👤 Lara-Sánchez A

A series of Ru(II) arene complexes of mono- and bidentate N-donor ligands with carboxyl or ester groups and chlorido ancillary ligands were synthesised and structurally characterised. The complexes have a distorted tetrahedral piano-stool geometry. The binding interaction was studied with calf thymus DNA (CT-DNA) by absorption titration, viscosity measurement, thermal melting, circular dichroism, ethidium bromide displacement assay and DNA cleavage of plasmid DNA (pBR322), investigated by gel electrophoresis. The dichlorido complexes bind covalently to DNA in the dark, similar to cisplatin, while the monochlorido complexes bind covalently on irradiation, similar to cisplatin analogues. The compounds are selectively cytotoxic against several tumour cell lines and show specific nonlinear correlation between dose and activity. This phenomenon is closely related to their potential to act preferentially as inhibitors of cell division. Show less

Herein we synthesized two new ruthenium(II) compounds [Ru(pySH)(bipy)(dppb)]PF6 (1) and [Ru(HSpym)(bipy)(dppb)]PF6 (2) that are analogs to an antitumor agent recently described, [Ru(SpymMe2)(bipy)(dppb)]PF6 (3), where [(Spy) = 2-mercaptopyridine anion; (Spym) = 2-mercaptopyrimidine anion and (SpymMe2) = 4,6-dimethyl-2-mercaptopyrimidine anion]. In vitro cell culture experiments revealed significant anti-proliferative activity for 1-3 against HepG2 and MDA-MB-231 tumor cells, higher than the standard anti-cancer drugs doxorubicin and cisplatin. No mutagenicity is detected when compounds are evaluated by cytokinesis-blocked micronucleus cytome and Ames test in the presence and absence of S9 metabolic activation from rat liver. Interaction studies show that compounds 1-3 can bind to DNA through electrostatic interactions and to albumin through hydrophobic interactions. The three compounds are able to inhibit the DNA supercoiled relaxation mediated by human topoisomerase IB (Top1). Compound 3 is the most efficient Top1 inhibitor and the inhibitory effect is enhanced upon pre-incubation with the enzyme. Analysis of different steps of Top1 catalytic cycle indicates that 3 inhibits the cleavage reaction impeding the binding of the enzyme to DNA and slows down the religation reaction. Molecular docking shows that 3 preferentially binds closer to the residues of the active site when Top1 is free and lies on the DNA groove downstream of the cleavage site in the Top1-DNA complex. Thus, 3 can be considered in further studies for a possible use as an anticancer agent. Show less

Two thermally activated ruthenium(ii) polypyridyl complexes, cis-Ru(bpy)2Cl2 and trans-Ru(qpy)Cl2 were investigated to determine the impact of the geometric arrangement of the exchangable ligands on the potential of the compounds to act as chemotherapeutics. In contrast to the geometry requirements for cisplatin, trans-Ru(qpy)Cl2 was 7.1-9.5× more cytotoxic than cis-Ru(bpy)2Cl2. This discovery could open up a new area of metal-based chemotherapeutic research. Show less

A series of 6 substitutionally inert and luminescent iridium(iii) antitumor agents of the type [Ir(C^∧N)₂(N^∧N)][PF₆] containing a benzimidazole N^∧N ligand with an ester group as a handle for further functionalization has been prepared. They exhibit IC₅₀ values in the high nanomolar range in some ovarian and breast cancer cell lines (approximately 100× more cytotoxic than cisplatin (CDDP) in MDA-MB-231) and are located in the actin cortex predominantly as shown by confocal luminescence microscopy. This discovery could open the door to a new large family of drug bioconjugates with diverse and simultaneous functions. Show less

Organelle-targeted photosensitizers have been reported to be effective photodynamic therapy (PDT) agents. In this work, we designed and synthesized two iridium(III) complexes that specifically stain the mitochondria and lysosomes of living cells, respectively. Both complexes exhibited long-lived phosphorescence, which is sensitive to oxygen quenching. The photocytotoxicity of the complexes was evaluated under normoxic and hypoxic conditions. The results showed that HeLa cells treated with the mitochondria-targeted complex maintained a slower respiration rate, leading to a higher intracellular oxygen level under hypoxia. As a result, this complex exhibited an improved PDT effect compared to the lysosome-targeted complex, especially under hypoxia conditions, suggestive of a higher practicable potential of mitochondria-targeted PDT agents in cancer therapy. Show less

