Antibacterial Optimization of Highly Deformed Titanium Alloys for Spinal Implants

Abstract

The goal of the work was to develop materials dedicated to spine surgery that minimized the potential for infection originating from the transfer of bacteria during long surgeries. The bacteria form biofilms, causing implant loosening, pain and finally, a risk of paralysis for patients. Our strategy focused both on improvement of antibacterial properties against bacteria adhesion and on wear and corrosion resistance of tools for spine surgery. Further, a ~35% decrease in implant and tool dimensions was expected by introducing ultrahigh-strength titanium alloys for less-invasive surgeries. The tested materials, in the form of thin, multi-layered coatings, showed nanocrystalline microstructures. Performed direct-cytotoxicity studies (including lactate dehydrogenase activity measurement) showed that there was a low probability of adverse effects on surrounding SAOS-2 (Homo sapiens bone osteosarcoma) cells. The microbiological studies (e.g., ISO 22196 contact tests) showed that implanting Ag nanoparticles into Ti/TixN coatings inhibited the growth of E. coli and S. aureus cells and reduced their adhesion to the material surface. These findings suggest that Ag-nanoparticles present in implant coatings may potentially minimize infection risk and lower inherent stress.

Effect of Substrates Performance on the Microstructure and Properties of Phosphate Chemical Conversion Coatings on Metal Surfaces

“…However, when Ti alloys are used for bone repair and replacement, whether used for a long time or only stored for a short time, they are prone to form a biofilm because of bacterial adhesion and postoperative infection [ 6 ]. Furthermore, as bioinert materials, Ti and its alloys lack active repair capabilities, resulting in the loosening of the implant due to the inability to form a long-term fusion with the surrounding tissue [ 7 , 8 ]. Hence, postoperative bacterial infection and poor osseointegration may directly lead to the failure of implant surgery [ 9 ], which is not conducive to long-term service.…”