Scope of organometallic compounds based on transition metal-arene systems as anticancer agents: starting from the classical paradigm to targeting multiple strategies

Design, synthesis and mechanistic studies of novel arylformylhydrazone butylphenyltin complexes as potential anticancer agents

Many diorganotin complexes with various alkyl groups exhibit excellent in vitro anticancer activity. However, most diorganotin is the same alkyl group, and the asymmetric alkyl R group has been rarely reported. Hence, in this paper, twenty butylphenyl mixed dialkyltin arylformylhydrazone complexes have been synthesized by microwave "one-pot" reaction with arylformylhydrazine, substituted α-keto acid or its sodium salt and butylphenyltin dichloride. The crystal structures of nine complexes were determined, indicating that the complexes C1, C2, C11, C12, and C16 ∼ C19 possessed a central symmetric structure of a dinuclear Sn2O2 tetrahedral ring; while the complex C9 is a trinuclear tin-oxygen cluster with a 6-membered ring encased in a 12-membered macrocyclic structure. The inhibiting activity of complexes was tested against the human cell lines NCI-H460, MCF-7, HepG2, Huh-7 and HL-7702. Complex C2 demonstrated the optimal inhibitory effect on HepG2 cells, with an IC50 value of 0.82 ± 0.03 μM. Cellular biology experiments revealed that complex C2 could induce apoptosis and G2/M phase cell cycle arrest in HepG2 and Huh-7 cells. The complex also caused the collapse of the mitochondrial membrane potential and increased intracellular reactive oxygen species in HepG2 and Huh-7 cells. Western blot analysis further clarified that complex C2 could induce cell apoptosis through the mitochondrial pathway along with the release of reactive oxygen species.

2-Aryl-1H-imidazo[4,5-f][1,10]phenanthroline-Based Binuclear Ru(II)/Ir(III)/Re(I) Complexes as Mitochondria Targeting Cancer Stem Cell Therapeutic Agents

A series of novel Ru(II)/Ir(III)/Re(I)-based organometallic complexes [Ru2L1, Ru2L2, Ir2L1, Ir2L2, Re2L1, and Re2L2] have been synthesized to assess their potency and selectivity against multiple cancer cells A549, HCT-116, and HCT-116 colon CSCs. The cytotoxic screening of the synthesized complexes has revealed that complex Ru2L1 and Ir2L2 are two proficient complexes among all, but Ru2L1 is the most potent complex. A significant binding constant value was observed for DNA and BSA in all complexes. Significant lipophilic properties allow them to penetrate cancer cell membranes, and substantial quantum yield (ϕf) values support bioimaging potential. Again, these complexes are particular for mitochondrial localization and produce a profuse amount of ROS to damage the mitochondrial DNA and then G1 phase cell-cycle arrest. Protein expression analysis unveiled that pro-apoptotic Bax protein overexpressed in Ru2L1-treated cells, whereas antiapoptotic Bcl-2 protein was expressed twofold in Ir2L2-treated cells, which correlated with autophagy reticence.

Ligand Regulation Strategy to Modulate ROS Nature in a Rhodamine-Iridium(III) Hybrid System for Phototherapy

The efficacy of photodynamic therapy (PDT) is highly dependent on the photosensitizer features. The reactive oxygen species (ROS) generated by photosensitizers is proven to be associated with immunotherapy by triggering immunogenic cell death (ICD) as well. In this work, we establish a rhodamine-iridium(III) hybrid model functioning as a photosensitizer to comprehensively understand its performance and potential applications in photodynamic immunotherapy. Especially, the correlation between the ROS generation efficiency and the energy level of the Ir(III)-based excited state (T1'), modulated by the cyclometalating (C∧N) ligand, is systematically investigated and correlated. We prove that in addition to the direct population of the rhodamine triplet state (T1) formed through the intersystem crossing process with the assistance of a heavy Ir(III) metal center, the fine-tuned T1' state could act as a relay to provide an additional pathway for promoting the cascade energy transfer process that leads to enhanced ROS generation ability. Moreover, type I ROS can be effectively produced by introducing sulfur-containing thiophene units in C∧N ligands, providing a stronger M1 macrophage-activation efficiency under hypoxia to evoke in vivo antitumor immunity. Overall, our work provides a fundamental guideline for the molecular design and exploration of advanced transition-metal-based photosensitizers for biomedical applications.

Exploiting Co(III)-Cyclopentadienyl Complexes To Develop Anticancer Agents

In recent years, organometallic complexes have attracted much attention as anticancer therapeutics aiming at overcoming the limitations of platinum drugs that are currently marketed. Still, the development of half-sandwich organometallic cobalt complexes remains scarcely explored. Four new cobalt(III)-cyclopentadienyl complexes containing N,N-heteroaromatic bidentate, and phosphane ligands were synthesized and fully characterized by elemental analysis, spectroscopic techniques, and DFT methods. The cytotoxicity of all complexes was determined in vitro by the MTS assay in colorectal (HCT116), ovarian (A2780), and breast (MDA-MB-231 and MCF-7) human cancer cell lines and in a healthy human cell line (fibroblasts). The complexes showed high cytotoxicity in cancer cell lines, mostly due to ROS production, apoptosis, autophagy induction, and disruption of the mitochondrial membrane. Also, these complexes were shown to be nontoxic in vivo in an ex ovo chick embryo yolk sac membrane (YSM) assay.

