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Liquid Interface (liquid + interface)
Selected AbstractsMass Transfer in a Flat Gas/Liquid Interface using non-Newtonian MediaCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 10 2003D. Gómez-Díaz Abstract Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non-Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non-Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients. [source] Facilitated Transfer of Alkali Metal Ions by a Tetraester Derivative of Thiacalix[4]arene at the Liquid,Liquid InterfaceELECTROANALYSIS, Issue 12 2008Akgemci, Emine Guler Abstract The facilitated transfer of alkali metal ions (Na+, K+, Rb+, and Cs+) by 25,26,27,28-tetraethoxycarbonylmethoxy-thiacalix[4]arene across the water/1,2-dichloroethane interface was investigated by cyclic voltammetry. The dependence of the half-wave transfer potential on the metal and ligand concentrations was used to formulate the stoichiometric ratio and to evaluate the association constants of the complexes formed between ionophore and metal ions. While the facilitated transfer of Li+ ion was not observed across the water/1,2-dichloroethane interface, the facilitated transfers were observed by formation of 1,:,1 (metal:ionophore) complex for Na+, K+, and Rb+ ions except for Cs+ ion. In the case of Cs+ a 1,:,2 (metal:ionophore) complex was obtained from its special electrochemical response to the variation of ligand concentrations in the organic phase. The logarithms of the complex association constants, for facilitated transfer of Na+, K+, Rb+, and Cs+, were estimated as 6.52, 7.75, 7.91 (log ,1°), and 8.36 (log ,2°), respectively. [source] Rigid Bisphenanthrolines: Synthesis, Structure and Self-Assembly at a Solid,Liquid Interface,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2006Michael Schmittel Abstract Several rigid linear bisphenanthrolines with and without bulky groups at the bisimine sites were synthesized. For three representatives, the solid-state structures were elucidated. Their potential for self-assembled monolayers was explored by scanning tunneling microscopy (STM) at the solid,liquid interface, and the resulting architectures were found to be promising candidates for templating metal-ion nanopatterns. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Supramolecular Crystal Engineering at the Solid,Liquid Interface from First Principles: Toward Unraveling the Thermodynamics of 2D Self-AssemblyADVANCED MATERIALS, Issue 13 2009Carlos-Andres Palma Abstract The formation of highly ordered 2D supramolecular architectures self-assembled at the solid,solution interfaces is subject to complex interactions between the analytes, the solvent, and the substrate. These forces have to be mastered in order to regard self-assembly as an effective bottom-up approach for functional-device engineering. At such interfaces, prediction of the thermodynamics governing the formation of spatially ordered 2D arrangements is far from being fully understood, even for the physisorption of a single molecular component on the basal plane of a flat surface. Two recent contributions on controlled polymorphism and nanopattern formation render it possible to gain semi-quantitative insight into the thermodynamics of physisorption at interfaces, paving the way towards 2D supramolecular crystal engineering. Although in these two works different systems have been chosen to tackle such a complex task, authors showed that the chemical design of molecular building blocks is not the only requirement to fulfill when trying to preprogram self-assembled patterns at the solid,liquid interface. [source] Scanning Probe Studies of Porphyrin Assemblies and Their Supramolecular Manipulation at a Solid,Liquid InterfaceADVANCED MATERIALS, Issue 24 2003J.A.A.W. Elemans Dynamic self-assembly and metal,ligand coordination processes of porphyrin hexamers on a solid,liquid interface have been visualized with scanning tunneling microscopy. The organization of these hexamers into stable and highly organized arrays of "edge-on" or "face-on" oriented molecules can be controlled by the addition of different ditopic axial ligands (see Figure). [source] Titelbild: Dynamers at the Solid,Liquid Interface: Controlling the Reversible Assembly/Reassembly Process between Two Highly Ordered Supramolecular Guanine Motifs (Angew. Chem.ANGEWANDTE CHEMIE, Issue 11 201011/2010) Dynamere in Aktion können mit geeigneten supramolekularen Architekturen an Grenzflächen beobachtet werden. In der Zuschrift auf S.,2007,ff. beschreiben G.,P. Spada, P. Samorì et,al. den Einsatz der Rastertunnelmikroskopie, um die metallvermittelte reversible Anordnung/Neuanordnung von N9 -Alkylguaninmonoschichten auf der submolekularen Ebene zu visualisieren. Durch pH-Wert-Änderung werden an der Graphit-Lösungs-Grenzfläche hoch geordnete Quartett- in bandartige Architekturen überführt. [source] Dynamers at the Solid,Liquid Interface: Controlling the Reversible Assembly/Reassembly