Ethanol steam reforming kinetics of a Pd-Ag membrane reactor

Energy Technology Data Exchange (ETDEWEB)

Tosti, Silvano; Borelli, Rodolfo; Borgognoni, Fabio [ENEA, Dipartimento FPN, C.R. ENEA Frascati, Via E. Fermi 45, Frascati (RM) I-00044 (Italy); Basile, Angelo [Institute on Membrane Technology, ITM-CNR, c/o Univ. of Calabria, via P. Bucci, Cubo 17/C, 87030 Rende (CS) (Italy); Castelli, Stefano [ENEA, Dipartimento ACS, C.R. ENEA Casaccia, Via Anguillarese 301, Roma I-00123 (Italy); Fabbricino, Massimiliano; Licusati, Celeste [Dept. of Hydraulic and Environmental Engineering, Univ. of Naples Federico II, Via Claudio 21, Naples 80125 (Italy); Gallucci, Fausto [Fundamentals of Chemical Reaction Engineering Group, Faculty of Science and Technology, University of Twente, Enschede (Netherlands)

2009-06-15

The ethanol steam reforming reaction carried out in a Pd-based tubular membrane reactor has been modelled via a finite element code. The model considers the membrane tube divided into finite volume elements where the mass balances for both lumen and shell sides are carried out accordingly to the reaction and permeation kinetics. Especially, a simplified ''power law'' has been applied for the reaction kinetics: the comparison with experimental data obtained by using three different kinds of catalyst (Ru, Pt and Ni based) permitted defining the coefficients of the kinetics expression as well as to validate the model. Based on the Damkohler-Peclet analysis, the optimization of the membrane reformer has been also approached. (author)

The glycocalyx promotes cooperative binding and clustering of adhesion receptors.

Science.gov (United States)

Xu, Guang-Kui; Qian, Jin; Hu, Jinglei

2016-05-18

Cell adhesion plays a pivotal role in various biological processes, e.g., immune responses, cancer metastasis, and stem cell differentiation. The adhesion behaviors depend subtly on the binding kinetics of receptors and ligands restricted at the cell-substrate interfaces. Although much effort has been directed toward investigating the kinetics of adhesion molecules, the role of the glycocalyx, anchored on cell surfaces as an exterior layer, is still unclear. In this paper, we propose a theoretical approach to study the collective binding kinetics of a few and a large number of binders in the presence of the glycocalyx, representing the cases of initial and mature adhesions of cells, respectively. The analytical results are validated by finding good agreement with our Monte Carlo simulations. In the force loading case, the on-rate and affinity increase as more bonds form, whereas this cooperative effect is not observed in the displacement loading case. The increased thickness and stiffness of the glycocalyx tend to decrease the affinity for a few bonds, while they have less influence on the affinity for a large number of bonds. Moreover, for a flexible membrane with thermally-excited shape fluctuations, the glycocalyx is exhibited to promote the formation of bond clusters, mainly due to the cooperative binding of binders. This study helps to understand the cooperative kinetics of adhesion receptors under physiologically relevant loading conditions and sheds light on the novel role of the glycocalyx in cell adhesion.

Chitosan-Coated Collagen Membranes Promote Chondrocyte Adhesion, Growth, and Interleukin-6 Secretion

Directory of Open Access Journals (Sweden)

Nabila Mighri

2015-11-01

Full Text Available Designing scaffolds made from natural polymers may be highly attractive for tissue engineering strategies. We sought to produce and characterize chitosan-coated collagen membranes and to assess their efficacy in promoting chondrocyte adhesion, growth, and cytokine secretion. Porous collagen membranes were placed in chitosan solutions then crosslinked with glutaraldehyde vapor. Fourier transform infrared (FTIR analyses showed elevated absorption at 1655 cm-1 of the carbon–nitrogen (N=C bonds formed by the reaction between the (NH2 of the chitosan and the (C=O of the glutaraldehyde. A significant peak in the amide II region revealed a significant deacetylation of the chitosan. Scanning electron microscopy (SEM images of the chitosan-coated membranes exhibited surface variations, with pore size ranging from 20 to 50 µm. X-ray photoelectron spectroscopy (XPS revealed a decreased C–C groups and an increased C–N/C–O groups due to the reaction between the carbon from the collagen and the NH2 from the chitosan. Increased rigidity of these membranes was also observed when comparing the chitosan-coated and uncoated membranes at dried conditions. However, under wet conditions, the chitosan coated collagen membranes showed lower rigidity as compared to dried conditions. Of great interest, the glutaraldehyde-crosslinked chitosan-coated collagen membranes promoted chondrocyte adhesion, growth, and interleukin (IL-6 secretion. Overall results confirm the feasibility of using designed chitosan-coated collagen membranes in future applications, such as cartilage repair.

Thermo-elasticity and adhesion as regulators of cell membrane architecture and function

International Nuclear Information System (INIS)

Sackmann, Erich

2006-01-01

Elastic forces and structural phase transitions control the architecture and function of bio-membranes from the molecular to the microscopic scale of organization. The multi-component lipid bilayer matrix behaves as a pseudo-ternary system. Together with elastically and electrostatically mediated specific lipid-protein interaction mechanisms, fluid-fluid phase separation can occur at physiological temperatures. This can drive the transient generation of micro-domains of distinct composition within multi-component lipid-protein alloys, enabling cells to optimize the efficiency of biochemical reactions by facilitating or inhibiting the access of enzymes by distinct substrates or regulatory proteins. Together with global shape changes governed by the principle of minimum bending energy and induced curvature by macromolecular adsorption, phase separation processes can also play a key role for the sorting of lipids and proteins between intracellular compartments during the vesicle mediated intracellular material transport. Cell adhesion is another example of mechanical force controlled membrane processes. By interplay of attractive lock and key forces, long range disjoining pressures mediated by repeller molecules or membrane undulations and elastic interfacial forces, adhesion induced domain formation can play a dual role for the immunological stimulation of lymphocytes and for the rapid control of the adhesion strength. The present picture of the thermo-elastic control of membrane processes based on concepts of local thermal equilibrium is still rudimentary and has to be extended in the future to account for the intrinsic non-equilibrium situation associated with the constant restructuring of the cellular compartments on a timescale of minutes. (topical review)

Local elasticity and adhesion of nanostructures on Drosophila melanogaster wing membrane studied using atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Wagner, Ryan, E-mail: rbwagner@purdue.edu [School of Mechanical Engineering, Purdue University, West Lafayette (United States); Brick Nanotechnology Center, Purdue University, West Lafayette (United States); Pittendrigh, Barry R. [Department of Entomology, University of Illinois, Champaign (United States); Raman, Arvind, E-mail: raman@purdue.edu [School of Mechanical Engineering, Purdue University, West Lafayette (United States); Brick Nanotechnology Center, Purdue University, West Lafayette (United States)

2012-10-15

Highlights: Black-Right-Pointing-Pointer We studied the wing membrane of Drosophila melanogaster with atomic force microscopy. Black-Right-Pointing-Pointer We report the structure, elasticity, and adhesion on the wing membrane in air and nitrogen environments. Black-Right-Pointing-Pointer Results provide insight into the nature of the wing membrane enabling the development of biomimetic surface and micro air vehicles. - Abstract: Insect wings have a naturally occurring, complex, functional, hierarchical microstructure and nanostructure, which enable a remarkably water-resistant and self-cleaning surface. Insect wings are used as a basis for engineering biomimetic materials; however, the material properties of these nanostructures such as local elastic modulus and adhesion are poorly understood. We studied the wings of the Canton-S strain of Drosophila melanogaster (hereafter referred to as Drosophila) with atomic force microscopy (AFM) to quantify the local material properties of Drosophila wing surface nanostructures. The wings are found to have a hierarchical structure of 10-20 {mu}m long, 0.5-1 {mu}m diameter hair, and at a much smaller scale, 100 nm diameter and 30-60 nm high bumps. The local properties of these nanoscale bumps were studied under ambient and dry conditions with force-volume AFM. The wing membrane was found to have a elastic modulus on the order of 1000 MPa and the work of adhesion between the probe and wing membrane surface was found to be on the order of 100 mJ/m{sup 2}, these properties are the same order of magnitude as common thermoplastic polymers such as polyethylene. The difference in work of adhesion between the nanoscale bump and membrane does not change significantly between ambient (relative humidity of 30%) or dry conditions. This suggests that the nanoscale bumps and the surrounding membrane are chemically similar and only work to increase hydrophobicity though surface roughening or the geometric lotus effect.

Local elasticity and adhesion of nanostructures on Drosophila melanogaster wing membrane studied using atomic force microscopy

International Nuclear Information System (INIS)

Wagner, Ryan; Pittendrigh, Barry R.; Raman, Arvind

2012-01-01

Highlights: ► We studied the wing membrane of Drosophila melanogaster with atomic force microscopy. ► We report the structure, elasticity, and adhesion on the wing membrane in air and nitrogen environments. ► Results provide insight into the nature of the wing membrane enabling the development of biomimetic surface and micro air vehicles. - Abstract: Insect wings have a naturally occurring, complex, functional, hierarchical microstructure and nanostructure, which enable a remarkably water-resistant and self-cleaning surface. Insect wings are used as a basis for engineering biomimetic materials; however, the material properties of these nanostructures such as local elastic modulus and adhesion are poorly understood. We studied the wings of the Canton-S strain of Drosophila melanogaster (hereafter referred to as Drosophila) with atomic force microscopy (AFM) to quantify the local material properties of Drosophila wing surface nanostructures. The wings are found to have a hierarchical structure of 10–20 μm long, 0.5–1 μm diameter hair, and at a much smaller scale, 100 nm diameter and 30–60 nm high bumps. The local properties of these nanoscale bumps were studied under ambient and dry conditions with force-volume AFM. The wing membrane was found to have a elastic modulus on the order of 1000 MPa and the work of adhesion between the probe and wing membrane surface was found to be on the order of 100 mJ/m 2 , these properties are the same order of magnitude as common thermoplastic polymers such as polyethylene. The difference in work of adhesion between the nanoscale bump and membrane does not change significantly between ambient (relative humidity of 30%) or dry conditions. This suggests that the nanoscale bumps and the surrounding membrane are chemically similar and only work to increase hydrophobicity though surface roughening or the geometric lotus effect.

An adhesion-based method for plasma membrane isolation: evaluating cholesterol extraction from cells and their membranes.

Science.gov (United States)

Bezrukov, Ludmila; Blank, Paul S; Polozov, Ivan V; Zimmerberg, Joshua

2009-11-15

A method to isolate large quantities of directly accessible plasma membrane from attached cells is presented. The method is based on the adhesion of cells to an adsorbed layer of polylysine on glass plates, followed by hypotonic lysis with ice-cold distilled water and subsequent washing steps. Optimal conditions for coating glass plates and time for cell attachment were established. No additional chemical or mechanical treatments were used. Contamination of the isolated plasma membrane by cell organelles was less than 5%. The method uses inexpensive, commercially available polylysine and reusable glass plates. Plasma membrane preparations can be made in 15 min. Using this method, we determined that methyl-beta-cyclodextrin differentially extracts cholesterol from fibroblast cells and their plasma membranes and that these differences are temperature dependent. Determination of the cholesterol/phospholipid ratio from intact cells does not reflect methyl-beta-cyclodextrin plasma membrane extraction properties.

Amyloid protein unfolding and insertion kinetics on neuronal membrane mimics

Science.gov (United States)

Qiu, Liming; Buie, Creighton; Vaughn, Mark; Cheng, Kwan

2010-03-01

Atomistic details of beta-amyloid (Aβ ) protein unfolding and lipid interaction kinetics mediated by the neuronal membrane surface are important for developing new therapeutic strategies to prevent and cure Alzheimer's disease. Using all-atom MD simulations, we explored the early unfolding and insertion kinetics of 40 and 42 residue long Aβ in binary lipid mixtures with and without cholesterol that mimic the cholesterol-depleted and cholesterol-enriched lipid nanodomains of neurons. The protein conformational transition kinetics was evaluated from the secondary structure profile versus simulation time plot. The extent of membrane disruption was examined by the calculated order parameters of lipid acyl chains and cholesterol fused rings as well as the density profiles of water and lipid headgroups at defined regions across the lipid bilayer from our simulations. Our results revealed that both the cholesterol content and the length of the protein affect the protein-insertion and membrane stability in our model lipid bilayer systems.

Regulation of adhesion behavior of murine macrophage using supported lipid membranes displaying tunable mannose domains

International Nuclear Information System (INIS)

Kaindl, T; Oelke, J; Kaufmann, S; Tanaka, M; Pasc, A; Konovalov, O V; Funari, S S; Engel, U; Wixforth, A

2010-01-01

Highly uniform, strongly correlated domains of synthetically designed lipids can be incorporated into supported lipid membranes. The systematic characterization of membranes displaying a variety of domains revealed that the equilibrium size of domains significantly depends on the length of fluorocarbon chains, which can be quantitatively interpreted within the framework of an equivalent dipole model. A mono-dispersive, narrow size distribution of the domains enables us to treat the inter-domain correlations as two-dimensional colloidal crystallization and calculate the potentials of mean force. The obtained results demonstrated that both size and inter-domain correlation can precisely be controlled by the molecular structures. By coupling α-D-mannose to lipid head groups, we studied the adhesion behavior of the murine macrophage (J774A.1) on supported membranes. Specific adhesion and spreading of macrophages showed a clear dependence on the density of functional lipids. The obtained results suggest that such synthetic lipid domains can be used as a defined platform to study how cells sense the size and distribution of functional molecules during adhesion and spreading.

Single Molecule Kinetics of ENTH Binding to Lipid Membranes

Energy Technology Data Exchange (ETDEWEB)

Rozovsky, Sharon [Univ. of Delaware, Newark, DE (United States); Forstner, Martin B. [Syracuse Univ., NY (United States); Sondermann, Holger [Cornell Univ., Ithaca, NY (United States); Groves, Jay T. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2012-04-03

Transient recruitment of proteins to membranes is a fundamental mechanism by which the cell exerts spatial and temporal control over proteins’ localization and interactions. Thus, the specificity and the kinetics of peripheral proteins’ membrane residence are an attribute of their function. In this article, we describe the membrane interactions of the interfacial epsin N-terminal homology (ENTH) domain with its target lipid phosphatidylinositol (4,5)-bisphosphate (PtdIns(4,5)P₂). The direct visualization and quantification of interactions of single ENTH molecules with supported lipid bilayers is achieved using total internal reflection fluorescence microscopy (TIRFM) with a time resolution of 13 ms. This enables the recording of the kinetic behavior of ENTH interacting with membranes with physiologically relevant concentrations of PtdIns(4,5)P₂ despite the low effective binding affinity. Subsequent single fluorophore tracking permits us to build up distributions of residence times and to measure ENTH dissociation rates as a function of membrane composition. In addition, due to the high time resolution, we are able to resolve details of the motion of ENTH associated with a simple, homogeneous membrane. In this case ENTH’s diffusive transport appears to be the result of at least three different diffusion processes.

Kinetic models of controllable pore growth of anodic aluminum oxide membrane

Science.gov (United States)

Huang, Yan; Zeng, Hong-yan; Zhao, Ce; Qu, Ye-qing; Zhang, Pin

2012-06-01

An anodized Al2O3 (AAO) membrane with apertures about 72 nm in diameter was prepared by two-step anodic oxidation. The appearance and pore arrangement of the AAO membrane were characterized by energy dispersive x-ray spectroscopy and scanning electron microscopy. It was confirmed that the pores with high pore aspect ratio were parallel, well-ordered, and uniform. The kinetics of pores growth in the AAO membrane was derived, and the kinetic models showed that pores stopped developing when the pressure ( σ) trended to equal the surface tension at the end of anodic oxidation. During pore expansion, the effects of the oxalic acid concentration and expansion time on the pore size were investigated, and the kinetic behaviors were explained with two kinetic models derived in this study. They showed that the pore size increased with extended time ( r= G· t+ G'), but decreased with increased concentration ( r = - K·ln c- K') through the derived mathematic formula. Also, the values of G, G', K, and K' were derived from our experimental data.

Dynamic bio-adhesion of polymer nanoparticles on MDCK epithelial cells and its impact on bio-membranes, endocytosis and paracytosis.

Science.gov (United States)

He, Bing; Yuan, Lan; Dai, Wenbing; Gao, Wei; Zhang, Hua; Wang, Xueqing; Fang, Weigang; Zhang, Qiang

2016-03-21

Nowadays, concern about the use of nanotechnology for biomedical application is unprecedentedly increasing. In fact, nanosystems applied for various potential clinical uses always have to cross the primary biological barrier consisting of epithelial cells. However, little is really known currently in terms of the influence of the dynamic bio-adhesion of nanosystems on bio-membranes as well as on endocytosis and transcytosis. This was investigated here using polymer nanoparticles (PNs) and MDCK epithelial cells as the models. Firstly, the adhesion of PNs on cell membranes was found to be time-dependent with a shift of both location and dispersion pattern, from the lateral adhesion of mainly mono-dispersed PNs initially to the apical coverage of the PN aggregate later. Then, it was interesting to observe in this study that the dynamic bio-adhesion of PNs only affected their endocytosis but not their transcytosis. It was important to find that the endocytosis of PNs was not a constant process. A GM1 dependent CDE (caveolae dependent endocytosis) pathway was dominant in the preliminary stage, followed by the co-existence of a CME (clathrin-mediated endocytosis) pathway for the PN aggregate at a later stage, in accordance with the adhesion features of PNs, suggesting the modification of PN adhesion patterns on the endocytosis pathways. Next, the PN adhesion was noticed to affect the structure of cell junctions, via altering the extra- and intra-cellular calcium levels, leading to the enhanced paracellular transport of small molecules, but not favorably enough for the obviously increased passing of PNs themselves. Finally, FRAP and other techniques all demonstrated the obvious impact of PN adhesion on the membrane confirmation, independent of the adhesion location and time, which might lower the threshold for the internalization of PNs, even their aggregates. Generally, these findings confirm that the transport pathway mechanism of PNs through epithelial cells is rather

Dynamic bio-adhesion of polymer nanoparticles on MDCK epithelial cells and its impact on bio-membranes, endocytosis and paracytosis

Science.gov (United States)

He, Bing; Yuan, Lan; Dai, Wenbing; Gao, Wei; Zhang, Hua; Wang, Xueqing; Fang, Weigang; Zhang, Qiang

2016-03-01

Nowadays, concern about the use of nanotechnology for biomedical application is unprecedentedly increasing. In fact, nanosystems applied for various potential clinical uses always have to cross the primary biological barrier consisting of epithelial cells. However, little is really known currently in terms of the influence of the dynamic bio-adhesion of nanosystems on bio-membranes as well as on endocytosis and transcytosis. This was investigated here using polymer nanoparticles (PNs) and MDCK epithelial cells as the models. Firstly, the adhesion of PNs on cell membranes was found to be time-dependent with a shift of both location and dispersion pattern, from the lateral adhesion of mainly mono-dispersed PNs initially to the apical coverage of the PN aggregate later. Then, it was interesting to observe in this study that the dynamic bio-adhesion of PNs only affected their endocytosis but not their transcytosis. It was important to find that the endocytosis of PNs was not a constant process. A GM1 dependent CDE (caveolae dependent endocytosis) pathway was dominant in the preliminary stage, followed by the co-existence of a CME (clathrin-mediated endocytosis) pathway for the PN aggregate at a later stage, in accordance with the adhesion features of PNs, suggesting the modification of PN adhesion patterns on the endocytosis pathways. Next, the PN adhesion was noticed to affect the structure of cell junctions, via altering the extra- and intra-cellular calcium levels, leading to the enhanced paracellular transport of small molecules, but not favorably enough for the obviously increased passing of PNs themselves. Finally, FRAP and other techniques all demonstrated the obvious impact of PN adhesion on the membrane confirmation, independent of the adhesion location and time, which might lower the threshold for the internalization of PNs, even their aggregates. Generally, these findings confirm that the transport pathway mechanism of PNs through epithelial cells is rather

State diagram for adhesion dynamics of deformable capsules under shear flow.

Science.gov (United States)

Luo, Zheng Yuan; Bai, Bo Feng

2016-08-17

Due to the significance of understanding the underlying mechanisms of cell adhesion in biological processes and cell capture in biomedical applications, we numerically investigate the adhesion dynamics of deformable capsules under shear flow by using a three-dimensional computational fluid dynamic model. This model is based on the coupling of the front tracking-finite element method for elastic mechanics of the capsule membrane and the adhesion kinetics simulation for adhesive interactions between capsules and functionalized surfaces. Using this model, three distinct adhesion dynamic states are predicted, such as detachment, rolling and firm-adhesion. Specifically, the effects of capsule deformability quantified by the capillary number on the transitions of these three dynamic states are investigated by developing an adhesion dynamic state diagram for the first time. At low capillary numbers (e.g. Ca state no longer appears, since capsules exhibit large deviation from the spherical shape.

Cell-Adhesive Bioinspired and Catechol-Based Multilayer Freestanding Membranes for Bone Tissue Engineering

Directory of Open Access Journals (Sweden)

Maria P. Sousa

2017-10-01

Full Text Available Mussels are marine organisms that have been mimicked due to their exceptional adhesive properties to all kind of surfaces, including rocks, under wet conditions. The proteins present on the mussel’s foot contain 3,4-dihydroxy-l-alanine (DOPA, an amino acid from the catechol family that has been reported by their adhesive character. Therefore, we synthesized a mussel-inspired conjugated polymer, modifying the backbone of hyaluronic acid with dopamine by carbodiimide chemistry. Ultraviolet–visible (UV–Vis spectroscopy and nuclear magnetic resonance (NMR techniques confirmed the success of this modification. Different techniques have been reported to produce two-dimensional (2D or three-dimensional (3D systems capable to support cells and tissue regeneration; among others, multilayer systems allow the construction of hierarchical structures from nano- to macroscales. In this study, the layer-by-layer (LbL technique was used to produce freestanding multilayer membranes made uniquely of chitosan and dopamine-modified hyaluronic acid (HA-DN. The electrostatic interactions were found to be the main forces involved in the film construction. The surface morphology, chemistry, and mechanical properties of the freestanding membranes were characterized, confirming the enhancement of the adhesive properties in the presence of HA-DN. The MC3T3-E1 cell line was cultured on the surface of the membranes, demonstrating the potential of these freestanding multilayer systems to be used for bone tissue engineering.

Compensation effect in H 2 permeation kinetics of PdAg membranes

KAUST Repository

Zeng, Gaofeng

2012-08-30

Knowledge about the (inter)dependence of permeation kinetic parameters on the stoichiometry of H 2-selective alloys is still rudimentary, although uncovering the underlying systematic correlations will greatly facilitate current efforts into the design of novel high-performance H 2 separation membranes. Permeation measurements with carefully engineered, 2-7 μm thick supported Pd 100-xAg x membranes reveal that the activation energy and pre-exponential factor of H 2 permeation laws vary systematically with alloy composition, and both kinetic parameters are strongly correlated for x ≤ 50. We show that this permeation kinetic compensation effect corresponds well with similar correlations in the hydrogen solution thermodynamics and diffusion kinetics of PdAg alloys that govern H 2 permeation rates. This effect enables the consistent description of permeation characteristics over wide temperature and alloy stoichiometry ranges, whereas hydrogen solution thermodynamics may play a role, too, as a yet unrecognized source of kinetic compensation in, for example, H 2-involving reactions over metal catalysts or hydrogenation/ dehydrogenation of hydrogen storage materials. © 2012 American Chemical Society.

Short-term adhesion and long-term biofouling testing of polydopamine and poly(ethylene glycol) surface modifications of membranes and feed spacers for biofouling control

KAUST Repository

Miller, Daniel J.

2012-08-01

Ultrafiltration, nanofiltration membranes and feed spacers were hydrophilized with polydopamine and polydopamine- g-poly(ethylene glycol) surface coatings. The fouling propensity of modified and unmodified membranes was evaluated by short-term batch protein and bacterial adhesion tests. The fouling propensity of modified and unmodified membranes and spacers was evaluated by continuous biofouling experiments in a membrane fouling simulator. The goals of the study were: 1) to determine the effectiveness of polydopamine and polydopamine- g-poly(ethylene glycol) membrane coatings for biofouling control and 2) to compare techniques commonly used in assessment of membrane biofouling propensity with biofouling experiments under practical conditions. Short-term adhesion tests were carried out under static, no-flow conditions for 1 h using bovine serum albumin, a common model globular protein, and Pseudomonas aeruginosa, a common model Gram-negative bacterium. Biofouling tests were performed in a membrane fouling simulator (MFS) for several days under flow conditions similar to those encountered in industrial modules with the autochthonous drinking water population and acetate dosage as organic substrate. Polydopamine- and polydopamine- g-poly(ethylene glycol)-modified membranes showed significantly reduced adhesion of bovine serum albumin and P. aeruginosa in the short-term adhesion tests, but no reduction of biofouling was observed during longer biofouling experiments with modified membranes and spacers. These results demonstrate that short-term batch adhesion experiments using model proteins or bacteria under static conditions are not indicative of biofouling, while continuous biofouling experiments showed that membrane surface modification by polydopamine and polydopamine- g-poly(ethylene glycol) is not effective for biofouling control. © 2012 Elsevier Ltd.

PLGA nanofiber membranes loaded with epigallocatechin-3-O-gallate are beneficial to prevention of postsurgical adhesions

Directory of Open Access Journals (Sweden)

Shin YC

2014-08-01

Full Text Available Yong Cheol Shin,1,* Won Jun Yang,1,* Jong Ho Lee,1 Jin-Woo Oh,2 Tai Wan Kim,3 Jong-Chul Park,4 Suong-Hyu Hyon,5 Dong-Wook Han1 1Department of Cogno-Mechatronics Engineering, Pusan National University, Busan, Republic of Korea; 2Department of Nanomaterials Engineering, College of Nanoscience and Nanotechnology, Pusan National University, Busan, Republic of Korea; 3Department of Design, College of Arts, Pusan National University, Busan, Republic of Korea; 4Department of Medical Engineering, Yonsei University College of Medicine, Seoul, Republic of Korea; 5Center for Fiber and Textile Science, Kyoto Institute of Technology, Kyoto, Japan *These authors contributed equally to this work Abstract: This study concentrates on the development of biodegradable nanofiber membranes with controlled drug release to ensure reduced tissue adhesion and accelerated healing. Nanofibers of poly(lactic-co-glycolic acid (PLGA loaded with epigallocatechin-3-O-gallate (EGCG, the most bioactive polyphenolic compound in green tea, were electrospun. The physicochemical and biomechanical properties of EGCG-releasing PLGA (E-PLGA nanofiber membranes were characterized by atomic force microscopy, EGCG release and degradation profiles, and tensile testing. In vitro antioxidant activity and hemocompatibility were evaluated by measuring scavenged reactive oxygen species levels and activated partial thromboplastin time, respectively. In vivo antiadhesion efficacy was examined on the rat peritonea with a surgical incision. The average fiber diameter of E-PLGA membranes was approximately 300–500 nm, which was almost similar to that of pure PLGA equivalents. E-PLGA membranes showed sustained EGCG release mediated by controlled diffusion and PLGA degradation over 28 days. EGCG did not adversely affect the tensile strength of PLGA membranes, whereas it significantly decreased the elastic modulus and increased the strain at break. E-PLGA membranes were significantly effective in

Multiscale approaches to protein-mediated interactions between membranes—relating microscopic and macroscopic dynamics in radially growing adhesions

International Nuclear Information System (INIS)

Bihr, Timo; Smith, Ana-Suncana; Seifert, Udo

2015-01-01

Macromolecular complexation leading to coupling of two or more cellular membranes is a crucial step in a number of biological functions of the cell. While other mechanisms may also play a role, adhesion always involves the fluctuations of deformable membranes, the diffusion of proteins and the molecular binding and unbinding. Because these stochastic processes couple over a multitude of time and length scales, theoretical modeling of membrane adhesion has been a major challenge. Here we present an effective Monte Carlo scheme within which the effects of the membrane are integrated into local rates for molecular recognition. The latter step in the Monte Carlo approach enables us to simulate the nucleation and growth of adhesion domains within a system of the size of a cell for tens of seconds without loss of accuracy, as shown by comparison to 10 6 times more expensive Langevin simulations. To perform this validation, the Langevin approach was augmented to simulate diffusion of proteins explicitly, together with reaction kinetics and membrane dynamics. We use the Monte Carlo scheme to gain deeper insight to the experimentally observed radial growth of micron sized adhesion domains, and connect the effective rate with which the domain is growing to the underlying microscopic events. We thus demonstrate that our technique yields detailed information about protein transport and complexation in membranes, which is a fundamental step toward understanding even more complex membrane interactions in the cellular context. (paper)

Dependence of cancer cell adhesion kinetics on integrin ligand surface density measured by a high-throughput label-free resonant waveguide grating biosensor.

Science.gov (United States)

Orgovan, Norbert; Peter, Beatrix; Bősze, Szilvia; Ramsden, Jeremy J; Szabó, Bálint; Horvath, Robert

2014-02-07

A novel high-throughput label-free resonant waveguide grating (RWG) imager biosensor, the Epic® BenchTop (BT), was utilized to determine the dependence of cell spreading kinetics on the average surface density (v(RGD)) of integrin ligand RGD-motifs. v(RGD) was tuned over four orders of magnitude by co-adsorbing the biologically inactive PLL-g-PEG and the RGD-functionalized PLL-g-PEG-RGD synthetic copolymers from their mixed solutions onto the sensor surface. Using highly adherent human cervical tumor (HeLa) cells as a model system, cell adhesion kinetic data of unprecedented quality were obtained. Spreading kinetics were fitted with the logistic equation to obtain the spreading rate constant (r) and the maximum biosensor response (Δλmax), which is assumed to be directly proportional to the maximum spread contact area (Amax). r was found to be independent of the surface density of integrin ligands. In contrast, Δλmax increased with increasing RGD surface density until saturation at high densities. Interpreting the latter behavior with a simple kinetic mass action model, a 2D dissociation constant of 1753 ± 243 μm(-2) (corresponding to a 3D dissociation constant of ~30 μM) was obtained for the binding between RGD-specific integrins embedded in the cell membrane and PLL-g-PEG-RGD. All of these results were obtained completely noninvasively without using any labels.

Kinetic studies of chemical shrinkage and residual stress formation in thermoset epoxy adhesives under confined curing conditions

Science.gov (United States)

Schumann, M.; Geiß, P. L.

2015-05-01

Faultless processing of thermoset polymers in demanding applications requires a profound mastering of the curing kinetics considering both the physico-chemical changes in the transition from the liquid to the solid state and the consolidation of the polymers network in the diffusion controlled curing regime past the gel point. Especially in adhesive joints shrinkage stress occurring at an early state of the curing process under confined conditions is likely to cause defects due to local debonding and thus reduce their strength and durability1. Rheometry is considered the method of choice to investigate the change of elastic and viscous properties in the progress of curing. Drawbacks however relate to experimental challenges in accessing the full range of kinetic parameters of thermoset resins with low initial viscosity from the very beginning of the curing reaction to the post-cure consolidation of the polymer due to the formation of secondary chemical bonds. Therefore the scope of this study was to interrelate rheological data with results from in-situ measurements of the shrinkage stress formation in adhesive joints and with the change of refractive index in the progress of curing. This combination of different methods has shown to be valuable in gaining advanced insight into the kinetics of the curing reaction. The experimental results are based on a multi component thermoset epoxy-amine adhesive.

The Effect of Thermal Fluctuation on the Receptor-Mediated Adhesion of a Cell Membrane to an Elastic Substrate

Directory of Open Access Journals (Sweden)

Bahador Marzban

2017-04-01

Full Text Available Mechanics of the bilayer membrane play an important role in many biological and bioengineering problems such as cell–substrate and cell–nanomaterial interactions. In this work, we study the effect of thermal fluctuation and the substrate elasticity on the cell membrane–substrate adhesion. We model the adhesion of a fluctuating membrane on an elastic substrate as a two-step reaction comprised of the out-of-plane membrane fluctuation and the receptor–ligand binding. The equilibrium closed bond ratio as a function of substrate rigidity was computed by developing a coupled Fourier space Brownian dynamics and Monte Carlo method. The simulation results show that there exists a crossover value of the substrate rigidity at which the closed bond ratio is maximal.

Repairing Fetal Membranes with a Self-adhesive Ultrathin Polymeric Film: Evaluation in Mid-gestational Rabbit Model.

Science.gov (United States)

Pensabene, Virginia; Patel, Premal P; Williams, Phillip; Cooper, Trisha L; Kirkbride, Kellye C; Giorgio, Todd D; Tulipan, Noel B

2015-08-01

Preterm premature rupture of membranes causes 40% of all preterm births, affecting 150000 women each year in the United States. Prenatal diagnostic procedures and surgical interventions increase incidence of adverse events, leading to iatrogenic membrane rupture after a fetoscopic procedure in 45% of cases. We propose an ultrathin, self-adherent, poly-L-lactic acid patch ("nanofilm") as a reparative wound closure after endoscopic/fetoscopic procedures. These nanofilms are compatible with application in wet conditions and with minimally invasive instrumentation. Ex vivo studies to evaluate the nanofilm were conducted using human chorion-amnion (CA) membranes. A custom-built inflation device was used for mechanical characterization of CA membranes and for assessment of nanofilm adhesion and sealing of membrane defects up to 3 mm in size. These ex vivo tests demonstrated the ability of the nanofilm to seal human CA defects ranging in size from 1 to 3 mm in diameter. In vivo survival studies were conducted in 25 mid-gestational rabbits, defects were created by perforating the uterus and the CA membranes and subsequently using the nanofilm to seal these wounds. These in vivo studies confirmed the successful sealing of defects smaller than 3 mm observed ex vivo. Histological analysis of whole harvested uteri 7 days after surgery showed intact uterine walls in 59% of the nanofilm repaired fetuses, along with increased uterine size and intrauterine development in 63% of the cases. In summary, we have developed an ultrathin, self-adhesive nanofilm for repair of uterine membrane defects.

Association of membrane/lipid rafts with the platelet cytoskeleton and the caveolin PY14: participation in the adhesion process.

Science.gov (United States)

Cerecedo, Doris; Martínez-Vieyra, Ivette; Maldonado-García, Deneb; Hernández-González, Enrique; Winder, Steve J

2015-11-01

Platelets are the most prominent elements of blood tissue involved in hemostasis at sites of blood vessel injury. Platelet cytoskeleton is responsible for their shape modifications observed during activation and adhesion to the substratum; therefore the interactions between cytoskeleton and plasma membrane are critical to modulate blood platelet functions. Several cytoskeletal components and binding partners, as well as enzymes that regulate the cytoskeleton, localize to membrane/lipid rafts (MLR) and regulate lateral diffusion of membrane proteins and lipids. Resting, thrombin-activated, and adherent human platelets were processed for biochemical studies including western-blot and immunprecipitation assays and confocal analysis were performed to characterize the interaction of MLR with the main cytoskeleton elements and β-dystroglycan as well as with the association of caveolin-1 PY14 with focal adhesion proteins. We transfected a megakaryoblast cell line (Meg-01) to deplete β-dystroglycan, subsequent to their differentiation to the platelet progenitors. Our data showed a direct interaction of the MLR with cytoskeleton to regulate platelet shape, while an association of caveolin-1 PY14 with vinculin is needed to establish focal adhesions, which are modulated for β-dystroglycan. In conclusion, caveolin-1 PY14 in association with platelet cytoskeleton participate in focal adhesions dynamics. © 2015 Wiley Periodicals, Inc.

Bone conditioned media (BCM) improves osteoblast adhesion and differentiation on collagen barrier membranes.

Science.gov (United States)

Fujioka-Kobayashi, Masako; Caballé-Serrano, Jordi; Bosshardt, Dieter D; Gruber, Reinhard; Buser, Daniel; Miron, Richard J

2016-07-04

The use of autogenous bone chips during guided bone regeneration procedures has remained the gold standard for bone grafting due to its excellent combination of osteoconduction, osteoinduction and osteogenesis. Recent protocols established by our group have characterized specific growth factors and cytokines released from autogenous bone that have the potential to be harvested and isolated into bone conditioned media (BCM). Due to the advantageous osteo-promotive properties of BCM, the aims of the present study was to pre-coat collagen barrier membranes with BCM and investigate its effect on osteoblast adhesion, proliferation and differentiation for possible future clinical use. Scanning electron microscopy (SEM) was first used to qualitative assess BCM protein accumulation on the surface of collagen membranes. Thereafter, undifferentiated mouse ST2 stromal bone marrow cells were seeded onto BioGide porcine derived collagen barrier membranes (control) or barrier membranes pre-coated with BCM (test group). Control and BCM samples were compared for cell adhesion at 8 h, cell proliferation at 1, 3 and 5 days and real-time PCR at 5 days for osteoblast differentiation markers including Runx2, alkaline phosphatase (ALP), osteocalcin (OCN) and bone sialoprotein (BSP). Mineralization was further assessed with alizarin red staining at 14 days post seeding. SEM images demonstrated evidence of accumulated proteins found on the surface of collagen membranes following coating with BCM. Analysis of total cell numbers revealed that the additional pre-coating with BCM markedly increased cell attachment over 4 fold when compared to cells seeded on barrier membranes alone. No significant difference could be observed for cell proliferation at all time points. BCM significantly increased mRNA levels of osteoblast differentiation markers including ALP, OCN and BSP at 5 days post seeding. Furthermore, barrier membranes pre-coated with BCM demonstrated a 5-fold increase in alizarin

Investigation of cell adhesion in chitosan membranes for peripheral nerve regeneration

Energy Technology Data Exchange (ETDEWEB)

Carvalho, Cristiana R.; López-Cebral, Rita; Silva-Correia, Joana; Silva, Joana M.; Mano, João F.; Silva, Tiago H. [3B' s Research Group - Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark – Parque de Ciência e Tecnologia, 4805-017, Barco, Guimarães (Portugal); ICVS/3B' s - PT Government Associate Laboratory, Braga, Guimarães (Portugal); Freier, Thomas [MEDOVENT GmbH, Friedrich-Koenig-Str. 3, D-55129 Mainz (Germany); Reis, Rui L. [3B' s Research Group - Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark – Parque de Ciência e Tecnologia, 4805-017, Barco, Guimarães (Portugal); ICVS/3B' s - PT Government Associate Laboratory, Braga, Guimarães (Portugal); Oliveira, Joaquim M., E-mail: miguel.oliveira@dep.uminho.pt [3B' s Research Group - Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, AvePark – Parque de Ciência e Tecnologia, 4805-017, Barco, Guimarães (Portugal); ICVS/3B' s - PT Government Associate Laboratory, Braga, Guimarães (Portugal)

2017-02-01

Peripheral nerve injuries have produced major concerns in regenerative medicine for several years, as the recovery of normal nerve function continues to be a significant clinical challenge. Chitosan (CHT), because of its good biocompatibility, biodegradability and physicochemical properties, has been widely used as a biomaterial in tissue engineering scaffolding. In this study, CHT membranes were produced with three different Degrees of Acetylation (DA), envisioning its application in peripheral nerve regeneration. The three CHT membranes (DA I: 1%, DA II: 2%, DA III: 5%) were extensively characterized and were found to have a smooth and flat surface, with DA III membrane having slightly higher roughness and surface energy. All the membranes presented suitable mechanical properties and did not show any signs of calcification after SBF test. Biodegradability was similar for all samples, and adequate to physically support neurite outgrowth. The in vitro cell culture results indicate selective cell adhesion. The CHT membranes favoured Schwann cells invasion and proliferation, with a display of appropriate cytoskeletal morphology. At the same time they presented low fibroblast infiltration. This fact may be greatly beneficial for the prevention of fibrotic tissue formation, a common phenomenon impairing peripheral nerve regeneration. The great deal of results obtained during this work permitted to select the formulation with the greatest potential for further biological tests. - Highlights: • Three chitosan membranes were produced with very specific degrees of acetylation (DA I: 1%, DA II: 2%, DA III: 5%). • Physicochemical characterization of the membranes showed their suitability for peripheral nerve regeneration purposes. • In vitro cellular tests confirmed the potential of the membranes as peripheral nerve regeneration systems. • The results indicated that DA III membrane should be the one considered for further peripheral nerve regeneration studies.

Investigation of cell adhesion in chitosan membranes for peripheral nerve regeneration

International Nuclear Information System (INIS)

Carvalho, Cristiana R.; López-Cebral, Rita; Silva-Correia, Joana; Silva, Joana M.; Mano, João F.; Silva, Tiago H.; Freier, Thomas; Reis, Rui L.; Oliveira, Joaquim M.

2017-01-01

Peripheral nerve injuries have produced major concerns in regenerative medicine for several years, as the recovery of normal nerve function continues to be a significant clinical challenge. Chitosan (CHT), because of its good biocompatibility, biodegradability and physicochemical properties, has been widely used as a biomaterial in tissue engineering scaffolding. In this study, CHT membranes were produced with three different Degrees of Acetylation (DA), envisioning its application in peripheral nerve regeneration. The three CHT membranes (DA I: 1%, DA II: 2%, DA III: 5%) were extensively characterized and were found to have a smooth and flat surface, with DA III membrane having slightly higher roughness and surface energy. All the membranes presented suitable mechanical properties and did not show any signs of calcification after SBF test. Biodegradability was similar for all samples, and adequate to physically support neurite outgrowth. The in vitro cell culture results indicate selective cell adhesion. The CHT membranes favoured Schwann cells invasion and proliferation, with a display of appropriate cytoskeletal morphology. At the same time they presented low fibroblast infiltration. This fact may be greatly beneficial for the prevention of fibrotic tissue formation, a common phenomenon impairing peripheral nerve regeneration. The great deal of results obtained during this work permitted to select the formulation with the greatest potential for further biological tests. - Highlights: • Three chitosan membranes were produced with very specific degrees of acetylation (DA I: 1%, DA II: 2%, DA III: 5%). • Physicochemical characterization of the membranes showed their suitability for peripheral nerve regeneration purposes. • In vitro cellular tests confirmed the potential of the membranes as peripheral nerve regeneration systems. • The results indicated that DA III membrane should be the one considered for further peripheral nerve regeneration studies.

Tailored adhesion behavior of polyelectrolyte thin films deposited on plasma-treated poly(dimethylsiloxane) for functionalized membranes

Energy Technology Data Exchange (ETDEWEB)

Bassil, Joelle, E-mail: joelle.bassil@univ-lorraine.fr [Institut Jean Lamour (IJL), UMR CNRS 7198, Université de Lorraine, Parc de Saurupt CS50840, 54011 Nancy (France); Alem, Halima, E-mail: halima.alem@univ-lorraine.fr [Institut Jean Lamour (IJL), UMR CNRS 7198, Université de Lorraine, Parc de Saurupt CS50840, 54011 Nancy (France); Henrion, Gérard, E-mail: gerard.henrion@univ-lorraine.fr [Institut Jean Lamour (IJL), UMR CNRS 7198, Université de Lorraine, Parc de Saurupt CS50840, 54011 Nancy (France); Roizard, Denis, E-mail: denis.roizard@univ-lorraine.fr [Laboratoire Réactions et Génie des Procédés (LRGP), UMR CNRS 7274, ENSIC, Université de Lorraine, 1 rue Grandville, 54011 Nancy (France)

2016-04-30

Graphical abstract: - Highlights: • The surface of PDMS membrane was first modified by Ar/O{sub 2} plasma to increase its surface energy. • Subsequently, a homogeneous multilayer of the well-known couple of polyelectrolyte PDADMAC/PSS was deposited on the plasma treated PDMS. • The relation between the parameters of the modification processes and the morphology, wettability, structure and adhesion of the polyelectrolytes layers based PDMS membranes is investigated and enlightened. - Abstract: Completely homogenous films formed via the layer-by-layer assembly of poly(diallyldimethylammonium chloride) (PDADMAC) and the poly(styrene sulfonate) were successfully obtained on plasma-treated poly(dimethylsiloxane) (PDMS) substrates. To modify the hydrophobicity of the PDMS surface, a cold plasma treatment was previously applied to the membrane, which led to the creation of hydrophilic groups on the surface of the membrane. PDMS wettability and surface morphology were successfully correlated with the plasma parameters. A combination of contact angle measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis was used to demonstrate that homogeneous and hydrophilic surfaces could be achieved on PDMS cold-plasma-treated membranes. The stability of the assembled PEL layer on the PDMS was evaluated using a combination of pull-off testing and X-ray photoelectron spectroscopy (XPS), which confirmed the relevance of a plasma pre-treatment as the adhesion of the polyelectrolyte multilayers was greatly enhanced when the deposition was completed on an activated PDMS surface at 80 W for 5 min.

Efficient adhesion-based plasma membrane isolation for cell surface N-glycan analysis.

Science.gov (United States)

Mun, Ji-Young; Lee, Kyung Jin; Seo, Hoon; Sung, Min-Sun; Cho, Yee Sook; Lee, Seung-Goo; Kwon, Ohsuk; Oh, Doo-Byoung

2013-08-06

Glycans, which decorate cell surfaces, play crucial roles in various physiological events involving cell surface recognition. Despite the importance of surface glycans, most analyses have been performed using total cells or whole membranes rather than plasma membranes due to difficulties related to isolation. In the present study, we employed an adhesion-based method for plasma membrane isolation to analyze N-glycans on cell surfaces. Cells were attached to polylysine-coated glass plates and then ruptured by hypotonic pressure. After washing to remove intracellular organelles, only a plasma membrane fraction remained attached to the plates, as confirmed by fluorescence imaging using organelle-specific probes. The plate was directly treated with trypsin to digest and detach the glycoproteins from the plasma membrane. From the resulting glycopeptides, N-glycans were released and analyzed using MALDI-TOF mass spectrometry and HPLC. When N-glycan profiles obtained by this method were compared to those by other methods, the amount of high-mannose type glycans mainly contaminated from the endoplasmic reticulum was dramatically reduced, which enabled the efficient detection of complex type glycans present on the cell surface. Moreover, this method was successfully used to analyze the increase of high-mannose glycans on the surface as induced by a mannosidase inhibitor treatment.

The kinetics of crossflow dynamic membrane bioreactor | Li | Water SA

African Journals Online (AJOL)

Crossflow dynamic membrane bioreactor (CDMBR) kinetics was investigated by treating caprolactam wastewater over a period of 180 d. The removal efficiencies of organic substances and nitrogen averaged over 99% and 80%, respectively. The observed sludge yield was only 0.14 g SS·g-1 COD·d-1 at an SRT of 30 d ...

Evaluating adhesion reduction efficacy of type I/III collagen membrane and collagen-GAG resorbable matrix in primary flexor tendon repair in a chicken model.

Science.gov (United States)

Turner, John B; Corazzini, Rubina L; Butler, Timothy J; Garlick, David S; Rinker, Brian D

2015-09-01

Reduction of peritendinous adhesions after injury and repair has been the subject of extensive prior investigation. The application of a circumferential barrier at the repair site may limit the quantity of peritendinous adhesions while preserving the tendon's innate ability to heal. The authors compare the effectiveness of a type I/III collagen membrane and a collagen-glycosaminoglycan (GAG) resorbable matrix in reducing tendon adhesions in an experimental chicken model of a "zone II" tendon laceration and repair. In Leghorn chickens, flexor tendons were sharply divided using a scalpel and underwent repair in a standard fashion (54 total repairs). The sites were treated with a type I/III collagen membrane, collagen-GAG resorbable matrix, or saline in a randomized fashion. After 3 weeks, qualitative and semiquantitative histological analysis was performed to evaluate the "extent of peritendinous adhesions" and "nature of tendon healing." The data was evaluated with chi-square analysis and unpaired Student's t test. For both collagen materials, there was a statistically significant improvement in the degree of both extent of peritendinous adhesions and nature of tendon healing relative to the control group. There was no significant difference seen between the two materials. There was one tendon rupture observed in each treatment group. Surgical handling characteristics were subjectively favored for type I/III collagen membrane over the collagen-GAG resorbable matrix. The ideal method of reducing clinically significant tendon adhesions after injury remains elusive. Both materials in this study demonstrate promise in reducing tendon adhesions after flexor tendon repair without impeding tendon healing in this model.

Actin filaments regulate the adhesion between the plasma membrane and the cell wall of tobacco guard cells.

Science.gov (United States)

Yu, Qin; Ren, Jing-Jing; Kong, Lan-Jing; Wang, Xiu-Ling

2018-01-01

During the opening and closing of stomata, guard cells undergo rapid and reversible changes in their volume and shape, which affects the adhesion of the plasma membrane (PM) to the cell wall (CW). The dynamics of actin filaments in guard cells are involved in stomatal movement by regulating structural changes and intracellular signaling. However, it is unclear whether actin dynamics regulate the adhesion of the PM to the CW. In this study, we investigated the relationship between actin dynamics and PM-CW adhesion by the hyperosmotic-induced plasmolysis of tobacco guard cells. We found that actin filaments in guard cells were depolymerized during mannitol-induced plasmolysis. The inhibition of actin dynamics by treatment with latrunculin B or jasplakinolide and the disruption of the adhesion between the PM and the CW by treatment with RGDS peptide (Arg-Gly-Asp-Ser) enhanced guard cell plasmolysis. However, treatment with latrunculin B alleviated the RGDS peptide-induced plasmolysis and endocytosis. Our results reveal that the actin depolymerization is involved in the regulation of the PW-CW adhesion during hyperosmotic-induced plasmolysis in tobacco guard cells.

Enhancement of growth and osteogenic differentiation of MC3T3-E1 cells via facile surface functionalization of polylactide membrane with chitooligosaccharide based on polydopamine adhesive coating

International Nuclear Information System (INIS)

Li, Huihua; Luo, Chuang; Luo, Binghong; Wen, Wei; Wang, Xiaoying; Ding, Shan; Zhou, Changren

2016-01-01

Graphical abstract: - Highlights: • COS was conveniently immobilized on PDLLA membrane based on PDOPA adhesive layer. • The hydrophilicity of PDLLA membrane was improved by modified with PDOPA and COS. • COS-functionalized PDLLA membrane is favorable to cell adhesion and proliferation. • COS-coated PDLLA membrane notably promote osteogenic differentiation of MC3T3-E1. - Abstract: To develop a chitooligosaccharide(COS)-functionalized poly(D,L-lactide) (PDLLA) membrane to enhance growth and osteogenic differentiation of MC3T3-E1 cells, firstly a thin polydopamine (PDOPA) layer was adhered to the PDLLA membrane via the self-polymerization and strong adhesion behavior of dopamine. Subsequently, COS was immobilized covalently on the resultant PDLLA/PDOPA composite membrane by coupling with PDOPA active coating. The successful immobilization of the PDOPA and COS was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Scanning electronic microscopy (SEM) and atomic force microscopy (AFM) results indicated that the surface topography and roughness of the membranes were changed, and the root mean square increased from 0.613 nm to 6.96 and 7.12 nm, respectively after coating PDOPA and COS. Water contact angle and surface energy measurements revealed that the membrane hydrophilicity was remarkably improved by surface modification. In vitro cells culture results revealed that the PDOPA- and COS-functionalized surfaces showed a significant increase in MC3T3-E1 cells adhesion, proliferation, osteogenic differentiation and alkaline phosphate activity compared to the pristine PDLLA substrate. Furthermore the COS-functionalized PDLLA membrane was more effectively at enhancing osteoblast activity than the PDOPA-functionalized PDLLA membrane.

A kinetic study of mercury(II transport through a membrane assisted by new transport reagent

Directory of Open Access Journals (Sweden)

Görgülü Ahmet

2011-07-01

Full Text Available Abstract Background A new organodithiophosphorus derivative, namely O-(1,3-Bispiperidino-2-propyl-4-methoxy phenyldithiophosphonate, was synthesized and then the kinetic behavior of the transport process as a function of concentration, temperature, stirring rate and solvents was investigated. Results The compound 1 was characterized by elemental analysis, IR, 1H and 31P NMR spectroscopies. The transport of mercury(II ion by a zwitterionic dithiophosphonate 1 in the liquid membrane was studied and the kinetic behavior of the transport process as a function of concentration, temperature, stirring rate and solvents was investigated. The compound 1 is expected to serve as a model liquid membrane transport with mercury(II ions. Conclusion A kinetic study of mercury(II transport through a membrane assisted by O-(1,3-Bispiperidino-2-propyl-4-methoxy phenyldithiophosphonate was performed. It can be concluded that the compound 1 can be provided a general and straightforward route to remove toxic metals ions such as mercury(II ion from water or other solution.

Kinetics of structural reorganizations in multilamellarphotosynthetic membranes monitored by small-angle neutronscattering

DEFF Research Database (Denmark)

Nagy, Gergely; Kovacs, Laszlo; Unnep, Renata

2013-01-01

and in unicellular organisms, we discuss the advantages and technical and methodological limitations of timeresolved SANS. We present a detailed and more systematical investigation of the kinetics of light-induced structural reorganizations in isolated spinach thylakoid membranes, which show how changes...

Mathematical modeling of cell adhesion in shear flow: application to targeted drug delivery in inflammation and cancer metastasis.

Science.gov (United States)

Jadhav, Sameer; Eggleton, Charles D; Konstantopoulos, Konstantinos

2007-01-01

Cell adhesion plays a pivotal role in diverse biological processes that occur in the dynamic setting of the vasculature, including inflammation and cancer metastasis. Although complex, the naturally occurring processes that have evolved to allow for cell adhesion in the vasculature can be exploited to direct drug carriers to targeted cells and tissues. Fluid (blood) flow influences cell adhesion at the mesoscale by affecting the mechanical response of cell membrane, the intercellular contact area and collisional frequency, and at the nanoscale level by modulating the kinetics and mechanics of receptor-ligand interactions. Consequently, elucidating the molecular and biophysical nature of cell adhesion requires a multidisciplinary approach involving the synthesis of fundamentals from hydrodynamic flow, molecular kinetics and cell mechanics with biochemistry/molecular cell biology. To date, significant advances have been made in the identification and characterization of the critical cell adhesion molecules involved in inflammatory disorders, and, to a lesser degree, in cancer metastasis. Experimental work at the nanoscale level to determine the lifetime, interaction distance and strain responses of adhesion receptor-ligand bonds has been spurred by the advent of atomic force microscopy and biomolecular force probes, although our current knowledge in this area is far from complete. Micropipette aspiration assays along with theoretical frameworks have provided vital information on cell mechanics. Progress in each of the aforementioned research areas is key to the development of mathematical models of cell adhesion that incorporate the appropriate biological, kinetic and mechanical parameters that would lead to reliable qualitative and quantitative predictions. These multiscale mathematical models can be employed to predict optimal drug carrier-cell binding through isolated parameter studies and engineering optimization schemes, which will be essential for developing

Stability and dewetting kinetics of thin gold films on Ti, TiOx and ZnO adhesion layers

International Nuclear Information System (INIS)

Schaefer, Brian T.; Cheung, Jeffrey; Ihlefeld, Jon F.; Jones, Jacob L.; Nagarajan, Valanoor

2013-01-01

We present an in situ high-temperature confocal laser microscopy study on the thermal stability of 40 nm thick gold thin films grown on 40 nm Ti, TiO x and ZnO adhesion layers on (0 0 1) Si. In situ observation of the dewetting process was performed over a wide range of set temperatures (400–800 °C) and ramp rates (10–50 °C min −1 ) for each gold/adhesion layer combination. We found that significant dewetting and subsequent formation of gold islands occurs only at and above 700 °C for all adhesion layers. The dewetting is driven to equilibrium for gold/ZnO compared to gold/Ti and gold/TiO x as confirmed by ex situ X-ray diffraction and scanning electron microscopy characterization. Quantification of the in situ data through stretched exponential kinetic models reveals an underlying apparent activation energy of the dewetting process. This energy barrier for dewetting is higher for gold/Ti and gold/TiO x compared to gold/ZnO, thus confirming the ex situ observations. We rationalize that these apparent activation energies correspond to the underlying thermal stability of each gold/adhesion layer system

Fabrication and evaluation of novel zeolite membranes to control the neoplastic activity and anti-tumoral drug treatments in human breast cancer cells. Part 1: Synthesis and characterization of Pure Zeolite Membranes and Mixed Matrix Membranes for adhesion and growth of cancer cells

International Nuclear Information System (INIS)

Tavolaro, Palmira; Martino, Guglielmo; Andò, Sebastiano; Tavolaro, Adalgisa

2016-01-01

Novel pure and hybrid zeolite membranes were prepared with appropriate different physicochemical characteristics such as frameworks, hydrophilicity, crystal size, chemical composition, acid-base properties (Point of Zero Charge, PZC) and surface morphology and used in inorganic cell/scaffold constructs. Because the control of cell interactions, as the adhesion, proliferation, remodelling and mobility, is important for differentiation and progression of tumors, this work focused on response of cancer cells adhered and grown on synthesized zeolite surfaces in order to study the influence of these scaffolds in controlled conditions. We have selected the MCF-7 and MDA-MB-231 human breast cancer cell line as model tumor cell lines. This study showed that all the zeolite membranes synthesized are excellent scaffolds because they are very selective materials to support the adhesion and growth of neoplastic cells. All zeolite scaffolds were characterized by FESEM, FTIR ATR, XRD, AFM, PZC and contact angle analyses. Cell adhesion, viability and morphology were measured by count, MTT assay and FESEM microphotography analysis, at various incubation times. - Highlights: • Novel pure and hybrid zeolite scaffolds were developed. • PZMs and MMMs were characterized and used with human cancer cells. • A systematic study of zeolite scaffolds influence on cell adhesion and morphology was performed. • The PZC value of zeolite membranes controls the cell-cell and scaffold-cell interactions.

Fabrication and evaluation of novel zeolite membranes to control the neoplastic activity and anti-tumoral drug treatments in human breast cancer cells. Part 1: Synthesis and characterization of Pure Zeolite Membranes and Mixed Matrix Membranes for adhesion and growth of cancer cells

Energy Technology Data Exchange (ETDEWEB)

Tavolaro, Palmira, E-mail: p.tavolaro@unical.it [Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Cubo 4/c, 87036 Rende (Italy); Martino, Guglielmo [Department Di.B.E.S.T. (Biologia, Ecologia, Scienze della Terra), Unit of Physiology, University of Calabria, Cubo 4/c, 87036 Rende (Italy); Andò, Sebastiano [Department of Pharmacy, Health and Nutritional Sciences, University of Calabria, Cubo 4/c, 87036 Rende (Italy); Tavolaro, Adalgisa [Research Institute on Membrane Technology, Unit of Zeolite Membranes, ITM-CNR, University of Calabria, Cubo 17/c, 87036 Rende (Italy)

2016-12-01

Novel pure and hybrid zeolite membranes were prepared with appropriate different physicochemical characteristics such as frameworks, hydrophilicity, crystal size, chemical composition, acid-base properties (Point of Zero Charge, PZC) and surface morphology and used in inorganic cell/scaffold constructs. Because the control of cell interactions, as the adhesion, proliferation, remodelling and mobility, is important for differentiation and progression of tumors, this work focused on response of cancer cells adhered and grown on synthesized zeolite surfaces in order to study the influence of these scaffolds in controlled conditions. We have selected the MCF-7 and MDA-MB-231 human breast cancer cell line as model tumor cell lines. This study showed that all the zeolite membranes synthesized are excellent scaffolds because they are very selective materials to support the adhesion and growth of neoplastic cells. All zeolite scaffolds were characterized by FESEM, FTIR ATR, XRD, AFM, PZC and contact angle analyses. Cell adhesion, viability and morphology were measured by count, MTT assay and FESEM microphotography analysis, at various incubation times. - Highlights: • Novel pure and hybrid zeolite scaffolds were developed. • PZMs and MMMs were characterized and used with human cancer cells. • A systematic study of zeolite scaffolds influence on cell adhesion and morphology was performed. • The PZC value of zeolite membranes controls the cell-cell and scaffold-cell interactions.

Kinetic study of seawater reverse osmosis membrane fouling

KAUST Repository

Khan, Muhammad

2013-10-01

Reverse osmosis (RO) membrane fouling is not a static state but a dynamic phenomenon. The investigation of fouling kinetics and dynamics of change in the composition of the foulant mass is essential to elucidate the mechanism of fouling and foulant-foulant interactions. The aim of this work was to study at a lab scale the fouling process with an emphasis on the changes in the relative composition of foulant material as a function of operating time. Fouled membrane samples were collected at 8 h, and 1, 2, and 4 weeks on a lab-scale RO unit operated in recirculation mode. Foulant characterization was performed by CLSM, AFM, ATR-FTIR, pyrolysis GC-MS, and ICP-MS techniques. Moreover, measurement of active biomass and analysis of microbial diversity were performed by ATP analysis and DNA extraction, followed by pyro-sequencing, respectively. A progressive increase in the abundance of almost all the foulant species was observed, but their relative proportion changed over the age of the fouling layer. Microbial population in all the membrane samples was dominated by specific groups/species belonging to Proteobacteria and Actinobacteria phyla; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age. © 2013 American Chemical Society.

