👤 Danelon C

Ruthenium-based compounds are developed for anticancer treatment, but their mode of action including their import mechanism and subcellular localization remains elusive. Here, we used the intrinsic luminescent properties of cytotoxic organoruthenium (Ru(II)) compounds obtained with an anionic cyclometalated 2-phenylpyridine chelate and neutral aromatic chelating ligands (e.g., phenanthrolines) to follow their behavior in living cells. We established that the difference in sensitivity between cancer cells and noncancerous cells toward one of the compounds correlates with its import kinetics and follows a balance between active and passive transport. The active-transport mechanism involves iron and amino-acid transporters, which are transcriptionally regulated by the drug. We also demonstrated a correlation between the accumulation of these compounds in specific compartments (endoplasmic reticulum, nucleus, mitochondria) and the activation of specific cytotoxic mechanisms such as the mitochondrial stress pathway. Our study pinpoints a novel and complex mechanism of accumulation of ruthenium drugs in cancer cells. Show less

A series of ferrocene and (arene)ruthenium(II) complexes attached to the naturally occurring anticancer naphthoquinones plumbagin and juglone was tested for efficacy against various cancer cell lines and for alterations in the mode of action. The plumbagin ferrocene and (p-cymene)Ru(II) conjugates 1c and 2a overcame the multi-drug drug resistance of KB-V1/Vbl cervix carcinoma cells and showed IC50 (72 h) values around 1 μM in growth inhibition assays using 3-(4,5-dimethyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT). They were further investigated for their influence on the cell cycle of KB-V1/Vbl and HCT-116 colon carcinoma cells, on the generation of reactive oxygen species (ROS) by the latter cell line, for their substrate character for the P-glycoprotein drug eflux pump via the calcein-AM efflux assays, and for DNA affinity by the electrophoretic mobility shift assay (EMSA). The derivatives 1c and 2a increased the number of dead cancer cells (sub-G0/G1 fraction) in a dose- and time-dependent manner. ROS levels were significantly increased upon treatment with 1c and 2a. These compounds also showed a greater affinity to linear DNA than plumbagin. While plumbagin did not affect calcein-AM transport by P-glycoprotein the derivatives 1c and 2a exhibited a 50% or 80% inhibition of the P-glycoprotein-mediated calcein-AM efflux relative to the clinically established sensitizer verapamil. Show less

Six substitutionally inert [Ru(II) (bipy)2 dppz](2+) derivatives (bipy=2,2'-bipyridine, dppz=dipyrido[3,2-a:2',3'-c]phenazine) bearing different functional groups on the dppz ligand [NH2 (1), OMe (2), OAc (3), OH (4), CH2 OH (5), CH2 Cl (6)] were synthesized and studied as potential photosensitizers (PSs) in photodynamic therapy (PDT). As also confirmed by DFT calculations, all complexes showed promising (1) O2 production quantum yields, well comparable with PSs available on the market. They can also efficiently intercalate into the DNA double helix, which is of high interest in view of DNA targeting. The cellular localization and uptake quantification of 1-6 were assessed by confocal microscopy and high-resolution continuum source atomic absorption spectrometry. Compound 1, and especially 2, showed very good uptake in cervical cancer cells (HeLa) with preferential nuclear accumulation. None of the compounds studied was found to be cytotoxic in the dark on both HeLa cells and, interestingly, on noncancerous MRC-5 cells (IC50 >100 μM). However, 1 and 2 showed very promising behavior with an increment of about 150 and 42 times, respectively, in their cytotoxicities upon light illumination at 420 nm in addition to a very good human plasma stability. As anticipated, the preferential nuclear accumulation of 1 and 2 and their very high DNA binding affinity resulted in very efficient DNA photocleavage, suggesting a DNA-based mode of phototoxic action. Show less

