Intercalation processes of copper complexes in DNA

Theoretical determination of half-wave potentials for phenanthroline-, bipyridine-, acetylacetonate-, and glycinate-containing copper (II) complexes

We report a protocol for the evaluation of theoretical half-wave potential (E_1/2) using a set of 22 mixed chelate copper (II) complexes containing 1,10-phenanthroline and 2,2'-bipyridine derivatives as primary ligands, and acetylacetonate or glycinate as secondary ligands (formally from the Casiopeínas® family) for which accurate experimental values were determined in a 2/5 mixture of ethanol/water. We have calibrated the BP86, PBE, PBE0, B3LYP, M06-2X, and ω-B97XD functionals, using the Los Alamos LANL2DZ and Stuttgart-Köln SDDAll effective core potentials for the Cu and Fe atoms and the 6-311+G* basis set for the C, H, O, and N atoms. To address the solvent effects, we have saturated the first solvation shell with up to 9 water molecules for the explicit model and compared it with the Continuum Like-Polarizable Continuum Model (CPCM) implicit solvent scheme. We found that the PBE/LANL2DZ-6-311+G* protocol (with the CPCM implicit solvent scheme with an effective dielectric constant ε = 64.9121 for the 2/5 mixture of ethanol/water) yields the overall best performance. The theoretical values are compared with experimental data, three of which are reported here for the first time. We find good correlations between the theoretical and experimental E_1/2 values for the 2,2'-bipyridine derivatives (R² = 0.987, MAE = 86 mV) and 1,10-phenanthroline derivatives (R² = 0.802, MAE = 58.4 mV). The correlation trends have been explained in terms of the copper atom's ability to be reduced in the presence of the ligands. The Gibbs free energy differences at 298 K obtained for the redox reactions show that the more flexible secondary ligands (acetylacetonate) lead to larger entropic contributions which, as expected, increase the average MAE values as compared with the more rigid ligands (glycine). The present protocol yields lower MAEs as compared with previous approaches for similar mixed and flexible Cu(II) complexes.

Copper Complexes with 1,10-Phenanthroline Derivatives: Underlying Factors Affecting Their Cytotoxicity

The interpretation of in vitro cytotoxicity data of Cu(II)-1,10-phenanthroline (phen) complexes normally does not take into account the speciation that complexes undergo in cell incubation media and its implications in cellular uptake and mechanisms of action. We synthesize and test the activity of several distinct Cu(II)-phen compounds; up to 24 h of incubation, the cytotoxic activity differs for the Cu complexes and the corresponding free ligands, but for longer incubation times (e.g., 72 h), all compounds display similar activity. Combining the use of several spectroscopic, spectrometric, and electrochemical techniques, the speciation of Cu-phen compounds in cell incubation media is evaluated, indicating that the originally added complex almost totally decomposed and that Cu(II) and phen are mainly bound to bovine serum albumin. Several methods are used to disclose relationships between structure, activity, speciation in incubation media, cellular uptake, distribution of Cu in cells, and cytotoxicity. Contrary to what is reported in most studies, we conclude that interaction with cell components and cell death involves the separate action of Cu ions and phen molecules, not [Cu(phen)_n] species. This conclusion should similarly apply to many other Cu-ligand systems reported to date.

Copper Coordination Compounds as Biologically Active Agents

Copper-containing coordination compounds attract wide attention due to the redox activity and biogenicity of copper ions, providing multiple pathways of biological activity. The pharmacological properties of metal complexes can be fine-tuned by varying the nature of the ligand and donor atoms. Copper-containing coordination compounds are effective antitumor agents, constituting a less expensive and safer alternative to classical platinum-containing chemotherapy, and are also effective as antimicrobial, antituberculosis, antimalarial, antifugal, and anti-inflammatory drugs. 64Сu-labeled coordination compounds are promising PET imaging agents for diagnosing malignant pathologies, including head and neck cancer, as well as the hallmark of Alzheimer's disease amyloid-β (Aβ). In this review article, we summarize different strategies for possible use of coordination compounds in the treatment and diagnosis of various diseases, and also various studies of the mechanisms of antitumor and antimicrobial action.

