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 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.