pH-Responsive Double-Network Janus Hydrogel Incorporates Tannic Acid-iron Nanoparticles for Chronic Wound Healing and...

Polyacrylic acid-based composites hold substantial promise for intelligent wound dressing applications, owing to their intrinsic hydrophilicity and pH responsiveness. Nevertheless, their clinical translation is hindered by insufficient mechanical properties and excessive adhesion, which are directly induced by high hydrophilicity. Herein, a dual-network Janus hydrogel based on polyacrylic acid (PAA) and sodium alginate (SA), denoted as tannic acid-iron nanoparticles@polyacrylic acid/sodium alginate (TA-Fe NPs@PS Janus), was rationally fabricated. This hydrogel incorporates self-assembled TA-Fe nanoparticles (TA-Fe NPs) with inherent antibacterial activity and magnetic responsiveness. Magnetic enrichment of nanoparticles at the bottom side of the hydrogel not only significantly enhances mechanical toughness via metal-phenolic network (MPN) but also renders the top and bottom layers with distinct intelligent responses to heterogeneous pH microenvironments, thus enabling effective antibiotic-free treatment of infected wounds. TA-Fe NPs@PS Janus integrates high mechanical toughness, sensing performance, and pH responsiveness, enabling monitoring of wound microenvironmental changes through combined responses to pH and ionic variations throughout the recovery process. The physicochemical, mechanical, and rheological properties of the hydrogel were systematically characterized, and in vitro antibacterial assessments were conducted. Results demonstrate that TA-Fe NPs significantly enhance hydrogel toughness: compared with the pristine PAA/SA hydrogel (PS), the composite hydrogel incorporating 0.3% (w/v) TA-Fe NPs exhibits a 1200% increase in tensile toughness (from 0.06 MJ m⁻³ to 0.78 MJ m⁻³). The hydrogel displays high sensitivity and undergoes reversible deformation and intelligent responsive behavior under cyclic pH changes. It not only exhibits high antibacterial efficacy but also demonstrates favorable cytocompatibility. Therefore, this study proposes a smart, stimuli-responsive multifunctional hydrogel dressing for treating chronic wound inflammation and monitoring the healing process, highlighting its potential for clinical applications. STATEMENT OF SIGNIFICANCE: Chronic infected wounds severely threaten human health, yet clinically viable smart wound dressings are lacking. Polyacrylic acid (PAA) hydrogels are attractive for wound management but suffer from poor mechanical toughness and over-adhesion. We fabricate a dual-network Janus hydrogel (TA-Fe NPs@PS Janus) incorporating PAA, sodium alginate and tannic acid-iron nanoparticles. Magnetically concentrated TA-Fe NPs form metal-phenolic networks, boosting toughness by 1044.2% and creating asymmetric pH responsiveness. This cytocompatible hydrogel achieves antibiotic-free antibacterial function and real-time infection monitoring via pH changes. It overcomes key drawbacks of PAA hydrogels, integrates diagnosis and therapy, and offers a translatable strategy for intelligent chronic wound dressings.