Following O and OH in He/O₂ and He/H₂O gas mixtures—from the gas phase through the liquid phase to modifications on a biological sample

Abstract

Applied cold atmospheric plasma allows for the controlled delivery of reactive oxygen and nitrogen species tailored for specific applications. Through the manipulation of the plasma parameters, feed gases, and careful consideration of the environment surrounding the treatment target, selective chemistries that preferentially influence the target can be produced and delivered. To demonstrate this, the COST reference microscale atmospheric pressure plasma jet is used to study the generation and transport of O and ⋅ OH from the gas phase through the liquid to the biological model target cysteine. Relative and absolute species densities of ⋅ OH and O are measured in the gas phase through laser induced fluorescence (LIF) and two-photon absorption LIF respectively. The transport of these species is followed into the liquid phase by hydrogen peroxide quantification and visualized by a fluorescence assay. Modifications to the model biological sample cysteine exposed to ⋅ OH and H2O2 dominated chemistry (He/H2O (0.25%)) and O dominated chemistry (He/O2 (0.6%)) is measured by FTIR spectroscopy. The origin of these species that modify cysteine is considered through the use of heavy water (H 2 18 O) and mass spectrometry. It is found that the reaction pathways differ significantly for He/O2 and He/H2O. Hydrogen peroxide is formed mainly in the liquid phase in the presence of a substrate for He/O2 whereas for He/H2O it forms in the gas phase. The liquid chemistry resulting from the He/O2 admixture mainly targets the sulfur moiety of cysteine for oxidation up to irreversible oxidation states, while He/H2O treatment leads preferentially to reversible oxidation products. The more O or OH/H2O2 dominated chemistry produced by the two gas admixtures studied offers the possibility to select species for target modification.

Plasma‐driven biocatalysis: In situ hydrogen peroxide production with an atmospheric pressure plasma jet increases the performance of OleTJE when compared to adding the same molar amount of hydrogen peroxide in bolus

“…[34] Here, the He/H 2 O admixture was selected based on the extensive characterization of the gas and liquid phase performed in previous experiments. [30,35,36] To limit the effect of impurities in the discharge, gas delivery was regulated via stainless steel tubing. As a reference jet, the COST-Jet is well studied and previous research has reported its reproducibility, [37] gas-phase densities of reactive species, [34,36,38,39] and liquid phase densities, [30,35,[40][41][42] among others.…”

“…[30,35,36] To limit the effect of impurities in the discharge, gas delivery was regulated via stainless steel tubing. As a reference jet, the COST-Jet is well studied and previous research has reported its reproducibility, [37] gas-phase densities of reactive species, [34,36,38,39] and liquid phase densities, [30,35,[40][41][42] among others. The nozzle of the COST-Jet was placed 4 mm above the liquid surface, see Figure 1.…”

“…Dissipated power was measured during treatment following Golda et al [29,43] and kept constant at 750 ± 10 mW, corresponding to an applied voltage of V RMS ~240 V. This dissipated power was also selected to coincide with previous experiments. [30,35] Before each measurement, the COST-Jet was operated for 30 min to mitigate the influence of impurities.…”

Chloramines of amino acids as precursors of bactericidal activity in cell culture media DMEM and RPMI treated by RF‐driven He/O2 plasma jet

“…The O atoms can survive contact with the water surface, dissolve into the liquid, and react in the liquid phase with dissolved species. [31,32] Oxidations of chloride anions, [33][34][35][36] phenol, [30,31,33] glucose, [37] amino acids (AAs), and peptides [38][39][40] were reported. Among other processes, the reactions of ROS in chloride solutions are of great importance because the Cl − ions are inherently present in biological tissue, the cellular environment, culture media, and physiological solutions (0.9%).…”

“…For example, the thiol-group containing AAs oxidized by plasma were shown to be responsible for the cytotoxic activity of plasma-treated cell culture media. [39,[42][43][44][45] A comprehensive study was performed on mixtures of AAs and simple peptides treated by an Ar plasma jet with an admixture of O 2 / N 2 . [38] Oxidation, nitration, and chlorination of AAs depended upon the type of discharge feed gas.…”