TAp73 is essential for germ cell adhesion and maturation in testis

PubMed Central

Holembowski, Lena; Kramer, Daniela; Riedel, Dietmar; Sordella, Raffaella; Nemajerova, Alice; Dobbelstein, Matthias

2014-01-01

A core evolutionary function of the p53 family is to protect the genomic integrity of gametes. However, the role of p73 in the male germ line is unknown. Here, we reveal that TAp73 unexpectedly functions as an adhesion and maturation factor of the seminiferous epithelium orchestrating spermiogenesis. TAp73 knockout (TAp73KO) and p73KO mice, but not ΔNp73KO mice, display a “near-empty seminiferous tubule” phenotype due to massive premature loss of immature germ cells. The cellular basis of this phenotype is defective cell–cell adhesions of developing germ cells to Sertoli nurse cells, with likely secondary degeneration of Sertoli cells, including the blood–testis barrier, which leads to disruption of the adhesive integrity and maturation of the germ epithelium. At the molecular level, TAp73, which is produced in germ cells, controls a coordinated transcriptional program of adhesion- and migration-related proteins including peptidase inhibitors, proteases, receptors, and integrins required for germ–Sertoli cell adhesion and dynamic junctional restructuring. Thus, we propose the testis as a unique organ with strict division of labor among all family members: p63 and p53 safeguard germ line fidelity, whereas TAp73 ensures fertility by enabling sperm maturation. PMID:24662569

Mechanical properties, microstructure, and specific adhesion of phospholipid monolayer-coated microbubbles

NASA Astrophysics Data System (ADS)

Kim, Dennis Heejong

1999-10-01

The objective of this study was to characterize properties of phospholipid monolayer shells formed on gas microbubbles, specifically (1)yield shear and shear viscosity as a function of the shell composition, (2)yield shear, shear viscosity, and microstructural domain density as a function of the quenching rate of the microbubbles following production, and (3)the adhesion of a lipid-coated microbubble to a colloidal substrate via receptor-ligand mediated specific interaction, either enhanced or inhibited by the presence of surface-grafted polymeric structures. The primary experimental technique employed was the micromanipulation method, wherein tapered fluid-filled pipets with bores on the order of 4-10 microns were used to (1)capture and maneuver individual micron scale bubbles in aqueous medium, and (2)apply suction pressures over the range of 1 dyn cm-2 to 10 5 dyn cm-2 (10-6 to 10 -1 atm) and track the corresponding deformation of the microbubble under applied pressure. The yield shear and shear viscosity increase with increasing acyl chain length of the lipid; an equivalent statement is that the yield shear and shear viscosity increase with reduced temperature of the shell material. Crystalline lipid domain sizes are dictated by the rate at which the system is (temperature) quenched in a manner predicted by classic materials science and metallurgy: rapidly cooled samples form the smallest grains and exhibit the lowest levels of yield shear and shear viscosity. Slowly cooled samples produce large grains and exhibit high levels of yield and viscosity. The success and strength of adhesion of a microbubble to a substrate is dictated by the identity of the adhesive molecules participating in the adhesion, as well as the surface architecture of the interfaces participating in adhesion. The term surface architecture is used to describe the physical arrangement of the full complement of steric stabilizers, spacers, and binding molecules present at the surface of a typical coated microbubble shell. Adhesion is successful for systems where the binding ligand is not impeded by the presence of surface-grafted poly(ethylene glycol) (PEG) moieties. Like the shell composition itself, the surface construct can be engineered to produce optimal performance in adhesion.

Back-surface gold mirrors for vibrationally resonant sum-frequency (VR-SFG) spectroscopy using 3-mercaptopropyltrimethoxysilane as an adhesion promoter.

PubMed

Quast, Arthur D; Zhang, Feng; Linford, Matthew R; Patterson, James E

2011-06-01

Back-surface mirrors are needed as reference materials for vibrationally resonant sum-frequency generation (VR-SFG) probing of liquid-solid interfaces. Conventional noble metal mirrors are not suitable for back-surface applications due to the presence of a metal adhesion layer (chromium or titanium) between the window substrate and the reflective metal surface. Using vapor deposited 3-mercaptopropyltrimethoxysilane (MPTMS) as a bi-functional adhesion promoter, gold mirrors were fabricated on fused silica substrates. These mirrors exhibit excellent gold adhesion as determined by the Scotch(®) tape test. They also produce minimal spectroscopic interference in the C-H stretching region (2800-3000 cm(-1)), as characterized by VR-SFG. These mirrors are thus robust and can be used as back-surface mirrors for a variety of applications, including reference mirrors for VR-SFG.

A low-cost, high-yield fabrication method for producing optimized biomimetic dry adhesives

NASA Astrophysics Data System (ADS)

Sameoto, D.; Menon, C.

2009-11-01

We present a low-cost, large-scale method of fabricating biomimetic dry adhesives. This process is useful because it uses all photosensitive polymers with minimum fabrication costs or complexity to produce molds for silicone-based dry adhesives. A thick-film lift-off process is used to define molds using AZ 9260 photoresist, with a slow acting, deep UV sensitive material, PMGI, used as both an adhesion promoter for the AZ 9260 photoresist and as an undercutting material to produce mushroom-shaped fibers. The benefits to this process are ease of fabrication, wide range of potential layer thicknesses, no special surface treatment requirements to demold silicone adhesives and easy stripping of the full mold if process failure does occur. Sylgard® 184 silicone is used to cast full sheets of biomimetic dry adhesives off 4" diameter wafers, and different fiber geometries are tested for normal adhesion properties. Additionally, failure modes of the adhesive during fabrication are noted and strategies for avoiding these failures are discussed. We use this fabrication method to produce different fiber geometries with varying cap diameters and test them for normal adhesion strengths. The results indicate that the cap diameters relative to post diameters for mushroom-shaped fibers dominate the adhesion properties.

A test of the adhesion approximation for gravitational clustering

NASA Technical Reports Server (NTRS)

Melott, Adrian L.; Shandarin, Sergei; Weinberg, David H.

1993-01-01

We quantitatively compare a particle implementation of the adhesion approximation to fully non-linear, numerical 'N-body' simulations. Our primary tool, cross-correlation of N-body simulations with the adhesion approximation, indicates good agreement, better than that found by the same test performed with the Zel-dovich approximation (hereafter ZA). However, the cross-correlation is not as good as that of the truncated Zel-dovich approximation (TZA), obtained by applying the Zel'dovich approximation after smoothing the initial density field with a Gaussian filter. We confirm that the adhesion approximation produces an excessively filamentary distribution. Relative to the N-body results, we also find that: (a) the power spectrum obtained from the adhesion approximation is more accurate than that from ZA or TZA, (b) the error in the phase angle of Fourier components is worse than that from TZA, and (c) the mass distribution function is more accurate than that from ZA or TZA. It appears that adhesion performs well statistically, but that TZA is more accurate dynamically, in the sense of moving mass to the right place.

A test of the adhesion approximation for gravitational clustering

NASA Technical Reports Server (NTRS)

Melott, Adrian L.; Shandarin, Sergei F.; Weinberg, David H.

1994-01-01

We quantitatively compare a particle implementation of the adhesion approximation to fully nonlinear, numerical 'N-body' simulations. Our primary tool, cross-correlation of N-body simulations with the adhesion approximation, indicates good agreement, better than that found by the same test performed with the Zel'dovich approximation (hereafter ZA). However, the cross-correlation is not as good as that of the truncated Zel'dovich approximation (TZA), obtained by applying the Zel'dovich approximation after smoothing the initial density field with a Gaussian filter. We confirm that the adhesion approximation produces an excessively filamentary distribution. Relative to the N-body results, we also find that: (a) the power spectrum obtained from the adhesion approximation is more accurate that that from ZA to TZA, (b) the error in the phase angle of Fourier components is worse that that from TZA, and (c) the mass distribution function is more accurate than that from ZA or TZA. It appears that adhesion performs well statistically, but that TZA is more accurate dynamically, in the sense of moving mass to the right place.

Effect of sulfur removal on Al2O3 scale adhesion

NASA Astrophysics Data System (ADS)

Smialek, James L.

1991-03-01

If the role of reactive element dopants in producing A12O3 scale adhesion on NiCrAl alloys is to getter sulfur and prevent interfacial segregation, then eliminating sulfur from undoped alloys should also produce adherence. Four experiments successfully produced scale adhesion by sulfur removal alone. (1) Repeated oxidation and polishing of a pure NiCrAl alloy lowered the sulfur content from 10 to 2 parts per million by weight (ppmw), presumably by removing the segregated interfacial layer after each cycle. Total scale spallation changed to total retention after 13 such cycles, with no changes in the scale or interfacial morphology. (2) Thinner samples became adherent after fewer oxidation polishing cycles because of a more limited supply of sulfur. (3) Spalling in subsequent cyclic oxidation tests of samples from experiment (1) was a direct function of the initial sulfur content. (4) Desulfurization to 0.1 ppmw levels was accomplished by annealing melt-spun foil in 1 arm H2. These foils produced oxidation weight change curves for 500 1-hour cycles at 1100 °C similar to those for Y- or Zr-doped NiCrAl. The transition between adherent and nonadherent behavior was modeled in terms of sulfur flux, sulfur content, and sulfur segregation.

Single molecule force spectroscopy reveals the adhesion mechanism of hydrophobins

NASA Astrophysics Data System (ADS)

Cao, Yi; Li, Bing; Qin, Meng; Wang, Wei

Hydrophobins are a special class of amphiphilic proteins produced by filamentous fungi. They show outstanding interfacial self-assembly and adhesion properties, which are critical to their biological function. Such feature also inspires their broad applications in bio-engineering, surface modification, and nanotechnology. However, the biophysical properties of hydrophobins are not well understood. We combined atomic force microscopy based single molecule force spectroscopy and protein engineering to directly quantify the adhesion strength of a hydorphobin (HFB1) to various surfaces in both the monomer and oligomer states to reveal the molecular determinant of the adhesion strength of hydrophobins. We found that the monomer HFB1 showed distinct adhesion properties towards hydrophobic and hydrophilic surfaces. The adhesion to hydrophobic surfaces (i.e. graphite and gold) was significantly higher than that to the hydrophilic ones (e.g. mica and silicon). However, when self-assembled monolayers were formed, the adhesion strengths to various surfaces were similar and were ubiquitously stronger than the monomer cases. We hypothesized that the interactions among hydrophobins in the monolayer played significant roles for the enhance adhesion strengths. Extracting any single hydrophobin monomers from the surface required the break of interactions not only with the surface but also with the neighboring units. We proposed that such a mechanism may be widely explored in nature for many biofilms for surface adhesion. May also inspire the design of novel adhesives.

Exosomes from eosinophils autoregulate and promote eosinophil functions.

PubMed

Cañas, José Antonio; Sastre, Beatriz; Mazzeo, Carla; Fernández-Nieto, Mar; Rodrigo-Muñoz, José Manuel; González-Guerra, Andrés; Izquierdo, Manuel; Barranco, Pilar; Quirce, Santiago; Sastre, Joaquín; Del Pozo, Victoria

2017-05-01

Eosinophils are able to secrete exosomes that have an undefined role in asthma pathogenesis. We hypothesized that exosomes released by eosinophils autoregulate and promote eosinophil function. Eosinophils of patients with asthma ( n = 58) and healthy volunteers ( n = 16) were purified from peripheral blood, and exosomes were isolated and quantified from eosinophils of the asthmatic and healthy populations. Apoptosis, adhesion, adhesion molecules expression, and migration assays were performed with eosinophils in the presence or absence of exosomes from healthy and asthmatic individuals. Reactive oxygen species (ROS) were evaluated by flow cytometry with an intracellular fluorescent probe and nitric oxide (NO) and a colorimetric kit. In addition, exosomal proteins were analyzed by mass spectrometry. Eosinophil-derived exosomes induced an increase in NO and ROS production on eosinophils. Moreover, exosomes could act as a chemotactic factor on eosinophils, and they produced an increase in cell adhesion, giving rise to a specific augmentation of adhesion molecules, such as ICAM-1 and integrin α2. Protein content between exosomes from healthy and asthmatic individuals seems to be similar in both groups. In conclusion, we found that exosomes from the eosinophils of patients with asthma could modify several specific eosinophil functions related to asthma pathogenesis and that they could contribute fundamentally to the development and maintenance of asthma. © Society for Leukocyte Biology.

The Effect of Hydrogen Annealing and Sulfur Content on the Oxidation Resistance of PWA 1480

NASA Technical Reports Server (NTRS)

Smialek, James L.

1997-01-01

For many decades the dramatic effect of trace amounts of reactive elements on alumina and chromia scale adhesion has been recognized and widely studied. Although various theories have been used to account for such behavior, the connection between scale adhesion and sulfur segregation was initially reported by Smeggil et al. This study found strong surface segregation of sulfur from very low levels in the bulk which could then be curtailed by the addition of reactive elements. It was assumed that the reactive elements, which are strong sulfide formers, acted by getting sulfur in the bulk thus precluding sulfur segregation and weakening of the oxide-metal bond. Subsequent studies confirmed that adhesion could be produced by reducing the sulfur impurity level, without reactive elements. The understanding of this phenomenon has been applied to modern single crystal superalloys, where the addition of Y, although very effective, is problematic. Also problematic is definition of the level of sulfur that is acceptable and below which no further adhesion benefit is reached. Published works have indicated a broad transition defined by various materials and oxidation tests. The present study describes the oxidation behavior of one superalloy (PWA 1480) as a function of various sulfur contents produced by hydrogen annealing for various temperatures, times, and sample thicknesses. The purpose is to define more precisely a criterion for adhesion based on total sulfur reservoir and segregation potential.

Natural Underwater Adhesives

PubMed Central

Stewart, Russell J.; Ransom, Todd C.; Hlady, Vladimir

2011-01-01

The general topic of this review is protein-based underwater adhesives produced by aquatic organisms. The focus is on mechanisms of interfacial adhesion to native surfaces and controlled underwater solidification of natural water-borne adhesives. Four genera that exemplify the broad range of function, general mechanistic features, and unique adaptations are discussed in detail: blue mussels, acorn barnacles, sandcastle worms, and freshwater caddisfly larva. Aquatic surfaces in nature are charged and in equilibrium with their environment, populated by an electrical double layer of ions as well as adsorbed natural polyelectrolytes and microbial biofilms. Surface adsorption of underwater bioadhesives likely occurs by exchange of surface bound ligands by amino acid sidechains, driven primarily by relative affinities and effective concentrations of polymeric functional groups. Most aquatic organisms exploit modified amino acid sidechains, in particular phosphorylated serines and hydroxylated tyrosines (dopa), with high-surface affinity that form coordinative surface complexes. After delivery to the surfaces as a fluid, permanent natural adhesives solidify to bear sustained loads. Mussel plaques are assembled in a manner superficially reminiscent of in vitro layer-by-layer strategies, with sequentially delivered layers associated through Fe(dopa)3 coordination bonds. The adhesives of sandcastle worms, caddisfly larva, and barnacles may be delivered in a form somewhat similar to in vitro complex coacervation. Marine adhesives are secreted, or excreted, into seawater that has a significantly higher pH and ionic strength than the internal environment. Empirical evidence suggests these environment triggers could provide minimalistic, fail-safe timing mechanisms to prevent premature solidification (insolubilization) of the glue within the secretory system, yet allow rapid solidification after secretion. Underwater bioadhesives are further strengthened by secondary covalent curing. PMID:21643511

Silk-based biomaterials functionalized with fibronectin type II promotes cell adhesion.

PubMed

Pereira, Ana Margarida; Machado, Raul; da Costa, André; Ribeiro, Artur; Collins, Tony; Gomes, Andreia C; Leonor, Isabel B; Kaplan, David L; Reis, Rui L; Casal, Margarida

2017-01-01

The objective of this work was to exploit the fibronectin type II (FNII) module from human matrix metalloproteinase-2 as a functional domain for the development of silk-based biopolymer blends that display enhanced cell adhesion properties. The DNA sequence of spider dragline silk protein (6mer) was genetically fused with the FNII coding sequence and expressed in Escherichia coli. The chimeric protein 6mer+FNII was purified by non-chromatographic methods. Films prepared from 6mer+FNII by solvent casting promoted only limited cell adhesion of human skin fibroblasts. However, the performance of the material in terms of cell adhesion was significantly improved when 6mer+FNII was combined with a silk-elastin-like protein in a concentration-dependent behavior. With this work we describe a novel class of biopolymer that promote cell adhesion and potentially useful as biomaterials for tissue engineering and regenerative medicine. This work reports the development of biocompatible silk-based composites with enhanced cell adhesion properties suitable for biomedical applications in regenerative medicine. The biocomposites were produced by combining a genetically engineered silk-elastin-like protein with a genetically engineered spider-silk-based polypeptide carrying the three domains of the fibronectin type II module from human metalloproteinase-2. These composites were processed into free-standing films by solvent casting and characterized for their biological behavior. To our knowledge this is the first report of the exploitation of all three FNII domains as a functional domain for the development of bioinspired materials with improved biological performance. The present study highlights the potential of using genetically engineered protein-based composites as a platform for the development of new bioinspired biomaterials. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Association of Cell-adhesion Activities with Virulence in Shiga toxin-producing Escherichia coli O103：H2.

PubMed

Kobayashi, Naoki; Maeda, Eriko; Saito, Shioko; Furukawa, Ichiro; Ohnishi, Takahiro; Watanabe, Maiko; Terajima, Jun; Hara-Kudo, Yukiko

2016-01-01

The characteristics of 11 strains of Stx1-producing and Stx2-non-producing STEC O103：H2 were analyzed to investigate the differences in virulence in a single serotype of Shiga toxin (Stx) -producing Escherichia coli (STEC). Differences in the cell-adhesion activity to Caco-2 cells were observed among the strains. The activity of the one strain, isolated from a patient with hemolytic uremic syndrome was 4-20-fold higher than those of the other strains. Although the strains with high cell-adhesion activity showed high expressions of eae, espB, espD, and tir in the locus of enterocyte effacement related with cell-adhesion, those were not specific for this strain. In addition, the Stx1 production level of the strain was not particularly high. It was indicated that the high adhesion activity might be a potential factor to associate serious symptom.

Underwater locomotion in a terrestrial beetle: combination of surface de-wetting and capillary forces

PubMed Central

Hosoda, Naoe; Gorb, Stanislav N.

2012-01-01

For the first time, we report the remarkable ability of the terrestrial leaf beetle Gastrophysa viridula to walk on solid substrates under water. These beetles have adhesive setae on their feet that produce a secretory fluid having a crucial role in adhesion on land. In air, adhesion is produced by capillary forces between the fluid-covered setae and the substrate. In general, capillary forces do not contribute to adhesion under water. However, our observations showed that these beetles may use air bubbles trapped between their adhesive setae to walk on flooded, inclined substrata or even under water. Beetle adhesion to hydrophilic surfaces under water was lower than that in air, whereas adhesion to hydrophobic surfaces under water was comparable to that in air. Oil-covered hairy pads had a pinning effect, retaining the air bubbles on their feet. Bubbles in contact with the hydrophobic substrate de-wetted the substrate and produced capillary adhesion. Additional capillary forces are generated by the pad's liquid bridges between the foot and the substrate. Inspired by this idea, we designed an artificial silicone polymer structure with underwater adhesive properties. PMID:22874756

Dynamic surface tension measurement for the screening of biosurfactants produced by Lactobacillus plantarum subsp. plantarum PTCC 1896.

PubMed

Bakhshi, Nafiseh; Soleimanian-Zad, Sabihe; Sheikh-Zeinoddin, Mahmoud

2017-06-01

Currently, screening of microbial biosurfactants (BSs) is based on their equilibrium surface tension values obtained using static surface tension measurement. However, a good surfactant should not only have a low equilibrium surface tension, but its dynamic surface tension (DST) should also decrease rapidly with time. In this study, screening of BSs produced by Lactobacillus plantarum subsp. plantarum PTCC 1896 (probiotic) was performed based on their DST values measured by Wilhelmy plate tensiometry. The relationship between DST and structural and functional properties (anti-adhesive activity) of the BSs was investigated. The results showed that the changes in the yield, productivity and structure of the BSs were growth medium and incubation time dependent (p<0.05). Structurally different BSs produced exhibited identical equilibrium surface tension values. However, differences among the structure/yield of the BSs were observed through the measurement of their DST. The considerable dependence of DST on the concentration and composition of the BS proteins was observed (p<0.05). Moreover, the anti-adhesive activity of the BS was found to be positively correlated with its DST. The results suggest that the DST measurement could serve as an efficient method for the clever screening of BSs producer/production condition, and consequently, for the investigation of probiotic features of bacteria, since the anti-adhesive activity is an important criterion of probiotics. Copyright © 2017 Elsevier Inc. All rights reserved.

Extracellular matrix production by human osteoblasts cultured on biodegradable polymers applicable for tissue engineering.

PubMed

El-Amin, S F; Lu, H H; Khan, Y; Burems, J; Mitchell, J; Tuan, R S; Laurencin, C T

2003-03-01

The nature of the extracellular matrix (ECM) is crucial in regulating cell functions via cell-matrix interactions, cytoskeletal organization, and integrin-mediated signaling. In bone, the ECM is composed of proteins such as collagen (CO), fibronectin (FN), laminin (LM), vitronectin (VN), osteopontin (OP) and osteonectin (ON). For bone tissue engineering, the ECM should also be considered in terms of its function in mediating cell adhesion to biomaterials. This study examined ECM production, cytoskeletal organization, and adhesion of primary human osteoblastic cells on biodegradable matrices applicable for tissue engineering, namely polylactic-co-glycolic acid 50:50 (PLAGA) and polylactic acid (PLA). We hypothesized that the osteocompatible, biodegradable polymer surfaces promote the production of bone-specific ECM proteins in a manner dependent on polymer composition. We first examined whether the PLAGA and PLA matrices could support human osteoblastic cell growth by measuring cell adhesion at 3, 6 and 12h post-plating. Adhesion on PLAGA was consistently higher than on PLA throughout the duration of the experiment, and comparable to tissue culture polystyrene (TCPS). ECM components, including CO, FN, LM, ON, OP and VN, produced on the surface of the polymers were quantified by ELISA and localized by immunofluorescence staining. All of these proteins were present at significantly higher levels on PLAGA compared to PLA or TCPS surfaces. On PLAGA, OP and ON were the most abundant ECM components, followed by CO, FN, VN and LN. Immunofluorescence revealed an extracellular distribution for CO and FN, whereas OP and ON were found both intracellularly as well as extracellularly on the polymer. In addition, the actin cytoskeletal network was more extensive in osteoblasts cultured on PLAGA than on PLA or TCPS. In summary, we found that osteoblasts plated on PLAGA adhered better to the substrate, produced higher levels of ECM molecules, and showed greater cytoskeletal organization than on PLA and TCPS. We propose that this difference in ECM composition is functionally related to the enhanced cell adhesion observed on PLAGA. There is initial evidence that specific composition of the PLAGA polymer favors the ECM. Future studies will seek to optimize ECM production on these matrices for bone tissue engineering applications.

Sequence basis of Barnacle Cement Nanostructure is Defined by Proteins with Silk Homology

NASA Astrophysics Data System (ADS)

So, Christopher R.; Fears, Kenan P.; Leary, Dagmar H.; Scancella, Jenifer M.; Wang, Zheng; Liu, Jinny L.; Orihuela, Beatriz; Rittschof, Dan; Spillmann, Christopher M.; Wahl, Kathryn J.

2016-11-01

Barnacles adhere by producing a mixture of cement proteins (CPs) that organize into a permanently bonded layer displayed as nanoscale fibers. These cement proteins share no homology with any other marine adhesives, and a common sequence-basis that defines how nanostructures function as adhesives remains undiscovered. Here we demonstrate that a significant unidentified portion of acorn barnacle cement is comprised of low complexity proteins; they are organized into repetitive sequence blocks and found to maintain homology to silk motifs. Proteomic analysis of aggregate bands from PAGE gels reveal an abundance of Gly/Ala/Ser/Thr repeats exemplified by a prominent, previously unidentified, 43 kDa protein in the solubilized adhesive. Low complexity regions found throughout the cement proteome, as well as multiple lysyl oxidases and peroxidases, establish homology with silk-associated materials such as fibroin, silk gum sericin, and pyriform spidroins from spider silk. Distinct primary structures defined by homologous domains shed light on how barnacles use low complexity in nanofibers to enable adhesion, and serves as a starting point for unraveling the molecular architecture of a robust and unique class of adhesive nanostructures.

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

PubMed

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.

Isolation and characterization of lignin from the oak wood bioethanol production residue for adhesives.

PubMed

Lee, Soo Jung; Kim, Hyun Joo; Cho, Eun Jin; Song, Younho; Bae, Hyeun-Jong

2015-01-01

Lignin was isolated from the residue of bioethanol production with oak wood via alkaline and catalyzed organosolv treatments at ambient temperature to improve the purity of lignin for the materials application. The isolated lignins were analyzed for their chemical composition by nitrobenzene oxidation method and their functionality was characterized via wet chemistry method, element analysis, (1)H NMR, GPC and FTIR-ATR. The isolated lignin by acid catalyzed organosolv treatment (Acid-OSL) contained a higher lignin content, aromatic proton, phenolic hydroxyl group and a lower nitrogen content that is more reactive towards chemical modification. The lignin-based adhesives were prepared and the bond strength was measured to evaluate the enhanced reactivity of lignin by the isolation. Two steps of phenolation and methylolation were applied for the modification of the isolated lignins and their tensile strengths were evaluated for the use as an adhesive. The acid catalyzed organosolv lignin-based adhesives had comparable bond strength to phenol-formaldehyde adhesives. The analysis of lignin-based adhesives by FTIR-ATR and TGA showed structural similarity to phenol adhesive. The results demonstrate that the reactivity of lignin was enhanced by isolation from hardwood bioethanol production residues at ambient temperature and it could be used in a value-added application to produce lignin-based adhesives. Copyright © 2014 Elsevier B.V. All rights reserved.

Cloning, Characterization, and Expression Levels of the Nectin Gene from the Tube Feet of the Sea Urchin Paracentrotus Lividus.

PubMed

Toubarro, Duarte; Gouveia, Analuce; Ribeiro, Raquel Mesquita; Simões, Nélson; da Costa, Gonçalo; Cordeiro, Carlos; Santos, Romana

2016-06-01

Marine bioadhesives perform in ways that manmade products simply cannot match, especially in wet environments. Despite their technological potential, bioadhesive molecular mechanisms are still largely understudied, and sea urchin adhesion is no exception. These animals inhabit wave-swept shores, relying on specialized adhesive organs, tube feet, composed by an adhesive disc and a motile stem. The disc encloses a duo-gland adhesive system, producing adhesive and deadhesive secretions for strong reversible substratum attachment. The disclosure of sea urchin Paracentrotus lividus tube foot disc proteome led to the identification of a secreted adhesion protein, Nectin, never before reported in adult adhesive organs but, that given its adhesive function in eggs/embryos, was pointed out as a putative substratum adhesive protein in adults. To further understand Nectin involvement in sea urchin adhesion, Nectin cDNA was amplified for the first time from P. lividus adhesive organs, showing that not only the known Nectin mRNA, called Nectin-1 (GenBank AJ578435), is expressed in the adults tube feet but also a new mRNA sequence, called Nectin-2 (GenBank KT351732), differing in 15 missense nucleotide substitutions. Nectin genomic DNA was also obtained for the first time, indicating that both Nectin-1 and Nectin-2 derive from a single gene. In addition, expression analysis showed that both Nectins are overexpressed in tube feet discs, its expression being significantly higher in tube feet discs from sea urchins just after collection from the field relative to sea urchin from aquarium. These data further advocate for Nectin involvement in sea urchin reversible adhesion, suggesting that its expression might be regulated according to the hydrodynamic conditions.

Simulated Microgravity Alters Actin Cytoskeleton and Integrin-Mediated Focal Adhesions of Cultured Human Mesenchymal Stromal Cells

NASA Astrophysics Data System (ADS)

Gershovich, P. M.; Gershovic, J. G.; Buravkova, L. B.

2008-06-01

Cytoskeletal alterations occur in several cell types including lymphocytes, glial cells, and osteoblasts, during spaceflight and under simulated microgravity (SMG) (3, 4). One potential mechanism for cytoskeletal gravisensitivity is disruption of extracellular matrix (ECM) and integrin interactions. Focal adhesions are specialized sites of cell-matrix interaction composed of integrins and the diversity of focal adhesion-associated cytoplasmic proteins including vinculin, talin, α-actinin, and actin filaments (4, 5). Integrins produce signals essential for proper cellular function, survival and differentiation. Therefore, we investigated the effects of SMG on F-actin cytoskeleton structure, vinculin focal adhesions, expression of some integrin subtypes and cellular adhesion molecules (CAMs) in mesenchymal stem cells derived from human bone marrow (hMSCs). Simulated microgravity was produced by 3D-clinostat (Dutch Space, Netherlands). Staining of actin fibers with TRITC-phalloidin showed reorganization even after 30 minutes of simulated microgravity. The increasing of cells number with abnormal F-actin was observed after subsequent terms of 3D-clinorotation (6, 24, 48, 120 hours). Randomization of gravity vector altered dimensional structure of stress fibers and resulted in remodeling of actin fibers inside the cells. In addition, we observed vinculin redistribution inside the cells after 6 hours and prolonged terms of clinorotation. Tubulin fibers in a contrast with F-actin and vinculin didn't show any reorganization even after long 3Dclinorotation (120 hours). The expression of integrin α2 increased 1,5-6-fold in clinorotated hMSCs. Also we observed decrease in number of VCAM-1-positive cells and changes in expression of ICAM-1. Taken together, our findings indicate that SMG leads to microfilament and adhesion alterations of hMSCs most probably associated with involvement of some integrin subtypes.

Cell adhesion on nanotopography

NASA Astrophysics Data System (ADS)

Tsai, Irene; Kimura, Masahiro; Stockton, Rebecca; Jacobson, Bruce; Russell, Thomas

2003-03-01

Cell adhesion, a key element in understanding the cell-biomaterial interactions, underpins proper cell growth, function and survival. Understanding the parameters influencing cell adhesion is critical for applications in biosensors, implants and bioreactors. A gradient surface is used to study the effect of the surface topography on cell adhesion. A gradient surface is generated by block copolymer and homopolymer blends. The two homopolymers will phase separate on the micron scale and gradually decrease to nano-scale by the microphase separation of the diblock. Gradient surfaces offer a unique opportunity to probe lateral variations in the topography and interactions. Using thin films of mixtures of diblock copolymers of PS-b-MMA with PS and PMMA homopolymers, where the concentration of the PS-b-MMA varies across the surface, a gradient in the size scale of the morphology, from the nanoscopic to microscopic, was produced. By UV exposure, the variation in morphology translated into a variation in topography. The extent of cell spreading and cytoskeleton formation was investigated and marked dependence on the length scale of the surface topography was found.

Interference of functional monomers with polymerization efficiency of adhesives.

PubMed

Hanabusa, Masao; Yoshihara, Kumiko; Yoshida, Yasuhiro; Okihara, Takumi; Yamamoto, Takatsugu; Momoi, Yasuko; Van Meerbeek, Bart

2016-04-01

The degree of conversion (DC) of camphorquinone/amine-based adhesives is affected by acidic functional monomers as a result of inactivation of the amine co-initiator through an acid-base reaction. During bonding, functional monomers of self-etch adhesives chemically interact with hydroxyapatite (HAp). Here, we tested in how far the latter interaction of functional monomers with HAp counteracts the expected reduction in DC of camphorquinone/amine-based adhesives. The DC of three experimental adhesive formulations, containing either of the two functional monomers [10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) or 4-methacryloxyethyl trimellitic acid anhydride (4-META)] or no functional monomer (no-FM; control), was measured with and without HAp powder added to the adhesive formulations. Both the variables 'functional monomer' and 'HAp' were found to be significant, with the functional monomer reducing the DC and HAp counteracting this effect. It is concluded that the functional monomers 10-MDP and 4-META interfere with the polymerization efficiency of adhesives. This interference is less prominent in the presence of HAp, which would clinically correspond to when these two functional monomers of the adhesive simultaneously interact with HAp in tooth tissue. © 2016 Eur J Oral Sci.

Surgery-derived reactive oxygen species produced by polymorphonuclear leukocytes promote tumor recurrence: studies in an in vitro model.

PubMed

van Grevenstein, Wilhelmina M U; Aalbers, Arend G J; Ten Raa, Sander; Sluiter, Wim; Hofland, Leo J; Jeekel, Hans; van Eijck, Casper H J

2007-06-01

Tissue injury induces the acute phase response, aimed at minimizing damage and starting the healing process. Polymorphonuclear leukocytes (PMNs) respond to the presence of specific chemoattractants and begin to appear in large numbers. The aim of this study was to investigate the influence of reactive oxygen species (ROS) produced by PMNs on the interaction between colon carcinoma cells and mesothelial cells. An experimental human in vitro model was designed using Caco-2 colon carcinoma cells and primary cultures of mesothelial cells. Tumor cell adhesion to a mesothelial monolayer was assessed after preincubation of the mesothelium with stimulated PMNs and unstimulated PMNs. Mesothelial cells were also incubated with xanthine/xanthine oxidase (X/XO) complex producing ROS after which adhesion of Caco-2 cells was investigated and the expression of adhesion molecules (ICAM-1, VCAM-1, and CD44) by means of enzyme immunoassay. In the control situation the average adhesion of Caco-2 cells to the mesothelial monolayers was 23%. Mesothelial monolayers incubated with unstimulated PMNs showed a 25% increase of tumor cell adhesion (P < 0.05). The adhesion of tumor to the monolayers incubated with the N-formyl-methionyl-leucyl-phenylalanine-stimulated PMNs increased with 40% (P < 0.01). Incubation of the mesothelium with X/XO resulted in an enhancement of adhesion of Caco-2 cells of 70% and an up-regulation of expression of ICAM-1, VCAM-1, and CD44. This study reveals an increase of tumor cell adhesion to the mesothelium induced by incubating the mesothelial monolayers with PMNs. PMNs are producing a number of products, like proteolytic enzymes, cytokines, and ROS. These factors up-regulate the expression of adhesion molecules and in that way stimulate the adhesion of tumor to the mesothelium.

