|Articles about Biomaterials|
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| Gel strength and solution viscosity of temperature-sensitive, in-situ-gelling polymers for endovascular embolization
Vernon, B. and A. Martinez (2005), J Biomater Sci Polym Ed 16(9): 1153-66.
Abstract: The goal of this work was to investigate the relationship of the gel strength and stiffness (at 37 degrees C) to solution viscosity (at 25 degrees C) in poly(N-isopropylacrylamide-co-acrylic acid) solutions with regard to acid content, molecular weight and solution concentration. It was hypothesized that the gel strength could be maximized while minimizing the increase in solution viscosity. If so, there would be motivation to investigate these materials for arteriovenous malformation embolization. The co-polymers were synthesized with 0-2 mol% content of acrylic acid (AAc) in benzene, dioxane, THF, 50:50 benzene/dioxane, or 50:50 dioxane/THF to obtain polymers of different molecular weight. The polymers were characterized for molecular weight by GPC/light scattering, for acrylic acid content by acid titration, for lower critical solution temperature by differential scanning calorimetry, and for solution viscosity (at 25 degrees C) and gel strength (at 37 degrees C) by rheometry. Solutions of lower-molecular-weight polymers were shown to have lower viscosities while possessing higher strengths as gels than the highest manageable concentrations of higher-molecular-weight polymers. This work demonstrates that the mechanical properties of poly(N-isopropylacrylamide-co-acrylic acid) can be increased while minimizing the increase in solution viscosity.
| Gelatin blending improves the performance of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) films for biomedical application
Wang, Y. W., Q. Wu, et al. (2005), Biomacromolecules 6(2): 566-71.
Abstract: To improve the performance of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), gelatin was blended with PHBHHx at different ratios. With increasing gelatin content, the weight loss of gelatin/PHBHHx blend in simulated body fluid at 37 degrees C was accelerated. After 2 months, there was about 15% weight loss in PHBHHx blending with 30% gelatin. Scanning electron microscopy and X-ray diffraction results showed that gelatin blending increased the surface porosity and decreased the crystallinity, which may be responsible for the acceleration of the weight loss. Second harmonic generation results indicated that 10% gelatin blending had less disruption to PHBHHx spatial structure, resulting in better tensile mechanical properties. At the same time, increased surface porosity and decreased crystallinity caused by gelatin incorporation may be beneficial for cell growth compared with pure PHBHHx. All these indicated that gelatin incorporation may improve the performances of PHBHHx to meet the need of different situations during medical implantation.
| Gelatin/chondroitin-6-sulfate copolymer scaffold for culturing human nucleus pulposus cells in vitro with production of extracellular matrix
Yang, S. H., P. Q. Chen, et al. (2005), J Biomed Mater Res B Appl Biomater 74(1): 488-94.
Abstract: Tissue-engineering approaches for treating degenerative intervertebral discs aim to regenerate intervertebral disc tissues in order to retard or even reverse the degenerative process. This study was designed to investigate the feasibility of the glutaraldehyde crosslinked gelatin/chondroitin-6-sulfate copolymer scaffold to serve as a bioactive scaffold for culturing human nucleus pulposus (NP) cells in vitro with preservation of the cell viability, cell proliferation, and production of important extracellular matrix, including glycoaminoglycans (GAG) and Type II collagen. Each experimental sample was seeded with 1 x 10(6) human NP cells, and then the cell-scaffold hybrids were cultured in vitro for 6 or 12 weeks. SEM showed a highly porous structure with an average pore size of 100 microm in the copolymer scaffold. Immediately after cell seeding, SEM showed that the seeded cells penetrated deeply and distributed evenly in the copolymer scaffold. Water-soluble tetrazolium salt-1 (WST-1) assay showed good viability and active proliferation of cultured human NP cells in the copolymer scaffolds up to 12 weeks. The cell-scaffold hybrids contained significantly higher levels of sulfated GAG than the control samples (41.29 mug vs 6.04 mug per scaffold). Immunohistochemical study showed Type II collagen fibrils on the surface of scaffold substrate after 6 weeks of cultivation. More abundant deposition of Type II collagen could be detected after 12 weeks. The results achieved in this study indicate that the gelatin/chondroitin-6-sulfate copolymer scaffold is a promising bioactive scaffold for regeneration of nucleus pulposus tissue.
| Gelatinases in soft tissue biomaterials. Analysis of different crosslinking agents
Calero, P., E. Jorge-Herrero, et al. (2002), Biomaterials 23(16): 3473-8.
