In vitro testing of new Ir(III) complexes as phosphorescent sensors of molecular oxygen for cancer studies
Anastasia KOMAROVA (Privolzhskiy Research Medical University; Lobachevsky State University of Nizhny Novgorod);
Maria LUKINA (Privolzhskiy Research Medical University);
Varvara DUDENKOVA (Privolzhskiy Research Medical University);
Leonid BOCHKAREV (G.A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences);
Ilya KRITCHENKOV (Saint Petersburg State University);
Sergey TUNIK (Saint Petersburg State University);
Marina SHIRMANOVA (Privolzhskiy Research Medical University)
Abstract
Analysis of the molecular oxygen content in tissues and cells is of great interest for oncology. Hypoxia is one of the main factors underlying metabolic changes in tumor cells, their aggressive behavior and resistance to therapies. Phosphorescence lifetime imaging (PLIM) is a powerful method to determine oxygen concentration in biological tissues based on measuring the phosphorescence lifetime of oxygen-sensitive dyes. The phosphorescence lifetime decreases with increasing oxygen concentration. Currently, an urgent task is to develop phosphorescent sensors that have a high degree of oxygen-dependent phosphorescence quenching, can effectively accumulate in target cells or tissues and do not have severe toxicity.
The purpose of our study is to investigate the possibility of using new iridium (III) complexes as phosphorescent sensors of molecular oxygen in cancer cells.
Several water-soluble polymers with Ir(III) were tested as phosphorescent oxygen sensors: RP7, RP8, RP9 (IOC RAS) and IR-1 (SPbSU). The phosphorescence of sensors in solutions in the presence of oxygen and in vacuum was evaluated using a two-channel FLIM/PLIM confocal macroscanner (Becker&Hickl, Germany). In vitro studies were performed on CT26 tumor cells (mouse colorectal cancer). The cytotoxicity of iridium complexes was determined by the MTT assay. The ability of sensors to penetrate cells in vitro was studied using a laser scanning microscope LSM 880 (Carl Zeiss, Germany).
It was found that the RP7, RP8, RP9 and IR-1 complexes have a high degree of oxygen-dependent phosphorescence quenching. For example, for the RP7 the phosphorescence lifetime in the presence of 21% oxygen was 1.243 µs, in vacuum – 2.410 µs, for the IR-1 it was 1.03 µs and 4.3 µs, correspondingly. RP7, RP8, and RP9 did not penetrate into the cells up to 6 hours of incubation, whereas IR-1 accumulated in the cell cytoplasm after 1 hour. None of the dyes showed cytotoxic effects at the concentrations used in cellular experiments.
We conclude that the RP7 and IR-1 complexes have a great potential for using as oxygen sensors in biological applications.
This work was supported by the Russian Science Foundation, project 18-73-10021 (IR-1) and the Russian Foundation for Basic Research, project 20-03-00102 A (RP7, RP8, and RP9).
Speaker
Anastasia Komarova
Privolzhskiy Research Medical University; Lobachevsky State University of Nizhny Novgorod
Russia
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