Harnessing the Antimicrobial Potential of Baicalein-Coated Fe₃O₄/Ag Nanoparticles for Biomedical and Environmental...

The increasing prevalence of antimicrobial resistance (AMR) and biofilm-associated infections represents a major challenge in both biomedical and environmental settings. Herein, we report the synthesis and comprehensive evaluation of a multifunctional nanocomposite composed of baicalein-coated Fe₃O₄/Ag nanoparticles (FAB NPs), designed to combine magnetic recoverability, controlled silver (Ag⁺) release, antimicrobial activity, and improved biocompatibility. FAB NPs were synthesized via a stepwise coprecipitation approach and characterized in terms of morphology, structure, surface chemistry, magnetic properties (normalized saturation magnetization of 27.2 ± 0.1 emu/g), antioxidant capacity (43.8% 2,2-diphenyl-1-picrylhydrazyl inhibition at 1.5 mg/mL), and antibacterial potential (minimum inhibitory concentrations of 0.19-0.38 mg/mL), as well as Ag⁺ release behavior. The developed nanocomposite exhibited strong broad-spectrum antibacterial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, together with pronounced inhibition of biofilm formation (>60%) and quorum sensing (QS), while achieving a 33-fold reduction in Ag⁺ release compared to nonfunctionalized Fe₃O₄/Ag nanoparticles. Mechanistic studies revealed that FAB NPs disrupt bacterial membranes and interfere with QS pathways (suppressing 25% of violacein expression), contributing to their antibiofilm efficacy. Importantly, FAB NPs displayed improved biocompatibility toward human keratinocytes and fibroblasts and did not promote significant resistance development during 55 days of exposure in both Gram-positive and Gram-negative bacteria. As a proof of concept for environmental applications, FAB NPs incorporated into activated carbon packed-bed columns achieved complete removal of the reference faecal indicator E. coli from contaminated water, with negligible Ag⁺ leaching. Overall, this work demonstrates that baicalein functionalization enables the design of safe and highly effective Ag-based magnetic nanocomposites, offering a versatile strategy to combat microbial contamination and AMR in both biomedical and water treatment applications.