Atomically precise Au nanocluster-embedded carrageenan for single near-infrared light-triggered photothermal and photodynamic antibacterial therapy

In this study, we report atomically precise gold nanoclusters-embedded natural polysaccharide carrageenan as a novel hydrogel platform for single near-infrared light-triggered photothermal (PTT) and photodynamic (PDT) antibacterial therapy. Briefly, atomically precise captopril-capped Au nanoclusters (Au₂₅Capt₁₈) prepared by an alkaline NaBH₄ reduction method and then embedded them into the biosafe carrageenan to achieve superior PTT and PDT dual-mode antibacterial effect. In this platform, the embedded Au₂₅Capt₁₈, as simple-component phototherapeutic agents, exhibit superior thermal effects and singlet oxygen generation under a single near-infrared (NIR, 808 nm) light irradiation, which enables rapid elimination of bacteria. Carrageenan endows the hydrogel platform with superior gelation characteristics and wound microenvironmental regulation. The Au₂₅Capt₁₈-embedded hydrogels exhibited good water retention, hemostasis, and breathability, providing a favorable niche environment for promoting wound healing. In vitro experiments confirmed the excellent antibacterial activity of the Au₂₅Capt₁₈ hydrogels against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The antibacterial effect and promoting wound healing function were further validated in a S. aureus-infected wound model. Biosafety evaluation showed that the Au₂₅Capt₁₈ hydrogel has excellent biocompatibility. This PTT/PDT dual-mode therapy offers an alternative strategy for battling bacterial infections without antibiotics. More importantly, this hydrogel is facile to prepare which is helpful for expanding applications.