New porous polyurethane urea and polyurethane amide scaffolds for meniscal
reconstruction have been developed in a solvent-free process. As soft segments,
copolymers of 50/50 L-lactide/epsilon-caprolactone have been used. After
terminating the soft segment with diisocyanates, chain extension was performed
with adipic acid and water. Reaction between the isocyanate groups and adipic
acid or water provides carbon dioxide and results in a porous polymer. Extra
hydroxyl-terminated prepolymer was added in order to regulate the amount of
carbon dioxide formed in the foaming reaction. Furthermore, salt crystals ranging
in size from 150 to 355 microm were added in order to induce macroporosity. The
pore size was regulated by addition of surfactant and by the use of ultrasonic
waves. The resulting porous polymer scaffolds exhibit 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 nucleophilicity of carboxylic acids compared to water and
alcohols. By adjusting the reaction conditions, materials in which macropores are
interconnected by micropores can be obtained. On degradation only non-toxic
products will be released; importantly, the materials were obtained by a simple,
reproducible and solvent-free procedure.
