Synthesis, characterization and biological evaluation of novel Ru(II)-arene complexes containing intercalating ligands

Ruthenium p-Cymene Complexes Incorporating Substituted Pyridine-Quinoline-Based Ligands: Synthesis, Characterization, and Cytotoxic Properties

Organometallic complexes of the formula [Ru(N^N)(p-cymene)Cl][X] (N^N = bidentate polypyridyl ligands, p-cymene = 1-methyl-4-(1-methylethyl)-benzene, X = counter anion), are currently studied as possible candidates for the potential treatment of cancer. Searching for new organometallic compounds with good to moderate cytotoxic activities, a series of mononuclear water-soluble ruthenium(II)-arene complexes incorporating substituted pyridine-quinoline ligands, with pending -CH2OH, -CO2H and -CO2Me groups in the 4-position of quinoline ring, were synthesized, for the first time, to study their possible effect to modulate the activity of the ruthenium p-cymene complexes. These include the [Ru(η6-p-cymene)(pqhyme)Cl][X] (X = Cl- (1-Cl), PF6- (1-PF6), pqhyme = 4-hydroxymethyl-2-(pyridin-2-yl)quinoline), [Ru(η6-p-cymene)(pqca)Cl][Cl] ((2-Cl), pqca = 4-carboxy-2-(pyridin-2-yl)quinoline), and [Ru(η6-p-cymene)(pqcame)Cl][X] (X = Cl- (3-Cl), PF6- (3-PF6), pqcame = 4-carboxymethyl-2-(pyridin-2-yl)quinoline) complexes, respectively. Identification of the complexes was based on multinuclear NMR and ATR-IR spectroscopic methods, elemental analysis, conductivity measurements, UV-Vis spectroscopic, and ESI-HRMS techniques. The solid-state structures of 1-PF6 and 3-PF6 have been elucidated by single-crystal X-ray diffraction revealing a three-legged piano stool geometry. This is the first time that the in vitro cytotoxic activities of these complexes are studied. These were conducted in HEK293T (human embryonic kidney cells) and HeLa cells (cervical cancer cells) via the MTT assay. The results show poor in vitro anticancer activities for the HeLa cancer cell lines and 3-Cl proved to be the most potent (IC50 > 80 μΜ). In both cell lines, the cytotoxicity of the ligand precursor pqhyme is significantly higher than that of cisplatin.

Re(I)[2-aryl-1H-imidazo[4,5-f][1,10]phenanthroline] tricarbonyl chloride complexes for selective cancer therapy via a potential DNA damage mechanism

Recently, achieving selective cancer therapy with trifling side effects has been a great challenge in the eradication of cancer. Thus, to amplify the cytoselective approach of complexes, herein, we developed a series of Re(I)[2-aryl-1H-imidazo[4,5-f][1,10]phenanthroline] tricarbonyl chloride complexes and screened their potency against HeLa and MCF-7 cell lines together with the evaluation of their toxicity towards a normal kidney cell line (HEK-293). On meticulous investigation, complex [ReI(CO)3Cl(K2-N,N-(2c))] (3c) was found to be the most potent anticancer entity among other complexes. Complex 3c also showed competency to induce apoptosis in MCF-7 cells through G2/M phase cell-cycle arrest in association with the generation of ample reactive oxygen species (ROS), eventually leading to DNA intercalation and internucleosomal cleavage. The order of the cytotoxicity of these complexes depended on their lipophilic character and the electron-withdrawing halogen substitution at the para-position of the phenyl ring in the imidazophenanthroline ligand.