Isoxazole-Derived Aroylhydrazones and Their Dinuclear Copper(II) Complexes Show Antiproliferative Activity on Breast Cancer Cells with a Potentially Alternative Mechanism Of Action

This paper reports the design, synthesis and cytotoxicity studies of two new isoxazole-derived aroylhydrazone ligands and their dinuclear copper(II) complexes. Compounds were fully characterized by various spectroscopic and analytical techniques. The molecular structures of four derivatives were confirmed by X-ray crystallography. The stability of the ligands and the complexes in aqueous medium was monitored spectroscopically. Both the ligands and the complexes were shown to interact with calf thymus DNA (ct-DNA). Additionally, structures containing a phenol pendant arm were significantly more cytotoxic than those carrying a pendant pyridine substituent, reaching sub-micromolar IC₅₀ values on the triple-negative human breast cancer cell line MDA-MB-231. The metal chelation and transchelation ability of the compounds towards Fe^II , Fe^III and Zn^II ions was explored as a possible mechanism of action of these compounds.

Translation of the copper/bipyridine-promoted Petasis reaction to solid phase-coupled DNA for encoded library synthesis

The Petasis three-component reaction gives rise to diverse substituted α-aryl glycines from readily available amines, boronic acids and glyoxalic acid. Thus, this reaction is highly attractive for DNA-encoded small molecule screening library synthesis. The Petasis reaction is for instance promoted by a potentially DNA damaging copper(I)/bipyridine reagent system in dry organic solvents. We found that solid phase-coupled DNA strands tolerated this reagent system at elevated temperature allowing for synthesis of diverse substituted DNA-tagged α-aryl glycines from DNA-conjugated secondary amines.

DNA-Binding and Anticancer Activity of Binuclear Gold(I) Alkynyl Complexes with a Phenanthrenyl Bridging Ligand

3,6-Diethynyl-9,10-diethoxyphenanthrene (4) was synthesized from phenanthrene and employed in the synthesis of the binuclear gold(I) alkynyl complexes (R3P)Au(C≡C-3-[C14H6-9,10-diethoxy]-6-C≡C)Au(PR3) (R = Ph (5a), Cy (5b)). The diyne 4 and complexes 5a and 5b were characterized by NMR spectroscopy, mass spectrometry, and elemental analysis. UV-Vis spectroscopy studies of the metal complexes and precursor diyne show strong p à p* transitions in the near UV region that red shift by ca. 50 nm upon coordination at the gold centers. The emission spectrum of 4 shows an intense fluorescence band centered at 420 nm which red shifts, slightly upon coordination of 4 to gold. Binding studies of 4, 5a, and 5b against calf thymus DNA were carried out, revealing that 4, 5a, and 5b have >40% stronger binding affinities than the commonly used intercalating agent ethidium bromide. The molecular docking scores of 4, 5a, and 5b with B-DNA suggest a similar trend in behavior to that observed in the DNA-binding study. Unlike the ligand 4, promising anticancer properties for 5a and 5b were observed against several cell lines; the DNA binding capability of the precursor alkyne was maintained, and its anticancer efficacy enhanced by the gold centers. Such phenanthrenyl complexes could be promising candidates in certain biological applications because the two components (phenanthrenyl bridge and metal centers) can be altered independently to improve the targeting of the complex, as well as the biological and physicochemical properties.

Heteroleptic NiII complexes: Synthesis, structural characterization, computational studies and amoebicidal activity evaluation

In this work, we present the synthesis, characterization, electrochemical studies, DFT calculations, and in vitro amoebicidal effect of seven new heteroleptic Ni^II coordination compounds. The crystal structures of [H₂(pdto)](NO₃)₂ and [Ni(pdto)(NO₃)]PF₆ are presented, pdto = 2,2'-[1,2-ethanediylbis-(sulfanediyl-2,1-ethanediyl)]dipyridine. The rest of the compounds have general formulae: [Ni(pdto)(NN)](PF₆) where N-N = 2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (44dmbpy), 5,5'-dimethyl-2,2'-bipyridine (55dmbpy), 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (47dmphen) and 5,6-dimethyl-1,10-phenanthroline (56dmphen). The size of NN ligand and its substituents modulate the compound electronic features and influence their antiproliferative efficiency against Entamoeba histolytica. 56dmphen derivative, shows the biggest molar volume and presents a powerful amoebicidal activity (IC₅₀ = 1.2 μM), being seven times more effective than the first-line drug for human amoebiasis metronidazole. Also, increases the reactive oxygen species concentration within the trophozoites. This could be the trigger of the E. histolytica growth inhibition. The antiparasitic effect is described using Ni^II electron density, molar volume, estimated by DFT, as well as the experimental redox potential and diffusion coefficients. In general, amoebicidal efficiency is directly proportional to the increment of the molar volume and decreases when the redox potential becomes more positive.

