The influence of thioether-substituted ligands in dicopper(II) complexes: Enhancing oxidation and biological activities.

This paper describes the synthesis, structural analysis, as well as the magnetic and spectroscopic characterizations of three new dicopper(II) complexes with dinucleating phenol-based ligands containing different thioether donor substituents: aromatic (1), aliphatic (2) or thiophene (3). Temperature-dependent magnetometry reveals the presence of antiferromagnetic coupling for 1 and 3 (J = -2.27 cm-1 and -5.01 cm-1, respectively, H = -2JS1S2) and ferromagnetic coupling for 2 (J = 5.72 cm-1). Broken symmetry DFT calculations attribute this behavior to a major contribution from the dz2 orbitals for 1 and 3, and from the dx2-y2 orbitals for 2, along with the p orbitals of the oxygens. The bioinspired catalytic activities of these complexes related to catechol oxidase were studied using 3,5-di-tert-butylcatechol as substrate. The order of catalytic rates for the substrate oxidation follows the trend 1 > 2 > 3 with kcat of (90.79 ± 2.90) × 10-3 for 1, (64.21 ± 0.99) × 10-3 for 2 and (14.20 ± 0.32) × 10-3 s-1 for 3. The complexes also cleave DNA through an oxidative mechanism with minor-groove preference, as indicated by experimental and molecular docking assays. Antimicrobial potential of these highly active complexes has shown that 3 inhibits both Staphylococcus aureus bacterium and Epidermophyton floccosum fungus. Notably, the complexes were found to be nontoxic to normal cells but exhibited cytotoxicity against epidermoid carcinoma cells, surpassing the activity of the metallodrug cisplatin. This research shows the multifaceted properties of these complexes, making them promising candidates for various applications in catalysis, nucleic acids research, and antimicrobial activities.

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

Five ternary copper(II) complexes, [Cu2(phen)2(L1)(ClO4)2] (1), [Cu2(phen)2(L1)(DMSO)2](PF6)2 (2), [Cu2(bpy)2(L1)(ClO4)2(H2O)2] (3), [Cu2(dmp)2(L1)(ClO4)2(H2O)2] (4), and [Cu(phen)(L2)]2(ClO4)2 (5), in which phen = 1,10-phenanthroline, bpy = 2,2'-bipyridine, dmp = 2,9-dimethyl-1,10-phenanthroline, H2L1 = 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. The compounds bind to calf thymus DNA and oxidatively cleave pUC19 DNA according to the following order of activity 1 > 4-5 > 3. Furthermore, complexes 1, 3, 4 and 5 inhibit topoisomerase-I activity and the growth of myelogenous leukemia cells with the IC50 values of 1.13, 10.60, 0.078, and 1.84 µmol L-1, respectively. Complexes 1 and 4 are the most active in cancer cells and in DNA cleavage.

Synthesis, characterization and cytotoxicity of copper (II) complex containing a 2H-benzo[e][1,3]oxazin derivative.

A new cis-dihalo copper(II) complex, [CuII(HLbz)(Cl)2].CH3CN (1), where HLbz = (S)-2-(((2-(2-(pyridin-2-yl)-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethyl)amino)methyl)phenol), was isolated by reacting copper(II) chloride dihydrate and the H2L ligand (H2L = 2,2'-((2-(pyridin-2-yl)imidazolidine-1,3-diyl)bis(methylene))diphenol) in a MeOH/CH3CN (1:3 v/v) mixture. The complex formation occurred via the ligand modification during complexation, producing a unique structure containing 2H-benzo[e][1,3]oxazin, as observed from the single crystal X-ray structure determination. The complex was characterized by elemental analysis, potentiometric titration, spectroscopic techniques (UV-Vis, FT-IR) and conductance measurements. Complex 1 inhibits the growth of myelogenous leukemia cells with an IC50 of 17.3 µmol L-1.

Preparation, cytotoxic activity and DNA interaction studies of new platinum(II) complexes with 1,10-phenanthroline and 5-alkyl-1,3,4-oxadiazol-2(3H)-thione derivatives.

