Inhibition of cancer cell growth by ruthenium(II) cyclopentadienyl derivative complexes with heteroaromatic ligands

Colorectal cancer: Recent advances in management and treatment

Colorectal cancer (CRC) is the third most common cancer worldwide, and the second most common cause of cancer-related death. In 2020, the estimated number of deaths due to CRC was approximately 930000, accounting for 10% of all cancer deaths worldwide. Accordingly, there is a vast amount of ongoing research aiming to find new and improved treatment modalities for CRC that can potentially increase survival and decrease overall morbidity and mortality. Current management strategies for CRC include surgical procedures for resectable cases, and radiotherapy, chemotherapy, and immunotherapy, in addition to their combination, for non-resectable tumors. Despite these options, CRC remains incurable in 50% of cases. Nonetheless, significant improvements in research techniques have allowed for treatment approaches for CRC to be frequently updated, leading to the availability of new drugs and therapeutic strategies. This review summarizes the most recent therapeutic approaches for CRC, with special emphasis on new strategies that are currently being studied and have great potential to improve the prognosis and lifespan of patients with CRC.

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.

Synthesis, structure, properties, and cytotoxicity of a (quinoline)RuCp+ complex

A rare example of a structurally characterized metal quinoline complex was prepared using a non-covalent quinoline-based proteasome inhibitor (Quin1), and a related complex bearing an inactive quinoline ligand (Quin2) was also synthesized. The quinolines are prepared by a one-pot procedure involving titanium-catalyzed alkyne iminoamination and are bound to ruthenium by reaction with CpRu(NCMe)₃⁺ PF₆^- in CH₂Cl₂. The arene of the quinoline is η⁶-bonded to the ruthenium metal center. The kinetics of quinoline displacement were investigated, and reactivity with deuterated solvents follows the order acetonitrile > DMSO > water. Quinolines with more methyl groups on the arene are more kinetically stable, and RuCp(Quin1)⁺ PF₆^- (1), which has two methyl groups on the arene, is stable for days in DMSO. In contrast, a very similar complex (2) made with Quin2 having no methyl groups on the arene was readily displaced by DMSO. Both 1 and 2 are stable in 9 : 1 water/DMSO for days with no measurable displacement of the quinoline. The cytotoxicity of the quinolines, their CpRu⁺-complexes, and CpRu(DMSO)₃⁺ PF₆^- was investigated towards two multiple myeloma cell lines: MC/CAR and RPMI 8226. To determine whether the activity of the complexes was related to the nature of the quinoline ligands, two structurally similar quinoline ligands with vastly different biological properties were investigated. Quin1 is a cytotoxic proteasome inhibitor, whereas Quin2 is not a proteasome inhibitor and showed no discernable cytotoxicity. The ruthenium complexes showed poor cellular proteasome inhibition. However, both 1 and 2 showed good cytotoxicity towards RPMI 8226 and MC/CAR, with 1 being slightly more cytotoxic. For example, 1 has a CC₅₀ = 2 μM in RPMI 8226, and 2 has a CC₅₀ = 5 μM for the same cell line. In contrast, CpRu(DMSO)₃⁺ PF₆^- was quite active towards MC/CAR with CC₅₀ = 2.8 μM but showed no discernible cytotoxicity toward RPMI 8226. The mechanism of action responsible for the observed cytotoxicity is not known, but the new Ru(Cp)(Quin)⁺ PF₆^- complexes do not cross-link DNA as found for platinum-based drugs. It is concluded that the Ru(Cp)(Quin)⁺ PF₆^- complexes remain intact in the cellular assays and constitute a new class of cytotoxic metal complexes.

New insights into ruthenium(ii) metallodendrimers as anticancer drug nanocarriers: from synthesis to preclinic behaviour

Pre-clinical results highlight the potential of the low-generation poly(alkylidenamine)-based dendrimers as ruthenium metallodrug nanocarriers.

