Computational approach to the study of morphological properties of polymer/fullerene blends in photovoltaics

NASA Astrophysics Data System (ADS)

Gaitho, Francis M.; Mola, Genene T.; Pellicane, Giuseppe

2018-02-01

Organic solar cells have the ability to transform solar energy efficiently and have a promising energy balance. Producing these cells is economical and makes use of methods of printing using inks built on solvents that are well-matched with a variety of cheap materials like flexible plastic or paper. The primary materials used to manufacture organic solar cells include carbon-based semiconductors, which are good light absorbers and efficient charge generators. In this article, we review previous research of interest based on morphology of polymer blends used in bulk heterojunction (BHJ) solar cells and introduce their basic principles. We further review computational models used in the analysis of surface behavior of polymer blends in BHJ as well as the trends in the field of polymer surface science as applied to BHJ photovoltaics. We also give in brief, the opportunities and challenges in the area of polymer blends on BHJ organic solar cells.

Facile Fabrication of Hierarchically Thermoresponsive Binary Polymer Pattern for Controlled Cell Adhesion.

PubMed

Hou, Jianwen; Cui, Lele; Chen, Runhai; Xu, Xiaodong; Chen, Jiayue; Yin, Ligang; Liu, Jingchuan; Shi, Qiang; Yin, Jinghua

2018-03-01

A versatile platform allowing capture and detection of normal and dysfunctional cells on the same patterned surface is important for accessing the cellular mechanism, developing diagnostic assays, and implementing therapy. Here, an original and effective method for fabricating binary polymer brushes pattern is developed for controlled cell adhesion. The binary polymer brushes pattern, composed of poly(N-isopropylacrylamide) (PNIPAAm) and poly[poly(ethylene glycol) methyl ether methacrylate] (POEGMA) chains, is simply obtained via a combination of surface-initiated photopolymerization and surface-activated free radical polymerization. This method is unique in that it does not utilize any protecting groups or procedures of backfilling with immobilized initiator. It is demonstrated that the precise and well-defined binary polymer patterns with high resolution are fabricated using this facile method. PNIPAAm chains capture and release cells by thermoresponsiveness, while POEGMA chains possess high capability to capture dysfunctional cells specifically, inducing a switch of normal red blood cells (RBCs) arrays to hemolytic RBCs arrays on the pattern with temperature. This novel platform composed of binary polymer brush pattern is smart and versatile, which opens up pathways to potential applications as microsensors, biochips, and bioassays. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Method for separating biological cells. [suspended in aqueous polymer systems

NASA Technical Reports Server (NTRS)

Brooks, D. E. (Inventor)

1980-01-01

A method for separating biological cells by suspending a mixed cell population in a two-phase polymer system is described. The polymer system consists of droplet phases with different surface potentials for which the cell populations exhibit different affinities. The system is subjected to an electrostatic field of sufficient intensity to cause migration of the droplets with an attendant separation of cells.

Enhanced adherence of mouse fibroblast and vascular cells to plasma modified polyethylene.

PubMed

Reznickova, Alena; Novotna, Zdenka; Kolska, Zdenka; Kasalkova, Nikola Slepickova; Rimpelova, Silvie; Svorcik, Vaclav

2015-01-01

Since the last decade, tissue engineering has shown a sensational promise in providing more viable alternatives to surgical procedures for harvested tissues, implants and prostheses. Biomedical polymers, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE) and ultra-high molecular weight polyethylene (UHMWPE), were activated by Ar plasma discharge. Degradation of polymer chains was examined by determination of the thickness of ablated layer. The amount of an ablated polymer layer was measured by gravimetry. Contact angle, measured by goniometry, was studied as a function of plasma exposure and post-exposure aging times. Chemical structure of modified polymers was characterized by angle resolved X-ray photoelectron spectroscopy. Surface chemistry and polarity of the samples were investigated by electrokinetic analysis. Changes in surface morphology were followed using atomic force microscopy. Cytocompatibility of plasma activated polyethylene foils was studied using two distinct model cell lines; VSMCs (vascular smooth muscle cells) as a model for vascular graft testing and connective tissue cells L929 (mouse fibroblasts) approved for standardized material cytotoxicity testing. Specifically, the cell number, morphology, and metabolic activity of the adhered and proliferated cells on the polyethylene matrices were studied in vitro. It was found that the plasma treatment caused ablation of the polymers, resulting in dramatic changes in their surface morphology and roughness. ARXPS and electrokinetic measurements revealed oxidation of the polymer surface. It was found that plasma activation has a positive effect on the adhesion and proliferation of VSMCs and L929 cells. Copyright © 2015 Elsevier B.V. All rights reserved.

Modeling of organic solar cell using response surface methodology

NASA Astrophysics Data System (ADS)

Suliman, Rajab; Mitul, Abu Farzan; Mohammad, Lal; Djira, Gemechis; Pan, Yunpeng; Qiao, Qiquan

Polymer solar cells have drawn much attention during the past few decades due to their low manufacturing cost and incompatibility for flexible substrates. In solution-processed organic solar cells, the optimal thickness, annealing temperature, and morphology are key components to achieving high efficiency. In this work, response surface methodology (RSM) is used to find optimal fabrication conditions for polymer solar cells. In order to optimize cell efficiency, the central composite design (CCD) with three independent variables polymer concentration, polymer-fullerene ratio, and active layer spinning speed was used. Optimal device performance was achieved using 10.25 mg/ml polymer concentration, 0.42 polymer-fullerene ratio, and 1624 rpm of active layer spinning speed. The predicted response (the efficiency) at the optimum stationary point was found to be 5.23% for the Poly(diketopyrrolopyrrole-terthiophene) (PDPP3T)/PC60BM solar cells. Moreover, 97% of the variation in the device performance was explained by the best model. Finally, the experimental results are consistent with the CCD prediction, which proves that this is a promising and appropriate model for optimum device performance and fabrication conditions.

Laser surface texturing of polymers for biomedical applications

NASA Astrophysics Data System (ADS)

Riveiro, Antonio; Maçon, Anthony L. B.; del Val, Jesus; Comesaña, Rafael; Pou, Juan

2018-02-01

Polymers are materials widely used in biomedical science because of their biocompatibility, and good mechanical properties (which, in some cases, are similar to those of human tissues); however, these materials are, in general, chemically and biologically inert. Surface characteristics, such as topography (at the macro-, micro, and nanoscale), surface chemistry, surface energy, charge or wettability are interrelated properties, and they cooperatively influence the biological performance of materials when used for biomedical applications. They regulate the biological response at the implant/tissue interface (e.g., influencing the cell adhesion, cell orientation, cell motility, etc.). Several surface processing techniques have been explored to modulate these properties for biomedical applications. Despite their potentials, these methods have limitations that prevent their applicability. In this regard, laser-based methods, in particular laser surface texturing (LST), can be an interesting alternative. Different works have showed the potentiality of this technique to control the surface properties of biomedical polymers and enhance their biological performance; however, more research is needed to obtain the desired biological response. This work provides a general overview of the basics and applications of LST for the surface modification of polymers currently used in the clinical practice (e.g. PEEK, UHMWPE, PP, etc.). The modification of roughness, wettability, and their impact on the biological response is addressed to offer new insights on the surface modification of biomedical polymers.

Enhancing the biocompatibility of the polyurethane methacrylate and off-stoichiometry thiol-ene polymers by argon and nitrogen plasma treatment.

PubMed

Chen, Tiam Foo; Siow, Kim Shyong; Ng, Pei Yuen; Majlis, Burhanuddin Yeop

2017-10-01

Our studies focused on improving the biocompatibility properties of two microfluidic prototyping substrates i.e. polyurethane methacrylate (PUMA) and off-stoichiometry thiol-ene (OSTE-80) polymer by Ar and N 2 plasma treatment. The contact angle (CA) measurement showed that both plasma treatments inserted oxygen and nitrogen moieties increased the surface energy and hydrophilicity of PUMA and OSTE-80 polymer which corresponded to an increase of nitrogen to carbon ratios (N/C), as measured by XPS, to provide a conducive environment for cell attachments and proliferation. Under the SEM observation, the surface topography of PUMA and OSTE-80 polymer showed minimal changes after the plasma treatments. Furthermore, ageing studies showed that plasma-treated PUMA and OSTE-80 polymer had stable hydrophilicity and nitrogen composition during storage in ambient air for 15days. After in vitro cell culture of human umbilical vein endothelial cells (HUVECs) on these surfaces for 24h and 72h, both trypan blue and alamar blue assays indicated that PUMA and OSTE-80 polymer treated with N 2 plasma had the highest viability and proliferation. The polar nitrogen moieties, specifically amide groups, encouraged the HUVECs adhesion on the plasma-treated PUMA and OSTE-80 surfaces. Interestingly, PUMA polymer treated with Ar and N 2 plasma showed different HUVECs morphology which was spindle and cobblestone-shaped respectively after 72h of incubation. On the contrary, a monolayer of well-spread HUVECs formed on the Ar and N 2 plasma-treated OSTE-80 polymers. These variable morphologies observed can be ascribed to the adherence HUVECs on the different elastic moduli of these surfaces whereby further investigation might be needed. Overall, Ar and N 2 plasma treatment had successfully altered the surface properties of PUMA and OSTE-80 polymer by increasing its surface energy, hydrophilicity and chemical functionalities to create a biocompatible surface for HUVECs adhesion and proliferation. Copyright © 2017 Elsevier B.V. All rights reserved.

Algal antifouling and fouling-release properties of metal surfaces coated with a polymer inspired by marine mussels.

PubMed

Statz, Andrea; Finlay, John; Dalsin, Jeffrey; Callow, Maureen; Callow, James A; Messersmith, Phillip B

2006-01-01

The marine antifouling and fouling-release performance of titanium surfaces coated with a bio-inspired polymer was investigated. The polymer consisted of methoxy-terminated poly(ethylene glycol) (mPEG) conjugated to the adhesive amino acid l-3,4-dihydroxyphenylalanine (DOPA) and was chosen based on its successful resistance to protein and mammalian cell fouling. Biofouling assays for the settlement and release of the diatom Navicula perminuta and settlement, growth and release of zoospores and sporelings (young plants) of the green alga Ulva linza were carried out. Results were compared to glass, a poly(dimethylsiloxane) elastomer (Silastic T2) and uncoated Ti. The mPEG-DOPA3 modified Ti surfaces exhibited a substantial decrease in attachment of both cells of N. perminuta and zoospores of U. linza as well as the highest detachment of attached cells under flow compared to control surfaces. The superior performance of this polymer over a standard silicone fouling-release coating in diatom assays and approximately equivalent performance in zoospore assays suggests that this bio-inspired polymer may be effective in marine antifouling and fouling-release applications.

Biocompatibility of modified ultra-high-molecular-weight polyethylene

NASA Astrophysics Data System (ADS)

Novotná, Z.; Lacmanová, V.; Rimpelová, S.; Juřik, P.; Polívková, M.; Å vorčik, V.

2016-09-01

Ultra-high-molecular-weight polyethylene (UHMWPE, PE) is a synthetic polymer used for biomedical applications because of its high impact resistance, ductility and stability in contact with physiological fluids. Therefore this material is being used in human orthopedic implants such as total joint replacements. Surface modification of this material relates to changes of its surface hydrophilicity, energy, microstructure, roughness, and morphology, all influencing its biological response. In our recent work, PE was treated by an Ar+ plasma discharge and then grafted with biologically active polyethylene glycol in order to enhance adhesion and proliferation of mouse fibroblast (L929). The surface properties of pristine PE and its grafted counterparts were studied by goniometry (surface wettability). Furthermore, Atomic Force Microscopy was used to determine the surface morphology and roughness. The biological response of the L929 cell lines seeded on untreated and plasma treated PE matrices was quantified in terms of the cell adhesion, density, and metabolic activity. Plasma treatment leads to the ablation of the polymer surface layers. Plasma treatment and subsequent poly(ethylene glycol) grafting lead to dramatic changes in the polymer surface morphology and roughness. Biological tests, performed in vitro, show increased adhesion and proliferation of cells on modified polymers. Grafting with poly(ethylene glycol) increases cell proliferation compared to plasma treatment.

Modification of anti-bacterial surface properties of textile polymers by vacuum arc ion source implantation

NASA Astrophysics Data System (ADS)

Nikolaev, A. G.; Yushkov, G. Yu.; Oks, E. M.; Oztarhan, A.; Akpek, A.; Hames-Kocabas, E.; Urkac, E. S.; Brown, I. G.

2014-08-01

Ion implantation provides an important technology for the modification of material surface properties. The vacuum arc ion source is a unique instrument for the generation of intense beams of metal ions as well as gaseous ions, including mixed metal-gas beams with controllable metal:gas ion ratio. Here we describe our exploratory work on the application of vacuum arc ion source-generated ion beams for ion implantation into polymer textile materials for modification of their biological cell compatibility surface properties. We have investigated two specific aspects of cell compatibility: (i) enhancement of the antibacterial characteristics (we chose to use Staphylococcus aureus bacteria) of ion implanted polymer textile fabric, and (ii) the "inverse" concern of enhancement of neural cell growth rate (we chose Rat B-35 neuroblastoma cells) on ion implanted polymer textile. The results of both investigations were positive, with implantation-generated antibacterial efficiency factor up to about 90%, fully comparable to alternative conventional (non-implantation) approaches and with some potentially important advantages over the conventional approach; and with enhancement of neural cell growth rate of up to a factor of 3.5 when grown on suitably implanted polymer textile material.

Surface design of antibody-immobilized thermoresponsive cell culture dishes for recovering intact cells by low-temperature treatment.

PubMed

Kobayashi, Jun; Hayashi, Masaki; Ohno, Takahiro; Nishi, Masanori; Arisaka, Yoshinori; Matsubara, Yoshinori; Kakidachi, Hiroshi; Akiyama, Yoshikatsu; Yamato, Masayuki; Horii, Akihiro; Okano, Teruo

2014-11-01

Antibody-immobilized thermoresponsive poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) [poly(IPAAm-co-CIPAAm)]-grafted cell culture surfaces were designed to enhance both the initial adhesion of weakly adhering cells and the ability of cells to detach in response to low temperature through the regulation of affinity binding between immobilized antibodies and antigens on the cellular surface. Ty-82 cells and neonatal normal human dermal fibroblasts (NHDFs), which express CD90 on the cell surface, adhered to anti-CD90 antibody-immobilized thermoresponsive surfaces at 37°C, a condition at which the grafted thermoresponsive polymer chains shrank. Adherent Ty-82 cells were detached from the surfaces by lowering the temperature to 20°C and applying external forces, such as pipetting, whereas cultured NHDF sheets spontaneously detached themselves from the surface in response to reduced temperature alone. When the temperature was decreased to 20°C, the swelling of grafted thermoresponsive polymer chains weakened the affinity binding between immobilized antibody and antigen on the cells due to the increasing steric hindrance of the polymer chains around the antigen-recognition site of the immobilized antibodies. No contamination was detected on cells harvested from covalently immobilized antibodies on the culture surfaces by low-temperature treatment, whereas a carryover of the antibody and avidin from the avidin-biotin binding surface was observed. Furthermore, the initial adhesion of adipose tissue-derived cells, which adhere weakly to PIPAAm-grafted surfaces, was enhanced on the antibody-immobilized thermoresponsive surfaces. © 2013 Wiley Periodicals, Inc.

Nano-patterned SU-8 surface using nanosphere-lithography for enhanced neuronal cell growth

NASA Astrophysics Data System (ADS)

Kim, Eunhee; Yoo, Seung-Jun; Kim, Eunjung; Kwon, Tae-Hwan; Zhang, Li; Moon, Cheil; Choi, Hongsoo

2016-04-01

Mimicking the nanoscale surface texture of the extracellular matrix can affect the regulation of cellular behavior, including adhesion, differentiation, and neurite outgrowth. In this study, SU-8-based polymer surfaces with well-ordered nanowell arrays were fabricated using nanosphere lithography with polystyrene nanoparticles. We show that the SU-8 surface with nanowells resulted in similar neuronal development of rat pheochromocytoma (PC12) cells compared with an unpatterned poly-L-lysine (PLL)-coated SU-8 surface. Additionally, even after soaking the substrate in cell culture medium for two weeks, cells on the nanowell SU-8 surface showed long-term neurite outgrowth compared to cells on the PLL-coated SU-8 surface. The topographical surface modification of the nanowell array demonstrates potential as a replacement for cell adhesive material coatings such as PLL, for applications requiring long-term use of polymer-based implantable devices.

Conductivity fuel cell collector plate and method of fabrication

DOEpatents

Braun, James C.

2002-01-01

An improved method of manufacturing a PEM fuel cell collector plate is disclosed. During molding a highly conductive polymer composite is formed having a relatively high polymer concentration along its external surfaces. After molding the polymer rich layer is removed from the land areas by machining, grinding or similar process. This layer removal results in increased overall conductivity of the molded collector plate. The polymer rich surface remains in the collector plate channels, providing increased mechanical strength and other benefits to the channels. The improved method also permits greater mold cavity thickness providing a number of advantages during the molding process.

Fuel cell membranes and crossover prevention

DOEpatents

Masel, Richard I [Champaign, IL; York, Cynthia A [Newington, CT; Waszczuk, Piotr [White Bear Lake, MN; Wieckowski, Andrzej [Champaign, IL

2009-08-04

A membrane electrode assembly for use with a direct organic fuel cell containing a formic acid fuel includes a solid polymer electrolyte having first and second surfaces, an anode on the first surface and a cathode on the second surface and electrically linked to the anode. The solid polymer electrolyte has a thickness t:.gtoreq..times..times..times..times. ##EQU00001## where C.sub.f is the formic acid fuel concentration over the anode, D.sub.f is the effective diffusivity of the fuel in the solid polymer electrolyte, K.sub.f is the equilibrium constant for partition coefficient for the fuel into the solid polymer electrolyte membrane, I is Faraday's constant n.sub.f is the number of electrons released when 1 molecule of the fuel is oxidized, and j.sub.f.sup.c is an empirically determined crossover rate of fuel above which the fuel cell does not operate.

Induced Infiltration of Hole-Transporting Polymer into Photocatalyst for Staunch Polymer-Metal Oxide Hybrid Solar Cells.

PubMed

Park, Jong Hwan; Jung, Youngsuk; Yang, Yooseong; Shin, Hyun Suk; Kwon, Soonchul

2016-10-05

For efficient solar cells based on organic semiconductors, a good mixture of photoactive materials in the bulk heterojunction on the length scale of several tens of nanometers is an important requirement to prevent exciton recombination. Herein, we demonstrate that nanoporous titanium dioxide inverse opal structures fabricated using a self-assembled monolayer method and with enhanced infiltration of electron-donating polymers is an efficient electron-extracting layer, which enhances the photovoltaic performance. A calcination process generates an inverse opal structure of titanium dioxide (<70 nm of pore diameters) providing three-dimensional (3D) electron transport pathways. Hole-transporting polymers was successfully infiltrated into the pores of the surface-modified titanium dioxide under vacuum conditions at 200 °C. The resulting geometry expands the interfacial area between hole- and electron-transport materials, increasing the thickness of the active layer. The controlled polymer-coating process over titanium dioxide materials enhanced photocurrent of the solar cell device. Density functional theory calculations show improved interfacial adhesion between the self-assembled monolayer-modified surface and polymer molecules, supporting the experimental result of enhanced polymer infiltration into the voids. These results suggest that the 3D inverse opal structure of the surface-modified titanium dioxide can serve as a favorable electron-extracting layer in further enhancing optoelectronic performance based on organic or organic-inorganic hybrid solar cell.

Surface-charge-dependent cell localization and cytotoxicity of cerium oxide nanoparticles.

PubMed

Asati, Atul; Santra, Santimukul; Kaittanis, Charalambos; Perez, J Manuel

2010-09-28

Cerium oxide nanoparticles (nanoceria) have shown great potential as antioxidant and radioprotective agents for applications in cancer therapy. Recently, various polymer-coated nanoceria preparations have been developed to improve their aqueous solubility and allow for surface functionalization of these nanoparticles. However, the interaction of polymer-coated nanoceria with cells, their uptake mechanism, and subcellular localization are poorly understood. Herein, we engineered polymer-coated cerium oxide nanoparticles with different surface charges (positive, negative, and neutral) and studied their internalization and toxicity in normal and cancer cell lines. The results showed that nanoceria with a positive or neutral charge enters most of the cell lines studied, while nanoceria with a negative charge internalizes mostly in the cancer cell lines. Moreover, upon entry into the cells, nanoceria is localized to different cell compartments (e.g., cytoplasm and lysosomes) depending on the nanoparticle's surface charge. The internalization and subcellular localization of nanoceria plays a key role in the nanoparticles' cytotoxicity profile, exhibiting significant toxicity when they localize in the lysosomes of the cancer cells. In contrast, minimal toxicity is observed when they localize into the cytoplasm or do not enter the cells. Taken together, these results indicate that the differential surface-charge-dependent localization of nanoceria in normal and cancer cells plays a critical role in the nanoparticles' toxicity profile.

Dispersing Zwitterions into Comb Polymers for Nonviral Transfection: Experiments and Molecular Simulation.

PubMed

Ghobadi, Ahmadreza F; Letteri, Rachel; Parelkar, Sangram S; Zhao, Yue; Chan-Seng, Delphine; Emrick, Todd; Jayaraman, Arthi

2016-02-08

Polymer-based gene delivery vehicles benefit from the presence of hydrophilic groups that mitigate the inherent toxicity of polycations and that provide tunable polymer-DNA binding strength and stable complexes (polyplexes). However, hydrophilic groups screen charge, and as such can reduce cell uptake and transfection efficiency. We report the effect of embedding zwitterionic sulfobetaine (SB) groups in cationic comb polymers, using a combination of experiments and molecular simulations. Ring-opening metathesis polymerization (ROMP) produced comb polymers with tetralysine (K4) and SB pendent groups. Dynamic light scattering, zeta potential measurements, and fluorescence-based experiments, together with coarse-grained molecular dynamics simulations, described the effect of SB groups on the size, shape, surface charge, composition, and DNA binding strength of polyplexes formed using these comb polymers. Experiments and simulations showed that increasing SB composition in the comb polymers decreased polymer-DNA binding strength, while simulations indicated that the SB groups distributed throughout the polyplex. This allows polyplexes to maintain a positive surface charge and provide high levels of gene expression in live cells. Notably, comb polymers with nearly 50 mol % SB form polyplexes that exhibit positive surface charge similarly as polyplexes formed from purely cationic comb polymers, indicating the ability to introduce an appreciable amount of SB functionality without screening surface charge. This integrated simulation-experimental study demonstrates the effectiveness of incorporating zwitterions in polyplexes, while guiding the design of new and effective gene delivery vectors.

Computational modeling of in vitro biological responses on polymethacrylate surfaces

PubMed Central

Ghosh, Jayeeta; Lewitus, Dan Y; Chandra, Prafulla; Joy, Abraham; Bushman, Jared; Knight, Doyle; Kohn, Joachim

2011-01-01

The objective of this research was to examine the capabilities of QSPR (Quantitative Structure Property Relationship) modeling to predict specific biological responses (fibrinogen adsorption, cell attachment and cell proliferation index) on thin films of different polymethacrylates. Using 33 commercially available monomers it is theoretically possible to construct a library of over 40,000 distinct polymer compositions. A subset of these polymers were synthesized and solvent cast surfaces were prepared in 96 well plates for the measurement of fibrinogen adsorption. NIH 3T3 cell attachment and proliferation index were measured on spin coated thin films of these polymers. Based on the experimental results of these polymers, separate models were built for homo-, co-, and terpolymers in the library with good correlation between experiment and predicted values. The ability to predict biological responses by simple QSPR models for large numbers of polymers has important implications in designing biomaterials for specific biological or medical applications. PMID:21779132

Conjugation of bioactive groups to poly(lactic acid) and poly[(lactic acid)-co-(glycolic acid)] films.

PubMed

Prime, Emma L; Cooper-White, Justin J; Qiao, Greg G

2007-12-06

A novel PLA-based polymer containing reactive pendent ketone or hydroxyl groups was synthesized by the copolymerization of L-lactide with epsilon-caprolactone-based monomers. The polymer was activated with NPC, resulting in an amine-reactive polymer which was then cast into thin polymeric films, either alone or as part of a blend with PLGA, before immersion into a solution of the cell adhesion peptide GRGDS in PBS buffer allowed for conjugation of GRGDS to the film surfaces. Subsequent 3T3 fibroblast cell adhesion studies demonstrated an increase in cellular adhesion and spreading over films cast from unmodified PLGA. Hence the new polymer can be used to obtain covalent linkage of amine-containing molecules to polymer surfaces.

Control of Surface Chemistry, Substrate Stiffness, and Cell Function in a Novel Terpolymer Methacrylate Library

PubMed Central

Joy, Abraham; Cohen, Daniel M.; Luk, Arnold; Anim-Danso, Emmanuel; Chen, Christopher; Kohn, Joachim

2011-01-01

A focused library of methacrylate terpolymers was synthesized to explore the effects of varying surface chemistry and adhesive peptide ligands on cell function. The chemical diversity of methacrylate monomers enabled construction of a library of polymers in which one can systematically vary the chemical composition to achieve a wide range of contact angle, Young's modulus, and Tg values. Furthermore, the materials were designed to allow surface immobilization of bioactive peptides. We then examined the effects of these material compositions on protein adsorption and cell attachment, proliferation, and differentiation. We observed that chemical composition of the polymers was an important determinant for NIH 3T3 cell attachment and proliferation, as well as human mesenchymal stem cell differentiation, and correlated directly with the ability of the polymers to adsorb proteins that mediate cell adhesion. Importantly, functionalization of the methacrylate terpolymer library with an adhesive GRGDS peptide normalized cellular responses. RGD-functionalized polymers uniformly exhibited robust attachment, proliferation, and differentiation irrespective of the underlying substrate chemistry. These studies provide a library-based approach to rapidly explore the biological functionality of biomaterials with a wide range of compositions, and highlights the importance of cell and protein cell adhesion in predicting their performance. PMID:21226505

Preparation of protein- and cell-resistant surfaces by hyperthermal hydrogen induced cross-linking of poly(ethylene oxide).

PubMed

Bonduelle, Colin V; Lau, Woon M; Gillies, Elizabeth R

2011-05-01

The functionalization of surfaces with poly(ethylene oxide) (PEO) is an effective means of imparting resistance to the adsorption of proteins and the attachment and growth of cells, properties that are critical for many biomedical applications. In this work, a new hyperthermal hydrogen induced cross-linking (HHIC) method was explored as a simple one-step approach for attaching PEO to surfaces through the selective cleavage of C-H bonds and subsequent cross-linking of the resulting carbon radicals. In order to study the effects of the process on the polymer, PEO-coated silicon wafers were prepared and the effects of different treatment times were investigated. Subsequently, using an optimized treatment time and a modified butyl polymer with increased affinity for PEO, the technique was applied to butyl rubber surfaces. All of the treated surfaces exhibited significantly reduced protein adsorption and cell growth relative to control surfaces and compared favorably with surfaces that were functionalized with PEO using conventional chemical methods. Thus HHIC is a simple and effective means of attaching PEO to non-functional polymer surfaces.

Method for estimating protein binding capacity of polymeric systems.

PubMed

Sharma, Vaibhav; Blackwood, Keith A; Haddow, David; Hook, Lilian; Mason, Chris; Dye, Julian F; García-Gareta, Elena

2015-01-01

Composite biomaterials made from synthetic and protein-based polymers are extensively researched in tissue engineering. To successfully fabricate a protein-polymer composite, it is critical to understand how strongly the protein binds to the synthetic polymer, which occurs through protein adsorption. Currently, there is no cost-effective and simple method for characterizing this interfacial binding. To characterize this interfacial binding, we introduce a simple three-step method that involves: 1) synthetic polymer surface characterisation, 2) a quick, inexpensive and robust novel immuno-based assay that uses protein extraction compounds to characterize protein binding strength followed by 3) an in vitro 2D model of cell culture to confirm the results of the immuno-based assay. Fibrinogen, precursor of fibrin, was adsorbed (test protein) on three different polymeric surfaces: silicone, poly(acrylic acid)-coated silicone and poly(allylamine)-coated silicone. Polystyrene surface was used as a reference. Characterisation of the different surfaces revealed different chemistry and roughness. The novel immuno-based assay showed significantly stronger binding of fibrinogen to both poly(acrylic acid) and poly(allylamine) coated silicone. Finally, cell studies showed that the strength of the interaction between the protein and the polymer had an effect on cell growth. This novel immuno-based assay is a valuable tool in developing composite biomaterials of synthetic and protein-based polymers with the potential to be applied in other fields of research where protein adsorption onto surfaces plays an important role.

In situ immobilization of proteins and RGD peptide on polyurethane surfaces via poly(ethylene oxide) coupling polymers for human endothelial cell growth.

PubMed

Wang, Dong-an; Ji, Jian; Sun, Yong-hong; Shen, Jia-cong; Feng, Lin-xian; Elisseeff, Jennifer H

2002-01-01

A "CBABC"-type pentablock coupling polymer, mesylMPEO, was designed and synthesized to promote human endothelial cell growth on the surfaces of polyurethane biomaterials. The polymer was composed of a central 4,4'-methylenediphenyl diisocyanate (MDI) coupling unit and poly(ethylene oxide) (PEO) spacer arms with methanesulfonyl (mesyl) end groups pendent on both ends. As the presurface modifying additive (pre-SMA), the mesylMPEO was noncovalently introduced onto the poly(ether urethane) (PEU) surfaces by dip coating, upon which the protein/peptide factors (gelatin, albumin, and arginine-glycine-aspartic acid tripeptide [RGD]) were covalently immobilized in situ by cleavage of the original mesyl end groups. The pre-SMA synthesis and PEU surface modification were characterized using nuclear magnetic resonance spectroscopy ((1)H NMR), attenuated total reflection infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS). Human umbilical vein endothelial cells (HUVEC) were harvested manually by collagenase digestion and seeded on the modified PEU surfaces. Cell adhesion ratios (CAR) and cell proliferation ratios (CPR) were measured using flow cytometry, and the individual cell viability (ICV) was determined by MTT assay. The cell morphologies were investigated by optical inverted microscopy (OIM) and scanning electrical microscopy (SEM). The gelatin- and RGD-modified surfaces were HUVEC-compatible and promoted HUVEC growth. The albumin-modified surfaces were compatible but inhibited cell adhesion. The results also indicated that, for HUVEC in vitro cultivation, the cell adhesion stage was of particular importance and had a significant impact on the cell responses to the modified surfaces.

Surface modification of starch based blends using potassium permanganate-nitric acid system and its effect on the adhesion and proliferation of osteoblast-like cells.

PubMed

Pashkuleva, I; Marques, A P; Vaz, F; Reis, R L

2005-01-01

The surface modification of three starch based polymeric biomaterials, using a KMnO4/HNO3 oxidizing system, and the effect of that modification on the osteoblastic cell adhesion has been investigated. The rationale of this work is as follows--starch based polymers have been proposed for use as tissue engineering scaffolds in several publications. It is known that in biodegradable systems it is quite difficult to have both cell adhesion and proliferation. Starch based polymers have shown to perform better than poly-lactic acid based materials but there is still room for improvement. This particular work is aimed at enhancing cell adhesion and proliferation on the surface of several starch based polymer blends that are being proposed as tissue engineering scaffolds. The surface of the polymeric biomaterials was chemically modified using a KMnO4/HNO3 system. This treatment resulted in more hydrophilic surfaces, which was confirmed by contact angle measurements. The effect of the treatment on the bioactivity of the surface modified biomaterials was also studied. The bioactivity tests, performed in simulated body fluid after biomimetic coating, showed that a dense film of calcium phosphate was formed after 30 days. Finally, human osteoblast-like cells were cultured on unmodified (control) and modified materials in order to observe the effect of the presence of higher numbers of polar groups on the adhesion and proliferation of those cells. Two of the modified polymers presented changes in the adhesion behavior and a significant increase in the proliferation rate kinetics when compared to the unmodified controls.

Review paper: progress in the field of conducting polymers for tissue engineering applications.

PubMed

Bendrea, Anca-Dana; Cianga, Luminita; Cianga, Ioan

2011-07-01

This review focuses on one of the most exciting applications area of conjugated conducting polymers, which is tissue engineering. Strategies used for the biocompatibility improvement of this class of polymers (including biomolecules' entrapment or covalent grafting) and also the integrated novel technologies for smart scaffolds generation such as micropatterning, electrospinning, self-assembling are emphasized. These processing alternatives afford the electroconducting polymers nanostructures, the most appropriate forms of the materials that closely mimic the critical features of the natural extracellular matrix. Due to their capability to electronically control a range of physical and chemical properties, conducting polymers such as polyaniline, polypyrrole, and polythiophene and/or their derivatives and composites provide compatible substrates which promote cell growth, adhesion, and proliferation at the polymer-tissue interface through electrical stimulation. The activities of different types of cells on these materials are also presented in detail. Specific cell responses depend on polymers surface characteristics like roughness, surface free energy, topography, chemistry, charge, and other properties as electrical conductivity or mechanical actuation, which depend on the employed synthesis conditions. The biological functions of cells can be dramatically enhanced by biomaterials with controlled organizations at the nanometer scale and in the case of conducting polymers, by the electrical stimulation. The advantages of using biocompatible nanostructures of conducting polymers (nanofibers, nanotubes, nanoparticles, and nanofilaments) in tissue engineering are also highlighted.

Thermoresponsive PNIPAM Coatings on Nanostructured Gratings for Cell Alignment and Release

DOE PAGES

Zhernenkov, Mikhail; Ashkar, Rana; Feng, Hao; ...

2015-05-20

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) has been widely used as a surface coating to thermally control the detachment of adsorbed cells without the need for extreme stimuli such as enzyme treatment. Recently, the use of 2D and 3D scaffolds in controlling cell positioning, growth, spreading, and migration has been of a great interest in tissue engineering and cell biology. We use a PNIPAM polymer surface coating atop a nanostructured linear diffraction grating to controllably change the surface topography of 2D linear structures using temperature stimuli. Neutron reflectometry and surface diffraction are utilized to examine the conformity of the polymer coating to themore » grating surface, its hydration profile, and its evolution in response to temperature variations. Our results show that, in the collapsed state, the PNIPAM coating conforms to the grating structures and retains a uniform hydration of 63%. In the swollen state, the polymer expands beyond the grating channels and absorbs up to 87% water. Such properties are particularly desirable for 2D cell growth scaffolds with a built-in nonextreme tissue-release mechanism. Indeed, the current system demonstrates advanced performance in the effective alignment of cultured fibroblast cells and the easy release of the cells upon temperature change.« less

Thermoresponsive PNIPAM Coatings on Nanostructured Gratings for Cell Alignment and Release

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhernenkov, Mikhail; Ashkar, Rana; Feng, Hao

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) has been widely used as a surface coating to thermally control the detachment of adsorbed cells without the need for extreme stimuli such as enzyme treatment. Recently, the use of 2D and 3D scaffolds in controlling cell positioning, growth, spreading, and migration has been of a great interest in tissue engineering and cell biology. We use a PNIPAM polymer surface coating atop a nanostructured linear diffraction grating to controllably change the surface topography of 2D linear structures using temperature stimuli. Neutron reflectometry and surface diffraction are utilized to examine the conformity of the polymer coating to themore » grating surface, its hydration profile, and its evolution in response to temperature variations. Our results show that, in the collapsed state, the PNIPAM coating conforms to the grating structures and retains a uniform hydration of 63%. In the swollen state, the polymer expands beyond the grating channels and absorbs up to 87% water. Such properties are particularly desirable for 2D cell growth scaffolds with a built-in nonextreme tissue-release mechanism. Indeed, the current system demonstrates advanced performance in the effective alignment of cultured fibroblast cells and the easy release of the cells upon temperature change.« less

Functional patterned coatings by thin polymer film dewetting.

PubMed

Telford, Andrew M; Thickett, Stuart C; Neto, Chiara

2017-12-01

An approach for the fabrication of functional polymer surface coatings is introduced, where micro-scale structure and surface functionality are obtained by means of self-assembly mechanisms. We illustrate two main applications of micro-patterned polymer surfaces obtained through dewetting of bilayers of thin polymer films. By tuning the physical and chemical properties of the polymer bilayers, micro-patterned surface coatings could be produced that have applications both for the selective attachment and patterning of proteins and cells, with potential applications as biomaterials, and for the collection of water from the atmosphere. In all cases, the aim is to achieve functional coatings using approaches that are simple to realize, use low cost materials and are potentially scalable. Copyright © 2017 Elsevier Inc. All rights reserved.

Fuel cell anode configuration for CO tolerance

DOEpatents

Uribe, Francisco A.; Zawodzinski, Thomas A.

2004-11-16

A polymer electrolyte fuel cell (PEFC) is designed to operate on a reformate fuel stream containing oxygen and diluted hydrogen fuel with CO impurities. A polymer electrolyte membrane has an electrocatalytic surface formed from an electrocatalyst mixed with the polymer and bonded on an anode side of the membrane. An anode backing is formed of a porous electrically conductive material and has a first surface abutting the electrocatalytic surface and a second surface facing away from the membrane. The second surface has an oxidation catalyst layer effective to catalyze the oxidation of CO by oxygen present in the fuel stream where at least the layer of oxidation catalyst is formed of a non-precious metal oxidation catalyst selected from the group consisting of Cu, Fe, Co, Tb, W, Mo, Sn, and oxides thereof, and other metals having at least two low oxidation states.

Mitigated reactive oxygen species generation leads to an improvement of cell proliferation on poly[glycidyl methacrylate-co-poly(ethylene glycol) methacrylate] functionalized polydimethylsiloxane surfaces.

PubMed

Yu, Ling; Shi, ZhuanZhuan; Gao, LiXia; Li, ChangMing

2015-09-01

In vitro cell-based analysis is strongly affected by material's surface chemical properties. The cell spreading, migration, and proliferation on a substrate surface are initiated and controlled by successful adhesion, particularly for anchor-dependent cells. Unfortunately, polydimethylsiloxane (PDMS), one of the most used polymeric materials for construction of microfluidic and miniaturized biomedical analytic devices, is not a cell-friendly surface because of its inherent hydrophobic property. Herein, a poly[glycidyl methacrylate-co-poly(ethylene glycol) methacrylate] (poly(GMA-co-pEGMA)) polymer brush was synthesized on a PDMS surface through a surface-initiated atom-transfer radical polymerization method. Contact angle and Fourier transform infrared characterization show that the poly (GMA-co-pEGMA) polymer brush functionalization can increase wettability of PDMS and introduce epoxy, hydroxyl, and ether groups into PDMS surface. In vitro cell growth assay demonstrates that cell adhesion and proliferation on poly(GMA-co-pEGMA) polymer brush-functionalized PDMS (poly(GMA-co-pEGMA)@PDMS) are better than on pristine PDMS. Additionally, immobilization of collagen type I (CI) and fibronectin (FN) on poly(GMA-co-pEGMA)@PDMS is better than direct coating of CI and FN on pristine PDMS to promote cell adhesion. Furthermore, increased intracellular reactive oxygen species and cell mitochondrial membrane depolarization, two indicators of cell oxidative stress, are observed from cells growing on pristine PDMS, but not from those on poly(GMA-co-pEGMA)@PDMS. Collectively, we demonstrate that poly(GMA-co-pEGMA) functionalization can enhance cell adhesion and proliferation on PDMS, and thus can be potentially used for microfluidic cell assay devices for cellular physiology study or drug screening. © 2015 Wiley Periodicals, Inc.

Reassessment of MxiH subunit orientation and fold within native Shigella T3SS needles using surface labelling and solid-state NMR.

PubMed

Verasdonck, Joeri; Shen, Da-Kang; Treadgold, Alexander; Arthur, Christopher; Böckmann, Anja; Meier, Beat H; Blocker, Ariel J

2015-12-01

T3SSs are essential virulence determinants of many Gram-negative bacteria, used to inject bacterial effectors of virulence into eukaryotic host cells. Their major extracellular portion, a ∼50 nm hollow, needle-like structure, is essential to host cell sensing and the conduit for effector secretion. It is formed of a small, conserved subunit arranged as a helical polymer. The structure of the subunit has been studied by electron cryomicroscopy within native polymers and by solid-state NMR in recombinant polymers, yielding two incompatible atomic models. To resolve this controversy, we re-examined the native polymer used for electron cryomicroscopy via surface labelling and solid-state NMR. Our data show the orientation and overall fold of the subunit within this polymer is as established by solid-state NMR for recombinant polymers. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Material- and feature-dependent effects on cell adhesion to micro injection moulded medical polymers.

PubMed

Choi, Seong Ying; Habimana, Olivier; Flood, Peter; Reynaud, Emmanuel G; Rodriguez, Brian J; Zhang, Nan; Casey, Eoin; Gilchrist, Michael D

2016-09-01

Two polymers, polymethylmethacrylate (PMMA) and cyclic olefin copolymer (COC), containing a range of nano- to micron- roughness surfaces (Ra 0.01, 0.1, 0.4, 1.0, 2.0, 3.2 and 5.0μm) were fabricated using electrical discharge machining (EDM) and replicated using micro injection moulding (μIM). Polymer samples were characterized using optical profilometry, atomic force microscopy (AFM) and water surface contact angle. Cell adhesion tests were carried out using bacterial Pseudomonas fluorescens and mammalian Madin-Darby Canine Kidney (MDCK) cells to determine the effect of surface hydrophobicity, surface roughness and stiffness. It is found that there are features which gave insignificant differences (feature-dependent effect) in cell adhesion, albeit a significant difference in the physicochemical properties (material-dependent effect) of substrata. In bacterial cell adhesion, the strongest feature-dependence is found at Ra 0.4μm surfaces, with material-dependent effects strongest at Ra 0.01μm. Ra 0.1μm surfaces exhibited strongest feature-dependent effects and Ra 5.0μm has strongest material-dependent effects on mammalian cell adhesion. Bacterial cell adhesion is found to be favourable to hydrophobic surfaces (COC), with the lowest adhesion at Ra 0.4μm for both materials. Mammalian cell adhesion is lowest in Ra 0.1μm and highest in Ra 1.0μm, and generally favours hydrophilic surfaces (PMMA). These findings can be used as a basis for developing medical implants or microfluidic devices using micro injection moulding for diagnostic purposes, by tuning the cell adhesion on different areas containing different surface roughnesses on the diagnostic microfluidic devices or medical implants. Copyright © 2016 Elsevier B.V. All rights reserved.

Polymer network/carbon layer on monolith support and monolith catalytic reactor

DOEpatents

Nordquist, Andrew Francis; Wilhelm, Frederick Carl; Waller, Francis Joseph; Machado, Reinaldo Mario

2003-08-26

The present invention relates to an improved monolith catalytic reactor and a monolith support. The improvement in the support resides in a polymer network/carbon coating applied to the surface of a porous substrate and a catalytic metal, preferably a transition metal catalyst applied to the surface of the polymer network/carbon coating. The monolith support has from 100 to 800 cells per square inch and a polymer network/carbon coating with surface area of from 0.1 to 15 m.sup.2 /gram as measured by adsorption of N.sub.2 or Kr using the BET method.

Chlorine-rich plasma polymer coating for the prevention of attachment of pathogenic fungal cells onto materials surfaces

NASA Astrophysics Data System (ADS)

Lamont-Friedrich, Stephanie J.; Michl, Thomas D.; Giles, Carla; Griesser, Hans J.; Coad, Bryan R.

2016-07-01

The attachment of pathogenic fungal cells onto materials surfaces, which is often followed by biofilm formation, causes adverse consequences in a wide range of areas. Here we have investigated the ability of thin film coatings from chlorinated molecules to deter fungal colonization of solid materials by contact killing of fungal cells reaching the surface of the coating. Coatings were deposited onto various substrate materials via plasma polymerization, which is a substrate-independent process widely used for industrial coating applications, using 1,1,2-trichloroethane as the process vapour. XPS surface analysis showed that the coatings were characterized by a highly chlorinated hydrocarbon polymer nature, with only a very small amount of oxygen incorporated. The activity of these coatings against human fungal pathogens was quantified using a recently developed, modified yeast assay and excellent antifungal activity was observed against Candida albicans and Candida glabrata. Plasma polymer surface coatings derived from chlorinated hydrocarbon molecules may therefore offer a promising solution to preventing yeast and mould biofilm formation on materials surfaces, for applications such as air conditioners, biomedical devices, food processing equipment, and others.

Construction of conducting polymer/cytochrome C/thylakoid membrane based photo-bioelectrochemical fuel cells generating high photocurrent via photosynthesis.

PubMed

Cevik, Emre; Carbas, Buket Bezgin; Senel, Mehmet; Yildiz, Huseyin Bekir

2018-08-15

In this study, a photo-bioelectrochemical fuel cell was constructed for photocurrent generation by illuminating the electrodes within an aqueous solution. In this purpose, gold electrode was coated with poly 4-(4H-Dithieno [3,2-b:2',3'-d]pyrol-4-yl) aniline, P(DTP-Ph-NH 2 ) conductive polymer film by using electrochemical polymerization. Then, P(DTP-Ph-NH 2 ) conductive polymer film coated surface was electrochemically modified with cytochrome C which covalently linked onto the surface via bis-aniline functionality of the polymer film and formed crosslinked-structure. The thylakoid membrane was attached on the surface of this electrode by using bissulfosaxinimidyl suberate (BS 3 ) and used as photo-anode in photo-bioelectrochemical fuel cell. The photo-cathode of the photo-bioelectrochemical fuel cell fabrication was followed by the modification of conductive polymer poly[5-(4H-dithieno [3,2-b:2',3'-d]pyrol-4-yl) naphtalene-1-amine] film coating, glutaraldehyde activation, and bilirubin oxidase enzyme immobilization. During the photosynthesis occurring in thylakoid membrane under the light, water was oxidized and separated; while oxygen was released in anode side, the cathode side was reduced the oxygen gas into the water via a bio-electro-catalytic method. The cytochrome C was used for binding of thylakoid membrane to the electrode surface and play an important role for transferring of electrons released as a result of photosynthesis. Copyright © 2018 Elsevier B.V. All rights reserved.

Workshop II: Nanotechnology and Advanced Cell Concepts

NASA Technical Reports Server (NTRS)

2007-01-01

Workshop focused on few emerging concepts(beyond tandem cells): 1. Engineering incident sun spectrum and transparency losses a) Nano emitters (dot concentrator); b) Surface plasmonics; c) Up converters; d) Down converter. 2. Intermediate band solar cells a) Efficiency projections (detail energy balance projections); b) Inserting 0,1 and 2D semiconductor structures in solar cells 3. Polymer and hybrid cells a) Nanotubes/dot polymers; b) Exciton dissociation.

Use of Atomic Oxygen for Increased Water Contact Angles of Various Polymers for Biomedical Applications

NASA Technical Reports Server (NTRS)

Beger, Lauren; Roberts, Lily; deGroh, Kim; Banks, Bruce

2007-01-01

In the low Earth orbit (LEO) space environment, spacecraft surfaces can be altered during atomic oxygen exposure through oxidation and erosion. There can be terrestrial benefits of such interactions, such as the modification of hydrophobic or hydrophilic properties of polymers due to chemical modification and texturing. Such modification of the surface may be useful for biomedical applications. For example, atomic oxygen texturing may increase the hydrophilicity of polymers, such as chlorotrifluoroethylene (Aclar), thus allowing increased adhesion and spreading of cells on textured Petri dishes. The purpose of this study was to determine the effect of atomic oxygen exposure on the hydrophilicity of nine different polymers. To determine whether hydrophilicity remains static after atomic oxygen exposure or changes with exposure, the contact angles between the polymer and a water droplet placed on the polymer s surface were measured. The polymers were exposed to atomic oxygen in a radio frequency (RF) plasma asher. Atomic oxygen plasma treatment was found to significantly alter the hydrophilicity of non-fluorinated polymers. Significant decreases in the water contact angle occurred with atomic oxygen exposure. Fluorinated polymers were found to be less sensitive to changes in hydrophilicity for equivalent atomic oxygen exposures, and two of the fluorinated polymers became more hydrophobic. The majority of change in water contact angle of the non-fluorinated polymers was found to occur with very low fluence exposures, indicating potential cell culturing benefit with short treatment time.

Influence of polymer architecture on antigens camouflage, CD47 protection and complement mediated lysis of surface grafted red blood cells.

PubMed

Chapanian, Rafi; Constantinescu, Iren; Rossi, Nicholas A A; Medvedev, Nadia; Brooks, Donald E; Scott, Mark D; Kizhakkedathu, Jayachandran N

2012-11-01

Hyperbranched polyglycerol (HPG) and polyethylene glycol (PEG) polymers with similar hydrodynamic sizes in solution were grafted to red blood cells (RBCs) to investigate the impact of polymer architecture on the cell structure and function. The hydrodynamic sizes of polymers were calculated from the diffusion coefficients measured by pulsed field gradient NMR. The hydration of the HPG and PEG was determined by differential scanning calorimetry analyses. RBCs grafted with linear PEG had different properties compared to the compact HPG grafted RBCs. HPG grafted RBCs showed much higher electrophoretic mobility values than PEG grafted RBCs at similar grafting concentrations and hydrodynamic sizes indicating differences in the structure of the polymer exclusion layer on the cell surface. PEG grafting impacted the deformation properties of the membrane to a greater degree than HPG. The complement mediated lysis of the grafted RBCs was dependent on the type of polymer, grafting concentration and molecular size of grafted chains. At higher molecular weights and graft concentrations both HPG and PEG triggered complement activation. The magnitude of activation was higher with HPG possibly due to the presence of many hydroxyl groups per molecule. HPG grafted RBCs showed significantly higher levels of CD47 self-protein accessibility than PEG grafted RBCs at all grafting concentrations and molecular sizes. PEG grafted polymers provided, in general, a better shielding and protection to ABO and minor antigens from antibody recognition than HPG polymers, however, the compact HPGs provided greater protection of certain antigens on the RBC surface. Our data showed that HPG 20 kDa and HPG 60 kDa grafted RBCs exhibited properties that are more comparable to the native RBC than PEG 5 kDa and PEG 10 kDa grafted RBCs of comparable hydrodynamic sizes. The study shows that small compact polymers such as HPG 20 kDa have a greater potential in the generation of functional RBC for therapeutic delivery applications. The intermediate sized polymers (PEG or HPG) which showed greater antigen camouflage at lower grafting concentrations have significant potential in transfusion as universal red blood donor cells. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biomimetic surface coatings from modular amphiphilic proteins

NASA Astrophysics Data System (ADS)

Harden, James; Wan, Fan; Fischer, Stephen; Dick, Scott

2010-03-01

Recombinant DNA methods have been used to develop a library of diblock protein polymers for creating designer biofunctional interfaces. These proteins are composed of a surface-active, amphiphilic block joined to a disordered, water soluble block with an end terminal bioactive domain. The amphiphilic block has a strong affinity for many synthetic polymer surfaces, providing a facile means of imparting biological functionality to otherwise bio-neutral materials through physical self-assembly. We have incorporated a series of bioactive end domains into this diblock motif, including sequences that encode specific cell binding and signaling functions of extracellular matrix constituents (e.g. RGD and YIGSR). In this talk, we show that these diblock constructs self-assemble into biofunctional surface coatings on several model synthetic polymer materials. We demonstrate that surface adsorption of the proteins has minimal impacts on the presentation of the bioactive domains in the soluble block, and through the use of microscopic and cell proliferation assays, we show that the resulting biofunctional interfaces are capable of inducing appropriate cellular responses in a variety of human cell types.

Osteoselection supported by phase separated polymer blend films.

PubMed

Gulsuner, Hilal Unal; Gengec, Nevin Atalay; Kilinc, Murat; Erbil, H Yildirim; Tekinay, Ayse B

2015-01-01

The instability of implants after placement inside the body is one of the main obstacles to clinically succeed in periodontal and orthopedic applications. Adherence of fibroblasts instead of osteoblasts to implant surfaces usually results in formation of scar tissue and loss of the implant. Thus, selective bioadhesivity of osteoblasts is a desired characteristic for implant materials. In this study, we developed osteoselective and biofriendly polymeric thin films fabricated with a simple phase separation method using either homopolymers or various blends of homopolymers and copolymers. As adhesive and proliferative features of cells are highly dependent on the physicochemical properties of the surfaces, substrates with distinct chemical heterogeneity, wettability, and surface topography were developed and assessed for their osteoselective characteristics. Surface characterizations of the fabricated polymer thin films were performed with optical microscopy and SEM, their wettabilities were determined by contact angle measurements, and their surface roughness was measured by profilometry. Long-term adhesion behaviors of cells to polymer thin films were determined by F-actin staining of Saos-2 osteoblasts, and human gingival fibroblasts, HGFs, and their morphologies were observed by SEM imaging. The biocompatibility of the surfaces was also examined through cell viability assay. Our results showed that heterogeneous polypropylene polyethylene/polystyrene surfaces can govern Saos-2 and HGF attachment and organization. Selective adhesion of Saos-2 osteoblasts and inhibited adhesion of HGF cells were achieved on micro-structured and hydrophobic surfaces. This work paves the way for better control of cellular behaviors for adjustment of cell material interactions. © 2014 Wiley Periodicals, Inc.

New stent surface materials: the impact of polymer-dependent interactions of human endothelial cells, smooth muscle cells, and platelets.

PubMed

Busch, Raila; Strohbach, Anne; Rethfeldt, Stefanie; Walz, Simon; Busch, Mathias; Petersen, Svea; Felix, Stephan; Sternberg, Katrin

2014-02-01

Despite the development of new coronary stent technologies, in-stent restenosis and stent thrombosis are still clinically relevant. Interactions of blood and tissue cells with the implanted material may represent an important cause of these side effects. We hypothesize material-dependent interaction of blood and tissue cells. The aim of this study is accordingly to investigate the impact of vascular endothelial cells, smooth muscle cells and platelets with various biodegradable polymers to identify a stent coating or platform material that demonstrates excellent endothelial-cell-supportive and non-thrombogenic properties. Human umbilical venous endothelial cells, human coronary arterial endothelial cells and human coronary arterial smooth muscle cells were cultivated on the surfaces of two established biostable polymers used for drug-eluting stents, namely poly(ethylene-co-vinylacetate) (PEVA) and poly(butyl methacrylate) (PBMA). We compared these polymers to new biodegradable polyesters poly(l-lactide) (PLLA), poly(3-hydroxybutyrate) (P(3HB)), poly(4-hydroxybutyrate) (P(4HB)) and a polymeric blend of PLLA/P(4HB) in a ratio of 78/22% (w/w). Biocompatibility tests were performed under static and dynamic conditions. Measurement of cell proliferation, viability, glycocalix width, eNOS and PECAM-1 mRNA expression revealed strong material dependency among the six polymer samples investigated. Only the polymeric blend of PLLA/P(4HB) achieved excellent endothelial markers of biocompatibility. Data show that PLLA and P(4HB) tend to a more thrombotic response, whereas the polymer blend is characterized by a lower thrombotic potential. These data demonstrate material-dependent endothelialization, smooth muscle cell growth and thrombogenicity. Although polymers such as PEVA and PBMA are already commonly used for vascular implants, they did not sufficiently meet the criteria for biocompatibility. The investigated biodegradable polymeric blend PLLA/P(4HB) evidently represents a promising material for vascular stents and stent coatings. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Catechol-Functionalized Synthetic Polymer as a Dental Adhesive to Contaminated Dentin Surface for a Composite Restoration.

PubMed

Lee, Sang-Bae; González-Cabezas, Carlos; Kim, Kwang-Mahn; Kim, Kyoung-Nam; Kuroda, Kenichi

2015-08-10

This study reports a synthetic polymer functionalized with catechol groups as dental adhesives. We hypothesize that a catechol-functionalized polymer functions as a dental adhesive for wet dentin surfaces, potentially eliminating the complications associated with saliva contamination. We prepared a random copolymer containing catechol and methoxyethyl groups in the side chains. The mechanical and adhesive properties of the polymer to dentin surface in the presence of water and salivary components were determined. It was found that the new polymer combined with an Fe(3+) additive improved bond strength of a commercial dental adhesive to artificial saliva contaminated dentin surface as compared to a control sample without the polymer. Histological analysis of the bonding structures showed no leakage pattern, probably due to the formation of Fe-catechol complexes, which reinforce the bonding structures. Cytotoxicity test showed that the polymers did not inhibit human gingival fibroblast cells proliferation. Results from this study suggest a potential to reduce failure of dental restorations due to saliva contamination using catechol-functionalized polymers as dental adhesives.

Catechol-Functionalized Synthetic Polymer as a Dental Adhesive to Contaminated Dentin Surface for a Composite Restoration

PubMed Central

2015-01-01

This study reports a synthetic polymer functionalized with catechol groups as dental adhesives. We hypothesize that a catechol-functionalized polymer functions as a dental adhesive for wet dentin surfaces, potentially eliminating the complications associated with saliva contamination. We prepared a random copolymer containing catechol and methoxyethyl groups in the side chains. The mechanical and adhesive properties of the polymer to dentin surface in the presence of water and salivary components were determined. It was found that the new polymer combined with an Fe3+ additive improved bond strength of a commercial dental adhesive to artificial saliva contaminated dentin surface as compared to a control sample without the polymer. Histological analysis of the bonding structures showed no leakage pattern, probably due to the formation of Fe–catechol complexes, which reinforce the bonding structures. Cytotoxicity test showed that the polymers did not inhibit human gingival fibroblast cells proliferation. Results from this study suggest a potential to reduce failure of dental restorations due to saliva contamination using catechol-functionalized polymers as dental adhesives. PMID:26176305

Method of forming a continuous polymeric skin on a cellular foam material

DOEpatents

Duchane, David V.; Barthell, Barry L.

1985-01-01

Hydrophobic cellular material is coated with a thin hydrophilic polymer skin which stretches tightly over the outer surface of the foam but which does not fill the cells of the foam, thus resulting in a polymer-coated foam structure having a smoothness which was not possible in the prior art. In particular, when the hydrophobic cellular material is a specially chosen hydrophobic polymer foam and is formed into arbitrarily chosen shapes prior to the coating with hydrophilic polymer, inertial confinement fusion (ICF) targets of arbitrary shapes can be produced by subsequently coating the shapes with metal or with any other suitable material. New articles of manufacture are produced, including improved ICF targets, improved integrated circuits, and improved solar reflectors and solar collectors. In the coating method, the cell size of the hydrophobic cellular material, the viscosity of the polymer solution used to coat, and the surface tensin of the polymer solution used to coat are all very important to the coating.

Defining an optimal surface chemistry for pluripotent stem cell culture in 2D and 3D

NASA Astrophysics Data System (ADS)

Zonca, Michael R., Jr.

Surface chemistry is critical for growing pluripotent stem cells in an undifferentiated state. There is great potential to engineer the surface chemistry at the nanoscale level to regulate stem cell adhesion. However, the challenge is to identify the optimal surface chemistry of the substrata for ES cell attachment and maintenance. Using a high-throughput polymerization and screening platform, a chemically defined, synthetic polymer grafted coating that supports strong attachment and high expansion capacity of pluripotent stem cells has been discovered using mouse embryonic stem (ES) cells as a model system. This optimal substrate, N-[3-(Dimethylamino)propyl] methacrylamide (DMAPMA) that is grafted on 2D synthetic poly(ether sulfone) (PES) membrane, sustains the self-renewal of ES cells (up to 7 passages). DMAPMA supports cell attachment of ES cells through integrin beta1 in a RGD-independent manner and is similar to another recently reported polymer surface. Next, DMAPMA has been able to be transferred to 3D by grafting to synthetic, polymeric, PES fibrous matrices through both photo-induced and plasma-induced polymerization. These 3D modified fibers exhibited higher cell proliferation and greater expression of pluripotency markers of mouse ES cells than 2D PES membranes. Our results indicated that desirable surfaces in 2D can be scaled to 3D and that both surface chemistry and structural dimension strongly influence the growth and differentiation of pluripotent stem cells. Lastly, the feasibility of incorporating DMAPMA into a widely used natural polymer, alginate, has been tested. Novel adhesive alginate hydrogels have been successfully synthesized by either direct polymerization of DMAPMA and methacrylic acid blended with alginate, or photo-induced DMAPMA polymerization on alginate nanofibrous hydrogels. In particular, DMAPMA-coated alginate hydrogels support strong ES cell attachment, exhibiting a concentration dependency of DMAPMA. This research provides a new avenue for stem cell culture and maintenance using an optimal organic-based chemistry.

Command Surface of Self-Organizing Structures by Radical Polymers with Cooperative Redox Reactivity.

PubMed

Sato, Kan; Mizuma, Takahiro; Nishide, Hiroyuki; Oyaizu, Kenichi

2017-10-04

Robust radical-substituted polymers with ideal redox capability were used as "command surfaces" for liquid crystal orientation. The alignment of the smectic liquid crystal electrolytes with low-dimensional ion conduction pathways was reversible and readily switched in response to the redox states of the polymers. In one example, a charge storage device with a cooperative redox effect was fabricated. The bulk ionic conductivity of the cell was significantly decreased only after the electrode was fully charged, due to the anisotropic ionic conductivity of the electrolytes (ratio >10 3 ). The switching enabled both a rapid cell response and long charge retention. Such a cooperative command surface of self-assembled structures will give rise to new highly energy efficient supramolecular-based devices including batteries, charge carriers, and actuators.

Bioorthogonal layer-by-layer encapsulation of pancreatic islets via hyperbranched polymers

PubMed Central

Gattás-Asfura, Kerim M.; Stabler, Cherie L.

2013-01-01

The encapsulation of viable tissues via layer-by-layer polymer assembly provides a versatile platform for cell surface engineering, with nanoscale control over capsule properties. Herein, we report the development of a hyperbranched polymer-based, ultrathin capsule architecture expressing bioorthogonal functionality and tailored physiochemical properties. Random carbodiimide-based condensation of 3,5-dicarboxyphenyl glycineamide on alginate yielded a highly branched polysaccharide with multiple, spatially restricted, and readily functionalizable terminal carboxylate moieties. Poly(ethylene glycol) (PEG) was utilized to link azido end groups to the structured alginate. Together with phosphine functionalized poly(amido amine) (PAMAM) dendrimer, nanoscale layer-by-layer coatings, covalently stabilized via Staudinger ligation, were assembled onto solid surfaces and pancreatic islets. The effects of electrostatic and/or bioorthogonal covalent interlayer interactions on the resulting coating efficiency and stability, as well as pancreatic islet viability and function, were studied. These hyperbranched polymers provide a flexible platform for the formation of covalently stabilized ultrathin coatings on viable cells and tissues. In addition, the hyperbranched nature of the polymers presents a highly functionalized surface capable of bioorthogonal conjugation of additional bioactive or labeling motifs. PMID:24063764

2D spatially controlled polymer micro patterning for cellular behavior studies

NASA Astrophysics Data System (ADS)

Dinca, V.; Palla-Papavlu, A.; Paraico, I.; Lippert, T.; Wokaun, A.; Dinescu, M.

2011-04-01

A simple and effective method to functionalize glass surfaces that enable polymer micropatterning and subsequent spatially controlled adhesion of cells is reported in this paper. The method involves the application of laser induced forward transfer (LIFT) to achieve polymer patterning in a single step onto cell repellent substrates (i.e. polyethyleneglycol (PEG)). This approach was used to produce micron-size polyethyleneimine (PEI)-patterns alternating with cell-repellent areas. The focus of this work is the ability of SH-SY5Y human neuroblastoma cells to orient, migrate, and produce organized cellular arrangements on laser generated PEI patterns.

A Synopsis of Interfacial Phenomena in Lithium-Based Polymer Electrolyte Electrochemical Cells

NASA Technical Reports Server (NTRS)

Baldwin, Richard S.; Bennett, William R.

2007-01-01

The interfacial regions between electrode materials, electrolytes and other cell components play key roles in the overall performance of lithium-based batteries. For cell chemistries employing lithium metal, lithium alloy or carbonaceous materials (i.e., lithium-ion cells) as anode materials, a "solid electrolyte interphase" (SEI) layer forms at the anode/electrolyte interface, and the properties of this "passivating" layer significantly affect the practical cell/battery quality and performance. A thin, ionically-conducting SEI on the electrode surface can beneficially reduce or eliminate undesirable side reactions between the electrode and the electrolyte, which can result in a degradation in cell performance. The properties and phenomena attributable to the interfacial regions existing at both anode and cathode surfaces can be characterized to a large extent by electrochemical impedance spectroscopy (EIS) and related techniques. The intention of the review herewith is to support the future development of lithium-based polymer electrolytes by providing a synopsis of interfacial phenomena that is associated with cell chemistries employing either lithium metal or carbonaceous "composite" electrode structures which are interfaced with polymer electrolytes (i.e., "solvent-free" as well as "plasticized" polymer-binary salt complexes and single ion-conducting polyelectrolytes). Potential approaches to overcoming poor cell performance attributable to interfacial effects are discussed.

Increasing binding density of yeast cells by control of surface charge with allylamine grafting to ion modified polymer surfaces.

PubMed

Tran, Clara T H; Kondyurin, Alexey; Chrzanowski, Wojciech; Bilek, Marcela M M; McKenzie, David R

2014-10-01

Plasma immersion ion implantation (PIII) treatment of polymers creates a biointerface capable of direct covalent immobilization of biomolecules. The immobilization of protein molecules is achieved by covalent bonds formed between embedded radicals on the treated surface and amino acid side chains and cells can be immobilized through cell-wall proteins. The attachment density of negatively charged entities on a PIII treated surface is inhibited by its negative surface charge at neutral pH. To reduce the negative charge of PIII treated surfaces in phosphate buffer (pH 7.4, 11mM), we develop an effective approach of grafting allylamine monomers onto the treated surface. The results reveal reactions between allylamine and radicals on the PIII treated surface. One of these triggers polymerization, increasing the number of amine groups grafted. As a consequence, the PIII treated polystyrene surface after allylamine exposure becomes more hydrophobic and less negatively charged in phosphate buffer. Using yeast cells as an example, we have shown a significant improvement (6-15 times) of cell density immobilized on the PIII treated surface after exposure to allylamine. Copyright © 2014 Elsevier B.V. All rights reserved.

Strategies for the chemical and biological functionalization of scaffolds for cardiac tissue engineering: a review.

PubMed

Tallawi, Marwa; Rosellini, Elisabetta; Barbani, Niccoletta; Cascone, Maria Grazia; Rai, Ranjana; Saint-Pierre, Guillaume; Boccaccini, Aldo R

2015-07-06

The development of biomaterials for cardiac tissue engineering (CTE) is challenging, primarily owing to the requirement of achieving a surface with favourable characteristics that enhances cell attachment and maturation. The biomaterial surface plays a crucial role as it forms the interface between the scaffold (or cardiac patch) and the cells. In the field of CTE, synthetic polymers (polyglycerol sebacate, polyethylene glycol, polyglycolic acid, poly-l-lactide, polyvinyl alcohol, polycaprolactone, polyurethanes and poly(N-isopropylacrylamide)) have been proven to exhibit suitable biodegradable and mechanical properties. Despite the fact that they show the required biocompatible behaviour, most synthetic polymers exhibit poor cell attachment capability. These synthetic polymers are mostly hydrophobic and lack cell recognition sites, limiting their application. Therefore, biofunctionalization of these biomaterials to enhance cell attachment and cell material interaction is being widely investigated. There are numerous approaches for functionalizing a material, which can be classified as mechanical, physical, chemical and biological. In this review, recent studies reported in the literature to functionalize scaffolds in the context of CTE, are discussed. Surface, morphological, chemical and biological modifications are introduced and the results of novel promising strategies and techniques are discussed.

Strategies for the chemical and biological functionalization of scaffolds for cardiac tissue engineering: a review

PubMed Central

Tallawi, Marwa; Rosellini, Elisabetta; Barbani, Niccoletta; Cascone, Maria Grazia; Rai, Ranjana; Saint-Pierre, Guillaume; Boccaccini, Aldo R.

2015-01-01

The development of biomaterials for cardiac tissue engineering (CTE) is challenging, primarily owing to the requirement of achieving a surface with favourable characteristics that enhances cell attachment and maturation. The biomaterial surface plays a crucial role as it forms the interface between the scaffold (or cardiac patch) and the cells. In the field of CTE, synthetic polymers (polyglycerol sebacate, polyethylene glycol, polyglycolic acid, poly-l-lactide, polyvinyl alcohol, polycaprolactone, polyurethanes and poly(N-isopropylacrylamide)) have been proven to exhibit suitable biodegradable and mechanical properties. Despite the fact that they show the required biocompatible behaviour, most synthetic polymers exhibit poor cell attachment capability. These synthetic polymers are mostly hydrophobic and lack cell recognition sites, limiting their application. Therefore, biofunctionalization of these biomaterials to enhance cell attachment and cell material interaction is being widely investigated. There are numerous approaches for functionalizing a material, which can be classified as mechanical, physical, chemical and biological. In this review, recent studies reported in the literature to functionalize scaffolds in the context of CTE, are discussed. Surface, morphological, chemical and biological modifications are introduced and the results of novel promising strategies and techniques are discussed. PMID:26109634

Surface modification for interaction study with bacteria and preosteoblast cells

NASA Astrophysics Data System (ADS)

Song, Qing

Surface modification plays a pivotal role in bioengineering. Polymer coatings can provide biocompatibility and biofunctionalities to biomaterials through surface modification. In this dissertation, initiated chemical vapor deposition (iCVD) was utilized to coat two-dimensional (2D) and three-dimensional (3D) substrates with differently charged polyelectrolytes in order to generate antimicrobial and osteocompatible biomaterials. ICVD is a modified CVD technique that enables surface modification in an all-dry condition without substrate damage and solvent contamination. The free-radical polymerization allows the vinyl polymers to conformally coat on various micro- and nano-structured substrates and maintains the delicate structure of the functional groups. The vapor deposition of polycations provided antimicrobial activity to planar and porous substrates through destroying the negatively charged bacterial membrane and brought about high contact-killing efficiency (99.99%) against Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. Additionally, the polyampholytes synthesized by iCVD exhibited excellent antifouling performance against the adhesion of Gram-positive Listeria innocua and Gram-negative E. coli in phosphate buffered saline (PBS). Their antifouling activities were attributed to the electrostatic interaction and hydration layers that served as physical and energetic barriers to prevent bacterial adhesion. The contact-killing and antifouling polymers synthesized by iCVD can be applied to surface modification of food processing equipment and medical devices with the aim of reducing foodborne diseases and medical infections. Moreover, the charged polyelectrolyte modified 2D polystyrene surfaces displayed good osteocompatibility and enhanced osteogenesis of preosteoblast cells than the un-modified polystyrene surface. In order to promote osteoinduction of hydroxyapatite (HA) scaffolds, bioinspired polymer-controlled mineralization was conducted on the polyelectrolyte modified HA scaffolds. The mineralized scaffolds stimulated osteogenesis of preosteoblast cells compared with the control HA scaffolds. Therefore, the surface modification through vapor deposition of polyelectrolytes and polymer-controlled mineralization can improve osteoinduction of bone materials. In summary, the iCVD-mediated surface modification is a simple and promising approach to biofunctionalizing various structured substrates and generating antimicrobial and biocompatible biomaterials.

Extreme Activity of Drug Nanocrystals Coated with A Layer of Non-Covalent Polymers from Self-Assembled Boric Acid

NASA Astrophysics Data System (ADS)

Zhan, Honglei; Liang, Jun F.

2016-12-01

Non-covalent polymers have remarkable advantages over synthetic polymers for wide biomedical applications. In this study, non-covalent polymers from self-assembled boric acid were used as the capping reagent to replace synthetic polymers in drug crystallization. Under acidic pH, boric acid self-assembled on the surface of drug nanocrystals to form polymers with network-like structures held together by hydrogen bonds. Coating driven by boric acid self-assembly had negligible effects on drug crystallinity and structure but resulted in drug nanocrystals with excellent dispersion properties that aided in the formation of a more stable suspension. Boric acid coating improved drug stability dramatically by preventing drug molecules from undergoing water hydrolysis in a neutral environment. More importantly, the specific reactivity of orthoboric groups to diols in cell glycocalyx facilitated a rapid cross-membrane translocation of drug nanocrystals, leading to efficient intracellular drug delivery, especially on cancer cells with highly expressed sialic acids. Boric acid coated nanocrystals of camptothecin, an anticancer drug with poor aqueous solubility and stability, demonstrated extreme cytotoxic activity (IC50 < 5.0 μg/mL) to cancer cells compared to synthetic polymer coated CPT nanocrystals and free CPT. Surface coating using non-covalent polymers from self-assembled boric acid will have wide biomedical applications especially in biomaterials and drug delivery field.

Extreme Activity of Drug Nanocrystals Coated with A Layer of Non-Covalent Polymers from Self-Assembled Boric Acid.

PubMed

Zhan, Honglei; Liang, Jun F

2016-12-09

Non-covalent polymers have remarkable advantages over synthetic polymers for wide biomedical applications. In this study, non-covalent polymers from self-assembled boric acid were used as the capping reagent to replace synthetic polymers in drug crystallization. Under acidic pH, boric acid self-assembled on the surface of drug nanocrystals to form polymers with network-like structures held together by hydrogen bonds. Coating driven by boric acid self-assembly had negligible effects on drug crystallinity and structure but resulted in drug nanocrystals with excellent dispersion properties that aided in the formation of a more stable suspension. Boric acid coating improved drug stability dramatically by preventing drug molecules from undergoing water hydrolysis in a neutral environment. More importantly, the specific reactivity of orthoboric groups to diols in cell glycocalyx facilitated a rapid cross-membrane translocation of drug nanocrystals, leading to efficient intracellular drug delivery, especially on cancer cells with highly expressed sialic acids. Boric acid coated nanocrystals of camptothecin, an anticancer drug with poor aqueous solubility and stability, demonstrated extreme cytotoxic activity (IC 50  < 5.0 μg/mL) to cancer cells compared to synthetic polymer coated CPT nanocrystals and free CPT. Surface coating using non-covalent polymers from self-assembled boric acid will have wide biomedical applications especially in biomaterials and drug delivery field.

Extreme Activity of Drug Nanocrystals Coated with A Layer of Non-Covalent Polymers from Self-Assembled Boric Acid

PubMed Central

Zhan, Honglei; Liang, Jun F.

2016-01-01

Non-covalent polymers have remarkable advantages over synthetic polymers for wide biomedical applications. In this study, non-covalent polymers from self-assembled boric acid were used as the capping reagent to replace synthetic polymers in drug crystallization. Under acidic pH, boric acid self-assembled on the surface of drug nanocrystals to form polymers with network-like structures held together by hydrogen bonds. Coating driven by boric acid self-assembly had negligible effects on drug crystallinity and structure but resulted in drug nanocrystals with excellent dispersion properties that aided in the formation of a more stable suspension. Boric acid coating improved drug stability dramatically by preventing drug molecules from undergoing water hydrolysis in a neutral environment. More importantly, the specific reactivity of orthoboric groups to diols in cell glycocalyx facilitated a rapid cross-membrane translocation of drug nanocrystals, leading to efficient intracellular drug delivery, especially on cancer cells with highly expressed sialic acids. Boric acid coated nanocrystals of camptothecin, an anticancer drug with poor aqueous solubility and stability, demonstrated extreme cytotoxic activity (IC50 < 5.0 μg/mL) to cancer cells compared to synthetic polymer coated CPT nanocrystals and free CPT. Surface coating using non-covalent polymers from self-assembled boric acid will have wide biomedical applications especially in biomaterials and drug delivery field. PMID:27934922

Biofouling on polymeric heat exchanger surfaces with E. coli and native biofilms.

PubMed

Pohl, S; Madzgalla, M; Manz, W; Bart, H J

2015-01-01

The biofouling affinity of different polymeric surfaces (polypropylene, polysulfone, polyethylene terephthalate, and polyether ether ketone) in comparison to stainless steel (SS) was studied for the model bacterium Escherichia coli K12 DSM 498 and native biofilms originating from Rhine water. The biofilm mass deposited on the polymer surfaces was minimized by several magnitudes compared to SS. The cell count and the accumulated biomass of E. coli on the polymer surfaces showed an opposing linear trend. The promising low biofilm formation on the polymers is attributed to the combination of inherent surface properties (roughness, surface energy and hydrophobicity) when compared to SS. The fouling characteristics of E. coli biofilms show good conformity with the more complex native biofilms investigated. The results can be utilized for the development of new polymer heat exchangers when using untreated river water as coolant or for other processes needing antifouling materials.

Programmable and electrically controllable light scattering from surface-polymer stabilized liquid crystals.

PubMed

Bédard-Arcand, Jean-Philippe; Galstian, Tigran

2012-08-01

We report the creation and study of a polarization independent light scattering material system based on surface-polymer stabilized liquid crystals. Originally isotropic cell substrates with thin nonpolymerized reactive mesogen layers are used for the alignment of pure nonreactive nematic liquid crystals. The partial interdiffusion of the two materials followed by the application of orienting external electric and magnetic fields and the photo polymerization of the reactive mesogen allow us the control of electro-optic scattering properties of obtained cells.

Fuel cell collector plate and method of fabrication

DOEpatents

Braun, James C.; Zabriskie, Jr., John E.; Neutzler, Jay K.; Fuchs, Michel; Gustafson, Robert C.

2001-01-01

An improved molding composition is provided for compression molding or injection molding a current collector plate for a polymer electrolyte membrane fuel cell. The molding composition is comprised of a polymer resin combined with a low surface area, highly-conductive carbon and/or graphite powder filler. The low viscosity of the thermoplastic resin combined with the reduced filler particle surface area provide a moldable composition which can be fabricated into a current collector plate having improved current collecting capacity vis-a-vis comparable fluoropolymer molding compositions.

Round-patterned ZnO nanostructure coated with siloxane-based polymer for nerve agent detection

NASA Astrophysics Data System (ADS)

Choi, Hyun Ji; Lee, Ji Won; Jeong, Dong-Cheol; Ha, Seonggyun; Song, Changsik; Boo, Jin-Hyo

2018-01-01

The alignment of zinc oxide (ZnO) nanostructures is expected to improve device sensitivities due to large surface areas which can be utilized to capture significant quantities of gas particles. In this study, we investigated patterned ZnO nanorods modified with polystyrene monolayers synthesized directly onto a quartz crystal microbalance (QCM) cell to increase the coating surface area of the sensing material. Also, we designed and synthesized a siloxane-based polymer (S1 polymer) as a sensing material. The patterned ZnO nanorods coated with S1 polymers were fabricated and used for the detection of dimethyl methylphosphonate (DMMP). The resonance frequency of QCM was shifted due to the adsorption and desorption of a compound at the surface of the modified electrodes. We have synthesized an S1 polymer that exhibited high sensitivity to DMMP. The patterned ZnO nanorods coated with the polymer also exhibited improved sensitivity due to an enhanced surface area capable of adsorbing more DMMP vapor.

Polymer based organic solar cells using ink-jet printed active layers

NASA Astrophysics Data System (ADS)

Aernouts, T.; Aleksandrov, T.; Girotto, C.; Genoe, J.; Poortmans, J.

2008-01-01

Ink-jet printing is used to deposit polymer:fullerene blends suitable as active layer for organic solar cells. We show that merging of separately deposited ink droplets into a continuous, pinhole-free organic thin film results from a balance between ink viscosity and surface wetting, whereas for certain of the studied solutions clear coffee drop effect occurs for single droplets; this can be minimized for larger printed areas, yielding smooth layers with minimal surface roughness. Resulting organic films are used as active layer for solar cells with power conversion efficiency of 1.4% under simulated AM1.5 solar illumination.

Synthesis and patterning of polymers for biomedical applications

NASA Astrophysics Data System (ADS)

He, Wei

The goal of this dissertation is to synthesize and characterize novel polymers, as well as to explore alternative techniques for biomedical applications. Although significant progress has been achieved in the design and preparation of new biomaterials over the past years, much remains to be accomplished. The interactions between biomaterials and cells are very important, especially in the emerging field of tissue engineering. The focus of this research is to improve such interactions via several different approaches. One way to engineer cellular interaction is by modifying surface topography through micro-patterning. Although photolithography is widely used for patterning, it is not suitable for direct cell and protein patterning because of the usage of organic solvent for feature development. To address this issue, a biocompatible chemically amplified resist derived from N-vinyl-2-pyrrolidone (NVP) was prepared. The results have shown that no organic solvent development was required to reveal the patterns and cells can be cultured on these patterned surfaces directly. Strong cell alignment was observed. The other issue addressed in this research is to develop a technique that can modify surface morphology and surface chemistry simultaneously. Such a technique is called masked ion beam lithography (MIBL). By implanting phosphorous ions on polymeric substrates through masks, not only micron/nano size patterns were generated on the surface, but also the phosphorous ions were incorporated. Incubation of bone forming osteoblast cells on these ion beam processed samples has shown that osteoblast cell attachment to the substrate was enhanced, as a consequence of the increased surface roughness as well as the implanted phosphorous ions. This indicates that MIBL can not only generate micro/nanostructures on the surface of a biocompatible polymer, but can also selectively modify the surface chemistry by implanting with specific ions. These factors can contribute to an osteogenic environment.

Selective cell response on natural polymer bio-interfaces textured by femtosecond laser

NASA Astrophysics Data System (ADS)

Daskalova, A.; Trifonov, A.; Bliznakova, I.; Nathala, C.; Ajami, A.; Husinsky, W.; Declercq, H.; Buchvarov, I.

