Anti-parasitic dinuclear thiolato-bridged arene ruthenium complexes alter the mitochondrial ultrastructure and membrane potential in Trypanosoma brucei bloodstream forms.

Trypanosoma brucei causes human African trypanosomiasis and Nagana disease in cattle, imposing substantial medical and economic burden in sub-Saharan Africa. The current treatments have limitations, including the requirement for elaborated protocols, development of drug resistance, and they are prone to adverse side effects. In vitro screening of a library of 14 dinuclear-thiolato bridged arene ruthenium complexes, originally developed for treatment of cancer cells, resulted in the identification of 7 compounds with IC50 values ranging from 3 to 26 nM. Complex [(η6-p-MeC6H4Pri)2Ru2(µ2-SC6H4-o-Pri)3]Cl (2) (IC50 = 4 nM) and complex [(η6-p-MeC6H4Pri)2Ru2(µ2-SCH2C6H4-p-But)2(µ2-SC6H4-p-OH)]BF4(9) (IC50 = 26 nM) were chosen for further assessments. Application of complex 2 and 9 at 20 nM and 200 nM, respectively, for 4.5 h induced alterations in the trypanosome mitochondrion as evidenced by immunofluorescence employing an antibody against mitochondrial Hsp70 and Mitotracker labeling. Transmission electron microscopy of parasites taken at 2 and 4h of treatment demonstrated massive alterations in the mitochondrial ultrastructure, while other organelles and structural elements of the parasites remained unaffected. Complex 2 treated trypanosomes exhibited a distorted mitochondrial membrane, and the mitochondrial matrix was transformed into an amorphous mass with different degrees of electron densities. Complex 9 did not notably impair the integrity of the membrane, but the interior of the mitochondrion appeared either completely translucent, or was filled with filamentous structures of unknown nature. Dose- and time-dependent effects of these two compounds on the mitochondrial membrane potential were detected by tetramethylrhodamine ethyl ester assay. Thus, the mitochondrion and associated metabolic processes are an important target of dinuclear thiolato-bridged arene ruthenium complexes in T. brucei.

Targeting of the mitochondrion by dinuclear thiolato-bridged arene ruthenium complexes in cancer cells and in the apicomplexan parasite Neospora caninum.

A library of 18 dinuclear-thiolato bridged arene ruthenium complexes, some of which with demonstrated activity against cancer cells, was screened for activity against a transgenic Neospora caninum strain that constitutively expresses beta-galactosidase. Initial assessments were done at concentrations of 2500, 250, 25 and 2.5 nM, and 5 compounds were further evaluated with regard to their half maximal proliferation-inhibiting concentration (IC50). Among those, [(η6-p-MeC6H4Pri)2Ru2(µ2-SC6H4-p-CH3)3]Cl (1), [(η6-p-MeC6H4Pri)2Ru2(µ2-SC6H4-p-But)3]Cl (2) and [(η6-p-MeC6H4Pri)2Ru2(µ2-SCH2C6H4-p-But)2(µ2-SC6H4-p-OH)]BF4 (9) inhibited N. caninum proliferation with low C50 values of 15, 5 and 1 nM, respectively, while [(η6-p-MeC6H4Pri)2Ru2(µ2-SC6H4-p-OH)3]Cl (3) and [(η6-p-MeC6H4Pri)2Ru2(µ2-SC6H4-p-mco)3]Cl (5, mco = 4-methylcoumarinyl) were less active (IC50 = 280 and 108 nM, respectively). These compounds did not affect human foreskin fibroblast (HFF) host cells at dosages of 5 µM and above, but impaired proliferation of the human ovarian carcinoma cell line A2780 (IC50 values of 130 nM (1), 30 nM (2), 530 nM (3), 7730 nM (5), 130 nM (9)). A2780 cancer cells were treated with complexes 1, 2, and 5, and biodistribution analysis using inductively coupled plasma mass spectrometry (ICP-MS) showed that most of the drugs accumulated in the mitochondrial fractions. Transmission electron microscopy showed that the parasite mitochondrion is the primary target also in N. caninum tachyzoites, but these compounds, when applied at 200 nM for 15 days in vitro, did not act parasiticidal. Complexes 1, 2 and 9 applied orally at 2 and 10 mg kg-1 day-1 during 5 days in a neosporosis mouse model did not reduce parasite load and did not limit parasite dissemination to the central nervous system. In accordance with these results, ICP-MS carried out on different organs of mice orally administrated with complexes 1 and 9, demonstrated that the drugs were readily absorbed, and after 3 and 48 h, were mainly detected in liver and kidney, but were largely absent from the brain. Thus, dinuclear thiolato-bridged arene ruthenium complexes exhibit interesting activities against N. caninum in vitro, but further modifications of these promising molecules are required to improve their bioavailability and pharmacokinetic properties in order to exert a pronounced and selective effect against N. caninum in vivo.

