An engineered POSS drug delivery system for copper(II) anticancer metallodrugs in a selective application toward melanoma cells.

In this work, a polyhedral silsesquioxane (POSS) was used as an engineered drug delivery system for two oxindolimine-copper(II) anticancer complexes, [Cu(isaepy)] and [Cu(isapn)]. The interest in hybrid POSS comes from the necessity of developing materials that can act as adjuvants to improve the cytotoxicity of non-soluble metallodrugs. Functionalization of POSS with a triazole ligand (POSS-atzac) permitted the anchorage of such copper complexes, producing hybrid materials with efficient cytotoxic effects.

Interaction studies of oxindole-derivatives with β-amyloid peptides inhibiting its aggregation induced by metal ions.

Some hydrazones and Schiff bases derived from isatin, an endogenous oxindole formed in the metabolism of tryptophan, were obtained to investigate their effects on in vitro aggregation of β-amyloid peptides (Aβ), macromolecules implicated in Alzheimer's disease. Some hydrazone ligands, prepared by condensation reactions of isatin with hydrazine derivatives, showed a large affinity binding to the synthetic peptides Aβ, particularly to Aβ. Measurements by NMR spectroscopy indicated that those interactions occur mainly at the metal binding site of the peptide, involving His6, His13, and His14 residues, and that hydrazone E-diastereoisomer interacts preferentially with the amyloid peptides.

A new strategy for improving cytotoxicity of a copper complex toward metastatic melanoma cells unveiled by EPR spectroscopy.

A novel strategy of improving cytotoxicity against metastatic melanoma cells using an oxindolimine copper(ii) complex immobilized and dimerized on a modified Polyhedral Oligomeric Silsesquioxane (POSS) matrix was developed, as revealed by electron paramagnetic resonance (EPR) spectroscopy. An assured correlation between continuous-wave (CW) and pulsed EPR spectroscopies provided a complete characterization of the actual active species, its coordination environment, as well as the efficiency/selectivity of the bioconjugate materials.

Antitumor copper(II) complexes with hydroxyanthraquinones and N,N-heterocyclic ligands.

Five ternary copper(II) complexes, [Cu(phen)(L1)(ClO)] (1), [Cu(phen)(L1)(DMSO)](PF6) (2), [Cu(bpy)(L1)(ClO)(HO)] (3), [Cu(dmp)(L1)(ClO)(HO)] (4), and [Cu(phen)(L2)](ClO) (5), in which phen = 1,10-phenanthroline, bpy = 2,2'-bipyridine, dmp = 2,9-dimethyl-1,10-phenanthroline, HL1 = 1,4-dihydroxyanthracene-9,10-dione and HL2 = 1-hydroxyanthracene-9,10-dione, DMSO = dimethylsulfoxide, were synthesized and fully characterized. Complex 2 was obtained through the substitution of perchlorate for DMSO. When two hydroxyquinone groups are present, L1 makes a bridge between two Cu(II) ions, which also bind two nitrogens of the respective diimine ligand.

Investigating the antiproliferative activities of new Cu complexes with pyridine hydrazone derivatives of nalidixic acid.

To further explore the structural features and potential antibacterial and antitumor activities of polynuclear Cu coordination compounds with nalidixic acid (nx) derivatives, new complexes bearing nx hydrazones with N-pyridinyl moieties substituted at positions 2 and 3 (h2py and h3py) were synthesized. Complexes [Cu(CHNO)(CHNO)(HO)]4BF∙HO (1), and [Cu(CHNO)(CHNO)(HO)]4BF∙3HO (%) (2) were synthesized using h2py and h3py with Cu(BF)∙nHO as precursor, whereas the [Cu(CHNO)Cl]∙0.5HO complex (3) was synthesized with h2py and CuCl∙2HO.

A bioinspired nitrone precursor to a stabilized nitroxide radical.

Nitrones derived from natural antioxidants are emerging as highly specific therapeutics against various human diseases, including stroke, neurodegenerative pathologies, and cancer. However, the development of useful pseudo-natural nitrones requires the judicious choice of a secondary metabolite as the precursor. Betalains are nitrogen-containing natural pigments that exhibit marked antioxidant capacity and pharmacological properties and, hence, are ideal candidates for designing multifunctional nitrones.

