Highly sensitive electrochemical detection of mercury (II) via single ion-induced three-way junction of DNA

• Electrochemical detection of Hg2 + was proposed via a three-way junction of DNA.
• Single Hg2 +-induced SDH led to a highly sensitive method for Hg2 + detection.
• The detection limit of 5 pM was achieved without any additional amplification step.
• The electrochemical assay with a wide concentration range was simple and fast.

A “signal-on” electrochemical sensing strategy was designed for highly sensitive and selective detection of mercury (II) via its induction to three-way junction of DNA (DNA-TWJ). The TWJ consisted of the capture probe that was self-assembled on a gold electrode surface through SAu bond, the signal probe that was labeled with ferrocene (Fc) and contained single T–T mismatch to capture probe, and an assistant probe for the formation of DNA-TWJ upon the presence of mercury (II). This process caused the Fc tag approaching the electrode for fast electron transfer and thus increased the oxidation current. The “signal-on” sensing method could detect Hg2 + ranging from 0.005 to 100 nM. The assay was simple and fast. It showed potential application in on-site and real-time Hg2 + detection.

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