H ₂ O ₂ –Activatable Peptide Nanozyme–Alginate Dual-Network Hydrogel Coating Reconciling Antibacterial and Moisture Retention in Postharvest Preservation

Nearly 40% of fruits spoil annually before consumption, yet reconciling the contradiction between dehydration-induced shriveling and high-humidity-facilitated microbial decay in biomass coatings without invoking antimicrobial resistance and biosafety concerns remains an unsolved challenge. We addressed this by fabricating a dip-coated dual-network hydrogel comprising self-assembling peptide nanoenzyme filaments (SPEFs) embedded in Ca²⁺-cross-linked sodium alginate (SPEF-CaAlg), which exhibits enhanced mechanical properties and sustained catalytic readiness. The interpenetrating network provided controlled water retention (∼300% equilibrium swelling) to prevent tissue desiccation while maintaining dimensional stability. Upon periodic spraying of dilute H₂O₂ solution, the embedded nanoenzymes catalytically generate •OH on demand, achieving >90% bacterial reduction against E. coli and S. aureus and inhibiting biofilm formation; concurrently, the aqueous phase replenishes transpiration-induced water losses. This creates an integrated preservation microenvironment that sustains both hydration and antibacterial protection. In strawberry preservation tests, the coating maintained by intermittent H₂O₂ misting reduced weight loss from 55 to 37%, maintained higher firmness (8.1 vs 6.7 N/cm²), preserved soluble solids (only 8% loss), and extended shelf life to 8 days with excellent biocompatibility. This replenishable catalytic hydrogel strategy offers a sustainable, safe, and efficient solution for postharvest fruit preservation, paving the way for active food preservation systems with on-demand functionality.