Zhong-Ying Ma

Study on potential antitumor mechanism of a novel Schiff base copper(II) complex: synthesis, crystal structure, DNA binding, cytotoxicity and apoptosis induction activity.

A new cytotoxic copper(II) complex with Schiff base ligand [Cu(II)(5-Cl-pap)(OAc)(H(2)O)]·2H(2)O (1) (5-Cl-pap=N-2-pyridiylmethylidene-2-hydroxy-5-chloro-phenylamine), was synthesized and structurally characterized by X-ray diffraction. Single-crystal analysis revealed that the copper atom shows a 4+1 pyramidal coordination, a water oxygen appears in the apical position, and three of the basal positions are occupied by the NNO tridentate ligand and the fourth by an acetate oxygen. The interaction of Schiff base copper(II) complex 1 with DNA was investigated by UV-visible spectra, fluorescence spectra and agarose gel electrophoresis. The apparent binding constant (K(app)) value of 6.40×10(5) M(-1) for 1 with DNA suggests moderate intercalative binding mode. This copper(II) complex displayed efficient oxidative cleavage of supercoiled DNA, which might indicate that the underlying mechanism involve hydroxyl radical, singlet oxygen-like species, and hydrogen peroxide as reactive oxygen species. In addition, our present work showed the antitumor effect of 1 on cell cycle and apoptosis. Flow cytometric analysis revealed that HeLa cells were arrested in the S phase after treatment with 1. Fluorescence microscopic observation indicated that complex 1 can induce apoptosis of HeLa cells, whose process was mediated by intrinsic mitochondrial apoptotic pathway owing to the activation of caspase-9 and caspase-3.

Activities of a novel Schiff Base copper(II) complex on growth inhibition and apoptosis induction toward MCF-7 human breast cancer cells via mitochondrial pathway

In this study, we investigated the newly synthesized Schiff base copper(II) complex, [Cu(II)(5-Cl-pap)(OAc)(H(2)O)]·2H(2)O (1) (5-Cl-pap=N-2-pyridiylmethylidene-2-hydroxy-5-chloro-phenylamine), inducing growth inhibition and apoptosis in human breast cancer cell line MCF-7 and its potential antitumor mechanism. The results of cytotoxicity research, fluorescence microscopic observation and flow cytometric analysis revealed that complex 1 could significantly suppress MCF-7 cell viability and induce apoptosis. Comet assay indicated that severe DNA fragmentation in MCF-7 cells was induced after treatment with complex 1. Flow cytometric analysis showed that the antitumor effect of complex 1 on MCF-7 cells was associated with the cell cycle arrest. In addition, atomic absorption analyses displayed that complex 1 caused a rapid increase of intracellular copper uptake in MCF-7 cells in a time-dependent manner. The present work suggested that the antitumor mechanism of complex 1 on MCF-7 cells might be via the mitochondrial pathway, based on the up-regulated expression of Bax and activation of caspase-9 and caspase-3.

Thiosemicarbazone Cu(II) and Zn(II) complexes as potential anticancer agents: syntheses, crystal structure, DNA cleavage, cytotoxicity and apoptosis induction activity.

Four novel thiosemicarbazone metal complexes, [Cu(Am4M)(OAc)]·H2O (1), [Zn(HAm4M)Cl2] (2), [Zn2(Am4M)2Br2] (3) and [Zn2(Am4M)2(OAc)2]·2MeOH (4) [HAm4M=(Z)-2-(amino(pyridin-2-yl)methylene)-N-methylhydrazinecarbothioamide], have been synthesized and characterized by X-ray crystallography, elemental analysis, ESI-MS and IR. X-ray analysis revealed that complexes 1 and 2 are mononuclear, which possess residual coordination sites for Cu(II) ion in 1 and good leaving groups (Cl(-)) for Zn(II) ion in 2. Both 3 and 4 displayed dinuclear units, in which the metal atoms are doubly bridged by S atoms of two Am4M(-) ligands in 3 and by two acetate ions in bi- and mono-dentate forms, respectively, in 4. Their antiproliferative activities on human epithelial cervical cancer cell line (HeLa), human liver hepatocellular carcinoma cell line (HepG-2) and human gastric cancer cell line (SGC-7901) were screened. Inspiringly, IC50 value (11.2±0.9 μM) of complex 1 against HepG-2 cells was nearly 0.5 fold of that against human hepatic cell lines LO2, showing a lower toxicity to human liver cells. Additionally, it displayed a stronger inhibition on the viability of HepG-2 cells than cisplatin (IC50=25±3.1 μM), suggesting complex 1 might be a potential high efficient antitumor agent. Furthermore, fluorescence microscopic observation and flow cytometric analysis revealed that complex 1 could significantly suppress HepG-2 cell viability and induce apoptosis. Several indexes, such as DNA cleavage, reactive oxygen species (ROS) generation, comet assay and cell cycle analysis indicated that the antitumor mechanism of complex 1 on HepG-2 cells might be via ROS-triggered apoptosis pathway.