Multivariate probing of antitumor metal-based complexes damage on living cells through Raman imaging.

Intracellular modifications caused by two metal-based antitumor compounds were assessed by confocal Raman imaging assisted by multivariate curve resolution method, a very powerful deconvolution tool that can be used to extract the characteristic spectral profile of the individual or "purest" components from an image dataset. The use of this Raman methodology has the advantage of being non-invasive and totally label-free. Four main different intracellular processes were observed under the Raman imaging and multivariate approach combination, and even, significant differences could be identified between the treatments with both metallodrugs.

Heterobinuclear copper(II)‑platinum(II) complexes with oxindolimine ligands: Interactions with DNA, and inhibition of kinase and alkaline phosphatase proteins.

Two mononuclear copper(II) compounds, [Cu(isad)(HO)Cl]Cl 1 and [Cu(isah)(HO)Cl]Cl 2, and its corresponding heterobinuclear species containing also platinum(II), [CuCl(isad)Pt(NH)Cl] 3 and [CuCl(isah)Pt(NH)Cl] 4 (where isad and isah are oxindolimine ligands, (E)-3-(2-(3-aminopropylamino)ethylimino)indolin-2-one, and (E)-3-(3-amino-2-hydroxypropylimino)indolin-2-one, respectively), have been previously synthesized and characterized by different spectroscopic techniques in our laboratory. Cytotoxicity assays performed with B16F10 murine cancer cells, and MES-SA human uterine sarcoma cells, showed IC values lower or in the same order of cisplatin. Herein, in order to better elucidate their probable modes of action, possible interaction and damage to DNA, as well as their effect on the activity of crucial proteins were verified.

Unlike reactivity of mono- and binuclear imine-copper(II) complexes toward melanoma cells via a tyrosinase-dependent mechanism.

The cytotoxicity of a dinuclear imine-copper (II) complex 2, and its analogous mononuclear complex 1, toward different melanoma cells, particularly human SKMEL-05 and SKMEL-147, was investigated. Complex 2, a tyrosinase mimic, showed much higher activity in comparison to complex 1, and its reactivity was verified to be remarkably activated by UVB-light, while the mononuclear compound showed a small or negligible effect. Further, a significant dependence on the melanin content in the tumor cells, both from intrinsic pigmentation or stimulated by irradiation, was observed in the case of complex 2.

Novel copper(II) complexes with hydrazides and heterocyclic bases: Synthesis, structure and biological studies.

Five new copper(II) complexes of the type [Cu(NO)(NN)(ClO)], in which NO=4-fluorophenoxyacetic acid hydrazide (4-FH) or 4-nitrobenzoic hydrazide (4-NH) and NN=1,10-phenanthroline (phen), 4-4'-dimethoxy-2-2'-bipyridine (dmb) or 2,2-bipyridine (bipy) were synthesized and characterized using various spectroscopic methods. The X-ray structural analysis of one representative compound indicates that the geometry around the copper ion is distorted octahedron, in which the ion is coordinated to hydrazide via the terminal nitrogen and the carbonyl oxygen, and to heterocyclic bases via their two nitrogen atoms. Two perchlorate anions occupy the apical positions, completing the coordination sphere.

A Nanostructured Lipid System as a Strategy to Improve the in Vitro Antibacterial Activity of Copper(II) Complexes.

The aim of this study was to construct a nanostructured lipid system as a strategy to improve the in vitro antibacterial activity of copper(II) complexes. New compounds with the general formulae [CuX₂(INH)₂]·nH₂O (X = Cl(-) and n = 1 (1); X = NCS(-) and n = 5 (2); X = NCO(-) and n = 4 (3); INH = isoniazid, a drug widely used to treat tuberculosis) derived from the reaction between the copper(II) chloride and isoniazid in the presence or absence of pseudohalide ions (NCS(-) or NCO(-)) were synthesized and characterized by infrared spectrometry, electronic absorption spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, elemental analysis, melting points and complexometry with 2,2',2'',2'''-(Ethane-1,2-diyldinitrilo)tetraacetic acid (EDTA). The characterization techniques allowed us to confirm the formation of the copper(II) complexes.

Inhibition of cyclin-dependent kinase CDK1 by oxindolimine ligands and corresponding copper and zinc complexes.

