New copper(II) and oxidovanadium(IV) complexes with a vitamin B6 Schiff base: mechanism of action and synergy studies on 2D and 3D human osteosarcoma cell models.

We report the synthesis, characterization and anticancer activity of a new Schiff base (H2L) derived from the condensation of pyridoxamine with pyridoxal and its novel copper(II) and oxidovanadium(IV) complexes: [Cu(HL)Cl] (1), [Cu(LH2)(phen)]Cl2 (2), [Cu(LH2)(amphen)]Cl2 (3), [VIVO(HL)Cl] (4), and [VIVO(LH2)(phen)]Cl2 (5), where phen is 1,10-phenanthroline and amphen is its 5-amino derivative. All compounds were characterized by analytical and spectroscopic techniques, namely FTIR, UV-vis and EPR spectroscopy. Their stability in aqueous media was evaluated, revealing that the presence of the phen co-ligand significantly increases the stability. The ternary Cu(II) complexes (2 and 3) impaired cell viability of osteosarcoma cells (MG-63) (IC50 values of 3.6 ± 0.6 and 7 ± 1.9 µM for 2 and 3), while 1 and the VIVO complexes did not show relevant anticancer activity. Complexes 2 and 3 are also more active than cisplatin (CDDP). Synergistic studies between 2 and sorafenib showed significant synergism on MG-63 cells for the following combinations: 2 (2.0 µM) + sorafenib (10.0 µM) and 2 (2.5 µM) + sorafenib (12.5 µM), whilst the combination of 2 and CDDP did not show synergy. Complex 2 interacts with DNA, inducing significant genotoxic effects on MG-63 cells from 1.0 to 2.5 µM and it increases the ROS levels 880% over basal. Moreover, 2 induces apoptosis at 1.0 and 2.0 µM, while its combination with sorafenib induces apoptosis and necrosis. Finally, compound 2 reduces the cell viability of MG-63 spheroids showing an IC50 value 7-fold lower than that of CDDP (8.5 ± 0.4 µM vs. 65 ± 6 µM). The combination of 2 and sorafenib also showed synergism on spheroids, suggesting that the combination of these drugs improves the anticancer effect against bone cancer cells.

Copper(II) and oxidovanadium(IV) complexes of chromone Schiff bases as potential anticancer agents.

We report the synthesis, characterization and biological screening of new chromone Schiff bases derived from the condensation of three 6-substituted-3-formyl-chromones with pyridoxal (HL1-3) and its Cu(II) complexes [Cu(L1-3)Cl], 1-3. For the 6-methyl derivative, HL2, the VIVO-complex [VO(L2)Cl] (5), as well as ternary Cu and VIVO complexes with 1,10-phenanthroline (phen), [Cu(L2)(phen)Cl] (4) and [VO(L2)(phen)Cl] (6), were also prepared and evaluated. Their stability in aqueous medium and radical scavenging activity toward DPPH are screened, with [Cu(L2)(phen)Cl] (4) showing hydrolytic stability and [VO(L2)(phen)Cl] (6) high radical scavenging activity. Spectroscopic studies establish bovine serum albumin (BSA), a model for HSA, as a potential reversible carrier of [Cu(L2)(phen)Cl] in blood with KBC ≈ 105 M-1. The cytotoxic activity of a group of compounds is evaluated against a panel of human cancer cell lines of different origin (ovary, cervix, brain and breast) and compared to normal cells. Our results indicate that Cu complexes are more cytotoxic than the ligands but not selective towards cancer cells. The most potent complexes (4 and 6) are further evaluated for their apoptotic potential, induction of reactive oxygen species (ROS) and genotoxicity. Both complexes efficiently triggered cell death through apoptosis as evaluated by DNA morphology and TUNEL assay, increased ROS formation as determined by DCFDA (2',7'-dichlorodihydrofluorescein diacetate) analysis, and induced genotoxic damage as visualized via COMET assay in all cancer cells under study. Therefore, 4 and 6 may be potential precursor anticancer molecules, yet they need to be targeted toward cancer cells.

Therapeutic potential of vanadium complexes with 1,10-phenanthroline ligands, quo vadis? Fate of complexes in cell media and cancer cells.

VIVO-complexes formulated as [VIVO(OSO3)(phen)2] (1) (phen = 1,10-phenanthroline), [VIVO(OSO3)(Me2phen)2] (2) (Me2phen = 4,7-dimethyl-1,10-phenanthroline) and [VIVO(OSO3)(amphen)2] (3) (amphen = 5-amino-1,10-phenanthroline) were prepared and stability in cell incubation media evaluated. Their cytotoxicity was determined against the A2780 (ovarian), MCF7 (breast) and PC3 (prostate) human cancer cells at different incubation times. While at 3 and 24 h the cytotoxicity differs for complexes and corresponding free ligands, at 72 h incubation all compounds are equally active presenting low IC50 values. Upon incubation of A2780 cells with 1-3, cellular distribution of vanadium in cytosol, membranes, nucleus and cytoskeleton, indicate that the uptake of V is low, particularly for 1, and that the uptake pattern depends on the ligand. Nuclear microscopic techniques are used for imaging and elemental quantification in whole PC3 cells incubated with 1. Once complexes are added to cell culture media, they decompose, and with time most VIV oxidizes to VV-species. Modeling of speciation when [VIVO(OSO3)(phen)2] (1) is added to cell media is presented. At lower concentrations of 1, VIVO- and phen-containing species are mainly bound to bovine serum albumin, while at higher concentrations [VIVO(phen)n]2+-complexes become relevant, being predicted that the species taken up and mechanisms of action operating depend on the total concentration of complex. This study emphasizes that for these VIVO-systems, and probably for many others involving oxidovanadium or other labile metal complexes, it is not possible to identify active species or propose mechanisms of cytotoxic action without evaluating speciation occurring in cell media.

