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Model systems are critical to our understanding of self-assembly processes. As such, we have studied the surface self-assembly of a small and simple molecule, indole-2-carboxylic acid (I2CA). We combine density functional theory gas-phase (DFT) calculations with scanning tunneling microscopy to reveal details of I2CA assembly in two different solvents at the solution/solid interface, and on Au(111) in ultrahigh vacuum (UHV). In UHV and at the trichlorobenzene/highly oriented pyrolytic graphite (HOPG) interface, I2CA forms epitaxial lamellar structures based on cyclic OH...O carboxylic dimers. The structure formed at the heptanoic acid/HOPG interface is different and can be interpreted in a model where heptanoic acid molecules co-adsorb on the substrate with the I2CA, forming a bicomponent commensurate unit cell. DFT calculations of dimer energetics elucidate the basic building blocks of these structures, whereas calculations of periodic two-dimensional assemblies reveal the epitaxial effects introduced by the different substrates. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) nanomaterials, such as graphene and single layer covalent organic frameworks (sCOFs) are being widely studied due to their unusual structure/property relationships. sCOFs typically feature atomic thickness, intrinsic nanoscale porosity and a crystalline lattice. Compared to other organic 2D materials, sCOFs exhibit major advantages including topological designation and constitutional tunability. This review describes the state of the art of surface-confined sCOFs, emphasizing reticular design, synthesis approaches, and key challenges related to improving quality and exploring applications. [ABSTRACT FROM AUTHOR]

We report on the synthesis of a covalent organic framework based on the low-symmetry 1,3-benzenediboronic acid precursor. Two distinct polymorphs are obtained, a honeycomb network and Sierpiński triangles, as elucidated by scanning tunneling microscopy. Control over polymorph formation was achieved by varying the precursor concentration for on-surface synthesis. [ABSTRACT FROM AUTHOR]

Over the past two decades, solution/solid STM has made clear contributions to our fundamental understanding of the thermodynamic and kinetic processes that occur in molecular self-assembly at surfaces. As the field matures, we provide an overview of how solution/solid STM is emerging as a tool to elucidate and guide the use of self-assembled molecular systems in practical applications, focusing on small molecule device engineering, molecular recognition and sensing and electronic modification of 2D materials. [ABSTRACT FROM AUTHOR]

Hydrophilic CuO nanoparticle embedded carbon-based nanoporous composites are constructed through a simple gelation-pyrolysis route, demonstrating potential applications for removal of antibiotics in wastewater by synergetic adsorption-photodegradation process. • Hydrophilic 3D N -doped carbon/CuO composites were prepared by a simple gelation-pyrolysis method. • Synergetic removal of tetracycline by adsorption–photodegradation was achieved. • The intermediates and reaction pathway of tetracycline were identified. Adsorption and photocatalytic oxidation are promising technologies for eliminating antibiotics (e.g. tetracycline) in aquatic environments. However, traditional powdery nanomaterials are limited by drawbacks of difficult separation and lack of synergistic function, which do not conform to the practical demand. Herein, we developed a simple one-step gelation-pyrolysis route to fabricate hydrophilic three-dimensional (3D) porous photocatalytic adsorbent, in which CuO nanoparticles are uniformly and firmly embedded in nitrogen-doped (N -doped) porous carbon frameworks. The obtained N -doped carbon/CuO bulky composites exhibited excellent ability to adsorb tetracycline hydrochloride (TC), which was subsequently photo-oxidized under visible light. Their hydrophilic nature favors the adsorption processes toward TC, with a maximum adsorption capacity reaching 25.03 mg∙g−1. In addition, >94.4% of TC molecules could be photo-degraded in 4 h with good cycling efficiency after three consecutive tests. Finally, a reaction scheme for removal process of TC was proposed. The obtained 3D porous N -doped carbon/CuO nanocomposites show great promise for efficient removal of antibiotics in aqueous solution by synergistically utilizing adsorption and photocatalytic oxidation processes. [ABSTRACT FROM AUTHOR]