Oxindolimine-copper(II) and zinc(II) complexes that previously have shown to induce apoptosis, with DNA and mitochondria as main targets, exhibit here significant inhibition of kinase CDK1/cyclin B protein. Copper species are more active than the corresponding zinc, and the free ligand shows to be less active, indicating a major influence of coordination in the process, and a further modulation by the coordinated ligand. Molecular docking and classical molecular dynamics provide a better understanding of the effectiveness and kinase inhibition mechanism by these compounds, showing that the metal complex provides a stronger interaction than the free ligand with the ATP-binding site.

Antischistosomal Activity of Oxindolimine-Metal Complexes.

In recent years, a class of oxindole-copper and -zinc complex derivatives have been reported as compounds with efficient proapoptotic activity toward different tumor cells (e.g., neuroblastomas, melanomas, monocytes).

Reactivity of dinuclear copper(II) complexes towards melanoma cells: Correlation with its stability, tyrosinase mimicking and nuclease activity.

In this work, the influence of two new dinuclear copper(II) complexes in the viability of melanoma cells (B16F10 and TM1MNG3) was investigated, with the aim of verifying possible correlations between their cytotoxicity and their structure. One of the complexes had a polydentate dinucleating amine-imine ligand (complex 2), and the other a tridentate imine and a diamine-bridging ligand (complex 4). The analogous mononuclear copper(II) species (complexes 1 and 3, respectively) were also prepared for comparative studies.

Effect of oxindolimine copper(II) and zinc(II) complexes on human topoisomerase I activity.

The ability of oxindolimine copper(II) and zinc(II) complexes, known to have antitumor activity, to inhibit human topoisomerase IB has been tested through enzymatic kinetic assays and molecular docking simulations. These copper and zinc compounds are able to inhibit remarkably the cleavage reaction and only partially the religation step, the copper compound being more efficient than the zinc one. A complete inhibition activity of the cleavage is only obtained when the enzyme is pre-incubated with the compound, the inhibition being irreversible and reversible for the copper and zinc compounds, respectively.

Correlation between DNA interactions and cytotoxic activity of four new ternary compounds of copper(II) with N-donor heterocyclic ligands.

Four new ternary complexes of copper(II) were synthesized and characterized: [Cu(hyd)(bpy)(acn)(ClO4)](ClO4)] (1), [Cu(hyd)(phen)(acn)(ClO4)](ClO4)] (2), [Cu(Shyd)(bpy)(acn)(ClO4)](ClO4)] (3) and [Cu(Shyd)(phen)(acn)(ClO4)](ClO4)] (4), in which acn=acetonitrile; hyd=2-furoic acid hydrazide, bpy=2,2-bipyridine; phen=1,10-phenanthroline and Shyd=2-thiophenecarboxylic acid hydrazide. The cytotoxic activity of the complexes in a chronic myelogenous leukemia cell line was investigated. All complexes are able to enter cells and inhibit cellular growth in a concentration-dependent manner, with an activity higher than that of the corresponding free ligands.

De novo galectin-3 expression influences the response of melanoma cells to isatin-Schiff base copper (II) complex-induced oxidative stimulus.

Galectin-3, a ubiquitous member of the galectin family, has been shown to control cellular proliferation, adhesion, migration and apoptosis; thus, it has a role in tumor development and progression. Galectin-3 expression is both up- and down-regulated during melanoma progression. However, conflicting data regarding its roles in tumor biology prompted us to investigate if the presence of galectin-3 influences the response of melanoma cells to a novel metallodrug because metastatic melanoma acquires chemo resistance and is reported to be redox-sensitive.

Peculiar reactivity of a di-imine copper(II) complex regarding its binding to albumin protein.

