Iron(III)-salen damages DNA and induces apoptosis in human cell via mitochondrial pathway

Involvement of Mitophagy in Primary Cultured Rat Neurons Treated with Nanoalumina

The aim of this study was to explore the influence of the neurotoxicity of nanoalumina on primarily cultured neurons. Normal control, particle size control, aluminum, micron-alumina, and nanoalumina at 50-nm and 13-nm particle sizes were included as subjects to evaluate the level of apoptosis, necrosis, and autophagy in primarily cultured neurons and further explore the mitophagy induced by nanoalumina. The results demonstrated that nanoalumina could induce neuronal cell apoptosis, necrosis, and autophagy, among which autophagy was the most notable. When the autophagy inhibitor was added to the nanoalumina-treated group, it significantly downregulated the protein expression levels of Beclin-1 and LC3II/LC3. Observation under a transmission electron microscope and a fluorescence microscope revealed mitophagy characteristics induced by nanoalumina. Additionally, the neurotoxicological effects induced by nanoalumina were more significant than those induced by aluminum and in a particle size-dependent manner.

‘Oxygen-Consuming Complexes’–Catalytic Effects of Iron–Salen Complexes with Dioxygen

[(salen)FeIII]+MeCN complex is a useful catalyst for cyclohexene oxidation with dioxygen. As the main products, ketone and alcohol are formed. In acetonitrile, [(salen)FeII]MeCN is rapidly oxidized by dioxygen, forming iron(III) species. Voltammetric electroreduction of the [(salen)FeIII]+MeCN complex in the presence of dioxygen causes the increase in current observed, which indicates the existence of a catalytic effect. Further transformations of the oxygen-activated iron(III) salen complex generate an effective catalyst. Based on the catalytic and electrochemical results, as well as DFT calculations, possible forms of active species in c-C6H10 oxidation have been proposed.

Substituted effect on some water-soluble Mn(II) salen complexes: DNA binding, cytotoxicity, molecular docking, DFT studies and theoretical IR & UV studies

Based on the importance of central metal complexes to interact with DNA, in this research focused on synthesis of some new water soluble Mn(II) complexes 1-4 which modified substituted in ligand at the same position with N, Me, H, and Cl. These complexes were isolated and characterized by elemental analyses, FT-IR, electrospray ionization mass spectrometry (ESI-MS) and UV-vis spectroscopy. DNA binding studies had been studied by using circular dichroism (CD) spectroscopy, UV-vis absorption spectroscopy, cyclic voltammetry (CV), viscosity measurements, emission spectroscopy and gel electrophoresis which proposed the metal buildings go about as effective DNA binders were studied in the presence of Fish-DNA (FS-DNA) which showed the highest binding affinity to DNA with hydrophobic and electron donating substituent. Cell toxicity assays against two human leukemia (Jurkat) and breast cancer (MCF-7) cell lines showed that the complex 3 exhibited a remarkable effects equal to a famous anticancer drug, cisplatin that high cytotoxic activity strongly depend on the hydrophobic substituted ligand. In the theoretical part, density functional theory (DFT) was performed to optimize the geometry of complexes through IR and UV spectra of the complexes that ligand substitution did not affect the geometry and theoretical IR and UV spectra showed good resemblance to the experimental data. The docking studies calculated the lowest-energy between complexes and DNA with the minor grooves mode.

Metal-free salan-type compound induces apoptosis and overcomes multidrug resistance in leukemic and lymphoma cells in vitro

PURPOSE

We report on our preclinical findings of a simple salicylic diamine compound (THG 1213) which has yielded exceptional results as a potential chemotherapeutic drug. THG 1213 is an easy to synthesize chiral and metal-free salan compound.

METHODS

THG 1213 was tested on several leukemia, lymphoma and solid tumor cell lines in vitro. The effects have been studied by LDH release essay, FACS flow cytometry, photometric cell count, immunoblotting, and NMR spectroscopy.

