Nontarget Biomolecules Alter Macromolecular Changes Induced by Bactericidal Low-Temperature Plasma

Area of Science:

• Plasma physics and chemistry
• Microbiology
• Biomedical engineering

Background:

• Low-temperature plasmas (LTPs) generate reactive oxygen and nitrogen species (RONS) with known bactericidal properties.
• RONS can interact with organic biomolecules present in the surrounding environment.
• Understanding these interactions is crucial for optimizing LTP applications in sterilization and medicine.

Purpose of the Study:

• To investigate the impact of organic content in liquid suspensions on the bactericidal efficacy of LTPs.
• To elucidate the mechanisms behind the altered bactericidal activity in the presence of biomolecules.
• To assess the influence of environmental chemistry on LTP-based antimicrobial treatments.

Main Methods:

• Exposure of *Salmonella enterica* serovar Typhimurium in suspensions with varying organic content (PBS, DMEM, DMEM+serum, LB) to an atmospheric-pressure dielectric barrier discharge plasma jet.
• Assessment of bacterial viability and membrane integrity post-plasma treatment.
• Analysis of reactive oxygen and nitrogen species (RONS) concentrations in the treated solutions.

Main Results:

• Bactericidal activity of LTPs against *Salmonella* was observed in phosphate-buffered saline (PBS) but significantly reduced in media with high organic content (DMEM, LB).
• Reduced bacterial viability in PBS correlated with loss of membrane integrity; DNA double-strand breaks were not detected.
• Inhibition of bactericidal activity in organic-rich media was linked to decreased hydroxyl radical (•OH) and ozone (O3)/singlet oxygen (O2(a1Δ)) levels, and increased hydrogen peroxide (H2O2) and nitrite (NO2-) concentrations.

Conclusions:

• The bactericidal efficacy of LTPs is diminished in environments with high organic content due to redox reactions between RONS and biomolecules.
• These reactions alter the RONS composition, leading to a less potent antimicrobial effect.
• Consideration of the chemical environment is essential for the effective development and application of LTPs in antimicrobial therapies and other biomedical fields.