Study On Antibacterial Properties And Tribocorosion Behavior Of In Situ Synthesized Cu_xO/TiO₂ Coatings

Medical implant materials are in high demand due to a growing ageing population and a scarcity of medical resources.However,conventional medical titanium alloys have limitations such as bio inertness and poor wear resistance,which render them prone to failure.Bacterial adhesion and biofilm formation on the implant material surface are not inhibited by bio inertness,and implant material degradation or damage due to poor wear resistance may occur during long-term use in a body fluid environment.Therefore,it is imperative and challenging to develop novel medical titanium implant materials that exhibit both antibacterial properties and tribocorrosion resistance at the interface of materials science,medicine and biology.In this work,Cu_xO/TiO₂ coatings were in situ synthesized on Ti-6Al-4V alloy by plasma electrolytic oxidation（PEO）process in an electrolyte with different concentrations of Na₂Cu-EDTA.The influence of the Na₂Cu-EDTA concentration on coating morphology,composition and structure was investigated,and the biological performance and tribocorrosion resistance of the Cu_xO/TiO₂ coatings were assessed.In addition,the link between tribocorrosion and antibacterial properties was further explored.The results revealed that the Cu_xO/TiO₂ coatings mainly consisted of anatase phase,rutile phase and amorphous SiO₂,and Cu was mainly present in the coating in the form of Cu₂O.As the Na₂Cu-EDTA concentration increased,the Cu content and microhardness of the Cu_xO/TiO₂coatings increased,and the coating color gradually changed from grayish gray to dark brown.Meanwhile,the increase of Cu_xO on the coating surface led to the relative surface area decrease of TiO₂ and SiO₂,which reduced the hydrophilicity of the coatings.In addition,the increase of Na₂Cu-EDTA concentration led to the decrease of plasma discharge density during the growth of the coating,resulting in the decrease of porosity and roughness of the Cu_xO/TiO₂ coating.However,when the concentration of Na₂Cu-EDTA was increased to 10 g/L,the plasma showed a localized and continuous discharge,resulting in the porosity and roughness of the coating eventually increasing to 9.2%and 1.369μm,respectively.Furthermore,the Cu_xO/TiO₂ coatings showed no cytotoxicity to osteoblast-like cells.The antibacterial rate of Cu_xO/TiO₂ coatings against S.aureus increased with increasing Na₂Cu-EDTA concentration and incubation time,reaching 99.99%.The Cu_xO/TiO₂ coatings prevented bacterial adhesion and biofilm formation on the coating surface by the synergistic effect of contact antibacterial and Cu²⁺ion release,where contact antibacterial was the dominant antibacterial mechanism.The mass loss and volume loss of the coating prepared at a Na₂Cu-EDTA concentration of 7 g/L in simulated body fluid（SBF）was reduced by 53.5%and 46.3%respectively,compared to the coating without Na₂Cu-EDTA addition.The tribocorrosion facilitated the formation of apatite at the worn surfaces and the oxidation of Cu₂O to CuO,and this tribo-layer hindered the direct contact of the Cu_xO/TiO₂ coatings with the counter material,improving the wear conditions on the coatings surface.It is worth noting that the tribocorrosion process enhances the long-term antibacterial effect of the Cu_xO/TiO₂ coatings by exposing more Cu elements on the coating surface.This study demonstrates a novel approach for in situ preparation of antibacterial coatings that can address the challenges of bacterial biofilm formation in the initial stage and tribocorrosion in the long-term use of medical implant materials,and provides valuable insights for developing long-term antibacterial strategies for medical implant materials.