Silver-doped diamond-like carbon antibacterial coating for 3D-printed titanium alloy total joint implants: Fabrication, characterization and biological function evaluation

Diamond-like carbon (DLC) coatings have been extensively investigated in total joint replacement due to their excellent mechanical properties and biocompatibility. However, challenges remain in enhancing their adhesion strength to 3D-printed (selective laser melting, SLM) Ti6Al4V substrates and improving their ability to prevent implant-related infections. In this study, silver-doped DLC (Ag-DLC) coatings were deposited on SLM-fabricated Ti6Al4V substrates via filtered cathodic vacuum arc (FCVA) technology. Nano indentation and nano scratch tests revealed that, compared with traditional DLC coatings, the Ag-DLC coating exhibited a 55% increase in adhesion strength to the substrate. Meanwhile, its hardness decreased to 2.43 GPa while the elastic modulus remained nearly unchanged. Tribological tests demonstrated that the Ag-DLC coating had a more stable friction coefficient, providing better protection for the Ti6Al4V substrate against wear. In vitro cell culture experiments with MC3T3-E1 preosteoblasts confirmed that the Ag-DLC coating showed no significant inhibitory effect on cell proliferation, indicating good biocompatibility. Antibacterial evaluation results showed that a distinct inhibition zone formed around the Ag-DLC-coated samples in the 48 h inhibition zone test; bacterial growth curves further verified the long-term antibacterial capability of the Ag-DLC coating. These findings highlight that the Ag-DLC coating maintains mechanical durability for orthopedic applications while demonstrating significant potential in addressing implant-related infections, thereby providing an effective surface modification strategy for 3D-printed Ti6Al4V implants.