Current Biomedical Use of Copper Chelation Therapy

Copper is an essential microelement that plays an important role in a wide variety of biological processes. Copper concentration has to be finely regulated, as any imbalance in its homeostasis can induce abnormalities. In particular, excess copper plays an important role in the etiopathogenesis of the genetic disease Wilson's syndrome, in neurological and neurodegenerative pathologies such as Alzheimer's and Parkinson's diseases, in idiopathic pulmonary fibrosis, in diabetes, and in several forms of cancer. Copper chelating agents are among the most promising tools to keep copper concentration at physiological levels. In this review, we focus on the most relevant compounds experimentally and clinically evaluated for their ability to counteract copper homeostasis deregulation. In particular, we provide a general overview of the main disorders characterized by a pathological increase in copper levels, summarizing the principal copper chelating therapies adopted in clinical trials.

Understanding enhanced mechanical stability of DNA in the presence of intercalated anticancer drug: Implications for DNA associated processes

Most of the anticancer drugs bind to double-stranded DNA (dsDNA) by intercalative-binding mode. Although experimental studies have become available recently, a molecular-level understanding of the interactions between the drug and dsDNA that lead to the stability of the intercalated drug is lacking. Of particular interest are the modifications of the mechanical properties of dsDNA observed in experiments. The latter could affect many biological functions, such as DNA transcription and replication. Here, we probe, via all-atom molecular dynamics (MD) simulations, the change in the mechanical properties of intercalated drug-DNA complexes for two intercalators, daunomycin and ethidium. We find that, upon drug intercalation, the stretch modulus of DNA increases significantly, whereas its persistence length and bending modulus decrease. Steered MD simulations reveal that it requires higher forces to stretch the intercalated dsDNA complexes than the normal dsDNA. Adopting various pulling protocols to study force-induced DNA melting, we find that the dissociation of dsDNA becomes difficult in the presence of intercalators. The results obtained here provide a plausible mechanism of function of the anticancer drugs, i.e., via altering the mechanical properties of DNA. We also discuss long-time consequences of using these drugs, which require further in vivo investigations.

Tuning the reaction pathways of phenanthroline-Schiff bases: routes to novel phenanthroline ligands

Pyrido-phenanthrolin-7-one compounds are structural analogues of the cytotoxic alkaloid, ascididemin, and would be expected to have interesting biological activities. Synthetic strategies are reported for a novel simple route to form this class of ligand. 1,10-Phenanthrolin-5,6-dione reacts with l-phenylalanine alkyl esters and their para-substituted analogues to form both a phenanthroline-oxazine and a pyrido-phenanthrolin-7-one product. The nature of the major product is dependent on the electronic properties of the para substituent. Successful metal coordination to the pyrido-phenanthrolin-7-one ligand is also presented.

DNA/lysozyme binding propensity and nuclease properties of benzimidazole/2,2'-bipyridine based binuclear ternary transition metal complexes

In the present contribution, new binuclear ternary complexes; [M2(bpy)4L](ClO4)4 (M = Co(ii) (1) and Ni(ii) (2); bpy = 2,2'-bipyridine; L = 1,1'-(hexane-1,6-diyl)bis[2-(pyridin-2-yl)1H-benzimidazole] and [Cu2(bpy)2(OH2)2L](BF4)4 (3) were synthesized, characterized and screened for their antimicrobial activity and cytotoxicity against human liver carcinoma cells (HepG-2) as well as non-malignant human embryonic kidney cells (HEK-293). The structural studies were complemented by density functional theory (DFT) calculations. DNA binding of 1-3 was spectrophotometrically studied. The DNA cleavage ability of 1-3 towards the supercoiled plasmid DNA (pBR322 DNA) was examined through gel electrophoresis. Compound 3 has the highest cytotoxic activity (IC50 = 3.5 μg mL-1) against HepG-2 among the investigated complexes and is non cytotoxic to noncancerous HEK-293. Complexes (1 and 2) exhibited toxicity to HEK-293 with IC50 values of 30.3 and 23.5 μg mL-1 in that order. While compound 1 showed antifungal activity against Cryptococcus neoformans, complex 2 exhibited its toxicity against Candida albicans.