Characterization of the Activities of Dinuclear Thiolato-Bridged Arene Ruthenium Complexes against Toxoplasma gondii.

The in vitro effects of 18 dinuclear thiolato-bridged arene ruthenium complexes (1 monohiolato compound, 4 dithiolato compounds, and 13 trithiolato compounds), originally designed as anticancer agents, on the apicomplexan parasite Toxoplasma gondii grown in human foreskin fibroblast (HFF) host cells were studied. Some trithiolato compounds exhibited antiparasitic efficacy at concentrations of 250 nM and below. Among those, complex 1 and complex 2 inhibited T. gondii proliferation with 50% inhibitory concentrations (IC50s) of 34 and 62 nM, respectively, and they did not affect HFFs at dosages of 200 µM or above, resulting in selectivity indices of >23,000. The IC50s of complex 9 were 1.2 nM for T. gondii and above 5 µM for HFFs. Transmission electron microscopy detected ultrastructural alterations in the matrix of the parasite mitochondria at the early stages of treatment, followed by a more pronounced destruction of tachyzoites. However, none of the three compounds applied at 250 nM for 15 days was parasiticidal. By affinity chromatography using complex 9 coupled to epoxy-activated Sepharose followed by mass spectrometry, T. gondii translation elongation factor 1α and two ribosomal proteins, RPS18 and RPL27, were identified to be potential binding proteins. In conclusion, organometallic ruthenium complexes exhibit promising activities against Toxoplasma, and the potential mechanisms of action of these compounds as well as their prospective applications for the treatment of toxoplasmosis are discussed.

Insights into the in†vitro Anticancer Effects of Diruthenium-1.

The in vitro anticancer activity of the dinuclear trithiolato-bridged arene ruthenium complex diruthenium-1 (DiRu-1) was evaluated against a panel of human cancer cell lines used as in vitro models for hepatocellular carcinoma (HepG2 cells), estrogen-responsive breast adenocarcinoma (MCF-7 cells), and triple-negative breast adenocarcinoma (MDA-MB-231 cells). DiRu-1 is highly cytotoxic to these cell lines, demonstrating half-maximal inhibitory concentrations (IC50 ) in the low-nanomolar range (77±1.4 to 268.2±4.4 nm). The main molecular mechanisms responsible for the high cytotoxicity of DiRu-1 against the most responsive MCF-7 cell line (IC50 =77±1.4 nm) were investigated on the basis of the capacity of DiRu-1 to induce oxidative stress, apoptosis, and DNA damage, and to inhibit the cell cycle and proliferation. The results show that DiRu-1 triggers caspase-dependent apoptosis in MCF-7 cells on both the intrinsic and extrinsic pathways. Moreover, the Ru complex also causes necrosis, mitotic catastrophe, and autophagy. DiRu-1 increases the intracellular levels of reactive oxygen species (ROS), which play a significant role in its cytotoxicity and pro-apoptotic activity. An important mechanism of the anticancer activity of DiRu-1 appears to be the induction of DNA lesions, mainly due to apoptotic DNA fragmentation and cell-cycle arrest at the G2 /M checkpoint. These changes are correlated with the concentration of DiRu-1, the duration of the cell treatment, and the post-treatment time.