The family of iodido Os^II arene phenylazopyridine complexes [Os(η⁶ -p-cym)(5-R¹ -pyridylazo-4-R² -phenyl))I]⁺ (where p-cym=para-cymene) exhibit potent sub-micromolar antiproliferative activity towards human cancer cells and are active in vivo. Their chemical behavior is distinct from that of cisplatin: they do not readily hydrolyze, nor bind to DNA bases. We report here a mechanism by which they are activated in cancer cells, involving release of the I^- ligand in the presence of glutathione (GSH). The X-ray crystal structures of two active complexes are reported, 1-I (R¹ =OEt, R² =H) and 2-I (R¹ =H, R² =NMe₂ ). They were labelled with the radionuclide ¹³¹ I (β^- /γ emitter, t_1/2 8.02 d), and their activity in MCF-7 human breast cancer cells was studied. 1-[¹³¹ I] and 2-[¹³¹ I] exhibit good stability in both phosphate-buffered saline and blood serum. In contrast, once taken up by MCF-7 cells, the iodide ligand is rapidly pumped out. Intriguingly, GSH catalyzes their hydrolysis. The resulting hydroxido complexes can form thiolato and sulfenato adducts with GSH, and react with H₂ O₂ generating hydroxyl radicals. These findings shed new light on the mechanism of action of these organo-osmium complexes. Show less

A new mononuclear rhodium(III) complex, [Rh(bzimpy)Cl₃] (bzimpy = 2,6-bis(2-benzimidazolyl)pyridine), was synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structure of the complex was confirmed by single-crystal X-ray crystallography. The interaction of the complex with fish sperm DNA (FS-DNA) was investigated by UV spectroscopy, emission titration, and viscosity measurement in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constant. The results reveal that the Rh(III) complex interacts with DNA through groove binding mode with a binding affinity on the order of 10⁴. In addition, the binding of the Rh(III) complex to bovine serum albumin (BSA) was monitored by UV-Vis and fluorescence emission spectroscopy at different temperatures. The mechanism of the complex interaction was found to be static quenching. The thermodynamic parameters (ΔH, ΔS, and ΔG) obtained from the fluorescence spectroscopy data show that van der Waals interactions and hydrogen bonds play a major role in the binding of the Rh(III) complex to BSA. For the comparison of the DNA- and BSA-binding affinities of the free bzimpy ligand with its Rh(III) complex, the absorbance titration and fluorescence quenching experiments of the free bzimpy ligand with DNA and BSA were carried out. Competitive experiments using eosin Y and ibuprofen as site markers indicated that the complex was mainly located in the hydrophobic cavity of site I of the protein. These experimental results were confirmed by the results of molecular docking. Finally, the in vitro cytotoxicity properties of the Rh(III) complex against the MCF-7, K562, and HT-29 cell lines were evaluated and compared with those of the free ligand (bzimpy). It was found that the complexation process improved the anticancer activity significantly. Show less

Oncogenic KRAS mutations found in 20% to 30% of all non-small cell lung cancers (NSCLC) are associated with chemoresistance and poor prognosis. Here we demonstrate that activation of the cell protective stress response gene NRF2 by KRAS is responsible for its ability to promote drug resistance. RNAi-mediated silencing of NRF2 was sufficient to reverse resistance to cisplatin elicited by ectopic expression of oncogenic KRAS in NSCLC cells. Mechanistically, KRAS increased NRF2 gene transcription through a TPA response element (TRE) located in a regulatory region in exon 1 of NRF2. In a mouse model of mutant KrasG12D-induced lung cancer, we found that suppressing the NRF2 pathway with the chemical inhibitor brusatol enhanced the antitumor efficacy of cisplatin. Cotreatment reduced tumor burden and improved survival. Our findings illuminate the mechanistic details of KRAS-mediated drug resistance and provide a preclinical rationale to improve the management of lung tumors harboring KRAS mutations with NRF2 pathway inhibitors. Show less