Novel Copper Complexes That Inhibit the Proteasome and Trigger Apoptosis in Triple-Negative Breast Cancer Cells

Five innovative ternary copper(II) complexes [Cu(OH-PIP)(Phe)Cl](1), [Cu(OH-PIP)(Gly)(H2O)]NO3·2H2O (2), [Cu(OH-PIP)(Ala)(Cl)]·H2O (3), [Cu(OH-PIP)(Met)]PF6·2H2O (4), and [Cu(OH-PIP)(Gln)(H2O)](Cl)·3H2O (5) have been synthesized and characterized by infrared spectroscopy, elemental analysis, and single crystal X-ray diffraction analysis. X-ray crystallography indicates that all Cu atoms are five-coordinated in a square-pyramidal configuration. The complexes have been screened for cytotoxicity against human breast cancer cell lines MCF-7, MDA-MB-231, and CAL-51. The best anticancer activity is obtained with triple-negative breast cancer CAL-51 and MDA-MB-231 cell lines, with IC50 values in the range of 0.082-0.69 μM. Importantly, the copper compounds were more effective than carboplatin at triggering cell death. Mechanistically, the complexes inhibit proteasomal chymotrypsin-like activity, and docking studies reveal their 20S proteasome binding sites. As a consequence, they cause the accumulation of ubiquitinated proteins, inhibit cell proliferation, and induce apoptosis. In addition, these copper complexes decrease the stemness of triple-negative breast cancer cells and have synergistic effects with CBP on TNBC cells, indicating their great potential as a novel therapy for triple-negative breast cancer.

Di-copper metallodrugs promote NCI-60 chemotherapy via singlet oxygen and superoxide production with tandem TA/TA and AT/AT oligonucleotide discrimination

In order to expand the current repertoire of cancer treatments and to help circumvent limitations associated with resistance, the identification of new metallodrugs with high potency and novel mechanisms of action is of significant importance. Here we present a class of di-copper(II) complex based on the synthetic chemical nuclease [Cu(Phen)2]+ (where Phen = 1,10-phenanthroline) that is selective against solid epithelial cancer cells from the National Cancer Institute's 60 human cell line panel (NCI-60). Two metallodrug leads are studied and in each case two [Cu(Phen)2]+ units are bridged by a dicarboxylate linker but the length and rigidity of the linkers differ distinctly. Both agents catalyze intracellular superoxide (O2•-) and singlet oxygen (1O2) formation with radical species mediating oxidative damage within nuclear DNA in the form of double strand breaks and to the mitochondria in terms of membrane depolarization. The complexes are effective DNA binders and can discriminate AT/AT from TA/TA steps of duplex DNA through induction of distinctive Z-like DNA or by intercalative interactions.

Exploring the cytotoxic activity of new phenanthroline salicylaldimine Zn(II) complexes

Zinc(II) complexes bearing N-salicylideneglycinate (Sal-Gly) and 1,10-phenanthroline (phen) or phenanthroline derivatives [NN = 5-chloro-1,10-phenanthroline, 5-amine-1,10-phenanthroline (amphen), 4,7-diphenyl-1,10-phenanthroline (Bphen) and 5,6-epoxy-5,6-dihydro-1,10-phenanthroline] are synthesized. Complexes formulated as [Zn(NN)₂(H₂O)₂]²⁺(NN = phen and amphen), are also prepared. The cytotoxicity of the compounds is evaluated towards a panel of human cancer cells: ovarian (A2780), breast (MCF7) and cervical (HeLa), as well as non-tumoral V79 fibroblasts. All compounds display higher cytotoxicity than cisplatin (IC₅₀ = 22.5 ± 5.0 μM) towards ovarian cells, showing IC₅₀values in the low micromolar range. Overall, all compounds show higher selectivity for the A2780 cells than for the non-tumoral cells and higher selectivity indexes (IC₅₀(V79)/IC₅₀(A2780) than cisplatin. [Zn(Sal-Gly)(NN)(H₂O)] complexes induce caspase-dependent apoptosis in A2780 cells, except [Zn(Sal-Gly)(Bphen)(H₂O)], one of the most cytotoxic of the series. The cellular uptake in the ovarian cells analyzed by Inductively Coupled Plasma mass spectrometry indicates different Zn distribution profiles. Transmission electronic microscopy shows mitochondria alterations and apoptotic features consistent with caspase activation; cells incubated with [Zn(Sal-Gly)(amphen)(H₂O)] present additional nuclear membrane alterations in agreement with significant association with the nucleus. The increase of reactive oxygen species and lipid peroxidation forms could be related to apoptosis induction. [Zn(NN)₂(H₂O)₂]²⁺complexes have high ability to bind DNA through intercalation/groove binding, and circular dichroism data suggests that the main type of species that interact with DNA is [Zn(NN)]²⁺. Studies varying the % of fetal bovine serum (1-15%) in cell media show that albumin binding decreases the complex activity, indicating that distinct speciation of Zn- and phen-containing species in cell media may affect the cytotoxicity.