Four related mixed-ligand nickel(II) complexes: effect of steric encumbrance on the structure, DNA/BSA binding, DNA cleavage and cytotoxicity

Four closely related mononuclear nickel(II) complexes [Ni(L)(diimine)Cl](ClO4) (1–4), where L is a tridentate polypyridyl ligand of 4-methyl-N,N-bis(pyridin-2-ylmethyl)aniline and diimine is 2,2′-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), dipyrido[3,2-d:20,30-f]quinoxaline (dpq, 3) or dipyrido[3,2-a:20,30-c]phenazine (dppz, 4), have been synthesized and characterized using various physico-chemical techniques. All Ni centers adopt a distorted octahedral geometry with N5Cl donor sets. From 1 to 4, the dihedral angles between the benzene ring of L and the plane of the diimine gradually decline (52.5–6.8°), leading to increasing steric encumbrance. The interactions of the complexes with CT-DNA and BSA have been explored using absorption and emission spectral methods. These complexes display binding propensity to CT-DNA in the order: 4 (dppz) > 3 (dpq) > 2 (phen) > 1 (bpy), and the quenching mechanisms of BSA by all the complexes are static procedures. In the absence of any external agents, only 1 (bpy) and 4 (dppz) exhibit apparent DNA cleavage activity, while with the addition of GSH or on the irradiation with UV-A light of 365 nm, the DNA cleavage abilities of the complexes are obviously enhanced, which vary as 1 > 2 > 3 > 4 (GSH) and 4 > 3 > 2 > 1 (UV-A). In addition, the in vitro cytotoxicity of the complexes on tumor cells lines (MCF-7, HepG-2 and SGC-7901) have been examined by MTT and the morphological assessment obtained using Hoechst 33342 staining reveals that 4 induces apoptosis against HepG-2.

Synthesis, crystal structures, DNA binding, and cytotoxicity activities of two copper(II) complexes based on unsymmetrical tripodal ligands

[Cu(L1)Cl2]∙3H2O (1) and [Cu(L2)Cl]∙2H2O (2) based on new unsymmetrical tripodal ligands (L1 = {(N-methyl-imidazolylmethyl)[N-methyl-N-(N-methyl-imidazolylmethyl)imidazolylmethyl]amino}ethanesulfonic acid, L2 = [bis(2-pyridylmethyl)amino]ethanesulfonic acid) have been synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. In the discrete mononuclear structures of 1 and 2, copper is five-coordinate in a distorted trigonal bipyramidal structure. Interaction of the complexes with CT-DNA was investigated by UV–vis spectra, fluorescence spectra, and viscosity; the data reveal that 1 and 2 bind to CT-DNA by partial intercalation. Gel electrophoresis assays demonstrate that these two complexes display efficient oxidative cleavage of supercoiled DNA in the presence of H2O2, and MTT assays indicated that both 1 and 2 showed significant cytotoxicity toward human hepatoma cell HepG-2.

Two dpa-based zinc(II) complexes as potential anticancer agents: nuclease activity, cytotoxicity and apoptosis studies

Two new mononuclear zinc(II) complexes [ZnLX2]2·CH3OH (X = Br for 1, Cl for 2) of a tridentate polypyridyl ligand L (L = 4-methyl-N,N-bis(pyridin-2-ylmethyl)aniline) have been synthesized and structurally characterized. The interactions of two complexes with CT-DNA, pBR322 plasmid DNA and BSA have been explored respectively by using various physico-chemical techniques. Furthermore, the anticancer activities of the complexes towards three human tumor cells lines (HeLa, MCF-7 and RL952) have been studied. The IC50 values of 1 (on MCF-7 cells) and 2 (on RL952 cells) are 12.58 μM and 11.71 μM, respectively. The apoptosis-inducing activity of 1 was assessed by Hoechst 33342 staining, Annexin V binding and cell cycle analyses.