Bioactive platinum complex of ligand bearing pyrimidine skeleton: DNA/BSA binding, molecular docking, anticancer, antioxidant and antimicrobial activities

A new octahedral platinum complex [PtLCl₄] of Schiff base ligand containing pyrimidine and morpholine skeleton (where, L is 4,6-dichloropyrimidin-5-yl)methylene)-2-morpholinoethanamine) was isolated and characterized by elemental analysis, ¹H-NMR, FTIR, UV-visible and ESI-MS techniques. DNA interaction of isolated compounds with calf thymus (CT-DNA) was explored by UV-vis absorption, fluorescence, cyclic voltametric and viscometric methods. The result shows that prepared compounds can interact with CT-DNA through electrostatic interactions. Bovine serum album (BSA) binding behavior of isolated compounds was also studied by UV-vis absorption and fluorescence techniques. Both the spectroscopic results suggest that the isolated ligand and its complex bind with BSA through static quenching. The optimized structure of ligand and platinum complex were achieved by the DFT calculations. Moreover, molecular docking of ligand and its complex were studied. These analysis results reveal that ligand has low binding affinity on DNA and BSA molecules in contrast to its complex. In vitro anticancer activity of isolated compounds toward normal cell line (NHDF) as well as cancer cell lines (MCF-7, HepG2, HeLa and A549) was studied by MTT assay. The results supports that isolated platinum complex can control the growth of cancer cells (MCF-7, 20.12 ± 1.00 µg/mL; HepG2, 32.2 ± 1.69 µg/mL; HeLa, 24.68 ± 1.29 µg/mL; A549, 23.46 ± 1.17 µg/mL) without inhibiting the normal cell line (NHDF, 109.26 ± 5.46 µg/mL). Antioxidant and antimicrobial activities of isolated compounds indicate that ligand and Pt complex are found to have good radical scavenging against four different free radicals and antimicrobial abilities on E. coli and C. albicans antimicrobial species. HighlightsPlatinum complex of Schiff base with pyrimidine and morpholine linkage was synthesized.Pt complex has better biomolecular interaction with DNA and BSA.Molecular docking of Pt complex with DNA and BSA has been studiedPt complex has good anticancer activities.Pt complex has better antioxidant and antimicrobial activities.

Heterofunctional ruthenium(II) carbosilane dendrons, a new class of dendritic molecules to fight against prostate cancer

A family of heterofunctional Schiff base carbosilane metallodendrons with [Ru(η⁵-C₅H₅)(PTA)Cl] (PTA = 1,3,5-triaza-7-phosphatricyclo-[3.3.1.1]decane) at the focal point and dimethylamino groups on the periphery are described. The new systems have proved their ability to interact with biological molecules such as Human Serum Albumin (HSA) without affecting its secondary structure and erythrocytes membranes, causing haemolysis in a dose and generation dependent way. The combination of two active functional groups in one single dendritic platform has shown a cooperative effect in the viability of HeLa and PC-3 cells, with the second generation derivative standing out as the most promising with the lowest IC₅₀. Experiments focused on advanced prostate cancer have shown an antimetastasic activity for those metallodendrons, hindering the adhesion of cells in one of the main targets of metastasis, bones, and inhibiting cell migration. Finally, the second generation metallodendron with one single metal centre and four dimethylamino groups on the dendritic wedge, was selected for an ex vivo experiment in nude mice with advanced prostate cancer inhibiting the tumour growth in a 40% compared to control mice.

Gold(III) Complexes: An Overview on Their Kinetics, Interactions With DNA/BSA, Cytotoxic Activity, and Computational Calculations

In the last few years, metallodrugs play a key role in the development of medicinal chemistry. The choice of metal ion, its oxidation state and stability, and the choice of inert and labile ligands are just some of the very important facts which must be considered before starting the synthesis of complexes with utilization in medicinal purpose. As a result, a lot of compounds of different transition metal ions found application for diagnostic and therapeutic purpose. Beside all, gold compounds have attracted particular attention. It is well-known that gold compounds could be used for the treatment of cancer, HIV, rheumatoid arthritis (chrysotherapy), and other diseases. This metal ion has unoccupied d-sublevels and possibility to form compounds with different oxidation states, from -1 to +5. However, gold(I) and gold(III) complexes are dominant in chemistry and medicine. Especially, gold(III) complexes are of great interest due to their structural similarity with cisplatin. Accordingly, this review summarizes the chemistry of some mononuclear and polynuclear gold(III) complexes. Special attention is given to gold(III) complexes with nitrogen-donor inert ligands (aliphatic or aromatic that have a possibility to stabilize complex) and their kinetic behavior toward different biologically relevant nucleophiles, mechanism of interaction with DNA/bovine serum albumin (BSA), cytotoxic activity, as well as computational calculations.

