Target-induced electronic switch for ultrasensitive detection of Pb2+ based on three dimensionally ordered macroporous Au-Pd bimetallic electrode

A novel strategy for selective and sensitive amperometric detections of Pb2+ was proposed based on the three dimensional ordered macroporous (3DOM) Au-Pd bimetallic electrode and target-induced methylene blue-single walled carbon nanotubes (MB-SWCNTs) as signal reporter. A DNA biosensor was fabricated by immobilizing capture probe DNA on the 3DOM Au-Pd bimetallic electrode, which further hybridized with the reporter DNA loaded on the MB-SWCNTs adduct upon the exposure of Pb2+, inducing measurable electrochemical signal. Due to the dramatic signal amplification by the enhanced immobilization of DNA on the surface of 3DOM Au-Pd bimetallic electrode and MB-SWCNTs, coupling the low background signal produced by blank solution, ultra-low level (1 x 10(-19) M) of Pb2+ could be detected. Under the optimal conditions, the electrochemical signal of the MB increased with the increasing Pb2+ concentration, exhibiting a linear response in the range of 1 x 10(-17)-1 x 10(-4) M. Furthermore, with the application of Pb2+ dependent DNAzyme, the proposed sensing system demonstrated high selectivity. This work represented a promising potential for on-site testing Pb2+ in real drinking water and serum sample analysis. (C) 2013 Elsevier B.V. All rights reserved.