Sodium alginate modified by dopamine multifunctional injectable hydrogel with photothermal, antibacterial, and...

Sodium alginate (SA)-based wound dressings have attracted increasing attention for wound management. In this study, a multifunctional injectable alginate hydrogel was developed via a dopamine modification strategy. Dopamine-grafted sodium alginate (SA-DA) was synthesized and combined with polydopamine nanoparticles (PDA) to obtain an SA-DA/PDA hydrogel with strong tissue adhesion and photothermal functionality. In situ crosslinking was achieved using a calcium carbonate (CaCO₃)/glucono-δ-lactone (GL) system, enabling rapid gelation and conformal coverage of irregular wounds. Benefiting from the hydrophilic SA backbone and PDA incorporation, the hydrogel exhibited favorable swelling behavior, structural stability, and enhanced photothermal responsiveness. Upon 808 nm near-infrared (NIR) irradiation (1.5 W cm^-2) for 10 min, the hydrogel temperature increased to approximately 46 °C, generating an effective mild photothermal effect. This response resulted in efficient antibacterial activity, eliminating about 97% of Escherichia coli and Staphylococcus aureus in vitro, along with rapid pro-coagulant performance. In a rat model of infected full-thickness skin defects, a single injection followed by NIR irradiation significantly accelerated wound closure, reducing the residual wound area to 1% by day 9 without observable systemic toxicity. Overall, the SA-DA/PDA hydrogel integrates injectability, photothermal antibacterial activity, and biocompatibility, demonstrating strong potential as a multifunctional dressing for accelerated healing of infected wounds.