Ruthenium complexes containing bis-benzimidazole derivatives as a new class of apoptosis inducers

A Comparison of In Vitro Studies between Cobalt(III) and Copper(II) Complexes with Thiosemicarbazone Ligands to Treat Triple Negative Breast Cancer

Metal complexes have gained significant attention as potential anti-cancer agents. The anti-cancer activity of [Co(phen)2(MeATSC)](NO3)3•1.5H2O•C2H5OH 1 (where phen = 1,10-phenanthroline and MeATSC = 9-anthraldehyde-N(4)-methylthiosemicarbazone) and [Cu(acetylethTSC)Cl]Cl•0.25C2H5OH 2 (where acetylethTSC = (E)-N-ethyl-2-[1-(thiazol-2-yl)ethylidene]hydrazinecarbothioamide) was investigated by analyzing DNA cleavage activity. The cytotoxic effect was analyzed using CCK-8 viability assay. The activities of caspase 3/7, 9, and 1, reactive oxygen species (ROS) production, cell cycle arrest, and mitochondrial function were further analyzed to study the cell death mechanisms. Complex 2 induced a significant increase in nicked DNA. The IC50 values of complex 1 were 17.59 μM and 61.26 μM in cancer and non-cancer cells, respectively. The IC50 values of complex 2 were 5.63 and 12.19 μM for cancer and non-cancer cells, respectively. Complex 1 induced an increase in ROS levels, mitochondrial dysfunction, and activated caspases 3/7, 9, and 1, which indicated the induction of intrinsic apoptotic pathway and pyroptosis. Complex 2 induced cell cycle arrest in the S phase, ROS generation, and caspase 3/7 activation. Thus, complex 1 induced cell death in the breast cancer cell line via activation of oxidative stress which induced apoptosis and pyroptosis while complex 2 induced cell cycle arrest through the induction of DNA cleavage.

Recent Advances in Mitochondria-Localized Luminescent Ruthenium(II) Metallodrugs as Anticancer Agents

Presently, the most effective way to transport drugs specifically to mitochondria inside the cells is of pharmacophoric interest, as mitochondria are recognized as one of the most important targets for new drug design in cancer diagnosis. To date, there are many reviews covering the photophysical, photochemical, and anticancer properties of ruthenium(II) based metallodrugs owing to their high interest in biological applications. There are, however, no reviews specifically covering the mitochondria-localized luminescent Ru(II) complexes and their subsequent mitochondria-mediated anticancer activities. Therefore, this review describes the physicochemical basis for the mitochondrial accumulation of ruthenium complexes, their synthetic strategies to localize and monitor the mitochondria in living cells, and their related underlying anticancer results. Finally, we review the related areas from previous works describing the mitochondria-localized ruthenium complexes for the treatment of cancer-related diseases. Along with this, we also deliberate the perspectives and future directions for emerging more bifunctional Ru(II) complexes that can target, image, and kill tumors more efficiently in comparison with the existing mitochondria-targeted cancer therapeutics.

New Ruthenium-Cyclopentadienyl Complexes Affect Colorectal Cancer Hallmarks Showing High Therapeutic Potential

Colorectal cancer (CRC) is among the most deadly cancers worldwide. Current therapeutic strategies have low success rates and several side effects. This relevant clinical problem requires the discovery of new and more effective therapeutic alternatives. Ruthenium drugs have arisen as one of the most promising metallodrugs, due to their high selectivity to cancer cells. In this work we studied, for the first time, the anticancer properties and mechanisms of action of four lead Ru-cyclopentadienyl compounds, namely PMC79, PMC78, LCR134 and LCR220, in two CRC-derived cell lines (SW480 and RKO). Biological assays were performed on these CRC cell lines to evaluate cellular distribution, colony formation, cell cycle, proliferation, apoptosis, and motility, as well as cytoskeleton and mitochondrial alterations. Our results show that all the compounds displayed high bioactivity and selectivity, as shown by low half-maximal inhibitory concentrations (IC₅₀) against CRC cells. We observed that all the Ru compounds have different intracellular distributions. In addition, they inhibit to a high extent the proliferation of CRC cells by decreasing clonogenic ability and inducing cell cycle arrest. PMC79, LCR134, and LCR220 also induce apoptosis, increase the levels of reactive oxygen species, lead to mitochondrial dysfunction, induce actin cytoskeleton alterations, and inhibit cellular motility. A proteomic study revealed that these compounds cause modifications in several cellular proteins associated with the phenotypic alterations observed. Overall, we demonstrate that Ru compounds, especially PMC79 and LCR220, display promising anticancer activity in CRC cells with a high potential to be used as new metallodrugs for CRC therapy.

