States)

    Irwan, Anastasia W; Berania, Jacqueline E; Liu, Xueming


    This paper reports the use of two crystalline polymers, an amphiphilic Pluronic® F-127 (PF-127) and a hydrophilic poly(ethylene glycol) (PEG6000) as drug delivery carriers for improving the drug release of a poorly water-soluble drug, fenofibrate (FEN), via micelle formation and formation of a solid dispersion (SD). In 10% PF-127 (aq.), FEN showed an equilibrium solubility of ca. 0.6 mg/mL, due to micelle formation. In contrast, in 10% PEG6000 (aq.), FEN only exhibited an equilibrium solubility of 0.0037 mg/mL. FEN-loaded micelles in PF-127 were prepared by direct dissolution and membrane dialysis. Both methods only yielded a highest drug loading (DL) of 0.5%. SDs of FEN in PF-127 and PEG6000, at DLs of 5-80%, were prepared by solvent evaporation. In-vitro dissolution testing showed that both micelles and SDs significantly improved FEN's release rate. The SDs of FEN in PF-127 showed significantly faster release than crystalline FEN, when the DL was as high as 50%, whereas SDs of PEG6000 showed similar enhancement in the release rate when the DL was not more than 20%. The DSC thermograms of SDs of PF-127 exhibited a single phase transition peak at ca. 55-57 °C when the DL was not more than 50%, whereas those in PEG6000 exhibited a similar peak at ca. 61-63 °C when the DL was not more than 35%. When the DL exceeded 50% for SDs of PF-127 and 35% for SDs of PEG6000, DSC thermograms showed two melting peaks for the carrier polymer and FEN, respectively. FT-IR studies revealed that PF-127 has a stronger hydrophobic-hydrophobic interaction with FEN than PEG6000. It is likely that both dispersion and micelle formation contributed to the stronger effect of PF-127 on enhancing the release rate of FEN in its SDs.

  17. Bioefficacy evaluation of controlled release formulations based on amphiphilic nano-polymer of carbofuran against Meloidogyne incognita infecting tomato. (United States)

    Pankaj; Shakil, Najam Akhtar; Kumar, Jitendra; Singh, M K; Singh, Khajan


    In the present investigation, the bioefficacy of developed carbofuran formulations, with PEG-600 (7a, CP1) & PEG-900 (7b, CP2) @ 5, 10 and 20 ppm, along with commercial formulation of carbofuran 3G (CP0) were evaluated against the root-knot nematode, Meloidogyne incognita infecting tomato (cv. Pusa Ruby) in pot and field conditions. The bioefficacy data indicated that the formulations developed by utilizing polymers having PEG - 900 (7b) as hydrophilic segment were effective even at 14 days post inoculation (dpi) as evident from shoot and root length. Also, the reduction in penetration was found to be maximum with CP2 (3.6 - 4.6 J2s) at all concentrations compared to CP1 (6.6-16.4 J2s) and CP0 (29.3-32.6 J2s). Overall, CP2 was more effective in reducing the number of nematodes up to 14 days, compared to CP1 and CP0. Both the CR formulations (CP1 and CP2) in general significantly reduced the number of galls, when compared to CP0. However, under field conditions, lower concentrations (5, and 10 ppm) of CP2, were less effective in controlling the gall formation whereas, CP2 at 20 ppm, was most effective than other treatments. The study revealed that the developed CR formulations of carbofuran have the potential for effective management of M. incognita in tomato under field conditions.

  18. Anchoring Distortions Coupled with Plane Couette & Poiseuille Flows of Nematic Polymers in Viscous Solvents: Morphology in Molecular Orientation, Stress & Flow (United States)


    COUETTE & POISEUILLE FLOWS OF NEMATIC POLYMERS IN VISCOUS SOLVENTS: MORPHOLOGY IN MOLECULAR ORIENTATION, STRESS & FLOW Hong Zhou...viscoelastic stresses, and flow feedback. Pre- vious studies in plane Couette & Poiseuille flow (with the exception of [7]) have focused on the coupling between...with Plane Couette & Poiseuille Flows of Nematic Polymers in Viscous Solvents: Morphology in Molecular Orientation, Stress & Flow 5a. CONTRACT

  19. Shape-anchored porous polymer monoliths for integrated online solid-phase extraction-microchip electrophoresis-electrospray ionization mass spectrometry. (United States)

    Nordman, Nina; Barrios-Lopez, Brianda; Laurén, Susanna; Suvanto, Pia; Kotiaho, Tapio; Franssila, Sami; Kostiainen, Risto; Sikanen, Tiina


    We report a simple protocol for fabrication of shape-anchored porous polymer monoliths (PPMs) for on-chip SPE prior to online microchip electrophoresis (ME) separation and on-chip (ESI/MS). The chip design comprises a standard ME separation channel with simple cross injector and a fully integrated ESI emitter featuring coaxial sheath liquid channel. The monolith zone was prepared in situ at the injection cross by laser-initiated photopolymerization through the microchip cover layer. The use of high-power laser allowed not only maskless patterning of a precisely defined monolith zone, but also faster exposure time (here, 7 min) compared with flood exposure UV lamps. The size of the monolith pattern was defined by the diameter of the laser output (∅500 μm) and the porosity was geared toward high through-flow to allow electrokinetic actuation and thus avoid coupling to external pumps. Placing the monolith at the injection cross enabled firm anchoring based on its cross-shape so that no surface premodification with anchoring linkers was needed. In addition, sample loading and subsequent injection (elution) to the separation channel could be performed similar to standard ME setup. As a result, 15- to 23-fold enrichment factors were obtained already at loading (preconcentration) times as short as 25 s without sacrificing the throughput of ME analysis. The performance of the SPE-ME-ESI/MS chip was repeatable within 3.1% and 11.5% RSD (n = 3) in terms of migration time and peak height, respectively, and linear correlation was observed between the loading time and peak area.

  20. Amphiphile nanoarchitectonics: from basic physical chemistry to advanced applications. (United States)

    Ramanathan, Muruganathan; Shrestha, Lok Kumar; Mori, Taizo; Ji, Qingmin; Hill, Jonathan P; Ariga, Katsuhiko


    Amphiphiles, either synthetic or natural, are structurally simple molecules with the unprecedented capacity to self-assemble into complex, hierarchical geometries in nanospace. Effective self-assembly processes of amphiphiles are often used to mimic biological systems, such as assembly of lipids and proteins, which has paved a way for bottom-up nanotechnology with bio-like advanced functions. Recent developments in nanostructure formation combine simple processes of assembly with the more advanced concept of nanoarchitectonics. In this perspective, we summarize research on self-assembly of amphiphilic molecules such as lipids, surfactants or block copolymers that are a focus of interest for many colloid, polymer, and materials scientists and which have become increasingly important in emerging nanotechnology and practical applications, latter of which are often accomplished by amphiphile-like polymers. Because the fundamental science of amphiphiles was initially developed for their solution assembly then transferred to assemblies on surfaces as a development of nanotechnological techniques, this perspective attempts to mirror this development by introducing solution systems and progressing to interfacial systems, which are roughly categorized as (i) basic properties of amphiphiles, (ii) self-assembly of amphiphiles in bulk phases, (iii) assembly on static surfaces, (iv) assembly at dynamic interfaces, and (v) advanced topics from simulation to application. This progression also represents the evolution of amphiphile science and technology from simple assemblies to advanced assemblies to nanoarchitectonics.

  1. The role of amphiphiles

    NARCIS (Netherlands)

    Hoekstra, F.A.; Golovina, E.A.


    This paper reviews our work on the partitioning of amphiphilic compounds from the cytoplasm into membranes during drying of plant systems, and discusses how relevant this phenomenon might be for anhydrobiosis. Amphiphilic guest molecules do partition into membranes and oil bodies, as demonstrated by

  2. Microfluidics-assisted generation of stimuli-responsive hydrogels based on alginates incorporated with thermo-responsive and amphiphilic polymers as novel biomaterials. (United States)

    Karakasyan, C; Mathos, J; Lack, S; Davy, J; Marquis, M; Renard, D


    We used a droplet-based microfluidics technique to produce monodisperse responsive alginate-block-polyetheramine copolymer microgels. The polyetheramine group (PEA), corresponding to a propylene oxide /ethylene oxide ratio (PO/EO) of 29/6 (Jeffamine(®) M2005), was condensed, via the amine link, to alginates with various mannuronic/guluronic acids ratios and using two alginate:jeffamine mass ratios. The size of the grafted-alginate microgels varied from 60 to 80 μm depending on the type of alginate used and the degree of substitution. The droplet-based microfluidics technique offered exquisite control of both the dimension and physical chemical properties of the grafted-alginate microgels. These microgels were therefore comparable to isolated grafted-alginate chains in retaining both their amphiphilic and thermo-sensitive properties. Amphiphilicity was demonstrated at the oil-water interface where grafted-alginate microgels were found to decrease interfacial tension by ∼ 50%. The thermo-sensitivity of microgels was clearly demonstrated and a 10 to 20% reduction in size between was evidenced on increasing the temperature above the lower critical solution temperature (TLCST) of Jeffamine. In addition, the reversibility of thermo-sensitivity was demonstrated by studying the oil-water affinity of microgels with temperature after Congo red labeling. Finally, droplet-based microfluidics was found to be a good and promising tool for generating responsive biobased hydrogels for drug delivery applications and potential new colloidal stabilizers for dispersed systems such as Pickering emulsions.

  3. Change in the Affinity of Ethylene Glycol Methacrylate Phosphate Monomer and Its Polymer Anchored on a Graphene Oxide Platform toward Uranium(VI) and Plutonium(IV) Ions. (United States)

    Chappa, Sankararao; Singha Deb, Ashish K; Ali, Sk Musharaf; Debnath, A K; Aswal, D K; Pandey, Ashok K


    The complexation behavior of the carbonyl and phosphoryl ligating groups bearing ethylene glycol methacrylate phosphate (EGMP) monomer and its polymer fixed on a graphene oxide (GO) platform was studied to understand the coordination ability of segregated EGMP units and polymer chains toward UO2(2+) and Pu(4+) ions. The cross-linked poly(EGMP) gel and EGMP dissolved in solution have a similar affinity toward these ions. UV-initiator induced polymerization was used to graft poly(EGMP) on the GO platform utilizing a double bond of EGMP covalently fixed on it. X-ray photoelectron spectroscopy (XPS) of the GO and GO-EGMP was done to confirm covalent attachment of the EGMP via a -C-O-P- link between GO and EGMP. The extent of poly(EGMP) grafting on GO by thermal analyses was found to be 5.88 wt %. The EGMP units fixed on the graphene oxide platform exhibited a remarkable selectivity toward Pu(4+) ions at high HNO3 conc. where coordination is a dominant mode involved in the sorption of ions. The ratio of distribution coefficients of Pu(IV) to U(VI) (DPu(IV)/DU(VI)) followed a trend as cross-linked poly(EGMP) (0.95) ions with the EGMP molecule anchored on GO in the presence of nitrate ions. This computational modeling suggested that Pu(4+) ion formed a strong coordination complex with phosphoryl and carbonyl ligating groups of the GO-EGMP as compared to UO2(2+) ions. Thus, the nonselective EGMP becomes highly selective to Pu(IV) ions when it interacts as a single unit fixed on a GO platform.

  4. Preparation and Characterization of Amphiphilic Triblock Terpolymer-Based Nanofibers as Antifouling Biomaterials

    KAUST Repository

    Cho, Youngjin


    Antifouling surfaces are critical for the good performance of functional materials in various applications including water filtration, medical implants, and biosensors. In this study, we synthesized amphiphilic triblock terpolymers (tri-BCPs, coded as KB) and fabricated amphiphilic nanofibers by electrospinning of solutions prepared by mixing the KB with poly(lactic acid) (PLA) polymer. The resulting fibers with amphiphilic polymer groups exhibited superior antifouling performance to the fibers without such groups. The adsorption of bovine serum albumin (BSA) on the amphiphilic fibers was about 10-fold less than that on the control surfaces from PLA and PET fibers. With the increase of the KB content in the amphiphilic fibers, the resistance to adsorption of BSA was increased. BSA was released more easily from the surface of the amphiphilic fibers than from the surface of hydrophobic PLA or PET fibers. We have also investigated the structural conformation of KB in fibers before and after annealing by contact angle measurements, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and coarse-grained molecular dynamics (CGMD) simulation to probe the effect of amphiphilic chain conformation on antifouling. The results reveal that the amphiphilic KB was evenly distributed within as-spun hybrid fibers, while migrated toward the core from the fiber surface during thermal treatment, leading to the reduction in antifouling. This suggests that the antifouling effect of the amphiphilic fibers is greatly influenced by the arrangement of amphiphilic groups in the fibers. © 2012 American Chemical Society.

  5. Anchor Modeling (United States)

    Regardt, Olle; Rönnbäck, Lars; Bergholtz, Maria; Johannesson, Paul; Wohed, Petia

    Maintaining and evolving data warehouses is a complex, error prone, and time consuming activity. The main reason for this state of affairs is that the environment of a data warehouse is in constant change, while the warehouse itself needs to provide a stable and consistent interface to information spanning extended periods of time. In this paper, we propose a modeling technique for data warehousing, called anchor modeling, that offers non-destructive extensibility mechanisms, thereby enabling robust and flexible management of changes in source systems. A key benefit of anchor modeling is that changes in a data warehouse environment only require extensions, not modifications, to the data warehouse. This ensures that existing data warehouse applications will remain unaffected by the evolution of the data warehouse, i.e. existing views and functions will not have to be modified as a result of changes in the warehouse model.

  6. The role of amphiphiles. (United States)

    Hoekstra, Folkert A; Golovina, Elena A


    This paper reviews our work on the partitioning of amphiphilic compounds from the cytoplasm into membranes during drying of plant systems, and discusses how relevant this phenomenon might be for anhydrobiosis. Amphiphilic guest molecules do partition into membranes and oil bodies, as demonstrated by the results of in vivo electron paramagnetic resonance spectroscopy on incorporated spin probes. Arguments for the likelihood of endogenous cytoplasmic amphiphiles behaving similarly during dehydration and rehydration of plant systems are presented. Negative and positive aspects of the partitioning are summarized. Positive aspects are the automatic insertion of amphiphilic antioxidants into membranes of the dehydrating organism, and the control of membrane fluidity and the phase transition temperature. A negative aspect is the perturbation of membrane structure, leading to increased permeability and loss of function. The finding that after an initial fluidization during dehydration, the membrane surface becomes immobilized in desiccation-tolerant systems and not in desiccation-sensitive systems, is discussed in the light of a strict control of the effect of partitioning. The adaptive significance of amphiphile partitioning into the membranes of anhydrobiotes is discussed.

  7. Contribution of hydrophobic/hydrophilic modification on cationic chains of poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) amphiphilic co-polymer in gene delivery. (United States)

    Han, Shangcong; Wan, Haiying; Lin, Daoshu; Guo, Shutao; Dong, Hongxu; Zhang, Jianhua; Deng, Liandong; Liu, Ruming; Tang, Hua; Dong, Anjie


    Nanoparticles (NPs) assembled from amphiphilic polycations have been certified as potential carriers for gene delivery. Structural modification of polycation moieties may be an efficient route to further enhance gene delivery efficiency. In this study two electroneutral monomers with different hydrophobicities, 2-hydroxyethyl methacrylate (HEMA) and 2-hydroxyethyl acrylate (HEA), were incorporated into the cationic poly(dimethylamino ethyl methacrylate) (PDMAEMA) side-chains of amphiphilic poly(ε-caprolactone)-graft-poly(dimethylamino ethylmethacrylate) (PCD) by random co-polymerization, to obtain poly(ε-caprolactone)-graft-poly(dimethylamino ethyl methacrylate-co-2-hydroxyethyl methacrylate) (PCD-HEMA) and poly(ε-caprolactone)-graft-poly(dimethylamino ethyl methacrylate-co-2-hydroxyethyl acrylate) (PCD-HEA). Minimal HEA or HEMA moieties in PDMAEMA do not lead to statistically significant changes in particle size, zeta potential, DNA condensation properties and buffering capacity of the naked NPs. However, the incorporation of HEMA and HEA lead to reductions and increases, respectively, in the surface hydrophilicity of the naked NPs and NPs/DNA complexes, which was confirmed by water contact angle assay. These simple modifications of PDMAEMA with HEA and HEMA moieties significantly affect the gene transfection efficiency on HeLa cells in vitro: PCD-HEMA NP/DNA complexes show a much higher transfection efficiency than PCD NPs/DNA complexes, while PCD-HEA NPs/DNA complexes show a lower transfection efficiency than PCD NP/DNA complexes. Fluorescence activated cell sorter and confocal laser scanning microscope results indicate that the incorporation of hydrophobic HEMA moieties facilitates an enhancement in both cellular uptake and endosomal/lysosomal escape, leading to a higher transfection efficiency. Moreover, the process of endosomal/lysosomal escape confirmed in our research that PCD and its derivatives do not just rely on the proton sponge mechanism, but also

  8. Release kinetics of controlled release formulations of thiamethoxam employing nano-ranged amphiphilic PEG and diacid based block polymers in soil. (United States)

    Sarkar, Dhruba Jyoti; Kumar, Jitendra; Shakil, N A; Walia, S


    Amphiphilic copolymers, synthesized from poly(ethylene glycols) and various aliphatic and aromatic diacids, which self-assemble into nanomicellar aggregates in aqueous media, were used to develop controlled release (CR) formulations of thiamethoxam (3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro)amine) using encapsulation technique Formulations were characterised by Infrared (IR) spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). Encapsulation efficiency, loading capacity and stability after accelerated storage test of the developed formulations were checked. The kinetics of thiamethoxam, released in sandy loam soil from the different formulations was studied. Release from the commercial formulation was faster than the CR formulations. The time taken for release of 50 % of thiamethoxam ranged from 3.56 to 6.07 days for the CR formulations. Although the diffusion exponent (n value) of thiamethoxam in soil ranged from 0.532 to 0.881 in the tested formulations showing non-Fickian transport. These CR formulations may be used in safer, effective and economic crop protection.

  9. Blends of Amphiphilic, Hyperbranched Polyesters and Different Polyolefins

    NARCIS (Netherlands)

    Schmaljohann, D.; Pötschke, P.; Hässler, R.; Voit, B.I.; Froehling, P.E.; Mostert, B.; Loontjens, J.A.


    A hyperbranched polyester based on 3,5-dihydroxybenzoic acid was completely modified with dodecanoyl chloride to result in an amphiphilic, globular polymer, which has a polar core and a nonpolar outer sphere with the ability both to incorporate an organic dye and to interact with a nonpolar matrix.

  10. Stimuli Responsive Amphiphilic Assemblies (United States)


    Amphiphilic Nanocontainers, Angewandte Chemie International Edition , (03 2011): 0. doi: 10.1002/anie.201006193 TOTAL: 4 Number of Papers published in... International Conference on Novel Materials and their Synthesis, Xi An, China, October 14-19, 2012 (Organizers: Anning Zhou, Min Zhang & Yuping Wu, Fudan...University) Plenary Lecture, PolyTech – 2012: International Conference on Advances in Polymeric Materials & Nanotechnology, Pune, India, Dec. 15

  11. New amphiphilic glycopolymers by click functionalization of random copolymers – application to the colloidal stabilisation of polymer nanoparticles and their interaction with concanavalin A lectin

    Directory of Open Access Journals (Sweden)

    Otman Otman


    Full Text Available Glycopolymers with mannose units were readily prepared by click chemistry of an azido mannopyranoside derivative and a poly(propargyl acrylate-co-N-vinyl pyrrolidone. These glycopolymers were used as polymer surfactants, in order to obtain glycosylated polycaprolactone nanoparticles. Optimum stabilization for long time storage was achieved by using a mixture of glycopolymers and the non-ionic triblock copolymer Pluronic® F-68. The mannose moieties are accessible at the surface of nanoparticles and available for molecular recognition by concanavalin A lectin. Interaction of mannose units with the lectin were evaluated by measuring the changes in nanoparticles size by dynamic light scattering in dilute media.

  12. Amphiphiles Self-Assembly: Basic Concepts and Future Perspectives of Supramolecular Approaches

    Directory of Open Access Journals (Sweden)

    Domenico Lombardo


    Full Text Available Amphiphiles are synthetic or natural molecules with the ability to self-assemble into a wide variety of structures including micelles, vesicles, nanotubes, nanofibers, and lamellae. Self-assembly processes of amphiphiles have been widely used to mimic biological systems, such as assembly of lipids and proteins, while their integrated actions allow the performance of highly specific cellular functions which has paved a way for bottom-up bionanotechnology. While amphiphiles self-assembly has attracted considerable attention for decades due to their extensive applications in material science, drug and gene delivery, recent developments in nanoscience stimulated the combination of the simple approaches of amphiphile assembly with the advanced concept of supramolecular self-assembly for the development of more complex, hierarchical nanostructures. Introduction of stimulus responsive supramolecular amphiphile assembly-disassembly processes provides particularly novel approaches for impacting bionanotechnology applications. Leading examples of these novel self-assembly processes can be found, in fact, in biosystems where assemblies of different amphiphilic macrocomponents and their integrated actions allow the performance of highly specific biological functions. In this perspective, we summarize in this tutorial review the basic concept and recent research on self-assembly of traditional amphiphilic molecules (such as surfactants, amphiphile-like polymers, or lipids and more recent concepts of supramolecular amphiphiles assembly which have become increasingly important in emerging nanotechnology.

  13. Grafting amphiphilic brushes onto halloysite nanotubes via a living RAFT polymerization and their Pickering emulsification behavior. (United States)

    Hou, Yifan; Jiang, Junqing; Li, Kai; Zhang, Yanwu; Liu, Jindun


    Amphiphilic brushes of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) are grafted onto halloysite nanotubes (HNTs) via a surface reversible addition-fragmentation chain transfer (RAFT) living polymerization through anchoring R group in RAFT agent S-1-dodecyl-S'-(R,R'-dimethyl-R″-acetic acid) trithiocarbonates (DDMAT). The characterization of TGA, TEM, and GPC show that amphiphilic brushes are successfully grafted onto HNTs in a living manner. To verify the amphiphilicity of HNTs grafted with block copolymers, their Pickering emulsification behavior in water/soybean oil diphase mixture is studied. The results show that modified HNTs can emulsify water/soybean oil diphase mixture and the emulsification performance is dependent on microstructure of amphiphilic brushes such as hydrophilic/hydrophobic segment size and sequence.

  14. Interaction between amphiphilic ionic liquid 1-butyl-3-methylimidazolium octyl sulfate and anionic polymer of sodium polystyrene sulfonate in aqueous medium (United States)

    Barhoumi, Z.; Saini, M.; Amdouni, N.; Pal, A.


    The micellization of an aqueous solution of the surface active ionic liquid (SAIL), 1-butyl-3-methylimidazolium octylsufate (C4mim)(C8OSO3) and its interaction with an anionic polymer sodium polystyrene sulfonate, (NaPSS) were studied using conductimetry, tensiometry and fluorimetry. Surface tension profile shows a more dramatic increase in the value of surface tension of aqueous (C4mim)(C8OSO3) before the critical micelle concentration (cmc) of IL. The critical micelle concentration (cmc) value of this surfactant was found out from conductance measurements. The thermodynamic parameters, i.e., Gibb's free energy, enthalpy, and entropy of micellization of the IL in aqueous solution have been calculated. Behavior of fluorescence probe confirms the binding interactions between SAIL and the polyelectrolyte.

  15. Immobilization of amphiphilic polycations by catechol functionality for antimicrobial coatings. (United States)

    Han, Hua; Wu, Jianfeng; Avery, Christopher W; Mizutani, Masato; Jiang, Xiaoming; Kamigaito, Masami; Chen, Zhan; Xi, Chuanwu; Kuroda, Kenichi


    A new strategy for preparing antimicrobial surfaces by a simple dip-coating procedure is reported. Amphiphilic polycations with different mole ratios of monomers containing dodecyl quaternary ammonium, methoxyethyl, and catechol groups were synthesized by free-radical polymerization. The polymer coatings were prepared by immersing glass slides into a polymer solution and subsequent drying and heating. The quaternary ammonium side chains endow the coatings with potent antibacterial activity, the methoxyethyl side chains enable tuning the hydrophobic/hydrophilic balance, and the catachol groups promote immobilization of the polymers into films. The polymer-coated surfaces displayed bactericidal activity against Escherichia coli and Staphylococcus aureus in a dynamic contact assay and prevented the accumulation of viable E. coli, S. aureus, and Acinetobacter baumannii for up to 96 h. Atomic force microscopy (AFM) images of coating surfaces indicated that the surfaces exhibit virtually the same smoothness for all polymers except the most hydrophobic. The hydrophobic polymer without methoxyethyl side chains showed clear structuring into polymer domains, causing high surface roughness. Sum-frequency generation (SFG) vibrational spectroscopy characterization of the surface structures demonstrated that the dodecyl chains are predominantly localized at the surface-air interface of the coatings. SFG also showed that the phenyl groups of the catechols are oriented on the substrate surface. These results support our hypothesis that the adhesive or cross-linking functionality of catechol groups discourages polymer leaching, allowing the tuning of the amphiphilic balance by incorporating hydrophilic components into the polymer chains to gain potent biocidal activity.

  16. Amphiphilic poly-N-vinylpyrrolidone nanocarriers with incorporated model proteins (United States)

    Kuskov, A. N.; Villemson, A. L.; Shtilman, M. I.; Larionova, N. I.; Tsatsakis, A. M.; Tsikalas, I.; Rizos, A. K.


    New nanoscaled polymeric carriers have been prepared on the basis of different amphiphilic water-soluble derivatives of poly-N-vinylpyrrolidone (PVP). The polymer self-assembly and interaction with model proteins (Bowman-Birk soybean proteinase inhibitor (BBI) and its hydrophobized derivatives) were studied in aqueous media. The possibility of inclusion of both BBI and hydrophobized oleic acid derivatives of BBI in amphiphilic PVP aggregates was investigated. It was ascertained that polymeric particles of size 50-80 nm were formed in certain concentrations of amphiphilic PVP and poorly soluble dioleic acid derivatives of BBI. Such polymeric aggregates are capable of solubilization of dioleoyl BBI with a concomitant prevention of its inactivation at low pH values.

  17. Amphiphilic poly-N-vinylpyrrolidone nanocarriers with incorporated model proteins

    Energy Technology Data Exchange (ETDEWEB)

    Kuskov, A N [Department of Polymers, D I Mendeleyev University of Chemical Technology, 9 Miusskaya Square, Moscow 125047 (Russian Federation); Villemson, A L [Department of Chemistry, M V Lomonosov Moscow State University, 119992 Moscow (Russian Federation); Shtilman, M I [Department of Polymers, D I Mendeleyev University of Chemical Technology, 9 Miusskaya Square, Moscow 125047 (Russian Federation); Larionova, N I [Department of Chemistry, M V Lomonosov Moscow State University, 119992 Moscow (Russian Federation); Tsatsakis, A M [Medical School, University of Crete, Voutes, 71409 Heraklion, Crete (Greece); Tsikalas, I [Department of Chemistry and Foundation for Research and Technology-Hellas (FORTH), University of Crete, PO Box 2208, Heraklion 71003, Crete (Greece); Rizos, A K [Department of Chemistry and Foundation for Research and Technology-Hellas (FORTH), University of Crete, PO Box 2208, Heraklion 71003, Crete (Greece)


    New nanoscaled polymeric carriers have been prepared on the basis of different amphiphilic water-soluble derivatives of poly-N-vinylpyrrolidone (PVP). The polymer self-assembly and interaction with model proteins (Bowman-Birk soybean proteinase inhibitor (BBI) and its hydrophobized derivatives) were studied in aqueous media. The possibility of inclusion of both BBI and hydrophobized oleic acid derivatives of BBI in amphiphilic PVP aggregates was investigated. It was ascertained that polymeric particles of size 50-80 nm were formed in certain concentrations of amphiphilic PVP and poorly soluble dioleic acid derivatives of BBI. Such polymeric aggregates are capable of solubilization of dioleoyl BBI with a concomitant prevention of its inactivation at low pH values.

  18. Formation and antifouling properties of amphiphilic coatings on polypropylene fibers. (United States)

    Goli, Kiran K; Rojas, Orlando J; Genzer, Jan


    We describe the formation of amphiphilic polymeric assemblies via a three-step functionalization process applied to polypropylene (PP) nonwovens and to reference hydrophobic self-assembled n-octadecyltrichlorosilane (ODTS) monolayer surfaces. In the first step, denatured proteins (lysozyme or fibrinogen) are adsorbed onto the hydrophobic PP or the ODTS surfaces, followed by cross-linking with glutaraldehyde in the presence of sodium borohydride (NaBH(4)). The hydroxyl and amine functional groups of the proteins permit the attachment of initiator molecules, from which poly (2-hydroxyethyl methacrylate) (PHEMA) polymer grafts are grown directly through "grafting from" atom transfer radical polymerization. The terminal hydroxyls of HEMA's pendent groups are modified with fluorinating moieties of different chain lengths, resulting in amphiphilic brushes. A palette of analytical tools, including ellipsometry, contact angle goniometry, Fourier transform infrared spectroscopy in the attenuated total reflection mode, and X-ray photoelectron spectroscopy is employed to determine the changes in physicochemical properties of the functionalized surfaces after each modification step. Antifouling properties of the resultant amphiphilic coatings on PP are analyzed by following the adsorption of fluorescein isothiocyanate-labeled bovine serum albumin as a model fouling protein. Our results suggest that amphiphilic coatings suppress significantly adsorption of proteins as compared with PP fibers or PP surfaces coated with PHEMA brushes. The type of fluorinated chain grafted to PHEMA allows modulation of the surface composition of the topmost layer of the amphiphilic coating and its antifouling capability.

  19. Paper-Based Analytical Biosensor Chip Designed from Graphene-Nanoplatelet-Amphiphilic-diblock-co-Polymer Composite for Cortisol Detection in Human Saliva. (United States)

    Khan, Muhammad S; Misra, Santosh K; Wang, Zhen; Daza, Enrique; Schwartz-Duval, Aaron S; Kus, Joseph M; Pan, Debanjan; Pan, Dipanjan


    Cortisol has been identified as a biomarker in saliva to monitor psychological stress. In this work, we report a label-free paper-based electrical biosensor chip to quantify salivary cortisol at a point-of-care (POC) level. A high specificity of the sensor chip to detect cortisol with a detection limit of 3 pg/mL was achieved by conjugating anticortisol antibody (anti-CAB) on top of gold (Au) microelectrodes using 3,3'-dithiodipropionic acid di(N-hydroxysuccinimide ester (DTSP) as a self-assembled monolayer (SAM) agent. The electrode design utilized poly(styrene)-block-poly(acrylic acid) (PS67-b-PAA27) polymer and graphene nanoplatelets (GP) suspension coated on filter paper to increase the sensitivity of the immune response. A biosensor chip was then integrated with a lab-built low-cost miniaturized printed circuit board (PCB) to provide an electrical connection and to wirelessly transmit/receive electrical signals using MATLAB. This fully integrated proposed hand-held device successfully exhibited a wide cortisol-detection range from 3 pg/mL to 10 μg/mL, with a sensitivity of 50 Ω (pg mL(-1))(-1). The performance of the proposed cortisol sensor chip was validated using an enzyme-linked immunosorbent assay (ELISA) technique with a regression value of 0.9951. The advantages of the newly developed cortisol immune biosensor over previously reported chips include an improved limit of detection, no need for additional redox medium for electron exchange, faster response to achieve stable data, excellent shelf life, and its economical production.

  20. Synthesis of antibacterial amphiphilic elastomer based on polystyrene-block-polyisoprene-block-polystyrene via thiol-ene addition

    Energy Technology Data Exchange (ETDEWEB)

    Keleş, Elif, E-mail: [Department of Chemistry, Bülent Ecevit University, Zonguldak 67100 (Turkey); Hazer, Baki, E-mail: [Department of Chemistry, Bülent Ecevit University, Zonguldak 67100 (Turkey); Cömert, Füsun B. [Department of Microbiology, Faculty of Medicine, Bülent Ecevit University, 67600 Zonguldak (Turkey)


    A new type of amphiphilic antibacterial elastomer has been described. Thermoplastic elastomer, polystyrene–block-polyisoprene–block-polystyrene (PS–b-PI–b-PS) triblock copolymer was functionalized in toluene solution by free radical mercaptan addition in order to obtain an amphiphilic antibacterial elastomer. Thiol terminated PEG was grafted through the double bonds of PS–b-PI–b-PS via free radical thiol-ene coupling reaction. The antibacterial properties of the amphiphilic graft copolymers were observed. The original and the modified polymers were used to create microfibers in an electro-spinning process. Topology of the electrospun micro/nanofibers were studied by using scanning electron microscopy (SEM). The chemical structures of the amphiphilic comb type graft copolymers were elucidated by the combination of elemental analysis, {sup 1}H NMR, {sup 13}C NMR, GPC and FTIR. - Graphical abstract: Double bonds of polyisoprene units in polystyrene–block-polyisoprene–block-polystyrene triblock copolymer were partially capped with PEG containing mercapto end group via thiol-ene addition in order to obtain antibacterial amphiphilic elastomer. Nano fibers from amphiphilic graft polymers solution were produced by electrospinning. The PEG grafted copolymer inhibits very effectively bacterial growth. Highlights: ► A commercial synthetic elastomer was grafted with PEG to obtain amphiphilic elastomer. ► Amphiphilic elastomer shows antibacterial properties. ► Electrospun micro fibers of the amphiphilic elastomer tend to globular formation.

  1. Self-assembling Characteristics of Amphiphilic Star Block Copolymers with a Polyelectrolyte Shell

    Institute of Scientific and Technical Information of China (English)

    S.Strandman; A.Zarembo; V.Aseyev; S.J.Butcher; H.Tenhu


    1 Results Amphiphilic block copolymers are capable of forming supramolecular assemblies resembling those observed in nature,such as spherical micelles,worm micelles,and vesicles.Changing the solvent composition,ionic strength or pH of the polymer solution may induce the self-assembly of block copolymers or trigger the transition between the geometries of noncovalent assemblies.In the current work,we have synthesised starlike amphiphilic block copolymers having hydrophobic poly(methyl methacrylate),PMMA,...

  2. Precisely Controlled 2D Free-Floating Nanosheets of Amphiphilic Molecules through Frame-Guided Assembly. (United States)

    Zhou, Chao; Zhang, Yiyang; Dong, Yuanchen; Wu, Fen; Wang, Dianming; Xin, Ling; Liu, Dongsheng


    2D assembly of amphiphilic molecules in aqueous solution is a challenging and intriguing topic as it is normally thermodynamically unfavorable. However, through frame-guided assembly strategy and using DNA origami as the frame, monodispersed and shape-defined nanosheets are prepared. As leading hydrophobic groups (LHGs) are anchored on the frames, amphiphilic molecules in aqueous solution are guided to assemble in the hydrophobic region. By adjusting the distribution of the LHGs, the size and shape of the assemblies can be controlled precisely.

  3. Solid-supported biomimetic membranes based on amphiphilic block copolymers


    Kowal, Justyna


    Planar artificial membranes based on amphiphilic block copolymers are of high interest due to their potential applications in catalysis, drug screening, sensing, etc. Such polymeric membranes can successfully mimic biological membranes, providing high robustness and stability, which makes them good candidates to be developed in direction of applications. Even though solid-supported polymer membranes have been already investigated to a certain extent, it is still an emerging area. This thesis ...


    Institute of Scientific and Technical Information of China (English)

    K.C. Gupta; H.K. Abdulkadir; S. Chand


    A new chelating polymer support has been prepared by suspension copolymeriz a tion of synthesized N,N'-bis(3-allyl salicylidene)ethylenediamine monomer Schiff base (N,N'-BSEDA) with styrene (St) and divinylbenzene (DVB) using azobisisobutyronitrile (AIBN) as initiator in the presence of poly(vinyl alcohol). The content and complexation ability of monomer Schiff base (N,N'-BSEDA) for cobalt(II) ions in prepared crosslinked polymer beads have shown dependence on the amount of DVB used in reaction mixture. The amount of monomer Schiff base (N,N'-BSEDA) in crosslinked beads showed a substantial decreasing trend at high concentration of DVB in the reaction mixture (> 1.5 mol dm-3), hence the efficiency of complexation (EC%) and cobalt(II) ion loading (EL%) of polymer beads showed a decreasing trend. The structure of monomer Schiff base (N,N'-BSEDA) and its cobalt(II) complex on polymer support was elucidated by IR, UV and magnetic measurements. The catalytic activity of polymer bound cobalt(Ⅱ) Schiff base complex was evaluated by analyzing kinetic data of decomposition of hydrogen peroxide in the presence of either supported cobalt (II) complex or free cobalt(II) complex. The activation energy for the decomposition of hydrogen peroxide by polymer supported cobalt(II)complex was found to be low (33.37 kJ mol-l) in comparison with unsupported cobalt(II) complex (56.35 kJ mol-1). On the basis of experimental observations, reaction steps are proposed and a suitable rate expression derived.

  5. Hypersensitivity to Suture Anchors

    Directory of Open Access Journals (Sweden)

    Masafumi Goto


    Full Text Available Hypersensitivity to suture anchor is extremely rare. Herein, we present a case in which hypersensitivity to suture anchor was strongly suspected. The right rotator cuff of a 50-year-old woman was repaired with a metal suture anchor. Three weeks after the surgery, she developed erythema around her face, trunk, and hands, accompanied by itching. Infection was unlikely because no abnormalities were detected by blood testing or by medical examination. Suspicious of a metallic allergy, a dermatologist performed a patch testing 6 months after the first surgery. The patient had negative reactions to tests for titanium, aluminum, and vanadium, which were the principal components of the suture anchor. The anchor was removed 7 months after the first surgery, and the erythema disappeared immediately. When allergic symptoms occur and persist after the use of a metal anchor, removal should be considered as a treatment option even if the patch test result is negative.

  6. Porous organic polymers with anchored aldehydes: A new platform for post-synthetic amine functionalization en route for enhanced CO2 adsorption properties

    KAUST Repository

    Guillerm, Vincent


    A novel porous organic polymer has been synthesized using the molecular building block approach to deliberately encompass aldehyde functionalities amenable to post functionalization. The resultant porous framework allows a facile, one-step quantitative and post-synthetic functionalization by amines, permitting enhanced CO2 sorption properties. © 2014 The Royal Society of Chemistry.

  7. Anchor Loads on Pipelines


    Wei, Ying


    Anchor hooking on a subsea pipeline has been investigated in this thesis. Anchor loads on pipelines is in general a rarely occurring event, however, the severity when it occurs could easily jeopardize the integrity of any pipeline. It is considered as an accidental load in the design of pipelines. Pipeline Loads, limit state criteria and anchor categories are defined by the DNV standards. For pipeline, DNV-OS-F101 (08.2012), Submarine Pipeline Systems is adopted. Offshore standard DNV-RP...

  8. Membrane analysis with amphiphilic carbon dots. (United States)

    Nandi, Sukhendu; Malishev, Ravit; Parambath Kootery, Kaviya; Mirsky, Yelena; Kolusheva, Sofiya; Jelinek, Raz


    Newly-synthesized amphiphilic carbon dots were used for spectroscopic analysis and multicolour microscopic imaging of membranes and live cells. We show that Förster resonance energy transfer (FRET) occurred from the amphiphilic carbon dots to different membrane-associated fluorescence acceptors. The amphiphilic carbon dots enabled imaging of membrane disruption by the beta-amyloid peptide.

  9. Susceptibility to anchoring effects

    Directory of Open Access Journals (Sweden)

    Todd McElroy


    Full Text Available Previous research on anchoring has shown this heuristic to be a very robust psychological phenomenon ubiquitous across many domains of human judgment and decision-making. Despite the prevalence of anchoring effects, researchers have only recently begun to investigate the underlying factors responsible for how and in what ways a person is susceptible to them. This paper examines how one such factor, the Big-Five personality trait of openness-to-experience, influences the effect of previously presented anchors on participants' judgments. Our findings indicate that participants high in openness-to-experience were significantly more influenced by anchoring cues relative to participants low in this trait. These findings were consistent across two different types of anchoring tasks providing convergent evidence for our hypothesis.

  10. Solvent-free, molecular-level modeling of self-assembling amphiphiles in water (United States)

    Dey, Somajit; Saha, Jayashree


    Aggregation mesophases of self-assembling amphiphiles in water are highly important in the context of biology (biomembranes), therapy (liposomes), industry (polymer surfactants), and condensed-matter physics (lyotropic liquid crystals). Besides helping to increase fundamental understanding of collective molecular behavior, simulations of these lyotropic phases are pivotal to technological and medical developments such as smart drug carriers for gene therapy. Implicit-solvent, coarse-grained, low resolution modeling with a simple pair potential is the key to realizing the larger length and time scales associated with such mesoscopic phenomena during a computer simulation. Modeling amphiphiles by directed, soft, ellipsoidal cores interacting via a computationally simple yet tunable anisotropic pair potential, we have come to such a single-site model amphiphile that can rapidly self-assemble to give diverse lyotropic phases (such as fluid bilayers, micelles, etc.) without requiring the explicit incorporation of solvent particles. The model directly represents a tunable packing parameter that manifests in the spontaneous curvature of the amphiphile aggregates. Besides the all-important hydrophobic interaction, the hydration force is also treated implicitly. Thanks to the efficient solvent-free molecular-level coarse graining, this model is suitable for generic mesoscale studies of phenomena such as self-assembly, amphiphile mixing, domain formation, fusion, elasticity, etc., in amphiphile aggregates.

  11. Anchor Trial Launch (United States)

    NCI has launched a multicenter phase III clinical trial called the ANCHOR Study -- Anal Cancer HSIL (High-grade Squamous Intraepithelial Lesion) Outcomes Research Study -- to determine if treatment of HSIL in HIV-infected individuals can prevent anal canc

  12. Non-Surface Activity of Cationic Amphiphilic Diblock Copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, Rati Ranjan; Yamada, Tasuku; Matsuoka, Hideki, E-mail:, E-mail: [Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510 (Japan)


    Cationic amphiphilic diblock copolymers containing quaternized poly (2-vinylpyridine) chain as a hydrophilic segment (PIp-b-PNMe2VP) were synthesized by living anionic polymerization. By IR measurement, we confirmed the quaternization of the polymer (PIp-b-PNMe2VP), and determined the degree of quaternization by conductometric titration. The surface tension experiment showed that the polymers are non-surface active in nature. The foam formation of the polymer solutions was also investigated with or without added salt. Almost no foam formation behavior was observed without added salt, while a little foam was observed in the presence of 1M NaCl. The critical micelle concentration (cmc) of the diblock copolymers with 3 different chain lengths was measured by the static light scattering method. The cmc values obtained in this study were much lower than the values obtained for anionic non-surface active diblock polymers studied previously. The hydrodynamic radii of the polymer micelle increased slightly in the presence of 1 M NaCl. The transmission electron microscopic images revealed spherical micelles in pure water. In the presence of salt, the cmc values increased as was the case for anionic polymers, which is unlike conventional surfactant systems but consistent with non-surface active anionic block copolymers. The microviscosity of the micelle core was evaluated using Coumarin-153 as a fluorescent anisotropy probe using steady-sate fluorescence depolarization. Non-surface activity has been proved to be universal for ionic amphiphilic block copolymers both for anionic and cationic. Hence, the origin of non-surface activity is not the charged state of water surface itself, but should be an image charge repulsion at the air/water interface.

  13. Amphiphilic Polyphosphazene with Poly(ethylene oxide) Side Chains Prepared through the Decker-Forster Reaction

    Institute of Scientific and Technical Information of China (English)

    LIU Chengmei; HU Fuzhen; QIU Jinjun; LEI Guofu; BAO Rui


    Poly(4-methylphenoxyphosphazene)-graft-poly(ethylene oxide) (PPZ-g-PEO), a novel amphiphilic grafting polymer was prepared via the Decker-Forster reaction. It is found that the graft efficiency increased with extension of reaction time. Low molecular weight of poly(ethylene oxide) favored the grafting reaction. The grafted polymer has two different glass transition temperatures(Tg) with those of pure poly(4-methylphenoxy-phopsphazene) and PEO. The emulsifying ability of grafted polymer was studied with benzene-water mixture. The emulsifying volumes increased with the decreasing of PEO's molecular weight. The contact angle of film forming from grafted polymer decreased after introduction of PEO grafting chain.

  14. Synergistic effect of a new wedge-bond-type anchor for CFRP tendons

    Institute of Scientific and Technical Information of China (English)

    谢桂华; 刘荣桂; 陈蓓; 李明君; 石天罡


    In order to improve the anchoring force of anchors for carbon fiber reinforced polymer (CFRP) tendons further, a new wedge-bond-type anchor for CFRP tendons was developed. The increment in anchoring force induced by the clamping segment of anchor was studied. Taking the deformation of all parts in clamping segment in the transverse direction into consideration, the calculation formula for the increment of anchoring force was proposed based on the linear elastic hypotheses. The proposed model is verified by experiments and conclusions are drawn that the anchoring force is influenced mainly by the inclination angle of clamping pieces, the length of clamping part and the thickness of bonding medium. Especially, the thickness of bonding medium should be lowered in design to improve the synergistic effect of anchors.

  15. Monte Carlo simulation for the micellar behavior of amphiphilic comb-like copolymers

    Institute of Scientific and Technical Information of China (English)

    冯莺; 隋家贤; 赵季若; 陈欣方


    Micellar behaviors in 2D and 3D lattice models for amphiphilic comb-like copolymers in water phase and in water/oil mixtures were simulated. A dynamical algorithm together with chain reptation movements was used in the simulation. Three-dimension displaying program was pro-grammed and free energy was estimated by Monte Carlo technigue. The results demonstrate that reduced interaction energy influences morphological structures of micelle and emulsion ??stems greatly; 3D simulation showing can display more direct images of morphological structures; the amphiphilic comb-like polymers with a hydrophobic main chain and hydrophilic side chains have lower energy in water than in oil.


    Directory of Open Access Journals (Sweden)

    Christina Yacoob


    Full Text Available Amphiphilic molecules are challenging to be incorporatedinto polymeric particles for sustained release due to their significant solubility in both water and organic solvent used in the fabrication process. Here, we investigated an extensive panel of fabrication methods for the incorporation and release of amphiphilic molecules, in particular, novel amphiphilic bumped kinase inhibitors (BKIs. Previously, BKIswere shown to reduce malaria transmission by blocking of gametocyte exflagellation. Prolonged BKI bioavailability for effective transmission blocking is crucial since infectious gametocytes circulate for several weeks inthe mammalian host, well beyond the half-life of BKIs. So far, delivery systems for sustained release of those BKIs have not been successfully formulated yet. Here we demonstrate that out of several delivery vehicles the partition-optimized single emulsion particles are the ideal system for incorporation and sustained release of amphiphilic BKIs. They increased the incorporation greater than 90% through optimized partitioning of amphiphilic molecules to the polymer phase and sustained release of BKIs up to several weeks with a reduction in the initial burst release. Overall this work provides a method for the incorporation and sustained release of amphiphilic BKIs, and can be adapted for other amphiphilic molecules.

  17. Antibacterial Activity of Geminized Amphiphilic Cationic Homopolymers. (United States)

    Wang, Hui; Shi, Xuefeng; Yu, Danfeng; Zhang, Jian; Yang, Guang; Cui, Yingxian; Sun, Keji; Wang, Jinben; Yan, Haike


    The current study is aimed at investigating the effect of cationic charge density and hydrophobicity on the antibacterial and hemolytic activities. Two kinds of cationic surfmers, containing single or double hydrophobic tails (octyl chains or benzyl groups), and the corresponding homopolymers were synthesized. The antimicrobial activity of these candidate antibacterials was studied by microbial growth inhibition assays against Escherichia coli, and hemolysis activity was carried out using human red blood cells. It was interestingly found that the homopolymers were much more effective in antibacterial property than their corresponding monomers. Furthermore, the geminized homopolymers had significantly higher antibacterial activity than that of their counterparts but with single amphiphilic side chains in each repeated unit. Geminized homopolymers, with high positive charge density and moderate hydrophobicity (such as benzyl groups), combine both advantages of efficient antibacterial property and prominently high selectivity. To further explain the antibacterial performance of the novel polymer series, the molecular interaction mechanism is proposed according to experimental data which shows that these specimens are likely to kill microbes by disrupting bacterial membranes, leading them unlikely to induce resistance.

  18. Cyclodextrin polymer nanoassemblies: strategies for stability improvement. (United States)

    Wintgens, Véronique; Layre, Anne-Magali; Hourdet, Dominique; Amiel, Catherine


    The main goal of this work was to develop two strategies for stabilization of nanoassemblies made of β-cyclodextrin polymer and amphiphilic dextran associated through host-guest complexes. The first strategy was to coat the nanoassemblies with a dextran derivative bearing adamantyl anchoring groups and hydrophilic poly(ethylene oxide-co-propylene oxide) side chains to increase the steric repulsion between the nanoassemblies. The second strategy developed was to post-reticulate the nanoassemblies upon UV irradiation. Photo-cross-linkable nanoassemblies have been prepared from new host or guest polymers bearing allylether or methacrylate groups. The modified nanoassemblies have been characterized by dynamic light scattering as a function of time and for various salt and competitor concentrations. The results of the first strategy show an improvement of shelf stability and resistance at relatively low concentrations of competitors. The second strategy is the most efficient in providing good shelf stability, much larger than with the first strategy, together with a large resistance to dissociation in presence of competitors.

  19. Synthesis of antibacterial amphiphilic elastomer based on polystyrene-block-polyisoprene-block-polystyrene via thiol-ene addition. (United States)

    Keleş, Elif; Hazer, Baki; Cömert, Füsun B


    A new type of amphiphilic antibacterial elastomer has been described. Thermoplastic elastomer, polystyrene-block-polyisoprene-block-polystyrene (PS-b-PI-b-PS) triblock copolymer was functionalized in toluene solution by free radical mercaptan addition in order to obtain an amphiphilic antibacterial elastomer. Thiol terminated PEG was grafted through the double bonds of PS-b-PI-b-PS via free radical thiol-ene coupling reaction. The antibacterial properties of the amphiphilic graft copolymers were observed. The original and the modified polymers were used to create microfibers in an electro-spinning process. Topology of the electrospun micro/nanofibers were studied by using scanning electron microscopy (SEM). The chemical structures of the amphiphilic comb type graft copolymers were elucidated by the combination of elemental analysis, (1)H NMR, (13)C NMR, GPC and FTIR.

  20. Tandem Facial Amphiphiles for Membrane Protein Stabilization

    DEFF Research Database (Denmark)

    Chae, Pil Seok; Gotfryd, Kamil; Pacyna, Jennifer;


    We describe a new type of synthetic amphiphile that is intended to support biochemical characterization of intrinsic membrane proteins. Members of this new family displayed favorable behavior with four of five membrane proteins tested, and these amphiphiles formed relatively small micelles....

  1. Cationic Amphiphiles Increase Activity of Aminoglycoside Antibiotic Tobramycin in the Presence of Airway Polyelectrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Purdy Drew, Kirstin R.; Sanders, Lori K.; Culumber, Zachary W.; Zribi, Olena; Wong, Gerard C.L.; (UIUC)


    It is empirically known that anionic polyelectrolytes present in cystic fibrosis (CF) airways due to bacterial infection significantly decrease the activity of cationic antimicrobials via electrostatic binding. In this work, we use synchrotron small-angle X-ray scattering to investigate the interaction between tobramycin, an aminoglycoside antibiotic commonly administered to CF patients via inhalation, with DNA, which is found in high concentrations in the CF airway. We find that interactions between DNA and tobramycin are significantly modified by the presence of mixtures of amphiphilic molecules. We measure a hierarchy of self-assembled structures formed between tobramycin, DNA, and the amphiphile mixtures and show how interactions between these components can be controlled. Results indicate that mixtures of cationic and negative curvature amphiphiles optimized for DNA binding via charge matching and curvature matching can competitively displace bound tobramycin from DNA and thereby drastically suppress tobramycin-DNA binding and resultant antimicrobial inactivation. Growth inhibition assays confirm the increased activity of tobramycin in the presence of DNA with the addition of the amphiphiles. These results suggest that optimized cationic amphiphile solutions have the potential to enhance antimicrobial function in highly infected environments that contain increased concentrations of anionic inflammatory polymers.

  2. Cationic Amphiphiles Increase Activity of Aminoglycoside Antibiotic Tobramycin in the Presence of Airway Polyelectrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Drew, K.R.Purdy; Sanders, L.K.; Culumber, Z.W.; Zribi, O.; Wong, G.C.L.


    It is empirically known that anionic polyelectrolytes present in cystic fibrosis (CF) airways due to bacterial infection significantly decrease the activity of cationic antimicrobials via electrostatic binding. In this work, we use synchrotron small-angle X-ray scattering to investigate the interaction between tobramycin, an aminoglycoside antibiotic commonly administered to CF patients via inhalation, with DNA, which is found in high concentrations in the CF airway. We find that interactions between DNA and tobramycin are significantly modified by the presence of mixtures of amphiphilic molecules. We measure a hierarchy of self-assembled structures formed between tobramycin, DNA, and the amphiphile mixtures and show how interactions between these components can be controlled. Results indicate that mixtures of cationic and negative curvature amphiphiles optimized for DNA binding via charge matching and curvature matching can competitively displace bound tobramycin from DNA and thereby drastically suppress tobramycin-DNA binding and resultant antimicrobial inactivation. Growth inhibition assays confirm the increased activity of tobramycin in the presence of DNA with the addition of the amphiphiles. These results suggest that optimized cationic amphiphile solutions have the potential to enhance antimicrobial function in highly infected environments that contain increased concentrations of anionic inflammatory polymers.