Microbial Adhesion and Biofilm Formation on Microfiltration Membranes: A Detailed Characterization Using Model Organisms with Increasing Complexity

Directory of Open Access Journals (Sweden)

L. Vanysacker

2013-01-01

Full Text Available Since many years, membrane biofouling has been described as the Achilles heel of membrane fouling. In the present study, an ecological assay was performed using model systems with increasing complexity: a monospecies assay using Pseudomonas aeruginosa or Escherichia coli separately, a duospecies assay using both microorganisms, and a multispecies assay using activated sludge with or without spiked P. aeruginosa. The microbial adhesion and biofilm formation were evaluated in terms of bacterial cell densities, species richness, and bacterial community composition on polyvinyldifluoride, polyethylene, and polysulfone membranes. The data show that biofouling formation was strongly influenced by the kind of microorganism, the interactions between the organisms, and the changes in environmental conditions whereas the membrane effect was less important. The findings obtained in this study suggest that more knowledge in species composition and microbial interactions is needed in order to understand the complex biofouling process. This is the first report describing the microbial interactions with a membrane during the biofouling development.

Microbial Adhesion and Biofilm Formation on Microfiltration Membranes: A Detailed Characterization Using Model Organisms with Increasing Complexity

Science.gov (United States)

Vanysacker, L.; Denis, C.; Declerck, P.; Piasecka, A.; Vankelecom, I. F. J.

2013-01-01

Since many years, membrane biofouling has been described as the Achilles heel of membrane fouling. In the present study, an ecological assay was performed using model systems with increasing complexity: a monospecies assay using Pseudomonas aeruginosa or Escherichia coli separately, a duospecies assay using both microorganisms, and a multispecies assay using activated sludge with or without spiked P. aeruginosa. The microbial adhesion and biofilm formation were evaluated in terms of bacterial cell densities, species richness, and bacterial community composition on polyvinyldifluoride, polyethylene, and polysulfone membranes. The data show that biofouling formation was strongly influenced by the kind of microorganism, the interactions between the organisms, and the changes in environmental conditions whereas the membrane effect was less important. The findings obtained in this study suggest that more knowledge in species composition and microbial interactions is needed in order to understand the complex biofouling process. This is the first report describing the microbial interactions with a membrane during the biofouling development. PMID:23986906

Removal of Congo Red from Aqueous Solution by Anion Exchange Membrane (EBTAC): Adsorption Kinetics and Themodynamics

Science.gov (United States)

Khan, Muhammad Imran; Akhtar, Shahbaz; Zafar, Shagufta; Shaheen, Aqeela; Khan, Muhammad Ali; Luque, Rafael; ur Rehman, Aziz

2015-01-01

The adsorption behavior of anionic dye congo red (CR) from aqueous solutions using an anion exchange membrane (EBTAC) has been investigated at room temperature. The effect of several factors including contact time, membrane dosage, ionic strength and temperature were studied. Kinetic models, namely pseudo-first-order and pseudo-second-order, liquid film diffusion and Elovich models as well as Bangham and modified freundlich Equations, were employed to evaluate the experimental results. Parameters such as adsorption capacities, rate constant and related correlation coefficients for every model were calculated and discussed. The adsorption of CR on anion exchange membranes followed pseudo-second-order Kinetics. Thermodynamic parameters, namely changes in Gibbs free energy (∆G°), enthalpy (∆H°) and entropy (∆S°) were calculated for the adsorption of congo red, indicating an exothermic process. PMID:28793430

Arrays of membrane isolated yttrium-barium-copper-oxide kinetic inductance bolometers

International Nuclear Information System (INIS)

Lindeman, M. A.; Bonetti, J. A.; Bumble, B.; Day, P. K.; Holmes, W. A.; Kleinsasser, A. W.; Eom, B. H.

2014-01-01

We are developing of arrays of membrane isolated resonator-bolometers, each with a kinetic inductance device (KID) to measure the temperature of the membrane. The KIDs are fabricated out of the high temperature superconductor YBCO to allow operation at relatively high temperatures. The bolometers are designed to offer higher sensitivity than sensors operating at 300 K, but they require less expensive and lighter weight cooling than even more sensitive conventional superconducting detectors operating at lower temperatures. The bolometer arrays are applicable as focal planes in infrared imaging spectrometers, such as for planetary science missions or earth observing satellites. We describe the devices and present measurements of their sensitivity.

Arrays of membrane isolated yttrium-barium-copper-oxide kinetic inductance bolometers

Energy Technology Data Exchange (ETDEWEB)

Lindeman, M. A., E-mail: mark.a.lindeman@jpl.nasa.gov; Bonetti, J. A.; Bumble, B.; Day, P. K.; Holmes, W. A.; Kleinsasser, A. W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); Eom, B. H. [California Institute of Technology, Pasadena, California 91125 (United States)

2014-06-21

We are developing of arrays of membrane isolated resonator-bolometers, each with a kinetic inductance device (KID) to measure the temperature of the membrane. The KIDs are fabricated out of the high temperature superconductor YBCO to allow operation at relatively high temperatures. The bolometers are designed to offer higher sensitivity than sensors operating at 300 K, but they require less expensive and lighter weight cooling than even more sensitive conventional superconducting detectors operating at lower temperatures. The bolometer arrays are applicable as focal planes in infrared imaging spectrometers, such as for planetary science missions or earth observing satellites. We describe the devices and present measurements of their sensitivity.

Adhesion structures and their cytoskeleton-membrane interactions at podosomes of osteoclasts in culture.

Science.gov (United States)

Akisaka, Toshitaka; Yoshida, Hisaho; Suzuki, Reiko; Takama, Keiko

2008-03-01

The organization of the cytoskeleton in the podosomes of osteoclasts was studied by use of cell shearing, rotary replication, and fluorescence cytochemical techniques. After shearing, clathrin plaques and particles associated with the cytoskeleton were left behind on the exposed cytoplasmic side of the membrane. The cytoskeleton of the podosomes was characterized by two types of actin filaments: relatively long filaments in the portion surrounding the podosome core, and highly branched short filaments in the core. Individual actin filaments radiating from the podosomes interacted with several membrane particles along the length of the filaments. Many lateral contacts with the membrane surface by the particles were made along the length of individual actin filaments. The polarity of actin filaments in podosomes became oriented such that their barbed ends were directed toward the core of podosomes. The actin cytoskeletons terminated or branched at the podosomes, where the membrane tightly adhered to the substratum. Microtubules were not usually present in the podosome structures; however, certain microtubules appeared to be morphologically in direct contact with the podosome core. Most of the larger clathrin plaques consisted of flat sheets of clathrin lattices that interconnected neighboring clathrin lattices to form an extensive clathrin area. However, the small deeply invaginated clathrin plaques and the podosomal cytoskeleton were located close together. Thus, the clathrin plaques on the ventral membrane of osteoclasts might be involved in both cell adhesion and the formation of receptor-ligand complexes, i.e., endocytosis.

Lipase kinetics: hydrolysis of triacetin by lipase from Candida cylindracea in a hollow-fiber membrane reactor

NARCIS (Netherlands)

Guit, R.P.M.; Kloosterman, M.; Meindersma, G.W.; Mayer, M.; Meijer, E.M.

1991-01-01

The aptitude of a hollow-fiber membrane reactor to det. lipase kinetics was investigated using the hydrolysis of triacetin catalyzed by lipase from C. cylindracea as a model system. The binding of the lipase to the membrane appears not to be very specific (surface adsorption), and probably its

A bioabsorbable membrane (Seprafilm®) may prevent postoperative mediastinal adhesions following mediastinoscopy: an experimental study in rats.

Science.gov (United States)

Büyükkale, Songül; Çıtak, Necati; İşgörücü, Özgür; Sayar, Adnan

2015-01-01

The aim of this experimental study was to investigate the anti-adhesion property of a bioabsorbable membrane following mediastinoscopy in a rat model. The study was conducted in 20 male Sprague-Dawley rats. Mediastinoscopy was performed all of them. Rats were divided into two groups; control group (n=10); mediastinoscopy alone, study group (n=10); mediastinoscopy and sodiumhyaluronate-carboxymethlycellulose film (Seprafilm®; Genzyme Corporation, Cambridge, Mass. USA). It was used to the mediastinal surface at the end of the surgical procedure in study group. Re-mediastinoscopy was performed after 7 days. Adhesion and vascularity grade description scores were analyzed. The parameters evaluated were presence of polymorhphonucleer leucocyte, macrophage, lymphocyte, fibroblasts, edema, neovascularisation, collagenisation, and foreing body reaction. All the rats survived uneventfully until being sacrificed without any postoperative complications. The mean adhesion score was found to be significantly higher in control group (n=2.5±0.5) compared with study group (n=1.0±0.1) (P=0.007). Vascularity grade description score was significantly higher in control group (n=2.3±0.6) than in study group (n=1.4±0.6) (P=0.009). There were no statistical differences between the groups with regard to edema, lymphocyte and macrophage infiltration, fibroblast proliferation and foreign body reactions (P>0.05). The used of Seprafilm® during the primary procedure can reduce to the mediastinal adhesions. However, further studies are required to assess the precise impact of the anti-adhesive agents on adhesion.

Time-Dependent Effect of Refrigeration on Viscosity and Conversion Kinetics of Dental Adhesive Resins

Science.gov (United States)

Faria-e-Silva, André L; Piva, Evandro; Moraes, Rafael R

2010-01-01

Objectives: This study evaluated the effect of refrigeration at 4°C and post-refrigeration times (immediate, 5, 10, 15, or 20 min) on the viscosity and conversion kinetics of adhesive bonding resins. Methods: Scotchbond Dual-Cure (3M ESPE) and Clearfil SE Bond (Kuraray) were tested. Control samples were kept at 25°C for 24 h. At each post-refrigeration time, the temperature was checked with a K-type thermocouple. Viscosity measurements as a function of temperature were performed using a cone-plate viscometer. Real-time polymerization was monitored by infrared spectroscopy. Degree of conversion (DC) was calculated for each second during polymerization, and the rate of polymerization analyzed. Data were separately submitted to two-way ANOVA and Tukey’s test (P<.05). Results: Clearfil presented faster increase in temperature after exposure to room temperature than Scotchbond. A continuous decrease in viscosity (Pa.s) was observed for both Scotchbond (0.49, 0.34, 0.30, 0.26, 0.23, 0.23) and Clearfil (0.38, 0.37, 0.34, 0.25, 0.24, 0.22). For Scotchbond, higher final DC was detected for the control (62.7%) compared with the immediate (53.3%) and 5 min (54.7%) groups. For Clearfil, the control sample (81.4%) showed higher DC than all refrigerated groups (68.8–69.5%). Clearfil always showed significantly higher DC than Scotchbond. Conclusions: Refrigeration presented a significant time- and material-dependent effect on the viscosity and polymerization kinetics of the bonding resins. Under clinical conditions, adhesive agents should be removed from the refrigerator at least 20 min before being used. PMID:20396445

Quantification of Protein-Induced Membrane Remodeling Kinetics In Vitro with Lipid Multilayer Gratings

Science.gov (United States)

Lowry, Troy W.; Hariri, Hanaa; Prommapan, Plengchart; Kusi-Appiah, Aubrey; Vafai, Nicholas; Bienkiewicz, Ewa A.; Van Winkle, David H.; Stagg, Scott M.

2016-01-01

The dynamic self-organization of lipids in biological systems is a highly regulated process that enables the compartmentalization of living systems at micro- and nanoscopic scales. Consequently, quantitative methods for assaying the kinetics of supramolecular remodeling such as vesicle formation from planar lipid bilayers or multilayers are needed to understand cellular self-organization. Here, a new nanotechnology-based method for quantitative measurements of lipid–protein interactions is presented and its suitability for quantifying the membrane binding, inflation, and budding activity of the membrane-remodeling protein Sar1 is demonstrated. Lipid multilayer gratings are printed onto surfaces using nanointaglio and exposed to Sar1, resulting in the inflation of lipid multilayers into unilamellar structures, which can be observed in a label-free manner by monitoring the diffracted light. Local variations in lipid multilayer volume on the surface is used to vary substrate availability in a microarray format. A quantitative model is developed that allows quantification of binding affinity (KD) and kinetics (kon and koff). Importantly, this assay is uniquely capable of quantifying membrane remodeling. Upon Sar1-induced inflation of single bilayers from surface supported multilayers, the semicylindrical grating lines are observed to remodel into semispherical buds when a critical radius of curvature is reached. PMID:26649649

Adhesion and removal kinetics of Bacillus cereus biofilms on Ni-PTFE modified stainless steel.

Science.gov (United States)

Huang, Kang; McLandsborough, Lynne A; Goddard, Julie M

2016-01-01

Biofilm control remains a challenge to food safety. A well-studied non-fouling coating involves codeposition of polytetrafluoroethylene (PTFE) during electroless plating. This coating has been reported to reduce foulant build-up during pasteurization, but opportunities remain in demonstrating its efficacy in inhibiting biofilm formation. Herein, the initial adhesion, biofilm formation, and removal kinetics of Bacillus cereus on Ni-PTFE-modified stainless steel (SS) are characterized. Coatings lowered the surface energy of SS and reduced biofilm formation by > 2 log CFU cm(-2). Characterization of the kinetics of biofilm removal during cleaning demonstrated improved cleanability on the Ni-PTFE coated steel. There was no evidence of biofilm after cleaning by either solution on the Ni-PTFE coated steel, whereas more than 3 log and 1 log CFU cm(-2) of bacteria remained on the native steel after cleaning with water and an alkaline cleaner, respectively. This work demonstrates the potential application of Ni-PTFE non-fouling coatings on SS to improve food safety by reducing biofilm formation and improving the cleaning efficiency of food processing equipment.

Focal adhesions and cell-matrix interactions

DEFF Research Database (Denmark)

Woods, A; Couchman, J R

1988-01-01

Focal adhesions are areas of cell surfaces where specializations of cytoskeletal, membrane and extracellular components combine to produce stable cell-matrix interactions. The morphology of these adhesions and the components identified in them are discussed together with possible mechanisms...

H2-assisted CO2 thermochemical reduction on La0.9Ca0.1FeO3-δ membranes: a kinetics study

KAUST Repository

Wu, Xiao-Yu; Ghoniem, Ahmed F.

2017-01-01

Kinetics data for CO2 thermochemical reduction in an isothermal membrane reactor is required to identify the rate-limiting steps. Here, we report a detailed reaction kinetics study on this process supported by an La0.9Ca0.1FeO3-δ (LCF-91) membrane. The dependence of CO2 reduction rate on various operating conditions is examined such as CO2 concentration on the feed side, fuel concentrations on the sweep side and temperatures. CO2 reduction rate is proportional to the oxygen flux across the membrane, and the measured maximum fluxes are 0.191 and 0.164 μmol cm-2 s-1 with 9.5% H2 and 11.6% CO on the sweep side at 990oC, respectively. Fuel is used to maintain the chemical potential gradient across the membrane and CO is used by construction to derive the surface reaction kinetics. This membrane also exhibits stable performances for 106 hours. A resistance-network model is developed to describe the oxygen transport process and the kinetics data are parameterized using the experimental values. The model shows a transition of the rate limiting step between the surface reactions on the feed side and the sweep side depending on the operating conditions.

H2-assisted CO2 thermochemical reduction on La0.9Ca0.1FeO3-δ membranes: a kinetics study

KAUST Repository

Wu, Xiao-Yu

2017-11-04

Kinetics data for CO2 thermochemical reduction in an isothermal membrane reactor is required to identify the rate-limiting steps. Here, we report a detailed reaction kinetics study on this process supported by an La0.9Ca0.1FeO3-δ (LCF-91) membrane. The dependence of CO2 reduction rate on various operating conditions is examined such as CO2 concentration on the feed side, fuel concentrations on the sweep side and temperatures. CO2 reduction rate is proportional to the oxygen flux across the membrane, and the measured maximum fluxes are 0.191 and 0.164 μmol cm-2 s-1 with 9.5% H2 and 11.6% CO on the sweep side at 990oC, respectively. Fuel is used to maintain the chemical potential gradient across the membrane and CO is used by construction to derive the surface reaction kinetics. This membrane also exhibits stable performances for 106 hours. A resistance-network model is developed to describe the oxygen transport process and the kinetics data are parameterized using the experimental values. The model shows a transition of the rate limiting step between the surface reactions on the feed side and the sweep side depending on the operating conditions.

Adhesion kinetics of human primary monocytes, dendritic cells, and macrophages: Dynamic cell adhesion measurements with a label-free optical biosensor and their comparison with end-point assays.

Science.gov (United States)

Orgovan, Norbert; Ungai-Salánki, Rita; Lukácsi, Szilvia; Sándor, Noémi; Bajtay, Zsuzsa; Erdei, Anna; Szabó, Bálint; Horvath, Robert

2016-09-01

obtained with the high-temporal-resolution Epic BT, but could only provide end-point data. In contrast, complex, nonmonotonic cell adhesion kinetics measured by the high-throughput optical biosensor is expected to open a window on the hidden background of the immune cell-extracellular matrix interactions.

Spatial distribution of mechanical forces and ionic flux in electro-kinetic instability near a permselective membrane

Science.gov (United States)

Magnico, Pierre

2018-01-01

This paper is devoted to the numerical investigation of electro-kinetic instability in a polarization layer next to a cation-exchange membrane. An analysis of some properties of the electro-kinetic instability is followed by a detailed description of the fluid flow structure and of the spatial distribution of the ionic flux. In this aim, the Stokes-Poisson-Nernst-Planck equation set is solved until the Debye length scale. The results show that the potential threshold of the marginal instability and the current density depend on the logarithm of the concentration at the membrane surface. The size of the stable vortices seems to be an increasing function of the potential drop. The fluid motion is induced by the electric force along the maximum concentration in the extended space charge (ESC) region and by the pressure force in the region around the inner edge of the ESC layer. Two spots of kinetic energy are located in the ESC region and between the vortices. The cationic motion, controlled by the electric field and the convection, presents counter-rotating vortices in the stagnation zone located in the fluid ejection region. The anion transport is also characterized by two independent layers which contain counter-rotating vortices. The first one is in contact with the stationary reservoir. In the second layer against the membrane, the convection, and the electric field control, the transversal motion, the Fickian diffusion, and the convection are dominant in the longitudinal direction. Finally, the longitudinal disequilibrium of potential and pressure along the membrane is analyzed.

Phosphotyrosine-mediated LAT assembly on membranes drives kinetic bifurcation in recruitment dynamics of the Ras activator SOS.

Science.gov (United States)

Huang, William Y C; Yan, Qingrong; Lin, Wan-Chen; Chung, Jean K; Hansen, Scott D; Christensen, Sune M; Tu, Hsiung-Lin; Kuriyan, John; Groves, Jay T

2016-07-19

The assembly of cell surface receptors with downstream signaling molecules is a commonly occurring theme in multiple signaling systems. However, little is known about how these assemblies modulate reaction kinetics and the ultimate propagation of signals. Here, we reconstitute phosphotyrosine-mediated assembly of extended linker for the activation of T cells (LAT):growth factor receptor-bound protein 2 (Grb2):Son of Sevenless (SOS) networks, derived from the T-cell receptor signaling system, on supported membranes. Single-molecule dwell time distributions reveal two, well-differentiated kinetic species for both Grb2 and SOS on the LAT assemblies. The majority fraction of membrane-recruited Grb2 and SOS both exhibit fast kinetics and single exponential dwell time distributions, with average dwell times of hundreds of milliseconds. The minor fraction exhibits much slower kinetics, extending the dwell times to tens of seconds. Considering this result in the context of the multistep process by which the Ras GEF (guanine nucleotide exchange factor) activity of SOS is activated indicates that kinetic stabilization from the LAT assembly may be important. This kinetic proofreading effect would additionally serve as a stochastic noise filter by reducing the relative probability of spontaneous SOS activation in the absence of receptor triggering. The generality of receptor-mediated assembly suggests that such effects may play a role in multiple receptor proximal signaling processes.

Bilateral PLA/alginate membranes for the prevention of postsurgical adhesions.

Science.gov (United States)

Kessler, Martina; Esser, Eva; Groll, Jürgen; Tessmar, Jörg

2016-11-01

A bilateral barrier membrane for the prevention of postsurgical adhesions was developed. Thereby, a smooth PLA side was supposed to keep the affected tissues glidingly separated, while a mucoadhesive side made of alginate was meant to keep the barrier resident on the site of injury so that suturing becomes redundant or at least the membrane stays long enough to facilitate surgical handling. Because hydrophilic alginate and lipophilic PLA films show only low cohesion, solution electrospun meshes of PLA and PLA-PEG-PLA triblock copolymers with varying poly(ethylene glycol) [PEG] content were investigated as cohesion promoter to avoid an easy separation of the functionally different layers. Using direct electrospinning onto the PLA film, a modified contact surface of the mesh was created, which allowed the tested alginate solutions (3%, 5%) to infiltrate to different extents. Thereby, an increasing content of hydrophilic PEG within the mesh copolymer and a lower alginate concentration facilitated the infiltration. As a result, the PLA film with a PLA35k-PEG10k-PLA35k (racemic PLA chains) mesh and an alginate layer cast from a 3% alginate solution appeared to be the most effective combination as examined by means of a t peel test, a mucoadhesion test, a tensile test and optical evaluations. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1563-1570, 2016. © 2015 Wiley Periodicals, Inc.

Soft grippers using micro-fibrillar adhesives for transfer printing.

Science.gov (United States)

Song, Sukho; Sitti, Metin

2014-07-23

The adhesive characteristics of fibrillar adhesives on a soft deformable membrane are reported. A soft gripper with an inflatable membrane covered by elastomer mushroom-shaped microfibers have a superior conformation to non-planar 3D part geometries, enabling the transfer printing of various parts serially or in parallel. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of the anti-adhesive effect of milk fat globule membrane glycoproteins on Helicobacter pylori in the human NCI-N87 cell line and C57BL/6 mouse model.

Science.gov (United States)

Horemans, Tessa; Kerstens, Monique; Clais, Sofie; Struijs, Karin; van den Abbeele, Pieter; Van Assche, Tim; Maes, Louis; Cos, Paul

2012-08-01

 The interest in non-antibiotic therapies for Helicobacter pylori infections in man has considerably grown because increasing numbers of antibiotic-resistant strains are being reported. Intervention at the stage of bacterial attachment to the gastric mucosa could be an approach to improve the control/eradication rate of this infection.  Fractions of purified milk fat globule membrane glycoproteins were tested in vitro for their cytotoxic and direct antibacterial effect. The anti-adhesive effect on H. pylori was determined first in a cell model using the mucus-producing gastric epithelial cell line NCI-N87 and next in the C57BL/6 mouse model after dosing at 400 mg/kg protein once or twice daily from day -2 to day 4 post-infection. Bacterial loads were determined by using quantitative real-time PCR and the standard plate count method.  The milk fat globule membrane fractions did not show in vitro cytotoxicity, and a marginal antibacterial effect was demonstrated for defatted milk fat globule membrane at 256 μg/mL. In the anti-adhesion assay, the results varied from 56.0 ± 5.3% inhibition for 0.3% crude milk fat globule membrane to 79.3 ± 3.5% for defatted milk fat globule membrane. Quite surprisingly, in vivo administration of the same milk fat globule membrane fractions did not confirm the anti-adhesive effects and even caused an increase in bacterial load in the stomach.  The promising anti-adhesion in vitro results could not be confirmed in the mouse model, even after the highest attainable exposure. It is concluded that raw or defatted milk fat globule membrane fractions do not have any prophylactic or therapeutic potential against Helicobacter infection. © 2012 Blackwell Publishing Ltd.

The Molecular Architecture of Cell Adhesion: Dynamic Remodeling Revealed by Videonanoscopy

Directory of Open Access Journals (Sweden)

Arnauld eSergé

2016-05-01

Full Text Available The plasma membrane delimits the cell, which is the basic unit of living organisms, and is also a privileged site for cell communication with the environment. Cell adhesion can occur through cell-cell and cell-matrix contacts. Adhesion proteins such as integrins and cadherins also constitute receptors for inside-out and outside-in signaling within proteolipidic platforms. Adhesion molecule targeting and stabilization relies on specific features such as preferential segregation by the sub-membrane cytoskeleton meshwork and within membrane proteolipidic microdomains. This review presents an overview of the recent insights brought by the latest developments in microscopy, to unravel the molecular remodeling occurring at cell contacts. The dynamic aspect of cell adhesion was recently highlighted by super-resolution videomicroscopy, also named videonanoscopy. By circumventing the diffraction limit of light, nanoscopy has allowed the monitoring of molecular localization and behavior at the single-molecule level, on fixed and living cells. Accessing molecular-resolution details such as quantitatively monitoring components entering and leaving cell contacts by lateral diffusion and reversible association has revealed an unexpected plasticity. Adhesion structures can be highly specialized, such as focal adhesion in motile cells, as well as immune and neuronal synapses. Spatiotemporal reorganization of adhesion molecules, receptors and adaptors directly relates to structure/function modulation. Assembly of these supramolecular complexes is continuously balanced by dynamic events, remodeling adhesions on various timescales, notably by molecular conformation switches, lateral diffusion within the membrane and endo/exocytosis. Pathological alterations in cell adhesion are involved in cancer evolution, through cancer stem cell interaction with stromal niches, growth, extravasation and metastasis.

CO2 adsorption using TiO2 composite polymeric membranes: A kinetic study.

Science.gov (United States)

Hafeez, Sarah; Fan, X; Hussain, Arshad; Martín, C F

2015-09-01

CO2 is the main greenhouse gas which causes global climatic changes on larger scale. Many techniques have been utilised to capture CO2. Membrane gas separation is a fast growing CO2 capture technique, particularly gas separation by composite membranes. The separation of CO2 by a membrane is not just a process to physically sieve out of CO2 through the controlled membrane pore size. It mainly depends upon diffusion and solubility of gases, particularly for composite dense membranes. The blended components in composite membranes have a high capability to adsorb CO2. The adsorption kinetics of the gases may directly affect diffusion and solubility. In this study, we have investigated the adsorption behaviour of CO2 in pure and composite membranes to explore the complete understanding of diffusion and solubility of CO2 through membranes. Pure cellulose acetate (CA) and cellulose acetate-titania nanoparticle (CA-TiO2) composite membranes were fabricated and characterised using SEM and FTIR analysis. The results indicated that the blended CA-TiO2 membrane adsorbed more quantity of CO2 gas as compared to pure CA membrane. The high CO2 adsorption capacity may enhance the diffusion and solubility of CO2 in the CA-TiO2 composite membrane, which results in a better CO2 separation. The experimental data was modelled by Pseudo first-order, pseudo second order and intra particle diffusion models. According to correlation factor R(2), the Pseudo second order model was fitted well with experimental data. The intra particle diffusion model revealed that adsorption in dense membranes was not solely consisting of intra particle diffusion. Copyright © 2015. Published by Elsevier B.V.

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

Science.gov (United States)

Song, Sukho; Drotlef, Dirk-Michael; Majidi, Carmel; Sitti, Metin

2017-05-01

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ˜26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.

Effects of fiber density and plasma modification of nanofibrous membranes on the adhesion and growth of HaCaT keratinocytes.

Science.gov (United States)

Bacakova, Marketa; Lopot, Frantisek; Hadraba, Daniel; Varga, Marian; Zaloudkova, Margit; Stranska, Denisa; Suchy, Tomas; Bacakova, Lucie

2015-01-01

It may be possible to regulate the cell colonization of biodegradable polymer nanofibrous membranes by plasma treatment and by the density of the fibers. To test this hypothesis, nanofibrous membranes of different fiber densities were treated by oxygen plasma with a range of plasma power and exposure times. Scanning electron microscopy and mechanical tests showed significant modification of nanofibers after plasma treatment. The intensity of the fiber modification increased with plasma power and exposure time. The exposure time seemed to have a stronger effect on modifying the fiber. The mechanical behavior of the membranes was influenced by the plasma treatment, the fiber density, and their dry or wet state. Plasma treatment increased the membrane stiffness; however, the membranes became more brittle. Wet membranes displayed significantly lower stiffness than dry membranes. X-ray photoelectron spectroscopy (XPS) analysis showed a slight increase in oxygen-containing groups on the membrane surface after plasma treatment. Plasma treatment enhanced the adhesion and growth of HaCaT keratinocytes on nanofibrous membranes. The cells adhered and grew preferentially on membranes of lower fiber densities, probably due to the larger area of void spaces between the fibers. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Expression and organization of basement membranes and focal adhesion proteins in pregnant myometrium is regulated by uterine stretch.

Science.gov (United States)

Shynlova, Oksana; Chow, Michelle; Lye, Stephen J

2009-10-01

The mechanisms underlying the preparation of the uterus for labor are not fully understood. We have previously found a significant increase in the expression of messenger RNA (mRNAs) encoding extracellular basement membrane (BM) proteins of the smooth muscle cells (SMCs) in late pregnant rat myometrium. At term, the myometrium is stretched by growing fetuses and these mechanical signals are transmitted from extracellular matrix into SMCs through focal adhesions (FA). The aim of this study was to investigate the effect of gravidity on the expression and spatiotemporal distribution of major BM proteins, laminin-gamma2 and collagen IV, as well as typical FA constituents, vinculin and paxillin, in the myometrium during gestation and parturition, using a unilaterally pregnant rat model. We found that the expression of laminin-gamma2 and collagen IV proteins increased significantly with gestational age (P proteins were not affected. Near term, BM proteins from gravid horn myometrium demonstrated increased extracellular immunostaining and major rearrangement from sporadic protein distribution to organized, continuous, and regular structures surrounding the plasma membrane of each myocyte. Examination of FA proteins revealed that paxillin was translocated from the cytoplasm to the cell periphery, while vinculin was sequestered specifically to FAs. At labor, BM and FA proteins, organized in similar bead-like structures, were localized on opposing sides of SMC plasma membrane into 2 different compartments. We suggest that these stretch-induced changes facilitate formation of stable cell-matrix adhesions and provide the molecular basis for optimal force transduction during labor contractions.

Ciprofloxacin release using natural rubber latex membranes as carrier.

Science.gov (United States)

Dias Murbach, Heitor; Jaques Ogawa, Guilherme; Azevedo Borges, Felipe; Romeiro Miranda, Matheus Carlos; Lopes, Rute; Roberto de Barros, Natan; Guedes Mazalli, Alexandre Vinicius; Gonçalves da Silva, Rosângela; Ferreira Cinman, José Luiz; de Camargo Drago, Bruno; Donizetti Herculano, Rondinelli

2014-01-01

Natural rubber latex (NRL) from Hevea brasiliensis is easily manipulated, low cost, is of can stimulate natural angiogenesis and cellular adhesion, is a biocompatible, material and presents high mechanical resistance. Ciprofloxacin (CIP) is a synthetic antibiotic (fluoroquinolone) used in the treatment of infection at external fixation screws sites and remote infections, and this use is increasingly frequent in medical practice. The aim of this study was to develop a novel sustained delivery system for CIP based on NRL membranes and to study its delivery system behavior. CIP was found to be adsorbed on the NRL membrane, according to results of energy dispersive X-ray spectroscopy. Results show that the membrane can release CIP for up to 59.08% in 312 hours and the mechanism is due to super case II (non-Fickian). The kinetics of the drug release could be fitted with double exponential function X-ray diffraction and Fourier transform infrared (FTIR) spectroscopy shows some interaction by hydrogen bound, which influences its mechanical behavior.

Scalable bonding of nanofibrous polytetrafluoroethylene (PTFE) membranes on microstructures

Science.gov (United States)

Mortazavi, Mehdi; Fazeli, Abdolreza; Moghaddam, Saeed

2018-01-01

Expanded polytetrafluoroethylene (ePTFE) nanofibrous membranes exhibit high porosity (80%-90%), high gas permeability, chemical inertness, and superhydrophobicity, which makes them a suitable choice in many demanding fields including industrial filtration, medical implants, bio-/nano- sensors/actuators and microanalysis (i.e. lab-on-a-chip). However, one of the major challenges that inhibit implementation of such membranes is their inability to bond to other materials due to their intrinsic low surface energy and chemical inertness. Prior attempts to improve adhesion of ePTFE membranes to other surfaces involved surface chemical treatments which have not been successful due to degradation of the mechanical integrity and the breakthrough pressure of the membrane. Here, we report a simple and scalable method of bonding ePTFE membranes to different surfaces via the introduction of an intermediate adhesive layer. While a variety of adhesives can be used with this technique, the highest bonding performance is obtained for adhesives that have moderate contact angles with the substrate and low contact angles with the membrane. A thin layer of an adhesive can be uniformly applied onto micro-patterned substrates with feature sizes down to 5 µm using a roll-coating process. Membrane-based microchannel and micropillar devices with burst pressures of up to 200 kPa have been successfully fabricated and tested. A thin layer of the membrane remains attached to the substrate after debonding, suggesting that mechanical interlocking through nanofiber engagement is the main mechanism of adhesion.

Surface interactions and fouling properties of Micrococcus luteus with microfiltration membranes.

Science.gov (United States)

Feng, Lei; Li, Xiufen; Song, Ping; Du, Guocheng; Chen, Jian

2011-11-01

This study was conducted to investigate microbial adhesion of Micrococcus luteus to polypropylene (PP) and polyvinylidene fluoride (PVDF) membranes in relation to the variation of the interfacial energies in the membrane-bacteria systems, for revealing effects of short-range surface interactions on filtration behavior. Both the membranes and M. luteus showed typical strong electron donors and hydrophilic properties. The AB component was dominant in the interfacial energies of the two membrane-bacteria systems. M. luteus presented larger negative U(mlb)(XDLVO) to the PP membrane than to the PVDF membrane. The adhesion experiments also proved that M. luteus had higher adhesion percentage to the PP membrane. This study demonstrated that the adhesion potentials of M. luteus to the PP and PVDF membranes might be explained in terms of bacterium, membrane, and intervening medium surface properties, which are mainly determined by the interfacial energies in the systems according to the XDLVO theory.

Vaginal epithelial cells regulate membrane adhesiveness to co-ordinate bacterial adhesion

NARCIS (Netherlands)

Younes, Jessica A.; Klappe, Karin; Kok, Jan Willem; Busscher, Henk J.; Reid, Gregor; van der Mei, Henny C.

Vaginal epithelium is colonized by different bacterial strains and species. The bacterial composition of vaginal biofilms controls the balance between health and disease. Little is known about the relative contribution of the epithelial and bacterial cell surfaces to bacterial adhesion and whether

Programming Cell Adhesion for On-Chip Sequential Boolean Logic Functions.

Science.gov (United States)

Qu, Xiangmeng; Wang, Shaopeng; Ge, Zhilei; Wang, Jianbang; Yao, Guangbao; Li, Jiang; Zuo, Xiaolei; Shi, Jiye; Song, Shiping; Wang, Lihua; Li, Li; Pei, Hao; Fan, Chunhai

2017-08-02

Programmable remodelling of cell surfaces enables high-precision regulation of cell behavior. In this work, we developed in vitro constructed DNA-based chemical reaction networks (CRNs) to program on-chip cell adhesion. We found that the RGD-functionalized DNA CRNs are entirely noninvasive when interfaced with the fluidic mosaic membrane of living cells. DNA toehold with different lengths could tunably alter the release kinetics of cells, which shows rapid release in minutes with the use of a 6-base toehold. We further demonstrated the realization of Boolean logic functions by using DNA strand displacement reactions, which include multi-input and sequential cell logic gates (AND, OR, XOR, and AND-OR). This study provides a highly generic tool for self-organization of biological systems.

First study on gene expression of cement proteins and potential adhesion-related genes of a membranous-based barnacle as revealed from Next-Generation Sequencing technology

KAUST Repository

Lin, Hsiu Chin; Wong, Yue Him; Tsang, Ling Ming; Chu, Ka Hou; Qian, Pei Yuan; Chan, Benny K K

2013-01-01

This is the first study applying Next-Generation Sequencing (NGS) technology to survey the kinds, expression location, and pattern of adhesion-related genes in a membranous-based barnacle. A total of 77,528,326 and 59,244,468 raw sequence reads of total RNA were generated from the prosoma and the basis of Tetraclita japonica formosana, respectively. In addition, 55,441 and 67,774 genes were further assembled and analyzed. The combined sequence data from both body parts generates a total of 79,833 genes of which 47.7% were shared. Homologues of barnacle cement proteins - CP-19K, -52K, and -100K - were found and all were dominantly expressed at the basis where the cement gland complex is located. This is the main area where transcripts of cement proteins and other potential adhesion-related genes were detected. The absence of another common barnacle cement protein, CP-20K, in the adult transcriptome suggested a possible life-stage restricted gene function and/or a different mechanism in adhesion between membranous-based and calcareous-based barnacles. © 2013 © 2013 Taylor & Francis.

First study on gene expression of cement proteins and potential adhesion-related genes of a membranous-based barnacle as revealed from Next-Generation Sequencing technology

KAUST Repository

Lin, Hsiu Chin

2013-12-12

This is the first study applying Next-Generation Sequencing (NGS) technology to survey the kinds, expression location, and pattern of adhesion-related genes in a membranous-based barnacle. A total of 77,528,326 and 59,244,468 raw sequence reads of total RNA were generated from the prosoma and the basis of Tetraclita japonica formosana, respectively. In addition, 55,441 and 67,774 genes were further assembled and analyzed. The combined sequence data from both body parts generates a total of 79,833 genes of which 47.7% were shared. Homologues of barnacle cement proteins - CP-19K, -52K, and -100K - were found and all were dominantly expressed at the basis where the cement gland complex is located. This is the main area where transcripts of cement proteins and other potential adhesion-related genes were detected. The absence of another common barnacle cement protein, CP-20K, in the adult transcriptome suggested a possible life-stage restricted gene function and/or a different mechanism in adhesion between membranous-based and calcareous-based barnacles. © 2013 © 2013 Taylor & Francis.

Coordination kinetics of different metal ions with the amidoximated polyacrylonitrile nanofibrous membranes and catalytic behaviors of their complexes

Energy Technology Data Exchange (ETDEWEB)

Li, Fu; Dong, Yong Chun; Kang, Wei Min; Cheng, Bowen; Qu, Xiang; Cui, Guixin [School of Textiles, Tianjin Polytechnic University, Tianjin (China)

2016-12-15

Two transition metal ions (Fe{sup 3+} and Cu{sup 2+}) and a rare earth metal ion (Ce{sup 3+}) were selected to coordinate with amidoximated polyacrylonitrile (PAN) nanofibrous membrane for preparing three metal modified PAN nanofibrous membrane complexes (M-AO-n-PANs, M = Fe, Cu, or Ce) as the heterogeneous Fenton catalysts for the dye degradation in water under visible irradiation. The coordination kinetics of three metal ions with modified PAN nanofibrous membranes was studied and the catalytic properties of the resulting complexes were also compared. The results indicated that increasing metal ion concentrations in solution or higher coordination temperature led to a significant increase in metal content, particularly in Fe and Cu contents of the complexes. Their coordination process could be described using Langmuir isotherm and pseudo-second-order kinetic equations. Moreover, Fe-AO-n-PAN had the best photocatalytic efficiency for the dye degradation in acidic medium, but a lower photocatalytic activity than Cu-AO-n-PAN in alkali medium.

CX3CL1, a chemokine finely tuned to adhesion: critical roles of the stalk glycosylation and the membrane domain

Directory of Open Access Journals (Sweden)

Mariano A. Ostuni

2014-11-01

Full Text Available The multi-domain CX3CL1 transmembrane chemokine triggers leukocyte adherence without rolling and migration by presenting its chemokine domain (CD to its receptor CX3CR1. Through the combination of functional adhesion assays with structural analysis using FRAP, we investigated the functional role of the other domains of CX3CL1, i.e., its mucin stalk, transmembrane domain, and cytosolic domain. Our results indicate that the CX3CL1 molecular structure is finely adapted to capture CX3CR1 in circulating cells and that each domain has a specific purpose: the mucin stalk is stiffened by its high glycosylation to present the CD away from the membrane, the transmembrane domain generates the permanent aggregation of an adequate amount of monomers to guarantee adhesion and prevent rolling, and the cytosolic domain ensures adhesive robustness by interacting with the cytoskeleton. We propose a model in which quasi-immobile CX3CL1 bundles are organized to quickly generate adhesive patches with sufficiently high strength to capture CX3CR1+ leukocytes but with sufficiently low strength to allow their patrolling behavior.

Vesicle-associated membrane protein 2 mediates trafficking of α5β1 integrin to the plasma membrane

International Nuclear Information System (INIS)

Hasan, Nazarul; Hu, Chuan

2010-01-01

Integrins are major receptors for cell adhesion to the extracellular matrix (ECM). As transmembrane proteins, the levels of integrins at the plasma membrane or the cell surface are ultimately determined by the balance between two vesicle trafficking events: endocytosis of integrins at the plasma membrane and exocytosis of the vesicles that transport integrins. Here, we report that vesicle-associated membrane protein 2 (VAMP2), a SNARE protein that mediates vesicle fusion with the plasma membrane, is involved in the trafficking of α5β1 integrin. VAMP2 was present on vesicles containing endocytosed β1 integrin. Small interfering RNA (siRNA) silencing of VAMP2 markedly reduced cell surface α5β1 and inhibited cell adhesion and chemotactic migration to fibronectin, the ECM ligand of α5β1, without altering cell surface expression of α2β1 integrin or α3β1 integrin. By contrast, silencing of VAMP8, another SNARE protein, had no effect on cell surface expression of the integrins or cell adhesion to fibronectin. In addition, VAMP2-mediated trafficking is involved in cell adhesion to collagen but not to laminin. Consistent with disruption of integrin functions in cell proliferation and survival, VAMP2 silencing diminished proliferation and triggered apoptosis. Collectively, these data indicate that VAMP2 mediates the trafficking of α5β1 integrin to the plasma membrane and VAMP2-dependent integrin trafficking is critical in cell adhesion, migration and survival.

Cell surface clustering of Cadherin adhesion complex induced by antibody coated beads

Institute of Scientific and Technical Information of China (English)

无

2000-01-01

Cadherin receptors mediate cell-cell adhesion, signal transduction and assembly of cytoskeletons. How a single transmembrane molecule Cadherin can be involved in multiple functions through modulating its binding activities with many membrane adhesion molecules and cytoskeletal components is an unanswered question which can be elucidated by clues from bead experiments. Human lung cells expressing N-Cadherin were examined. After co-incubation with anti-N-Cadherin monoclonal antibody coated beads, cell surface clustering of N-Cadherin was induced. Immunofluorescent detection demonstrated that in addition to Cadherin, β-Catenin, α-Catenin, α-Actinin and Actin fluorescence also aggregated respectively at the membrane site of bead attachment. Myosin heavy chain (MHC), another major component of Actin cytoskeleton, did not aggregate at the membrane site of bead attachment. Adhesion unrelated protein Con A and polylysine conjugated beads did not induce the clustering of adhesion molecules. It is indicated that the Cadherin/Catenins/α-Actinin/Actin complex is formed at Cadherin mediated cell adherens junction; occupancy and cell surface clustering of Cadherin is crucial for the formation of Cadherin adhesion protein complexes.

Green tea polyphenol tailors cell adhesivity of RGD displaying surfaces: multicomponent models monitored optically.

Science.gov (United States)

Peter, Beatrix; Farkas, Eniko; Forgacs, Eniko; Saftics, Andras; Kovacs, Boglarka; Kurunczi, Sandor; Szekacs, Inna; Csampai, Antal; Bosze, Szilvia; Horvath, Robert

2017-02-10

The interaction of the anti-adhesive coating, poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) and its Arg-Gly-Asp (RGD) functionalized form, PLL-g-PEG-RGD, with the green tea polyphenol, epigallocatechin-gallate (EGCg) was in situ monitored. After, the kinetics of cellular adhesion on the EGCg exposed coatings were recorded in real-time. The employed plate-based waveguide biosensor is applicable to monitor small molecule binding and sensitive to sub-nanometer scale changes in cell membrane position and cell mass distribution; while detecting the signals of thousands of adhering cells. The combination of this remarkable sensitivity and throughput opens up new avenues in testing complicated models of cell-surface interactions. The systematic studies revealed that, despite the reported excellent antifouling properties of the coatings, EGCg strongly interacted with them, and affected their cell adhesivity in a concentration dependent manner. Moreover, the differences between the effects of the fresh and oxidized EGCg solutions were first demonstrated. Using a semiempirical quantumchemical method we showed that EGCg binds to the PEG chains of PLL-g-PEG-RGD and effectively blocks the RGD sites by hydrogen bonds. The calculations supported the experimental finding that the binding is stronger for the oxidative products. Our work lead to a new model of polyphenol action on cell adhesion ligand accessibility and matrix rigidity.

Adhesive F-actin Waves: A Novel Integrin-Mediated Adhesion Complex Coupled to Ventral Actin Polymerization

OpenAIRE

Case, Lindsay B.; Waterman, Clare M.

2011-01-01

At the leading lamellipodium of migrating cells, protrusion of an Arp2/3-nucleated actin network is coupled to formation of integrin-based adhesions, suggesting that Arp2/3-mediated actin polymerization and integrin-dependent adhesion may be mechanistically linked. Arp2/3 also mediates actin polymerization in structures distinct from the lamellipodium, in "ventral F-actin waves" that propagate as spots and wavefronts along the ventral plasma membrane. Here we show that integrins engage the ex...

Nanodiscs for immobilization of lipid bilayers and membrane receptors: kinetic analysis of cholera toxin binding to a glycolipid receptor

DEFF Research Database (Denmark)

Borch, Jonas; Torta, Federico; Sligar, Stephen G

2008-01-01

nanodiscs and their incorporated membrane receptors can be attached to surface plasmon resonance sensorchips and used to measure the kinetics of the interaction between soluble molecules and membrane receptors inserted in the bilayer of nanodiscs. Cholera toxin and its glycolipid receptor G(M1) constitute...... a system that can be considered a paradigm for interactions of soluble proteins with membrane receptors. In this work, we have investigated different technologies for capturing nanodiscs containing the glycolipid receptor G(M1) in lipid bilayers, enabling measurements of binding of its soluble interaction...

Combined modeling of cell aggregation and adhesion mediated by receptor–ligand interactions under shear flow

Directory of Open Access Journals (Sweden)

Yu Du

2015-11-01

Full Text Available Blood cell aggregation and adhesion to endothelial cells under shear flow are crucial to many biological processes such as thrombi formation, inflammatory cascade, and tumor metastasis, in which these cellular interactions are mainly mediated by the underlying receptor–ligand bindings. While theoretical modeling of aggregation dynamics and adhesion kinetics of interacting cells have been well studied separately, how to couple these two processes remains unclear. Here we develop a combined model that couples cellular aggregation dynamics and adhesion kinetics under shear flow. The impacts of shear rate (or shear stress and molecular binding affinity were elucidated. This study provides a unified model where the action of a fluid flow drives cell aggregation and adhesion under the modulations of the mechanical shear flow and receptor–ligand interaction kinetics. It offers an insight into understanding the relevant biological processes and functions.

Functionality Effect of Pressure Sensitive Adhesives on In Vitro Drug Release Behavior of Fentanyl Drug in an Adhesive Patch

Directory of Open Access Journals (Sweden)

S.M. Taghizadeh

2009-12-01

Full Text Available Some formulations of drug in adhesive transdermal drug delivery systems (TDDSs( with different functional and non-functional acrylic pressure sensitive adhesives PSAs( were prepared. For this purpose fentanyl was used as a drug component. The effects of PSAs type on skin permeation and in vitro drug release from devices were evaluated using hydrodynamically well-characterized Chien permeation system fitted with excised rat abdominal skin. The adhesion properties of devices (peel strength and tack values( were obtained. It was found that TDDS with –COOH functional PSA had the lowest steady state flux. Drug release was followed by Higuchi's kinetic model. Adhesion properties of the samples were improved by addition of functional PSA in the formulations.

Kinetic model of continuous ethanol fermentation in closed-circulating process with pervaporation membrane bioreactor by Saccharomyces cerevisiae.

Science.gov (United States)

Fan, Senqing; Chen, Shiping; Tang, Xiaoyu; Xiao, Zeyi; Deng, Qing; Yao, Peina; Sun, Zhaopeng; Zhang, Yan; Chen, Chunyan

2015-02-01

Unstructured kinetic models were proposed to describe the principal kinetics involved in ethanol fermentation in a continuous and closed-circulating fermentation (CCCF) process with a pervaporation membrane bioreactor. After ethanol was removed in situ from the broth by the membrane pervaporation, the secondary metabolites accumulated in the broth became the inhibitors to cell growth. The cell death rate related to the deterioration of the culture environment was described as a function of the cell concentration and fermentation time. In CCCF process, 609.8 g L(-1) and 750.1 g L(-1) of ethanol production were obtained in the first run and second run, respectively. The modified Gompertz model, correlating the ethanol production with the fermentation period, could be used to describe the ethanol production during CCCF process. The fitting results by the models showed good agreement with the experimental data. These models could be employed for the CCCF process technology development for ethanol fermentation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Peptide-modified PELCL electrospun membranes for regulation of vascular endothelial cells

Energy Technology Data Exchange (ETDEWEB)

Zhou, Fang [School of Materials Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Jia, Xiaoling [Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083 (China); Yang, Yang [School of Materials Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Yang, Qingmao; Gao, Chao [Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083 (China); Zhao, Yunhui [School of Materials Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Fan, Yubo, E-mail: yubofan@buaa.edu.cn [Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083 (China); National Research Center for Rehabilitation Technical Aids, Beijing 100176 (China); Yuan, Xiaoyan, E-mail: yuanxy@tju.edu.cn [School of Materials Science and Engineering, Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China)

2016-11-01

The efficiency of biomaterials used in small vascular repair depends greatly on their ability to interact with vascular endothelial cells (VECs). Rapid endothelialization of the vascular grafts is a promising way to prevent thrombosis and intimal hyperplasia. In this work, modification of electrospun membranes of poly(ethylene glycol)-b-poly(L-lactide-co-ε-caprolactone) (PELCL) by three different peptides for regulation of VECs were studied in order to obtain ideal bioactive biomaterials as small diameter vascular grafts. QK (a mimetic peptide to vascular endothelial growth factor), Arg-Glu-Asp-Val (REDV, a specific adhesive peptide to VECs) and Val-Ala-Pro-Gly (VAPG, a specific adhesive peptide to vascular smooth muscle cells) were investigated. Surface properties of the modified membranes and the response of VECs were verified. It was found that protein adsorption and platelet adhesion were effectively suppressed with the introduction of QK, REDV or VAPG peptides on the PELCL electrospun membranes. Both QK- and REDV-modified electrospun membranes could accelerate the proliferation of VECs in the first 9 days, and the QK-modified electrospun membrane promoted cell proliferation more significantly than the REDV-modified one. The REDV-modified PELCL membrane was the most favorable for VECs adhesion than QK- and VAPG-modified membranes. It was suggested that QK- or REDV-modified PELCL electrospun membranes may have great potential applications in cardiovascular biomaterials for rapid endothelialization in situ. - Highlights: • A series of peptide-modified PELCL electrospun membranes were prepared. • Hemocompatibility of the membranes was greatly improved by the modification. • QK-modified PELCL membrane promoted VECs proliferation more significantly. • REDV-modified PELCL membrane was the most favorable for VEC adhesion.

Peptide-modified PELCL electrospun membranes for regulation of vascular endothelial cells

International Nuclear Information System (INIS)

Zhou, Fang; Jia, Xiaoling; Yang, Yang; Yang, Qingmao; Gao, Chao; Zhao, Yunhui; Fan, Yubo; Yuan, Xiaoyan

2016-01-01

The efficiency of biomaterials used in small vascular repair depends greatly on their ability to interact with vascular endothelial cells (VECs). Rapid endothelialization of the vascular grafts is a promising way to prevent thrombosis and intimal hyperplasia. In this work, modification of electrospun membranes of poly(ethylene glycol)-b-poly(L-lactide-co-ε-caprolactone) (PELCL) by three different peptides for regulation of VECs were studied in order to obtain ideal bioactive biomaterials as small diameter vascular grafts. QK (a mimetic peptide to vascular endothelial growth factor), Arg-Glu-Asp-Val (REDV, a specific adhesive peptide to VECs) and Val-Ala-Pro-Gly (VAPG, a specific adhesive peptide to vascular smooth muscle cells) were investigated. Surface properties of the modified membranes and the response of VECs were verified. It was found that protein adsorption and platelet adhesion were effectively suppressed with the introduction of QK, REDV or VAPG peptides on the PELCL electrospun membranes. Both QK- and REDV-modified electrospun membranes could accelerate the proliferation of VECs in the first 9 days, and the QK-modified electrospun membrane promoted cell proliferation more significantly than the REDV-modified one. The REDV-modified PELCL membrane was the most favorable for VECs adhesion than QK- and VAPG-modified membranes. It was suggested that QK- or REDV-modified PELCL electrospun membranes may have great potential applications in cardiovascular biomaterials for rapid endothelialization in situ. - Highlights: • A series of peptide-modified PELCL electrospun membranes were prepared. • Hemocompatibility of the membranes was greatly improved by the modification. • QK-modified PELCL membrane promoted VECs proliferation more significantly. • REDV-modified PELCL membrane was the most favorable for VEC adhesion.

Kinetic energy budget for electroconvective flows near ion selective membranes

Science.gov (United States)

Wang, Karen; Mani, Ali

2017-11-01

Electroconvection occurs when ions are driven from a bulk fluid through an ion-selective surface. When the driving voltage is beyond a threshold, this process undergoes a hydrodynamic instability called electroconvection, which can become chaotic due to nonlinear coupling between ion-transport, fluid flow, and electrostatic forces. Electroconvection significantly enhances ion transport and plays an important role in a wide range of electrochemical applications. We investigate this phenomenon by considering a canonical geometry consisting of a symmetric binary electrolyte between an ion-selective membrane and a reservoir using 2D direct numerical simulation (DNS). Our simulations reveal that for most practical regimes, DNS of electroconvection is expensive. Thus, a plan towards development of reduced-order models is necessary to facilitate the adoption of analysis of this phenomenon in industry. Here we use DNS to analyze the kinetic energy budget to shed light into the mechanisms sustaining flow and mixing in electroconvective flows. Our analysis reveals the relative dominance of kinetic energy sources, dissipation, and transport mechanisms sustaining electroconvection at different distances from the interface and over a wide range of input parameters. Karen Wang was supported by the National Defense Science & Engineering Graduate Fellowship (NDSEG). Ali Mani was supported by the National Science Foundation Award.

Kinetics of the membrane current mediated by serotonin 5-HT3 receptors in cultured mouse neuroblastoma cells.

NARCIS (Netherlands)

Neijt, H.C.; Plomp, J.J.; Vijverberg, H.P.M.

1989-01-01

1. Ionic currents mediated by serotonin 5-HT3 receptors were studied in the mouse neuroblastoma cell line N1E-115, using suction pipettes for intracellular perfusion and voltage clamp recording. The dependence of the kinetics of the membrane current on serotonin concentration was investigated. 2. At

Desmosome Assembly and Disassembly Are Membrane Raft-Dependent

Science.gov (United States)

Faundez, Victor; Koval, Michael; Mattheyses, Alexa L.; Kowalczyk, Andrew P.

2014-01-01

Strong intercellular adhesion is critical for tissues that experience mechanical stress, such as the skin and heart. Desmosomes provide adhesive strength to tissues by anchoring desmosomal cadherins of neighboring cells to the intermediate filament cytoskeleton. Alterations in assembly and disassembly compromise desmosome function and may contribute to human diseases, such as the autoimmune skin blistering disease pemphigus vulgaris (PV). We previously demonstrated that PV auto-antibodies directed against the desmosomal cadherin desmoglein 3 (Dsg3) cause loss of adhesion by triggering membrane raft-mediated Dsg3 endocytosis. We hypothesized that raft membrane microdomains play a broader role in desmosome homeostasis by regulating the dynamics of desmosome assembly and disassembly. In human keratinocytes, Dsg3 is raft associated as determined by biochemical and super resolution immunofluorescence microscopy methods. Cholesterol depletion, which disrupts rafts, prevented desmosome assembly and adhesion, thus functionally linking rafts to desmosome formation. Interestingly, Dsg3 did not associate with rafts in cells lacking desmosomal proteins. Additionally, PV IgG-induced desmosome disassembly occurred by redistribution of Dsg3 into raft-containing endocytic membrane domains, resulting in cholesterol-dependent loss of adhesion. These findings demonstrate that membrane rafts are required for desmosome assembly and disassembly dynamics, suggesting therapeutic potential for raft targeting agents in desmosomal diseases such as PV. PMID:24498201

Injectible candidate sealants for fetal membrane repair: Bonding and toxicity in vitro

Science.gov (United States)

Bilic, Grozdana; Brubaker, Carrie; Messersmith, Phillip B.; Mallik, Ajit S.; Quinn, Thomas M.; Haller, Claudia; Done, Elisa; Gucciardo, Leonardo; Zeisberger, Steffen M.; Zimmermann, Roland; Deprest, Jan; Zisch, Andreas H.

2010-01-01

Objective This study was undertaken to test injectible surgical sealants that are biocompatible with fetal membranes, eventually for closure of iatrogenic membrane defects. Study Design Dermabond, Histoacryl, Tissucol fibrin glue, and three types of in situ forming poly(ethylene glycol)-based polymer hydrogels were tested for acute toxicity upon direct contact with fetal membranes for 24h. For determination of elution toxicity, extracts of sealants were incubated on amnion cell cultures for 72h. Bonding and toxicity was assessed through morphological and/or biochemical analysis. Results Extracts of all adhesives were non-toxic for cultured cells. However, only Tissucol and one type of poly(ethylene glycol)-based hydrogel, mussel-mimetic tissue adhesive, showed efficient, non-disruptive, non-toxic bonding to fetal membranes. Mussel-mimetic tissue adhesive applied over membrane defects created with a 3.5 mm trocar accomplished leak-proof closure that withstood membrane stretch in an in vitro model. Conclusion A synthetic hydrogel-type tissue adhesive emerged as potential sealing modality for iatrogenic membrane defects that merits further evaluation in vivo. PMID:20096254

Kinetics of the flash-induced P515 response in relation to the H+-permeability of the membrane bound ATPase in spinach chloroplasts

Energy Technology Data Exchange (ETDEWEB)

Peters, R.L.; van Kooten, O.; Vredenberg, W.J.

1985-08-01

The effect of dicyclohexylcarbodiimide (DCCD) on the kinetics of the flash-induced P515 response and on the activity of the ATPase was investigated in isolated spinach chloroplasts. It was found that after the addition of 5 X 10(-8)mol DCCD the rate of ATP hydrolysis induced by a period of 60 sec illumination was decreased to less than 5% of its original value. At this concentration, hardly any effect, if at all, could be detected on the kinetics of the flash-induced P515 response, neither in dark-adapted nor in light-activated chloroplasts. It was concluded that the presence of concentrations of DCCD, sufficiently high to affect the ATPase activity, does not affect the kinetics of the flash-induced P515 response. Since DCCD decreases the H+ permeability of the membrane-bound ATPase, it was concluded that this permeability coefficient for protons is not an important factor in the regulation of the flash-induced membrane potential and, therefore, does not affect the kinetics of the flash-induced P515 response.

Development of composite metallic membranes for hydrogen purification

International Nuclear Information System (INIS)

Gaillard, F.

2003-12-01

Fuel cells are able to convert chemical energy into electric power. There are different types of cells; the best for automotive applications are Proton Exchange Membrane Fuel Cells. But, these systems need hydrogen of high purity. However, fuel reforming generates a mixture of gases, from which hydrogen has to be extracted before supplying the electrochemical cell. The best way for the purification of hydrogen is the membrane separation technology. Palladium is selectively permeable to hydrogen and this is the reason why this metal is largely used for the membrane development. This work deals with the development of hydrogen-selective membranes by deposition of a thin film of palladium onto a porous mechanical support. For this, we have used the electroless plating technique: a palladium salt and a reducing agent are mixed and the deposition takes place onto the catalytic surface of the substrate. After bibliographic investigations, experimental studies have been performed first with a dense metallic substrate in order to better understand the different parameters controlling the deposition. First of all, potentiometric measurements have been carried out to follow the electrochemical reactions in the bath. Then, kinetic measurements of the coating thickness have been recorded to understand the effect of the bath conditions on the yield and the adhesion of the film. Finally, the electroless plating method has been applied to deposit palladium membranes onto porous stainless steel substrates. After optimisation, the resulting membranes were tested for their hydrogen permeation properties. (author)

A method for visualizing surface-exposed and internal PfEMP1 adhesion antigens in Plasmodium falciparum infected erythrocytes

Directory of Open Access Journals (Sweden)

Arnot David E

2008-06-01

Full Text Available Abstract Background The insertion of parasite antigens into the host erythrocyte membrane and the structure and distribution of Plasmodium falciparum adhesion receptors on that membrane are poorly understood. Laser scanning confocal microscopy (LSCM and a novel labelling and fixation method have been used to obtain high resolution immuno-fluorescent images of erythrocyte surface PfEMP1 and internal antigens which allow analysis of the accumulation of PfEMP1 on the erythrocyte membrane during asexual development. Methods A novel staining technique has been developed which permits distinction between erythrocyte surface PfEMP1 and intracellular PfEMP1, in parasites whose nuclear material is exceptionally well resolved. Primary antibody detection by fluorescence is carried out on the live parasitized erythrocyte. The surface labelled cells are then fixed using paraformaldehyde and permeabilized with a non-ionic detergent to permit access of antibodies to internal parasite antigens. Differentiation between surface and internal antigens is achieved using antibodies labelled with different fluorochromes and confocal microscopy Results Surface exposed PfEMP1 is first detectable by antibodies at the trophozoite stage of intracellular parasite development although the improved detection method indicates that there are differences between different laboratory isolates in the kinetics of accumulation of surface-exposed PfEMP1. Conclusion A sensitive method for labelling surface and internal PfEMP1 with up to three different fluorochromes has been developed for laser scanning confocal optical microscopy and the analysis of the developmental expression of malaria adhesion antigens.

