👤 Burhop A

The reactions of [Ru(NO)Cl5](2-) with glycine (Gly), L-alanine (L-Ala), L-valine (L-Val), L-proline (L-Pro), D-proline (D-Pro), L-serine (L-Ser), L-threonine (L-Thr), and L-tyrosine (L-Tyr) in n-butanol or n-propanol afforded eight new complexes (1-8) of the general formula [RuCl3(AA-H)(NO)](-), where AA = Gly, L-Ala, L-Val, L-Pro, D-Pro, L-Ser, L-Thr, and L-Tyr, respectively. The compounds were characterized by elemental analysis, electrospray ionization mass spectrometry (ESI-MS), (1)H NMR, UV-visible and ATR IR spectroscopy, cyclic voltammetry, and X-ray crystallography. X-ray crystallography studies have revealed that in all cases the same isomer type (from three theoretically possible) was isolated, namely mer(Cl),trans(NO,O)-[RuCl3(AA-H)(NO)], as was also recently reported for osmium analogues with Gly, L-Pro, and D-Pro (see Z. Anorg. Allg. Chem. 2013, 639, 1590-1597). Compounds 1, 4, 5, and 8 were investigated by ESI-MS with regard to their stability in aqueous solution and reactivity toward sodium ascorbate. In addition, cell culture experiments in three human cancer cell lines, namely, A549 (nonsmall cell lung carcinoma), CH1 (ovarian carcinoma), and SW480 (colon carcinoma), were performed, and the results are discussed in conjunction with the lipophilicity of compounds. Show less

We report the synthesis and characterization of eight half-sandwich cyclopentadienyl Ir^III pyridine complexes of the type [(η⁵-Cp^xph)Ir(phpy)Z]PF₆, in which Cp^xph = C₅Me₄C₆H₅ (tetramethyl(phenyl)cyclopentadienyl), phpy = 2-phenylpyridine as C^∧N-chelating ligand, and Z = pyridine (py) or a pyridine derivative. Three X-ray crystal structures have been determined. The monodentate py ligands blocked hydrolysis; however, antiproliferative studies showed that all the Ir compounds are highly active toward A2780, A549, and MCF-7 human cancer cells. In general the introduction of an electron-donating group (e.g., Me, NMe₂) at specific positions on the pyridine ring resulted in increased antiproliferative activity, whereas electron-withdrawing groups (e.g., COMe, COOMe, CONEt₂) decreased anticancer activity. Complex 5 displayed the highest anticancer activity, exhibiting submicromolar potency toward a range of cancer cell lines in the National Cancer Institute NCI-60 screen, ca. 5 times more potent than the clinical platinum(II) drug cisplatin. DNA binding appears not to be the major mechanism of action. Although complexes [(η⁵-Cp^xph)Ir(phpy)(py)]⁺ (1) and [(η⁵-Cp^xph)Ir(phpy)(4-NMe₂-py)]⁺ (5) did not cause cell apoptosis or cell cycle arrest after 24 h drug exposure in A2780 human ovarian cancer cells at IC₅₀ concentrations, they increased the level of reactive oxygen species (ROS) dramatically and led to a loss of mitochondrial membrane potential (ΔΨm), which appears to contribute to the anticancer activity. This class of organometallic Ir complexes has unusual features worthy of further exploration in the design of novel anticancer drugs. Show less

Re(I) tricarbonyl polypyridine-based complexes are particularly attractive metal complexes in the field of inorganic chemical biology due to their luminescent properties, ease of conjugation to targeting biomolecules, and the possibility to prepare their "hot" (99m)Tc analogues for radioimaging. In this study, we prepared and characterized a novel, "clickable" complex, [Re(2,2'-bipyridine)(3-ethynylpyridine)(CO)3](BF4) ([Re(CO) 3 (bipy)(py-alkyne)](BF 4 )), exhibiting the characteristic luminescent properties and moderate cytotoxicity of this general class of compound. Using Cu(I)-catalyzed "click" chemistry, the complex was efficiently attached to a lipidated peptide known to increase cell permeability, namely, the myristoylated HIV-1 Tat peptide (myr-Tat), to give Re-myr-Tat. Fluorescence microscopy localization in human cervical cancer cells (HeLa) confirmed enhanced cellular uptake of Re-myr-Tat compared with [Re(CO) 3 (bipy)(py-alkyne)](BF 4 ), and cytotoxicity studies showed that this resulted in an increase in potency to a level comparable with cisplatin (13.0 ± 2.0 μM). Show less