Abstract: Chemical modification of pericardium-based cardiac valves tends to reduce the relatively high degree of biodegradation and calcification of the implanted bioprostheses. We analysed the tissue properties of pericardium from young calves and pigs after crosslinking with different agents (glutaraldehyde. diphenylphosphorylazide (DDPA), 1-ethyl-3,3-dimethyl-aminopropyl-carbodiimide (EDAC)) and when exposed to anticalcification treatments (chloroform/methanol or ethanol) prior to glutaraldehyde (GA) crosslinking. Protein extraction after tissue homogenisation in the presence of detergents showed that crosslinking using GA or DPPA was much more effective. The amounts of protein extracted from these two groups of chemically modified pericardium were significantly lower: the other modified tissues presented only a slight reduction when compared with untreated tissue. Matrix metalloproteinases- (MMP) 2 and 9 were detected in native pericardium from calf and pig by zymography. While the MMP-9/MMP-2 activity ratio was close to 1 in pig pericardium, it was 8.5-fold higher in bovine tissue. Crosslinking with GA and with DPPA almost completely abolished gelatinase activities, even when equal amounts of solubilised protein were loaded onto the zymograms. Anticalcification treatments followed by GA crosslinking or treatment with EDAC were not as effective in reducing gelatinase activities; but, interestingly, a relative reduction of MMP-9 versus MMP-2 was detected. The presence of these gelatinase activities in pericardium may contribute to the in vivo degradability of pericardium-based cardiac valves.
| Gene delivery through cell culture substrate adsorbed DNA complexes
Bengali, Z., A. K. Pannier, et al. (2005), Biotechnol Bioeng 90(3): 290-302.
Abstract: Efficient gene delivery is a fundamental goal of biotechnology and has numerous applications in both basic and applied science. Substrate-mediated delivery and reverse transfection enhance gene transfer by increasing the concentration of DNA in the cellular microenvironment through immobilizing a plasmid to a cell culture substrate prior to cell seeding. In this report, we examine gene delivery of plasmids that were complexed with cationic polymers (polyplexes) or lipids (lipoplexes) and subsequently immobilized to cell culture or biomaterial substrates by adsorption. Polyplexes and lipoplexes were adsorbed to either tissue culture polystyrene or serum-adsorbed tissue culture polystyrene. The quantity of DNA immobilized increased with time of exposure, and the deposition rate and final amount deposited depended upon the properties of the substrate and complex. For polyplexes, serum modification enhanced reporter gene expression up to 1500-fold relative to unmodified substrates and yielded equivalent or greater expression compared to bolus delivery. For lipoplexes, serum modification significantly increased the number of transfected cells relative to unmodified substrates yet provided similar levels of expression. Immobilized complexes transfect primary cells with improved cellular viability relative to bolus delivery. Finally, this substrate-mediated delivery approach was extended to a widely used biomaterial, poly(lactide-co-glycolide). Immobilization of DNA complexes to tissue culture polystyrene substrates can be a useful tool for enhancing gene delivery for in vitro studies. Additionally, adapting this system to biomaterials may facilitate application to fields such as tissue engineering.
| Gene expression clustering using self-organizing maps: analysis of the macrophage response to particulate biomaterials
Garrigues, G. E., D. R. Cho, et al. (2005), Biomaterials 26(16): 2933-45.
Abstract: The most common cause of total joint replacement failure is peri-implant bone loss causing pain and prosthesis loosening. This process, known as osteolysis or aseptic loosening, is characterized by macrophage phagocytosis of particulate implant wear debris. In an incompletely defined step, particulate biomaterial debris induces macrophages to release a variety of inflammatory mediators and signaling proteins that lead to bone loss. In an in vitro model of this process, we used microarray technology and data analysis techniques, including the use of self-organizing maps (SOMs), to understand the mRNA gene expression changes occurring in macrophages exposed to clinically relevant particles of ultra-high molecular weight polyethylene and TiAlV alloy. Earlier studies have been limited by technology that only allowed analysis of a few genes at a time, but the microarray techniques used in this paper generate the quantitative analysis of over a thousand genes simultaneously. Our microarray analysis utilized an SOM clustering to elucidate general patterns in the data, lists of top up- and down-regulated genes for each time point and genes with differential expression under different biomaterial exposures. The expression levels of the majority of genes (>95%) did not vary over time or with exposure to different biomaterials, but a few important genes, such as TNF-alpha, IL-1beta, IL-6, and MIP1alpha, proved to be highly regulated in response to biomaterial exposure. We also uncovered a novel set of genes, which not only validates and logically extends the current model of the pathogenesis of osteolysis and aseptic loosening, but also provides new targets for further research and therapeutics.
| Gene expression in tilapia following oral delivery of chitosan-encapsulated plasmid DNA incorporated into fish feeds
Ramos, E. A., J. L. Relucio, et al. (2005), Mar Biotechnol (NY) 7(2): 89-94.
