Physicochemical and in vitro bioactivity studies of bioactive glasses in the SiO2-CaO-MgO-P2O5, SiO2-Na2O-CaO-P2O5 and SiO2-Na2O-CaO-MgO-P2O5 systems

Glasses in the quaternary and quinary system SiO 2 -CaO-MgO-P 2 O 5 (SCMP), SiO 2 -Na 2 O-CaO-P 2 O 5 (SNCP) and SiO 2- Na 2 O-CaO-MgO-P 2 O 5 (SNCMP), have been prepared by using the sol-gel technique. Investigations of structural and bioactive properties of these glasses have been undertaken by using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). The in vitro bioactivity was assessed by determining the changes in surface morphology and composition after soaking in simulated body fluid (SBF) for up to 30 days at 37°C. X-ray diffraction patterns indicated the formation of hydroxycarbonated apatite layer (HCA) after only one hour for SNCMP glass and after four days for SCMP and SNCP glasses. Furthermore, observed bands of FTIR spectra confirmed the growth of HCA layer during in vitro test. Moreover, the dissolution rate has been investigated using energy-dispersive X-ray spectroscopy. The observed EDS patterns confirmed the growth of HCA layer on all samples surfaces during in vitro analysis. On the one hand, we report the existence of Na 2 Ca 2 Si 3 O 9 (that couple good mechanical strength with satisfactory biodegradability) as a single crystalline phase in the SNCP glass when calcined at 600°C. On the other hand, we have noticed that the coexistence of magnesium and sodium both enhanced the dissolution rate and hindered the crystallization in the SNCMP glass at 600°C.