Label-free colorimetric detection of glutathione by autocatalytic oxidation of o-phenylenediamine based on Au3+ regulation and its application

Abstract

A label-free, rapid, and highly sensitive colorimetric assay for the detection of glutathione (GSH) was developed. o-Phenylenediamine (OPD) can be selectively oxidized by Au³⁺ in phosphate buffer to produce light yellow 2,3-diaminophenazine. After the addition of GSH, the autocatalytic redox reaction between OPD and Au³⁺ can be effectively inhibited, resulting in a significant decrease in chroma and absorbance intensity. Reduced absorbance intensity can be used for the quantification of GSH. In addition, this method can achieve the discriminative detection of biothiols, such as cysteine and homocysteine. Based on these findings, a simple colorimetric assay was developed for the detection of GSH in the range of 1 nM to 1 mM with a low detection limit of 0.08 nM. More importantly, this procedure is simple, and the whole assay can be accomplished quickly within 15 min. Additionally, the proposed method was successfully used for the determination of GSH in biological fluids, such as serum samples.