Co-immobilization and interaction of heparin and plasmin on collageno-elastic tubes.

Heparin and plasmin were co-immobilized on collageno-elastic tubes (CETs) in order to develop a thromboresistant and fibrinolytic vascular prosthesis. The mutual interaction between heparin and plasmin both in the soluble and in the immobilized state was studied. The immobilization condition rendering maximum co-immobilized heparin and plasmin activity was identified to require heparin immobilization followed by plasmin immobilization. Soluble heparin exerts a positive synergistic effect on soluble plasmin. Immobilized heparin enhances plasmin loading on the CET as compared to the heparin-free graft. Heparin, in both the soluble or immobilized state, significantly decreases the Michaelis-Menten (M-M) parameter Km for immobilized plasmin over heparin-free immobilized plasmin. Furthermore, the M-M parameter Vmax for the immobilized plasmin in the presence of heparin decreases over heparin-free immobilized plasmin. These results suggest a decrease in the kinetic constant k3 for heparin-modified immobilized plasmin over the heparin-free form. Co-immobilized heparin-plasmin collagenous grafts represent a unique advance in the development of fibrinolytically active prostheses.