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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. Show less

The rational design of anticancer agents that acts in specific biological targets is one of the most effective strategies for developing chemotherapeutic agents. Aiming at obtaining new ruthenium (II) compounds with good cytotoxicity against tumor cells, a series of new complexes of general formula [RuCl(PPh₃)(Hdpa)(NN)]Cl [PPh₃ = triphenylphosphine, N-N = 2,2'-dipyridylamine (Hdpa) (1), 1,2-diaminoethane (en) (2), 2,2'-bipyridine (bipy) (3), 5,5'-dimethyl-2,2'-bipyridine (dmbipy) (4), 1,10-phenanthroline (phen) (5) and 4,7-diphenyl-1,10-phenanthroline (dphphen) (6)] were synthesized. The complexes were characterized by elemental analysis and spectroscopic techniques (IR, UV/Visible, and 1D and 2D NMR) and three of their X-ray structures were determined: [RuCl(PPh₃)(Hdpa)₂]Cl, [RuCl(PPh₃)(Hdpa)(en)]Cl and [RuCl(PPh₃)(Hdpa)(dmbipy)]Cl. All the complexes are more cytotoxic against the cancer cell line than against the non-tumor cell line, highlighting complexes 1 and 5, which have an index selectivity of 18 and 15, respectively. The binding constants of compounds 1-6 with human serum albumin (HSA) were determined by tryptophan fluorescence quenching, indicating moderate to strong interactions. The binding mode of the complexes to calf thymus (CT) DNA was explored by several techniques, which reveal that only the dphphen compound 6 causes distortions in the secondary and tertiary structures of DNA. The studies demonstrated that the nature of the NN co-ligand and the presence of the PPh₃ and Hdpa ligands are features that can influence the binding affinity of the complexes by the biomolecules and in the cytotoxic activity of the complexes. Overall, the complexes with diimine co-ligand are much more cytotoxic than compound 2 with the aliphatic diamine. Show less

Ruthenium(ii) diclofenac-based complexes of the general formula [Ru(dicl)(P-P)(bpy)]PF6 [dicl = diclofenac, bpy = 2,2'-bipyridine, and P-P = 1,4'-bis(diphenylphosphino)butane (dppb) (1), 1,2'-bis(diphenylphosphino)ethane (dppe) (2), 1,3'-bis(diphenylphosphino)propane (dppp) (3) and 1,1'-bis(diphenylphosphino)ferrocene (dppf) (4)] are synthesized. The complexes (1-4) are characterized by elemental analyses, infrared, NMR, and UV-vis spectroscopy and (3) and (4) are characterized by single crystal X-ray diffraction. The DNA binding of complexes (1-4), studied by circular dichroism (CD) and Hoechst 33 258 staining assay, indicates their binding with the minor grooves. The complexes interact with BSA with binding constants (Kb) in the range of 2.5 × 103-5.5 × 104 M-1. The complexes exhibit high cytotoxicity against the tumor cell lines A549, MDA-MB-231, and MCF-7 with IC50 values ranging from 0.56 to 15.28 μM. The complexes are more selective for the hormone-dependent MCF-7 breast tumor cell line and complex (1) is the most potent one. The study demonstrates the anticancer activity of ruthenium(ii)/diclofenac-based complexes. Show less

