Electrochemical detection of glutathione based on Hg2+-mediated strand displacement reaction strategy

Glutathione (GSH) plays an important role in numerous cellular functions, and the abnormal GSH expression is closely related with many dangerous human diseases. In this work, we have proposed a simple but sensitive electrochemical method for quantitative detection of GSH based on an Hg2+-mediated strand displacement reaction. Owing to the specific binding of Hg2+ with T-T mismatches, helper DNA can bind to 3′ terminal of probe DNA 1 and initiate the displacement of probe DNA 2 immobilized on an electrode surface. However, Hg2+-mediated strand displacement reaction can be inhibited by the chelation of GSH with Hg2+, thereby leading to an obvious electrochemical response obtained from methylene blue that is modified onto the probe DNA. Our method can sensitively detect GSH in a wide linear range from 0.5 nM to 5 μM with a low detection limit of 0.14 nM, which can also easily distinguish target molecules in complex serum samples and even cell extractions. Therefore, this method may have great potential to monitor GSH in the physiological and pathological condition in the future.