Impedimetric DNA sensor for detection of Hg2+ and Pb2+

An electrochemical DNA sensor based on DNA conformational changes for simultaneous detection of Hg2+ and Pb2+ was reported. The sensor was consisted of a probe strand (DNA), a Pb2+-specific DNAzyme, and a substrate strand contains mercury-specific oligonucleotide (MSO). When Hg2+ and Pb2+ interacted with DNA, the induced conformational changes were tracked by electrochemical impedance spectroscopy (EIS), which led to a decreased RCT. The RCT difference (ΔRCT) was applied to selectively detect Hg2+ and Pb2+ with detection limit of 1 pM and 0.1 pM, respectively. Through using masking agents, such as cysteine (masking Hg2+) and G-DNA (CTG-GGA-GGG-AGG-GAG-GGA) (masking Pb2+), Hg2+ and Pb2+ were simultaneously detected in buffer solution, human serum and river water, respectively.