Effects of surface roughness on anti-thrombogenicity of diamond-like carbon films

The mechanism of biomaterial-associated thrombosis has not been fully elucidated. It is believed that surface roughness of biomaterials is a key factor in influencing thrombogenicity. Diamond-like carbon (DLC) is being considered for widespread clinical use as a surface coating for cardiovascular devices. We previously reported that fluorine doping in DLC films (F-DLC) markedly inhibits platelet adhesion and activation in human blood. To evaluate the effects of surface roughness of coatings on thrombus formation, DLC and F-DLC films were deposited on the three different roughness-controlled polycarbonate (PC) substrates, and platelet adhesion and activation was investigated on each substrate. The surface roughness of DLC-coated PC and F-DLC-coated PC ranged from 4.1 nm to 97 nm. In this range, there were no significant differences in the platelet-covered area among the three grades of differing surface roughness for each coated surface. However, evaluation of the F-DLC films showed significant reductions in platelet adhesion and activation when compared with DLC films for every grade of roughness, suggesting that the inherent chemical characteristics of the surface, such as wettability, interfacial free energy and higher ratios of albumin/fibrinogen adsorption, might be more important in the mechanism of F-DLC non-thrombogenicity.