DNA as a Target for Anticancer Phen-Imidazole Pd(II) Complexes

Effect of geometric isomerism on the anticancer property of new platinum complexes with glycine derivatives as asymmetric N, O donate ligands against human cancer

In this project, to fallow the anticancer ability of new Pt drugs, several new Pt complexes were synthesized with the asymmetric bidentate glycine derivatives, as named propyl- and hexyl glycine (L), in the general formula: [Pt(NH3)2(L)]NO3, and cis- and trans-[Pt(L)2]. The structure of two cis- and trans-[Pt(propylgly)2] complexes was proved by single crystallography analysis. However, all complex structures were characterized by various methods of 1H NMR, 13C NMR, 195Pt NMR, FTIR, LC-Mass, and Raman spectroscopy. To study the passage of water-soluble complexes of [Pt(NH3)2(L)]NO3 via cell membrane, their solubility, and lipophilicity were analyzed. In addition, the cytotoxic properties of these complexes were evaluated against normal and malignant cell lines (skin, breast, and lung cancer cells). The results indicated that they were either comparable to cisplatin or less damaging than carboplatin and oxaliplatin. It was expected that due to less steric effect, and the presence of length aliphatic hydrocarbon chain in the complex structure, trans-[Pt(hexylgly)2] is more toxic on cancerous cell lines than trans-[Pt(propylgly)2]. Cellular accumulation of all complexes was evaluated on A549 and MCF7 cell lines, and the amount of platinum metal (ng) was measured by the ICP method. Results showed that trans-[Pt(hexylgly)2] complex has the highest accumulation inside both mentioned cell lines and [Pt(NH3)2(L)]NO3 complexes behave like clinical Pt-drugs. Ultimately, the interaction patterns of DNA were examined using spectroscopic methods and molecular docking simulations for all substances.

Targeting DNA junction sites by bis-intercalators induces topological changes with potent antitumor effects

Targeting inter-duplex junctions in catenated DNA with bidirectional bis-intercalators is a potential strategy for enhancing anticancer effects. In this study, we used d(CGTATACG)2, which forms a tetraplex base-pair junction that resembles the DNA-DNA contact structure, as a model target for two alkyl-linked diaminoacridine bis-intercalators, DA4 and DA5. Cross-linking of the junction site by the bis-intercalators induced substantial structural changes in the DNA, transforming it from a B-form helical end-to-end junction to an over-wounded side-by-side inter-duplex conformation with A-DNA characteristics and curvature. These structural perturbations facilitated the angled intercalation of DA4 and DA5 with propeller geometry into two adjacent duplexes. The addition of a single carbon to the DA5 linker caused a bend that aligned its chromophores with CpG sites, enabling continuous stacking and specific water-mediated interactions at the inter-duplex contacts. Furthermore, we have shown that the different topological changes induced by DA4 and DA5 lead to the inhibition of topoisomerase 2 activities, which may account for their antitumor effects. Thus, this study lays the foundations for bis-intercalators targeting biologically relevant DNA-DNA contact structures for anticancer drug development.

Biological interaction of Pt complex with imidazole derivative as an anticancer compound with DNA: Experimental and theoretical studies

This investigation is applied to find out interesting information on DNA binding mode with Pt(II) derivative of two N, N bidentate ligands in treating cancer. Thus, one new water-soluble platinum complex with FIP and phen with a new formula of [Pt(phen)(FIP)](NO3)2 was prepared and specified. DFT data can be used to evaluate geometry parameters. Based on the ADMET prediction, this complex can be considered a drug-like agent. Cytotoxicity property was evaluated against some human cancerous MCF7, A549, and HCT116 cell lines. Accumulation of Pt complex, cisplatin, and oxaliplatin in each cancerous cell was determined, which is probably related to their lipophilicity and solubility properties. The binding mode of the complex to ct-DNA was investigated by fluorescence spectroscopy, circular dichroism, and molecular docking simulation. The viscosity of DNA by different concentrations of EB and Pt complex titration shows Pt complex interacts with DNA via groove binding like the spectroscopic binding result. In the MD study, DNA helix, RMSD, and RMSF analysis showed that DNA stability decreased and that the majority of residues left the initial state. DNA increased residual deviations and flexibility are linked to an increase in its gyratory radius, which is consistent with the findings of the experiments.

