DNA cleavage, DNA/HSA binding study, and antiproliferative activity of a phenolate-bridged binuclear copper(II)...

A novel phenolate-bridged binuclear copper(II) complex, [Cu ₂^II (L-3H)Cl] (1, where L = 2,6-bis[((2-hydroxybenzyl)(2-pyridylmethyl)amino)methyl]-4-methylphenol), have been synthesized and characterized. The antiproliferative activity of the complex has been tested in vitro against the human cervical cancer cell line HeLa, human non-small-cell lung cancer cell line A-549, the human breast cancer cell line MCF-7, and the human hepatic cell line LO2. The results show the complex has the low micromolar range (9.4-11.2 µM) of IC₅₀ values towards the three cancer cell lines, which is markedly comparable to those of cisplatin. However 1 exhibited 10.6-fold less toxicity than cisplatin toward normal cells LO2, suggesting that complex 1 had high selectivity between tumor cells and normal cells. The interactions with DNA were investigated by UV-Vis absorption, fluorescence, circular dichroism, and gel electrophoresis. The results show that the copper(II) complex could strongly bind to DNA mainly by the groove binding mode and efficiently cleave the pBR322 plasmid DNA into its nicked and linear forms in the presence of excessive ascorbic acid. In addition, the evaluation of the protein binding ability shows that complex 1 could bind to human serum albumin (HSA) with a moderate binding affinity and quench the intrinsic fluorescence of HSA.