Diamond like carbon coatings doped by Si fabricated by a multi-target DC-RF magnetron sputtering method - Mechanical properties, chemical analysis and biological evaluation

Doped diamond-like carbon coatings (DLC) are a promising solution for improvement of the performance of medical implants. Among various additives that can alter either mechanical or biological properties of DLC, silicon is a possible choice. This work focuses on the improvement of mechanical and biological properties by silicon incorporation into a DLC matrix. The successful deposition of Si-DLC coatings was demonstrated by FTIR spectra revealing the presence of Si-C, Si-O-Si and Si-Mex bonds (where Me - methyl group). The amount of dopant ranged from similar to 1.2 at.% to similar to similar to 21.9 at.%. Increasing the Si content resulted in the increase of hydrophilic character of the doped DLC coatings. Incorporation of silicon also increased the films' hardness, by 40% in the case of the most highly-doped coating. The biological evaluation with use of human osteosarcoma cells (Saos-2) revealed the possibility of tailoring the proliferation of mammalian cells by varying the amount of silicon dopant in such coatings. All of the examined coatings reduced the microbial colonisation of E. coli bacteria, compared to uncoated substrate. The most highly-doped coating was shown to be the most promising material among the examined samples for biomedical use, due to exhibiting highest hardness and critical force as well as low number of adhered bacteria. (C) 2017 Published by Elsevier Ltd.