Development of four ruthenium polypyridyl complexes as antitumor agents: Design, biological evaluation and mechanism investigation

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.

Anticancer Potential of Dendritic Poly(aryl ether)-Substituted Polypyridyl Ligand-Based Ruthenium(II) Coordination Entities

This paper studies the anticancer potency of dendritic poly(aryl ether)-substituted polypyridyl ligand-based ruthenium(II) coordination entities. The dendritic coordination entities were successfully designed, synthesized, and characterized by different spectral methods such as Fourier transform infrared (FTIR), 1H and 13C- NMR, and mass spectrometry. Further, to understand the structure and solvation behavior of the coordination entities, we performed all-atom molecular dynamics (MD) simulations. The behavior, configuration, and size of the coordination entities in DMSO and water were studied by calculating the radius of gyration (Rg) and solvent-accessible surface area (SASA). The MTT assay was used to assess the in vitro cytotoxicity of all of the coordination entities against cancerous A549 (lung cancer cells), MDA MB 231 (breast cancer cells), and HepG2 (liver cancer cells) and was found to be good with comparable IC50 values with respect to the standard drug cisplatin. The coordination entities exhibited dose dependence, and the highest activity was shown against HepG2 cell lines in comparison to the other cancer cell lines. In addition, fluorescence staining studies, such as AO/EB, DAPI, and cell death analysis by PI staining, were performed on the coordination entities to understand the apoptosis mechanism. Furthermore, reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) assays confirmed apoptosis in cancer cells via the mitochondrial pathway. The DNA fragmentation assay was done followed by molecular docking analysis with DNA executed to strengthen and support the experimental observations.

CuAAC "Click"-Derived Luminescent 2-(2-(4-(4-(Pyridin-2-yl)-1H-1,2,3-triazol-1-yl)butoxy)phenyl)benzo[d]thiazole-Based Ru(II)/Ir(III)/Re(I) Complexes as Anticancer Agents

To enhance the cytoselective behavior of the complexes, we intended to develop a CuAAC "click"-derived synthetic protocol for the preparation of 2-(2-(4-(4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)butoxy)phenyl)benzo[d]thiazole-based Ru(II)/Ir(III)/Re(I) complexes, and their cytotoxicity against three different cancer cell lines (MCF-7, HeLa, and U87MG) in consort with one normal cell line (HEK-293) was evaluated. In our detailed investigations, the significant cytotoxic nature of the Ru(II) complex 7a compared to Ir(III) and Re(I) complexes (7b and 7c, respectively) was observed. Complex 7a was capable of MCF-7 cell apoptosis via the inhibition of both S- and G2/M-phase cell cycle arrest in association with a substantial quantity of ROS production and DNA intercalation.

Controlled therapeutic delivery of CO from carbon monoxide-releasing molecules (CORMs)

Carbon monoxide (CO) has been regarded as a "silent killer" for its toxicity toward biological systems. However, a low concentration of endogenously produced CO has shown a number of therapeutic benefits such as anti-inflammatory, anti-proliferative, anti-apoptosis, and cytoprotective activities. Carbon monoxide-releasing molecules (CORMs) have been developed as alternatives to direct CO inhalation, which requires a specialized setting for strict dose control. CORMs are efficient CO donors, with central transition metals (such as ruthenium, iron, cobalt, and manganese) surrounded by CO as a ligand. CORMs can stably store and subsequently release their CO payload in the presence of certain triggers including solvent, light, temperature, and ligand substitution. However, CORMs require appropriate delivery strategies to improve short CO release half-life and target specificity. Herein, we highlighted the therapeutic potential of inhalation and CORMs-delivered CO. The applications of conjugate and nanocarrier systems for controlling CO release and improving therapeutic efficacy of CORMs are also described in detail. The review concludes with some of the hurdles that limit clinical translation of CORMs. Keeping in mind the tremendous potential and growing interest in CORMs, this review would be helpful for designing controlled CO release systems for clinical applications.

