Polydopamine Nanoparticle-Integrated Smart Bletilla striata Polysaccharide Hydrogel: Photothermal-Triggered CO2 Release for Diabetic Wound Microenvironment Modulation

Abstract

Purpose: Bacterial infection, oxidative stress, vascular damage, and nutrient deficiencies significantly hinder the repair of diabetic skin wounds. Conventional wound dressings offer limited protection and fail to effectively promote the healing of diabetic wounds. To address these challenges, we developed a photothermal-responsive Bletilla striata polysaccharide hydrogel capable of releasing carbon dioxide (CO 2 @PDA Hydrogel). Methods: This hydrogel utilizes carboxymethylated Bletilla striata polysaccharide as the primary matrix, cross-linked through metal coordination bonds, and incorporates bicarbonate-containing polydopamine nanoparticles (CO 2 @PDA NPs) with photothermal conversion properties to generate CO 2 . The structure and morphology of CO 2 @PDA NPs were characterized by DLS, SEM, FTIR, and XRD, and the hydrogel properties of CO 2 @PDA Hydrogel were characterized by SEM, rheological properties, and FTIR. The photothermal properties of the CO 2 @PDA Hydrogel were studied by measuring the temperature change and CO 2 release after irradiation with an NIR laser (808nm). The improvement effect of CO 2 @PDA Hydrogel on the diabetes wound microenvironment was comprehensively evaluated by promoting L929 cell proliferation, inhibiting bacterial growth ( Staphylococcus aureus and Escherichia coli ), and treating diabetes wound infection in rat models. Results: Under 808 nm near-infrared laser irradiation, the embedded CO 2 @PDA NPs convert light into heat, triggering the decomposition of HCO 3 − and releasing a substantial amount of CO 2 locally at the diabetic wound site. The released CO 2 responds to the Bohr effect, alleviating hypoxia and promoting angiogenesis. Simultaneously, the Bletilla striata polysaccharide in the hydrogel exerts antioxidant and anti-inflammatory effects, while the cross-linking agent Fe 3+ and the photothermal properties of CO 2 @PDA NPs provide robust antibacterial activity. Conclusion: The self-assembled cross-linked carboxymethyl Bletilla striata polysaccharide Hydrogel with CO 2 @PDA NPs prepared in this study has a good photothermal conversion effect. It improves the microenvironment of diabetes wounds by improving hypoxia, antibacterial, antioxidant, and other effects, providing a good multi-functional alternative material for the treatment of refractory diabetes wounds. Keywords: multi-functional photothermal hydrogel, polydopamine nanoparticles, improving hypoxia, antibacterial activity, antioxidant effect

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