Platelet repellent properties of hydrogel coatings on polyurethane-coated glass surfaces

Thromboembolism is a severe complication in patients with ventricular assist devices. Interactions of platelets with the artificial surface and pathological blood flow conditions could contribute to thrombus formation. Previous studies suggested that strongly swellable polymer coatings prepared from various poly(N-alkyl acrylamides) are bioinert as they repel proteins and cells. In this study, we tested structurally similar polymer coatings with varying degrees of crosslinking and swelling to explore if the bioinert character of such coatings is also valid under whole blood perfusion and shear stress. Glass substrates coated with medical grade polyurethane (PU) were modified with surface-attached poly(N-alkyl acrylamide) layers, which differed in crosslinking and in swelling. Slides were perfused with human blood containing fluoresceinated platelets at a shear rate of 1500 s for 3 minutes. Noncoated and PU-coated glass slides served as a reference for thrombogenic surfaces. We detected severe platelet adhesion on the reference surfaces. There was no platelet adhesion on poly(N-alkyl acrylamide) coatings with a swelling factor above 1.5-2 (p < 0.001 compared with PU). A lower swelling factor resulted in severe platelet adhesion. Different degrees of crosslinking ranging from 1% to 10% did not reverse platelet repellent properties of the representative polymer tested (p < 0.001 compared with PU).