  3. Precisely Size-Tunable Monodisperse Hairy Plasmonic Nanoparticles via Amphiphilic Star-Like Block Copolymers. (United States)

    Chen, Yihuang; Yoon, Young Jun; Pang, Xinchang; He, Yanjie; Jung, Jaehan; Feng, Chaowei; Zhang, Guangzhao; Lin, Zhiqun


    In situ precision synthesis of monodisperse hairy plasmonic nanoparticles with tailored dimensions and compositions by capitalizing on amphiphilic star-like diblock copolymers as nanoreactors are reported. Such hairy plasmonic nanoparticles comprise uniform noble metal nanoparticles intimately and perpetually capped by hydrophobic polymer chains (i.e., "hairs") with even length. Interestingly, amphiphilic star-like diblock copolymer nanoreactors retain the spherical shape under reaction conditions, and the diameter of the resulting plasmonic nanoparticles and the thickness of polymer chains situated on the surface of the nanoparticle can be readily and precisely tailored. These hairy nanoparticles can be regarded as hard/soft core/shell nanoparticles. Notably, the polymer "hairs" are directly and permanently tethered to the noble metal nanoparticle surface, thereby preventing the aggregation of nanoparticles and rendering their dissolution in nonpolar solvents and the homogeneous distribution in polymer matrices with long-term stability. This amphiphilic star-like block copolymer nanoreactor-based strategy is viable and robust and conceptually enables the design and synthesis of a rich variety of hairy functional nanoparticles with new horizons for fundamental research on self-assembly and technological applications in plasmonics, catalysis, energy conversion and storage, bioimaging, and biosensors.

  4. Synthesis of amphiphilic diblock copolymer for surface modification of Ethylene-Norbornene copolymers

    DEFF Research Database (Denmark)

    Levinsen, Simon; Svendsen, Winnie Edith; Horsewell, Andy


    The aim of this work is to produce polymer modifiers in order to develop hydrophilic polymeric surfaces for use in microfluidics. The use of hydrophilic polymers in microfluidics will have many advantages e.g. preventing protein absorbance. Here we present an amphiphilic diblock copolymer......-norbornene copolymer TOPAS. Through matching of the radius of gyration for the model polymer and TOPAS the miscibility was achieved. The poly(ethylene-1-butene) polymer was synthesized from a hydrogenated anionic polymerized polybutadiene polymer. As hydrophilic block poly(ethylene oxide) was subsequently added also...... with anionic polymerization. Recent miscibility results between the model polymer and TOPAS will be presented, as well ongoing efforts to study the hydrophilic surface....

  5. Amphiphilic NO-donor antioxidants. (United States)

    Chegaev, Konstantin; Lazzarato, Loretta; Rolando, Barbara; Marini, Elisabetta; Lopez, Gloria V; Bertinaria, Massimo; Di Stilo, Antonella; Fruttero, Roberta; Gasco, Alberto


    Models of amphiphilic NO-donor antioxidants 24-26 were designed and synthesized. The products were obtained by linking a lipophilic tail (C(6), C(8), C(10)) with a polar head constituted by the 2,6-dimethoxyphenol antioxidant joined to the NO-donor 3-furoxancarboxamide substructure through a bridge containing a quaternary ammonium group. Compound 23, containing the shortest C(2)-alkyl chain, was also studied as a reference. The antioxidant properties (TBARS and LDL oxidation assays) and the vasodilator properties of the compounds were studied in vitro. The ability of these products to interact with phospholipid vesicles was also investigated by NMR techniques. The results indicate that both activities are modulated by the ability of the compounds to accumulate on phospholipid layers.

  6. A minimal hydrophobicity is needed to employ amphiphilic p(HPMA)-co-p(LMA) random copolymers in membrane research. (United States)

    Stangl, Michael; Hemmelmann, Mirjam; Allmeroth, Mareli; Zentel, Rudolf; Schneider, Dirk


    Because a polymer environment might be milder than a detergent micelle, amphiphilic polymers have attracted attention as alternatives to detergents in membrane biochemistry. The polymer poly[N-(2-hydroxypropyl)-methacrylamid] [p(HPMA)] has recently been modified with hydrophobic lauryl methacrylate (LMA) moieties, resulting in the synthesis of amphiphilic p(HPMA)-co-p(LMA) polymers. p(HPMA)-co-p(LMA) polymers with a LMA content of 5 or 15% have unstable hydrophobic cores. This, on one hand, promotes interactions of the hydrophobic LMA moieties with membranes, resulting in membrane rupture, but at the same time prevents formation of a hydrophobic, membrane mimetic environment that is sufficiently stable for the incorporation of transmembrane proteins. On the other hand, the p(HPMA)-co-p(LMA) polymer with a LMA content of 25% forms a stable hydrophobic core structure, which prevents hydrophobic interactions with membrane lipids but allows stable incorporation of membrane proteins. On the basis of our data, it becomes obvious that amphiphilic polymers have to have threshold hydrophobicities should an application in membrane protein research be anticipated.

  7. Terpene and dextran renewable resources for the synthesis of amphiphilic biopolymers. (United States)

    Alvès, Marie-Hélène; Sfeir, Huda; Tranchant, Jean-François; Gombart, Emilie; Sagorin, Gilles; Caillol, Sylvain; Billon, Laurent; Save, Maud


    The present work shows the synthesis of amphiphilic polymers based on the hydrophilic dextran and the hydrophobic terpenes as renewable resources. The first step concerns the synthesis of functional terpene molecules by thiol-ene addition chemistry involving amino or carboxylic acid thiols and dihydromyrcenol terpene. The terpene-modified polysaccharides were subsequently synthesized by coupling the functional terpenes with dextran. A reductive amination step produced terpene end-modified dextran with 94% of functionalization, while the esterification step produced three terpene-grafted dextrans with a number of terpene units per dextran of 1, 5, and 10. The amphiphilic renewable grafted polymers were tested as emulsifiers for the stabilization of liquid miniemulsion of terpene droplets dispersed in an aqueous phase. The average hydrodynamic diameter of the stable droplets was observed at about 330 nm.

  8. Anchoring visions in organizations

    DEFF Research Database (Denmark)

    Simonsen, Jesper


    This paper introduces the term 'anchoring' within systems development: Visions, developed through early systems design within an organization, need to be deeply rooted in the organization. A vision's rationale needs to be understood by those who decide if the vision should be implemented as well...... as by those involved in the actual implementation. A model depicting a recent trend within systems development is presented: Organizations rely on purchasing generic software products and/or software development outsourced to external contractors. A contemporary method for participatory design, where...

  9. Amphiphilic biopolymers (amphibiopols) as new surfactants for membrane protein solubilization (United States)

    Duval-Terrié, Caroline; Cosette, Pascal; Molle, Gérard; Muller, Guy; Dé, Emmanuelle


    The aim of this study was to develop new surfactants for membrane protein solubilization, from a natural, biodegradable polymer: the polysaccharide pullulan. A set of amphiphilic pullulans (HMCMPs), differing in hydrophobic modification ratio, charge ratio, and the nature of the hydrophobic chains introduced, were synthesized and tested in solubilization experiments with outer membranes of Pseudomonas fluorescens. The membrane proteins were precipitated, and then resolubilized with various HMCMPs. The decyl alkyl chain (C10) was the hydrophobic graft that gave the highest level of solubilization. Decyl alkyl chain-bearing HMCMPs were also able to extract integral membrane proteins from their lipid environment. The best results were obtained with an amphiphilic pullulan bearing 18% decyl groups (18C10). Circular dichroism spectroscopy and membrane reconstitution experiments were used to test the structural and functional integrity of 18C10-solubilized proteins (OmpF from Escherichia coli and bacteriorhodopsin from Halobacterium halobium). Whatever their structure type (α or β), 18C10 did not alter either the structure or the function of the proteins analyzed. Thus, HMCMPs appear to constitute a promising new class of polymeric surfactants for membrane protein studies. PMID:12649425

  10. Structure-property relationship in cytotoxicity and cell uptake of poly(2-oxazoline) amphiphiles

    KAUST Repository

    Luxenhofer, Robert


    The family of poly(2-oxazoline)s (POx) is being increasingly investigated in the context of biomedical applications. We tested the relative cytotoxicity of POx and were able to confirm that these polymers are typically not cytotoxic even at high concentrations. Furthermore, we report structure-uptake relationships of a series of amphiphilic POx block copolymers that have different architectures, molar mass and chain termini. The rate of endocytosis can be fine-tuned over a broad range by changing the polymer structure. The cellular uptake increases with the hydrophobic character of the polymers and is observed even at nanomolar concentrations. Considering the structural versatility of this class of polymers, the relative ease of preparation and their stability underlines the potential of POx as a promising platform candidate for the preparation of next-generation polymer therapeutics.

  11. Terminal groups control self-assembly of amphiphilic block copolymers in solution (United States)

    Grzelakowski, M.; Kita-Tokarczyk, K.


    The terminal groups of amphiphilic block copolymers are shown to control macromolecular self-assembly in aqueous solutions, in the micellar/lamellar region of the phase diagram. At the same concentration and using the same self-assembly conditions, dramatic differences are observed in polymer hydration and the resulting nano-/microstructure for two series of polymers with identical block chemistry and hydrophilic-lipophilic balance (HLB). This suggests a strong contribution from end groups to the hydration as the initial step of the self-assembly process, and could be conveniently used to guide the particle morphology and size. Additionally, for polymers with those head groups which drive vesicular structures, differences in membrane organization affect their physical properties, such as permeability.The terminal groups of amphiphilic block copolymers are shown to control macromolecular self-assembly in aqueous solutions, in the micellar/lamellar region of the phase diagram. At the same concentration and using the same self-assembly conditions, dramatic differences are observed in polymer hydration and the resulting nano-/microstructure for two series of polymers with identical block chemistry and hydrophilic-lipophilic balance (HLB). This suggests a strong contribution from end groups to the hydration as the initial step of the self-assembly process, and could be conveniently used to guide the particle morphology and size. Additionally, for polymers with those head groups which drive vesicular structures, differences in membrane organization affect their physical properties, such as permeability. Electronic supplementary information (ESI) available: Fig. S1: Particle diameters for hydrated NH2-ABA-NH2 polymers with different degrees of functionalization; Fig. S2: TEM characterization of compound micelles from BA-OH polymer after extrusion; Fig. S3: Cryo-TEM and stopped flow characterization of lipid vesicles; Fig. S4 and S5: NMR spectra for ABA and BA polymers

  12. Aminoglycoside-derived amphiphilic nanoparticles for molecular delivery. (United States)

    Miryala, Bhavani; Godeshala, Sudhakar; Grandhi, Taraka Sai Pavan; Christensen, Matthew D; Tian, Yanqing; Rege, Kaushal


    The development of effective drug carriers can lead to improved outcomes in a variety of disease conditions. Aminoglycosides have been used as antibacterial therapeutics, and are attractive as monomers for the development of polymeric materials in various applications. Here, we describe the development of novel aminoglycoside-derived amphiphilic nanoparticles for drug delivery, with an eye towards ablation of cancer cells. The aminoglycoside paromomycin was first cross-linked with resorcinol diglycidyl ether leading to the formation of a poly (amino ether), PAE. PAE molecules were further derivatized with methoxy-terminated poly(ethylene glycol) or mPEG resulting in the formation of mPEG-PAE polymer, which self-assembled to form nanoparticles. Formation of the mPEG-PAE amphiphile was characterized using (1)H NMR, (13)C NMR, gel permeation chromatography (GPC) and FTIR spectroscopy. Self-assembly of the polymer into nanoparticles was characterized using dynamic light scattering, zeta potential analyses, atomic force microscopy (AFM) and the pyrene fluorescence assay. mPEG-PAE nanoparticles were able to carry significant amounts of doxorubicin (DOX), presumably by means of hydrophobic interactions between the drug and the core. Cell-based studies indicated that mPEG-PAE nanoparticles, loaded with doxorubicin, were able to induce significant loss in viabilities of PC3 human prostate cancer, MDA-MB-231 human breast cancer, and MB49 murine bladder cancer cells; empty nanoparticles resulted in negligible losses of cell viability under the conditions investigated. Taken together, our results indicate that the mPEG-PAE nanoparticle platform is attractive for drug delivery in different applications, including cancer.

  13. Intelligent Educational Systems for Anchored Instruction? (United States)

    Kumar, David D.


    Explores the potential for using Intelligent Educational Systems (IES) for anchoring instruction in macro contexts in science education. Topics include anchored instruction; situated cognition; problem solving; cognitivism; interactive video environments; and examples of combining IES and anchored instruction. (LRW)

  14. Sunfish amphiphiles : Conceptually new carriers for DNA delivery

    NARCIS (Netherlands)

    Hulst, R; Muizebelt, [No Value; Oosting, P; van der Pol, C; Wagenaar, A; Smisterova, J; Bulten, E; Driessen, C; Hoekstra, D; Engberts, JBFN; Muizebelt, Inouk; Šmisterová, Jarmila


    A conceptually new class of cationic amphiphiles, Sunfish amphiphiles, designed for the delivery of genes into cells is introduced. Sunfish amphiphiles have two hydrophobic tails, connected at the 4- and the N-position to the cationic pyridinium headgroup. Two extreme morphologies visualised by back

  15. Prediction on amphiphilicity of hypocrellin derivatives

    Institute of Scientific and Technical Information of China (English)

    谢杰; 马江华; 赵井泉


    Hypocrellins are most suitable for photodynamic therapy (PDT) of the diseases occurring in the superficial layer, such as microvascular diseases, because of their special absorption spectral properties. However, hypocrellins and most of their derivatives are basically lipophilic, while the hydrophilic derivatives lose the PDT activity in vivo. Therefore, the key problem for practical application of PDT of microvascular diseases focuses on finding the derivatives which possess optimized amphiphilicity. Herein, we developed a theoretical method to estimate the amphiphilicity of a molecule by the calculated average polarity. Compared with the experimentally measured results, the method is proved to be applicable. Based on the computation and available experimental results, it can be concluded that the derivative must have the polarities around 0.22 for optimized amphiphilicity.

  16. Prediction on amphiphilicity of hypocrellin derivatives

    Institute of Scientific and Technical Information of China (English)

    谢杰; 马江华; 赵井泉


    Hypocrellins are most suitable for photodynamic therapy (PDT) of the diseases occurring in the superficial layer, such as microvascular diseases, because of their special absorption spectral properties. However, hypocrellins and most of their derivatives are basically lipophilic, while the hydrophilic derivatives lose the PDT activity in vivo. Therefore, the key problem for practical application of PDT of microvascular diseases focuses on finding the derivatives which possess optimized amphiphilicity. Herein, we developed a theoretical method to estimate the amphi-philicity of a molecule by the calculated average polarity. Compared with the experimentally measured results, the method is proved to be applicable. Based on the computation and available experimental results, it can be concluded that the derivative must have the polarities around C.22 for optimized amphiphilicity.

  17. Computational Amphiphilic Materials for Drug Delivery

    Directory of Open Access Journals (Sweden)

    Naresh eThota


    Full Text Available Amphiphilic materials can assemble into a wide variety of morphologies and have emerged as a novel class of candidates for drug delivery. Along with a large number of experiments reported, computational studies have been also conducted in this field. At an atomistic/molecular level, computations can facilitate quantitative understanding of experimental observations and secure fundamental interpretation of underlying phenomena. This review summarizes the recent computational efforts on amphiphilic copolymers and peptides for drug delivery. Atom-resolution and time-resolved insights are provided from bottom-up to microscopically elucidate the mechanisms of drug loading/release, which are indispensable in the rational screening and design of new amphiphiles for high-efficacy drug delivery.

  18. Robust dithiocarbamate-anchored amine functionalization of Au nanoparticles (United States)

    Chen, Kai; Robinson, Hans D.


    We introduce an effective and facile technique that achieves robust amine functionalization of Au nanoparticles by binding the polyamine poly(allylamine hydrochloride) (PAH) to the surface using a dithiocarbamate (DTC) modification of the side group amines. The DTC anchor confers superior short- and long-term colloidal stability compared to a physisorbed layer of the same polymer. We also demonstrate that the surface amines are available for further functionalization and that at least four alternately charged polyelectrolyte layers can be assembled onto the particles. The latter modification could not be performed on a physisorbed functional layer, so this demonstrates the effectiveness of the DTC groups in robustly anchoring the polymer to the particle surface. At the same time, the DTC-anchored polymer layer is less than 2 nm thick in the dry state. This is one-third of the thickness of a physisorbed polyamine layer deposited under the same conditions, and sufficiently thin that the plasmonic field enhancement on the metal particle remains accessible to the outside environment. We attribute the difference in thickness to multiple DTC bonds on each polymer chain forcing it into much closer conformity to the particle surface than in the physisorbed case.

  19. Design of a multi-coordinating polymer as a platform for functionalizing metal, metal oxide and semiconductor nanocrystals (United States)

    Wang, Wentao; Ji, Xin; Kapur, Anshika; Mattoussi, Hedi


    We introduce a new set of amphiphilic polymers as multifunctional, metal-coordinating ligands adapted to surfacefunctionalize quantum dots (QDs), iron oxide nanoparticles (IONPs) and gold nanoparticles/nanorods (AuNPs/AuNRs). The ligand design relies on the introduction of several anchoring groups, hydrophilic moieties and reactive functionalities into a polymer chain, via one-step nucleophilic addition reaction. Such synthetic scheme also allows the insertion of target biomolecules during the ligand synthesis. This functionalization strategy yields nanocrystals that exhibit long-term colloidal stability over a broad range of biological conditions, such as pH changes and when mixed with growth media. When zwitterion groups are used as hydrophilic motifs, this provides compact nanocrystals that are compatible with conjugation to proteins via metal-polyhistidine self-assembly. In addition, we show that QDs ligated with these polymers can engage in energy or charge transfer interactions. Furthermore, nanocrystals coated with folic acid-modified polymers could promote the delivery of nanoparticle-conjugates into cancer cells via folate receptormediated endocytosis.

  20. Design of a multi-dopamine-modified polymer ligand optimally suited for interfacing magnetic nanoparticles with biological systems. (United States)

    Wang, Wentao; Ji, Xin; Na, Hyon Bin; Safi, Malak; Smith, Alexandra; Palui, Goutam; Perez, J Manuel; Mattoussi, Hedi


    We have designed a set of multifunctional and multicoordinating polymer ligands that are optimally suited for surface functionalizing iron oxide and potentially other magnetic nanoparticles (NPs) and promoting their integration into biological systems. The amphiphilic polymers are prepared by coupling (via nucleophilic addition) several amine-terminated dopamine anchoring groups, poly(ethylene glycol) moieties, and reactive groups onto a poly(isobutylene-alt-maleic anhydride) (PIMA) chain. This design greatly benefits from the highly efficient and reagent-free one-step reaction of maleic anhydride groups with amine-containing molecules. The availability of several dopamine groups in the same ligand greatly enhances the ligand affinity, via multiple coordination, to the magnetic NPs, while the hydrophilic and reactive groups promote colloidal stability in buffer media and allow subsequent conjugation with target biomolecules. Iron oxide nanoparticles ligand exchanged with these polymer ligands have a compact hydrodynamic size and exhibit enhanced long-term colloidal stability over the pH range of 4-12 and in the presence of excess electrolytes. Nanoparticles ligated with terminally reactive polymers have been easily coupled to target dyes and tested in live cell imaging with no measurable cytotoxicity. Finally, the resulting hydrophilic nanoparticles exhibit large and size-dependent r2 relaxivity values.

  1. Nose to Brain Delivery: New Trends in Amphiphile-Based "Soft" Nanocarriers. (United States)

    Marianecci, Carlotta; Rinaldi, Federica; Hanieh, Patrizia N; Paolino, Donatella; Marzio, Luisa Di; Carafa, Maria


    The aim of the present paper is to highlight the potential of nasal mucosa as an administration route for targeting the central nervous system, in particular, the brain. Among the formulation strategies for enhance nose to brain drug delivery, the use of colloidal carriers has became a revolutionary approach. These systems should be able to entrap drugs in the desired amount, to penetrate through anatomical barriers, to efficiently release the loaded drugs in the site of action and moreover to show a good physicochemical, biological stability and good biocompatibility. The use of vesicular systems (liposomes and niosomes) together with the use of micelles, in nose to brain delivery are here presented. Vesicle structure is characterized by the presence of a hydrophobic bilayer and an aqueous core that is absent in micelles. Amphiphilic molecules are responsible for soft nanocarriers formation, in particular: liposomes are formed by phospholipids, while niosomes by non-ionic surfactant and micelles by amphiphilic polymers.

  2. Synthesis of an amphiphilic dendrimer-like block copolymer and its application on drug delivery

    KAUST Repository

    Wang, Shuaipeng


    Dendrimer-like amphiphilic copolymer is a kind of three-dimensional spherical structure polymer. An amphiphilic dendrimer-like diblock copolymer, PEEGE-G2-b-PEO(OH)12, constituted of a hydrophobic poly(ethoxyethyl glycidol ether) inner core and a hydrophilic poly(ethylene oxide) outer layer, has been successfully synthesized by the living anionic ring-opening polymerization method. The intermediates and targeted products were characterized with 1H NMR spectroscopy and gel permeation chromatography. The application on drug delivery of dendrimer-like diblock copolymer PEEGE-G2-b-PEO(OH)12 using DOX as a model drug was also studied. The drug loading content and encapsulation efficiency were found at 13.07% and 45.75%, respectively. In vitro release experiment results indicated that the drug-loaded micelles exhibited a sustained release behavior under acidic media.

  3. An Amylase-Responsive Bolaform Supra-Amphiphile. (United States)

    Kang, Yuetong; Cai, Zhengguo; Tang, Xiaoyan; Liu, Kai; Wang, Guangtong; Zhang, Xi


    An amylase-responsive bolaform supra-amphiphile was constructed by the complexation between β-cyclodextrin and a bolaform covalent amphiphile on the basis of host-guest interaction. The bolaform covalent amphiphile could self-assemble in solution, forming sheet-like aggregates and displaying weak fluorescence because of aggregation-induced quenching. The addition of β-cyclodextrin led to the formation of the bolaform supra-amphiphile, prohibiting the aggregation of the bolaform covalent amphiphile and accompanying with the significant recovery of fluorescence. Upon the addition of α-amylase, with the degradation β-cyclodextrin, the fluorescence of the supra-amphiphile would quench gradually and significantly, and the quenching rate linearly correlated to the concentration of α-amylase. This study enriches the field of supra-amphiphiles on the basis of noncovalent interactions, and moreover, it may provide a facile way to estimate the activity of α-amylase.

  4. Self-Assembly and Hydrogelation of Peptide Amphiphiles

    Directory of Open Access Journals (Sweden)

    Wahyudi Priyono Suwarso


    Full Text Available Seven peptide amphiphiles were successfully synthesized using solid phase peptide synthesis method. Peptide amphiphiles were characterized using matrix assisted laser desorption/ionization (MALDI. Atomic force microscopy (AFM study showed that peptide amphiphiles having glycine, valine, or proline as linker, self-assembled into 100-200 nm nanofibers structure. According to our research, both peptide amphiphile with positive and negative charges bear similar self-assembly properties. Peptide amphiphile also showed its capability as low molecular weight gelator (LMWG. Peptide amphiphiles bearing C-16 and C-12 as alkyl showed better hydrogelation properties than C-8 alkyl. Five out of seven peptide amphiphiles have minimum gelation concentration (MGC lower than 1% (w/v.

  5. Synthesis of Hydrophilic and Amphiphilic Acryl Sucrose Monomers and Their Copolymerisation with Styrene, Methylmethacrylate and α- and β-Pinenes

    Directory of Open Access Journals (Sweden)

    Maria Teresa Barros


    Full Text Available Herein, we report the synthesis of monomethacryloyl sucrose esters, and their successful free radical homo- and co-polymerisation with styrene, methylmethacrylate, α- and β-pinene. The chemical, physical, structural and surface chemical properties of these polymers, containing a hydrophobic olefin backbone and hydrophilic sugar moieties as side chains, have been investigated. Biodegradation tests of the copolymer samples by a microbial fungal culture (Aspergillus niger method showed good biodegradability. The chemical structure and surface chemistry of the synthesized homo- and co-polymers demonstrate their potential technological relevance as amphiphilic and biodegradable polymers.

  6. Designing new symmetrical facial oligothiophene amphiphiles

    NARCIS (Netherlands)

    Janeliunas, Dainius; Eelkema, Rienk; Nieto-Ortega, Belén; Ramírez Aguilar, Francisco J; López Navarrete, Juan T; van der Mee, Lars; Stuart, Marc C A; Casado, Juan; van Esch, Jan H


    In this study we designed a new class of symmetrical facial oligothiophene amphiphiles, which could be obtained in fewer steps than for previously reported analogues, but still possess the specific substituent sequence to control their backbone curvature. This novel design allows the late-stage intr

  7. Plasmonic Vesicles of Amphiphilic Nanocrystals: Optically Active Multifunctional Platform for Cancer Diagnosis and Therapy. (United States)

    Song, Jibin; Huang, Peng; Duan, Hongwei; Chen, Xiaoyuan


    Vesicular structures with compartmentalized, water-filled cavities, such as liposomes of natural and synthetic amphiphiles, have tremendous potential applications in nanomedicine. When block copolymers self-assemble, the result is polymersomes with tailored structural properties and built-in releasing mechanisms, controlled by stimuli-responsive polymer building blocks. More recently, chemists are becoming interested in multifunctional hybrid vesicles containing inorganic nanocrystals with unique optical, electronic, and magnetic properties. In this Account, we review our recent progress in assembling amphiphilic plasmonic nanostructures to create a new class of multifunctional hybrid vesicles and applying them towards cancer diagnosis and therapy. Localized surface plasmon resonance (LSPR) gives plasmonic nanomaterials a unique set of optical properties that are potentially useful for both biosensing and nanomedicine. For instance, the strong light scattering at their LSPR wavelength opens up the applications of plasmonic nanostructures in single particle plasmonic imaging. Their superior photothermal conversion properties, on the other hand, make them excellent transducers for photothermal ablation and contrast agents for photoacoustic imaging. Of particular note for ultrasensitive detection is that the confined electromagnetic field resulting from excitation of LSPR can give rise to highly efficient surface enhanced Raman scattering (SERS) for molecules in close proximity. We have explored several ways to combine well-defined plasmonic nanocrystals with amphiphilic polymer brushes of diverse chemical functionalities. In multiple systems, we have shown that the polymer grafts impart amphiphilicity-driven self-assembly to the hybrid nanoparticles. This has allowed us to synthesize well-defined vesicles in which we have embedded plasmonic nanocrystals in the shell of collapsed hydrophobic polymers. The hydrophilic brushes extend into external and interior aqueous

  8. Rigid rod anchored to infinite membrane. (United States)

    Guo, Kunkun; Qiu, Feng; Zhang, Hongdong; Yang, Yuliang


    We investigate the shape deformation of an infinite membrane anchored by a rigid rod. The density profile of the rod is calculated by the self-consistent-field theory and the shape of the membrane is predicted by the Helfrich membrane elasticity theory [W. Helfrich, Z. Naturforsch. 28c, 693 (1973)]. It is found that the membrane bends away from the rigid rod when the interaction between the rod and the membrane is repulsive or weakly attractive (adsorption). However, the pulled height of the membrane at first increases and then decreases with the increase of the adsorption strength. Compared to a Gaussian chain with the same length, the rigid rod covers much larger area of the membrane, whereas exerts less local entropic pressure on the membrane. An evident gap is found between the membrane and the rigid rod because the membrane's curvature has to be continuous. These behaviors are compared with that of the flexible-polymer-anchored membranes studied by previous Monte Carlo simulations and theoretical analysis. It is straightforward to extend this method to more complicated and real biological systems, such as infinite membrane/multiple chains, protein inclusion, or systems with phase separation.

  9. Anchoring FRP laminates for the seismic strengthening of RC columns


    Sadone, Raphaëlle; Quiertant, Marc; FERRIER, Emmanuel; Chataigner, Sylvain; Mercier, Julien


    This paper aims to examine the effectiveness of seismic strengthening of reinforced concrete (RC) columns by externally bonded Fibre Reinforced Polymer (FRP). Particularly, a novel strengthening system, designed for the flexural strengthening of columns is studied. This flexural strengthening is achieved by FRP plates bonded longitudinally and anchored at the column-stub junction. The proposed system is validated through an experimental campaign carried out on full-scale RC columns. Different...

  10. Anchored Instruction and Situated Cognition Revisited. (United States)

    Educational Technology, 1993


    Reviews theories of anchored instruction and addresses issues related to learning, transfer, and assessment. Highlights include video-based macrocontexts; videodisc anchors versus computer-based simulations; cooperative learning; transfer outside the classroom; authenticity; visual anchors versus verbal anchors; situated cognition; and using…

  11. Polymer nanoassemblies for cancer treatment and imaging. (United States)

    Lee, Hyun Jin; Ponta, Andrei; Bae, Younsoo


    Amphiphilic polymers represented by block copolymers self-assemble into well-defined nanostructures capable of incorporating therapeutics. Polymer nanoassemblies currently developed for cancer treatment and imaging are reviewed in this article. Particular attention is paid to three representative polymer nanoassemblies: polymer micelles, polymer micellar aggregates and polymer vesicles. Rationales, design and performance of these polymer nanoassemblies are addressed, focusing on increasing the solubility and chemical stability of drugs. Also discussed are polymer nanoassembly formation, the distribution of polymer materials in the human body and applications of polymer nanoassemblies for combined therapy and imaging of cancer. Updates on tumor-targeting approaches, based on preclinical and clinical results are provided, as well as solutions for current issues that drug-delivery systems have, such as in vivo stability, tissue penetration and therapeutic efficacy. These are discussed to provide insights on the future development of more effective polymer nanoassemblies for the delivery of therapeutics in the body.

  12. Dynamic Polymer Brush at Polymer/Water Interface (United States)

    Yokoyama, Hideaki; Inoue, Kazuma; Ito, Kohzo; Inutsuka, Manabu; Tanaka, Keiji; Yamada, Norifumi


    A layer of polymer chains tethered by one end to a surface is called polymer brush and known to show various unique properties such as anti-fouling. The surface segregation phenomena of copolymers with surface-active blocks should be useful for preparing such a brush layer in spontaneous process. We report hydrophilic polymer brushes formed at the interface between water and polymer by the segregation of amphiphilic diblock copolymers blended in a crosslinked rubbery matrix and call it ``dynamic polymer brush.'' In this system, the hydrophilic block with high surface energy avoids air surface, but segregates to cover the interface between hydrophobic elastomer and water. The structures of the brush layers at D2O/polymer interfaces were measured by neutron reflectivity. The dynamic polymer brush layer surprisingly reached 75% of the contour length of the chain and 2.7 chains/nm2. The brush density was surprisingly comparable to the polymer brush fabricated by the ``grafting-from'' method. We will discuss the dependence of the brush structure on molecular weight and block fraction of amphiphilic block copolymers. Such a surprisingly thick and dense polymer brush were induced by the large enthalpy gain of hydration of hydrophilic block.

  13. A comparative study of interaction of ibuprofen with biocompatible polymers. (United States)

    Khan, Iqrar A; Anjum, Kahkashan; Ali, Mohd Sajid; Kabir-ud Din


    In this paper we are reporting the interaction of a non-steroidal anti-inflammatory drug ibuprofen (IBF) with various biocompatible polymers. Being amphiphilic, the drug interacts with the polymers similar to the interaction of surfactants and polymers. Therefore, we have considered the polymer-amphiphile interaction approach using conductimetry. The polymers of different charges (cationic, anionic, and nonionic) have been taken for the study. It was found that the critical aggregation concentration (cac) decreases on increasing the polymer concentrations of cationic as well as nonionic polymers whereas it increases for anionic polymers. The results imply that anionic IBF interacts with cationic and nonionic polymers more strongly as compared to the anionic polymers. A possible anionic-anionic repulsion is responsible for the weak interaction of IBF with anionic polymers. On the other side, the critical micelle concentration (cmc) increases for all polymers which is a usual indication of the interaction between amphiphiles and polymers. Free energies of aggregation (ΔG(agg)) and micellization (ΔG(mic)) were also computed with the help of degrees of micelle ionization obtained from the specific conductivity - [IBF] isotherms.

  14. Formation and Mechanism of Superhydrophobic/Hydrophobic Surfaces Made from Amphiphiles through Droplet-Mediated Evaporation-Induced Self-Assembly. (United States)

    Dong, Fangyuan; Zhang, Mi; Tang, Wai-Wa; Wang, Yi


    Superhydrophobic/hydrophobic surfaces have attracted wide attention because of their broad applications in various regions, including coating, textile, packaging, electronic devices, and bioengineering. Many studies have been focused on the fabrication of superhydrophobic/hydrophobic surfaces using natural materials. In this paper, superhydrophobic/hydrophobic surfaces were formed by an amphiphilic natural protein, zein, using electrospinning. Water contact angle (WCA) and scanning electron microscopy (SEM) were used to characterize the hydrophobicity and surface morphology of the electrospun structures. The highest WCA of the zein electrospun surfaces could reach 155.5 ± 1.4°. To further understand the mechanism of superhydrophobic surface formation from amphiphiles using electrospinning, a synthetic amphiphilic polymer was selected, and also, a method similar to electrospinning, spray drying, was tried. The electrospun amphiphilic polymer surface showed a high hydrophobicity with a WCA of 141.4 ± 0.7°. WCA of the spray-dried zein surface could reach 125.3 ± 2.1°. The secondary structures of the zein in the electrospun film and cast-dried film were studied using ATR-FTIR, showing that α-helix to β-sheet transformation happened during the solvent evaporation in the cast drying process but not in the electrospinning process. A formation mechanism was proposed on the basis of the orientation of the amphiphiles during the solvent evaporation of different fabrication methods. The droplet-based or jet-based evaporation during electrospinning and spray drying led to the formation of the superhydrophobic/hydrophobic surface by the accumulation of the hydrophobic groups of the amphiphiles on the surface, while the surface-based evaporation during cast drying led to the formation of the hydrophilic surface by the accumulation of the hydrophilic groups of the amphiphiles on the surface.

  15. Microgravity Drill and Anchor System (United States)

    Parness, Aaron; Frost, Matthew A.; King, Jonathan P.


    This work is a method to drill into a rock surface regardless of the gravitational field or orientation. The required weight-on-bit (WOB) is supplied by a self-contained anchoring mechanism. The system includes a rotary percussive coring drill, forming a complete sampling instrument usable by robot or human. This method of in situ sample acquisition using micro - spine anchoring technology enables several NASA mission concepts not currently possible with existing technology, including sampling from consolidated rock on asteroids, providing a bolt network for astronauts visiting a near-Earth asteroid, and sampling from the ceilings or vertical walls of lava tubes and cliff faces on Mars. One of the most fundamental parameters of drilling is the WOB; essentially, the load applied to the bit that allows it to cut, creating a reaction force normal to the surface. In every drilling application, there is a minimum WOB that must be maintained for the system to function properly. In microgravity (asteroids and comets), even a small WOB could not be supported conventionally by the weight of the robot or astronaut. An anchoring mechanism would be needed to resist the reactions, or the robot or astronaut would push themselves off the surface and into space. The ability of the system to anchor itself to a surface creates potential applications that reach beyond use in low gravity. The use of these anchoring mechanisms as end effectors on climbing robots has the potential of vastly expanding the scope of what is considered accessible terrain. Further, because the drill is supported by its own anchor rather than by a robotic arm, the workspace is not constrained by the reach of such an arm. Yet, if the drill is on a robotic arm, it has the benefit of not reflecting the forces of drilling back to the arm s joints. Combining the drill with the anchoring feet will create a highly mobile, highly stable, and highly reliable system. The drilling system s anchor uses hundreds of

  16. A Peptide Amphiphile Organogelator of Polar Organic Solvents (United States)

    Rouse, Charlotte K.; Martin, Adam D.; Easton, Christopher J.; Thordarson, Pall


    A peptide amphiphile is reported, that gelates a range of polar organic solvents including acetonitrile/water, N,N-dimethylformamide and acetone, in a process dictated by β-sheet interactions and facilitated by the presence of an alkyl chain. Similarities with previously reported peptide amphiphile hydrogelators indicate analogous underlying mechanisms of gelation and structure-property relationships, suggesting that peptide amphiphile organogel design may be predictably based on hydrogel precedents. PMID:28255169

  17. Complexation between a macromolecule and an amphiphile by Monte Carlo technique. (United States)

    Gharibi, Hussein; Behjatmanesh-Ardakani, Reza; Hashemianzadeh, Majid; Mousavi-Khoshdel, Morteza


    Using a simple modified version of Larson's model, we studied the complexation between a macromolecule and an amphiphile in a dilute range of concentrations. The main characteristic of amphiphile molecules, that is, the hydrophobicity of the tails and hydrophilicity of the heads, is used to model the self-assembling process. Contrary to the molecular thermodynamics approaches, no prior shape was considered for the aggregates and the system was allowed to choose the most stable structure. For true ensemble averaging, without any synthetic results, configurational bias Monte Carlo and reptation moves are used to produce a Markov chain of configurations. From the results, it is found that the macromolecule causes the clusters of surfactants to be formed at a concentration much lower than the critical micelle concentration. Furthermore, the shape of the clusters tends to be more spherical, which is in line with theory and experiments. From the results, it is learned how a polymer can change the behavior of an amphiphilic molecule. All of the results are in good qualitative agreement with experimental and molecular thermodynamics results. Furthermore, the model predicts network formation between bound clusters at high concentrations of the surfactant.

  18. Understanding Peptide Oligomeric State in Langmuir Monolayers of Amphiphilic 3-Helix Bundle-Forming Peptide-PEG Conjugates (United States)

    Shu, Jessica Y.; Xu, Ting


    Coiled-coil peptide–polymer conjugates are an emerging class of biomaterials. Fundamental understanding of the coiled-coil oligomeric state and assembly process of these hybrid building blocks is necessary to exert control over their assembly into well-defined structures. Here, we studied the effect of peptide structure and PEGylation on the self-assembly process and oligomeric state of a Langmuir monolayer of amphiphilic coiled-coil peptide–polymer conjugates using X-ray reflectivity (XR) and grazing-incidence X-ray diffraction (GIXD). Our results show that the oligomeric state of PEGylated amphiphiles based on 3-helix bundle-forming peptide is surface pressure dependent, a mixture of dimers and trimers was formed at intermediate surface pressure but transitions into trimers completely upon increasing surface pressure. Moreover, the interhelical distance within the coiled-coil bundle of 3-helix peptide-PEG conjugate amphiphiles was not perturbed under high surface pressure. Present studies provide valuable insights into the self-assembly process of hybrid peptide–polymer conjugates and guidance to develop biomaterials with controlled multivalency of ligand presentation. PMID:27784156


    Institute of Scientific and Technical Information of China (English)

    李国维; 戴剑; 倪春; 殷建华; 余亮


      纤维增强聚合物筋是一种新型复合材料,具有优异的力学性能和耐腐蚀性能,用其替代钢筋用于边坡加固是解决锚杆耐久性问题的途径之一。采用内置光纤光栅的 GFRP 筋制作锚杆结构模型,用空心液压千斤顶施加拉拔荷载,用光栅传感技术监测杆体应变,研究大直径喷砂 GFRP 锚杆在框架梁锚固条件下的受力破坏机制。研究表明,本试验大直径25 mm GFRP 锚杆在拉拔力、平均黏结强度方面均达到相同直径螺纹钢筋锚杆的设计指标,最合理的框架梁厚度为30~40 cm;瞬时荷载循环对 GFRP 锚杆界面黏结状态无明显影响;持续荷载作用下杆体界面的黏结状态会发生蜕化,随时间延续蜕化向深部扩展,荷载越大扩展深度越大,蜕化速度越快;光纤光栅监测技术是发现和观察锚杆界面黏结状态蜕化过程的有效手段。%  Fiber reinforced polymer(FRP) is a new composite material with excellent mechanical properties and corrosion resistance. It is a significant way to solve the durability problem of anchor rod by substituting this polymer for steel bars. Using anchor-rod-structure specimen made from glass fiber reinforced polymer(GFRP) bars with fiber grating installed internally,loaded by hollow hydraulic jack,monitored by grating sensing technology,this paper focuses on the failure mechanism of large-diameter sand-coated GFRP rebar in the frame beams under the condition of anchoring. Research shows that in the experiment,in terms of tensile force and average bond strength,this large-diameter(25 mm) GFRP rebar has reached the design strength of ribbed steel with the same diameter. The most reasonable thickness of frame beam varies from 30 to 40 cm. Transient loading cycles have no obvious influence on GFRP rebar interface-bond state;the degradation of rod body interface-bond state will occur under sustained loads,and it continues to develop and expand to

  20. Nano-Assemblies of Modified Cyclodextrins and Their Complexes with Guest Molecules: Incorporation in Nanostructured Membranes and Amphiphile Nanoarchitectonics Design

    Directory of Open Access Journals (Sweden)

    Leïla Zerkoune


    Full Text Available A variety of cyclodextrin-based molecular structures, with substitutions of either primary or secondary faces of the natural oligosaccharide macrocycles of α-, β-, or γ-cyclodextrins, have been designed towards innovative applications of self-assembled cyclodextrin nanomaterials. Amphiphilic cyclodextrins have been obtained by chemical or enzymatic modifications of their macrocycles using phospholipidyl, peptidolipidyl, cholesteryl, and oligo(ethylene oxide anchors as well as variable numbers of grafted hydrophobic hydrocarbon or fluorinated chains. These novel compounds may self-assemble in an aqueous medium into different types of supramolecular nanoassemblies (vesicles, micelles, nanorods, nanospheres, and other kinds of nanoparticles and liquid crystalline structures. This review discusses the supramolecular nanoarchitectures, which can be formed by amphiphilic cyclodextrin derivatives in mixtures with other molecules (phospholipids, surfactants, and olygonucleotides. Biomedical applications are foreseen for nanoencapsulation of drug molecules in the hydrophobic interchain volumes and nanocavities of the amphiphilic cyclodextrins (serving as drug carriers or pharmaceutical excipients, anticancer phototherapy, gene delivery, as well as for protection of instable active ingredients through inclusion complexation in nanostructured media.


    Institute of Scientific and Technical Information of China (English)

    Kan Yue; Jinlin He; Chang Liu; Mingjun Huang; Xue-Hui Dong; Kai Guo; Peihong Ni


    "Click chemistry" is,by definition,a general functionalization methodology (GFM) and its marriage with living anionic polymerization is particularly powerful in precise macromolecular synthesis.This paper reports the synthesis of a "clickable" middle-chain azide-functionalized polystyrene (mPS-N3) by anionic polymerization and its application in the preparation of novel shape amphiphiles based on polyhedral oligomeric silsesquioxane (POSS).The mPS-N3 was synthesized by coupling living poly(styryl)lithium chains (PSLi) with 3-chloropropylmethyldichlorosilane and subsequent nucleophilic substitution of the chloro group in the presence of sodium azide.Excess PSLi was end-capped with ethylene oxide to facilitate its removal by flash chromatography.The mPS-N3 was then derived into a giant lipid-like shape amphiphile in two steps following a sequential "click" strategy.The copper(I)-catalyzed azide-alkyne cycloaddition between mPS-N3 and alkyne-functionalized vinyl-substituted POSS derivative (VPOSS-alkyne) ensured quantitative ligation to give polystyrene with VPOSS tethered at the middle of the chain (mPS-VPOSS).The thiol-ene reaction with 1-thioglycerol transforms the vinyl groups on the POSS periphery to hydroxyls,resulting in an amphiphilic shape amphiphile,mPS-DPOSS.This synthetic approach is highly efficient and modular.It demonstrates the "click" philosophy of facile complex molecule construction from a library of simple building blocks and also suggests that mPS-N3 can be used as a versatile "clickable" motif in polymer science for the precise synthesis of complex macromolecules.

  2. Amphiphilic Cellulose Ethers Designed for Amorphous Solid Dispersion via Olefin Cross-Metathesis. (United States)

    Dong, Yifan; Mosquera-Giraldo, Laura I; Taylor, Lynne S; Edgar, Kevin J


    The design of cellulose ether-based amphiphiles has been difficult and limited because of the harsh conditions typically required for appending ether moieties to cellulose. Olefin cross-metathesis recently has been shown to be a valuable approach for appending a variety of functional groups to cellulose ethers and esters, provided that an olefin handle for metathesis can be attached. This synthetic pathway gives access to these functional derivatives under very mild conditions and at high efficiency. Modification of ethyl cellulose by metathesis to prepare useful derivatives, for example, for solubility and bioavailability enhancement of drugs by amorphous solid dispersion (ASD), has been limited by the low DS(OH) of commercial ethyl cellulose derivatives. This is problematic because ethyl cellulose is otherwise a very attractive substrate for synthesis of amphiphilic derivatives by olefin metathesis. Herein we explore two methods for opening up this design space for ether-based amphiphiles, for example, permitting synthesis of more hydrophilic derivatives. One approach is to start with the more hydrophilic commercial methyl cellulose, which contains much higher DS(OH) and therefore is better suited for introduction of high DS of olefin metathesis "handles". In another approach, we explored a homogeneous one-pot synthesis methodology from cellulose, where controlled DS of ethyl groups was introduced at the same time as the ω-unsaturated alkyl groups, thereby permitting complete control of DS(OH), DS(Et), and ultimately DS of the functional group added by metathesis. We describe the functionalized derivatives available by these successful approaches. In addition, we explore new methods for reduction of the unsaturation in initial metathesis products to provide robust methods for enhancing product stability against further radical-catalyzed reactions. We demonstrate initial evidence that the products show strong promise as amphiphilic matrix polymers for amorphous

  3. Seals, Concrete Anchors, and Connections (United States)


    the system the cable sizes can be changed even after concreting work _ is finished. i W The structure is also suitable for modern concrete formwork ...1 ruiinn 0i all 3up-H-Stud is a heavy-duty, all steel, expansion wedge anchor types of equipment. Typical applications: tunnel liner panels, air

  4. How anchoring proteins shape pain. (United States)

    Fischer, Michael J M; McNaughton, Peter A


    Cellular responsiveness to external stimuli can be altered by extracellular mediators which activate membrane receptors, in turn signalling to the intracellular space via calcium, cyclic nucleotides, membrane lipids or enzyme activity. These signalling events trigger a cascade leading to an effector which can be a channel, an enzyme or a transcription factor. The effectiveness of these intracellular events is enhanced when they are maintained in close proximity by anchoring proteins, which assemble complexes of signalling molecules such as kinases together with their targets, and in this way enhance both the speed and the precision of intracellular signalling. The A kinase anchoring protein (AKAP) family are adaptor proteins originally named for their ability to associate Protein Kinase A and its targets, but several other enzymes bound by AKAPs have now been found and a wide variety of target structures has been described. This review provides an overview of anchoring proteins involved in pain signalling. The key anchoring proteins and their ion channel targets in primary sensory neurons responding to painful stimuli (nociceptors) are discussed.

  5. Cellular recognition of synthetic peptide amphiphiles in supported bioartificial membranes (United States)

    Pakalns, Teika

    The goal of this study was to demonstrate that lipidated cell adhesion peptides could form well-ordered biomimetic surfaces that were capable of influencing cellular behavior in a controlled and specific manner. The first step taken was to covalently link synthetic dialkyl tails to the amino-termini of the collagen-derived peptide IV-H1 (amino acid sequence GVKGDKGNPGWPGAP) and the well-known tripeptide Arg-Gly-Asp (RGD) to produce amino-coupled peptide amphiphiles. Other spatial orientations of RGD were also generated by coupling tails to the carboxyl-terminus to give carboxyl-coupled RGD amphiphiles and to both the amino- and carboxyl-termini to give looped RGD amphiphiles. The next step taken was to let the peptide amphiphile self-assemble along with methyl ester-capped dialkyl tails into mixed films. It was found that all the peptide amphiphiles formed stable monolayers at the air-water interface in a Langmuir trough. IV-H1 amphiphiles and carboxyl-coupled and looped RGD amphiphiles deposited well as Langmuir-Blodgett mixed films on solid surfaces at all peptide concentrations, but aminocoupled RGD amphiphiles did not deposit well at high RGD concentrations. FT-IR studies of films containing RGD amphiphiles showed that amino-coupled RGD head groups formed the strongest lateral hydrogen bonds. The final step was to study cellular response to mixed films containing IV-H1 or RGD amphiphiles. The spreading of melanoma cells was influenced by both the molar concentration and spatial orientation of the amphiphilic peptides. Cells spread on IV-H1 and looped RGD films in a concentration-dependent manner, but spread indiscriminately on carboxyl-coupled RGD films and did not spread at all on well-deposited amino-coupled RGD films. The specificity of the cellular response to looped RGD amphiphiles was investigated. Control films of looped Arg-Gly-Glu (RGE) amphiphiles inhibited the adhesion and spreading of melanoma and endothelial cells, and antibody inhibition of the

  6. 24 CFR 3285.401 - Anchoring instructions. (United States)


    ... wind by use of anchor assembly type installations or by connecting the home to an alternative foundation system. See § 3285.301. (b) For anchor assembly type installations, the installation instructions... instructions and design for anchor type assemblies must be prepared by a registered professional engineer...

  7. Effect of Amphiphiles on the Rheology of Triglyceride Networks (United States)

    Seth, Jyoti


    Networks of aggregated crystallites form the structural backbone of many products from the food, cosmetic and pharmaceutical industries. Such materials are generally formulated by cooling a saturated solution to yield the desired solid fraction. Crystal nucleation and growth followed by aggregation leads to formation of a space percolating fractal-network. It is understood that microstructural hierarchy and particle-particle interactions determine material behavior during processing, storage and use. In this talk, rheology of suspensions of triglycerides (TAG, like tristearin) will be explored. TAGs exhibit a rich assortment of polymorphs and form suspensions that are evidently sensitive to surface modifying additives like surfactants and polymers. Here, a theoretical framework will be presented for suspensions containing TAG crystals interacting via pairwise potentials. The work builds on existing models of fractal aggregates to understand microstructure and its correlation with material rheology. Effect of amphiphilic additives is derived through variation of particle-particle interactions. Theoretical predictions for storage modulus will be compared against experimental observations and data from the literature and micro structural predictions against microscopy. Such a theory may serve as a step towards predicting short and long-term behavior of aggregated suspensions formulated via crystallization.

  8. Perfluorocyclobutyl-containing Amphiphilic Block Copolymers Synthesized by RAFT Polymerization

    Institute of Scientific and Technical Information of China (English)

    LI, Yongjun; ZHANG, Sen; FENG, Chun; ZHANG, Yaqin; LI, Qingnuan; LI, Wenxin; HUANG, Xiaoyu


    Amphiphilic block copolymers containing hydrophobic perfluorocyclobutyl-based (PFCB) polyacrylate and hydrophilic poly(ethylene glycol) (PEG) segments were prepared via reversible addition-fragmentation chain transfer (RAP-T) polymerization. The PFCB-containing acrylate monomer, p-(2-(p-tolyloxy)perfluorocyclobutoxy)phenyl acrylate, was first synthesized from commercially available compounds in good yields, and this kind of acrylate monomer can be homopolymerized by free radical polymerization or RAFT polymerization. Kinetic study showed the 2,2'-azobis(isobutyronitrile) (AIBN) initiated and cumyl dithiobenzoate (CDB) mediated RAFT polymerization was in a living fashion, as suggested by the fact that the number-average molecular weights (M_n) increased linearly with the conversions of the monomer, while the polydispersity indices kept less than 1.10. The block polymers with narrow molecular weight distributions (M_w/M_n≤1.21) were prepared through RAFT polymerization using PEG monomethyl ether capped with 4-cyanopentanoic acid dithiobenzoate end group as the macro chain transfer agent (mPEG-CTA). The length of the hydrophobic segment can be tuned by the feed ratio of the PFCB-based acrylate monomer and the extending of the polymerization time. The micellization behavior of the block copolymers in aqueous media was investigated by the fluorescence probe technique.

  9. Fluctuations and structure of amphiphilic films; Fluctuations et structure de films d`amphiphiles

    Energy Technology Data Exchange (ETDEWEB)

    Gourier, CH


    This thesis is divided in three parts.The first part exposes in a theoretical point of view, how the fluctuations spectrum of an amphiphilic film is governed by its properties and its bidimensional characteristics.The measurements of fluctuations spectra of an interface are accessible with the measurement of intensity that interface diffuses out of the specular angle, we present in the second chapter the principles of the X rays diffusion by a real interface and see how the diffuse diffusion experiments allow to determine the fluctuations spectrum of an amphiphilic film. The second part is devoted to the different experimental techniques that have allowed to realize the study of fluctuation as well as the structural study.The third part is devoted to experimental results concerning the measurements of fluctuations spectra and to the study of the structure of amphiphilic films. We show that it is possible by using an intense source of X rays (ESRF: European Synchrotron Radiation Facility) to measure the water and amphiphilic films fluctuations spectra until molecular scales. The last chapter is devoted to the structural study and film fluctuations made of di-acetylenic molecules. (N.C.)

