This study investigates a novel photothermal composite hydrogel (PGS-Cu/PTCP) derived from cuttlebone β-tricalcium phosphate, which is responsive to near-infrared (NIR) laser for oral photothermal therapy (PTT). This study can potentially contribute to enhancements in the safety and efficacy of bone-defect reconstruction materials via the incorporation of photothermal and antibacterial properties.

A PGS-Cu/PTCP hydrogel was synthesized using cuttlebone β-tricalcium phosphate, polyvinyl alcohol, gelatin, sodium alginate, copper ions, and polydopamine. The porosity, mechanical properties, photothermal antibacterial activity, and biocompatibility of the hydrogel were evaluated. Photothermal performance was assessed by irradiating the hydrogel samples with an 808 nm NIR laser at different power settings, and the temperature changes were recorded using an infrared thermal imaging camera. Cytotoxicity tests were conducted using L929 fibroblast cells, and antibacterial performance was tested against Escherichia coli and Staphylococcus aureus.

The PGS-Cu/PTCP hydrogel exhibits excellent porosity, which is beneficial for nutrient supply and waste removal in bone-tissue engineering. Under 808 nm NIR laser irradiation at 1.05 W, the hydrogel's temperature reached 49.4 ℃ within 420 s, thus indicating high photothermal conversion efficiency (Fig. 3). The hydrogel shows low cytotoxicity and >90% cell viability for L929 cells (Fig. 2). Antibacterial tests showed significantly reduced survival rates of Escherichia coli and Staphylococcus aureus upon NIR irradiation, which differ considerably from those of non-irradiated samples (Fig. 5). The combination of copper ions and polydopamine in the hydrogel contributed to its superior antibacterial properties, which is likely owing to the disruption of bacterial membranes and enhanced photothermal effects.

The novel PGS-Cu/PTCP hydrogel efficiently converts NIR light into thermal energy, thus providing precise in-vivo photothermal antibacterial activity. This material significantly enhances the safety of oral bone-repair applications, thereby rendering it a promising candidate for future clinical use in maxillofacial-bone reconstruction.