Preparation and antibacterial properties of a copper-niobium coating on a titanium surface by a microarc oxidation-microwave hydrothermal method

Objective To prepare a copper-nobium antibacterial coating on a titanium surface by a microarc oxidation-microwave hydrothermal two-step method and to study its surface structure and antibacterial properties. Methods Using titanium coated with a microarc oxidation coating (MAO group) as the substrate, copper and niobium were introduced by a microwave hydrothermal method in low (MHL-Cu group), medium (MHM-Cu group) and high (MHH-Cu group) copper chloride solutions and niobium oxalate (MH-Nb group) solutions, respectively. The component with the highest copper content was determined by energy spectrum analysis, and the copper-niobium composite coating (MH-Cu/Nb group) was prepared by microwave hydrothermal mixing with niobium oxalate. The microstructure, element distribution and phase composition of the specimens were characterized by scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction, and the bacteriostatic effect of the coating onEscherichia coliand Staphylococcus aureus was determined by the film method. Results Energy dispersive spectrometry showed that Cu was introduced onto the surface of the MHL-Cu, MHM-Cu, and MHH-Cu groups, and the atomic ratios of copper in each group were （0.68 ± 0.04）%,（1.17 ± 0.06）%, and （1.64 ± 0.03）%. The difference between groups was statistically significant (P< 0.01). Scanning electron microscopy showed a crater-like porous structure on the surface of the MAO group, and the MHL-Cu, MHM-Cu, MHH-Cu, MH-Nb, MH-Cu/Nb groups maintained micropore morphology. The roughness increased with increasing Cu2+ concentration, in which the MH-Nb and MH-Cu/Nb groups showed gully like structures simultaneously. X-ray diffraction showed that the coating of the MAO group was mainly composed of titanium and anatase phase TiO2, and the coatings of the MHL-Cu, MHM-Cu, MHH-Cu, MH-Nb, MH-Cu/Nb groups were mainly composed of anatase and rutile phase TiO2. Compared with the MAO group, Escherichia coli and Staphylococcus aureus in the MHH-Cu, MH-Nb, MH-Cu/Nb groups decreased to varying degrees, with significant differences (P< 0.001); compared with the MH-Cu/Nb group, the colony number difference had statistical significance (P> 0.05).Conclusion The rough, porous coating containing copper and niobium prepared by the microarc oxidation-microwave hydrothermal two-step method can effectively inhibit the growth ofEscherichia coli and Staphylococcus aureus.