Biocompatibility tests and adhesion improvements for hydrogen-free amorphous carbon for blood-contacting medical devices

The hydrogenated amorphous carbon (a-C:H) film has been known as a coating material that imparts improved biocompatibility to base materials and has been used for many clinical applications. Recent studies have revealed that hydrogen-free amorphous carbon (H-free a-C) on stainless steel (SUS) has beneficial antibacterial properties, which allow avoidance of the risk of bacterial infection. In our study, to evaluate the biocompatibility of H-free a-C itself for blood-contacting devices, we investigated not only the ability to grow bacteria but also platelet aggregation on the surfaces of H-free a-C. Moreover, to apply H-free a-C to polytetrafluoroethylene (PTFE), we evaluated the adhesive properties of H-free a-C deposited after Ar or O₂ plasma pre-treatment and fluorine-incorporated a-C:H (a-C:H:F) interlayer deposition. Antibacterial tests and antithrombogenic tests indicated that H-free a-C coating reduced bacterial adhesion and platelet activation in comparison with a-C:H coating. The adhesive strength of plasma-treated Ar and the interlayer deposited PTFE was five times larger than those of untreated PTFE from film adhesion tests. These results indicated that the pre-treated PTFE coated with H-free a-C is a promising candidate biomaterial for medical devices.