Construction of colorimetric-fluorescent dual-signal aptamer-based assay using COF-Au nanozyme and magnetic nanoparticle-based CdTe quantum dots for sensitive zearalenone determination.

A dual-signal aptamer-based assay utilizing colorimetric and fluorescence techniques was developed for the determination of zearalenone (ZEN). The CdTe quantum dots, serving as the fluorescent signal source, were surface-modified onto FeO@SiO and subsequently functionalized with the aptamer. The COF-Au was modified with complementary chain, which possessed peroxide (POD)-like enzyme properties, and could catalyze the peroxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to ox TMB, resulting in the generation of colorimetric signals. The two parts were merged based on the principle of base complementary pairing, resulting in an assembled structure exhibiting a diminished fluorescence signal due to the Förster resonance energy transfer (FRET) effect. Due to the higher affinity of the aptamer towards the target, the presence of ZEN resulted in the detachment of COF-Au, leading to an increase in supernatant concentration of COF-Au proportional to ZEN concentration. Consequently, this enhanced the catalytic ability and amplified the colorimetric signal. The fluorescence of precipitation increased simultaneously with the reduction of FRET, enabling linear detection of colorimetry in the range 0.5 ~ 10,000 μg·kg and fluorescence in the range 0.1 ~ 10,000 μg·kg, with respective detection limits of 0.36 μg·kg and 0.09 μg·kg. The spike recovery in wheat flour and corn ranged from 93.4 to 122.0%. This technology was simple to operate and had low cost and good application prospects.