Design, synthesis, in vitro anticancer, antioxidant and antibacterial activity; DNA/BSA binding, photoleavage and docking studies of Cu(II) ternary metal complexes

Three mononuclear, mixed ligand ternary Cu(II) complexes of 3-((Z)-1-(2-hydroxyphenylimino)ethyl)-4-hydroxy-6-methyl-2H-pyran-2-one (HEHMP) viz; [Cu-(Phen) (HEHMP)] (1a), [Cu-(Bpy)(HEHMP)] (1 b) and [Cu-Bpy(NCS)(HEHMP)] (1c) were synthesized and characterized by data obtained from various spectral techniques. The binding affinities of these complexes with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) protein were explored by absorption and fluorescence quenching titrations. The results indicated strong affinity of the title compounds to bind with both CT-DNA and BSA. The antioxidant properties of the synthesized compounds evaluated by free-radical scavenging method using spectrophotometric technique indicated their affirmative potential activity. Gel electrophoresis experiments revealed the efficacy of metal complexes in resulting the cleavage of pBR322 supercoiled DNA. In vitro cytotoxicity studies of these complexes evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay against HeLa and MCF-7 cancer cell lines indicated relatively high effectiveness of the complex 1c. Confocal microscopy signified the potential of the complexes to induce apoptosis in HeLa cell lines. In addition, the antibacterial activity of the compounds carried out by disc diffusion method revealed significantly enhanced antibacterial activity in Cu (II) ternary complexes compared to the activity of ligands in unbound form signifying the implicit role of metal ion in inducing lipophilic character.

Solvent-driven structural topology involving energetically significant intra- and intermolecular chelate ring contacts and anticancer activities of Cu(ii) phenanthroline complexes involving benzoates: experimental and theoretical studies

Two new coordination solids [Cu₂(μ²-Bz)₄(CH₃OH)₂][Cu₂(η²-Bz)₂(phen)₂(H₂O)₂]·(NO₃)₂ (1) and [Cu(phen)(H₂O)(Bz)(η²-Bz)] (2) (phen = 1,10-phenanthroline; Bz = benzoate) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (IR, UV-vis-NIR and ESR) and single crystal X-ray diffraction techniques. Change of the solvent from methanol to DMF results in changes in the architectures that are triggered by a change from square pyramidal to octahedral coordination at the divalent metal centers for complexes 1 and 2 respectively. The structural topology of the complexes is established by the interplay of strong O-H⋯O and weak C-H⋯O, C-H⋯C, π-π stacking interactions. Unconventional parallel intramolecular and anti-parallel intermolecular contacts involving the chelate rings (CR) also stabilize the structures. The energetic analyses of the structures evidence that the parallel arrangement is energetically favoured which is likely due to the presence of the Cu⋯Cu cuprophilic interaction in 1 that is not established in 2. Compound 1 exhibits the highest antibacterial activity against Rhizobium leguminosarum among the tested cultures. In vitro cytotoxicity and apoptosis studies were carried out for compounds 1 and 2 on malignant Dalton's lymphoma cell line (DL). Both compounds showed a significant effect on the decrease in cell viability as compared to a control, while compound 2 induced remarkable cytotoxicity towards DL cells. Treatment also showed the appearance of membrane blebbing, chromatin condensation and fragmented nuclei which are typical characteristic features of apoptotic cell death. Furthermore, a docking study revealed that both compounds docked in the active sites of all the cancer target proteins under study. Moreover, SAR analysis revealed that oxygen and nitrogen atoms of compound 1 and the oxygen atoms of compound 2 are crucial for biological activities.

