Anomalous behavior of pentacoordinate copper complexes of dimethylphenanthroline and derivatives of terpyridine ligands: Studies on DNA binding, cleavage and apoptotic activity

A novel copper(II) complex with a salicylidene carbohydrazide ligand that promotes oxidative stress and apoptosis in triple negative breast cancer cells

We report the synthesis, characterization, anti-cancer activity and mechanism of action of a novel water-soluble Cu(II) complex with salicylidene carbohydrazide as the ligand and o-phenanthroline as the co-ligand. The synthesized complex (1) was characterized by FT-IR, EPR, and electronic spectroscopy, as well as single crystal X-ray diffraction. This compound was found to be paramagnetic from EPR spectra and X-ray crystallography revealed that the molecule crystallized in an orthorhombic crystal system. The crystal lattice was asymmetric containing two distinct binuclear copper complexes containing the Schiff base as the major ligand, o-phenanthroline as a co-ligand, two nitrate anions, and two water molecules. The Cu(II) in the first site coordinated with the enolised ligand comprising enolate O-, phenolate O-, and the imine N and N,N from o-phen. The major part of this complex exists as Cu(II) coordinated with two H2O molecules at the second site with nitrate acting as the counter anion. However, a smaller portion of the complex exists where Cu(II) is coordinated with NO3- and H2O, and the remaining water molecule acts as lattice water. It was tested for DNA binding and cleavage properties which revealed that it binds in an intercalative mode to CT-DNA with Kb value of 1.25 × 104 M-1. Furthermore, cleavage studies reveal that the complex has potential for efficient DNA cleavage under both oxidative and hydrolytic conditions. It was able to enhance the rate of cleavage by 2.8 × 108 times. The complex shows good cytotoxicity to breast cancer monolayer (2D) as well as spheroid (3D) systems. The IC50 values for MDA-MB-231 and MCF-7 monolayer culture was calculated as 1.86 ± 0.17 μM and 2.22 ± 0.08 μM, respectively, and in (3D) spheroids of MDA-MB-231 cells, the IC50 value was calculated to be 1.51 ± 0.29 μM. It was observed that the complex outperformed cisplatin in both breast cancer cell lines. The cells treated with complex 1 underwent severe DNA damage, increased oxidative stress and cell cycle arrest which finally led to programmed cell death or apoptosis in triple negative breast cancer cells through an intrinsic pathway.

Synthesis, Characterization, DNA/HSA Interaction, and Cytotoxic Activity of a Copper(II) Thiolate Schiff Base Complex and Its Corresponding Water-Soluble Stable Sulfinato-O Complex Containing Imidazole as a Co-ligand

A Cu(II) thiolato complex [CuL(imz)] (1) (H₂L = o-HOC₆H₄C(H)=NC₆H₄SH-o) and the corresponding water-soluble stable sulfinato-O complex [CuL'(imz)] (2) (H₂L' = o-HOC₆H₄C(H)=NC₆H₄S(=O)OH) were synthesized and characterized using physicochemical techniques. Compound 2 is found to be a dimer in the solid state as characterized using single-crystal X-ray crystallography. XPS studies clearly showed the differences in the sulfur oxidation states in 1 and 2. Both compounds are found to be monomers in solution as revealed from their four-line X-band electron paramagnetic resonance spectra in CH₃CN at room temperature (RT). 1-2 were tested to assess their ability to exhibit DNA binding and cleavage activity. Spectroscopic studies and viscosity experiments suggest that 1-2 bind to CT-DNA through the intercalation mode having moderate binding affinity (K_b ∼ 10⁴ M^-1). This is further supported by molecular docking studies of complex 2 with CT-DNA. Both complexes display significant oxidative cleavage of pUC19 DNA. Complex 2 also showed hydrolytic DNA cleavage. The interaction of 1-2 with HSA revealed that they have strong ability to quench the intrinsic fluorescence of HSA by a static quenching mechanism (k_q ∼ 10¹³ M^-1 s^-1). This is further complemented by Förster resonance energy transfer studies that revealed binding distances of r = 2.85 and 2.75 nm for 1 and 2, respectively, indicating high potential for energy transfer from HSA to complex. 1-2 were capable of inducing conformational changes of HSA at secondary and tertiary levels as observed from synchronous and three-dimensional fluorescence spectroscopy. Molecular docking studies with 2 indicate that it forms strong hydrogen bonds with Gln221 and Arg222 located near the entrance of site-I of HSA. 1-2 showed potential toxicity in human cervical cancer HeLa cells, lung cancer A549 cells, and cisplatin-resistant breast cancer MDA-MB-231 cells and appeared to be most potent against HeLa cells (IC₅₀ = 2.04 μM for 1 and 1.86 μM for 2). In HeLa cells, 1-2 mediated cell cycle arrest in S and G2/M phases, which progressed into apoptosis. Apoptotic features seen from Hoechst and AO/PI staining, damaged cytoskeleton actin viewed from phalloidin staining, and increased caspase-3 activity upon treatment with 1-2 collectively suggested that they induced apoptosis in HeLa cells via caspase activation. This is further supported by western blot analysis of the protein sample extracted from HeLa cells treated with 2.

