Whole-flax valorization for a bio-based thermosensitive hydrogel dressing: In situ silver-functionalized fibers and leaf-derived carbon dots for infected wound repair

Industrial flax is an important fiber crop with considerable potential for the development of high-value bio-based materials beyond its conventional textile applications. In this study, a whole-flax valorization strategy was proposed to construct a multifunctional thermosensitive hydrogel dressing by simultaneously utilizing flax fibers and flax leaves. Silver nanoparticles (Ag NPs) were in situ reduced and immobilized on flax fibers to provide sustained antibacterial activity and mechanical reinforcement, while carbon dots (CDs) were synthesized from flax leaves via a hydrothermal process to confer antioxidant capacity. These crop-derived components were further integrated with FGF2 into a poloxamer-based thermosensitive hydrogel to obtain a multifunctional composite dressing (FAFCG) for infected wound management. The underlying hypothesis was that the structural function of flax fibers, the antibacterial activity of fiber-anchored Ag NPs, and the redox-regulating effect of leaf-derived CDs could synergistically modulate the hostile wound microenvironment characterized by bacterial infection, excessive reactive oxygen species (ROS), and persistent inflammation. FAFCG exhibited rapid gelation at body-surface temperature, favorable swelling and degradability, and improved mechanical properties. In vitro, FAFCG showed broad-spectrum antibacterial activity against Escherichia coli and Staphylococcus aureus, reduced intracellular ROS accumulation, and promoted fibroblast proliferation and migration under oxidative stress. In vivo, FAFCG significantly decreased bacterial burden, accelerated wound closure, and promoted re-epithelialization, collagen deposition, and angiogenesis in an infected full-thickness skin defect model. Mechanistically, FAFCG activated the Nrf2 antioxidant pathway and suppressed NF-κB signaling, thereby exerting coordinated antibacterial, antioxidant, and anti-inflammatory effects. Overall, this work establishes a crop-derived, whole-flax, value-added material platform that links industrial flax utilization with advanced biomedical application, providing a promising route for converting flax biomass into high-performance functional products.