Over the recent years, several Re(I) organometallic compounds have been shown to be toxic to various cancer cell lines. However, these compounds lacked sufficient selectivity towards cancer tissues to be used as novel chemotherapeutic agents. In this study, we probe the potential of two known N,N-bis(quinolinoyl) Re(I) tricarbonyl complex derivatives, namely Re(I) tricarbonyl [N,N-bis(quinolin-2-ylmethyl)amino]-4-butane-1-amine (Re-NH₂) and Re(I) tricarbonyl [N,N-bis(quinolin-2-ylmethyl)amino]-5-valeric acid (Re-COOH), as photodynamic therapy (PDT) photosensitizers. Re-NH₂ and Re-COOH proved to be excellent singlet oxygen generators in a lipophilic environment with quantum yields of about 75%. Furthermore, we envisaged to improve the selectivity of Re-COOH via conjugation to two types of peptides, namely a nuclear localization signal (NLS) and a derivative of the neuropeptide bombesin, to form Re-NLS and Re-Bombesin, respectively. Fluorescent microscopy on cervical cancer cells (HeLa) showed that the conjugation of Re-COOH to NLS significantly enhanced the compound's accumulation into the cell nucleus and more specifically into its nucleoli. Importantly, in view of PDT applications, the cytotoxicity of the Re complexes and their bioconjugates increased significantly upon light irradiation. In particular, Re-Bombesin was found to be at least 20-fold more toxic after light irradiation. DNA photo-cleavage studies demonstrated that all compounds damaged DNA via singlet oxygen and, to a minor extent, superoxide production. Show less

The reaction of the dimer [Rh(III)(pentamethylcyclopentadienyl)(μ-Cl)Cl]2 ([Rh(III)(Cp*)(μ-Cl)Cl]2) with the hydroxypyrone ligands maltol and allomaltol affords complexes of the general formula [Rh(III)(Cp*)(L)Cl] under standard and microwave conditions. The organometallic compounds were characterized by standard analytical methods and in the case of the allomaltol derivative in the solid state by single-crystal X-ray diffraction analysis. The complexes showed similar cytotoxicity profiles and were proved to be moderately active against various human cancer cell lines. The stoichiometry and stability of these complexes were determined in aqueous solution by pH-potentiometry, (1)H NMR spectroscopy and UV-visible spectrophotometry. Speciation was studied in the presence and in the absence of chloride ions. Hydrolysis of [Rh(III)(Cp*)(H2O)3](2+) gave dimeric mixed hydroxido species [(Rh(III)(Cp*))2(μ-OH)3](+) and [(Rh(III)(Cp*))2(μ-OH)2Z2] (Z=H2O/Cl(-)). Formation of the mononuclear complexes [Rh(III)(Cp*)(L)Z] of maltol and allomaltol with similar and moderate stability was found. These species predominate at physiological pH and decompose only partially at micromolar concentrations. In addition, hydrolysis of the aqua complex or a chlorido/hydroxido co-ligand exchange resulted in the formation of the mixed-hydroxido species [Rh(III)(Cp*)(L)(OH)] in the basic pH range. Replacement of the chlorido by an aqua ligand in the complex [Rh(III)(Cp*)(L)Cl] was monitored and with the help of the equilibrium constants the extent of aquation at various chloride concentrations of the extra- and intracellular milieu can be predicted. Complexation of these Rh(III) complexes was compared to analogous [Ru(II)(η(6)-p-cymene)] species and higher conditional stabilities were found in the case of the Rh(III) compounds at pH7.4. Show less

Nucleotide excision repair is the sole mechanism for removing the major UV photoproducts from genomic DNA in human cells. In vitro with human cell-free extract or purified excision repair factors, the damage is removed from naked DNA or nucleosomes in the form of 24- to 32-nucleotide-long oligomers (nominal 30-mer) by dual incisions. Whether the DNA damage is removed from chromatin in vivo in a similar manner and what the fate of the excised oligomer was has not been known previously. Here, we demonstrate that dual incisions occur in vivo identical to the in vitro reaction. Further, we show that transcription-coupled repair, which operates in the absence of the XPC protein, also generates the nominal 30-mer in UV-irradiated XP-C mutant cells. Finally, we report that the excised 30-mer is released from the chromatin in complex with the repair factors TFIIH and XPG. Taken together, our results show the congruence of in vivo and in vitro data on nucleotide excision repair in humans. Show less

