Carrier‐Free Hydrogel From Metal Ion and Near‐linear Herbal Polysaccharide With Photothermal and Self‐adaptive Multienzyme‐Like Activity for Healing MRSA‐infected Diabetic Wound

ABSTRACT

Carrier‐free hydrogel from herbal polysaccharide and metal ion coordination holds great potential for diabetic wound therapy, yet near‐linear/linear herbal polysaccharide suffers from intramolecular hydrogen‐bond‐mediated chain entanglement that blocks metal ion coordination and hydrogel assembly. Herein, Polygonatum sibiricum polysaccharide (PSP) with a linear β‐1,4‐linked glucan/mannan backbone was isolated and served as model to investigate the assembly of near‐linear polysaccharide via metal ion coordination. Rapid gelation can be realized by adjusting the pH of PSP solution to 11‐12 followed by Cu ²⁺ introduction. In resultant hydrogel, PSP functions as carrier and exhibits ROS‐scavenging and immunomodulatory capacity, whereas Cu ²⁺ acts as cross‐linker and endows the hydrogel with POD‐, SOD‐, CAT‐mimicking and photothermal activity. This hydrogel displays pH‐adaptive enzyme behavior: SOD converts excess superoxide anion radical into H ₂ O ₂ under initial nearly neutral conditions, subsequent weakly acidic microenvironment trigger POD‐mediated hydroxyl radical generation for synergistic photothermal sterilization. After bacterial clearance, restored neutral pH activates SOD‐ and CAT‐like activity to decompose H ₂ O ₂ into O ₂ and alleviate tissue hypoxia, driving wound transition from inflammation to remodeling for high‐quality diabetic wound repair. Overall, this study establishes a carrier‐free hydrogel fabrication strategy based on near‐linear polysaccharide and metal ion coordination, and provides an enzyme‐mimetic catalytic hydrogel dressing for infected diabetic wound.