Silver-Doped Diamond-Like Carbon Coatings on Ti₆Al₄V Alloy with Enhanced Antibacterial and Cytocompatible Properties

To address persistent challenges in the longevity of biomedical and dental implants, particularly those related to bacterial colonization at metal interfaces, this study investigates the surface modification of Ti₆Al₄V alloy using diamond-like carbon (DLC) and silver-containing DLC (Ag-DLC) films deposited by plasma-enhanced chemical vapor deposition (PECVD) with a SiC _x Oy interlayer to promote adhesion. Raman spectroscopy and energy-dispersive X-ray spectroscopy (EDS) confirmed the formation of amorphous carbon coatings and verified the presence and spatial homogeneity of silver in the Ag-DLC films. Stylus profilometry and scratch testing indicated successful coating formation and favorable tribological performance, with Ag-DLC exhibiting a modest increase in friction coefficient relative to DLC. Contact-angle measurements revealed hydrophobic surfaces and a small decrease in surface energy following silver incorporation. Antibacterial assays against Enterococcus faecalis (ATCC 29212) demonstrated a significant reduction in viable colony-forming units on both DLC- and Ag-DLC-coated surfaces compared with uncoated Ti₆Al₄V (p < 0.05), while no statistically significant difference was observed between DLC and Ag-DLC under the tested conditions. SEM analysis showed denser bacterial adhesion on Ag-DLC surfaces, consistent with their measured topography; however, SEM and CFU data alone do not establish a definitive antibacterial killing mechanism. Cytocompatibility assays using NIH-3T3 fibroblasts over 24 h confirmed noncytotoxic behavior according to ISO 10993-5:2009. Overall, PECVD-deposited DLC and Ag-DLC coatings on Ti₆Al₄V combine favorable tribological behavior with reduced bacterial viability and short-term cytocompatibility, supporting their further evaluation for titanium-based implant surface engineering.