Different bactericidal abilities of plasma-activated saline with various reactive species prepared by surface plasma-activated air and plasma jet combinations

Plasma-activated water (PAW), as an extended form of cold atmospheric-pressure plasma, greatly expands the application of plasma-based technology. The biological effects of PAW are closely related to the aqueous reactive species, which can be regulated by the activation process. In this study, surface plasma-activated air (SAA) and a He + O₂ plasma jet (Jet) were parallelly combined (the SAA + Jet combination) or sequentially combined (the SAA → Jet combination and the Jet → SAA combination) to prepare plasma-activated saline (PAS). The PAS activated by the combinations exhibited stronger bactericidal effects than that activated by the SAA or the Jet alone. The concentrations of H₂O₂ and \mathrmNO^-_2 were higher in the PAS activated by the Jet → SAA combination, while ONOO⁻ concentrations were close in the three kinds of PAS and ¹O₂ concentrations were higher in the PAS activated by the SAA + Jet combination. The analysis of scavengers also demonstrated that H₂O₂, ¹O₂, and ONOO^‒ in the PAS activated by the SAA + Jet combination, and ¹O₂ in the PAS activated by the Jet → SAA combination played critical roles in bactericidal effects. Further, the effective placement time of the three PAS varied, and the PAS activated by the Jet → SAA combination could also inactivate 2.6-log₁₀ of MRSA cells after placement for more than 60 min. The regulation of reactive species in plasma-activated water via different combinations of plasma devices could improve the directional application of plasma-activated water in the biomedical field.