A carbon nanocages-mediated fluorescent aptasensor for aflatoxin B1 detection based on T7 exonuclease double recycling amplification

Aflatoxin B1 (AFB1) is strongly toxic and carcinogenic to human body and has been found in many agricultural products, so rapid and sensitive detection of AFB1 is essential for food safety and human health. Herein, a fluorescent aptasensor based on T7 exonuclease (T7 EXO) double recycling amplification was established, and novel nanomaterial carbon nanocages (CNCs) were introduced as fluorescence resonance energy transfer (FRET) receptors to quench the fluorophore-labeled DNA probe (FAM-cDNA). The CNCs as three-dimensional structured nanomaterials have higher quenching efficiency than conventional quenching materials due to their larger specific surface area and strong conjugated adsorption capacity. In the presence of target AFB1, the T7 EXO drives a double recycling amplification reaction, which ultimately causes a large amount of FAM-cDNA to be digested. In this process, the FAM labeled on the cDNA will be separated from the strand with the digestion procedure, thus avoiding adsorption by CNCs and maintaining its signal. The limit of detection (LOD) is as low as 1.4 pg/mL. The successful determination of AFB1 in real samples demonstrated that this method has excellent potential application prospects. In addition, the effect of potential interfering substances in real samples was analyzed, and the aptasensor presented a good interference immunity.