A new Ru(II)-Se complex, Ru(bpy)2L2Cl2 (bpy = 2,2'-bipyridine, L = 1,10-phenanthrolineselenazole) (Ru-Se) has been synthesized and characterized. The G-quadruplex DNA-binding properties of the complex and its selenium ligand (Phen-Se) were evaluated by thermal denaturation study, polymerase chain reaction (PCR) stop assay, and telomerase repeat amplification protocol (TRAP). The results showed that the obtained complex could induce and stabilize G-quadruplex structure as well as exhibit potent inhibitory activity against telomerase. In vitro cytotoxicity studies showed that complex Ru-Se inhibited the cancer cell growth through apoptosis. However, the presence of the ligand Phen-Se did not appear to have a significant effect either on G-quadruplex binding or on biological activity. Furthermore, the cell migration assay and the tube formation assay also demonstrated that the complex Ru-Se significantly inhibited human umbilical vascular endothelial cell (HUVEC) proliferation, migration, and tube formation. These findings indicate that the Ru-Se complex may be a potential telomerase inhibitor and a viable drug candidate in antiangiogenesis for anticancer therapies. Show less

Transition metal complexes with dual functions of DNA photobinding via coordination and DNA photocleavage via(1)O2 may present potent antitumor activities with high selectivity and a wide anticancer spectrum. We herein report such a complex, [(η(6)-p-cymene)Ru(dpb)(py)](2+) (dpb = 2,3-bis(2-pyridyl)benzoquinoxaline, py = pyridine, 1). The highly delocalized nature of dpb provides 1 with long wavelength-absorbing properties and a long-lived excited state, facilitating (1)O2 generation. Additionally, the bulky nature of dpb leads to a distorted coordination geometry, and allow the (3)MC (metal-centered) state to be more accessible. From this, dissociation of py and dpb may occur, followed by the coordination of the resultant Ru fragment to nucleic bases if DNA is present. The dissociation of dpb can turn on fluorescence of its own, enabling real-time imaging of the photoactivation process. The fascinating properties of 1 and the underlying mechanisms that occur may provide guidelines for developing more efficient metallodrugs with dual potential for photodynamic therapy (PDT) and photoactivated chemotherapy (PACT). Show less

We report on the synthesis of novel water-soluble [(arene)Ru(II)(Q)Cl] and [(arene)Ru(II)(Q)(X)]BF4 compounds (arene = p-cymene, benzene, hexamethylbenzene; HQ = 1,3-dimethyl-4-R-(C═O)-5-pyrazolone, HQ(Me), R = methyl, HQ(Ph), R = phenyl, HQ(Naph), R = naphthyl; X = H2O, 9-ethylguanine), and their in vitro antitumor activity toward the cell lines MCF7 (HTB-22, human breast adenocarcinoma), HCT116 (CCL-247, human colorectal carcinoma), A2780 (human ovarian carcinoma), A549 (CCL-185, human lung carcinoma), and U87 MG (HTB-1, human glioblastoma). The X-ray crystal structures of two complexes were determined. One of them, {chlorido-(p-cymene)-[(1,3-dimethyl-4-(1-naphthoyl)-pyrazolon-5-ato]ruthenium(II)}, was also studied with density functional theory methods and was selected for docking on a DNA octamer showing intercalation between DNA bases by the naphthyl moiety and for Ru-N7(guanine) bonding. Show less

Novel ruthenium half-sandwich complexes containing (N,O)-bound pyrazolone-based β-ketoamine ligands have been prepared, and the solid-state structures of one ligand and five complexes have been determined by single-crystal X-ray diffraction. Some of the complexes display moderate cytotoxicity toward the human ovarian cancer cell lines A2780 and A2780cisR, the latter line having acquired resistance to cisplatin. Show less