Organotin(IV)-Decorated Graphene Quantum Dots as Dual Platform for Molecular Imaging and Treatment of Triple Negative Breast Cancer

The pharmacological activity of organotin(IV) complexes in cancer therapy is well recognized but their large applicability is hampered by their poor water solubility. Hence, carbon dots, in particular nitrogen-doped graphene quantum dots (NGQDs), may be a promising alternative for the efficient delivery of organotin(IV) compounds as they have a substantial aqueous solubility, a good chemical stability, and non-toxicity as well as a bright photoluminescence that make them ideal for theranostic applications against cancer. Two different multifunctional nanosystems have been synthesized and fully characterized based on two fragments of organotin-based cytotoxic compounds and 4-formylbenzoic acid (FBA), covalently grafted onto the NGQDs surface. Subsequently, an in vitro determination of the therapeutic and theranostic potential of the achieved multifunctional systems was carried out. The results showed a high cytotoxic potential of the NGQDs-FBA-Sn materials against breast cancer cell line (MDA-MB-231) and a lower effect on a non-cancer cell line (kidney cells, HEK293T). Besides, thanks to their optical properties, the dots enabled their fluorescence molecular imaging in the cytoplasmatic region of the cells pointing towards a successful cellular uptake and a release of the metallodrug inside cancer cells (NGQDs-FBA-Sn).

Anticancer Potential of Diruthenium Complexes with Bridging Hydrocarbyl Ligands from Bioactive Alkynols

Diruthenacyclopentenone complexes of the general composition [Ru2Cp2(CO)2{μ-η1:η3-CH═C(C(OH)(R))C(═O)}] (2a-c; Cp = η5-C5H5) were synthesized in 94-96% yields from the reactions of [Ru2Cp2(CO)2{μ-η1:η3-C(Ph)═C(Ph)C(═O)}] (1) with 1-ethynylcyclopentanol, 17α-ethynylestradiol, and 17-ethynyltestosterone, respectively, in toluene at reflux. Protonation of 2a-c by HBF4 afforded the corresponding allenyl derivatives [Ru2Cp2(CO)3{μ-η1:η2-CH═C═R}]BF4 (3a-c) in 85-93% yields. All products were thoroughly characterized by elemental analysis, mass spectrometry, and IR, UV-vis, and nuclear magnetic resonance spectroscopy. Additionally, 2a and 3a were investigated by cyclic voltammetry, and the single-crystal diffraction method was employed to establish the X-ray structures of 2b and 3a. The cytotoxicity in vitro of 2b and 3a-c was evaluated against nine human cancer cell lines (A2780, A2780R, MCF-7, HOS, A549, PANC-1, Caco-2, PC-3, and HeLa), while the selectivity was assessed on normal human lung fibroblast (MRC-5). Overall, complexes exert stronger cytotoxicity than cisplatin, and 3b (comprising 17α-estradiol derived ligand) emerged as the best-performing complex. Inductively coupled plasma mass spectrometry cellular uptake studies in A2780 cells revealed a higher level of internalization for 3b and 3c compared to 2b, 3a, and the reference compound RAPTA-C. Experiments conducted on A2780 cells demonstrated a noteworthy impact of 3a and 3b on the cell cycle, leading to the majority of the cells being arrested in the G0/G1 phase. Moreover, 3a moderately induced apoptosis and oxidative stress, while 3b triggered autophagy and mitochondrial membrane potential depletion.

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.

In Silico and In Vitro Studies of 4-Hydroxycoumarin-Based Heterocyclic Enamines as Potential Anti-Tumor Agents

The present study reports the one-step synthesis of several 3-formyl-4-hydroxycouramin-derived enamines (4a-4i) in good yields (65-94%). The characterization of the synthesized compounds was carried out via advanced analytical and spectroscopic techniques, such as melting point, electron impact mass spectrometry (EI-MS), 1H-NMR, 13C-NMR, elemental analysis, FTIR, and UV-Visible spectroscopy. The reaction conditions were optimized, and the maximum yield was obtained at 3-4 h of reflux of the reactants, using 2-butanol as a solvent. The potato disc tumor assay was used to assess Agrobacterium tumefaciens-induced tumors to evaluate the anti-tumor activities of compounds (4a-4i), using Vinblastine as a standard drug. The compound 4g showed the lowest IC50 value (1.12 ± 0.2), which is even better than standard Vinblastine (IC50 7.5 ± 0.6). For further insight into their drug actions, an in silico docking of the compounds was also carried out against the CDK-8 protein. The binding energy values of compounds were found to agree with the experimental results. The compounds 4g and 4h showed the best affinities toward protein, with a binding energy value of -6.8 kcal/mol.

Gold Complexes in Anticancer Therapy: From New Design Principles to Particle-Based Delivery Systems

The discovery of the medicinal properties of gold complexes has fuelled the design and synthesis of new anticancer metallodrugs, which have received special attention due to their unique modes of action. Current research in the development of gold compounds with therapeutic properties is predominantly focused on the molecular design of drug leads with superior pharmacological activities, e.g., by introducing targeting features. Moreover, intensive research aims at improving the physicochemical properties of gold compounds, such as chemical stability and solubility in the physiological environment. In this regard, the encapsulation of gold compounds in nanocarriers or their chemical grafting onto targeted delivery vectors could lead to new nanomedicines that eventually reach clinical applications. Herein, we provide an overview of the state-of-the-art progress of gold anticancer compounds, andmore importantly we thoroughly revise the development of nanoparticle-based delivery systems for gold chemotherapeutics.

