Development of a Ta/TaN/TaNx(Ag)y/TaN nanocomposite coating system and bio-response study for biomedical applications

TaN(Ag) composited coatings are being investigated to improve biocompatibility of different biomedical devices due to the mechanical and chemical stability of TaN and bactericidal effect of silver nanoparticles. However, controlling the size, density, shape and especially the release of silver ions (Ag) into the surrounding medium becomes a challenge, since elevated levels of Ag could be cytotoxic. The aim of this work is to design and develop a new Ta/TaN/TaNx(Ag)y/TaN coating system, deposited by unbalanced DC magnetron sputtering technique, presenting an adequate balance between biocompatibility and bactericidal effect for potential applications in biomedical field. For this purpose, four different coating systems were deposited on 316 L stainless steel and silicon (100) samples applying a bias voltage of -30, -60, -90 and -120 V during the deposition of the top layer of TaN to vary its density. This manufacturing strategy allowed controlling the diffusion of silver nanoparticles to the coating surface and the release kinetics of silver ions in simulated body fluid (SBF). Biologic characterization has been performed with MC3T3-E1 pre-osteoblastic cells in terms of cell adhesion and long-term differentiation. Additionally, the adhesion and biofilm formation of the bacteria Streptococcus sanguinis strain in the deposited coating systems of Ta/TaNiTaNx(Ag)y/TaN were analyzed. The results indicated an improvement of cell adhesion and differentiation of the composited coating deposited with a bias of 30 V compared to other coatings. Concordantly, this coating showed the lowest bacterial adhesion and biofilm formation, representing an attractive and suitable composited material for biomedical applications. (C) 2017 Elsevier Ltd. All rights reserved.