Phosphorescence Lifetime Imaging of Labile Zn²⁺ in Mitochondria via a Phosphorescent Iridium(III) Complex

Phosphorescence lifetime Zn²⁺ imaging possesses the advantage over normal fluorescence imaging in offering the more accurate temporal-spatial Zn²⁺ information. Herein, we report a new phosphorescent cyclometalated Ir(III) complex with a Zn²⁺-chelator bearing 1,10-phenanthrolin acting as ancillary ligand, Zin-IrDPA, which displays the specific Zn²⁺-induced enhancement of phosphorescence and phosphorescence lifetime, and the mitochondria-targeting ability. Moreover, its Zn²⁺-induced phosphorescence lifetime enhancement factor is not affected by medium lipophilicity, viscosity, polarity, and especially ambient oxygen. The reversible tracking of introduced exogenous labile Zn²⁺ in MCF-7 and HeLa cells via phosphorescence imaging and phosphorescence lifetime imaging (PLIM) have been realized with Zin-IrDPA. Moreover, PLIM with Zin-IrDPA is able to track the SNOC-stimulated endogenous Zn²⁺ release in mitochondria.