Cell lines are invaluable biomedical research tools, and recent literature has emphasized the importance of genotype authentication and characterization. In the present study, 24 out of 27 cell line identities were confirmed by short tandem repeat profiling. The molecular phenotypes of the 24 colon cancer cell lines were examined, and microsatellite instability (MSI) and CpG island methylator phenotype (CIMP) were determined, using the Bethesda panel mononucleotide repeat loci and two epimarker panels, respectively. Furthermore, the BRAF, KRAS and PIK3CA oncogenes were analyzed for mutations in known hotspots, while the entire coding sequences of the PTEN and TP53 tumor suppressors were investigated. Nine cell lines showed MSI. Thirteen and nine cell lines were found to be CIMP positive, using the Issa panel and the Weisenberger et al. panel, respectively. The latter was found to be superior for CIMP classification of colon cancer cell lines. Seventeen cell lines harbored disrupting TP53 mutations. Altogether, 20/24 cell lines had the mitogen-activated protein kinase pathway activating mutually exclusive KRAS or BRAF mutations. PIK3CA and PTEN mutations leading to hyperactivation of the phosphoinositide 3-kinase/AKT pathway were observed in 13/24 cell lines. Interestingly, in four cell lines there were no mutations in neither BRAF, KRAS, PIK3CA nor in PTEN. In conclusion, this study presents molecular features of a large number of colon cancer cell lines to aid the selection of suitable in vitro models for descriptive and functional research. Show less

Organometallic Ru(II), Os(II) and Rh(III) complexes of lapachol induce apoptosis in human tumour cell lines in the low μM range by a mode of action involving oxidative stress, especially in the case of the ruthenium compound. Show less

A series of half-sandwich Ru(II) arene complexes of the type [Ru(η(6)-arene)(L)Cl](PF6) 1-4, where arene is benzene (1, 2) or p-cymene (3, 4) and L is N-methylhomopiperazine (L1) or 1-(anthracen-10-ylmethyl)-4-methylhomopiperazine (L2), has been isolated and characterized by using spectral methods. The X-ray crystal structures of 2, 3 and 4 reveal that the compounds possess a pseudo-octahedral "piano-stool" structure equipped with the arene ligand as the seat and the bidentate ligand and the chloride ion as the legs of the stool. The DNA binding affinity determined using absorption spectral titrations with CT DNA and competitive DNA binding studies varies as 4 > 2 > 3 > 1, depending upon both the arene and diazacycloalkane ligands. Complexes 2 and 4 with higher DNA binding affinities show strong hypochromism (56%) and a large red-shift (2, 10; 4, 11 nm), which reveals that the anthracenyl moiety of the ligand is stacked into the DNA base pairs and that the arene ligand hydrophobicity also dictates the DNA binding affinity. In contrast, the monocationic complexes 1 and 3 are involved in electrostatic binding in the minor groove of DNA. The enhancement in viscosities of CT DNA upon binding to 2 and 4 are higher than those for 1 and 3 supporting the DNA binding modes of interaction inferred. All the complexes cleave DNA effectively even in the absence of an external agent and the cleavage ability is enhanced in the presence of an activator like H2O2. Tryptophan quenching measurements suggest that the protein binding affinity of the complexes varies as 4 > 2 > 3 > 1, which is the same as that for DNA binding and that the fluorescence quenching of BSA occurs through a static mechanism. The positive ΔH(0) and ΔS(0) values for BSA binding of complexes indicate that the interaction between the complexes and BSA is mainly hydrophobic in nature and the energy transfer efficiency has been analysed according to the Förster non-radiative energy transfer theory. The variation in the ability of complexes to cleave BSA in the presence of H2O2, namely, 4 > 2 > 3 > 1, as revealed from SDS-PAGE is consistent with their strong hydrophobic interaction with the protein. The IC50 values of 1-4 (IC50: 1, 28.1; 2, 23.1; 3, 26.2; 4, 16.8 μM at 24 h; IC50: 1, 19.0; 2, 15.9; 3, 18.1; 4, 9.7 μM at 48 h) obtained for MCF 7 breast cancer cells indicate that they have the potency to kill cancer cells in a time dependent manner, which is similar to cisplatin. The anticancer activity of complexes has been studied by employing various biochemical methods involving different staining agents, AO/EB and Hoechst 33258, which reveal that complexes 1-4 establish a specific mode of cell death in MCF 7 breast cancer cells. The comet assay has been employed to determine the extent of DNA fragmentation in cancer cells. Show less

A novel water soluble organometallic compound, [RuCp(mTPPMSNa)(2,2'-bipy)][CF3SO3] (TM85, where Cp=η(5)-cyclopentadienyl, mTPPMS=diphenylphosphane-benzene-3-sulfonate and 2,2'-bipy=2,2'-bipyridine) is presented herein. Studies of interactions with relevant proteins were performed to understand the behavior and mode of action of this complex in the biological environment. Electrochemical and fluorescence studies showed that TM85 strongly binds to albumin. Studies carried out to study the formation of TM85 which adducts with ubiquitin and cytochrome c were performed by electrospray ionization mass spectrometry (ESI-MS). Antitumor activity was evaluated against a variety of human cancer cell lines, namely A2780, A2780cisR, MCF7, MDAMB231, HT29, PC3 and V79 non-tumorigenic cells and compared with the reference drug cisplatin. TM85 cytotoxic effect was reduced in the presence of endocytosis modulators at low temperatures, suggesting an energy-dependent mechanism consistent with endocytosis. Ultrastructural analysis by transmission electron microscopy (TEM) revealed that TM85 targets the endomembranar system disrupting the Golgi and also affects the mitochondria. Disruption of plasma membrane observed by flow cytometry could lead to cellular damage and cell death. On the whole, the biological activity evaluated herein combined with the water solubility property suggests that complex TM85 could be a promising anticancer agent. Show less