Process between Two Highly Ordered Supramolecular Guanine Motifs,ANGEWANDTE CHEMIE, Issue 11 2010Artur Ciesielski Band oder Quartett: Die Zugabe von [2.2.2]Cryptand, Kaliumpicrat (K+(pic),) und Trifluormethansulfonsäure löst eine dynamische Neuanordnung in Octadecylguanin(G)-Monoschichten aus. Die gebildeten Strukturen, die zwischen einem H-Brücken-gebundenen G-Band und einem G-Quartett alternieren, wurden an einer Graphit-flüssig-Grenzfläche mit STM verfolgt (siehe Bild). [source] Nanostructured Catalysts from the Liquid,Liquid InterfaceCHEMCATCHEM, Issue 4 2009Face to Face: Understanding and utilizing nanoscale materials in catalysis requires control not only over size and shape, but also over surface structuring. A recent study by O,Brien,et al. demonstrated the assembly of nanoscale ceria by growth at liquid,liquid interfaces, which, by alteration of growth times, pH,values, and temperatures, affords a high level of control over ceria particle size. [source] A New Method for the Study of Processes at the Liquid,Liquid Interface Using an Array of Microdroplets on a Au ElectrodeCHEMPHYSCHEM, Issue 12 2006Andrew O. Simm Dr. Abstract We report the fabrication of partially blocked gold electrodes, with regularly and hexagonally spaced inert hydrophobic blocks on their surface. The hydrophobic blocks, with diameters of 5 ,m, are used to support liquid 5-nonyl-salicylaldoxime (Acorga-P50) droplets on the surface. By voltametrically monitoring the transport-controlled reduction rate of CuII (in pH 5 solution) at the unblocked part of the gold surface it is possible to deduce, via simulation, the parameters controlling the rate of uptake of CuII at the droplet,aqueous solution interface as the droplet "fills up" with CuII. Experimentally, it is recorded that the reduction current increases until the droplet is filled completely; after this, there is no further noticeable effect of the droplet coating. A rigorous theoretical analysis of the transients permits the deduction of partition coefficients between the aqueous solution and the organic-droplet phase and of diffusion coefficients within the droplet. The partition coefficient for CuII between water and 5-nonyl-salicylaldoxime was found to be 200 at 25,°C and the diffusion coefficient of CuII inside the organic phase was determined to be 5×10,11 cm2,s,1. [source] Insights into the Role of the Liquid,Liquid Interface in Biphasic Reactions: The Reaction of Vitamin B12s(aq) with Vicinal Dibromides(oil)CHEMPHYSCHEM, Issue 12 2005Trevor J. Davies Dr. Abstract Electrocatalytic processes can take place either homogeneously in a single liquid phase or heterogeneously at the liquid,liquid interface formed in emulsions. This Article addresses the question as to whether a change in rate and/or mechanism can occur between the two possibilities. Specifically, cyclic voltammetry and electrosynthetic experiments are used to demonstrate that for the vitamin B12 mediated reduction of vicinal dibromides producing olefins, electric field effects likely operate at the liquid,liquid interface which can change the populations of different conformers relative to the single homogeneous-phase experiment, leading to significant changes in rate. [source] Molecular Arrangement of Fatty Acids at the Solid,Liquid Interface Visualized by Chemical DecorationCHEMPHYSCHEM, Issue 5 2003Stephanie Hoeppener Dr. Finding finely formed fat: A method to visualize the carboxylic groups of a highly ordered fatty acid template layer (see picture) by utilizing small probe molecules is demonstrated. STM investigations of the decorated surface strongly indicate a head-to-head arrangement of the fatty acid molecules at the solid,liquid interface. [source] Fast Ion-Transfer Processes at Nanoscopic Liquid/Liquid Interfaces,ANGEWANDTE CHEMIE, Issue 43 2009Qing Li Mitgehalten: Die schnellsten Geschwindigkeiten für den Ionentransfer an einer Flüssig-flüssig-Grenzfläche wurden mithilfe der Nanopipetten-Voltammetrie ermittelt. Die Voltammogramme des stationären Zustands können mit theoretischen Modellen erklärt werden. Das systematische Unterschätzen von k0 in früheren elektrochemischen Messungen liegt wahrscheinlich an einem ineffizienten Massentransfer zu der relativ großen Grenzfläche. [source] Molecular Tectonics at the Solid/Liquid Interface: Controlling the Nanoscale Geometry, Directionality, and Packing of 1D Coordination Networks on Graphite SurfacesADVANCED MATERIALS, Issue 10-11 2009Artur Ciesielski Supramolecular arrays composed of 1-D coordination networks on surfaces, with nanoscale control over both the geometry and the directionality, are achieved through the design and combination of organic tectons with metal complexes (CoCl2) or metal centers (Pd(BF4)2). Scanning tunneling microscope at the solid/liquid interface allows the visualization of long and shape-persistent arrays, with either linear or zig-zag geometries. [source] Effects of annealing lyophilized and spray-lyophilized formulations