Solution and Gas-Phase Stability of DNA Junctions from Temperature-Controlled Electrospray Ionization and Surface-Induced Dissociation

DNA three-way junction (TWJ) structures transiently form during key cellular processes such as transcription, replication, and DNA repair. Despite their significance, the thermodynamics of TWJs, including the influence of strand length, base pair composition, and ligand binding on TWJ stability and dissociation mechanisms, are poorly understood. To address these questions, we interfaced temperature-controlled nanoelectrospray ionization mass spectrometry (TC-nESI-MS) with a cyclic ion mobility spectrometry (cIMS) instrument that was also equipped with a surface-induced dissociation (SID) stage. This novel combination allowed us to investigate the structural intermediates of three TWJ complexes and examine the effects of GC base pairs on their dissociation pathways. We found that two TWJ-specific ligands, 2,7-tris-naphthalene (2,7-TrisNP) and tris-phenoxybenzene (TrisPOB), lead to TWJ stabilization, revealed by an increase in the melting temperature (Tm) by 13 or 26 °C, respectively. To gain insights into conformational changes in the gas phase, we employed cIMS and SID to analyze TWJs and their complexes with ligands. Analysis of IM arrival distributions suggested a single-step dissociation of TWJs and their intermediates for the three studied TWJ complexes. Upon ligand binding, a higher SID energy by 3 V (2,7-TrisNP) and 5 V (TrisPOB) was required to induce 50% dissociation of TWJ, compared to 38 V in the absence of ligands. Our results demonstrate the power of utilizing TC-nESI-MS in combination with cIMS and SID for thermodynamic characterization of TWJ complexes and investigation of ligand binding. These techniques are essential for the TWJ design and development as drug targets, aptamers, and structural units for functional biomaterials.

Spectroscopic study and molecular simulation: Bovine serum albumin binding with anticancer Pt complex of amyl dithiocarbamate ligand

Until now, many methods have been proposed to treat cancer, such as radiation therapy and drug therapy, but none of them have caused a complete cure for cancer. Heavy metal complexes such as cisplatin are among the compounds used as drugs in chemotherapy against cancer cells. These compounds cause cell death and have anti-cancer properties, but they have side effects. The biochemical mechanism of cisplatin is related to its interaction with DNA through covalent binding. To reduce the toxicity of metallodrugs, new complexes can be designed containing S, S- bidentate ligands such as diethyldithiocarbamate. Moreover, anti-cancer compounds probably interact with proteins, such as HSA, before passing the cancerous cell membrane and DNA as a target. So, the function of proteins and their stabilities are expected to change. In this research, the mode of binding of [Pt (bpy) (amyl.dtc)]NO3 complex with BSA was evaluated by various thermodynamic methods. Negative binding enthalpy and entropy changes amounts show that the connection between the Platinum compound and BSA occurs via the van Der Waals type of hydrogen bond. The negative Gibbs free energy change was obtained through isothermal titration, which showed interaction proceeds spontaneously. Moreover, the emission titration data showed that protein fluorescence quenching by platinum agent titration is static. Binding, quenching constants, and binding site number were obtained by the Stern-Volmer equation, and only one binding site was determined for this interaction. A Scatchard plot with a positive slope shows the Pt agent-BSA formation is proceeding positively cooperative. The kinetic study displayed that the absorption monitoring followed the second-order model. Finally, molecular docking simulation showed that the position of the Pt agent on protein is placed I under region II.