  10. [Amphiphilic cyclodextrins and their applications. Preparation of nanoparticles based on amphiphilic cyclodextrins for biomedical applications]. (United States)

    Parrot-Lopez, H; Perret, F; Bertino-Ghera, B


    Solubilization of hydrophobic drugs at the molecular level as inclusion complexes inside cyclodextrins (CDs) offers a good alternative for improving their stability, solubility and bioavailability, and for preventing against their possible toxicity or controlling secondary effects. Therefore CDs are widely used as solubilizing excipients. However since dissociation takes place too readily upon dilution, inclusion complexes inside simple water-soluble CD appears ineffective for drug delivery applications. Chemical modifications of CDs allow them to self-organize as larger assemblies useful for resolving this lability issue. Depending on the position, the number and the nature of these groups, amphiphilic CDs can form assemblies such as vesicles, solid-lipid nanoparticles, nanospheres, liquid crystals, or micellar systems. This review deals with the synthesis of amphiphilic cyclodextrins leading to supramolecular assemblies and the physical properties of these assemblies. From the first sulfonated amphiphilic cyclodextrins isolated in our laboratory in 2003, to the latest ones being regioselectively functionalized by two or four fluoroalkyl chains, through the persubstituted fluorinated cyclodextrines, all these amphiphilic cyclodextrins have shown good abilities for encapsulation. Complexation of bioactive molecules (acyclovir) by these modified alpha-cyclodextrin derivatives, the encapsulation efficiency and release profile were measured as an assessment of the properties of such nanoparticles regarding drug delivery applications.

  11. Multilayers of Fluorinated Amphiphilic Polyions for Marine Fouling Prevention

    NARCIS (Netherlands)

    Zhu, X.; Guo, S.; Janczewski, D.; Parra-Velandia, F.J.; Teo, S.L-M.; Vancso, G.J.


    Sequential layer-by-layer (LbL) deposition of polyelectrolytes followed by chemical cross-linking was investigated as a method to fabricate functional amphiphilic surfaces for marine biofouling prevention applications. A novel polyanion, grafted with amphiphilic perfluoroalkyl polyethylene glycol (

  12. Confined supramolecular nanostructures of mesogen-bearing amphiphiles. (United States)

    Zou, Bo; Wang, Mingfeng; Qiu, Dengli; Zhang, Xi; Chi, Lifeng; Fuchs, Harald


    Stable surface nanostructures with different morphology have been successfully constructed by modifying the chemical structure of synthetic amphiphiles; by introducing mesogenic groups into bolaform amphiphiles, stable spaghetti-like or stripe-like nanostructures can be obtained; it is believed that such a kind of surface structure could be used for templating synthesis and assembly.

  13. Incorporation of Amphiphilic Cyclodextrins into Liposomes as Artificial Receptor Units

    NARCIS (Netherlands)

    Kauscher, Ulrike; Stuart, Marc C. A.; Druecker, Patrick; Galla, Hans-Joachim; Ravoo, Bart Jan


    In this article, we describe the introduction of amphiphilic beta-cyclodextrins into liposomes to act as artificial receptor units. Using dynamic light scattering, dye encapsulation, and cryogenic transmission electron microscopy, we show that amphiphilic beta-cyclodextrins can be mixed in any propo

  14. Colloidosomes formed by nonpolar/polar/nonpolar nanoball amphiphiles. (United States)

    Chang, Hung-Yu; Tu, Sheng-Hung; Sheng, Yu-Jane; Tsao, Heng-Kwong


    Fullerene-based amphiphiles are able to form bilayer vesicles in aqueous solution. In this study, the self-assembly behavior of polymer-tethered nanoballs (NBs) with nonpolar/polar/nonpolar (n-p-n') motif in a selective solvent is investigated by dissipative particle dynamics. A model NB bears two hydrophobic polymeric arms (n'-part) tethered on an extremely hydrophobic NB (n-part) with hydrophilic patch (p-part) patterned on its surface. Dependent on the hydrophobicity and length of tethered arms, three types of aggregates are exhibited, including NB vesicle, core-shell micelle, and segmented-worm. NB vesicles are developed for a wide range of hydrophobic arm lengths. The presence of tethered arms perturbs the bilayer structure formed by NBs. The structural properties including the order parameter, membrane thickness, and area density of the inner leaflet decrease with increasing the arm length. These results indicate that for NBs with longer arms, the extent of interdigitation in the membrane rises so that the overcrowded arms in the inner corona are relaxed. The transport and mechanical properties are evaluated as well. As the arm length grows, the permeability increases significantly because the steric bulk of tethered arms loosens the packing of NBs. By contrast, the membrane tension decreases owing to the reduction of NB/solvent contacts by the polymer corona. Although fusion can reduce membrane tension, NB vesicles show strong resistance to fusion. Moreover, the size-dependent behavior observed in small liposomes is not significant for NB vesicles due to isotropic geometry of NB. Our simulation results are consistent with the experimental findings.

  15. Biolabeling and Binding Evaluation of Amphiphilic Nanocrystallopolymers

    Directory of Open Access Journals (Sweden)

    Kwang-Suk Jang


    Full Text Available Surfactant-like inorganic-organic hybrid molecules named as nanocrystallopolymers were designed by conjugation of the hydrophilic synthetic poly(amino acid, poly-α,β-(N-(2-hydroxyethyll-aspartamide, with hydrophobic inorganic nanoparticles. In aqueous media, amphiphilic nanocrystallopolymers form self-aggregates with unique morphologies. Here, a simple biolabeling method of nanocrystallopolymers was developed. Biotin was selected as a model biomolecule. The specific binding of biotin-labeled nanocrystallopolymers to the targeted surface was evaluated with a surface plasmon resonance sensor.

  16. Anchoring Bias in Online Voting

    CERN Document Server

    Yang, Zimo; Zhou, Tao


    Voting online with explicit ratings could largely reflect people's preferences and objects' qualities, but ratings are always irrational, because they may be affected by many unpredictable factors like mood, weather, as well as other people's votes. By analyzing two real systems, this paper reveals a systematic bias embedding in the individual decision-making processes, namely people tend to give a low rating after a low rating, as well as a high rating following a high rating. This so-called \\emph{anchoring bias} is validated via extensive comparisons with null models, and numerically speaking, the extent of bias decays with interval voting number in a logarithmic form. Our findings could be applied in the design of recommender systems and considered as important complementary materials to previous knowledge about anchoring effects on financial trades, performance judgements, auctions, and so on.

  17. Inconspicuous anchoring effects generated by false information

    Institute of Scientific and Technical Information of China (English)

    Chen Qu; Jun Wang; Yuejia Luo


    The impact of false information on numerical judgments was examined on young normal subjects by an event-related potential (ERP) experiment. To imitate the judgments in real world, we ensured the subjects acknowledged of the target task. The behavioral results found that both uncertain information and false information assimilated the final estimates: higher after higher anchors and lower after lower anchors; and false information caused a weaker anchoring bias than uncertain information. ERP results provided further electrophysiological evidence for the mechanism of anchoring. In the early phrase, it was an accessibility-dominated process in which two kinds of anchors elicited an N300 component related to the accessibility of anchors propositions. The knowledge relevant to targets joined the process in the late phrase, which caused a larger amplitude of late positive component (LPC) for implausible lower anchors than that for plausible higher anchors. Source analysis showed that medial frontal gyrus, whose activity was suggested to signal the need of adjustment, was more reliable to explain the LPC elicited by implausible lower anchors. Therefore, we suggest that accessibility is facilitated when the external anchor is consistent with the world knowledge, and adjustment is initiated when the external anchor is inconsistent.

  18. Anchoring in Numeric Judgments of Visual Stimuli. (United States)

    Langeborg, Linda; Eriksson, Mårten


    This article investigates effects of anchoring in age estimation and estimation of quantities, two tasks which to different extents are based on visual stimuli. The results are compared to anchoring in answers to classic general knowledge questions that rely on semantic knowledge. Cognitive load was manipulated to explore possible differences between domains. Effects of source credibility, manipulated by differing instructions regarding the selection of anchor values (no information regarding anchor selection, information that the anchors are randomly generated or information that the anchors are answers from an expert) on anchoring were also investigated. Effects of anchoring were large for all types of judgments but were not affected by cognitive load or by source credibility in either one of the researched domains. A main effect of cognitive load on quantity estimations and main effects of source credibility in the two visually based domains indicate that the manipulations were efficient. Implications for theoretical explanations of anchoring are discussed. In particular, because anchoring did not interact with cognitive load, the results imply that the process behind anchoring in visual tasks is predominantly automatic and unconscious.

  19. Upper section for anchor timbering

    Energy Technology Data Exchange (ETDEWEB)

    Shirokov, A.P.; Isachenko, V.M.; Kuntsevich, V.I.; Pishulin, V.V.


    The purpose of the invention is to exclude rotation of the fixing device around the anchor with screwing of the tightening nut and simplification of the fixing device design. The support fixing device is made of a section of pipe and is equipped with a rotation delimiter made in the form of a female fixing device of the projection arranged on it at an angle to the longitudinal axis.


    Institute of Scientific and Technical Information of China (English)

    Zhao-qiang Wu; Shu Yang; Wen-yan Liao; Ling-zhi Meng


    Novel amphiphilic fluorescent graft copolymer (PVP-PyAHy) was successfully synthesized by the free radical copolymerization of hydrophobic monomer N-(1-pyrenebutyryl)-N'-acryloyl hydrazide (PyAHy) with hydrophilic precursor polymers of vinyl-functionalized poly(N-vinylpyrrolidone) (PVP) in DMF. The copolymer is amphiphilic and has intrinsic fluorescence. FT-IR, 1H-NMR, TEM, gel permeation chromatography-multi-angle laser light scattering, UV-Vis spectroscopy and fluorescence spectroscopy were used to characterize this copolymer. The TEM observation shows that the copolymer PVP-PyAHy forms micelles in aqueous solution. Results of fluorometric measurements illustrate that the critical micelle concentration (CMC) value of PVP-PyAHy in aqueous solution is about 0.90 mg/mL. To examine the encapsulation ability of the copolymer in aqueous media, methyl yellow was employed as a model hydrophobic agent. The loading level of the polymer to methyl yellow is 8.8 mg/g. The cytotoxicity assays for Madin Darby Canine Kidney (MDCK) cells shows good biocompatibility of PVP-PyAHy in vitro. These results suggest the potential of this copolymer PVP-PyAHy as drugs delivery carrier and fluorescent tracer.

  1. Linear-g-hyperbranched and cyclodextrin-based amphiphilic block copolymer as a multifunctional nanocarrier

    Directory of Open Access Journals (Sweden)

    Yamei Zhao


    Full Text Available In this paper, a novel, multifunctional polymer nanocarrier was designed to provide adequate volume for high drug loading, to afford a multiregion encapsulation ability, and to achieve controlled drug release. An amphiphilic, triblock polymer (ABC with hyperbranched polycarbonsilane (HBPCSi and β-cyclodextrin (β-CD moieties were first synthesized by the combination of a two-step reversible addition-fragmentation transfer polymerization into a pseudo-one-step hydrosilylation and quaternization reaction. The ABC then self-assembled into stable micelles with a core–shell structure in aqueous solution. These resulting micelles are multifunctional nanocarriers which possess higher drug loading capability due to the introduction of HBPCSi segments and β-CD moieties, and exhibit controlled drug release based on the diffusion release mechanism. The novel multifunctional nanocarrier may be applicable to produce highly efficient and specialized delivery systems for drugs, genes, and diagnostic agents.

  2. Foaming behaviour of polymer-surfactant solutions

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes-MartInez, Alfredo [Departamento de Investigacion en PolImeros y Materiales, Universidad de Sonora, Apartado Postal 130, 83000 Hermosillo, Sonora (Mexico); Maldonado, Amir [Departamento de Fisica, Universidad de Sonora, Apartado Postal 1626, 83000 Hermosillo, Sonora (Mexico)


    We study the effect of a non-ionic amphiphilic polymer (PEG-100 stearate also called Myrj 59) on the foaming behaviour of aqueous solutions of an anionic surfactant (sodium dodecyl sulfate or SDS). The SDS concentration was kept fixed while the Myrj 59 concentration was varied. Measurements of foamability, surface tension and electrical conductivity were carried out. The results show two opposite effects depending on the polymer concentration: foamability is higher when the Myrj 59 concentration is low; however, it decreases considerably when the polymer concentration is increased. This behaviour is due to the polymer adsorption at the air/liquid interface at lower polymer concentrations, and to the formation of a polymer-surfactant complex in the bulk at higher concentrations. The results are confirmed by surface tension and electrical conductivity measurements, which are interpreted in terms of the microstructure of the polymer-surfactant solutions. The observed behaviour is due to the amphiphilic nature of the studied polymer. The increased hydrophobicity of Myrj 59, compared to that of water-soluble polymers like PEG or PEO, increases its 'reactivity' towards SDS, i.e. the strength of its interaction with this anionic surfactant. Our results show that hydrophobically modified polymers have potential applications as additives in order to control the foaming properties of surfactant solutions.

  3. Amphiphilic polymeric micelle as pseudostationary phase in electrokinetic chromatography for analysis of eight corticosteroids in cosmetics. (United States)

    Xu, Xiaojin; Ni, Xinjiong; Cao, Yuhua; Zhuo, Xiaolu; Yang, Xiaoxiao; Cao, Guangqun


    Amphiphilic polymeric micelle, as a novel pseudostationary phase in EKC was used to determine eight kinds of corticosteroids namely hydrocortisone, prednisolone, hydrocortisone acetate, prednisone, cortisone acetate, prednisolone acetate, dexamethasone, and triamcinolone acetonide in cosmetics. Amphiphilic random copolymer poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) was micellizated via neutralization in alkaline aqueous solution. The influences of the molar ratio of monomer MMA to MAA, the concentration of polymer and pH on the polymeric micelle microstructure and EKC performances were investigated. As molar ratio of MMA to MAA in P(MMA-co-MAA) increased, both CMC and environmental polarity of the inner core in polymeric micelle decreased dramatically. With increasing monomer ratio, the size of polymeric micelles increased firstly, and then decreased, finally increased again. ζ potential of the micelle had a slight decline trend. As increment of polymer concentration, the size of the polymeric micelle increased steadily. By optimizing the monomer ratio, the polymer concentration, and pH of the running buffer, as well as operation conditions such as separation voltage and temperature, the eight analytes could be separated within 16.5 min using 7.5 mg/mL polymer with the monomer ratio of 7:3 dissolved in pH 9.2 borax buffer as the running buffer. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for eight analytes were between 85.9 and 106%. This method was of accuracy, repeatability, pretreatment simplicity, and could be applied to the quality control of cosmetics.

  4. A lunar/Martian anchor emplacement system (United States)

    Clinton, Dustin; Holt, Andrew; Jantz, Erik; Kaufman, Teresa; Martin, James; Weber, Reed


    On the Moon or Mars, it is necessary to have an anchor, or a stable, fixed point able to support the forces necessary to rescue a stuck vehicle, act as a stake for a tent in a Martian gale, act as a fulcrum in the erection of general construction poles, or support tent-like regolith shields. The anchor emplacement system must be highly autonomous. It must supply the energy and stability for anchor deployment. The goal of the anchor emplacement system project is to design and build a prototype anchor and to design a conceptual anchor emplacement system. Various anchors were tested in a 1.3 cubic meter test bed containing decomposed granite. A simulated lunar soil was created by adjusting the moisture and compaction characteristics of the soil. We conducted tests on emplacement torque, amount of force the anchor could withstand before failure, anchor pull out force at various angles, and soil disturbances caused by placing the anchor. A single helix auger anchor performed best in this test bed based on energy to emplace, and the ultimate holding capacity. The anchor was optimized for ultimate holding capacity, minimum emplacement torque, and minimum soil disturbance in sandy soils yielding the following dimensions: helix diameter (4.45 cm), pitch (1.27 cm), blade thickness (0.15 cm), total length (35.56 cm), shaft diameter (0.78 cm), and a weight of 212.62 g. The experimental results showed that smaller diameter, single-helix augers held more force than larger diameter augers for a given depth. The emplacement system consists of a flywheel and a motor for power, sealed in a protective box supported by four legs. The flywheel system was chosen over a gear system based on its increased reliability in the lunar environment.

  5. Repurposing Cationic Amphiphilic Antihistamines for Cancer Treatment

    DEFF Research Database (Denmark)

    Ellegaard, Anne-Marie; Dehlendorff, Christian; Vind, Anna C.;


    Non-small cell lung cancer (NSCLC) is one of the deadliest cancers worldwide. In search for new NSCLC treatment options, we screened a cationic amphiphilic drug (CAD) library for cytotoxicity against NSCLC cells and identified several CAD antihistamines as inducers of lysosomal cell death. We...... then performed a cohort study on the effect of CAD antihistamine use on mortality of patients diagnosed with non-localized cancer in Denmark between 1995 and 2011. The use of the most commonly prescribed CAD antihistamine, loratadine, was associated with significantly reduced all-cause mortality among patients...... with non-localized NSCLC or any non-localized cancer when compared with use of non-CAD antihistamines and adjusted for potential confounders. Of the less frequently described CAD antihistamines, astemizole showed a similar significant association with reduced mortality as loratadine among patients with any...

  6. Phase behavior of an amphiphilic fluid. (United States)

    Schoen, Martin; Giura, Stefano; Klapp, Sabine H L


    We invoke mean-field density functional theory (DFT) to investigate the phase behavior of an amphiphilic fluid composed of a hard-sphere core plus a superimposed anisometric Lennard-Jones perturbation. The orientation dependence of the interactions consists of a contribution analogous to the interaction potential between a pair of "spins" in the classical, three-dimensional Heisenberg fluid and another one reminiscent of the interaction between (electric or magnetic) point dipoles. At fixed orientation both contributions are short-range in nature decaying as r-6 (r being the separation between the centers of mass of a pair of amphiphiles). Based upon two mean-field-like approximations for the pair correlation function that differ in the degree of sophistication we derive expressions for the phase boundaries between various isotropic and polar phases that we solve numerically by the Newton-Raphson method. For sufficiently strong coupling between the Heisenberg "spins" both mean-field approximations generate three topologically different and generic types of phase diagrams that are observed in agreement with earlier work [see, for example, Tavares et al., Phys. Rev. E 52, 1915 (1995)]. Whereas the dipolar contribution alone is incapable of stabilizing polar phases on account of its short-range nature it is nevertheless important for details of the phase diagram such as location of the gas-isotropic liquid critical point, triple, and tricritical points. By tuning the dipolar coupling constant suitably one may, in fact, switch between topologically different phase diagrams. Employing also Monte Carlo simulations in the isothermal-isobaric ensemble the general topology of the DFT phase diagrams is confirmed.

  7. Anchored Lagrangian submanifolds and their Floer theory

    CERN Document Server

    Fukaya, Kenji; Ohta, Hiroshi; Ono, Kaoru


    We introduce the notion of (graded) anchored Lagrangian submanifolds and use it to study the filtration of Floer' s chain complex. We then obtain an anchored version of Lagrangian Floer homology and its (higher) product structures. They are somewhat different from the more standard non-anchored version. The anchored version discussed in this paper is more naturally related to the variational picture of Lagrangian Floer theory and so to the likes of spectral invariants. We also discuss rationality of Lagrangian submanifold and reduction of the coefficient ring of Lagrangian Floer cohomology of thereof.

  8. Facially amphiphilic thiol capped gold and silver nanoparticles

    Indian Academy of Sciences (India)

    Shreedhar Bhata; Uday Maitra


    A series of bile acid-derived facially amphiphilic thiols have been used to cap sliver and gold nanoparticles. The self-assembling properties of these steroid-capped nanoparticles have been investigated and reported in this article.


    Institute of Scientific and Technical Information of China (English)

    Mikiharu Kamachi


    The inclusion complex formation of α-CD, β-CD, and γ-CD with various water-soluble polymers has been investigated, and the relationship between the chain cross-sectional areas of the polymers and the diameters of the cavities of cyclodextrins (molecular recognition) was found. Polyrotaxanes and tubular polymers were prepared on the basis of molecular recognition. Several kinds of polymers having tetraphenylporphyrin (TPP) and paramagnetic metallotetraphenylporphyrin (AgTPP, CuTPP, VOTPP or ZnTPP) have been prepared by radical polymerization of the corresponding monomers. Visible spectra of these polymers show hypochromism in the Soret bands of TPP moieties as compared with those of monomers. Polymer effects were observed in the magnetic behavior and oxygen adsorption of paramagnetic metallotetraphenylporphyrin moieties. Moreover, polymer effects on photophysical and photochemical behavior were found in the amphiphilic polymers covalently tethered with small amounts of zinc(Ⅱ)-tetraphenylporphyrin (ZnTPP).

  10. Anchored Instruction and Anchored Assessment: An Ecological Approach to Measuring Situated Learning. (United States)

    Young, Michael F.; Kulikowich, Jonna M.

    Anchored instruction and anchored assessment are described and illustrated through a mathematics problem from the Jasper problem solving series developed at Vanderbilt University in Nashville (Tennessee). Anchored instruction is instruction situated in a context complex enough to provide meaning and reasons for why information is useful. Problems…

  11. Amphiphilic poly(L-amino acids) - new materials for drug delivery. (United States)

    Lalatsa, Aikaterini; Schätzlein, Andreas G; Mazza, Mariarosa; Le, Thi Bich Hang; Uchegbu, Ijeoma F


    The formulation of drug compounds into medicines will increasingly rely on the use of specially tailored molecules, which fundamentally alter the drug's pharmacokinetics to enable its therapeutic activity. This is particularly true of the more challenging hydrophobic drugs or therapeutic biological molecules. The demand for such enabled medicines will translate into a demand for advanced highly functionalised drug delivery materials. Polymers have been used to formulate medicines for many decades and this is unlikely to change soon. Amphiphilic polymers based on amino acids are the subject of this review. These molecules, which present as either poly(L-amino acid) block copolymers or poly(L-amino acid) backbones with hydrophobic substituents, self assemble into micelles, vesicles, nanofibres and solid nanoparticles and such self assemblies, have drug delivery capabilities. The nature of the self-assembly depends on the chemistry of the constituent molecules, with the more hydrophilic molecules forming nanosized micellar aggregates including peptide nanofibres, molecules of intermediate hydrophobicity forming polymeric vesicles and the more hydrophobic variants forming amorphous polymeric nanoparticles of 100-1000 nm in diameter. The self-assemblies may be loaded with drugs or may present as micelle forming polymer-drug conjugates and the supramolecular aggregates have been employed as drug solubilisers, tumour targeting agents, gene delivery vectors and facilitators of intracellular drug uptake, with a more promising polymer-drug conjugate progressing to clinical testing.

  12. Antimicrobial polymers prepared by ROMP with unprecedented selectivity: a molecular construction kit approach. (United States)

    Lienkamp, Karen; Madkour, Ahmad E; Musante, Ashlan; Nelson, Christopher F; Nüsslein, Klaus; Tew, Gregory N


    Synthetic Mimics of Antimicrobial Peptides (SMAMPs) imitate natural host-defense peptides, a vital component of the body's immune system. This work presents a molecular construction kit that allows the easy and versatile synthesis of a broad variety of facially amphiphilic oxanorbornene-derived monomers. Their ring-opening metathesis polymerization (ROMP) and deprotection provide several series of SMAMPs. Using amphiphilicity, monomer feed ratio, and molecular weight as parameters, polymers with 533 times higher selectivitiy (selecitviy = hemolytic concentration/minimum inhibitory concentration) for bacteria over mammalian cells were discovered. Some of these polymers were 50 times more selective for Gram-positive over Gram-negative bacteria while other polymers surprisingly showed the opposite preference. This kind of "double selectivity" (bacteria over mammalian and one bacterial type over another) is unprecedented in other polymer systems and is attributed to the monomer's facial amphiphilicity.

  13. Uplift of Symmetrical Anchor Plates by Using Grid-Fixed Reinforced Reinforcement in Cohesionless Soil

    Institute of Scientific and Technical Information of China (English)

    Hamed Niroumand; Khairul Anuar Kassim


    Uplift response of symmetrical anchor plates with and without grid fixed reinforced (GFR) reinforcement was evaluated in model tests and numerical simulations by Plaxis. Many variations of reinforcement layers were used to reinforce the sandy soil over symmetrical anchor plates. In the current research, different factors such as relative density of sand, embedment ratios, and various GFR parameters including size, number of layers, and the proximity of the layer to the symmetrical anchor plate were investigated in a scale model. The failure mechanism and the associated rupture surface were observed and evaluated. GFR, a tied up system made of fiber reinforcement polymer (FRP) strips and end balls, was connected to the geosynthetic material and anchored into the soil. Test results showed that using GFR reinforcement significantly improved the uplift capacity of anchor plates. It was found that the inclusion of one layer of GFR, which rested directly on the top of the anchor plate, was more effective in enhancing the anchor capacity itself than other methods. It was found that by including GFR the uplift response was improved by 29%. Multi layers of GFR proved more effective in enhancing the uplift capacity than a single GFR reinforcement. This is due to the additional anchorage provided by the GFR at each level of reinforcement. In general, the results show that the uplift capacity of symmetrical anchor plates in loose and dense sand can be significantly increased by the inclusion of GFR. It was also observed that the inclusion of GFR reduced the requirement for a large L/D ratio to achieve the required uplift capacity. The laboratory and numerical analysis results are found to be in agreement in terms of breakout factor and failure mechanism pattern.

  14. Anchor Bolt Position in Base Plate In Terms Of T and J Anchor Bolt

    Directory of Open Access Journals (Sweden)

    b Osman Mohamad Hairi


    Full Text Available Generally, L anchor bolt system has been used for a long period of time in construction industry as one of the distributing load structures. However, there are some weaknesses in L anchor bolt which may straighten and pullup when charged with tensile load. Current practices prefer to use other types of anchor bolt systems, such as headed studs anchor bolt system to replace the L anchor bolt design. There has been lack of studies to prove that it is more effective in terms of performance. A new T anchor bolt which was basically modified from headed studs anchor bolt was proposed in this study to compare its performance of tensile loading in concrete failure to typical L design. This study aims to determine whether the T anchor bolt system gives better performance as compared to an L anchor bolt system. The performance was rated based on tensile loading on concrete failure pattern. A pullout test was conducted on two different anchor bolt systems, namely L and T. The anchor bolt embedded depth, h in concrete were varied according to their hook or bend radius. Each sample was repeated twice. There were totally eight samples. The hook or bend radius used were 50 mm and 57.5 mm for sample L1 and L2, respectively. 90-degree bend were used on sample T1 and T2. Based on test results, it can be seen that the performance of concrete failure pattern under tensile load on both L and T anchor bolt design samples with 200 mm embedment depth was better than deeper embedment depth of 230 mm. But the L anchor bolt design gives the best results as compared to T design. Although T anchor bolt design shows higher resistance before first bond failure to the concrete sample. T anchor bolt was analysed and needed deeper embedment depth to allow formation of cone pull-out shape to acquire better performance.

  15. Anchored Instruction in a Situated Learning Environment. (United States)

    Lee, Miwha

    The purpose of this study was to design and develop a multimedia-based anchored program and to examine the effects of students' and group characteristics on the problem-solving process in anchored instruction with the multimedia program in a situated learning environment. Sixty-eight students were assigned to small groups via a stratified random…

  16. DSSC anchoring groups: a surface dependent decision. (United States)

    O'Rourke, C; Bowler, D R


    Electrodes in dye sensitised solar cells are typically nanocrystalline anatase TiO2 with a majority (1 0 1) surface exposed. Generally the sensitising dye employs a carboxylic anchoring moiety through which it adheres to the TiO₂ surface. Recent interest in exploiting the properties of differing TiO₂ electrode morphologies, such as rutile nanorods exposing the (1 1 0) surface and anatase electrodes with high percentages of the (0 0 1) surface exposed, begs the question of whether this anchoring strategy is best, irrespective of the majority surface exposed. Here we address this question by presenting density functional theory calculations contrasting the binding properties of two promising anchoring groups, phosphonic acid and boronic acid, to that of carboxylic acid. Anchor-electrode interactions are studied for the prototypical anatase (1 0 1) surface, along with the anatase (0 0 1) and rutile (1 1 0) surfaces. Finally the effect of using these alternative anchoring groups to bind a typical coumarin dye (NKX-2311) to these TiO₂ substrates is examined. Significant differences in the binding properties are found depending on both the anchor and surface, illustrating that the choice of anchor is necessarily dependent upon the surface exposed in the electrode. In particular the boronic acid is found to show the potential to be an excellent anchor choice for electrodes exposing the anatase (0 0 1) surface.

  17. Method of fabrication of anchored nanostructure materials (United States)

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei


    Methods for fabricating anchored nanostructure materials are described. The methods include heating a nano-catalyst under a protective atmosphere to a temperature ranging from about C. to about C. and contacting the heated nano-catalysts with an organic vapor to affix carbon nanostructures to the nano-catalysts and form the anchored nanostructure material.

  18. Anchoring of proteins to lactic acid bacteria

    NARCIS (Netherlands)

    Leenhouts, K; Buist, Girbe; Kok, Jan


    The anchoring of proteins to the cell surface of lactic acid bacteria (LAB) using genetic techniques is an exciting and emerging research area that holds great promise for a wide variety of biotechnological applications. This paper reviews five different types of anchoring domains that have been exp

  19. Amphiphilic nanosheet self-assembly at the water/oil interface: computer simulations. (United States)

    Xiang, Wenjun; Zhao, Shuangliang; Song, Xianyu; Fang, Shenwen; Wang, Fen; Zhong, Cheng; Luo, Zhaoyang


    In this paper, dissipative particle dynamics simulations are performed to study the interfacial and emulsion stabilizing properties of various systems of amphiphilic nanosheets (ANs) self-assembled at the oil/water (O/W) interface. The ANs have a dimensional symmetry structure that encompasses a triangular-plate at the center and two soft comb-like shells constructed with hydrophilic and hydrophobic polymers. As the simulation results show, the AN molecules are highly oriented in interfacial films with their triangular nanosheets parallel to the O/W interface, while their hydrophobic and hydrophilic segments attempt to immerse into the oil phase and aqueous phase, respectively. These results reveal that the rotation of ANs at oil/water interfaces is greatly restricted, meanwhile, their nanosheet (or planar) configuration facilitates their favorable orientation thereby, thus making the emulsion more stable. At higher concentrations, a wrapped-like or micelle morphology is observed. The O/W emulsions stabilized by ANs were also simulated, and it is interesting to find AN 'patches' at the O/W interface which resembles the leather patches on a football. By introducing the "amphiphilic nanosheet balance" concept, the hydrophilic-lipophilic balance (HLB) values of ANs were calculated. Due to their properties of two-dimensional symmetry, the HLB values of ANs tend to approximately 1 which reveals a stronger stability for emulsions.

  20. Polydispersity-Driven Block Copolymer Amphiphile Self-Assembly into Prolate-Spheroid Micelles

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Andrew L.; Repollet-Pedrosa, Milton H.; Mahanthappa, Mahesh K. (UW)


    The aqueous self-assembly behavior of polydisperse poly(ethylene oxide-b-1,4-butadiene-b-ethylene oxide) (OBO) macromolecular triblock amphiphiles is examined to discern the implications of continuous polydispersity in the hydrophobic block on the resulting aqueous micellar morphologies of otherwise monodisperse polymer surfactants. The chain length polydispersity and implicit composition polydispersity of these samples furnishes a distribution of preferred interfacial curvatures, resulting in dilute aqueous block copolymer dispersions exhibiting coexisting spherical and rod-like micelles with vesicles in a single sample with a O weight fraction, w{sub O}, of 0.18. At higher w{sub O} = 0.51-0.68, the peak in the interfacial curvature distribution shifts and we observe the formation of only American football-shaped micelles. We rationalize the formation of these anisotropically shaped aggregates based on the intrinsic distribution of preferred curvatures adopted by the polydisperse copolymer amphiphiles and on the relief of core block chain stretching by chain-length-dependent intramicellar segregation.

  1. Bionanoparticles of amphiphilic copolymers polyacrylate bearing cholesterol and ascorbate for drug delivery. (United States)

    Liu, Yijiang; Wang, Yanzhai; Zhuang, Dequan; Yang, Junjiao; Yang, Jing


    In this study, a series of amphiphilic polymers with poly(ascorbyl acrylate) (PAAA) as hydrophilic blocks and polyacrylate bearing side-chain cholesteryl mesogens (PCholDEGA) as hydrophobic blocks were prepared using a combination of four-step reactions consisting of two consecutive reversible addition-fragmentation chain transfer (RAFT), desulfurization, and hydrogenolysis under normal pressure. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) as well as wide-angle X-ray diffraction (WAXD) studies showed that the copolymers with PCholDEGA as major block had relatively high stability and clear isotropization temperature (T(i)). Small-angle X-ray diffraction (SAXD) investigation exhibited that the copolymers had bilayer smectic A structure. Their self-assembly behavior was monitored by turbidity change using UV-vis spectrometer, and the morphology and size of the nanoparticles via self-assembly were detected using transmission electron microscopy (TEM) and dynamic light scattering (DLS). The entrapment efficiency and loading capacity of these amphiphilic copolymers were investigated using nile red and drug molecule Ibuprofen. These polymeric micelles with PAAA shell extending into the aqueous solution and strong hydrophobic PCholDEGA core have potential abilities to act as promising nanovehicles with high loading and targeting delivery.

  2. Effects of hydrophobic and hydrophilic modifications on gene delivery of amphiphilic chitosan based nanocarriers. (United States)

    Wang, Bingqing; He, Chunbai; Tang, Cui; Yin, Chunhua


    The structure-activity relationships between hydrophobic and hydrophilic modification on chitosan and resultant physicochemical properties along with performances in dealing with critical gene delivery barriers were investigated through amphiphilic linoleic acid(LA) and poly (β-malic acid) (PMLA) double grafted chitosan (LMC)/plasmid DNA (pDNA) nanocomplexes. LMC polymers with various LA and PMLA substitution degrees were synthesized and their hydrophilicity/hydrophobicity was characterized. Compared to chitosan, LMC nanoparticles retained the pDNA binding ability at pH 5.5 when they formed nanocomplexes with pDNA encoding enhanced green fluorescence protein (pEGFP) and the resultant complexes showed diameters below 300 nm. Hydrophobic LA and hydrophilic PMLA substitution contributed to suppressed non-specific adsorption, reduced interactions inside LMC/pDNA nanocomplexes, and enhanced pDNA dissociation. However, enzymatic degradation resistance, cell adsorption, and cellular uptake through clathrin-mediated pathway were promoted by hydrophobic LA grafting while being inhibited by hydrophilic PMLA substitution. In vitro transfection assay suggested the optimal LMC/pEGFP nanocomplexes mediated an 8.0-fold improved transfection compared to chitosan/pEGFP nanocomplexes. The 4.2-fold and 2.2-fold higher intramuscular gene expression in mice compared to chitosan/pEGFP and polyethyleneimine (PEI)/pEGFP nanocomplexes further demonstrated the superiority of LMC/pDNA nanocomplexes. Therefore, amphiphilic chitosan derivates with appropriate combination of hydrophobic and hydrophilic modification would be promising gene delivery nanocarriers.

  3. Self-Assembly of Amphiphilic Block Copolypeptoids with C 2 -C 5 Side Chains in Aqueous Solution

    KAUST Repository

    Fetsch, Corinna


    © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Nowadays, amphiphilic molecules play an important role in our life. In medical applications, amphiphilic block copolymers have attracted much attention as excipients in drug delivery systems. Here, the polymers are used as emulsifiers, micelles, or polymersomes with a hydrophilic corona block and a hydrophobic core or membrane. The aggregation behavior in aqueous solutions of a series of different amphiphilic block copolypeptoids comprising polysarcosine as a hydrophilic part is here reported. The formation of aggregates is investigated with 1H NMR spectroscopy and dynamic light scattering, and the determination of the critical micelle concentration (cmc) is performed using pyrene fluorescence spectroscopy. For the different block copolypeptoids cmc values ranging from 0.6 × 10-6 M to 0.1 × 10-3 M are found. The tendency to form micelles increases with increasing hydrophobicity at the nitrogen side chain in the hydrophobic moiety. Furthermore, in the case of the same hydrophobic side chain, a decreasing hydrophilic/lipophilic balance leads to the formation of larger aggregates. The aggregates formed in the buffer are able to solubilize the hydrophobic model compounds Reichardt\\'s dye and pyrene, and exhibit versatile microenvironments. Final investigations about the cytotoxicity reveal that the block copolypeptoids are well tolerated by mammalian cells up to high concentrations.

  4. Hydrophobic Effect of Amphiphilic Derivatives of Chitosan on the Antifungal Activity against Aspergillus flavus and Aspergillus parasiticus

    Directory of Open Access Journals (Sweden)

    Vera Ap. de Oliveira Tiera


    Full Text Available Low molecular weight amphiphilic derivatives of chitosan were synthesized, characterized and their antifungal activities against Aspergillus flavus and Aspergillus parasiticus were tested. The derivatives were synthesized using as starting material a deacetylated chitosan sample in a two step process: the reaction with propyltrimethyl-ammonium bromide (Pr, followed by reductive amination with dodecyl aldehyde. Aiming to evaluate the effect of the hydrophobic modification of the derivatives on the antifungal activity against the pathogens, the degree of substitution (DS1 by Pr groups was kept constant and the proportion of dodecyl (Dod groups was varied from 7 to 29% (DS2. The derivatives were characterized by 1H-NMR and FTIR and their antifungal activities against the pathogens were tested by the radial growth of the colony and minimum inhibitory concentration (MIC methods. The derivatives substituted with only Pr groups exhibited modest inhibition against A. flavus and A. parasiticus, like that obtained with deacetylated chitosan. Results revealed that the amphiphilic derivatives grafted with Dod groups exhibited increasing inhibition indexes, depending on polymer concentration and hydrophobic content. At 0.6 g/L, all amphiphilic derivatives having from 7.0 to 29% of Dod groups completely inhibited fungal growth and the MIC values were found to decrease from 4.0 g/L for deacetylated chitosan to 0.25–0.50 g/L for the derivatives. These new derivatives open up the possibility of new applications and avenues to develop effective biofungicides based on chitosan.

  5. From superamphiphobic to amphiphilic polymeric surfaces with ordered hierarchical roughness fabricated with colloidal lithography and plasma nanotexturing. (United States)

    Ellinas, K; Tserepi, A; Gogolides, E


    Ordered, hierarchical (triple-scale), superhydrophobic, oleophobic, superoleophobic, and amphiphilic surfaces on poly(methyl methacrylate) PMMA polymer substrates are fabricated using polystyrene (PS) microparticle colloidal lithography, followed by oxygen plasma etching-nanotexturing (for amphiphilic surfaces) and optional subsequent fluorocarbon plasma deposition (for amphiphobic surfaces). The PS colloidal microparticles were assembled by spin-coating. After etching/nanotexturing, the PMMA plates are amphiphilic and exhibit hierarchical (triple-scale) roughness with microscale ordered columns, and dual-scale (hundred nano/ten nano meter) nanoscale texture on the particles (top of the column) and on the etched PMMA surface. The spacing, diameter, height, and reentrant profile of the microcolumns are controlled with the etching process. Following the design requirements for superamphiphobic surfaces, we demonstrate enhancement of both hydrophobicity and oleophobicity as a result of hierarchical (triple-scale) and re-entrant topography. After fluorocarbon film deposition, we demonstrate superhydrophobic surfaces (contact angle for water 168°, compared to 110° for a flat surface), as well as superoleophobic surfaces (153° for diiodomethane, compared to 80° for a flat surface).

  6. The effect of accuracy motivation on anchoring and adjustment: do people adjust from provided anchors? (United States)

    Simmons, Joseph P; LeBoeuf, Robyn A; Nelson, Leif D


    Increasing accuracy motivation (e.g., by providing monetary incentives for accuracy) often fails to increase adjustment away from provided anchors, a result that has led researchers to conclude that people do not effortfully adjust away from such anchors. We challenge this conclusion. First, we show that people are typically uncertain about which way to adjust from provided anchors and that this uncertainty often causes people to believe that they have initially adjusted too far away from such anchors (Studies 1a and 1b). Then, we show that although accuracy motivation fails to increase the gap between anchors and final estimates when people are uncertain about the direction of adjustment, accuracy motivation does increase anchor-estimate gaps when people are certain about the direction of adjustment, and that this is true regardless of whether the anchors are provided or self-generated (Studies 2, 3a, 3b, and 5). These results suggest that people do effortfully adjust away from provided anchors but that uncertainty about the direction of adjustment makes that adjustment harder to detect than previously assumed. This conclusion has important theoretical implications, suggesting that currently emphasized distinctions between anchor types (self-generated vs. provided) are not fundamental and that ostensibly competing theories of anchoring (selective accessibility and anchoring-and-adjustment) are complementary.

  7. Ringstone anchors from Gujarat, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Gaur, A.S.; Sundaresh; Tripati, S.; Bandodkar, S.N.

    of Dwarka and Somanath have yielded several ringstone anchors along with other stone anchors such as triangular and grapnel types. The raw material used for these ring stones comprises basalt, sandstone and limestone. Earlier, these anchors were identified...

  8. Structure of the Membrane Anchor of Pestivirus Glycoprotein Erns, a Long Tilted Amphipathic Helix (United States)

    Aberle, Daniel; Muhle-Goll, Claudia; Bürck, Jochen; Wolf, Moritz; Reißer, Sabine; Luy, Burkhard; Wenzel, Wolfgang; Ulrich, Anne S.; Meyers, Gregor


    Erns is an essential virion glycoprotein with RNase activity that suppresses host cellular innate immune responses upon being partially secreted from the infected cells. Its unusual C-terminus plays multiple roles, as the amphiphilic helix acts as a membrane anchor, as a signal peptidase cleavage site, and as a retention/secretion signal. We analyzed the structure and membrane binding properties of this sequence to gain a better understanding of the underlying mechanisms. CD spectroscopy in different setups, as well as Monte Carlo and molecular dynamics simulations confirmed the helical folding and showed that the helix is accommodated in the amphiphilic region of the lipid bilayer with a slight tilt rather than lying parallel to the surface. This model was confirmed by NMR analyses that also identified a central stretch of 15 residues within the helix that is fully shielded from the aqueous layer, which is C-terminally followed by a putative hairpin structure. These findings explain the strong membrane binding of the protein and provide clues to establishing the Erns membrane contact, processing and secretion. PMID:24586172

  9. J-Aggregates of Amphiphilic Cyanine Dyes for Dye-Sensitized Solar Cells: A Combination between Computational Chemistry and Experimental Device Physics

    Directory of Open Access Journals (Sweden)

    M. S. A. Abdel-Mottaleb


    Full Text Available We report on the design and structure principles of 5,5′-6,6′-tetrachloro-1,1′-dioctyl-3,3′-bis-(3-carboxypropyl-benzimidacarbocyanine (Dye 1. Such metal-free amphiphilic cyanine dyes have many applications in dye-sensitized solar cells. AFM surface topographic investigation of amphiphilic molecules of Dye 1 adsorbed on TiO2 anode reveals the ability of spontaneous self-organization into highly ordered aggregates of fiber-like structure. These aggregates are known to exhibit outstanding optical properties of J-aggregates, namely, efficient exciton coupling and fast exciton energy migration, which are essential for building up artificial light harvesting to the photovoltaic device. A light-to-electricity conversion efficiency of DSSC based on the metal free amphiphilic Dye 1 is η=3.75, which is about 50% of that based on metal-based N719 Ru-dye (Di-tetrabutylammoniumcis-bis(isothiocyanatobis(2,2′-bipyridyl-4,4′-dicarboxylatoruthenium(II. DFT and TD-DFT studies show that large intramolecular charge transfer takes place from the HOMO to LUMO. HOMO is localized on a part of the molecule with almost no contribution from the carboxylic moiety. This clearly indicates that the anchoring carboxylic group plays a minor role.

  10. Selection of Prebiotic Molecules in Amphiphilic Environments

    Directory of Open Access Journals (Sweden)

    Christian Mayer


    Full Text Available A basic problem in all postulated pathways of prebiotic chemistry is the low concentration which generally is expected for interesting reactants in fluid environments. Even though compounds, like nucleobases, sugars or peptides, principally may form spontaneously under environmental conditions, they will always be rapidly diluted in an aqueous environment. In addition, any such reaction leads to side products which often exceed the desired compound and generally hamper the first steps of a subsequent molecular evolution. Therefore, a mechanism of selection and accumulation of relevant prebiotic compounds seems to be crucial for molecular evolution. A very efficient environment for selection and accumulation can be found in the fluid continuum circulating in tectonic fault zones. Vesicles which form spontaneously at a depth of approximately 1 km present a selective trap for amphiphilic molecules, especially for peptides composed of hydrophilic and hydrophobic amino acids in a suitable sequence. The accumulation effect is shown in a numeric simulation on a simplified model. Further, possible mechanisms of a molecular evolution in vesicle membranes are discussed. Altogether, the proposed scenario can be seen as an ideal environment for constant, undisturbed molecular evolution in and on cell-like compartments.

  11. Repurposing Cationic Amphiphilic Antihistamines for Cancer Treatment

    Directory of Open Access Journals (Sweden)

    Anne-Marie Ellegaard


    Full Text Available Non-small cell lung cancer (NSCLC is one of the deadliest cancers worldwide. In search for new NSCLC treatment options, we screened a cationic amphiphilic drug (CAD library for cytotoxicity against NSCLC cells and identified several CAD antihistamines as inducers of lysosomal cell death. We then performed a cohort study on the effect of CAD antihistamine use on mortality of patients diagnosed with non-localized cancer in Denmark between 1995 and 2011. The use of the most commonly prescribed CAD antihistamine, loratadine, was associated with significantly reduced all-cause mortality among patients with non-localized NSCLC or any non-localized cancer when compared with use of non-CAD antihistamines and adjusted for potential confounders. Of the less frequently described CAD antihistamines, astemizole showed a similar significant association with reduced mortality as loratadine among patients with any non-localized cancer, and ebastine use showed a similar tendency. The association between CAD antihistamine use and reduced mortality was stronger among patients with records of concurrent chemotherapy than among those without such records. In line with this, sub-micromolar concentrations of loratadine, astemizole and ebastine sensitized NSCLC cells to chemotherapy and reverted multidrug resistance in NSCLC, breast and prostate cancer cells. Thus, CAD antihistamines may improve the efficacy of cancer chemotherapy.

  12. Salt Effect on the Cloud Point Phenomenon of Amphiphilic Drug-Hydroxypropylmethyl Cellulose System

    Directory of Open Access Journals (Sweden)

    Mohd. Sajid Ali


    Full Text Available Effect of two amphiphilic drugs (tricyclic antidepressant, nortriptyline hydrochloride (NORT, and nonsteroidal anti-inflammatory drug, sodium salt of ibuprofen (IBF on the cloud point of biopolymer hydroxypropylmethyl cellulose (HPMC was studied. Effect of NaCl was also seen on the CP of HPMC-drug system. CP of HPMC increases uniformly on increasing the (drug. Both drugs, though one being anionic (IBF and other cationic (NORT, affect the CP in almost the same manner but with different extent implying the role of hydrophobicity in the interaction between drug and polymer. Salt affects the CP of the drug in a dramatic way as low concentration of salt was only able to increase the value of the CP, though not affecting the pattern. However, in presence of high concentration of salts, minimum was observed on CP versus (drug plots. Various thermodynamic parameters were evaluated and discussed on the basis of the observed results.

  13. Azimuthal anchoring of a nematic liquid crystal on a grooved interface with anisotropic polar anchoring

    Institute of Scientific and Technical Information of China (English)

    Zhou Xuan; Zhang Zhi-Dong; Ye Wen-Jiang; Xuan Li


    Zhang Y Jet al.[Zhang Y J,Zhang Z D,Zhu L Z and Xuan L 2011 Liquid Cryst.38 355] investigated the effects of finite polar anchoring on the azimuthal anchoring energy at a grooved interface,in which polar anchoring was isotropic in the local tangent plane of the surface.In this paper,we investigate the effects of both isotropic and anisotropic polar anchoring on the surface anchoring energy in the frame of Fukuda et al.'s theory.The results show that anisotropic polar anchoring strengthens the azimuthal anchoring of grooved surfaces.In the one-elastic-constant approximation (K11 =K22 =K33 =K),the surface-groove-induced azimuthal anchoring energy is entirely consistent with the result of Faetti,and it reduces to the original result of Berreman with an increase in polar anchoring.Moreover,the contribution of the surface-like elastic term to the Rapini-Papoular anchoring energy is zero.

  14. Synthesis of Bioinspired Carbohydrate Amphiphiles that Promote and Inhibit Biofilms. (United States)

    Dane, Eric L; Ballok, Alicia E; O'Toole, George A; Grinstaff, Mark W


    The synthesis and characterization of a new class of bioinspired carbohydrate amphiphiles that modulate Pseudomonas aeruginosa biofilm formation are reported. The carbohydrate head is an enantiopure poly-amido-saccharide (PAS) prepared by a controlled anionic polymerization of β-lactam monomers derived from either glucose or galactose. The supramolecular assemblies formed by PAS amphiphiles are investigated in solution using fluorescence assays and dynamic light scattering. Dried samples are investigated using X-ray, infrared spectroscopy, and transmission electron microscopy. Additionally, the amphiphiles are evaluated for their ability to modulate biofilm formation by the Gram-negative bacterium Pseudomonas aeruginosa. Remarkably, from a library of eight amphiphiles, we identify a structure that promotes biofilm formation and two structures that inhibit biofilm formation. Using biological assays and electron microscopy, we relate the chemical structure of the amphiphiles to the observed activity. Materials that modulate the formation of biofilms by bacteria are important both as research tools for microbiologists to study the process of biofilm formation and for their potential to provide new drug candidates for treating biofilm-associated infections.

  15. Anchored nanostructure materials and method of fabrication (United States)

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei


    Anchored nanostructure materials and methods for their fabrication are described. The anchored nanostructure materials may utilize nano-catalysts that include powder-based or solid-based support materials. The support material may comprise metal, such as NiAl, ceramic, a cermet, or silicon or other metalloid. Typically, nanoparticles are disposed adjacent a surface of the support material. Nanostructures may be formed as anchored to nanoparticles that are adjacent the surface of the support material by heating the nano-catalysts and then exposing the nano-catalysts to an organic vapor. The nanostructures are typically single wall or multi-wall carbon nanotubes.

  16. Redox-controllable amphiphilic [2]rotaxanes. (United States)

    Tseng, Hsian-Rong; Vignon, Scott A; Celestre, Paul C; Perkins, Julie; Jeppesen, Jan O; Di Fabio, Alberto; Ballardini, Roberto; Gandolfi, M Teresa; Venturi, Margherita; Balzani, Vincenzo; Stoddart, J Fraser


    With the fabrication of molecular electronic devices (MEDs) and the construction of nanoelectromechanical systems (NEMSs) as incentives, two constitutionally isomeric, redox-controllable [2]rotaxanes have been synthesized and characterized in solution. Therein, they both behave as near-perfect molecular switches, that is, to all intents and purposes, these two rotaxanes can be switched precisely by applying appropriate redox stimuli between two distinct chemomechanical states. Their dumbbell-shaped components are composed of polyether chains interrupted along their lengths by i) two pi-electron rich recognition sites-a tetrathiafulvalene (TTF) unit and a 1,5-dioxynaphthalene (DNP) moiety-with ii) a rigid terphenylene spacer placed between the two recognition sites, and then terminated by iii) a hydrophobic tetraarylmethane stopper at one end and a hydrophilic dendritic stopper at the other end of the dumbbells, thus conferring amphiphilicity upon these molecules. A template-directed protocol produces a means to introduce the tetracationic cyclophane, cyclobis(paraquat-p-phenylene) (CBPQT(4+)), which contains two pi-electron accepting bipyridinium units, mechanically interlocked around the dumbbell-shaped components. Both the TTF unit and the DNP moiety are potential stations for CBPQT(4+), since they can establish charge-transfer and hydrogen bonding interactions with the bipyridinium units of the cyclophane, thereby introducing bistability into the [2]rotaxanes. In both constitutional isomers, (1)H NMR and absorption spectroscopies, together with electrochemical investigations, reveal that the CBPQT(4+) ring is predominantly located on the TTF unit, leading to the existence of a single translational isomer (co-conformation) in both cases. In addition, a model [2]rotaxane, incorporating hydrophobic tetraarylmethane stoppers at both ends of its dumbbell-shaped component, has also been synthesized as a point of reference. Molecular synthetic approaches were used to

  17. Rheological and phase behaviour of amphiphilic lipids

    Directory of Open Access Journals (Sweden)

    Alfaro, M. C.


    Full Text Available This chapter reviews the different association structures which are likely to be formed by amphiphilic lipids in the liquid-crystalline state and their corresponding shear flow properties. The structure and rheological behaviour of thermotropic liquid crystals, emphasizing the properties of smectic mesophases, and those of lyotropic liquid crystals such as: nematic, lamellar, diluted lamellar, lamellar dispersions, hexagonal and cubic mesophases are described. The importance of a comprehensive rheological characterisation, including rheo-optical techniques, is pointed out for their practical applications, development of formulations and as a useful technique to assist in the determination of phase diagrams. A historical approach has been used to discuss the evolving field of the rheology and structure identification of liquid crystals formed by amphiphilic lipids and surfactants. Non-Newtonian viscous shear flow, thixotropic and antithixotropic phenomena, linear viscoelastic properties -described by dynamic and creep compliance experiments- and non-linear viscoelastic properties - described by the difference of normal stresses and stress relaxation tests are interpreted on the basis of a microstructure-rheology relationship. The polycrystalline nature of liquid crystals turns out to be rather sensitive to shear due to the change of both size and orientation of the liquid-crystalline monodomains under flow.En este capítulo se realiza una revisión de las distintas estructuras coloidales de asociación que pueden formar los lípidos anfifílicos en estado líquido-cristalino y de sus correspondientes propiedades de flujo en cizalla. Se describe la estructura y comportamiento reológico de cristales líquidos termotrópicos, con énfasis en los de tipo esméctico, fases gel, y cristales líquidos liotrópicos: nemáticos, laminares, laminares diluidos, dispersiones de laminares, hexagonales y cúbicos. Se hace hincapié en la importancia de una

  18. A New Class of Amphiphiles Bearing Rigid Hydrophobic Groups for Solubilization and Stabilization of Membrane Proteins

    DEFF Research Database (Denmark)

    Chae, Pil Seok; Rasmussen, Søren G F; Rana, Rohini R;


    Non-traditional amphiphiles: Conferring aqueous solubility on membrane proteins generally requires the use of a detergent or other amphiphilic agent. A new class of amphiphiles was synthesized, based on steroidal lipophilic groups, and evaluated with several membrane proteins. The results show th...

