Construction of photo-activated berberine-rhein self-assembled nanoparticle/gelatin-chitosan composite films and their antibacterial performance.

To address the persistent environmental burden of petroleum-based plastics and the intrinsic limitations of natural biopolymer films, this study developed an enhanced active packaging material (GC/BR composite film) via the strategic incorporation of self-assembled berberine-rhein nanoparticles (BR NPs) into a gelatin/chitosan (GC) hybrid matrix. Molecular dynamics simulations coupled with various spectroscopic analyses revealed that the co-assembly of BR NPs was primarily stabilized by robust π-π stacking, electrostatic interactions, and hydrogen bonding. The reinforcement effect of BR NPs is attributed to their uniform dispersion and interfacial interactions with the GC matrix, which facilitate efficient stress transfer. As a result, the composite film exhibits notable mechanical enhancements relative to the pure GC film: tensile strength increases by 62% and elongation at break by 88%, accompanied by an improved water vapor barrier. Notably, the GC/BR film retained the aggregation-induced emission characteristics of the photosensitizer, and exhibited effective photodynamic sterilization upon visible-light irradiation. In vitro antibacterial assays demonstrated 100% inactivation against Staphylococcus aureus and 99% against Escherichia coli within 20 min of visible-light irradiation. Real-food preservation trials using chicken breasts further validated the film's capacity to suppress microbial proliferation. Crucially, migration tests revealed a maximum BR NPs leachate concentration of 0.0032 mg/mL (60-fold lower than the highest concentration in hemolysis assays), suggesting a low migration risk and a favorable preliminary biosafety profile. This work provides a promising strategy for the rational design of robust, biodegradable active packaging materials with integrated photodynamic functionality.