Novel "ruthenium cyclopentadienyl"-peptide conjugate complexes against human FGFR(+) breast cancer

In this work we explored the possibility of improving the selectivity of a cytotoxic Ru complex [RuCp(PPh₃)(2,2'-bipy)][CF₃SO₃] (where Cp = η⁵-cyclopentadienyl) TM34 towards FGFR(+) breast cancer cells. Molecular dynamics (MD) simulations of TM34 in a phosphatidylcholine membrane model pinpointed the cyclopentadienyl group as a favorable derivatization position for the peptide conjugation approach. Three new Ru(ii) complexes presenting a functionalized η⁵-cyclopentadienyl were synthesized, namely [Ru(η⁵-C₅H₄COOH)(2,2'-bipy)(PPh₃)][CF₃SO₃] (TM281) and its precursors, [Ru(η⁵-C₅H₄COOCH₂CH₃)(η²-2,2'-bipy)(PPh₃)][CF₃SO₃] (3) and [Ru(η⁵-C₅H₄COOCH₂CH₃)(PPh₃)₂Cl] (2). Complex TM281 was prepared by the hydrolysis of the ethyl ester group appended to the η⁵-cyclopentadienyl ligand of complex 3 with K₂CO₃ in water/acetonitrile, followed by mild protonation using an ion exchange resin. The newly synthesized complexes were fully characterized by NMR, FTIR and UV-vis spectroscopic techniques. Also, electrochemical studies were carried out by means of cyclic voltammetry in order to evaluate the stability of the compounds. Single crystal X-ray diffraction studies were carried out for compounds 3 and TM281 which crystallized in the monoclinic system, space group P21/n. The unprecedented synthesis and characterization of three half-sandwich ruthenium(ii)-cyclopentadienyl peptide conjugates and their preliminary biological evaluation against human FGFR(+) and FGFR(-) breast cancer cells are also reported.

Spectroscopic, Computational, Antimicrobial, DNA Interaction, In Vitro Anticancer and Molecular Docking Properties of Biochemically Active Cu(II) and Zn(II) Complexes of Pyrimidine-Ligand

Biochemically active Cu(II) and Zn(II) complexes [CuL(ClO₄)₂(1) and ZnL(ClO₄)₂(2)] have been synthesized from N,N donor Schiff base ligand L derived from4,6-dichloropyrimdine-5-carboxaldehyde with 4-(2-aminoethyl)morpholine. The L, complexes 1 and 2 have been structurally characterized by elemental analysis, ¹H-NMR, FTIR, MS, UV-Visible and ESR techniques. The results obtained from the spectral studies supports the complexes 1 and 2 are coordinated with L through square planar geometry. DFT calculations results supports, the ligand to metal charge transfer mechanism can occur between L and metal(II) ions. The antimicrobial efficacy results have been recommended that, complexes 1 and 2 are good anti-pathogenic agents than ligand L. The interaction of complexes 1 and 2 with calf thymus (CT) DNA has been studied by electronic absorption, viscometric, fluorometric and cyclic voltammetric measurements. The calculated K_b values for L, complexes 1 and 2 found from absorption titrations was 4.45 × 10⁴, L; 1.92 × 10⁵, 1 and 1.65 × 10⁵, 2. The Ksv values were found to be 3.0 × 10³, 3.68 × 10³and 3.52 × 10³ for L, complexes 1 and 2 by using competitive binding with ethidium bromide (EB). These results suggest that, the compounds are interacted with DNA may be electrostatic binding. The molecular docking studies have been carried out to confirm the interaction of compounds with DNA. Consequently, in vitro anticancer activities of L, complexes 1 and 2 against selected cancer (lung cancer A549, liver cancer HepG2 and cervical carcinoma HeLa) and normal (NHDF) cell lines were assessed by MTT assay.