  19. Competitive Binding of Natural Amphiphiles with Graphene Derivatives (United States)

    Radic, Slaven; Geitner, Nicholas K.; Podila, Ramakrishna; Käkinen, Aleksandr; Chen, Pengyu; Ke, Pu Chun; Ding, Feng


    Understanding the transformation of graphene derivatives by natural amphiphiles is essential for elucidating the biological and environmental implications of this emerging class of engineered nanomaterials. Using rapid discrete-molecular-dynamics simulations, we examined the binding of graphene and graphene oxide with peptides, fatty acids, and cellulose, and complemented our simulations by experimental studies of Raman spectroscopy, FTIR, and UV-Vis spectrophotometry. Specifically, we established a connection between the differential binding and the conformational flexibility, molecular geometry, and hydrocarbon content of the amphiphiles. Importantly, our dynamics simulations revealed a Vroman-like competitive binding of the amphiphiles for the graphene oxide substrate. This study provides a mechanistic basis for addressing the transformation, evolution, transport, biocompatibility, and toxicity of graphene derivatives in living systems and the natural environment.

  20. Magnetic Amphiphilic Composites Applied for the Treatment of Biodiesel Wastewaters

    Directory of Open Access Journals (Sweden)

    Bruno R. S. Lemos


    Full Text Available In this work, new magnetic amphiphilic composites were prepared by chemical vapor deposition with ethanol on the surface of hydrophilic natural chrysotile matrix containing Fe catalyst. XRD, Raman, Mössbauer and SEM analyses suggest the formation of a complex nanostructured material composed of hydrophobic carbon nanotubes/nanofibers grown on the hydrophilic surface of the MgSi fiber mineral and the presence of Fe metallic nanoparticles coated by carbon. These nanostructured particles show amphiphilic properties and interact very well with both oil and aqueous phases. When added to emulsions the amphiphilic particles locate on the oil/water interface and, under a magnetic field, the oil droplets collapsed leading to the separation of the aqueous and oil phases. Preliminary work showed excellent results on the use of these particles to break wastewater emulsions in the biodiesel process.

  1. Starting point anchoring effects in choice experiments

    DEFF Research Database (Denmark)

    Ladenburg, Jacob; Olsen, Søren Bøye

    of preferences in Choice Experiments resembles the Dichotomous Choice format, there is reason to suspect that Choice Experiments are equally vulnerable to anchoring bias. Employing different sets of price levels in a so-called Instruction Choice Set presented prior to the actual choice sets, the present study......Anchoring is acknowledged as a potential source of considerable bias in Dichotomous Choice Contingent Valuation studies. Recently, another stated preference method known as Choice Experiments has gained in popularity as well as the number of applied studies. However, as the elicitation...... finds that preferences elicited by Choice Experiments can be subject to starting point anchoring bias. Different price levels provoked significantly different distributions of choice in two otherwise identical choice set designs. On a more specific level, the results indicate that the anchoring...

  2. Starting point anchoring effects in choice experiments

    DEFF Research Database (Denmark)

    Ladenburg, Jacob; Olsen, Søren Bøye

    Anchoring is acknowledged as a potential source of considerable bias in Dichotomous Choice Contingent Valuation studies. Recently, another stated preference method known as Choice Experiments has gained in popularity as well as the number of applied studies. However, as the elicitation...... of preferences in Choice Experiments resembles the Dichotomous Choice format, there is reason to suspect that Choice Experiments are equally vulnerable to anchoring bias. Employing different sets of price levels in a so-called Instruction Choice Set presented prior to the actual choice sets, the present study...... finds that preferences elicited by Choice Experiments can be subject to starting point anchoring bias. Different price levels provoked significantly different distributions of choice in two otherwise identical choice set designs. On a more specific level, the results indicate that the anchoring...

  3. Surface functionalization of carbon nanotubes by direct encapsulation with varying dosages of amphiphilic block copolymers (United States)

    Yao, Xueping; Li, Jie; Kong, Liang; Wang, Yong


    Encapsulation of carbon nanotubes (CNTs) by amphiphilic block copolymers is an efficient way to stabilize CNTs in solvents. However, the appropriate dosages of copolymers and the assembled structures are difficult to predict and control because of the insufficient understanding on the encapsulation process. We encapsulate multiwalled CNTs with polystyrene-block-poly (4-vinyl pyridine) (PS-b-P4VP) by directly mixing them in acetic acid under sonication. The copolymer forms a lamellar structure along the surface of CNTs with the PS blocks anchoring on the tube wall and the P4VP blocks exposed to the outside. The encapsulated CNTs achieve good dispersibility in polar solvents over long periods. To increase our understanding of the encapsulation process we investigate the assembled structures and stability of copolymer/CNTs mixtures with changing mass ratios. Stable dispersions are obtained at high mass ratios between the copolymer and CNTs, i.e. 2 or 3, with the presence of free spherical micelles. Transmission electron microscopy and thermal gravimetric analysis determine that the threshold for the complete coverage of CNTs by the copolymer occurs at the mass ratio of 1.5. The coated copolymer layer activates the surface of CNTs, enabling further functionalization of CNTs. For instance, atomic layer deposition of TiO2 produces conformal thin layers on the encapsulated CNTs while isolated TiO2 bumps are produced on the pristine, inert CNTs.

  4. A heterostructure composed of conjugated polymer and copper sulfide nanoparticles. (United States)

    Narizzano, Riccardo; Erokhin, Victor; Nicolini, Claudio


    A heterostructure formed by a conjugated polymer and semiconducting nanoparticles was produced. The conjugated polymer was synthesized by oxidative copolymerization of 3-thiopheneacetic acid and 3-hexylthiophene, thus obtaining an amphiphilic polythiophene that allows the formation of a stable polymer layer at the air-water interface. Different numbers of monolayers were deposited on solid substrates. CuS nanoparticles were grown directly in the polymeric matrix using the carboxylic groups as nucleation centers. The reactions were monitored by quartz crystal microbalance, Brewster angle, and fluorescence microscopy. The heterostructure showed increased conductivity as compared to the pristine polymer.

  5. The Use of Comics-Based Cases in Anchored Instruction (United States)

    Kneller, Matthew F.


    The primary purpose of this research was to understand how comics fulfill the role of anchor in an anchored instruction learning environment. Anchored instruction addresses the inert knowledge problem through the use of realistic multimedia stories, or "anchors," that embed a problem and the necessary data to solve it within the narrative. In the…

  6. Anchoring FRP Composite Armor in Flexible Offshore Riser Systems

    DEFF Research Database (Denmark)

    Costache, Andrei

    capabilities.The structure of flexible pipes consists of several concentric layers, each with a specific purpose. The most common used flexible pipe is the type III, which contains a central component, made from an interlocking stainless steel structure that provides collapse strength. The central component...... armor layer is made from steel. However, as oil exploitation goes to deeper and deeper waters, the strength/weight ratio of steel armor become sunfavorable. In order to achieve higher tensile strength and to reduce the overall weight of the pipe, in the future, the tensile armor must be made...... of composite materials. One of the problems related to the substitution of tensile steel members is that anchoring in the metallic end fittings of the pipe is very challenging.The purpose of this thesis is to ensure the transfer of tensile loads between a unidirectional fiber reinforced polymer and a metallic...

  7. Synthesis and Characterization of Biodegradable Amphiphilic Star and Y-Shaped Block Copolymers as Potential Carriers for Vinorelbine

    Directory of Open Access Journals (Sweden)

    Fatemeh Bahadori


    Full Text Available Two amphiphilic block copolymers using hydrophobic poly(ε-caprolactone (PCL and hydrophilic poly(ethylene glycol (PEG were successfully synthesized. One of them is an (A-b-B4 type star polymer [(PCL-b-PEG4] and the other one is a Y-shaped PEG–(PCL2. A star-shaped polymer (PCL-b-PEG4 was prepared by ring-opening polymerization (ROP of ε-caprolactone continued by click reaction of (PCL-azide4 and PEG-alkyne. The synthesis of Y-shaped PEG–(PCL2 block copolymer was carried out via Diels-Alder click reaction of a furan protected maleimide end-functionalized PEG (PEG-MI with an anthracene end-functionalized PCL following the ROP of ε-caprolactone. The characterization of micelles is carried out using both materials in aqueous media as drug delivery vehicles, which showed satisfying results and enhanced the cytotoxic effect of the anti-cancer drug vinorelbine (VLB. However, micelles consisted of Y-shaped unimers were found to be more convenient for delivery of hydrophobic drugs such as VLB because they formed in lower concentration, carrying a higher amount of drugs and owing a monomodal distribution. We concluded that the free tails of hydrophobic chains in Y-shaped block copolymer facilitate the assembly of amphiphilic material in water to form micelles.

  8. Pd loaded amphiphilic COF as catalyst for multi-fold Heck reactions, C-C couplings and CO oxidation. (United States)

    Mullangi, Dinesh; Nandi, Shyamapada; Shalini, Sorout; Sreedhala, Sheshadri; Vinod, Chathakudath P; Vaidhyanathan, Ramanathan


    COFs represent a class of polymers with designable crystalline structures capable of interacting with active metal nanoparticles to form excellent heterogeneous catalysts. Many valuable ligands/monomers employed in making coordination/organic polymers are prepared via Heck and C-C couplings. Here, we report an amphiphilic triazine COF and the facile single-step loading of Pd(0) nanoparticles into it. An 18-20% nano-Pd loading gives highly active composite working in open air at low concentrations (Conc. Pd(0) couplings and C-C couplings using 'non-boronic acid' substrates, and exhibits good recyclability with no sign of catalyst leaching. As an oxidation catalyst, it shows 100% conversion of CO to CO2 at 150 °C with no loss of activity with time and between cycles. Both vapor sorptions and contact angle measurements confirm the amphiphilic character of the COF. DFT-TB studies showed the presence of Pd-triazine and Pd-Schiff bond interactions as being favorable.

  9. Anchors as Semantic Primes in Value Construction: An EEG Study of the Anchoring Effect. (United States)

    Ma, Qingguo; Li, Diandian; Shen, Qiang; Qiu, Wenwei


    Previous research regarding anchoring effects has demonstrated that human judgments are often assimilated to irrelevant information. Studies have demonstrated that anchors influence the economic valuation of various products and experiences; however, the cognitive explanations of this effect remain controversial, and its neural mechanisms have rarely been explored. In the current study, we conducted an electroencephalography (EEG) experiment to investigate the anchoring effect on willingness to accept (WTA) for an aversive hedonic experience and the role of anchors in this judgment heuristic. The behavioral results demonstrated that random numbers affect participants' WTA for listening to pieces of noise. The participants asked for higher pay after comparing their WTA with higher numbers. The EEG results indicated that anchors also influenced the neural underpinnings of the valuation process. Specifically, when a higher anchor number was drawn, larger P2 and late positive potential amplitudes were elicited, reflecting the anticipation of more intensive pain from the subsequent noise. Moreover, higher anchors induced a stronger theta band power increase compared with lower anchors when subjects listened to the noises, indicating that the participants felt more unpleasant during the actual experience of the noise. The levels of unpleasantness during both anticipation and experience were consistent with the semantic information implied by the anchors. Therefore, these data suggest that a semantic priming process underlies the anchoring effect in WTA. This study provides proof for the robustness of the anchoring effect and neural evidence of the semantic priming model. Our findings indicate that activated contextual information, even seemingly irrelevant, can be embedded in the construction of economic value in the brain.

  10. Anchors as Semantic Primes in Value Construction: An EEG Study of the Anchoring Effect.

    Directory of Open Access Journals (Sweden)

    Qingguo Ma

    Full Text Available Previous research regarding anchoring effects has demonstrated that human judgments are often assimilated to irrelevant information. Studies have demonstrated that anchors influence the economic valuation of various products and experiences; however, the cognitive explanations of this effect remain controversial, and its neural mechanisms have rarely been explored. In the current study, we conducted an electroencephalography (EEG experiment to investigate the anchoring effect on willingness to accept (WTA for an aversive hedonic experience and the role of anchors in this judgment heuristic. The behavioral results demonstrated that random numbers affect participants' WTA for listening to pieces of noise. The participants asked for higher pay after comparing their WTA with higher numbers. The EEG results indicated that anchors also influenced the neural underpinnings of the valuation process. Specifically, when a higher anchor number was drawn, larger P2 and late positive potential amplitudes were elicited, reflecting the anticipation of more intensive pain from the subsequent noise. Moreover, higher anchors induced a stronger theta band power increase compared with lower anchors when subjects listened to the noises, indicating that the participants felt more unpleasant during the actual experience of the noise. The levels of unpleasantness during both anticipation and experience were consistent with the semantic information implied by the anchors. Therefore, these data suggest that a semantic priming process underlies the anchoring effect in WTA. This study provides proof for the robustness of the anchoring effect and neural evidence of the semantic priming model. Our findings indicate that activated contextual information, even seemingly irrelevant, can be embedded in the construction of economic value in the brain.

  11. Amphiphilic copolymers for fouling-release coatings

    DEFF Research Database (Denmark)

    Noguer, Albert Camós; Olsen, Stefan Møller; Hvilsted, Søren

    Polydimethylsiloxane (PDMS) resins are extensively used as binder in fouling-release coatings due to the low critical surface energy and low elastic modulus of PDMS. These properties result in poor adhesion of the fouling organisms, which are therefore detached by hydrodynamic forces during...... navigation [1,2,3]. Other compounds are usually mixed together with the binder (e.g. silica and pigments) in order to improve the mechanical, thixotropic and visual properties of the coatings. It has ben shown, however, that these ingredients have a negative effect on the fouling-release properties...... of the coatings [1,2,4]. Together with the PDMS-system, non-reactive polymers have been used to improve the fouling-release properties of the coatings. Initially, hydrophobic siloxane-based polymers were used, which aimed to increase the hydrophobicity of the PDMS surface [5,6]. However, copolymers comprising...

  12. Amphiphilic diblock copolymers for molecular recognition


    Nehring, Rainer


    In this thesis, the synthesis and the characterization of poly(butadiene)-blockpoly( ethylene oxide) copolymers with terminal Me2+-NTA groups (copper or nickel) is described for the first time. A convenient “one-pot” procedure that allows control over the individual block lengths of the copolymer and the end-group functionalization was successfully established. The formation of the metal-polymer complex has been confirmed by EPR and UV/VIS spectroscopy. Mixing of the Ni2+-NT...

  13. Drug release from hydrazone-containing peptide amphiphiles

    Energy Technology Data Exchange (ETDEWEB)

    Matson, John B.; Stupp, Samuel I. (NWU)


    Hydrolytically-labile hydrazones in peptide amphiphiles were studied as degradable tethers for release of the drug nabumetone from nanofiber gels. On-resin addition of the novel compound tri-Boc-hydrazido adipic acid to a lysine E-amine allowed for precise placement of a hydrazide in a peptide sequence.

  14. Nucleic acid amphiphiles : synthesis and self-assembled nanostructures

    NARCIS (Netherlands)

    Kwak, Minseok; Herrmann, Andreas; Clever, Guido; Mao, Chengde; Shionoya, Mitsuhiko; Stulz, Eugen


    This review provides an overview of a relatively new class of bio-conjugates, DNA amphiphiles, which consist of oligonucleotides covalently bonded to synthetic hydrophobic units. The reader will find the basic principles for the structural design and preparation methods of the materials. Moreover, t

  15. Hydrophobicity and thermodynamic response for aqueous solutions of amphiphiles (United States)

    Zemánková, Katerina; Troncoso, Jacobo; Cerdeiriña, Claudio A.; Romaní, Luis; Anisimov, Mikhail A.


    The anomalous behavior of aqueous solutions of amphiphiles in the water-rich region is analyzed via a phenomenological approach that utilizes the isobaric heat capacity Cp as an experimental probe. We report extensive data for solutions of 14 amphiphiles as a function of temperature at atmospheric pressure. Beyond that, Cp data but also isobaric thermal expansivities and isothermal compressibilities for three solutions of tert-butanol as a function of both temperature and pressure are presented. Results rule out the possibility that the observed phenomenology is associated with the anomalous thermodynamics of pure water. Indeed, our Cp data, quantitatively consistent with recent spectroscopic analyses, suggest that water-mediated interactions between the nonpolar parts of amphiphiles are at the origin of anomalies, with the effects of such "hydrophobic aggregation" being observed at mole fractions as small as 0.01. Physicochemical details like the size, the electronic charge distribution and the geometry of amphiphile molecules as well as third-order derivatives of the Gibbs energy and the associated Koga lines support the above claims while they further contribute to characterizing the role of hydrophobicity in these phenomena. Progress with a view to gain a deeper, more concrete understanding remains.

  16. Reinforcement of latex rubber by the incorporation of amphiphilic nanoparticles (United States)

    Latex rubbers are fabricated from latex suspensions. During the fabrication process, latex particles are bound together while water is removed from the suspension. This report shows the mechanical properties of latex rubbers can be improved by incorporating a small amount of amphiphilic nanoparticle...

  17. Loading of Vesicles into Soft Amphiphilic Nanotubes using Osmosis

    NARCIS (Netherlands)

    Erne, Petra M.; van Bezouwen, Laura S.; Stacko, Peter; van Dtjken, Derk Jan; Chen, Jiawen; Stuart, Marc C. A.; Boekema, Eghert J.; Feringa, Ben L.


    The facile assembly of higher-order nanoarchitectures from simple building blocks is demonstrated by the loading of vesicles into soft amphiphilic nanotubes using osmosis. The nanotubes are constructed from rigid interdigitated bilayers which are capped with vesicles comprising phospholipid-based fl

  18. Peptide amphiphiles and their use in supramolecular chemistry

    NARCIS (Netherlands)

    Versluis, Frank


    In this thesis the behavior and functionality of peptide amphiphiles at the surface of bilayer vesicles is examined. By controlling the behavior of the surface bound peptides, I was able to construct assemblies which could: 1) release their content (triggered by pH), 2) fuse in a targeted and contro

  19. Bio-based amphiphilic materials development and applications (United States)

    Farm-based raw materials are increasingly used in the development of amphiphilic materials that have potential applications in the production of a variety of consumer and industrial products, including lubricants. Raw materials of interest include: starches, proteins, fats, oils, and sugars. These ...

  20. Preparation and self-folding of amphiphilic DNA origami. (United States)

    Zhou, Chao; Wang, Dianming; Dong, Yuanchen; Xin, Ling; Sun, Yawei; Yang, Zhongqiang; Liu, Dongsheng


    Amphiphilic DNA origami is prepared by dressing multiple hydrophobic molecules on a rectangular single layer DNA origami, which is then folded or coupled in sandwich-like structures with two outer DNA origami layer and one inner hydrophobic molecules layer. The preference to form different kinds of structures could be tailored by rational design of DNA origami.

  1. Amphiphiles containing aromatic groups in the hydrophobic part

    NARCIS (Netherlands)

    Visscher, Inge


    Aggregation processes are essential for life on this planet. For example, the membranes of all living cells are bilayered aggregates, consisting of lipid molecules, proteins and steroids. In many biological processes, aggregates play a role. The main driving force for aggregation of amphiphiles is h

  2. Cationic amphiphiles as delivery system for genes into eukaryotic cells

    NARCIS (Netherlands)

    Oberle, Volker; Zuhorn, Inge S.; Audouy, Sandrine; Bakowsky, Udo; Smisterová, Jarmila; Engberts, Jan B.F.N.; Hoekstra, Dick; Gregoriadis, G; McCormack, B


    Cationic liposomes, consisting of synthetic amphiphiles and a so-called helper lipid, rapidly form complexes with DNA, known as lipoplexes. When incubated with cells in culture, the DNA can be delivered into the cell and becomes expressed. Because of these properties, lipoplexes are considered a use

  3. Synthesis and characterization of polymer layers for control of fluid transport (United States)

    Vatansever, Fehime

    The level of wetting of fiber surface with liquids is an important characteristic of fibrous materials. It is related to fiber surface energy and the structure of the material. Surface energy can be changed by surface modification via the grafting methodologies that have been reported for introducing new and stable functionality to fibrous substrates without changing bulk properties. Present work is dedicated to synthesis and characterization of macromolecular layers grafted to fiber surface in order to achieve directional liquid transport for the modified fabric. Modification technique used here is based on formation of stable polymer layer on fabric surface using "grafting to" technique. Specifically, modification of fabric with wettability gradient for facilitated one way-liquid transport, and pointed modification of yarn-based channels on textile microfluidic device for directional liquid transport are reported here. First, fabric was activated with alkali (NaOH) solution. Second, poly (glycidyl methacrylate) (PGMA) was deposited on fabric as an anchoring layer. Finally, polymers of interest were grafted to surface through the epoxy functionality of PGMA. Effect of polymer grafting on the wicking property of the fabric has been evaluated by vertical wicking technique at the each step of surface modification. The results shows that wicking performance of fabric can be altered by grafting of a thin nanoscale polymeric film. For the facilitated liquid transport, the gradient polymer coating was created using "grafting to" technique and its dependence on the grafting temperature. Wettability gradient from hydrophilic to hydrophobic (change in water contact angle from 0 to 140 degrees on fabric) was achieved by grafting of polystyrene (PS) and polyacrylic acid (PAA) sequentially with concentration gradient. This study proposes that fabric with wettability gradient property can be used to transfer sweat from skin and support moisture management when it is used in a

  4. Self-assembly of fibronectin mimetic peptide-amphiphile nanofibers (United States)

    Rexeisen, Emilie Lynn

    Many therapeutic strategies incorporate peptides into their designs to mimic the natural protein ligands found in vivo. A few examples are the short peptide sequences RGD and PHSRN that mimic the primary and synergy-binding domains of the extracellular matrix protein, fibronectin, which is recognized by the cell surface receptor, alpha5beta 1 integrin. Even though scaffold modification with biomimetic peptides remains one of the most promising approaches for tissue engineering, the use of these peptides in therapeutic tissue-engineered products and drug delivery systems available on the commercial market is limited because the peptides are not easily able to mimic the natural protein. The design of a peptide that can effectively target the alpha5beta1 integrin would greatly increase biomimetic scaffold therapeutic potential. A novel peptide containing both the RGD primary binding domain and PHSRN synergy-binding domain for fibronectin joined with the appropriate linker should bind alpha 5beta1 integrin more efficiently and lead to greater cell adhesion over RGD alone. Several fibronectin mimetic peptides were designed and coupled to dialkyl hydrocarbon tails to make peptide-amphiphiles. The peptides contained different linkers connecting the two binding domains and different spacers separating the hydrophobic tails from the hydrophilic headgroups. The peptide-amphiphiles were deposited on mica substrates using the Langmuir-Blodgett technique. Langmuir isotherms indicated that the peptide-amphiphiles that contained higher numbers of serine residues formed a more tightly packed monolayer, but the increased number of serines also made transferring the amphiphiles to the mica substrate more difficult. Atomic force microscopy (AFM) images of the bilayers showed that the headgroups might be bent, forming small divots in the surface. These divots may help expose the PHSRN synergy-binding domain. Parallel studies undertaken by fellow group members showed that human

  5. In vitro evaluation of anticancer nanomedicines based on doxorubicin and amphiphilic Y-shaped copolymers

    Directory of Open Access Journals (Sweden)

    Li D


    Full Text Available Di Li,1,2,* Jian Xun Ding,1,3,* Zhao Hui Tang,1 Hai Sun,1 Xiu Li Zhuang,1 Jing Zhe Xu,2 Xue Si Chen1 1Key Laboratory of Polymer Ecomaterials, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 2Department of Chemistry, Yanbian University, Yanji, 3Graduate University of Chinese Academy of Sciences, Beijing, China *These authors contributed equally to this workAbstract: Four monomethoxy poly(ethylene glycol-poly(L-lactide-co-glycolide2 (mPEG-P(LA-co-GA2 copolymers were synthesized by ring-opening polymerization of L-lactide and glycolide with double hydroxyl functionalized mPEG (mPEG-(OH2 as macroinitiator and stannous octoate as catalyst. The copolymers self-assembled into nanoscale micellar/vesicular aggregations in phosphate buffer at pH 7.4. Doxorubicin (DOX, an anthracycline anticancer drug, was loaded into the micellar/vesicular nanoparticles, yielding micellar/vesicular nanomedicines. The in vitro release behaviors could be adjusted by content of hydrophobic polyester and pH of the release medium. In vitro cell experiments showed that the intracellular DOX release could be adjusted by content of P(LA-co-GA, and the nanomedicines displayed effective proliferation inhibition against Henrietta Lacks’s cells with different culture times. Hemolysis tests indicated that the copolymers were hemocompatible, and the presence of copolymers could reduce the hemolysis ratio of DOX significantly. These results suggested that the novel anticancer nanomedicines based on DOX and amphiphilic Y-shaped copolymers were attractive candidates as tumor tissular and intracellular targeting drug delivery systems in vivo, with enhanced stability during circulation and accelerated drug release at the target sites.Keywords: amphiphilic Y-shaped copolymer, anticancer nanomedicine, cellular proliferation inhibition, doxorubicin

  6. Synthesis and characterization of an elastin-mimetic amphiphilic block copolymer protein (United States)

    Lee, Terrence Anita-Talley


    The overall goal in material science is to be able to control the molecular architecture of a material and thus its end properties. There is no method that offers greater control than the biological synthesis of proteins. From the DNA sequence to the final synthesized protein, the entire process is finitely controlled. This present work describes methods developed and used to synthesize protein polymers by manipulating this process. From the initial DNA sequence chosen, the end properties that the protein polymer will have are dictated. An amphiphilic diblock copolymer was designed based on environmentally responsive elastin-mimetic peptide sequences [(Val/Ile)-Pro-Gly-Xaa-Gly] (Xaa = Ala or Glu for the hydrophilic block, Val or Phe for the hydrophobic block) and synthesized using a genetic engineering approach. Differential scanning calorimetry measurements in aqueous solution revealed that reversible hydrophobic folding and assembly of the copolymer occurs above the inverse temperature transition, Tt, of the hydrophobic block. This process results in the formation of 50 nm protein-based micellar aggregates, which were characterized by electron microscopy and temperature-dependent dynamic light scattering techniques. The distribution of micellar aggregates can be altered reproducibly through variation of environmental conditions including pH and temperature. The uniform and defined macromolecular architecture of this protein copolymer permits greater control over the physical properties of the micelles, which therefore may facilitate applications in controlled release of small molecules.

  7. Self-Assembly of Amphiphilic Block Copolypeptoids – Micelles, Worms and Polymersomes (United States)

    Fetsch, Corinna; Gaitzsch, Jens; Messager, Lea; Battaglia, Giuseppe; Luxenhofer, Robert


    Polypeptoids are an old but recently rediscovered polymer class with interesting synthetic, physico-chemical and biological characteristics. Here, we introduce new aromatic monomers, N-benzyl glycine N-carboxyanhydride and N-phenethyl glycine N-carboxyanhydride and their block copolymers with the hydrophilic polysarcosine. We compare their self-assembly in water and aqueous buffer with the self-assembly of amphiphilic block copolypeptoids with aliphatic side chains. The aggregates in water were investigated by dynamic light scattering and electron microscopy. We found a variety of morphologies, which were influenced by the polymer structure as well as by the preparation method. Overall, we found polymersomes, worm-like micelles and oligo-lamellar morphologies as well as some less defined aggregates of interconnected worms and vesicles. Such, this contribution may serve as a starting point for a more detailed investigation of the self-assembly behavior of the rich class of polypeptoids and for a better understanding between the differences in the aggregation behavior of non-uniform polypeptoids and uniform peptoids. PMID:27666081

  8. Biomedical applications of glycosylphosphatidylinositol-anchored proteins (United States)

    Heider, Susanne; Dangerfield, John A.


    Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) use a unique posttranslational modification to link proteins to lipid bilayer membranes. The anchoring structure consists of both a lipid and carbohydrate portion and is highly conserved in eukaryotic organisms regarding its basic characteristics, yet highly variable in its molecular details. The strong membrane targeting property has made the anchors an interesting tool for biotechnological modification of lipid membrane-covered entities from cells through extracellular vesicles to enveloped virus particles. In this review, we will take a closer look at the mechanisms and fields of application for GPI-APs in lipid bilayer membrane engineering and discuss their advantages and disadvantages for biomedicine. PMID:27542385

  9. Cationic Antimicrobial Polymers and Their Assemblies

    Directory of Open Access Journals (Sweden)

    Ana Maria Carmona-Ribeiro


    Full Text Available Cationic compounds are promising candidates for development of antimicrobial agents. Positive charges attached to surfaces, particles, polymers, peptides or bilayers have been used as antimicrobial agents by themselves or in sophisticated formulations. The main positively charged moieties in these natural or synthetic structures are quaternary ammonium groups, resulting in quaternary ammonium compounds (QACs. The advantage of amphiphilic cationic polymers when compared to small amphiphilic molecules is their enhanced microbicidal activity. Besides, many of these polymeric structures also show low toxicity to human cells; a major requirement for biomedical applications. Determination of the specific elements in polymers, which affect their antimicrobial activity, has been previously difficult due to broad molecular weight distributions and random sequences characteristic of radical polymerization. With the advances in polymerization control, selection of well defined polymers and structures are allowing greater insight into their structure-antimicrobial activity relationship. On the other hand, antimicrobial polymers grafted or self-assembled to inert or non inert vehicles can yield hybrid antimicrobial nanostructures or films, which can act as antimicrobials by themselves or deliver bioactive molecules for a variety of applications, such as wound dressing, photodynamic antimicrobial therapy, food packing and preservation and antifouling applications.

  10. Lash Transported Anchor for a Tanker Mooring. (United States)


    including additional model tests, is needed. The anchor configurations presented in Figures llb and llc will function adequately for the ATTF on all...causeways at sea) and offshore oil companies (mating jacket type structures at sea). 4. A suitable anchor for rock would be twice as heavy (4,000 kips) as the...NIARINF FNVIRON. LAW .. IIAIVl’RN): Seattle "A (E. ianger): Sceittle. %%A.’ Itransportation, ( oust rUCtIo & CO1m IN %IR(.IN IA INST. OF- MARINE SOI

  11. Spin-Casting Polymer Brush Films for Stimuli-Responsive and Anti-Fouling Surfaces. (United States)

    Xu, Binbin; Feng, Chun; Hu, Jianhua; Shi, Ping; Gu, Guangxin; Wang, Lei; Huang, Xiaoyu


    Surfaces modified with amphiphilic polymers can dynamically alter their physicochemical properties in response to changes of their environmental conditions; meanwhile, amphiphilic polymer coatings with molecular hydrophilic and hydrophobic patches, which can mitigate biofouling effectively, are being actively explored as advanced coatings for antifouling materials. Herein, a series of well-defined amphiphilic asymmetric polymer brushes containing hetero side chains, hydrophobic polystyrene (PS) and hydrophilic poly(ethylene glycol) (PEG), was employed to prepare uniform thin films by spin-casting. The properties of these films were investigated by water contact angle, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and quartz crystal microbalance (QCM). AFM showed smooth surfaces for all films with the roughness less than 2 nm. The changes in water contact angle and C/O ratio (XPS) evidenced the enrichment of PEG or PS chains at film surface after exposed to selective solvents, indicative of stimuli- responsiveness. The adsorption of proteins on PEG functionalized surface was quantified by QCM and the results verified that amphiphilic polymer brush films bearing PEG chains could lower or eliminate protein-material interactions and resist to protein adsorption. Cell adhesion experiments were performed by using HaCaT cells and it was found that polymer brush films possess good antifouling ability.

  12. Periodically Grafted Amphiphilic Copolymers: Effects of Steric Crowding and Reversal of Amphiphilicity. (United States)

    Mandal, Joydeb; Ramakrishnan, S


    Two series of periodically clickable polyesters were prepared; one of them carries alkylene segments along its backbone, whereas the other carries poly(ethylene glycol) (PEG) segments. These polyesters were clicked with either MPEG-350 azide or docosyl (C22) azide to yield periodically grafted amphiphilic copolymers (PGACs) carrying either flexible hydrophilic or crystallizable hydrophobic backbone segments. The immiscibility between hydrocarbon and PEG segments causes both of these systems to fold in either a zigzag or hairpin-like conformation; the hairpin-like conformation appears to be preferred when flexible PEG segments are present in the backbone. The folded chains further reorganize in the solid state to develop a lamellar morphology that permits the collocation of the PEG and hydrocarbon (HC) segments within alternate domains; evidence for the self-segregation was gained from DSC, SAXS, and AFM studies. SAXS studies revealed the formation of an extended lamellar structure, whereas AFM images showed uniform layered morphology with layer heights that matched reasonably well with the interlamellar spacing obtained from the SAXS study. Labeling one representative PGAC, carrying crystallizable long alkylene segments in the backbone and pendant PEG-350 side chains, with a small mole fraction of pyrene fluorophore permitted the examination of the conformational transition that occurs upon going from a good to a poor solvent; this single-chain folded conformation, we postulate, is the intermediate that organizes into the lamellar morphology.

  13. Substrate-anchored and degradation-sensitive anti-inflammatory coatings for implant materials (United States)

    Wu, Duo; Chen, Xingyu; Chen, Tianchan; Ding, Chunmei; Wu, Wei; Li, Jianshu


    Implant materials need to be highly biocompatible to avoid inflammation in clinical practice. Although biodegradable polymeric implants can eliminate the need for a second surgical intervention to remove the implant materials, they may produce acidic degradation products in vivo and cause non-bacterial inflammation. Here we show the strategy of “substrate-anchored and degradation-sensitive coatings” for biodegradable implants. Using poly(lactic acid)/hydroxyapatite as an implant material model, we constructed a layer-by-layer coating using pH-sensitive star polymers and dendrimers loaded with an anti-inflammatory drug, which was immobilised through a hydroxyapatite-anchored layer. The multifunctional coating can effectively suppress the local inflammation caused by the degradation of implant materials for at least 8 weeks in vivo. Moreover, the substrate-anchored coating is able to modulate the degradation of the substrate in a more homogeneous manner. The “substrate-anchored and degradation-sensitive coating” strategy therefore exhibits potential for the design of various self-anti-inflammatory biodegradable implant materials.

  14. Polymer dynamics in nanoconfinement: Interfaces and interphases

    Directory of Open Access Journals (Sweden)

    Krutyeva Margarita


    Full Text Available The dynamics of polymers in nanoconfinement was studied by using neutron spectroscopy. A number of pronounced effects on different time and length scales for the polymers confined in nanopores of anodic aluminium oxide were observed. Local segmental dynamics was found to be dependent on the type of the interaction between the solid pore wall and polymer: attractive interactions lead to the formation of a surface layer with the dynamics slowed down as compared to the dynamics of pure polymer; neutral/repulsive interaction do not change the local dynamics. Attractive interactions cause anchoring of polymer segments on the surface creating an interphase between the polymer in close vicinity to the solid surface and pure polymer. In addition, at strong confinement conditions the dilution of the entanglement network is observed.

  15. Polymer-Peptide Nanoparticles: Synthesis and Characterization (United States)

    Dong, He; Shu, Jessica Y.; Xu, Ting


    Conjugation of synthetic polymers to peptides offers an efficient way to produce novel supramolecular structures. Herein, we report an attempt to prepare synthetic micellar nanoparticles using amphiphilic peptide-polymer conjugates as molecular building blocks. Spherical nanoparticles were formed upon dissolution of peptides in PBS buffer through the segregation of hydrophobic and hydrophilic segments. Both molecular and nano- structures were thoroughly investigated by a variety of biophysical techniques, including circular dichroism (CD), dynamic light scattering (DLS), size exclusion chromatography (SEC), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). The results demonstrate that structural properties of these biohybrid materials depend on both the geometry of the hydrophobic domain and the size of synthetic polymers. Given the diversity of functional peptide sequences, hydrophilic polymers and hydrophobic moieties, these materials would be expected to self-assemble into various types of nanostructures to cover a wide range of biological applications.

  16. Anchoring the Panic Disorder Severity Scale (United States)

    Keough, Meghan E.; Porter, Eliora; Kredlow, M. Alexandra; Worthington, John J.; Hoge, Elizabeth A.; Pollack, Mark H.; Shear, M. Katherine; Simon, Naomi M.


    The Panic Disorder Severity Scale (PDSS) is a clinician-administered measure of panic disorder symptom severity widely used in clinical research. This investigation sought to provide clinically meaningful anchor points for the PDSS both in terms of clinical severity as measured by the Clinical Global Impression-Severity Scale (CGI-S) and to extend…

  17. The bone-anchored hearing aid

    DEFF Research Database (Denmark)

    Foghsgaard, Søren


    The bone-anchored hearing aid (Baha) was introduced in 1977 by Tjellström and colleagues and has now been used clinically for over 30 years. Generally, the outcomes are good, and several studies have shown improved audiological- and quality of life outcomes. The principle of the Baha is, that sound...

  18. Multimodality of Learning Through Anchored Instruction (United States)

    Love, Mary Susan


    Multimodality of learning results from the intertextual relationship between multimodal design and other meaning-making modes. Meaning making is becoming more multimodal because language is continually reshaped by new forms of communication media. This article examines anchored instruction from a multimodal perspective. The first section includes…

  19. Effects of Media Attributes in Anchored Instruction. (United States)

    Shyu, Hsin-Yih


    Investigates the effects of computer-assisted video-based anchored instruction on promoting students' attitudes toward mathematical instruction and problem-solving skills. Examines the effects of different media attributes on students' mathematical achievement and attitudes in a situated learning environment. Findings suggest that anchored…

  20. Anchor Stress Checking of Security Injection Tank

    Institute of Scientific and Technical Information of China (English)


    The intention of the calculating is to check the anchor stresses of the security injection tank to know whether the stress is satisfied the code requirements on the basis of all the reaction forces gained in the static, seismic and thermal stress results.

  1. The "Anchor" Method: Principle and Practice. (United States)

    Selgin, Paul

    This report discusses the "anchor" language learning method that is based upon derivation rather than construction, using Italian as an example of a language to be learned. This method borrows from the natural process of language learning as it asks the student to remember whole expressions that serve as vehicles for learning both words and rules,…

  2. Fouled Anchors: The CONSTELLATION Question Answered (United States)


    1711804 87AU 73 89-1-3401 11. TITLE (kcn e S.cE) Caut,.cawn) Fouled Anchors: The Constellation Question Answered IL. PERSONA .. AUTHOPS) Wegner, Dana M...was familia , with the unaltered Constellation in Newport and, unknown to the Committee, had indeed visited the ship once in Baltimore (see p. 45). It is

  3. Predicting Anchor Links between Heterogeneous Social Networks

    CERN Document Server

    Sajadmanesh, Sina; Khodadadi, Ali


    People usually get involved in multiple social networks to enjoy new services or to fulfill their needs. Many new social networks try to attract users of other existing networks to increase the number of their users. Once a user (called source user) of a social network (called source network) joins a new social network (called target network), a new inter-network link (called anchor link) is formed between the source and target networks. In this paper, we concentrated on predicting the formation of such anchor links between heterogeneous social networks. Unlike conventional link prediction problems in which the formation of a link between two existing users within a single network is predicted, in anchor link prediction, the target user is missing and will be added to the target network once the anchor link is created. To solve this problem, we use meta-paths as a powerful tool for utilizing heterogeneous information in both the source and target networks. To this end, we propose an effective general meta-pat...

  4. Finding Chemical Anchors in the Kitchen (United States)

    Haim, Liliana


    ''The Chemistry Kitchen'', a unit composed of five activities with kitchen elements for elementary students ages 9-11, introduces the children to the skills and chemical working ideas to be used later as anchors for chemical concepts. These activities include kitchen elements, determining the relative mass and so on.

  5. Stone anchors of India: Findings, classification and significance.

    Digital Repository Service at National Institute of Oceanography (India)

    Tripati, S.

    and size do not resemble the anchors found during maritime archaeological explorations since 1986. The stone anchors until now recovered from many sites of India can broadly be classified into four types: namely composite, Indo-Arabian, ring stone (mushroom...

  6. A defect mediated lamellar to isotropic transition of amphiphile bilayers


    Pal, Antara; Pabst, Georg; Raghunathan, V. A.


    We report the observation of a novel isotropic phase of amphiphile bilayers in a mixed system consisting of the ionic surfactant, sodium docecylsulphate (SDS), and the organic salt p-toludine hydrochloride (PTHC). This system forms a collapsed lamellar ($L_\\alpha$) phase over a wide range of water content, which transforms into an isotropic phase on heating. This transition is not observed in samples without excess water, where the $L_\\alpha$ phase is stable at higher temperatures. Our observ...

  7. Tuning Amphiphilicity of Particles for Controllable Pickering Emulsion


    Zhen Wang; Yapei Wang


    Pickering emulsions with the use of particles as emulsifiers have been extensively used in scientific research and industrial production due to their edge in biocompatibility and stability compared with traditional emulsions. The control over Pickering emulsion stability and type plays a significant role in these applications. Among the present methods to build controllable Pickering emulsions, tuning the amphiphilicity of particles is comparatively effective and has attracted enormous attent...

  8. Real-time monitoring of the penetration of amphiphilic acrylate copolymer in leather using a fluorescent copolymer as tracer. (United States)

    Du, Jin-Xia; Shi, Lu; Peng, Bi-Yu


    A fluorescent tracer, poly (acrylic-co-stearyl acrylate-co-3-acryloyl fluorescein) [poly (AA-co-SA-co-Ac-Flu)], used for real-time monitoring the penetration of amphiphilic acrylate copolymer, poly (acrylic-co-stearyl acrylate) [poly (AA-co-SA)], in leather was synthesized by radical polymerization of acrylic, stearyl acrylate and fluorescent monomer, 3-acryloyl fluorescein (Ac-Flu). The structure, molecular weight, introduced fluorescent group content and fluorescent characteristics of the fluorescent tracer and target copolymer, amphiphilic acrylate copolymer, were also characterized. The results show that the tracer presents the similar structural characteristics to the target and enough fluorescence intensity with 1.68 wt % of the fluorescent monomer introduced amount. The vertical section of the leather treated with the target copolymer mixing with 7% of the tracer exhibits evident fluorescence, and the change of fluorescence intensity along with the vertical section with treating time increasing can reflect the penetration depth of the target copolymer. The introduction of the fluorescent group in polymer structure through copolymerization with a limited amount of fluorescent monomer, Ac-Flu, is an effective way to make a tracer to monitor the penetration of the target in leather, which provides a new thought for the penetration research of syntans such as vinyl copolymer materials in leather manufacture.

  9. Interaction of multidrug-resistant Chinese hamster ovary cells with amphiphiles.


    Loe, D. W.; Sharom, F J


    The interaction of membrane-active amphiphiles with a series of MDR Chinese hamster ovary (CHO) cell lines was investigated. Cross-resistance to cationic amphiphiles was observed, which was effectively sensitised by verapamil. MDR cells showed collateral sensitivity to polyoxyethylene amphiphiles (Triton X-100/Nonidet P-40), which reached a maximum at 9-10 ethylene oxide units. Resistant lines were also highly collaterally sensitive (17-fold) to dibutylphthalate. mdrl transfectants showed cro...

  10. Incorporation of amphiphilic cyclodextrins into liposomes as artificial receptor units. (United States)

    Kauscher, Ulrike; Stuart, Marc C A; Drücker, Patrick; Galla, Hans-Joachim; Ravoo, Bart Jan


    In this article, we describe the introduction of amphiphilic β-cyclodextrins into liposomes to act as artificial receptor units. Using dynamic light scattering, dye encapsulation, and cryogenic transmission electron microscopy, we show that amphiphilic β-cyclodextrins can be mixed in any proportion with a typical mixture of phospholipids and cholesterol to provide stable, spherical, and unilamellar mixed vesicles. It is also possible to form giant unilamellar vesicles with mixtures of lipids and cyclodextrin. The permeability of the mixed vesicles increases with the percentage of cyclodextrin. The cyclodextrins can act as host molecules for hydrophobic guest molecules, even when they are dispersed at a low percentage in the vesicle membrane. It is shown that mixed vesicles can be decorated with carbohydrate-functionalized guest molecules, with photoresponsive guest molecules, and with dye-functionalized guest molecules. Taken together, it is demonstrated that the host-guest chemistry of amphiphilic cyclodextrins is fully compatible with a liposomal bilayer membrane and the advantages of each can be combined to give superior nanocontainers.

  11. Anchored Instruction and Its Relationship to Situated Cognition. (United States)

    Educational Researcher, 1990


    Discusses anchored instruction, a teaching technique using videodisc-based problem-solving environments, and describes two research projects involving anchored instruction. Argues that anchored instruction provides a way to recreate and improve upon some of the advantages of situated cognition. (FMW)

  12. Anchored Instruction for Chinese Students: Enhancing Attitudes toward Mathematics. (United States)

    Shyu, Hsin-Yih


    The purpose of this study was to develop a videodisc-based computer-aided multimedia-anchored instruction for Chinese students and to examine its effects on student attitudes toward mathematics and anchored instruction. Participants were 74 fifth graders. Results indicated that anchored instruction improved students' attitudes toward mathematics…

  13. Students' Anchoring Predisposition: An Illustration from Spring Training Baseball (United States)

    Mohrweis, Lawrence C.


    The anchoring tendency results when decision makers anchor on initial values and then make final assessments that are adjusted insufficiently away from the initial values. The professional literature recognizes that auditors often risk falling into the judgment trap of anchoring and adjusting (Ranzilla et al., 2011). Students may also be unaware…

  14. Passivation of nanocrystalline TiO2 junctions by surface adsorbed phosphinate amphiphiles enhances the photovoltaic performance of dye sensitized solar cells

    KAUST Repository

    Wang, Mingkui


    We report a new class of molecular insulators that electronically passivate the surface of nanocrystalline titania films for high performance dye sensitized solar cells (DSC). Using electrical impedance measurements we demonstrate that co-adsorption of dineohexyl bis-(3,3-dimethyl-butyl)-phosphinic acid (DINHOP), along with the amphiphilic ruthenium sensitizer Z907Na increased substantially the power output of the cells mainly due to a retardation of interfacial recombination of photo-generated charge carriers. The use of phosphinates as anchoring groups opens up new avenues for modification of the surface by molecular insulators, sensitizers and other electro-active molecules to realize the desired optoelectronic performance of devices based on oxide junctions. © 2009 The Royal Society of Chemistry.

  15. Polymer films (United States)

    Granick, Steve; Sukhishvili, Svetlana A.


    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  16. Anchoring energy enhancement and pretilt angle control of liquid crystal alignment on polymerized surfaces

    Directory of Open Access Journals (Sweden)

    Libo Weng


    Full Text Available We demonstrate enhanced surface anchoring energy and control of pretilt angle in a nematic liquid crystal cell with vertical alignment and polymerized surfaces (PS-VA. The polymerized surfaces are formed by ultraviolet (UV irradiation-induced phase separation of a minute amount of a reactive monomer in the vertical-aligned nematic liquid crystal. By introducing a bias voltage during UV curing, surface-localized polymer protrusions with a dimension of 100nm and a field-induced pretilt angle are observed. Experimental evidences and theoretical analyses validate that PS-VA has increased surface anchoring strength by two folds and pretilt angle has been changed from 89° to 86° compared to those of a VA cell. The enabling PS-VA cell technique with excel electro-optical properties such as very good dark state, high optical contrast, and fast rise and decay times may lead to development of a wide range of applications.

  17. Anchoring energy enhancement and pretilt angle control of liquid crystal alignment on polymerized surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Weng, Libo; Chien, Liang-Chy [Liquid Crystal Institute, Kent State University, Kent, Ohio 44242 (United States); Liao, Pei-Chun [Liquid Crystal Institute, Kent State University, Kent, Ohio 44242 (United States); AU Optronics Corporation, Hsinchu, 300, Taiwan (China); Lin, Chen-Chun; Ting, Tien-Lun; Hsu, Wen-Hao; Su, Jenn-Jia [AU Optronics Corporation, Hsinchu, 300, Taiwan (China)


    We demonstrate enhanced surface anchoring energy and control of pretilt angle in a nematic liquid crystal cell with vertical alignment and polymerized surfaces (PS-VA). The polymerized surfaces are formed by ultraviolet (UV) irradiation-induced phase separation of a minute amount of a reactive monomer in the vertical-aligned nematic liquid crystal. By introducing a bias voltage during UV curing, surface-localized polymer protrusions with a dimension of 100nm and a field-induced pretilt angle are observed. Experimental evidences and theoretical analyses validate that PS-VA has increased surface anchoring strength by two folds and pretilt angle has been changed from 89° to 86° compared to those of a VA cell. The enabling PS-VA cell technique with excel electro-optical properties such as very good dark state, high optical contrast, and fast rise and decay times may lead to development of a wide range of applications.

  18. Amphiphilic dendritic peptides: Synthesis and behavior as an organogelator and liquid crystal

    Directory of Open Access Journals (Sweden)

    Xinwu Ba


    Full Text Available New amphiphilic dendritic peptides on dendritic polyaspartic acid were designed and synthesized. The organogel and liquid crystal properties of these amphiphilic dendritic peptides were fully studied by field-emission SEM, temperature dependent FT-IR, differential scanning calorimetry, polarization optical microscopy and X-ray diffraction experiments. Amphiphilic dendritic peptides G3 show good organogel properties with a minimum gelation concentration as low as 1 wt %. Furthermore, amphiphilic dendritic peptides G3 can form a hexagonal columnar liquid crystal assembly over a wide temperature range.

  19. Edge-modified amphiphilic Laponite nano-discs for stabilizing Pickering emulsions. (United States)

    Yang, Ying; Liu, Zhi; Wu, Dayong; Wu, Man; Tian, Ye; Niu, Zhongwei; Huang, Yong


    We investigated the effect of amphiphilic Laponite nano-discs, which were edge-modified by hydrophobic chains, on the properties of Pickering emulsions and Pickering emulsions polymerization. Comparing to unmodified Laponites, these amphiphilic nano-discs can greatly reduce the surface tension, resulting in very stable Pickering emulsions. These particles uniquely combine the Pickering effect with amphiphilic properties similar to the surfactant. Taking advantage of these amphiphilic Pickering emulsifiers, miniemulsion polymerization of styrene was performed. Homogeneous polystyrene nanoparticles with size around 150 nm could thus be prepared.

  20. Hybrids of silver nanoparticles with amphiphilic hyperbranched macromolecules exhibiting antimicrobial properties


    Aymonier, Cyril; Schlotterbeck, Ulf; Antonietti, Lydie; Zacharias, Philipp; Thomann, Ralf; Till, Joerg C.; Mecking, Stefan


    Hybrids of silver particles of 1 to 2 nm in size with highly branched amphiphilically modified polyethyleneimines adhere effectively to polar substrates providing environmentally friendly antimicrobial coatings.

  1. Cationic amphiphiles with fatty acyl chain asymmetry of coconut oil deliver genes selectively to mouse lung. (United States)

    Chandrashekhar, Voshavar; Srujan, Marepally; Prabhakar, Rairala; Reddy, Rakesh C; Sreedhar, Bojja; Rentam, Kiran K R; Kanjilal, Sanjit; Chaudhuri, Arabinda


    Recent structure-activity studies have revealed a dramatic influence of hydrophobic chain asymmetry in enhancing gene delivery efficacies of synthetic cationic amphiphiles (Nantz, M. H. et al. Mol. Pharmaceutics2010, 7, 786-794; Koynova, R. et al. Mol. Pharmaceutics2009, 6, 951-958). The present findings demonstrate for the first time that such a transfection enhancing influence of asymmetric hydrocarbon chains observed in pure synthetic cationic amphiphiles also works for cationic amphiphiles designed with natural, asymmetric fatty acyl chains of a food-grade oil. Herein, we demonstrate that cationic amphiphiles designed with the natural fatty acyl chain asymmetry of food-grade coconut oil are less cytotoxic and deliver genes selectively to mouse lung. Despite lauroyl chains being the major fatty acyl chains of coconut oil, both the in vitro and In vivo gene transfer efficiencies of such cationic amphiphiles were found to be remarkably superior (>4-fold) to those of their pure dilauroyl analogue. Mechanistic studies involving the technique of fluorescence resonance energy transfer (FRET) revealed higher biomembrane fusibility of the cationic liposomes of the coconut amphiphiles than that of the symmetric dilauroyl analogue. AFM study revealed pronounced fusogenic nonlamellar structures of the liposomes of coconut amphiphiles. Findings in the FRET and cellular uptake study, taken together, support the notion that the higher cellular uptake resulting from the more fusogenic nature of the liposomes of coconut amphiphiles 1 are likely to play a dominant role in making the coconut amphiphiles transfection competent.

