Abstract
With the widespread contamination of ochratoxin A (OTA), it is of significant importance for detecting OTA in foods and traditional Chinese medicine (TCM). In this study, a novel label-free fluorescent aptasensor utilizing the interaction between OTA-triggered antiparallel G-quadruplex and (N-methyl-4-pyridy) porphyrin (TMPyP) for the rapid and sensitive determination of OTA was established. The fluorescence of CdTe quantum dots (QDs) could be quenched by TMPyP. In the presence of analyte (OTA), the aptamer could recognize OTA and transform from a random coil to the antiparallel G-quadruplex. The interaction between G-quadruplex and TMPyP could release CdTe QDs from TMPyP, and thus recover the fluorescence of CdTe QDs. Under optimized conditions, the detection limit of the designed aptasensor was 0.16 ng mL−1, with a linear range of 0.2 to 20 ng mL−1. Furthermore, this aptasensor showed high selectivity toward OTA against other structural analogs and other mycotoxins, and was successfully applied in Astragalus membranaceus samples. The presented aptasensor for OTA detection could be a promising tool for the field monitoring of food and TCM.
Highlights
Ochratoxin A (OTA) is a toxic metabolite derived mainly from Aspergillus ochraceus and Penicillium verrucosum [1,2], which are widely present as contaminants in a variety of products, including wines, corn, coffee, milk, and traditional Chinese medicine (TCM) [3,4]
Since ochratoxin A (OTA) presents a serious threat to the health and safety of humans, it was classified as being possibly carcinogenic to humans (Group 2B) by the International Agency for Research on Cancer (IARC) [6]
The fluorescence intensity of CdTe quantum dots (QDs) was effectively quenched by TMPyP through photo-induced electron transfer (PET) [27]
Summary
Ochratoxin A (OTA) is a toxic metabolite derived mainly from Aspergillus ochraceus and Penicillium verrucosum [1,2], which are widely present as contaminants in a variety of products, including wines, corn, coffee, milk, and traditional Chinese medicine (TCM) [3,4]. Current analysis of OTA is conducted by various methods, including high-performance liquid chromatography (HPLC) [10], HPLC tandem mass spectrometry (HPLC-MS/MS) [11], and the enzyme-linked immunosorbent assay (ELISA) [12] These methods have both high accuracy and sensitivity, they still have some shortcomings, such as being time consuming, and requiring tedious sample pretreatment and expensive instruments [13]. Porphyrins have been intensively reported as sensing materials in optical sensors [23] They possess many attractive properties, including high chemical and thermal stability, high molar absorptivity, and a large extinction coefficient in the visible light region [24]. These optical advantages make porphyrin an ideal choice as the receptor in the photo-induced electron transfer (PET)-based “turn off” process. It is expected that the aptasensor has tremendous potential for detecting OTA in TCM samples
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