Synthesis, characterization and biological applications of a new nano-sized binuclear copper(II) complex containing bathophenanthroline and ellagic acid as ligands

Abstract

A new binuclear copper(II) complex, nano-[Cu2-(DIP)2-EA], was synthesized by using bathophenanthroline and ellagic acid ligands in a multi-component/one-pot method, and then characterized by electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectrophotometry (UV-vis), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FE-SEM). The antioxidant, antibacterial, and anticancer properties of the synthesized nano-[Cu2-(DIP)2-EA] were studied. The DPPH radical test pointed out that the nano-[Cu2-(DIP)2-EA] enjoys a good potential (28.4 %) to scavenge free radicals and the bacteria culture indicated a moderate ability of the complex to prevent the growth and proliferation of gram-positive bacteria (Staphylococcus aureus ATCC 29213) and gram-negative ones (Pseudomonas aeruginosa ATCC 27853). The cell culture displayed a superior ability of nano-[Cu2-(DIP)2-EA] to destroy breast cancer cells (MCF-7) compared to ellagic acid. In addition, the binding interaction of nano-[Cu2-(DIP)2-EA] with ct-DNA was studied in vitro (pH 7.40) by ultraviolet-visible absorption spectrophotometry, fluorescence emission spectrofluorimetry, circular dichroism (CD) spectropolarimetry, viscosity assessment technique, and molecular docking computer simulation. The results of the fluorescence enhancement spectra clearly showed a desirable affinity of nano-[Cu2-(DIP)2-EA] to ct-DNA. A hyperchromic effect was observed along with a slight red shift in the UV-visible spectra of nano-[Cu2-(DIP)2-EA]-DNA adduct, indicating that the nano-[Cu2-(DIP)2-EA] can form a conjugate with ct-DNA molecule. Thermodynamic properties exhibited an exothermic spontaneous formation of nano-[Cu2-(DIP)2-EA]-DNA adduct favored by H-bonds and van der Waals forces. The competitive emission investigations using methylene blue (MB) and Hoechst 33258 demonstrated that the binuclear copper(II) can replace the DNA-bound Hoechst and interact via minor grooves, as confirmed also by negligible viscosity alterations. The CD observations proposed that the nano-[Cu2-(DIP)2-EA] induces conformational changes in the ct-DNA. Molecular docking modeling results recognized a minor groove mechanism of nano-[Cu2-(DIP)2-EA] to interact with ct-DNA, and the complexation process is supported by H-bonds and van der Waals interactions.