Abstract
Reactive oxygen and nitrogen species released by cold physical plasma are being proposed as effectors in various clinical conditions connected to inflammatory processes. As these plasmas can be tailored in a wide range, models to compare and control their biochemical footprint are desired to infer on the molecular mechanisms underlying the observed effects and to enable the discrimination between different plasma sources. Here, an improved model to trace short-lived reactive species is presented. Using FTIR, high-resolution mass spectrometry, and molecular dynamics computational simulation, covalent modifications of cysteine treated with different plasmas were deciphered and the respective product pattern used to generate a fingerprint of each plasma source. Such, our experimental model allows a fast and reliable grading of the chemical potential of plasmas used for medical purposes. Major reaction products were identified to be cysteine sulfonic acid, cystine, and cysteine fragments. Less-abundant products, such as oxidized cystine derivatives or S-nitrosylated cysteines, were unique to different plasma sources or operating conditions. The data collected point at hydroxyl radicals, atomic O, and singlet oxygen as major contributing species that enable an impact on cellular thiol groups when applying cold plasma in vitro or in vivo.
Highlights
It is generally assumed that reactive oxygen and nitrogen species (RONS) are key players in atmospheric pressure plasmas[12], with many different types present including nitrite (NO2−), nitric oxide (NO), hydrogen peroxide (H2O2), superoxide (O2−), hydroxyl radical (OH), peroxynitrite (ONOO−), and singlet oxygen (1O2)
FTIR analysis reveals the impact of plasma derived species on cysteine in dependence of plasma source and working gas parameters
No macroscopically visible changes to the liquid was observed after cold physical plasma treatment and FTIR spectroscopy was performed to gain an overview of the plasma’s chemical impact on the cysteine model
Summary
FTIR analysis reveals the impact of plasma derived species on cysteine in dependence of plasma source and working gas parameters. In pH can have an impact on thiol reactivity[53], besides the general slight acidic conditions due to the presence of cysteine, a drop of pH from initial 6.8 to about 5.8 was observed after treatment This most likely stems from the fact that even though treatment time was relatively long, the treated volume was quite large compared to other studies and treatment with jets affect the pH less than direct treatment with e.g. DBDs. An alternative kINPen source using a shielding gas setup[54] has already been presented, though investigations regarding its chemical potential are still absent. The far higher complexity of the full cellular environment will have to be addressed in the step either by a more refined model or by the direct investigation of cells
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