Influence of cross-linkers on the cohesive and adhesive self-healing ability of polysulfide-based thermosets.

PubMed

Lafont, U; van Zeijl, H; van der Zwaag, S

2012-11-01

Synthetic systems with intrinsic self-repairing or self-healing abilities have emerged during the past decade. In this work, the influence of the cross-linker and chain rigidity on the healing ability of thermoset rubbers containing disulfide bonds have been investigated. The produced materials exhibit adhesive and cohesive self-healing properties. The recovery of these two functionalities upon the thermally triggered healing events has shown to be highly dependent on the network cross-link density and chain rigidity. As a result, depending on the rubber thermoset intrinsic physical properties, the thermal mending leading to full cohesive recovery can be achieved in 20-300 min at a modest healing temperature of 65 °C. The adhesive strength ranges from 0.2 to 0.5 MPa and is fully recovered even after multiple failure events.

Rapid adhesive bonding of advanced composites and titanium

NASA Technical Reports Server (NTRS)

Stein, B. A.; Tyeryart, J. R.; Hodgest, W. T.

1985-01-01

Rapid adhesive bonding (RAB) concepts utilize a toroid induction technique to heat the adhesive bond line directly. This technique was used to bond titanium overlap shear specimens with 3 advanced thermoplastic adhesives and APC-2 (graphite/PEEK) composites with PEEK film. Bond strengths equivalent to standard heated-platen press bonds were produced with large reductions in process time. RAB produced very strong bonds in APC-2 adherend specimens; the APC-2 adherends were highly resistant to delamination. Thermal cycling did not significantly affect the shear strengths of RAB titanium bonds with polyimide adhesives. A simple ultrasonic non-destructive evaluation process was found promising for evaluating bond quality.

Chemistry technology: Adhesives and plastics: A compilation

NASA Technical Reports Server (NTRS)

1973-01-01

Technical information on chemical formulations for improving and/or producing adhesives is presented. Data are also reported on polymeric plastics with special characteristics or those plastics that were produced by innovative means.

Dynamic Adhesion of Umbilical Cord Blood Endothelial Progenitor Cells under Laminar Shear Stress

PubMed Central

Angelos, Mathew G.; Brown, Melissa A.; Satterwhite, Lisa L.; Levering, Vrad W.; Shaked, Natan T.; Truskey, George A.

2010-01-01

Late outgrowth endothelial progenitor cells (EPCs) represent a promising cell source for rapid reendothelialization of damaged vasculature after expansion ex vivo and injection into the bloodstream. We characterized the dynamic adhesion of umbilical-cord-blood-derived EPCs (CB-EPCs) to surfaces coated with fibronectin. CB-EPC solution density affected the number of adherent cells and larger cells preferentially adhered at lower cell densities. The number of adherent cells varied with shear stress, with the maximum number of adherent cells and the shear stress at maximum adhesion depending upon fluid viscosity. CB-EPCs underwent limited rolling, transiently tethering for short distances before firm arrest. Immediately before arrest, the instantaneous velocity decreased independent of shear stress. A dimensional analysis indicated that adhesion was a function of the net force on the cells, the ratio of cell diffusion to sliding speed, and molecular diffusivity. Adhesion was not limited by the settling rate and was highly specific to α5β1 integrin. Total internal reflection fluorescence microscopy showed that CB-EPCs produced multiple contacts of α5β1 with the surface and the contact area grew during the first 20 min of attachment. These results demonstrate that CB-EPC adhesion from blood can occur under physiological levels of shear stress. PMID:21112278

Multi-scale Finite Element Modeling of Eustachian Tube Function: Influence of Mucosal Adhesion

PubMed Central

Malik, J.E.; Swarts, J.D.; Ghadiali, S. N.

2017-01-01

The inability to open the collapsible Eustachian tube (ET) leads to the development of chronic Otitis Media (OM). Although mucosal inflammation during OM leads to increased mucin gene expression and elevated adhesion forces within the ET lumen, it is not known how changes in mucosal adhesion alter the biomechanical mechanisms of ET function. In this study, we developed a novel multi-scale finite element model of ET function in adults that utilizes adhesion spring elements to simulate changes in mucosal adhesion. Models were created for six adult subjects and dynamic patterns in muscle contraction were used to simulate the wave-like opening of the ET that occurs during swallowing. Results indicate that ET opening is highly sensitive to the level of mucosal adhesion and that exceeding a critical value of adhesion leads to rapid ET dysfunction. Parameter variation studies and sensitivity analysis indicate that increased mucosal adhesion alters the relative importance of several tissue biomechanical properties. For example, increases in mucosal adhesion reduced the sensitivity of ET function to tensor veli palatini muscle forces but did not alter the insensitivity of ET function to levator veli palatini muscle forces. Interestingly, although changes in cartilage stiffness did not significantly influence ET opening under low adhesion conditions, ET opening was highly sensitive to changes in cartilage stiffness under high adhesion conditions. Therefore, our multi-scale computational models indicate that changes in mucosal adhesion as would occur during inflammatory OM alter the biomechanical mechanisms of ET function. PMID:26891171

Emergence of the interplay between hierarchy and contact splitting in biological adhesion highlighted through a hierarchical shear lag model.

PubMed

Brely, Lucas; Bosia, Federico; Pugno, Nicola M

2018-06-20

Contact unit size reduction is a widely studied mechanism as a means to improve adhesion in natural fibrillar systems, such as those observed in beetles or geckos. However, these animals also display complex structural features in the way the contact is subdivided in a hierarchical manner. Here, we study the influence of hierarchical fibrillar architectures on the load distribution over the contact elements of the adhesive system, and the corresponding delamination behaviour. We present an analytical model to derive the load distribution in a fibrillar system loaded in shear, including hierarchical splitting of contacts, i.e. a "hierarchical shear-lag" model that generalizes the well-known shear-lag model used in mechanics. The influence on the detachment process is investigated introducing a numerical procedure that allows the derivation of the maximum delamination force as a function of the considered geometry, including statistical variability of local adhesive energy. Our study suggests that contact splitting generates improved adhesion only in the ideal case of extremely compliant contacts. In real cases, to produce efficient adhesive performance, contact splitting needs to be coupled with hierarchical architectures to counterbalance high load concentrations resulting from contact unit size reduction, generating multiple delamination fronts and helping to avoid detrimental non-uniform load distributions. We show that these results can be summarized in a generalized adhesion scaling scheme for hierarchical structures, proving the beneficial effect of multiple hierarchical levels. The model can thus be used to predict the adhesive performance of hierarchical adhesive structures, as well as the mechanical behaviour of composite materials with hierarchical reinforcements.

Osteoclast cytosolic calcium, regulated by voltage-gated calcium channels and extracellular calcium, controls podosome assembly and bone resorption

NASA Technical Reports Server (NTRS)

Miyauchi, A.; Hruska, K. A.; Greenfield, E. M.; Duncan, R.; Alvarez, J.; Barattolo, R.; Colucci, S.; Zambonin-Zallone, A.; Teitelbaum, S. L.; Teti, A.

1990-01-01

The mechanisms of Ca2+ entry and their effects on cell function were investigated in cultured chicken osteoclasts and putative osteoclasts produced by fusion of mononuclear cell precursors. Voltage-gated Ca2+ channels (VGCC) were detected by the effects of membrane depolarization with K+, BAY K 8644, and dihydropyridine antagonists. K+ produced dose-dependent increases of cytosolic calcium ([Ca2+]i) in osteoclasts on glass coverslips. Half-maximal effects were achieved at 70 mM K+. The effects of K+ were completely inhibited by dihydropyridine derivative Ca2+ channel blocking agents. BAY K 8644 (5 X 10(-6) M), a VGCC agonist, stimulated Ca2+ entry which was inhibited by nicardipine. VGCCs were inactivated by the attachment of osteoclasts to bone, indicating a rapid phenotypic change in Ca2+ entry mechanisms associated with adhesion of osteoclasts to their resorption substrate. Increasing extracellular Ca2+ ([Ca2+]e) induced Ca2+ release from intracellular stores and Ca2+ influx. The Ca2+ release was blocked by dantrolene (10(-5) M), and the influx by La3+. The effects of [Ca2+]e on [Ca2+]i suggests the presence of a Ca2+ receptor on the osteoclast cell membrane that could be coupled to mechanisms regulating cell function. Expression of the [Ca2+]e effect on [Ca2+]i was similar in the presence or absence of bone matrix substrate. Each of the mechanisms producing increases in [Ca2+]i, (membrane depolarization, BAY K 8644, and [Ca2+]e) reduced expression of the osteoclast-specific adhesion structure, the podosome. The decrease in podosome expression was mirrored by a 50% decrease in bone resorptive activity. Thus, stimulated increases of osteoclast [Ca2+]i lead to cytoskeletal changes affecting cell adhesion and decreasing bone resorptive activity.

Liquefaction of kenaf (Hibiscus cannabinus L.) core for wood laminating adhesive.

PubMed

Juhaida, M F; Paridah, M T; Mohd Hilmi, M; Sarani, Z; Jalaluddin, H; Mohamad Zaki, A R

2010-02-01

A study was carried out to produce polyurethane (PU) as a wood laminating adhesive from liquefied kenaf core (LKC) polyols by reacting it with toluene-2,4-diisocyanate (TDI) and 1,4-butanediol (BDO). The LKC polyurethane (LKCPU) adhesive has a molecular weight (MW) of 2666, viscosity of 5370 mPa s, and solids content of 86.9%. The average shear strength of the rubberwood (RW) bonded with LKCPU adhesive was 2.9 MPa. Most of the sheared specimens experienced a total adhesive failure. The formation of air bubbles through the liberation of carbon dioxide was observed to reduce the adhesive penetration and bonding strength which was obviously seen on the sheared specimens. The percentage of catalyst used can be varied based on the usage and working time needed. Nonetheless, the physical properties of LKCPU produced in this work had shown good potential as edge-bonding adhesive.

Functionally Graded Adhesives for Composite Joints

NASA Technical Reports Server (NTRS)

Stapleton, Scott E.; Waas, Anthony M.; Arnold, Steven M.

2012-01-01

Adhesives with functionally graded material properties are being considered for use in adhesively bonded joints to reduce the peel stress concentrations located near adherend discontinuities. Several practical concerns impede the actual use of such adhesives. These include increased manufacturing complications, alterations to the grading due to adhesive flow during manufacturing, and whether changing the loading conditions significantly impact the effectiveness of the grading. An analytical study is conducted to address these three concerns. An enhanced joint finite element, which uses an analytical formulation to obtain exact shape functions, is used to model the joint. Furthermore, proof of concept testing is conducted to show the potential advantages of functionally graded adhesives. In this study, grading is achieved by strategically placing glass beads within the adhesive layer at different densities along the joint.

Predicting adhesion and biofilm formation boundaries on stainless steel surfaces by five Salmonella enterica strains belonging to different serovars as a function of pH, temperature and NaCl concentration.

PubMed

Moraes, Juliana O; Cruz, Ellen A; Souza, Enio G F; Oliveira, Tereza C M; Alvarenga, Verônica O; Peña, Wilmer E L; Sant'Ana, Anderson S; Magnani, Marciane

2018-05-26

This study aimed to assess the capability of 97 epidemic S. enterica strains belonging to 18 serovars to form biofilm. Five strains characterized as strong biofilm-producers, belonging to distinct serovars (S. Enteritidis 132, S. Infantis 176, S. Typhimurium 177, S. Heidelberg 281 and S. Corvallis 297) were assayed for adhesion/biofilm formation on stainless steel surfaces. The experiments were conducted in different combinations of NaCl (0, 2, 4, 5, 6, 8 and 10% w/v), pH (4, 5, 6 and 7) and temperatures (8 °C, 12 °C, 20 °C and 35 °C). Only adhesion was assumed to occur when S. enterica counts were ≥3 and <5 log CFU/cm 2 , whereas biofilm formation was defined as when the counts were ≥5 log CFU/cm 2 . The binary responses were used to develop models to predict the probability of adhesion/biofilm formation on stainless steel surfaces by five strains belonging to different S. enterica serovars. A total of 99% (96/97) of the tested S. enterica strains were characterized as biofilm-producers in the microtiter plate assays. The ability to form biofilm varied (P < 0.05) within and among the different serovars. Among the biofilm-producers, 21% (20/96), 45% (43/96), and 35% (34/96) were weak, moderate and strong biofilm-producers, respectively. The capability for adhesion/biofilm formation on stainless steel surfaces under the experimental conditions studied varied among the strains studied, and distinct secondary models were obtained to describe the behavior of the five S. enterica tested. All strains showed adhesion at pH 4 up to 4% of NaCl and at 20 °C and 35 °C. The probability of adhesion decreased when NaCl concentrations were >8% and at 8 °C, as well as in pH values ≤ 5 and NaCl concentrations > 6%, for all tested strains. At pH 7 and 6, biofilm formation for S. Enteritidis, S. Infantis, S. Typhimurium, S. Heidelberg was observed up to 6% of NaCl at 35 °C and 20 °C. The predicted boundaries for adhesion were pH values < 5 and NaCl ≥ 4% and at temperatures <20 °C. For biofilm formation, the predicted boundaries were pH values < 5 and NaCl concentrations ≥ 2% and at temperatures <20 °C for all strains. The secondary models obtained describe the variability in boundaries of adhesion and biofilm formation on stainless steel by five strains belonging to different S. enterica serovars. The boundary models can be used to predict adhesion and biofilm formation ability on stainless steel by S. enterica as affected by pH, NaCl and temperature. Copyright © 2018 Elsevier B.V. All rights reserved.

Multi-scale finite element modeling of Eustachian tube function: influence of mucosal adhesion.

PubMed

Malik, J E; Swarts, J D; Ghadiali, S N

2016-12-01

The inability to open the collapsible Eustachian tube (ET) leads to the development of chronic Otitis Media (OM). Although mucosal inflammation during OM leads to increased mucin gene expression and elevated adhesion forces within the ET lumen, it is not known how changes in mucosal adhesion alter the biomechanical mechanisms of ET function. In this study, we developed a novel multi-scale finite element model of ET function in adults that utilizes adhesion spring elements to simulate changes in mucosal adhesion. Models were created for six adult subjects, and dynamic patterns in muscle contraction were used to simulate the wave-like opening of the ET that occurs during swallowing. Results indicate that ET opening is highly sensitive to the level of mucosal adhesion and that exceeding a critical value of adhesion leads to rapid ET dysfunction. Parameter variation studies and sensitivity analysis indicate that increased mucosal adhesion alters the relative importance of several tissue biomechanical properties. For example, increases in mucosal adhesion reduced the sensitivity of ET function to tensor veli palatini muscle forces but did not alter the insensitivity of ET function to levator veli palatini muscle forces. Interestingly, although changes in cartilage stiffness did not significantly influence ET opening under low adhesion conditions, ET opening was highly sensitive to changes in cartilage stiffness under high adhesion conditions. Therefore, our multi-scale computational models indicate that changes in mucosal adhesion as would occur during inflammatory OM alter the biomechanical mechanisms of ET function. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Mussel-inspired nano-building block assemblies for mimicking extracellular matrix microenvironments with multiple functions.

PubMed

Wang, Zhenming; Jia, Zhanrong; Jiang, Yanan; Li, Pengfei; Han, Lu; Lu, Xiong; Ren, Fuzeng; Wang, Kefeng; Yuan, Huiping

2017-08-03

The assembly of nano-building blocks is an effective way to produce artificial extracellular matrix microenvironments with hierarchical micro/nano structures. However, it is hard to assemble different types of nano-building blocks, to form composite coatings with multiple functions, by traditional layer-by-layer (LbL) self-assembly methods. Inspired by the mussel adhesion mechanism, we developed polydopamine (PDA)-decorated bovine serum albumin microspheres (BSA-MS) and nano-hydroxyapatite (nano-HA), and assembled them to form bioactive coatings with micro/nano structures encapsulating bone morphogenetic protein-2 (BMP-2). First, PDA-decorated nano-HA (nano-pHA) was obtained by oxidative polymerization of dopamine on nano-HA. Second, BMP-2-encapsulated BSA microspheres were prepared through desolvation, and then were also decorated by PDA (pBSA-MS). Finally, the nano-pHA and pBSA-MS were assembled using the adhesive properties of PDA. Bone marrow stromal cell cultures and in vivo implantation, showed that the pHA/pBSA (BMP-2) coatings can promote cell adhesion, proliferation, and benefited for osteoinductivity. PDA decoration was also applied to assemble various functional nanoparticles, such as nano-HA, polystyrene, and Fe 3 O 4 nanoparticles. In summary, this study provides a novel strategy for the assembly of biofunctional nano-building blocks, which surpasses traditional LbL self-assembly of polyelectrolytes, and can find broad applications in bioactive agents delivery or multi-functional coatings.

Focal adhesions, stress fibers and mechanical tension

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burridge, Keith, E-mail: Keith_Burridge@med.unc.edu; Guilluy, Christophe, E-mail: christophe.guilluy@univ-nantes.fr

Stress fibers and focal adhesions are complex protein arrays that produce, transmit and sense mechanical tension. Evidence accumulated over many years led to the conclusion that mechanical tension generated within stress fibers contributes to the assembly of both stress fibers themselves and their associated focal adhesions. However, several lines of evidence have recently been presented against this model. Here we discuss the evidence for and against the role of mechanical tension in driving the assembly of these structures. We also consider how their assembly is influenced by the rigidity of the substratum to which cells are adhering. Finally, we discussmore » the recently identified connections between stress fibers and the nucleus, and the roles that these may play, both in cell migration and regulating nuclear function. - Highlights: • The different types of stress fiber and focal adhesion are described. • We discuss the controversy about tension and assembly of these structures. • We describe the different models used to investigate assembly of these structures. • The influence of substratum rigidity is discussed. • Stress fiber connections to the nucleus are reviewed.« less

Cell Adhesions: Actin-Based Modules that Mediate Cell-Extracellular Matrix and Cell-Cell Interactions

PubMed Central

Bachir, Alexia; Horwitz, Alan Rick; Nelson, W. James; Bianchini, Julie M.

2018-01-01

Cell adhesions link cells to the extracellular matrix (ECM) and to each other, and depend on interactions with the actin cytoskeleton. Both cell-ECM and cell-cell adhesion sites contain discrete, yet overlapping functional modules. These modules establish physical association with the actin cytoskeleton, locally modulate actin organization and dynamics, and trigger intracellular signaling pathways. Interplay between these modules generates distinct actin architectures that underlie different stages, types, and functions of cell-ECM and cell-cell adhesions. Actomyosin contractility is required to generate mature, stable adhesions, as well as sense and translate the mechanical properties of the cellular environment to changes in cell organization and behavior. In this chapter we discuss the organization and function of different adhesion modules and how they interact with the actin cytoskeleton. We highlight the molecular mechanisms of mechanotransduction in adhesions, and how adhesion molecules mediate crosstalk between cell-ECM and cell-cell adhesion sites. PMID:28679638

Adhesion and friction in gecko toe attachment and detachment

PubMed Central

Tian, Yu; Pesika, Noshir; Zeng, Hongbo; Rosenberg, Kenny; Zhao, Boxin; McGuiggan, Patricia; Autumn, Kellar; Israelachvili, Jacob

2006-01-01

Geckos can run rapidly on walls and ceilings, requiring high friction forces (on walls) and adhesion forces (on ceilings), with typical step intervals of ≈20 ms. The rapid switching between gecko foot attachment and detachment is analyzed theoretically based on a tape model that incorporates the adhesion and friction forces originating from the van der Waals forces between the submicron-sized spatulae and the substrate, which are controlled by the (macroscopic) actions of the gecko toes. The pulling force of a spatula along its shaft with an angle θ between 0 and 90° to the substrate, has a “normal adhesion force” contribution, produced at the spatula-substrate bifurcation zone, and a “lateral friction force” contribution from the part of spatula still in contact with the substrate. High net friction and adhesion forces on the whole gecko are obtained by rolling down and gripping the toes inward to realize small pulling angles θ between the large number of spatulae in contact with the substrate. To detach, the high adhesion/friction is rapidly reduced to a very low value by rolling the toes upward and backward, which, mediated by the lever function of the setal shaft, peels the spatulae off perpendicularly from the substrates. By these mechanisms, both the adhesion and friction forces of geckos can be changed over three orders of magnitude, allowing for the swift attachment and detachment during gecko motion. The results have obvious implications for the fabrication of dry adhesives and robotic systems inspired by the gecko's locomotion mechanism. PMID:17148600

Preventing Pseudomonas aeruginosa and Chromobacterium violaceum infections by anti-adhesion-active components of edible seeds

PubMed Central

2012-01-01

Background Pseudomonas aeruginosa adhesion to animal/human cells for infection establishment involves adhesive proteins, including its galactose- and fucose-binding lectins PA-IL (LecA) and PA-IIL (LecB). The lectin binding to the target-cell receptors may be blocked by compatible glycans that compete with those of the receptors, functioning as anti-adhesion glycodecoys. The anti-adhesion treatment is of the utmost importance for abrogating devastating antibiotic-resistant P. aeruginosa infections in immunodeficient and cystic fibrosis (CF) patients. This strategy functions in nature in protecting embryos and neonates. We have shown that PA-IL, PA-IIL, and also CV-IIL (a PA-IIL homolog produced in the related pathogen Chromobacterium violaceum) are highly useful for revealing natural glycodecoys that surround embryos in diverse avian eggs and are supplied to neonates in milks and royal jelly. In the present study, these lectins were used as probes to search for seed embryo-protecting glycodecoys. Methods The lectin-blocking glycodecoy activities were shown by the hemagglutination-inhibition test. Lectin-binding glycoproteins were detected by Western blotting with peroxidase-labeled lectins. Results The present work reports the finding - by using PA-IL, PA-IIL, and CV-IIL - of rich glycodecoy activities of low (< 10 KDa) and high MW (> 10 kDa) compounds (including glycoproteins) in extracts of cashew, cocoa, coffee, pumpkin, and tomato seeds, resembling those of avian egg whites, mammal milks, and royal jelly. Conclusions Edible seed extracts possess lectin-blocking glycodecoys that might protect their embryos from infections and also might be useful for hampering human and animal infections. PMID:22336073

Deregulation of focal adhesion formation and cytoskeletal tension due to loss of A-type lamins.

PubMed

Corne, Tobias D J; Sieprath, Tom; Vandenbussche, Jonathan; Mohammed, Danahe; Te Lindert, Mariska; Gevaert, Kris; Gabriele, Sylvain; Wolf, Katarina; De Vos, Winnok H

2017-09-03

The nuclear lamina mechanically integrates the nucleus with the cytoskeleton and extracellular environment and regulates gene expression. These functions are exerted through direct and indirect interactions with the lamina's major constituent proteins, the A-type lamins, which are encoded by the LMNA gene. Using quantitative stable isotope labeling-based shotgun proteomics we have analyzed the proteome of human dermal fibroblasts in which we have depleted A-type lamins by means of a sustained siRNA-mediated LMNA knockdown. Gene ontology analysis revealed that the largest fraction of differentially produced proteins was involved in actin cytoskeleton organization, in particular proteins involved in focal adhesion dynamics, such as actin-related protein 2 and 3 (ACTR2/3), subunits of the ARP2/3 complex, and fascin actin-bundling protein 1 (FSCN1). Functional validation using quantitative immunofluorescence showed a significant reduction in the size of focal adhesion points in A-type lamin depleted cells, which correlated with a reduction in early cell adhesion capacity and an increased cell motility. At the same time, loss of A-type lamins led to more pronounced stress fibers and higher traction forces. This phenotype could not be mimicked or reversed by experimental modulation of the STAT3-IL6 pathway, but it was partly recapitulated by chemical inhibition of the ARP2/3 complex. Thus, our data suggest that the loss of A-type lamins perturbs the balance between focal adhesions and cytoskeletal tension. This imbalance may contribute to mechanosensing defects observed in certain laminopathies.

Development and characterization of a novel hydrogel adhesive for soft tissue applications

NASA Astrophysics Data System (ADS)

Sanders, Lindsey Kennedy

With laparoscopic and robotic surgical techniques advancing, the need for an injectable surgical adhesive is growing. To be effective, surgical adhesives for internal organs require bulk strength and compliance to avoid rips and tears, and adhesive strength to avoid leakage at the application site, while not hindering the natural healing process. Although a number of tissue adhesives and sealants approved by the FDA for surgical use are currently available, attaining a useful balance in all of these qualities has proven difficult, particularly when considering applications involving highly expandable tissue, such as bladder and lung. The long-term goal of this project is to develop a hydrogel-based tissue adhesive that provides proper mechanical properties to eliminate the need for sutures in various soft tissue applications. Tetronic (BASF), a 4-arm poly(propylene oxide)-poly(ethylene oxide) (PPO-PEO) block copolymer, has been selected as the base material for the adhesive hydrogel system. Solutions of Tetronic T1107 can support reverse thermal gelation at physiological temperatures, which can be combined with covalent crosslinking to achieve a "tandem gelation" process making it ideal for use as a tissue adhesive. The objective of this doctoral thesis research is to improve the performance of the hydrogel based tissue adhesive developed previously by Cho and co-workers by applying a multi-functionalization of Tetronic. Specifically, this research aimed to improve bonding strength of Tetronic tissue adhesive using bi-functional modification, incorporate hemostatic function to the bi-functional Tetronic hydrogel, and evaluate the safety of bi-functional Tetronic tissue adhesive both in vitro and in vivo. In summary, we have developed a fast-curing, mechanically strong hemostatic tissue adhesive that can control blood loss in wet conditions during wound treatment applications (bladder, liver and muscle). Specifically, the bi-functional Tetronic adhesive (TAS) with a proper blend ratio may be used to achieve an accurate balance in bulk and tissue bond strengths, as well as the compliance and durability for expandable organ application, such as the bladder. Incorporation of chitosan expanded the utility of the bi-functional modified T1107 (TAS) adhesive to tissue wounds on highly vascularized organs (e.g., liver, kidney). Further, we demonstrated that the modified Tetronic adhesive is biocompatible and safe for treatment of small soft tissue wounds on rat's muscle using FDA requirements. The current findings helped our understanding of the material and mechanical properties of the modified Tetronic adhesive and ultimately progress the field of surgical adhesives and sealants by providing a tunable adhesive system for various internal soft tissue wound applications.

Strategies to improve the adhesion of rubbers to adhesives by means of plasma surface modification

NASA Astrophysics Data System (ADS)

Martín-Martínez, J. M.; Romero-Sánchez, M. D.

2006-05-01

The surface modifications produced by treatment of a synthetic sulfur vulcanized styrene-butadiene rubber with oxidizing (oxygen, air, carbon dioxide) and non oxidizing (nitrogen, argon) RF low pressure plasmas, and by treatment with atmospheric plasma torch have been assessed by ATR-IR and XPS spectroscopy, SEM, and contact angle measurements. The effectiveness of the low pressure plasma treatment depended on the gas atmosphere used to generate the plasma. A lack of relationship between surface polarity and wettability, and peel strength values was obtained, likely due to the cohesive failure in the rubber obtained in the adhesive joints. In general, acceptable adhesion values of plasma treated rubber were obtained for all plasmas, except for nitrogen plasma treatment during 15 minutes due to the creation of low molecular weight moieties on the outermost rubber layer. A toluene wiping of the N{2 } plasma treated rubber surface for 15 min removed those moieties and increased adhesion was obtained. On the other hand, the treatment of the rubber with atmospheric pressure by means of a plasma torch was proposed. The wettability of the rubber was improved by decreasing the rubber-plasma torch distance and by increasing the duration because a partial removal of paraffin wax from the rubber surface was produced. The rubber surface was oxidized by the plasma torch treatment, and the longer the duration of the plasma torch treatment, the higher the degree of surface oxidation (mainly creation of C O moieties). However, although the rubber surface was effectively modified by the plasma torch treatment, the adhesion was not greatly improved, due to the migration of paraffin wax to the treated rubber-polyurethane adhesive interface once the adhesive joint was produced. On the other hand, the extended treatment with plasma torch facilitated the migration of zinc stearate to the rubber-adhesive interface, also contributing to deteriorate the adhesion in greater extent. Finally, it has been found that cleaning of SBS rubber in an ultrasonic bath prior to plasma torch treatment produced a partial removal of paraffin waxes from the surface, and thus improved adhesion was obtained.

Specific degradation of the mucus adhesion-promoting protein (MapA) of Lactobacillus reuteri to an antimicrobial peptide.

PubMed

Bøhle, Liv Anette; Brede, Dag Anders; Diep, Dzung B; Holo, Helge; Nes, Ingolf F

2010-11-01

The intestinal flora of mammals contains lactic acid bacteria (LAB) that may provide positive health effects for the host. Such bacteria are referred to as probiotic bacteria. From a pig, we have isolated a Lactobacillus reuteri strain that produces an antimicrobial peptide (AMP). The peptide was purified and characterized, and it was unequivocally shown that the AMP was a well-defined degradation product obtained from the mucus adhesion-promoting protein (MapA); it was therefore termed AP48-MapA. This finding demonstrates how large proteins might inherit unexpected pleiotropic functions by conferring antimicrobial capacities on the producer. The MapA/AP48-MapA system is the first example where a large protein of an intestinal LAB is shown to give rise to such an AMP. It is also of particular interest that the protein that provides this AMP is associated with the binding of the bacterium producing it to the surface/lining of the gut. This finding gives us new perspective on how some probiotic bacteria may successfully compete in this environment and thereby contribute to a healthy microbiota.

The Problems of Ensure of Safe Labor Conditions on Workplaces for Adhesive Bonding

NASA Astrophysics Data System (ADS)

Ciecińska, Barbara; Homik, Wojciech

2016-06-01

In the performance a variety of technological operations a human may come into contact with a variety of factors causing deterioration of safety at work. As an example of which is described in article, adhesive bonding operations are requiring use of specific chemicals, which are adhesives. They are produced on the basis of a variety of compounds, often hazardous to human health. Furthermore, adhesive bonding requires a series of preparatory operations such as degreasing or surface preparation with a specific structure and roughness and auxiliary operations such as measurement of the wettability of surface. In this paper are described examples of risks occurring during adhesive bonding, it is a simple way to estimate the risks associated with the performance of operations. The examples of the determination by the producers of chemicals are described which are used in adhesive bonding and fragment of international chemical safety card (ICSC), as a source of information important to the workplace organization and ensuring safety during adhesive bonding.

A novel water-based process produces eco-friendly bio-adhesive made from green cross-linked soybean soluble polysaccharide and soy protein.

PubMed

Yuan, Cheng; Chen, Mingsong; Luo, Jing; Li, Xiaona; Gao, Qiang; Li, Jianzhang

2017-08-01

In this study, an eco-friendly soy protein adhesive was developed that utilized two components from soybean meal without addition of any toxic material. A plant-based, water-soluble and inexpensive soybean soluble polysaccharide was used as the novel renewable material to combine with soy protein to produce a soy protein adhesive. Three-plywood was fabricated with the resulting adhesive, and its wet shear strength was measured. The results showed the wet shear strength of plywood bonded by the adhesive reached 0.99MPa, meeting the water resistance requirement for interior use panels. This improvement was attributed to the following reasons: (1) Combination of cross-linked soybean soluble polysaccharide and soy protein formed an interpenetrating network structure, improving the thermal stability and water resistance of the cured adhesive. (2) Adding CL-SSPS decreased the adhesive viscosity to 15.14Pas, which increased the amount of the adhesive that penetrate the wood's surface and formed more interlocks. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural and compositional characterization of the adhesive produced by reef building oysters.

PubMed

Alberts, Erik M; Taylor, Stephen D; Edwards, Stephanie L; Sherman, Debra M; Huang, Chia-Ping; Kenny, Paul; Wilker, Jonathan J

2015-04-29

Oysters have an impressive ability to overcome difficulties of life within the stressful intertidal zone. These shellfish produce an adhesive for attaching to each other and building protective reef communities. With their reefs often exceeding kilometers in length, oysters play a major role in balancing the health of coastal marine ecosystems. Few details are available to describe oyster adhesive composition or structure. Here several characterization methods were applied to describe the nature of this material. Microscopy studies indicated that the glue is comprised of organic fiber-like and sheet-like structures surrounded by an inorganic matrix. Phospholipids, cross-linking chemistry, and conjugated organics were found to differentiate this adhesive from the shell. Symbiosis in material synthesis could also be present, with oysters incorporating bacterial polysaccharides into their adhesive. Oyster glue shows that an organic-inorganic composite material can provide adhesion, a property especially important when constructing a marine ecosystem.