An Overview of the Potential Medicinal and Pharmaceutical Properties of Ru(II)/(III) Complexes

This review examines the existing knowledge about Ru(II)/(III) ion complexes with a potential application in medicine or pharmacy, which may offer greater potential in cancer chemotherapy than Pt(II) complexes, which are known to cause many side effects. Hence, much attention has been paid to research on cancer cell lines and clinical trials have been undertaken on ruthenium complexes. In addition to their antitumor activity, ruthenium complexes are under evaluation for other diseases, such as type 2 diabetes, Alzheimer's disease and HIV. Attempts are also being made to evaluate ruthenium complexes as potential photosensitizers with polypyridine ligands for use in cancer chemotherapy. The review also briefly examines theoretical approaches to studying the interactions of Ru(II)/Ru(III) complexes with biological receptors, which can facilitate the rational design of ruthenium-based drugs.

New Nanostructured Materials Based on Mesoporous Silica Loaded with Ru(II)/Ru(III) Complexes with Anticancer and Antimicrobial Properties

A new series of nanostructured materials was obtained by functionalization of SBA-15 mesoporous silica with Ru(II) and Ru(III) complexes bearing Schiff base ligands derived from salicylaldehyde and various amines (1,2-diaminocyclohexane, 1,2-phenylenediamine, ethylenediamine, 1,3-diamino-2-propanol, N,N-dimethylethylenediamine, 2-aminomethyl-pyridine, and 2-(2-aminoethyl)-pyridine). The incorporation of ruthenium complexes into the porous structure of SBA-15 and the structural, morphological, and textural features of the resulting nanostructured materials were investigated by FTIR, XPS, TG/DTA, zeta potential, SEM, and N₂ physisorption. The ruthenium complex-loaded SBA-15 silica samples were tested against A549 lung tumor cells and MRC-5 normal lung fibroblasts. A dose-dependent effect was observed, with the highest antitumoral efficiency being recorded for the material containing [Ru(Salen)(PPh₃)Cl] (50%/90% decrease in the A549 cells' viability at a concentration of 70 μg/mL/200 μg/mL after 24 h incubation). The other hybrid materials have also shown good cytotoxicity against cancer cells, depending on the ligand included in the ruthenium complex. The antibacterial assay revealed an inhibitory effect for all samples, the most active being those containing [Ru(Salen)(PPh₃)Cl], [Ru(Saldiam)(PPh₃)Cl], and [Ru(Salaepy)(PPh₃)Cl], especially against Staphylococcus aureus and Enterococcus faecalis Gram-positive strains. In conclusion, these nanostructured hybrid materials could represent valuable tools for the development of multi-pharmacologically active compounds with antiproliferative, antibacterial, and antibiofilm activity.

