Y-tetrahedral DNA nanostructures assisted dual signal aptasensor for simultaneous detection of isocarbophos and edifenphos

We reported a novel gold particles-modified three-dimensional reduced graphene oxide (3D-rGO/AuNPs) electrochemical aptasensor for the simultaneous detection of isocarbophos and edifenphos. In this study, the use of different metal ions resulted in the generation of discrete differential pulse voltammetry (DPV) peaks. These discrete peaks allowed the identification of different pesticides and their respective concentrations, thereby achieving simultaneous detection. Five designed aptamers were processed to form a Y-shaped tetrahedral DNA nanostructure (Y-TDN) as a skeleton, which could specifically bind to the aptamers of edifenphos and isocarbophos. Herein, Pb2+ was used to label an edifenphos aptamer (Pb2+-APTEd), and Cd2+ was used to label an isocarbophos aptamer (Cd2+-APTIs), respectively. Notably, due to the force of specific recognition between aptamer and targets being stronger than the force between the aptamer and the complementary strand of Y-TDN, Pb2+-APTEd and Cd2+-APTIs were dissociated from Y-TDN, thereby causing the reduced oxidation currents of Pb2+ and Cd2+. In addition, 3D-rGO/AuNPs could enhance the electron transfer ability to amplify a signal, and immobilize the aptamer on the electrode surface through Au-S bonds. Linear calibration curves were obtained over the concentration range of 0.01–1000 ng/mL for edifenphos and 0.1–1000 ng/mL for isocarbophos with a limit of detection (LOD) was 3.3 pg/mL and 33 pg/mL, respectively. This conceptual model provides the theoretical basis for the simultaneous detection of environmental contaminants, with the flexibility to be reprogrammed by simple modification of the aptamer for the detection of various toxins, antibiotics, and other small contaminants.