Cobalt-assisted in situ synthesis of crystalline bismuth nanoparticle arrays.

Almost monodisperse, crystalline Bi nanoparticle arrays were synthesized using a newly developed method, magnetically assisted growth of Bi nanoparticles (MAGBINs). The MAGBIN utilizes co-sputtering from Bi and Co targets at an elevated temperature. Crystalline Bi nanoparticles with hexagonal morphology were formed in situ on a Si substrate with a thin surface oxide during this process. The size and density of Bi nanoparticles could be controlled by adjusting the relative powers applied to Bi and Co targets, and they showed opposite trends against the relative powers. Several physical processes such as Co agglomeration, element-selective growth, and Ostwald ripening were proposed to be involved in this Bi nanoparticle growth. The MAGBIN is a facile method to synthesize crystalline Bi nanoparticle arrays, which does not need any chemical agents, complex process, or lithography.

High stability silver nanoparticles-graphene/poly(ionic liquid)-based chemoresistive sensors for volatile organic compounds' detection.

Hybrids of silver nanoparticle-decorated reduced graphene oxide (Ag-RGO) have been prepared with the use of poly(ionic liquid) (PIL) as a versatile capping agent to develop volatile organic compound (VOC) sensors. The hybrid materials of Ag-RGO/PIL were assembled into three-dimensional-laminated nanostructures, where spherical Ag nanoparticles with diameters between 50 and 300 nm were homogeneously distributed on the graphene sheets and interspaced between them. Ag-RGO/PIL sensors were fabricated by spray layer-by-layer technique and used to detect a set of polar (methanol, ethanol, methyl acetate, acetone and water) and non-polar (chloroform, dichlorobenzene, toluene and styrene) organic vapours. Much higher sensitivity and discriminability were obtained for polar vapours although non-polar ones could also be detected. In comparison with either simple reduced graphene oxide or carbon nanotubes (CNT) functionalised by PIL, the hybrid Ag-RGO/PIL-based sensors showed superior performances in terms of sensitivity, selectivity, stability and high reliability. For example, a signal-to-noise ratio up to 168 was obtained for 1 ppm of methanol and signals drift between two experiments spaced out in the time of 3 months was less than 3%. It is expected that by extrapolation, a limit of detection at the parts per billion level can be reached. These results are promising to design e-noses based on high stability chemoresistive sensors for emerging applications such as anticipated diagnostic of food degradation or diseases by the analysis of VOC, some of them being in this case considered as biomarkers.

Activated graphene-based carbons as supercapacitor electrodes with macro- and mesopores.

Electric double layer capacitors (or supercapacitors) store charges through the physisorption of electrolyte ions onto porous carbon electrodes. The control over structure and morphology of carbon electrode materials is therefore an effective strategy to render them high surface area and efficient paths for ion diffusion. Here we demonstrate the fabrication of highly porous graphene-derived carbons with hierarchical pore structures in which mesopores are integrated into macroporous scaffolds. The macropores were introduced by assembling graphene-based hollow spheres, and the mesopores were derived from the chemical activation with potassium hydroxide. The unique three-dimensional pore structures in the produced graphene-derived carbons give rise to a Brunauer-Emmett-Teller surface area value of up to 3290 m(2) g(-1) and provide an efficient pathway for electrolyte ions to diffuse into the interior surfaces of bulk electrode particles. These carbons exhibit both high gravimetric (174 F g(-1)) and volumetric (~100 F cm(-3)) specific capacitance in an ionic liquid electrolyte in acetonitrile. The energy density and power density of the cell assembled with this carbon electrode are also high, with gravimetric values of 74 Wh kg(-1) and 338 kW kg(-1) and volumetric values of 44 Wh L(-1) and 199 kW L(-1), respectively. The supercapacitor performance achieved with these graphene-derived carbons is attributed to their unique pore structure and makes them potentially promising for diverse energy storage devices.

Flexible thermochromic window based on hybridized VO2/graphene.