Studies have shown that ruthenium complexes have relatively strong anticancer activity, cell uptake of drugs have a crucial impact on the pharmacological activity, using autofluorescence of ruthenium complexes could effectively track cancer cells and drug distribution, transport accurately in real time. In this work, we present the synthesis and detailed characterization of two novel Ru(II) complexes with hydrophobic ancillary ligands, namely [Ru(bpy)2(5-idip)](2+) (RBD) and [Ru(phen)2(5-idip)](2+) (RPD) (5-idip = 2-indole-[4,5-f][1,10]phenanthroline). We have shown that RPD can enter the HeLa cells efficiently through non-endocytotic, but energy-dependent mechanism and first accumulated in lysosomes, and then escape from the lysosomes and localize within the nuclei, efficiently lead to the inhibition of DNA transcription and translation and induced cell apoptosis. Further studies on the mechanism of apoptosis in HeLa cells demonstrate that RPD is able to induce mitochondria-mediated apoptosis in HeLa cells through activation of initiator caspase-9 and down-stream effector caspase-3 and -7 and cleavage of PARP. We have also demonstrated that RPD bind to telomeric G-quadruplex DNA effectively and selectively, together with increased p21 and p16 expression. Our findings suggest that RPD induces HeLa cell apoptosis through mitochondria-mediated pathway and inhibition of telomerase activity. RPD may be a candidate for further evaluation as a chemotherapeutic agent for human cancers. Show less

A series of ruthenium(II) arene complexes with the 4-(biphenyl-4-carbonyl)-3-methyl-1-phenyl-5-pyrazolonate ligand, and related 1,3,5-triaza-7-phosphaadamantane (PTA) derivatives, has been synthesized. The compounds have been characterized by NMR and IR spectroscopy, ESI mass spectrometry, elemental analysis, and X-ray crystallography. Antiproliferative activity in four human cancer cell lines was determined by MTT assay, yielding dose- and cancer cell line-dependent IC50 values of 9-34 μM for three hexamethylbenzene-ruthenium complexes, whereas the other metal complexes were much less active. Apoptosis was the mechanism involved in the anticancer activity of such compounds. In fact, the hexamethylbenzene-ruthenium complexes activated caspase activity, with consequent DNA fragmentation, accumulation of pro-apoptotic proteins (p27, p53, p89 PARP fragments), and the concomitant down-regulation of antiapoptotic protein Bcl-2. Biosensor-based binding studies indicated that the ancillary ligands were critical in determining the DNA binding affinities, and competition binding experiments further characterized the nature of the interaction. Show less

Here, we examine the photophysical properties of five ruthenium(II) complexes comprising two 4,7-diphenyl-1,10-phenanthroline (dip) ligands and functionalized bipyridine (R₁bpy-R₂, where R₁= H or CH3, R₂= H, CH₃, COO⁻,4-[3-(2-nitro-1H-imidazol-1-yl)propyl] or 1,3-dicyclohexyl-1-carbonyl-urea) towards development of luminescence probes for cellular imaging. These complexes have been shown to interact with albumin and the formed adducts exhibited up to eightfold increase in the luminescence quantum yield as well as the average lifetime of emission. It was demonstrated that they cannot bind to DNA through the intercalation mode and its luminescence in the presence of DNA is quenching. Cell viability experiments indicated that all complexes possess significant dose-dependent cytotoxicity (with IC₅₀ 5-19 μM) on 4T1 breast cancer cell line and their anti-proliferative activity correlates very well with their lipophilicity. Cellular uptake was studied by measuring the ruthenium content in cells using ICP-MS technique. As expected, the better uptake is directly related to higher lipophilicity of doubly charged ruthenium complexes while uptake of monocationic one is much lower in spite of the highest lipophilicity. Additionally staining properties were assessed using flow cytometry and fluorescence microscopy. These experiments showed that complex with 1,3-dicyclohexyl-1-carbonyl-urea substituent exhibits the best staining properties in spite of the lowest luminescence quantum yield in buffered solution (pH 7.4). Our results point out that both the imaging and cytotoxic properties of the studied ruthenium complexes are strongly influence by the level of internalization and protein interaction. Show less

