An efficient electrochemical biosensor for the detection of heavy metal lead in food based on magnetic separation strategy and Y-DNA structure.

Herein, an electrochemical biosensor was developed based on a magnetic separation strategy for the sensitive detection of the heavy metal Pb 2+ . The specific binding of Pb 2+ and the aptamer (Apt) is used to trigger the release of the complementary chain (cDNA) on the magnetic bead system. The cDNA completes base complementary pairing with hairpins HP1 and HP2 at the electrode to form a Y-DNA structure. Then, the Y-DNA runs continuously with the assistance of the signal tag methylene blue (MB) and the current signal increases. However, in the absence of Pb 2+ , cDNA cannot be released and the Y-DNA structure cannot be formed on the electrode, resulting in a relatively low current signal. Under the optimal experimental conditions, the reduced peak current difference (Δ I ) showed a good linear relationship with lg  C Pb 2+ between 0.1 and 1000 nM, with a detection limit of 5.9 pM. In addition, the stability, reproducibility and detection capability of the sensors were investigated with satisfactory results.