An ultra-sensitive electrochemical aptasensor for simultaneous quantitative detection of Pb2+ and Cd2+ in fruit and vegetable

An electrochemical aptasensor based on aptamer was designed for the first time to simultaneously detect Cd2+ and Pb2+ in fruit and vegetable. The double-stranded DNA including aptamers were immobilized on the electrode via Au-S bond. Due to the specific binding of aptamer and metal ions, the aptamers labelled with methylene blue or ferrocene were competed off the gold electrode, and the electrochemical signal was decreased. Under the optimal conditions, the electrochemical aptasensor showed linear response to Cd2+ and Pb2+ in the range of 0.1 to 1000 nmol/L, and the detection limits of Cd2+ and Pb2+ achieved 89.31 and 16.44 pmol/L (3σ), respectively. Excellent stability and reproducibility were exhibited with RSD 2.27% (Cd2+) and 3.61% (Pb2+). The digested fruit and vegetable were also tested, and the recoveries were in the range of 90.06% to 97.24%. Thus, this strategy held great potential in monitoring cadmium and lead pollution.