33 research outputs found

    N‑Doped Graphene: An Alternative Carbon-Based Matrix for Highly Efficient Detection of Small Molecules by Negative Ion MALDI-TOF MS

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    Gas-phase N-doped graphene (gNG) was synthesized by a modified thermal annealing method using gaseous melamine as nitrogen source and then for the first time applied as a matrix in negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for small molecule analysis. Unlike the complicated adducts produced in positive ion mode, MS spectra obtained on gNG matrix in negative ion mode was only featured by deprotonated molecule ion peaks without matrix interference. By the gNG assisted desorption/ionization (D/I) process, some applications were carried out on a wide range of low-molecular weight (MW) analytes including amino acids, fatty acids, peptides, anabolic androgenic steroids as well as anticancer drugs, with an extraordinary laser desorption/ionization (LDI) efficiency over traditional α-cyano-4-hydroxycinnamic acid (CHCA) and other carbon-based materials in the negative ion detection mode. By comparison of a series of graphene-based matrixes, two main factors of matrix gNG were unveiled to play a decisive role in assisting negative ion D/I process: a well-ordered π-conjugated system for laser absorption and energy transfer; pyridinic-doped nitrogen species functioning as deprotonation sites for proton capture on negative ionization. The good salt tolerance and high sensitivity allowed further therapeutic monitoring of anticancer drug nilotinib in the spiked human serum, a real case of biology. Signal response was definitely obtained between 1 mM and 1 μM, meeting the demand of assessing drug level in the patient serum. This work creates a new application branch for nitrogen-doped graphene and provides an alternative solution for small molecule analysis

    Effect of Bromine Substitution on the Ion Migration and Optical Absorption in MAPbI<sub>3</sub> Perovskite Solar Cells: The First-Principles Study

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    In the past few years, the remarkable energy conversion efficiency of lead-halide-based perovskite solar cells (PSCs) has drawn extraordinary attention. However, some exposed problems in PSCs such as the low chemical stability and so forth are tough to eliminate. A fundamental understanding of ionic transport at the nanoscale is essential for developing high-performance PSCs based on the anomalous hysteresis current–voltage (<i>I</i>–<i>V</i>) curves and the poor stability. Our work is to understand the ionic transport mechanism by introducing suitable halogen substitution with insignificant impact on light absorption to hinder ion diffusion and thereby to seek a method to improve the stability. Herein, we used first-principles density functional theory (DFT) to calculate the band gaps and the optical absorption coefficients, and the interstitial and the vacancy defect diffusion barriers of halide in the orthogonal phase MAPbX<sub>3</sub> (MA = CH<sub>3</sub>NH<sub>3</sub>, X = I, Br, I<sub>0.5</sub>Br<sub>0.5</sub>) perovskite, respectively. The research results show that a half bromine substitution not only prevents ion migration in perovskite, but also maintains a favorable light absorption capacity. It may be helpful to maintain the PSC’s property of light absorption with a similar atomic substitution. Furthermore, smaller atomic substitution for the halogen atoms may be essential for increasing the diffusion barrier

    Effects of the Mycotoxin Nivalenol on Bovine Articular Chondrocyte Metabolism <i>In Vitro</i>

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    <div><p>Objective</p><p>Kashin-Beck Disease (KBD) is an endemic, age-related degenerative osteoarthropathy and its cause is hypothesised to involve <i>Fusarium</i> mycotoxins. This study investigated the <i>Fusarium</i> mycotoxin Nivalenol (NIV) on the metabolism of bovine articular chondrocytes <i>in vitro</i>.</p><p>Design</p><p>The effect 0.0–0.5 µg/ml NIV on transcript levels of types I and II collagen, aggrecan, matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS) and the tissue inhibitors of MMPs (TIMPs) was investigated using quantitative PCR. Amounts of sulphated glycosaminoglycans, MMPs and TIMPs were assessed using the Dimethylmethylene Blue assay, gelatin zymography and reverse gelatin zymography respectively. Cytoskeletal organisation was analysed using confocal microscopy and cytoskeletal gene and protein levels were measured by quantitative PCR and Western blot analysis, respectively.</p><p>Results</p><p>NIV caused a dose-dependent increase in aggrecan transcription with a concomitant retention of sGAG in the cell lysate. Furthermore, NIV significantly increased MMPs-2, -3 & -9, ADAMTS-4 and -5, and TIMP-2 and -3 transcript levels but inhibited type I collagen, MMP 1 and TIMP 1 mRNA levels. NIV promoted extensive cytoskeletal network remodelling, particularly with vimentin where a dose-dependent peri-nuclear aggregation occurred.</p><p>Conclusion</p><p>NIV exposure to chondrocytes decreased matrix deposition, whilst enhancing selective catabolic enzyme production, suggesting its potential for induction of cellular catabolism. This NIV-induced extracellular matrix remodelling may be due to extensive remodelling/disassembly of the cytoskeletal elements. Collectively, these findings support the hypothesis that trichothecene mycotoxins, and in particular NIV, have the potential to induce matrix catabolism and propagate the pathogenesis of KBD.</p></div

    Nivalenol (NIV) alters the organisation and expression of β-tubulin.

