Urethane Membrane Research Articles

Synthesis and characterization of polyether urethane coatings for preventing implant infection

The common complication associated with implants is microbial infection due to biofilm formation. Among bacterial infections Staphlyococcus aureus remains a major challenge. This threat posed by implant associated infection affects a large percentage of population. One of the strategies to combat this risk is to coat the implant surface with polymers loaded with antibiotics. The antibiotics release at implantation site will prevent microbial infection. We have synthesized polyether urethane membrane using biocompatible isocyanate. Synthesis of the polyether urethane membrane was confirmed through Fourier transform infrared spectroscopy analysis. The membranes were further characterized by X-ray diffraction, swelling study (in water, simulated body fluid, tetrahydrofuran), drug release study, and antibiotic assay. Information of swelling study is used for drug loading and explanation of drug release from the membranes. We have used antibiotics for drug release study as they find application to combat infections. From the results, it was observed that antibiotic-loaded implant coatings may find application for preventing implant infection.

Plasma surface modification of fibroporous polycarbonate urethane membrane by polydimethyl siloxane: Structural characterization, mechanical properties, andin vitrocytocompatibility evaluation

This article reports the surface modification of electrospun polycarbonate urethane membrane with polydimethyl siloxane (PDMS) using plasma-induced grafting technique for biomedical applications. The nonwoven membranes were characterized for their structure, performance, and compatibility with cells. The surface modification was confirmed by means of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and energy dispersive X-ray analysis (EDXA). ATR-FTIR and EDXA analyses displayed characteristic absorption peaks of PDMS for the membrane. The structure and morphology of the developed membranes were studied using scanning electron microscope and microcomputed tomography (µCT). Scanning electron microscopy and µCT revealed the fibrous morphology and percentage porosity of the membranes before and after plasma modification. Static mechanical tests showed that the tensile strength was greater than 8 MPa. Physical characterization of the membranes after immersion in hydrolytic and oxidative media supports their biostability. Cytotoxicity of the membrane was evaluated using L929 fibroblast cells, and the results indicated that the membrane is cytocompatible. Accordingly, these results highlight the potential of this fibrous membrane for biomedical applications.

Structural characterization, mechanical properties, and in vitro cytocompatibility evaluation of fibrous polycarbonate urethane membranes for biomedical applications

This paper reports the electrospinning of a series of oxidatively stable polycarbonate urethanes (PCU) [carbothane (ECT), bionate (EBN), and chronoflex (ECF)] using N,N-dimethyl formamide and tetrahydrofuran as the mixed solvent. The nonwoven membranes were characterized for their structure, performance, and compatibility with cells. Scanning electron microscope was utilized to study the structural morphology and fiber diameter. Microcomputed tomography (micro-CT) was used to characterize the 3D architecture, pore size distribution, and percentage porosity. All the membranes displayed a porous architecture with average fiber diameter in the range of 1.5-2 μm. Static mechanical tests on the membranes revealed that the tensile strength was greater than 7 MPa and the dynamic mechanical tests showed that the average storage modulus (E(i) ) is 2 MPa at 37°C. PCU membranes were subjected to accelerated in vitro degradation for 90 days in 20% hydrogen peroxide/0.1M cobalt chloride solution. Mechanical characterization of the membranes postdegradation confirmed a 64% reduction in tensile strength for EBN at the end of 90 days where as ECF and ECT did not show any significant mechanical property deterioration in the oxidative medium. Cytotoxicity of the membranes was evaluated using L929 fibroblast cells and the results indicated that all the PCU membranes were cytocompatible and showed good adherence to L929 cells. Accordingly, these results highlight the potential of these fibrous PCU membranes for biomedical applications but further in vivo correlation studies are required for better understanding of the biodegradation and biological efficacy.

屋外での防水層温度の推定値に基づく熱劣化シミュレーション

Thermal degradation of elastomeric roofing materials exposed outdoors was predicted. Temperature of urethane membranes set on concrete substrate and on insulation layer was monitored hourly for three years in Tsukuba, Japan and was estimated applying multi-regression equation of meteorological elements, ambient temperature, solar radiation and wind velocity. The ratio of elongation of EPDM+IIR roofing tested under high temperatures was expressed as power function of elapsed time combined with Arrhenius' model including temperature. Referring the database of calculated temperature of roofing around Japan for 1991-2000, the property change was simulated and plotted on maps.

Totally implantable artificial hearts and left ventricular assist devices: Selecting impermeable polycarbonate urethane to manufacture ventricles

