Containerless-prepared bioactive glasses with mild alkalinity: Combining biocompatibility and bioactivity

Biomaterials-induced mild alkaline microenvironment can positively modulate osteoblast activity, contributing to bone regeneration. However, the challenge associated with silicate bioactive glasses, including melt-derived 45S5 Bioglass^® (45S5-Glass) and sol-gel bioactive glasses, lies in rapid release of cations in the early stage, resulting in a significant increase in local pH level, which could induce inflammation reaction and even hinder the process of bone regeneration. Therefore, it is crucial to develop bioactive glass with mild alkaline capacity and moderate release rate of bioactive ions. In this study, a novel class of bioactive glass (SP-Glass, CaTiSiO₅ glass) is fabricated via a containerless melting approach to avoid phase separation and heterogeneous nucleation during the glass formation process. Compared to 45S5-Glass, SP-Glass exhibits enhanced stability of the network structure, resulting in a significant reduction in pH value and release rate of bioactive ions. SP-Glass creates a favorable mild alkaline microenvironment for promoting osteogenic differentiation of osteoblasts while inhibiting osteoclastic activity. Moreover, SP-Glass facilitates the shift of macrophages from pro-inflammatory M1 state to anti-inflammatory M2 state and promotes bone regeneration in vivo. Therefore, the containerless melting-prepared bioactive glasses with mild alkalinity combine excellent biocompatibility and bone-forming bioactivity, representing a new class of bioactive materials for tissue regeneration.