Sixteen hydrazinyl-thiazolo arene ruthenium complexes of the general formula [(η(6)-p-cymene)Ru(N,N'-hydrazinyl-thiazolo)Cl]Cl were synthesized. All complexes were tested in vitro for their antiproliferative activity on three tumor cell lines (HeLa, A2780, and A2780cisR) and on a noncancerous cell line (HFL-1). A superior cytotoxic activity of the ruthenium complexes as compared to cisplatin and oxaliplatin, on both cisplatin-sensitive and cisplatin resistant ovarian cancer cells, was observed. In addition, the biological activity of two selected derivatives was evaluated using microarray gene expression assay and ingenuity pathway analysis. p53 signaling was identified as an important pathway modulated by both arene ruthenium compounds. New activated molecules such as FAS, ZMAT3, PRMT2, BBC3/PUMA, and PDCD4, whose overexpressions are correlated with overcoming resistance to cisplatin therapy, were also identified as potential targets. Moreover, the arene ruthenium complexes can be used in association with cisplatin to prevent cisplatin resistance development and synergistically to induce cell death in ovarian cancer cells. Show less

Ruthenium(II)-arene complexes with biotin-containing ligands were prepared so that a novel drug delivery system based on tumor-specific vitamin-receptor mediated endocytosis could be developed. The complexes were characterized by spectroscopic methods and their in vitro anticancer activity in cancer cell lines with various levels of major biotin receptor (COLO205, HCT116 and SW620 cells) was tested in comparison with the ligands. In all cases, coordination of ruthenium resulted in significantly enhanced cytotoxicity. The affinity of Ru(II) -biotin complexes to avidin was investigated and was lower than that of unmodified biotin. Hill coefficients in the range 2.012-2.851 suggest strong positive cooperation between the complexes and avidin. To estimate the likelihood of binding to the biotin receptor/transporter, docking studies with avidin and streptavidin were conducted. These explain, to some extent, the in vitro anticancer activity results and support the conclusion that these novel half-sandwich ruthenium(II)-biotin conjugates may act as biological vectors to cancer cells, although no clear relationship between the cellular Ru content, the cytotoxicity, and the presence of the biotin moiety was observed. Show less

Aiming for novel tools for anticancer therapies, a ruthenium complex, covalently linked to a cholesterol-containing nucleolipid and stabilized by co-aggregation with a biocompatible lipid, is here presented. The amphiphilic ruthenium complex, named ToThyCholRu, is intrinsically negatively charged and has been inserted into liposomes formed by the cationic 1,2-dioleyl-3-trimethylammoniumpropane chloride (DOTAP) to hinder the degradation kinetics typically observed for known ruthenium-based antineoplastic agents. The here described nanovectors contain up to 30% in moles of the ruthenium complex and are stable for several weeks. This drug delivery system has been characterized using dynamic light scattering (DLS), small angle neutron scattering (SANS), neutron reflectivity (NR) and electron paramagnetic resonance (EPR) techniques. Fluorescence microscopy, following the incorporation of rhodamine-B within the ruthenium-loaded liposomes, showed fast cellular uptake in human carcinoma cells, with a strong fluorescence accumulation within the cells. The in vitro bioactivity profile revealed an important antiproliferative activity and, most remarkably, the highest ability in ruthenium vectorization measured so far. Cellular morphological changes and DNA fragmentation provided evidence of an apoptosis-inducing activity, in line with several in vitro studies supporting apoptotic events as the main cause for the anticancer properties of ruthenium derivatives. Overall, these data highlighted the crucial role played by the cellular uptake properties in determining the anticancer efficacy of ruthenium-based drugs, showing DOTAP as a very efficient nanocarrier for their stabilization in aqueous media and transport in cells. In vitro bioscreens have shown the high antiproliferative activity of ToThyCholRu-DOTAP liposomes against specific human adenocarcinoma cell types. Furthermore, these formulations have proved to be over 20-fold more effective against MCF-7 and WiDr adenocarcinoma cells with respect to the nude ruthenium complex AziRu we have previously described. Show less

