Aptamer-based ratiometric fluorescent nanoprobe for specific and visual detection of zearalenone

We firstly proposed a ratiometric fluorescent nanoprobe with aptamer-labeled CdTe quantum dots (QDs) for the determination of zearalenone (ZEN). The nanoprobe was designed with dual-color emission fluorescence by single-wavelength excitation. Red-emitting silica-coated QDs (r-QDs@SiO₂) with the maximum excitation/emission at 400/608 nm were used as a reference. Green-emitting QDs linked with aptamer and covalently bonded to r-QDs@SiO₂ with the maximum excitation/emission at 400/518 nm were used as the responsive fluorophore for specific recognition of ZEN. The green fluorescence was quenched in the presence of ZEN. The ratio of fluorescence at 518 nm/608 nm decreased linearly against the increase of ZEN concentrations in the range of 31.4-628 nmol/L. The color of the solution changed from green to red as the concentration of ZEN increased. This method offered a ratiometric, specific and visual determination of ZEN. The limit of detection was 7.5 nM. The aptamer-labeled ratiometric strategy showed acceptable stability and selectivity. Therefore, the approach was successfully used to measure ZEN in food and can provide guidance for the design of point-of-care, multiplexed biosensors.