Nanobubbles as a promising bacterial deactivation tool: Deactivation mechanism and ROS detection.

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Bacterial deactivation is crucial for infection control.
• Nanobubbles (NBs) show promise as antimicrobial agents.
• The mechanism of NB antibacterial activity, particularly the role of oxidative damage, requires further elucidation.

Purpose of the Study:

• To investigate the hypothesis that bacterial deactivation by NBs is driven by oxidative damage.
• To compare the antibacterial efficacy of NBs containing different gases (O3, O2, Air).
• To correlate NB gas composition with reactive oxygen species (ROS) and oxidizing potential (ORP) generation and subsequent bacterial damage.

Main Methods:

• Comparative antibacterial activity analysis of O3-NBs, O2-NBs, and Air-NBs against E. coli and S. aureus.
• Quantification of ROS and ORP levels for each NB type.
• Measurement of protein release from bacterial cells as a biomarker of oxidative damage.
• Field Emission Scanning Electron Microscopy (FESEM) for visualizing bacterial cell wall degradation.

Main Results:

• O3-NBs achieved 99.99% bacterial reduction in 15 min, significantly outperforming O2-NBs and Air-NBs.
• O2-NBs and Air-NBs showed lower efficacy over 60 min (e.g., 83.89% and 79.38% reduction for E. coli, respectively).
• Elevated ORP and ROS generation in O3-NBs correlated with superior antibacterial activity and confirmed oxidative damage via protein release and FESEM.

Conclusions:

• The antibacterial efficacy of NBs is primarily driven by their ORP and ROS generation capabilities.
• The type of gas contained within NBs significantly influences their oxidative potential and antibacterial effectiveness.
• O3-NBs represent a highly effective antimicrobial agent due to enhanced ROS and ORP production, leading to significant bacterial cell wall degradation.