Switchable aptamer micelle flares respond to target ATP molecules in vitro. (a) Fluorescence titration of SAMF (1 μM) against increased concentrations of ATP (0.1-3.0 mM). (b) Time course of fluorescence associated with the binding of target molecules. The concentration of ATP was 1 mM. (c) Switchable aptamer micelle flares distinguish ATP from its analogs: TTP, GTP, CTP and UTP. The concentration of ATP and its analogs were 2 mM. (d) Cytotoxicity assay of HeLa cells treated with different concentrations of SAMFs (0, 0.2, 0.5, 1, 2 μM).