Electron-beam modification of DLC coatings for biomedical applications

The interest in diamond like carbon (DLC) coatings and their modification for biomedical applications is strongly increasing during the last years. Improvement of surface resistance to scratching and biocompatibility are the main goals of recent developments. Moreover, different capabilities of adjacent areas on surfaces are often required by complex applications. In this study, different deposition methods for diamond-like carbon (DLC) coatings were compared for their suitability in biomedical applications. In addition, DLC coatings modified by non-thermal electron-beams were investigated with regard to their biological interactions. The DLC coatings were deposited using four different methods (plasma-activated chemical vapor deposition, physical vapor deposition by magnetron sputtering, and physical vapor deposition via cathodic arc - both unfiltered and filtered). The different DLC coatings were characterized with regard to their wettability, morphology, roughness, and coating adhesion. The ability of coatings to withstand repeated sterilization cycles was investigated using a specialized test protocol parallel to standard sterilization procedures for medical devices. Biological evaluation was performed using human fibroblasts by assessing metabolic activity and cell counts. Electron-beam modification of the coatings was performed under ambient conditions using a low-energy electron-beam facility (150 kV acceleration voltage). All DLC coatings investigated were found to be biocompatible, with the coating deposited by magnetron sputtering showing the best results. In general, electron-beam modification resulted in the hydrophilicity of the different DLC coatings increasing, but no changes in surface morphology or roughness were observed. The cell adhesion to electron-beam-modified DLC coatings was reduced to 30% of the untreated DLC coatings, what can be attributed to changes in the surface chemistry. The long-term stability of the modified DLC coatings was also confirmed. Therefore, electron-beam treatment represents a promising tool for modifying and functionalizing DLC coatings, especially if varying requirements concerning biomedical functionality and cell adhesion are involved.