Sadayoshi Aoyagi

Anticoagulant activity of artificial biomedical materials with co-immobilized antithrombin III and heparin

An approach to providing anticoagulant activity to biomedical materials was presented, applying an immobilization technique. Antithrombin III (AT III) inactivates the activated coagulation factors including Factor Xa and thrombin. Heparin stimulates the inactivation of Factor Xa and thrombin by AT III. Thus AT III and heparin were co-immobilized on Sepharose 4B, polyvinyl alcohol, polyhydroxy-ethyl methacrylate and silicone-coated nylon by the cyanogen bromide procedure. Those co-immobilized preparations, abbreviated as I-AT III . Hep, actively neutralized both Factor Xa and thrombin. The activity of I-AT III . Hep was much higher than immobilized heparin and/or immobilized AT III. I-AT III . Hep, like soluble AT III and heparin, instantaneously neutralized both thrombin and Factor Xa. When two enzymes, thrombin and Factor Xa, were present, I-AT III . Hep neutralized Factor Xa in preference to thrombin : The neutralization of thrombin was inhibited by the presence of Factor Xa, but neutralization of Factor Xa was independent of the presence of thrombin. The amount of Factor Xa neutralized was higher than that of thrombin.

A new method for estimation of adhesiveness of blood platelets

Abstract A new method for the estimation of platelet adhesiveness is proposed and demonstrated. In a glass bead column for a conventional adhesiveness test, many platelet aggregates were formed which were covering platelets adherent to the beads surface. The platelet aggregation in the column was found to be induced by ADP released from erythrocytes. Enzymatic conversion of ADP to ATP with the aid of pyruvate kinase and phosphoenolpyruvate (PK-PEP), decreased significantly the platelet retention in the column. Scanning electron microscopic observation revealed that there were no aggregates but only adherent platelets on the bead surface exposed to the PK-PEP blood. Employing our new modification of glass bead column method, it has become feasible to demonstrate the difference in platelet adhesiveness to various artificial materials.

Antithrombogenic Activity of Artificial Medical Materials Improved by Enzyme Immobilization Techniques

The immobilization of proteins onto the surface of artificial polymers was investigated in order to prepare antithrombotic medical materials which can inhibit blood coagulation, activate the fibrinolytic system, and block platelet aggregation.