This work describes the synthesis, characterization and in vitro anticancer activity of two platinum(II) complexes of the type [Pt(L1)2(1,10-phen)] 1 and [Pt(L2)2(1,10-phen)] 2, where L1 = 5-heptyl-1,3,4-oxadiazole-2-(3H)-thione, L2 = 5-nonyl-1,3,4-oxadiazole-2-(3H)-thione and 1,10-phen = 1,10-phenanthroline. As to the structure of these complexes, the X-ray structural analysis of 1 indicates that the geometry around the platinum(II) ion is distorted square-planar, where two 5-alkyl-1,3,4-oxadiazol-2-thione derivatives coordinate a platinum(II) ion through the sulfur atom. A chelating bidentate phenanthroline molecule completes the coordination sphere. We tested these complexes in two breast cancer cell lines, namely, MCF-7 (a hormone responsive cancer cell) and MDA-MB-231 (triple negative breast cancer cell). In both cells, the most lipophilic platinum compound, complex 2, was more active than cisplatin, one of the most widely used anticancer drugs nowadays. DNA binding studies indicated that such complexes are able to bind to ct-DNA with Kb values of 104 M-1. According to data from dichroism circular and fluorescence spectroscopy, these complexes appear to bind to the DNA in a non-intercalative, probably via minor groove. Molecular docking followed by semiempirical simulations indicated that these complexes showed favorable interactions with the minor groove of the double helix of ct-DNA in an A-T rich region. Thereafter, flow cytometry analysis showed that complex 2 induced apoptosis and necrosis in MCF-7 cells.

Dual anticancer and antibacterial activities of bismuth compounds based on asymmetric [NN'O] ligands.

Two new bismuth(III) complexes, [BiL1Cl2] (1) and [BiL2Cl2] (2), in which L1 is (2-hydroxy-4-6-di-tert-butylbenzyl-2-pyridylmethyl)amine and L2 is 2,4-diiodo-6-((pyridine-2-ylmethylamino)methyl)phenol, were synthesized and characterized by elemental and conductivity analyses, atomic absorption spectrometry, infrared and 1H NMR spectroscopies. The molecular structure of 1 reveals that the NN'O ligand forms a 1:1 complex with bismuth through coordination via the nitrogen of the aliphatic amine, the nitrogen of the pyridine ring and the oxygen of the phenolate. The coordination sphere is completed with two chloride anions in a distorted square pyramidal geometry. Bismuth exhibits the same coordination mode in compound 2. The cytotoxic activity of 1 and 2 was investigated in a chronic myelogenous leukemia cell line. The complexes are approximately three times more potent than the corresponding free ligands, with the IC50 values 0.30 and 0.38 µM for complex 1 and 2, respectively. To address the cellular mechanisms underlying cell demise, apoptosis was quantified by flow cytometry analysis. From 0.1 µM, both complexes induce apoptosis and there is a remarkable concentration-dependent increase in the population of cells in apoptosis. The complexes were also evaluated against Gram-positive and Gram-negative bacteria. Both inhibited the bacterial growth in a concentration-dependent way, with remarkable activity in some of the tested strains, for example, complex 2 was more active than its free ligand against all bacterial strains and approximately fourteen times more potent against S. dysenteriae and S. typhimurium.

Photocytotoxic Activity of Ruthenium(II) Complexes with Phenanthroline-Hydrazone Ligands.

This paper reports on the synthesis and characterization of two new polypyridyl-hydrazone Schiff bases, (E)-N'-(6-oxo-1,10-phenanthrolin-5(6H)-ylidene)thiophene-2-carbohydrazide (L1) and (E)-N'-(6-oxo-1,10-phenanthrolin-5(6H)-ylidene)furan-2-carbohydrazide (L2), and their two Ru(II) complexes of the general formula [RuCl(DMSO)(phen)(Ln)](PF6). Considering that hydrazides are a structural part of severa l drugs and metal complexes containing phenanthroline derivatives are known to interact with DNA and to exhibit antitumor activity, more potent anticancer agents can be obtained by covalently linking the thiophene acid hydrazide or the furoic acid hydrazide to a 1,10-phenanthroline moiety. These ligands and the Ru(II) complexes were characterized by elemental analyses, electronic, vibrational, 1H NMR, and ESI-MS spectroscopies. Ru is bound to two different N-heterocyclic ligands. One chloride and one S-bonded DMSO in cis-configuration to each other complete the octahedral coordination sphere around the metal ion. The ligands are very effective in inhibiting cellular growth in a chronic myelogenous leukemia cell line, K562. Both complexes are able to interact with DNA and present moderate cytotoxic activity, but 5 min of UV-light exposure increases cytotoxicity by three times.

