Dual-mode aptasensor based on a coumarin–benzothiazole fluorescent and colorimetric probe for label-free and visual detection of ochratoxin A

Ochratoxin A (OTA) is regarded as a harmful mycotoxin that severely influences human health by increasing the risk of diseases. Although conventional quantitative methods for OTA detection have been developed, there remain drawbacks of limited signal transduction, bulky instrument requirements, high cost, and sophisticated sample pretreatment. Herein, we successfully synthesize a coumarin-benzothiazole molecule named DR1 to construct a dual-mode aptasensor (DR1/OBA) by simultaneously producing fluorescent and colorimetric signals when binding to OTA binding aptamer (OBA). In fluorescent mode, the fluorescence of DR1/OBA will be switched off and provide rapid, label-free, and sensitive detection efficacies via the OTA competition. In colorimetric mode, the purple-color of DR1 tends to a blue-color state with a red-shifted absorbance by forming DR1/OBA. The blue-shifted absorbance will be observed with OTA competition and the purple-color state of DR1 can be recovered. Based on this unique phenomenon, a smartphone-based detection platform has been established to convert the color change into RGB values and realize the visual detection for spiked OTA quantification in real samples. As expected, the dual-mode aptasensor allows portable, reliable, sensitive, and visual detection for OTA in sophisticated scenarios. It will hold great potential in advancing research in mycotoxins and the development of aptamer-based biosensing.