Poly(alkylidenimine) Dendrimers Functionalized with the Organometallic Moiety [Ru(η⁵-C₅H₅)(PPh₃)₂]⁺ as Promising Drugs Against Cisplatin-Resistant Cancer Cells and Human Mesenchymal Stem Cells

Here and for the first time, we show that the organometallic compound [Ru(η⁵-C₅H₅)(PPh₃)₂Cl] (RuCp) has potential to be used as a metallodrug in anticancer therapy, and further present a new approach for the cellular delivery of the [Ru(η⁵-C₅H₅)(PPh₃)₂]⁺ fragment via coordination on the periphery of low-generation poly(alkylidenimine) dendrimers through nitrile terminal groups. Importantly, both the RuCp and the dendrimers functionalized with [Ru(η⁵-C₅H₅)(PPh₃)₂]⁺ fragments present remarkable toxicity towards a wide set of cancer cells (Caco-2, MCF-7, CAL-72, and A2780 cells), including cisplatin-resistant human ovarian carcinoma cell lines (A2780cisR cells). Also, RuCp and the prepared metallodendrimers are active against human mesenchymal stem cells (hMSCs), which are often found in the tumor microenvironment where they seem to play a role in tumor progression and drug resistance.

pH-Switchability and Second-Order Nonlinear Optical Properties of Monocyclopentadienylruthenium(II)/iron(II) Tetrazoles/Tetrazolates: Synthesis, Characterization, and Time-Dependent Density Functional Theory Calculations

Tetrazole/tetrazolate monocyclopentadienyliron(II) and ruthenium(II) compounds of general formulas [(η⁵-C₅H₅)M(dppe)(N₄(H)CC₆H₄NO₂)][PF₆]/[(η⁵-C₅H₅)M(dppe)(N₄CC₆H₄NO₂)] were investigated for their pH-switching second-order nonlinear optical (SONLO) properties. Compounds [(η⁵-C₅H₅)M(dppe)(N₄CC₆H₄NO₂)] (M = Fe, Ru) and compound [(η⁵-C₅H₅)Ru(dppe)(N₄(H)CC₆H₄NO₂)][PF₆] were fully characterized by (¹H-, ¹³C-, ³¹P-) NMR, cyclic voltammetry, and elemental analysis, and compounds [(η⁵-C₅H₅)Fe(dppe)(N₄CC₆H₄NO₂)] and [(η⁵-C₅H₅)Ru(dppe)(N₄(H)CC₆H₄NO₂)][PF₆] were further characterized by single-crystal X-ray diffraction; the synthesis of [(η⁵-C₅H₅)Fe(dppe)(N₄(H)CC₆H₄NO₂)][PF₆] was unsuccessful. Time-dependent density functional theory calculations were performed using PBE0 and CAM-B3LYP functionals to evaluate the first hyperpolarizability (β_tot) of the tetrazole/tetrazolate complexes and for a detailed analysis of the experimental data. Both functionals predict (i) high first hyperpolarizabilities for the tetrazolate complexes [(η⁵-C₅H₅)M(dppe)(N₄CC₆H₄NO₂)], with β_tot[Ru] ≈ 1.2β_tot[Fe], and (ii) a 3-fold reduction in β_tot[Ru] upon protonation, in complex [(η⁵-C₅H₅)Ru(dppe)(N₄(H)CC₆H₄NO₂)]⁺, forecasting [(η⁵-C₅H₅)Ru(dppe)(N₄CC₆H₄NO₂)]/[(η⁵-C₅H₅)Ru(dppe)(N₄(H)CC₆H₄NO₂)]⁺ complexes as on/off, pH-switchable SONLO forms.

