Chemical methods for improving the haemocompatibility of synthetic polymers

Synthetic high polymers differ widely in their interactions with blood, and unfortunately polymers offering promising combinations of mechanical properties for prosthetic applications are rarely those with the highest haemocompatibility. This paper is concerned with methods available for reducing the thrombogenicity of polymer surfaces but does not include discussion of other important issues such as complement activation. A brief review of the processes occurring in blood coagulation is followed by a statement of the chief methods for improving haemocompatibility: (1) coupling anti-platelet agents (e.g. prostaglandins or analogues) or anti-coagulants such as heparin to the surface: (2) 'passivation', for example by increasing the hydrophilicity of the surface: (3) coupling an inert biomaterial (e.g. albumin) or biomimetic (e.g. phosphatidyl choline) to the surface. Chemical techniques for effecting these processes are described, together with some results obtained. An account is also included of solution studies, carried out for mechanistic purposes, of bioactivities of appropriate polymer-drug adducts.