Yb/Chitosan Catalyzed Synthesis of Highly Substituted Piperidine Derivatives for Potential Nuclease Activity and DNA Binding Study

BACKGROUND

Herein, a new chitosan-supported ytterbium nano-catalyst has been prepared and used in a mild, efficient, and expeditious method for the synthesis of substituted piperidine derivatives via threecomponent condensation of substituted anilines, formaldehyde and different cyclic/acyclic active methylene compounds at room temperature.

METHODS

The catalyst was characterized by FTIR, XRD, SEM, EDX, TEM, ICP-AES and the stability of the catalyst was evaluated by TG analysis. The synthesized compound 3,3,11,11-Tetramethyl-15-(phenyl)-15- azadispiro[5.1.5.3]hexadecane-1,5,9,13-tetrone (3a) was explored for pBR322 DNA cleavage activity and genotoxicity. Further, the interaction of 3a with CT-DNA was investigated through UV-vis, fluorescence and viscosity.

RESULTS

The preparation of Yb/chitosan nano-catalyst was verified and the catalyst was found effective towards substituted piperidine formations with the catalyst reusability. Compound 3a was successfully tested for DNA cleavage activity. In addition, fluorescence results revealed that compound 3a interacted with DNA with a binding affinity of 4.84 x 10⁴ M^-1.

CONCLUSION

Our findings suggest that compounds bearing spiro-piperidine scaffold, synthesized using reusable nano-catalyst, could be effective biological agents.

Hexaferrocenium tri[hexa(isothiocyanato)iron(III)] trihydroxonium complex as a new DNA intercalator for electrochemical DNA biosensor

Ferrocene or ferrocenium has been widely studied in the field of organometallic complexes because of its stable thermodynamic, kinetic and redox properties. Novel hexaferrocenium tri[hexa(isothiocyanato)iron(III)]trihydroxonium (HexaFc) complex was the product from the reaction of ferrocene, maleic acid and ammonium thiocyanate and was confirmed by elemental analysis CHNS, FTIR and single crystal X-ray crystallography. In this study, HexaFc was used for the first time as an electroactive indicator for porcine DNA biosensor. The UV-Vis DNA titrations with this compound showed hypochromism and redshift at 250 nm with increasing DNA concentrations. The binding constant (Kb) for HexaFc complex towards CT-DNA (calf-thymus DNA) was 3.1 × 104 M-1, indicated intercalator behaviour of the complex. To test the usefulness of this complex for DNA biosensor application, a porcine DNA biosensor was constructed. The recognition probes were covalently immobilised onto silica nanospheres (SiNSs) via glutaraldehyde linker on a screen-printed electrode (SPE). After intercalation with the HexaFc complex, the response of the biosensor to the complementary porcine DNA was measured using differential pulse voltammetry. The DNA biosensor demonstrated a linear response range to the complementary porcine DNA from 1 × 10-6 to 1 × 10-3 µM (R2 = 0.9642) with a limit detection of 4.83 × 10-8 µM and the response was stable up to 23 days of storage at 4 °C with 86% of its initial response. The results indicated that HexaFc complex is a feasible indicator for the DNA hybridisation without the use of a chemical label for the detection of porcine DNA.

