Abstract
Background: Glutathione (GSH) is a water-soluble tripeptide which is contained in biological fluids (blood plasma, cell fluid) and plays an important role in redox processes in the organisms of humans and animals. The lack of GSH leads to oxidative stress in living cells and causes dangerous diseases. In this regard, the development of rapid and simple analytical methods to determine GSH in biological fluids is an important task. The purpose of the present paper was to explore the possibility of electrochemical determination of GSH using AuNPs-modified graphite electrodes to develop a sensitive voltammetric method.
Methods: Electrochemical sensor (AuNP-GCE) for the determination of GSH in solutions was prepared by deposition of gold nanoparticles (5-15 nm) from Au-hydrosol at graphite electrode surface. Composition of electrodes was controlled using scanning electron microscopy and EDX-analysis (JSM 5500). Electrochemical behavior of GSH at graphite-based electrodes in alkaline medium was investigated using cyclic voltammetry (CV) by means of electrochemical analytical device TA-4 (Tomsk, Russia). Results: Electrocatalytic oxidation of GSH at AuNP-GCE occurs at +0.05 V (vs. silver chloride ref. electrode) in 0.1 M NaOH and is revealed from CV as an “inverse” current peak in the cathodic direction of potential scan. The sequence of electrode reactions has been suggested which includes oxidation of Au nanoparticles when potentials scanned towards positive direction up to 0.8 V and consequent GSH electrocatalytic oxidation by Au(I)-oxide during the backward potential scan represented as the “inverse” peak. Conclusion: Au-nanoparticles modified graphite electrode exhibits electrocatalytic activity towards GSH oxidation in alkaline medium. An “inverse” current peak in cathodic part of CVs can be used to determine concentration of GSH in a solution. The current of this peak linearly depends on GSH concentration in the interval 2-14 pM (detection minimum 0.7 pM) in supporting solution 0.1 M NaOH. The proposed method can be applied for determination of glutathione in biological fluids.Keywords: Cyclic voltammetry, electrocatalysis, glutathione, gold nanoparticles, biological fluids, redox processes.
Graphical Abstract
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