Abstract
Ochratoxin A (OTA) is one of the most abundant food-contaminating mycotoxins that is also a potential carcinogen and responsible for many diseases affecting humans. Consequently, a sensitive, portable device for the detection of OTA is highly desirable. In this study, a miniaturized electrochemical aptamer-based sensor was developed for the label-free, sensitive detection of OTA. For the construction of the sensor, a gold thin-film three-electrode system was fabricated using standard microfabrication techniques on a polystyrene substrate (25 mm × 25 mm). Subsequently, the thiol-modified linker, 6-mercaptohexanol, DNA aptamer, and methylene blue (MB) were sequentially applied to the working electrode to construct a sensing layer. MB served as a redox indicator that interacted with the aptamer via the guanine bases and phosphate backbone to form complexes. The addition of OTA to the sensor induced the folding of the aptamer, which was accompanied by the release of the aptamer–MB–OTA complex from the sensor....
Highlights
Ochratoxin A (OTA) is a toxin produced by the secondary metabolism of Penicillium and Aspergillus fungal strains
The aptamer-modified electrode was incubated with the methylene blue (MB) solution and washed to remove unbound MB molecules
As shown in the original work by Cruz-Aguado and Penner, this aptamer has a rather high affinity to OTA, and binding depends on the presence of divalent cations such as Mg2+, which are possibly responsible for the bridge-mediated interactions between the aptamer and the OTA molecules.[14]
Summary
Ochratoxin A (OTA) is a toxin produced by the secondary metabolism of Penicillium and Aspergillus fungal strains. To verify the selectivity of the aptamer to OTA, the current responses were measured using sensors immobilized with several oligonucleotides (polyC, poly-G, poly-T, and poly-A) possessing the complementary sequence with the linker in the absence and presence of OTA (Figure S5). These DNAs were treated under the same conditions as the aptamer. The differences observed between both current signals (see curves b and c in Figure 5B) were not statistically significant This result suggested that the proposed sensor has good selectivity toward OTA. This result confirmed that the sensor could be successfully regenerated at least six times without any significant loss of sensitivity; note, that we did not carry out further tests
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