A simple electrochemical method to monitor an azo dye reaction with a liver protein

• Published in: Analytical biochemistry 2018-07, Vol.553, p.46-53
• Main Authors: Materón, Elsa Maria, Marchetto, Reinaldo, Araujo, Angela Regina, Vega-Chacon, Jaime, Pividori, Maria I., Jafelicci, Miguel, Shimizu, Flavio M., Oliveira, Osvaldo N., Zanoni, Maria Valnice Boldrin
• Format: Article
• Language: English
• Subjects: Azo Compounds - chemistry; Catalysis; Density Functional Theory; Electrochemical Techniques - methods; Glutathione Transferase - metabolism; Humans; Liver - enzymology; Liver - metabolism; Magnetite Nanoparticles - chemistry; Oxidation-Reduction; Proteins - metabolism
• ISSN: 0003-2697; 1096-0309
• DOI: 10.1016/j.ab.2018.05.016

Disperse Orange 37 (DO37) is an efficient azo dye for dyeing synthetic textile materials owing to its resistance to degradation that may also be harmful to humans as DO37 is not entirely eliminated in wastewater treatment. In this paper, we demonstrate that DO37 is bleached by reduced glutathione (GSH) in a reaction catalyzed by glutathione-s-transferase (GST), a phase II detoxification enzyme. The reaction included a nucleophilic attack involving sulfhydryl groups, confirmed using density functional theory (DFT) calculations. DO37 also induced quenching in the fluorescence of GST through static suppression. The reaction was determined using differential pulse voltammetry (DPV) by monitoring the oxidation peak at 0.65 V of GSH sulfhydryl group. Quantitative estimation of the product reaction could be made by measuring an additional oxidation peak at 0.91 V which increased linearly with DO37 concentration. These electrochemical determinations were made possible by preconcentrating the reaction product on a graphite-epoxy electrode with immobilization of GST onto magnetite nanoparticles. Straightforward biological implications from the results are associated with the known toxicity of azo dyes such as DO37, which has been proven here to interact strongly with both GSH and the liver enzyme GST, and may induce hepatocarcinogenesis or other types of cancer. [Display omitted] •The mechanisms of interaction between DO37 and GST are proposed.•Reaction kinetics between DO37 and GST were determined through optical techniques.•Density functional theory (DFT) calculations confirmed the mechanism proposed.•The product of the reaction were identified via electrochemical experiments.