Single cell adhesion strength assessed with variable-angle total internal reflection fluorescence microscopy

Directory of Open Access Journals (Sweden)

Marcelina Cardoso Dos Santos

2017-06-01

Full Text Available We propose a new strategy to evaluate adhesion strength at the single cell level. This approach involves variable-angle total internal reflection fluorescence microscopy to monitor in real time the topography of cell membranes, i.e. a map of the membrane/substrate separation distance. According to the Boltzmann distribution, both potential energy profile and dissociation energy related to the interactions between the cell membrane and the substrate were determined from the membrane topography. We have highlighted on glass substrates coated with poly-L-lysine and fibronectin, that the dissociation energy is a reliable parameter to quantify the adhesion strength of MDA-MB-231 motile cells.

Doxycycline-loaded nanotube-modified adhesives inhibit MMP in a dose-dependent fashion.

Science.gov (United States)

Palasuk, Jadesada; Windsor, L Jack; Platt, Jeffrey A; Lvov, Yuri; Geraldeli, Saulo; Bottino, Marco C

2018-04-01

This article evaluated the drug loading, release kinetics, and matrix metalloproteinase (MMP) inhibition of doxycycline (DOX) released from DOX-loaded nanotube-modified adhesives. DOX was chosen as the model drug, since it is the only MMP inhibitor approved by the U.S. Food and Drug Administration. Drug loading into the nanotubes was accomplished using DOX solution at distinct concentrations. Increased concentrations of DOX significantly improved the amount of loaded DOX. The modified adhesives were fabricated by incorporating DOX-loaded nanotubes into the adhesive resin of a commercial product. The degree of conversion (DC), Knoop microhardness, DOX release kinetics, antimicrobial, cytocompatibility, and anti-MMP activity of the modified adhesives were investigated. Incorporation of DOX-loaded nanotubes did not compromise DC, Knoop microhardness, or cell compatibility. Higher concentrations of DOX led to an increase in DOX release in a concentration-dependent manner from the modified adhesives. DOX released from the modified adhesives did not inhibit the growth of caries-related bacteria, but more importantly, it did inhibit MMP-1 activity. The loading of DOX into the nanotube-modified adhesives did not compromise the physicochemical properties of the adhesives and the released levels of DOX were able to inhibit MMP activity without cytotoxicity. Doxycycline released from the nanotube-modified adhesives inhibited MMP activity in a concentration-dependent fashion. Therefore, the proposed nanotube-modified adhesive may hold clinical potential as a strategy to preserve resin/dentin bond stability.

Flip-flop of phospholipids in proteoliposomes reconstituted from detergent extract of chloroplast membranes: kinetics and phospholipid specificity.

Directory of Open Access Journals (Sweden)

Archita Rajasekharan

Full Text Available Eukaryotic cells are compartmentalized into distinct sub-cellular organelles by lipid bilayers, which are known to be involved in numerous cellular processes. The wide repertoire of lipids, synthesized in the biogenic membranes like the endoplasmic reticulum and bacterial cytoplasmic membranes are initially localized in the cytosolic leaflet and some of these lipids have to be translocated to the exoplasmic leaflet for membrane biogenesis and uniform growth. It is known that phospholipid (PL translocation in biogenic membranes is mediated by specific membrane proteins which occur in a rapid, bi-directional fashion without metabolic energy requirement and with no specificity to PL head group. A recent study reported the existence of biogenic membrane flippases in plants and that the mechanism of plant membrane biogenesis was similar to that found in animals. In this study, we demonstrate for the first time ATP independent and ATP dependent flippase activity in chloroplast membranes of plants. For this, we generated proteoliposomes from Triton X-100 extract of intact chloroplast, envelope membrane and thylakoid isolated from spinach leaves and assayed for flippase activity using fluorescent labeled phospholipids. Half-life time of flipping was found to be 6 ± 1 min. We also show that: (a intact chloroplast and envelope membrane reconstituted proteoliposomes can flip fluorescent labeled analogs of phosphatidylcholine in ATP independent manner, (b envelope membrane and thylakoid reconstituted proteoliposomes can flip phosphatidylglycerol in ATP dependent manner, (c Biogenic membrane ATP independent PC flipping activity is protein mediated and (d the kinetics of PC translocation gets affected differently upon treatment with protease and protein modifying reagents.

Membrane fluctuations mediate lateral interaction between cadherin bonds

Science.gov (United States)

Fenz, Susanne F.; Bihr, Timo; Schmidt, Daniel; Merkel, Rudolf; Seifert, Udo; Sengupta, Kheya; Smith, Ana-Sunčana

2017-09-01

The integrity of living tissues is maintained by adhesion domains of trans-bonds formed between cadherin proteins residing on opposing membranes of neighbouring cells. These domains are stabilized by lateral cis-interactions between the cadherins on the same cell. However, the origin of cis-interactions remains perplexing since they are detected only in the context of trans-bonds. By combining experimental, analytical and computational approaches, we identify bending fluctuations of membranes as a source of long-range cis-interactions, and a regulator of trans-interactions. Specifically, nanometric membrane bending and fluctuations introduce cooperative effects that modulate the affinity and binding/unbinding rates for trans-dimerization, dramatically affecting the nucleation and growth of adhesion domains. Importantly, this regulation relies on physical principles and not on details of protein-protein interactions. These omnipresent fluctuations can thus act as a generic control mechanism in all types of cell adhesion, suggesting a hitherto unknown physiological role for recently identified active fluctuations of cellular membranes.

Differential expression of cell adhesion genes

DEFF Research Database (Denmark)

Stein, Wilfred D; Litman, Thomas; Fojo, Tito

2005-01-01

that compare cells grown in suspension to similar cells grown attached to one another as aggregates have suggested that it is adhesion to the extracellular matrix of the basal membrane that confers resistance to apoptosis and, hence, resistance to cytotoxins. The genes whose expression correlates with poor...... in cell adhesion and the cytoskeleton. If the proteins involved in tethering cells to the extracellular matrix are important in conferring drug resistance, it may be possible to improve chemotherapy by designing drugs that target these proteins....

Continuous esterification to produce biodiesel by SPES/PES/NWF composite catalytic membrane in flow-through membrane reactor: experimental and kinetic studies.

Science.gov (United States)

Shi, Wenying; He, Benqiao; Cao, Yuping; Li, Jianxin; Yan, Feng; Cui, Zhenyu; Zou, Zhiqun; Guo, Shiwei; Qian, Xiaomin

2013-02-01

A novel composite catalytic membrane (CCM) was prepared from sulfonated polyethersulfone (SPES) and polyethersulfone (PES) blend supported by non-woven fabrics, as a heterogeneous catalyst to produce biodiesel from continuous esterification of oleic acid with methanol in a flow-through mode. A kinetic model of esterification was established based on a plug-flow assumption. The effects of the CCM structure (thickness, area, porosity, etc.), reaction temperature and the external and internal mass transfer resistances on esterification were investigated. The results showed that the CCM structure had a significant effect on the acid conversion. The external mass transfer resistance could be neglected when the flow rate was over 1.2 ml min(-1). The internal mass transfer resistance impacted on the conversion when membrane thickness was over 1.779 mm. An oleic acid conversion kept over 98.0% for 500 h of continuous running. The conversions obtained from the model are in good agreement with the experimental data. Copyright © 2012 Elsevier Ltd. All rights reserved.

A short-time scale colloidal system reveals early bacterial adhesion dynamics.

Directory of Open Access Journals (Sweden)

Christophe Beloin

2008-07-01

Full Text Available The development of bacteria on abiotic surfaces has important public health and sanitary consequences. However, despite several decades of study of bacterial adhesion to inert surfaces, the biophysical mechanisms governing this process remain poorly understood, due, in particular, to the lack of methodologies covering the appropriate time scale. Using micrometric colloidal surface particles and flow cytometry analysis, we developed a rapid multiparametric approach to studying early events in adhesion of the bacterium Escherichia coli. This approach simultaneously describes the kinetics and amplitude of early steps in adhesion, changes in physicochemical surface properties within the first few seconds of adhesion, and the self-association state of attached and free-floating cells. Examination of the role of three well-characterized E. coli surface adhesion factors upon attachment to colloidal surfaces--curli fimbriae, F-conjugative pilus, and Ag43 adhesin--showed clear-cut differences in the very initial phases of surface colonization for cell-bearing surface structures, all known to promote biofilm development. Our multiparametric analysis revealed a correlation in the adhesion phase with cell-to-cell aggregation properties and demonstrated that this phenomenon amplified surface colonization once initial cell-surface attachment was achieved. Monitoring of real-time physico-chemical particle surface properties showed that surface-active molecules of bacterial origin quickly modified surface properties, providing new insight into the intricate relations connecting abiotic surface physicochemical properties and bacterial adhesion. Hence, the biophysical analytical method described here provides a new and relevant approach to quantitatively and kinetically investigating bacterial adhesion and biofilm development.

Focal adhesion interactions with topographical structures: a novel method for immuno-SEM labelling of focal adhesions in S-phase cells.

Science.gov (United States)

Biggs, M J P; Richards, R G; Wilkinson, C D W; Dalby, M J

2008-07-01

Current understanding of the mechanisms involved in osseointegration following implantation of a biomaterial has led to adhesion quantification being implemented as an assay of cytocompatibility. Such measurement can be hindered by intra-sample variation owing to morphological changes associated with the cell cycle. Here we report on a new scanning electron microscopical method for the simultaneous immunogold labelling of cellular focal adhesions and S-phase nuclei identified by BrdU incorporation. Prior to labelling, cellular membranes are removed by tritonization and antigens of non-interest blocked by serum incubation. Adhesion plaque-associated vinculin and S-phase nuclei were both separately labelled with a 1.4 nm gold colloid and visualized by subsequent colloid enhancement via silver deposition. This study is specifically concerned with the effects microgroove topographies have on adhesion formation in S-phase osteoblasts. By combining backscattered electron (BSE) imaging with secondary electron (SE) imaging it was possible to visualize S-phase nuclei and the immunogold-labelled adhesion sites in one energy 'plane' and the underlying nanotopography in another. Osteoblast adhesion to these nanotopographies was ascertained by quantification of adhesion complex formation.

Cytotoxicity of four denture adhesives on human gingival fibroblast cells.

Science.gov (United States)

Lee, Yoon; Ahn, Jin-Soo; Yi, Young-Ah; Chung, Shin-Hye; Yoo, Yeon-Jee; Ju, Sung-Won; Hwang, Ji-Yun; Seo, Deog-Gyu

2015-02-01

The purpose of this study was to compare the cytotoxicity of four denture adhesives on human gingival fibroblast cells. Immortalized human gingival fibroblasts were cultured with one of four different denture adhesives, Polident, Protefix, Staydent or Denfix-A, which was placed in insert dishes (10% w/v concentration) for 48 h. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and flow cytometric apoptosis assay were used to evaluate cell viability and apoptosis rates. The fibroblasts were also examined under a scanning electron microscope. The MTT assay showed that all denture adhesives resulted in a significantly lower cell viability compared to the control cells propagated in normal culture medium (p 0.05). Staydent showed the highest apoptosis rate. Scanning electron microscopy showed that the cells of the Staydent group underwent cytoplasmic membrane shrinkage, with cell free areas containing residual fragments of the membrane of dead cells. The four denture adhesives evaluated in this study imparted cytotoxic effects on human gingival fibroblast cells. Staydent showed the highest toxicity.

Molecular Grafting of Fluorinated and Nonfluorinated Alkylsiloxanes on Various Ceramic Membrane Surfaces for the Removal of Volatile Organic Compounds Applying Vacuum Membrane Distillation.

Science.gov (United States)

Kujawa, Joanna; Al-Gharabli, Samer; Kujawski, Wojciech; Knozowska, Katarzyna

2017-02-22

Four main tasks were presented: (i) ceramic membrane functionalization (TiO 2 5 kDa and 300 kDa), (ii) extended material characterization (physicochemistry and tribology) of pristine and modified ceramic samples, (iii) evaluation of chemical and mechanical stability, and finally (iv) assessment of membrane efficiency in vacuum membrane distillation applied for volatile organic compounds (VOCs) removal from water. Highly efficient molecular grafting with four types of perfluoroalkylsilanes and one nonfluorinated agent was developed. Materials with controllable tribological and physicochemical properties were achieved. The most meaningful finding is associated with the applicability of fluorinated and nonfluorinated grafting agents. The results of contact angle, hysteresis of contact angle, sliding angle, and critical surface tension as well as Young's modulus, nanohardness, and adhesion force for grafting by these two modifiers are comparable. This provides insight into the potential applicability of environmental friendly hydrophobic and superhydrophobic surfaces. The achieved hydrophobic membranes were very effective in the removal of VOCs (butanol, methyl-tert-butyl ether, and ethyl acetate) from binary aqueous solutions in vacuum membrane distillation. The correlation between membrane effectiveness and separated solvent polarity was compared in terms of material properties and resistance to the wetting (kinetics of wetting and in-depth liquid penetration). Material properties were interpreted considering Zisman theory and using Kao diagram. The significant influence of surface chemistry on the membrane performance was noticed (5 kDa, influence of hydrophobic nanolayer and separation controlled by solution-diffusion model; 300 kDa, no impact of surface chemistry and separation controlled by liquid-vapor equilibrium).

Ligand-mediated adhesive mechanics of two static, deformed spheres.

Science.gov (United States)

Sircar, Sarthok; Nguyen, Giang; Kotousov, Andrei; Roberts, Anthony J

2016-10-01

A self-consistent model is developed to investigate attachment/detachment kinetics of two static, deformable microspheres with irregular surface and coated with flexible binding ligands. The model highlights how the microscale binding kinetics of these ligands as well as the attractive/repulsive potential of the charged surface affects the macroscale static deformed configuration of the spheres. It is shown that in the limit of smooth, neutrally charged surface (i.e., the dimensionless inverse Debye length, [Formula: see text]), interacting via elastic binders (i.e., the dimensionless stiffness coefficient, [Formula: see text]) the adhesion mechanics approaches the regime of application of the JKR theory, and in this particular limit, the contact radius, R c , scales with the particle radius, R, according to the scaling law, [Formula: see text]. We show that static, deformed, highly charged, ligand-coated surface of micro-spheres exhibit strong adhesion. Normal stress distribution within the contact area adjusts with the binder stiffness coefficient, from a maximum at the center to a maximum at the periphery of the region. Although reported in some in vitro experiments involving particle adhesion, until now a physical interpretation for this variation of the stress distribution for deformable, charged, ligand-coated microspheres is missing. Surface roughness results in a diminished adhesion with a distinct reduction in the pull-off force, larger separation gap, weaker normal stress and limited area of adhesion. These results are in agreement with the published experimental findings.

Dynamic coating of mf/uf membranes for fouling mitigation

KAUST Repository

Tabatabai, S. Assiyeh Alizadeh

2017-01-19

A membrane system including an anti-fouling layer and a method of applying an anti-fouling layer to a membrane surface are provided. In an embodiment, the surface is a microfiltration (MF) or an ultrafiltration (UF) membrane surface. The anti-fouling layer can include a stimuli responsive layer and a dynamic protective layer applied over the stimuli responsive layer that can be a coating on a surface of the membrane. The stimuli responsive polymer layer can act as an adhesive prior to coating with the dynamic protective layer to aid in adhering the dynamic protective layer to the membrane surface. The dynamic protective layer can be formed by suitable nanoparticles that can prevent adhesion of foulants directly to the membrane surface. The stimuli responsive layer can be responsive to physio- chemical stimuli to cause a release of the stimuli responsive layer and the dynamic protective layer including foulants from the membrane.

A Theoretical Characterization of Curvature Controlled Adhesive Properties of Bio-Inspired Membranes

DEFF Research Database (Denmark)

Afferante, Luciano; Heepe, Lars; Casdorff, Kirstin

2016-01-01

Some biological systems, such as the tree frog, Litoria caerulea, and the bush-cricket, Tettigonia viridissima, have developed the ability to control adhesion by changing the curvature of their pads. Active control systems of adhesion inspired by these biological models can be very attractive...

Shear Adhesion of Tapered Nanopillar Arrays.

Science.gov (United States)

Cho, Younghyun; Minsky, Helen K; Jiang, Yijie; Yin, Kaiyang; Turner, Kevin T; Yang, Shu

2018-04-04

Tapered nanopillars with various cross sections, including cone-shaped, stepwise, and pencil-like structures (300 nm in diameter at the base of the pillars and 1.1 μm in height), are prepared from epoxy resin templated by nanoporous anodic aluminum oxide (AAO) membranes. The effect of pillar geometry on the shear adhesion behavior of these nanopillar arrays is investigated via sliding experiments in a nanoindentation system. In a previous study of arrays with the same geometry, it was shown that cone-shaped nanopillars exhibit the highest adhesion under normal loading while stepwise and pencil-like nanopillars exhibit lower normal adhesion strength due to significant deformation of the pillars that occurs with increasing indentation depth. Contrary to the previous studies, here, we show that pencil-like nanopillars exhibit the highest shear adhesion strength at all indentation depths among three types of nanopillar arrays and that the shear adhesion increases with greater indentation depth due to the higher bending stiffness and closer packing of the pencil-like nanopillar array. Finite element simulations are used to elucidate the deformation of the pillars during the sliding experiments and agree with the nanoindentation-based sliding measurements. The experiments and finite element simulations together demonstrate that the shape of the nanopillars plays a key role in shear adhesion and that the mechanism is quite different from that of adhesion under normal loading.

[Biocompatibility of poly-L-lactic acid/Bioglass-guided bone regeneration membranes processed with oxygen plasma].

Science.gov (United States)

Fang, Wei; Zeng, Shu-Guang; Gao, Wen-Feng

2015-04-01

To prepare and characterize a nano-scale fibrous hydrophilic poly-L-lactic acid/ Bioglass (PLLA/BG) composite membrane and evaluate its biocompatibility as a composite membrane for guiding bone regeneration (GBR). PLLA/BG-guided bone regeneration membrane was treated by oxygen plasma to improved its hydrophilicity. The growth of MG-63 osteoblasts on the membrane was observed using Hoechst fluorescence staining, and the biocompatibility of the membrane was evaluated by calculating the cells adhesion rate and proliferation rate. Osteogenesis of MG-63 cells was assessed by detecting alkaline phosphatase (ALP), and the formation of calcified nodules and cell morphology changes were observed using scanning electron microscope (SEM). The cell adhesion rates of PLLA/BG-guided bone regeneration membrane treated with oxygen plasma were (30.570±0.96)%, (47.27±0.78)%, and (66.78±0.69)% at 1, 3, and 6 h, respectively, significantly higher than those on PLLA membrane and untreated PLLA/BG membrane (Pmembranes increased with time, but highest on oxygen plasma-treated PLLA/BG membrane (Pplasma treatment of the PLLA/BG membrane promoted cell adhesion. The membranes with Bioglass promoted the matrix secretion of the osteoblasts. Under SEM, the formation of calcified nodules and spindle-shaped cell morphology were observed on oxygen plasma-treated PLLA/BG membrane. Oxygen plasma-treated PLLA/BG composite membrane has good biocompatibility and can promote adhesion, proliferation and osteogenesis of the osteoblasts.

Tetraspanin-enriched microdomains: a functional unit in cell plasma membranes.

Science.gov (United States)

Yáñez-Mó, María; Barreiro, Olga; Gordon-Alonso, Mónica; Sala-Valdés, Mónica; Sánchez-Madrid, Francisco

2009-09-01

Membrane lipids and proteins are non-randomly distributed and are unable to diffuse freely in the plane of the membrane. This is because of multiple constraints imposed both by the cortical cytoskeleton and by the preference of lipids and proteins to cluster into diverse and specialized membrane domains, including tetraspanin-enriched microdomains, glycosylphosphatidyl inositol-linked proteins nanodomains and caveolae, among others. Recent biophysical characterization of tetraspanin-enriched microdomains suggests that they might be specially suited for the regulation of avidity of adhesion receptors and the compartmentalization of enzymatic activities. Moreover, modulation by tetraspanins of the function of adhesion receptors involved in inflammation, lymphocyte activation, cancer and pathogen infection suggests potential as therapeutic targets. This review explores this emerging picture of tetraspanin microdomains and discusses the implications for cell adhesion, proteolysis and pathogenesis.

Single-cell force spectroscopy of pili-mediated adhesion

Science.gov (United States)

Sullan, Ruby May A.; Beaussart, Audrey; Tripathi, Prachi; Derclaye, Sylvie; El-Kirat-Chatel, Sofiane; Li, James K.; Schneider, Yves-Jacques; Vanderleyden, Jos; Lebeer, Sarah; Dufrêne, Yves F.

2013-12-01

Although bacterial pili are known to mediate cell adhesion to a variety of substrates, the molecular interactions behind this process are poorly understood. We report the direct measurement of the forces guiding pili-mediated adhesion, focusing on the medically important probiotic bacterium Lactobacillus rhamnosus GG (LGG). Using non-invasive single-cell force spectroscopy (SCFS), we quantify the adhesion forces between individual bacteria and biotic (mucin, intestinal cells) or abiotic (hydrophobic monolayers) surfaces. On hydrophobic surfaces, bacterial pili strengthen adhesion through remarkable nanospring properties, which - presumably - enable the bacteria to resist high shear forces under physiological conditions. On mucin, nanosprings are more frequent and adhesion forces larger, reflecting the influence of specific pili-mucin bonds. Interestingly, these mechanical responses are no longer observed on human intestinal Caco-2 cells. Rather, force curves exhibit constant force plateaus with extended ruptures reflecting the extraction of membrane nanotethers. These single-cell analyses provide novel insights into the molecular mechanisms by which piliated bacteria colonize surfaces (nanosprings, nanotethers), and offer exciting avenues in nanomedicine for understanding and controlling the adhesion of microbial cells (probiotics, pathogens).

Kinetics of Ca2+- and ATP-dependent, voltage-controlled anion conductance in the plasma membrane of mesophyll cells of Pisum sativum

NARCIS (Netherlands)

Elzenga, J.T.M.; van Volkenburgh, E.

Whole-cell patch-clamp techniques were used to measure anion currents through the plasma membrane of protoplasts of mesophyll cells of expanding pea (Pisum sativum L.) leaves. Voltage-induced changes of the currents could be modelled with single exponential activation and deactivation kinetics. The

Effect of x-irradiation on cell kinetics of esophageal membrane cells in mice

International Nuclear Information System (INIS)

Ando, Koichi; Tsunemoto, Hiroshi; Urano, Muneyasu; Koike, Sachiko

1977-01-01

Effect of x-irradiation on the cell kinetics of esophageal membrane cells was studied in C3Hf/He male mice. Experimental methods include; counting the number of basal and superficial cells, and pulse or continuous labelling by tritiated thymidine. Esophageal area was irradiated with 1000 rad of 200 kVp x-rays and cell kinetics were studied on the 5th post-irradiation day. Autoradiography revealed the shortening of the cell cycle time, specifically in G- and G- phases. Numbers of basal cells and of superficial cells were found to increase for 5 days after irradiation. Continuous labelling experiments using infusion technique demonstrated than growth fraction of irradiated basal cells was 1.0 as well as that of non-irradiated cells. It was of interest that the migration time, i.e., the time required for labelled cells to migrate from basal cell layer to superficial cell layer, was shortened approximately 1/3 of that of non-irradiated control after irradiation. Diurnal variation was observed not only in normal basal cells but also in irradiated ones, and the rate of increase of labelling index after continuous labelling was independent of the time when the labelling was started. (auth.)

Effect of x irradiation on cell kinetics of esophageal membrane cells in mice

Energy Technology Data Exchange (ETDEWEB)

Ando, K; Tsunemoto, H; Urano, M; Koike, S [National Inst. of Radiological Sciences, Chiba (Japan)

1977-05-01

Effect of x irradiation on the cell kinetics of esophageal membrane cells was studied in C3Hf/He male mice. Experimental methods include; counting the number of basal and superficial cells, and pulse or continuous labelling by tritiated thymidine. Esophageal area was irradiated with 1000 rad of 200 kVp x rays and cell kinetics were studied on the 5th post-irradiation day. Autoradiography revealed the shortening of the cell cycle time, specifically in G- and G- phases. Numbers of basal cells and of superficial cells were found to increase for 5 days after irradiation. Continuous labelling experiments using infusion technique demonstrated than growth fraction of irradiated basal cells was 1.0 as well as that of non-irradiated cells. It was of interest that the migration time, i.e., the time required for labelled cells to migrate from basal cell layer to superficial cell layer, was shortened approximately 1/3 of that of non-irradiated control after irradiation. Diurnal variation was observed not only in normal basal cells but also in irradiated ones, and the rate of increase of labelling index after continuous labelling was independent of the time when the labelling was started.

The conveyor belt hypothesis for thymocyte migration: participation of adhesion and de-adhesion molecules.

Science.gov (United States)

Villa-Verde, D M; Calado, T C; Ocampo, J S; Silva-Monteiro, E; Savino, W

1999-05-01

Thymocyte differentiation is the process by which bone marrow-derived precursors enter the thymus, proliferate, rearrange the genes and express the corresponding T cell receptors, and undergo positive and/or negative selection, ultimately yielding mature T cells that will represent the so-called T cell repertoire. This process occurs in the context of cell migration, whose cellular and molecular basis is still poorly understood. Kinetic studies favor the idea that these cells leave the organ in an ordered pattern, as if they were moving on a conveyor belt. We have recently proposed that extracellular matrix glycoproteins, such as fibronectin, laminin and type IV collagen, among others, produced by non-lymphoid cells both in the cortex and in the medulla, would constitute a macromolecular arrangement allowing differentiating thymocytes to migrate. Here we discuss the participation of both molecules with adhesive and de-adhesive properties in the intrathymic T cell migration. Functional experiments demonstrated that galectin-3, a soluble beta-galactoside-binding lectin secreted by thymic microenvironmental cells, is a likely candidate for de-adhesion proteins by decreasing thymocyte interaction with the thymic microenvironment.

Single Cell Force Spectroscopy for Quantification of Cellular Adhesion on Surfaces

Science.gov (United States)

Christenson, Wayne B.

Cell adhesion is an important aspect of many biological processes. The atomic force microscope (AFM) has made it possible to quantify the forces involved in cellular adhesion using a technique called single cell force spectroscopy (SCFS). AFM based SCFS offers versatile control over experimental conditions for probing directly the interaction between specific cell types and specific proteins, surfaces, or other cells. Transmembrane integrins are the primary proteins involved in cellular adhesion to the extra cellular matix (ECM). One of the chief integrins involved in the adhesion of leukocyte cells is alpha Mbeta2 (Mac-1). The experiments in this dissertation quantify the adhesion of Mac-1 expressing human embryonic kidney (HEK Mac-1), platelets, and neutrophils cells on substrates with different concentrations of fibrinogen and on fibrin gels and multi-layered fibrinogen coated fibrin gels. It was shown that multi-layered fibrinogen reduces the adhesion force of these cells considerably. A novel method was developed as part of this research combining total internal reflection microscopy (TIRFM) with SCFS allowing for optical microscopy of HEK Mac-1 cells interacting with bovine serum albumin (BSA) coated glass after interacting with multi-layered fibrinogen. HEK Mac-1 cells are able to remove fibrinogen molecules from the multi-layered fibrinogen matrix. An analysis methodology for quantifying the kinetic parameters of integrin-ligand interactions from SCFS experiments is proposed, and the kinetic parameters of the Mac-1 fibrinogen bond are quantified. Additional SCFS experiments quantify the adhesion of macrophages and HEK Mac-1 cells on functionalized glass surfaces and normal glass surfaces. Both cell types show highest adhesion on a novel functionalized glass surface that was prepared to induce macrophage fusion. These experiments demonstrate the versatility of AFM based SCFS, and how it can be applied to address many questions in cellular biology offering

Exploring the elasticity and adhesion behavior of cardiac fibroblasts by atomic force microscopy indentation

Energy Technology Data Exchange (ETDEWEB)

Codan, B.; Del Favero, G. [Department of Engineering and Architecture, University of Trieste (Italy); Martinelli, V. [Department of Engineering and Architecture, University of Trieste (Italy); International Center for Genetic Engineering and Biotechnology, Trieste (Italy); Long, C.S.; Mestroni, L. [University of Colorado Cardiovascular Institute, University of Colorado Denver, Aurora, CO (United States); Sbaizero, O., E-mail: sbaizero@units.it [Department of Engineering and Architecture, University of Trieste (Italy)

2014-07-01

AFM was used to collect the whole force–deformation cell curves. They provide both the elasticity and adhesion behavior of mouse primary cardiac fibroblasts. To confirm the hypothesis that a link exists between the membrane receptors and the cytoskeletal filaments causing therefore changing in both elasticity and adhesion behavior, actin-destabilizing Cytochalsin D was administrated to the fibroblasts. From immunofluorescence observation and AFM loading/unloading curves, cytoskeletal reorganization as well as a change in the elasticity and adhesion was indeed observed. Elasticity of control fibroblasts is three times higher than that for fibroblasts treated with 0.5 μM Cytochalasin. Moreover, AFM loading–unloading curves clearly show the different mechanical behavior of the two different cells analyzed: (i) for control cells the AFM cantilever rises during the dwell time while cells with Cytochalasin fail to show such an active resistance; (ii) the maximum force to deform control cells is quite higher and as far as adhesion is concern (iii) the maximum separation force, detachment area and the detachment process time are much larger for control compared to the Cytochalasin treated cells. Therefore, alterations in the cytoskeleton suggest that a link must exist between the membrane receptors and the cytoskeletal filaments beneath the cellular surface and inhibition of actin polymerization has effects on the whole cell mechanical behavior as well as adhesion. - Highlights: • The whole AFM force–deformation cell curves were analyzed. • They provide information on both the elasticity and adhesion behavior. • Actin-destabilizing Cytochalasin D was administrated to the fibroblasts. • Change in elasticity and adhesion was ascribed to cytoskeletal reorganization. • A link exists between the membrane receptors and the cytoskeletal filaments.

Exploring the elasticity and adhesion behavior of cardiac fibroblasts by atomic force microscopy indentation

International Nuclear Information System (INIS)

Codan, B.; Del Favero, G.; Martinelli, V.; Long, C.S.; Mestroni, L.; Sbaizero, O.

2014-01-01

AFM was used to collect the whole force–deformation cell curves. They provide both the elasticity and adhesion behavior of mouse primary cardiac fibroblasts. To confirm the hypothesis that a link exists between the membrane receptors and the cytoskeletal filaments causing therefore changing in both elasticity and adhesion behavior, actin-destabilizing Cytochalsin D was administrated to the fibroblasts. From immunofluorescence observation and AFM loading/unloading curves, cytoskeletal reorganization as well as a change in the elasticity and adhesion was indeed observed. Elasticity of control fibroblasts is three times higher than that for fibroblasts treated with 0.5 μM Cytochalasin. Moreover, AFM loading–unloading curves clearly show the different mechanical behavior of the two different cells analyzed: (i) for control cells the AFM cantilever rises during the dwell time while cells with Cytochalasin fail to show such an active resistance; (ii) the maximum force to deform control cells is quite higher and as far as adhesion is concern (iii) the maximum separation force, detachment area and the detachment process time are much larger for control compared to the Cytochalasin treated cells. Therefore, alterations in the cytoskeleton suggest that a link must exist between the membrane receptors and the cytoskeletal filaments beneath the cellular surface and inhibition of actin polymerization has effects on the whole cell mechanical behavior as well as adhesion. - Highlights: • The whole AFM force–deformation cell curves were analyzed. • They provide information on both the elasticity and adhesion behavior. • Actin-destabilizing Cytochalasin D was administrated to the fibroblasts. • Change in elasticity and adhesion was ascribed to cytoskeletal reorganization. • A link exists between the membrane receptors and the cytoskeletal filaments

Limited and selective transfer of plasma membrane glycoproteins to membrane of secondary lysosomes

International Nuclear Information System (INIS)

Haylett, T.; Thilo, L.

1986-01-01

Radioactive galactose, covalently bound to cell surface glycoconjugates on mouse macrophage cells, P388D 1 , was used as a membrane marker to study the composition, and the kinetics of exchange, of plasma membrane-derived constituents in the membrane of secondary lysosomes. Secondary lysosomes were separated from endosomes and plasma membrane by self-forming Percoll density gradients. Horseradish peroxidase, taken up by fluid-phase pinocytosis, served as a vesicle contents marker to monitor transfer of endosomal contents into secondary lysosomes. Concurrently, the fraction of plasma membrane-derived label of secondary lysosomes increased by first order kinetics from 4 PAGE, labeled molecules of M/sub r/ 160-190 kD were depleted and of the M/sub r/ 100-120 kD were enriched in lysosome membrane compared with the relative composition of label on the cell surface. No corresponding selectivity was observed for the degradation of label, with all M/sub r/ classes being affected to the same relative extent. The results indicate that endocytosis-derived transfer of plasma membrane constitutents to secondary lysosomes is a limited and selective process, and that only ∼1% of internalized membrane is recycled via a membrane pool of secondary lysosomes

Integrative systems and synthetic biology of cell-matrix adhesion sites.

Science.gov (United States)

Zamir, Eli

2016-09-02

The complexity of cell-matrix adhesion convolves its roles in the development and functioning of multicellular organisms and their evolutionary tinkering. Cell-matrix adhesion is mediated by sites along the plasma membrane that anchor the actin cytoskeleton to the matrix via a large number of proteins, collectively called the integrin adhesome. Fundamental challenges for understanding how cell-matrix adhesion sites assemble and function arise from their multi-functionality, rapid dynamics, large number of components and molecular diversity. Systems biology faces these challenges in its strive to understand how the integrin adhesome gives rise to functional adhesion sites. Synthetic biology enables engineering intracellular modules and circuits with properties of interest. In this review I discuss some of the fundamental questions in systems biology of cell-matrix adhesion and how synthetic biology can help addressing them.

Preparation of an Adhesive in Emulsion for Maxillofacial Prosthetic

Directory of Open Access Journals (Sweden)

Joaquín Palacios-Alquisira

2010-10-01

Full Text Available Maxillofacial prostheses is a dental medicine specialty aimed at restoring anatomical facial defects caused by cancer, trauma or congenital malformations through an artificial device, which is commonly attached to the skin with the help of an adhesive. The purpose of our research was to develop a pressure-sensitive adhesive (PSA based on acrylic monomers, characterizing and determining its drying kinetics, that is to say the time it takes to lose 50 to 90% of its moisture. The adhesive synthesis was realized by means of emulsion polymerization; the composition of formulations was: (AA‑MMA‑EA and (AA‑MMA‑2EHA with different molar ratios. The formulation based on (AA‑MMA‑2EHA with 50 w% of solids, presented good adhesive properties such as tack, bond strength, and short drying time. We propose this formulation as a PSA, because it offers an alternative for systemically compromised patients, by less irritation compared to organic solvent-based adhesives.

Polydopamine/Cysteine surface modified isoporous membranes with self-cleaning properties

KAUST Repository

Shevate, Rahul; Kumar, Mahendra; Karunakaran, Madhavan; Hedhili, Mohamed N.; Peinemann, Klaus-Viktor

2017-01-01

The major challenge in membrane filtration is fouling which reduces the membrane performance. Fouling is mainly due to the adhesion of foulants on the membrane surfaces. In this work, we studied the fouling behaviour of polystyrene-b-poly(4

Numerical simulation of kinetic demixing and decomposition in a LaCoO3-δ oxygen membrane under an oxygen potential gradient

DEFF Research Database (Denmark)

Ta, Na; Chen, Ming; Zhang, Lijun

2018-01-01

A composition- and temperature-dependent mobility database of all ionic species in the LaCoO3-δ phase was developed and combined with a La-Co-O thermodynamic database to simulate kinetic demixing and partial decomposition in LaCoO3-δ oxygen membranes operated under a 0.0001/0.21 bar oxygen partial...... pressure difference at 1073 K for 1 year. Formation of La2O3, Co3O4 and CoO phases across the membrane is predicted. The kinetic demixing process can be divided into two stages, namely, establishment of the oxygen potential gradient (fast) and demixing of the cations (slow); the former is controlled...... by the mobility of oxygen ions, and the latter is determined by the higher mobility of Co ions as compared to the La ion in the ABO3-type perovskite. A drift motion of both oxide surfaces towards the high PO2 side occurs with the movement of cations....

Interaction between bacterial outer membrane proteins and periplasmic quality control factors: a kinetic partitioning mechanism.

Science.gov (United States)

Wu, Si; Ge, Xi; Lv, Zhixin; Zhi, Zeyong; Chang, Zengyi; Zhao, Xin Sheng

2011-09-15

The OMPs (outer membrane proteins) of Gram-negative bacteria have to be translocated through the periplasmic space before reaching their final destination. The aqueous environment of the periplasmic space and high permeability of the outer membrane engender such a translocation process inevitably challenging. In Escherichia coli, although SurA, Skp and DegP have been identified to function in translocating OMPs across the periplasm, their precise roles and their relationship remain to be elucidated. In the present paper, by using fluorescence resonance energy transfer and single-molecule detection, we have studied the interaction between the OMP OmpC and these periplasmic quality control factors. The results of the present study reveal that the binding rate of OmpC to SurA or Skp is much faster than that to DegP, which may lead to sequential interaction between OMPs and different quality control factors. Such a kinetic partitioning mechanism for the chaperone-substrate interaction may be essential for the quality control of the biogenesis of OMPs.

Micropipette Deflection Measurements of Agar-Glass Adhesion

Science.gov (United States)

Parg, Richard; Shelton, Erin; Dutcher, John

Micropipette deflection experiments were used to study the adhesive strength at an agar-glass interface. Agar is a hydrogel commonly used in biological research; however, many of the mechanical properties of this hydrogel are not well characterized. By measuring the peak force required to slide an agar puck supported by a Teflon ring across a clean glass slide, we are able to compare the adhesive strength of 1 % w/w and 1.5 % w/w agar. On average, the force required to break the agar-glass interface was approximately a factor of 2 larger for 1.5 % w/w agar than for 1 % w/w agar. We discuss this result within the context of a simple model of agar adhesion. Additional experiments were performed to measure the kinetic friction between agar and glass to obtain insight into its dependence on agar concentration.

Phospho-Caveolin-1 Mediates Integrin-Regulated Membrane Domain Internalisation

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del Pozo, Miguel A.; Alderson, Nazilla B.; Grande-García, Araceli; Balasubramanian, Nagaraj; Schwartz, Martin A.; Kiosses, William B.; Anderson, Richard G.W.

2005-01-01

Growth of normal cells is anchorage-dependent because signalling through multiple pathways including Erk, PI 3-kinase and Rac requires integrin-mediated cell adhesion 1. Components of these pathways localize to low density, cholesterol-rich domains in the plasma membrane named “lipid rafts” 2,3 or “cholesterol enriched membrane microdomains” (CEMM) 4. We previously reported that integrin-mediated adhesion regulates CEMM trafficking such that cell detachment from the extracellular matrix (ECM) triggers CEMM internalisation and clearance from the plasma membrane 5. We now report that this internalisation is mediated by dynamin-2 and caveolin-1. Internalisation requires phosphorylation of caveolin-1 on tyrosine 14. A shift in localisation of phospho-caveolin-1 from focal adhesions to caveolae induces CEMM internalisation upon cell detachment, which mediates inhibition of Erk, PI 3-kinase and Rac. These data define a novel molecular mechanism for growth and tumour suppression by caveolin-1. PMID:16113676

Gigaseal Mechanics: Creep of the Gigaseal under the Action of Pressure, Adhesion, and Voltage

Science.gov (United States)

2015-01-01

Patch clamping depends on a tight seal between the cell membrane and the glass of the pipet. Why does the seal have such high electric resistance? Why does the patch adhere so strongly to the glass? Even under the action of strong hydrostatic, adhesion, and electrical forces, it creeps at a very low velocity. To explore possible explanations, we examined two physical models for the structure of the seal zone and the adhesion forces and two respective mechanisms of patch creep and electric conductivity. There is saline between the membrane and glass in the seal, and the flow of this solution under hydrostatic pressure or electroosmosis should drag a patch. There is a second possibility: the lipid core of the membrane is liquid and should be able to flow, with the inner monolayer slipping over the outer one. Both mechanisms predict the creep velocity as a function of the properties of the seal and the membrane, the pipet geometry, and the driving force. These model predictions are compared with experimental data for azolectin liposomes with added cholesterol or proteins. It turns out that to obtain experimentally observed creep velocities, a simple viscous flow in the seal zone requires ∼10 Pa·s viscosity; it is unclear what structure might provide that because that viscosity alone severely constrains the electric resistance of the gigaseal. Possibly, it is the fluid bilayer that allows the motion. The two models provide an estimate of the adhesion energy of the membrane to the glass and membrane’s electric characteristics through the comparison between the velocities of pressure-, adhesion-, and voltage-driven creep. PMID:25295693

Progress in surface and membrane science

CERN Document Server

Danielli, J F; Cadenhead, D A

1972-01-01

Progress in Surface and Membrane Science, Volume 5 covers the developments in the study of surface and membrane science. The book discusses the Mössbauer effect in surface science; the surface functional groups on carbon and silica; and the wetting phenomena pertaining to adhesion. The text also describes the physical state of phospholipids and cholesterol in monolayers, bilayers, and membranes; the characteristics of heterocoagulation; and the effects of calcium on excitable membranes and neurotransmitter action. Chemists, physiologists, biophysicists, and civil engineers will find the book i

The structure of cell-matrix adhesions: the new frontier.

Science.gov (United States)

Hanein, Dorit; Horwitz, Alan Rick

2012-02-01

Adhesions between the cell and the extracellular matrix (ECM) are mechanosensitive multi-protein assemblies that transmit force across the cell membrane and regulate biochemical signals in response to the chemical and mechanical environment. These combined functions in force transduction, signaling and mechanosensing contribute to cellular phenotypes that span development, homeostasis and disease. These adhesions form, mature and disassemble in response to actin organization and physical forces that originate from endogenous myosin activity or external forces by the extracellular matrix. Despite advances in our understanding of the protein composition, interactions and regulation, our understanding of matrix adhesion structure and organization, how forces affect this organization, and how these changes dictate specific signaling events is limited. Insights across multiple structural levels are acutely needed to elucidate adhesion structure and ultimately the molecular basis of signaling and mechanotransduction. Here we describe the challenges and recent advances and prospects for unraveling the structure of cell-matrix adhesions and their response to force. Copyright © 2011 Elsevier Ltd. All rights reserved.

Effects of solvent evaporation on water sorption/solubility and nanoleakage of adhesive systems

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Talita Baumgratz Cachapuz CHIMELI

2014-07-01

Full Text Available Objective: To evaluate the influence of solvent evaporation in the kinetics of water diffusion (water sorption-WS, solubility-SL, and net water uptake and nanoleakage of adhesive systems. Material and Methods: Disk-shaped specimens (5.0 mm in diameter x 0.8 mm in thickness were produced (N=48 using the adhesives: Clearfil S3 Bond (CS3/Kuraray, Clearfil SE Bond - control group (CSE/Kuraray, Optibond Solo Plus (OS/Kerr and Scotchbond Universal Adhesive (SBU/3M ESPE. The solvents were either evaporated for 30 s or not evaporated (N=24/per group, and then photoactivated for 80 s (550 mW/cm2. After desiccation, the specimens were weighed and stored in distilled water (N=12 or mineral oil (N=12 to evaluate the water diffusion over a 7-day period. Net water uptake (% was also calculated as the sum of WS and SL. Data were submitted to 3-way ANOVA/Tukey's test (α=5%. The nanoleakage expression in three additional specimens per group was also evaluated after ammoniacal silver impregnation after 7 days of water storage under SEM. Results: Statistical analysis revealed that only the factor "adhesive" was significant (p<0.05. Solvent evaporation had no influence in the WS and SL of the adhesives. CSE (control presented significantly lower net uptake (5.4%. The nanoleakage was enhanced by the presence of solvent in the adhesives. Conclusions: Although the evaporation has no effect in the kinetics of water diffusion, the nanoleakage expression of the adhesives tested increases when the solvents are not evaporated.

Mechanical collapse of confined fluid membrane vesicles.

Science.gov (United States)

Rim, Jee E; Purohit, Prashant K; Klug, William S

2014-11-01

Compact cylindrical and spherical invaginations are common structural motifs found in cellular and developmental biology. To understand the basic physical mechanisms that produce and maintain such structures, we present here a simple model of vesicles in confinement, in which mechanical equilibrium configurations are computed by energy minimization, balancing the effects of curvature elasticity, contact of the membrane with itself and the confining geometry, and adhesion. For cylindrical confinement, the shape equations are solved both analytically and numerically by finite element analysis. For spherical confinement, axisymmetric configurations are obtained numerically. We find that the geometry of invaginations is controlled by a dimensionless ratio of the adhesion strength to the bending energy of an equal area spherical vesicle. Larger adhesion produces more concentrated curvatures, which are mainly localized to the "neck" region where the invagination breaks away from its confining container. Under spherical confinement, axisymmetric invaginations are approximately spherical. For extreme confinement, multiple invaginations may form, bifurcating along multiple equilibrium branches. The results of the model are useful for understanding the physical mechanisms controlling the structure of lipid membranes of cells and their organelles, and developing tissue membranes.

Effects of solvent evaporation on water sorption/solubility and nanoleakage of adhesive systems.

Science.gov (United States)

Chimeli, Talita Baumgratz Cachapuz; D'Alpino, Paulo Henrique Perlatti; Pereira, Patrícia Nóbrega; Hilgert, Leandro Augusto; Di Hipólito, Vinicius; Garcia, Fernanda Cristina Pimentel

2014-01-01

To evaluate the influence of solvent evaporation in the kinetics of water diffusion (water sorption-WS, solubility-SL, and net water uptake) and nanoleakage of adhesive systems. Disk-shaped specimens (5.0 mm in diameter x 0.8 mm in thickness) were produced (N=48) using the adhesives: Clearfil S3 Bond (CS3)/Kuraray, Clearfil SE Bond - control group (CSE)/Kuraray, Optibond Solo Plus (OS)/Kerr and Scotchbond Universal Adhesive (SBU)/3M ESPE. The solvents were either evaporated for 30 s or not evaporated (N=24/per group), and then photoactivated for 80 s (550 mW/cm2). After desiccation, the specimens were weighed and stored in distilled water (N=12) or mineral oil (N=12) to evaluate the water diffusion over a 7-day period. Net water uptake (%) was also calculated as the sum of WS and SL. Data were submitted to 3-way ANOVA/Tukey's test (α=5%). The nanoleakage expression in three additional specimens per group was also evaluated after ammoniacal silver impregnation after 7 days of water storage under SEM. Statistical analysis revealed that only the factor "adhesive" was significant (padhesives. CSE (control) presented significantly lower net uptake (5.4%). The nanoleakage was enhanced by the presence of solvent in the adhesives. Although the evaporation has no effect in the kinetics of water diffusion, the nanoleakage expression of the adhesives tested increases when the solvents are not evaporated.

The conveyor belt hypothesis for thymocyte migration: participation of adhesion and de-adhesion molecules

Directory of Open Access Journals (Sweden)

Villa-Verde D.M.S.

1999-01-01

Full Text Available Thymocyte differentiation is the process by which bone marrow-derived precursors enter the thymus, proliferate, rearrange the genes and express the corresponding T cell receptors, and undergo positive and/or negative selection, ultimately yielding mature T cells that will represent the so-called T cell repertoire. This process occurs in the context of cell migration, whose cellular and molecular basis is still poorly understood. Kinetic studies favor the idea that these cells leave the organ in an ordered pattern, as if they were moving on a conveyor belt. We have recently proposed that extracellular matrix glycoproteins, such as fibronectin, laminin and type IV collagen, among others, produced by non-lymphoid cells both in the cortex and in the medulla, would constitute a macromolecular arrangement allowing differentiating thymocytes to migrate. Here we discuss the participation of both molecules with adhesive and de-adhesive properties in the intrathymic T cell migration. Functional experiments demonstrated that galectin-3, a soluble ß-galactoside-binding lectin secreted by thymic microenvironmental cells, is a likely candidate for de-adhesion proteins by decreasing thymocyte interaction with the thymic microenvironment.

A comparative spectroscopic and kinetic study of photoexcitations in detergent-isolated and membrane-embedded LH2 light-harvesting complexes.

Science.gov (United States)

Freiberg, Arvi; Rätsep, Margus; Timpmann, Kõu

2012-08-01

Integral membrane proteins constitute more than third of the total number of proteins present in organisms. Solubilization with mild detergents is a common technique to study the structure, dynamics, and catalytic activity of these proteins in purified form. However beneficial the use of detergents may be for protein extraction, the membrane proteins are often denatured by detergent solubilization as a result of native lipid membrane interactions having been modified. Versatile investigations of the properties of membrane-embedded and detergent-isolated proteins are, therefore, required to evaluate the consequences of the solubilization procedure. Herein, the spectroscopic and kinetic fingerprints have been established that distinguish excitons in individual detergent-solubilized LH2 light-harvesting pigment-protein complexes from them in the membrane-embedded complexes of purple photosynthetic bacteria Rhodobacter sphaeroides. A wide arsenal of spectroscopic techniques in visible optical range that include conventional broadband absorption-fluorescence, fluorescence anisotropy excitation, spectrally selective hole burning and fluorescence line-narrowing, and transient absorption-fluorescence have been applied over broad temperature range between physiological and liquid He temperatures. Significant changes in energetics and dynamics of the antenna excitons upon self-assembly of the proteins into intracytoplasmic membranes are observed, analyzed, and discussed. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. Copyright © 2011. Published by Elsevier B.V.

A method for visualizing surface-exposed and internal PfEMP1 adhesion antigens in Plasmodium falciparum infected erythrocytes

DEFF Research Database (Denmark)

Bengtsson, Dominique; Sowa, Kordai M; Salanti, Ali

2008-01-01

BACKGROUND: The insertion of parasite antigens into the host erythrocyte membrane and the structure and distribution of Plasmodium falciparum adhesion receptors on that membrane are poorly understood. Laser scanning confocal microscopy (LSCM) and a novel labelling and fixation method have been used...... fluorochromes has been developed for laser scanning confocal optical microscopy and the analysis of the developmental expression of malaria adhesion antigens....

Contact Angle and Adhesion Dynamics and Hysteresis on Molecularly Smooth Chemically Homogeneous Surfaces.

Science.gov (United States)

Chen, Szu-Ying; Kaufman, Yair; Schrader, Alex M; Seo, Dongjin; Lee, Dong Woog; Page, Steven H; Koenig, Peter H; Isaacs, Sandra; Gizaw, Yonas; Israelachvili, Jacob N

2017-09-26

Measuring truly equilibrium adhesion energies or contact angles to obtain the thermodynamic values is experimentally difficult because it requires loading/unloading or advancing/receding boundaries to be measured at rates that can be slower than 1 nm/s. We have measured advancing-receding contact angles and loading-unloading adhesion energies for various systems and geometries involving molecularly smooth and chemically homogeneous surfaces moving at different but steady velocities in both directions, ±V, focusing on the thermodynamic limit of ±V → 0. We have used the Bell Theory (1978) to derive expressions for the dynamic (velocity-dependent) adhesion energies and contact angles suitable for both (i) dynamic adhesion measurements using the classic Johnson-Kendall-Roberts (JKR, 1971) theory of "contact mechanics" and (ii) dynamic contact angle hysteresis measurements of both rolling droplets and syringe-controlled (sessile) droplets on various surfaces. We present our results for systems that exhibited both steady and varying velocities from V ≈ 10 mm/s to 1 nm/s, where in all cases but one, the advancing (V > 0) and receding (V contact angles converged toward the same theoretical (thermodynamic) values as V → 0. Our equations for the dynamic contact angles are similar to the classic equations of Blake & Haynes (1969) and fitted the experimental adhesion data equally well over the range of velocities studied, although with somewhat different fitting parameters for the characteristic molecular length/dimension or area and characteristic bond formation/rupture lifetime or velocity. Our theoretical and experimental methods and results unify previous kinetic theories of adhesion and contact angle hysteresis and offer new experimental methods for testing kinetic models in the thermodynamic, quasi-static, limit. Our analyses are limited to kinetic effects only, and we conclude that hydrodynamic, i.e., viscous, and inertial effects do not play a role at the

The role of membrane microdomains in transmembrane signaling through the epithelial glycoprotein Gp140/CDCP1

Science.gov (United States)

Alvares, Stacy M.; Dunn, Clarence A.; Brown, Tod A.; Wayner, Elizabeth E.; Carter, William G.

2008-01-01

Cell adhesion to the extracellular matrix (ECM) via integrin adhesion receptors initiates signaling cascades leading to changes in cell behavior. While integrin clustering is necessary to initiate cell attachment to the matrix, additional membrane components are necessary to mediate the transmembrane signals and the cell adhesion response that alter downstream cell behavior. Many of these signaling components reside in glycosphingolipid-rich and cholesterol-rich membrane domains such as Tetraspanin Enriched Microdomains (TEMs)/Glycosynapse 3 and Detergent-Resistant Microdomains (DRMs), also known as lipid rafts. In the following article, we will review examples of how components in these membrane microdomains modulate integrin adhesion after initial attachment to the ECM. Additionally, we will present data on a novel adhesion-responsive transmembrane glycoprotein Gp140/CUB Domain Containing Protein 1, which clusters in epithelial cell-cell contacts. Gp140 can then be phosphorylated by Src Family Kinases at tyrosine 734 in response to outside-in signals- possibly through interactions involving the extracellular CUB domains. Data presented here suggests that outside-in signals through Gp140 in cell-cell contacts assemble membrane clusters that associate with membrane microdomains to recruit and activate SFKs. Active SFKs then mediate phosphorylation of Gp140, SFK and PKCδ with Gp140 acting as a transmembrane scaffold for these kinases. We propose that the clustering of Gp140 and signaling components in membrane microdomains in cell-cell contacts contributes to changes in cell behavior. PMID:18269919

Adhesive joint evaluation by ultrasonic interface and lamb waves

Science.gov (United States)

Rokhlin, S. I.

1986-01-01

Some results on the application of interface and Lamb waves for the study of curing of thin adhesive layers were summarized. In the case of thick substrates (thickness much more than the wave length) the interface waves can be used. In this case the experimental data can be inverted and the shear modulus of the adhesive film may be explicitly found based on the measured interface wave velocity. It is shown that interface waves can be used for the study of curing of structural adhesives as a function of different temperatures and other experimental conditions. The kinetics of curing was studied. In the case of thin substrates the wave phenomena are much more complicated. It is shown that for successful measurements proper selection of experimental conditions is very important. This can be done based on theoretical estimations. For correctly selected experimental conditions the Lamb waves may be a sensitive probe of adhesive bond quality and may be used or cure monitoring.

The Neural Cell Adhesion Molecule NCAM2/OCAM/RNCAM, a Close Relative to NCAM

DEFF Research Database (Denmark)

Kulahin, Nikolaj; Walmod, Peter

2008-01-01

molecule (NCAM) is a well characterized, ubiquitously expressed CAM that is highly expressed in the nervous system. In addition to mediating cell adhesion, NCAM participates in a multitude of cellular events, including survival, migration, and differentiation of cells, outgrowth of neurites, and formation......Cell adhesion molecules (CAMs) constitute a large class of plasma membrane-anchored proteins that mediate attachment between neighboring cells and between cells and the surrounding extracellular matrix (ECM). However, CAMs are more than simple mediators of cell adhesion. The neural cell adhesion...... and plasticity of synapses. NCAM shares an overall sequence identity of approximately 44% with the neural cell adhesion molecule 2 (NCAM2), a protein also known as olfactory cell adhesion molecule (OCAM) and Rb-8 neural cell adhesion molecule (RNCAM), and the region-for-region sequence homology between the two...

Improving Hemocompatibility of Membranes for Extracorporeal Membrane Oxygenators by Grafting Nonthrombogenic Polymer Brushes.

Science.gov (United States)

Obstals, Fabian; Vorobii, Mariia; Riedel, Tomáš; de Los Santos Pereira, Andres; Bruns, Michael; Singh, Smriti; Rodriguez-Emmenegger, Cesar

2018-03-01

Nonthrombogenic modifications of membranes for extracorporeal membrane oxygenators (ECMOs) are of key interest. The absence of hemocompatibility of these membranes and the need of anticoagulation of patients result in severe and potentially life-threatening complications during ECMO treatment. To address the lack of hemocompatibility of the membrane, surface modifications are developed, which act as barriers to protein adsorption on the membrane and, in this way, prevent activation of the coagulation cascade. The modifications are based on nonionic and zwitterionic polymer brushes grafted directly from poly(4-methyl-1-pentene) (TPX) membranes via single electron transfer-living radical polymerization. Notably, this work introduces the first example of well-controlled surface-initiated radical polymerization of zwitterionic brushes. The antifouling layers markedly increase the recalcification time (a proxy of initiation of coagulation) compared to bare TPX membranes. Furthermore, platelet and leukocyte adhesion is drastically decreased, rendering the ECMO membranes hemocompatible. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deferoxamine immobilized poly(D,L-lactide) membrane via polydopamine adhesive coating: The influence on mouse embryo osteoblast precursor cells and human umbilical vein endothelial cells

Energy Technology Data Exchange (ETDEWEB)

Li, Huihua [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Luo, Binghong, E-mail: tluobh@jnu.edu.cn [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Wen, Wei [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Zhou, Changren, E-mail: tcrz9@jnu.edu.cn [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Tian, Lingling [Center for Nanofibers & Nanotechnology, Department of Mechanical Engineering, National University of Singapore, Singapore 117576 (Singapore); Ramakrishna, Seeram [Center for Nanofibers & Nanotechnology, Department of Mechanical Engineering, National University of Singapore, Singapore 117576 (Singapore); Guangdong-Hongkong-Macau Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou 510632 (China)

2017-01-01

Osteogenesis and angiogenesis play the prominent role in the bone regeneration. In this study, deferoxamine (DFO), an induced agent for osteogenesis and angiogenesis, was modified onto the surface of poly(D,L-lactide) (PDLLA) membrane via a facile and convenient approach based on the self-polymerization of dopamine (DOPA). The surface composition, morphology, hydrophilicity and surface energy of the original and modified PDLLA membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM), atomic force microscopy (AFM) and contact angle measurement. The surface roughness and hydrophilicity of the PDLLA membrane were obviously increased by introducing either the single polydopamine (PDOPA) or the dual layers of PDOPA and DFO. In vitro cells culture experiments indicated that both the PDLLA/PDOPA and PDLLA/PDOPA-DFO composite membranes were more beneficial to the attachment, proliferation and spreading of MC3T3-E1 cells and HUVECs compared to the original PDLLA membrane. The PDLLA/PDOPA-DFO membrane was supportive for the proliferation of both MC3T3-E1 cells and HUVECs, and especially for HUVECs. The results suggested that the as-prepared PDLLA/PDOPA-DFO composite can be expected to be used as a promising bone regenerative material with promoted angiogenesis. - Highlights: • DFO was conveniently immobilized on PDLLA membrane based on PDOPA adhesive layer. • Hydrophilicity of PDLLA membrane was improved by modification with PDOPA and DFO. • Modified membranes were more favorable to the growth of MC3T3-E1 cells and HUVECs. • DFO was supportive for the growth of two kinds of cells, especially for HUVECs.