of recombinant human interferon-,JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2003Serena D. Webb Abstract The purpose of this study was to examine the effects of adsorption of recombinant human interferon-, (rhIFN-,) on ice surfaces and subsequent drying during processing by spray-lyophilization and lyophilization. Ice/liquid interfacial areas were manipulated by the freezing method as well as by the addition of an annealing step during lyophilization; that is, rhIFN-, adsorption was modified by the addition of nonionic surfactants. rhIFN-, was lyophilized or spray-lyophilized at a concentration of 1 mg/mL in 5% sucrose, 5% hydroxyethyl starch (HES),±,0.03% polysorbate 20 in 140 mM KCl, and 10 mM potassium phosphate, pH 7.5. After the samples were frozen, half were annealed on the lyophilizer shelf. Recovery of soluble protein was measured at intermediate points during processing. On drying, the secondary structure of rhIFN-, was determined by second-derivative infrared (IR) spectroscopy, specific surface areas (SSAs) were measured, scanning electron micrographs (SEM) were taken, and dissolution times were recorded. Adsorption of rhIFN-, to ice/liquid interfaces alone was not responsible for aggregation. Rather, drying was necessary to cause aggregation in lyophilized sucrose formulations. Addition of an annealing step to the lyophilization cycle resulted in more native-like secondary protein structure in the dried solid, eliminated cracking of the dried cakes, and suppressed both the formation of air/liquid interfaces and rhIFN-, aggregation on reconstitution. © 2003 Wiley-Liss, Inc. and the American pharmaceutical Association J Pharm Sci 92:715,729, 2003 [source] Direct Volumetric Measurement of Gas Oversolubility in Nanoliquids: Beyond Henry's LawCHEMPHYSCHEM, Issue 12 2009Marc Pera-Titus Dr. Abstract The properties of condensed matter are strongly affected by confinement and size effects at the nanoscale. Herein, we measured by microvolumetry the increased solubility of H2 in a series of solvents (CHCl3, CCl4, n -hexane, ethanol, and water) when confined in the cavities of mesoporous solids (,-alumina, silica, and MCM-41). Gas/liquid solubilities are enhanced by up to 15 times over the corresponding bulk values for nanoliquid sizes smaller than 15 nm as long as gas/liquid interfaces are mesoconfined in a porous network. Although Henry's law constant apparently no longer applies under these confinement, the concentration of dissolved H2 still increases linearly with increasing pressure in the range 1,5 bar. We discuss the role and main implications of surface excess concentrations at mesoconfined gas/liquid interfaces in enhancing gas solubility. [source] Rigid Bisphenanthrolines: Synthesis, Structure and Self-Assembly at a Solid,Liquid Interface,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2006Michael Schmittel Abstract Several rigid linear bisphenanthrolines with and without bulky groups at the bisimine sites were synthesized. For three representatives, the solid-state structures were elucidated. Their potential for self-assembled monolayers was explored by scanning tunneling microscopy (STM) at the solid,liquid interface, and the resulting architectures were found to be promising candidates for templating metal-ion nanopatterns. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Selective Formation of Bi-Component Arrays Through H-Bonding of Multivalent Molecular ModulesADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Luc Piot Abstract Here, the formation of discrete supramolecular mono- and bi-component architectures from novel and multivalent molecular modules bearing complementary recognition moieties that are prone to undergo multiple H-bonds, such as 2,6-di(acetylamino)pyridine and uracil residues, is described. These nanostructured H-bonded arrays, including dimeric and pentameric species, are thoroughly characterized in solution by NMR, in the solid state by FT-IR, and at the solid,liquid interface by means of scanning tunneling microscopy. The employed strategy is extremely versatile as it relies on the tuning of the valency, size, and geometry of the molecular modules; thus, it may be of interest for the bottom-up fabrication of nanostructured functional materials with sub-nanometer precision. [source] Transient flow patterns in a microfluidic chip with a complicated microstructureHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2008Wei Zhang Abstract The transient flow patterns of the boiling flow in a microfluidic chip with a complicated microstructure were studied at low mass fluxes and high heat fluxes. The periodic flow pattern in the timescale of milliseconds and the stratified flow pattern were observed. For a specific separated zone, the liquid film thickness was increased along the flow direction and the dry-out always occurred earlier at the microchannel upstream rather than downstream. However, for different microchannel zones, the dry-out took place earlier in the downstream zone. It was determined that the low liquid Froude number was responsible for the formation of the stratified flow. The large boiling number resulted in a large shear stress at the vapor,liquid interface, leading to the accumulation of the liquid in the microchannel downstream, causing the increased liquid film thickness along the flow direction. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(4): 224,231, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20201 [source] Supramolecular Crystal Engineering at the Solid,Liquid Interface from First Principles: Toward Unraveling the Thermodynamics of 2D Self-AssemblyADVANCED MATERIALS, Issue 13 2009Carlos-Andres Palma Abstract The formation of highly ordered 2D supramolecular architectures self-assembled at the solid,solution interfaces is subject to complex interactions between the analytes, the solvent, and the substrate. These forces have to be mastered in order to regard self-assembly as an effective bottom-up approach for functional-device engineering. At such interfaces, prediction of the thermodynamics governing the formation of spatially ordered 2D arrangements is far from being fully understood, even for the physisorption of a single molecular component on the basal plane of a flat surface. Two recent contributions on controlled polymorphism and nanopattern formation render it possible to gain semi-quantitative insight into the thermodynamics of physisorption at interfaces, paving the way towards 2D supramolecular crystal engineering. Although in these two works different systems have been chosen to tackle such a complex task, authors showed that the chemical design of molecular building blocks is not the only requirement to fulfill when trying to preprogram self-assembled patterns at the solid,liquid interface. [source] Numerical approximation of a thermally driven interface using finite elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2003P. Zhao Abstract A two-dimensional finite element model for dendritic solidification has been developed that is based on the direct solution of the energy equation over a fixed mesh. The model tracks the position of the sharp solid,liquid interface using a set of marker points placed on the interface. The simulations require calculation of the temperature gradients on both sides of the interface in the direction normal to it; at the interface the heat flux is discontinuous due to the release of latent heat during the solidification (melting) process. Two ways to calculate the temperature gradients at the interface, evaluating their interpolants at Gauss points, were proposed. Using known one- and two-dimensional solutions to stable solidification problems (the Stefan problem), it was shown that the method converges with second-order accuracy. When applied to the unstable solidification of a crystal into an undercooled liquid, it was found that the numerical solution is extremely sensitive to the mesh size and the type of approximation used to calculate the temperature gradients at the interface, i.e. different approximations and different meshes can yield different solutions. The cause of these difficulties is examined, the effect of different types of interpolation on the simulations is investigated, and the necessary criteria to ensure converged solutions are established. Copyright © 2003 John Wiley & Sons, Ltd. [source] Dendritic solidification of binary alloys with free and forced convectionINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2005P. Zhao Abstract Dendritic solidification with forced convection and free convection driven by contraction and thermo- solutal buoyancy is simulated in two-dimensional space using a sharp-interface model. Both pure substances and alloys are considered. The model is formulated using the finite element method and works directly with primitive variables. The coupled energy- and solutal concentration-equations, along with the Navier,Stokes equations for incompressible flow, are solved using different meshes. Temperature is solved in a fixed mesh that covers the whole domain (solid + liquid) where the solid,liquid interface is explicitly tracked using marker points. The concentration and momentum equations are solved in the liquid region using an adaptive mesh of triangular elements that conforms to the interface. The velocity boundary conditions are applied directly on the interface. The model is validated using a series of problems that have analytical, experimental and numerical results. Four simulations are presented: (1) crystal growth of succinonitrile with thermal convection under two small undercoolings; (2) dendritic growth into an undercooled pure melt with a uniform forced flow; (3) equiaxial dendritic growth of a pure substance and an alloy with contraction-induced convection; and (4) directional solidification of Pb,0.2 wt% Sb alloy with convection driven by the combined action of contraction, thermal and solutal buoyancy. Some of