Sustainable photothermal composite hydrogels from sunflower exine capsules for combating drug-resistant bacteria and promoting wound healing

Wound healing is often hindered by persistent infection, delayed hemostasis, and impaired tissue regeneration, while conventional dressings typically lack a combination of antibacterial, hemostatic, and regenerative functions. Meanwhile, the overuse of antibiotics not only exacerbates bacterial resistance but also causes adverse side effects, highlighting the urgent need for non-antibiotic antimicrobial strategies. In this study, an antibiotic-free photothermal composite hydrogel for skin wound repair was constructed based on natural sunflower pollen exine capsules (SECs). SECs possess an intrinsic three-dimensional porous structure and abundant surface functional groups, exhibiting excellent non-antibiotic antibacterial activity and biocompatibility. Furthermore, polydopamine (PDA) modification markedly enhanced their photothermal conversion efficiency under near-infrared (808 nm) irradiation and antibacterial activity against Escherichia coli. By incorporating SECs or PDA-modified SECs into a chitosan (CS) hydrogel matrix, SECs/CS and SECs/PDA/CS composite hydrogels were successfully fabricated. The resulting materials exhibited a porous architecture, photothermal responsiveness, structural stability, and rapid hemostatic capability. In vitro experiments demonstrated that these hydrogels effectively inhibited E. coli and Staphylococcus aureus, and exhibited remarkable antibacterial activity against drug-resistant strains such as methicillin-resistant S. aureus (MRSA), with SECs/PDA/CS showing superior performance under NIR irradiation. Biocompatibility tests confirmed their excellent cytocompatibility, while in vivo studies revealed that the hydrogels significantly shortened the hemostasis time, accelerated wound closure, and promoted tissue regeneration. In summary, this study proposes a sustainable non-antibiotic strategy that integrates natural microstructures with photothermal functionality to develop multifunctional wound dressings with antibacterial (especially against drug-resistant bacteria), hemostatic, and regenerative properties, offering a new paradigm for chronic wound management.