Biomimetic Dual-Layer Architectural Hydrogel Bandage with Smart Thermally Self-Contraction for Enhanced Wound Closure and Burn Wound Healing

Severe burn injuries disrupt cutaneous barrier integrity, leading to elevated infection susceptibility, substantial fluid loss, and delayed tissue regeneration, which collectively deteriorate patient outcomes. While early stage wound closure is critical for mitigating these complications, current hydrogel dressings often lack dynamic contractile properties to synergistically facilitate both physical closure and biological healing. Inspired by the mechanobiology of embryonic wound contraction, we develop a nested poly(N-isopropylacrylamide)-sodium alginate hydrogel bandage (PNS-HB) featuring a biomimetic dual-layer architecture. The outer layer comprises a polydopamine-poly(acrylic acid) (PDA-PAA) adhesive framework, enabling tissue-conformal fixation (interfacial toughness of 162 J/m²; Young's modulus of 45 kPa; fracture strain of 85%). The inner layer is a thermoresponsive PNS-HB exhibiting excellent mechanical flexibility (Young's modulus of 9.9-16.7 kPa) and programmable shape-morphing capabilities, including temperature-dependent bending (118° angle) and contraction (contraction rate of 56%). In a deep second-degree burn model, the PNS-HB demonstrated a three-stage therapeutic mechanism: thermally triggered wound edge closure through contractile strain generation, inflammatory modulation through downregulation of IL-6 and TNF-α (>60% reduction), and pro-regenerative microenvironment establishment evidenced by accelerated angiogenesis and re-epithelialization. This biomimetic dual-layer architecture offers a paradigm-shifting approach for bridging the gap between physical wound closure and biological tissue restoration in burn care.