Ratiometric fluorescent sensing of endogenous hypochlorous acid in lysosomes using AIE-based polymeric nanoprobe

Abstract

The emergence of novel lysosome-targetable and ratiometric fluorescent probes for visualizing intracellular hypochlorous acid (HClO) is useful for exploring HClO-associated diseases. However, the notorious aggregation-caused quenching (ACQ) effect universally observed in conventional organic small lysosomal HClO fluorescent probes could greatly limited their biological applications. In addition, the “alkalizing effect” of morpholine group severed as the lysosome guiding unit would also lead to the enhancement of lysosome pH and even cell apoptosis. To circumvent the above problems, we herein report on the fabrication of a simple yet efficient polymeric nanoparticles-based ratiometric fluorescence nanoprobe (PNRFN) for lysosomal HClO imaging in living cells. The unique nanostructure can not only effectively separate the HClO sensing unit (on the surface of nanoparticles) and aggregation induced emission (AIE)-based reference fluorogen (in the core of nanoparticles) to prevent severe ACQ phenomenon, but also possess high water solubility, well-resolved fluorescence signals, good biocompatibility and excellent photostability, etc. Significantly, thanks to the positive charge and good cell-membrane permeability of nanoparticles, the as-prepared PNRFN can selectively accumulate in lysosomes, and it can be further successfully used to tracking exogenous/endogenous HClO in lysosomes. We expect that such ratiometric nanoprobe with well-resolved emission spectra can be served as an excellent platform for targeting specific biomolecule populations at subcellular levels.