Papain immobilized polyurethane as an ureteral stent material.

Long term use of polyurethane-based ureteral stent is hampered by the development of infection due to the formation of bacterial biofilm and salt deposition. Here papain, is covalently immobilized to polyurethane using glutarldehyde and is investigated as a possible anti-infective ureteral stent material. Fourier transform infrared spectrum confirmed its immobilization. Immobilized enzyme retained 85% of the activity of the free enzyme and about 12% loss of enzyme was observed from the polymer surface in one month. The modified polyurethane showed 8 log reduction in Staphylococcus aureus and 7 log reduction in Escherichia coli live colonies and 3-4 times decrease in the protein and carbohydrate in the biofilms than bare polymer. The amount of calcium and magnesium salts deposited on the polymer surface reduced by 40% after enzyme immobilization. 80% of L6 myoblast cells were viable on this material which indicated that it was noncytotoxic. A linear regression equation with hydrophilicity of the polymer surface and the cell surface hydrophobicity as the two independent variables was able to predict the number of live cells attached on the modified PU. This study indicated the possibility of using such an approach to overcome the problems of ureteral stent associated biofilm and salt encrustation.