Understanding the differences between antimicrobial and cytotoxic properties of plasma activated liquids

The aqueous environment plays an important role in the transmission of cold plas­ma effects to both prokaryotic and eukaryotic cells. The exposure of liquids to cold atmospheric plasma discharges results in the generation of secondary reactive species; specifically, hydrogen peroxide (H₂O₂) seems to be one of the most important amongst the reactive species contained in plasma activated liquids (PALs) in causing cytotoxicity. Detailed understanding of the effects of PALs on cells is essential to harness this new technology. Liquids acting as models for non-complex solutions were generated using a dielectric barrier discharge atmospheric cold plasma (DBD-ACP) system. The chemical characterization of the PAL included its pH and concentra­tions of hydrogen peroxide, nitrite, and nitrate. The antimicrobial effects of PALs on Gram-pos­itive and Gram-negative bacteria were examined, and cytotoxicity assays were used to elucidate the cytotoxic properties of PALs. The research outcomes showed acidification of plasma activated nonbuffered solutions and differences in concentrations of hydrogen peroxide, nitrite, and ni­trate. PALs with different compositions varied in their antibacterial activity and cytotoxic effects, indicating that different reactive species may be responsible for these inactivation processes. Our results suggest that antimicrobial and cytotoxic effects are distinct from each other, which may offer promising approaches for future targeted applications in medicine.