Cellular imaging properties of phosphorescent iridium(III) complexes substituted with ester or amide groups

Area of Science:

• Coordination Chemistry
• Bioinorganic Chemistry
• Cellular Imaging

Background:

• Phosphorescent iridium(III) complexes are valuable tools for cellular imaging and sensing.
• Intracellular localization of these complexes depends on factors like charge, size, lipophilicity, and bioactive groups.

Purpose of the Study:

• To develop and investigate novel phosphorescent iridium(III) complexes for live-cell imaging.
• To understand the factors governing the intracellular localization and nuclear uptake of these complexes.

Main Methods:

• Synthesis of four phosphorescent iridium(III) complexes with modified diimine ligands.
• Live-cell imaging of HeLa cells using the synthesized complexes.
• Investigating nuclear uptake mechanisms using chlorpromazine and nocodazole.
• Analyzing cell division cycle effects on nuclear uptake.
• Photoluminescence lifetime imaging microscopy (PLIM) to study luminescence properties.

Main Results:

• Complexes 2-4 localized in the cytoplasm, while complex 1 showed whole-cell and nuclear staining.
• Nuclear uptake of complex 1 was mediated by clathrin and microtubules.
• Nuclear uptake efficiency varied with the cell division cycle, concentrating in the nucleus during mitosis.
• Complex 1 exhibited a longer luminescence lifetime in the nucleus compared to the cytoplasm.
• Hypoxia affected cytoplasmic complex luminescence but not intranuclear complex luminescence.

Conclusions:

• A novel phosphorescent iridium(III) complex (complex 1) demonstrates efficient, clathrin- and microtubule-dependent nuclear uptake.
• Nuclear localization is cell cycle-dependent, with higher accumulation during mitosis.
• The unique luminescence properties of complex 1 within the nucleus offer potential for advanced cellular sensing.