the simulation results are compared to those reported using other methods including the phase-field method; others are new. In each case, the effects of convection on dendritic solidification are analysed. Copyright © 2005 John Wiley & Sons, Ltd. [source] Scanning Probe Studies of Porphyrin Assemblies and Their Supramolecular Manipulation at a Solid,Liquid InterfaceADVANCED MATERIALS, Issue 24 2003J.A.A.W. Elemans Dynamic self-assembly and metal,ligand coordination processes of porphyrin hexamers on a solid,liquid interface have been visualized with scanning tunneling microscopy. The organization of these hexamers into stable and highly organized arrays of "edge-on" or "face-on" oriented molecules can be controlled by the addition of different ditopic axial ligands (see Figure). [source] Growth of large protein crystals by a large-scale hanging-drop methodJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2010Keisuke Kakinouchi A method for growing large protein crystals is described. In this method, a cut pipette tip is used to hang large-scale droplets (maximum volume 200,µl) consisting of protein and precipitating agents. A crystal grows at the vapor,liquid interface; thereafter the grown crystal can be retrieved by droplet,droplet contact both for repeated macroseeding and for mounting crystals in a capillary. Crystallization experiments with peroxiredoxin of Aeropyrum pernix K1 (thioredoxin peroxidase, ApTPx) and hen egg white lysozyme demonstrated that this large-scale hanging-drop method could produce a large-volume crystal very effectively. A neutron diffraction experiment confirmed that an ApTPx crystal (6.2,mm3) obtained by this method diffracted to beyond 3.5,Å resolution. [source] Interfacial formation of porous membranes with poly(ethylene glycol) in a microfluidic environmentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Dongshin Kim Abstract In a microfluidic environment, the liquid,liquid interface, formed by laminar flows of immiscible solutions, can be used to generate thin membranes via interfacial polymerization. Because these thin nylon membranes have a very small pore size or lack porosity entirely, their utilization in some biological applications is greatly limited. We introduce an in situ fabrication method using the interfacial reaction of a two-phase system to generate a porous nylon membrane. The membranes were characterized with scanning electron microscopy and fluorescent beads. Scanning electron microscopy micrographs verified the asymmetrical structure of the porous membrane, and the membrane pore sizes ranged from 0.1 to 1 ,m. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008. [source] One-dimensional model of vacuum filtration of compressible flocculated suspensionsAICHE JOURNAL, Issue 10 2010Anthony D. Stickland Abstract This work details the one-dimensional modeling of the different processes that may occur during the vacuum filtration of compressible flocculated suspensions. Depending on the operating conditions of the applied pressure and the initial solids concentration relative to the material properties of the compressive yield stress and the effective capillary pressure at the air,liquid interface, the dewatering process undergoes a combination of cake formation, consolidation, and/or desaturation. Mathematical models for these processes based on the compressional rheology approach are presented and appropriate solution methods outlined. Results using customary material properties are given for different operating conditions to illustrate the three dewatering processes. This approach lays the theoretical basis for further work understanding two- and three-dimensional effects during desaturation, such as cracking and wall detachment. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Passage of a bubble through a liquid,liquid interfaceAICHE JOURNAL, Issue 3 2008N. Dietrich Abstract The aim of this study is to investigate the bubble passage at a liquid,liquid interface using a high-speed video camera (950 images per second) and a Particle Image Velocimetry (PIV) system. Experiments were conducted in a square Plexiglas column of 0.1 m. Bubbles were generated through a submerged orifice (D = 1 × 10,3 m). The Newtonian Emkarox (HV45) solution was employed for the heavy phase whereas two different organic liquids of different viscosity (Silicone oil 10 mPa s and 100 mPa s) were used as light phase. Experimental results show the effect of the bubble size and the viscosity of the light phase on the retention time, the length of the column of fluid entrained behind the bubble, the bubble velocity as well as the velocity fields at the liquid,liquid interface. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] Characterization of antibody aggregation: Role of buried, unpaired cysteines in particle formationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2010Stephen R. Brych Abstract Proteins are susceptible to degradation upon exposure to a variety of stresses during product manufacturing, transportation and storage. In this study, we investigated the aggregation properties of a monoclonal antibody during agitation stress. Agitation exclusively led to insoluble aggregates, or particle formation. Removal or modification of the air,liquid interface with a surfactant (e.g., polysorbate) abrogated particle formation. The supernatant postagitation was analyzed using SE-HPLC, FTIR, and AUC analyses and revealed no changes in conformation and aggregation profile when compared to the nonagitated antibody sample. The antibody particles were comprised of a combination of nonnative intermolecular disulfide-linked covalent as well as noncovalent interactions. Analysis of the antibody's unpaired cysteines revealed that the nonnative intermolecular disulfide bonds were formed through buried cysteines, which suggested at least partial unfolding of the antibody domains. FTIR analysis indicated that the particulated antibody maintained significant native-like secondary structure suggesting that particle formation led to minimal structure changes, but capable of exposing free cysteines to solvent to form the nonnative intermolecular disulfide bonds. The results presented in this study indicate the importance of the interactions between the antibody and the air,liquid interface during agitation in the formation of particles and suggests that reduced disulfide bonds may play a significant role in the particulation reaction. This phenomenon can be applicable to other proteins with similar free cysteine and structural characteristics. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:764,781, 2010 [source] Evaluation of human nasal RPMI 2650 cells grown at an air,liquid interface as a model for nasal drug transport studiesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2008Shuhua Bai Abstract This study tests the hypothesis that human nasal RPMI 2650 cells grown at an air,liquid interface is a feasible model for drug transport studies via the nasal route. RPMI 2650 cells were cultured in Eagle's minimal essential medium (MEM) at both air,liquid and liquid,liquid interfaces. For each culture regimen, monolayer integrity was tested by measuring the transepithelial resistance (TEER) as well as the transport of paracellular and transcellular markers across the monolayer. The expression of tight junction proteins,differentiation markers,in cells of the different monolayers was studied by western blot analysis and confocal microscopy. The highest TEER values (192,±,3 ,,·,cm2) were observed for RPMI 2650 cells seeded onto collagen-coated permeable polytetrafluoroethylene inserts and grown at an air,liquid interface for 10 days; a seeding density of 4,×,105/cm2 generated and maintained a cell monolayer with suitable barrier properties at days 9,12. Microscopic examination showed that RPMI 2650 cells grown on filter inserts formed a fully confluent monolayer. The apparent permeability coefficients of the paracellular marker, [14C] mannitol, and the transcellular marker, [3H] propranolol, were 5.07,±,0.01,×,10,6 cm/s and 16.1,±,0.1,×,10,6 cm/s, respectively. Western blot analysis indicated the presence of four tight junction proteins: ZO-1, occludin, claudin-1 and E-cadherin; and the quantities of ZO-1, occludin, and E-cadherin were significantly higher in cells grown at an air,liquid interface than in cells grown at a liquid,liquid interface. Confocal microscopic studies showed ZO-1, F-actin, occludin and claudin-1 proteins at cell-cell contacts and revealed significant differences in the distributions and densities of ZO-1 protein in cells grown at the two types of interface. The data indicate that RPMI 2650 cells grown at an air,liquid interface form polarized monolayers with the cells interconnected by tight junction proteins. This human nasal cell line model could provide a useful tool for in vitro screening of nasal drug candidates. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1165,1178, 2008 [source] Lipase deactivation at gas,liquid interface and its subsequent reactivationAICHE JOURNAL, Issue 6 2000N. S. Patil First page of article [source] Dissipative Particle Dynamics Simulations of Polymer Brushes: Comparison with Molecular Dynamics SimulationsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2006Sandeep Pal Abstract Summary: The structure of polymer brushes is investigated by dissipative particle dynamics (DPD) simulations that include explicit solvent particles. With an appropriate choice of the DPD interaction parameters , we obtain good agreement with previous molecular dynamics (MD) results where the good solvent behavior has been modeled by an effective Lennard,Jones potential. The present results confirm that DPD simulation techniques can be applied for large length scale simulations of polymer brushes. A relation between the different length scales and is established. Polymer brush at a solid,liquid interface. [source] | ||||||||||||||||||||||||||||||||||