Pectic oligosaccharide structure-function relationships: prebiotics, inhibitors of Escherichia coli O157:H7 adhesion and reduction of Shiga toxin cytotoxicity in HT29 cells

USDA-ARS?s Scientific Manuscript database

Shiga toxin (Stx)-producing, food-contaminating Escherichia coli (STEC) is a major health concern. Plant-derived pectin and pectic-oligosaccharides (POS) that are abundant in biomass have been considered as prebiotics and for the protection of humans from Stx intoxication. Five structurally differ...

In vitro comparison of the tensile bond strength of denture adhesives on denture bases.

PubMed

Kore, Doris R; Kattadiyil, Mathew T; Hall, Dan B; Bahjri, Khaled

2013-12-01

With several denture adhesives available, it is important for dentists to make appropriate patient recommendations. The purpose of this study was to evaluate the tensile bond strength of denture adhesives on denture base materials at time intervals of up to 24 hours. Fixodent, Super Poligrip, Effergrip, and SeaBond denture adhesives were tested with 3 denture base materials: 2 heat-polymerized (Lucitone 199 and SR Ivocap) and 1 visible-light-polymerized (shade-stable Eclipse). Artificial saliva with mucin was used as a control. Tensile bond strength was tested in accordance with American Dental Association specifications at 5 minutes, 3 hours, 6 hours, 12 hours, and 24 hours after applying the adhesive. Maximum forces before failure were recorded in megapascals (MPa), and the data were subjected to a 2-way analysis of variance (α=.05). All 4 adhesives had greater tensile bond strength than the control. Fixodent, Super Poligrip, and SeaBond had higher tensile bond strength values than Effergrip. All adhesives had the greatest tensile bond strength at 5 minutes and the least at 24 hours. The 3 denture bases produced significantly different results with each adhesive (P<.001). Lucitone 199 with the adhesives had the greatest tensile bond strength, followed by Ivocap and Eclipse. All 4 adhesives had greater tensile bond strength than the control, and all 4 adhesives were strongest at the 5-minute interval. On all 3 types of denture bases, Effergrip produced significantly lower tensile bond strength, and Fixodent, Super Poligrip, and SeaBond produced significantly higher tensile bond strength. At 24 hours, the adhesive-base combinations with the highest tensile bond strength were Fixodent on Lucitone 199, Fixodent on Eclipse, Fixodent on Ivocap, and Super Poligrip on Ivocap. Copyright © 2013 Editorial Council for the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

Actin-Based Adhesion Modules Mediate Cell Interactions with the Extracellular Matrix and Neighboring Cells.

PubMed

Bachir, Alexia I; Horwitz, Alan Rick; Nelson, W James; Bianchini, Julie M

2017-07-05

Cell adhesions link cells to the extracellular matrix (ECM) and to each other and depend on interactions with the actin cytoskeleton. Both cell-ECM and cell-cell adhesion sites contain discrete, yet overlapping, functional modules. These modules establish physical associations with the actin cytoskeleton, locally modulate actin organization and dynamics, and trigger intracellular signaling pathways. Interplay between these modules generates distinct actin architectures that underlie different stages, types, and functions of cell-ECM and cell-cell adhesions. Actomyosin contractility is required to generate mature, stable adhesions, as well as to sense and translate the mechanical properties of the cellular environment into changes in cell organization and behavior. Here, we review the organization and function of different adhesion modules and how they interact with the actin cytoskeleton. We highlight the molecular mechanisms of mechanotransduction in adhesions and how adhesion molecules mediate cross talk between cell-ECM and cell-cell adhesion sites. Copyright © 2017 Cold Spring Harbor Laboratory Press; all rights reserved.

Short communication: pre- and co-curing effect of adhesives on shear bond strengths of composite resins to primary enamel and dentine: an in vitro study.

PubMed

Viswanathan, R; Shashibhushan, K K; Subba Reddy, V V

2011-12-01

To evaluate and compare shear bond strengths of composite resins to primary enamel and dentine when the adhesives are pre-cured (light cured before the application of the resin) or co-cured (adhesive and the resin light cured together). Buccal surfaces of 80 caries-free primary molars were wet ground to create bonding surfaces on enamel and dentine and specimens mounted on acrylic blocks. Two bonding agents (Prime and Bond NT® and Xeno III®) were applied to either enamel or dentine as per manufacturer's instructions. In 40 specimens, the bonding agent was light cured immediately after the application (pre-cured). The other 40 specimens were not light cured until the composite resin application (co-cured). Resin composite cylinders were made incrementally using acrylic moulds over the adhesives and light cured. Specimens were stored in deionised water for 24 hours at room temperature. Shear bond strength was measured using an Instron universal testing machine (in MPa) and was analysed with Student's unpaired t test. Light curing the adhesive separately produced significantly higher bond strengths to primary dentine than co-curing (p<0.001). At the same time light curing the adhesive separately did not produce significantly different bond strengths to primary enamel (p>0.05). Curing sequence had no significant effect on shear bond strength of adhesives on the primary enamel. Pre-curing adhesives before curing composite resins produced greater shear bond strength to primary dentine.

Bioadhesion of mussels and geckos: Molecular mechanics, surface chemistry, and nanoadhesives

NASA Astrophysics Data System (ADS)

Lee, Haeshin

The adhesive strategies of living creatures are diverse, ranging from temporary to permanent adhesions with various functions such as locomotion, self-defense, communication, colony formation, and so on. The classic example of temporary adhesion is the gecko, which is known for its ability to walk along vertical and even inverted surfaces; this remarkable adhesion arises from the interfacial weak interactions of van der Waals and capillary forces. In contrast, a celerbrated example of permanent adhesion is found in marine mussels which secrete protein adhesives that function in aqueous environments without mechanical failure against turbulent conditions on the seashore. In addition, mussel adhesives stick to virtually all inorganic and organic surfaces. However, most commonly used man-made adhesives lack such unique adhesion properties compared to their natural counterparts. For example, many commercial adhesives quickly lose their adhesive strength when exposed to solvents, particularly water. The first part of this thesis focused on adhesion mechanics of mussels at a single-molecule level, in which the adhesive molecule showed surprisingly strong yet reversible adhesion on inorganic surfaces but exhibited irreversible covalent bond formation on organic surfaces. Strong and reversible adhesion on mucin surfaces was found, indicating potential application for drug delivery via mucus layers. Next, inspired by the mussel's versatile adhesion on a wide variety of material surfaces, a material-independent surface modification chemistry called 'polydopamine coating' is described. This concept was subsequently adapted to develop a surface-independent polymeric primer for layer-by-layer assembly of multifunctional coatings. Finally, a new bio-hybrid adhesive 'geckel' was developed by the functional combination of adhesion strategies of geckos and mussels. The new bio-inspired adhesive and material-independent surface chemistry can revolutionize the research areas such as medical devices, adhesives, and diagnostics, nanotechnology, biointerface, and catalysis.

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

PubMed

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.

Super-resolution links vinculin localization to function in focal adhesions.

PubMed

Giannone, Grégory

2015-07-01

Integrin-based focal adhesions integrate biochemical and biomechanical signals from the extracellular matrix and the actin cytoskeleton. The combination of three-dimensional super-resolution imaging and loss- or gain-of-function protein mutants now links the nanoscale dynamic localization of proteins to their activation and function within focal adhesions.

Effect of functional monomers in all-in-one adhesive systems on formation of enamel/dentin acid-base resistant zone.

PubMed

Nikaido, Toru; Ichikawa, Chiaki; Li, Na; Takagaki, Tomohiro; Sadr, Alireza; Yoshida, Yasuhiro; Suzuki, Kazuomi; Tagami, Junji

2011-01-01

This study aimed at evaluating the effect of functional monomers in all-in-one adhesive systems on formation of acid-base resistant zone (ABRZ) in enamel and dentin. Experimental adhesive systems containing one of three functional monomers; MDP, 3D-SR and 4-META were applied to enamel or dentin surface and light-cured. A universal resin composite was then placed. The specimens were subjected to a demineralizing solution (pH 4.5) and 5% NaClO for acid-base challenge and then observed by SEM. The ABRZ was clearly observed in both enamel and dentin interfaces. However, enamel ABRZ was thinner than dentin ABRZ in all adhesives. Morphology of the ABRZ was different between enamel and dentin, and also among the adhesives. Funnel-shaped erosion was observed only in the enamel specimen with the 4-META adhesive. The formation of enamel/dentin ABRZ was confirmed in all adhesives, but the morphology was influenced by the functional monomers.

Influence of CVD diamond tips and Er:YAG laser irradiation on bonding of different adhesive systems to dentin.

PubMed

da Silva, Melissa Aline; Di Nicolo, Rebeca; Barcellos, Daphne Camara; Batista, Graziela Ribeiro; Pucci, Cesar Rogerio; Rocha Gomes Torres, Carlos; Borges, Alessandra Bühler

2013-01-01

The aim of this study was to compare the microtensile bond strength of three adhesive systems, using different methods of dentin preparation. A hundred and eight bovine teeth were used. The dentin from buccal face was exposed and prepared with three different methods, divided in 3 groups: Group 1 (DT)- diamond tip on a high-speed handpiece; Group 2 (CVD)-CVD tip on a ultrasonic handpiece; Group 3 (LA)-Er: YAG laser. The teeth were divided into 3 subgroups, according adhesive systems used: Subgroup 1-Adper Single Bond Plus/3M ESPE (SB) total-etch adhesive; Subgroup 2-Adper Scotchbond SE/3M ESPE (AS) selfetching adhesive; Subgroup 3-Clearfil SE Bond/Kuraray (CS) selfetching adhesive. Blocks of composite (Filtek Z250-3M ESPE) 4 mm high were built up and specimens were stored in deionized water for 24 hours at 37°C. Serial mesiodistal and buccolingual cuts were made and stick-like specimens were obtained, with transversal section of 1.0 mm(2). The samples were submitted to microtensile test at 1 mm/min and load of 10 kg in a universal testing machine. Data (MPa) were subjected to ANOVA and Tukey's tests (p < 0.05). Surface treatment with Diamond or CVD tips associated with Clearfil SE Bond adhesive produced significantly lower bond strength values compared to other groups. Surface treatment with Er: YAG laser associated with Single Bond Plus or Clearfil SE Bond adhesives and surface treatment with CVD tip associated with Adper Scotchbond SE adhesive produced significantly lower bond strength values compared to surface treatment with diamond or CVD tips associated with Single Bond Plus or Adper Scotchbond SE adhesives. Interactions between laser and the CVD tip technologies and the different adhesive systems can produce a satisfactory bonding strength result, so that these associations may be beneficial and enhance the clinical outcomes.

Peptides based on alphaV-binding domains of erythrocyte ICAM-4 inhibit sickle red cell-endothelial interactions and vaso-occlusion in the microcirculation.

PubMed

Kaul, Dhananjay K; Liu, Xiao-du; Zhang, Xiaoqin; Mankelow, Tosti; Parsons, Stephen; Spring, Frances; An, Xiuli; Mohandas, Narla; Anstee, David; Chasis, Joel Anne

2006-11-01

Growing evidence shows that adhesion molecules on sickle erythrocytes interact with vascular endothelium leading to vaso-occlusion. Erythrocyte intercellular adhesion molecule-4 (ICAM-4) binds alphaV-integrins, including alphaVbeta3 on endothelial cells. To explore the contribution of ICAM-4 to vascular pathology of sickle cell disease, we tested the effects of synthetic peptides, V(16)PFWVRMS (FWV) and T(91)RWATSRI (ATSR), based on alphaV-binding domains of ICAM-4 and capable of inhibiting ICAM-4 and alphaV-binding in vitro. For these studies, we utilized an established ex vivo microvascular model system that enables intravital microscopy and quantitation of adhesion under shear flow. In this model, the use of platelet-activating factor, which causes endothelial oxidant generation and endothelial activation, mimicked physiological states known to occur in sickle cell disease. Infusion of sickle erythrocytes into platelet-activating factor-treated ex vivo rat mesocecum vasculature produced pronounced adhesion of erythrocytes; small-diameter venules were sites of maximal adhesion and frequent blockage. Both FWV and ATSR peptides markedly decreased adhesion, and no vessel blockage was observed with either of the peptides, resulting in improved hemodynamics. ATSR also inhibited adhesion in unactivated microvasculature. Although infused fluoresceinated ATSR colocalized with vascular endothelium, pretreatment with function-blocking antibody to alphaVbeta3-integrin markedly inhibited this interaction. Our data strengthen the thesis that ICAM-4 on sickle erythrocytes binds endothelium via alphaVbeta3 and that this interaction contributes to vaso-occlusion. Thus peptides or small molecule mimetics of ICAM-4 may have therapeutic potential.

Epigallocatechin 3-gallate inhibits 7-ketocholesterol-induced monocyte-endothelial cell adhesion.

PubMed

Yamagata, Kazuo; Tanaka, Noriko; Suzuki, Koichi

2013-07-01

7-Ketocholesterol (7KC) induces monocytic adhesion to endothelial cells, and induces arteriosclerosis while high-density lipoprotein (HDL) inhibits monocytic adhesion to the endothelium. Epigallocatechin 3-gallate (EGCG) was found to have a protective effect against arteriosclerosis. Therefore, the purpose of this study was to examine the possible HDL-like mechanisms of EGCG in endothelial cells by investigating whether EGCG inhibits 7KC-induced monocyte-endothelial cell adhesion by activating HDL-dependent signal transduction pathways. 7KC and/or EGCG were added to human endothelial cells (ISO-HAS), and the adhesion of pro-monocytic U937 cells was examined. The expression of genes associated with HDL effects such as Ca(2+)/calmodulin-dependent kinase II (CaMKKII), liver kinase B (LKD1), PSD-95/Dlg/ZO-1 kinase 1 (PDZK1), phosphatidylinositol 3-kinase (PI3K), intercellular adhesion molecule-1 (ICAM-1), monocyte chemotactic protein-1 (MCP-1), and endothelial nitric oxide synthase (eNOS) was examined by RT-PCR, and ICAM-1 protein expression was evaluated by western blot (WB). Production of reactive oxygen species (ROS) was examined with H2DCFDA. 7KC significantly induced adhesion of U937 cells to human endothelial cells while significantly increasing gene expressions of ICAM-1 and MCP-1 and decreasing eNOS and CaMKKII gene expressions. EGCG inhibited 7KC-induced monocytic adhesion to endothelial cells, and induced expression of eNOS and several genes involved in the CaMKKII pathway. Stimulation of endothelial cells with EGCG produced intracellular ROS, whereas treatment with N-acetylcysteine (NAC) blocked EGCG-induced expression of eNOS and CaMKKII. These results suggest that inhibition of monocyte-endothelial cell adhesion by EGCG is associated with CaMKKII pathway activation by ROS. Inhibition of 7KC-induced monocyte-endothelial cell adhesion induced by EGCG may function similarly to HDL. Copyright © 2013 Elsevier Inc. All rights reserved.

Develop, demonstrate, and verify large area composite structural bonding with polyimide adhesives. [adhesively bonding graphite-polyimide structures

NASA Technical Reports Server (NTRS)

Bhombal, B. D.; Wykes, D. H.; Hong, K. C.; Stenersen, A. A.

1982-01-01

The technology required to produce graphite-polyimide structural components with operational capability at 598 K (600 F) is considered. A series of polyimide adhesives was screened for mechanical and physical properties and processibility in fabricating large midplane bonded panels and honeycomb sandwich panels in an effort to fabricate a structural test component of the space shuttle aft body flap. From 41 formulations, LaRC-13, FM34B-18, and a modified LaRC-13 adhesive were selected for further evaluation. The LaRC-13 adhesive was rated as the best of the three adhesives in terms of availability, cost, processibility, properties, and ability to produce void fee large area (12" x 12") midplane bonds. Surface treatments and primers for the adhesives were evaluated and processes were developed for the fabrication of honeycomb sandwich panels of very good quality which was evidenced by rupture in the honeycomb core rather than in the facesheet bands on flatwise tensile strength testing. The fabrication of the adhesively bonded honeycomb sandwich cover panels, ribs, and leading edge covers of Celion graphite/LARC-160 polyimide laminates is described.

In Vitro Evaluation of Beneficial Properties of Bacteriocinogenic Lactobacillus plantarum ST8Sh.

PubMed

Todorov, Svetoslav Dimitrov; Holzapfel, Wilhelm; Nero, Luis Augusto

2017-06-01

Lactobacillus plantarum ST8Sh, isolated from Bulgarian salami "shpek" and previously characterized as bacteriocin producer, was evaluated for its beneficial properties. Based on the PCR analysis, Lb. plantarum ST8Sh was shown to host a gene related to the production of adhesion proteins such as Mab, Mub, EF, and PrgB. Genetic and physiological tests suggest Lb. plantarum ST8Sh to represent a potential probiotic candidate, including survival in the presence of low levels of pH and high levels of ox bile, production of β-galactosidase, bile salt deconjugation, high level of hydrophobicity, functional auto- and co-aggregation properties, and adhesion to cell lines. Application of semi-purified bacteriocin produced by Lb. plantarum ST8Sh in combination with ciprofloxacin presented synergistic effect on inhibition of Listeria monocytogenes Scott A. Based on observed properties, Lb. plantarum ST8Sh can be considered as a potential probiotic candidate with additional bacteriocinogenic properties.

Advanced use of tissue adhesive in hair transplantation.

PubMed

Elliott, R M; Thomas, R A; True, R H

1993-09-01

Cobblestoning is an unsightly result of graft elevation in the recipient site after hair transplantation. To describe the use of tissue adhesives for the avoidance of cobblestoning. The long-term cosmetic appearance of hair transplants may be improved through the use of cyanoacrylate adhesives is the virtual elimination of the common problem of graft elevation or cobblestoning, which produces an unsightly bumpiness in the recipient area. The choice of type of adhesive and the method of application are central to successful use of this technique. The indirect benefits of elimination of the need for postoperative bandages and restrictions in activities couple with the cosmetic results to produce a high degree of patient satisfaction.

Synthesis and evaluation of novel siloxane-methacrylate monomers used as dentin adhesives

PubMed Central

Ge, Xueping; Ye, Qiang; Song, Linyong; Misra, Anil; Spencer, Paulette

2014-01-01

Objectives The objectives of this study were to synthesize two new siloxane-methacrylate (SM) monomers for application in dentin adhesives and to investigate the influence of different functionality of the siloxane-containing monomers on the adhesive photopolymerization, water sorption, and mechanical properties. Materials and method Two siloxane-methacrylate monomers (SM1 and SM2) with four and eight methacrylate groups were synthesized. Dentin adhesives containing BisGMA, HEMA and the siloxane-methacrylate monomers were photo-polymerized. The experimental adhesives were compared with the control adhesive (HEMA/BisGMA 45/55 w/w) and characterized with regard to degree of conversion (DC), water miscibility of the liquid resin, water sorption and dynamic mechanical analysis (DMA). Results The experimental adhesives exhibited improved water miscibility as compared to the control. When cured in the presence of 12 wt % water to simulate the wet environment of the mouth, the SM-containing adhesives showed DC comparable to the control. The experimental adhesives showed higher rubbery modulus than the control under dry conditions. Under wet conditions, the mechanical properties of the formulations containing SM monomer with increased functionality were comparable with the control, even with more water sorption. Significance The concentration and functionality of the newly synthesized siloxane-methacrylate monomers affected the water miscibility, water sorption and mechanical properties of the adhesives. The experimental adhesives show improved water compatibility compared with the control. The mechanical properties were enhanced with an increase of the functionality of the siloxane-containing monomers. The results provide critical structure/property relationships and important information for future development of durable, versatile siloxane-containing dentin adhesives. PMID:24993811

Synthesis and evaluation of novel siloxane-methacrylate monomers used as dentin adhesives.

PubMed

Ge, Xueping; Ye, Qiang; Song, Linyong; Misra, Anil; Spencer, Paulette

2014-09-01

The objectives of this study were to synthesize two new siloxane-methacrylate (SM) monomers for application in dentin adhesives and to investigate the influence of different functionality of the siloxane-containing monomers on the adhesive photopolymerization, water sorption, and mechanical properties. Two siloxane-methacrylate monomers (SM1 and SM2) with four and eight methacrylate groups were synthesized. Dentin adhesives containing BisGMA, HEMA and the siloxane-methacrylate monomers were photo-polymerized. The experimental adhesives were compared with the control adhesive (HEMA/BisGMA, 45/55, w/w) and characterized with regard to degree of conversion (DC), water miscibility of the liquid resin, water sorption and dynamic mechanical analysis (DMA). The experimental adhesives exhibited improved water miscibility as compared to the control. When cured in the presence of 12 wt% water to simulate the wet environment of the mouth, the SM-containing adhesives showed DC comparable to the control. The experimental adhesives showed higher rubbery modulus than the control under dry conditions. Under wet conditions, the mechanical properties of the formulations containing SM monomer with increased functionality were comparable with the control, even with more water sorption. The concentration and functionality of the newly synthesized siloxane-methacrylate monomers affected the water miscibility, water sorption and mechanical properties of the adhesives. The experimental adhesives show improved water compatibility compared with the control. The mechanical properties were enhanced with an increase of the functionality of the siloxane-containing monomers. The results provide critical structure/property relationships and important information for future development of durable, versatile siloxane-containing dentin adhesives. Published by Elsevier Ltd.

Functional Surface of the golden mussel's foot: morphology, structures and the role of cilia on underwater adhesion.

PubMed

Andrade, Gabriela Rabelo; de Araújo, João Locke Ferreira; Nakamura Filho, Arnaldo; Guañabens, Anna Carolina Paganini; Carvalho, Marcela David de; Cardoso, Antônio Valadão

2015-09-01

In this study we characterized the surface morphology and ultrastructure of the foot of the golden mussel, Limnoperna fortunei (Dunker, 1857), relating its characteristics to the attaching mechanisms of this mollusk. The observation of the foot of this bivalve reveals the presence of micro-scaled cilia with a unique shape, which has a narrowing at its end. This characteristic was associated to the capacity for underwater adhesion to substrates through the employment of van der Waals forces, resembling the adhesion phenomenon of the gecko foot. The temporary attachment during locomotion by means of the foot to substrates was observed to be strong even on smooth surfaces, like glass, or hydrophobic waxy surfaces. Comparing TEM and light microscopy results it was possible to associate the mucous secretions and secreting cells found along the tissues to the production of the byssus inside the groove on the ventral portion of the foot. Not only our experiments, but also the state of the art allowed us to discard the involvement of secretions produced in the foot of the mussel to the temporary adhesion. Through SEM images it was possible to build a virtual three-dimensional model where total foot surface was measured for the estimated calculation of van der Waals forces. Also, some theoretical analysis and considerations have been made concerning the characteristics of the functional surface of L. fortunei foot. Copyright © 2015 Elsevier B.V. All rights reserved.

Infrared spectroscopic investigations on the distribution of residual grease on textiles

NASA Astrophysics Data System (ADS)

Siedler, J.; Schumacher-Hamedat, Ursula; Hoecker, Hartwig

1992-03-01

Surface modification of textile materials is of major importance in the modern textile industry. Several methods are commonly applied to produce a broad range of coated materials. The adhesion between the coating polymers and the textile fibers often determines the quality. Improved adhesion of the coating is achieved by a chemical bonding (covalent or ionic) between the coating materials and the textile. The efficiency,however, is dependent on the orientation of the functional groups of the outmost molecular layers of the fibers. Therefore, we have used surface sensitive methods to analyze the surface structure of proteinaceous fibers. Homopoly(aminoacid) films like poly(-(gamma) -benzyl-L-glutamate) and poly(- (Beta) -benzyl-L-aspartate) have been chosen as models for natural fibers like wool.

Increased adhesive and inflammatory properties in blood outgrowth endothelial cells from sickle cell anemia patients.

PubMed

Sakamoto, Tatiana Mary; Lanaro, Carolina; Ozelo, Margareth Castro; Garrido, Vanessa Tonin; Olalla-Saad, Sara Teresinha; Conran, Nicola; Costa, Fernando Ferreira

2013-11-01

The endothelium plays an important role in sickle cell anemia (SCA) pathophysiology, interacting with red cells, leukocytes and platelets during the vaso-occlusive process and undergoing activation and dysfunction as a result of intravascular hemolysis and chronic inflammation. Blood outgrowth endothelial cells (BOECs) can be isolated from adult peripheral blood and have been used in diverse studies, since they have a high proliferative capacity and a stable phenotype during in vitro culture. This study aimed to establish BOEC cultures for use as an in vitro study model for endothelial function in sickle cell anemia. Once established, BOECs from steady-state SCA individuals (SCA BOECs) were characterized for their adhesive and inflammatory properties, in comparison to BOECs from healthy control individuals (CON BOECs). Cell adhesion assays demonstrated that control individual red cells adhered significantly more to SCA BOEC than to CON BOEC. Despite these increased adhesive properties, SCA BOECs did not demonstrate significant differences in their expression of major endothelial adhesion molecules, compared to CON BOECs. SCA BOECs were also found to be pro-inflammatory, producing a significantly higher quantity of the cytokine, IL-8, than CON BOECs. From the results obtained, we suggest that BOEC may be a good model for the in vitro study of SCA. Data indicate that endothelial cells of sickle cell anemia patients may have abnormal inflammatory and adhesive properties even outside of the chronic inflammatory and vaso-occlusive environment of patients. © 2013.

Microscopic modulation of mechanical properties in transparent insect wings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arora, Ashima; Kumar, Pramod; Bhagavathi, Jithin

We report on the measurement of local friction and adhesion of transparent insect wings using an atomic force microscope cantilever down to nanometre length scales. We observe that the wing-surface is decorated with 10 μm long and 2 μm wide islands that have higher topographic height. The friction on the islands is two orders of magnitude higher than the back-ground while the adhesion on the islands is smaller. Furthermore, the high islands are decorated with ordered nano-wire-like structures while the background is full of randomly distributed granular nano-particles. Coherent optical diffraction through the wings produce a stable diffraction pattern revealing a quasi-periodicmore » organization of the high islands over the entire wing. This suggests a long-range order in the modulation of friction and adhesion which is directly correlated with the topography. The measurements unravel novel functional design of complex wing surface and could find application in miniature biomimetic devices.« less

Cell directional migration and oriented division on three-dimensional laser-induced periodic surface structures on polystyrene.

PubMed

Wang, Xuefeng; Ohlin, Christian A; Lu, Qinghua; Hu, Jun

2008-05-01

The extracellular matrix in animal tissues usually provides a three-dimensional structural support to cells in addition to performing various other important functions. In the present study, wavy submicrometer laser-irradiated periodic surface structures (LIPSS) were produced on a smooth polystyrene film by polarized laser irradiation with a wavelength of 266 nm. Rat C6 glioma cells exhibited directional migration and oriented division on laser-irradiated polystyrene, which was parallel to the direction of LIPSS. However, rat C6 glioma cells on smooth polystyrene moved in a three-step invasion cycle, with faster migration speed than that on laser-irradiated polystyrene. In addition, focal adhesions examined by immunostaining focal adhesion kinase in human epithelial carcinoma HeLa cells were punctuated on smooth polystyrene, whereas dash-like on laser-irradiated polystyrene. We hypothesized that LIPSS on laser-irradiated polystyrene acted as an anisotropic and persistent mechanical stimulus to guide cell anisotropic spreading, migration and division through focal adhesions.

Biomimetic DNA emulsions: specific, thermo-reversible and adjustable binding from a liquid-like DNA layer

NASA Astrophysics Data System (ADS)

Pontani, Lea-Laetitia; Feng, Lang; Dreyfus, Remi; Seeman, Nadrian; Chaikin, Paul; Brujic, Jasna

2013-03-01

We develop micron-sized emulsions coated with specific DNA sequences and complementary sticky ends. The emulsions are stabilized with phospholipids on which the DNA strands are grafted through biotin-streptavidin interactions, which allows the DNA to diffuse freely on the surface. We produce two complementary emulsions: one is functionalized with S sticky ends and dyed with red streptavidin, the other displays the complementary S' sticky ends and green streptavidin. Mixing those emulsions reveals specific adhesion between them due to the short-range S-S' hybridization. As expected this interaction is thermo-reversible: the red-green adhesive droplets dissociate upon heating and reassemble after cooling. Here the fluid phospholipids layer also leads to diffusive adhesion patches, which allows the bound droplets to rearrange throughout the packing structure. We quantify the adhesion strength between two droplets and build a theoretical framework that captures the observed trends through parameters such as the size of the droplets, the DNA surface density, the various DNA constructs or the temperature. This colloidal-scale, specific, thermo-reversible biomimetic emulsion offers a new versatile and powerful tool for the development of complex self-assembled materials.

Mussel-mimetic, bioadhesive polymers from plant-derived materials.

PubMed

Hiraishi, Noriko; Kaneko, Daisaku; Taira, Shu; Wang, Siqian; Otsuki, Masayuki; Tagami, Junji

2015-02-01

Mussel-mimetic, bioadhesive polymers are synthesized from plant-derived sources. The strong adhesive action is caused by interactions between the catechol groups at the end of the polymer terminal chains and the substrate surface. Here, we present a preliminary study of the adhesion properties and a discussion of the adhesion mechanism. Two bioadhesive polymers were synthesized from natural plant-derived monomers by the transesterification of: (a) caffeic acid (3,4-dihydroxycinnamic acid; DHCA) and p-coumaric acid (4-hydroxycinnamic acid; 4HCA) to produce poly(DHCA-co-4HCA); and (b) 4-dihydroxyhydrocinnamic acid (DHHCA) and 3-(3-hydroxyphenyl) propionic acid (3HPPA) to produce poly(DHHCA-co-3HPPA). Thermoplastic poly(DHCA-co-4HCA) or poly(DHHCA-co-3HPPA) was placed between glass, carbon, steel, or bovine dentin substrates, and a lap shear adhesion test was conducted to compare them using conventional cyanoacrylate glue and epoxy resin. The greatest adhesion for all tested substrates was exhibited by poly(DHHCA-co-3HPPA), followed by epoxy resin adhesive, poly(DHCA-co-4HCA), and cyanoacrylate adhesive. The adhesive strength of poly(DHHCA-co-3HPPA) was greater than 25.6 MPa for glass, 29.6 MPa for carbon, 15.7 MPa for steel, and 16.3 MPA for bovine dentin. The adhesion of poly(DHHCA-co-3HPPA) might be the strongest reported for a mussel-mimic adhesive system, and could be a feasible alternative to petroleum adhesives. © 2013 Wiley Publishing Asia Pty Ltd.

Surfactant Functionalization Induces Robust, Differential Adhesion of Tumor Cells and Blood Cells to Charged Nanotube-Coated Biomaterials Under Flow

PubMed Central

Mitchell, Michael J.; Castellanos, Carlos A.; King, Michael R.

2015-01-01

The metastatic spread of cancer cells from the primary tumor to distant sites leads to a poor prognosis in cancers originating from multiple organs. Increasing evidence has linked selectin-based adhesion between circulating tumor cells (CTCs) and endothelial cells of the microvasculature to metastatic dissemination, in a manner similar to leukocyte adhesion during inflammation. Functionalized biomaterial surfaces hold promise as a diagnostic tool to separate CTCs and potentially treat metastasis, utilizing antibody and selectin-mediated interactions for cell capture under flow. However, capture at high purity levels is challenged by the fact that CTCs and leukocytes both possess selectin ligands. Here, a straightforward technique to functionalize and alter the charge of naturally occurring halloysite nanotubes using surfactants is reported to induce robust, differential adhesion of tumor cells and blood cells to nanotube-coated surfaces under flow. Negatively charged sodium dodecanoate-functionalized nanotubes simultaneously enhanced tumor cell capture while negating leukocyte adhesion, both in the presence and absence of adhesion proteins, and can be utilized to isolate circulating tumor cells regardless of biomarker expression. Conversely, diminishing nanotube charge via functionalization with decyltrimethylammonium bromide both abolished tumor cell capture while promoting leukocyte adhesion. PMID:25934290

Mapping cell surface adhesion by rotation tracking and adhesion footprinting

NASA Astrophysics Data System (ADS)

Li, Isaac T. S.; Ha, Taekjip; Chemla, Yann R.

2017-03-01

Rolling adhesion, in which cells passively roll along surfaces under shear flow, is a critical process involved in inflammatory responses and cancer metastasis. Surface adhesion properties regulated by adhesion receptors and membrane tethers are critical in understanding cell rolling behavior. Locally, adhesion molecules are distributed at the tips of membrane tethers. However, how functional adhesion properties are globally distributed on the individual cell’s surface is unknown. Here, we developed a label-free technique to determine the spatial distribution of adhesive properties on rolling cell surfaces. Using dark-field imaging and particle tracking, we extract the rotational motion of individual rolling cells. The rotational information allows us to construct an adhesion map along the contact circumference of a single cell. To complement this approach, we also developed a fluorescent adhesion footprint assay to record the molecular adhesion events from cell rolling. Applying the combination of the two methods on human promyelocytic leukemia cells, our results surprisingly reveal that adhesion is non-uniformly distributed in patches on the cell surfaces. Our label-free adhesion mapping methods are applicable to the variety of cell types that undergo rolling adhesion and provide a quantitative picture of cell surface adhesion at the functional and molecular level.

