Enhanced chitosan films for fruit preservation via active nanovesicles and metal coordination

We present a polysaccharide-based film that integrates self-assembled active vesicles derived from glycyrrhizic acid (GA) and a metal-coordination reinforced network, achieving simultaneous improvements in structural performance and functional properties. The GA-based nanovesicles not only provided stable encapsulation and sustained release of hydrophobic essential oils, but also facilitate enhanced antibacterial activity through membrane-permeabilizing effects that disrupt bacterial cell integrity. Additionally, we introduce a reversible metal-coordination cross-linking network, which establishes a robust three-dimensional framework that markedly improves both the mechanical properties and water vapor barrier capacity of the film. Specifically, the resulting chitosan-Cu²⁺-GA@oregano essential oil composite film presentd a low water vapor permeability of 1.33 × 10^-11 g m^-1s^-1Pa^-1, water contact angle up to 94.83°, tensile strength of 45.87 MPa and elongation at break of 28.89%, while the release rate of active substances reaches 72.90% within 84 h. Moreover, the film displayed exceptional antibacterial activity, achieving a 100% bactericidal rate against E. coli and S. aureus, and possessed antioxidant capacity, with 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging rates of 88% and 98%, respectively. In cherry tomato preservation experiments, the CCGO film effectively delays the deterioration of cherry tomatoes.