Comprehensive Insights into Medicinal Research on Imidazole-Based Supramolecular Complexes

The electron-rich five-membered aromatic aza-heterocyclic imidazole, which contains two nitrogen atoms, is an important functional fragment widely present in a large number of biomolecules and medicinal drugs; its unique structure is beneficial to easily bind with various inorganic or organic ions and molecules through noncovalent interactions to form a variety of supramolecular complexes with broad medicinal potential, which is being paid an increasing amount of attention regarding more and more contributions to imidazole-based supramolecular complexes for possible medicinal application. This work gives systematical and comprehensive insights into medicinal research on imidazole-based supramolecular complexes, including anticancer, antibacterial, antifungal, antiparasitic, antidiabetic, antihypertensive, and anti-inflammatory aspects as well as ion receptors, imaging agents, and pathologic probes. The new trend of the foreseeable research in the near future toward imidazole-based supramolecular medicinal chemistry is also prospected. It is hoped that this work provides beneficial help for the rational design of imidazole-based drug molecules and supramolecular medicinal agents and more effective diagnostic agents and pathological probes.

The Novel 5-Fluorouracil Loaded Ruthenium-based Nanocarriers Enhanced Anticancer and Apoptotic Efficiency while Reducing Multidrug Resistance in Colorectal Cancer Cells

Recently, nanocarriers have been made to eliminate the disadvantages of chemotherapeutic agents by nanocarriers. Nanocarriers show their efficacy through their targeted and controlled release. In this study, 5-fluorouracil (5FU) was loaded into ruthenium (Ru)-based nanocarrier (5FU-RuNPs) for the first time to eliminate the disadvantages of 5FU, and its cytotoxic and apoptotic effects on HCT116 colorectal cancer cells were compared with free 5FU. 5FU-RuNPs with a size of approximately 100 nm showed a 2.61-fold higher cytotoxic effect compared to free 5FU. Apoptotic cells were detected by Hoechst/propidium iodide double staining, and the expression levels of BAX/Bcl-2 and p53 proteins, in which apoptosis occurred intrinsically, were revealed. In addition, 5FU-RuNPs was also found to reduce multidrug resistance (MDR) according to BCRP/ABCG2 gene expression levels. When all the results were evaluated, the fact that Ru-based nanocarriers alone did not cause cytotoxicity proved that they were ideal nanocarriers. Moreover, 5FU-RuNPs did not show any significant effect on the cell viability of normal human epithelial cell lines BEAS-2B. Consequently, the 5FU-RuNPs synthesized for the first time may be ideal candidates for cancer treatment because they can minimize the potential drawbacks of free 5FU.

Ru(II)(ƞ6-p-cymene) Conjugates Loaded onto Graphene Oxide: An Effective pH-Responsive Anticancer Drug Delivery System

Graphene oxide-based nanodrug delivery systems are considered one of the most promising platforms to deliver therapeutic drugs at the target site. In this study, Ru(II)(ƞ6-p-cymene) complexes containing the benzothiazole ligand were covalently anchored on graphene oxide using the ultrasonication method. The nanoconjugates GO-NCD-1 and GO-NCD-2 were characterized by FT-IR, UV-visible, 1H NMR, TGA, SEM, and TEM techniques, which confirmed the successful loading of both the complexes (NCD 1 and NCD 2) on the carrier with average particle diameter sizes of 17 ± 6.9 nm and 25 ± 6.5 nm. In vitro DNA binding studies of the nanoconjugates were carried out by employing various biophysical methods to investigate the binding interaction with the therapeutic target biomolecule and to quantify the intrinsic binding constant values useful to understand their binding affinity. Our results suggest (i) high Kb and Ksv values of the graphene-loaded conjugates (ii) effective cleavage of plasmid DNA at a lower concentration of 7.5 µM and 10 µM via an oxidative pathway, and (iii) fast release of NCD 2 at an acidic pH that could have a good impact on the controlled delivery of drug. It was found that 90% of the drug was released in an acidic pH (5.8 pH) environment in 48 h, therefore suggesting pH-responsive behavior of the drug delivery system. Molecular docking, DFT studies, and cytotoxicity activity against three cancer cell lines by SRB assay were also performed.