In-vitro and in-vivo evaluation of the anticancer activity of diruthenium-2, a new trithiolato arene ruthenium complex [(η6-p-MeC6H4Pri)2Ru2(µ-S-p-C6H4OH)3]Cl.

In the present study, we investigated the anticancer action of the trithiolato arene ruthenium complex, [(η-p-MeC6H4Pr)2Ru2(µ-S-p-C6H4OH)3]Cl, named diruthenium-2, both in vitro and in vivo. The mechanism of antiproliferative, cytotoxic, and DNA-damaging activity, and the effect on expressions of cell cycle regulatory proteins were investigated using a WST-1-based proliferation assay, lactate dehydrogenase leakage assay, comet assay, flow cytometry, and western blot analysis. In-vivo anticancer activity was evaluated using Ehrlich tumor-bearing NMRI mice. Diruthenium-2 inhibited the growth of all cancer cell lines used, the most sensitive being gastric (AGS), breast cancer (BT-549, MCF-7, MDA-MB-231), and leukemic (HL-60, MOLT-4) cells. In MCF-7 cells, it caused a G1/S cell cycle arrest, along with an increase in the expression of protein p21 and cyclin B1. We also observed increased levels of MRN complex proteins, which, together with the results from the comet assay, indicate the formation of DNA double-strand breaks. In tumor-bearing mice, diruthenium-2 at doses of 3 and 5 mg/kg inhibits the growth of solid Ehrlich tumor, although weaker than cisplatin. However, it did not prolong the post-therapeutic survival. Our results suggest the in-vitro potential of diruthenium-2 should be further evaluated in studies using other in-vivo models.

Chlorambucil conjugates of dinuclear p-cymene ruthenium trithiolato complexes: synthesis, characterization and cytotoxicity study in vitro and in vivo.

Four diruthenium trithiolato chlorambucil conjugates have been prepared via Steglich esterification from chlorambucil and the corresponding trithiolato precursors. All conjugates are highly cytotoxic towards human ovarian A2780 and A2780cisR cancer cell lines with IC50 values in the nanomolar range. The conjugates exhibit selectivity towards A2780 cells as compared to non-cancerous HEK293 cells, while being only slightly selective for RF24 and A2780cisR cells. In vivo, the conjugate [10]BF4 suppressed the growth of a solid Ehrlich tumor in immunocompetent NMRI mice but did not prolong their overall survival. The reactivity of the chlorambucil conjugates with glutathione, a potential target of the dinuclear ruthenium motive, and with the 2-deoxyguanosine 5'-monophosphate (dGMP-a model target of chlorambucil) was studied by mass spectrometry and NMR spectroscopy. The conjugates did not show catalytic activity for the oxidation of glutathione nor binding to nucleotides, indicating that glutathione oxidation and DNA alkylation are not key mechanisms of action. Four highly cytotoxic diruthenium trithiolato chlorambucil conjugates have been prepared. All conjugates exhibit selectivity towards A2780 cells as compared to HEK293 cells, while being only slightly active in RF24 and A2780cisR cells. In vivo, the best candidate suppressed the growth of a solid Ehrlich tumor in immunocompetent NMRI mice but did not prolong their overall survival.

Crystal structure of (µ-4-hy-droxy-benzene-thiol-ato-κ(2) S:S)bis-(µ-phenyl-methane-thiol-ato-κ(2) S:S)bis-[(η(6)-1-isopropyl-4-methyl-benzene)-ruthenium(II)] tetra-fluorido-borate.

