Specific pH effect for selective colorimetric assay of glutathione using anti-aggregation of label-free gold nanoparticles

Abstract

An operationally simple colorimetric method for measuring glutathione (GSH) concentration was developed using anti-aggregation of gold nanoparticles (AuNPs) in this work. At a pH of 5.8, cysteine (Cys) could rapidly induce the aggregation of AuNPs, thereby resulting in color change and AuNPs absorbance ratio (A_{650 nm}/A_{520 nm}) change. However, the added glutathione (GSH) can cause the anti-aggregation process to occur. This method was based on the regulation of pH, which on one hand can selectively detect GSH over Cys by the process of anti-aggregation of AuNPs and on the other hand can distinguish GSH from homocysteine (Hcys), and cystine (Cye) through specific selectivity. Under optical conditions, the detection of GSH can be finished within 5 min. The concentration range of the probe is 0.1–1.0 μM and the limit of detection (LOD) can be reached to 20.3 nM.