Robust and ultrasensitive electrochemical detection of ochratoxin a using a highly reactive DNAzyme wired via primer exchange reaction.

Ochratoxin A (OTA) is a fungus-produced secondary metabolite, which causes food safety issues and exposures to health threats to humans. In this study, an electrochemical biosensor based on target-initiated detection was constructed to accurately and efficiently detect OTA. After the identification and specific hybridization of OTA and its aptamer, the primer exchange reaction (PER) was initiated to generate vast quantities of DNAzymes. The DNAzymes specifically cleave the hairpin modified with silver nanoclusters (AgNCs), allowing the released DNA–AgNC strands to attach to capture DNA probes (cDNA) on the electrode surface with detectable electrochemical signal transforms. The detection of this electrochemical biosensor can only be initiated after OTA is identified with the aptamer, which guarantees that the reaction products in the detection process can only be specifically generated, providing assurance for the ultimate generation of authentic and dependable detection results. The biosensor has the advantages of effortless operation, rapid reaction, and cost-effectiveness, and the OTA targets can be detected by this strategy up to 0.65 ng mL−1. Furthermore, the detection of diverse targets can be accomplished by simply replacing the aptamer, offering huge possibilities in the field of food security and environmental detection. [ABSTRACT FROM AUTHOR]