The effect of fatigue and environment on the adhesion and delamination of thin polymer films

NASA Astrophysics Data System (ADS)

Snodgrass, Jeffrey Matthew

Polymers are increasingly used in the interconnect and packaging levels of microelectronic devices. Thus, adhesion of polymer films to their adjacent inorganic layers is critical to the manufacturability and reliability of microelectronic components. Weak interfacial adhesion can result in delamination, causing a loss of package hermeticity or the failure of electrical contacts. Recently, interface fracture mechanics techniques have been applied to the problem of thin film delamination and are now used to measure interface adhesion. These techniques allow for characterization of interface adhesion in terms of the critical strain energy release rate, GC, in units of J/m2. In this dissertation, studies are described that quantify the effects of fundamental parameters on the critical adhesion and resistance to subcritical (time-dependent) delamination of benzocyclobutene (BCB)/silica and epoxy underfill/polyimide interfaces. Results are presented detailing the action of small-molecule adhesion promoters on the critical interface adhesion energy of BCB/silica. Silane coupling agents with different functional end groups were used to increase chemical bonding at this interface in order to achieve optimized adhesion. Testing was performed at different mode mixities to evaluate the effect of loading mode on the polymer interface fracture. Subcritical debonding data were measured under two different loading conditions and results are presented in terms of the debond growth rate as a function of applied strain energy release rate. Monotonic loading was used to examine environment-assisted delamination processes, while fatigue loading was used to understand the effects of thermomechanical cycling. Debond growth rates over the range of 10-3 to 10-9 m/s were characterized under mode I and mixed-mode loading. Atomic force microscopy and X-ray photoelectron spectroscopy were used to characterize the fracture surfaces of these interfaces and to generate detailed information about the debond fracture path and mechanisms. The AFM and XPS results suggest that the failure mode of BCB/silica interfaces is cohesive in the BCB layer, in a region very close to the interface. Mechanical fatigue was found to considerably accelerate subcritical debond growth rates and decrease debond growth thresholds to as low as 25% of the critical adhesion energy. Fatigue loading produced fatigue striations on the BCB surface with a striation height of ˜1--2 nm and a spacing that was correlated with the debond growth rate. Finally, a model is presented for the mechanism of striation formation.

The influence of nanostructured features on bacterial adhesion and bone cell functions on severely shot peened 316L stainless steel.

PubMed

Bagherifard, Sara; Hickey, Daniel J; de Luca, Alba C; Malheiro, Vera N; Markaki, Athina E; Guagliano, Mario; Webster, Thomas J

2015-12-01

Substrate grain structure and topography play major roles in mediating cell and bacteria activities. Severe plastic deformation techniques, known as efficient metal-forming and grain refining processes, provide the treated material with novel mechanical properties and can be adopted to modify nanoscale surface characteristics, possibly affecting interactions with the biological environment. This in vitro study evaluates the capability of severe shot peening, based on severe plastic deformation, to modulate the interactions of nanocrystallized metallic biomaterials with cells and bacteria. The treated 316L stainless steel surfaces were first investigated in terms of surface topography, grain size, hardness, wettability and residual stresses. The effects of the induced surface modifications were then separately studied in terms of cell morphology, adhesion and proliferation of primary human osteoblasts (bone forming cells) as well as the adhesion of multiple bacteria strains, specifically Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and ampicillin-resistant Escherichia coli. The results indicated a significant enhancement in surface work hardening and compressive residual stresses, maintenance of osteoblast adhesion and proliferation as well as a remarkable decrease in the adhesion and growth of gram-positive bacteria (S. aureus and S. epidermidis) compared to non-treated and conventionally shot peened samples. Impressively, the decrease in bacteria adhesion and growth was achieved without the use of antibiotics, for which bacteria can develop a resistance towards anyway. By slightly grinding the surface of severe shot peened samples to remove differences in nanoscale surface roughness, the effects of varying substrate grain size were separated from those of varying surface roughness. The expression of vinculin focal adhesions from osteoblasts was found to be singularly and inversely related to grain size, whereas the attachment of gram-positive bacteria (S. aureus and S. epidermidis) decreased with increasing nanoscale surface roughness, and was not affected by grain refinement. Ultimately, this study demonstrated the advantages of the proposed shot peening treatment to produce multifunctional 316L stainless steel materials for improved implant functions without necessitating the use of drugs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Catechol-Cation Synergy in Wet Adhesive Materials

NASA Astrophysics Data System (ADS)

Maier, Gregory Peter

In physiological fluids and seawater, adhesion of synthetic polymers to solid surfaces is impaired by high salt, pH, and hydration. However, mussels have evolved effective strategies for wet adhesion despite these impediments. Inspection of mussel foot proteins (Mfps) provides insights into adhesive adaptations. Catecholic Dopa (3,4-dihydroxyphenylalanine) and lysine residues are present in high mole percent in the interfacial Mfps. The siderophore cyclic trichrysobactin also contains high mole percent of catechol and lysine and serves as a simplified mimic of Mfps. This work is focused on use of Mfp-mimetic siderophores and synthetic siderophore analogs as model systems for dissecting the chemical and physical interactions that enable wet adhesion. Variation in number and identity of functional groups appended to the synthetic siderophore analogs allows identification of the specific contributions of those functional groups to wet adhesion. Both catechol and amine functional groups are critical to strong wet adhesion. The primary amine of lysine and catechol cooperatively displace interfacial hydration and bind to the underlying substrate. Variation in the amine identity as well as the amine to catechol ratio within siderophore analogs also has a significant impact on wet adhesive performance. Catechol undergoes a pH-dependent autoxidation in which higher pH leads to faster oxidation by dioxygen. This oxidation abolishes all adhesion of Mfps to mica by pH 7.5, yet many applications of synthetic wet adhesives require adhesion at physiological or oceanic pH. A better understanding of catechol redox chemistry is critical to the design of wet adhesives. To this end, the pH-dependent autoxidation of catechol and substituted catechols was investigated and results are consistent with a mechanism in which O2 oxidizes both the mono-deprotonated and di-deprotonated catechol. A linear Hammett correlation for the pH-independent second order rate constants for catechol autoxidation indicates that catechols become resistant to autoxidation when functionalized with electron withdrawing groups and more susceptible to autoxidation when functionalized with electron donating groups. Analysis of substituent effects through Hammett correlation allows for selection of functionalized catechols with redox properties ideally suited for a given application.

Interplay between Rolling and Firm Adhesion Elucidated with a Cell-Free System Engineered with Two Distinct Receptor-Ligand Pairs

PubMed Central

Eniola, A. Omolola; Willcox, P. Jeanene; Hammer, Daniel A.

2003-01-01

The firm arrest of leukocytes to the endothelium during inflammation is known to be mediated by endothelial intercellular adhesion molecules (ICAMs) binding to activated integrins displayed on leukocyte surface. Selectin-ligand interactions, which mediate rolling, are believed to be important for facilitating firm adhesion, either by activating integrins or by facilitating the transition to firm adhesion by making it easier for integrins to bind. Although leukocytes employ two distinct adhesion molecules that mediate different states of adhesion, the fundamental biophysical mechanisms by which two pairs of adhesion molecules facilitate cell adhesion is not well understood. In this work, we attempt to understand the interaction between two molecular systems using a cell-free system in which polystyrene microspheres functionalized with the selectin ligand, sialyl LewisX (sLeX), and an antibody against ICAM-1, aICAM-1, are perfused over P-selectin/ICAM-1 coated surfaces in a parallel plate flow chamber. Separately, sLeX/P-selectin interactions support rolling and aICAM-1/ICAM-1 interactions mediate firm adhesion. Our results show that sLeX/aICAM-1 microspheres will firmly adhere to P-selectin/ICAM-1 coated surfaces, and that the extent of firm adhesion of microspheres is dependent on wall shear stress within the flow chamber, sLeX/aICAM-1 microsphere site density, and P-selectin/ICAM-1 surface density ratio. We show that P-selectin's interaction with sLeX mechanistically facilitates firm adhesion mediated by antibody binding to ICAM-1: the extent of firm adhesion for the same concentration of aICAM-1/ICAM-1 interaction is greater when sLeX/P-selectin interactions are present. aICAM-1/ICAM-1 interactions also stabilize rolling by increasing pause times and decreasing average rolling velocities. Although aICAM-1 is a surrogate for β2-integrin, the kinetics of association between aICAM-1 and ICAM-1 is within a factor of 1.5 of activated integrin binding ICAM-1, suggesting the findings from this model system may be insightful to the mechanism of leukocyte firm adhesion. In particular, these experimental results show how two molecule systems can interact to produce an effect not achievable by either system alone, a fundamental mechanism that may pervade leukocyte adhesion biology. PMID:14507735

Specific Degradation of the Mucus Adhesion-Promoting Protein (MapA) of Lactobacillus reuteri to an Antimicrobial Peptide ▿

PubMed Central

Bøhle, Liv Anette; Brede, Dag Anders; Diep, Dzung B.; Holo, Helge; Nes, Ingolf F.

2010-01-01

The intestinal flora of mammals contains lactic acid bacteria (LAB) that may provide positive health effects for the host. Such bacteria are referred to as probiotic bacteria. From a pig, we have isolated a Lactobacillus reuteri strain that produces an antimicrobial peptide (AMP). The peptide was purified and characterized, and it was unequivocally shown that the AMP was a well-defined degradation product obtained from the mucus adhesion-promoting protein (MapA); it was therefore termed AP48-MapA. This finding demonstrates how large proteins might inherit unexpected pleiotropic functions by conferring antimicrobial capacities on the producer. The MapA/AP48-MapA system is the first example where a large protein of an intestinal LAB is shown to give rise to such an AMP. It is also of particular interest that the protein that provides this AMP is associated with the binding of the bacterium producing it to the surface/lining of the gut. This finding gives us new perspective on how some probiotic bacteria may successfully compete in this environment and thereby contribute to a healthy microbiota. PMID:20833791

Use of additives to enhance the properties of cottonseed protein as wood adhesives

USDA-ARS?s Scientific Manuscript database

Soy protein is currently being used commercially as a “green” wood adhesive. Previous work in this laboratory has shown that cottonseed protein isolate, tested on maple wood veneer, produced higher adhesive strength and hot water resistance relative to soy protein. In the present study, cottonseed...

Streptococcus pyogenes CAMP factor promotes bacterial adhesion and invasion in pharyngeal epithelial cells without serum via PI3K/Akt signaling pathway.

PubMed

Kurosawa, Mie; Oda, Masataka; Domon, Hisanori; Isono, Toshihito; Nakamura, Yuki; Saitoh, Issei; Hayasaki, Haruaki; Yamaguchi, Masaya; Kawabata, Shigetada; Terao, Yutaka

2018-01-01

Streptococcus pyogenes is a bacterium that causes systemic diseases, such as pharyngitis and toxic shock syndrome, via oral- or nasal-cavity infection. S. pyogenes produces various molecules known to function with serum components that lead to bacterial adhesion and invasion in human tissues. In this study, we identified a novel S. pyogenes adhesin/invasin. Our results revealed that CAMP factor promoted streptococcal adhesion and invasion in pharyngeal epithelial Detroit562 cells without serum. Recombinant CAMP factor initially localized on the membranes of cells and then became internalized in the cytosol following S. pyogenes infection. Additionally, CAMP factor phosphorylated phosphoinositide 3-kinase and serine-threonine kinase in the cells. ELISA results demonstrate that CAMP factor affected the amount of phosphorylated phosphoinositide 3-kinase and serine-threonine kinase in Detroit562 cells. Furthermore, CAMP factor did not reverse the effect of phosphoinositide 3-kinase knockdown by small interfering RNA in reducing the level of adhesion and invasion of S. pyogenes isogenic cfa-deficient mutant. These results suggested that S. pyogenes CAMP factor activated the phosphoinositide 3-kinase/serine-threonine kinase signaling pathway, promoting S. pyogenes invasion of Detroit562 cells without serum. Our findings suggested that CAMP factor played an important role on adhesion and invasion in pharyngeal epithelial cells. Copyright © 2017 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

Catechol-Functionalized Synthetic Polymer as a Dental Adhesive to Contaminated Dentin Surface for a Composite Restoration.

PubMed

Lee, Sang-Bae; González-Cabezas, Carlos; Kim, Kwang-Mahn; Kim, Kyoung-Nam; Kuroda, Kenichi

2015-08-10

This study reports a synthetic polymer functionalized with catechol groups as dental adhesives. We hypothesize that a catechol-functionalized polymer functions as a dental adhesive for wet dentin surfaces, potentially eliminating the complications associated with saliva contamination. We prepared a random copolymer containing catechol and methoxyethyl groups in the side chains. The mechanical and adhesive properties of the polymer to dentin surface in the presence of water and salivary components were determined. It was found that the new polymer combined with an Fe(3+) additive improved bond strength of a commercial dental adhesive to artificial saliva contaminated dentin surface as compared to a control sample without the polymer. Histological analysis of the bonding structures showed no leakage pattern, probably due to the formation of Fe-catechol complexes, which reinforce the bonding structures. Cytotoxicity test showed that the polymers did not inhibit human gingival fibroblast cells proliferation. Results from this study suggest a potential to reduce failure of dental restorations due to saliva contamination using catechol-functionalized polymers as dental adhesives.

Catechol-Functionalized Synthetic Polymer as a Dental Adhesive to Contaminated Dentin Surface for a Composite Restoration

PubMed Central

2015-01-01

This study reports a synthetic polymer functionalized with catechol groups as dental adhesives. We hypothesize that a catechol-functionalized polymer functions as a dental adhesive for wet dentin surfaces, potentially eliminating the complications associated with saliva contamination. We prepared a random copolymer containing catechol and methoxyethyl groups in the side chains. The mechanical and adhesive properties of the polymer to dentin surface in the presence of water and salivary components were determined. It was found that the new polymer combined with an Fe3+ additive improved bond strength of a commercial dental adhesive to artificial saliva contaminated dentin surface as compared to a control sample without the polymer. Histological analysis of the bonding structures showed no leakage pattern, probably due to the formation of Fe–catechol complexes, which reinforce the bonding structures. Cytotoxicity test showed that the polymers did not inhibit human gingival fibroblast cells proliferation. Results from this study suggest a potential to reduce failure of dental restorations due to saliva contamination using catechol-functionalized polymers as dental adhesives. PMID:26176305

There are four dynamically and functionally distinct populations of E-cadherin in cell junctions

PubMed Central

Erami, Zahra; Timpson, Paul; Yao, Wu; Zaidel-Bar, Ronen; Anderson, Kurt I.

2015-01-01

ABSTRACT E-cadherin is a trans-membrane tumor suppressor responsible for epithelial cell adhesion. E-cadherin forms adhesive clusters through combined extra-cellular cis- and trans-interactions and intracellular interaction with the actin cytoskeleton. Here we identify four populations of E-cadherin within cell junctions based on the molecular interactions which determine their mobility and adhesive properties. Adhesive and non-adhesive populations of E-cadherin each consist of mobile and immobile fractions. Up to half of the E-cadherin immobilized in cell junctions is non-adhesive. Incorporation of E-cadherin into functional adhesions require all three adhesive interactions, with deletion of any one resulting in loss of effective cell-cell adhesion. Interestingly, the only interaction which could independently slow the diffusion of E-cadherin was the tail-mediated intra-cellular interaction. The adhesive and non-adhesive mobile fractions of E-cadherin can be distinguished by their sensitivity to chemical cross-linking with adhesive clusters. Our data define the size, mobility, and adhesive properties of four distinct populations of E-cadherin within cell junctions, and support association with the actin cytoskeleton as the first step in adhesion formation. PMID:26471767

pH and effects on Streptococcus mutans growth of denture adhesives: an in vitro study.

PubMed

Chen, Fengying; Mao, Tiantian; Cheng, Xiangrong

2014-06-01

To evaluate the pH and effects on Streptococcus mutans growth of denture adhesives. There is little information regarding the pH of contemporary adhesives and their influences on S. mutans growth. The adhesives tested were Polident® cream, Protefix® cream and Protefix® powder. Samples of each adhesive were added to deionized water to produce solutions of 10.0, 5.0, 2.5 and 1.0% w/v (cream formulations) or 5.0, 2.5,1.0 and 0.5% (powder formulation). The pH values were measured immediately after preparation and at 1-, 2-, 3-, 6-, 12-, and 24-h intervals using a digital pH meter. Streptococcus mutans UA159 was inoculated in the Brain Heart Infusion medium with or without the adhesive extracts (control). Bacterial growth was observed by measuring absorption at 600 nm every 1 h for 12 h using a spectrophotometer. The tested adhesives generally remained relatively pH-stable over 24 h, ranging from 5.5 to 7.0. There were no statistically significant differences in S. mutans growth rates between the extract-treated and control cultures (p>0.5). Some adhesives produce a pH below the critical pH of hydroxyapatite and may not be suitable for patients with natural teeth. None of the tested adhesives significantly affect S. mutans growth. © 2012 The Gerodontology Society and John Wiley & Sons A/S.

Generating multiplex gradients of biomolecules for controlling cellular adhesion in parallel microfluidic channels.

PubMed

Didar, Tohid Fatanat; Tabrizian, Maryam

2012-11-07

Here we present a microfluidic platform to generate multiplex gradients of biomolecules within parallel microfluidic channels, in which a range of multiplex concentration gradients with different profile shapes are simultaneously produced. Nonlinear polynomial gradients were also generated using this device. The gradient generation principle is based on implementing parrallel channels with each providing a different hydrodynamic resistance. The generated biomolecule gradients were then covalently functionalized onto the microchannel surfaces. Surface gradients along the channel width were a result of covalent attachments of biomolecules to the surface, which remained functional under high shear stresses (50 dyn/cm(2)). An IgG antibody conjugated to three different fluorescence dyes (FITC, Cy5 and Cy3) was used to demonstrate the resulting multiplex concentration gradients of biomolecules. The device enabled generation of gradients with up to three different biomolecules in each channel with varying concentration profiles. We were also able to produce 2-dimensional gradients in which biomolecules were distributed along the length and width of the channel. To demonstrate the applicability of the developed design, three different multiplex concentration gradients of REDV and KRSR peptides were patterned along the width of three parallel channels and adhesion of primary human umbilical vein endothelial cell (HUVEC) in each channel was subsequently investigated using a single chip.

Soluble adhesion molecules in human cancers: sources and fates.

PubMed

van Kilsdonk, Jeroen W J; van Kempen, Léon C L T; van Muijen, Goos N P; Ruiter, Dirk J; Swart, Guido W M

2010-06-01

Adhesion molecules endow tumor cells with the necessary cell-cell contacts and cell-matrix interactions. As such, adhesion molecules are involved in cell signalling, proliferation and tumor growth. Rearrangements in the adhesion repertoire allow tumor cells to migrate, invade and form metastases. Besides these membrane-bound adhesion molecules several soluble adhesion molecules are detected in the supernatant of tumor cell lines and patient body fluids. Truncated soluble adhesion molecules can be generated by several conventional mechanisms, including alternative splicing of mRNA transcripts, chromosomal translocation, and extracellular proteolytic ectodomain shedding. Secretion of vesicles (ectosomes and exosomes) is an alternative mechanism mediating the release of full-length adhesion molecules. Soluble adhesion molecules function as modulators of cell adhesion, induce proteolytic activity and facilitate cell signalling. Additionally, adhesion molecules present on secreted vesicles might be involved in the vesicle-target cell interaction. Based on currently available data, released soluble adhesion molecules contribute to cancer progression and therefore should not be regarded as unrelated and non-functional side products of tumor progression. 2010 Elsevier GmbH. All rights reserved.

9-cis-Retinoic Acid Promotes Cell Adhesion Through Integrin Dependent and Independent Mechanisms Across Immune Lineages

PubMed Central

Whelan, Jarrett T.; Chen, Jianming; Miller, Jabin; Morrow, Rebekah L.; Lingo, Joshuah D.; Merrell, Kaitlin; Shaikh, Saame Raza; Bridges, Lance C.

2012-01-01

Retinoids are essential in the proper establishment and maintenance of immunity. Although retinoids are implicated in immune related processes, their role in immune cell adhesion has not been well established. In this study, the effect of 9-cis-retinoic acid (9-cis-RA) on human hematopoietic cell adhesion was investigated. 9-cis-RA treatment specifically induced cell adhesion of the human immune cell lines HuT-78, NB4, RPMI 8866, and U937. Due to the prominent role of integrin receptors in mediating immune cell adhesion, we sought to evaluate if cell adhesion was integrin-dependent. By employing a variety of integrin antagonist including function-blocking antibodies and EDTA, we establish that 9-cis-RA prompts immune cell adhesion through established integrin receptors in addition to a novel integrin-independent process. The novel integrin-independent adhesion required the presence of retinoid and was attenuated by treatment with synthetic corticosteroids. Finally, we demonstrate that 9-cis-RA treatment of primary murine B-cells induces ex vivo adhesion that persists in the absence of integrin function. Our study is the first to demonstrate that 9-cis-retinoic acid influences immune cell adhesion through at least two functionally distinct mechanisms. PMID:22925918

Inspiration, simulation and design for smart robot manipulators from the sucker actuation mechanism of cephalopods.

PubMed

Grasso, Frank W; Setlur, Pradeep

2007-12-01

Octopus arms house 200-300 independently controlled suckers that can alternately afford an octopus fine manipulation of small objects and produce high adhesion forces on virtually any non-porous surface. Octopuses use their suckers to grasp, rotate and reposition soft objects (e.g., octopus eggs) without damaging them and to provide strong, reversible adhesion forces to anchor the octopus to hard substrates (e.g., rock) during wave surge. The biological 'design' of the sucker system is understood to be divided anatomically into three functional groups: the infundibulum that produces a surface seal that conforms to arbitrary surface geometry; the acetabulum that generates negative pressures for adhesion; and the extrinsic muscles that allow adhered surfaces to be rotated relative to the arm. The effector underlying these abilities is the muscular hydrostat. Guided by sensory input, the thousands of muscle fibers within the muscular hydrostats of the sucker act in coordination to provide stiffness or force when and where needed. The mechanical malleability of octopus suckers, the interdigitated arrangement of their muscle fibers and the flexible interconnections of its parts make direct studies of their control challenging. We developed a dynamic simulator (ABSAMS) that models the general functioning of muscular hydrostat systems built from assemblies of biologically constrained muscular hydrostat models. We report here on simulation studies of octopus-inspired and artificial suckers implemented in this system. These simulations reproduce aspects of octopus sucker performance and squid tentacle extension. Simulations run with these models using parameters from man-made actuators and materials can serve as tools for designing soft robotic implementations of man-made artificial suckers and soft manipulators.

Mussel-Inspired Adhesives and Coatings

PubMed Central

Lee, Bruce P.; Messersmith, P.B.; Israelachvili, J.N.; Waite, J.H.

2011-01-01

Mussels attach to solid surfaces in the sea. Their adhesion must be rapid, strong, and tough, or else they will be dislodged and dashed to pieces by the next incoming wave. Given the dearth of synthetic adhesives for wet polar surfaces, much effort has been directed to characterizing and mimicking essential features of the adhesive chemistry practiced by mussels. Studies of these organisms have uncovered important adaptive strategies that help to circumvent the high dielectric and solvation properties of water that typically frustrate adhesion. In a chemical vein, the adhesive proteins of mussels are heavily decorated with Dopa, a catecholic functionality. Various synthetic polymers have been functionalized with catechols to provide diverse adhesive, sealant, coating, and anchoring properties, particularly for critical biomedical applications. PMID:22058660

Surfactant functionalization induces robust, differential adhesion of tumor cells and blood cells to charged nanotube-coated biomaterials under flow.

PubMed

Mitchell, Michael J; Castellanos, Carlos A; King, Michael R

2015-07-01

The metastatic spread of cancer cells from the primary tumor to distant sites leads to a poor prognosis in cancers originating from multiple organs. Increasing evidence has linked selectin-based adhesion between circulating tumor cells (CTCs) and endothelial cells of the microvasculature to metastatic dissemination, in a manner similar to leukocyte adhesion during inflammation. Functionalized biomaterial surfaces hold promise as a diagnostic tool to separate CTCs and potentially treat metastasis, utilizing antibody and selectin-mediated interactions for cell capture under flow. However, capture at high purity levels is challenged by the fact that CTCs and leukocytes both possess selectin ligands. Here, a straightforward technique to functionalize and alter the charge of naturally occurring halloysite nanotubes using surfactants is reported to induce robust, differential adhesion of tumor cells and blood cells to nanotube-coated surfaces under flow. Negatively charged sodium dodecanoate-functionalized nanotubes simultaneously enhanced tumor cell capture while negating leukocyte adhesion, both in the presence and absence of adhesion proteins, and can be utilized to isolate circulating tumor cells regardless of biomarker expression. Conversely, diminishing nanotube charge via functionalization with decyltrimethylammonium bromide both abolished tumor cell capture while promoting leukocyte adhesion. Copyright © 2015 Elsevier Ltd. All rights reserved.

Smart biomaterials: Surfaces functionalized with proteolytically stable osteoblast-adhesive peptides.

PubMed

Zamuner, Annj; Brun, Paola; Scorzeto, Michele; Sica, Giuseppe; Castagliuolo, Ignazio; Dettin, Monica

2017-09-01

Engineered scaffolds for bone tissue regeneration are designed to promote cell adhesion, growth, proliferation and differentiation. Recently, covalent and selective functionalization of glass and titanium surfaces with an adhesive peptide (HVP) mapped on [351-359] sequence of human Vitronectin allowed to selectively increase osteoblast attachment and adhesion strength in in vitro assays, and to promote osseointegration in in vivo studies. For the first time to our knowledge, in this study we investigated the resistance of adhesion sequences to proteolytic digestion: HVP was completely cleaved after 5 h. In order to overcome the enzymatic degradation of the native peptide under physiological conditions we synthetized three analogues of HVP sequence. A retro-inverted peptide D-2HVP, composed of D amino acids, was completely stable in serum-containing medium. In addition, glass surfaces functionalized with D-2HVP increased human osteoblast adhesion as compared to the native peptide and maintained deposition of calcium. Interestingly, D-2HVP increased expression of IBSP, VTN and SPP1 genes as compared to HVP functionalized surfaces. Total internal reflection fluorescence microscope analysis showed cells with numerous filopodia spread on D-2HVP-functionalized surfaces. Therefore, the D-2HVP sequence is proposed as new osteoblast adhesive peptide with increased bioactivity and high proteolytic resistance.

2D spatially controlled polymer micro patterning for cellular behavior studies

NASA Astrophysics Data System (ADS)

Dinca, V.; Palla-Papavlu, A.; Paraico, I.; Lippert, T.; Wokaun, A.; Dinescu, M.

2011-04-01

A simple and effective method to functionalize glass surfaces that enable polymer micropatterning and subsequent spatially controlled adhesion of cells is reported in this paper. The method involves the application of laser induced forward transfer (LIFT) to achieve polymer patterning in a single step onto cell repellent substrates (i.e. polyethyleneglycol (PEG)). This approach was used to produce micron-size polyethyleneimine (PEI)-patterns alternating with cell-repellent areas. The focus of this work is the ability of SH-SY5Y human neuroblastoma cells to orient, migrate, and produce organized cellular arrangements on laser generated PEI patterns.

Mussel-inspired hyperbranched poly(amino ester) polymer as strong wet tissue adhesive.

PubMed

Zhang, Hong; Bré, Lígia P; Zhao, Tianyu; Zheng, Yu; Newland, Ben; Wang, Wenxin

2014-01-01

Current medical adhesives based on cyanoacrylates typically exhibit cellular toxicity. In contrast, fibrin adhesives are non-toxic but have poor adhesive properties. To overcome these drawbacks we designed a simple and scalable adhesive precursor inspired by marine mussel adhesion that functioned with strong adhesion in wet conditions and with low cytotoxicity. Dopamine, an-amine derivative of an amino acid abundantly present in mussel adhesive proteins, was co-polymerised with a tri-functional vinyl monomer, to form a hyperbranched poly(β-amino ester) polymer termed poly(dopamine-co-acrylate) (PDA). A variety of molecular weights and crosslinking methods were analysed using an ex vivo porcine skin model and an almost 4 fold increase in wet adhesion strength was observed compared to TISSEEL(®) fibrin sealant. With a fast curing time, degradable properties and low cytotoxicity, PDA is highly attractive for medical purposes and could have a broad impact on surgeries where surgical tissue adhesives, sealants, and haemostatic agents are used. Copyright © 2013 Elsevier Ltd. All rights reserved.

High-performance mussel-inspired adhesives of reduced complexity.

PubMed

Ahn, B Kollbe; Das, Saurabh; Linstadt, Roscoe; Kaufman, Yair; Martinez-Rodriguez, Nadine R; Mirshafian, Razieh; Kesselman, Ellina; Talmon, Yeshayahu; Lipshutz, Bruce H; Israelachvili, Jacob N; Waite, J Herbert

2015-10-19

Despite the recent progress in and demand for wet adhesives, practical underwater adhesion remains limited or non-existent for diverse applications. Translation of mussel-inspired wet adhesion typically entails catechol functionalization of polymers and/or polyelectrolytes, and solution processing of many complex components and steps that require optimization and stabilization. Here we reduced the complexity of a wet adhesive primer to synthetic low-molecular-weight catecholic zwitterionic surfactants that show very strong adhesion (∼50 mJ m(-2)) and retain the ability to coacervate. This catecholic zwitterion adheres to diverse surfaces and self-assembles into a molecularly smooth, thin (<4 nm) and strong glue layer. The catecholic zwitterion holds particular promise as an adhesive for nanofabrication. This study significantly simplifies bio-inspired themes for wet adhesion by combining catechol with hydrophobic and electrostatic functional groups in a small molecule.

Platelet-Rich Plasma for Frozen Shoulder: A Case Report.

PubMed

Aslani, Hamidreza; Nourbakhsh, Seyed Taghi; Zafarani, Zohreh; Ahmadi-Bani, Monireh; Ananloo, Mohammad Ebrahim Shahsavand; Beigy, Maani; Salehi, Shahin

2016-01-01

Frozen shoulder is a glenohumeral joint disorder that movement because of adhesion and the existence of fibrosis in the shoulder capsule. Platelet-rich plasma can produce collagen and growth factors, which increases stem cells and consequently enhances the healing. To date, there is no evidence regarding the effectiveness of platelet-rich plasma in frozen shoulder. A 45-year-old man with shoulder adhesive capsulitis volunteered for this treatment. He underwent two consecutive platelet-rich plasma injections at the seventh and eighth month after initiation of symptoms. We measured pain, function, ROM by the visual analogue scale (VAS), scores from the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire and goniometer; respectively. After first injection, the patient reported 60% improvement regarding diurnal shoulder pain, and no night pain. Also, two-fold improvement for ROM and more than 70% improvement for function were reported. This study suggests the use of platelet-rich plasma in frozen shoulder to be tested in randomized trials.

Husk to caryopsis adhesion in barley is influenced by pre- and post-anthesis temperatures through changes in a cuticular cementing layer on the caryopsis.

PubMed

Brennan, M; Shepherd, T; Mitchell, S; Topp, C F E; Hoad, S P

2017-10-23

At ripeness, the outer husk of "covered" barley grains firmly adheres to the underlying caryopsis. A cuticular cementing layer on the caryopsis is required for husk adhesion, however the quality of adhesion varies significantly among cultivars which produce the cementing layer, resulting in the economically important malting defect, grain skinning. The composition of the cementing layer, and grain organ development have been hypothesised to influence the quality of husk adhesion. Plants of Hordeum vulgare 'Concerto' were grown at different temperatures pre- and post-anthesis to effect changes in the development of the husk, caryopsis and cuticular cementing layer, to determine how these variables influence the quality of husk-to-caryopsis adhesion. Warm conditions pre-anthesis decreased the quality of husk adhesion, and consequently increased the incidence of grain skinning. Cool post-anthesis conditions further decreased the quality of husk adhesion. The composition of the cementing layer, rather than its structure, differed with respect to husk adhesion quality. This cementing layer was produced at the late milk stage, occurring between nine and 29 days post-anthesis, conditional on the temperature-dependent growth rate. The compounds octadecanol, tritriacontane, campesterol and β-sitosterol were most abundant in caryopses with high-quality husk adhesion. The differences in adhesion quality were not due to incompatible husk and caryopsis dimensions affecting organ contact. This study shows that husk-to-caryopsis adhesion is dependent on cementing layer composition, and implies that this composition is regulated by temperature before, and during grain development. Understanding this regulation will be key to improving husk-to-caryopsis adhesion.

Study protocol for a multi-center, randomized controlled trial to develop Japanese denture adhesive guidelines for patients with complete dentures: the Denture Adhesive Guideline trial: study protocol for a randomized controlled trial.

