Dinuclear Organoruthenium Complex for Mitochondria-Targeted Near-Infrared Imaging and Anticancer Therapy to Overcome Platinum Resistance

New mononuclear and dinuclear Ru(II) coordination compounds with the 2,7-bisbenzoimidazolyl-naphthyridine ligand have been synthesized and characterized by UV-vis, NMR, and MALDI-TOF. The molecular structures for Ru(II) compounds were determined by single-crystal X-ray diffraction. With the expansion of ligand π-conjugation and the increase in the complexed Ru number, the maximum emission wavelength red-shifted from 696 to 786 nm. The binding mode between complexes and DNA was predicted by molecular docking, which is intercalations and π-π stacking interactions with the surrounding bases. The intercalation mode of DNA binding was then determined by DNA titration and ethidium bromide (EB) displacement experiments. The antigrowth effects of complexes RuY, RuY1, and RuY2 were tested in HaCat (normal cells), HeLa (cervical cancer), A549 (lung cancer), and A549/DDP (cisplatin-resistant lung cancer) through the MTT assay. The dinuclear complex RuY2 was superior to mononuclear complexes and cisplatin in the cisplatin-resistant cell line. Confocal imaging proved that the subcellular localization of Ru(II) complexes was mitochondria; moreover, apoptosis was detected by flow cytometry. All three complexes showed a dose-dependent manner in all four cell lines. All Ru(II) complexes were found to have reactive oxygen species (ROS). The finding indicated that these Ru(II) complexes caused cell death by both DNA disruption and ROS. This study helps to explore the potential of the polynuclear Ru(II) complexes for the combination of NIR imaging and Pt-resistant cancer therapy.