A study of the effect of precursors on physical and biological properties of mesoporous bioactive glass

A novel mesoporous bioactive glass (MBG) of composition 64SiO₂–26CaO–10P₂O₅ (mol %) was prepared by hydrothermal method using H₃PO₄ as a precursor for P₂O₅. The effect of use of organic triethylphosphate (TEP) and inorganic H₃PO₄ in MBG synthesis on glass transition temperature (T _g), crystallinity, morphology and bioactivity of MBGs was studied. Phase purity determination and structural analysis were done using powder X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, respectively. XRD revealed that MBG prepared from H₃PO₄ (MBG-H₃PO₄) when sintered at 700 °C was partially glassy/amorphous in nature and contained a mixture of crystalline apatite, wollastonite, calcium phosphate and calcium silicate phases. Calcined MBG prepared from TEP (MBG-TEP) contained only wollastonite and calcium silicate phases. Particle size and surface area determined by BET surface area analysis showed higher surface area (310 m² g⁻¹) for MBG-H₃PO₄ as compared to MBG-TEP (86 m² g⁻¹). It also had a smaller particle size (20 nm) and 70 % higher pore volume (0.88 cm³ g⁻¹) for MBG-H₃PO₄ as compared to MBG-TEP (60 nm particle size and 0.23 cm³ g⁻¹ pore volume). Thermal studies showed that use of H₃PO₄ decreases T _g and increased ΔT (difference between T _g and crystallization initiation temperature Tc_o). Low T _g and high ΔT also enhanced bioactivity of MBGs. Bioactivity was determined by immersion in a simulated body fluid for varying time intervals for a maximum period of 14 days. It revealed enhanced bioactivity, as evident by the formation of apatite layer on the surface, for MBG-H₃PO₄ as compared to MBG-TEP. Scanning electron microscopy and FTIR spectroscopy also supported this observation. Antibacterial studies with Escherichia Coli bacteria, MBG-H₃PO₄ showed better antibacterial behaviour than MBG-TEP.