ZnS/MnO2 metal organic framework based conductive hydrogel for highly selective and sensitive detection of glutathione in serum samples

Glutathione (GSH) is a vital natural antioxidant that plays a central role in protecting cells from toxins and free radicals. This work reports the synthesis of a novel ZnS/MnO2 – metal organic framework hydrogel (MOF-HG) via a lyophilization process for the highly sensitive and selective detection of GSH in stimulated blood serum. The hydrogel is synthesized by crosslinking ZnS/MnO2 – MOF with polyvinyl alcohol (PVA) and nafion (5 % solution). The hydrogel exhibits high porosity, resulting in a large surface area for enhanced electron transport, excellent electrical conductivity, sample absorption, and oxygen and sulphur vacancies that offer electro-oxidation of glutathione (GSH). Morphological and structural analysis of the hydrogel shows uniform porosity and a cubic structure for the ZnS/MnO2 - MOF, which are evenly distributed on the hydrogel surface. For the detection of glutathione (GSH), the differential pulse voltammetry (DPV) technique is used, showcasing a linear detection range of 10 nM to 10 mM, high sensitivity of 8.45 µA.nM−1.cm−2 and a low limit of detection (LOD) of 6.88 nM (=3S/m), making it highly effective for physiological GSH sensing. One of the key advantages of the substrate is its exceptional selectivity for GSH, even in the presence of a 2-fold concentration of interfering substances such as ascorbic acid (AA), uric acid (UA), Na+, Cl-, Ca2+, K+, bovine serum albumin (BSA), and glucose (GLU). In real samples, the sensor displays significant recovery percentages of 92.59 %, 101.00 %, and 120.22 %, further confirming the reliability and effectiveness of the developed sensor in detecting glutathione.