Synthesis, characterization, and DNA-binding studies of ruthenium complexes [Ru(tpy)(ptn)]2+ and Ru(dmtpy)(ptn)]2+

Redox and apoptotic potential of novel ruthenium complexes in rat blood and heart

Ruthenium(II) complexes offer the potential for lower toxicity compared with platinum(II) complexes. Our study aimed to compare cardiotoxicity of [Ru(Cl-tpy)(en)Cl][Cl], [Ru(Cl-tpy)(dach)Cl][Cl], [Ru(Cl-tpy)(bpy)Cl][Cl], cisplatin, and saline through assessment of redox status and relative expression of apoptosis-related genes. A total of 40 Wistar albino rats were divided into five groups. Ruthenium groups received a single dose of complexes intraperitoneally (4 mg/kg/week) for a 4-week period; cisplatin group received cisplatin (4 mg/kg/week) and control group received saline (4 mL/kg/week) in the same manner as ruthenium groups. In collected blood and heart tissue samples, spectrophotometric determination of oxidative stress biomarkers was performed. The relative expression of apoptosis-related genes (Bcl-2, Bax, and caspase-3) in hearts was examined by real-time polymerase chain reaction. Our results showed that systemic and cardiac pro-oxidative markers (thiobarbituric acid reactive substances and nitrite) were significantly lower in ruthenium groups compared with cisplatin group, while concentrations of antioxidative parameters (catalase, superoxide dismutase, and oxidized glutathione) were significantly higher. Ruthenium administration led to significantly lower gene expression of Bax and caspase-3 compared with cisplatin-treated rats, while Bcl-2 remained unchanged. Applied ruthenium complexes have less pronounced potential for induction of oxidative stress-mediated cardiotoxicity compared with cisplatin. These findings may help for future studies that should clarify the mechanisms of cardiotoxicity of ruthenium-based metallodrugs.

Applications of Ruthenium Complex in Tumor Diagnosis and Therapy

Ruthenium complexes are a new generation of metal antitumor drugs that are currently of great interest in multidisciplinary research. In this review article, we introduce the applications of ruthenium complexes in the diagnosis and therapy of tumors. We focus on the actions of ruthenium complexes on DNA, mitochondria, and endoplasmic reticulum of cells, as well as signaling pathways that induce tumor cell apoptosis, autophagy, and inhibition of angiogenesis. Furthermore, we highlight the use of ruthenium complexes as specific tumor cell probes to dynamically monitor the active biological component of the microenvironment and as excellent photosensitizer, catalyst, and bioimaging agents for phototherapies that significantly enhance the diagnosis and therapeutic effect on tumors. Finally, the combinational use of ruthenium complexes with existing clinical antitumor drugs to synergistically treat tumors is discussed.

Synthesis, Characterization, and Cytotoxicity of the Cobalt (III) Complex with N,N-Diethyl-4-(2,2':6',2''-terpyridin-4'-yl)aniline

A cobalt(III) complex, [Co(L)₂ ](ClO₄ )₃ (1), in which the ligand L was N,N-diethyl-4-(2,2':6',2''-terpyridin-4'-yl)aniline (L), was synthesized and fully characterized. This new cobalt(III) complex 1 exhibited selective cytotoxicity against HeLa, T-24, A549, MGC80-3, HepG2, and SK-OV-3 cells with IC₅₀ values in the micromolar range (0.52 - 4.33 μm), and it exhibited low cytotoxicity against normal HL-7702 cells. The complex 1 was the most potent against the T-24 cells. It was found that 1 could cause the cell cycle arrest in G1 phase, and it exerted its antitumor activity mainly via disruption of mitochondrial function.

Interfering with DNA High-Order Structures using Chiral Ruthenium(II) Complexes

In this work, it was found that DNA can undergo B-Z transformational changes and compaction in the presence of DNA intercalators such as ruthenium(II) polypyridyl complexes. The link between B-Z transition and condensation is weak but can be strengthened under certain circumstances with slight alterations to the structures of the ruthenium(II) complexes. Here, following on from previous research, this work reports a series of ruthenium(II) complexes with imidazophenanthroline ligands, which vary in size and planarity. The complexes exhibit distinct effects on DNA structures, ranging from little impact to the transformation of DNA secondary structures to the formation of higher-order DNA structures. Further studies on DNA morphological changes induced by chiral ruthenium(II) complexes are observed by atomic force microscopy and transmission electron microscopy.

