Biogenic silver–copper oxide nanocomposites as functional food safety agents for pathogenic microbial control in aquatic food systems

Background: Multidrug-resistant (MDR) pathogens pose a significant threat to aquatic food systems and water safety. In response, functional food science increasingly focuses on bioactive compounds derived from natural sources for food preservation and safety applications. Objectives: This study aims to investigate the antimicrobial efficacy of biogenic silver-copper-oxide nanocomposites (Ag-CuO NCs) as functional food safety agents. Methods: Biogenic Ag-CuO nanocomposites were synthesized using aqueous extracts from locally sourced botanicals at Prince Abubakar Audu University. Antimicrobial activity was evaluated against six multidrug-resistant (MDR) environmental pathogens commonly found in aquatic ecosystems (Vibrio parahaemolyticus, Escherichia coli, Salmonella enterica, Listeria monocytogenes, Pseudomonas aeruginosa, and Staphylococcus aureus) using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Synergistic effects with conventional food preservation methods were also assessed. Biomarker analysis included quantification of reactive oxygen species (ROS) production and assessment of membrane integrity disruption using flow cytometry and scanning electron microscopy (SEM). Results: Biogenic Ag-CuO nanocomposites demonstrated significant antimicrobial activity, with MIC values ranging from 2.5–15 μg/mL across all tested pathogens. The nanocomposites exhibited predominantly bactericidal activity. V. parahaemolyticus was the most susceptible (MIC: 2.5 μg/mL), whereas S. aureus displayed the highest resistance (MIC: 15 μg/mL). ROS quantification revealed a significant elevation in treated bacterial cells (p < 0.001), indicating oxidative stress-mediated antimicrobial mechanisms. SEM imaging confirmed cellular membrane disruption in all treated organisms. Furthermore, synergistic applications with a mild thermal treatment (50°C) enhanced antimicrobial efficacy by 3.8-fold, positioning these nanocomposites as adjuvant agents for food safety. Conclusions: Biogenic Ag-CuO nanocomposites exhibit promising functional antimicrobial properties relevant to food safety applications in aquatic food systems. Their natural derivation, dual-metal composition, and non-toxic profile at therapeutic concentrations suggest viability as bioactive food-grade safety compounds. Novelty of the Study: This study is among the first to systematically evaluate biogenic silver-copper oxide nanocomposites as functional food safety agents against multidrug-resistant aquatic pathogens, combining traditional food safety science with green nanotechnology to create novel bioactive food preservation solutions. The integration of mechanistic characterization (ROS quantification and cellular imaging), pathogen panel testing (six clinically relevant MDR organisms), and synergistic evaluation with mild thermal processing represents an original contribution advancing functional food antimicrobial applications. Keywords: functional foods, biogenic nanocomposites, antimicrobial agents, aquatic pathogens, food safety, bioactive compounds, multidrug-resistant bacteria