Metal-containing and related polymers for biomedical applications

A survey of the most recent progress in the biomedical applications of metal-containing polymers is given. Due to the unique optical, electrochemical, and magnetic properties, at least 30 different metal elements, most of them transition metals, are introduced into polymeric frameworks for interactions with biology-relevant substrates via various means. Inspired by the advance of metal-containing small molecular drugs and promoted by the great progress in polymer chemistry, metal-containing polymers have gained momentum during recent decades. According to their different applications, this review summarizes the following biomedical applications: (1) metal-containing polymers as drug delivery vehicles; (2) metal-containing polymeric drugs and biocides, including antimicrobial and antiviral agents, anticancer drugs, photodynamic therapy agents, radiotherapy agents and biocides; (3) metal-containing polymers as biosensors, and (4) metal-containing polymers in bioimaging.

Tracking antitumor metallodrugs: promising agents with the Ru(II)- and Fe(II)-cyclopentadienyl scaffolds

Research on the field of metal complexes for the treatment of cancer diseases has attracted increasing interest due to the urgency in finding more efficient and selective treatments. Owing to their wide structural diversity, organometallic complexes appear as potential alternatives to the design of new anticancer candidates. Herein, we review recent progress in our work toward the development of new drugs based on Ru(II)- and Fe(II)-cyclopentadienyl scaffolds. Their design and chemical properties are reviewed and correlated with their biological effects, in particular the key role that coligands play in the overall behavior of the complex.

Development of ruthenium-based complexes as anticancer agents: toward a rational design of alternative receptor targets

In the search for novel anticancer agents, the development of metal-based complexes that could serve as alternatives to cisplatin and its derivatives has received considerable attention in recent years. This becomes necessary because, at present, cisplatin and its derivatives are the only coordination complexes being used as anticancer agents in spite of inherent serious side effects and their limitation against metastasized platinum-resistant cancer cells. Although many metal ions have been considered as possible alternatives to cisplatin, the most promising are ruthenium (Ru) complexes and two Ru compounds, KP1019 and NAMI-A, which are currently in phase II clinical trials. The major obstacle against the rational design of these compounds is the fact that their mode of action in relation to their therapeutic activities and selectivity is not fully understood. There is an urgent need to develop novel metal-based anticancer agents, especially Ru-based compounds, with known mechanism of actions, probable targets, and pharmacodynamic activity. In this paper, we review the current efforts in developing metal-based anticancer agents based on promising Ru complexes and the development of compounds targeting receptors and then examine the future prospects.

Novel ruthenium(II) cyclopentadienyl thiosemicarbazone compounds with antiproliferative activity on pathogenic trypanosomatid parasites

Searching for new prospective antitrypanosomal agents, three novel Ru(II)-cyclopentadienyl compounds, [Ru(η(5)-C5H5)(PPh3)L], with HL=bioactive 5-nitrofuryl containing thiosemicarbazones were synthesized and characterized in the solid state and in solution. The compounds were evaluated in vitro on the blood circulating trypomastigote form of Trypanosoma cruzi (Dm28c strain), the infective form of Trypanosoma brucei brucei (strain 427) and on J774 murine macrophages and human-derived EA.hy926 endothelial cells. The compounds were active against both parasites with IC50 values in the micromolar or submicromolar range. Interestingly, they are much more active on T. cruzi than previously developed Ru(II) classical and organometallic compounds with the same bioactive ligands. The new compounds showed moderate to very good selectivity towards the parasites in respect to mammalian cells. The global results point at [RuCp(PPh3)L2] (L2=N-methyl derivative of 5-nitrofuryl containing thiosemicarbazone and Cp=cyclopentadienyl) as the most promising compound for further developments (IC50T. cruzi=0.41μM; IC50T. brucei brucei=3.5μM). Moreover, this compound shows excellent selectivity towards T. cruzi (SI>49) and good selectivity towards T. brucei brucei (SI>6). In order to get insight into the mechanism of antiparasitic action, the intracellular free radical production capacity of the new compounds was assessed by ESR. DMPO (5,5-dimethyl-1-pirroline-N-oxide) spin adducts related to the bioreduction of the complexes and to redox cycling processes were characterized. In addition, DNA competitive binding studies with ethidium bromide by fluorescence measurements showed that the compounds interact with this biomolecule.

