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  • Title: Facile combination of beta-cyclodextrin host-guest recognition with exonuclease-assistant signal amplification for sensitive electrochemical assay of ochratoxin A.
    Author: Wang Y, Ning G, Wu Y, Wu S, Zeng B, Liu G, He X, Wang K.
    Journal: Biosens Bioelectron; 2019 Jan 15; 124-125():82-88. PubMed ID: 30343160.
    Abstract:
    Smartly coupling exonuclease-induced target recycling signal amplifications with β-cyclodextrin host-guest recognition, a novel "signal-on" aptamer sensor for sensitive determination of ochratoxin A (OTA) was proposed for the first time. Firstly, the formation of double-strand DNA (dsDNA) was occurred by hybridizing OTA aptamer with its complementary DNA (cDNA) and as the probe DNA the cDNA at its 3' terminal was labeled with methylene blue (MB). Next, when OTA was present, the aptamer tended to form aptamer-OTA complex with conformation of G-quadruplex instead of aptamer-cDNA duplex, leading to thus the probe DNA separating from dsDNA complex. Then the RecJf exonuclease was added, demolishing partially G-quadruplex structure and releasing a certain number of OTA. Sequentially, those released OTA would continue to react with the rest of aptamer in dsDNA, drawn into development of a new round of G-quadruplex complex, where the target cycling was realized. Meanwhile, as a signal molecule, MB modified on cDNA was liberated along with the cDNA being digested into monoucleotides by RecJf exonuclease, capable of diffusing onto the electrode surface due to host-guest recognition with β-cyclodextrin, whereupon the signal was enriched and yielded. In this way, cycles of target with continuous output of signal indicators were undergone, in which the detection of target was in return fulfilled with signal amplification owing to the joint endeavor of exonuclease and β-cyclodextrin. Under the optimal conditions, the raising signal maintained a linear relation with the logarithm of the target concentrations ranging from 10 pg/mL to 10.0 ng/mL and the detection limit reached as low as 3 pg/mL. This brand-new strategy was simple and low-cost but satisfactory in terms of detection limit, range and sensitivity, in all possibility to be applied extensively for diverse targets detection by easily alternating the corresponding aptamers.
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