  2. Order-disorder transitions in self-assembled polymers : A positron annihilation study

    NARCIS (Netherlands)

    Ramani, Ramasubbu; Valkama, Sami; Kilpeläinen, Simo; Tumisto, Filip; Brinke, Gerrit ten; Ruokolainen, Janne; Alam, Sarfaraz; Ikkala, Olli


    We report here the first results of order-disorder transition (ODT) in a self-assembled comb-like polymer-amphiphile supramolecular system as identified from the change in positron lifetime parameters. We have used poly(4-vinyl pyridine) hydrogen bonded with 3-pentadecyl phenol, which upon heating s

  3. Composite materials formed with anchored nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Seals, Roland D; Menchhofer, Paul A; Howe, Jane Y; Wang, Wei


    A method of forming nano-structure composite materials that have a binder material and a nanostructure fiber material is described. A precursor material may be formed using a mixture of at least one metal powder and anchored nanostructure materials. The metal powder mixture may be (a) Ni powder and (b) NiAl powder. The anchored nanostructure materials may comprise (i) NiAl powder as a support material and (ii) carbon nanotubes attached to nanoparticles adjacent to a surface of the support material. The process of forming nano-structure composite materials typically involves sintering the mixture under vacuum in a die. When Ni and NiAl are used in the metal powder mixture Ni.sub.3Al may form as the binder material after sintering. The mixture is sintered until it consolidates to form the nano-structure composite material.

  4. Electrochromic mirror using viologen-anchored nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han Na [Electronics and Telecommunications Research Institute, Nature-mimic I/O interface Research Section, 218 Gajeong-roYuseong-gu, Daejeon 305-700 (Korea, Republic of); University of Science and Technology, Advanced Device Technology, 217 Gajeong-roYuseong-gu, Daejeon 305-350 (Korea, Republic of); Cho, Seong M.; Ah, Chil Seong; Song, Juhee; Ryu, Hojun; Kim, Yong Hae [Electronics and Telecommunications Research Institute, Nature-mimic I/O interface Research Section, 218 Gajeong-roYuseong-gu, Daejeon 305-700 (Korea, Republic of); Kim, Tae-Youb, E-mail: [Electronics and Telecommunications Research Institute, Nature-mimic I/O interface Research Section, 218 Gajeong-roYuseong-gu, Daejeon 305-700 (Korea, Republic of); University of Science and Technology, Advanced Device Technology, 217 Gajeong-roYuseong-gu, Daejeon 305-350 (Korea, Republic of)


    Highlights: • Three types of ECM device were fabricated using viologen-anchored ECDs. • The devices were investigated according to their optical structures. • The anti-reflection material affects the reflectance and the coloration efficiency. • The device design of ECMs is a crucial factor for clear reflected images. - Abstract: Electrochromic mirrors (ECMs) that are used in automobile mirrors need to have high reflectance, a high contrast ratio, and a clear image. In particular, it is critical that distortions of clear images are minimized for safety. Therefore, an ECM is fabricated using viologen-anchored nanoparticles and a magnesium fluoride (MgF{sub 2}) layer with an anti-reflection function. The ECM has approximately 30.42% in the reflectance dynamic range and 125 cm{sup 2}/C high coloration efficiency.

  5. An Analytical Method for Positioning Drag Anchors in Seabed Soils

    Institute of Scientific and Technical Information of China (English)

    张炜; 刘海笑; 李新仲; 李清平; 曹静


    Positioning drag anchors in seabed soils are strongly influenced not only by the properties of the anchor and soil, but also by the characteristics of the installation line. The investigation on the previous prediction methods related to anchor positioning demonstrates that the prediction of the anchor position during dragging has inevitably introduced some key and unsubstantiated hypotheses and the applicability of these methods is limited. In the present study, the interactional system between the drag anchor and installation line is firstly introduced for the analysis of anchor positioning. Based on the two mechanical models for embedded lines and drag anchors, the positioning equations for drag anchors have been derived both for cohesive and noncohesive soils. Since the drag angle at the shackle is the most important parameter in the positioning equations, a novel analytical method that can predict both the variation and the exact value of the drag angle at the shackle is proposed. The analytical method for positioning drag anchors which combines the interactional system between the drag anchor and the installation line has provided a reasonable theoretic approach to investigate the anchor behaviors in soils. By comparing with the model flume experiments, the sensitivity, effectiveness and veracity of the positioning method are well verified.

  6. Anchored Instruction: Situiertes Lernen in multimedialen Lernumgebungen



    «Anchored Instruction» ist ein konstruktivistischer Ansatz aus den USA, dessen Vertreter technologisch unterstützte, situierte Lernumgebungen für verschiedene schulische Fächer und Altersstufen entwickeln, implementieren und erforschen. Wichtige Ziele, Gestaltungsprinzipien und Merkmale solcher Lernumgebungen sowie ihre Implementation im Unterricht werden anhand von zwei Anwendungen näher dargestellt: (1) «The Adventures of Jasper Woodbury», eine Serie von Video-Geschichten und Zusatzmaterial...

  7. Developing an "anchor" system to enhance postural control. (United States)

    Mauerberg-deCastro, Eliane


    This article uses an anchor metaphor to explain the dynamic interplay between the human body's active uses of nonrigid tools to mediate information about its adjacent environment to enhance postural control. The author used an "anchor" system (ropes attached to varying weights resting on the floor) to test blindfolded adults who performed a restricted-balance task (30 s one-foot standing). Participants were tested while holding the anchors under a variety of weight conditions (125 g, 250 g, 500 g, and 1 kg) and again during a baseline condition (no anchors). When compared with the baseline condition, there was a significant reduction in the amount of body sway across the anchor conditions. The author found that mechanical support provided by the anchor system was secondary to its haptic exploratory function and that an individual can use the anchoring strategy with a dual purpose: for resting and for reorientation after intrinsic disruptions.

  8. Anchoring properties of substrate with a grating surface

    Institute of Scientific and Technical Information of China (English)

    Ye Wen-Jiang; Xing Hong-Yu; Yang Guo-Chen


    The anchoring properties of substrate with a grating surface are investigated analytically. The alignment of nematic liquid crystal (NLC) in a grating surface originates from two mechanisms, thus the anchoring energy consists of two parts. One originates from the interaction potential between NLC molecules and the molecules on the substrate surface,and the other stems from the increased elastic strain energy. Based on the two mechanisms, the expression of anchoring energy per unit area of a projected plane of this grating surface is deduced and called the equivalent anchoring energy formula. Both the strength and the easy direction of equivalent anchoring energy are a function of the geometrical parameters (amplitude and pitch) of a grating surface. By using this formula, the grating surface can be replaced by its projected plane and its anchoring properties can be described by the equivalent anchoring energy formula.

  9. Anchored design of protein-protein interfaces.

    Directory of Open Access Journals (Sweden)

    Steven M Lewis

    Full Text Available BACKGROUND: Few existing protein-protein interface design methods allow for extensive backbone rearrangements during the design process. There is also a dichotomy between redesign methods, which take advantage of the native interface, and de novo methods, which produce novel binders. METHODOLOGY: Here, we propose a new method for designing novel protein reagents that combines advantages of redesign and de novo methods and allows for extensive backbone motion. This method requires a bound structure of a target and one of its natural binding partners. A key interaction in this interface, the anchor, is computationally grafted out of the partner and into a surface loop on the design scaffold. The design scaffold's surface is then redesigned with backbone flexibility to create a new binding partner for the target. Careful choice of a scaffold will bring experimentally desirable characteristics into the new complex. The use of an anchor both expedites the design process and ensures that binding proceeds against a known location on the target. The use of surface loops on the scaffold allows for flexible-backbone redesign to properly search conformational space. CONCLUSIONS AND SIGNIFICANCE: This protocol was implemented within the Rosetta3 software suite. To demonstrate and evaluate this protocol, we have developed a benchmarking set of structures from the PDB with loop-mediated interfaces. This protocol can recover the correct loop-mediated interface in 15 out of 16 tested structures, using only a single residue as an anchor.

  10. The Effect of Molecular Anchoring and Curvature on Confined Liquid Crystals (United States)

    Ondris-Crawford, Renate Johanna

    of the liquid crystal material. The investigation of stable nematic director-fields in supramicrometer droplets with tangential (bipolar droplets) and homeotropic anchoring (axial and radial droplet) encompassed simulating optical birefringence patterns computed from Frank elastic theory and comparing these to the observed textures of polymer dispersed liquid crystal droplets.

  11. Dehydration-induced redistribution of amphiphilic molecules between cytoplasm and lipids is associated with desiccation tolerance in seeds

    NARCIS (Netherlands)

    Buitink, J.; Leprince, O.; Hoekstra, F.A.


    This study establishes a relationship between desiccation tolerance and the transfer of amphiphilic molecules from the cytoplasm into lipids during drying, using electron paramagnetic resonance spectroscopy of amphiphilic spin probes introduced into imbibed radicles of pea (Pisum sativum) and cucumb

  12. Robotic Ankle for Omnidirectional Rock Anchors (United States)

    Parness, Aaron; Frost, Matthew; Thatte, Nitish


    Future robotic exploration of near-Earth asteroids and the vertical and inverted rock walls of lava caves and cliff faces on Mars and other planetary bodies would require a method of gripping their rocky surfaces to allow mobility without gravitational assistance. In order to successfully navigate this terrain and drill for samples, the grippers must be able to produce anchoring forces in excess of 100 N. Additionally, the grippers must be able to support the inertial forces of a moving robot, as well gravitational forces for demonstrations on Earth. One possible solution would be to use microspine arrays to anchor to rock surfaces and provide the necessary load-bearing abilities for robotic exploration of asteroids. Microspine arrays comprise dozens of small steel hooks supported on individual suspensions. When these arrays are dragged along a rock surface, the steel hooks engage with asperities and holes on the surface. The suspensions allow for individual hooks to engage with asperities while the remaining hooks continue to drag along the surface. This ensures that the maximum possible number of hooks engage with the surface, thereby increasing the load-bearing abilities of the gripper. Using the microspine array grippers described above as the end-effectors of a robot would allow it to traverse terrain previously unreachable by traditional wheeled robots. Furthermore, microspine-gripping robots that can perch on cliffs or rocky walls could enable a new class of persistent surveillance devices for military applications. In order to interface these microspine grippers with a legged robot, an ankle is needed that can robotically actuate the gripper, as well as allow it to conform to the large-scale irregularities in the rock. The anchor serves three main purposes: deploy and release the anchor, conform to roughness or misalignment with the surface, and cancel out any moments about the anchor that could cause unintentional detachment. The ankle design contains a

  13. Amphiphilic diblock copolymer and polycaprolactone blends to produce new vesicular nanocarriers. (United States)

    Penott-Chang, Evis; Walther, Andreas; Millard, Pierre; Jäger, Alessandro; Jäger, Eliezer; Müller, Axel H E; Guterres, Sílvia S; Pohlmann, Adriana R


    New Melatonin-loaded vesicular nanocarriers were prepared by interfacial deposition using a blend of an amphiphilic diblock copolymer, poly(methyl methacrylate)-block-poly(2-(dimethylamino)ethyl methacrylate), PMMA-b-PDMAEMA, with poly(epsilon-caprolactone), PCL. Particle size and morphology of the nanocarriers was evaluated. Dynamic light scattering shows that the nanocarriers have hydrodynamic radii between 100 and 180 nm, with unimodal particle size distribution for each formulation. Shape and structure were visualized by transmission electron microscopy (TEM), cryogenic TEM and scanning electron microscopy. Standard TEM for nanocapsules showed an oily core surrounded by a thin layer composed by PCL/PMMA-b-PDMAEMA. Cryo-TEM also indicated the presence of spherical nano-objects with a diffuse polymer corona. Encapsulation efficiencies were determined assaying the nanoparticles by HPLC and higher values of ca. 25% are shown by the nanocapsules. We could successfully incorporate platinum nanoparticles into the nanocarrier as evidenced by TEM, which opens up the possibility for promising applications like monitoring the encapsulated drug in the body.

  14. Activity and Mechanism of Antimicrobial Peptide-Mimetic Amphiphilic Polymethacrylate Derivatives

    Directory of Open Access Journals (Sweden)

    Kenichi Kuroda


    Full Text Available Cationic amphiphilic polymethacrylate derivatives (PMAs have shown potential as a novel class of synthetic antimicrobials. A panel of PMAs with varied ratios of hydrophobic and cationic side chains were synthesized and tested for antimicrobial activity and mechanism of action. The PMAs are shown to be active against a panel of pathogenic bacteria, including a drug-resistant Staphylococcus aureus, compared to the natural antimicrobial peptide magainin which did not display any activity against the same strain. The selected PMAs with 47–63% of methyl groups in the side chains showed minimum inhibitory concentrations of ≤2–31 µg/mL, but cause only minimal harm to human red blood cells. The PMAs also exhibit rapid bactericidal kinetics. Culturing Escherichia coli in the presence of the PMAs did not exhibit any potential to develop resistance against the PMAs. The antibacterial activities of PMAs against E. coli and S. aureus were slightly reduced in the presence of physiological salts. The activity of PMAs showed bactericidal effects against E. coli and S. aureus in both exponential and stationary growth phases. These results demonstrate that PMAs are a new antimicrobial platform with no observed development of resistance in bacteria. In addition, the PMAs permeabilized the E. coli outer membrane at polymer concentrations lower than their MIC values, but they did not show any effect on the bacterial inner membrane. This indicates that mechanisms other than membrane permeabilization may be the primary factors determining their antimicrobial activity.

  15. FragAnchor: A Large-Scale Predictor of Glycosylphosphatidylinositol Anchors in Eukaryote Protein Sequences by Qualitative Scoring

    Institute of Scientific and Technical Information of China (English)


    A glycosylphosphatidylinositol (GPI) anchor is a common but complex C-terminal post-translational modification of extracellular proteins in eukaryotes. Here we investigate the problem of correctly annotating GPI-anchored proteins for the growing number of sequences in public databases. We developed a computational system, called FragAnchor, based on the tandem use of a neural network (NN) and a hidden Markov model (HMM). Firstly, NN selects potential GPI-anchored proteins in a dataset, then HMM parses these potential GPI signals and refines the prediction by qualitative scoring. FragAnchor correctly predicted 91% of all the GPI-anchored proteins annotated in the Swiss-Prot database.In a large-scale analysis of 29 eukaryote proteomes, FragAnchor predicted that the percentage of highly probable GPI-anchored proteins is between 0.21% and 2.01%. The distinctive feature of FragAnchor, compared with other systems,is that it targets only the C-terminus of a protein, making it less sensitive to the background noise found in databases and possible incomplete protein sequences. Moreover, FragAnchor can be used to predict GPI-anchored proteins in all eukaryotes. Finally, by using qualitative scoring, the predictions combine both sensitivity and information content. The predictor is publicly available at http: // navet. ics.

  16. H-shaped supra-amphiphiles based on a dynamic covalent bond. (United States)

    Wang, Guangtong; Wang, Chao; Wang, Zhiqiang; Zhang, Xi


    The imine bond, a kind of dynamic covalent bond, is used to bind two bolaform amphiphiles together with spacers, yielding H-shaped supra-amphiphiles. Micellar aggregates formed by the self-assembly of the H-shaped supra-amphiphiles are observed. When pH is tuned down from basic to slightly acidic, the benzoic imine bond can be hydrolyzed, leading to the dissociation of H-shaped supra-amphiphiles. Moreover, H-shaped supra-amphiphiles have a lower critical micelle concentration than their building blocks, which is very helpful in enhancing the stability of the benzoic imine bond being hydrolyzed by acid. The surface tension isotherms of the H-shaped supra-amphiphiles with different spacers indicate their twisty conformation at a gas-water interface. The study of H-shaped supra-amphiphiles can enrich the family of amphiphiles, and moreover, the pH-responsiveness may make them apply to controlled or targetable drug delivery in a biological environment.

  17. Synthesis and characteristics of biodegradable pyridinium amphiphiles used for in vitro DNA delivery

    NARCIS (Netherlands)

    Roosjen, Astrid; Smisterova, Jarmila; Driessen, Cecile; Anders, Joachim T.; Wagenaar, Anno; Hoekstra, Dirk; Hulst, Ron; Engberts, Jan B.F.N.


    Pyridinium amphiphiles have found practical application for the delivery of DNA into eukaryotic cells. A general synthetic method starting from (iso)nicotinoyl chloride has been devised for the preparation of pyridinium amphiphiles based on (bio)degradable esters, allowing structural variation both

  18. Self-assembly of peptide-amphiphile nanofibers under physiological conditions (United States)

    Stupp, Samuel I.; Hartgerink, Jeffrey D.; Beniash, Elia


    The present invention provides a method of promoting neuron growth and development by contacting cells with a peptide amphiphile molecule in an aqueous solution in the presence of a metal ion. According to the method, the peptide amphiphile forms a cylindrical micellar nanofiber composed of beta-sheets, which promote neuron growth and development.

  19. Composition and method for self-assembly and mineralization of peptide-amphiphiles (United States)

    Stupp, Samuel I [Chicago, IL; Beniash, Elia [Newton, MA; Hartgerink, Jeffrey D [Pearland, TX


    The present invention is directed to a composition useful for making homogeneously mineralized self assembled peptide-amphiphile nanofibers and nanofiber gels. The composition is generally a solution comprised of a positively or negatively charged peptide-amphiphile and a like signed ion from the mineral. Mixing this solution with a second solution containing a dissolved counter-ion of the mineral and/or a second oppositely charged peptide amphiphile, results in the rapid self assembly of the peptide-amphiphiles into a nanofiber gel and templated mineralization of the ions. Templated mineralization of the initially dissolved mineral cations and anions in the mixture occurs with preferential orientation of the mineral crystals along the fiber surfaces within the nanofiber gel. One advantage of the present invention is that it results in homogenous growth of the mineral throughout the nanofiber gel. Another advantage of the present invention is that the nanofiber gel formation and mineralization reactions occur in a single mixing step and under substantially neutral or physiological pH conditions. These homogeneous nanostructured composite materials are useful for medical applications especially the regeneration of damaged bone in mammals. This invention is directed to the synthesis of peptide-amphiphiles with more than one amphiphilic moment and to supramolecular compositions comprised of such multi-dimensional peptide-amphiphiles. Supramolecular compositions can be formed by self assembly of multi-dimensional peptide-amphiphiles by mixing them with a solution comprising a monovalent cation.

  20. Composition and method for self-assembly and mineralization of peptide amphiphiles (United States)

    Stupp, Samuel I.; Beniash, Elia; Hartgerink, Jeffrey D.


    The present invention is directed to a composition useful for making homogeneously mineralized self assembled peptide-amphiphile nanofibers and nanofiber gels. The composition is generally a solution comprised of a positively or negatively charged peptide-amphiphile and a like signed ion from the mineral. Mixing this solution with a second solution containing a dissolved counter-ion of the mineral and/or a second oppositely charged peptide amphiphile, results in the rapid self assembly of the peptide-amphiphiles into a nanofiber gel and templated mineralization of the ions. Templated mineralization of the initially dissolved mineral cations and anions in the mixture occurs with preferential orientation of the mineral crystals along the fiber surfaces within the nanofiber gel. One advantage of the present invention is that it results in homogenous growth of the mineral throughout the nanofiber gel. Another advantage of the present invention is that the nanofiber gel formation and mineralization reactions occur in a single mixing step and under substantially neutral or physiological pH conditions. These homogeneous nanostructured composite materials are useful for medical applications especially the regeneration of damaged bone in mammals. This invention is directed to the synthesis of peptide-amphiphiles with more than one amphiphilic moment and to supramolecular compositions comprised of such multi-dimensional peptide-amphiphiles. Supramolecular compositions can be formed by self assembly of multi-dimensional peptide-amphiphiles by mixing them with a solution comprising a monovalent cation.

  1. Adsorption of alkyltriphenylphosphonium amphiphiles on nafion membranes. X-ray photoelectron spectroscopy and static secondary ion mass spectrometry analysis

    NARCIS (Netherlands)

    Straaten-Nijenhuis, van Wilma F.; Sudholter, Ernst J.R.; Jong, de Feike; Reinhoudt, David N.; Mahy, Jan W.G.


    Conductivity, UV, and attenuated total reflectance IR measurements show that n-alkyltriphenylphosphonium amphiphiles adsorb on a Ndion 117 membrane. Approximately 20% of the Ndion protons are exchanged for a cationic amphiphile (n-hexadecyltriphenylphoephonium). Diffusion of amphiphile through the m

  2. Dynamic performance of concrete undercut anchors for Nuclear Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Mahrenholtz, Christoph, E-mail:; Eligehausen, Rolf


    Graphical abstract: - Highlights: • Behavior of undercut anchors under dynamic actions simulating earthquakes. • First high frequency load and crack cycling tests on installed concrete anchors ever. • Comprehensive review of anchor qualification for Nuclear Power Plants. - Abstract: Post-installed anchors are widely used for structural and nonstructural connections to concrete. In many countries, concrete anchors used for Nuclear Power Plants have to be qualified to ensure reliable behavior even under extreme conditions. The tests required for qualification of concrete anchors are carried out at quasi-static loading rates well below the rates to be expected for dynamic actions deriving from earthquakes, airplane impacts or explosions. To investigate potentially beneficial effects of high loading rates and cycling frequencies, performance tests on installed undercut anchors were conducted. After introductory notes on anchor technology and a comprehensive literature review, this paper discusses the qualification of anchors for Nuclear Power Plants and the testing carried out to quantify experimentally the effects of dynamic actions on the load–displacement behavior of undercut anchors.

  3. Metal-free synthesis of amphiphilic functional polycarbonates

    Institute of Scientific and Technical Information of China (English)


    Amphiphilic block copolymers of poly(5-benzyloxy trimethylene carbonate) (PBTMC) and poly(ethylene glycol) (PEG) were synthesized through enzymatic polymerization using immobilized porcine pancreas lipase (IPPL). The obtained copolymers with different compositions were characterized by GPC and 1H NMR. The copolymer composition was in agreement with the feed ratio.The molecular weight of the copolymers showed an increasing trend with the decrease of PEG contents. Micelles of the copolymers were formed by dialysis procedure, and characterized by transmission electron microscopy (TEM).

  4. From Vesicles to Protocells: The Roles of Amphiphilic Molecules

    Directory of Open Access Journals (Sweden)

    Yuka Sakuma


    Full Text Available It is very challenging to construct protocells from molecular assemblies. An important step in this challenge is the achievement of vesicle dynamics that are relevant to cellular functions, such as membrane trafficking and self-reproduction, using amphiphilic molecules. Soft matter physics will play an important role in the development of vesicles that have these functions. Here, we show that simple binary phospholipid vesicles have the potential to reproduce the relevant functions of adhesion, pore formation and self-reproduction of vesicles, by coupling the lipid geometries (spontaneous curvatures and the phase separation. This achievement will elucidate the pathway from molecular assembly to cellular life.

  5. Micellar structure of amphiphilic poly(2-oxazoline) diblock copolymers

    DEFF Research Database (Denmark)

    Papadakis, C.M.; Ivanova, R.; Lüdtke, K.


    Amphiphilic diblock copolymers from poly(2-oxazoline)s in aqueous solution can form micelles. By means of small-angle neutron scattering, we have found that poly[(n-nonyl-2-oxazoline)-b-(methyl-2-oxazoline)] {P[(NOx)-b-(MOx)]} diblock copolymers in aqueous solution form micelles of core-shell type....... We have determined the core radius and the shell thickness of the micelles. Comparing the values obtained to the stretched lengths of the blocks leads to the conclusion that the P(NOx) core blocks are stretched, whereas the P(MOx) shell blocks are coiled....

  6. Bolaform supramolecular amphiphiles as a novel concept for the buildup of surface-imprinted films. (United States)

    Zhang, Jiawei; Liu, Yiliu; Wu, Guanglu; Schönhoff, Monika; Zhang, Xi


    Stable multilayer films were fabricated on the basis of the alternating layer-by-layer assembly of a two-component bolaform supramolecular amphiphile and diazoresins, followed by photochemical cross-linking of the structure. UV-visible spectroscopy and atomic force microscopy revealed a uniform deposition process. Moreover, one component of the supramolecular amphiphile can be removed from the multilayer films after cross-linking between the second component and the diazoresin. The release and uptake of the imprinted supramolecular amphiphile component are shown to be reversible. Furthermore, uptake experiments of different molecules show the selectivity of the imprinted sites for the template molecule. Thus, surface-imprinted films can be formed by employing dissociable two-component supramolecular amphiphiles. This research reveals that supramolecular amphiphiles can be used as a novel concept for the construction of multilayer films, and it also provides a new method of generating surface-imprinted multilayers.

  7. Thermally induced anchoring of fullerene in copolymers with Si-bridging atom: Spectroscopic evidences (United States)

    Marchiori, Cleber F. N.; Garcia-Basabe, Yunier; de A. Ribeiro, Fabio; Koehler, Marlus; Roman, Lucimara S.; Rocco, Maria Luiza M.


    We use X-ray photoelectron spectroscopy (XPS), Near-edge X-ray absorption fine structure (NEXAFS), resonant Auger spectroscopy (RAS), Attenuation Total Reflection Infrared (ATR-IR) and Atomic Force Microscopy (AFM) to study the blend between the copolymer poly[2,7-(9,9-bis(2-ethylhexyl)-dibenzosilole)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PSiF-DBT) and the fullerene derivative PC71BM submitted to different annealing temperatures. Those measurements indicate that there is an incidental anchoring of a fullerene derivative to the Si-bridging atoms of a copolymer induced by thermal annealing of the film. Insights about the physical properties of one possible PSiF-DBT/PC71BM anchored structure are obtained using Density Functional Theory calculations. Since the performance of organic photovoltaic based on polymer-fullerene blends depends on the chemical structure of the blend components, the anchoring effect might affect the photovoltaic properties of those devices.

  8. Endocytosis of glycosylphosphatidylinositol-anchored proteins

    Directory of Open Access Journals (Sweden)

    Sabharanjak Shefali


    Full Text Available Abstract Glycosylphosphatidylinositol-anchored proteins (GPI-APs represent an interesting amalgamation of the three basic kinds of cellular macromolecules viz. proteins, carbohydrates and lipids. An unusually hybrid moiety, the GPI-anchor is expressed in a diverse range of organisms from parasites to mammalian cells and serves to anchor a large number of functionally diverse proteins and has been the center of attention in scientific debate for some time now. Membrane organization of GPI-APs into laterally-organized cholesterol-sphingolipid ordered membrane domains or "rafts" and endocytosis of GPI-APs has been intensely debated. Inclusion into or exclusion from these membrane domains seems to be the critical factor in determining the endocytic mechanisms and intracellular destinations of GPI-APs. The intracellular signaling as well as endocytic trafficking of GPI-APs is critically dependent upon the cell surface organization of GPI-APs, and the associations with these lipid rafts play a vital role during these processes. The mechanism of endocytosis for GPI-APs may differ from other cellular endocytic pathways, such as those mediated by clathrin-coated pits (caveolae, and is necessary for unique biological functions. Numerous intracellular factors are involved in and regulate the endocytosis of GPI-APs, and these may be variably dependent on cell-type. The central focus of this article is to describe the significance of the endocytosis of GPI-APs on a multitude of biological processes, ranging from nutrient-uptake to more complex immune responses. Ultimately, a thorough elucidation of GPI-AP mediated signaling pathways and their regulatory elements will enhance our understanding of essential biological processes and benefit as components of disease intervention strategies.


    Directory of Open Access Journals (Sweden)

    Tatyana L. Shklyar


    Full Text Available The main purpose of marketing, both ineconomy and in politics is to attract themaximum number of customers or voters, maximizing customer satisfaction and ,ideally, improve the quality of life.The author, in various aspects, thetechnology of anchoring used in NLP, to attract customers and voters, both in the economy and in politics.In different examples demonstrate theoverall impact on the psychology of the consumer. Separating policy and the economy, marketers are missing something. The author proposes to look at how psychologicalanchors affect these two, at fi rst glance, different vector.

  10. Adsorption phenomena and anchoring energy in nematic liquid crystals

    CERN Document Server

    Barbero, Giovanni


    Despite the large quantity of phenomenological information concerning the bulk properties of nematic phase liquid crystals, little is understood about the origin of the surface energy, particularly the surface, interfacial, and anchoring properties of liquid crystals that affect the performance of liquid crystal devices. Self-contained and unique, Adsorption Phenomena and Anchoring Energy in Nematic Liquid Crystals provides an account of new and established results spanning three decades of research into the problems of anchoring energy and adsorption phenomena in liquid crystals.The book contains a detailed discussion of the origin and possible sources of anchoring energy in nematic liquid crystals, emphasizing the dielectric contribution to the anchoring energy in particular. Beginning with fundamental surface and anchoring properties of liquid crystals and the definition of the nematic phase, the authors explain how selective ion adsorption, dielectric energy density, thickness dependence, and bias voltage...

  11. The effect of hydrophilic and hydrophobic block length on the rheology of amphiphilic diblock Polystyrene-b-Poly(sodium methacrylate) copolymers prepared by ATRP. (United States)

    Raffa, Patrizio; Stuart, Marc C A; Broekhuis, Antonius A; Picchioni, Francesco


    Following our previous investigation on the effect of molecular architecture on the rheology of Polystyrene-b-Poly(sodium methacrylate) copolymers (PS-b-PMAA), we consider here diblock PS-b-PMAA copolymers characterized by a different length of either the hydrophilic or the hydrophobic block. Various copolymers characterized by different PS or PMAA block length have been prepared by ATRP (kinetics is also discussed) and studied from the point of view of their rheological behaviour in water. To the best of our knowledge, this is the first systematic investigation concerning the effect of block length on the rheology of diblock polyelectrolytes. We found that the hydrophobic block length has small influence on the rheology. Surprisingly, the polymers with shortest PMAA blocks yield the strongest gels at high concentration. A simple model based on the classical theories of self-assembly and percolation of amphiphilic polymers has been here developed in order to explain the observed data.

  12. Lipophosphoramidate-based bipolar amphiphiles: their syntheses and transfection properties. (United States)

    Berchel, Mathieu; Le Gall, Tony; Lozach, Olivier; Haelters, Jean-Pierre; Montier, Tristan; Jaffrès, Paul-Alain


    Six new cationic bolaamphiphiles (also called bipolar amphiphiles, bolaform amphiphiles, or bolalipids) were readily prepared by a thiol-ene click reaction that engaged a mercapto-alcohol (mercapto-ethanol or mercapto-hexanol) and a cationic based lipophosphoramidate. The cationic lipophosphoramidates contain two lipid chains that end in an alkene group and a selected cationic polar head group (trimethylammonium, dimethyl hydroxyethyl ammonium, or methylimidazolium). These compounds were formulated in water (with or without DOPE as a colipid) to produce supramolecular aggregates. These aggregates, before (i.e. bolasomes) and after (i.e. bolaplexes) mixing with plasmid DNA (pDNA) at various charge ratios, were characterized with regard to their sizes and zeta potentials. In the case of bolasomes, the suspensions were unstable since precipitation occurred after only a few hours at room temperature. On the other hand, bolaplex formulations exhibited clearly a better colloidal stability. Then, the gene delivery properties of the cationic bolasomes were investigated using two human-derived epithelial cell lines (A549 and 16HBE). Compared to the commercially available lipofection reagent (Lipofectamine), most of the cationic bolaamphiphiles were able to efficiently transfect these cells when they were formulated with DOPE in a 1 : 1 molar ratio. We report herein that bolaamphiphiles possessing a trimethylammonium or a dimethyl hydroxyethyl ammonium head group were the most efficient in terms of transfection efficiency while exhibiting no significant cytotoxicity.

  13. Thermotropic organization of hydrogen-bond-bridged bolaform amphiphiles. (United States)

    Zhang, Jing; Zhou, Mingjun; Wang, Shan; Carr, Jessica; Li, Wen; Wu, Lixin


    A series of quaternary ammonium amphiphiles (A-n) bearing carboxylic acid groups were designed and synthesized. The branched bolaform structures can be constructed by dimerizations of carboxylic acid groups through intermolecular hydrogen bonding, as demonstrated by the Fourier transform infrared (FT-IR) spectra and the temperature-dependent FT-IR spectra. The thermotropic organizations of branched bolaform ammonium dimer complexes were characterized by differential scanning calorimetry, polarized optical microscopy, and X-ray diffraction. We investigated the influence of the spacer between the cationic group and the benzene ring on the thermotropic organization. A-6 with short lateral alkyl chains formed a simple layered structure at room temperature and exhibited smectic A mesophase above 145 °C, whereas A-8 with intermediate lateral chain length organized into smectic A phase over a wide temperature range. A further increase of the length (n = 10, 12) of the lateral chains resulted in the formation of lamellar structure with in-plane layered periodicity, which is rare in the organization of ionic compounds. A packing model of the quasi-2D lamellar was proposed on the basis of the experimental data of X-ray diffraction results. Notably, the quasi-2D lamellar structure could evolve into a simple layer with the increase of temperature. The present results showed a direct relationship in which the branched architecture can be applied to tune the self-assembly behavior of ionic amphiphiles and is allowed to construct new layered superstructure.

  14. Preparation and Properties of Vesicles from Condensable Amphiphilic Amino Acids

    Institute of Scientific and Technical Information of China (English)

    熊向源; 何巍; 李子臣; 李福绵


    Three double-chain amphiphiles with amino acid groups as hydrphilic moiety were synthesized. These amphiphiles can be easily dispersed in buffer solution to form transparent dispersion. Examination of the dispersion by transmission electron microscopy (TEM) showed the formation of stable vesicular aggregates, which was also confirmed by the ability to encapsulate water-soluble dyes. Since amino acid groups are located on the surface of the vesicles, water-soluble carbodiimide can induce the condensation of these groups to form peptide. The phase transition temperatures of these vesicles were estimated by differential scanning calorimetry (DSC), and a decrease of phase transition temperature was observed after polycondensation due to the disturbance of the ordered arrangement of the hydrophobic chains. The leakage rate of the vesicles before and after condensation was studied by monitoring the increase of fluorescence intensity of water-soluble dye. These vesicles belong to the least permeable ones and the leakage rate can be controlled by varying the degree of condensation or the temperature.

  15. Nanoassemblies from amphiphilic cytarabine prodrug for leukemia targeted therapy. (United States)

    Liu, Jing; Zhao, Dujuan; He, Wenxiu; Zhang, Huiyuan; Li, Zhonghao; Luan, Yuxia


    The anti-leukemia effect of cytarabine (Ara-C) is severely restricted by its high hydrophilic properties and rapid plasma degradation. Herein, a novel amphiphilic small molecular prodrug of Ara-C was developed by coupling a short aliphatic chain, hexanoic acid (HA) to 4-NH2 of the parent drug. Based on the amphiphilic nature, the resulting bioconjugate (HA-Ara) could spontaneously self-assemble into stable spherical nanoassemblies (NAs) with an extremely high drug loading (∼71wt%). Moreover, folate receptor (FR)-targeting NAs with high grafting efficient folic acid - bovine serum albumin (FA-BSA) conjugate immobilized on the surface (NAs/FA-BSA) was prepared. The results of MTT assays on FR-positive K562 cells and FR-negative A549 cells demonstrated higher cytotoxicity of HA-Ara NAs than the native drug. Especially, the IC50 values revealed that NAs/FA-BSA was 3 and 2-fold effective than non-targeted NAs after 24 and 48h treatment with K562 cells, respectively indicating FR-mediated enhanced anti-tumor efficacy. In vitro cellular uptake, larger accumulation of HA-Ara NAs were observed in comparative with the free FITC and the results further confirmed the selective uptake of NAs/FA-BSA in folate receptor enriched cancer cells. Above all, self-assembled HA-Ara NAs exhibited potential superiority for Ara-C delivery and FA-modified NAs would be an excellent candidate for targeting leukemia therapy.


    Institute of Scientific and Technical Information of China (English)

    Xiao-chun Qin; Chun-lai Ren


    Combining self-consistent-field theory and density-functional theory,we systematically study the deformation of copolymer micelles induced by the presence of amphiphilic dimer particles.Due to the amphiphilic nature,dimer particles tend to accumulate onto the interface of the copolymer micelle.With increasing concentration of the symmetric dimer particles,which are made of two identical spherical particles,the micelle deforms from the initial sphere to ellipse,dumbbell,and finally separates into two micelles.Furthermore,asymmetric dimer particles,composed by two particles with different sizes,are considered to investigate the influence of geometry of dimer particles on the deformation of the micelle.It is found that the micelle inclines to deform into dumbbell due to the additional curvature originating in the gathering of asymmetric dimer particles onto the interface of the micelle.The present study on the deformation of micelles is useful to understand the possible shape variation in the course of cell division/fusion.

  17. Polymer fractionation

    Energy Technology Data Exchange (ETDEWEB)

    Hadermann, A. F.


    Soluble polymers are fractionated according to molecular weight by cryogenically comminuting the polymer and introducing the polymer particles, while still in the active state induced by cryogenic grinding, into a liquid having a solvent power selected to produce a coacervate fraction containing high molecular weight polymer species and a dilute polymer solution containing lower molecular weight polymer species. The coacervate may be physically separated from the solution and finds use in the production of antimisting jet fuels and the like.

  18. Influence of Anchoring on Burial Depth of Submarine Pipelines


    Yuan Zhuang; Yang Li; Wei Su


    Since the beginning of the twenty-first century, there has been widespread construction of submarine oil-gas transmission pipelines due to an increase in offshore oil exploration. Vessel anchoring operations are causing more damage to submarine pipelines due to shipping transportation also increasing. Therefore, it is essential that the influence of anchoring on the required burial depth of submarine pipelines is determined. In this paper, mathematical models for ordinary anchoring and emerge...

  19. Anchor-induced chondral damage in the hip. (United States)

    Matsuda, Dean K; Bharam, Srino; White, Brian J; Matsuda, Nicole A; Safran, Marc


    The purpose of this study is to investigate the outcomes from anchor-induced chondral damage of the hip, both with and without frank chondral penetration. A multicenter retrospective case series was performed of patients with chondral deformation or penetration during initial hip arthroscopic surgery. Intra-operative findings, post-surgical clinical courses, hip outcome scores and descriptions of arthroscopic treatment in cases requiring revision surgery and anchor removal are reported. Five patients (three females) of mean age 32 years (range, 16-41 years) had documented anchor-induced chondral damage with mean 3.5 years (range, 1.5-6.0 years) follow-up. The 1 o'clock position (four cases) and anterior and mid-anterior portals (two cases each) were most commonly implicated. Two cases of anchor-induced acetabular chondral deformation without frank penetration had successful clinical and radiographic outcomes, while one case progressed from deformation to chondral penetration with clinical worsening. Of the cases that underwent revision hip arthroscopy, all three had confirmed exposed hard anchors which were removed. Two patients have had clinical improvement and one patient underwent early total hip arthroplasty. Anchor-induced chondral deformation without frank chondral penetration may be treated with close clinical and radiographic monitoring with a low threshold for revision surgery and anchor removal. Chondral penetration should be treated with immediate removal of offending hard anchor implants. Preventative measures include distal-based portals, small diameter and short anchors, removable hard anchors, soft suture-based anchors, curved drill and anchor insertion instrumentation and attention to safe trajectories while visualizing the acetabular articular surface.

  20. Anchor-induced chondral damage in the hip (United States)

    Matsuda, Dean K.; Bharam, Srino; White, Brian J.; Matsuda, Nicole A.; Safran, Marc


    The purpose of this study is to investigate the outcomes from anchor-induced chondral damage of the hip, both with and without frank chondral penetration. A multicenter retrospective case series was performed of patients with chondral deformation or penetration during initial hip arthroscopic surgery. Intra-operative findings, post-surgical clinical courses, hip outcome scores and descriptions of arthroscopic treatment in cases requiring revision surgery and anchor removal are reported. Five patients (three females) of mean age 32 years (range, 16–41 years) had documented anchor-induced chondral damage with mean 3.5 years (range, 1.5–6.0 years) follow-up. The 1 o'clock position (four cases) and anterior and mid-anterior portals (two cases each) were most commonly implicated. Two cases of anchor-induced acetabular chondral deformation without frank penetration had successful clinical and radiographic outcomes, while one case progressed from deformation to chondral penetration with clinical worsening. Of the cases that underwent revision hip arthroscopy, all three had confirmed exposed hard anchors which were removed. Two patients have had clinical improvement and one patient underwent early total hip arthroplasty. Anchor-induced chondral deformation without frank chondral penetration may be treated with close clinical and radiographic monitoring with a low threshold for revision surgery and anchor removal. Chondral penetration should be treated with immediate removal of offending hard anchor implants. Preventative measures include distal-based portals, small diameter and short anchors, removable hard anchors, soft suture-based anchors, curved drill and anchor insertion instrumentation and attention to safe trajectories while visualizing the acetabular articular surface. PMID:27011815

  1. Synthesis and evaluation of amphiphilic peptides as nanostructures and drug delivery tools (United States)

    Sayeh, Naser Ali

    Intracellular delivery of cell-impermeable compounds in a variety cells using delivery systems have been extensively studied in recent years. Obtaining desirable cellular uptake levels often requires the administration of high quantities of drugs to achieve the expected intracellular biological effect. Thus, improving the translocation process across the plasma membrane will significantly reduce the quantity of required administered drug and consequently minimize the side effects in most of the cases. Efficient delivery of these molecules to the cells and tissues is a difficult challenge. Compounds with low cellular permeability are commonly considered to be of limited therapeutic value. Over the past few decades, several biomedical carriers, such as polymers, nanospheres, nanocapsules, liposomes, micelles, peptides and dendrimers have been widely used to deliver therapeutic and diagnostic agents to the cells. Biomaterials generated from nano-scale compounds have shown some promising data for delivery of many compounds in a number of diseases, such as viral infections, cancer, and genetic disorders. Although much progress has been achieved in this field, many challenges still remain, such as toxicity and limited stability. Liposomes suffer from poor stability in the bloodstream and leakage during storage. They tend to aggregate and fuse with or leak entrapped drugs, especially highly hydrophilic small molecules. For solid lipid nanoparticles (SLNs), drug expulsion after polymorphic transition during storage, inadequate loading capacity, and relatively high water content of the dispersions have been observed. Poly(lactic-coglycolic acid (PLGA) degrades in the body producing its original monomers of lactic acid and glycolic acid, which are the by-products of various metabolic pathways. However, this acidic microenvironment that occurs during degradation could negatively affect the stability of the loaded compound. Dendrimers can carry drugs as complexes or as

  2. AUV Load Separation Motion with Constraint of Anchor Chain

    Institute of Scientific and Technical Information of China (English)

    SHAO Cheng; SONG Bao-wei; DU Xiao-xu; WANG Peng; LI Jia-wang


    Motion equations of AUV(autonomous underwater vehicle) load separation with the constraint of anchor chain is derived. Based on proper engineering assumptions for anchor chain,system viewpoint is used to found the motion equations, and the D'Alembert principle is used to eliminate the constraint force of anchor chain. Based on the equations, the motion simulation is carried out to a certain AUV, which reflects the actual condition, and is used for the reference of resrarching AUV load separation motion with the constraint of anchor chain.

  3. Infrastructure anchor bolt inspection program with NDE applications (United States)

    Fish, Philip E.


    In 1990, Wisconsin Department of Transportation found a high mast light pole with two of six anchor bolts failed. This failure along with published reports from Michigan DOT about anchor bolt failures on cantilever sign structures, raised concern about the quality and condition of anchor bolts on the Wisconsin DOT system. Wisconsin Department of Transportation implemented an Anchor Bolt Inspection Program in 1990 for cantilever sign structures, high mast light towers, interstate light towers, and signal masts. The program requires an experienced inspection team and a practical inspection approach. Inspection preparation includes review of all background information such as design plans, design computations, construction plans, shop plans, and maintenance history. An inspection plan is developed. Special emphasis is placed on determining material type, cut or rolled threads, and type of coating for anchor bolts. Inspection emphasis are on "hands on" and Nondestructive evaluation. Special emphasis is placed on visual conditions of anchor bolts (cut or rolled threads, straightness, corrosion, nut tension etc.) along with ultrasonic inspection. This program places a strong emphasis on Non Destructive Testing (NDT), especially ultrasonic. Procedures and inspection calibrations are developed from similar anchor bolt geometry and material type. Cut notches are placed in the anchor bolts at locations of possible failure. NDT inspection calibrations are performed from these bolts. Report documentation includes all design plans, pictorial documentation of structural deficiencies, sketches, nondestructive evaluation reports, conclusions, and recommendations. This program has been successful in locating failed anchor bolts and critical cracks before failure of an entire structure.

  4. Calculation of prestressed anchor segment by 3D infiniteelement

    Institute of Scientific and Technical Information of China (English)

    Yanfen WANG; Hongyang XIE; Yuanhan WANG


    Based on 1D infinite element theory, the coordinate transformation and shape function of 3D point-radiation 4-node infinite elements were derived.They were coupled with 8-node finite elements to compute the compressive deformation of the prestressed anchor segment. The results indicate that when the prestressed force acts on the anchor segment, the stresses and displacements in the rock around the anchor segment are concentrated in the zone center with the anchor axis and are subjected to exponential decay. Therefore, the stresses and the displacement spindles are formed. The calculation results of the infinite element are close to the theoretical results.

  5. Temperature-Dependent Deicing Properties of Electrostatically Anchored Branched Brush Layers of Poly(ethylene oxide). (United States)

    Heydari, Golrokh; Tyrode, Eric; Visnevskij, Ceslav; Makuska, Ricardas; Claesson, Per M


    The hydration water of hydrophilic polymers freezes at subzero temperatures. The adsorption of such polymers will result in a hydrophilic surface layer that strongly binds water. Provided this interfacial hydration water remains liquidlike at subzero temperatures, its presence could possibly reduce ice adhesion, in particular, if the liquidlike layer is thicker than or comparable to the surface roughness. To explore this idea, a diblock copolymer, having one branched bottle-brush block of poly(ethylene oxide) and one linear cationic block, was electrostatically anchored on flat silica surfaces. The shear ice adhesion strength on such polymer-coated surfaces was investigated down to -25 °C using a homebuilt device. In addition, the temperature dependence of the ice adhesion on surfaces coated with only the cationic block, only the branched bottle-brush block, and with linear poly(ethylene oxide) was investigated. Significant ice adhesion reduction, in particular, at temperatures above -15 °C, was observed on silica surfaces coated with the electrostatically anchored diblock copolymer. Differential scanning calorimetry measurements on bulk polymer solutions demonstrate different thermal transitions of water interacting with branched and linear poly(ethylene oxide) (with hydration water melting points of about -18 and -10 °C, respectively). This difference is consistent with the low shear ice adhesion strength measured on surfaces carrying branched bottle-brush structured poly(ethylene oxide) at -10 °C, whereas no significant adhesion reduction was obtained with linear poly(ethylene oxide) at this temperature. We propose a lubrication effect of the hydration water bound to the branched bottle-brush structured poly(ethylene oxide), which, in the bulk, does not freeze until -18 °C.

  6. Electron paramagnetic resonance study of amphiphiles partitioning behavior in desiccation-tolerant moss during dehydration

    Institute of Scientific and Technical Information of China (English)


    Desiccation tolerance is a crucial characteristic for desert moss surviving in arid regions. Desiccation procedure always induces amphiphiles transferring from the polar cytoplasm into lipid bodies. The behavior of amphiphiles transferring can contribute to the enhancement of desiccation tolerance and the reduction of plasma membrane integrity simultaneously. The effects of amphiphiles partitioning into the lipid phase during water loss has been studied for pollen and seeds using electron paramagnetic resonance (EPR) spectroscopy. However, desiccation-tolerant high plants occur among mosses, several angiosperms and higher plants seeds or pollens. They have different strategies for survival in dehydration and rehydration. A desiccation-tolerant moss Tortula desertorurn was used to investigate the behaviors of amphiphilic molecules during drying by spin label technology. There are small amount of amphiphilic probes partitioning into membrane during moss leaves dehydration, comparing with that in higher plants. Cytoplasm viscosity changed from 1.14 into glass state only dehydration less than 60 min. Moss leaves lost plasma membrane integrity slightly,from 0.115 to 0.237, occurred simultaneously with amphiphiles partition. The results showed the more advantages of mosses than higher plants in adapting fast dehydration. We propose that EPR spin label is feasible for studying the amphiphiles partitioning mechanisms in membrane protection and damage for desiccation-tolerant mosses.(C) 2007 Yan Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

  7. Self-assembly of phosphate amphiphiles in mixtures of prebiotically plausible surfactants. (United States)

    Albertsen, A N; Duffy, C D; Sutherland, J D; Monnard, P-A


    The spontaneous formation of closed bilayer structures from prebiotically plausible amphiphiles is an essential requirement for the emergence of early cells on prebiotic Earth. The sources of amphiphiles could have been both endo- and exogenous (accretion of meteorite carbonaceous material or interstellar dust particles). Among all prebiotic possible amphiphile candidates, those containing phosphate are the least investigated species because their self-assembly occurs in a seemingly too narrow range of conditions. The self-assembly of simple phosphate amphiphiles should, however, be of great interest, as contemporary membranes predominantly contain phospholipids. In contrast to common expectations, we show that these amphiphiles can be easily synthesized under prebiotically plausible environmental conditions and can efficiently form bilayer structures in the presence of various co-surfactants across a large range of pH values. Vesiculation was even observed in crude reaction mixtures that contained 1-decanol as the amphiphile precursor. The two best co-surfactants promoted vesicle formation over the entire pH range in aqueous solutions. Expanding the pH range where bilayer membranes self-assemble and remain intact is a prerequisite for the emergence of early cell-like compartments and their preservation under fluctuating environmental conditions. These mixed bilayers also retained small charged solutes, such as dyes. These results demonstrate that alkyl phosphate amphiphiles might have played a significant role as early compartment building blocks.

  8. Synthesis of Polymerizable Amphiphiles with Systematic Variation of Critical Packing Parameters

    Institute of Scientific and Technical Information of China (English)

    M. H. Li; W. L. Yang; J. Qian; C. C. Wang; S. K. Fu


    @@ 1Introduction An amphiphile is a molecule composed of hydrophilic part and hydrophobic part, which are incompatible and tend to separate from each other. The tendency of separation is often promoted by addition of water and sometimes also oil. Under balanced conditions the mixtures form macroscopically homogeneous phases, including isotropic solution phases and liquid crystalline phases. Correlation of the amphiphile structure with its preferred phases could be understood with a simple geometric model[1], which defines a dimensionless Critical Packing Parameter (CPP) to describe the relative bulkiness of the hydrophobic part and the hydrophilic part in an amphiphile. With CPP increasing from a small value to a high value the amphiphile changes from hydrophilic to hydrophobic, its preferred phase structure from direct structures via lamellar structure to reverse structures. This model provides a basis for the molecular design of amphiphiles. To immobilize the microstructure of the phases formed by amphiphiles is a challenge for current material chemists. Techniques of both inorganic polymerization[2] and organic polymerization[3] have been developed. With organic polymerization the molecular design of polymerizable amphiphiles is critical for the successful immobilization of the vulnerable precursor microstructures.

  9. Amphiphilic HPMA-LMA copolymers increase the transport of Rhodamine 123 across a BBB model without harming its barrier integrity. (United States)

    Hemmelmann, Mirjam; Metz, Verena V; Koynov, Kaloian; Blank, Kerstin; Postina, Rolf; Zentel, Rudolf


    The successful non-invasive treatment of diseases associated with the central nervous system (CNS) is generally limited by poor brain permeability of various developed drugs. The blood-brain barrier (BBB) prevents the passage of therapeutics to their site of action. Polymeric drug delivery systems are promising solutions to effectively transport drugs into the brain. We recently showed that amphiphilic random copolymers based on the hydrophilic p(N-(2-hydroxypropyl)-methacrylamide), pHPMA, possessing randomly distributed hydrophobic p(laurylmethacrylate), pLMA, are able to mediate delivery of domperidone into the brain of mice in vivo. To gain further insight into structure-property relations, a library of carefully designed polymers based on p(HPMA) and p(LMA) was synthesized and tested applying an in vitro BBB model which consisted of human brain microvascular endothelial cells (HBMEC). Our model drug Rhodamine 123 (Rh123) exhibits, like domperidone, a low brain permeability since both substances are recognized by efflux transporters at the BBB. Transport studies investigating the impact of the polymer architecture in relation to the content of hydrophobic LMA revealed that random p(HPMA)-co-p(LMA) having 10mol% LMA is the most auspicious system. The copolymer significantly increased the permeability of Rh123 across the HBMEC monolayer whereas transcytosis of the polymer was very low. Further investigations on the mechanism of transport showed that integrity and barrier function of the BBB model were not harmed by the polymer. According to our results, p(HPMA)-co-p(LMA) copolymers are a promising delivery system for neurological therapeutics and their application might open alternative treatment strategies.

  10. Asymmetric and symmetric bolaform supra-amphiphiles: formation of imine bond influenced by aggregation. (United States)

    Wang, Guangtong; Wu, Guanglu; Wang, Zhiqiang; Zhang, Xi


    A series of bolaform supra-amphilphiles with different symmetries were fabricated through dynamic benzoic imine bond formation. The pH dependence of imine formations of these supra-amphiphiles were characterazied. We found that the extent of the imine formation of these supra-amphiphies were different. The supra-amphiphiles with a poorer symmetry always exhibited a lower imine formation at a given pH. Therefore, the varied extent of imine bond formation indicate the different aggregations of these supra-amphilphiles, which are controlled by the molecular symmetry of the supra-amphiphiles.

  11. Stable Vesicles Composed of Mono- or Dicarboxylic Fatty Acids and Trimethylammonium Amphiphiles

    DEFF Research Database (Denmark)

    Caschera, Filippo; Bernardino de la Serna, Jorge; Löffler, Philipp M. G.


    shown to be more stable than those formed by pure fatty acids. Those containing bola-amphiphile even showed encapsulation of a small hydrophilic solute (8-hydroxypyrene-1,3,6-trisulfonic-acid) suggesting a denser packing of the amphiphiles. Compression and kinetics analysis of monolayers composed...... of these amphiphiles mixtures at the air/water interface suggest that the stabilization of the structures can be attributed to two main interactions between headgroups, predominantly the formation of hydrogen bonds between protonated and deprotonated acids and then the additional electrostatic interactions between...