With the aim of systematically studying fundamental structure-activity relationships as a basis for the development of Ru(II) arene complexes (arene = p-cymene or biphenyl) bearing mono-, bi-, or tridentate am(m)ine ligands as anticancer agents, a series of ammine, ethylenediamine, and diethylenetriamine complexes were prepared by different synthetic routes. Especially the synthesis of mono-, di-, and triammine complexes was found to be highly dependent on the reaction conditions, such as stoichiometry, temperature, and time. Hydrolysis and protein-binding studies were performed to determine the reactivity of the compounds, and only those containing chlorido ligands undergo aquation or form protein adducts. These properties correlate well with in vitro tumor-inhibiting potency of the compounds. The complexes were found to be active in anticancer assays when meeting the following criteria: stability in aqueous solution and low rates of hydrolysis and binding to proteins. Therefore, the complexes least reactive to proteins were found to be the most cytotoxic in cancer cells. In general, complexes with biphenyl as arene ligand inhibited the growth of tumor cells more effectively than the cymene analogues, consistent with the increase in lipophilicity. This study highlights the importance of finding a proper balance between reactivity and stability in the development of organometallic anticancer agents. Show less

An efficient drug delivery strategy is presented for novel anticancer amphiphilic ruthenium anionic complexes, based on the formation of stable nanoparticles with the cationic lipid 1,2-dioleyl-3-trimethylammoniumpropane chloride (DOTAP). This strategy is aimed at ensuring high ruthenium content within the formulation, long half-life in physiological media, and enhanced cell uptake. An in-depth microstructural characterization of the aggregates obtained mixing the ruthenium complex and the phospholipid carrier at 50/50 molar ratio is realized by combining a variety of techniques, including dynamic light scattering (DLS), small angle neutron scattering (SANS), neutron reflectivity (NR), electron paramagnetic resonance (EPR), and zeta potential measurements. The in vitro bioactivity profile of the Ru-loaded nanoparticles is investigated on human and non-human cancer cell lines, showing IC(50) values in the low μM range against MCF-7 and WiDr cells, that is, proving to be 10-20-fold more active than AziRu, a previously synthesized NAMI-A analog, used for control. Fluorescence microscopy studies demonstrate that the amphiphilic Ru-complex/DOTAP formulations, added with rhodamine-B, are efficiently and rapidly incorporated in human MCF-7 breast adenocarcinoma cells. The intracellular fate of the amphiphilic Ru-complexes was investigated in the same in vitro model by means of an ad hoc designed fluorescently tagged analog, which exhibited a marked tendency to accumulate within or in proximity of the nuclei. Show less

d-glucose end-capped polylactide ruthenium cyclopentadienyl complex (RuPMC) was newly synthesized by a straightforward method. RuPMC was tested against human MCF7 and MDAMB231 breast and A2780 ovarian adenocarcinoma revealing IC50 values in the micromolar range. A pH dependent hydrolysis is advanced by preliminary UV-visible spectroscopy. Cellular distribution studies showed that RuPMC is predominantly found in the nucleus and in the membrane. Data suggest potential application of RuPMC as a new drug delivery system for Ru(II)Cp compounds. Show less

New cationic, half-sandwich Ru(II) arene compounds of general formula [(η(6)-arene)RuCl(κ(2)-N,N-L)]X (where L are functionalized phenanthrolines such as 1,10-phenanthroline-5-amine (aphen); 5,6-epoxy-5,6-dihydro-[1,10]phenanthroline (ephen); or 4,7-dihydroxy-1,10-phenanthroline (dhphen)) have been prepared to study their anticancer potential. All the isolated complexes have been fully characterized by spectroscopic and analytical techniques. The structure of endo-[(η(6)-p-cymene)RuCl(κ(2)-N,N-ephen)]BF4, [2a](BF4), has been determined by X-ray crystallography. The in vitro cytotoxicity of the aphen and ephen phenanthrolines and their Ru derivatives [(η(6)-p-cymene)RuCl(κ(2)-N,N-L)]Cl ([1a]Cl and [2a]Cl, respectively) assessed in tumour cell lines has shown that the free ligands are more active than the organometallic products, with aphen being the most potent specimen. Furthermore, the binding interaction of both [1a]Cl and aphen with calf thymus DNA (CT-DNA) has been investigated using a variety of thermodynamic and kinetic techniques. The aphen free ligand intercalates into DNA at low ligand content, whereas [1a]Cl forms with DNA a bifunctional partially intercalated-covalent complex, in which the intercalation constant is nearly three orders of magnitude lower than that of aphen. This finding demonstrates that the covalent binding noticeably weakens the intercalation, a feature presumably related to the higher cytotoxic activity of aphen relative to that of [1a]Cl. Show less