A thiosemicarbazone copper(II) complex as a potential anticancer agent

The preparation and the structure of a copper(II) complex, [Cu(4ML)Cl] (1) (H4ML = 2-acetylpyridine-4-methylthiosemicarbazone), are described. Complex 1 crystallizes in a monoclinic P21/c space group with a = 7.977(2) Å, b = 15.824(5) Å, c = 9.126(2) Å, α = γ = 90°, β = 91.974(2)°, V = 1151.26(5) Å3, Z = 4, F(0 0 0) = 620. According to X-ray crystallographic studies, each Cu(II) ion lies in a square planar coordination geometry based on the 4ML− and Cl− ligands. The complex displayed excellent inhibitory activity against various tumor cells (HeLa, HepG-2 and SGC-7901), offering lower IC50 value of 3.2 ± 0.7 μM than cisplatin (10 ± 2 μM) on HeLa cells at 48 h. Complex 1 could significantly suppress HeLa cell viability in a dose-dependent manner. Flow cytometric analysis showed that 1 induced HeLa cell apoptosis, which might be associated with cell cycle arrests at S and G2 phases. Consistent with results of DNA cleavage experiments, comet assay indicated that 1 caused severe DNA fragmentation. The production of ROS was elevated with increasing concentration of 1, suggesting that 1 was capable of promoting HeLa cell apoptosis through an oxidative DNA damage pathway. Thiosemicarbazone Cu(II) complex exhibited great growth inhibition and induction of apoptosis in HeLa cells via oxidative DNA damage pathway which can act as a potential anticancer agent.

Highly selective and sensitive turn-on fluorescent sensor for detection of Al3+ based on quinoline-base Schiff base

A new aluminum ion fluorescent probe (4-(diethylamino)-2-hydroxybenzylidene)isoquinoline-1-carbohydrazide (HL1) has been conveniently synthesized and characterized. HL1 exhibited a highly selective and pronounced enhancement for Al3+ in the fluorescence emission over other common cations by forming a 2:1 complex, with a recognition mechanism based on excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT). The strong fluorescent emission can be observed even at ppm level concentration of the probe in the presence of Al3+ with 41 fold intensity enhancement at 545 nm. HL1 displays good linear relationship with Al3+ in the low concentration and the limit of detection is 8.08 × 10-8 mol/L. Similar molecules with different substituents on salicylaldehyde phenyl ring were synthesized for studying the structure-activity relationship. Density-functional theory (DFT) calculations are in agreement with the proposed mechanism. It is confirmed that HL1 could be used to detect Al3+ ions in real sample by fluorescence spectrometry and Al3+ ions in cells by bioimaging.

Chlorambucil-conjugated platinum(IV) prodrugs to treat triple-negative breast cancer in vitro and in vivo

Modification of platinum (II) into lipophilic platinum (IV) compounds by introducing biologically active molecules were widely employed to develop new platinum-based prodrugs in the past decade. In this paper, two chlorambucil platinum (IV) complexes, CLB-Pt and CLB-Pt-CLB, were synthesized and displayed very potent antiproliferative activity against all the tested cancer cell lines, such as A549, HeLa and MCF-7, especially to treat the well-known refractory triple-negative breast cancer. CLB-Pt-CLB significantly improved cell-killing effect in triple-negative subtype MDA-MB-231 cells, and showed much stronger cytotoxicity than either monotherapy or combination of cisplatin and chlorambucil. CLB-Pt-CLB prodrug entered cells in dramatically increased amount compared with cisplatin and enhanced DNA damage, inducing cancer cell apoptosis. It exhibited high anticancer activity and no observable toxicity in BALB/c nude mice bearing MDA-MB-231 tumors. The chlorambucil moiety not only greatly assisted the passive diffusion of CLB-Pt-CLB into cells, but also produced the synergism with cisplatin in targeting DNA.

Synthesis, Structure, and Photoluminescent Property of a Novel 2D Silver(I) Polymer Based on Short Ag-Ag Interactions

A new two-dimensional (2D) polymer, [Ag(2-Clnic)]n (2-Clnic = 2-chloronicotinate) (1), has been synthesized and characterized by IR, elemental analysis, single-crystal X-ray diffraction, and luminescence spectroscopy. X-ray crystal analysis reveals that complex 1 is constructed through π-π stacking and Ag…O interactions, which provide important roles in the assembly of intriguing structures and specific photophysical properties. In the solid state at room temperature, 1 is found to be luminescent with a purple emission band at 411 nm upon excitation at 360 nm.