Large-scale integration of vanadium dioxide (VO2) on mechanically flexible substrates is critical to the realization of flexible smart window films that can respond to environmental temperatures to modulate light transmittance. Until now, the formation of highly crystalline and stoichiometric VO2 on flexible substrate has not been demonstrated due to the high-temperature condition for VO2 growth. Here, we demonstrate a VO2-based thermochromic film with unprecedented mechanical flexibility by employing graphene as a versatile platform for VO2. The graphene effectively functions as an atomically thin, flexible, yet robust support which enables the formation of stoichiometric VO2 crystals with temperature-driven phase transition characteristics. The graphene-supported VO2 was capable of being transferred to a plastic substrate, forming a new type of flexible thermochromic film. The flexible VO2 films were then integrated into the mock-up house, exhibiting its efficient operation to reduce the in-house temperature under infrared irradiation. These results provide important progress for the fabrication of flexible thermochromic films for energy-saving windows.

Large-scale graphene micropatterns via self-assembly-mediated process for flexible device application.

We report on a method for the large-scale production of graphene micropatterns by a self-assembly mediated process. The evaporation-induced self-assembly technique was engineered to produce highly ordered graphene patterns on flexible substrates in a simplified and scalable manner. The crossed stripe graphene patterns have been produced over a large area with regions consisting of single- and two-layer graphene. Based on these graphene patterns, flexible graphene-based field effect transistors have been fabricated with an ion-gel gate dielectric, which operates at low voltages of < 2 V with a hole and electron mobility of 214 and 106 cm(2)/V·s, respectively. The self-assembly approach described here may pave the way for the nonlithographic production of graphene patterns, which is scalable to large areas and compatible with roll-to-roll system.

Shape-controlled synthesis of silver crystals mediated by imidazolium-based ionic liquids.

This work presents an approach toward the shape-controlled synthesis of Ag crystals with hierarchical structures by exploitation of ionic liquids (ILs) as a shape-regulating agent. The synthesis of Ag crystals involves the reduction of AgNO(3) by EG in the presence of ILs, specifically 1-butyl-3-methylimidazolium methylsulfate (bmim-MeSO(4)). In accordance with non-classical crystallization growth mechanism, the primary Ag nanoparticles were formed at the early stage of the reaction, and then self-organized into 1D or 3D Ag superstructures via an IL-mediated self-assembly process. Their final morphologies were strongly dependent on the reaction conditions such as the concentration of ILs in the reaction mixture and the reaction temperature, which suggests that ILs play an important role in controlling the shape of the Ag crystals.

High-performance supercapacitors based on poly(ionic liquid)-modified graphene electrodes.

We report a high-performance supercapacitor incorporating a poly(ionic liquid)-modified reduced graphene oxide (PIL:RG-O) electrode and an ionic liquid (IL) electrolyte (specifically, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide or EMIM-NTf(2)). PIL:RG-O provides enhanced compatibility with the IL electrolyte, thereby increasing the effective electrode surface area accessible to electrolyte ions. The supercapacitor assembled with PIL:RG-O electrode and EMIM-NTf(2) electrolyte showed a stable electrochemical response up to 3.5 V operating voltage and was capable of yielding a maximum energy density of 6.5 W·h/kg with a power density of 2.4 kW/kg. These results demonstrate the potential of the PIL:RG-O material as an electrode in high-performance supercapacitors.

S-nitrosylation regulates nuclear translocation of chloride intracellular channel protein CLIC4.

Nuclear translocation of chloride intracellular channel protein CLIC4 is essential for its role in Ca(2+)-induced differentiation, stress-induced apoptosis, and modulating TGF-beta signaling in mouse epidermal keratinocytes. However, post-translational modifications on CLIC4 that govern nuclear translocation and thus these activities remain to be elucidated. The structure of CLIC4 is dependent on the redox environment, in vitro, and translocation may depend on reactive oxygen and nitrogen species in the cell. Here we show that NO directly induces nuclear translocation of CLIC4 that is independent of the NO-cGMP pathway. Indeed, CLIC4 is directly modified by NO through S-nitrosylation of a cysteine residue, as measured by the biotin switch assay. NO enhances association of CLIC4 with the nuclear import proteins importin alpha and Ran. This is likely a result of the conformational change induced by S-nitrosylated CLIC4 that leads to unfolding of the protein, as exhibited by CD spectra analysis and trypsinolysis of the modified protein. Cysteine mutants of CLIC4 exhibit altered nitrosylation, nuclear residence, and stability, compared with the wild type protein likely as a consequence of altered tertiary structure. Moreover, tumor necrosis factor alpha-induced nuclear translocation of CLIC4 is dependent on nitric-oxide synthase activity. Inhibition of nitric-oxide synthase activity inhibits tumor necrosis factor alpha-induced nitrosylation and association with importin alpha and Ran and ablates CLIC4 nuclear translocation. These results suggest that S-nitrosylation governs CLIC4 structure, its association with protein partners, and thus its intracellular distribution.

