Thioflavin T behaves as an efficient fluorescent ligand for label-free ATP aptasensor

Here, we for the first time demonstrated thioflavin T (ThT) as an efficient fluorescent ligand for 27-mer ATP-binding aptamer (ABA27), providing a novel signal readout mode for label-free selective ATP detection. ABA27 can promote the fluorescence emission of ThT with an unprecedentedly high efficiency, attributed to the specific structure of ABA27 rather than the G-tracts. Polyacrylamide gel electrophoresis, fluorescence spectroscopy, and fluorometric titration reveal that ThT interacts with ABA27 with a lower binding affinity (Kd ~89 μM) than ATP, which allows ATP to easily compete with ThT for the DNA binder. In the presence of ThT, adding ATP induces ABA27 to undergo a structural change, thereby not favoring the binding to ThT, verified by circular dichroism and UV-Vis absorption spectroscopy. As a result, the fluorescence intensity of ThT decreases dramatically, enabling the sensitive detection of ATP with high selectivity over other analogs. Such a sensing strategy may make ThT able to serve as a facile signal reporter for DNA nanomechanical devices fueled with ATP. Graphical Abstract The principle of the displacement of ThT by ATP.