Radiolytic Synthesis of Chitosan-Stabilized Silver Nanoparticles via Electron Beam Irradiation for Enhanced Antibacterial Activity Against Staphylococcus aureus and Escherichia coli

Antimicrobial resistance is a major global health threat, creating an urgent need for effective non-antibiotic antimicrobial strategies. In this study, CS–AgNPs were synthesized by electron-beam radiolysis, providing a clean, dose-controllable route that avoids additional chemical reducing agents. The effects of irradiation dose and chitosan concentration on nanoparticle formation, physicochemical properties, and antibacterial activity were systematically evaluated. Spectroscopic and structural analyses confirmed the formation of highly crystalline, face-centered cubic silver nanoparticles uniformly dispersed within the chitosan matrix, with Ag–polymer coordination involving –NH2 and –OH functional groups. Under the optimal conditions (8 kGy, 0.06 mmol AgNO3, and 0.05% w/v chitosan), ultrasmall, well-dispersed CS–AgNPs were obtained, with an average size of 5.30 ± 2.01 nm and high phase purity. Antibacterial evaluation demonstrated potent, concentration-dependent activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, with low minimum inhibitory and minimum bactericidal concentrations (MIC/MBC = 1.96 µg/mL). These findings define a clear structure–property–activity relationship and support a synergistic antibacterial effect between nanosilver and chitosan, while maintaining favorable in vitro cytocompatibility and hemocompatibility within the effective concentration range. Overall, electron-beam radiolysis represents a promising scalable platform for producing broad-spectrum antimicrobial nanomaterials with potential utility in addressing antimicrobial resistance.