Surface-modified magnetic polymeric–silver nanocomposites for broad-spectrum antibacterial applications

Magnetic antimicrobial nanocomposites have potential for applications in healthcare, food safety, and environmental settings. This study describes the synthesis of a multifunctional nanocomposite combining SPIONs with polylactic acid, an M8 polymer blend including PVA, PEG, PVP and chitosan, along with AgNPs to enhance antimicrobial activity while retaining potential for magnetic recovery. Strategies of surface modification, including carbon coating, SeNPs and chloramphenicol loading, were also systematically compared. Overall, SPION/PLA/M8Ag achieved > 92% OD-derived growth inhibition against Staphylococcus aureus , Pseudomonas aeruginosa , Salmonella enterica , and Escherichia coli without antibiotic loading. This was supported by physicochemical characterization (FE-SEM, XRD, FTIR, EDS and VSM), which revealed particle sizes of 12–24 nm, retention of the magnetite-like crystalline phase after surface functionalization, and superparamagnetism indicating potential for magnetic separation and recovery. The observed antibacterial activity may involve multiple factors, including Ag-associated effects, possible oxidative stress, electrostatic interactions, and interactions between the composite surface and bacterial cells; however, these mechanisms were not directly verified in the present study. These findings suggest that SPION/PLA/M8Ag may serve as a promising research platform for antibiotic-free antimicrobial materials.