A fluorescent aptasensor for sensitive detection of isocarbophos based on AT-rich three-way junctions DNA templated copper nanoparticles and Fe3O4@GO

Abstract A novel fluorescent aptasensor for sensitive determination of pesticide was successfully established, using AT-rich three-way junctions (AT-TWJ) DNA stabilized copper nanoparticle (CuNP) as a fluorescent signal and magnetic Fe3O4@GO as a single-stranded DNA (ssDNA) adsorbent to reduce the detection background. The detection just involves one strand of dsDNA and two strands of ssDNA. The dsDNA is hybridized by the target aptamer and the partially complementary DNA, acting as a recognition unit. After the specific combination between targets with its aptamer, the released ssDNA and the other two ssDNA can assemble into AT-TWJ DNA. The added Fe3O4@GO cannot adsorb the nascent blunt-ended AT-TWJ DNA. Then, the inputting of ascorbic acid (AA) and Cu2+ into the supernatant facilitates the formation of AT-TWJ DNA templated CuNPs, generating strong fluorescence. The developed strategy presents a sensitive and specific isocarbophos detection in the linear range of 10–500 nM with a detection limit of 3.38 nM, providing a new path for the detection of pesticides in the fields of food and environmental monitoring.