2018-02-01

This study reports on the evaluation of laser processed natural polymer-chitosan, which is under consideration as a biointerface used for temporary applications as skin and cartilage substitutes. It is employed for tissue engineering purposes, since it possesses a significant degree of biocompatibility and biodegradability. Chitosan-based thin films were processed by femtosecond laser radiation to enhance the surface properties of the material. Various geometry patterns were produced on polymer surfaces and employed to examine cellular adhesion and orientation. The topography of the modified zones was observed using scanning electron microscopy and confocal microscopy. Test of the material cytotoxicity was performed by evaluating the life/dead cell correlation. The obtained results showed that texturing with femtosecond laser pulses is appropriate method to initiate a predefined cellular response. Formation of surface modifications in the form of foams with an expansion of the material was created under laser irradiation with a number of applied laser pulses from N = 1-5. It is shown that irradiation with N > 5 results in disturbance of microfoam. Material characterization reveals a decrease in water contact angle values after laser irradiation of chitosan films. Consequently, changes in surface roughness of chitosan thin-film surface result in its functionalization. Cultivation of MC3T3 and ATMSC cells show cell orientational migration concerning different surface patterning. The influence of various pulse durations (varying from τ = 30-500 fs) over biofilms surface was examined regarding the evolution of surface morphology. The goal of this study was to define the optimal laser conditions (laser energy, number of applied pulses, and pulse duration) to alter surface wettability properties and porosity to improve material performance. The acquired set of results indicate the way to tune the surface properties to optimize cell-interface interaction.

Bioresponsive polymer coated drug nanorods for breast cancer treatment

NASA Astrophysics Data System (ADS)

Laemthong, Tunyaboon; Kim, Hannah H.; Dunlap, Kelly; Brocker, Caitlin; Barua, Dipak; Forciniti, Daniel; Huang, Yue-Wern; Barua, Sutapa

2017-01-01

Ineffective drug release at the target site is among the top challenges for cancer treatment. This reflects the facts that interaction with the physiological condition can denature active ingredients of drugs, and low delivery to the disease microenvironment leads to poor therapeutic outcomes. We hypothesize that depositing a thin layer of bioresponsive polymer on the surface of drug nanoparticles would not only protect drugs from degradation but also allow the release of drugs at the target site. Here, we report a one-step process to prepare bioresponsive polymer coated drug nanorods (NRs) from liquid precursors using the solvent diffusion method. A thin layer (10.3 ± 1.4 nm) of poly(ε-caprolactone) (PCL) polymer coating was deposited on the surface of camptothecin (CPT) anti-cancer drug NRs. The mean size of PCL-coated CPT NRs was 500.9 ± 91.3 nm length × 122.7 ± 10.1 nm width. The PCL polymer coating was biodegradable at acidic pH 6 as determined by Fourier transform infrared spectroscopy. CPT drugs were released up to 51.5% when PCL coating dissolved into non-toxic carboxyl and hydroxyl groups. Trastuzumab (TTZ), a humanized IgG monoclonal antibody, was conjugated to the NR surface for breast cancer cell targeting. Combination treatments using CPT and TTZ decreased the HER-2 positive BT-474 breast cancer cell growth by 66.9 ± 5.3% in vitro. These results suggest effective combination treatments of breast cancer cells using bioresponsive polymer coated drug delivery.

Preparation and antifouling properties of 2-(meth-acryloyloxy)ethyl cholinephosphate based polymers modified surface with different molecular architectures by ATRP.

PubMed

Jiang, Yuchen; Su, Yuling; Zhao, Lili; Meng, Fancui; Wang, Quanxin; Ding, Chunmei; Luo, Jianbin; Li, Jianshu

2017-08-01

Choline phosphate (CP) containing polymers modified surfaces have been shown good resist to the adhesion of proteins while prompt the attaching of mammalian cells due to the dipole pairing between the CP groups of the polymer and the phosphorylcholine (PC) groups on the cell membrane. However, the antifouling activities of CP modified surface against microbes have not been investigated at present. In addition, CP containing polymers modified surface with different molecular architectures has not been prepared and studied. To this end, glass slides surface modified with two different 2-(meth-acryloyloxy)ethyl cholinephosphate (MCP) containing polymer (PMCP) structures, i.e. brush-like (Glass-PMCP) and bottle brush-like (Glass-PHEMA-g-PMCP) architectures, were prepared in this work by surface-initiated atom transfer radical polymerization (SI-ATRP). The surface physichemical and antifouling properties of the prepared surfaces were characterized and studied. The Glass-PMCP shows improved antifouling properties against proteins and bacteria as compared to pristine glass slides (Glass-OH) and glass slides grafted with poly(2-hydroxyethyl methacrylate) (Glass-PHEMA). Notably, a synergetic fouling resistant properties of PHEMA and PMCP is presented for Glass-PHEMA-g-PMCP, which shows superior antifouling activities over Glass-PHEMA and Glass-PMCP. Furthermore, glass slides containing PMCP, i.e. Glass-PMCP and Glas-PHEMA-g-PMCP, decrease platelet adhesion and prevent their activation significantly. Therefore, the combination of antifouling PHEMA and PMCP into one system holds potential for prevention of bacterial fouling and biomaterial-centered infections. Copyright © 2017 Elsevier B.V. All rights reserved.

Imprint Molding of a Microfluidic Optical Cell on Thermoplastics with Reduced Surface Roughness for the Detection of Copper Ions.

PubMed

Wu, Jing; Lee, Nae Yoon

2016-01-01

Here, we introduce a simple and facile technique for fabricating microfluidic optical cells by utilizing a micropatterned polymer mold, followed by imprinting on thermoplastic substrates. This process has reduced the surface roughness of the microchannel, making it suitable for microscale optical measurements. The micropatterned polymer mold was fabricated by first micromilling on a poly(methylmethacrylate) (PMMA) substrate, and then transferring the micropattern onto an ultraviolet (UV)-curable optical adhesive. After an anti-adhesion treatment of the polymer mold fabricated using the UV-curable optical adhesive, the polymer mold was used repeatedly for imprinting onto various thermoplastics, such as PMMA, polycarbonate (PC), and poly(ethyleneterephthalate) (PET). The roughness values for the PMMA, PC, and PET microchannels were approximately 11.3, 20.3, and 14.2 nm, respectively, as compared to those obtained by micromilling alone, which were 15.9, 76.8, and 207.5 nm, respectively. Using the imprint-molded thermoplastic optical cell, rhodamine B and copper ions were successfully quantified. The reduced roughness of the microchannel surface resulted in improved sensitivity and reduced noise, paving the way for integration of the detection module so as to realize totally integrated microdevices.

Photo-assisted generation of phospholipid polymer substrates for regiospecific protein conjugation and control of cell adhesion.

PubMed

Tanaka, Masako; Iwasaki, Yasuhiko

2016-08-01

Novel photo-reactive phospholipid polymers were synthesized for use in the preparation of nonfouling surfaces with protein conjugation capacity. Poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-ran-N-methacryloyl-(l)-tyrosinemethylester (MAT)] (P(MPC/MAT)) was synthesized by conventional radical polymerization, with the MAT units capable of being oxidized by 254nm UV irradiation. Because of this photo-oxidation, active species such as catechol and quinone were alternately generated in the copolymer. A silicon wafer was subjected to surface modification through spin coating of P(MPC/MAT) from an aqueous solution for use as a model substrate. The surface was then irradiated several times with UV light. The thickness of the polymer layers formed on the Si wafers was influenced by various parameters such as polymer concentration, UV irradiation time, and composition of the MAT units in P(MPC/MAT). Oxidized MAT units were advantageous not only for polymer adhesion to a solid surface but also for protein conjugation with the adhered polymers. The amount of protein immobilized on UV-irradiated P(MPC/MAT) was dependent on the composition of the MAT units in the polymer. Furthermore, it was confirmed that protein immobilization on the polymer occurred through the oxidized MAT units because the protein adsorption was significantly reduced upon blocking these units through pretreatment with glycine. Conjugation of regiospecific protein could also be achieved through the use of a photomask. In addition, nonspecific protein adsorption was reduced on the non-irradiated regions whose surface was covered with physisorbed P(MPC/MAT). Therefore, P(MPC/MAT) can be used in the preparation of nonfouling substrates, which enable micrometer-sized manipulation of proteins through photo-irradiation. Function of proteins immobilized on MPC copolymers was also confirmed by cell adhesion test. As such, photo-reactive MPC copolymers are suitable for performing controlled protein conjugation and preparing polymer-protein hybrid platforms for use in biomedical and diagnostic devices. Novel photo-reactive phospholipid polymers have been synthesized for immobilization on solid surfaces and regiospecific protein conjugation. Tyrosine residues embedded in 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymers could be photo-oxidized, resulting in polymers able to form layers on a solid surface and conjugate with proteins. Moreover, nonspecific biofouling on the surface significantly reduced when the oxidized tyrosine units in the polymer layers were blocked. Upon UV irradiation through a photomask, the UV-exposed tyrosine units were selectively oxidized, forming the only specific regions in which protein conjugation could occur. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Initial biocompatibility of plasma polymerized hexamethyldisiloxane films with different wettability

NASA Astrophysics Data System (ADS)

Krasteva, N. A.; Toromanov, G.; Hristova, K. T.; Radeva, E. I.; Pecheva, E. V.; Dimitrova, R. P.; Altankov, G. P.; Pramatarova, L. D.

2010-11-01

Understanding the relationships between material surface properties, behaviour of adsorbed proteins and cellular responses is essential to design optimal material surfaces for tissue engineering. In this study we modify thin layers of plasma polymerized hexamethyldisiloxane (PPHMDS) by ammonia treatment in order to increase surface wettability and the corresponding biological response. The physico-chemical properties of the polymer films were characterized by contact angle (CA) measurements and Fourier Transform Infrared Spectroscopy (FTIR) analysis.Human umbilical vein endothelial cells (HUVEC) were used as model system for the initial biocompatibility studies following their behavior upon preadsorption of polymer films with three adhesive proteins: fibronectin (FN), fibrinogen (FG) and vitronectin (VN). Adhesive interaction of HUVEC was evaluated after 2 hours by analyzing the overall cell morphology, and the organization of focal adhesion contacts and actin cytoskeleton. We have found similar good cellular response on FN and FG coated polymer films, with better pronounced vinculin expression on FN samples while. Conversely, on VN coated surfaces the wettability influenced significantly initial celular interaction spreading. The results obtained suggested that ammonia plasma treatment can modulate the biological activity of the adsorbed protein s on PPHMDS surfaces and thus to influence the interaction with endothelial cells.

Surface-initiated polymerization within mesoporous silica spheres for the modular design of charge-neutral polymer particles.

PubMed

Müllner, Markus; Cui, Jiwei; Noi, Ka Fung; Gunawan, Sylvia T; Caruso, Frank

2014-06-03

We report a templating approach for the preparation of functional polymer replica particles via surface-initiated polymerization in mesoporous silica templates. Subsequent removal of the template resulted in discrete polymer particles. Furthermore, redox-responsive replica particles could be engineered to disassemble in a reducing environment. Particles, made of poly(methacryloyloxyethyl phosphorylcholine) (PMPC) or poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA), exhibited very low association to human cancer cells (below 5%), which renders the reported charge-neutral polymer particles a modular and versatile class of highly functional carriers with potential applications in drug delivery.

Controlling Film Morphology in Conjugated Polymer

PubMed Central

Park, Lee Y.; Munro, Andrea M.; Ginger, David S.

2009-01-01

We study the effects of patterned surface chemistry on the microscale and nanoscale morphology of solution-processed donor/acceptor polymer-blend films. Focusing on combinations of interest in polymer solar cells, we demonstrate that patterned surface chemistry can be used to tailor the film morphology of blends of semiconducting polymers such as poly-[2-(3,7-dimethyloctyloxy)-5-methoxy-p-phenylenevinylene] (MDMO-PPV), poly-3-hexylthiophene (P3HT), poly[(9,9-dioctylflorenyl-2,7-diyl)-co-benzothiadiazole)] (F8BT), and poly(9,9-dioctylfluorene-co-bis-N,N’-(4-butylphenyl)-bis-N,N’-phenyl-1,4-phenylendiamine) (PFB) with the fullerene derivative, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We present a method for generating patterned, fullerene-terminated monolayers on gold surfaces, and use microcontact printing and Dip-Pen Nanolithography (DPN) to pattern alkanethiols with both micro- and nanoscale features. After patterning with fullerenes and other functional groups, we backfill the rest of the surface with a variety of thiols to prepare substrates with periodic variations in surface chemistry. Spin coating polymer:PCBM films onto these substrates, followed by thermal annealing under nitrogen, leads to the formation of structured polymer films. We characterize these films with Atomic Force Microscopy (AFM), Raman spectroscopy, and fluorescence microscopy. The surface patterns are effective in guiding phase separation in all of the polymer:PCBM systems investigated, and lead to a rich variety of film morphologies that are inaccessible with unpatterned substrates. We demonstrate our ability to guide pattern formation in films thick enough of be of interest for actual device applications (up to 200 nm in thickness) using feature sizes as small as 100 nm. Finally, we show that the surface chemistry can lead to variations in film morphology on length scales significantly smaller than those used in generating the original surface patterns. The variety of behaviors observed and the wide range of control over polymer morphology achieved at a variety of different length scales have important implications for the development of bulk heterojunction solar cells. PMID:18983150

Using Polymer Electrolyte Membrane Fuel Cells in a Hybrid Surface Ship Propulsion Plant to Increase Fuel Efficiency

DTIC Science & Technology

2010-06-01

cell ( PEMFC ), and the phosphoric acid fuel cell (PAFC). 2.3.1 Solid Oxide Fuel Cells (SOFC) The first type of fuel cell considered is the SOFC. This...durability issues for use within a given application. 2.3.2 Polymer Electrolyte Membrane Fuel Cells ( PEMFC ) The PEMFC operates by passing hydrogen that has...cells. Some advantages of PEMFC operating at such low temperatures is that the fuel cell doesn’t require as meticulous of a support system infrastructure

Chemical copatterning strategies using azlactone-based block copolymers

DOE PAGES

Masigol, Mohammadali; Barua, Niloy; Retterer, Scott T.; ...

2017-09-01

Interfaces can be modified with azlactone-functional polymers in order to manipulate the chemical surface reactivity. Azlactone groups are highly reactive toward amine, thiol, and alcohol nucleophiles, providing a versatile coupling chemistry for secondary surface modification. Azlactone-based surface polymers have been explored in numerous applications, including chemical and biological capture, sensing, and cell culture. These applications often require that the polymer is copatterned within a chemically or biologically inert background; however, common fabrication methods degrade azlactone groups during processing steps or result in polymer films with poorly controlled thicknesses. Here, the authors develop fabrication strategies using parylene lift-off and interface-directed assemblymore » methods to generate microscale patterns of azlactone-based block copolymer in chemically or biologically inert backgrounds. The functionality of azlactone groups was preserved during fabrication, and patterned films appeared as uniform, 80–120nm brushlike films. The authors also develop a patterning approach that uses a novel microcontact stamping method to generate cross-linked, three-dimensional structures of azlactone-based polymers with controllable, microscale thicknesses. The authors identify the benefits of each approach and expect these polymers and patterning strategies to provide a versatile toolbox for developing synthetic interfaces with tuned chemical and physical features for sensing, cell culture, or material capture applications.« less

Chemical copatterning strategies using azlactone-based block copolymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masigol, Mohammadali; Barua, Niloy; Retterer, Scott T.

Interfaces can be modified with azlactone-functional polymers in order to manipulate the chemical surface reactivity. Azlactone groups are highly reactive toward amine, thiol, and alcohol nucleophiles, providing a versatile coupling chemistry for secondary surface modification. Azlactone-based surface polymers have been explored in numerous applications, including chemical and biological capture, sensing, and cell culture. These applications often require that the polymer is copatterned within a chemically or biologically inert background; however, common fabrication methods degrade azlactone groups during processing steps or result in polymer films with poorly controlled thicknesses. Here, the authors develop fabrication strategies using parylene lift-off and interface-directed assemblymore » methods to generate microscale patterns of azlactone-based block copolymer in chemically or biologically inert backgrounds. The functionality of azlactone groups was preserved during fabrication, and patterned films appeared as uniform, 80–120nm brushlike films. The authors also develop a patterning approach that uses a novel microcontact stamping method to generate cross-linked, three-dimensional structures of azlactone-based polymers with controllable, microscale thicknesses. The authors identify the benefits of each approach and expect these polymers and patterning strategies to provide a versatile toolbox for developing synthetic interfaces with tuned chemical and physical features for sensing, cell culture, or material capture applications.« less

Fullerene derivative-doped zinc oxide nanofilm as the cathode of inverted polymer solar cells with low-bandgap polymer (PTB7-Th) for high performance.

PubMed

Liao, Sih-Hao; Jhuo, Hong-Jyun; Cheng, Yu-Shan; Chen, Show-An

2013-09-14

Modification of a ZnO cathode by doping it with a hydroxyl-containing derivative - giving a ZnO-C60 cathode - provides a fullerene-derivative-rich surface and enhanced electron conduction. Inverted polymer solar cells with the ZnO-C60 cathode display markedly improved power conversion efficiency compared to those with a pristine ZnO cathode, especially when the active layer includes the low-bandgap polymer PTB7-Th. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dual-Color Fluorescence Imaging of Magnetic Nanoparticles in Live Cancer Cells Using Conjugated Polymer Probes

PubMed Central

Sun, Minjie; Sun, Bin; Liu, Yun; Shen, Qun-Dong; Jiang, Shaojun

2016-01-01

Rapid growth in biological applications of nanomaterials brings about pressing needs for exploring nanomaterial-cell interactions. Cationic blue-emissive and anionic green-emissive conjugated polymers are applied as dual-color fluorescence probes to the surface of negatively charged magnetic nanoparticles through sequentially electrostatic adsorption. These conjugated polymers have large extinction coefficients and high fluorescence quantum yield (82% for PFN and 62% for ThPFS). Thereby, one can visualize trace amount (2.7 μg/mL) of fluorescence-labeled nanoparticles within cancer cells by confocal laser scanning microscopy. Fluorescence labeling by the conjugated polymers is also validated for quantitative determination of the internalized nanoparticles in each individual cell by flow cytometry analysis. Extensive overlap of blue and green fluorescence signals in the cytoplasm indicates that both conjugated polymer probes tightly bind to the surface of the nanoparticles during cellular internalization. The highly charged and fluorescence-labeled nanoparticles non-specifically bind to the cell membranes, followed by cellular uptake through endocytosis. The nanoparticles form aggregates inside endosomes, which yields a punctuated staining pattern. Cellular internalization of the nanoparticles is dependent on the dosage and time. Uptake efficiency can be enhanced three-fold by application of an external magnetic field. The nanoparticles are low cytotoxicity and suitable for simultaneously noninvasive fluorescence and magnetic resonance imaging application. PMID:26931282

Human Fetal Osteoblast Response on Poly(Methyl Methacrylate)/Polystyrene Demixed Thin Film Blends: Surface Chemistry Vs Topography Effects.

PubMed

D'Sa, Raechelle A; Raj, Jog; Dickinson, Peter J; McCabe, Fiona; Meenan, Brian J

2016-06-22

Recent advances in materials sciences have allowed for the development and fabrication of biomaterials that are capable of providing requisite cues to instigate cells to respond in a predictable fashion. We have developed a series of poly(methyl methacrylate)/polystyrene (PMMA/PS) polymer demixed thin films with nanotopographies ranging from nanoislands to nanopits to study the response of human fetal osteoblast cells (hFOBs). When PMMA was in excess in the blend composition, a nanoisland topography dominated, whereas a nanopit topography dominated when PS was in excess. PMMA was found to segregate to the top of the nanoisland morphology with PS preferring the substrate interface. To further ascertain the effects of surface chemistry vs topography, we plasma treated the polymer demixed films using an atmospheric pressure dielectric barrier discharge reactor to alter the surface chemistry. Our results have shown that hFOBs did not have an increased short-term cellular response on pristine polymer demixed surfaces. However, increasing the hydrophilicty/wettability of the surfaces by oxygen functionalization causes an increase in the cellular response. These results indicate that topography alone is not sufficient to induce a positive cellular response, but the underlying surface chemistry is also important in regulating cell function.

Gold nanoparticle-polymer nanocomposites synthesized by room temperature atmospheric pressure plasma and their potential for fuel cell electrocatalytic application

PubMed Central

Zhang, Ri-Chao; Sun, Dan; Zhang, Ruirui; Lin, Wen-Feng; Macias-Montero, Manuel; Patel, Jenish; Askari, Sadegh; McDonald, Calum; Mariotti, Davide; Maguire, Paul

2017-01-01

Conductive polymers have been increasingly used as fuel cell catalyst support due to their electrical conductivity, large surface areas and stability. The incorporation of metal nanoparticles into a polymer matrix can effectively increase the specific surface area of these materials and hence improve the catalytic efficiency. In this work, a nanoparticle loaded conductive polymer nanocomposite was obtained by a one-step synthesis approach based on room temperature direct current plasma-liquid interaction. Gold nanoparticles were directly synthesized from HAuCl4 precursor in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The resulting AuNPs/PEDOT:PSS nanocomposites were subsequently characterized under a practical alkaline direct ethanol fuel cell operation condition for its potential application as an electrocatalyst. Results show that AuNPs sizes within the PEDOT:PSS matrix are dependent on the plasma treatment time and precursor concentration, which in turn affect the nanocomposites electrical conductivity and their catalytic performance. Under certain synthesis conditions, unique nanoscale AuNPs/PEDOT:PSS core-shell structures could also be produced, indicating the interaction at the AuNPs/polymer interface. The enhanced catalytic activity shown by AuNPs/PEDOT:PSS has been attributed to the effective electron transfer and reactive species diffusion through the porous polymer network, as well as the synergistic interfacial interaction at the metal/polymer and metal/metal interfaces. PMID:28436454

Gold nanoparticle-polymer nanocomposites synthesized by room temperature atmospheric pressure plasma and their potential for fuel cell electrocatalytic application

NASA Astrophysics Data System (ADS)

Zhang, Ri-Chao; Sun, Dan; Zhang, Ruirui; Lin, Wen-Feng; Macias-Montero, Manuel; Patel, Jenish; Askari, Sadegh; McDonald, Calum; Mariotti, Davide; Maguire, Paul

2017-04-01

Conductive polymers have been increasingly used as fuel cell catalyst support due to their electrical conductivity, large surface areas and stability. The incorporation of metal nanoparticles into a polymer matrix can effectively increase the specific surface area of these materials and hence improve the catalytic efficiency. In this work, a nanoparticle loaded conductive polymer nanocomposite was obtained by a one-step synthesis approach based on room temperature direct current plasma-liquid interaction. Gold nanoparticles were directly synthesized from HAuCl4 precursor in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The resulting AuNPs/PEDOT:PSS nanocomposites were subsequently characterized under a practical alkaline direct ethanol fuel cell operation condition for its potential application as an electrocatalyst. Results show that AuNPs sizes within the PEDOT:PSS matrix are dependent on the plasma treatment time and precursor concentration, which in turn affect the nanocomposites electrical conductivity and their catalytic performance. Under certain synthesis conditions, unique nanoscale AuNPs/PEDOT:PSS core-shell structures could also be produced, indicating the interaction at the AuNPs/polymer interface. The enhanced catalytic activity shown by AuNPs/PEDOT:PSS has been attributed to the effective electron transfer and reactive species diffusion through the porous polymer network, as well as the synergistic interfacial interaction at the metal/polymer and metal/metal interfaces.

Amide side chain amphiphilic polymers disrupt surface established bacterial bio-films and protect mice from chronic Acinetobacter baumannii infection.

PubMed

Uppu, Divakara S S M; Samaddar, Sandip; Ghosh, Chandradhish; Paramanandham, Krishnamoorthy; Shome, Bibek R; Haldar, Jayanta

2016-01-01

Bacterial biofilms represent the root-cause of chronic or persistent infections in humans. Gram-negative bacterial infections due to nosocomial and opportunistic pathogens such as Acinetobacter baumannii are more difficult to treat because of their inherent and rapidly acquiring resistance to antibiotics. Due to biofilm formation, A. baumannii has been noted for its apparent ability to survive on artificial surfaces for an extended period of time, therefore allowing it to persist in the hospital environment. Here we report, maleic anhydride based novel cationic polymers appended with amide side chains that disrupt surface established multi-drug resistant A. baumannii biofilms. More importantly, these polymers significantly (p < 0.0001) decrease the bacterial burden in mice with chronic A. baumannii burn wound infection. The polymers also show potent antibacterial efficacy against methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant Enterococci (VRE) and multi-drug resistant clinical isolates of A. baumannii with minimal toxicity to mammalian cells. We observe that optimal hydrophobicity dependent on the side chain chemical structure of these polymers dictate the selective toxicity to bacteria. Polymers interact with the bacterial cell membranes by causing membrane depolarization, permeabilization and energy depletion. Bacteria develop rapid resistance to erythromycin and colistin whereas no detectable development of resistance occurs against these polymers even after several passages. These results suggest the potential use of these polymeric biomaterials in disinfecting biomedical device surfaces after the infection has become established and also for the topical treatment of chronic bacterial infections. Copyright © 2015 Elsevier Ltd. All rights reserved.

High-content profiling of cell responsiveness to graded substrates based on combinyatorially variant polymers.

PubMed

Liu, Er; Treiser, Matthew D; Patel, Hiral; Sung, Hak-Joon; Roskov, Kristen E; Kohn, Joachim; Becker, Matthew L; Moghe, Prabhas V

2009-08-01

We have developed a novel approach combining high information and high throughput analysis to characterize cell adhesive responses to biomaterial substrates possessing gradients in surface topography. These gradients were fabricated by subjecting thin film blends of tyrosine-derived polycarbonates, i.e. poly(DTE carbonate) and poly(DTO carbonate) to a gradient temperature annealing protocol. Saos-2 cells engineered with a green fluorescent protein (GFP) reporter for farnesylation (GFP-f) were cultured on the gradient substrates to assess the effects of nanoscale surface topology and roughness that arise during the phase separation process on cell attachment and adhesion strength. The high throughput imaging approach allowed us to rapidly identify the "global" and "high content" structure-property relationships between cell adhesion and biomaterial properties such as polymer chemistry and topography. This study found that cell attachment and spreading increased monotonically with DTE content and were significantly elevated at the position with intermediate regions corresponding to the highest "gradient" of surface roughness, while GFP-f farnesylation intensity descriptors were sensitively altered by surface roughness, even in cells with comparable levels of spreading.

Polymer-encapsulated organic nanoparticles for fluorescence and photoacoustic imaging.

PubMed

Li, Kai; Liu, Bin

2014-09-21

Polymer encapsulated organic nanoparticles have recently attracted increasing attention in the biomedical field because of their unique optical properties, easy fabrication and outstanding performance as imaging and therapeutic agents. Of particular importance is the polymer encapsulated nanoparticles containing conjugated polymers (CP) or fluorogens with aggregation induced emission (AIE) characteristics as the core, which have shown significant advantages in terms of tunable brightness, superb photo- and physical stability, good biocompatibility, potential biodegradability and facile surface functionalization. In this review, we summarize the latest advances in the development of polymer encapsulated CP and AIE fluorogen nanoparticles, including preparation methods, material design and matrix selection, nanoparticle fabrication and surface functionalization for fluorescence and photoacoustic imaging. We also discuss their specific applications in cell labeling, targeted in vitro and in vivo imaging, blood vessel imaging, cell tracing, inflammation monitoring and molecular imaging. We specially focus on strategies to fine-tune the nanoparticle property (e.g. size and fluorescence quantum yield) through precise engineering of the organic cores and careful selection of polymer matrices. The review also highlights the merits and limitations of these nanoparticles as well as strategies used to overcome the limitations. The challenges and perspectives for the future development of polymer encapsulated organic nanoparticles are also discussed.

Bacteria-instructed synthesis of polymers for self-selective microbial binding and labelling

PubMed Central

Magennis, E. Peter; Fernandez-Trillo, Francisco; Sui, Cheng; Spain, Sebastian G.; Bradshaw, David; Churchley, David; Mantovani, Giuseppe; Winzer, Klaus; Alexander, Cameron

2014-01-01

The detection and inactivation of pathogenic strains of bacteria continues to be an important therapeutic goal. Hence, there is a need for materials that can bind selectively to specific microorganisms, for diagnostic or anti-infective applications, but which can be formed from simple and inexpensive building blocks. Here, we exploit bacterial redox systems to induce a copper-mediated radical polymerisation of synthetic monomers at cell surfaces, generating polymers in situ that bind strongly to the microorganisms which produced them. This ‘bacteria-instructed synthesis’ can be carried out with a variety of microbial strains, and we show that the polymers produced are self-selective binding agents for the ‘instructing’ cell types. We further expand on the bacterial redox chemistries to ‘click’ fluorescent reporters onto polymers directly at the surfaces of a range of clinical isolate strains, allowing rapid, facile and simultaneous binding and visualisation of pathogens. PMID:24813421

Bacteria-instructed synthesis of polymers for self-selective microbial binding and labelling

NASA Astrophysics Data System (ADS)

Magennis, E. Peter; Fernandez-Trillo, Francisco; Sui, Cheng; Spain, Sebastian G.; Bradshaw, David J.; Churchley, David; Mantovani, Giuseppe; Winzer, Klaus; Alexander, Cameron

2014-07-01

The detection and inactivation of pathogenic strains of bacteria continues to be an important therapeutic goal. Hence, there is a need for materials that can bind selectively to specific microorganisms for diagnostic or anti-infective applications, but that can be formed from simple and inexpensive building blocks. Here, we exploit bacterial redox systems to induce a copper-mediated radical polymerization of synthetic monomers at cell surfaces, generating polymers in situ that bind strongly to the microorganisms that produced them. This ‘bacteria-instructed synthesis’ can be carried out with a variety of microbial strains, and we show that the polymers produced are self-selective binding agents for the ‘instructing’ cell types. We further expand on the bacterial redox chemistries to ‘click’ fluorescent reporters onto polymers directly at the surfaces of a range of clinical isolate strains, allowing rapid, facile and simultaneous binding and visualization of pathogens.

Highly Flexible and Planar Supercapacitors Using Graphite Flakes/Polypyrrole in Polymer Lapping Film.

PubMed

Raj, C Justin; Kim, Byung Chul; Cho, Won-Je; Lee, Won-gil; Jung, Sang-Don; Kim, Yong Hee; Park, Sang Yeop; Yu, Kook Hyun

2015-06-24

Flexible supercapacitor electrodes have been fabricated by simple fabrication technique using graphite nanoflakes on polymer lapping films as flexible substrate. An additional thin layer of conducting polymer polypyrrole over the electrode improved the surface conductivity and exhibited excellent electrochemical performances. Such capacitor films showed better energy density and power density with a maximum capacitance value of 37 mF cm(-2) in a half cell configuration using 1 M H2SO4 electrolyte, 23 mF cm(-2) in full cell, and 6 mF cm(-2) as planar cell configuration using poly(vinyl alcohol) (PVA)/phosphoric acid (H3PO4) solid state electrolyte. Moreover, the graphite nanoflakes/polypyrrole over polymer lapping film demonstrated good flexibility and cyclic stability.

Extracellular matrix production by human osteoblasts cultured on biodegradable polymers applicable for tissue engineering.

PubMed

El-Amin, S F; Lu, H H; Khan, Y; Burems, J; Mitchell, J; Tuan, R S; Laurencin, C T

2003-03-01

The nature of the extracellular matrix (ECM) is crucial in regulating cell functions via cell-matrix interactions, cytoskeletal organization, and integrin-mediated signaling. In bone, the ECM is composed of proteins such as collagen (CO), fibronectin (FN), laminin (LM), vitronectin (VN), osteopontin (OP) and osteonectin (ON). For bone tissue engineering, the ECM should also be considered in terms of its function in mediating cell adhesion to biomaterials. This study examined ECM production, cytoskeletal organization, and adhesion of primary human osteoblastic cells on biodegradable matrices applicable for tissue engineering, namely polylactic-co-glycolic acid 50:50 (PLAGA) and polylactic acid (PLA). We hypothesized that the osteocompatible, biodegradable polymer surfaces promote the production of bone-specific ECM proteins in a manner dependent on polymer composition. We first examined whether the PLAGA and PLA matrices could support human osteoblastic cell growth by measuring cell adhesion at 3, 6 and 12h post-plating. Adhesion on PLAGA was consistently higher than on PLA throughout the duration of the experiment, and comparable to tissue culture polystyrene (TCPS). ECM components, including CO, FN, LM, ON, OP and VN, produced on the surface of the polymers were quantified by ELISA and localized by immunofluorescence staining. All of these proteins were present at significantly higher levels on PLAGA compared to PLA or TCPS surfaces. On PLAGA, OP and ON were the most abundant ECM components, followed by CO, FN, VN and LN. Immunofluorescence revealed an extracellular distribution for CO and FN, whereas OP and ON were found both intracellularly as well as extracellularly on the polymer. In addition, the actin cytoskeletal network was more extensive in osteoblasts cultured on PLAGA than on PLA or TCPS. In summary, we found that osteoblasts plated on PLAGA adhered better to the substrate, produced higher levels of ECM molecules, and showed greater cytoskeletal organization than on PLA and TCPS. We propose that this difference in ECM composition is functionally related to the enhanced cell adhesion observed on PLAGA. There is initial evidence that specific composition of the PLAGA polymer favors the ECM. Future studies will seek to optimize ECM production on these matrices for bone tissue engineering applications.

Catechol polymers for pH-responsive, targeted drug delivery to cancer cells.

PubMed

Su, Jing; Chen, Feng; Cryns, Vincent L; Messersmith, Phillip B

2011-08-10

A novel cell-targeting, pH-sensitive polymeric carrier was employed in this study for delivery of the anticancer drug bortezomib (BTZ) to cancer cells. Our strategy is based on facile conjugation of BTZ to catechol-containing polymeric carriers that are designed to be taken up selectively by cancer cells through cell surface receptor-mediated mechanisms. The polymer used as a building block in this study was poly(ethylene glycol), which was chosen for its ability to reduce nonspecific interactions with proteins and cells. The catechol moiety was exploited for its ability to bind and release borate-containing therapeutics such as BTZ in a pH-dependent manner. In acidic environments, such as in cancer tissue or the subcellular endosome, BTZ dissociates from the polymer-bound catechol groups to liberate the free drug, which inhibits proteasome function. A cancer-cell-targeting ligand, biotin, was presented on the polymer carriers to facilitate targeted entry of drug-loaded polymer carriers into cancer cells. Our study demonstrated that the cancer-targeting drug-polymer conjugates dramatically enhanced cellular uptake, proteasome inhibition, and cytotoxicity toward breast carcinoma cells in comparison with nontargeting drug-polymer conjugates. The pH-sensitive catechol-boronate binding mechanism provides a chemoselective approach for controlling the release of BTZ in targeted cancer cells, establishing a concept that may be applied in the future toward other boronic acid-containing therapeutics to treat a broad range of diseases. © 2011 American Chemical Society

Thermo-responsive cell culture carrier: Effects on macrophage functionality and detachment efficiency.

PubMed

Rennert, Knut; Nitschke, Mirko; Wallert, Maria; Keune, Natalie; Raasch, Martin; Lorkowski, Stefan; Mosig, Alexander S

2017-01-01

Harvesting cultivated macrophages for tissue engineering purposes by enzymatic digestion of cell adhesion molecules can potentially result in unintended activation, altered function, or behavior of these cells. Thermo-responsive polymer is a promising tool that allows for gentle macrophage detachment without artificial activation prior to subculture within engineered tissue constructs. We therefore characterized different species of thermo-responsive polymers for their suitability as cell substrate and to mediate gentle macrophage detachment by temperature shift. Primary human monocyte- and THP-1-derived macrophages were cultured on thermo-responsive polymers and characterized for phagocytosis and cytokine secretion in response to lipopolysaccharide stimulation. We found that both cell types differentially respond in dependence of culture and stimulation on thermo-responsive polymers. In contrast to THP-1 macrophages, primary monocyte-derived macrophages showed no signs of impaired viability, artificial activation, or altered functionality due to culture on thermo-responsive polymers compared to conventional cell culture. Our study demonstrates that along with commercially available UpCell carriers, two other thermo-responsive polymers based on poly(vinyl methyl ether) blends are attractive candidates for differentiation and gentle detachment of primary monocyte-derived macrophages. In summary, we observed similar functionality and viability of primary monocyte-derived macrophages cultured on thermo-responsive polymers compared to standard cell culture surfaces. While this first generation of custom-made thermo-responsive polymers does not yet outperform standard culture approaches, our results are very promising and provide the basis for exploiting the unique advantages offered by custom-made thermo-responsive polymers to further improve macrophage culture and recovery in the future, including the covalent binding of signaling molecules and the reduction of centrifugation and washing steps. Optimizing these and other benefits of thermo-responsive polymers could greatly improve the culture of macrophages for tissue engineering applications.

Efficient inverted polymer solar cells based on conjugated polyelectrolyte and zinc oxide modified ITO electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Tao; Zhu, Xiaoguang; Tu, Guoli, E-mail: tgl@hust.edu.cn

Efficient inverted polymer solar cells (PSCs) were constructed by utilizing a conjugated polyelectrolyte PF{sub EO}SO{sub 3}Na and zinc oxide to modify the indium tin oxide (ITO) electrode. The ITO electrode modified by PF{sub EO}SO{sub 3}Na and zinc oxide possesses high transparency, increased electron mobility, smoothened surface, and lower work function. PTB7:PC{sub 71}BM inverted PSCs containing the modified ITO electrode achieved a high power conversion efficiency (PCE) of 8.49%, exceeding that of the control device containing a ZnO modified ITO electrode (7.48%). Especially, PCE-10:PC{sub 71}BM inverted polymer solar cells achieved a high PCE up to 9.4%. These results demonstrate a usefulmore » approach to improve the performance of inverted polymer solar cells.« less

Shape-memory surfaces for cell mechanobiology

PubMed Central

Ebara, Mitsuhiro

2015-01-01

Shape-memory polymers (SMPs) are a new class of smart materials, which have the capability to change from a temporary shape ‘A’ to a memorized permanent shape ‘B’ upon application of an external stimulus. In recent years, SMPs have attracted much attention from basic and fundamental research to industrial and practical applications due to the cheap and efficient alternative to well-known metallic shape-memory alloys. Since the shape-memory effect in SMPs is not related to a specific material property of single polymers, the control of nanoarchitecture of polymer networks is particularly important for the smart functions of SMPs. Such nanoarchitectonic approaches have enabled us to further create shape-memory surfaces (SMSs) with tunable surface topography at nano scale. The present review aims to bring together the exciting design of SMSs and the ever-expanding range of their uses as tools to control cell functions. The goal for these endeavors is to mimic the surrounding mechanical cues of extracellular environments which have been considered as critical parameters in cell fate determination. The untapped potential of SMSs makes them one of the most exciting interfaces of materials science and cell mechanobiology. PMID:27877747

Fate of Eight Different Polymers under Uncontrolled Composting Conditions: Relationships Between Deterioration, Biofilm Formation, and the Material Surface Properties.

PubMed

Mercier, Anne; Gravouil, Kevin; Aucher, Willy; Brosset-Vincent, Sandra; Kadri, Linette; Colas, Jenny; Bouchon, Didier; Ferreira, Thierry

2017-02-21

With the ever-increasing volume of polymer wastes and their associated detrimental impacts on the environment, the plastic life cycle has drawn increasing attention. Here, eight commercial polymers selected from biodegradable to environmentally persistent materials, all formulated under a credit card format, were incubated in an outdoor compost to evaluate their fate over time and to profile the microbial communities colonizing their surfaces. After 450 days in compost, the samples were all colonized by multispecies biofilms, these latest displaying different amounts of adhered microbial biomass and significantly distinct bacterial and fungal community compositions depending on the substrate. Interestingly, colonization experiments on the eight polymers revealed a large core of shared microbial taxa, predominantly composed of microorganisms previously reported from environments contaminated with petroleum hydrocarbons or plastics debris. These observations suggest that biofilms may contribute to the alteration process of all the polymers studied. Actually, four substrates, independently of their assignment to a polymer group, displayed a significant deterioration, which might be attributed to biologically mediated mechanisms. Relevantly, the deterioration appears strongly associated with the formation of a high-cell density biofilm onto the polymer surfaces. The analysis of various surface properties revealed that roughness and hydrophilicity are likely prominent parameters for driving the biological interactions with the polymers.

Facile surface modification of glass with zwitterionic polymers for improving the blood compatibility

NASA Astrophysics Data System (ADS)

Zhang, Lingling; Chen, Xiaojuan; Liu, Pingsheng; Wang, Jing; Zhu, Haomiao; Li, Li

2018-06-01

A facile procedure to modify glass film with zwitterionic polymers for improving the blood compatibility was introduced. The glass slides were first silanized with 3-methacryloxypropyltrimethoxysilane (MPT) to generate methacrylate groups on the surface. Then, N, N’-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA), a sulfobetaine zwitterionic monomer, was polymerized on the silanized glass substrates by free-radical polymerization in order to graft the zwitterionic polymers onto the substrates. X-ray Photoelectron Spectroscopy (XPS), water contact angle, scanning electron microscope (SEM) and atomic force microscopy (AFM) were utilized to analyze the surface properties of the grafted glass. The blood compatibility of the grafted glass was verified by whole blood contacting and platelet adhesion experiments in vitro. The results showed that the zwitterionic polymers were successfully grafted on the glass surface, and consequently significantly inhibited the platelet adhesion and whole blood cell attachment.

A carbon nanotube-polymer composite for T-cell therapy

NASA Astrophysics Data System (ADS)

Fadel, Tarek R.; Sharp, Fiona A.; Vudattu, Nalini; Ragheb, Ragy; Garyu, Justin; Kim, Dongin; Hong, Enping; Li, Nan; Haller, Gary L.; Pfefferle, Lisa D.; Justesen, Sune; Harold, Kevin C.; Fahmy, Tarek M.

2014-08-01

Clinical translation of cell therapies requires strategies that can manufacture cells efficiently and economically. One promising way to reproducibly expand T cells for cancer therapy is by attaching the stimuli for T cells onto artificial substrates with high surface area. Here, we show that a carbon nanotube-polymer composite can act as an artificial antigen-presenting cell to efficiently expand the number of T cells isolated from mice. We attach antigens onto bundled carbon nanotubes and combined this complex with polymer nanoparticles containing magnetite and the T-cell growth factor interleukin-2 (IL-2). The number of T cells obtained was comparable to clinical standards using a thousand-fold less soluble IL-2. T cells obtained from this expansion were able to delay tumour growth in a murine model for melanoma. Our results show that this composite is a useful platform for generating large numbers of cytotoxic T cells for cancer immunotherapy.

Influence of Surface Energy on Organic Alloy Formation in Ternary Blend Solar Cells Based on Two Donor Polymers.

PubMed

Gobalasingham, Nemal S; Noh, Sangtaik; Howard, Jenna B; Thompson, Barry C

2016-10-05

The compositional dependence of the open-circuit voltage (V oc ) in ternary blend bulk heterojunction (BHJ) solar cells is correlated with the miscibility of polymers, which may be influenced by a number of attributes, including crystallinity, the random copolymer effect, or surface energy. Four ternary blend systems featuring poly(3-hexylthiophene-co-3-(2-ethylhexyl)thiophene) (P3HT 75 -co-EHT 25 ), poly(3-hexylthiophene-co-(hexyl-3-carboxylate)), herein referred to as poly(3-hexylthiophene-co-3-hexylesterthiophene) (P3HT 50 -co-3HET 50 ), poly(3-hexylthiophene-thiophene-diketopyrrolopyrrole) (P3HTT-DPP-10%), and an analog of P3HTT-DPP-10% with 40% of 3-hexylthiophene exchanged for 2-(2-methoxyethoxy)ethylthiophen-2-yl (3MEO-T) (featuring an electronically decoupled oligoether side-chain), referred to as P3HTTDPP-MEO40%, are explored in this work. All four polymers are semicrystalline and rich in rr-P3HT content and perform well in binary devices with PC 61 BM. Except for P3HTTDPP-MEO40%, all polymers exhibit similar surface energies (∼21-22 mN/m). P3HTTDPP-MEO40% exhibits an elevated surface energy of around 26 mN/m. As a result, despite the similar optoelectronic properties and binary solar cell performance of P3HTTDPP-MEO40% compared to P3HTT-DPP-10%, the former exhibits a pinned V oc in two different sets of ternary blend devices. This is a stark contrast to previous rr-P3HT-based systems and demonstrates that surface energy, and its influence on miscibility, plays a critical role in the formation of organic alloys and can supersede the influence of crystallinity, the random copolymer effect, similar backbone structures, and HOMO/LUMO considerations. Therefore, we confirm surface energy compatibility as a figure-of-merit for predicting the compositional dependence of the V oc in ternary blend solar cells and highlight the importance of polymer miscibility in organic alloy formation.

Preparation and biocompatibility of crosslinked poly(3-hydroxyundecenoate).

PubMed

Chung, Chungwook; Chung, Kyudon; Kim, Do Young; Lee, Sun Hee; Kim, Jong-Sik; Rhee, Young Ha

2018-02-01

A sticky polymer, poly(3-hydroxyundecenoate) (PHU), was produced by Pseudomonas oleovorans when nonanoate and undecenoate were used as carbon sources. Crosslinked PHU (CL-PHU) was prepared by heating using benzoyl peroxide as a crosslinker. According to the degree of crosslinking in the polymer, three types of CL-PHU were prepared: CL-PHU50, CL-PHU60 and CL-PHU70. Fourier transform-infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry results suggested that crosslinking of PHU was successfully achieved by heat, which increased the crosslinking density and decreased stiffness and flexibility of the polymer. Water contact angle measurements revealed no differences of hydrophilicity as the crosslinking density. Slight morphological changes of CL-PHU film surfaces were observed by atomic force microscopy. Chinese hamster ovary cells were used to investigate the biocompatibility of CL-PHU films using poly(l-lactide) surfaces as control. Surface properties of the film, such as roughness and adhesive force, enhanced the adhesion and proliferation of cells on the films. CL-PHU might be useful for cell compatible biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Multifunctional poly(methacrylate) polyplex libraries: A platform for gene delivery inspired by nature.

PubMed

Favretto, M E; Krieg, A; Schubert, S; Schubert, U S; Brock, R

2015-07-10

Polymer-based gene delivery systems have enormous potential in biomedicine, but their efficiency is often limited by poor biocompatibility. Poly(methacrylate)s (PMAs) are an interesting class of polymers which allow to explore structure-activity relationships of polymer functionalities for polyplex formation in oligonucleotide delivery. Here, we synthesized and tested a library of PMA polymers, containing functional groups contributing to the different steps of gene delivery, from oligonucleotide complexation to cellular internalization and endosomal escape. By variation of the molar ratios of the individual building blocks, the physicochemical properties of the polymers and polyplexes were fine-tuned to reduce toxicity as well as to increase activity of the polyplexes. To further enhance transfection efficiency, a cell-penetrating peptide (CPP)-like functionality was introduced on the polymeric backbone. With the ability to synthesize large libraries of polymers in parallel we also developed a workflow for a mid-to-high throughput screening, focusing first on safety parameters that are accessible by high-throughput approaches such as blood compatibility and toxicity towards host cells and only at a later stage on more laborious tests for the ability to deliver oligonucleotides. To arrive at a better understanding of the molecular basis of activity, furthermore, the effect of the presence of heparan sulfates on the surface of host cells was assessed and the mechanism of cell entry and intracellular trafficking investigated for those polymers that showed a suitable pharmacological profile. Following endocytic uptake, rapid endosomal release occurred. Interestingly, the presence of heparan sulfates on the cell surface had a negative impact on the activity of those polyplexes that were sensitive to decomplexation by heparin in solution. In summary, the screening approach identified two polymers, which form polyplexes with high stability and transfection capacity exceeding the one of poly(ethylene imine) also in the presence of serum. Copyright © 2015 Elsevier B.V. All rights reserved.

Surface chemistry of photoluminescent F8BT conjugated polymer nanoparticles determines protein corona formation and internalization by phagocytic cells.

PubMed

Ahmad Khanbeigi, Raha; Abelha, Thais Fedatto; Woods, Arcadia; Rastoin, Olivia; Harvey, Richard D; Jones, Marie-Christine; Forbes, Ben; Green, Mark A; Collins, Helen; Dailey, Lea Ann

2015-03-09

Conjugated polymer nanoparticles are being developed for a variety of diagnostic and theranostic applications. The conjugated polymer, F8BT, a polyfluorene derivative, was used as a model system to examine the biological behavior of conjugated polymer nanoparticle formulations stabilized with ionic (sodium dodecyl sulfate; F8BT-SDS; ∼207 nm; -31 mV) and nonionic (pegylated 12-hydroxystearate; F8BT-PEG; ∼175 nm; -5 mV) surfactants, and compared with polystyrene nanoparticles of a similar size (PS200; ∼217 nm; -40 mV). F8BT nanoparticles were as hydrophobic as PS200 (hydrophobic interaction chromatography index value: 0.96) and showed evidence of protein corona formation after incubation with serum-containing medium; however, unlike polystyrene, F8BT nanoparticles did not enrich specific proteins onto the nanoparticle surface. J774A.1 macrophage cells internalized approximately ∼20% and ∼60% of the F8BT-SDS and PS200 delivered dose (calculated by the ISDD model) in serum-supplemented and serum-free conditions, respectively, while cell association of F8BT-PEG was minimal (<5% of the delivered dose). F8BT-PEG, however, was more cytotoxic (IC50 4.5 μg cm(-2)) than F8BT-SDS or PS200. The study results highlight that F8BT surface chemistry influences the composition of the protein corona, while the properties of the conjugated polymer nanoparticle surfactant stabilizer used determine particle internalization and biocompatibility profile.

The Effect of Covalently-Attached ATRP-Synthesized Polymers on Membrane Stability and Cytoprotection in Human Erythrocytes

PubMed Central

Clafshenkel, William P.; Murata, Hironobu; Andersen, Jill; Creeger, Yehuda; Russell, Alan J.

2016-01-01

Erythrocytes have been described as advantageous drug delivery vehicles. In order to ensure an adequate circulation half-life, erythrocytes may benefit from protective enhancements that maintain membrane integrity and neutralize oxidative damage of membrane proteins that otherwise facilitate their premature clearance from circulation. Surface modification of erythrocytes using rationally designed polymers, synthesized via atom-transfer radical polymerization (ATRP), may further expand the field of membrane-engineered red blood cells. This study describes the fate of ATRP-synthesized polymers that were covalently attached to human erythrocytes as well as the effect of membrane engineering on cell stability under physiological and oxidative conditions in vitro. The biocompatible, membrane-reactive polymers were homogenously retained on the periphery of modified erythrocytes for at least 24 hours. Membrane engineering stabilized the erythrocyte membrane and effectively neutralized oxidative species, even in the absence of free-radical scavenger-containing polymers. The targeted functionalization of Band 3 protein by NHS-pDMAA-Cy3 polymers stabilized its monomeric form preventing aggregation in the presence of the crosslinking reagent, bis(sulfosuccinimidyl)suberate (BS3). A free radical scavenging polymer, NHS-pDMAA-TEMPO˙, provided additional protection of surface modified erythrocytes in an in vitro model of oxidative stress. Preserving or augmenting cytoprotective mechanisms that extend circulation half-life is an important consideration for the use of red blood cells for drug delivery in various pathologies, as they are likely to encounter areas of imbalanced oxidative stress as they circuit the vascular system. PMID:27331401

The Effect of Covalently-Attached ATRP-Synthesized Polymers on Membrane Stability and Cytoprotection in Human Erythrocytes.

PubMed

Clafshenkel, William P; Murata, Hironobu; Andersen, Jill; Creeger, Yehuda; Koepsel, Richard R; Russell, Alan J

2016-01-01

Erythrocytes have been described as advantageous drug delivery vehicles. In order to ensure an adequate circulation half-life, erythrocytes may benefit from protective enhancements that maintain membrane integrity and neutralize oxidative damage of membrane proteins that otherwise facilitate their premature clearance from circulation. Surface modification of erythrocytes using rationally designed polymers, synthesized via atom-transfer radical polymerization (ATRP), may further expand the field of membrane-engineered red blood cells. This study describes the fate of ATRP-synthesized polymers that were covalently attached to human erythrocytes as well as the effect of membrane engineering on cell stability under physiological and oxidative conditions in vitro. The biocompatible, membrane-reactive polymers were homogenously retained on the periphery of modified erythrocytes for at least 24 hours. Membrane engineering stabilized the erythrocyte membrane and effectively neutralized oxidative species, even in the absence of free-radical scavenger-containing polymers. The targeted functionalization of Band 3 protein by NHS-pDMAA-Cy3 polymers stabilized its monomeric form preventing aggregation in the presence of the crosslinking reagent, bis(sulfosuccinimidyl)suberate (BS3). A free radical scavenging polymer, NHS-pDMAA-TEMPO˙, provided additional protection of surface modified erythrocytes in an in vitro model of oxidative stress. Preserving or augmenting cytoprotective mechanisms that extend circulation half-life is an important consideration for the use of red blood cells for drug delivery in various pathologies, as they are likely to encounter areas of imbalanced oxidative stress as they circuit the vascular system.

Monitoring the degrafting of polyelectrolyte brushes by using surface gradients

NASA Astrophysics Data System (ADS)

Ko, Yeongun; Genzer, Jan

Polymer brushes comprise densely grafted polymer chains on surfaces, which possess high stability and high concentration of reactive centers per unit area compared to physisorbed polymer film. Polymer brushes are employed in many applications, including anti-fouling surfaces, cell adhesive surfaces, responsive surfaces, low-friction surfaces, etc. Recently, researchers reported that charged (or chargeable) polymer brushes can be degrafted from substrate while incubated in buffer solutions. Based on previous experiments conducted in our group and by others, we assume that chain degrafting results from the hydrolysis of Si-O groups in head-group of the initiator and/or the ester groups in main body of the initiator. The kinetic of hydrolysis is affected by mechanical forces acting on the initiator. Those forces depend on the molecular weight and the grafting density of the brush, and the concentration and distribution of charges along the macromolecule (tuned by pH - for weak electrolytes - and concentration of external salt). In this work, we study the stability of poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) brushes in two solvents (ethanol and water) at various pH values in water and under different levels of external salt concentration. National Science Foundation.

Electrical characterization of fluorinated benzothiadiazole based conjugated copolymer - a promising material for high-performance solar cells

NASA Astrophysics Data System (ADS)

Toušek, J.; Toušková, J.; Remeš, Z.; Chomutová, R.; Čermák, J.; Helgesen, M.; Carlé, J. E.; Krebs, F. C.

2015-12-01

Measurements of electrical conductivity, electron work function, carrier mobility of holes and the diffusion length of excitons were performed on samples of conjugated polymers relevant to polymer solar cells. A state of the art fluorinated benzothiadiazole based conjugated copolymer (PBDTTHD - DTBTff) was studied and benchmarked against the reference polymer poly-3-hexylthiophene (P3HT). We employed, respectively, four electrode conductivity measurements, Kelvin probe work function measurements, carrier mobility using charge extraction by linearly increasing voltage (CELIV) measurements and diffusion length determinaton using surface photovoltage measurements.

Emulsion-Based RIR-MAPLE Deposition of Conjugated Polymers: Primary Solvent Effect and Its Implications on Organic Solar Cell Performance.

PubMed

Ge, Wangyao; Li, Nan K; McCormick, Ryan D; Lichtenberg, Eli; Yingling, Yaroslava G; Stiff-Roberts, Adrienne D

2016-08-03

Emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) has been demonstrated as an alternative technique to deposit conjugated polymer films for photovoltaic applications; yet, a fundamental understanding of how the emulsion target characteristics translate into film properties and solar cell performance is unclear. Such understanding is crucial to enable the rational improvement of organic solar cell (OSC) efficiency and to realize the expected advantages of emulsion-based RIR-MAPLE for OSC fabrication. In this paper, the effect of the primary solvent used in the emulsion target is studied, both experimentally and theoretically, and it is found to determine the conjugated polymer cluster size in the emulsion as well as surface roughness and internal morphology of resulting polymer films. By using a primary solvent with low solubility-in-water and low vapor pressure, the surface roughness of deposited P3HT and PCPDTBT polymer films was reduced to 10 nm, and the efficiency of P3HT:PC61BM OSCs was increased to 3.2% (∼100 times higher compared to the first MAPLE OSC demonstration [ Caricato , A. P. ; Appl. Phys. Lett. 2012 , 100 , 073306 ]). This work unveils the mechanism of polymer film formation using emulsion-based RIR-MAPLE and provides insight and direction to determine the best ways to take advantage of the emulsion target approach to control film properties for different applications.

Synthesis and characterization of antifouling poly(N-acryloylaminoethoxyethanol) with ultralow protein adsorption and cell attachment.

PubMed

Chen, Hong; Zhang, Mingzhen; Yang, Jintao; Zhao, Chao; Hu, Rundong; Chen, Qiang; Chang, Yung; Zheng, Jie

2014-09-02

Rational design of effective antifouling polymers is challenging but important for many fundamental and applied applications. Herein we synthesize and characterize an N-acryloylaminoethoxyethanol (AAEE) monomer, which integrates three hydrophilic groups of hydroxyl, amide, and ethylene glycol in the same material. AAEE monomers were further grafted and polymerized on gold substrates to form polyAAEE brushes with well-controlled thickness via surface-initiated atomic transfer radical polymerization (SI-ATRP), with particular attention to a better understanding of the molecular structure-antifouling property relationship of hydroxyl-acrylic-based polymers. The surface hydrophilicity and antifouling properties of polyAAEE brushes as a function of film thickness are studied by combined experimental and computational methods including surface plasmon resonance (SPR) sensors, atomic force microscopy (AFM), cell adhesion assay, and molecular dynamics (MD) simulations. With the optimal polymer film thicknesses (∼10-40 nm), polyAAEE-grafted surfaces can effectively resist protein adsorption from single-protein solutions and undiluted human blood plasma and serum to a nonfouling level (i.e., <0.3 ng/cm(2)). The polyAAEE brushes also highly resist mammalian cell attachment up to 3 days. MD simulations confirm that the integration of three hydrophilic groups induce a stronger and closer hydration layer around polyAAEE, revealing a positive relationship between surface hydration and antifouling properties. The molecular structure-antifouling properties relationship of a series of hydroxyl-acrylic-based polymers is also discussed. This work hopefully provides a promising structural motif for the design of new effective antifouling materials beyond traditional ethylene glycol-based antifouling materials.

High-Affinity Interaction between the S-Layer Protein SbsC and the Secondary Cell Wall Polymer of Geobacillus stearothermophilus ATCC 12980 Determined by Surface Plasmon Resonance Technology▿ †

PubMed Central

Ferner-Ortner, Judith; Mader, Christoph; Ilk, Nicola; Sleytr, Uwe B.; Egelseer, Eva M.

2007-01-01

Surface plasmon resonance studies using C-terminal truncation forms of the S-layer protein SbsC (recombinant SbsC consisting of amino acids 31 to 270 [rSbsC31-270] and rSbsC31-443) and the secondary cell wall polymer (SCWP) isolated from Geobacillus stearothermophilus ATCC 12980 confirmed the exclusive responsibility of the N-terminal region comprising amino acids 31 to 270 for SCWP binding. Quantitative analyses indicated binding behavior demonstrating low, medium, and high affinities. PMID:17644609

Polymeric stent materials dysregulate macrophage and endothelial cell functions: implications for coronary artery stent

PubMed Central

Wang, Xintong; Zachman, Angela L.; Chun, Young Wook; Shen, Fang-Wen; Hwang, Yu-Shik; Sung, Hak-Joon

2014-01-01

Background Biodegradable polymers have been applied as bulk or coating materials for coronary artery stents. The degradation of polymers, however, could induce endothelial dysfunction and aggravate neointimal formation. Here we use polymeric microparticles to simulate and demonstrate the effects of degraded stent materials on phagocytic activity, cell death and dysfunction of macrophages and endothelial cells. Methods Microparticles made of low molecular weight polyesters were incubated with human macrophages and coronary artery endothelial cells (ECs). Microparticle-induced phagocytosis, cytotoxicity, apoptosis, cytokine release and surface marker expression were determined by immunostaining or ELISA. Elastase expression was analyzed by ELISA and the elastase-mediated polymer degradation was assessed by mass spectrometry. Results We demonstrated poly(D,L-lactic acid) (PLLA) and polycaprolactone (PCL) microparticles induced cytotoxicity in macrophages and ECs, partially through cell apoptosis. The particle treatment alleviated EC phagocytosis, as opposed to macrophages, but enhanced the expression of vascular cell adhesion molecule-1 (VCAM) along with decreased nitric oxide production, indicating ECs were activated and lost their capacity to maintain homeostasis. The activation of both cell types induced release of elastase or elastase-like protease, which further accelerated polymer degradation. Conclusions This study revealed that low molecule weight PLLA and PCL microparticles increased cytotoxicity and dysregulated endothelial cell function, which in turn enhanced elastase release and polymer degradation. These indicate polymer or polymer-coated stents impose a risk of endothelial dysfunction after deployment which can potentially lead to delayed endothelialization, neointimal hyperplasia and late thrombosis. PMID:24820736

Towards Biomimicking Wood: Fabricated Free-standing Films of Nanocellulose, Lignin, and a Synthetic Polycation

PubMed Central

Pillai, Karthik; Navarro Arzate, Fernando; Zhang, Wei; Renneckar, Scott

2014-01-01

Woody materials are comprised of plant cell walls that contain a layered secondary cell wall composed of structural polymers of polysaccharides and lignin. Layer-by-layer (LbL) assembly process which relies on the assembly of oppositely charged molecules from aqueous solutions was used to build a freestanding composite film of isolated wood polymers of lignin and oxidized nanofibril cellulose (NFC). To facilitate the assembly of these negatively charged polymers, a positively charged polyelectrolyte, poly(diallyldimethylammomium chloride) (PDDA), was used as a linking layer to create this simplified model cell wall. The layered adsorption process was studied quantitatively using quartz crystal microbalance with dissipation monitoring (QCM-D) and ellipsometry. The results showed that layer mass/thickness per adsorbed layer increased as a function of total number of layers. The surface coverage of the adsorbed layers was studied with atomic force microscopy (AFM). Complete coverage of the surface with lignin in all the deposition cycles was found for the system, however, surface coverage by NFC increased with the number of layers. The adsorption process was carried out for 250 cycles (500 bilayers) on a cellulose acetate (CA) substrate. Transparent free-standing LBL assembled nanocomposite films were obtained when the CA substrate was later dissolved in acetone. Scanning electron microscopy (SEM) of the fractured cross-sections showed a lamellar structure, and the thickness per adsorption cycle (PDDA-Lignin-PDDA-NC) was estimated to be 17 nm for two different lignin types used in the study. The data indicates a film with highly controlled architecture where nanocellulose and lignin are spatially deposited on the nanoscale (a polymer-polymer nanocomposites), similar to what is observed in the native cell wall. PMID:24961302

Biodegradable Polymers Influence the Effect of Atorvastatin on Human Coronary Artery Cells

PubMed Central

Strohbach, Anne; Begunk, Robert; Petersen, Svea; Felix, Stephan B.; Sternberg, Katrin; Busch, Raila

2016-01-01

Drug-eluting stents (DES) have reduced in-stent-restenosis drastically. Yet, the stent surface material directly interacts with cascades of biological processes leading to an activation of cellular defense mechanisms. To prevent adverse clinical implications, to date almost every patient with a coronary artery disease is treated with statins. Besides their clinical benefit, statins exert a number of pleiotropic effects on endothelial cells (ECs). Since maintenance of EC function and reduction of uncontrolled smooth muscle cell (SMC) proliferation represents a challenge for new generation DES, we investigated the effect of atorvastatin (ATOR) on human coronary artery cells grown on biodegradable polymers. Our results show a cell type-dependent effect of ATOR on ECs and SMCs. We observed polymer-dependent changes in IC50 values and an altered ATOR-uptake leading to an attenuation of statin-mediated effects on SMC growth. We conclude that the selected biodegradable polymers negatively influence the anti-proliferative effect of ATOR on SMCs. Hence, the process of developing new polymers for DES coating should involve the characterization of material-related changes in mechanisms of drug actions. PMID:26805825

High-Efficiency Polymer Solar Cells by Using Co-solvents 1-Chloronaphthalene and 1,8-Octanedithiol as Processing Additives

NASA Astrophysics Data System (ADS)

Gao, Bowen; Meng, Jing

2018-07-01

The copolymer poly-BDT-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (PC20BDTDPP) with the bulkier alkoxy on BDT and alkyl on DPP is widely used in organic photovoltaic cells as a potential donor material. Power conversion efficiency (PCE) of polymer solar cells fabricated withPC20BDTDPP as the electron donor blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the electron acceptor was improved from 4.90% to 9.10% by adding 1-5% of the co-solvents (1-chloronaphthalene and 1,8-octanedithiol) as processing additives. The enhanced PCE was attributed to optimized surface morphology and packed polymer chains leading to better phase separation morphology by the solvent additive. Furthermore, owing to its very narrow band gap, the synthesized polymer demonstrates a great potential for tandem or parallel-like solar cells.

High-Efficiency Polymer Solar Cells by Using Co-solvents 1-Chloronaphthalene and 1,8-Octanedithiol as Processing Additives

NASA Astrophysics Data System (ADS)

Gao, Bowen; Meng, Jing

2018-04-01

The copolymer poly-BDT-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (PC20BDTDPP) with the bulkier alkoxy on BDT and alkyl on DPP is widely used in organic photovoltaic cells as a potential donor material. Power conversion efficiency (PCE) of polymer solar cells fabricated withPC20BDTDPP as the electron donor blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the electron acceptor was improved from 4.90% to 9.10% by adding 1-5% of the co-solvents (1-chloronaphthalene and 1,8-octanedithiol) as processing additives. The enhanced PCE was attributed to optimized surface morphology and packed polymer chains leading to better phase separation morphology by the solvent additive. Furthermore, owing to its very narrow band gap, the synthesized polymer demonstrates a great potential for tandem or parallel-like solar cells.

Non-Fouling Biodegradable Poly(ϵ-caprolactone) Nanofibers for Tissue Engineering.

PubMed

Kostina, Nina Yu; Pop-Georgievski, Ognen; Bachmann, Michael; Neykova, Neda; Bruns, Michael; Michálek, Jiří; Bastmeyer, Martin; Rodriguez-Emmenegger, Cesar

2016-01-01

Poly(ϵ-caprolactone) (PCL) nanofibers are very attractive materials for tissue engineering (TE) due to their degradability and structural similarity to the extracellular matrix (ECM). However, upon exposure to biological media, their surface is rapidly fouled by proteins and cells, which may lead to inflammation and foreign body reaction. In this study, an approach for the modification of PCL nanofibers to prevent protein fouling from biological fluids and subsequent cell adhesion is introduced. A biomimetic polydopamine (PDA) layer was deposited on the surface of the PCL nanofibers and four types of antifouling polymer brushes were grown by surface-initiated atom transfer radical polymerization (SI-ATRP) from initiator moieties covalently attached to the PDA layer. Cell adhesion was assessed with mouse embryonic fibroblasts (MEFs). MEFs rapidly adhered and formed cell-matrix adhesions (CMAs) with PCL and PCL-PDA nanofibers. Importantly, the nanofibers modified with antifouling polymer brushes were able to suppress non-specific protein adsorption and thereby cell adhesion. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pyro-electrification of polymer membranes for cell patterning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rega, R.; Gennari, O.; Mecozzia, L.

2016-05-18

In the recent years, much attention has been devoted to the possibility of charging polymer-based materials, due to their potential in developing large-scale and inexpensive flexible thin-film technology. The availability of localized electrostatic fields is in of great interest for a huge amount of applications such as distribution of biomolecules and cells from the liquid phase. Here we report a voltage-free pyro-electrification (PE) process able to induce permanent dipoles into polymer layers; the lithium niobate (LN) crystal is the key component that plays the multi-purpose role of sustaining, heating and poling the polymer layer that is then peeled-off easily inmore » order to have a free-standing charged membrane. The results show the fascinating application for the living cell patterning. It well known that cell behaviour is affected by chemical and topographical cues of substrate. In fact, polymers, such as polystyrene (PS) and poly(methyl methacrylate) (PMMA), are naturally cytophobic and require specific functionalization treatments in order to promote cell adhesion. Through our proposal technique, it’s possible to obtain spontaneous organization and a driven growth of SH-SY5Y cells that is solely dictated by the nature of the charge polymer surface, opening, in this way, the innovative chance to manipulate and transfer biological samples on a free-standing polymer layer [1].« less

Poly(4-Vinylpyridine)-Based Interfacial Passivation to Enhance Voltage and Moisture Stability of Lead Halide Perovskite Solar Cells.

PubMed

Chaudhary, Bhumika; Kulkarni, Ashish; Jena, Ajay Kumar; Ikegami, Masashi; Udagawa, Yosuke; Kunugita, Hideyuki; Ema, Kazuhiro; Miyasaka, Tsutomu

2017-06-09

It is well known that the surface trap states and electronic disorders in the solution-processed CH 3 NH 3 PbI 3 perovskite film affect the solar cell performance significantly and moisture sensitivity of photoactive perovskite material limits its practical applications. Herein, we show the surface modification of a perovskite film with a solution-processable hydrophobic polymer (poly(4-vinylpyridine), PVP), which passivates the undercoordinated lead (Pb) atoms (on the surface of perovskite) by its pyridine Lewis base side chains and thereby eliminates surface-trap states and non-radiative recombination. Moreover, it acts as an electron barrier between the perovskite and hole-transport layer (HTL) to reduce interfacial charge recombination, which led to improvement in open-circuit voltage (V oc ) by 120 to 160 mV whereas the standard cell fabricated in same conditions showed V oc as low as 0.9 V owing to dominating interfacial recombination processes. Consequently, the power conversion efficiency (PCE) increased by 3 to 5 % in the polymer-modified devices (PCE=15 %) with V oc more than 1.05 V and hysteresis-less J-V curves. Advantageously, hydrophobicity of the polymer chain was found to protect the perovskite surface from moisture and improved stability of the non-encapsulated cells, which retained their device performance up to 30 days of exposure to open atmosphere (50 % humidity). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Characteristics of tenocyte adhesion to biologically-modified surface of polymer].

PubMed

Qin, Tingwu; Yang, Zhiming; Xie, Huiqi; Li, Hong; Qin, Jian; Wu, Zezhi; Xu, Shirong; Cai, Shaoxi

2002-12-01

In this study we examined the in vitro characteristics of tenocyte adhesion to biologically-modified surface of polymer. Polylactic-co-glycolic acid (PLGA) 85/15 films were prepared by a solvent-casting technique. Each film was adhered onto the bottom of a chamber. The film was precoated with poly-D-lysine (PDL), and then coated with serum-free F12 medium containing various concentrations of fibronectin (FN), type I collagen (CN I), and insulin-like growth factor1 (IGF-1). The monoclonal antibodies (to FN and to CN I) with various dilutions were used to inhibit attachment of tenocytes to surface precoated with FN or CN I. Human embryonic tendon cells (HETCs) and transformed human embryonic tendon cells (THETCs) were used as the seeding cells. The system used for the measurement of adhesion force was the micropipette aspiration experiment system. The micropipette was manipulated to aspirate a small portion of the tenocyte body by using a small aspiration pressure. Then the pipette was pulled away from the adhesion area by micromanipulation. The minimum force required to detach the tenocyte from the substrate was defined as the adhesion force. The results showed that modification of FN or CN I by precoating significantly enhanced attachment of tenocytes to surface of polymer (P < 0.05). As antibodies to FN or CN I were added to a polymer film precoated with FN or CN I, the adhesion force decreased significantly (P < 0.05). We concluded that the specific adhesion forces of tenocytes to extracellular matrix adhesion proteins (FN and CN I) had coordinated action and showed good dependence on their precoating concentrations, and were inhibited by the antibodies to these adhesion proteins. Films precoated with IGF-1 strongly accelerated the adhesion of tenocytes to polymer. These results indicate that the specific adhesion of tenocytes to polymer can be promoted by coating extracellular matrix adhesive proteins and insulin-like growth factor1. It is of great importance to construct tissue-engineered tendon.

Substrate micropatterns produced by polymer demixing regulate focal adhesions, actin anisotropy, and lineage differentiation of stem cells.

PubMed

Vega, Sebastián L; Arvind, Varun; Mishra, Prakhar; Kohn, Joachim; Sanjeeva Murthy, N; Moghe, Prabhas V

2018-06-12

Stem cells are adherent cells whose multipotency and differentiation can be regulated by numerous microenvironmental signals including soluble growth factors and surface topography. This study describes a simple method for creating distinct micropatterns via microphase separation resulting from polymer demixing of poly(desaminotyrosyl-tyrosine carbonate) (PDTEC) and polystyrene (PS). Substrates with co-continuous (ribbons) or discontinuous (islands and pits) PDTEC regions were obtained by varying the ratio of PDTEC and sacrificial PS. Human mesenchymal stem cells (MSCs) cultured on co-continuous PDTEC substrates for 3 days in bipotential adipogenic/osteogenic (AD/OS) induction medium showed no change in cell morphology but exhibited increased anisotropic cytoskeletal organization and larger focal adhesions when compared to MSCs cultured on discontinuous micropatterns. After 14 days in bipotential AD/OS induction medium, MSCs cultured on co-continuous micropatterns exhibited increased expression of osteogenic markers, whereas MSCs on discontinuous PDTEC substrates showed a low expression of adipogenic and osteogenic differentiation markers. Substrates with graded micropatterns were able to reproduce the influence of local underlying topography on MSC differentiation, thus demonstrating their potential for high throughput analysis. This work presents polymer demixing as a simple, non-lithographic technique to produce a wide range of micropatterns on surfaces with complex geometries to influence cellular and tissue regenerative responses. Gaining a better understanding of how engineered microenvironments influence stem cell differentiation is integral to increasing the use of stem cells and materials in a wide range of tissue engineering applications. In this study, we show the range of topography obtained by polymer demixing is sufficient for investigating how surface topography affects stem cell morphology and differentiation. Our findings show that co-continuous topographies favor early (3-day) cytoskeletal anisotropy and focal adhesion maturation as well as long-term (14-day) expression of osteogenic differentiation markers. Taken together, this study presents a simple approach to pattern topographies that induce divergent responses in stem cell morphology and differentiation. Copyright © 2018. Published by Elsevier Ltd.

Polymer-based protein engineering grown ferrocene-containing redox polymers improve current generation in an enzymatic biofuel cell.

PubMed

Campbell, Alan S; Murata, Hironobu; Carmali, Sheiliza; Matyjaszewski, Krzysztof; Islam, Mohammad F; Russell, Alan J

2016-12-15

Enzymatic biofuel cells (EBFCs) are capable of generating electricity from physiologically present fuels making them promising power sources for the future of implantable devices. The potential application of such systems is limited, however, by inefficient current generation. Polymer-based protein engineering (PBPE) offers a unique method to tailor enzyme function through tunable modification of the enzyme surface with functional polymers. In this study, we report on the modification of glucose oxidase (GOX) with ferrocene-containing redox polymers to increase current generation efficiency in an enzyme-modified anode. Poly(N-(3-dimethyl(ferrocenyl)methylammonium bromide)propyl acrylamide) (pFcAc) was grown from covalently attached, water-soluble initiator molecules on the surface of GOX in a "grafting-from" approach using atom transfer radical polymerization (ATRP). The covalently-coupled ferrocene-containing polymers on the enzyme surface promoted the effective "wiring" of the GOX active site to an external electrode. The resulting GOX-pFcAc conjugates generated over an order of magnitude increase in current generation efficiency and a 4-fold increase in maximum EBFC power density (≈1.7µWcm(-2)) with similar open circuit voltage (0.27V) compared to native GOX when physically adsorbed onto paddle-shaped electrodes made up of electrospun polyacrylonitrile fibers coated with gold nanoparticles and multi-wall carbon nanotubes. The formation of electroactive enzyme-redox polymer conjugates using PBPE represents a powerful new tool for the improvement of mediated enzyme-based bioelectronics without the need for free redox mediators or anode/cathode compartmentalization. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Simulation of Biomimetic Recognition between Polymers and Surfaces

NASA Astrophysics Data System (ADS)

Golumbfskie, Aaron J.; Pande, Vijay S.; Chakraborty, Arup K.

1999-10-01

Many biological processes, such as transmembrane signaling and pathogen-host interactions, are initiated by a protein recognizing a specific pattern of binding sites on part of a membrane or cell surface. By recognition, we imply that the polymer quickly finds and then adsorbs strongly on the pattern-matched region and not on others. The development of synthetic systems that can mimic such recognition between polymers and surfaces could have significant impact on advanced applications such as the development of sensors, molecular-scale separation processes, and synthetic viral inhibition agents. Attempting to affect recognition in synthetic systems by copying the detailed chemistries to which nature has been led over millenia of evolution does not seem practical for most applications. This leads us to the following question: Are there any universal strategies that can affect recognition between polymers and surfaces? Such generic strategies may be easier to implement in abiotic applications. We describe results that suggest that biomimetic recognition between synthetic polymers and surfaces is possible by exploiting certain generic strategies, and we elucidate the kinetic mechanisms by which this occurs. Our results suggest convenient model systems for experimental studies of dynamics in free energy landscapes characteristic of frustrated systems.

Micellar Polymer Encapsulation of Enzymes.

PubMed

Besic, Sabina; Minteer, Shelley D

2017-01-01

Although enzymes are highly efficient and selective catalysts, there have been problems incorporating them into fuel cells. Early enzyme-based fuel cells contained enzymes in solution rather than immobilized on the electrode surface. One problem utilizing an enzyme in solution is an issue of transport associated with long diffusion lengths between the site of bioelectrocatalysis and the electrode. This issue drastically decreases the theoretical overall power output due to the poor electron conductivity. On the other hand, enzymes immobilized at the electrode surface have eliminated the issue of poor electron conduction due to close proximity of electron transfer between electrode and the biocatalyst. Another problem is inefficient and short term stability of catalytic activity within the enzyme that is suspended in free flowing solution. Enzymes in solutions are only stable for hours to days, whereas immobilized enzymes can be stable for weeks to months and now even years. Over the last decade, there has been substantial research on immobilizing enzymes at electrode surfaces for biofuel cell and sensor applications. The most commonly used techniques are sandwich or wired. Sandwich techniques are powerful and successful for enzyme immobilization; however, the enzymes optimal activity is not retained due to the physical distress applied by the polymer limiting its applications as well as the non-uniform distribution of the enzyme and the diffusion of analyte through the polymer is slowed significantly. Wired techniques have shown to extend the lifetime of an enzyme at the electrode surface; however, this technique is very hard to master due to specific covalent bonding of enzyme and polymer which changes the three-dimensional configuration of enzyme and with that decreases the optimal catalytic activity. This chapter details encapsulation techniques where an enzyme will be immobilized within the pores/pockets of the hydrophobically modified micellar polymers such as Nafion ® and chitosan. This strategy has been shown to safely immobilize enzymes at electrode surfaces with storage and continuous operation lifetime of more than 2 years.

Polymer-ceramic nanocomposites for applications in the bone surgery

NASA Astrophysics Data System (ADS)

Stodolak, E.; Gadomska, K.; Lacz, A.; Bogun, M.

2009-01-01

The subject of this work was preparation and investigation of properties of a nanocomposite material based on polymer matrix modified with nanometric silica particles (SiO2). The composite matrix consisted of resorbable P(L/DL)LA polymer with certified biocompatibility. Nanometric silica was introduced into the matrix by means of ultrasonic homogenisation and/or mechanical stirring. The silica was introduced directly e.g. as nanoparticles or inside calcium alginate fibres which contained 3 wt.% of amorphous SiO2. Proper dispersion of nano-filliers was confirmed by means of thermal analysis (TG/DTA, DSC). It was observed, that the presence of inorganic nanoparticles influenced several surface parameters of the nanocomposites i.e. hydrophility (a decrease of surface energy) and topography (both in micro- and nano-scale). Additionally, the nanocomposites exhibited enhanced mechanical properties (Young's modulus, tensile strength) compared to the pure polymer. The nanocomposites were bioactive materials (SBF/3 days/37oC). Biological tests (MTT test) showed a good viability of human osteoblasts (hFOB 1.19) in contact with the nanocomposites surface. Results of preliminary biological tests carried out with the use of mother cells extracted from human bone marrow showed that the nanocomposites may provide differenation of bone cells.

Surface engineered biosensors for the early detection of cancer

NASA Astrophysics Data System (ADS)

Islam, Muhymin

Cancer commences in the building block of human body which is cells and in most of the cases remains silent at early stage. Diseases are only expressed at molecular and cellular level at primary stages. Recognition of diseases at this micro and nano level might reduce the mortality rate of cancer significantly. This research work aimed to introduce novel electronic biosensors for for identification of cancer at cellular level. The dissertation study focuses on 1) Label-Free Isolation of Metastatic Tumor Cells Using Filter Based Microfluidic device; 2) Nanotextured Polymer Substrates for Enhanced Cancer Cell Isolation and Cell Growth; 3) Nanotextured Microfluidic Channel for Electrical Profiling and Detection of Tumor Cells from Blood; and 4) Single Biochip for the Detection of Tumor Cells by Electrical Profile and Surface Immobilized Aptamer. Standard silicon processing techniques were followed to fabricate all of the biosensors. Nantoextruing and surface functionalizon were also incorporated to elevate the efficiency of the devices. The first approach aimed to detect cancer cells from blood based on their mechanophysical properties. Cancer cells are larger than blood cells but highly elastic in nature. These cells can squeeze through small microchannels much smaller than their size. The cross sectional area of the microchannels was optimized to isolate tumor cells from blood. Nanotextured polymer substrates, a platform inspired from the natural basement membrane was used to enhance the isolation and growth of tumor cells. Micro reactive ion etching was performed to have better control on features of nantoxtured surfaces and did not require any template. Next, electrical measurement of ionic current was performed across single microchannel to detect tumor cells from blood. Later, nanotexturing enhanced the efficiency of the device by selectively altering the translocation profile of cancer cells. Eventually aptamer functionalized nanotextured polymer surface was integrated with current measurement facilities in a single biochip to discriminate tumor cells from blood with higher efficiency and selectivity. This biochip can be an implemented as a point-of-care device for the early detection of cancer at cellular level.