New AlIIIZnII and AlIIICuII dinuclear complexes: Phosphatase-like activity and cytotoxicity.

Herein, we report the synthesis and characterization of the first two AlIII(µ-OH)MII (M = Zn (1) and Cu (2)) complexes with the unsymmetrical ligand H2L{2-[[(2-hydroxybenzyl)(2-pyridylmethyl)]aminomethyl]-6-bis(pyridylmethyl)aminomethyl}-4-methylphenol. The complexes were characterized through elemental analysis, X-ray crystallography, IR spectroscopy, mass spectrometry and potentiometric titration. In addition, complex 2 was characterized by electronic spectroscopy. Kinetics studies on the hydrolysis of the model substrate bis(2,4-dinitrophenyl)phosphate by 1 and 2 show Michaelis-Menten behavior, with 1 being slightly more active (8.31%) than 2 (at pH 7.0). The antimicrobial effect of the compounds was studied using four bacterial strains (Staphylococcus aureus, Pseudomonas aeuruginosa, Shigella sonnei and Shigella dysenteriae) and for both complexes the inhibition of bacterial growth was superior to that caused by sulfapyridine, but inferior to that of tetracycline. The dark cytotoxicity and photocytotoxicity (under UV-A light) of the complexes in a chronic myelogenous leukemia cell line were investigated. Complexes 1 and 2 exhibited significant cytotoxic activity against K562 cells, which undergoes a 2-fold increase on applying 5 min of irradiation with UV-A light. Complex 2 was more effective and a good correlation between cytotoxicity and intracellular concentration was observed, the intracellular copper concentration required to inhibit 50% of cell growth being 3.5 × 10-15 mol cell-1.

In vitro and in vivo antitumoral activity of a ternary copper (II) complex.

Recently, a high number of copper derivatives has been evaluated as DNA-targeting metallodrugs, due to the lower toxicity and its potential to cleave DNA. Several strategies have been testing to develop metal compounds effective against tumour cells. In this work, the ternary copper (doxycycline)-(1,10-phenanthroline) complex [Cu(dox)(phen)]2+ was especially designed as an antitumoral drug, previously showing high cytotoxicity and DNA cleavage activity. We aimed to further investigate the in vitro cytotoxic activity in both tumoral and non-tumoral cells, in vitro genotoxic potential, and in vivo antitumor activity using BALB/C mouse injected with sarcoma S180 and Ehrlich cell lines. Our results indicated that this compound exhibits a moderate genotoxic potential, with selective growth inhibition of tumor cells, especially the murine melanoma B16F10. Its main mechanism of action seems to be through ROS generation. We have further shown a significant reduction of the implanted tumor size in the animal model, suggesting that this compound has great antitumoral potential against many tumor types. [Cu(dox)(phen)]2+ is selectively cytotoxic for melanoma B16F10 and showed high chemotherapeutic potential in vivo against implanted sarcoma S180 and Ehrlich ascites tumours.

The physicochemical and biological characterization of a 24-month-stored nanocomplex based on gold nanoparticles conjugated with cetuximab demonstrated long-term stability, EGFR affinity and cancer cell death due to apoptosis.

Nanotechnology is one of the most promising tools for future diagnosis and therapy. Thus, we have produced gold nanoparticles coated with cetuximab at a dose-range from 5 µg up to 200 µg, and prolonged stable nanocomplexes were obtained. The nanocomplexes were characterized by UV-Vis, zeta potential, TEM, fluorometry, infrared regions, XPS and atomic absorption spectrometry. For biological characterization the A431 cell line was used. Cellular uptake, target affinity and cell death were assessed using ICP-OES, immunocytochemistry and flow cytometry, respectively. The immobilization of cetuximab on the AuNPs surfaces was confirmed. The nanocomplex with 24 months of manufacturing promoted efficient EGFR binding and induced tumour cell death due to apoptosis. Significant (p < 0.05) cell death was achieved using relatively low cetuximab concentration for AuNPs coating compared to the antibody alone. Therefore, our results provided robust physicochemical and biological characterization data corroborating the cetuximab-bioconjugate AuNPs as a feasible nanocomplex for biomedical applications.

New Heteroleptic Ruthenium(II) Complexes with Sulfamethoxypyridazine and Diimines as Potential Antitumor Agents.

