43 research outputs found

    Application of Filtered Model for Reacting Gas–Solid Flows and Optimization in a Large-Scale Methanol-to-Olefin Fluidized-Bed Reactor

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    A reactor model for a methanol-to-olefin (MTO) reaction system was constructed by incorporating a filtered drag model, a filtered gas–solid heat-transfer model, and an MTO kinetic model to probe large-scale reactor behavior and explore optimization. First, the efficiency of several typical gas–solid heat-transfer models and kinetic models was evaluated by comparing predicted results with experimental data. Second, the effect of two significant operation parameters, namely, reaction temperature and water-to-methanol ratio, were studied based on the above-mentioned model. Predictions suggested an optimum catalyst residence time (∼33 min) and an average coke content (∼6.74%) of this MTO system. In addition, relatively high temperature maximized ethylene production, and the water introduced into the feed significantly attenuated coke deposition. This work is the first to conduct coarse-grid simulations by using the developed effective filtered-CFD coupled model to probe the reaction flow and explore optimization for a large-scale MTO reactor

    Defined Nanoscale Chemistry Influences Delivery of Peptido-Toxins for Cancer Therapy

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    <div><p>We present an <i>in-silico-to-in-vitro</i> approach to develop well-defined, self-assembled, rigid-cored polymeric (Polybee) nano-architecture for controlled delivery of a key component of bee venom, melittin. A competitive formulation with lipid-encapsulated (Lipobee) rigid cored micelle is also synthesized. In a series of sequential experiments, we show how nanoscale chemistry influences the delivery of venom toxins for cancer regression and help evade systemic disintegrity and cellular noxiousness. A relatively weaker association of melittin in the case of lipid-based nanoparticles is compared to the polymeric particles revealed by energy minimization and docking studies, which are supported by biophysical studies. For the first time, the authors’ experiment results indicate that melittin can play a significant role in DNA association-dissociation processes, which may be a plausible route for their anticancer activity.</p></div

    Hydrodynamic diameter distribution, anhydrous state particle size, particle height and electrophoretic potential distribution of PRCM, Polybee and LRCM and Lipobee in tabular form.

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    <p>Hydrodynamic diameter distribution, anhydrous state particle size, particle height and electrophoretic potential distribution of PRCM, Polybee and LRCM and Lipobee in tabular form.</p

    Scores of different docking poses of melittin superimposed and energy minimized with lipid or amphiphilic polymer system.

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    <p>Scores of different docking poses of melittin superimposed and energy minimized with lipid or amphiphilic polymer system.</p

    Defined Nanoscale Chemistry Influences Delivery of Peptido-Toxins for Cancer Therapy - Fig 7

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    <p>Defined Nanoscale Chemistry Influences Delivery of Peptido-Toxins for Cancer Therapy</p> - Fig

    Preparation and physico-chemical characterization studies.

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    <p>Synthesis and characterization of rigid core micelles and melittin loaded particles: (a) Synthesis of PRCM and Polybee nanoparticles; (b) representative TEM images of Polybee; (c) representative AFM images of Polybee; (d) Synthesis of LRCM and Lipobee nanoparticles; (e) representative TEM images of Lipobee; (c) representative AFM images of Lipobee; (f) UV-vis spectroscopy of melittin, LRCM, PRCM, Lipobee and Polybee; (g) hydrodynamic diameter distribution (number averaged, nm). TEM samples (20 μL) were prepared on formvar-coated carbon grids and negatively stained with uranyl acetate and vacuum dried before performing the microscopy. Samples (20 μL) were drop casted on freshly cleaved mica sheets and air dried for >24h before performing the tapping mode AFM.</p

    DNA interaction studies.

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    <p>(a) Illustration of docked structure of melittin with DNA. (b) Key interactions of melittin with DNA. Melittin is shown as green links. (c) Molcad surface picture of docked structure.</p

    Molecular docking studies.

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    <p>Super-imposition of the five best docking poses of melittin with lecithin PC and PS<sub>67</sub>-<i>b</i>-PAA<sub>27</sub> polymer: (a) Docking poses of melittin to PS<sub>67</sub>-<i>b</i>-PAA<sub>27</sub> polymer; (b) docking poses of melittin to lecithin PC. The best scored pose is in the green linked chains with the following smaller attachments listed in order according to their score as indicated by their color: Magenta, 2nd; yellow, 3rd; white, 4th, and cyan, 5th.</p

    Release mechanism, systemic toxicity and stability studies.

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    <p>(a) Complementing activation and (b) melittin leaching behavior of Lipobee and Polybees. Free melittin, LRCM and PRCM were used as controls; (c) optical microscopy images of blood smear untreated (i) and treated with melittin (1:10) (ii), LRCM (1:10) (iii), Lipobee (1:10) (iv), PRCM (1:10) (v) and polybee (1:10) (vi), respectively, (with 20x magnification). Melittin- and Lipobee-treated pig blood in the severely clumped, morphologically distorted state are shown in (ii) and (iv). Insets in (ii) and (iv) show red blood cell morphology to emphasize other similar morphological patterns throughout the sample.</p

    Quantitative Analysis of the Enhanced Permeation and Retention (EPR) Effect

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    <div><p>Tumor vasculature is characterized by a variety of abnormalities including irregular architecture, poor lymphatic drainage, and the upregulation of factors that increase the paracellular permeability. The increased permeability is important in mediating the uptake of an intravenously administered drug in a solid tumor and is known as the enhanced permeation and retention (EPR) effect. Studies in animal models have demonstrated a cut-off size of 500 nm - 1 µm for molecules or nanoparticles to extravasate into a tumor, however, surprisingly little is known about the kinetics of the EPR effect. Here we present a pharmacokinetic model to quantitatively assess the influence of the EPR effect on the uptake of a drug into a solid tumor. We use pharmacokinetic data for Doxil and doxorubicin from human clinical trials to illustrate how the EPR effect influences tumor uptake. This model provides a quantitative framework to guide preclinical trials of new chemotherapies and ultimately to develop design rules that can increase targeting efficiency and decrease unwanted side effects in normal tissue.</p></div
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