Pectins, Hemicelluloses and Celluloses Show Specific Dynamics in the Internal and External Surfaces of Grape Berry Skin During Ripening.

PubMed

Fasoli, Marianna; Dell'Anna, Rossana; Dal Santo, Silvia; Balestrini, Raffaella; Sanson, Andrea; Pezzotti, Mario; Monti, Francesca; Zenoni, Sara

2016-06-01

Grapevine berry skin is a complex structure that contributes to the final size and shape of the fruit and affects its quality traits. The organization of cell wall polysaccharides in situ and their modification during ripening are largely uncharacterized. The polymer structure of Corvina berry skin, its evolution during ripening and related modifying genes were determined by combing mid-infrared micro-spectroscopy and multivariate statistical analysis with transcript profiling and immunohistochemistry. Spectra were acquired in situ using a surface-sensitive technique on internal and external sides of the skin without previous sample pre-treatment, allowing comparison of the related cell wall polymer dynamics. The external surface featured cuticle-related bands; the internal surface showed more adsorbed water. Application of surface-specific normalization revealed the major molecular changes related to hemicelluloses and pectins in the internal surface and to cellulose and pectins in the external surface and that they occur between mid-ripening and full ripening in both sides of the skin. Transcript profiling of cell wall-modifying genes indicated a general suppression of cell wall metabolism during ripening. Genes related to pectin metabolism-a β-galactosidase, a pectin(methyl)esterase and a pectate lyase-and a xyloglucan endotransglucosylase/hydrolase, involved in hemicellulose modification, showed enhanced expression. In agreement with Fourier transform infrared spectroscopy, patterns due to pectin methyl esterification provided new insights into the relationship between pectin modifications and the associated transcript profile during skin ripening. This study proposes an original description of polymer dynamics in grape berries during ripening, highlighting differences between the internal and external sides of the skin. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Calculating the mean time to capture for tethered ligands and its effect on the chemical equilibrium of bound ligand pairs

NASA Astrophysics Data System (ADS)

Shen, Lu; Decker, Caitlin; Maynard, Heather; Levine, Alex

Cells interact with a number of extracellular proteins including growth factors, which are essential for e.g., wound healing and development. Some of these growth factors must form dimers on the cell surface to initiate their signaling pathway. This suggests one can more efficiently induce signaling via polymer-linked proteins. Motivated by experiments on a family of fibroblast growth factors linked by polymers of varying molecular weight we investigate theoretically the effect of the length of the linking polymer on the binding kinetics of the dimers to a receptor-covered surface. We show, through a first-passage time calculation, how the number of bound dimers in chemical equilibrium depends on the linker molecular weight. We discuss more broadly the implications for a variety of signaling molecules. This work was supported by the NSF-DMR-1309188. HDM thanks the NIH NIBIB (R01EB013674) for support of the cell assay data.

Fabrication of cell container arrays with overlaid surface topographies.

PubMed

Truckenmüller, Roman; Giselbrecht, Stefan; Escalante-Marun, Maryana; Groenendijk, Max; Papenburg, Bernke; Rivron, Nicolas; Unadkat, Hemant; Saile, Volker; Subramaniam, Vinod; van den Berg, Albert; van Blitterswijk, Clemens; Wessling, Matthias; de Boer, Jan; Stamatialis, Dimitrios

2012-02-01

This paper presents cell culture substrates in the form of microcontainer arrays with overlaid surface topographies, and a technology for their fabrication. The new fabrication technology is based on microscale thermoforming of thin polymer films whose surfaces are topographically prepatterned on a micro- or nanoscale. For microthermoforming, we apply a new process on the basis of temporary back moulding of polymer films and use the novel concept of a perforated-sheet-like mould. Thermal micro- or nanoimprinting is applied for prepatterning. The novel cell container arrays are fabricated from polylactic acid (PLA) films. The thin-walled microcontainer structures have the shape of a spherical calotte merging into a hexagonal shape at their upper circumferential edges. In the arrays, the cell containers are arranged densely packed in honeycomb fashion. The inner surfaces of the highly curved container walls are provided with various topographical micro- and nanopatterns. For a first validation of the microcontainer arrays as in vitro cell culture substrates, C2C12 mouse premyoblasts are cultured in containers with microgrooved surfaces and shown to align along the grooves in the three-dimensional film substrates. In future stem-cell-biological and tissue engineering applications, microcontainers fabricated using the proposed technology may act as geometrically defined artificial microenvironments or niches.

Realization of 13.6% Efficiency on 20 μm Thick Si/Organic Hybrid Heterojunction Solar Cells via Advanced Nanotexturing and Surface Recombination Suppression.

PubMed

He, Jian; Gao, Pingqi; Liao, Mingdun; Yang, Xi; Ying, Zhiqin; Zhou, Suqiong; Ye, Jichun; Cui, Yi

2015-06-23

Hybrid silicon/polymer solar cells promise to be an economically feasible alternative energy solution for various applications if ultrathin flexible crystalline silicon (c-Si) substrates are used. However, utilization of ultrathin c-Si encounters problems in light harvesting and electronic losses at surfaces, which severely degrade the performance of solar cells. Here, we developed a metal-assisted chemical etching method to deliver front-side surface texturing of hierarchically bowl-like nanopores on 20 μm c-Si, enabling an omnidirectional light harvesting over the entire solar spectrum as well as an enlarged contact area with the polymer. In addition, a back surface field was introduced on the back side of the thin c-Si to minimize the series resistance losses as well as to suppress the surface recombination by the built high-low junction. Through these improvements, a power conversion efficiency (PCE) up to 13.6% was achieved under an air mass 1.5 G irradiation for silicon/organic hybrid solar cells with the c-Si thickness of only about 20 μm. This PCE is as high as the record currently reported in hybrid solar cells constructed from bulk c-Si, suggesting a design rule for efficient silicon/organic solar cells with thinner absorbers.

A stable perovskite electrolyte in moist air for Li-ion batteries.

PubMed

Li, Yutao; Xu, Henghui; Chien, Po-Hsiu; Wu, Nan; Xin, Sen; Xue, Leigang; Park, Kyusung; Hu, Yan-Yan; Goodenough, John B

2018-05-07

Solid-oxide Li+ electrolytes of a rechargeable cell are generally sensitive to moisture in the air, H+ exchanges for the mobile Li+ of the electrolyte and forms insulating surface phases at the electrolyte interfaces and in the grain boundaries of a polycrystalline membrane. These surface phases dominate the total interfacial resistance of a conventional rechargeable cell having a solid-electrolyte separator. We report a new perovskite Li+ solid electrolyte, Li0.38Sr0.44Ta0.7Hf0.3O2.95F0.05, having a Li-ion conductivity σLi = 4.8×10-4 S cm-1 at 25 oC that does not react with water having 3≤pH≤14. The solid electrolyte with a thin Li+-conducting polymer on its surface to prevent reduction of Ta5+ is wet by metallic lithium and provides low-impedance dendrite-free plating/stripping of a lithium anode. It is also stable on contact with a composite polymer cathode. With this solid electrolyte, we demonstrate excellent cycling performance of an all-solid-state Li/LiFePO4 cell, a Li-S cell with a polymer-gel cathode, and a supercapacitor. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical properties and osteocompatibility of novel biodegradable alanine based polyphosphazenes: Side group effects.

PubMed

Sethuraman, Swaminathan; Nair, Lakshmi S; El-Amin, Saadiq; Nguyen, My-Tien; Singh, Anurima; Krogman, Nick; Greish, Yaser E; Allcock, Harry R; Brown, Paul W; Laurencin, Cato T

2010-06-01

The versatility of polymers for tissue regeneration lies in the feasibility to modulate the physical and biological properties by varying the side groups grafted to the polymers. Biodegradable polyphosphazenes are high-molecular-weight polymers with alternating nitrogen and phosphorus atoms in the backbone. This study is the first of its kind to systematically investigate the effect of side group structure on the compressive strength of novel biodegradable polyphosphazene based polymers as potential materials for tissue regeneration. The alanine polyphosphazene based polymers, poly(bis(ethyl alanato) phosphazene) (PNEA), poly((50% ethyl alanato) (50% methyl phenoxy) phosphazene) (PNEA(50)mPh(50)), poly((50% ethyl alanato) (50% phenyl phenoxy) phosphazene) (PNEA(50)PhPh(50)) were investigated to demonstrate their mechanical properties and osteocompatibility. Results of mechanical testing studies demonstrated that the nature and the ratio of the pendent groups attached to the polymer backbone play a significant role in determining the mechanical properties of the resulting polymer. The compressive strength of PNEA(50)PhPh(50) was significantly higher than poly(lactide-co-glycolide) (85:15 PLAGA) (p<0.05). Additional studies evaluated the cellular response and gene expression of primary rat osteoblast cells on PNEA, PNEA(50)mPh(50) and PNEA(50)PhPh(50) films as candidates for bone tissue engineering applications. Results of the in vitro osteocompatibility evaluation demonstrated that cells adhere, proliferate, and maintain their phenotype when seeded directly on the surface of PNEA, PNEA(50)mPh(50), and PNEA(50)PhPh(50). Moreover, cells on the surface of the polymers expressed type I collagen, alkaline phosphatase, osteocalcin, osteopontin, and bone sialoprotein, which are characteristic genes for osteoblast maturation, differentiation, and mineralization. Copyright 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Mechanical Properties and Osteocompatibility of Novel Biodegradable Alanine Based Polyphosphazenes: Side Group Effects

PubMed Central

Sethuraman, Swaminathan; Nair, Lakshmi S.; El-Amin, Saadiq; Nguyen, My-Tien; Singh, Anurima; Krogman, Nick; Greish, Yaser E.; Allcock, Harry R.; Brown, Paul W.; Laurencin, Cato T.

2010-01-01

The versatility of polymers for tissue regeneration lies in the feasibility to modulate the physical and biological properties by varying the side groups grafted to the polymers. Biodegradable polyphosphazenes are high molecular weight polymers with alternating nitrogen and phosphorus atoms in the backbone. This study is the first of its kind to systematically investigate the effect of side group structure on the compressive strength of novel biodegradable polyphosphazene based polymers as potential materials for tissue regeneration. The alanine polyphosphazene based polymers, poly[bis(ethyl alanato) phosphazene] (PNEA), poly[(50% ethyl alanato) (50% methyl phenoxy) phosphazene] (PNEA50mPh50), poly[(50% ethyl alanato) (50% phenyl phenoxy) phosphazene] (PNEA50PhPh50) where investigated to demonstrate their mechanical properties and osteocompatibility. Results of mechanical testing studies demonstrated the nature and the ratio of the pendent groups attached to the polymer backbone play a significant role in determining the mechanical properties of the resulting polymer. The compressive strength of PNEA50PhPh50 was significantly higher than poly(lactide-co-glycolide) (85:15 PLAGA) (p<0.05). Additional studies evaluated the cellular response and gene expression of primary rat osteoblast cells on PNEA, PNEA50mPh50 and PNEA50PhPh50 films as candidates for bone tissue engineering applications. Results of the in vitro osteocompatibility evaluation demonstrated that cells adhere, proliferate, and maintain their phenotype when seeded directly on the surface of PNEA, PNEA50mPh50, and PNEA50PhPh50 Moreover cells on the surface of the polymers expressed type I collagen, alkaline phosphatase, osteocalcin, osteopontin, and bone sialoprotein which are characteristic genes for osteoblast maturation, differentiation, and mineralization. PMID:20004751

Polymers and biopolymers at interfaces

NASA Astrophysics Data System (ADS)

Hall, A. R.; Geoghegan, M.

2018-03-01

This review updates recent progress in the understanding of the behaviour of polymers at surfaces and interfaces, highlighting examples in the areas of wetting, dewetting, crystallization, and ‘smart’ materials. Recent developments in analysis tools have yielded a large increase in the study of biological systems, and some of these will also be discussed, focussing on areas where surfaces are important. These areas include molecular binding events and protein adsorption as well as the mapping of the surfaces of cells. Important techniques commonly used for the analysis of surfaces and interfaces are discussed separately to aid the understanding of their application.

Coated foams, preparation, uses and articles

DOEpatents

Duchane, D.V.; Barthell, B.L.

1982-10-21

Hydrophobic cellular material is coated with a thin hydrophilic polymer skin which stretches tightly over the foam but which does not fill the cells of the foam, thus resulting in a polymer-coated foam structure having a smoothness which was not possible in the prior art. In particular, when the hydrophobic cellular material is a specially chosen hydrophobic polymer foam and is formed into arbitrarily chosen shapes prior to the coating with hydrophilic polymer, inertial confinement fusion (ICF) targets of arbitrary shapes can be produced by subsequently coating the shapes with metal or with any other suitable material. New articles of manufacture are produced, including improved ICF targets, improved integrated circuits, and improved solar reflectors and solar collectors. In the coating method, the cell size of the hydrophobic cellular material, the viscosity of the polymer solution used to coat, and the surface tension of the polymer solution used to coat are all very important to the coating.

Chemical characterization of solid polymer electrolyte membrane surfaces in LiFePO4 half-cells

NASA Astrophysics Data System (ADS)

Kyu, Thein; He, Ruixuan; Peng, Fang; Dunn, William E.; Kyu's Group Team, Dr.

High temperature (60 °C) capacity retention of succinonitrile plasticized solid polymer electrolyte membrane (PEM) in a LiFePO4 half-cell was investigated with or without lithium bis(oxalato)borate (LiBOB) modification. Various symmetric cells and half-cells were studied under different thermal and electrochemical conditions. At room temperature cycling, the unmodified PEM in the half-cell appeared stable up to 50 cycles tested. Upon cycling at 60 °C, the capacity decays rapidly and concurrently the cell resistance increased. The chemical compositions of the solid PEM surfaces on both cathode and anode sides were analyzed. New IR bands (including those belonged to amide) were discerned on the unmodified PEM surface of the Li electrode side at 60 °C suggestive of side reaction, but no new bands develop during room temperature cycling. To our astonishment, the side reaction was effectively suppressed upon LiBOB addition (0.4 wt%) into the PEM, contributing to increased high temperature capacity retention at 60°C. Plausible mechanisms of capacity fading and improved cycling performance due to LiBOB modification are discussed.

Analysis and modification of defective surface aggregates on PCDTBT:PCBM solar cell blends using combined Kelvin probe, conductive and bimodal atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noh, Hanaul; Diaz, Alfredo J.; Solares, Santiago D.

Organic photovoltaic systems comprising donor polymers and acceptor fullerene derivatives are attractive for inexpensive energy harvesting. Extensive research on polymer solar cells has provided insight into the factors governing device-level efficiency and stability. However, the detailed investigation of nanoscale structures is still challenging. Here we demonstrate the analysis and modification of unidentified surface aggregates. The aggregates are characterized electrically by Kelvin probe force microscopy and conductive atomic force microscopy (C-AFM), whereby the correlation between local electrical potential and current confirms a defective charge transport. Bimodal AFM modification confirms that the aggregates exist on top of the solar cell structure, andmore » is used to remove them and to reveal the underlying active layer. The systematic analysis of the surface aggregates suggests that the structure consists of PCBM molecules.« less

Analysis and modification of defective surface aggregates on PCDTBT:PCBM solar cell blends using combined Kelvin probe, conductive and bimodal atomic force microscopy

DOE PAGES

Noh, Hanaul; Diaz, Alfredo J.; Solares, Santiago D.

2017-03-08

Organic photovoltaic systems comprising donor polymers and acceptor fullerene derivatives are attractive for inexpensive energy harvesting. Extensive research on polymer solar cells has provided insight into the factors governing device-level efficiency and stability. However, the detailed investigation of nanoscale structures is still challenging. Here we demonstrate the analysis and modification of unidentified surface aggregates. The aggregates are characterized electrically by Kelvin probe force microscopy and conductive atomic force microscopy (C-AFM), whereby the correlation between local electrical potential and current confirms a defective charge transport. Bimodal AFM modification confirms that the aggregates exist on top of the solar cell structure, andmore » is used to remove them and to reveal the underlying active layer. The systematic analysis of the surface aggregates suggests that the structure consists of PCBM molecules.« less

Analysis and modification of defective surface aggregates on PCDTBT:PCBM solar cell blends using combined Kelvin probe, conductive and bimodal atomic force microscopy

PubMed Central

Noh, Hanaul; Diaz, Alfredo J

2017-01-01

Organic photovoltaic systems comprising donor polymers and acceptor fullerene derivatives are attractive for inexpensive energy harvesting. Extensive research on polymer solar cells has provided insight into the factors governing device-level efficiency and stability. However, the detailed investigation of nanoscale structures is still challenging. Here we demonstrate the analysis and modification of unidentified surface aggregates. The aggregates are characterized electrically by Kelvin probe force microscopy and conductive atomic force microscopy (C-AFM), whereby the correlation between local electrical potential and current confirms a defective charge transport. Bimodal AFM modification confirms that the aggregates exist on top of the solar cell structure, and is used to remove them and to reveal the underlying active layer. The systematic analysis of the surface aggregates suggests that the structure consists of PCBM molecules. PMID:28382247

Synthesis and characterization of hydroxyl-functionalized caprolactone copolymers and their effect on adhesion, proliferation, and differentiation of human mesenchymal stem cells.

PubMed

Seyednejad, Hajar; Vermonden, Tina; Fedorovich, Natalja E; van Eijk, Roel; van Steenbergen, Mies J; Dhert, Wouter J A; van Nostrum, Cornelus F; Hennink, Wim E

2009-11-09

The aim of this study was to develop new hydrophilic polyesters for tissue engineering applications. In our approach, poly(benzyloxymethyl glycolide-co-epsilon-caprolactone)s (pBHMG-CLs) were synthesized through melt copolymerization of epsilon-caprolactone (CL) and benzyl-protected hydroxymethyl glycolide (BHMG). Deprotection of the polymers yielded copolymers with pendant hydroxyl groups, poly(hydroxymethylglycolide-co-epsilon-caprolactone) (pHMG-CL). The synthesized polymers were characterized by GPC, NMR, and DSC techniques. The resulting copolymers consisting of up to 10% of HMG monomer were semicrystalline with a melting temperature above body temperature. Water contact angle measurements of polymeric films showed that increasing HMG content resulted in higher surface hydrophilicity, as evidenced from a decrease in receding contact angle from 68 degrees for PCL to 40 degrees for 10% HMG-CL. Human mesenchymal stem cells showed good adherence onto pHMG-CL films as compared to the more hydrophobic PCL surfaces. The cells survived and were able to differentiate toward osteogenic lineage on pHMG-CL surfaces. This study shows that the aforementioned hydrophilic polymers are attractive candidates for the design of scaffolds for tissue engineering applications.

In vitro blood and fibroblast responses to BisGMA-TEGDMA/bioactive glass composite implants.

PubMed

Abdulmajeed, Aous A; Kokkari, Anne K; Käpylä, Jarmo; Massera, Jonathan; Hupa, Leena; Vallittu, Pekka K; Närhi, Timo O

2014-01-01

This in vitro study was designed to evaluate both blood and human gingival fibroblast responses to bisphenol A-glycidyl methacrylate-triethyleneglycol dimethacrylate (BisGMA-TEGDMA)/bioactive glass (BAG) composite, aimed to be used as composite implant abutment surface modifier. Three different types of substrates were investigated: (a) plain polymer (BisGMA 50 wt%-TEGDMA 50 wt%), (b) BAG-composite (50 wt% polymer + 50 wt% fraction of BAG-particles, <50 μm), and (c) plain BAG plates (100 wt% BAG). The blood response, including the blood-clotting ability and platelet adhesion morphology were evaluated. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 10 days, then the cell proliferation rate was assessed using AlamarBlue assay™. The BAG-composite and plain BAG substrates had a shorter clotting time than plain polymer substrates. Platelet activation and aggregation were most extensive, qualitatively, on BAG-composite. Analysis of the normalized cell proliferation rate on the different surfaces showed some variations throughout the experiment, however, by day 10 the BAG-composite substrate showed the highest (P < 0.001) cell proliferation rate. In conclusion, the presence of exposed BAG-particles enhances fibroblast and blood responses on composite surfaces in vitro.

Design and development of low cost polyurethane biopolymer based on castor oil and glycerol for biomedical applications

PubMed Central

Tan, A. C. W.; Polo‐Cambronell, B. J.; Provaggi, E.; Ardila‐Suárez, C.; Ramirez‐Caballero, G. E.; Baldovino‐Medrano, V. G.

2017-01-01

Abstract In the current study, we present the synthesis of novel low cost bio‐polyurethane compositions with variable mechanical properties based on castor oil and glycerol for biomedical applications. A detailed investigation of the physicochemical properties of the polymer was carried out by using mechanical testing, ATR‐FTIR, and X‐ray photoelectron spectroscopy (XPS). Polymers were also tested in short term in‐vitro cell culture with human mesenchymal stem cells to evaluate their biocompatibility for potential applications as biomaterial. FTIR analysis confirmed the synthesis of castor oil and glycerol based PU polymers. FTIR also showed that the addition of glycerol as co‐polyol increases crosslinking within the polymer backbone hence enhancing the bulk mechanical properties of the polymer. XPS data showed that glycerol incorporation leads to an enrichment of oxidized organic species on the surface of the polymers. Preliminary investigation into in vitro biocompatibility showed that serum protein adsorption can be controlled by varying the glycerol content with polymer backbone. An alamar blue assay looking at the metabolic activity of the cells indicated that castor oil based PU and its variants containing glycerol are non‐toxic to the cells. This study opens an avenue for using low cost bio‐polyurethane based on castor oil and glycerol for biomedical applications. PMID:29159831

Improving polymer/nanocrystal hybrid solar cell performance via tuning ligand orientation at CdSe quantum dot surface.

PubMed

Fu, Weifei; Wang, Ling; Zhang, Yanfang; Ma, Ruisong; Zuo, Lijian; Mai, Jiangquan; Lau, Tsz-Ki; Du, Shixuan; Lu, Xinhui; Shi, Minmin; Li, Hanying; Chen, Hongzheng

2014-11-12

Achieving superior solar cell performance based on the colloidal nanocrystals remains challenging due to their complex surface composition. Much attention has been devoted to the development of effective surface modification strategies to enhance electronic coupling between the nanocrystals to promote charge carrier transport. Herein, we aim to attach benzenedithiol ligands onto the surface of CdSe nanocrystals in the "face-on" geometry to minimize the nanocrystal-nanocrystal or polymer-nanocrystal distance. Furthermore, the "electroactive" π-orbitals of the benzenedithiol are expected to further enhance the electronic coupling, which facilitates charge carrier dissociation and transport. The electron mobility of CdSe QD films was improved 20 times by tuning the ligand orientation, and high performance poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT):CdSe nanocrystal hybrid solar cells were also achieved, showing a highest power conversion efficiency of 4.18%. This research could open up a new pathway to improve further the performance of colloidal nanocrystal based solar cells.

Poly(dopamine) coating to biodegradable polymers for bone tissue engineering.

PubMed

Tsai, Wei-Bor; Chen, Wen-Tung; Chien, Hsiu-Wen; Kuo, Wei-Hsuan; Wang, Meng-Jiy

2014-02-01

In this study, a technique based on poly(dopamine) deposition to promote cell adhesion was investigated for the application in bone tissue engineering. The adhesion and proliferation of rat osteoblasts were evaluated on poly(dopamine)-coated biodegradable polymer films, such as polycaprolactone, poly(l-lactide) and poly(lactic-co-glycolic acid), which are commonly used biodegradable polymers in tissue engineering. Cell adhesion was significantly increased to a plateau by merely 15 s of dopamine incubation, 2.2-4.0-folds of increase compared to the corresponding untreated substrates. Cell proliferation was also greatly enhanced by poly(dopamine) deposition, indicated by shortened cell doubling time. Mineralization was also increased on the poly(dopamine)-deposited surfaces. The potential of poly(dopamine) deposition in bone tissue engineering is demonstrated in this study.

Fabrication of biocompatible and efficient antimicrobial porous polymer surfaces by the Breath Figures approach.

PubMed

Vargas-Alfredo, Nelson; Martínez-Campos, Enrique; Santos-Coquillat, Ana; Dorronsoro, Ane; Cortajarena, Aitziber L; Del Campo, Adolfo; Rodríguez-Hernández, Juan

2018-03-01

We designed and fabricated highly efficient and selective antibacterial substrates, i.e. surface non-cytotoxic against mammalian cells but exhibiting strong antibacterial activity. For that purpose, microporous substrates (pore sizes in the range of 3-5 μm) were fabricated using the Breath Figures approach (BFs). These substrates have additionally a defined chemical composition in the pore cavity (herein either a poly(acrylic acid) or the antimicrobial peptide Nisin) while the composition of the rest of the surface is identical to the polymer matrix. As a result, considering the differences in size of bacteria (1-4 μm) in comparison to mammalian cells (above 10 µm) the bacteria were able to enter in contact with the inner part of the pores where the antimicrobial functionality has been placed. On the opposite, mammalian cells remain in contact with the top surface thus preventing cytotoxic effects and enhancing the biocompatibility of the substrates. The resulting antimicrobial surfaces were exposed to Staphylococcus aureus as a model bacteria and murine endothelial C166-GFP cells. Superior antibacterial performance while maintaining an excellent biocompatibility was obtained by those surfaces prepared using PAA while no evidence of significant antibacterial activity was observed at those surfaces prepared using Nisin. Copyright © 2017 Elsevier Inc. All rights reserved.

Amino Acid Hydrolysis and Analysis System for Investigation of Site Directed Nucleation and Growth of Ceramic Films on Metallic Surfaces

DTIC Science & Technology

2008-09-30

that composed the proteinaceous polymers found at the interface between calcite crystals deposited by oyster cells and the various n1etal substrates...proteinaceous polymers found at the interface between calcite crystals deposited by oyster cells and the various metal substrates. A recently...required for the mechanism of biomineralization and site-specific deposition of ceramic crystals on aluminum alloy substrates. These calcite crystals

In Vitro Endothelialization Test of Biomaterials Using Immortalized Endothelial Cells.

PubMed

Kono, Ken; Hiruma, Hitomi; Kobayashi, Shingo; Sato, Yoji; Tanaka, Masaru; Sawada, Rumi; Niimi, Shingo

2016-01-01

Functionalizing biomaterials with peptides or polymers that enhance recruitment of endothelial cells (ECs) can reduce blood coagulation and thrombosis. To assess endothelialization of materials in vitro, primary ECs are generally used, although the characteristics of these cells vary among the donors and change with time in culture. Recently, primary cell lines immortalized by transduction of simian vacuolating virus 40 large T antigen or human telomerase reverse transcriptase have been developed. To determine whether immortalized ECs can substitute for primary ECs in material testing, we investigated endothelialization on biocompatible polymers using three lots of primary human umbilical vein endothelial cells (HUVEC) and immortalized microvascular ECs, TIME-GFP. Attachment to and growth on polymer surfaces were comparable between cell types, but results were more consistent with TIME-GFP. Our findings indicate that TIME-GFP is more suitable for in vitro endothelialization testing of biomaterials.

Electroactive polymer-peptide conjugates for adhesive biointerfaces.

PubMed

Maione, Silvana; Gil, Ana M; Fabregat, Georgina; Del Valle, Luis J; Triguero, Jordi; Laurent, Adele; Jacquemin, Denis; Estrany, Francesc; Jiménez, Ana I; Zanuy, David; Cativiela, Carlos; Alemán, Carlos

2015-10-15

Electroactive polymer-peptide conjugates have been synthesized by combining poly(3,4-ethylenedioxythiophene), a polythiophene derivative with outstanding properties, and an Arg-Gly-Asp (RGD)-based peptide in which Gly has been replaced by an exotic amino acid bearing a 3,4-ethylenedioxythiophene ring in the side chain. The incorporation of the peptide at the ends of preformed PEDOT chains has been corroborated by both FTIR and X-ray photoelectron spectroscopy. Although the morphology and topology are not influenced by the incorporation of the peptide at the ends of PEDOT chains, this process largely affects other surface properties. Thus, the wettability of the conjugates is considerably higher than that of PEDOT, independently of the synthetic strategy, whereas the surface roughness only increases when the conjugate is obtained using a competing strategy (i.e. growth of the polymer chains against termination by end capping). The electrochemical activity of the conjugates has been found to be higher than that of PEDOT, evidencing the success of the polymer-peptide links designed by chemical similarity. Density functional theory calculations have been used not only to ascertain the conformational preferences of the peptide but also to interpret the electronic transitions detected by UV-vis spectroscopy. Electroactive surfaces prepared using the conjugates displayed the higher bioactivities in terms of cell adhesion, with the relative viabilities being dependent on the roughness, wettability and electrochemical activity of the conjugate. In addition to the influence of the peptide fragment in the initial cell attachment and subsequent cell spreading and survival, the results indicate that PEDOT promotes the exchange of ions at the conjugate-cell interface.

Polymer stabilized liquid crystals: Topology-mediated electro-optical behavior and applications

NASA Astrophysics Data System (ADS)

Weng, Libo

There has been a wide range of liquid crystal polymer composites that vary in polymer concentration from as little as 3 wt.% (polymer stabilized liquid crystal) to as high as 60 wt.% (polymer dispersed liquid crystals). In this dissertation, an approach of surface polymerization based on a low reactive monomer concentration about 1 wt.% is studied in various liquid crystal operation modes. The first part of dissertation describes the development of a vertical alignment (VA) mode with surface polymer stabilization, and the effects of structure-performance relationship of reactive monomers (RMs) and polymerization conditions on the electro-optical behaviors of the liquid crystal device has been explored. The polymer topography plays an important role in modifying and enhancing the electro-optical performance of stabilized liquid crystal alignment. The enabling surface-pinned polymer stabilized vertical alignment (PSVA) approach has led to the development of high-performance and fast-switching displays with controllable pretilt angle, increase in surface anchoring energy, high optical contrast and fast response time. The second part of the dissertation explores a PSVA mode with in-plane switching (IPS) and its application for high-efficiency and fast-switching phase gratings. The diffraction patterns and the electro-optical behaviors including diffraction efficiency and response time are characterized. The diffraction grating mechanism and performance have been validated by computer simulation. Finally, the advantages of surface polymerization approach such as good optical contrast and fast response time have been applied to the fringe-field switching (FFS) system. The concentration of reactive monomer on the electro-optical behavior of the FFS cells is optimized. The outstanding electro-optical results and mechanism of increase in surface anchoring strength are corroborated by the director field simulation. The density and topology of nanoscale polymer protrusions are analyzed and confirmed by morphological study. The developed high-performance polymer-stabilized fringe-field-switching (PS-FFS) could open new types of device applications.

Surface Acoustic Waves Grant Superior Spatial Control of Cells Embedded in Hydrogel Fibers.

PubMed

Lata, James P; Guo, Feng; Guo, Jinshan; Huang, Po-Hsun; Yang, Jian; Huang, Tony Jun

2016-10-01

By exploiting surface acoustic waves and a coupling layer technique, cells are patterned within a photosensitive hydrogel fiber to mimic physiological cell arrangement in tissues. The aligned cell-polymer matrix is polymerized with short exposure to UV light and the fiber is extracted. These patterned cell fibers are manipulated into simple and complex architectures, demonstrating feasibility for tissue-engineering applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

From honeycomb- to microsphere-patterned surfaces of poly(lactic acid) and a starch-poly(lactic acid) blend via the breath figure method.

PubMed

Duarte, Ana Rita C; Maniglio, Devid; Sousa, Nuno; Mano, João F; Reis, Rui L; Migliaresi, Claudio

2017-01-26

This study investigated the preparation of ordered patterned surfaces and/or microspheres from a natural-based polymer, using the breath figure and reverse breath figure methods. Poly(D,L-lactic acid) and starch poly(lactic acid) solutions were precipitated in different conditions - namely, polymer concentration, vapor atmosphere temperature and substrate - to evaluate the effect of these conditions on the morphology of the precipitates obtained. The possibility of fine-tuning the properties of the final patterns simply by changing the vapor atmosphere was also demonstrated here using a range of compositions of the vapor phase. Porous films or discrete particles are formed when the differences in surface tension determine the ability of polymer solution to surround water droplets or methanol to surround polymer droplets, respectively. In vitro cytotoxicity was assessed applying a simple standard protocol to evaluate the possibility to use these materials in biomedical applications. Moreover, fluorescent microscopy images showed a good interaction of cells with the material, which were able to adhere on the patterned surfaces after 24 hours in culture. The development of patterned surfaces using the breath figure method was tested in this work for the preparation of both poly(lactic acid) and a blend containing starch and poly(lactic acid). The potential of these films to be used in the biomedical area was confirmed by a preliminary cytotoxicity test and by morphological observation of cell adhesion.

Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

PubMed

Venkatesan, Swaminathan; Ngo, Evan; Khatiwada, Devendra; Zhang, Cheng; Qiao, Qiquan

2015-07-29

The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a suitable passivation layer to suppress oxidation in metal oxide thin films for enhanced lifetime in inverted organic solar cells.

New Avenue for Limiting Degradation in NanoLi4Ti5O12 for Ultrafast-Charge Lithium-Ion Batteries: Hybrid Polymer-Inorganic Particles.

PubMed

Daigle, Jean-Christophe; Asakawa, Yuichiro; Beaupré, Mélanie; Vieillette, René; Laul, Dharminder; Trudeau, Michel; Zaghib, Karim

2017-12-13

Lithium titanium oxide (Li 4 Ti 5 O 12 )-based cells are a very promising battery technology for ultrafast-charge-discharge and long-cycle-life batteries. However, the surface reactivity of lithium titanium oxide in the presence of organic electrolytes continues to be a problem that may cause expansion of pouch cells. In this study, we report on the development of a simple and economical grafting method for forming hybrid polymer-Li 4 Ti 15 O 12 nanoparticles, which can be successfully applied in lithium-ion batteries. This method utilizes a low-cost and scalable hydrophobic polymer that is applicable in industrial processes. The hybrid materials demonstrated exceptional capability for preventing the degradation of cells in accelerated aging and operating over 150 cycles at 1C and 45 °C.

Development and Application of a Sample Holder for In Situ Gaseous TEM Studies of Membrane Electrode Assemblies for Polymer Electrolyte Fuel Cells.

PubMed

Kamino, Takeo; Yaguchi, Toshie; Shimizu, Takahiro

2017-10-01

Polymer electrolyte fuel cells hold great potential for stationary and mobile applications due to high power density and low operating temperature. However, the structural changes during electrochemical reactions are not well understood. In this article, we detail the development of the sample holder equipped with gas injectors and electric conductors and its application to a membrane electrode assembly of a polymer electrolyte fuel cell. Hydrogen and oxygen gases were simultaneously sprayed on the surfaces of the anode and cathode catalysts of the membrane electrode assembly sample, respectively, and observation of the structural changes in the catalysts were simultaneously carried out along with measurement of the generated voltages.

Steric Pressure among Membrane-Bound Polymers Opposes Lipid Phase Separation.

PubMed

Imam, Zachary I; Kenyon, Laura E; Carrillo, Adelita; Espinoza, Isai; Nagib, Fatema; Stachowiak, Jeanne C

2016-04-19

Lipid rafts are thought to be key organizers of membrane-protein complexes in cells. Many proteins that interact with rafts have bulky polymeric components such as intrinsically disordered protein domains and polysaccharide chains. Therefore, understanding the interaction between membrane domains and membrane-bound polymers provides insights into the roles rafts play in cells. Multiple studies have demonstrated that high concentrations of membrane-bound polymeric domains create significant lateral steric pressure at membrane surfaces. Furthermore, our recent work has shown that lateral steric pressure at membrane surfaces opposes the assembly of membrane domains. Building on these findings, here we report that membrane-bound polymers are potent suppressors of membrane phase separation, which can destabilize lipid domains with substantially greater efficiency than globular domains such as membrane-bound proteins. Specifically, we created giant vesicles with a ternary lipid composition, which separated into coexisting liquid ordered and disordered phases. Lipids with saturated tails and poly(ethylene glycol) (PEG) chains conjugated to their head groups were included at increasing molar concentrations. When these lipids were sparse on the membrane surface they partitioned to the liquid ordered phase. However, as they became more concentrated, the fraction of GUVs that were phase-separated decreased dramatically, ultimately yielding a population of homogeneous membrane vesicles. Experiments and physical modeling using compositions of increasing PEG molecular weight and lipid miscibility phase transition temperature demonstrate that longer polymers are the most efficient suppressors of membrane phase separation when the energetic barrier to lipid mixing is low. In contrast, as the miscibility transition temperature increases, longer polymers are more readily driven out of domains by the increased steric pressure. Therefore, the concentration of shorter polymers required to suppress phase separation decreases relative to longer polymers. Collectively, our results demonstrate that crowded, membrane-bound polymers are highly efficient suppressors of phase separation and suggest that the ability of lipid domains to resist steric pressure depends on both their lipid composition and the size and concentration of the membrane-bound polymers they incorporate.

Surface functionalization of quantum dots with fine-structured pH-sensitive phospholipid polymer chains.

PubMed

Liu, Yihua; Inoue, Yuuki; Ishihara, Kazuhiko

2015-11-01

To add novel functionality to quantum dots (QDs), we synthesized water-soluble and pH-responsive block-type polymers by reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymers were composed of cytocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer segments, which contain a small fraction of active ester groups and can be used to conjugate biologically active compounds to the polymer, and pH-responsive poly(2-(N,N-diethylamino) ethyl methacrylate (DEAEMA)) segments. One terminal of the polymer chain had a hydrophobic alkyl group that originated from the RAFT initiator. This hydrophobic group can bind to the hydrophobic layer on the QD surface. A fluorescent dye was conjugated to the polymer chains via the active ester group. The block-type polymers have an amphiphilic nature in aqueous medium. The polymers were thus easily bound to the QD surface upon evaporation of the solvent from a solution containing the block-type polymer and QDs, yielding QD/fluorescence dye-conjugated polymer hybrid nanoparticles. Fluorescence resonance energy transfer (FRET) between the QDs (donors) and the fluorescent dye molecules (acceptors) was used to obtain information on the conformational dynamics of the immobilized polymers. Higher FRET efficiency of the QD/fluorescent dye-conjugated polymer hybrid nanoparticles was observed at pH 7.4 as compared to pH 5.0 due to a stretching-shrinking conformational motion of the poly(DEAEMA) segments in response to changes in pH. We concluded that the block-type MPC polymer-modified nanoparticles could be used to evaluate the pH of cells via FRET fluorescence based on the cytocompatibility of the MPC polymer. Copyright © 2015 Elsevier B.V. All rights reserved.

PEG attachment to osteoblasts enhances mechanosensitivity.

PubMed

Hamamura, Kazunori; Weng, Yiming; Zhao, Jun; Yokota, Hiroki; Xie, Dong

2008-06-01

Fluid flow induces proliferation and differentiation of osteoblasts, and fibrous structure like a primary cilium on a cell surface contributes to flow sensing and flow-driven gene regulation. We address a question: Does attachment of synthetic polymers on a cell surface enhance mechanosensitivity of osteoblasts? Using MC3T3 osteoblast cells (C4 clone) and a PEG polymer, one of whose termini was covalently linked to a succinimidyl succinate group (functionalized PEG-PEGSS), we examined attachment of PEGSS to osteoblasts and evaluated its effects on the mRNA expression of stress-responsive genes. AFM images exhibited globular PEGSS conformation of approximately 100 nm in size, and SEM images confirmed the attachment of a cluster of pancake-like PEGSS molecules on the osteoblast surface. Compared to control cells incubated with unfunctionalized PEG, real-time PCR revealed that RNA upregulation of c-fos, egr1, ATF3 and Cox2 genes was magnified in the cells incubated with PEGSS. These results support a PEG-induced increase in mechanosensitivity of osteoblasts and indicate that the described approach would be useful to accelerate growth and development of osteoblasts for bone repair and tissue engineering.

Biomimetic oligosaccharide and peptide surfactant polymers designed for cardiovascular biomaterials

NASA Astrophysics Data System (ADS)

Ruegsegger, Mark Andrew

A common problem associated with cardiovascular devices is surface induced thrombosis initiated by the rapid, non-specific adsorption of plasma proteins onto the biomaterial surface. Control of the initial protein adsorption is crucial to achieve the desired longevity of the implanted biomaterial. The cell membrane glycocalyx acts as a non-thrombogenic interface through passive (dense oligosaccharide structures) and active (ligand/receptor interactions) mechanisms. This thesis is designed to investigate biomimicry of the cell glycocalyx to minimize non-specific protein adsorption and promote specific ligand/receptor interactions. Biomimetic macromolecules were designed through the molecular-scale engineering of polymer surfactants, utilizing a poly(vinyl amine) (PVAm) backbone to which hydrophilic (dextran, maltose, peptide) and hydrophobic alkyl (hexanoyl or hexanal) chains are simultaneously attached. The structure was controlled through the molar feed ratio of hydrophobic-to-hydrophilic groups, which also provided control of the solution and surface-active properties. To mimic passive properties, a series of oligomaltose surfactants were synthesized with increasing saccharide length (n = 2, 7, 15 where n is number of glucose units) to investigate the effect of coating height on protein adsorption. The surfactants were characterized by infra red (IR) and nuclear magnetic resonance (NMR) spectroscopies for structural properties and atomic force microscopy (AFM) and contact angle goniometry for surface activity. Protein adsorption under dynamic flow (5 dyn/cm2) was reduced by 85%--95% over the bare hydrophobic substrate; platelet adhesion dropped by ˜80% compared to glass. Peptide ligands were incorporated into the oligosaccharide surfactant to promote functional activity of the passive coating. The surfactants were synthesized to contain 0%, 25%, 50%, 75%, and 100% peptide ligand density and were stable on hydrophobic surfaces. The peptide surface density was calculated to be 0.86 ligands/nm2 for PVAm(Pep)(100%), as determined by total internal reflection fluorescence (TIRF) spectroscopy. Similar cell growth was observed on the 100% peptide surfactant as for the fibronectin control, and no cell growth was seen on the 0% peptide. Increasing cell viability was observed for the surfaces with increasing peptide density. These results indicate much promise for surfactant polymers in surface modification and the capability to mimic the passive and active properties of the cell glycocalyx.

Simulation and modelling of slip flow over surfaces grafted with polymer brushes and glycocalyx fibres

PubMed Central

Deng, Mingge; Li, Xuejin; Liang, Haojun; Caswell, Bruce; Karniadakis, George Em

2013-01-01

Fabrication of functionalized surfaces using polymer brushes is a relatively simple process and parallels the presence of glycocalyx filaments coating the luminal surface of our vasculature. In this paper, we perform atomistic-like simulations based on dissipative particle dynamics (DPD) to study both polymer brushes and glycocalyx filaments subject to shear flow, and we apply mean-field theory to extract useful scaling arguments on their response. For polymer brushes, a weak shear flow has no effect on the brush density profile or its height, while the slip length is independent of the shear rate and is of the order of the brush mesh size as a result of screening by hydrodynamic interactions. However, for strong shear flow, the polymer brush is penetrated deeper and is deformed, with a corresponding decrease of the brush height and an increase of the slip length. The transition from the weak to the strong shear regime can be described by a simple ‘blob’ argument, leading to the scaling γ̇0 ∝ σ3/2, where γ̇0 is the critical transition shear rate and σ is the grafting density. Furthermore, in the strong shear regime, we observe a cyclic dynamic motion of individual polymers, causing a reversal in the direction of surface flow. To study the glycocalyx layer, we first assume a homogeneous flow that ignores the discrete effects of blood cells, and we simulate microchannel flows at different flow rates. Surprisingly, we find that, at low Reynolds number, the slip length decreases with the mean flow velocity, unlike the behaviour of polymer brushes, for which the slip length remains constant under similar conditions. (The slip length and brush height are measured with respect to polymer mesh size and polymer contour length, respectively.) We also performed additional DPD simulations of blood flow in a tube with walls having a glycocalyx layer and with the deformable red blood cells modelled accurately at the spectrin level. In this case, a plasma cell-free layer is formed, with thickness more than three times the glycocalyx layer. We then find our scaling arguments based on the homogeneous flow assumption to be valid for this physiologically correct case as well. Taken together, our findings point to the opposing roles of conformational entropy and bending rigidity – dominant effects for the brush and glycocalyx, respectively – which, in turn, lead to different flow characteristics, despite the apparent similarity of the two systems. PMID:24353347

Polymer-metal hybrid transparent electrodes for flexible electronics

NASA Astrophysics Data System (ADS)

Kang, Hongkyu; Jung, Suhyun; Jeong, Soyeong; Kim, Geunjin; Lee, Kwanghee

2015-03-01

Despite nearly two decades of research, the absence of ideal flexible and transparent electrodes has been the largest obstacle in realizing flexible and printable electronics for future technologies. Here we report the fabrication of ‘polymer-metal hybrid electrodes’ with high-performance properties, including a bending radius <1 mm, a visible-range transmittance>95% and a sheet resistance <10 Ω sq-1. These features arise from a surface modification of the plastic substrates using an amine-containing nonconjugated polyelectrolyte, which provides ideal metal-nucleation sites with a surface-density on the atomic scale, in combination with the successive deposition of a facile anti-reflective coating using a conducting polymer. The hybrid electrodes are fully functional as universal electrodes for high-end flexible electronic applications, such as polymer solar cells that exhibit a high power conversion efficiency of 10% and polymer light-emitting diodes that can outperform those based on transparent conducting oxides.

Polymer-metal hybrid transparent electrodes for flexible electronics

PubMed Central

Kang, Hongkyu; Jung, Suhyun; Jeong, Soyeong; Kim, Geunjin; Lee, Kwanghee

2015-01-01

Despite nearly two decades of research, the absence of ideal flexible and transparent electrodes has been the largest obstacle in realizing flexible and printable electronics for future technologies. Here we report the fabrication of ‘polymer-metal hybrid electrodes’ with high-performance properties, including a bending radius <1 mm, a visible-range transmittance>95% and a sheet resistance <10 Ω sq−1. These features arise from a surface modification of the plastic substrates using an amine-containing nonconjugated polyelectrolyte, which provides ideal metal-nucleation sites with a surface-density on the atomic scale, in combination with the successive deposition of a facile anti-reflective coating using a conducting polymer. The hybrid electrodes are fully functional as universal electrodes for high-end flexible electronic applications, such as polymer solar cells that exhibit a high power conversion efficiency of 10% and polymer light-emitting diodes that can outperform those based on transparent conducting oxides. PMID:25790133

Thiol-Reactive Star Polymers Display Enhanced Association with Distinct Human Blood Components.

PubMed

Glass, Joshua J; Li, Yang; De Rose, Robert; Johnston, Angus P R; Czuba, Ewa I; Khor, Song Yang; Quinn, John F; Whittaker, Michael R; Davis, Thomas P; Kent, Stephen J

2017-04-12

Directing nanoparticles to specific cell types using nonantibody-based methods is of increasing interest. Thiol-reactive nanoparticles can enhance the efficiency of cargo delivery into specific cells through interactions with cell-surface proteins. However, studies to date using this technique have been largely limited to immortalized cell lines or rodents, and the utility of this technology on primary human cells is unknown. Herein, we used RAFT polymerization to prepare pyridyl disulfide (PDS)-functionalized star polymers with a methoxy-poly(ethylene glycol) brush corona and a fluorescently labeled cross-linked core using an arm-first method. PDS star polymers were examined for their interaction with primary human blood components: six separate white blood cell subsets, as well as red blood cells and platelets. Compared with control star polymers, thiol-reactive nanoparticles displayed enhanced association with white blood cells at 37 °C, particularly the phagocytic monocyte, granulocyte, and dendritic cell subsets. Platelets associated with more PDS than control nanoparticles at both 37 °C and on ice, but they were not activated in the duration examined. Association with red blood cells was minor but still enhanced with PDS nanoparticles. Thiol-reactive nanoparticles represent a useful strategy to target primary human immune cell subsets for improved nanoparticle delivery.

Biocompatible polymer coating of titania nanotube arrays for improved drug elution and osteoblast adhesion.

PubMed

Gulati, Karan; Ramakrishnan, Saminathan; Aw, Moom Sinn; Atkins, Gerald J; Findlay, David M; Losic, Dusan

2012-01-01

Bacterial infection, extensive inflammation and poor osseointegration have been identified as the major reasons for [early] orthopaedic implant failures based on titanium. Creating implants with drug-eluting properties to locally deliver drugs is an appealing way to address some of these problems. To improve properties of titanium for orthopaedic applications, this study explored the modification of titanium surfaces with titaniananotube (TNT) arrays, and approach that combines drug delivery into bone and potentially improved bone integration. A titania layer with an array of nanotube structures (∼120 nm in diameter and 50 μm in length) was synthesized on titanium surfaces by electrochemical anodization and loaded with the water-insoluble anti-inflammatory drug indomethacin. A simple dip-coating process of polymer modification formed thin biocompatible polymer films over the drug-loaded TNTs to create TNTs with predictable drug release characteristics. Two biodegradable and antibacterial polymers, chitosan and poly(lactic-co-glycolic acid), were tested for their ability to extend the drug release time of TNTs and produce favourable bone cell adhesion properties. Dependent on polymer thickness, a significant improvement in the drug release characteristics was demonstrated, with reduced burst release (from 77% to >20%) and extended overall release from 4 days to more than 30 days. Excellent osteoblast adhesion and cell proliferation on polymer-coated TNTs compared with uncoated TNTs were also observed. These results suggest that polymer-modified implants with a TNT layer are capable of delivering a drug to a bone site over an extended period and with predictable kinetics. In addition, favourable bone cell adhesion suggests that such an implant would have good biocompatibility. The described approach is broadly applicable to a wide range of drugs and implants currently used in orthopaedic practice. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

A study of water electrolysis using ionic polymer-metal composite for solar energy storage

NASA Astrophysics Data System (ADS)

Keow, Alicia; Chen, Zheng

2017-04-01

Hydrogen gas can be harvested via the electrolysis of water. The gas is then fed into a proton exchange membrane fuel cell (PEMFC) to produce electricity with clean emission. Ionic polymer-metal composite (IPMC), which is made from electroplating a proton-conductive polymer film called Nafion encourages ion migration and dissociation of water under application of external voltage. This property has been proven to be able to act as catalyst for the electrolysis of pure water. This renewable energy system is inspired by photosynthesis. By using solar panels to gather sunlight as the source of energy, the generation of electricity required to activate the IPMC electrolyser is acquired. The hydrogen gas is collected as storable fuel and can be converted back into energy using a commercial fuel cell. The goal of this research is to create a round-trip energy efficient system which can harvest solar energy, store them in the form of hydrogen gas and convert the stored hydrogen back to electricity through the use of fuel cell with minimal overall losses. The effect of increasing the surface area of contact is explored through etching of the polymer electrolyte membrane (PEM) with argon plasma or manually sanding the surface and how it affects the increase of energy conversion efficiency of the electrolyser. In addition, the relationship between temperature and the IPMC is studied. Experimental results demonstrated that increases in temperature of water and changes in surface area contact correlate with gas generation.

Poly(2-oxazoline) hydrogels as next generation three-dimensional cell supports

PubMed Central

Dargaville, Tim R; Hollier, Brett G; Shokoohmand, Ali; Hoogenboom, Richard

2014-01-01

Synthetic hydrogels selectively decorated with cell adhesion motifs are rapidly emerging as promising substrates for 3D cell culture. When cells are grown in 3D they experience potentially more physiologically relevant cell–cell interactions and physical cues compared with traditional 2D cell culture on stiff surfaces. A newly developed polymer based on poly(2-oxazoline)s has been used for the first time to control attachment of fibroblast cells and is discussed here for its potential use in 3D cell culture with particular focus on cancer cells toward the ultimate aim of high-throughput screening of anticancer therapies. Advantages and limitations of using poly(2-oxazoline) hydrogels are discussed and compared with more established polymers, especially polyethylene glycol (PEG). PMID:24714592

Electrode assembly for use in a solid polymer electrolyte fuel cell

DOEpatents

Raistrick, Ian D.

1989-01-01

A gas reaction fuel cell may be provided with a solid polymer electrolyte membrane. Porous gas diffusion electrodes are formed of carbon particles supporting a catalyst which is effective to enhance the gas reactions. The carbon particles define interstitial spaces exposing the catalyst on a large surface area of the carbon particles. A proton conducting material, such as a perfluorocarbon copolymer or ruthenium dioxide contacts the surface areas of the carbon particles adjacent the interstitial spaces. The proton conducting material enables protons produced by the gas reactions adjacent the supported catalyst to have a conductive path with the electrolyte membrane. The carbon particles provide a conductive path for electrons. A suitable electrode may be formed by dispersing a solution containing a proton conducting material over the surface of the electrode in a manner effective to coat carbon surfaces adjacent the interstitial spaces without impeding gas flow into the interstitial spaces.

Surface derivatization strategy for combinatorial analysis of cell response to mixtures of protein domains.

PubMed

Chiang, Chunyi; Karuri, Stella W; Kshatriya, Pradnya P; Schwartz, Jeffrey; Schwarzbauer, Jean E; Karuri, Nancy W

2012-01-10

We report a robust strategy for conjugating mixtures of two or more protein domains to nonfouling polyurethane surfaces. In our strategy, the carbamate groups of polyurethane are reacted with zirconium alkoxide from the vapor phase to give a surface-bound oxide that serves as a chemical layer that can be used to bond organics to the polymer substrate. A hydroxyalkylphosphonate monolayer was synthesized on this layer, which was then used to covalently bind primary amine groups in protein domains using chloroformate-derived cross-linking. The effectiveness of this synthesis strategy was gauged by using an ELISA to measure competitive, covalent bonding of cell-binding (III(9-10)) and fibronectin-binding (III(1-2)) domains of the cell adhesion protein fibronectin. Cell adhesion, spreading, and fibronectin matrix assembly were examined on surfaces conjugated with single domains, a 1:1 surface mixture of III(1-2) and III(9-10), and a recombinant protein "duplex" containing both domains in one fusion protein. The mixture performed as well as or better than the other surfaces in these assays. Our surface activation strategy is amenable to a wide range of polymer substrates and free amino group-containing protein fragments. As such, this technique may be used to create biologically specific materials through the immobilization of specific protein groups or mixtures thereof on a substrate surface.

Improved hybrid solar cells via in situ UV-polymerization.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tepavcevic, S.; Darling, S. B.; Dimitrijevic, N. M.

One approach for making inexpensive inorganic-organic hybrid photovoltaic (PV) cells is to fill highly ordered TiO{sub 2} nanotube (NT) arrays with solid organic hole conductors such as conjugated polymers. Here, a new in situ UV polymerization method for growing polythiophene (UV-PT) inside TiO{sub 2} NTs is presented and compared to the conventional approach of infiltrating NTs with pre-synthesized polymer. A nanotubular TiO{sub 2} substrate is immersed in a 2,5-diiodothiophene (DIT) monomer precursor solution and then irradiated with UV light. The selective UV photodissociation of the C-I bond produces monomer radicals with intact {pi}-ring structure that further produce longer oligothiophene/PT molecules.more » Complete photoluminescence quenching upon UV irradiation suggests coupling between radicals created from DIT and at the TiO{sub 2} surface via a charge transfer complex. Coupling with the TiO{sub 2} surface improves UV-PT crystallinity and {pi}-{pi} stacking; flat photocurrent values show that charge recombination during hole transport through the polymer is negligible. A non-ideal, backside-illuminated setup under illumination of 620-nm light yields a photocurrent density of {approx} 5 {micro}A cm{sup -2} - surprisingly much stronger than with comparable devices fabricated with polymer synthesized ex situ. Since in this backside architecture setup we illuminate the cell through the Ag top electrode, there is a possibility for Ag plasmon-enhanced solar energy conversion. By using this simple in situ UV polymerization method that couples the conjugated polymer to the TiO{sub 2} surface, the absorption of sunlight can be improved and the charge carrier mobility of the photoactive layer can be enhanced.« less

Ultrathin Polymer Films, Patterned Arrays, and Microwells

NASA Astrophysics Data System (ADS)

Yan, Mingdi

2002-05-01

The ability to control and tailor the surface and interface properties of materials is important in microelectronics, cell growth control, and lab-on-a-chip devices. Modification of material surfaces with ultrathin polymer films is attractive due to the availability of a variety of polymers either commercially or by synthesis. We have developed two approaches to the attachment of ultrathin polymer films on solid substrates. In the first method, a silane-functionalized perfluorophenyl azide (PFPA-silane) was synthesized and used to covalently immobilize polymer thin films on silicon wafers. Silanization of the wafer surface with the PFPA-silane introduced a monolayer of azido groups which in turn covalently attached the polymer film by way of photochemically initiated insertion reactions. The thickness of the film could be adjusted by the type and the molecular weight of the polymer. The method is versatile due to the general C-H and/or N-H insertion reactions of crosslinker; and therefore, no specific reactive functional groups on the polymers are required. Using this method, a new type of microwell array was fabricated from covalently immobilized polymer thin films on flat substrates. The arrays were characterized with AFM, XPS, and TOF-SIMS. The second method describes the attachment of polymer thin films on solid substrates via UV irradiation. The procedure consisted of spin-coating a polymer film and irradiating the film with UV light. Following solvent extraction, a thin film remained. The thickness of the film, from a few to over a hundred nanometers, was controlled by varying solution concentration and the molecular weight of the polymer.

Hyaluronic Acid-Based pH-Sensitive Polymer-Modified Liposomes for Cell-Specific Intracellular Drug Delivery Systems.

PubMed

Miyazaki, Maiko; Yuba, Eiji; Hayashi, Hiroshi; Harada, Atsushi; Kono, Kenji

2018-01-17

For the enhancement of therapeutic effects and reduction of side effects derived from anticancer drugs in cancer chemotherapy, it is imperative to develop drug delivery systems with cancer-specificity and controlled release function inside cancer cells. pH-sensitive liposomes are useful as an intracellular drug delivery system because of their abilities to transfer their contents into the cell interior through fusion or destabilization of endosome, which has weakly acidic environment. We earlier reported liposomes modified with various types of pH-sensitive polymers based on synthetic polymers and biopolymers as vehicles for intracellular drug delivery systems. In this study, hyaluronic acid (HA)-based pH-sensitive polymers were designed as multifunctional polymers having not only pH-sensitivity but also targeting properties to cells expressing CD44, which is known as a cancer cell surface marker. Carboxyl group-introduced HA derivatives of two types, MGlu-HA and CHex-HA, which have a more hydrophobic side chain structure than that of MGlu-HA, were synthesized by reaction with various dicarboxylic anhydrides. These polymer-modified liposomes were stable at neutral pH, but showed content release under weakly acidic conditions. CHex-HA-modified liposomes delivered their contents into CD44-expressing cells more efficiently than HA-modified or MGlu-HA-modified liposomes or unmodified liposomes, whereas the same liposomes were taken up only slightly by cells expressing CD44 proteins less. Competition assay using free HA or other polymers revealed that HA derivative-modified liposomes might be recognized by CD44. Therefore, HA-derivative-modified liposomes are useful as cell-specific intracellular drug delivery systems.

A functionalized poly(ethylene glycol)-based bioassay surface chemistry that facilitates bio-immobilization and inhibits non-specific protein, bacterial, and mammalian cell adhesion

PubMed Central

Harbers, Gregory M.; Emoto, Kazunori; Greef, Charles; Metzger, Steven W.; Woodward, Heather N.; Mascali, James J.; Grainger, David W.; Lochhead, Michael J.

2008-01-01

This paper describes a new bioassay surface chemistry that effectively inhibits non-specific biomolecular and cell binding interactions, while providing a capacity for specific immobilization of desired biomolecules. Poly(ethylene glycol) (PEG) as the primary component in nonfouling film chemistry is well-established, but the multicomponent formulation described here is unique in that it (1) is applied in a single, reproducible, solution-based coating step; (2) can be applied to diverse substrate materials without the use of special primers; and (3) is readily functionalized to provide specific attachment chemistries. Surface analysis data are presented, detailing surface roughness, polymer film thickness, and film chemistry. Protein non-specific binding assays demonstrate significant inhibition of serum, fibrinogen, and lysozyme adsorption to coated glass, indium tin oxide, and tissue culture polystyrene dishes. Inhibition of S. aureus and K. pneumoniae microbial adhesion in a microfluidic flow cell, and inhibition of fibroblast cell adhesion from serum-based cell culture is shown. Effective functionalization of the coating is demonstrated by directing fibroblast adhesion to polymer surfaces activated with an RGD peptide. Batch-to-batch reproducibility data are included. The in situ cross-linked PEG-based coating chemistry is unique in its formulation, and its surface properties are attractive for a broad range of in vitro bioassay applications. PMID:18815622

Smart Polymers with Special Wettability.

PubMed

Chang, Baisong; Zhang, Bei; Sun, Taolei

2017-01-01

Surface wettability plays a key role in addressing issues ranging from basic life activities to our daily life, and thus being able to control it is an attractive goal. Learning from nature, both of its structure and function, brings us much inspiration in designing smart polymers to tackle this major challenge. Life functions particularly depend on biomolecular recognition-induced interfacial properties from the aqueous phase onto either "soft" cell and tissue or "hard" inorganic bone and tooth surfaces. The driving force is noncovalent weak interactions rather than strong covalent combinations. An overview is provided of the weak interactions that perform vital actions in mediating biological processes, which serve as a basis for elaborating multi-component polymers with special wettabilities. The role of smart polymers from molecular recognitions to macroscopic properties are highlighted. The rationale is that highly selective weak interactions are capable of creating a dynamic synergetic communication in the building components of polymers. Biomolecules could selectively induce conformational transitions of polymer chains, and then drive a switching of physicochemical properties, e.g., roughness, stiffness and compositions, which are an integrated embodiment of macroscopic surface wettabilities. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dewetting Based Fabrication of Fibrous Micro-Scaffolds as Potential Injectable Cell Carriers

PubMed Central

Song, Hokyung; Yin, Liya; Chilian, William M.; Newby, Bi-min Zhang

2014-01-01

Although regenerative medicine utilizing tissue scaffolds has made enormous strides in recent years, many constraints still hamper their effectiveness. A limitation of many scaffolds is that they form surface patches, which are not particularly effective for some types of “wounds” that are deep within tissues, e.g., stroke, myocardial infarction. In this study, we reported the generation of fibrous micro-scaffolds feasible for delivering cells by injection into the tissue parenchyma. The micro-scaffolds (widths < 100 μm) were made by dewetting of poly (lactic-coglycolic acid) thin films containing parallel strips, and cells were seeded to form cell/polymer micro-constructs during or post the micro-scaffold fabrication process. Five types of cells including rat induced vascular progenitor cells were assessed for the formation of the micro-constructs. Critical factors in forming fibrous micro-scaffolds via dewetting of polymer thin films were found to be properties of polymers and supporting substrates, temperature, and proteins in the culture medium. Also, the ability of cells to attach to the micro-scaffolds was essential for forming cell/polymer micro-constructs. Both in vitro and in vivo assessments of injecting these micro-scaffolding constructs showed, as compared to free cells, enhanced cell retention at the injected site, which could lead to improved tissue engineering and regeneration. PMID:25579969

One pot electrochemical synthesis of polymer/CNT/metal nanoparticles for fuel cell applications

NASA Astrophysics Data System (ADS)

Ventrapragada, Lakshman; Zhu, Jingyi; Karakaya, Mehmet; Podila, Ramakrishna; Rao, Apparao; Clemson Nanomaterials center Team

Carbon nanotubes (CNTs) have become a key player in the design of materials for energy applications. They gained their popularity in industrial and scientific research due to their unique properties like excellent conductivity, high surface area, etc. Here we used chemical vapor deposition (CVD) to synthesize two types of CNTs namely, helically coiled CNTs and vertically aligned CNTs. These CNTs were subsequently used to make composites with conducting polymers and metal nanoparticles. One pot electrochemical synthesis was designed to electropolymerize aniline, pyrrole etc. on the surface of the electrode with simultaneous deposition of platinum and gold metal nanoparticles, and CNTs in the polymer matrix. The as synthesized composite materials were characterized with scanning electron microscope for surface morphology and spectroscopic techniques like Raman, UV-Vis for functionality. These were used to study electrocatalytic oxidation of methanol and ethanol for alkaline fuel cell applications. Electrodes fabricated from these composites not only showed good kinetics but also exhibited excellent stability. Uniqueness of this composite lies in its simple two step synthesis and it doesn't involve any surfactants unlike conventional chemical synthesis routes.

Biomaterials functionalization using a novel peptide that selectively binds to a conducting polymer

NASA Astrophysics Data System (ADS)

Sanghvi, Archit B.; Miller, Kiley P.-H.; Belcher, Angela M.; Schmidt, Christine E.

2005-06-01

The goal in biomaterial surface modification is to retain a material's bulk properties while modifying only its surface to possess desired recognition and specificity. Here we develop a unique strategy for surface functionalization of an electrically conductive polymer, chlorine-doped polypyrrole (PPyCl), which has been widely researched for various electronic and biomedical applications. An M13 bacteriophage library was used to screen 109 different 12-mer peptide inserts against PPyCl. A binding phage (ϕT59) was isolated, and its binding stability and specificity to PPyCl was assessed using fluorescence microscopy and titer count analysis. The relative binding strength and mechanism of the corresponding 12-mer peptide and its variants was studied using atomic force microscopy and fluorescamine assays. Further, the T59 peptide was joined to a cell adhesive sequence and used to promote cell attachment on PPyCl. This strategy can be extended to immobilize a variety of molecules to PPyCl for numerous applications. In addition, phage display can be applied to other polymers to develop bioactive materials without altering their bulk properties.

Artificial membrane-binding proteins stimulate oxygenation of stem cells during engineering of large cartilage tissue

NASA Astrophysics Data System (ADS)

Armstrong, James P. K.; Shakur, Rameen; Horne, Joseph P.; Dickinson, Sally C.; Armstrong, Craig T.; Lau, Katherine; Kadiwala, Juned; Lowe, Robert; Seddon, Annela; Mann, Stephen; Anderson, J. L. Ross; Perriman, Adam W.; Hollander, Anthony P.

2015-06-01

Restricted oxygen diffusion can result in central cell necrosis in engineered tissue, a problem that is exacerbated when engineering large tissue constructs for clinical application. Here we show that pre-treating human mesenchymal stem cells (hMSCs) with synthetic membrane-active myoglobin-polymer-surfactant complexes can provide a reservoir of oxygen capable of alleviating necrosis at the centre of hyaline cartilage. This is achieved through the development of a new cell functionalization methodology based on polymer-surfactant conjugation, which allows the delivery of functional proteins to the hMSC membrane. This new approach circumvents the need for cell surface engineering using protein chimerization or genetic transfection, and we demonstrate that the surface-modified hMSCs retain their ability to proliferate and to undergo multilineage differentiation. The functionalization technology is facile, versatile and non-disruptive, and in addition to tissue oxygenation, it should have far-reaching application in a host of tissue engineering and cell-based therapies.

Improved mucoadhesion and cell uptake of chitosan and chitosan oligosaccharide surface-modified polymer nanoparticles for mucosal delivery of proteins.

PubMed

Dyawanapelly, Sathish; Koli, Uday; Dharamdasani, Vimisha; Jain, Ratnesh; Dandekar, Prajakta

2016-08-01

The main aim of the present study was to compare mucoadhesion and cellular uptake efficiency of chitosan (CS) and chitosan oligosaccharide (COS) surface-modified polymer nanoparticles (NPs) for mucosal delivery of proteins. We have developed poly (D, L-lactide-co-glycolide) (PLGA) NPs, surface-modified COS-PLGA NPs and CS-PLGA NPs, by using double emulsion solvent evaporation method, for encapsulating bovine serum albumin (BSA) as a model protein. Surface modification of NPs was confirmed using physicochemical characterization methods such as particle size and zeta potential, SEM, TEM and FTIR analysis. Both surface-modified PLGA NPs displayed a slow release of protein compared to PLGA NPs. Furthermore, we have explored the mucoadhesive property of COS as a material for modifying the surface of polymeric NPs. During in vitro mucoadhesion test, positively charged COS-PLGA NPs and CS-PLGA NPs exhibited enhanced mucoadhesion, compared to negatively charged PLGA NPs. This interaction was anticipated to improve the cell interaction and uptake of NPs, which is an important requirement for mucosal delivery of proteins. All nanoformulations were found to be safe for cellular delivery when evaluated in A549 cells. Moreover, intracellular uptake behaviour of FITC-BSA loaded NPs was extensively investigated by confocal laser scanning microscopy and flow cytometry. As we hypothesized, positively charged COS-PLGA NPs and CS-PLGA NPs displayed enhanced intracellular uptake compared to negatively charged PLGA NPs. Our results demonstrated that CS- and COS-modified polymer NPs could be promising carriers for proteins, drugs and nucleic acids via nasal, oral, buccal, ocular and vaginal mucosal routes.

Physical properties and biocompatibility of UHMWPE-derived materials modified by synchrotron radiation.

PubMed

Bykova, Iu; Weinhardt, V; Kashkarova, A; Lebedev, S; Baumbach, T; Pichugin, V; Zaitsev, K; Khlusov, I

2014-08-01

The applications of synchrotron radiation (SR) in medical imaging have become of great use, particularly in angiography, bronchography, mammography, computed tomography, and X-ray microscopy. Thanks to recently developed phase contrast imaging techniques non-destructive preclinical testing of low absorbing materials such as polymers has become possible. The focus of the present work is characterization and examination of UHMWPE-derived materials widely used in medicine, before and after their exposure to SR during such testing. Physical properties, such as wettability, surface energy, IR-spectroscopy, roughness, optical microscopy, microhardness measurements of UHMWPE samples were studied before and after SR. The relationship between a growth of UHMWPE surface hydrophilicity after SR and surface colonization by stromal cells was studied in vitro. Obtained results demonstrate that SR may be used as prospective direction to examine bulk (porous) structure of polymer materials and/or to modify polymer surface and volume for tissue engineering.

New strategy for design and fabrication of polymer hydrogel with tunable porosity as artificial corneal skirt.

PubMed

Cao, Danfeng; Zhang, Yingchao; Cui, Zhanchen; Du, Yuanyuan; Shi, Zuosen

2017-01-01

In order to obtain an ideal material using for artificial corneal skirt, a porous polymer hydrogel containing 2-hydroxyethyl methacrylate (HEMA), trimethylolpropane triacrylate (TMPTA) and butyl acrylate was prepared through one-step radical polymerization method and the usage of CaCO 3 whisker as porogen. The physical-chemical properties of the fabricated polymer hydrogel can be adjusted by CaCO 3 whisker content, such as pore size, porosity, water content of materials and surface topography. Then a series of cell biology experiments of human corneal fibroblasts (HCFs) were carried out to evaluate its properties as an artificial corneal skirt, such as the adhesion of cells on the materials with different pore size and porosity, the apoptosis on materials with different characteristics, the distribution of the cells on the material surface. The results revealed that high porosity not only could improve water content of hydrogel, but also strengthen the adhesion of HCFs on hydrogel. In addition, high porosity hydrogel with the whisker shape of pores showed much elongate spindle-like morphology than those low porosity hydrogels. MTT assay certified that the resulted polymer hydrogel material possessed excellent biocompatibility and was suitable for HCFs growing, making it promising for being developed as artificial corneal skirt. Copyright © 2016 Elsevier B.V. All rights reserved.

Design and development of low cost polyurethane biopolymer based on castor oil and glycerol for biomedical applications.

PubMed

Tan, A C W; Polo-Cambronell, B J; Provaggi, E; Ardila-Suárez, C; Ramirez-Caballero, G E; Baldovino-Medrano, V G; Kalaskar, D M

2018-02-01

In the current study, we present the synthesis of novel low cost bio-polyurethane compositions with variable mechanical properties based on castor oil and glycerol for biomedical applications. A detailed investigation of the physicochemical properties of the polymer was carried out by using mechanical testing, ATR-FTIR, and X-ray photoelectron spectroscopy (XPS). Polymers were also tested in short term in-vitro cell culture with human mesenchymal stem cells to evaluate their biocompatibility for potential applications as biomaterial. FTIR analysis confirmed the synthesis of castor oil and glycerol based PU polymers. FTIR also showed that the addition of glycerol as co-polyol increases crosslinking within the polymer backbone hence enhancing the bulk mechanical properties of the polymer. XPS data showed that glycerol incorporation leads to an enrichment of oxidized organic species on the surface of the polymers. Preliminary investigation into in vitro biocompatibility showed that serum protein adsorption can be controlled by varying the glycerol content with polymer backbone. An alamar blue assay looking at the metabolic activity of the cells indicated that castor oil based PU and its variants containing glycerol are non-toxic to the cells. This study opens an avenue for using low cost bio-polyurethane based on castor oil and glycerol for biomedical applications. © 2017 The Authors Biopolymers Published by Wiley Periodicals, Inc.

A hydrophilic polymer based microfluidic system with planar patch clamp electrode array for electrophysiological measurement from cells.

PubMed

Xu, Baojian; Ye, WeiWei; Zhang, Yu; Shi, JingYu; Chan, ChunYu; Yao, XiaoQiang; Yang, Mo

2014-03-15

This paper presents a microfluidic planar patch clamp system based on a hydrophilic polymer poly(ethylene glycol) diacrylate (PEGDA) for whole cell current recording. The whole chip is fabricated by UV-assisted molding method for both microfluidic channel structure and planar electrode partition. This hydrophilic patch clamp chip has demonstrated a relatively high gigaseal success rate of 44% without surface modification compared with PDMS based patch clamp devices. This chip also shows a capability of rapid intracellular and extracellular solution exchange with high stability of gigaseals. The capillary flow kinetic experiments demonstrate that the flow rates of PEGDA microfluidic channels are around two orders of magnitude greater than those for PDMS-glass channels with the same channel dimensions. This hydrophilic polymer based patch clamp chips have significant advantages over current PDMS elastomer based systems such as no need for surface modification, much higher success rate of cell gigaseals and rapid solution exchange with stable cell gigaseals. Our results indicate the potential of these devices to serve as useful tools for pharmaceutical screening and biosensing tasks. © 2013 Elsevier B.V. All rights reserved.

Polyethyleneimine Coating Enhances the Cellular Uptake of Mesoporous Silica Nanoparticles and Allows Safe Delivery of siRNA and DNA Constructs

PubMed Central

Xia, Tian; Kovochich, Michael; Liong, Monty; Meng, Huan; Kabehie, Sanaz; Zink, Jeffrey I.; Nel, Andre E.

2014-01-01

Surface-functionalized mesoporous silica nanoparticles (MSNP) can be used as an efficient and safe carrier for bioactive molecules. In order to make the MSNP a more efficient delivery system, we modified the surface of the particles by a functional group that enhances cellular uptake and allows nucleic acid delivery in addition to traditional drug delivery. Non-covalent attachment of polyethyleneimine (PEI) polymers to the surface not only increases MSNP cellular uptake, but also generates a cationic surface to which DNA and siRNA constructs could be attached. While efficient for intracellular delivery of these nucleic acids, the 25 KD PEI polymer unfortunately changes the safety profile of the MSNP that is otherwise very safe. By experimenting with several different polymer molecular weights, it was possible to retain high cellular uptake and transfection efficiency while reducing or even eliminating cationic MSNP cytotoxicity. The particles coated with the 10 KD PEI polymer was particularly efficient for transducing HEPA-1 cells with a siRNA construct that was capable of knocking down GFP expression. Similarly, transfection of a GFP plasmid induced effective expression of the fluorescent protein in > 70% cells in the population. These outcomes were quantitatively assessed by confocal microscopy and flow cytometry. We also demonstrated that the enhanced cellular uptake of the non-toxic cationic MSNP enhance the delivery of the hydrophobic anticancer drug, paclitaxel, to pancreatic cancer cells. In summary, we demonstrate that by a careful selection of PEI size, it is possible to construct cationic MSNP that are capable of nucleotide and enhanced drug delivery with minimal or no cytotoxicity. This novel use of a cationic MSNP extends its therapeutic use potential. PMID:19739605

PPV-Based Conjugated Polymer Nanoparticles as a Versatile Bioimaging Probe: A Closer Look at the Inherent Optical Properties and Nanoparticle-Cell Interactions.

PubMed

Peters, Martijn; Zaquen, Neomy; D'Olieslaeger, Lien; Bové, Hannelore; Vanderzande, Dirk; Hellings, Niels; Junkers, Thomas; Ethirajan, Anitha

2016-08-08

Conjugated polymers have attracted significant interest in the bioimaging field due to their excellent optical properties and biocompatibility. Tailor-made poly(p-phenylenevinylene) (PPV) conjugated polymer nanoparticles (NPs) are in here described. Two different nanoparticle systems using poly[2-methoxy-5-(3',7'-dimethoxyoctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and a functional statistical copolymer 2-(5'-methoxycarbonylpentyloxy)-5-methoxy-1,4-phenylenevinylene (CPM-MDMO-PPV), containing ester groups on the alkoxy side chains, were synthesized by combining miniemulsion and solvent evaporation processes. The hydrolysis of ester groups into carboxylic acid groups on the CPM-MDMO-PPV NPs surface allows for biomolecule conjugation. The NPs exhibited excellent optical properties with a high fluorescent brightness and photostability. The NPs were in vitro tested as potential fluorescent nanoprobes for studying cell populations within the central nervous system. The cell studies demonstrated biocompatibility and surface charge dependent cellular uptake of the NPs. This study highlights that PPV-derivative based particles are a promising bioimaging probe and can cater potential applications in the field of nanomedicine.

The Influence of Chain Microstructure of Biodegradable Copolyesters Obtained with Low-Toxic Zirconium Initiator to In Vitro Biocompatibility

PubMed Central

Orchel, Arkadiusz; Kasperczyk, Janusz; Marcinkowski, Andrzej; Pamula, Elzbieta; Orchel, Joanna; Bielecki, Ireneusz

2013-01-01

Because of the wide use of biodegradable materials in tissue engineering, it is necessary to obtain biocompatible polymers with different mechanical and physical properties as well as degradation ratio. Novel co- and terpolymers of various composition and chain microstructure have been developed and applied for cell culture. The aim of this study was to evaluate the adhesion and proliferation of human chondrocytes to four biodegradable copolymers: lactide-coglycolide, lactide-co-ε-caprolactone, lactide-co-trimethylene carbonate, glycolide-co-ε-caprolactone, and one terpolymer glycolide-colactide-co-ε-caprolactone synthesized with the use of zirconium acetylacetonate as a nontoxic initiator. Chain microstructure of the copolymers was analyzed by means of 1H and 13C NMR spectroscopy and surface properties by AFM technique. Cell adhesion and proliferation were determined by CyQUANT Cell Proliferation Assay Kit. After 4 h the chondrocyte adhesion on the surface of studied materials was comparable to standard TCPS. Cell proliferation occurred on all the substrates; however, among the studied polymers poly(L-lactide-coglycolide) 85 : 15 that characterized the most blocky structure best supported cell growth. Chondrocytes retained the cell membrane integrity evaluated by the LDH release assay. As can be summarized from the results of the study, all the studied polymers are well tolerated by the cells that make them appropriate for human chondrocytes growth. PMID:24062998

Probing the structural dependence of carbon space lengths of poly(N-hydroxyalkyl acrylamide)-based brushes on antifouling performance.

PubMed

Yang, Jintao; Zhang, Mingzhen; Chen, Hong; Chang, Yung; Chen, Zhan; Zheng, Jie

2014-08-11

Numerous biocompatible antifouling polymers have been developed for a wide variety of fundamental and practical applications in drug delivery, biosensors, marine coatings, and many other areas. Several antifouling mechanisms have been proposed, but the exact relationship among molecular structure, surface hydration property, and antifouling performance of antifouling polymers still remains elusive. Here this work strives to provide a better understanding of the structure-property relationship of poly(N-hydroxyalkyl acrylamide)-based materials. We have designed, synthesized, and characterized a series of polyHAAA brushes of various carbon spacer lengths (CSLs), that is, poly(N-hydroxymethyl acrylamide) (polyHMAA), poly(N-(2-hydroxyethyl)acrylamide) (polyHEAA), poly(N-(3-hydroxypropyl)acrylamide) (polyHPAA), and poly(N-(5-hydroxypentyl)acrylamide) (polyHPenAA), to study the structural dependence of CSLs on their antifouling performance. HMAA, HEAA, HPAA, and HPenAA monomers contained one, two, three, and five methylene groups between hydroxyl and amide groups, while the other groups in polymer backbones were the same as each other. The relation of such small structural differences of polymer brushes to their surface hydration and antifouling performance was studied by combined experimental and computational methods including surface plasmon resonance sensors, sum frequency generation (SFG) vibrational spectroscopy, cell adhesion assay, and molecular simulations. Antifouling results showed that all polyHAAA-based brushes were highly surface resistant to protein adsorption from single protein solutions, undiluted blood serum and plasma, as well as cell adhesion up to 7 days. In particular, polyHMAA and polyHEAA with the shorter CSLs exhibited higher surface hydration and better antifouling ability than polyHPMA and polyHPenAA. SFG and molecular simulations further revealed that the variation of CSLs changed the ratio of hydrophobicity/hydrophilicity of polymers, resulting in different hydration characteristics. Among them, polyHMAA and polyHEAA with the shorter CSLs showed the highest potency for surface hydration and antifouling abilities, while polyHPenAA showed the lowest potency. The combination of both hydroxyl and amide groups in the same polymer chain provides a promising structural motif for the design of new effective antifouling materials.

