A Sensitive Electrochemical Aptasensor for Ochratoxin A Detection Based on Double Cascade Amplification Strategy with Nb.BbvCI-Driven DNA Walker and Porous Co3O4 Nanozyme

Developing a strategy for the determination of trace ochratoxin A (OTA) in food is very important to ensure food safety. Here, based on a tripod probe, an electrochemical aptasensing platform for detected OTA sensitively was designed, which used the 3D DNA walker by endonuclease Nb.BbvCI powered and the nanozyme of porous Co3O4 nanodisks loaded Pt nanoparticles (Pt NPs@Co3O4) as a cascaded signal amplifying device. With OTA as a model target, the swing-arm probe of DNA walker was triggered. Next, probe on the magnetic beads was cleaved and released by Nb.BbvCI to realize the first signal amplification. After that, the partial sequence of the released probe is well assembled with triple-strand DNA by strand reaction and the other sequence exposed as a capture probe was combined with the Pt NPs@Co3O4. It can efficiently make the decomposition of H2O2, bring about significant current, and the signal was amplified again. The designed electrochemical aptasensor demonstrated outstanding detection linearity in the OTA concentration range of 1 pg/mL to 100 ng/mL, with a detection limit of 0.194 pg/mL (S/N = 3), with excellent reproducibility and high specificity. It can be used to find OTA in food. This research supplies a potential split-new avenue for the sensitive detection of electrochemical aptasensor.