Cobalt (III) complex exerts anti-cancer effects on T cell lymphoma through induction of cell cycle arrest and promotion of apoptosis

PURPOSE

Cobalt-based compounds are emerging as a non-platinum-based anti-cancer effective therapeutic agent. However, there is a limited study regarding the therapeutic efficacy of Cobalt-based drugs against Non-Hodgkin's Lymphoma (NHLs) such as T cell lymphoma. Therefore, in the present study we investigated the anti-tumor role of cobalt(III) complex [Co(ptsm)NH₃(o-phen)]·CH₃OH on Dalton's Lymphoma (DL) cells.

MATERIALS AND METHODS

Cytotoxicity of the cobalt complex was estimated by MTT assay. Analysis of mitochondrial membrane potential, cell cycle and Reactive oxygen species (ROS) generation, and Annexin V/PI staining was done by Flow cytometry, while AO/EtBr staining by fluorescence microscopy in cobalt complex treated DL cell. Expression of cell cycle and apoptosis regulatory protein was analyzed by Western blotting. In addition, in vivo study of the cobalt complex was evaluated in well-established DL bearing mice by monitoring physiological parameters and mean survival time.

RESULTS

Our study showed that cobalt complex triggered apoptosis and induced cell cycle arrest in DL cells. Furthermore, this also decreased mitochondrial membrane potential and increased intracellular ROS generation in cancer cells. In addition, changed expression of cell cycle and apoptosis regulatory protein was found with enhanced activity of caspase-3 and 9 in the treated cells. Additionally, administration of cobalt complex showed a significant increase in the survivability of tumor-bearing host, which was accomplished by decreasing physiological parameters.

CONCLUSION

Taken together, these data revealed anti-tumor potential of cobalt complex against DL cells through cell cycle arrest and mitochondrial-dependent apoptosis. Henceforth, cobalt-based drugs could be a new generation therapeutic drug to treat hematological malignancies.

Ruthenium(II)/Benzonitrile Complex Induces Cytotoxic Effect in Sarcoma-180 Cells by Caspase-Mediated and Tp53/p21-Mediated Apoptosis, with Moderate Brine Shrimp Toxicity

Ruthenium(II)/benzonitrile complexes have demonstrated promising anticancer properties. Considering that there are no specific therapies for treating sarcoma, we decided to evaluate the cytotoxic, genotoxic, and lethal effects of cis-[RuCl(BzCN)(phen)(dppb)]PF₆ (BzCN = benzonitrile; phen = 1,10-phenanthroline; dppb = 1,4-bis-(diphenylphosphino)butane), as well as the mechanism of cell death induction that occurs against murine sarcoma-180 tumor. Thus, MTT assay was applied to assess the ruthenium cytotoxicity, showing that the compound is a more potent inhibitor for the sarcoma-180 tumor cell viability than normal cells (lymphocytes). The comet assay indicated low genotoxic for normal cells. cis-[RuCl(BzCN)(phen)(dppb)]PF₆ also showed moderate lethality in Artemia salina. The complex induced cell cycle arrest in the G0/G1 phase in sarcoma-180 cells. In addition, the complex caused S180 cells to die by apoptosis by an increase in Annexin-V-positive cells and morphological changes typical of apoptotic cells. Additionally, cis-[RuCl(BzCN)(phen)(dppb)]PF₆ increased the gene expression of Bax, Casp3, and Tp53 in S180 cells. By using a western blot, we observed an increased protein level of TNF-R2, Bax, and p21. In conclusion, cis-[RuCl(BzCN)(phen)(dppb)]PF₆ is active and selective for sarcoma-180 cells, leading to cell cycle arrest at the G0/G1 and cell death through a caspases-mediated and Tp53/p21-mediated pathway.