Title: Ru(II)- Abstract: Half-sandwich Ru(II) complexes containing nitro-substituted furoylthiourea ligands, bearing the general formula [(η6-p-cymene)RuCl2(L)] (1-6) and [(η6-p-cymene)RuCl(L)(PPh3)]+ (7--12), have been synthesized and characterized. In contrast to the spectroscopic data which revealed monodentate coordination of the ligands to the Ru(II) ion via a "S" atom, single crystal X-ray structures revealed an unusual bidentate N, S coordination with the metal center forming a four-membered ring. Interaction studies by absorption, emission, and viscosity measurements revealed intercalation of the Ru(II) complexes with calf thymus (CT) DNA. The complexes showed good interactions with bovine serum albumin (BSA) as well. Further, their cytotoxicity was explored exclusively against breast cancer cells, namely, MCF-7, T47-D, and MDA-MB-231, wherein all of the complexes were found to display more pronounced activity than their ligand counterparts. Complexes 7-12 bearing triphenylphosphine displayed significant cytotoxicity, among which complex 12 showed IC50 values of 0.6 ± 0.9, 0.1 ± 0.8, and 0.1 ± 0.2 μM against MCF-7, T47-D, and MDA-MB-231 cell lines, respectively. The most active complexes were tested for their mode of cell death through staining assays, which confirmed apoptosis. The upregulation of apoptotic inducing and downregulation of apoptotic suppressing proteins as inferred from the western blot analysis also corroborated the apoptotic mode of cell death. The active complexes effectively generated reactive oxygen species (ROS) in MDA-MB-231 cells as analyzed from the 2',7'-dichlorofluorescein diacetate (DCFH-DA) staining. Finally, in vivo studies of the highly active complexes (6 and 12) were performed on the mice model. Histological analyses revealed that treatment with these complexes at high doses of up to 8 mg/kg did not induce any visible damage to the tested organs. Show less

Two bifunctional ruthenium(II)-p-cymene complexes with perfluorinated side chains, attached via pyridine ligands, have been evaluated in a series of in vitro and in vivo assays. Their effects on human endothelial (ECRF24 and HUVEC) cells, noncancerous human embryonic kidney (HEK-293) cells, and various human tumor cells were investigated. The complex with the shorter chain, 1, inhibits the proliferation of the tumor cell lines and ECRF24, whereas 2 selectively inhibits ECRF24 and HUVEC proliferation. Neither inhibits the migration of ECRF24 cells whereas both compounds inhibit sprout formation in HUVEC cells. Using three preclinical models, i.e., vasculature formation in the chorioallantoic membrane (CAM) of the chicken embryo, human A2780 ovarian carcinoma tumors xenografted on the CAM, and human LS174T colorectal adenocarcinoma tumors grown in athymic mice, the angiostatic and anticancer activities of these two complexes were studied. Overall, 1 inhibited tumor growth predominantly through an anticancer effect whereas 2 inhibited tumor growth predominately via an antiangiogenic mechanism. Show less

Two new Ru(II) complexes, [Ru(bpy)2(FAMP)](ClO4)2 1 and 2, are synthesized and characterized by elemental analysis, electrospray mass spectrometry, and 1H nuclear magnetic resonance. The in vitro cytotoxicities and apoptosis-inducing properties of these complexes are extensively studied. Complexes 1 and 2 exhibit potent antiproliferative activities against a panel of human cancer cell lines. The cell cycle analysis shows that complexes 1 and 2 exhibit effective cell growth inhibition by triggering G0/G1 phase arrest and inducing apoptosis by mitochondrial dysfunction. The in vitro DNA binding properties of the two complexes are investigated by different spectrophotometric methods and viscosity measurements. Show less

Ruthenium complexes have been considered as promising substitutes for cisplatin in cancer chemotherapy. However, novel ruthenium-based therapies are faced with some limitations, such as unimpressive cytotoxicity toward solid tumors. Herein, we designed and synthesized phenyl-substituted terpyridyl ruthenium(ii) complexes ([Ru(tpy)(bpy)Cl](+) (Ru1), [Ru(phtpy)(bpy)Cl](+) (Ru2) and [Ru(biphtpy)(bpy)Cl](+) (Ru3)) which exhibited distinctly different anticancer activity. Ru1-Ru3 all underwent moderate aquation in buffer solution and this process was significantly inhibited by high chloride concentration. Cancer cells were found to readily uptake the relatively hydrophobic Ru3, as quantified using inductively coupled plasma mass spectrometry (ICP-MS). Ru1 was found to be non-cytotoxic (IC50 > 100 μM) while Ru3 exhibited very promising cytotoxicity on both two-dimensional (2D) cancer cell monolayers and 3D MCTSs. An antiproliferative assay revealed that Ru3 significantly inhibited cellular DNA replication which ultimately induced apoptosis of cancer cells. Show less

