Design and fabrication of surface capped palladium nanoclusters for the subnanomolar sensing of glutathione

Abstract

In this work, a palladium atomic cluster modified glassy carbon electrode (PdAC/GCE) was developed by potentiodynamic electrodeposition in the presence of an anionic surfactant for the electrochemical detection of glutathione (GSH). The morphology and structure of the prepared clusters were characterized by dynamic light scattering, matrix-assisted laser desorption ionization time of flight mass spectrometry, high-resolution transmission electron microscopy and spectroscopic methods. The modified electrode detects subnanomolar levels of glutathione, by monitoring the reduction peak of the Pd(0)/Pd(II) redox couple at the interface of Pd clusters deposited on a glassy carbon electrode in phosphate buffer using the differential pulse cathodic stripping voltammetry (DPCSV) technique. Under optimum conditions, the modified electrode shows a strong electrocatalytic response for GSH with high selectivity and sensitivity, a fast response, a wide linear range, a low detection limit (32 pM), excellent reproducibility with a limit of quantification of 1.6 × 10⁻¹⁰ M and a good precision of 0.38% for 1 × 10⁻⁸ M glutathione. Thus, it shows moderately good reproducibility and has reasonable selectivity towards some of the other important amino acids and biologically relevant molecules. To gain a better understanding of such an excellent sensor performance achieved with this electrode, studies were undertaken to pinpoint the electrode kinetics of charge transfer processes. The developed sensor was demonstrated for the quantification of glutathione in human serum samples with satisfactory accuracy. These features indicate that the prepared Pd cluster modified GCE with a unique electronic structure offers an excellent biosensing platform for sensitive and selective detection of glutathione.