Abstract: DNA delivery into fish is important for transient gene expression, (e.g., DNA vaccination). Previous studies have generally focused on intramuscular injection of DNA vaccines into fish. However, this method is obviously impractical and laborious for injecting large numbers of fishes. This study reports oral delivery of a construct expressing the beta-galactosidase reporter gene into fish by encapsulating the DNA in chitosan and incorporating it into fish feeds. We found that beta-galactosidase expression could be observed in the stomachs, spleens, and gills of fishes fed with flakes containing the chitosan-DNA complex. These results suggest that DNA vaccines and other constructs can be easily and cheaply delivered into fishes orally by use of carriers and incorporation into fish feeds.
| Gene expression profiling of bone cells on smooth and rough titanium surfaces
Harle, J., V. Salih, et al. (2004), J Mater Sci Mater Med 15(11): 1255-8.
Abstract: Titanium (Ti) and Ti alloys are widely used as dental and orthopaedic implants, but the effects of the surface characteristics of these materials on the response of cells and target tissues is not well understood. The present study has therefore examined the effects of a rough Ti (RT) and a smooth Ti (ST) surface on human bone cells in vitro. Scanning electron microscopy showed attachment and spreading of cells on both surfaces. Expression profiling using ATLAS gene arrays showed marked differences in gene responses after 3 h of culture. A number of osteoblast genes were identified as "roughness response" genes on the basis of changes in expression on the RT compared with the ST surfaces. The surface roughness of Ti was thus found to have a profound effect on the profile of genes expressed by the bone cells, and suggests that improvements in the biological activity and possibly the clinical efficacy of these materials could be achieved by selective regulation of gene expression mediated by controlled modification of Ti surface.
| Gene expressions screening of human cell line exposed to locally produced biomaterial
Azlina, A. and A. R. Samsudin (2004), Med J Malaysia 59 Suppl B: 166-7.
Abstract: In Malaysia, the field of genomics in toxicology is still in infancy. The purpose of this study is to focus on the use of toxicogenomics for determination of gene expressions changes in cultured human fibroblast cells treated with genotoxicology free biomaterial (using Ames test), a locally produced hyroxyapatite. Dose and time response is similar to Ames test with time interval up to 21 days. mRNA is extracted, followed with RT-PCR and polyacrilamide gel electrophoresis. Changes of the gene expressions compared to the non-treated fibroblast mRNA would suggest some gene interactions in the molecule level associated with the exposure of the fibroblast cell line to the biomaterials. Further analysis (cloning & sequencing) shall be carried out to investigate the genes involved as simple changes might not signified toxicity.
| Generation of cell adhesive substrates using peptide fluoralkyl surface modifiers
Ernsting, M. J., G. C. Bonin, et al. (2005), Biomaterials 26(33): 6536-46.
Abstract: Previous studies reported on the delivery of vitamin E to the surface of a polycarbonate polyurethane (PCNU) to produce antioxidant surfaces, using a bioactive fluorinated surface modifer (BFSM). In the current report, a cell adhesive peptide sequence was coupled to the BFSM, and when blended into PCNU, generated a cell adhesive substrate. An NH2-GK*GRGD-CONH2 peptide sequence (referred to as RGD) with a dansyl label (*) on the lysine residue was coupled via the N-terminal to a BFSM precursor molecule. The resulting RGD BFSM was purified and the pmol peptide/mg BFSM value was assayed by amino acid quantification. The migration of the RGD BFSM in a PCNU blend was confirmed by X-ray photoelectron spectroscopy analysis. U937 macrophage-like cells and human monocytes were seeded onto the PCNU and blends of PCNU with non-bioactive fluorinated surface modifier or the RGD BFSM, in order to study the cell response. Both U937 cells and human monocytes adhered in greater numbers to the RGD BFSM substrate when compared to unmodified PCNU or the blend of PCNU with the non-bioactive fluorinated surface modifying macromolecule substrate. The study demonstrated a novel approach for the introduction of peptides onto the surface of polymers by modifying the surface from within the polymer as opposed to the use of cumbersome post-surface modification techniques. The generation of a peptide substrate points to the possibility of producing complex bioactive surfaces using various peptide BFSMs or pharmaceuticals simultaneously to manipulate cell functions.