Half-sandwich ruthenium(II), rhodium(III) and iridium(III) fluorescent metal complexes containing pyrazoline based ligands: DNA binding, cytotoxicity and antibacterial activities

A series of nine new complexes of ruthenium(II), rhodium(III), and iridium(III) incorporated with pyrazoline-based ligands were synthesized and characterized by various spectroscopic techniques such as FTIR, ¹H NMR, ¹³C NMR, UV-Vis spectroscopy, ESI-MS spectrometry and X-ray crystallographic studies. All the synthesized compounds were assessed for their antibacterial abilities against Gram-positive and Gram-negative bacterial strains. The compounds showed better antibacterial activity against two Gram-positive bacteria (Staphylococcus aureus and Bacillus Thuringiensis), with activities superior to standard kanamycin. Antioxidant studies revealed the mild radical scavenging proficiency of the compounds. DNA binding studies using fluorescence spectroscopy showed that the compounds could bind to Salmon Milt DNA electrostatically via external contact and groove surface binding with moderate affinity. The synthesized complexes were tested for anticancer activity using cell cytotoxicity and apoptosis assays in Dalton's lymphoma (DL) cell lines. The findings were compared to cisplatin (the standard drug) under identical experimental conditions. The cell viability results showed that complex 7 induced higher cytotoxicity in the DL cell line than the other tested compounds. The results of the molecular docking analysis further suggest that selective complexes have complete contact with the active amino acids sites of anti-apoptotic Bcl-2 family protein.

Light Triggers the Antiproliferative Activity of Naphthalimide-Conjugated (η6-arene)ruthenium(II) Complexes

We report the synthesis and characterization of three half-sandwich Ru(II) arene complexes [(η⁶-arene)Ru(N,N')L][PF₆]₂ containing arene = p-cymene, N,N' = bipyridine, and L = pyridine meta- with methylenenaphthalimide (C1), methylene(nitro)naphthalimide (C2), or methylene(piperidinyl)naphthalimide (C3). The naphthalimide acts as an antenna for photoactivation. After 3 h of irradiation with blue light, the monodentate pyridyl ligand had almost completely dissociated from complex C3, which contains an electron donor on the naphthalimide ring, whereas only 50% dissociation was observed for C1 and C2. This correlates with the lower wavelength and strong absorption of C3 in this region of the spectrum (λ_max = 418 nm) compared with C1 and C2 (λ_max = 324 and 323 nm, respectively). All the complexes were relatively non-toxic towards A549 human lung cancer cells in the dark, but only complex C3 exhibited good photocytoxicity towards these cancer cells upon irradiation with blue light (IC₅₀ = 10.55 ± 0.30 μM). Complex C3 has the potential for use in photoactivated chemotherapy (PACT).

Natural Products in Preventing Tumor Drug Resistance and Related Signaling Pathways

Drug resistance is still an obstacle in cancer therapy, leading to the failure of tumor treatment. The emergence of tumor drug resistance has always been a main concern of oncologists. Therefore, overcoming tumor drug resistance and looking for new strategies for tumor treatment is a major focus in the field of tumor research. Natural products serve as effective substances against drug resistance because of their diverse chemical structures and pharmacological effects. We reviewed the signaling pathways involved in the development of tumor drug resistance, including Epidermal growth factor receptor (EGFR), Renin-angiotensin system (Ras), Phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), Wnt, Notch, Transforming growth factor-beta (TGF-β), and their specific signaling pathway inhibitors derived from natural products. This can provide new ideas for the prevention of drug resistance in cancer therapy.

Metal Complexes as DNA Synthesis and/or Repair Inhibitors: Anticancer and Antimicrobial Agents

Medicinal inorganic chemistry involving the utilization of metal-based compounds as therapeutics has become a field showing distinct promise. DNA and RNA are ideal drug targets for therapeutic intervention in the case of various diseases, such as cancer and microbial infection. Metals play a vital role in medicine, with at least 10 metals known to be essential for human life and a further 46 nonessential metals having been involved in drug therapies and diagnosis. These metal-based complexes interact with DNA in various ways, and are often delivered as prodrugs which undergo activation in vivo. Metal complexes cause DNA crosslinking, leading to the inhibition of DNA synthesis and repair. In this review, the various interactions of metal complexes with DNA nucleic acids, as well as the underlying mechanism of action, were highlighted. Furthermore, we also discussed various tools used to investigate the interaction between metal complexes and the DNA. The tools included in vitro techniques such as spectroscopy and electrophoresis, and in silico studies such as protein docking and density-functional theory that are highlighted for preclinical development.

Fabrication of eco-friendly chitosan functionalized few-layered WS2 nanocomposite implanted with ruthenium nanoparticles for in vitro antibacterial and anticancer activity: Synthesis, characterization, and pharmaceutical applications

The abundance of two-dimensional (2D) components has provided them with a broad material platform for building nano and atomic-level applications. So, 2D nanomaterials are unique because of their physicochemical properties. Over many years, graphene is a conventional 2D layered element that has significant attention in the scientific community. In recent years numerous new 2D nanomaterials other than graphene have been reported. The study of 2D nanomaterials is also in its infant stages, with the majority of research focusing on the explanation of special material properties, but very few articles are focusing on the biological applications of 2D nanomaterials. As a result, we focused on the transition metal dichalcogenides (TMDCs) such as MoS₂ and WS₂, which were emerging and exciting groups of elements with display great opportunities in several fields, such as cancer nanomedicine. Herein, we synthesized biologically active CS/WS₂/Ru composite by liquid exfoliation approach. The CS/WS₂/Ru composites exhibit significant antibacterial action towards (S. aureus, and E. coli) bacteria. Also, the composite suggests synergetic anticancer action against MCF-7 cancer cells. These reports are possible to explore the innovative aspects of biological outcomes in carcinological applications.

