Katarzyna Gorna

The use of biodegradable polyurethane scaffolds for cartilage tissue engineering: potential and limitations.

The aim of the present study was to evaluate the capability of novel biodegradable polyurethane scaffolds to support attachment, growth and maintenance of differentiated chondrocytes in vitro for up to 42 days. After an initial decrease, although not significant, the DNA content of the constructs remained constant over the culture time. A progressive increase in glycosaminoglycans and collagen was observed during the culture period. However, a significant release of matrix molecules into the culture medium was also noticeable. At the transcriptional level, a decrease in aggrecan and procollagen II mRNA expression was noticeable, whereas procollagen I expression was increased. To conclude, the present data demonstrate that biodegradable polyurethane porous scaffolds seeded with articular chondrocytes support cell attachment and the production of extracellular matrix proteins. The limitations of the system are the diffusion of large amounts of matrix molecules into the culture medium and the dedifferentiation of the chondrocytes with prolonged time in culture. However, due to the favourable mechanical properties of the polyurethane scaffold, stimulation of chondrocytes by mechanical loading can be considered in order to improve the formation of a functional cartilage-like extracellular matrix.

The effect of gamma radiation on molecular stability and mechanical properties of biodegradable polyurethanes for medical applications

Abstract Experimental biodegradable medical polyurethanes with varying hydrophilic-to-hydrophobic segment ratios based on hydrophilic poly(ethylene oxide) MW=600 (PEO) and hydrophobic poly(e-caprolactone) diol MW=530 and 2000 (PCL), were exposed to gamma radiation at the standard dose of 25 kGy used for sterilization. Irradiated polymers degraded to a various extent, this being associated with a reduction of mechanical properties. For the more hydrophobic polyurethanes based exclusively on polycaprolactone diol the decrease of molecular weight was in the range of 12–30% and the decrease of tensile strength was 12%. For the more hydrophilic polyurethanes based on mixtures of polycaprolactone diol and polyethylene oxide the decrease of molecular weight was in the range of 30–50% and the decrease of tensile strength was 50%. Gamma radiation insignificantly affected surface roughness of hydrophobic polycaprolactone-based polyurethanes and caused a slight increase of contact angle. For the hydrophilic polymers based on polycaprolactone diol and polyethylene oxide, gamma radiation increased by 36–76% surface roughness and decreased by 20–45% contact angle. There was also an evident change in thermal properties of the irradiated materials.

Molecular stability, mechanical properties, surface characteristics and sterility of biodegradable polyurethanes treated with low-temperature plasma ☆

Abstract Biodegradable medical polyurethanes with varying hydrophilic-to-hydrophobic segment ratios based on hydrophilic poly(ethylene oxide) and hydrophobic poly(ϵ-caprolactone) diol, were treated with low-temperature, low-pressure plasmas of hydrogen peroxide, oxygen, carbon dioxide and ammonia. All samples treated with hydrogen peroxide plasma were sterile, while samples treated with oxygen, carbon dioxide and ammonia plasmas were nonsterile. The treatment caused a 7% drop in molecular weight and a 15% reduction in tensile strength for polyurethanes with a higher content of the hydrophobic segment; and a 27% reduction of molecular weight and a 20% decrease in tensile strength for the most hydrophilic materials. The hydrogen peroxide plasma extensively etched the surface of the materials, this being accompanied by a significant, 100–200% increase in the surface roughness. In contrast, the oxygen, carbon dioxide and ammonia plasma reduced the surface roughness of most hydrophilic PEO–PCL70–30 material, but minimally affected the surfaces of the remaining polymers. The hydrogen peroxide and oxygen plasmas increased the surface content of oxygen and decreased the content of nitrogen and carbon. The carbon dioxide plasma increased the carbon content, but decreased the oxygen and nitrogen content. The ammonia plasma decreased the nitrogen content, increased the carbon content and decreased the oxygen content. The surface contact angles slightly decreased for polyurethanes treated with oxygen and hydrogen peroxide plasmas, and increased for the samples treated with ammonia and carbon dioxide plasmas. Plasma treatment minimally affected the thermal characteristics of polyurethanes.