| Genetic effects of anorganic bovine bone (Bio-Oss((R))) on osteoblast-like MG63 cells
Carinci, F., A. Piattelli, et al. (2005), Arch Oral Biol
Abstract: Bio-Oss((R)) (Geistlich, Wolhusen, Switzerland) is composed by anorganic bovine bone and is widely used in several bone regeneration procedures in oral surgery. How this biomaterial alters osteoblast gene expression to promote bone formation is poorly understood. We therefore attempted to address this question by using microarray techniques to identify genes that are differentially regulated in osteoblasts exposed to Bio-Oss((R)). By using DNA microarrays containing 20,000 genes, we identified in osteoblast-like cells line (MG-63) cultured with Bio-Oss((R)) several genes which expression was significantly up- and down-regulated. The differentially expressed genes cover a broad range of functional activities: (a) signaling transduction, (b) transcription, (c) cell cycle regulation, (d) vesicular transport, (e) apoptosis, and (f) immunity. These results could explain the reported bioaffinity of Bio-Oss((R)) to host animals, its biological affinity to osteogenic cells and its capability to stimulate osteoblastic differentiation. The data reported are, to our knowledge, the first genetic portrait of Bio-Oss((R)) effects. They can be relevant to our improved understanding of the molecular mechanism underlying bone regenerative procedures and as a model for comparing other materials with similar clinical effects.
| Gentamicin-loaded microspheres for treatment of experimental Brucella abortus infection in mice
Prior, S., B. Gander, et al. (2005), J Antimicrob Chemother 55(6): 1032-6.
Abstract: OBJECTIVES: To evaluate the efficacy of gentamicin-loaded poly (lactide-co-glycolide) 50:50H (PLGA 50:50H) microspheres for the treatment of mice experimentally infected with Brucella abortus 2308. METHODS: The microspheres were dispersed in either 2% (w/v) poloxamer 188 saline solution, or deionized water with the help of a cell homogenizer to break up particle aggregates, and were administered intravenously or intraperitoneally to B. abortus-infected mice 7 days post-infection. RESULTS: Neither a single intravenous or intraperitoneal dose of 67 microg of gentamicin per mouse, nor three intraperitoneal doses of 100 microg of gentamicin per mouse, reduced the Brucella infection in the spleen compared with untreated mice 1 and 3 weeks post-treatment. Histological examination revealed granulation and tissue reaction in the periphery of spleen and liver of animals given three doses of the gentamicin-loaded microspheres. CONCLUSIONS: The lack of therapeutic activity of the gentamicin-loaded microspheres might be related to inappropriate microsphere size and aggregation, resulting also in a poor distribution of the microspheres in the spleen. The results might provide an example of practical problems related to particle size and aggregation for in vivo therapy with PLGA microspheres.
| Get a grip: integrins in cell-biomaterial interactions
Garcia, A. J. (2005), Biomaterials 26(36): 7525-9.
Abstract: Integrin adhesion receptors have emerged as central regulators of cell-biomaterial interactions. This opinion paper discusses how integrins control cellular and host responses to biomaterials and new strategies to manipulate these adhesive interactions in order to elicit specific cellular responses.
| Giant cell myocarditis associated with silicone. An unusual case of biomaterials pathology discovered at autopsy using X-ray energy spectroscopic techniques
Kossovsky, N., P. Cole, et al. (1990), Am J Clin Pathol 93(1): 148-52.
Abstract: Silicones, used extensively in the fabrication of medical devices because they were presumed inert and biocompatible, are now well-recognized inducers of localized granulomatous inflammation. Silicones less commonly are also associated with more complex clinico-pathologic entities. In this communication, the authors present a case of a patient on chronic hemodialysis involving tubing probably fabricated from silicone rubber who died from a giant cell myocarditis associated with silicone rubber. This case is presented to expand the interpretive paradigm of human pathology and underscores the need for pathologists to consider medical-device associated phenomena in the differential diagnosis of clinical specimens.
