Novel binuclear and trinuclear metal (II) complexes: DNA interactions and in vitro anticancer activity through apoptosis.

A water soluble trinuclear copper(II) complex and a binuclear cobalt(II) complex, namely Cu3(ppbm)2(SO4)3 (1) and Co2(ppbm)2(NO3)4 (2) (ppbm = 2-(pyridin-2-yl)-1-(pyridin-3-ylmethyl)- 1H-benzo[d]imidazole), have been successfully synthesized and characterized by elemental analysis, IR Spectroscopy, electrospray ionization mass spectra (ESI-MS). The interaction of the new complexes with DNA has been explored using spectroscopy methods, indicating that the complexes 1 and 2 bind to DNA via noncovalent interactions. DNA cleavage experiment suggested that the complex 1 exhibits efficient DNA cleavage activities in the presence of ascorbate (Asc), hydrogen peroxide may serve as the major cleavage active species. The cytotoxicity assay showed that complex 1 exhibited significant inhibitory activity toward the proliferation of several tumor cell lines, with a lower IC50 value than cisplatin and complex 2, indicating that it had the potential to act as effective anticancer agent. The morphological staining assays showed that 1 apparently induced the TFK-1 cells apoptosis. Besides, cellular uptake experiment on TFK-1 cells revealed that complex 1 accumulates primarily inside the nucleus. The apoptosis was attributable to the metal-assisted generation of reactive oxygen species (ROS).