Investigating Early-Stage Mineralization Behavior and Bioactivity of Acid-Free Bioactive Glass 45S5 with Enhanced Dissolution Kinetics

Abstract

Nanostructured bioactive glass (BG) was synthesized through an acid-free sol–gel route (bioglass-AF) and the conventional acid-catalyst sol–gel process (bioglass-AC). The aim here is to eliminate the risk of residual acidic components in the BG while enhancing its functionality through nano-scale propduction. Scanning electron microscopy revealed the presence of highly porous structures and dense agglomerates composed of particles with a mean diameter of 45 nm in both samples. Bioglass-AC and bioglass-AF had specific surface areas of 1.48 m2/g and 2.73 m2/g, respectively, with an average pore size of ~ 5 nm. Faster mineralization kinetics were evident in bioglass-AF, compared to bioglass-AC, in Hepes-buffered salt solution. Following 14 days of immersion in artificial saliva, bioglass-AC and bioglass-AF lost 16% and 20% of their initial weight, respectively, confirming their bioactivity. None of the synthesized BGs stimulated cell growth up to 24 h but longer exposure to moderate concentrations (1.25 and 2.5 mg/mL) of bioglass-AF significantly enhanced cell viability, reaching 170% at 48 h. Overall, the comparative in vitro investigations proved that nano-structured 45S5 bioglass powders with improved mineralization and dissolution kinetics can be produced with an acid-free route, eliminating the risk of residual acidic components in the final product.