Electrochemical DNA sensor based on T-Hg-T pairs and exonuclease III for sensitive detection of Hg2+

Abstract Mercury ion, as a kind of toxic ion, seriously endangers human health and ecological environment. It is necessary to establish an accurate and sensitive method for detecting Hg2+. In our work, we develop an electrochemical sensor for Hg2+ detection based on thymine-Hg2+-thymine (T-Hg2+-T) coordination. The cleavage of the double-stranded DNA with T-Hg2+-T pairs catalyzed by Exonuclease III (Exo III) is prompted to happen upon binding target Hg2+. [Ru(NH3)6]3+, which can be electrostatically adsorbed on the negatively charged DNA backbone, was used to convert the electronic signal. A wide linear range (1 pM-1 μM) was obtained with a detection limit of 0.22 pM, which meets the requirements of environmental sample analysis. In addition, the sensor also shows excellent selectivity for Hg2+ detection in the presence of other high-level interfering substances. More importantly, the electrochemical sensor could successfully detect Hg2+ in river water samples, demonstrating its promising potential for detecting Hg2+ in the real world.