Past, present and future-sample environments for materials research studies in scattering and spectroscopy; a UK perspective

Small angle x-ray scattering and x-ray absorption fine structure are two techniques that have been employed at synchrotron sources ever since their inception. Over the course of the development of the techniques, the introduction of sample environments for added value experiments has grown dramatically. This article reviews past successes, current developments and an exploration of future possibilities for these two x-ray techniques with an emphasis on the developments in the United Kingdom between 1980-2020.

Coordination Complexes as a New Generation Photosensitizer for Photodynamic Anticancer Therapy

Photodynamic therapy (PDT) has become an alternative to standard cancer treatment methods such as surgery, chemotherapy and radiotherapy. The uniqueness of this method relies on the possibility of using various photosensitizers (PS) that absorb and convert light emission in radical oxygen-derived species (ROS). They can be present alone or in the presence of other compounds such as metal organic frameworks (MOFs), non-tubules or polymers. The interaction between DNA and metal-based complexes plays a key role in the development of new anti-cancer drugs. The use of coordination compounds in PDT has a significant impact on the amount ROS generated, quantum emission efficiency (Φem) and phototoxic index (PI). In this review, we will attempt to systematically review the recent literature and analyze the coordination complexes used as PS in PDT. Finally, we compared the anticancer activities of individual coordination complexes and discuss future perspectives. So far, only a few articles link so many transition metal ion coordination complexes of varying degrees of oxidation, which is why this review is needed by the scientific community to further expand this field worldwide. Additionally, it serves as a convenient collection of important, up-to-date information.

Accelerated Redox Reaction of Hydrogen Peroxide by Employing Locally Concentrated State of Copper Catalysts on Polymer Chain

Copper complexes act as catalysts for redox reactions to generate reactive oxygen species that destroy biomolecules and, therefore, are utilized to design drugs including antitumor and antibacterial medicines. Especially, catalytic reaction for hydrogen peroxide decomposition is important because it includes the process for generating highly toxic hydroxyl radical, i.e., Fenton-like reaction. Considering that multicoppers/hydrogen peroxide species are the important intermediates for the redox reaction, herein a polymer having copper complexes in the side chains is designed to facilitate the formation of the intermediates by building locally concentrated state of the copper complexes. The polymer increases their catalytic activities for hydrogen peroxide decomposition and promotes reactive oxygen species' generation, eventually leading to higher antibacterial activity. This reveals the virtue of building a locally concentrated state of catalysts on polymers toward drug design with low amounts of transition metals.

Arene-Osmium(II) Complexes in Homogeneous Catalysis

Although the application of arene-osmium(II) complexes in homogeneous catalysis has been much less studied than that of their ruthenium analogues, different works have shown that, in some instances, a comparable or even superior effectiveness can be achieved with this particular class of compounds. This review article focuses on the catalytic applications of arene-osmium(II) complexes. Among others, transfer hydrogenation, hydrogenation, oxidation, and nitrile hydration reactions, as well as different C-C bond forming processes, are comprehensively discussed.

Investigation into antiproliferative activity and apoptosis mechanism of new arene Ru(ii) carbazole-based hydrazone complexes

Ruthenium complexes with bioactive ligands are becoming promising substitutes for platinum complexes due to their precise action against various cancers. In the present study, the synthesis of three new arene Ru(ii) complexes containing new carbazole-based hydrazone ligands of general formula [(η6-benzene)Ru(L)Cl] (1-3; L = carbazolone benzhydrazone ligands), and their anticancer properties are described. The structural characterization of the ligands and their ruthenium complexes has been realized with the aid of elemental analysis, IR, UV-vis, NMR and HR-MS techniques. The molecular structures of all three complexes have been elucidated by single crystal X-ray crystallography and reveal the existence of pseudo-octahedral geometry around the ruthenium. The in vitro cancer cell growth inhibition property of the complexes against A549 (lung carcinoma), A2780 (ovarian adenocarcinoma) and non-cancerous 16HBE (human lung bronchial epithelium) cells were examined by MTT assay. All the complexes display good cytotoxicity towards both of these types of cancer cell compared to the standard drug cisplatin, with low IC50 values. Remarkably, complex 3, which contains an electron-donating substituent, induces a significant reduction of viability in A2780 cells. The inhibition capacity of the complexes towards A2780 cells proliferation was further confirmed using 5-ethynyl-2-deoxyuridine (EdU) assay via minimal DNA synthesis. The result of the acridine orange-ethidium bromide (AO-EB) fluorescent staining assay establishes that the cytotoxicity of the complexes was mediated by apoptosis in cancer cells. Furthermore, flow cytometry using Annexin V-FITC/propidium iodide (PI) double staining determines the quantitative discrimination of early apoptosis by the externalization of phosphatidylserine. In addition, cell cycle distribution indicates that the complexes block the cell cycle progression in the S-phase. The outcome of our investigation shows the promising scope and potency of tailored arene ruthenium complexes for precise cancer chemotherapy beyond platinum drugs.