RESULTS

THG 1213 selectively inhibits proliferation and induces apoptosis in leukemia, lymphoma and solid tumor cell lines. Necrosis or effects on healthy leucocytes could not be detected. Apoptosis is induced via the intrinsic and extrinsic pathways. The salan THG 1213 overcomes multidrug resistance in tumor cells and acts synergistically with vincristine and daunorubicin.

CONCLUSIONS

THG 1213 displays remarkable antitumor properties. In particular, the lack of metallic components of THG 1213 could prove to be beneficial in future clinical trials, as metal-containing drugs are known to show severe side effects.

New Fe(iii) and Co(ii) salen complexes with pendant distamycins: selective targeting of cancer cells by DNA damage and mitochondrial pathways

Minor groove binding distamycin like moieties were conjugated with core salens and the corresponding Fe(iii) and Co(ii) complexes were synthesized. Herein, we have shown efficient DNA minor groove binding specificities along with excellent DNA cleavage capacities with metallosalen conjugates. The metal complexes showed toxicity toward various cancer cells over normal cells with high specificity. Interestingly, the Co(ii) complexes exhibited greater activity than the Fe(iii) complexes in accordance with the stronger affinity of the former in the biophysical studies. Active DNA damage, and prominent nuclear condensation along with the release of cytochrome-c from the mitochondria unanimously showed that the metal complexes followed apoptotic pathways to induce cell death.

Iron oxide nanoparticles induced cytotoxicity, oxidative stress and DNA damage in lymphocytes

Over the past few decades nanotechnology and material science has progressed extremely rapidly. Iron oxide nanoparticles (IONPs) owing to their unique magnetic properties have a great potential for their biomedical and bioengineering applications. However, there is an inevitable need to address the issue of safety and health effects of these nanoparticles. Hence, the present study was aimed to assess the cytotoxic effects of IONPs on rats' lymphocytes. Using different assays, we studied diverse parameters including mitochondrial membrane potential, intracellular accumulation of reactive oxygen species (ROS), lactate dehydrogenase activity, antioxidant enzymes activity and DNA damage measurements. Intracellular metal uptake and ultrastructure analysis were also carried out through inductively coupled plasma atomic emission spectroscopy, transmission electron microscopy respectively. The results show that the IONP-induced oxidative stress was concentration-dependent in nature, with significant (P < 0.05) increase in ROS levels, lipid peroxidation level as well as depletion of antioxidant enzymes and glutathione. Moreover, we observed morphological changes in the cell after intracellular uptake and localization of nanoparticles in cells. From the findings of the study, it may be concluded that IONPs induce ROS-mediated cytotoxicity in lymphocytes. Copyright © 2017 John Wiley & Sons, Ltd.

Cu(I) complexes of bis(methyl)(thia/selena) salen ligands: Synthesis, characterization, redox behavior and DNA binding studies

Mononuclear cuprous complexes 1 and 2, [{CH₃E(o-C₆H₄)CH=NCH₂}₂Cu]ClO₄; E=S/Se, have been synthesized by the reaction of bis(methyl)(thia/selena) salen ligands and [Cu(CH₃CN)₄]ClO₄. Both the products were characterized by elemental analysis, ESI-MS, FT-IR, ¹H/¹³C/⁷⁷Se NMR, and cyclic voltammetry. The complexes possess tetrahedral geometry around metal center with the N₂S₂/N₂Se₂ coordination core. Cyclic voltammograms of complexes 1 and 2 displayed reversible anodic waves at E_1/2=+0.08V and +0.10V, respectively, corresponding to the Cu(I)/Cu(II) redox couple. DNA binding studies of both the complexes were performed applying absorbance, fluorescence and molecular docking techniques. Competitive binding experiment of complexes with ct-DNA against ethidium bromide is performed to predict the mode of binding. The results indicate the groove binding mode of complexes 1 and 2 to DNA. The binding constants revealed the strong binding affinity of complexes towards ct-DNA.

