Size-Dependent Bacterial Toxicity of Hematite Particles.

Area of Science:

• Environmental Science
• Microbiology
• Materials Science

Background:

• Submicron iron oxide particles' influence on bacterial activity is known, but the precise mechanisms of toxicity are unclear.
• Understanding these mechanisms is crucial for developing novel antimicrobial strategies.

Purpose of the Study:

• To elucidate the size-dependent interfacial interactions between hematite particles and bacteria.
• To determine the mechanisms underlying the antimicrobial properties of iron oxide nanoparticles.

Main Methods:

• Atomic force microscopy (AFM) for surface adhesion analysis.
• Soft X-ray tomography (Nano-CT) for visualizing particle-cell interactions.
• Fourier transform infrared (FTIR) spectrometry for structural analysis of bacterial components.

Main Results:

• Hematite particle adhesion to bacteria involves Lifshitz van der Waals and electrostatic forces, followed by P-O-Fe bond formation.
• Bacterial membrane protein structures are altered, leading to loss of integrity and particle internalization within 10 hours.
• Reactive oxygen species generation on hematite surfaces causes cell permeabilization, with Gram-negative bacteria being more susceptible than Gram-positive bacteria.

Conclusions:

• Hematite nanoparticles demonstrate significant antimicrobial activity through direct interfacial interactions with bacterial cells.
• The enhanced toxicity of nanoparticles is attributed to stronger physicochemical interactions compared to microscaled particles.
• The findings provide insights into the antimicrobial mechanisms of iron oxide nanoparticles, relevant for environmental and biomedical applications.