| Glassy state in Bacillus subtilis spores analyzed by differential scanning calorimetry
Stecchini, M. L., M. Del Torre, et al. (2005), Int J Food Microbiol
Abstract: Thermal properties of dried spores of Bacillus subtilis, investigated by differential scanning calorimetry (DSC), were studied. A reversible heat capacity shift ascribable to glass-rubber transition was observed at 90-115 degrees C. The transition was found to be a pressure-inhibited volume-activated event. The decoated spores and the extracted peptidoglycan material exhibited glass transition, suggesting that the cortex could be involved in the event. Furthermore, the glass transition was evident when spores were treated with strong acid, and when the isogenic strain PS578 was scanned, indicating that core integrity and core components are not involved in the occurrence of the event. These results suggest that in the dried B. subtilis spores an amorphous biomaterial, possibly the cortex peptidoglycan, is present as a glass.
| Glow discharge plasma deposition (GDPD) technique for the local controlled delivery of hirudin from biomaterials
Kim, D. D., M. M. Takeno, et al. (1998), Pharm Res 15(5): 783-6.
Abstract: PURPOSE: Biomaterials which release locally high concentrations of antithrombotic agents should lessen the thrombogenicity of the materials. To evaluate this approach, we prepared novel polyurethane matrices loaded with hirudin and coated them with 2-hydroxyethyl methacrylate (HEMA) by glow discharge plasma deposition (GDPD) to reduce the release rate. METHODS: Polyurethane (BioSpan) matrices containing hirudin and pore former (d-mannitol or BSA) were prepared by the solvent casting method. HEMA plasma deposition was then applied using GDPD technique to create a diffusional barrier film on the surface of the matrices. The effect of pore former and HEMA plasma coating on the release of hirudin was systematically investigated. Surface properties of matrices was also studied using Scanning Electron Microscopy (SEM) and Electron Spectroscopy for Chemical Analysis (ESCA). RESULTS: The release of hirudin from BioSpan matrix could be controlled by changing the weight fraction and particle size of pore former. HEMA plasma treatment of matrices produced a thin, highly cross-linked film on the surface. The initial burst and subsequent release of hirudin was significantly reduced after HEMA plasma coating, which suggested that the plasma disposition acted as a diffusional barrier and limited the release of hirudin incorporated in the polyurethane matrix. CONCLUSIONS: The plasma coating served as a diffusional barrier, and could work to control the release kinetics of hirudin by changing the various plasma coating conditions. Local delivery of hirudin using these biomaterials at the site of cardiovascular diseases can have the advantage of regional high levels of hirudin, as well as lowering systemic hirudin exposure, thereby minimizing the possibility of side effects.
| Glow discharge plasma deposition of tetraethylene glycol dimethyl ether for fouling-resistant biomaterial surfaces
Lopez, G. P., B. D. Ratner, et al. (1992), J Biomed Mater Res 26(4): 415-39.
Abstract: The glow discharge plasma deposition (GDPD) of tetraethylene glycol dimethyl ether is introduced as a novel method for obtaining surfaces that are resistant to protein adsorption and cellular attachment. Analysis of films by x-ray photoelectron spectroscopy and several biological assays indicate the formation of a fouling-resistant, PEO-like surface on several substrata (e.g., glass, polytetrafluoroethylene, polyethylene). Adsorption of 125I-radiolabelled proteins (fibrinogen, albumin and IgG) from buffer and plasma was very low (typically less than 20 ng/cm2) when compared to the untreated substrata, which exhibited much higher levels of protein adsorption. Not all coated substrata adsorbed equal amounts of protein (e.g., coated glass samples typically adsorbed more protein than coated polyethylene or coated polytetrafluoroethylene samples), suggesting that the substratum used may affect the amount of protein adsorbed. Measurement of dynamic platelet adhesion, using epifluorescent video microscopy, and endothelial cell attachment further demonstrates the short-term nonadhesiveness of these surfaces.
| Glow discharge plasma treatment for surface cleaning and modification of metallic biomaterials
Aronsson, B. O., J. Lausmaa, et al. (1997), J Biomed Mater Res 35(1): 49-73.
