A combination of electrochemistry and mass spectrometry to monitor the interaction of reactive species with supported lipid bilayers

Abstract

Reactive oxygen and nitrogen species (RONS), e.g. generated by cold physical plasma (CPP) or photodynamic therapy, interfere with redox signaling pathways of mammalian cells, inducing downstream consequences spanning from migratory impairment to apoptotic cell death. However, the more austere impact of RONS on cancer cells remains yet to be clarified. In the present study, a combination of electrochemistry and high-resolution mass spectrometry was developed to investigate the resilience of solid-supported lipid bilayers towards plasma-derived reactive species in dependence of their composition. A 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayer was undisturbed by 200 µM H2O2 (control) but showed full permeability after CPP treatment and space-occupying oxidation products such as PoxnoPC, PAzePC, and POPC hydroperoxide were found. Electron paramagnetic resonance spectroscopy demonstrated the presence of hydroxyl radicals and superoxide anion/hydroperoxyl radicals during the treatment. In contrast, small amounts of the intramembrane antioxidant coenzyme Q10 protected the bilayer to 50% and LysoPC was the only POPC derivative found, confirming the membrane protective effect of Q10. Such, the lipid membrane composition including the presence of antioxidants determines the impact of pro-oxidant signals. Given the differences in membrane composition of cancer and healthy cells, this supports the application of cold physical plasma for cancer treatment. In addition, the developed model using the combination of electrochemistry and mass spectrometry could be a promising method to study the effect of reactive species or mixes thereof generated by chemical or physical sources.

Protective Role of Sphingomyelin in Eye Lens Cell Membrane Model against Oxidative Stress

“…The dependence of the protective effect on SM fraction in PLPC bilayers is in agreement with electrochemical results (30% and 42% for lipid bilayers with 25 and 75% SM, respectively). Electron paramagnetic resonance (EPR) studies on similar set up in our previous work indicated that the hydroxyl radical, superoxide anion and hydrogen peroxide are the main reactive species produced in aqueous phase during plasma treatment [ 66 ]. Interestingly, these reactive species play a significant role in cataract formation in eye [ 17 ].…”

“…Interestingly, these reactive species play a significant role in cataract formation in eye [ 17 ]. Several reports indicated that hydrogen peroxide does not generate a direct oxidative damage in lipid bilayer [ 66 , 83 ]. Therefore, short-lived reactive species play the dominant role in PLPC oxidation.…”

“…The surface of a polycrystalline gold electrode (Ø 2 mm; Metrohm, Filderstadt, Germany) was cleaned by mechanical polishing with Al 2 O 3 powder (Buehler, Esslingen, Germany); grain sizes 300 and 50 nm), and electrochemical cleaning by cyclic voltammetry (CV) from 0 to 1.5 V in 0.1 M H 2 SO 4 at 0.1 V s −1 for about 40 cycles. Moreover, by additional 10 cycles in 0.1 M H 2 SO 4 from 0.75 to 0.2 V at 0.1 V·s −1 the gold oxides were removed from the surface of the electrode [ 66 , 76 ].…”

“…Moreover, there are several complementary techniques to study the effect of ROS on membrane. Recently, a protocol combining electrochemistry and mass spectrometry has been proposed to monitor the interaction of reactive species with supported POPC bilayers and the protective role of lipophilic antioxidants [ 66 ]. While, electrochemical measurements provided a fast information on the residual functionality of the SLB, subsequent high-resolution mass spectroscopy (HR-MS) measurements revealed covalent changes to the molecular structure of the lipids.…”

Recent Advances of In‐Source Electrochemical Mass Spectrometry

“…The combination of electrochemistry (EC) and mass spectrometry (MS) has become a powerful and versatile strategy that allows one to characterize a broad range of electrochemical and biological reactions, and extends the scope of analytes for mass spectrometric analysis. [1][2][3][4][5][6][7][8][9][10][11][12] In this hyphenation, MS has often been used due to its high sensitivity and specificity for determination of electrochemical reactions, providing structural information unavailable from EC methods. Electrochemical reactions can be used to oxidize or reduce analytes so as to improve the ionization of analytes for mass spectrometric analysis.…”