Exonuclease-Catalyzed Target Recycling Amplification and Immobilization-free Electrochemical Aptasensor

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Abstract
A simple, sensitive, and selective immobilization-free electrochemical aptasensor had been developed which combines the advantages of the discrimination of the aggregation of long and short DNA on a negatively charged indium tin oxide (ITO) electrode, high selectivity of the aptamer, and high efficiency of exonuclease-catalyzed target recycling amplification. Ochratoxin A (OTA), a type of mycotoxin, has been chosen as the model target. Methylene blue (MB) labeled probe DNA had been hybridized with the OTA aptamer first, which cannot diffuse freely to the negative charged ITO electrode surface due to the repulsion of the negative charges, since the hybridized DNA contains large negative charges. In the presence of target (OTA), the aptamer prefers to form an OTA–aptamer complex in lieu of an aptamer–DNA duplex, which results in the dissociation of probe DNA from the probe DNA–aptamer complex. The released probe DNA could be digested into mononucleotides, including a MB-labeled electroactive mononucleotide ...
Funding Information
  • Natural Science Foundation of Fujian Province (2014J06005)
  • National Natural Science Foundation of China (21175024, 21222506, 21275031)
  • Program for New Century Excellent Talents in University (NCET-12-0619)

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