Functionalized PCL/HA nanocomposites as microporous membranes for bone regeneration

Energy Technology Data Exchange (ETDEWEB)

Basile, Maria Assunta; Gomez d' Ayala, Giovanna; Malinconico, Mario [Institute for Polymers, Composites and Biomaterials, CNR, Via Campi Flegrei 34, Pozzuoli (Naples) (Italy); Laurienzo, Paola, E-mail: paola.laurienzo@ipcb.cnr.it [Institute for Polymers, Composites and Biomaterials, CNR, Via Campi Flegrei 34, Pozzuoli (Naples) (Italy); Coudane, Jean; Nottelet, Benjamin [Institut des Biomolécules Max Mousseron (IBMM), Artificial Biopolymers Group, CNRS UMR 5247, University of Montpellier 1, Faculty of Pharmacy, 15 Av. C. Flahault, Montpellier 34093 (France); Ragione, Fulvio Della [Department of Biochemistry and Biophysics, Second University of Naples, Via L. De Crecchio 7, Naples (Italy); Oliva, Adriana, E-mail: adriana.oliva@unina2.it [Department of Biochemistry and Biophysics, Second University of Naples, Via L. De Crecchio 7, Naples (Italy)

2015-03-01

In the present work, microporous membranes based on poly(ε-caprolactone) (PCL) and PCL functionalized with amine (PCL-DMAEA) or anhydride groups (PCL-MAGMA) were realized by solvent–non solvent phase inversion and proposed for use in Guided Tissue Regeneration (GTR). Nanowhiskers of hydroxyapatite (HA) were also incorporated in the polymer matrix to realize nanocomposite membranes. Scanning Electron Microscopy (SEM) showed improved interfacial adhesion with HA for functionalized polymers, and highlighted substantial differences in the porosity. A relationship between the developed porous structure of the membrane and the chemical nature of grafted groups was proposed. Compared to virgin PCL, hydrophilicity increases for functionalized PCL, while the addition of HA influences significantly the hydrophilic characteristics only in the case of virgin polymer. A significant increase of in vitro degradation rate was found for PCL-MAGMA based membranes, and at lower extent of PCL-DMAEA membranes. The novel materials were investigated regarding their potential as support for cell growth in bone repair using multipotent mesenchymal stromal cells (MSC) as a model. MSC plated onto the various membranes were analyzed in terms of adhesion, proliferation and osteogenic capacity that resulted to be related to chemical as well as porous structure. In particular, PCL-DMAEA and the relative nanocomposite membranes are the most promising in terms of cell-biomaterial interactions. - Graphical abstract: Functionalized PCL is used to realize nanocomposites with hydroxyapatite (HA) in the form of microporous membranes. The influence of different grafted groups on mechanical properties, in vitro degradation, porous membrane structure and interaction with mesenchymal stromal cells (MSC) is discussed. - Highlights: • Functionalized PCL shows faster in vitro degradation rate. • Functionalized PCL shows superior cell adhesion, proliferation and differentiation. • Nanocomposites based

Functionalized PCL/HA nanocomposites as microporous membranes for bone regeneration

International Nuclear Information System (INIS)

Basile, Maria Assunta; Gomez d'Ayala, Giovanna; Malinconico, Mario; Laurienzo, Paola; Coudane, Jean; Nottelet, Benjamin; Ragione, Fulvio Della; Oliva, Adriana

2015-01-01

In the present work, microporous membranes based on poly(ε-caprolactone) (PCL) and PCL functionalized with amine (PCL-DMAEA) or anhydride groups (PCL-MAGMA) were realized by solvent–non solvent phase inversion and proposed for use in Guided Tissue Regeneration (GTR). Nanowhiskers of hydroxyapatite (HA) were also incorporated in the polymer matrix to realize nanocomposite membranes. Scanning Electron Microscopy (SEM) showed improved interfacial adhesion with HA for functionalized polymers, and highlighted substantial differences in the porosity. A relationship between the developed porous structure of the membrane and the chemical nature of grafted groups was proposed. Compared to virgin PCL, hydrophilicity increases for functionalized PCL, while the addition of HA influences significantly the hydrophilic characteristics only in the case of virgin polymer. A significant increase of in vitro degradation rate was found for PCL-MAGMA based membranes, and at lower extent of PCL-DMAEA membranes. The novel materials were investigated regarding their potential as support for cell growth in bone repair using multipotent mesenchymal stromal cells (MSC) as a model. MSC plated onto the various membranes were analyzed in terms of adhesion, proliferation and osteogenic capacity that resulted to be related to chemical as well as porous structure. In particular, PCL-DMAEA and the relative nanocomposite membranes are the most promising in terms of cell-biomaterial interactions. - Graphical abstract: Functionalized PCL is used to realize nanocomposites with hydroxyapatite (HA) in the form of microporous membranes. The influence of different grafted groups on mechanical properties, in vitro degradation, porous membrane structure and interaction with mesenchymal stromal cells (MSC) is discussed. - Highlights: • Functionalized PCL shows faster in vitro degradation rate. • Functionalized PCL shows superior cell adhesion, proliferation and differentiation. • Nanocomposites based

Infusion of hypertonic saline (7.5%) does not change neutrophil oxidative burst or expression of endothelial adhesion molecules after abdominal hysterectomy

DEFF Research Database (Denmark)

Kølsen-Petersen, Jens Aage; Rasmussen, Torsten Bøgh; Krog, Jan

2006-01-01

of leukocyte and differential count, neutrophil membrane expression of endothelial adhesion molecules by flow cytometry, and O2- -generation by superoxide dismutase-inhibitable reduction of cytochrome C. RESULTS: Surgery induced well-known changes in the number and distribution of white blood cells, reduced...... the expression of adhesion molecules, and halved the superoxide production unrelated to the tonicity or volume of the infused fluids. CONCLUSION: Infusion of a clinically relevant dose of hypertonic saline has no detectable effect on the membrane expression of endothelial adhesion molecules or O2- -generation...

Reverse adhesion of a gecko-inspired synthetic adhesive switched by an ion-exchange polymer-metal composite actuator.

Science.gov (United States)

Guo, Dong-Jie; Liu, Rui; Cheng, Yu; Zhang, Hao; Zhou, Li-Ming; Fang, Shao-Ming; Elliott, Winston Howard; Tan, Wei

2015-03-11

Inspired by how geckos abduct, rotate, and adduct their setal foot toes to adhere to different surfaces, we have developed an artificial muscle material called ion-exchange polymer-metal composite (IPMC), which, as a synthetic adhesive, is capable of changing its adhesion properties. The synthetic adhesive was cast from a Si template through a sticky colloid precursor of poly(methylvinylsiloxane) (PMVS). The PMVS array of setal micropillars had a high density of pillars (3.8 × 10(3) pillars/mm(2)) with a mean diameter of 3 μm and a pore thickness of 10 μm. A graphene oxide monolayer containing Ag globular nanoparticles (GO/Ag NPs) with diameters of 5-30 nm was fabricated and doped in an ion-exchanging Nafion membrane to improve its carrier transfer, water-saving, and ion-exchange capabilities, which thus enhanced the electromechanical response of IPMC. After being attached to PMVS micropillars, IPMC was actuated by square wave inputs at 1.0, 1.5, or 2.0 V to bend back and forth, driving the micropillars to actively grip or release the surface. To determine the adhesion of the micropillars, the normal adsorption and desorption forces were measured as the IPMC drives the setal micropillars to grip and release, respectively. Adhesion results demonstrated that the normal adsorption forces were 5.54-, 14.20-, and 23.13-fold higher than the normal desorption forces under 1.0, 1.5, or 2.0 V, respectively. In addition, shear adhesion or friction increased by 98, 219, and 245%, respectively. Our new technique provides advanced design strategies for reversible gecko-inspired synthetic adhesives, which might be used for spiderman-like wall-climbing devices with unprecedented performance.

Bidirectional remodeling of β1-integrin adhesions during chemotropic regulation of nerve growth

Directory of Open Access Journals (Sweden)

Carlstrom Lucas P

2011-11-01

Full Text Available Abstract Background Chemotropic factors in the extracellular microenvironment guide nerve growth by acting on the growth cone located at the tip of extending axons. Growth cone extension requires the coordination of cytoskeleton-dependent membrane protrusion and dynamic adhesion to the extracellular matrix, yet how chemotropic factors regulate these events remains an outstanding question. We demonstrated previously that the inhibitory factor myelin-associated glycoprotein (MAG triggers endocytic removal of the adhesion receptor β1-integrin from the growth cone surface membrane to negatively remodel substrate adhesions during chemorepulsion. Here, we tested how a neurotrophin might affect integrin adhesions. Results We report that brain-derived neurotropic factor (BDNF positively regulates the formation of substrate adhesions in axonal growth cones during stimulated outgrowth and prevents removal of β1-integrin adhesions by MAG. Treatment of Xenopus spinal neurons with BDNF rapidly triggered β1-integrin clustering and induced the dynamic formation of nascent vinculin-containing adhesion complexes in the growth cone periphery. Both the formation of nascent β1-integrin adhesions and the stimulation of axon extension by BDNF required cytoplasmic calcium ion signaling and integrin activation at the cell surface. Exposure to MAG decreased the number of β1-integrin adhesions in the growth cone during inhibition of axon extension. In contrast, the BDNF-induced adhesions were resistant to negative remodeling by MAG, correlating with the ability of BDNF pretreatment to counteract MAG-inhibition of axon extension. Pre-exposure to MAG prevented the BDNF-induced formation of β1-integrin adhesions and blocked the stimulation of axon extension by BDNF. Conclusions Altogether, these findings demonstrate the neurotrophin-dependent formation of integrin-based adhesions in the growth cone and reveal how a positive regulator of substrate adhesions can block

Prostaglandins in Cancer Cell Adhesion, Migration, and Invasion

Directory of Open Access Journals (Sweden)

David G. Menter

2012-01-01

Full Text Available Prostaglandins exert a profound influence over the adhesive, migratory, and invasive behavior of cells during the development and progression of cancer. Cyclooxygenase-2 (COX-2 and microsomal prostaglandin E2 synthase-1 (mPGES-1 are upregulated in inflammation and cancer. This results in the production of prostaglandin E2 (PGE2, which binds to and activates G-protein-coupled prostaglandin E1-4 receptors (EP1-4. Selectively targeting the COX-2/mPGES-1/PGE2/EP1-4 axis of the prostaglandin pathway can reduce the adhesion, migration, invasion, and angiogenesis. Once stimulated by prostaglandins, cadherin adhesive connections between epithelial or endothelial cells are lost. This enables cells to invade through the underlying basement membrane and extracellular matrix (ECM. Interactions with the ECM are mediated by cell surface integrins by “outside-in signaling” through Src and focal adhesion kinase (FAK and/or “inside-out signaling” through talins and kindlins. Combining the use of COX-2/mPGES-1/PGE2/EP1-4 axis-targeted molecules with those targeting cell surface adhesion receptors or their downstream signaling molecules may enhance cancer therapy.

Structurally stable graphene oxide-based nanofiltration membranes with bioadhesive polydopamine coating

Science.gov (United States)

Wang, Chongbin; Li, Zhiyuan; Chen, Jianxin; Yin, Yongheng; Wu, Hong

2018-01-01

Graphene oxide (GO)-based membranes possess promising potential in liquid separation for its high flux. The state-of-art GO-based membranes need to be supported by a substrate to ensure that the ultra-thin GO layer can withstand transmembrane pressure in practical applications. The interfacial compatibility of this kind of composite membrane remains a great challenge due to the intrinsic difference in chemical/physical properties between the GO sheets and the substrate. In this paper, a structurally stable GO-based composite nanofiltration membrane was fabricated by coupling the mussel-inspired adhesive platform and filtration-assisted assembly of GO laminates. The water flux for the prepared GO-based nanofiltration membrane reached up to 85 L m-2 h-1 bar-1 with a high retention above 95% and 100% for Orange G and Congo Red, respectively. The membrane exhibited highly stable structure owing to the covalent and noncovalent interactions between GO separation layer and dopamine adhesive platform.

Evaluation of mechanical and morphologic features of PLLA membranes as supports for perfusion cells culture systems

Energy Technology Data Exchange (ETDEWEB)

Montesanto, S., E-mail: salvatore.montesanto1985@gmail.com [Department of Civil, Environmental, Aerospace, Materials Engineering (DICAM), University of Palermo, Viale delle Scienze Ed. 8, 90128 Palermo (Italy); Brucato, V. [Department of Civil, Environmental, Aerospace, Materials Engineering (DICAM), University of Palermo, Viale delle Scienze Ed. 8, 90128 Palermo (Italy); La Carrubba, V. [Department of Civil, Environmental, Aerospace, Materials Engineering (DICAM), University of Palermo, Viale delle Scienze Ed. 8, 90128 Palermo (Italy); Euro-Mediterranean Institute of Science and Technology (IEMEST), Via Michele Miraglia, 20, 90128 Palermo (Italy)

2016-12-01

Porous biodegradable PLLA membranes, which can be used as supports for perfusion cell culture systems were designed, developed and characterized. PLLA membranes were prepared via diffusion induced phase separation (DIPS). A glass slab was coated with a binary PLLA–dioxane solution (8 wt.% PLLA) via dip coating, then pool immersed in two subsequent coagulation baths, and finally dried in a humidity-controlled environment. Surface and mechanical properties were evaluated by measuring pore size, porosity via scanning electron microscopy, storage modulus, loss modulus and loss angle by using a dynamic mechanical analysis (DMA). Cell adhesion assays on different membrane surfaces were also performed by using a standard count method. Results provide new insights into the foaming methods for producing polymeric membranes and supply indications on how to optimise the fabrication parameters to design membranes for tissue cultures and regeneration. - Highlights: • Design, development and characterization of porous biodegradable PLLA membranes via DIPS technology. • Easy-to-tune processing parameters in terms of surface and volumetric properties and cell adhesion. • Evaluation of the impact of the interconnection degree on membrane's mechanical properties. • Evaluation of cell adhesion on different membrane surface textures.

Evaluation of mechanical and morphologic features of PLLA membranes as supports for perfusion cells culture systems

International Nuclear Information System (INIS)

Montesanto, S.; Brucato, V.; La Carrubba, V.

2016-01-01

Porous biodegradable PLLA membranes, which can be used as supports for perfusion cell culture systems were designed, developed and characterized. PLLA membranes were prepared via diffusion induced phase separation (DIPS). A glass slab was coated with a binary PLLA–dioxane solution (8 wt.% PLLA) via dip coating, then pool immersed in two subsequent coagulation baths, and finally dried in a humidity-controlled environment. Surface and mechanical properties were evaluated by measuring pore size, porosity via scanning electron microscopy, storage modulus, loss modulus and loss angle by using a dynamic mechanical analysis (DMA). Cell adhesion assays on different membrane surfaces were also performed by using a standard count method. Results provide new insights into the foaming methods for producing polymeric membranes and supply indications on how to optimise the fabrication parameters to design membranes for tissue cultures and regeneration. - Highlights: • Design, development and characterization of porous biodegradable PLLA membranes via DIPS technology. • Easy-to-tune processing parameters in terms of surface and volumetric properties and cell adhesion. • Evaluation of the impact of the interconnection degree on membrane's mechanical properties. • Evaluation of cell adhesion on different membrane surface textures.

Quantitative analysis of dynamic adhesion properties in human hepatocellular carcinoma cells with fullerenol.

Science.gov (United States)

Liu, Yang; Wang, Zuobin; Wang, Xinyue; Huang, Yanhong

2015-12-01

In this study, the effect of fullerenol (C60(OH)24) on the cellular dynamic biomechanical behaviors of living human hepatocellular carcinoma (SMCC-7721) cancer cells were investigated by atomic force microscope (AFM) nanoindentation. As an important biomarker of cellular information, the cell adhesion is essential to maintain proper functioning as well as links with the pathogenesis and canceration. Nonetheless, it is challenging to properly evaluate the complex adhesion properties as all the biomechanical parameters interfere with each other. To investigate the dynamic adhesion changes, especially in the case of the fullerenol treatment, the detachment force and work, adhesion events, and membrane tether properties were measured and analyzed systematically with the proposed quantitative method. The statistical analyses suggest that, under the same operating parameters of AFM, the dependence of adhesion energy on the tip-cell contact area is weakened after the fullerenol treatment and the probability of adhesion decreases significantly from 30.6% to 4.2%. In addition, the disruption of the cytoskeleton resulted in a 34% decrease of the average membrane tether force and a 21% increase of the average tether length. Benefiting from the quantitative method, this work contributes to revealing the effects of fullerenol on the cellular biomechanical properties of the living SMCC-7721 cells in a precise and rigorous way and additionally is further instructive to interpret the interaction mechanism of other potential nanomedicines with living cells. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Effect of Spatholobus suberctus on adhesion, invasion, migration and metastasis of melanoma cells].

Science.gov (United States)

Xu, Jian-Ya; Gu, Qin; Xia, Wei-Jun

2010-10-01

To study the effect of Spatholobus suberctus, a kind of Chinese Traditional Medicine which can dissolve the stasis by activating the blood circulation, on invasion, adhesion, migration and metastasis of B16-BL6 metastatic mouse melanoma cells and its mechanism. The proliferation, adhesion, invasion and migration capacity of B16-BL6 metastatic cells was evaluated by MTP assay, adhesion assay and reconstituted basement membrane invasion and migration assay in vitro respectively. Mouse spontaneous motility melanoma model was used to study the effect of Spatholobus suberctus on metastasis in vivo. At the highest innoxious concentration, the extracts of Spatholobus suberctus inhibited the adhesion and invasion capacity of B16-BL6 metastatic cells significantly. In the mouse spontaneous melanoma model, the lung metastatic nodes number and its volume were significantly decreased after continuously treated with the extracts of Spatholobus suberctu. The extracts of Spatholobus suberctu can inhibit the metastasis of of B16-BI6 metastatic mouse melanoma cells and its mechanism may be inhibiting the capability of B16-BL6 cells in adhering to the ECM and invading the basement membrane.

Pathogen-Specific Binding Soluble Down Syndrome Cell Adhesion Molecule (Dscam Regulates Phagocytosis via Membrane-Bound Dscam in Crab

Directory of Open Access Journals (Sweden)

Xue-Jie Li

2018-04-01

Full Text Available The Down syndrome cell adhesion molecule (Dscam gene is an extraordinary example of diversity that can produce thousands of isoforms and has so far been found only in insects and crustaceans. Cumulative evidence indicates that Dscam may contribute to the mechanistic foundations of specific immune responses in insects. However, the mechanism and functions of Dscam in relation to pathogens and immunity remain largely unknown. In this study, we identified the genome organization and alternative Dscam exons from Chinese mitten crab, Eriocheir sinensis. These variants, designated EsDscam, potentially produce 30,600 isoforms due to three alternatively spliced immunoglobulin (Ig domains and a transmembrane domain. EsDscam was significantly upregulated after bacterial challenge at both mRNA and protein levels. Moreover, bacterial specific EsDscam isoforms were found to bind specifically with the original bacteria to facilitate efficient clearance. Furthermore, bacteria-specific binding of soluble EsDscam via the complete Ig1–Ig4 domain significantly enhanced elimination of the original bacteria via phagocytosis by hemocytes; this function was abolished by partial Ig1–Ig4 domain truncation. Further studies showed that knockdown of membrane-bound EsDscam inhibited the ability of EsDscam with the same extracellular region to promote bacterial phagocytosis. Immunocytochemistry indicated colocalization of the soluble and membrane-bound forms of EsDscam at the hemocyte surface. Far-Western and coimmunoprecipitation assays demonstrated homotypic interactions between EsDscam isoforms. This study provides insights into a mechanism by which soluble Dscam regulates hemocyte phagocytosis via bacteria-specific binding and specific interactions with membrane-bound Dscam as a phagocytic receptor.

G-protein signaling leverages subunit-dependent membrane affinity to differentially control βγ translocation to intracellular membranes.

Science.gov (United States)

O'Neill, Patrick R; Karunarathne, W K Ajith; Kalyanaraman, Vani; Silvius, John R; Gautam, N

2012-12-18

Activation of G-protein heterotrimers by receptors at the plasma membrane stimulates βγ-complex dissociation from the α-subunit and translocation to internal membranes. This intermembrane movement of lipid-modified proteins is a fundamental but poorly understood feature of cell signaling. The differential translocation of G-protein βγ-subunit types provides a valuable experimental model to examine the movement of signaling proteins between membranes in a living cell. We used live cell imaging, mathematical modeling, and in vitro measurements of lipidated fluorescent peptide dissociation from vesicles to determine the mechanistic basis of the intermembrane movement and identify the interactions responsible for differential translocation kinetics in this family of evolutionarily conserved proteins. We found that the reversible translocation is mediated by the limited affinity of the βγ-subunits for membranes. The differential kinetics of the βγ-subunit types are determined by variations among a set of basic and hydrophobic residues in the γ-subunit types. G-protein signaling thus leverages the wide variation in membrane dissociation rates among different γ-subunit types to differentially control βγ-translocation kinetics in response to receptor activation. The conservation of primary structures of γ-subunits across mammalian species suggests that there can be evolutionary selection for primary structures that confer specific membrane-binding affinities and consequent rates of intermembrane movement.

Measurement of cell adhesion force by vertical forcible detachment using an arrowhead nanoneedle and atomic force microscopy

International Nuclear Information System (INIS)

Ryu, Seunghwan; Hashizume, Yui; Mishima, Mari; Kawamura, Ryuzo; Tamura, Masato; Matsui, Hirofumi; Matsusaki, Michiya; Akashi, Mitsuru; Nakamura, Chikashi

2014-01-01

Graphical abstract: - Highlights: • We developed a method to measure cell adhesion force by detaching cell using an arrowhead nanoneedle and AFM. • A nanofilm consisting of fibronectin and gelatin was formed on cell surface to reinforce the cell cortex. • By the nanofilm lamination, detachment efficiencies of strongly adherent cell lines were improved markedly. - Abstract: The properties of substrates and extracellular matrices (ECM) are important factors governing the functions and fates of mammalian adherent cells. For example, substrate stiffness often affects cell differentiation. At focal adhesions, clustered–integrin bindings link cells mechanically to the ECM. In order to quantitate the affinity between cell and substrate, the cell adhesion force must be measured for single cells. In this study, forcible detachment of a single cell in the vertical direction using AFM was carried out, allowing breakage of the integrin–substrate bindings. An AFM tip was fabricated into an arrowhead shape to detach the cell from the substrate. Peak force observed in the recorded force curve during probe retraction was defined as the adhesion force, and was analyzed for various types of cells. Some of the cell types adhered so strongly that they could not be picked up because of plasma membrane breakage by the arrowhead probe. To address this problem, a technique to reinforce the cellular membrane with layer-by-layer nanofilms composed of fibronectin and gelatin helped to improve insertion efficiency and to prevent cell membrane rupture during the detachment process, allowing successful detachment of the cells. This method for detaching cells, involving cellular membrane reinforcement, may be beneficial for evaluating true cell adhesion forces in various cell types

Single-molecule tracking of small GTPase Rac1 uncovers spatial regulation of membrane translocation and mechanism for polarized signaling

Science.gov (United States)

Das, Sulagna; Yin, Taofei; Yang, Qingfen; Zhang, Jingqiao; Wu, Yi I.; Yu, Ji

2015-01-01

Polarized Rac1 signaling is a hallmark of many cellular functions, including cell adhesion, motility, and cell division. The two steps of Rac1 activation are its translocation to the plasma membrane and the exchange of nucleotide from GDP to GTP. It is, however, unclear whether these two processes are regulated independent of each other and what their respective roles are in polarization of Rac1 signaling. We designed a single-particle tracking (SPT) method to quantitatively analyze the kinetics of Rac1 membrane translocation in living cells. We found that the rate of Rac1 translocation was significantly elevated in protrusions during cell spreading on collagen. Furthermore, combining FRET sensor imaging with SPT measurements in the same cell, the recruitment of Rac1 was found to be polarized to an extent similar to that of the nucleotide exchange process. Statistical analysis of single-molecule trajectories and optogenetic manipulation of membrane lipids revealed that Rac1 membrane translocation precedes nucleotide exchange, and is governed primarily by interactions with phospholipids, particularly PI(3,4,5)P3, instead of protein factors. Overall, the study highlights the significance of membrane translocation in spatial Rac1 signaling, which is in addition to the traditional view focusing primarily on GEF distribution and exchange reaction. PMID:25561548

Structural Insights into Ail-Mediated Adhesion in Yersinia pestis

Energy Technology Data Exchange (ETDEWEB)

Yamashita, Satoshi; Lukacik, Petra; Barnard, Travis J.; Noinaj, Nicholas; Felek, Suleyman; Tsang, Tiffany M.; Krukonis, Eric S.; Hinnebusch, B. Joseph; Buchanan, Susan K. (Michigan); (NIH); (Michigan-Med)

2012-01-30

Ail is an outer membrane protein from Yersinia pestis that is highly expressed in a rodent model of bubonic plague, making it a good candidate for vaccine development. Ail is important for attaching to host cells and evading host immune responses, facilitating rapid progression of a plague infection. Binding to host cells is important for injection of cytotoxic Yersinia outer proteins. To learn more about how Ail mediates adhesion, we solved two high-resolution crystal structures of Ail, with no ligand bound and in complex with a heparin analog called sucrose octasulfate. We identified multiple adhesion targets, including laminin and heparin, and showed that a 40 kDa domain of laminin called LG4-5 specifically binds to Ail. We also evaluated the contribution of laminin to delivery of Yops to HEp-2 cells. This work constitutes a structural description of how a bacterial outer membrane protein uses a multivalent approach to bind host cells.

Fluorescent Protein Voltage Probes Derived from ArcLight that Respond to Membrane Voltage Changes with Fast Kinetics

Science.gov (United States)

Han, Zhou; Jin, Lei; Platisa, Jelena; Cohen, Lawrence B.; Baker, Bradley J.; Pieribone, Vincent A.

2013-01-01

We previously reported the discovery of a fluorescent protein voltage probe, ArcLight, and its derivatives that exhibit large changes in fluorescence intensity in response to changes of plasma membrane voltage. ArcLight allows the reliable detection of single action potentials and sub-threshold activities in individual neurons and dendrites. The response kinetics of ArcLight (τ1-on ~10 ms, τ2-on ~ 50 ms) are comparable with most published genetically-encoded voltage probes. However, probes using voltage-sensing domains other than that from the Ciona intestinalis voltage sensitive phosphatase exhibit faster kinetics. Here we report new versions of ArcLight, in which the Ciona voltage-sensing domain was replaced with those from chicken, zebrafish, frog, mouse or human. We found that the chicken and zebrafish-based ArcLight exhibit faster kinetics, with a time constant (τ) less than 6ms for a 100 mV depolarization. Although the response amplitude of these two probes (8-9%) is not as large as the Ciona-based ArcLight (~35%), they are better at reporting action potentials from cultured neurons at higher frequency. In contrast, probes based on frog, mouse and human voltage sensing domains were either slower than the Ciona-based ArcLight or had very small signals. PMID:24312287

Fluorescent protein voltage probes derived from ArcLight that respond to membrane voltage changes with fast kinetics.

Directory of Open Access Journals (Sweden)

Zhou Han

Full Text Available We previously reported the discovery of a fluorescent protein voltage probe, ArcLight, and its derivatives that exhibit large changes in fluorescence intensity in response to changes of plasma membrane voltage. ArcLight allows the reliable detection of single action potentials and sub-threshold activities in individual neurons and dendrites. The response kinetics of ArcLight (τ1-on ~10 ms, τ2-on ~ 50 ms are comparable with most published genetically-encoded voltage probes. However, probes using voltage-sensing domains other than that from the Ciona intestinalis voltage sensitive phosphatase exhibit faster kinetics. Here we report new versions of ArcLight, in which the Ciona voltage-sensing domain was replaced with those from chicken, zebrafish, frog, mouse or human. We found that the chicken and zebrafish-based ArcLight exhibit faster kinetics, with a time constant (τ less than 6 ms for a 100 mV depolarization. Although the response amplitude of these two probes (8-9% is not as large as the Ciona-based ArcLight (~35%, they are better at reporting action potentials from cultured neurons at higher frequency. In contrast, probes based on frog, mouse and human voltage sensing domains were either slower than the Ciona-based ArcLight or had very small signals.

Lipophilic drug transfer between liposomal and biological membranes

DEFF Research Database (Denmark)

Fahr, Alfred; van Hoogevest, Peter; Kuntsche, Judith

2006-01-01

This review presents the current knowledge on the interaction of lipophilic, poorly water soluble drugs with liposomal and biological membranes. The center of attention will be on drugs having the potential to dissolve in a lipid membrane without perturbing them too much. The degree of interaction...... is described as solubility of a drug in phospholipid membranes and the kinetics of transfer of a lipophilic drug between membranes. Finally, the consequences of these two factors on the design of lipid-based carriers for oral, as well as parenteral use, for lipophilic drugs and lead selection of oral...... lipophilic drugs is described. Since liposomes serve as model-membranes for natural membranes, the assessment of lipid solubility and transfer kinetics of lipophilic drug using liposome formulations may additionally have predictive value for bioavailability and biodistribution and the pharmacokinetics...

Enhanced H2/CH4 and H2/CO2 Separation by Carbon Molecular Sieve Membrane Coated on Titania Modified Alumina Support: Effects of TiO2 Intermediate Layer Preparation Variables on Interfacial Adhesion.

Czech Academy of Sciences Publication Activity Database

Tseng, H.-H.; Wang, Ch.-T.; Zhuang, G.-L.; Uchytil, Petr; Řezníčková Čermáková, Jiřina; Setničková, Kateřina

2016-01-01

Roč. 510, JUL 15 (2016), s. 391-404 ISSN 0376-7388 Grant - others:NSC(TW) NSC100-2221-E- 040-004-MY3 Institutional support: RVO:67985858 Keywords : carbon membrane * intermediate layer * adhesion Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 6.035, year: 2016

Monocyte chemoattractant protein 1, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1 in exudative age-related macular degeneration.

Science.gov (United States)

Jonas, Jost B; Tao, Yong; Neumaier, Michael; Findeisen, Peter

2010-10-01

To examine intraocular concentrations of monocyte chemoattractant protein 1 (MCP-1), soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cell adhesion molecule 1 (sVCAM-1), and vascular endothelial growth factor (VEGF) in eyes with exudative age-related macular degeneration (AMD). The investigation included a study group of 28 patients (28 eyes) with exudative AMD and a control group of 25 patients (25 eyes) with cataract. The concentrations of MCP-1, sICAM-1, sVCAM-1, and VEGF in aqueous humor samples obtained during surgery were measured using a solid-phase chemiluminescence immunoassay. The study group as compared with the control group had higher aqueous concentrations of sICAM-1 (mean [SD], 844 [2073] vs 246 [206] pg/mL, respectively; P < .001), sVCAM-1 (mean [SD], 7978 [7120] vs 2999 [1426] pg/mL, respectively; P < .001), and MCP-1 (mean [SD], 587 [338] vs 435 [221] pg/mL, respectively; P = .07). The concentration of VEGF did not vary significantly between the groups (P = .76). The MCP-1 concentration was significantly associated with macular thickness (r = 0.40; P = .004). It decreased significantly with the type of subfoveal neovascular membrane (classic membrane type, occult membrane, retinal pigment epithelium detachment) (P = .009). The concentrations of sICAM-1, sVCAM-1, and VEGF were not significantly associated with membrane type and macular thickness (P ≥ .18). Concentrations of MCP-1, sICAM-1, and sVCAM-1 are significantly associated with exudative AMD, even in the presence of normal VEGF concentrations. Intraocular MCP-1 concentrations are correlated with the subfoveal neovascular membrane type and the amount of macular edema. One may infer that MCP-1, sICAM-1, and sVCAM-1 could potentially be additional target molecules in therapy for exudative AMD.

Fast kinetics of calcium dissociation from calsequestrin

Directory of Open Access Journals (Sweden)

MARIANELA BELTRÁN

2006-01-01

Full Text Available We measured the kinetics of calcium dissociation from calsequestrin in solution or forming part of isolated junctional sarcoplasmic reticulum membranes by mixing calsequestrin equilibrated with calcium with calcium-free solutions in a stopped-flow system. In parallel, we measured the kinetics of the intrinsic fluorescence changes that take place following calcium dissociation from calsequestrin. We found that at 25ºC calcium dissociation was 10-fold faster for calsequestrin attached to junctional membranes (k = 109 s-1 than in solution. These results imply that calcium dissociation from calsequestrin in vivo is not rate limiting during excitation-contraction coupling. In addition, we found that the intrinsic fluorescence decrease for calsequestrin in solution or forming part of junctional membranes was significantly slower than the rates of calcium dissociation. The kinetics of intrinsic fluorescence changes had two components for calsequestrin associated to junctional membranes and only one for calsequestrin in solution; the faster component was 8-fold faster (k = 54.1 s-1 than the slower component (k = 6.9 s-1, which had the same k value as for calsequestrin in solution. These combined results suggest that the presence of calsequestrin at high concentrations in a restricted space, such as when bound to the junctional membrane, accelerates calcium dissociation and the resulting structural changes, presumably as a result of cooperative molecular interactions.

Osteoblasts Interaction with PLGA Membranes Functionalized with Titanium Film Nanolayer by PECVD. In vitro Assessment of Surface Influence on Cell Adhesion during Initial Cell to Material Interaction

Science.gov (United States)

Terriza, Antonia; Vilches-Pérez, José I.; González-Caballero, Juan L.; de la Orden, Emilio; Yubero, Francisco; Barranco, Angel; Gonzalez-Elipe, Agustín R.; Vilches, José; Salido, Mercedes

2014-01-01

New biomaterials for Guided Bone Regeneration (GBR), both resorbable and non-resorbable, are being developed to stimulate bone tissue formation. Thus, the in vitro study of cell behavior towards material surface properties turns a prerequisite to assess both biocompatibility and bioactivity of any material intended to be used for clinical purposes. For this purpose, we have developed in vitro studies on normal human osteoblasts (HOB®) HOB® osteoblasts grown on a resorbable Poly (lactide-co-glycolide) (PLGA) membrane foil functionalized by a very thin film (around 15 nm) of TiO2 (i.e., TiO2/PLGA membranes), designed to be used as barrier membrane. To avoid any alteration of the membranes, the titanium films were deposited at room temperature in one step by plasma enhanced chemical vapour deposition. Characterization of the functionalized membranes proved that the thin titanium layer completely covers the PLGA foils that remains practically unmodified in their interior after the deposition process and stands the standard sterilization protocols. Both morphological changes and cytoskeletal reorganization, together with the focal adhesion development observed in HOB osteoblasts, significantly related to TiO2 treated PLGA in which the Ti deposition method described has revealed to be a valuable tool to increase bioactivity of PLGA membranes, by combining cell nanotopography cues with the incorporation of bioactive factors. PMID:28788538

Osteoblasts Interaction with PLGA Membranes Functionalized with Titanium Film Nanolayer by PECVD. In vitro Assessment of Surface Influence on Cell Adhesion during Initial Cell to Material Interaction

Directory of Open Access Journals (Sweden)

Antonia Terriza

2014-03-01

Full Text Available New biomaterials for Guided Bone Regeneration (GBR, both resorbable and non-resorbable, are being developed to stimulate bone tissue formation. Thus, the in vitro study of cell behavior towards material surface properties turns a prerequisite to assess both biocompatibility and bioactivity of any material intended to be used for clinical purposes. For this purpose, we have developed in vitro studies on normal human osteoblasts (HOB® HOB® osteoblasts grown on a resorbable Poly (lactide-co-glycolide (PLGA membrane foil functionalized by a very thin film (around 15 nm of TiO2 (i.e., TiO2/PLGA membranes, designed to be used as barrier membrane. To avoid any alteration of the membranes, the titanium films were deposited at room temperature in one step by plasma enhanced chemical vapour deposition. Characterization of the functionalized membranes proved that the thin titanium layer completely covers the PLGA foils that remains practically unmodified in their interior after the deposition process and stands the standard sterilization protocols. Both morphological changes and cytoskeletal reorganization, together with the focal adhesion development observed in HOB osteoblasts, significantly related to TiO2 treated PLGA in which the Ti deposition method described has revealed to be a valuable tool to increase bioactivity of PLGA membranes, by combining cell nanotopography cues with the incorporation of bioactive factors.

Anti-adhesion therapy following operative hysteroscopy for treatment of female subfertility

NARCIS (Netherlands)

Bosteels, Jan; Weyers, Steven; D'Hooghe, Thomas M.; Torrance, Helen; Broekmans, Frank J.; Chua, Su Jen; Mol, Ben Willem J.

2017-01-01

Background: Observational evidence suggests a potential benefit with several anti-adhesion therapies in women undergoing operative hysteroscopy (e.g. insertion of an intrauterine device or balloon, hormonal treatment, barrier gels or human amniotic membrane grafting) for decreasing intrauterine

Studies on carboxylated graphene oxide incorporated polyetherimide mixed matrix ultrafiltration membranes

Energy Technology Data Exchange (ETDEWEB)

Kaleekkal, Noel Jacob, E-mail: noeljacob89@gmail.com [Membrane Laboratory, Department of Chemical Engineering, ACT, Anna University, Chennai, 600025 (India); Thanigaivelan, A., E-mail: thanichemstar@gmail.com [Membrane Laboratory, Department of Chemical Engineering, ACT, Anna University, Chennai, 600025 (India); Rana, Dipak, E-mail: rana@uottawa.ca [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis Pasteur Private, Ottawa, Ontario, K1N 6N5 (Canada); Mohan, D., E-mail: mohantarun@gmail.com [Membrane Laboratory, Department of Chemical Engineering, ACT, Anna University, Chennai, 600025 (India)

2017-01-15

In this work the graphene oxide prepared by the modified Hummers’ method was effectively carboxylated. These carboxylated graphene oxide (c-GO) microsheets was characterized by X-ray diffraction analysis, Raman shift, zeta potential, and their morphology was observed using a high resolution scanning/transmission electron microscopy. Polyetherimide mixed matrix membranes (MMMs) were fabricated by the non-solvent induced phase separation technique with varying concentration of this microsheet. The presence of these microsheets on the membrane surface was confirmed by Fourier transform infrared spectroscopy, Raman spectroscopy and could also be confirmed visually by optical images. The membranes were further characterized; they showed a greater water flux, higher porosity, and sufficient thermal stability. Incorporation of these microsheets improved the hydrophilicity of the membrane confirmed by the lower contact angle values, which in turn explained the lower interfacial free energy, the increase in work of adhesion, the higher solid-vapor free energy and the spreading coefficient. Membranes loaded with 0.3 wt% of c-GO showed a flux recovery of 94% and only a small flux decline even after 180 min of filtration of humic acid (HA) solution. The efficiency of these membranes in removal of HA, toxic metal ions was also investigated. The bacterial anti-adhesion property of c-GO in the membranes was also explored using Escherichia coli, as a model bio-foulant. The charge of the microsheets and their unique architecture imparts higher hydrophilicity and greater fouling resistance along with improved permeation flux when incorporated into the polymer matrix. - Highlights: • Novel membranes by incorporating carboxylated GO into polyetherimide matrix. • Modified membranes exhibited greater porosity, flux and high humic acid rejection. • Nanoplatelets improved the flux recovery ratio to >94%. • Liquid phase polymer based retention utilized for toxic heavy metal

Development of a fast curing tissue adhesive for meniscus tear repair.

Science.gov (United States)

Bochyńska, Agnieszka Izabela; Hannink, Gerjon; Janssen, Dennis; Buma, Pieter; Grijpma, Dirk W

2017-01-01

Isocyanate-terminated adhesive amphiphilic block copolymers are attractive materials to treat meniscus tears due to their tuneable mechanical properties and good adhesive characteristics. However, a drawback of this class of materials is their relatively long curing time. In this study, we evaluate the use of an amine cross-linker and addition of catalysts as two strategies to accelerate the curing rates of a recently developed biodegradable reactive isocyanate-terminated hyper-branched adhesive block copolymer prepared from polyethylene glycol (PEG), trimethylene carbonate, citric acid and hexamethylene diisocyanate. The curing kinetics of the hyper-branched adhesive alone and in combination with different concentrations of spermidine solutions, and after addition of 2,2-dimorpholinodiethylether (DMDEE) or 1,4-diazabicyclo [2.2.2] octane (DABCO) were determined using FTIR. Additionally, lap-shear adhesion tests using all compositions at various time points were performed. The two most promising compositions of the fast curing adhesives were evaluated in a meniscus bucket handle lesion model and their performance was compared with that of fibrin glue. The results showed that addition of both spermidine and catalysts to the adhesive copolymer can accelerate the curing rate and that firm adhesion can already be achieved after 2 h. The adhesive strength to meniscus tissue of 3.2-3.7 N was considerably higher for the newly developed compositions than for fibrin glue (0.3 N). The proposed combination of an adhesive component and a cross-linking component or catalyst is a promising way to accelerate curing rates of isocyanate-terminated tissue adhesives.

[Germ cell membrane lipids in spermatogenesis].

Science.gov (United States)

Wang, Ting; Shi, Xiao; Quan, Song

2016-05-01

Spermatogenesis is a complex developmental process in which a diploid progenitor germ cell transforms into highly specialized spermatozoa. During spermatogenesis, membrane remodeling takes place, and cell membrane permeability and liquidity undergo phase-specific changes, which are all associated with the alteration of membrane lipids. Lipids are important components of the germ cell membrane, whose volume and ratio fluctuate in different phases of spermatogenesis. Abnormal lipid metabolism can cause spermatogenic dysfunction and consequently male infertility. Germ cell membrane lipids are mainly composed of cholesterol, phospholipids and glycolipids, which play critical roles in cell adhesion and signal transduction during spermatogenesis. An insight into the correlation of membrane lipids with spermatogenesis helps us to better understand the mechanisms of spermatogenesis and provide new approaches to the diagnosis and treatment of male infertility.

Plasma-modified polyethylene membrane as a separator for lithium-ion polymer battery

International Nuclear Information System (INIS)

Kim, Jun Young; Lee, Yongbeom; Lim, Dae Young

2009-01-01

The surface of polyethylene (PE) membranes as a separator for lithium-ion polymer battery was modified with acrylonitrile (AN) using the plasma technology. The plasma-induced acrylonitrile coated PE (PiAN-PE) membrane was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and contact angle measurement. The electrochemical performance of the lithium-ion polymer cell fabricated with the PE and the PiAN-PE membranes were also analyzed. The surface characterization demonstrates that the enhanced adhesion of the PiAN-PE membrane resulted from the increased polar component of surface energy for the PiAN-PE membrane. The presence of the PiAN induced onto the surface of the membrane via the plasma modification plays a critical role in improving the wettability and electrolyte retention, the interfacial adhesion between the electrodes and the separator, the cycle performance of the resulting lithium-ion polymer cell assembly. The PiAN-PE membrane modified by the plasma treatment holds a great potential to be used as a high-performance and cost-effective separator for lithium-ion polymer battery.

Cell adhesion monitoring of human induced pluripotent stem cell based on intrinsic molecular charges

Science.gov (United States)

Sugimoto, Haruyo; Sakata, Toshiya

2014-01-01

We have shown a simple way for real-time, quantitative, non-invasive, and non-label monitoring of human induced pluripotent stem (iPS) cell adhesion by use of a biologically coupled-gate field effect transistor (bio-FET), which is based on detection of molecular charges at cell membrane. The electrical behavior revealed quantitatively the electrical contacts of integrin-receptor at the cell membrane with RGDS peptide immobilized at the gate sensing surface, because that binding site was based on cationic α chain of integrin. The platform based on the bio-FET would provide substantial information to evaluate cell/material bio-interface and elucidate biding mechanism of adhesion molecules, which could not be interpreted by microscopic observation.

Development of test method for assessing the bonding characteristics of membrane layers in wearing course laid on orthotropic steel bridge decks

NARCIS (Netherlands)

Liu, X.; Scarpas, A.; Li, J.; Tzimiris, G.; Hofman, R.; Voskuilen, J.

2013-01-01

In order to adequately characterize the adhesive bonding strength of the various membranes with surrounding materials on orthotropic steel decks and collect the necessary parameters for FE modeling, details of the Membrane Adhesion Test (MAT) are introduced. Analytical constitutive relations of the

Elongated membrane tethers, individually anchored by high affinity α4β1/VCAM-1 complexes, are the quantal units of monocyte arrests.

Directory of Open Access Journals (Sweden)

Calvin Chu

Full Text Available The α4β1 integrin facilitates both monocyte rolling and adhesion to the vascular endothelium and is physiologically activated by monocyte chemoattractant protein (MCP-1. The current study investigated the initial events in the adhesion of THP-1 cells to immobilized Vascular Cell Adhesion Molecule 1 (VCAM-1. Using AFM force measurements, cell adhesion was shown to be mediated by two populations of α4β1/VCAM-1 complexes. A low affinity form of α4β1 was anchored to the elastic elements of the cytoskeleton, while a higher affinity conformer was coupled to the viscous elements of the cell membrane. Within 100 ms of contact, THP-1 cells, stimulated by co-immobilized MCP-1, exhibited a tremendous increase in adhesion to VCAM-1. Enhanced cell adhesion was accompanied by a local decoupling of the cell membrane from the cytoskeleton and the formation of long membrane tethers. The tethers were individually anchored by multiple α4β1/VCAM-1 complexes that prolonged the extension of the viscous tethers. In vivo, the formation of these membrane tethers may provide the quantal structural units for the arrest of rolling monocytes within the blood vessels.

Nature of the elements transporting long-chain fatty acids through the red cell membrane

DEFF Research Database (Denmark)

Bojesen, Inge Norby; Bojesen, Eigil

1998-01-01

Docosahexaenoic acid, linoleic acid, red cell membrane, transporting elements, transport kinetics, fatty acid transport......Docosahexaenoic acid, linoleic acid, red cell membrane, transporting elements, transport kinetics, fatty acid transport...

Natural organic matter interactions with polyamide and polysulfone membranes: Formation of conditioning film

KAUST Repository

Gutierrez, Leonardo

2015-03-31

A conditioning film changes the physicochemical properties of the membrane surface and strongly affects subsequent fouling behavior. Results from this Atomic Force Microscopy study indicate that Natural Organic Matter (NOM) characteristics, membrane surface properties, and solution chemistry are fundamental during conditioning film formation. Repulsive forces were observed between HUM (humic-NOM) and Polyamide (PA) or Polysulfone (PS) membranes during approach in Na+ and Ca2+ solutions. However, repulsive and attractive forces were randomly recorded during BIOP (biopolymer-NOM) approach to both membranes, possibly caused by low electrostatic repulsion, hydrogen bonding, and presence of chemically/physically heterogeneous regions on membrane surfaces. During retracting, Ca2+ ions increased HUM adhesion to PA and PS membrane, indicating cation bridging/complexation as dominant interacting mechanism for this isolate. BIOP adsorption on PS and PA membrane was stronger than HUM under similar solution conditions, where hydrogen bonding would play an important role. Additionally, irrespective of solution conditions, higher adhesion energy was recorded on PS than on PA membrane for both NOM isolates, indicating membrane hydrophobicity as an important interacting factor. Results from this research will advance our understanding of conditioning film formation for NOM isolates and membranes of different physicochemical characteristics.

Highly Hydrophilic Thin-Film Composite Forward Osmosis Membranes Functionalized with Surface-Tailored Nanoparticles

KAUST Repository

Tiraferri, Alberto

2012-09-26

Thin-film composite polyamide membranes are state-of-the-art materials for membrane-based water purification and desalination processes, which require both high rejection of contaminants and high water permeabilities. However, these membranes are prone to fouling when processing natural waters and wastewaters, because of the inherent surface physicochemical properties of polyamides. The present work demonstrates the fabrication of forward osmosis polyamide membranes with optimized surface properties via facile and scalable functionalization with fine-tuned nanoparticles. Silica nanoparticles are coated with superhydrophilic ligands possessing functional groups that impart stability to the nanoparticles and bind irreversibly to the native carboxyl moieties on the membrane selective layer. The tightly tethered layer of nanoparticles tailors the surface chemistry of the novel composite membrane without altering the morphology or water/solute permeabilities of the membrane selective layer. Surface characterization and interfacial energy analysis confirm that highly hydrophilic and wettable membrane surfaces are successfully attained. Lower intermolecular adhesion forces are measured between the new membrane materials and model organic foulants, indicating the presence of a bound hydration layer at the polyamide membrane surface that creates a barrier for foulant adhesion. © 2012 American Chemical Society.

Fluorescence lifetime microscopy for monitoring cell adhesion using metal induced energy transfer

Science.gov (United States)

Hwang, Wonsang; Seo, JinWon; Song, Jun ho; Kim, DongEun; Won, YoungJae; Choi, In-Hong; Yoo, Kyung-Hwa; Kim, Dug Young

2018-02-01

A precise control and a reliable monitoring tool for the adhesion properties of a cell are very important in atherosclerosis studies. If endothelial cells in contact with the intracellular membrane are not attached securely, low-density lipoprotein (LDL) particles can enter into the inner membrane. It is therefore necessary to measure conditions under which endothelial cell detachment occurs. When a cell is attached to a metal thin film, the lifetime of a fluorescence probe attached to the membrane of the cell is reduced by the metal-induced energy transfer (MIET). Fluorescence lifetime imaging microscopy (FLIM) is used to monitor the attachment condition of a cell to a metal surface using FRET. However, this requires high numerical aperture (NA) objective lens because axial confocal resolution must be smaller than the cell thickness. This requirement limits the field of view of the measurement specimen. In this study we provides a new method which can measure adhesion properties of endothelial cells even with a low NA objective lens by resolving two lifetime components in FLIM.

Communication Between the Cell Membrane and the Nucleus: Role of Protein Compartmentalization

Energy Technology Data Exchange (ETDEWEB)

Lelievre, Sophie A; Bissell, Mina J

1998-10-21

Understanding how the information is conveyed from outside to inside the cell is a critical challenge for all biologists involved in signal transduction. The flow of information initiated by cell-cell and cell-extracellular matrix contacts is mediated by the formation of adhesion complexes involving multiple proteins. Inside adhesion complexes, connective membrane skeleton (CMS) proteins are signal transducers that bind to adhesion molecules, organize the cytoskeleton, and initiate biochemical cascades. Adhesion complex-mediated signal transduction ultimately directs the formation of supramolecular structures in the cell nucleus, as illustrated by the establishment of multi complexes of DNA-bound transcription factors, and the redistribution of nuclear structural proteins to form nuclear subdomains. Recently, several CMS proteins have been observed to travel to the cell nucleus, suggesting a distinctive role for these proteins in signal transduction. This review focuses on the nuclear translocation of structural signal transducers of the membrane skeleton and also extends our analysis to possible translocation of resident nuclear proteins to the membrane skeleton. This leads us to envision the communication between spatially distant cellular compartments (i.e., membrane skeleton and cell nucleus) as a bidirectional flow of information (a dynamic reciprocity) based on subtle multilevel structural and biochemical equilibria. At one level, it is mediated by the interaction between structural signal transducers and their binding partners, at another level it may be mediated by the balance and integration of signal transducers in different cellular compartments.

One-dimensional statistical model of active transfer of substances in membranes

International Nuclear Information System (INIS)

Melkikh, A.V.; Seleznev, V.D.

1995-01-01

A matrix of kinetic coefficients that describe the processes of particle and heat transfer in a double membrane is obtained. The kinetic coefficients are considered as functions of the membrane parameters. Conditions are found under which the energy expended on transfer of one atom through the membrane is minimum. The obtained theoretical value of this energy is compared with the corresponding value for active transport of ions in biomembranes

Kinetic stability and membrane structure of liposomes during in vitro infant intestinal digestion: Effect of cholesterol and lactoferrin.

Science.gov (United States)

Liu, Weilin; Wei, Fuqiang; Ye, Aiqian; Tian, Mengmeng; Han, Jianzhong

2017-09-01

The effects of cholesterol and lactoferrin on the kinetic stability and membrane structural integrity of negatively charged liposomes under in vitro infant intestinal digestion conditions were elucidated using dynamic light scattering, pH-stat titration, Fourier transform infrared spectroscopy, and pyrene steady state fluorescence probes. The liposomes had a smaller particle diameter, a wider size distribution, and a greater negative charge after digestion. The incorporation of cholesterol into the phospholipid bilayers resulted in a more ordered conformation in the aliphatic tail region and reduced micropolarity, indicating that cholesterol can improve the structural stability of liposomal membranes against intestinal environmental stress. Lactoferrin coverage facilitated the release of free fatty acids and increased the microfluidity of the bilayers, reducing the structural integrity of the liposomes. This study provides useful information on the design of liposomes and other microcapsules with improved and controlled release properties during digestion for particular groups of people. Copyright © 2017 Elsevier Ltd. All rights reserved.

Role of Membrane Biophysics in Alzheimer's - related cell pathways

Directory of Open Access Journals (Sweden)

Donghui eZhu

2015-05-01

Full Text Available Cellular membrane alterations are commonly observed in many diseases, including Alzheimer’s disease (AD. Membrane biophysical properties, such as membrane molecular order, membrane fluidity, organization of lipid rafts, and adhesion between membrane and cytoskeleton, play an important role in various cellular activities and functions. While membrane biophysics impacts a broad range of cellular pathways, this review addresses the role of membrane biophysics in amyloid-β peptide aggregation, Aβ-induced oxidative pathways, amyloid precursor protein processing, and cerebral endothelial functions in AD. Understanding the mechanism(s underlying the effects of cell membrane properties on cellular processes should shed light on the development of new preventive and therapeutic strategies for this devastating disease.

Ion Transport through Diffusion Layer Controlled by Charge Mosaic Membrane

Directory of Open Access Journals (Sweden)

Akira Yamauchi

2012-01-01

Full Text Available The kinetic transport behaviors in near interface of the membranes were studied using commercial anion and cation exchange membrane and charge mosaic membrane. Current-voltage curve gave the limiting current density that indicates the ceiling of conventional flux. From chronopotentiometry above the limiting current density, the transition time was estimated. The thickness of boundary layer was derived with conjunction with the conventional limiting current density and the transition time from steady state flux. On the other hand, the charge mosaic membrane was introduced in order to examine the ion transport on the membrane surface in detail. The concentration profile was discussed by the kinetic transport number with regard to the water dissociation (splitting on the membrane surface.

Proton exchange membrane fuel cells

CERN Document Server

Qi, Zhigang

2013-01-01

Preface Proton Exchange Membrane Fuel CellsFuel CellsTypes of Fuel CellsAdvantages of Fuel CellsProton Exchange Membrane Fuel CellsMembraneCatalystCatalyst LayerGas Diffusion MediumMicroporous LayerMembrane Electrode AssemblyPlateSingle CellStackSystemCell Voltage Monitoring Module (CVM)Fuel Supply Module (FSM)Air Supply Module (ASM)Exhaust Management Module (EMM)Heat Management Module (HMM)Water Management Module (WMM)Internal Power Supply Module (IPM)Power Conditioning Module (PCM)Communications Module (COM)Controls Module (CM)SummaryThermodynamics and KineticsTheoretical EfficiencyVoltagePo

Study of Kinetic coefficients of a Membrane Bioreactor (MBR for municipal wastewater treatment

Directory of Open Access Journals (Sweden)

Ali Naghizadeh

2013-08-01

Full Text Available Background & Aims of the Study: In order to design membrane bioreactors (MBR properly, it is essential to comprehend the behavior of microorganisms in such wastewater treatment processes. Materials & Methods: In this study, a lab-scale MBR process was operated to determine the biokinetic coefficients of the MBR system under different MLSS concentrations of 6800, 7000, 7400, and 7800 mg/l and organic loading rates of 0.5 kg COD/m3/day. Results: The results of this study showed that the yield of microorganisms (Y, the endogenous decay coefficient (kd, the maximum specific growth rate (μmax and the saturation constant (Ks were in the range of 0.67 g VSS/g COD, 0.56 d−1, 1.86 d−1 and 6.65 mg COD/l, respectively. Conclusions: The kinetic coefficients in this study can be used to improve the operation and design the MBR system in full scale.

Comparative kinetics of damage to the plasma and mitochondrial membranes by intra-cellularly synthesized and externally-provided photosensitizers using multi-color FACS.

Science.gov (United States)

Haupt, Sara; Malik, Zvi; Ehrenberg, Benjamin

2014-01-01

Photodynamic therapy (PDT) of cancer involves inflicting lethal damage to the cells of malignant tumors, primarily by singlet oxygen that is generated following light-absorption in a photosensitizer molecule. Dysfunction of cells is manifested in many ways, including peroxidation of cellular components, membrane rupture, depolarization of electric potentials, termination of mitochondrial activity, onset of apoptosis and necrosis and eventually cell lysis. These events do not necessarily occur in linear fashion and different types of damage to cell components occur, most probably, in parallel. In this report we measured the relative rates of damage to two cellular membranes: the plasma membrane and the mitochondrial membrane. We employed photosensitizers of diverse hydrophobicities and used different incubation procedures, which lead to their different intra-cellular localizations. We monitored the damage that was inflicted on these membranes, by employing optical probes of membrane integrity, in a multi-color FACS experiment. The potentiometric indicator JC-1 monitored the electric cross-membrane potential of the mitochondria and the fluorometric indicator Draq7 monitored the rupture of the plasma membrane. We show that the electric depolarization of the mitochondrial membrane and the damage to the enveloping plasma membrane proceed with different kinetics that reflect the molecular character and intracellular location of the sensitizer: PpIX that is synthesized in the cells from ALA causes rapid mitochondrial damage and very slow damage to the plasma membrane, while externally added PpIX has an opposite effect. The hydrophilic sensitizer HypS4 can be taken up by the cells by different incubation conditions, and these affect its intracellular location, and as a consequence either the plasma membrane or the mitochondria is damaged first. A similar correlation was found for additional extracellularly-provided photosensitizers HP and PpIX.

Mobility of drugs in lipid membranes by NMR

International Nuclear Information System (INIS)

Yoshii, Noriyuki; Okamura, Emiko

2011-01-01

Mobility of drugs and biomembrane constituents is a key to elucidate the membrane transport mechanism in the cell. Lipid bilayer membrane is a dynamic structure where molecules are always fluctuating under physiological conditions. The mechanism of drug transport is related to the molecular dynamics in such soft, fluid membrane interface. To gain insight into molecular movements in membranes, we develop a noninvasive method to monitor dynamics properties of drugs and lipid components in membranes by applying multinuclear high-resolution solution NMR in combination with the pulsed-field-gradient (PFG) technique. We have quantified the diffusivity, the kinetics of membrane binding, and the bound fraction of the drug in situ by using large unilamellar vesicles of egg phosphatidylcholine as model cell membranes. The combination of 1D and PFG NMR serves to quantify the kinetics of membrane binding where the bound and the free components are unable to distinguish because of the rapid exchange on the NMR timescale. A small-sized 5-fluorouracil and fluorinated bisphenol A are used as model drug. (author)

The Cdc42 guanine nucleotide exchange factor FGD6 coordinates cell polarity and endosomal membrane recycling in osteoclasts.

Science.gov (United States)

Steenblock, Charlotte; Heckel, Tobias; Czupalla, Cornelia; Espírito Santo, Ana Isabel; Niehage, Christian; Sztacho, Martin; Hoflack, Bernard

2014-06-27

The initial step of bone digestion is the adhesion of osteoclasts onto bone surfaces and the assembly of podosomal belts that segregate the bone-facing ruffled membrane from other membrane domains. During bone digestion, membrane components of the ruffled border also need to be recycled after macropinocytosis of digested bone materials. How osteoclast polarity and membrane recycling are coordinated remains unknown. Here, we show that the Cdc42-guanine nucleotide exchange factor FGD6 coordinates these events through its Src-dependent interaction with different actin-based protein networks. At the plasma membrane, FGD6 couples cell adhesion and actin dynamics by regulating podosome formation through the assembly of complexes comprising the Cdc42-interactor IQGAP1, the Rho GTPase-activating protein ARHGAP10, and the integrin interactors Talin-1/2 or Filamin A. On endosomes and transcytotic vesicles, FGD6 regulates retromer-dependent membrane recycling through its interaction with the actin nucleation-promoting factor WASH. These results provide a mechanism by which a single Cdc42-exchange factor controlling different actin-based processes coordinates cell adhesion, cell polarity, and membrane recycling during bone degradation. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

The adhesive strength and initial viscosity of denture adhesives.

Science.gov (United States)

Han, Jian-Min; Hong, Guang; Dilinuer, Maimaitishawuti; Lin, Hong; Zheng, Gang; Wang, Xin-Zhi; Sasaki, Keiichi

2014-11-01

To examine the initial viscosity and adhesive strength of modern denture adhesives in vitro. Three cream-type denture adhesives (Poligrip S, Corect Cream, Liodent Cream; PGS, CRC, LDC) and three powder-type denture adhesives (Poligrip Powder, New Faston, Zanfton; PGP, FSN, ZFN) were used in this study. The initial viscosity was measured using a controlled-stress rheometer. The adhesive strength was measured according to ISO-10873 recommended procedures. All data were analyzed independently by one-way analysis of variance combined with a Student-Newman-Keuls multiple comparison test at a 5% level of significance. The initial viscosity of all the cream-type denture adhesives was lower than the powder-type adhesives. Before immersion in water, all the powder-type adhesives exhibited higher adhesive strength than the cream-type adhesives. However, the adhesive strength of cream-type denture adhesives increased significantly and exceeded the powder-type denture adhesives after immersion in water. For powder-type adhesives, the adhesive strength significantly decreased after immersion in water for 60 min, while the adhesive strength of the cream-type adhesives significantly decreased after immersion in water for 180 min. Cream-type denture adhesives have lower initial viscosity and higher adhesive strength than powder type adhesives, which may offer better manipulation properties and greater efficacy during application.

Ultramicroelectrode studies of oxygen reduction in polyelectrolyte membranes

Energy Technology Data Exchange (ETDEWEB)

Holdcroft, S.; Abdou, M.S.; Beattie, P.; Basura, V. [Simon Fraser Univ., Burnaby, BC (Canada). Dept. of Chemistry

1997-12-31

A study on the oxygen reduction reaction in a solid state electrochemical cell was presented. The oxygen reduction reaction is a rate limiting reaction in the operation of solid polymer electrolyte fuel cells which use H{sub 2} and O{sub 2}. Interest in the oxygen reduction reaction of platinum electrodes in contact with Nafion electrolytes stems from its role in fuel cell technology. The kinetics of the oxygen reduction reaction in different polyelectrolyte membranes, such as Nafion and non-Nafion membranes, were compared. The electrode kinetics and mass transport parameters of the oxygen reduction reaction in polyelectrolyte membranes were measured by ultramicroelectrode techniques. The major difference found between these two classes of membrane was the percentage of water, which is suggestive of superior electrochemical mass transport properties of the non-Nafion membranes. 2 refs. 1 fig.

