Nanoenzyme-Based Colorimetric Assay for Rapid Glutathione Determination Using Microwave-Synthesized Palladium Nanocrystals

Glutathione (GSH) is a critical bioactive molecule that plays an essential part in regulating the body’s redox homeostasis, and its concentration is of significant importance for the diagnosis of clinical conditions. In recent years, colorimetric techniques utilizing nanoenzymes have emerged as a novel approach for GSH determination. The development of nanoenzymes featuring straightforward synthesis, high catalytic efficiency, and cost-effectiveness is essential for achieving rapid and sensitive GSH determination. In this study, palladium nanocrystals (PdNCs) exhibiting peroxidase-like activity were successfully synthesized via a facile microwave-assisted method. Based on the specific thiol-PdNCs interaction and the associated color change of the catalytic system, a fast, straightforward, and highly sensitive colorimetric method was developed for the determination of GSH. Small-sized PdNCs with exposed (100) crystal planes exhibited exceptional peroxidase-like activity and efficiently catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 to produce a blue product. By exploiting the inhibitory effect of GSH on this catalytic system, sensitive GSH determination was achieved with linear ranges of 3–40 μM and 55–110 μM, as well as a low limit of detection (LOD) of 0.14 μM, outperforming previously reported methods. The method was further validated using serum samples, showing recovery rates of 96.36%–103.65% and relative standard deviations (RSDs) of 1.99%–3.38%. This PdNCs-based colorimetric strategy demonstrates promising potential for real-time GSH determination in clinical diagnostics.