Abstract:

Objective To discuss the optimal doping concentration of vanadium （V） and silicon （Si） co-doped TiO? coating （V-Si TiO?） formed on titanium surface by electrochemical treatment， to evaluate its antibacterial effect under visible light irradiation， and to clarify its visible light response mechanism. Methods The medical pure titanium sheets were subjected to micro-arc oxidation followed by high-temperature calcination， and V-Si TiO₂ coatings with different doping concentrations were prepared by adjusting the ratio of V to Si in the electrolyte. The experiment was divided into 1V∶10Si （V5Si50） group， 2V∶10Si （V10Si50） group， and 3V∶10Si （V15Si50） group； control group was set up（contains only bacterial culture medium）. The optimal doping concentration was screened based on comprehensive evaluation of surface morphology， ion release， photocatalytic ability， and biocompatibility； cell counting kit-8（CCK-8） method was used to detect the proliferation activities and the survival rates of the cells in various group. Subsequently， the optimized coating was characterized and compared by scanning electron microscope （SEM）， atomic force microscopy （AFM）， digital eddy current coating thickness gauge， X-ray diffraction （XRD）， X-ray photoelectron spectroscope （XPS）， and ultraviolet-visible absorption spectroscopy （UV-vis）. The experiment was divided into PT group （blank control）， PEO group （no element doping）， V10 group （V doping）， Si50 group （Si doping）， and V10Si50 group （2V∶10Si）. The ability of the coating materials to degrade methylene blue （MB） and generation of reactive oxygen species （ROS） under visible light were detected. For antibacterial experiments， Staphylococcus aureus （S.aureus） and Escherichia coli （E.coli） were used. The colony counts on plates in various groups were recorded after visible light irradiation for 2 h and dark treatment for 2 h， respectively. The ROS levels were detected using 2'，7'-dichlorofluorescein diacetate （DCFH-DA） ROS probe. ROS scavenging experiment was performed using the optimal doping concentration V10Si50 group， and the two kinds of bacteria were divided into blank control group， N-acetylcysteine （NAC） group， V10Si50 group， and NAC+V10Si50 group. The colony counts on plates in various groups were recorded after visible light irradiation for 2 h. Results The V concentration of 0.01 mol·L?1 and Si concentration of 0.05 mol·L?1 in the electrolyte solution were the optimal doping concentrations for the V-Si TiO? coating. The SEM observation results showed that compared with V5Si50 group and V15Si50 group， the surface pore size of the coating material in V10Si50 group was significantly decreased （P<0.05）， and the coating thickness was significantly increased （P<0.05）； its crystal structure was mainly anatase type， and the MB degradation rate of the coating material in V10Si50 group after 9 h of visible light catalysis was significantly increased （P<0.05）. Compared with control group， the cell proliferation activity and cell survival rate in V10Si50 group were significantly increased at 1， 2， and 4 d of cell culture （P<0.05）； at 2 and 4 d of cell culture， the cell proliferation activity and cell survival rate in V5Si50 group and V15Si50 group were significantly decreased （P<0.05）. Compared with PT， PEO， and Si50 groups， the colony counts of two kinds of the bacteria in V10 group and V10Si50 group after visible light irradiation for 2 h were significantly decreased （P<0.05）. Compared with PT group and PEO group， the ROS levels in two kinds of the bacteria in V10Si50 group after 2 h of irradiation were significantly increased （P<0.05）. Compared with V10Si50 group， the colony counts of two kinds of the bacteria in NAC+V10Si50 group were significantly increased （P<0.05）. Conclusion A reasonably loaded V-Si TiO? coating material （V10Si50） was screened out， which maintained good biological activity and significantly enhanced the antibacterial effect under visible light irradiation.

Key words: Titanium implant, Antibacterial coating, Photodynamic, Reactive oxygen species, Vanadium, Silicon