Structural and in vitro biological evaluation of sol-gel derived multifunctional Ti+4/Sr+2 co-doped bioactive glass with enhanced properties for bone healing

The principal focus of this study was to evaluate the effect of different strontium (Sr) percentages substitution (Sr content = 0, 1, 3, 6, 9, and 12 mol. %) and fixed 5 mol. % titanium (Ti) in bioactive glass (T-BG) in terms of in vitro biological, bactericidal, and structural behaviors of SiO2-60%, CaO-(31-x)%, P2O5-4%, TiO2-5%, SrO-X% (mol. %) TS-BG. The structural analysis of BGs specimens containing Ti and Sr was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectrum (FTIR), Transmittance electron microscopy (TEM), and Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analyses. The alkaline phosphatase (ALP) activity test and 3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analysis were also conducted to investigate in vitro biological behavior of TS-BGs. Meanwhile, the bactericidal efficiency of TS-BGs against MRSA was examined. The SEM results indicated that hydroxyapatite (HA) appeared on TS-BGs' surface after one and two weeks of immersion in the simulated body fluid (SBF). HA characteristic peaks in XRD patterns as well as P–O and C–O bands in FTIR spectra confirmed the in vitro bioactivity. A similar trend in altering MC3T3 cell proliferation and cell differentiation was observed by increasing Sr amount up to 6 mol. %. Then, it had a downward trend up to 12 mol. % Sr. Meanwhile, the more Sr amounts added, the more TS-BGs antibacterial activity was achieved, and the specimen with 12 mol. % Sr and fixed 5 mol. % Ti (TS12) showed 34.27% bactericidal efficiency more than the control specimen (TS0). Taken together, the specimen with 6 mol.% Sr and fixed 5 mol. % Ti (TS6) was chosen as an optimal specimen among the other synthesized TS-BGs because of its higher in vitro bioactivity (HA forming ability after 7 days), MC3T3 cell proliferation, differentiation, and bactericidal efficiency than other specimens.