Synthesis of phase transferable graphene sheets using ionic liquid polymers.

A practical route to the production of solution phase transferable graphene sheets using ionic liquid polymers (PIL) as a transferring medium is developed. Chemically converted graphene sheets decorated with PIL were found to be stable against the chemical reduction and well dispersed in the aqueous phase without any agglomeration. Upon the anion exchange of the PIL on graphene sheets, these PIL-modified graphene sheets in aqueous phase are readily transferred into the organic phase by changing their properties from hydrophilic to hydrophobic.

TGF-beta signalling is regulated by Schnurri-2-dependent nuclear translocation of CLIC4 and consequent stabilization of phospho-Smad2 and 3.

CLIC4 (chloride intracellular channel 4), a multifunctional protein that traffics between the cytoplasm and nucleus, interacts with Schnurri-2, a transcription factor in the bone morphogenetic protein (BMP) signalling pathway. Here we show that transforming growth factor beta (TGF-beta) promotes the expression of CLIC4 and Schnurri-2 as well as their association in the cytoplasm and their translocation to the nucleus. In the absence of CLIC4 or Schnurri-2, TGF-beta signalling is abrogated. Direct nuclear targeting of CLIC4 enhances TGF-beta signalling and removes the requirement for Schnurri-2. Nuclear CLIC4 associates with phospho (p)-Smad2 and p-Smad3, protecting them from dephosphorylation by nuclear phosphatases. An intact TGF-beta signalling pathway is essential for CLIC4-mediated growth-arrest. These results newly identify Schnurri-2 and CLIC4 as modifiers of TGF-beta signalling through their stabilization of p-Smad2 and 3 in the nucleus.

Ionic-liquid-assisted formation of silver nanowires.

Down to the wire: A simple and effective method to synthesize silver nanowires through an ionic-liquid-assisted polyol process is developed (see scheme; scale bar=5 nm). The ionic liquids are tuned to provide the anisotropic growth of silver nanoparticles into nanowires.

Poly(3,4-ethylenedioxythiophene) Derived from Poly(ionic liquid) for the Use as Hole-Injecting Material in Organic Light-Emitting Diodes.

We report that poly(3,4-ethylenedioxythiophene) derived from poly(ionic liquid) (PEDOT:PIL) constitutes a unique polymeric hole-injecting material capable of improving device lifetime in organic light-emitting diodes (OLEDs). Imidazolium-based poly(ionic liquid)s were engineered to impart non-acidic and non-aqueous properties to PEDOT without compromising any other properties of PEDOT. A fluorescent OLED was fabricated using PEDOT:PIL as a hole-injection layer and subjected to a performance evaluation test. In comparison with a control device using a conventional PEDOT-based material, the device with PEDOT:PIL was found to achieve a significant improvement in terms of device lifetime. This improvement was attributed to a lower indium content in the PEDOT:PIL layer, which can be also interpreted as the effective protection characteristics of PEDOT:PIL for indium extraction from the electrodes.

CLIC4 mediates and is required for Ca2+-induced keratinocyte differentiation.

Keratinocyte differentiation requires integrating signaling among intracellular ionic changes, kinase cascades, sequential gene expression, cell cycle arrest, and programmed cell death. We now show that Cl(-) intracellular channel 4 (CLIC4) expression is increased in both mouse and human keratinocytes undergoing differentiation induced by Ca(2+), serum and the protein kinase C (PKC)-activator, 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Elevation of CLIC4 is associated with signaling by PKCdelta, and knockdown of CLIC4 protein by antisense or shRNA prevents Ca(2+)-induced keratin 1, keratin 10 and filaggrin expression and cell cycle arrest in differentiating keratinocytes. CLIC4 is cytoplasmic in actively proliferating keratinocytes in vitro, but the cytoplasmic CLIC4 translocates to the nucleus in keratinocytes undergoing growth arrest by differentiation, senescence or transforming growth factor beta (TGFbeta) treatment. Targeting CLIC4 to the nucleus of keratinocytes via adenoviral transduction increases nuclear Cl(-) content and enhances expression of differentiation markers in the absence of elevated Ca(2+). In vivo, CLIC4 is localized to the epidermis in mouse and human skin, where it is predominantly nuclear in quiescent cells. These results suggest that CLIC4 participates in epidermal homeostasis through both alterations in the level of expression and subcellular localization. Nuclear CLIC4, possibly by altering the Cl(-) and pH of the nucleus, contributes to cell cycle arrest and the specific gene expression program associated with keratinocyte terminal differentiation.

