Chemical fingerprints of cold physical plasmas – an experimental and computational study using cysteine as tracer compound

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.

Activation of Murine Immune Cells upon Co-culture with Plasma-treated B16F10 Melanoma Cells

“…Cold physical plasma introduces oxidants into liquids surrounding cells, with hydrogen peroxide (H 2 O 2 ) being among the long-lasting products of redox chemistry [40]. In pure PBS ( Figure 1a) and fully supplemented cell culture medium (Figure 1b), H 2 O 2 accumulated in a dose-dependent manner, validating the introduction of plasma-derived species in culture systems.…”

Medical Gas Plasma Jet Technology Targets Murine Melanoma in an Immunogenic Fashion

“…It has also been established with this plasma jet technology that changing the feed gas condition has a significant impact on the ROS composition and its subsequent post‐translational modifications of biomolecules. [ 82 ] As a functional consequence, some ROS mixtures are associated with a potent cell kill, while others are not. [ 83 ] We recently identified atomic oxygen, and possibly singlet delta oxygen, to be an essential mediator of toxicity in a leukemia model.…”

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

“…Furthermore, the generalised effects of plasma RONS on proteins were studied using cysteine as a model molecule. Using a He-only fed COST jet, almost no changes in the cysteine structure were detected, whereas adding O 2 admixtures to He revealed multiple oxidation sites [50], expectedly due to the generation of highly oxidising O atoms. Here, the COST jet was used as a plasma device without an active effluent, as opposed to plasmas with high densities of high-energy particles in the effluent [10].…”