Mixed Ligand Mononuclear Copper(II) Complex as a Promising Anticancer Agent: Interaction Studies with DNA/HSA, Molecular Docking, and In Vitro Cytotoxicity Studies.

The isolated copper(II) complex [CuL(-phen)]·HO () [HL = -HO-CHC(H)=N-CH-SH-, -phen = 1,10-phenanthroline] was structurally characterized using single-crystal X-ray crystallography. in CHCN at liquid nitrogen temperature displayed a characteristic monomeric X-band electron paramagnetic resonance spectrum having a tetragonal character with = 2.1479 and = 2.0691 and ≈ 18.0 mT and ≤ 3.9 mT, respectively. showed a strong binding affinity toward calf thymus DNA as reflected from its intrinsic binding constant ( = 7.88 × 10 M), and its competitive displacement of ethidium bromide suggested an intercalative DNA-binding mode ( = 1.32 × 10 M). This was confirmed from the viscosity study that showed an increase in the viscosity of DNA with an increasing concentration of . Complex is highly efficient in promoting oxidative and hydrolytic DNA cleavage ( = 1.987 h). showed a strong binding affinity with the carrier protein human serum albumin (HSA) ( = 5.22 × 10 M). A high bimolecular quenching constant = 2.29 × 10 Ms indicated a static quenching mechanism involved in the fluorescence quenching of HSA by . Fluorescence resonance energy transfer theory suggested that the distance ( = 3.52 nm) between and HSA is very close. Molecular docking studies suggested that primarily binds to HSA in subdomain IIA. A protein-ligand interaction profiler was used to visualize hydrophobic, hydrogen bonds, and π-cation interactions between HSA and . A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay using HeLa and MDA-MB-231 cells showed a significant in vitro anticancer activity of (IC 2.63 and 2.68 μM, respectively). Nuclear staining assays suggested apoptotic cell death in HeLa cells treated with . The effect of on the cytoskeletal actin filaments visualized using phalloidin staining showed extensive destruction of actin filaments. Flow cytometric analysis indicated that inhibits the growth of HeLa cells through cell cycle arrest in the S phase. Western blot analysis showed upregulation in the expression of apoptotic marker proteins caspase 3, p53, and Bax. These results collectively indicate that induces apoptosis by promoting DNA damage and has a high potential to act as an anticancer agent.