Protein binding and biological evaluation of a polymer-anchored cobalt(iii) complex containing a 2,2′-bipyridine ligand

Abstract

The molecular interaction of polymer-anchored cobalt(III) complex, cis-[Co(bpy)2(BPEI)Cl]Cl2·4H2O (bpy = 2,2′-bipyridine, BPEI = branched polyethyleneimine) with two plasma proteins, human serum albumin (HSA) and bovine serum albumin (BSA) using various spectrophotomeric techniques has been investigated. The steady-state and time-resolved fluorescence spectra clearly demonstrated the static quenching mechanism. The calculated thermodynamic parameters revealed that the interaction between the polymer–cobalt(III) complex and HSA/BSA was driven mainly by van der Waals forces and hydrogen bonds. The results observed from three dimensional fluorescence and circular dichorism (CD) spectral studies manifested the conformational changes of HSA/BSA upon addition of the polymer–cobalt(III) complex. Furthermore, the antimicrobial result showed that the polymer–cobalt(III) complex exhibits good antibacterial and antifungal activities against certain human pathogenic microorganisms. In addition, the antiproliferative properties of the polymer–cobalt(III) complex on the HEp-2 human larynx cancer cells were determined using the MTT assay. The mode of cell death induced by the complex following treatment was analyzed adopting specific staining techniques. MTT assay revealed that the viability of the cells thus treated was significantly decreased and the cells succumbed to apoptosis as well as necrosis as reflected in changes in the nuclear morphology and cytoplasmic features by AO & EB and Hoechst staining methods.