Molecular docking and spectroscopic study of bovine serum albumin interaction with new anticancer Pt complex with isopentyl dithiocarbamate ligand

Although cisplatin is useful in the treatment of cancer, it has a series of side effects that limit its use. Dithiocarbamates reduce the toxicity of platinum due to their structure and the presence of S, and N donating groups. In this article, the interaction of [Pt(bpy)(isopentyl.dtc)]NO3, where bpy is bipyridine and isopentyl.dtc is isopentyl-dithiocarbamate, with BSA, bovine serum albumin has been studied. The molecular binding method, including UV-Vis and fluorescence titration, was carried out in conditions including pH = 7.4 and temperatures of 27 and 37 °C. The negative values of enthalpy (ΔH°b) and entropy (ΔS°b) show that the driving forces of this interaction are hydrogen and van der Waals, and the negative value of the Gibbs free energy, ΔG°b indicates that the interaction proceeds spontaneously. The fluorescence results showed that the quenching mechanism is the static type and the Stern Volmer constant, KSV, was also obtained. The fluorescence titration method data displayed that the quenching mechanism is static. Binding constant (Kb), binding point (n), Hill coefficients, nH, Hill constant, KH, number of binding sites, g, BSA melting temperature, Tm, were also obtained. Finally, the molecular docking method result shows the binding constant, Ki and binding free energy for the platinum complex are -6.53 and 16.39 kcal mol-1, respectively, and also the proper position of binding on BSA can be considered the site I in the subdomain IIA.

Study of novel bidentate heterocyclic amine-based metal complexes and their biological activities: cytotoxicity and antimicrobial activity evaluation

Metallic antitumor drugs with heterocyclic ligands, such as novel AMI (amino methyl imidazole) complexes [Pd(AMI)Cl₂](1), [Cu(AMI)L¹](2), and [Cu(AMI)L²·2H₂O](3) where L¹ = oxalate and L² = malonate, were synthesized and characterized. Assessments included elemental analyses, mass spectrometry, Fourier transform-infrared spectroscopy, ultraviolet-visible spectroscopy, and thermal analysis. The cytotoxicity of AMI complexes compared to cisplatin was assessed using MTT (3-[4,5-dimethylthiazol-2-yl] 2,5diphenyl tetrazolium bromide) assay with breast (MCF-7) and cervical (HeLa) cancer cell lines. After treating these cells with the AMI complexes' IC₅₀ values for 48 h, malondialdehyde levels and catalase activity were used to assess oxidative stress, antioxidant activity was evaluated with DPPH radical scavenging method, comet assays assessed DNA damage, and DNA fragmentation was evaluated using the gel electrophoresis. In vitro, antimicrobial activity was assessed using a disc diffusion method. The anticancer activity results showed that IC₅₀ (half-maximal inhibitory concentration) values of complex one, two, and three against MCF-7 and HeLa cancer cells are 0.156 ± 0.0006, 0.125 ± 0.001, 0.277 ± 0.002 μM respectively for MCF-7 cells and 0.222 ± 0.0005, 0.126 ± 0.0009, 0.152 ± 0.001 μM respectively for HeLa cells. Complex two demonstrated strong anticancer activity against MCF-7 and Hela cells. The study of oxidative stress parameters revealed that Malondialdehyde levels increased in cancer cell lines treated with complexes compared to untreated cells. Catalase activity decreased in cells treated with palladium chelate. The DPPH radical scavenging assay results identified that complex one was a more potent antioxidant in MCF-7 and Hela cells than other complexes with SC₅₀ values of 227.5 ± 0.28 and 361 ± 1.2 μL/mL, respectively. The comet assay results showed that complex two caused significant DNA damage in MCF-7 and HeLa cancer cells treated. Antimicrobial assays identified complex three as the most effective. Copper complexes give better antifungal activity against A. flavus than the palladium complex. We conclude that complex two is the most active in both cell types and might be assessed as a clinically useful drug for breast cancer treatment. The significance of the current study is the synthesis of antitumor drugs containing heterocyclic ligands, such as novel AMI complexes, and the study of their biological activities.

