Surface characterization and platelet adhesion studies on polyethylene surface with hirudin immobilization

Hirudin, a protein composed of 65 or 66 amino acid, is a newly risen antico agulant agent and has been considered as the most potent thrombin inhibitor . Hirudin can block the active site of thrombin by means of its carboxylic acid reaction with the active regime of thrombin, and becomes a tightly bou nd complex, and thus controls the formation of thrombus. Hirudin was covale ntly immobilized onto the water-soluble carbodiimide preactivated and chrom ic acid oxidized PE surface. Surface chemistry analysis indicated that a ce rtain amount of carboxylic acid groups was generated on the polyethylene su rface after oxidation with chromic acid solution. The amount of carboxylic acid functional group increased with the oxidation time. In addition, polye thylene surface was etched by chromic acid solution, and a rougher surface was created. The morphology of oxidized polyethylene surface was similar to each other among the samples with oxidation time from 1 to 8 min. ESCA res ults indicated the number of hirudin molecules immobilized was constant at the reaction time studied. In vitro platelet adhesion assay indicated the n umber of adhered platelets on the oxidized polyethylene surface increased s ignificantly after oxidation. In contrast, surface with hirudin immobilizat ion showed a reduction in adhered platelet density than the chromic acid ox idized counterpart due to the decrease of platelet-activating capability by the hirudin-thrombin complex and the differences in the adsorbed protein c omposition. (C) 2001 Kluwer Academic Publishers.