Generation of Species-Specific High-Strength Plasma Activated Water at Neutral pH and its Antimicrobial Characteristics

Understanding the individual effects of species in plasma activated water (PAW) is indeed necessary for its selective application as an antimicrobial agent. The current study describes a setup and a methodology to generate species-specific high strength PAW at neutral pH. Three types of PAW i.e., ROS-rich PAW (Reactive Oxygen Species-rich Plasma Activated Water), RNS-rich PAbW (Reactive Nitrogen Species- Rich Plasma Activated buffer Water) and hs-PAbW (High strength Plasma Activated buffer Water) were generated in the developed set-up, the concentration of species was measured, shelf-life studies under ambient condition were carried out and each water type was studied for its antimicrobial activity. Results show that, after 60 min of activation, hs-PAbW had ROS and RNS concentrations of 215 mg/l and 650 mg/l respectively. The ROS-rich PAW had ROS and RNS concentration of 218 mg/l and 0 mg/l respectively. The RNS-rich PAbW had ROS and RNS concentration of 16 mg/l and 858 mg/l respectively after 60 min of activation. Antimicrobial studies showed that individual species i.e., high concentrations of ROS alone and high concentrations of RNS alone, were ineffective in achieving microbial degradation, whereas hs-PAbW containing high concentrations of both ROS and RNS showed significant antimicrobial effect. This study marks an important step in generating high concentrations of species-specific PAW, which is crucial to understand the mechanistic pathways of bacterial death in PAW systems.