PubMed

Kimoto, Suguru; Kawai, Yasuhiko; Gunji, Atsuko; Kondo, Hisatomo; Nomura, Taro; Murakami, Tomohiko; Tsuboi, Akito; Hong, Guang; Minakuchi, Shunsuke; Sato, Yusuke; Ohwada, Gaku; Suzuki, Tetsuya; Kimoto, Katsuhiko; Hoshi, Noriyuki; Saita, Makiko; Yoneyama, Yoshikazu; Sato, Yohei; Morokuma, Masakazu; Okazaki, Joji; Maeda, Takeshi; Nakai, Kenichiro; Ichikawa, Tetsuo; Nagao, Kan; Fujimoto, Keiko; Murata, Hiroshi; Kurogi, Tadafumi; Yoshida, Kazuhiro; Nishimura, Masahiro; Nishi, Yasuhiro; Murakami, Mamoru; Hosoi, Toshio; Hamada, Taizo

2016-10-18

Denture adhesives, characterized as medical products in 1935 by the American Dental Association, have been considered useful adjuncts for improving denture retention and stability. However, many dentists in Japan are hesitant to acknowledge denture adhesives in daily practice because of the stereotype that dentures should be inherently stable, without the aid of adhesives. The aim of this study is to verify the efficacy of denture adhesives to establish guidelines for Japanese users. The null hypothesis is that the application of denture adhesives, including the cream and powder types, or a control (isotonic sodium chloride solution) would not produce different outcomes nor would they differentially improve the set outcomes between baseline and day 4 post-application. This ten-center, randomized controlled trial with parallel groups is ongoing. Three hundred edentulous patients with complete dentures will be allocated to three groups (cream-type adhesive, powder-type adhesive, and control groups). The participants will wear their dentures with the denture adhesive for 4 days, including during eight meals (three breakfasts, two lunches, and three dinners). The baseline measurements and final measurements for the denture adhesives will be performed on the first day and after breakfast on the fourth day. The primary outcome is a general satisfaction rating for the denture. The secondary outcomes are denture satisfaction ratings for various denture functions, occlusal bite force, resistance to dislodgement, masticatory performance, perceived chewing ability, and oral health-related quality of life. Between-subjects comparisons among the three groups and within-subjects comparisons of the pre- and post-intervention measurements will be performed. Furthermore, a multiple regression analysis will be performed. The main analyses will be based on the intention-to-treat principle. A sample size of 100 subjects per group, including an assumed dropout rate of 10 %, will be required to achieve 80 % power with a 5 % alpha level. This randomized clinical trial will provide information about denture adhesives to complete denture wearers, prosthodontic educators, and dentists in Japan. We believe this new evidence on denture adhesive use from Japan will aid dentists in their daily practice even in other countries. ClinicalTrials.gov NCT01712802 . Registered on 17 October 2012.

Analysis of cellular adhesion on superhydrophobic and superhydrophilic vertically aligned carbon nanotube scaffolds.

PubMed

Machado, M M; Lobo, A O; Marciano, F R; Corat, E J; Corat, M A F

2015-03-01

We analyzed GFP cells after 24h cultivated on superhydrophilic vertically aligned carbon nanotube scaffolds. We produced two different densities of VACNT scaffolds on Ti using Ni or Fe catalysts. A simple and fast oxygen plasma treatment promoted the superhydrophilicity of them. We used five different substrates, such as: as-grown VACNT produced using Ni as catalyst (Ni), as-grown VACNT produced using Fe as catalyst (Fe), VACNT-O produced using Ni as catalyst (NiO), VACNT-O produced using Fe as catalyst (FeO) and Ti (control). The 4',6-diamidino-2-phenylindole reagent nuclei stained the adherent cells cultivated on five different analyzed scaffolds. We used fluorescence microscopy for image collect, ImageJ® to count adhered cell and GraphPad Prism 5® for statistical analysis. We demonstrated in crescent order: Fe, Ni, NiO, FeO and Ti scaffolds that had an improved cellular adhesion. Oxygen treatment associated to high VACNT density (group FeO) presented significantly superior cell adhesion up to 24h. However, they do not show significant differences compared with Ti substrates (control). We demonstrated that all the analyzed substrates were nontoxic. Also, we proposed that the density and hydrophilicity influenced the cell adhesion behavior. Copyright © 2014 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becker, Ines; Schillig, Cora

A double-sided adhesive metal-based tape for use as contacting aid for SOFC fuel cells is provided. The double-sided metal-based adhesive tape is suitable for simplifying the construction of cell bundles. The double-sided metal-based adhesive tape is used for electrical contacting of the cell connector with the anode and for electrical contacting of the interconnector of the fuel cells with the cell connector. A method for producing the double-sided adhesive metal-base tape is also provided.

Polymer surface functionalities that control human embryoid body cell adhesion revealed by high throughput surface characterization of combinatorial material microarrays

PubMed Central

Yang, Jing; Mei, Ying; Hook, Andrew L.; Taylor, Michael; Urquhart, Andrew J.; Bogatyrev, Said R.; Langer, Robert; Anderson, Daniel G.; Davies, Martyn C.; Alexander, Morgan R.

2010-01-01

High throughput materials discovery using combinatorial polymer microarrays to screen for new biomaterials with new and improved function is established as a powerful strategy. Here we combine this screening approach with high throughput surface characterisation (HT-SC) to identify surface structure-function relationships. We explore how this combination can help to identify surface chemical moieties that control protein adsorption and subsequent cellular response. The adhesion of human embryoid body (hEB) cells to a large number (496) of different acrylate polymers synthesized in a microarray format is screened using a high throughput procedure. To determine the role of the polymer surface properties on hEB cell adhesion, detailed HT-SC of these acrylate polymers is carried out using time of flight secondary ion mass spectrometry (ToF SIMS), x-ray photoelectron spectroscopy (XPS), pico litre drop sessile water contact angle (WCA) measurement and atomic force microscopy (AFM). A structure-function relationship is identified between the ToF SIMS analysis of the surface chemistry after a fibronectin (Fn) pre-conditioning step and the cell adhesion to each spot using the multivariate analysis technique partial least squares (PLS) regression. Secondary ions indicative of the adsorbed Fn correlate with increased cell adhesion whereas glycol and other functionalities from the polymers are identified that reduce cell adhesion. Furthermore, a strong relationship between the ToF SIMS spectra of bare polymers and the cell adhesion to each spot is identified using PLS regression. This identifies a role for both the surface chemistry of the bare polymer and the pre-adsorbed Fn, as-represented in the ToF SIMS spectra, in controlling cellular adhesion. In contrast, no relationship is found between cell adhesion and wettability, surface roughness, elemental or functional surface composition. The correlation between ToF SIMS data of the surfaces and the cell adhesion demonstrates the ability of identifying surface moieties that control protein adsorption and subsequent cell adhesion using ToF SIMS and multivariate analysis. PMID:20832108

Mechanics of the Adhesive Properties of Ivy Nanoparticles

DTIC Science & Technology

2013-11-21

macromolecule with multiple physiological functions in the growth of plants, such as signaling, cell wall plasticizer, guiding pollen tube growth, and many...others. The AGPs on the stigma surface were believed to act as an adhesive base for pollens , indicating the adhesion function that AGPs play in plants

Understanding Marine Mussel Adhesion

PubMed Central

Roberto, Francisco F.

2007-01-01

In addition to identifying the proteins that have a role in underwater adhesion by marine mussels, research efforts have focused on identifying the genes responsible for the adhesive proteins, environmental factors that may influence protein production, and strategies for producing natural adhesives similar to the native mussel adhesive proteins. The production-scale availability of recombinant mussel adhesive proteins will enable researchers to formulate adhesives that are water-impervious and ecologically safe and can bind materials ranging from glass, plastics, metals, and wood to materials, such as bone or teeth, biological organisms, and other chemicals or molecules. Unfortunately, as of yet scientists have been unable to duplicate the processes that marine mussels use to create adhesive structures. This study provides a background on adhesive proteins identified in the blue mussel, Mytilus edulis, and introduces our research interests and discusses the future for continued research related to mussel adhesion. PMID:17990038

Platelet impedance adhesiometry: A novel technique for the measurement of platelet adhesion and spreading.

PubMed

Polgár, L; Soós, P; Lajkó, E; Láng, O; Merkely, B; Kőhidai, L

2018-06-01

Thrombogenesis plays an important role in today's morbidity and mortality. Antithrombotics are among the most frequently prescribed drugs. Thorough knowledge of platelet function is needed for optimal clinical care. Platelet adhesion is a separate subprocess of platelet thrombus formation; still, no well-standardized technique for the isolated measurement of platelet adhesion exists. Impedimetry is one of the most reliable, state-of-art techniques to analyze cell adhesion, proliferation, viability, and cytotoxicity. We propose impedimetry as a feasible novel method for the isolated measurement of 2 significant platelet functions: adhesion and spreading. Laboratory reference platelet agonists (epinephrine, ADP, and collagen) were applied to characterize platelet functions by impedimetry using the xCELLigence SP system. Platelet samples were obtained from 20 healthy patients under no drug therapy. Standard laboratory parameters and clinical patient history were also analyzed. Epinephrine and ADP increased platelet adhesion in a concentration-dependent manner, while collagen tended to have a negative effect. Serum sodium and calcium levels and age had a negative correlation with platelet adhesion induced by epinephrine and ADP, while increased immunoreactivity connected with allergic diseases was associated with increased platelet adhesion induced by epinephrine and ADP. ADP increased platelet spreading in a concentration-dependent manner. Impedimetry proved to be a useful and sensitive method for the qualitative and quantitated measurement of platelet adhesion, even differentiating between subgroups of a healthy population. This novel technique is offered as an important method in the further investigation of platelet function. © 2018 John Wiley & Sons Ltd.

Bioinspired superhydrophobic, self-cleaning and low drag surfaces

NASA Astrophysics Data System (ADS)

Bhushan, Bharat

2013-09-01

Nature has evolved objects with desired functionality using commonly found materials. Nature capitalizes on hierarchical structures to achieve functionality. The understanding of the functions provided by objects and processes found in nature can guide us to produce nanomaterials, nanodevices, and processes with desirable functionality. This article provides an overview of four topics: (1) Lotus Effect used to develop superhydrophobic and self-cleaning/antifouling surfaces with low adhesion, (2) Shark Skin Effect to develop surfaces with low fluid drag and anti-fouling characteristics, and (3-4) Rice Leaf and Butterfly Wing Effect to develop superhydrophobic and self-cleaning surfaces with low drag. Rice Leaf and Butterfly Wings combine the Shark Skin and Lotus Effects.

Heat-sterilized PD fluid blocks leukocyte adhesion and increases flow velocity in rat peritoneal venules.

PubMed

Jonasson, P; Bagge, U; Wieslander, A; Braide, M

1996-01-01

Data from cell culture experiments indicate that heat sterilization of peritoneal dialysis (PD) fluids produces cytotoxic glucose degradation products. The present vital microscopic study investigated the effects of different sterilization methods on the biocompatibility of PD fluids. Thus, heat-sterilized (commercially obtained and experimentally produced) and filter-sterilized PD fluids (pH = 5.30-5.40; 1.5% glucose) were compared with Tyrode buffer, with respect to the effects on microvascular blood flow velocity and leukocyte adhesion in the rat mesentery. Exteriorization of the mesentery produced a mild inflammation, known from the literature and characterized by the adhesive rolling of leukocytes along venular walls. Superfusion of the mesentery with filter-sterilized PD fluid had no significant effects on leukocyte rolling or flow velocity in venules 25-40 microns in diameter compared with buffer superfusion. Heat-sterilized PD fluid decreased the concentration of rolling leukocytes and increased flow velocity significantly, as compared with buffer and filter-sterilized PD fluid. The results indicate that heat sterilization of PD fluids produces substances that interact with microvascular tone and leukocyte-endothelial adhesion, which hypothetically could impair the acute, granulocyte-mediated defense against bacterial infections.

High-performance mussel-inspired adhesives of reduced complexity

PubMed Central

Ahn, B. Kollbe; Das, Saurabh; Linstadt, Roscoe; Kaufman, Yair; Martinez-Rodriguez, Nadine R.; Mirshafian, Razieh; Kesselman, Ellina; Talmon, Yeshayahu; Lipshutz, Bruce H.; Israelachvili, Jacob N.; Waite, J. Herbert

2015-01-01

Despite the recent progress in and demand for wet adhesives, practical underwater adhesion remains limited or non-existent for diverse applications. Translation of mussel-inspired wet adhesion typically entails catechol functionalization of polymers and/or polyelectrolytes, and solution processing of many complex components and steps that require optimization and stabilization. Here we reduced the complexity of a wet adhesive primer to synthetic low-molecular-weight catecholic zwitterionic surfactants that show very strong adhesion (∼50 mJ m−2) and retain the ability to coacervate. This catecholic zwitterion adheres to diverse surfaces and self-assembles into a molecularly smooth, thin (<4 nm) and strong glue layer. The catecholic zwitterion holds particular promise as an adhesive for nanofabrication. This study significantly simplifies bio-inspired themes for wet adhesion by combining catechol with hydrophobic and electrostatic functional groups in a small molecule. PMID:26478273

Biophysical effects of repetitive removal of adhesive dressings on peri-ulcer skin.

PubMed

Zillmer, R; Agren, M S; Gottrup, F; Karlsmark, T

2006-05-01

To study the effect of repeated removal of four different adhesive dressings on peri-ulcer skin using quantitative non-invasive techniques. Forty-five patients with open (n = 29) or healed (n = 16) venous leg ulcers were included. Peri-ulcer skin was treated for 14 days with patches of two different hydrocolloid-based adhesive dressings, one polyurethane adhesive and one soft silicone adhesive dressing. Normal skin of the patients' ventral forearm was also treated identically. Adhesive patches of the dressings were replaced every second day. The skin barrier function was assessed by measuring transepidermal water loss and stratum corneum hydration by measuring electrical conductance. Thirty-nine patients completed the study. The hydrocolloid adhesives increased transepidermal water loss and conductance while the polyurethane and soft silicone adhesives did not influence these parameters significantly compared with adjacent non-treated peri-ulcer skin. For normal forearm skin, similar relative effects among the four adhesives were found. Repetitive treatment with hydrocolloid-based adhesive dressings induced major functional alterations of the stratum corneum. In contrast, a polyurethane adhesive and a soft silicone adhesive dressing did not alter transepidermal water loss or conductance of peri-ulcer skin.

Intraplatelet reactive oxygen species (ROS) correlate with the shedding of adhesive receptors, microvesiculation and platelet adhesion to collagen during storage: Does endogenous ROS generation downregulate platelet adhesive function?

PubMed

Ghasemzadeh, Mehran; Hosseini, Ehteramolsadat; Roudsari, Zahra Oushyani; Zadkhak, Parvin

2018-03-01

Platelets storage lesion is mainly orchestrated by platelet activating signals during storage. Reactive oxygen species (ROS) are being considered as important signaling molecules modulating platelet function while their production has also been shown to be augmented by platelet activation. This study investigated to what extent endogenous ROS generation during platelet storage could be correlated with platelet receptor shedding, microvesiculation and adhesive function. 10 PRP-platelet concentrates were subjected to flow cytometry analysis to examine the generation of intraplatelet ROS on days 1, 5 and 7 after storage. In 5 day-stored platelets considering 40% of ROS generation as a cutoff point, samples were divided into two groups of those with higher or lower levels of ROS. The expression of adhesion receptors (GPVI, GPIbα), the amount of microparticles and phosphatidylserine exposure in each group were then examined by flow cytometry. Platelet receptor shedding and adhesion to collagen matrix were respectively measured by western blotting and microscopic assays. Our data showed lowered expression of GPIbα (p < 0.05) and GPVI in samples with ROS > 40% than those with ROS ≤ 40%, whereas receptors shedding and microvesiculation were (p < 0.05) elevated in platelets with higher levels of ROS. Functionally, we observed significantly (p < 0.05) lower levels of platelet adhesion to collagen matrix in samples with ROS generation more than 40%. Taken together, we showed correlations between intraplatelet ROS generation and either platelet receptors or microparticle shedding as well as platelet adhesive capacity to collagen. These findings suggest that augmented ROS generation during storage might be relevant to down-regulation of platelet adhesive function. Copyright © 2018 Elsevier Ltd. All rights reserved.

The roles of cell adhesion molecules in tumor suppression and cell migration: a new paradox.

PubMed

Moh, Mei Chung; Shen, Shali

2009-01-01

In addition to mediating cell adhesion, many cell adhesion molecules act as tumor suppressors. These proteins are capable of restricting cell growth mainly through contact inhibition. Alterations of these cell adhesion molecules are a common event in cancer. The resulting loss of cell-cell and/or cell-extracellular matrix adhesion promotes cell growth as well as tumor dissemination. Therefore, it is conventionally accepted that cell adhesion molecules that function as tumor suppressors are also involved in limiting tumor cell migration. Paradoxically, in 2005, we identified an immunoglobulin superfamily cell adhesion molecule hepaCAM that is able to suppress cancer cell growth and yet induce migration. Almost concurrently, CEACAM1 was verified to co-function as a tumor suppressor and invasion promoter. To date, the reason and mechanism responsible for this exceptional phenomenon remain unclear. Nevertheless, the emergence of these intriguing cell adhesion molecules with conflicting roles may open a new chapter to the biological significance of cell adhesion molecules.

A clinical study to evaluate denture adhesive use in well-fitting dentures.

PubMed

Munoz, Carlos A; Gendreau, Linda; Shanga, Gilbert; Magnuszewski, Tabetha; Fernandez, Patricia; Durocher, John

2012-02-01

The objective of this study was the assessment of retention and stability and functional benefits of denture adhesive applied to well-fitting and well-made dentures. This was a randomized, crossover study to compare two marketed denture adhesives (test cream, Super Poligrip® Free, and test strip, Super Poligrip® Comfort Seal Strips) and an unmarketed cream adhesive (GlaxoSmith Kline Consumer Healthcare) with no adhesive as the negative control. Thirty-six subjects completed the study. One hour after the application of denture adhesive, retention and stability were measured using the Kapur Index and maxillary incisal bite force. Two hours after application, functional tests were used to assess denture movement and peanut particle migration under the denture. Subjects also rated confidence, comfort, satisfaction with dentures, and denture wobble in conjunction with the functional tests. Denture adhesives significantly (p < 0.05) improved retention and stability of well-fitting dentures. Subjects experienced significantly (p < 0.05) fewer dislodgements while eating an apple after adhesive was applied to dentures. Significant (p < 0.05) increases in subjective ratings of confidence and comfort as well as decreases in denture wobble were associated with the use of adhesive. There was significant (p < 0.05) improvement in satisfaction ratings for cream adhesives. A single application of each denture adhesive was well tolerated. The results of this study provide evidence that use of Super Poligrip® denture adhesives can enhance aspects of performance of complete well-fitting dentures as well as provide increased comfort, confidence, and satisfaction with dentures. © 2011 by the American College of Prosthodontists.

Development of the weldbond process for joining titanium

NASA Technical Reports Server (NTRS)

Fields, D.

1972-01-01

High quality resistance spot welds were produced by welding through epoxy adhesive on titanium alloys. Weldbond joints were consistently stronger than those of either mechanical fasteners, structural adhesive bonds, or mechanical fasteners with adhesive at the joint interface. Weldbond joints and/or spot weld joints showed superior strength at all temperature ranges as compared to other joints tested.

Bioinspired Superdurable Pestle‐Loop Mechanical Interlocker with Tunable Peeling Force, Strong Shear Adhesion, and Low Noise

PubMed Central

Jiao, Junrong; Zhang, Feilong; Jiao, Tian; Gu, Zhen

2018-01-01

Abstract Velcro, the most typical hook‐loop interlocker, often suffers from undesirable deformation, breaking, and noise because of the structure of the hook. Inspired by the arrester system of dragonfly, a new mechanical interlocker with a nylon pestle instead of the traditional hook is developed. The pestle‐loop mechanical interlocker shows a tunable peeling force from 0.4 ± 0.14 to 6.5 ± 0.72 N and the shear adhesion force of pestle‐loop mechanical interlocker is about twice as much as that of velcro. The pestle tape can be separated and fastened with the loop tape up to 30 000 cycles while keeping the original adhesive force and the pestle structure. In comparison, only after 4000 cycles most hooks of the commercial velcro are deformed and even broken, completely losing their adhesive function and their hook structure. These experimental results are further supported by finite element simulitions—the base of pestle mainly bears the separation‐caused strain while the middle of hook does. Notably, the sound volume during the separation of pestle‐loop mechanical interlocker is merely 49 ± 7.4 dB, much lower than 70 ± 3.5 dB produced by the velcro. PMID:29721425

A cohort of new adhesive proteins identified from transcriptomic analysis of mussel foot glands.

PubMed

DeMartini, Daniel G; Errico, John M; Sjoestroem, Sebastian; Fenster, April; Waite, J Herbert

2017-06-01

The adaptive attachment of marine mussels to a wide range of substrates in a high-energy, saline environment has been explored for decades and is a significant driver of bioinspired wet adhesion research. Mussel attachment relies on a fibrous holdfast known as the byssus, which is made by a specialized appendage called the foot. Multiple adhesive and structural proteins are rapidly synthesized, secreted and moulded by the foot into holdfast threads. About 10 well-characterized proteins, namely the mussel foot proteins (Mfps), the preCols and the thread matrix proteins, are reported as representing the bulk of these structures. To explore how robust this proposition is, we sequenced the transcriptome of the glandular tissues that produce and secrete the various holdfast components using next-generation sequencing methods. Surprisingly, we found around 15 highly expressed genes that have not previously been characterized, but bear key similarities to the previously defined mussel foot proteins, suggesting additional contribution to byssal function. We verified the validity of these transcripts by polymerase chain reaction, cloning and Sanger sequencing as well as confirming their presence as proteins in the byssus. These newly identified proteins greatly expand the palette of mussel holdfast biochemistry and provide new targets for investigation into bioinspired wet adhesion. © 2017 The Author(s).

Seafood delicacy makes great adhesive

ScienceCinema

Idaho National Laboratory - Frank Roberto, Heather Silverman

2017-12-09

Technology from Mother Nature is often hard to beat, so Idaho National Laboratory scientistsgenetically analyzed the adhesive proteins produced by blue mussels, a seafood delicacy. Afterobtaining full-length DNA sequences encoding these proteins, reprod

A single-chain fragment variable recombinant antibody against F5 fimbria of enterotoxigenic Escherichia coli inhibits agglutination of horse red blood cells induced by F5 protein.

PubMed

Bhaskaran, S; Jay, C M; Berghman, L R; Wagner, G G; Waghela, S D

2005-08-01

Bovine colibacillosis caused by enterotoxigenic Escherichia coli (ETEC) is a worldwide problem. Adhesion of ETEC to intestinal cell receptors mediated by the surface protein F5 fimbriae is the initial step in the establishment of colibacillosis. Prevention of ETEC F5(+) adhesion to enterocytes protects newborn calves against collibacillosis. On the enterocytes, the F5 fimbriae bind to a ganglioside that is also found on horse red blood cells. Thus, the presence of F5 fimbriae induces haemagglutination, which is useful as an indicator in a functional assay system. In this study, recombinant anti-F5 scFv antibody fragment produced in E. coli HB2151 reacted with F5 fimbriae in ELISA and Western immunoblot, and prevented haemagglutination induced by the binding of the F5 fimbriae to its natural host receptors on horse red blood cells. Given the ease with which recombinant antibodies can be mass-produced, the presently described scFv may hold promise as a prophylactic agent for colibacillosis.

Cysteine protease 30 (CP30) contributes to adhesion and cytopathogenicity in feline Tritrichomonas foetus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gould, Emily N.; Giannone, Richard; Kania, Stephen A.

Tritrichomonas foetus ( T. foetus) is a flagellated protozoan parasite that is recognized as a significant cause of diarrhea in domestic cats with a prevalence rate as high as 30%. No drugs have been shown to consistently eliminate T. foetus infection in all cats. Cysteine proteases (CPs) have been identified as mediators of T. foetus-induced adhesion-dependent cytotoxicity to the intestinal epithelium. These CPs represent novel targets for the treatment of feline trichomonosis. However, cats also produce CPs that are part of life-critical systems. Thus, parasitic CPs need to be selectively targeted to reduce the potential for host toxicity. Previous studiesmore » have demonstrated the importance of a specific CP, CP30, in mediating bovine and human trichomonad cytopathogenicity. This CP has also recently been identified in feline T. foetus, although the function of this protease in the feline genotype remains unknown. Furthermore, the study objectives were to characterize the presence of CP30 in feline T. foetus isolates and to evaluate the effect of targeted inhibition of CP30 on feline T. foetus-induced adhesion dependent cytotoxicity.« less

Nanomesh of Cu fabricated by combining nanosphere lithography and high power pulsed magnetron sputtering and a preliminary study about its function

NASA Astrophysics Data System (ADS)

Xie, Wanchuan; Chen, Jiang; Jiang, Lang; Yang, Ping; Sun, Hong; Huang, Nan

2013-10-01

The Cu nanomesh was obtained by a combination of nanosphere lithography (NSL) and high power pulsed magnetron sputtering (HiPPMS). A deposition mask was formed on TiO2 substrates by the self-assembly of polystyrene latex spheres with a diameter of 1 μm, then Cu nanomesh structure was produced on the substrate using sputtering. The structures were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results show the increase of temperature of the polystyrene mask caused by the thermal radiation from the target and the bombardment of sputtering particles would affect the quality of the final nanopattern. The tests of photocatalytic degradation, platelet adhesion and human umbilical artery smooth muscle cells (HUASMCs) culture show Cu deposition could promote the photocatalytic efficiency of TiO2, affect platelet adhesion and inhibit smooth muscle cell adhesion and proliferation. It is highlighted that these findings may serve as a guide for the research of multifunctional surface structure.

β-Catenin–regulated myeloid cell adhesion and migration determine wound healing

PubMed Central

Amini-Nik, Saeid; Cambridge, Elizabeth; Yu, Winston; Guo, Anne; Whetstone, Heather; Nadesan, Puviindran; Poon, Raymond; Hinz, Boris; Alman, Benjamin A.

2014-01-01

A β-catenin/T cell factor–dependent transcriptional program is critical during cutaneous wound repair for the regulation of scar size; however, the relative contribution of β-catenin activity and function in specific cell types in the granulation tissue during the healing process is unknown. Here, cell lineage tracing revealed that cells in which β-catenin is transcriptionally active express a gene profile that is characteristic of the myeloid lineage. Mice harboring a macrophage-specific deletion of the gene encoding β-catenin exhibited insufficient skin wound healing due to macrophage-specific defects in migration, adhesion to fibroblasts, and ability to produce TGF-β1. In irradiated mice, only macrophages expressing β-catenin were able to rescue wound-healing deficiency. Evaluation of scar tissue collected from patients with hypertrophic and normal scars revealed a correlation between the number of macrophages within the wound, β-catenin levels, and cellularity. Our data indicate that β-catenin regulates myeloid cell motility and adhesion and that β-catenin–mediated macrophage motility contributes to the number of mesenchymal cells and ultimate scar size following cutaneous injury. PMID:24837430

F4/80: the macrophage-specific adhesion-GPCR and its role in immunoregulation.

PubMed

Lin, Hsi-Hsien; Stacey, Martin; Stein-Streilein, Joan; Gordon, Siamon

2010-01-01

As a macrophage-restricted reagent, the generation and application of the F4/80 mAb has greatly benefited the phenotypic characterization of mouse tissue macrophages for three decades. Following the molecular identification of the F4/80 antigen as an EGF-TM7 member of the adhesion-GPCR family, great interest was ignited to understand its cell type-specific expression pattern as well as its functional role in macrophage biology. Recent studies have shown that the F4/80 gene is regulated by a novel set of transcription factors that recognized a unique promoter sequence. Gene targeting experiments have produced two F4/80 knock out animal models and showed that F4/80 is not required for normal macrophage development. Nevertheless, the F4/80 receptor was found to be necessary for the induction of efferent CD8+ regulatory T cells responsible for peripheral immune tolerance. The identification of cellular ligands for F4/80 and delineation of its signaling pathway remain elusive but are critical to understand the in vivo role of this macrophage-specific adhesion-GPCR.

Formaldehyde Emissions from Urea-Formaldehyde- and no-added-formaldehyde-Bonded particleboard as Influenced by Temperature and Relative Humidity

Treesearch

Charles R. Frihart; James M. Wescott; Timothy L. Chaffee; Kyle M. Gonner

2012-01-01

It is well documented that temperature and humidity can influence formaldehyde emissions from composite panels that are produced using urea-formaldehyde (UF)–type adhesives. This work investigates the effect of temperature and humidity on newer commercial California Air Resources Board (CARB) phase II–compliant particleboard produced with UF-type adhesives. These...

Passion fruit hulls particleboard: the effect of urea formaldehyde level on physical and mechanical properties

NASA Astrophysics Data System (ADS)

Iswanto, A. H.; Sucipto, T.; Adlina, E.; Prabuningrum, D. S.

2018-02-01

The purpose of this research was to explore the suitability of Passion Fruit Hulls (PFH) as a raw material particleboard with variants of urea formaldehyde adhesive content (UF). In this research, PFH particles filtered by sieve in size of 10 mesh to throw dust particles. Furthermore, the particles dried until reaches of 5% moisture content. Levels of UF adhesive was using comprise of 10%, 12% and 14%. Hot pressing conducted at 120°C temperature for 10 minutes at a pressure of 30 kg/cm2. The results showed that in moisture content for 10% adhesive level, almost all the parameters such as thickness swelling, modulus of elasticity (MOE) and modulus of rupture (MOR) that produced did not fulfiled the standard. The 14% adhesive level produced of the best of PFH particleboard.

Designing Hydrogel Adhesives for Corneal Wound Repair

PubMed Central

Grinstaff, Mark W.

2013-01-01

Today, corneal wounds are repaired using nylon sutures. Yet there are a number of complications associated with suturing the cornea, and thus there is interest in an adhesive to replace or supplement sutures in the repair of corneal wounds. We are designing and evaluating corneal adhesives prepared from dendrimers – single molecular weight, highly branched polymers. We have explored two strategies to form these ocular adhesives. The first involves a photocrosslinking reaction and the second uses a peptide ligation reactions to couple the individual dendrimers together to from the adhesive. These adhesives were successfully used to repair corneal perforations, close the flap produced in a LASIK procedure, and secure a corneal transplant. PMID:17889330

Coordination of contractility, adhesion and flow in migrating Physarum amoebae.

PubMed

Lewis, Owen L; Zhang, Shun; Guy, Robert D; del Álamo, Juan C

2015-05-06

This work examines the relationship between spatio-temporal coordination of intracellular flow and traction stress and the speed of amoeboid locomotion of microplasmodia of Physarum polycephalum. We simultaneously perform particle image velocimetry and traction stress microscopy to measure the velocity of cytoplasmic flow and the stresses applied to the substrate by migrating Physarum microamoebae. In parallel, we develop a mathematical model of a motile cell which includes forces from the viscous cytosol, a poro-elastic, contractile cytoskeleton and adhesive interactions with the substrate. Our experiments show that flow and traction stress exhibit back-to-front-directed waves with a distinct phase difference. The model demonstrates that the direction and speed of locomotion are determined by this coordination between contraction, flow and adhesion. Using the model, we identify forms of coordination that generate model predictions consistent with experiments. We demonstrate that this coordination produces near optimal migration speed and is insensitive to heterogeneity in substrate adhesiveness. While it is generally thought that amoeboid motility is robust to changes in extracellular geometry and the nature of extracellular adhesion, our results demonstrate that coordination of adhesive forces is essential to producing robust migration. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Superplastic Forming/Adhesive Bonding of Aluminum (SPF/AB) Multi-Sheet Structures

NASA Technical Reports Server (NTRS)

Wagner, John A. (Technical Monitor); Will, Jeff D.; Cotton, James D.

2003-01-01

A significant fraction of airframe structure consists of stiffened panels that are costly and difficult to fabricate. This program explored a potentially lower-cost processing route for producing such panels. The alternative process sought to apply concurrent superplastic forming and adhesive bonding of aluminum alloy sheets. Processing conditions were chosen to balance adequate superplasticity of the alloy with thermal stability of the adhesive. As a first objective, an air-quenchable, superplastic aluminum-lithium alloy and a low-volatile content, low-viscosity adhesive with compatible forming/curing cycles were identified. A four-sheet forming pack was assembled which consisted of a welded two-sheet core separated from the face sheets by a layer of adhesive. Despite some preliminary success, of over 30 forming trials none was completely successful. The main problem was inadequate superplasticity in the heat-affected zones of the rib welds, which generally fractured prior to completion of the forming cycle. The welds are a necessary component in producing internal ribs by the 'four-sheet' process. Other challenges, such as surface preparation and adhesive bonding, were adequately solved. But without the larger issue of tearing at the weld locations, complex panel fabrication by SPF/AB does not appear viable.

Mena binds α5 integrin directly and modulates α5β1 function.

PubMed

Gupton, Stephanie L; Riquelme, Daisy; Hughes-Alford, Shannon K; Tadros, Jenny; Rudina, Shireen S; Hynes, Richard O; Lauffenburger, Douglas; Gertler, Frank B

2012-08-20

Mena is an Ena/VASP family actin regulator with roles in cell migration, chemotaxis, cell-cell adhesion, tumor cell invasion, and metastasis. Although enriched in focal adhesions, Mena has no established function within these structures. We find that Mena forms an adhesion-regulated complex with α5β1 integrin, a fibronectin receptor involved in cell adhesion, motility, fibronectin fibrillogenesis, signaling, and growth factor receptor trafficking. Mena bound directly to the carboxy-terminal portion of the α5 cytoplasmic tail via a 91-residue region containing 13 five-residue "LERER" repeats. In fibroblasts, the Mena-α5 complex was required for "outside-in" α5β1 functions, including normal phosphorylation of FAK and paxillin and formation of fibrillar adhesions. It also supported fibrillogenesis and cell spreading and controlled cell migration speed. Thus, fibroblasts require Mena for multiple α5β1-dependent processes involving bidirectional interactions between the extracellular matrix and cytoplasmic focal adhesion proteins.