Lung cancer is one of the leading causes of death in the world, and non-small cell lung carcinoma accounts for approximately 75-85 % of all lung cancers. In the present work, we studied the antitumor activity of the compound cis-(dichloro)tetramineruthenium(III) chloride {cis-[RuCl2(NH3)4]Cl} against human lung carcinoma tumor cell line A549. The present study aimed to investigate the relationship between the expression of MDR1 and CYP450 genes in human lung carcinoma cell lines A549 treated with cisCarboPt, cisCRu(III) and cisDRu(III). The ruthenium-based coordinated complexes presented low cytotoxic and antiproliferative activities, with high IC50 values, 196 (±15.49), 472 (±20.29) and 175 (±1.41) for cisCarboPt, cisCRu(III) and cisDRu(III), respectively. The tested compounds induced apoptosis in A549 tumor cells as evidenced by caspase 3 activation, but only at high concentrations. Results also revealed that the amplification of P-gp gene is greater in A549 cells exposed to cisCarboPt and cisCRu(III) than cisDRu(III). Taken together all these results strongly demonstrate that MDR-1 over-expression in A549 cells could be associated to a MDR phenotype of these cells and moreover, it is also contributing to the platinum, and structurally-related compound, resistance in these cells. The identification and characterization of novel mechanisms of drug resistance will enable the development of a new generation of anti-cancer drugs that increase cancer sensitivity and/or represent more effective chemotherapeutic agents. Show less

The interaction of ruthenium (II) complex [Ru(bpy)2(mal)](2+) (RBM) and [Ru(phen)2(mal)](2+) (RPM) (bpy = 2, 2-bipyridine, phen = 1,10-phenanthroline, mal = malonyl carboxylate) with human serum albumin (HSA) has been investigated by using fluorescence, UV absorption and circular dichroism (CD) spectroscopy approaches. A strong fluorescence quenching reaction of complexes to HSA was observed and the quenching mechanism was suggested as static quenching according to the Stern-Volmer (S-V) equation. The number of binding sites n and observed binding constant Kb was measured by fluorescence quenching method. The thermodynamic parameters ΔH, ΔS, and ΔG at different temperatures were calculated and the results indicate the binding reaction is mainly entropy-driven and Vander Waals force played a major role in the reaction. The result of CD showed that the secondary structure of HSA molecules was changed in the presence of the ruthenium (II) complexes. Furthermore, the cell viability of ruthenium (II) complexes was evaluated by MTT and complex RPM has shown significant higher anticancer potency than RBM against all the cell lines screened. RPM showed a significant antitumor activity through induction of apoptosis in A549 cells. Show less

Heteroleptic C^N cyclometalated iridium(iii) complexes incorporating a monostyryl/distyryl BODIPY ligand via acetylide bonds of 2,2'-bipyridine (bpy) with both absorption (ca. ε = 8.96 × 10⁴ M^-1 cm^-1, 9.89 × 10⁴ M^-1 cm^-1, and 7.89 × 10⁴ M^-1 cm^-1 at 664 nm, 644 nm, and 729 nm for Ir-2, Ir-3 and Ir-4, respectively) and fluorescence emission bands (ca. 624-794 nm for Ir-1, Ir-2, Ir-3 and Ir-4) in the near infra-red region (NIR) and exceptionally long-lived triplet excited states (τ = 156.5 μs for Ir-2) have been reported. Ir(ppy)₃ (Ir-0; ppy = 2-phenylpyridine) was used as reference, which gives the typical weak absorption in visible range (ε = 1.51 × 10⁴ M^-1 cm^-1 M^-1 cm^-1 at 385 nm). The nanosecond time-resolved transient absorption and DFT calculations proposed that styryl BODIPY-localized long lived ³IL states were populated for Ir-1, Ir-2, Ir-3 and Ir-4 (τ_T = 106.6 μs, 156.5 μs, 92.5 μs and 31.4 μs, respectively) upon photoexcitation. The complexes were used as triplet photosensitizers for singlet oxygen (¹O₂) mediated photooxidation of 1,5-dihydronaphthalene to produce juglone. The ¹O₂ quantum yields (Φ_Δ) of Ir-1 (0.53) and Ir-2 (0.81) are ca. 9-fold of Ir-3 (0.06) and 40-fold of Ir-4 (0.02), respectively. Ir-2 has high molar absorption coefficient at 664 nm, moderate fluorescence in the NIR region, and high singlet oxygen quantum yield (Φ_Δ = 0.81), exhibits predominate photocytotoxicity over dark cytotoxicity in LLC cells (lung cancer cells) upon irradiation, making it potentially suitable for use in in vivo photodynamic therapy (PDT). Our results are useful for preparation of transition metal complexes that show strong absorption of visible light in the NIR region with long-lived triplet excited states and for the application of these complexes in photocatalysis and theranostics such as simultaneous photodynamic therapy (PDT) and luminescent bioimaging. Show less

