Abstract
Nucleic acid aptamers are emerging as useful molecular recognition tools for food safety monitoring. However, practical and technical challenges limit the number and diversity of available aptamer probes that can be incorporated into novel sensing schemes. This work describes the selection of novel DNA aptamers that bind to the important food contaminant ochratoxin A (OTA). Following 15 rounds of in vitro selection, sequences were analyzed for OTA binding. Two of the isolated aptamers demonstrated high affinity binding and selectivity to this mycotoxin compared to similar food adulterants. These sequences, as well as a truncated aptamer (minimal sequence required for binding), were incorporated into a SYBR® Green I fluorescence-based OTA biosensing scheme. This label-free detection platform is capable of rapid, selective, and sensitive OTA quantification with a limit of detection of 9 nM and linear quantification up to 100 nM.
Highlights
Ochratoxins are a group of mycotoxins produced by several fungal species of the genera Aspergillus and Penicillium [1]
Though aptamers were first isolated over two decades ago, very few have been developed that bind to small molecule targets
Many changes have been implemented to the original selection method to improve selection success and the resulting aptamers
Summary
Ochratoxins are a group of mycotoxins produced by several fungal species of the genera Aspergillus and Penicillium [1]. There are several reports demonstrating the immobilization of OTA aptamers to agarose and sepharose resins for OTA clean-up from food samples [24,25] These aptamer-based clean-up strategies perform to the commonly-used immunoaffinity columns but have an improved shelf-life. High sensitivity OTA detection has been achieved with many electrochemical-based aptasensors, with detection limits as low as pg/mL [34,35,36,37,38,39,40,41,42] Regardless of their promise, many of these methods require direct labeling with fluorescent or electrochemical probes which results in increased cost of synthesis or possible interference with aptamer folding and target binding. The results suggest that this sensing scheme may be valuable in the development of low cost, portable assays for future OTA testing
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