In the development of a new generation of totally implantable artificial hearts and left ventricular assist devices (VADs) for long-term use, the selection of an acceptable material for the fabrication of the ventricles probably represents one of the greatest challenges. Segmented polyether urethanes used to be the material of choice due to their superior flexural performance, acceptable blood compatibility, and ease of processing. However, because they are known to degrade and to be readily permeable to water, they cannot meet the rigorous requirements needed for a new generation of implantable artificial hearts and VADs. Therefore, the objective of the present study was to identify alternative polymeric materials that would be satisfactory for fabricating the ventricles, and in particular, to determine the water permeability through membranes made from four commercial polycarbonate urethanes (Carbothane® PC3570A, Chronoflex® AR, Corethane® 80A, and Corethane® 55D) in comparison to those made from two traditional polyether urethanes (Tecoflex® EG80A and Tecothane® TT-1074A). In addition to determining the rate of water transmission through the six membranes by exposing them to deionized water, saline, and albumin–Krebs solution under pressure and measuring the displacement of liquid by means of a recently developed capillary method, the inherent surface and chemical properties of the six membranes were characterized by SEM, contact angle measurements, FTIR, DSC, and GPC techniques. The results of the study demonstrated that the rate of water transmission through the four polycarbonate urethane membranes was significantly lower than through the two polyether urethanes. In fact the lowest values were recorded with the two Corethane® membranes, and the harder type 55D polymer had a lower value (2.7 × 10−7 g/s cm2) than the softer 80A version (3.3 × 10−7 g/s cm2). This level of water vapor permeability, which appears to be controlled primarily by a Fickian diffusion mechanism, is between 2 and 4 times lower than that obtained with traditional polyether urethane membranes of equivalent thickness. The superior performance of the polycarbonate urethanes is likely due to the inherently lower chain mobility of the carbonate structure in the soft segment phase. In addition, the study shows that additional impermeability to water vapor can be achieved by selecting a polyurethane polymer with a high hard segment content, an aromatic rather than aliphatic diisocyanate comonomer, and a more hydrophobic surface. The use of a higher molecular weight polyurethane is not necessarily efficacious if the above requirements are not met. As expected by Raoult's Law, the study found that the use of physiological media instead of deionized water further decreases the rate of water vapor transmission. Because none of today's commercial polyurethanes are totally impervious to water vapor transmission, additional work is needed to develop permeable polymers or to apply additional treatments to existing candidates to achieve an acceptable impermeable ventricle material. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 13–23, 1999

Proliferation and Interactions of Several Cell Types Encapsulated Within Dense (Non-Porous) Protein-Permeable Polyurethane Membranes

AbstractProtein-permeable dense (non-porous) urethane membranes have been evaluated forin vitrocell culture, and in vivo cell encapsulation. Polyurethane membranes were designed to exhibit permeability to proteins, gases, and nutrients without the existence of pores. The membranes are non-cytotoxic, angiogenic, and permeable to gases, nutrients, secretagogues and cell products via purely concentration-driven transport. Non-anchorage and anchorage dependent cells were grown encapsulated within the membrane and with the membrane as a growth substrate. Several non-anchorage dependent cell types proliferated within the membrane bothin-vitroandin-vivo. Anchorage-dependent cells were grown on the membranes as a substrate. Encapsulated cells have been maintained in culture for up to six months with nutrients supplied only by the external media. Immuno-isolation has been demonstrated with cells implanted into murine hosts. Explants of membrane encapsulated cells exhibited a high degree of vascularization, with little or no fibrous tissue. The ability to support cell growth and function, and the ability to protect xenogenic cells from immunologic rejection suggest that the membranes would be useful in the construction of hybrid artificial organs, devices for cell transplantation, and substrates for cell and tissue culture.

Study on Conjugated Redox Membranes Containing an Intercellular Component of Wool as an Electron Carrier

Abstract To realize artificially such a conjugated redox reaction as that which is drived across the biological cell membrane, two enzymic redox reactions were conjugated across a hydrogel membrane prepared with urethane prepolymer holding stabilized isocyanate groups. As redox couples, glucose 6-phosphate (G6P)/glucose 6-phosphate dehydrogenase (G6PD)/gluconolactone 6-phosphate (GL6P) and glutathione oxidized form (GSSG)/glutathione reductase (GRD)/glutathione reduced form (GSH) were chosen together with their common coenzyme, NADP+/NADPH. The driving of a system consisting of two redox couples separated with the hydrogel membrane containing the coenzyme NADP+ was intiated by the reduction of NADP+ on the membrane surface in contact with the G6PD/G6P solution. The conjugated redox reaction proceeded by electron exchange between coenzymes in the membrane and the reproducing of NADP+, which was accompanied with the GRD/GSSG solution. The rate of electron transfer across the urethane membrane was markedly accelerated by incorporating a nonkeratinous intercellular cement compound extracted from wool into the membrane. From cyclic voltammograms of a methyl viologen mediator, using a bare electrode and an intercellular compound modified carbon electrode, it was confirmed that the intercellular component could surely act as a good electron carrier.

Gas permeability of various block copolyether—urethanes

The effect of chemical structure and fabrication variables on the gas permeability of several block copolyether—urethane—urea and copolyether—urethane membranes was determined. It was found that the gas permeability of the copolyether—urethane—ureas increased in a linear manner with an increase in the polypropylene glycol segment molecular weight. Copolymers with a polyethylene glycol segment were found to be less permeable than those with propylene glycol segments. This may be due to the ability of polyethylene glycol to crystallize. For both copolymer systems, the type of chain extender used affected gas permeability. Again, these effects may be due to the degree of phase separation and to the nature of chain packing with the different extenders (i.e., the better the packing the lower the permeability). Changes in casting solvent, or the addition of salts such as LiBr or urea, had only minor effects on gas permeability.