The synthesis and in vitro cytotoxicity of a series of Ru(II)(arene) complexes with carbohydrate-derived phosphite ligands and various arene co-ligands is described. The arene ligand has a strong influence on the in vitro anticancer activity of this series of compounds, which correlates fairly well with cellular accumulation. The most lipophilic compound bearing a biphenyl moiety and a cyclohexylidene-protected carbohydrate is the most cytotoxic with unprecedented IC50 values for the compound class in three human cancer cell lines. This compound shows reactivity to the DNA model nucleobase 9-ethylguanine, but does not alter the secondary structure of plasmid DNA, indicating that other biological targets are responsible for its cytotoxic effect. Show less

Four new ruthenium(II) polypyridyl complexes-[Ru(phen)2(7-F-dppz)](2+) (7-F-dppz is 7-fluorodipyrido[3,2-a:2',3'-c]phenazine, phen is 1,10-phenanthroline), [Ru(bpy)2(7-F-dppz)](2+)(2) (bpy is 2,2'-bipyridine), [Ru(dmb)2(7-F-dppz)](2+) (dmb is 4,4'-dimethyl-2,2'-bipyridine), and [Ru(hdpa)2(7-F-dppz)](2+) (hdpa is 2,2'-dipyridylamine)-have been synthesized and characterized. Their DNA binding behavior has been explored by various spectroscopic titrations and viscosity measurements, which indicated that all the complexes bind to calf thymus DNA by means of intercalation with different binding strengths. The light switching properties of these complexes have been evaluated, and their antimicrobial activities have been investigated. Photoinduced DNA cleavage studies have been performed. All the complexes exhibited efficient photocleavage of pBR322 DNA on irradiation. The cytotoxicity of these complexes has been evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay with various tumor cell lines. Cellular uptake was studied by flow cytometry and confocal microscopy. Flow cytometry experiments showed that these complexes induced apoptosis of HeLa cell lines. Show less

Smart design and efficient synthesis of benzimidazole Ru, Ir and Rh cyclometalated complexes are reported with promising cytotoxic activity against HT29, T47D, A2780 and A2780cisR cancer cell lines. Their apoptosis, accumulation, cell cycle arrest, protein binding and DNA binding effects are also discussed. Show less

A straightforward methodology for the synthesis of conjugates between a cytotoxic organometallic ruthenium(II) complex and amino- and guanidinoglycosides, as potential RNA-targeted anticancer compounds, is described. Under microwave irradiation, the imidazole ligand incorporated on the aminoglycoside moiety (neamine or neomycin) was found to replace one triphenylphosphine ligand from the ruthenium precursor [(η(6)-p-cym)RuCl(PPh3)2](+), allowing the assembly of the target conjugates. The guanidinylated analogue was easily prepared from the neomycin-ruthenium conjugate by reaction with N,N'-di-Boc-N″-triflylguanidine, a powerful guanidinylating reagent that was compatible with the integrity of the metal complex. All conjugates were purified by semipreparative high-performance liquid chromatography (HPLC) and characterized by electrospray ionization (ESI) and matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) and NMR spectroscopy. The cytotoxicity of the compounds was tested in MCF-7 (breast) and DU-145 (prostate) human cancer cells, as well as in the normal HEK293 (Human Embryonic Kidney) cell line, revealing a dependence on the nature of the glycoside moiety and the type of cell (cancer or healthy). Indeed, the neomycin-ruthenium conjugate (2) displayed moderate antiproliferative activity in both cancer cell lines (IC50 ≈ 80 μM), whereas the neamine conjugate (4) was inactive (IC50 ≈ 200 μM). However, the guanidinylated analogue of the neomycin-ruthenium conjugate (3) required much lower concentrations than the parent conjugate for equal effect (IC50 = 7.17 μM in DU-145 and IC50 = 11.33 μM in MCF-7). Although the same ranking in antiproliferative activity was found in the nontumorigenic cell line (3 ≫ 2 > 4), IC50 values indicate that aminoglycoside-containing conjugates are about 2-fold more cytotoxic in normal cells (e.g., IC50 = 49.4 μM for 2) than in cancer cells, whereas an opposite tendency was found with the guanidinylated conjugate, since its cytotoxicity in the normal cell line (IC50 = 12.75 μM for 3) was similar or even lower than that found in MCF-7 and DU-145 cancer cell lines, respectively. Cell uptake studies performed by ICP-MS with conjugates 2 and 3 revealed that guanidinylation of the neomycin moiety had a positive effect on accumulation (about 3-fold higher in DU-145 and 4-fold higher in HEK293), which correlates well with the higher antiproliferative activity of 3. Interestingly, despite the slightly higher accumulation in the normal cell than in the cancer cell line (about 1.4-fold), guanidinoneomycin-ruthenium conjugate (3) was more cytotoxic to cancer cells (about 1.8-fold), whereas the opposite tendency applied for neomycin-ruthenium conjugate (2). Such differences in cytotoxic activity and cellular accumulation between cancer and normal cells open the way to the creation of more selective, less toxic anticancer metallodrugs by conjugating cytotoxic metal-based complexes such as ruthenium(II) arene derivatives to guanidinoglycosides. Show less