  12. Degradable copolymer based on amphiphilic N-octyl-N-quatenary chitosan and low-molecular weight polyethylenimine for gene delivery

    Directory of Open Access Journals (Sweden)

    Liu CC


    Full Text Available Chengchu Liu,1,2,* Qing Zhu,1,* Wenhui Wu,1 Xiaolin Xu,1 Xiaoyu Wang,3 Shen Gao,3 Kehai Liu11Department of Biopharmaceutics, College of Food Science and Technology, Shanghai Ocean University, Shanghai, China; 2Shanghai Engineering Research Center of Aquatic-Product Processing and Preservation, Shanghai, China; 3Department of Pharmaceutics, Changhai Hospital, Second Military Medical University, Shanghai China*The first two authors contributed equally to this workBackground: Chitosan shows particularly high biocompatibility and fairly low cytotoxicity. However, chitosan is insoluble at physiological pH. Moreover, it lacks charge, so shows poor transfection. In order to develop a new type of gene vector with high transfection efficiency and low cytotoxicity, amphiphilic chitosan was synthesized and linked with low-molecular weight polyethylenimine (PEI.Methods: We first synthesized amphiphilic chitosan – N-octyl-N-quatenary chitosan (OTMCS, then prepared degradable PEI derivates by cross-linking low-molecular weight PEI with amphiphilic chitosan to produce a new polymeric gene vector (OTMCS–PEI. The new gene vector was characterized by various physicochemical methods. We also determined its cytotoxicity and gene transfecton efficiency in vitro and in vivo.Results: The vector showed controlled degradation. It was very stable and showed excellent buffering capacity. The particle sizes of the OTMCS–PEI/DNA complexes were around 150–200 nm with proper zeta potentials from 10 mV to 30 mV. The polymer could protect plasmid DNA from being digested by DNase I at a concentration of 2.25 U DNase I/µg DNA. Furthermore, they were resistant to dissociation induced by 50% fetal bovine serum and 1100 µg/mL sodium heparin. OTMCS–PEI revealed lower cytotoxicity, even at higher doses. Compared with PEI 25 KDa, the OTMCS–PEI/DNA complexes also showed higher transfection efficiency in vitro and in vivo.Conclusion: OTMCS–PEI was a potential candidate as

  13. Synthesis and studies of polypeptide materials: Self-assembled block copolypeptide amphiphiles, DNA-condensing block copolypeptides and membrane-interactive random copolypeptides (United States)

    Wyrsta, Michael Dmytro

    A new class of transition metal initiators for the controlled polymerization of alpha-aminoacid-N-carboxyanhydrides (alpha-NCAs), has been developed by Deming et al. This discovery has allowed for the synthesis of well-defined "protein-like" polymers. Using this chemistry we have made distinct block/random copolypeptides for biomedical applications. Drug delivery, gene delivery, and antimicrobial polymers were the focus of our research efforts. The motivation for the synthesis and study of synthetic polypeptide based materials comes from proteins. Natural proteins are able to adopt a staggeringly large amount of uniquely well-defined folded structures. These structures account for the diversity in properties of proteins. As catalysts (enzymes) natural proteins perform some of the most difficult chemistry with ease and precision at ambient pressures and temperatures. They also exhibit incredible structural properties that directly result from formation of complex hierarchical assemblies. Self-assembling block copolymers were synthesized with various compositions and architectures. In general, di- and tri-block amphiphiles were studied for their self-assembling properties. Both spherical and tubular vesicles were found to assemble from di- and tri-block amphiphiles, respectively. In addition to self-assembly, pH responsiveness was engineered into these amphiphiles by the incorporation of basic residues (lysine) into the hydrophobic block. Another form of self-assembly studied was the condensation of DNA using cationic block copolymers. It was found that cationic block copolymers could condense DNA into compact, ordered, water-soluble aggregates on the nanoscale. These aggregates sufficiently protected DNA from nucleases and yet were susceptible to proteases. These studies form the basis of a gene delivery platform. The ease with which NCAs are polymerized renders them completely amenable to parallel synthetic methods. We have employed this technique to discover new

  14. Hexanoic acid and polyethylene glycol double grafted amphiphilic chitosan for enhanced gene delivery: influence of hydrophobic and hydrophilic substitution degree. (United States)

    Layek, Buddhadev; Haldar, Manas K; Sharma, Gitanjali; Lipp, Lindsey; Mallik, Sanku; Singh, Jagdish


    Gene therapy holds immense potential as a future therapeutic strategy for the treatment of numerous genetic diseases which are incurable to date. Nevertheless, safe and efficient gene delivery remains the most challenging aspects of gene therapy. To overcome this difficulty a series of hexanoic acid (HA) and monomethoxy poly(ethylene glycol) (mPEG) double grafted chitosan-based (HPC) nanomicelles were developed as nonviral gene carrier. HPC polymers with various HA and mPEG substitution degrees were synthesized, and their chemical structures were confirmed by (1)H NMR spectroscopy. HPC nanomicelles exhibited excellent blood compatibility and cell viability, as demonstrated by in vitro hemolysis and MTT assay, respectively. The cationic HPC nanomicelles retained the plasmid DNA (pDNA) binding capacity of chitosan and formed stable HPC/pDNA polyplexes with diameters below 200 nm. Both hydrophobic and hydrophilic substitution resulted in suppressed nonspecific protein adsorption on HPC/pDNA polyplexes and increased pDNA dissociation. However, resistance against DNase I degradation was enhanced by HA conjugation while being inhibited by mPEG substitution. Amphiphilic modification resulted in 3-4.5-fold higher cellular uptake in human embryonic kidney 293 cells (HEK 293) mainly through clathrin-mediated pathway. The optimal HPC/pDNA polyplexes displayed 50-fold and 1.2-fold higher gene transfection compared to unmodified chitosan and Fugene, respectively, in HEK 293 cells. Moreover, both the cellular uptake and in vitro transfection study suggested a clear dependence of gene expression on the extent of HA and mPEG substitution. These findings demonstrate that amphiphilic HPC nanomicelles with the proper combination of HA and mPEG substitution could be used as a promising gene carrier for efficient gene therapy.

  15. Biodegradable Polymers

    Directory of Open Access Journals (Sweden)

    Isabelle Vroman


    Full Text Available Biodegradable materials are used in packaging, agriculture, medicine and other areas. In recent years there has been an increase in interest in biodegradable polymers. Two classes of biodegradable polymers can be distinguished: synthetic or natural polymers. There are polymers produced from feedstocks derived either from petroleum resources (non renewable resources or from biological resources (renewable resources. In general natural polymers offer fewer advantages than synthetic polymers. The following review presents an overview of the different biodegradable polymers that are currently being used and their properties, as well as new developments in their synthesis and applications.

  16. Polymer electronics

    CERN Document Server

    Hsin-Fei, Meng


    Polymer semiconductor is the only semiconductor that can be processed in solution. Electronics made by these flexible materials have many advantages such as large-area solution process, low cost, and high performance. Researchers and companies are increasingly dedicating time and money in polymer electronics. This book focuses on the fundamental materials and device physics of polymer electronics. It describes polymer light-emitting diodes, polymer field-effect transistors, organic vertical transistors, polymer solar cells, and many applications based on polymer electronics. The book also disc

  17. Anchored Instruction in Preservice Educational Technology Classes: A Research Project. (United States)

    Bauer, Jeffrey W.

    This study examined the effectiveness of the anchored instruction (i.e., using a theme or anchor around which various learning activities take place) approach in preparing preservice teachers to integrate technology. Participants were 48 students enrolled in the three sections of a preservice educational technology class during the summer of 1997.…

  18. Effects of Knowledge Abstraction with Anchored Instruction on Learning Transfer. (United States)

    Shih, Yu-Fen; And Others

    Transfer of learning is one of the major purposes of education. Theories and research have tried hard to answer questions such as: how does transfer occur? and how is transfer enhanced? Situated cognitive theory and research about anchored instruction together bring some positive findings. Anchored instruction provides the learner with a situated,…

  19. Using Anchored Instruction to Teach about Assistive Technology. (United States)

    Blackhurst, A. Edward; Morse, Timothy E.


    A training module about assistive technology using an integrated hypermedia format and principles of anchored instruction was developed and field tested with 57 undergraduate students, graduate students, and professionals. The trainees responded positively to the anchored instruction. This article details the module's development, evaluation, and…

  20. Using Anchored Instruction to Evaluate Mathematical Growth and Understanding (United States)

    Kurz, Terri L.; Batarelo, Ivana


    Anchored instruction is designed to present problems in a meaningful context to allow for investigations into real life environments. The Jasper Project was created to allow students to investigate mathematical dilemmas using anchored instruction techniques. This study uses case study methods to examine the perceptions that preservice teachers…

  1. Electrically insulated MLI and thermal anchor (United States)

    Kamiya, Koji; Furukawa, Masato; Hatakenaka, Ryuta; Miyakita, Takeshi; Murakami, Haruyuki; Kizu, Kaname; Tsuchiya, Katsuhiko; Koidea, Yoshihiko; Yoshida, Kiyoshi


    The thermal shield of JT-60SA is kept at 80 K and will use the multilayer insulation (MLI) to reduce radiation heat load to the superconducting coils at 4.4 K from the cryostat at 300 K. Due to plasma pulse operation, the MLI is affected by eddy current in toroidal direction. The MLI is designed to suppress the current by electrically insulating every 20 degree in the toroidal direction by covering the MLI with polyimide films. In this paper, two kinds of designs for the MLI system are proposed, focusing on a way to overlap the layers. A boil-off calorimeter method and temperature measurement has been performed to determine the thermal performance of the MLI system. The design of the electrical insulated thermal anchor between the toroidal field (TF) coil and the thermal shield is also explained.

  2. Stabilizing bolaform amphiphile interfacial assemblies by introducing mesogenic groups. (United States)

    Wang, Mingfeng; Qiu, Dengli; Zou, Bo; Wu, Tao; Zhang, Xi


    We describe the synthesis and characterization of the mesogen-bearing bolaform amphiphile 4,4'-dihydroxybiphenylbis(11-pyridinium-N-yl-undecanoic ester) dibromide (BP-10) and its solid/liquid interfacial self-assembly. Cylindrical micelles are directly observed by atomic force microscopy (AFM) at the interface between mica and the aqueous solution above the critical micelle concentration (cmc). In situ and ex situ AFM studies indicate that the cylindrical micelles are stable both at the mica/solution interface and in the dry state. The enhanced stability of the micellar structures enables a detailed investigation of their self-assembly behavior and supramolecular structures at the interface. The adsorption model proposed here is supported by the variation of the interfacial self-assemblies on changing the solution concentration and substrate temperature.

  3. Bulk modification of PDMS microchips by an amphiphilic copolymer. (United States)

    Xiao, Yan; Yu, Xiao-Dong; Xu, Jing-Juan; Chen, Hong-Yuan


    A simple and rapid bulk-modification method based on adding an amphiphilic copolymer during the fabrication process was employed to modify PDMS microchips. Poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) was used as the additive substance. Compared to the native PDMS microchips, both the contact angle and the EOF of the bulk-modified PDMS microchips decreased. The effects of the additive loading and the pH on the EOF were investigated in detail. The bulk-modified PDMS microchips exhibited reproducible and stable EOF behavior. The application of the bulk-modified PDMS microchips was also studied and the results indicated that they could be successfully used to separate amino acids and to suppress protein adsorption.

  4. Novel polystyrene-anchored zinc complex:Efficient catalyst for phenol oxidation

    Institute of Scientific and Technical Information of China (English)

    Alekha Kumar Sutar a; Yasobanta Das ab; Sasmita Pattnaik a; Anita Routaray a; Nibedita Nath a; Prasanta Rath b; Tungabidya Maharana c


    The novel recyclable free -ONNO- tetradentate Schiff base ligand N,N′-bis(2-hydroxy-3-methox-ybenzaldehyde)4-methylbenzene-1,2-diamine (3-MOBdMBn) was synthesized. Complexation of this ligand with zinc (3-MOBdMBn-Zn) was performed, and the catalytic activity of the complex was evaluated. The polymer-supported analog of this complex (P-3-MOBdMBn-Zn) was synthesized, and its catalytic activity was studied. These free and polymer-anchored zinc complexes were prepared by the reactions of metal solutions with one molar equivalent of unsupported 3-MOBdMBn or P-3-MOBdMBn in methanol under nitrogen. The catalytic activity of 3-MOBdMBn-Zn and P-3-MOBdMBn-Zn was evaluated in phenol oxidation. The activity of P-3-MOBdMBn-Zn was signif-icantly affected by the polymer support, and the rate of phenol conversion was around 50%for polystyrene-supported 3-MOBdMBn. The experimental results indicated that the reaction rate was affected by the polymer support, and the rate of phenol conversion was 1.64 μmol/(L·s) in the presence of polystyrene-supported 3-MOBdMBn.

  5. Breaking anchored droplets in a microfluidic Hele-Shaw cell

    CERN Document Server

    Amselem, Gabriel; Gallaire, François; Baroud, Charles N


    We study microfluidic self digitization in Hele-Shaw cells using pancake droplets anchored to surface tension traps. We show that above a critical flow rate, large anchored droplets break up to form two daughter droplets, one of which remains in the anchor. Below the critical flow velocity for breakup the shape of the anchored drop is given by an elastica equation that depends on the capillary number of the outer fluid. As the velocity crosses the critical value, the equation stops admitting a solution that satisfies the boundary conditions; the drop breaks up in spite of the neck still having finite width. A similar breaking event also takes place between the holes of an array of anchors, which we use to produce a 2D array of stationary drops in situ.

  6. Fundamental behavior of a model biomolecular amphiphile system (United States)

    Haverstick, Kraig Leonard

    An interest in the fundamental interactions between protein components, in the form of either single amino acids or peptides, unifies the work represented in this thesis. These fundamental interactions drive protein folding, enzyme-substrate binding, and cell adhesion to extracellular ligands. The technology of lipidation was used to isolate these protein interactions. Lipidation of a water-soluble amino acid or peptide sequence confined the protein component to the air-water interface or to a self-assembled structure in water. Compression of the molecules at the air-water interface ordered them into a solid-like monolayer, and Langmuir-Blodgett deposition produced a surface modification with protein component presented in a controlled, orderly manner. These molecules have potential applications as biomaterials coatings or drug delivery devices. A method for determination of specific hydrogen bonding interactions through cocrystallization of two complementary peptide sequences is also described. In order to understand the effect of lipidation and lipid structure on peptide behavior, a comprehensive study of tail designs was first undertaken. Tail length, linkage group, linker, spacer length, and headgroup chirality, orientation, and terminal group were systematically varied in simple amino acid amphiphiles. Monolayer assembly, thermal stability, and structure were studied with Langmuir isotherms and Fourier transform infrared spectroscopy. Each part of the tail structure was found to affect monolayer behavior. With lipid effects better understood, peptide amphiphiles were designed, synthesized, and studied using peptide sequences of importance for cell adhesion. The sequences [IV-H1] from type IV collagen and Arg-Gly-Asp (RGD) were lipidated and characterized in monolayers by Langmuir isotherms and Fourier transform infrared spectroscopy. Biological functionality was determined by melanoma cell spreading assays. Peptide presentation was found to be critical for

  7. Antifungal amphiphilic aminoglycoside K20: bioactivities and mechanism of action

    Directory of Open Access Journals (Sweden)

    Sanjib K. Shrestha


    Full Text Available K20 is a novel amphiphilic antifungal aminoglycoside that is synthetically derived from the antibiotic kanamycin A. Reported here are investigations of K20’s antimicrobial activities, cytotoxicity, and fungicidal mechanism of action. In vitro growth inhibitory activities against a variety of human and plant pathogenic yeasts, filamentous fungi, and bacteria were determined using microbroth dilution assays and time-kill curve analyses, and hemolytic and animal cell cytotoxic activities were determined. Effects on Cryptococcus neoformans H-99 infectivity were determined with a preventive murine lung infection model. The antifungal mechanism of action was studied using intact fungal cells, yeast lipid mutants, and small unilamellar lipid vesicles. K20 exhibited broad-spectrum in vitro antifungal activities but not antibacterial activities. Pulmonary, single dose-administration of K20 reduced C. neoformans lung infection rates 4-fold compared to controls. Hemolysis and half-maximal cytotoxicities of mammalian cells occurred at concentrations that were 10 to 32-fold higher than fungicidal MICs. With fluorescein isothiocyanate, 20 to 25 mg/L K20 caused staining of >95% of C. neoformans and Fusarium graminearum cells and at 31.3 mg/L caused rapid leakage (30 to 80% in 15 min of calcein from preloaded small unilamellar lipid vesicles. K20 appears to be a broad-spectrum fungicide, capable of reducing the infectivity of C. neoformans, and exhibits low hemolytic activity and mammalian cell toxicity. It perturbs the plasma membrane by mechanisms that are lipid modulated. K20 is a novel amphiphilic aminoglycoside amenable to scalable production and a potential lead antifungal for therapeutic and crop protection applications.

  8. Amphiphilic, cross-linkable diblock copolymers for multifunctionalized nanoparticles as biological probes (United States)

    Schmidtke, Christian; Pöselt, Elmar; Ostermann, Johannes; Pietsch, Andrea; Kloust, Hauke; Tran, Huong; Schotten, Theo; Bastús, Neus G.; Eggers, Robin; Weller, Horst


    Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging applications. However, preserving their useful properties in an aqueous biological environment remains challenging, even more as NPs therein have to be long-time stable, biocompatible and nontoxic. For in vivo applications, size control is crucial in order to route excretion pathways, e.g. renal clearance vs. hepato-biliary accumulation. Equally necessary, cellular and tissue specific targeting demands suitable linker chemistry for surface functionalization with affinity molecules, like peptides, proteins, carbohydrates and nucleotides. Herein, we report a three stage encapsulation process for NPs comprised of (1) a partial ligand exchange by a multidentate polyolefinic amine ligand, PI-N3, (2) micellar encapsulation with a precisely tuned amphiphilic diblock PI-b-PEG copolymer, in which the PI chains intercalate to the PI-N3 prepolymer and (3) radical cross-linking of the adjacent alkenyl bonds. As a result, water-soluble NPs were obtained, which virtually maintained their primal physical properties and were exceptionally stable in biological media. PEG-terminal functionalization of the diblock PI-b-PEG copolymer with numerous functional groups was mostly straightforward by chain termination of the living anionic polymerization (LAP) with the respective reagents. More complex affinity ligands, e.g. carbohydrates or biotin, were introduced in a two-step process, prior to micellar encapsulation. Advantageously, this pre-assembly approach opens up rapid access to precisely tuned multifunctional NPs, just by using mixtures of diverse functional PI-b-PEG polymers in a combinatorial manner. All constructs showed no toxicity from 0.001 to 1 μM (particle concentration) in standard WST and LDH assays on A549 cells, as well as only marginal unspecific cellular uptake, even in serum-free medium.Nanoparticles (NPs) play an increasingly important role in biological labeling and imaging

  9. Formation of nanoscale networks: selectively swelling amphiphilic block copolymers with CO2-expanded liquids (United States)

    Gong, Jianliang; Zhang, Aijuan; Bai, Hua; Zhang, Qingkun; Du, Can; Li, Lei; Hong, Yanzhen; Li, Jun


    Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO2-expanded liquid (CXL), CO2-methanol. The phase behavior of the CO2-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO2, forming homogeneous CXL under the experimental conditions. When treated with the CO2-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a temperature range of 45-60 °C. The formation mechanism of the network, involving plasticization of PS and selective swelling of P4VP, was proposed. Because the diblock copolymer diffusion process is controlled by the activated hopping of individual block copolymer chains with the thermodynamic barrier for moving PVP segments from one to another, the formation of the network structures is achieved in a short time scale and shows ``thermodynamically restricted'' character. Furthermore, the resulting polymer networks were employed as templates, for the preparation of polypyrrole networks, by an electrochemical polymerization process. The prepared porous polypyrrole film was used to fabricate a chemoresistor-type gas sensor which showed high sensitivity towards ammonia.Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO2-expanded liquid (CXL), CO2-methanol. The phase behavior of the CO2-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO2, forming homogeneous CXL under the experimental conditions. When treated with the CO2-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a

  10. Effects of accuracy motivation and anchoring on metacomprehension judgment and accuracy. (United States)

    Zhao, Qin


    The current research investigates how accuracy motivation impacts anchoring and adjustment in metacomprehension judgment and how accuracy motivation and anchoring affect metacomprehension accuracy. Participants were randomly assigned to one of six conditions produced by the between-subjects factorial design involving accuracy motivation (incentive or no) and peer performance anchor (95%, 55%, or no). Two studies showed that accuracy motivation did not impact anchoring bias, but the adjustment-from-anchor process occurred. Accuracy incentive increased anchor-judgment gap for the 95% anchor but not for the 55% anchor, which induced less certainty about the direction of adjustment. The findings offer support to the integrative theory of anchoring. Additionally, the two studies revealed a "power struggle" between accuracy motivation and anchoring in influencing metacomprehension accuracy. Accuracy motivation could improve metacomprehension accuracy in spite of anchoring effect, but if anchoring effect is too strong, it could overpower the motivation effect. The implications of the findings were discussed.

  11. Grapnel stone anchors from Saurashtra: Remnants of Indo-Arab trade on the Indian coast

    Digital Repository Service at National Institute of Oceanography (India)

    Gaur, A.S.; Sundaresh; Tripati, S.

    Stone anchors have been used as a primary source of information on ancient navigation by marine archaeologists since long. These anchors used by ancient mariners are often noticed underwater at various places across the world. Stone anchors are also...

  12. Amphiphilic macromolecule nanoassemblies suppress smooth muscle cell proliferation and platelet adhesion. (United States)

    Chan, Jennifer W; Lewis, Daniel R; Petersen, Latrisha K; Moghe, Prabhas V; Uhrich, Kathryn E


    While the development of second- and third-generation drug-eluting stents (DES) have significantly improved patient outcomes by reducing smooth muscle cell (SMC) proliferation, DES have also been associated with an increased risk of late-stent thrombosis due to delayed re-endothelialization and hypersensitivity reactions from the drug-polymer coating. Furthermore, DES anti-proliferative agents do not counteract the upstream oxidative stress that triggers the SMC proliferation cascade. In this study, we investigate biocompatible amphiphilic macromolecules (AMs) that address high oxidative lipoprotein microenvironments by competitively binding oxidized lipid receptors and suppressing SMC proliferation with minimal cytotoxicity. To determine the influence of nanoscale assembly on proliferation, micelles and nanoparticles were fabricated from AM unimers containing a phosphonate or carboxylate end-group, a sugar-based hydrophobic domain, and a hydrophilic poly(ethylene glycol) domain. The results indicate that when SMCs are exposed to high levels of oxidized lipid stimuli, nanotherapeutics inhibit lipid uptake, downregulate scavenger receptor expression, and attenuate scavenger receptor gene transcription in SMCs, and thus significantly suppress proliferation. Although both functional end-groups were similarly efficacious, nanoparticles suppressed oxidized lipid uptake and scavenger receptor expression more effectively compared to micelles, indicating the relative importance of formulation characteristics (e.g., higher localized AM concentrations and nanotherapeutic stability) in scavenger receptor binding as compared to AM end-group functionality. Furthermore, AM coatings significantly prevented platelet adhesion to metal, demonstrating its potential as an anti-platelet therapy to treat thrombosis. Thus, AM micelles and NPs can effectively repress early stage SMC proliferation and thrombosis through non-cytotoxic mechanisms, highlighting the promise of nanomedicine for

  13. The Effect of Hydrophilic and Hydrophobic Structure of Amphiphilic Polymeric Micelles on Their Transportation in Rats. (United States)

    Deng, Feiyang; Yu, Chao; Zhang, Hua; Dai, Wenbing; He, Bing; Zheng, Ying; Wang, Xueqing; Zhang, Qiang


    In the previous study, we have clarified how the hydrophilic and hydrophobic structures of amphiphilic polymers impact the transport of their micelles (PEEP-PCL, PEG-PCL and PEG-DSPE micelles) in epithelial MDCK cells (Biomaterials 2013, 34: 6284-6298). In this study, we attempt to clarify the behavior of the three micelles in rats. Coumarin-6 loaded micelles were injected into different sections of intestine of rats and observed by confocal laser scanning microscope (CLSM) or orally administrated and conducted pharmacokinetic study. All of the three kinds of micelles were able to cross the intestinal epithelial cells and enter blood circulation. The PEEP-PCL micelles demonstrated the fastest distribution mainly in duodenum, while the PEGDSPE micelles showed the longest distribution with the highest proportion in ileum of the three. No significant difference was observed among the pharmacokinetic parameters of the three micelles. The results were consistent in the two analysis methods mentioned above, yet there were some differences between in vivo and in vitro results reported previously. It might be the distinction between the environments in MDCK model and intestine that led to the discrepancy. The hydrophobicity of nanoparticles could both enhance uptake and hinder the transport across the mucus. However, there was no intact mucus in MDCK model, which preferred hydrophobic nanoparticles. PEEP was the most hydrophilic material constructing the micelles in the study and its uptake would be increased in rats compared to that in MDCK model, while DSPE was more hydrophobic than the others and MDCK model would be more ideal for its uptake. Considering the inconsistency of the results in the two models, whether the methods researchers were generally using at present were reasonable needs further investigation.

  14. Self-Assembly and Headgroup Effect in Nanostructured Organogels via Cationic Amphiphile-Graphene Oxide Composites (United States)

    Jiao, Tifeng; Wang, Yujin; Zhang, Qingrui; Yan, Xuehai; Zhao, Xiaoqing; Zhou, Jingxin; Gao, Faming


    Self-assembly of hierarchical graphene oxide (GO)-based nanomaterials with novel functions has received a great deal of attentions. In this study, nanostructured organogels based on cationic amphiphile-GO composites were prepared. The gelation behaviors of amphiphile-GO composites in organic solvents can be regulated by changing the headgroups of amphiphiles. Ammonium substituted headgroup in molecular structures in present self-assembled composites is more favorable for the gelation in comparison to pyridinium headgroup. A possible mechanism for headgroup effects on self-assembly and as-prepared nanostructures is proposed. It is believed that the present amphiphile-GO self-assembled system will provide an alternative platform for the design of new GO nanomaterials and soft matters. PMID:24983466

  15. Superior SWNT dispersion by amino acid based amphiphiles: designing biocompatible cationic nanohybrids. (United States)

    Brahmachari, Sayanti; Das, Dibyendu; Das, Prasanta Kumar


    Stable aqueous SWNT dispersion up to 92% was achieved using amino acid based amphiphiles through a structure-property investigation. The nanohybrids showed remarkable serum stability and biocompatibility to mammalian cells.

  16. Tunable catalysts for solvent-free biphasic systems: pickering interfacial catalysts over amphiphilic silica nanoparticles. (United States)

    Zhou, Wen-Juan; Fang, Lin; Fan, Zhaoyu; Albela, Belén; Bonneviot, Laurent; De Campo, Floryan; Pera-Titus, Marc; Clacens, Jean-Marc


    Stabilization of oil/oil Pickering emulsions using robust and recyclable catalytic amphiphilic silica nanoparticles bearing alkyl and propylsulfonic acid groups allows fast and efficient solvent-free acetalization of immiscible long-chain fatty aldehydes with ethylene glycol.

  17. Nucleoside, nucleotide and oligonucleotide based amphiphiles: a successful marriage of nucleic acids with lipids. (United States)

    Gissot, Arnaud; Camplo, Michel; Grinstaff, Mark W; Barthélémy, Philippe


    Amphiphilic molecules based on nucleosides, nucleotides and oligonucleotides are finding more and more biotechnological applications. This Perspective highlights their synthesis, supramolecular organization as well as their applications in the field of biotechnology.

  18. Branched peptide amphiphiles, related epitope compounds and self assembled structures thereof (United States)

    Stupp, Samuel I.; Guler, Mustafa O.


    Branched peptide amphiphilic compounds incorporating one or residues providing a pendant amino group for coupling one or more epitope sequences thereto, such compounds and related compositions for enhanced epitope presentation.

  19. Self-assembling peptide amphiphiles and related methods for growth factor delivery (United States)

    Stupp, Samuel I.; Donners, Jack J. J. M.; Silva, Gabriel A.; Behanna, Heather A.; Anthony, Shawn G.


    Amphiphilic peptide compounds comprising one or more epitope sequences for binding interaction with one or more corresponding growth factors, micellar assemblies of such compounds and related methods of use.

  20. Multifunctional Composites Obtained by Incorporating Nanocrystals into Decorated PVK Polymers

    Directory of Open Access Journals (Sweden)

    Haizhu Sun


    Full Text Available Poly(vinylcarbazole (PVK was decorated with surfactant group to achieve amphiphilic polymer with luminescent property. The composition and properties of the polymers were systematically investigated using FTIR, EA, TGA, UV-Vis, and PL characterizations. Different CdTe nanocrystals (NCs prepared in aqueous medium were directly transferred to organic phase using the PVK-based polymers. The quantum yield of NCs in the composites had been improved by 50% compared with their parent aqueous solution due to the short distance from carbazole moieties to NCs, which facilitated the Förster resonant energy transfer (FRET between them. Moreover, efficient electron transfer at the interface of NCs and polymers had been confirmed which also indicated the application in photovoltaic cell for such composites.

  1. Amphiphilic organoplatinum(II) complexes: Self-assembly in solution and at interfaces (United States)

    Maran, Umamageswaran

    Organoplatinum(II) gemini amphiphiles with three different chain lengths and a predefined angle of 60° are synthesized. Self-organization at the air-water interface is investigated as a function of chain length and reduction in surface area, by using Langmuir-trough techniques. The atomic force microscopy (AFM) images of the transferred Langmuir-Schaefer (LS) films reveals wormlike aggregates for the organoplatinum(II) gemini amphiphiles, possessing hexyloxy- and dodecyloxy-chains. A neutral crown ether functionalized [1+1] facial amphiphile was self-assembled from a flexible 32-membered dibenzo crown ether and a diplatinum acceptor clip. A homologous series of charged triangle-shaped amphiphilic metallomacrocyles was self-assembled from stoichiometric amounts of organoplatinum(II) gemini amphiphiles and bipyridyl donor molecules in quantitative yields. The amphiphilic triangular scaffolds were characterized by multinuclear NMR and ESI-MS. A new amphiphilic organoplatinum(II) precursor with a predefined angle of 90° was synthesized. The precursor was mixed in stoichiometric ratios with two different 3-substituted pyridines and a rigid bipyridyl ligand to construct three charged amphiphilic metallomacrocyles. The computational calculations on the assemblies constructed from flexible 3-substituted pyridines indicate that the assemblies exist largely as chair isomers. The self-organization of the hexacationic triangular amphiphiles at liquid-liquid, air-water and solid-air interfaces was studied using confocal microscopy, in situ Raman spectroscopy, Langmuir-trough techniques, fluorescence spectroscopy and AFM. The amphiphilic triangle with octadecyloxy-chains was found to form a bicontinuous coacervate with pores in a chloroform/water solvent mixture. The pressure-area isotherms revealed formation of surface aggregates at the air-water interface. Fluid AFM studies on the transferred LS layers reveal ridge-like patterns with a flat top. Models were constructed to

  2. Self-assembly of a peptide amphiphile: transition from nanotape fibrils to micelles


    Miravet Celades, Juan Felipe; Escuder Gil, Beatriu; Segarra Maset, María Dolores; Tena Solsona, Marta; Hamley, Ian W; Dehsorkhi, Ashkan; Castelletto, Valeria


    A thermal transition is observed in the peptide amphiphile C16-KTTKS (TFA salt) from nanotapes at 20 °C to micelles at higher temperature (the transition temperature depending on concentration). The formation of extended nanotapes by the acetate salt of this peptide amphiphile, which incorporates a pentapeptide from type I procollagen, has been studied previously [V. Castelletto et al., Chem. Commun., 2010, 46, 9185]. Here, proton NMR and SAXS provide evidence for the TFA salt spherical micel...

  3. Self-restoring polymer brushes under tribological stress and the biomedical applications

    DEFF Research Database (Denmark)

    Røn, Troels; Javakhishvili, Irakli; Hvilsted, Søren;


    ”, the hydrophilic polymer chains of amphiphilic diblock copolymers dispersed within a poly(dimethylsiloxane) (PDMS) network are selectively segregated upon exposure to aqueous solution. This allows formation of extremely stable brush-like polymer layers. Tribological application of inverted grafting-to approach......For biological and mechanical systems involving moving parts, surface slipperiness is often a critical attribute for their optimal functions. Surface grafting with hydrophilic polymers is a powerful means to render materials slippery in aqueous environment. In “inverted grafting-to approach...

  4. Long-distance electronic energy transfer in light-harvesting supramolecular polymers. (United States)

    Winiger, Christian B; Li, Shaoguang; Kumar, Ganesh R; Langenegger, Simon M; Häner, Robert


    The efficient collection of solar energy relies on the design and construction of well-organized light-harvesting systems. Herein we report that supramolecular phenanthrene polymers doped with pyrene are effective collectors of light energy. The linear polymers are formed through the assembly of short amphiphilic oligomers in water. Absorption of light by phenanthrene residues is followed by electronic energy transfer along the polymer over long distances (>100 nm) to the accepting pyrene molecules. The high efficiency of the energy transfer, which is documented by large fluorescence quantum yields, suggests a quantum coherent process.

  5. Stable and robust nanotubes formed from self-assembled polymer membranes (United States)

    Helmerson, Kristian; Reiner, Joseph E.; Kishore, Rani B.; Jofre, Ana; Allegrini, Maria; Pfefferkorn, Candace; Wells, Jeffrey M.


    We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. We stabilize the pulled nanotubes by subsequent chemical cross-linking. The cross-linked nanotubes are extremely robust and can be moved to another medium for use elsewhere. We demonstrate the ability to form networks of polymer nanotubes and polymersomes by optical manipulation. The aqueous core of the polymer nanotubes together with their robust character makes them interesting candidates for nanofluidics and other applications in biotechnology.

  6. Synthesis of polymer-biohybrids: from small to giant surfactants. (United States)

    Reynhout, Irene C; Cornelissen, Jeroen J L M; Nolte, Roeland J M


    Amphiphiles or surfactants, more popularly known as soaps, are among the oldest known chemical compounds used by man. Written text on a clay tablet dated to 2200 B.C. indicates that the Babylonians were familiar with soap-like substances. According to the Ebers papyrus (1550 B.C.), the ancient Egyptians bathed regularly in a mixture of animal oils, vegetable extracts, and alkaline salts, and a soap factory with bars of scented soap was found in the ruins of Pompeii (79 A.D.). In modern times, the use of soap has become universal, and we now understand reasonably well what happens when soap molecules are dispersed in aqueous solution and how the cleaning properties of soap work. The latter is related to the surface-active behavior of soap molecules, which is a result of their amphiphilic, also called amphipathic, character. Although the cleaning aspect is still an important issue, scientists are increasingly focusing on other properties of soaps, for example, self-assembling behavior and how this can be used in the design and non-covalent synthesis of new (macro)molecular architectures. These new molecules can be employed in nanotechnology and drug delivery, among other applications. This Account will focus on three different classes of amphiphiles. The first is the low molecular weight amphiphiles, also called classical amphiphiles in this context. A short overview will be given on the research carried out by our group and others on the self-assembly behavior and properties of these compounds; in particular, we focus on the ones that can be stabilized by polymerization (polymerized vesicles). Next, we will introduce the still relatively young field of superamphiphiles, macromolecules consisting of a hydrophobic and a hydrophilic polymeric block. Finally, and this constitutes the main part of this Account, we will provide an overview of a new class of amphiphiles, the so-called giant amphiphiles. These macromolecules have an enzyme or protein as the polar head group

  7. Mimicking cell membrane-like structures on alkylated silicon surfaces by peptide amphiphiles

    Energy Technology Data Exchange (ETDEWEB)

    Shamsi, Fahimeh, E-mail: [Biophysics and Bioengineering, School of Chemical and Biomolecular Engineering, University of Sydney, Sydney, NSW 2006 (Australia); Coster, Hans G.L. [Biophysics and Bioengineering, School of Chemical and Biomolecular Engineering, University of Sydney, Sydney, NSW 2006 (Australia)


    Highlights: {yields} Lipidated peptide amphiphiles were hydrophobically attached onto an alkylated surface. {yields} Morphology of nanofibres of the peptide amphiles depended on the acyl chain length. {yields} We show that extended 2D analogues of the nanofibre surface can be constructed. {yields} Peptide amphiphiles with shorter acyl chains formed more homogeneous layers. - Abstract: We present a new strategy for flexible attachment of peptide amphiphiles on functionalized silicon surfaces. This method involves the production of an alkylated surface on which a lipidated peptide can then be attached through hydrophobic interaction. We applied this to two derivatives of amphiphilic peptide molecules with the same amino acid sequence (A-A-A-A-G-G-G-E-R-G-D) but different in alkyl chain lengths (palmitic acid, undecanoic acid). The basis of this work was to develop substrates which are more biocompatible and bioactive. The ultra-thin peptide amphiphile films were characterized using electrical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (ATR-FTIR) spectroscopy. The results demonstrated that the length of the alkyl chain in the peptide amphiphile affects the packing and coverage of the peptides on the silicon surface.

  8. Distributed localization for anchor-free sensor networks

    Institute of Scientific and Technical Information of China (English)

    Cui Xunxue; Shan Zhiguan; Liu Jianjun


    Geographic location of nodes is very useful in a sensor network. Previous localization algorithms assume that there exist some anchor nodes in this kind of network, and then other nodes are estimated to create their coordinates. Once there are not anchors to be deployed, those localization algorithms will be invalidated. Many papers in this field focus on anchor-based solutions. The use of anchors introduces many limitations, since anchors require external equipments such as global position system, cause additional power consumption. A novel positioning algorithm is proposed to use a virtual coordinate system based on a new concept-virtual anchor. It is executed in a distributed fashion according to the connectivity of a node and the measured distances to its neighbors. Both the adjacent member information and the ranging distance result are combined to generate the estimated position of a network, one of which is independently adopted for localization previously. At the position refinement stage the intermediate estimation of a node begins to be evaluated on its reliability for position mutation; thus the positioning optimization process of the whole network is avoided falling into a local optimal solution. Simulation results prove that the algorithm can resolve the distributed localization problem for anchor-free sensor networks, and is superior to previous methods in terms of its positioning capability under a variety of circumstances.

  9. The effect of hydrophilic and hydrophobic structure of amphiphilic polymeric micelles on their transport in epithelial MDCK cells. (United States)

    Yu, Chao; He, Bing; Xiong, Meng-Hua; Zhang, Hua; Yuan, Lan; Ma, Ling; Dai, Wen-Bing; Wang, Jun; Wang, Xing-Lin; Wang, Xue-Qing; Zhang, Qiang


    The interaction of nanocarriers with cells including their transcellular behavior is vital not only for a drug delivery system, but also for the safety of nanomaterials. In an attempt to clarify how the structures of polymers impact the transport mechanisms of their nanocarriers in epithelial cells, three amphiphilic polymers (PEEP-PCL, PEG-PCL and PEG-DSPE) with different hydrophilic or hydrophobic blocks were synthesized or chosen to form different micelle systems here. The endocytosis, exocytosis, intracellular colocalization, paracellular permeability and transcytosis of these micelle systems were compared using Förster resonance energy transfer analysis, real-time confocal images, colocalization assay, transepithelial electrical resistance study, and so on. All micelle systems were found intact during the studies with cells. The endocytosis and exocytosis studies with undifferentiated MDCK cells and the transcytosis study with differentiated MDCK monolayers all indicated the fact that PEG-DSPE micelles achieved the most and fastest transport, followed by PEG-PCL and PEEP-PCL in order. These might be because DSPE has higher hydrophobicity than PCL while PEG has lower hydrophilicity than PEEP. Different in hydrophilic or hydrophobic structures, all kinds of micelles demonstrated similar pathways during endocytosis and exocytosis, both caveolae- and clathrin-mediated but with difference in degree. The colocalization studies revealed different behaviors in intracellular trafficking among the three polymer micelles, suggesting the decisive role of hydrophilic shells on this process. Finally, all micelle systems did not impact the paracellular permeability of test cell monolayer. In conclusion, the hydrophilic and hydrophobic structures of test micelles could influence their transport ability, intracellular trafficking and the transport level under each pathway in MDCK cells.

  10. Amphiphilic star block copolymers as gene carrier Part I: Synthesis via ATRP using calix[4]resorcinarene-based initiators and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Anna; Xue, Yan; Wei, Dafu [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Guan, Yong, E-mail: [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Xiao, Huining [Department of Chemical Engineering, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3 (Canada)


    In this work, a cationic star polymer [poly(2-dimethylamino)ethyl methacrylate (PDMAEMA)] was prepared via atom transfer radical polymerization (ATRP), using brominated calix[4]resorcinarene as an initiator. Hydrophobic moieties, methyl methacrylate (MMA) and butyl acrylate (BA), were further incorporated via 'one-pot' method. Well-defined eight-armed star block copolymers bearing hydrophilic blocks inside and hydrophobic blocks outside were synthesized. The molecular weight, particle size, electrophoretic mobility and apparent charge density were determined by gel permeation chromatography (GPC), dynamic light scattering (DLS), phase analysis light scattering (PALS) and colloidal titration, respectively. The zeta potentials and apparent charge densities of the products exhibited the characteristics of polyelectrolyte. The incorporation of hydrophobic moieties generated electrostatic screening effect. The as-synthesized amphiphilic star copolymer is promising as a thermo-sensitive gene carrier for gene therapy. Highlights: Black-Right-Pointing-Pointer Amphiphilic cationic star block copolymers with well-controlled structures were prepared via ATRP. Black-Right-Pointing-Pointer The molecular structures and properties of the initiator and copolymers were systematically characterized. Black-Right-Pointing-Pointer The products exhibited the positive charged character, and hydrophobic moieties generated electrostatic screening effect.

  11. Neurostimulation leads, intrathecal catheters and anchoring devices evolution

    Directory of Open Access Journals (Sweden)

    Laura Demartini


    Full Text Available Many scientific studies highlight the usefulness of spinal cord stimulation and intrathecal therapy for the management of chronic pain syndromes resistant to pharmacological or less invasive interventional therapies. One of the possible complications of these techniques, reported in literature, is migration of the lead or catheter; thus the use of an anchoring system is considered mandatory. Every company that produces devices for neurostimulation or neuromodulation provides various anchoring devices evolved over time. In the study, the authors discuss about the most common anchoring devices based on their clinical experience.


    NARCIS (Netherlands)

    Morichere, D; Malliaras, G.G; Krasnikov, V.V.; Bolink, H.J; Hadziioannou, G


    The use of polymers as photorefractive materials offers many advantages : flexibility in synthesis, doping, processing and low cost. The required functionalities responsible for photorefractivity, namely charge generation, transport, trapping and linear electrooptic effect are given in the polymer w

  13. Self-assembly of amphiphilic molecules in organic liquids (United States)

    Tung, Shih-Huang


    Amphiphilic molecules are well-known for their ability to self-assemble in water to form structures such as micelles and vesicles. In comparison, much less is known about amphiphilic self-assembly in nonpolar organic liquids. Such "reverse" self assembly can produce many of the counterparts to structures found in water. In this dissertation, we focus on the formation and dynamics of such reverse structures. We seek to obtain fundamental insight into the driving forces for reverse self-assembly processes. Three specific types of reverse structures are studied: (a) reverse wormlike micelles, i.e., long, flexible micellar chains; (b) reverse vesicles, i.e., hollow containers enclosed by reverse bilayers; and (c) organogel networks. While our focus is on the fundamentals, we note that reverse structures can be useful in a variety of applications ranging from drug delivery, controlled release, hosts for enzymatic reactions, and templates for nanomaterials synthesis. In the first part of this study, we describe a new route for forming reverse wormlike micelles in nonpolar organic liquids. This route involves the addition of trace amounts of a bile salt to solutions of the phospholipid, lecithin. We show that bile salts, due to their unique "facially amphiphilic" structure, can promote the aggregation of lecithin molecules into these reverse micellar chains. The resulting samples are viscoelastic and show interesting rheological properties. Unusual trends are seen in the temperature dependence of their rheology, which indicates the importance of hydrogen-bonding interactions in the formation of these micelles. Another remarkable feature of their rheology is the presence of strain-stiffening, where the material becomes stiffer at high deformations. Strain-stiffening has been seen before for elastic gels of biopolymers; here, we demonstrate the same properties for viscoelastic micellar solutions. The second reverse aggregate we deal with is the reverse vesicle. We present a

  14. Anchored boundary conditions for locally isostatic networks (United States)

    Theran, Louis; Nixon, Anthony; Ross, Elissa; Sadjadi, Mahdi; Servatius, Brigitte; Thorpe, M. F.


    Finite pieces of locally isostatic networks have a large number of floppy modes because of missing constraints at the surface. Here we show that by imposing suitable boundary conditions at the surface the network can be rendered effectively isostatic. We refer to these as anchored boundary conditions. An important example is formed by a two-dimensional network of corner sharing triangles, which is the focus of this paper. Another way of rendering such networks isostatic is by adding an external wire along which all unpinned vertices can slide (sliding boundary conditions). This approach also allows for the incorporation of boundaries associated with internal holes and complex sample geometries, which are illustrated with examples. The recent synthesis of bilayers of vitreous silica has provided impetus for this work. Experimental results from the imaging of finite pieces at the atomic level need such boundary conditions, if the observed structure is to be computer refined so that the interior atoms have the perception of being in an infinite isostatic environment.

  15. Polymer Brushes

    NARCIS (Netherlands)

    Vos, de W.M.; Kleijn, J.M.; Keizer, de A.; Cosgrove, T.; Cohen Stuart, M.A.


    A polymer brush can be defined as a dense array of polymers end-attached to an interface that stretch out into the surrounding medium. Polymer brushes have been investigated for the past 30 years and have shown to be an extremely useful tool to control interfacial properties. This review is intended

  16. Anchoring of development workings in a zone of influence of mining in case of the level anchoring system (United States)

    Demin, V. F.; Fofanov, O. B.; Demina, T. V.; Yavorskiy, V. V.


    Regularities of the change of the stress-strain state of coal containing rock masses, depending on mining-geological factors, were revealed. These factors allow establishing rational parameters of anchoring of wall rocks to enhance the stability of development workings. Specific conditions of the deflected mode, displays of rock pressure, terms of maintenance depending on technological parameters are investigated. Researches allowed determining the degree of their development influence on the efficiency of application of the anchoring of the hollow making and will allow a reasonable application of anchoring certificates, provide stability of the rocks mining and reduce expenses on its realization and maintenance.

  17. Effect of a preload force on anchor system frequency

    Institute of Scientific and Technical Information of China (English)

    Lu Aihong; Xu Jinhai; Liu Haishun


    The interrelationship between preload forces and natural frequencies of anchors was obtained from the structure of an anchor and its mechanical characteristics.We established a numerical model for the dynamic analysis of a bolt support system taking into consideration the working surroundings of the anchor.The natural frequency distribution of the system under various preload forces of the anchor was analyzed with ANSYS.Our results show that each order of the system frequency varied with an increase in preload forces.A single order frequency decreased with an increase in the preload force.A preload force affected low-order frequencies more than high-order frequencies.We obtained a functional relationship by fitting preload forces and fundamental frequencies,which was in agreement with our theoretical considerations.This study provides theoretical support for the detection of preload forces.

  18. Reaching the top: career anchors and professional development in nursing. (United States)

    Kaplan, Ruth; Shmulevitz, Carmela; Raviv, Dennie


    This study, based on Shein's conceptual theory of career anchors, examined the relationship between career anchors, professional development and emerging career patterns for graduates of 12 consecutive two year second career programs in nursing (N=231) compared to graduates of concurrent four year academic programs (N=273). A 2-group comparison design was used and data collection tools included a demographic profile, a professional profile and a career anchor questionnaire. Statistically significant differences were found in regard to career anchors (pdevelopment (pnurses were specialization and lifestyle where academic graduates chose management, autonomy and service. Academics displayed a statistically significant preference for administrative specialization (34%) compared to the second career tract (6.5%). Researchers propose that each group develops differently and contributes to the workplace and the importance of both certification and academic incentives to ensure recruitment.

  19. Anchor-induced chondral damage in the hip


    Matsuda, Dean K.; Bharam, Srino; White, Brian J.; Matsuda, Nicole A.; SAFRAN, Marc


    The purpose of this study is to investigate the outcomes from anchor-induced chondral damage of the hip, both with and without frank chondral penetration. A multicenter retrospective case series was performed of patients with chondral deformation or penetration during initial hip arthroscopic surgery. Intra-operative findings, post-surgical clinical courses, hip outcome scores and descriptions of arthroscopic treatment in cases requiring revision surgery and anchor removal are reported. Five ...

  20. Medial rectus muscle anchoring in complete oculomotor nerve palsy. (United States)

    Lee, Si Hyung; Chang, Jee Ho


    The management of exotropia resulting from complete oculomotor nerve palsy is challenging. Conventional therapeutic interventions, including supramaximal resection and recession, superior oblique tendon resection and transposition, and several ocular anchoring procedures have yielded less-than-adequate results. Here we describe a novel surgical technique of anchoring the medial rectus muscle to the medial orbital wall in combination with lateral rectus disinsertion and reattachment to the lateral orbital wall.

  1. Behavioral Biases of Individual Investors: The Effect of Anchoring

    Directory of Open Access Journals (Sweden)

    Salma Zaiane


    Full Text Available The objective of this paper is to investigate the presence of the anchoring bias in the financial decision making of individual investors. A survey study is carried out to find out how the studied bias affects the investment behavior on the Tunisian stock market. The survey is for exploratory purpose and it is based on multiple factorial correspondence analyses. The results reveal that Tunisian investors do not suffer from the anchoring bias.

  2. Self-assembly of model amphiphilic Janus particles. (United States)

    Rosenthal, Gerald; Gubbins, Keith E; Klapp, Sabine H L


    We apply molecular dynamics simulations to investigate the structure formation of amphiphilic Janus particles in the bulk phase. The Janus particles are modeled as (soft) spheres composed of a hydrophilic and hydrophobic part. Their orientation is described by a vector representing an internal degree of freedom. Investigating energy fluctuations and cluster size distributions, we determine the aggregation line in a temperature-density-diagram, where the reduced temperature is an inverse measure for the anisotropic coupling. Below this aggregation line clusters of various sizes depending on density and reduced temperature are found. For low densities in the range ρ∗ ≤ 0.3, the cluster size distribution has a broad maximum, indicating simultaneous existence of various cluster sizes between 5 and 10. We find no hint of a condensation transition of these clustered systems. In the case of higher densities (ρ∗ = 0.5 and 0.6), the cluster size distribution shows an extremely narrow peak at clusters of size 13. In these icosahedrons, the particles are arranged in a closed-packed manner, thereby maximizing the number of bonds. Analyzing the translational mean-square displacement we also observe indications of hindered diffusion due to aggregation.

  3. Preparation and self-assembly of amphiphilic polylysine dendrons

    DEFF Research Database (Denmark)

    Mirsharghi, Sahar; Knudsen, Kenneth D.; Bagherifam, Shahla


    Polylysine dendrons with lipid tails prepared by divergent solid-phase synthesis showed self-assembling properties in aqueous solutions., Herein, we present the synthesis of new amphiphilic polylysine dendrons with variable alkyl chain lengths (C1–C18) at the C-terminal. The dendrons were synthes...... and 20 μM concentrations. The dendrons showed low cytotoxicity, displaying cell viability well above 80%....... were influenced by the length of the alkyl chain and the generation number (Gn). Increasing the temperature and concentration did not have significant impact on the hydrodynamic diameter, but the self-assembling properties were influenced by the pH value. This demonstrated the need for positively...... with alkyl chain lengths above C12 are ascribed to intermicellar aggregates stabilized by hydrophobic and electrostatic forces in accordance with the observed pH effect. Finally, the cytotoxicity of the dendrons was evaluated in mouse fibroblast (NIH/3T3) and human embryonic kidney (HEK 293T) cells at 5, 10...

  4. Tissue Regeneration through Self-Assembled Peptide Amphiphile Nanofibers

    Directory of Open Access Journals (Sweden)

    Hossein Hosseinkhani


    Full Text Available Introduction: In the present study, we hypothesized that a novelapproach to promote vascularization would be to create injectablethree dimensional (3-D scaffolds within growth factor that enhancethe sustained release of growth factor and induce the angiogenesis.Material and Methods: We demonstrate that a 3-D scaffold can beformed by mixing of peptide-amphiphile (PA aqueous solution withhepatocyte growth factor (HGF solution. PA was synthesized bystandard solid phase chemistry that ends with the alkylation of theNH2 terminus of the peptide. The sequence of arginine-glycineasparticacid (RGD was included in peptide design as well. A 3-Dnetwork of nanofibers was formed by mixing HGF suspensions withdilute aqueous solution of PA.Results: Scanning electron microscopy (SEM examination revealedthe formation of fibrous assemblies with an extremely high aspectratio and high surface areas with mean diameter of less than 200 nm.In vitro HGF release profile of 3-D nanofibers was investigated whileangiogenesis induced by the released HGF was being assessed. Invivo potential ability of PA nanofibers to induce angiogenesis wasassessed through subcutaneous injection of PA solution, HGFsolution, and PA in combination with HGF solutions. Injection of PAwith HGF induced significant angiogenesis around the injected site,in marked contrast to HGF injection alone and PA injection alone.Conclusion: The combination of HGF-induced angiogenesis is apromising procedure to improve tissue regeneration.

