Antibacterial ability and osteogenic activity of porous Sr/Ag-containing TiO ₂ coatings

Abstract

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.

Ag‐loaded MgSrFe‐layered double hydroxide/chitosan composite scaffold with enhanced osteogenic and antibacterial property for bone engineering tissue

“…Bonnelye et al have reported that 0.1 m M of Sr 2+ promotes the differentiation osteoblast precursors into mature osteoblasts, increases bone nodule number, and enhances the expression of osteoblastic markers ALP, bonesialoprotein and osteocalcin . However, high doses of strontium may induce defective bone mineralization and reduce the 25‐hydroxyvitamin D3‐hydroxylase activity …”

“…For bone scaffold materials, osteogenic property is an important property to induce in vivo bone formation in the absence of osteogenic factors . Some trace elements may affect bone formation and resorption through direct or indirect effects on bone cells or bone mineral . Because LDHs possess compositional flexibility, it is feasible to improve the biocompatibility and osteogenic differentiation of LDHs by the substitution of the divalent cation ( M 2+ ) and trivalent cation ( M 3+ ) with essential bioactive elements such as Mg, Fe, Sr, and so forth.…”

“…Moreover, strontium (Sr) element that is closely chemically related to calcium (Ca) element possesses antiresorptive activity and anabolic activity. In vivo studies have indicated that Sr at a low dose promotes bone formation, leading to increase bone mass in animals …”

Surface modification of valve metals using plasma electrolytic oxidation for antibacterial applications: A review

“…Strontium (Sr) which is known to improve osseointegration, has also been incorporated through PEO on the sputtering‐deposited TiAg layer by adding strontium acetate hemihydrate in the electrolyte. The resultant layer with antibacterial behavior also exhibited excellent adhesion, proliferation and differentiation of preosteoblastic cells due to the combined effect of porosity and the presence of Sr …”

Review of Antibacterial Activity of Titanium-based Implants Surfaces Fabricated by Micro-arc Oxidation

“…On this basis, He et al [112] fabricated porous Ag/Sr-containing TiO2 coatings via the similar method in the MAO electrolyte containing 0.167 M CA, 0.02 M β-GP and 0.033 M strontium acetate hemihydrate (SA). The coating displayed long-lasting antibacterial ability even up to 28 d due to the incorporation of Ag.…”