A dual-modal electrochemical aptasensor based on intelligent DNA Walker with cascade signal amplification powered by Nb.BbvCI for Pb2.

As a unique nanomachine, DNA Walker can move continuously along a specific orbit to amplify signal. Therefore, based on DNA Walker and endonuclease assisted signal amplification strategy, a novel dual-mode visual electrochemical aptasensor was constructed for the detection of Pb2+. Ceric dioxide@mesoporous carbon (CeO2/CS)@AuNPs not only could improve the conductivity of sensing interface but also could fix the aptamer. DNA Walker moved on the surface of the electrode to realize the pairing with the Ag-γFe2O3/cDNA probe, forming a special base sequence that could be spliced by the Nb.BbvCI. Under the action of endonuclease Nb.BbvCI, the Ag-γFe2O3/cDNA probe was continuously sheared and the amount on the electrode was decreased to amplify the signal. Besides, the nanoenzyme of Ag-γFe2O3 could catalyze 3'3'5'5'-tetramethylbenzidine (TMB) to blue color realizing the visual detection of Pb2+. The sensor has been successfully applied to the visual and accurate rapid detection of Pb2+ in aquatic products. The fabricated method of the sensor open up a new way for visual and accurate the detection of environmental pollutants.