Simultaneous Electrochemical Speciation of Oxidized and Reduced Glutathione. Redox Profiling of Oxidative Stress in Biological Fluids with a Modified Carbon Electrode

Abstract

The simultaneous electrochemical quantification of oxidized (GSSG) and reduced glutathione (GSH), biomarkers of oxidative stress, is demonstrated in biological fluids. The detection was accomplished by the development of a modified carbon electrode and was applied to the analysis of biological fluids of model organisms under oxidative stress caused by lead intoxication. Nanocomposite molecular material based on cobalt phthalocyanine (CoPc) and multiwalled carbon nanotubes functionalized with carboxyl groups (MWCNT) was developed to modify glassy carbon electrodes (GCE) for the detection of reduced and oxidized glutathione. The morphology of the nanocomposite film was characterized by scanning electron microscopy (SEM) and profilometry. The electrochemical behavior of the modified electrode was assessed by cyclic voltammetry (CV) to determine the surface coverage (Γ) by CoPc. The electrocatalytic behavior of the modified electrode toward reduced (GSH) and oxidized (GSSG) forms of glutathione was assessed by CV studies at physiological pH. The obtained results show that the combined use of CoPc and MWCNT results in an electrocatalytic activity for GSH oxidation and GSSG reduction, enabling the simultaneous detection of both species. Differential pulse voltammetry reveals detection limits of 100 μM for GSH and 8.3 μM for GSSG, respectively. The potential interference from ascorbic acid, cysteine, glutamic acid, and glucose was also studied, and the obtained results show limited effects from these species. Finally, the hybrid electrode was used for the determination of GSH and GSSG in rat urine and plasma samples, intoxicated or not by lead. Both glutathione forms were detected in these complex biological matrixes without any pretreatment. Our results portray the role of GSH and GSSG as markers of oxidative stress in live organisms under lead intoxication.

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“…S12 † ). The current responses caused by H 2 O 2 oxidation increased with the increase of CoPc contents and reached a peak at a level of 20 mM, and the declining response at a concentration of 25 mM or even higher probably resulted from the formation of CoPc precipitates 45 with low electrocatalytic efficiency towards H 2 O 2 oxidization.…”

On-Capillary Surface-Enhanced Raman Spectroscopy: Determination of Glutathione in Whole Blood Microsamples

“…Besides, GSH is easily oxidized under normal conditions, ,− requiring laborious and time-consuming sample processing. The most widely used approaches involve a previous sample derivatization with, for example, N -ethylmaleimide followed by acidic protein precipitation ,,,,, and a chromatographic or electrophoretic separation with different detectors. ,− Alternative approaches based on enzymatic assays or electrochemical determinations have also been reported. However, none of them enables a direct analysis of GSH, and they suffer from relevant limitations for their application in neonatal intensive care units such as the use of relatively large sample volumes (typically tens to hundreds of microliters of whole blood); time required for sample collection, pretreatment, and analysis; the use of expensive equipment and reagents; and the need of experienced personnel.…”

Advancements in 2D Materials Based Biosensors for Oxidative Stress Biomarkers

“…A composite of cobalt phthalocyanine and functionalized multiwalled carbon nanotubes was fabricated for detection of glutathione. The LOD value was found to be 100 μM and 8.3 μM for reduced glutathione and oxidized glutathione respectively . Several sensing platforms for electrochemical detection of glutathione are compiled in Table .…”