Molecular methods for assessment of non-covalent metallodrug-DNA interactions

Herein we provide an accessible account of molecular methods to probe inorganic–nucleic acid interactions. Techniques are described using copper(ii) and platinum(ii) complexes prepared in our laboratories.

The binding of small molecule metallodrugs to discrete regions of nucleic acids is an important branch of medicinal chemistry and the nature of these interactions, allied with sequence selectivity, forms part of the backbone of modern medicinal inorganic chemistry research. In this tutorial review we describe a range of molecular methods currently employed within our laboratories to explore novel metallodrug–DNA interactions. At the outset, an introduction to DNA from a structural perspective is provided along with descriptions of non-covalent DNA recognition focusing on intercalation, insertion, and phosphate binding. Molecular methods, described from a non-expert perspective, to identify non-covalent and pre-associative nucleic acid recognition are then demonstrated using a variety of techniques including direct (non-optical) and indirect (optical) methods. Direct methods include: X-ray crystallography; NMR spectroscopy; mass spectrometry; and viscosity while indirect approaches detail: competitive inhibition experiments; fluorescence and absorbance spectroscopy; circular dichroism; and electrophoresis-based techniques. For each method described we provide an overview of the technique, a detailed examination of results obtained and relevant follow-on of advanced biophysical/analytical techniques. To achieve this, a selection of relevant copper(ii) and platinum(ii) complexes developed within our laboratories are discussed and are compared, where possible, to classical DNA binding agents. Applying these molecular methods enables us to determine structure–activity factors important to rational metallodrug design. In many cases, combinations of molecular methods are required to comprehensively elucidate new metallodrug–DNA interactions and, from a drug discovery perspective, coupling this data with cellular responses helps to inform understanding of how metallodrug–DNA binding interactions manifest cytotoxic action.

A phosphate-targeted dinuclear Cu(II) complex combining major groove binding and oxidative DNA cleavage

Free radical generation is an inevitable consequence of aerobic existence and is implicated in a wide variety of pathological conditions including cancer, cardiovascular disease, ageing and neurodegenerative disorder. Free radicals can, however, be used to our advantage since their production is catalysed by synthetic inorganic molecules-termed artificial metallonucleases-that cut DNA strands by oxidative cleavage reactions. Here, we report the rational design and DNA binding interactions of a novel di-Cu2+ artificial metallonuclease [Cu2(tetra-(2-pyridyl)-NMe-naphthalene)Cl4] (Cu2TPNap). Cu2TPNap is a high-affinity binder of duplex DNA with an apparent binding constant (Kapp) of 107 M(bp)-1. The agent binds non-intercalatively in the major groove causing condensation and G-C specific destabilization. Artificial metallonuclease activity occurs in the absence of exogenous reductant, is dependent on superoxide and hydrogen peroxide, and gives rise to single strand DNA breaks. Pre-associative molecular docking studies with the 8-mer d(GGGGCCCC)2, a model for poly[d(G-C)2], identified selective major groove incorporation of the complex with ancillary Cu2+-phosphate backbone binding. Molecular mechanics methods then showed the d(GGGGCCCC)2 adduct to relax about the complex and this interaction is supported by UV melting experiments where poly[d(G-C)2] is selectively destabilized.

Copper complex with sulfamethazine and 2,2'-bipyridine supported on mesoporous silica microspheres improves its antitumor action toward human osteosarcoma cells: cyto- and genotoxic effects

Ideal drugs to cure cancer leave normal cells unharmed while selectively turning tumor cells unviable. Several copper complexes have been able to selectively slow down tumor proliferation. We hypothesized that Cu(smz)₂(bipy)·H₂O (1)-a copper-complex that has two ligands capable of interacting with DNA-would outperform Cu(smz)₂(OH₂)·2H₂O (2), and also that supporting 1 on mesoporous silica spheres would decrease even further tumor cell viability in vitro. After exposing osteosarcoma cells (MG-63) and normal phenotype cells of bone origin (MC3T3-E1) to either complex, we studied their toxic effect and mechanisms of action. We determined cell viability (MTT assay) and quantified formation of reactive oxygen species (oxidation of DHR-123 to rhodamine). Moreover, we assessed genotoxicity from (i) formation of micronucleus (MN assay) and (ii) damage of DNA (Comet assay). After the exposure of 1 supported on silica spheres, we tested cell viability. Our results confirm our hypotheses: inhibition of tumor cells follows: supported 1 > dissolved 1 > 2. Future work that enhances the load of the complex exclusively in mesopores may improve the ability of 1 to further inhibit tumor cell viability.

