Rational design of ratiometric and lysosome-targetable AIE dots for imaging endogenous HClO in live cells

Rational design of novel ratiometric and targetable fluorescent probes for selective imaging of lysosomal hypochlorous acid (HClO) is conducive to investigating the function of HClO in pathophysiological processes. Herein, we for the first time combine 1-pyrenecarboxaldehyde (with a π-π stacking effect) and 2-methylquinoline derivatives to synthesize an aggregation-induced-emission (AIE) probe (SA-C2-PCD) for ratiometric detection of HClO in living cells. Subsequently, a kind of novel lysosome-targetable AIE dot (AIED-Lyso) with dual emission features is prepared via a simple co-precipitation of a lysosome-targeting surfactant MAA-CO720, an amphiphilic block copolymer PEO-b-PS and the HClO-responsive probe (SA-C2-PCD). The free AIED-Lyso shows only strong red AIE fluorescence without addition of HClO. However, when exposed to HClO, a strong oxidizing agent, the SA-C2-PCD would release 1-pyrenecarboxaldehyde that aggregates through π-π stacking interaction in aqueous solutions, inducing a distinct fluorescence change from red to blue. Interestingly, the as-prepared AIED-Lyso displays good water dispersity, high selectivity and sensitivity (∼70.4 nM), strong anti-interference ability, prominent long-term fluorescence stability (>10 weeks), and low cytotoxicity, and it can be successfully applied to visually detect endogenous lysosomal HClO in live cells.