Cyclopentadienyl-ruthenium(II) and iron(II) organometallic compounds with carbohydrate derivative ligands as good colorectal anticancer agents

New ruthenium(II) and iron(II) organometallic compounds of general formula [(η(5)-C5H5)M(PP)Lc][PF6], bearing carbohydrate derivative ligands (Lc), were prepared and fully characterized and the crystal structures of five of those compounds were determined by X-ray diffraction studies. Cell viability of colon cancer HCT116 cell line was determined for a total of 23 organometallic compounds and SAR's data analysis within this library showed an interesting dependency of the cytotoxic activity on the carbohydrate moiety, linker, phosphane coligands, and metal center. More importantly, two compounds, 14Ru and 18Ru, matched oxaliplatin IC50 (0.45 μM), the standard metallodrug used in CC chemotherapeutics, and our leading compound 14Ru was shown to be significantly more cytotoxic than oxaliplatin to HCT116 cells, triggering higher levels of caspase-3 and -7 activity and apoptosis in a dose-dependent manner.

Anticancer Activities of Mononuclear Ruthenium(II) Coordination Complexes

Ruthenium compounds are highly regarded as potential drug candidates. The compounds offer the potential of reduced toxicity and can be tolerated in vivo. The various oxidation states, different mechanism of action, and the ligand substitution kinetics of ruthenium compounds give them advantages over platinum-based complexes, thereby making them suitable for use in biological applications. Several studies have focused attention on the interaction between active ruthenium complexes and their possible biological targets. In this paper, we review several ruthenium compounds which reportedly possess promising cytotoxic profiles: from the discovery of highly active compounds imidazolium [trans-tetrachloro(dmso)(imidazole)ruthenate(III)] (NAMI-A), indazolium [trans-tetrachlorobis(1H-indazole)ruthenate(III)](KP1019), and sodium trans-[tetrachloridobis(1H-indazole)ruthenate(III)] (NKP-1339) to the recent work based on both inorganic and organometallic ruthenium(II) compounds. Half-sandwich organometallic ruthenium complexes offer the opportunity of derivatization at the arene moiety, while the three remaining coordination sites on the metal centre can be functionalised with various coordination groups of various monoligands. It is clear from the review that these mononuclear ruthenium(II) compounds represent a strongly emerging field of research that will soon culminate into several ruthenium based antitumor agents.

Synthesis and anticancer activity evaluation of η5-C5(CH3)4R ruthenium complexes bearing chelating diphosphine ligands

A series of ruthenium complexes with η⁵-C₅(CH₃)₄R and diphosphine ligands have been synthesised and evaluated in vitro as anticancer agents. IC₅₀ values in the nanomolar range have been obtained against two types of cell lines.

Metal based photosensitizers of tetradentate Schiff base: promising role in anti-tumor activity through singlet oxygen generation mechanism

In the present investigation, a Schiff base N'(1),N'(3)-bis[(Z)-(2-hydroxynapthyl)methylidene]benzene-1,3-dicarbodihydrazide (L1) and its Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized as novel photosensitizing agents for photodynamic therapy (PDT). The interaction of these complexes with calf thymus DNA (CT DNA) has been explored using absorption, thermal denaturation and viscometric studies. The experimental results revealed that Co(II) and Ni(II) complexes on binding to CT DNA imply a covalent mode, most possibly involving guanine N7 nitrogen of DNA, with an intrinsic binding constant Kb of 4.5×10(4)M(-1) and 4.2×10(4)M(-1), respectively. However, interestingly, the Cu(II) complex is involved in the surface binding to minor groove via phosphate backbone of DNA double helix with an intrinsic binding constant Kb of 5.7×10(4)M(-1). The Co(II), Ni(II) and Cu(II) complexes are active in cleaving supercoiled (SC) pUC19 DNA on photoexposure to UV-visible light of 365nm, through (1)O2 generation with quantum yields of 0.28, 0.25 and 0.30, respectively. Further, these complexes are cytotoxic in A549 lung cancer cells, showing an enhancement of cytotoxicity upon light irradiation.