Two new complexes of Ru(II) with mixed ligands were prepared: [Ru(bpy)2smp](PF6) (1) and [Ru(phen)2smp](PF6) (2), in which smp = sulfamethoxypyridazine; bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline. The complexes have been characterized by elemental and conductivity analyses; infrared, NMR, and electrospray ionization mass spectroscopies; and X-ray diffraction of single crystal. Structural analyses reveal a distorted octahedral geometry around Ru(II) that is bound to two bpy (in 1) or two phen (in 2) via their two heterocyclic nitrogens and to two nitrogen atoms from sulfamethoxypyridazine-one of the methoxypyridazine ring and the sulfonamidic nitrogen, which is deprotonated. Both complexes inhibit the growth of chronic myelogenous leukemia cells. The interaction of the complexes with bovine serum albumin and DNA is described. DNA footprinting using an oligonucleotide as substrate showed the complexes' preference for thymine base rich sites. It is worth notifying that the complexes interact with the Src homology SH3 domain of the Abl tyrosine kinase protein. Abl protein is involved in signal transduction and implicated in the development of chronic myelogenous leukemia. Nuclear magnetic resonance (NMR) studies of the interaction of complex 2 with the Abl-SH3 domain showed that the most affected residues were T79, G97, W99, and Y115.

Peroxoniobium inhibits leukemia cell growth.

A new class of polyoxoniobate complex has been synthesized and characterized as a novel anticancer agent for photodynamic therapy. The complex inhibits the growth of chronic myelogenous leukemia cells with an IC50 value of 30 µM, in the dark. However, upon exposure to light (365 nm) there is a fivefold increase in the cytotoxic activity. Light radiation activate the complex with the formation of radical species capable of interacting with DNA according to our experimental and theoretical data.

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)(ClO4)2], 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. The cytotoxic activity of compounds was investigated in three tumor cell lines (K562, MDA-MB-231 and MCF-7). Concerning K562 cell line, the complexes with 1,10-phenanthroline exhibit high cytotoxic activity and are more active than carboplatin, free ligands and [Cu(phen)2]2+. Considering the cytotoxicity results, further investigations for the compounds [Cu(4-FH)(phen)(ClO4)2] I and [Cu(4-NH)(phen)(ClO4)2]∙H2O III were performed. Flow cytometric analysis revealed that these complexes induce apoptotic cell death in MDA-MB-231 cell line and bind to DNA with K values of 4.38×104 and 2.62×104, respectively. These compounds were also evaluated against wild type Mycobacterium tuberculosis (ATCC 27294) and exhibited antimycobacterial activity, displayed MIC values lower than those of the corresponding free ligands.

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. The substitution of Shyd for hyd increases the activity, while the substitution of bpy for phen renders the complex less active. Therefore, the most potent complex is 4 with an IC50 value of 1.5±0.2µM. The intracellular copper concentration needed to inhibit 50% of cell growth is approximately 7×10(-15)mol/cell. It is worth notifying that a correlation between cytotoxic activity, DNA binding affinity and DNA cleavage was found: 1<3<2<4.

Crystal structure, antibacterial and cytotoxic activities of a new complex of bismuth(III) with sulfapyridine.

A new complex of Bi(III) and sulfapyridine was synthesized and characterized by elemental analysis, atomic absorption spectrometry, conductivity analysis, electrospray ionization mass spectrometry (ESI-MS), infrared spectroscopy, and single crystal X-ray diffraction methods. The antimicrobial and the cytotoxic activities of the compound were investigated. Elemental and conductivity analyses are in accordance to the formulation [BiCl3(C11H11N3O2S)3]. The structure of the complex reveals a distorted octahedral geometry around the bismuth atom, which is bound to three sulfonamidic nitrogens from sulfapyridine, acting as a monodentate ligand, and to three chloride ions. The presence of the compound in solution was confirmed by ESI-MS studies. The complex is 3 times more potent than the ligand against Salmonella typhimurium, 4 times against Staphylococcus aureus, Shigella dysenteriae, and Shigella sonnei and 8 times more potent against Pseudomonas aeruginosa and Escherichia coli. The compound inhibits the growth of chronic myelogenous leukemia cells with an IC50 value of 44 µM whereas the free ligand has no effect up to 100 µM.

