Photophysical, Cellular-Uptake, and Bioimaging Studies of Luminescent Ruthenium(II)–Polypyridine Complexes Containing a D-Fructose Pendant

Two luminescent ruthenium(II)–polypyridine complexes, appended with a d-fructose unit, [Ru(N^{^}N)₂(bpy-fructose)](PF₆)₂ [bpy-fructose = 4-(1-deoxy-d-fructos-1-yl)aminocarbonyl-4′-methyl-2,2′-bipyridine; N^{^}N = 4,7-diphenyl-1,10-phenanthroline (Ph₂-phen) (1a) and 2,2′-bipyridine (bpy) (2a)] and their d-fructose-free counterparts [Ru(N^{^}N)₂(bpy-Et)](PF₆)₂ [bpy-Et = 4-(ethylaminocarbonyl)-4′-methyl-2,2′-bipyridine; N^{^}N = Ph₂-phen (1b) and bpy (2b)] are synthesized and characterized. The photophysical properties, lipophilicity, cytotoxicity, and cellular uptake of the complexes are studied. Laser-scanning confocal microscopy reveals that both complexes 1a and 1b display intense membrane staining toward human breast adenocarcinoma (MCF-7) cells. However, while complex 1a retains its membrane-staining characteristic when incubated with human cervical epithelioid carcinoma (HeLa) cells, complex 1b is localized in the mitochondria. Additionally, fructose-dependent cellular-uptake experiments suggest that complex 1a is transported into MCF-7 cells through a glucose transporter (GLUT) mediated pathway.