MicroRNAs play key roles in many biological processes, and are frequently dysregulated in tumor cells. However, there are few studies on how microRNAs are dysregulated. miR-139-5p, an important tumor suppressor, is often underexpressed in gastrointestinal cancer cells. Here, we describe post-transcriptional regulation of this intronic microRNA in human colorectal cancer. miR-139-5p is expressed independently of its overexpressed host gene PDE2A in colorectal cancer tissues and cell lines. The miR-139-5p target genes IGF1R, ROCK2 and RAP1B exert regulatory effects on the miR-139-5p expression level, relying on their ability to compete for miR-139-5p binding. These overexpressed target genes also regulate each others' protein levels through 3'-UTRs, thus regulating tumor cell growth and motility properties. Our study provides a mechanistic, experimentally validated rationale for intronic microRNA dysregulation in colorectal cancer, revealing novel oncogenic roles of IGF1R, ROCK2 and RAP1B 3'-UTRs. [ABSTRACT FROM AUTHOR]

Abstract: Colorectal carcinoma is a frequent cause of cancer-related death in men and women throughout the world. MicroRNAs are endogenous small noncoding RNAs that negatively regulate gene expression at the posttranscriptional level. We investigated the role of ADAM-17 (a desintegrin and metalloproteases 17) as a novel multidrug resistance (MDR) mechanism in multidrug-resistant colorectal carcinoma (CRC) and the role of miR-222 in the development of MDR in CRC cells. We found that the high expression of ADAM-17, which results in growth factor shedding and growth factor receptor activation could induce drug resistance in CRC. Pharmacological inhibition of ADAM-17, in conjunction with chemotherapy, may have therapeutic potential for the treatment of CRC. ADAM-17 is a predicted target of miR-222, which was downregulated in multidrug-resistant CRC cells. The presence of miR-222 was consistently inversely proportionate to the expression levels of ADAM-17. We found that elevated levels of miR-222 in the mimics-transfected HCT116/L-OHP and HCT-8/VCR cells reduced the ADAM-17 protein level and the luciferase activity of an ADAM-17 3′ untranslated region-based reporter and sensitized these cells’ apoptosis to some anticancer drugs. Our findings suggest that miR-222 could play a role in the development of MDR by modulation of ADAM-17, the new MDR treatment target in colorectal carcinoma cells. [Copyright &y& Elsevier]

Colorectal carcinoma is a frequent cause of cancer-related death in men and women. miRNAs (microRNAs) are endogenous small non-coding RNAs that regulate gene expression negatively at the post-transcriptional level. In the present study we investigated the possible role of microRNAs in the development of MDR (multidrug resistance) in colorectal carcinoma cells. We analysed miRNA expression levels between MDR colorectal carcinoma cell line HCT116/L-OHP cells and their parent cell line HCT116 using a miRNA microarray. miR-297 showed lower expression in HCT116/L-OHP cells compared with its parental cells. MRP- 2 (MDR-associated protein 2) is an important MDR protein in platinum-drug-resistance cells and is a predicted target of miR- 297. Additionally miR-297 was down-regulated in a panel of human colorectal carcinoma tissues and negatively correlated with expression levels of MRP-2. Furthermore, we found that ectopic expression of miR-297 in MDRcolorectal carcinoma cells reduced MRP-2 protein level and sensitized these cells to anticancer drugs in vitro and in vivo. Taken together, our findings suggest that miR-297 could play a role in the development of MDR in colorectal carcinoma cells, at least in part by modulation of MRP-2. [ABSTRACT FROM AUTHOR]

Abstract: MicroRNAs (miRNAs), which are noncoding RNAs that regulate gene expression, are involved in tumor metastasis. In this study, we describe the down-regulation and function of miR-139 in colorectal cancer (CRC) metastasis. MiR-139 was found underexpressed in 34 CRC tissues compared to their corresponding nontumor tissues. Decreased miR-139 in CRC tissue was associated with disease progression and metastasis. Re-expression of miR-139 did not inhibit CRC cell growth but suppresses CRC cell metastasis and invasion in vitro and in vivo. MiR-139 might suppress CRC cells invasion and metastasis by targeting type I insulin-like growth factor receptor (IGF-IR). We also found miR-139 directed migration inactivation of human CRC cells involves down-regulation of matrix metalloproteinase 2 (MMP-2). The IGF-IR/MEK/ERK signaling was inhibited by miR-139 overexpression and then resulted in MMP-2 promoter suppression. Taken together, our results provide evidence that miR-139 might function as a metastasis suppressor in CRC. Targeting miR-139 may provide a strategy for blocking CRC metastasis. [Copyright &y& Elsevier]