Syntheses, crystal structures and DNA-binding activities of divalent Fe, Cu, Zn and Cd complexes with 4′-(furan-2-yl)-2,2′:6′,2″-terpyridine

Five coordination complexes [Fe(ftpy)2](ClO4)2·(H2O)2 (1), [Cu(ftpy)(NO3)(H2O)](NO3) (2), [Cu(ftpy)2]2(ClO4)4·(C2H5OH) (3), [Zn(ftpy)2]·(ClO4)2·(H2O)1.5 (4) and [Cd(ftpy)2]2(ClO4)4·(C2H5OH) (5) (ftpy=4′-(furan-2-yl)-2,2′:6′,2′-terpyridine) have been synthesized and characterized by IR, elemental analysis and single-crystal X-ray diffraction. With the exception of 4, all complexes adopt normal homoleptic [M(ftpy)2]2+ motifs. In the crystal, both hydrogen bonds and face-to-face interactions between furyl and pyridyl rings facilitate the construction of three-dimensional networks. The DNA-binding activities of the five complexes have been investigated by fluorescence emission titration at room temperature suggesting an intercalative mode for 1–3 with a relative order, 3>2>1, and a combined static and dynamic mode for 4 and 5.

Human topoisomerase inhibition and DNA/BSA binding of Ru(II)-SCAR complexes as potential anticancer candidates for oral application

Three ruthenium(II) phosphine/diimine/picolinate complexes were selected aimed at investigating anticancer activity against several cancer cell lines and the capacity of inhibiting the supercoiled DNA relaxation mediated by human topoisomerase IB (Top 1). The structure-lipophilicity relationship in membrane permeability using the Caco-2 cells have also been evaluated in this study. SCAR 5 was found to present 45 times more cytotoxicity against breast cancer cell when compared to cisplatin. SCAR 4 and 5 were both found to be capable of inhibiting the supercoiled DNA relaxation mediated by Top 1. Interaction studies showed that SCAR 4 and 5 can bind to DNA through electrostatic interactions while SCAR 6 is able to bind covalently to DNA. The complexes SCAR were found to interact differently with bovine serum albumin (BSA) suggesting hydrophobic interactions with albumin. The permeability of all complexes was seen to be dependent on their lipophilicity. SCAR 4 and 5 exhibited high membrane permeability (P _app  > 10 × 10^-6 cm·s^-1) in the presence of BSA. The complexes may pass through Caco-2 monolayer via passive diffusion mechanism and our results suggest that lipophilicity and interaction with BSA may influence the complexes permeation. In conclusion, we demonstrated that complexes have powerful pharmacological activity, with different results for each complex depending on the combination of their ligands.

Synthesis, crystal structure, cytotoxicity and action mechanism of Zn(ii) and Mn(ii) complexes with 4-([2,2′:6′,2′′-terpyridin]-4′-yl)-N,N-diethylaniline as a ligand

Two metallo-complexes inhibited telomerase by interacting with c-myc G4-DNA and induced cell cycle arrest at the S phase.

Dual inhibition of topoisomerases I and IIα by ruthenium(II) complexes containing asymmetric tridentate ligands

Five novel ruthenium(II) complexes, [Ru(dtzp)(dppt)](2+) (1), [Ru(dtzp)(pti)](2+) (2), [Ru(dtzp)(ptn)](2+) (3), [Ru(dtzp)(pta)](2+) (4) and [Ru(dtzp)(ptp)](2+) (5) (where dtzp = 2,6-di(thiazol-2-yl)pyridine, dppt = 3-(1,10-phenanthroline-2-yl)-5,6-diphenyl-as-triazine), pti = 3-(1,10-phenanthroline-2-yl)-as-triazino-[5,6-f]isatin, ptn = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]naphthalene, pta = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]acenaphthylene, and ptp = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-phenanthrene), were synthesised and characterised. The structures of complexes 3-5 were determined by X-ray diffraction. The DNA binding behaviours of the complexes were studied by spectroscopic and viscosity measurements. The results suggested that the Ru(II) complexes, except for complex 1, bind to DNA in an intercalative mode. Topoisomerase inhibition and DNA strand passage assay confirmed that Ru(II) complexes 3, 4, and 5 acted as efficient dual inhibitors of topoisomerases I and IIα. In vitro cytotoxicity assays indicated that these complexes exhibited anticancer activity against various cancer cell lines. Ruthenium(ii) complexes were confirmed to preferentially accumulate in the nucleus of cancer cells and induced DNA damage. Flow cytometric analysis and AO/EB staining assays indicated that these complexes induced cell apoptosis. With the loss of the mitochondrial membrane potential, the Ru(ii) complexes induce apoptosis via the mitochondrial pathway.

