Thermal and hydrolytic stability of silver nanoparticle polyurethane biocomposites for medical applications

Polyurethane-extracellular matrix bionanocomposites containing in situ generated silver nanoparticles and biocompatible polymers such as hydrolyzed collagen, elastin, hyaluronic acid or chondroitin sulfate, were obtained by solvent casting method in order to achieve improved antibacterial biomaterials for medical devices. Using thermal analyses the stabilizing effect of polymeric components on the incorporated silver nanoparticles (metallic silver and/or silver in oxidized state) was evidenced. The non-isothermal kinetic parameters of the thermal degradation of studied bionanocomposites are evaluated in terms of integral methods. The variation of kinetic parameters in function of conversion was determined. By means of FTIR spectroscopy analysis the hydrolytic stability in PBS solutions (pH 4.6 and 7.4) of the studied silver bionanocomposites was investigated. It was found that the hydrolytic degradation occurred at the ester and urethane bonds in the poly(ester urethanes). The incorporated extracellular matrix components increased the hydrophilicity and favoured the hydrolysis. During hydrolysis increased hydrogen bonding and crystallinity principally for AgNPs stabilized polyurethane matrices which indicate a “chemicrystallization” effect.