Thermal Spraying of Bioactive Polymer Coatings for Orthopaedic Applications

NASA Astrophysics Data System (ADS)

Chebbi, A.; Stokes, J.

2012-06-01

Flame sprayed biocompatible polymer coatings, made of biodegradable and non-biodegradable polymers, were investigated as single coatings on titanium and as top coatings on plasma sprayed Hydroxyapatite. Biocompatible polymers can act as drug carriers for localized drug release following implantation. The polymer matrix consisted of a biodegradable polymer, polyhydroxybutyrate 98%/ polyhydroxyvalerate 2% (PHBV) and a non-biodegradable polymer, polymethylmethacrylate (PMMA). Screening tests were performed to determine the suitable range of spraying parameters, followed by a Design of Experiments study to determine the effects of spraying parameters on coating characteristics (thickness, roughness, adhesion, wettability), and to optimize the coating properties accordingly. Coatings characterization showed that optimized flame sprayed biocompatible polymers underwent little chemical degradation, did not produce acidic by-products in vitro, and that cells proliferated well on their surface.

Plasma treatment induces internal surface modifications of electrospun poly(L-lactic) acid scaffold to enhance protein coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin Seo, Hyok; Hee Lee, Mi; Kwon, Byeong-Ju

2013-08-21

Advanced biomaterials should also be bioactive with regard to desirable cellular responses, such as selective protein adsorption and cell attachment, proliferation, and differentiation. To enhance cell-material interactions, surface modifications have commonly been performed. Among the various surface modification approaches, atmospheric pressure glow discharge plasma has been used to change a hydrophobic polymer surface to a hydrophilic surface. Poly(L-lactic acid) (PLLA)-derived scaffolds lack cell recognition signals and the hydrophobic nature of PLLA hinders cell seeding. To make PLLA surfaces more conducive to cell attachment and spreading, surface modifications may be used to create cell-biomaterial interfaces that elicit controlled cell adhesion andmore » maintain differentiated phenotypes. In this study, (He) gaseous atmospheric plasma glow discharge was used to change the characteristics of a 3D-type polymeric scaffold from hydrophobic to hydrophilic on both the outer and inner surfaces of the scaffold and the penetration efficiency with fibronectin was investigated. Field-emission scanning electron microscope images showed that some grooves were formed on the PLLA fibers after plasma treatment. X-ray photoelectron spectroscopy data also showed chemical changes in the PLLA structure. After plasma treatment, -CN (285.76 eV) was increased in C1s and -NH{sub 2} (399.70 eV) was increased significantly and –N=CH (400.80 eV) and –NH{sub 3}{sup +} (402.05 eV) were newly appeared in N1s. These changes allowed fibronectin to penetrate into the PLLA scaffold; this could be observed by confocal microscopy. In conclusion, helium atmospheric pressure plasma treatment was effective in modifying the polymeric scaffold, making it hydrophilic, and this treatment can also be used in tissue engineering research as needed to make polymers hydrophilic.« less

Surface tailoring of newly developed amorphous Znsbnd Sisbnd O thin films as electron injection/transport layer by plasma treatment: Application to inverted OLEDs and hybrid solar cells

NASA Astrophysics Data System (ADS)

Yang, Hongsheng; Kim, Junghwan; Yamamoto, Koji; Xing, Xing; Hosono, Hideo

2018-03-01

We report a unique amorphous oxide semiconductor Znsbnd Sisbnd O (a-ZSO) which has a small work function of 3.4 eV for as-deposited films. The surface modification of a-ZSO thin films by plasma treatments is examined to apply it to the electron injection/transport layer of organic devices. It turns out that the energy alignment and exciton dissociation efficiency at a-ZSO/organic semiconductor interface significantly changes by choosing different gas (oxygen or argon) for plasma treatments (after a-ZSO was exposed to atmospheric environment for 5 days). In situ ultraviolet photoelectron spectroscopy (UPS) measurement reveals that the work function of a-ZSO is increased to 4.0 eV after an O2-plasma treatment, while the work function of 3.5 eV is recovered after an Ar-plasma treatment which indicates this treatment is effective for surface cleaning. To study the effects of surface treatments to device performance, OLEDs and hybrid polymer solar cells with O2-plasma or Ar-plasma treated a-ZSO are compared. Effects of these surface treatments on performance of inverted OLEDs and hybrid polymer solar cells are examined. Ar-plasma treated a-ZSO works well as the electron injection layer in inverted OLEDs (Alq3/a-ZSO) because the injection barrier is small (∼ 0.1 eV). On the other hands, O2-plasma treated a-ZSO is more suitable for application to hybrid solar cells which is benefiting from higher exciton dissociation efficiency at polymer (P3HT)/ZSO interface.

Charge-discharge characteristics of nickel/zinc battery with polymer hydrogel electrolyte

NASA Astrophysics Data System (ADS)

Iwakura, Chiaki; Murakami, Hiroki; Nohara, Shinji; Furukawa, Naoji; Inoue, Hiroshi

A new nickel/zinc (Ni/Zn) battery was assembled by using polymer hydrogel electrolyte prepared from cross-linked potassium poly(acrylate) and KOH aqueous solution, and its charge-discharge characteristics were investigated. The experimental Ni/Zn cell with the polymer hydrogel electrolyte exhibited well-defined charge-discharge curves and remarkably improved charge-discharge cycle performance, compared to that with a KOH aqueous solution. Moreover, it was found that dendritic growth hardly occurred on the zinc electrode surface during charge-discharge cycles in the polymer hydrogel electrolyte. These results indicate that the polymer hydrogel electrolyte can successfully be used in Ni/Zn batteries as an electrolyte with excellent performance.

Highly dynamic biodegradable micelles capable of lysing Gram-positive and Gram-negative bacterial membrane.

PubMed

Qiao, Yuan; Yang, Chuan; Coady, Daniel J; Ong, Zhan Yuin; Hedrick, James L; Yang, Yi-Yan

2012-02-01

The development of biodegradable antimicrobial polymers adds to the toolbox of attractive antimicrobial agents against antibiotic-resistant microbes. To this end, the potential of polycarbonate polymers as such materials were explored. A series of random polycarbonate polymers consisting of monomers MTC-OEt and MTC-CH(2)CH(3)Cl were designed and synthesized using metal-free organocatalytic ring-opening polymerization. Random polycarbonate polymers self-assembled in solution but appeared highly dynamic; such behaviors are desirable as ready disassembly of polymers at the microbial membrane facilitates membrane disruption. Their activities against clinically relevant Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (E.coli and Pseudomonas aeruginosa) revealed that the hydrophobic-hydrophilic composition balance in polymers are important to render antimicrobial potency. Scanning electron microscopy (SEM) studies indicated microbial cell surface damage after treatment with polymers, and confocal microscopy studies also showed entry of FITC-dextran dye in Escherichia coli as a result of membrane disruption. On the other hand, the polymers exhibited minimal toxicity against red blood cells in hemolysis tests. Therefore, these random polycarbonate polymers are promising antimicrobial agents against both Gram-positive and Gram-negative bacteria for various biomedical applications. Copyright © 2011 Elsevier Ltd. All rights reserved.

Pectin Metabolism and Assembly in the Cell Wall of the Charophyte Green Alga Penium margaritaceum1[W][OPEN

PubMed Central

Domozych, David S.; Sørensen, Iben; Popper, Zoë A.; Ochs, Julie; Andreas, Amanda; Fangel, Jonatan U.; Pielach, Anna; Sacks, Carly; Brechka, Hannah; Ruisi-Besares, Pia; Willats, William G.T.; Rose, Jocelyn K.C.

2014-01-01

The pectin polymer homogalacturonan (HG) is a major component of land plant cell walls and is especially abundant in the middle lamella. Current models suggest that HG is deposited into the wall as a highly methylesterified polymer, demethylesterified by pectin methylesterase enzymes and cross-linked by calcium ions to form a gel. However, this idea is based largely on indirect evidence and in vitro studies. We took advantage of the wall architecture of the unicellular alga Penium margaritaceum, which forms an elaborate calcium cross-linked HG-rich lattice on its cell surface, to test this model and other aspects of pectin dynamics. Studies of live cells and microscopic imaging of wall domains confirmed that the degree of methylesterification and sufficient levels of calcium are critical for lattice formation in vivo. Pectinase treatments of live cells and immunological studies suggested the presence of another class of pectin polymer, rhamnogalacturonan I, and indicated its colocalization and structural association with HG. Carbohydrate microarray analysis of the walls of P. margaritaceum, Physcomitrella patens, and Arabidopsis (Arabidopsis thaliana) further suggested the conservation of pectin organization and interpolymer associations in the walls of green plants. The individual constituent HG polymers also have a similar size and branched structure to those of embryophytes. The HG-rich lattice of P. margaritaceum, a member of the charophyte green algae, the immediate ancestors of land plants, was shown to be important for cell adhesion. Therefore, the calcium-HG gel at the cell surface may represent an early evolutionary innovation that paved the way for an adhesive middle lamella in multicellular land plants. PMID:24652345

X-Ray-Based Imaging for Characterizing Heterogeneous Gas Diffusion Layers for Polymer Electrolyte Membrane Fuel Cells

NASA Astrophysics Data System (ADS)

George, Michael G.

Characterization of gas diffusion layers (GDLs) for polymer electrolyte membrane (PEM) fuel cells informs modeling studies and the manufacturers of next generation fuel cell materials. Identifying the physical properties related to the primary functions of the modern GDL (thermal, electrical, and mass transport) is necessary for understanding the impact of GDL design choices. X-ray micro-computed tomographic reconstructions of GDLs were studied to isolate GDL surface morphologies. Surface roughness was measured for a wide variety of samples and a sensitivity study highlighted the scale-dependence of surface roughness measurements. Furthermore, a spatially resolved distribution map of polytetrafluoroethylene (PTFE) in the microporous layer (MPL), critical for water management and mass transport, was identified and the existence of PTFE agglomerations was highlighted. Finally, the impact of accelerated degradation on GDL wettability and water transport increases in liquid water accumulation and oxygen mass transport resistance were quantified as a result of accelerated GDL degradation.

Shape Memory Polymers Containing Higher Acrylate Content Display Increased Endothelial Cell Attachment

PubMed Central

Govindarajan, Tina; Shandas, Robin

2018-01-01

Shape Memory Polymers (SMPs) are smart materials that can recall their shape upon the application of a stimulus, which makes them appealing materials for a variety of applications, especially in biomedical devices. Most prior SMP research has focused on tuning bulk properties; studying surface effects of SMPs may extend the use of these materials to blood-contacting applications, such as cardiovascular stents, where surfaces that support rapid endothelialization have been correlated to stent success. Here, we evaluate endothelial attachment onto the surfaces of a family of SMPs previously developed in our group that have shown promise for biomedical devices. Nine SMP formulations containing varying amounts of tert-Butyl acrylate (tBA) and Poly(ethylene glycol) dimethacrylate (PEGDMA) were analyzed for endothelial cell attachment. Dynamic mechanical analysis (DMA), contact angle studies, and atomic force microscopy (AFM) were used to verify bulk and surface properties of the SMPs. Human umbilical vein endothelial cell (HUVEC) attachment and viability was verified using fluorescent methods. Endothelial cells preferentially attached to SMPs with higher tBA content, which have rougher, more hydrophobic surfaces. HUVECs also displayed an increased metabolic activity on these high tBA SMPs over the course of the study. This class of SMPs may be promising candidates for next generation blood-contacting devices. PMID:29707382

Imaging the Dynamics of Cell Wall Polymer Deposition in the Unicellular Model Plant, Penium margaritaceum.

PubMed

Domozych, David; Lietz, Anna; Patten, Molly; Singer, Emily; Tinaz, Berke; Raimundo, Sandra C

2017-01-01

The unicellular green alga, Penium margaritaceum, represents a novel and valuable model organism for elucidating cell wall dynamics in plants. This organism's cell wall contains several polymers that are highly similar to those found in the primary cell walls of land plants. Penium is easily grown in laboratory culture and is effectively manipulated in various experimental protocols including microplate assays and correlative microscopy. Most importantly, Penium can be live labeled with cell wall-specific antibodies or other probes and returned to culture where specific cell wall developmental events can be monitored. Additionally, live cells can be rapidly cryo-fixed and cell wall surface microarchitecture can be observed with variable pressure scanning electron microscopy. Here, we describe the methodology for maintaining Penium for experimental cell wall enzyme studies.

Plasma-deposited fluorocarbon polymer films on titanium for preventing cell adhesion: a surface finishing for temporarily used orthopaedic implants

NASA Astrophysics Data System (ADS)

Finke, B.; Testrich, H.; Rebl, H.; Walschus, U.; Schlosser, M.; Zietz, C.; Staehlke, S.; Nebe, J. B.; Weltmann, K. D.; Meichsner, J.; Polak, M.

2016-06-01

The design of a titanium implant surface should ideally support its later application in clinical use. Temporarily used implants have to fulfil requirements different from permanent implants: they should ensure the mechanical stabilization of the bone stock but in trauma surgery they should not be integrated into the bone because they will be removed after fracture healing. Finishing of the implant surface by a plasma-fluorocarbon-polymer (PFP) coating is a possible approach for preventing cell adhesion of osteoblasts. Two different low pressure gas-discharge plasma processes, microwave (MW 2.45 GHz) and capacitively coupled radio frequency (RF 13.56 MHz) plasma, were applied for the deposition of the PFP film using a mixture of the precursor octafluoropropane (C3F8) and hydrogen (H2). The thin films were characterized by x-ray photoelectron spectroscopy, Fourier transform infrared reflection absorption spectroscopy, and water contact angle measurements. Cell culture experiments show that cell adhesion and spreading of MG-63 osteoblasts were clearly reduced or nonexistent on these surfaces, also after 24 h of storage in the cell culture medium. In vivo data demonstrated that the local inflammatory tissue response for the PFP films deposited in MW and RF plasma were comparable to uncoated controls.

Novel device for continuous spatial control and temporal delivery of nitric oxide for in vitro cell culture☆

PubMed Central

Romanowicz, Genevieve E.; He, Weilue; Nielsen, Matthew; Frost, Megan C.

2013-01-01

Nitric oxide (NO) is an ubiquitous signaling molecule of intense interest in many physiological processes. Nitric oxide is a highly reactive free radical gas that is difficult to deliver with precise control over the level and timing that cells actually experience. We describe and characterize a device that allows tunable fluxes and patterns of NO to be generated across the surface upon which cells are cultured. The system is based on a quartz microscope slide that allows for controlled light levels to be applied to a previously described photosensitive NO-releasing polydimethylsiloxane (PDMS). Cells are cultured in separate wells that are either NO-releasing or a chemically similar PDMS that does not release NO. Both wells are then top coated with DowCorning RTV-3140 PDMS and a polydopamine/gelatin layer to allow cells to grow in the culture wells. When the waveguide is illuminated, the surface of the quartz slide propagates light such that the photosensitive polymer is evenly irradiated and generates NO across the surface of the cell culture well and no light penetrates into the volume of the wells where cells are growing. Mouse smooth muscle cells (MOVAS) were grown in the system in a proof of principle experiment, whereby 60% of the cells were present in the NO-releasing well compared to control wells after 17 h. The compelling advantage of illuminating the NO-releasing polymers with the waveguide system is that light can be used to tunably control NO release while avoiding exposing cells to optical radiation. This device provides means to quantitatively control the surface flux, timing and duration of NO cells experience and allows for systematic study of cellular response to NO generated at the cell/surface interface in a wide variety of studies. PMID:24024168

Characterization of biodegradable polymers irradiated with swift heavy ions

NASA Astrophysics Data System (ADS)

Salguero, N. G.; del Grosso, M. F.; Durán, H.; Peruzzo, P. J.; Amalvy, J. I.; Arbeitman, C. R.; García Bermúdez, G.

2012-02-01

In view of their application as biomaterials, there is an increasing interest in developing new methods to induce controlled cell adhesion onto polymeric materials. The critical step in all these methods involves the modification of polymer surfaces, to induce cell adhesion, without changing theirs degradation and biocompatibility properties. In this work two biodegradable polymers, polyhydroxybutyrate (PHB) and poly- L-lactide acid (PLLA) were irradiated using carbon and sulfur beams with different energies and fluences. Pristine and irradiated samples were degradated by immersion in a phosphate buffer at pH 7.0 and then characterized. The analysis after irradiation and degradation showed a decrease in the contact angle values and changes in their crystallinity properties.

Constrained ceramic-filled polymer armor

DOEpatents

Sandstrom, Donald J.; Calkins, Noel C.; Gac, Frank D.

1990-01-01

An armor system in which a plurality of constraint cells are mounted on a surface of a substrate, which is metal armor plate or a similar tough material, such that the cells almost completely cover the surface of the substrate. Each constraint cell has a projectile-receiving wall parallel to the substrate surface and has sides which are perpendicular to and surround the perimeter of the receiving wall. The cells are mounted such that, in one embodiment, the substrate surface serves as a sixth side or closure for each cell. Each cell has inside of it a plate, termed the front plate, which is parallel to and in contact with substantially all of the inside surface of the receiving wall. The balance of each cell is completely filled with a projectile-abrading material, which is a ceramic material in particulate form dispersed in a polymeric matrix.

Design Concept of Dialyzer Biomaterials: How to Find Biocompatible Polymers Based on the Biointerfacial Water Structure.

PubMed

Tanaka, Masaru

2017-01-01

Although various types of materials have been used widely in dialyzers, most biomaterials lack the desired functional properties to interface with blood and have not been engineered for optimum performance. Therefore, there is increasing demand to develop novel materials to address such problems in the dialysis arena. Numerous parameters of polymeric biomaterials can affect biocompatibility in a controlled manner. The mechanisms responsible for the biocompatibility of polymers at the molecular level have not been clearly demonstrated, although many theoretical and experimental efforts have been made to try and understand them. Moreover, water interactions have been recognized as fundamental for the blood response to contact with polymers. We have proposed the 'intermediate water' concept and hypothesized that intermediate water, which prevents the proteins and blood cells from directly contacting the polymer surface, or nonfreezing water on the polymer surface, plays an important role in the biocompatibility of polymers. This chapter provides an overview of the recent experimental progress of biocompatible polymers measured by thermal, spectroscopic, and surface force techniques. Additionally, it highlights recent developments in the use of biocompatible polymeric biomaterials for dialyzers and provides an overview of the progress made in the design of multifunctional biomedical polymers by controlling the biointerfacial water structure through precision polymer synthesis. Key Messages: Intermediate water was found only in hydrated biopolymers (proteins, polysaccharides, and nucleic acids, DNA and RNA) and hydrated biocompatible synthetic polymers. Intermediate water could be one of the main screening factors for the design of appropriate dialyzer materials. © 2017 S. Karger AG, Basel.

Human monocyte adhesion and activation on crystalline polymers with different morphology and wettability in vitro.

PubMed

Young, T H; Lin, D T; Chen, L Y

2000-06-15

This study evaluated the effects of crystalline polyamide (Nylon-66), poly(ethylene-co-vinyl alcohol) (PEVA), and poly(vinylidene fluoride) (PVDF) polymers with nonporous and porous morphologies on the ability of monocytes to adhere and subsequently activate to produce IL-1beta, IL-6, and tumor necrosis factor alpha. The results indicated monocyte adhesion and activation on a material might differ to a great extent, depending on the surface morphology and wettability. As the polymer wettability increases, the ability of monocytes to adhere increases but the ability to produce cytokines decreases. Similarly, these polymers, when prepared with porous surfaces, enhance monocyte adhesion but suppress monocyte release of cytokines. Therefore, the hydrophobic PVDF with a nonporous surface stimulates the most activity in adherent monocytes but shows the greatest inhibition of monocyte adhesion when compared with all of the other membranes. In contrast, the hydrophilic Nylon-66, which has a porous surface, is a relatively better substrate for this work. Therefore, monocyte behavior on a biomaterial may be influenced by a specific surface property. Based on this result, we propose that monocyte adhesion is regulated by a different mechanism than monocyte activation. Consequently, the generation of cytokines by monocytes is not proportional to the number of cells adherent to the surface. Copyright 2000 John Wiley & Sons, Inc.

Differential partition of virulent Aeromonas salmonicida and attenuated derivatives possessing specific cell surface alterations in polymer aqueous-phase systems

NASA Technical Reports Server (NTRS)

Van Alstine, J. M.; Trust, T. J.; Brooks, D. E.

1986-01-01

Two-polymer aqueous-phase systems in which partitioning of biological matter between the phases occurs according to surface properties such as hydrophobicity, charge, and lipid composition are used to compare the surface properties of strains of the fish pathogen Aeromonas salmonicida. The differential ability of strains to produce a surface protein array crucial to their virulence, the A layer, and to produce smooth lipopolysaccharide is found to be important in the partitioning behavior of Aeromonas salmonicida. The presence of the A layer is shown to decrease the surface hydrophilicity of the pathogen, and to increase specifically its surface affinity for fatty acid esters of polyethylene glycol. The method has application to the analysis of surface properties crucial to bacterial virulence, and to the selection of strains and mutants with specific surface characteristics.

Functionalized scaffolds to enhance tissue regeneration

PubMed Central

Guo, Baolin; Lei, Bo; Li, Peng; Ma, Peter X.

2015-01-01

Tissue engineering scaffolds play a vital role in regenerative medicine. It not only provides a temporary 3-dimensional support during tissue repair, but also regulates the cell behavior, such as cell adhesion, proliferation and differentiation. In this review, we summarize the development and trends of functional scaffolding biomaterials including electrically conducting hydrogels and nanocomposites of hydroxyapatite (HA) and bioactive glasses (BGs) with various biodegradable polymers. Furthermore, the progress on the fabrication of biomimetic nanofibrous scaffolds from conducting polymers and composites of HA and BG via electrospinning, deposition and thermally induced phase separation is discussed. Moreover, bioactive molecules and surface properties of scaffolds are very important during tissue repair. Bioactive molecule-releasing scaffolds and antimicrobial surface coatings for biomedical implants and scaffolds are also reviewed. PMID:25844177

In-vitro biocompatibility, bioactivity, and mechanical strength of PMMA-PCL polymer containing fluorapatite and graphene oxide bone cements.

PubMed

Pahlevanzadeh, F; Bakhsheshi-Rad, H R; Hamzah, E

2018-06-01

In this study, a bone cement consisting of poly methyl methacrylate (PMMA)-poly caprolactone (PCL)-fluorapatite (FA)-graphene oxide (GO) was synthesized as bone filler for application in orthopedic surgeries. The FA and GO particulates were homogenously distributed in the PMMA-PCL polymer matrix and no defects and agglomeration were found in the PMMA-PCL/FA/GO bone cement. The in-vitro bioactivity result exhibited that addition of FA and GO to the polymer cement (PMMA-PCL) improved the apatite formation ability on the surface of polymer. The results also showed that addition of FA to the polymer bone cement escalated the compressive strength and elastic modulus while reducing elongation to 8 ± 2%. However, after addition of GO into the PMMA-PCL/FA bone cement, both compressive strength and elongation considerably increased to 101 ± 5 MPa and 35 ± 6%, respectively. Furthermore, tensile tests exhibited that inclusion of GO was favorable in improving the tensile modulus, UTS and elongation of the PMMA-PCL/FA bone cement. The cytotoxicity test pointed out that MG63 osteoblast cells viability increased to 279 ± 15% after addition of FA and GO to the PMMA-PCL polymer bone cement. The DAPI (4',6-diamidino-2-phenylindole) staining demonstrated better spreading and attachment of MG63 cells on PMMA-PCL/FA/GO surface compared to the PMMA-PCL bone cements. These results confirm the suitable mechanical properties and favorable bioactivity along with high cells viability of PMMA-PCL/FA/GO bone cement, indicating its potentials for orthopedic applications. Copyright © 2018 Elsevier Ltd. All rights reserved.

The deposition of thin titanium-nitrogen coatings on the surface of PCL-based scaffolds for vascular tissue engineering

NASA Astrophysics Data System (ADS)

Kudryavtseva, Valeriya; Stankevich, Ksenia; Kibler, Elina; Golovkin, Alexey; Mishanin, Alexander; Bolbasov, Evgeny; Choynzonov, Evgeny; Tverdokhlebov, Sergei

2018-04-01

Biodegradable polymer scaffolds for tissue engineering is a promising technology for therapies of patients suffering from the loss of tissue or its function including cardiac tissues. However, limitations such as hydrophobicity of polymers prevent cell attachment, cell conductivity, and endothelialization. Plasma modification of polymers allows producing materials for an impressive range of applications due to their unique properties. Here, we demonstrate the possibility of bioresorbable electrospun polycaprolacton (PCL) scaffold surface modification by reactive magnetron sputtering of the titanium target in a nitrogen atmosphere. The influence of the plasma treatment time on the structure and properties of electrospun PCL scaffolds was studied. We show that the plasma treatment does not change the physico-mechanical properties of electrospun PCL scaffolds, leads to an increase in PCL scaffold biocompatibility, and, simultaneously, increases their hydrophilicity. In conclusion, this modification method opens a route to producing scaffolds with enhanced biocompatibility for tissue engineered vascular grafts.

Infinite Coordination Polymer Nano- and Micro-Particles

DTIC Science & Technology

2015-06-12

Mirkin, Tobin J. Marks, Joseph T. Hupp. SiO2 Aerogel-templated, Porous TiO2 Photoanodes for Enhanced Performances in Dye-Sensitized Solar Cells ...nano-scale ICPs and their selective surface functionalization, we examined if indeed these ICP-DNA hybrid structures could enter cells and...surface functionalization. In particular, we aimed to utilize this fundamental understanding for the realization of nano-scale ICP-biomolecule hybrids

Fibronectin and bovine serum albumin adsorption and conformational dynamics on inherently conducting polymers: a QCM-D study.

PubMed

Molino, Paul J; Higgins, Michael J; Innis, Peter C; Kapsa, Robert M I; Wallace, Gordon G

2012-06-05

Quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to characterize the adsorption of the model proteins, bovine serum albumin (BSA) and fibronectin (FN), to polypyrrole doped with dextran sulfate (PPy-DS) as a function of DS loading and surface roughness. BSA adsorption was greater on surfaces of increased roughness and was above what could be explained by the increase in surface area alone. Furthermore, the additional mass adsorbed on the rough films was concomitant with an increase in the rigidity of the protein layer. Analysis of the dynamic viscoelastic properties of the protein adlayer reveal BSA adsorption on the rough films occurs in two phases: (1) arrival and initial adsorption of protein to the polymer surface and (2) postadsorption molecular rearrangement to a more dehydrated and compact conformation that facilitates further recruitment of protein to the polymer interface, likely forming a multilayer. In contrast, FN adsorption was independent of surface roughness. However, films prepared from solutions containing the highest concentration of DS (20 mg/mL) demonstrated both an increase in adsorbed mass and adlayer viscoelasticity. This is attributed to the higher DS loading in the conducting polymer film resulting in presentation of a more hydrated molecular structure indicative of a more unfolded and bioactive conformation. Modulating the redox state of the PPy-DS polymers was shown to modify both the adsorbed mass and viscoelastic nature of FN adlayers. An oxidizing potential increased both the total adsorbed mass and the adlayer viscoelasticity. Our findings demonstrate that modification of polymer physicochemical and redox condition alters the nature of protein-polymer interaction, a process that may be exploited to tailor the bioactivity of protein through which interactions with cells and tissues may be controlled.

Dewetting based fabrication of fibrous micro-scaffolds as potential injectable cell carriers.

PubMed

Song, Hokyung; Yin, Liya; Chilian, William M; Zhang Newby, Bi-Min

2015-03-01

Although regenerative medicine utilizing tissue scaffolds has made enormous strides in recent years, many constraints still hamper their effectiveness. A limitation of many scaffolds is that they form surface patches, which are not particularly effective for some types of "wounds" that are deep within tissues, e.g., stroke and myocardial infarction. In this study, we reported the generation of fibrous micro-scaffolds feasible for delivering cells by injection into the tissue parenchyma. The micro-scaffolds (widths<100μm) were made by dewetting of poly(lactic-co-glycolic acid) thin films containing parallel strips, and cells were seeded to form cell/polymer micro-constructs during or post the micro-scaffold fabrication process. Five types of cells including rat induced vascular progenitor cells were assessed for the formation of the micro-constructs. Critical factors in forming fibrous micro-scaffolds via dewetting of polymer thin films were found to be properties of polymers and supporting substrates, temperature, and proteins in the culture medium. Also, the ability of cells to attach to the micro-scaffolds was essential in forming cell/polymer micro-constructs. Both in vitro and in vivo assessments of injecting these micro-scaffolding constructs showed, as compared to free cells, enhanced cell retention at the injected site, which could lead to improved tissue engineering and regeneration. Copyright © 2014 Elsevier B.V. All rights reserved.

Redox-induced surface stress of polypyrrole-based actuators.

PubMed

Tabard-Cossa, Vincent; Godin, Michel; Grütter, Peter; Burgess, Ian; Lennox, R B

2005-09-22

We measure the surface stress induced by electrochemical transformations of a thin conducting polymer film. One side of a micromechanical cantilever-based sensor is covered with an electropolymerized dodecyl benzenesulfonate-doped polypyrrole (PPyDBS) film. The microcantilever serves as both the working electrode (in a conventional three-electrode cell configuration) and as the mechanical transducer for simultaneous, in situ, and real-time measurements of the current and interfacial stress changes. A compressive change in surface stress of about -2 N/m is observed when the conducting polymer is electrochemically switched between its oxidized (PPy+) and neutral (PPy0) state by cyclic voltammetry. The surface stress sensor's response during the anomalous first reductive scan is examined. The effect of long-term cycling on the mechanical transformation ability of PPy(DBS) films in both surfactant and halide-based electrolytes is also discussed. We have identified two main competing origins of surface stress acting on the PPy(DBS)/ gold-coated microcantilever: one purely mechanical due to the volume change of the conducting polymer, and a second charge-induced, owing to the interaction of anions of the supporting electrolyte with the gold surface.

Method for nanoencapsulation of aerogels and nanoencapsulated aerogels produced by such method

NASA Technical Reports Server (NTRS)

Sullivan, Thomas A. (Inventor)

2007-01-01

A method for increasing the compressive modulus of aerogels comprising: providing aerogel substrate comprising a bubble matrix in a chamber; providing monomer to the chamber, the monomer comprising vapor phase monomer which polymerizes substantially free of polymerization byproducts; depositing monomer from the vapor phase onto the surface of the aerogel substrate under deposition conditions effective to produce a vapor pressure sufficient to cause the vapor phase monomer to penetrate into the bubble matrix and deposit onto the surface of the aerogel substrate, producing a substantially uniform monomer film; and, polymerizing the substantially uniform monomer film under polymerization conditions effective to produce polymer coated aerogel comprising a substantially uniform polymer coating substantially free of polymerization byproducts.Polymer coated aerogel comprising aerogel substrate comprising a substantially uniform polymer coating, said polymer coated aerogel comprising porosity and having a compressive modulus greater than the compressive modulus of the aerogel substrate, as measured by a 100 lb. load cell at 1 mm/minute in the linear range of 20% to 40% compression.

Usnic Acid, a Natural Antimicrobial Agent Able To Inhibit Bacterial Biofilm Formation on Polymer Surfaces

PubMed Central

Francolini, I.; Norris, P.; Piozzi, A.; Donelli, G.; Stoodley, P.

2004-01-01

In modern medicine, artificial devices are used for repair or replacement of damaged parts of the body, delivery of drugs, and monitoring the status of critically ill patients. However, artificial surfaces are often susceptible to colonization by bacteria and fungi. Once microorganisms have adhered to the surface, they can form biofilms, resulting in highly resistant local or systemic infections. At this time, the evidence suggests that (+)-usnic acid, a secondary lichen metabolite, possesses antimicrobial activity against a number of planktonic gram-positive bacteria, including Staphylococcus aureus, Enterococcus faecalis, and Enterococcus faecium. Since lichens are surface-attached communities that produce antibiotics, including usnic acid, to protect themselves from colonization by other bacteria, we hypothesized that the mode of action of usnic acid may be utilized in the control of medical biofilms. We loaded (+)-usnic acid into modified polyurethane and quantitatively assessed the capacity of (+)-usnic acid to control biofilm formation by either S. aureus or Pseudomonas aeruginosa under laminar flow conditions by using image analysis. (+)-Usnic acid-loaded polymers did not inhibit the initial attachment of S. aureus cells, but killing the attached cells resulted in the inhibition of biofilm. Interestingly, although P. aeruginosa biofilms did form on the surface of (+)-usnic acid-loaded polymer, the morphology of the biofilm was altered, possibly indicating that (+)-usnic acid interfered with signaling pathways. PMID:15504865

The effect of cationically-modified phosphorylcholine polymers on human osteoblasts in vitro and their effect on bone formation in vivo.

PubMed

Lawton, Jonathan M; Habib, Mariam; Ma, Bingkui; Brooks, Roger A; Best, Serena M; Lewis, Andrew L; Rushton, Neil; Bonfield, William

2017-08-17

The effect of introducing cationic charge into phosphorylcholine (PC)-based polymers has been investigated in this study with a view to using these materials as coatings to improve bone formation and osseointegration at the bone-implant interface. PC-based polymers, which have been used in a variety of medical devices to improve biocompatibility, are associated with low protein adsorption resulting in reduced complement activation, inflammatory response and cell adhesion. However, in some applications, such as orthopaedics, good integration between the implant and bone is needed to allow the distribution of loading stresses and a bioactive response is required. It has previously been shown that the incorporation of cationic charge into PC-based polymers may increase protein adsorption that stimulates subsequent cell adhesion. In this paper, the effect of cationic charge in PC-based polymers on human osteoblasts (HObs) in vitro and the effect of these polymers on bone formation in the rat tibia was assessed. Increasing PC positive surface charge increased HOb cell adhesion and stimulated increased cell differentiation and the production of calcium phosphate deposits. However, when implanted in bone these materials were at best biotolerant, stimulating the production of fibrous tissue and areas of loosely associated matrix (LAM) around the implant. Their development, as formulated in this study, as bone interfacing implant coatings is therefore not warranted.

Alginate/nanohydroxyapatite scaffolds with designed core/shell structures fabricated by 3D plotting and in situ mineralization for bone tissue engineering.

PubMed

Luo, Yongxiang; Lode, Anja; Wu, Chengtie; Chang, Jiang; Gelinsky, Michael

2015-04-01

Composite scaffolds, especially polymer/hydroxyapatite (HAP) composite scaffolds with predesigned structures, are promising materials for bone tissue engineering. Various methods including direct mixing of HAP powder with polymers or incubating polymer scaffolds in simulated body fluid for preparing polymer/HAP composite scaffolds are either uncontrolled or require long times of incubation. In this work, alginate/nano-HAP composite scaffolds with designed pore parameters and core/shell structures were fabricated using 3D plotting technique and in situ mineralization under mild conditions (at room temperature and without the use of any organic solvents). Light microscopy, scanning electron microscopy, microcomputer tomography, X-ray diffraction, and Fourier transform infrared spectroscopy were applied to characterize the fabricated scaffolds. Mechanical properties and protein delivery of the scaffolds were evaluated, as well as the cell response to the scaffolds by culturing human bone-marrow-derived mesenchymal stem cells (hBMSC). The obtained data indicate that this method is suitable to fabricate alginate/nano-HAP composite scaffolds with a layer of nano-HAP, coating the surface of the alginate strands homogeneously and completely. The surface mineralization enhanced the mechanical properties and improved the cell attachment and spreading, as well as supported sustaining protein release, compared to pure alginate scaffolds without nano-HAP shell layer. The results demonstrated that the method provides an interesting option for bone tissue engineering application.

Encapsulation of Multiple Microalgal Cells via a Combination of Biomimetic Mineralization and LbL Coating.

PubMed

Kim, Minjeong; Choi, Myoung Gil; Ra, Ho Won; Park, Seung Bin; Kim, Yong-Joo; Lee, Kyubock

2018-02-13

The encapsulation of living cells is appealing for its various applications to cell-based sensors, bioreactors, biocatalysts, and bioenergy. In this work, we introduce the encapsulation of multiple microalgal cells in hollow polymer shells of rhombohedral shape by the following sequential processes: embedding of microalgae in CaCO₃ crystals; layer-by-layer (LbL) coating of polyelectrolytes; and removal of sacrificial crystals. The microcapsule size was controlled by the alteration of CaCO₃ crystal size, which is dependent on CaCl₂/Na₂CO₃ concentration. The microalgal cells could be embedded in CaCO₃ crystals by a two-step process: heterogeneous nucleation of crystal on the cell surface followed by cell embedment by the subsequent growth of crystal. The surfaces of the microalgal cells were highly favorable for the crystal growth of calcite; thus, micrometer-sized microalgae could be perfectly occluded in the calcite crystal without changing its rhombohedral shape. The surfaces of the microcapsules, moreover, could be decorated with gold nanoparticles, Fe₃O₄ magnetic nanoparticles, and carbon nanotubes (CNTs), by which we would expect the functionalities of a light-triggered release, magnetic separation, and enhanced mechanical and electrical strength, respectively. This approach, entailing the encapsulation of microalgae in semi-permeable and hollow polymer microcapsules, has the potential for application to microbial-cell immobilization for high-biomass-concentration cultivation as well as various other bioapplications.

A versatile strategy for grafting polymers to wood cell walls.

PubMed

Keplinger, T; Cabane, E; Chanana, M; Hass, P; Merk, V; Gierlinger, N; Burgert, I

2015-01-01

The hierarchical structure of wood is composed of a cellulose skeleton of high structural order at various length scales. At the nanoscale and microscale the specific structural features of the cells and cell walls result in a lightweight structure with an anisotropic material profile of excellent mechanical performance. By being able to specifically functionalize wood at the level of cell and cell walls one can insert new properties and inevitably upscale them along the intrinsic hierarchical structure, to a level of large-scale engineering materials applications. For this purpose, however, precise control of the spatial distribution of the modifying substances in the complex wood structure is needed. Here we demonstrate a method to insert methacryl groups into wood cell walls using two different chemistry routes. By using these methacryl groups as the anchor points for grafting, various polymers can be inserted into the wood structure. Strikingly, depending on the methacryl precursor, the spatial distribution of the polymer differs strongly. As a proof of concept we grafted polystyrene as a model compound in the second modification step. In the case of methacryloyl chloride the polymer was located mainly at the interface between the cell lumina and the cell wall covering the inner surface of the cells and being traceable up to 2-3 μm in the cell wall, whereas in the case of methacrylic anhydride the polymer was located inside the whole cell wall. Scanning electron microscopy, Fourier transform infrared spectroscopy and especially Raman spectroscopy were used for an in-depth analysis of the modified wood at the cell wall level. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Rho-associated kinase (ROCK) inhibition reverses low cell activity on hydrophobic surfaces.

PubMed

Tian, Yu Shun; Kim, Hyun Jung; Kim, Hyun-Man

2009-08-28

Hydrophobic polymers do not offer an adequate scaffold surface for cells to attach, migrate, proliferate, and differentiate. Thus, hydrophobic scaffolds for tissue engineering have traditionally been physicochemically modified to enhance cellular activity. However, modifying the surface by chemical or physical treatment requires supplementary engineering procedures. In the present study, regulation of a cell signal transduction pathway reversed the low cellular activity on a hydrophobic surface without surface modification. Inhibition of Rho-associated kinase (ROCK) by Y-27632 markedly enhanced adhesion, migration, and proliferation of osteoblastic cells cultured on a hydrophobic polystyrene surface. ROCK inhibition regulated cell-cycle-related molecules on the hydrophobic surface. This inhibition also decreased expression of the inhibitors of cyclin-dependent kinases such as p21(cip1) and p27(kip1) and increased expression of cyclin A and D. These results indicate that defective cellular activity on the hydrophobic surface can be reversed by the control of a cell signal transduction pathway without physicochemical surface modification.

Performance enhancement of polymer electrolyte membrane fuel cells by dual-layered membrane electrode assembly structures with carbon nanotubes.

PubMed

Jung, Dong-Won; Kim, Jun-Ho; Kim, Se-Hoon; Kim, Jun-Bom; Oh, Eun-Suok

2013-05-01

The effect of dual-layered membrane electrode assemblies (d-MEAs) on the performance of a polymer electrolyte membrane fuel cell (PEMFC) was investigated using the following characterization techniques: single cell performance test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). It has been shown that the PEMFC with d-MEAs has better cell performance than that with typical mono-layered MEAs (m-MEAs). In particular, the d-MEA whose inner layer is composed of multi-walled carbon nanotubes (MWCNTs) showed the best fuel cell performance. This is due to the fact that the d-MEAs with MWCNTs have the highest electrochemical surface area and the lowest activation polarization, as observed from the CV and EIS test.

Polymer brushes infiltrated by nanoparticles and applications to the nuclear pore complex

NASA Astrophysics Data System (ADS)

Opferman, Michael G.

Systems of grafted polymers in the presence of additives are useful in a variety of contexts including industrial applications, solar cells, organic electronics, drug delivery, and nucleocytoplasmic transport. In this thesis, we will consider the morphologies that polymer brushes attain when exposed to a solution of additives (which we generically term "nanoparticles"), particularly when those nanparticles interact attractively with the polymers. We find that nanoparticles of this type can have a dramatic effect on the height of the polymer chains above the grafting surface, and they can induce highly non-uniform morphologies, including ones in which a dense layer of nanoparticles and monomers forms near the grafting surface. We consider especially the relevance of the system to several experiments performed on biopolymers in the nuclear pore complex when they interact attractively with transport factors that regulate nucleocytoplasmic transport. We find that, although these experiments appear to give inconsistent results, the inconsistencies can be reconciled through two simple models: the Alexander-de Gennes polymer brush, and the Milner-Witten-Cates polymer brush. Our findings should contribute to the understanding of the nuclear pore complex in that experiments can be better understood in the context of their relevant control parameters.

Constrained ceramic-filled polymer armor

DOEpatents

Sandstrom, D.J.; Calkins, N.C.; Gac, F.D.

1990-11-13

An armor system is disclosed in which a plurality of constraint cells are mounted on a surface of a substrate, which is metal armor plate or a similar tough material, such that the cells almost completely cover the surface of the substrate. Each constraint cell has a projectile-receiving wall parallel to the substrate surface and has sides which are perpendicular to and surround the perimeter of the receiving wall. The cells are mounted such that, in one embodiment, the substrate surface serves as a sixth side or closure for each cell. Each cell has inside of it a plate, termed the front plate, which is parallel to and in contact with substantially all of the inside surface of the receiving wall. The balance of each cell is completely filled with a projectile-abrading material, which is a ceramic material in particulate form dispersed in a polymeric matrix. 5 figs.

Functional lignocellulosic materials prepared by ATRP from a wood scaffold.

PubMed

Cabane, Etienne; Keplinger, Tobias; Künniger, Tina; Merk, Vivian; Burgert, Ingo

2016-08-10

Wood, a natural and abundant source of organic polymers, has been used as a scaffold to develop novel wood-polymer hybrid materials. Through a two-step surface-initiated Atom Transfer Radical Polymerization (ATRP), the porous wood structure can be effectively modified with polymer chains of various nature. In the present study, polystyrene and poly(N-isopropylacrylamide) were used. As shown with various characterization techniques including confocal Raman microscopy, FTIR, and SEM/EDX, the native wood ultrastructure and features are retained and the polymer chains can be introduced deep within the wood, i.e. inside the wood cell walls. The physical properties of the new materials have been studied, and results indicate that the insertion of polymer chains inside the wood cell wall alters the intrinsic properties of wood to yield a hybrid composite material with new functionalities. This approach to the functionalization of wood could lead to the fabrication of a new class of interesting functional materials and promote innovative utilizations of the renewable resource wood.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Hui; Wei, Yang; Wang, Cheng

The excessive volume changes during cell cycling of Si-based anode in lithium ion batteries impeded its application. One major reason for the cell failure is particle isolation during volume shrinkage in delithiation process, which makes strong adhesion between polymer binder and anode active material particles a highly desirable property. Here, a biomimetic side-chain conductive polymer incorporating catechol, a key adhesive component of the mussel holdfast protein, was synthesized. Atomic force microscopy-based single-molecule force measurements of mussel-inspired conductive polymer binder contacting a silica surface revealed a similar adhesion toward substrate when compared with an effective Si anode binder, homo-poly(acrylic acid), withmore » the added benefit of being electronically conductive. Electrochemical experiments showed a very stable cycling of Si-alloy anodes realized via this biomimetic conducting polymer binder, leading to a high loading Si anode with a good rate performance. We attribute the ability of the Si-based anode to tolerate the volume changes during cycling to the excellent mechanical integrity afforded by the strong interfacial adhesion of the biomimetic conducting polymer.« less

Functional lignocellulosic materials prepared by ATRP from a wood scaffold

PubMed Central

Cabane, Etienne; Keplinger, Tobias; Künniger, Tina; Merk, Vivian; Burgert, Ingo

2016-01-01

Wood, a natural and abundant source of organic polymers, has been used as a scaffold to develop novel wood-polymer hybrid materials. Through a two-step surface-initiated Atom Transfer Radical Polymerization (ATRP), the porous wood structure can be effectively modified with polymer chains of various nature. In the present study, polystyrene and poly(N-isopropylacrylamide) were used. As shown with various characterization techniques including confocal Raman microscopy, FTIR, and SEM/EDX, the native wood ultrastructure and features are retained and the polymer chains can be introduced deep within the wood, i.e. inside the wood cell walls. The physical properties of the new materials have been studied, and results indicate that the insertion of polymer chains inside the wood cell wall alters the intrinsic properties of wood to yield a hybrid composite material with new functionalities. This approach to the functionalization of wood could lead to the fabrication of a new class of interesting functional materials and promote innovative utilizations of the renewable resource wood. PMID:27506369

Polymerization speed and diffractive experiments in polymer network LC test cells

NASA Astrophysics Data System (ADS)

Braun, Larissa; Gong, Zhen; Habibpourmoghadam, Atefeh; Schafforz, Samuel L.; Wolfram, Lukas; Lorenz, Alexander

2018-02-01

Polymer-network liquid crystals (LCs), where the response properties of a LC can be enhanced by the presence of a porous polymer network, are investigated. In the reported experiments, liquid crystals were doped with a small amount (< 10%) of photo-curable acrylate monomers. Samples with surface grafted photoinitiators, dissolvable photoinitiators, and samples with both kinds of photoinitiators were prepared. Both conventional (planar electrodes) and diffractive (interdigitated electrodes) test cells were used. These samples were exposed with a UV light source and changes of their capacitance were investigated with an LCR meter during exposure. Due to the presence of the in-situ generated polymer network, the electro-optic response properties of photo cured samples were enhanced. For example, their continuous phase modulation properties led to more localized responses in samples with interdigitated electrodes, which caused suppression of selected diffraction orders in the diffraction patterns recorded in polymer network LC samples. Moreover, capacitance changes were investigated during photopolymerization of a blue phase LC.

Poly(methyl vinyl ether-alt-maleic acid)-functionalized porous silicon nanoparticles for enhanced stability and cellular internalization.

PubMed

Shahbazi, Mohammad-Ali; Almeida, Patrick V; Mäkilä, Ermei; Correia, Alexandra; Ferreira, Mónica P A; Kaasalainen, Martti; Salonen, Jarno; Hirvonen, Jouni; Santos, Hélder A

2014-03-01

Currently, developing a stable nanocarrier with high cellular internalization and low toxicity is a key bottleneck in nanomedicine. Here, we have developed a successful method to covalently conjugate poly(methyl vinyl ether-co-maleic acid) (PMVE-MA) copolymer on the surface of (3-aminopropyl)triethoxysilane-functionalized thermally carbonized porous silicon nanoparticles (APSTCPSi NPs), forming a surface negatively charged nanovehicle with unique properties. This polymer conjugated NPs could modify surface smoothness, charge, and hydrophilicity of the developed NPs, leading to considerable improvement in the colloidal and plasma stabilities via enhanced suspensibility and charge repulsion. Furthermore, despite the surface negative charge of the polymer-conjugated NPs, the cellular internalization was increased in both MDA-MB-231 and MCF-7 breast cancer cells. These results provide a proof-of-concept evidence that such polymer-based PSi nanocomposite can be extensively used as a promising candidate for intracellular drug delivery. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Comparison of Electrospun Polymers Reveals Poly(3-Hydroxybutyrate) Fiber as a Superior Scaffold for Cardiac Repair

PubMed Central

Castellano, Delia; Blanes, María; Marco, Bruno; Cerrada, Inmaculada; Ruiz-Saurí, Amparo; Pelacho, Beatriz; Araña, Miriam; Montero, Jose A.; Cambra, Vicente; Prosper, Felipe

2014-01-01

The development of biomaterials for myocardial tissue engineering requires a careful assessment of their performance with regards to functionality and biocompatibility, including the immune response. Poly(3-hydroxybutyrate) (PHB), poly(e-caprolactone) (PCL), silk, poly-lactic acid (PLA), and polyamide (PA) scaffolds were generated by electrospinning, and cell compatibility in vitro, and immune response and cardiac function in vitro and in vivo were compared with a noncrosslinked collagen membrane (Col) control material. Results showed that cell adhesion and growth of mesenchymal stem cells, cardiomyocytes, and cardiac fibroblasts in vitro was dependent on the polymer substrate, with PHB and PCL polymers permitting the greatest adhesion/growth of cells. Additionally, polymer substrates triggered unique expression profiles of anti- and pro-inflammatory cytokines in human peripheral blood mononuclear cells. Implantation of PCL, silk, PLA, and PA patches on the epicardial surface of healthy rats induced a classical foreign body reaction pattern, with encapsulation of polymer fibers and induction of the nonspecific immune response, whereas Col and PHB patches were progressively degraded. When implanted on infarcted rat heart, Col, PCL, and PHB reduced negative remodeling, but only PHB induced significant angiogenesis. Importantly, Col and PHB modified the inflammatory response to an M2 macrophage phenotype in cardiac tissue, indicating a more beneficial reparative process and remodeling. Collectively, these results identify PHB as a superior substrate for cardiac repair. PMID:24564648

Nanostructured Conjugated Polymers for Energy-Related Applications beyond Solar Cells.

PubMed

Xie, Jian; Zhao, Cui-E; Lin, Zong-Qiong; Gu, Pei-Yang; Zhang, Qichun

2016-05-20

To meet the ever-increasing requirements for the next generation of sustainable and versatile energy-related devices, conjugated polymers, which have potential advantages over small molecules and inorganic materials, are among the most promising types of green candidates. The properties of conjugated polymers can be tuned through modification of the structure and incorporation of different functional moieties. In addition, superior performances can be achieved as a result of the advantages of nanostructures, such as their large surface areas and the shortened pathways for charge transfer. Therefore, nanostructured conjugated polymers with different properties can be obtained to be applied in different energy-related organic devices. This review focuses on the application and performance of the recently reported nanostructured conjugated polymers for high-performance devices, including rechargeable lithium batteries, microbial fuel cells (MFCs), thermoelectric generators, and photocatalytic systems. The design strategies, reaction mechanisms, advantages, and limitations of nanostructured conjugated polymers are further discussed in each section. Finally, possible routes to improve the performances of the current systems are also included in the conclusion. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mussel-Inspired Conductive Polymer Binder for Si-Alloy Anode in Lithium-Ion Batteries

DOE PAGES

Zhao, Hui; Wei, Yang; Wang, Cheng; ...

2018-01-15

The excessive volume changes during cell cycling of Si-based anode in lithium ion batteries impeded its application. One major reason for the cell failure is particle isolation during volume shrinkage in delithiation process, which makes strong adhesion between polymer binder and anode active material particles a highly desirable property. Here, a biomimetic side-chain conductive polymer incorporating catechol, a key adhesive component of the mussel holdfast protein, was synthesized. Atomic force microscopy-based single-molecule force measurements of mussel-inspired conductive polymer binder contacting a silica surface revealed a similar adhesion toward substrate when compared with an effective Si anode binder, homo-poly(acrylic acid), withmore » the added benefit of being electronically conductive. Electrochemical experiments showed a very stable cycling of Si-alloy anodes realized via this biomimetic conducting polymer binder, leading to a high loading Si anode with a good rate performance. We attribute the ability of the Si-based anode to tolerate the volume changes during cycling to the excellent mechanical integrity afforded by the strong interfacial adhesion of the biomimetic conducting polymer.« less

High performance all polymer solar cells fabricated via non-halogenated solvents (Presentation Recording)

NASA Astrophysics Data System (ADS)

Zhou, Yan; Bao, Zhenan

2015-10-01

The performance of organic solar cells consisting of a donor/acceptor bulk heterojunction (BHJ) has rapidly improved over the past few years.1. Major efforts have been focused on developing a variety of donor materials to gain access to different regions of the solar spectrum as well as to improve carrier transport properties.2 On the other hand, the most utilized acceptors are still restricted to the fullerene family, which includes PC61BM, PC71BM and ICBA.2b, 3 All-polymer solar cells, consisting of polymers for both the donor and acceptor, gained significantly increased interests recently, because of their ease of solution processing, potentially low cost, versatility in molecular design, and their potential for good chemical and morphological stability due to entanglement of polymers. Unlike small molecular fullerene acceptors, polymer acceptors can benefit from the high mobility of intra-chain charge transport and exciton generation by both donor and acceptor. Despite extensive efforts on all-polymer solar cells in the past decade, the fundamental understanding of all-polymer solar cells is still in its inceptive stage regarding both the materials chemistry and structure physics.4 Thus, rational design rules must be utilized to enable fundamental materials understanding of the all polymer solar cells. We report high performance all-polymer solar cells employing polymeric donors based on isoindigo and acceptor based on perylenedicarboximide. The phase separation domain length scale correlates well with the JSC and is found to be highly sensitive to the aromatic co-monomer structures used in the crystalline donor polymers. With the PS polymer side chain engineering, the phase separation domain length scale decreased by more than 45%. The PCE and JSC of the devices increased accordingly by more than 20%. A JSC as high as 10.0 mA cm-2 is obtained with the donor-acceptor pair despite of a low LUMO-LUMO energy offset of less than 0.1 eV. All the factors such as crystallinity, surface roughness, charge carrier mobility, and absorptions of the polymers blends are found irrelevant to the performance of these all polymer solar cells. This work demonstrates that a better understanding of tuning polymer phase separation domain size provides an important path towards high performance, all-polymer solar cells. The use of polymer side-chain engineering provides an effective molecular engineering approach that may be combined with additional processing parameter control to further elevate the performance of all-polymer solar cells. We obtained a record PCE of 4.8% (avarage from 20 devices), with an average JSC of 9.8 mA cm-2. The highest PCE shoots to 5.1%, with JSC as high as 10.2 mA cm-2, and VOC of 1.02 V. It is the highest performance ever published for an all-polymer solar cell.4 1. Li, G.; Zhu, R.; Yang, Y., Nat. Photon. 2012, 6 , 153-161. 2. (a) Nelson, J., Mater. Today 2011, 14 , 462-470; (b) Lin, Y.; Li, Y.; Zhan, X., Chem. Soc. Rev. 2012, 41, 4245-4272; (c) Chen, J.; Cao, Y., Acc. Chem. Res. 2009, 42, 1709-1718. 3. Sonar, P.; Fong Lim, J. P.; Chan, K. L., Energy Environ. Sci. 2011, 4, 1558. 4. Facchetti, A., Mater. Today 2013, 16 , 123-132.

Mesoporous silica nanoparticles engineered for ultrasound-induced uptake by cancer cells.

PubMed

Paris, Juan L; Manzano, Miguel; Cabañas, M Victoria; Vallet-Regí, María

2018-04-05

A novel smart hierarchical ultrasound-responsive mesoporous silica nanocarrier for cancer therapy is presented here. This dynamic nanosystem has been designed to display different surface characteristics during its journey towards tumor cells. Initially, the anticancer-loaded nanocarriers are shielded with a polyethylene glycol layer. Upon exposure to high frequency ultrasound, the polymer shell detaches from the nanoparticles, exposing a positively charged surface. This favors the internalization in human osteosarcoma cells, where the release of topotecan takes place, drastically enhancing the cytotoxic effect.

Fabrication and Characterization of Conductive Conjugated Polymer-Coated Antheraea mylitta Silk Fibroin Fibers for Biomedical Applications.

PubMed

Gh, Darshan; Kong, Dexu; Gautrot, Julien; Vootla, Shyam Kumar

2017-07-01

Conductive polymers are interesting materials for a number of biological and medical applications requiring electrical stimulation of cells or tissues. Highly conductive polymers (polypyrrole and polyaniline)/Antheraea mylitta silk fibroin coated fibers are fabricated successfully by in situ polymerization without any modification of the native silk fibroin. Coated fibers characterized by scanning electron microscopy confirm the silk fiber surface is covered by conductive polymers. Thermogravimetric analysis reveals preserved thermal stability of silk fiber after coating process. X-ray diffraction of degummed fiber diffraction peaks at around 2θ = 20.4 and 16.5 confirms the preservation of the β-sheet structure typical of degummed silk II fibers. This phenomenon implies that both polypyrrole and polyaniline chains form interactions with peptide linkages in degummed fiber macromolecules, without significantly disrupting protein assembly. Fourier transform infrared spectroscopy of coated fibers indicates hydrogen bonding and electrostatic interactions exist between silk fibroin macromolecules and conductive polymers. Resulting fibers display good conductive properties compared to corresponding conjugated polymers. In vitro analysis (live/dead assay) of the behavior of human immortalized keratinocytes (HaCaTs) on coated fibers demonstrates improved cell-adhesive properties and viability after polymers coating. Hence, polypyrrole- and polyaniline-coated A. mylitta silk fibers are suitable for application in cell culture and for tissue engineering, where electrical conduction properties are required. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Applicability of electrospun polypropylene carbonate polymers as a drug carrier for sirolimus.

PubMed

Sun, Hourong; Gu, Xinghua; Liu, Kai; Fang, Changcun; Tang, Mengmeng

2017-06-01

Polypropylene carbonate (PPC), a biodegradable aliphatic polyester, exhibits one particular advantage over other polyesters, which is that following degradation in vivo, it primarily produces H2O and CO2, causing minimal side effects. Although PPC exhibits limited mechanical strength, and is therefore not able to serve as a scaffold to support tissue regeneration, it may be suitable for drug delivery; however, this requires further investigation. In the present study, electrospinning was applied to generate PPC polymers containing sirolimus, a cell growth‑inhibiting drug which is used to treat restenosis. The properties of PPC‑sirolimus polymers were examined using scanning electron microscopy, differential scanning calorimetry and in vitro degradation assays. Drug loading and entrapment efficiency were determined, and in vitro sirolimus‑release from the polymer was assessed. Furthermore, the effect of PPC‑sirolimus polymers on cell growth was measured using an MTT assay in vitro. The results of the present study demonstrated that electrospun PPC polymers formed a uniform three‑dimensional, grid‑intertwined, net‑like structure; the surface of the polymers was smooth and the diameter was ~3 µm. Differential scanning calorimetry analysis demonstrated that sirolimus existed in an amorphous state in the polymer. Following soaking in PBS for 4 weeks, the polymer swelled and the net‑like structure broke down and fragmented. Sirolimus loading and entrapment efficiency were 10.3±3.2 and 95.1±10.6%, respectively. Sirolimus‑release from PPC‑sirolimus polymers continued for 28 days in PBS. PPC‑sirolimus markedly inhibited the growth of rat aortic adventitial fibroblast cells, an effect which was not observed with PPC alone. The results of the present study suggest that PPC polymers are a promising alternative drug carrier for sirolimus.

Diketopyrrolopyrrole-based Conjugated Polymers Bearing Branched Oligo(Ethylene Glycol) Side Chains for Photovoltaic Devices.

PubMed

Chen, Xingxing; Zhang, Zijian; Ding, Zicheng; Liu, Jun; Wang, Lixiang

2016-08-22

Conjugated polymers are essential for solution-processable organic opto-electronic devices. In contrast to the great efforts on developing new conjugated polymer backbones, research on developing side chains is rare. Herein, we report branched oligo(ethylene glycol) (OEG) as side chains of conjugated polymers. Compared with typical alkyl side chains, branched OEG side chains endowed the resulting conjugated polymers with a smaller π-π stacking distance, higher hole mobility, smaller optical band gap, higher dielectric constant, and larger surface energy. Moreover, the conjugated polymers with branched OEG side chains exhibited outstanding photovoltaic performance in polymer solar cells. A power conversion efficiency of 5.37 % with near-infrared photoresponse was demonstrated and the device performance could be insensitive to the active layer thickness. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stimuli-responsive polymers for antimicrobial therapy: drug targeting, contact-killing surfaces and competitive release.

PubMed

Alvarez-Lorenzo, Carmen; Garcia-Gonzalez, Carlos A; Bucio, Emilio; Concheiro, Angel

2016-08-01

Polymers can be designed to modify their features as a function of the level and nature of the surrounding microorganisms. Such responsive polymers can endow drug delivery systems and drug-medical device combination products with improved performance against intracellular infections and biofilms. Knowledge on microorganism growth environment outside and inside cells and formation of biofilm communities on biological and synthetic surfaces, together with advances in materials science and drug delivery are prompting strategies with improved efficacy and safety compared to traditional systemic administration of antimicrobial agents. This review deals with antimicrobial strategies that rely on: (i) polymers that disintegrate or undergo phase-transitions in response to changes in enzymes, pH and pO2 associated to microorganism growth; (ii) stimuli-responsive polymers that expose contact-killing groups when microorganisms try to adhere; and (iii) bioinspired polymers that recognize microorganisms for triggered (competitive/affinity-driven) drug release. Prophylaxis and treatment of infections may benefit from polymers that are responsive to the unique changes that microbial growth causes in the surrounding environment or that even recognize the microorganism itself or its quorum sensing signals. These polymers may offer novel tools for the design of macrophage-, bacteria- and/or biofilm-targeted nanocarriers as well as of medical devices with switchable antibiofouling properties.

Zwitterionic sulfobetaine polymer-immobilized surface by simple tyrosinase-mediated grafting for enhanced antifouling property.

PubMed

Kwon, Ho Joon; Lee, Yunki; Phuong, Le Thi; Seon, Gyeung Mi; Kim, Eunsuk; Park, Jong Chul; Yoon, Hyunjin; Park, Ki Dong

2017-10-01

Introducing antifouling property to biomaterial surfaces has been considered an effective method for preventing the failure of implanted devices. In order to achieve this, the immobilization of zwitterions on biomaterial surfaces has been proven to be an excellent way of improving anti-adhesive potency. In this study, poly(sulfobetaine-co-tyramine), a tyramine-conjugated sulfobetaine polymer, was synthesized and simply grafted onto the surface of polyurethane via a tyrosinase-mediated reaction. Surface characterization by water contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy demonstrated that the zwitterionic polymer was successfully introduced onto the surface of polyurethane and remained stable for 7days. In vitro studies revealed that poly(sulfobetaine-co-tyramine)-coated surfaces dramatically reduced the adhesion of fibrinogen, platelets, fibroblasts, and S. aureus by over 90% in comparison with bare surfaces. These results proved that polyurethane surfaces grafted with poly(sulfobetaine-co-tyramine) via a tyrosinase-catalyzed reaction could be promising candidates for an implantable medical device with excellent bioinert abilities. Antifouling surface modification is one of the key strategy to prevent the thrombus formation or infection which occurs on the surface of biomaterial after transplantation. Although there are many methods to modify the surface have been reported, necessity of simple modification technique still exists to apply for practical applications. The purpose of this study is to modify the biomaterial's surface by simply immobilizing antifouling zwitterion polymer via enzyme tyrosinase-mediated reaction which could modify versatile substrates in mild aqueous condition within fast time period. After modification, pSBTA grafted surface becomes resistant to various biological factors including proteins, cells, and bacterias. This approach appears to be a promising method to impart antifouling property on biomaterial surfaces. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Attachment and spreadout study of 3T3 cells onto PP track etched films

NASA Astrophysics Data System (ADS)

Smolko, Eduardo; Mazzei, Ruben; Tadey, Daniel; Lombardo, Daniel

2001-12-01

Polymer surface modifications are obtained by the application of radiation treatments and other physico-chemical methods: fission fragment (ff) irradiation and etching. The biocompatibility of the surface is then observed by cell seeding and cell adhesion experiments. Approaches to improvement of the cell adhesion are obtained by different methods: for example, in PS, cell adhesion is improved after ion implantation; in PMMA, after bombarding the polymer, the surface is reconditioned with surfactants and proteins and in PVDF, cell adhesion is assayed on nuclear tracks membranes. In this work, we obtained important cell adhesion improvements in PP films by irradiation with swift heavy ions and subsequent etching of the nuclear tracks. We use BOPP (isotactic -25 μm thickness). Irrradiations were performed with a Cf-252 californium ff source. The source has a heavy ff and a light one, with 160-200 MeV energy divided among them corresponding to ff energies between 1 and 2 MeV/amu. A chemical etching procedure consisting of a solution of sulphuric acid and chromium three oxide at 85 °C was used. The 3T3 NIH fibroblast cell line was used for the cell adhesion experiment. Here we report for the first time, the results of a series of experiments by varying the ff fluence and the etching time showing that attachment and spreadout of cells are very much improved in this cell line according to the number of pores and the pore size.

Toward a Flying MEMS Robot

DTIC Science & Technology

2007-03-01

63 Figure 45: Proposed energy harvesting and storage system which will be made of polymer solar cells and lithium polymer batteries [35...University of California, Berkeley used four piezoelectric actuators and fiber-reinforced composites in an attempt to achieve lift [9]. The device...Entomopter. The RCM powers the wing flapping motion while the exhaust gasses act as gas bearings between all movable surfaces. The exhaust gasses can

Methods of conditioning direct methanol fuel cells

DOEpatents

Rice, Cynthia; Ren, Xiaoming; Gottesfeld, Shimshon

2005-11-08

Methods for conditioning the membrane electrode assembly of a direct methanol fuel cell ("DMFC") are disclosed. In a first method, an electrical current of polarity opposite to that used in a functioning direct methanol fuel cell is passed through the anode surface of the membrane electrode assembly. In a second method, methanol is supplied to an anode surface of the membrane electrode assembly, allowed to cross over the polymer electrolyte membrane of the membrane electrode assembly to a cathode surface of the membrane electrode assembly, and an electrical current of polarity opposite to that in a functioning direct methanol fuel cell is drawn through the membrane electrode assembly, wherein methanol is oxidized at the cathode surface of the membrane electrode assembly while the catalyst on the anode surface is reduced. Surface oxides on the direct methanol fuel cell anode catalyst of the membrane electrode assembly are thereby reduced.

Tailorable Surface Morphology of 3D Scaffolds by Combining Additive Manufacturing with Thermally Induced Phase Separation.

PubMed

Di Luca, Andrea; de Wijn, Joost R; van Blitterswijk, Clemens A; Camarero-Espinosa, Sandra; Moroni, Lorenzo

2017-08-01

The functionalization of biomaterials substrates used for cell culture is gearing towards an increasing control over cell activity. Although a number of biomaterials have been successfully modified by different strategies to display tailored physical and chemical surface properties, it is still challenging to step from 2D substrates to 3D scaffolds with instructive surface properties for cell culture and tissue regeneration. In this study, additive manufacturing and thermally induced phase separation are combined to create 3D scaffolds with tunable surface morphology from polymer gels. Surface features vary depending on the gel concentration, the exchanging temperature, and the nonsolvent used. When preosteoblasts (MC-3T3 cells) are cultured on these scaffolds, a significant increase in alkaline phosphatase activity is measured for submicron surface topography, suggesting a potential role on early cell differentiation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Targeted delivery of 10-hydroxycamptothecin to human breast cancers by cyclic RGD-modified lipid-polymer hybrid nanoparticles.

PubMed

Yang, Zhe; Luo, Xingen; Zhang, Xiaofang; Liu, Jie; Jiang, Qing

2013-04-01

Lipid-polymer hybrid nanoparticles (NPs) combining the positive attributes of both liposomes and polymeric NPs are increasingly being considered as promising candidates to carry therapeutic agents safely and efficiently into targeted sites. Herein, a modified emulsification technique was developed and optimized for the targeting lipid-polymer hybrid NPs fabrication; the surface properties and stability of the hybrid NPs were systematically investigated, which confirmed that the hybrid NPs consisted of a poly (lactide-co-glycolide) core with ∼90% surface coverage of the lipid monolayer and a ∼4.4 nm hydrated polyethylene glycol (PEG) shell. Optimization results showed that the lipid:polymer mass ratio and the lipid-PEG:lipid molar ratio could affect the size, lipid association efficiency and stability of hybrid NPs. Furthermore, a model chemotherapy drug, 10-hydroxycamptothecin, was encapsulated into hybrid NPs with a higher drug loading compared to PLGA NPs. Surface modification of the lipid layer and the PEG conjugated targeting ligand did not affect their drug release kinetics. Finally, the cytotoxicity and cellular uptake studies indicated that the lipid coverage and the c(RGDyk) conjugation of the hybrid NPs gained a significantly enhanced ability of cell killing and endocytosis. Our results suggested that lipid-polymer hybrid NPs prepared by the modified emulsion technique have great potential to be utilized as an engineered drug delivery system with precise control ability of surface targeting modification.

Methods for generation of reporter phages and immobilization of active bacteriophages on a polymer surface

NASA Technical Reports Server (NTRS)

Morgan, Mark Thomas (Inventor); Kothapalli, Aparna (Inventor); Applegate, Bruce Michael (Inventor); Perry, Lynda Louise (Inventor)

2012-01-01

Novel reporter bacteriophages are provided. Provided are compositions and methods that allow bacteriophages that are used for specific detection or killing of E. coli 0157:H7 to be propagated in nonpathogenic E. coli, thereby eliminating the safety and security risks of propagation in E. coli 0157:H7. Provided are compositions and methods for attaching active bacteriophages to the surface of a polymer in order to kill target bacteria with which the phage comes into contact. Provided are modified bacteriophages immobilized to a surface, which capture E. coli 0157:H7 and cause the captured cells to emit light or fluorescence, allowing detection of the bacteria in a sample.

Cell partition in two phase polymer systems

NASA Technical Reports Server (NTRS)

Brooks, D. E.

1979-01-01

Aqueous phase-separated polymer solutions can be used as support media for the partition of biological macromolecules, organelles and cells. Cell separations using the technique have proven to be extremely sensitive to cell surface properties but application of the systems are limited to cells or aggregates which do not significantly while the phases are settling. Partition in zero g in principle removes this limitation but an external driving force must be applied to induce the phases to separate since their density difference disappears. We have recently shown that an applied electric field can supply the necessary driving force. We are proposing to utilize the NASA FES to study field-driven phase separation and cell partition on the ground and in zero g to help define the separation/partition process, with the ultimate goal being to develop partition as a zero g cell separation technique.

Nanometer-sized extracellular matrix coating on polymer-based scaffold for tissue engineering applications.

PubMed

Uchida, Noriyuki; Sivaraman, Srikanth; Amoroso, Nicholas J; Wagner, William R; Nishiguchi, Akihiro; Matsusaki, Michiya; Akashi, Mitsuru; Nagatomi, Jiro

2016-01-01

Surface modification can play a crucial role in enhancing cell adhesion to synthetic polymer-based scaffolds in tissue engineering applications. Here, we report a novel approach for layer-by-layer (LbL) fabrication of nanometer-size fibronectin and gelatin (FN-G) layers on electrospun fibrous poly(carbonate urethane)urea (PCUU) scaffolds. Alternate immersions into the solutions of fibronectin and gelatin provided thickness-controlled FN-G nano-layers (PCUU(FN-G) ) which maintained the scaffold's 3D structure and width of fibrous bundle of PCUU as evidenced by scanning electron miscroscopy. The PCUU(FN-G) scaffold improved cell adhesion and proliferation of bladder smooth muscles (BSMCs) when compared to uncoated PCUU. The high affinity of PCUU(FN-G) for cells was further demonstrated by migration of adherent BSMCs from culture plates to the scaffold. Moreover, the culture of UROtsa cells, human urothelium-derived cell line, on PCUU(FN-G) resulted in an 11-15 μm thick multilayered cell structure with cell-to-cell contacts although many UROtsa cells died without forming cell connections on PCUU. Together these results indicate that this approach will aid in advancing the technology for engineering bladder tissues in vitro. Because FN-G nano-layers formation is based on nonspecific physical adsorption of fibronectin onto polymer and its subsequent interactions with gelatin, this technique may be applicable to other polymer-based scaffold systems for various tissue engineering/regenerative medicine applications. © 2015 Wiley Periodicals, Inc.

Efficient transfer of genetic material into mammalian cells using Starburst polyamidoamine dendrimers.

PubMed Central

Kukowska-Latallo, J F; Bielinska, A U; Johnson, J; Spindler, R; Tomalia, D A; Baker, J R

1996-01-01

Starburst polyamidoamine dendrimers are a new class of synthetic polymers with unique structural and physical characteristics. These polymers were investigated for the ability to bind DNA and enhance DNA transfer and expression in a variety of mammalian cell lines. Twenty different types of polyamidoamine dendrimers were synthesized, and the polymer structure was confirmed using well-defined analytical techniques. The efficiency of plasmid DNA transfection using dendrimers was examined using two reporter gene systems: firefly luciferase and bacterial beta-galactosidase. The transfections were performed using various dendrimers, and levels of expression of the reporter protein were determined. Highly efficient transfection of a broad range of eukaryotic cells and cell lines was achieved with minimal cytotoxicity using the DNA/dendrimer complexes. However, the ability to transfect cells was restricted to certain types of dendrimers and in some situations required the presence of additional compounds, such as DEAE-dextran, that appeared to alter the nature of the complex. A few cell lines demonstrated enhanced transfection with the addition of chloroquine, indicating endosomal localization of the complexes. The capability of a dendrimer to transfect cells appeared to depend on the size, shape, and number of primary amino groups on the surface of the polymer. However, the specific dendrimer most efficient in achieving transfection varied between different types of cells. These studies demonstrate that Starburst dendrimers can transfect a wide variety of cell types in vitro and offer an efficient method for producing permanently transfected cell lines. Images Fig. 1 Fig. 2 Fig. 4 PMID:8643500

Expansion and Differentiation of Germline-Derived Pluripotent Stem Cells on Biomaterials

PubMed Central

Šarić, Tomo; Denecke, Bernd; Peinkofer, Gabriel; Bovi, Manfred; Groll, Jürgen; Ko, Kinarm; Salber, Jochen; Halbach, Marcel; Schöler, Hans R.; Zenke, Martin; Neuss, Sabine

2013-01-01

Stem cells with broad differentiation potential, such as the recently described germline-derived pluripotent stem cells (gPS cells), are an appealing source for tissue engineering strategies. Biomaterials can inhibit, support, or induce proliferation and differentiation of stem cells. Here we identified (1) polymers that maintain self-renewal and differentiation potential of gPS cells for feeder-free expansion and (2) polymers supporting the cardiomyogenic fate of gPS cells by analyzing a panel of polymers of an established biomaterial bank previously used to assess growth of diverse stem cell types. Identification of cytocompatible gPS cell/biomaterial combinations required analysis of several parameters, including morphology, viability, cytotoxicity, apoptosis, proliferation, and differentiation potential. Pluripotency of gPS cells was visualized by the endogenous Oct4-promoter-driven GFP and by Sox2 and Nanog immunofluorescence. Viability assay, proliferation assay, and flow cytometry showed that gPS cells efficiently adhere and are viable on synthetic polymers, such as Resomer® LR704 (poly(L-lactic-D,L-lactic acid), poly(tetrafluor ethylene) (PTFE), poly(vinylidene fluoride) (PVDF), and on gelatine-coated tissue culture polystyrene. Expansion experiments showed that Resomer LR704 is an alternative substrate for feeder-free gPS cell maintenance. Resomer LR704, PTFE, and PVDF were found to be suitable for gPS cell differentiation. Spontaneous beating in embryoid bodies cultured on Resomer LR704 occurred already on day 8 of differentiation, much earlier compared to the other surfaces. This indicates that Resomer LR704 supports spontaneous cardiomyogenic differentiation of gPS cells, which was also confirmed on molecular, protein and functional level. PMID:23234562

Expansion and differentiation of germline-derived pluripotent stem cells on biomaterials.

PubMed

Hoss, Mareike; Šarić, Tomo; Denecke, Bernd; Peinkofer, Gabriel; Bovi, Manfred; Groll, Jürgen; Ko, Kinarm; Salber, Jochen; Halbach, Marcel; Schöler, Hans R; Zenke, Martin; Neuss, Sabine

2013-05-01

Stem cells with broad differentiation potential, such as the recently described germline-derived pluripotent stem cells (gPS cells), are an appealing source for tissue engineering strategies. Biomaterials can inhibit, support, or induce proliferation and differentiation of stem cells. Here we identified (1) polymers that maintain self-renewal and differentiation potential of gPS cells for feeder-free expansion and (2) polymers supporting the cardiomyogenic fate of gPS cells by analyzing a panel of polymers of an established biomaterial bank previously used to assess growth of diverse stem cell types. Identification of cytocompatible gPS cell/biomaterial combinations required analysis of several parameters, including morphology, viability, cytotoxicity, apoptosis, proliferation, and differentiation potential. Pluripotency of gPS cells was visualized by the endogenous Oct4-promoter-driven GFP and by Sox2 and Nanog immunofluorescence. Viability assay, proliferation assay, and flow cytometry showed that gPS cells efficiently adhere and are viable on synthetic polymers, such as Resomer(®) LR704 (poly(L-lactic-D,L-lactic acid), poly(tetrafluor ethylene) (PTFE), poly(vinylidene fluoride) (PVDF), and on gelatine-coated tissue culture polystyrene. Expansion experiments showed that Resomer LR704 is an alternative substrate for feeder-free gPS cell maintenance. Resomer LR704, PTFE, and PVDF were found to be suitable for gPS cell differentiation. Spontaneous beating in embryoid bodies cultured on Resomer LR704 occurred already on day 8 of differentiation, much earlier compared to the other surfaces. This indicates that Resomer LR704 supports spontaneous cardiomyogenic differentiation of gPS cells, which was also confirmed on molecular, protein and functional level.

Friction-Controlled Traction Force in Cell Adhesion

PubMed Central

Pompe, Tilo; Kaufmann, Martin; Kasimir, Maria; Johne, Stephanie; Glorius, Stefan; Renner, Lars; Bobeth, Manfred; Pompe, Wolfgang; Werner, Carsten

2011-01-01

The force balance between the extracellular microenvironment and the intracellular cytoskeleton controls the cell fate. We report a new (to our knowledge) mechanism of receptor force control in cell adhesion originating from friction between cell adhesion ligands and the supporting substrate. Adherent human endothelial cells have been studied experimentally on polymer substrates noncovalently coated with fluorescent-labeled fibronectin (FN). The cellular traction force correlated with the mobility of FN during cell-driven FN fibrillogenesis. The experimental findings have been explained within a mechanistic two-dimensional model of the load transfer at focal adhesion sites. Myosin motor activity in conjunction with sliding of FN ligands noncovalently coupled to the surface of the polymer substrates is shown to result in a controlled traction force of adherent cells. We conclude that the friction of adhesion ligands on the supporting substrate is important for mechanotransduction and cell development of adherent cells in vitro and in vivo. PMID:22004739

Ratiometric Array of Conjugated Polymers-Fluorescent Protein Provides a Robust Mammalian Cell Sensor.

PubMed

Rana, Subinoy; Elci, S Gokhan; Mout, Rubul; Singla, Arvind K; Yazdani, Mahdieh; Bender, Markus; Bajaj, Avinash; Saha, Krishnendu; Bunz, Uwe H F; Jirik, Frank R; Rotello, Vincent M

2016-04-06

Supramolecular complexes of a family of positively charged conjugated polymers (CPs) and green fluorescent protein (GFP) create a fluorescence resonance energy transfer (FRET)-based ratiometric biosensor array. Selective multivalent interactions of the CPs with mammalian cell surfaces caused differential change in FRET signals, providing a fingerprint signature for each cell type. The resulting fluorescence signatures allowed the identification of 16 different cell types and discrimination between healthy, cancerous, and metastatic cells, with the same genetic background. While the CP-GFP sensor array completely differentiated between the cell types, only partial classification was achieved for the CPs alone, validating the effectiveness of the ratiometric sensor. The utility of the biosensor was further demonstrated in the detection of blinded unknown samples, where 121 of 128 samples were correctly identified. Notably, this selectivity-based sensor stratified diverse cell types in minutes, using only 2000 cells, without requiring specific biomarkers or cell labeling.

Silica nanoparticles carrying boron-containing polymer brushes

NASA Astrophysics Data System (ADS)

Brozek, Eric M.; Mollard, Alexis H.; Zharov, Ilya

2014-05-01

A new class of surface-modified silica nanoparticles has been developed for potential applications in boron neutron capture therapy. Sub-50 nm silica particles were synthesized using a modified Stöber method and used in surface-initiated atom transfer radical polymerization of two biocompatible polymers, poly(2-(hydroxyethyl)methacrylate) and poly(2-(methacryloyloxy)ethyl succinate). The carboxylic acid and hydroxyl functionalities of the polymeric side chains were functionalized with carboranyl clusters in high yields. The resulting particles were characterized using DLS, TEM, solution 1H NMR, solid state 11B NMR and thermogravimetric analysis. The particles contain between 13 and 18 % of boron atoms by weight, which would provide a high amount of 10B nuclides for BNCT, while the polymer chains are suitable for further modification with cell targeting ligands.

Biomimicry 1: PC.

