COVALENT BONDING OF HEPARIN TO VINYL COPOLYMER FOR BIOMEDICAL APPLICATIONS

In order to prepare polymer surface of vinyl type, provided with long term haemocompatibility, a commercial ethylene vinyl alcohol copolymer (EVAL) was covalently heparinized, employing two different bifunctional reagents (adipoil chloride and hexamethylene diisocyanate). the amount and activity of the heparin bonded to the polymer films were evaluated as a function of the concentration of the heparin solutions employed. Also, the influence exterted by the presence of various hydrophilic spacing arms of different molecular weights, either neutral or provided with electrical charge, was investigated. By in vitro measurements of APTT it was seen that all the heparinized samples possessed a high degree of haemocompatibility. For sake of comparison, heparin was also bonded ionically to EVAL functionalized by introduction of quaternary ammonium groups bonded covalently to the hydroxyl gropus of the polymer. It was seen that the covalent immobilization system provides the polymer surfaces with a superior haemocompatibility.