Synthesis, characterization, DNA binding, cleavage activity, cytotoxicity and molecular docking of new nano water-soluble [M(5-CH₂PPh₃-3,4-salpyr)](ClO₄)₂ (M = Ni, Zn) complexes

Some new water soluble complexes [N,N'-bis{5-[(triphenyl phosphonium chloride)-methyl]salicylidine}-3,4-diaminopyridine] M(ii), which are formulated as nano-[Zn(5-CH2PPh3-3,4-salpyr)](ClO4)2 (), [Zn(5-CH2PPh3-3,4-salpyr)](ClO4)2 (), nano-[Ni(5-CH2PPh3-3,4-salpyr)](ClO4)2 (), [Ni(5-CH2PPh3-3,4-salpyr)](ClO4)2 (), and [N,N'-bis{5-[(triphenyl phosphonium chloride)-methyl]salicylidine}-2,3-diaminopyridine]Ni(ii) [Ni(5-CH2PPh3-2,3-salpyr)](ClO4)2 () have been isolated and characterized by elemental analysis, FT-IR, (1)H NMR, (13)C NMR, (31)P NMR, and UV-vis spectroscopy. The morphology and size of the nano complexes were determined using FE-SEM and TEM. In vitro DNA binding studies were investigated by UV-vis absorption spectroscopy, viscosity measurements, CD spectroscopy, cyclic voltammetry, emission spectra and gel electrophoresis, which suggest that the metal complexes act as efficient DNA binders. The absorption spectroscopy of the compounds with DNA reveals that the DNA binding affinity (Kb) has this order: > > > > > Ligand. The metal complexes show DNA binding stronger than the ligand, which is expected due to the nature of the metal. The nano complexes display DNA binding stronger than the other complexes which is related to the effect of size on binding affinity and the Ni(ii) complexes reveal DNA binding stronger than the corresponding Zn(ii) analogues, which is expected due to their z* effect and geometry. The prominent double strand DNA cleavage abilities of compound are observed in the absence of H2O2 with efficiencies of more than 50% even at 70 μM complex concentration. Surprisingly, Zn(ii) complexes (compounds & ) exhibit a higher cytotoxicity (IC50: 7.3 & 10.9 μM at 24 h; IC50: 4.6 & 8.7 μM at 48 h) against human hepatoma (HepG2) and HeLa cell lines than the Ni(ii) complexes (compounds , & ) and 5-fluorouracil as control in spite of their inability to cleave DNA. Finally, DNA binding interactions were performed by docking studies. Density functional theory (DFT) studies were performed using the GAUSSIAN 03 program. The DFT method with B3LYP functional, LANL2DZ basis set for metal centers and 6-311g* for other atoms was used. The synthesized compounds and DNA were simulated by molecular docking to explore more details of the ligands conformation and their orientations in the active site of the receptor.

DNA interaction, SOD, peroxidase and nuclease activity studies of iron complex having ligand with carboxamido nitrogen donors

Complex (Et3HN)[Fe(III)(bpb)Cl2], 1 {where H2bpb: N,N'-(1,2-phenylene)bis(pyridine-2-carboxamide)} was synthesized and characterized by reported procedure (Yang et al., 1991). Complex 1 was found to be effective in superoxide scavenging activity and an IC50 value of 4.1 μM was obtained in xanthine-xanthine oxidase nitro blue tetrazolium assay. Peroxidase-like activity of this complex was determined by the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS). DNA interaction studies of complex 1 showed binding of DNA through external or groove binding. Complex 1 exhibited chemical nuclease activity in the presence of hydrogen peroxide and cleaved supercoiled pBR322 DNA to its linear and nicked circular form at physiological pH. Mechanistic studies indicated possible role of hydroxyl radical (·OH) species in DNA cleavage activity via hydroperoxo intermediate: [Fe(III)OOH(-)](2+)→[Fe(IV)O](2+)+(·)OH.