p21WAF1/CIP1 is a common transcriptional target of retinoid receptors: pleiotropic regulatory mechanism through retinoic acid receptor (RAR)/retinoid X receptor (RXR) heterodimer and RXR/RXR homodimer.

The divergent response and the molecular mechanisms underlying the anti-cancer effects of retinoid X receptor (RXR) ligand (rexinoid) therapy are poorly understood. This study demonstrates that ligand-activated RXR homodimer facilitated G(1) arrest by up-regulation of p21 in vitro and in vivo but failed to induce G(1) arrest when p21 expression was blocked by p21 small interfering RNA. RXR ligand-dependent p21 up-regulation was transcriptionally controlled through the direct binding of RXR homodimers to two consecutive retinoid X response elements in the p21 promoter. Structural overlap of a retinoic acid response element with these retinoid X response elements led to a high affinity binding of retinoic acid receptor/RXR heterodimer to the retinoic acid response element, resulting in the prevention of RXR ligand-mediated p21 transactivation. These data show that p21 is a potential and novel molecular target for RXR ligand-mediated anti-cancer therapy and that the expression level of retinoic acid receptor and RXR in tumors may be crucial to induce p21-mediated cell growth arrest in RXR ligand therapy.

CLIC4, skin homeostasis and cutaneous cancer: surprising connections.

Chloride intracellular channel 4 (CLIC4) is a putative chloride channel for intracellular organelles. CLIC4 has biological activities in addition to or because of its channel activity. In keratinocytes, CLIC4 resides in the mitochondria and cytoplasm, and CLIC4 gene expression is regulated by p53, TNF-alpha, and c-Myc. Cytoplasmic CLIC4 translocates to the nucleus in response to cellular stress conditions including DNA damage, metabolic inhibition, senescence, and exposure to certain trophic factors such as TNF-alpha and LPS. Nuclear translocation is associated with growth arrest or apoptosis, depending on the level of expression. In the nucleus CLIC4 interacts with several nuclear proteins as demonstrated by yeast two-hybrid screening and co-immunoprecipitation. Nuclear CLIC4 appears to act on the TGF-beta pathway, and TGF-beta also causes CLIC4 nuclear translocation. In human and mouse cancer cell lines, CLIC4 levels are reduced, and CLIC4 is excluded from the nucleus. CLIC4 soluble or membrane-inserted status is dependent on redox state, and redox alterations in cancer cells could underly the defect in nuclear translocation. CLIC4 is reduced and excluded from the nucleus of many human epithelial neoplasms. Paradoxically, CLIC4 is reciprocally upregulated in tumor stroma in conjunction with the expression of alpha-smooth muscle actin in the fibroblast to myofibroblast transition. Overexpression of CLIC4 in cancer cells inhibits tumor growth in vivo. Conversely, overexpression of CLIC4 in tumor stromal cells stimulates tumor growth in vivo. Thus, CLIC4 participates in normal and pathological processes and may serve as a useful target for therapies in disturbances of homeostasis and neoplastic transformation.

Reciprocal modifications of CLIC4 in tumor epithelium and stroma mark malignant progression of multiple human cancers.