Organometallic compounds which contain metals, such as ruthenium or gold, have been investigated as a replacement for platinum-derived anticancer drugs. They often show good antitumor effects, but the identification of their precise mode of action or their pharmacological optimization is still challenging. We have previously described a class of ruthenium(II) compounds with interesting anticancer properties. In comparison to cisplatin, these molecules have lower side effects, a reduced ability to interact with DNA, and they induce cell death in absence of p53 through CHOP/DDIT3. We have now optimized these molecules by improving their cytotoxicity and their water solubility. In this article, we demonstrate that by changing the ligands around the ruthenium we modify the ability of the compounds to interact with DNA. We show that these optimized molecules reduce tumor growth in different mouse models and retain their ability to induce CHOP/DDIT3. However, they are more potent inducers of cancer cell death and trigger the production of reactive oxygen species and the activation of caspase 8. More importantly, we show that blocking reactive oxygen species production or caspase 8 activity reduces significantly the activity of the compounds. Altogether our data suggest that water-soluble ruthenium(II)-derived compounds represent an interesting class of molecules that, depending on their structures, can target several pro-apoptotic signaling pathways leading to reactive oxygen species production and caspase 8 activation. Show less

In an attempt to combine the ability of indolobenzazepines (paullones) to inhibit cyclin-dependent kinases (Cdks) and that of platinum-group metal ions to interact with proteins and DNA, ruthenium(II) and osmium(II) arene complexes with paullones were prepared, expecting synergies and an increase of solubility of paullones. Complexes with the general formula [M(II)Cl(η(6)-p-cymene)L]Cl, where M=Ru (1, 3) or Os (2, 4), and L=L(1) (1, 2) or L(2) (3, 4), L(1)=N-(9-bromo-7,12-dihydroindolo[3,2-d][1]-benzazepin-6(5H)-yliden-N'-(2-hydroxybenzylidene)azine and L(2)=N-(9-bromo-7,12-dihydroindolo[3,2-d][1]benzazepin-6-yl)-N'-[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl-methylene]azinium chloride (L(2)(*)HCl), were now investigated regarding cytotoxicity and accumulation in cancer cells, impact on the cell cycle, capacity of inhibiting DNA synthesis and inducing apoptosis as well as their ability to inhibit Cdk activity. The MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay yielded IC(50) values in the nanomolar to low micromolar range. In accordance with cytotoxicity data, the BrdU assay showed that 1 is the most and 4 the least effective of these compounds regarding inhibition of DNA synthesis. Effects on the cell cycle are minor, although concentration-dependent inhibition of Cdk2/cyclin E activity was observed in cell-free experiments. Induction of apoptosis is most pronounced for complex 1, accompanied by a low fraction of necrotic cells, as observed by annexin V-fluorescein isothiocyanate/propidium iodide staining and flow cytometric analysis. Show less

KP1339 is a promising ruthenium-based anticancer compound in early clinical development. This study aimed to test the effects of KP1339 on the in vitro and in vivo activity of the multi-kinase inhibitor sorafenib, the current standard first-line therapy for advanced hepatoma. Anticancer activity of the parental compounds as compared to the drug combination was tested against a panel of cancer cell lines with a focus on hepatoma. Combination of KP1339 with sorafenib induced in the majority of all cases distinctly synergistic effects, comprising both sorafenib-resistant as well as sorafenib-responsive cell models. Several mechanisms were found to underlie these multifaceted synergistic activities. Firstly, co-exposure induced significantly enhanced accumulation levels of both drugs resulting in enhanced apoptosis induction. Secondly, sorafenib blocked KP1339-mediated activation of P38 signalling representing a protective response against the ruthenium drug. In addition, sorafenib treatment also abrogated KP1339-induced G2/M arrest but resulted in check point-independent DNA-synthesis block and a complete loss of the mitotic cell populations. The activity of the KP1339/sorafenib combination was evaluated in the Hep3B hepatoma xenograft. KP1339 monotherapy led to a 2.4-fold increase in life span and, thus, was superior to sorafenib, which induced a 1.9-fold prolonged survival. The combined therapy further enhanced the mean survival by 3.9-fold. Synergistic activity was also observed in the VM-1 melanoma xenograft harbouring an activating braf mutation. Together, our data indicate that the combination of KP1339 with sorafenib displays promising activity in vitro and in vivo especially against human hepatoma models. Show less

