Short communication Electro-generated reactive oxygen species at Au surface as an indicator to explore glutathione redox chemistry and quantification Gopi Kalaiyarasan, Alam Venugopal Narendra Kumar, Chinnaiah Sivakumar, James Joseph Electrodics and Electrocatalysis Division, CSIR-Central Electrochemical Research Institute, Karaikudi, 630006 Tamilnadu, India abstract article info Article history: Received 27 February 2015 Received in revised form 18 March 2015 Accepted 30 March 2015 Available online 8 April 2015 Keywords: Glutathione Glutathione disulfide Electroanalysis Oxygen reduction Gold electrode The thiol to disulfide inter-conversion plays vital role in the glutathione (GSH) metabolism in human body. Mimicking the GSH conversion to disulfide by electro-generated reactive oxygen species at gold electrode interface and the use of electro-reduction of the produced disulfides for the electro-analysis of low levels of GSH is reported. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Investigating the GSH metabolism in human at intercellular level is one important subject researchers are interested in recent times. An appreciable amount of GSH can be bound to the –SH group of protein cysteinyl residues by a mechanism called S-Glutathionylation. The S- Glutathionylation can be reversed and therefore can be regulated by means of enzymatic reactions in the presence of thiol transferases [1]. S-Glutathionylation protects sensitive protein thiols from irreversible oxidation during oxidative stress formation by generated reactive oxygen species (ROS) [1–5]. The ratio of GSH and its oxidized disulfide product (GSSG) has significant role in creating cancer [6], Parkinson's disease [7], and related problems in the body [8]. To troubleshoot these problems, one requires standard method for monitoring/quanti- fying these biomolecules GSH/GSSH in the human body with high accuracy. Although, many quantifying methods using highly sophisti- cated instrumentations (HPLC) were developed, electrochemical mode of quantification has found more reverence, because of ease in handling and portability. With the advent of microelectrodes and micro fabrica- tion techniques, it is possible to measure inter cellular analytes using electrochemical techniques. Recently, electrochemical determination of GSH was extensively reviewed by Compton's group [9]. Initially, electrochemical method of GSH determination involves oxidative conversion of GSH to GSSG at electrodes such as Mercury [10] or at other chemically modified electrodes [11,12]. Attempts to use Au elec- trodes for the electro analytical determination of GSH by electro oxidation had inherent problems due to the strong concentration dependent adsorption of GSH on to Au surface and the concomitant for- mation of gold oxide which overlaps with GSH electro oxidation signal. Attempts made for GSH determination are based on the electro oxida- tion of GSH to GSSG at a chemically modified interface. The formation of GSSG from GSHNO at neutral pH through γ-rays radiolysis generated OH • radicals from water are reported [13]. On the contrary, we report details of our attempts to determine GSH by electro-reduction of GSSG formed chemically by electro-generated reactive oxygen species [14–16] (ROS) such as superoxides (O 2 •- ) hydroxyls (OH •- ) and hydroperoxyl (HO 2 •- ) at Au electrode/electrolyte interfaces. This approach is new and reported for the first time and mimics the reaction which causes oxidative stress. 2. Materials and methods 2.1. Materials L-Reduced glutathione (GSH) was purchased from Sigma Aldrich, potassium chloride was purchased from Merck and sodium sulfite was purchased from SRL, India. All chemicals were of analytical grade and used without further purification. 2.2. Instruments The electrochemical evaluation was carried out using AUTOLAB potentiostat (Eco chemie, Netherland) for Cyclic Voltammetry (CV) and BAS 100B electrochemical analyzer for Differential Pulse Electrochemistry Communications 56 (2015) 29–33 E-mail addresses: jameskavalam@yahoo.com, jamescecri@cecri.res.in (J. Joseph). http://dx.doi.org/10.1016/j.elecom.2015.03.021 1388-2481/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Electrochemistry Communications journal homepage: www.elsevier.com/locate/elecom