Cytostatic agents that interfere with specific cellular components to prevent cancer cell growth offer an attractive alternative, or complement, to traditional cytotoxic chemotherapy. Here, we describe the synthesis and characterization of a new binuclear Ru(II) -Pt(II) complex [Ru(tpy)(tpypma)Pt(Cl)(DMSO)](3+) (tpy=2,2':6',2''-terpyridine and tpypma=4-([2,2':6',2''-terpyridine]-4'-yl)-N-(pyridin-2-ylmethyl)aniline), VR54, which employs the extended terpyridine tpypma ligand to link the two metal centres. In cell-free conditions, VR54 binds DNA by non-intercalative reversible mechanisms (Kb =1.3×10(5)  M(-1) ) and does not irreversibly bind guanosine. Cellular studies reveal that VR54 suppresses proliferation of A2780 ovarian cancer cells with no cross-resistance in the A2780CIS cisplatin-resistant cell line. Through the preparation of mononuclear Ru(II) and Pt(II) structural derivatives it was determined that both metal centres are required for this anti-proliferative activity. In stark contrast to cisplatin, VR54 neither activates the DNA-damage response network nor induces significant levels of cell death. Instead, VR54 is cytostatic and inhibits cell proliferation by up-regulating the cyclin-dependent kinase inhibitor p27(KIP1) and inhibiting retinoblastoma protein phosphorylation, which blocks entry into S phase and results in G1 cell cycle arrest. Thus, VR54 inhibits cancer cell growth by a gain of function at the G1 restriction point. This is the first metal-coordination compound to demonstrate such activity. Show less

1,3-Diaryltriazenes (1) were let to react with [RuCl2(p-cymene)]2 in the presence of trimethylamine to give neutral 1,3-diaryltriazenido(p-cymene)ruthenium(II) complexes, [RuCl(p-cymene)(ArNNNAr)] (2). The molecular composition of the products 2 was confirmed by NMR spectroscopy and mass spectrometry. The structures of the selected complexes were confirmed by a single crystal X-ray analysis. All triazenido-ruthenium complexes were highly cytotoxic against human cervical carcinoma HeLa cells with IC50 below 6μM, as determined by a spectrophotometric MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) method. The most active was [RuCl(p-cymene)(ArNNNAr)] (Ar=4-Cl-3-(CF3)-C6H3) (2g) with IC50 of 0.103±0.006μM. In comparison with the data for the non-coordinated triazenes 1, the triazenido-ruthenium complexes 2 exhibited up to 560-times higher activity. Three selected complexes were highly cytotoxic also against several tumor cell lines: laryngeal carcinoma HEp-2 cells and their drug-resistant HEp-2 subline (7T), colorectal carcinoma HCT-116 cells, lung adenocarcinoma H460 cells, and mammary carcinoma MDA-MB-435 cells. The compounds 2g and [RuCl(p-cymene)(ArNNNAr)] (Ar=4-I-C6H4) (2j) were similarly cytotoxic against parental and drug-resistant cells. Time and dose dependent accumulation of the cells in the S phase of the cell cycle was induced by the compound 2g, triggering apoptosis. Our preliminary results indicate triazenido-ruthenium complexes as promising anticancer drug candidates. Show less

The complexes [RuCp*(PP)Cl] (Cp* = C5Me5; [], PP = dppm; [], PP = Xantphos), [RuCp(#)(PP)Cl] (Cp(#) = C5Me4(CH2)5OH; [], PP = dppm; [], PP = Xantphos) and [RuCp*(dppm)(CH3CN)][SbF6] [] were synthesized and evaluated in vitro as anticancer agents. Compounds gave nanomolar IC50 values against normoxic A2780 and HT-29 cell lines, and were also tested against hypoxic HT-29 cells, maintaining their high activity. Complex yielded an IC50 value of 0.55 ± 0.03 μM under a 0.1% O2 concentration. Show less

A series of novel C,N-cyclometalated benzimidazole ruthenium(II) and iridium(III) complexes of the types [(η(6)-p-cymene)RuCl(κ(2)-N,C-L)] and [(η(5)-C5Me5)IrCl(κ(2)-N,C-L)] (HL = methyl 1-butyl-2-arylbenzimidazolecarboxylate) with varying substituents (H, Me, F, CF3, MeO, NO2, and Ph) in the R4 position of the phenyl ring of 2-phenylbenzimidazole chelating ligand of the ruthenium (3a-g) and iridium complexes (4a-g) have been prepared. The cytotoxic activity of the new ruthenium(II) and iridium(III) compounds has been evaluated in a panel of cell lines (A2780, A2780cisR, A427, 5637, LCLC, SISO, and HT29) in order to investigate structure-activity relationships. Phenyl substitution at the R4 position shows increased potency in both Ru and Ir complexes (3g and 4g, respectively) as compared to their parent compounds (3a and 4a) in all cell lines. In general, ruthenium complexes are more active than the corresponding iridium complexes. The new ruthenium and iridium compounds increased caspase-3 activity in A2780 cells, as shown for 3a,d and 4a,d. Compound 4g is able to increase the production of ROS in A2780 cells. Furthermore, all the new compounds are able to overcome the cisplatin resistance in A2780cisR cells. In addition, some of the metal complexes effectively inhibit angiogenesis in the human umbilical vein endothelial cell line EA.hy926 at 0.5 μM, the ruthenium derivatives 3g (Ph) and 3d (CF3) being the best performers. QC calculations performed on some ruthenium model complexes showed only moderate or slight electron depletion at the phenyl ring of the C,N-cyclometalated ligand and the chlorine atom on increasing the electron withdrawing effect of the R substituent. Show less

