The activation of human plasma prekallikrein as a haemocompatibility test for biomaterials.I. Results obtained with the "end point" method

The contact of blood with foreign surfaces causes the activation of factor XII to Xlla, which, through the conversion of plasma prekallikrein into kallikrein, starts the coagulation cascade. The spectrophotometrical detection of the p-nitroaniline released in the reaction of kallikrein with the chromogenic substrate H-D-Pro-Phe-Arg-NH-Ph-NO is a test able to measure the contact activation induced by materials to be employed in contact with blood. The prekallikrein activation was e valuated by using the so called "end-point method", and the dependence of the activation on the geometry of the reaction vessels and on the volume of the plasma samples was found for silica-borate glass. Then, the activation as a function of plasma contact time was measured for glass, silicone, two commercial biomaterials, and a composite biomaterial of our production. The results obtained confirm the haemocompatibility of the biomaterials tested.