Aptamers are structured nucleic acid sequences that selectively bind a molecular target with high
affinity. Aptamer sequences can be found in nature as gene regulation elements located in the untranslated
regions of mRNAs,1 or discovered in the laboratory by in vitro selection (also known as SELEX: systematic
evolution of ligands by exponential enrichment) from a random pool of nucleic acids.2,3 Some in vitroselected
aptamers can bind and increase the fluorescence quantum yield (FF) of fluorogenic smallmolecule
ligands that are otherwise poorly fluorescent in their unbound state.4,5 These aptamers, often
referred to as fluorescent light-up aptamers (FLAPs),6 have attracted significant attention due to their
potential for biosensing.7–10