Hypoxia is the critical feature of the tumor microenvironment that is known to lead to resistance to many chemotherapeutic drugs. Six novel ruthenium(II) anthraquinone complexes were designed and synthesized; they exhibit similar or superior cytotoxicity compared to cisplatin in hypoxic HeLa, A549, and multidrug-resistant (A549R) tumor cell lines. Their anticancer activities are related to their lipophilicity and cellular uptake; therefore, these physicochemical properties of the complexes can be changed by modifying the ligands to obtain better anticancer candidates. Complex 1, the most potent member of the series, is highly active against hypoxic HeLa cancer cells (IC50 =0.53 μM). This complex likely has 46-fold better activity than cisplatin (IC50 =24.62 μM) in HeLa cells. This complex tends to accumulate in the mitochondria and the nucleus of hypoxic HeLa cells. Further mechanistic studies show that complex 1 induced cell apoptosis during hypoxia through multiple pathways, including those of DNA damage, mitochondrial dysfunction, and the inhibition of DNA replication and HIF-1α expression, making it an outstanding candidate for further in vivo studies. Show less

Following our strategy of coupling cyclin-dependent kinase (Cdk) inhibitors with organometallic moieties to improve their physicochemical properties and bioavailability, five organoruthenium complexes (1c-5c) of the general formula [RuCl(η(6)-arene)(L)]Cl have been synthesized in which the arene is 4-formylphenoxyacetyl-η(6)-benzylamide and L is a Cdk inhibitor [3-(1H-benzimidazol-2-yl)-1H-pyrazolo[3,4-b]pyridines (L1-L3) and indolo[3,2-d]benzazepines (L4 and L5)]. All of the compounds were characterized by spectroscopic and analytical methods. Upon prolonged standing (2-3 months) at room temperature, the dimethyl sulfoxide (DMSO) solutions of 1c and 2c(-HCl) afforded residues, which after recrystallization from EtOH and EtOH/H(2)O, respectively, were shown by X-ray diffraction to be cis,cis-[Ru(II)Cl(2)(DMSO)(2)(L1)]·H(2)O and mer-[Ru(II)Cl(DMSO)(3)(L2-H)]·H(2)O. Compound 5c, with a coordinated amidine unit, undergoes E/Z isomerization in solution. The antiproliferative activities and effects on the cell cycle of the new compounds were evaluated. Complexes 1c-5c are moderately cytotoxic to cancer cells (CH1, SW480, A549, A2780, and A2780cisR cell lines). Therefore, in order to improve their antiproliferative effects, as well as their drug targeting and delivery to cancer cells, 1c-5c were conjugated to recombinant human serum albumin, potentially exploiting the so-called "enhanced permeability and retention" effect that results in the accumulation of macromolecules in tumors. Notably, a marked increase in cytotoxicity of the albumin conjugates was observed in all cases. Show less

Ruthenium polypyridyl complexes show great promise as new photodynamic therapy (PDT) agents. However, a lack of detailed understanding of their mode of action in cells poses a challenge to their development. We have designed a new Ru(II) PDT candidate that efficiently enters cells by incorporation of the lipophilic aromatic pdppz ([2,3-h]dipyrido[3,2-a:2',3'-c]phenazine) ligand and exhibits photoactivity through incorporation of 1,4,5,8-tetraazaphenanthrene ancillary ligands. Its photoreactivity toward biomolecules was studied in vitro, where light activation caused DNA cleavage. Cellular internalization occurred via an energy dependent mechanism. Confocal and transmission electron microscopy revealed that the complex localizes in various organelles, including the mitochondria. The complex is nontoxic in the dark, with cellular clearance within 96 h; however, upon visible light activation it induces caspase-dependent and reactive-oxygen-species-dependent apoptosis, with low micromolar IC50 values. This investigation greatly increases our understanding of such systems in cellulo, aiding development and realization of their application in cancer therapy. Show less

