Development of plasma-polymerized nanocomposite coatings with targeted antimicrobial activity utilizing glycine-coated ZnO nanoparticles

Designing sustainable food packaging materials with targeted antimicrobial activity is a promising approach to extend food shelf life while minimizing environmental pollution. This study employs a green, atmospheric pressure, aerosol-assisted plasma deposition (AAPD) to develop nanocomposite coatings based on polyethylene glycol (PEG) and glycine (Gly)-coated zinc oxide nanoparticles (ZnO NPs), aiming for targeted antimicrobial activity. The results indicate that Gly-coated ZnO NPs can be homogeneously dispersed into the PEG matrix, forming uniform coatings with a well-structured nanoscale roughness, when using up to 2 wt% of Gly-coated ZnO NPs. In contrast, using uncoated ZnO NPs leads to non-homogeneous coatings with enhanced NP agglomeration. The developed nanocomposite coatings closely resemble the chemical structure of conventional PEG polymers and exhibit enhanced hydrophilic characteristics, particularly the coatings with Gly-coated ZnO NPs. Furthermore, the Gly-coated ZnO NPs exhibited stronger activity against S. aureus (Gram-positive), whereas uncoated ZnO NPs were more potent against E. coli (Gram-negative). The release of Zn ions from the coatings in different food simulants was below the specific migration limit. To evaluate the antibacterial activity when exposed to actual food products, sterilized pork sausages inoculated with a combination of Listeria monocytogenes (L. monocytogenes) and Lactic Acid Bacteria (LAB) strains were wrapped in the polyethylene (PE) film coated with PEG/ZnO and sealed in vacuum packaging, after which the growth of bacteriawas evaluated while stored at 7 °C. The nanocomposite coatings, particularly those containing Gly-coated ZnO NPs, effectively inhibited bacterial growth during storage time. Overall, novel nanocomposite coatings indicate potential as efficient targeted antimicrobial coatings for food storage.