Weak-emission iridium(III) complexes as fluorescent turn-on probes for ultrasensitive and selective imaging histidine in living cells and rat tissues

Visualizing endogenous histidine (His) in living systems is an important and challenging work in life science field. Herein, two weak-emission iridium(III) complexes (IrL1 and IrL2) with solvent ligands (CH3CN) were designed and synthesized. It was found that IrL2 showed a better performance for detecting His with more remarkable fluorescence enhancement and lower limit of detection (LOD = 35 nM). Moreover, the recognition mechanism was confirmed to be a substitution of solvent ligands by His. Importantly, probe IrL2 was applicable to visualize endogenous His in living cells and rat tissue slices via an energy-dependent endocytotic pathway. We hope that this probe can serve as a useful tool for the diagnosis of His-related diseases. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Visualizing endogenous histidine in living systems is important and challenging work. Two weak-emission iridium(III) complexes (IrL1 and IrL2) were designed and synthesized, with IrL2 showing better performance for detecting histidine. The recognition mechanism involves histidine substituting solvent ligands, and IrL2 can be used to visualize endogenous histidine in living cells.