CuAAC "Click"-Derived Luminescent 2-(2-(4-(4-(Pyridin-2-yl)-1H-1,2,3-triazol-1-yl)butoxy)phenyl)benzo[d]thiazole-Based Ru(II)/Ir(III)/Re(I) Complexes as Anticancer Agents

To enhance the cytoselective behavior of the complexes, we intended to develop a CuAAC "click"-derived synthetic protocol for the preparation of 2-(2-(4-(4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)butoxy)phenyl)benzo[d]thiazole-based Ru(II)/Ir(III)/Re(I) complexes, and their cytotoxicity against three different cancer cell lines (MCF-7, HeLa, and U87MG) in consort with one normal cell line (HEK-293) was evaluated. In our detailed investigations, the significant cytotoxic nature of the Ru(II) complex 7a compared to Ir(III) and Re(I) complexes (7b and 7c, respectively) was observed. Complex 7a was capable of MCF-7 cell apoptosis via the inhibition of both S- and G2/M-phase cell cycle arrest in association with a substantial quantity of ROS production and DNA intercalation.

Interaction of organoruthenium(II)-polypyridyl complexes with DNA and BSA

The interaction of four arene ruthenium complexes [(η⁶-p-cymene)Ru(Me₂dppz)Cl]PF₆ (1) with Me₂dppz = 11,12-dimethyldipyrido[3,2-a:2',3'-c]phenazine, [(η⁶-p-cymene)Ru(aip)Cl]PF₆ (2) with aip = 2-(9-anthryl)-1H-imidazo[4,5-f][1,10] phenanthroline), ([(ƞ⁶-toluene)Ru(ppf)Cl]PF₆) (3) and ([(ƞ⁶-p-cymene)Ru(ppf)Cl]PF₆) (4) with ppf = pyrido[2',3':5,6] pyrazino[2,3-f][1,10]phenanthroline with calf thymus DNA were investigated. All of four complexes exhibit DNA-binding activity. UV-Vis spectroscopic studies revealed the intrinsic binding constants of the order 10⁴ M^-1 of magnitude, indicating non-intercalative mode. Fluorescence quenching analysis showed that all complexes interfere with intercalator ethidium bromide and minor groove binder Hoechst 33258 by a singular non-intercalative mode with extent that differs by two orders of magnitude. Gel electrophoresis results on DNA cleavage assay demonstrated that all complexes produced conformational changes of supercoiled circular plasmid pUC19 in concentration dependent way. The results of fluorescence titration bovine serum albumin by 1, 2, 3 and 4 showed that all complexes significantly quench tryptophan residues fluorescence through a static quenching mechanism. The antimicrobial activity against both Gram-positive and Gram-negative bacteria analyzed. Complex 1 was most active, even on Escherichia coli was more active than positive control compound.

Iridium(III)-Cp*-(imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol analogues as hypoxia active, GSH-resistant cancer cytoselective and mitochondria-targeting cancer stem cell therapeutic agents

Herein, we have introduced a series of iridium(III)-Cp*-(imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol complexes via a convenient synthetic methodology, which act as hypoxia active and glutathione-resistant anticancer metallotherapeutics. The [Ir^III(Cp*)(L5)(Cl)](PF₆) (IrL5) complex exhibited the best cytoselectivity, GSH resistance and hypoxia effectivity in HeLa and Caco-2 cells among the synthesized complexes. IrL5 also exhibited highly cytotoxic effects on the HCT-116 CSC cell line. This complex was localized in the mitochondria and subsequent mitochondrial dysfunction was observed via MMP alteration and ROS generation on colorectal cancer stem cells. Cell cycle analysis also established the potential of this complex in mediating G2/M phase cell cycle arrest.

GSH-resistant and highly cytoselective ruthenium(II)-p-cymene-(imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol complexes as potential anticancer agents

To avoid the side effects of the current popular platinum-based anticancer drugs, researchers have made tireless attempts to design appropriate GSH-resistant Ru(ii)-arene complexes. In this regard, luminescent ruthenium(ii)-p-cymene-imidazophenanthroline complexes were developed as promising highly cytoselective cancer theraputic agents for HeLa and Caco-2 cells.