Ru(II)(η(6)-arene) complexes, especially with bioactive ligands, are considered to be very promising compounds for anticancer drug design. We have shown recently that Ru(II)(η(6)-p-cymene) complexes with 3-hydroxyflavone ligands exhibit very high in vitro cytotoxic activities correlating with a strong inhibition of topoisomerase IIα. In order to expand our knowledge about the structure-activity relationships and to determine the impact of lipophilicity of the arene ligand and of the hydrolysis rate on anticancer activity, a series of novel 3-hydroxyflavone derived Ru(II)(η(6)-arene) complexes were synthesised. Furthermore, the impact of the heteroatom in the bioactive ligand backbone was studied by comparing the cytotoxic activity of Ru(II)(η(6)-p-cymene) complexes of 3-hydroxyquinolinone ligands with that of their 3-hydroxyflavone analogues. To better understand the behaviour of these Ru(II) complexes in aqueous solution, the stability constants and pK(a) values for complexes and the corresponding ligands were determined. Furthermore, the interaction with the DNA model 5'-GMP and with a series of amino acids was studied in order to identify potential biological target structures. Show less

Rhodium(I) complexes bearing N-heterocyclic carbene (NHC) ligands have been widely used in catalytic chemistry, but there are very few reports of biological properties of these organometallics. A series of Rh(I)-NHC derivatives with 1,5-cyclooctadiene and CO as secondary ligands were synthesized, characterized, and biologically investigated as prospective antitumor drug candidates. Pronounced antiproliferative effects were noted for all complexes, along with moderate inhibitory activity of thioredoxin reductase (TrxR) and efficient binding to biomolecules (DNA, albumin). Biodistribution studies showed that the presence of albumin lowered the cellular uptake and confirmed the transport of rhodium into the nuclei. Changes in the mitochondrial membrane potential (MMP) were observed as well as DNA fragmentation in wild-type and daunorubicin- or vincristine-resistant Nalm-6 leukemia cells. Overall, these studies indicated that Rh(I)-NHC fragments could be used as partial structures of new antitumor agents, in particular in those drugs designed to address resistant malignant tissues. Show less

The regulation of hydrogen ion concentration (pH) is fundamental to cell viability, metabolism, and enzymatic function. Within the nervous system, the control of pH is also involved in diverse and dynamic processes including development, synaptic transmission, and the control of network excitability. As pH affects neuronal activity, and can also itself be altered by neuronal activity, the existence of tools to accurately measure hydrogen ion fluctuations is important for understanding the role pH plays under physiological and pathological conditions. Outside of their use as a marker of synaptic release, genetically encoded pH sensors have not been utilized to study hydrogen ion fluxes associated with network activity. By combining whole-cell patch clamp with simultaneous two-photon or confocal imaging, we quantified the amplitude and time course of neuronal, intracellular, acidic transients evoked by epileptiform activity in two separate in vitro models of temporal lobe epilepsy. In doing so, we demonstrate the suitability of three genetically encoded pH sensors: deGFP4, E(2)GFP, and Cl-sensor for investigating activity-dependent pH changes at the level of single neurons. Show less

Novel ruthenium-letrozole complexes have been prepared, and cell viability of two human cancer cell types (breast and glioblastoma) was determined. Some ruthenium compounds are known for their cytotoxicity to cancer cells, whereas letrozole is an aromatase inhibitor administered after surgery to post-menopausal women with hormonally responsive breast cancer. A significant in vitro activity was established for complex 5·Let against breast cancer MCF-7 cells and significantly lower activity against glioblastoma U251N cells. The activity of 5·Let was even higher than that of 4, a compound analogous to the well-known drug RAPTA-C. Results from the combination of 5·Let (or 4) with 3-methyladenine (3-MA) or with curcumin, respectively, revealed that the resultant cancer cell death likely involves 5·Let-induced autophagy. Show less

