Synthesis, Characterisation, Interaction with DNA, Cytotoxicity, and Apoptotic Studies of Ruthenium(ii) Polypyridyl Complexes

We report the synthesis and characterisation of two new ruthenium(ii) polypyridyl complexes containing monodentate ancillary ligands [Ru(L)(4)(4HEPIP)], where L = 4-aminopyridine (1) or pyridine (2) and 4HEPIP = 2-(4-hydroxy-3-ethoxyphenyl)-1H-imidazo[4,5-f][1,10](phenanthroline). These complexes were characterised by elemental analysis and ultraviolet-visible, infrared, and H-1 NMR spectroscopy. The binding properties of the two complexes towards calf thymus (CT)-DNA were investigated with different spectrophotometric methods, viscosity measurements, and salt dependent studies. Experimental results indicated that the complexes interact with CT-DNA base pairs by intercalation. Upon irradiation at 365 nm, these complexes efficiently cleave pBR322 DNA from super coiled form I to nicked form II. Their cytotoxicity on different cancer cell lines such as A549, Du145, and HeLa was investigated. The IC50 values are 39.5, 28.3, and 27.3 mu M for complex 1, and 55, 67.9, and 47.9 mu M for complex 2 respectively. Cellular uptake and apoptosis induced by these complexes was also studied.