In an endeavor toward the development of metal-based anticancer drugs, we present here the design, synthesis and characterization of three ruthenium(II) functionalized phenanthroline complexes with extended π-conjugation. These complexes have been shown to act as promising CT-DNA intercalators as evidenced by UV-visible, luminescence, emission quenching by [Fe(CN)6](4-), DNA competitive binding with ethidium bromide and salt dependent studies. All three complexes [Ru(Hdpa)2PPIP](2+) (1), [Ru(Hdpa)2PIP](2+) (2), [Ru(Hdpa)24HEPIP](2+) (3) clearly demonstrated that they can bind to DNA through the intercalation mode. Cell viability experiments indicated that all complexes showed significant dose dependent cytotoxicity in selected cell lines. The apoptosis and cell cycle arrest were also investigated. The complexes were docked into DNA-base-pairs using the 'GOLD' (Genetic Optimization for Ligand Docking), docking program. Show less

A series of ketone-N(4)-substituted thiosemicarbazone (TSC) compounds (L1-L9) and their corresponding [(η(6)-p-cymene)Ru(II)(TSC)Cl](+/0) complexes (1-9) were synthesized and characterized by NMR, IR, elemental analysis, and HR-ESI-mass spectrometry. The molecular structures of L4, L9, 1-6, and 9 were determined by single-crystal X-ray diffraction analysis. The compounds were further evaluated for their in vitro antiproliferative activities against the SGC-7901 human gastric cancer, BEL-7404 human liver cancer, and HEK-293T noncancerous cell lines. Furthermore, the interactions of the compounds with DNA were followed by electrophoretic mobility spectrometry studies. 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

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

Three new compounds, [Ru(Hdpa)2PyIP](ClO4)2·2H2O (1) [Ru(Hdpa)2FyIP](ClO4)2·2H2O (2) and [Ru(Hdpa)2IIP](ClO4)2·2H2O (3) have been synthesized and characterized by spectroscopic techniques such as elemental analysis, UV/Vis, FT-IR, (1)H NMR, (13)C NMR and mass spectra. The CT-DNA binding properties of 1-3 have been investigated by absorption, emission spectroscopy and viscosity measurements. Experimental results suggested that they can interact with DNA through intercalative mode with different binding strengths. These were found to promote the cleavage of plasmid DNA. Cell viability results indicated that all compounds showed significant dose dependent cytotoxicity in selected cell lines and 1 shown higher cytotoxicity than cisplatin on HeLa cells. Cellular uptake studies were studied by flow cytometry and confocal microscopy. Show less

Four ruthenium(ii) asymmetric complexes, [Ru(bpy)2(PAIDH)](2+) (bpy = 2,2'-bipyridine, PAIDH = 2-pyridyl-1H-anthra[1,2-d]imidazole-6,11-dione, ), [Ru(phen)2(PAIDH)](2+) (phen = 1,10-phenanthroline, ), [Ru(dmp)2(PAIDH)](2+) (dmp = 4,7-dimethyl-1,10-phenanthroline, ) and [Ru(dip)2(PAIDH)](2+) (dip = 4,7-diphenyl-1,10-phenanthroline, ), have been synthesized and characterized. These complexes displayed potent anti-proliferation activity against various cancer cell lines and had high selectivity between tumor cells and normal cells. HeLa cells exhibited the highest sensitivity to complex , accounting for the greatest cellular uptake. Complex was shown to accumulate preferentially in the mitochondria of HeLa cells and induced apoptosis via the mitochondrial pathway, which involved ROS generation, mitochondrial membrane potential depolarisation, and Bcl-2 and caspase family members activation. These results demonstrated that complex induced cancer cell apoptosis by acting on mitochondrial pathways. Show less