Synthesis, Structural, and Cytotoxic Properties of New Water-Soluble Copper(II) Complexes based on 2,9-Dimethyl-1,10-Phenanthroline and Their One Derivative Containing 1,3,5-Triaza-7-Phosphaadamantane-7-Oxide

A series of water-soluble copper(II) complexes based on 2,9-dimethyl-1,10-phenanthroline (dmphen) and mixed-ligands, containing PTA=O (1,3,5-triaza-7-phosphaadamantane-7-oxide) have been synthesized and fully characterized. Two types of complexes have been obtained, monocationic [Cu(NO₃)(O-PTA=O)(dmphen)][PF₆] (1), [Cu(Cl)(dmphen)₂][PF₆] (2), and neutral [Cu(NO₃)₂(dmphen)] (3). The solid-state structures of all complexes have been determined by single-crystal X-ray diffraction. Magnetic studies for the complex 1–3 indicated a very weak antiferromagnetic interaction between copper(II) ions in crystal lattice. Complexes were successfully evaluated for their cytotoxic activities on the normal human dermal fibroblast (NHDF) cell line and the antitumor activity using the human lung carcinoma (A549), epithelioid cervix carcinoma (HeLa), colon (LoVo), and breast adenocarcinoma (MCF-7) cell lines. Complexes 1 and 3 revealed lower toxicity to NHDF than A549 and HeLa cells, meanwhile compound 2 appeared to be more toxic to NHDF cell line in comparison to all cancer lines. Additionally, interactions between the complexes and human apo-transferrin (apo-Tf) using fluorescence and circular dichroism (CD) spectroscopy were also investigated. All compounds interacted with apo-transferrin, causing same changes of the protein conformation. Electrostatic interactions dominate in the 1/2 – apo- Tf systems and hydrophobic and ionic interactions in the case of 3.

Comparative studies of Schiff base-copper(ii) and zinc(ii) complexes regarding their DNA binding ability and cytotoxicity against sarcoma cells

Schiff base-copper(ii) and zinc(ii) complexes were prepared and characterized, and their binding ability to DNA and cytotoxicity against healthy and carcinogenic cells were studied.

Some new nano-sized Cr(III), Fe(II), Co(II), and Ni(II) complexes incorporating 2-((E)-(pyridine-2-ylimino)methyl)napthalen-1-ol ligand: Structural characterization, electrochemical, antioxidant, antimicrobial, antiviral assessment and DNA interaction

To estimate the biological preference of synthetic small drugs towards DNA target, new metal based chemotherapeutic agents of nano-sized Cr(III), Fe(II), Co(II) and Ni(II) Schiff base complexes having N,N,O donor system were synthesized and thoroughly characterized by physic-chemical techniques. The redox behavior of the Cr(III), Fe(II) and Co(II) complex was investigated by electrochemical method using cyclic voltammetry. IR results proven that the tridentate binding of Schiff base ligand with metal center during complexation reflects the proposed structure. Magnetic and spectroscopic data give support to octahedral geometry for Cr(III) and Fe(II) complexes and tetrahedral geometry for Ni(II) and Co(II) complexes. The activation thermodynamic parameters, such as, E(⁎), ΔH(⁎), ΔS(⁎) and ΔG(⁎) are calculated using Coats-Redfern method by analyzing the TGA data. The particle size of the investigated metal complexes was estimated by TEM. In addition to, the interaction of the nanosized complexes with CT-DNA was estimated by electronic absorption, viscosity and gel electrophoresis. These techniques revealed that the complexes could bind to CT-DNA through intercalation mode. Moreover, the in vitro cytotoxic and antiviral activities of the nanosized complexes were checked against Herpes Simplex virus and Tobacco Mosaic viruses. Moreover, investigation of antioxidant activities of the new nanosized compounds was done by ABTS assay. Among the compounds tested, Fe(II) complex showed the strongest potent radical scavenging activity with percent of 58.60%. Furthermore, the antimicrobial bustle of the prepared compounds was screened against different types of bacteria and fungi and the results show that all metal complexes have superior activity than its free ligand.

