DNA tetrahedron-besieged primer and DNAzyme-activated programmatic RCA for low-background electrochemical detection of ochratoxin A.

Ochratoxin A (OTA) is the most toxic class of ochratoxins and has become a major threat to the environment, humans and animals. Therefore, research on the methods for its detection is also more urgent. Herein, we propose a low-background electrochemical biosensor based on a DNA tetrahedron-besieged primer and a DNAzyme-activated programmatic rolling circle amplification (RCA) that can be ultimately utilized for OTA detection in wine samples. Low-background detection can be achieved using the besieged primer via sequenced assembly of DNA tetrahedral nanostructures so that non-specific extensions of primer can be avoided. The target OTA-mediated DNAzyme activation initiates the programmatic RCA. Additionally, the catalytic property of silver nanoclusters (AgNCs) is integrated with the electrochemical assay to achieve high sensitivity for OTA detection. Benefiting from the aforementioned processes, a low-background, and highly sensitive electrochemical biosensor has been successfully constructed. This design is capable of detecting OTA at concentrations from 1 pg/mL to 10 ng/mL, and its lowest concentration limit is 0.773 pg/mL. Simultaneously, its validation in the detection of actual samples reveals that the proposed electrochemical biosensor has a lot of potential in food safety and environmental detection.