Anticancer evaluation of a manganese complex on HeLa and MCF-7 cancer cells: design, deterministic solvothermal synthesis approach, Hirshfeld analysis, DNA binding, intracellular reactive oxygen species production, electrochemical characterization and density functional theory

Herein, a deterministic solvothermal strategy was employed to synthesize an efficient anticancer agent 'cis-dichlorobis(1,10-phenanthroline)manganese(II)' (Mn(phen)(2)Cl-2). A single-crystal X-ray diffraction analysis revealed that Mn(phen)(2)Cl-2 crystallizes in a triclinic system with the space group P-1. Cyclic voltammetric studies of Mn(phen)(2)Cl-2 indicated that the electrode process occurs only due to complex formation and has a diffusion-controlled mechanism. Density functional theory estimations showed that the Mn(phen)(2)Cl-2 is quite stable and exists in sextet spin state (five unpaired electrons) as the most stable form and hence, Mn(phen)(2)Cl-2 is a high spin complex. Mn(phen)(2)Cl-2 demonstrated significant anticancer potential against HeLa and MCF-7 cancer cells and less toxic behaviour towards normal BHK-21 cells. Fluorescence imaging confirmed that the production of reactive oxygen species (ROS) in HeLa cells by Mn(phen)(2)Cl-2 induces oxidized fluorescence of dichlorofluorescein which emitted fluorescence at 530 nm after excitation at 488 nm. The microscopic investigation of apoptotic effect of Mn(phen)(2)Cl-2 using propidium iodide and 4 ',6-diamidino-2-phenylindole staining indicated that nuclear condensation, cell detachment and shrinkage occur after treatment with IC50 values of Mn(phen)(2)Cl-2. Furthermore, an assessment of caspase-9 and caspase-3 activity after exposure to Mn(phen)(2)Cl-2 in HeLa cells indicated that at IC50 values of Mn(phen)(2)Cl-2, 1.5 fold and 4.8 fold increase in caspase-9 and caspase-3 activity, respectively, occurs. The measurement of mitochondrial membrane potential of a cationic dye (JC-1) showed a decrease in mitochondrial membrane potential in both HeLa and MCF-7 cells depicting that compound might have adopted intrinsic pathway of apoptosis. Ability of Mn(phen)(2)Cl-2 to interact with HS-DNA demonstrates hyperchromicity with slight blue shift from 269 nm to 265 nm showing a non-covalent interaction with Gibbs free energy of Delta G = -14.62 kJ/mol. Communicated by Ramaswamy H. Sarma

Automated summary

A deterministic solvothermal strategy was employed to synthesize an efficient anticancer agent Mn(phen)(2)Cl-2, which showed significant anticancer potential against specific cancer cells and low toxicity towards normal cells. Various experiments confirmed its anticancer mechanisms, including inducing oxidative stress and apoptosis in cancer cells.