Innovative DNA-Targeted Metallo-prodrug Strategy Combining Histone Deacetylase Inhibition with Oxidative Stress

Cancer remains a global health challenge. There is an urgent need to develop innovative therapeutics that can overcome the shortcomings of existing cancer therapies. DNA enzymes involved in nucleic acid compaction and organization are an attractive cancer drug target for therapeutic exploitation. In this work, a family of Cu(II) prodrugs containing suberoylanilide hydroxamic acid (SAHA), a well-established histone deacetylase inhibitor (HDACi) and clinically approved cancer drug, and phenanthrene ligands as DNA intercalative components have been rationally developed. The complexes, of general formula [Cu(SAHA_-1H)( N, N'-phenanthrene)]⁺, exhibit excellent DNA recognition with binding affinity of lead agents in the order of ∼10⁷ M(bp)^-1. Biophysical studies involving nucleic acid polymers indicate intercalative binding at both adenine-thymine (A-T) and guanine-cytosine (G-C) rich sequences but thermodynamically stable interactions are favored in G-C tracts. The complexes mediate DNA damage by producing reactive oxygen species (ROS) with spin trapping experiments showing that superoxide, the hydroxyl radical, and hydrogen peroxide play critical roles in strand scission. The agents were found to have promising antiproliferative effects against a panel of epithelial cancers, and in two representative cell lines possessing mutated p53 (SK-OV-3 and DU145), enhanced cytotoxicity was observed. Significantly, mechanistic experiments with the most promising candidates revealed HDAC inhibition activity was achieved over a shorter time frame as compared to clinical standards with DNA damage-response markers identifying upregulation of both DNA synthesis and nucleotide excision repair (NER) pathways. Finally, confocal imaging and gene expression analysis show this metallodrug class exerts cytotoxic activity predominantly through an apoptotic pathway.

Computational Approach to Unravel the Role of Hydrogen Bonding in the Interaction of NAMI-A with DNA Nucleobases and Nucleotides

Density functional theory method in combination with a continuum solvation model is used to understand the role of hydrogen bonding in the interactions of tertiary nitrogen centers of guanine and adenine with monoaqua and diaqua NAMI-A. In the case of adenine, the interaction of N3 with monoaqua NAMI-A is preferred over that of N7 and N1 whereas, N7 site is the most preferred site over N3 and N1 in the diaqua ruthenium-adenine interaction. In the monoaqua and diaqua NAMI-A-guanine interactions, the N7 site is the most preferred site over the N3 site. Here, the strength and number of H-bonds play important roles in stabilizing intermediates and transition states involved in the interaction of NAMI-A and purine bases. Atoms in molecules and Becke surface analysis confirm that the interactions between monoaqua and diaqua NAMI-A with the base pairs of GC and AT dinucleotides leads to the structural deformation in the geometry of the base pairs of dinucleotides. The diaqua NAMI-A adducts induce more disruption in the base pairs as compared to monoaqua NAMI-A adducts. which suggests that diaqua NAMI-A could be a better anticancer agent than monoaqua NAMI-A. This study can be extended to envisage the potential applications of computational studies in the development of new drugs and targeted drug delivery systems.

A Perspective - can copper complexes be developed as a novel class of therapeutics?

Although copper-ligand complexes appear to be promising as a new class of therapeutics, other than the family of copper(ii) coordination compounds referred to as casiopeínas these compounds have yet to reach the clinic for human use. The pharmaceutical challenges associated with developing copper-based therapeutics will be presented in this article along with a discussion of the potential for high-throughput chemistry, computer-aided drug design, and nanotechnology to address the development of this important class of drug candidates.

