Synthesis, Characterization, and Antibacterial Activity of Silver Nanoparticle-Based Biopolymer Formulations Against Escherichia coli for Food-Related Applications

Foodborne microbial contamination remains a major challenge for the safety and shelf life of poultry and other perishable foods. This study developed a silver nanoparticle (AgNP)-based antimicrobial formulation and evaluated its physicochemical characteristics, antibacterial activity against Escherichia coli, and preliminary concentration-dependent effects on bovine sperm viability. AgNPs were synthesized using a modified glucose–citrate reduction method. UV–Vis measurements showed characteristic surface plasmon resonance maxima within approximately 411–422 nm across the evaluated synthesis experiments. Transmission electron microscopy revealed predominantly quasi-spherical particles with a mean diameter of 23.14 ± 8.31 nm (n = 100), a median diameter of 25.30 nm, and a size range of 5.07–34.88 nm. The mean hydrodynamic radius was 15.47 nm, and the zeta potential was −38.80 ± 0.63 mV, indicating pronounced electrostatic stabilization of the colloidal dispersion. In antibacterial assays, the complete AgNP–chitosan–lactic acid–collagen formulation resulted in complete absence of visible E. coli growth at all tested concentrations, including the lowest evaluated nominal Ag concentration of 6.5 mg/L in the prepared formulation, corresponding to approximately 3.25 µg/mL in the final antibacterial assay mixture, whereas the other tested formulation variants did not achieve complete growth suppression. In the preliminary bovine sperm assay, AgNP dispersion alone caused a concentration-dependent decline in viability, with statistically significant effects observed from 1.37 mg/L onward. These findings demonstrate that the complete multicomponent formulation provides strong antibacterial activity at relatively low nominal Ag concentrations while also highlighting the need for further toxicological and migration assessment. Future studies should validate the formulation in real food matrices and evaluate silver release, migration, and safety under relevant storage and application conditions.