Design and Properties of Novel Substituted Borosilicate Bioactive Glasses and Their Glass-Ceramic Derivatives

Three novel borosilicate bioactive glasses (BBGs) of general formula of 0.05Na2O·0.35x·0.20B2O3·0.40SiO2 (molar ratio, where x = MgO or CaO or SrO) were prepared and used to investigate the effect of crystallization on their properties including cytotoxicity. The three postmelt compositions were determined using X-ray fluorescence spectroscopy, and crystallization events were studied using differential thermal analysis and X-ray diffraction. This information was used to determine heat treatments to prepare glass-ceramics by controlled crystallization. X-ray diffraction analysis and Fourier transform infrared spectroscopy showed that, after higher heat treatment temperatures (800–900 °C), borosilicate bioactive glass-ceramics (BBGCs) contained mainly borate and silicate crystalline phases. Specifically, BBG-Mg, BBG-Ca, and BBG-Sr glass-ceramics detected the presence of magnesium silicate-Mg2(SiO3)2 and magnesium borate-Mg2B2O5; wollastonite-2M-CaSiO3 and calcium borate-Ca(BO2)2; and strontium silicate-SrSiO3 and strontium borate-Sr2B2O5, respectively. In vitro cytotoxicity tests were performed using the mouse fibroblast cell line (L929). Glass and glass ceramic at concentrations lower than 50 mg/mL did not exhibit any level of cytotoxicity when compared with the control. However, quantitative evaluation indicated that greater cell growth occurred in the presence of materials with crystalline phases. Control of BBGs crystallization may therefore be used to influence the biocompatibility of these glass-ceramic systems.