New water-soluble ruthenium(II) cytotoxic complex: biological activity and cellular distribution

A novel water soluble organometallic compound, [RuCp(mTPPMSNa)(2,2'-bipy)][CF3SO3] (TM85, where Cp=η(5)-cyclopentadienyl, mTPPMS=diphenylphosphane-benzene-3-sulfonate and 2,2'-bipy=2,2'-bipyridine) is presented herein. Studies of interactions with relevant proteins were performed to understand the behavior and mode of action of this complex in the biological environment. Electrochemical and fluorescence studies showed that TM85 strongly binds to albumin. Studies carried out to study the formation of TM85 which adducts with ubiquitin and cytochrome c were performed by electrospray ionization mass spectrometry (ESI-MS). Antitumor activity was evaluated against a variety of human cancer cell lines, namely A2780, A2780cisR, MCF7, MDAMB231, HT29, PC3 and V79 non-tumorigenic cells and compared with the reference drug cisplatin. TM85 cytotoxic effect was reduced in the presence of endocytosis modulators at low temperatures, suggesting an energy-dependent mechanism consistent with endocytosis. Ultrastructural analysis by transmission electron microscopy (TEM) revealed that TM85 targets the endomembranar system disrupting the Golgi and also affects the mitochondria. Disruption of plasma membrane observed by flow cytometry could lead to cellular damage and cell death. On the whole, the biological activity evaluated herein combined with the water solubility property suggests that complex TM85 could be a promising anticancer agent.

Cellular uptake mechanisms of an antitumor ruthenium compound: the endosomal/lysosomal system as a target for anticancer metal-based drugs

Previous studies have described promising antitumor activity of an organometallic Ru(II) complex, η⁵-cyclopentadienyl(2,2'-bipyridyl)(triphenylphosphane) Ruthenium(II) triflate ([η⁵-C₅H₅)Ru(2,2'-bipyridyl)(PPh₃)][CF₃SO₃]) herein designated as TM34. Its broad spectrum of activity against a panel of human tumor cell lines and high antiproliferative efficiency prompted us to focus on its mode of action. We present herein results obtained with two human tumor cell lines A2780 and MDAMB231 on the compound distribution within the cell, the mechanism of its activity, and its cellular targets. The prospective metallodrug TM34 revealed: (a) fast antiproliferative effects even at short incubation times for both cell lines; (b) preferential localization at the cell membrane and cytosol; (c) cellular activity by a temperature-dependent process, probably macropinocytosis; (d) inhibition of a lysosomal enzyme, acid phosphatase, in a dose-dependent mode; and (e) disruption and vesiculation of the Golgi apparatus, which suggest the involvement of the endosomal/lysosomal system in its mode of action. These results are essential to elucidate the basis for the cytotoxic activity and mechanism of action of this Ru(II)(η⁵-cyclopentadienyl) complex.

Exploring the effect of the ligand design on the interactions between [Ru(η(5)-C5H5)(PPh3)(N,O)][CF3SO3] complexes and human serum albumin

Ruthenium complexes hold a great potential in chemotherapy as an alternative to the classical platinum based drugs. The organometallic compounds studied in the present work were previously found to exhibit important anticancer activities. Here we have investigated the binding of three ruthenium compounds, namely [Ru(η(5)-C5H5)(PPh3)(bopy)][CF3SO3] 1, [Ru(η(5)-C5H5)(PPh3)(2-ap)][CF3SO3] 2, and [Ru(η(5)-C5H5)(PPh3)(isoquinpk)][CF3SO3] 3 (bopy=2-benzoylpyridine; 2-ap=2-acetylpyridine; isoquinpk=1-isoquinolinyl phenyl ketone) to fatty acid human serum albumin (HSA) and fatty acid-free human serum albumin (HSA(faf)) at physiological pH7.4. The influence of the substituent groups on the heteroaromatic (N,O) coordinated ligand was also studied by fluorescence spectroscopy to get information about this binding. The Stern-Volmer quenching constants (KSV) were calculated at 293, 298 and 310K, with the corresponding thermodynamic parameters ∆G, ∆H and ∆S as well. The fluorescence quenching method was used to determine the number of binding sites (n) and association constants (Ka) at the same temperatures. The binding site to HSA was confirmed by competitive studies of the ruthenium compounds with warfarin.

