Abstract
This study describes a novel quencher-free fluorescent method for ochratoxin A (OTA) detection based on the photoinduced electron transfer (PIET) between guanine and fluorophore. In the absence of OTA, carboxyfluorescein (FAM)-labeled aptamer can partly hybridize with the complementary strand of OTA aptamer (OTA-cAPT), which contains four guanines at its 3′-end. As a result, the fluorescence of FAM is quenched due to PIET and stacked guanines. In the presence of OTA, FAM-labeled OTA aptamer can bind specifically to OTA, and thereby the high fluorescence intensity of the dye can be maintained. Under the optimal conditions, the method had a detection limit of 1.3 nM. In addition, the method we proposed is highly sensitive and specific for OTA. Furthermore, the method was proven to be reliable based on its successful application in the detection of OTA in red wine samples. Therefore, this promising, facile, and quencher-free method may be applied to detect other toxins by using other appropriate aptamers.
Highlights
Discovered in 1965, Ochratoxin A (OTA), a secondary metabolite in fungi, is one of the most common mycotoxins primarily produced by Aspergillus ochraceus, Aspergillus carbonarius, and Penicillium verrucosum (FAO/WHO, 2001) [1]
The principle of the proposed fluorescence assay in the detection of OTA is depicted in Scheme 1
OTA-cAPT partly hybridizes with its complementary OTA aptamer containing four guanines at its 30 -end, which are the fluorescence quenchers
Summary
Discovered in 1965, Ochratoxin A (OTA), a secondary metabolite in fungi, is one of the most common mycotoxins primarily produced by Aspergillus ochraceus, Aspergillus carbonarius, and Penicillium verrucosum (FAO/WHO, 2001) [1] Food commodities, such as grains, beans, nuts, dried fruits, spices, wine, coffee, and meat products, are vulnerable to OTA contamination [2,3]. The determination of OTA has been carried out by a number of analytical methods, including thin layer chromatography (TLC), high-performance liquid chromatography (HPLC), mass spectrometry (MS), gas chromatography (GC), surface plasmon resonance (SPR), and so on [6,7,8,9,10] These conventional methods have a number of advantages, such as high accuracy and selectivity, and low detection limits, they have many shortcomings, because they are time-consuming, but they require high-priced instrumentation, sophisticated sample pretreatment, and trained personnel. Several economical and rapid immunoassays, including enzyme-linked immunosorbent assay (ELISA), have been employed to detect OTA [11,12,13]
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