The in vitro antiproliferative activity of the title compound on five tumor cell lines shows preference for the colon-rectal tumor HCT116, IC(50) = 13.98 μM, followed by breast MCF7 (19.58 μM) and ovarian A2780 (23.38 μM) cell lines; human glioblastoma U-87 and lung carcinoma A549 are less sensitive. A commercial curcumin reagent, also containing demethoxy and bis-demethoxy curcumin, was used to synthesize the title compound, and so (p-cymene)Ru(demethoxy-curcuminato)chloro was also isolated and chemically characterized. The crystal structure of the title compound shows (1) the chlorine atom linking two neighboring complexes through H-bonds with two O(hydroxyl), forming an infinite two-step network; (2) significant twist in the curcuminato, 20° between the planes of the two phenyl rings. This was also seen in the docking of the Ru-complex onto a rich guanine B-DNA decamer, where a Ru-N7(guanine) interaction is detected. This Ru-N7(guanine) interaction is also seen with ESI-MS on a Ru-complex-guanosine derivative. Show less

RuII(arene) complexes have been shown to be promising anticancer agents, capable of overcoming major drawbacks of currently used chemotherapeutics. We have synthesized RuII(η6-arene) compounds carrying bioactive flavonol ligands with the aim to obtain multitargeted anticancer agents. To validate this concept, studies on the mode of action of the complexes were conducted which indicated that they form covalent bonds to DNA, have only minor impact on the cell cycle, but inhibit CDK2 and topoisomerase IIα in vitro. The cytotoxic activity was determined in human cancer cell lines, resulting in very low IC50 values as compared to other RuII(arene) complexes and showing a structure-activity relationship dependent on the substitution pattern of the flavonol ligand. Furthermore, the inhibition of cell growth correlates well with the topoisomerase inhibitory activity. Compared to the flavonol ligands, the RuII(η6-p-cymene) complexes are more potent antiproliferative agents, which can be explained by potential multitargeted properties. Show less

A great majority of the Ru complexes currently studied in anticancer research exert their antiproliferative activity, at least partially, through ligand exchange. In recent years, however, coordinatively saturated and substitutionally inert polypyridyl Ru(II) compounds have emerged as potential anticancer drug candidates. In this work, we present the synthesis and detailed characterization of two novel inert Ru(II) complexes, namely, [Ru(bipy)(2)(Cpp-NH-Hex-COOH)](2+) (2) and [Ru(dppz)(2)(CppH)](2+) (3) (bipy = 2,2'-bipyridine; CppH = 2-(2'-pyridyl)pyrimidine-4-carboxylic acid; Cpp-NH-Hex-COOH = 6-(2-(pyridin-2-yl)pyrimidine-4-carboxamido)hexanoic acid; dppz = dipyrido[3,2-a:2',3'-c]phenazine). 3 is of particular interest as it was found to have IC(50) values comparable to cisplatin, a benchmark standard in the field, on three cancer cell lines and a better activity on one cisplatin-resistant cell line than cisplatin itself. The mechanism of action of 3 was then investigated in detail and it could be demonstrated that, although 3 binds to calf-thymus DNA by intercalation, the biological effects that it induces did not involve a nuclear DNA related mode of action. On the contrary, confocal microscopy colocalization studies in HeLa cells showed that 3 specifically targeted mitochondria. This was further correlated by ruthenium quantification using High-resolution atomic absorption spectrometry. Furthermore, as determined by two independent assays, 3 induced apoptosis at a relatively late stage of treatment. The generation of reactive oxygen species could be excluded as the cause of the observed cytotoxicity. It was demonstrated that the mitochondrial membrane potential in HeLa was impaired by 3 as early as 2 h after its introduction and even more with increasing time. Show less

The pathways involved in cellular uptake and accumulation of iminopyridine complexes of general formula [Ru(η(6)-p-cymene)(N,N-dimethyl-N'-[(E)-pyridine-2-ylmethylidene]benzene-1,4-diamine)X]PF(6) bearing two different halido ligands X = Cl or I, have been explored. The ratio of passive/active cellular accumulation of Ru in A2780 human ovarian cancer cells is compared and contrasted with cisplatin. Also, saturation of cellular uptake, time-dependence of cellular influx/efflux equilibria, together with endocytotic pathways such as caveolae and facilitated diffusion are investigated and discussed. Temperature dependence studies of Ru accumulation in the A2780 cells show that in contrast to cisplatin (CDDP) and chlorido complex , which are taken up largely through active transport, the iodido complex enters cells via passive transport. The cellular efflux of Ru is slow (ca. 25% retained after 72 h) and is partially inhibited by verapamil, implicating the P-gp protein in the efflux mechanism. Ouabain inhibition experiments suggest that the cellular uptake of these ruthenium complexes relies at least in part on facilitated diffusion, and in particular is dependent on the membrane potential. In addition the finding that depletion of cellular ATP with antimycin A had little effect on cellular Ru accumulation from iodido complex is consistent with passive diffusion. In contrast, ATP depletion caused a major increase in cellular accumulation of ruthenium from chlorido complex . Show less

