Green-synthesized α-Fe2O3-nanoparticles as potent antibacterial, anti-biofilm and anti-virulence agent against pathogenic bacteria.

Abstract

Background: Antimicrobial resistance (AMR) presents a serious threat to health, highlighting the urgent need for more effective antimicrobial agents with innovative mechanisms of action. Nanotechnology offers promising solutions by enabling the creation of nanoparticles (NPs) with antibacterial properties. This study aimed to explore the antibacterial, anti-biofilm, and anti-virulence effects of eco-friendly synthesized α-Fe₂O₃ nanoparticles (α-Fe₂O₃-NPs) against pathogenic bacteria.

Methods: The α-Fe₂O₃-NPs were synthesized using a green synthesis method that involved Bacillus sp. GMS10, with iron sulfate as a precursor. The NPs were characterized through ultraviolet-visible (UV-Vis) spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDX), Dynamic Light Scattering (DLS), Zeta Potential Analysis, X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). Their antimicrobial activity was assessed against Gram-positive and Gram-negative bacteria. The study also evaluated the effect of the α-Fe₂O₃-NPs on bacterial cell membrane disruption, biofilm formation, efflux pump inhibition, and swarming motility.

Results: The UV-Visible spectrum showed a peak at 228 nm, indicating plasmon absorbance of the α-Fe₂O₃-NPs. FESEM revealed spherical NPs (~ 30 nm), and DLS confirmed a hydrodynamic size of 36.3 nm with a zeta potential of -25.1 mV, indicating good stability. XRD identified the rhombohedral α-Fe₂O₃ phase, and FTIR detected O-H, C-H, C = O, and Fe-O functional groups, suggesting organic capping for stability. Antibacterial assays demonstrated that the α-Fe₂O₃-NPs had MIC values ranging from 0.625 to 5 µg/mL and MBC values between 5 and 20 µg/mL, with a strong effect against Gram-positive bacteria. The NPs significantly increased membrane permeability, inhibited biofilm formation in S. aureus and E. coli, and disrupted efflux pumps in S. aureus SA-1199B (a fluoroquinolone-resistant strain overexpressing norA). Additionally, the α-Fe₂O₃-NPs inhibited P. aeruginosa swarming motility.

Conclusion: The bacteria-synthesized α-Fe₂O₃-NPs demonstrated significant antimicrobial activity, particularly against Gram-positive bacteria, and exhibited strong potential for inhibiting biofilm formation and efflux pump activity, offering a promising strategy to address AMR. Focus on further evaluating their therapeutic potential in clinical settings and conducting comprehensive assessments of their safety profiles to ensure their applicability in medical treatments.

Clinical trial number: Not applicable.