Highly Bioactive Sol-Gel-Derived Borate Glasses

Abstract

Attributable to their low chemical durability, borate-based glasses have been demonstrated to convert rapidly to hydroxy-carbonated apatite (HCA), the inorganic component of bone. However, the effect of sol-gel processing on the bioactivity of borate-based glasses has not been investigated. In this study, the gel and glass forming abilities of six different borate-based glass formulations with borate content ranging from 36 to 61 mol % and based on a previously studied four component melt-derived glass system [(46.1)B2O3–(26.9)CaO–(24.4)Na2O–(2.6)P2O5; mol %] were investigated. Compared to melt-quench, sol-gel processing fabricated nanoporous glass particles with at least 2 orders of magnitude greater values for specific surface areas and total pore volumes, which translated to dramatically higher aqueous interaction and ion release rates. Surprisingly, when immersed in simulated body fluid, HCA conversion was achieved in as little as 3 h for sol-gel derived borate based glasses, demonstrating a 25-fold increase in mineralization rate when compared to melt derived equivalents. The ability of the sol-gel derived borate-based glasses to rapidly convert to bone-like HCA holds promise in numerous potential tissue engineering applications, including the repair and augmentation of mineralized tissues.