PubMed

Cumberland, D C; Gunn, J; Malik, N; Holt, C M

1998-01-01

The surface properties of stents can be modified by coating them, for example with a polymer. Phosphorylcoline (PC) is the major component of the outer layer of the cell membrane. The haemo- and biocompatibility of a PC-containing polymer is thus based on biomimicry, and has been confirmed by several experiments showing much reduced thrombogenicity of PC-coated surfaces, and porcine coronary artery implants showing no sign of adverse effect. Clinical experience with the PC-coated BiodivYsio appears favourable. The PC coating can be tailored for take up and controlled elution of various drugs for stent-based local delivery, a property which is being actively explored.

Solar Cell Polymer Based Active Ingredients PPV and PCBM

NASA Astrophysics Data System (ADS)

Hardeli, H.; Sanjaya, H.; Resikarnila, R.; Nitami H, R.

2018-04-01

A polymer solar cell is a solar cell based on a polymer bulk heterojunction structure using the method of thin film, which can convert solar energy into electrical energy. Absorption of light is carried by active material layer PPV: PCBM. This study aims to make solar cells tandem and know the value of converting solar energy into electrical energy and increase the value of efficiency generated through morphological control, ie annealing temperature and the ratio of active layer mixture. The active layer is positioned above the PEDOT:PSS layer on ITO glass substrate. The characterization results show the surface morphology of the PPV:PCBM active layer is quite evenly at annealing temperature of 165 ° C. The result of conversion of electrical energy with a UV light source in annealing samples with temperature 165 ° C is 0.03 mA and voltage of 4.085 V with an efficiency of 2.61% and mixed ratio variation was obtained in comparison of P3HT: PCBM is 1: 3

Hybrid Nanomaterial Complexes for Advanced Phage-guided Gene Delivery

PubMed Central

Yata, Teerapong; Lee, Koon-Yang; Dharakul, Tararaj; Songsivilai, Sirirurg; Bismarck, Alexander; Mintz, Paul J; Hajitou, Amin

2014-01-01

Developing nanomaterials that are effective, safe, and selective for gene transfer applications is challenging. Bacteriophages (phage), viruses that infect bacteria only, have shown promise for targeted gene transfer applications. Unfortunately, limited progress has been achieved in improving their potential to overcome mammalian cellular barriers. We hypothesized that chemical modification of the bacteriophage capsid could be applied to improve targeted gene delivery by phage vectors into mammalian cells. Here, we introduce a novel hybrid system consisting of two classes of nanomaterial systems, cationic polymers and M13 bacteriophage virus particles genetically engineered to display a tumor-targeting ligand and carry a transgene cassette. We demonstrate that the phage complex with cationic polymers generates positively charged phage and large aggregates that show enhanced cell surface attachment, buffering capacity, and improved transgene expression while retaining cell type specificity. Moreover, phage/polymer complexes carrying a therapeutic gene achieve greater cancer cell killing than phage alone. This new class of hybrid nanomaterial platform can advance targeted gene delivery applications by bacteriophage. PMID:25118171

A Study of influence on sulfonated TiO2-Poly (Vinylidene fluoride-co-hexafluoropropylene) nano composite membranes for PEM Fuel cell application

NASA Astrophysics Data System (ADS)

kumar, K. Selva; Rajendran, S.; Prabhu, M. Ramesh

2017-10-01

The present work describes the sulfonated Titania directly blended with Poly (Vinylidene fluoride-co-hexafluoropropylene) as a host polymer by solvent casting technique for PEM fuel cell application. Characterization studies such as FT-IR, SEM, EDX, AFM, Proton conductivity, contact angle measurement, IEC, TG, water uptake, tensile strength were performed by for synthesized proton conducting polymer electrolytes. The maximum proton conductivity value was found to be 3.6 × 10-3S/cm for 25 wt% sulfonated Titania based system at 80 °C. The temperature dependent proton conductivity of the polymer electrolyte follows an Arrhenius relationship. Surface morphology of the composite membranes was investigated by tapping mode. Thermal stability of the system was studied by TG analysis. The fabricated composite membranes with high proton conductivity, good water uptake and IEC parameters exhibited a maximum fuel cell power density of 85 Mw/cm2for PEM fuel cell application.

Characteristics of Diamond-Like Carbon Films Deposited on Polymer Dental Materials

NASA Astrophysics Data System (ADS)

Ohtake, Naoto; Uchi, Tomio; Yasuhara, Toshiyuki; Takashima, Mai

2012-09-01

Characterizations of diamond-like carbon (DLC) deposited on a polymer artificial tooth were performed. DLC films were deposited on dental parts made of poly(methyl methacrylate) (PMMA) resin by dc-pulse plasma chemical vapor deposition (CVD) from methane. Wear resistance test results revealed that a DLC-coated resin tooth has a very high wear resistance against tooth brushing, and endures 24 h brushing without a marked weight decrease. Cell cultivation test results show that DLC plays an important role in preventing cell death. Moreover, a biocompatibility test using a rabbit revealed that a connective tissue in the vicinity of DLC-coated PMMA is significantly thinner than that of noncoated PMMA. The numbers of inflammatory cells in the vicinity of DLC-coated and noncoated surfaces are 0 and 508 cells/mm2, respectively. These results led us to conclude that DLC films are an excellent material for use as the coating of a polymer artificial tooth in terms of not only high wear resistance but also biocompatibility.

HER2 Targeted Breast Cancer Therapy with Switchable "Off/On" Multifunctional "Smart" Magnetic Polymer Core-Shell Nanocomposites.

PubMed

Vivek, Raju; Thangam, Ramar; Kumar, Selvaraj Rajesh; Rejeeth, Chandrababu; Kumar, Gopal Senthil; Sivasubramanian, Srinivasan; Vincent, Savariar; Gopi, Dhanaraj; Kannan, Soundarapandian

2016-01-27

Multifunctional magnetic polymer nanocombinations are gaining importance in cancer nanotheranostics due to their safety and their potential in delivering targeted functions. Herein, we report a novel multifunctional core-shell magnetic polymer therapeutic nanocomposites (NCs) exhibiting pH dependent "Off-On" release of drug against breast cancer cells. The NCs are intact in blood circulation ("Off" state), i.e., at physiological pH, whereas activated ("On" state) at intracellular acidic pH environment of the targeted breast cancer cells. The NCs are prepared by coating the cannonball (iron nanocore) with hydrophobic nanopockets of pH-responsive poly(d,l-lactic-co-glycolic acid) (PLGA) polymer nanoshell that allows efficient loading of therapeutics. Further, the nanocore-polymer shell is stabilized by poly(vinylpyrrolidone) (PVP) and functionalized with a targeting HER2 ligand. The prepared Her-Fe3O4@PLGA-PVP nanocomposites facilitate packing of anticancer drug (Tamoxifen) without premature release in the bloodstream, recognizing the target cells through binding of Herceptin antibody to HER2, a cell surface receptor expressed by breast cancer cells to promote HER2 receptor mediated endocytosis and finally releasing the drug at the intracellular site of tumor cells ("On" state) to induce apoptosis. The therapeutic efficiency of hemo/cytocompatible NCs drug delivery system (DDS) in terms of targeted delivery and sustained release of therapeutic agent against breast cancer cells was substantiated by in vitro and in vivo studies. The multifunctional properties of Her-Tam-Fe3O4@PLGA-PVP NCs may open up new avenues in cancer therapy through overcoming the limitations of conventional cancer therapy.

Effect of Surface Hydration on Antifouling Properties of Mixed Charged Polymers.

PubMed

Leng, Chuan; Huang, Hao; Zhang, Kexin; Hung, Hsiang-Chieh; Xu, Yao; Li, Yaoxin; Jiang, Shaoyi; Chen, Zhan

2018-05-07

Interfacial water structure on a polymer surface in water (or surface hydration) is related to the antifouling activity of the polymer. Zwitterionic polymer materials exhibit excellent antifouling activity due to their strong surface hydration. It was proposed to replace zwitterionic polymers using mixed charged polymers because it is much easier to prepare mixed charged polymer samples with much lower costs. In this study, using sum frequency generation (SFG) vibrational spectroscopy, we investigated interfacial water structures on mixed charged polymer surfaces in water, and how such structures change while exposing to salt solutions and protein solutions. The 1:1 mixed charged polymer exhibits excellent antifouling property while other mixed charged polymers with different ratios of the positive/negative charges do not. It was found that on the 1:1 mixed charged polymer surface, SFG water signal is dominated by the contribution of the strongly hydrogen bonded water molecules, indicating strong hydration of the polymer surface. The responses of the 1:1 mixed charged polymer surface to salt solutions are similar to those of zwitterionic polymers. Interestingly, exposure to high concentrations of salt solutions leads to stronger hydration of the 1:1 mixed charged polymer surface after replacing the salt solution with water. Protein molecules do not substantially perturb the interfacial water structure on the 1:1 mixed charged polymer surface and do not adsorb to the surface, showing that this mixed charged polymer is an excellent antifouling material.

Co-precipitation of DEAE-dextran coated SPIONs: how synthesis conditions affect particle properties, stem cell labelling and MR contrast.

PubMed

Barrow, Michael; Taylor, Arthur; García Carrión, Jaime; Mandal, Pranab; Park, B Kevin; Poptani, Harish; Murray, Patricia; Rosseinsky, Matthew J; Adams, Dave J

2016-09-01

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used as contrast agents for stem cell tracking using magnetic resonance imaging (MRI). The total mass of iron oxide that can be internalised into cells without altering their viability or phenotype is an important criterion for the generation of contrast, with SPIONs designed for efficient labelling of stem cells allowing for an increased sensitivity of detection. Although changes in the ratio of polymer and iron salts in co-precipitation reactions are known to affect the physicochemical properties of SPIONs, particularly core size, the effects of these synthesis conditions on stem cell labelling and magnetic resonance (MR) contrast have not been established. Here, we synthesised a series of cationic SPIONs with very similar hydrodynamic diameters and surface charges, but different polymer content. We have investigated how the amount of polymer in the co-precipitation reaction affects core size and modulates not only the magnetic properties of the SPIONs but also their uptake into stem cells. SPIONs with the largest core size and lowest polymer content presented the highest magnetisation and relaxivity. These particles also had the greatest uptake efficiency without any deleterious effect on either the viability or function of the stem cells. However, for all particles internalised in cells, the T 2 and T 2 * relaxivity was independent of the SPION's core size. Our results indicate that the relative mass of iron taken up by cells is the major determinant of MR contrast generation and suggest that the extent of SPION uptake can be regulated by the amount of polymer used in co-precipitation reactions. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Plasma deposited composite coatings to control biological response of osteoblast-like MG-63 cells

NASA Astrophysics Data System (ADS)

Keremidarska, M.; Radeva, E.; Eleršič, K.; Iglič, A.; Pramatarova, L.; Krasteva, N.

2014-12-01

The successful osseointegration of a bone implant is greatly dependent on its ability to support cellular adhesion and functions. Deposition of thin composite coatings onto the implant surface is a promising approach to improve interactions with cells without compromising implant bulk properties. In this work, we have developed composite coatings, based on hexamethyldisiloxane (HMDS) and detonation nanodiamond (DND) particles and have studied adhesion, growth and function of osteoblast-like MG-63 cells. PPHMDS/DND composites are of interest for orthopedics because they combine superior mechanical properties and good biocompatibility of DND with high adherence of HMDS to different substrata including glass, metals and plastics. We have used two approaches of the implementation of DND particles into a polymer matrix: pre-mixture of both components followed by plasma polymerization and layer-by-layer deposition of HMDS and DND particles and found that the deposition approach affects significantly the surface properties of the resulting layers and cell behaviour. The composite, prepared by subsequent deposition of monomer and DND particles was hydrophilic, with a rougher surface and MG-63 cells demonstrated better spreading, growth and function compared to the other composite which was hydrophobic with a smooth surface similarly to unmodified polymer. Thus, by varying the deposition approach, different PPHMDS/DND composite coatings, enhancing or inhibiting osteoblast adhesion and functions, can be obtained. In addition, the effect of fibronectin pre-adsorption was studied and was found to increase greatly MG-63 cell spreading.

Catechol chemistry inspired approach to construct self-cross-linked polymer nanolayers as versatile biointerfaces.

PubMed

Liu, Xinyue; Deng, Jie; Ma, Lang; Cheng, Chong; Nie, Chuanxiong; He, Chao; Zhao, Changsheng

2014-12-16

In this study, we proposed a catechol chemistry inspired approach to construct surface self-cross-linked polymer nanolayers for the design of versatile biointerfaces. Several representative biofunctional polymers, P(SS-co-AA), P(SBMA-co-AA), P(EGMA-co-AA), P(VP-co-AA), and P(MTAC-co-AA), were first synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization, and then the catecholic molecules (dopamine, DA) were conjugated to the acrylic acid (AA) units by the facile carbodiimide chemistry. Then, the catechol (Cat) group conjugated biofunctional polymers, named PSS-Cat, PSBMA-Cat, PEGMA-Cat, PVP-Cat, and PMTAC-Cat, were applied for the construction of self-cross-linked nanolayers on polymeric substrates via the pH induced catechol cross-linking and immobilization. The XPS spectra, surface morphology, and wettability gave robust evidence that the catechol conjugated polymers were successfully coated, and the coated substrates possessed increased surface roughness and hydrophilicity. Furthermore, the systematic in vitro investigation of protein adsorption, platelet adhesion, activated partial thromboplastin time (APTT), thrombin time (TT), cell viability, and antibacterial ability confirmed that the coated nanolayers conferred the substrates with versatile biological performances. The PSS-Cat coated substrate had low blood component activation and excellent anticoagulant activity; while the PEGMA-Cat and PSBMA-Cat showed ideal resistance to protein fouling and inhibition of platelet activation. The PSS-Cat and PVP-Cat coated substrates exhibited promoted endothelial cell proliferation and viability. The PMTAC-Cat coated substrate showed an outstanding activity on bacterial inhibition. In conclusion, the catechol chemistry inspired approach allows the self-cross-linked nanolayers to be easily immobilized on polymeric substrates with the stable conformation and multiple biofunctionalities. It is expected that this low-cost and facile bioinspired coating system will present great potential in creating novel and versatile biointerfaces.

Gold nanostar-polymer hybrids for siRNA delivery: Polymer design towards colloidal stability and in vitro studies on breast cancer cells.

PubMed

Sardo, Carla; Bassi, Barbara; Craparo, Emanuela F; Scialabba, Cinzia; Cabrini, Elisa; Dacarro, Giacomo; D'Agostino, Agnese; Taglietti, Angelo; Giammona, Gaetano; Pallavicini, Piersandro; Cavallaro, Gennara

2017-03-15

To overcome the low bioavailability of siRNA (small interfering RNA) and to improve their transfection efficiency, the use of non-viral delivery carriers is today a feasible approach to transform the discovery of these incredibly potent and versatile drugs into clinical practice. Polymer-modified gold nanoconstructs (AuNCs) are currently viewed as efficient and safe intracellular delivery carriers for siRNA, as they have the possibility to conjugate the ability to stably entrap and deliver siRNAs inside cells with the advantages of gold nanoparticles, which can act as theranostic agents and radiotherapy enhancers through laser-induced hyperthermia. In this study, AuNCs were prepared by coating Gold Nano Stars (GNS) with suitable functionalised polymers, to give new insight on the choice of the coating in order to obtain colloidal stability, satisfying in vitro transfection behaviour and reliability in terms of homogeneous results upon GNS type changing. For this goal, GNS synthesized with three different sizes and shapes were coated with two different polymers: i) α-mercapto-ω-amino polyethylene glycol 3000Da (SH-PEG 3000 -NH 2 ), a hydrophilic linear polymer; ii) PHEA-PEG 2000 -EDA-LA (PPE-LA), an amphiphilic hydroxyethylaspartamide copolymer containing a PEG moiety. Both polymers contain SH or SS groups for anchoring on gold surface and NH 2 groups, which can be protonated in order to obtain a positive surface for successive siRNA layering. The effect of the features of the coating polymers on siRNA layering, and the extent of intracellular uptake and luciferase gene silencing effect were evaluated for each of the obtained coated GNS. The results highlight that amphiphilic biocompatible polymers with multi-grafting function are more suitable for ensuring the colloidal stability and the effectiveness of these colloidal systems, compared to the coating with linear PEG. Copyright © 2017 Elsevier B.V. All rights reserved.

Encapsulation of Multiple Microalgal Cells via a Combination of Biomimetic Mineralization and LbL Coating

PubMed Central

Kim, Minjeong; Choi, Myoung Gil; Ra, Ho Won; Park, Seung Bin; Kim, Yong-Joo; Lee, Kyubock

2018-01-01

The encapsulation of living cells is appealing for its various applications to cell-based sensors, bioreactors, biocatalysts, and bioenergy. In this work, we introduce the encapsulation of multiple microalgal cells in hollow polymer shells of rhombohedral shape by the following sequential processes: embedding of microalgae in CaCO3 crystals; layer-by-layer (LbL) coating of polyelectrolytes; and removal of sacrificial crystals. The microcapsule size was controlled by the alteration of CaCO3 crystal size, which is dependent on CaCl2/Na2CO3 concentration. The microalgal cells could be embedded in CaCO3 crystals by a two-step process: heterogeneous nucleation of crystal on the cell surface followed by cell embedment by the subsequent growth of crystal. The surfaces of the microalgal cells were highly favorable for the crystal growth of calcite; thus, micrometer-sized microalgae could be perfectly occluded in the calcite crystal without changing its rhombohedral shape. The surfaces of the microcapsules, moreover, could be decorated with gold nanoparticles, Fe3O4 magnetic nanoparticles, and carbon nanotubes (CNTs), by which we would expect the functionalities of a light-triggered release, magnetic separation, and enhanced mechanical and electrical strength, respectively. This approach, entailing the encapsulation of microalgae in semi-permeable and hollow polymer microcapsules, has the potential for application to microbial-cell immobilization for high-biomass-concentration cultivation as well as various other bioapplications. PMID:29438340

Characterization of Hydrophobic Interactions of Polymers with Water and Phospholipid Membranes Using Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Drenscko, Mihaela

Polymers and lipid membranes are both essential soft materials. The structure and hydrophobicity/hydrophilicity of polymers, as well as the solvent they are embedded in, ultimately determines their size and shape. Understating the variation of shape of the polymer as well as its interactions with model biological membranes can assist in understanding the biocompatibility of the polymer itself. Computer simulations, in particular molecular dynamics, can aid in characterization of the interaction of polymers with solvent, as well as polymers with model membranes. In this thesis, molecular dynamics serve to describe polymer interactions with a solvent (water) and with a lipid membrane. To begin with, we characterize the hydrophobic collapse of single polystyrene chains in water using molecular dynamics simulations. Specifically, we calculate the potential of mean force for the collapse of a single polystyrene chain in water using metadynamics, comparing the results between all atomistic with coarse-grained molecular simulation. We next explore the scaling behavior of the collapsed globular shape at the minimum energy configuration, characterized by the radius of gyration, as a function of chain length. The exponent is close to one third, consistent with that predicted for a polymer chain in bad solvent. We also explore the scaling behavior of the Solvent Accessible Surface Area (SASA) as a function of chain length, finding a similar exponent for both all-atomistic and coarse-grained simulations. Furthermore, calculation of the local water density as a function of chain length near the minimum energy configuration suggests that intermediate chain lengths are more likely to form dewetted states, as compared to shorter or longer chain lengths. Next, in order to investigate the molecular interactions between single hydrophobic polymer chains and lipids in biological membranes and at lipid membrane/solvent interface, we perform a series of molecular dynamics simulations of small membranes using all atomistic and coarse-grained methods. The molecular interaction between common polymer chains used in biomedical applications and the cell membrane is unknown. This interaction may affect the biocompatibility of the polymer chains. Molecular dynamics simulations offer an emerging tool to characterize the interaction between common degradable polymer chains used in biomedical applications, such as polycaprolactone, and model cell membranes. We systematically characterize with long-time all-atomistic molecular dynamics simulations the interaction between single polycaprolactone chains of varying chain lengths with a model phospholipid membrane. We find that the length of polymer chain greatly affects the nature of interaction with the membrane, as well as the membrane properties. Furthermore, we next utilize advanced sampling techniques in molecular dynamics to characterize the two-dimensional free energy surface for the interaction of varying polymer chain lengths (short, intermediate, and long) with model cell membranes. We find that the free energy minimum shifts from the membrane-water interface to the hydrophobic core of the phospholipid membrane as a function of chain length. These results can be used to design polymer chain lengths and chemistries to optimize their interaction with cell membranes at the molecular level.

Laser-assisted immobilization of colloid silver nanoparticles on polyethyleneterephthalate

NASA Astrophysics Data System (ADS)

Siegel, Jakub; Lyutakov, Oleksiy; Polívková, Markéta; Staszek, Marek; Hubáček, Tomáš; Švorčík, Václav

2017-10-01

Immobilization of nanoobjects on the surface of underlying material belongs to current issues of material science. Such altered materials exhibits completely exceptional properties exploitable in a broad spectrum of industrially important applications ranging from catalysts up to health-care industry. Here we present unique approach for immobilization of electrochemically synthesized silver nanoparticles on polyethyleneterephthalate (PET) foil whose essence lies in physical incorporation of particles into thin polymer surface layer induced by polarized excimer laser light. Changes in chemical composition and surface structure of polymer after particle immobilization were recorded by wide range of analytical techniques such as ARXPS, EDX, RBS, AAS, Raman, ICP-MS, DLS, UV-vis, SEM, TEM, and AFM. Thorough analysis of both nanoparticles entering the immobilization step as well as modified PET surface allowed revealing the mechanism of immobilization process itself. Silver nanoparticles were physically embedded into a thin surface layer of polymer reaching several nanometers beneath the surface rather than chemically bonded to PET macromolecules. Laser-implanted nanoparticles open up new possibilities especially in the development of the next generation cell-conform antimicrobial coatings of polymeric materials, namely due to the considerable immobilization strength which is strong enough to prevent particle release into the surrounding environment.

A Simultaneously Antimicrobial, Protein-Repellent, and Cell-Compatible Polyzwitterion Network.

PubMed

Kurowska, Monika; Eickenscheidt, Alice; Guevara-Solarte, Diana-Lorena; Widyaya, Vania Tanda; Marx, Franziska; Al-Ahmad, Ali; Lienkamp, Karen

2017-04-10

A simultaneously antimicrobial, protein-repellent, and cell-compatible surface-attached polymer network is reported, which reduces the growth of bacterial biofilms on surfaces through its multifunctionality. The coating was made from a poly(oxonorbornene)-based zwitterion (PZI), which was surface-attached and cross-linked in one step by simultaneous UV-activated CH insertion and thiol-ene reaction. The process was applicable to both laboratory surfaces like silicon, glass, and gold and real-life surfaces like polyurethane foam wound dressings. The chemical structure and physical properties of the PZI surface and the two reference surfaces SMAMP ("synthetic mimic of an antimicrobial peptide"), an antimicrobial but protein-adhesive polymer coating, and PSB (poly(sulfobetaine)), a protein-repellent but not antimicrobial polyzwitterion coating were characterized by Fourier transform infrared spectroscopy, ellipsometry, contact angle measurements, photoelectron spectroscopy, swellability measurements (using surface plasmon resonance spectroscopy, SPR), zeta potential measurements, and atomic force microscopy. The time-dependent antimicrobial activity assay (time-kill assay) confirmed the high antimicrobial activity of the PZI; SPR was used to demonstrate that it was also highly protein-repellent. Biofilm formation studies showed that the material effectively reduced the growth of Escherichia coli and Staphylococcus aureus biofilms. Additionally, it was shown that the PZI was highly compatible with immortalized human mucosal gingiva keratinocytes and human red blood cells using the Alamar Blue assay, the live-dead stain, and the hemolysis assay. PZI thus may be an attractive coating for biomedical applications, particularly for the fight against bacterial biofilms on medical devices and in other applications.

Surface grafting of poly(ethylene glycol) onto poly(acrylamide-co-vinyl amine) cross-linked films under mild conditions.

PubMed

Yamamoto, Y; Sefton, M V

1998-01-01

Poly(ethylene glycol) (PEG) was grafted onto poly(acrylamide-co-vinyl amine) (poly(AM-co-VA)) film using tresylated PEG (TPEG) at 37 degrees C in aqueous buffers (pH 7.4) with a view to surface-modifying microencapsulated mammalian cells. Poly(AM-co-VA) film was synthesized by Hofmann degradation of a cross-linked poly(acrylamide) film. Conversion to vinyl amine on the surface of the film was approximately 50%, but bulk conversion was not observed; surface specificity was thought to be the result of cleavage of aminated polymer chains at the surface due to chain scission. Reaction between primary amine and TPEG gave a graft yield of 2 mol% (based on XPS) with respect to available surface amine groups, equivalent to 54 mol% ethylene oxide based on monomer units. Physical adsorption of non-activated polymer was done under identical conditions as a control and the difference in oxygen content was significant compared to TPEG. The type of buffer agent and buffer concentration did not influence graft yields. This graft reaction, which was completed in as little as 2 h was considered to be mild enough to be used for a surface modification of microcapsules containing cells without affecting their viability. Such a surface modification technique may prove to be a useful means of enhancing the biocompatibility of microcapsules (or any tissue engineering construct) even after cell encapsulation or seeding.

Large-scale and highly efficient synthesis of micro- and nano-fibers with controlled fiber morphology by centrifugal jet spinning for tissue regeneration

NASA Astrophysics Data System (ADS)

Ren, Liyun; Pandit, Vaibhav; Elkin, Joshua; Denman, Tyler; Cooper, James A.; Kotha, Shiva P.

2013-02-01

PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a highly efficient synthesis method for micron- to nano-sized fibers with a production rate up to 0.5 g min-1. During the centrifugal jet spinning process, a polymer solution jet is stretched by the centrifugal force of a rotating chamber. By engineering the rheological properties of the polymer solution, solvent evaporation rate and centrifugal force that are applied on the solution jet, polyvinylpyrrolidone (PVP) and poly(l-lactic acid) (PLLA) composite fibers with various diameters are fabricated. Viscosity measurements of polymer solutions allowed us to determine critical polymer chain entanglement limits that allow the generation of continuous fiber as opposed to beads or beaded fibers. Above a critical concentration at which polymer chains are partially or fully entangled, lower polymer concentrations and higher centrifugal forces resulted in thinner fibers. Etching of PVP from the PLLA-PVP composite fibers doped with increasing PVP concentrations yielded PLLA fibers with increasing nano-scale surface roughness and porosity, which increased the fiber hydrophilicity dramatically. Scanning electron micrographs of the etched composite fibers suggest that PVP and PLLA were co-contiguously phase separated within the composite fibers during spinning and nano-scale roughness features were created after the partial etching of PVP. To study the tissue regeneration efficacy of the engineered PLLA fiber matrix, human dermal fibroblasts are used to simulate partial skin graft. Fibers with increased PLLA surface roughness and porosity demonstrated a trend towards higher cell attachment and proliferation.PLLA fibrous tissue scaffolds with controlled fiber nanoscale surface roughness are fabricated with a novel centrifugal jet spinning process. The centrifugal jet spinning technique is a highly efficient synthesis method for micron- to nano-sized fibers with a production rate up to 0.5 g min-1. During the centrifugal jet spinning process, a polymer solution jet is stretched by the centrifugal force of a rotating chamber. By engineering the rheological properties of the polymer solution, solvent evaporation rate and centrifugal force that are applied on the solution jet, polyvinylpyrrolidone (PVP) and poly(l-lactic acid) (PLLA) composite fibers with various diameters are fabricated. Viscosity measurements of polymer solutions allowed us to determine critical polymer chain entanglement limits that allow the generation of continuous fiber as opposed to beads or beaded fibers. Above a critical concentration at which polymer chains are partially or fully entangled, lower polymer concentrations and higher centrifugal forces resulted in thinner fibers. Etching of PVP from the PLLA-PVP composite fibers doped with increasing PVP concentrations yielded PLLA fibers with increasing nano-scale surface roughness and porosity, which increased the fiber hydrophilicity dramatically. Scanning electron micrographs of the etched composite fibers suggest that PVP and PLLA were co-contiguously phase separated within the composite fibers during spinning and nano-scale roughness features were created after the partial etching of PVP. To study the tissue regeneration efficacy of the engineered PLLA fiber matrix, human dermal fibroblasts are used to simulate partial skin graft. Fibers with increased PLLA surface roughness and porosity demonstrated a trend towards higher cell attachment and proliferation. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr33423f

Cyclodextrin-based star polymers as a versatile platform for nanochemotherapeutics: Enhanced entrapment and uptake of idarubicin.

PubMed

Nafee, N; Hirosue, M; Loretz, B; Wenz, G; Lehr, C-M

2015-05-01

A series of cyclodextrin-based star polymers were synthesized using β-cyclodextrin (CD) as hydrophilic core, methyl methacrylate (MMA) and tert-butyl acrylate (tBA) as hydrophobic arms. Star polymers, either homopolymers or random/block copolymers, showed narrow molecular weight distributions. Grafting hydrophobic arms created CD-based nanoparticles (CD-NPs) in the size range (130-200nm) with narrow PdI <0.15 and slightly negative ζ-potential. Particle surface could be modified with chitosan to impart a positive surface charge. Colloidal stability of CD-NPs was a function of pH as revealed by the pH-titration curves. CD-NPs were used as carrier for the chemotherapeutic drug idarubicin (encapsulation efficiency, EE ∼40%) ensuring prolonged release profile (∼80% after 48h). For cell-based studies, coumarin-6 was encapsulated as a fluorescent marker (EE ∼75%). Uptake studies carried out on A549 and Caco-2 cell lines proved the uptake of coumarin-loaded NPs as a function of time and preferential localization in the cytoplasm. Uptake kinetics revealed no saturation or plateau over 6h. Chitosan-modified NPs showed significantly improved, concentration-dependent cellular uptake. Meanwhile, CD-NPs were non-cytotoxic on both cell lines over the concentration range (0.25-3mg/ml) as studied by MTT and LDH assays. In conclusion, CD star polymers can be considered a versatile platform for a new class of biocompatible nanochemotherapy. Copyright © 2015 Elsevier B.V. All rights reserved.

Amine-Rich Organic Thin Films for Cell Culture: Possible Electrostatic Effects in Cell-Surface Interactions

NASA Astrophysics Data System (ADS)

Wertheimer, Michael R.; St-Georges-Robillard, Amélie; Lerouge, Sophie; Mwale, Fackson; Elkin, Bentsian; Oehr, Christian; Wirges, Werner; Gerhard, Reimund

2012-11-01

In recent communications from these laboratories, we observed that amine-rich thin organic layers are very efficient surfaces for the adhesion of mammalian cells. We prepare such deposits by plasma polymerization at low pressure, atmospheric pressure, or by vacuum-ultraviolet photo-polymerization. More recently, we have also investigated a commercially available material, Parylene diX AM. In this article we first briefly introduce literature relating to electrostatic interactions between cells, proteins, and charged surfaces. We then present certain selected cell-response results that pertain to applications in orthopedic and cardiovascular medicine: we discuss the influence of surface properties on the observed behaviors of two particular cell lines, human U937 monocytes, and Chinese hamster ovary cells. Particular emphasis is placed on possible electrostatic attractive forces due to positively charged R-NH3+ groups and negatively charged proteins and cells, respectively. Experiments carried out with electrets, polymers with high positive or negative surface potentials are added for comparison.

Uptake and transfection with polymeric nanoparticles are dependent on polymer end-group structure, but largely independent of nanoparticle physical and chemical properties

PubMed Central

Sunshine, Joel C.; Peng, Daniel Y.; Green, Jordan J.

2012-01-01

Development of non-viral particles for gene delivery requires a greater understanding of the properties that enable gene delivery particles to overcome the numerous barriers to intracellular DNA delivery. Linear poly(beta-amino) esters (PBAE) have shown substantial promise for gene delivery, but the mechanism behind their effectiveness is not well quantified with respect to these barriers. In this study, we synthesized, characterized, and evaluated for gene delivery an array of linear PBAEs that differed by small changes along the backbone, side chain, and end-group of the polymers. We examined particle size and surface charge, polymer molecular weight, polymer degradation rate, buffering capacity, cellular uptake, transfection, and cytotoxicity of nanoparticles formulated with these polymers. Significantly, this is the first study that has quantified how small differential structural changes to polymers of this class modulate buffering capacity and polymer degradation rate and relates these findings to gene delivery efficacy. All polymers formed positively charged (zeta potential 21–29 mV) nanosized articles (~ 150 nm). The polymers hydrolytically degraded quickly in physiological conditions, with half-lives ranging from 90 minutes to 6 hours depending on polymer structure. The PBAE buffering capacities in the relevant pH range (pH 5.1 – 7.4) varied from 34% to 95% protonable amines, and on a per mass basis, PBAEs buffered 1.4–4.6 mmol H+/g. When compared to 25 kDa branched polyethyleneimine (PEI), PBAEs buffer significantly fewer protons/mass, as PEI buffers 6.2 mmol H+/g over the same range. However, due to the relatively low cytotoxicity of PBAEs, higher polymer mass can be used to form particles than with PEI and total buffering capacity of PBAE-based particles significantly exceeds that of PEI. Uptake into COS-7 cells ranged from 0% to 95% of cells and transfection ranged from 0% to 93% of cells, depending on the base polymer structure and the end-modifications examined. Five polymers achieved higher uptake and transfection efficacy with less toxicity than branched-PEI control. Surprisingly, acrylate-terminated base polymers were dramatically less efficacious than their end-capped versions, both in terms of uptake (1–3% for acrylate, 75–94% for end-capped) and transfection efficacy (0–1% vs. 20–89%), even though there are minimal differences between acrylate and end-capped polymers in terms of DNA retardation in gel electrophoresis, particle size, zeta potential, and cytotoxicity. These studies further elucidate the role of polymer structure for gene delivery and highlight that small molecule end-group modification of a linear polymer can be critical for cellular uptake in a manner that is largely independent of polymer/DNA binding, particle size, and particle surface charge. PMID:22970908

Reversible Stabilization of Vesicles: Redox-Responsive Polymer Nanocontainers for Intracellular Delivery.

PubMed

de Vries, Wilke C; Grill, David; Tesch, Matthias; Ricker, Andrea; Nüsse, Harald; Klingauf, Jürgen; Studer, Armido; Gerke, Volker; Ravoo, Bart Jan

2017-08-01

We present the self-assembly of redox-responsive polymer nanocontainers comprising a cyclodextrin vesicle core and a thin reductively cleavable polymer shell anchored via host-guest recognition on the vesicle surface. The nanocontainers are of uniform size, show high stability, and selectively respond to a mild reductive trigger as revealed by dynamic light scattering, transmission electron microscopy, atomic force microscopy, a quantitative thiol assay, and fluorescence spectroscopy. Live cell imaging experiments demonstrate a specific redox-responsive release and cytoplasmic delivery of encapsulated hydrophilic payloads, such as the pH-probe pyranine, and the fungal toxin phalloidin. Our results show the high potential of these stimulus-responsive nanocontainers for cell biological applications requiring a controlled delivery. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inverted organic electronic and optoelectronic devices

NASA Astrophysics Data System (ADS)

Small, Cephas E.

The research and development of organic electronics for commercial application has received much attention due to the unique properties of organic semiconductors and the potential for low-cost high-throughput manufacturing. For improved large-scale processing compatibility and enhanced device stability, an inverted geometry has been employed for devices such as organic light emitting diodes and organic photovoltaic cells. These improvements are attributed to the added flexibility to incorporate more air-stable materials into the inverted device geometry. However, early work on organic electronic devices with an inverted geometry typically showed reduced device performance compared to devices with a conventional structure. In the case of organic light emitting diodes, inverted devices typically show high operating voltages due to insufficient carrier injection. Here, a method for enhancing hole injection in inverted organic electronic devices is presented. By incorporating an electron accepting interlayer into the inverted device, a substantial enhancement in hole injection efficiency was observed as compared to conventional devices. Through a detailed carrier injection study, it is determined that the injection efficiency enhancements in the inverted devices are due to enhanced charge transfer at the electron acceptor/organic semiconductor interface. A similar situation is observed for organic photovoltaic cells, in which devices with an inverted geometry show limited carrier extraction in early studies. In this work, enhanced carrier extraction is demonstrated for inverted polymer solar cells using a surface-modified ZnO-polymer composite electron-transporting layer. The insulating polymer in the composite layer inhibited aggregation of the ZnO nanoparticles, while the surface-modification of the composite interlayer improved the electronic coupling with the photoactive layer. As a result, inverted polymer solar cells with power conversion efficiencies of over 8% were obtained. To further study carrier extraction in inverted polymer solar cells, the active layer thickness dependence of the efficiency was investigated. For devices with active layer thickness < 200 nm, power conversion efficiencies over 8% was obtained. This result is important for demonstrating improved large-scale processing compatibility. Above 200 nm, significant reduction in cell efficiency were observed. A detailed study of the loss processes that contributed to the reduction in efficiency for thick-film devices are presented.

All-polymer solar cells with bulk heterojunction nanolayers of chemically doped electron-donating and electron-accepting polymers.

PubMed

Nam, Sungho; Shin, Minjung; Park, Soohyeong; Lee, Sooyong; Kim, Hwajeong; Kim, Youngkyoo

2012-11-21

We report the improved performance of all-polymer solar cells with bulk heterojunction nanolayers of an electron-donating polymer (poly(3-hexylthiophene) (P3HT)) and an electron-accepting polymer (poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT)), which were both doped with 4-ethylbenzenesulfonic acid (EBSA). To choose the doping ratio of P3HT for all-polymer solar cells, various EBSA doping ratios (0, 1, 3, 5, 10, 20 wt%) were tested by employing optical absorption spectroscopy, photoluminescence spectroscopy, photoelectron yield spectroscopy, and space-charge-limited current (SCLC) mobility measurement. The doping reaction of P3HT with EBSA was followed by observing the colour change in solutions. The final doping ratio for P3HT was chosen as 1 wt% from the best hole mobility measured in the thickness direction, while that for F8BT was fixed as 10 wt% (F8BT-EBSA). The polymer:polymer solar cells with bulk heterojunction nanolayers of P3HT-EBSA (EBSA-doped P3HT) and F8BT-EBSA (EBSA-doped F8BT) showed greatly improved short circuit current density (J(SC)) and open circuit voltage (V(OC)), compared to the undoped solar cells. As a result, the power conversion efficiency (PCE) was enhanced by ca. 300% for the 6 : 4 (P3HT-EBSA : F8BT-EBSA) composition and ca. 400% for the 8 : 2 composition. The synchrotron-radiation grazing incidence angle X-ray diffraction (GIXD) measurement revealed that the crystallinity of the doped nanolayers significantly increased by EBSA doping owing to the formation of advanced phase segregation morphology, as supported by the surface morphology change measured by atomic force microscopy. Thus the improved PCE can be attributed to the enhanced charge transport by the formation of permanent charges and better charge percolation paths by EBSA doping.

Interfacial behavior of polymer electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kerr, John; Kerr, John B.; Han, Yong Bong

2003-06-03

Evidence is presented concerning the effect of surfaces on the segmental motion of PEO-based polymer electrolytes in lithium batteries. For dry systems with no moisture the effect of surfaces of nano-particle fillers is to inhibit the segmental motion and to reduce the lithium ion transport. These effects also occur at the surfaces in composite electrodes that contain considerable quantities of carbon black nano-particles for electronic connection. The problem of reduced polymer mobility is compounded by the generation of salt concentration gradients within the composite electrode. Highly concentrated polymer electrolytes have reduced transport properties due to the increased ionic cross-linking. Combinedmore » with the interfacial interactions this leads to the generation of low mobility electrolyte layers within the electrode and to loss of capacity and power capability. It is shown that even with planar lithium metal electrodes the concentration gradients can significantly impact the interfacial impedance. The interfacial impedance of lithium/PEO-LiTFSI cells varies depending upon the time elapsed since current was turned off after polarization. The behavior is consistent with relaxation of the salt concentration gradients and indicates that a portion of the interfacial impedance usually attributed to the SEI layer is due to concentrated salt solutions next to the electrode surfaces that are very resistive. These resistive layers may undergo actual phase changes in a non-uniform manner and the possible role of the reduced mobility polymer layers in dendrite initiation and growth is also explored. It is concluded that PEO and ethylene oxide-based polymers are less than ideal with respect to this interfacial behavior.« less

Ultra-low density microcellular polymer foam and method

DOEpatents

Simandl, Ronald F.; Brown, John D.

1996-01-01

An ultra-low density, microcellular open-celled polymer foam and a method for making such foam. A polymer is dissolved in a heated solution consisting essentially of at least one solvent for the dissolution of the polymer in the heated solution and the phase inversion of the dissolved polymer to a liquid gel upon sufficient cooling of the heated solution. The heated solution is contained in a containment means provided with a nucleating promoting means having a relatively rough surface formed of fixed nucleating sites. The heated solution is cooled for a period of time sufficient to form a liquid gel of the polymer by phase inversion. From the gel, a porous foam having a density of less than about 12.0 mg/cm.sup.3 and open porosity provided by well interconnected strut morphology is formed.

Ultra-low density microcellular polymer foam and method

DOEpatents

Simandl, R.F.; Brown, J.D.

1996-03-19

An ultra-low density, microcellular open-celled polymer foam and a method for making such foam are disclosed. A polymer is dissolved in a heated solution consisting essentially of at least one solvent for the dissolution of the polymer in the heated solution and the phase inversion of the dissolved polymer to a liquid gel upon sufficient cooling of the heated solution. The heated solution is contained in a containment means provided with a nucleating promoting means having a relatively rough surface formed of fixed nucleating sites. The heated solution is cooled for a period of time sufficient to form a liquid gel of the polymer by phase inversion. From the gel, a porous foam having a density of less than about 12.0 mg/cm{sup 3} and open porosity provided by well interconnected strut morphology is formed.

Surface modification and characterization of indium-tin oxide for organic light-emitting devices.

PubMed

Zhong, Z Y; Jiang, Y D

2006-10-15

In this work, we used different treatment methods (ultrasonic degreasing, hydrochloric acid treatment, and oxygen plasma) to modify the surfaces of indium-tin oxide (ITO) substrates for organic light-emitting devices. The surface properties of treated ITO substrates were studied by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), sheet resistance, contact angle, and surface energy measurements. Experimental results show that the ITO surface properties are closely related to the treatment methods, and the oxygen plasma is more efficient than the other treatments since it brings about smoother surfaces, lower sheet resistance, higher work function, and higher surface energy and polarity of the ITO substrate. Moreover, polymer light-emitting electrochemical cells (PLECs) with differently treated ITO substrates as device electrodes were fabricated and characterized. It is found that surface treatments of ITO substrates have a certain degree of influence upon the injection current, brightness, and efficiency, but hardly upon the turn-on voltages of current injection and light emission, which are in agreement with the measured optical energy gap of the electroluminescent polymer. The oxygen plasma treatment on the ITO substrate yields the best performance of PLECs, due to the improvement of interface formation and electrical contact of the ITO substrate with the polymer blend in the PLECs.

Phospholipid Polymer Biointerfaces for Lab-on-a-Chip Devices.

PubMed

Xu, Yan; Takai, Madoka; Ishihara, Kazuhiko

2010-06-01

This review summarizes recent achievements and progress in the development of various functional 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer biointerfaces for lab-on-a-chip devices and applications. As phospholipid polymers, MPC polymers can form cell-membrane-like surfaces by surface chemistry and physics and thereby provide biointerfaces capable of suppressing protein adsorption and many subsequent biological responses. In order to enable application to microfluidic devices, a number of MPC polymers with diverse functions have been specially designed and synthesized by incorporating functional units such as charge and active ester for generating the microfluidic flow and conjugating biomolecules, respectively. Furthermore, these polymers were incorporated with silane or hydrophobic moiety to construct stable interfaces on various substrate materials such as glass, quartz, poly(methyl methacrylate), and poly(dimethylsiloxane), via a silane-coupling reaction or hydrophobic interactions. The basic interfacial properties of these interfaces have been characterized from multiple aspects of chemistry, physics, and biology, and the suppression of nonspecific bioadsorption and control of microfluidic flow have been successfully achieved using these biointerfaces on a chip. Further, many chip-based biomedical applications such as immunoassays and DNA separation have been accomplished by integrating these biointerfaces on a chip. Therefore, functional phospholipid polymer interfaces are promising and useful for application to lab-on-a-chip devices in biomedicine.

Charge carrier dynamics and surface plasmon interaction in gold nanorod-blended organic solar cell

NASA Astrophysics Data System (ADS)

Rana, Aniket; Gupta, Neeraj; Lochan, Abhiram; Sharma, G. D.; Chand, Suresh; Kumar, Mahesh; Singh, Rajiv K.

2016-08-01

The inclusion of plasmonic nanoparticles into organic solar cell enhances the light harvesting properties that lead to higher power conversion efficiency without altering the device configuration. This work defines the consequences of the nanoparticle overloading amount and energy transfer process between gold nanorod and polymer (active matrix) in organic solar cells. We have studied the hole population decay dynamics coupled with gold nanorods loading amount which provides better understanding about device performance limiting factors. The exciton and plasmon together act as an interacting dipole; however, the energy exchange between these two has been elucidated via plasmon resonance energy transfer (PRET) mechanism. Further, the charge species have been identified specifically with respect to their energy levels appearing in ultrafast time domain. The specific interaction of these charge species with respective surface plasmon resonance mode, i.e., exciton to transverse mode of oscillation and polaron pair to longitudinal mode of oscillations, has been explained. Thus, our analysis reveals that PRET enhances the carrier population density in polymer via non-radiative process beyond the concurrence of a particular plasmon resonance oscillation mode and polymer absorption range. These findings give new insight and reveal specifically the factors that enhance and control the performance of gold nanorods blended organic solar cells. This work would lead in the emergence of future plasmon based efficient organic electronic devices.

Charge carrier dynamics and surface plasmon interaction in gold nanorod-blended organic solar cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rana, Aniket; Lochan, Abhiram; Chand, Suresh

The inclusion of plasmonic nanoparticles into organic solar cell enhances the light harvesting properties that lead to higher power conversion efficiency without altering the device configuration. This work defines the consequences of the nanoparticle overloading amount and energy transfer process between gold nanorod and polymer (active matrix) in organic solar cells. We have studied the hole population decay dynamics coupled with gold nanorods loading amount which provides better understanding about device performance limiting factors. The exciton and plasmon together act as an interacting dipole; however, the energy exchange between these two has been elucidated via plasmon resonance energy transfer (PRET)more » mechanism. Further, the charge species have been identified specifically with respect to their energy levels appearing in ultrafast time domain. The specific interaction of these charge species with respective surface plasmon resonance mode, i.e., exciton to transverse mode of oscillation and polaron pair to longitudinal mode of oscillations, has been explained. Thus, our analysis reveals that PRET enhances the carrier population density in polymer via non-radiative process beyond the concurrence of a particular plasmon resonance oscillation mode and polymer absorption range. These findings give new insight and reveal specifically the factors that enhance and control the performance of gold nanorods blended organic solar cells. This work would lead in the emergence of future plasmon based efficient organic electronic devices.« less

Light-switchable polymer from cationic to zwitterionic form: synthesis, characterization, and interactions with DNA and bacterial cells.

PubMed

Sobolčiak, Patrik; Spírek, Mário; Katrlík, Jaroslav; Gemeiner, Peter; Lacík, Igor; Kasák, Peter

2013-04-25

A novel cationic polymer poly(N,N-dimethyl-N-[3-(methacroylamino) propyl]-N-[2-[(2-nitrophenyl)methoxy]-2-oxo-ethyl]ammonium chloride) is synthesized by free-radical polymerization of N-[3-(dimethylamino)propyl] methacrylamide and subsequent quaternization with o-nitrobenzyl 2-chloroacetate. The photolabile o-nitrobenzyl carboxymethyl pendant moiety is transformed to the zwitterionic carboxybetaine form upon the irradiation at 365 nm. This feature is used to condense and, upon the light irradiation, to release double-strand DNA tested by gel electrophoresis and surface plasmon resonance experiments as well as to switch the antibacterial activity to non-toxic character demonstrated for Escherichia coli bacterial cells in solution and at the surface using the self-assembled monolayers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic and Hybrid Organic Solid-State Photovoltaic Materials and Devices

DTIC Science & Technology

2014-02-19

hybrids have potential applications in solar cells and may thus provide mobile energy sources for aircraft and soldier technologies. Modeling and...modeling and simulation developed in this project are encouraging further development. 2. Technical Activities Hybrid organic solar cells are an...between surface-modified semiconducting nanoparticles and polymers often contributes to the limited efficiency of hybrid photovoltaic cells and

Co-Pt core-shell nanostructured catalyst prepared by selective chemical vapor pulse deposition of Pt on Co as a cathode in polymer electrolyte fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seo, Sang-Joon; Chung, Ho-Kyoon; Yoo, Ji-Beom

2014-01-15

A new type of PtCo/C catalyst for use as a cathode in polymer electrolyte fuel cells was prepared by selective chemical vapor pulse deposition (CVPD) of Pt on the surface of Co. The activity of the prepared catalyst for oxygen reduction was higher than that of a catalyst prepared by sequential impregnation (IMP) with the two metallic components. This catalytic activity difference occurs because the former catalyst has smaller Pt crystallites that produce stronger Pt-Co interactions and have a larger Pt surface area. Consequently, the CVPD catalyst has a great number of Co particles that are in close contact withmore » the added Pt. The Pt surface was also electronically modified by interactions with Co, which were stronger in the CVPD catalyst than in the IMP catalyst, as indicated by X-ray diffraction, X-ray photoemission spectroscopy, and cyclic voltammetry measurements of the catalysts.« less

Urokinase Receptor Counteracts Vascular Smooth Muscle Cell Functional Changes Induced by Surface Topography

PubMed Central

Kiyan, Yulia; Kurselis, Kestutis; Kiyan, Roman; Haller, Hermann; Chichkov, Boris N.; Dumler, Inna

2013-01-01

Current treatments for human coronary artery disease necessitate the development of the next generations of vascular bioimplants. Recent reports provide evidence that controlling cell orientation and morphology through topographical patterning might be beneficial for bioimplants and tissue engineering scaffolds. However, a concise understanding of cellular events underlying cell-biomaterial interaction remains missing. In this study, applying methods of laser material processing, we aimed to obtain useful markers to guide in the choice of better vascular biomaterials. Our data show that topographically treated human primary vascular smooth muscle cells (VSMC) have a distinct differentiation profile. In particular, cultivation of VSMC on the microgrooved biocompatible polymer E-shell induces VSMC modulation from synthetic to contractile phenotype and directs formation and maintaining of cell-cell communication and adhesion structures. We show that the urokinase receptor (uPAR) interferes with VSMC behavior on microstructured surfaces and serves as a critical regulator of VSMC functional fate. Our findings suggest that microtopography of the E-shell polymer could be important in determining VSMC phenotype and cytoskeleton organization. They further suggest uPAR as a useful target in the development of predictive models for clinical VSMC phenotyping on functional advanced biomaterials. PMID:23843899

A liposome-based antigen delivery system using pH-sensitive fusogenic polymers for cancer immunotherapy.

PubMed

Yuba, Eiji; Harada, Atsushi; Sakanishi, Yuichi; Watarai, Shinobu; Kono, Kenji

2013-04-01

Highly pH-sensitive liposomes that deliver antigenic molecules into cytosol through fusion with or destabilization of endosome were prepared by surface modification of egg yolk phosphatidylcholine/dioleoylphosphatidylethanolamine (1/1, mol/mol) liposomes with 3-methylglutarylated poly(glycidol) of linear (MGlu-LPG) or hyperbranched structure (MGlu-HPG). These polymer-modified liposomes were stable at neutral pH, but they became strongly destabilized below pH 6, which corresponds to the pH of endosome. These polymer-modified liposomes were taken up by murine dendritic cells (DCs) more efficiently than the unmodified liposomes were through an endocytic pathway. They introduced entrapped ovalbumin (OVA) molecules into cytosol. Subcutaneous or nasal administration of the polymer-modified liposomes loaded with OVA induced generation of OVA-specific cytotoxic T cells (CTL) much more effectively than the unmodified liposomes loaded with OVA. Furthermore, administration of the polymer-modified OVA-loaded liposomes to mice bearing E.G7-OVA tumor significantly reduced the tumor burden, although the OVA-loaded unmodified liposomes only slightly affected tumor growth. Results suggest that the polymer-modified liposomes with highly pH-sensitive destabilizing property are promising as antigen carriers for efficient cancer immunotherapy. Copyright © 2012 Elsevier Ltd. All rights reserved.

Molecular Design of Antifouling Polymer Brushes Using Sequence-Specific Peptoids.

PubMed

Lau, King Hang Aaron; Sileika, Tadas S; Park, Sung Hyun; Sousa, Ana Maria Leal; Burch, Patrick; Szleifer, Igal; Messersmith, Phillip B

2015-01-07

Material systems that can be used to flexibly and precisely define the chemical nature and molecular arrangement of a surface would be invaluable for the control of complex biointerfacial interactions. For example, progress in antifouling polymer biointerfaces that prevent non-specific protein adsorption and cell attachment, which can significantly improve the performance of an array of biomedical and industrial applications, is hampered by a lack of chemical models to identify the molecular features conferring their properties. Poly(N-substituted glycine) "peptoids" are peptidomimetic polymers that can be conveniently synthesized with specific monomer sequences and chain lengths, and are presented as a versatile platform for investigating the molecular design of antifouling polymer brushes. Zwitterionic antifouling polymer brushes have captured significant recent attention, and a targeted library of zwitterionic peptoid brushes with a different charge densities, hydration, separations between charged groups, chain lengths, and grafted chain densities, is quantitatively evaluated for their antifouling properties through a range of protein adsorption and cell attachment assays. Specific zwitterionic brush designs were found to give rise to distinct but subtle differences in properties. The results also point to the dominant roles of the grafted chain density and chain length in determining the performance of antifouling polymer brushes.

Synthesis of polymer coated Co0.5Zn0.5Fe2O4 nanoparticles and their enhanced anticancer activity against HepG2 cell line

NASA Astrophysics Data System (ADS)

Ali, Z.; Abbasi, R.; Khan, A. J.; Arshad, J.; Atif, M.; Ahmad, N.; Khalid, W.

2018-05-01

Cobalt zinc ferrite nanoparticles with stoichiometry Co0.5Zn0.5Fe2O4 (CZFN) were synthesized by sol-gel method with high colloidal stability having room temperature ferromagnetism. For biological applications, CZFN were transferred to aqueous phase by polymer coating with amphiphilic polymer, whereas fluorescent dye (ATTO-590) was used as model system for anti-cancer drug loaded polymer shell. The amount of functional molecule varied up to 25% of the anhydride rings, which provides greater affinity of drug loading in polymer shell. CZFN were characterized by x-ray diffraction, Fourier transformed infrared spectroscopy, UV–vis absorption spectroscopy, gel electrophoresis and vibrating sample magnetometer. The in vitro cytotoxicity of CZFN was examined against HepG2 which revealed that CZFN (IC50:3.01 nM) strongly inhabits growth of the cells. Further the particles did not induce any significant hemolysis. Stimulatingly, this seems to be a noteworthy improvement towards the ability of surface functionalized multifunctional CZFN as carriers for drugs for anti-cancer therapy and their use as nanomedicine.

Exploring the effects of electrospinning processing protocols on fiber surface morphology and polymer chain conformation

NASA Astrophysics Data System (ADS)

Stephens, Jean S.

Electrospinning is a fiber formation technique that uses electrostatic forces to create continuous, nanometer diameter fibers. The work presented here focuses on the continuing efforts to build a stronger fundamental understanding of electrospinning by exploring structure/property/process relationships by investigating the effects of process protocols on fiber surface morphology and polymer chain conformation. By varying the processing parameters it has been possible to produce fibers with unique surface features, microtextured/nanoporous fibers and nanowebs. In the microtextured/nanoporous fiber studies, changing the solution concentration, solvent volatility, and relative humidity was found to alter the size, shape, and distribution of pores on the fiber surface. The mechanisms that can explain the pore formation and texturing on the surface of the fibers are phase separation (aggregation into polymer rich and polymer lean regions) and breath figures (evaporative cooling and vapor condensation). Through a judicious choice of the electrospinning processing parameters we have also been able to create "web" like structures of nanofibers (5--25 nm) from collagen, dragline silk analog, nylon, and denatured collagen. Electrostatic repulsion and thin film dewetting are thought to be responsible for the formation of the nanowebs. These unique structures were characterized using FESEM, TEM, OM, and AFM. Raman spectroscopy, initially developed as a "real time" characterization technique to study electrospun fiber formation, has also been used to investigate the effect of electrospinning on the chain conformation of bioinspired polymers. Comparing the spectrum of the bulk material to that of the electrospun material identified conformational changes in nylon 6 and dragline silk analog. The conformational change in nylon 6 (alpha-form to gamma-form) results from the stresses induced on the electrospinning jet during fiber formation, whereas the conformational change in the silk analog (beta-sheet to alpha-helical) result from electric field assembling of the charged a-helical segments of the protein polymer in solution. The investigations described here have allowed us to build a virtual database of the processing conditions needed to create materials for tissue engineering constructs. Electrospun collagen membranes have been used in preliminary cell attachment studies. From the trials it was observed that the cells migrated into the membranes indicating that the membranes are suitable for tissue engineering scaffolds.

Electrically switchable polymer liquid crystal and polymer birefringent flake in fluid host systems and optical devices utilizing same

DOEpatents

Marshall, Kenneth L.; Kosc, Tanya Z.; Jacobs, Stephen D.; Faris, Sadeg M.; Li, Le

2003-12-16

Flakes or platelets of polymer liquid crystals (PLC) or other birefringent polymers (BP) suspended in a fluid host medium constitute a system that can function as the active element in an electrically switchable optical device when the suspension is either contained between a pair of rigid substrates bearing transparent conductive coatings or dispersed as microcapsules within the body of a flexible host polymer. Optical properties of these flake materials include large effective optical path length, different polarization states and high angular sensitivity in their selective reflection or birefringence. The flakes or platelets of these devices need only a 3-20.degree. rotation about the normal to the cell surface to achieve switching characteristics obtainable with prior devices using particle rotation or translation.

Conducting Polymer 3D Microelectrodes

PubMed Central

Sasso, Luigi; Vazquez, Patricia; Vedarethinam, Indumathi; Castillo-León, Jaime; Emnéus, Jenny; Svendsen, Winnie E.

2010-01-01

Conducting polymer 3D microelectrodes have been fabricated for possible future neurological applications. A combination of micro-fabrication techniques and chemical polymerization methods has been used to create pillar electrodes in polyaniline and polypyrrole. The thin polymer films obtained showed uniformity and good adhesion to both horizontal and vertical surfaces. Electrodes in combination with metal/conducting polymer materials have been characterized by cyclic voltammetry and the presence of the conducting polymer film has shown to increase the electrochemical activity when compared with electrodes coated with only metal. An electrochemical characterization of gold/polypyrrole electrodes showed exceptional electrochemical behavior and activity. PC12 cells were finally cultured on the investigated materials as a preliminary biocompatibility assessment. These results show that the described electrodes are possibly suitable for future in-vitro neurological measurements. PMID:22163508

Engineering micropatterned surfaces to modulate the function of vascular stem cells.

PubMed

Li, Jennifer; Wu, Michelle; Chu, Julia; Sochol, Ryan; Patel, Shyam

2014-02-21

Multipotent vascular stem cells have been implicated in vascular disease and in tissue remodeling post therapeutic intervention. Hyper-proliferation and calcified extracellular matrix deposition of VSC cause blood vessel narrowing and plaque hardening thereby increasing the risk of myocardial infarct. In this study, to optimize the surface design of vascular implants, we determined whether micropatterned polymer surfaces can modulate VSC differentiation and calcified matrix deposition. Undifferentiated rat VSC were cultured on microgrooved surfaces of varied groove widths, and on micropost surfaces. 10μm microgrooved surfaces elongated VSC and decreased cell proliferation. However, microgrooved surfaces did not attenuate calcified extracellular matrix deposition by VSC cultured in osteogenic media conditions. In contrast, VSC cultured on micropost surfaces assumed a dendritic morphology, were significantly less proliferative, and deposited minimal calcified extracellular matrix. These results have significant implications for optimizing the design of cardiovascular implant surfaces. Copyright © 2014 Elsevier Inc. All rights reserved.

Interfacing nanostructures to biological cells

DOEpatents

Chen, Xing; Bertozzi, Carolyn R.; Zettl, Alexander K.

2012-09-04

Disclosed herein are methods and materials by which nanostructures such as carbon nanotubes, nanorods, etc. are bound to lectins and/or polysaccharides and prepared for administration to cells. Also disclosed are complexes comprising glycosylated nanostructures, which bind selectively to cells expressing glycosylated surface molecules recognized by the lectin. Exemplified is a complex comprising a carbon nanotube functionalized with a lipid-like alkane, linked to a polymer bearing repeated .alpha.-N-acetylgalactosamine sugar groups. This complex is shown to selectively adhere to the surface of living cells, without toxicity. In the exemplified embodiment, adherence is mediated by a multivalent lectin, which binds both to the cells and the .alpha.-N-acetylgalactosamine groups on the nanostructure.

Lipogels: surface-adherent composite hydrogels assembled from poly(vinyl alcohol) and liposomes

NASA Astrophysics Data System (ADS)

Jensen, Bettina E. B.; Hosta-Rigau, Leticia; Spycher, Philipp R.; Reimhult, Erik; Städler, Brigitte; Zelikin, Alexander N.

2013-07-01

Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus illustrating the potential of the lipogels as a drug eluting interface for biomedical applications.Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus illustrating the potential of the lipogels as a drug eluting interface for biomedical applications. Electronic supplementary information (ESI) available: Paclitaxel calibration curve and images of DIC of PLL blended PVA physical hydrogels, lipogel FRAP, and different cell lines attached to lipogels are available. See DOI: 10.1039/c3nr01662e

PEG-PE/clay composite carriers for doxorubicin: Effect of composite structure on release, cell interaction and cytotoxicity.

PubMed

Kohay, Hagay; Sarisozen, Can; Sawant, Rupa; Jhaveri, Aditi; Torchilin, Vladimir P; Mishael, Yael G

2017-06-01

A novel drug delivery system for doxorubicin (DOX), based on organic-inorganic composites was developed. DOX was incorporated in micelles (M-DOX) of polyethylene glycol-phosphatidylethanolamine (PEG-PE) which in turn were adsorbed by the clay, montmorillonite (MMT). The nano-structures of the PEG-PE/MMT composites of LOW and HIGH polymer loadings were characterized by XRD, TGA, FTIR, size (DLS) and zeta measurements. These measurements suggest that for the LOW composite a single layer of polymer intercalates in the clay platelets and the polymer only partially covers the external surface, while for the HIGH composite two layers of polymer intercalate and a bilayer may form on the external surface. These nanostructures have a direct effect on formulation stability and on the rate of DOX release. The release rate was reversely correlated with the degree of DOX interaction with the clay and followed the sequence: M-DOX>HIGH formulation>LOW formulation>DOX/MMT. Despite the slower release from the HIGH formulation, its cytotoxicity effect on sensitive cells was as high as the "free" DOX. Surprisingly, the LOW formulation, with the slowest release, demonstrated the highest cytotoxicity in the case of Adriamycin (ADR) resistant cells. Confocal microscopy images and association tests provided an insight into the contribution of formulation-cell interactions vs. the contribution of DOX release rate. Internalization of the formulations was suggested as a mechanism that increases DOX efficiency, particularly in the ADR resistant cell line. The employment of organic-inorganic hybrid materials as drug delivery systems, has not reached its full potential, however, its functionality as an efficient tunable release system was demonstrated. DOX PEG-PE/clay formulations were design as an efficient drug delivery system. The main aim was to develop PEG-PE/clay formulations of different structures based on various PEG-PE/clay ratios in order to achieve tunable release rates, to control the external surface characteristics and formulation stability. The formulations showed significantly higher toxicity in comparison to "free" DOX, explained by formulation internalization. For each cell line tested, sensitive and ADR resistant, a different formulation structure was found most efficient. The potential of PEG-PE/clay-DOX formulations to improve DOX administration efficacy was demonstrated and should be further explored and implemented for other cancer drugs and cells. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Vitamin-C delivery from CoCr alloy surfaces using polymer-free and polymer-based platforms for cardiovascular stent applications.

PubMed

Thiruppathi, Eagappanath; Mani, Gopinath

2014-06-03

Antiproliferative drugs such as paclitaxel and sirolimus are delivered from stents to inhibit the growth of smooth muscle cells (SMCs) for preventing neointimal hyperplasia. However, these drugs delay the growth of endothelial cells (ECs) as well and cause late stent thrombosis. We recently demonstrated the use of Vitamin-C (l-ascorbic acid, l-AA) over paclitaxel and sirolimus for inhibiting SMCs growth and promoting EC growth simultaneously. In this study, we have investigated the delivery of l-AA from CoCr alloy surfaces for potential use in stents. A polymer-free phosphoric acid (PA) platform and a polymer-based poly(lactic-co-glycolic acid) (PLGA) platform were used for coating l-AA onto CoCr surfaces. For the PA platform, FTIR confirmed that the PA was coated on CoCr, while the AFM showed that the PA coating on the CoCr surface was homogeneous. The successful deposition of l-AA on PA-coated CoCr was also confirmed by FTIR. The uniform distribution of l-AA crystals on PA-coated CoCr was shown by SEM, optical profilometer, and AFM. The drug release studies showed that l-AA (276 μg/cm(2)) was burst released from the PA platform by 1 h. For the PLGA platform, SEM showed that the l-AA incorporated polymer films were smoothly and uniformly coated on CoCr. FTIR showed that l-AA was incorporated into the bulk of the PLGA film. DSC showed that the l-AA was present in an amorphous form and formed an intermolecular bonding interaction with PLGA. The drug release studies showed that l-AA was sustained released from the PLGA coated CoCr for up to 24 h. The SEM, FTIR, and DSC characterizations of samples collected post drug release shed light on the mechanism of l-AA release from PLGA coated CoCr. Thus, this study demonstrated the delivery of l-AA from biomaterial surfaces for potential applications in stents and other implantable medical devices.

Bioadhesive control of plasma proteins and blood cells from umbilical cord blood onto the interface grafted with zwitterionic polymer brushes.

PubMed

Chang, Yu; Chang, Yung; Higuchi, Akon; Shih, Yu-Ju; Li, Pei-Tsz; Chen, Wen-Yih; Tsai, Eing-Mei; Hsiue, Ging-Ho

2012-03-06

In this work, bioadhesive behavior of plasma proteins and blood cells from umbilical cord blood (UCB) onto zwitterionic poly(sulfobetaine methacrylate) (polySBMA) polymer brushes was studied. The surface coverage of polySBMA brushes on a hydrophobic polystyrene (PS) well plate with surface grafting weights ranging from 0.02 mg/cm(2) to 0.69 mg/cm(2) can be effectively controlled using the ozone pretreatment and thermal-induced radical graft-polymerization. The chemical composition, grafting structure, surface hydrophilicity, and hydration capability of prepared polySBMA brushes were determined to illustrate the correlations between grafting properties and blood compatibility of zwitterionic-grafted surfaces in contact with human UCB. The protein adsorption of fibrinogen in single-protein solutions and at complex medium of 100% UCB plasma onto different polySBMA brushes with different grafting coverage was measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. The grafting density of the zwitterionic brushes greatly affects the PS surface, thus controlling the adsorption of fibrinogen, the adhesion of platelets, and the preservation of hematopoietic stem and progenitor cells (HSPCs) in UCB. The results showed that PS surfaces grafted with polySBMA brushes possess controllable hydration properties through the binding of water molecules, regulating the bioadhesive and bioinert characteristics of plasma proteins and blood platelets in UCB. Interestingly, it was found that the polySBMA brushes with an optimized grafting weight of approximately 0.1 mg/cm(2) at physiologic temperatures show significant hydrated chain flexibility and balanced hydrophilicity to provide the best preservation capacity for HSPCs stored in 100% UCB solution for 2 weeks. This work suggests that, through controlling grafting structures, the hemocompatible nature of grafted zwitterionic polymer brushes makes them well suited to the molecular design of regulated bioadhesive interfaces for use in the preservation of HSPCs from human UCB.

Vertically Aligned and Continuous Nanoscale Ceramic-Polymer Interfaces in Composite Solid Polymer Electrolytes for Enhanced Ionic Conductivity.

PubMed

Zhang, Xiaokun; Xie, Jin; Shi, Feifei; Lin, Dingchang; Liu, Yayuan; Liu, Wei; Pei, Allen; Gong, Yongji; Wang, Hongxia; Liu, Kai; Xiang, Yong; Cui, Yi

2018-06-13

Among all solid electrolytes, composite solid polymer electrolytes, comprised of polymer matrix and ceramic fillers, garner great interest due to the enhancement of ionic conductivity and mechanical properties derived from ceramic-polymer interactions. Here, we report a composite electrolyte with densely packed, vertically aligned, and continuous nanoscale ceramic-polymer interfaces, using surface-modified anodized aluminum oxide as the ceramic scaffold and poly(ethylene oxide) as the polymer matrix. The fast Li + transport along the ceramic-polymer interfaces was proven experimentally for the first time, and an interfacial ionic conductivity higher than 10 -3 S/cm at 0 °C was predicted. The presented composite solid electrolyte achieved an ionic conductivity as high as 5.82 × 10 -4 S/cm at the electrode level. The vertically aligned interfacial structure in the composite electrolytes enables the viable application of the composite solid electrolyte with superior ionic conductivity and high hardness, allowing Li-Li cells to be cycled at a small polarization without Li dendrite penetration.

Identification of a Novel Cancer Biomarker | Center for Cancer Research

Cancer.gov

During cancer development, cells accumulate a variety of mutations which alter their normal components and activities. One potential change is in the carbohydrate or sugar polymers which decorate proteins predominately found on the cell surface. The accessibility of these residues makes them ideal targets for the development of diagnostics or therapeutics.

Air-cooled, hydrogen-air fuel cell

NASA Technical Reports Server (NTRS)

Shelekhin, Alexander B. (Inventor); Bushnell, Calvin L. (Inventor); Pien, Michael S. (Inventor)

1999-01-01

An air-cooled, hydrogen-air solid polymer electrolyte (SPE) fuel cell with a membrane electrode assembly operatively associated with a fluid flow plate having at least one plate cooling channel extending through the plate and at least one air distribution hole extending from a surface of the cathode flow field into the plate cooling channel.

Liquid water breakthrough location distances on a gas diffusion layer of polymer electrolyte membrane fuel cells

NASA Astrophysics Data System (ADS)

Yu, Junliang; Froning, Dieter; Reimer, Uwe; Lehnert, Werner

2018-06-01

The lattice Boltzmann method is adopted to simulate the three dimensional dynamic process of liquid water breaking through the gas diffusion layer (GDL) in the polymer electrolyte membrane fuel cell. 22 micro-structures of Toray GDL are built based on a stochastic geometry model. It is found that more than one breakthrough locations are formed randomly on the GDL surface. Breakthrough location distance (BLD) are analyzed statistically in two ways. The distribution is evaluated statistically by the Lilliefors test. It is concluded that the BLD can be described by the normal distribution with certain statistic characteristics. Information of the shortest neighbor breakthrough location distance can be the input modeling setups on the cell-scale simulations in the field of fuel cell simulation.

N-Isopropylacrylamide-co-glycidylmethacrylate as a Thermoresponsive Substrate for Corneal Endothelial Cell Sheet Engineering

PubMed Central

Madathil, Bernadette K.; Anil Kumar, Pallickaveedu RajanAsari; Kumary, Thrikkovil Variyath

2014-01-01

Endothelial keratoplasty is a recent shift in the surgical treatment of corneal endothelial dystrophies, where the dysfunctional endothelium is replaced whilst retaining the unaffected corneal layers. To overcome the limitation of donor corneal shortage, alternative use of tissue engineered constructs is being researched. Tissue constructs with intact extracellular matrix are generated using stimuli responsive polymers. In this study we evaluated the feasibility of using the thermoresponsive poly(N-isopropylacrylamide-co-glycidylmethacrylate) polymer as a culture surface to harvest viable corneal endothelial cell sheets. Incubation below the lower critical solution temperature of the polymer allowed the detachment of the intact endothelial cell sheet. Phase contrast and scanning electron microscopy revealed the intact architecture, cobble stone morphology, and cell-to-cell contact in the retrieved cell sheet. Strong extracellular matrix deposition was also observed. The RT-PCR analysis confirmed functionally active endothelial cells in the cell sheet as evidenced by the positive expression of aquaporin 1, collagen IV, Na+-K+ ATPase, and FLK-1. Na+-K+ ATPase protein expression was also visualized by immunofluorescence staining. These results suggest that the in-house developed thermoresponsive culture dish is a suitable substrate for the generation of intact corneal endothelial cell sheet towards transplantation for endothelial keratoplasty. PMID:25003113

MTA-enriched nanocomposite TiO(2)-polymeric powder coatings support human mesenchymal cell attachment and growth.

PubMed

Shi, Wen; Mozumder, Mohammad Sayem; Zhang, Hui; Zhu, Jesse; Perinpanayagam, Hiran

2012-10-01

The objective of the study described in this paper was the development of novel polymer/ceramic nanocomposite coatings for implants through the application of ultrafine powder coating technology. Polyester resins were combined with µm-sized TiO(2) (25%) as the biocompatibility agent, nTiO(2) (0.5%) as the flow additive and mineral trioxide aggregates (ProRoot® MTA, 5%) as bioactive ceramics. Ultrafine powders were prepared and applied to titanium to create continuous polymeric powder coatings (PPCs) through the application of electrostatic ultrafine powder coating technology. Energy dispersive x-ray analysis confirmed that MTA had been incorporated into the PPCs, and elemental mapping showed that it had formed small clusters that were evenly distributed across the surface. Scanning electron microscopy (SEM) revealed continuous and smooth, but highly textured surface coatings that contrasted with the scalloped appearance of commercially pure titanium (cpTi) controls. Atomic force microscopy revealed intricate nano-topographies with an abundance of submicron-sized pits and nano-projections, evenly dispersed across their surfaces. Inverted fluorescence microscopy, SEM and cell counts showed that human embryonic palatal mesenchymal cells attached and spread out onto PPC and MTA-enriched PPCs within 24 h. Mitochondrial enzyme activity measured viable and metabolically active cells on all of the surfaces. After 72 h of growth, cell counts and metabolic activity were significantly higher (P < 0.05) on the grey-MTA enriched PPC surfaces, than on unmodified PPC and cpTi. The novel polymer/ceramic nanocomposites that were created with ultrafine powder coating technology were continuous, homogenous and nano-rough coatings that enhanced human mesenchymal cell attachment and growth.

Effects of pentacene-doped PEDOT:PSS as a hole-conducting layer on the performance characteristics of polymer photovoltaic cells.

PubMed

Kim, Hyunsoo; Lee, Jungrae; Ok, Sunseong; Choe, Youngson

2012-01-05

We have investigated the effect of pentacene-doped poly(3,4-ethylenedioxythiophene:poly(4-styrenesulfonate) [PEDOT:PSS] films as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the amount of pentacene and the annealing temperature of pentacene-doped PEDOT:PSS layer, the changes of performance characteristics were evaluated. Pentacene-doped PEDOT:PSS thin films were prepared by dissolving pentacene in 1-methyl-2-pyrrolidinone solvent and mixing with PEDOT:PSS. As the amount of pentacene in the PEDOT:PSS solution was increased, UV-visible transmittance also increased dramatically. By increasing the amount of pentacene in PEDOT:PSS films, dramatic decreases in both the work function and surface resistance were observed. However, the work function and surface resistance began to sharply increase above the doping amount of pentacene at 7.7 and 9.9 mg, respectively. As the annealing temperature was increased, the surface roughness of pentacene-doped PEDOT:PSS films also increased, leading to the formation of PEDOT:PSS aggregates. The films of pentacene-doped PEDOT:PSS were characterized by AFM, SEM, UV-visible transmittance, surface analyzer, surface resistance, and photovoltaic response analysis.

Effects of pentacene-doped PEDOT:PSS as a hole-conducting layer on the performance characteristics of polymer photovoltaic cells

PubMed Central

2012-01-01

We have investigated the effect of pentacene-doped poly(3,4-ethylenedioxythiophene:poly(4-styrenesulfonate) [PEDOT:PSS] films as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the amount of pentacene and the annealing temperature of pentacene-doped PEDOT:PSS layer, the changes of performance characteristics were evaluated. Pentacene-doped PEDOT:PSS thin films were prepared by dissolving pentacene in 1-methyl-2-pyrrolidinone solvent and mixing with PEDOT:PSS. As the amount of pentacene in the PEDOT:PSS solution was increased, UV-visible transmittance also increased dramatically. By increasing the amount of pentacene in PEDOT:PSS films, dramatic decreases in both the work function and surface resistance were observed. However, the work function and surface resistance began to sharply increase above the doping amount of pentacene at 7.7 and 9.9 mg, respectively. As the annealing temperature was increased, the surface roughness of pentacene-doped PEDOT:PSS films also increased, leading to the formation of PEDOT:PSS aggregates. The films of pentacene-doped PEDOT:PSS were characterized by AFM, SEM, UV-visible transmittance, surface analyzer, surface resistance, and photovoltaic response analysis. PMID:22221320

SFG and AFM Studies of Polymer Surface Monolayers

NASA Astrophysics Data System (ADS)

Somorjai, Gabor A.

2003-03-01

Sum frequency generation vibrational spectroscopy and atomic force microscopy techniques were utilized to study the structure and composition of polymer surfaces ranging from polyethylene and polypropylene to copolymers of polyurethane and polystyrene. The surface methyl groups aligned perpendicular to the surface above the glass transition temperature of polypropylene. Large side groups such as the phenyl group on polystyrene is also near the surface normal at the polymer-air interface. At the air interface hydrophobic groups are dominant on the polymer surface while at solid-water interface hydrophilic groups segregate to the surface. Minimizing surface energy is the cause of readjusting the surface composition at polymer-water interfaces as compared to polymer-air interfaces. Upon stretching the soft component of two-component polymer systems segregates to the surface and both the surface structure and the surface composition undergo reversible or irreversible changes depending on the magnitude of the stretch. Since the heart beat forces bio-polymers to stretch over 40 million times a year the molecular behavior due to stretching has important physiological consequences.

Physicochemical modifications accompanying UV laser induced surface structures on poly(ethylene terephthalate) and their effect on adhesion of mesenchymal cells.

PubMed

Rebollar, Esther; Pérez, Susana; Hernández, Margarita; Domingo, Concepción; Martín, Margarita; Ezquerra, Tiberio A; García-Ruiz, Josefa P; Castillejo, Marta

2014-09-07

This work reports on the formation of different types of structures on the surface of polymer films upon UV laser irradiation. Poly(ethylene terephthalate) was irradiated with nanosecond UV pulses at 193 and 266 nm. The polarization of the laser beam and the irradiation angle of incidence were varied, giving rise to laser induced surface structures with different shapes and periodicities. The irradiated surfaces were topographically characterized by atomic force microscopy and the chemical modifications induced by laser irradiation were inspected via micro-Raman and fluorescence spectroscopies. Contact angle measurements were performed with different liquids, and the results evaluated in terms of surface free energy components. Finally, in order to test the influence of surface properties for a potential application, the modified surfaces were used for mesenchymal stem cell culture assays and the effect of nanostructure and surface chemistry on cell adhesion was evaluated.

Nanofiber Based Optical Sensors for Oxygen Determination

NASA Astrophysics Data System (ADS)

Xue, Ruipeng

Oxygen sensors based on luminescent quenching of nanofibers were developed for measurement of both gaseous and dissolved oxygen concentrations. Electrospinning was used to fabricate "core-shell" fiber configurations in which oxygen-sensitive transition metal complexes are embedded into a polymer 'core' while a synthetic biocompatible polymer provides a protective 'shell.' Various matrix polymers and luminescent probes were studied in terms of their sensitivity, linear calibration, reversibility, response time, stability and probe-matrix interactions. Due to the small size and high surface area of these nanofibers, all samples showed rapid response and a highly linear response to oxygen. The sensitivity and photostability of the sensors were controlled by the identity of both the probe molecule and the polymer matrix. Such nanofiber sensor forms are particularly suitable in biological applications due to the fact that they do not consume oxygen, are biocompatible and biomimetic and can be easily incorporated into cell culture. Applications of these fibers in cancer cell research, wound healing, breath analysis and waste water treatment were explored.

Design guideline for Si/organic hybrid solar cell with interdigitated back contact structure

NASA Astrophysics Data System (ADS)

Bimo Prakoso, Ari; Rusli; Li, Zeyu; Lu, Chenjin; Jiang, Changyun

2018-03-01

We study the design of Si/organic hybrid (SOH) solar cells with interdigitated back contact (IBC) structure. SOH solar cells formed between n-Si and poly(3,4-ethylenedioxythiophene): polystyrenesulphonate (PEDOT:PSS) is a promising concept that combines the excellent electronic properties of Si with the solution-based processing advantage of an organic polymer. The IBC cell structure is employed to minimize parasitic absorption losses in the organic polymer, eliminate grid shadowing losses, and allow excellent passivation of the front Si surface in one step over a large area. The influence of Si thickness, doping concentration and contact geometry are simulated in this study to optimize the performance of the SOH-IBC solar cell. We found that a high power conversion efficiency of >20% can be achieved for optimized SOH-IBC cell based on a thin c-Si substrate of 40 μm thickness.

Surface modification of PLGA nanoparticles by carbopol to enhance mucoadhesion and cell internalization.

