Impact of substituting K2O for Na2O on physico-chemical properties and in vitro bioactivity of bioactive glass S53P4

The impact of substituting K2O for Na2O (0–100%) on the physico-chemical and bioactive properties of bioactive glass S53P4 was studied. The thermal properties were evaluated using differential thermal analysis and high-temperature microscopy. Ion release kinetics was measured in static and dynamic TRIS-buffer and SBF using inductively coupled plasma optical emission spectroscopy. Substituting K2O for Na2O showed a mixed-alkali effect (MAE) for the thermal properties with a minimum value for the glass containing around 20% K2O. The hot-working range increased with the potassium content. The glass with 66% of Na2O replaced with K2O exhibited MAE in static TRIS by giving the biggest pH change and ion release at 24 h. The same glass showed the lowest pH and Si species release in dynamic SBF at the longest dissolution time, 72 h. Both single-alkali glasses showed higher in vitro bioactivity in dynamic SBF. The results provide tools for tailoring new bioactive glass compositions with desired properties.