A mitochondria-targeting time-gated luminescence probe for hypochlorous acid based on a europium complex.

Bioresponsive luminescence probes based on lanthanide complexes have shown great utility in a variety of time-gated luminescence bioassays. However, functional lanthanide complexes that can target individual organelles for probing biospecies therein have rarely been investigated. In this work, a unique Eu complex, Mito-NPSTTA-Eu, was designed and synthesized as a probe for the time-gated luminescence sensing of HOCl inside the mitochondria of living cells. The probe showed a fast, highly sensitive and selective luminescence response to HOCl with a wide available pH range (pH 3-10), and highly specific mitochondria-localization performance. Taking advantage of time-gated luminescence bioimaging and the excellent properties of the Eu complex, the generation of endogenous HOCl in RAW 264.7 cells and the uptake of exogenous HOCl by zebrafish were successfully imaged, respectively. The results demonstrated the feasibility of Mito-NPSTTA-Eu for the imaging of mitochondrial HOCl, and validated the potential of our strategy for the design of lanthanide complex-based organelle-targeting bioresponsive probes.