Why Concurrent CDDP and Radiotherapy Has Synergistic Antitumor Effects: A Review of In Vitro Experimental and Clinical-Based Studies

Chemo-radiotherapy, which combines chemotherapy with radiotherapy, has been clinically practiced since the 1970s, and various anticancer drugs have been shown to have a synergistic effect when used in combination with radiotherapy. In particular, cisplatin (CDDP), which is often the cornerstone of multi-drug combination cancer therapies, is highly versatile and frequently used in combination with radiotherapy for the treatment of many cancers. Therefore, the mechanisms underlying the synergistic effect of CDDP and radiotherapy have been widely investigated, although no definitive conclusions have been reached. We present a review of the combined use of CDDP and radiotherapy, including the latest findings, and propose a mechanism that could explain their synergistic effects. Our hypothesis involves the concepts of overlap and complementation. “Overlap” refers to the overlapping reactions of CDDP and radiation-induced excessive oxidative loading, which lead to accumulating damage to cell components, mostly within the cytoplasm. “Complementation” refers to the complementary functions of CDDP and radiation that lead to DNA damage, primarily in the nucleus. In fact, the two concepts are inseparable, but conceptualizing them separately will help us understand the mechanism underlying the synergism between radiation therapy and other anticancer drugs, and help us to design future radiosensitizers.

Mitochondria specific highly cytoselective iridium(iii)-Cp* dipyridophenazine (dppz) complexes as cancer cell imaging agents

Cancer is the most incurable pernicious disease to date after cardiovascular disease with an immeasurable rate of mortality. However, effective cancer medication and therapy are still castles in the sky to researchers. Therefore, in search of an appropriate strategy to annihilate cancer, we have designed a set of Ir(iii)-Cp* dipyridophenazine complexes as luminescent anticancer agents combining the cancer inhibiting potency of the planar dipyridophenazine (dppz) moiety through DNA interaction and mitochondrial dysfunction with the wonderful photoluminescence ability and target specificity of iridium metal. Hence, with the synergy of these dual aspects in the same system, we have aspired to emphasize the theranostic approach of cancer treatment in the present study by preparing effective, aqueous-soluble, mitochondria-targeting, highly cytoselective, luminescent, cancer cell-permeable scaffolds, enabling diagnosis as well as the healing of cancer cells in the body. Here, the presence of the cyclopentadienyl (Cp*) moiety in association with the fluorine group has boosted the lipophilic character of the complexes. Also, the cytotoxicity screening of the prepared Cp*Ir(iii)-dipyridophenazine complexes (IrL1-IrL7) against colorectal adenocarcinoma cells (Caco-2) and human epitheloid cervix carcinoma cells (HeLa) clearly identified them as potential anticancer agents and imaging studies unveiled their superb cellular imaging properties. Among them, the complex [(η⁵-Cp*)IrCl(11-fluorodipyrido[3,2-a:2',3'-c]phenazine)] (IrL6) achieved the best cytoselectivity. However, the superiority of the anticancer potency of [(η⁵-Cp*)IrCl(benzo[i]dipyrido[3,2-a:2',3'-c]phenazine)] (IrL3) was also corroborated by its activity against the most aggressive colorectal carcinoma cell line (HT-29), whereas (η⁵-Cp*)IrCl(11-(trifluoromethyl)dipyrido[3,2-a:2',3'-c]phenazine (IrL5) came into the limelight as the best theranostic agent as it showed remarkable cytoselectivity as well as significant cellular imaging properties, endowing it with the highest quantum yield value among all the complexes.

