Multifunctional pectin films based on mussel-inspired modified 2D Ag nanosheets for long-lasting antibacterial and enhanced barrier properties

Abstract

Two-dimensional (2D) silver (Ag) nanosheets are ideal fillers to improve the barrier and antimicrobial properties of bio-based nanocomposite films for food packaging due to their high aspect ratio features and superior bactericidal activity. However, the nano-Ag directly added to the matrix is prone to aggregation, which will weaken its effect. In this study, Ag nanosheets were surface non-covalently functionalized with polydopamine (PDA) formed by dopamine oxidative self-polymerization. The PDA modification improved the dispersibility and biocompatibility of the nanosheets in pectin matrixes and immobilized them, delaying their release rate. The potential of the prepared pectin-based nanocomposite film in food packaging was investigated. Results showed that the composite film containing PDA-modified Ag nanosheets (PDA@Ag) had superior UV resistance and mechanical properties, a more hydrophobic surface with a water contact angle close to 90°. Compared with pure pectin film, the barrier capacity of the film to both water vapor and oxygen was significantly improved. It also exhibited excellent bactericidal efficiency against E. coli and S. aureus. When applied to Agaricus bisporus, the film effectively protected them from UV light, oxygen and microorganisms, thus delaying browning and spoilage, maintaining their texture, color and nutrients, and extended their freshness period up to 6 days.