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Insight into the Impact of Oxidative Stress on the Barrier Properties of Lipid Bilayer Models
(2022)
As a new field of oxidative stress-based therapy, cold physical plasma is a promising tool for several biomedical applications due to its potential to create a broad diversity of reactive oxygen and nitrogen species (RONS). Although proposed, the impact of plasma-derived RONS on the cell membrane lipids and properties is not fully understood. For this purpose, the changes in the lipid bilayer functionality under oxidative stress generated by an argon plasma jet (kINPen) were investigated by electrochemical techniques. In addition, liquid chromatography-tandem mass spectrometry was employed to analyze the plasma-induced modifications on the model lipids. Various asymmetric bilayers mimicking the structure and properties of the erythrocyte cell membrane were transferred onto a gold electrode surface by Langmuir-Blodgett/Langmuir-Schaefer deposition techniques. A strong impact of cholesterol on membrane permeabilization by plasma-derived species was revealed. Moreover, the maintenance of the barrier properties is influenced by the chemical composition of the head group. Mainly the head group size and its hydrogen bonding capacities are relevant, and phosphatidylcholines are significantly more susceptible than phosphatidylserines and other lipid classes, underlining the high relevance of this lipid class in membrane dynamics and cell physiology.
Scholz et al. developed an electrochemical assay to study the impact of reactive species on self-assembled monolayer (SAM). The aim of this thesis is to use this electrochemical assay with gold supported lipid bilayers instead of SAM to study the effect of reactive species on model membranes that mimic oxidative damage to the biological cell membrane. Here, three questions will be addressed: I) how specific substances such as lipophilic and hydrophilic antioxidants protect a membrane from oxidative damage, II) what are the lipid oxidation products after oxidative damage of the model membrane, and III) whether oxidative damage of the model membranes causes pore formation on lipid bilayer. Electrochemistry was first used to measure the oxidative damage over the entire lipid membrane. Then, mass spectroscopy was used to characterize how lipids as the molecular building blocks of the membrane, change when exposed to reactive species. Imaging the membrane with AFM showed how oxidative damage in the model membrane alters lipid self-assembly within the supported lipid bilayer in nanometer scale. In addition, cold physical plasma (CPP) was used to produce the biological relevant reactive species. This fundamental research demonstrates the great potential of supported lipid bilayers as model membranes and cold physical plasma as a source for the production of biologically relevant reactive species to study the effect of oxidative stress on cell membranes.