Recent graphene research has triggered enormous interest in new two-dimensional ordered crystals constructed by the inclusion of elements other than carbon for bandgap opening. The design of new multifunctional two-dimensional materials with proper bandgap has become an important challenge. Here we report a layered two-dimensional network structure that possesses evenly distributed holes and nitrogen atoms and a C 2 N stoichiometry in its basal plane. The two-dimensional structure can be efficiently synthesized via a simple wetchemical reaction and confirmed with various characterization techniques, including scanning tunnelling microscopy. Furthermore, a field-effect transistor device fabricated using the material exhibits an on/off ratio of 10 7 , with calculated and experimental bandgaps of approximately 1.70 and 1.96 eV, respectively. In view of the simplicity of the production method and the advantages of the solution processability, the C 2 N-h2D crystal has potential for use in practical applications.

Angiogenesis is regulated by the dynamic interaction between endothelial cells (ECs).Hippo-Yes-associated protein (YAP) signalling has emerged as a key pathway that controls organ size and tissue growth by mediating cell contact inhibition. However, the role of YAP in EC has not been defined yet. Here, we show expression of YAP in the developing front of mouse retinal vessels. YAP subcellular localization, phosphorylation and activity are regulated by VE-cadherin-mediated-EC contacts. This VE-cadherin-dependent YAP phosphorylation requires phosphoinositide 3-kinase-Akt activation. We further identify angiopoietin-2 (ANG-2) as a potential transcriptional target of YAP in regulating angiogenic activity of EC in vitro and in vivo. Overexpression of YAP-active form in EC enhances angiogenic sprouting, and this effect is blocked by ANG-2 depletion or soluble Tie-2 treatment. These findings implicate YAP as a critical regulator in angiogenesis and provide new insights into the mechanism coordinating junctional stability and angiogenic activation of ECs.

IntroductionAngiogenesis is a critical process in physiologic and pathologic conditions, including embryo development, wound healing, tumor progression, and inflammatory diseases. 1 Inflammation and angiogenesis are closely associated, and pathologic angiogenesis has been implicated in the development of chronic inflammatory diseases. Interplay between inflammation and angiogenesis is mediated largely by cytokines, chemokines, and growth factors. Some of these molecules, including vascular endothelial growth factor (VEGF), induce endothelial permeability, allowing the infiltration of leukocytes to inflammatory sites, resulting in tissue damage. 2 Interleukin-33 (IL-33) is a newly identified cytokine of the IL-1 family, which also includes the inflammatory cytokines IL-1␣, It has been shown to signal via ST2 receptor. 4 IL-33 expression is broadly detected in various tissues, including stomach, lung, spinal cord, brain, and skin, as well as in cells, including smooth muscle cells and epithelial cells lining bronchus and small airways. 4 Notably, IL-33 expression is induced by IL-1␤ and tumor necrosis factor-␣ (TNF-␣) in lung and dermal fibroblast and, to a lesser extent, by macrophage activation. 4 IL-33 treatment has been shown to induce T-helper (Th) type 2 responses in mice as indicated by an increase in Th2 cytokine production and serum immunoglobulin. Systemic treatment of mice with IL-33 results in pathologic changes in the lung and the digestive tract. In the lung, vascular changes accompanied with eosinophilic and mononuclear infiltrates were observed in small muscular arteries. 4 Recently, functions of IL-33 in cardiovascular diseases have been reported. For example, IL-33 can reduce the development of atherosclerosis in apolipoprotein E Ϫ/Ϫ mice on a high-fat diet. 5 Furthermore, IL-33/ST2 complexes also have been shown to activate cardioprotective signaling pathways. 6 IL-33 is produced as a 30-kDa precursor protein that is cleaved in vitro by caspase-1, releasing the mature 18-kDa form. 4 Upon binding to the ST2 receptor, IL-33 promotes the activation of nuclear factor (NF)-B and mitogen-activated protein kinase (MAPK), leading to increased transcription of Th2 cytokines. 4 The ST2 receptor, a member of IL-1 receptor family, has long been known as an orphan receptor. Despite its structural and functional similarity to IL-1 receptor family, the ST2 receptor does not bind to IL-1␣ or IL-1␤ or other members of the IL-1 family. Two isoforms, a soluble (sST2) and a membrane bound form (ST2L), are produced through differential mRNA processing. 7,8 ST2L is expressed mainly in mast cells and Th2 cells. 7,8 Both ST2 forms also are expressed in freshly isolated human umbilical vein endothelial cells (HUVECs), and they are up-regulated by proinflammatory stimuli such as TNF, IL-1␣, and IL-1␤. 9 Nitric oxide (NO) production in endothelial cells (ECs) is transiently regulated by multiple inflammatory angiogenic factors such as VEGF and angiopoietin-1. 10,11 NO, in turn, modulates the angiogenic function of these ...

We developed a simple, versatile method of integrating hybrid thin films of reduced graphene oxide (RGO) nanosheets with multiwalled carbon nanotubes (MWNTs) via LbL assembly. This approach involves the electrostatic interactions of two oppositely charged suspensions of the RGO nanosheet with MWNTs. This method affords a hybrid multilayer of graphenes with excellent control over the optical and electrical properties. Moreover, the hybrid multilayer exhibits a significant increase of electronic conductivity after the thermal treatment, producing transparent and conducting thin films possessing a sheet resistance of 8 kOmega/sq with a transmittance of 81%. By taking advantage of the conducting network structure of MWNTs, which provides an additional flexibility and mechanical stability of RGO nanosheets, we demonstrate the potential application of hybrid graphene multilayer as a highly flexible and transparent electrode. Because of the highly versatile and tunable properties of LbL-assembled thin films, we anticipate that the general concept presented here offers a unique potential platform for integrating active carbon nanomaterials for advanced electronic, energy, and sensor applications.

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