Phototunable Cell Killing by Photochromic Diarylethene of Thiazoyl and Thienyl Derivatives

We report a unique phototunable cell killing technique using diarylethene molecules as photo-isomerizing-molecular switches. These molecules were delivered to DNA in the cell nucleus due to closed-form generated by UV light, and then blue light triggered cell killing. A UV light irradiation switches the open form, having no DNA intercalation activity, to the closed form to induce intercalation in DNA. This isomer, thus prepared ready for the action, exerts photocytotoxicity upon the subsequent blue light irradiation. Molecular biological analysis clarifies that photocytotoxicity is due to DNA double-strand breaks. Since cell death is observed only when irradiated with light where both the open- and closed-ring isomers have absorption, the possible mechanism of cell death is assumed to be due to the repeated photocyclization and photocycloreversion reactions of the diarylethene molecules, which induce irreparable damage to DNA. This unique photo-controllable action in a cell system can provide the basis of a novel scheme of phototherapy.

A biophysical study of the interactions of palladium(II), platinum(II) and gold(III) complexes of aminopyridyl-2,2'-bipyridine ligands with RNAs and other nucleic acid structures

Metal compounds form an attractive class of ligands for a variety of nucleic acids. Five metal complexes bearing aminopyridyl-2,2'-bipyridine tetradentate ligands and possessing a quasi-planar geometry were challenged toward different types of nucleic acid molecules including RNA polynucleotides in the duplex or triplex form, an RNA Holliday four-way junction, natural double helix DNA and a DNA G-quadruplex. The binding process was monitored comparatively using different spectroscopic and melting methods. The binding preferences that emerge from our analysis are discussed in relation to the structural features of the metal complexes.

Synthesis, characterization of ruthenium(II), nickel(II), palladium(II), and platinum(II) triphenylphosphine-based complexes bearing an ONS-donor chelating agent: Interaction with biomolecules, antioxidant, in vitro cytotoxic, apoptotic activity and cell cycle analysis

Four new transition metal complexes, [M(PPh₃)(L)]^.CH₃OH (M = Ni(II) (1), Pd(II) (2)) [Pt (PPh₃)₂(HL)]Cl (3) and [Ru(CO)(PPh₃)₂(L)] (4) (H₂L = 2,4-dihydroxybenzaldehyde-S-methyldithiocarbazate, PPh₃ = triphenylphosphine) have been synthesized and characterized by elemental analyses (C, H, N), FTIR, NMR (¹H, ³¹P), ESI-MS and UV-visible spectroscopy. The molecular structure of (1) and (2) complexes was confirmed by single-crystal X-ray crystallography. It showed a distorted square planar geometry for both complexes around the metal center, and the H₂L adopt a bi-negative tridentate chelating mode. The interaction with biomolecules viz., calf thymus DNA (ct DNA), yeast RNA (tRNA), and BSA (bovine serum albumin) was examined by both UV-visible and fluorescence spectroscopies. The antioxidant activity of all compounds is discussed on basis of DPPH^• (2,2-diphenyl-1-picrylhydrazyl) scavenging activity and showed better antioxidant activity for complexes compared to the ligand. The in vitro cytotoxicity of the compounds was tested on human (breast cancer (MCF7), colon cancer (HCT116), liver cancer (HepG2), and normal lung fibroblast (WI38)) cell lines, showing that complex (1) the most potent against MCF7 and complex (4) against HCT116 cell lines based on IC₅₀ and selective indices (SI) values. So, both complexes were chosen for further studies such as DNA fragmentation, cell apoptosis, and cell cycle analyses. Complex (1) induced MCF7 cell death by cellular apoptosis and arrest cells at S phase. Complex (4) induced HCT116 cell death predominantly by cellular necrosis and arrested cell division at G2/M phase due to DNA damage.

