Synthesis and Modifications of Polyurethanes for Biomedical Purposes

Polyurethanes are known as a class of polymers with very high ‘hemocompatible‘ properties. In this study polyurethanes were prepared in various compositions and in medical purity without using any solvent, catalyst or additives. For the synthesis of polyurethanes, toluene diisocynate, diphenylmethane diisocynate or hexamethylene diisocynate were used as diisocyanate compounds and polypropylene-ethylene glycol or polypropylene glycol were used as polyol compounds. The surfaces were modified with plasma glow-discharge by using various gas atmospheres and by applying different powers. Some samples were also modified by heparin immobilization to increase the blood compatibility. Chemical structure, mechanical strength, thermal behavior, oxygen permeability, water contact angle values, as well as protein and cell attachment capabilities of the prepared and modified polyurethanes were examined as possible candidates for biomedical applications. Plasma altered the chemistry of the surface, increased hydrophilic character, and caused a decrease in protein adsorption as the applied power was increased. On the other hand, an optimum power value which caused maximum attachment for Vero cells was observed. In-vitro experiments carried out with blood cells, plasma modification caused an increase on cell adhesion while further heparin immobilization resulted with a significant decrease.