COVALENT BONDING OF HEPARIN TO A VINYL COPOLYMER FOR BIOMEDICAL APPLICATIONS

In order to prepare polymer surfaces of Vinyl type, provided with long -term haemocompatibility, a commercial ethylene-vinyl alcohol copolyme r (EVAL) was covalently heparinized, employing two different bifunctio nal reagents (adipoil chloride and hexamethylene diisocyanate). The am ount and activity of the heparin bonded to the polymer films were eval uated as a function of the concentration of the heparin solutions empl oyed. Also, the influence exerted by the presence of various hydrophil ic 'spacing arms' of different molecular weights, either neutral or pr ovided with electrical charge, was investigated. By in vitro measureme nts of activated partial thromboplastin time it was seen that all the heparinized samples possessed a high degree of haemocompatibility. For the sake of comparison, heparin was also bonded ionically to EVAL fun ctionalized by introduction of quaternary ammonium groups bonded coval ently (by adipoil chloride) to the hydroxyl groups of the polymer. It was seen that the covalent immobilization system provides the polymer surfaces with a superior haemocompatibility. (C) 1997 published by Els evier Science Limited.