Spectroscopic and docking molecular study of new anticancer Pt complex binding with human serum albumin

After synthesizing and identifying the nature of the new complex based on platinum metal, [Pt(NH₃)₂(butylgly)]NO₃, the interaction of this complex with human serum albumin (HSA) was performed by spectroscopy and molecular docking methods at two temperatures of 27 and 37 °C and under physiological conditions of the body. The toxicity test of this complex was performed on the MCF-7 cell line (IC₅₀ = 300 µM). Enthalpy, entropy, Gibbs free energy, binding constant, number of complex binding sites on the HSA, Scatchard diagrams, Hill coefficient, and Hill constant were calculated and then plotted via UV/Vis. According to the Gibbs free energy obtained at two temperatures of 27 and 37 °C (-20.6, -21.2 kJ mol^-1), the interaction was done spontaneously. Moreover, the melting temperature of human serum albumin with this complex; and the kinetics of this interaction (the second-order) were calculated. Using fluorescence at three temperatures of 25, 27, and 37 °C, the binding constant (2.9 × 10⁴, 1.0 × 10⁴, and 5.7 × 10³ M^-1), the quenching constant, average aggregation number of HSA, and the number of binding sites of the complex on the protein were obtained. As well, the static quenching mechanism was also observed. Molecular docking results showed that the site of binding of this complex to the HSA, is the site II subdomain IIIA, and the hydrogen and hydrophobic bonds are superior.

Kinetic and Thermodynamic Investigation of Human Serum Albumin Interaction with Anticancer Glycine Derivative of Platinum Complex by Using Spectroscopic Methods and Molecular Docking

In this paper, a new anticancer Pt (II) complex, cis-[Pt (NH₃)₂(tertpentylgly)]NO₃, was synthesized with glycine-derivative ligand and characterized. Cytotoxicity of this water-soluble Pt complex was studied against human cancer breast cell line of MCF-7. The interaction of human serum albumin (HSA) with Pt complex was studied by using UV-Vis, fluorescence spectroscopy methods, and molecular docking at 27 and 37 °C in the physiological situation (I = 10 mM, pH = 7.4). The negative [Formula: see text] and positive [Formula: see text] indicated that electrostatic force may be a major mode in the binding between Pt complex and HSA. Binding constant values were obtained through UV-Vis and fluorescence spectroscopy that reveal strong interaction. The negative Gibbs free energy that was obtained by using the UV-Vis method offers spontaneous interaction. Fluorescence quenching the intensity of HSA by adding Pt complex confirms the static mode of interaction is effective for this binding process. Hill coefficients, n_H, Hill constant, k_H, complex aggregation number around HSA, <J>, number of binding sites, g, HSA melting temperature, T_m, and Stern-Volmer constant, k_SV, were also obtained. The kinetics of the interaction was studied, which showed a second-order kinetic. The results of molecular docking demonstrate the position of binding of Pt complex on HSA is the site I in the subdomain IIA.

Half Sandwich Rhodium(III) and Iridium(III) Complexes as Cytotoxic and Metallonuclease Agents

Half sandwich complexes of the type [(η5-C₅Me₅)M(L^1-3)Cl]Cl.2H₂O were synthesized using [{(η⁵-C₅Me₅)M(μ-Cl)Cl}₂], where M = Rh(III)/Ir(III) and L^1-3 = pyrimidine-based ligands. The complexes were characterized by spectral analysis. DNA interaction studies by absorption titration and hydrodynamic measurement and suggest intercalative mode of binding of complexes with CT-DNA. The molecular docking study also supports intercalation of the complexes between the stacks of nucleotide base pairs. The gel electrophoresis assay demonstrated the ability of the complexes to interact and cleave plasmid DNA. Minimum inhibitory concentrations (MIC) of the complexes were investigated by the microdilution broth method. The cytotoxic properties of the metal complexes were evaluated using brine shrimp lethality bioassay.