Cytotoxic Ruthenium(II) Complexes Containing a Dangling Pyridine: Selectivity for Diseased Cells Mediated by pH-Dependent DNA Binding

Ruthenium(II) complexes of the type [Ru(bpy)₂(L¹/L²/L³)]PF₆ [where bpy = 2,2'-bipyridine, H(L¹) = N-(pyrid-2-yl)salicylaldimine (1), H(L²) = N-(6-methylpyrid-2-yl)salicylaldimine (2), and H(L³) = N-(4,6-dimethylpyrid-2-yl)salicylaldimine (3)] have been isolated. The X-ray structures of 1-3 reveal distorted octahedral coordination geometry with a planar ruthenium phenolate moiety. They exhibit interpair dimeric association in their solid state such as (a) π-π-stacking interactions (1-3) and (b) C-H···π interactions (2). The ¹H NMR spectral data shed light on the characteristics of metal-ligand bonding and chelate ring conformations. The complexes exhibit strong metal-to-ligand charge-transfer transitions in the visible region. The complexes also undergo two successive metal-based oxidative processes corresponding to the Ru^II/Ru^III and Ru^III/Ru^IV couples. Resonance Raman studies strongly suggest that the lowest unoccupied molecular orbital of 1-3 is localized at the bpy ligand. Absorption, emission, and circular dichroic spectral measurements for 1-3 with calf-thymus DNA reveal a groove binding mode of interaction. Interestingly, all of the complexes exhibit pH-dependent DNA damage, and the pH at which the damage is highest corresponds to the pH conditions of the cancer cells. The DNA damage is in the order of 3 > 2 > 1, in which a hydrolytic mechanism dominates. The protein binding properties of the complexes examined by the tryptophan quenching measurements suggest a static mechanism. The positive ΔH and ΔS values indicate that the force acting between the complexes and bovine serum albumin (BSA) is mainly a hydrophobic interaction, and thus BSA may act as a targeted drug-delivery vehicle for ruthenium(II) complexes (K ∼ 10⁵). It is noteworthy that 3 exhibits selectivity with high cytotoxicity against breast cancer cells (EVSA-T and MCF-7), and its potency is comparable to that of cisplatin.

Recent Advances in Photorelease Complexes for Therapeutic Applications”

Photorelease complexes represent a class of agents for which UV-visible light triggers the expulsion of a specfic molecule that is intrinsically part of the inner coordination sphere or held in...

Systematic evaluation of the antitumor activity of three ruthenium polypyridyl complexes

Ruthenium-containing complexes have emerged as good alternative to the currently used platinum-containing drugs for malignant tumor therapy. In this work, cytotoxic effects of recently synthesized ruthenium polypyridyl complexes [Ru(bpy)₂(CFPIP)](ClO₄)₂ (bpy = 2,2'-bipyridine, CFPIP = (E)-2-(4-fluorostyryl)-1H-imidazo[4,5-f][1,10]phenanthroline, Ru(II)-1), [Ru(phen)₂(CFPIP)](ClO₄)₂ (phen = 1,10-phenanthroline, Ru(II)-2) and [Ru(dmb)₂(CFPIP)](ClO₄)₂ (dmb = 4,4'-dimethyl-2,2'-bipyridine, Ru(II)-3) toward different tumor cells were investigated in vitro and compared with cisplatin, the most widely used chemotherapeutic drug against hepatocellular carcinoma (HepG-2). The results demonstrate that target complexes show excellent cytotoxicity against HepG-2 cells with low IC₅₀ value of 21.4 ± 1.5, 18.0 ± 2.1 and 22.3 ± 1.7 μM, respectively. It was important noting that target Ru(II) complexes exhibited better antitumor activity than cisplatin (IC50 = 28.5 ± 2.4 μM) against HepG-2 cells, and has no obvious toxicity to normal cell LO2. DNA binding results suggest that Ru(II)-1, Ru(II)-2 and Ru(II)-3 interact with CT DNA (calf thymus DNA) through intercalative mode. Complexes exerted its antitumor activity through increasing anti-migration and inducing cell cycle arrest at the S phase. In addition, the apoptosis was tested by AO (acridine orange)/EB (ethidium bromide) staining and flow cytometry. Mitochondrial membrane potential (MMP), reactive oxygen species (ROS), and colocalization tests were also evaluated by ImageXpress Micro XLS system. Overall, the results show that the ruthenium polypyridyl complexes induce apoptosis in HepG-2 cells through ROS-mediated mitochondria dysfunction pathway.

