Sol-gel derived S53P4 bioactive glass

Here, we report the first synthesis of amorphous sol-gel bioactive glass of the S53P4 (53.8 mol% SiO2, 21.8 mol% CaO, 22.7 mol% Na2O, and 1.7 mol% P2O5) composition. Sol-gel-derived bioactive glasses have higher surface area and, therefore, biodegrade faster and have higher bioactivity compared to their melt-derived counterparts. There is a clinical and commercial drive to produce sol-gel glasses of the original Bioglass 45S5 composition and S53P4 composition because they have a long track record as medical devices in their melt-derived form. However, previous reports of sol-gel-derived sodium-containing bioactive glasses (such as 45S5 and S53P4 bioactive glass) showed crystallization or incorrect composition and lacked evidence of successful alkaline ion incorporation into the glass network. Here, the first amorphous S53P4 sol-gel-derived bioactive glass was synthesized with evidence of successful sodium ion incorporation, by using sodium nitrite as the precursor and vacuum furnace stabilization, instead of the traditional sodium nitrate. According to 29Si magic angle spinning nuclear magnetic resonance, the glass (S53P4-NO2) contained 8.6% Q1, 59.1% Q2, and 32.3% Q3 silica species; its network connectivity was similar to that of melt-derived S53P4. Its composition was measured by lithium metaborate fusion/ICP, and its amorphous nature was confirmed by X-ray diffraction. The glass was mesoporous, with a specific surface area of 80.54 m2 g-1 (gas sorption analysis). The glass released calcium and sodium and increased the local pH more rapidly than melt-derived glass during dissolution in simulated body fluid (SBF), and caused more rapid reduction in phosphorus content in the SBF, an indicator of apatite layer formation. These characteristics make the sol-gel-derived S53P4 potentially suitable for regenerating bone defects and inhibiting acidophilic bacteria proliferation.