IN-VITRO BLOOD COMPATIBILITY OF SURFACE-MODIFIED POLYURETHANES

Polyurethanes have proven durable materials for the manufacture of fle xible trileaflet heart valves, during in vitro tests. The response of two polyurethanes of differing primary structure to parameters of bloo d compatibility has now been investigated, using an in vitro test cell . Platelet (beta-thromboglobulin) release, complement (C3a) activation , the activation of free plasma and surface-bound factor XII were stud ied using fresh, human blood (no anticoagulant) or citrated plasma in control and surface-modified polyurethane. Surface modifications were designed to affect material thrombogenicity and included covalent atta chment of heparin, taurine, a platelet membrane glycoprotein fragment, polyethylene oxide (PEO), 3-aminopropyltriethoxysilane, and glucose o r glucosamine. Unmodified control polyurethanes caused platelet releas e and complement activation. High molecular weight (2000 D) polyethyle ne oxide reduced platelet release slightly but only glucose attachment to the surface produced a significant reduction in platelet activatio n All modifications reduced C3 activation compared with controls, but the greatest reduction was achieved with polyethylene oxide attachment or glycosylation. Most surface modifications were more activating of factor XII, both in plasma and on the material surfaces, than the cont rol polyurethanes. Heparin and high molecular weight PEO produced the greatest activation of factor XII in the free plasma form, but low mol ecular weight PEO and glucosamine produced the greatest activation of surface-bound factor XIIa. The least activating surfaces, affecting bo th free plasma and surface-bound factor XIIa, were those treated with platelet membrane glycoprotein fragment and glucose. PEO surfaces perf ormed relatively well, compared with controls and most surface modific ations. The best overall surface, however, was the glucose-modified su rface which was least activating considering all parameters of blood c ompatibility. (C) 1998 Published by Elsevier Science Ltd. All rights r eserved.