Biofouling behavior and performance of forward osmosis membranes with bioinspired surface modification in osmotic membrane bioreactor.

Science.gov (United States)

Li, Fang; Cheng, Qianxun; Tian, Qing; Yang, Bo; Chen, Qianyuan

2016-07-01

Forward osmosis (FO) has received considerable interest for water and energy related applications in recent years. Biofouling behavior and performance of cellulose triacetate (CTA) forward osmosis membranes with bioinspired surface modification via polydopamine (PD) coating and poly (ethylene glycol) (PEG) grafting (PD-g-PEG) in a submerged osmotic membrane bioreactor (OMBR) were investigated in this work. The modified membranes exhibited lower flux decline than the pristine one in OMBR, confirming that the bioinspired surface modification improved the antifouling ability of the CTA FO membrane. The result showed that the decline of membrane flux related to the increase of the salinity and MLSS concentration of the mixed liquid. It was concluded that the antifouling ability of modified membranes ascribed to the change of surface morphology in addition to the improvement of membrane hydrophilicity. The bioinspired surface modifications might improve the anti-adhesion for the biopolymers and biocake. Copyright © 2016 Elsevier Ltd. All rights reserved.

Membrane fusion by VAMP3 and plasma membrane t-SNAREs

International Nuclear Information System (INIS)

Hu Chuan; Hardee, Deborah; Minnear, Fred

2007-01-01

Pairing of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins on vesicles (v-SNAREs) and SNARE proteins on target membranes (t-SNAREs) mediates intracellular membrane fusion. VAMP3/cellubrevin is a v-SNARE that resides in recycling endosomes and endosome-derived transport vesicles. VAMP3 has been implicated in recycling of transferrin receptors, secretion of α-granules in platelets, and membrane trafficking during cell migration. Using a cell fusion assay, we examined membrane fusion capacity of the ternary complexes formed by VAMP3 and plasma membrane t-SNAREs syntaxin1, syntaxin4, SNAP-23 and SNAP-25. VAMP3 forms fusogenic pairing with t-SNARE complexes syntaxin1/SNAP-25, syntaxin1/SNAP-23 and syntaxin4/SNAP-25, but not with syntaxin4/SNAP-23. Deletion of the N-terminal domain of syntaxin4 enhanced membrane fusion more than two fold, indicating that the N-terminal domain negatively regulates membrane fusion. Differential membrane fusion capacities of the ternary v-/t-SNARE complexes suggest that transport vesicles containing VAMP3 have distinct membrane fusion kinetics with domains of the plasma membrane that present different t-SNARE proteins

Switching "on" and "off" the adhesion in stimuli-responsive elastomers.

Science.gov (United States)

Kaiser, S; Radl, S V; Manhart, J; Ayalur-Karunakaran, S; Griesser, T; Moser, A; Ganser, C; Teichert, C; Kern, W; Schlögl, S

2018-03-28

The present work aims at the preparation of dry adhesives with switchable bonding properties by using the reversible nature of the [4πs+4πs] cycloaddition of anthracenes. Photo-responsive hydrogenated carboxylated nitrile butadiene rubber with photo-responsive pendant anthracene groups is prepared by one-pot synthesis. The formation of 3D networks relies on the photodimerization of the anthracene moieties upon UV exposure (λ > 300 nm). Controlled cleavage of the crosslink sites is achieved by either deep UV exposure (λ = 254 nm) or thermal dissociation at 70 °C. The kinetics of the optical and thermal cleavage routes are compared in thin films using UV-vis spectroscopy and their influence on the reversibility of the network is detailed. Going from thin films to free standing samples the modulation of the network structure and thermo-mechanical properties over repeated crosslinking and cleavage cycles are characterized by low-field NMR spectroscopy and dynamic mechanical analysis. The applicability of the stimuli-responsive networks as adhesives with reversible bonding properties is demonstrated. The results evidence that the reversibility of the crosslinking reaction enables a controlled switching "on" and "off" of adhesion properties. The recovery of the adhesion force amounts to 75 and 80% for photo- and thermal dissociation, respectively. Spatial control of adhesion properties is evidenced by adhesion force mapping experiments of photo-patterned films.

Adhesion of leukocytes under oscillating stagnation point conditions: a numerical study.

Science.gov (United States)

Walker, P G; Alshorman, A A; Westwood, S; David, T

2002-01-01

Leukocyte recruitment from blood to the endothelium plays an important role in atherosclerotic plaque formation. Cells show a primary and secondary adhesive process with primary bonds responsible for capture and rolling and secondary bonds for arrest. Our objective was to investigate the role played by this process on the adhesion of leukocytes in complex flow. Cells were modelled as rigid spheres with spring like adhesion molecules which formed bonds with endothelial receptors. Models of bond kinetics and Newton's laws of motion were solved numerically to determine cell motion. Fluid force was obtained from the local shear rate obtained from a CFD simulation of the flow over a backward facing step.In stagnation point flow the shear rate near the stagnation point has a large gradient such that adherent cells in this region roll to a high shear region preventing permanent adhesion. This is enhanced if a small time dependent perturbation is imposed upon the stagnation point. For lower shear rates the cell rolling velocity may be such that secondary bonds have time to form. These bonds resist the lower fluid forces and consequently there is a relatively large permanent adhesion region.

Diffuse Charge Effects in Fuel Cell Membranes

NARCIS (Netherlands)

Biesheuvel, P.M.; Franco, A.A.; Bazant, M.Z.

2009-01-01

It is commonly assumed that electrolyte membranes in fuel cells are electrically neutral, except in unsteady situations, when the double-layer capacitance is heuristically included in equivalent circuit calculations. Indeed, the standard model for electron transfer kinetics at the membrane/electrode

Fuel cell subassemblies incorporating subgasketed thrifted membranes

Science.gov (United States)

Iverson, Eric J.; Pierpont, Daniel M.; Yandrasits, Michael A.; Hamrock, Steven J.; Obradovich, Stephan J.; Peterson, Donald G.

2016-03-01

A fuel cell roll good subassembly is described that includes a plurality of individual electrolyte membranes. One or more first subgaskets are attached to the individual electrolyte membranes. Each of the first subgaskets has at least one aperture and the first subgaskets are arranged so the center regions of the individual electrolyte membranes are exposed through the apertures of the first subgaskets. A second subgasket comprises a web having a plurality of apertures. The second subgasket web is attached to the one or more first subgaskets so the center regions of the individual electrolyte membranes are exposed through the apertures of the second subgasket web. The second subgasket web may have little or no adhesive on the subgasket surface facing the electrolyte membrane.

The synaptic cell adhesion molecule, SynCAM1, mediates astrocyte-to-astrocyte and astrocyte-to-GnRH neuron adhesiveness in the mouse hypothalamus.

Science.gov (United States)

Sandau, Ursula S; Mungenast, Alison E; McCarthy, Jack; Biederer, Thomas; Corfas, Gabriel; Ojeda, Sergio R

2011-06-01

We previously identified synaptic cell adhesion molecule 1 (SynCAM1) as a component of a genetic network involved in the hypothalamic control of female puberty. Although it is well established that SynCAM1 is a synaptic adhesion molecule, its contribution to hypothalamic function is unknown. Here we show that, in addition to the expected neuronal localization illustrated by its presence in GnRH neurons, SynCAM1 is expressed in hypothalamic astrocytes. Cell adhesion assays indicated that SynCAM is recognized by both GnRH neurons and astrocytes as an adhesive partner and promotes cell-cell adhesiveness via homophilic, extracellular domain-mediated interactions. Alternative splicing of the SynCAM1 primary mRNA transcript yields four mRNAs encoding membrane-spanning SynCAM1 isoforms. Variants 1 and 4 are predicted to be both N and O glycosylated. Hypothalamic astrocytes and GnRH-producing GT1-7 cells express mainly isoform 4 mRNA, and sequential N- and O-deglycosylation of proteins extracted from these cells yields progressively smaller SynCAM1 species, indicating that isoform 4 is the predominant SynCAM1 variant expressed in astrocytes and GT1-7 cells. Neither cell type expresses the products of two other SynCAM genes (SynCAM2 and SynCAM3), suggesting that SynCAM-mediated astrocyte-astrocyte and astrocyte-GnRH neuron adhesiveness is mostly mediated by SynCAM1 homophilic interactions. When erbB4 receptor function is disrupted in astrocytes, via transgenic expression of a dominant-negative erbB4 receptor form, SynCAM1-mediated adhesiveness is severely compromised. Conversely, SynCAM1 adhesive behavior is rapidly, but transiently, enhanced in astrocytes by ligand-dependent activation of erbB4 receptors, suggesting that erbB4-mediated events affecting SynCAM1 function contribute to regulate astrocyte adhesive communication.

Enhancing Membrane Protein Identification Using a Simplified Centrifugation and Detergent-Based Membrane Extraction Approach.

Science.gov (United States)

Zhou, Yanting; Gao, Jing; Zhu, Hongwen; Xu, Jingjing; He, Han; Gu, Lei; Wang, Hui; Chen, Jie; Ma, Danjun; Zhou, Hu; Zheng, Jing

2018-02-20

Membrane proteins may act as transporters, receptors, enzymes, and adhesion-anchors, accounting for nearly 70% of pharmaceutical drug targets. Difficulties in efficient enrichment, extraction, and solubilization still exist because of their relatively low abundance and poor solubility. A simplified membrane protein extraction approach with advantages of user-friendly sample processing procedures, good repeatability and significant effectiveness was developed in the current research for enhancing enrichment and identification of membrane proteins. This approach combining centrifugation and detergent along with LC-MS/MS successfully identified higher proportion of membrane proteins, integral proteins and transmembrane proteins in membrane fraction (76.6%, 48.1%, and 40.6%) than in total cell lysate (41.6%, 16.4%, and 13.5%), respectively. Moreover, our method tended to capture membrane proteins with high degree of hydrophobicity and number of transmembrane domains as 486 out of 2106 (23.0%) had GRAVY > 0 in membrane fraction, 488 out of 2106 (23.1%) had TMs ≥ 2. It also provided for improved identification of membrane proteins as more than 60.6% of the commonly identified membrane proteins in two cell samples were better identified in membrane fraction with higher sequence coverage. Data are available via ProteomeXchange with identifier PXD008456.

Laser-induced stabilisation of the tympanic membrane

Science.gov (United States)

Schacht, Sophie A. L.; Stahn, Patricia; Hinsberger, Marius; Hoetzer, Benjamin; Schick, Bernhard; Wenzel, Gentiana I.

2017-07-01

Repeated pathologies of the tympanic membrane (TM) decrease its tension inducing conductive hearing loss and adhesive processes up to cholesteatoma. Our results regarding the development of a laser based noninvasive procedure to strengthen the structure of the TM are herein presented.

Modeling cell adhesion and proliferation: a cellular-automata based approach.

Science.gov (United States)

Vivas, J; Garzón-Alvarado, D; Cerrolaza, M

Cell adhesion is a process that involves the interaction between the cell membrane and another surface, either a cell or a substrate. Unlike experimental tests, computer models can simulate processes and study the result of experiments in a shorter time and lower costs. One of the tools used to simulate biological processes is the cellular automata, which is a dynamic system that is discrete both in space and time. This work describes a computer model based on cellular automata for the adhesion process and cell proliferation to predict the behavior of a cell population in suspension and adhered to a substrate. The values of the simulated system were obtained through experimental tests on fibroblast monolayer cultures. The results allow us to estimate the cells settling time in culture as well as the adhesion and proliferation time. The change in the cells morphology as the adhesion over the contact surface progress was also observed. The formation of the initial link between cell and the substrate of the adhesion was observed after 100 min where the cell on the substrate retains its spherical morphology during the simulation. The cellular automata model developed is, however, a simplified representation of the steps in the adhesion process and the subsequent proliferation. A combined framework of experimental and computational simulation based on cellular automata was proposed to represent the fibroblast adhesion on substrates and changes in a macro-scale observed in the cell during the adhesion process. The approach showed to be simple and efficient.

Nanotechnology-based polymeric bio(muco)adhesive platforms for controlling drug delivery - properties, methodologies and applications

International Nuclear Information System (INIS)

Carvalho, Flavia Chiva; Chorilli, Marlus; Gremiao, Maria Palmira Daflon

2014-01-01

Studies using bio(muco)adhesive drug delivery systems have recently gained great interest, which can promote drug targeting and more specific contact of the drug delivery system with the various absorptive membranes of the body. This technological platform associated with nanotechnology offers potential for controlling drug delivery; therefore, they are excellent strategies to increase the bioavailability of drugs. The objective of this work was to study nanotechnology-based polymeric bio(muco)adhesive platforms for controlling drug delivery, highlighting their properties, how the bio(muco)adhesion can be measured and their potential applications for different routes of administration. (author)

Viral membrane fusion

International Nuclear Information System (INIS)

Harrison, Stephen C.

2015-01-01

Membrane fusion is an essential step when enveloped viruses enter cells. Lipid bilayer fusion requires catalysis to overcome a high kinetic barrier; viral fusion proteins are the agents that fulfill this catalytic function. Despite a variety of molecular architectures, these proteins facilitate fusion by essentially the same generic mechanism. Stimulated by a signal associated with arrival at the cell to be infected (e.g., receptor or co-receptor binding, proton binding in an endosome), they undergo a series of conformational changes. A hydrophobic segment (a “fusion loop” or “fusion peptide”) engages the target-cell membrane and collapse of the bridging intermediate thus formed draws the two membranes (virus and cell) together. We know of three structural classes for viral fusion proteins. Structures for both pre- and postfusion conformations of illustrate the beginning and end points of a process that can be probed by single-virion measurements of fusion kinetics. - Highlights: • Viral fusion proteins overcome the high energy barrier to lipid bilayer merger. • Different molecular structures but the same catalytic mechanism. • Review describes properties of three known fusion-protein structural classes. • Single-virion fusion experiments elucidate mechanism

Viral membrane fusion

Energy Technology Data Exchange (ETDEWEB)

Harrison, Stephen C., E-mail: harrison@crystal.harvard.edu

2015-05-15

Membrane fusion is an essential step when enveloped viruses enter cells. Lipid bilayer fusion requires catalysis to overcome a high kinetic barrier; viral fusion proteins are the agents that fulfill this catalytic function. Despite a variety of molecular architectures, these proteins facilitate fusion by essentially the same generic mechanism. Stimulated by a signal associated with arrival at the cell to be infected (e.g., receptor or co-receptor binding, proton binding in an endosome), they undergo a series of conformational changes. A hydrophobic segment (a “fusion loop” or “fusion peptide”) engages the target-cell membrane and collapse of the bridging intermediate thus formed draws the two membranes (virus and cell) together. We know of three structural classes for viral fusion proteins. Structures for both pre- and postfusion conformations of illustrate the beginning and end points of a process that can be probed by single-virion measurements of fusion kinetics. - Highlights: • Viral fusion proteins overcome the high energy barrier to lipid bilayer merger. • Different molecular structures but the same catalytic mechanism. • Review describes properties of three known fusion-protein structural classes. • Single-virion fusion experiments elucidate mechanism.

Wood : adhesives

Science.gov (United States)

A.H. Conner

2001-01-01

This chapter on wood adhesives includes: 1) Classification of wood adhesives 2) Thermosetting wood adhesives 3) Thermoplastic adhesives, 4) Wood adhesives based on natural sources 5) Nonconventional bonding of wood 6) Wood bonding.

Influence of Irradiance, Flow Rate, Reactor Geometry, and Photopromoter Concentration in Mineralization Kinetics of Methane in Air and in Aqueous Solutions by Photocatalytic Membranes Immobilizing Titanium Dioxide

Directory of Open Access Journals (Sweden)

Ignazio Renato Bellobono

2008-01-01

Full Text Available Photomineralization of methane in air (10.0–1000 ppm (mass/volume of C at 100% relative humidity (dioxygen as oxygen donor was systematically studied at 318±3 K in an annular laboratory-scale reactor by photocatalytic membranes immobilizing titanium dioxide as a function of substrate concentration, absorbed power per unit length of membrane, reactor geometry, and concentration of a proprietary vanadium alkoxide as photopromoter. Kinetics of both substrate disappearance, to yield intermediates, and total organic carbon (TOC disappearance, to yield carbon dioxide, were followed. At a fixed value of irradiance (0.30 W⋅cm-1, the mineralization experiments in gaseous phase were repeated as a function of flow rate (4–400 m3⋅h−1. Moreover, at a standard flow rate of 300 m3⋅h−1, the ratio between the overall reaction volume and the length of the membrane was varied, substantially by varying the volume of reservoir, from and to which circulation of gaseous stream took place. Photomineralization of methane in aqueous solutions was also studied, in the same annular reactor and in the same conditions, but in a concentration range of 0.8–2.0 ppm of C, and by using stoichiometric hydrogen peroxide as an oxygen donor. A kinetic model was employed, from which, by a set of differential equations, four final optimised parameters, k1 and K1, k2 and K2, were calculated, which is able to fit the whole kinetic profile adequately. The influence of irradiance on k1 and k2, as well as of flow rate on K1 and K2, is rationalized. The influence of reactor geometry on k values is discussed in view of standardization procedures of photocatalytic experiments. Modeling of quantum yields, as a function of substrate concentration and irradiance, as well as of concentration of photopromoter, was carried out very satisfactorily. Kinetics of hydroxyl radicals reacting between themselves, leading to hydrogen peroxide, other than with substrate or

Impact of operation conditions, foulant adsorption, and chemical cleaning on the nanomechanical properties of ultrafiltraion hollow fiber membranes

KAUST Repository

Gutierrez, Leonardo

2018-04-06

This study analyzed the change in nanomechanical properties of ultrafiltration hollow fiber membranes harvested from pilot-scale units after twelve months of operation. Quantitative Nanomechanical Mapping technique was used to distinguish between adhesion, dissipation, deformation, and modulus while simultaneously generating a topographic image of membranes. Nanomechanical maps of virgin membranes evidenced surfaces of heterogeneous properties and were described by probability density functions. Operating conditions and feed quality exerted an impact on membranes. Clean harvested membranes showed a higher mean modulus and dissipation, and a lower deformation than virgin membranes, indicating stiffer membranes of lower elastic deformation. A significant fraction of these measurements displayed peak values deviating from the distribution; which represents regions of the membrane with properties highly differing from the probability density function. The membrane polymeric material experienced severe physicochemical changes by foulant adsorption and reaction with cleaning agents. Foulant adsorption on membranes was heterogeneous in both morphology and mechanical properties and could not be statistically described. Foulants, i.e., mainly consisting of polysaccharides and proteinaceous structures, displayed low elastic deformation and high roughness and adhesion. The presence of foulants after chemical cleaning and their high adhesion would be a direct nanoscale evidence of irreversible fouling. By the end of the operation, the Trans-Membrane Pressure experienced a 40% increase. The cleaning process was not able to fully recover the initial TMP, indicating irreversible fouling, i.e., permanent change in membrane characteristics and decrease in performance. These results suggest a link between the macroscopic properties and nanomechanical characteristics of membranes. This study advances our nanoscale understanding of the impact of fouling and operating conditions on

Membrane distillation for wastewater reverse osmosis concentrate treatment with water reuse potential

KAUST Repository

Naidu, Gayathri; Jeong, Sanghyun; Choi, Youngkwon; Vigneswaran, Saravanamuthu

2016-01-01

Membrane distillation (MD) was evaluated as a treatment option of wastewater reverse osmosis concentrate (WWROC) discharged from wastewater reclamation plants (WRPs). A direct contact MD (DCMD), at obtaining 85% water recovery of WWROC showed only 13–15% flux decline and produced good quality permeate (10–15 µS/cm, 99% ion rejection) at moderate feed temperature of 55 °C. Prevalent calcium carbonate (CaCO3) deposition on the MD membrane occurred in treating WWROC at elevated concentrations. The combination of low salinity and loose CaCO3 adhesion on the membrane did not significantly contribute to DCMD flux decline. Meanwhile, high organic content in WWROC (58–60 mg/L) resulted in a significant membrane hydrophobicity reduction (70% lower water contact angle than virgin membrane) attributed to low molecular weight organic adhesion onto the MD membrane. Granular activated carbon (GAC) pretreatment helped in reducing organic contents of WWROC by 46–50%, and adsorbed a range of hydrophobic and hydrophilic micropollutants. This ensured high quality water production by MD (micropollutants-free) and enhanced its reuse potential. The MD concentrated WWROC was suitable for selective ion precipitation, promising a near zero liquid discharge in WRPs.

Membrane distillation for wastewater reverse osmosis concentrate treatment with water reuse potential

KAUST Repository

Naidu, Gayathri

2016-11-29

Membrane distillation (MD) was evaluated as a treatment option of wastewater reverse osmosis concentrate (WWROC) discharged from wastewater reclamation plants (WRPs). A direct contact MD (DCMD), at obtaining 85% water recovery of WWROC showed only 13–15% flux decline and produced good quality permeate (10–15 µS/cm, 99% ion rejection) at moderate feed temperature of 55 °C. Prevalent calcium carbonate (CaCO3) deposition on the MD membrane occurred in treating WWROC at elevated concentrations. The combination of low salinity and loose CaCO3 adhesion on the membrane did not significantly contribute to DCMD flux decline. Meanwhile, high organic content in WWROC (58–60 mg/L) resulted in a significant membrane hydrophobicity reduction (70% lower water contact angle than virgin membrane) attributed to low molecular weight organic adhesion onto the MD membrane. Granular activated carbon (GAC) pretreatment helped in reducing organic contents of WWROC by 46–50%, and adsorbed a range of hydrophobic and hydrophilic micropollutants. This ensured high quality water production by MD (micropollutants-free) and enhanced its reuse potential. The MD concentrated WWROC was suitable for selective ion precipitation, promising a near zero liquid discharge in WRPs.

Biofouling of reverse osmosis membranes: effects of cleaning on biofilm microbial communities, membrane performance, and adherence of extracellular polymeric substances.

Science.gov (United States)

Al Ashhab, Ashraf; Sweity, Amer; Bayramoglu, Bihter; Herzberg, Moshe; Gillor, Osnat

2017-05-01

Laboratory-scale reverse osmosis (RO) flat-sheet systems were used with two parallel flow cells, one treated with cleaning agents and a control (ie undisturbed). The cleaning efforts increased the affinity of extracellular polymeric substances (EPS) to the RO membrane and altered the biofilm surface structure. Analysis of the membrane biofilm community composition revealed the dominance of Proteobacteria. However, within the phylum Proteobacteria, γ-Proteobacteria dominated the cleaned membrane biofilm, while β-Proteobacteria dominated the control biofilm. The composition of the fungal phyla was also altered by cleaning, with enhancement of Ascomycota and suppression of Basidiomycota. The results suggest that repeated cleaning cycles select for microbial groups that strongly attach to the RO membrane surface by producing rigid and adhesive EPS that hampers membrane performance.

Possible mechanism of adhesion in a mica supported phospholipid bilayer

International Nuclear Information System (INIS)

Pertsin, Alexander; Grunze, Michael

2014-01-01

Phospholipid bilayers supported on hydrophilic solids like silica and mica play a substantial role in fundamental studies and technological applications of phospholipid membranes. In both cases the molecular mechanism of adhesion between the bilayer and the support is of primary interest. Since the possibilities of experimental methods in this specific area are rather limited, the methods of computer simulation acquire great importance. In this paper we use the grand canonical Monte Carlo technique and an atomistic force field to simulate the behavior of a mica supported phospholipid bilayer in pure water as a function of the distance between the bilayer and the support. The simulation reveals a possible adhesion mechanism, where the adhesion is due to individual lipid molecules that protrude from the bilayer and form widely spaced links with the support. Simultaneously, the bilayer remains separated from the bilayer by a thin water interlayer which maintains the bilayer fluidity

Kinetic Characteristics of Hydrogen Transfer Through Palladium-Modified Membrane

Science.gov (United States)

Petriev, I. S.; Frolov, V. Yu.; Bolotin, S. N.; Baryshev, M. G.; Kopytov, G. F.

2018-01-01

The paper deals with hydrogen transfer through Pd-23%Ag alloy membrane, the surface of which is modified by the electrolytic deposition of highly dispersed palladium. The dependence between the density of hydrogen flow and its excess pressure on the input surface of membrane is well approximated by the first-order curve. This fact indicates that the process of hydrogen permeability is defined by its dissociation on the input surface. Activation energy of this process is 47.9 kJ/mol which considerably exceeds that of the process of hydrogen transfer through palladium (22-30 kJ/mol). This confirms the fact that the chemisorption is a rate-controlling step of the hydrogen transfer through membrane.

Transfected HEK293 Cells Expressing Functional Recombinant Intercellular Adhesion Molecule 1 (ICAM-1) - A Receptor Associated with Severe Plasmodium falciparum Malaria

DEFF Research Database (Denmark)

Bengtsson, Anja; Joergensen, Louise; Barbati, Zachary R

2013-01-01

Intercellular adhesion molecule 1 (ICAM-1) is a membrane-bound glycoprotein expressed on endothelial cells and cells of the immune system. Human ICAM-1 mediates adhesion and migration of leucocytes, and is implicated in inflammatory pathologies, autoimmune diseases and in many cancer processes....... Additionally, ICAM-1 acts as receptor for pathogens like human rhinovirus and Plasmodium falciparum malaria parasites. A group of related P. falciparum erythrocyte membrane protein 1 (PfEMP1) domains, the DBLβ, mediates ICAM-1 binding of P. falciparum-infected erythrocytes. This ICAM‑1-binding phenotype has...

Analysis of proton exchange membrane fuel cell performance with alternate membranes

Energy Technology Data Exchange (ETDEWEB)

Wakizoe, Masanobu; Velev, O A; Srinivasan, S [Texas A and M Univ., College Station, TX (United States). Texas Engineering Experiment Station

1995-02-01

Renewed interest in proton exchange membrane fuel cell technology for space and terrestrial (particularly electric vehicles) was stimulated by the demonstration, in the mid 1980s, of high energy efficiencies and high power densities. One of the most vital components of the PEMFC is the proton conducting membrane. In this paper, an analysis is made of the performances of PEMFCs with Dupont`s Nafion, Dow`s experimental, and Asahi Chemical`s Aciplex-S membranes. Attempts were also made to draw correlations between the PEMFC performances with the three types of membranes and their physico-chemical characteristics. Practically identical levels of performances (energy efficiency, power density, and lifetime) were achieved in PEMFCs with the Dow and the Aciplex-S membranes and these performances were better than in the PEMFCs with the Nafion-115 membrane. The electrode kinetic parameters for oxygen reduction are better for the PEMFCs with the Aciplex-S and Nafion membranes than with the Dow membranes. The PEMFCs with the Aciplex-S and Dow membranes have nearly the same internal resistances which are considerably lower than for the PEMFC with the Nafion membrane. The desired membrane characteristics to obtain high levels of performance are low equivalent weight and high water content. (Author)

Energetics and Kinetics of trans-SNARE Zippering

Science.gov (United States)

Rebane, Aleksander A.; Shu, Tong; Krishnakumar, Shyam; Rothman, James E.; Zhang, Yongli

Synaptic exocytosis relies on assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins into a four-helix bundle to drive membrane fusion. Complementary SNAREs anchored to the synaptic vesicle (v-SNARE) and the plasma membrane (t-SNARE) associate from their N-termini, transiting a half-assembled intermediate (trans-SNARE), and ending at their C-termini with a rapid power stroke that leads to membrane fusion. Although cytosolic SNARE assembly has been characterized, it remains unknown how membranes modulate the energetics and kinetics of SNARE assembly. Here, we present optical tweezers measurements on folding of single membrane proteins in phospholipid bilayers. To our knowledge, this is the first such report. We measured the energetics, kinetics, and assembly intermediates of trans-SNAREs formed between a t-SNARE inserted into a bead-supported bilayer and a v-SNARE in a nanodisc. We found that the repulsive force of the apposed membranes increases the lifetime of the half-assembled intermediate. Our findings provide a single-molecule platform to study the regulation of trans-SNARE assembly by proteins that act on the half-assembled state, and thus reveal the mechanistic basis of the speed and high fidelity of synaptic transmission. This work was supported by US National Institutes of Health Grants F31 GM119312-01 (to A.A.R) and R01 GM093341 (to Y.Z.).

Surface grafting of carboxylic groups onto thermoplastic polyurethanes to reduce cell adhesion

Energy Technology Data Exchange (ETDEWEB)

Alves, P., E-mail: palves@eq.uc.pt [CIEPQPF, Departamento de Engenharia Química, Universidade de Coimbra, Polo II, Pinhal de Marrocos, 3030-790 Coimbra (Portugal); Ferreira, P. [CIEPQPF, Departamento de Engenharia Química, Universidade de Coimbra, Polo II, Pinhal de Marrocos, 3030-790 Coimbra (Portugal); Kaiser, Jean-Pierre [EMPA, St. Gallen, Lerchenfeldstrasse 5, CH-9014 St. Gallen (Switzerland); Salk, Natalie [Mikrofertigung – Micro Engineering, Fraunhofer IFAM, Wiener Strasse 12, D-288359 Bremen (Germany); Bruinink, Arie [EMPA, St. Gallen, Lerchenfeldstrasse 5, CH-9014 St. Gallen (Switzerland); Sousa, Hermínio C. de; Gil, M.H. [CIEPQPF, Departamento de Engenharia Química, Universidade de Coimbra, Polo II, Pinhal de Marrocos, 3030-790 Coimbra (Portugal)

2013-10-15

The interaction of polymers with other materials is an important issue, being their surface properties clearly crucial. For some important polymer applications, their surfaces have to be modified. Surface modification aims to tailor the surface characteristics of a material for a specific application without affecting its bulk properties. Materials can be surface modified by using biological, chemical or physical methods. The aim of this work was to improve the reactivity of the thermoplastic polyurethane (TPU) material (Elastollan{sup ®}) surface and to make its surface cell repellent by grafting carboxylic groups onto its surface. Two TPU materials were studied: a polyether-based TPU and a polyester-based TPU. The grafting efficiency was evaluated by contact angle measurements and by analytical determination of the COOH groups. Scanning electron microscopy (SEM) of the membranes surface was performed as well as cell adhesion tests. It was proved that the surfaces of the TPUs membranes were successfully modified and that cell adhesion was remarkably reduced.

Organization of cellular receptors into a nanoscale junction during HIV-1 adhesion.

Directory of Open Access Journals (Sweden)

Terrence M Dobrowsky

2010-07-01

Full Text Available The fusion of the human immunodeficiency virus type 1 (HIV-1 with its host cell is the target for new antiretroviral therapies. Viral particles interact with the flexible plasma membrane via viral surface protein gp120 which binds its primary cellular receptor CD4 and subsequently the coreceptor CCR5. However, whether and how these receptors become organized at the adhesive junction between cell and virion are unknown. Here, stochastic modeling predicts that, regarding binding to gp120, cellular receptors CD4 and CCR5 form an organized, ring-like, nanoscale structure beneath the virion, which locally deforms the plasma membrane. This organized adhesive junction between cell and virion, which we name the viral junction, is reminiscent of the well-characterized immunological synapse, albeit at much smaller length scales. The formation of an organized viral junction under multiple physiopathologically relevant conditions may represent a novel intermediate step in productive infection.

Reproducible Biofilm Cultivation of Chemostat-Grown Escherichia coli and Investigation of Bacterial Adhesion on Biomaterials Using a Non-Constant-Depth Film Fermenter

Science.gov (United States)

Lüdecke, Claudia; Jandt, Klaus D.; Siegismund, Daniel; Kujau, Marian J.; Zang, Emerson; Rettenmayr, Markus; Bossert, Jörg; Roth, Martin

2014-01-01

Biomaterials-associated infections are primarily initiated by the adhesion of microorganisms on the biomaterial surfaces and subsequent biofilm formation. Understanding the fundamental microbial adhesion mechanisms and biofilm development is crucial for developing strategies to prevent such infections. Suitable in vitro systems for biofilm cultivation and bacterial adhesion at controllable, constant and reproducible conditions are indispensable. This study aimed (i) to modify the previously described constant-depth film fermenter for the reproducible cultivation of biofilms at non-depth-restricted, constant and low shear conditions and (ii) to use this system to elucidate bacterial adhesion kinetics on different biomaterials, focusing on biomaterials surface nanoroughness and hydrophobicity. Chemostat-grown Escherichia coli were used for biofilm cultivation on titanium oxide and investigating bacterial adhesion over time on titanium oxide, poly(styrene), poly(tetrafluoroethylene) and glass. Using chemostat-grown microbial cells (single-species continuous culture) minimized variations between the biofilms cultivated during different experimental runs. Bacterial adhesion on biomaterials comprised an initial lag-phase I followed by a fast adhesion phase II and a phase of saturation III. With increasing biomaterials surface nanoroughness and increasing hydrophobicity, adhesion rates increased during phases I and II. The influence of materials surface hydrophobicity seemed to exceed that of nanoroughness during the lag-phase I, whereas it was vice versa during adhesion phase II. This study introduces the non-constant-depth film fermenter in combination with a chemostat culture to allow for a controlled approach to reproducibly cultivate biofilms and to investigate bacterial adhesion kinetics at constant and low shear conditions. The findings will support developing and adequate testing of biomaterials surface modifications eventually preventing biomaterial

Fetuin-A associates with histones intracellularly and shuttles them to exosomes to promote focal adhesion assembly resulting in rapid adhesion and spreading in breast carcinoma cells.

Science.gov (United States)

Nangami, Gladys; Koumangoye, Rainelli; Shawn Goodwin, J; Sakwe, Amos M; Marshall, Dana; Higginbotham, James; Ochieng, Josiah

2014-11-01

The present analyses were undertaken to define the mechanisms by which fetuin-A modulates cellular adhesion. FLAG-tagged fetuin-A was expressed in breast carcinoma and HEK-293T cells. We demonstrated by confocal microscopy that fetuin-A co-localizes with histone H2A in the cell nucleus, forms stable complexes with histones such as H2A and H3 in solution, and shuttles histones to exosomes. The rate of cellular adhesion and spreading to either fibronectin or laminin coated wells was accelerated significantly in the presence of either endogenous fetuin-A or serum derived protein. More importantly, the formation of focal adhesion complexes on surfaces coated by laminin or fibronectin was accelerated in the presence of fetuin-A or histone coated exosomes. Cellular adhesion mediated by histone coated exosomes was abrogated by heparin and heparinase III. Heparinase III cleaves heparan sulfate from cell surface heparan sulfate proteoglycans. Lastly, the uptake of histone coated exosomes and subsequent cellular adhesion, was abrogated by heparin. Taken together, the data suggest a mechanism where fetuin-A, either endogenously synthesized or supplied extracellularly can extract histones from the nucleus or elsewhere in the cytosol/membrane and load them on cellular exosomes which then mediate adhesion by interacting with cell surface heparan sulfate proteoglycans via bound histones. Copyright © 2014 Elsevier Inc. All rights reserved.

Study on optimal conditions and adsorption kinetics of copper from water by collodion membrane cross-linked poly-γ-glutamic acid

Energy Technology Data Exchange (ETDEWEB)

Wu, Xiangting; Wang, Aiyin; Li, Guoxing; Dong, Xinjiao; Wu, Mingjiang [Wenzhou University, Wenzhou (China); Zheng, Xiaojie [Wenzhou Vocational College of Technology and Science, Wenzhou (China)

2013-06-15

Poly-γ-glutamic acid (γ-PGA) is a novel polyamino acid formed through microorganism fermentation and biosynthesis. In the present test, membrane (PGA-C) formation by γ-PGA and collodion was performed by using 0.1% glutaraldehyde as a cross-linking agent. A study was conducted on the PGA-C adsorption of Cu{sup 2+}, specifically the related adsorption equilibrium and kinetics, desorption and regeneration. The results show that with an initial solution pH=5.5 and at 318 K, the static adsorption isotherm behavior of PGA-C is in compliance with the Langmuir model and is beneficial to the adsorption of the metal. Meanwhile, with the reaction lasting for 30min, adsorption equilibrium was reached with a maximum adsorption capacity up to 7.431 mg/g. The entire reaction process follows the pseudo-second-order kinetics. By using PGA-C, good regeneration results were obtained after adsorption-generation-adsorption cycling with an HCl solution (0.1 mol/L) as regeneration liquid.

Myosin 1g Contributes to CD44 Adhesion Protein and Lipid Rafts Recycling and Controls CD44 Capping and Cell Migration in B Lymphocytes

Directory of Open Access Journals (Sweden)

Orestes López-Ortega

2017-12-01

Full Text Available Cell migration and adhesion are critical for immune system function and involve many proteins, which must be continuously transported and recycled in the cell. Recycling of adhesion molecules requires the participation of several proteins, including actin, tubulin, and GTPases, and of membrane components such as sphingolipids and cholesterol. However, roles of actin motor proteins in adhesion molecule recycling are poorly understood. In this study, we identified myosin 1g as one of the important motor proteins that drives recycling of the adhesion protein CD44 in B lymphocytes. We demonstrate that the lack of Myo1g decreases the cell-surface levels of CD44 and of the lipid raft surrogate GM1. In cells depleted of Myo1g, the recycling of CD44 was delayed, the delay seems to be caused at the level of formation of recycling complex and entry into recycling endosomes. Moreover, a defective lipid raft recycling in Myo1g-deficient cells had an impact both on the capping of CD44 and on cell migration. Both processes required the transportation of lipid rafts to the cell surface to deliver signaling components. Furthermore, the extramembrane was essential for cell expansion and remodeling of the plasma membrane topology. Therefore, Myo1g is important during the recycling of lipid rafts to the membrane and to the accompanied proteins that regulate plasma membrane plasticity. Thus, Myosin 1g contributes to cell adhesion and cell migration through CD44 recycling in B lymphocytes.

High performance ZIF-8/6FDA-DAM mixed matrix membrane for propylene/propane separations

KAUST Repository

Zhang, Chen; Dai, Ying; Johnson, Justin R.; Karvan, Oguz; Koros, William J.

2012-01-01

We report significantly enhanced propylene/propane (C 3H 6/C 3H 8) selectivity in mixed matrix membranes fabricated using 6FDA-DAM polyimide and a zeolitic imidazolate framework (ZIF-8). Equilibrium isotherms and sorption kinetics of C 3H 6 and C 3H 8 at 35°C were studied on a 200nm commercially available ZIF-8 sample produced by BASF. Mixed matrix dense films were formed with 6FDA-DAM and 200nm BASF ZIF-8 particles. SEM imaging showed generally good adhesion between the ZIF-8 and 6FDA-DAM without the need for surface-treating ZIF-8. Pure gas permeation showed significantly enhanced mixed matrix ZIF-8/6FDA-DAM membrane C 3H 6/C 3H 8 separation performance over the pure 6FDA-DAM membrane performance. A C 3H 6 permeability of 56.2Barrer and C 3H 6/C 3H 8 ideal selectivity of 31.0 was found in ZIF-8/6FDA-DAM mixed matrix membrane with 48.0wt% ZIF-8 loading, which are 258% and 150% higher than the pure 6FDA-DAM membrane, respectively for permeability and selectivity. Permeation properties of C 3H 6 and C 3H 8 in ZIF-8 were back-calculated by the Maxwell model for composite permeability using pure gas permeation data, leading to a C 3H 6 permeability of 277Barrer and C 3H 6/C 3H 8 selectivity of 122. Mixed gas permeation also verified that selectivity enhancements were achievable in mixed gas environment by ZIF-8. © 2011 Elsevier B.V.

High performance ZIF-8/6FDA-DAM mixed matrix membrane for propylene/propane separations

KAUST Repository

Zhang, Chen

2012-02-01

We report significantly enhanced propylene/propane (C 3H 6/C 3H 8) selectivity in mixed matrix membranes fabricated using 6FDA-DAM polyimide and a zeolitic imidazolate framework (ZIF-8). Equilibrium isotherms and sorption kinetics of C 3H 6 and C 3H 8 at 35°C were studied on a 200nm commercially available ZIF-8 sample produced by BASF. Mixed matrix dense films were formed with 6FDA-DAM and 200nm BASF ZIF-8 particles. SEM imaging showed generally good adhesion between the ZIF-8 and 6FDA-DAM without the need for surface-treating ZIF-8. Pure gas permeation showed significantly enhanced mixed matrix ZIF-8/6FDA-DAM membrane C 3H 6/C 3H 8 separation performance over the pure 6FDA-DAM membrane performance. A C 3H 6 permeability of 56.2Barrer and C 3H 6/C 3H 8 ideal selectivity of 31.0 was found in ZIF-8/6FDA-DAM mixed matrix membrane with 48.0wt% ZIF-8 loading, which are 258% and 150% higher than the pure 6FDA-DAM membrane, respectively for permeability and selectivity. Permeation properties of C 3H 6 and C 3H 8 in ZIF-8 were back-calculated by the Maxwell model for composite permeability using pure gas permeation data, leading to a C 3H 6 permeability of 277Barrer and C 3H 6/C 3H 8 selectivity of 122. Mixed gas permeation also verified that selectivity enhancements were achievable in mixed gas environment by ZIF-8. © 2011 Elsevier B.V.

Kinetics of Single-Enzyme Reactions on Vesicles: Role of Substrate Aggregation

Science.gov (United States)

Zhdanov, Vladimir P.

2015-03-01

Enzymatic reactions occurring in vivo on lipid membranes can be influenced by various factors including macromolecular crowding in general and substrate aggregation in particular. In academic studies, the role of these factors can experimentally be clarified by tracking single-enzyme kinetics occurring on individual lipid vesicles. To extend the conceptual basis for such experiments, we analyze herein the corresponding kinetics mathematically with emphasis on the role of substrate aggregation. In general, the aggregation may occur on different length scales. Small aggregates may e.g. contain a few proteins or peptides while large aggregates may be mesoscopic as in the case of lipid domains which can be formed in the membranes composed of different lipids. We present a kinetic model describing comprehensively the effect of aggregation of the former type on the dependence of the reaction rate on substrate membrane concentration. The results obtained with physically reasonable parameters indicate that the aggregation-related deviations from the conventional Michaelis-Menten kinetics may be appreciable. Special Issue Comments: This theoretical article is focused on single-enzyme reactions occurring in parallel with substrate aggregation on individual vesicles. This subject is related to a few Special Issue articles concerning enzyme dynamics6,7 and function8 and mathematical aspects of stochastic kinetics.9

Cellular Adhesion and Adhesion Molecules

OpenAIRE

SELLER, Zerrin

2014-01-01

In recent years, cell adhesion and cell adhesion molecules have been shown to be important for many normal biological processes, including embryonic cell migration, immune system functions and wound healing. It has also been shown that they contribute to the pathogenesis of a large number of common human disorders, such as rheumatoid arthritis and tumor cell metastasis in cancer. In this review, the basic mechanisms of cellular adhesion and the structural and functional features of adhes...

Antifouling coatings via plasma polymerization and atom transfer radical polymerization on thin film composite membranes for reverse osmosis

Science.gov (United States)

Hirsch, Ulrike; Ruehl, Marco; Teuscher, Nico; Heilmann, Andreas

2018-04-01

A major drawback to otherwise highly efficient membrane-based desalination techniques like reverse osmosis (RO) is the susceptibility of the membranes to biofouling. In this work, a combination of plasma activation, plasma bromination and surface-initiated atom transfer radical polymerization (si-ATRP) of hydrophilic and zwitterionic monomers, namely hydroxyethyl methacrylate (HEMA), 2-methacryloyloxyethyl phosphorylcholine (MPC) and [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was applied to generate non-specific, anti-adhesive coatings on thin film composite (TFC) membranes. The antifouling effect of the coatings was shown by short-time batch as well as long-time steady state cultivation experiments with the microorganism Pseudomonas fluorescens. It could be shown that plasma functionalization and polymerization is possible on delicate thin film composite membranes without restricting their filtration performance. All modified membranes showed an increased resistance towards the adhesion of Pseudomonas fluorescens. On average, the biofilm coverage was reduced by 51.4-12.6% (for HEMA, SBMA, and MPC), the highest reduction was monitored for MPC with a biofilm reduction by 85.4%. The hydrophilic coatings applied did not only suppress the adhesion of Pseudomonas fluorescens, but also significantly increase the permeate flux of the membranes relative to uncoated membranes. The stability of the coatings was however not ideal and will have to be improved for future commercial use.

Proteomic analysis of glycosylphosphatidylinositol-anchored membrane proteins

DEFF Research Database (Denmark)

Elortza, Felix; Nühse, Thomas S; Foster, Leonard J

2003-01-01

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are a functionally and structurally diverse family of post-translationally modified membrane proteins found mostly in the outer leaflet of the plasma membrane in a variety of eukaryotic cells. Although the general role of GPI-APs remains...... unclear, they have attracted attention because they act as enzymes and receptors in cell adhesion, differentiation, and host-pathogen interactions. GPI-APs may represent potential diagnostic and therapeutic targets in humans and are interesting in plant biotechnology because of their key role in root...... and 44 GPI-APs in an Arabidopsis thaliana membrane preparation, representing the largest experimental dataset of GPI-anchored proteins to date....

Engineering emergent multicellular behavior through synthetic adhesion

Science.gov (United States)

Glass, David; Riedel-Kruse, Ingmar

In over a decade, synthetic biology has developed increasingly robust gene networks within single cells, but constructed very few systems that demonstrate multicellular spatio-temporal dynamics. We are filling this gap in synthetic biology's toolbox by developing an E. coli self-assembly platform based on modular cell-cell adhesion. We developed a system in which adhesive selectivity is provided by a library of outer membrane-displayed peptides with intra-library specificities, while affinity is provided by consistent expression across the entire library. We further provide a biophysical model to help understand the parameter regimes in which this tool can be used to self-assemble into cellular clusters, filaments, or meshes. The combined platform will enable future development of synthetic multicellular systems for use in consortia-based metabolic engineering, in living materials, and in controlled study of minimal multicellular systems. Stanford Bio-X Bowes Fellowship.

Binding constants of membrane-anchored receptors and ligands: A general theory corroborated by Monte Carlo simulations.

Science.gov (United States)

Xu, Guang-Kui; Hu, Jinglei; Lipowsky, Reinhard; Weikl, Thomas R

2015-12-28

Adhesion processes of biological membranes that enclose cells and cellular organelles are essential for immune responses, tissue formation, and signaling. These processes depend sensitively on the binding constant K2D of the membrane-anchored receptor and ligand proteins that mediate adhesion, which is difficult to measure in the "two-dimensional" (2D) membrane environment of the proteins. An important problem therefore is to relate K2D to the binding constant K3D of soluble variants of the receptors and ligands that lack the membrane anchors and are free to diffuse in three dimensions (3D). In this article, we present a general theory for the binding constants K2D and K3D of rather stiff proteins whose main degrees of freedom are translation and rotation, along membranes and around anchor points "in 2D," or unconstrained "in 3D." The theory generalizes previous results by describing how K2D depends both on the average separation and thermal nanoscale roughness of the apposing membranes, and on the length and anchoring flexibility of the receptors and ligands. Our theoretical results for the ratio K2D/K3D of the binding constants agree with detailed results from Monte Carlo simulations without any data fitting, which indicates that the theory captures the essential features of the "dimensionality reduction" due to membrane anchoring. In our Monte Carlo simulations, we consider a novel coarse-grained model of biomembrane adhesion in which the membranes are represented as discretized elastic surfaces, and the receptors and ligands as anchored molecules that diffuse continuously along the membranes and rotate at their anchor points.

Single-particle tracking: applications to membrane dynamics.

Science.gov (United States)

Saxton, M J; Jacobson, K

1997-01-01

Measurements of trajectories of individual proteins or lipids in the plasma membrane of cells show a variety of types of motion. Brownian motion is observed, but many of the particles undergo non-Brownian motion, including directed motion, confined motion, and anomalous diffusion. The variety of motion leads to significant effects on the kinetics of reactions among membrane-bound species and requires a revision of existing views of membrane structure and dynamics.

Surface modification of polypropylene membrane by polyethylene glycol graft polymerization

Energy Technology Data Exchange (ETDEWEB)

Abednejad, Atiye Sadat, E-mail: atiyeabednejad@gmail.com [Department of Biomedical Engineering, Faculty of New Sciences and Technologies, University of Tehran, P.O. Box 14395-1561, Tehran (Iran, Islamic Republic of); Amoabediny, Ghasem [Department of Life Science Engineering, Faculty of New Sciences and Technologies, University of Tehran, P.O. Box 14395-1561, Tehran (Iran, Islamic Republic of); Research Center for New Technologies in Life Science Engineering, University of Tehran, P.O. Box 63894-14179, Tehran (Iran, Islamic Republic of); Ghaee, Azadeh [Department of Biomedical Engineering, Faculty of New Sciences and Technologies, University of Tehran, P.O. Box 14395-1561, Tehran (Iran, Islamic Republic of)

2014-09-01

Polypropylene hollow fiber microporous membranes have been used in a wide range of applications, including blood oxygenator. The hydrophobic feature of the polypropylene surface causes membrane fouling. To minimize fouling, a modification consisting of three steps: surface activation in H{sub 2} and O{sub 2} plasma, membrane immersion in polyethylene glycol (PEG) and plasma graft polymerization was performed. The membranes were characterized by contact angle measurement, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), tensile test, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Oxygen transfer of modified membranes was also tested. The stability of grafted PEG was measured in water and in phosphate buffer saline (PBS) at 37 °C. Blood compatibility of modified surfaces was evaluated by the platelet adhesion method. Water contact angel reduction from 110° to 72° demonstrates the enhanced hydrophilicity, and XPS results verify the presence of oxygenated functional groups due to the peak existence in 286 eV as a result of PEG grafting. The results clearly indicate that plasma graft-polymerization of PEG is an effective way for antifouling improvement of polypropylene membranes. Also, the results show that oxygen transfer changes in PEG grafted membranes are not significant. - Highlights: • H{sub 2} and O{sub 2} plasma graft polymerization of PEG on polypropylene membrane was carried out. • Changes in surface properties were investigated by FTIR, XPS, SEM, and AFM. • Surface wettability enhanced as a result of poly ethylene glycol grafting. • PEG grafting degree increase causes reduction of fouling and adhesion.

Biomimetic honeycomb-patterned surface as the tunable cell adhesion scaffold.

Science.gov (United States)

Chen, Shuangshuang; Lu, Xuemin; Hu, Ying; Lu, Qinghua

2015-01-01

Inspired by the typically adhesive behaviors of fish skin and Parthenocissus tricuspidata, two different decorations of polystyrene honeycomb membrane (PSHCM) prepared by the breath figure approach were carried out with poly(N-(3-Sulfopropyl)-N-(methacryloxyethyl)-N,N-dimethylammonium betaine)(polySBMA) to explore controllable bioadhesive surfaces. Casting and dip-coating were employed to graft polySBMA onto the plasma treated PSHCM. The polySBMA casted PSHCM showed a uniform covering layer on the PSHCM similar to the mucus layer of fish skin, presenting excellent antifouling properties. On the contrary, a dip-coated one showed the polySBMA aggregating on the honeycomb pore walls forming a large number of sucking disks such as the adhesive disks of the tendrils of P. tricuspidata, which remarkably boosts cell adhesion on substrates. Thus, bioadhesion could be regulated as desired by tuning the distribution of zwitterionic polymer on the honeycomb surface. The results may provide a new approach for the design of biomaterial surfaces.

The emerin-binding transcription factor Lmo7 is regulated by association with p130Cas at focal adhesions

Directory of Open Access Journals (Sweden)

Michele A. Wozniak

2013-08-01

Full Text Available Loss of function mutations in the nuclear inner membrane protein, emerin, cause X-linked Emery-Dreifuss muscular dystrophy (X-EDMD. X-EDMD is characterized by contractures of major tendons, skeletal muscle weakening and wasting, and cardiac conduction system defects. The transcription factor Lmo7 regulates muscle- and heart-relevant genes and is inhibited by binding to emerin, suggesting Lmo7 misregulation contributes to EDMD disease. Lmo7 associates with cell adhesions and shuttles between the plasma membrane and nucleus, but the regulation and biological consequences of this dual localization were unknown. We report endogenous Lmo7 also associates with focal adhesions in cells, and both co-localizes and co-immunoprecipitates with p130Cas, a key signaling component of focal adhesions. Lmo7 nuclear localization and transcriptional activity increased significantly in p130Cas-null MEFs, suggesting Lmo7 is negatively regulated by p130Cas-dependent association with focal adhesions. These results support EDMD models in which Lmo7 is a downstream mediator of integrin-dependent signaling that allows tendon cells and muscles to adapt to and withstand mechanical stress.

Printing-assisted surface modifications of patterned ultrafiltration membranes

International Nuclear Information System (INIS)

Wardrip, Nathaniel C.; Dsouza, Melissa; Urgun-Demirtas, Meltem; Snyder, Seth W.

2016-01-01

Understanding and restricting microbial surface attachment will enhance wastewater treatment with membranes. We report a maskless lithographic patterning technique for the generation of patterned polymer coatings on ultrafiltration membranes. Polyethylene glycol, zwitterionic, or negatively charged hydrophilic polymer compositions in parallel- or perpendicular-striped patterns with respect to feed flow were evaluated using wastewater. Membrane fouling was dependent on the orientation and chemical composition of the coatings. Modifications reduced alpha diversity in the attached microbial community (Shannon indices decreased from 2.63 to 1.89) which nevertheless increased with filtration time. Sphingomonas species, which condition membrane surfaces and facilitate cellular adhesion, were depleted in all modified membranes. Microbial community structure was significantly different between control, different patterns, and different chemistries. Lastly, this study broadens the tools for surface modification of membranes with polymer coatings and for understanding and optimization of antifouling surfaces.

Membrane transport of anandamide through resealed human red blood cell membranes

DEFF Research Database (Denmark)

Bojesen, I.N.; Hansen, Harald S.

2005-01-01

The use of resealed red blood cell membranes (ghosts) allows the study of the transport of a compound in a nonmetabolizing system with a biological membrane. Transmembrane movements of anandamide (N-arachidonoylethanolamine, arachidonoylethanolamide) have been studied by exchange efflux experiments...... at 0°C and pH 7.3 with albumin-free and albumin-filled human red blood cell ghosts. The efflux kinetics is biexponential and is analyzed in terms of compartment models. The distribution of anandamide on the membrane inner to outer leaflet pools is determined to be 0.275 ± 0.023, and the rate constant...... of unidirectional flux from inside to outside is 0.361 ± 0.023 s. The rate constant of unidirectional flux from the membrane to BSA in the medium ([BSA]) increases with the square root of [BSA] in accordance with the theory of an unstirred layer around ghosts. Anandamide passed through the red blood cell membrane...

Protein nanocoatings on synthetic polymeric nanofibrous membranes designed as carriers for skin cells.

Science.gov (United States)

Bacakova, Marketa; Pajorova, Julia; Stranska, Denisa; Hadraba, Daniel; Lopot, Frantisek; Riedel, Tomas; Brynda, Eduard; Zaloudkova, Margit; Bacakova, Lucie

2017-01-01

Protein-coated resorbable synthetic polymeric nanofibrous membranes are promising for the fabrication of advanced skin substitutes. We fabricated electrospun polylactic acid and poly(lactide- co -glycolic acid) nanofibrous membranes and coated them with fibrin or collagen I. Fibronectin was attached to a fibrin or collagen nanocoating, in order further to enhance the cell adhesion and spreading. Fibrin regularly formed a coating around individual nanofibers in the membranes, and also formed a thin noncontinuous nanofibrous mesh on top of the membranes. Collagen also coated most of the fibers of the membrane and randomly created a soft gel on the membrane surface. Fibronectin predominantly adsorbed onto a thin fibrin mesh or a collagen gel, and formed a thin nanofibrous structure. Fibrin nanocoating greatly improved the attachment, spreading, and proliferation of human dermal fibroblasts, whereas collagen nanocoating had a positive influence on the behavior of human HaCaT keratinocytes. In addition, fibrin stimulated the fibroblasts to synthesize fibronectin and to deposit it as an extracellular matrix. Fibrin coating also showed a tendency to improve the ultimate tensile strength of the nanofibrous membranes. Fibronectin attached to fibrin or to a collagen coating further enhanced the adhesion, spreading, and proliferation of both cell types.

Adhesion

Science.gov (United States)

... Supplements Videos & Tools Español You Are Here: Home → Medical Encyclopedia → Adhesion URL of this page: //medlineplus.gov/ency/article/001493.htm Adhesion To use the sharing features on this page, please enable JavaScript. Adhesions are bands of scar-like tissue that form between two ...

Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives.

Science.gov (United States)

Purtov, Julia; Frensemeier, Mareike; Kroner, Elmar

2015-11-04

Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structures. In this study, we demonstrate that these adhesives are capable of switching adhesion not only in ambient air conditions but also in vacuum. Our bioinspired patterned adhesive with an area of 1 cm(2) provided an adhesion force of 2.6 N ± 0.2 N in air, which was reduced to 1.9 N ± 0.2 N if measured in vacuum. Detachment was induced by buckling of the structures due to a high compressive preload and occurred, independent of air pressure, at approximately 0.9 N ± 0.1 N. The switch in adhesion was observed at a compressive preload between 5.6 and 6.0 N and was independent of air pressure. The difference between maximum adhesion force and adhesion force after buckling gives a reasonable window of operation for pick and place processes. High reversibility of the switching behavior is shown over 50 cycles in air and in vacuum, making the bioinspired switchable adhesive applicable for handling operations of fragile objects.

Mechanics of the Adhesive Properties of Ivy Nanoparticles

Science.gov (United States)

2013-11-21

centrifuged at 1000g to remove any remaining debris. Finally, the sample was dialyzed through a 300 kDa Spectra/Por cellulose ester dialysis membrane...macromolecule with multiple physiological functions in the growth of plants, such as signaling, cell wall plasticizer , guiding pollen tube growth, and many...927 KPa (2.5 fold higher than the pure CS) after 3d reaction. Compared to 0.1and 1 Au CSNC, the 0.5 Au CSNC showed a significantly higher adhesion

A biodegradable vascularizing membrane: a feasibility study.

Science.gov (United States)

Kaushiva, Anchal; Turzhitsky, Vladimir M; Darmoc, Marissa; Backman, Vadim; Ameer, Guillermo A

2007-09-01

Regenerative medicine and in vivo biosensor applications require the formation of mature vascular networks for long-term success. This study investigated whether biodegradable porous membranes could induce the formation of a vascularized fibrous capsule and, if so, the effect of degradation kinetics on neovascularization. Poly(l-lactic acid) (PLLA) and poly(dl-lactic-co-glycolic) acid (PLGA) membranes were created by a solvent casting/salt leaching method. Specifically, PLLA, PLGA 75:25 and PLGA 50:50 polymers were used to vary degradation kinetics. The membranes were designed to have an average 60mum pore diameter, as this pore size has been shown to be optimal for inducing blood vessel formation around nondegradable polymer materials. Membrane samples were imaged by scanning electron microscopy at several time points during in vitro degradation to assess any changes in pore structure. The in vivo performance of the membranes was assessed in Sprague-Dawley rats by measuring vascularization within the fibrous capsule that forms adjacent to implants. The vascular density within 100microm of the membranes was compared with that seen in normal tissue, and to that surrounding the commercially available vascularizing membrane TheraCyte. The hemoglobin content of tissue containing the membranes was measured by four-dimensional elastic light scattering as a novel method to assess tissue perfusion. Results from this study show that slow-degrading membranes induce greater amounts of neovascularization and a thinner fibrous capsule relative to fast degrading membranes. These results may be due both to an initially increased number of macrophages surrounding the slower degrading membranes and to the maintenance of their initial pore structure.

Effect of surface tension on the behavior of adhesive contact based on Lennard-Jones potential law

Science.gov (United States)

Zhu, Xinyao; Xu, Wei

2018-02-01

The present study explores the effect of surface tension on adhesive contact behavior where the adhesion is interpreted by long-range intermolecular forces. The adhesive contact is analyzed using the equivalent system of a rigid sphere and an elastic half space covered by a membrane with surface tension. The long-range intermolecular forces are modeled with the Lennard‒Jones (L‒J) potential law. The current adhesive contact issue can be represented by a nonlinear integral equation, which can be solved by Newton‒Raphson method. In contrast to previous studies which consider intermolecular forces as short-range, the present study reveals more details of the features of adhesive contact with surface tension, in terms of jump instabilities, pull-off forces, pressure distribution within the contact area, etc. The transition of the pull-off force is not only consistent with previous studies, but also presents some new interesting characteristics in the current situation.

Control of biofouling on reverse osmosis polyamide membranes modified with biocidal nanoparticles and antifouling polymer brushes

KAUST Repository

Rahaman, Md. Saifur

2014-01-01

Thin-film composite (TFC) polyamide reverse osmosis (RO) membranes are prone to biofouling due to their inherent physicochemical surface properties. In order to address the biofouling problem, we have developed novel surface coatings functionalized with biocidal silver nanoparticles (AgNPs) and antifouling polymer brushes via polyelectrolyte layer-by-layer (LBL) self-assembly. The novel surface coating was prepared with polyelectrolyte LBL films containing poly(acrylic acid) (PAA) and poly(ethylene imine) (PEI), with the latter being either pure PEI or silver nanoparticles coated with PEI (Ag-PEI). The coatings were further functionalized by grafting of polymer brushes, using either hydrophilic poly(sulfobetaine) or low surface energy poly(dimethylsiloxane) (PDMS). The presence of both LBL films and sulfobetaine polymer brushes at the interface significantly increased the hydrophilicity of the membrane surface, while PDMS brushes lowered the membrane surface energy. Overall, all surface modifications resulted in significant reduction of irreversible bacterial cell adhesion. In microbial adhesion tests with E. coli bacteria, a normalized cell adhesion in the range of only 4 to 16% on the modified membrane surfaces was observed. Modified surfaces containing silver nanoparticles also exhibited strong antimicrobial activity. Membranes coated with LBL films of PAA/Ag-PEI achieved over 95% inactivation of bacteria attached to the surface within 1 hour of contact time. Both the antifouling and antimicrobial results suggest the potential of using these novel surface coatings in controlling the fouling of RO membranes. © The Royal Society of Chemistry 2014.