Docking and in vitro molecular biology studies of p-anisidine-appended 1-hydroxy-2-acetonapthanone Schiff base lanthanum(iii) complexes

A new series of lanthanum(iii) complexes was synthesized using a p-anisidine-appended 1-hydroxy-2-acetonapthanone (3) Schiff base and characterized via spectroscopic methods. The ligand was synthesized via sonication and the crystalline product was characterized using X-ray crystallography. The genotoxicity of the compound was assessed primarily by the bacterial reverse mutation (Ames) test and the in vitro mammalian chromosome aberration test; in both cases, the samarium complex 5 was found to be non-mutagenic. The anti-tumor activity of complexes 4, 5, and 6 was assayed against HeLa tumor cells and screened using the MTT assay. The IC₅₀ value of complex 5 was found to be 34 ± 1.2 μg mL^-1 and this compound exhibited superior activity towards the cells compared to 4 and 6. These results were further confirmed by Hoechst 33258 staining and AO/EI dual staining, which indicated that the cells underwent an apoptosis mechanism in a dose-dependent manner. The apoptosis was further confirmed by the formation of ladders in the DNA fragmentation assay, and the western blot analysis of complex 5 suggested that the cells underwent the caspase-3-dependent pathway with PARP cleavage. Furthermore, the docking studies of complex 5 with HSA showed that it was situated in a hydrophilic cavity held by the electrostatic attraction of four hydrogen-bonding interactions. PDB ID:1BNA binds with complex 5via strong π-π stacking interactions, which facilitate binding with the major grooves of DNA strands. The above-mentioned results illustrate that for complex 5, mitochondrion-mediated apoptosis occurs via caspase-3 activation. Complex 5 binds with DNA via intercalation because of S-phase cell cycle arrest in the HeLa cells.

Functionalization and cancer-targeting design of ruthenium complexes for precise cancer therapy

The successful clinical application of the three generation platinum anticancer drugs, cisplatin, carboplatin and oxaliplatin, has promoted research interest in metallodrugs; however, the problems of drug resistance and adverse effects have hindered their further application and effects. Thus, scientists are searching for new anticancer metallodrugs with lower toxicity and higher efficacy. The ruthenium complexes have emerged as the most promising alternatives to platinum-based anticancer agents because of their unique multifunctional biochemical properties. In this review, we first focus on the anticancer applications of various ruthenium complexes in different signaling pathways, including the mitochondria-mediated pathway, the DNA damage-mediated pathway, and the death receptor-mediated pathway. We then discuss the functionalization and cancer-targeting designs of different ruthenium complexes in conjunction with other therapies such as photodynamic therapy, photothermal therapy, radiosensitization, targeted therapy and nanotechnology for precise cancer therapy. This review will help in designing and accelerating the research progress regarding new anticancer ruthenium complexes.

Design and synthesis of new ruthenium polypyridyl complexes with potent antitumor activity in vitro

We herein report the synthesis, characterization and anticancer activity of BTPIP (2-(4-(benzo[b]thiophen-2-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) and its four ruthenium(II) polypyridyl complexes [Ru(NN)₂(BTPIP)](ClO₄)₂ (N-N = bpy = 2,2'-bipyridine, Ru(II)-1; phen = 1,10-phenanthroline, Ru(II)-2; dmb = 4,4'-dimethyl-2,2'-bipyridine, Ru(II)-3; dmp = 2,9-dimethyl-1,10-phenanthroline, Ru(II)-4). The DNA binding behaviors reveal that the complexes bind to calf thymus DNA by intercalation. Cytotoxicity of the complexes against A549, HepG-2, SGC-7901 and Hela cells were evaluated in vitro. Complexes Ru(II)-1, Ru(II)-2, Ru(II)-3, Ru(II)-4 show moderate activity on the cell proliferation in A549 cells with IC₅₀ values of 9.3 ± 1.2, 12.1 ± 1.6, 10.3 ± 1.6, 8.9 ± 1.2 μM, respectively. Apoptosis assessment, intracellular mitochondrial membrane potential (MMP), location in mitochondria, reactive oxygen species (ROS), cell invasion assay and cell cycle arrest were also performed to explore the mechanism of this action. When the concentration of the ruthenium(II) complexes is increased, the amount of reactive oxygen species increases obviously and the mitochondrial membrane potential decreases dramatically in A549 cells. Most importantly, the ruthenium(II) polypyridyl complexes could arrive the cytoplasm through the cell membrane and accumulate in the mitochondria. These results showed that the ruthenium(II) complexes could induce apoptosis in A549 cells through an ROS-mediated mitochondrial dysfunction pathway.