A magnetic anti-cancer compound for magnet-guided delivery and magnetic resonance imaging

Research on controlled drug delivery for cancer chemotherapy has focused mainly on ways to deliver existing anti-cancer drug compounds to specified targets, e.g., by conjugating them with magnetic particles or encapsulating them in micelles. Here, we show that an iron-salen, i.e., μ-oxo N,N'- bis(salicylidene)ethylenediamine iron (Fe(Salen)), but not other metal salen derivatives, intrinsically exhibits both magnetic character and anti-cancer activity. X-Ray crystallographic analysis and first principles calculations based on the measured structure support this. It promoted apoptosis of various cancer cell lines, likely, via production of reactive oxygen species. In mouse leg tumor and tail melanoma models, Fe(Salen) delivery with magnet caused a robust decrease in tumor size, and the accumulation of Fe(Salen) was visualized by magnetic resonance imaging. Fe(Salen) is an anti-cancer compound with magnetic property, which is suitable for drug delivery and imaging. We believe such magnetic anti-cancer drugs have the potential to greatly advance cancer chemotherapy for new theranostics and drug-delivery strategies.

Mononuclear iron(iii) complexes of tridentate ligands with efficient nuclease activity and studies of their cytotoxicity

Mono- and bis-chelated iron(iii) complexes derived from phenolato-based tridentate ligands have been synthesised and characterized. These complexes show electrostatic DNA interactions and efficient DNA cleavage via OH˙ radicals, and induce cytotoxicity in MCF7 cell lines.

Different apoptotic effects of [Pt(O,O'-acac)(γ-acac)(DMS)] and cisplatin on normal and cancerous human epithelial breast cells in primary culture

BACKGROUND AND PURPOSE

The aim of this study was to determine whether [platinum (Pt)(O,O'-acetylacetonate (acac))(γ-acac)(dimethylsulphide (DMS))] is differentially cytotoxic in normal and cancer cells, and to measure comparative levels of cytotoxicity compared with cisplatin in the same cells.

EXPERIMENTAL APPROACH

We performed experiments on cancerous and normal epithelial breast cells in primary culture obtained from the same patients. The apoptotic effects [Pt(O,O'-acac)(γ-acac)(DMS)] and cisplatin in cancerous and normal breast cells were compared.

KEY RESULTS

Cancer cells were more sensitive to [Pt(O,O'-acac)(γ-acac)(DMS)] (IC50 = 5.22 ± 1.2 μmol·L(-1)) than normal cells (IC50 = 116.9 ± 8.8 μmol·L(-1)). However, the difference was less strong when cisplatin was used (IC50 = 96.0 ± 6.9 and 61.9 ± 6.1 μmol·L(-1) for cancer and normal cells respectively). Both compounds caused reactive oxygen species (ROS) production with different mechanisms: [Pt(O,O'-acac)(γ-acac)(DMS)] quickly activated NAD(P)H oxidase while cisplatin caused a slower formation of mitochondrial ROS. Cisplatin and [Pt(O,O'-acac)(γ-acac)(DMS)] caused activation of caspases, proteolysis of PARP and modulation of Bcl-2, Bax and Bid. [Pt(O,O'-acac)(γ-acac)(DMS)] also caused leakage of cytochrome c from the mitochondria. Overall, these processes proceeded more quickly in cells treated with [Pt(O,O'-acac)(γ-acac)(DMS)] compared with cisplatin. [Pt(O,O'-acac)(γ-acac)(DMS)] effects were faster and quantitatively greater in cancer than in normal cells. [Pt(O,O'-acac)(γ-acac)(DMS)] caused a fast decrease of mitochondrial membrane potential, especially in cancer cells.

CONCLUSIONS AND IMPLICATIONS

[Pt(O,O'-acac)(γ-acac)(DMS)] was specific to breast cancer cells in primary culture, and this observation makes this compound potentially more interesting than cisplatin.

