Kinetics of fibrinogen and platelet adherence to biomaterials

The initial task was to establish a conceptually and materially simple test procedure that could quantitate and evaluate the thrombogenic potential of a biomaterial surface. Since the primary events of thrombus formation on prosthetic surfaces are believed to involve the deposition of a plasma protein monolayer followed by platelet adhesion to its fibrinogen component, it seemed reasonable to focus on the binding kinetics of fibrinogen and platelets to a commonly used biomaterial. Employing solutions of 125I-fibrinogen in buffered saline, the adsorption characteristics of several types of biomedical tubing could be compared, and the competition and exchange among plasma proteins at surface binding sites of PVC were evaluated. Human platelets with 51Cr were found to adhere to PVC surfaces proportional to surface fibrinogen concentration, but only in the presence of plasma; the circulation of labelled platelets in buffered saline only resulted in significant adherence to the native surface, while surface fibrinogen was inhibitory. Physiological concentrations of albumin were the most effective in preventing both fibrinogen adsorption and platelet adherence. The most important consequence of this work, perhaps, is the many avenues of future experimentation discovered from this methodological approach, not only in the thrombogenic evaluation of a specific biomedical surface, but also in the delineation of thrombogenic sequelae in general.