DNA-Binding Capabilities and Anticancer Activities of Ruthenium(II) Cymene Complexes with (Poly)cyclic Aromatic Diamine Ligands

Ruthenium(II) arene complexes of the general formula [RuCl(η⁶-p-cymene)(diamine)]PF₆ (diamine = 1,2-diaminobenzene (1), 2,3-diaminonaphthalene (2), 9,10-diaminophenanthrene (3), 2,3-diaminophenazine (4), and 1,2-diaminoanthraquinone (5) were synthesized. Chloro/aqua exchange was evaluated experimentally for complexes 1 and 2. The exchange process was investigated theoretically for all complexes, revealing relatively fast exchange with no significant influence from the polycyclic aromatic diamines. The calf thymus DNA (CT-DNA) binding of the complexes increased dramatically upon extending the aromatic component of the diamines, as evaluated by changes in absorption spectra upon titration with different concentrations of CT-DNA. An intercalation binding mode was established for the complexes using the increase in the relative viscosity of the CT-DNA following addition of complexes 1 and 2. Theoretical studies showed strong preference for replacement of water by guanine for all the complexes, and relatively strong Ru-N_guanine bonds. The plane of the aromatic systems can assume angles that support non-classical interactions with the DNA and covalent binding, leading to higher binding affinities. The ruthenium arenes illustrated in this study have promising anticancer activities, with the half maximal inhibitory concentration (IC₅₀) values comparable to or better than cisplatin against three cell lines.

Ru(II) Complexes Bearing O, O-Chelated Ligands Induced Apoptosis in A549 Cells through the Mitochondrial Apoptotic Pathway

Two new Ru(II) complexes containing O, O-chelated ligands, Ru(dip)₂(SA) (Ru-1) and Ru(dmp)₂(SA) (Ru-2) (dip = 4,7-diphenyl-1,10-phenanthroline; dmp = 2,9-dimethyl-1,10-phenanthroline; SA = salicylate) were synthesized to evaluate their cytotoxicity in vitro. These complexes were found to exhibit moderate antitumor activity to different types of human cancers, including A549 (human lung carcinoma), MCF-7 (breast cancer), HeLa (human cervical cancer), and HepG2 (human hepatocellular carcinoma) cell lines, but displayed low toxicity to human normal cell lines BEAS-2B (immortalized human bronchial epithelial cells) when compared with that of cisplatin. Further studies revealed that these complexes could induce apoptosis in A549 cells, including activating caspase family proteins and poly (ADP-ribose) polymerase (PARP), reducing Bcl-2/Bax and Bcl-xl/Bad ratio, enhancing cellular reactive oxygen species (ROS) accumulation, triggering DNA damage, decreasing mitochondrial membrane potential (MMP), and leading cytochrome c release from mitochondria. Notably, complex Ru-1 showed low toxicity to developing zebrafish embryos. The obtained results suggest that these new synthetic complexes have the potential to be developed as low-toxicity agents for lung cancer treatment.

Synthesis, chemical characterization, PARP inhibition, DNA binding and cellular uptake of novel ruthenium(II)-arene complexes bearing benzamide derivatives in human breast cancer cells

Inhibitors of poly(ADP-ribose) polymerase-1 (PARP-1) showed remarkable clinical efficacy in BRCA-mutated tumors. Based on the rational drug design, derivatives of PARP inhibitor 3-aminobenzamide (3-AB), 2-amino-4-methylbenzamide (L1) and 3-amino-N-methylbenzamide (L2), were coordinated to the ruthenium(II) ion, to form potential drugs affecting DNA and inhibiting PARP enzyme. The four conjugated complexes of formula: C1 [(ƞ⁶-toluene)Ru(L1)Cl]PF₆, C2 [(ƞ⁶-p-cymene)Ru(L1)Cl]PF₆, C3 [(ƞ⁶-toluene)Ru(L2)Cl₂] and C4 [(ƞ⁶-p-cymene)Ru(L2)Cl₂], have been synthesized and characterized. Colorimetric 3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide (MTT) assay showed the highest antiproliferative activity of C1 in HCC1937, MDA-MB-231, and MCF-7 breast cancer cells. Efficiency of inhibition of PARP-1 enzymatic activity in vitro decreased in order: C2 > C4 > 3-AB>C1 > C3. ICP-MS study of intracellular accumulation and distribution in BRCA1-mutated HCC1937 revealed that C1-C4 entered cells within 24 h. The complex C1 showed the highest intracellular accumulation, nuclear-targeting properties, and exhibited the highest DNA binding (39.2 ± 0.6 pg of Ru per μg of DNA) that resulted in the cell cycle arrest in the S phase.

