Highly Sensitive Detection of Silver Ions Enabled by RecJf Exonuclease Cleavage and Reductant-Mediated Electrochemical Amplification

A novel electrochemical approach for a silver ion (Ag+) assay is proposed based on Ag+-induced DNA structure transformation for target recognition, RecJf exonuclease mediated cleavage for background signal decline, and a specific reductant-assisted reaction for electrochemical amplification. Generally, in the presence of Ag+, cytosine-Ag+-cytosine with high stability forms and the single-stranded DNA probe on the electrode transforms into a hairpin structure, which resists degradation by RecJf exonuclease. A DNA probe is labeled with methylene blue (MB), which supplies an intense electrochemical signal. Moreover, the employment of a reductant can assist the oxidation of MB, which amplifies the signal in situ. High sensitivity is thus achieved and the calculated detection limit for Ag+ detection is 3 pm. This method also demonstrates excellent selectivity in the presence of interfering ions. Moreover, it can be successfully applied to the voltammetric determination of Ag+ in drinking and lake water.