Disassembly-driven fluorescence turn-on of polymerized micelles by reductive stimuli in living cells.

Stimuli-response nanoparticles have emerged as powerful tools for imaging and therapeutic applications. Ideally, they should be assembled from biodegradable materials featuring small size and cooperative response to biological stimuli that trigger particle disassembly and release of an active molecule that could be readily monitored in situ. A concept is developed that consists of organic nanoparticles, assembled from fluorescent amphiphiles and polymerized with a redox-cleavable cross-linker. We obtained 20 nm nanoparticles bearing self-quenched Nile Red dye residues, which can disassemble in living cells into highly fluorescent molecular units owing to an external or internal reductive stimulus. The obtained results pave the way to new stimuli-responsive nanomaterials for applications in background-free imaging as well as in drug delivery, as the concept can be further extended to other active molecules including drugs and to cross-linkers cleavable by other biological stimuli.