Imaging of the nuclei of living tumor cells by novel ruthenium(II) complexes coordinated with 6-chloro-5-hydroxylpyrido[3,2-a]phenazine

Two novel ruthenium(II) complexes coordinated with 6-chloro-5-hydroxylpyrido[3,2-a]phenazine (CQM), [Ru(L)2(CQM)]ClO4 [L = 1,10-phenanthroline, (1) and 2,2′-bipyridine, (2)], were investigated as potential fluorescent probes to track dynamic changes in the nuclei of living cells. Confocal laser technology was used to observe their co-location inside the cells. The results showed that both complexes were taken up by HepG2 cells, especially 1, which was localized in the cell nuclei, whereas 2 was distributed in the cell nuclei and mitochondria. Further studies by real-time fluorescence observations revealed that 1 rapidly entered the living cells, namely, HepG2, HeLa and MCF-7 cells, imaged the dynamic changes of the nuclei of living tumor cells, and exhibited low toxicity toward cells. The results demonstrated that 1 may be developed into a novel fluorescent probe for living cell nuclei. This study facilitates the development of fluorescent chemosensors with metal complexes.