Anti-thrombotic effect of amorphous hydrogenated carbon (a-C:H) films: Influence of electron structure

Recently, amorphous carbon films have being developed to take advantage of their good biocompatibility in blood contacting devices because of their anti-thrombotic effect. However, it has not been revealed how the anti-thrombotic effect roots from a certain amorphous carbon films with particular structure and surface properties. In this work, we focus on the relationship between the electron structure and wettability of amorphous hydrogenated carbon (a-C:H) and its blood compatibility. A series of films with different electron structure and wettability were fabricated using plasma immersion ion implantation - deposition (PIII-D), followed by annealing in vacuum between 200-600°C. They were characterized by Raman, elastic recoil detection (ERD) and atomic force microscopy (AFM). The physical properties and surface characteristics of the films including the carrier concentration and mobility, resistivity and band gap were also examined. The thrombogenesis of the films was evaluated employing in vitro platelet adhesion tests. The results were correlated with the biological data to elucidate the blood compatibility mechanism of a-C:H films. The platelet adhesion and activation of a-C:H is affected by annealing. It is believed that the possible factors affecting blood compatibility are the adhesion energy of blood plasma, band gap, carrier type and concentration. Improving the electronic structure of a-C:H films is critical to the abatement of platelet activation.