Mussel-inspired chitosan/alginate bilayer films with superior UV barrier and antibacterial activity for food preservation.

Abstract

Food spoilage during post-harvest storage underscores the critical need for sustainable active packaging, yet single-layer polysaccharide films suffer from limited functionality and conventional bilayer strategies lack molecular-level integration. Herein, we proposed a mussel-inspired bilayer composite system fabricated by layer-by-layer casting, which addresses these limitations through synergistic interfacial design. This design integrated the molecular-level functionalization of chitosan (CS) layer with polyphenols to impart enhanced adhesion and biological activity, combined with nano-reinforcement of alginate (ALG) layer using a metal-phenolic network (MPN) functionalized layered clay to achieve superior barrier function. The resultant bilayer composite system demonstrated outstanding antibacterial activities against E. coli (up to 98.8%) and S. aureus (up to 98.0%), excellent UV barrier capacity in the UVB (up to 99.99%) and UVA (up to 99.91%) regions, alongside improved hydrophobicity, antioxidant activity, and acceptable opacity. In addition, the tensile strength reached as high as 14.40 MPa, representing an improvement of 221.43% compared with pure ALG film. In the strawberry preservation experiment, the bilayer composite system effectively extended the shelf life of strawberries to seven days, owing to the structural complementarity and the high bioactivity of polyphenols. These results reveal that utilizing natural polysaccharides, polyphenols, and layered clay to construct a mussel-inspired bilayer composite system is a feasible strategy, providing a sustainable and promising approach for designing multifunctional packaging materials to mitigate food waste.