In this study we examined the influence of ultra-small gold and magnetite‑gold nanoparticles (NPs) stabilized with d,l-methionine, Fe3O4@Au@Met, on their antibacterial efficacy against three of twelve the worst bacterial family members included in the World Health Organization (WHO) list. In particular, gram-negative Acinetobacter baumannii, Salmonella enterica and gram-positive methicillin-resistant Staphylococcus aureus and Micrococcus luteus were tested. Apart from the synthesis, gold species reduction and NP stabilization, an excess of methionine has been used herein to detach ultra-small gold NPs from the Fe3O4@Au@Met surface, collect them and investigate. The antimicrobial efficiency of the ultra-small (Ø ~ 1.8 nm) Au@Met NPs and Fe3O4@Au@Met NPs was evaluated through the quantitative analysis by comparing with that of naked magnetite NPs, d,l-Met and BSA. It has been determined that compared with the control sample, 70 mg L-1 probe of Au@Met NPs exhibited the killing efficiency of 84.4-58.5% against gram-negative bacteria and 89.1-75.7% against gram-positive bacteria. The composition, structure, and morphology of the synthesized and tested herein NPs were investigated by inductively coupled plasma optical emission spectrometry, magnetic measurements, FTIR, XRD, XPS, AFM and HRTEM.
Keywords: Antimicrobial behavior; Gold species; Magnetite nanoparticles; Methionine.
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