Synthesis of a Novel Thermoresponsive S53P4 Bioactive Glass Extract–Poloxamer 407 Injectable Hydrogels: Assessment of Biocompatibility and Antimicrobial Properties

This study reports the development and characterization of thermoresponsive injectable hydrogels based on S53P4 bioactive glass (BG) extracts and poloxamer 407. S53P4 BG was selected for its established release of therapeutic ions, including silicon species, calcium, sodium, and phosphate. Hydrogels were prepared using ion-rich S53P4 BG extracts, and their pH, ion release, rheological behavior, syringeability, biocompatibility, and antibacterial activity were evaluated. The hydrogels exhibited gelation temperatures between 17.2°C and 19.7°C, enabling application in a sol state and rapid gelation upon warming. Syringeability tests demonstrated high mass-delivery fidelity, with 97%–100% recovery for sol-state formulations and 91%–95% recovery for gel-state formulations. Frequency-sweep confirmed shear-thinning behavior, supporting practical injectability. Inductively coupled plasma-optical emission spectrometer (ICP-OES) analysis verified stable ionic composition before and after thermal cycling. Biocompatibility assays with L929 fibroblasts and human umbilical vein endothelial cells (HUVECs) exhibited ≥70% cell viability for all formulations, meeting ISO 10 993–5 criteria. Antibacterial testing demonstrated up to a 5-log reduction in Staphylococcus aureus ATCC 25 923 and Escherichia coli ATCC 25 922 compared to the initial inoculum, confirming strong bactericidal effects.Overall, the S53P4 BG extract–poloxamer 407 hydrogels display injectability, thermoreversible gelation, stability, biocompatibility, and potent antibacterial properties, supporting their suitability for future in vivo applications.