An electrochemical aptasensor based on gold@polypyrrole composites for detection of lead ions.

This work describes an electrochemical aptasensor for determination of lead ions (Pb). Composites prepared from gold nanoparticles and polypyrrole (Au@PPy) with good electrical conductivity were used to modify the surface of a screen printed carbon electrode for amplifying the current signal. Single strand DNA was immobilized on the electrode and binds lead(II) as confirmed by cyclic voltammetry at voltage of -0.2 V~0.6 V. Differential pulse voltammetry, measured at 0.10 V (vs.  Ag/AgCl), was used to monitor the interaction between aptamer and lead(II) using hexacyanoferrate as an electrochemical probe. In the presence of Pb, the aptamer forms a G-quadruplex, and the peak current is increased. By this method, Pb can be detected in the range of 0.5-10 nM with a low detection limit of 0.36 nM. The aptasensor was successfully applied to the determination of Pb in polluted soil and baby's nail. The method showed outstanding sensitivity and selectivity in detecting Pb, therefore is considered to have great potential in developing an environmental monitoring platform. Graphical abstract Schematic illustration of Pb detection procedure and principle using an electrochemical aptasensor.