In vitro bioactivity evaluation, mechanical properties and microstructural characterization of Na2O–CaO–B2O3–P2O5 glasses

• In vitro bioactivity of Ca-borophosphate glasses was tested by soaking in the SBF.
• Density, Vickers microhardness and fracture toughness of the glasses were measured.
• Nano-HA formation on fine glass grains was analyzed by XRD, FTIR, TEM and ICP-AES.
• Formation of HA surface layer on glass bulk slabs was characterized by SEM-EDAX.
• Increasing B2O3 content in glass composition enhances the bioactivity of glasses.

Na2O–CaO–B2O3–P2O5 glasses have been prepared by the melt-quenching method. B2O3 content was systematically increased from 5 to 30 mol%, at the expense of P2O5, in the chemical composition of these glasses. Density, Vickers microhardness and fracture toughness of the prepared glasses were measured. In vitro bioactivity of the glasses was assessed by soaking in the simulated body fluid (SBF) at 37 ± 0.5 °C for 3, 7, 14 and 30 days. The glasses were tested in the form of glass grains as well as bulk slabs. The structure and composition of the solid reaction products were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The kinetics of degradation of the glass particles were monitored by measuring the weight loss of the particles and the ionic concentration of Ca, P and B in the SBF solution using inductive coupled plasma-atomic emission spectroscopy (ICP-AES). The obtained results revealed the formation of a bioactive hydroxyapatite (HA) layer, composed of nano-crystallites, on the surface of glass grains after the in vitro assays. The results have been used to understand the formation of HA as a function of glass composition and soaking time in the SBF. It can be pointed out that increasing B2O3 content in glass composition enhances the bioactivity of glasses. The nanometric particle size of the formed HA and in vitro bioactivity of the studied glasses make them possible candidates for tissue engineering application.

TEM images of the nano-HA formed on surface of glass grains after soaking in the SBF for 1 month: (a) glass sample B5, (b) B15 and (c) B30.Figure optionsDownload as PowerPoint slide