Two heterobimetallic complexes, i.e. [RuCl2(p-cymene)(μ-dppm)AuC] (1) and [RuCl2(p-cymene)(μ-dppm)Au(S-thiazoline)] (3), based on known cytotoxic [Ru(p-cymene)Cl2(PR3)] and [AuX(PR3)] (X = Cl, SR) molecular scaffolds, with the diphosphane linker 1,1-bis(diphenylphosphino)methane, dppm, were conveniently prepared and characterised. Remarkably, the new compounds manifested a more favourable in vitro pharmacological profile toward cancer cells than individual ruthenium and gold species being either more cytotoxic or more selective. The interactions of the studied compounds with (pBR322) DNA and their inhibitory effects on cathepsin B were also assessed. In addition, their reactivity toward suitable models of protein targets was explored and clear evidence gained for disruption of the bimetallic motif and for protein binding of monometallic fragments. Overall, the data reported here strongly support the concept of multifunctional heterometallic compounds as "improved" candidate agents for cancer treatment. The mechanistic and pharmacological implications of the present findings are discussed. Show less

The cysteine protease cathepsin B has been causally linked to progression and metastasis of breast cancers. We demonstrate inhibition by a dipeptidyl nitrile inhibitor (compound 1) of cathepsin B activity and also of pericellular degradation of dye-quenched collagen IV by living breast cancer cells. To image, localize and quantify collagen IV degradation in real-time we used 3D pathomimetic breast cancer models designed to mimic the in vivo microenvironment of breast cancers. We further report the synthesis and characterization of a caged version of compound 1, [Ru(bpy)2(1)2](BF4)2 (compound 2), which can be photoactivated with visible light. Upon light activation, compound 2, like compound 1, inhibited cathepsin B activity and pericellular collagen IV degradation by the 3D pathomimetic models of living breast cancer cells, without causing toxicity. We suggest that caged inhibitor 2 is a prototype for cathepsin B inhibitors that can control both the site and timing of inhibition in cancer. Show less

Four ruthenium(II)-based complexes with N-(acyl)-N',N'-(disubstituted)thiourea derivatives (Th) were obtained. The compounds, with the general formula trans-[Ru(PPh3)2(Th)(bipy)]PF6, interact with bovine serum albumin (BSA) and DNA. BSA-binding constants, which were in the range of 3.3-6.5×10(4) M(-1), and the thermodynamic parameters (ΔG, ΔH and ΔS), suggest spontaneous interactions with this protein by electrostatic forces due to the positive charge of the complexes. Also, binding constant by spectrophotometric DNA titration (Kb = 0.8-1.8×10(4) M(-1)) and viscosity studies indicate weak interactions between the complexes and DNA. Cytotoxicity assays against DU-145 (prostate cancer) and A549 (lung cancer) tumour cells revealed that the complexes are more active in tumour cells than in normal (L929) cells, and that they present high cytotoxicity (low IC50 values) compared with the reference metallodrug, cisplatin. Show less

