Hierarchically engineered nonwoven/hydrogel composites incorporating ZnO/Fe2O3 heterojunctions: Synergistic mechanical reinforcement and antibacterial mechanisms

Hierarchically structured composite hydrogels were fabricated by integrating a poly(vinyl alcohol)–hyaluronic acid (PVA–HA) network with a medical‑grade hydroentangled nonwoven (NW) scaffold, and trace amounts of ZnO/Fe 2 O 3 nanoparticles (ZnO/Fe 2 O 3 NPs, 2500/100 ppm). A simple dip‑pad–freeze–thaw process produced an interpenetrating hydrogel–fiber architecture that substantially reinforced the soft matrix while preserving high water uptake. Transmission electron microscopy revealed ultra‑small Fe 2 O 3 NPs (2–3 nm) homogeneously dispersed within the hydrogel network. These nanoparticles acted as nano‑spacers and hydrophilic centers, respectively, thereby modulating the polymer network density and free volume. Consequently, the equilibrium swelling ratio increased from ∼575% for the pristine PVA–HA hydrogel, to ∼650% for the ZnO/Fe 2 O 3 ‑loaded composite, while an appropriate water vapor transmission rate was maintained. X‑ray photoelectron spectroscopy and electron spin resonance measurements indicated that ZnO/Fe₂O₃ heterojunctions promoted efficient charge separation and enhanced reactive oxygen species (ROS) generation at the hydrogel–bacteria interface. This led to > 99% killing efficiency against both Escherichia coli and Staphylococcus aureus at ultra‑low nanoparticle loadings, without compromising fibroblast viability. Overall, this study demonstrates how nanoscale inorganic inclusions and a fibrous scaffold can be combined to tailor the colloidal network structure, transport properties, and interfacial antibacterial performance of PVA‑based hydrogels, outlining a versatile route towards multifunctional soft materials.