Structure-activity relationship for Fe(III)-salen-like complexes as potent anticancer agents

Quantitative structure activity relationship (QSAR) for the anticancer activity of Fe(III)-salen and salen-like complexes was studied. The methods of density function theory (B3LYP/LANL2DZ) were used to optimize the structures. A pool of descriptors was calculated: 1497 theoretical descriptors and quantum-chemical parameters, shielding NMR, and electronic descriptors. The study of structure and activity relationship was performed with multiple linear regression (MLR) and artificial neural network (ANN). In nonlinear method, the adaptive neuro-fuzzy inference system (ANFIS) was applied in order to choose the most effective descriptors. The ANN-ANFIS model with high statistical significance (R²_train = 0.99, RMSE = 0.138, and Q²_LOO = 0.82) has better capability to predict the anticancer activity of the new compounds series of this family. Based on this study, anticancer activity of this compound is mainly dependent on the geometrical parameters, position, and the nature of the substituent of salen ligand.

Mitochondria are the primary target in the induction of apoptosis by chiral ruthenium(II) polypyridyl complexes in cancer cells

A series of novel chiral ruthenium(II) polypyridyl complexes (Δ-Ru1, Λ-Ru1, Δ-Ru2, Λ-Ru2, Δ-Ru3, Λ-Ru3) were synthesized and evaluated to determine their antiproliferative activities. Colocalization, inductively coupled plasma mass spectrometry, and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay studies showed that these ruthenium(II) complexes accumulated preferentially in the mitochondria and exhibited cytotoxicity against various cancer cells in vitro. The complex Δ-Ru1 is of particular interest because it was found to have half-maximal inhibitory concentrations comparable to those of cisplatin and better activity than cisplatin against a cisplatin-resistant cell line, A549-CP/R. Δ-Ru1 induced alterations in the mitochondrial membrane potential and triggered intrinsic mitochondria-mediated apoptosis in HeLa cells, which involved the regulation of Bcl-2 family members and the activation of caspases. Taken together, these data suggest that Δ-Ru1 may be a novel mitochondria-targeting anticancer agent.

Antisense transcript long noncoding RNA (lncRNA) HOTAIR is transcriptionally induced by estradiol

HOTAIR (HOX antisense intergenic RNA) is a long noncoding RNA (lncRNA) that is transcribed from the antisense strand of homeobox C gene locus in chromosome 12. HOTAIR coordinates with chromatin-modifying enzymes and regulates gene silencing. It is overexpressed in various carcinomas including breast cancer. Herein, we demonstrated that HOTAIR is crucial for cell growth and viability and its knockdown induced apoptosis in breast cancer cells. We also demonstrated that HOTAIR is transcriptionally induced by estradiol (E2). Its promoter contains multiple functional estrogen response elements (EREs). Estrogen receptors (ERs) along with various ER coregulators such as histone methylases MLL1 (mixed lineage leukemia 1) and MLL3 and CREB-binding protein/p300 bind to the promoter of HOTAIR in an E2-dependent manner. Level of histone H3 lysine-4 trimethylation, histone acetylation, and RNA polymerase II recruitment is enriched at the HOTAIR promoter in the presence of E2. Knockdown of ERs and MLLs downregulated the E2-induced HOTAIR expression. Thus, similar to protein-coding gene transcription, E2-induced transcription of antisense transcript HOTAIR is coordinated via ERs and ER coregulators, and this mechanism of HOTAIR overexpression potentially contributes towards breast cancer progression.

Antisense oligonucleotide mediated knockdown of HOXC13 affects cell growth and induces apoptosis in tumor cells and over expression of HOXC13 induces 3D-colony formation

HOXC13 is a homeobox containing gene that plays crucial roles in hair development and origin of replication. Herein, we investigated the biochemical functions of HOXC13 and explored its potential roles in tumor cell viability. We have designed a phosphorothioate based antisense-oligonucleotide that specifically knockdown HOXC13 in cultured cells. Cell viability and cytotoxicity assays demonstrated that HOXC13 is essential for cell growth and viability. Antisense-mediated knockdown of HOXC13 affected the cell viability and induced apoptosis in cultured tumor cells. HOXC13 regulates the expression of cyclins and antisense-mediated knockdown of HOXC13 resulted in cell cycle arrest and apoptosis in colon cancer cells. Finally over expression of HOXC13 resulted in 3D-colony formation in soft-agar assay indicating its potential roles in cell proliferation and tumorigenesis.

