Solvent-free fabrication of micro-porous polyurethane amide and polyurethane-urea scaffolds for repair and replacement of the knee-joint meniscus

New porous polyurethane urea and polyurethane amide scaffolds for meniscal reconstruction have been developed in a solvent-free process. As soft segme nts, copolymers of 50/50 L-lactide/epsilon-caprolactone have been used. Aft er terminating the soft segment with diisocyanates, chain extension was per formed with adipic acid and water. Reaction between the isocyanate groups a nd adipic acid or water provides carbon dioxide and results in a porous pol ymer. Extra hydroxyl-terminated prepolymer was added in order to regulate t he amount of carbon dioxide formed in the foaming reaction. Furthermore, sa lt crystals ranging in size from 150 to 355 mu m were added in order to ind uce macroporosity, The pore size was regulated by addition of surfactant an d by the use of ultrasonic waves. The resulting porous polymer scaffolds ex hibit good mechanical properties like a high-compression modulus of 150 kPa . Chain extension with adipic acid results in better mechanical properties due to better defined hard segments. This results from the lower nucleophil icity of carboxylic acids compared to water and alcohols. By adjusting the reaction conditions, materials in which macropores are interconnected by mi cropores can be obtained. On degradation only non-toxic products will be re leased; importantly, the materials were obtained by a simple, reproducible and solvent-free procedure. (C) 2000 Published by Elsevier Science Ltd.