An ultrasensitive fluorescence aptasensor for chloramphenicol based on FRET between quantum dots as donor and the magnetic SiO2@Au NPs probe as acceptor with exonuclease-assisted target recycling

In this work, a fluorescence aptasensor has been developed to detect trace chloramphenicol based on FRET and exonuclease-assisted target recycling. Firstly, the composite probe for CAP was prepared through the immunoreactions between the capture probe based on dsDNA antibody labeled on Fe3O4@Au nanoparticles and the nanotracer using double strand aptamer (aptamer hybrid with its complementary DNA) labeled on core-shell SiO2@Au. When the composite probe solution was mixed with CAP, the aptamer on the nanotracer preferentially bounded with CAP, and then released cDNA-SiO2@Au and CAP-Apt complex to the supernatant. This is because anti-DNA on capture probes can't recognize the ssDNA. The exonuclease I (Exo I) added into the supernatant can further digest the aptamer-CAP from the 3'-end of aptamer and release CAP again, which can further participate in new cycle to react with the probes. The supernatant containing numerous SiO2@Au could efficiently quench the fluorescence response of CdSe QDs by FRET. Experimental results showed the CAP detection owning a linearity range of 0.001-10 ng mL(-1) and detection of limit (LOD) of 0.0002 ng mL(-1). Besides, the results of our method for CAP detection in the fish samples agreed well with those from ELISA, verifying its accuracy and reliability. (C) 2015 Elsevier B.V. All rights reserved.