Fluorometric aptamer-based determination of ochratoxin A based on the use of graphene oxide and RNase H-aided amplification

The authors describe a fluorometric assay for ochratoxin A (OTA) that is based on the use of graphene oxide and RNase H-aided amplification. On addition of OTA, cAPT is replaced from the APT/cAPT hybridization complex and then hybridizes with RNA labeled with a fluorophore at the 5′-end. Eventually, the fluorophore is released by RNase H cleavage. As the concentration of OTA increases, more cAPTs are displaced, this leading to fluorescence enhancement (best measured at excitation/emission wavelengths of 495/515 nm). This RNase H-assisted cycle response results in strong signal amplification. The limit of detection, calculated on the basis of a signal to noise ratio of 3, is 0.08 ng·mL. Response is linear in the 0.08–200 ng·mL OTA concentration range. The method is highly selective for OTA over ochratoxin B and aflatoxin B. It was applied to the determination of OTA in red wine samples spiked at levels of 1, 7, and 50 ng·mL, and the recoveries ranged from 90.9 to 112%. [Figure not available: see fulltext.].