The skin is the largest human organ and is susceptible to injury and form infected wounds that ultimately cause serious health problems.[1], [2], [3], [4] Hydrogel wound dressings are rapidly evolving owing to their good mimicking of the microenvironment of wound repair. [5], [6], [7] Polyvinyl alcohol (PVA) is a synthetic hydrophilic polymer that is non-toxic, biodegradable, and water-soluble. [8], [9], [10], [11] As a flexible material [12], PVA meets the softness[13] and fit required for wound dressings and has been widely used in hydrogel development. To endow hydrogels with antimicrobial properties, functional antimicrobial substances such as antibiotics [14], [15] and anti-inflammatory substances (e.g. Ag nanoparticles) [16], [17] are often introduced. However, overuse of antibiotics has led to increased resistance, complicating the choice of antimicrobial drugs. [18], [19] Traditional anti-inflammatory substances (e.g. Ag nanoparticles) accumulate in wounds or in vivo, and enter the body through transport proteins or endocytosis, causing toxic damage to epithelial cells and macrophages. [20], [21] The selection and optimization of suitable functional antimicrobial substances urgently require great efforts from researchers.

The emerging functional substance Fe3+ is enabled to cross-link with phenolic hydroxyl substances (such as polydopamine, tannin (TA), catechol, etc.), thus endowing hydrogels with good electrical conductivity [22], antibacterial [23], [24] and toughness [25]. In terms of functional bacterial inhibition, Li et al.[26] developed tannic acid-chelated Fe-decorated molybdenum disulfide nanosheets (MoS2 @TA/Fe NSs), which showed great potential for infected wound healing. Xu et al.[27] investigated the physical antibacterial activity and photodynamic antibacterial therapy (PAT) effects possessed by TA/Fe/AgNPs nanofilms. Intriguingly, TA is mostly used for chelation [28], [29], [30], [31], and the TA-adjacent hydroxyl groups provide chelating sites for Fe3+ [32], forming a three-dimensional cross-linked metal-phenol network [33] that further enhances their anti-inflammatory and antioxidant properties [34]. However, the cross-linking of Fe3+ with TA is difficult to avoid the defect of high hardness. By the flexibility of PVA, it was employed to encapsulate Fe3+ and TA, thus improving the flexibility of the hydrogel. [35], [36], [37] In addition, the chelation process of Fe3+ and TA is very rapid and tends to agglomerate and sink. Therefore, the homogeneity of the internal intrinsic structure and composition distribution of TA/Fe3+ functionalized hydrogels faces great challenges.

Herein, a PVA-encapsulated TA/Fe3+ functional dual-network homogeneous hydrogel (PDH gel) was developed via chelating crosslinking and glycol dispersion for accelerated infected wound healing (Scheme 1 A&B). Ethylene glycol has hydrophilic hydroxyl groups and good dispersion in aqueous solutions. The oxy ether group formed by its polymerization easily interacts with the surface of oxygenated rubber particles with homonymous ionic affinity and is wrapped and adsorbed on the surface of rubber particles, producing a spatial site barrier effect. This property is expected to solve the non-homogeneous situation caused by chelation. [38], [39], [40] In other words, ethylene glycol can wrap the TA-Fe component and keep the particles relatively isolated to avoid aggregation and sinking. It enables the homogeneous dispersion of TA-Fe particles in dense PVA. [41] Compared with previous studies, the ingenious design of the PDH gel not only promises to avoid the hazards of drug resistance and heavy metal biotoxicity [15], [42], but also improves its homogeneity, mechanical strength, and skin-friendliness. Finally, the antimicrobial activity and healing-promoting properties of the above PDH gels were investigated to accomplish synergistic antimicrobial and healing-promoting effects[43], [44] in order to develop their potential as infected skin wound dressings.