An organoruthenium(II) complex with pyrithione (2-mercaptopyridine N-oxide) 1 a has previously been identified by our group as a compound with promising anticancer potential without cytotoxicity towards non-cancerous cells. To expand the rather limited research on compounds of this type, an array of novel chlorido and 1,3,5-triaza-7-phosphaadamantane (pta) organoruthenium(II) complexes with methyl-substituted pyrithiones has been prepared. After thorough investigation of the aqueous stability of these complexes, their modes of action have been elucidated at the cellular level. Minor structural alterations in the ruthenium-pyrithionato compounds resulted in fine-tuning of their cytotoxicities. The best performing compounds, 1 b and 2 b, with a chlorido or pta ligand bound to ruthenium, respectively, and a methyl group at the 3-position of the pyrithione scaffold, have been further investigated. Both compounds trigger early apoptosis, induce the generation of reactive oxygen species and G1 arrest in A549 cancer cells, and show no strong interaction with DNA. However, only 1 b also inhibits thioredoxin reductase. Wound healing assays and mitochondrial function evaluation have revealed differences between these two compounds at the cellular level. Show less

New mononuclear and dinuclear Ru(II) coordination compounds with the 2,7-bisbenzoimidazolyl-naphthyridine ligand have been synthesized and characterized by UV-vis, NMR, and MALDI-TOF. The molecular structures for Ru(II) compounds were determined by single-crystal X-ray diffraction. With the expansion of ligand π-conjugation and the increase in the complexed Ru number, the maximum emission wavelength red-shifted from 696 to 786 nm. The binding mode between complexes and DNA was predicted by molecular docking, which is intercalations and π-π stacking interactions with the surrounding bases. The intercalation mode of DNA binding was then determined by DNA titration and ethidium bromide (EB) displacement experiments. The antigrowth effects of complexes RuY, RuY1, and RuY2 were tested in HaCat (normal cells), HeLa (cervical cancer), A549 (lung cancer), and A549/DDP (cisplatin-resistant lung cancer) through the MTT assay. The dinuclear complex RuY2 was superior to mononuclear complexes and cisplatin in the cisplatin-resistant cell line. Confocal imaging proved that the subcellular localization of Ru(II) complexes was mitochondria; moreover, apoptosis was detected by flow cytometry. All three complexes showed a dose-dependent manner in all four cell lines. All Ru(II) complexes were found to have reactive oxygen species (ROS). The finding indicated that these Ru(II) complexes caused cell death by both DNA disruption and ROS. This study helps to explore the potential of the polynuclear Ru(II) complexes for the combination of NIR imaging and Pt-resistant cancer therapy. Show less

The synthesis, characterisation, and evaluation of the in vitro cytotoxicity of five maleonitriledithiolate-based ruthenium metal complexes bearing various phosphine ligands towards two ovarian cancer cell lines (A2780 and A2780cisR), one non-small-cell lung cancer cell line (H460) and one normal prostate cell line (PNT2) are presented herein. These 18-electron complexes were designed with four water-soluble phosphine ligands to increase the water-solubility character of the corresponding electron-deficient ruthenium complex which showed great in vitro promises, and triphenylphosphine for comparison. The complexes with triphenylphosphine-3,3',3''-trisulfonic acid and triphenylphosphine present similar cytotoxicity compared to the 16-electron precursor, with equal cytotoxicity to both A2780 and A2780cisR. Hints at the mechanism of action suggest an apoptotic pathway based on reactive oxygen species (ROS) production. No toxicity was observed in preliminary in vivo pilot studies for these two complexes in subcutaneous A2780 and A2780cisR xenograft models, with some evidence of tumour growth delay. Show less

Following the identification of [Ru(η(6)-p-cymene)Cl2(1H,1H,2H,2H-perfluorodecyl-3-(pyridin-3-yl)propanoate)], a ruthenium(II)-arene complex with a perfluoroalkyl-modified ligand that displays remarkable in vitro cancer cell selectivity, a series of structurally related compounds were designed. In the new derivatives, the p-cymene ring and/or the chloride ligands are substituted by other ligands to modulate the steric bulk or aquation kinetics. The new compounds were evaluated in both in vitro (cytotoxicity and migration assays) and in vivo (chicken chorioallantoic membrane) models and were found to exhibit potent antivascular effects. Show less

