A fluorescent aptasensor based on DNA-scaffolded silver nanoclusters coupling with Zn(II)-ion signal-enhancement for simultaneous detection of OTA and AFB1

The simultaneous detection of various mycotoxins is indispensable for food safety since the agricultural products are often contaminated by multiple mycotoxins. Herein, we report a signal-enhancement fluorescent aptasensor based on DNA-scaffolded silver nanoculsters (DNA/AgNCs) for simultaneous detection of Ochratoxin A (OTA) and Aflatoxin B1 (AFB1). The OTA aptamer (Ap1) and the AFB1 aptamer (Ap2) immobilized on magnetic beads surface hybridize with signal probe1 (Sp1) and signal probe2 (Sp2), respectively. In the presence of these two mycotoxins, the single-strand Sps are released after Aps binding with mycotoxins due to the higher stability of mycotoxin-Ap. Through the magnetic separation, the Sps in the supernatant liquid are acted as the corresponding scaffolds to synthesize AgNCs with different photoluminescence emission bands. Intriguingly, we find that the fluorescence intensity is obviously increased after adding Zn(II)-ion into the system, leading to a linear range from 0.001 ng/mL to 0.05 ng/mL both for OTA and AFB1 with the detection limit of 0.2 pg/mL for OTA and 0.3 pg/mL for AFB1. The proposed fluorescent aptasensor shows excellent performance towards the analytical application in real samples, providing a new model for the simultaneous detection for other mycotoxins by simple change of the aptamer.