Cellular uptake, cytotoxicity, apoptosis, DNA-binding, photocleavage and molecular docking studies of ruthenium(II) polypyridyl complexes

Three new mononuclear [Ru (phen)2 ptip]2+ (1), [Ru (bpy)2 ptip]2+ (2) and [Ru (dmb)2 ptip]2+ (3) [ptip = (2-(5-phenylthiophen-2-yl)-1H-imidazo[4, 5-f][1,10 phenanthroline, phen = 1, 10 phenanthroline, bpy = 2, 2′ bipyridine, dmb = 4, 4′-dimethyl 2, 2′ bipyridine] complexes were synthesized and characterised by elemental analysis, IR, NMR and Mass spectra. The DNA-binding behaviours were investigated by electronic absorption titration, luminescence spectra, viscosity measurements and photo-activated cleavage. The DNA-binding constants Kb of complexes 1, 2 and 3 were determined to be 7.0 (±0.06) × 105, 3.87 (±0.04) × 105, 2.79 (±0.07) × 105 respectively. The results showed that these complexes interact with CT-DNA by intercalative mode. Cell viability experiments indicated that the Ru(II) complex showed significant dose-dependent cytotoxicity to HeLa tumour cell lines. Further flow cytometry experiments showed that the cytotoxic Ru(II) complex induced apoptosis of HeLa tumour cell lines. Our data demonstrated that the Ru(II) polypyridyl complex binds to DNA and thereby induces apoptosis in tumor cells, suggesting that anti-tumor activity of the Ru(II) complex could be related to its interaction with DNA. The molecular dynamic simulations and docking methods were used to predict the DNA binding affinity of ruthenium complexes and with good visualisation images supporting with experimental results.