Nanoporous Au-based chronocoulometric aptasensor for amplified detection of Pb2+ using DNAzyme modified with Au nanoparticles

The authors herein described an amplified detection strategy employing nanoporous Au (NPG) and gold nanoparticles (AuNPs) to detect Pb2+ ions in aqueous solution. The thiol modified Pb2+-specific DNAzyme was self-assembled onto the surface of the NPG modified electrode for hybridizing with the AuNPs labeled oligonucleotide and for forming the DNA double helix structure. Electrochemical signal, redox charge of hexaammineruthenium(III) chloride (RuHex), was measured by chronocoulometry. Taking advantage of amplification effects of the NPG electrode for increasing the reaction sites of capture probe and DNA-AuNPs complexes for bringing about the adsorption of large numbers of RuHex molecules, this electrochemical sensor could detect Pb2+ quantitatively, in the range of 0.05-100 nM, with a limit of detection as low as 0.012 nM. Selectivity measurements revealed that the sensor was specific for Pb2+ even with interference by high concentrations of other metal ions. This sensor was also used to detect Pb2+ ions from samples of tap water, river water, and landfill leachate samples spiked with Pb2+ ions, and the results showed good agreement with the found values determined by an atomic fluorescence spectrometer. This simple aptasensor represented a promising potential for on-site detecting Pb2+ in drinking water.