New Dual CK2/HDAC1 Inhibitors with Nanomolar Inhibitory Activity against Both Enzymes

Four potent CK2 inhibitors derived from CX-4945 are described. They also provided nanomolar activity against HDAC1, therefore having promising utility as dual-target agents for cancer. The linker length between the hydroxamic acid and the CX-4945 scaffold plays an important role in dictating balanced activity against the targeted enzymes. The seven-carbon linker (compound 15c) was optimal for inhibition of both CK2 and HDAC1. Remarkably, 15c showed 3.0 and 3.5 times higher inhibitory activity than the reference compounds CX-4945 (against CK2) and SAHA (against HDAC1), respectively. Compound 15c exhibited micromolar activity in cell-based cytotoxic assays against multiple cell lines.

Targeting of the mitochondrion by dinuclear thiolato-bridged arene ruthenium complexes in cancer cells and in the apicomplexan parasite Neospora caninum

A library of 18 dinuclear-thiolato bridged arene ruthenium complexes, some of which with demonstrated activity against cancer cells, was screened for activity against a transgenic Neospora caninum strain that constitutively expresses beta-galactosidase. Initial assessments were done at concentrations of 2500, 250, 25 and 2.5 nM, and 5 compounds were further evaluated with regard to their half maximal proliferation-inhibiting concentration (IC50). Among those, [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-p-CH3)3]Cl (1), [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-p-But)3]Cl (2) and [(η6-p-MeC6H4Pri)2Ru2(μ2-SCH2C6H4-p-But)2(μ2-SC6H4-p-OH)]BF4 (9) inhibited N. caninum proliferation with low C50 values of 15, 5 and 1 nM, respectively, while [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-p-OH)3]Cl (3) and [(η6-p-MeC6H4Pri)2Ru2(μ2-SC6H4-p-mco)3]Cl (5, mco = 4-methylcoumarinyl) were less active (IC50 = 280 and 108 nM, respectively). These compounds did not affect human foreskin fibroblast (HFF) host cells at dosages of 5 μM and above, but impaired proliferation of the human ovarian carcinoma cell line A2780 (IC50 values of 130 nM (1), 30 nM (2), 530 nM (3), 7730 nM (5), 130 nM (9)). A2780 cancer cells were treated with complexes 1, 2, and 5, and biodistribution analysis using inductively coupled plasma mass spectrometry (ICP-MS) showed that most of the drugs accumulated in the mitochondrial fractions. Transmission electron microscopy showed that the parasite mitochondrion is the primary target also in N. caninum tachyzoites, but these compounds, when applied at 200 nM for 15 days in vitro, did not act parasiticidal. Complexes 1, 2 and 9 applied orally at 2 and 10 mg kg-1 day-1 during 5 days in a neosporosis mouse model did not reduce parasite load and did not limit parasite dissemination to the central nervous system. In accordance with these results, ICP-MS carried out on different organs of mice orally administrated with complexes 1 and 9, demonstrated that the drugs were readily absorbed, and after 3 and 48 h, were mainly detected in liver and kidney, but were largely absent from the brain. Thus, dinuclear thiolato-bridged arene ruthenium complexes exhibit interesting activities against N. caninum in vitro, but further modifications of these promising molecules are required to improve their bioavailability and pharmacokinetic properties in order to exert a pronounced and selective effect against N. caninum in vivo.

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.