  5. Optimization of hypocrellin B derivative amphiphilicity and biological activity

    Institute of Scientific and Technical Information of China (English)

    LIU Xin; XIE Jie; ZHANG LuYong; CHEN HongXia; GU Ying; ZHAO JingQuan


    To satisfy the dual requirements of the fluent transportation in blood and the affinity to the target tissues of vascular diseases, hypocrellin derivatives with optimized amphiphilicity are expected. In this work, 3-amino-1-propanesulfonic acid and 4-amino-1-butanesulfonic acid substituted hypocrellin B,named compounds 1 and 2, were designed, synthesized in high yields and characterized. Besides greatly strengthened red absorption, the maximum solubility of compound 2 in phosphate buffered saline (PBS) is 4.2 mg/mL which is just enough to prepare an aqueous solution for intravenous injection in clinically acceptable concentration, while the partition coefficient between n-octanol and PBS,5.6, benefits the cell-uptake and biological activity as well. Furthermore, EPR measurements reveal that the photosensitization activities of the two compounds to generate semiquinone anion radicals, superoxide anion radicals and singlet oxygen are a little bit higher than those of taurine substituted hypocrellin B (THB), but the photodynamic activities to human lung cancer A549 cells are several times that of THB, mainly due to increases in lipophilicity and cell-uptake.

  6. Amphiphilic organic ion pairs in solution: a theoretical study. (United States)

    Pradines, Vincent; Poteau, Romuald; Pimienta, Veronique


    The macroscopic manifestation of hydrophobic interactions for amphiphilic organic ion pairs (tetraalkylammonium-anion) has been shown experimentally by measuring their association constants and their affinity with the organic phase. Beyond a certain size, there is a direct relation between association constants and chain lengths in tetraalkylammonium ions. We propose to cast a bridge between these results and geometrical properties considered at the level of a single ion pair by means of quantum chemistry calculations performed on model systems: trimethylalkylammonium-pentyl sulfate instead of tetraalkylammonium-dodecyl sulfate. Two limiting cases are considered: head-to-head configurations, which yield an optimal electrostatic interaction between polar heads, and parallel configurations with a balance between electrostatic and hydrophobic interactions. All properties (geometries, complexation energies, and atomic charges) were obtained at the MP2 level of calculation, with water described by a continuum model (CPCM). Dispersion forces link hydrocarbon chains of tetraalkylammonium ions and pentyl sulfate, thus yielding (for the largest ion pairs) parallel configurations favored with respect to head-to-head geometries by solute-solvent electrostatic interactions. Given the small experimental association energies, we probe the accuracy limit of the MP2 and CPCM methods. However, clear trends are obtained as a function of chain length, which agree with the experimental observations. The calculated monotonic stabilization of ion pairs when the hydrocarbon chain increases in length is discussed in terms of electrostatic interactions (between ions and between ion pairs and water), dispersion forces, and cavitation energies.

  7. Photochemical Isomerization and Topochemical Polymerization of the Programmed Asymmetric Amphiphiles (United States)

    Kim, Dae-Yoon; Lee, Sang-A.; Jung, Daseal; Jeong, Kwang-Un


    For the advancement in multi-stimuli responsive optical devices, we report the elaborate molecular engineering of the dual photo-functionalized amphiphile (abbreviated as AZ1DA) containing both a photo-isomerizable azobenzene and a photo-polymerizable diacetylene. To achieve the efficient photochemical reactions in thin solid films, the self-assembly of AZ1DA molecules into the ordered phases should be precisely controlled and efficiently utilized. First, the remote-controllable light shutter is successfully demonstrated based on the reversible trans-cis photo-isomerization of azobenzene group in the smectic A mesophase. Second, the self-organized monoclinic crystal phase allows us to validate the photo-polymerization of diacetylene moiety for the photo-patterned thin films and the thermo-responsible color switches. From the demonstrations of optically tunable thin films, it is realized that the construction of strong relationships between chemical structures, molecular packing structures and physical properties of the programmed molecules is the core research for the development of smart and multifunctional soft materials.

  8. Dynamic in vivo biocompatibility of angiogenic peptide amphiphile nanofibers. (United States)

    Ghanaati, Shahram; Webber, Matthew J; Unger, Ronald E; Orth, Carina; Hulvat, James F; Kiehna, Sarah E; Barbeck, Mike; Rasic, Angela; Stupp, Samuel I; Kirkpatrick, C James


    Biomaterials that promote angiogenesis have great potential in regenerative medicine for rapid revascularization of damaged tissue, survival of transplanted cells, and healing of chronic wounds. Supramolecular nanofibers formed by self-assembly of a heparin-binding peptide amphiphile and heparan sulfate-like glycosaminoglycans were evaluated here using a dorsal skinfold chamber model to dynamically monitor the interaction between the nanofiber gel and the microcirculation, representing a novel application of this model. We paired this model with a conventional subcutaneous implantation model for static histological assessment of the interactions between the gel and host tissue. In the static analysis, the heparan sulfate-containing nanofiber gels were found to persist in the tissue for up to 30 days and revealed excellent biocompatibility. Strikingly, as the nanofiber gel biodegraded, we observed the formation of a de novo vascularized connective tissue. In the dynamic experiments using the dorsal skinfold chamber, the material again demonstrated good biocompatibility, with minimal dilation of the microcirculation and only a few adherent leukocytes, monitored through intravital fluorescence microscopy. The new application of the dorsal skinfold model corroborated our findings from the traditional static histology, demonstrating the potential use of this technique to dynamically evaluate the biocompatibility of materials. The observed biocompatibility and development of new vascularized tissue using both techniques demonstrates the potential of these angiogenesis-promoting materials for a host of regenerative strategies.

  9. Use of polymer nanoparticles as functional nano-absorbents for low-molecular weight hydrophobic pollutants. (United States)

    Kim, Ju-Young; Wainaina, James; Kim, Jung-Hun; Shim, Jin-Kie


    To use amphiphilic polymer nanoparticles as a new nano-absorbent for improving environmental process, urethane acrylate nonionomer (UAN) chain having hydrophobic polypropylene oxide-based segment and hydrophilic polyethylene oxide-based segment at the same backbone was synthesized and dispersed as nanoparticles at water phase without using a surfactant or dispersion agent. These UAN nanoparticles were converted to crosslinked amphiphilic polymer (CAP) nanoparticles through soap-free emulsion polymerization and suspension agent-free suspension polymerization process. Emulsion polymerization process exhibited higher conversion of polymerization compared to suspension polymerization process. CAP nanoparticles showed interfacial activity and solubilize hydrophobic pollutants (phenanthrene and toluene) like surfactant micelles. This result indicates possible application of CAP nanoparticles as nano-absorbent for improving efficiency of soil washing and micellar-enhanced ultrafiltration (MEUF) process.

  10. Increasing the Fill Factor of Inverted P3HT:PCBM Solar Cells Through Surface Modification of Al-Doped ZnO via Phosphonic Acid-Anchored C60 SAMs

    DEFF Research Database (Denmark)

    Stubhan, Tobias; Salinas, Michael; Ebel, Alexander;


    The influence of aluminum-doped zinc oxide (AZO) electron extraction layers modified with self-assembled monolayers (SAMs) on inverted polymer solar cells is investigated. It is found that AZO modification with phosphonic acid-anchored Fullerene–SAMs leads to a reduction of the series resistance,...

  11. Poor anchoring limits dyslexics' perceptual, memory, and reading skills. (United States)

    Oganian, Yulia; Ahissar, Merav


    The basic deficits underlying the severe and persistent reading difficulties in dyslexia are still highly debated. One of the major topics of debate is whether these deficits are language specific, or affect both verbal and non-verbal stimuli. Recently, Ahissar and colleagues proposed the "anchoring-deficit hypothesis" (Ahissar, Lubin, Putter-Katz, & Banai, 2006), which suggests that dyslexics have a general difficulty in automatic extraction of stimulus regularities from auditory inputs. This hypothesis explained a broad range of dyslexics' verbal and non-verbal difficulties. However, it was not directly tested in the context of reading and verbal memory, which poses the main stumbling blocks to dyslexics. Here we assessed the abilities of adult dyslexics to efficiently benefit from ("anchor to") regularities embedded in repeated tones, orally presented syllables, and written words. We also compared dyslexics' performance to that of individuals with attention disorder (ADHD), but no reading disability. We found an anchoring effect in all groups: all gained from stimulus repetition. However, in line with the anchoring-deficit hypothesis, controls and ADHD participants showed a significantly larger anchoring effect in all tasks. This study is the first that directly shows that the same domain-general deficit, poor anchoring, characterizes dyslexics' performance in perceptual, working memory and reading tasks.

  12. Evaluation of mitral valve replacement anchoring in a phantom (United States)

    McLeod, A. Jonathan; Moore, John; Lang, Pencilla; Bainbridge, Dan; Campbell, Gordon; Jones, Doug L.; Guiraudon, Gerard M.; Peters, Terry M.


    Conventional mitral valve replacement requires a median sternotomy and cardio-pulmonary bypass with aortic crossclamping and is associated with significant mortality and morbidity which could be reduced by performing the procedure off-pump. Replacing the mitral valve in the closed, off-pump, beating heart requires extensive development and validation of surgical and imaging techniques. Image guidance systems and surgical access for off-pump mitral valve replacement have been previously developed, allowing the prosthetic valve to be safely introduced into the left atrium and inserted into the mitral annulus. The major remaining challenge is to design a method of securely anchoring the prosthetic valve inside the beating heart. The development of anchoring techniques has been hampered by the expense and difficulty in conducting large animal studies. In this paper, we demonstrate how prosthetic valve anchoring may be evaluated in a dynamic phantom. The phantom provides a consistent testing environment where pressure measurements and Doppler ultrasound can be used to monitor and assess the valve anchoring procedures, detecting pararvalvular leak when valve anchoring is inadequate. Minimally invasive anchoring techniques may be directly compared to the current gold standard of valves sutured under direct vision, providing a useful tool for the validation of new surgical instruments.

  13. Covalent Anchoring of Chloroperoxidase and Glucose Oxidase on the Mesoporous Molecular Sieve SBA-15

    Directory of Open Access Journals (Sweden)

    Martin Hartmann


    Full Text Available Functionalization of porous solids plays an important role in many areas, including heterogeneous catalysis and enzyme immobilization. In this study, large-pore ordered mesoporous SBA-15 molecular sieves were synthesized with tetraethyl orthosilicate (TEOS in the presence of the non-ionic triblock co-polymer Pluronic P123 under acidic conditions. These materials were grafted with 3 aminopropyltrimethoxysilane (ATS, 3-glycidoxypropyltrimethoxysilane (GTS and with 3 aminopropyltrimethoxysilane and glutaraldehyde (GA-ATS in order to provide covalent anchoring points for enzymes. The samples were characterized by nitrogen adsorption, powder X-ray diffraction, solid-state NMR spectroscopy, elemental analysis, diffuse reflectance fourier transform infrared spectroscopy and diffuse reflectance UV/Vis spectroscopy. The obtained grafted materials were then used for the immobilization of chloroperoxidase (CPO and glucose oxidase (GOx and the resulting biocatalysts were tested in the oxidation of indole. It is found that enzymes anchored to the mesoporous host by the organic moieties can be stored for weeks without losing their activity. Furthermore, the covalently linked enzymes are shown to be less prone to leaching than the physically adsorbed enzymes, as tested in a fixed-bed reactor under continuous operation conditions.

  14. Correlation between surface free energy and anchoring energy of 6CHBT on polyimide surface (United States)

    Borycki, Jerzy; Okulska-Bozek, Malgorzata; Kedzierski, Jerzy; Kojdecki, Marek A.


    Polyimides were prepared in the classical two-step method via poly(amic acids). Poly(amic acids) were obtained from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 4,4'- (hexafluoroisopropylidene)diphthalic anhydride (6FDA), pyromellitic dianhydride (PMDA), 3,3',4,4'- diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'- oxydiphthalic anhydride (ODPA) and amines 4,4'-oxydianiline (ODA), 1,3-phenylenediamine (MPD), 1,4-phenylenediamine (PPD), 4,4'-diaminodiphenylmethane (MDA), 4,4'- ethylenedianiline (DAB), 2,4,6-trimethyl-1,3- phenylenediamine (TMPD), 4-methyl-1,3-phenylenediamine (MMPD) and 2,3,5,6-tetramethyl-1,4-phenylenediamine (DAD) in dimethylformamide. The indium tin oxide (ITO)-glass plates were spin-coated with the poly(amic acids) solutions and dried. A thermal imidization process was then carried out at 250 degree(s)C for 4 h. In this study the anchoring energies of 6CHBT molecules were evaluated on rubbing aligning layers of PI films. The polar anchoring energy coefficient was determined by wedge cell method. The surface free energy and its components of polyimide layers were determined by measuring the contact angles of water, ethylene glycol, formamide and diiodomethane drops on the rubbing polymer surfaces. The Lifshitz-van der Waals and acidic-basic components of surface free energies were found from van Oss equation.

  15. Nematic Liquid Crystal Alignment Behaviors between Crossed Stretched Miropolymer Filaments with Anchoring Effects (United States)

    Fujikake, Hideo; Murashige, Takeshi; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio


    We observed the molecular alignment of a liquid crystal (LC) induced by crossing two stretched micropolymer filaments between glass substrates and confirmed its light modulation property. The two microfilaments, which were extracted from a cellulose cloth by stretching it in advance, had surface molecular alignment and stabilized nematic LC alignment between the microfilaments crossed with a small angle. In the fabricated LC cell, a spatially-uniform LC planar alignment is achieved in the area of a filament interval of less than 60 μm. By polarizing microscopy observation of the isotropic-to-nematic wetting transition of the LC material between the polymer filaments, it was confirmed that the stable LC alignment area is formed by the surface anchoring of the filaments. When external voltages were applied to the obtained uniformed alignment LC area, a characteristic periodic electrooptic property was confirmed on the basis of electrically-controlled birefringence under the alignment control of the in-plane anchoring of the filaments.

  16. Pyramidal anchor stone from Baga waters of Goa, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Tripati, S.

    . Pyramidal anchor stones have an apex hole which goes up to the round hole, however Goa anchor stone has no such perforation, but, instead has a rectangular cutting on the apex. The anchor stone is compared with Greek pyramidal anchor stones, and probably...

  17. Enhanced vapor transport in membrane distillation via functionalized carbon nanotubes anchored into electrospun nanofibres (United States)

    Kyoungjin An, Alicia; Lee, Eui-Jong; Guo, Jiaxin; Jeong, Sanghyun; Lee, Jung-Gil; Ghaffour, Noreddine


    To ascertain membrane distillation (MD) as an emerging desalination technology to meet the global water challenge, development of membranes with ideal material properties is crucial. Functionalized carbon nanotubes (CNTs) were anchored to nanofibres of electrospun membranes. Covalent modification and fluorination of CNTs improved their dispersibility and interfacial interaction with the polymer membrane, resulting in well-aligned CNTs inside crystalline fibres with superhydrophobicity. Consideration for the chemical/physical properties of the CNT composite membranes and calculation of their theoretical fluxes revealed the mechanism of MD: CNTs facilitated the repulsive force for Knudsen and molecular diffusions, reduced the boundary-layer effect in viscous flow, and assisted surface diffusion, allowing for fast vapor transport with anti-wetting. This study shows that the role of CNTs and an optimal composite ratio can be used to reduce the gap between theoretical and experimental approaches to desalination.

  18. Enhanced vapor transport in membrane distillation via functionalized carbon nanotubes anchored into electrospun nanofibres

    KAUST Repository

    An, Alicia Kyoungjin


    To ascertain membrane distillation (MD) as an emerging desalination technology to meet the global water challenge, development of membranes with ideal material properties is crucial. Functionalized carbon nanotubes (CNTs) were anchored to nanofibres of electrospun membranes. Covalent modification and fluorination of CNTs improved their dispersibility and interfacial interaction with the polymer membrane, resulting in well-aligned CNTs inside crystalline fibres with superhydrophobicity. Consideration for the chemical/physical properties of the CNT composite membranes and calculation of their theoretical fluxes revealed the mechanism of MD: CNTs facilitated the repulsive force for Knudsen and molecular diffusions, reduced the boundary-layer effect in viscous flow, and assisted surface diffusion, allowing for fast vapor transport with anti-wetting. This study shows that the role of CNTs and an optimal composite ratio can be used to reduce the gap between theoretical and experimental approaches to desalination.

  19. Enhanced vapor transport in membrane distillation via functionalized carbon nanotubes anchored into electrospun nanofibres (United States)

    Kyoungjin An, Alicia; Lee, Eui-Jong; Guo, Jiaxin; Jeong, Sanghyun; Lee, Jung-Gil; Ghaffour, Noreddine


    To ascertain membrane distillation (MD) as an emerging desalination technology to meet the global water challenge, development of membranes with ideal material properties is crucial. Functionalized carbon nanotubes (CNTs) were anchored to nanofibres of electrospun membranes. Covalent modification and fluorination of CNTs improved their dispersibility and interfacial interaction with the polymer membrane, resulting in well-aligned CNTs inside crystalline fibres with superhydrophobicity. Consideration for the chemical/physical properties of the CNT composite membranes and calculation of their theoretical fluxes revealed the mechanism of MD: CNTs facilitated the repulsive force for Knudsen and molecular diffusions, reduced the boundary-layer effect in viscous flow, and assisted surface diffusion, allowing for fast vapor transport with anti-wetting. This study shows that the role of CNTs and an optimal composite ratio can be used to reduce the gap between theoretical and experimental approaches to desalination. PMID:28134288

  20. Microwave assisted click chemistry on a conductive polymer film

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Hansen, Thomas S.; Larsen, Niels Bent


    Microwave (MW) irradiation has been used to accelerate the functionalization of an azide functional poly(3,4-ethylenedioxythiophene) film by click chemistry. The absorption of MW energy by the conductive polymer has been exploited for localized activation of the reaction on the polymer surface....... The method has been applied for anchoring of the chelating agent nitrilotriacetic acid (NTA) on the conductive polymer. The chelating linkage ability of NTA on the surface was investigated through a sandwich ELISA study confirming the selective bonding of a histidine tagged protein....

  1. Phases and phase transition in insoluble and adsorbed monolayers of amide amphiphiles: Specific characteristics of the condensed phases. (United States)

    Vollhardt, D


    For understanding the role of amide containing amphiphiles in inherently complex biological processes, monolayers at the air-water interface are used as simple biomimetic model systems. The specific characteristics of the condensed phases and phase transition in insoluble and adsorbed monolayers of amide amphiphiles are surveyed to highlight the effect of the chemical structure of the amide amphiphiles on the interfacial interactions in model monolayers. The mesoscopic topography and/or two-dimensional lattice structures of selected amino acid amphiphiles, amphiphilic N-alkylaldonamide, amide amphiphiles with specific tailored headgroups, such as amide amphiphiles based on derivatized ethanolamine, e.g. acylethanolamines (NAEs) and N-,O-diacylethanolamines (DAEs) are presented. Special attention is devoted the dominance of N,O-diacylated ethanolamine in mixed amphiphilic acid amide monolayers. The evidence that a first order phase transition can occur in adsorption layers and that condensed phase domains of mesoscopic scale can be formed in adsorption layers was first obtained on the basis of the experimental characteristics of a tailored amide amphiphile. New thermodynamic and kinetic concepts for the theoretical description of the characteristics of amide amphiphile's monolayers were developed. In particular, the equation of state for Langmuir monolayers generalized for the case that one, two or more phase transitions occur, and the new theory for phase transition in adsorbed monolayers are experimentally confirmed at first by amide amphiphile monolayers. Despite the significant progress made towards the understanding the model systems, these model studies are still limited to transfer the gained knowledge to biological systems where the fundamental physical principles are operative in the same way. The study of biomimetic systems, as described in this review, is only a first step in this direction.

  2. Self-assembly of ssDNA-amphiphiles into micelles, nanotapes and nanotubes (United States)

    Pearce, Timothy R.

    The field of DNA nanotechnology utilizes DNA as a construction material to create functional supramolecular and multi-dimensional structures like two-dimensional periodic lattices and three-dimensional polyhedrons with order on the nanometer scale for many nanotechnology applications including molecular templating, nanosensors, and drug delivery. Single-stranded DNA (ssDNA) is often used to create these nanostructures as the DNA bases provide an intrinsic molecular code that can be exploited to allow for the programmed assembly of structures based upon Watson-Crick base-pairing. However, engineering these complex structures from biopolymers alone requires careful design to ensure that the intrinsic forces responsible for organizing the materials can produce the desired structures. Additional control over supramolecular assembly can be achieved by chemically modifying the ssDNA with hydrophobic moieties to create amphiphilic molecules, which adds the hydrophobic interaction to the list of contributing forces that drive the self-assembly process. We first explored the self-assembly behavior of a set of ssDNA aptamer-amphiphiles composed of the same hydrophobic tail and hydrophilic ssDNA aptamer headgroup but with different spacer molecules linking these groups together. Through the use of cryo-transmission electron microscopy (cryo-TEM), small angle x-ray scattering (SAXS), and circular dichroism (CD) we show that the aptamer-amphiphiles can assemble into a variety of structures depending on the spacer used. We demonstrated, for the first time, the creation of self-assembled aptamer-amphiphile nanotape structures and show that the choice of the spacer used in the design of aptamer-amphiphiles can influence their supramolecular self-assembly as well as the secondary structure of the aptamer headgroup. We next explored the role of the ssDNA headgroup on the amphiphile self-assembly behavior by designing amphiphiles with headgroups of multiple lengths and nucleotides

  3. DNA nanotubes and helical nanotapes via self-assembly of ssDNA-amphiphiles. (United States)

    Pearce, Timothy R; Kokkoli, Efrosini


    DNA nanotubes were created using molecular self-assembly of single-stranded DNA (ssDNA)-amphiphiles composed of a hydrophobic dialkyl tail and polycarbon spacer and a hydrophilic ssDNA headgroup. The nanotube structures were formed by bilayers of amphiphiles, with the hydrophobic components forming an inner layer that was shielded from the aqueous solvent by an outer layer of ssDNA. The nanotubes appeared to form via an assembly process that included transitions from twisted nanotapes to helical nanotapes to nanotubes. Amphiphiles that contained different ssDNA headgroups were created to explore the effect of the length and secondary structure of the ssDNA headgroup on the self-assembly behavior of the amphiphiles in the presence and absence of the polycarbon spacer. It was found that nanotubes could be formed using a variety of headgroup lengths and sequences. The ability to create nanotubes via ssDNA-amphiphile self-assembly offers an alternative to the other purely DNA-based approaches like DNA origami and DNA tile assembly for constructing these structures and may be useful for applications in drug delivery, biosensing, and electronics.

  4. Magnetic core–bilayer shell complex of magnetite nanoparticle stabilized with mPEG–polyester amphiphilic block copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Mekkapat, Supachai; Thong-On, Bandit; Rutnakornpituk, Boonjira; Wichai, Uthai; Rutnakornpituk, Metha, E-mail: [Naresuan University, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science (Thailand)


    In this article, we report the synthesis of magnetite nanoparticles (Fe{sub 3}O{sub 4}) coated with methoxy poly(ethylene glycol) (mPEG)–polyester amphiphilic block copolymers. The coating polymer layer contains a hydrophobic inner layer of polyester and a hydrophilic corona of mPEG. The copolymers were first prepared via a direct condensation between diacid, diol compounds and mPEG oligomer to obtain a hydrophobic polyester block and hydrophilic mPEG block and then “grafted onto” a magnetite nanoparticle surface. The copolymer composition was varied by changing the structure of the diacid, diol, and the molecular weight ( M-bar {sub n} ) of the mPEG such that particles with good dispersibility and stability in water were obtained. It was found that the copolymer prepared from 1,6-hexanediol can effectively stabilize the particles in water regardless of the types of diacid and M-bar {sub n} of mPEG used. The particle size was approximately 10 nm in diameter, and the particle dispersibility in water was quite dependent on the type and concentration of the copolymer used. Thermogravimetric analysis revealed the presence of less than 37 % Fe{sub 3}O{sub 4} and about 48–53 % of the copolymer in the complexes. The percent entrapment efficiency and loading efficiency of indomethacin model drug in the copolymer-coated magnetite nanoparticles were 19 and 77 %, respectively.

  5. Effect of inorganic salts on the clouding behavior of hydroxypropyl methyl cellulose in presence of amphiphilic drugs. (United States)

    Khan, Iqrar Ahmad; Anjum, Kahkashan; Koya, P Ajmal; Kabir-Ud-Din


    In this paper we report the effect of two cationic (imipramine hydrochloride (IMP) and promazine hydrochloride (PMZ)) and one anionic (sodium salt of ibuprofen (IBF)) drugs on the clouding behavior of a nonionic polymer hydroxypropyl methyl cellulose (HPMC). Though all the three drugs increase the cloud point (CP) of HPMC, the effect was found to be minimum in the case of IBF. Further, the effect of adding salts (NaF, NaCl, NaBr, NaNO(3), Na(2)SO(4), Na(3)PO(4), KCl, KBr, KNO(3)) in the presence of amphiphilic drugs (IMP and PMZ) on the CP of HPMC was seen. Almost linear decrease in the CP was observed with the [salt] at fixed concentrations of these drugs whereas in the absence of drugs the decrement in the CP was slight. The energetic parameters (ΔG(c)(0), ΔH(c)(0) and TΔS(c)(0)) were evaluated and it implies that the disruption of water structure becomes significantly prominent at lower concentrations of the drugs at fixed salt concentrations.

  6. Protein Modification with Amphiphilic Block Copoly(2-oxazoline)s as a New Platform for Enhanced Cellular Delivery

    KAUST Repository

    Tong, Jing


    Several homopolymers, random copolymers and block copolymers based on poly(2-oxazoline)s (POx) were synthesized and conjugated to horseradish peroxidase (HRP) using biodegradable and nonbiodegradable linkers. These conjugates were characterized by amino group titration, polyacrylamide gel electrophoresis (PAGE), isoelectric focusing, enzymatic activity assay and conformation analysis. The conjugates contained on average from about one to two polymer chains per enzyme. From 70% to 90% of enzymatic activity was retained in most cases. Circular dichroism (CD) analysis revealed that HRP modification affected the secondary structure of the apoprotein but did not affect the tertiary structure and heme environment. Enhanced cellular uptake was found in the conjugates of two block copolymers using both MDCK cells and Caco-2 cells, but not in the conjugates of random copolymer and homopolymer. Conjugation with a block copolymer of 2-methyl-2-oxazoline and 2-butyl-2-oxazoline led to the highest cellular uptake as compared to other conjugates. Our data indicates that modification with amphiphilic POx has the potential to modulate and enhance cellular delivery of proteins.

  7. Preparing high-density polymer brushes by mechanically assisted polymer assembly (MAPA) (United States)

    Wu, Tao; Efimenko, Kirill; Genzer, Jan


    We introduce a novel method of modifying the surface properties of materials. This technique, called MAPA (="mechanically assisted polymer assembly"), is based on: 1) chemically attaching polymerization initiators to the surface of an elastomeric network that has been previously stretched by a certain length, Δx, and 2) growing end-anchored macromolecules using surface initiated ("grafting from") atom transfer living radical polymerization. After the polymerization, the strain is removed from the substrate, which returns to its original size causing the grafted macromolecules to stretch away from the substrate and form a dense polymer brush. We demonstrate the feasibility of the MAPA method by preparing high-density polymer brushes of poly(acryl amide), PAAm. We show that, as expected, the grafting density of the PAAm brushes can be increased by increasing Δx. We demonstrate that polymer brushes with extremely high grafting densities can be successfully prepared by MAPA.

  8. Stable and robust polymer nanotubes stretched from polymersomes (United States)

    Reiner, Joseph E.; Wells, Jeffrey M.; Kishore, Rani B.; Pfefferkorn, Candace; Helmerson, Kristian


    We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers, and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. We stabilize the pulled nanotubes by subsequent chemical cross-linking. The cross-linked nanotubes are extremely robust and can be moved to another medium for use elsewhere. We demonstrate the ability to form networks of polymer nanotubes and polymersomes by optical manipulation. The aqueous core of the polymer nanotubes together with their robust character makes them interesting candidates for nanofluidics and other applications in biotechnology. cross-link | optical tweezers | nanofluidics | vesicles

  9. The heat-chill method for preparation of self-assembled amphiphilic poly(ε-caprolactone)-poly(ethylene glycol) block copolymer based micellar nanoparticles for drug delivery. (United States)

    Payyappilly, Sanal Sebastian; Dhara, Santanu; Chattopadhyay, Santanu


    A new method is developed for preparation of amphiphilic block copolymer micellar nanoparticles and investigated as a delivery system for celecoxib, a hydrophobic model drug. Biodegradable block copolymers of poly(ethylene glycol) (PEG) and poly(ε-caprolactone) (PCL) were synthesized by ring opening copolymerization and characterized thoroughly using FTIR, (1)H NMR and GPC. The block copolymer was dispersed in distilled water at 60 °C and then it was chilled in an ice bath for the preparation of the micellar nanoparticles. Polymers self-assembled to form micellar nanoparticles (HR-TEM, DLS and DSC. The cytotoxicity of the polymer micellar nanoparticles was investigated against HaCaT cell lines. The study of celecoxib release from the micellar nanoparticles was carried out to assess their suitability as a drug delivery vehicle. Addition of the drug to the system at low temperature is an added advantage of this method compared to the other temperature assisted nanoparticle preparation techniques. In a nutshell, polymer micellar nanoparticles prepared using the heat-chill method are believed to be promising for the controlled drug release system of labile drugs, which degrade in toxic organic solvents and at higher temperatures.

  10. Perceptual anchoring in preschool children: not adultlike, but there.

    Directory of Open Access Journals (Sweden)

    Karen Banai

    Full Text Available BACKGROUND: Recent studies suggest that human auditory perception follows a prolonged developmental trajectory, sometimes continuing well into adolescence. Whereas both sensory and cognitive accounts have been proposed, the development of the ability to base current perceptual decisions on prior information, an ability that strongly benefits adult perception, has not been directly explored. Here we ask whether the auditory frequency discrimination of preschool children also improves when given the opportunity to use previously presented standard stimuli as perceptual anchors, and whether the magnitude of this anchoring effect undergoes developmental changes. METHODOLOGY/PRINCIPAL FINDINGS: Frequency discrimination was tested using two adaptive same/different protocols. In one protocol (with-reference, a repeated 1-kHz standard tone was presented repeatedly across trials. In the other (no-reference, no such repetitions occurred. Verbal memory and early reading skills were also evaluated to determine if the pattern of correlations between frequency discrimination, memory and literacy is similar to that previously reported in older children and adults. Preschool children were significantly more sensitive in the with-reference than in the no-reference condition, but the magnitude of this anchoring effect was smaller than that observed in adults. The pattern of correlations among discrimination thresholds, memory and literacy replicated previous reports in older children. CONCLUSIONS/SIGNIFICANCE: The processes allowing the use of context to form perceptual anchors are already functional among preschool children, albeit to a lesser extent than in adults. Nevertheless, immature anchoring cannot fully account for the poorer frequency discrimination abilities of young children. That anchoring is present among the majority of typically developing preschool children suggests that the anchoring deficits observed among individuals with dyslexia represent a

  11. Membrane behavior as influenced by partitioning of amphiphiles during drying : a comparative study in anhydrobiotic plant systems

    NARCIS (Netherlands)

    Golovina, E.A.; Hoekstra, F.A.


    During cellular desiccation, reduction in volume can in principle cause amphiphilic compounds to partition from the cytoplasm into membranes, with structural perturbance as the result. Here, we studied the effect of partitioning of endogenous amphiphiles on membrane surface dynamics in desiccation-t

  12. Tuning peptide amphiphile supramolecular structure for biomedical applications (United States)

    Pashuck, Eugene Thomas, III

    The use of biomaterials in regenerative medicine has been an active area of research for more than a decade. Peptide amphiphiles, which are short peptide sequences coupled to alkyl tails, have been studied in the Stupp group since the beginning of the decade and been used for a variety of biomedical applications. Most of the work has focused on the bioactive epitopes places on the periphery of the PA molecules, but the interior amino acids, known as the beta-sheet region, give the PA nanofiber gel much of its mechanical strength. To study the important parameters in the beta-sheet region, six PA molecules were constructed to determine the influence of beta-sheet length and order of the amino acids in the beta-sheet. It was found that having beta-sheet forming amino acids near the center of the fiber improves PA gel stiffness, and that having extra amino acids that have preferences for other secondary structures, like alpha-helix decreased the gels stiffness. Using FTIR and circular dichroism it was found that the mechanical properties are influenced by the amount of twist in the beta-sheet, and PAs that have more twisted beta-sheets form weaker gels. The effect amino acid properties have on peptide amphiphile self-assembly where studied by synthesizining molecules with varying side group size and hydrophobicity. It was found that smaller amino acids lead to stiffer gels and when two amino acids had the same size the amino acid with the larger beta-sheet propensity lead to a stiffer gel. Furthermore, small changes in peptide structure were found to lead to big changes in nanostructure, as leucine and isoleucine, which have the same size but slightly different structures, form flat ribbons and cylindrical nanofibers, respectively. Phenylalanine and alanine were studied more indepth because they represent the effects of adding an aromatic group to amino acids in the beta-sheet regon. These phenylalanine PAs formed short, twisted ribbons when freshly dissolved in water

  13. Amphiphilic phase-transforming catalysts for transesterification of triglycerides (United States)

    Nawaratna, Gayan Ivantha

    Heterogeneous catalytic reactions that involve immiscible liquid-phase reactants are challenging to conduct due to limitations associated with mass transport. Nevertheless, there are numerous reactions such as esterification, transesterification, etherification, and hydrolysis where two immiscible liquid reactants (such as polar and non-polar liquids) need to be brought into contact with a catalyst. With the intention of alleviating mass transport issues associated with such systems but affording the ability to separate the catalyst once the reaction is complete, the overall goal of this study is geared toward developing a catalyst that has emulsification properties as well as the ability to phase-transfer (from liquid-phase to solid-phase) while the reaction is ongoing and evaluating the effectiveness of such a catalytic process in a practical reaction. To elucidate this concept, the transesterification reaction was selected. Metal-alkoxides that possess acidic and basic properties (to catalyze the reaction), amphiphilic properties (to stabilize the alcohol/oil emulsion) and that can undergo condensation polymerization when heated (to separate as a solid subsequent to the completion of the reaction) were used to test the concept. Studies included elucidating the effect of metal sites and alkoxide sites and their concentration effects on transesterification reaction, effect of various metal alkoxide groups on the phase stability of the reactant system, and kinetic effects of the reaction system. The studies revealed that several transition-metal alkoxides, especially, titanium and yttrium based, responded positively to this reaction system. These alkoxides were able to be added to the reaction medium in liquid phase and were able to stabilize the alcohol/oil system. The alkoxides were selective to the transesterification reaction giving a range of ester yields (depending on the catalyst used). It was also observed that transition-metal alkoxides were able to be

  14. High Selective Performance of Designed Antibacterial and Anticancer Peptide Amphiphiles. (United States)

    Chen, Cuixia; Chen, Yucan; Yang, Cheng; Zeng, Ping; Xu, Hai; Pan, Fang; Lu, Jian Ren


    Short designed peptide amphiphiles are attractive at killing bacteria and inhibiting cancer cell growth, and the flexibility in their structural design offers a great potential for improving their potency and biocompatibility to mammalian host cells. Amino acid sequences such as G(IIKK)nI-NH2 (n≥3) have been shown to be membrane lytic, but terminal amino acid modifications could impose a huge influence on their performance. We report in this work how terminal amino acid modifications to G(IIKK)3I-NH2 influence its α-helical structure, membrane penetrating ability, and selective actions against different cell types. Deletion of an N-terminal Gly or a C-terminal Ile did not affect their antibacterial activity much, an observation consistent with their binding behavior to negatively charged membrane lipid monolayers. However, the cytotoxicity against mammalian cells was much worsened by the N-terminal Gly deletion, consistent with an increase in its helical content. Despite little impact on the antibacterial activity of G(IIKK)3I-NH2, deletion of both terminal amino acids greatly reduced its antitumor activity. Cholesterol present in tumor cell membrane-mimic was thought to constrain (IIKK)3-NH2 from penetrating into the cancerous membranes, evident from its lowest surface physical activity at penetrating model lipid membranes. On the other hand, its low toxicity to normal mammalian cells and high antibacterial activity in vitro and in vivo made it an attractive antibacterial agent. Thus, terminal modifications can help rebalance the different interactions involved and are highly effective at manipulating their selective membrane responses.

  15. Redox-sensitive micelles assembled from amphiphilic mPEG-PCL-SS-DTX conjugates for the delivery of docetaxel. (United States)

    Zhang, Huiyuan; Wang, Kaiming; Zhang, Pei; He, Wenxiu; Song, Aixin; Luan, Yuxia


    Docetaxel (DTX) can produce anti-tumor effects by inhibiting cell growth and inducing apoptosis. However, the poor solubility of DTX restricts its application and its clinical formulation has caused serious adverse reaction due to the use of Tween-80. In the present study, DTX was conjugated to an amphiphilic di-block polymer to solve these problems. Methoxy poly(ethylene glycol)-poly(ε-caprolactone) (mPEG-PCL) was selected as the polymer skeleton and a redox sensitive disulfide bond was used as the linker between DTX and mPEG-PCL. The synthesized mPEG-PCL-SS-DTX conjugates were characterized by (1)H-nuclear magnetic resonance ((1)H NMR) and Fourier transform infrared spectroscopy (FTIR). Interestingly, the mPEG-PCL-SS-DTX conjugates could self-assemble into micelles in aqueous solution. The critical micelle concentration (CMC) of mPEG-PCL-SS-DTX micelles was about 2.3mgL(-1) determined using pyrene molecule fluorescent probe method while the size of mPEG-PCL-SS-DTX micelles was determined to be ca. 17.6nm and 116.0nm with a bimodal distribution by dynamic light scattering (DLS). The in vitro release results indicated that the as-prepared micelles exhibited a sustained release profile with good redox sensitive properties. In particular, the hemolytic toxicity test indicated the as-prepared mPEG-PCL-SS-DTX micelles had negligible hemolytic activity, demonstrating their safety in drug delivery system. Cytotoxicity assay of the mPEG-PCL-SS-DTX micelles verified their highly enhanced cytotoxicity to MCF-7/A and A549 cells. These results thus demonstrated that the present redox-sensitive mPEG-PCL-SS-DTX micelle was an efficient and safe sustained drug delivery system in the biomedical area.



    Ch. von Ferber; Yu.Holovatch


    It is our great pleasure to present a collection of papers devoted to theoretical, numerical, and experimental studies in the field of star polymers. Since its introduction in the early 80-ies, this field has attracted increasing interest and has become an important part of contemporary polymer physics. While research papers in this field appear regularly in different physical and chemical journals, the present collection is an attempt to join together the studies of star polymers showing the...

  17. Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations (United States)

    Mazzaglia, Antonino; Ganazzoli, Fabio


    Summary Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a “bottom up” approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties. PMID:26734094

  18. Poly(glycidyl ether)-Based Monolayers on Gold Surfaces: Control of Grafting Density and Chain Conformation by Grafting Procedure, Surface Anchor, and Molecular Weight. (United States)

    Heinen, Silke; Weinhart, Marie


    For a meaningful correlation of surface coatings with their respective biological response reproducible coating procedures, well-defined surface coatings, and thorough surface characterization with respect to layer thickness and grafting density are indispensable. The same applies to polymeric monolayer coatings which are intended to be used for, e.g., fundamental studies on the volume phase transition of surface end-tethered thermoresponsive polymer chains. Planar gold surfaces are frequently used as model substrates, since they allow a variety of straightforward surface characterization methods. Herein we present reproducible grafting-to procedures performed with thermoresponsive poly(glycidyl ether) copolymers composed of glycidyl methyl ether (GME) and ethyl glycidyl ether (EGE). The copolymers feature different molecular weights (2 kDa, 9 kDa, 24 kDa) and are equipped with varying sulfur-containing anchor groups in order to achieve adjustable grafting densities on gold surfaces and hence control the tethered polymers' chain conformation. We determined "wet" and "dry" thicknesses of these coatings by QCM-D and ellipsometry measurements and deduced anchor distances and degrees of chain overlap of the polymer chains assembled on gold. Grafting under cloud point conditions allowed for higher degrees of chain overlap compared to grafting from a good solvent like ethanol, independent of the used sulfur-containing anchor group for polymers with low (2 kDa) and medium (9 kDa) molecular weights. By contrast, the achieved grafting densities and thus chain overlaps of surface-tethered polymers with high (24 kDa) molecular weights were identical for both grafting methods. Monolayers prepared from an ethanolic solution of poly(glycidyl ether)s equipped with sterically demanding disulfide-containing anchors revealed the lowest degrees of chain overlap. The ratio of the radius of gyration to the anchor distance (2 Rg/l) of the latter coating was found to be lower than 1

  19. Polymer Chemistry (United States)

    Williams, Martha; Roberson, Luke; Caraccio, Anne


    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  20. Engineering Molecular Recognition with Bio-mimetic Polymers on Single Walled Carbon Nanotubes. (United States)

    Del Bonis-O'Donnell, Jackson T; Beyene, Abraham; Chio, Linda; Demirer, Gözde; Yang, Darwin; Landry, Markita P


    Semiconducting single-wall carbon nanotubes (SWNTs) are a class of optically active nanomaterial that fluoresce in the near infrared, coinciding with the optical window where biological samples are most transparent. Here, we outline techniques to adsorb amphiphilic polymers and polynucleic acids onto the surface of SWNTs to engineer their corona phases and create novel molecular sensors for small molecules and proteins. These functionalized SWNT sensors are both biocompatible and stable. Polymers are adsorbed onto the nanotube surface either by direct sonication of SWNTs and polymer or by suspending SWNTs using a surfactant followed by dialysis with polymer. The fluorescence emission, stability, and response of these sensors to target analytes are confirmed using absorbance and near-infrared fluorescence spectroscopy. Furthermore, we demonstrate surface immobilization of the sensors onto glass slides to enable single-molecule fluorescence microscopy to characterize polymer adsorption and analyte binding kinetics.

  1. Magnetic amphiphilic hybrid carbon nanotubes containing N-doped and undoped sections: powerful tensioactive nanostructures (United States)

    Purceno, Aluir D.; Machado, Bruno F.; Teixeira, Ana Paula C.; Medeiros, Tayline V.; Benyounes, Anas; Beausoleil, Julien; Menezes, Helvecio C.; Cardeal, Zenilda L.; Lago, Rochel M.; Serp, Philippe


    In this work, unique amphiphilic magnetic hybrid carbon nanotubes (CNTs) are synthesized and used as tensioactive nanostructures in different applications. These CNTs interact very well with aqueous media due to the hydrophilic N-doped section, whereas the undoped hydrophobic one has strong affinity for organic molecules. The amphiphilic character combined with the magnetic properties of these CNTs opens the door to completely new and exciting applications in adsorption science and catalysis. These amphiphilic N-doped CNTs can also be used as powerful tensioactive emulsification structures. They can emulsify water/organic mixtures and by a simple magnetic separation the emulsion can be easily broken. We demonstrate the application of these CNTs in the efficient adsorption of various molecules, in addition to promoting biphasic processes in three different reactions, i.e. transesterification of soybean oil, quinoline extractive oxidation with H2O2 and a metal-catalyzed aqueous oxidation of heptanol with molecular oxygen.In this work, unique amphiphilic magnetic hybrid carbon nanotubes (CNTs) are synthesized and used as tensioactive nanostructures in different applications. These CNTs interact very well with aqueous media due to the hydrophilic N-doped section, whereas the undoped hydrophobic one has strong affinity for organic molecules. The amphiphilic character combined with the magnetic properties of these CNTs opens the door to completely new and exciting applications in adsorption science and catalysis. These amphiphilic N-doped CNTs can also be used as powerful tensioactive emulsification structures. They can emulsify water/organic mixtures and by a simple magnetic separation the emulsion can be easily broken. We demonstrate the application of these CNTs in the efficient adsorption of various molecules, in addition to promoting biphasic processes in three different reactions, i.e. transesterification of soybean oil, quinoline extractive oxidation with H2O2 and

  2. Anchoring a Leviathan: How the Nuclear Membrane Tethers the Genome. (United States)

    Czapiewski, Rafal; Robson, Michael I; Schirmer, Eric C


    It is well established that the nuclear envelope has many distinct direct connections to chromatin that contribute to genome organization. The functional consequences of genome organization on gene regulation are less clear. Even less understood is how interactions of lamins and nuclear envelope transmembrane proteins (NETs) with chromatin can produce anchoring tethers that can withstand the physical forces of and on the genome. Chromosomes are the largest molecules in the cell, making megadalton protein structures like the nuclear pore complexes and ribosomes seem small by comparison. Thus to withstand strong forces from chromosome dynamics an anchoring tether is likely to be much more complex than a single protein-protein or protein-DNA interaction. Here we will briefly review known NE-genome interactions that likely contribute to spatial genome organization, postulate in the context of experimental data how these anchoring tethers contribute to gene regulation, and posit several hypotheses for the physical nature of these tethers that need to be investigated experimentally. Significantly, disruption of these anchoring tethers and the subsequent consequences for gene regulation could explain how mutations in nuclear envelope proteins cause diseases ranging from muscular dystrophy to lipodystrophy to premature aging progeroid syndromes. The two favored hypotheses for nuclear envelope protein involvement in disease are (1) weakening nuclear and cellular mechanical stability, and (2) disrupting genome organization and gene regulation. Considerable experimental support has been obtained for both. The integration of both mechanical and gene expression defects in the disruption of anchoring tethers could provide a unifying hypothesis consistent with both.

  3. An Analysis for Cross Beam-Ground Anchor Reinforcement

    Institute of Scientific and Technical Information of China (English)

    Xu Yingzi; Zhang Baiqing; Tang Huiming


    With the rapid development of water facilities, hydroelectric projects, highways and railways in China, beam-anchor reinforcement has been widely used to stabilize slopes in recent years. But the theory for the design of beam-anchor reinforcement is far behind the application. Cross beam-ground anchor reinforcement is a combination of beams and anchors forming a new structure to prevent slope sliding. The forces in the beams are discussed using theoretical analysis and numerical modeling. The Winkler model is used to analyze the beams, and reasonable values of λ, length, spacing and cantilevered length for the beams are determined through a theoretical analysis. A three-dimensional finite element method is adopted to model the interaction of the beams and soils and a structure analysis is applied to treat the beams and to study the stress distribution in external and internal beams. The analytical results show that it is better to satisfy λ≥2π, the spacing between anchors ls should be lsλ<π/2 and cantilever length should be (0.3-0.5)ls for the optimum design. The numerical results show that the same design can be used for all beams in different directions, including the internal and external beams. The application of the analytical method for reinforcement beam analysis is acceptable. It is better to choose a safety coefficient of 1.3 for design based on the analytical method for safety.

  4. Synthesis of amphiphilic aminated inulin via 'click chemistry' and evaluation for its antibacterial activity. (United States)

    Dong, Fang; Zhang, Jun; Yu, Chunwei; Li, Qing; Ren, Jianming; Wang, Gang; Gu, Guodong; Guo, Zhanyong


    Inulins are a group of abundant, water-soluble, renewable polysaccharides, which exhibit attractive bioactivities and natural properties. Improvement such as chemical modification of inulin is often performed prior to further utilization. We hereby presented a method to modify inulin at its primary hydroxyls to synthesize amphiphilic aminated inulin via 'click chemistry' to facilitate its chemical manipulation. Additionally, its antibacterial property against Staphylococcus aureus (S. aureus) was also evaluated and the best inhibitory index against S. aureus was 58% at 1mg/mL. As the amphiphilic aminated inulin is easy to prepare and exhibits improved bioactivity, this material may represent as an attractive new platform for chemical modifications of inulin.

  5. Trapping of polycyclic aromatic hydrocarbons by amphiphilic cyclodextrin functionalized polypropylene nonwovens

    DEFF Research Database (Denmark)

    Lumholdt, Ludmilla; Nielsen, Ronnie Bo Højstrup; Larsen, Kim Lambertsen

    Recently, there has been an augmented focus on the increasing amount of pesticides, drug residues and endocrine disruptors present in waste and drinking water1. These pollutants represent a challenge in water purification since they may be hazardous to human health even in low doses2. Cyclodextrins...... of the textile fibers. In this study we present the ability of amphiphilic CD coated polypropylene nonwovens to trap 8 different polycyclic aromatic hydrocarbons/endocrine disruptors from aqueous solutions thus demonstrating the potential of using the amphiphilic cyclodextrins for water purification....

  6. Polymers & People (United States)

    Lentz, Linda; Robinson, Thomas; Martin, Elizabeth; Miller, Mary; Ashburn, Norma


    Each Tuesday during the fall of 2002, teams of high school students from three South Carolina counties conducted a four-hour polymer institute for their peers. In less than two months, over 300 students visited the Charleston County Public Library in Charleston, South Carolina, to explore DNA, nylon, rubber, gluep, and other polymers. Teams of…

  7. Polymer supported nickel complex: Synthesis, structure and catalytic application

    Indian Academy of Sciences (India)

    Alekha Kumar Sutar; Tungabidya Maharana; Yasobanta Das; Prasanta Rath


    In the present investigation, a new synthetic route for a novel recyclable free [3-MOBdMBn-Ni] and polystyrene-anchored [P-3-MOBdMBn-Ni] nickel complexes is presented. The free and polymer-anchored metal complexes were synthesized by the reaction of nickel (II) with one molar equivalent of unsupported N N′-bis (2-Hydroxy-3-methoxybenzaldehyde) 4-Methylbenzene-1,2-diamine (3-MOBdMBn) or polymersupported (P-3-MOBdMBn) Schiff-base ligand in methanol under nitrogen atmosphere. The advantages of these polymer-supported catalysts are the low cost of catalyst and recyclability up to six times, due to easy availability of materials and simple synthetic route. The higher efficiency of complexation of nickel on the polymer-anchored 3-MOBdMBn Schiff base than the unsupported analogue is another advantage of this catalyst system. The structural study reveals that nickel(II) complex of 3-MOBdMBn is square planar in geometry. The catalytic activity of nickel complex towards the oxidation of phenol was investigated in the presence of hydrogen peroxide. Experimental results indicate that the reactivity of P-3-MOBdMBn-Ni was dramatically affected by the polymer support compared to free 3-MOBdMBn-Ni. The rates of oxidation (R) for unsupported and supported catalysts are 1.37 × 10-6 mole dm-3 s-1 and 2.33 × 10-6 mole dm-3 s-1 respectively.

  8. Optical Fiber Grating Sensor for Force Measurement of Anchor Cable

    Institute of Scientific and Technical Information of China (English)

    JIANG Desheng; FU Jinghua; LIU Shengchun; SUI Lingfeng; FU Rong


    The development of the sensor suitable for measuring large load stress to the anchor cable becomes an important task in bridge construction and maintenance. Therefore, a new type of optical fiber sensor was developed in the laboratory - optical fiber grating sensor for force measurement of anchor cable (OFBFMAC). No similar report about this kind of sensor has been found up to now in China and other countries. This sensor is proved to be an effective way of monitoring in processes of anchor cable installation, cable cutting, cable force regulation, etc, with the accurate and repeatable measuring results. Its successful application in the tie bar cable force safety monitoring for Wuhan Qingchuan bridge is a new exploration of optical fiber grating sensing technology in bridge tie bar monitoring system.

  9. Proteomic analysis of GPI-anchored membrane proteins

    DEFF Research Database (Denmark)

    Jung, Hye Ryung; Jensen, Ole Nørregaard


    Glycosyl-phosphatidyl-inositol-anchored proteins (GPI-APs) represent a subset of post-translationally modified proteins that are tethered to the outer leaflet of the plasma membrane via a C-terminal GPI anchor. GPI-APs are found in a variety of eukaryote species, from pathogenic microorganisms...... to humans. GPI-APs confer important cellular functions as receptors, enzymes and scaffolding molecules. Specific enzymes and detergent extraction methods combined with separation technologies and mass spectrometry permit proteomic analysis of GPI-APs from plasma membrane preparations to reveal cell...

  10. Experience-based, body-anchored qualitative research interviewing

    DEFF Research Database (Denmark)

    Stelter, Reinhard


    Two theoretical constructs that lay the foundation for experience-based, body-anchored interviewing are presented: the first-person perspective and the concept of meaning. These theoretical concepts are concretized, first, by means of a methodological framework for experience-based, body......-anchored interviewing, and second, by an interview guide that explores a research participant's personal experience with mindfulness meditation. An excerpt from an interview is discussed to illustrate the advantages of this interview form, namely its value as a methodological instrument for qualitative research...... in areas such as traditional and holistic medicine, Western alternative and complementary medicine, nursing, psychotherapy, coaching, physiotherapy, movement arts, and physical education....

