Dual-signal intrinsic self-calibration ratio electrochemical sensor for glutathione based on silver nanoparticle decorated Prussian Blue analog

A sensitive dual-signal intrinsic self-calibration electrochemical sensor for glutathione (GSH) was developed based on the in situ electrodeposited silver nanoparticles modified nickel and iron contained Prussian Blue analog (Ag/NiFe PBA). Two different oxidation peaks ascribed to species of Ag and Fe with wide peak-to-peak potential can be found on the Ag/NiFe PBA modified electrode. In the presence of chloride ions, owing to the solid-state electrochemistry of silver chloride (AgCl), a sharp characteristic peak appeared with largely enhanced current intensity. After adding GSH, sensitive decline in the peak current of AgCl can be found for the specific interaction of Ag-GSH accompany with the "crowding-out effect", while the peak current of NiFe PBA remains unchanged. Using the ratio of the peak currents (IAgCl/IFe) as the signal output, Ag/NiFe PBA modified electrode showed wide linear range of 0.5 nM-5 μM for the quantitative of GSH with an extremely low detection limit of 0.12 nM, showing superior performance compared with previous electrochemical methods. The sensor can be utilized for the determination of GSH in various vegetable and serum samples. The ultrasensitive solid-state electrochemistry of AgCl promoted signal amplification strategy as well as the specific recognition and competitive reaction increasing the selectivity make the ratiometric sensor great potential in bioanalysis, food analysis and early diagnosis of cancer in clinics.