Ph-Sensitive Near-Ir Emitting Dinuclear Ruthenium Complex For Recognition, Two-Photon Luminescent Imaging, And Subcellular Localization Of Cancer Cells

A dinuclear Ru(II) complex of [(bpy)(2)Ru(Hdip)Ru(H(2)bip)](ClO4)(4) {bpy is 2,2'-bipyridine, Hdip is 2-(2,6-di(pyridin-2-yl)-pyridin-4-yl)-1H-imidazo[4,5f]-[1,10]-phenanthroline, and H2bip is 2,6-bis(imidazole-2-yl)- pyridine} was synthesized and characterized by elemental analysis, mass spectrometry, and H-1 NMR spectroscopy. Spectrophotometric pH titrations in aqueous buffer and in vitro cell experiments indicated the response ability of the complex to pH fluctuations in the physiological pH range (6.0-8.0). The complex was found to be capable of differentiating live HeLa cells from healthy HEK293 cells by selectively accumulating in lysosomes of the HeLa cells. The low cytotoxicity (IC50 > 100 mu M), a large Stokes shift (similar to 200 nm), strong near-IR emission at similar to 700 nm, a relatively long excited state lifetime, high photostability, and solubility make this complex considerably promising in real-time tracking and visualization of lysosomes in live cells. More interestingly, the tumor cell-specific two-photon luminescent imaging properties also endow this Ru complex with potential for applications in high-resolution tumor imaging and luminescence-guided tumor resection.