A FRET-based aptasensor for ochratoxin A detection using graphitic carbon nitride quantum dots and CoOOH nanosheets as donor-acceptor pair

A new fluorescence aptasensor for Ochratoxin A (OTA) analysis in corn and barley flour was developed owing to the favourable quenching function of cobalt oxyhydroxide (CoOOH) nanosheets . The first combination of graphitic carbon nitride quantum dots (g-CNQDs) and CoOOH nanosheets as efficient energy donor-acceptor pair was reported, and the quenching mechanism was proved by investigating the fluorescence lifetime of g-CNQDs. The aptamer-modified g-CNQDs (g-CNQDs-apt) were adsorbed onto CoOOH nanosheets surface by van der Waals force . Consequently, the Förster resonance energy transfer (FRET) from g-CNQDs-apt to CoOOH nanosheets was initiated, leading to quenched fluorescence. With the addition of OTA, the linear aptamer specifically bound with OTA to form G-quadruplex, which had relatively weak interaction with the CoOOH nanosheets and separated from the nanosheets surface. Thus, the FRET process between g-CNQDs-apt and CoOOH nanosheets was hindered, leading to the fluorescence of g-CNQDs-apt recovered clearly. The developed aptasensor exhibited acceptable detection limit with 0.5 nM and desirable linear relationship from 1 nM to 140 nM. Meanwhile, the aptasensor possessed multiple advantages, including easy operation, rapid detection and high selectivity . Moreover, the aptamer sensing platform was favorably applied for OTA determination in cereal (barley and corn flour), in which the recoveries varied from 94.5% to 101% with the relative standard deviation under 2.24%.