Physico-mechanical properties, hydroxyapatite conversion, biodegradability and antibacterial activity studies of melt-derived BGs based on SiO2-CaO-Na2O-P2O5 quaternary system

Abstract

The slow biodegradation and low hydroxyapatite (HA) conversion of silicate-based bioactive glasses (BGs) have severely limited their compatibility with biological tissues. To address these challenges, four samples in the form of (52-x)SiO₂-24Na₂O-24CaO-xP₂O₅, where x is 2, 4, 6, and 8 mol%, were prepared by a unified melt-quenching method, and the feasibility of P₂O₅ content fine-tuning in improving glass structure, biodegradability, bioactivity, and antibacterial efficiency was evaluated. The results indicated that as the degree of P₂O₅ substitution increased, the network structure of the glass became looser, which provided favourable conditions for its degradation. The variation in activation energy for Si⁴⁺ ion release from 0.39 eV to 0.25 eV also supported this observation. After 7 days of immersion in simulated body fluid (SBF), analyses by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) confirmed that the Ca-P compounds deposited on the glass surfaces were essentially hydroxycarbonated apatite (HCA), and scanning electron microscopy (SEM) images revealed that the generation rate of the HCA were positively correlated with the P₂O₅ content in the glass system. Meanwhile, antibacterial studies showed that after 24 h of incubation, the antibacterial activity of the four glass samples against Escherichia coli (E. coli) successively increased, with the highest percentage reaching 87.13 ± 2.51%. In conclusion, this study demonstrates that controllable degradation and high-level bioactivity can be achieved by modulating the P₂O₅ content in silicate-based BGs, which proves to be an effective and practicable strategy.