Submitted to: Carbohydrate Polymer Technologies and Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2024
Publication Date: 9/19/2024
Citation: Qu, B., Xiao, Z., Luo, Y., Luo, Y. 2024. Carboxymethyl cellulose capped zinc oxide nanoparticles dispersed in ionic liquid and its antimicrobial effects against foodborne human pathogens. Carbohydrate Polymer Technologies and Applications. 6: Article e100364. https://doi.org/10.1016/j.carpta.2023.100364.
DOI: https://doi.org/10.1016/j.carpta.2023.100364

Interpretive Summary: Antimicrobial agents are needed to control microbial growth on food contact surfaces for improved food safety. While zinc oxide nanoparticles have shown strong antimicrobial efficacy, their high tendency to aggregate hinders their practical applications. In this study, a green and eco-friendly method involving choline acetate was used to improve the dispersibility of the zinc oxide nanoparticles. Results showed that choline acetate treatment effectively maintained uniform and small particles of zinc oxide throughout the process without aggregation. The treatment complex showed strong antimicrobial efficacy against harmful bacteria Listeria monocytogenes. Findings benefit the food industry in developing novel approaches to control harmful microorganisms.

Technical Abstract: ZnO nanoparticles (NPs) have been proven with antimicrobial function, but the high tendency to aggregate hinders their practical applications. To improve the dispersibility of ZnO NPs as antimicrobial agent, choline acetate (ChAc), a class of ionic liquids, was employed to facilitate the dispersion of ZnO NPs capped with carboxymethyl cellulose (CMC). In this study, ZnO-CMC NPs at various concentrations were added in DI water with or without ChAc followed by sonication. Uniform and small particles were observed in ChAc-dispersed ZnO-CMC (ChAc/ZnO-CMC) by atomic force microscopy, due to the formation of a double layer on their surface via the positive and negative charged ionic clusters from ChAc, thereby enhancing repulsion and inhibiting aggregation. The antimicrobial capacity was tested against two strains - Listeria monocytogenes (L. monocytogenes) and Escherichia coli K-12 (E. coli K-12), based on minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and bacteria growth kinetics. The ChAc/ZnO-CMC exhibited the strongest antimicrobial activities as compared with commercial ZnO and as-prepared ZnO-CMC without ChAc. The antimicrobial capacity was related to occurrence of cytolysis, disruption of cell walls and ROS production. Overall, ChAc/ZnO-CMC NPs hold great potential as an antimicrobial agent and may be incorporated into different food packaging films and coatings.