Nucleic acid binding study of surfactant copper(ii) complex containing dipyrido[3,2-a:2′-3′-c]phenazine ligand as an intercalator: in vitro antitumor activity of complex in human liver carcinoma (HepG2) cancer cells

Abstract

A new surfactant copper(II) complex, [Cu(dppz)₂DA](ClO₄)₂, where dppz = dipyrido[3,2-a:2′-3′-c]phenazine and DA-dodecylamine, has been synthesized and characterized by physico-chemical and spectroscopic methods. The critical micelle concentration (CMC) value of this surfactant copper(II) complex in aqueous solution was determined from conductance measurements. Specific conductivity data at different temperatures was obtained for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔG⁰_m, ΔH⁰_m and ΔS⁰_m). The binding interaction of this complex with nucleic acids (calf thymus DNA and yeast t-RNA) was investigated using electronic absorption, fluorescence spectroscopy, viscometry, cyclic voltammetry (CV) and thermal denaturation studies. In the presence of the nucleic acids, the UV-Vis spectrum of our complex exhibited a redshift of the absorption band at 268 nm along with significant hypochromicity, indicating intercalation of our complex with the nucleic acids. The intrinsic binding constant values are K_b = 1.1 × 10⁶ M⁻¹ for DNA and 1.6 × 10⁶ M⁻¹ for RNA. The viscosity measurements confirmed that the complex–nucleic acid interaction occurs through intercalation. A competitive binding study with ethidium bromide (EB) showed that the complex exhibits the ability to displace the nucleic acid-bound EB, indicating that the complex binds to nucleic acids in strong competition with EB for the intercalative binding site. CV results also confirmed this mode of binding. Some significant thermodynamic parameters of the binding of the titled complex to DNA were also determined. The antimicrobial and antifungal screening tests of this complex have shown good results. The copper(II) complex exhibited pronounced activity against a human liver carcinoma (HepG2) cancer cell line.