We report the synthesis, characterization, and antiproliferative activity of 15 iridium(III) half-sandwich complexes of the type [(η⁵-Cp*)Ir(2-(R'-phenyl)-R-pyridine)Cl] bearing either an electron-donating (-OH, -CH₂OH, -CH₃) or electron-withdrawing (-F, -CHO, -NO₂) group at various positions on the 2-phenylpyridine (2-PhPy) chelating ligand giving rise to six sets of structural isomers. The X-ray crystal structures of [(η⁵-Cp*)Ir(2-(2'-fluorophenyl)pyridine)Cl] (1) and [(η⁵-Cp*)Ir(2-(4'-fluorophenyl)pyridine)Cl] (2) exhibit the expected "piano-stool" configuration. DFT calculations showed that substituents caused only localized effects on the electrostatic potential surface of the chelating 2-PhPy ligand of the complexes. Hydrolysis of all complexes is rapid, but readily reversed by addition of NaCl. The complexes show preferential binding to 9-ethylguanine over 9-methyladenine and are active catalysts for the oxidation of NADH to NAD⁺. Antiproliferative activity experiments in A2780 ovarian, MCF-7 breast, A549 lung, and HCT116 colon cancer cell lines showed IC₅₀ values ranging from 1 to 89 μM, with the most potent complex, [(η⁵-Cp*)Ir(2-(2'-methylphenyl)pyridine)Cl] (13) (A2780 IC₅₀ = 1.18 μM), being 10× more active than the parent, [(η⁵-Cp*)Ir(2-phenylpyridine)Cl], and 2× more active than [(η⁵-Cp^xPh)Ir(2-phenylpyridine)Cl]. Intriguingly, contrasting biological activities are observed between structural isomers despite exhibiting similar chemical reactivity. For pairs of structural isomers both the nature and position of the functional group can affect the hydrophobicity of the complex. An increase in hydrophobicity resulted in enhanced cellular-iridium accumulation in A2780 ovarian cells, which generally gave rise to an increase in potency. The structural isomers [(η⁵-Cp*)Ir(2-(4'-fluorophenyl)pyridine)Cl] (2) and [(η⁵-Cp*)Ir(2-phenyl-5-fluoropyridine)Cl] (4) preferentially localized in the cytosol > membrane and particulate > nucleus > cytoskeleton. This work highlights the strong dependence of biological behavior on the nature and position of the substituent on the chelating ligand and shows how this class of organometallic anticancer complexes can be fine-tuned to increase their potency without using extended cyclopentadienyl systems. Show less

Ruthenium-based anticancer complexes have become increasingly popular for study over the last two decades. Although ruthenium complexes are currently being investigated in clinical trials, there are still some difficulties with their delivery and associated side effects. Human serum albumin (HSA)-based delivery systems are promising for improving anticancer drug targeting and reducing negative side effects. However, there have been few studies regarding the HSA delivery system for metal-based anticancer compounds and no mention of its structural mechanism. Therefore, we studied the structure and anticancer properties of the ruthenium-based compound [RuCl5(ind)](2-) in complex with HSA. The structure revealed that [RuCl5(ind)](2-) has two binding sites in HSA. In the IB subdomain, [RuCl5(ind)](2-) binds to a new sub-site by coordinating with His-146. In the IIA subdomain, ruthenium (III) of [RuCl5(ind)](2-) binds to the hydrophobic cavity and forms coordination bonds by replacing chlorine atoms with the His-242 and Lys-199 residues of HSA. Interestingly, [RuCl5(ind)](2-), together with HSA, can enhance cytotoxicity by two to five times in cancer cells but has no effect on normal cells in vitro. Compared with unbound drug, the HSA-[RuCl5(ind)](2-) complex promotes MGC-803 cell apoptosis and also has a stronger capacity for cell cycle arrest at the G2 phase in MGC-803. In conclusion, this study will guide the rational design and development of ruthenium-containing or ruthenium-centered drugs and an HSA delivery system for ruthenium-based drugs. Show less

A set of structurally related Ru(η(5)-C5H5) complexes with bidentate N,N'-heteroaromatic ligands have been evaluated as prospective metallodrugs, with focus on exploring the uptake and cell death mechanisms and potential cellular targets. We have extended these studies to examine the potential of these complexes to target cancer cell metabolism, the energetic-related phenotype of cancer cells. The observations that these complexes can enter cells, probably facilitated by binding to plasma transferrin, and can be retained preferentially at the membranes prompted us to explore possible membrane targets involved in cancer cell metabolism. Most malignant tumors present the Warburg effect, which consists in increasing glycolytic rates with production of lactate, even in the presence of oxygen. The reliance of glycolytic cancer cells on trans-plasma-membrane electron transport (TPMET) systems for their continued survival raises the question of their appropriateness as a target for anticancer drug development strategies. Considering the interesting findings that some anticancer drugs in clinical use are cytotoxic even without entering cells and can inhibit TPMET activity, we investigated whether redox enzyme modulation could be a potential mechanism of action of antitumor ruthenium complexes. The results from this study indicated that ruthenium complexes can inhibit lactate production and TPMET activity in a way dependent on the cancer cell aggressiveness and the concentration of the complex. Combination approaches that target cell metabolism (glycolytic inhibitors) as well as proliferation are needed to successfully cure cancer. This study supports the potential use of some of these ruthenium complexes as adjuvants of glycolytic inhibitors in the treatment of aggressive cancers. Show less

