Photoinduced cytotoxic activity of a rare ruthenium nitrosyl phenanthroline complex showing NO generation in human cells

Abstract

A new nitro-nitrosyl complex [RuNO(Phen)(NO₂)₂OH] (1) was synthesized and characterized by X-ray diffraction, where Phen = 1,10-phenanthroline. The complex was crystallized in two different modifications without (1) and with a solvent molecule of DMF (1a). The photolysis process together with the determination of the quantum yield of NO release was investigated in acetonitrile solution using a special flow-through system for the simultaneous registration of infrared (IR) and optical absorption (UV-vis) spectra under irradiation with 450 nm light. The quantum yield of photoinduced NO release was 4.0 ± 0.2%. DFT calculations showed that the main contribution to the absorption band at 450 nm is made by the HOMO/HOMO−1 → LUMO transitions, which are represented by the transfer of electron density from the –OH and –NO₂ ligands to the orbitals located on the Ru–NO bond. The dark and photoinduced cytotoxicity of the complex was studied against the human breast adenocarcinoma (MCF-7) and lung carcinoma (A549) cell lines and human non-tumor lung fibroblasts (MRC5). The complex shows a low cytotoxicity on MCF-7 cells (IC^dark₅₀ = 90.6 ± 6.2 μM and IC^irr.₅₀ = 95.3 ± 11.4 μM) and a moderate dark cytotoxicity on A549 and MRC5 cells (IC^dark₅₀ = 33.4 ± 2.6 μM and IC^dark₅₀ = 62.6 ± 3.1 μM, respectively), which slightly increases after irradiation (IC^irr.₅₀ = 21.2 ± 3.3 μM and IC^irr.₅₀ = 47.2 ± 2.3 μM, respectively).