Phosphorescent cyclometalated iridium(III) complexes incorporated into polynorbornene polymeric platform as potential probes for assessments of oxygen in cancer cells

• Published in: Journal of organometallic chemistry 2024-10, Vol.1020, p.123349, Article 123349
• Main Authors: Bochkarev, Leonid N., Parshina, Yulia P., Komarova, Anastasia D., Baber, Polina O., Kovylina, Tatyana A., Konev, Aleksey N., Mozherov, Artem M., Shcheslavskiy, Vladislav I., Shirmanova, Marina V.
• Format: Article
• Language: English
• Subjects: In vitro; Oxygen sensing; Phosphorescence lifetime imaging; Phosphorescent polymeric iridium(III) complexes; tumor cells; Tumor spheroids
• ISSN: 0022-328X
• DOI: 10.1016/j.jorganchem.2024.123349

•New polymeric iridium(III) complexes PnIr1-PnIr4 were synthesized by metathesis polymerization method.•Polymeric complexes PnIr1-PnIr4 demonstrated intense deep-red emission and strong oxygen-dependent quenching of phosphorescence in organic and water solutions.•Polymeric probes PnIr1-PnIr4 showed low cytotoxicity in cultured cancer cells. The PnIr1 probe easily penetrated into cancer cells and tumor spheroids and was applied for the assessments of intracellular oxygen level. Phosphorescent transition metal complexes are considered as promising probes for oxygen sensing in living cells and tissues. Red light-emitting complexes are more valuable because the red irradiation better penetrates into biological tissues. In the present study, far-red light-emitting iridium(III) complexes PnIr1-PnIr4 on polyoxanorbornene platform were synthesized and their oxygen sensing properties were tested in water and in cells in vitro. Iridium(III) complexes incorporated into polymeric platform contained 1-(thien-2-yl)isoquinoline cyclometalating ligands and norbornene-substituted picolinate (PnIr1) and diimine (PnIr2-PnIr4) ancillary ligands. The quantum yields and phosphorescence lifetimes of the synthesized polymeric iridium probes in degassed water solutions were 1.5–2 times higher than in aerated solutions demonstrating oxygen-dependent quenching of phosphorescence. Of the four probes, PnIr1 easily penetrated into cultured cancer cells grown as monolayer and 3D spheroids and showed reliable response to hypoxia with increase of lifetime from 1.31 to 3.06 µs. Good water solubility, far-red oxygen-sensitive emission and low cytotoxicity make the new probe a promising tool for intracellular oxygen assessments in cancer research. [Display omitted]