Iridium(III) Complex‐Based Activatable Probe for Phosphorescent/Time‐Gated Luminescent Sensing and Imaging of Cysteine in Mitochondria of Live Cells and Animals

Abstract

This study reports an activatable iridium(III) complex probe for phosphorescence/time‐gated luminescence detection of cysteine (Cys) in vitro and in vivo. The probe, [Ir(ppy)2(NTY‐bpy)](PF6) [ppy: 2‐phenylpyridine; NTY‐bpy: 4‐methyl‐4′‐(2‐nitrovinyl)‐2,2′‐bipyridine], is developed by incorporating a strong electron‐withdrawing group, nitroolefin, into a bipyridine ligand of the IrIII complex. The luminescence of the probe is quenched owing to the intramolecular charge transfer (ICT) process, but switched on by a specific recognition reaction between the probe and Cys. [Ir(ppy)2(NTY‐bpy)](PF6) shows high sensitivity and selectivity for Cys detection and good biocompatibility. The long‐lived emission of [Ir(ppy)2(NTY‐bpy)](PF6) allows time‐gated luminescence analysis of Cys in cells and human sera. These properties make it convenient for the phosphorescence and time‐gated luminescence imaging and flow cytometry analysis of Cys in live samples. The Cys images in cancer cells and inflamed macrophage cells reveal that [Ir(ppy)2(NTY‐bpy)](PF6) is distributed in mitochondria after cellular internalization. Visualizations and flow cytometry analysis of mitochondrial Cys levels and Cys‐mediated redox activities of live cells are achieved. By using [Ir(ppy)2(NTY‐bpy)](PF6) as a probe, in vivo sensing and imaging of Cys in D. magna, zebrafish, and mice are then demonstrated.

Cyclometalated Iridium (III) complexes: Recent advances in phosphorescence bioimaging and sensing applications

“…It has been recently established that the probes, having strong electron withdrawing groups such as nitroolefin, are highly sensitive, selective and biocompatible towards cystein molecule …”

Recent progress in H2S activated diagnosis and treatment agents

“…Phosphorescent transition metal complexes have attracted much attention owing to their strong visible light absorption and emission, large Stokes shi, and stable photochemical properties. 81,82 A ruthenium(II) complex-based responsive luminescence probe (Ru-MDB) for H 2 S detection was studied by Du et al 83 MBD is a masking moiety for the Ru-MDB complex H 2 S response. The metal-to-ligand charge transfer (MLCT) excited state of the Ru II complex is destroyed by an intramolecular lightinduced electron transfer photo-induced electron transfer (PET) process when the electron acceptor group MDB is linked (Fig.…”

A Ruthenium(II) complex-based probe for colorimetric and luminescent detection and imaging of hydrogen sulfide in living cells and organisms

“…Luminescent transition metal complexes, especially ruthenium (II) (Ru(II)) and iridium (III) (Ir(III)) complexes, have received considerable attention in the development of bioassay and imaging probes [35][36][37][38][39].…”