Quercetin-Fe3+ Coordination Mediates Rapid Ambient Gelation of a Composite Hydrogel for Multifunctional Biointerfaces

Rapid preparation of composite hydrogels typically relies on external energy input, forcing a compromise among fabrication simplicity, mechanical durability, and biological functionality. Herein, a redox-active quercetin-Fe3+ (QCT-Fe3+) coordination complex is designed to address this conflict, acting simultaneously as a mild catalyst and an active functional component. QCT-Fe3+ mediated activation of ammonium persulfate enables acrylic acid polymerization in ∼5 s without ultraviolet light or external heating. After optimizing the QCT:Fe3+ ratio and the Fe3+ concentration, chitosan was incorporated to form a poly(acrylic acid)/chitosan composite hydrogel, which gelated in 21.0 ± 1.6 s at room temperature. This hydrogel exhibited a tensile modulus of 103.09 ± 4.98 kPa and an equilibrium swelling ratio of 193.91 ± 11.60% and retained ∼88.7% of its peak stress after 500 consecutive loading–unloading cycles. Multiple interfacial interactions render firm adhesion with wet tissues (63.11 ± 4.00 kPa on porcine skin and 19.31 ± 2.40 kPa on porcine subcutaneous fat). The strain-dependent electrical response, with a gauge factor of up to 2.54, enables conformal monitoring of finger, elbow, and knee movements. Sustained QCT-Fe3+ complex release over 168 h endows the hydrogel with radical-scavenging ability and antibacterial activity. The hydrogel suppresses fibroblasts proliferation and migration selectively while remaining compatible with myoblasts, suggesting potential for wound status monitoring and antifibrotic application. By coupling rapid network formation with mechanical, sensing, and biological functions through a single metal-polyphenol coordination motif, this study provides a versatile strategy for engineering multifunctional hydrogel biointerfaces.