Toehold-Mediated Cascade Catalytic Assembly for Mycotoxin Detection and Its Logic Applications

摘要

In this work, an enzyme-free biosensor is reported for mycotoxindetection based on a toehold-mediated catalytic hairpin assembly (CHA) and aDNAzyme-cascaded hydrolysis reaction. In the presence of a mycotoxin, therecognition between an aptamer and the mycotoxin releases the trigger DNA. Thetrigger DNA initiates the toehold-mediated CHA, generating large amounts ofpartial duplex B/C with four toeholds, which can be used to assemble theDNAzyme-cascaded hydrolysis reaction. Furthermore, through a collaborativeautoassembly reaction among the B/C duplex, DNA1, and DNA2, supramolecularnanostructures corresponding to Mg2+-dependent DNAzymes can be formed. Withthe incubation of Mg2+, the dual-modified (TAMRA/BHQ2) substrate strandDNA2 will be cleaved into two fragments, yielding a high TAMRAfluorescencesignal for mycotoxin testing. Under optimal conditions, the sensing system wasultrasensitive and showed low detection limits of 0.2 pM for ochratoxin A (OTA),0.13 pM for aflatoxin B1 (AFB1), and 0.17 pM for zearalenone (ZEN). The mycotoxin aptasensor also exhibited high selectivity andwas successfully applied for the quantitative analysis of OTA, AFB1, and ZEN in wine samples. Due to the advantages offlexibilityand versatility, this mycotoxin platform was used to fabricate several concatenated logic gates including"AND-INHIBIT","INHIBIT-OR","OR-AND", and"OR-INHIBIT"logic biocomputings. Such multiple functions of the logic system provided auniversal sensing strategy for the intelligent detection of multiplex mycotoxins, demonstrating considerable potential in food safetyand environmental monitoring

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