Anti-melanoma effect of ruthenium(II)-diphosphine complexes containing naphthoquinone ligand

The use of natural products as potential ligands has been explored as a strategy in the development of metal-based chemotherapy. Since ruthenium complexes are promising alternatives to traditional antitumor agents, this study evaluated the anti-melanoma potential of two ruthenium(II) complexes containing the naphthoquinone ligands lapachol (lap), [Ru(lap)(dppm)2]PF6, and lawsone (law), [Ru(law)(dppm)2]PF6, in addition to the bis(diphenylphosphino)methane (dppm) ligand, referred to as complexes (1) and (2), respectively, using a syngeneic murine melanoma model. Activation of the apoptotic pathway by the treatments was assessed by immunohistochemistry in tumor tissue. Additionally, toxicity of the treatments was evaluated by variation in body and organ weight, quantification of biochemical indicators of renal damage, and genotoxicity in bone marrow and hepatocytes. First, the antiproliferative activity of (1) and (2) was observed in B16F10 cells, with IC50 values of 2.78 and 1.68 μM, respectively. The results obtained in mice showed that, unlike complex (1), (2) possesses significant anti-melanoma activity demonstrated by a reduction in tumor volume and mass (88.42%), as well as in mitosis frequency (83.86%). Additionally, complex (2) increased the levels of cleaved caspase-3, inducing tumor cell apoptosis. When compared to the metallodrug cisplatin, complex (2) exhibited similar anti-melanoma activity and lower toxicity considering all parameters evaluated. In silico studies demonstrated no difference in the binding energy of the naphthoquinone complex between complexes (1) and (2). However, the complex containing the lawsone ligand has a lower molar volume, which may be important for interactions with minor DNA grooves. The present results demonstrate the antitumor efficiency of complex (2) and a significantly lower systemic toxicity compared to cisplatin.

GSH-resistant and highly cytoselective ruthenium(II)-p-cymene-(imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol complexes as potential anticancer agents

To avoid the side effects of the current popular platinum-based anticancer drugs, researchers have made tireless attempts to design appropriate GSH-resistant Ru(ii)-arene complexes. In this regard, luminescent ruthenium(ii)-p-cymene-imidazophenanthroline complexes were developed as promising highly cytoselective cancer theraputic agents for HeLa and Caco-2 cells.

Ruthenium Complexes in the Fight against Pathogenic Microorganisms. An Extensive Review

The widespread use of antibiotics has resulted in the emergence of drug-resistant populations of microorganisms. Clearly, one can see the need to develop new, more effective, antimicrobial agents that go beyond the explored 'chemical space'. In this regard, their unique modes of action (e.g., reactive oxygen species (ROS) generation, redox activation, ligand exchange, depletion of substrates involved in vital cellular processes) render metal complexes as promising drug candidates. Several Ru (II/III) complexes have been included in, or are currently undergoing, clinical trials as anticancer agents. Based on the in-depth knowledge of their chemical properties and biological behavior, the interest in developing new ruthenium compounds as antibiotic, antifungal, antiparasitic, or antiviral drugs has risen. This review will discuss the advantages and disadvantages of Ru (II/III) frameworks as antimicrobial agents. Some aspects regarding the relationship between their chemical structure and mechanism of action, cellular localization, and/or metabolism of the ruthenium complexes in bacterial and eukaryotic cells are discussed as well. Regarding the antiviral activity, in light of current events related to the Covid-19 pandemic, the Ru (II/III) compounds used against SARS-CoV-2 (e.g., BOLD-100) are also reviewed herein.

