Disassembly-driven turn-on fluorescent nanoprobes for selective protein detection.

"Switchable" fluorescent probes, which induce changes in the fluorescence properties (e.g., intensity and/or wavelength) only at the intended target protein, are particularly useful for selective protein detection or imaging. However, the strategy for designing such smart probes remains very limited. We report herein a novel mechanism for generating protein-specific "turn-on" fluorescent probes. Our approach uses an amphiphilic, self-assembling compound consisting of a fluorophore and a protein ligand. In the absence of target protein, the probe forms self-assembled aggregates in aqueous solution and displays almost no fluorescence because of efficient quenching. On the other hand, it emits bright fluorescence in response to the target protein through recognition-induced disassembly of the probe. On the basis of this strategy, we successfully developed three types of fluorescent probes that allow the detection of carbonic anhydrase, avidin, and trypsin via turn-on emission signals. It is anticipated that the present supramolecular approach may facilitate the development of new protein-specific switchable fluorescent probes that are useful for a wide range of applications, such as diagnosis and molecular imaging.