High oxygen barrier and synergistically enhanced photodynamic antibacterial films via Berberine/layered double hydroxide for food packaging.

Abstract

Microbial contamination and oxygen ingress are primary drivers of food spoilage, but advanced materials that simultaneously offer high oxygen barrier and effective antibacterial functions remain scarce. To address this dual challenge, we engineered a polyvinyl alcohol-based composite coating, incorporating the natural aggregation-induced emission photosensitizer berberine (BBR) and non-toxic layered double hydroxide nanosheets (LDH NS), on a polyethylene terephthalate substrate. The developed composite film demonstrated a low oxygen transmission rate of 0.06 cm3 m-2 day-1 atm-1. Furthermore, it achieved 100 % inhibition rate against both Staphylococcus aureus and Escherichia coli upon light irradiation. Crucially, we propose and elucidate a novel antimicrobial enhancement mechanism mediated by the orderly-arranged LDH NS for BBR. This mechanism involves (i) promoting BBR molecular aggregation to enhance reactive oxygen species (ROS) generation, and (ii) improving bacterial capture capacity via electrostatic interactions. These effects collectively establish a synergistic "capture-ROS enrichment-bacterial killing" pathway on the film surface. In a practical application, the composite film effectively suppressed microbial growth on packaged bread, extending its shelf life by more than 4-fold compared to conventional packaging. This work not only presents a promising multifunctional material for food preservation but also provides fundamental insights into the design of nanomaterial-enhanced, natural photosensitizer-based systems for advanced active packaging.