Antibacterial activity on electrospun poly(lactide-co-glycolide) based membranes via Magainin II grafting

Energy Technology Data Exchange (ETDEWEB)

Yüksel, Emre; Karakeçili, Ayşe, E-mail: akarakecili@eng.ankara.edu.tr

2014-12-01

An antimicrobial peptide (AMP), Magainin II (Mag II) was covalently immobilized on poly(lactide-co-glycolide) (PLGA) and PLGA/gelatin electrospun fibrous membranes. The surface immobilization was characterized by X-ray Photoelectron Spectroscopy (XPS). Scanning Electron Microscopy (SEM) and Atomic Force Microscopy studies showed that the surface morphology of the fibers at micron scale was not affected by the immobilization process. The antibacterial activity of the bound Mag II was tested against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Bacterial adhesion tests, SEM and confocal analyses revealed that the attachment and survival of bacteria were inhibited on Mag II functionalized membranes. AMP immobilization strategy was introduced as a new perspective for the modulation of antibacterial properties on PLGA based materials prepared by electrospinning. - Highlights: • PLGA and PLGA/gelatin fibrous membranes were prepared by electrospinning. • Antimicrobial peptide Mag II was successfully immobilized on PLGA based membranes. • The antibacterial activity was tested against E. coli and S. aureus. • Bacterial adhesion was inhibited on Mag II functionalized membranes.

Systems and methods for using a boehmite bond-coat with polyimide membranes for gas separation

Science.gov (United States)

Polishchuk, Kimberly Ann

2013-03-05

The subject matter disclosed herein relates to gas separation membranes and, more specifically, to polyimide gas separation membranes. In an embodiment, a gas separation membrane includes a porous substrate, a substantially continuous polyimide membrane layer, and one or more layers of boehmite nanoparticles disposed between the porous substrate and the polyimide membrane layer to form a bond-coat layer. The bond-coat layer is configured to improve the adhesion of the polyimide membrane layer to the porous substrate, and the polyimide membrane layer has a thickness approximately 100 nm or less.

Biocompatibility Assessment of PLCL-Sericin Copolymer Membranes Using Wharton’s Jelly Mesenchymal Stem Cells

Directory of Open Access Journals (Sweden)

Kewalin Inthanon

2016-01-01

Full Text Available Stem cells based tissue engineering requires biocompatible materials, which allow the cells to adhere, expand, and differentiate in a large scale. An ideal biomaterial for clinical application should be free from mammalian products which cause immune reactivities and pathogen infections. We invented a novel biodegradable poly(L-lactic-co-ε-caprolactone-sericin (PLCL-SC copolymer membrane which was fabricated by electrospinning. Membranes with concentrations of 2.5 or 5% (w/v SC exhibited qualified texture characteristics with a noncytotoxic release profile. The hydrophilic properties of the membranes were 35–40% higher than those of a standard PLCL and commercial polystyrene (PS. The improved characteristics of the membranes were due to an addition of new functional amide groups, C=O, N–H, and C–N, onto their surfaces. Degradation of the membranes was controllable, depending on the content proportion of SC. Results of thermogram indicated the superior stability and crystallinity of the membranes. These membranes enhanced human Wharton’s jelly mesenchymal stem cells (hWJMSC proliferation by increasing cyclin A and also promoted cell adhesion by upregulating focal adhesion kinase (FAK. On the membranes, hWJMSC differentiated into a neuronal lineage with the occurrence of nestin. These data suggest that PLCL-SC electrospun membrane represents some properties which will be useful for tissue engineering and medical applications.

The CD157-integrin partnership controls transendothelial migration and adhesion of human monocytes.

Science.gov (United States)

Lo Buono, Nicola; Parrotta, Rossella; Morone, Simona; Bovino, Paola; Nacci, Giulia; Ortolan, Erika; Horenstein, Alberto L; Inzhutova, Alona; Ferrero, Enza; Funaro, Ada

2011-05-27

CD157, a member of the CD38 gene family, is an NAD-metabolizing ectoenzyme and a signaling molecule whose role in polarization, migration, and diapedesis of human granulocytes has been documented; however, the molecular events underpinning this role remain to be elucidated. This study focused on the role exerted by CD157 in monocyte migration across the endothelial lining and adhesion to extracellular matrix proteins. The results demonstrated that anti-CD157 antibodies block monocyte transmigration and adhesion to fibronectin and fibrinogen but that CD157 cross-linking is sufficient to overcome the block, suggesting an active signaling role for the molecule. Consistent with this is the observation that CD157 is prevalently located within the detergent-resistant membrane microdomains to which, upon clustering, it promotes the recruitment of β(1) and β(2) integrin, which, in turn, leads to the formation of a multimolecular complex favoring signal transduction. This functional cross-talk with integrins allows CD157 to act as a receptor despite its intrinsic structural inability to do so on its own. Intracellular signals mediated by CD157 rely on the integrin/Src/FAK (focal adhesion kinase) pathway, resulting in increased activity of the MAPK/ERK1/2 and the PI3K/Akt downstream signaling pathways, which are crucial in the control of monocyte transendothelial migration. Collectively, these findings indicate that CD157 acts as a molecular organizer of signaling-competent membrane microdomains and that it forms part of a larger molecular machine ruled by integrins. The CD157-integrin partnership provides optimal adhesion and transmigration of human monocytes.

An Adaptable Spectrin/Ankyrin-Based Mechanism for Long-Range Organization of Plasma Membranes in Vertebrate Tissues.

Science.gov (United States)

Bennett, Vann; Lorenzo, Damaris N

2016-01-01

Ankyrins are membrane-associated proteins that together with their spectrin partners are responsible for micron-scale organization of vertebrate plasma membranes, including those of erythrocytes, excitable membranes of neurons and heart, lateral membrane domains of columnar epithelial cells, and striated muscle. Ankyrins coordinate functionally related membrane transporters and cell adhesion proteins (15 protein families identified so far) within plasma membrane compartments through independently evolved interactions of intrinsically disordered sequences with a highly conserved peptide-binding groove formed by the ANK repeat solenoid. Ankyrins are coupled to spectrins, which are elongated organelle-sized proteins that form mechanically resilient arrays through cross-linking by specialized actin filaments. In addition to protein interactions, cellular targeting and assembly of spectrin/ankyrin domains also critically depend on palmitoylation of ankyrin-G by aspartate-histidine-histidine-cysteine 5/8 palmitoyltransferases, as well as interaction of beta-2 spectrin with phosphoinositide lipids. These lipid-dependent spectrin/ankyrin domains are not static but are locally dynamic and determine membrane identity through opposing endocytosis of bulk lipids as well as specific proteins. A partnership between spectrin, ankyrin, and cell adhesion molecules first emerged in bilaterians over 500 million years ago. Ankyrin and spectrin may have been recruited to plasma membranes from more ancient roles in organelle transport. The basic bilaterian spectrin-ankyrin toolkit markedly expanded in vertebrates through gene duplications combined with variation in unstructured intramolecular regulatory sequences as well as independent evolution of ankyrin-binding activity by ion transporters involved in action potentials and calcium homeostasis. In addition, giant vertebrate ankyrins with specialized roles in axons acquired new coding sequences by exon shuffling. We speculate that

Measuring kinetic drivers of pneumolysin pore structure.

Science.gov (United States)

Gilbert, Robert J C; Sonnen, Andreas F-P

2016-05-01

Most membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) proteins are thought to form pores in target membranes by assembling into pre-pore oligomers before undergoing a pre-pore to pore transition. Assembly during pore formation is into both full rings of subunits and incomplete rings (arcs). The balance between arcs and full rings is determined by a mechanism dependent on protein concentration in which arc pores arise due to kinetic trapping of the pre-pore forms by the depletion of free protein subunits during oligomerization. Here we describe the use of a kinetic assay to study pore formation in red blood cells by the MACPF/CDC pneumolysin from Streptococcus pneumoniae. We show that cell lysis displays two kinds of dependence on protein concentration. At lower concentrations, it is dependent on the pre-pore to pore transition of arc oligomers, which we show to be a cooperative process. At higher concentrations, it is dependent on the amount of pneumolysin bound to the membrane and reflects the affinity of the protein for its receptor, cholesterol. A lag occurs before cell lysis begins; this is dependent on oligomerization of pneumolysin. Kinetic dissection of cell lysis by pneumolysin demonstrates the capacity of MACPF/CDCs to generate pore-forming oligomeric structures of variable size with, most likely, different functional roles in biology.

Dynamic nanoplatforms in biosensor and membrane constitutional systems.

Science.gov (United States)

Mahon, Eugene; Aastrup, Teodor; Barboiu, Mihail

2012-01-01

Molecular recognition in biological systems occurs mainly at interfacial environments such as membrane surfaces, enzyme active sites, or the interior of the DNA double helix. At the cell membrane surface, carbohydrate-protein recognition principles apply to a range of specific non-covalent interactions including immune response, cell proliferation, adhesion and death, cell-cell interaction and communication. Protein-protein recognition meanwhile accounts for signalling processes and ion channel structure. In this chapter we aim to describe such constitutional dynamic interfaces for biosensing and membrane transport applications. Constitutionally adaptive interfaces may mimic the recognition capabilities intrinsic to natural recognition processes. We present some recent examples of 2D and 3D constructed sensors and membranes of this type and describe their sensing and transport capabilities.

In vitro evaluation of tissue adhesives composed of hydrophobically modified gelatins and disuccinimidyl tartrate

Directory of Open Access Journals (Sweden)

Miyuki Matsuda

2012-01-01

Full Text Available The effect of the hydrophobic group content in gelatin on the bonding strength of novel tissue–penetrating tissue adhesives was evaluated. The hydrophobic groups introduced into gelatin were the saturated hexanoyl, palmitoyl, and stearoyl groups, and the unsaturated oleoyl group. A collagen casing was employed as an adherend to model soft tissue for the in vitro determination of bonding strength of tissue adhesives composed of various hydrophobically modified gelatins and disuccinimidyl tartrate. The adhesive composed of stearoyl-modified gelatin (7.4% stearoyl; 10Ste and disuccinimidyl tartrate showed the highest bonding strength. The bonding strength of the adhesives decreased as the degree of substitution of the hydrophobic groups increased. Cell culture experiments demonstrated that fluorescein isothiocyanate-labeled 10Ste was integrated onto the surface of smooth muscle cells and showed no cytotoxicity. These results suggest that 10Ste interacted with the hydrophobic domains of collagen casings, such as hydrophobic amino acid residues and cell membranes. Therefore, 10Ste–disuccinimidyl tartrate is a promising adhesive for use in aortic dissection.

Mechanisms of proton conductance in polymer electrolyte membranes

DEFF Research Database (Denmark)

Eikerling, M.; Kornyshev, A. A.; Kuznetsov, A. M.

2001-01-01

We provide a phenomenological description of proton conductance in polymer electrolyte membranes, based on contemporary views of proton transfer processes in condensed media and a model for heterogeneous polymer electrolyte membrane structure. The description combines the proton transfer events...... in a single pore with the total pore-network performance and, thereby, relates structural and kinetic characteristics of the membrane. The theory addresses specific experimentally studied issues such as the effect of the density of proton localization sites (equivalent weight) of the membrane material...

Ethanol steam reforming kinetics of a Pd-Ag membrane reactor

NARCIS (Netherlands)

Tosti, S.; Basile, A.; Borelli, R.; Borgognoni, F.; Castelli, S.; Fabbricino, M.; Gallucci, F.; Licusati, C.

2009-01-01

The ethanol steam reforming reaction carried out in a Pd-based tubular membrane reactor has been modelled via a finite element code. The model considers the membrane tube divided into finite volume elements where the mass balances for both lumen and shell sides are carried out accordingly to the

Quorum Sensing Regulation of Adhesion in Serratia Marcescens MG1 is surface dependent

DEFF Research Database (Denmark)

Labbate, M.; Zhu, H.; Thung, L.

2007-01-01

in a non-QS-controlled fashion. Therefore, the expression of these two genes appears to be cocontrolled by regulators other than the QS system for mediation of attachment to HCE cells. We also found that QS in S. marcescens regulates other potential cell surface adhesins, including exopolysaccharide...... and the outer membrane protein OmpX. We concluded that S. marcescens MG1 utilizes different regulatory systems and adhesins in attachment to biotic and abiotic surfaces and that QS is a main regulatory pathway in adhesion to an abiotic surface but not in adhesion to a biotic surface....

Phosphoric acid doped membranes based on Nafion®, PBI and their blends – Membrane preparation, characterization and steam electrolysis testing

DEFF Research Database (Denmark)

Aili, David; Hansen, Martin Kalmar; Pan, Chao

2011-01-01

Proton exchange membrane steam electrolysis at temperatures above 100 °C has several advantages from thermodynamic, kinetic and engineering points of view. A key material for this technology is the high temperature proton exchange membrane. In this work a novel procedure for preparation of Nafion......® and polybenzimidazole blend membranes was developed. Homogeneous binary membranes covering the whole composition range were prepared and characterized with respect to chemical and physiochemical properties such as water uptake, phosphoric acid doping, oxidative stability, mechanical strength and proton conductivity...

Pseudomonas aeruginosa outer membrane vesicles triggered by human mucosal fluid and lysozyme can prime host tissue surfaces for bacterial adhesion

Directory of Open Access Journals (Sweden)

Matteo Maria Emiliano Metruccio

2016-06-01

Full Text Available Pseudomonas aeruginosa is a leading cause of human morbidity and mortality that often targets epithelial surfaces. Host immunocompromise, or the presence of indwelling medical devices, including contact lenses, can predispose to infection. While medical devices are known to accumulate bacterial biofilms, it is not well understood why resistant epithelial surfaces become susceptible to P. aeruginosa. Many bacteria, including P. aeruginosa, release Outer Membrane Vesicles (OMVs in response to stress that can fuse with host cells to alter their function. Here, we tested the hypothesis that mucosal fluid can trigger OMV release to compromise an epithelial barrier. This was tested using tear fluid and corneal epithelial cells in vitro and in vivo. After 1 h both human tear fluid, and the tear component lysozyme, greatly enhanced OMV release from P. aeruginosa strain PAO1 compared to PBS controls (~100 fold. TEM and SDS-PAGE showed tear fluid and lysozyme-induced OMVs were similar in size and protein composition, but differed from biofilm-harvested OMVs, the latter smaller with fewer proteins. Lysozyme-induced OMVs were cytotoxic to human corneal epithelial cells in vitro and murine corneal epithelium in vivo. OMV exposure in vivo enhanced Ly6G/C expression at the corneal surface, suggesting myeloid cell recruitment, and primed the cornea for bacterial adhesion (~4-fold, P < 0.01. Sonication disrupted OMVs retained cytotoxic activity, but did not promote adhesion, suggesting the latter required OMV-mediated events beyond cell killing. These data suggest that mucosal fluid induced P. aeruginosa OMVs could contribute to loss of epithelial barrier function during medical device-related infections.

Micromechanical and surface adhesive properties of single saccharomyces cerevisiae cells

Science.gov (United States)

Farzi, Bahman; Cetinkaya, Cetin

2017-09-01

The adhesion and mechanical properties of a biological cell (e.g. cell membrane elasticity and adhesiveness) are often strong indicators for the state of its health. Many existing techniques for determining mechanical properties of cells require direct physical contact with a single cell or a group of cells. Physical contact with the cell can trigger complex mechanotransduction mechanisms, leading to cellular responses, and consequently interfering with measurement accuracy. In the current work, based on ultrasonic excitation and interferometric (optical) motion detection, a non-contact method for characterizing the adhesion and mechanical properties of single cells is presented. It is experimentally demonstrated that the rocking (rigid body) motion and internal vibrational resonance frequencies of a single saccharomyces cerevisiae (SC) (baker’s yeast) cell can be acquired with the current approach, and the Young’s modulus and surface tension of the cell membrane as well as surface adhesion energy can be extracted from the values of these acquired resonance frequencies. The detected resonance frequency ranges for single SC cells include a rocking (rigid body) frequency of 330  ±  70 kHz and two breathing resonance frequencies of 1.53  ±  0.12 and 2.02  ±  0.31 MHz. Based on these values, the average work-of-adhesion of SC cells on a silicon substrate in aqueous medium is extracted, for the first time, as WASC-Si=16.2+/- 3.8 mJ {{m}-2} . Similarly, the surface tension and the Young’s modulus of the SC cell wall are predicted as {{σ }SC}=0.16+/- 0.02 N {{m}-1} and {{E}SC}= 9.20  ±  2.80 MPa, respectively. These results are compared to those reported in the literature by utilizing various methods, and good agreements are found. The current approach eliminates the measurement inaccuracies associated with the physical contact. Exciting and detecting cell dynamics at micro-second time-scales is significantly faster than the

Fouling Kinetics and Associated Dynamics of Structural Modifications

DEFF Research Database (Denmark)

Jacob, Jerome; Prádanos, Pedro; Calvo, J. I.

1998-01-01

It is shown that the fouling behaviour of microfiltration membranes does not agree within all the time ranges of any of the commonly used membrane blocking models (i.e. complete, standard, intermediate or cake blocking). The resulting experimental kinetics of flux decline do not fit to only one...... of these models, but according to a successive or simultaneous coexistence of two or more of them. This is studied by analysing the structural modifications associated with the fouling kinetics. To achieve this goal, here we analyse the dynamical changes on the structure of four microporous membranes made...... by Sartorius (ST02 and ST045, neutral) and Spectrum (SP02 and SP045, positively charged) when fouled by permeating a protein aqueous solution (bovine serum albumin (BSA) at 1 g l(-1)) under 10 kPa in a dead-end device. The structure after different fouling times is obtained by using an extended bubble point...

Block copolymer/homopolymer dual-layer hollow fiber membranes

KAUST Repository

Hilke, Roland

2014-12-01

We manufactured the first time block copolymer dual-layer hollow fiber membranes and dual layer flat sheet membranes manufactured by double solution casting and phase inversion in water. The support porous layer was based on polystyrene and the selective layer with isopores was formed by micelle assembly of polystyrene-. b-poly-4-vinyl pyridine. The dual layers had an excellent interfacial adhesion and pore interconnectivity. The dual membranes showed pH response behavior like single layer block copolymer membranes with a low flux for pH values less than 3, a fast increase between pH4 and pH6 and a constant high flux level for pH values above 7. The dry/wet spinning process was optimized to produce dual layer hollow fiber membranes with polystyrene internal support layer and a shell block copolymer selective layer.

Adhesion in microelectronics

CERN Document Server

Mittal, K L

2014-01-01

This comprehensive book will provide both fundamental and applied aspects of adhesion pertaining to microelectronics in a single and easily accessible source. Among the topics to be covered include; Various theories or mechanisms of adhesionSurface (physical or chemical) characterization of materials as it pertains to adhesionSurface cleaning as it pertains to adhesionWays to improve adhesionUnraveling of interfacial interactions using an array of pertinent techniquesCharacterization of interfaces / interphasesPolymer-polymer adhesionMetal-polymer adhesion  (metallized polymers)Polymer adhesi

Adhesion science

CERN Document Server

Comyn, John

1997-01-01

The use of adhesives is widespread and growing, and there are few modern artefacts, from the simple cereal packet, to the jumbo jet, that are without this means of joining. Adhesion Science provides an illuminating account of the science underlying the use of adhesives, a branch of chemical technology which is fundamental to the science of coatings and composite materials and to the performance of all types of bonded structures. This book guides the reader through the essential basic polymer science, and the chemistry of adhesives in use at present. It discusses surface preparation for adhesive bonding, and the use of primers and coupling agents. There is a detailed chapter on contact angles and what can be predicted from them. A simple guide on stress distribution joints and how this relates to testing is included. It also examines the interaction of adhesives and the environment, including an analysis of the resistance of joints to water, oxygen and ultra-violet light. Adhesion Science provides a comprehens...

Uranium preconcentration from seawater using adsorptive membranes

International Nuclear Information System (INIS)

Das, Sadananda; Pandey, A.K.; Manchanda, V.K.; Athawale, A.A.

2009-01-01

Uranium recovery from bio-aggressive but lean feed like seawater is a challenging problem as it requires in situ preconcentration of uranium in presence of huge excess of competing ions with fast sorption kinetics. In our laboratory, widely used amidoxime membrane (AO-membrane) was evaluated for uranium sorption under seawater conditions. This study indicated that AO-membrane was inherently slow because of the complexation chemistry involved in transfer of U(VI) from (UO 2 (CO 3 ) 3 ) 4 - to AO sites in membrane. In order to search better options, several chemical compositions of membrane were scanned for their efficacy for uranium preconcentration from seawater, and concluded that EGMP-membrane offers several advantages over AO-membrane. In this paper, the comparison of EGMP-membrane with AO-membrane for uranium sorption under seawater conditions has been reviewed. (author)

Characterization and Antibiofouling Performance Investigation of Hydrophobic Silver Nanocomposite Membranes: A Comparative Study.

Science.gov (United States)

Amouamouha, Maryam; Badalians Gholikandi, Gagik

2017-11-12

Biofouling is one of the drawbacks restricting the industrial applications of membranes. In this study, different thicknesses of silver nanoparticles with proper adhesion were deposited on poly(vinylidenefluoride) (PVDF) and polyethersulfone (PES) surfaces by physical vapor deposition (PVD). The crystalline and structural properties of modified and pure membranes were investigated by carrying out X-ray diffraction (XRD) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Scanning electron microscope (SEM) and atomic force microscopy (AFM) analyses were employed to examine the surface morphology and the bacteria anti-adhesion property of the membranes. The morphology measurements confirmed that even though after silver grafting the surface became more hydrophobic, the homogeneity increased and the flux reduction decreased after coating. Moreover a comparison between PVDF and PES revealed that CFU (colony forming units) reduced 64.5% on PVDF surface and 31.1% on PES surface after modification. In conclusion, PVD improved the performance of the membrane antibiofouling, and it is more promising to be used for PVDF rather than PES.

Characterization and Antibiofouling Performance Investigation of Hydrophobic Silver Nanocomposite Membranes: A Comparative Study

Directory of Open Access Journals (Sweden)

Maryam Amouamouha

2017-11-01

Full Text Available Biofouling is one of the drawbacks restricting the industrial applications of membranes. In this study, different thicknesses of silver nanoparticles with proper adhesion were deposited on poly(vinylidenefluoride (PVDF and polyethersulfone (PES surfaces by physical vapor deposition (PVD. The crystalline and structural properties of modified and pure membranes were investigated by carrying out X-ray diffraction (XRD and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR. Scanning electron microscope (SEM and atomic force microscopy (AFM analyses were employed to examine the surface morphology and the bacteria anti-adhesion property of the membranes. The morphology measurements confirmed that even though after silver grafting the surface became more hydrophobic, the homogeneity increased and the flux reduction decreased after coating. Moreover a comparison between PVDF and PES revealed that CFU (colony forming units reduced 64.5% on PVDF surface and 31.1% on PES surface after modification. In conclusion, PVD improved the performance of the membrane antibiofouling, and it is more promising to be used for PVDF rather than PES.

Kinetic study of seawater reverse osmosis membrane fouling

KAUST Repository

Khan, Muhammad; De, Carmemlara; Aubry, Cyril; Gutié rrez, Leonardo A.; Croue, Jean-Philippe

2013-01-01

population in all the membrane samples was dominated by specific groups/species belonging to Proteobacteria and Actinobacteria phyla; however, similar to abiotic foulant, their relative abundance also changed with the biofilm age. © 2013 American Chemical

Denture Adhesives

Science.gov (United States)

... Devices Products and Medical Procedures Dental Devices Denture Adhesives Share Tweet Linkedin Pin it More sharing options ... Wearers Reporting Problems to the FDA Background Denture adhesives are pastes, powders or adhesive pads that may ...

Neural cell adhesion molecule (NCAM) marks adult myogenic cells committed to differentiation

International Nuclear Information System (INIS)

Capkovic, Katie L.; Stevenson, Severin; Johnson, Marc C.; Thelen, Jay J.; Cornelison, D.D.W.

2008-01-01

Although recent advances in broad-scale gene expression analysis have dramatically increased our knowledge of the repertoire of mRNAs present in multiple cell types, it has become increasingly clear that examination of the expression, localization, and associations of the encoded proteins will be critical for determining their functional significance. In particular, many signaling receptors, transducers, and effectors have been proposed to act in higher-order complexes associated with physically distinct areas of the plasma membrane. Adult muscle stem cells (satellite cells) must, upon injury, respond appropriately to a wide range of extracellular stimuli: the role of such signaling scaffolds is therefore a potentially important area of inquiry. To address this question, we first isolated detergent-resistant membrane fractions from primary satellite cells, then analyzed their component proteins using liquid chromatography-tandem mass spectrometry. Transmembrane and juxtamembrane components of adhesion-mediated signaling pathways made up the largest group of identified proteins; in particular, neural cell adhesion molecule (NCAM), a multifunctional cell-surface protein that has previously been associated with muscle regeneration, was significant. Immunohistochemical analysis revealed that not only is NCAM localized to discrete areas of the plasma membrane, it is also a very early marker of commitment to terminal differentiation. Using flow cytometry, we have sorted physically homogeneous myogenic cultures into proliferating and differentiating fractions based solely upon NCAM expression

Insect Analogue to the Lotus Leaf: A Planthopper Wing Membrane Incorporating a Low-Adhesion, Nonwetting, Superhydrophobic, Bactericidal, and Biocompatible Surface.

Science.gov (United States)

Watson, Gregory S; Green, David W; Cribb, Bronwen W; Brown, Christopher L; Meritt, Christopher R; Tobin, Mark J; Vongsvivut, Jitraporn; Sun, Mingxia; Liang, Ai-Ping; Watson, Jolanta A

2017-07-19

Nature has produced many intriguing and spectacular surfaces at the micro- and nanoscales. These small surface decorations act for a singular or, in most cases, a range of functions. The minute landscape found on the lotus leaf is one such example, displaying antiwetting behavior and low adhesion with foreign particulate matter. Indeed the lotus leaf has often been considered the "benchmark" for such properties. One could expect that there are animal counterparts of this self-drying and self-cleaning surface system. In this study, we show that the planthopper insect wing (Desudaba danae) exhibits a remarkable architectural similarity to the lotus leaf surface. Not only does the wing demonstrate a topographical likeness, but some surface properties are also expressed, such as nonwetting behavior and low adhering forces with contaminants. In addition, the insect-wing cuticle exhibits an antibacterial property in which Gram-negative bacteria (Porphyromonas gingivalis) are killed over many consecutive waves of attacks over 7 days. In contrast, eukaryote cell associations, upon contact with the insect membrane, lead to a formation of integrated cell sheets (e.g., among human stem cells (SHED-MSC) and human dermal fibroblasts (HDF)). The multifunctional features of the insect membrane provide a potential natural template for man-made applications in which specific control of liquid, solid, and biological contacts is desired and required. Moreover, the planthopper wing cuticle provides a "new" natural surface with which numerous interfacial properties can be explored for a range of comparative studies with both natural and man-made materials.

Functional dynamics of cell surface membrane proteins.

Science.gov (United States)

Nishida, Noritaka; Osawa, Masanori; Takeuchi, Koh; Imai, Shunsuke; Stampoulis, Pavlos; Kofuku, Yutaka; Ueda, Takumi; Shimada, Ichio

2014-04-01

Cell surface receptors are integral membrane proteins that receive external stimuli, and transmit signals across plasma membranes. In the conventional view of receptor activation, ligand binding to the extracellular side of the receptor induces conformational changes, which convert the structure of the receptor into an active conformation. However, recent NMR studies of cell surface membrane proteins have revealed that their structures are more dynamic than previously envisioned, and they fluctuate between multiple conformations in an equilibrium on various timescales. In addition, NMR analyses, along with biochemical and cell biological experiments indicated that such dynamical properties are critical for the proper functions of the receptors. In this review, we will describe several NMR studies that revealed direct linkage between the structural dynamics and the functions of the cell surface membrane proteins, such as G-protein coupled receptors (GPCRs), ion channels, membrane transporters, and cell adhesion molecules. Copyright © 2013 Elsevier Inc. All rights reserved.

A novel silanized CoFe{sub 2}O{sub 4}/fluorinated waterborne polyurethane pressure sensitive adhesive

Energy Technology Data Exchange (ETDEWEB)

Fu, Heqing, E-mail: fuhq@scut.edu.cn; Wang, Yin; Chen, Weifeng; Zhou, Wei; Xiao, Jing

2015-10-01

Highlights: • The hydrophobicity, thermal stability, dynamic mechanical properties, as well as adhesive properties of silanized. • CoFe{sub 2}O{sub 4}/fluorinated waterborne polyurethane (SC/FWPU) were improved with the incorporation of silanized CoFe{sub 2}O{sub 4} into FWPU. • The higher the spreading-penetration parameter is, the faster the contact angle reaches equilibrium, and the faster the SC/FWPU pressure sensitive adhesive penetrates and spreads. - Abstract: A novel silanized CoFe{sub 2}O{sub 4}/fluorinated waterborne polyurethane (SC/FWPU) pressure sensitive adhesive was synthesized and characterized by atomic force microscopy (AFM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and contact angle tester. The adhesive properties were measured in a test machine. Experimental results showed that the hydrophobicity, thermal stability, dynamic mechanical properties, as well as adhesive properties of SC/FWPU were improved with the incorporation of SC into FWPU. The dynamic hydrophobicity can be well described by the wetting kinetic model. The spreading-penetration parameter increased with an increase in SC content. The higher the spreading-penetration parameter is, the faster the contact angle reaches equilibrium, and the faster the SC/FWPU pressure sensitive adhesive penetrates and spreads.

Reversible adhesion switching of porous fibrillar adhesive pads by humidity.

Science.gov (United States)

Xue, Longjian; Kovalev, Alexander; Dening, Kirstin; Eichler-Volf, Anna; Eickmeier, Henning; Haase, Markus; Enke, Dirk; Steinhart, Martin; Gorb, Stanislav N

2013-01-01

We report reversible adhesion switching on porous fibrillar polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP) adhesive pads by humidity changes. Adhesion at a relative humidity of 90% was more than nine times higher than at a relative humidity of 2%. On nonporous fibrillar adhesive pads of the same material, adhesion increased only by a factor of ~3.3. The switching performance remained unchanged in at least 10 successive high/low humidity cycles. Main origin of enhanced adhesion at high humidity is the humidity-induced decrease in the elastic modulus of the polar component P2VP rather than capillary force. The presence of spongelike continuous internal pore systems with walls consisting of P2VP significantly leveraged this effect. Fibrillar adhesive pads on which adhesion is switchable by humidity changes may be used for preconcentration of airborne particulates, pollutants, and germs combined with triggered surface cleaning.

Superhydrophilic Thin-Film Composite Forward Osmosis Membranes for Organic Fouling Control: Fouling Behavior and Antifouling Mechanisms

KAUST Repository

Tiraferri, Alberto

2012-10-16

This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes. © 2012 American Chemical Society.

Superhydrophilic thin-film composite forward osmosis membranes for organic fouling control: fouling behavior and antifouling mechanisms.

Science.gov (United States)

Tiraferri, Alberto; Kang, Yan; Giannelis, Emmanuel P; Elimelech, Menachem

2012-10-16

This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes.

Improved Adhesion and Compliancy of Hierarchical Fibrillar Adhesives.

Science.gov (United States)

Li, Yasong; Gates, Byron D; Menon, Carlo

2015-08-05

The gecko relies on van der Waals forces to cling onto surfaces with a variety of topography and composition. The hierarchical fibrillar structures on their climbing feet, ranging from mesoscale to nanoscale, are hypothesized to be key elements for the animal to conquer both smooth and rough surfaces. An epoxy-based artificial hierarchical fibrillar adhesive was prepared to study the influence of the hierarchical structures on the properties of a dry adhesive. The presented experiments highlight the advantages of a hierarchical structure despite a reduction of overall density and aspect ratio of nanofibrils. In contrast to an adhesive containing only nanometer-size fibrils, the hierarchical fibrillar adhesives exhibited a higher adhesion force and better compliancy when tested on an identical substrate.

OXYGEN TRANSPORT CERAMIC MEMBRANES

Energy Technology Data Exchange (ETDEWEB)

Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

2000-10-01

This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

Dual-Bioinspired Design for Constructing Membranes with Superhydrophobicity for Direct Contact Membrane Distillation.

Science.gov (United States)

Zhu, Zhigao; Liu, Yuanren; Hou, Haoqing; Shi, Wenxin; Qu, Fangshu; Cui, Fuyi; Wang, Wei

2018-03-06

Water flux and durability are the two critical parameters that are closely associated with the practical application of membrane distillation (MD). Herein, we report a facile approach to fabricate superhydrophobic polyimide nanofibrous membranes (PI NFMs) with hierarchical structures, interconnected pores, and high porosity, which was derived from the electrospinning, dual-bioinspired design, and fluorination processes. Bioinspired adhesive based on polydopamine /polyethylenimine (PDA/PEI) composite was first linked onto membrane substrates and then assembled lotus leaf hierarchical structure by binding the negatively charged silica nanoparticles (SiO 2 NPs) via electrostatic attraction. The resultant superhydrophobic PI NFMs exhibit a water contact angle of 152°, robust hot water resistance of 85 °C, and high water entry pressure of 42 kPa. Moreover, the membrane with omniphobicity presents high water flux over 31 L m -2 h -1 and high salts rejection of ∼100% as well as robust durability for treating high salinity wastewater containing typical low surface tension and dissolved contaminants (Δ T = 40 °C). Significantly, the novel dual-bioinspired method can be used as a universal tool to modify various materials with hierarchical structures, which is expected to provide more effective alternative membranes for MD and even for other selective wetting separation fields.

The CD157-Integrin Partnership Controls Transendothelial Migration and Adhesion of Human Monocytes*

Science.gov (United States)

Lo Buono, Nicola; Parrotta, Rossella; Morone, Simona; Bovino, Paola; Nacci, Giulia; Ortolan, Erika; Horenstein, Alberto L.; Inzhutova, Alona; Ferrero, Enza; Funaro, Ada

2011-01-01

CD157, a member of the CD38 gene family, is an NAD-metabolizing ectoenzyme and a signaling molecule whose role in polarization, migration, and diapedesis of human granulocytes has been documented; however, the molecular events underpinning this role remain to be elucidated. This study focused on the role exerted by CD157 in monocyte migration across the endothelial lining and adhesion to extracellular matrix proteins. The results demonstrated that anti-CD157 antibodies block monocyte transmigration and adhesion to fibronectin and fibrinogen but that CD157 cross-linking is sufficient to overcome the block, suggesting an active signaling role for the molecule. Consistent with this is the observation that CD157 is prevalently located within the detergent-resistant membrane microdomains to which, upon clustering, it promotes the recruitment of β1 and β2 integrin, which, in turn, leads to the formation of a multimolecular complex favoring signal transduction. This functional cross-talk with integrins allows CD157 to act as a receptor despite its intrinsic structural inability to do so on its own. Intracellular signals mediated by CD157 rely on the integrin/Src/FAK (focal adhesion kinase) pathway, resulting in increased activity of the MAPK/ERK1/2 and the PI3K/Akt downstream signaling pathways, which are crucial in the control of monocyte transendothelial migration. Collectively, these findings indicate that CD157 acts as a molecular organizer of signaling-competent membrane microdomains and that it forms part of a larger molecular machine ruled by integrins. The CD157-integrin partnership provides optimal adhesion and transmigration of human monocytes. PMID:21478153

Sensing pH via p-cyanophenylalanine fluorescence: Application to determine peptide pKa and membrane penetration kinetics.

Science.gov (United States)

Pazos, Ileana M; Ahmed, Ismail A; Berríos, Mariana I León; Gai, Feng

2015-08-15

We expand the spectroscopic utility of a well-known infrared and fluorescence probe, p-cyanophenylalanine, by showing that it can also serve as a pH sensor. This new application is based on the notion that the fluorescence quantum yield of this unnatural amino acid, when placed at or near the N-terminal end of a polypeptide, depends on the protonation status of the N-terminal amino group of the peptide. Using this pH sensor, we are able to determine the N-terminal pKa values of nine tripeptides and also the membrane penetration kinetics of a cell-penetrating peptide. Taken together, these examples demonstrate the applicability of using this unnatural amino acid fluorophore to study pH-dependent biological processes or events that accompany a pH change. Copyright © 2015 Elsevier Inc. All rights reserved.

Membrane-Wrapping Contributions to Malaria Parasite Invasion of the Human Erythrocyte

Science.gov (United States)

Dasgupta, Sabyasachi; Auth, Thorsten; Gov, Nir S.; Satchwell, Timothy J.; Hanssen, Eric; Zuccala, Elizabeth S.; Riglar, David T.; Toye, Ashley M.; Betz, Timo; Baum, Jake; Gompper, Gerhard

2014-01-01

The blood stage malaria parasite, the merozoite, has a small window of opportunity during which it must successfully target and invade a human erythrocyte. The process of invasion is nonetheless remarkably rapid. To date, mechanistic models of invasion have focused predominantly on the parasite actomyosin motor contribution to the energetics of entry. Here, we have conducted a numerical analysis using dimensions for an archetypal merozoite to predict the respective contributions of the host-parasite interactions to invasion, in particular the role of membrane wrapping. Our theoretical modeling demonstrates that erythrocyte membrane wrapping alone, as a function of merozoite adhesive and shape properties, is sufficient to entirely account for the first key step of the invasion process, that of merozoite reorientation to its apex and tight adhesive linkage between the two cells. Next, parasite-induced reorganization of the erythrocyte cytoskeleton and release of parasite-derived membrane can also account for a considerable energetic portion of actual invasion itself, through membrane wrapping. Thus, contrary to the prevailing dogma, wrapping by the erythrocyte combined with parasite-derived membrane release can markedly reduce the expected contributions of the merozoite actomyosin motor to invasion. We therefore propose that invasion is a balance between parasite and host cell contributions, evolved toward maximal efficient use of biophysical forces between the two cells. PMID:24988340

Dopaminergic enhancement of cellular adhesion in bone marrow derived mesenchymal stem cells (MSCs).

Science.gov (United States)

Chen, Si; Bai, Bing; Lee, Dong Joon; Diachina, Shannon; Li, Yina; Wong, Sing Wai; Wang, Zhengyan; Tseng, Henry C; Ko, Ching-Chang

2017-08-01

Dopamine (DA) is a well-known neurotransmitter and critical element in the mussel adhesive protein that has gained increasing attention for its role in cellular growth enhancement in biomaterials, including cellular adhesion improvement. As the mechanism underlying this remains unclear, the objective of this study was to explore the effects of DA on the adhesion properties of bone marrow derived rat mesenchymal stem cells (rMSCs) using an hydroxyapatite gelatin nanocomposite biomaterial and to test whether the effects are mediated through various endogenously expressed DA receptors. Primary rMSCs were pretreated with D1-like antagonist, D2-like antagonist, or a combination of these antagonists followed by treatment with 50 μM DA and cellular adhesion quantification at 0.5, 1, 2 and 4 hours post DA addition. DA was found to increase rMSC adhesion and spreading at the 0.5 hour time-point and the dopaminergic effect on cell adhesion was partially blocked by DA antagonists. In addition, the D1-like and D2-like antagonists appeared to have a similar effect on rMSCs. Immunofluorescent staining indicated that the rMSC spreading area was significantly increased in the DA treated group versus the control group. Treatment of the D1-like DA antagonists with DA revealed that the actin filaments of rMSCs could not connect the membrane with the nucleus. In summary, DA was found to enhance early rMSC adhesion partially via DA receptor activation.

Purification of a large molecular weight transglutaminase substrate from liver plasma membranes

International Nuclear Information System (INIS)

Slife, C.W.; Morris, G.S.; Tyrrell, D.J.

1986-01-01

Transglutaminases are enzymes which catalyze the covalent crosslinking of proteins by forming epsilon(γ-glutamyl)lysine isopeptide linkages. In earlier studies, the authors reported that a large molecular weight protein aggregate in rat liver plasma membranes served as a substrate for a plasma membrane-associated transglutaminase. The enzyme specifically incorporated a lysine analog, [ 3 H]putrescine, into a protein complex which remained at the top of an acrylamide gel upon electrophoresis in SDS and reducing agents. The complex has now been isolated by extracting the plasma membranes with detergent (octylglucoside) resuspending the detergent insoluble residues in 6 M guanidine HCl and chromatographing the residue on a 4% agarose column in 6 M guanidine HCl. Most of the radioactivity is found in the void volume fractions from the column. SDS polyacrylamide gel electrophoresis shows that these fractions contain mostly proteins that do not enter the acrylamide gel. Since this purification procedure is essentially the same as that used to isolate a rat hepatocyte adhesion factor from rat liver plasma membranes it is possible that the large molecular weight transglutaminase substrate and the adhesion factor are contained in the same protein aggregate

Surface-Modified Membrane as A Separator for Lithium-Ion Polymer Battery

Directory of Open Access Journals (Sweden)

Jun Young Kim

2010-04-01

Full Text Available This paper describes the fabrication of novel modified polyethylene (PE membranes using plasma technology to create high-performance and cost-effective separator membranes for practical applications in lithium-ion polymer batteries. The modified PE membrane via plasma modification process plays a critical role in improving wettability and electrolyte retention, interfacial adhesion between separators and electrodes, and cycle performance of lithium-ion polymer batteries. This paper suggests that the performance of lithium-ion polymer batteries can be greatly enhanced by the plasma modification of commercial separators with proper functional materials for targeted application.

Annexin A6 contributes to the invasiveness of breast carcinoma cells by influencing the organization and localization of functional focal adhesions

Energy Technology Data Exchange (ETDEWEB)

Sakwe, Amos M., E-mail: asakwe@mmc.edu [Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, TN 37208 (United States); Koumangoye, Rainelli; Guillory, Bobby [Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, TN 37208 (United States); Ochieng, Josiah [Department of Biochemistry and Cancer Biology, Meharry Medical College, Nashville, TN 37208 (United States); Center for Aids Health Disparity Research, Meharry Medical College, Nashville, TN 37208 (United States); Department of Cancer Biology, Vanderbilt University, Nashville, TN (United States)

2011-04-01

The interaction of annexin A6 (AnxA6) with membrane phospholipids and either specific extracellular matrix (ECM) components or F-actin suggests that it may influence cellular processes associated with rapid plasma membrane reorganization such as cell adhesion and motility. Here, we examined the putative roles of AnxA6 in adhesion-related cellular processes that contribute to breast cancer progression. We show that breast cancer cells secrete annexins via the exosomal pathway and that the secreted annexins are predominantly cell surface-associated. Depletion of AnxA6 in the invasive BT-549 breast cancer cells is accompanied by enhanced anchorage-independent cell growth but cell-cell cohesion, cell adhesion/spreading onto collagen type IV or fetuin-A, cell motility and invasiveness were strongly inhibited. To explain the loss in adhesion/motility, we show that vinculin-based focal adhesions in the AnxA6-depleted BT-549 cells are elongated and randomly distributed. These focal contacts are also functionally defective because the activation of focal adhesion kinase and the phosphoinositide-3 kinase/Akt pathway were strongly inhibited while the MAP kinase pathway remained constitutively active. Compared with normal human breast tissues, reduced AnxA6 expression in breast carcinoma tissues correlates with enhanced cell proliferation. Together this suggests that reduced AnxA6 expression contributes to breast cancer progression by promoting the loss of functional cell-cell and/or cell-ECM contacts and anchorage-independent cell proliferation.

Annexin A6 contributes to the invasiveness of breast carcinoma cells by influencing the organization and localization of functional focal adhesions

International Nuclear Information System (INIS)

Sakwe, Amos M.; Koumangoye, Rainelli; Guillory, Bobby; Ochieng, Josiah

2011-01-01

The interaction of annexin A6 (AnxA6) with membrane phospholipids and either specific extracellular matrix (ECM) components or F-actin suggests that it may influence cellular processes associated with rapid plasma membrane reorganization such as cell adhesion and motility. Here, we examined the putative roles of AnxA6 in adhesion-related cellular processes that contribute to breast cancer progression. We show that breast cancer cells secrete annexins via the exosomal pathway and that the secreted annexins are predominantly cell surface-associated. Depletion of AnxA6 in the invasive BT-549 breast cancer cells is accompanied by enhanced anchorage-independent cell growth but cell-cell cohesion, cell adhesion/spreading onto collagen type IV or fetuin-A, cell motility and invasiveness were strongly inhibited. To explain the loss in adhesion/motility, we show that vinculin-based focal adhesions in the AnxA6-depleted BT-549 cells are elongated and randomly distributed. These focal contacts are also functionally defective because the activation of focal adhesion kinase and the phosphoinositide-3 kinase/Akt pathway were strongly inhibited while the MAP kinase pathway remained constitutively active. Compared with normal human breast tissues, reduced AnxA6 expression in breast carcinoma tissues correlates with enhanced cell proliferation. Together this suggests that reduced AnxA6 expression contributes to breast cancer progression by promoting the loss of functional cell-cell and/or cell-ECM contacts and anchorage-independent cell proliferation.

Stretchable, Adhesion-Tunable Dry Adhesive by Surface Wrinkling

KAUST Repository

Jeong, Hoon Eui

2010-02-16

We introduce a simple yet robust method of fabricating a stretchable, adhesion-tunable dry adhesive by combining replica molding and surface wrinkling. By utilizing a thin, wrinkled polydimethyl siloxane (PDMS) sheet with a thickness of 1 mm with built-in micropillars, active, dynamic control of normal and shear adhesion was achieved. Relatively strong normal (∼10.8 N/cm2) and shear adhesion (∼14.7 N/cm2) forces could be obtained for a fully extended (strained) PDMS sheet (prestrain of∼3%), whereas the forces could be rapidly reduced to nearly zero once the prestrain was released (prestrain of ∼0.5%). Moreover, durability tests demonstrated that the adhesion strength in both the normal and shear directions was maintained over more than 100 cycles of attachment and detachment. © 2010 American Chemical Society.

Stretchable, Adhesion-Tunable Dry Adhesive by Surface Wrinkling

KAUST Repository

Jeong, Hoon Eui; Kwak, Moon Kyu; Suh, Kahp Y.

2010-01-01

We introduce a simple yet robust method of fabricating a stretchable, adhesion-tunable dry adhesive by combining replica molding and surface wrinkling. By utilizing a thin, wrinkled polydimethyl siloxane (PDMS) sheet with a thickness of 1 mm with built-in micropillars, active, dynamic control of normal and shear adhesion was achieved. Relatively strong normal (∼10.8 N/cm2) and shear adhesion (∼14.7 N/cm2) forces could be obtained for a fully extended (strained) PDMS sheet (prestrain of∼3%), whereas the forces could be rapidly reduced to nearly zero once the prestrain was released (prestrain of ∼0.5%). Moreover, durability tests demonstrated that the adhesion strength in both the normal and shear directions was maintained over more than 100 cycles of attachment and detachment. © 2010 American Chemical Society.

Kinetics of the formation of the titanium nitruro film (TiN)

International Nuclear Information System (INIS)

Rojas Andres; Devia C, Alfonso; Alzate Rafael

1999-01-01

They are presented in succinct form the factors that intervene in the growth, adhesion of the film and election of the support material in the process of formation of TiN film. Equally it's carried out the kinetic development of the possible reactions (ionization and excitement) involved in the process

Actin dynamics at focal adhesions: a common endpoint and putative therapeutic target for proteinuric kidney diseases.

Science.gov (United States)

Sever, Sanja; Schiffer, Mario

2018-06-01

Proteinuria encompasses diverse causes including both genetic diseases and acquired forms such as diabetic and hypertensive nephropathy. The basis of proteinuria is a disturbance in size selectivity of the glomerular filtration barrier, which largely depends on the podocyte: a terminally differentiated epithelial cell type covering the outer surface of the glomerulus. Compromised podocyte structure is one of the earliest signs of glomerular injury. The phenotype of diverse animal models and podocyte cell culture firmly established the essential role of the actin cytoskeleton in maintaining functional podocyte structure. Podocyte foot processes, actin-based membrane extensions, contain 2 molecularly distinct "hubs" that control actin dynamics: a slit diaphragm and focal adhesions. Although loss of foot processes encompasses disassembly of slit diaphragm multiprotein complexes, as long as cells are attached to the glomerular basement membrane, focal adhesions will be the sites in which stress due to filtration flow is counteracted by forces generated by the actin network in foot processes. Numerous studies within last 20 years have identified actin binding and regulatory proteins as well as integrins as essential components of signaling and actin dynamics at focal adhesions in podocytes, suggesting that some of them may become novel, druggable targets for proteinuric kidney diseases. Here we review evidence supporting the idea that current treatments for chronic kidney diseases beneficially and directly target the podocyte actin cytoskeleton associated with focal adhesions and suggest that therapeutic reagents that target the focal adhesion-regulated actin cytoskeleton in foot processes have potential to modernize treatments for chronic kidney diseases. Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Basic study of healing of injuries to the myometrium and amniotic membrane using photocrosslinkable chitosan.

Science.gov (United States)

Suzuki, Keitaro; Shinya, Masaru; Kitagawa, Michihiro

2006-04-01

We performed in vivo and in vitro adhesion experiments on the use of photocrosslinkable chitosan (PC) for healing of the myometrium and the amniotic membrane to test its usefulness in the perinatal field. To determine the adhesion conditions of PC in the healing of the myometrium and amniotic membrane, we applied two concentrations (30 and 50 mg/mL) of PC to the postpartum amniotic membrane, and radiated it with ultraviolet (UV) light for 10, 20, 30 or 60 s. Next, we created incisions of three sizes (pinhole, 5 mm and 10 mm), and performed PC adhesion followed by pressure application experiments. Subsequently, we laparotomized 12-day-pregnant rats under anesthesia, created a 5-mm incision, applied PC and closed the abdomen. We removed the uterus at 20 days of pregnancy, and histologically examined the site of PC application. The optimal adhesion conditions of PC were 50 mg/mL, and the optimal time of UV irradiation was 30 s or longer. In pressure application experiments, the bonding strength of PC was so high that even 10-mm incisions withstood a mean pressure of 92 mmH2O. The bonding strength of PC was significantly higher than that of fibrin glue that was tested in parallel. Histological examination of the rat myometrium showed a mild foreign body reaction with no inflammatory findings, confirming the usefulness of PC. PC is a wound-healing drug, an improvement on the naturally occurring polysaccharide chitosan, and is safer and has a higher bonding strength than biological adhesives including fibrin, making it promising for fetal surgical and perinatal applications.

Mathematical modeling of liquid/liquid hollow fiber membrane contactor accounting for interfacial transport phenomena: Extraction of lanthanides as a surrogate for actinides

International Nuclear Information System (INIS)

Rogers, J.D.

1994-01-01

This report is divided into two parts. The second part is divided into the following sections: experimental protocol; modeling the hollow fiber extractor using film theory; Graetz model of the hollow fiber membrane process; fundamental diffusive-kinetic model; and diffusive liquid membrane device-a rigorous model. The first part is divided into: membrane and membrane process-a concept; metal extraction; kinetics of metal extraction; modeling the membrane contactor; and interfacial phenomenon-boundary conditions-applied to membrane transport

Kinetics of americium(VI) mass transfer through solid supported liquid membrane with HDEHP

International Nuclear Information System (INIS)

Mikheeva, M.N.; Novicoov, P.; Myasoedov, B.F.; Tikhomirov, S.V.

1994-01-01

The main regularities of membrane extraction of americium under conditions of different redox potentials in aqueous phases have been studied. The physico-chemical model of the process including steps of americium oxidation in feed solution, extraction by membrane, partial reduction on membrane surface, trans-membrane diffusion and reextraction to strip solution has been developed. The calculation of reduction rate constant on membrane surface has been carried out. (author) 9 refs.; 4 figs.; 3 tabs

Response of MG63 osteoblast-like cells onto polycarbonate membrane surfaces with different micropore sizes.

Science.gov (United States)

Lee, Sang Jin; Choi, Jin San; Park, Ki Suk; Khang, Gilson; Lee, Young Moo; Lee, Hai Bang

2004-08-01

Response of different types of cells on materials is important for the applications of tissue engineering and regenerative medicine. It is recognized that the behavior of the cell adhesion, proliferation, and differentiation on materials depends largely on surface characteristics such as wettability, chemistry, charge, rigidity, and roughness. In this study, we examined the behavior of MG63 osteoblast-like cells cultured on a polycarbonate (PC) membrane surfaces with different micropore sizes (0.2-8.0 microm in diameter). Cell adhesion and proliferation to the PC membrane surfaces were determined by cell counting and MTT assay. The effect of surface micropore on the MG63 cells was evaluated by cell morphology, protein content, and alkaline phosphatase (ALP) specific activity. It seems that the cell adhesion and proliferation were progressively inhibited as the PC membranes had micropores with increasing size, probably due to surface discontinuities produced by track-etched pores. Increasing micropore size of the PC membrane results in improved protein synthesis and ALP specific activity in isolated cells. There was a statistically significant difference (Pmicropore sizes. The MG63 cells also maintained their phenotype under conditions that support a round cell shape. RT-PCR analysis further confirmed the osteogenic phenotype of the MG63 cells onto the PC membranes with different micropore sizes. In results, as micropore size is getting larger, cell number is reduced and cell differentiation and matrix production is increased. This study demonstrated that the surface topography plays an important role for phenotypic expression of the MG63 osteoblast-like cells.

Universal adhesives: the next evolution in adhesive dentistry?

Science.gov (United States)

Alex, Gary

2015-01-01

Every so often a new material, technique, or technological breakthrough spurs a paradigm shift in the way dentistry is practiced. The development and evolution of reliable enamel and dentin bonding agents is one such example. Indeed, the so-called "cosmetic revolution" in dentistry blossomed in large part due to dramatic advances in adhesive technology. It is the ability to bond various materials in a reasonably predictable fashion to both enamel and dentin substrates that enables dentists to routinely place porcelain veneers, direct and indirect composites, and a plethora of other restorative and esthetic materials. In fact, the longevity and predictability of many (if not most) current restorative procedures is wholly predicated on the dentist's ability to bond various materials to tooth tissues. Adhesive systems have progressed from the largely ineffective systems of the 1970s and early 1980s to the relatively successful total- and self-etching systems of today. The latest players in the adhesive marketplace are the so-called "universal adhesives." In theory, these systems have the potential to significantly simplify and expedite adhesive protocols and may indeed represent the next evolution in adhesive dentistry. But what defines a universal system, and are all these new systems truly "universal" and everything they are claimed to be? This article will examine the origin, chemistry, strengths, weaknesses, and clinical relevance of this new genre of dental adhesives.

Adhesion of living cells revealed by variable-angle total internal reflection fluorescence microscopy (Conference Presentation)

Science.gov (United States)

Cardoso Dos Santos, Marcelina; Vézy, Cyrille; Jaffiol, Rodolphe

2016-02-01

Total Internal Reflection Fluorescence Microscopy (TIRFM) is a widespread technique to study cellular process occurring near the contact region with the glass substrate. In this field, determination of the accurate distance from the surface to the plasma membrane constitutes a crucial issue to investigate the physical basis of cellular adhesion process. However, quantitative interpretation of TIRF pictures regarding the distance z between a labeled membrane and the substrate is not trivial. Indeed, the contrast of TIRF images depends on several parameters more and less well known (local concentration of dyes, absorption cross section, angular emission pattern…). The strategy to get around this problem is to exploit a series of TIRF pictures recorded at different incident angles in evanescent regime. This technique called variable-angle TIRF microscopy (vaTIRFM), allowing to map the membrane-substrate separation distance with a nanometric resolution (10-20 nm). vaTIRFM was developed by Burmeister, Truskey and Reichert in the early 1990s with a prism-based TIRF setup [Journal of Microscopy 173, 39-51 (1994)]. We propose a more convenient prismless setup, which uses only a rotatable mirror to adjust precisely the laser beam on the back focal plane of the oil immersion objective (no azimuthal scanning is needed). The series of TIRF images permit us to calculate accurately membrane-surface distances in each pixel. We demonstrate that vaTIRFM are useful to quantify the adhesion of living cells for specific and unspecific membrane-surface interactions, achieved on various functionalized substrates with polymers (BSA, poly-L-lysin) or extracellular matrix proteins (collagen and fibronectin).

Fabrication of cell outer membrane mimetic polymer brush on polysulfone surface via RAFT technique

International Nuclear Information System (INIS)

Ma Qian; Zhang Hui; Zhao Jiang; Gong Yongkuan

2012-01-01

Highlights: ► Cell membrane mimetic antifouling polymer brush was grown on polysulfone surface. ► Graft density and polymerization degree were calculated from XPS results. ► Water contact angle measurements showed an extremely hydrophilic surface. ► Platelet adhesion and protein adsorption results suggested excellent antifouling ability. - Abstract: Cell membrane mimetic antifouling polymer brush was grown on polysulfone (PSF) membrane by surface-induced reversible addition–fragmentation chain transfer (RAFT) polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC). The RAFT agent immobilized PSF substrate was prepared by successive chloromethylation, amination with ethylenediamine (EDA) and amidation of the amine group of grafted EDA with the carboxylic group of 4-cyanopentanoic acid dithiobenzoate (CPAD). The surface RAFT polymerization of MPC was initiated in aqueous solution by 4,4′-azobis-4-cyanopentanoic acid (ACPA). The formation of PMPC brush coating is evidenced by X-ray photoelectron spectroscopy and water contact angle measurements. The degree of polymerization of PMPC and the polymer grafting density were calculated from the high resolution XPS spectra. The platelet adhesion and protein adsorption results showed that the PMPC-grafted PSF surface has excellent antifouling ability to resist platelet adhesion completely and suppress protein adsorption significantly. This biomimetic and bio-friendly surface RAFT polymerization strategy could be promising for a variety of biomedical applications.

Enhanced mechanical properties and cytocompatibility of electrospun poly(L-lactide) composite fiber membranes assisted by polydopamine-coated halloysite nanotubes

Energy Technology Data Exchange (ETDEWEB)

Luo, Chuang; Zou, Ziping [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Luo, Binghong, E-mail: tluobh@jnu.edu.cn [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Wen, Wei [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Li, Huihua [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Liu, Mingxian [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Zhou, Changren, E-mail: tcrz9@jnu.edu.cn [Biomaterial Research Laboratory, Department of Material Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China)

2016-04-30

Graphical abstract: - Highlights: • D-HNTs was prepared by a facile approach based on the self-polymerization of DOPA. • The D-HNTs can disperse more uniformly in PLLA matrix than untreated HNTs. • The interfacial adhesion between D-HNTs and PLLA matrix was obviously improved. • D-HNTs/PLLA fiber membrane has better tensile properties compared with HNTs/PLLA. • The D-HNTs/PLLA fiber membrane is favorable to cell adhesion and proliferation. - Abstract: To improve the dispersion and interfacial interaction between halloysite nanotubes (HNTs) and poly(L-lactide) (PLLA) matrix, and hence to increase the mechanical properties and cytocompatibility of the HNTs/PLLA composite, a facile approach was developed to prepare polydopamine-coated HNTs (D-HNTs) by the self-polymerization of dopamine (DOPA), and then HNTs and D-HNTs were further introduced into PLLA matrix to fabricate HNTs/PLLA and D-HNTs/PLLA fiber membranes based on electrospinning technique. The successful immobilization of the polydopamine (PDOPA) coating on the surfaces of HNTs was confirmed, and such PDOPA coating played an important role in improving the interfacial interaction between the nanotubes and PLLA matrix. The D-HNTs were dispersed in the matrix more uniformly than untreated HNTs, and relative smooth and uniform fiber were obtained for the D-HNTs/PLLA fiber membrane. As a result, the tensile strength and modulus of the D-HNTs/PLLA fiber membrane were obviously superior to those of the HNTs/PLLA fiber membrane. Cell culture results revealed that D-HNTs/PLLA fiber membrane was more effectively to promote MC3T3-E1 cells adhesion and proliferation than neat PLLA and HNTs/PLLA fiber membrane.