The crystal structure of the dinuclear arene ruthenium title complex, [Ru2(C6H5OS)(C7H7S)2(C10H14)2]BF4, shows the two Ru(II) atoms to be bridged by two benzyl-thio-pheno-late units and one 4-hy-droxy-thio-pheno-late unit, with the remaining three coordination sites of each Ru(II) atom being occupied by p-cymene ligands, completing the typical piano-stool coordination geometry. The BF4 (-) counter-anion is surrounded by four cationic dinuclear complexes, showing an O-H⋯F hydrogen bond and several weak C-H⋯F inter-actions. This is the first example of an X-ray analysis of a mixed dinuclear tri-thiol-ate arene ruthenium(II) complex.

Crystal structure of bis-[µ-(4-meth-oxy-phen-yl)methane-thiol-ato-κ(2) S:S]bis-[chlorido-(η(6)-1-isopropyl-4-methyl-benzene)-ruthenium(II)] chloro-form disolvate.

The mol-ecular structure of the title complex, [Ru2(C8H9OS)2Cl2(C10H14)2]·2CHCl3 or (p-MeC6H4Pr (i) )2Ru2(SCH2-p-C6H5-OCH3)2Cl2·2CHCl3, shows inversion symmetry. The two symmetry-related Ru(II) atoms are bridged by two 4-meth-oxy-α-toluene-thiol-ato [(4-meth-oxy-phen-yl)methane-thiol-ato] units. One chlorido ligand and the p-cymene ligand complete the typical piano-stool coordination environment of the Ru(II) atom. In the crystal, the CH moiety of the chloro-form mol-ecule inter-acts with the chlorido ligand of the dinuclear complex, while one Cl atom of the solvent inter-acts more weakly with the methyl group of the bridging 4-meth-oxy-α-toluene-thiol-ato unit. This assembly leads to the formation of supra-molecular chains extending parallel to [021].

Synthesis, molecular structure, computational study and in vitro anticancer activity of dinuclear thiolato-bridged pentamethylcyclopentadienyl Rh(III) and Ir(III) complexes.

Neutral dinuclear dithiolato-bridged pentamethylcyclopentadienyl Rh(III) complexes of the type (C5Me5)2Rh2(µ-SR)2Cl2 (R = CH2Ph, 1; R = CH2CH2Ph, 2) and cationic dinuclear trithiolato-bridged pentamethylcyclopentadienyl Rh(III) and Ir(III) complexes of the type [(C5Me5)2M2(µ-SR)3](+) (M = Rh, R = CH2Ph, 3; M = Rh, R = CH2CH2Ph, 5; M = Rh, R = CH2C6H4-p-(t)Bu, 7: M = Ir, R = CH2Ph, 4; M = Ir, R = CH2CH2Ph, 6; M = Ir, R = CH2C6H4-p-(t)Bu, 8) have been synthesized from the chloro-bridged pentamethylcyclopentadienyl Rh(III) and Ir(III) dimers (C5Me5)2M2(µ-Cl)2Cl2 by reaction with the corresponding thiol derivative (RSH). Complexes 3-8 were isolated as chloride salts. All complexes were obtained in good yield and were fully characterized by spectroscopic methods. The molecular structures of the neutral complexes (1 and 2) show interesting features: the two rhodium atoms are bridged by two thiolato ligands with no metal-metal bonds and the pentamethylcyclopentadienyl and chlorido ligands are oriented syn to each other, an uncommon conformation for such dinuclear complexes. These structural features were rationalized using DFT calculations. Additionally, the antiproliferative activity of the complexes was evaluated against the cancerous A2780 (cisplatin sensitive) and A2780cisR (cisplatin resistant) human ovarian cell lines and on the noncancerous HEK293 human embryonic kidney cells. All complexes were found to be active and the cationic iridium complexes , and are particularly cytotoxic, with IC50 values in the nanomolar range (IC50 < 0.1 µM). The catalytic activity of the complexes for the oxidation of glutathione (GSH) to GSSG was evaluated by NMR spectroscopy.

Synthesis, characterisation and in vitro anticancer activity of hexanuclear thiolato-bridged arene ruthenium metalla-prisms.