Abstract: Glow discharge plasma treatment is a frequently used method for cleaning, preparation, and modification of biomaterial and implant surfaces. The merits of such treatments are, however, strongly dependent on the process parameters. In the present work the possibilities, limitations, and risks of plasma treatment for surface preparation of metallic materials are investigated experimentally using titanium as a model system, and also discussed in more general terms. Samples were treated by different low-pressure direct current plasmas and analyzed using Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), atomic force microscopy, scanning electron microscopy, and light microscopy. The plasma system is a home-built, ultra-high vacuum-compatible system that allows sample introduction via a load-lock, and precise control of pressure, gas composition and flow rate, etc. This system allows uniform treatment of cylindrical and screw-shaped samples. With appropriate plasma parameters, argon plasma remove all chemical traces from former treatments (adsorbed contaminants and other impurities, and native oxide layers), in effect producing cleaner and more well-controlled surfaces than with conventional preparation methods. Removal (sputtering) rates up to 30 nm/min are possible. However, when inappropriate plasma parameters are used, the result may be increased contamination and formation of unintentional or undesired surface layers (e.g., carbides and nitrides). Plasma-cleaned surfaces provide a clean and reproducible starting condition for further plasma treatments to form well-controlled surface layers. Oxidation in pure O2 (thermally or in oxygen plasmas) results in uniform and stoichiometric TiO2 surface oxide layers of reproducible composition and thicknesses in the range 0.5-150 nm, as revealed by AES and XPS analyses. Titanium nitride layers were prepared by using N2 plasmas. While mild plasma treatments leave the surface microstructure unaffected, heavy plasma treatment can give rise to dramatic morphologic changes. Comparison of these results with corresponding analyses of commercial implants and electropolished and/or anodically oxidized samples shows that the plasma treatment offers superior control of the surface status. However, it is also shown that improper control of the plasma process can produce unwanted and irreproducible results.
| Glucocorticoid-treated sheep as a model for osteopenic trabecular bone in biomaterials research
Augat, P., S. Schorlemmer, et al. (2003), J Biomed Mater Res A 66(3): 457-62.
Abstract: The purpose of this study was to determine the alterations in ovine trabecular bone induced by a combination of ovariectomy and steroid treatment. Twenty-four female skeletally mature Merino sheep were randomly assigned to ovariectomy alone (OVX), ovariectomy combined with glucocorticoid treatment for 6 months (OVX + GC), or no treatment (control). Biopsies of trabecular bone were harvested 6 and 12 months after the beginning of the study from the proximal tibia. The biopsies were scanned for apparent bone mineral density by quantitative computed tomography and were mechanically tested. Three-dimensional bone reconstructions were obtained by micro-computed tomography. Trabecular bone from the OVX + GC animals had a markedly reduced apparent bone mineral density (27% less than control), bone volume (34%), and elastic modulus (36%) at 6 months. At 12 months, the reductions in apparent bone mineral density (33%), bone volume (37%), and elastic modulus (62%) appeared to be even more pronounced. Ovariectomy alone did not result in a perceptible reduction in any parameter. The combination of ovariectomy and glucocorticoid treatment in sheep resulted in a successful induction of substantial loss of trabecular bone and thus may serve as a large-animal model for osteopenic trabecular bone for the development and testing of orthopedic implants and techniques under osteoporotic conditions.
| Glucose permeable poly (dimethyl siloxane) poly (N-isopropyl acrylamide) interpenetrating networks as ophthalmic biomaterials
Liu, L. and H. Sheardown (2005), Biomaterials 26(3): 233-44.
Abstract: Poly (dimethyl siloxane) (PDMS) has been widely used as a biomaterial in ophthalmic and other applications due to its good compatibility, high mechanical strength, excellent oxygen permeability and transparency. However, for use as an artificial cornea, contact lens and in other applications, modifications with hydrophilic functional groups or polymers are necessary to improve wettability for tear protein and mucin interactions and to improve glucose permeability for cellular health. Poly (N-isopropyl acrylamide) (PNIPAAM) is a biocompatible and hydrophilic polymer that has been extensively studied on controlled drug release applications due to its lower critical solution temperature (LCST) phenomenon. In the current work, a composite interpenetrating network (IPN) of PDMS and PNIPAAM was formed to generate polymers with oxygen and glucose permeability as well as improved wettability compared to PDMS homopolymers and greater mechanical strength than PNIPAAM homopolymers. Transparent vinyl and hydroxyl terminated PDMS/PNIPAAM IPNs (PDMS-V and PDMS-OH IPNs, respectively) were successfully synthesized. Transmission electron microscopy images verified the structure of the IPNs. Surface analysis suggested that PNIPAAM was present on the surface as well as in the bulk material. PDMS-OH IPNs generated from a PDMS-OH matrix cured in the presence of solvent had the highest glucose permeability at 10(-7)cm2/s, comparable to that of the native cornea. The LCST phenomenon remained in these materials, although changes were not as abrupt as with pure PNIPAAM. These results suggest that these materials may be further developed as ophthalmic biomaterials or for controlled drug-release applications.
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