PubMed

Surassmo, Suvimol; Saengkrit, Nattika; Ruktanonchai, Uracha Rungsardthong; Suktham, Kunat; Woramongkolchai, Noppawan; Wutikhun, Tuksadon; Puttipipatkhachorn, Satit

2015-06-01

Mucoadhesive poly (lactic-co-glycolic acid) (PLGA) nanoparticles having a modified shell-matrix derived from polyvinyl alcohol (PVA) and Carbopol (CP), a biodegradable polymer coating, to improve the adhesion and cell transfection properties were developed. The optimum formulations utilized a CP concentration in the range of 0.05-0.2%w/v, and were formed using modified emulsion-solvent evaporation technique. The resulting CP-PLGA nanoparticles were characterized in terms of their physical and chemical properties. The absorbed CP on the PLGA shell-matrix was found to affect the particle size and surface charge, with 0.05% CP giving rise to smooth spherical particles (0.05CP-PLGA) with the smallest size (285.90 nm), and strong negative surface charge (-25.70 mV). The introduction of CP results in an enhancement of the mucoadhesion between CP-PLGA nanoparticles and mucin particles. In vitro cell internalization studies highlighted the potential of 0.05CP-PLGA nanoparticles for transfection into SiHa cells, with uptake being time dependent. Additionally, cytotoxicity studies of CP-PLGA nanoparticles against SiHa cancer cells indicated that low concentrations of the nanoparticles were non-toxic to cells (cell viability >80%). From the various formulations studied, 0.05CP-PLGA nanoparticles proved to be the optimum model carrier having the required mucoadhesive profile and could be an alternative therapeutic efficacy carrier for targeted mucosal drug delivery systems with biodegradable polymer. Copyright © 2015 Elsevier B.V. All rights reserved.

A novel surface modification approach for protein and cell microarrays

NASA Astrophysics Data System (ADS)

Kurkuri, Mahaveer D.; Driever, Chantelle; Thissen, Helmut W.; Voelcker, Nicholas H.

2007-01-01

Tissue engineering and stem cell technologies have led to a rapidly increasing interest in the control of the behavior of mammalian cells growing on tissue culture substrates. Multifunctional polymer coatings can assist research in this area in many ways, for example, by providing low non-specific protein adsorption properties and reactive functional groups at the surface. The latter can be used for immobilization of specific biological factors that influence cell behavior. In this study, glass slides were coated with copolymers of glycidyl methacrylate (GMA) and poly(ethylene glycol) methacrylate (PEGMA). The coatings were prepared by three different methods based on dip and spin coating as well as polymer grafting procedures. Coatings were characterized by X-ray photoelectron spectroscopy, surface sensitive infrared spectroscopy, ellipsometry and contact angle measurements. A fluorescently labelled protein was deposited onto reactive coatings using a contact microarrayer. Printing of a model protein (fluorescein labeled bovine serum albumin) was performed at different protein concentrations, pH, temperature, humidity and using different micropins. The arraying of proteins was studied with a microarray scanner. Arrays printed at a protein concentration above 50 μg/mL prepared in pH 5 phosphate buffer at 10°C and 65% relative humidity gave the most favourable results in terms of the homogeneity of the printed spots and the fluorescence intensity.

Nanowell-Trapped Charged Ligand-Bearing Nanoparticle Surfaces – A Novel Method of Enhancing Flow-Resistant Cell Adhesion

PubMed Central

Tran, Phat L.; Gamboa, Jessica R.; McCracken, Katherine E.; Riley, Mark R.

2014-01-01

Assuring cell adhesion to an underlying biomaterial surface is vital in implant device design and tissue engineering, particularly under circumstances where cells are subjected to potential detachment from overriding fluid flow. Cell-substrate adhesion is a highly regulated process involving the interplay of mechanical properties, surface topographic features, electrostatic charge, and biochemical mechanisms. At the nanoscale level the physical properties of the underlying substrate are of particular importance in cell adhesion. Conventionally, natural, pro-adhesive, and often thrombogenic, protein biomaterials are frequently utilized to facilitate adhesion. In the present study nanofabrication techniques are utilized to enhance the biological functionality of a synthetic polymer surface, polymethymethacrylate, with respect to cell adhesion. Specifically we examine the effect on cell adhesion of combining: 1. optimized surface texturing, 2. electrostatic charge and 3. cell adhesive ligands, uniquely assembled on the substrata surface, as an ensemble of nanoparticles trapped in nanowells. Our results reveal that the ensemble strategy leads to enhanced, more than simply additive, endothelial cell adhesion under both static and flow conditions. This strategy may be of particular utility for enhancing flow-resistant endothelialization of blood-contacting surfaces of cardiovascular devices subjected to flow-mediated shear. PMID:23225491

Polymer scaffolds with no skin-effect for tissue engineering applications fabricated by thermally induced phase separation.

PubMed

Kasoju, Naresh; Kubies, Dana; Sedlačík, Tomáš; Janoušková, Olga; Koubková, Jana; Kumorek, Marta M; Rypáček, František

2016-01-11

Thermally induced phase separation (TIPS) based methods are widely used for the fabrication of porous scaffolds for tissue engineering and related applications. However, formation of a less-/non-porous layer at the scaffold's outer surface at the air-liquid interface, often known as the skin-effect, restricts the cell infiltration inside the scaffold and therefore limits its efficacy. To this end, we demonstrate a TIPS-based process involving the exposure of the just quenched poly(lactide-co-caprolactone):dioxane phases to the pure dioxane for a short time while still being under the quenching strength, herein after termed as the second quenching (2Q). Scanning electron microscopy, mercury intrusion porosimetry and contact angle analysis revealed a direct correlation between the time of 2Q and the gradual disappearance of the skin, followed by the widening of the outer pores and the formation of the fibrous filaments over the surface, with no effect on the internal pore architecture and the overall porosity of scaffolds. The experiments at various quenching temperatures and polymer concentrations revealed the versatility of 2Q in removing the skin. In addition, the in vitro cell culture studies with the human primary fibroblasts showed that the scaffolds prepared by the TIPS based 2Q process, with the optimal exposure time, resulted in a higher cell seeding and viability in contrast to the scaffolds prepared by the regular TIPS. Thus, TIPS including the 2Q step is a facile, versatile and innovative approach to fabricate the polymer scaffolds with a skin-free and fully open porous surface morphology for achieving a better cell response in tissue engineering and related applications.

Cytocompatibility of polyethylene grafted with triethylenetetramine functionalized carbon nanoparticles

NASA Astrophysics Data System (ADS)

Žáková, Pavlína; Slepičková Kasálková, Nikola; Slepička, Petr; Kolská, Zdeňka; Karpíšková, Jana; Stibor, Ivan; Švorčík, Václav

2017-11-01

Various carbon nanostructures are widely researched as scaffolds for tissue engineering. We evaluated the surface properties and cell-substrate interactions of carbon nanoparticles functionalized with triethylenetetramine (CNPs) grafted polymer film. Two forms of polyethylene (HDPE, LDPE) were treated in an inert argon plasma discharge and, subsequently, grafted with CNPs. The surface properties were studied using multiple methods, including Raman spectroscopy, goniometry, atomic force microscopy, X-ray photoelectron spectroscopy and electrokinetic analysis. Cell-substrate interactions were determined in vitro by studying adhesion, proliferation and viability of vascular smooth muscle cells (VSMCs) from the aorta of a rat. Cell-substrate interactions on pristine and modified substrates were compared to standard tissue culture polystyrene. Our results show that CNPs affect surface morphology and wettability and therefore adhesion, proliferation and viability of cultured muscle cells.

Nanotextured polymer substrates show enhanced cancer cell isolation and cell culture

NASA Astrophysics Data System (ADS)

Islam, Muhymin; Sajid, Adeel; Arif Iftakher Mahmood, M.; Motasim Bellah, Mohammad; Allen, Peter B.; Kim, Young-Tae; Iqbal, Samir M.

2015-06-01

Detection of circulating tumor cells (CTCs) in the early stages of cancer is a great challenge because of their exceedingly small concentration. There are only a few approaches sensitive enough to differentiate tumor cells from the plethora of other cells in a sample like blood. In order to detect CTCs, several antibodies and aptamers have already shown high affinity. Nanotexture can be used to mimic basement membrane to further enhance this affinity. This article reports an approach to fabricate nanotextured polydimethylsiloxane (PDMS) substrates using micro reactive ion etching (micro-RIE). Three recipes were used to prepare nanotextured PDMS using oxygen and carbon tetrafluoride. Micro-RIE provided better control on surface properties. Nanotexturing improved the affinity of PDMS surfaces to capture cancer cells using surface immobilized aptamers against cell membrane overexpressed with epidermal growth factor receptors. In all cases, nanotexture of PDMS increased the effective surface area by creating nanoscale roughness on the surface. Nanotexture also enhanced the growth rate of cultured cells compared to plain surfaces. A comparison among the three nanotextured surfaces demonstrated an almost linear relationship between the surface roughness and density of captured tumor cells. The nanotextured PDMS mimicked biophysical environments for cells to grow faster. This can have many implications in microfluidic platforms used for cell handling.

In vitro and in vivo biocompatibility study on laser 3D microstructurable polymers

NASA Astrophysics Data System (ADS)

Malinauskas, Mangirdas; Baltriukiene, Daiva; Kraniauskas, Antanas; Danilevicius, Paulius; Jarasiene, Rasa; Sirmenis, Raimondas; Zukauskas, Albertas; Balciunas, Evaldas; Purlys, Vytautas; Gadonas, Roaldas; Bukelskiene, Virginija; Sirvydis, Vytautas; Piskarskas, Algis

2012-09-01

Films and microstructured scaffolds have been fabricated using direct laser writing out of different polymers: hybrid organic-inorganic ORMOCORE b59, acrylate-based AKRE23, novel organic-inorganic Zr containing hybrid SZ2080, and biodegradable PEG-DA-258. Adult myogenic stem cells were grown on these surfaces in vitro. Their adhesion, growth, and viability test results suggest good potential applicability of the materials in biomedical practice. Pieces of these polymers were implanted in rat's paravertebral back tissue. Histological examination of the implants and surrounding tissue ex vivo after 3 weeks of implantation was conducted and results show the materials to be at least as biocompatible as surgical clips or sutures. The applied direct laser writing technique seems to offer good future prospects in a polymeric 3D scaffold design for artificial tissue engineering with autologous stem cells.

Development of an electro-responsive platform for the controlled transfection of mammalian cells

NASA Astrophysics Data System (ADS)

Hook, Andrew L.; Thissen, Helmut W.; Hayes, Jason P.; Voelcker, Nicolas H.

2005-02-01

The recent development of living microarrays as novel tools for the analysis of gene expression in an in-situ environment promises to unravel gene function within living organisms. In order to significantly enhance microarray performance, we are working towards electro-responsive DNA transfection chips. This study focuses on the control of DNA adsorption and desorption by appropriate surface modification of highly doped p++ silicon. Silicon was modified by plasma polymerisation of allylamine (ALAPP), a non-toxic surface that sustains cell growth. Subsequent high surface density grafting of poly(ethylene oxide) formed a layer resistant to biomolecule adsorption and cell attachment. Spatially controlled excimer laser ablation of the surface produced micron resolution patterns of re-exposed plasma polymer whilst the rest of the surface remained non-fouling. We observed electro-stimulated preferential adsorption of DNA to the ALAPP surface and subsequent desorption by the application of a negative bias. Cell culture experiments with HEK 293 cells demonstrated efficient and controlled transfection of cells using the expression of green fluorescent protein as a reporter. Thus, these chemically patterned surfaces are promising platforms for use as living microarrays.

Regulating the migration of smooth muscle cells by a vertically distributed poly(2-hydroxyethyl methacrylate) gradient on polymer brushes covalently immobilized with RGD peptides.

PubMed

Wu, Sai; Du, Wang; Duan, Yiyuan; Zhang, Deteng; Liu, Yixiao; Wu, Bingbing; Zou, Xiaohui; Ouyang, Hongwei; Gao, Changyou

2018-05-30

The gradient localization of biological cues is of paramount importance to guide directional migration of cells. In this study, poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate)-block- poly(2-hydroxyethyl methacrylate) (P(HEMA-co-GMA)-b-PHEMA) brushes with a uniform underneath P(HEMA-co-GMA) layer and a gradient thickness of PHEMA blocks were prepared by using surface-initiated atom-transfer radical polymerization and a dynamically controlled polymerization process. The polymer chains were subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) peptides by reaction with the glycidyl groups, and their structures and properties were characterized by X-ray photoelectron spectrometry (XPS), quartz crystal microbalance with dissipation (QCM-D) and air contact angle. Adhesion and migration processes of smooth muscle cells (SMCs) were then studied. Compared with those on the sufficiently exposed RGD surface, the cell adhesion and mobility were well maintained when the RGD peptides were localized at 18.9 nm depth, whereas the adhesion, spreading and migration rate of SMCs were significantly impaired when the RGD peptides were localized at a depth of 38.4 nm. On the RGD depth gradient surface, the SMCs exhibited preferential orientation and enhanced directional migration toward the direction of reduced thickness of the second PHEMA brushes. Half of the cells were oriented within ± 30° to the x-axis direction, and 72% of the cells moved directionally at the optimal conditions. Cell adhesion strength, arrangement of cytoskeleton, and gene and protein expression levels of adhesion-related proteins were studied to corroborate the mechanisms, demonstrating that the cell mobility is regulated by the complex and synergetic intracellular signals resulted from the difference in surface properties. Cell migration is of paramount importance for the processes of tissue repair and regeneration. So far, the gradient localization of biological cues perpendicular to the substrate, which is the usual case for the biological signaling molecules to locate in ECM in vivo, has been scarcely studied, and has not been used to guide the directional migration of cells. In this study, we prepare a depth gradient of RGD peptides along the polymer chains, which is used to guide the directional migration of SMCs after a second hydrophilic bock is prepared in a gradient manner. For the first time the directional migration of SMCs is achieved under the guidance of a depth gradient of RGD ligands. The mechanisms of different cell migration abilities are further discussed based on the results of cell adhesion, cell adhesion force, cytoskeleton alignment and expression of relative proteins and genes. This work paves a new strategy by fabricating a gradient polymer brushes with immobilized bioactive molecules to dominate the directional cell migration, and elucidates the mechanisms underlining the biased migration along RGD depth localization gradients, shedding a light for the design of novel biomaterials to control and guide cell migration and invasion. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Making the invisible visible: a microfluidic chip using a low refractive index polymer.

PubMed

Hanada, Yasutaka; Ogawa, Tatsuya; Koike, Kazuhiko; Sugioka, Koji

2016-07-07

Microfluidic frameworks known as micro-total-analysis-systems or lab-on-a-chip have become versatile tools in cell biology research, since functional biochips are able to streamline dynamic observations of various cells. Glass or polymers are generally used as the substrate due to their high transparency, chemical stability and cost-effectiveness. However, these materials are not well suited for the microscopic observation of cell migration at the fluid boundary due to the refractive index mismatch between the medium and the biochip material. For this reason, we have developed a new method of fabricating three-dimensional (3D) microfluidic chips made of the low refractive index fluoric polymer CYTOP. This novel fabrication procedure involves the use of a femtosecond laser for direct writing, followed by wet etching with a dilute fluorinated solvent and annealing, to create high-quality 3D microfluidic chips inside a polymer substrate. A microfluidic chip made in this manner enabled us to more clearly observe the flagellum motion of a Dinoflagellate moving in circles near the fluid surface compared to the observations possible using conventional microfluidic chips. We believe that CYTOP microfluidic chips made using this new method may allow more detailed analysis of various cell migrations near solid boundaries.

The agmatine-containing poly(amidoamine) polymer AGMA1 binds cell surface heparan sulfates and prevents attachment of mucosal human papillomaviruses.

PubMed

Cagno, Valeria; Donalisio, Manuela; Bugatti, Antonella; Civra, Andrea; Cavalli, Roberta; Ranucci, Elisabetta; Ferruti, Paolo; Rusnati, Marco; Lembo, David

2015-09-01

The agmatine-containing poly(amidoamine) polymer AGMA1 was recently shown to inhibit the infectivity of several viruses, including human papillomavirus 16 (HPV-16), that exploit cell surface heparan sulfate proteoglycans (HSPGs) as attachment receptors. The aim of this work was to assess the antiviral activity of AGMA1 and its spectrum of activity against a panel of low-risk and high-risk HPVs and to elucidate its mechanism of action. AGMA1 was found to be a potent inhibitor of mucosal HPV types (i.e., types 16, 31, 45, and 6) in pseudovirus-based neutralization assays. The 50% inhibitory concentration was between 0.34 μg/ml and 0.73 μg/ml, and no evidence of cytotoxicity was observed. AGMA1 interacted with immobilized heparin and with cellular heparan sulfates, exerting its antiviral action by preventing virus attachment to the cell surface. The findings from this study indicate that AGMA1 is a leading candidate compound for further development as an active ingredient of a topical microbicide against HPV and other sexually transmitted viral infections. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Bone formation by three-dimensional stromal osteoblast culture in biodegradable polymer scaffolds

NASA Technical Reports Server (NTRS)

Ishaug, S. L.; Crane, G. M.; Miller, M. J.; Yasko, A. W.; Yaszemski, M. J.; Mikos, A. G.; McIntire, L. V. (Principal Investigator)

1997-01-01

Bone formation was investigated in vitro by culturing stromal osteoblasts in three-dimensional (3-D), biodegradable poly(DL-lactic-co-glycolic acid) foams. Three polymer foam pore sizes, ranging from 150-300, 300-500, and 500-710 microns, and two different cell seeding densities, 6.83 x 10(5) cells/cm2 and 22.1 x 10(5) cells/cm2, were examined over a 56-day culture period. The polymer foams supported the proliferation of seeded osteoblasts as well as their differentiated function, as demonstrated by high alkaline phosphatase activity and deposition of a mineralized matrix by the cells. Cell number, alkaline phosphatase activity, and mineral deposition increased significantly over time for all the polymer foams. Osteoblast foam constructs created by seeding 6.83 x 10(5) cells/cm2 on foams with 300-500 microns pores resulted in a cell density of 4.63 x 10(5) cells/cm2 after 1 day in culture; they had alkaline phosphatase activities of 4.28 x 10(-7) and 2.91 x 10(-6) mumol/cell/min on Days 7 and 28, respectively; and they had a cell density that increased to 18.7 x 10(5) cells/cm2 by Day 56. For the same constructs, the mineralized matrix reached a maximum penetration depth of 240 microns from the top surface of the foam and a value of 0.083 mm for mineralized tissue volume per unit of cross sectional area. Seeding density was an important parameter for the constructs, but pore size over the range tested did not affect cell proliferation or function. This study suggests the feasibility of using poly(alpha-hydroxy ester) foams as scaffolding materials for the transplantation of autogenous osteoblasts to regenerate bone tissue.

Fuel cell with interdigitated porous flow-field

DOEpatents

Wilson, Mahlon S.

1997-01-01

A polymer electrolyte membrane (PEM) fuel cell is formed with an improved system for distributing gaseous reactants to the membrane surface. A PEM fuel cell has an ionic transport membrane with opposed catalytic surfaces formed thereon and separates gaseous reactants that undergo reactions at the catalytic surfaces of the membrane. The fuel cell may also include a thin gas diffusion layer having first and second sides with a first side contacting at least one of the catalytic surfaces. A macroporous flow-field with interdigitated inlet and outlet reactant channels contacts the second side of the thin gas diffusion layer for distributing one of the gaseous reactants over the thin gas diffusion layer for transport to an adjacent one of the catalytic surfaces of the membrane. The porous flow field may be formed from a hydrophilic material and provides uniform support across the backside of the electrode assembly to facilitate the use of thin backing layers.

Fuel cell with interdigitated porous flow-field

DOEpatents

Wilson, M.S.

1997-06-24

A polymer electrolyte membrane (PEM) fuel cell is formed with an improved system for distributing gaseous reactants to the membrane surface. A PEM fuel cell has an ionic transport membrane with opposed catalytic surfaces formed thereon and separates gaseous reactants that undergo reactions at the catalytic surfaces of the membrane. The fuel cell may also include a thin gas diffusion layer having first and second sides with a first side contacting at least one of the catalytic surfaces. A macroporous flow-field with interdigitated inlet and outlet reactant channels contacts the second side of the thin gas diffusion layer for distributing one of the gaseous reactants over the thin gas diffusion layer for transport to an adjacent one of the catalytic surfaces of the membrane. The porous flow field may be formed from a hydrophilic material and provides uniform support across the backside of the electrode assembly to facilitate the use of thin backing layers. 9 figs.

Electrochemically triggered release of acetylcholine from scCO2 impregnated conductive polymer films evokes intracellular Ca2+ signaling in neurotypic SH-SY5Y cells.

PubMed

Löffler, Susanne; Seyock, Silke; Nybom, Rolf; Jacobson, Gunilla B; Richter-Dahlfors, Agneta

2016-12-10

Implantable devices for electronically triggered drug release are attractive to achieve spatial and temporal control over drug concentrations in patients. Realization of such devices is, however, associated with technical and biological challenges. Among these are containment of drug reservoirs, lack of precise control cues, as well as the charge and size of the drug. Here, we present a method for electronically triggered release of the quaternary ammonium cation acetylcholine (ACh) from an impregnated conductive polymer film. Using supercritical carbon dioxide (scCO 2 ), a film of PEDOT/PSS (poly(3,4)-ethylenedioxythiophene doped with poly(styrenesulfonate)) is impregnated with the neurotransmitter acetylcholine. The gentle scCO 2 process generated a dry, drug-impregnated surface, well suited for interaction with biological material, while maintaining normal electrochemical properties of the polymer. Electrochemical switching of impregnated PEDOT/PSS films stimulated release of ACh from the polymer matrix, likely due to swelling mediated by the influx and efflux of charged and solvated ions. Triggered release of ACh did not affect the biological activity of the drug. This was shown by real-time monitoring of intracellular Ca 2+ signaling in neurotypic cells growing on the impregnated polymer surface. Collectively, scCO 2 impregnation of conducting polymers offers the first one-step, dopant-independent drug impregnation process, potentially facilitating loading of both anionic and cationic drugs that can be dissolved in scCO2 on its own or by using a co-solvent. We foresee that scCO 2 -loaded devices for electronically triggered drug release will create novel opportunities when generating active bio-coatings, tunable for specific needs, in a variety of medical settings. Copyright © 2016 Elsevier B.V. All rights reserved.

Formation of three-dimensional cell/polymer constructs for bone tissue engineering in a spinner flask and a rotating wall vessel bioreactor

NASA Technical Reports Server (NTRS)

Sikavitsas, Vassilios I.; Bancroft, Gregory N.; Mikos, Antonios G.; McIntire, L. V. (Principal Investigator)

2002-01-01

The aim of this study is to investigate the effect of the cell culture conditions of three-dimensional polymer scaffolds seeded with rat marrow stromal cells (MSCs) cultured in different bioreactors concerning the ability of these cells to proliferate, differentiate towards the osteoblastic lineage, and generate mineralized extracellular matrix. MSCs harvested from male Sprague-Dawley rats were culture expanded, seeded on three-dimensional porous 75:25 poly(D,L-lactic-co-glycolic acid) biodegradable scaffolds, and cultured for 21 days under static conditions or in two model bioreactors (a spinner flask and a rotating wall vessel) that enhance mixing of the media and provide better nutrient transport to the seeded cells. The spinner flask culture demonstrated a 60% enhanced proliferation at the end of the first week when compared to static culture. On day 14, all cell/polymer constructs exhibited their maximum alkaline phosphatase activity (AP). Cell/polymer constructs cultured in the spinner flask had 2.4 times higher AP activity than constructs cultured under static conditions on day 14. The total osteocalcin (OC) secretion in the spinner flask culture was 3.5 times higher than the static culture, with a peak OC secretion occurring on day 18. No considerable AP activity and OC secretion were detected in the rotating wall vessel culture throughout the 21-day culture period. The spinner flask culture had the highest calcium content at day 14. On day 21, the calcium deposition in the spinner flask culture was 6.6 times higher than the static cultured constructs and over 30 times higher than the rotating wall vessel culture. Histological sections showed concentration of cells and mineralization at the exterior of the foams at day 21. This phenomenon may arise from the potential existence of nutrient concentration gradients at the interior of the scaffolds. The better mixing provided in the spinner flask, external to the outer surface of the scaffolds, may explain the accelerated proliferation and differentiation of marrow stromal osteoblasts, and the localization of the enhanced mineralization on the external surface of the scaffolds. Copyright 2002 Wiley Periodicals, Inc.

Controlled method of reducing electrophoretic mobility of macromolecules, particles, or cells

NASA Technical Reports Server (NTRS)

Vanalstine, James M. (Inventor)

1992-01-01

A method of reducing electrophoretic mobility of macromolecules, particles, cells, and other substances is provided which comprises interacting in a conventional electrophoretic separating procedure, the substances with a polymer-linked affinity compound comprised of a hydrophilic neutral polymer such as polyethylene glycol bound to a second component such as a hydrophobic compound, an immunocompound such as an antibody or antibody active fragment, or a ligand such as a hormone, drug, antigen, or a hapten. The reduction of electrophoretic mobility achieved is directly proportional to the concentration of the polymer-linked affinity compound employed, and such reduction can comprise up to 100 percent for particular particles and cells. The present invention is advantageous in that electrophoretic separation can now be achieved for substances whose native surface charge structure had prevented them from being separated by normal electrophoretic means. Depending on the affinity component utilized, separation can be achieved on the basis of the specific/irreversible, specific/reversible, semi-specific/reversible, relatively nonspecific/reversible, or relatively nonspecific/irreversible ligand-substance interactions.

Communication — Modeling polymer-electrolyte fuel-cell agglomerates with double-trap kinetics

DOE PAGES

Pant, Lalit M.; Weber, Adam Z.

2017-04-14

A new semi-analytical agglomerate model is presented for polymer-electrolyte fuel-cell cathodes. The model uses double-trap kinetics for the oxygen-reduction reaction, which can capture the observed potential-dependent coverage and Tafel-slope changes. An iterative semi-analytical approach is used to obtain reaction rate constants from the double-trap kinetics, oxygen concentration at the agglomerate surface, and overall agglomerate reaction rate. The analytical method can predict reaction rates within 2% of the numerically simulated values for a wide range of oxygen concentrations, overpotentials, and agglomerate sizes, while saving simulation time compared to a fully numerical approach.

Bioinspired interface for nanobiodevices based on phospholipid polymer chemistry

PubMed Central

Ishihara, Kazuhiko; Takai, Madoka

2009-01-01

This review paper describes novel biointerfaces for nanobiodevices. Biocompatible and non-biofouling surfaces are designed largely based on cell membrane structure, and the preparation and functioning of the bioinspired interface are evaluated and compared between living and artificial systems. A molecular assembly of polymers with a phospholipid polar group has been developed as the platform of the interface. At the surface, protein adsorption is effectively reduced and the subsequent bioreactions are suppressed. Through this platform, biomolecules with a high affinity to the specific molecules are introduced under mild conditions. The activity of the biomolecules is retained even after immobilization. This bioinspired interface is adapted to construct bionanodevices, that is, microfluidic chips and nanoparticles for capturing target molecules and cells. The interface functions well and has a very high efficiency for biorecognition. This bioinspired interface is a promising universal platform that integrates various fields of science and has useful applications. PMID:19324688

Controlled method of reducing electrophoretic mobility of various substances

NASA Technical Reports Server (NTRS)

Vanalstine, James M. (Inventor)

1989-01-01

A method of reducing electrophoretic mobility of macromolecules, particles, cells, and the like is provided. The method comprises interacting the particles or cells with a polymer-linked affinity compound composed of: a hydrophilic neutral polymer such as polyethylene glycol, and an affinity component consisting of a hydrophobic compound such as a fatty acid ester, an immunocompound such as an antibody or active fragment thereof or simular macromolecule, or other ligands. The reduction of electrophoretic mobility achieved is directly proportional to the concentration of the polymer-linked affinity compound employed, and the mobility reduction obtainable is up to 100 percent for particular particles and cells. The present invention is advantageous in that analytical electrophoretic separation can not be achieved for macromolecules, particles, and cells whose native surface charge structure had prevented them from being separated by normal electrophoretic means. Depending on the affinity component utilized, separation can be achieved on the basis of specific/irreversible, specific/reversible, semi-specific/reversible, relatively nonspecific/reversible, or relatively nonspecific/irreversible ligand-substance interactions. The present method is also advantageous in that it can be used in a variety of standard laboratory electrophoresis equipment.

Method of making a membrane having hydrophilic and hydrophobic surfaces for adhering cells or antibodies by using atomic oxygen or hydroxyl radicals

NASA Technical Reports Server (NTRS)

Koontz, Steven L. (Inventor); Spaulding, Glenn F. (Inventor)

1994-01-01

A portion of an organic polymer article such as a membrane is made hydrophilic by exposing a hydrophobic surface of the article to a depth of about 50 to about 5000 angstroms to atomic oxygen or hydroxyl radicals at a temperature below 100C., preferably below 40 C, to form a hydrophilic uniform surface layer of hydrophilic hydroxyl groups. The atomic oxygen and hydroxyl radicals are generated by a flowing afterglow microwave discharge, and the surface is outside of a plasma produced by the discharge. A membrane having both hydrophilic and hydrophobic surfaces can be used in an immunoassay by adhering antibodies to the hydrophobic surface. In another embodiment, the membrane is used in cell culturing where cells adhere to the hydrophilic surface. Prior to adhering cells, the hydrophilic surface may be grafted with a compatibilizing compound. A plurality of hydrophilic regions bounded by adjacent hydrophobic regions can be produced such that a maximum of one cell per each hydrophilic region adheres.

Hydrogel films and coatings by swelling-induced gelation

PubMed Central

Moreau, David; Chauvet, Caroline; Etienne, François; Rannou, François P.

2016-01-01

Hydrogel films used as membranes or coatings are essential components of devices interfaced with biological systems. Their design is greatly challenged by the need to find mild synthesis and processing conditions that preserve their biocompatibility and the integrity of encapsulated compounds. Here, we report an approach to produce hydrogel films spontaneously in aqueous polymer solutions. This method uses the solvent depletion created at the surface of swelling polymer substrates to induce the gelation of a thin layer of polymer solution. Using a biocompatible polymer that self-assembles at high concentration [poly(vinyl alcohol)], hydrogel films were produced within minutes to hours with thicknesses ranging from tens to hundreds of micrometers. A simple model and numerical simulations of mass transport during swelling capture the experiments and predict how film growth depends on the solution composition, substrate geometry, and swelling properties. The versatility of the approach was verified with a variety of swelling substrates and hydrogel-forming solutions. We also demonstrate the potential of this technique by incorporating other solutes such as inorganic particles to fabricate ceramic-hydrogel coatings for bone anchoring and cells to fabricate cell-laden membranes for cell culture or tissue engineering. PMID:27821765

Degradation of polymer electrolyte membrane fuel cell by siloxane in biogas

NASA Astrophysics Data System (ADS)

Seo, Ji-Sung; Kim, Da-Yeong; Hwang, Sun-Mi; Seo, Min Ho; Seo, Dong-Jun; Yang, Seung Yong; Han, Chan Hui; Jung, Yong-Min; Guim, Hwanuk; Nahm, Kee Suk; Yoon, Young-Gi; Kim, Tae-Young

2016-06-01

We studied the degradation and durability of polymer electrolyte membrane fuel cell (PEMFC) at membrane-electrode-assembly (MEA) level by injection of octamethylcyclotetrasiloxane (D4) as a representative siloxane, which has been found in many industrial and personal products. Specifically, i) GC/MS analysis demonstrated that the ring-opening polymerization of D4 could result in the formation of various linear and cyclic siloxanes in both electrodes of MEA; ii) post-test analysis revealed that the transformed siloxanes were transported from the anode to the cathode via free-volumes in the polymer membrane; iii) RDE measurement and DFT calculation revealed that D4 was not directly responsible for the electrocatalytic activity of Pt; iv) electrochemical analysis demonstrated that the residual methyl groups of siloxane and various siloxanes did not hinder the proton transport in the polymer membrane; and v) siloxanes accumulated in the primary and secondary pores with the exception of an external surface of carbon, causing an increase in the oxygen reactant's resistance and resulting in a decrease of the cell performance. In addition, we confirmed that injection of D4 did not affect the carbon corrosion adversely because the siloxane had little influence on water sorption in the catalyst layer.

Passive approach for the improved dispersion of polyvinyl alcohol-based functionalized multi-walled carbon nanotubes/Nafion membranes for polymer electrolyte membrane fuel cells.

PubMed

Abu Sayeed, M D; Talukdar, Krishan; Kim, Hee Jin; Park, Younjin; Gopalan, A I; Kim, Young Ho; Lee, Kwang-Pill; Choi, Sang-June

2014-12-01

Multi-walled carbon nanotubes (MWCNTs) are regarded as ideal fillers for Nafion polymer electrolyte membranes (PEMs) for fuel cell applications. The highly aggregated properties of MWCNTs can be overcome by the successful cross-linking with polyvinyl alcohol (PVA) into the MWCNTs/Nafion membrane. In this study, a series of nanocomposite membranes were fabricated with the PVA-influenced functionalized MWCNTs reinforced into the Nafion polymer matrix by a solution casting method. Several different PVA contents were blended to f-MWCNTs/Nafion nanocomposite membranes followed by successful cross-linking by annealing. The surface morphologies and the inner structures of the resulting PVA-MWCNTs/Nafion nanocomposite membranes were then observed by optical microscopy and scanning electron microscopy (SEM) to investigate the dispersion of MWCNTs into the PVA/Nafion composite membranes. After that, the nanocomposite membranes were characterized by thermo-gravimetric analysis (TGA) to observe the thermal enhancement caused by effective cross-linking between the f-MWCNTs with the composite polymer matrixes. Improved water uptake with reduced methanol uptake revealed the successful fabrication of PVA-blended f-MWCNTs/Nafion membranes. In addition, the ion exchange capacity (IEC) was evaluated for PEM fuel cell (PEMFC) applications.

Outlines on nanotechnologies applied to bladder tissue engineering.

PubMed

Alberti, C

2012-01-01

Tissue engineering technologies are more and more expanding as consequence of recent developments in the field of biomaterial science and nanotechnology research. An important issue in designing scaffold materials is that of recreating the ECM (extra-cellular matrix) functional features - particularly ECM-derived complex molecule signalling - to mimic its capability of directing cell-growth and neotissue morphogenesis. In this way the nanotechnology may offer intriguing chances, biomaterial nanoscale-based scaffold geometry behaving as nanomechanotransducer complex interacting with different cell nanosize proteins, especially with those of cell surface mechanoreceptors. To fabricate 3D-scaffold complex architectures, endowed with controlled geometry and functional properties, bottom-up approaches, based on molecular self-assembling of small building polymer units, are used, sometimes functionalizing them by incorporation of bioactive peptide sequences such as RDG (arginine - glycine - aspartic acid, a cell-integrin binding domain of fibronectin), whereas the top-down approaches are useful to fabricate micro/nanoscale structures, such as a microvasculature within an existing complex bioarchitecture. Synthetic polymer-based nanofibers, produced by electrospinning process, may be used to create fibrous scaffolds that can facilitate, given their nanostructured geometry and surface roughness, cell adhesion and growth. Also bladder tissue engineering may benefit by nanotechnology advances to achieve a better reliability of the bladder engineered tissue. Particularly, bladder smooth muscle cell adhesion to nanostructured polymeric surfaces is significantly enhanced in comparison with that to conventional biomaterials. Moreover nanostructured surfaces of bladder engineered tissue show a decreased calcium stone production. In a bladder tumor animal model, the dispersion of carbon nanofibers in a polymeric scaffold-based tissue engineered replacement neobladder, appears to inhibit a carcinogenic relapse in bladder prosthetic material. Facing the future, a full success of bladder tissue engineering will mainly depend on the progress of both biomaterial nanotechnologies and stem cell biology research.

Novel biodegradable calcium phosphate/polymer composite coating with adjustable mechanical properties formed by hydrothermal process for corrosion protection of magnesium substrate.

PubMed

Kaabi Falahieh Asl, Sara; Nemeth, Sandor; Tan, Ming Jen

2016-11-01

Ceramic type coatings on metallic implants, such as calcium phosphate (Ca-P), are generally stiff and brittle, potentially leading to the early failure of the bone-implant interface. To reduce material brittleness, polyacrylic acid and carboxymethyl cellulose were used in this study to deposit two types of novel Ca-P/polymer composite coatings on AZ31 magnesium alloy using a one-step hydrothermal process. X-ray diffraction and scanning electron microscopy showed that the deposited Ca-P crystal phase and morphology could be controlled by the type and concentration of polymer used. Incorporation of polymer in the Ca-P coatings reduced the coating elastic modulus bringing it close to that of magnesium and that of human bone. Nanoindentation test results revealed significantly decreased cracking tendency with the incorporation of polymer in the Ca-P coating. Apart from mechanical improvements, the protective composite layers had also enhanced the corrosion resistance of the substrate by a factor of 1000 which is sufficient for implant application. Cell proliferation studies indicated that the composite coatings induced better cell attachment compared with the purely inorganic Ca-P coating, confirming that the obtained composite materials could be promising candidates for surface protection of magnesium for implant application with the multiple functions of corrosion protection, interfacial stress reduction, and cell attachment/cell growth promotion. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1643-1657, 2016. © 2015 Wiley Periodicals, Inc.

Planar Solid-Oxide Fuel Cell Research and Development

DTIC Science & Technology

2013-03-28

electrolyte membrane ( PEM ) fuel cells ", Applied Surface Sei., 227 (2004) 56-72. [10] Grujicic, M., and Chittajallu, K. M., "Optimization of the...cathode geometry in polymer electrolyte membrane ( PEM ) fuel cells ", Chem. Eng. Sei., 59 (2004) 5883-5895. 36 [11] Anderson, W.K., Newman, J.C., Whitfield...M., Djilali, N, Suleman, A., "Optimization of a planar self-breathing PEM fuel cell cathode", AIAA 2006-6917, 11th AIAA/ISSMO Multidisciplinary

Synthesis, Biodegradability, and Biocompatibility of Lysine Diisocyanate–Glucose Polymers

PubMed Central

ZHANG, JIAN-YING; BECKMAN, ERIC J.; HU, JING; YANG, GUO-GUANG; AGARWAL, SUDHA; HOLLINGER, JEFFREY O.

2016-01-01

The success of a tissue-engineering application depends on the use of suitable biomaterials that degrade in a timely manner and induce the least immunogenicity in the host. With this purpose in mind, we have attempted to synthesize a novel nontoxic biodegradable lysine diisocyanate (LDI)-and glucose-based polymer via polymerization of highly purified LDI with glucose and its subsequent hydration to form a spongy matrix. The LDI–glucose polymer was degradable in aqueous solutions at 37, 22, and 4°C, and yielded lysine and glucose as breakdown products. The degradation products of the LDI–glucose polymer did not significantly affect the pH of the solution. The physical properties of the polymer were found to be adequate for supporting cell growth in vitro, as evidenced by the fact that rabbit bone marrow stromal cells (BMSCs) attached to the polymer matrix, remained viable on its surface, and formed multilayered confluent cultures with retention of their phenotype over a period of 2 to 4 weeks. These observations suggest that the LDI–glucose polymer and its degradation products were nontoxic in vitro. Further examination in vivo over 8 weeks revealed that subcutaneous implantation of hydrated matrix degraded in vivo three times faster than in vitro. The implanted polymer was not immunogenic and did not induce antibody responses in the host. Histological analysis of the implanted polymer showed that LDI–glucose polymer induced a minimal foreign body reaction, with formation of a capsule around the degrading polymer. The results suggest that biodegradable peptide-based polymers can be synthesized, and may potentially find their way into biomedical applications because of their biodegradability and biocompatibility. PMID:12459056

Optimized organic photovoltaics with surface plasmons

NASA Astrophysics Data System (ADS)

Omrane, B.; Landrock, C.; Aristizabal, J.; Patel, J. N.; Chuo, Y.; Kaminska, B.

2010-06-01

In this work, a new approach for optimizing organic photovoltaics using nanostructure arrays exhibiting surface plasmons is presented. Periodic nanohole arrays were fabricated on gold- and silver-coated flexible substrates, and were thereafter used as light transmitting anodes for solar cells. Transmission measurements on the plasmonic thin film made of gold and silver revealed enhanced transmission at specific wavelengths matching those of the photoactive polymer layer. Compared to the indium tin oxide-based photovoltaic cells, the plasmonic solar cells showed overall improvements in efficiency up to 4.8-fold for gold and 5.1-fold for the silver, respectively.

Method of making molten carbonate fuel cell ceramic matrix tape

DOEpatents

Maricle, Donald L.; Putnam, Gary C.; Stewart, Jr., Robert C.

1984-10-23

A method of making a thin, flexible, pliable matrix material for a molten carbonate fuel cell is described. The method comprises admixing particles inert in the molten carbonate environment with an organic polymer binder and ceramic particle. The composition is applied to a mold surface and dried, and the formed compliant matrix material removed.

Temperature sensor based on a polymer diffraction grating with silver nanoparticles

NASA Astrophysics Data System (ADS)

Nuzhdin, V. I.; Valeev, V. F.; Galyautdinov, M. F.; Osin, Yu. N.; Stepanov, A. L.

2018-01-01

The method is suggested for producing an optical temperature noncontact sensor on a polymer polymethylmethacrylate (PMMA) substrate with a diffraction optical element formed by implanting low-energy high-dose silver ions through a surface mask. Ion implantation is performed at an energy of 30 keV, a radiation dose of 5.0 × 1016 ion cm-2 and an ion beam current density of 2 μA cm-2 through a surface metal mask having the form of grid with square periodical holes (cells) of size 25 μm. In the course of implantation, silver nanoparticles are produced in periodical unmasked domains of irradiated PMMA. Operation of the temperature sensor on diffraction microstructures made of polymer with silver nanoparticles is demonstrated in the range from 20 °C to 95 °C by testing it with a probe radiation of a He - Ne laser.

Poly(dopamine) coating of 3D printed poly(lactic acid) scaffolds for bone tissue engineering.

PubMed

Kao, Chia-Tze; Lin, Chi-Chang; Chen, Yi-Wen; Yeh, Chia-Hung; Fang, Hsin-Yuan; Shie, Ming-You

2015-11-01

3D printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating to regulate cell adhesion, proliferation and differentiation of human adipose-derived stem cells (hADSCs). We prepared PLA 3D scaffolds coated with polydopamine (PDA). The chemical composition and surface properties of PDA/PLA were characterized by XPS. PDA/PLA modulated hADSCs' responses in several ways. Firstly, adhesion and proliferation, and cell cycle of hADSCs cultured on PDA/PLA were significantly enhanced relative to those on PLA. In addition, the collagen I secreted from cells was increased and promoted cell attachment and cell cycle progression were depended on the PDA content. In osteogenesis assay, the ALP activity and osteocalcin of hADSCs cultured on PDA/PLA were significantly higher than seen in those cultured on pure PLA scaffolds. Moreover, hADSCs cultured on PDA/PLA showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hADSCs. Copyright © 2015 Elsevier B.V. All rights reserved.

Surface grafted glycopolymer brushes to enhance selective adhesion of HepG2 cells.

PubMed

Chernyy, Sergey; Jensen, Bettina E B; Shimizu, Kyoko; Ceccato, Marcel; Pedersen, Steen Uttrup; Zelikin, Alexander N; Daasbjerg, Kim; Iruthayaraj, Joseph

2013-08-15

This work demonstrates the application of carbohydrate based methacrylate polymer brush, poly(2-lactobionamidoethyl methacrylate), for the purpose of cell adhesion studies. The first part of the work illustrates the effects of the structure of the aminosilane based ATRP initiator layer on the polymerization kinetics of 2-lactobionamidoethyl methacrylate) (LAMA) monomer on thermally oxidized silicon wafer. Both monolayer and multilayered aminosilane precursor layers have been prepared followed by reaction with 2-bromoisobutyrylbromide to form the ATRP initiator layer. It is inferred from the kinetic studies that the rate of termination is low on a multilayered initiator layer compared to a disordered monolayer structure. However both initiator types results in similar graft densities. Furthermore, it is shown that thick comb-like poly(LAMA) brushes can be constructed by initiating a second ATRP process on a previously formed poly(LAMA) brushes. The morphology of human hepatocellular carcinoma cancer cells (HepG2) on the comb-like poly(LAMA) brush layer has been studied. The fluorescent images of the HepG2 cells on the glycopolymer brush surface display distinct protrusions that extend outside of the cell periphery. On the other hand the cells on bare glass substrate display spheroid morphology. Further analysis using ToF-SIMS imaging shows that the HepG2 cells on glycopolymer surfaces is enriched with protein fragment along the cell periphery which is absent in the case of cells on bare glass substrate. It is suggested that the interaction of the galactose units of the polymer brush with the asialoglycoprotein receptor (ASGPR) of HepG2 cells has resulted in the protein enrichment along the cell periphery. Copyright © 2013 Elsevier Inc. All rights reserved.

Incorporating functionalized polyethylene glycol lipids into reprecipitated conjugated polymer nanoparticles for bioconjugation and targeted labeling of cells

NASA Astrophysics Data System (ADS)

Kandel, Prakash K.; Fernando, Lawrence P.; Ackroyd, P. Christine; Christensen, Kenneth A.

2011-03-01

We report a simple and rapid method to prepare extremely bright, functionalized, stable, and biocompatible conjugated polymer nanoparticles incorporating functionalized polyethylene glycol (PEG) lipids by reprecipitation. These nanoparticles retain the fundamental spectroscopic properties of conjugated polymer nanoparticles prepared without PEG lipid, but demonstrate greater hydrophilicity and quantum yield compared to unmodified conjugated polymer nanoparticles. The sizes of these nanoparticles, as determined by TEM, were 21-26 nm. Notably, these nanoparticles were prepared with several PEG lipid functional end groups, including biotin and carboxy moieties that can be easily conjugated to biomolecules. We have demonstrated the availability of these end groups for functionalization using the interaction of biotin PEG lipid conjugated polymer nanoparticles with streptavidin. Biotinylated PEG lipid conjugated polymer nanoparticles bound streptavidin-linked magnetic beads, while carboxy and methoxy PEG lipid modified nanoparticles did not. Similarly, biotinylated PEG lipid conjugated polymer nanoparticles bound streptavidin-coated glass slides and could be visualized as diffraction-limited spots, while nanoparticles without PEG lipid or with non-biotin PEG lipid end groups were not bound. To demonstrate that nanoparticle functionalization could be used for targeted labelling of specific cellular proteins, biotinylated PEG lipid conjugated polymer nanoparticles were bound to biotinylated anti-CD16/32 antibodies on J774A.1 cell surface receptors, using streptavidin as a linker. This work represents the first demonstration of targeted delivery of conjugated polymer nanoparticles and demonstrates the utility of these new nanoparticles for fluorescence based imaging and sensing.We report a simple and rapid method to prepare extremely bright, functionalized, stable, and biocompatible conjugated polymer nanoparticles incorporating functionalized polyethylene glycol (PEG) lipids by reprecipitation. These nanoparticles retain the fundamental spectroscopic properties of conjugated polymer nanoparticles prepared without PEG lipid, but demonstrate greater hydrophilicity and quantum yield compared to unmodified conjugated polymer nanoparticles. The sizes of these nanoparticles, as determined by TEM, were 21-26 nm. Notably, these nanoparticles were prepared with several PEG lipid functional end groups, including biotin and carboxy moieties that can be easily conjugated to biomolecules. We have demonstrated the availability of these end groups for functionalization using the interaction of biotin PEG lipid conjugated polymer nanoparticles with streptavidin. Biotinylated PEG lipid conjugated polymer nanoparticles bound streptavidin-linked magnetic beads, while carboxy and methoxy PEG lipid modified nanoparticles did not. Similarly, biotinylated PEG lipid conjugated polymer nanoparticles bound streptavidin-coated glass slides and could be visualized as diffraction-limited spots, while nanoparticles without PEG lipid or with non-biotin PEG lipid end groups were not bound. To demonstrate that nanoparticle functionalization could be used for targeted labelling of specific cellular proteins, biotinylated PEG lipid conjugated polymer nanoparticles were bound to biotinylated anti-CD16/32 antibodies on J774A.1 cell surface receptors, using streptavidin as a linker. This work represents the first demonstration of targeted delivery of conjugated polymer nanoparticles and demonstrates the utility of these new nanoparticles for fluorescence based imaging and sensing. Electronic supplementary information (ESI) available: Additional TEM data, supplemental light scattering measurements, absorbance and fluorescence emission spectra, and photostability measurements. See DOI: 10.1039/c0nr00746c

Polymer-Derived Silicoboron Carbonitride Foams for CO2 Capture: From Design to Application as Scaffolds for the in Situ Growth of Metal-Organic Frameworks.

PubMed

Sandra, Fabien; Depardieu, Martin; Mouline, Zineb; Vignoles, Gérard L; Iwamoto, Yuji; Miele, Philippe; Backov, Rénal; Bernard, Samuel

2016-06-06

A template-assisted polymer-derived ceramic route is investigated for preparing a series of silicoboron carbonitride (Si/B/C/N) foams with a hierarchical pore size distribution and tailorable interconnected porosity. A boron-modified polycarbosilazane was selected to impregnate monolithic silica and carbonaceous templates and form after pyrolysis and template removal Si/B/C/N foams. By changing the hard template nature and controlling the quantity of polymer to be impregnated, controlled micropore/macropore distributions with mesoscopic cell windows are generated. Specific surface areas from 29 to 239 m(2)  g(-1) and porosities from 51 to 77 % are achieved. These foams combine a low density with a thermal insulation and a relatively good thermostructural stability. Their particular structure allowed the in situ growth of metal-organic frameworks (MOFs) directly within the open-cell structure. MOFs offered a microporosity feature to the resulting Si/B/C/N@MOF composite foams that allowed increasing the specific surface area to provide CO2 uptake of 2.2 %. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface deformation during an action potential in pearled cells

NASA Astrophysics Data System (ADS)

Mussel, Matan; Fillafer, Christian; Ben-Porath, Gal; Schneider, Matthias F.

2017-11-01

Electric pulses in biological cells (action potentials) have been reported to be accompanied by a propagating cell-surface deformation with a nanoscale amplitude. Typically, this cell surface is covered by external layers of polymer material (extracellular matrix, cell wall material, etc.). It was recently demonstrated in excitable plant cells (Chara braunii) that the rigid external layer (cell wall) hinders the underlying deformation. When the cell membrane was separated from the cell wall by osmosis, a mechanical deformation, in the micrometer range, was observed upon excitation of the cell. The underlying mechanism of this mechanical pulse has, to date, remained elusive. Herein we report that Chara cells can undergo a pearling instability, and when the pearled fragments were excited even larger and more regular cell shape changes were observed (˜10 -100 μ m in amplitude). These transient cellular deformations were captured by a curvature model that is based on three parameters: surface tension, bending rigidity, and pressure difference across the surface. In this paper these parameters are extracted by curve-fitting to the experimental cellular shapes at rest and during excitation. This is a necessary step to identify the mechanical parameters that change during an action potential.

Analysis of the K1 capsule biosynthesis genes of Escherichia coli: definition of three functional regions for capsule production.

PubMed

Boulnois, G J; Roberts, I S; Hodge, R; Hardy, K R; Jann, K B; Timmis, K N

1987-06-01

Transposon and deletion analysis of the cloned K1 capsule biosynthesis genes of Escherichia coli revealed that approximately 17 kb of DNA, split into three functional regions, is required for capsule production. One block (region 1) is required for translocation of polysaccharide to the cell surface and mutations in this region result in the intracellular appearance of polymer indistinguishable on immunoelectrophoresis to that found on the surface of K1 encapsulated bacteria. This material was released from the cell by osmotic shock indicating that the polysaccharide was probably present in the periplasmic space. Insertions in a second block (region 2) completely abolished polymer production and this second region is believed to encode the enzymes for the biosynthesis and polymerisation of the K1 antigen. Addition of exogenous N-acetylneuraminic acid to one insertion mutant in this region restored its ability to express surface polymer as judged by K1 phage sensitivity. This insertion probably defines genes involved in biosynthesis of N-acetylneuraminic acid. Insertions in a third block (region 3) result in the intracellular appearance of polysaccharide with a very low electrophoretic mobility. The presence of the cloned K1 capsule biosynthesis genes on a multicopy plasmid in an E. coli K-12 strain did not increase the yields of capsular polysaccharide produced compared to the K1+ isolate from which the genes were cloned.

Preparation of Caco-2 cell sheets using plasma polymerised acrylic acid as a weak boundary layer.

PubMed

Majani, Ruby; Zelzer, Mischa; Gadegaard, Nikolaj; Rose, Felicity R; Alexander, Morgan R

2010-09-01

The use of cell sheets for tissue engineering applications has considerable advantages over single cell seeding techniques. So far, only thermoresponsive surfaces have been used to manufacture cell sheets without chemically disrupting the cell-surface interactions. Here, we present a new and facile technique to prepare sheets of epithelial cells using plasma polymerised acrylic acid films. The cell sheets are harvested by gentle agitation of the media without the need of any additional external stimulus. We demonstrate that the plasma polymer deposition conditions affect the viability and metabolic activity of the cells in the sheet and relate these effects to the different surface properties of the plasma polymerised acrylic acid films. Based on surface analysis data, a first attempt is made to explain the mechanism behind the cell sheet formation. The advantage of the epithelial cell sheets generated here over single cell suspensions to seed a PLGA scaffold is presented. The scaffold itself, prepared using a mould fabricated via photolithography, exhibits a unique architecture that mimics closely the dimensions of the native tissue (mouse intestine). Copyright 2010 Elsevier Ltd. All rights reserved.

Coating carbon nanotubes with a polystyrene-based polymer protects against pulmonary toxicity.

PubMed

Tabet, Lyes; Bussy, Cyrill; Setyan, Ari; Simon-Deckers, Angélique; Rossi, Michel J; Boczkowski, Jorge; Lanone, Sophie

2011-01-21

carbon nanotubes (CNT) can have adverse effects on health. Therefore, minimizing the risk associated with CNT exposure is of crucial importance. The aim of this work was to evaluate if coating multi-walled CNT (MWCNT) with polymers could modify their toxicity, thus representing a useful strategy to decrease adverse health effects of CNT. We used industrially-produced MWCNT uncoated (NT1) or coated (50/50 wt%) with acid-based (NT2) or polystyrene-based (NT3) polymer, and exposed murine macrophages (RAW 264.7 cell line) or Balb/c mice by intratracheal administration. Biological experiments were performed both in vitro and in vivo, examining time- and dose-dependent effects of CNT, in terms of cytotoxicity, expression of genes and proteins related to oxidative stress, inflammation and tissue remodeling, cell and lung tissue morphology (optical and transmission electron microscopy), and bronchoalveolar lavage fluid content analysis. extensive physico-chemical characterization of MWCNT was performed, and showed, although similar dimensions for the 3 MWCNT, a much smaller specific surface area for NT2 and NT3 as compared to NT1 (54.1, 34 and 227.54 m(2)/g respectively), along with different surface characteristics. MWCNT-induced cytotoxicity, oxidative stress, and inflammation were increased by acid-based and decreased by polystyrene-based polymer coating both in vitro in murine macrophages and in vivo in lung of mice monitored for 6 months. these results demonstrate that coating CNT with polymers, without affecting their intrinsic structure, may constitute a useful strategy for decreasing CNT toxicity, and may hold promise for improving occupational safety and that of general the user.

Mechanisms of chain adsorption on porous substrates and critical conditions of polymer chromatography.

PubMed

Cimino, Richard T; Rasmussen, Christopher J; Brun, Yefim; Neimark, Alexander V

2016-11-01

Polymer adsorption is a ubiquitous phenomenon with numerous technological and healthcare applications. The mechanisms of polymer adsorption on surfaces and in pores are complex owing to a competition between various entropic and enthalpic factors. Due to adsorption of monomers to the surface, the chain gains in enthalpy yet loses in entropy because of confining effects. This competition leads to the existence of critical conditions of adsorption when enthalpy gain and entropy loss are in balance. The critical conditions are controlled by the confining geometry and effective adsorption energy, which depends on the solvent composition and temperature. This phenomenon has important implications in polymer chromatography, since the retention at the critical point of adsorption (CPA) is chain length independent. However, the mechanisms of polymer adsorption in pores are poorly understood and there is an ongoing discussion in the theoretical literature about the very existence of CPA for polymer adsorption on porous substrates. In this work, we examine the mechanisms of chain adsorption on a model porous substrate using Monte Carlo (MC) simulations. We distinguish three adsorption mechanisms depending on the chain location: on external surface, completely confined in pores, and also partially confined in pores in so-called "flower" conformations. The free energies of different conformations of adsorbed chains are calculated by the incremental gauge cell MC method that allows one to determine the partition coefficient as a function of the adsorption potential, pore size, and chain length. We confirm the existence of the CPA for chain length independent separation on porous substrates, which is explained by the dominant contributions of the chain adsorption at the external surface, in particular in flower conformations. Moreover, we show that the critical conditions for porous and nonporous substrates are identical and depend only on the surface chemistry. The theoretical results are confirmed by comparison with experimental data on chromatographic separation of a series of linear polystyrenes. Copyright © 2016 Elsevier Inc. All rights reserved.

Novel donor-acceptor polymer containing 4,7-bis(thiophen-2-yl)benzo[c][1,2,5]thiadiazole for polymer solar cells with power conversion efficiency of 6.21%.

PubMed

Han, Liangliang; Bao, Xichang; Hu, Tong; Du, Zhengkun; Chen, Weichao; Zhu, Dangqiang; Liu, Qian; Sun, Mingliang; Yang, Renqiang

2014-06-01

In order to improve the solution processability of 4,7-bis(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (DTBT)-based polymers, novel donor-acceptor polymer PTOBDTDTBT containing DTBT and benzo[1,2-b:4,5-b']dithiophene (BDT) with conjugated side chain is designed and synthesized with narrow band gap 1.67 eV and low lying HOMO energy level -5.4 eV. The blend film of PTOBDTDTBT and PC71 BM exhibits uniform and smooth film with root-mean-square (RMS) surface roughness 1.15 nm because of the excellent solubility of PTOBDTDTBT when six octyloxy side chains are introduced. The hole mobility of the blend film is measured to be 4.4 × 10(-5) cm(2) V(-1) s(-1) by the space-charge-limited current (SCLC) model. The optimized polymer solar cells (PSCs) based on PTOBDTDTBT/PC71 BM exhibits an improved PCE of 6.21% with Voc = 0.80 V, Jsc = 11.94 mA cm(-2) and FF = 65.10%, one of the highest PCE in DTBT containing polymers. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of a slow mode of BMP-2 delivery on the inflammatory response provoked by bone-defect-filling polymeric scaffolds.

PubMed

Wu, Gang; Liu, Yuelian; Iizuka, Tateyuki; Hunziker, Ernst Bruno

2010-10-01

We investigated the inflammatory response to, and the osteoinductive efficacies of, four polymers (collagen, Ethisorb, PLGA and Polyactive) that bore either an adsorbed (fast-release kinetics) or a calcium-phosphate-coating-incorporated (slow-release kinetics) depot of BMP-2. Titanium-plate-supported discs of each polymer (n = 6 per group) were implanted at an ectopic (subcutaneous) ossification site in rats (n = 48). Five weeks later, they were retrieved for a histomorphometric analysis of the volumes of ectopic bone and foreign-body giant cells (a gauge of inflammatory reactivity), and the degree of polymer degradation. For each polymer, the osteoinductive efficacy of BMP-2 was higher when it was incorporated into a coating than when it was directly adsorbed onto the material. This mode of BMP-2 carriage was consistently associated with an attenuation of the inflammatory response. For coated materials, the volume density of foreign-body giant cells was inversely correlated with the volume density of bone (r(2) = 0.96), and the volume density of bone was directly proportional to the surface-area density of the polymer (r(2) = 0.97). Following coating degradation, other competitive factors, such as the biocompatibility and the biodegradability of the polymer itself, came into play. 2010 Elsevier Ltd. All rights reserved.

Molecular Design of Antifouling Polymer Brushes Using Sequence-Specific Peptoids

DOE PAGES

Lau, King Hang Aaron; Sileika, Tadas S.; Park, Sung Hyun; ...

2014-11-26

Material systems that can be used to flexibly and precisely define the chemical nature and molecular arrangement of a surface would be invaluable for the control of complex biointerfacial interactions. For example, progress in antifouling polymer biointerfaces that prevents nonspecific protein adsorption and cell attachment, which can significantly improve the performance of an array of biomedical and industrial applications, is hampered by a lack of chemical models to identify the molecular features conferring their properties. Poly(N-substituted glycine) “peptoids” are peptidomimetic polymers that can be conveniently synthesized with specific monomer sequences and chain lengths, and are presented as a versatile platformmore » for investigating the molecular design of antifouling polymer brushes. Zwitterionic antifouling polymer brushes have captured significant recent attention, and a targeted library of zwitterionic peptoid brushes with different charge densities, hydration, separations between charged groups, chain lengths, and grafted chain densities, is quantitatively evaluated for their antifouling properties through a range of protein adsorption and cell attachment assays. Specific zwitterionic brush designs are found to give rise to distinct but subtle differences in properties. In conclusion, the results also point to the dominant roles of the grafted chain density and chain length in determining the performance of antifouling polymer brushes.« less

Polydopamine-mediated surface modification of scaffold materials for human neural stem cell engineering.

PubMed

Yang, Kisuk; Lee, Jung Seung; Kim, Jin; Lee, Yu Bin; Shin, Heungsoo; Um, Soong Ho; Kim, Jeong Beom; Park, Kook In; Lee, Haeshin; Cho, Seung-Woo

2012-10-01

Surface modification of tissue engineering scaffolds and substrates is required for improving the efficacy of stem cell therapy by generating physicochemical stimulation promoting proliferation and differentiation of stem cells. However, typical surface modification methods including chemical conjugation or physical absorption have several limitations such as multistep, complicated procedures, surface denaturation, batch-to-batch inconsistencies, and low surface conjugation efficiency. In this study, we report a mussel-inspired, biomimetic approach to surface modification for efficient and reliable manipulation of human neural stem cell (NSC) differentiation and proliferation. Our study demonstrates that polydopamine coating facilitates highly efficient, simple immobilization of neurotrophic growth factors and adhesion peptides onto polymer substrates. The growth factor or peptide-immobilized substrates greatly enhance differentiation and proliferation of human NSCs (human fetal brain-derived NSCs and human induced pluripotent stem cell-derived NSCs) at a level comparable or greater than currently available animal-derived coating materials (Matrigel) with safety issues. Therefore, polydopamine-mediated surface modification can provide a versatile platform technology for developing chemically defined, safe, functional substrates and scaffolds for therapeutic applications of human NSCs. Copyright © 2012 Elsevier Ltd. All rights reserved.

Phosphate functionalized and lactic acid containing graft copolymer: synthesis and evaluation as biomaterial for bone tissue engineering applications.

PubMed

Datta, Pallab; Chatterjee, Jyotirmoy; Dhara, Santanu

2013-01-01

Polyvinyl alcohol (PVA) and polylactic acids (PLA) are biocompatible materials possessing some inherent contrasting limitations which have reduced the scope of their individual applicability. Specifically, overcoming strong hydrophobicity and introducing chemical groups for biofunctionalization are unmet challenges for PLA whilst chemical endeavors to render adequate aqueous stability and cell adhesion properties to PVA have not produced completely intended results. Objective of the present work is to explore synthesis of a graft polymer as an approach towards coupling biofunctional groups with PLA materials. In a two-step reaction, PPVA (phosphorylated polyvinyl alcohol or PVA pre-functionalized with phosphate) is esterified with lactic acid followed by polymerization into PLA in presence of stannous chloride as catalyst to obtain phosphorylated polyvinyl alcohol-graft-polylactic acid (PPVA-g-LA) copolymer. Product is characterized by nuclear magnetic resonance, X-ray diffraction, and thermogravimetric analysis. PPVA-g-LA shows an increase in uniaxial elongation compared to parent PPVA under condition of tensile loading. The graft copolymer also exhibits higher water contact angles compared to PPVA, but a more hydrophilic surface compared to PLA. Culture of MG-63 cells on solvent cast films of polymers demonstrates that PPVA-g-LA as a cell substrate can significantly (p < 0.05) improve proliferation and differentiation of cells compared to PPVA substrate whereas in comparison to PLA can significantly ameliorate osteoblast function of cultured cells. Overall, results illustrate the feasibility of PVA to act as a carrier for biofunctional agents to be coupled to lactic acid-based biomaterials with subsequent improvement in cell response on the polymers. In this attempt, it also affords materials with tunable surface or bulk properties of relevance for tissue engineering applications.

Generic delivery of payload of nanoparticles intracellularly via hybrid polymer capsules for bioimaging applications.

PubMed

Sami, Haider; Maparu, Auhin K; Kumar, Ashok; Sivakumar, Sri

2012-01-01

Towards the goal of development of a generic nanomaterial delivery system and delivery of the 'as prepared' nanoparticles without 'further surface modification' in a generic way, we have fabricated a hybrid polymer capsule as a delivery vehicle in which nanoparticles are loaded within their cavity. To this end, a generic approach to prepare nanomaterials-loaded polyelectrolyte multilayered (PEM) capsules has been reported, where polystyrene sulfonate (PSS)/polyallylamine hydrochloride (PAH) polymer capsules were employed as nano/microreactors to synthesize variety of nanomaterials (metal nanoparticles; lanthanide doped inorganic nanoparticles; gadolinium based nanoparticles, cadmium based nanoparticles; different shapes of nanoparticles; co-loading of two types of nanoparticles) in their hollow cavity. These nanoparticles-loaded capsules were employed to demonstrate generic delivery of payload of nanoparticles intracellularly (HeLa cells), without the need of individual nanoparticle surface modification. Validation of intracellular internalization of nanoparticles-loaded capsules by HeLa cells was ascertained by confocal laser scanning microscopy. The green emission from Tb(3+) was observed after internalization of LaF(3):Tb(3+)(5%) nanoparticles-loaded capsules by HeLa cells, which suggests that nanoparticles in hybrid capsules retain their functionality within the cells. In vitro cytotoxicity studies of these nanoparticles-loaded capsules showed less/no cytotoxicity in comparison to blank capsules or untreated cells, thus offering a way of evading direct contact of nanoparticles with cells because of the presence of biocompatible polymeric shell of capsules. The proposed hybrid delivery system can be potentially developed to avoid a series of biological barriers and deliver multiple cargoes (both simultaneous and individual delivery) without the need of individual cargo design/modification.

Generic Delivery of Payload of Nanoparticles Intracellularly via Hybrid Polymer Capsules for Bioimaging Applications

PubMed Central

Sami, Haider; Maparu, Auhin K.; Kumar, Ashok; Sivakumar, Sri

2012-01-01

Towards the goal of development of a generic nanomaterial delivery system and delivery of the ‘as prepared’ nanoparticles without ‘further surface modification’ in a generic way, we have fabricated a hybrid polymer capsule as a delivery vehicle in which nanoparticles are loaded within their cavity. To this end, a generic approach to prepare nanomaterials-loaded polyelectrolyte multilayered (PEM) capsules has been reported, where polystyrene sulfonate (PSS)/polyallylamine hydrochloride (PAH) polymer capsules were employed as nano/microreactors to synthesize variety of nanomaterials (metal nanoparticles; lanthanide doped inorganic nanoparticles; gadolinium based nanoparticles, cadmium based nanoparticles; different shapes of nanoparticles; co-loading of two types of nanoparticles) in their hollow cavity. These nanoparticles-loaded capsules were employed to demonstrate generic delivery of payload of nanoparticles intracellularly (HeLa cells), without the need of individual nanoparticle surface modification. Validation of intracellular internalization of nanoparticles-loaded capsules by HeLa cells was ascertained by confocal laser scanning microscopy. The green emission from Tb3+ was observed after internalization of LaF3:Tb3+(5%) nanoparticles-loaded capsules by HeLa cells, which suggests that nanoparticles in hybrid capsules retain their functionality within the cells. In vitro cytotoxicity studies of these nanoparticles-loaded capsules showed less/no cytotoxicity in comparison to blank capsules or untreated cells, thus offering a way of evading direct contact of nanoparticles with cells because of the presence of biocompatible polymeric shell of capsules. The proposed hybrid delivery system can be potentially developed to avoid a series of biological barriers and deliver multiple cargoes (both simultaneous and individual delivery) without the need of individual cargo design/modification. PMID:22649489

Spontaneous Packaging and Hypothermic Storage of Mammalian Cells with a Cell-Membrane-Mimetic Polymer Hydrogel in a Microchip.

PubMed

Xu, Yan; Mawatari, Kazuma; Konno, Tomohiro; Kitamori, Takehiko; Ishihara, Kazuhiko

2015-10-21

Currently, continuous culture/passage and cryopreservation are two major, well-established methods to provide cultivated mammalian cells for experiments in laboratories. Due to the lack of flexibility, however, both laboratory-oriented methods are unable to meet the need for rapidly growing cell-based applications, which require cell supply in a variety of occasions outside of laboratories. Herein, we report spontaneous packaging and hypothermic storage of mammalian cells under refrigerated (4 °C) and ambient conditions (25 °C) using a cell-membrane-mimetic methacryloyloxyethyl phosphorylcholine (MPC) polymer hydrogel incorporated within a glass microchip. Its capability for hypothermic storage of cells was comparatively evaluated over 16 days. The results reveal that the cytocompatible MPC polymer hydrogel, in combination with the microchip structure, enabled hypothermic storage of cells with quite high viability, high intracellular esterase activity, maintained cell membrane integrity, and small morphological change for more than 1 week at 4 °C and at least 4 days at 25 °C. Furthermore, the stored cells could be released from the hydrogel and exhibited the ability to adhere to a surface and achieve confluence under standard cell culture conditions. Both hypothermic storage conditions are ordinary flexible conditions which can be easily established in places outside of laboratories. Therefore, cell packaging and storage using the hydrogel incorporated within the microchip would be a promising miniature and portable solution for flexible supply and delivery of small amounts of cells from bench to bedside.

Screening Nylon-3 Polymers, a New Class of Cationic Amphiphiles, for siRNA Delivery

PubMed Central

2015-01-01

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. PMID:25437915

Screening nylon-3 polymers, a new class of cationic amphiphiles, for siRNA delivery.

PubMed

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

2015-02-02

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.

Influence of electrospun scaffolds prepared from distinct polymers on proliferation and viability of endothelial cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matveeva, V. G., E-mail: matveeva-vg@mail.ru; Antonova, L. V., E-mail: antonova.la@mail.ru; Velikanova, E. A.

We compared electrospun nonwoven scaffolds from polylactic acid (PLA), polycaprolactone (PCL), and polyhydroxybutyrate/valerate (PHBV)/polycaprolactone (PHBV/PCL). The surface of PHBV/PCL and PCL scaffolds was highly porous and consisted of randomly distributed fibers, whilst the surface of PLA scaffolds consisted of thin straight fibers, which located more sparsely, forming large pores. Culture of EA.hy 926 endothelial cells on these scaffolds during 7 days and further fluorescent microscopy demonstrated that the surface of PHBV/PCL scaffolds was most favorable for efficient adhesion, proliferation, and viability of endothelial cells. The lowest proliferation rate and cell viability were detected on PLA scaffolds. Therefore, PHBV/PCL electrospun nonwovenmore » scaffolds demonstrated the best results regarding endothelial cell proliferation and viability as compared to PCL and PLA scaffolds.« less

Glass matrix armor

DOEpatents

Calkins, Noel C.

1991-01-01

An armor system which utilizes glass. A plurality of constraint cells are mounted on a surface of a substrate, which is metal armor plate or a similar tough material, such that the cells almost completely cover the surface of the substrate. Each constraint cell has a projectile-receiving wall parallel to the substrate surface and has sides which are perpendicular to and surround the perimeter of the receiving wall. The cells are mounted such that, in one embodiment, the substrate surface serves as a sixth side or closure for each cell. Each cell has inside of it a plate, termed the front plate, which is parallel to and in contact with substantially all of the inside surface of the receiving wall. The balance of each cell is completely filled with a projectile-abrading material consisting of glass and a ceramic material and, in certain embodiments, a polymeric material. The glass may be in monolithic form or particles of ceramic may be dispersed in a glass matrix. The ceramic material may be in monolithic form or may be in the form of particles dispersed in glass or dispersed in said polymer.

96X Screen-Printed Gold Electrode Platform to Evaluate Electroactive Polymers as Marine Antifouling Coatings.

PubMed

Brisset, Hugues; Briand, Jean-François; Barry-Martinet, Raphaëlle; Duong, The Hy; Frère, Pierre; Gohier, Frédéric; Leriche, Philippe; Bressy, Christine

2018-04-17

Several alternatives are currently investigated to prevent and control the natural process of colonization of any seawater submerged surfaces by marine organisms. Since few years we develop an approach based on addressable electroactive coatings containing conducting polymers or polymers with lateral redox groups. In this article we describe the use of a screen-printed plate formed by 96 three-electrode electrochemical cells to assess the potential of these electroactive coatings to prevent the adhesion of marine bacteria. This novel platform is intended to control and record the redox properties of the electroactive coating in each well during the bioassay (15 h) and to allow screening its antiadhesion activity with enough replicates to support significant conclusions. Validation of this platform was carried out with poly(ethylenedioxythiophene) (PEDOT) as electroactive coating obtained by electropolymerization of EDOT monomer in artificial seawater electrolyte on the working electrode of each electrochemical cell of the 96-well microplate.

[Application of electrostatic spinning technology in nano-structured polymer scaffold].

PubMed

Chen, Denglong; Li, Min; Fang, Qian

2007-04-01

To review the latest development in the research on the application of the electrostatic spinning technology in preparation of the nanometer high polymer scaffold. The related articles published at home and abroad during the recent years were extensively reviewed and comprehensively analyzed. Micro/nano-structure and space topology on the surfaces of the scaffold materials, especially the weaving structure, were considered to have an important effect on the cell adhesion, proliferation, directional growth, and biological activation. The electrospun scaffold was reported to have a resemblance to the structure of the extracellular matrix and could be used as a promising scaffold for the tissue engineering application. The electrospun scaffolds were applied to the cartilage, bone, blood vessel, heart, and nerve tissue engineering fields. The nano-structured polymer scaffold can support the cell adhesion, proliferation, location, and differentiation, and this kind of scaffold has a considerable value in the tissue engineering field.

Development of PVA based micro-porous polymer electrolyte by a novel preferential polymer dissolution process

NASA Astrophysics Data System (ADS)

Subramania, A.; Kalyana Sundaram, N. T.; Sukumar, N.

A micro-porous polymer electrolyte based on PVA was obtained from PVA-PVC based polymer blend film by a novel preferential polymer dissolution technique. The ionic conductivity of micro-porous polymer electrolyte increases with increase in the removal of PVC content. Finally, the effect of variation of lithium salt concentration is studied for micro-porous polymer electrolyte of high ionic conductivity composition. The ionic conductivity of the micro-porous polymer electrolyte is measured in the temperature range of 301-351 K. It is observed that a 2 M LiClO 4 solution of micro-porous polymer electrolyte has high ionic conductivity of 1.5055 × 10 -3 S cm -1 at ambient temperature. Complexation and surface morphology of the micro-porous polymer electrolytes are studied by X-ray diffraction and SEM analysis. TG/DTA analysis informs that the micro-porous polymer electrolyte is thermally stable upto 277.9 °C. Chronoamperommetry and linear sweep voltammetry studies were made to find out lithium transference number and stability of micro-porous polymer electrolyte membrane, respectively. Cyclic voltammetry study was performed for carbon/micro-porous polymer electrolyte/LiMn 2O 4 cell to reveal the compatibility and electrochemical stability between electrode materials.

3D silicon doped hydroxyapatite scaffolds decorated with Elastin-like Recombinamers for bone regenerative medicine.

PubMed

Vila, Mercedes; García, Ana; Girotti, Alessandra; Alonso, Matilde; Rodríguez-Cabello, Jose Carlos; González-Vázquez, Arlyng; Planell, Josep A; Engel, Elisabeth; Buján, Julia; García-Honduvilla, Natalio; Vallet-Regí, María

2016-11-01

The current study reports on the manufacturing by rapid prototyping technique of three-dimensional (3D) scaffolds based on silicon substituted hydroxyapatite with Elastin-like Recombinamers (ELRs) functionalized surfaces. Silicon doped hydroxyapatite (Si-HA), with Ca 10 (PO 4 ) 5.7 (SiO 4 ) 0.3 (OH) 1.7 h 0.3 nominal formula, was surface functionalized with two different types of polymers designed by genetic engineering: ELR-RGD that contain cell attachment specific sequences and ELR-SN A 15/RGD with both hydroxyapatite and cells domains that interact with the inorganic phase and with the cells, respectively. These hybrid materials were subjected to in vitro assays in order to clarify if the ELRs coating improved the well-known biocompatible and bone regeneration properties of calcium phosphates materials. The in vitro tests showed that there was a total and homogeneous colonization of the 3D scaffolds by Bone marrow Mesenchymal Stromal Cells (BMSCs). In addition, the BMSCs were viable and able to proliferate and differentiate into osteoblasts. Bone tissue engineering is an area of increasing interest because its main applications are directly related to the rising life expectancy of the population, which promotes higher rates of several bone pathologies, so innovative strategies are needed for bone tissue regeneration therapies. Here we use the rapid prototyping technology to allow moulding ceramic 3D scaffolds and we use different bio-polymers for the functionalization of their surfaces in order to enhance the biological response. Combining the ceramic material (silicon doped hydroxyapatite, Si-HA) and the Elastin like Recombinamers (ELRs) polymers with the presence of the integrin-mediate adhesion domain alone or in combination with SNA15 peptide that possess high affinity for hydroxyapatite, provided an improved Bone marrow Mesenchymal Stromal Cells (BMSCs) differentiation into osteoblastic linkage. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Development and use of culture systems to modulate specific cell responses

NASA Astrophysics Data System (ADS)

Martin, Yves

Culture surfaces that induce specific localized cell responses are required to achieve tissue-like cell growth in three-dimensional (3D) environments, as well as to develop more efficient cell-based diagnostic techniques, noticeably when working with fragile cells such as stem cells or platelets. As such, Chapter 1 of this thesis work is devoted to the review of 3D cell-material interactions in vitro and the corresponding existing culture systems available to achieve in vivo-like cell responses. More adequate 3D culture systems will need to be developed to mimic several characteristics of in vivo environments, including lowered non-specific cell-material interactions and localized biochemical signaling. The experimental work in this thesis is based on the hypothesis that well-studied and optimized surface treatments will be able to lower non-specific cell-material interactions and allow local chemical modification in order to achieve specific localized cell-material interactions for different applications. As such, in Chapter 2 and Chapter 3 of this thesis, surface treatments were developed using plasma polymerization and covalent immobilization of a low-fouling polymer (i.e., poly(ethylene glycol)) and characterized and optimized using a large number of techniques including atomic force microscopy, quartz crystal microbalance, surface plasmon resonance, x-ray photoelectron spectroscopy and fluorescence-based techniques. The main plasma polymerization parameter important for surface chemical content, specifically nitrogen to carbon content, was identified as being glow discharge power, while reaction time and power determined plasma film thickness. Moreover, plasma films were shown to be stable in aqueous environments. Covalently-bound poly(ethylene glycol) (PEG) layers physicochemical and mechanical properties are dependent on fabrication methods. Polymer concentration in solution is an important indicator of final layer properties, and use of a theta solvent induces complex aggregation phenomena in solution yielding layers with widely different properties. Chemically available primary amine groups are also shown to be present, paving the way for the immobilization of bio-active molecules. An application of low-fouling locally modified surfaces is given in Chapter 4 by the development of a novel diagnostic surface to evaluate platelet activation which is until now very difficult as platelets are readily activated by in vitro manipulations. Significant results from volunteer donors indicate that this diagnostic instrument has the potential to allow the rapid estimation of platelet activation levels in whole blood.

Adhesion and proliferation of OCT-1 osteoblast-like cells on micro- and nano-scale topography structured poly(L-lactide).

PubMed

Wan, Yuqing; Wang, Yong; Liu, Zhimin; Qu, Xue; Han, Buxing; Bei, Jianzhong; Wang, Shenguo

2005-07-01

The impact of the surface topography of polylactone-type polymer on cell adhesion was to be concerned because the micro-scale texture of a surface can provide a significant effect on the adhesion behavior of cells on the surface. Especially for the application of tissue engineering scaffold, the pore size could have an influence on cell in-growth and subsequent proliferation. Micro-fabrication technology was used to generate specific topography to investigate the relationship between the cells and surface. In this study the pits-patterned surfaces of polystyrene (PS) film with diameters 2.2 and 0.45 microm were prepared by phase-separation, and the corresponding scale islands-patterned PLLA surface was prepared by a molding technique using the pits-patterned PS as a template. The adhesion and proliferation behavior of OCT-1 osteoblast-like cells morphology on the pits- and islands-patterned surface were characterized by SEM observation, cell attachment efficiency measurement and MTT assay. The results showed that the cell adhesion could be enhanced on PLLA and PS surface with nano-scale and micro-scale roughness compared to the smooth surfaces of the PLLA and PS. The OCT-1 osteoblast-like cells could grow along the surface with two different size islands of PLLA and grow inside the micro-scale pits of the PS. However, the proliferation of cells on the micro- and nano-scale patterned surface has not been enhanced compared with the controlled smooth surface.

H-aggregate analysis of P3HT thin films-Capability and limitation of photoluminescence and UV/Vis spectroscopy.

