A fluorescence aptasensor based on semiconductor quantum dots and MoS2 nanosheets for ochratoxin A detection

Molybdenum disulfide (MoS2) nanosheet has been extensively investigated as an effective fluorescence quencher. However, its combination with semiconductor quantum dots (QDs) for the development of an aptasensor based on the fluorescence quenching has not be explored. Herein, a novel aptamer-CdTe QDs-MoS2 nanosheets fluorescence quenching system was developed for the detection of ochratoxin A (OTA) with QDs as donors and MoS2 nanosheets as quenchers. The QDs-conjugated aptamers with the linear conformation can assemble on the MoS2 nanosheets, causing the fluorescence quenching. In the presence of OTA, the aptamers wrap around the targets to form folded structures with a low affinity to the nanosheets, thus resulting in an OTA concentration-dependent restoration of the fluorescence intensity. The platform shows good specificity, a limit of detection of 1.0 ng/mL and a dynamic range over 1.0-1000 ng/mL in laboratory buffers. The platform is also successfully used to detect OTA in spiked red wine samples, verifying its feasibility in real sample analysis. The QDs-MoS2 nanosheets fluorescence quenching system could be easily adapted to measure other biomolecules by changing the thiol-modified aptamer.