Aptamer based fluorescence recovery assay for aflatoxin B1 using a quencher system composed of quantum dots and graphene oxide

Aflatoxin B1 (AFB1), a secondary fungal metabolite of Aspergillus flavus, was employed as a model mycotoxin to establish an aptamer based assay that exploits the quenching of the fluorescence of CdTe quantum dots (Q-dots) by graphene oxide (GO). A thiolated aptamer specific for AFB1 was linked to the surface of Q-dots via ligand exchange. The fluorescence of the aptamer modified-Q-dots is strongly quenched by GO. If, however, AFB1 is added, fluorescence is restored depending on the quantity of AFB1 added. The system was evaluated both in phosphate buffer solution and in peanut oil. If performed in an aqueous system, the assay possesses good selectivity, a wide dynamic range (from 3.2 nM to 320 μM) and a low limit of detection (1.0 nM). If performed in peanut oil solution, the dynamic range is from 1.6 nM to 160 μM, and the limit of detection is 1.4 nM. In our perception, this is a simple, sensitive and selective method for the determination of AFB1 that also may be extended to the analysis of other mycotoxins.