Phosphorescent iridium(iii) complexes capable of imaging and distinguishing between exogenous and endogenous analytes in living cells.

Kenneth Yin Zhang,Qi Wu,Huanjie Wei,Shujuan Liu,Taiwei Zhang,Wei Huang,Qiang Zhao

doi:10.1039/c8sc02984a

Kenneth Yin Zhang, Qi Wu + Show 5 more

Open Access

https://doi.org/10.1039/c8sc02984a

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Abstract

Many luminescent probes have been developed for intracellular imaging and sensing. During cellular luminescence sensing, it is difficult to distinguish species generated inside cells from those internalized from extracellular environments since they are chemically the same and lead to the same luminescence response of the probes. Considering that endogenous species usually give more information about the physiological and pathological parameters of the cells while internalized species often reflect the extracellular environmental conditions, we herein reported a series of cyclometalated iridium(iii) complexes as phosphorescent probes that are partially retained in the cell membrane during their cellular uptake. The utilization of the probes for sensing and distinguishing between exogenous and endogenous analytes has been demonstrated using hypoxia and hypochlorite as two examples of target analytes. The endogenous analytes lead to the luminescence response of the intracellular probes while the exogenous analytes are reported by the probes retained in the cell membrane during their internalization.

Highlights

Considering that endogenous species usually give more information about the physiological and pathological parameters of the cells while internalized species often reflect the extracellular environmental conditions, we reported a series of cyclometalated iridium(III) complexes as phosphorescent probes that are partially retained in the cell membrane during their cellular uptake
The complexes have been characterized by 1H and 13C nuclear magnetic resonance (NMR), matrix-assisted laser desorption ionization time-of- ight (MALDI-TOF) mass spectrometry (MS), infrared (IR), and ultraviolet-visible (UV-Vis) absorption spectroscopy
CellMask. (d) Laser-scanning luminescence confocal microscopy images of living HeLa cells treated with elesclomol (125 nM, 2 h, 37 C) followed by incubation with complex 3a (5 mM, 20 min, 37 C) and costaining with CellMask

Summary

Introduction

Molecular probes showing a luminescence response toward speci c analytes have been widely used for the detection of intracellular species related to physiological and pathological processes.[1,2,3,4,5] The targets of interest mainly include metal cations involved in cellular processes,[6,7,8] reactive oxygen/ nitrogen species (RONS) that induce high oxidative stress,[9,10,11] gasotransmitters that play roles in neurotransmission,[11,12,13] enzymes that catalyze speci c cellular reactions,[14,15,16] characteristics of diseases such as pH values[16,17,18] and hypoxia,[19,20] etc. Phosphorescent iridium(III) polypyridine complexes are selected for this study because of their advantageous photophysical properties[21,22,23,24,25] including intense phosphorescence and large Stokes shi. Their long luminescence lifetimes and high photostability facilitate photoluminescence lifetime imaging.[26,27,28,29] the cytotoxicity[30,31] and cellular distribution of iridium(III) complexes are tunable via structural modi cation of the ligands. The utilization of iridium(III) complexes to stain the cellular membrane,[32] mitochondria,[31] lysosomes,[33] Golgi apparatus,[34] nuclei,[35] and nucleoli[36] has been reported

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