Enhanced mechanical properties and cytocompatibility of electrospun poly(L-lactide) composite fiber membranes assisted by polydopamine-coated halloysite nanotubes

International Nuclear Information System (INIS)

Luo, Chuang; Zou, Ziping; Luo, Binghong; Wen, Wei; Li, Huihua; Liu, Mingxian; Zhou, Changren

2016-01-01

Graphical abstract: - Highlights: • D-HNTs was prepared by a facile approach based on the self-polymerization of DOPA. • The D-HNTs can disperse more uniformly in PLLA matrix than untreated HNTs. • The interfacial adhesion between D-HNTs and PLLA matrix was obviously improved. • D-HNTs/PLLA fiber membrane has better tensile properties compared with HNTs/PLLA. • The D-HNTs/PLLA fiber membrane is favorable to cell adhesion and proliferation. - Abstract: To improve the dispersion and interfacial interaction between halloysite nanotubes (HNTs) and poly(L-lactide) (PLLA) matrix, and hence to increase the mechanical properties and cytocompatibility of the HNTs/PLLA composite, a facile approach was developed to prepare polydopamine-coated HNTs (D-HNTs) by the self-polymerization of dopamine (DOPA), and then HNTs and D-HNTs were further introduced into PLLA matrix to fabricate HNTs/PLLA and D-HNTs/PLLA fiber membranes based on electrospinning technique. The successful immobilization of the polydopamine (PDOPA) coating on the surfaces of HNTs was confirmed, and such PDOPA coating played an important role in improving the interfacial interaction between the nanotubes and PLLA matrix. The D-HNTs were dispersed in the matrix more uniformly than untreated HNTs, and relative smooth and uniform fiber were obtained for the D-HNTs/PLLA fiber membrane. As a result, the tensile strength and modulus of the D-HNTs/PLLA fiber membrane were obviously superior to those of the HNTs/PLLA fiber membrane. Cell culture results revealed that D-HNTs/PLLA fiber membrane was more effectively to promote MC3T3-E1 cells adhesion and proliferation than neat PLLA and HNTs/PLLA fiber membrane.

Biofouling in capillary and spiral wound membranes facilitated by marine algal bloom

DEFF Research Database (Denmark)

Villacorte, L.O.; Ekowati, Y.; Calix-Ponce, H.N.

2017-01-01

blooms. The tendency of AOM from bloom-forming marine algae to adhere to membranes and its ability to enhance biofilm growth were measured using atomic force microscopy, flow cytometry, liquid chromatography and accelerated membrane biofouling experiments. Adhesion force measurements indicate that AOM......Algal-derived organic matter (AOM), particularly transparent exopolymer particles, has been suspected to facilitate biofilm development in membrane systems (e.g., seawater reverse osmosis). This study demonstrates the possible role of AOM on biofouling in membrane systems affected by marine algal...... biodegradable nutrients. The abovementioned findings indicate that AOM facilitates the onset of membrane biofouling primarily as a conditioning platform and to some extent as a nutrient source for biofilm-forming bacteria....

Energy harvesting from vibration using a piezoelectric membrane

Energy Technology Data Exchange (ETDEWEB)

Ericka, M.; Vasic, D.; Costa, F.; Tliba, S. [Ecole Normale Superieure de Cachan, Systemes et Applications des Technologies de l' Information et de l' Energie (SATIE, UMR 8029), 94 - Cachan (France); Poulin, G. [Ecole Nationale Superieure d' Ingenieurs Electriciens de Grenoble, Laboratoire d' Automatique de Grenoble, 38 (France)

2005-09-01

In this paper we investigate the capability of harvesting the electric energy from mechanical vibrations in a dynamic environment through a piezoelectric membrane transducer. This transducer consists of 2 layers lead zirconate titanate (PZT)/brass, the brass layer is embedded over the whole circumference by epoxy adhesive. A very small vibration gives a consequent deformation of the membrane which generates electric energy. Due to the impedance matrices connecting the efforts and flows of the membrane, we have established the dynamic electric equivalent circuit of the transducer. In a first study and in order to validate theoretical results, we performed experiments with a vibrating machine moving a macroscopic 25 mm diameter piezoelectric membrane. A power of 1.8 mW was generated at the resonance frequency (2.58 kHz) across a 56 k{omega} optimal resistor and for a 2 g acceleration. (authors)

Activation of PVDF membranes through facile hydroxylation of the polymeric dope

KAUST Repository

Al-Gharabli, Samer; Mavukkandy, Musthafa O.; Kujawa, Joanna; Nunes, Suzana Pereira; Arafat, Hassan A.

2017-01-01

A method comprising a two-step alkali/acid treatment of poly (vinylidene fluoride) (PVDF) polymer is developed for the fabrication of flat-sheet PVDF membranes functionalized with labile hydroxyl groups. This method involves the application of a short-duration modification in alkali medium (5% KOH). Extensive characterizations were performed on the prepared membranes. Modification of the polymer altered the crystallinity of the PVDF from a mixture of both α and β phases to a predominant β phase. Lower work of adhesion of the modified membrane indicated the formation of a more hydrophobic and wetting-resistant membrane surface. Centrifugation of the polymer dope after the modification had a pronounced impact on the properties of the resultant membranes. This protocol could be utilized in fine-tuning the properties of PVDF membranes for various target-specific applications such as membrane distillation. This method can also be used in functionalizing PVDF membranes further by exploiting the labile –OH group present on the membrane surface.

Activation of PVDF membranes through facile hydroxylation of the polymeric dope

KAUST Repository

Al-Gharabli, Samer

2017-10-30

A method comprising a two-step alkali/acid treatment of poly (vinylidene fluoride) (PVDF) polymer is developed for the fabrication of flat-sheet PVDF membranes functionalized with labile hydroxyl groups. This method involves the application of a short-duration modification in alkali medium (5% KOH). Extensive characterizations were performed on the prepared membranes. Modification of the polymer altered the crystallinity of the PVDF from a mixture of both α and β phases to a predominant β phase. Lower work of adhesion of the modified membrane indicated the formation of a more hydrophobic and wetting-resistant membrane surface. Centrifugation of the polymer dope after the modification had a pronounced impact on the properties of the resultant membranes. This protocol could be utilized in fine-tuning the properties of PVDF membranes for various target-specific applications such as membrane distillation. This method can also be used in functionalizing PVDF membranes further by exploiting the labile –OH group present on the membrane surface.

Bacterial Adhesion & Blocking Bacterial Adhesion

DEFF Research Database (Denmark)

Vejborg, Rebecca Munk

2008-01-01

, which influence the transition from a planktonic lifestyle to a sessile lifestyle, have been studied. Protein conditioning film formation was found to influence bacterial adhesion and subsequent biofilm formation considerable, and an aqueous extract of fish muscle tissue was shown to significantly...... tract to the microbial flocs in waste water treatment facilities. Microbial biofilms may however also cause a wide range of industrial and medical problems, and have been implicated in a wide range of persistent infectious diseases, including implantassociated microbial infections. Bacterial adhesion...... is the first committing step in biofilm formation, and has therefore been intensely scrutinized. Much however, still remains elusive. Bacterial adhesion is a highly complex process, which is influenced by a variety of factors. In this thesis, a range of physico-chemical, molecular and environmental parameters...

Adhesion enhancement of biomimetic dry adhesives by nanoparticle in situ synthesis

International Nuclear Information System (INIS)

Díaz Téllez, J P; Harirchian-Saei, S; Li, Y; Menon, C

2013-01-01

A novel method to increase the adhesion strength of a gecko-inspired dry adhesive is presented. Gold nanoparticles are synthesized on the tips of the microfibrils of a polymeric dry adhesive to increase its Hamaker constant. Formation of the gold nanoparticles is qualitatively studied through a colour change in the originally transparent substance and quantitatively analysed using ultraviolet–visible spectrophotometry. A pull-off force test is employed to quantify the adhesion enhancement. Specifically, adhesion forces of samples with and without embedded gold nanoparticles are measured and compared. The experimental results indicate that an adhesion improvement of 135% can be achieved. (paper)

Kinetics of membrane damage to high (HNA) and low (LNA) nucleic acid bacterial clusters in drinking water by ozone, chlorine, chlorine dioxide, monochloramine, ferrate(VI), and permanganate.

Science.gov (United States)

Ramseier, Maaike K; von Gunten, Urs; Freihofer, Pietro; Hammes, Frederik

2011-01-01

Drinking water was treated with ozone, chlorine, chlorine dioxide, monochloramine, ferrate(VI), and permanganate to investigate the kinetics of membrane damage of native drinking water bacterial cells. Membrane damage was measured by flow cytometry using a combination of SYBR Green I and propidium iodide (SGI+PI) staining as indicator for cells with permeabilized membranes and SGI alone to measure total cell concentration. SGI+PI staining revealed that the cells were permeabilized upon relatively low oxidant exposures of all tested oxidants without a detectable lag phase. However, only ozonation resulted in a decrease of the total cell concentrations for the investigated reaction times. Rate constants for the membrane damage reaction varied over seven orders of magnitude in the following order: ozone > chlorine > chlorine dioxide ≈ ferrate > permanganate > chloramine. The rate constants were compared to literature data and were in general smaller than previously measured rate constants. This confirmed that membrane integrity is a conservative and therefore safe parameter for disinfection control. Interestingly, the cell membranes of high nucleic acid (HNA) content bacteria were damaged much faster than those of low nucleic acid (LNA) content bacteria during treatment with chlorine dioxide and permanganate. However, only small differences were observed during treatment with chlorine and chloramine, and no difference was observed for ferrate treatment. Based on the different reactivity of these oxidants it was suggested that HNA and LNA bacterial cell membranes have a different chemical constitution. Copyright © 2010 Elsevier Ltd. All rights reserved.

Membrane extraction instead of solvent extraction - what does it give

International Nuclear Information System (INIS)

Macasek, F.

1989-01-01

Membrane extraction, i.e. separation in double-emulsion systems, is analyzed theoretically as a three-phase distribution process. Its efficiency is evaluated from the point of view of chemical equilibria and diffusion transport kinetics. The main advantages of membrane extraction as compared with solvent extraction are in higher yields (for preconcentration) and higher capacity for recovery of solutes. A pertraction factor and multiplication factor were defined. They are convenient parameters for numerical characterization of solute distribution, system capacity, process economics, and separation kinetics (both at a linear and non-linear extraction isotherm). 17 refs.; 4 figs

Protein adhesives

Science.gov (United States)

Charles R. Frihart; Linda F. Lorenz

2018-01-01

Nature uses a wide variety of chemicals for providing adhesion internally (e.g., cell to cell) and externally (e.g., mussels to ships and piers). This adhesive bonding is chemically and mechanically complex, involving a variety of proteins, carbohydrates, and other compounds.Consequently,the effect of protein structures on adhesive properties is only partially...

Simulation of polyethylene glycol and calcium-mediated membrane fusion

International Nuclear Information System (INIS)

Pannuzzo, Martina; De Jong, Djurre H.; Marrink, Siewert J.; Raudino, Antonio

2014-01-01

We report on the mechanism of membrane fusion mediated by polyethylene glycol (PEG) and Ca 2+ by means of a coarse-grained molecular dynamics simulation approach. Our data provide a detailed view on the role of cations and polymer in modulating the interaction between negatively charged apposed membranes. The PEG chains cause a reduction of the inter-lamellar distance and cause an increase in concentration of divalent cations. When thermally driven fluctuations bring the membranes at close contact, a switch from cis to trans Ca 2+ -lipid complexes stabilizes a focal contact acting as a nucleation site for further expansion of the adhesion region. Flipping of lipid tails induces subsequent stalk formation. Together, our results provide a molecular explanation for the synergistic effect of Ca 2+ and PEG on membrane fusion

Characterization of the in vitro binding and inhibition kinetics of primary amine oxidase/vascular adhesion protein-1 by glucosamine.

LENUS (Irish Health Repository)

Olivieri, Aldo

2012-04-01

Primary-amine oxidase (PrAO) catalyzes the oxidative deamination of endogenous and exogenous primary amines and also functions, in some tissues, as an inflammation-inducible endothelial factor, known as vascular adhesion protein-1. VAP-1 mediates the slow rolling and adhesion of lymphocytes to endothelial cells in a number of inflammatory conditions, including inflammation of the synovium.

Photo-crosslinkable cyanoacrylate bioadhesive: shrinkage kinetics, dynamic mechanical properties, and biocompatibility of adhesives containing TMPTMA and POSS nanostructures as crosslinking agents.

Science.gov (United States)

Ghasaban, S; Atai, M; Imani, M; Zandi, M; Shokrgozar, M-A

2011-11-01

The study investigates the photo-polymerization shrinkage behavior, dynamic mechanical properties, and biocompatibility of cyanoacrylate bioadhesives containing POSS nanostructures and TMPTMA as crosslinking agents. Adhesives containing 2-octyl cyanoacrylate (2-OCA) and different percentages of POSS nanostructures and TMPTMA as crosslinking agents were prepared. The 1-phenyl-1, 2-propanedione (PPD) was incorporated as photo-initiator into the adhesive in 1.5, 3, and 4 wt %. The shrinkage strain of the specimens was measured using bonded-disk technique. Shrinkage strain, shrinkage strain rate, maximum and time at maximum shrinkage strain rate were measured and compared. Mechanical properties of the adhesives were also studied using dynamic mechanical thermal analysis (DMTA). Biocompatibility of the adhesives was examined by MTT method. The results showed that shrinkage strain increased with increasing the initiator concentration up to 3 wt % in POSS-containing and 1.5 wt % in TMPTMA-containing specimens and plateaued out at higher concentrations. By increasing the crosslinking agent, shrinkage strain, and shrinkage strain rate increased and the time at maximum shrinkage strain rate decreased. The study indicates that the incorporation of crosslinking agents into the cyanoacrylate adhesives resulted in improved mechanical properties. Preliminary MTT studies also revealed better biocompatibility profile for the adhesives containing crosslinking agents comparing to the neat specimens. Copyright © 2011 Wiley Periodicals, Inc.

Reducing post-surgical adhesions utilizing a drug-enhanced device: sodium carboxymethylcellulose aqueous gel/poly(p-dioxanone) and Tranilast

International Nuclear Information System (INIS)

Cui, Helen; Gensini, Michel; Kataria, Ram; Twaddle, Tricia; Zhang, John; Wadsworth, Scott; Cooper, Kevin; Petrilli, Janel; Rodgers, Kathleen; DiZerega, Gere

2009-01-01

Post-surgical adhesion formation has numerous deleterious side effects in a wide variety of surgical settings. Physical barriers used together with laparoscopy were developed to reduce tissue trauma seen with open procedures. However, despite surgeons' meticulous techniques and the use of such barriers, adhesion formation remains a serious clinical problem, creating complications that cost the health care system over $1 billion annually. Our laboratories have combined a previously marketed drug, Tranilast, with a sodium carboxymethylcellulose (NaCMC) gel in a sustained release formulation using poly(p-dioxanone) (PDO) to provide a locally delivered medicated device that significantly reduces adhesions. This paper describes the preparation of the gel and the sustained release formulation, its key physical properties, and its sustained release kinetics. Pre-clinical data on inhibition of adhesion formation by the sustained release poly(p-dioxanone)/sodium carboxymethylcellulose/Tranilast drug enhanced device are also presented.

Zwitterionic materials for antifouling membrane surface construction.

Science.gov (United States)

He, Mingrui; Gao, Kang; Zhou, Linjie; Jiao, Zhiwei; Wu, Mengyuan; Cao, Jialin; You, Xinda; Cai, Ziyi; Su, Yanlei; Jiang, Zhongyi

2016-08-01

Membrane separation processes are often perplexed by severe and ubiquitous membrane fouling. Zwitterionic materials, keeping electric neutrality with equivalent positive and negative charged groups, are well known for their superior antifouling properties and have been broadly utilized to construct antifouling surfaces for medical devices, biosensors and marine coatings applications. In recent years, zwitterionic materials have been more and more frequently utilized for constructing antifouling membrane surfaces. In this review, the antifouling mechanisms of zwitterionic materials as well as their biomimetic prototypes in cell membranes will be discussed, followed by the survey of common approaches to incorporate zwitterionic materials onto membrane surfaces including surface grafting, surface segregation, biomimetic adhesion, surface coating and so on. The potential applications of these antifouling membranes are also embedded. Finally, we will present a brief perspective on the future development of zwitterionic materials modified antifouling membranes. Membrane fouling is a severe problem hampering the application of membrane separation technology. The properties of membrane surfaces play a critical role in membrane fouling and antifouling behavior/performance. Antifouling membrane surface construction has evolved as a hot research issue for the development of membrane processes. Zwitterionic modification of membrane surfaces has been recognized as an effective strategy to resist membrane fouling. This review summarizes the antifouling mechanisms of zwitterionic materials inspired by cell membranes as well as the popular approaches to incorporate them onto membrane surfaces. It can help form a comprehensive knowledge about the principles and methods of modifying membrane surfaces with zwitterionic materials. Finally, we propose the possible future research directions of zwitterionic materials modified antifouling membranes. Copyright © 2016 Acta Materialia Inc

Uranium extraction process in a sulfuric medium by means of liquid emulsified membranes

International Nuclear Information System (INIS)

Monteillet, A.

1985-02-01

Uranium ore processing, after leaching by sulfuric acid, by liquid-liquid extraction is a rather heavy process, not suitable for small deposits. Extraction by emulsions was suggested. In this process the leachate is contacted with an oil in water type emulsion, a liquid organic membrane is formed by the continuous phase. Uranium complexes diffuse through the liquid membrane towards the dispersed aqueous phase of the emulsion (stripping solution). Uranium is recovered by breaking the emulsion. Are successively studied: development of stable emulsions, influence of emulsion composition on uranium transfer kinetics, transfer mechanisms through the membrane and modelling of kinetics data obtained in the experimental study [fr

Radiation-curable adhesives

International Nuclear Information System (INIS)

Woods, J.G.

1992-01-01

Radiation-curable adhesives may be classified into two broad categories. In the first category, adhesive bonding occurs as a direct result of irradiation. The second category includes pressure-sensitive and hot-melt adhesives, which are composed of linear or lightly cross-linked polymers prepared by a radiation-induced polymerization reaction. This chapter is mainly concerned with radiation-curable adhesives of the first category. The various adhesive types are discussed and adhesive performance is examined, particularly in relation to the chemistry and chemical technology which underlies the individual materials. A description of a limited number of representative applications is included as is an outline of recent developments of curing and dispensing equipment. 268 refs., 14 figs., 13 tabs

Facet development for a faceted stretched-membrane dish by Solar Kinetics, Inc

Energy Technology Data Exchange (ETDEWEB)

Schertz, P.T.; Brown, D.C.; Konnerth, A. III (Solar Kinetics, Inc., Dallas, TX (United States))

1991-07-01

A 3.6-meter diameter stretched-membrane optical facet for a parabolic dish has been successfully designed and demonstrated under contract with Sandia National Laboratories. Twelve facets identical to them will be used to make the lightweight reflector of the dish. The project goal of 2.5-mrad surface accuracy was met with each of the two full-sized prototypes, and accuracies of as low as 1.1 mrad were achieved. The facet weight is 11.7 kg/m{sup 2} (2.4lbs/ft{sup 2}). The facet is similar in construction to the successful stretched-membrane heliostat; it has two thin metal membranes attached to a ring. However, the front membrane for this facet is plastically formed at the factor in order to achieve a shorter facet f/D (approximately 3.0). A passive tether restrains the from membrane when not in operation, that is, when the stabilizing vacuum is off. The optical surface is achieved with a silvered-acrylic film laminated to the metal membrane. The facet is expected to cost $55.40/m{sup 2} at a production rate of 10,000 facets per year and $115, 000/m{sup 2}-at a production rate of 500 facets a year. Several key issues have been resolved. Stress concentrations due to seams in the reflective laminate did not cause membrane rupture during forming as they have for dishes with lower focal length-to-diameter ratios. The laminate survived the forming process and simulated operation without deterioration. The optical effect of the tether on the membrane was tested and found to be very small. Most important, highly accurate shapes were obtained using a simple forming procedure. Additional tests are needed to demonstrate process repeatablility and facet performance in typical operating conditions. 18 refs., 36 figs., 11 tabs.

Switchable bio-inspired adhesives

Science.gov (United States)

Kroner, Elmar

2015-03-01

Geckos have astonishing climbing abilities. They can adhere to almost any surface and can run on walls and even stick to ceilings. The extraordinary adhesion performance is caused by a combination of a complex surface pattern on their toes and the biomechanics of its movement. These biological dry adhesives have been intensely investigated during recent years because of the unique combination of adhesive properties. They provide high adhesion, allow for easy detachment, can be removed residue-free, and have self-cleaning properties. Many aspects have been successfully mimicked, leading to artificial, bio-inspired, patterned dry adhesives, and were addressed and in some aspects they even outperform the adhesion capabilities of geckos. However, designing artificial patterned adhesion systems with switchable adhesion remains a big challenge; the gecko's adhesion system is based on a complex hierarchical surface structure and on advanced biomechanics, which are both difficult to mimic. In this paper, two approaches are presented to achieve switchable adhesion. The first approach is based on a patterned polydimethylsiloxane (PDMS) polymer, where adhesion can be switched on and off by applying a low and a high compressive preload. The switch in adhesion is caused by a reversible mechanical instability of the adhesive silicone structures. The second approach is based on a composite material consisting of a Nickel- Titanium (NiTi) shape memory alloy and a patterned adhesive PDMS layer. The NiTi alloy is trained to change its surface topography as a function of temperature, which results in a change of the contact area and of alignment of the adhesive pattern towards a substrate, leading to switchable adhesion. These examples show that the unique properties of bio-inspired adhesives can be greatly improved by new concepts such as mechanical instability or by the use of active materials which react to external stimuli.

Proton exchange membrane water electrolysers

International Nuclear Information System (INIS)

Millet, P.

2007-01-01

This work deals with the PEM water electrolysis process. Are successively described: the thermodynamical, kinetic and energetic aspects, the different possible used electrolysis cells, the preparation of the membrane-electrode assembling, the used electrolysers, the annex production equipment, the uses fields and the limits of the process. (O.M.)

Multilayered ion-imprinted membranes with high selectivity towards Li+ based on the synergistic effect of 12-crown-4 and polyether sulfone

Science.gov (United States)

Lu, Jian; Qin, Yingying; Zhang, Qi; Wu, Yilin; Cui, Jiuyun; Li, Chunxiang; Wang, Liang; Yan, Yongsheng

2018-01-01

High-selective multilayered Li+-imprinted membranes (Li-IIMs) with enhanced hydrophilicity and stability were developed based on polyether sulfone substrate membranes. The multilayered structure was prepared with polydopamine (pDA) as the interfacial adhesion layer, SiO2 nanoparticles as the hydrophilic layer and Li+-imprinted polymers as the imprinted layer. The selective ;Li+-recognition sites; were formed using 12-crown-4 (12C4) as the adsorbing units. The optimal relative selectivity coefficients (α) of Li+/Na+ and Li+/K+ reached up to 1.85 and 2.07 with the imprinting factor (β) of 2.51, and the high permselectivity factors (γ) of Na+/Li+ (7.39) and K+/Li+ (9.86) were achieved on Li-IIMs. The Langmuir isotherm model and the pseudo-second-order kinetics model best fitted the rebinding data of Li-IIMs, as well as the rebinding capacities reached up to 90.3% of initial binding after 5 cycles of adsorption/desorption and just declined to 88.1% after another 5 cycles a month later. Therefore, the as-prepared Li-IIMs would have potential applications for the separation of lithium ions from salt lake brines.

TRIM15 is a focal adhesion protein that regulates focal adhesion disassembly

Science.gov (United States)

Uchil, Pradeep D.; Pawliczek, Tobias; Reynolds, Tracy D.; Ding, Siyuan; Hinz, Angelika; Munro, James B.; Huang, Fang; Floyd, Robert W.; Yang, Haitao; Hamilton, William L.; Bewersdorf, Joerg; Xiong, Yong; Calderwood, David A.; Mothes, Walther

2014-01-01

ABSTRACT Focal adhesions are macromolecular complexes that connect the actin cytoskeleton to the extracellular matrix. Dynamic turnover of focal adhesions is crucial for cell migration. Paxillin is a multi-adaptor protein that plays an important role in regulating focal adhesion dynamics. Here, we identify TRIM15, a member of the tripartite motif protein family, as a paxillin-interacting factor and a component of focal adhesions. TRIM15 localizes to focal contacts in a myosin-II-independent manner by an interaction between its coiled-coil domain and the LD2 motif of paxillin. Unlike other focal adhesion proteins, TRIM15 is a stable focal adhesion component with restricted mobility due to its ability to form oligomers. TRIM15-depleted cells display impaired cell migration and reduced focal adhesion disassembly rates, in addition to enlarged focal adhesions. Thus, our studies demonstrate a cellular function for TRIM15 as a regulatory component of focal adhesion turnover and cell migration. PMID:25015296

Post-operative adhesions after digestive surgery: their incidence and prevention: review of the literature.

Science.gov (United States)

Ouaïssi, M; Gaujoux, S; Veyrie, N; Denève, E; Brigand, C; Castel, B; Duron, J J; Rault, A; Slim, K; Nocca, D

2012-04-01

Post-operative adhesions after gastrointestinal surgery are responsible for significant morbidity and constitute an important public health problem. The aim of this study was to review the surgical literature to determine the incidence, consequences and the variety of possible countermeasures to prevent adhesion formation. A systematic review of English and French language surgical literature published between 1995 and 2009 was performed using the keywords "adhesion" and "surgery". Peritoneal adhesions are reported as the cause of 32% of acute intestinal obstruction and 65-75% of all small bowel obstructions. It is estimated that peritoneal adhesions develop after 93-100% of upper abdominal laparotomies and after 67-93% of lower abdominal laparotomies. Nevertheless, only 15-18% of these adhesions require surgical re-intervention. The need for re-intervention for adhesion-related complications varies depending on the initial type of surgery, the postoperative course and the type of incision. The laparoscopic approach appears to decrease the risk of adhesion formation by 45% and the need for adhesion-related re-intervention to 0.8% after appendectomy and to 2.5% after colorectal surgery. At the present time, only one product consisting of hyaluronic acid applied to a layer of carboxymethylcellulose (Seprafilm(®)) has been shown to significantly reduce the incidence of postoperative adhesion formation; but this product is also associated with a significant increase in the incidence of anastomotic leakage when the membrane is applied in direct contact with the anastomosis. The use of this product has not been shown to decrease the risk of re-intervention for bowel obstruction. The prevention of postoperative adhesions is an important public health goal, particularly in light of the frequency of this complication. The routine use of anti-adhesion products is not recommended given the lack of studies with a high level of evidence concerning their efficacy and safety of

Endoscopy-Assisted Ear Surgery for Treatment of Chronic Otitis Media With Cholesteatoma, Adhesion, or Retraction Pockets.

Science.gov (United States)

Ulku, Cagatay Han

2017-06-01

The objective of this study was to analyze the results of endoscopy-assisted ear surgery for the treatment of chronic otitis media with cholesteatoma, adhesion, or retraction pockets.Fifty-one patients who underwent oto-endoscopy-assisted canal wall up tympanomastoid surgery and/or limited anterior atticotomy with tympanoplasty for chronic otitis media with cholesteatoma, adhesion, or retraction pocket from 2006 to 2013 have been included in this study. Eradication of the disease from the middle ear and mastoid air cells was achieved by combination of the oto-microscobic and oto-endoscopic approaches. Second look surgery was performed 18 months later from the initial surgery in selected patients. Age, gender, pre-/postoperative otoscopy findings/audiograms, type of the used prostheses, and follow-up time were obtained from the patient's file. Anatomic integrity rates of the tympanic membrane, the mean gains of air bone gap, on pure-tone audiogram at 4 frequencies and existence of the residual disease were reviewed parameters. Functional evaluation was made in patients with intact tympanic membrane.Of the 51 patients, the ratios of the chronic otitis media with cholesteatoma and isolated adhesive otitis or retraction pocket cases were 74.5% (38/51) and 25.5% (13/51), respectively. Ossicular chain reconstruction was made with PORP in 27 patients and TORP in 20 patients, whereas the ossicular chain was intact in 4 patients. Anatomic integrity rates of the tympanic membrane were 90.2% (46/51). The overall (n = 46) pre-/postoperative mean ABG obtained at 4 frequencies were 28.3 ± 12.26 and 9.18 ± 5.68 dB (P otitis media with cholesteatoma patients. However, there was no recurrence or new cholesteatoma formation in isolated retraction pockets or adhesive otitis patients.Oto-endoscopic eradication of the cholesteatoma or epithelial tissue from hidden area after the all visible cholesteatoma removal by oto-microscope improves the quality of surgery

Human Endometrial CD98 Is Essential for Blastocyst Adhesion

Science.gov (United States)

Domínguez, Francisco; Simón, Carlos; Quiñonero, Alicia; Ramírez, Miguel Ángel; González-Muñoz, Elena; Burghardt, Hans; Cervero, Ana; Martínez, Sebastián; Pellicer, Antonio; Palacín, Manuel; Sánchez-Madrid, Francisco; Yáñez-Mó, María

2010-01-01

Background Understanding the molecular basis of embryonic implantation is of great clinical and biological relevance. Little is currently known about the adhesion receptors that determine endometrial receptivity for embryonic implantation in humans. Methods and Principal Findings Using two human endometrial cell lines characterized by low and high receptivity, we identified the membrane receptor CD98 as a novel molecule selectively and significantly associated with the receptive phenotype. In human endometrial samples, CD98 was the only molecule studied whose expression was restricted to the implantation window in human endometrial tissue. CD98 expression was restricted to the apical surface and included in tetraspanin-enriched microdomains of primary endometrial epithelial cells, as demonstrated by the biochemical association between CD98 and tetraspanin CD9. CD98 expression was induced in vitro by treatment of primary endometrial epithelial cells with human chorionic gonadotropin, 17-β-estradiol, LIF or EGF. Endometrial overexpression of CD98 or tetraspanin CD9 greatly enhanced mouse blastocyst adhesion, while their siRNA-mediated depletion reduced the blastocyst adhesion rate. Conclusions These results indicate that CD98, a component of tetraspanin-enriched microdomains, appears to be an important determinant of human endometrial receptivity during the implantation window. PMID:20976164

Proteomic dataset of the sea urchin Paracentrotus lividus adhesive organs and secreted adhesive.

Science.gov (United States)

Lebesgue, Nicolas; da Costa, Gonçalo; Ribeiro, Raquel Mesquita; Ribeiro-Silva, Cristina; Martins, Gabriel G; Matranga, Valeria; Scholten, Arjen; Cordeiro, Carlos; Heck, Albert J R; Santos, Romana

2016-06-01

Sea urchins have specialized adhesive organs called tube feet, which mediate strong but reversible adhesion. Tube feet are composed by a disc, producing adhesive and de-adhesive secretions for substratum attachment, and a stem for movement. After detachment the secreted adhesive remains bound to the substratum as a footprint. Recently, a label-free quantitative proteomic approach coupled with the latest mass-spectrometry technology was used to analyze the differential proteome of Paracentrotus lividus adhesive organ, comparing protein expression levels in the tube feet adhesive part (the disc) versus the non-adhesive part (the stem), and also to profile the proteome of the secreted adhesive (glue). This data article contains complementary figures and results related to the research article "Deciphering the molecular mechanisms underlying sea urchin reversible adhesion: a quantitative proteomics approach" (Lebesgue et al., 2016) [1]. Here we provide a dataset of 1384 non-redundant proteins, their fragmented peptides and expression levels, resultant from the analysis of the tube feet differential proteome. Of these, 163 highly over-expressed tube feet disc proteins (>3-fold), likely representing the most relevant proteins for sea urchin reversible adhesion, were further annotated in order to determine the potential functions. In addition, we provide a dataset of 611 non-redundant proteins identified in the secreted adhesive proteome, as well as their functional annotation and grouping in 5 major protein groups related with adhesive exocytosis, and microbial protection. This list was further analyzed to identify the most abundant protein groups and pinpoint putative adhesive proteins, such as Nectin, the most abundant adhesive protein in sea urchin glue. The obtained data uncover the key proteins involved in sea urchins reversible adhesion, representing a step forward to the development of new wet-effective bio-inspired adhesives.

Proteomic dataset of the sea urchin Paracentrotus lividus adhesive organs and secreted adhesive

Directory of Open Access Journals (Sweden)

Nicolas Lebesgue

2016-06-01

Full Text Available Sea urchins have specialized adhesive organs called tube feet, which mediate strong but reversible adhesion. Tube feet are composed by a disc, producing adhesive and de-adhesive secretions for substratum attachment, and a stem for movement. After detachment the secreted adhesive remains bound to the substratum as a footprint. Recently, a label-free quantitative proteomic approach coupled with the latest mass-spectrometry technology was used to analyze the differential proteome of Paracentrotus lividus adhesive organ, comparing protein expression levels in the tube feet adhesive part (the disc versus the non-adhesive part (the stem, and also to profile the proteome of the secreted adhesive (glue. This data article contains complementary figures and results related to the research article “Deciphering the molecular mechanisms underlying sea urchin reversible adhesion: a quantitative proteomics approach” (Lebesgue et al., 2016 [1]. Here we provide a dataset of 1384 non-redundant proteins, their fragmented peptides and expression levels, resultant from the analysis of the tube feet differential proteome. Of these, 163 highly over-expressed tube feet disc proteins (>3-fold, likely representing the most relevant proteins for sea urchin reversible adhesion, were further annotated in order to determine the potential functions. In addition, we provide a dataset of 611 non-redundant proteins identified in the secreted adhesive proteome, as well as their functional annotation and grouping in 5 major protein groups related with adhesive exocytosis, and microbial protection. This list was further analyzed to identify the most abundant protein groups and pinpoint putative adhesive proteins, such as Nectin, the most abundant adhesive protein in sea urchin glue. The obtained data uncover the key proteins involved in sea urchins reversible adhesion, representing a step forward to the development of new wet-effective bio-inspired adhesives.

Energetics, kinetics, and pathway of SNARE folding and assembly revealed by optical tweezers.

Science.gov (United States)

Zhang, Yongli

2017-07-01

Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) are universal molecular engines that drive membrane fusion. Particularly, synaptic SNAREs mediate fast calcium-triggered fusion of neurotransmitter-containing vesicles with plasma membranes for synaptic transmission, the basis of all thought and action. During membrane fusion, complementary SNAREs located on two apposed membranes (often called t- and v-SNAREs) join together to assemble into a parallel four-helix bundle, releasing the energy to overcome the energy barrier for fusion. A long-standing hypothesis suggests that SNAREs act like a zipper to draw the two membranes into proximity and thereby force them to fuse. However, a quantitative test of this SNARE zippering hypothesis was hindered by difficulties to determine the energetics and kinetics of SNARE assembly and to identify the relevant folding intermediates. Here, we first review different approaches that have been applied to study SNARE assembly and then focus on high-resolution optical tweezers. We summarize the folding energies, kinetics, and pathways of both wild-type and mutant SNARE complexes derived from this new approach. These results show that synaptic SNAREs assemble in four distinct stages with different functions: slow N-terminal domain association initiates SNARE assembly; a middle domain suspends and controls SNARE assembly; and rapid sequential zippering of the C-terminal domain and the linker domain directly drive membrane fusion. In addition, the kinetics and pathway of the stagewise assembly are shared by other SNARE complexes. These measurements prove the SNARE zippering hypothesis and suggest new mechanisms for SNARE assembly regulated by other proteins. © 2017 The Protein Society.

Effect of adhesive thickness on adhesively bonded T-joint

International Nuclear Information System (INIS)

Abdullah, A R; Afendi, Mohd; Majid, M S Abdul

2013-01-01

The aim of this work is to analyze the effect of adhesive thickness on tensile strength of adhesively bonded stainless steel T-joint. Specimens were made from SUS 304 Stainless Steel plate and SUS 304 Stainless Steel perforated plate. Four T-joint specimens with different adhesive thicknesses (0.5, 1.0, 1.5 and 2.0 mm) were made. Experiment result shows T-joint specimen with adhesive thickness of 1.0 mm yield highest maximum load. Identical T-joint specimen jointed by spot welding was also tested. Tensile test shows welded T-Joint had eight times higher tensile load than adhesively bonded T-joint. However, in low pressure application such as urea granulator chamber, high tensile strength is not mandatory. This work is useful for designer in fertilizer industry and others who are searching for alternative to spot welding

Membrane manufacture for peptide separations

KAUST Repository

Kim, Dooli; Salazar Moya, Octavio Ruben; Nunes, Suzana Pereira

2016-01-01

Nanostructured polymeric membranes are key tools in biomedical applications such as hemodialysis, protein separations, in the food industry, and drinking water supply from seawater. Despite of the success in different separation processes, membrane manufacture itself is at risk, since the most used solvents are about to be banned in many countries due to environmental and health issues. We propose for the first time the preparation of polyethersulfone membranes based on dissolution in the ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM]DEP). We obtained a series of membranes tailored for separation of solutes with molecular weight of 30, 5, 1.3, and 1.25 kg mol-1 with respective water permeances of 140, 65, 30 and 20 Lm-2h-1bar-1. We demonstrate their superior efficiency in the separation of complex mixtures of peptides with molecular weights in the range of 800 to 3500 gmol-1. Furthermore, the thermodynamics and kinetics of phase separation leading to the pore formation in the membranes were investigated. The rheology of the solutions and the morphology of the prepared membranes were examed and compared to those of polyethersulfone in organic solvents currently used for membrane manufacture.

Membrane manufacture for peptide separations

KAUST Repository

Kim, Dooli

2016-06-07

Nanostructured polymeric membranes are key tools in biomedical applications such as hemodialysis, protein separations, in the food industry, and drinking water supply from seawater. Despite of the success in different separation processes, membrane manufacture itself is at risk, since the most used solvents are about to be banned in many countries due to environmental and health issues. We propose for the first time the preparation of polyethersulfone membranes based on dissolution in the ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM]DEP). We obtained a series of membranes tailored for separation of solutes with molecular weight of 30, 5, 1.3, and 1.25 kg mol-1 with respective water permeances of 140, 65, 30 and 20 Lm-2h-1bar-1. We demonstrate their superior efficiency in the separation of complex mixtures of peptides with molecular weights in the range of 800 to 3500 gmol-1. Furthermore, the thermodynamics and kinetics of phase separation leading to the pore formation in the membranes were investigated. The rheology of the solutions and the morphology of the prepared membranes were examed and compared to those of polyethersulfone in organic solvents currently used for membrane manufacture.

Proteomic dataset of the sea urchin Paracentrotus lividus adhesive organs and secreted adhesive

NARCIS (Netherlands)

Lebesgue, Nicolas; da Costa, Gonçalo; Ribeiro, Raquel Mesquita; Ribeiro-Silva, Cristina; Martins, Gabriel G; Matranga, Valeria; Scholten, Arjen; Cordeiro, Carlos; Heck, Albert J R; Santos, Romana

Sea urchins have specialized adhesive organs called tube feet, which mediate strong but reversible adhesion. Tube feet are composed by a disc, producing adhesive and de-adhesive secretions for substratum attachment, and a stem for movement. After detachment the secreted adhesive remains bound to the

Membrane filtration device for studying compression of fouling layers in membrane bioreactors.

Directory of Open Access Journals (Sweden)

Mads Koustrup Jørgensen

Full Text Available A filtration devise was developed to assess compressibility of fouling layers in membrane bioreactors. The system consists of a flat sheet membrane with air scouring operated at constant transmembrane pressure to assess the influence of pressure on resistance of fouling layers. By fitting a mathematical model, three model parameters were obtained; a back transport parameter describing the kinetics of fouling layer formation, a specific fouling layer resistance, and a compressibility parameter. This stands out from other on-site filterability tests as model parameters to simulate filtration performance are obtained together with a characterization of compressibility. Tests on membrane bioreactor sludge showed high reproducibility. The methodology's ability to assess compressibility was tested by filtrations of sludges from membrane bioreactors and conventional activated sludge wastewater treatment plants from three different sites. These proved that membrane bioreactor sludge showed higher compressibility than conventional activated sludge. In addition, detailed information on the underlying mechanisms of the difference in fouling propensity were obtained, as conventional activated sludge showed slower fouling formation, lower specific resistance and lower compressibility of fouling layers, which is explained by a higher degree of flocculation.

Contribution of a submerged membrane bioreactor in the treatment of synthetic effluent contaminated by Bisphenol-A: Mechanism of BPA removal and membrane fouling

International Nuclear Information System (INIS)

Seyhi, Brahima; Drogui, Patrick; Buelna, Gerardo; Azaïs, Antonin; Heran, Marc

2013-01-01

A submerged membrane bioreactor has been operated at the laboratory scale for the treatment of a synthetic effluent containing Bisphenol-A (BPA). COD, NH 4 –N, PO 4 –P and BPA were eliminated respectively, at 99%, 99%, 61% and 99%. The increase of volumetric loading rate from 0 to 21.6 g/m 3 /d did not affect the performance of the MBR system. However, the removal rate decreased rapidly when the BPA loading rate increased above 21.6 g/m 3 /d. The adsorption process of BPA on the biomass was very well described by Freundlich and Langmuir isotherms. Subsequently, biodegradation of BPA occurred and followed the first order kinetic reaction, with a constant rate of 1.13 ± 0.22 h −1 . During treatment, membrane fouling was reversible in the first 84 h of filtration, and then became irreversible. The membrane fouling was mainly due to the accumulation of suspended solid and development of biofilm on the membrane surface. -- Highlights: •High BPA removal rates (up to 99%) were obtained in the MBR. •A limit of the toxicity of 21.6 g/m 3 /d of BPA was recorded for the MBR. •The first order kinetic model described very well the biodegradation process for BPA. •The kinetic rates (0.61–1.13 h −1 ) depend on BPA loading (0.10–0.50 mg/g TSS). •The initial organic loading (0.04 and 0.20 g COD g −1 TSS) did not affect the kinetic. -- High BPA removal rates (up to 99%) were obtained in the MBR, with a limit of the toxicity closed to 21.6 g/m 3 /d of BPA

Bioactive 3D-Shaped Wound Dressings Synthesized from Bacterial Cellulose: Effect on Cell Adhesion of Polyvinyl Alcohol Integrated In Situ

Directory of Open Access Journals (Sweden)

Marlon Osorio

2017-01-01

Full Text Available We investigated wound dressing composites comprising fibrils of bacterial cellulose (BC grown by fermentation in the presence of polyvinyl alcohol (PVA followed by physical crosslinking. The reference biointerface, neat BC, favoured adhesion of fibroblasts owing to size exclusion effects. Furthermore, it resisted migration across the biomaterial. Such effects were minimized in the case of PVA/BC membranes. Therefore, the latter are suggested in cases where cell adhesion is to be avoided, for instance, in the design of interactive wound dressings with facile exudate control. The bioactivity and other properties of the membranes were related to their morphology and structure and considered those of collagen fibres. Bioactive materials were produced by simple 3D templating of BC during growth and proposed for burn and skin ulcer treatment.

Chapter 9:Wood Adhesion and Adhesives

Science.gov (United States)

Charles R. Frihart

2013-01-01

The recorded history of bonding wood dates back at least 3000 years to the Egyptians (Skeist and Miron 1990, River 1994a), and adhesive bonding goes back to early mankind (Keimel 2003). Although wood and paper bonding are the largest applications for adhesives, some of the fundamental aspects leading to good bonds are not fully understood. Better understanding of these...

Effects of physical and chemical aspects on membrane fouling and cleaning using interfacial free energy analysis in forward osmosis.

Science.gov (United States)

Zhang, Wanzhu; Dong, Bingzhi

2018-05-20

Natural organic matter (NOM) in micro-polluted water purification using membranes is a critical issue to handle. Understanding the fouling mechanism in the forward osmosis (FO) process, particularly identifying the predominant factor that controls membrane fouling, could have significant effects on exerting the advantages of FO technique. Cellulose triacetate no-woven (CTA-NW) membrane is applied to experiments with a high removal efficiency (> 99%) for the model foulant. Tannic acid (TA) is used as a surrogate foulant for NOM in the membrane fouling process, thus enabling the analysis of the effects of physical and chemical aspects of water flux, retention, and adsorption. The membrane fouling behavior is affected mainly by the combined effects of the osmotic dragging force and the interaction of the pH in the working solution, foulants, and calcium ions, as demonstrated by the water flux loss and the changes of membrane retention and adsorption. The fouled CTA-NW membrane (in PRO mode) could be flux-recovered by > 85% through physical cleaning methods. The interfacial free energy analysis theory was used to analyze the membrane fouling behavior with calculating the interfacial cohesion and adhesion free energies. The cohesion free energy refers to the deposition of foulants (TA or TA combined with calcium ions) on a fouled membrane. In addition, the adhesion free energy could be used to evaluate the interaction between foulants and a clean membrane.

Structure formation of lipid membranes: Membrane self-assembly and vesicle opening-up to octopus-like micelles

Science.gov (United States)

Noguchi, Hiroshi

2013-02-01

We briefly review our recent studies on self-assembly and vesicle rupture of lipid membranes using coarse-grained molecular simulations. For single component membranes, lipid molecules self-assemble from random gas states to vesicles via disk-shaped clusters. Clusters aggregate into larger clusters, and subsequently the large disks close into vesicles. The size of vesicles are determined by kinetics than by thermodynamics. When a vesicle composed of lipid and detergent types of molecules is ruptured, a disk-shaped micelle called bicelle can be formed. When both surfactants have negligibly low critical micelle concentration, it is found that bicelles connected with worm-like micelles are also formed depending on the surfactant ratio and spontaneous curvature of the membrane monolayer.

Biomimetic surface modification of polypropylene by surface chain transfer reaction based on mussel-inspired adhesion technology and thiol chemistry

Energy Technology Data Exchange (ETDEWEB)

Niu, Zhijun; Zhao, Yang; Sun, Wei; Shi, Suqing, E-mail: shisq@nwu.edu.cn; Gong, Yongkuan

2016-11-15

Highlights: • Biomimetic surface modification of PP was successfully conducted by integrating mussel-inspired technology, thiol chemistry and cell outer membranes-like structures. • The resultant biomimetic surface exhibits good interface and surface stability. • The obvious suppression of protein adsorption and platelet adhesion is also achieved. • The residue thoil groups on the surface could be further functionalized. - Abstract: Biomimetic surface modification of polypropylene (PP) is conducted by surface chain transfer reaction based on the mussel-inspired versatile adhesion technology and thiol chemistry, using 2-methacryloyloxyethylphosphorylcholine (MPC) as a hydrophilic monomer mimicking the cell outer membrane structure and 2,2-azobisisobutyronitrile (AIBN) as initiator in ethanol. A layer of polydopamine (PDA) is firstly deposited onto PP surface, which not only offers good interfacial adhesion with PP, but also supplies secondary reaction sites (-NH{sub 2}) to covalently anchor thiol groups onto PP surface. Then the radical chain transfer to surface-bonded thiol groups and surface re-initiated polymerization of MPC lead to the formation of a thin layer of polymer brush (PMPC) with cell outer membrane mimetic structure on PP surface. X-ray photoelectron spectrophotometer (XPS), atomic force microscopy (AFM) and water contact angle measurements are used to characterize the PP surfaces before and after modification. The protein adsorption and platelet adhesion experiments are also employed to evaluate the interactions of PP surface with biomolecules. The results show that PMPC is successfully grafted onto PP surface. In comparison with bare PP, the resultant PP-PMPC surface exhibits greatly improved protein and platelet resistance performance, which is the contribution of both increased surface hydrophilicity and zwitterionic structure. More importantly, the residue thiol groups on PP-PMPC surface create a new pathway to further functionalize such

Biomimetic surface modification of polypropylene by surface chain transfer reaction based on mussel-inspired adhesion technology and thiol chemistry

International Nuclear Information System (INIS)

Niu, Zhijun; Zhao, Yang; Sun, Wei; Shi, Suqing; Gong, Yongkuan

2016-01-01

Highlights: • Biomimetic surface modification of PP was successfully conducted by integrating mussel-inspired technology, thiol chemistry and cell outer membranes-like structures. • The resultant biomimetic surface exhibits good interface and surface stability. • The obvious suppression of protein adsorption and platelet adhesion is also achieved. • The residue thoil groups on the surface could be further functionalized. - Abstract: Biomimetic surface modification of polypropylene (PP) is conducted by surface chain transfer reaction based on the mussel-inspired versatile adhesion technology and thiol chemistry, using 2-methacryloyloxyethylphosphorylcholine (MPC) as a hydrophilic monomer mimicking the cell outer membrane structure and 2,2-azobisisobutyronitrile (AIBN) as initiator in ethanol. A layer of polydopamine (PDA) is firstly deposited onto PP surface, which not only offers good interfacial adhesion with PP, but also supplies secondary reaction sites (-NH 2 ) to covalently anchor thiol groups onto PP surface. Then the radical chain transfer to surface-bonded thiol groups and surface re-initiated polymerization of MPC lead to the formation of a thin layer of polymer brush (PMPC) with cell outer membrane mimetic structure on PP surface. X-ray photoelectron spectrophotometer (XPS), atomic force microscopy (AFM) and water contact angle measurements are used to characterize the PP surfaces before and after modification. The protein adsorption and platelet adhesion experiments are also employed to evaluate the interactions of PP surface with biomolecules. The results show that PMPC is successfully grafted onto PP surface. In comparison with bare PP, the resultant PP-PMPC surface exhibits greatly improved protein and platelet resistance performance, which is the contribution of both increased surface hydrophilicity and zwitterionic structure. More importantly, the residue thiol groups on PP-PMPC surface create a new pathway to further functionalize such

Adhesion behavior of endothelial progenitor cells to endothelial cells in simple shear flow

Science.gov (United States)

Gong, Xiao-Bo; Li, Yu-Qing; Gao, Quan-Chao; Cheng, Bin-Bin; Shen, Bao-Rong; Yan, Zhi-Qiang; Jiang, Zong-Lai

2011-12-01

The adhesion of endothelial progenitor cells (EPCs) on endothelial cells (ECs) is one of the critical physiological processes for the regenesis of vascular vessels and the prevention of serious cardiovascular diseases. Here, the rolling and adhesion behavior of EPCs on ECs was studied numerically. A two-dimensional numerical model was developed based on the immersed boundary method for simulating the rolling and adhesion of cells in a channel flow. The binding force arising from the catch bond of a receptor and ligand pair was modeled with stochastic Monte Carlo method and Hookean spring model. The effect of tumor necrosis factor alpha (TNF- α) on the expression of the number of adhesion molecules in ECs was analyzed experimentally. A flow chamber system with CCD camera was set up to observe the top view of the rolling of EPCs on the substrate cultivated with ECs. Numerical results prove that the adhesion of EPC on ECs is closely related to membrane stiffness of the cell and shear rate of the flow. It also suggests that the adhesion force between EPC and EC by P-selectin glycoprotein ligand-1 only is not strong enough to bond the cell onto vessel walls unless contributions of other catch bond are considered. Experimental results demonstrate that TNF- α enhanced the expressions of VCAM, ICAM, P-selectin and E-selectin in ECs, which supports the numerical results that the rolling velocity of EPC on TNF- α treated EC substrate decreases obviously compared with its velocity on the untreated one. It is found that because the adhesion is affected by both the rolling velocity and the deformability of the cell, an optimal stiffness of EPC may exist at a given shear rate of flow for achieving maximum adhesion rates.

Inertial and stick-slip regimes of unstable adhesive tape peeling.

Science.gov (United States)

Dalbe, Marie-Julie; Villey, Richard; Ciccotti, Matteo; Santucci, Stéphane; Cortet, Pierre-Philippe; Vanel, Loïc

2016-05-18

We present an experimental characterization of the detachment front unstable dynamics observed during the peeling of pressure sensitive adhesives. We use an experimental set-up specifically designed to control the peeling angle θ and the peeled tape length L, while peeling an adhesive tape from a flat substrate at a constant driving velocity V. High-speed imaging allows us to report the evolution of the period and amplitude of the front oscillations, as well as the relative durations of their fast and slow phases, as a function of the control parameters V, L and θ. Our study shows that, as the driving velocity or the peeling angle increases, the oscillations of the peeling front progressively evolve from genuine "stick-slip" oscillations, made of alternating long stick phases and very brief slip phases, to sinusoidal oscillations of amplitude twice the peeling velocity. We propose a model which, taking into account the peeling angle-dependent kinetic energy cost to accelerate and decelerate the peeled tape, explains the transition from the "stick-slip" to the "inertial" regime of the dynamical instability. Using independent direct measurements of the effective fracture energy of the adhesive-substrate joint, we show that our model quantitatively accounts for the two regimes of the unstable dynamics.

Polymer Electrolyte Membranes for Water Photo-Electrolysis

Science.gov (United States)

Aricò, Antonino S.; Girolamo, Mariarita; Siracusano, Stefania; Sebastian, David; Baglio, Vincenzo; Schuster, Michael

2017-01-01

Water-fed photo-electrolysis cells equipped with perfluorosulfonic acid (Nafion® 115) and quaternary ammonium-based (Fumatech® FAA3) ion exchange membranes as separator for hydrogen and oxygen evolution reactions were investigated. Protonic or anionic ionomer dispersions were deposited on the electrodes to extend the interface with the electrolyte. The photo-anode consisted of a large band-gap Ti-oxide semiconductor. The effect of membrane characteristics on the photo-electrochemical conversion of solar energy was investigated for photo-voltage-driven electrolysis cells. Photo-electrolysis cells were also studied for operation under electrical bias-assisted mode. The pH of the membrane/ionomer had a paramount effect on the photo-electrolytic conversion. The anionic membrane showed enhanced performance compared to the Nafion®-based cell when just TiO2 anatase was used as photo-anode. This was associated with better oxygen evolution kinetics in alkaline conditions compared to acidic environment. However, oxygen evolution kinetics in acidic conditions were significantly enhanced by using a Ti sub-oxide as surface promoter in order to facilitate the adsorption of OH species as precursors of oxygen evolution. However, the same surface promoter appeared to inhibit oxygen evolution in an alkaline environment probably as a consequence of the strong adsorption of OH species on the surface under such conditions. These results show that a proper combination of photo-anode and polymer electrolyte membrane is essential to maximize photo-electrolytic conversion. PMID:28468242

Receptor-like Molecules on Human Intestinal Epithelial Cells Interact with an Adhesion Factor from Lactobacillus reuteri.

Science.gov (United States)

Matsuo, Yosuke; Miyoshi, Yukihiro; Okada, Sanae; Satoh, Eiichi

2012-01-01

A surface protein of Lactobacillus reuteri, mucus adhesion-promoting protein (MapA), is considered to be an adhesion factor. MapA is expressed in L. reuteri strains and adheres to piglet gastric mucus, collagen type I, and human intestinal epithelial cells such as Caco-2. The aim of this study was to identify molecules that mediate the attachment of MapA from L. reuteri to the intestinal epithelial cell surface by investigating the adhesion of MapA to receptor-like molecules on Caco-2 cells. MapA-binding receptor-like molecules were detected in Caco-2 cell lysates by 2D-PAGE. Two proteins, annexin A13 (ANXA13) and paralemmin (PALM), were identified by MALDI TOF-MS. The results of a pull-down assay showed that MapA bound directly to ANXA13 and PALM. Fluorescence microscopy studies confirmed that MapA binding to ANXA13 and PALM was colocalized on the Caco-2 cell membrane. To evaluate whether ANXA13 and PALM are important for MapA adhesion, ANXA13 and PALM knockdown cell lines were established. The adhesion of MapA to the abovementioned cell lines was reduced compared with that to wild-type Caco-2 cells. These knockdown experiments established the importance of these receptor-like molecules in MapA adhesion.

Analysis of the kinetics of ovine follitropin agonist-antagonist interactions with pig ovarian membranes

Energy Technology Data Exchange (ETDEWEB)

Sebok, K.; De Lean, A.; Sairam, M.R.

1987-06-16

The binding of /sup 125/I-labeled ovine follitropin (oFSH) and /sup 125/I-labeled deglycosylated ovine follitropin (DG-oFSH) to porcine granulosa cell membranes was studied at equilibrium and nonequilibrium binding conditions and statically analyzed. Saturation and competition binding experiments revealed homogeneity in the population of binding sites labeled with /sup 125/I-oFSH, having a pK estimation of approx.10. /sup 125/I-DG-oFSH similarly interacts with a single uniform class of receptors of equal affinity (pK approx. 10) and binding capacity as oFSH. In contrast, displacement experiments using /sup 125/I-DG-oFSH as tracer and unlabeled oFSH as competing ligand demonstrate slope factors less than unity, suggesting apparent heterogeneity of sites not observed with /sup 125/I-DG-oFSH vs. DG-oFSH competition experiments. Under these conditions, it appears that FSH binds to two sites in near equal proportion but of unequal affinities. The total specific binding capacities of these sites equal those observed in /sup 125/I-DG-oFSH/unlabeled DG-oFSH competition experiments. Analysis of oFSH association kinetics at 37 /sup 0/C by curve-fitting methods is best explained by a biexponential rate equation describing a fast and a slow association component that are equally distributed. DG-oFSH demonstrates a disproportionately greater amount of fast vs. slow binding component. Dissociation, promoted by the same unlabeled hormone, of bound /sup 125/I-DG-oFSH and /sup 125/I-oFSH induces biphasic kinetics consisting of a fast and a slow dissociable pool of prebound tracer. Computer analysis reveals that both tracers dissociate with similar fast t/sub 1/2/ times; however, DG-oFSH exhibited a t/sub 1/2/ approximately 2 times slower for the component vs. oFSH. From this study, it is concluded that oFSH and DG-oFSH bind to the receptor(s) in a complex reaction scheme, more so for oFSH than DG-oFSH.

Design and fabrication of polymer based dry adhesives inspired by the gecko adhesive system

Science.gov (United States)

Jin, Kejia

There has been significant interest in developing dry adhesives mimicking the gecko adhesive system, which offers several advantages compared to conventional pressure sensitive adhesives. Specifically, gecko adhesive pads have anisotropic adhesion properties: the adhesive pads (spatulae) stick strongly when sheared in one direction but are non-adherent when sheared in the opposite direction. This anisotropy property is attributed to the complex topography of the array of fine tilted and curved columnar structures (setae) that bear the spatulae. In this thesis, easy, scalable methods, relying on conventional and unconventional techniques are presented to incorporate tilt in the fabrication of synthetic polymer-based dry adhesives mimicking the gecko adhesive system, which provide anisotropic adhesion properties. In the first part of the study, the anisotropic adhesion and friction properties of samples with various tilt angles to test the validity of a nanoscale tape-peeling model of spatular function are measured. Consistent with the Peel Zone model, samples with lower tilt angles yielded larger adhesion forces. Contact mechanics of the synthetic array were highly anisotropic, consistent with the frictional adhesion model and gecko-like. Based on the original design, a new design of gecko-like dry adhesives was developed which showed superior tribological properties and furthermore showed anisotropic adhesive properties without the need for tilt in the structures. These adhesives can be used to reversibly suspend weights from vertical surfaces (e.g., walls) and, for the first time to our knowledge, horizontal surfaces (e.g., ceilings) by simultaneously and judiciously activating anisotropic friction and adhesion forces. Furthermore, adhesion properties between artificial gecko-inspired dry adhesives and rough substrates with varying roughness are studied. The results suggest that both adhesion and friction forces on a rough substrate depends significantly on the

Binding kinetics of Clostridium difficile toxins A and B to intestinal brush border membranes from infant and adult hamsters

International Nuclear Information System (INIS)

Rolfe, R.D.

1991-01-01

This study was undertaken to determine if the relative resistance of neonates and infants to Clostridium difficile-associated intestinal disease can be related to age-dependent differences in intestinal receptors for C. difficile toxins A and B. Brush border membranes (BBMs) from the small intestines of adult and infant hamsters were examined for their ability to bind radiolabeled toxins A and B. [125I]toxin A bound to both infant and adult hamster BBMs at physiological temperature, whereas [125I]toxin B did not bind to the BBMs under any of the conditions examined. The number of [125I]toxin A molecules bound at saturation was approximately 4 x 10(10) per micrograms of membrane protein for adult BBMs and 1 x 10(11) per micrograms of membrane protein for infant BBMs. Scatchard plot analysis suggested the presence of a single class of toxin A binding sites on both infant and adult hamster BBMs. Maximal binding capacity and Kd values were 0.63 pmol/mg of protein and 66.7 nM, respectively, for the infant BBMs, and 0.24 pmol/mg of protein and 27 nM, respectively, for the adult BBMs. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analyses of extracted BBM proteins revealed differences in the proteins of infant and adult BBMs. However, there were not any detectable differences in the protein bands which bound [125I]toxin A between infant and adult hamsters. The results from these investigations indicate that differences in the binding kinetics of toxins A and/or B to infant and adult hamster BBMs do not account for the observed differences in their susceptibility to C. difficile-associated intestinal disease

Binding kinetics of Clostridium difficile toxins A and B to intestinal brush border membranes from infant and adult hamsters

Energy Technology Data Exchange (ETDEWEB)

Rolfe, R.D. (Texas Tech Univ. Health Sciences Center, Lubbock (USA))

1991-04-01

This study was undertaken to determine if the relative resistance of neonates and infants to Clostridium difficile-associated intestinal disease can be related to age-dependent differences in intestinal receptors for C. difficile toxins A and B. Brush border membranes (BBMs) from the small intestines of adult and infant hamsters were examined for their ability to bind radiolabeled toxins A and B. (125I)toxin A bound to both infant and adult hamster BBMs at physiological temperature, whereas (125I)toxin B did not bind to the BBMs under any of the conditions examined. The number of (125I)toxin A molecules bound at saturation was approximately 4 x 10(10) per micrograms of membrane protein for adult BBMs and 1 x 10(11) per micrograms of membrane protein for infant BBMs. Scatchard plot analysis suggested the presence of a single class of toxin A binding sites on both infant and adult hamster BBMs. Maximal binding capacity and Kd values were 0.63 pmol/mg of protein and 66.7 nM, respectively, for the infant BBMs, and 0.24 pmol/mg of protein and 27 nM, respectively, for the adult BBMs. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analyses of extracted BBM proteins revealed differences in the proteins of infant and adult BBMs. However, there were not any detectable differences in the protein bands which bound (125I)toxin A between infant and adult hamsters. The results from these investigations indicate that differences in the binding kinetics of toxins A and/or B to infant and adult hamster BBMs do not account for the observed differences in their susceptibility to C. difficile-associated intestinal disease.

