Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Biocompatible Phosphorescent O2-sensors Based on Ir(III) Complexes for in vivo Hypoxia Imaging

Version 1 : Received: 10 May 2023 / Approved: 11 May 2023 / Online: 11 May 2023 (04:40:33 CEST)

A peer-reviewed article of this Preprint also exists.

Samandarsangari, M.; Kozina, D.O.; Sokolov, V.V.; Komarova, A.D.; Shirmanova, M.V.; Kritchenkov, I.S.; Tunik, S.P. Biocompatible Phosphorescent O2 Sensors Based on Ir(III) Complexes for In Vivo Hypoxia Imaging. Biosensors 2023, 13, 680. Samandarsangari, M.; Kozina, D.O.; Sokolov, V.V.; Komarova, A.D.; Shirmanova, M.V.; Kritchenkov, I.S.; Tunik, S.P. Biocompatible Phosphorescent O2 Sensors Based on Ir(III) Complexes for In Vivo Hypoxia Imaging. Biosensors 2023, 13, 680.

Abstract

In this work, we obtained three new phosphorescent iridium complexes (Ir1-Ir3) of general stoichiometry [Ir(N^C)2(N^N)]Cl decorated with oligo(ethylene glycol) fragments to make them water soluble and biocompatible, as well as to protect them from aggregation with biomolecules such as albumin. The major photophysical characteristics of these phosphorescent complexes are determined by the nature of two cyclometallating ligands (N^C) based on 2-pyridine-benzothiophene, since quantum chemical calculations revealed that the electronic transitions responsible for the excitation and emission are localized mainly at these fragments. However, the use of various diimine ligands (N^N) proved to affect the quantum yield of phosphorescence and allows for changing the complexes sensitivity to oxygen, due to the variations in the steric accessibility of the chromophore center for O2 molecules. It was also found that the N^N ligands made possible to tune the biocompatibility of the resulting compounds. The wavelengths of the Ir1-Ir3 emission maxima fall in the range of 630-650 nm, the quantum yields reach 17% (Ir1) in deaerated solution and sensitivity to molecular oxygen, estimated as ratio of emission lifetime in deaerated and aerated water solution, displays the highest value 8.2 for Ir1. The obtained complexes feature low toxicity, good water solubility and the absence of a significant effect of biological environment components on the parameters of their emission. Of the studied compounds Ir1 and Ir2 have been chosen for in vitro and in vivo biological experiments aimed at estimation of oxygen concentration in cell lines and tumors. These sensors have demonstrated their effectiveness for mapping the distribution of oxygen and for monitoring hypoxia in biological objects studied.

Keywords

oxygen sensing; iridium complexes; phosphorescence; hypoxia; bioimaging; phosphorescence lifetime imaging

Subject

Chemistry and Materials Science, Applied Chemistry

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