Ruthenium anticancer drugs belong to the most promising non-platinum anticancer metal compounds in clinical evaluation. However, although the clinical results are promising regarding both activity and very low adverse effects, the clinical application is currently hampered by the limited solubility and stability of the drug in aqueous solution. Here, we present a new nanoparticle formulation based on polymer-based micelles loaded with the anticancer lead ruthenium compound KP1019. Nanoprepared KP1019 was characterised by enhanced stability in aqueous solutions. Moreover, the nanoparticle formulation facilitated cellular accumulation of KP1019 (determined by ICP-MS measurements) resulting in significantly lowered IC50 values. With regard to the mode of action, increased cell cycle arrest in G2/M phase (PI-staining), DNA damage (Comet assay) as well as enhanced levels of apoptotic cell death (caspase 7 and PARP cleavage) were found in HCT116 cells treated with the new nanoformulation of KP1019. Summarizing, we present for the first time evidence that nanoformulation is a feasible strategy for improving the stability as well as activity of experimental anticancer ruthenium compounds. Show less

The novel ligand (dmbip) 2-(4-N, N-dimethylbenzenamine)1H-imidazo[4, 5-f][1, 10]phenanthroline and its complexes [Ru(phen)2dmbip](2+) (1), [Ru(bpy)2dmbip](2+) (2), [Co(phen)2dmbip](3+) (3) and [Co(bpy)2dmbip](3+) (4) [where phen = 1, 10-phenanthroline, bpy = 2, 2'-bipyridine], have been synthesized and characterized by elemental analysis, IR, UV-Vis, (1)H NMR, (13)C NMR and Mass spectra. The DNA binding properties of the complexes were investigated by absorption, emission, quenching studies, light switch "on and off", salt dependent, sensor (cation and anion) studies, viscosity measurements, cyclic voltammetry, molecular modeling and docking studies. The four complexes were screened for Photo cleavage of pBR322 DNA, antimicrobial activity and cytotoxicity. The experimental results indicate that the four complexes can intercalate into DNA base pairs. The DNA-binding affinities of these complexes follow the order [Ru(phen)2dmbip](2+) > [Co(phen)2dmbip](3+) > [Ru(bpy)2dmbip](2+) > [Co(bpy)2dmbip](3+). Show less

Two Ru(II) polypyridyl complexes, Ru(DIP)2(bdt) (1) and [Ru(dqpCO2Me)(ptpy)](2+) (2) (DIP = 4,7-diphenyl-1,10-phenanthroline, bdt = 1,2-benzenedithiolate, dqpCO2Me = 4-methylcarboxy-2,6-di(quinolin-8-yl)pyridine), ptpy = 4'-phenyl-2,2':6',2″-terpyridine) have been investigated as photosensitizers (PSs) for photodynamic therapy (PDT). In our experimental settings, the phototoxicity and phototoxic index (PI) of 2 (IC50(light): 25.3 μM, 420 nm, 6.95 J/cm(2); PI >4) and particularly of 1 (IC50(light): 0.62 μM, 420 nm, 6.95 J/cm(2); PI: 80) are considerably superior compared to the two clinically approved PSs porfimer sodium and 5-aminolevulinic acid. Cellular uptake and distribution of these complexes was investigated by confocal microscopy (1) and by inductively coupled plasma mass spectrometry (1 and 2). Their phototoxicity was also determined against the Gram-(+) Staphylococcus aureus and Gram-(-) Escherichia coli for potential antimicrobial PDT (aPDT) applications. Both complexes showed significant aPDT activity (420 nm, 8 J/cm(2)) against Gram-(+) (S. aureus; >6 log10 CFU reduction) and, for 2, also against Gram-(-) E. coli (>4 log10 CFU reduction). Show less

