Clotting Phenomena at the Blood-Polymer Interface and Development of Blood Compatible Polymeric Surfaces

In the past two decades many attempts have been made t o relate surface and interfacial parameters with the blood compatibility of polymeric surfaces. It is however doubtful if by a single parameter the behaviour of blood on a surface can be predicted. Two major aspects of blood compatibility -the prevention of platelet adhesion and the deactivation of the intrinsic coagulation system are determined by the measure and nature of competitive blood protein adsorption on the foreign surface. The adhesion of blood platelets is promoted by adsorbed fibrinogen and gamma globulin, while adsorbed albumin inhibits platelct adhesion. Heparinised surfaces d o not adsorb fibrin and consequently no adhesion of platelets takes place. Othcr surfaces with low platelct adhesion are the hydrogels, certain block copolyetherurethanes, polyelectrolyte complexes and biolised proteins. Heparinised surfaces of the cationically bonded type inhibit the intrinsic coagulation as well, however this may be due to unstable coatings and heparin leakage.