Exonuclease III-amplified electrochemical detection of ochratoxin A based on AuPt bimetallic signal enhancer

Ochratoxin A (OTA) as one of the most hazardous mycotoxins has drawn particular concern owing to its widespread occurrence in food and severe threat on human health. Herein, an exonuclease III (Exo III)-amplified electrochemical biosensor is developed for the sensitive detection of OTA by using bimetallic AuPt as signal enhancer. AuPt bimetallic nanoparticles loaded with massive electrochemical species thionine are employed as the excellent signal amplification probes (AuPt@Thi). The specific recognition of OTA triggers the conformational switching of DNA probes and induces the Exo III-assisted nucleic acid cycle amplification, generating a significant amount of DNA segments which are then introduced to the sensing interface to allow the attachment of signal probes AuPt@Thi. Bimetallic AuPt with outstanding electrical conductivity, exceptional loading capacity, and high catalytic activity enables the enhancement of Thi redox signal, resulting in a remarkable increase of signal response. Benefiting from the synergistic effect of Exo III-catalyzed cycle amplification and signal enhancement of electrochemically active AuPt@Thi, the proposed biosensor demonstrates superior analytical performance for OTA detection with the advantages of rapid response, fine robustness, cost-effectiveness and simple operation. Under the optimal conditions, a broad linear detection range of 0.1 pg mL −1 –100 ng mL −1 and the limit of detection down to 0.07 pg mL −1 are achieved. Furthermore, the as-prepared electrochemical biosensor shows good specificity, acceptable stability, satisfactory repeatability, and reliable capability for monitoring the OTA in actual food samples, implying promising practical applicability in the realm of food safety testing.