Hexanuclear thiolato-bridged arene ruthenium metalla-prisms of the general formula [(p-cymene)(6)Ru(6)(SR)(6)(tpt)(2) ](6+) (R=CH(2)Ph, CH(2)C(6)H(4)-p-tBu, CH(2)CH(2)Ph; tpt=2,4,6-tris(4-pyridyl)-1,3,5-triazine), obtained from the dinuclear precursors [(p-cymene)(2)Ru(2)(SR)(2)Cl(2)], AgCF(3)SO(3) and tpt, have been isolated and fully characterised as triflate salts. The metalla-prisms are highly cytotoxic against human ovarian cancer cells, especially towards the cisplatin-resistant cell line A2780cisR (IC(50) <0.25 µM).

Highly cytotoxic trithiophenolatodiruthenium complexes of the type [(η6-p-MeC6H4Pri)2Ru2(SC6H4-p-X)3]+: synthesis, molecular structure, electrochemistry, cytotoxicity, and glutathione oxidation potential.

A series of cationic dinuclear p-cymene ruthenium trithiophenolato complexes of the type [(η(6)-p-MeC(6)H(4)Pr(i))(2)Ru(2)(SC(6)H(4)-p-X)(3)](+) (1 X is H, 2 X is Me, 3 X is Ph, 4 X is Br, 5 X is OH, 6 X is NO(2), 7 X is OMe, 8 X is CF(3), 9 X is F, 10 X is Pr(i), 11 X is Bu(t)) have been synthesized from the reaction of [(η(6)-p-MeC(6)H(4)Pr(i))RuCl(2)](2) with the corresponding thiol, isolated as the chloride salts, and further studied for their electrochemical properties, cytotoxicity towards human ovarian cancer cells, and catalytic activity for glutathione (GSH) oxidation. Complex 1 was also compared with the benzene and hexamethylbenzene analogues [(η(6)-C(6)H(6))(2)Ru(2)(SC(6)H(5))(3)](+) (12) and [(η(6)-C(6)Me(6))(2)Ru(2)(SC(6)H(5))(3)](+) (13). The most active compound [11]Cl was structurally studied by single-crystal X-ray diffraction analysis. The concentrations corresponding to 50 % inhibition of cancer cell growth (IC(50) values) in the A2780 and A2780cisR cell lines of these complexes except for 6 were in the submicromolar range, complex 11 showing an IC(50) value of 0.03 µM in both cell lines. The high in vitro anticancer activity of these complexes may be at least partially due to their catalytic potential for the oxidation of GSH, although there is no clear correlation between the IC(50) values and the turnover frequencies at about 50 % conversion. However, the cytotoxicity is tentatively correlated to the physicochemical properties of the compounds determined by the electronic influence of the substituents X (Hammett constants σ(p)) and the lipophilicity of the thiols p-XC(6)H(4)SH (calculated log P parameters).

Organometallic cages as vehicles for intracellular release of photosensitizers.

Water-soluble metalla-cages were used to deliver hydrophobic porphin molecules to cancer cells. After internalization, the photosensitizer was photoactivated, significantly increasing the cytotoxicity in cells. During the transport, the photosensitizer remains nonreactive to light, offering a new strategy to tackle overall photosensitization, a limitation often encountered in photodynamic therapy.

Efficient oxidation of cysteine and glutathione catalyzed by a dinuclear areneruthenium trithiolato anticancer complex.

The highly cytotoxic diruthenium complex [(p-MeC(6)H(4)Pr(i))(2)Ru(2)(SC(6)H(4)-p-Me)(3)](+) (1), water-soluble as the chloride salt, is shown to efficiently catalyze oxidation of the thiols cysteine and glutathione to give the corresponding disulfides, which may explain its high in vitro anticancer activity.

Dichlorido(furfuryl-amine-κN)(η-hexa-methyl-benzene)-ruthenium(II).

The single-crystal X-ray structure analysis of [RuCl(2)(C(12)H(18))(C(5)H(7)NO)] reveals a distorted piano-stool geometry around the Ru(II) atom, with a hexa-methyl-benzene ligand, two chloride ligands and a furfuryl-amine ligand, the latter coordinating through the amine group. In the crystal, a dimeric structure is observed as a result of N-H⋯Cl inter-actions between two symmetry-related mol-ecules.

