Comparison of plasma-activated saline prepared with plasma gases with different N/O ratios activated by gliding arc discharge

Methicillin-resistant Staphylococcus aureus (MRSA) presents a significant threat due to the multiple resistance to antibiotics, leading to severe and challenging-to-treat infections. Plasma-activated saline (PAS) prepared by plasma gases, could efficiently inactivate various pathogenic bacteria including both sensitive and antibiotic-resistant bacteria. In this study, the PAS was prepared by plasma gases with different ratios of N and O activated by gliding arc discharge. First, the gaseous reactive species in the plasma gases were compared, revealing that the highest levels of NO including NO and NO were generated in the gases with the N/O ratios of 4:6, 5:5, and 6:4. Subsequently, the PAS prepared by the two plasma-activated gases at the N/O ratios of 5:5 and 6:4 exhibited the strongest inactivation effects on both planktic MRSA and biofilms. Furthermore, the aqueous reactive species in the PAS exhibited varied change trends with the increasing N/O ratios. Additionally, ultraviolet spectroscopy combined with the probe of N, N-diethyl-p-phenylenediamine was applied for the detection of ONOO in the PAS, and the levels of ONOO in the PAS were positively correlated with the inactivation effects. Moreover, the PAS induced varying levels of nitration modification on the soluble proteins in MRSA cells, which were related to the intensities of ONOO in the PAS. This study regulated the reactive species in the PAS through gas composition and explored the inactivation mechanism of the PAS, providing a new strategy to promote the preparation efficiency of plasma-activated solutions for biomedical applications.