Dual modification of nickel nanoclusters for selective detection of glutathione through a competitive displacement mechanism

Abstract

Glutathione (GSH) is a vital biomolecule that plays a fundamental role in biological systems, regulating numerous cellular functions. Given its physiological significance, the development of analytical sensors capable of sensitively and selectively detecting GSH is of great importance. In this study, a novel fluorescent probe was designed for the detection of GSH in dietary supplements and human biological fluids. The probe consists of nickel nanoclusters (NiNCs) stabilized by polyethyleneimine (PEI) and dithioerythritol (DTH) (PEI/DTH@NiNCs) as dual-protecting ligands. DTH functions as both a stabilizing and reducing agent, while PEI serves as an additional stabilizer, enhancing the structural integrity and stability of the nanoclusters. The fluorescence emission of PEI/DTH@NiNCs was significantly quenched in the presence of Fe³⁺ ions due to aggregation-induced quenching. However, upon the introduction of GSH, a stronger coordination interaction occurs between GSH and Fe³⁺, leading to the formation of a more stable chelate complex. This competitive binding disrupts the aggregation process, effectively restoring the fluorescence emission of the probe. Under optimized conditions, the fluorescence response exhibited a linear increase with GSH concentration in the range of 0–250 μM. The limit of detection (LOD), calculated based on the signal-to-noise ratio, was determined to be 7.0 nM. The developed probe was successfully applied for GSH detection in dietary supplements and biological samples, yielding recovery rates ranging from 96.9% to 104.1%, with relative standard deviation (RSD) values between 1.87% and 4.01%.