Characterization of antiproliferative potential and biological targets of a copper compound containing 4'-phenyl terpyridine

Several copper complexes have been assessed as anti-tumor agents against cancer cells. In this work, a copper compound [Cu(H2O){OS(CH3)2}L](NO3)2 incorporating the ligand 4'-phenyl-terpyridine antiproliferative activity against human colorectal, hepatocellular carcinomas and breast adenocarcinoma cell lines was determined, demonstrating high cytotoxicity. The compound is able to induce apoptosis and a slight delay in cancer cell cycle progression, probably by its interaction with DNA and induction of double-strand pDNA cleavage, which is enhanced by oxidative mechanisms. Moreover, proteomic studies indicate that the compound induces alterations in proteins involved in cytoskeleton maintenance, cell cycle progression and apoptosis, corroborating its antiproliferative potential.

Exploration of DNA binding mode, chemical nuclease, cytotoxic and apoptotic potentials of diketone based oxovanadium(IV) complexes

Two diketone based oxovanadium complexes, viz., bis(4,4,4-trifluoro-1-phenylbutane-1,3-dionato)oxovanadium(IV) (1) and bis(1,1,1-trifluoropentane-2,4-dionato)oxovanadium(IV) (2), have been synthesized and characterized by spectroscopic and analytical techniques. The DNA binding and the cleaving ability of the complexes is assessed by UV-vis spectroscopy, fluorescence spectroscopy, viscometry and gel electrophoretic studies. The DNA binding constant values (Kb) are found to be 1.95 ± 0.16 × 10(3)M(-1) for complex 1 and 1.064 ± 0.17 × 10(3)M(-1) for complex 2, respectively. Based on the results of the spectral and viscosity studies, it is observed that the complexes, interestingly, have preferred minor groove binding with DNA. Further, the concentration-dependent oxidative cleavage pattern of pBR322 in the presence of the activating reagent, hydrogen peroxide, has also been discussed. In addition, the complexes have shown moderate cytotoxic activity by inducing apoptosis against the cervical cancer cell line, HeLa. The results of in silico analysis and logP predictions are found to be in good agreement with the experimental observations. Thus, synthesized oxovanadium complexes have displayed promising DNA binding behavior and DNA cleavage activity with moderately cytotoxic nature.

Antiproliferative effects of copper(II)-polypyridyl complexes in breast cancer cells through inducing apoptosis

Although cisplatin has been used for decades to treat human cancer, some toxic side effects and resistance are observed. Previous investigations have suggested copper complexes as a novel class of tumor-cell apoptosis inducers. The present study aimed to evaluate the anti-breast cancer activities of two polypyridyl-based copper(II) complexes, [Cu(tpy)(dppz)](NO3)2 (1) and [Cu(tptz)2](NO3)2 (2) (tpy = 2,2':6',2″-terpyridine, dppz = dipyrido[3,2-a:2',3'-c]phenazine, tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine), using human breast adenocarcinoma cell line (MCF-7). The ability of the complexes to cleave supercoiled DNA in the presence and absence of external agents was also examined. The apoptotic activities of the complexes were assessed using flow cytometry, fluorescence microscope and western blotting analysis. Our results indicated the high DNA affinity and nuclease activity of complexes 1 and 2. The cleavage mechanisms between the complexes and plasmid DNA are likely to involve a singlet oxygen or singlet oxygen-like entity as the reactive oxygen species. Complexes 1 and 2 also significantly inhibited the proliferation of MCF-7 cells in a dose-dependent manner (IC50 values = 4.57 and 1.98 μM at 24 h, respectively). Complex 2 remarkably induced MCF-7 cells to undergo apoptosis, which was demonstrated by cell morphology, annexin-V and propidium iodide staining. The caspase cascade was activated as shown by the proteolytic cleavage of caspase-3 after treatment of MCF-7 cells with complex 2. Additionally, complex 2 significantly increased the expression of the Bax-to-Bcl-2 ratio to induce apoptosis. In conclusion, these results revealed that complex 2 may be a potential and promising chemotherapeutic agent to treat breast cancer.