In the present study, the interaction between GC-rich sequence of bcl-2 gene P1 promoter (Pu39) and two ruthenium (II) polypyridyl complexes, [Ru(bpy)₂(tip)]²⁺ (1) and [Ru(phen)₂(tip)]²⁺ (2), was investigated by UV-Visible, fluorescence spectroscopy, circular dichroism, fluorescence resonance energy transfer melting assay and polymerase chain reaction stop assay. Those experimental results indicated that the two complexes can effectively stabilize the G-quadruplex of Pu39. It was found that the complex 2 exhibited greater cytotoxic activity than 1 against human Hela cells and can enter into Hela cells in a short period of time to effectively induce apoptosis of cells. Further experiments found that complexes 1 and 2 had as potent inhibitory effects on ECV-304 cell migration as suramin. Those noteworthy results provide new insights into the development of anticancer agents for targeting G-quadruplex DNA. Show less

The emission enhancement behavior and photocleavage activity of a ruthenium(II) arene complex, [(η(6)-p-cymene)Ru(dppn)(py)](2+) (1) (dppn = 4,5,9,16-tetraaza-dibenzo[a,c]naphthacene, py = pyridine), towards DNA were compared with [(η(6)-p-cymene)Ru(bpy)(py)](2+) (2), [Ru(bpy)2(dppz)](2+) (3) and [Ru(bpy)2(dppn)](2+) (4) (bpy = 2,2'-bipyridine, dppz = dipyrido-[3,2-a:2',3'-c]phenazine). It was found that 1 emits fluorescence from the dppn-based ligand-centered (LC) singlet excited state and generates singlet oxygen ((1)O2) from the dppn-based LC triplet excited state. As a result, 1 displays emission enhancement behavior and photocleavage activity towards DNA simultaneously. In contrast, 3 is the most classical DNA light switch but shows poor DNA photocleavage activity, while 4 is an efficient DNA photocleaver but cannot report DNA binding by luminescence enhancement. An increased cytotoxicity against human lung carcinoma cells A549 by about 10-fold was also observed for 1 upon visible light activation. These intriguing properties result from the unique combination of the Ru(II) arene and dppn subunits. Show less

A series of new organoiridium(III) complexes [Ir(N-C)(2)(N-S)]Cl (HN-C = 2-phenylpyridine (Hppy), N-S = methyl thiosemicarbazide (1), phenyl thiosemicarbazide (2) and naphtyl thiosemicarbazide (3)) have been synthesized and characterized. The crystal structure of (1) has been established by X-ray diffraction, showing the thiosemicarbazide ligand bound to the iridium atom as N,S-chelate. The cytotoxicity studies show that they are more active than cisplatin (about 5-fold) in T47D (breast cancer) at 48 h incubation time. On the other hand, very low resistance factors (RF) of 1-3 in A2780cisR (cisplatin-resistant ovarian carcinoma) at 48 h were observed (RF ≈ 1). Ir accumulation in T47D cell line after 48 h continuous exposure for complexes 1-3 are higher than that corresponding to cisplatin (about 10 times). The complexes 1-3 bind strongly to HSA with binding constants of about 10(4) M(-1) at 296 K, binding occurring at the warfarin site I for 2. Complexes 2 and 3 are also capable of binding in the minor groove of DNA as shown by Hoechst 33258 displacement experiments. Furthermore, complex 2 is also a good cathepsin B inhibitor (an enzyme implicated in a number of cancer related events), being the enzyme reactivated by cysteine. 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

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