An ultrasensitive and switch-on platform for aflatoxin B-1 detection in peanut based on the fluorescence quenching of graphene oxide-gold nanocomposites

Graphene oxide-gold nanocomposites (GO/AuNCs) were prepared and used as a novel fluorescence quenching platform for ultrasensitive detection of aflatoxin B-1 (AFB(1)) coupled with hybridization chain reaction (HCR) amplification. In the designed system, two fluorophore labeled hairpin probes (HP1/HP2) were introduced, and the fluorescence signals of them were effectively quenched due to the adsorption on GO/AuNCs. Associate probe (AP) was used for the specific recognition of AFB(1), and the stem-loop structure of it was opened. Meanwhile, the exposed section of AP was utilized as an initiator for the happen of HCR between HP1 and HP2, a strong fluorescence signal was obtained due to the formation of long nicked dsDNA duplex and desorbed of them from the surface of GO/AuNCs. Under the optimal conditions, GO/AuNCs displayed 94% of the quenching efficiency to the fluorescent probes, and a detection limit down to 0.03 pg/mL was obtained for AFB(1) detection. In particular, the assay exhibited excellent selectivity for the detection of AFB(1) against other interfering agents that normally coexist with AFB(1) in mildewed agriculture products. Moreover, the assay could realize the detection of AFB(1) effectively in peanut samples.