Anthracene derivatives of ruthenium(II) arene compounds with 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane (pta) or a sugar phosphite ligand, viz., 3,5,6-bicyclophosphite-1,2-O-isopropylidene-α-d-glucofuranoside, were prepared in order to evaluate their anticancer properties compared to the parent compounds and to use them as models for intracellular visualization by fluorescence microscopy. Similar IC(50) values were obtained in cell proliferation assays, and similar levels of uptake and accumulation were also established. The X-ray structure of [{Ru(η(6)-C(6)H(5)CH(2)NHCO-anthracene)Cl(2)(pta)] is also reported. Show less

A modified paullone ligand bearing a TEMPO free-radical unit (HL) and its ruthenium(II) and osmium(II)-arene complexes [M(p-cymene)(HL)Cl]Cl·nH(2)O (M = Ru, Os) exhibit high antiproliferative activity in human cancer cell lines. Show less

Aminophosphines 2-(diphenylphosphino)-1-methylimidazole (dpim) and diphenyl-2-pyridylphosphine (PPh(2)py) have been used to prepare two series of Ru(II) arene complexes of formulae [(η(6)-p-cymene)Ru(κ(2)-O,O'-X)(κ(1)-P-dpim)]Y (series a: 1a·Y-3a·Y) and [(η(6)-p-cymene)Ru(κ(2)-O,O'-X)(κ(1)-P-PPh(2)py)]Y (series b: 1b·Y-3b·Y) (where X=acac, acetylacetonate; bzac, benzoyl acetonate; dbzm, dibenzoyl methanoate; Y=BF(4), BPh(4)). The structures of 1a·BF(4), 1a·BPh(4), 3a·BF(4), 1b·BPh(4) and 3b·BPh(4) were determined by X-ray diffraction. The tetrafluoroborate derivatives are more soluble in organic solvents than their tetraphenylborate counterparts. Five BF(4)(-) derivatives (all except the unstable 1b·BF(4)) were selected to evaluate the cytotoxic behavior in vitro against the human cancer cell lines MCF-7 (breast cancer) and CAPAN-1 (pancreatic cancer). 2b·BF(4) and 3b·BF(4) exhibited IC(50) values similar to those of cisplatin. Electrophoresis and AFM studies showed good correspondence between the biological activity levels of 2b·BF(4) and 3b·BF(4) and their ability to modify the DNA structure. Hydrolytic studies indicate that aquation could be involved in the activation mechanism of these complexes and confirm that the hydrolysis rate of 3b·BF(4) is higher than that of 3a·BF(4). Thus, the cytotoxic activity trends are explained in terms of the higher reactivity of derivatives from series b, which in turn is rationalized as being the result of the electronic features of dpim and PPh(2)py established by cyclic voltammetry measurements. Show less

With the aim of expanding the structure-activity relationship investigation, the series of Ru(II) half sandwich coordination compounds of the type [Ru([9]aneS3)(chel)(L)](n+) previously described by us (where [9]aneS3 is the neutral face-capping ligand 1,4,7-trithiacyclononane, chel is a neutral or anonic chelating ligand, L = Cl(-) or dmso-S, n = 0-2) was extended to 1,4,7-triazacyclononane ([9]aneN3). In addition, new neutral N-N, and anionic N-O and O-O chelating ligands, i.e. dach (trans-1,2-diaminocyclohexane), pic(-) (picolinate), and acac(-) (acetylacetonate), were investigated in combination with both [9]aneS3 and [9]aneN3. Overall, ten new half-sandwich complexes were prepared and fully characterized and their chemical behaviour in aqueous solution was established. The single-crystal X-ray structures of eight of them, including the versatile precursor [Ru([9]aneN3)(dmso-S)(2)Cl]Cl (9), were also determined. The results of in vitro antiproliferative tests performed on selected compounds against MDA-MB-231 human mammary carcinoma cells confirmed that, in this series, only compounds that hydrolyse the monodentate ligand at a reasonable rate show moderate activity, provided that the chelate ligand is a hydrogen bond donor. Show less