Abstract
Cold atmospheric pressure plasma is an attractive new research area in clinical trials to treat skin diseases. However, the principles of plasma modification of biomolecules in aqueous solutions remain elusive. It is intriguing how reactive oxygen and nitrogen species (RONS) produced by plasma interact on a molecular level in a biological environment. Previously, we identified the chemical effects of dielectric barrier discharges (DBD) on the glutathione (GSH) and glutathione disulphide (GSSG) molecules as the most important redox pair in organisms responsible for detoxification of intracellular reactive species. However, in the human body there are also present redox-active metals such as iron, which is the most abundant transition metal in healthy humans. In the present study, the time-dependent chemical modifications on GSH and GSSG in the presence of iron(II) and iron(III) complexes caused by a dielectric barrier discharge (DBD) under ambient conditions were investigated by IR spectroscopy, mass spectrometry and High Performance Liquid Chromatography (HPLC). HPLC chromatograms revealed one clean peak after treatment of both GSH and GSSH with the dielectric barrier discharge (DBD) plasma, which corresponded to glutathione sulfonic acid GSO3H. The ESI-MS measurements confirmed the presence of glutathione sulfonic acid. In our experiments, involving either iron(II) or iron(III) complexes, glutathione sulfonic acid GSO3H appeared as the main oxidation product. This is in sharp contrast to GSH/GSSG treatment with DBD plasma in the absence of metal ions, which gave a wild mixture of products. Also interesting, no nitrosylation of GSH/GSSG was oberved in the presence of iron complexes, which seems to indicate a preferential oxygen activation chemistry by this transition metal ion.
Highlights
Challenging to understand and control the interactions of plasma with cellular components of living cells and biomolecules, such as sugars, lipids, vitamins and amino acids, which are the major chemical species in cell culture medium
According to our previous findings, plasma treatment caused a number of chemical modifications on GSH and GSH molecules are oxidized to glutathione disulphide (GSSG) in solution, giving a large number of S- and N-modified glutathione species as intermediates and final products (Fig. 1)
Our findings show that plasma treatment causes clean oxidation of GSH as well as GSSG to one product only, namely GSO3H
Summary
Challenging to understand and control the interactions of plasma with cellular components of living cells and biomolecules, such as sugars, lipids, vitamins and amino acids, which are the major chemical species in cell culture medium. This study showed that plasma exposure times longer than 2 min resulted in hemorheological alterations such as hemolytic activity, elongation index and higher aggregation index than in the untreated RBC samples All these studies of plasma treatments were performed for samples in aqueous solutions and all organic molecues decomposed to smaller chemical species. The extensive mixture of different oxidation species made this system difficult to monitor (see Fig. 1) It is well-known that transition metals like manganese, iron, cobalt, copper or zinc have noticeable effects on human health. To further develop our understanding of the impact of plasma treatment on GSH and GSSG as the central cellular redox system, we utilized the iron(II) complex ferrocenecarboxylic acid (complex 1) and the iron(III) complexes iron(III) acetylacetonate (Fe(acac)3) (complex 2) and chloro(protoporphyrinato)iron(III) (hemin) (complex 3 Fig. 2) to mimic the environment in human cells, and in particular the presence and possible influence of further ubiquitous redox-active cellular components. We investigated: (i) the influence of plasma on iron(II) and iron(III) complexes and subsequently (ii) chemical modifications on GSH and GSSG caused by DBD plasma in the presence of these iron complexes
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