Rheological kinetics of crosslinking gellan gum— bioactive glass composites

Abstract

Gelation kinetics and viscoelastic properties are critical for the biomedical application of hydrogel composites. Specifically, gelation time dictates the injection or processing window. In this study, we aimed to develop mechanically strong, viscoelastic gellan gum-bioactive glass composites by investigating their crosslinking behavior at physiologically relevant pH and temperature. We examined how small variations in pH and bioactive glass loading influence gelation time, stiffness, and elasticity. Using strain-controlled rheology, we found that gelation occurred from 7.5 to 28 min for composites containing 20–30 wt% glass, demonstrating their suitability for injection and 3D printing. Rheological characterization further confirmed an elastically dominant behavior (G’ > G’’) at all conditions. The strongest crosslinking was observed at 20 wt% glass loading (at pH 6.5 and 6.8) and 30 wt% glass loading (at pH 7.0). Increasing the glass loading and pH broadened the viscoelastic region and shifted the G’/G’’ crossover point to higher strains. A key finding of this study was the observed strong influence of small pH changes within the range of 6.5–7.0 to the gelation kinetics of the gellan gum-bioactive glass composites.