Osmium-arene complexes with high potency towards Mycobacterium tuberculosis

The treatment of tuberculosis (TB) poses a major challenge as frontline therapeutic agents become increasingly ineffective with the emergence and spread of drug-resistant strains of Mycobacterium tuberculosis (Mtb). To combat this global health problem, new antitubercular agents with novel modes of action are needed. We have screened a close family of 17 organometallic half-sandwich Os(II) complexes [(arene)Os(phenyl-azo/imino-pyridine)(Cl/I)]+Y- containing various arenes (p-cymene, biphenyl, or terphenyl), and NMe2, F, Cl, or Br phenyl or pyridyl substituents, for activity towards Mtb in comparison with normal human lung cells (MRC5). In general, complexes with a monodentate iodido ligand were more potent than chlorido complexes, and the five most potent iodido complexes (MIC 1.25-2.5 µM) have an electron-donating Me2N or OH substituent on the phenyl ring. As expected, the counter anion Y (PF6-, Cl-, I-) had little effect on the activity. The pattern of potency of the complexes towards Mtb is similar to that towards human cells, perhaps because in both cases intracellular thiols are likely to be involved in their activation and their redox mechanism of action. The most active complex against Mtb is the p-cymene Os(II) NMe2-phenyl-azopyridine iodido complex (2), a relatively inert complex that also exhibits potent activity towards cancer cells. The uptake of Os from complex 2 by Mtb is rapid and peaks after 6 h, with temperature-dependence studies suggesting a major role for active transport. Significance to Metallomics Antimicrobial resistance is a global health problem. New advances are urgently needed in the discovery of new antibiotics with novel mechanisms of action. Half-sandwich organometallic complexes offer a versatile platform for drug design. We show that with an appropriate choice of the arene, an N,N-chelated ligand, and monodentate ligand, half-sandwich organo-osmium(II) complexes can exhibit potent activity towards Mycobacterium tuberculosis (Mtb), the leading cause of death from a single infectious agent. The patterns of activity of the 17 azo- and imino-pyridine complexes studied here towards Mtb and normal lung cells suggest a common redox mechanism of action involving intracellular thiols.

N,N-Ru(II)-p-cymene-poly(N-vinylpyrrolidone) surface functionalized gold nanoparticles: from organoruthenium complex to nanomaterial for antiproliferative activity

Organometallic Ru-arene complexes are promising as anticancer agents, but the lack of tumor uptake and poor solubility in the physiological medium impede their development. In order to deal with these challenges, we developed gold nanoparticles coated with Ru(arene)-functionalized PNVP-Py, where PNVP-Py is pyridine end-functionalized poly(N-vinylpyrrolidone). It is demonstrated that these particles exhibit higher anti-proliferative activity than the individual organometallic ruthenium(ii) complex of the type [Ru(η6-p-cymene)(NN)Cl]PF6, where NN is bis(4-methoxyphenylimino)acenaphthene, against colorectal adenocarcinoma cell lines. More specifically, a RuII(η6-p-cymene) complex containing a NN bidentate ligand has been prepared and characterized by spectral studies and X-ray crystallography. To tether the isolated complex onto the surface of the AuNPs, PNVP-Py, which contains a pyridine group at one end to coordinate to the Ru-complex and a suitable functional group at the other end to bind on the surface of the AuNPs, has been prepared and utilized to obtain the macromolecular complex [Ru(η6-p-cymene)(NN)(PNVP-Py)]Cl2. Next, stable Ru(p-cym)(NN)(PNVP-Py)@AuNPs were obtained via a ligand exchange reaction of citrate-stabilized AuNPs with a macromolecular complex by a direct 'grafting to' approach and characterized well. Despite the lower DNA cleavage activity, the nanoconjugate exhibits better cytotoxicity than the individual complex against HT-29 colorectal adenocarcinoma cells on account of its enhanced permeability across the cell membrane. The AO/EB staining assay revealed that the nanoconjugate is able to induce an apoptotic mode of cell death, which was further quantitatively evaluated by Annexin V-FITC/PI double assay. An immunofluorescence assay indicated the higher potency of the nanoconjugate to inhibit cyclin D1 gene expression that is required for cancer cell growth. To the best of our knowledge, this is the first report of the modification of an organometallic Ru(arene) complex into a Ru(arene)metallopolymer-gold nanoconjugate for the development of ruthenium-based nanomedicine for cancer treatment.

Conjugates Containing Two and Three Trithiolato-Bridged Dinuclear Ruthenium(II)-Arene Units as In Vitro Antiparasitic and Anticancer Agents

The synthesis, characterization, and in vitro antiparasitic and anticancer activity evaluation of new conjugates containing two and three dinuclear trithiolato-bridged ruthenium(II)-arene units are presented. Antiparasitic activity was evaluated using transgenic Toxoplasmagondii tachyzoites constitutively expressing β-galactosidase grown in human foreskin fibroblasts (HFF). The compounds inhibited T.gondii proliferation with IC50 values ranging from 90 to 539 nM, and seven derivatives displayed IC50 values lower than the reference compound pyrimethamine, which is currently used for treatment of toxoplasmosis. Overall, compound flexibility and size impacted on the anti-Toxoplasma activity. The anticancer activity of 14 compounds was assessed against cancer cell lines A2780, A2780cisR (human ovarian cisplatin sensitive and resistant), A24, (D-)A24cisPt8.0 (human lung adenocarcinoma cells wild type and cisPt resistant subline). The compounds displayed IC50 values ranging from 23 to 650 nM. In A2780cisR, A24 and (D-)A24cisPt8.0 cells, all compounds were considerably more cytotoxic than cisplatin, with IC50 values lower by two orders of magnitude. Irrespective of the nature of the connectors (alkyl/aryl) or the numbers of the di-ruthenium units (two/three), ester conjugates 6-10 and 20 exhibited similar antiproliferative profiles, and were more cytotoxic than amide analogues 11-14, 23, and 24. Polynuclear conjugates with multiple trithiolato-bridged di-ruthenium(II)-arene moieties deserve further investigation.

