Enhanced biological performance of Sr2+-doped nanorods on titanium implants by surface thermal-chemical treatment

Abstract

Titanium alloys, as artificial implants for orthopedic diseases, are prone to aseptic loosening and infection after surgery because their smooth surface restricts the attachment and movement of osteoblasts, resulting in a lack of osteogenic and antimicrobial properties. This study aimed to prepare SrTiO₃ nanostructures with varying Sr content on the surface of titanium through a thermal-chemical treatment, enhancing the osteogenic capacity of titanium while providing antibacterial properties. The results indicated that the SrTiO₃ nanostructures are primarily composed of pure titanium and SrTiO₃ phases, exhibiting a rod-like surface morphology. Sr is uniformly distributed across the surface of the samples, and increasing the Sr content does not alter the morphology of the nanostructures. Wettability tests demonstrated that the SrTiO₃ nanostructures exhibited superhydrophilicity, promoting cell adhesion. Electrochemical tests revealed that the SrTiO₃ nanostructures prepared on the titanium surface significantly enhanced its corrosion resistance. After 14 days of immersion in simulated body fluids, a significant amount of hydroxyapatite formed on the surface of STN3, indicating that the SrTiO₃ nanostructures possess good bioactivity. In vitro antimicrobial tests demonstrated that SrTiO₃ nanostructures were effective against both Escherichia coli and Staphylococcus aureus, with the antimicrobial rates increasing alongside the Sr content, reaching 48.1% and 38.6%, respectively.

Fig. 1

a Film surface of the four sample groups; (b) cross-section of the four sample groups; (c) SEM images and EDS mappings of STN3

Fig. 2

Four sample groups: (a) XRD patterns; (b) XPS full spectra; (c) Ti 2p; (d) O 1 s; (e) Sr 3 d

Fig. 3

Different samples: (a) Sr²⁺ release curve in SBF; (b) water contact angles. The results are expressed as the means ± SDs (compared with the TN group, * p < 0.05)

Fig. 4

Polarization curves for TN, STN1, STN2 and STN3

Fig. 5

After immersion for 14 days: (a) surface morphology of TN, STN1, STN2 and STN3; (b) XRD pattern of STN3; (c) FT-IR spectrum of STN3

Fig. 6

Four sample groups: (a) Antibacterial plate diagrams for E. coli and S. aureus; (b) number of colonies on the plate; (c) morphology of bacteria on the surface of the film; (d) diagram of antibacterial mechanism. The results are expressed as the means ± SDs (compared with the TN group, * p < 0.05)