Synthesis and crystal structure determination of a mononuclear cobalt(ii) complex derived from 4-(pyridin-4-ylmethoxy)-benzoic acid: evaluation of the DNA/protein interaction and photo-induced pBR322 DNA cleavage

New Co(ii)-based chemotherapeutic drug candidate was synthesized and thoroughly characterized by spectroscopic, analytical and single crystal X-ray techniques.

Five water-soluble zwitterionic copper(ii)-carboxylate polymers: role of dipyridyl coligands in enhancing the DNA-binding, cleaving and anticancer activities

Five water-soluble zwitterionic copper-carboxylate polymers were prepared and their DNA-binding, cleaving and anticancer activities were studied.

Structural modeling, in vitro antiproliferative activity, and the effect of substituents on the DNA fastening and scission actions of heteroleptic copper(ii) complexes with terpyridines and naproxen

A new series of heteroleptic copper(ii) complexes with terpyridines and naproxen are reported. The results of biological activity are laying a foundation for the design of new anticancer agents.

Lanthanide-Based Polymers with Charged Ligand Backbones: Triple-Stranded Chain Structures and their DNA Cleavage Studies

Four rare-earth metal complexes, [Ln(Ccbp)3(H2O)3]n (Ln = La (1), Ce (2), Pr (3) and Nd (4)) are synthesised from the ligand H2CcbpBr (H2CcbpBr = 4-carboxy-1-(4-carboxybenzyl)pyridinium bromide) and the respective lanthanide metal ions. Complexes 1–4 are isostructural in that every three Ccbp– ligands juxtapose two Ln3+ ions in a monodentate coordination mode to form triple-stranded one-dimensional chain structures. Each central Ln3+ atom further associates with three H2O molecules, furnishing a monocapped square-antiprism geometry. Agarose gel electrophoresis studies indicate that 1–4 are capable of cleaving DNA in the presence of H2O2, most probably via an oxidative cleavage mechanism. Complexes 1 and 2 exhibited catalytic efficiencies (kmax/KM) of 37.69 and 34.11 h–1 mM–1, and are approx. 15- and 20-fold more effective than those of complexes 3 (kmax/KM = 1.75 h–1 mM–1) and 4 (kmax/KM = 2.21 h–1 mM–1).

Synthesis of isatin thiosemicarbazones derivatives: in vitro anti-cancer, DNA binding and cleavage activities

New derivatives of thiosemicarbazone Schiff base with isatin moiety were synthesized L1-L6. The structures of these compounds were characterized based on the spectroscopic techniques. Compound L6 was further characterized by XRD single crystal. The interaction of these compounds with calf thymus (CT-DNA) exhibited high intrinsic binding constant (k(b)=5.03-33.00×10(5) M(-1)) for L1-L3 and L5 and (6.14-9.47×10(4) M(-1)) for L4 and L6 which reflect intercalative activity of these compounds toward CT-DNA. This result was also confirmed by the viscosity data. The electrophoresis studies reveal the higher cleavage activity of L1-L3 than L4-L6. The in vitro anti-proliferative activity of these compounds against human colon cancer cell line (HCT 116) revealed that the synthesized compounds (L3, L6 and L2) exhibited good anticancer potency.