Antimony(V) and bismuth(V) complexes of lapachol: synthesis, crystal structure and cytotoxic activity.

Antimony(V) and bismuth(V) complexes of lapachol have been synthesized by the reaction of Ph3SbCl2 or Ph3BiCl2 with lapachol (Lp) and characterized by several physicochemical techniques such as IR, and NMR spectroscopy and X-ray crystallography. The compounds contain six-coordinated antimony and bismuth atoms. The antimony(V) complex is a monomeric derivative, (Lp)(Ph3Sb)OH, and the bismuth(V) complex is a dinuclear compound bridged by an oxygen atom, (Lp)2(Ph3Bi)2O. Both compounds inhibited the growth of a chronic myelogenous leukemia cell line and the complex of Bi(V) was about five times more active than free lapachol. This work provides a rare example of an organo-Bi(V) complex showing significant cytotoxic activity.

Photoinduced DNA cleavage promoted by two copper(II) complexes of tetracyclines and 1,10-phenanthroline.

In this report, we demonstrate how UV-light exposure can enhance DNA cleavage promoted by two copper(II) complexes of tetracyclines and 1,10-phenanthroline about 40 times in comparison to nonirradiated conditions. In addition, new aspects regarding their DNA binding properties, as well as the mechanism of the cleavage reaction, were also investigated.

Two new ternary complexes of copper(II) with tetracycline or doxycycline and 1,10-phenanthroline and their potential as antitumoral: cytotoxicity and DNA cleavage.

This paper reports on the synthesis and characterization of two new ternary copper(II) complexes: [Cu(doxycycline)(1,10-phenanthroline)(H(2)O)(ClO(4))](ClO(4)) (1) and [Cu(tetracycline)(1,10-phenanthroline)(H(2)O)(ClO(4))](ClO(4)) (2). These compounds exhibit a distorted tetragonal geometry around copper, which is coordinated to two bidentate ligands, 1,10-phenanthroline and tetracycline or doxycyline, a water molecule, and a perchlorate ion weakly bonded in the axial positions. In both compounds, copper(II) binds to tetracyclines via the oxygen of the hydroxyl group and oxygen of the amide group at ring A and to 1,10-phenanthroline via its two heterocyclic nitrogens. We have evaluated the binding of the new complexes to DNA, their capacity to cleave it, their cytotoxic activity, and uptake in tumoral cells. The complexes bind to DNA preferentially by the major groove, and then cleave its strands by an oxidative mechanism involving the generation of ROS. The cleavage of DNA was inhibited by radical inhibitors and/or trappers such as superoxide dismutase, DMSO, and the copper(I) chelator bathocuproine. The enzyme T4 DNA ligase was not able to relegate the products of DNA cleavage, which indicates that the cleavage does not occur via a hydrolytic mechanism. Both complexes present an expressive plasmid DNA cleavage activity generating single- and double-strand breaks, under mild reaction conditions, and even in the absence of any additional oxidant or reducing agent. In the same experimental conditions, [Cu(phen)(2)](2+) is approximately 100-fold less active than our complexes. These complexes are among the most potent DNA cleavage agents reported so far. Both complexes inhibit the growth of K562 cells with the IC(50) values of 1.93 and 2.59 µmol L(-1) for compounds 1 and 2, respectively. The complexes are more active than the free ligands, and their cytotoxic activity correlates with intracellular copper concentration and the number of Cu-DNA adducts formed inside cells.

Electronic structure and spectro-structural correlations of Fe(III)Zn(II) biomimetics for purple acid phosphatases: relevance to DNA cleavage and cytotoxic activity.

