Probing Mercury(II)–DNA Interactions by Nanopore Stochastic Sensing

In this work, DNA–Hg(II) interactions were investigated by monitoring the translocation of DNA hairpins in a protein ion channel in the absence and presence of metal ions. Our experiments demonstrate that target-specific hairpin structures could be stabilized much more significantly by mercuric ions than by the stem length and the loop size of the hairpin due to the formation of Thymine–Hg(II)–Thymine complexes. In addition, the designed DNA probe allows the development of a highly sensitive nanopore sensor for Hg2+ with a detection limit of 25 nM. Further, the sensor is specific, and other tested metal ions including Pb2+, Cu2+, Cd2+, and so on with concentrations of up to 2 orders of magnitude greater than that of Hg2+ would not interfere with the mercury detection.