Mena binds α5 integrin directly and modulates α5β1 function

PubMed Central

Riquelme, Daisy; Hughes-Alford, Shannon K.; Tadros, Jenny; Rudina, Shireen S.; O.Hynes, Richard; Lauffenburger, Douglas

2012-01-01

Mena is an Ena/VASP family actin regulator with roles in cell migration, chemotaxis, cell–cell adhesion, tumor cell invasion, and metastasis. Although enriched in focal adhesions, Mena has no established function within these structures. We find that Mena forms an adhesion-regulated complex with α5β1 integrin, a fibronectin receptor involved in cell adhesion, motility, fibronectin fibrillogenesis, signaling, and growth factor receptor trafficking. Mena bound directly to the carboxy-terminal portion of the α5 cytoplasmic tail via a 91-residue region containing 13 five-residue “LERER” repeats. In fibroblasts, the Mena–α5 complex was required for “outside-in” α5β1 functions, including normal phosphorylation of FAK and paxillin and formation of fibrillar adhesions. It also supported fibrillogenesis and cell spreading and controlled cell migration speed. Thus, fibroblasts require Mena for multiple α5β1-dependent processes involving bidirectional interactions between the extracellular matrix and cytoplasmic focal adhesion proteins. PMID:22908313

A Review of Cell Adhesion Studies for Biomedical and Biological Applications.

PubMed

Khalili, Amelia Ahmad; Ahmad, Mohd Ridzuan

2015-08-05

Cell adhesion is essential in cell communication and regulation, and is of fundamental importance in the development and maintenance of tissues. The mechanical interactions between a cell and its extracellular matrix (ECM) can influence and control cell behavior and function. The essential function of cell adhesion has created tremendous interests in developing methods for measuring and studying cell adhesion properties. The study of cell adhesion could be categorized into cell adhesion attachment and detachment events. The study of cell adhesion has been widely explored via both events for many important purposes in cellular biology, biomedical, and engineering fields. Cell adhesion attachment and detachment events could be further grouped into the cell population and single cell approach. Various techniques to measure cell adhesion have been applied to many fields of study in order to gain understanding of cell signaling pathways, biomaterial studies for implantable sensors, artificial bone and tooth replacement, the development of tissue-on-a-chip and organ-on-a-chip in tissue engineering, the effects of biochemical treatments and environmental stimuli to the cell adhesion, the potential of drug treatments, cancer metastasis study, and the determination of the adhesion properties of normal and cancerous cells. This review discussed the overview of the available methods to study cell adhesion through attachment and detachment events.

A Review of Cell Adhesion Studies for Biomedical and Biological Applications

PubMed Central

Ahmad Khalili, Amelia; Ahmad, Mohd Ridzuan

2015-01-01

Cell adhesion is essential in cell communication and regulation, and is of fundamental importance in the development and maintenance of tissues. The mechanical interactions between a cell and its extracellular matrix (ECM) can influence and control cell behavior and function. The essential function of cell adhesion has created tremendous interests in developing methods for measuring and studying cell adhesion properties. The study of cell adhesion could be categorized into cell adhesion attachment and detachment events. The study of cell adhesion has been widely explored via both events for many important purposes in cellular biology, biomedical, and engineering fields. Cell adhesion attachment and detachment events could be further grouped into the cell population and single cell approach. Various techniques to measure cell adhesion have been applied to many fields of study in order to gain understanding of cell signaling pathways, biomaterial studies for implantable sensors, artificial bone and tooth replacement, the development of tissue-on-a-chip and organ-on-a-chip in tissue engineering, the effects of biochemical treatments and environmental stimuli to the cell adhesion, the potential of drug treatments, cancer metastasis study, and the determination of the adhesion properties of normal and cancerous cells. This review discussed the overview of the available methods to study cell adhesion through attachment and detachment events. PMID:26251901

Detachment of Chain-Forming Neuroblasts by Fyn-Mediated Control of cell-cell Adhesion in the Postnatal Brain.

PubMed

Fujikake, Kazuma; Sawada, Masato; Hikita, Takao; Seto, Yayoi; Kaneko, Naoko; Herranz-Pérez, Vicente; Dohi, Natsuki; Homma, Natsumi; Osaga, Satoshi; Yanagawa, Yuchio; Akaike, Toshihiro; García-Verdugo, Jose Manuel; Hattori, Mitsuharu; Sobue, Kazuya; Sawamoto, Kazunobu

2018-05-09

In the rodent olfactory system, neuroblasts produced in the ventricular-subventricular zone of the postnatal brain migrate tangentially in chain-like cell aggregates toward the olfactory bulb (OB) through the rostral migratory stream (RMS). After reaching the OB, the chains are dissociated and the neuroblasts migrate individually and radially toward their final destination. The cellular and molecular mechanisms controlling cell-cell adhesion during this detachment remain unclear. Here we report that Fyn, a nonreceptor tyrosine kinase, regulates the detachment of neuroblasts from chains in the male and female mouse OB. By performing chemical screening and in vivo loss-of-function and gain-of-function experiments, we found that Fyn promotes somal disengagement from the chains and is involved in neuronal migration from the RMS into the granule cell layer of the OB. Fyn knockdown or Dab1 (disabled-1) deficiency caused p120-catenin to accumulate and adherens junction-like structures to be sustained at the contact sites between neuroblasts. Moreover, a Fyn and N-cadherin double-knockdown experiment indicated that Fyn regulates the N-cadherin-mediated cell adhesion between neuroblasts. These results suggest that the Fyn-mediated control of cell-cell adhesion is critical for the detachment of chain-forming neuroblasts in the postnatal OB. SIGNIFICANCE STATEMENT In the postnatal brain, newly born neurons (neuroblasts) migrate in chain-like cell aggregates toward their destination, where they are dissociated into individual cells and mature. The cellular and molecular mechanisms controlling the detachment of neuroblasts from chains are not understood. Here we show that Fyn, a nonreceptor tyrosine kinase, promotes the somal detachment of neuroblasts from chains, and that this regulation is critical for the efficient migration of neuroblasts to their destination. We further show that Fyn and Dab1 (disabled-1) decrease the cell-cell adhesion between chain-forming neuroblasts, which involves adherens junction-like structures. Our results suggest that Fyn-mediated regulation of the cell-cell adhesion of neuroblasts is critical for their detachment from chains in the postnatal brain. Copyright © 2018 the authors 0270-6474/18/384599-12$15.00/0.

Functionalization of polydimethylsiloxane membranes to be used in the production of voice prostheses

NASA Astrophysics Data System (ADS)

Ferreira, Paula; Carvalho, Álvaro; Ruivo Correia, Tiago; Paiva Antunes, Bernardo; Joaquim Correia, Ilídio; Alves, Patrícia

2013-10-01

The voice is produced by the vibration of vocal cords which are located in the larynx. Therefore, one of the major consequences for patients subjected to laryngectomy is losing their voice. In these cases, a synthetic one-way valve set (voice prosthesis) can be implanted in order to allow restoration of speech. Most voice prostheses are produced with silicone-based materials such as polydimethylsiloxane (PDMS). This material has excellent properties, such as optical transparency, chemical and biological inertness, non-toxicity, permeability to gases and excellent mechanical resistance that are fundamental for its application in the biomedical field. However, PDMS is very hydrophobic and this property causes protein adsorption which is followed by microbial adhesion and biofilm formation. To overcome these problems, surface modification of materials has been proposed in this study. A commercial silicone elastomer, SylgardTM 184 was used to prepare membranes whose surface was modified by grafting 2-hydroxyethylmethacrylate and methacrylic acid by low-pressure plasma treatment. The hydrophilicity, hydrophobic recovery and surface energy of the produced materials were determined. Furthermore, the cytotoxicity and antibacterial activity of the materials were also assessed. The results obtained revealed that the PDMS surface modification performed did not affect the material's biocompatibility, but decreased their hydrophobic character and bacterial adhesion and growth on its surface.

Microstructure and Properties of Thermally Sprayed Functionally Graded Coatings for Polymeric Substrates

NASA Technical Reports Server (NTRS)

Ivosevic, M.; Knight, R.; Kalidindi, S. R.; Palmese, G. R.; Sutter, J. K.

2003-01-01

The use of polymer matrix composites (PMCs) in the gas flow path of advanced turbine engines offers significant benefits for aircraft engine performance but their useful lifetime is limited by their poor erosion resistance. High velocity oxy-fuel (HVOF) sprayed polymer/cermet functionally graded (FGM) coatings are being investigated as a method to address this technology gap by providing erosion and oxidation protection to polymer matrix composites. The FGM coating structures are based on a polyimide matrix filled with varying volume fractions of WC-Co. The graded coating architecture was produced using a combination of internal and external feedstock injection, via two computer-controlled powder feeders and controlled substrate preheating. Porosity, coating thickness and volume fraction of the WC-Co filler retained in the coatings were determined using standard metallographic techniques and computer image analysis. The pull-off strength (often referred to as the adhesive strength) of the coatings was evaluated according to the ASTM D 4541 standard test method, which measured the greatest normal tensile force that the coating could withstand. Adhesive/cohesive strengths were determined for three different types of coating structures and compared based on the maximum indicated load and the surface area loaded. The nature and locus of the fractures were characterized according to the percent of adhesive and/or cohesive failure, and the tested interfaces and layers involved were analyzed by Scanning Electron Microscopy.

The Effects of Curcuma Longa on the Functionality of Pigmentation for Thin Film Coating

NASA Astrophysics Data System (ADS)

Marsi, N.; Rus, A. Z. M.; Tan, N. A. M. S.

2017-08-01

This project presents the effects of turmeric (Curcuma Longa) on the functionality of pigmentation was carried out to improve the sustainability, environment impact and reduction of potential cost saving without sacrificing the performance of thin film coating. The Curcuma Longa pigment was extracted by grating the turmeric into small particles at different percentages which is 20%, 40%, 60% and 80% of Curcuma Longa pigment with 3, 6 and 9 layers of coating. The different percentages of Curcuma Longa pigment was formulated and synthesized with polyols by crosslinking agent of glycerol and calcium carbonate into temperature at 140 °C for 2 hours. The results of water droplet test (ASTM D5964) showed the water contact angle was achieved the optimum superhydrophobic characteristic up to 60% of Curcuma Longa at 153°. The formulation of 60% Curcuma Longa was revealed the optimum adhesion resistance test with no flaking and detachment when the coating applied at 9 layers in the classification grading of adhesion test at 5B. It is indicated that the adhesion resistance of thin film coating on metal substrate was obviously increased as the layer of coating as well as the Curcuma Longa pigment percentage up to 60% at 9 layers. This project also highlighted the potential of Curcuma Longa pigment to produce quality in the natural pigmentation as a replacement synthetic pigment which is long-term health hazards.

Curli mediate bacterial adhesion to fibronectin via tensile multiple bonds

NASA Astrophysics Data System (ADS)

Oh, Yoo Jin; Hubauer-Brenner, Michael; Gruber, Hermann J.; Cui, Yidan; Traxler, Lukas; Siligan, Christine; Park, Sungsu; Hinterdorfer, Peter

2016-09-01

Many enteric bacteria including pathogenic Escherichia coli and Salmonella strains produce curli fibers that bind to host surfaces, leading to bacterial internalization into host cells. By using a nanomechanical force-sensing approach, we obtained real-time information about the distribution of molecular bonds involved in the adhesion of curliated bacteria to fibronectin. We found that curliated E. coli and fibronectin formed dense quantized and multiple specific bonds with high tensile strength, resulting in tight bacterial binding. Nanomechanical recognition measurements revealed that approximately 10 bonds were disrupted either sequentially or simultaneously under force load. Thus the curli formation of bacterial surfaces leads to multi-bond structural components of fibrous nature, which may explain the strong mechanical binding of curliated bacteria to host cells and unveil the functions of these proteins in bacterial internalization and invasion.

Evidence for the Adhesive Function of the Exopolysaccharide of Hyphomonas Strain MHS-3 in Its Attachment to Surfaces

PubMed Central

Quintero, E. J.; Weiner, R. M.

1995-01-01

Hyphomonas strain MHS-3 (MHS-3) is a marine procaryote with a biphasic life cycle and which has prosthecate stages that adhere to submerged substrata. We found that adherent forms produced an exopolysaccharide (EPS) capsule that bound Glycine max lectin, Arachis hypogaea lectin, and Bauhinia purpurea lectin (BPA), each having affinity for N-acetyl-d-galactosamine. It also bound the dye Calcofluor. BPA and Calcofluor were tested for the ability to hinder MHS-3 adhesion to glass surfaces; they reduced attachment by >50 and >85%, respectively. Periodate treatment also reduced attachment (by >80%), but pronase treatment did not. Furthermore, an EPS(sup-) variant, Hyphomonas strain MHS-3 rad, did not attach well to surfaces. These results suggest that the MHS-3 EPS capsule is an adhesin. PMID:16535028

Covalent Functionalization of NiTi Surfaces with Bioactive Peptide Amphiphile Nanofibers

PubMed Central

Sargeant, Timothy D.; Rao, Mukti S.; Koh, Chung-Yan

2009-01-01

Surface modification enables the creation of bioactive implants using traditional material substrates without altering the mechanical properties of the bulk material. For applications such as bone plates and stents, it is desirable to modify the surface of metal alloy substrates to facilitate cellular attachment, proliferation, and possibly differentiation. In this work we present a general strategy for altering the surface chemistry of nickel-titanium shape memory alloy (NiTi) in order to covalently attach self-assembled peptide amphiphile (PA) nanofibers with bioactive functions. Bioactivity in the systems studied here includes biological adhesion and proliferation of osteoblast and endothelial cell types. The optimized surface treatment creates a uniform TiO2 layer with low levels of Ni on the NiTi surface, which is subsequently covered with an aminopropylsilane coating using a novel, lower temperature vapor deposition method. This method produces an aminated surface suitable for covalent attachment of PA molecules containing terminal carboxylic acid groups. The functionalized NiTi surfaces have been characterized by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), and atomic force microscopy (AFM). These techniques offer evidence that the treated metal surfaces consist primarily of TiO2 with very little Ni, and also confirm the presence of the aminopropylsilane overlayer. Self-assembled PA nanofibers presenting the biological peptide adhesion sequence Arg-Gly-Asp-Ser are capable of covalently anchoring to the treated substrate, as demonstrated by spectrofluorimetry and AFM. Cell culture and scanning electron microscopy (SEM) demonstrate cellular adhesion, spreading, and proliferation on these functionalized metal surfaces. Furthermore, these experiments demonstrate that covalent attachment is crucial for creating robust PA nanofiber coatings, leading to confluent cell monolayers. PMID:18083225

Effects of physical and nutritional stress conditions during mycelial growth on conidial germination speed, adhesion to host cuticle, and virulence of Metarhizium anisopliae, an entomopathogenic fungus.

PubMed

Rangel, Drauzio E N; Alston, Diane G; Roberts, Donald W

2008-11-01

Growth under stress may influence pathogen virulence and other phenotypic traits. Conidia of the entomopathogenic fungus Metarhizium anisopliae var. anisopliae (isolate ARSEF 2575) were produced under different stress conditions and then examined for influences on in vitro conidial germination speed, adhesion to the insect cuticle, and virulence to an insect host, Tenebrio molitor. Conidia were produced under non-stress conditions [on potato-dextrose agar plus 1gl(-1) yeast extract (PDAY; control)], or under the following stress conditions: osmotic (PDAY+sodium chloride or potassium chloride, 0.6 or 0.8m); oxidative [(PDAY+hydrogen peroxide, 5mm) or UV-A (irradiation of mycelium on PDAY)]; heat shock (heat treatment of mycelium on PDAY at 45 degrees C, 40min); and nutritive [minimal medium (MM) with no carbon source, or on MM plus 3gl(-1) lactose (MML)]. Conidia were most virulent (based on mortality at 3d) and had the fastest germination rates when produced on MML, followed by MM. In addition, conidial adhesion to host cuticle was greatest when the conidia were produced on MML. Media with high osmolarity (0.8m) produced conidia with slightly elevated virulence and faster germination rates than conidia produced on the control medium (PDAY), but this trend did not hold for media with the lower osmolarity, (0.6m). Conidia produced from mycelium irradiated with UV-A while growing on PDAY had somewhat elevated virulence levels similar to that of conidia produced on MM, but their germination rate was not increased. Hydrogen peroxide and heat shock treatments did not alter virulence. These results demonstrate that the germination, adhesion and virulence of M. anisopliae conidia can be strongly influenced by culture conditions (including stresses) during production of the conidia.

Microscopic and infrared spectroscopic comparison of the underwater adhesives produced by germlings of the brown seaweed species Durvillaea antarctica and Hormosira banksii.

PubMed

Dimartino, Simone; Savory, David M; Fraser-Miller, Sara J; Gordon, Keith C; McQuillan, A James

2016-04-01

Adhesives from marine organisms are often the source of inspiration for the development of glues able to create durable bonds in wet environments. In this work, we investigated the adhesive secretions produced by germlings of two large seaweed species from the South Pacific, Durvillaea antarctica, also named 'the strongest kelp in the word', and its close relative Hormosira banksii The comparative analysis was based on optical and scanning electron microscopy imaging as well as Fourier transform infrared (FTIR) spectroscopy and principal component analysis (PCA). For both species, the egg surface presents peripheral vesicles which are released soon after fertilization to discharge a primary adhesive. This is characterized by peaks representative of carbohydrate molecules. A secondary protein-based adhesive is then secreted in the early developmental stages of the germlings. Energy dispersive X-ray, FTIR and PCA indicate that D. antarctica secretions also contain sulfated moieties, and become cross-linked with time, both conferring strong adhesive and cohesive properties. On the other hand, H. banksii secretions are complemented by the putative adhesive phlorotannins, and are characterized by a simple mechanism in which all constituents are released with the same rate and with no apparent cross-linking. It is also noted that the release of adhesive materials appears to be faster and more copious in D. antarctica than in H. banksii Overall, this study highlights that both quantity and quality of the adhesives matter in explaining the superior attachment ability of D. antarctica. © 2016 The Author(s).

Microscopic and infrared spectroscopic comparison of the underwater adhesives produced by germlings of the brown seaweed species Durvillaea antarctica and Hormosira banksii

PubMed Central

Savory, David M.; McQuillan, A. James

2016-01-01

Adhesives from marine organisms are often the source of inspiration for the development of glues able to create durable bonds in wet environments. In this work, we investigated the adhesive secretions produced by germlings of two large seaweed species from the South Pacific, Durvillaea antarctica, also named ‘the strongest kelp in the word’, and its close relative Hormosira banksii. The comparative analysis was based on optical and scanning electron microscopy imaging as well as Fourier transform infrared (FTIR) spectroscopy and principal component analysis (PCA). For both species, the egg surface presents peripheral vesicles which are released soon after fertilization to discharge a primary adhesive. This is characterized by peaks representative of carbohydrate molecules. A secondary protein-based adhesive is then secreted in the early developmental stages of the germlings. Energy dispersive X-ray, FTIR and PCA indicate that D. antarctica secretions also contain sulfated moieties, and become cross-linked with time, both conferring strong adhesive and cohesive properties. On the other hand, H. banksii secretions are complemented by the putative adhesive phlorotannins, and are characterized by a simple mechanism in which all constituents are released with the same rate and with no apparent cross-linking. It is also noted that the release of adhesive materials appears to be faster and more copious in D. antarctica than in H. banksii. Overall, this study highlights that both quantity and quality of the adhesives matter in explaining the superior attachment ability of D. antarctica. PMID:27122179

Epithelial adhesion molecules and the regulation of intestinal homeostasis during neutrophil transepithelial migration

PubMed Central

Sumagin, Ronen; Parkos, Charles A

2014-01-01

Epithelial adhesion molecules play essential roles in regulating cellular function and maintaining mucosal tissue homeostasis. Some form epithelial junctional complexes to provide structural support for epithelial monolayers and act as a selectively permeable barrier separating luminal contents from the surrounding tissue. Others serve as docking structures for invading viruses and bacteria, while also regulating the immune response. They can either obstruct or serve as footholds for the immune cells recruited to mucosal surfaces. Currently, it is well appreciated that adhesion molecules collectively serve as environmental cue sensors and trigger signaling events to regulate epithelial function through their association with the cell cytoskeleton and various intracellular adapter proteins. Immune cells, particularly neutrophils (PMN) during transepithelial migration (TEM), can modulate adhesion molecule expression, conformation, and distribution, significantly impacting epithelial function and tissue homeostasis. This review discusses the roles of key intestinal epithelial adhesion molecules in regulating PMN trafficking and outlines the potential consequences on epithelial function. PMID:25838976

Adhesive Property of Bacteria and Its Relationship to Microbial Spoilage of Shrimp.

DTIC Science & Technology

1983-01-04

that it may be either homopolymers or complex heteropolymers, made up of varying monosaccharides . However, neutral hexoses, 6-deoxyhexoses, polyols...a surface, surrounds itself with addi- tional exopolysaccharide and then replicates within this environment. This protective polysaccharide shell... polysaccharide adhesions produced by S. mutans to be alpha 1,3 and alpha 1,6 branched glucans produced by a group of glucosyltransferaces. 6 Hamada and

Characterization of a Distinct Population of Circulating Human Non-Adherent Endothelial Forming Cells and Their Recruitment via Intercellular Adhesion Molecule-3

PubMed Central

Thompson, Emma J.; Barrett, Jeffrey M.; Tooley, Katie; Sen, Shaundeep; Sun, Wai Yan; Grose, Randall; Nicholson, Ian; Levina, Vitalina; Cooke, Ira; Talbo, Gert; Lopez, Angel F.; Bonder, Claudine S.

2012-01-01

Circulating vascular progenitor cells contribute to the pathological vasculogenesis of cancer whilst on the other hand offer much promise in therapeutic revascularization in post-occlusion intervention in cardiovascular disease. However, their characterization has been hampered by the many variables to produce them as well as their described phenotypic and functional heterogeneity. Herein we have isolated, enriched for and then characterized a human umbilical cord blood derived CD133+ population of non-adherent endothelial forming cells (naEFCs) which expressed the hematopoietic progenitor cell markers (CD133, CD34, CD117, CD90 and CD38) together with mature endothelial cell markers (VEGFR2, CD144 and CD31). These cells also expressed low levels of CD45 but did not express the lymphoid markers (CD3, CD4, CD8) or myeloid markers (CD11b and CD14) which distinguishes them from ‘early’ endothelial progenitor cells (EPCs). Functional studies demonstrated that these naEFCs (i) bound Ulex europaeus lectin, (ii) demonstrated acetylated-low density lipoprotein uptake, (iii) increased vascular cell adhesion molecule (VCAM-1) surface expression in response to tumor necrosis factor and (iv) in co-culture with mature endothelial cells increased the number of tubes, tubule branching and loops in a 3-dimensional in vitro matrix. More importantly, naEFCs placed in vivo generated new lumen containing vasculature lined by CD144 expressing human endothelial cells (ECs). Extensive genomic and proteomic analyses of the naEFCs showed that intercellular adhesion molecule (ICAM)-3 is expressed on their cell surface but not on mature endothelial cells. Furthermore, functional analysis demonstrated that ICAM-3 mediated the rolling and adhesive events of the naEFCs under shear stress. We suggest that the distinct population of naEFCs identified and characterized here represents a new valuable therapeutic target to control aberrant vasculogenesis. PMID:23144795

Electroless Plating of Copper on Polyimide Film Modified by 50 Hz Plasma Graft Polymerization with 1-Vinylimidazole

NASA Astrophysics Data System (ADS)

Wong, Chiow San; Lem, Hon Pong; Goh, Boon Tong; Wong, Cin Wie

2009-03-01

This paper reports on the proof of concept work on the novel process of producing metalized polyimide (PI) film by coating a layer of copper (Cu) thin film on the surface of the PI film without using any adhesive. The method which is employed to produce a metalized PI film used in flexible printed circuit (FPC) is based on plasma graft polymerization of 1-vinlyimidazole (VIDz) on plasma pre-treated PI surface. The plasma grafted PI film (VIDz-g-PI) surfaces are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). AFM results show that the PI film surface has been successfully treated and grafted with VIDz. As post-thermal treatment is known to promote adhesion strength between the metallic film and the PI surface, the effects of post-thermal treatment environment and temperature on the adhesion property of Cu plated VIDz-g-PI (Cu/VIDz-g-PI) are evaluated. Post-thermal treatment in air shows better adhesion strength than in vacuum. The adhesion strength decreases as the post-thermal treatment temperature is increased. In the present development work, the adhesion strength obtained has met the initial market targeted 9-10 N/cm adhesion strength. Samples obtained at a pre-selected plasma power and time window are able to maintain their adhesion strength after being subjected to ageing at 100 °C for 168 h.

Adaptive Shape Functions and Internal Mesh Adaptation for Modelling Progressive Failure in Adhesively Bonded Joints

NASA Technical Reports Server (NTRS)

Stapleton, Scott; Gries, Thomas; Waas, Anthony M.; Pineda, Evan J.

2014-01-01

Enhanced finite elements are elements with an embedded analytical solution that can capture detailed local fields, enabling more efficient, mesh independent finite element analysis. The shape functions are determined based on the analytical model rather than prescribed. This method was applied to adhesively bonded joints to model joint behavior with one element through the thickness. This study demonstrates two methods of maintaining the fidelity of such elements during adhesive non-linearity and cracking without increasing the mesh needed for an accurate solution. The first method uses adaptive shape functions, where the shape functions are recalculated at each load step based on the softening of the adhesive. The second method is internal mesh adaption, where cracking of the adhesive within an element is captured by further discretizing the element internally to represent the partially cracked geometry. By keeping mesh adaptations within an element, a finer mesh can be used during the analysis without affecting the global finite element model mesh. Examples are shown which highlight when each method is most effective in reducing the number of elements needed to capture adhesive nonlinearity and cracking. These methods are validated against analogous finite element models utilizing cohesive zone elements.

Molecular basis of crystal morphology-dependent adhesion behavior of mefenamic acid during tableting.

PubMed

Waknis, Vrushali; Chu, Elza; Schlam, Roxana; Sidorenko, Alexander; Badawy, Sherif; Yin, Shawn; Narang, Ajit S

2014-01-01

The molecular basis of crystal surface adhesion leading to sticking was investigated by exploring the correlation of crystal adhesion to oxidized iron coated atomic force microscope (AFM) tips and bulk powder sticking behavior during tableting of two morphologically different crystals of a model drug, mefenamic acid (MA), to differences in their surface functional group orientation and energy. MA was recrystallized into two morphologies (plates and needles) of the same crystalline form. Crystal adhesion to oxidized iron coated AFM tips and bulk powder sticking to tablet punches was assessed using a direct compression formulation. Surface functional group orientation and energies on crystal faces were modeled using Accelrys Material Studio software. Needle-shaped morphology showed higher sticking tendency than plates despite similar particle size. This correlated with higher crystal surface adhesion of needle-shaped morphology to oxidized iron coated AFM probe tips, and greater surface energy and exposure of polar functional groups. Higher surface exposure of polar functional groups correlates with higher tendency to stick to metal surfaces and AFM tips, indicating involvement of specific polar interactions in the adhesion behavior. In addition, an AFM method is identified to prospectively assess the risk of sticking during the early stages of drug development.

The state diagram for cell adhesion under flow: leukocyte rolling and firm adhesion.

PubMed

Chang, K C; Tees, D F; Hammer, D A

2000-10-10

Leukocyte adhesion under flow in the microvasculature is mediated by binding between cell surface receptors and complementary ligands expressed on the surface of the endothelium. Leukocytes adhere to endothelium in a two-step mechanism: rolling (primarily mediated by selectins) followed by firm adhesion (primarily mediated by integrins). Using a computational method called "Adhesive Dynamics," we have simulated the adhesion of a cell to a surface in flow, and elucidated the relationship between receptor-ligand functional properties and the dynamics of adhesion. We express this relationship in a state diagram, a one-to-one map between the biophysical properties of adhesion molecules and various adhesive behaviors. Behaviors that are observed in simulations include firm adhesion, transient adhesion (rolling), and no adhesion. We varied the dissociative properties, association rate, bond elasticity, and shear rate and found that the unstressed dissociation rate, k(r)(o), and the bond interaction length, gamma, are the most important molecular properties controlling the dynamics of adhesion. Experimental k(r)(o) and gamma values from the literature for molecules that are known to mediate rolling adhesion fall within the rolling region of the state diagram. We explain why L-selectin-mediated rolling, which has faster k(r)(o) than other selectins, is accompanied by a smaller value for gamma. We also show how changes in association rate, shear rate, and bond elasticity alter the dynamics of adhesion. The state diagram (which must be mapped for each receptor-ligand system) presents a concise and comprehensive means of understanding the relationship between bond functional properties and the dynamics of adhesion mediated by receptor-ligand bonds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aden, Bethany; Kite, Camille M.; Hopkins, Benjamin W.

Designing thin films or surface scaffolds with an appropriate display of chemical functionality is useful for biomedical applications, sensing platforms, adhesives, and barrier coatings. Relationships between the structural characteristics of model thin films based on reactive poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) brushes and the amount and distribution of primary amines used to chemically functionalize these layers in situ are quantitatively detailed via neutron reflectometry and compared with results from ellipsometry. After functionalization, the PVDMA brush thickness increases as a result of the primary amines reacting with the azlactone rings. Both techniques show that the extent of functionalization by small-molecule amines depends onmore » the size of the amine, the grafting density of brush chains, and their molecular weight. However, constrained analysis of neutron reflectivity data predicated on that technique’s sensitivity to isotopic substitution and its ability to resolve structure at the nanoscale shows that the extent of functionalization is not accurately represented by the average extent of functionalization determined from ellipsometric thickness: reactive modification is not uniform, even in modestly dense brushes, except when the penetrant is small. In addition, there appears to be a loss of PVDMA chains during functionalization, attributed to chain scission resulting from additional stretching brought about by functionalization. In conclusion, these findings provide unprecedented insight into the alteration of surface properties by reactive modification and broadly support efforts to produce tailored surfaces in which properties such as friction, colloidal stability, adhesion, wettability, and biocompatibility can be modulated in situ by chemical modification.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aden, Bethany; Kite, Camille M.; Hopkins, Benjamin W.

Designing thin films or surface scaffolds with an appropriate display of chemical functionality is useful for biomedical applications, sensing platforms, adhesives, and barrier coatings. Relationships between the structural characteristics of model thin films based on reactive poly(2-vinyl-4,4-dimethylazlactone) (PVDMA) brushes and the amount and distribution of primary amines used to chemically functionalize the layer in situ are quantitatively detailed via neutron reflectometry and compared with results from ellipsometry. After functionalization, the PVDMA brush thickness increases as a result of the primary amines reacting with the azlactone rings. Both techniques show that the extent of functionalization by small-molecule amines depends on themore » size of the amine, the grafting density of brush chains and their molecular weight. However, constrained analysis of neutron reflectivity data predicated on that technique’s sensitivity to isotopic substitution and its ability to resolve structure at the nanoscale, shows that the extent of functionalization is not accurately represented by the average extent of functionalization determined from ellipsometric thickness: reactive modification is not uniform, even in modestly dense brushes, except when the penetrant is small. Additionally, there appears to be a loss of PVDMA chains during functionalization, attributed to chain scission resulting from additional stretching brought about by functionalization. These findings provide unprecedented insight into the alteration of surface properties by reactive modification and broadly support efforts to produce tailored surfaces in which properties such as friction, colloidal stability, adhesion, wettability, and biocompatibility can be modulated in situ by chemical modification.« less

Modifying Matrix Materials to Increase Wetting and Adhesion

NASA Technical Reports Server (NTRS)

Zhong, Katie

2011-01-01

In an alternative approach to increasing the degrees of wetting and adhesion between the fiber and matrix components of organic-fiber/polymer matrix composite materials, the matrix resins are modified. Heretofore, it has been common practice to modify the fibers rather than the matrices: The fibers are modified by chemical and/or physical surface treatments prior to combining the fibers with matrix resins - an approach that entails considerable expense and usually results in degradation (typically, weakening) of fibers. The alternative approach of modifying the matrix resins does not entail degradation of fibers, and affords opportunities for improving the mechanical properties of the fiber composites. The alternative approach is more cost-effective, not only because it eliminates expensive fiber-surface treatments but also because it does not entail changes in procedures for manufacturing conventional composite-material structures. The alternative approach is best described by citing an example of its application to a composite of ultra-high-molecular- weight polyethylene (UHMWPE) fibers in an epoxy matrix. The epoxy matrix was modified to a chemically reactive, polarized epoxy nano-matrix to increase the degrees of wetting and adhesion between the fibers and the matrix. The modification was effected by incorporating a small proportion (0.3 weight percent) of reactive graphitic nanofibers produced from functionalized nanofibers into the epoxy matrix resin prior to combining the resin with the UHMWPE fibers. The resulting increase in fiber/matrix adhesion manifested itself in several test results, notably including an increase of 25 percent in the maximum fiber pullout force and an increase of 60-65 percent in fiber pullout energy. In addition, it was conjectured that the functionalized nanofibers became involved in the cross linking reaction of the epoxy resin, with resultant enhancement of the mechanical properties and lower viscosity of the matrix.

Evidence-Based Nanoscopic and Molecular Framework for Excipient Functionality in Compressed Orally Disintegrating Tablets

PubMed Central

Al-khattawi, Ali; Alyami, Hamad; Townsend, Bill; Ma, Xianghong; Mohammed, Afzal R.

