Enzyme-free autocatalysis-driven DNA cascade circuits for amplified electrochemical sensing of Ochratoxin A in food

Ochratoxin A (OTA) poses a great threat to food and environmental safety owing to its high toxicity. Herein, we developed a sensitive electrochemical aptasensor that integrates aptamer, enzyme-free DNA circuits, and electrochemical technology for OTA detection. In the presence of target OTA, the aptamer recognition first initiated the EDC circuit to releasing DNA (T2) from a ternary DNA complex (S-O-T2). The released T2 as the trigger to activate the CHA circuit and expose amounts of G-quadruplex sequences on modified electrode surface. Eventually, hemin was embedded in the G-quadruplex structure and generated an amplified electrochemical signal. Under optimal conditions, this developed biosensor is capable of detecting OTA ranging from 1 pg/mL to 10 ng/mL with a low detection limit of 0.135 pg/mL, which could be contributed to the design of target-triggered EDC and CHA cascade amplification. Additionally, the proposed biosensor was applied to analyze OTA in corn samples with satisfactory results, demonstrating that the proposed method has great potential in food safety and environmental monitoring.