Electrochemical amplification for Hg(II) quantification by anchoring an enzymatically extended aptamer

A novel indirect electrochemical approach is reported to improve the sensitivity of Hg2+ quantification in environmental water samples. This strategy is based on the Hg2+ induced selective interaction of thymine mismatched pairs in a thymine-rich aptamer DNA to improve the specificity, while template-independent terminal deoxynucleotidyl transferase (TdT) extended the 3 '-OH aptamer termini with repeated bases and increased the sensitivity. The introduction of the target Hg2+ blocked aptamer extension. Taking advantage of an electrochemical platform, this aptamer-TdT based amplification sensor enabled the specific quantification of Hg2+ ion over a wide linear range from 2 pM to 20 nM with a low limit of detection equal to 0.1 pM. The proposed strategy is promising for the detection of other metal ions.