Evaluation of cold atmospheric pressure plasma irradiation of water as a method of singlet oxygen generation

We used cold atmospheric pressure plasma jet to examine in detail O-1 (2) generation in water. ESR with 2,2,5,5-tetramethyl-3pyrroline-3-carboxamide, a secondary amine probe, was used for the detection of O-1 (2). Nitroxide radical formation was detected after cold atmospheric pressure plasma jet irradiation of a 2,2,5,5tetramethyl-3-pyrroline-3-carboxamide solution. An O-1 (2) scavenger/ quencher inhibited the ESR signal intensity induced by cold atmospheric pressure plasma jet irradiation, but this inhibition was not 100%. As 2,2,5,5-tetramethyl-3-pyrroline-3-carboxamide reacts with oxidizing species other than O-1 (2), it was assumed that the signal intensity inhibited by NaN 3 corresponds to only the nitroxide radical generated by O-1 (2). The concentration of O-1 (2) produced by cold atmospheric pressure plasma jet irradiation for 60 s was estimated at 8 mu M. When this O-1 (2) generation was compared to methods of O-1 (2) generation like rose bengal photoirradiation and 4-methyl-1,4-etheno-2,3-benzodioxin-1(4H)propanoic acid (endoperoxide) thermal decomposition, O-1 (2) generation was found to be, in decreasing order, rose bengal photoirradiation = cold atmospheric pressure plasma jet > endoperoxide thermal decomposition. Cold atmospheric pressure plasma jet is presumed to not specifically generate O-1 (2), but can be used to mimic states of oxidative stress involving multiple ROS.

Automated summary

In this study, a cold atmospheric pressure plasma jet was used to investigate the generation of O-1 (2) in water. ESR was used to detect the nitroxide radicals formed by O-1 (2). It was found that the ESR signal intensity induced by plasma jet irradiation was inhibited by an O-1 (2) scavenger/quencher, indicating the presence of nitroxide radicals. The concentration of O-1 (2) produced by plasma jet irradiation for 60 s was estimated to be 8 μM. Cold atmospheric pressure plasma jet can mimic oxidative stress involving multiple ROS.