MIL-88B-Stabilized Anthocyanin-Catechin Films with DFT-Revealed Electron Transfer for Biodegradable Meat Freshness Indicators
摘要
This study describes the development of a biodegradable colorimetric membrane by co-pigmenting Lycium ruthenicum anthocyanins (LRA) with catechins, and loading the stabilised complex onto MIL-88B(Fe) dispersed in a chitosan/polyvinyl alcohol (PVA) matrix. Molecular docking simulations revealed favorable non-covalent interactions, primarily hydrogen bonding and π-π stacking, between the anthocyanin and the MIL-88B framework, particularly in proximity to its iron-based coordination nodes. The LRA complex exhibited the highest binding affinity and conformational stability. Density functional theory (DFT) calculations revealed interfacial electron transfer between the LRA and Fe centers, Bader charge analysis indicated electron transfer, with the Fe center losing ~ 0.927 e upon adsorption, providing a possible electronic-level explanation for the enhanced photothermal stability observed in thermogravimetric analysis (TGA) and color retention tests. The optimized film (containing LRA 3% + MIL-88B) exhibits enhanced tensile strength, increased water contact angle to 89.9°, indicating reduced surface hydrophilicity, and significant antioxidant activity, with ABTS radical scavenging rates exceeding 80%. The films exhibited rapid (< 5 min) pH responsiveness over a wide pH range (pH 2–13), demonstrating the potential to reflect the spoilage of beef, lamb, and shrimp through visible colour changes. Soil burial experiments confirmed that the film degraded by approximately 70% within 30 days. This MOF-assisted strategy significantly improved the inherent instability of anthocyanins and provides a sustainable functionalisation solution for smart food packaging systems.