Influence of Ag2O on structural evolution, dissolution behavior and antibacterial response of sodium-calcium aluminoborophosphate glasses

Abstract

The influence of low-level (0.25–0.75 mol%) silver oxide (Ag 2 O) substitution for Na 2 O on glass structure and in vitro dissolution of sodium–calcium aluminoborophosphate glasses was investigated. Spectroscopic analysis showed that the borate sub-network is dominated by BO 4 units (>78%), whereas the phosphate sub-network contains mainly Q 1 species with an increasing contribution of Q 2 environments at higher Ag 2 O content, accompanied by Al 2 O 3 enrichment. These changes are consistent with increased network connectivity, including a higher contribution of more polymerized phosphate environments and changes in mixed B–O–P-related environments. In vitro dissolution tests showed that the glass with 0.75 mol% Ag 2 O exhibited lower mass loss and more pronounced pH increase than the lower-Ag and Al compositions. These trends are consistent with a more connected and chemically durable borophosphate network. After immersion, EDX, XRD, and FTIR confirmed the formation of calcium-phosphate-rich surface deposits, mainly apatite-like in character. No measurable antibacterial activity against E. coli and MRSA was observed under the applied test conditions. The results indicate that sub-mol% Ag 2 O substitution is associated with measurable changes in the structure and reactivity of sodium–calcium aluminoborophosphate glasses, but at the investigated concentrations it does not provide measurable antibacterial functionality.