An Electrochemiluminescence Biosensor for Determination of Pb2+ Based on G-Quadruplex of Aptamer Probe
A “turn on” model of electrochemiluminescence Pb2+ biosensor based on G-quadruplex of aptamer probe was developed by using quantum dots as labels. The biosensor was prepared by immobilizing a hairpin aptamer probe with a thiol group at 5′-end and an amino group at 3′-end on gold electrode via an Au-S bond. In the presence of Pb2+, the G-rich hairpin aptamer probe opens the stem-loop and forms G-quadruplex, which exposes the amino group at 3′-end that could covalently link to CdS quantum dots with carboxyl group on the surface. The fabrication and reaction process of the Pb2+ biosensor were characterized. The responsive electrochemiluminescence intensity was linearly related to the Pb2+ concentrations in the range of 2.0 × 10−10−5.0 × 10−8 M, with a detection limit of 3.74 × 10−11 M. The ECL biosensor has high sensitivity, good selectivity, satisfying stability and repeatability.