Dichlorido[1-(2-chloro-eth-yl)-3-(pyridin-4-ylmethyl-κN)urea](η-hexa-methyl-benzene)-ruthenium(II) chloro-form monosolvate.

The Ru(II) atom in the title compound, [RuCl(2)(C(12)H(18))(C(9)H(12)ClN(3)O)]·CHCl(3), exhibits a typical piano-stool coordination, defined by a hexa-methyl-benzene ligand, two chloride ligands and a pyridyl-urea ligand coordinated through the pyridine N atom. In the crystal, a dimeric structure is observed due to two strong N-H⋯Cl inter-actions between the NH groups of urea and the two chloride ligands of neighbouring mol-ecules. In addition, the C=O group of the urea moiety inter-acts with the solvent mol-ecule through weak C-H⋯O interactions.

[6-(Hy-droxy-meth-yl)pyridin-2-yl]methyl ferrocene-1-carboxyl-ate.

The crystal structure of the title ferrocene derivative, [Fe(C(5)H(5))(C(13)H(12)NO(3))], shows strong inter-molecular O-H⋯N hydrogen bonds between the alcohol function and the pyridine group of a neighbouring mol-ecule, while the pyridine function forms another hydrogen bond with the alcohol function of another neighbouring mol-ecule, resulting in the formation of chains along the a-axis direction.

Thiophenolato-bridged dinuclear arene ruthenium complexes: a new family of highly cytotoxic anticancer agents.

New cationic diruthenium complexes of the type [(arene)(2)Ru(2)(SPh)(3)](+), arene being C(6)H(6), p-(i)PrC(6)H(4)Me, C(6)Me(6), C(6)H(5)R, where R = (CH(2))(n)OC(O)C(6)H(4)-p-O(CH(2))(6)CH(3) or (CH(2))(n)OC(O)CH=CHC(6)H(4)-p-OCH(3) and n = 2 or 4, are obtained from the reaction of the corresponding precursor [(arene)RuCl(2)](2) and thiophenol and isolated as their chloride salts. The complexes have been fully characterised by spectroscopic methods and the solid state structure of [(C(6)H(6))(2)Ru(2)(SPh)(3)](+), crystallised as the hexafluorophosphate salt, has been established by single crystal X-ray diffraction. The complexes are highly cytotoxic against human ovarian cancer cells (cell lines A2780 and A2780cisR), with the IC(50) values being in the submicromolar range. In comparison the analogous trishydroxythiophenolato compounds [(arene)(2)Ru(2)(S-p-C(6)H(4)OH)(3)]Cl (IC(50) values around 100 µM) are much less cytotoxic. Thus, it would appear that the increased antiproliferative effect of the arene ruthenium complexes is due to the presence of the phenyl or toluyl substituents at the three thiolato bridges.

Arene ruthenium complexes as anticancer agents.

Neutral or cationic arene ruthenium complexes providing both hydrophilic as well as hydrophobic properties due to the robustness of the ruthenium-arene unit hold a high potential for the development of metal-based anticancer drugs. Mononuclear arene ruthenium complexes containing P- or N-donor ligands or N,N-, N,O- or O,O-chelating ligands, dinuclear arene ruthenium systems with adjustable organic linkers, trinuclear arene ruthenium clusters containing an oxo cap, tetranuclear arene ruthenium porphyrin derivatives that are photoactive, as well as hexanuclear ruthenium cages that are either empty or filled with other molecules have been shown to be active against a variety of cancer cells.

Sawhorse-type diruthenium tetracarbonyl complexes containing porphyrin-derived ligands as highly selective photosensitizers for female reproductive cancer cells.

