An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation

Abstract

Non-thermal atmospheric pressure ('cold') plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O 2 , N 2 , air, H 2 O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of 'high' voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry.

Reduction of Human Glioblastoma Spheroids Using Cold Atmospheric Plasma: The Combined Effect of Short- and Long-Lived Reactive Species

“…The short-lived species cannot be detected directly and requires the use of spin traps (which react with radicals to form more persistent nitroxide radical adducts) [ 30 ]. We used 5,5-dimethyl-1-pyrroline N -oxide (DMPO) to detect •OH, and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N -oxide (DEPMPO) for O 2 • – /•OOH radicals ( Figures S2 and S3 ) [ 30 , 31 , 32 ]. DMPO-OH and DEPMPO-OOH adducts were detected in the μM range.…”

Applications of the COST Plasma Jet: More than a Reference Standard

“…This required differentiating between the water from the exposed liquid, water in the feed gas, and water in the effluent of the jet. It was done by isolating all components of the jet from the ambient air and using isotopically labelled water molecules [47]. As a result, it was found that even in the interaction with liquids, RONS produced by the COST jet are formed almost exclusively inside the plasma jet, from the components of the feed gas.…”

Reaction of chloride anion with atomic oxygen in aqueous solutions: can cold plasma help in chemistry research?

“…Although we previously observed oxidation of TEMP by O 3 , 18 later all formed TEMPO was ascribed to the reaction of TEMP with O (in the absence of 1 O 2 ). 19 To investigate this further, the plasma effluent was not exposed to ambient air, but instead propagated inside an air-free reactor 14,20 (Fig. S1).…”