Design and Synthesis of 2-(5-Phenylindol-3-yl)benzimidazole Derivatives with Antiproliferative Effects towards Triple-Negative Breast Cancer Cells by Activation of ROS-Mediated Mitochondria Dysfunction

Benzimidazole derivatives are widely studied because of their broad-spectrum biological activity, such as antitumor properties and excellent fluorescence performance. Herein, two types of 2-(5-phenylindol-3-yl)benzimidazole derivatives (1 a-1 h and 2 a-2 e) were rationally designed and synthesized. When these compounds were investigated in vitro anti-screening assays, we found that all of them possessed antitumor effect, in particular compound 1 b, which showed an outstanding antiproliferative effect on MDA-MB-231 cells (IC₅₀ ≈2.6 μm). A study of the drug action mechanisms in cells showed that the antitumor activity of the compounds is proportional to their lipophilicity and cellular uptake; the tested compounds all entered the lysosome of MDA-MB-231 cells and caused changes in the levels of reactive oxygen species (ROS), and then caused mitochondrial damage. Apparent differences in the ROS levels for each compound suggest that the lethality of these compounds towards MDA-MB-231 cells is closely related to the ROS levels. Taken together, this study not only provides a theoretical basis for 2-(5-phenylindol-3-yl)benzimidazole anticarcinogens but also offers new thinking on the rational design of next-generation antitumor benzimidazole derivatives.

Mitochondria-Targeting Anticancer Metal Complexes

Background:

Since the serendipitous discovery of the antitumor activity of cisplatin there has been a continuous surge in studies aimed at the development of new cytotoxic metal complexes. While the majority of these complexes have been designed to interact with nuclear DNA, other targets for anticancer metallodrugs attract increasing interest. In cancer cells the mitochondrial metabolism is deregulated. Impaired apoptosis, insensitivity to antigrowth signals and unlimited proliferation have been linked to mitochondrial dysfunction. It is therefore not surprising that mitochondria have emerged as a major target for cancer therapy. Mitochondria-targeting agents are able to bypass resistance mechanisms and to (re-) activate cell-death programs.

Methods:

Web-based literature searching tools such as SciFinder were used to search for reports on cytotoxic metal complexes that are taken up by the mitochondria and interact with mitochondrial DNA or mitochondrial proteins, disrupt the mitochondrial membrane potential, facilitate mitochondrial membrane permeabilization or activate mitochondria-dependent celldeath signaling by unbalancing the cellular redox state. Included in the search were publications investigating strategies to selectively accumulate metallodrugs in the mitochondria.

Results:

This review includes 241 references on antimitochondrial metal complexes, the use of mitochondria-targeting carrier ligands and the formation of lipophilic cationic complexes.

Conclusion:

Recent developments in the design, cytotoxic potency, and mechanistic understanding of antimitochondrial metal complexes, in particular of cyclometalated Au, Ru, Ir and Pt complexes, Ru polypyridine complexes and Au-N-heterocyclic carbene and phosphine complexes are summarized and discussed.

Anticancer activity and mechanism of bis-pyrimidine based dimetallic Ru(II)(η6-p-cymene) complex in human non-small cell lung cancer via p53-dependent pathway