Copper Complexes with 1,10-Phenanthroline Derivatives: Underlying Factors Affecting Their Cytotoxicity.

The interpretation of in vitro cytotoxicity data of Cu(II)-1,10-phenanthroline (phen) complexes normally does not take into account the speciation that complexes undergo in cell incubation media and its implications in cellular uptake and mechanisms of action. We synthesize and test the activity of several distinct Cu(II)-phen compounds; up to 24 h of incubation, the cytotoxic activity differs for the Cu complexes and the corresponding free ligands, but for longer incubation times (e.g., 72 h), all compounds display similar activity. Combining the use of several spectroscopic, spectrometric, and electrochemical techniques, the speciation of Cu-phen compounds in cell incubation media is evaluated, indicating that the originally added complex almost totally decomposed and that Cu(II) and phen are mainly bound to bovine serum albumin. Several methods are used to disclose relationships between structure, activity, speciation in incubation media, cellular uptake, distribution of Cu in cells, and cytotoxicity. Contrary to what is reported in most studies, we conclude that interaction with cell components and cell death involves the separate action of Cu ions and phen molecules, not [Cu(phen)n] species. This conclusion should similarly apply to many other Cu-ligand systems reported to date.

Experimental data on novel Fe(III)-complexes containing phenanthroline derivatives for their anticancer properties.

This dataset is related to the research article entitled "May iron(III) complexes containing phenanthroline derivatives as ligands be prospective anticancer agents?" [1]. It includes the characterization by UV-Vis absorption spectroscopy and magnetic techniques of a group of mixed ligand Fe(III) complexes bearing a tripodal aminophenolate ligand L2-, H2L = N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N-(2-pyridylmethyl)amine, and different aromatic bases (NN = 2,2'-bipyridine [Fe(L)(bipy)]PF6 (1), 1,10-phenanthroline [Fe(L)(phen)]PF6 (2), or a phenanthroline derivative co-ligand: [Fe(L)(amphen)]NO3 (3), [Fe(L)(amphen)]PF6 (3a), [Fe(L)(Clphen)]PF6 (4), [Fe(L)(epoxyphen)]PF6 (5) (where amphen = 1,10-phenanthroline-5-amine, epoxyphen = 5,6-epoxy-5,6-dihydro-1,10-phenanthroline, Clphen = 5-chloro-1,10-phenanthroline), as well as [Fe(L)(EtOH)]NO3 (6), [Fe(phen)Cl3] (7) and [Fe(amphen)Cl3] (8). Data on their hydrolytic stability in physiological buffers is shown, as well as on their interaction with calf thymus DNA by spectroscopic tools. Additionally, the anticancer efficacy and the cellular death mechanisms activated in response to these drugs in HeLa, H1299 and MDA-MB-231 cells are provided.

Exploring the cytotoxic activity of new phenanthroline salicylaldimine Zn(II) complexes.

Zinc(II) complexes bearing N-salicylideneglycinate (Sal-Gly) and 1,10-phenanthroline (phen) or phenanthroline derivatives [NN = 5-chloro-1,10-phenanthroline, 5-amine-1,10-phenanthroline (amphen), 4,7-diphenyl-1,10-phenanthroline (Bphen) and 5,6-epoxy-5,6-dihydro-1,10-phenanthroline] are synthesized. Complexes formulated as [Zn(NN)2(H2O)2]2+(NN = phen and amphen), are also prepared. The cytotoxicity of the compounds is evaluated towards a panel of human cancer cells: ovarian (A2780), breast (MCF7) and cervical (HeLa), as well as non-tumoral V79 fibroblasts. All compounds display higher cytotoxicity than cisplatin (IC50 = 22.5 ±â€¯5.0 µM) towards ovarian cells, showing IC50values in the low micromolar range. Overall, all compounds show higher selectivity for the A2780 cells than for the non-tumoral cells and higher selectivity indexes (IC50(V79)/IC50(A2780) than cisplatin. [Zn(Sal-Gly)(NN)(H2O)] complexes induce caspase-dependent apoptosis in A2780 cells, except [Zn(Sal-Gly)(Bphen)(H2O)], one of the most cytotoxic of the series. The cellular uptake in the ovarian cells analyzed by Inductively Coupled Plasma mass spectrometry indicates different Zn distribution profiles. Transmission electronic microscopy shows mitochondria alterations and apoptotic features consistent with caspase activation; cells incubated with [Zn(Sal-Gly)(amphen)(H2O)] present additional nuclear membrane alterations in agreement with significant association with the nucleus. The increase of reactive oxygen species and lipid peroxidation forms could be related to apoptosis induction. [Zn(NN)2(H2O)2]2+complexes have high ability to bind DNA through intercalation/groove binding, and circular dichroism data suggests that the main type of species that interact with DNA is [Zn(NN)]2+. Studies varying the % of fetal bovine serum (1-15%) in cell media show that albumin binding decreases the complex activity, indicating that distinct speciation of Zn- and phen-containing species in cell media may affect the cytotoxicity.