2014-01-01

The work investigates the adhesive/cohesive molecular and physical interactions together with nanoscopic features of commonly used orally disintegrating tablet (ODT) excipients microcrystalline cellulose (MCC) and D-mannitol. This helps to elucidate the underlying physico-chemical and mechanical mechanisms responsible for powder densification and optimum product functionality. Atomic force microscopy (AFM) contact mode analysis was performed to measure nano-adhesion forces and surface energies between excipient-drug particles (6-10 different particles per each pair). Moreover, surface topography images (100 nm2–10 µm2) and roughness data were acquired from AFM tapping mode. AFM data were related to ODT macro/microscopic properties obtained from SEM, FTIR, XRD, thermal analysis using DSC and TGA, disintegration testing, Heckel and tabletability profiles. The study results showed a good association between the adhesive molecular and physical forces of paired particles and the resultant densification mechanisms responsible for mechanical strength of tablets. MCC micro roughness was 3 times that of D-mannitol which explains the high hardness of MCC ODTs due to mechanical interlocking. Hydrogen bonding between MCC particles could not be established from both AFM and FTIR solid state investigation. On the contrary, D-mannitol produced fragile ODTs due to fragmentation of surface crystallites during compression attained from its weak crystal structure. Furthermore, AFM analysis has shown the presence of extensive micro fibril structures inhabiting nano pores which further supports the use of MCC as a disintegrant. Overall, excipients (and model drugs) showed mechanistic behaviour on the nano/micro scale that could be related to the functionality of materials on the macro scale. PMID:25025427

Delineating the Tes Interaction Site in Zyxin and Studying Cellular Effects of Its Disruption.

PubMed

Hadzic, Ermin; Catillon, Marie; Halavatyi, Aliaksandr; Medves, Sandrine; Van Troys, Marleen; Moes, Michèle; Baird, Michelle A; Davidson, Michael W; Schaffner-Reckinger, Elisabeth; Ampe, Christophe; Friederich, Evelyne

2015-01-01

Focal adhesions are integrin-based structures that link the actin cytoskeleton and the extracellular matrix. They play an important role in various cellular functions such as cell signaling, cell motility and cell shape. To ensure and fine tune these different cellular functions, adhesions are regulated by a large number of proteins. The LIM domain protein zyxin localizes to focal adhesions where it participates in the regulation of the actin cytoskeleton. Because of its interactions with a variety of binding partners, zyxin has been proposed to act as a molecular scaffold. Here, we studied the interaction of zyxin with such a partner: Tes. Similar to zyxin, Tes harbors three highly conserved LIM domains of which the LIM1 domain directly interacts with zyxin. Using different zyxin variants in pull-down assays and ectopic recruitment experiments, we identified the Tes binding site in zyxin and showed that four highly conserved amino acids are crucial for its interaction with Tes. Based upon these findings, we used a zyxin mutant defective in Tes-binding to assess the functional consequences of abrogating the zyxin-Tes interaction in focal adhesions. Performing fluorescence recovery after photobleaching, we showed that zyxin recruits Tes to focal adhesions and modulates its turnover in these structures. However, we also provide evidence for zyxin-independent localization of Tes to focal adhesions. Zyxin increases focal adhesion numbers and reduces focal adhesion lifetimes, but does so independent of Tes. Quantitative analysis showed that the loss of interaction between zyxin and Tes affects the process of cell spreading. We conclude that zyxin influences focal adhesion dynamics, that it recruits Tes and that this interaction is functional in regulating cell spreading.

Delineating the Tes Interaction Site in Zyxin and Studying Cellular Effects of Its Disruption

PubMed Central

Hadzic, Ermin; Catillon, Marie; Halavatyi, Aliaksandr; Medves, Sandrine; Van Troys, Marleen; Moes, Michèle; Baird, Michelle A.; Davidson, Michael W.; Schaffner-Reckinger, Elisabeth; Ampe, Christophe; Friederich, Evelyne

2015-01-01

Focal adhesions are integrin-based structures that link the actin cytoskeleton and the extracellular matrix. They play an important role in various cellular functions such as cell signaling, cell motility and cell shape. To ensure and fine tune these different cellular functions, adhesions are regulated by a large number of proteins. The LIM domain protein zyxin localizes to focal adhesions where it participates in the regulation of the actin cytoskeleton. Because of its interactions with a variety of binding partners, zyxin has been proposed to act as a molecular scaffold. Here, we studied the interaction of zyxin with such a partner: Tes. Similar to zyxin, Tes harbors three highly conserved LIM domains of which the LIM1 domain directly interacts with zyxin. Using different zyxin variants in pull-down assays and ectopic recruitment experiments, we identified the Tes binding site in zyxin and showed that four highly conserved amino acids are crucial for its interaction with Tes. Based upon these findings, we used a zyxin mutant defective in Tes-binding to assess the functional consequences of abrogating the zyxin-Tes interaction in focal adhesions. Performing fluorescence recovery after photobleaching, we showed that zyxin recruits Tes to focal adhesions and modulates its turnover in these structures. However, we also provide evidence for zyxin-independent localization of Tes to focal adhesions. Zyxin increases focal adhesion numbers and reduces focal adhesion lifetimes, but does so independent of Tes. Quantitative analysis showed that the loss of interaction between zyxin and Tes affects the process of cell spreading. We conclude that zyxin influences focal adhesion dynamics, that it recruits Tes and that this interaction is functional in regulating cell spreading. PMID:26509500

Effect of Heat Treatment on Some Mechanical Properties of Laminated Window Profiles Manufactured Using Two Types of Adhesives

PubMed Central

Korkut, Derya Sevim; Korkutand, Suleyman; Dilik, Tuncer

2008-01-01

The mechanical properties of laminated window profiles manufactured using two types of adhesives were determined. The objective of this study is to evaluate the effects of heat treatment on some mechanical properties of laminated window profiles that manufactured from Kosipo (Entandrophragma candollei Harms.) using differenet type adhesives. Commercially produced polyurethane based Macroplast UR 7221 and polyvinyl acetate (PVAc) adhesive were used for experiments. The overall test results were found to be comparable to those obtained in the previous studies. Both types of adhesives resulted in significant differences in their strength characteristics at 95% confidence level. Adhesive UR 7221 improved the overall properties of the samples in contrast to PVAc. PMID:19325761

Laser Surface Preparation for Adhesive Bonding of Ti-6Al-4V

NASA Technical Reports Server (NTRS)

Belcher, Marcus A.; List, Martina S.; Wohl, Christopher J.; Ghose, Sayata; Watson, Kent A.; Hopkins, John W.; Connell, John W.

2010-01-01

Adhesively bonded structures are potentially lighter in weight than mechanically fastened ones, but existing surface treatments are often considered unreliable. Two main problems in achieving reproducible and durable adhesive bonds are surface contamination and variability in standard surface preparation techniques. In this work three surface pretreatments were compared: laser etching with and without grit blasting and conventional Pasa-Jell treatment. Ti-6Al-4V surfaces were characterized by contact angle goniometry, optical microscopy, and X-ray photoelectron spectroscopy (XPS). Laser -etching was found to produce clean surfaces with precisely controlled surface topographies and PETI-5 lap shear strengths and durabilities were equivalent to those produced with Pasa-Jell.

Medium density fibreboard production by hot pressing without adhesive using Triarrhena sacchariflora residue bio-pretreated by white-rot fungus Coriolus versicolor.

PubMed

Wu, J G; Zhang, X; Liu, J; Xiong, M; Lu, X Y; Fan, H D; Wang, X F; Zhang, X Y

2016-08-01

To produce fibreboard with Triarrhena sacchariflora residue (TSR) without adhesive and understand the relationship between bio-pretreatment and mechanical property of fibreboard. White-rot fungus Coriolus versicolor was used to pretreat TSR, and biochemical and physical analysis were investigated by ultraviolet spectrophotometry, Fourier transform infrared spectroscopy and environmental scanning electron microscopy method. TSR was suitable to produce fibreboard without adhesive by bio-pretreatment with C. versicolor. The property of fibreboard became stronger by optimization of bio-pretreatment parameters, and the moduli of rupture and elasticity of fibreboard were increased to 18·12 MPa and 4·3 GPa, respectively, which were close to national standard of medium-density fibreboard with adhesive. Bio-pretreated TSR increased the mechanical properties of fibreboard because of 1·4-fold content of polysaccharide and 1·15 U g(-1) laccase, more hydroxyl group and more porous surface structure than that of untreated TSR. TSR-based fibreboard production without adhesive eliminated potential formaldehyde gas emission. © 2016 The Society for Applied Microbiology.

Focal adhesions and Ras are functionally and spatially integrated to mediate IL-1 activation of ERK

PubMed Central

Wang, Qin; Downey, Gregory P.; McCulloch, Christopher A.

2011-01-01

In connective tissue cells, IL-1-induced ERK activation leading to matrix metalloproteinase (MMP)-3 expression is dependent on cooperative interactions between focal adhesions and the endoplasmic reticulum (ER). As Ras can be activated on the ER, we investigated the role of Ras in IL-1 signaling and focal adhesion formation. We found that constitutively active H-Ras, K-Ras or N-Ras enhanced focal adhesion maturation and β1-integrin activation. IL-1 promoted the accumulation of Ras isoforms in ER and focal adhesion fractions, as shown in cells cotransfected with GFP-tagged Ras isoforms and YFP-ER protein and by analysis of subcellular fractions enriched for ER or focal adhesion proteins. Dominant-negative H-Ras or K-Ras reduced accumulation of H-Ras and K-Ras in focal adhesions induced by IL-1 and also blocked ERK activation and focal adhesion maturation. Ras-GRF was enriched constitutively in focal adhesion fractions and was required for Ras recruitment to focal adhesions. We conclude that Ras activation and IL-1 signaling are interactive processes that regulate the maturation of focal adhesions, which, in turn, is required for ERK activation.—Wang, Q., Downey, G. P., McCulloch, C. A. Focal adhesions and Ras are functionally and spatially integrated to mediate IL-1 activation of ERK. PMID:21719512

Fabrication and Characterization of Gecko-inspired Fibrillar Adhesive

NASA Astrophysics Data System (ADS)

Kim, Yongkwan

Over the last decade, geckos' remarkable ability to stick to and climb surfaces found in nature has motivated a wide range of scientific interest in engineering gecko-mimetic surface for various adhesive and high friction applications. The high adhesion and friction of its pads have been attributed to a complex array of hairy structures, which maximize surface area for van der Waals interaction between the toes and the counter-surface. While advances in micro- and nanolithography technique have allowed fabrication of increasingly sophisticated gecko mimetic surfaces, it remains a challenge to produce an adhesive as robust as that of the natural gecko pads. In order to rationally design gecko adhesives, understanding the contact behavior of fibrillar interface is critical. The first chapter of the dissertation introduces gecko adhesion and its potential applications, followed by a brief survey of gecko-inspired adhesives. Challenges that limit the performance of the current adhesives are presented. In particular, it is pointed out that almost all testing of gecko adhesives have been on clean, smooth glass, which is ideal for adhesion due to high surface energy and low roughness. Surfaces in application are more difficult to stick to, so the understanding of failure modes in low energy and rough surfaces is important. The second chapter presents a fabrication method for thermoplastic gecko adhesive to be used for a detailed study of fibrillar interfaces. Low-density polyethylene nanofibers are replicated from a silicon nanowire array fabricated by colloidal lithography and metal-catalyzed chemical etching. This process yields a highly ordered array of nanofibers over a large area with control over fiber diameter, length, and number density. The high yield and consistency of the process make it ideal for a systematic study on factors that affect adhesion and friction of gecko adhesives. The following three chapters examine parameters that affect macroscale friction of fibrillar adhesives. Basic geometric factors, namely fiber length and diameter, are optimized on smooth glass for high friction. The test surfaces are then processed to intentionally introduce roughness or lower the surface energy in a systematic and quantifiable manner, so that the failure mechanisms of the adhesive can be investigated in detail. In these studies, observed macroscale friction is related to the nano-scale contact behavior with simple mechanical models to establish criteria to ensure high performance of fibrillar adhesives. Chapter 6 presents various methods to produce more complex fiber structures. The metal-assisted chemical etching of silicon nanowires is studied in detail, where the chemical composition of the etching bath can be varied to produce clumped, tapered, tilted, and curved nanowires, which provide interesting templates for molding and are potentially useful for applications in various silicon nanowire devices. Hierarchical fiber structures are fabricated by a few different methods, as well as composite structures where the fibers are embedded in another material. A way to precisely control tapering of microfibers is demonstrated, and the effect of tapering on macroscale friction is studied in detail. The final chapter summarizes the dissertation and suggests possible future works for both further investigating fibrillar interfaces and improving the current gecko adhesive.

Weld bonding of titanium with polyimide adhesives

NASA Technical Reports Server (NTRS)

Vaughan, R. W.; Sheppard, C. H.; Orell, M. K.

1975-01-01

A conductive adhesive primer and a capillary flow adhesive were developed for weld bonding titanium alloy joints. Both formulations contained ingredients considered to be non-carcinogenic. Lap-shear joint test specimens and stringer-stiffened panels were weld bonded using a capillary flow process to apply the adhesive. Static property information was generated for weld bonded joints over the temperature range of 219K (-65 F) to 561K (550 F). The capillary flow process was demonstrated to produce weld bonded joints of equal strength to the weld through weld bonding process developed previously.

Water soluble/dispersible and easy removable cationic adhesives and coating for paper recycling

DOEpatents

Deng, Yulin; Yan, Zegui

2005-11-29

The present invention is an adhesive or coating composition that is dispersible or dissolvable in water, making it useful in as a coating or adhesive in paper intended for recycling. The composition of the present invention is cationically charged thereby binding with the fibers of the paper slurry and thus, resulting in reduced deposition of adhesives on equipment during the recycling process. The presence of the composition of the present invention results in stronger interfiber bonding in products produced from the recycled fibers.

Interfacial adhesion of dental ceramic-resin systems

NASA Astrophysics Data System (ADS)

Della Bona, Alvaro

The clinical success of resin bonding procedures for indirect ceramic restorations and ceramic repairs depends on the quality and durability of the bond between the ceramic and the resin. The quality of this bond will depend upon the bonding mechanisms that are controlled in part by the surface treatment that promotes micromechanical and/or chemical bonding to the substrate. The objective of this study is to correlate interfacial toughness (K A) with fracture surface morphological parameters of the dental ceramic-resin systems as a function of ceramic surface treatment. The analytical procedures focused on characterizing the microstructure and fracture properties of EmpressRTM ceramics (a leucite-based core ceramic, two lithia disilicate-based core ceramics, and a glass veneer) and determining the ceramic-resin adhesion zone bond strength characteristics. Microstructure and composition are controlling factors in the development of micromechanical retention produced by etching. Silane treated ceramics negated the effect of surface roughening produced by etching, inducing lower surface energy of the ceramic and, reduced bonding effectiveness. There was a positive correlation between WA, tensile bond strength (a), and KA, i.e., higher mean WA value, and higher mean sigma and KA values. This study suggests that (1) the sigma and KA values for ceramic bonded to resin are affected by the ceramic microstructure and the ceramic surface treatments; (2) the definition of the adhesion zone is essential to classify the modes of failure, which should be an integral component of all failure analyses; (3) the microtensile test may be preferable to conventional shear or flexural tests as an indicator of composite-ceramic bond quality; and (4) careful microscopic analysis of fracture surfaces and an x-ray dot map can produce a more consistent and complete description of the fracture process and interpretation of the modes of failure. The mode of failure and fractographic analyses provide important a more comprehensive assessment of mechanisms that control the survival times of dental adhesive systems. Thus, the quality of the bond should not be assessed based on bond strength data alone.

A conserved phosphorylation switch controls the interaction between cadherin and β-catenin in vitro and in vivo

DOE PAGES

Choi, Hee -Jung; Loveless, Timothy; Lynch, Allison M.; ...

2015-04-06

In metazoan adherens junctions, β-catenin links the cytoplasmic tail of classical cadherins to the F-actin-binding protein α-catenin. Phosphorylation of a Ser/Thr-rich region in the cadherin tail dramatically enhances affinity for β-catenin and promotes cell-cell adhesion in cell culture systems, but its importance has not been demonstrated in vivo. In this paper, we identify a critical phosphorylated serine in the C. elegans cadherin HMR-1 required for strong binding to the β-catenin homolog HMP-2. Ablation of this phosphoserine interaction produces developmental defects that resemble full loss-of-function (Hammerhead and Humpback) phenotypes. Most metazoans possess a single gene for β-catenin, which is also amore » transcriptional coactivator in Wnt signaling. Nematodes and planaria, however, have a set of paralogous β-catenins; for example, C. elegans HMP-2 functions only in cell-cell adhesion, whereas SYS-1 mediates transcriptional activation through interactions with POP-1/Tcf. Finally, our structural data define critical sequence differences responsible for the unique ligand specificities of these two proteins.« less

Microbial specificity of metallic surfaces exposed to ambient seawater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaidi, B.R.; Bard, R.F.; Tosteson, T.R.

1984-09-01

High-molecular-weight materials associated with the extracellular matrix and film found on titanium and aluminum surfaces after exposure to flowing coastal seawater were isolated. This material was purified by hydroxylapatite chromatography and subsequently employed to produce antibodies in the toad, Bufo marinus. The antibodies were immobilized on a solid support and employed to isolate adhesion-enhancing, high-molecular-weight materials from the laboratory culture media of bacterial strains recovered from the respective metallic surfaces during the course of their exposure to seawater. The adhesion-enhancing materials produced by the surface-associated bacterial strains were immunologically related to the extracellular biofouling matrix material found on the surfacesmore » from which these bacteria were isolated. The surface selectivity of these bacterial strains appeared to be based on the specificity of the interaction between adhesion-enhancing macromolecules produced by these bacteria and the surfaces in question. 30 references, 6 tables.« less

Comparison of a new single-donor human fibrin adhesive with suture for posterior tibial nerve repair in rat: biomechanical resistance and functional analysis.

PubMed

Erfanian, Reza; Firouzi, Masoumeh; Nabian, Mohammad Hossein; Darvishzadeh, Masoud; Zanjani, Leila Oryadi; Zadegan, Shayan Abdollah; Kamrani, Reza Shahryar

2014-01-01

The use of fibrin adhesives has a broad background in nerve repair. Currently the suboptimal physical properties of single- donor fibrin adhesives have restricted their usage. The present experiment studies the performance and physical characteristics of a modified fibrin glue prepared from single-donor human plasma in the repair of posterior tibial nerve of rat. Forty Wistar rats were divided into 5 groups; in the control group, tibial nerve was completely transected and no treatment was done, while in the four experimental groups the nerve stumps were reconnected by one suture, three sutures, one suture with fibrin glue and fibrin glue alone respectively. During 8 weeks of follow-up, Tibial Function Index was measured weekly and adhesive strength, inflammation and scar formation were assessed at the end of the study. Nerve stumps dehiscence rate and adhesive strength were similar in all experimental groups and significantly differed from control group (P<0.05). By the end of the eighth follow-up week, functional recovery of one and three sutures groups were significantly higher than groups in which fibrin glue was used for repair (P<0.05). The amount of inflammation and scar tissue formation was similar among all groups. The study results show that the prepared single-donor fibrin adhesive has acceptable mechanical properties which could provide required adhesiveness and hold nerve stumps in the long term; yet, we acknowledge that more studies are needed to improve functional outcome of single donor fibrin adhesive repair.

The Analysis of Adhesively Bonded Advanced Composite Joints Using Joint Finite Elements

NASA Technical Reports Server (NTRS)

Stapleton, Scott E.; Waas, Anthony M.

2012-01-01

The design and sizing of adhesively bonded joints has always been a major bottleneck in the design of composite vehicles. Dense finite element (FE) meshes are required to capture the full behavior of a joint numerically, but these dense meshes are impractical in vehicle-scale models where a course mesh is more desirable to make quick assessments and comparisons of different joint geometries. Analytical models are often helpful in sizing, but difficulties arise in coupling these models with full-vehicle FE models. Therefore, a joint FE was created which can be used within structural FE models to make quick assessments of bonded composite joints. The shape functions of the joint FE were found by solving the governing equations for a structural model for a joint. By analytically determining the shape functions of the joint FE, the complex joint behavior can be captured with very few elements. This joint FE was modified and used to consider adhesives with functionally graded material properties to reduce the peel stress concentrations located near adherend discontinuities. Several practical concerns impede the actual use of such adhesives. These include increased manufacturing complications, alterations to the grading due to adhesive flow during manufacturing, and whether changing the loading conditions significantly impact the effectiveness of the grading. An analytical study is conducted to address these three concerns. Furthermore, proof-of-concept testing is conducted to show the potential advantages of functionally graded adhesives. In this study, grading is achieved by strategically placing glass beads within the adhesive layer at different densities along the joint. Furthermore, the capability to model non-linear adhesive constitutive behavior with large rotations was developed, and progressive failure of the adhesive was modeled by re-meshing the joint as the adhesive fails. Results predicted using the joint FE was compared with experimental results for various joint configurations, including double cantilever beam and single lap joints.

Prediction of Thrombus Growth: Effect of Stenosis and Reynolds Number.

PubMed

Hosseinzadegan, Hamid; Tafti, Danesh K

2017-06-01

Shear stresses play a major role in platelet-substrate interactions and thrombus formation and growth in blood flow, where under both pathological and physiological conditions platelet adhesion and accumulation occur. In this study, a shear-dependent continuum model for platelet activation, adhesion and aggregation is presented. The model was first verified under three different shear conditions and at two heparin levels. Three-dimensional simulations were then carried out to evaluate the performance of the model for severely damaged (stripped) aortas with mild and severe stenosis degrees in laminar flow regime. For these cases, linear shear-dependent functions were developed for platelet-surface and platelet-platelet adhesion rates. It was confirmed that the platelet adhesion rate is not only a function of Reynolds number (or wall shear rate) but also the stenosis severity of the vessel. General correlations for adhesion rates of platelets as functions of stenosis and Reynolds number were obtained based on these cases. Finally using the new platelet adhesion rates, the model was applied to different experimental systems and shown to agree well with measured platelet deposition.

Geckos significantly alter foot orientation to facilitate adhesion during downhill locomotion

PubMed Central

Birn-Jeffery, Aleksandra V.; Higham, Timothy E.

2014-01-01

Geckos employ their adhesive system when moving up an incline, but the directionality of the system may limit function on downhill surfaces. Here, we use a generalist gecko to test whether limb modulation occurs on downhill slopes to allow geckos to take advantage of their adhesive system. We examined three-dimensional limb kinematics for geckos moving up and down a 45° slope. Remarkably, the hind limbs were rotated posteriorly on declines, resulting in digit III of the pes facing a more posterior direction (opposite to the direction of travel). No significant changes in limb orientation were found in any other condition. This pes rotation leads to a dramatic shift in foot function that facilitates the use of the adhesive system as a brake/stabilizer during downhill locomotion and, although this rotation is not unique to geckos, it is significant for the deployment of adhesion. Adhesion is not just advantageous for uphill locomotion but can be employed to help deal with the effects of gravity during downhill locomotion, highlighting the incredible multi-functionality of this key innovation. PMID:25319816

Do adhesive systems leave resin coats on the surfaces of the metal matrix bands? An adhesive remnant characterization.

PubMed

Arhun, Neslihan; Cehreli, Sevi Burcak

2013-01-01

Reestablishing proximal contacts with composite resins may prove challenging since the applied adhesives may lead to resin coating that produces additional thickness. The aim of this study was to investigate the surface of metal matrix bands after application of adhesive systems and blowing or wiping off the adhesive before polymerization. Seventeen groups of matrix bands were prepared. The remnant particles were characterized by energy dispersive spectrum and scanning electron microscopy. Total etch and two-step self-etch adhesives did not leave any resin residues by wiping and blowing off. All-in-one adhesive revealed resin residues despite wiping off. Prime and Bond NT did not leave any remnant with compomer. Clinicians must be made aware of the consequences of possible adhesive remnants on matrix bands that may lead to a defective definitive restoration. The adhesive resin used for Class II restorations may leave resin coats on metal matrix bands after polymerization, resulting in additional thickness on the metal matrix bands and poor quality of the proximal surface of the definitive restoration when the adhesive system is incorporated in the restoration.

Experimental strategies for the identification and characterization of adhesive proteins in animals: a review

PubMed Central

Hennebert, Elise; Maldonado, Barbara; Ladurner, Peter; Flammang, Patrick; Santos, Romana

2015-01-01

Adhesive secretions occur in both aquatic and terrestrial animals, in which they perform diverse functions. Biological adhesives can therefore be remarkably complex and involve a large range of components with different functions and interactions. However, being mainly protein based, biological adhesives can be characterized by classical molecular methods. This review compiles experimental strategies that were successfully used to identify, characterize and obtain the full-length sequence of adhesive proteins from nine biological models: echinoderms, barnacles, tubeworms, mussels, sticklebacks, slugs, velvet worms, spiders and ticks. A brief description and practical examples are given for a variety of tools used to study adhesive molecules at different levels from genes to secreted proteins. In most studies, proteins, extracted from secreted materials or from adhesive organs, are analysed for the presence of post-translational modifications and submitted to peptide sequencing. The peptide sequences are then used directly for a BLAST search in genomic or transcriptomic databases, or to design degenerate primers to perform RT-PCR, both allowing the recovery of the sequence of the cDNA coding for the investigated protein. These sequences can then be used for functional validation and recombinant production. In recent years, the dual proteomic and transcriptomic approach has emerged as the best way leading to the identification of novel adhesive proteins and retrieval of their complete sequences. PMID:25657842

Adhesion of new bioactive glass coating.

PubMed

Schrooten, J; Van Oosterwyck, H; Vander Sloten, J; Helsen, J A

1999-03-05

A valuable alternative to the existing biomedical implant coatings is a bioactive glass (BAG) coating that is produced by reactive plasma spraying. A mechanical performance requirement that is of the utmost importance is the adhesion strength of the coating. Considering the application as dental implant, a new adhesion test (shear test), which was close to the service conditions, was designed. A Ti6Al4V rod (3 mm) with a sprayed BAG coating of 50 microm was glued with an epoxy glue to a hollow cylindrical counterpart and was used as such in the tensile machine. This test was evaluated by finite element analysis (FEA). Preliminary experiments showed that a conversion from shear to tensile adhesion strength is possible by using the Von Mises criterion (sigma = 3(1/2)tau), indicating that thin coatings of brittle materials can behave as a ductile material. The new coating technique was proved to produce a high quality coating with an adhesion strength of 40.1 +/- 4.8 MPa in shear and 69.4 +/- 8.4 MPa in tension. The FEA revealed that no one homogeneously distributed shear stress is present but several nonhomogeneously distributed stress components (shear and tensile) are present in the coating. This analysis indicated that real service conditions are much more complicated than standard adhesion tests. Copyright 1999 John Wiley & Sons, Inc.

Arginine-glycine-aspartic acid functional branched semi-interpenetrating hydrogels.

PubMed

Plenderleith, Richard A; Pateman, Christopher J; Rodenburg, Cornelia; Haycock, John W; Claeyssens, Frederik; Sammon, Chris; Rimmer, Stephen

2015-10-14

For the first time a series of functional hydrogels based on semi-interpenetrating networks with both branched and crosslinked polymer components have been prepared and we show the successful use of these materials as substrates for cell culture. The materials consist of highly branched poly(N-isopropyl acrylamide)s with peptide functionalised end groups in a continuous phase of crosslinked poly(vinyl pyrrolidone). Functionalisation of the end groups of the branched polymer component with the GRGDS peptide produces a hydrogel that supports cell adhesion and proliferation. The materials provide a new synthetic functional biomaterial that has many of the features of extracellular matrix, and as such can be used to support tissue regeneration and cell culture. This class of high water content hydrogel material has important advantages over other functional hydrogels in its synthesis and does not require post-processing modifications nor are functional-monomers, which change the polymerisation process, required. Thus, the systems are amenable to large scale and bespoke manufacturing using conventional moulding or additive manufacturing techniques. Processing using additive manufacturing is exemplified by producing tubes using microstereolithography.

On the stabilization of viscoelastic laminated beams with interfacial slip

NASA Astrophysics Data System (ADS)

Mustafa, Muhammad I.

2018-04-01

In this paper, we consider a viscoelastic laminated beam model. This structure is given by two identical uniform layers on top of each other, taking into account that an adhesive of small thickness is bonding the two surfaces and produces an interfacial slip. We use viscoelastic damping with general assumptions on the relaxation function and establish explicit energy decay result from which we can recover the optimal exponential and polynomial rates. Our result generalizes the earlier related results in the literature.

Strong underwater adhesives made by self-assembling multi-protein nanofibres.

PubMed

Zhong, Chao; Gurry, Thomas; Cheng, Allen A; Downey, Jordan; Deng, Zhengtao; Stultz, Collin M; Lu, Timothy K

2014-10-01

Many natural underwater adhesives harness hierarchically assembled amyloid nanostructures to achieve strong and robust interfacial adhesion under dynamic and turbulent environments. Despite recent advances, our understanding of the molecular design, self-assembly and structure-function relationships of these natural amyloid fibres remains limited. Thus, designing biomimetic amyloid-based adhesives remains challenging. Here, we report strong and multi-functional underwater adhesives obtained from fusing mussel foot proteins (Mfps) of Mytilus galloprovincialis with CsgA proteins, the major subunit of Escherichia coli amyloid curli fibres. These hybrid molecular materials hierarchically self-assemble into higher-order structures, in which, according to molecular dynamics simulations, disordered adhesive Mfp domains are exposed on the exterior of amyloid cores formed by CsgA. Our fibres have an underwater adhesion energy approaching 20.9 mJ m(-2), which is 1.5 times greater than the maximum of bio-inspired and bio-derived protein-based underwater adhesives reported thus far. Moreover, they outperform Mfps or curli fibres taken on their own and exhibit better tolerance to auto-oxidation than Mfps at pH ≥ 7.0.

Performance and scaling of a novel locomotor structure: adhesive capacity of climbing gobiid fishes.

PubMed

Maie, Takashi; Schoenfuss, Heiko L; Blob, Richard W

2012-11-15

Many species of gobiid fishes adhere to surfaces using a sucker formed from fusion of the pelvic fins. Juveniles of many amphidromous species use this pelvic sucker to scale waterfalls during migrations to upstream habitats after an oceanic larval phase. However, adults may still use suckers to re-scale waterfalls if displaced. If attachment force is proportional to sucker area and if growth of the sucker is isometric, then increases in the forces that climbing fish must resist might outpace adhesive capacity, causing climbing performance to decline through ontogeny. To test for such trends, we measured pressure differentials and adhesive suction forces generated by the pelvic sucker across wide size ranges in six goby species, including climbing and non-climbing taxa. Suction was achieved via two distinct growth strategies: (1) small suckers with isometric (or negatively allometric) scaling among climbing gobies and (2) large suckers with positively allometric growth in non-climbing gobies. Species using the first strategy show a high baseline of adhesive capacity that may aid climbing performance throughout ontogeny, with pressure differentials and suction forces much greater than expected if adhesion were a passive function of sucker area. In contrast, large suckers possessed by non-climbing species may help compensate for reduced pressure differentials, thereby producing suction sufficient to support body weight. Climbing Sicyopterus species also use oral suckers during climbing waterfalls, and these exhibited scaling patterns similar to those for pelvic suckers. However, oral suction force was considerably lower than that for pelvic suckers, reducing the ability for these fish to attach to substrates by the oral sucker alone.

Plant pressure sensitive adhesives: similar chemical properties in distantly related plant lineages.

PubMed

Frenzke, Lena; Lederer, Albena; Malanin, Mikhail; Eichhorn, Klaus-Jochen; Neinhuis, Christoph; Voigt, Dagmar

2016-07-01

A mixture of resins based on aliphatic esters and carboxylic acids occurs in distantly related genera Peperomia and Roridula , serving different functions as adhesion in seed dispersal and prey capture. According to mechanical characteristics, adhesive secretions on both leaves of the carnivorous flypaper Roridula gorgonias and epizoochorous fruits of Peperomia polystachya were expected to be similar. The chemical analysis of these adhesives turned out to be challenging because of the limited available mass for analysis. Size exclusion chromatography and Fourier transform infrared spectroscopy were suitable methods for the identification of a mixture of compounds, most appropriately containing natural resins based on aliphatic esters and carboxylic acids. The IR spectra of the Peperomia and Roridula adhesive resemble each other; they correspond to that of a synthetic ethylene-vinyl acetate copolymer, but slightly differ from that of natural tree resins. Thus, the pressure sensitive adhesive properties of the plant adhesives are chemically proved. Such adhesives seem to appear independently in distantly related plant lineages, habitats, life forms, as well as plant organs, and serve different functions such as prey capture in Roridula and fruit dispersal in Peperomia. However, more detailed chemical analyses still remain challenging because of the small available volume of plant adhesive.

A Facile All-Solution-Processed Surface with High Water Contact Angle and High Water Adhesive Force.