Organometallic half-sandwich complexes [M(p-cymene)(azo/imino-pyridine)X](+) where M = Ru(II) or Os(II) and X ═ Cl or I, exhibit potent antiproliferative activity toward a range of cancer cells. Not only are the iodido complexes more potent than the chlorido analogues, but they are not cross-resistant with the clinical platinum drugs cisplatin and oxaliplatin. They are also more selective for cancer cells versus normal cells (fibroblasts) and show high accumulation in cell membranes. They arrest cell growth in G1 phase in contrast to cisplatin (S phase) with a high incidence of late-stage apoptosis. The iodido complexes retain potency in p53 mutant colon cells. All complexes activate caspase 3. In general, antiproliferative activity is greatly enhanced by low levels of the glutathione synthase inhibitor l-buthionine sulfoxime. The work illustrates how subtle changes to the design of low-spin d(6) metal complexes can lead to major changes in cellular metabolism and to potent complexes with novel mechanisms of anticancer activity. Show less

Ruthenium compounds have become promising alternatives to platinum drugs by displaying specific activities against different cancers and favourable toxicity and clearance properties. Nonetheless, their molecular targeting and mechanism of action are poorly understood. Here we study two prototypical ruthenium-arene agents-the cytotoxic antiprimary tumour compound [(η(6)-p-cymene)Ru(ethylene-diamine)Cl]PF6 and the relatively non-cytotoxic antimetastasis compound [(η(6)-p-cymene)Ru(1,3,5-triaza-7-phosphaadamantane)Cl2]-and discover that the former targets the DNA of chromatin, while the latter preferentially forms adducts on the histone proteins. Using a novel 'atom-to-cell' approach, we establish the basis for the surprisingly site-selective adduct formation behaviour and distinct cellular impact of these two chemically similar anticancer agents, which suggests that the cytotoxic effects arise largely from DNA lesions, whereas the protein adducts may be linked to the other therapeutic activities. Our study shows promise for developing new ruthenium drugs, via ligand-based modulation of DNA versus protein binding and thus cytotoxic potential, to target distinguishing epigenetic features of cancer cells. Show less

The designing of metal-based anticancer therapeutic agents can be optimized in a better and rapid way if the ligands utilized have standalone properties. Therefore, even when the organometallic/coordination complex (i.e., metallodrug) gets dissociated in extreme conditions, the ligand can endorse its biological properties. Herein, we have synthesized and characterized ɳ⁶-p-cymene ruthenium diclofenac complex. Furthermore, the ruthenium complex interactions with human serum albumin (HSA) and ct-DNA have been studied using various spectroscopic studies viz., UV, fluorescence, and circular dichroism and exhibited a significant binding propensity. Furthermore, in vitro cytotoxicity assays were carried out against human breast cancer "MCF-7" cell line. The ɳ⁶-p-cymene ruthenium diclofenac complex registered significant cytotoxicity with an IC₅₀ value of ∼25.0 µM which is comparable to the standard drugs. The ɳ⁶-p-cymene ruthenium diclofenac complex was able to decrease the MCF-7 cell proliferation and induced significant levels of apoptosis with relatively low toxicity. Show less