Non-small cell lung cancer (NSCLC) is the most common cancer worldwide, which is related with poor prognosis and resistance to chemotherapy. Notably, ruthenium-based complexes have emerged as good alternative to the currently used platinum-based drugs for cancer therapy. In the present study, we synthesized a novel bis-pyrimidine based ligand 1,3-bis(2-methyl-6-(pyridin-2-yl)pyrimidin-4-yl)benzene (L) and used it in the synthesis of a dimetallic Ru(II) cymene complex [(Ru(η⁶-p-cymene)Cl)₂(1,3-bis(2-methyl-6-(pyridin-2-yl)pyrimidin-4-yl)benzene)] (L-Ru). We checked the stability of this complex in solution state in D₂O/DMSO‑d₆ mixture and found it to be highly stable under these conditions. We determined the anticancer activity and mechanism of action of L-Ru in human NSCLC A549 and A427 by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and related biological analyses. These results revealed that L-Ru exerted a strong inhibitory effect on the cells proliferation,G0/G1-arrest, accompanied with upregulation of p53, p21, p15, cleaved Poly (ADP-ribose) polymerase (PARP) protein and downregulation of cell cycle markers. L-Ru inhibited cell migration and invasion. The mitochondria-mediated apoptosis of NSCLC induced by L-Ru was also observed followed by the increase of apoptosis regulator B-cell lymphoma 2 associated X (BAX), and activation of caspase-3/-9. The effects of L-Ru on the cell viability, Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) positive cells and Annexin V-positive cells apoptosis induction were remarkably attenuated. This complex induced DNA damage, cell cycle arrest and cell death via caspase-dependent apoptosis involving PARP activation and induction of p53-dependent pathway. These findings suggested that this ruthenium complex might be a potential effective chemotherapeutic agent in NSCLC therapy.

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.

The development of anticancer ruthenium(ii) complexes: from single molecule compounds to nanomaterials

Cancer is rapidly becoming the top killer in the world. Most of the FDA approved anticancer drugs are organic molecules, while metallodrugs are very scarce. The advent of the first metal based therapeutic agent, cisplatin, launched a new era in the application of transition metal complexes for therapeutic design. Due to their unique and versatile biochemical properties, ruthenium-based compounds have emerged as promising anti-cancer agents that serve as alternatives to cisplatin and its derivertives. Ruthenium(iii) complexes have successfully been used in clinical research and their mechanisms of anticancer action have been reported in large volumes over the past few decades. Ruthenium(ii) complexes have also attracted significant attention as anticancer candidates; however, only a few of them have been reported comprehensively. In this review, we discuss the development of ruthenium(ii) complexes as anticancer candidates and biocatalysts, including arene ruthenium complexes, polypyridyl ruthenium complexes, and ruthenium nanomaterial complexes. This review focuses on the likely mechanisms of action of ruthenium(ii)-based anticancer drugs and the relationship between their chemical structures and biological properties. This review also highlights the catalytic activity and the photoinduced activation of ruthenium(ii) complexes, their targeted delivery, and their activity in nanomaterial systems.

Characterization of the Activities of Dinuclear Thiolato-Bridged Arene Ruthenium Complexes against Toxoplasma gondii

The in vitro effects of 18 dinuclear thiolato-bridged arene ruthenium complexes (1 monohiolato compound, 4 dithiolato compounds, and 13 trithiolato compounds), originally designed as anticancer agents, on the apicomplexan parasite Toxoplasma gondii grown in human foreskin fibroblast (HFF) host cells were studied. Some trithiolato compounds exhibited antiparasitic efficacy at concentrations of 250 nM and below. Among those, complex 1 and complex 2 inhibited T. gondii proliferation with 50% inhibitory concentrations (IC₅₀s) of 34 and 62 nM, respectively, and they did not affect HFFs at dosages of 200 μM or above, resulting in selectivity indices of >23,000. The IC₅₀s of complex 9 were 1.2 nM for T. gondii and above 5 μM for HFFs. Transmission electron microscopy detected ultrastructural alterations in the matrix of the parasite mitochondria at the early stages of treatment, followed by a more pronounced destruction of tachyzoites. However, none of the three compounds applied at 250 nM for 15 days was parasiticidal. By affinity chromatography using complex 9 coupled to epoxy-activated Sepharose followed by mass spectrometry, T. gondii translation elongation factor 1α and two ribosomal proteins, RPS18 and RPL27, were identified to be potential binding proteins. In conclusion, organometallic ruthenium complexes exhibit promising activities against Toxoplasma, and the potential mechanisms of action of these compounds as well as their prospective applications for the treatment of toxoplasmosis are discussed.

