Influence of silver content on microstructural, bactericidal, and cytotoxic behavior of TiAlVN (Ag) composite coatings deposited by magnetron sputtering

Abstract

Titanium alloys are attractive for the manufacture of bone implants, due to their high biocompatibility, chemical stability, and adequate resistance/specific weight ratio. However, its ability to reject the adhesion of bacteria and the formation of biofilms is very limited. Further, their low hardness and tribological resistance limits the scope of their application, so it is common to apply surface treatments to improve this property. In this work, the deposition of TiAlVN(Ag)x nanocomposite coatings using the direct current magnetron sputtering technique was proposed, with the aim of giving the coated substrates a significant bactericidal effect without significantly affecting their hardness and cell viability. The coatings were deposited from two independent targets of Ti6Al4V alloy and silver faced at 180° to each other. The atomic percent contents of silver in the compound were 8.1%; 10.6%; 12.6% and 14%, which was adjusted by varying the power applied to the silver target between 0 and 100W while maintaining the power supplied to the titanium alloy target constant at 2000W. The microstructural properties, elemental chemical composition, phase composition and surface topography of the deposited coatings were evaluated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and atomic force microscopy (AFM), respectively. The bactericidal effect of the composite coatings was assessed by evaluating the inhibition (JIS Z-2801 standard) and adhesion of the Pseudomonas aeruginosa bacteria, while the cell viability was assessed using human osteoblasts of the Saos-2 cell line, following the MTT method (colorimetric assay for assessing cell metabolic activity). All the deposited coatings showed a high bactericidal effect against P. aeruginosa, exhibiting inhibition greater than 99.99% and avoiding surface adherence by 100%. The TiAlVN(Ag) samples with 8.1 at% and 10.6 at% silver, and which presented the best ratio of mechanical and tribological properties (not shown here), exhibited high biocompatibility and adherence of the osteoblasts to the coated substrates.