A novel antimicrobial film AgNPs@γ-CD-MOFs/PLA: Preparation, characterization and its application for packaging of Agaricus bisporus

Abstract

Nano-sized cyclodextrin metal-organic frameworks (γ-CD-MOFs) have excellent guest substance loading capabilities. However, the traditional preparation of nano-sized γ-CD-MOFs is commonly achieved by the use of size regulators, which are toxic and cannot be completely removed, resulting in their inability to be applied in food packaging. In this study, a green synthesis method for nano-sized γ-CD-MOFs (200–800 nm) without the size regulators was successfully formulated. Crystal size was controlled by adjusting three factors: the concentrations of γ-CD and K⁺, the rate of ethanol addition and the number of ethanol washes. Ultrasmall-sized silver nanoparticles (AgNPs) of 1–2 nm were successfully prepared using nano-sized γ-CD-MOFs as templates, which increased the silver load rate up to 3.008 %. Moreover, a new packaging film assembled by AgNPs, γ-CD-MOFs and polylactic acid (AgNPs@γ-CD-MOFs/PLA) was prepared, and its inhibition rates against Escherichia coli, Staphylococcus aureus, and Pseudomonas tolaasii reached more than 80 %, which exhibited good antimicrobial capabilities. Furthermore, the oxygen and water vapor transmission rates (RH 50 %) of AgNPs@γ-CD-MOFs/PLA respectively reached 1204 cm³/ (m² ∙ d ∙ 0.1 MPa) and 1710.267 g/ (m² ∙ 24 h), which were significantly higher than traditional polyethylene (PE) packaging. In addition, compared with PE and PLA, the AgNPs@γ-CD-MOFs/PLA could effectively inhibit bacterial brown spot of Agaricus bisporus and maintained a better appearance after 12 days of storage. These findings will expand the applications of nano-sized γ-CD-MOFs in food preservation.