DNA binding properties and cytotoxic effects of two double rollover cycloplatinated (II) complexes on cancer cell lines

Abstract

In this study, the DNA binding capacity and cytotoxic effects of two double rollovers cycloplatinated complexes, [Pt2(μ-bpy-2H)(CF3COO)2(PPh3)2] and [Pt2(μ-bpy-2H)(I)2(PPh3)2] denoted as C1 and C2, respectively, were evaluated. By using UV–Visible spectroscopy the intrinsic binding constant (Kb) of C1 and C2 to DNA were determined as 2.9 × 105 M−1, and 5.4 × 105 M−1, respectively. Both the compounds were able to quench the fluorescence of ethidium bromide as a well known DNA intercalator. The calculated Stern-Volmer quenching constants (Ksv) for C1 and C2 were 3.5 × 103 M−1, and 1.2 × 104 M−1, respectively. Upon interaction of both the compounds with DNA, increase in viscosity of DNA solution were observed, further confiming the involvement of intercalative interactions between the complexes and DNA. The cytotoxic effects of complexes in compare to cisplatin were evaluated on different cancer cell lines by MTT assay. Interestingly, C2 showed the highest cytotoxicity on A2780R, a cisplatin resistant-cell line. Induction of apoptosis by the complexes was proved by flowcytometry. In all the studied cell lines, the extent of apoptosis induced by C2 was comparable or higher than cisplatin. Cisplatin induced more necrosis in all the cancer cell lines in the tested concentration.