PubMed

Ehrenreich, Philipp; Birkhold, Susanne T; Zimmermann, Eugen; Hu, Hao; Kim, Kwang-Dae; Weickert, Jonas; Pfadler, Thomas; Schmidt-Mende, Lukas

2016-09-01

Polymer morphology and aggregation play an essential role for efficient charge carrier transport and charge separation in polymer-based electronic devices. It is a common method to apply the H-aggregate model to UV/Vis or photoluminescence spectra in order to analyze polymer aggregation. In this work we present strategies to obtain reliable and conclusive information on polymer aggregation and morphology based on the application of an H-aggregate analysis on UV/Vis and photoluminescence spectra. We demonstrate, with P3HT as model system, that thickness dependent reflection behavior can lead to misinterpretation of UV/Vis spectra within the H-aggregate model. Values for the exciton bandwidth can deviate by a factor of two for polymer thicknesses below 150 nm. In contrast, photoluminescence spectra are found to be a reliable basis for characterization of polymer aggregation due to their weaker dependence on the wavelength dependent refractive index of the polymer. We demonstrate this by studying the influence of surface characteristics on polymer aggregation for spin-coated thin-films that are commonly used in organic and hybrid solar cells.

Molecular simulation of simple fluids and polymers in nanoconfinement

NASA Astrophysics Data System (ADS)

Rasmussen, Christopher John

Prediction of phase behavior and transport properties of simple fluids and polymers confined to nanoscale pores is important to a wide range of chemical and biochemical engineering processes. A practical approach to investigate nanoscale systems is molecular simulation, specifically Monte Carlo (MC) methods. One of the most challenging problems is the need to calculate chemical potentials in simulated phases. Through the seminal work of Widom, practitioners have a powerful method for calculating chemical potentials. Yet, this method fails for dense and inhomogeneous systems, as well as for complex molecules such as polymers. In this dissertation, the gauge cell MC method, which had previously been successfully applied to confined simple fluids, was employed and extended to investigate nanoscale fluids in several key areas. Firstly, the process of cavitation (the formation and growth of bubbles) during desorption of fluids from nanopores was investigated. The dependence of cavitation pressure on pore size was determined with gauge cell MC calculations of the nucleation barriers correlated with experimental data. Additional computational studies elucidated the role of surface defects and pore connectivity in the formation of cavitation bubbles. Secondly, the gauge cell method was extended to polymers. The method was verified against the literature results and found significantly more efficient. It was used to examine adsorption of polymers in nanopores. These results were applied to model the dynamics of translocation, the act of a polymer threading through a small opening, which is implicated in drug packaging and delivery, and DNA sequencing. Translocation dynamics was studied as diffusion along the free energy landscape. Thirdly, we show how computer simulation of polymer adsorption could shed light on the specifics of polymer chromatography, which is a key tool for the analysis and purification of polymers. The quality of separation depends on the physico-chemical mechanisms of polymer/pore interaction. We considered liquid chromatography at critical conditions, and calculated the dependence of the partition coefficient on chain length. Finally, solvent-gradient chromatography was modeled using a statistical model of polymer adsorption. A model for predicting separation of complex polymers (with functional groups or copolymers) was developed for practical use in chromatographic separations.

Comparison of the fouling release properties of hydrophobic fluorinated and hydrophilic PEGylated block copolymer surfaces: attachment strength of the diatom Navicula and the green alga Ulva.

PubMed

Krishnan, Sitaraman; Wang, Nick; Ober, Christopher K; Finlay, John A; Callow, Maureen E; Callow, James A; Hexemer, Alexander; Sohn, Karen E; Kramer, Edward J; Fischer, Daniel A

2006-05-01

To understand the role of surface wettability in adhesion of cells, the attachment of two different marine algae was studied on hydrophobic and hydrophilic polymer surfaces. Adhesion of cells of the diatom Navicula and sporelings (young plants) of the green macroalga Ulva to an underwater surface is mainly by interactions between the surface and the adhesive exopolymers, which the cells secrete upon settlement and during subsequent colonization and growth. Two types of block copolymers, one with poly(ethylene glycol) side-chains and the other with liquid crystalline, fluorinated side-chains, were used to prepare the hydrophilic and hydrophobic surfaces, respectively. The formation of a liquid crystalline smectic phase in the latter inhibited molecular reorganization at the surface, which is generally an issue when a highly hydrophobic surface is in contact with water. The adhesion strength was assessed by the fraction of settled cells (Navicula) or biomass (Ulva) that detached from the surface in a water flow channel with a wall shear stress of 53 Pa. The two species exhibited opposite adhesion behavior on the same sets of surfaces. While Navicula cells released more easily from hydrophilic surfaces, Ulva sporelings showed higher removal from hydrophobic surfaces. This highlights the importance of differences in cell-surface interactions in determining the strength of adhesion of cells to substrates.

Effect of the PTFE content in the gas diffusion layer on water transport in polymer electrolyte fuel cells (PEFCs)

NASA Astrophysics Data System (ADS)

Mortazavi, Mehdi; Tajiri, Kazuya

2014-01-01

The dynamic behavior of a liquid water droplet emerging and detaching from the surface of the gas diffusion layer (GDL) is investigated. The droplet growth and detachment are studied for different polytetrafluoroethylene (PTFE) contents within the GDL and for different superficial gas velocities flowing in the gas channel. To simulate the droplet behavior in the cathode and anode of an operating polymer electrolyte fuel cell, separate experiments are conducted with air and hydrogen being supplied in the gas channel, respectively. Both the superficial gas velocity and the PTFE content within the GDL are found to impact the droplet detachment diameter. Increasing the superficial gas velocity increases the drag force applied on the droplet sitting on the GDL surface. It is observed that the droplet detaches at a smaller diameter for higher superficial gas velocities. The droplets also detach at smaller diameters from GDLs with a higher amount of PTFE. Such observation is justified according to two different points of view: (1) heterogeneous through-plane PTFE distribution through the GDL and (2) reduced GDL surface roughness caused by PTFE loading.

Drug-Free Macromolecular Therapeutics – A New Paradigm in Polymeric Nanomedicines

PubMed Central

Chu, Te-Wei; Kopeček, Jindřich

2015-01-01

This review highlights a unique research area in polymer-based nanomedicine designs. Drug-free macromolecular therapeutics induce apoptosis of malignant cells by the crosslinking of surface non-internalizing receptors. The receptor crosslinking is mediated by the biorecognition of high-fidelity natural binding motifs (such as antiparallel coiled-coil peptides or complementary oligonucleotides) that are grafted to the side chains of polymers or attached to targeting moieties against cell receptors. This approach features the absence of low-molecular-weight cytotoxic compounds. Here, we summarize the rationales, different designs, and advantages of drug-free macromolecular therapeutics. Recent developments of novel therapeutic systems for B-cell lymphomas are discussed, as well as relevant approaches for other diseases. We conclude by pointing out various potential future directions in this exciting new field. PMID:26191406

Micropattern printing of adhesion, spreading, and migration peptides on poly(tetrafluoroethylene) films to promote endothelialization.

PubMed

Gauvreau, Virginie; Laroche, Gaétan

2005-01-01

We report here the development of an original multistep micropatterning technique for printing peptides on surfaces, based on the ink-jet printer technology. Contrary to most micropatterning methods used nowadays, this technique is advantageous because it allows displaying 2D-arrays of multiple biomolecules. Moreover, this low cost procedure allies the advantages of computer-aided design with high flexibility and reproducibility. A Hewlett-Packard printer was modified to print peptide solutions, and Adobe Illustrator was used as the graphic-editing software to design high-resolution checkerboard-like micropatterns. In a first step, PTFE films were treated with ammonia plasma to introduce amino groups on the surface. These chemical functionalities were reacted with heterobifunctional cross-linker sulfo-succinimidyl 4-(N-maleimidomethyl)cycloexane-1-carboxylate (S-SMCC) to allow the subsequent surface covalent conjugation of various cysteine-modified peptides to the polymer substrate. These peptidic molecules containing RGD and WQPPRARI sequences were selected for their adhesive, spreading, and migrational properties toward endothelial cells. On one hand, our data demonstrated that the initial cell adhesion does not depend on the chemical structure and combination of the peptides covalently bonded either through conventional conjugation or micropatterning. On the other hand, spreading and migration of endothelial cells is clearly enhanced while coconjugating the GRGDS peptide in conjunction with WQPPRARI. This behavior is further improved by micropatterning these peptides on specific areas of the polymer surface.

Surface segregation and surface tension of polydisperse polymer melts.

PubMed

Minnikanti, Venkatachala S; Qian, Zhenyu; Archer, Lynden A

2007-04-14

The effect of polydispersity on surface segregation of a lower molecular weight polymer component in a higher molecular weight linear polymer melt host is investigated theoretically. We show that the integrated surface excess zM of a polymer component of molecular weight M satisfies a simple relation zM=2Ue(M/Mw-1)phiM, where Mw is the weight averaged molecular weight, phiM is the polymer volume fraction, and Ue is the attraction of polymer chain ends to the surface. Ue is principally of entropic origin, but also reflects any energetic preference of chain ends to the surface. We further show that the surface tension gammaM of a polydisperse melt of high molar mass components depends on the number average degree of polymerization Mn as, gammaM=gammainfinity+2UerhobRT/Mn. The parameter gammainfinity is the asymptotic surface tension of an infinitely long polymer of the same chemistry, rhob is the bulk density of the polymer, R is the universal gas constant, and T is the temperature. The predicted gammaM compare favorably with surface tension values obtained from self-consistent field theory simulations that include equation of state effects, which account for changes in polymer density with molecular weight. We also compare the predicted surface tension with available experimental data.

Adhesion properties in systems of laminated pigmented polymers, carbon-graphite fiber composite framework and titanium surfaces in implant suprastructures.

PubMed

Segerström, Susanna; Ruyter, I Eystein

2009-09-01

For long-term stability the adhering interfaces of an implant-retained supraconstruction of titanium/carbon-graphite fiber-reinforced (CGFR) polymer/opaquer layer/denture base polymer/denture teeth must function as a unity. The aim was to evaluate adhesion of CGFR polymer to a titanium surface or CGFR polymer to two different opaquer layers/with two denture base polymers. Titanium plates were surface-treated and silanized and combined with a bolt of CGFR polymer or denture base polymer (Probase Hot). Heat-polymerized plates of CGFR polymer (47 wt% fiber) based on poly(methyl methacrylate) and a copolymer matrix were treated with an opaquer (Sinfony or Ropak) before a denture base polymer bolt was attached (Probase Hot or Lucitone 199). All specimens were heat-polymerized, water saturated (200 days) and thermally cycled (5000 cycles, 5/55 degrees C) before shear bond testing. Silicatized titanium surfaces gave higher bond strength to CGFR polymer (16.2+/-2.34 and 18.6+/-1.32) MPa and cohesive fracture than a sandblasted surface (5.9+/-2.11) MPa where the fracture was adhesive. The opaquer Sinfony gave higher adhesion values and mainly cohesive fractures than the opaquer Ropak. Different surface treatments (roughened or polished) of the CGFR polymer had no effect on bond strength. The fracture surfaces of silicatized titanium/CGFR polymer/opaquer layer (Sinfony)/denture base polymers were mainly cohesive. A combination of these materials in an implant-retained supraconstruction is promising for in vivo evaluation.

Electrolytic etch for preventing electrical shorts in solar cells on polymer surfaces

DOEpatents

Weber, Michael F.

1991-10-08

A method for preventing shorts and shunts in solar cells having in order, an insulating substrate, a conductive metal layer on the substrate, an amorphous silicon layer and a transparent conductive layer. The method includes anodic etching of exposed portions of the metal layer after deposition of the amorphous silicon and prior to depositing the transparent conductive layer.

Decoupling Polymer Properties to Elucidate Mechanisms Governing Cell Behavior

PubMed Central

Wang, Xintong; Boire, Timothy C.; Bronikowski, Christine; Zachman, Angela L.; Crowder, Spencer W.

2012-01-01

Determining how a biomaterial interacts with cells (“structure-function relationship”) reflects its eventual clinical applicability. Therefore, a fundamental understanding of how individual material properties modulate cell-biomaterial interactions is pivotal to improving the efficacy and safety of clinically translatable biomaterial systems. However, due to the coupled nature of material properties, their individual effects on cellular responses are difficult to understand. Structure-function relationships can be more clearly understood by the effective decoupling of each individual parameter. In this article, we discuss three basic decoupling strategies: (1) surface modification, (2) cross-linking, and (3) combinatorial approaches (i.e., copolymerization and polymer blending). Relevant examples of coupled material properties are briefly reviewed in each section to highlight the need for improved decoupling methods. This follows with examples of more effective decoupling techniques, mainly from the perspective of three primary classes of synthetic materials: polyesters, polyethylene glycol, and polyacrylamide. Recent strides in decoupling methodologies, especially surface-patterning and combinatorial techniques, offer much promise in further understanding the structure-function relationships that largely govern the success of future advancements in biomaterials, tissue engineering, and drug delivery. PMID:22536977

The use of three-dimensional nanostructures to instruct cells to produce extracellular matrix for regenerative medicine strategies

PubMed Central

Schenke-Layland, Katja; Rofail, Fady; Heydarkhan, Sanaz; Gluck, Jessica M.; Ingle, Nilesh P.; Angelis, Ekaterini; Choi, Chang-Hwan; MacLellan, W Robb; Beygui, Ramin E; Shemin, Richard J; Heydarkhan-Hagvall, Sepideh

2009-01-01

Synthetic polymers or naturally-derived extracellular matrix (ECM) proteins have been used to create tissue engineering scaffolds; however, the need for surface modification in order to achieve polymer biocompatibility and the lack of biomechanical strength of constructs built using proteins alone remain major limitations. To overcome these obstacles, we developed novel hybrid constructs composed of both strong biosynthetic materials and natural human ECM proteins. Taking advantage of the ability of cells to produce their own ECM, human foreskin fibroblasts were grown on silicon-based nanostructures exhibiting various surface topographies that significantly enhanced ECM protein production. After 4 weeks, cell-derived sheets were harvested and histology, immunochemistry, biochemistry and multiphoton imaging revealed the presence of collagens, tropoelastin, fibronectin and glycosaminoglycans. Following decellularization, purified sheet-derived ECM proteins were mixed with poly(ε-caprolactone) to create fibrous scaffolds using electrospinning. These hybrid scaffolds exhibited excellent biomechanical properties with fiber and pore sizes that allowed attachment and migration of adipose tissue-derived stem cells. Our study represents an innovative approach to generate strong, non-cytotoxic scaffolds that could have broad applications in tissue regeneration strategies. PMID:19524289

Polymer Electrolyte Membranes for Water Photo-Electrolysis

PubMed Central

Aricò, Antonino S.; Girolamo, Mariarita; Siracusano, Stefania; Sebastian, David; Baglio, Vincenzo; Schuster, Michael

2017-01-01

Water-fed photo-electrolysis cells equipped with perfluorosulfonic acid (Nafion® 115) and quaternary ammonium-based (Fumatech® FAA3) ion exchange membranes as separator for hydrogen and oxygen evolution reactions were investigated. Protonic or anionic ionomer dispersions were deposited on the electrodes to extend the interface with the electrolyte. The photo-anode consisted of a large band-gap Ti-oxide semiconductor. The effect of membrane characteristics on the photo-electrochemical conversion of solar energy was investigated for photo-voltage-driven electrolysis cells. Photo-electrolysis cells were also studied for operation under electrical bias-assisted mode. The pH of the membrane/ionomer had a paramount effect on the photo-electrolytic conversion. The anionic membrane showed enhanced performance compared to the Nafion®-based cell when just TiO2 anatase was used as photo-anode. This was associated with better oxygen evolution kinetics in alkaline conditions compared to acidic environment. However, oxygen evolution kinetics in acidic conditions were significantly enhanced by using a Ti sub-oxide as surface promoter in order to facilitate the adsorption of OH species as precursors of oxygen evolution. However, the same surface promoter appeared to inhibit oxygen evolution in an alkaline environment probably as a consequence of the strong adsorption of OH species on the surface under such conditions. These results show that a proper combination of photo-anode and polymer electrolyte membrane is essential to maximize photo-electrolytic conversion. PMID:28468242

Polymer Electrolyte Membranes for Water Photo-Electrolysis.

PubMed

Aricò, Antonino S; Girolamo, Mariarita; Siracusano, Stefania; Sebastian, David; Baglio, Vincenzo; Schuster, Michael

2017-04-29

Water-fed photo-electrolysis cells equipped with perfluorosulfonic acid (Nafion ® 115) and quaternary ammonium-based (Fumatech ® FAA3) ion exchange membranes as separator for hydrogen and oxygen evolution reactions were investigated. Protonic or anionic ionomer dispersions were deposited on the electrodes to extend the interface with the electrolyte. The photo-anode consisted of a large band-gap Ti-oxide semiconductor. The effect of membrane characteristics on the photo-electrochemical conversion of solar energy was investigated for photo-voltage-driven electrolysis cells. Photo-electrolysis cells were also studied for operation under electrical bias-assisted mode. The pH of the membrane/ionomer had a paramount effect on the photo-electrolytic conversion. The anionic membrane showed enhanced performance compared to the Nafion ® -based cell when just TiO₂ anatase was used as photo-anode. This was associated with better oxygen evolution kinetics in alkaline conditions compared to acidic environment. However, oxygen evolution kinetics in acidic conditions were significantly enhanced by using a Ti sub-oxide as surface promoter in order to facilitate the adsorption of OH species as precursors of oxygen evolution. However, the same surface promoter appeared to inhibit oxygen evolution in an alkaline environment probably as a consequence of the strong adsorption of OH species on the surface under such conditions. These results show that a proper combination of photo-anode and polymer electrolyte membrane is essential to maximize photo-electrolytic conversion.

Adhesion, Growth, and Maturation of Vascular Smooth Muscle Cells on Low-Density Polyethylene Grafted with Bioactive Substances

PubMed Central

Parizek, Martin; Slepickova Kasalkova, Nikola; Bacakova, Lucie; Bacakova, Marketa; Lisa, Vera; Svorcik, Vaclav

2013-01-01

The attractiveness of synthetic polymers for cell colonization can be affected by physical, chemical, and biological modification of the polymer surface. In this study, low-density polyethylene (LDPE) was treated by an Ar+ plasma discharge and then grafted with biologically active substances, namely, glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C), or BSA+C. All modifications increased the oxygen content, the wettability, and the surface free energy of the materials compared to the pristine LDPE, but these changes were most pronounced in LDPE with Gly or PEG, where all the three values were higher than in the only plasma-treated samples. When seeded with vascular smooth muscle cells (VSMCs), the Gly- or PEG-grafted samples increased mainly the spreading and concentration of focal adhesion proteins talin and vinculin in these cells. LDPE grafted with BSA or BSA+C showed a similar oxygen content and similar wettability, as the samples only treated with plasma, but the nano- and submicron-scale irregularities on their surface were more pronounced and of a different shape. These samples promoted predominantly the growth, the formation of a confluent layer, and phenotypic maturation of VSMC, demonstrated by higher concentrations of contractile proteins alpha-actin and SM1 and SM2 myosins. Thus, the behavior of VSMC on LDPE can be regulated by the type of bioactive substances that are grafted. PMID:23586032

Adhesion, growth, and maturation of vascular smooth muscle cells on low-density polyethylene grafted with bioactive substances.

PubMed

Parizek, Martin; Slepickova Kasalkova, Nikola; Bacakova, Lucie; Svindrych, Zdenek; Slepicka, Petr; Bacakova, Marketa; Lisa, Vera; Svorcik, Vaclav

2013-01-01

The attractiveness of synthetic polymers for cell colonization can be affected by physical, chemical, and biological modification of the polymer surface. In this study, low-density polyethylene (LDPE) was treated by an Ar(+) plasma discharge and then grafted with biologically active substances, namely, glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C), or BSA+C. All modifications increased the oxygen content, the wettability, and the surface free energy of the materials compared to the pristine LDPE, but these changes were most pronounced in LDPE with Gly or PEG, where all the three values were higher than in the only plasma-treated samples. When seeded with vascular smooth muscle cells (VSMCs), the Gly- or PEG-grafted samples increased mainly the spreading and concentration of focal adhesion proteins talin and vinculin in these cells. LDPE grafted with BSA or BSA+C showed a similar oxygen content and similar wettability, as the samples only treated with plasma, but the nano- and submicron-scale irregularities on their surface were more pronounced and of a different shape. These samples promoted predominantly the growth, the formation of a confluent layer, and phenotypic maturation of VSMC, demonstrated by higher concentrations of contractile proteins alpha-actin and SM1 and SM2 myosins. Thus, the behavior of VSMC on LDPE can be regulated by the type of bioactive substances that are grafted.

Hydrophilization and hydrophobic recovery in polymers obtained by casting of polymer solutions on water surface.

PubMed

Bormashenko, Edward; Chaniel, Gilad; Gendelman, Oleg

2014-12-01

We demonstrate the possibility of hydrophilization of polymer films in situ under the process of their preparation. The polymer surface is hydrophilized when the polymer solution is spread on the water surface and the solvent is evaporated. Essential hydrophilization of the polymer surface is achieved under this process. We relate the observed hydrophilization of polymer films to the dipole-dipole interaction of the polar moieties of polymer chains with highly polar water molecules. The dipole-dipole interaction between water molecules and polar groups of polymer chains, orienting the polar groups of a polymer, may prevail over the London dispersion forces. The process, reported in the paper, allows to manufacture the films in which the hydrophilic moieties of the polymer molecule are oriented toward the polymer/air interface. It is demonstrated that even such traditionally extremely hydrophobic polymers as polydimethylsiloxane can be markedly hydrophilized. This hydrophilization, however, does not persist forever. After removal from the water surface, hydrophobic recovery was observed, i.e. polymer films restored their hydrophobicity with time. The characteristic time of the hydrophobic recovery is on the order of magnitude of hours. Copyright © 2014 Elsevier Inc. All rights reserved.

Polymer Nanocomposites: Insights from Theory and Molecular Simulations

NASA Astrophysics Data System (ADS)

Pani, Rakhee

Advantages of polymer nanocomposites have attracted great industrial attention due to their multifunctionality and innovative technological properties. Addition of small amount of nanoparticle (nanospheres, nanotubes, nanorods, nanoplatelets, or sheets) to polymer matrix cause dramatic improvement in structural and functional properties, which is difficult to attain from those of individual components. The interaction between polymer and nanoparticle create bulk materials dominated by solid state physics at the nanoscale. Furthermore, morphology of nanocomposites depends on structural arrangements of nanoparticles. Thus, for achievement of optimized functionality like electrical, optical, mechanical and thermal properties control over the dispersion of the nanoparticle is essential. However, properties of polymer nanocomposites depend on morphology control and nature of interfacial interactions. In order to control the morphology it is necessary to understand how the processing conditions, shape and size of nanoparticle influence the structure of composite. Molecular simulations can help us to predict the parameters that control the structural changes and we could design polymer nanocomposite entailing their end-use. In this work, we addressed the following research questions: (1) the dependence of nanoparticle ligand corona structure on solvent quality and (2) the role of interfacial energy and interactions on the dispersion of molecules and nanoparticles. Specifically, this research assessed the effect of solvent interactions on the structure of nanoparticles on the example of redox core encapsulating dendrimer and ligand functionalized gold nanoparticles, role of chemical interaction on solubility of glucose in ionic liquids, diffusion of fullerene nanoparticles in polymer matrix and influence of solubility parameters on the compatibility of gold nanoparticles with diblock copolymers. Computational methods allow quantifying the structure and flexibility of the polymer chains, how energetics and surface tension change with chemical composition of the polymer/dendrimer blocks, influence of nanoparticle on structural properties of polymer and factors which may contribute to the phase separation of the polymer from nanoparticle. Interfacial characteristics are not only determined by the size-induced properties, but also the surface chemistry of the particles. Presence of solvent and the resultant interactions with the solvent are known to influence the morphology and prevent or induce aggregation of nanoparticles in polymers. We found that surface chemistry can induce change in the structure of dendrimers encapsulating a redox active core and change the solubility of the nanoparticles. The interactions between nanoparticles and polymers can also influence the morphology. We performed investigation on the role of orientation of fullerene derivatives and surface energy of polymer surface which may induce the aggregation of the fullerene nanoparticles. Furthermore, we used quantitative measurements like cluster analysis to understand the most probable orientation of the fullerene derivative with respect to the polymer chains and the diffusion of the fullerene nanoparticle, which is related to the efficiency of solar cells, can change on presence of regiorandom and regioregular polymer chains. Furthermore, we have also used different solvents based on their Hildebrand solubility parameters to investigate factors governing the morphology of polymer nanocomposite via solvent interactions. We showed that change in solvent interactions affect the compatibility, aggregation/dispersion of the gold nanoparticles, which will directly affect the morphology of polymer matrix and structural aspects which can impact their functionality. Overall, our research indicated that solvent interaction play a role in controlling the morphology of polymer nanocomposite and solubility parameter can help us to predict the resulting morphology.

Cytocompatibility and response of osteoblastic-like cells to starch-based polymers: effect of several additives and processing conditions.

PubMed

Gomes, M E; Reis, R L; Cunha, A M; Blitterswijk, C A; de Bruijn, J D

2001-07-01

This work reports on the biocompatibility evaluation of new biodegradable starch-based polymers that are under consideration for use in orthopaedic temporary applications and as tissue engineering scaffolds. It has been shown in previous works that by using these polymers it is both possible to produce polymer/hydroxyapatite (HA) composites (with or without the use of coupling agents) with mechanical properties matching those of the human bone, and to obtain 3D structures generated by solid blowing agents, that are suitable for tissue engineering applications. This study was focused on establishing the influence of several additives (ceramic fillers, blowing agents and coupling agents) and processing methods/conditions on the biocompatibility of the materials described above. The cytotoxicity of the materials was evaluated using cell culture methods, according to ISO/EN 109935 guidelines. A cell suspension of human osteosarcoma cells (HOS) was also seeded on a blend of corn starch with ethylene vinyl alcohol (SEVA-C) and on SEVA-C/HA composites, in order to have a preliminary indication on cell adhesion and proliferation on the materials surface. In general, the obtained results show that all the different materials based on SEVA-C, (which are being investigated for use in several biomedical applications), as well as all the additives (including the novel coupling agents) and different processing methods required to obtain the different properties/products, can be used without inducing a cytotoxic behaviour to the developed biomaterials.

Accelerated cell-surface interlocking on plasma polymer-modified porous ceramics.

PubMed

Rebl, Henrike; Finke, Birgit; Schmidt, Jürgen; Mohamad, Heba S; Ihrke, Roland; Helm, Christiane A; Nebe, J Barbara

2016-12-01

Excellent osseointegration of permanent implants is crucial for the long lasting success of the implantation. To improve the osseointegrative potential, bio-inert titanium alloy surfaces (Ti6Al4V) are modified by plasma chemical oxidation (PCO®) of the titanium-oxide layer to a non-stoichiometric, amorphous calcium phosphate layer. The native titanium-oxide film measuring only a few nanometers is converted by PCO® to a thick porous calcium phosphate layer of about 10μm. In a second step the PCO surface is combined with a cell adhesive plasma-polymerized allylamine (PPAAm) nano film (5 and 50nm). Independent of the PPAAm coating homogeneity, the human osteoblast-like MG-63 cells show a remarkable increase in cell size and well-developed filopodia. Analyses of the actin cytoskeleton reveal that the cells mold to the pore shape of the PPAAm-covered PCO, thereby establishing a strong attachment to the surface. Interestingly, we could demonstrate that even though our untreated PCO shows excellent hydrophilicity, this alone is not sufficient to facilitate fast cell spreading, but the positive surface charges mediated by PPAAm. This multilayer composite material guarantees enhanced interlocking of the cells with the porous surface. Copyright © 2016 Elsevier B.V. All rights reserved.

Interactions between antimicrobial polynorbornenes and phospholipid vesicles monitored by light scattering and microcalorimetry.

PubMed

Gabriel, Gregory J; Pool, Joanna G; Som, Abhigyan; Dabkowski, Jeffrey M; Coughlin, E Bryan; Muthukumar, M; Tew, Gregory N

2008-11-04

Antimicrobial polynorbornenes composed of facially amphiphilic monomers have been previously reported to accurately emulate the antimicrobial activity of natural host-defense peptides (HDPs). The lethal mechanism of most HDPs involves binding to the membrane surface of bacteria leading to compromised phospholipid bilayers. In this paper, the interactions between biomimetic vesicle membranes and these cationic antimicrobial polynorbornenes are reported. Vesicle dye-leakage experiments were consistent with previous biological assays and corroborated a mode of action involving membrane disruption. Dynamic light scattering (DLS) showed that these antimicrobial polymers cause extensive aggregation of vesicles without complete bilayer disintegration as observed with surfactants that efficiently solubilize the membrane. Fluorescence microscopy on vesicles and bacterial cells also showed polymer-induced aggregation of both synthetic vesicles and bacterial cells. Isothermal titration calorimetry (ITC) afforded free energy of binding values (Delta G) and polymer to lipid binding ratios, plus revealed that the interaction is entropically favorable (Delta S>0, Delta H>0). It was observed that the strength of vesicle binding was similar between the active polymers while the binding stoichiometries were dramatically different.

Enhanced electrochemical sensing of leukemia cells using drug/lipid co-immobilized on the conducting polymer layer.

PubMed

Gurudatt, N G; Naveen, M Halappa; Ban, Changill; Shim, Yoon-Bo

2016-12-15

Electrochemical biosensors using five anticancer drug and lipid molecules attached on the conducting polymer layer to obtain the orientation of drug molecules toward cancer cells, were evaluated as sensing materials and their performances were compared. Conjugation of the drug molecules with a lipid, phosphatidylcholine (PC) has enhanced the sensitivity towards leukemia cells and differentiates cancer cells from normal cells. The composition of each layer of sensor probe was confirmed by electrochemical and surface characterization experiments. Both impedance spectroscopy and voltammetry show the enhanced interaction of leukemia cells using the drug/lipid modified sensor probe. As the number of leukemia cells increased, the charge transfer resistance (Rct) in impedance spectra increased and the amine oxidation peak current of drug molecules in voltammograms decreased at around 0.7-1.0V. Of test drug molecules, raltitrexed (Rtx) showed the best performance for the cancer cells detection. Cancer and normal cell lines from different origins were examined to evaluate the degree of expression of folate receptors (FR) on cells surface, where cervical HeLa cell line was found to be shown the highest expression of the receptor. Impedance and chronoamperometric experiments for leukemia cell line (Jurkat E6-1) showed linear dynamic ranges of 1.0×10(3)-2.5×10(5) cells/mL and 1.0×10(3)-8.0×10(3) cells/mL with detection limits of 68±5 cells/mL and 21±3 cells/mL, respectively. Copyright © 2016 Elsevier B.V. All rights reserved.

Poly(Dopamine)-Assisted Immobilization of Xu Duan on 3D Printed Poly(Lactic Acid) Scaffolds to Up-Regulate Osteogenic and Angiogenic Markers of Bone Marrow Stem Cells.

PubMed

Yeh, Chia-Hung; Chen, Yi-Wen; Shie, Ming-You; Fang, Hsin-Yuan

2015-07-14

Three-dimensional printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating and Xu Duan (XD) immobilization to regulate cell adhesion, proliferation and differentiation of human bone-marrow mesenchymal stem cells (hBMSCs). We prepared PLA scaffolds and coated with polydopamine (PDA). The chemical composition and surface properties of PLA/PDA/XD were characterized by XPS. PLA/PDA/XD controlled hBMSCs' responses in several ways. Firstly, adhesion and proliferation of hBMSCs cultured on PLA/PDA/XD were significantly enhanced relative to those on PLA. In addition, the focal adhesion kinase (FAK) expression of cells was increased and promoted cell attachment depended on the XD content. In osteogenesis assay, the osteogenesis markers of hBMSCs cultured on PLA/PDA/XD were significantly higher than seen in those cultured on a pure PLA/PDA scaffolds. Moreover, hBMSCs cultured on PLA/PDA/XD showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hBMSCs.

Poly(Dopamine)-Assisted Immobilization of Xu Duan on 3D Printed Poly(Lactic Acid) Scaffolds to Up-Regulate Osteogenic and Angiogenic Markers of Bone Marrow Stem Cells

PubMed Central

Yeh, Chia-Hung; Chen, Yi-Wen; Shie, Ming-You; Fang, Hsin-Yuan

2015-01-01

Three-dimensional printing is a versatile technique to generate large quantities of a wide variety of shapes and sizes of polymer. The aim of this study is to develop functionalized 3D printed poly(lactic acid) (PLA) scaffolds and use a mussel-inspired surface coating and Xu Duan (XD) immobilization to regulate cell adhesion, proliferation and differentiation of human bone-marrow mesenchymal stem cells (hBMSCs). We prepared PLA scaffolds and coated with polydopamine (PDA). The chemical composition and surface properties of PLA/PDA/XD were characterized by XPS. PLA/PDA/XD controlled hBMSCs’ responses in several ways. Firstly, adhesion and proliferation of hBMSCs cultured on PLA/PDA/XD were significantly enhanced relative to those on PLA. In addition, the focal adhesion kinase (FAK) expression of cells was increased and promoted cell attachment depended on the XD content. In osteogenesis assay, the osteogenesis markers of hBMSCs cultured on PLA/PDA/XD were significantly higher than seen in those cultured on a pure PLA/PDA scaffolds. Moreover, hBMSCs cultured on PLA/PDA/XD showed up-regulation of the ang-1 and vWF proteins associated with angiogenic differentiation. Our results demonstrate that the bio-inspired coating synthetic PLA polymer can be used as a simple technique to render the surfaces of synthetic scaffolds active, thus enabling them to direct the specific responses of hBMSCs. PMID:28793441

Hydrocarbon-Based Polymer Electrolyte Membranes: Importance of Morphology on Ion Transport and Membrane Stability.

PubMed

Shin, Dong Won; Guiver, Michael D; Lee, Young Moo

2017-03-22

A fundamental understanding of polymer microstructure is important in order to design novel polymer electrolyte membranes (PEMs) with excellent electrochemical performance and stabilities. Hydrocarbon-based polymers have distinct microstructure according to their chemical structure. The ionic clusters and/or channels play a critical role in PEMs, affecting ion conductivity and water transport, especially at medium temperature and low relative humidity (RH). In addition, physical properties such as water uptake and dimensional swelling behavior depend strongly on polymer morphology. Over the past few decades, much research has focused on the synthetic development and microstructural characterization of hydrocarbon-based PEM materials. Furthermore, blends, composites, pressing, shear field, electrical field, surface modification, and cross-linking have also been shown to be effective approaches to obtain/maintain well-defined PEM microstructure. This review summarizes recent work on developments in advanced PEMs with various chemical structures and architecture and the resulting polymer microstructures and morphologies that arise for potential application in fuel cell, lithium ion battery, redox flow battery, actuators, and electrodialysis.

Structure and Dynamics of Solvated Polymers near a Silica Surface: On the Different Roles Played by Solvent.

PubMed

Perrin, Elsa; Schoen, Martin; Coudert, François-Xavier; Boutin, Anne

2018-04-26

Whereas it is experimentally known that the inclusion of nanoparticles in hydrogels can lead to a mechanical reinforcement, a detailed molecular understanding of the adhesion mechanism is still lacking. Here we use coarse-grained molecular dynamics simulations to investigate the nature of the interface between silica surfaces and solvated polymers. We show how differences in the nature of the polymer and the polymer-solvent interactions can lead to drastically different behavior of the polymer-surface adhesion. Comparing explicit and implicit solvent models, we conclude that this effect cannot be fully described in an implicit solvent. We highlight the crucial role of polymer solvation for the adsorption of the polymer chain on the silica surface, the significant dynamics of polymer chains on the surface, and details of the modifications in the structure solvated polymer close to the interface.

Microfluidic Fabrication of Cell Adhesive Chitosan Microtubes

PubMed Central

Oh, Jonghyun; Kim, Keekyoung; Won, Sung Wook; Cha, Chaenyung; Gaharwar, Akhilesh; Selimović, Šeila; Bae, Hojae; Lee, Kwang Ho; Lee, Dong Hwan; Lee, Sang-Hoon; Khademhosseini, Ali

2013-01-01

Chitosan has been used as a scaffolding material in tissue engineering due to its mechanical properties and biocompatibility. With increased appreciation of the effect of micro- and nanoscale environments on cellular behavior, there is increased emphasis on generating microfabricated chitosan structures. Here we employed a microfluidic coaxial flow-focusing system to generate cell adhesive chitosan microtubes of controlled sizes by modifying the flow rates of a chitosan pre-polymer solution and phosphate buffered saline (PBS). The microtubes were extruded from a glass capillary with a 300 μm inner diameter. After ionic crosslinking with sodium tripolyphosphate (TPP), fabricated microtubes had inner and outer diameter ranges of 70-150 μm and 120-185 μm. Computational simulation validated the controlled size of microtubes and cell attachment. To enhance cell adhesiveness on the microtubes, we mixed gelatin with the chitosan pre-polymer solution and adjusted the pH values of the chitosan pre-polymer solution with gelatin and TPP. During the fabrication of microtubes, fibroblasts suspended in core PBS flow adhered to the inner surface of chitosan-gelatin microtubes. To achieve physiological pH values, we adjusted pH values of chiotsan pre-polymer solution and TPP. In particular, we were able to improve cell viability to 92% with pH values of 5.8 and 7.4 for chitosan and TPP solution respectively. Cell culturing for three days showed that the addition of the gelatin enhanced cell spreading and proliferation inside the chitosan-gelatin microtubes. The microfluidic fabrication method for ionically crosslinked chitosan microtubes at physiological pH can be compatible with a variety of cells and used as a versatile platform for microengineered tissue engineering. PMID:23355068

The Design of Simple Bacterial Microarrays: Development towards Immobilizing Single Living Bacteria on Predefined Micro-Sized Spots on Patterned Surfaces.

PubMed

Arnfinnsdottir, Nina Bjørk; Ottesen, Vegar; Lale, Rahmi; Sletmoen, Marit

2015-01-01

In this paper we demonstrate a procedure for preparing bacterial arrays that is fast, easy, and applicable in a standard molecular biology laboratory. Microcontact printing is used to deposit chemicals promoting bacterial adherence in predefined positions on glass surfaces coated with polymers known for their resistance to bacterial adhesion. Highly ordered arrays of immobilized bacteria were obtained using microcontact printed islands of polydopamine (PD) on glass surfaces coated with the antiadhesive polymer polyethylene glycol (PEG). On such PEG-coated glass surfaces, bacteria were attached to 97 to 100% of the PD islands, 21 to 62% of which were occupied by a single bacterium. A viability test revealed that 99% of the bacteria were alive following immobilization onto patterned surfaces. Time series imaging of bacteria on such arrays revealed that the attached bacteria both divided and expressed green fluorescent protein, both of which indicates that this method of patterning of bacteria is a suitable method for single-cell analysis.

Polymer electrolyte fuel cell mini power unit for portable application

NASA Astrophysics Data System (ADS)

Urbani, F.; Squadrito, G.; Barbera, O.; Giacoppo, G.; Passalacqua, E.; Zerbinati, O.

This paper describes the design, realisation and test of a power unit based on a polymer electrolyte fuel cell, operating at room temperature, for portable application. The device is composed of an home made air breathing fuel cell stack, a metal hydride tank for H 2 supply, a dc-dc converter for power output control and a fan for stack cooling. The stack is composed by 10 cells with an active surface of 25 cm 2 and produces a rated power of 15 W at 6 V and 2 A. The stack successfully runs with end-off fed hydrogen without appreciable performance degradation during the time. The final assembled system is able to generate 12 W at 9.5 V, and power a portable DVD player for 3 h in continuous. The power unit has collected about 100 h of operation without maintenance.

Well-defined block copolymers for gene delivery to dendritic cells: probing the effect of polycation chain-length.

PubMed

Tang, Rupei; Palumbo, R Noelle; Nagarajan, Lakshmi; Krogstad, Emily; Wang, Chun

2010-03-03

The development of safe and efficient polymer carriers for DNA vaccine delivery requires mechanistic understanding of structure-function relationship of the polymer carriers and their interaction with antigen-presenting cells. Here we have synthesized a series of diblock copolymers with well-defined chain-length using atom transfer radical polymerization and characterized the influence of polycation chain-length on the physico-chemical properties of the polymer/DNA complexes as well as the interaction with dendritic cells. The copolymers consist of a hydrophilic poly(ethylene glycol) block and a cationic poly(aminoethyl methacrylate) (PAEM) block. The average degree of polymerization (DP) of the PAEM block was varied among 19, 39, and 75, with nearly uniform distribution. With increasing PAEM chain-length, polyplexes formed by the diblock copolymers and plasmid DNA had smaller average particle size and showed higher stability against electrostatic destabilization by salt and heparin. The polymers were not toxic to mouse dendritic cells (DCs) and only displayed chain-length-dependent toxicity at a high concentration (1mg/mL). In vitro gene transfection efficiency and polyplex uptake in DCs were also found to correlate with chain-length of the PAEM block with the longer polymer chain favoring transfection and cellular uptake. The polyplexes induced a modest up-regulation of surface markers for DC maturation that was not significantly dependent on PAEM chain-length. Finally, the polyplex prepared from the longest PAEM block (DP of 75) achieved an average of 20% enhancement over non-condensed anionic dextran in terms of uptake by DCs in the draining lymph nodes 24h after subcutaneous injection into mice. Insights gained from studying such structurally well-defined polymer carriers and their interaction with dendritic cells may contribute to improved design of practically useful DNA vaccine delivery systems. Copyright 2009 Elsevier B.V. All rights reserved.

Influence of surface charge on the potential toxicity of PLGA nanoparticles towards Calu-3 cells

PubMed Central

Mura, Simona; Hillaireau, Herve; Nicolas, Julien; Le Droumaguet, Benjamin; Gueutin, Claire; Zanna, Sandrine; Tsapis, Nicolas; Fattal, Elias

2011-01-01

Background Because of the described hazards related to inhalation of manufactured nanoparticles, we investigated the lung toxicity of biodegradable poly (lactide-co-glycolide) (PLGA) nanoparticles displaying various surface properties on human bronchial Calu-3 cells. Methods Positively and negatively charged as well as neutral nanoparticles were tailored by coating their surface with chitosan, Poloxamer, or poly (vinyl alcohol), respectively. Nanoparticles were characterized in terms of size, zeta potential, and surface chemical composition, confirming modifications provided by hydrophilic polymers. Results Although nanoparticle internalization by lung cells was clearly demonstrated, the cytotoxicity of the nanoparticles was very limited, with an absence of inflammatory response, regardless of the surface properties of the PLGA nanoparticles. Conclusion These in vitro results highlight the safety of biodegradable PLGA nanoparticles in the bronchial epithelium and provide initial data on their potential effects and the risks associated with their use as nanomedicines. PMID:22114491

Dual phase polymer gel electrolyte based on non-woven poly(vinylidenefluoride-co-hexafluoropropylene)–layered clay nanocomposite fibrous membranes for lithium ion batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shubha, Nageswaran; Prasanth, Raghavan; Energy Research Institute - NTU

2013-02-15

Graphical abstract: Display Omitted Highlights: ► P(VdF-co-HFP)–clay nanocomposite based electrospun membranes are prepared. ► The membranes are used as polymer gel electrolyte (PGE) in lithium ion batteries. ► The composite PGE shows ionic conductivity of 5.5 mS cm{sup −1} at room temperature. ► Li/PGE/LiFePO{sub 4} cell delivers initial discharge capacity of 160 mAh g{sup −1}. ► The use of prepared electrolyte significantly improved the cell performance. -- Abstract: A new approach for fabricating polymer gel electrolytes (PGEs) based on electrospun poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) incorporated with layered nanoclay has been employed to enhance the ionic conductivity and electrochemical properties of P(VdF-co-HFP) withoutmore » compromising its mechanical strength. The effect of layered nanoclay on properties of membranes has been evaluated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Surface morphology of the membranes has been studied using field-emission scanning electron microscopy (FE-SEM). Polymer gel electrolytes are prepared by soaking the fibrous membrane into 1 M LiPF{sub 6} in EC/DEC. The electrochemical studies show that incorporation of layered nanoclay into the polymer matrix greatly enhanced the ionic conductivity and compatibility with lithium electrodes. The charge–discharge properties and cycling performance of Li/LiFePO{sub 4} cells comprising nanocomposite polymer gel electrolytes have been evaluated at room temperature.« less

Synergistic effect of polyaniline coverage and surface microstructure on the inhibition of Pseudomonas aeruginosa biofilm formation.

PubMed

Gallarato, L A; Mulko, L E; Dardanelli, M S; Barbero, C A; Acevedo, D F; Yslas, E I

2017-02-01

Biofilm Formation is a survival strategy for microorganisms to adapt to their environment. Microbial cells in biofilm become tolerant and resistant to antibiotics and immune responses, increasing the difficulties for the clinical treatment of microbial infections. The surface chemistry and the micro/nano-topography of solid interfaces play a major role in mediating microorganism activity and adhesion. The effect of the surface chemical composition and topography on the adhesion and viability of Pseudomonas aeruginosa was studied. Polymeric (polyethylene terephthalate) surfaces were covered with a conducting polymer (polyaniline, PANI) film by in-situ polymerization and microstructured by Direct Laser Interference Patterning (DLIP). The viability of Pseudomonas aeruginosa on the different surfaces was investigated. The physicochemical properties of the surfaces were characterized by water contact angle measurements, scanning electron microscopy and atomic force microscopy. Bacterial biofilms were imaged by atomic force and scanning electron microscopies. The bacterial viability decreased on PANI compared with the substrate (polyethylene terephthalate) and it decreased even more upon micro-structuring the PANI films. In addition, the biofilm reduction could be improved using polymers with different chemical composition and/or the same polymer with different topographies. Both methods presented diminish the bacterial attachment and biofilm formation. These findings present a high impact related to materials for biomedical engineer applications regarding medical devices, as prostheses or catheters. Copyright © 2016 Elsevier B.V. All rights reserved.

Impact of micro-porous layer on liquid water distribution at the catalyst layer interface and cell performance in a polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Tabe, Yutaka; Aoyama, Yusuke; Kadowaki, Kazumasa; Suzuki, Kengo; Chikahisa, Takemi

2015-08-01

In polymer electrolyte membrane fuel cells, a gas diffusion layer (GDL) with a micro-porous layer (MPL) gives better anti-flooding performance than GDLs without an MPL. To investigate the function and mechanism of the MPL to suppress water flooding, the liquid water distribution at the cathode catalyst layer (CL) surface are observed by a freezing method; in the method liquid water is immobilized in ice form by rapid freezing, followed by disassembling the cell for observations. The ice covered area is quantified by image processing and cells with and without an MPL are compared. The results show that the MPL suppresses water accumulation at the interface due to smaller pore size and finer contact with the CL, and this results in less water flooding. Investigation of ice formed after -10 °C cold start shutdowns and the temporary performance deterioration at ordinary temperatures also indicates a significant influence of the liquid water accumulating at the interface. The importance of the fine contact between CL and MPL, the relative absence of gaps, is demonstrated by a gas diffusion electrode (GDE) which is directly coated with catalyst ink on the surface of the MPL achieving finer contact of the layers.

Anterior cruciate ligament regeneration using braided biodegradable scaffolds: in vitro optimization studies.

PubMed

Lu, Helen H; Cooper, James A; Manuel, Sharron; Freeman, Joseph W; Attawia, Mohammed A; Ko, Frank K; Laurencin, Cato T

2005-08-01

The anterior cruciate ligament (ACL) is the most commonly injured intra-articular ligament of the knee, and limitations in existing reconstruction grafts have prompted an interest in tissue engineered solutions. Previously, we reported on a tissue-engineered ACL scaffold fabricated using a novel, three-dimensional braiding technology. A critical factor in determining cellular response to such a graft is material selection. The objective of this in vitro study was to optimize the braided scaffold, focusing on material composition and the identification of an appropriate polymer. The selection criteria are based on cellular response, construct degradation, and the associated mechanical properties. Three compositions of poly-alpha-hydroxyester fibers, namely polyglycolic acid (PGA), poly-L-lactic acid (PLLA), and polylactic-co-glycolic acid 82:18 (PLAGA) were examined. The effects of polymer composition on scaffold mechanical properties and degradation were evaluated in physiologically relevant solutions. Prior to culturing with primary rabbit ACL cells, scaffolds were pre-coated with fibronectin (Fn, PGA-Fn, PLAGA-Fn, PLLA-Fn), an important protein which is upregulated during ligament healing. Cell attachment and growth were examined as a function of time and polymer composition. While PGA scaffolds measured the highest tensile strength followed by PLLA and PLAGA, its rapid degradation in vitro resulted in matrix disruption and cell death over time. PLLA-based scaffolds maintained their structural integrity and exhibited superior mechanical properties over time. The response of ACL cells was found to be dependent on polymer composition, with the highest cell number measured on PLLA-Fn scaffolds. Surface modification of polymer scaffolds with Fn improved cell attachment efficiency and effected the long-term matrix production by ACL cells on PLLA and PLAGA scaffolds. Therefore based on the overall cellular response and its temporal mechanical and degradation properties in vitro, the PLLA braided scaffold pre-coated with Fn was found to be the most suitable substrate for ACL tissue engineering.

Photoinitiated grafting of porous polymer monoliths and thermoplastic polymers for microfluidic devices

DOEpatents

Frechet, Jean M. J. [Oakland, CA; Svec, Frantisek [Alameda, CA; Rohr, Thomas [Leiden, NL

2008-10-07

A microfluidic device preferably made of a thermoplastic polymer that includes a channel or a multiplicity of channels whose surfaces are modified by photografting. The device further includes a porous polymer monolith prepared via UV initiated polymerization within the channel, and functionalization of the pore surface of the monolith using photografting. Processes for making such surface modifications of thermoplastic polymers and porous polymer monoliths are set forth.

Single Molecule Spectroelectrochemistry of Interfacial Charge Transfer Dynamics In Hybrid Organic Solar Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Shanlin

2014-11-16

Our research under support of this DOE grant is focused on applied and fundamental aspects of model organic solar cell systems. Major accomplishments are: 1) we developed a spectroelectorchemistry technique of single molecule single nanoparticle method to study charge transfer between conjugated polymers and semiconductor at the single molecule level. The fluorescence of individual fluorescent polymers at semiconductor surfaces was shown to exhibit blinking behavior compared to molecules on glass substrates. Single molecule fluorescence excitation anisotropy measurements showed the conformation of the polymer molecules did not differ appreciably between glass and semiconductor substrates. The similarities in molecular conformation suggest thatmore » the observed differences in blinking activity are due to charge transfer between fluorescent polymer and semiconductor, which provides additional pathways between states of high and low fluorescence quantum efficiency. Similar spectroelectrochemistry work has been done for small organic dyes for understand their charge transfer dynamics on various substrates and electrochemical environments; 2) We developed a method of transferring semiconductor nanoparticles (NPs) and graphene oxide (GO) nanosheets into organic solvent for a potential electron acceptor in bulk heterojunction organic solar cells which employed polymer semiconductor as the electron donor. Electron transfer from the polymer semiconductor to semiconductor and GO in solutions and thin films was established through fluorescence spectroscopy and electroluminescence measurements. Solar cells containing these materials were constructed and evaluated using transient absorption spectroscopy and dynamic fluorescence techniques to understand the charge carrier generation and recombination events; 3) We invented a spectroelectorchemistry technique using light scattering and electroluminescence for rapid size determination and studying electrochemistry of single NPs in an electrochemical cell. For example, we are able to use this technique to track electroluminescence of single Au NPs, and the electrodeposition of individual Ag NPs in-situ. These metallic NPs are useful to enhance light harvesting in organic photovoltaic systems. The scattering at the surface of an indium tin oxide (ITO) working electrode was measured during a potential sweep. Utilizing Mie scattering theory and high resolution scanning electron microscopy (SEM), the scattering data were used to calculate current-potential curves depicting the electrodeposition of individual Ag NPs. The oxidation of individual presynthesized and electrodeposited Ag NPs was also investigated using fluorescence and DFS microscopies. Our work has produced 1 US provisional patent, 15 published manuscripts, 1 submitted and two additional in-writing manuscripts. 5 graduate students, 1 postdoctoral student, 1 visiting professor, and two undergraduate students have received research training in the area of electrochemistry and optical spectroscopy under support of this award.« less

Engineering micropatterned surfaces to modulate the function of vascular stem cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jennifer; Wu, Michelle; Chu, Julia

2014-02-21

Highlights: • We examine vascular stem cell function on microgrooved and micropost patterned polymer substrates. • 10 μm microgrooved surfaces significantly lower VSC proliferation but do not modulate calcified matrix deposition. • Micropost surfaces significantly lower VSC proliferation and decrease calcified matrix deposition. - Abstract: Multipotent vascular stem cells have been implicated in vascular disease and in tissue remodeling post therapeutic intervention. Hyper-proliferation and calcified extracellular matrix deposition of VSC cause blood vessel narrowing and plaque hardening thereby increasing the risk of myocardial infarct. In this study, to optimize the surface design of vascular implants, we determined whether micropatterned polymermore » surfaces can modulate VSC differentiation and calcified matrix deposition. Undifferentiated rat VSC were cultured on microgrooved surfaces of varied groove widths, and on micropost surfaces. 10 μm microgrooved surfaces elongated VSC and decreased cell proliferation. However, microgrooved surfaces did not attenuate calcified extracellular matrix deposition by VSC cultured in osteogenic media conditions. In contrast, VSC cultured on micropost surfaces assumed a dendritic morphology, were significantly less proliferative, and deposited minimal calcified extracellular matrix. These results have significant implications for optimizing the design of cardiovascular implant surfaces.« less

Physicochemical properties and cytotoxicity of hydrogels based on Beetosan® containing sage and bee pollen.

PubMed

Tyliszczak, Bożena; Drabczyk, Anna; Kudłacik-Kramarczyk, Sonia; Grabowska, Beata; Kędzierska, Magdalena

2017-01-01

Currently, increasing attention is being paid to issues related to environmental protection, waste management, as well as to the development of polymers with useful properties. The research presented here involved preparation of hydrogels based on Beetosan® - a chitosan derived from the multi-stage processing of dead bees. Moreover, hydrogels were additionally modified with natural substances - i.e. bee pollen and extract of Salvia officinalis (sage) that are well known for the presence of many compounds with beneficial properties from a medical point of view. Materials have been first obtained by photopolymerization. Then, their surface morphology, wettability and cytotoxicity to selected cell lines have been determined. It can be stated that such combination of Beetosan® hydrogel matrix and the mentioned additives resulted in a preparation of polymers characterized by negative impact on cancer cells. Impact of hydrogels with sage is slightly more intense due to the presence of substances such as ursalic or rosmaric acid that are characterized to have anticancer activity. Such negative impact has not been observed in case of studies using fibroblasts. Furthermore, addition of natural substances into hydrogels resulted in a more homogeneous surface and in the decrease of wettability angle of the tested polymers. It can be concluded that the use of natural-derived reagents and synthesis of polymers using these reagents (as a result of environmentally friendly photopolymerization) yields materials with interesting properties for medical purposes, with particular emphasis on antitumor activity, and without significant negative impact on fibroblasts.

Xyloglucan endotransglucosylase/hydrolases (XTHs) are inactivated by binding to glass and cellulosic surfaces, and released in active form by a heat-stable polymer from cauliflower florets.

PubMed

Sharples, Sandra C; Nguyen-Phan, Tu C; Fry, Stephen C

2017-11-01

Xyloglucan endotransglucosylase (XET) activity, which cuts and re-joins hemicellulose chains in the plant cell wall, contributing to wall assembly and growth regulation, is the major activity of XTH proteins. During purification, XTHs often lose XET activity which, however, is restored by treatment with certain cold-water-extractable, heat-stable polymers (CHPs), e.g. from cauliflower florets. It was not known whether the XTH-activating factor (XAF) present in CHPs works by promoting (e.g. allosterically) XET activity or by re-solubilising sequestered XTH proteins. We now show that XTHs in dilute solution bind to diverse surfaces (e.g. glass and cellulose), and that CHPs can re-solubilise the bound enzyme, re-activating it. Cell walls prepared from cauliflower florets, mung bean shoots and Arabidopsis cell-suspension cultures each contained endogenous, tightly bound, inactive XTHs, which were likewise rapidly solubilised (within 0.5h) and thus activated by cauliflower XAF. We present a convenient quantitative assay for XAF acting on the native sequestered XTHs of Arabidopsis cell walls; using this assay, we show that CHPs from all plants tested possess XAF activity. The XAF activity of diverse CHPs does not correlate with their conductivity, showing that this activity is not a simple ionic effect. The XAF action of cauliflower CHPs was augmented by NaCl, although NaCl alone was much less effective than a CHP solution of similar conductivity, confirming that the cauliflower polymers did not simply exert a salt effect. We suggest that XAF is an endogenous regulator of XET action, modulating cell-wall loosening and/or assembly in vivo. Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.

Micro Solar Cells with Concentration and Light Trapping Optics

NASA Astrophysics Data System (ADS)

Li, Lanfang; Breuckner, Eric; Corcoran, Christopher; Yao, Yuan; Xu, Lu; Nuzzo, Ralph

2013-03-01

Compared with conventional bulk plate semiconductor solar cells, micro solar cells provide opportunity for novel design geometry and provide test bed for light trapping at the device level as well as module level. Surface recombination, however, will have to be addressed properly as the much increased surface area due to the reduced dimension is more prominent in these devices than conventional solar cells. In this poster, we present experimental demonstration of silicon micro solar cells with concentration and light trapping optics. Silicon micro solar cell with optimized surface passivation and doping profile that exhibit high efficiency is demonstrated. Effective incorporation of high quantum yield fluorescent centers in the polymer matrix into which micro solar cell was encapsulated was investigated for luminescent solar concentration application. Micro-cell on a semi-transparent, nanopatterned reflector formed by soft-imprint lithography was investigated for near field effect related solar conversion performance enhancement. This work is supported by the DOE `Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under grant DE-SC0001293

Self-supported fibrin-polyvinyl alcohol interpenetrating polymer networks: an easily handled and rehydratable biomaterial.

PubMed

Bidault, Laurent; Deneufchatel, Marie; Vancaeyzeele, Cédric; Fichet, Odile; Larreta-Garde, Véronique

2013-11-11

A fibrin hydrogel at physiological concentration (5 mg/mL) was associated with polyvinyl alcohol (PVA) inside an interpenetrating polymer networks (IPN) architecture. Previously, PVA has been modified with methacrylate functions in order to cross-link it by free-radical polymerization. The fibrin network was synthesized by the enzymatic hydrolysis of fibrinogen by thrombin. The resulting self-supported materials simultaneously exhibit the properties of the fibrin hydrogel and those of the synthetic polymer network. Their storage modulus is 50-fold higher than that of the fibrin hydrogel and they are completely rehydratable. These materials are noncytotoxic toward human fibroblast and the fibrin present on the surface of PVAm-based IPNs favors cell development.

Direct ink writing of silica-bonded calcite scaffolds from preceramic polymers and fillers.

PubMed

Fiocco, L; Elsayed, H; Badocco, D; Pastore, P; Bellucci, D; Cannillo, V; Detsch, R; Boccaccini, A R; Bernardo, E

2017-05-11

Silica-bonded calcite scaffolds have been successfully 3D-printed by direct ink writing, starting from a paste comprising a silicone polymer and calcite powders, calibrated in order to match a SiO 2 /CaCO 3 weight balance of 35/65. The scaffolds, fabricated with two slightly different geometries, were first cross-linked at 350 °C, then fired at 600 °C, in air. The low temperature adopted for the conversion of the polymer into amorphous silica, by thermo-oxidative decomposition, prevented the decomposition of calcite. The obtained silica-bonded calcite scaffolds featured open porosity of about 56%-64% and compressive strength of about 2.9-5.5 MPa, depending on the geometry. Dissolution studies in SBF and preliminary cell culture tests, with bone marrow stromal cells, confirmed the in vitro bioactivity of the scaffolds and their biocompatibility. The seeded cells were found to be alive, well anchored and spread on the samples surface. The new silica-calcite composites are expected to be suitable candidates as tissue-engineering 3D scaffolds for regeneration of cancellous bone defects.

Degradable phosphate glass fiber reinforced polymer matrices: mechanical properties and cell response.

PubMed

Brauer, Delia S; Rüssel, Christian; Vogt, Sebastian; Weisser, Jürgen; Schnabelrauch, Matthias

2008-01-01

The development of biodegradable materials for internal fracture fixation is of great interest, as they would both eliminate the problem of stress shielding and obviate the need for a second operation to remove fixation devices. Preliminary investigations for the production of degradable fiber reinforced polymer composite materials are detailed. Composites were produced of phosphate invert glass fibers of the glass system P(2)O(5)-CaO-MgO-Na(2)O-TiO(2), which showed a low solubility in previous work. The fibers were embedded into a matrix of a degradable organic polymer network based on methacrylate-modified oligolactide. Fracture behavior, bending strength and elastic modulus were evaluated during 3-point bending tests and the fracture surface of the composites was investigated using a scanning electron microscope. Short-term biocompatibility was tested in an FDA/EtBr viability assay using MC3T3-E1 murine pre-osteoblast cells and showed a good cell compatibility of the composite materials. Results suggested that these composite materials are biocompatible and show mechanical properties which are of interest for the production of degradable bone fixation devices.

Flexible, highly efficient all-polymer solar cells

PubMed Central

Kim, Taesu; Kim, Jae-Han; Kang, Tae Eui; Lee, Changyeon; Kang, Hyunbum; Shin, Minkwan; Wang, Cheng; Ma, Biwu; Jeong, Unyong; Kim, Taek-Soo; Kim, Bumjoon J.

2015-01-01

All-polymer solar cells have shown great potential as flexible and portable power generators. These devices should offer good mechanical endurance with high power-conversion efficiency for viability in commercial applications. In this work, we develop highly efficient and mechanically robust all-polymer solar cells that are based on the PBDTTTPD polymer donor and the P(NDI2HD-T) polymer acceptor. These systems exhibit high power-conversion efficiency of 6.64%. Also, the proposed all-polymer solar cells have even better performance than the control polymer-fullerene devices with phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor (6.12%). More importantly, our all-polymer solar cells exhibit dramatically enhanced strength and flexibility compared with polymer/PCBM devices, with 60- and 470-fold improvements in elongation at break and toughness, respectively. The superior mechanical properties of all-polymer solar cells afford greater tolerance to severe deformations than conventional polymer-fullerene solar cells, making them much better candidates for applications in flexible and portable devices. PMID:26449658

Specificity of marine microbial surface interactions.

PubMed Central

Imam, S H; Bard, R F; Tosteson, T R

1984-01-01

The macromolecular surface components involved in intraspecific cell surface interactions of the green microalga Chlorella vulgaris and closely associated bacteria were investigated. The specific surface attachment between this alga and its associated bacteria is mediated by lectin-like macromolecules associated with the surfaces of these cells. The binding activity of these surface polymers was inhibited by specific simple sugars; this suggests the involvement of specific receptor-ligand binding sites on the interactive surfaces. Epifluorescent microscopic evaluation of bacteria-alga interactions in the presence and absence of the macromolecules that mediate these interactions showed that the glycoproteins active in these processes were specific to the microbial sources from which they were obtained. The demonstration and definition of the specificity of these interactions in mixed microbial populations may play an important role in our understanding of the dynamics of marine microbial populations in the sea. PMID:6508293

Microengineering neocartilage scaffolds.

PubMed

Petersen, Erik F; Spencer, Richard G S; McFarland, Eric W

2002-06-30

Advances in micropatterning methodologies have made it possible to create structures with precise architecture on the surface of cell culture substrata. We applied these techniques to fabricate microfeatures (15-65 microm wide; 40 microm deep) on the surface of a flexible, biocompatible polysaccharide gel. The micropatterned polymer gels were subsequently applied as scaffolds for chondrocyte culture and proved effective in maintaining key aspects of the chondrogenic phenotype. These were rounded cell morphology and a positive and statistically significant (p < 0.0001) immunofluorescence assay for the production of type II collagen throughout the maximum culture time of 10 days after cell seeding. Further, cells housed within individual surface features were observed to proliferate, while serial application of chondrocytes resulted in the formation of cellular aggregates. These methods represent a novel approach to the problem of engineering reparative cartilage in vitro. Copyright 2002 Wiley Periodicals, Inc.

Use of Atomic Oxygen for Increased Water Contact Angles of Various Polymers for Biomedical Applications

NASA Technical Reports Server (NTRS)

deGroh, Kim; Berger, Lauren; Roberts, Lily

2009-01-01

The purpose of this study was to determine the effect of atomic oxygen (AO) exposure on the hydrophilicity of nine different polymers for biomedical applications. Atomic oxygen treatment can alter the chemistry and morphology of polymer surfaces, which may increase the adhesion and spreading of cells on Petri dishes and enhance implant growth. Therefore, nine different polymers were exposed to atomic oxygen and water-contact angle, or hydrophilicity, was measured after exposure. To determine whether hydrophilicity remains static after initial atomic oxygen exposure, or changes with higher fluence exposures, the contact angles between the polymer and water droplet placed on the polymer s surface were measured versus AO fluence. The polymers were exposed to atomic oxygen in a 100-W, 13.56-MHz radio frequency (RF) plasma asher, and the treatment was found to significantly alter the hydrophilicity of non-fluorinated polymers. Pristine samples were compared with samples that had been exposed to AO at various fluence levels. Minimum and maximum fluences for the ashing trials were set based on the effective AO erosion of a Kapton witness coupon in the asher. The time intervals for ashing were determined by finding the logarithmic values of the minimum and maximum fluences. The difference of these two values was divided by the desired number of intervals (ideally 10). The initial desired fluence was then multiplied by this result (2.37), as was each subsequent desired fluence. The flux in the asher was determined to be approximately 3.0 x 10(exp 15) atoms/sq cm/sec, and each polymer was exposed to a maximum fluence of 5.16 x 10(exp 20) atoms/sq cm.

Coating carbon nanotubes with a polystyrene-based polymer protects against pulmonary toxicity

PubMed Central

2011-01-01

Background carbon nanotubes (CNT) can have adverse effects on health. Therefore, minimizing the risk associated with CNT exposure is of crucial importance. The aim of this work was to evaluate if coating multi-walled CNT (MWCNT) with polymers could modify their toxicity, thus representing a useful strategy to decrease adverse health effects of CNT. We used industrially-produced MWCNT uncoated (NT1) or coated (50/50 wt%) with acid-based (NT2) or polystyrene-based (NT3) polymer, and exposed murine macrophages (RAW 264.7 cell line) or Balb/c mice by intratracheal administration. Biological experiments were performed both in vitro and in vivo, examining time- and dose-dependent effects of CNT, in terms of cytotoxicity, expression of genes and proteins related to oxidative stress, inflammation and tissue remodeling, cell and lung tissue morphology (optical and transmission electron microscopy), and bronchoalveolar lavage fluid content analysis. Results extensive physico-chemical characterization of MWCNT was performed, and showed, although similar dimensions for the 3 MWCNT, a much smaller specific surface area for NT2 and NT3 as compared to NT1 (54.1, 34 and 227.54 m2/g respectively), along with different surface characteristics. MWCNT-induced cytotoxicity, oxidative stress, and inflammation were increased by acid-based and decreased by polystyrene-based polymer coating both in vitro in murine macrophages and in vivo in lung of mice monitored for 6 months. Conclusions these results demonstrate that coating CNT with polymers, without affecting their intrinsic structure, may constitute a useful strategy for decreasing CNT toxicity, and may hold promise for improving occupational safety and that of general the user. PMID:21255417

Wrapping conformations of a polymer on a curved surface

NASA Astrophysics Data System (ADS)

Lin, Cheng-Hsiao; Tsai, Yan-Chr; Hu, Chin-Kun

2007-03-01

The conformation of a polymer on a curved surface is high on the agenda for polymer science. We assume that the free energy of the system is the sum of bending energy of the polymer and the electrostatic attraction between the polymer and surface. As is also assumed, the polymer is very stiff with an invariant length for each segment so that we can neglect its tensile energy and view its length as a constant. Based on the principle of minimization of free energy, we apply a variation method with a locally undetermined Lagrange multiplier to obtain a set of equations for the polymer conformation in terms of local geometrical quantities. We have obtained some numerical solutions for the conformations of the polymer chain on cylindrical and ellipsoidal surfaces. With some boundary conditions, we find that the free energy profiles of polymer chains behave differently and depend on the geometry of the surface for both cases. In the former case, the free energy of each segment distributes within a narrower range and its value per unit length oscillates almost periodically in the azimuthal angle. However, in the latter case the free energy distributes in a wider range with larger value at both ends and smaller value in the middle of the chain. The structure of a polymer wrapping around an ellipsoidal surface is apt to dewrap a polymer from the endpoints. The dependence of threshold lengths for a polymer on the initially anchored positions is also investigated. With initial conditions, the threshold wrapping length is found to increase with the electrostatic attraction strength for the ellipsoidal surface case. When a polymer wraps around a sphere surface, the threshold length increases monotonically with the radius without the self-intersection configuration for a polymer. We also discuss potential applications of the present theory to DNA/protein complex and further researches on DNA on the curved surface.

On the use of SPM to probe the interplay between polymer surface chemistry and polymer surface mechanics

NASA Astrophysics Data System (ADS)

Brogly, Maurice; Noel, Olivier; Awada, Houssein; Castelein, Gilles

2007-03-01

Adhesive properties of a polymer surface results from the complex contribution of surface chemistry and activation of sliding and dissipating mechanisms within the polymer surface layer. The purpose of this study is to dissociate the different contributions (chemical and mechanical) included in an AFM force-distance curve in order to establish relationships between the surface viscoelastic properties of the polymer, the surface chemistry of functionalized polymer surfaces and the adhesive forces, as determined by C-AFM experiments. Indeed we are interested in the measurements of local attractive or adhesive forces in AFM contact mode, of controlled chemical and mechanical model substrates. In order to investigate the interplay between mechanical or viscoelastic mechanisms and surface chemistry during the tip - polymer contact, we achieved force measurements on model PDMS polymer networks, whose surfaces are chemically controlled with the same functional groups as before (silicon substrates). On the basis of AFM nano-indentation experiments, surface Young moduli have been determined. The results show that the viscoelastic contribution is dominating in the adhesion force measurement. We propose an original model, which express the local adhesion force to the energy dissipated within the contact and the surface properties of the material (thermodynamic work of adhesion). Moreover we show that the dissipation function is related to Mc, the mass between crosslinks of the network.

Applications of conducting polymers and their issues in biomedical engineering

PubMed Central

Ravichandran, Rajeswari; Sundarrajan, Subramanian; Venugopal, Jayarama Reddy; Mukherjee, Shayanti; Ramakrishna, Seeram

2010-01-01

Conducting polymers (CPs) have attracted much interest as suitable matrices of biomolecules and have been used to enhance the stability, speed and sensitivity of various biomedical devices. Moreover, CPs are inexpensive, easy to synthesize and versatile because their properties can be readily modulated by (i) surface functionalization techniques and (ii) the use of a wide range of molecules that can be entrapped or used as dopants. This paper discusses the various surface modifications of the CP that can be employed in order to impart physico-chemical and biological guidance cues that promote cell adhesion/proliferation at the polymer–tissue interface. This ability of the CP to induce various cellular mechanisms widens its applications in medical fields and bioengineering. PMID:20610422

Polymer brush covalently attached to OH-functionalized mica surface via surface-initiated ATRP: control of grafting density and polymer chain length.

PubMed

Lego, Béatrice; François, Marion; Skene, W G; Giasson, Suzanne

2009-05-05

The controlled grafting density of poly(tert-butyl acrylate) was studied on OH-activated mica substrates via surface-initiated atom-transfer radical polymerization (ATRP). By properly adjusting parameters such as the immobilization reaction time and the concentration of an ATRP initiator, a wide range of initiator surface coverages and hence polymer densities on mica were possible. The covalently immobilized initiator successfully promoted the polymerization of tert-butyl acrylate on mica surfaces. The resulting polymer layer thickness was measured by AFM using a step-height method. Linear relationships of the polymer thickness with respect to the molecular weight of the free polymer and with respect to the monomer conversion were observed, suggesting that ATRP is well controlled and relatively densely end-grafted layers were obtained. The polymer grafting density controlled by adjusting the initiator surface coverage was confirmed by the polymer layer swelling capacity and film thickness measurements.

The relationship between surface tension and the industrial performance of water-soluble polymers prepared from acid hydrolysis lignin, a saccharification by-product from woody materials.

PubMed

Matsushita, Yasuyuki; Imai, Masanori; Iwatsuki, Ayuko; Fukushima, Kazuhiko

2008-05-01

In this study, water-soluble anionic and cationic polymers were prepared from sulfuric acid lignin (SAL), an acid hydrolysis lignin, and the relationship between the surface tension of these polymers and industrial performance was examined. The SAL was phenolized (P-SAL) to enhance its solubility and reactivity. Sulfonation and the Mannich reaction with aminocarboxylic acids produced water-soluble anionic polymers and high-dispersibility gypsum paste. The dispersing efficiency increased as the surface tension decreased, suggesting that the fluidity of the gypsum paste increased with the polymer adsorption on the gypsum particle surface. Water-soluble cationic polymers were prepared using the Mannich reaction with dimethylamine. The cationic polymers showed high sizing efficiency under neutral papermaking conditions; the sizing efficiency increased with the surface tension. This suggests that the polymer with high hydrophilicity spread in the water and readily adhered to the pulp surface and the rosin, showing good retention.

Detection of heart-type fatty acid-binding protein (h-FABP) using piezoresistive polymer microcantilevers functionalized by a dry method

NASA Astrophysics Data System (ADS)

Agarwal, Dilip Kumar; Prasad, Abhinav; Vinchurkar, Madhuri; Gandhi, Sahir; Prabhakar, Deepika; Mukherji, Soumyo; Rao, V. Ramgopal

2018-03-01

Piezoresistive microcantilever-based sensor platform is being used for the last two decades due to their low cost, rapid response and label-free detection system. In this work, we are reporting a microfabricated piezoresistive SU-8/carbon black (polymer cantilever)-based sensor platform for the detection of a clinically important early-stage cardiac marker, i.e., fatty acid-binding protein. It is a most preferred cardiac marker for the diagnosis of acute myocardial infarction. The embodiment of the sensor is a SU-8 microcantilever chip with an integrated nanoparticle composite (carbon black) as a piezoresistor for on-chip electrical transduction. Prior to improving the sensing and susceptibility towards the specific target biomolecule (i.e., h-FABP), the fabricated SU-8 polymer cantilevers were subjected to tailored functionalization. This includes the use of an in-house dry method of hot wire chemical vapour deposition technique to graft amine groups onto the SU-8 surface. The surface-modified microcantilevers were further integrated with a polydimethylsiloxane liquid flow cell and connected externally with an electrical read-out system. Immobilization of the antibody corresponding to the marker protein on the microcantilever surface and subsequent recording of the signal generated upon the antibody-antigen interaction were carried out inside the liquid flow cell. Using our optimized immobilization protocol with this experimental set-up, we were successfully able to detect h-FABP concentration as low as 100 ng/ml.

Surface functionalized magnetic nanoparticles for cancer therapy applications

NASA Astrophysics Data System (ADS)

Wydra, Robert John

Despite recent advances, cancer remains the second leading cause of deaths in the United States. Magnetic nanoparticles have found various applications in cancer research as drug delivery platforms, enhanced contrast agents for improved diagnostic imaging, and the delivery of thermal energy as standalone therapy. Iron oxide nanoparticles absorb the energy from an alternating magnetic field and convert it into heat through Brownian and Neel relaxations. To better utilize magnetic nanoparticles for cancer therapy, surface functionalization is essential for such factors as decreasing cytotoxicity of healthy tissue, extending circulation time, specific targeting of cancer cells, and manage the controlled delivery of therapeutics. In the first study, iron oxide nanoparticles were coated with a poly(ethylene glycol) (PEG) based polymer shell. The PEG coating was selected to prevent protein adsorption and thus improve circulation time and minimize host response to the nanoparticles. Thermal therapy application feasibility was demonstrated in vitro with a thermoablation study on lung carcinoma cells. Building on the thermal therapy demonstration with iron oxide nanoparticles, the second area of work focused on intracellular delivery. Nanoparticles can be appropriately tailored to enter the cell and deliver energy on the nanoscale eliminating individual cancer cells. The underlying mechanism of action is still under study, and we were interested in determining the role of reactive oxygen species (ROS) catalytically generated from the surface of iron oxide nanoparticles in this measured cytotoxicity. When exposed to an AMF, the nanoscale heating effects are capable of enhancing the Fenton-like generation of ROS determined through a methylene blue degradation assay. To deliver this enhanced ROS effect to cells, monosaccharide coated nanoparticles were developed and successfully internalized by colon cancer cell lines. Upon AMF exposure, there was a measured increase in cellular ROS and apoptosis that was attributed to lysosomal disruption since the surface functionalization selected inhibited the Fenton-like surface chemistry. To overcome this surface inhibition, a biodegradable poly(beta-amino ester) (PBAE) polymer coating was synthesized to deliver bare iron oxide to intracellular components. Delivering enhanced ROS to cancer cells is a promising new route of therapy that deserves future studies.

Atomic Origins of the Self-Healing Function in Cement–Polymer Composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Manh-Thuong; Wang, Zheming; Rod, Kenton A.

Motivated by recent advances in self-healing cement and epoxy polymer composites, we present a combined ab initio molecular dynamics and sum frequency generation (SFG) spectroscopy study of a calcium-silicate-hydrate/polymer interface. On stable, low-defect surfaces, the polymer only weakly adheres through coordination and hydrogen bonding interactions and can be easily mobilized towards defected surfaces. Conversely, on fractured surfaces, the polymer strongly anchors through ionic Ca-O bonds resulting from the deprotonation of polymer hydroxyl groups. In addition, polymer S-S groups are turned away from the cement/polymer interface, allowing for the self-healing function within the polymer. The overall elasticity and healing properties ofmore » these composites stem from a flexible hydrogen bonding network that can readily adapt to surface morphology. The theoretical vibrational signals associated with the proposed cement-polymer interfacial chemistry were confirmed experimentally by SFG spectroscopy.« less

Atomic Origins of the Self-Healing Function in Cement-Polymer Composites.

PubMed

Nguyen, Manh-Thuong; Wang, Zheming; Rod, Kenton A; Childers, M Ian; Fernandez, Carlos; Koech, Phillip K; Bennett, Wendy D; Rousseau, Roger; Glezakou, Vassiliki-Alexandra

2018-01-24

Motivated by recent advances in self-healing cement and epoxy polymer composites, we present a combined ab initio molecular dynamics and sum frequency generation (SFG) vibrational spectroscopy study of a calcium-silicate-hydrate/polymer interface. On stable, low-defect surfaces, the polymer only weakly adheres through coordination and hydrogen bonding interactions and can be easily mobilized toward defected surfaces. Conversely, on fractured surfaces, the polymer strongly anchors through ionic Ca-O bonds resulting from the deprotonation of polymer hydroxyl groups. In addition, polymer S-S groups are turned away from the cement-polymer interface, allowing for the self-healing function within the polymer. The overall elasticity and healing properties of these composites stem from a flexible hydrogen bonding network that can readily adapt to surface morphology. The theoretical vibrational signals associated with the proposed cement-polymer interfacial chemistry were confirmed experimentally by SFG vibrational spectroscopy.

Comblike poly(ethylene oxide)/hydrophobic C6 branched chitosan surfactant polymers as anti-infection surface modifying agents.

PubMed

Mai-ngam, Katanchalee

2006-05-01

A series of structurally well-defined poly(ethylene oxide)/hydrophobic C6 branched chitosan surfactant polymers that undergo surface induced self assembly on hydrophobic biomaterial surfaces were synthesized and characterized. The surfactant polymers consist of low molecular weight (Mw) chitosan backbone with hydrophilic poly(ethylene oxide) (PEO) and hydrophobic hexyl pendant groups. Chitosan was depolymerized by nitrous acid deaminative cleavage. Hexanal and aldehyde-terminated PEO chains were simultaneously attached to low Mw chitosan hydrochloride via reductive amination. The surfactant polymers were prepared with various ratios of the two side chains. The molecular composition of the surfactant polymers was determined by FT-IR and 1H NMR. Surface active properties at the air-water interface were determined by Langmuir film balance measurements. The surfactant polymers with PEO/hexyl ratios of 1:3.0 and 1:14.4 were used as surface modifying agents to investigate their anti-infection properties. E. coli adhesion on Silastic surface was decreased significantly by the surfactant polymer with PEO/hexyl 1:3.0. Surface growth of adherent E. coli was effectively suppressed by both tested surfactant polymers.

Pressing effect in polymer solar cells with bulk heterojunction nanolayers.

PubMed

Park, Jiho; Nam, Sungho; Kim, Hwajeong; Kim, Youngkyoo

2011-01-01

We report the effect of pressing light-absorbing layers on the performance of polymer solar cells. The light-absorbing active layer was prepared on the transparent conducting oxide coated substrates from solutions that contain a mixture of regioregular poly(3-hexylthiophene) and soluble fullerene molecules. The active layers were pressed using a home-built micro-press system by controlling temperature and pressure, followed by the top electrode deposition. The surface of the active layers pressed was examined using atomic force microscope, while the photovoltaic characteristics of devices were measured under simulated solar light illumination (air mass 1.5 G, 100 mW/cm2). Results showed that the dark current of devices was noticeably increased by pressing the active layer without respect to the pressing temperature. The highest power conversion efficiency was achieved for the device with the active layer pressed under 10 kgf at 70 degrees C. The result was explained in terms of surface morphology and thermophysical effect.

High-Efficiency and High-Color-Rendering-Index Semitransparent Polymer Solar Cells Induced by Photonic Crystals and Surface Plasmon Resonance.