Microwave-assisted synthesis of arene ruthenium(ii) complexes [(η6-RC6H5)Ru(m-MOPIP)Cl]Cl (R = -H and -CH3) as groove binder to c-myc G4 DNA

Two arene Ru(ii) complexes are prepared under microwave irradiation and display application potential as small molecule inhibitors of c-myc G4 DNA.

Mitochondria are the primary target in the induction of apoptosis by chiral ruthenium(II) polypyridyl complexes in cancer cells

A series of novel chiral ruthenium(II) polypyridyl complexes (Δ-Ru1, Λ-Ru1, Δ-Ru2, Λ-Ru2, Δ-Ru3, Λ-Ru3) were synthesized and evaluated to determine their antiproliferative activities. Colocalization, inductively coupled plasma mass spectrometry, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay studies showed that these ruthenium(II) complexes accumulated preferentially in the mitochondria and exhibited cytotoxicity against various cancer cells in vitro. The complex Δ-Ru1 is of particular interest because it was found to have half-maximal inhibitory concentrations comparable to those of cisplatin and better activity than cisplatin against a cisplatin-resistant cell line, A549-CP/R. Δ-Ru1 induced alterations in the mitochondrial membrane potential and triggered intrinsic mitochondria-mediated apoptosis in HeLa cells, which involved the regulation of Bcl-2 family members and the activation of caspases. Taken together, these data suggest that Δ-Ru1 may be a novel mitochondria-targeting anticancer agent.

Self-activating nuclease and anticancer activities of copper(II) complexes with aryl-modified 2,6-di(thiazol-2-yl)pyridine

Three mononuclear copper complexes [Cu(PDTP)Cl2] (PDTP = 4-phenyl-2,6-di(thiazole-2-yl)pyridine, CuPDTP), [Cu(ADTP)Cl2] (ADTP = 4-(anthracen-9-yl)-2,6-di(thiazole-2-yl)pyridine, CuADTP) and [Cu(BFDTP)Cl2] (BFDTP = 4-(benzofuran-2-yl)-2,6-di(thiazole-2-yl)pyridine, CuBFDTP) were synthesized and characterized. The X-ray single crystallography results indicated that the Cu(II) ions showed slightly distorted square pyramid coordination environments, and the ligands deviated from ideal planarity in all three compounds. Based on the DNA binding studies, it was demonstrated that these three complexes exhibited weak DNA binding strengths, which were most likely groove binding modes. CuPDTP, CuADTP and CuBFDTP induced efficient DNA cleavage in the dark without the addition of external catalysts (oxidant or reductant). In contrast, in the presence of reducing or oxidizing agents, the nuclease activities increased more than 10-fold. Mechanistic investigations revealed the participation of reactive oxygen species, which can be trapped by ROS radical scavengers and ROS sensors. In the same experimental conditions, the free ligands and CuCl2 did not display any DNA cleaving activity. This result indicates that the complexes, rather than their components, play a significant role in the nuclease reaction process and that DNA cleavage may be initiated in an oxidative pattern. The proposed mechanism was attributed to the in situ activation of molecular oxygen by the oxidation of the copper complexes. In the MTT cytotoxicity studies, the three Cu(II) complexes exhibited an antitumor activity against the HeLa, BEL-7402 and HepG2 tumor cell lines. The HeLa cells treated with Cu(II) complexes demonstrated marked changes in their nuclear morphology, which were detected by Hoechst 33258 nuclear staining and acridine orange/ethidium bromide (AO/EB) staining assays. Nuclear chromatin cleavage also was observed from alkaline single-cell gel electrophoresis (comet assay).

Colorimetric and luminescent dual-signaling responsive probing of thiols by a ruthenium(II)-azo complex

A dinuclear ruthenium(II) complex linked via a reducible azo group [Ru(bpy)2(azobpy)Ru(bpy)2]Cl4 (Ru2azo, bpy=2,2'-bipyridine, azobpy=4,4″-azobis (2,2'-bipyridine)) was adopted as a probe for thiols. Results showed that Ru2azo could selectively and effectively react with biological thiols (such as cysteine, homocysteine and glutathione) with a 10(-7)M detection limit. After it reacted with thiols, the original gray color of Ru2azo solution immediately turned yellow and the luminescence significantly enhanced, showing "naked-eye" colorimetric and "off-on" luminescent dual-signaling response for thiols. Mechanism studies demonstrated that Ru2azo reacted with thiols undergoing a two-electron transfer process, forming the azo(2-) anion product.