Hypoxia efficient and glutathione-resistant cytoselective ruthenium(ii)-p-cymene-arylimidazophenanthroline complexes: biomolecular interaction and live cell imaging

A series of ruthenium(ii)–arene-2-arylimidazophenanthroline based DNA targeting, cytoselective, hypoxia efficient and glutathione-resistant luminescent anticancer drugs have been developed which are also represented as HeLa cell imaging probes.

Ruthenium-Cyclopentadienyl Bipyridine-Biotin Based Compounds: Synthesis and Biological Effect

Prospective anticancer metallodrugs should consider target-specific components in their design in order to overcome the limitations of the current chemotherapeutics. The inclusion of vitamins, which receptors are overexpressed in many cancer cell lines, has proven to be a valid strategy. Therefore, in this paper we report the synthesis and characterization of a set of new compounds [Ru(η⁵-C₅H₅)(P(C₆H₄R)₃)(4,4'-R'-2,2'-bpy)]⁺ (R = F and R' = H, 3; R = F and R' = biotin, 4; R = OCH₃ and R' = H, 5; R = OCH₃ and R' = biotin, 6), inspired by the exceptional good results recently obtained for the analogue bearing a triphenylphosphane ligand. The precursors for these syntheses were also described following modified literature procedures, [Ru(η⁵-C₅H₅)(P(C₆H₄R)₃)₂Cl], where R is -F (1) or -OCH₃ (2). The structure of all compounds is fully supported by spectroscopic and analytical techniques and by X-ray diffraction studies for compounds 2, 3, and 5. All cationic compounds are cytotoxic in the two breast cancer cell lines tested, MCF7 and MDA-MB-231, and much better than cisplatin under the same experimental conditions. The cytotoxicity of the biotinylated compounds seems to be related with the Ru uptake by the cells expressing biotin receptors, indicating a potential mediated uptake. Indeed, a biotin-avidin study confirmed that the attachment of biotin to the organometallic fragment still allows biotin recognition by the protein. Therefore, the biotinylated compounds might be potent anticancer drugs as they show cytotoxic effect in breast cancer cells at low dose dependent on the compounds' uptake, induce cell death by apoptosis and inhibit the colony formation of cancer cells causing also less severe side effects in zebrafish.

Investigation of the cytotoxic potential of methyl imidazole-derived thiosemicarbazones and their copper(ii) complexes with dichloroacetate as a co-ligand

Investigation of the cytotoxic potential of imidazole-derived thiosemicarbazones and their copper(ii) complexes with CHCl₂CO₂⁻ as a co-ligand.

Luminescent anticancer ruthenium(ii)-p-cymene complexes of extended imidazophenanthroline ligands: synthesis, structure, reactivity, biomolecular interactions and live cell imaging

The violence of cancer triggered us to design lipophilic, target specific, water soluble, cytoselective and fluorescent Ru(ii)-p-cymene imidazophenanthroline scaffolds as effective DNA targeting agents as well as life cell imaging probes.

Polymeric micelle-mediated delivery of half-sandwich ruthenium(II) complexes with phosphanes derived from fluoroloquinolones for lung adenocarcinoma treatment

Novel half-sandwich ruthenium(II) complexes with aminomethyl(diphenyl)phosphine derived from fluoroloquinolones (RuPCp, RuPSf, RuPLm, RuPNr) were being investigated as alternatives to well-established metal-based chemotherapeutics. All compounds were characterized by elemental analysis, selected spectroscopic methods (i.e., absorption and fluorescence spectroscopies, ESI-MS, NMR, circular dichroizm), X-ray diffractometry, ICP-MS, and electrochemical techniques. To overcome low solubility, serious side effects connected with systemic cytotoxicity of ruthenium complexes, and acquiring the resistance of cancer cells, polymeric nanoformulations based on Pluronic P-123 micelles loaded with selected Ru(II) complexes were prepared and characterized. Resulting micelles (RuPCp_M, RuPNr_M) enabled efficient drug accumulation inside human lung adenocarcinoma (A549 tumor cell line), proved by confocal microscopy and ICP-MS analysis, allowing cytotoxic action. Studied complexes exhibited promising cytotoxicity in vitro with IC50 values significantly lower than the reference drug - cisplatin. The fluorescence spectroscopic data (CT-DNA titration, in vitro cell staining) together with analysis of DNA fragmentation (pBR322 plasmid, comet assay) provided clear evidence for the interaction with DNA inducing apoptotic cell death.

