EVALUATION OF PLATELET-ADHESION AND ACTIVATION ON MATERIALS FOR AN IMPLANTABLE CENTRIFUGAL BLOOD PUMP

A totally implantable centrifugal artificial heart has been developed in which a pivot bearing supported centrifugal pump is used as a blood pump. The following have been adopted as blood contacting materials i n our pump: titanium alloy (Ti-6Al-4V) for the housing and impeller, a lumina ceramic (Al2O3) for the male pivots, and ultrahigh molecular we ight polyethylene (PE) for the female pivots. Greater antithrombogenic ity is required for an implantable blood pump. To examine the thrombog enicity of these materials, we evaluated in vitro platelet adhesion an d activation, which may play key roles in thrombogenesis on foreign su rfaces. Ti-6Al-4V, Al2O3, and PE were compared with polycarbonate (PC) , silicone carbide (SiC), and pure titanium (pTi). Platelet adhesion w as assessed using monoclonal antibody (CD61) directed against glycopro tein IIIa. Platelet activation was evaluated by measuring P-selectin ( GMP-140) released from irreversibly activated platelets. Each material with a surface area of 16.6 cm(2) was incubated with 2.5 ml of plasma or 2.5 ml of heparinized fresh whole blood for 3 h at 37 degrees C. T he optical density (OD) at a wavelength of 450 nm for CD61 was 0.93 +/ - 0.35 in PC, 0.34 +/- 0.13 in PE, 0.27 +/- 0.13 in pTi, 0.26 +/- 0.01 in Al2O3, 0.21 +/- 0.04 in SiC, and 0.12 +/- 0.12 in Ti-6Al-4V. The G MP-140 levels of the tested materials were not significantly different from the control value (45.9 +/- 7.2 ng/ml). These results indicate t hat Al2O3, PE, and Ti-6Al-4V, which are incorporated into our implanta ble centrifugal pump, have satisfactory antithrombogenic properties in terms of platelet adhesion. However, platelet activation by any mater ial was not observed under the static condition in this study.