ANTITHROMBOGENICITY OF LUMBROKINASE-IMMOBILIZED POLYURETHANE

Lumbrokinase is a potent fibrinolytic enzyme purified from the earthwo rm, Lumbricus rubellus. We immobilized 18 IU/ cm(2) of lumbrokinase to polyurethane using maleic anhydride methylvinyl ether copolymer (MAME C) as an enzyme carrier, and the proteolytic and fibrinolytic activiti es of immobilized lumbrokinase were assayed. Immobilized lumbrokinase retained about 34% of its activity, compared with soluble lumbrokinase activity. Immobilized lumbrokinase showed stability against thermal i nactivation and degradation and within a various pH range. The optimal pH of immobilized lumbrokinase shifted 1.0 pH unit upward compared wi th soluble enzyme. Upon exposure to the human whole blood, less amount of I-125-fibrinogen was adsorbed to lumbrokinase-immobilized surface than to the polyurethane control surface. The lumbrokinase-immobilized surface showed less platelet adhesion than did the MAMEC-grafted surf ace. At the early stage of platelet adhesion, the number of adhered pl atelets increased on the lumbrokinase-immobilized surface with increas ing time; yet, the platelet number drastically deceased on the lumbrok inase-immobilized surface after 80 min incubation. This suggests that lumbrokinase-immobilized polyurethane digested the adsorbed fibrinogen and inhibited platelet adhesion on the surface, probably by inhibitin g fibrinogen adsorption to be highly antithrombogenic. Clinical applic ations of this material to artificial organs should be developed in th e near future. (C) 1994 John Wiley and Sons, Inc.