Adhesion property of epoxidized natural rubber (ENR-based adhesives containing calcium carbonate

Directory of Open Access Journals (Sweden)

2008-06-01

Full Text Available The adhesion property (i.e. viscosity, loop tack and peel strength of epoxidized natural rubber (ENR 25 and ENR 50 grade-based pressure-sensitive adhesive was studied in the presence of calcium carbonate. The range of calcium carbonate loaded was from 10 to 50 parts per hundred parts of rubber (phr. Coumarone-indene resin was used as the tackifier and its concentration was fixed at 80 phr. Toluene was chosen as the solvent throughout the investigation. The substrates (PET film/paper were coated with the adhesive using a SHEEN hand coater at a coating thickness of 60 µm. Viscosity of the adhesive was measured by a HAAKE Rotary Viscometer whereas loop tack and peel strength were determined by a Llyod Adhesion Tester operating at 30 cm/min. Results show that viscosity of ENR-based adhesives increases gradually with increase in calcium carbonate loading due to the concentration effect of the filler. However, for loop tack and peel strength, it passes through a maximum at 30 phr calcium carbonate, an observation which is attributed to the optimum wettability of adhesive on the substrate at this adhesive composition. ENR 25-based adhesive consistently exhibits higher adhesion property than ENR 50 for all calcium carbonate loadings studied.

The Kinetics of Carrier Transport Inhibition

DEFF Research Database (Denmark)

Rosenberg, T.; Wilbrandt, Robert Walter

1962-01-01

The kinetical treatment of enzymatic carrier transports as given in previous communications has been extended to conditions of inhibition. Various possible types of inhibitors have been considered differing in the site of attack (enzyme or carrier), in the mode of action (competing with the subst......The kinetical treatment of enzymatic carrier transports as given in previous communications has been extended to conditions of inhibition. Various possible types of inhibitors have been considered differing in the site of attack (enzyme or carrier), in the mode of action (competing...... with the substrate for the enzyme or the carrier or for both, competing with the carrier for the enzyme, or non-competitive) and in the ability of penetrating the membrane. Experiments are reported on the inhibition of glucose and fructose transport across the human red cell membrane by phlorizine, phloretine...... and polyphloretinephosphate. The results of the analysis for these inhibitors indicate a substrate competitive mode of action. The effect of reversing the transport direction by interchanging the substrate concentration has been treated for the case of a non-penetrating substrate competitive inhibitor in the external medium...

Single-cell force spectroscopy as a technique to quantify human red blood cell adhesion to subendothelial laminin.

Science.gov (United States)

Maciaszek, Jamie L; Partola, Kostyantyn; Zhang, Jing; Andemariam, Biree; Lykotrafitis, George

2014-12-18

Single-cell force spectroscopy (SCFS), an atomic force microscopy (AFM)-based assay, enables quantitative study of cell adhesion while maintaining the native state of surface receptors in physiological conditions. Human healthy and pathological red blood cells (RBCs) express a large number of surface proteins which mediate cell-cell interactions, or cell adhesion to the extracellular matrix. In particular, RBCs adhere with high affinity to subendothelial matrix laminin via the basal cell adhesion molecule and Lutheran protein (BCAM/Lu). Here, we established SCFS as an in vitro technique to study human RBC adhesion at baseline and following biochemical treatment. Using blood obtained from healthy human subjects, we recorded adhesion forces from single RBCs attached to AFM cantilevers as the cell was pulled-off of substrates coated with laminin protein. We found that an increase in the overall cell adhesion measured via SCFS is correlated with an increase in the resultant total force measured on 1 µm(2) areas of the RBC membrane. Further, we showed that SCFS can detect significant changes in the adhesive response of RBCs to modulation of the cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) pathway. Lastly, we identified variability in the RBC adhesion force to laminin amongst the human subjects, suggesting that RBCs maintain diverse levels of active BCAM/Lu adhesion receptors. By using single-cell measurements, we established a powerful new method for the quantitative measurement of single RBC adhesion with specific receptor-mediated binding. Copyright © 2014 Elsevier Ltd. All rights reserved.

Strong composition dependence of adhesive properties of ultraviolet curing adhesives with modified acrylates

Science.gov (United States)

Feng, Yefeng; Li, Yandong; Wang, Fupeng; Peng, Cheng; Xu, Zhichao; Hu, Jianbing

2018-05-01

Ultraviolet (UV) curable adhesives have been widely researched in fields of health care and electronic components. UV curing systems with modified acrylic ester prepolymers have been frequently employed. In order to clarify composition dependence of adhesive properties of adhesives containing modified acrylates, in this work, several UV curing adhesives bearing urethane and epoxy acrylates were designed and fabricated. The effects of prepolymer, diluent, feed ratio, initiator and assistant on adhesive performances were investigated. This work might offer a facile route to gain promising high-performance UV curable adhesives with desired adhesive traits through regulating their compositions.

Removal of glyphosate herbicide from water using biopolymer membranes.

Science.gov (United States)

Carneiro, Rafael T A; Taketa, Thiago B; Gomes Neto, Reginaldo J; Oliveira, Jhones L; Campos, Estefânia V R; de Moraes, Mariana A; da Silva, Camila M G; Beppu, Marisa M; Fraceto, Leonardo F

2015-03-15

Enormous amounts of pesticides are manufactured and used worldwide, some of which reach soils and aquatic systems. Glyphosate is a non-selective herbicide that is effective against all types of weeds and has been used for many years. It can therefore be found as a contaminant in water, and procedures are required for its removal. This work investigates the use of biopolymeric membranes prepared with chitosan (CS), alginate (AG), and a chitosan/alginate combination (CS/AG) for the adsorption of glyphosate present in water samples. The adsorption of glyphosate by the different membranes was investigated using the pseudo-first order and pseudo-second order kinetic models, as well as the Langmuir and Freundlich isotherm models. The membranes were characterized regarding membrane solubility, swelling, mechanical, chemical and morphological properties. The results of kinetics experiments showed that adsorption equilibrium was reached within 4 h and that the CS membrane presented the best adsorption (10.88 mg of glyphosate/g of membrane), followed by the CS/AG bilayer (8.70 mg of glyphosate/g of membrane). The AG membrane did not show any adsorption capacity for this herbicide. The pseudo-second order model provided good fits to the glyphosate adsorption data on CS and CS/AG membranes, with high correlation coefficient values. Glyphosate adsorption by the membranes could be fitted by the Freundlich isotherm model. There was a high affinity between glyphosate and the CS membrane and moderate affinity in the case of the CS/AG membrane. Physico-chemical characterization of the membranes showed low values of solubility in water, indicating that the membranes are stable and not soluble in water. The SEM and AFM analysis showed evidence of the presence of glyphosate on CS membranes and on chitosan face on CS/AG membranes. The results showed that the glyphosate herbicide can be adsorbed by chitosan membranes and the proposed membrane-based methodology was successfully used to

Biocompatibility studies of polyacrylonitrile membranes modified with carboxylated polyetherimide

Energy Technology Data Exchange (ETDEWEB)

Senthilkumar, S.; Rajesh, S.; Jayalakshmi, A.; Mohan, D., E-mail: mohantarun@gmail.com

2013-10-15

Poly (ether-imide) (PEI) was carboxylated and used as the hydrophilic modification agent for the preparation of polyacrylonitrile (PAN) membranes. Membranes were prepared with different blend compositions of PAN and CPEI by diffusion induced precipitation. The modified membranes were characterized by thermo gravimetric analysis (TGA), mechanical analysis, scanning electron microscopy (SEM) and contact angle measurement to understand the influence of CPEI on the properties of the membranes. The biocompatibility studies exhibited reduced plasma protein adsorption, platelet adhesion and thrombus formation on the modified membrane surface. The complete blood count (CBC) results of CPEI incorporated membranes showed stable CBC values and significant decrease in the complement activation were also observed. In addition to good cytocompatibility, monocytes cultured on these modified membranes exhibited improved functional profiles in 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. Thus it could be concluded that PAN/CPEI membranes with excellent biocompatibility can be useful for hemodialysis. Highlights: • Carboxylated PEI was prepared and utilized as hydrophilic modification agent. • CPEI incorporated into PAN to improved biocompatibility and cyto compatibility • Biocompatibility of membranes was correlated with morphology and hydrophilicity. • Antifouling studies of the PAN/CPEI membranes was studied by BSA as model foulant.

Feasibility of liquid membrane extraction in nuclear field. Vol. 1

Energy Technology Data Exchange (ETDEWEB)

Macasek, F [Department of Nuclear Chemistry, Comenius University SK-84215 Bratislava, (Slovakia)

1996-03-01

Membrane separation processes are widely used in separation science mainly in food and water processing. It is discussed, how far the liquid membranes, both supported and emulsion ones are suitable for trace metals, and radionuclides recovery from aqueous solutions and wastes. The advantage of liquid membranes processes are in high preconcentration capability, also emulsion membranes provides possibility to use kinetic effects for specific separation. Radiation sensitivity of the systems is considered as well as the main disadvantage because of surface active products accumulation in such systems. 3 figs.

Block Copolymers for Alkaline Fuel Cell Membrane Materials

Science.gov (United States)

2014-07-30

temperature fuel cells including proton exchange membrane fuel cell ( PEMFC ) and alkaline fuel cell (AFC) with operation temperature usually lower than 120...advantages over proton exchange membrane fuel cells ( PEMFCs ) resulting in the popularity of AFCs in the US space program.[8-11] The primary benefit AFC...offered over PEMFC is better electrochemical kinetics on the anode and cathode under the alkaline environment, which results in the ability to use

Adhesive properties and adhesive joints strength of graphite/epoxy composites

Science.gov (United States)

Rudawska, Anna; Stančeková, Dana; Cubonova, Nadezda; Vitenko, Tetiana; Müller, Miroslav; Valášek, Petr

2017-05-01

The article presents the results of experimental research of the adhesive joints strength of graphite/epoxy composites and the results of the surface free energy of the composite surfaces. Two types of graphite/epoxy composites with different thickness were tested which are used to aircraft structure. The single-lap adhesive joints of epoxy composites were considered. Adhesive properties were described by surface free energy. Owens-Wendt method was used to determine surface free energy. The epoxy two-component adhesive was used to preparing the adhesive joints. Zwick/Roell 100 strength device were used to determination the shear strength of adhesive joints of epoxy composites. The strength test results showed that the highest value was obtained for adhesive joints of graphite-epoxy composite of smaller material thickness (0.48 mm). Statistical analysis of the results obtained, the study showed statistically significant differences between the values of the strength of the confidence level of 0.95. The statistical analysis of the results also showed that there are no statistical significant differences in average values of surface free energy (0.95 confidence level). It was noted that in each of the results the dispersion component of surface free energy was much greater than polar component of surface free energy.

Adhesion of Plasmodium falciparum infected erythrocytes in ex vivo perfused placental tissue

DEFF Research Database (Denmark)

Pehrson, Caroline; Mathiesen, Line; Heno, Kristine K

2016-01-01

placental tissue. RESULTS: The ex vivo placental perfusion model was modified to study adhesion of infected erythrocytes binding to CSA, endothelial protein C receptor (EPCR) or a transgenic parasite where P. falciparum erythrocyte membrane protein 1 expression had been shut down. Infected erythrocytes......, such as binding to immunoglobulins. Furthermore, other parasite antigens have been associated with placental malaria. These findings have important implications for placental malaria vaccine design. The objective of this study was to adapt and describe a biologically relevant model of parasite adhesion in intact...... expressing VAR2CSA accumulated in perfused placental tissue whereas the EPCR binding and the transgenic parasite did not. Soluble CSA and antibodies specific against VAR2CSA inhibited binding of infected erythrocytes. CONCLUSION: The ex vivo model provides a novel way of studying receptor-ligand interactions...

Antimicrobial membrane surfaces via efficient polyethyleneimine immobilization and cationization

Science.gov (United States)

Qiu, Wen-Ze; Zhao, Zi-Shu; Du, Yong; Hu, Meng-Xin; Xu, Zhi-Kang

2017-12-01

Biofouling control is a major task in membrane separation processes for water treatment and biomedical applications. In this work, N-alkylated polyethylenimine (PEI) is facilely and efficiently introduced onto the membrane surfaces via the co-deposition of catechol (CCh) and PEI, followed by further grafting of PEIs (600 Da, 70 kDa and 750 kDa) and cationization with methyl iodide (CH3I). The physical and chemical properties of the constructed membrane surfaces are characterized with scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, zeta potential and water contact angle measurements. Antibacterial assay reveals that the optimized membrane surfaces possess around 95% antibacterial efficiency against Gram-positive Staphylococcus aureus (S. aureus) with weak adhesion of bacteria cells after 24 h of bacterial contact. Additionally, the membrane surfaces also exhibit much enhanced antifouling property during the filtration of opposite charged bovine serum albumin (BSA). These results demonstrate a useful strategy for the surface modification of separation membranes by a kind of antimicrobial and antifouling coating.

Bacterial endotoxin adhesion to different types of orthodontic adhesives

Directory of Open Access Journals (Sweden)

Priscilla Coutinho ROMUALDO

Full Text Available Abstract Bacterial endotoxin (LPS adhesion to orthodontic brackets is a known contributing factor to inflammation of the adjacent gingival tissues. Objective The aim of this study was to assess whether LPS adheres to orthodontic adhesive systems, comparing two commercial brands. Material and Methods Forty specimens were fabricated from Transbond XT and Light Bond composite and bonding agent components (n=10/component, then contaminated by immersion in a bacterial endotoxin solution. Contaminated and non-contaminated acrylic resin samples were used as positive and negative control groups, respectively. LPS quantification was performed by the Limulus Amebocyte Lysate QCL-1000™ test. Data obtained were scored and subjected to the Chi-square test using a significance level of 5%. Results There was endotoxin adhesion to all materials (p0.05. There was no significant difference (p>0.05 among commercial brands. Affinity of endotoxin was significantly greater for the bonding agents (p=0.0025. Conclusions LPS adhered to both orthodontic adhesive systems. Regardless of the brand, the endotoxin had higher affinity for the bonding agents than for the composites. There is no previous study assessing the affinity of LPS for orthodontic adhesive systems. This study revealed that LPS adheres to orthodontic adhesive systems. Therefore, additional care is recommended to orthodontic applications of these materials.

Neuron membrane trafficking and protein kinases involved in autism and ADHD.

Science.gov (United States)

Kitagishi, Yasuko; Minami, Akari; Nakanishi, Atsuko; Ogura, Yasunori; Matsuda, Satoru

2015-01-30

A brain-enriched multi-domain scaffolding protein, neurobeachin has been identified as a candidate gene for autism patients. Mutations in the synaptic adhesion protein cell adhesion molecule 1 (CADM1) are also associated with autism spectrum disorder, a neurodevelopmental disorder of uncertain molecular origin. Potential roles of neurobeachin and CADM1 have been suggested to a function of vesicle transport in endosomal trafficking. It seems that protein kinase B (AKT) and cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) have key roles in the neuron membrane trafficking involved in the pathogenesis of autism. Attention deficit hyperactivity disorder (ADHD) is documented to dopaminergic insufficiencies, which is attributed to synaptic dysfunction of dopamine transporter (DAT). AKT is also essential for the DAT cell-surface redistribution. In the present paper, we summarize and discuss the importance of several protein kinases that regulate the membrane trafficking involved in autism and ADHD, suggesting new targets for therapeutic intervention.

Neuron Membrane Trafficking and Protein Kinases Involved in Autism and ADHD

Directory of Open Access Journals (Sweden)

Yasuko Kitagishi

2015-01-01

Full Text Available A brain-enriched multi-domain scaffolding protein, neurobeachin has been identified as a candidate gene for autism patients. Mutations in the synaptic adhesion protein cell adhesion molecule 1 (CADM1 are also associated with autism spectrum disorder, a neurodevelopmental disorder of uncertain molecular origin. Potential roles of neurobeachin and CADM1 have been suggested to a function of vesicle transport in endosomal trafficking. It seems that protein kinase B (AKT and cyclic adenosine monophosphate (cAMP-dependent protein kinase A (PKA have key roles in the neuron membrane trafficking involved in the pathogenesis of autism. Attention deficit hyperactivity disorder (ADHD is documented to dopaminergic insufficiencies, which is attributed to synaptic dysfunction of dopamine transporter (DAT. AKT is also essential for the DAT cell-surface redistribution. In the present paper, we summarize and discuss the importance of several protein kinases that regulate the membrane trafficking involved in autism and ADHD, suggesting new targets for therapeutic intervention.

Glycosynapses: microdomains controlling carbohydrate-dependent cell adhesion and signaling

Directory of Open Access Journals (Sweden)

Senitiroh Hakomori

2004-09-01

Full Text Available The concept of microdomains in plasma membranes was developed over two decades, following observation of polarity of membrane based on clustering of specific membrane components. Microdomains involved in carbohydrate-dependent cell adhesion with concurrent signal transduction that affect cellular phenotype are termed "glycosynapse". Three types of glycosynapse have been distinguished: "type 1" having glycosphingolipid associated with signal transducers (small G-proteins, cSrc, Src family kinases and proteolipids; "type 2" having O-linked mucin-type glycoprotein associated with Src family kinases; and "type 3" having N-linked integrin receptor complexed with tetraspanin and ganglioside. Different cell types are characterized by presence of specific types of glycosynapse or their combinations, whose adhesion induces signal transduction to either facilitate or inhibit signaling. E.g., signaling through type 3 glycosynapse inhibits cell motility and differentiation. Glycosynapses are distinct from classically-known microdomains termed "caveolae", "caveolar membrane", or more recently "lipid raft", which are not involved in carbohydrate-dependent cell adhesion. Type 1 and type 3 glycosynapses are resistant to cholesterol-binding reagents, whereas structure and function of "caveolar membrane" or "lipid raft" are disrupted by these reagents. Various data indicate a functional role of glycosynapses during differentiation, development, and oncogenic transformation.O conceito de microdomínios em membrana plasmática foi desenvolvido há mais de duas décadas, após a observação da polaridade da membrana baseada no agrupamento de componentes específicos da membrana. Microdomínios envolvidos na adesão celular dependente de carboidrato, com transdução de sinal que afeta o fenótipo celular são denominados ''glicosinapses''. Três tipos de glicosinapse foram observados: ''tipo 1'' que possue glicoesfingolipídio associado com transdutores de sinal

The Membrane Modulates Internal Proton Transfer in Cytochrome c Oxidase

DEFF Research Database (Denmark)

Öjemyr, Linda Nasvik; Ballmoos, Christoph von; Faxén, Kristina

2012-01-01

The functionality of membrane proteins is often modulated by the surrounding membrane. Here, we investigated the effect of membrane reconstitution of purified cytochrome c oxidase (CytcO) on the kinetics and thermodynamics of internal electron and proton-transfer reactions during O-2 reduction...... DOPC lipids. In conclusion, the data show that the membrane significantly modulates internal charge-transfer reactions and thereby the function of the membrane-bound enzyme.......-glycerol) (DOPG). In addition, a small Change in the internal Cu-A-heme a electron equilibrium constant was observed. This effect was lipid-dependent and explained in terms of a lower electrostatic potential within the membrane-spanning part of the protein with the anionic DOPG lipids than with the zwitterionic...

Adhesive Strength of dry Adhesive Structures Depending on the Thickness of Metal Coating

International Nuclear Information System (INIS)

Kim, Gyu Hye; Kwon, Da Som; Kim, Mi Jung; Kim, Su Hee; Yoon, Ji Won; An, Tea Chang; Hwang, Hui Yun

2016-01-01

Recently, engineering applications have started to adopt solutions inspired by nature. The peculiar adhesive properties of gecko skin are an example, as they allow the animal to move freely on vertical walls and even on ceilings. The high adhesive forces between gecko feet and walls are due to the hierarchical microscopical structure of the skin. In this study, the effect of metal coatings on the adhesive strength of synthetic, hierarchically structured, dry adhesives was investigated. Synthetic dry adhesives were fabricated using PDMS micro-molds prepared by photolithography. Metal coatings on synthetic dry adhesives were formed by plasma sputtering. Adhesive strength was measured by pure shear tests. The highest adhesion strengths were found with coatings composed of 4 nm thick layers of Indium, 8 nm thick layers of Zinc and 6 nm thick layers of Gold, respectively

Adhesive Strength of dry Adhesive Structures Depending on the Thickness of Metal Coating

Energy Technology Data Exchange (ETDEWEB)

Kim, Gyu Hye; Kwon, Da Som; Kim, Mi Jung; Kim, Su Hee; Yoon, Ji Won; An, Tea Chang; Hwang, Hui Yun [Andong National Univ., Andong (Korea, Republic of)

2016-07-15

Recently, engineering applications have started to adopt solutions inspired by nature. The peculiar adhesive properties of gecko skin are an example, as they allow the animal to move freely on vertical walls and even on ceilings. The high adhesive forces between gecko feet and walls are due to the hierarchical microscopical structure of the skin. In this study, the effect of metal coatings on the adhesive strength of synthetic, hierarchically structured, dry adhesives was investigated. Synthetic dry adhesives were fabricated using PDMS micro-molds prepared by photolithography. Metal coatings on synthetic dry adhesives were formed by plasma sputtering. Adhesive strength was measured by pure shear tests. The highest adhesion strengths were found with coatings composed of 4 nm thick layers of Indium, 8 nm thick layers of Zinc and 6 nm thick layers of Gold, respectively.

Characterization of a poly(ether urethane)-based controlled release membrane system for delivery of ketoprofen

International Nuclear Information System (INIS)

Macocinschi, Doina; Filip, Daniela; Vlad, Stelian; Oprea, Ana Maria; Gafitanu, Carmen Anatolia

2012-01-01

Highlights: ► Ketoprofen incorporation in poly(ether urethane) microporous membrane. ► Moisture sorption properties of as-cast membrane. ► Drug release mechanisms in function of pH and composition of membranes. - Abstract: A poly(ether urethane) based on polytetrahydrofuran containing hydroxypropyl cellulose for biomedical applications was tested for its biocompatibility. Ketoprofen was incorporated (3% and 6%) in the polyurethane matrix as an anti-inflammatory drug. Kinetic and drug release mechanisms were studied. The pore size and pore size distribution of the polyurethane membranes were investigated by scanning electron microscopy. Surface tension characteristics as well as moisture sorption properties such as diffusion coefficients and equilibrium moisture contents of the membrane material were studied. It was found that kinetics and release mechanisms are in function of medium pH, composition of polymer–drug system, pore morphology and pore size distribution. Prolonged nature of release of ketoprofen is assured by low amount of drug in polyurethane membrane and physiological pH.

Physics of adhesion

International Nuclear Information System (INIS)

Gerberich, W W; Cordill, M J

2006-01-01

Adhesion physics was relegated to the lowest echelons of academic pursuit until the advent of three seemingly disconnected events. The first, atomic force microscopy (AFM), eventually allowed fine-scale measurement of adhesive point contacts. The second, large-scale computational materials science, now permits both hierarchical studies of a few thousand atoms from first principles or of billions of atoms with less precise interatomic potentials. The third is a microelectronics industry push towards the nanoscale which has provided the driving force for requiring a better understanding of adhesion physics. In the present contribution, an attempt is made at conjoining these separate events into an updating of how theoretical and experimental approaches are providing new understanding of adhesion physics. While all material couples are briefly considered, the emphasis is on metal/semiconductor and metal/ceramic interfaces. Here, adhesion energies typically range from 1 to 100 J m -2 where the larger value is considered a practical work of adhesion. Experimental emphasis is on thin-film de-adhesion for 10 to 1000 nm thick films. For comparison, theoretical approaches from first principles quantum mechanics to embedded atom methods used in multi-scale modelling are utilized

Intracellular targeting of annexin A2 inhibits tumor cell adhesion, migration, and in vivo grafting.

Science.gov (United States)

Staquicini, Daniela I; Rangel, Roberto; Guzman-Rojas, Liliana; Staquicini, Fernanda I; Dobroff, Andrey S; Tarleton, Christy A; Ozbun, Michelle A; Kolonin, Mikhail G; Gelovani, Juri G; Marchiò, Serena; Sidman, Richard L; Hajjar, Katherine A; Arap, Wadih; Pasqualini, Renata

2017-06-26

Cytoskeletal-associated proteins play an active role in coordinating the adhesion and migration machinery in cancer progression. To identify functional protein networks and potential inhibitors, we screened an internalizing phage (iPhage) display library in tumor cells, and selected LGRFYAASG as a cytosol-targeting peptide. By affinity purification and mass spectrometry, intracellular annexin A2 was identified as the corresponding binding protein. Consistently, annexin A2 and a cell-internalizing, penetratin-fused version of the selected peptide (LGRFYAASG-pen) co-localized and specifically accumulated in the cytoplasm at the cell edges and cell-cell contacts. Functionally, tumor cells incubated with LGRFYAASG-pen showed disruption of filamentous actin, focal adhesions and caveolae-mediated membrane trafficking, resulting in impaired cell adhesion and migration in vitro. These effects were paralleled by a decrease in the phosphorylation of both focal adhesion kinase (Fak) and protein kinase B (Akt). Likewise, tumor cells pretreated with LGRFYAASG-pen exhibited an impaired capacity to colonize the lungs in vivo in several mouse models. Together, our findings demonstrate an unrecognized functional link between intracellular annexin A2 and tumor cell adhesion, migration and in vivo grafting. Moreover, this work uncovers a new peptide motif that binds to and inhibits intracellular annexin A2 as a candidate therapeutic lead for potential translation into clinical applications.

Extracellular Membrane-proximal Domain of HAb18G/CD147 Binds to Metal Ion-dependent Adhesion Site (MIDAS) Motif of Integrin β1 to Modulate Malignant Properties of Hepatoma Cells*

Science.gov (United States)

Li, Yong; Wu, Jiao; Song, Fei; Tang, Juan; Wang, Shi-Jie; Yu, Xiao-Ling; Chen, Zhi-Nan; Jiang, Jian-Li

2012-01-01

Several lines of evidence suggest that HAb18G/CD147 interacts with the integrin variants α3β1 and α6β1. However, the mechanism of the interaction remains largely unknown. In this study, mammalian protein-protein interaction trap (MAPPIT), a mammalian two-hybrid method, was used to study the CD147-integrin β1 subunit interaction. CD147 in human hepatocellular carcinoma (HCC) cells was interfered with by small hairpin RNA. Nude mouse xenograft model and metastatic model of HCC were used to detect the role of CD147 in carcinogenesis and metastasis. We found that the extracellular membrane-proximal domain of HAb18G/CD147 (I-type domain) binds at the metal ion-dependent adhesion site in the βA domain of the integrin β1 subunit, and Asp179 in the I-type domain of HAb18G/CD147 plays an important role in the interaction. The levels of the proteins that act downstream of integrin, including focal adhesion kinase (FAK) and phospho-FAK, were decreased, and the cytoskeletal structures of HCC cells were rearranged bearing the HAb18G/CD147 deletion. Simultaneously, the migration and invasion capacities, secretion of matrix metalloproteinases, colony formation rate in vitro, and tumor growth and metastatic potential in vivo were decreased. These results indicate that the interaction of HAb18G/CD147 extracellular I-type domain with the integrin β1 metal ion-dependent adhesion site motif activates the downstream FAK signaling pathway, subsequently enhancing the malignant properties of HCC cells. PMID:22130661

Confining Domains Lead to Reaction Bursts: Reaction Kinetics in the Plasma Membrane

Science.gov (United States)

Kalay, Ziya; Fujiwara, Takahiro K.; Kusumi, Akihiro

2012-01-01

Confinement of molecules in specific small volumes and areas within a cell is likely to be a general strategy that is developed during evolution for regulating the interactions and functions of biomolecules. The cellular plasma membrane, which is the outermost membrane that surrounds the entire cell, was considered to be a continuous two-dimensional liquid, but it is becoming clear that it consists of numerous nano-meso-scale domains with various lifetimes, such as raft domains and cytoskeleton-induced compartments, and membrane molecules are dynamically trapped in these domains. In this article, we give a theoretical account on the effects of molecular confinement on reversible bimolecular reactions in a partitioned surface such as the plasma membrane. By performing simulations based on a lattice-based model of diffusion and reaction, we found that in the presence of membrane partitioning, bimolecular reactions that occur in each compartment proceed in bursts during which the reaction rate is sharply and briefly increased even though the asymptotic reaction rate remains the same. We characterized the time between reaction bursts and the burst amplitude as a function of the model parameters, and discussed the biological significance of the reaction bursts in the presence of strong inhibitor activity. PMID:22479350

Confining domains lead to reaction bursts: reaction kinetics in the plasma membrane.

Directory of Open Access Journals (Sweden)

Ziya Kalay

Full Text Available Confinement of molecules in specific small volumes and areas within a cell is likely to be a general strategy that is developed during evolution for regulating the interactions and functions of biomolecules. The cellular plasma membrane, which is the outermost membrane that surrounds the entire cell, was considered to be a continuous two-dimensional liquid, but it is becoming clear that it consists of numerous nano-meso-scale domains with various lifetimes, such as raft domains and cytoskeleton-induced compartments, and membrane molecules are dynamically trapped in these domains. In this article, we give a theoretical account on the effects of molecular confinement on reversible bimolecular reactions in a partitioned surface such as the plasma membrane. By performing simulations based on a lattice-based model of diffusion and reaction, we found that in the presence of membrane partitioning, bimolecular reactions that occur in each compartment proceed in bursts during which the reaction rate is sharply and briefly increased even though the asymptotic reaction rate remains the same. We characterized the time between reaction bursts and the burst amplitude as a function of the model parameters, and discussed the biological significance of the reaction bursts in the presence of strong inhibitor activity.

Profiling of kidney vascular endothelial cell plasma membrane proteins by liquid chromatography-tandem mass spectrometry.

Science.gov (United States)

Liu, Zan; Xu, Bo; Nameta, Masaaki; Zhang, Ying; Magdeldin, Sameh; Yoshida, Yutaka; Yamamoto, Keiko; Fujinaka, Hidehiko; Yaoita, Eishin; Tasaki, Masayuki; Nakagawa, Yuki; Saito, Kazuhide; Takahashi, Kota; Yamamoto, Tadashi

2013-06-01

Vascular endothelial cells (VECs) play crucial roles in physiological and pathologic conditions in tissues and organs. Most of these roles are related to VEC plasma membrane proteins. In the kidney, VECs are closely associated with structures and functions; however, plasma membrane proteins in kidney VECs remain to be fully elucidated. Rat kidneys were perfused with cationic colloidal silica nanoparticles (CCSN) to label the VEC plasma membrane. The CCSN-labeled plasma membrane fraction was collected by gradient ultracentrifugation. The VEC plasma membrane or whole-kidney lysate proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and digested with trypsin in gels for liquid chromatography-tandem mass spectrometry. Enrichment analysis was then performed. The VEC plasma membrane proteins were purified by the CCSN method with high yield (approximately 20 μg from 1 g of rat kidney). By Mascot search, 582 proteins were identified in the VEC plasma membrane fraction, and 1,205 proteins were identified in the kidney lysate. In addition to 16 VEC marker proteins such as integrin beta-1 and intercellular adhesion molecule-2 (ICAM-2), 8 novel proteins such as Deltex 3-like protein and phosphatidylinositol binding clathrin assembly protein (PICALM) were identified. As expected, many key functions of plasma membranes in general and of endothelial cells in particular (i.e., leukocyte adhesion) were significantly overrepresented in the proteome of CCSN-labeled kidney VEC fraction. The CCSN method is a reliable technique for isolation of VEC plasma membrane from the kidney, and proteomic analysis followed by bioinformatics revealed the characteristics of in vivo VECs in the kidney.

Zinc oxide nanoparticles induce migration and adhesion of monocytes to endothelial cells and accelerate foam cell formation

Energy Technology Data Exchange (ETDEWEB)

Suzuki, Yuka; Tada-Oikawa, Saeko [Graduate School of Regional Innovation Studies, Mie University, Tsu (Japan); Ichihara, Gaku [Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine, Nagoya (Japan); Yabata, Masayuki; Izuoka, Kiyora [Graduate School of Regional Innovation Studies, Mie University, Tsu (Japan); Suzuki, Masako; Sakai, Kiyoshi [Nagoya City Public Health Research Institute, Nagoya (Japan); Ichihara, Sahoko, E-mail: saho@gene.mie-u.ac.jp [Graduate School of Regional Innovation Studies, Mie University, Tsu (Japan)

2014-07-01

Metal oxide nanoparticles are widely used in industry, cosmetics, and biomedicine. However, the effects of exposure to these nanoparticles on the cardiovascular system remain unknown. The present study investigated the effects of nanosized TiO{sub 2} and ZnO particles on the migration and adhesion of monocytes, which are essential processes in atherosclerogenesis, using an in vitro set-up of human umbilical vein endothelial cells (HUVECs) and human monocytic leukemia cells (THP-1). We also examined the effects of exposure to nanosized metal oxide particles on macrophage cholesterol uptake and foam cell formation. The 16-hour exposure to ZnO particles increased the level of monocyte chemotactic protein-1 (MCP-1) and induced the migration of THP-1 monocyte mediated by increased MCP-1. Exposure to ZnO particles also induced adhesion of THP-1 cells to HUVECs. Moreover, exposure to ZnO particles, but not TiO{sub 2} particles, upregulated the expression of membrane scavenger receptors of modified LDL and increased cholesterol uptake in THP-1 monocytes/macrophages. In the present study, we found that exposure to ZnO particles increased macrophage cholesterol uptake, which was mediated by an upregulation of membrane scavenger receptors of modified LDL. These results suggest that nanosized ZnO particles could potentially enhance atherosclerogenesis and accelerate foam cell formation. - Highlights: • Effects of metal oxide nanoparticles on foam cell formation were investigated. • Exposure to ZnO nanoparticles induced migration and adhesion of monocytes. • Exposure to ZnO nanoparticles increased macrophage cholesterol uptake. • Expression of membrane scavenger receptors of modified LDL was also increased. • These effects were not observed after exposure to TiO{sub 2} nanoparticles.

Equilibration kinetics in isolated and membrane-bound photosynthetic reaction centers upon illumination: a method to determine the photoexcitation rate.

Science.gov (United States)

Manzo, Anthony J; Goushcha, Alexander O; Barabash, Yuri M; Kharkyanen, Valery N; Scott, Gary W

2009-07-01

Kinetics of electron transfer, following variation of actinic light intensity, for photosynthetic reaction centers (RCs) of purple bacteria (isolated and membrane-bound) were analyzed by measuring absorbance changes in the primary photoelectron donor absorption band at 865 nm. The bleaching of the primary photoelectron donor absorption band in RCs, following a sudden increase of illumination from the dark to an actinic light intensity of I(exp), obeys a simple exponential law with the rate constant alphaI(exp) + k(rec), in which alpha is a parameter relating the light intensity, measured in mW/cm(2), to a corresponding theoretical rate in units of reciprocal seconds, and k(rec) is the effective rate constant of the charge recombination in the photosynthetic RCs. In this work, a method for determining the alpha parameter value is developed and experimentally verified for isolated and membrane-bound RCs, allowing for rigorous modeling of RC macromolecule dynamics under varied photoexcitation conditions. Such modeling is necessary for RCs due to alterations of the forward photoexcitation rates and relaxation rates caused by illumination history and intramolecular structural dynamics effects. It is demonstrated that the classical Bouguer-Lambert-Beer formalism can be applied for the samples with relatively low scattering, which is not necessarily the case with strongly scattering media or high light intensity excitation.

Disruption of Var2csa Gene Impairs Placental Malaria Associated Adhesion Phenotype

OpenAIRE

Viebig, Nicola K.; Levin, Emily; Dechavanne, Sébastien; Rogerson, Stephen J.; Gysin, Jürg; Smith, Joseph D.; Scherf, Artur; Gamain, Benoit

2007-01-01

Infection with Plasmodium falciparum during pregnancy is one of the major causes of malaria related morbidity and mortality in newborn and mothers. The complications of pregnancy-associated malaria result mainly from massive adhesion of Plasmodium falciparum-infected erythrocytes (IE) to chondroitin sulfate A (CSA) present in the placental intervillous blood spaces. Var2CSA, a member of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family is the predominant parasite ligand mediati...

Modeling kinetics and equilibrium of membranes with fields: Milestoning analysis and implication to permeation

Energy Technology Data Exchange (ETDEWEB)

Cardenas, Alfredo E. [Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas 78712 (United States); Elber, Ron [Institute for Computational Engineering and Sciences, University of Texas at Austin, Austin, Texas 78712 (United States); Department of Chemistry, University of Texas at Austin, Austin, Texas 78712 (United States)

2014-08-07

Coarse graining of membrane simulations by translating atomistic dynamics to densities and fields with Milestoning is discussed. The space of the membrane system is divided into cells and the different cells are characterized by order parameters presenting the number densities. The dynamics of the order parameters are probed with Milestoning. The methodology is illustrated here for a phospholipid membrane system (a hydrated bilayer of DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) lipid molecules). Significant inhomogeneity in membrane internal number density leads to complex free energy landscape and local maps of transition times. Dynamics and distributions of cavities within the membrane assist the permeation of nonpolar solutes such as xenon atoms. It is illustrated that quantitative and detailed dynamics of water transport through DOPC membrane can be analyzed using Milestoning with fields. The reaction space for water transport includes at least two slow variables: the normal to the membrane plane, and the water density.

Modeling kinetics and equilibrium of membranes with fields: Milestoning analysis and implication to permeation

International Nuclear Information System (INIS)

Cardenas, Alfredo E.; Elber, Ron

2014-01-01

Coarse graining of membrane simulations by translating atomistic dynamics to densities and fields with Milestoning is discussed. The space of the membrane system is divided into cells and the different cells are characterized by order parameters presenting the number densities. The dynamics of the order parameters are probed with Milestoning. The methodology is illustrated here for a phospholipid membrane system (a hydrated bilayer of DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine) lipid molecules). Significant inhomogeneity in membrane internal number density leads to complex free energy landscape and local maps of transition times. Dynamics and distributions of cavities within the membrane assist the permeation of nonpolar solutes such as xenon atoms. It is illustrated that quantitative and detailed dynamics of water transport through DOPC membrane can be analyzed using Milestoning with fields. The reaction space for water transport includes at least two slow variables: the normal to the membrane plane, and the water density

A synergetic analysis method for antifouling behavior investigation on PES ultrafiltration membrane with self-assembled TiO2 nanoparticles.

Science.gov (United States)

Li, Xin; Li, Jiansheng; Fang, Xiaofeng; Bakzhan, Kariboz; Wang, Lianjun; Van der Bruggen, Bart

2016-05-01

Fouling of ultrafiltration (UF) membranes is a major impediment for their use in drinking water production. Mixed matrix membranes (MMMs) may have great opportunities in dealing with this challenge due to their hierarchical structures and multiple functionalities. In this study, a synergetic analysis method based on intermolecular adhesion force measurement and fouling process simulation was applied to investigate the fouling mechanism of polyethersulfone (PES) UF membranes containing in situ self-assembled TiO2 nanoparticles (NPs). The fouling resistance behavior and antifouling mechanism of the newly developed composite membranes were investigated with sodium alginate (SA), bovine serum albumin (BSA) and humic acid (HA) as model organic foulants. An improved antifouling effect was conspicuously observed for the composite membranes, expressed by a lower flux decline and significantly better cleaning efficiency. A strong correlation between the self-assembled structure of TiO2 NPs and the antifouling behavior of the composite membrane was observed. A lower magnitude and a narrower distribution of adhesion forces for the composite membrane suggest the effective suppression of foulants adsorption on the clean or fouled membrane. The simulation analysis indicates that the main fouling mechanism was standard blocking and cake filtration, further confirming the superiority of the NPs self-assembled structure in mitigating membrane fouling. This dual analysis method may provide a promising technological support for the application of modified UF membranes with self-assembled NPs in drinking water production. Copyright © 2016 Elsevier Inc. All rights reserved.

Viscoelastic Properties of Extracellular Polymeric Substances Can Strongly Affect Their Washing Efficiency from Reverse Osmosis Membranes.

Science.gov (United States)

Ferrando Chavez, Diana Lila; Nejidat, Ali; Herzberg, Moshe

2016-09-06

The role of the viscoelastic properties of biofouling layers in their removal from the membrane was studied. Model fouling layers of extracellular polymeric substances (EPS) originated from microbial biofilms of Pseudomonas aeruginosa PAO1 differentially expressing the Psl polysaccharide were used for controlled washing experiments of fouled RO membranes. In parallel, adsorption experiments and viscoelastic modeling of the EPS layers were conducted in a quartz crystal microbalance with dissipation (QCM-D). During the washing stage, as shear rate was elevated, significant differences in permeate flux recovery between the three different EPS layers were observed. According to the amount of organic carbon remained on the membrane after washing, the magnitude of Psl production provides elevated resistance of the EPS layer to shear stress. The highest flux recovery during the washing stage was observed for the EPS with no Psl. Psl was shown to elevate the layer's shear modulus and shear viscosity but had no effect on the EPS adhesion to the polyamide surface. We conclude that EPS retain on the membrane as a result of the layer viscoelastic properties. These results highlight an important relation between washing efficiency of fouling layers from membranes and their viscoelastic properties, in addition to their adhesion properties.

Membrane fusion and inverted phases

International Nuclear Information System (INIS)

Ellens, H.; Siegel, D.P.; Alford, D.; Yeagle, P.L.; Boni, L.; Lis, L.J.; Quinn, P.J.; Bentz, J.

1989-01-01

We have found a correlation between liposome fusion kinetics and lipid phase behavior for several inverted phase forming lipids. N-Methylated dioleoylphosphatidylethanolamine (DOPE-Me), or mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC), will form an inverted hexagonal phase (HII) at high temperatures (above TH), a lamellar phase (L alpha) at low temperatures, and an isotropic/inverted cubic phase at intermediate temperatures, which is defined by the appearance of narrow isotropic 31 P NMR resonances. The phase behavior has been verified by using high-sensitivity DSC, 31 P NMR, freeze-fracture electron microscopy, and X-ray diffraction. The temperature range over which the narrow isotropic resonances occur is defined as delta TI, and the range ends at TH. Extruded liposomes (approximately 0.2 microns in diameter) composed of these lipids show fusion and leakage kinetics which are strongly correlated with the temperatures of these phase transitions. At temperatures below delta TI, where the lipid phase is L alpha, there is little or no fusion, i.e., mixing of aqueous contents, or leakage. However, as the temperature reaches delta TI, there is a rapid increase in both fusion and leakage rates. At temperatures above TH, the liposomes show aggregation-dependent lysis, as the rapid formation of HII phase precursors disrupts the membranes. We show that the correspondence between the fusion and leakage kinetics and the observed phase behavior is easily rationalized in terms of a recent kinetic theory of L alpha/inverted phase transitions. In particular, it is likely that membrane fusion and the L alpha/inverted cubic phase transition proceed via a common set of intermembrane intermediates

Analysis of long- and short-range contribution to adhesion work in cardiac fibroblasts: An atomic force microscopy study

Energy Technology Data Exchange (ETDEWEB)

Sbaizero, O., E-mail: sbaizero@units.it [Department of Engineering and Architecture, University of Trieste (Italy); University of Colorado Cardiovascular Institute, University of Colorado Denver, Aurora (United States); DelFavero, G. [Department of Engineering and Architecture, University of Trieste (Italy); Martinelli, V. [International Center for Genetic Engineering and Biotechnology, Trieste (Italy); Long, C.S.; Mestroni, L. [University of Colorado Cardiovascular Institute, University of Colorado Denver, Aurora (United States)

2015-04-01

Atomic force microscopy (AFM) for single-cell force spectroscopy (SCFS) and Poisson statistic were used to analyze the detachment work recorded during the removal of gold-covered microspheres from cardiac fibroblasts. The effect of Cytochalasin D, a disruptor of the actin cytoskeleton, on cell adhesion was also tested. The adhesion work was assessed using a Poisson analysis also derived from single-cell force spectroscopy retracting curves. The use of Poisson analysis to get adhesion work from AFM curves is quite a novel method, and in this case, proved to be effective to study the short-range and long-range contributions to the adhesion work. This method avoids the difficult identification of minor peaks in the AFM retracting curves by creating what can be considered an average adhesion work. Even though the effect of actin depolymerisation is well documented, its use revealed that control cardiac fibroblasts (CT) exhibit a work of adhesion at least 5 times higher than that of the Cytochalasin treated cells. However, our results indicate that in both cells short-range and long-range contributions to the adhesion work are nearly equal and the same heterogeneity index describes both cells. Therefore, we infer that the different adhesion behaviors might be explained by the presence of fewer membrane adhesion molecules available at the AFM tip–cell interface under circumstances where the actin cytoskeleton has been disrupted. - Highlights: • AFM force–deformation curve was used to characterize the cardiac fibroblast adhesion behavior. • The amount and nature of adhesion were assessed using a Poisson analysis applied to the AFM curve. • The work of adhesion for control cells was about four times higher than that of the Cyt-D treated cells. • Short- and long-range contributions to adhesion are nearly equal for both control and treated cells.

Reflections about Adhesive Systems

OpenAIRE

de Freitas Borges, Marciano; Diesel, Pâmela Gutheil; Corrêa, Fernanda Gomez; Bernardi, Eledana; Fernandes Montagner, Anelise; Skupien, Jovito Adiel; Susin, Alexandre Henrique

2010-01-01

The adhesive systems are responsible for an efficient union between teeth and resin, resulting in a longevity restoration. They are organic molecules di or multifunctional that contain reactive groups that interact with dentin and with the resin monomer of composite resin. The adhesive systems are characterized by wet adhesion, which is a result of presence of hidrophylics radicals in their compositions, to promote a better bond and the best properties of the adhesion. Adhesive systems may us...

Preparation and performance of biofouling resistant PAN/chitosan hollow fiber membranes.

Science.gov (United States)

Shanthana Lakshmi, D; Jaiswar, Santlal; Saxena, Mayank; Tasselli, Franco; Raval, Hiren D

2017-07-01

The preparation of polyacrylonitrile (PAN) hollow fiber (HF) membranes has been carried out by dry-jet wet spinning. PAN HF membranes were coated with chitosan biopolymers 2 wt% by dip coating and further crosslinked by chemical reagents (Tri sodium polyphosphate). PAN HF (Virgin) and PAN/chitosan coated membrane were characterized by SEM and tested for water flux. Proteins Pepsin, Albumin, and Clay of 1000 ppm concentration were tested for separation efficiency. In addition, bacterial species Escherichia coli and Bacillus subtilis were tested for fouling control efficiency and found out that PAN/chitosan membranes were quite superior to virgin PAN fibers. The adhesion of bacterial cells on the surface of the hollow fiber membranes assessed through alcian blue staining and SEM analysis. It was observed that PAN/chitosan membranes (310A and 310C) possessed best antibacterial activities (based on SEM results), qualifying them as a very promising candidates for anti-biofouling coatings.

Fouling kinetics in microfiltration of protein solutions using different membrane configurations

DEFF Research Database (Denmark)

Jakobsen, Sune; Jonsson, Gunnar Eigil

1997-01-01

Protein fouling in microfiltration has a large impact on the permeate flux and observed retention of the proteins despite the fact that the protein molecule is several times smaller than the average pore size in microfiltration membranes. This is due to adsorption and deposition of protein...... molecules and aggregates. The effect of membrane configuration upon protein fouling was investigated in crossflow filtration with asymmetric membranes either in a normal mode or in a reverse mode. It was observed by Jonsson et al. [1] that beer filtration in a reverse mode results in a smaller decrease...... in the flux compared to beer filtration in a normal mode. Similar results for protein filtration were observed by Bowen et al. [2]. One possible way to avoid fouling is the novel backshock technique (see Jonsson et al. [1]). The effect of backshock on protein filtration was investigated using a hollow fiber...

Dry adhesives with sensing features

International Nuclear Information System (INIS)

Krahn, J; Menon, C

2013-01-01

Geckos are capable of detecting detachment of their feet. Inspired by this basic observation, a novel functional dry adhesive is proposed, which can be used to measure the instantaneous forces and torques acting on an adhesive pad. Such a novel sensing dry adhesive could potentially be used by climbing robots to quickly realize and respond appropriately to catastrophic detachment conditions. The proposed torque and force sensing dry adhesive was fabricated by mixing Carbon Black (CB) and Polydimethylsiloxane (PDMS) to form a functionalized adhesive with mushroom caps. The addition of CB to PDMS resulted in conductive PDMS which, when under compression, tension or torque, resulted in a change in the resistance across the adhesive patch terminals. The proposed design of the functionalized dry adhesive enables distinguishing an applied torque from a compressive force in a single adhesive pad. A model based on beam theory was used to predict the change in resistance across the terminals as either a torque or compressive force was applied to the adhesive patch. Under a compressive force, the sensing dry adhesive was capable of measuring compression stresses from 0.11 Pa to 20.9 kPa. The torque measured by the adhesive patch ranged from 2.6 to 10 mN m, at which point the dry adhesives became detached. The adhesive strength was 1.75 kPa under an applied preload of 1.65 kPa for an adhesive patch with an adhesive contact area of 7.07 cm 2 . (paper)

Dry adhesives with sensing features

Science.gov (United States)

Krahn, J.; Menon, C.

2013-08-01

Geckos are capable of detecting detachment of their feet. Inspired by this basic observation, a novel functional dry adhesive is proposed, which can be used to measure the instantaneous forces and torques acting on an adhesive pad. Such a novel sensing dry adhesive could potentially be used by climbing robots to quickly realize and respond appropriately to catastrophic detachment conditions. The proposed torque and force sensing dry adhesive was fabricated by mixing Carbon Black (CB) and Polydimethylsiloxane (PDMS) to form a functionalized adhesive with mushroom caps. The addition of CB to PDMS resulted in conductive PDMS which, when under compression, tension or torque, resulted in a change in the resistance across the adhesive patch terminals. The proposed design of the functionalized dry adhesive enables distinguishing an applied torque from a compressive force in a single adhesive pad. A model based on beam theory was used to predict the change in resistance across the terminals as either a torque or compressive force was applied to the adhesive patch. Under a compressive force, the sensing dry adhesive was capable of measuring compression stresses from 0.11 Pa to 20.9 kPa. The torque measured by the adhesive patch ranged from 2.6 to 10 mN m, at which point the dry adhesives became detached. The adhesive strength was 1.75 kPa under an applied preload of 1.65 kPa for an adhesive patch with an adhesive contact area of 7.07 cm2.

Reversible Thermoset Adhesives

Science.gov (United States)

Mac Murray, Benjamin C. (Inventor); Tong, Tat H. (Inventor); Hreha, Richard D. (Inventor)

2016-01-01

Embodiments of a reversible thermoset adhesive formed by incorporating thermally-reversible cross-linking units and a method for making the reversible thermoset adhesive are provided. One approach to formulating reversible thermoset adhesives includes incorporating dienes, such as furans, and dienophiles, such as maleimides, into a polymer network as reversible covalent cross-links using Diels Alder cross-link formation between the diene and dienophile. The chemical components may be selected based on their compatibility with adhesive chemistry as well as their ability to undergo controlled, reversible cross-linking chemistry.

Hyperbranched-polyol-tethered poly (amic acid) electrospun nanofiber membrane with ultrahigh adsorption capacity for boron removal

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhe; Wu, Zhongyu; Zhang, Yufeng; Meng, Jianqiang, E-mail: jianqiang.meng@hotmail.com

2017-04-30

Highlights: • Electrospun nanofiber membranes were grafted with hyperbranched polyols. • The membrane had a maximum boron uptake of 5.68 mmol/g. • The membrane could adsorb 0.82 mmol/g boron from a 5 mg/L solution in 15 min. • The membrane obeyed the Langmuir and the pseudo-first-order kinetic model. • The regeneration efficiency remained over 90% after 10 cycled uses. - Abstract: The development of efficient adsorbents with high sorption capacity remains as a challenge for the removal of micropollutants occurred globally in water resources. In this work, poly (amic acid) (PAA) electrospun nanofiber membranes grafted with hyperbranched polyols were synthesized and used for boron removal. The PAA nanofiber was reacted with hyperbranched polyethylenimine (HPEI) and further with glycidol to introduce the vicinal hydroxyl groups. The chemical composition and surface characteristics of the obtained PAA-g-PG membranes were evaluated by FESEM, FTIR, XPS and water contact angles (WCA) measurements. The boron adsorption thermodynamics and kinetics were investigated systematically. The results showed that the PAA nanofiber spun from concentration of 15% had uniform morphology and narrow diameter distribution. The PAA-g-PG nanofiber membrane had a maximum boron uptake of 5.68 mmol/g and could adsorb 0.82 mmol/g boron from a 5 mg/L solution in 15 min. Both the high surface area of nanofibers and the hyperbranched structure should contribute to the high boron uptake and high adsorption rate. The nanofiber membrane obeyed the Langmuir adsorption model and the pseudo-first-order kinetic model. The regeneration efficiency of the nanofiber membrane remained 93.9% after 10 cycled uses, indicating good regenerability of the membrane.

Plasma-polymerized alkaline anion-exchange membrane: Synthesis and structure characterization

International Nuclear Information System (INIS)

Hu Jue; Meng Yuedong; Zhang Chengxu; Fang Shidong

2011-01-01

After-glow discharge plasma polymerization was developed for alkaline anion-exchange membranes synthesis using vinylbenzyl chloride as monomer. X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy were used to characterize the chemical structure properties of plasma-polymerized membranes. Ion-exchange capacities of quaternized poly(vinylbenzyl chloride) (QPVBC) membranes were measured to evaluate their capability of hydroxyl ion transport. A mechanism of plasma polymerization using VBC as monomer that accounts for the competitive effects of free radicals polymerization and plasma ablation in the plasma polymerization process was proposed. Our results indicate that plasma discharge power influences the contents of functional groups and the structure of the plasma polymer membranes, which attribute to the coactions of polymerization and ablation. The properties of uniform morphology, good adhesion to the substrate, high thermal stability and satisfying anion conduction level suggest the potential application of QPVBC membrane deposited at discharge power of 20 W in alkaline direct methanol fuel cells.

High aspect ratio silicon nanowires control fibroblast adhesion and cytoskeleton organization

Science.gov (United States)

Andolfi, Laura; Murello, Anna; Cassese, Damiano; Ban, Jelena; Dal Zilio, Simone; Lazzarino, Marco

2017-04-01

Cell-cell and cell-matrix interactions are essential to the survival and proliferation of most cells, and are responsible for triggering a wide range of biochemical pathways. More recently, the biomechanical role of those interactions was highlighted, showing, for instance, that adhesion forces are essential for cytoskeleton organization. Silicon nanowires (Si NWs) with their small size, high aspect ratio and anisotropic mechanical response represent a useful model to investigate the forces involved in the adhesion processes and their role in cellular development. In this work we explored and quantified, by single cell force spectroscopy (SCFS), the interaction of mouse embryonic fibroblasts with a flexible forest of Si NWs. We observed that the cell adhesion forces are comparable to those found on collagen and bare glass coverslip, analogously the membrane tether extraction forces are similar to that on collagen but stronger than that on bare flat glass. Cell survival did not depend significantly on the substrate, although a reduced proliferation after 36 h was observed. On the contrary both cell morphology and cytoskeleton organization revealed striking differences. The cell morphology on Si-NW was characterized by a large number of filopodia and a significant decrease of the cell mobility. The cytoskeleton organization was characterized by the absence of actin fibers, which were instead dominant on collagen and flat glass support. Such findings suggest that the mechanical properties of disordered Si NWs, and in particular their strong asymmetry, play a major role in the adhesion, morphology and cytoskeleton organization processes. Indeed, while adhesion measurements by SCFS provide out-of-plane forces values consistent with those measured on conventional substrates, weaker in-plane forces hinder proper cytoskeleton organization and migration processes.

Zwitterionic sulfobetaine-grafted poly(vinylidene fluoride) membrane with highly effective blood compatibility via atmospheric plasma-induced surface copolymerization.

Science.gov (United States)

Chang, Yung; Chang, Wan-Ju; Shih, Yu-Ju; Wei, Ta-Chin; Hsiue, Ging-Ho

2011-04-01

Development of nonfouling membranes to prevent nonspecific protein adsorption and platelet adhesion is critical for many biomedical applications. It is always a challenge to control the surface graft copolymerization of a highly polar monomer from the highly hydrophobic surface of a fluoropolymer membrane. In this work, the blood compatibility of poly(vinylidene fluoride) (PVDF) membranes with surface-grafted electrically neutral zwitterionic poly(sulfobetaine methacrylate) (PSBMA), from atmospheric plasma-induced surface copolymerization, was studied. The effect of surface composition and graft morphology, electrical neutrality, hydrophilicity and hydration capability on blood compatibility of the membranes were determined. Blood compatibility of the zwitterionic PVDF membranes was systematically evaluated by plasma protein adsorption, platelet adhesion, plasma-clotting time, and blood cell hemolysis. It was found that the nonfouling nature and hydration capability of grafted PSBMA polymers can be effectively controlled by regulating the grafting coverage and charge balance of the PSBMA layer on the PVDF membrane surface. Even a slight charge bias in the grafted zwitterionic PSBMA layer can induce electrostatic interactions between proteins and the membrane surfaces, leading to surface protein adsorption, platelet activation, plasma clotting and blood cell hemolysis. Thus, the optimized PSBMA surface graft layer in overall charge neutrality has a high hydration capability and the best antifouling, anticoagulant, and antihemolytic activities when comes into contact with human blood. © 2011 American Chemical Society

MOF-mixed matrix membranes : precise dispersion of MOF particles with better compatibility via a particle fusion approach for enhanced gas separation properties

NARCIS (Netherlands)

Shahid, Salman; Nijmeijer, Kitty; Nehache, Sabrina; Vankelecom, Ivo; Deratani, Andre; Quemener, Damien

2015-01-01

Mixed matrix membranes (MMMs) incorporating conventional fillers frequently suffer from insufficient adhesion between the polymer matrix and the fillers. This often results in the formation of non-selective voids at the filler/polymer interface, which decreases the performance of the membrane. A

MOF-mixed matrix membranes: Precise dispersion of MOF particles with better compatibility via a particle fusion approach for enhanced gas separation properties

NARCIS (Netherlands)

Shahid, S.; Nijmeijer, Dorothea C.; Nehache, Sabrina; Vankelecom, Ivo; Deratani, Andre; Quemener, Damien

2015-01-01

Mixed matrix membranes (MMMs) incorporating conventional fillers frequently suffer from insufficient adhesion between the polymer matrix and the fillers. This often results in the formation of non-selective voids at the filler/polymer interface, which decreases the performance of the membrane. A

Regulation of epithelial and lymphocyte cell adhesion by adenosine deaminase-CD26 interaction.

Science.gov (United States)

Ginés, Silvia; Mariño, Marta; Mallol, Josefa; Canela, Enric I; Morimoto, Chikao; Callebaut, Christian; Hovanessian, Ara; Casadó, Vicent; Lluis, Carmen; Franco, Rafael

2002-01-01

The extra-enzymic function of cell-surface adenosine deaminase (ADA), an enzyme mainly localized in the cytosol but also found on the cell surface of monocytes, B cells and T cells, has lately been the subject of numerous studies. Cell-surface ADA is able to transduce co-stimulatory signals in T cells via its interaction with CD26, an integral membrane protein that acts as ADA-binding protein. The aim of the present study was to explore whether ADA-CD26 interaction plays a role in the adhesion of lymphocyte cells to human epithelial cells. To meet this aim, different lymphocyte cell lines (Jurkat and CEM T) expressing endogenous, or overexpressing human, CD26 protein were tested in adhesion assays to monolayers of colon adenocarcinoma human epithelial cells, Caco-2, which express high levels of cell-surface ADA. Interestingly, the adhesion of Jurkat and CEM T cells to a monolayer of Caco-2 cells was greatly dependent on CD26. An increase by 50% in the cell-to-cell adhesion was found in cells containing higher levels of CD26. Incubation with an anti-CD26 antibody raised against the ADA-binding site or with exogenous ADA resulted in a significant reduction (50-70%) of T-cell adhesion to monolayers of epithelial cells. The role of ADA-CD26 interaction in the lymphocyte-epithelial cell adhesion appears to be mediated by CD26 molecules that are not interacting with endogenous ADA (ADA-free CD26), since SKW6.4 (B cells) that express more cell-surface ADA showed lower adhesion than T cells. Adhesion stimulated by CD26 and ADA is mediated by T cell lymphocyte function-associated antigen. A role for ADA-CD26 interaction in cell-to-cell adhesion was confirmed further in integrin activation assays. FACS analysis revealed a higher expression of activated integrins on T cell lines in the presence of increasing amounts of exogenous ADA. Taken together, these results suggest that the ADA-CD26 interaction on the cell surface has a role in lymphocyte-epithelial cell adhesion. PMID