Cytotoxicity, dual-targeting apoptosis induction evaluation of multinuclear cu complexes based on pyrazine-benzimidazole derivative

To investigate the cytotoxicity and mechanism of action of multinuclear Cu complexes against tumor cell lines, two complexes, Cu6(bpbib)4Br8 (1) and Cu2(bpbib)2(BF4)2Cl2 (2) (bpbib = 1,4-bis((2-(pyrazin-2-yl)-1H-benzo[d]imidazol-1-yl)methyl)benzene) were synthesized and characterized. Both Cu complexes showed high selectivity toward cancer and not normal cells, and the SMMC7721 cell line showed most sensitivity toward both complexes. Complex 1 exhibited more potent cytotoxicity and enhanced cellular uptake, and therefore, was comprehensively investigated. Complex 1 exhibited dual effects in the inhibition of tumor cell proliferation of SMMC7721 cells, causing nuclear DNA damage and mitochondrial dysfunction involving simultaneous reactive oxygen species (ROS) generation and Ca2+ increase. DNA binding studies suggest that intercalation might be the most probable binding mode. Fluorescence spectrometry also detected a medium affinity of complex 1 to bovine serum albumin (BSA) at distinct temperatures and resulted in BSA fluorescence static quenching. Both multinuclear Cu complexes showed high selectivity toward cancer and not normal cells. Complex 1 with potent cytotoxicity exhibited dual effects in inhibition of tumor cell proliferation of SMMC7721 cells, causing nuclear DNA damage and mitochondrial dysfunction involving simultaneous reactive oxygen species generation and Ca2+ increase. [Display omitted] •The antitumor and action mechanism of multinuclear Cu complexes are few reported.•Complex 1 showed dual inhibition effects, causing DNA and mitochondrial damage.•Complex 1 strongly binds to biomacromolecule, involving DNA and bovine serum albumin.