Polyvinylpyrrolidone and 4-mercaptobenzoic acid-functionalized nickel nanoclusters for selective and sensitive detection of glutathione assisted by Fe3+

Abstract

Accurate determination of glutathione (GSH) in food supplements and human biological fluids is critical for preventing disorders related to GSH imbalances. To address this, a selective and sensitive fluorometric method was developed for GSH detection using nickel nanoclusters functionalized with polyvinylpyrrolidone (PVP) and 4-mercaptobenzoic acid (4-MBA) (PVP/4-MBA@Ni NCs). In this system, PVP serves as the stabilizer, while 4-MBA functions as both a stabilizer and reducing agent. In the presence of Fe³⁺ ions, the fluorescence response of the PVP/4-MBA@Ni NCs decreased due to aggregation and the inner-filter effect. Upon the addition of GSH, a bithiol compound that chelates Fe³⁺ ions, the fluorescence emission was restored. This recovery occurred due to the formation of a stable chelate between GSH and Fe³⁺ ions. The fluorescence intensity ratios (F/F⁰) increased linearly with GSH concentration in the range of 0.018–50 μM, with a detection limit (LOD, S/N = 3 : 1) of 0.005 μM. The PVP/4-MBA@Ni NCs/Fe³⁺ system offers several advantages, including rapid detection time, high selectivity, and a low detection limit. This system was successfully applied to detect GSH in real-world samples such as dietary supplement capsules and human biological fluids, showing good recovery percentages and low relative standard deviation (RSD) values. These results confirm the reliability of the fluorescent system for detecting GSH in various samples.