Ruthenium compounds as potential therapeutic agents for type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder which is globally responsible for millions of fatalities per year. Management of T2DM typically involves orally administered anti-hyperglycaemic drugs in conjunction with dietary interventions. However, the current conventional therapy seems to be largely ineffective as patients continue to develop complications such as cardiovascular diseases, blindness and kidney failure. Existing alternative treatment entails the administration of organic therapeutic pharmaceuticals, but these drugs have various side effects such as nausea, headaches, weight gain, respiratory and liver damage. Transition metal complexes have shown promise as anti-diabetic agents owing to their diverse mechanisms of activity. In particular, selected ruthenium compounds have exhibited intriguing biological behaviours as Protein Tyrosine Phosphatase (PTP) 1B and Glycogen Synthase Kinase 3 (GSK-3) inhibitors, as well as aggregation suppressants for the human islet amyloid polypeptide (hIAPP). This focussed review serves as a survey on studies pertaining to ruthenium compounds as metallo-drugs for T2DM. Herein, we also provide perspectives on directions to fully elucidate in vivo functions of this class of potential metallopharmaceuticals. More specifically, there is still a need to investigate the pharmacokinetics of ruthenium drugs in order to establish their biodistribution patterns which will affirm whether these metal complexes are substitutionally inert or serve as pro-drugs. In addition, embedding oral-administered ruthenium complexes into bio-compatible polymers can be a prospective means of enhancing stability during drug delivery.

The anti-cancer effect of series of strained photoactivatable Ru(II) polypyridyl complexes on non-small-cell lung cancer and triple negative breast cancer cells

Ruthenium complexes have been recently reported as potential chemotherapeutic agents that offer tumor selectivity and low tumor resistance. This study investigates the photochemistry and the effect of four strained photoactivatable polypyridyl ruthenium(II) complexes on non-small-cell lung cancer (A549) and triple negative breast cancer (MDA-MB-231) cells. All four ruthenium(II) complexes, [Ru(bpy)₂dmbpy]Cl₂ (C1) where (bpy = 2,2'-bipyridine and dmbpy = 6,6'-dimethyl-2,2'-bipyridine), [Ru(phen)₂dmbpy]Cl₂ (C2) where (phen = 1,10-phenanthroline), [Ru(dpphen)₂dmbpy]Cl₂ (C3) (where dpphen = 4,7-diphenyl-1,10-phenanthroline) and [Ru(BPS)₂dmbpy]Na₂ (C4) where (BPS = bathophenanthroline disulfonate) eject the dmbpy ligand upon activation by blue light. Determination of the octanol-water partition coefficient (log P) revealed that C3 was the only lipophilic complex (log P = 0.42). LC-MS/MS studies showed that C3 presented the highest cellular uptake. The cytotoxic effect of the complexes was evaluated with and without blue light activation using WST-1 kit. Data indicated that C3 exhibited the highest cytotoxicity after 72 h (MDA-MB-231, IC₅₀ = 0.73 µM; A549, IC₅₀ = 1.26 µM) of treatment. The phototoxicity indices of C3 were 6.56 and 4.64 for MDA-MB-230 and A549, respectively. Upon light activation, C3 caused significant ROS production and induced apoptosis in MDA-MB-231 cells as shown by flow cytometry. It also significantly increased Bax/Bcl2 ratio and PERK levels without affecting caspase-3 expression. C3 exhibited poor dark toxicity (IC₅₀ = 74 μM) on rat mesenchymal stem cells (MSCs). In conclusion, the physical property of the complexes dictated by the variable ancillary ligands influenced cellular uptake and cytotoxicity. C3 may be considered a promising selective photoactivatable chemotherapeutic agent that induces ROS production and apoptosis.

Hypoxia efficient and glutathione-resistant cytoselective ruthenium(ii)-p-cymene-arylimidazophenanthroline complexes: biomolecular interaction and live cell imaging

A series of ruthenium(ii)–arene-2-arylimidazophenanthroline based DNA targeting, cytoselective, hypoxia efficient and glutathione-resistant luminescent anticancer drugs have been developed which are also represented as HeLa cell imaging probes.