A novel amplification strategy based on target-induced multicomponent nuclease-mediated catalytic hairpin assembly for fluorescent DNA sensor

Ochratoxin A (OTA) is a highly hazardous mycotoxin widely found in food ingredients and processed products. In response to the demand for food safety, there is an urgent need to establish a highly sensitive, reliable, and costeffective method for the detection of OTA. In this study, a simple, enzyme-free, sensitive cascade amplification fluorescent strategy was developed to detect OTA based on a magnetic separation system-assisted, multicomponent nuclease (MNAzyme) and its induced catalytic hairpin assembly (CHA). The formation of a stable active MNAzyme was induced by the presence of the target, and the MNAzyme specifically cleaved multiple hairpin H1 to produce sDNA fragments. The sDNA could initiate the mismatched CHA cycle, leading to the production of a large number of H2-H3 complexes, with carboxyfluorescein (FAM) moving away from the quench group (BHQ1), and the fluorescent signal being significantly amplified. The constructed fluorescent aptasensor has a good linear range (0.5-100 ng/mL) and detection limit (0.45 ng/mL). The developed sensor was successfully applied to detect OTA in corn flour and black tea samples.