In-vivo evaluation of the response of Galleria mellonella larvae to novel copper(II) phenanthroline-phenazine complexes

Herein we report the in-vivo characterisation and metabolic changes in Galleria mellonella larvae to a series of bis-chelate copper(II) phenanthroline-phenazine cationic complexes of [Cu(phen)₂]²⁺ (Cu-Phen), [Cu(DPQ)(Phen)]²⁺ (Cu-DPQ-Phen) and [Cu(DPPZ)(Phen)]²⁺ (Cu-DPPZ-Phen) (where phen = 1,10-phenanthroline, DPQ = dipyrido[3,2-ƒ:2',3'-h]quinoxaline and DPPZ = dipyrido[3,2-a:2',3'-c]phenazine). Our aim was to investigate the influence of the systematic extension of the ligated phenazine ligand in the G. mellonella model as a first step towards assessing the in-vivo tolerance and mode of action of the complex series with respect to the well-studied oxidative chemical nuclease, Cu-Phen. The Lethal Dose₅₀ (LD₅₀) values were established over dose ranges of 2 - 30 μg at 4-, 24-, 48- and 72 h by mortality assessment, with Cu-Phen eliciting the highest mortality at 4 h (Cu-Phen, 12.62 μg < Cu-DPQ-Phen, 21.53 μg < Cu-DPPZ-Phen, 26.07 μg). At other timepoints, a similar profile was observed as the phenazine π-backbone within the complex scaffold was extended. Assessment of both cellular response and related gene expression demonstrated that the complexes did not initiate an immune response. However, Label-Free Quantification proteomic data indicated the larval response was associated with upregulation of key proteins such as Glutathione S-transferase, purine synthesis and glycolysis/gluconeogenesis (e.g. fructose-bisphosphate aldolase and glyceraldehyde-3-phosphate). Both Cu-Phen and Cu-DPQ-Phen elicited a similar in-vivo response in contrast to Cu-DPPZ-Phen, which displayed a substantial increase in nitrogen detoxification proteins and proteins with calcium binding sites. Overall, the response of G. mellonella larvae exposure to the complex series is dominated by detoxification and metabolic proteome response mechanisms.

Steady-State Linear and Non-linear Optical Spectroscopy of Organic Chromophores and Bio-macromolecules

Bio-macromolecules as DNA, lipid membranes and (poly)peptides are essential compounds at the core of biological systems. The development of techniques and methodologies for their characterization is therefore necessary and of utmost interest, even though difficulties can be experienced due to their intrinsic complex nature. Among these methods, spectroscopies, relying on optical properties are especially important to determine their macromolecular structures and behaviors, as well as the possible interactions and reactivity with external dyes—often drugs or pollutants—that can (photo)sensitize the bio-macromolecule leading to eventual chemical modifications, thus damages. In this review, we will focus on the theoretical simulation of electronic spectroscopies of bio-macromolecules, considering their secondary structure and including their interaction with different kind of (photo)sensitizers. Namely, absorption, emission and electronic circular dichroism (CD) spectra are calculated and compared with the available experimental data. Non-linear properties will be also taken into account by two-photon absorption, a highly promising technique (i) to enhance absorption in the red and infra-red windows and (ii) to enhance spatial resolution. Methodologically, the implications of using implicit and explicit solvent, coupled to quantum and thermal samplings of the phase space, will be addressed. Especially, hybrid quantum mechanics/molecular mechanics (QM/MM) methods are explored for a comparison with solely QM methods, in order to address the necessity to consider an accurate description of environmental effects on spectroscopic properties of biological systems.

Interaction of osmium(ii) redox probes with DNA: insights from theory

In the course of developing ultrasensitive and quantitative electrochemical point-of-care analytical tools for genetic detection of infectious diseases, osmium(ii) metallointercalators were revealed to be suitable and efficient redox probes to monitor the in vitro DNA amplification [Defever etal, Anal. Chem., 2011, 83, 1815-1821]. In this work, we thus propose a complete computational protocol in order to evaluate the affinity between Os(ii) complexes with double-stranded DNA. This protocol is based on molecular dynamics, with the parametrization of the GAFF force field for the Os(ii) complexes presenting an octahedral environment with polypyridine ligands, and QM/QM' calculations to evaluate the binding energy. For three Os(ii) probes and different binding sites, molecular dynamics simulations and interaction energies calculated at the QM/QM' level are successively discussed and compared to experimental data in order to identify the most stable binding sites. The computational protocol we propose should then be used to design more efficient Os(ii) metallointercalators.