  11. Charge-Transfer Supra-Amphiphiles Built by Water-Soluble Tetrathiafulvalenes and Viologen-Containing Amphiphiles: Supramolecular Nanoassemblies with Modifiable Dimensions. (United States)

    Lv, Zhong-Peng; Chen, Bin; Wang, Hai-Ying; Wu, Yue; Zuo, Jing-Lin


    In this study, multidimensional nanoassemblies with various morphologies such as nanosheets, nanorods, and nanofibers are developed via charge-transfer interaction and supra-amphiphile self-assembling in aqueous phase. The charge-transfer interactions between tetrathiafulvalene derivatives (TTFs) and methyl viologen derivatives (MVs) have been confirmed by the characteristic charger-transfer absorption. (1) H NMR and electrospray ionizsation mass spectrometry (ESI-MS) analyses also indicate supra-amphiphiles are formed by the combination of TTFs and MVs head group through charge-transfer interaction and Coulombic force. X-ray single crystal structural studies, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) reveal that both linkage pattern of TTFs in hydrophilic part and alkane chain structure in hydrophobic part have significant influence on nanoassemblies morphology and microstructure. Moreover, gold nanoparticles (AuNPs) are introduced in the above supramolecular nanoassemblies to construct a supra-amphiphile-driven organic-AuNPs assembly system. AuNPs could be assembled into 1D-3D structures by adding different amount of MVs.

  12. Self-Assembling Peptide Amphiphiles for Targeted Drug Delivery (United States)

    Moyer, Tyson

    The systemic delivery of therapeutics is currently limited by off-target side effects and poor drug uptake into the cells that need to be treated. One way to circumvent these issues is to target the delivery and release of therapeutics to the desired location while limiting systemic toxicity. Using self-assembling peptide amphiphiles (PAs), this work has investigated supramolecular nanostructures for the development of targeted therapies. Specifically, the research has focused on the interrelationships between presentation of targeting moeities and the control of nanostructure morphology in the context of systemic delivery for targeting cancer and vascular injuries. The self-assembly region of the PA was systematically altered to achieve control of nanostructure widths, from 100 nm to 10 nm, by the addition of valine-glutamic acid dimers into the chemical structure, subsequently increasing the degree of nanostructure twist. For the targeting of tumors, a homing PA was synthesized to include a dimeric, cyclic peptide sequence known to target the cancer-specific, death receptor 5 (DR5) and initiate apoptosis through the oligomerization of DR5. This PA presented a multivalent display of DR5-binding peptides, resulting in improved binding affinity measured by surface plasmon resonance. The DR5-targeting PA also showed enhanced efficacy in both in vitro and in vivo tumor models relative to non-targeted controls. Alternative modifications to the PA-based antitumor therapies included the use of a cytotoxic, membrane-lytic PA coassembled with a pegylated PA, which showed enhanced biodistribution and in vivo activity after coassembly. The functionalization of the hydrophobic core was also accomplished through the encapsulation of the chemotherapy camptothecin, which was shown to be an effective treatment in vivo. Additionally, a targeted PA nanostructure was designed to bind to the site of vascular intervention by targeting collagen IV. Following balloon angioplasty

  13. Self-assembling peptide amphiphile nanostructures for cancer therapy (United States)

    Soukasene, Stephen

    The application of nanotechnology to cancer therapy shows great promise for reducing the burden of the disease. By virtue of their size, nanoscale objects preferentially accumulate in tumor tissue through an enhanced permeability and retention (EPR) effect. However, to fully overcome the issues that limit current cancer treatments, viable nanostructures must also impart multifunctionality and be fully compatible with their biological surrounds. The self-assembling peptide amphiphile (PA) materials studied extensively in the Stupp Research Group form very biocompatible high aspect ratio nanostructures that meet these criteria. This thesis investigates the development of PA nanostructures designed to treat cancer. We first look to use the PA as a drug delivery vehicle by entrapping a small hydrophobic anti-cancer drug, camptothecin, in the core of the nanostructures. Using a solvent evaporation technique to load the drug into the PA nanofibers, we are able to improve the aqueous solubility of the molecule by nearly 30-fold. TEM and AFM studies show that entrapment of drug molecules does not disrupt the self-assembled morphology of the nanofiber. In vitro and in vivo studies are also conducted to demonstrate the bioactivity of the drug after its entrapment. As a potential platform for novel therapeutics, we next develop techniques for using light irradiation to trigger self-assembly inside the confined space of liposomes. We encapsulate PA monomers that assemble under acidic conditions along with a photoacid generator inside liposomes. Upon exposure to 254 nm light, the PA monomers self assemble inside the liposome to form nanostructures, which we observe through a quick freeze/deep etch technique that allows us to look inside the liposomes by SEM and TEM. Last of all, the development and discovery of epitopes for targeting PA nanostructures to tumors are explored. Using phage display technology we generate two groups of peptide sequences, one of which can potentially


    Institute of Scientific and Technical Information of China (English)

    Yotaro Morishima


    The self-assembling behavior of random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS)and hydrophobic comonomers possessing dodecyl groups linked by various spacer bonds was discussed with a focus on the effect of the spacer. The characterization of association behavior of such polymers in water using quasielastic light scattering,capillary electrophoresis, NMR relaxation, various fluorescence, and viscoelastic methods was described. These copolymers form a variety of self-assembled nanostructures depending on the type of the spacer. Random copolymers of AMPS and Ndodecylmethacrylamide show a strong preference for intrapolymer self-association even in concentrated aqueous solutions forming single-macromolecular self-assemblies (unimolecular micelles). In contrast, random copolymers of AMPS and dodecyl methacrylate are prone to undergo interpolymer associations yielding multipolymer micelles. In random copolymers of AMPS and a methacrylate substituted a nonionic surfactant (HO(CH2CH2O)25C12H25) (C12E25), dodecyl groups are much less restricted by the polymer backbone because they are linked via a long, flexible hydrophilic spacer. Thus, the polymerbound C12E25 surfactant moieties form micelles similar to those formed by discrete surfactants, but they are bridged by polymer chains forming a network structure.

  15. Mechanical behavior of the U-anchor of super-CFRP rod under tensile loading


    Djamaluddin, Rudy; yamaguchi, Kohei; Hino, Shinichi


    - A suitable anchoring system is required to anchor a CFRP tendon due to its sensitivity in lateral pressure. Recent developed anchors are still relying on lateral pressure in anchoring CFRP tendons. A new CFRP unit equipped with U-anchor at both end of the rod body without any jointing (namely of Super CFRP, S-CFRP) has been developed. This paper presents the mechanical behavior as well as failure mechanism of U-anchor under direct loading and loaded under embedded within concrete, respec...

  16. Arrangement of anchor reinforcement in roadway for fully mechanized sublevel caving

    Institute of Scientific and Technical Information of China (English)

    勾攀峰; 陈启永; 芦付松


    Bolting of mining roadway for fully mechanized sublevel caving has been practised successfully in Hebi mining area.It provides a new method for roadway support and settles the problem of support difficulty radically for sublevel caving in Hebi mining area.Where anchor reinforcement holds an important station in roadway support.This article brings forward the arrangement project of anchor based on theoretic analysis.Compared with arranged in the middle of the entry, anchor arranged in the vertex of the entry can reduces the length of anchor,shortens the anchor installation time,and heightens the reliability of anchor installation.

  17. Current status of frameless anchored IUD for immediate intracesarean insertion. (United States)

    Wildemeersch, Dirk; Goldstuck, Norman D; Hasskamp, Thomas


    Immediate postpartum intrauterine device (IUD) insertion deserves great attention as it can provide immediate, timely and convenient contraception plus the added benefit of preventing repeat unintended pregnancies. Although women post vaginal delivery can benefit from immediate post-placenta contraception, women undergoing Cesarean section clearly need contraception, as an inter-delivery interval shorter than 18 months places them at a high risk for uterine rupture. The main drawback of currently available framed IUD devices for immediate postpartum insertion of an IUD is their high expulsion and displacement rates when inserted immediately postpartum after both vaginal and Cesarean delivery. Current research suggests that a brief window of opportunity exists of 10 minutes for insertion of conventional IUDs after which time expulsion rates both immediately and over time are greatly enhanced. This paper summarizes the current research conducted to overcome the expulsion problems associated with conventional T-shaped devices as well as through the use of an anchored frameless device. In the 1970s and 1980s, attempts were made to solve the expulsion problem by modifying existing devices, such as adding absorbable sutures (Delta-T) or additional appendages. These attempts proved to be clinically unsuccessful as the catgut suture added to the transverse arms did not provide sufficient resistance to prevent downward displacement and expulsion. An anchoring technique to suspend a copper IUD to the fundus of the uterus was developed in Belgium in the 1980s and has been the subject of extensive ongoing clinical research since 1985. Recently the frameless copper releasing anchor IUD, GyneFix, has been tested for postplacental insertion. Initially, the anchor was modified by the inclusion of a biodegradable cone which was added below the anchoring knot. Clinical studies confirmed the adequacy of this approach suggesting that it was technically possible to anchor an IUD

  18. The encapsulation of an amphiphile into polystyrene microspheres of narrow size distribution

    Directory of Open Access Journals (Sweden)

    Pellach Michal


    Full Text Available Abstract Encapsulation of compounds into nano- or microsized organic particles of narrow size distribution is of increasing importance in fields of advanced imaging and diagnostic techniques and drug delivery systems. The main technology currently used for encapsulation of molecules within uniform template particles while retaining their size distribution is based on particle swelling methodology, involving penetration of emulsion droplets into the particles. The swelling method, however, is efficient for encapsulation only of hydrophobic compounds within hydrophobic template particles. In order to be encapsulated, the molecules must favor the hydrophobic phase of an organic/aqueous biphasic system, which is not easily achieved for molecules of amphiphilic character. The following work overcomes this difficulty by presenting a new method for encapsulation of amphiphilic molecules within uniform hydrophobic particles. We use hydrogen bonding of acid and base, combined with a pseudo salting out effect, for the entrapment of the amphiphile in the organic phase of a biphasic system. Following the entrapment in the organic phase, we demonstrated, using fluorescein and (antibiotic tetracycline as model molecules, that the swelling method usually used only for hydrophobes can be expanded and applied to amphiphilic molecules.

  19. Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive (United States)

    Li, Jian-Hua; Li, Mi-Zi; Miao, Jing; Wang, Jia-Bin; Shao, Xi-Sheng; Zhang, Qi-Qing


    An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.


    Institute of Scientific and Technical Information of China (English)

    Jian-hua Li; You-yi Xu; Jian-hua Wang; Chun-hui Du


    The synthesis of a novel amphiphilic comb-shaped copolymer consisting of a main chain of styrene-(N-(4-hydroxyphenyl) maleimide) (SHMI) copolymer and poly(ethylene glycol) methyl ether methacrylate (PEGMA) side groups was achieved by atom transfer radical polymerization (ATRP). The amphiphilic copolymers were characterized by ~1H-NMR, Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC). From thermogravimetric analysis (TGA), the decomposition temperature of SHMI-g-PEGMA is lower than that of SHMI, and the graft ratio of PEGMA in the SHMI is 18.6%. The experimental results of solubilities showed that SHMI, SHMI-Br and SHMI-g-PEGMA had excellent solubility in polar solvents, such as DMF, DMSO and NMP. SHMI-g-PEGMA had higher solubilities in H_2O and methanol, while lower solubility in CHCl_3 than SHMI and SHMI-Br. PVDF blend membranes were prepared via the standard immersion precipitation phase inversion process, using amphiphilic SHMI-g-PEGMA copolymer as additives. The morphology and hydrophilicity of the blend membrane surfaces were characterized by SEM and water contact angle. It is demonstrated that the blend membranes display enhanced hydrophilicity compared to unmodified PVDF membranes. Finally, the permeation and anti-fouling properties were investigated. The result shows that amphiphilic SHMI-g-PEGMA copolymer increases the permeatability and anti-fouling property of PVDF membranes greatly.

  1. Improved surface property of PVDF membrane with amphiphilic zwitterionic copolymer as membrane additive

    Energy Technology Data Exchange (ETDEWEB)

    Li Jianhua, E-mail: [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China); Li Mizi; Miao Jing; Wang Jiabin; Shao Xisheng [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China); Zhang Qiqing, E-mail: [Institute of Biomedical and Pharmaceutical Technology and College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350001 (China) and Institute of Biomedical Engineering, Chinese Academy of Medical Science, Peking Union Medical College, Tianjin 300192 (China)


    An attempt to improve hydrophilicity and anti-fouling properties of PVDF membranes, a novel amphiphilic zwitterionic copolymer poly(vinylidene fluoride)-graft-poly(sulfobetaine methacrylate) (PVDF-g-PSBMA) was firstly synthesized by atom transfer radical polymerization (ATRP) and used as amphiphilic copolymer additive in the preparation of PVDF membranes. The PVDF-g-PSBMA/PVDF blend membranes were prepared by immersion precipitation process. Fourier transform infrared attenuated reflection spectroscopy (FTIR-ATR) and X-ray photoelectronic spectroscopy (XPS) measurements confirmed that PSBMA brushes from amphiphilic additives were preferentially segregated to membrane-coagulant interface during membrane formation. The morphology of membranes was characterized by scanning electron microscopy (SEM). Water contact angle measurements showed that the surface hydrophilicity of PVDF membranes was improved significantly with the increasing of amphiphilic copolymer PVDF-g-PSBMA in cast solution. Protein static adsorption experiment and dynamic fouling resistance experiment revealed that the surface enrichment of PSBMA brush endowed PVDF blend membrane great improvement of surface anti-fouling ability.

  2. H-aggregation of azobenzene-substituted amphiphiles in vesicular membranes

    NARCIS (Netherlands)

    Kuiper, JM; Engberts, JBFN


    Photochemical switching has been studied of double-tailed phosphate amphiphiles containing azobenzene units in both tails in aqueous vesicular dispersions and in mixed vesicular systems with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). Since the ease of switching depends on the strength of the b

  3. Synthesis, Characterization, and Aqueous Lubricating Properties of Amphiphilic Graft Copolymers Comprising 2-Methoxyethyl Acrylate

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Røn, Troels; Jankova Atanasova, Katja;


    of the corresponding monomers followed by deblocking reaction leads to well-defined amphiphiles with narrow molecular weight distributions (PDI ≤ 1.29) and varying content of methacrylic acid. The graft copolymers showed effective surface adsorption and lubrication for self-mated poly(dimethylsiloxane) (PDMS) contacts...

  4. Amphiphile regulation of ion channel function by changes in the bilayer spring constant

    DEFF Research Database (Denmark)

    Lundbæk, Jens August; Koeppe, R.E.; Andersen, Oluf Sten


    Many drugs are amphiphiles that, in addition to binding to a particular target protein, adsorb to cell membrane lipid bilayers and alter intrinsic bilayer physical properties (e. g., bilayer thickness, monolayer curvature, and elastic moduli). Such changes can modulate membrane protein function b......-dependent sodium channels in living cells. The use of gA channels as molecular force probes provides a tool for quantitative, predictive studies of bilayer-mediated regulation of membrane protein function by amphiphiles....... by altering the energetic cost (Delta G(bilayer)) of bilayer deformations associated with protein conformational changes that involve the protein-bilayer interface. But amphiphiles have complex effects on the physical properties of lipid bilayers, meaning that the net change in Delta G(bilayer) cannot...... be predicted from measurements of isolated changes in such properties. Thus, the bilayer contribution to the promiscuous regulation of membrane proteins by drugs and other amphiphiles remains unknown. To overcome this problem, we use gramicidin A (gA) channels as molecular force probes to measure the net...

  5. Two-dimensional crystallography of amphiphilic molecules at the air-water interface

    DEFF Research Database (Denmark)

    Jacquemain, D.; Grayer Wolf, S.; Leveiller, F.;


    , and review recent results obtained from them for Langmuir films. The methods have been successfully applied in the elucidation of the structure of crystalline aggregates of amphiphilic molecules such as alcohols, carboxylic acids and their salts, alpha-amino acids, and phospholipids at the water surface...

  6. Synthesis of Novel Amphiphilic Azobenzenes and X-ray Scattering Studies of Their Langmuir Monolayers

    DEFF Research Database (Denmark)

    Sørensen, Thomas Just; Kjær, Kristian; Breiby, Dag Werner;


    . At the air-water interface, the amphiphilic azobenzenes form noncrystalline but stable Langmuir films that display an unusual reversible monolayer collapse close to 35 mN/m. The structures and phase transitions were studied by X-ray reflectivity (XR) and grazing-incidence X-ray diffraction, both utilizing...

  7. Thermodynamics of micellization of cholic acid based facial amphiphiles carrying three permanent ionic head groups

    NARCIS (Netherlands)

    Willemen, H.M.; Marcelis, A.T.M.; Sudhölter, E.J.R.


    This paper describes a series of cholic acid based facial amphiphiles carrying three ionic headgroups. Their micellization behavior in water was studied as a function of spacer length and alkyl tail length: both were found to have a small influence on the critical micellization concentration (cmc).

  8. Aggregation Properties of an Amphiphilic Methanofullerene Derivative in THF-H2O Solvent Mixtures

    Institute of Scientific and Technical Information of China (English)

    Guan Wu WANG; Li Juan JIAO; Er Hong HAO; Yong Ming LU; You Jun YANG


    Amphiphilic methanofullerene 1 exhibits strong tendency to form aggregates in THF-H2O solvent mixtures. Two different aggregation processes induced by either varying the solvent composition or upon standing have been found. Concentration has great influence on the aggregation process. Paralleling to the UV-Vis changes, an unusual solvatochromism has been observed in these two different processes.

  9. Transfection of small numbers of human endothelial cells by electroporation and synthetic amphiphiles

    NARCIS (Netherlands)

    van Leeuwen, E B; van der Veen, A Y; Hoekstra, D; Engberts, J B; Halie, M R; van der Meer, J; Ruiters, M H


    OBJECTIVES: This study compared the efficiency of electroporation and synthetic amphiphiles. (SAINT-2pp/DOPE) in transfecting small numbers of human endothelial cells. METHODS AND RESULTS: Optimal transfection conditions were tested and appeared to be 400 V and 960 microF for electroporation and a 1

  10. Macroscopic alignment of graphene stacks by Langmuir-Blodgett deposition of amphiphilic hexabenzocoronenes

    DEFF Research Database (Denmark)

    Laursen, B.W.; Nørgaard, K.; Reitzel, N.;


    e present structural studies of Langmuir V and Langmuir-Blodgett (LB) films of new amphiphilic hexa-peri-hexabenzocoronene (HBC) discotics, carrying five branched alkyl side chains and one polar group. The polar group is either a carboxylic acid moiety or an electron acceptor moiety (anthraquinone...

  11. Preparation of Vesicles and Nanoparticles of Amphiphilic Cyclodextrins Containing Labile Disulfide Bonds

    NARCIS (Netherlands)

    Nolan, Darren; Darcy, Raphael; Ravoo, Bart Jan


    Amphiphilic cyclodextrin derivatives were prepared in which a disulfide bond connects the hydrophobic substituents to the macrocycle. These compounds were obtained by 1,3-dicyclohexylcarbodiimide-mediated coupling reactions of heptakis(6-amino-6-deoxy)-B-cyclodextrins and disulfide-containing carbox

  12. Bilayer Vesicles of Amphiphilic Cyclodextrins: Host Membranes That Recognize Guest Molecules

    NARCIS (Netherlands)

    Falvey, Patrick; Lim, Choon Woo; Darcy, Raphael; Revermann, Tobias; Karst, Uwe; Giesbers, Marcel; Marcelis, Antonius T.M.; Lazar, Adina; Coleman, Anthony W.; Reinhoudt, David N.; Ravoo, Bart Jan


    A family of amphiphilic cyclodextrins (6, 7) has been prepared through 6-S-alkylation (alkyl=n-dodecyl and n-hexadecyl) of the primary side and 2-O-PEGylation of the secondary side of a-, B-, and Y-cyclodextrins (PEG=poly(ethylene glycol)). These cyclodextrins form nonionic bilayer vesicles in aqueo

  13. Bilayer vesicles of amphiphilic cyclodextrines: host membranes that recognize guest molecules

    NARCIS (Netherlands)

    Falvey, P.; Lim, C.W.; Darcy, R.; Revermann, T.; Karst, U.; Marcelis, A.T.M.; Coleman, A.W.; Reinhoudt, D.N.; Ravoo, B.J.


    A family of amphiphilic cyclodextrins (6, 7) has been prepared through 6-S-alkylation (alkyl=n-dodecyl and n-hexadecyl) of the primary side and 2-O-PEGylation of the secondary side of alpha-, beta-, and gamma-cyclodextrins (PEG=poly(ethylene glycol)). These cyclodextrins form nonionic bilayer vesicl

  14. Tunable Hydrophobicity in DNA Micelles : Design, Synthesis, and Characterization of a New Family of DNA Amphiphiles

    NARCIS (Netherlands)

    Anaya, Milena; Kwak, Minseok; Musser, Andrew J.; Muellen, Klaus; Herrmann, Andreas; Müllen, Klaus


    This work describes the synthesis and characterization of a new family of DNA amphiphiles containing modified nucleobases. The hydrophobicity was imparted by the introduction of a dodec-1-yne chain at the 5-position of the uracil base, which allowed precise and simple tuning of the hydrophobic prope

  15. Hydrophilic modification of PVDF microfiltration membranes by adsorption of facial amphiphile cholic acid. (United States)

    Hu, Meng-Xin; Li, Ji-Nian; Zhang, Shi-Lin; Li, Liang; Xu, Zhi-Kang


    Amphiphilic molecules have been widely used in surface modification of polymeric materials. Bile acids are natural biological compounds and possess special facial amphiphilic structure with a unusual distribution of hydrophobic and hydrophilic regions. Based on the facial amphiphilicity, cholic acid (CA), one of the bile acids, was utilized for the hydrophilic modification of poly(vinylidene fluoride) (PVDF) microfiltration membranes via the hydrophobic interactions between the hydrophobic face of CA and the membrane surfaces. Ethanol, methanol, and water were respectively used as solvent during CA adsorption procedure. Their polarity affects the CA adsorption amount, as similar to CA concentration and adsorption time. There are no changes on the membrane surface morphology after CA adsorption. The hydrophilicity of PVDF membranes is greatly enhanced and the water drops permeates into the CA modified membranes quickly after modification. All these factors benefit to the permeation flux of membrane for water. When CA concentration is higher than 0.088 M, the water permeation flux is doubled as compared with the nascent PVDF membrane and shows a good stability during filtration procedure. These results reveal the promising potential of facial amphiphilic bile acids for the surface modification of polymeric materials.

  16. Oxidized potato starch based thermoplastic films : Effect of combination of hydrophilic and amphiphilic plasticizers

    NARCIS (Netherlands)

    Niazi, Muhammad Bilal Khan; Broekhuis, Antonius A.


    Different combinations of hydrophilic (glycerol and water) and amphiphilic (isoleucine) plasticizers were studied in the production of thermoplastic starch (TPS) powders and films from oxidized potato starch. All powder samples had an irregular and shrivelled morphology. In all mixtures containing i

  17. Non-amphiphilic carbohydrate liquid crystals containing an intact monosaccharide moiety

    NARCIS (Netherlands)

    Smits, E; Engberts, J.B.F.N.; Kellogg, R.M; van Doren, H.A.


    A chiral rigid moiety which forms the basis of a new class of non-amphiphilic carbohydrate liquid crystals has been developed. This moiety contains a fully intact glucopyranose ring embedded in a trans-decalin structure. The original carbohydrate is substituted so that only two hydroxyl groups are l

  18. Gold Nanoparticles Protected with Thiol-Derivatized Amphiphilic Poly(epsilon-caprolactone)-b-poly(acrylic acid)

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Hvilsted, Søren


    Amphiphilic poly(epsilon-caprolactone)-b-poly(acrylic acid) (HS-PCL-b-PAA) with a thiol functionality in the PCL terminal has been prepared in a novel synthetic cascade. Initially, living anionic ring-opening polymerization (ROP) of epsilon-caprolactone (epsilon-CL) employing the difunctional...

  19. The encapsulation of an amphiphile into polystyrene microspheres of narrow size distribution. (United States)

    Pellach, Michal; Margel, Shlomo


    Encapsulation of compounds into nano- or microsized organic particles of narrow size distribution is of increasing importance in fields of advanced imaging and diagnostic techniques and drug delivery systems. The main technology currently used for encapsulation of molecules within uniform template particles while retaining their size distribution is based on particle swelling methodology, involving penetration of emulsion droplets into the particles. The swelling method, however, is efficient for encapsulation only of hydrophobic compounds within hydrophobic template particles. In order to be encapsulated, the molecules must favor the hydrophobic phase of an organic/aqueous biphasic system, which is not easily achieved for molecules of amphiphilic character.The following work overcomes this difficulty by presenting a new method for encapsulation of amphiphilic molecules within uniform hydrophobic particles. We use hydrogen bonding of acid and base, combined with a pseudo salting out effect, for the entrapment of the amphiphile in the organic phase of a biphasic system. Following the entrapment in the organic phase, we demonstrated, using fluorescein and (antibiotic) tetracycline as model molecules, that the swelling method usually used only for hydrophobes can be expanded and applied to amphiphilic molecules.

  20. Proteomic analysis of glycosylphosphatidylinositol-anchored membrane proteins

    DEFF Research Database (Denmark)

    Elortza, Felix; Nühse, Thomas S; Foster, Leonard J


    Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are a functionally and structurally diverse family of post-translationally modified membrane proteins found mostly in the outer leaflet of the plasma membrane in a variety of eukaryotic cells. Although the general role of GPI-APs remains un...

  1. Stepping stones of Amsterdam, Local and global anchor points 2010.

    NARCIS (Netherlands)

    Bois, G. de Peter


    This report shows the results of research on the relation between local and global anchor points in the city of Amsterdam, executed by a small group of international students from Italy and Spain within the scope of two research modules in their Bachelor education at the University of Applied Scienc

  2. Finding the Optimal Guidance for Enhancing Anchored Instruction (United States)

    Zydney, Janet Mannheimer; Bathke, Arne; Hasselbring, Ted S.


    This study investigated the effect of different methods of guidance with anchored instruction on students' mathematical problem-solving performance. The purpose of this research was to iteratively design a learning environment to find the optimal level of guidance. Two iterations of the software were compared. The first iteration used explicit…

  3. Implementing Anchored Instruction: Guiding Principles for Curriculum Development. (United States)

    McLarty, Kim; And Others

    A curriculum based on "anchored instruction" was developed to enhance students' literacy development and acquisition of knowledge. The curriculum was designed to create a rich, shared environment that generates interest and enables students to identify and define problems while they explore the content from many perspectives. Based on…

  4. Analytical Model for Hook Anchor Pull-out

    DEFF Research Database (Denmark)

    Brincker, Rune; Ulfkjær, J. P.; Adamsen, P.;

    A simple analytical model for the pull-out of a hook anchor is presented. The model is based on a simplified version of the fictitious crack model. It is assumed that the fracture process is the pull-off of a cone shaped concrete part, simplifying the problem by assuming pure rigid body motions...

  5. Analytical Model for Hook Anchor Pull-Out

    DEFF Research Database (Denmark)

    Brincker, Rune; Ulfkjær, J. P.; Adamsen, P.;


    A simple analytical model for the pull-out of a hook anchor is presented. The model is based on a simplified version of the fictitious crack model. It is assume that the fracture process is the pull-off of a cone shaped concrete part, simplifying the problem by assuming pure rigid body motions...

  6. Almost Lie structures on an anchored Banach bundle

    CERN Document Server

    Cabau, Patrick


    Under appropriate assumptions, we generalize the concept of linear almost Poisson struc- tures, almost Lie algebroids, almost differentials in the framework of Banach anchored bundles and the relation between these objects. We then obtain an adapted formalism for mechanical systems which is illustrated by the evolutionary problem of the "Hilbert snake"

  7. Modified Anchor Shaped Post Core Design for Primary Anterior Teeth


    R. Rajesh; Kusai Baroudi; K. Bala Kasi Reddy; Praveen, B. H.; V. Sumanth Kumar; Amit, S


    Restoring severely damaged primary anterior teeth is challenging to pedodontist. Many materials are tried as a post core but each one of them has its own drawbacks. This a case report describing a technique to restore severely damaged primary anterior teeth with a modified anchor shaped post. This technique is not only simple and inexpensive but also produces better retention.

  8. Modified Anchor Shaped Post Core Design for Primary Anterior Teeth

    Directory of Open Access Journals (Sweden)

    R. Rajesh


    Full Text Available Restoring severely damaged primary anterior teeth is challenging to pedodontist. Many materials are tried as a post core but each one of them has its own drawbacks. This a case report describing a technique to restore severely damaged primary anterior teeth with a modified anchor shaped post. This technique is not only simple and inexpensive but also produces better retention.

  9. Modified anchor shaped post core design for primary anterior teeth. (United States)

    Rajesh, R; Baroudi, Kusai; Reddy, K Bala Kasi; Praveen, B H; Kumar, V Sumanth; Amit, S


    Restoring severely damaged primary anterior teeth is challenging to pedodontist. Many materials are tried as a post core but each one of them has its own drawbacks. This a case report describing a technique to restore severely damaged primary anterior teeth with a modified anchor shaped post. This technique is not only simple and inexpensive but also produces better retention.

  10. Ten Anchor Points for Teaching Principles of Marketing (United States)

    Tomkovick, Chuck


    Effective marketing instructors commonly share a love for their students, an affinity for the subject matter, and a devotion to continuous quality improvement. The purpose of this article is to highlight 10 anchor points for teaching Principles of Marketing, which are designed to better engage students in the learning process. These anchor…

  11. Conventional Anchor Test Results at San Diego and Indian Island (United States)


    lines passed through open chocks welded at opposite ends of the barge. A crane barge was used to install and recover all test anchors at each site...DEPT OF FISH & GAME Long Beach CA (Marine Tech Info Ctr) CALIF. DEPT OF NAVIGATION & OCEAN DEV. Sacramento, CA (G. Armstrong) CALIF. MARITIME ACADEMY

  12. The bone-anchored hearing aid for children: recent developments.

    NARCIS (Netherlands)

    Snik, A.F.M.; Leijendeckers, J.M.; Hol, M.K.S.; Mylanus, E.A.M.; Cremers, C.


    In 1984 the Bone-Anchored Hearing Aid, or BAHA, system was introduced. Its transducer is coupled directly to the skull percutaneously to form a highly effective bone-conduction hearing device. Clinical studies on adults with conductive hearing loss have shown that the BAHA system outperforms convent

  13. Stone anchors from the Okhamandal region, Gujarat Coast, India

    Digital Repository Service at National Institute of Oceanography (India)

    Sundaresh; Gaur, A.S.; Gudigar, P.; Tripati, S.; Vora, K.H.; Bandodkar, S.N.

    period particularly on south-western coast of the island while stone anchors were noticed on the eastern coast of the island where medieval period remains can be noticed in the form of pottery, cannons and a few stone structures. Similar type of stone...

  14. A Proteomics Investigation of Anchored PKA-RI Signaling

    NARCIS (Netherlands)

    Kovanich, D.


    Compartmentalization of kinases and phosphatases plays an important role in the specificity of second messenger mediated signaling events. Localization of the cAMP-dependent protein kinase is mediated by interaction of its regulatory subunit (PKA-R) with the versatile family of A-kinase anchoring pr

  15. Anchoring return: the role of the Solutions Strategy

    Directory of Open Access Journals (Sweden)

    Pierfrancesco Maria Natta


    Full Text Available Providing a minimum standard of living and livelihood opportunities to help anchor those who have returned is critical for the future stability and security of Afghanistan. This is one of the three main objectives of the 2012 Solutions Strategy for Afghan Refugees.

  16. The importance of anchor text for ad hoc search revisited

    NARCIS (Netherlands)

    M. Koolen; J. Kamps


    It is generally believed that propagated anchor text is very important for effective Web search as offered by the commercial search engines. "Google Bombs" are a notable illustration of this. However, many years of TREC Web retrieval research failed to establish the effectiveness of link evidence fo

  17. Impact of Enhanced Anchored Instruction in Inclusive Math Classrooms (United States)

    Bottge, Brian A.; Toland, Michael D.; Gassaway, Linda; Butler, Mark; Choo, Sam; Griffen, Ann Katherine; Ma, Xin


    The Common Core State Standards for Mathematics will place more pressure on special education and math teachers to raise the skill levels of all students, especially those with disabilities in math (MD). The purpose of this study was to assess the effects of enhanced anchored instruction (EAI) on students with and without MD in co-taught general…

  18. Fullerene-based Anchoring Groups for Molecular Electronics

    DEFF Research Database (Denmark)

    Martin, Christian A.; Ding, Dapeng; Sørensen, Jakob Kryger


    We present results on a new fullerene-based anchoring group for molecular electronics. Using lithographic mechanically controllable break junctions in vacuum we have determined the conductance and stability of single-molecule junctions of 1,4-bis(fullero[c]pyrrolidin-1-yl)benzene. The compound can...

  19. Poor Anchoring Limits Dyslexics' Perceptual, Memory, and Reading Skills (United States)

    Oganian, Yulia; Ahissar, Merav


    The basic deficits underlying the severe and persistent reading difficulties in dyslexia are still highly debated. One of the major topics of debate is whether these deficits are language specific, or affect both verbal and non-verbal stimuli. Recently, Ahissar and colleagues proposed the "anchoring-deficit hypothesis" (Ahissar, Lubin,…

  20. The Effect of Anchor Test Construction on Scale Drift (United States)

    Antal, Judit; Proctor, Thomas P.; Melican, Gerald J.


    In common-item equating the anchor block is generally built to represent a miniature form of the total test in terms of content and statistical specifications. The statistical properties frequently reflect equal mean and spread of item difficulty. Sinharay and Holland (2007) suggested that the requirement for equal spread of difficulty may be too…

  1. Audiometric evaluation of bilaterally fitted bone-anchored hearing aids.

    NARCIS (Netherlands)

    Bosman, A.J.; Snik, A.F.M.; Pouw, C.T.M. van der; Mylanus, E.A.M.; Cremers, C.W.R.J.


    Bilateral fittings of bone-anchored hearing aids (BAHA) were evaluated in 25 patients with at least 3 months experience with using two BAHAs. For all patients, air conduction hearing aids were contraindicated due to either recurrent otorrhoea or otitis externa (19 cases) or to congenital aural atres

  2. Controlling molecular ordering in solution-state conjugated polymers. (United States)

    Zhu, J; Han, Y; Kumar, R; He, Y; Hong, K; Bonnesen, P V; Sumpter, B G; Smith, S C; Smith, G S; Ivanov, I N; Do, C


    Rationally encoding molecular interactions that can control the assembly structure and functional expression in a solution of conjugated polymers hold great potential for enabling optimal organic optoelectronic and sensory materials. In this work, we show that thermally-controlled and surfactant-guided assembly of water-soluble conjugated polymers in aqueous solution is a simple and effective strategy to generate optoelectronic materials with the desired molecular ordering. We have studied a conjugated polymer consisting of a hydrophobic thiophene backbone and hydrophilic, thermo-responsive ethylene oxide side groups, which shows a step-wise, multi-dimensional assembly in water. By incorporating the polymer into phase-segregated domains of an amphiphilic surfactant in solution, we demonstrate that both chain conformation and degree of molecular ordering of the conjugated polymer can be tuned in hexagonal, micellar and lamellar phases of the surfactant solution. The controlled molecular ordering in conjugated polymer assembly is demonstrated as a key factor determining the electronic interaction and optical function.

  3. Enhancing the protein resistance of silicone via surface-restructuring PEO-silane amphiphiles with variable PEO length


    Rufin, M. A.; Gruetzner, J. A.; Hurley, M. J.; Hawkins, M. L.; Raymond, E. S.; Raymond, J. E.; Grunlan, M. A.


    Silicones with superior protein resistance were produced by bulk-modification with poly(ethylene oxide) (PEO)-silane amphiphiles that demonstrated a higher capacity to restructure to the surface-water interface versus conventional non-amphiphilic PEO-silanes. The PEO-silane amphiphiles were prepared with a single siloxane tether length but variable PEO segment lengths: α-(EtO)3Si(CH2)2-oligodimethylsiloxane13-block-poly(ethylene oxide)n-OCH3 (n = 3, 8, and 16). Conventional PEO-silane analogu...

  4. Organometallic Polymers. (United States)

    Carraher, Charles E., Jr.


    Reactions utilized to incorporate a metal-containing moiety into a polymer chain (addition, condensation, and coordination) are considered, emphasizing that these reactions also apply to smaller molecules. (JN)

  5. The biggest stone anchors (Indo-Arab type) from Mithi Virdi, Bhavnagar, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Gaur, A.S.; Sundaresh; Kumar, B.

    A coastal archaeological exploration in Talaja taluka of Bhavnagar district, Gujarat, brought to light 5 grapnel stone anchors in an agriculture land. The site and these anchors are known as Bhima ka Khatiya ('Cot of Bhima', a famous character...

  6. Radiocarbon dates of the medieval period stone anchors from Dabhol, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Gaur, A; Sundaresh; Tripati, S.; Vora, K.H.

    Dabhol was an important medieval-period port town on the Maharashtra coast. An archaeological exploration at Dabhol has revealed four stone anchors with remains of wood in fluke hole. These anchors were retrieved from Dabhol creek during a dredging...

  7. Thermal conductivity of polymer composites with oriented boron nitride

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Hong Jun; Eoh, Young Jun [Department of Materials Engineering, Kyonggi University, Suwon (Korea, Republic of); Park, Sung Dae [Electronic Materials and Device Research Center, Korea Electronics Technology Institute, Seongnam (Korea, Republic of); Kim, Eung Soo, E-mail: [Department of Materials Engineering, Kyonggi University, Suwon (Korea, Republic of)


    Highlights: • Thermal conductivity depended on the orientation of BN in the polymer matrices. • Hexagonal boron nitride (BN) particles were treated by C{sub 27}H{sub 27}N{sub 3}O{sub 2} and C{sub 14}H{sub 6}O{sub 8}. • Amphiphilic-agent-treated BN particles are more easily oriented in the composite. • BN/PVA composites with C{sub 14}H{sub 6}O{sub 8}-treated BN showed the highest thermal conductivity. • Thermal conductivity of the composites was compared with several theoretical models. - Abstract: Thermal conductivity of boron nitride (BN) with polyvinyl alcohol (PVA) and/or polyvinyl butyral (PVB) was investigated as a function of the degree of BN orientation, the numbers of hydroxyl groups in the polymer matrices and the amphiphilic agents used. The composites with in-plane orientation of BN showed a higher thermal conductivity than the composites with out-of-plane orientation of BN due to the increase of thermal pathway. For a given BN content, the composites with in-plane orientation of BN/PVA showed higher thermal conductivity than the composites with in-plane orientation of BN/PVB. This result could be attributed to the improved degree of orientation of BN, caused by a larger number of hydroxyl groups being present. Those treated with C{sub 14}H{sub 6}O{sub 8} amphiphilic agent demonstrated a higher thermal conductivity than those treated by C{sub 27}H{sub 27}N{sub 3}O{sub 2}. The measured thermal conductivity of the composites was compared with that predicted by the several theoretical models.

  8. Anchoring a Leviathan: How the Nuclear Membrane Tethers the Genome

    Directory of Open Access Journals (Sweden)

    Rafal eCzapiewski


    Full Text Available It is well established that the nuclear envelope has many distinct direct connections to chromatin that contribute to genome organization. The functional consequences of genome organization on gene regulation are less clear. Even less understood is how interactions of lamins and nuclear envelope transmembrane proteins (NETs with chromatin can produce anchoring tethers that can withstand the physical forces of and on the genome. Chromosomes are the largest molecules in the cell, making megadalton protein structures like the nuclear pore complexes and ribosomes seem small by comparison. Thus to withstand strong forces from chromosome dynamics an anchoring tether is likely to be much more complex than a single protein-protein or protein-DNA interaction. Here we will briefly review known NE-genome interactions that likely contribute to spatial genome organization, postulate in the context of experimental data how these anchoring tethers contribute to gene regulation, and posit several hypotheses for the physical nature of these tethers that need to be investigated experimentally. Significantly, disruption of these anchoring tethers and the subsequent consequences for gene regulation could explain how mutations in nuclear envelope proteins cause diseases ranging from muscular dystrophy to lipodystrophy to premature ageing progeroid syndromes. The two favored hypotheses for nuclear envelope protein involvement in disease are 1 weakening nuclear and cellular mechanical stability, and 2 disrupting genome organization and gene regulation. Considerable experimental support has been obtained for both. The integration of both mechanical and gene expression defects in the disruption of anchoring tethers could provide a unifying hypothesis consistent with both.

  9. Large organized surface domains self-assembled from nonpolar amphiphiles. (United States)

    Krafft, Marie Pierre


    For years, researchers had presumed that Langmuir monolayers of small C(n)F(2n+1)C(m)H(2m+1) (FnHm) diblock molecules (such as F8H16) consisted of continuous, featureless films. Recently we have discovered that they instead form ordered arrays of unusually large (~30-60 nm), discrete self-assembled surface domains or hemimicelles both at the surface of water and on solid substrates. These surface micelles differ in several essential ways from all previously reported or predicted molecular surface aggregates. They self-assemble spontaneously, even at zero surface pressure, depending solely on a critical surface concentration. They are very large (~100 times the length of the diblock) and involve thousands of molecules (orders of magnitude more than classical micelles). At the same time, the surface micelles are highly monodisperse and self-organize in close-packed hexagonal patterns (two-dimensional crystals). Their size is essentially independent from pressure, and they do not coalesce and are unexpectedly sturdy for soft matter (persisting even beyond surface film collapse). We and other researchers have observed large surface micelles for numerous diblocks, using Langmuir-Blodgett (LB) transfer, spin-coating and dip-coating techniques, or expulsion from mixed monolayers, and on diverse supports, establishing that hemimicelle formation and ordering are intrinsic properties of (perfluoroalkyl)alkanes. Notably, they involve "incomplete" surfactants with limited amphiphilic character, which further illustrates the outstanding capacity for perfluoroalkyl chains to promote self-assembly and interfacial film structuring. Using X-ray reflectivity, we determined a perfluoroalkyl-chain-up orientation. Theoretical investigations assigned self-assembly and hemimicelle stability to electrostatic dipole-dipole interactions at the interface between Fn- and Hm-sublayers. Grazing-incidence small-angle X-ray scattering (GISAXS) data collected directly on the surface of water

  10. Sortase A substrate specificity in GBS pilus 2a cell wall anchoring. (United States)

    Necchi, Francesca; Nardi-Dei, Vincenzo; Biagini, Massimiliano; Assfalg, Michael; Nuccitelli, Annalisa; Cozzi, Roberta; Norais, Nathalie; Telford, John L; Rinaudo, C Daniela; Grandi, Guido; Maione, Domenico


    Streptococcus agalactiae, also referred to as Group B Streptococcus (GBS), is one of the most common causes of life-threatening bacterial infections in infants. In recent years cell surface pili have been identified in several Gram-positive bacteria, including GBS, as important virulence factors and promising vaccine candidates. In GBS, three structurally distinct types of pili have been discovered (pilus 1, 2a and 2b), whose structural subunits are assembled in high-molecular weight polymers by specific class C sortases. In addition, the highly conserved housekeeping sortase A (SrtA), whose main role is to link surface proteins to bacterial cell wall peptidoglycan by a transpeptidation reaction, is also involved in pili cell wall anchoring in many bacteria. Through in vivo mutagenesis, we demonstrate that the LPXTG sorting signal of the minor ancillary protein (AP2) is essential for pilus 2a anchoring. We successfully produced a highly purified recombinant SrtA (SrtA(ΔN40)) able to specifically hydrolyze the sorting signal of pilus 2a minor ancillary protein (AP2-2a) and catalyze in vitro the transpeptidation reaction between peptidoglycan analogues and the LPXTG motif, using both synthetic fluorescent peptides and recombinant proteins. By contrast, SrtA(ΔN40) does not catalyze the transpeptidation reaction with substrate-peptides mimicking sorting signals of the other pilus 2a subunits (the backbone protein and the major ancillary protein). Thus, our results add further insight into the proposed model of GBS pilus 2a assembly, in which SrtA is required for pili cell wall covalent attachment, acting exclusively on the minor accessory pilin, representing the terminal subunit located at the base of the pilus.

  11. Sortase A substrate specificity in GBS pilus 2a cell wall anchoring.

    Directory of Open Access Journals (Sweden)

    Francesca Necchi

    Full Text Available Streptococcus agalactiae, also referred to as Group B Streptococcus (GBS, is one of the most common causes of life-threatening bacterial infections in infants. In recent years cell surface pili have been identified in several Gram-positive bacteria, including GBS, as important virulence factors and promising vaccine candidates. In GBS, three structurally distinct types of pili have been discovered (pilus 1, 2a and 2b, whose structural subunits are assembled in high-molecular weight polymers by specific class C sortases. In addition, the highly conserved housekeeping sortase A (SrtA, whose main role is to link surface proteins to bacterial cell wall peptidoglycan by a transpeptidation reaction, is also involved in pili cell wall anchoring in many bacteria. Through in vivo mutagenesis, we demonstrate that the LPXTG sorting signal of the minor ancillary protein (AP2 is essential for pilus 2a anchoring. We successfully produced a highly purified recombinant SrtA (SrtA(ΔN40 able to specifically hydrolyze the sorting signal of pilus 2a minor ancillary protein (AP2-2a and catalyze in vitro the transpeptidation reaction between peptidoglycan analogues and the LPXTG motif, using both synthetic fluorescent peptides and recombinant proteins. By contrast, SrtA(ΔN40 does not catalyze the transpeptidation reaction with substrate-peptides mimicking sorting signals of the other pilus 2a subunits (the backbone protein and the major ancillary protein. Thus, our results add further insight into the proposed model of GBS pilus 2a assembly, in which SrtA is required for pili cell wall covalent attachment, acting exclusively on the minor accessory pilin, representing the terminal subunit located at the base of the pilus.

  12. Removal and recovery of toxic metal ions from aqueous waste sites using polymer pendant ligands

    Energy Technology Data Exchange (ETDEWEB)

    Fish, D. [Lawrence Berkeley National Lab., CA (United States)


    The purpose of this project is to investigate the use of polymer pendant ligand technology to remove and recover toxic metal ions from DOE aqueous waste sites. Polymer pendant lgiands are organic ligands, anchored to crosslinked, modified divinylbenzene-polystyrene beads, that can selectively complex metal ions. The metal ion removal step usually occurs through a complexation or ion exchange phenomena, thus recovery of the metal ions and reuse of the beads is readily accomplished.

  13. Dissipative Particle Dynamics Study on Aggregation of MPEG- PAE-PLA Block Polymer Micelles Loading Doxorubicine

    Institute of Scientific and Technical Information of China (English)

    杨楚芬; 孙尧; 章莉娟; 朱国典; 张灿阳; 钱宇


    To guide the molecular design of the pH-sensitive triblock amphiphilic polymer MPEG-PAE-PLA and the for- mula design of its doxorubicine (DOX)-loaded micelles, dissipative particle dynamics (DPD) simulations are em- ployed to investigate the aggregation behaviors of the DOX-loaded micelles. The simulation results showed that the aggregate morphologies of micelles and DOX distribution are influenced by degree of polymerization of blocks, and the proposed structure of polymer is MPEG44-PAE3-PLA4. With different contents of polymer or DOX, differ- ent aggregate morphologies of the micelles, like microsphere, spindle/column, reticulation or lamella are observed. To prepare the micro-spherical DOX-loaded micelles, the polymer content is proposed as 10%--15%, and the DOX content less than 10%.

  14. Tuning the sphere-to-rod transition in the self-assembly of thermoresponsive polymer hybrids. (United States)

    Lee, Jangwook; Park, Honghyun; Jeong, Eun Ju; Kwark, Young-Je; Lee, Kuen Yong


    Nano-scale drug delivery systems have undergone extensive development, and control of size and structure is critical for regulation of their biological responses and therapeutic efficacy. Amphiphilic polymers that form self-assembled structures in aqueous media have been investigated and used for the diagnosis and therapy of various diseases, including cancer. Here, we report the design and fabrication of thermoresponsive polymeric micelles from alginate conjugated with poly(N-isopropylacrylamide) (PNIPAAm). Alginate-PNIPAAm hybrids formed self-aggregated structures in response to temperature changes near body temperature. A structural transition from micellar spheres to rods of alginate-PNIPAAm hybrids was observed depending on the molecular weight of PNIPAAm and the polymer concentration. Additionally, hydrogels with nanofibrous structures were formed by simply increasing the polymer concentration. This approach to controlling the structure of polymer micelles from nanoparticles to fibrous hydrogels may be useful in applications in drug delivery and tissue engineering.

  15. Biomimetic Mussel Adhesive Inspired Clickable Anchors Applied to the Functionalization of Fe3O4 Nanoparticles

    NARCIS (Netherlands)

    Goldmann, Anja S.; Schoedel, Christine; Walther, Andreas; Yuan, Jiayin; Loos, Katja; Mueller, Axel H. E.; Müller, Axel H.E.


    The functionalization of magnetite (Fe3O4) nanoparticles with dopamine-derived clickable biomimetic anchors is reported. Herein, an alkyne-modified catechol-derivative is employed as the anchor, as i) the catechol-functional anchor groups possess irreversible covalent binding affinity to Fe3O4 nanop

  16. Perception of the Raison d'Etre in Anchored Instruction: An Ecological Psychology Perspective. (United States)

    Young, Michael F.; Barab, Sasha A.


    Anchored instruction calls for the establishment of a macrocontext to "anchor" instruction within a realistic situation. Evidence is provided that video anchors encourage students to adopt certain contrived goals over their more naturalistic goals. Suggests that goals that enable the problem solver to detect the "raison d'etre"…

  17. The influence of bone formation on anchoring percutaneous devices with titanium fibre mesh flanges.

    NARCIS (Netherlands)

    Shalabi, M.M.; Walboomers, X.F.; Jansen, J.A.


    For man-made percutaneous devices (PD), it is known that anchoring will improve the clinical success. Previously, our Department has designed PDs that use a sheet of titanium (Ti) fibre mesh for anchoring. In nature, a very successful natural PD occurs, namely the tooth. Teeth are anchored in the al

  18. A group of 20 stone anchors from the waters of Dwarka, on the Gujarat Coast, India

    Digital Repository Service at National Institute of Oceanography (India)

    Gaur, A.S; Sundaresh; Tripati, S; Gudigar, P.; Vora, K.H.; Bandodkar, S

    A large number of stone anchors were discovered in a water depth of 10-14 m off Dwarka during the 1998-99 season. The seabed near the anchors consists of a ledge with an average height of 1 m. Several anchors were found trapped between the rocks...

  19. Phosphorylcholine substituted polyolefins: New syntheses, solution assemblies, and polymer vesicles (United States)

    Kratz, Katrina A.

    This thesis describes the synthesis and applications of a new series of amphiphilic homopolymers and copolymers consisting of hydrophobic polyolefin backbone and hydrophilic phosphorylcholine (PC) pendant groups. These polymers are synthesized by ring opening metathesis polymerization (ROMP) of a novel PC- cyclooctene monomer, and copolymerization of various functionalized cyclooctene comonomers. Incorporation of different comonomers into the PC-polyolefin backbone affords copolymers with different functionalities, including crosslinkers, fluorophores, and other reactive groups, that tune the range of applications of these polymers, and their hydrophobic/hydrophilic balance. The amphiphilic nature of PC-polyolefins was exploited in oil-water interfacial assembly, providing robust polymer capsules to encapsulate and deliver nanoparticles to damaged regions of a substrate in a project termed `repair-and-go.' In repair-and-go, a flexible microcapsule filled with a solution of nanoparticles probes an imperfection-riddled substrate as it rolls over the surface. The thin capsule wall allows the nanoparticles to escape the capsules and enter into the cracks, driven in part by favorable interactions between the nanoparticle ligands and the cracked surface (i.e., hydrophobic-hydrophobic interactions). The capsules then continue their transport along the surface, filling more cracks and depositing particles into them. The amphiphilic nature of PC-polyolefins was also exploited in aqueous assembly, forming novel polymer vesicles in water. PC-polyolefin vesicles ranged in size from 50 nm to 30 µm. The mechanical properties of PC-polyolefin vesicles were measured by micropipette aspiration techniques, and found to be more robust than conventional liposomes or polymersomes prepared from block copolymers. PC-polyolefin vesicles have potential use in drug delivery; it was found that the cancer drug doxorubicin could be encapsulated efficiently in PC-polyolefin vesicles. In

  20. Star polymer unimicelles on graphene oxide flakes. (United States)

    Choi, Ikjun; Kulkarni, Dhaval D; Xu, Weinan; Tsitsilianis, Constantinos; Tsukruk, Vladimir V


    We report the interfacial assembly of amphiphilic heteroarm star copolymers (PSnP2VPn and PSn(P2VP-b-PtBA)n (n = 28 arms)) on graphene oxide flakes at the air-water interface. Adsorption, spreading, and ordering of star polymer micelles on the surface of the basal plane and edge of monolayer graphene oxide sheets were investigated on a Langmuir trough. This interface-mediated assembly resulted in micelle-decorated graphene oxide sheets with uniform spacing and organized morphology. We found that the surface activity of solvated graphene oxide sheets enables star polymer surfactants to subsequently adsorb on the presuspended graphene oxide sheets, thereby producing a bilayer complex. The positively charged heterocyclic pyridine-containing star polymers exhibited strong affinity onto the basal plane and edge of graphene oxide, leading to a well-organized and long-range ordered discrete micelle assembly. The preferred binding can be related to the increased conformational entropy due to the reduction of interarm repulsion. The extent of coverage was tuned by controlling assembly parameters such as concentration and solvent polarity. The polymer micelles on the basal plane remained incompressible under lateral compression in contrast to ones on the water surface due to strongly repulsive confined arms on the polar surface of graphene oxide and a preventive barrier in the form of the sheet edges. The densely packed biphasic tile-like morphology was evident, suggesting the high interfacial stability and mechanically stiff nature of graphene oxide sheets decorated with star polymer micelles. This noncovalent assembly represents a facile route for the control and fabrication of graphene oxide-inclusive ultrathin hybrid films applicable for layered nanocomposites.