Functional ionic liquids induced the formation of mitochondria targeted fluorescent core-shell ellipsoidal nanoparticles with anticancer properties

A functional ionic liquid (IL) (IL=4-acetyl-N-butyl pyridinium hexafluorophosphate) was synthesized and conjugated with low toxicity of nanospheres (RBITC@SiO(2)), forming a new kind of fluorescent core-shell ellipsoidal RBITC@SiO(2)-IL nanoparticle. In vitro assay results indicate that particle shape plays an important role in cellular interactions with NPs. Furthermore, the positively charged ellipsoidal RBITC@SiO(2)-IL nanoparticles can enter into HeLa cells and induce the cells to condense, split and decrease on the oxygen consumption. The enhanced cell image and decrease of mitochondria potential indicate that the ellipsoidal RBITC@SiO(2)-IL nanoparticles could be uptaken by HeLa cells through mitochondria involved path. Experimental results give us a new path to design nano-medicines through ionic liquid modified silica nanoparticles to target mitochondria.

Cytotoxic effects and the mechanism of three types of magnetic nanoparticles on human hepatoma BEL-7402 cells

The evaluation of the toxicity of magnetic nanoparticles (MNPs) has attracted much attention in recent years. The current study aimed to investigate the cytotoxic effects of Fe3O4, oleic acid-coated Fe3O4 (OA-Fe3O4), and carbon-coated Fe (C-Fe) nanoparticles on human hepatoma BEL-7402 cells and the mechanisms. WST-1 assay demonstrated that the cytotoxicity of three types of MNPs was in a dose-dependent manner. G1 (Fe3O4 and OA-Fe3O4) phase and G2 (C-Fe) phase cell arrests and apoptosis induced by MNPs were detected by flow cytometry analysis. The increase in apoptosis was accompanied with the Bax over-expression, mitochondrial membrane potential decrease, and the release of cytochrome C from mitochondria into cytosol. Moreover, apoptosis was further confirmed by morphological and biochemical hallmarks, such as swollen mitochondria with lysing cristae and caspase-3 activation. Our results revealed that certain concentrations of the three types of MNPs affect BEL-7402 cells viability via cell arrest and inducing apoptosis, and the MNPs-induced apoptosis is mediated through the mitochondrial-dependent pathway. The influence potency of MNPs observed in all experiments would be: C-Fe > Fe3O4 > OA-Fe3O4.

Organometallic iron(III)-salophene exerts cytotoxic properties in neuroblastoma cells via MAPK activation and ROS generation

The objective of the present study was to investigate the specific effects of Iron(III)-salophene (Fe-SP) on viability, morphology, proliferation, cell cycle progression, ROS generation and pro-apoptotic MAPK activation in neuroblastoma (NB) cells. A NCI-DTP cancer screen revealed that Fe-SP displayed high toxicity against cell lines of different tumor origin but not tumor type-specificity. In a viability screen Fe-SP exhibited high cytotoxicity against all three NB cell lines tested. The compound caused cell cycle arrest in G1 phase, suppression of cells progressing through S phase, morphological changes, disruption of the mitochondrial membrane depolarization potential, induction of apoptotic markers as well as p38 and JNK MAPK activation, DNA degradation, and elevated generation of reactive oxygen species (ROS) in SMS-KCNR NB cells. In contrast to Fe-SP, non-complexed salophene or Cu(II)-SP did not raise ROS levels in NB or SKOV-3 ovarian cancer control cells. Cytotoxicity of Fe-SP and activation of caspase-3, -7, PARP, pro-apoptotic p38 and JNK MAPK could be prevented by co-treatment with antioxidants suggesting ROS generation is the primary mechanism of cytotoxic action. We report here that Fe-SP is a potent growth-suppressing and cytotoxic agent for in vitro NB cell lines and, due to its high tolerance in previous animal toxicity studies, a potential therapeutic drug to treat NB tumors in vivo.

