A Novel Fluorescence Sensor for Cocaine with Signal Amplification through Cycling Exo-Cleaving with a Hairpin Probe

Abstract

A novel fluorescence assay, based on the signal amplification through cycling reactions of aptameric recognition and nucleic acid exo-cleaving, was established for the sensitive detection of cocaine. In this assay, a new single fluorophore-labeled DNA-hairpin probe was used. This smart probe was established based on the significant nucleobase quenching between the nucleobases and the fluorophore. In the presence of cocaine and its aptamer, the structure of the smart probe changed to recover the fluorescence. In order to enhance the sensitivity of this assay, exonuclease III was introduced to enable the inputted cocaine to react with multiple probes in a recycling manner. Under the optimal conditions, a linear range for cocaine from 4.0 × 10⁻⁹ to 8.0 × 10⁻⁸ M with a detection limit of 1.76 × 10⁻⁹ M (3σ, n = 11) was obtained.

Keywords:

• Cocaine aptamer
• Exonuclease III
• Fluorescence
• Smart probe

Acknowledgments

This work was supported by the National Natural Science Foundation of China (No. 21075073) and the Shandong Province Natural Science Foundation of China (No. ZR2010BZ006).

Notes

“F/F0” = fluorescence disparity obtained before and after the smart probe was opened, where F0 is the fluorescence before the smart probe was opened.