A set of four di-imine copper(II) complexes containing pyridine, pyrazine and/or imidazole moieties, [Cu(apyhist)H2O](2+) 1 (apyhist = 2-(1H-imidazol-4-yl)-N-(1-(pyridin-2-yl)ethylidene)ethanamine), [Cu(apzhist)OH](+) 2 (apzhist = 2-(1H-imidazol-4-yl)-N-(1-(pyrazin-2-yl)ethylidene)ethanamine), [Cu(apyepy)OH](+) 3 (apyepy = 2-(pyridin-2-yl)-N-(1-(pyridin-2-yl)ethylidene)ethanamine), and [Cu(apzepy)H2O](2+) 4 (apzepy = N-(1-(pyrazin-2-yl)ethylidene)-2-(pyridin-2-yl)ethanamine), were investigated regarding their capability of interacting with serum albumin (human, HSA and bovine, BSA), by using spectroscopic techniques, CD, UV/Vis and EPR. Like other similar di-imine copper(II) complexes, most of them showed an expected preferential insertion of the metal ion at the primary N-terminal site of the protein, very selective for copper and characterized by a CD band at 560 nm. Further insertion of the copper ion at a secondary site is expected when using an excess of the metal.

Metabolic oxidative stress elicited by the copper(II) complex [Cu(isaepy)2] triggers apoptosis in SH-SY5Y cells through the induction of the AMP-activated protein kinase/p38MAPK/p53 signalling axis: evidence for a combined use with 3-bromopyruvate in neuroblastoma treatment.

We have demonstrated previously that the complex bis[(2-oxindol-3-ylimino)-2-(2-aminoethyl)pyridine-N,N']copper(II), named [Cu(isaepy)(2)], induces AMPK (AMP-activated protein kinase)-dependent/p53-mediated apoptosis in tumour cells by targeting mitochondria. In the present study, we found that p38(MAPK) (p38 mitogen-activated protein kinase) is the molecular link in the phosphorylation cascade connecting AMPK to p53. Transfection of SH-SY5Y cells with a dominant-negative mutant of AMPK resulted in a decrease in apoptosis and a significant reduction in phospho-active p38(MAPK) and p53.

Oxindole-Schiff base copper(II) complexes interactions with human serum albumin: spectroscopic, oxidative damage, and computational studies.

CD and EPR were used to characterize interactions of oxindole-Schiff base copper(II) complexes with human serum albumin (HSA). These imine ligands form very stable complexes with copper, and can efficiently compete for this metal ion towards the specific N-terminal binding site of the protein, consisting of the amino acid sequence Asp-Ala-His. Relative stability constants for the corresponding complexes were estimated from CD data, using the protein as competitive ligand, with values of log K(CuL) in the range 15.

The isatin-Schiff base copper(II) complex Cu(isaepy)2 acts as delocalized lipophilic cation, yields widespread mitochondrial oxidative damage and induces AMP-activated protein kinase-dependent apoptosis.

We previously demonstrated that Bis[(2-oxindol-3-ylimino)-2-(2-aminoethyl)pyridine-N,N']copper(II) [Cu(isaepy)(2)] was an efficient inducer of the apoptotic mitochondrial pathway. Here, we deeply dissect the mechanisms underlying the ability of Cu(isaepy)(2) to cause mitochondriotoxicity. In particular, we demonstrate that Cu(isaepy)(2) increases NADH-dependent oxygen consumption of isolated mitochondria and that this phenomenon is associated with oxy-radical production and insensitive to adenosine diphosphate.

Double-strand DNA cleavage induced by oxindole-Schiff base copper(II) complexes with potential antitumor activity.

Some oxindole-Schiff base copper(II) complexes have already shown potential antitumor activity towards different cells, inducing apoptosis in a process modulated by the ligand, and having nuclei and mitochondria as main targets. Here, three novel copper(II) complexes with analogous ligands were isolated and characterized by spectroscopic techniques, having their reactivity compared to the so far most active complex in this class. Cytotoxicity experiments carried out toward human neuroblastoma SH-SY5Y cells confirmed its pro-apoptosis property.

A new dinuclear heme-copper complex derived from functionalized protoporphyrin IX.

A new biomimetic model for the heterodinuclear heme/copper center of respiratory oxidases is described. It is derived from iron(III) protoporphyrin IX by covalent attachment of a Gly-L-His-OMe residue to one propionic acid substituent and an amino-bis(benzimidazole) residue to the other propionic acid substituent of the porphyrin ring, yielding the Fe(III) complex 1, and subsequent addition of a copper(II) or copper(I) ion, according to needs. The fully oxidized Fe(III)/Cu(II) complex, 2, binds azide more strongly than 1, and likely contains azide bound as a bridging ligand between Fe(III) and Cu(II).