Purple acid phosphatases (PAPs) are a group of metallohydrolases that contain a dinuclear Fe(III)M(II) center (M(II) = Fe, Mn, Zn) in the active site and are able to catalyze the hydrolysis of a variety of phosphoric acid esters. The dinuclear complex [(H(2)O)Fe(III)(µ-OH)Zn(II)(L-H)](ClO(4))(2) (2) with the ligand 2-[N-bis(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N'-(2-pyridylmethyl)(2-hydroxybenzyl) aminomethyl]phenol (H(2)L-H) has recently been prepared and is found to closely mimic the coordination environment of the Fe(III)Zn(II) active site found in red kidney bean PAP (Neves et al. J. Am. Chem. Soc. 2007, 129, 7486). The biomimetic shows significant catalytic activity in hydrolytic reactions. By using a variety of structural, spectroscopic, and computational techniques the electronic structure of the Fe(III) center of this biomimetic complex was determined. In the solid state the electronic ground state reflects the rhombically distorted Fe(III)N(2)O(4) octahedron with a dominant tetragonal compression aligned along the µ-OH-Fe-O(phenolate) direction. To probe the role of the Fe-O(phenolate) bond, the phenolate moiety was modified to contain electron-donating or -withdrawing groups (-CH(3), -H, -Br, -NO(2)) in the 5-position. The effects of the substituents on the electronic properties of the biomimetic complexes were studied with a range of experimental and computational techniques. This study establishes benchmarks against accurate crystallographic structural information using spectroscopic techniques that are not restricted to single crystals. Kinetic studies on the hydrolysis reaction revealed that the phosphodiesterase activity increases in the order -NO(2) ←Br ←H ←CH(3) when 2,4-bis(dinitrophenyl)phosphate (2,4-bdnpp) was used as substrate, and a linear free energy relationship is found when log(k(cat)/k(0)) is plotted against the Hammett parameter σ. However, nuclease activity measurements in the cleavage of double stranded DNA showed that the complexes containing the electron-withdrawing -NO(2) and electron-donating -CH(3) groups are the most active while the cytotoxic activity of the biomimetics on leukemia and lung tumoral cells is highest for complexes with electron-donating groups.

A synthetic dinuclear copper(II) hydrolase and its potential as antitumoral: cytotoxicity, cellular uptake, and DNA cleavage.

We have studied the protonation equilibria of a dicopper(II) complex [Cu(2)(micro-OH)(C(21)H(33)ON(6))](ClO(4))(2).H(2)O, (1), in aqueous solution, its interactions with DNA, its cytotoxic activity, and its uptake in tumoral cells. C(21)H(33)ON(6) corresponds to the ligand 4-methyl-2,6-bis[(6-methyl-1,4-diazepan-6-yl)iminomethyl]phenol. From spectrophotometric data the following pKa values were calculated 3.27, 4.80 and 6.10. Complex 1 effectively promotes the hydrolytic cleavage of double-strand plasmid DNA under anaerobic and aerobic conditions. The following kinetic parameters were calculated k(cat) of 2.73 x 10(-4)s(-1), K(M) of 1.36 x 10(-4)M and catalytic efficiency of 2.01 s(-1)M(-1), a 2.73 x 10(7) fold increase in the rate of the reaction compared to the uncatalyzed hydrolysis rate of DNA. Competition assays with distamycin reveal minor groove binding. Complex 1 inhibited the growth of two tumoral cell lines, GLC4 and K562, with the IC(50) values of 14.83 microM and 34.21 microM, respectively. There is a good correlation between cell growth inhibition and intracellular copper content. When treated with 1, cells accumulate approximately twice as much copper as with CuCl(2). Copper-DNA adducts are formed inside cells when they are exposed to the complex. In addition, at concentrations that compound 1 inhibits tumoral cell growth it does not affect macrophage viability. These results show that complex 1 has a good therapeutic prospect.

Impact of intracellular chloride concentration on cisplatin accumulation in sensitive and resistant GLC4 cells.

Resistance to cisplatin [cis-diamminedichloroplatinum(II), CDDP] chemotherapy is a major problem in the clinic. Understanding the molecular basis of the intracellular accumulation of CDDP and other platinum-based anticancer drugs is of importance in delineating the mechanism of resistance to these clinically important therapies. Different molecular mechanisms may coexist, but defective uptake of CDDP is one of the most consistently identified characteristics of cells selected for CDDP resistance. We have studied the impact of intracellular chloride concentration on platinum-based compound accumulation in the human GLC4, GLC4/CDDP, and K562 tumor cell lines. We show that (1) a decrease of intracellular chloride concentration yielded an increase of CDDP accumulation and vice versa and (2) the intracellular chloride concentration in GLC4/CDDP cells is higher than in sensitive cells, whereas CDDP accumulation shows the opposite behavior. The identification of chloride as a critical determinant of CDDP intracellular accumulation and the molecular mechanisms by which CDDP-resistant cells modulate chloride concentration may allow alternative therapeutic approaches. Our findings indicate that increase of intracellular chloride concentration may be a major determinant of CDDP resistance.