ABSTRACT
An electrochemical aptasensor for Pb2+ was constructed based on the layer-by-layer assembly of graphene (GR) and anthraquinone -2-sulfonic acid sodium salt (AQMS) on the surface of Pb2+ aptamer. The mercapto-modified Pb2+ aptamer was first anchored on a gold electrode. Then the highly conductive material of GR was adsorbed on apt through the unique π-π stacking interaction, which was further used for the assembly and signal amplification of the electroactive AQMS. Upon interaction with Pb2+ ions, the apt on the aptasensor undergone conformational switch from a single-stranded form to the G-quadruplex structure, causing the GR assembled with AQMS releasing from the electrode surface into solution. As a result, the electrochemical signal of AQMS on the aptasensor was substantially reduced. Base on this concept, a useful platform for detection of Pb2+ ions was constructed. Under the optimal experimental conditions, the attenuation of peak currents (△Ipa ) showed linear relationship with the logarithm of Pb2+ concentrations (lgCPb2+) over the range from 5. 0×10-10 to 5. 0×10-8 mol/ L. The detection limit was estimated to be 6. 0×10-11 mol/ L.