Injectable carbon dioxide controlled releasing and photothermal carboxymethyl chitosan-alginate-black tea carbon hydrogel dressing for diabetic wound healing

The microenvironment of diabetic wounds is at risk of slow recovery, scarring and infection in medical treatment. Although many hydrogel dressings combine photothermal and gas therapies, few use CO₂'s Bohr effect to enhance oxygen release while offering precise, <i>in situ</i> control over gas and drug release. To address this, we designed an injectable multifunctional hydrogel dressing with photothermal, antibacterial, and near-infrared (NIR) - induced CO₂ properties. In this work, we developed carboxymethyl chitosan-alginate-black tea carbon conjugated with CO₂-precursors (CMCS/Alginate/BTC-CO₂) dressing. The black tea hydrothermal carbon nanoparticles attached CO₂ precursors on the surface, thermally decomposed under near-infrared irradiation to release CO₂ gas. Meanwhile, the excellent photothermal conversion efficiency enabled the hydrogel complex to demonstrate antimicrobial function. The high absorption in the UV range prevents the deposition of melanin. The CMCS/Alginate/BTC-CO₂ hydrogels exhibited good cytocompatibility and synergistically promoted NIH/3T3 cell migration. <i>In vivo</i> experiments in diabetic model mice verified that treatment of NIR-conjugated CMCS/Alginate/BTC-CO₂ hydrogels accelerated wound recovery, angiogenesis, and collagen deposition. Overall, we designed and verified the combination of stimuli-responsive photothermal CO₂ release from NIR, antimicrobial, and injectable multifunctional hydrogels, providing an effective solution for promoting diabetic wound healing both <i>in vivo</i> and <i>in vitro</i>. Such multifunctional dressing is expected to accelerate the process of wound treatment and alleviate the adverse reactions after recovery.