Cardamom essential oil-loaded zinc oxide nanoparticles: A sustainable antimicrobial strategy against multidrug-resistant foodborne pathogens

The globalization of the food trade has escalated challenges in ensuring food safety due to foodborne pathogens, including multidrug-resistant (MDR) strains, which pose significant public health risks and economic burdens. Innovative antimicrobial strategies are urgently required. In this study, cardamom essential oil-loaded zinc oxide nanoparticles (CEO-ZnO-NPs) were synthesized and evaluated for their antimicrobial potential and mechanisms of action against MDR Escherichia coli and Staphylococcus aureus. Dynamic light scattering and the transmission electron microscopy (TEM) micrograph confirmed a spherical nanocomposite with an average size of 141.4 nm with good dispersion and stability over 180 days. Antimicrobial activity assessed via the agar well diffusion method showed dose-dependent inhibition, with zones of 25.75 +/- 0.90 mm for E. coli and 31.05 +/- 0.46 mm for S. aureus at 400 mu g/mL. Minimum inhibitory concentrations (MIC) were 25 mu g/mL (E. coli) and 12.5 mu g/mL (S. aureus), while minimum bactericidal concentrations (MBC) were 50 mu g/mL and 25 mu g/mL, respectively. Killtime analysis revealed a marked reduction in bacterial viability after 120 min of exposure. Mechanistic studies using scanning electron microscopy showed structural damage, including disrupted membranes and cell shrinkage. Also, protein levels significantly decreased, with DNA and ATP levels reduced by 74.51 % and 91.15 % in E. coli and 79.40 % and 90.81 % in S. aureus. Enzymatic activities, including ATPase and alkaline phosphatase, were inhibited by up to 84.63 %. In addition, the low cytotoxicity of CEO-ZnO-NPs against Vero cells supporting their potential biosafety for food safety applications. These findings demonstrate that CEO-ZnO-NPs disrupt bacterial processes such as protein synthesis, membrane integrity, and enzymatic activity, offering a promising approach that aligns with the United Nations Sustainable Development Goals (SDGs), particularly SDGs 2, 3, and 12, while promoting circular economy principles by reducing reliance on synthetic preservatives to address antimicrobial resistance in foodborne pathogens.