A ruthenium-based 5-fluorouracil complex with enhanced cytotoxicity and apoptosis induction action in HCT116 cells

Combination of multifunctionalities into one compound is a rational strategy in medicinal chemical design, and have often been used with metallodrug-based compounds. In the present study, we synthesized a novel ruthenium-based 5-fluorouracil complex [Ru(5-FU)(PPh₃)₂(bipy)]PF₆ (PPh₃ = triphenylphosphine; and bipy = 2,2′-bipyridine) with enhanced cytotoxicity in different cancer cells, and assessed its apoptosis induction action in human colon carcinoma HCT116 cells. The complex was characterized by infrared, cyclic voltammetry, molar conductance measurements, elemental analysis, NMR experiments and X-ray crystallographic analysis. In both 2D and 3D cell culture models, the complex presented cytotoxicity to cancer cells more potent than 5-FU. A typical morphology of apoptotic cell death, increased internucleosomal DNA fragmentation, without cell membrane permeability, loss of the mitochondrial transmembrane potential, increased phosphatidylserine externalization and caspase-3 activation were observed in complex-treated HCT116 cells. Moreover, the pre-treatment with Z-DEVD-FMK, a caspase-3 inhibitor, reduced the apoptosis induced by the complex, indicating cell death by apoptosis through caspase-dependent and mitochondrial intrinsic pathways. The complex failed to induce reactive oxygen species production and DNA intercalation. In conclusion, the novel complex displays enhanced cytotoxicity to different cancer cells, and is able to induce caspase-mediated apoptosis in HCT116 cells.

Synthesis, characterization, cellular uptake and apoptosis-inducing properties of two highly cytotoxic cyclometalated ruthenium(II) β-carboline complexes

Two new cyclometalated Ru(II) complexes of the general formula [Ru(N-N)₂(1-Ph-βC)](PF₆), where N-N = 4,4'-dimethyl-2,2'-bipyridine (dmb, Ru1), 2,2'-bipyridine (bpy, Ru2), and 1-Ph-βC (1-phenyl-9H-pyrido[3,4-b]indole) is a β-carboline alkaloids derivatives, have been synthesized and characterized. The in vitro cytotoxicities, cellular uptake and localization, cell cycle arrest and apoptosis-inducing mechanisms of these complexes have been extensively explored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, inductively coupled plasma mass spectrometry (ICP-MS), flow cytometry, comet assay, inverted fluorescence microscope as well as western blotting experimental techniques. Notably, Ru1 and Ru2 exhibit potent antiproliferative activities against selected human cancer cell lines with IC₅₀ values lower than those of cisplatin and other non-cyclometalated Ru(II) β-carboline complexes. The cellular uptake and localization exhibit that these complexes can accumulate in the cell nuclei. Further antitumor mechanism studies show that Ru1 and Ru2 can cause cell cycle arrest in the G0/G1 phase by regulating cell cycle relative proteins and induce apoptosis through mitochondrial dysfunction, reactive oxygen species (ROS) accumulation and ROS-mediated DNA damage.

Ruthenium(ii) p-cymene complexes of a benzimidazole-based ligand capable of VEGFR2 inhibition: hydrolysis, reactivity and cytotoxicity studies

Ru(ii)-p-Cymene complexes of a bispyrazole-benzimidazole ligand inhibit vascular endothelial growth factor 2, reduce the cellular glutathione pool and inhibit cell migration.