Bioactivity of a CaO−SiO₂ Binary Glasses System

TLDR

The formation of hydroxycarbonate apatite (HCA) on glass surfaces depends on glass composition. Five CaO–SiO₂ glasses with 50–90 mol % SiO₂ were prepared by sol‑gel and tested for bioactivity by soaking in simulated body fluid at 37 °C. Characterization revealed compositional and surface differences between low‑ and high‑SiO₂ glasses, and in vitro assays showed HCA formation with faster kinetics in glasses containing 50–70 mol % SiO₂.

Abstract

Five glasses in the CaO−SiO2 binary system with different silica content (50−90% in mol) have been prepared by the sol−gel method. The referred glasses have been characterized by thermogravimetric and differential thermal analysis (TG/DTA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) showing clear differences in composition and specific surface and porosity between those glasses with low SiO2 content (50−70% in mol) and those with high SiO2 content (80−90% in mol). The in vitro bioactivity study of all glasses prepared were carried out by soaking in a simulated body fluid (SBF) at 37 °C. The FTIR, XRD, SEM, and EDS analysis of the surface of these glasses after the in vitro assays reveal the formation of a hydroxycarbonate apatite (HCA) layer. The formation process of this layer on the glass is a function of the glass composition. The rate of formation increases in those glasses with lower SiO2 (50−70% in mol).