[Fe(III)(salophene)Cl], a potent iron salophene complex overcomes multiple drug resistance in lymphoma and leukemia cells

We demonstrate the cytotoxic potential of the Schiff base iron complex [Fe(III)(salophene)Cl] in vitro and ex vivo and illustrate its ability to overcome multiple drug resistance in vincristine and daunorubicine resistant leukemic cells (Nalm-6). Treatment of lymphoma cells (BJAB) with [Fe(III)(salophene)Cl] led to the exclusion of unspecific necrosis, a concentration-dependent inhibition of proliferation and a specific apoptotic cell death. We further detected a significant loss of the mitochondrial membrane potential in lymphoma cells and an up- and downregulation of various apoptosis relevant genes, respectively, indicating the involvement of the intrinsic mitochondrial pathway.

Fe(III)-Salen and Salphen Complexes Induce Caspase Activation and Apoptosis in Human Cells

To explore the apoptotic and antitumor activities of metallo-salens, the authors have synthesized several Fe(III)-salen and salphen complexes and analyzed their effects on human cancer and noncancer cells. Their results demonstrated that Fe(III)-salen and salphen complexes affect cell viability and induce nuclear fragmentation and apoptosis in breast cancer (MCF7) cells. The IC50 values for the active metallo-salen complexes ranged between 0.3 and 22 µM in MCF7 cells. Biochemically active Fe(III)-salen and salphen complexes induced caspase-3/7 activation and release of cytochrome c from the mitochondria to cytosol, suggesting the involvement of the mitochondrial pathway of apoptosis. Comparison of IC50 values toward 3 different cell lines demonstrated that selected Fe(III)-salen complexes induce tumor cell-selective apoptosis in cultured cells. Overall, the studies demonstrated that Fe(III)-salen and salphen complexes induced efficient apoptosis in cultured human cells. The nature of the substituents and the bridging spacer between diamino groups play critical roles in determining the apoptotic activities of Fe(III)-salen and salphen complexes.

A molecular half-subtractor with Zn2+ and UV-light as inputs

The salen-type Schiff base (2,2'-bis(2-hydroxybenzylideneamino)-1,1'-binaphthyl (BHB)) has been synthesized and characterized. Exhibiting absorption and fluorescence changes in the presence of Zn(2+) in chloroform and ethanol mixed solution, BHB could be used as a fluorescent chemosensor for the detection of Zn(2+). Furthermore, by monitoring the fluorescence and absorbance as output signals, BHB can function as a combinatorial logic circuit for a molecular half-subtractor with Zn(2+) and UV irradiation as input variables.

Influence of methoxy groups on the antiproliferative effects of [Fe(III)(salophene-OMe)Cl] complexes

We synthesized methoxy-substituted iron(III)-salophene complexes ([Fe(III)(OMe-salophene)Cl] with salophene = N,N'-bis(salicylidene)-1,2-phenylenediamine) and analyzed their biological activity in MCF-7 and MDA-MB-231 breast cancer as well as in HT-29 colon carcinoma cells. The results obtained in a time-dependent chemosensitivity test clearly demonstrated the correlation between the cytotoxicity of the complexes and the position of methoxy substituents in the salicylidene moieties: 3-OCH(3) (4) < 5-OCH(3) (8) < H (2) < 4-OCH(3) (6) = 6-OCH(3) (10). Compounds 6 and 10 caused cytocidal effects already at a concentration of 0.5 μM. Both lead compound 2 and complex 8 showed similar time response curves, however, with a 5-fold lower activity compared to 6 and 10, respectively. Referring to [Fe(III)(salophene)Cl] (2), methoxy substitution was accompanied with the loss of tumor cell selectivity. Moreover, the free ligands (1, 3, 5, 7, and 9) were inactive.