Important cytotoxicity of novel iron(II) cyclopentadienyl complexes with imidazole based ligands

Four new compounds of general formula [FeCp(dppe)L][CF3SO3] with L=imidazole substituted ligands, and dppe=ethylenebis(diphenylphosphane) have been synthesized and characterized with the aim to evaluate their anticancer properties. The new compounds were fully characterized by spectroscopic and electrochemical methods and the structure of [Fe(η(5)-C5H5)(dppe)(1-BuIm)] [CF3SO3] (1), [Fe(η(5)-C5H5)(dppe) (ImH)][CF3SO3] (3) and [Fe(η(5)-C5H5)(dppe)(1HmIm)][CF3SO3] (4) (where 1-BuIm=1-butylimidazole, and 1HmIm=N-hydroxymethylimidazole) was determined by X-ray diffraction studies. Apparently, these compounds are the first reported 'Fe(η(5)-C5H5)' half sandwich derivatives presenting high cytotoxic activity against a set a human tumor cell lines predicting their potential value as antitumor drugs.

First polymer "ruthenium-cyclopentadienyl" complex as potential anticancer agent

d-glucose end-capped polylactide ruthenium cyclopentadienyl complex (RuPMC) was newly synthesized by a straightforward method. RuPMC was tested against human MCF7 and MDAMB231 breast and A2780 ovarian adenocarcinoma revealing IC50 values in the micromolar range. A pH dependent hydrolysis is advanced by preliminary UV-visible spectroscopy. Cellular distribution studies showed that RuPMC is predominantly found in the nucleus and in the membrane. Data suggest potential application of RuPMC as a new drug delivery system for Ru(II)Cp compounds.

Biological activity and cellular uptake of [Ru(η5-C5H5)(PPh3)(Me2bpy)][CF3SO3] complex

Anticancer activity of the new [Ru(η(5)-C5H5)(PPh3)(Me2bpy)][CF3SO3] (Me2bpy = 4,4'-dimethyl-2,2'-bipyridine) complex was evaluated in vitro against several human cancer cell lines, namely A2780, A2780CisR, HT29, MCF7, MDAMB231 and PC3. Remarkably, the IC50 values, placed in the nanomolar and sub-micromolar range, largely exceeded the activity of cisplatin. Binding to human serum albumin, either HSA (human serum albumin) or HSA(faf) (fatty acid-free human serum albumin) does not affect the complex activity. Fluorescence studies revealed that the present ruthenium complex strongly quench the intrinsic fluorescence of albumin. Cell death by the [Ru(η(5)-C5H5)(PPh3)(Me2bpy)][CF3SO3] complex was reduced in the presence of endocytosis modulators and at low temperature, suggesting an energy-dependent mechanism consistent with endocytosis. On the whole, the biological activity evaluated herein suggests that the complex could be a promising anticancer agent.

Cobalt(II), Nickel(II) and Copper(II) complexes of a tetradentate Schiff base as photosensitizers: Quantum yield of 1O2 generation and its promising role in anti-tumor activity

In the present investigation, a Schiff base N'1,N'3-bis[(E)-(5-bromo-2-hydroxyphenyl)methylidene]benzene-1,3-dicarbohydrazide and its metal complexes have been synthesized and characterized. The DNA-binding studies were performed using absorption spectroscopy, emission spectra, viscosity measurements and thermal denatuaration studies. The experimental evidence indicated that, the Co(II), Ni(II) and Cu(II) complexes interact with calf thymus DNA through intercalation with an intrinsic binding constant Kb of 2.6×10(4) M(-1), 5.7×10(4) M(-1) and 4.5×10(4) M(-1), respectively and they exhibited potent photodamage abilities on pUC19 DNA, through singlet oxygen generation with quantum yields of 0.32, 0.27 and 0.30 respectively. The cytotoxic activity of the complexes resulted that they act as a potent photosensitizers for photochemical reactions.