Binding of heparin onto ethylene-vinyl alcohol copolymer membrane

Heparin was ionically bound onto the surface of an ethylene-vinyl alcohol copolymer (EVAL) membrane which was derivatized by aminoacetalization to produce cationic surface charges. The amount of bound heparin was proportional to the ion exchange capacity of the aminoacetalized membrane and the maximal amount obtained in this experiment was 96 Unit/cm2 (0.59 mg/cm2). Plasma recalcification times were measured for the heparinized membrane thus obtained. Recalcification times increased proportionally with the amount of heparin bound on the membrane, while original EVAL membranes and the non-heparinized aminoacetalized membrane did not show increases in recalcification times. This means that the heparinized EVAL membrane has a more nonthrombogenic property due to the release of heparin. The apparent amount of heparin released from the membrane into plasma was estimated from plasma recalcification times. The release rate was 0.30-0.33 Unit/cm2/h (1.8 X 10(-3)-2.0 X 10(-3) mg/cm2/h) for the membranes whose surface was considered to be saturated with heparin. The release amount was about 0.6% compared to the adsorbed heparin in the case of the 96 Unit/cm2-heparinized membrane incubated in plasma for 60 min.