PubMed

Shen, Ping; Wang, Guoxin; Kang, Bonan; Guo, Wenbin; Shen, Liang

2018-02-21

Semitransparent polymer solar cells (ST-PSCs) show attractive potential in power-generating windows or building-integrated photovoltaics. However, the development of ST-PSCs is lagging behind opaque PSCs because of the contradiction between device efficiency and transmission. Herein, Ag/Au alloy nanoparticles and photonic crystals (PCs) were simultaneously introduced into ST-PSCs, acting compatibly as localized surface plasmon resonances and distributed Bragg reflectors to enhance light absorption and transmission. As a result, ST-PSCs based on a hybrid PTB7-Th:PC 71 BM active layer contribute an efficiency as high as 7.13 ± 0.15% and an average visible transmission beyond 20%, which are superior to most of the reported results. Furthermore, PCs can partly compensate valley range of transmission by balancing reflection and transmission regions, yielding a high color rendering index of 95. We believe that the idea of two light management methods compatibly enhancing the performance of ST-PSCs can offer a promising path to develop photovoltaic applications.

Vertical and lateral morphology effects on solar cell performance for a thiophene–quinoxaline copolymer:PC 70BM blend

DOE PAGES

Hansson, Rickard; Ericsson, Leif K. E.; Holmes, Natalie P.; ...

2015-02-13

The distribution of electron donor and acceptor in the active layer is known to strongly influence the electrical performance of polymer solar cells for most of the high performance polymer:fullerene systems. The formulation of the solution from which the active layer is spincoated plays an important role in the quest for morphology control. We have studied how the choice of solvent and the use of small amounts of a low vapour pressure additive in the coating solution influence the film morphology and the solar cell performance for blends of poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) and [6,6]-phenyl C 71-butyric acid methyl ester (PC 70BM).more » We have investigated the lateral morphology using atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM), the vertical morphology using dynamic secondary ion mass spectrometry (d-SIMS) and variable-angle spectroscopic ellipsometry (VASE), and the surface composition using near-edge X-ray absorption fine structure (NEXAFS). The lateral phase-separated domains observed in films spincoated from single solvents, increase in size with increasing solvent vapour pressure and decreasing PC 70BM solubility, but are not observed when 1-chloronaphthalene (CN) is added. A strongly TQ1-enriched surface layer is formed in all TQ1:PC 70BM blend films and rationalized by surface energy differences. The photocurrent and power conversion efficiency strongly increased upon the addition of CN, while the leakage current decreased by one to two orders of magnitude. The higher photocurrent correlates with the finer lateral structure and stronger TQ1-enrichment at the interface with the electron-collecting electrode. This indicates that the charge transport and collection are not hindered by this polymer-enriched surface layer. Neither the open-circuit voltage nor the series resistance of the devices are sensitive to the differences in morphology.« less

Encapsidated Atom-Transfer Radical Polymerization in Qβ Virus-like Nanoparticles

PubMed Central

2015-01-01

Virus-like particles (VLPs) are unique macromolecular structures that hold great promise in biomedical and biomaterial applications. The interior of the 30 nm-diameter Qβ VLP was functionalized by a three-step process: (1) hydrolytic removal of endogenously packaged RNA, (2) covalent attachment of initiator molecules to unnatural amino acid residues located on the interior capsid surface, and (3) atom-transfer radical polymerization of tertiary amine-bearing methacrylate monomers. The resulting polymer-containing particles were moderately expanded in size; however, biotin-derivatized polymer strands were only very weakly accessible to avidin, suggesting that most of the polymer was confined within the protein shell. The polymer-containing particles were also found to exhibit physical and chemical properties characteristic of positively charged nanostructures, including the ability to easily enter mammalian cells and deliver functional small interfering RNA. PMID:25073013

Design and fabrication of fluorescence resonance energy transfer-mediated fluorescent polymer nanoparticles for ratiometric sensing of lysosomal pH.

PubMed

Chen, Jian; Tang, Ying; Wang, Hong; Zhang, Peisheng; Li, Ya; Jiang, Jianhui

2016-12-15

The design of effective tools capable of sensing lysosome pH is highly desirable for better understanding its biological functions in cellular behaviors and various diseases. Herein, a lysosome-targetable ratiometric fluorescent polymer nanoparticle pH sensor (RFPNS) was synthesized via incorporation of miniemulsion polymerization and surface modification technique. In this system, the donor: 4-ethoxy-9-allyl-1,8-naphthalimide (EANI) and the acceptor: fluorescein isothiocyanate (FITC) were covalently linked to the polymer nanoparticle to construct pH-responsive fluorescence resonance energy transfer (FRET) system. The FITC moieties on the surface of RFPNS underwent structural and spectral transformation as the presence of pH changes, resulting in ratiometric fluorescent sensing of pH. The as-prepared RFPNS displayed favorable water dispersibility, good pH-induced spectral reversibility and so on. Following the living cell uptake, the as-prepared RFPNS with good cell-membrane permeability can mainly stain in the lysosomes; and it can facilitate visualization of the intracellular lysosomal pH changes. This nanosensor platform offers a novel method for future development of ratiometric fluorescent probes for targeting other analytes, like ions, metabolites,and other biomolecules in biosamples. Copyright © 2016 Elsevier Inc. All rights reserved.

Nanopatterned polystyrene-b-poly(acrylic acid) surfaces to modulate cell-material interaction.

PubMed

Lizundia, Erlantz; Sáenz-Pérez, Míriam; Patrocinio, David; Aurrekoetxea, Iskander; dM Vivanco, Maria; Vilas, José Luis

2017-06-01

In this work we explore the effect of surface nanoarchitecture of polystyrene (PS) and polystyrene-b-poly(acrylic acid) (PS-b-PAA) diblock copolymer films on cell viability. PS and PS-b-PAA have been nanopatterned at temperatures of 110, 120 and 140°C using nanoporous aluminium oxide membranes (AAO) as a template. Surface architecture strongly depends on the infiltration temperature and the nature of the infiltrated polymer. High patterning temperatures yield hollow fibre shape architecture at the nanoscale level, which substantially modifies the surface hydrophobicity of the resulting materials. Up to date very scarce reports could be found in the literature dealing with the interaction of microstructured/nanostructured polymeric surfaces with cancer cells. Therefore, MCF-7 breast cancer cells have been selected as a model to conduct cell viability assays. The findings reveal that the fine-tuning of the surface nanoarchitecture contributes to the modification of its biocompatibility. Overall, this study highlights the potential of AAO membranes to obtain well-defined tailored morphologies at nanoscale level and its importance to develop novel soft functional surfaces to be used in the biomedical field. Copyright © 2017 Elsevier B.V. All rights reserved.

Contact Killing of Bacteria on Copper Is Suppressed if Bacterial-Metal Contact Is Prevented and Is Induced on Iron by Copper Ions

PubMed Central

Mathews, Salima; Hans, Michael

2013-01-01

Bacteria are rapidly killed on copper surfaces, and copper ions released from the surface have been proposed to play a major role in the killing process. However, it has remained unclear whether contact of the bacteria with the copper surface is also an important factor. Using laser interference lithography, we engineered copper surfaces which were covered with a grid of an inert polymer which prevented contact of the bacteria with the surface. Using Enterococcus hirae as a model organism, we showed that the release of ionic copper from these modified surfaces was not significantly reduced. In contrast, killing of bacteria was strongly attenuated. When E. hirae cells were exposed to a solid iron surface, the loss of cell viability was the same as on glass. However, exposing cells to iron in the presence of 4 mM CuSO4 led to complete killing in 100 min. These experiments suggest that contact killing proceeds by a mechanism whereby the metal-bacterial contact damages the cell envelope, which, in turn, makes the cells susceptible to further damage by copper ions. PMID:23396344

Facile Synthesis of Conductive Polypyrrole Wrinkle Topographies on Polydimethylsiloxane via a Swelling-Deswelling Process and Their Potential Uses in Tissue Engineering.

PubMed

Aufan, M Rifqi; Sumi, Yang; Kim, Semin; Lee, Jae Young

2015-10-28

Electrically conducting biomaterials have gained great attention in various biomedical studies especially to influence cell and tissue responses. In addition, wrinkling can present a unique topography that can modulate cell-material interactions. In this study, we developed a simple method to create wrinkle topographies of conductive polypyrrole (wPPy) on soft polydimethylsiloxane surfaces via a swelling-deswelling process during and after PPy polymerization and by varying the thickness of the PPy top layers. As a result, various features of wPPy in the range of the nano- and microscales were successfully obtained. In vitro cell culture studies with NIH 3T3 fibroblasts and PC12 neuronal cells indicated that the conductive wrinkle topographies promote cell adhesion and neurite outgrowth of PC12 cells. Our studies help to elucidate the design of the surface coating and patterning of conducting polymers, which will enable us to simultaneously provide topographical and electrical signals to improve cell-surface interactions for potential tissue-engineering applications.

Photonic Devices Based on Surface and Composition-Engineered Infrared Colloidal Nanocrystals

DTIC Science & Technology

2012-01-27

NQD/P3HT solar cells , the need for submicron-phase-separated polymer-NQD blends is therefore expressed by the limiting exciton diffusion length ...P3HT:PbSe are very critical in designing the PM-HJ solar cells : The thickness of P3HT should approximate to the thickness of exciton diffuse length in... cells , luminescent solar concentrators, light emitting diodes, lasers, photonic crystals, CdSe, PbSe, Germanium Jian Xu Pennsylvania State University

Origin of change in molecular-weight dependence for polymer surface tension.

PubMed

Thompson, R B; Macdonald, J R; Chen, P

2008-09-01

Self-consistent-field theory is used to reproduce the behavior of polymer surface tension with molecular-weight for both lower and higher molecular-weight polymers. The change in behavior of the surface tension between these two regimes is shown to be due to the almost total exclusion of polymer from the nonpolymer bulk phase. The predicted two regime surface tension behavior with molecular-weight and the exclusion explanation are shown to be valid for a range of different polymer compressibilities.

Surface cell immobilization within perfluoroalkoxy microchannels

NASA Astrophysics Data System (ADS)

Stojkovič, Gorazd; Krivec, Matic; Vesel, Alenka; Marinšek, Marjan; Žnidaršič-Plazl, Polona

2014-11-01

Perfluoroalkoxy (PFA) is one of the most promising materials for the fabrication of cheap, solvent resistant and reusable microfluidic chips, which have been recently recognized as effective tools for biocatalytic process development. The application of biocatalysts significantly depends on efficient immobilization of enzymes or cells within the reactor enabling long-term biocatalyst use. Functionalization of PFA microchannels by 3-aminopropyltriethoxysilane (ATPES) and glutaraldehyde was used for rapid preparation of microbioreactors with surface-immobilized cells. X-ray photoelectron spectroscopy and scanning electron microscopy were used to accurately monitor individual treatment steps and to select conditions for cell immobilization. The optimized protocol for Saccharomyces cerevisiae immobilization on PFA microchannel walls comprised ethanol surface pretreatment, 4 h contacting with 10% APTES aqueous solution, 10 min treatment with 1% glutaraldehyde and 20 min contacting with cells in deionized water. The same protocol enabled also immobilization of Escherichia coli, Pseudomonas putida and Bacillus subtilis cells on PFA surface in high densities. Furthermore, the developed procedure has been proved to be very efficient also for surface immobilization of tested cells on other materials that are used for microreactor fabrication, including glass, polystyrene, poly (methyl methacrylate), polycarbonate, and two olefin-based polymers, namely Zeonor® and Topas®.

Noncontact viscoelastic measurement of polymer thin films in a liquid medium using a long-needle AFM

NASA Astrophysics Data System (ADS)

Guan, Dongshi; Barraud, Chloe; Charlaix, Elisabeth; Tong, Penger

We report noncontact measurement of the viscoelastic property of polymer thin films in a liquid medium using frequency-modulation atomic force microscopy (FM-AFM) with a newly developed long-needle probe. The probe contains a long vertical glass fiber with one end adhered to a cantilever beam and the other end with a sharp tip placed near the liquid-film interface. The nanoscale flow generated by the resonant oscillation of the needle tip provides a precise hydrodynamic force acting on the soft surface of the thin film. By accurately measuring the mechanical response of the thin film, we obtain the elastic and loss moduli of the thin film using the linear response theory of elasto-hydrodynamics. The experiment verifies the theory and demonstrates its applications. The technique can be used to accurately measure the viscoelastic property of soft surfaces, such as those made of polymers, nano-bubbles, live cells and tissues. This work was supported by the Research Grants Council of Hong Kong SAR.

A flexible thermoresponsive cell culture substrate for direct transfer of keratinocyte cell sheets.

PubMed

Praveen, Wulligundam; Madathil, Bernadette K; Sajin Raj, R S; Kumary, T V; Anil Kumar, P R

2017-10-25

Most cell sheet engineering systems require a support or carrier to handle the harvested cell sheets. In this study, polyethylene terephthalate-based overhead projection transparency sheets (OHPS) were subjected to surface hydrolysis by alkali treatment to increase pliability and hydrophilicity and enable poly(N-isopropylacrylamide-co-glycidylmethacrylate) copolymer (NGMA) coating to impart thermoresponsiveness. NGMA was applied on the modified OHPS by the technique of spin coating using an indigenously designed spin coater. The spin coating had the advantage of using low volumes of the polymer and a reduced coating time. The surface chemistry and thermoresponsive coating was analyzed by Fourier transform infrared spectroscopy and water contact angle. Human keratinocyte cells were cultured on the spin coated surface and scaffold-free cell sheets were successfully harvested by simple variation of temperature. These cell sheets were found to be viable, exhibited epithelial characteristic and cell-cell contact as confirmed by positive immunostaining for ZO-1. The integrity and morphology of the cell sheet was confirmed by stereomicroscopy and E-SEM. These results highlight the potential of the NGMA spin coated modified OHPS to serve as a thermoresponsive culture surface-cum-flexible transfer tool.

Activation of caspase-dependent apoptosis by intracellular delivery of cytochrome c-based nanoparticles

PubMed Central

2014-01-01

Background Cytochrome c is an essential mediator of apoptosis when it is released from the mitochondria to the cytoplasm. This process normally takes place in response to DNA damage, but in many cancer cells (i.e., cancer stem cells) it is disabled due to various mechanisms. However, it has been demonstrated that the targeted delivery of Cytochrome c directly to the cytoplasm of cancer cells selective initiates apoptosis in many cancer cells. In this work we designed a novel nano-sized smart Cytochrome c drug delivery system to induce apoptosis in cancer cells upon delivery. Results Cytochrome c was precipitated with a solvent-displacement method to obtain protein nanoparticles. The size of the Cytochrome c nanoparticles obtained was 100-300 nm in diameter depending on the conditions used, indicating good potential to passively target tumors by the Enhanced Permeability and Retention effect. The surface of Cytochrome c nanoparticles was decorated with poly (lactic-co-glycolic) acid-SH via the linker succinimidyl 3-(2-pyridyldithio) propionate to prevent premature dissolution during delivery. The linker connecting the polymer to the protein nanoparticle contained a disulfide bond thus allowing polymer shedding and subsequent Cytochrome c release under intracellular reducing conditions. A cell-free caspase-3 assay revealed more than 80% of relative caspase activation by Cytochrome c after nanoprecipitation and polymer modification when compared to native Cytochrome c. Incubation of HeLa cells with the Cytochrome c based-nanoparticles showed significant reduction in cell viability after 6 hours while native Cytochrome c showed none. Confocal microscopy confirmed the induction of apoptosis in HeLa cells when they were stained with 4’,6-diamidino-2-phenylindole and propidium iodide after incubation with the Cytochrome c-based nanoparticles. Conclusions Our results demonstrate that the coating with a hydrophobic polymer stabilizes Cytochrome c nanoparticles allowing for their delivery to the cytoplasm of target cells. After smart release of Cytochrome c into the cytoplasm, it induced programmed cell death. PMID:25179308

A Simple, Cost-Efficient Method to Separate Microalgal Lipids from Wet Biomass Using Surface Energy-Modified Membranes.

PubMed

Kwak, Moo Jin; Yoo, Youngmin; Lee, Han Sol; Kim, Jiyeon; Yang, Ji-Won; Han, Jong-In; Im, Sung Gap; Kwon, Jong-Hee

2016-01-13

For the efficient separation of lipid extracted from microalgae cells, a novel membrane was devised by introducing a functional polymer coating onto a membrane surface by means of an initiated chemical vapor deposition (iCVD) process. To this end, a steel-use-stainless (SUS) membrane was modified in a way that its surface energy was systemically modified. The surface modification by conformal coating of functional polymer film allowed for selective separation of oil-water mixture, by harnessing the tuned interfacial energy between each liquid phase and the membrane surface. The surface-modified membrane, when used with chloroform-based solvent, exhibited superb permeate flux, breakthrough pressure, and also separation yield: it allowed separation of 95.5 ± 1.2% of converted lipid (FAME) in the chloroform phase from the water/MeOH phase with microalgal debris. This result clearly supported that the membrane-based lipid separation is indeed facilitated by way of membrane being functionalized, enabling us to simplify the whole downstream process of microalgae-derived biodiesel production.

Periodically patterned structures for nanoplasmonic and biomedical applications

NASA Astrophysics Data System (ADS)

Peer, Akshit

Periodically patterned nanostructures have imparted profound impact on diverse scientific disciplines. In physics, chemistry, and materials science, artificially engineered photonic crystals have demonstrated an unprecedented ability to control the propagation of photons through light concentration and diffraction. The field of photonic crystals has led to many technical advances in fabricating periodically patterned nanostructures in dielectric/metallic materials and controlling the light-matter interactions at the nanoscale. In the field of biomaterials, it is of great interest to apply our knowledge base of photonic materials and explore how such periodically patterned structures control diverse biological functions by varying the available surface area, which is a key attribute for surface hydrophobicity, cell growth and drug delivery. Here we describe closely related scientific applications of large-scale periodically patterned polymers and metal nanostructures. The dissertation starts with nanoplasmonics for improving photovoltaic devices, where we design and optimize experimentally realizable light-trapping nanostructures using rigorous scattering matrix simulations for enhancing the performance of organic and perovskite solar cells. The use of periodically patterned plasmonic metal cathode in conjunction with polymer microlens array significantly improves the absorption in solar cells, providing new opportunities for photovoltaic device design. We further show the unprecedented ability of nanoplasmonics to concentrate light at the nanoscale by designing a large-area plasmonic nanocup array with frequency-selective optical transmission. The fabrication of nanostructure is achieved by coating non-uniform gold layer over a submicron periodic nanocup array imprinted on polystyrene using soft lithography. The gold nanocup array shows extraordinary optical transmission at a wavelength close to the structure period. The resonance wavelength for transmission can be tuned by changing the period of the gold nanocup array, which opens up new avenues in subwavelength optics for designing optoelectronic devices and biological sensors. We then demonstrate strong exciton-plasmon coupling between non-toxic CuInS2/ZnS quantum dots in solution and plasmonic gold nanocup array. The photoluminescence decay rate of quantum dots can be enhanced by more than an order of magnitude due to the high electric field intensity enhancement inside the plasmonic nanocup cavity. This solution based metal-nanocrystal coupled system has great promise for biological applications such as biosensing and biolabeling. Moving to the area of biomedical applications, we fabricate nanopatterned biopolymers as templates for controlling the release of therapeutic drugs coated on the polymer surface. From careful drug release experiments performed over extended time periods (e.g. eight days), we find that nanopatterned polymers release the drug slower as compared to the flat polymer surfaces. The slow-down in the drug release from nanopatterned surfaces is attributed to increase in the surface hydrophobicity confirmed by the contact angle measurements and microfluidic simulations. This nanoscale drug release control scheme has great promise for improving the performance of drug-eluting stents in cardiac therapies.

Proton conduction of polyAMPS brushes on titanate nanotubes

PubMed Central

Feng, Jun; Huang, Yaqin; Tu, Zhengkai; Zhang, Haining; Pan, Mu; Tang, Haolin

2014-01-01

Proton conducting materials having reasonable proton conductivity at low humidification conditions are critical for decrease in system complexity and improvement of power density for polymer electrolyte membrane fuel cells. This study shows that polyelectrolyte brushes on titanate nanotubes formed through surface-initiated free radical polymerization exhibit less humidity-dependent proton conduction because of the high grafting density of polymer electrolyte chains and well-distribution of ionic groups. The results described in this study provide an idea for design of new proton conductors with effective ion transport served at relatively low humidification levels. PMID:25169431

Polymer-based solar cells having an active area of 1.6 cm{sup 2} fabricated via spray coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scarratt, N. W.; Griffin, J.; Zhang, Y.

We demonstrate the fabrication of polymer solar cells in which both a PEDOT:PSS hole transport and a PCDTBT:PC{sub 71}BM photoactive layer are deposited by spray-casting. Two device geometries are explored, with devices having a pixel area of 165 mm{sup 2} attaining a power conversion efficiency of 3.7%. Surface metrology indicates that the PEDOT:PSS and PCDTBT:PC{sub 71}BM layers have a roughness of 2.57 nm and 1.18 nm over an area of 100 μm{sup 2}. Light beam induced current mapping reveals fluctuations in current generation efficiency over length-scales of ∼2 mm, with the average photocurrent being 75% of its maximum value.

Achieving 15% Tandem Polymer Solar Cells

DTIC Science & Technology

2015-06-23

solar cell structures – both polymer only and hybrid tandem cells to constantly pushing the envelope of solution processed solar cell ...performance – 11.6% polymer tandem cell , 7% transparent tandem polymer cell , and over 10% PCE hybrid tandem solar cells were achieved. In addition, AFOSR’s...final support also enabled us to explore novel hybrid perovskite solar cells in depth. For example, single junction cell efficiency

Estimation of polymer-surface interfacial interaction strength by a contact AFM technique.

PubMed

Dvir, H; Jopp, J; Gottlieb, M

2006-12-01

Atomic force microscopy (AFM) measurements were employed to assess polymer-surface interfacial interaction strength. The main feature of the measurement is the use of contact-mode AFM as a tool to scratch off the polymer monolayer adsorbed on the solid surface. Tapping-mode AFM was used to determine the depth of the scraped recess. Independent determination of the layer thickness obtained from optical phase interference microscopy (OPIM) confirmed the depth of the AFM scratch. The force required for the complete removal of the polymer layer with no apparent damage to the substrate surface was determined. Polypropylene (PP), low-density polyethylene (PE), and PP-grafted-maleic anhydride (PP-g-ma) were scraped off silane-treated glass slabs, and the strength of surface interaction of the polymer layer was determined. In all cases it was determined that the magnitude of surface interaction force is of the order of van der Waals (VDW) interactions. The interaction strength is influenced either by polymer ability to wet the surface (hydrophobic or hydrophilic interactions) or by hydrogen bonding between the polymer and the surface treatment.

Thiol-reactive amphiphilic block copolymer for coating gold nanoparticles with neutral and functionable surfaces

PubMed Central

Chen, Hongwei; Zou, Hao; Paholak, Hayley J.; Ito, Masayuki; Qian, Wei; Che, Yong; Sun, Duxin

2014-01-01

Nanoparticles designed for biomedical applications are often coated with polymers containing reactive functional groups, such as –COOH and –NH2, to conjugate targeting ligands or drugs. However, introducing highly charged surfaces promotes binding of the nanoparticles to biomolecules in biological systems through ionic interactions, causing the nanoparticles to aggregate in biological environments and consequently undergo strong non-specific binding to off-target cells and tissues. Developing a unique polymer with neutral surfaces that can be further functionalized directly would be critical to develop suitable nanomaterials for nanomedicine. Here, we report a thiol-reactive amphiphilic block copolymer poly(ethylene oxide)-block-poly(pyridyldisulfide ethylmeth acrylate) (PEO-b-PPDSM) for coating gold nanoparticles (AuNPs). The resultant polymer-coated AuNPs have almost neutral surfaces with slightly negative zeta potentials from -10 to 0 mV over a wide pH range from 2 to 12. Although the zeta potential is close to zero we show that the PEO-b-PPDSM copolymer-coated AuNPs have both good stability in various physiological conditions and reduced non-specific adsorption of proteins/biomolecules. Because of the multiple pyridyldisulfide groups on the PPDSM block, these individually dispersed nanocomplexes with an overall hydrodynamic size around 43.8 nm can be directly functionalized via disulfide-thiol exchange chemistry. PMID:24729795

The effect of polymer surface modification on polymer-protein interaction via interfacial polymerization and hydrophilic polymer grafting

USDA-ARS?s Scientific Manuscript database

Protein membrane separation is prone to fouling on the membrane surface resulting from protein adsorption onto the surface. Surface modification of synthetic membranes is one way to reduce fouling. We investigated surface modification of polyethersulfone (PES) as a way of improving hydrophilicity ...

Surface characteristic of chemically converted graphene coated low carbon steel by electro spray coating method for polymer electrolyte membrane fuel cell bipolar plate.

PubMed

Kim, Jungsoo; Kim, Yang Do; Nam, Dae Geun

2013-05-01

Graphene was coated on low carbon steel (SS400) by electro spray coating method to improve its properties of corrosion resistance and contact resistance. Exfoliated graphite was made of the graphite by chemical treatment (Chemically Converted Graphene, CCG). CCG is distributed using dispersing agent, and low carbon steel was coated with diffuse graphene solution by electro spray coating method. The structure of the CCG was analyzed using XRD and the coating layer of surface was analyzed using SEM. Analysis showed that multi-layered graphite structure was destroyed and it was transformed in to fine layers graphene structure. And the result of SEM analysis on the surface and the cross section, graphene layer was uniformly formed with 3-5 microm thickness on the surface of substrate. Corrosion resistance test was applied in the corrosive solution which is similar to the polymer electrolyte membrane fuel cell (PEMFC) stack inside. And interfacial contact resistance (ICR) test was measured to simulate the internal operating conditions of PEMFC stack. As a result of measuring corrosion resistance and contact resistance, it could be confirmed that low carbon steel coated with CCG was revealed to be more effective in terms of its applicability as PEMFC bipolar plate.

Polymer coated CaAl-layered double hydroxide nanomaterials for potential calcium supplement.

PubMed

Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

2014-12-05

We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement.

Strategies for interfacing inorganic nanocrystals with biological systems based on polymer-coating.

PubMed

Palui, Goutam; Aldeek, Fadi; Wang, Wentao; Mattoussi, Hedi

2015-01-07

Interfacing inorganic nanoparticles and biological systems with the aim of developing novel imaging and sensing platforms has generated great interest and much activity. However, the effectiveness of this approach hinges on the ability of the surface ligands to promote water-dispersion of the nanoparticles with long term colloidal stability in buffer media. These surface ligands protect the nanostructures from the harsh biological environment, while allowing coupling to target molecules, which can be biological in nature (e.g., proteins and peptides) or exhibit specific photo-physical characteristics (e.g., a dye or a redox-active molecule). Amphiphilic block polymers have provided researchers with versatile molecular platforms with tunable size, composition and chemical properties. Hence, several groups have developed a wide range of polymers as ligands or micelle capsules to promote the transfer of a variety of inorganic nanomaterials to buffer media (including magnetic nanoparticles and semiconductor nanocrystals) and render them biocompatible. In this review, we first summarize the established synthetic routes to grow high quality nanocrystals of semiconductors, metals and metal oxides. We then provide a critical evaluation of the recent developments in the design, optimization and use of various amphiphilic copolymers to surface functionalize the above nanocrystals, along with the strategies used to conjugate them to target biomolecules. We finally conclude by providing a summary of the most promising applications of these polymer-coated inorganic platforms in sensor design, and imaging of cells and tissues.

Construction of a multifunctional coating consisting of phospholipids and endothelial progenitor cell-specific peptides on titanium substrates

NASA Astrophysics Data System (ADS)

Chen, Huiqing; Li, Xiaojing; Zhao, Yuancong; Li, Jingan; Chen, Jiang; Yang, Ping; Maitz, Manfred F.; Huang, Nan

2015-08-01

A phospholipid/peptide polymer (PMMDP) with phosphorylcholine groups, endothelial progenitor cell (EPC)-specific peptides and catechol groups was anchored onto a titanium (Ti) surface to fabricate a biomimetic multifunctional surface. The PMMDP coating was characterized by X-ray photoelectron spectroscopy (XPS), water contact angle measurements and atomic force microscopy (AFM), respectively. The amount of PMMDP coating on the Ti surface was quantified by using the quartz crystal microbalance with dissipation (QCM-D). Interactions between blood components and the coated and bare Ti substrates were evaluated by platelet adhesion and activation assays and fibrinogen denaturation test using platelet rich plasma (PRP). The results revealed that the PMMDP-modified surface inhibited fibrinogen denaturation and reduced platelet adhesion and activation. EPC cell culture on the PMMDP-modified surface showed increased adhesion and proliferation of EPCs when compared to the cells cultured on untreated Ti surface. The inhibition of fibrinogen denaturation and platelet adhesion and support of EPCs attachment and proliferation indicated that this coating might be beneficial for future applications in blood-contacting implants, such as vascular stents.

Surface decorations of poly(amidoamine) dendrimer by various pendant moieties for improved delivery of nucleic acid materials.

PubMed

Dehshahri, Ali; Sadeghpour, Hossein

2015-08-01

In recent years, the discovery of novel nucleic acid-based drug candidates (e.g., siRNA and miRNA) and the groundbreaking studies for somatic cell reprogramming into a state of pluripotency have led to reconsideration for the use of human gene therapy as a new paradigm with great therapeutic potential. However, the success of gene therapy is dependent on overcoming intra- and extracellular barriers hampering the efficient delivery of nucleic acid therapeutics into the target cells or tissues. Despite relatively low transfection efficiency, great attention has been directed to cationic polymers and dendrimers due to their ability to condense DNA and RNA molecules into nano-sized particles which is a necessary prerequisite for efficient transfer of nucleic acids into cells. These gene carriers show remarkable adaptability and significant capacity to transfer larger sizes of nucleic acid materials. Polyamidoamine (PAMAM) dendrimer has been employed as non-viral gene carrier due to its globular shape and well-defined structure containing abundant amino surface groups which provide possibility for surface decoration of the dendrimer via the conjugation of various moieties. In this review, we have brought out the various functionalization strategies of the PAMAM surface amines using different pendant moieties such as amino acids, proteins, cyclodextrins, and hydrophobic units in order to overcome intra- and extracellular barriers. These surface-decorated dendrimers possessing favorable properties provide substantial information and insight for redesigning existing dendrimers and polymers. By understanding the role played by the conjugated moieties, more efficient and novel designs of gene vehicles may be possible. Copyright © 2015 Elsevier B.V. All rights reserved.

A general microchip surface modification approach using a spin-coated polymer resist film doped with hydroxypropyl cellulose.

PubMed

Sun, Xiuhua; Yang, Weichun; Geng, Yanli; Woolley, Adam T

2009-04-07

We have developed a simple and effective method for surface modification of polymer microchips by entrapping hydroxypropyl cellulose (HPC) in a spin-coated thin film on the surface. Poly(methyl methacrylate-8.5-methacrylic acid), a widely available commercial resist formulation, was utilized as a matrix for dissolving HPC and providing adherence to native polymer surfaces. Various amounts of HPC (0.1-2.0%) dissolved in the copolymer and spun on polymer surfaces were evaluated. The modified surfaces were characterized by contact angle measurement, X-ray photoelectron spectroscopy and atomic force microscopy. The developed method was applied on both poly(methyl methacrylate) and cyclic olefin copolymer microchips. A fluorescently labeled myoglobin digest, binary protein mixture, and human serum sample were all separated in these surface-modified polymer microdevices. Our work exhibits an easy and reliable way to achieve favorable biomolecular separation performance in polymer microchips.

A general microchip surface modification approach using a spin-coated polymer resist film doped with hydroxypropyl cellulose

PubMed Central

Sun, Xiuhua; Yang, Weichun; Geng, Yanli; Woolley, Adam T.

2009-01-01

We have developed a simple and effective method for surface modification of polymer microchips by entrapping hydroxypropyl cellulose (HPC) in a spin-coated thin film on the surface. Poly(methyl methacrylate-8.5-methacrylic acid), a widely available commercial resist formulation, was utilized as a matrix for dissolving HPC and providing adherence to native polymer surfaces. Various amounts of HPC (0.1–2.0%) dissolved in the copolymer and spun on polymer surfaces were evaluated. The modified surfaces were characterized by contact angle measurement, X-ray photoelectron spectroscopy and atomic force microscopy. The developed method was applied on both poly(methyl methacrylate) and cyclic olefin copolymer microchips. A fluorescently labeled myoglobin digest, binary protein mixture, and human serum sample were all separated in these surface-modified polymer microdevices. Our work exhibits an easy and reliable way to achieve favorable biomolecular separation performance in polymer microchips. PMID:19294306

Development of a new dynamic method for quantitative evaluation of in vitro hemocompatibility of biomedical materials.

PubMed

Groth, T; Vassilieff, C; Wolf, H; Richter, G; Foerster, F

1992-01-01

In this study a new dynamic method is introduced allowing the estimation of blood cell adhesion on flat test surfaces by measuring the cell loss in the bulk phase of surface contacting test blood under defined rheological conditions. This was achieved by constructing a novel test chamber permitting the contact of small amounts of blood with a large geometrical test surface. The construction consists of a spiral-shaped flow channel of 0.3 cm width, 0.02 cm height and 78 cm length covered with the biomaterials to be tested from both sides. Laminarity of blood flow in the conduit was confirmed theoretically by the calculation of an equivalent to the Reynolds number for curved systems the so-called Dean number. Furthermore, flow laminarity was proved experimentally finding that the flow rate of blood with different hematocrit values was proportional to the hydrostatic pressure applied. The applicability of the novel 'spiral method' for the estimation of hemocompatibility was demonstrated by evaluation of platelet adhesion onto different polymers in comparison to siliconized and fibrinogen coated glass as reference surfaces. Additionally, it was possible under distinct conditions to determine the adhesion of leucocytes and the detachment of platelet aggregates. Therefore, it was concluded that the spiral method can be used for the assessment of the hemocompatibility of flat biomedical polymers. As main advantages of the new method can be considered the high time efficiency and accuracy without labelling or optical detection of adherent cells.

Energy-independent intracellular gene delivery mediated by polymeric biomimetics of cell-penetrating peptides.

PubMed

Chae, Su Young; Kim, Hyun June; Lee, Min Sang; Jang, Yeon Lim; Lee, Yuhan; Lee, Soo Hyeon; Lee, Kyuri; Kim, Sun Hwa; Kim, Hong Tae; Chi, Sang-Cheol; Park, Tae Gwan; Jeong, Ji Hoon

2011-09-09

Efficient gene transfer into mammalian cells mediated by small molecular amphiphile-polymer conjugates, bile acid-polyethylenimine (BA-PEI), is demonstrated, opening an efficient transport route for genetic materials across the cell membrane. This process occurs without the aid of endocytosis or other energy-consuming processes, thus mimicking macromolecular transduction by cell-penetrating peptides. The exposure of a hydrophilic face of the amphiphilic BA moiety on the surface of BA-PEI/DNA complex that mediates direct contact of the BA molecules to the cell surface seems to play an important role in the endocytosis- and energy-independent internalization process. The new modality of the polymeric biomimetics can be applied to enhanced delivery of macromolecular therapeutics. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multifunctional DNA-gold nanoparticles for targeted doxorubicin delivery.

PubMed

Alexander, Colleen M; Hamner, Kristen L; Maye, Mathew M; Dabrowiak, James C

2014-07-16

In this report we describe the synthesis, characterization, and cytotoxic properties of DNA-capped gold nanoparticles having attached folic acid (FA), a thermoresponsive polymer (p), and/or poly(ethylene glycol) (PEG) oligomers that could be used to deliver the anticancer drug doxorubicin (DOX) in chemotherapy. The FA-DNA oligomer used in the construction of the delivery vehicle was synthesized through the reaction of the isolated folic acid N-hydroxysuccinimide ester with the amino-DNA and the conjugated DNA product was purified using high performance liquid chromatography (HPLC). This approach ultimately allowed control of the amount of FA attached to the surface of the delivery vehicle. Cytotoxicity studies using SK-N-SH neuroblastoma cells with drug loaded delivery vehicles were carried out using a variety of exposure times (1-48 h) and recovery times (1-72 h), and in order to access the effects of varying amounts of attached FA, in culture media deficient in FA. DOX loaded delivery vehicles having 50% of the DNA strands with attached FA were more cytotoxic than when all of the strands contained FA. Since FA stimulates cell growth, the reduced cytotoxicity of vehicles fully covered with FA suggests that the stimulatory effects of FA can more than compensate for the cytotoxic effects of the drug on the cell population. While attachment of hexa-ethylene glycol PEG(18) to the surface of the delivery vehicle had no effect on cytotoxicity, 100% FA plus the thermoresponsive polymer resulted in IC50 = 0.48 ± 0.01 for an exposure time of 24 h and a recovery time of 1 h, which is an order of magnitude more cytotoxic than free DOX. Confocal microscopic studies using fluorescence detection showed that SK-N-SH neuroblastoma cells exposed to DOX-loaded vehicles have drug accumulation inside the cell and, in the case of vehicles with attached FA and thermoresponsive polymer, the drug appears more concentrated. Since the biological target of DOX is DNA, the latter observation is consistent with the high cytotoxicity of vehicles having both FA and the thermoresponsive polymer. The study highlights the potential of DNA-capped gold nanoparticles as delivery vehicles for doxorubicin in cancer chemotherapy.

3D microfluidic fabrication using a low refractive index polymer for clear microscopic observation at the fluid boundary

NASA Astrophysics Data System (ADS)

Hanada, Y.

2018-02-01

Microfluidic chips known as μ-TAS or LoC have become versatile tools in cell research, since functional biochips are able to streamline dynamic observations of various cells. Glass or polymers are generally used as the substrate due to their high transparency, chemical stability and cost-effectiveness. However, these materials are not well suited to the microscopic observation at the fluid boundary due to the refractive index mismatch between the medium and the biochip material. For this reason, we have developed a method of fabricating three-dimensional (3D) microfluidic chips made of a low refractive index fluoric polymer CYTOP. CYTOP has a refractive index of 1.34, a value that is almost equivalent to that of water. This optical property is very important for clear 3D microscopic observations of cell motion near the solid boundary, due to the minimal mismatch between the refractive index values of the medium and the CYTOP substrate. Therefore, CYTOP microfluidics are expected to allow the generation of clear images of unique cell migratory processes near the microfluidic sidewall. Therefore, we established the fabrication procedure involving the use of femtosecond laser direct writing, followed by wet etching and annealing, to create high-quality 3D microfluidics inside a polymer substrate. A microfluidic chip made in this manner enables us to more clearly observe areas near the fluid surface, compared to the observations possible using conventional microfluidic chips.

A multivariate approach using attenuated total reflectance mid-infrared spectroscopy to measure the surface mannoproteins and β-glucans of yeast cell walls during wine fermentations.

PubMed

Moore, John P; Zhang, Song-Lei; Nieuwoudt, Hélène; Divol, Benoit; Trygg, Johan; Bauer, Florian F

2015-11-18

Yeast cells possess a cell wall comprising primarily glycoproteins, mannans, and glucan polymers. Several yeast phenotypes relevant for fermentation, wine processing, and wine quality are correlated with cell wall properties. To investigate the effect of wine fermentation on cell wall composition, a study was performed using mid-infrared (MIR) spectroscopy coupled with multivariate methods (i.e., PCA and OPLS-DA). A total of 40 yeast strains were evaluated, including Saccharomyces strains (laboratory and industrial) and non-Saccharomyces species. Cells were fermented in both synthetic MS300 and Chardonnay grape must to stationery phase, processed, and scanned in the MIR spectrum. PCA of the fingerprint spectral region showed distinct separation of Saccharomyces strains from non-Saccharomyces species; furthermore, industrial wine yeast strains separated from laboratory strains. PCA loading plots and the use of OPLS-DA to the data sets suggested that industrial strains were enriched with cell wall proteins (e.g., mannoproteins), whereas laboratory strains were composed mainly of mannan and glucan polymers.

In-situ electrochemically active surface area evaluation of an open-cathode polymer electrolyte membrane fuel cell stack

NASA Astrophysics Data System (ADS)

Torija, Sergio; Prieto-Sanchez, Laura; Ashton, Sean J.

2016-09-01

The ability to evaluate the electrochemically active surface area (ECSA) of fuel cell electrodes is crucial toward characterising designs and component suites in-situ, particularly when evaluating component durability in endurance testing, since it is a measure of the electrode area available to take part in the fuel cell reactions. Conventional methods to obtain the ECSA using cyclic voltammetry, however, rely on potentiostats that cannot be easily scaled to simultaneously evaluate all cells in a fuel cell stack of practical size, which is desirable in fuel cell development. In-situ diagnostics of an open-cathode fuel cell stack are furthermore challenging because the cells do not each possess an enclosed cathode compartment; instead, the cathodes are rather open to the environment. Here we report on a diagnostic setup that allows the electrochemically active surface area of each cell anode or cathode in an open-cathode fuel cell stack to be evaluated in-situ and simultaneously, with high resolution and reproducibility, using an easily scalable chronopotentiometry methodology and a gas-tight stack enclosure.

Cell adhesion and proliferation on poly(tetrafluoroethylene) with plasma-metal and plasma-metal-carbon interfaces

NASA Astrophysics Data System (ADS)

Reznickova, Alena; Kvitek, Ondrej; Kolarova, Katerina; Smejkalova, Zuzana; Svorcik, Vaclav

2017-06-01

The aim of this article is to investigate the effect of the interface between plasma activated, gold and carbon coated poly(tetrafluoroethylene) (PTFE) on in vitro adhesion and spreading of mouse fibroblasts (L929). Surface properties of pristine and modified PTFE were studied by several experimental techniques. The thickness of a deposited gold film is an increasing function of the sputtering time, conversely thickness of carbon layer decreases with increasing distance between carbon source and the substrate. Because all the used surface modification techniques take place in inert Ar plasma, oxidized degradation products are formed on the PTFE surface, which affects wettability of the polymer surface. Cytocompatibility tests indicate that on samples with Au/C interface, the cells accumulate on the part of sample with evaporated carbon. Number of L929 cells proliferated on the studied samples is comparable to tissue culture polystyrene standard.

Modeling the effect of dynamic surfaces on membrane penetration

NASA Astrophysics Data System (ADS)

van Lehn, Reid; Alexander-Katz, Alfredo

2011-03-01

The development of nanoscale materials for targeted drug delivery is an important current pursuit in materials science. One task of drug carriers is to release therapeutic agents within cells by bypassing the cell membrane to maximize the effectiveness of their payload and minimize bodily exposure. In this work, we use coarse-grained simulations to study nanoparticles (NPs) grafted with hydrophobic and hydrophilic ligands that rearrange in response to the amphiphilic lipid bilayer. We demonstrate that this dynamic surface permits the NP to spontaneously penetrate to the bilayer midplane when the surface ligands are near an order-disorder transition. We believe that this work will lead to the design of new drug carriers capable of non-specifically accessing cell interiors based solely on their dynamic surface properties. Our work is motivated by existing nanoscale systems such as micelles, or NPs grafted with highly mobile ligands or polymer brushes.

Ordered quasi-two-dimensional structure of nanoparticles in semiflexible ring polymer brushes under compression

NASA Astrophysics Data System (ADS)

Hua, Yunfeng; Deng, Zhenyu; Jiang, Yangwei; Zhang, Linxi

2017-06-01

Molecular dynamics simulations of a coarse-grained bead-spring model of ring polymer brushes under compression are presented. Flexible polymer brushes are always disordered during compression, whereas semiflexible polymer brushes tend to be ordered under sufficiently strong compression. Further, the polymer monomer density of the semiflexible polymer brush is very high near the brush surface, inducing a peak value of the free energy near the surface. Therefore, when nanoparticles are compressed in semiflexible ring polymer brushes, they tend to exhibit a closely packed single-layer structure between the brush surface and the impenetrable wall, and a quasi-two-dimensional ordered structure near the brush surface is formed under strong compression. These findings provide a new approach to designing responsive applications.

Process for hardening the surface of polymers

DOEpatents

Mansur, Louis K.; Lee, Eal H.

1992-01-01

Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance.

Electron beam-induced graft polymerization of acrylic acid and immobilization of arginine-glycine-aspartic acid-containing peptide onto nanopatterned polycaprolactone.

PubMed

Sun, Hui; Wirsén, Anders; Albertsson, Ann-Christine

2004-01-01

Electron beam- (EB-) induced graft polymerization of acrylic acid and the subsequent immobilization of arginine-glycine-aspartic acid (RGD) peptide onto nanopatterned polycaprolactone with parallel grooves is reported. A high concentration of carboxylic groups was introduced onto the polymer substrate by EB-induced polymerization of acrylic acid. In the coupling of the RGD peptide to the carboxylated polymer surface, a three-step peptide immobilization process was used. This process included the activation of surface carboxylic acid into an active ester intermediate by use of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), the introduction of disulfide groups by use of 2-(2-pyridinyldithio)ethanamine hydrochloride (PDEA), and final immobilization of the peptide via a thiol-disulfide exchange reaction. The extent of coupling was measured by UV spectroscopy. A preliminary study of the in vitro behavior of keratinocytes (NCTC 2544) cultured on the acrylic acid-grafted and RGD peptide-coupled surface showed that most cells grown on the coupled samples had a spread-rounded appearance, while the majority of cells tended to be elongated along the grooves on uncoupled substrates.

Predictive Model for the Design of Zwitterionic Polymer Brushes: A Statistical Design of Experiments Approach.

PubMed

Kumar, Ramya; Lahann, Joerg

2016-07-06

The performance of polymer interfaces in biology is governed by a wide spectrum of interfacial properties. With the ultimate goal of identifying design parameters for stem cell culture coatings, we developed a statistical model that describes the dependence of brush properties on surface-initiated polymerization (SIP) parameters. Employing a design of experiments (DOE) approach, we identified operating boundaries within which four gel architecture regimes can be realized, including a new regime of associated brushes in thin films. Our statistical model can accurately predict the brush thickness and the degree of intermolecular association of poly[{2-(methacryloyloxy) ethyl} dimethyl-(3-sulfopropyl) ammonium hydroxide] (PMEDSAH), a previously reported synthetic substrate for feeder-free and xeno-free culture of human embryonic stem cells. DOE-based multifunctional predictions offer a powerful quantitative framework for designing polymer interfaces. For example, model predictions can be used to decrease the critical thickness at which the wettability transition occurs by simply increasing the catalyst quantity from 1 to 3 mol %.

Waterproofing in Arabidopsis: Following phenolics and lipids in situ by Confocal Raman Microscopy

NASA Astrophysics Data System (ADS)

Prats Mateu, Batirtze; Hauser, Marie-Theres; Heredia, Antonio; Gierlinger, Notburga

2016-02-01

Waterproofing of the aerial organs of plants imposed a big evolutionary step during the colonization of the terrestrial environment. The main plant polymers responsible of water repelling are lipids and lignin, which play also important roles in the protection against biotic/abiotic stresses, regulation of flux of gases and solutes and mechanical stability against negative pressure, among others. While the lipids, non-polymerized cuticular waxes together with the polymerized cutin, protect the outer surface, lignin is confined to the secondary cell wall within mechanical important tissues. In the present work a micro cross-section of the stem of Arabidopsis thaliana was used to track in situ the distribution of these non-carbohydrate polymers by Confocal Raman Microscopy. Raman hyperspectral imaging gives a molecular fingerprint of the native waterproofing tissues and cells with diffraction limited spatial resolution (~300 nm) at relatively high speed and without any tedious sample preparation. Lipids and lignified tissues as well as their effect on water content was directly visualized by integrating the 1299 cm-1, 1600 cm-1 and 3400 cm-1 band, respectively. For detailed insights into compositional changes of these polymers vertex component analysis was performed on selected sample positions. Changes have been elucidated in the composition of lignin within the lignified tissues and between interfascicular fibers and xylem vessels. Hydrophobising changes were revealed from the epidermal layer to the cuticle as well as a change in the aromatic composition within the cuticle of trichomes. To verify Raman signatures of different waterproofing polymers additionally Raman spectra of the cuticle and cutin monomer from tomato (Solanum lycopersicum) as well as aromatic model polymers (milled wood lignin and dehydrogenation polymer of coniferyl alcohol) and phenolic acids were acquired. Keywords: Arabidopsis thaliana, lignin, cutin, wax, Raman, cuticle, waterproofing, secondary cell wall, trichomes

Influence of Surface Properties on the Adhesion of Staphylococcus epidermidis to Acrylic and Silicone

PubMed Central

Sousa, Cláudia; Teixeira, Pilar; Oliveira, Rosário

2009-01-01

The aim of the present study was to compare the ability of eight Staphylococcus epidermidis strains to adhere to acrylic and silicone, two polymers normally used in medical devices manufacture. Furthermore, it was tried to correlate that with the surface properties of substrata and cells. Therefore, hydrophobicity and surface tension components were calculated through contact angle measurements. Surface roughness of substrata was also assessed by atomic force microscopy (AFM). No relationship was found between microbial surface hydrophobicity and adhesion capability. Nevertheless, Staphylococcus epidermidis IE214 showed very unique adhesion behaviour, with cells highly aggregated between them, which is a consequence of their specific surface features. All strains, determined as being hydrophilic, adhered at a higher extent to silicone than to acrylic, most likely due to its more hydrophobic character and higher roughness. This demonstrates the importance of biomaterial surface characteristics for bacterial adhesion. PMID:20126579

A polymer foam conduit seeded with Schwann cells promotes guided peripheral nerve regeneration.

PubMed

Hadlock, T; Sundback, C; Hunter, D; Cheney, M; Vacanti, J P

2000-04-01

Alternatives to autografts have long been sought for use in bridging neural gaps. Many entubulation materials have been studied, although with generally disappointing results in comparison with autografts. The purpose of this study was to design a more effective neural guidance conduit, to introduce Schwann cells into the conduit, and to determine regenerative capability through it in an in vivo model. A novel, fully biodegradable polymer conduit was designed and fabricated for use in peripheral nerve repair, which approximates the macro- and microarchitecture of native peripheral nerves. It comprised a series of longitudinally aligned channels, with diameters ranging from 60 to 550 microns. The lumenal surfaces promoted the adherence of Schwann cells, whose presence is known to play a key role in nerve regeneration. This unique channel architecture increased the surface area available for Schwann cell adherence up to five-fold over that available through a simple hollow conduit. The conduit was composed of a high-molecular-weight copolymer of lactic and glycolic acids (PLGA) (MW 130,000) in an 85:15 monomer ratio. A novel foam-processing technique, employing low-pressure injection molding, was used to create highly porous conduits (approximately 90% pore volume) with continuous longitudinal channels. Using this technique, conduits were constructed containing 1, 5, 16, 45, or more longitudinally aligned channels. Prior to cellular seeding of these conduits, the foams were prewet with 50% ethanol, flushed with physiologic saline, and coated with laminin solution (10 microg/mL). A Schwann cell suspension was dynamically introduced into these processed foams at a concentration of 5 X 10(5) cells/mL, using a simple bioreactor flow loop. In vivo regeneration studies were carried out in which cell-laden five-channel polymer conduits (individual channel ID 500 microm, total conduit OD 2.3 mm) were implanted across a 7-mm gap in the rat sciatic nerve (n = 4), and midgraft axonal regeneration compared with autografts (n = 6). At 6 weeks, axonal regeneration was observed in the midconduit region of all five channels in each experimental animal. The cross-sectional area comprising axons relative to the open conduit cross sectional area (mean 26.3%, SD 10. 1%) compared favorably with autografts (mean 23.8%, SD 3.6%). Our methodology can be used to create polymer foam conduits containing longitudinally aligned channels, to introduce Schwann cells into them, and to implant them into surgically created neural defects. These conduits provide an environment permissive to axonal regeneration. Furthermore, this polymer foam-processing method and unique channeled architecture allows the introduction of neurotrophic factors into the conduit in a controlled fashion. Deposition of different factors into distinct regions within the conduit may be possible to promote more precisely guided neural regeneration.

Cell sheet engineering: a unique nanotechnology for scaffold-free tissue reconstruction with clinical applications in regenerative medicine.

PubMed

Elloumi-Hannachi, I; Yamato, M; Okano, T

2010-01-01

Cell sheet technology (CST) is based on the use of thermoresponsive polymers, poly(N-isopropylacrylamide) (PIPAAm). The surface of PIPAAms is formulated in such a way as to make its typical thickness <100 nm. In this review, we first focus on how the methods of PIPAAm-grafted surface preparations and functionalization are important to be able to harvest a functional cell sheet, to be further transplanted. Then, we present aspects of tissue mimics and three-dimensional reconstruction of a tissue in vitro. Finally, we give an overview of clinical applications and clinically relevant animal experimentations of the technology, such as cardiomyopathy, visual acuity, periodonty, oesophageal ulcerations and type 1 diabetes.

Surface Grafting of Thermoresponsive Microgel Nanoparticles (Postprint)

DTIC Science & Technology

2011-01-01

and cell immobilization, as biosensors, and for in vivo drug delivery .33,34,36,49–53 PNIPAM-containing microgels have been synthesized and...2007, 25, 577–583. 51 J. Jagur-Grodzinski, Polym. Adv. Technol., 2010, 21, 27–47.Soft Matter52 M. Hamidi, A. Azadi and P. Rafiei,Adv. Drug Delivery ...prospective applications in micro- and nanofluidics, biocompatible materials, controlled drug release, nano- and biotribology, controlled cell growth

Filtration device for rapid separation of biological particles from complex matrices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sangil; Naraghi-Arani, Pejman; Liou, Megan

2018-01-09

Methods and systems for filtering of biological particles are disclosed. Filtering membranes separate adjacent chambers. Through osmotic or electrokinetic processes, flow of particles is carried out through the filtering membranes. Cells, viruses and cell waste can be filtered depending on the size of the pores of the membrane. A polymer brush can be applied to a surface of the membrane to enhance filtering and prevent fouling.

Enhancement of Photovoltaic Performance by Utilizing Readily Accessible Hole Transporting Layer of Vanadium(V) Oxide Hydrate in a Polymer-Fullerene Blend Solar Cell.

PubMed

Jiang, Youyu; Xiao, Shengqiang; Xu, Biao; Zhan, Chun; Mai, Liqiang; Lu, Xinhui; You, Wei

2016-05-11

Herein, a successful application of V2O5·nH2O film as hole transporting layer (HTL) instead of PSS in polymer solar cells is demonstrated. The V2O5·nH2O layer was spin-coated from V2O5·nH2O sol made from melting-quenching sol-gel method by directly using vanadium oxide powder, which is readily accessible and cost-effective. V2O5·nH2O (n ≈ 1) HTL is found to have comparable work function and smooth surface to that of PSS. For the solar cell containing V2O5·nH2O HTL and the active layer of the blend of a novel polymer donor (PBDSe-DT2PyT) and the acceptor of PC71BM, the PCE was significantly improved to 5.87% with a 30% increase over 4.55% attained with PSS HTL. Incorporation of V2O5·nH2O as HTL in the polymer solar cell was found to enhance the crystallinity of the active layer, electron-blocking at the anode and the light-harvest in the wavelength range of 400-550 nm in the cell. V2O5·nH2O HTL improves the charge generation and collection and suppress the charge recombination within the PBDSe-DT2PyT:PC71BM solar cell, leading to a simultaneous enhancement in Voc, Jsc, and FF. The V2O5·nH2O HTL proposed in this work is envisioned to be of great potential to fabricate highly efficient PSCs with low-cost and massive production.

Poly(ethylene oxide) surfactant polymers.

PubMed

Vacheethasanee, Katanchalee; Wang, Shuwu; Qiu, Yongxing; Marchant, Roger E

2004-01-01

We report on a series of structurally well-defined surfactant polymers that undergo surface-induced self-assembly on hydrophobic biomaterial surfaces. The surfactant polymers consist of a poly(vinyl amine) backbone with poly(ethylene oxide) and hexanal pendant groups. The poly(vinyl amine) (PVAm) was synthesized by hydrolysis of poly(N-vinyl formamide) following free radical polymerization of N-vinyl formamide. Hexanal and aldehyde-terminated poly(ethylene oxide) (PEO) were simultaneously attached to PVAm via reductive amination. Surfactant polymers with different PEO:hexanal ratios and hydrophilic/hydrophobic balances were prepared, and characterized by FT-IR, 1H-NMR and XPS spectroscopies. Surface active properties at the air/water interface were determined by surface tension measurements. Surface activity at a solid surface/water interface was demonstrated by atomic force microscopy, showing epitaxially molecular alignment for surfactant polymers adsorbed on highly oriented pyrolytic graphite. The surfactant polymers described in this report can be adapted for simple non-covalent surface modification of biomaterials and hydrophobic surfaces to provide highly hydrated interfaces.

Novel conjugates of peptides and conjugated polymers for optoelectronics and neural interfaces

NASA Astrophysics Data System (ADS)

Bhagwat, Nandita

Peptide-polymer conjugates are a novel class of hybrid materials that take advantage of each individual component giving the opportunity to generate materials with unique physical, chemical, mechanical, optical, and electronic properties. In this dissertation peptide-polymer conjugates for two different applications are discussed. The first set of peptide-polymer conjugates were developed as templates to study the intermolecular interactions between electroactive molecules by manipulating the intermolecular distances at nano-scale level. A PEGylated, alpha-helical peptide template was employed to effectively display an array of organic chromophores (oxadiazole containing phenylenevinylene oligomers, Oxa-PPV). Three Oxa-PPV chromophores were strategically positioned on each template, at distances ranging from 6 to 17 A from each other, as dictated by the chemical and structural properties of the peptide. The Oxa-PPV modified PEGylated helical peptides (produced via Heck coupling strategies) were characterized by a variety of spectroscopic methods. Electronic contributions from multiple pairs of chromophores on a scaffold were detectable; the number and relative positioning of the chromophores dictated the absorbance and emission maxima, thus confirming the utility of these polymer--peptide templates for complex presentation of organic chromophores. The rest of the thesis is focused on using poly(3,4-alkylenedioxythiophene) based conjugated polymers as coatings for neural electrodes. This thiophene derivative is of considerable current interest for functionalizing the surfaces of a wide variety of devices including implantable biomedical electronics, specifically neural bio-electrodes. Toward these ends, copolymer films of 3,4-ethylenedioxythiophene (EDOT) with a carboxylic acid functional EDOT (EDOTacid) were electrochemically deposited and characterized as a systematic function of the EDOTacid content (0, 25, 50, 75, and 100%). The chemical surface characterization of the films confirmed the presence of both EODT and EDOTacid units. Cyclic voltammetry showed that the films had comparable charge storage capacities regardless of their composition. The morphology of the films varied depending on the monomer feed ratio. Thus we were able to develop a method for synthesizing electrically active carboxylic acid functional poly(3,4-ethylenedioxythiophene) copolymer films with tunable hydrophilicities and surface morphologies. For longer lifetime devices incorporating a biomolecule via covalent immobilization techniques are preferred over physical adsorption or entrapment. We took advantage of the carboxylic acid group on the PEDOTacid copolymer films to modify the surface of these films with a laminin based peptide, the nonapeptide sequence CDPGYIGSR. XPS and toluidine blue O assay proved the presence of the peptide on the surface and electrochemical analysis demonstrated unaltered properties of the peptide modified films. The bioactivity of the peptide along with the need of a spacer molecule for cell adhesion and differentiation was tested using the rat pheochromocytoma (PC12) cells. Films modified with the longest poly(ethylene glycol) spacer used in this study, a 3 nm long molecule, demonstrated the best attachment and neurite outgrowth compared to films with peptides with no spacer and a 1 nm spacer, PEG3. The films with PEG10-CDPGYISGR covalently modified to the surface demonstrated 11.5% neurite expression with the mean neurite length of 90 microm. Along with the acid functionalized PEDOT films, vinyl terminated ProDOT films were also investigated as coatings for neural electrodes. The vinyl group was successfully modified with a RGD peptide via thiol-ene click chemistry. Both the acid and vinyl functional conducting polymer films provide an effective approach to biofunctionalize conducting polymer films.

Donor polymer design enables efficient non-fullerene organic solar cells

PubMed Central

Li, Zhengke; Jiang, Kui; Yang, Guofang; Lai, Joshua Yuk Lin; Ma, Tingxuan; Zhao, Jingbo; Ma, Wei; Yan, He

2016-01-01

To achieve efficient organic solar cells, the design of suitable donor–acceptor couples is crucially important. State-of-the-art donor polymers used in fullerene cells may not perform well when they are combined with non-fullerene acceptors, thus new donor polymers need to be developed. Here we report non-fullerene organic solar cells with efficiencies up to 10.9%, enabled by a novel donor polymer that exhibits strong temperature-dependent aggregation but with intentionally reduced polymer crystallinity due to the introduction of a less symmetric monomer unit. Our comparative study shows that an analogue polymer with a C2 symmetric monomer unit yields highly crystalline polymer films but less efficient non-fullerene cells. Based on a monomer with a mirror symmetry, our best donor polymer exhibits reduced crystallinity, yet such a polymer matches better with small molecular acceptors. This study provides important insights to the design of donor polymers for non-fullerene organic solar cells. PMID:27782112

Atomic Oxygen Erosion Yield Dependence Upon Texture Development in Polymers

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Loftus, Ryan J.; Miller, Sharon K.

2016-01-01

The atomic oxygen erosion yield (volume of a polymer that is lost due to oxidation per incident atom) of polymers is typically assumed to be reasonably constant with increasing fluence. However polymers containing ash or inorganic pigments, tend to have erosion yields that decrease with fluence due to an increasing presence of protective particles on the polymer surface. This paper investigates two additional possible causes for erosion yields of polymers that are dependent upon atomic oxygen. These are the development of surface texture which can cause the erosion yield to change with fluence due to changes in the aspect ratio of the surface texture that develops and polymer specific atomic oxygen interaction parameters. The surface texture development under directed hyperthermal attack produces higher aspect ratio surface texture than isotropic thermal energy atomic oxygen attack. The fluence dependence of erosion yields is documented for low Kapton H (DuPont, Wilmington, DE) effective fluences for a variety of polymers under directed hyperthermal and isotropic thermal energy attack.

Glycodendritic structures: promising new antiviral drugs.

PubMed

Rojo, Javier; Delgado, Rafael

2004-09-01

DC-SIGN, a C-type lectin expressed by dendritic cells, is able to recognize high mannosylated glycoproteins at the surface of a broad range of pathogens including viruses, bacteria, fungi and parasites. For at least some of these agents this interaction appears to be an important part of the infection process. Therefore, this lectin might be considered in the design of new antiviral drugs. In this manner, multivalent carbohydrate systems based on dendrimers and dendritic polymers are promising candidates as antiviral drugs. Boltorn hyperbranched dendritic polymers functionalized with mannose have been used to inhibit DC-SIGN-mediated infection in an Ebola-pseudotyped viral model. Their physiological solubility, lack of toxicity and especially their low price suggest the application of these glycodendritic polymers for possible formulation as microbicides.

Mechanics governs single-cell signaling and multi-cell robustness in biofilm infections

NASA Astrophysics Data System (ADS)

Gordon, Vernita

In biofilms, bacteria and other microbes are embedded in extracellular polymers (EPS). Multiple types of EPS can be produced by a single bacterial strain - the reasons for this redundancy are not well-understood. Our work suggests that different polymers may confer distinct mechanical benefits. Our model organism is Pseudomonas aeruginosa, an opportunistic human pathogen that forms chronic biofilm infections associated with increased antibiotic resistance and evasion of the immune defense. Biofilms initiate when bacteria attach to a surface, sense the surface, and change their gene expression. Changes in gene expression are regulated by a chemical signal, cyclic-di-GMP. We find that one EPS material, called ``PEL,'' enhances surface sensing by increasing mechanical coupling of single bacteria to the surface. Measurements of bacterial motility suggest that PEL may increase frictional interactions between the surface and the bacteria. Consistent with this, we show that bacteria increase cyclic-di-GMP signaling in response to mechanical shear stress. Mechanosensing has long been known to be important to the function of cells in higher eukaryotes, but this is one of only a handful of studies showing that bacteria can sense and respond to mechanical forces. For the mature biofilm, the embedding polymer matrix can protect bacteria both chemically and mechanically. P. aeruginosa infections in the cystic fibrosis (CF) lung often last for decades, ample time for the infecting strain(s) to evolve. Production of another EPS material, alginate, is well-known to tend to increase over time in CF infections. Alginate chemically protects biofilms, but also makes them softer and weaker. Recently, it is being increasingly recognized that bacteria in chronic CF infections also evolve to increase PSL production. We use oscillatory bulk rheology to determine the unique contributions of EPS materials to biofilm mechanics. Unlike alginate, increased PSL stiffens biofilms. Increasing both PSL and alginate expression increases the energy cost to break the biofilm. We compare the elastic moduli of biofilms to estimated stresses exerted by phagocytotic immune cells, and infer that increased PSL could confer a mechanical fitness benefit. This work was supported by start-up funds from The University of Texas at Austin and a gift from ExxonMobile to VDG, and by Grants from the Human Frontiers Science Program (HFSP RGY0081/2012-GORDON) and the National Science Foundation (NSF 1337670).

Process for hardening the surface of polymers

DOEpatents

Mansur, L.K.; Lee, E.H.

1992-07-14

Hard surfaced polymers and the method for making them is generally described. Polymers are subjected to simultaneous multiple ion beam bombardment, that results in a hardening of the surface and improved wear resistance. 1 figure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yee, J.P.

The following studies were conducted using the resistive pulse spectroscopy (RPS) technique: cumulative spectra and individual pulse forms for rigid latex polymer spheres; acquisition and analysis of RPS spectral data by means of special computer program; interaction of red blood cells with glutaraldehyde; membrane properties of erythrocytes undergoing abrupt osmotic hemolysis; reversible effects of the binding of chlorpromazine HCl at the red cell membrane surface; effects of high cholesterol diet on erythrocytes of guinea pigs; and multi-population analysis for a mixture of fetal and maternal red cells. (HLW)

Bioactivity of Hybrid Polymeric Magnetic Nanoparticles and Their Applications in Drug Delivery.

PubMed

Mohammed, Leena; Ragab, Doaa; Gomaa, Hassan

2016-01-01

Engineered magnetic nanoparticles (MNPs) possess unique properties and hold great potential in biomedicine and clinical applications. With their magnetic properties and their ability to work at cellular and molecular level, MNP have been applied both in-vitro and in-vivo in targeted drug delivery and imaging. Focusing on Iron Oxide Superparamagnetic nanoparticles (SPIONs), this paper elaborates on the recent advances in development of hybrid polymeric-magnetic nanoparticles. Their main applications in drug delivery include Chemotherapeutics, Hyperthermia treatment, Radio-therapeutics, Gene delivary, and Biotheraputics. Physiochemical properties such as size, shape, surface and magnetic properties are key factors in determining their behavior. Additionally tailoring SPIONs surface is often vital for desired cell targetting and improved efficiency. Polymer coating is specifically reviewed with brief discussion of SPIONs administration routes. Commonly used drug release models for describing release mechanisms and the nanotoxicity aspects are also discussed. This review focus on superparamagnetic nanoparticles coated with different types of polymers starting with the key physiochemical features that dominate their behavior. The importance of surface modification is addressed. Subsequently, the major classes of polymer modified iron oxide nanoparticles is demonstrated according to their clinical use and application. Clinically approved nanoparticles are then addressed and the different routes of administration are mentioned. Lastly, mathematical models of drug release profile of the common used nanoparticles are addressed. MNPs emerging in recent medicine are remarkable for both imaging and therapeutics, particularly, as drug carriers for their great potential in targeted delivery and cancer treatment. Targeting ability and biocompatibility can be improved though surface coating which provides a mean to alter the surface features including physical characteristics and chemical functionality. The use of biocompatible polymers can prevent aggregation, increase colloidal stability, evades nanoparticles uptake by RES, and can provide a surface for conjugation of targeting ligands such as peptide and biomolecules with high affinity to target cells. Great efforts to bring MNPs from lab testing stage to clinic are needed to understand their physicochemical properties and how they behave in vivo, which resulted in few of them to exist in the market today. Although magnetic nanoparticles have not yet fully reached their optimal safety and efficiency due to the challenges they face in vivo, their shortcomings can be overcome through improvement of magnetictargeted carrier by pre-clinical trials and continuous studies.

Method of making a coating of a microtextured surface

DOEpatents

Affinito, John D [Tucson, AZ; Graff, Gordon L [West Richland, WA; Martin, Peter M [Kennewick, WA; Gross, Mark E [Pasco, WA; Burrows, Paul E [Kennewick, WA; Sapochak, Linda S [Henderson, NV

2004-11-02

A method for conformally coating a microtextured surface. The method includes flash evaporating a polymer precursor forming an evaporate, passing the evaporate to a glow discharge electrode creating a glow discharge polymer precursor plasma from the evaporate, cryocondensing the glow discharge polymer precursor plasma on the microtextured surface and crosslinking the glow discharge polymer precursor plasma thereon, wherein the crosslinking resulting from radicals created in the glow discharge polymer precursor plasma.

Polymerisation par plasma a pression atmospherique: Caracterisation des depots et leurs applications en biotechnologies

NASA Astrophysics Data System (ADS)

Girard-Lauriault, Pierre-Luc

Nitrogen (N)-containing polymer surfaces are attractive in numerous technological contexts, for example in biomedical applications. Here, we have used an atmospheric-pressure dielectric barrier discharge (DBD) apparatus to deposit novel families of N-rich plasma polymers, designated PP:N, using mixtures of three different hydrocarbon precursors (methane, ethylene, and acetylene) in nitrogen at varying respective gas flow ratios, typically parts per thousand. In preparation for subsequent cell-surface interaction studies, the first part of this research focuses on the chemical mapping of those materials, with specific attention to (semi)- quantitative analyses of functional groups. Well-established and some lesser-known analytical techniques have been combined to provide the best possible chemical and structural characterisations of these three families of PP:N thin films; namely, X-ray photoelectron spectroscopy (XPS), Near-edge X-ray absorption fine structure (NEXAFS), Fourier transform infrared spectroscopy (FTIR), contact angle goniometry (CAG), and elemental analysis (EA). High, "tunable" total nitrogen content was measured by both XPS and EA (between 6% and 25% by EA, or between 10% and 40% by XPS, which cannot detect hydrogen). Chemical derivatisation with 4-trifluoromethylbenzaldehyde (TFBA) enabled measurements of primary amine concentrations, the functionality of greatest bio-technological interest, which were found to account for 5 % to 20 % of the total bound nitrogen. By combining the above-mentioned complementary methods, we were further able to determine the complete chemical formulae, the degrees of unsaturation, and other major chemical functionalities in PP:N film structures. Several of these features are believed to be without precedents in the literature on hydrocarbon plasma polymers, for example measurements of absolute compositions (including hydrogen), and of unsaturation. It was shown that besides amines, nitriles, isonitriles and imines are the main nitrogenated functional groups in those materials. In a second part of this work, we have studied the interraction of these well-characterised surfaces with living cells. We have first demonstrated the adhesion, on both uniformly coated and micro-patterned PP:N deposits on BOPP, of three different cell types, namely, growth plate and articular chondrocytes, as well as U937 monocytes, the latter of which do not adhere at all to synthetic polymers used in tissue culture. In an effort to gain insight into cell adhesion mechanisms, we conducted a series of experiments where we cultured U937 monocytes on PP:N, as well as on two other families of chemically well-characterised N-rich thin films, the latter deposited by low pressure RF plasma and by vacuum ultra-violet (VUV) photo-polymerisation ("PVP:N" films). It was first shown that there exist sharply-defined ("critical") surface-chemical conditions that are necessary to induce cell adhesion. By comparing the extensively-characterised film chemistries at the " critical " conditions, we have clearly demonstrated the dominant role of primary amines in the cell adhesion mechanism. In the final aspect of this work, quantitative real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) experiments were conducted using U937 cells that had been made to adhere on PP:N and PVP:N materials for up to 24h. We have shown that the adhesion of U937 monocytes to PP:N and PVP:N surfaces induced a transient expression of cytokines, markers of macrophage activation, as well as a sustained expression of PPARgamma and ICAM-I, implicated in the adhesion and retention of monocytes. Keywords: biomaterials; dielectric barrier discharges (DBD); deposition; plasma polymerisation; ESCA/XPS; NEXAFS; FTIR; primary amines; cell adhesion; gene expression.

Direct observation of hole transfer from semiconducting polymer to carbon nanotubes.

PubMed

Lan, Fei; Li, Guangyong

2013-05-08

Carbon nanotubes have been proven to play significant roles in polymer-based solar cells. However, there is intensive debate on whether carbon nanotube behaves as a donor or acceptor in the semiconducting polymer:carbon nanotube composite. In this paper, we report a direct observation via Kelvin probe force microscopy (KPFM) that single walled carbon nanotubes (SWNTs) behave as hole transporting channels in poly(3-hexylthiophene-2,5-diyl) (P3HT)/SWNT heterojunctions. By comparing the surface potential (SP) change of SWNT in dark and under illumination, we observed that electrons are blocked from SWNT while holes are transferred to SWNT. This observation can be well-explained by our proposed band alignment model of P3HT/SWNT heterojunction. The finding is further verified by hole mobility measurement using the space charge limited current (SCLC) method. SCLC results indicate that the existence of small amount of SWNT (wt 0.5%) promotes device hole mobility to around 15-fold, indicating SWNT act as hole transfer channel. Our finding of hole transporting behavior of SWNT in P3HT/SWNT blend will provide a useful guidance for enhancing the performance of polymer solar cells by carbon nanotubes.

Rechargeable solid polymer electrolyte battery cell

DOEpatents

Skotheim, Terji

1985-01-01

A rechargeable battery cell comprising first and second electrodes sandwiching a solid polymer electrolyte comprising a layer of a polymer blend of a highly conductive polymer and a solid polymer electrolyte adjacent said polymer blend and a layer of dry solid polymer electrolyte adjacent said layer of polymer blend and said second electrode.

Polymer surface treatment with particle beams

DOEpatents

Stinnett, Regan W.; VanDevender, J. Pace

1999-01-01

A polymer surface and near surface treatment process produced by irradiation with high energy particle beams. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications.

Effect of cationic contaminants on polymer electrolyte fuel cell performance

NASA Astrophysics Data System (ADS)

Qi, Jing; Wang, Xiaofeng; Ozdemir, M. Ozan; Uddin, Md. Aman; Bonville, Leonard; Pasaogullari, Ugur; Molter, Trent

2015-07-01

The effect of cationic contaminants on polymer electrolyte fuel cell (PEFC) performance is investigated via in-situ injection of dilute cationic salt solutions. Four foreign cations (K+, Ba2+, Ca2+, Al3+) are chosen as contaminants in this study due to their prevalence and chemical structure (e.g. valence), however contaminants that have already received extensive coverage in the literature like sodium and iron are excluded. It is found that the cells with Ba(ClO4)2 and Ca(ClO4)2 injection exhibit little cell performance change during the current hold test, and the cells with Al(ClO4)3 and KClO4 injection show larger cell performance changes, i.e. decreasing cell voltage and increasing cell resistance. These cells with in-situ contaminant injection have a tendency to recover a portion of the lost performance after the recovery test when switched back to supersaturated air. The degradation in cell performance with the presence of cationic contaminants is mainly due, in addition to the membrane resistance increase associated with replacing protons on the sulfonate groups, to the increase in mass transport resistance and decrease in electrochemical surface area.

Molecular Level Investigations of Interfacial Friction of Polymer Brush Surfaces

NASA Astrophysics Data System (ADS)

Perry, Scott

2005-03-01

The development of synthetic polymer lubricants to mimic joint lubrication within the human body will be presented. Unlike most industrial applications involving oils and greases, lubrication of these joints is accomplished in an aqueous environment. Fundamentally, water is a poor lubricant in most settings due to the weak pressure dependence of its viscosity, yet the contacting surfaces of skeletal joints function with low friction throughout a lifetime. Motivated by the molecular structure of materials making up joint surfaces, interfacial friction between polymer brush surfaces under aqueous environments has been probed with an array of molecularly sensitive surface analytical techniques including atomic force microscopy. The brush surfaces, comprised of poly(L-lysine)-g-poly(ethylene glycol) (PLL-g-PEG), have been generated through the spontaneous adsorption of polymer from solution onto oxide substrates and sodium borosilicate surfaces (AFM tip). The character of the polymer films has been investigated in-situ with the quartz crystal microbalance (QCM) and atomic force microscope (AFM) and ex-situ with ellipsometry and X-ray photoelectron spectroscopy (XPS). The interfacial friction measurements have been carried out on polymer-coated substrates with bare or polymer-coated, microsphere-attached tips in over a range of solution conditions. It was found that the adsorption of polymer on oxides strikingly reduced the interfacial friction, resulting in ultra-low friction under certain conditions. By using a series of PLL-g-PEG polymers differing from each other in PEG side-chain length and grafting ratio, we observed that frictional properties of polymer-coated interfaces strongly depend on the architecture of PLL-g-PEG. Polymer-film formation and the influence of polymer architecture will be reviewed while the role of solvent and manifestation of ultra-low friction will be discussed in detail.

Experimental studies of contact angle hysteresis phenomena on polymer surfaces – Toward the understanding and control of wettability for different applications.

PubMed

Grundke, K; Pöschel, K; Synytska, A; Frenzel, R; Drechsler, A; Nitschke, M; Cordeiro, A L; Uhlmann, P; Welzel, P B

2015-08-01

Contact angle hysteresis phenomena on polymer surfaces have been studied by contact angle measurements using sessile liquid droplets and captive air bubbles in conjunction with a drop shape method known as Axisymmetric Drop Shape Analysis - Profile (ADSA-P). In addition, commercially available sessile drop goniometer techniques were used. The polymer surfaces were characterized with respect to their surface structure (morphology, roughness, swelling) and surface chemistry (elemental surface composition, acid-base characteristics) by scanning electron microscopy (SEM), scanning force microscopy (SFM), ellipsometry, X-ray photoelectron spectroscopy (XPS) and streaming potential measurements. Heterogeneous polymer surfaces with controlled roughness and chemical composition were prepared by different routes using plasma etching and subsequent dip coating or grafting of polymer brushes, anodic oxidation of aluminium substrates coated with thin polymer films, deposition techniques to create regular patterned and rough fractal surfaces from core-shell particles, and block copolymers. To reveal the effects of swelling and reorientation at the solid/liquid interface contact angle hysteresis phenomena on polyimide surfaces, cellulose membranes, and thermo-responsive hydrogels have been studied. The effect of different solutes in the liquid (electrolytes, surfactants) and their impact on contact angle hysteresis were characterized for solid polymers without and with ionizable functional surface groups in aqueous electrolyte solutions of different ion concentrations and pH and for photoresist surfaces in cationic aqueous surfactant solutions. The work is an attempt toward the understanding of contact angle hysteresis phenomena on polymer surfaces aimed at the control of wettability for different applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Polymer Scaffolds with Preferential Parallel Grooves Enhance Nerve Regeneration

PubMed Central

Mobasseri, Atefeh; Faroni, Alessandro; Minogue, Ben M.; Downes, Sandra; Reid, Adam J.

2015-01-01

We have modified the surface topography of poly ɛ-caprolactone (PCL) and polylactic acid (PLA) blended films to improve cell proliferation and to guide the regeneration of peripheral nerves. Films with differing shaped grooves were made using patterned silicon templates, sloped walls (SL), V-shaped (V), and square-shaped (SQ), and compared with nongrooved surfaces with micropits. The solvent cast films were tested in vitro using adult adipose-derived stem cells differentiated to Schwann cell-like cells. Cell attachment, proliferation, and cell orientation were all improved on the grooved surfaces, with SL grooves giving the best results. We present in vivo data on Sprague-Dawley rat sciatic nerve injury with a 10-mm gap, evaluating nerve regeneration at 3 weeks across a polymer nerve conduit modified with intraluminal grooves (SL, V, and SQ) and differing wall thicknesses (70, 100, 120, and 210 μm). The SL-grooved nerve conduit showed a significant improvement over the other topographical-shaped grooves, while increasing the conduit wall thickness saw no positive effect on the biological response of the regenerating nerve. Furthermore, the preferred SL-grooved conduit (C) with 70 μm wall thickness was compared with the current clinical gold standard of autologous nerve graft (Ag) in the rat 10-mm sciatic nerve gap model. At 3 weeks postsurgery, all nerve gaps across both groups were bridged with regenerated nerve fibers. At 16 weeks, features of regenerated axons were comparable between the autograft (Ag) and conduit (C) groups. End organ assessments of muscle weight, electromyography, and skin reinnervation were also similar between the groups. The comparable experimental outcome between conduit and autograft, suggests that the PCL/PLA conduit with inner lumen microstructured grooves could be used as a potential alternative treatment for peripheral nerve repair. PMID:25435096

Nanographene synthesized in triple-phase plasmas as a highly durable support of catalysts for polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Amano, Tomoki; Kondo, Hiroki; Takeda, Keigo; Ishikawa, Kenji; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

2018-04-01

Nanographene was synthesized in triple-phase plasmas comprising a gaseous phase, a gas-liquid boundary layer, and an in-liquid phase using a setup in which one electrode was placed in the gaseous phase while the other was immersed in the liquid phase. The triple-phase plasmas were generated using a pure alcohol, such as ethanol, 1-propanol, or 1-butanol, by applying a high voltage to a pair of electrodes made of copper or graphite. The nanographene synthesized using ethanol had high durability and thus could serve as a catalyst support in polymer electrolyte fuel cells (PEFCs). The PEFCs exhibited low degradation rates in the high-potential cycle test of a half-cell, as a result of which, a loss of only 10% was observed in the effective electrochemical surface area of Pt, even after 10,000 cycles.