Electrochemical Detection of Ultratrace Lead Ion through Attaching and Detaching DNA Aptamer from Electrochemically Reduced Graphene Oxide Electrode.

This paper describes a simple strategy for the ultratrace level detection of Pb ion based on G-quadruplex DNA and an electrochemically reduced graphene oxide (ERGO) electrode. First, ERGO was formed on a glassy carbon electrode (GCE) by the reduction of graphene oxide (GO) using cyclic voltammetry. Subsequently, a methylene blue (MB)-tagged, guanine-rich DNA aptamer (Apt) was attached to the surface of ERGO via π-π interaction, leading to the Apt-modified ERGO electrode. The presence of Pb could generate the folding of Apt to a G-quadruplex structure. The formation of G-quadruplex resulted in detaching the Apt from the ERGO/GCE, leading to a change in redox current of the MB tag. Electrochemical measurements showed the proposed sensor had an exceptional sensitivity for Pb with a linear range from 10 to 10 M and a detection limit of 0.51 fM. The sensor also exhibited high selectivity for Pb, as well as many other advantages, such as stability, reproducibility, regeneration, as well as simple fabrication and operation processes.