May iron(III) complexes containing phenanthroline derivatives as ligands be prospective anticancer agents?

We report the design, synthesis and biological studies on a group of mixed ligand Fe(III) complexes as anti-cancer drug candidates, namely their interaction with DNA, cytotoxicity and mechanism(s) of action. The aim is to obtain stable, efficient and selective Fe-complexes to be used as anti-cancer agents with less damaging side effects than previously reported compounds. Five ternary Fe(III) complexes bearing a tripodal aminophenolate ligand L2-, H2L = N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-N-(2-pyridylmethyl)amine, and different aromatic bases NN = 2,2'-bipyridine [Fe(L)(bipy)]PF6 (1), 1,10-phenanthroline [Fe(L)(phen)]PF6 (2), or a phenanthroline derivative co-ligand: [Fe(L)(amphen)]NO3 (3), [Fe(L)(amphen)]PF6 (3a), [Fe(L)(Clphen)]PF6 (4), [Fe(L)(epoxyphen)]PF6 (5) (where amphen = 1,10-phenanthroline-5-amine, epoxyphen = 5,6-epoxy-5,6-dihydro-1,10-phenanthroline, Clphen = 5-chloro-1,10-phenanthroline) and the [Fe(L)(EtOH)]NO3 (6) complex are synthesized. The compounds are characterized in the solid state and in solution by elemental analysis, ESI-MS, magnetic susceptibility measurements and FTIR, UV-Vis, 1H and 13C NMR and fluorescence spectroscopies. [Fe(phen)Cl3] and [Fe(amphen)Cl3] were also prepared for comparison purposes. Spectroscopic binding studies indicate groove binding as the main interaction for most complexes with DNA, and for those containing amphen a B- to Z-DNA conformational change is proposed to occur. As determined via MTT analysis all compounds 1-6 are cytotoxic against a panel of three different cell lines (HeLa, H1299, MDA-MB-231). For selected compounds with promising cytotoxic activity, apoptosis was evaluated using cell and DNA morphology, TUNEL, Annexin V/7AAD staining and caspase3/7 activity. The compounds induce oxidative DNA damage on plasmid DNA and in cell culture as assessed by 8-oxo-Guanine and γH2AX staining. Comet assay confirmed the presence of genomic damage. There is also increased reactive oxygen species formation following drug treatment, which may be the relevant mechanism of action, thus differing from that normally assumed for cisplatin. The Fe(III)-complexes were also tested against strains of M. Tuberculosis (MTb), complex 2 depicting higher anti-MTb activity than several known second line drugs. Hence, these initial studies show prospective anti-cancer and anti-MTb activity granting promise for further studies.

Isostructural Re(I)/(99m)Tc(I) tricarbonyl complexes for cancer theranostics.

Merging classical organic anticancer drugs with metal-based compounds in one single molecule offers the possibility of exploring new approaches for cancer theranostics, i.e. the combination of diagnostic and therapeutic modalities. For this purpose, we have synthesized and biologically evaluated a series of Re(I)/(99m)Tc(I) tricarbonyl complexes (Re1­Re4 and Tc1­Tc4, respectively) stabilized by a cysteamine-based (N,S,O) chelator and containing 2-(4'-aminophenyl)benzothiazole pharmacophores. With the exception of Re1, all the Re complexes have shown a moderate cytotoxicity in MCF7 and PC3 cancer cells (IC50 values in the 15.9­32.1 µM range after 72 h of incubation). The cytotoxic activity of the Re complexes is well correlated with cellular uptake that was quantified using the isostructural (99m)Tc congeners. There is an augmented cytotoxic effect for Re3 and Re4 (versusRe1 and Re2), and the highest cellular uptake for Tc3 and Tc4, which display a long ether-containing linker to couple the pharmacophore to the (N,S,O)-chelator framework. Moreover, fluorescence microscopy clearly confirmed the cytosolic accumulation of the most cytotoxic compound (Re3). Biodistribution studies of Tc1­Tc4 in mice confirmed that these moderately lipophilic complexes (logDo/w = 1.95­2.32) have a favorable bioavailability. Tc3 and Tc4 presented a faster excretion, as they undergo metabolic transformations, in contrast to complexes Tc1 and Tc2. In summary, our results show that benzothiazole-containing Re(I)/(99m)Tc(I) tricarbonyl complexes stabilized by cysteamine-based (N,S,O)-chelators have potential to be further applied in the design of new tools for cancer theranostics.