PURPOSE: CLIC4, a member of a family of intracellular chloride channels, is regulated by p53, c-Myc, and tumor necrosis factor-alpha. Regulation by factors involved in cancer pathogenesis, together with the previously shown proapoptotic activity of CLIC4, suggests that the protein may have a tumor suppressor function. To address this possibility, we characterized the expression profile, subcellular localization, and gene integrity of CLIC4 in human cancers and determined the functional consequences of CLIC4 expression in tumor epithelium and stromal cells. EXPERIMENTAL DESIGN: CLIC4 expression profiles were analyzed by genomics, proteomics, bioinformatics, and tissue microarrays. CLIC4 expression, as a consequence of crosstalk between stroma and epithelium, was tested in vitro by coculture of breast epithelial tumor cells and normal fibroblasts, and the functional consequences of CLIC4 expression was tested in vivo in xenografts of human breast tumor cell lines reconstituted with CLIC4 or mixed with fibroblasts that overexpress CLIC4 transgenically. RESULTS: In cDNA arrays of matched human normal and tumor tissues, CLIC4 expression was reduced in renal, ovarian, and breast cancers. However, CLIC4 protein levels were variable in tumor lysate arrays. Transcript sequences of CLIC4 from the human expressed sequence tag database and manual sequencing of cDNA from 60 human cancer cell lines (NCI60) failed to reveal deletion or mutations in the CLIC4 gene. On matched tissue arrays, CLIC4 was predominantly nuclear in normal human epithelial tissues but not cancers. With advancing malignant progression, CLIC4 staining became undetectable in tumor cells, but expression increased in stromal cells coincident with up-regulation of alpha-smooth muscle actin, suggesting that CLIC4 is up-regulated in myofibroblasts. Coculture of cancer cells and fibroblasts induced the expression of both CLIC4 and alpha-smooth muscle actin in fibroblasts adjacent to tumor nests. Introduction of CLIC4 or nuclear targeted CLIC4 via adenovirus into human breast cancer xenografts inhibited tumor growth, whereas overexpression of CLIC4 in stromal cells of xenografts enhanced tumor growth. CONCLUSION: Loss of CLIC4 in tumor cells and gain in tumor stroma is common to many human cancers and marks malignant progression. Up-regulation of CLIC4 in tumor stroma is coincident with myofibroblast conversion, generally a poor prognostic indicator. Reactivation and restoration of CLIC4 in tumor cells or the converse in tumor stromal cells could provide a novel approach to inhibit tumor growth.

Quantitative proteomic analysis of myc-induced apoptosis: a direct role for Myc induction of the mitochondrial chloride ion channel, mtCLIC/CLIC4.

Myc is a key regulatory protein in higher eukaryotes controlling important cellular functions such as proliferation, differentiation, and apoptosis. Myc is profoundly involved in the genesis of many human and animal cancers, and the abrogation of Myc-induced apoptosis is a critical event in cancer progression. Because the mechanisms that mediate Myc-induced apoptosis are largely unknown, we analyzed protein expression during Myc-induced apoptosis using an isotope-coded affinity tag quantitative proteomics approach and identified that a proapoptotic mitochondrial chloride ion channel, mtCLIC/CLIC4, is induced by Myc. Myc binds to the mtCLIC gene promoter and activates its transcription. Suppression of mtCLIC expression by RNA interference inhibited Myc-induced apoptosis in response to different stress conditions and abolished the cooperative induction of apoptosis by Myc and Bax. We also found that Myc reduces the expression of Bcl-2 and Bcl-xL and that the apoptosis-inducing stimuli up-regulate Bax expression. These results suggest that up-regulation of mtCLIC, together with a reduction in Bcl-2 and Bcl-xL, sensitizes Myc-expressing cells to the proapoptotic action of Bax.

CLIC4, an intracellular chloride channel protein, is a novel molecular target for cancer therapy.

Chloride intracellular channel (CLIC)4 is a p53- and tumor necrosis factor alpha (TNFalpha)-regulated chloride channel protein that is localized to the mitochondria and cytoplasm of mouse and human keratinocytes. CLIC4 protein increases in differentiating keratinocytes and in keratinocytes exposed to DNA-damaging agents and metabolic inhibitors. Increasing CLIC4 levels by transduction of recombinant CLIC4 causes apoptosis. CLIC4 translocates to the nucleus under a variety of conditions of cell stress, and nuclear CLIC4 is associated with cell cycle arrest and accelerated apoptosis. Reduction of CLIC4 and several other CLIC family members by expressing a doxycycline-regulated CLIC4 antisense also causes apoptosis in squamous cancer cell lines. Expressing antisense CLIC4 in tumors derived from transplanting these cells into nude mice inhibits tumor growth, increases tumor apoptosis, and reduces tumor cell proliferation. Co-administration of TNFalpha intraperitoneally enhances the tumor-inhibitory influence of CLIC4 antisense expression. Together, these results suggest that CLIC4 is important for keratinocyte viability and may be a novel target for anti-cancer therapy.