Cytotoxicity and DNA interaction in a series of aryl terminated iminopyridine Pt(II) complexes

A series of iminopyridine complexes of platinum(II), bearing a flexible diethereal, aryl terminated residue, where the size of aryl group is varied from phenyl to 9-anthracenyl, was synthesized. The new complexes are soluble and stable in DMSO/H₂O mixtures. Besides the metal center, aryl groups are available for further interactions with DNA, due to the good side chain flexibility. The new aryl functionalized iminopyridine dichlorido platinum(II) complexes show a significant antiproliferative activity on ovarian carcinoma cells and notably, complex 13 is able to overcome cisplatin resistance. The study of the interaction mode of 13 with DNA highlighted the ability to form a molecular complex characterized by a dual (intercalative and groove binding) geometry. The complex is also able to covalently add to DNA even though interstrand cross-links appear significantly hampered with respect to cisplatin. The interactions with the macromolecule are discussed in view of the observed cell effect.

p-Cymene Complexes of Ruthenium(II) as Antitumor Agents

In this work, the cytotoxic behavior of six ruthenium(II) complexes of stoichiometry [(η6-p-cymene)RuCl2L] (I-VI), L = 4-cyanopyridine (I), 2-aminophenol (II), 4-aminophenol (III), pyridazine (IV), and [(η6-p-cymene)RuClL2]PF6; L = cyanopyridine (V), L = 2-aminophenol(VI) towards three cell lines was studied. Two of them, HeLa and MCF-7, are human carcinogenic cells from cervical carcinoma and human breast cancer, respectively. A comparison with healthy cells was carried out with BGM cells which are monkey epithelial cells of renal origin. The behavior of complex II exhibits selectivity towards healthy cells, which is a promising feature for use in cancer treatment since it might reduce the side effects of most current therapies.

Bismuth as Smart Material and Its Application in the Ninth Principle of Sustainable Chemistry

This paper reports an overview of Green Chemistry and the concept of its twelve principles. This study focusses on the ninth principle of Green Chemistry, that is, catalysis. A report on catalysis, in line with its definition, background, classification, properties, and applications, is provided. The study also entails a green element called bismuth. Bismuth’s low toxicity and low cost have made researchers focus on its wide applications in catalysis. It exhibits smartness in all the catalytic activities with the highest catalytic performance among other metals.

Enantioselective Synthesis of Planar Chiral Ferrocifens that Show Chiral Discrimination in Antiproliferative Activity on Breast Cancer Cells

The design and first enantioselective synthesis of a series of chiral ferrocifens and ferrociphenols was realised by enantioselective palladium-catalysed intramolecular direct C-H bond activation followed by McMurry coupling. Biological evaluation revealed moderate anticancer activities on breast cancer cells and evidence of chiral discrimination between enantiomers. Treatment of the novel ferrocifens with Ag₂ O revealed that these systems are unable to form a neutral quinone methide, yet still demonstrate marked antiproliferative properties against both the hormone-dependent MCF-7 and hormone-independent MDA-MB-231 cell lines. This bioactivity arises from two mechanisms: Fenton-type chemistry and the anti-estrogenic activity associated with the tamoxifen-like structure.

New Tailored RNA-Targeted Organometallic Drug Candidates against Huh7 (Liver) and Du145 (Prostate) Cancer Cell Lines

New organometallic drug candidates [Ph2Sn(HL)], 1, and [Ru(η6--p-cymene)(HL)Cl], 2, were designed and synthesized by in situ reaction of a Schiff base ligand (HL) and diphenyltin dichloride and [RuCl2(p-cymene)]2, respectively. The drug candidates 1 and 2 have been characterized by spectroscopic methods (Fourier-transform infrared spectroscopy, UV-vis, and 1H/13C NMR), elemental analysis, and single X-ray crystallographic studies (in case of 1). The ground-state geometry optimization of 1 and 2 was performed by density functional theory calculations. The interaction of 1 and 2 with tRNA was assessed by absorption spectroscopy, cyclic voltammetry, circular dichroism, and ethidium bromide displacement assay using fluorescence emission spectroscopy to determine their potential to act as antitumor agents. The cytotoxicity of 1 and 2 was screened against human liver carcinoma (Huh7), prostate cancer (Du145), and the normal prostate cell line (PNT 2). The results implicated a dose-dependent growth inhibition of the two cancer cells at concentrations (2.5-15 μM) of 1 and 2 with the treatment after 48 h. Interestingly, 1 revealed good selective activity toward the liver cancer cell line (Huh7). Furthermore, both the drug candidates 1 and 2 were found to be nontoxic toward the PNT 2 normal cell line. These studies lay a paradigm for rational efficacious drug design for chemotherapeutic intervention in cancers using new tailored organometallic drug entities; organotin(IV) and organoruthenium(II) have been demonstrated to be viable for the safe administration and specific targeted drug uptake by the resistant cancerous cell lines at low intracellular concentrations.

