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 Tco). 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.