Selection and characterization of a DNA aptamer for Patulin and its application in a label-free fluorescence assay for fruit juices

Abstract Patulin (PTL, 154 Da) is a small molecule toxin produced as a mold metabolite. PTL is unstable in animals and is quickly converted to its metabolites. Thus, few successful antibodies were reported even after extensive efforts in hapten design. In this work, a library immobilization strategy was used to obtain DNA aptamers for PTL, where exposure of PTL to live animals or cells is no longer needed. After 20 rounds of selection, the most abundant aptamer named PTL-1 has a dissociation constant ( K d ) of 12.5 μM based on isothermal titration calorimetry and 18.4 μM based on thioflavin T (ThT) fluorescence spectroscopy. PTL-1 has excellent selectivity against nine other antibiotics. Compared to previously reported aptamers for PTL, PTL-1 is either shorter or has higher affinity. A label-free ThT fluorescence assay based on PTL-1 was developed, which has a detection limit of 0.2 μM (detection range 0.2–20 μM) for PTL in fruit juices. The PTL-1 aptamer shows resistance to matrix interference and can be applied to the rapid detection of PTL in a blended juice. This study is a nice demonstration of selecting aptamers for a target molecule difficult for the production of antibodies. Graphical Abstract