Effect of Regiochemistry and Methylation on the Anticancer Activity of a Ferrocene-Containing Organometallic Nucleoside Analogue

Four new bis-substituted ferrocene derivatives containing either a hydroxyalkyl or methoxyalkyl group and either a thyminyl or methylthyminyl group have been synthesised and characterised by a range of spectroscopic and analytical techniques. They were included in a structure-activity-relationship (SAR) study probing anticancer activities in osteosarcoma (bone cancer) cell lines and were compared with a known lead compound, 1-(S,R_p ), a nucleoside analogue that is highly toxic to cancer cells. Biological studies using the MTT assay revealed that a regioisomer of ferronucleoside 1-(S,R_p ), which only differs from the lead compound in being substituted on two cyclopentadienyl rings rather than one, was over 20 times less cytotoxic. On the other hand, methylated derivatives of 1-(S,R_p ) showed comparable cytotoxicities to the lead compound. Overall these studies indicate that a mechanism of action for 1-(S,R_p ) cannot proceed through alcohol phosphorylation and that its geometry and size, rather than any particular functional group, are crucial factors in explaining its high anticancer activity.

Co-delivery system of chemotherapy drugs and active ingredients from natural plants: a brief overview of preclinical research for cancer treatment

Introduction: Many active ingredients from natural plants (AINPs) have been revealed to possess remarkable anticancer properties. Combination chemotherapy of chemo-drugs and AINPs has also proven to be more advantageous than individual chemo-drug treatment with respect to enhancing efficiency, alleviating toxicity, and controlling the development of multidrug resistance (MDR). Co-delivery is considered a promising method to effectively achieve and manage combination chemotherapy of chemo-drugs and AINPs, and various distinctive and functional co-delivery systems have been designed for these purposes to date.Areas covered: This review focuses on recent preclinical investigations of co-delivery systems for chemo-drugs and AINPs as new cancer treatment modalities. We particularly emphasize the apparent treatment advantages of these approaches, including augmenting efficiency, reducing toxicity, and controlling MDR.Expert opinion: There has already been notable progress in the application of combination chemotherapy with co-delivery systems loaded with chemo-drugs and AINPs based on results with cellular and animal models. The main challenge is to translate these successes into new anticancer compound preparations and promote their clinical application in practice. Nevertheless, continuous efforts with new designs of co-delivery systems remain essential, providing a foundation for future clinical research and development of new anticancer drugs.

Encapsulation of a Ru(η6-p-cymene) complex of the antibacterial drug trimethoprim into a polydiacetylene-phospholipid assembly to enhance its in vitro anticancer and antibacterial activities

The first report of a Ru(arene)–liposome nanoaggregate to enhance the in vitro anticancer activity of a Ru–arene complex in liver cancer cells.

Water soluble palladium(ii) and platinum(ii) acyclic diaminocarbene complexes: solution behavior, DNA binding, and antiproliferative activity

Water soluble Pd(ii) and Pt(ii)–ADC species synthesized via the metal-mediated coupling of isocyanides and 1,2-diaminobenzene have demonstrated antitumor potential.

Identification and Profiling of Environmental Chemicals That Inhibit the TGFβ/SMAD Signaling Pathway

The transforming growth factor beta (TGFβ) superfamily of secreted signaling molecules and their cognate receptors regulate cell fate and behaviors relevant to many developmental and disease processes. Disruption of TGFβ signaling during embryonic development can, for example, affect morphogenesis and differentiation through complex pathways that may be SMAD (Small Mothers Against Decapentaplegic) dependent or SMAD independent. In the present study, the SMAD Binding Element (SBE)-beta lactamase (bla) HEK 293T cell line, which responds to the activation of the SMAD2/3/4 complex, was used in a quantitative high-throughput screening (qHTS) assay to identify potential TGFβ disruptors in the Tox21 10K compound library. From the primary screening we identified several kinase inhibitors, organometallic compounds, and dithiocarbamates (DTCs) that inhibited TGFβ1-induced SMAD signaling of reporter gene activation independent of cytotoxicity. Counterscreen of SBE antagonists on human embryonic neural stem cells demonstrated cytotoxicity, providing additional evidence to support evaluation of these compounds for developmental toxicity. We profiled the inhibitory patterns of putative SBE antagonists toward other developmental signaling pathways, including wingless-related integration site (WNT), retinoic acid α receptor (RAR), and sonic hedgehog (SHH). The profiling results from SBE-bla assay identify chemicals that disrupt TGFβ/SMAD signaling as part of an integrated qHTS approach for prioritizing putative developmental toxicants.

Half-sandwich ruthenium(ii) complexes with tethered arene-phosphinite ligands: synthesis, structure and application in catalytic cross dehydrogenative coupling reactions of silanes and alcohols