Diruthenium tetracarbonyl complexes of the type [Ru2(CO)4(l2-g2-O2CR)2L2] containing a Ru-Ru backbone with four equatorial carbonyl ligands, two carboxylato bridges, and two axial two-electron ligands in a sawhorse-like geometry have been synthesized with porphyrin-derived substituents in the axial ligands [1: R is CH3, L is 5-(4-pyridyl)-10,15,20-triphenyl-21,23H-porphyrin], in the bridging carboxylato ligands [2: RCO2H is 5-(4-carboxyphenyl)-10,15,20-triphenyl-21,23H-porphyrin, L is PPh3; 3: RCO2H is 5-(4-carboxyphenyl)-10,15,20-triphenyl-21,23H-porphyrin, L is 1,3,5-triaza-7-phosphatricyclo [3.3.1.1]decane], or in both positions [4: RCO2H is 5-(4-carboxyphenyl)-10,15,20-triphenyl-21,23H-porphyrin, L is 5-(4-pyridyl)-10,15,20-triphenyl-21,23H-porphyrin]. Compounds 1-3 were assessed on different types of human cancer cells and normal cells. Their uptake by cells was quantified by fluorescence and checked by fluorescence microscopy. These compounds were taken up by human HeLa cervix and A2780 and Ovcar ovarian carcinoma cells but not by normal cells and other cancer cell lines (A549 pulmonary, Me300 melanoma, PC3 and LnCap prostate, KB head and neck, MDAMB231 and MCF7 breast, or HT29 colon cancer cells). The compounds demonstrated no cytotoxicity in the absence of laser irradiation but exhibited good phototoxicities in HeLa and A2780 cells when exposed to laser light at 652 nm, displaying an LD50 between 1.5 and 6.5 J/cm2 in these two cell lines and more than 15 J/cm2 for the others. Thus, these types of porphyric compound present specificity for cancer cell lines of the female reproductive system and not for normal cells; thus being promising new organometallic photosensitizers.

Combined arene ruthenium porphyrins as chemotherapeutics and photosensitizers for cancer therapy.

Mononuclear 5-(4-pyridyl)-10,15,20-triphenylporphyrin and 5-(3-pyridyl)-10,15,20-triphenylporphyrin as well as tetranuclear 5,10,15,20-tetra(4-pyridyl)porphyrin (tetra-4-pp) and 5,10,15,20-tetra(3-pyridyl)porphyrin) (tetra-3-pp) arene ruthenium(II) derivatives (arene is C(6)H(5)Me or p-Pr(i)C(6)H(4)Me) were prepared and evaluated as potential dual photosensitizers and chemotherapeutics in human Me300 melanoma cells. In the absence of light, all tetranuclear complexes were cytotoxic (IC(50) < or = 20 microM), while the mononuclear derivatives were not (IC(50) > or = 100 microM). Kinetic studies of tritiated thymidine and tritiated leucine incorporations in cells exposed to a low concentration (5 microM) of tetranuclear p-cymene derivatives demonstrated a rapid inhibition of DNA synthesis, while protein synthesis was inhibited only later, suggesting arene ruthenium-DNA interactions as the initial cytotoxic process. All complexes exhibited phototoxicities toward melanoma cells when exposed to laser light of 652 nm. At low concentration (5 microM), LD(50) of the mononuclear derivatives was between 5 and 10 J/cm(2), while for the tetranuclear derivatives LD(50) was approximately 2.5 J/cm(2) for the [Ru(4)(eta(6)-arene)(4)(tetra-4-pp)Cl(8)] complexes and less than 0.5 J/cm(2) for the [Ru(4)(eta(6)-arene)(4)(tetra-3-pp)Cl(8)] complexes. Examination of cells under a fluorescence microscope revealed the [Ru(4)(eta(6)-arene)(4)(tetra-4-pp)Cl(8)] complexes as cytoplasmic aggregates, whereas the [Ru(4)(eta(6)-arene)(4)(tetra-3-pp)Cl(8)] complexes were homogenously dispersed in the cytoplasm. Thus, these complexes present a dual synergistic effect with good properties of both the arene ruthenium chemotherapeutics and the porphyrin photosensitizer.