Micellization Behaviour, DNA Binding, Antimicrobial, and Cytotoxicity Studies of Surfactant-Cobalt(III) Complexes Containing Di- and Tetramine Ligands

A new class of surfactant-cobalt(III) complexes, cis-[Co(en)(2)(C11H23NH2)Cl](ClO4)(2) (1), (en = ethylenediamine) and cis-[Co(trien)(C11H23NH2)Cl](ClO4)(2) (2) (trien = triethylenetetramine) have been synthesized and characterized by UV/Vis, IR, H-1 NMR, and C-13 NMR spectroscopic methods and elemental and metal analysis. The critical micelle concentration (CMC) values of these surfactant-cobalt(III) complexes in aqueous solution were obtained from conductance measurements. The specific conductivity data (at 298, 308, 318, and 328 K) served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (Delta G(m)(0), Delta H-m(0), and Delta S-m(0)). Absorption spectroscopy, emission spectroscopy, and viscosity measurements have been used to investigate the binding of these complexes with calf thymus DNA (CT-DNA). The intrinsic binding constants (K-b) of complexes 1 and 2 were determined as 1.70 x 10(4) M-1 and 2.91 x 10(4) M-1, respectively, which suggests that complex 2 binds more strongly to CT-DNA than complex 1. These complexes were screened for their antimicrobial and cytotoxic activities against certain human pathogenic microorganisms and cervical cancer cells. The complexes showed moderate antibacterial and antifungal activities against certain selected microorganisms. The cytotoxic property of the complexes was tested on human cervical cancer cells, SiHa, adopting the 3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and specific staining techniques. The complexes affected the viability of the cells significantly and the cell death was through apoptosis as seen in the changes in the nuclear morphology and cytoplasmic features.