Implant-associated infection and poor osseointegration remains a major clinical challenge in Ti-based implant materials. A versatile strategy to endow Ti-based implants with long-term antibacterial ability as well as better osteogenic activity is highly desirable for high quality implantation. Strontium (Sr) has been shown to be a significant element to favor bone growth by promoting new bone formation and inhibiting bone resorption. In this study, a novel duplex-treatment technique encompassing magnetron sputtering with micro-arc oxidation is utilized to fabricate porous Sr/Ag-containing TiO2 coatings loaded with different concentrations of Ag and Sr. All coatings are porous with pore size less than 5 µm. Ag is primarily distributed homogeneously inside the pores, and the concentrations of Ag in Sr/Ag-containing TiO2 coatings with low and high Ag contents are 0.40 at.% and 0.83 at.% respectively. We have demonstrated that this kind of coating displays long-lasting antibacterial ability even up to 28 d due to the incorporation of Ag. Further, Sr/Ag-containing TiO2 coatings with optimum Ag and Sr contents revealed good cytocompatibility, enhanced osteoblast spreading and osseointegration, which stemmed primarily from the synergistic effect exerted by the porous surface topography and the bioactive element Sr. However, this study has also identified, for the first time, that proper addition of Ag would further facilitate osteogenic effects. Besides, Sr may be able to alleviate the potential cytotoxic effect of excessive Ag. Thus, integration of optimum functional elements Ag and Sr into Ti-based implant materials would be expected to expedite osseointegration while simultaneously sustaining long-term antibacterial activity, which would provide new insights for relevant fundamental investigations and biomedical applications.
Ti and its alloys are the most commonly-used materials for biomedical applications. However, bacterial infection after implant placement is still one of the significant rising complications. Therefore, the application of the antimicrobial agents into implant surfaces to prevent implant-associated infection has attracted much attention. Scientific papers have shown that inorganic antibacterial metal elements (e.g., Ag, Cu, Zn) can be introduced into implant surfaces with the addition of metal nanoparticles or metallic compounds into an electrolyte via micro-arc oxidation (MAO) technology. In this review, the effects of the composition and concentration of electrolyte and process parameters (e.g., voltage, current density, oxidation time) on the morphological characteristics (e.g., surface morphology, bonding strength), antibacterial ability and biocompatibility of MAO antimicrobial coatings are discussed in detail. Anti-infection and osseointegration can be simultaneously accomplished with the selection of the proper antibacterial elements and operating parameters. Besides, MAO assisted by magnetron sputtering (MS) to endow Ti-based implant materials with superior antibacterial ability and biocompatibility is also discussed. Finally, the development trend of MAO technology in the future is forecasted.
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