Practical and regenerable electrochemical aptasensor based on nanoporous gold and thymine-Hg2+-thymine base pairs for Hg2+ detection

A simple, practical and reusable electrochemical aptasensor, based on thymine-Hg2+-thymine (T-Hg2+-T) coordination chemistry and nanoporous gold (NPG) for signal amplification, was designed for sensitive and selective detection of mercury ions (Hg2+). The thiol modified T-rich hairpin capture probe was self-assembled onto the surface of the NPG modified electrode for hybridizing with ferrocene-labeled T-rich probe in the presence of Hg2+ via T-Hg2+-T coordination chemistry. As a result, the hairpin capture probe was opened, and the ferrocene tags were close to the NPG modified electrode. Taking advantage of the amplification effect of NPG electrode for increasing the reaction sites of thiol modified capture probe, the proposed electrochemical aptasensor could detect Hg2+ quantitatively in the range of 0.01-5000 nM, with a detection limit as low as 0.0036 nM which is much lower than the maximum contamination level for Hg2+ in drinking water defined by the U.S. Environmental Protection Agency. Moreover, the proposed electrochemical aptasensor can be regenerated by adding cysteine and Mg2+. The aptasensor was also used to detect Hg2+ from real water samples, and the results showed excellent agreement with the values determined by atomic fluorescence spectrometer. This aptasensor showed a promising potential for on-site detecting Hg2+ in drinking water.