Herein, six ruthenium(ii) terpyridine complexes, i.e. [RuCl₂(4-EtN-Phtpy)(DMSO)] (Ru1), [RuCl₂(4-MeO-Phtpy)(DMSO)] (Ru2), [RuCl₂(2-MeO-Phtpy)(DMSO)] (Ru3), [RuCl₂(3-MeO-Phtpy)(DMSO)] (Ru4), [RuCl₂(1-Bip-Phtpy)(DMSO)] (Ru5), and [RuCl₂(1-Pyr-Phtpy)(DMSO)] (Ru6) with 4'-(4-diethylaminophenyl)-2,2':6',2''-terpyridine (4-EtN-Phtpy), 4'-(4-methoxyphenyl)-2,2':6',2''-terpyridine (4-MeO-Phtpy), 4'-(2-methoxyphenyl)-2,2':6',2''-terpyridine (2-MeO-Phtpy), 4'-(3-methoxyphenyl)-2,2':6',2''-terpyridine (3-MeO-Phtpy), 4'-(1-biphenylene)-2,2':6',2''-terpyridine (1-Bip-Phtpy), and 4'-(1-pyrene)-2,2':6',2''-terpyridine (1-Pyr-Phtpy), respectively, were synthesized and fully characterized. The MTT assay demonstrates that the in vitro anticancer activity of Ru1 is higher than that of Ru2-Ru6 and more selective for Hep-G2 cells than for normal HL-7702 cells. In addition, various biological assays show that Ru1 and Ru6, especially the Ru1 complex, are telomerase inhibitors targeting c-myc G4 DNA and also cause apoptosis of Hep-G2 cells. With the same Ru center, the in vitro antitumor activity and cellular uptake ability of the 4-EtN-Phtpy and 1-Bip-Phtpy ligands follow the order 4-EtN-Phtpy > 1-Bip-Phtpy. Show less

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. Show less

A set each of new bivalent and trivalent ruthenium complexes, [Ru(III)(HL)Cl2(EPh3)2] and [Ru(II)(L)(CO)(EPh3)2] (E = P (complexes and ) or As (complexes and )) were synthesised from the reactions of [Ru(III)Cl3(EPh3)3] with 2-hydroxynaphthaldehyde benzoic acid hydrazone (H2L) in methanol-chloroform and characterized by elemental analysis, spectral data and XRD study. A suitable mechanism to account for the formation of bivalent ruthenium carbonyl complexes from the corresponding trivalent precursors is provided by considering the role of added base in the reaction. Interaction of complexes with CT-DNA/bovine serum albumin was analysed with absorption and emission spectral titration studies. In vitro cytotoxic potential of the above ruthenium hydrazone complexes assayed against the A549 cell line revealed a significant growth inhibition. The test complexes added in IC50 concentration into the cell culture medium enhanced the release of lactate dehydrogenase, NO and reactive oxygen species in comparison with the control. Cell death induced by the complexes was studied using a propidium iodide staining assay and showed noticeable changes in the cell morphology which resembled apoptosis. Show less

A family of novel imine-N-heterocyclic carbene ruthenium(II) complexes of the general formula [(η⁶ -p-cymene)Ru(C^N)Cl]PF₆ ^- (where C^N is an imine-N-heterocyclic carbene chelating ligand with varying substituents) have been prepared and characterized. In this imine-N-heterocyclic carbene chelating ligand framework, there are three potential sites that can be modified, which distinguishes this class of ligand and provides a body of flexibilities and opportunities to tune the cytotoxicity of these ruthenium(II) complexes. The influence of substituent effects of three tunable domains on the anticancer activity and catalytic ability in converting coenzyme NADH to NAD⁺ is investigated. This family of complexes displays an exceedingly distinct anticancer activity against A549 cancer cells, despite their close structural similarity. Complex 9 shows the highest anticancer activity in this series against A549 cancer cells (IC₅₀ =14.36 μm), with an approximately 1.5-fold better activity than the clinical platinum drug cisplatin (IC₅₀ =21.30 μm) in A549 cancer cells. Mechanistic studies reveal that complex 9 mediates cell death mainly through cell stress, including cell cycle arrest, inducing apoptosis, increasing intracellular reactive oxygen species (ROS) levels, and depolarization of the mitochondrial membrane potential (MMP). Furthermore, lysosomal damage is also detected by confocal microscopy. Show less