Ru(II)/diphenylphosphine/pyridine-6-thiolate complexes induce S-180 cell apoptosis through intrinsic mitochondrial pathway involving inhibition of Bcl-2 and p53/Bax activation

The aim of this work was the synthesis, characterization, and cytotoxicity evaluation of three new Ru(II) complexes with a general formula [Ru(Spy)(bipy)(P-P)]PF₆ [Spy = pyridine-6-thiolate; bipy = 2,2'-bipyridine; P-P = 1,2-bis(diphenylphosphine)ethane (1); 1,3-bis(diphenylphosphine) propane (2); and 1,1'-bis(diphenylphosphino)ferrocene] (4). Complex (3) with the 1,4-bis(diphenylphosphine)butane ligand, already known from the literature, was also synthesized, to be better studied here. The cytotoxicities of the complexes toward two kinds of cancerous cells (K562 and S-180 cells) were evaluated and compared to normal cells (L-929 and PBMC) by MTT assay. The complex [Ru(Spy)(bipy)(dppb)]PF₆ (3) was selected to study both the cellular and molecular mechanisms underlying its promising anticancer action in S-180 cells. The results obtained from this study indicated that complex (3) induces cell cycle arrest in the G0/G1 phase in S-180 cells associated with a decrease in the number of cells in S phase. After 24 and 48 h of exposure to complex (3), the cell viability decreased when compared to the negative control. Complex (3) does not appear to be involved in the DNA damage, but induced changes in the mitochondrial membrane potential in S-180 cells. Furthermore, there was also an increase in the gene expression of Bax, Caspase 9, and Tp53. According to our results, complex (3) induces cell apoptosis through p53/Bax-dependent intrinsic pathway and suppresses the expression of active antiapoptotic Bcl-2 protein.

[Ru(pipe)(dppb)(bipy)]PF6: A novel ruthenium complex that effectively inhibits ERK activation and cyclin D1 expression in A549 cells

Lung cancer is the most frequent type of cancer worldwide. In Brazil, only 14% of the patients diagnosed with lung cancer survived 5years in the last decades. Although improvements in the therapeutic approach, it is relevant to identify new chemotherapeutic agents. In this framework, ruthenium metal compounds emerge as a promising alternative to platinum-based compounds once they displayed lower cytotoxicity and more selectivity for tumor cells. The present study aimed to evaluate the antitumor potential of innovative ruthenium(II) complex, [Ru(pipe)(dppb)(bipy)]PF₆ (PIPE) on A549 cells, which is derived from non-small cell lung cancer. Results demonstrated that PIPE effectively reduced the viability and proliferation rate of A549 cells. When PIPE was used at 9μM there was increase in G0/G1 cell population with concomitant reduction in frequency of cells in S-phase, indicating cell cycle arrest in G1/S transition. Antiproliferative activity of PIPE was associated to its ability of reducing cyclin D1 expression and ERK phosphorylation levels. Cytotoxic activity of PIPE on A549 cells was observed when PIPE was used at 18μM, which was associated to its ability of inducing apoptosis by intrinsic pathway. Taken together, the data demonstrated that PIPE is a promising antitumor agent and further in vivo studies should be performed.

Selenadiazole derivatives antagonize glucocorticoid-induced osteoblasts cells apoptosis by blocking ROS-mediated signaling, a new anti-osteoporosis strategy

Herein we demonstrate that synthetic selenadiazole derivatives could protect osteoblasts cells against Dex-induced cell apoptosisviaattenuating oxidative stress and downstream signalling pathways.

DNA-binding, molecular docking studies and biological activity studies of ruthenium(ii) polypyridyl complexes

Three new Ru(ii) complexes [Ru(N–N)₂(PTCP)]²⁺ were synthesized and characterized. The DNA-binding, in vitro cytotoxicity, apoptosis, autophagy and western blot analysis were investigated.