Tailoring structure and bioactivity of sol-gel derived borate glasses and glass-ceramics through calcination for tissue engineering

Borate bioactive glasses (BBGs) and glass ceramics are emerging biomaterials with enormous applications in repairing damaged tissues, owing to their controlled degradation, antimicrobial properties, and ability to promote tissue regeneration. In this work, BBG with composition B₂O₃-CaO-Li₂O-P₂O₅ was produced using the sol-gel technique and subsequently calcinated at temperatures of 600, 650, 700, 750, and 800 °C. A range of characterization techniques was employed to assess the impact of calcination temperature on the structural and biological responses of the glasses. BET analysis confirmed their mesoporous texture and observed the change in pore diameter with calcination temperatures, which is perfect for prolonged ion release and cell contact. Further, the structural modification with temperature and in vitro bioactivity, evidenced by hydroxyapatite (HAp) deposition on the material's surface, was verified by XRD, FTIR, and FESEM analysis. A dense and enhanced HAp layer was deposited with an immersion period in SBF, and it predominantly covers the crystalline phases CaB₂O_4, Li₂B₄O₇, and Ca₃(PO₄)₂ at 750 and 800 °C. This ability validated the glasses bioactivity and demonstrated their capacity to promote tissue regeneration. Moreover, the hemocompatibility experiments revealed that all BBGs were biocompatible, with no hemolytic effects and a lysis rate of below 5 %. The cell viability assays by culturing the cells with MG-63 osteoblast cells demonstrated superior cytocompatibility, non-toxic behavior, and increased cell proliferation. Over all these results demonstrate the promise of BBGs as useful materials for applications involving soft and hard tissue engineering.