The ligands L¹ and L² both form separable dinuclear double-stranded helicate and mesocate complexes with Ru^II . In contrast to clinically approved platinates, the helicate isomer of [Ru₂ (L¹ )₂ ]⁴⁺ was preferentially cytotoxic to isogenic cells (HCT116 p53^-/- ), which lack the critical tumour suppressor gene. The mesocate isomer shows the reverse selectivity, with the achiral isomer being preferentially cytotoxic towards HCT116 p53^+/+ . Other structurally similar Ru^II -containing dinuclear complexes showed very little cytotoxic activity. This study demonstrates that alterations in ligand or isomer can have profound effects on cytotoxicity towards cancer cells of different p53 status and suggests that selectivity can be "tuned" to either genotype. In the search for compounds that can target difficult-to-treat tumours that lack the p53 tumour suppressor gene, [Ru₂ (L¹ )₂ ]⁴⁺ is a promising compound for further development. Show less

Two new ligand PTTP (2-phenoxy-1,4,8,9-tetraazatriphenylene) and FTTP (2-(3-fluoronaphthalen-2-yloxy)-1,4,8,9-tetraazatriphenylene) and their six ruthenium(II) polypyridyl complexes [Ru(N-N)₂(PTTP)](ClO₄)₂ and [Ru(N-N)₂(FTTP)](ClO₄)₂ (N-N=dmb: 4,4'-dimethyl-2,2'-bipiridine; dmp: 2,9-dimethyl-1,10-phenanthroline; ttbpy: 4,4'-ditertiarybutyl-2,2'-bipyridine) were synthesized and characterized. The cytotoxic activity of the complexes against cancer cells HeLa, BEL-7402, A549, HepG-2, HOS and normal cell LO2 was evaluated by MTT method. The IC₅₀ values range from 1.5±0.1 to 55.9±7.5μM. Complex 3 shows the highest cytotoxic activity toward BEL-7402 cells (IC₅₀=1.5±0.1μM). Complex 5 displays most effective inhibition of the cell growth in A549 and HOS cells with low IC₅₀ values of 2.5±0.6 and 2.6±0.1μM, respectively. The apoptosis, reactive oxygen species, mitochondrial membrane potential, DNA damage, autophagy and anti-metastasis assay were investigated under a fluorescent microscope. The cell cycle arrest was assayed by flow cytometry, and the expression of caspases and Bcl-2 family proteins was studied by western blot. The results obtained show that the complexes induce apoptosis in BEL-7402 cells through a ROS-mediated mitochondrial dysfunction pathway. Show less

The design of Ru or other metal-based anticancer agents may achieve better and faster optimization if the ligands used are also designed to have standalone functions. In this scenario, even after dissociation from the metal complex under adverse conditions, the ligand would have anti-cancer properties. In our work, we have generated a bispyrazole-containing benzimidazole ligand with potency against vascular endothelial growth factor receptor 2 (VEGFR2), which is known to have roles in vasculogenesis/angiogenesis. This ligand was used to obtain ternary Ru(ii) p-cymene complexes with the formulations [(η⁶-p-cymene)Ru(HL)(Cl)](Cl) (1), [(η⁶-p-cymene)Ru(HL)(Br)](Br) (2) and [(η⁶-p-cymene)Ru(HL)(I)](I) (3). ¹H NMR data supports that hydrolysis of the complex is governed by halide substitution, and the extent of hydrolysis followed the trend 3 > 1 > 2. All the complexes have low affinity towards DNA bases (average K_b ∼ 10³ M^-1 for CT DNA); however, all the complexes are cytotoxic in nature, with IC₅₀ values less than 15 μM. The presence of excess glutathione (GSH) liberates HL from the complexes in solution. The ability of the Ru complex to impair mitochondrial function and reduce the cellular GSH pool is thought to be the reason that it retains activity in the presence of GSH despite the ability of GSH to degrade the complexes. The chloride analogue 1 shows the best in vitro cytotoxicity against a prostate cancer cell line (LNCaP), with an IC₅₀ of 6.4 μM. The complexes show anti-proliferative activity by the mitochondria-mediated intrinsic apoptotic pathway. Docking studies showed that HL has high affinity towards vascular endothelial growth factor receptor 2 (VEGFR2). The complexes show anti-metastatic activity (in vitro) at almost non-toxic dosages, and the effect is sustained even 48 h after removal of the complexes from the culture media. Show less