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    <p>Chondrocytes cultured as a high-density monolayer were treated with 0.1, 0.2 or 0.5 µg/ml NIV for 1 day. Untreated cells served as controls. <b>A.</b> Tubulin organisation as detected using anti-tubulin primary and TRITC-conjugated secondary antibodies in conjunction with confocal microscopy; nuclei are counterstained with DAPI. Representative serial sections through the middle of the cell and 3D-reconstructions are presented [scale bar  = 2 µm]. <b>B.</b> β-tubulin mRNA levels were assessed using quantitative PCR. Data were normalised to the housekeeping gene GAPDH and are presented as fold change relative to the untreated cells. <b>C.</b> β-tubulin protein levels were determined by Western blotting (equivalent protein loading) and data presented as fold change relative to the untreated cells [refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109536#pone-0109536-g002" target="_blank">Figure 2</a> for data analysis and statistical representation].</p

    Nivalenol (NIV) modulates MMP expression.

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    <p>Chondrocytes cultured as a high-density monolayer were treated with 0.1, 0.2 or 0.5 µg/ml NIV for 1 day. Untreated cells served as controls. Expression of <b>A.</b> MMP-1, <b>B.</b> MMP-2, <b>C.</b> MMP-3 and <b>D.</b> MMP-9 were assessed using quantitative PCR. Data were normalised to the housekeeping gene GAPDH and are presented as fold change relative to the untreated cells. <b>E.</b> Levels of MMP-2 released into the culture media, after 1 day of NIV treatment, was determined by gelatin zymography; data was normalised to protein content and presented as fold change relative to the untreated cells [refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109536#pone-0109536-g002" target="_blank">Figure 2</a> for data analysis and statistical representation].</p

    Nivalenol (NIV) disassembles the F-actin cytoskeleton and reduces β-actin expression.

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    <p>Chondrocytes cultured as a high-density monolayer were treated with 0.1, 0.2 or 0.5 µg/ml NIV for 1 day. Untreated cells served as controls. <b>A.</b> F-actin filament organisation as detected using Alexa488-phalloidin in conjunction with confocal microscopy; nuclei are counterstained with DAPI. Representative serial sections through the middle of the cell and 3D-reconstructions are presented [scale bar  = 2 µm]. <b>B.</b> β-actin mRNA levels were assessed using quantitative PCR. Data were normalised to the housekeeping gene GAPDH and are presented as fold change relative to the untreated cells. <b>C.</b> β-actin protein levels were determined by Western blotting (equivalent protein loading) and data presented as fold change relative to the untreated cells [refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109536#pone-0109536-g002" target="_blank">Figure 2</a> for data analysis and statistical representation].</p

    Nivalenol (NIV) decreases chondrocyte viability in a dose and duration-dependent manner.

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    <p>Chondrocytes cultured as a high-density monolayer were treated with 0.1 0.2 or 0.5 µg/ml NIV for 1 & 3 days. Cell viability was determined using <b>A.</b> MTT assay, and <b>B.</b> LDH assay. Untreated cells served as controls and were assigned a viability of 100%; cell viability after NIV treatment is relative to the control. Representative data is presented as Mean ±95% CI (n = 6) [** p≤0.01, *** p≤0.001].</p

    Nivalenol (NIV) induces peri-nuclear aggregation of the vimentin cytoskeleton.

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    <p>Chondrocytes cultured as a high-density monolayer were treated with 0.1, 0.2 or 0.5 µg/ml NIV for 1 day. Untreated cells served as controls. Vimentin organisation was detected using anti-vimentin primary and TRITC-conjugated secondary antibodies in conjunction with confocal microscopy; nuclei are counterstained with DAPI. Representative serial sections through the middle of the cell and 3D-reconstructions are presented [scale bar  = 2 µm].</p

    Differential effects of Nivalenol (NIV) on the expression of extracellular matrix components.

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    <p>Chondrocytes cultured as a high-density monolayer were treated with 0.1, 0.2 or 0.5 µg/ml NIV for 1 day. Untreated cells served as controls. Expression of <b>A.</b> Type I collagen, <b>B.</b> Type II collagen, and <b>C.</b> Aggrecan mRNAs were assessed using quantitative PCR. Data were normalised to the housekeeping gene GAPDH and are presented as fold change relative to the untreated cells. <b>D.</b> Total sGAG released into the culture media and sGAG levels in cell lysates (normalised to cell number) after NIV treatment for 1 day was determined using the DMMB assay. Representative data is presented as Mean ±95% CI (n = 6) [<sup>*</sup> p≤0.05, ** p≤0.01, *** p≤0.001 when compared to untreated cells].</p

    Nivalenol (NIV) induces ADAMTS-4 and -5 gene expression.

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    <p>Chondrocytes cultured as a high-density monolayer were treated with 0.1, 0.2 or 0.5 µg/ml NIV for 1 day. Untreated cells served as controls. Expression of <b>A.</b> ADAMTS-4 and <b>B.</b> ADAMTS-5 were assessed using quantitative PCR. Data were normalised to the housekeeping gene GAPDH and are presented as fold change relative to the untreated cells [refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0109536#pone-0109536-g002" target="_blank">Figure 2</a> for data analysis and statistical representation].</p
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