Three new ruthenium(II) polypyridyl complexes [Ru(phen)2BrIPC](2+) (1), [Ru(bpy)2 BrIPC](2+) (2) and [Ru(dmb)2BrIPC](2+) (3) where, BrIPC = (6-bromo-3-(1H-imidazo[4,5-f] [1,10]-phenanthroline, phen = 1,10-phenanthroline, bpy = 2,2' bipyridine, dmb = 4,4'-dimethyl 2,2' bipyridine, were synthesised and characterised. DNA-binding nature was investigated by spectroscopic titrations and mode of binding was assessed by viscosity measurements. The DNA-binding constants Kb of complexes 1, 2 and 3 were determined to be in the order of 10(5). Experimental results showed that these complexes interact with CT-DNA by intercalative mode. Photocleavage and antimicrobial activities were complex concentration dependent, at high concentration, high activity and vice versa. MTT assay was performed on HeLa cell lines, IC50 values of complexes in the order of 3 > 2 > 1 > cisplatin. From comet assay, cellular uptake studies, we observed that complexes could enter into the cell membrane and accumulate inside the nucleus. Molecular docking studies support the DNA binding affinity with hydrogen bonding and van der Waals attractions between base pairs and phosphate backbone of DNA with metal complexes. Show less

A water-stable phosphoramidate Ru(arene) metallodrug shows antiproliferative activity comparable to KP1019 in human cancer cell lines. This novel compound can cross-link the peptide backbone of cytochrome c, but features low apoptosis inducing properties. 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

Synthesis, spectroscopy, characterization, structures, and cytotoxicity studies of 2,6-bis(2,6-diisopropylphenyliminomethyl)pyridine (LLL) ruthenium compounds are described. The starting compound [RuCl3(LLL)] has been fully characterized using IR spectroscopy, UV-vis spectroscopy, electrospray ionization mass spectrometry, and NMR spectroscopy. In addition, the crystal structure of the ligand LLL has been determined using single-crystal X-ray diffraction. With the ruthenium(III) trichloride compound as starting material, a new family of Ru(II) complexes with a number of neutral and charged bidentate co-ligands have been synthesized and used for characterization and cytotoxicity studies. The synthesis of the corresponding [Ru(II)LLL(LL)Cl](+/0) complexes with co-ligands- LL is 1,10-phenanthroline, 2,2'-bipyridyl, 2-(phenylazo)pyridine, 2-(phenylazo)-3-methylpyridine, 2-(tolylazo)pyridine, or the anionic 2-picolinate-is reported. Analytical, spectroscopic (IR spectroscopy, UV-vis spectroscopy, (1)H NMR spectroscopy, and electrospray ionization mass spectrometry), and structural characterization of the new compounds is described. Crystal structure analyses of two Ru(II) compounds show a slightly distorted octahedral Ru(II) geometry with tridentate LLL coordinated in a planar meridional fashion, and the chelating co-ligand (LL) and a chloride ion complete the octahedron. The co-ligand plays a significant role in modulating the physicochemical and cytotoxic properties of these new ruthenium complexes. The in vitro cytotoxicity of these new Ru(II) complexes (half-maximal inhibitory concentration, IC50, of 0.5-1.5 μM), in comparison with the parent Ru(III) compound (half-maximal inhibitory concentration of 3.9-4.3 μM) is higher for several of the human cancer cell lines tested. The cytotoxic activity of some of the new ruthenium compounds is even higher than that of cisplatin in the same cancer cell lines. The cytotoxicity of these new anticancer compounds is discussed in the light of structure-based activity relationships, and a possible mechanism of action is suggested. Show less

The PTA N-alkyl derivatives (PTAC2H4OCOMe)X (1X: 1a, X = Br; 1b, X = I; 1c, X = PF6; 1d, X = BPh4), (PTACH2COOEt)X (2X: 2a, X = Br; 2b, X = Cl; 2c, X = PF6), and (PTACH2CH2COOEt)X (3X: 3a, X = Br; 3c, X = PF6), presenting all the functional groups of the natural cationic compounds acetylcholine or trimethylglycine combined with a P-donor site suitable for metal ion coordination, were prepared and characterized by NMR, ESI-MS, and elemental analysis. The X-ray crystal structures of 1d and 2c were determined. Ligands 1c, 2b, and 3c were coordinated to Pt(II) and Ru(II) to give the cationic complexes cis-[PtCl2(L)2]X2 and [RuCpCl(PPh3)(L)]X (L = 1, 2, 3, X = Cl or PF6) designed with a structure targeted for anticancer activity. The X-ray crystal structure of [CpRu(PPh3)(PTAC2H4OCOMe)Cl]PF6 (1cRu) was determined. The antiproliferative activity of the ligands and the complexes was evaluated on three human cancer cell lines. Show less