The preparation of the tethered arene-ruthenium(ii) complexes [RuCl₂{η⁶:κ¹(P)-C₆H₅(CH₂)_nOPR₂}] (R = Ph, n = 1 (9a), 2 (9b), 3 (9c); R = ⁱPr, n = 1 (10a), 2 (10b), 3 (10c)) from the corresponding phosphinite ligands R₂PO(CH₂)_nPh (R = Ph, n = 1 (1a), 2 (1b), 3 (1c); R = ⁱPr, n = 1 (2a), 2 (2b), 3 (2c)) is presented. Thus, in a first step, the treatment at room temperature of tetrahydrofuran solutions of dimers [{RuCl(μ-Cl)(η⁶-arene)}₂] (arene = p-cymene (3), benzene (4)) with 1-2a-c led to the clean formation of the corresponding mononuclear derivatives [RuCl₂(η⁶-p-cymene){R₂PO(CH₂)_nPh}] (5-6a-c) and [RuCl₂(η⁶-benzene){R₂PO(CH₂)_nPh}] (7-8a-c), which were isolated in 66-99% yield. The subsequent heating of 1,2-dichloroethane solutions of these compounds at 120 °C allowed the exchange of the coordinated arene. The substitution process proceeded faster with the benzene derivatives 7-8a-c, from which complexes 9-10a-c were generated in 61-82% yield after 0.5-10 h of heating. The molecular structures of [RuCl₂(η⁶-p-cymene){ⁱPr₂PO(CH₂)₃Ph}] (6c) and [RuCl₂{η⁶:κ¹(P)-C₆H₅(CH₂)_nOPⁱPr₂}] (n = 1 (10a), 2 (10b), 3 (10c)) were unequivocally confirmed by X-ray diffraction methods. In addition, complexes [RuCl₂{η⁶:κ¹(P)-C₆H₅(CH₂)_nOPR₂}] (9-10a-c) proved to be active catalysts for the dehydrogenative coupling of hydrosilanes and alcohols under mild conditions (r.t.). The best results were obtained with [RuCl₂{η⁶:κ¹(P)-C₆H₅(CH₂)₃OPⁱPr₂}] (10c), which reached TOF and TON values up to 117 600 h^-1 and 57 000, respectively.

Diversity of complexes based on p-nitrobenzoylhydrazide, benzoylformic acid and diorganotin halides or oxides self-assemble: Cytotoxicity, the induction of apoptosis in cancer cells and DNA-binding properties

Eight organotin(IV) complexes (C1-C8) have been synthesized and characterized by elemental analysis, fourier transform infrared spectroscopy (FT-IR), multinuclear nuclear magnetic resonance (¹H, ¹³C and ¹¹⁹Sn NMR), high resolution mass spectroscopy (HRMS) and single crystal X-ray structural analysis. Crystallographic data show that C1 was a tetranuclear 16-membered macrocycle complex, C2-C4 and C7 were centrosymmetric dimer distannoxane and there was a Sn₂O₂ four-membered ring in the middle of the molecule, respectively, C5 and C6 are monoorganotin complexes due to the dehydroalkylation effect during the reaction, while C8 forms a one-dimensional chain structure. The cytotoxicity of all complexes were tested by 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assays against three human tumor cell lines NCI-H460, MCF-7 and HepG2. The dibutyltin complex C2 has been shown to be more potent antitumor agents than other complexes and carboplatin. Cell apoptosis study of C2 with the high activity on HepG2 and MCF-7 cancer cell lines was investigated by flow cytometry, it was shown that the antitumor activity of C2 was related to apoptosis, but it has different cell cycle arrest characteristics from platinum compounds, and the proliferation was inhibited by blocking cells in S phase. The DNA binding activity of the C2 was studied by UV-visible absorption spectrometry, fluorescence competitive, viscosity measurements and gel electrophoresis, results shown C2 can be well embedded in the double helix of DNA and cleave DNA.

Ruthenium(ii) and palladium(ii) homo- and heterobimetallic complexes: synthesis, crystal structures, theoretical calculations and biological studies

Four Ru-Pd heterobimetallic complexes, each one in two different coordination modes (NNSS and NS) having metals connected by a binucleating dialkyldithiooxamidate [N(R)SC-CS(R)N] [R = methyl, ethyl, n-butyl and isopropyl], were prepared by reacting the monochelate [(triⁿpropyl-phosphine)ClPd(HR₂C₂N₂S₂κ-S,S-Pd)] with [(η⁶-p-cymene)RuCl₂]₂. Furthermore, two palladium homobimetallic complexes having two (triⁿpropyl-phosphine)ClPd moieties joined by a diethyldithiooxamidate in both κ-N,S Pd, κ-N',S' Pd' and κ-N,N' Pd, κ-S,S' Pd' coordination modes were synthesized. For both kinds of complexes, homo- and heterobimetallic, at room temperature and in chloroform solution, the NNSS coordination mode (kinetic compounds) turns out to be unstable and therefore the resulting complexes rearrange into a thermodynamically more stable form (NS coordination mode). The crystal structures of [(triⁿpropyl-phosphine)ClPd]₂[μ-(ethyl)₂-DTO κ-N,S Pd, κ-N',S' Pd'] (2) and [(η⁶-p-cymene)ClRu][μ-(methyl)₂-DTO κ-N,S Ru, κ-N,S Pd] [(triⁿpropyl-phosphine)ClPd] (1c) were determined by solid state X-ray crystallography. Moreover, the higher stability of the thermodynamic species in the heterobimetallic complexes (Ru-Pd) was evaluated by means of computational studies in accordance with the maximum hardness principle. All stable NS complexes (i.e.1c-4c, 2 and the previously reported homobimetallic Ru complex 3) were tested against two leukemia cell lines, namely the drug-sensitive CCRF-CEM cell line and its multidrug-resistant sub-cell line CEM/ADR5000 showing anti-proliferative activity in the low micromolar range (∼1-5 μM) and micromolar range (∼10-25 μM), respectively. In addition, these complexes efficaciously block at least two out of the three proteolytic activities of the tumor target 20S proteasome, with heterobimetallic complex 3c and homobimetallic complex 3 possessing the best inhibitory profile.