Interactions of enzymes and fungi with crosslinked polyurethanes prepared for biomedical applications.

Shelf life and long-term environmental stability of polyurethanes intended for percutaneous applications and various biomedical applications are largely depend on their resistance to fungal attack and growth. Two classes of aliphatic crosslinked polyurethanes based on hexamethylene diisocyanate (HDI) and bicyclo-hexyl-methane diisocyanate (SM DI) were subjected to cell-free enzymatic degradation using hydrolytic and oxidative enzymes and to fungal attack and fungal growth using Aspergillus niger and Penicillium Sp. The present crosslinked polyurethanes are not susceptible to degradation by hydrolytic enzymes. The marginal loss of tensile strength in buffered solution of papain is attributed to plasticization by the absorbed components of the enzyme solution. The PEG based crosslinked polyurethanes are marginally susceptible to degradation by lactic dehydrogenase solution. The present polyurethanes are resistant to fungal attack. The fungal growth was not observed with PTMG and PPG based Polyurethanes, however, a marginal growth was observed with PEG based polyurethanes.