Influence of strontium for calcium substitution on the glass–ceramic network and biomimetic behavior in the ternary system SiO2–CaO–MgO

Abstract

Strontium (Sr) enhances bone formation both in vitro and in vivo, while it reduces bone resorption. Thus, Sr incorporation in bioactive glass–ceramic scaffolds for bone tissue regeneration could further enhance osteogenesis. The aim of this work was the synthesis, characterization and investigation of the apatite-forming ability in inorganic environment of two sol–gel-derived bioactive Sr-containing glass–ceramic materials with 5 and 10% of SrO. The thermal properties of the synthesized materials were studied using differential thermal analysis (TG–DTA). The apatite-forming ability test was conducted in SBF for various immersion times for both thermally treated and untreated samples. The characterization of the samples before and after immersion in SBF was performed with Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD) and scanning electron microscopy with associated energy-dispersive spectroscopy. FTIR spectra revealed that all synthesized glass–ceramic materials presented the characteristic bands of silicate glasses, while XRD identified various crystalline phases, mostly calcium silicates. Strontium is present in the form of strontium silicate in both as-received and thermally treated specimens, and Sr-diopside in the thermally treated specimens. The apatite-forming ability of the glass–ceramic materials was confirmed by the formation of a hydroxyapatite layer after 3 and 5 days of immersion in SBF on the surface of the untreated and thermally treated samples, respectively. The apatite layer, also, became thicker as the immersion time increased.