PubMed

Chen, Mei; Hu, Wei; Liang, Xiao; Zou, Cheng; Li, Fasheng; Zhang, Lanying; Chen, Feiwu; Yang, Huai

2017-07-12

A series of sticky superhydrophobicity surfaces with high water contact angle and high water adhesive force is facilely prepared via an all-solution-processed method based on polymerization-induced phase separation between liquid crystals (LCs) and epoxy resin, which produces layers of epoxy microspheres (EMSs) with nanofolds on the surface of a substrate. The morphologies and size distributions of EMSs are confirmed by scanning electron microscopy. Results reveal that the obtained EMS coated-surface exhibits high apparent contact angle of 152.0° and high water adhesive force up to 117.6 μN. By varying the composition of the sample or preparing conditions, the sizes of the produced EMSs can be artificially regulated and, thus, control the wetting properties and water adhesive behaviors. Also, the sticky superhydrophobic surface exhibits excellent chemical stability, as well as long-term durability. Water droplet transportation experiments further prove that the as-made surface can be effectively used as a mechanical hand for water transportation applications. Based on this, it is believed that the simple method proposed in this paper will pave a new way for producing a sticky superhydrophobic surface and obtain a wide range of use.

Mucin- and carbohydrate-stimulated adhesion and subproteome changes of the probiotic bacterium Lactobacillus acidophilus NCFM.

PubMed

Celebioglu, Hasan Ufuk; Olesen, Sita Vaag; Prehn, Kennie; Lahtinen, Sampo J; Brix, Susanne; Abou Hachem, Maher; Svensson, Birte

2017-06-23

Adhesion to intestinal mucosa is a crucial property for probiotic bacteria. Adhesion is thought to increase host-bacterial interactions, thus potentially enabling health benefits to the host. Molecular events connected with adhesion and surface proteome changes were investigated for the probiotic Lactobacillus acidophilus NCFM cultured with established or emerging prebiotic carbohydrates as carbon source and in the presence of mucin, the glycoprotein of the epithelial mucus layer. Variation in adhesion to HT29-cells and mucin was associated with carbon source and mucin-induced subproteome abundancy differences. Specifically, while growth on fructooligosaccharides (FOS) only stimulated adhesion to intestinal HT-29 cells, cellobiose and polydextrose in addition increased adhesion to mucin. Adhesion to HT-29 cells increased by about 2-fold for bacteria grown on mucin-supplemented glucose. Comparative 2DE-MS surface proteome analysis showed different proteins in energy metabolism appearing on the surface, suggesting they exert moonlighting functions. Mucin-supplemented bacteria had relative abundance of pyruvate kinase and fructose-bisphosphate aldolase increased by about 2-fold while six spots with 3.2-2.1 fold reduced relative abundance comprised elongation factor G, phosphoglycerate kinase, BipAEFTU family GTP-binding protein, ribonucleoside triphosphate reductase, adenylosuccinate synthetase, 30S ribosomal protein S1, and manganese-dependent inorganic pyrophosphatase. Surface proteome of cellobiose- compared to glucose-grown L. acidophilus NCFM had phosphate starvation inducible protein stress-related, thermostable pullulanase, and elongation factor G increasing 4.4-2.4 fold, while GAPDH, elongation factor Ts, and pyruvate kinase were reduced by 2.0-1.5 fold in relative abundance. Addition of recombinant L. acidophilus NCFM elongation factor G and pyruvate kinase to a coated mucin layer significantly suppressed subsequent adhesion of the bacterium. Human diet is important for intestinal health and food components, especially non-digestible carbohydrates can beneficially modify the microbiota. In the present study, effects of emerging and established prebiotic carbohydrates on the probiotic potential of Lactobacillus acidophilus NCFM were investigated by testing adhesion to a mucin layer and intestinal cells, and comparing this with changes in abundancy of surface proteins thought to be important for host interactions. Increased adhesion was observed following culturing of the bacterium with fructooligosaccharides, cellobiose or polydextrose, as well as mucin-supplemented glucose as carbon source. Enhanced adhesion ability can prolong bacterial residence in GIT yielding positive health effects. Higher relative abundance of certain surface proteins under various conditions (i.e. grown on cellobiose or mucin-supplemented glucose) suggested involvement of these proteins in adhesion, as confirmed by competition in case of two recombinantly produced moonlighting proteins. Combination of Lactobacillus acidophilus NCFM with different carbohydrates revealed potential bacterial determinants of synbiotic interactions, including stimulation of adhesion. Copyright © 2017 Elsevier B.V. All rights reserved.

Multi-functional electrospun antibacterial core-shell nanofibrous membranes for prolonged prevention of post-surgical tendon adhesion and inflammation.

PubMed

Shalumon, K T; Sheu, Chialin; Chen, Chih-Hao; Chen, Shih-Heng; Jose, Gils; Kuo, Chang-Yi; Chen, Jyh-Ping

2018-05-01

The possibility of endowing an electrospun anti-adhesive barrier membrane with multi-functionality, such as lubrication, prevention of fibroblast attachment and anti-infection and anti-inflammation properties, is highly desirable for the management of post-surgical tendon adhesion. To this end, we fabricated core-shell nanofibrous membranes (CSNMs) with embedded silver nanoparticles (Ag NPs) in the poly(ethylene glycol) (PEG)/poly(caprolactone) (PCL) shell and hyaluronic acid (HA)/ibuprofen in the core. HA imparted a lubrication effect for smooth tendon gliding and reduced fibroblast attachment, while Ag NPs and ibuprofen functioned as anti-infection and anti-inflammation agents, respectively. CSNMs with a PEG/PCL/Ag shell (PPA) and HA core containing 0% (H/PPA), 10% (HI10/PPA), 30% (HI30/PPA) and 50% (HI50/PPA) ibuprofen were fabricated through co-axial electrospinning and assessed through microscopic, spectroscopic, thermal, mechanical and drug release analyses. Considering nutrient passage through the barrier, the microporous CSNMs exerted the same barrier effect but drastically increased the mass transfer coefficients of bovine serum albumin compared with the commercial anti-adhesive membrane SurgiWrap®. Cell attachment/focal adhesion formation of fibroblasts revealed effective reduction of initial cell attachment on the CSNM surface with minimum cytotoxicity (except HI50/PPA). The anti-bacterial effect against both Gram-negative and Gram-positive bacteria was verified to be due to the Ag NPs in the membranes. In vivo studies using H/PPA and HI30/PPA CSNMs and SurgiWrap® in a rabbit flexor tendon rupture model demonstrated the improved efficacy of HI30/PPA CSNMs in reducing inflammation and tendon adhesion formation based on gross observation, histological analysis and functional assays. We conclude that HI30/PPA CSNMs can act as a multifunctional barrier membrane to prevent peritendinous adhesion after tendon surgery. A multi-functional anti-adhesion barrier membrane that could reduce fibroblasts attachment and penetration while simultaneously prevent post-surgical infection and inflammation is urgently needed. To this end, we prepared electrospun core-shell hyaluronic acid + ibuprofen/polyethylene glycol + polycaprolactone + Ag nanoparticles nanofibrous membranes by co-axial electrospinning as an ideal anti-adhesive membrane. The core-shell structure could meet the need of a desirable anti-adhesion barrier through release of ibuprofen and Ag nanoparticles to reduce infection and inflammation while hyaluronic acid can reduce fibroblasts adhesion. The superior performance of this multi-functional core-shell nanofibrous membrane in preventing peritendinous adhesion and post-surgical inflammation was demonstrated in a rabbit flexor tendon rupture model. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Bonding effectiveness of self-etch adhesives to dentin after 24 h water storage.

PubMed

Sarr, Mouhamed; Benoist, Fatou Leye; Bane, Khaly; Aidara, Adjaratou Wakha; Seck, Anta; Toure, Babacar

2018-01-01

This study evaluated the immediate bonding effectiveness of five self-etch adhesive systems bonded to dentin. The microtensile bond strength of five self-etch adhesives systems, including one two-step and four one-step self-etch adhesives to dentin, was measured. Human third molars had their superficial dentin surface exposed, after which a standardized smear layer was produced using a medium-grit diamond bur. The selected adhesives were applied according to their respective manufacturer's instructions for μTBS measurement after storage in water at 37°C for 24 h. The μTBS varied from 11.1 to 44.3 MPa; the highest bond strength was obtained with the two-step self-etch adhesive Clearfil SE Bond and the lowest with the one-step self-etch adhesive Adper Prompt L-Pop. Pretesting failures mainly occurring during sectioning with the slow-speed diamond saw were observed only with the one-step self-etch adhesive Adper Prompt L-Pop (4 out of 18). When bonded to dentin, the self-etch adhesives with simplified application procedures (one-step self-etch adhesives) still underperform as compared to the two-step self-etch adhesive Clearfil SE Bond.

Bonding effectiveness of self-etch adhesives to dentin after 24 h water storage

PubMed Central

Sarr, Mouhamed; Benoist, Fatou Leye; Bane, Khaly; Aidara, Adjaratou Wakha; Seck, Anta; Toure, Babacar

2018-01-01

Purpose: This study evaluated the immediate bonding effectiveness of five self-etch adhesive systems bonded to dentin. Materials and Methods: The microtensile bond strength of five self-etch adhesives systems, including one two-step and four one-step self-etch adhesives to dentin, was measured. Human third molars had their superficial dentin surface exposed, after which a standardized smear layer was produced using a medium-grit diamond bur. The selected adhesives were applied according to their respective manufacturer's instructions for μTBS measurement after storage in water at 37°C for 24 h. Results: The μTBS varied from 11.1 to 44.3 MPa; the highest bond strength was obtained with the two-step self-etch adhesive Clearfil SE Bond and the lowest with the one-step self-etch adhesive Adper Prompt L-Pop. Pretesting failures mainly occurring during sectioning with the slow-speed diamond saw were observed only with the one-step self-etch adhesive Adper Prompt L-Pop (4 out of 18). Conclusions: When bonded to dentin, the self-etch adhesives with simplified application procedures (one-step self-etch adhesives) still underperform as compared to the two-step self-etch adhesive Clearfil SE Bond. PMID:29674814

The role of adhesive materials and oral biofilm in the failure of adhesive resin restorations.

PubMed

Pinna, Roberto; Usai, Paolo; Filigheddu, Enrica; Garcia-Godoy, Franklin; Milia, Egle

2017-10-01

To critically discuss adhesive materials and oral cariogenic biofilm in terms of their potential relevance to the failures of adhesive restorations in the oral environment. The literature regarding adhesive restoration failures was reviewed with particular emphasis on the chemistry of adhesive resins, weakness in dentin bonding, water fluids, cariogenic oral biofilm and the relations that influence failures. Particular attention was paid to evidence derived from clinical studies. There was much evidence that polymerization shrinkage is one of the main drawbacks of composite formulations. Stress results in debonding and marginal leakage into gaps with deleterious effects in bond strength, mechanical properties and the whole stability of restorations. Changes in resins permit passage of fluids and salivary proteins with a biological breakdown of the restorations. Esterases enzymes in human saliva catalyze exposed ester groups in composite producing monomer by-products, which can favor biofilm accumulation and secondary caries. Adhesive systems may not produce a dense hybrid layer in dentin. Very often this is related to the high viscous solubility and low wettability in dentin of the hydrophobic BisGMA monomer. Thus, dentin hybrid layer may suffer from hydrolysis using both the Etch&Rinse and Self-Etching adhesive systems. In addition, exposed and non-resin enveloped collagen fibers may be degraded by activation of the host-derived matrix metalloproteinase. Plaque accumulation is significantly influenced by the surface properties of the restorations. Biofilm at the contraction gap has demonstrated increased growth of Streptococcus mutans motivated by the chemical hydrolysis of the adhesive monomers at the margins. Streptococcus mutans is able to utilize some polysaccharides from the biofilm to increase the amount of acid in dental plaque with an increase in virulence and destruction of restorations. Stability of resin restorations in the oral environment is highly dependent on the structure of the monomers used in composite and adhesive systems. Still, the issues related to microleakage of fluids into the gap and bacteria leaching from the surface of composites represent the main causes of failure of adhesive restorations. Modifications of adhesive materials are necessary to address their instability in the oral environment.

Biophysical Effects of a Polymeric Biosurfactant in Candida krusei and Candida albicans Cells.

PubMed

Ferreira, Gabriella Freitas; Dos Santos Pinto, Bruna Lorrana; Souza, Eliene Batista; Viana, José Lima; Zagmignan, Adrielle; Dos Santos, Julliana Ribeiro Alves; Santos, Áquila Rodrigues Costa; Tavares, Priscila Batista; Denadai, Ângelo Márcio Leite; Monteiro, Andrea Souza

2016-12-01

This study evaluated the effects of a polymeric biosurfactant produced by Trichosporon montevideense CLOA72 in the adhesion of Candida albicans and Candida krusei cells to human buccal epithelial cells and its interference in biofilm formation by these strains. The biofilm inhibition by biosurfactant (25 mg/mL) in C. krusei and C. albicans in polystyrene was reduced up to 79.5 and 85 %, respectively. In addition, the zeta potential and hydrodynamic diameter of the yeasts altered as a function of the biosurfactant concentration added to the cell suspension. The changes in the cell surface characteristics and the interface modification can contribute to the inhibition of the initial adherence of yeasts cells to the surface. In addition, the analyses of the biofilm matrix and planktonic cell surfaces demonstrated differences in carbohydrate and protein concentrations for the two studied strains, which may contribute to the modulation of cell adhesion or consolidation of biofilms, especially in C. krusei. This study suggests a possible application of the of CLOA72 biosurfactant in inhibiting the adhesion and formation of biofilms on biological surfaces by yeasts of the Candida genus.

Size and Structure of Clusters Formed by Shear Induced Coagulation: Modeling by Discrete Element Method.

PubMed

Kroupa, Martin; Vonka, Michal; Soos, Miroslav; Kosek, Juraj

2015-07-21

The coagulation process has a dramatic impact on the properties of dispersions of colloidal particles including the change of optical, rheological, as well as texture properties. We model the behavior of a colloidal dispersion with moderate particle volume fraction, that is, 5 wt %, subjected to high shear rates employing the time-dependent Discrete Element Method (DEM) in three spatial dimensions. The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was used to model noncontact interparticle interactions, while contact mechanics was described by the Johnson-Kendall-Roberts (JKR) theory of adhesion. The obtained results demonstrate that the steady-state size of the produced clusters is a strong function of the applied shear rate, primary particle size, and the surface energy of the particles. Furthermore, it was found that the cluster size is determined by the maximum adhesion force between the primary particles and not the adhesion energy. This observation is in agreement with several simulation studies and is valid for the case when the particle-particle contact is elastic and no plastic deformation occurs. These results are of major importance, especially for the emulsion polymerization process, during which the fouling of reactors and piping causes significant financial losses.

Simvastatin Attenuates Endothelial Activation through 15-Epi-Lipoxin A4 Production in Murine Chronic Chagas Cardiomyopathy.

PubMed

González-Herrera, Fabiola; Cramer, Allysson; Pimentel, Pollyana; Castillo, Christian; Liempi, Ana; Kemmerling, Ulrike; Machado, Fabiana S; Maya, Juan D

2017-03-01

Current treatments for chronic Chagas cardiomyopathy, a disease with high mortality rates and caused by the protozoan Trypanosoma cruzi , are unsatisfactory. Myocardial inflammation, including endothelial activation, is responsible for the structural and functional damage seen in the chronic phase. The clinical efficacy of benznidazole could be improved by decreasing chronic inflammation. Statins, which have anti-inflammatory properties, may improve the action of benznidazole. Here, the action of simvastatin in a murine model of chronic Chagas cardiomyopathy and the link with the production of the proresolving eicosanoid 15-epi-lipoxin A4, produced by 5-lipoxygenase, are evaluated. Simvastatin decreased the expression of the adhesion molecules E-selectin, intracellular adhesion molecule type 1 (ICAM-1), and vascular cell adhesion molecule type 1 (VCAM-1) in T. cruzi -infected mice. However, when this drug was administered to 5-lipoxygenase-deficient mice, the anti-inflammatory effect was not observed unless exogenous 15-epi-lipoxin A4 was administered. Thus, in chronic Chagas disease, 5-epi-lipoxin A4 induced by simvastatin treatment could improve the pathophysiological condition of patients by increasing the trypanocidal action of benznidazole. Copyright © 2017 American Society for Microbiology.

Characterization of adhesive from oysters: A structural and compositional study

NASA Astrophysics Data System (ADS)

Alberts, Erik

The inability for man-made adhesives to set in wet or humid environments is an ongoing challenging the design of biomedical and marine adhesive materials. However, we see that nature has already overcome this challenge. Mussels, barnacles, oysters and sandcastle worms all have unique mechanisms by which they attach themselves to surfaces. By understanding what evolution has already spent millions of years perfecting, we can design novel adhesive materials inspired by nature's elegant designs. The well-studied mussel is currently the standard for design of marine inspired biomimetic polymers. In the work presented here, we aim to provide new insights into the adhesive produced by the eastern oyster, Crassostrea virginica. Unlike the mussel, which produces thread-like plaques comprised of DOPA containing-protein, the oyster secretes an organic-inorganic hybrid adhesive as it settles and grows onto a surface. This form of adhesion renders the oyster to be permanently fixed in place. Over time, hundreds of thousands of oyster grow and agglomerate to form extensive reef structures. These reefs are not only essential to survival of the oyster, but are also vital to intertidal ecosystems. While the shell of the oyster has been extensively studied, curiously, only a few conflicting insights have been made into the nature of the adhesive and contact zone between shell and substrate, and even lesfs information has been ascertained on organic and inorganic composition. In this work, we provide microscopy and histochemical studies to characterize the structure and composition of the adhesive, using oyster in the adult and juvenile stages of life. Preliminary work on extracting and characterizing organic components through collaborative help with solid-state NMR (SSNMR) and proteomics are also detailed here. We aim to provide a full, comprehensive characterization of oyster adhesive so that in the future, we may apply what we learn to the design of new materials.

Microtensile bond strength of etch and rinse versus self-etch adhesive systems.

PubMed

Hamouda, Ibrahim M; Samra, Nagia R; Badawi, Manal F

2011-04-01

The aim of this study was to compare the microtensile bond strength of the etch and rinse adhesive versus one-component or two-component self-etch adhesives. Twelve intact human molar teeth were cleaned and the occlusal enamel of the teeth was removed. The exposed dentin surfaces were polished and rinsed, and the adhesives were applied. A microhybride composite resin was applied to form specimens of 4 mm height and 6 mm diameter. The specimens were sectioned perpendicular to the adhesive interface to produce dentin-resin composite sticks, with an adhesive area of approximately 1.4 mm(2). The sticks were subjected to tensile loading until failure occurred. The debonded areas were examined with a scanning electron microscope to determine the site of failure. The results showed that the microtensile bond strength of the etch and rinse adhesive was higher than that of one-component or two-component self-etch adhesives. The scanning electron microscope examination of the dentin surfaces revealed adhesive and mixed modes of failure. The adhesive mode of failure occurred at the adhesive/dentin interface, while the mixed mode of failure occurred partially in the composite and partially at the adhesive/dentin interface. It was concluded that the etch and rinse adhesive had higher microtensile bond strength when compared to that of the self-etch adhesives. Copyright © 2010 Elsevier Ltd. All rights reserved.

Induction of trap formation in nematode-trapping fungi by bacteria-released ammonia.

PubMed

Su, H N; Xu, Y Y; Wang, X; Zhang, K Q; Li, G H

2016-04-01

A total of 11 bacterial strains were assayed for bacteria-induced trap formation in the nematode-trapping fungus Arthrobotrys oligospora YMF1·01883 with two-compartmented Petri dish. These strains were identified on the basis of their 16S rRNA gene sequences. Volatile organic compounds (VOCs) of eight isolates were extracted using solid-phase micro-extraction (SPME) and their structures were identified based on gas chromatography-mass spectrometry (GC-MS). At the same time, all isolates were used for quantitative measurement of ammonia by the indophenol blue method. The effects of pure commercial compounds on inducement of trap formation in A. oligospora were tested. Taken together, results demonstrated that the predominant bacterial volatile compound inducing trap formation was ammonia. Meanwhile, ammonia also played a role in other nematode-trapping fungi, including Arthrobotrys guizhouensis YMF1·00014, producing adhesive nets; Dactylellina phymatopaga YMF1·01474, producing adhesive knobs; Dactylellina cionopaga YMF1·01472, producing adhesive columns and Drechslerella brochopaga YMF1·01829, producing constricting rings. © 2016 The Society for Applied Microbiology.

Blister Test for Measurements of Adhesion and Adhesion Degradation of Organic Polymers on AA2024-T3

NASA Astrophysics Data System (ADS)

Rincon Troconis, Brendy Carolina

A key parameter for the performance of corrosion protective coatings applied to metals is adhesion. Surface preparation prior to coating application is known to be critical, but there is a lack of understanding of what controls adhesion. Numerous techniques have been developed in the last decades to measure the adhesion strength of coatings to metals. Nonetheless, they are generally non-quantitative, non-reproducible, performed in dry conditions, or overestimate adhesion. In this study, a quantitative and reproducible technique, the Blister Test (BT), is used. The BT offers the ability to study the effects of a range of parameters, including the presence or absence of a wetting liquid, and simulates the stress situation in the coating/substrate interface. The effects of roughness and surface topography were studied by the BT and Optical Profilometry, using AA2024-T3 substrates coated with polyvinyl butyral (PVB). Random abrasion generated a surface with lower average roughness than aligned abrasion due to the continual cross abrasion of the grooves. The BT could discern the effects of different mechanical treatments. An adhesion strength indicator was defined and found to be a useful parameter. The effectiveness of standard adhesion techniques such as ASTM D4541 (Pull-off Test) and ASTM D3359 (Tape Test) was compared to the BT. Also, different attempts to measure adhesion and adhesion degradation of organic polymers to AA2024-T3 were tested. The pull-off test does not produce adhesive failure across the entire interface, while the tape test is a very qualitative technique and does not discern between the effects of different coating systems on the adhesion performance. The BT produces adhesive failure of the primer studied, is very reproducible, and is able to rank different coating systems. Therefore, it was found to be superior to the others. The approaches tested for adhesion degradation were not aggressive enough to have a measurable effect. The effects of cleaning/desmutting and conversion coating (CC) on the adhesion strength of acetoacetate to AA2024-T3 and the effects of improper water rinse temperature after cleaner were assessed using the BT. The results showed that pretreatments improve the adhesion strength of acetoacetate primer on AA2024-T3, but the comparative behavior depends on the specific treatment. Process control is of paramount importance for the performance of acetoacetate coated systems applied on AA2024-T3. The lack of thermal activity in the water rinse after cleaning step produces deleterious effects on the adhesion and blistering resistance of CC. Finally, a test sample incorporating a coated and scribed Al alloy panel and uncoated through-hole fasteners (Ti, SS316, AA2024-T3) was designed to provide accelerated response during atmospheric corrosion testing in the field (long-term beach exposure) or in laboratory chambers (ASTM B117). The results after only three weeks of exposure to ASTM B117 correlated well with long-term beach exposure, allowing rapid ranking of different coating systems. Of the fastener materials studied, visual observation and volume lost determination indicated that the worst attack occurred near SS316 fasteners its effect was explained by Scanning Kelvin Probe measurements and the available cathodic current measured in chloride solution.

Function-blocking antibodies to human vascular adhesion protein-1: a potential anti-inflammatory therapy.

PubMed

Kirton, Christopher M; Laukkanen, Marja-Leena; Nieminen, Antti; Merinen, Marika; Stolen, Craig M; Armour, Kathryn; Smith, David J; Salmi, Marko; Jalkanen, Sirpa; Clark, Michael R

2005-11-01

Human vascular adhesion protein-1 (VAP-1) is a homodimeric 170-kDa sialoglycoprotein that is expressed on the surface of endothelial cells and functions as a semicarbazide-sensitive amine oxidase and as an adhesion molecule. Blockade of VAP-1 has been shown to reduce leukocyte adhesion and transmigration in in vivo and in vitro models, suggesting that VAP-1 is a potential target for anti-inflammatory therapy. In this study we have constructed mouse-human chimeric antibodies by genetic engineering in order to circumvent the potential problems involved in using murine antibodies in man. Our chimeric anti-VAP-1 antibodies, which were designed to lack Fc-dependent effector functions, bound specifically to cell surface-expressed recombinant human VAP-1 and recognized VAP-1 in different cell types in tonsil. Furthermore, the chimeric antibodies prevented leukocyte adhesion and transmigration in vitro and in vivo. Hence, these chimeric antibodies have the potential to be used as a new anti-inflammatory therapy.

Mechanical Characterization of a Bi-functional Tetronic Hydrogel Adhesive for Soft Tissues

PubMed Central

Sanders, Lindsey; Stone, Roland; Webb, C. Kenneth; Mefford, O. Thompson; Nagatomi, Jiro

2014-01-01

Although a number of tissue adhesives and sealants for surgical use are currently available, attaining a useful balance in high strength, high compliance, and low swelling has proven difficult. Recent studies have demonstrated that a 4-arm poly(propylene oxide)-poly(ethylene oxide) (PPO-PEO) block copolymer, Tetronic, can be chemically modified to form a hydrogel tissue adhesive21–23. Building on the success of these studies, the present study explored bi-functionalization of Tetronic with acrylates for chemical crosslinking of the hydrogel and N-hydroxysuccinimide (NHS) for reaction with tissue amines. The adhesive bond strengths of various uni- and bi-functional Tetronic blends (T1107 ACR: T1107 ACR/NHS) determined by lap shear testing ranged between 8 and 74 kPa, with the 75:25 (T1107 ACR: T1107 ACR/NHS) blend displaying the highest value. These results indicated that addition of NHS led to improvement of tissue bond strength over acrylation alone Furthermore, ex vivo pressure tests using the rat bladder demonstrated that the bi-functional Tetronic adhesive exhibited high compliance and maintained pressures under hundreds of filling and emptying cycles. Together, the results of the present study provided evidence that the bi-functional Tetronic adhesive with a proper blend ratio may be used to achieve an accurate balance in bulk and tissue bond strengths, as well as the compliance and durability for soft tissue such as the bladder. PMID:25111445

Rac1 and Rac3 have opposing functions in cell adhesion and differentiation of neuronal cells.

PubMed

Hajdo-Milasinović, Amra; Ellenbroek, Saskia I J; van Es, Saskia; van der Vaart, Babet; Collard, John G

2007-02-15

Rac1 and Rac3 are highly homologous members of the Rho small GTPase family. Rac1 is ubiquitously expressed and regulates cell adhesion, migration and differentiation in various cell types. Rac3 is primarily expressed in brain and may therefore have a specific function in neuronal cells. We found that depletion of Rac1 by short interference RNA leads to decreased cell-matrix adhesions and cell rounding in neuronal N1E-115 cells. By contrast, depletion of Rac3 induces stronger cell adhesions and dramatically increases the outgrowth of neurite-like protrusions, suggesting opposite functions for Rac1 and Rac3 in neuronal cells. Consistent with this, overexpression of Rac1 induces cell spreading, whereas overexpression of Rac3 results in a contractile round morphology. Rac1 is mainly found at the plasma membrane, whereas Rac3 is predominantly localized in the perinuclear region. Residues 185-187, present in the variable polybasic rich region at the carboxyl terminus are responsible for the difference in phenotype induced by Rac1 and Rac3 as well as for their different intracellular localization. The Rac1-opposing function of Rac3 is not mediated by or dependent on components of the RhoA signaling pathway. It rather seems that Rac3 exerts its function through negatively affecting integrin-mediated cell-matrix adhesions. Together, our data reveal that Rac3 opposes Rac1 in the regulation of cell adhesion and differentiation of neuronal cells.

Dismantlable Thermosetting Adhesives Composed of a Cross-Linkable Poly(olefin sulfone) with a Photobase Generator.

PubMed

Sasaki, Takeo; Hashimoto, Shouta; Nogami, Nana; Sugiyama, Yuichi; Mori, Madoka; Naka, Yumiko; Le, Khoa V

2016-03-02

A novel photodetachable adhesive was prepared using a photodepolymerizable cross-linked poly(olefin sulfone). A mixture of a cross-linkable poly(olefin sulfone), a cross-linking reagent, and a photobase generator functioned as a thermosetting adhesive and exhibited high adhesive strength on quartz plates comparable to that obtained for commercially available epoxy adhesives. The cured resin was stable in the absence of UV light irradiation but completely lost its adhesive strength upon exposure of glued quartz plates to UV light in conjunction with heating to 100 °C.

A comparison of the application of fibrin glue and adhesive film for repair of anastomotic leaks in the rat.

PubMed

Ayhan, Baris; Erikoglu, Mehmet; Tavli, Süleyman S; Toy, Hatice

2012-08-04

Anastomotic leaks constitute one of the most serious intraoperative complications and although many studies have been devoted to finding a solution for this problem, none of them has yet been able offer a decisive, successful method. In this study, the ability of fibrin glue and adhesive film to repair anastomotic leaks in an experimental model was compared. The sample comprised four groups of seven rats: Group 1 (Control): the distal colon was transected and anastomosis was performed. Group 2 (Primary repair): incomplete anastomosis produced a leak that was closed by primary repair on day 3. Group 3 (Fibrin glue): incomplete anastomosis produced a leak that was closed by primary repair and fibrin glue applied on day 3. Group 4 (Adhesive film): incomplete anastomosis produced a leak that was closed by primary repair and adhesive film was applied on day 3. The rats were sacrificed on day 6 following anastomosis. Anastomotic blast compressions were measured and fibroblast activation, inflammation, neovascularization and levels of collagen were evaluated. The results from Group 4 showed that blast compression values were high and statistically significantly increased over control values (p < 0.05). Inflammation in Group 2 was significantly higher than the other groups (p < 0.05). No significant differences were detected in the comparison of the groups regarding the other scoring criteria (p > 0.05). Adhesive film is more effective in reducing anastomotic leakage than fibrin glue.

Polyacrylates with High Biomass Contents for Pressure-Sensitive Adhesives Prepared via Mini-emulsion Polymerization

Treesearch

Gang Pu; Matthew R. Dubay; Jiguang Zhang; Steven J. Severtson; Carl J. Houtman

2012-01-01

n-Butyl acrylate and other acrylic monomers were copolymerized with an acrylated macromonomer to produce polymers for pressure-sensitive adhesive (PSA) applications. Macromonomers were generated through the ring-opening copolymerization of L-lactide and ε-caprolactone with 2-hydroxyethyl...

Screening of high temperature adhesives for large area bonding

NASA Technical Reports Server (NTRS)

Stenersen, A. A.; Wykes, D. H.

1980-01-01

High temperature-resistant adhesive systems were screened for processability, mechanical and physical properties, operational capability at 589 K (600 F), and the ability to produce large area bonds of high quality in fabricating Space Shuttle components. The adhesives consisted primarily of polyimide systems, including FM34B-18, NR-150B2 (DuPont), PMR-15, LARC-13, LARC-160, Thermid 600, and AI-1130L (AMOCA). The processing studies included preparation of polyimide resins, fabrication of film adhesives, development of lay-up and cure procedures, fabrication of honeycomb sandwich panels, and fabrication of mid-plane bonded panels in joints up to 30.5 cm (12 in.) wide. The screening program included tests for tack and drape properties, reticulation and filleting characteristics, ability to produce void-free or low porosity bonds in mid-plane bonded panels, out-time stability, lap shear strength, climbing drum peel strength, and glass transition temperature (Tg). This paper describes the processing methods developed and the test results.

ZnO Nanostructure Templates as a Cost-Efficient Mass-Producible Route for the Development of Cellular Networks

PubMed Central

Makarona, Eleni; Peter, Beatrix; Szekacs, Inna; Tsamis, Christos; Horvath, Robert

2016-01-01

The development of artificial surfaces which can regulate or trigger specific functions of living cells, and which are capable of inducing in vivo-like cell behaviors under in vitro conditions has been a long-sought goal over the past twenty years. In this work, an alternative, facile and cost-efficient method for mass-producible cellular templates is presented. The proposed methodology consists of a cost-efficient, two-step, all-wet technique capable of producing ZnO-based nanostructures on predefined patterns on a variety of substrates. ZnO—apart from the fact that it is a biocompatible material—was chosen because of its multifunctional nature which has rendered it a versatile material employed in a wide range of applications. Si, Si3N4, emulated microelectrode arrays and conventional glass cover slips were patterned at the micrometer scale and the patterns were filled with ZnO nanostructures. Using HeLa cells, we demonstrated that the fabricated nanotopographical features could promote guided cellular adhesion on the pre-defined micron-scale patterns only through nanomechanical cues without the need for further surface activation or modification. The basic steps of the micro/nanofabrication are presented and the results from the cell adhesion experiments are discussed, showing the potential of the suggested methodology for creating low-cost templates for engineered cellular networks. PMID:28773382

Nano-anisotropic surface coating based on drug immobilized pendant polymer to suppress macrophage adhesion response.

PubMed

Kaladhar, K; Renz, H; Sharma, C P

2015-04-01

Exploring drug molecules for material design, to harness concepts of nano-anisotropy and ligand-receptor interactions, are rather elusive. The aim of this study is to demonstrate the bottom-up design of a single-step and bio-interactive polymeric surface coating, based on drug based pendant polymer. This can be applied on to polystyrene (PS) substrates, to suppress macrophage adhesion and spreading. The drug molecule is used in this coating for two purposes. The first one is drug as a "pendant" group, to produce nano-anisotropic properties that can enable adhesion of the coatings to the substrate. The second purpose is to use the drug as a "ligand", to produce ligand-receptor interaction, between the bound ligand and receptors of albumin, to develop a self-albumin coat over the surface, by the preferential binding of albumin in biological environment, to reduce macrophage adhesion. Our in silico studies show that, diclofenac (DIC) is an ideal drug based "ligand" for albumin. This can also act as a "pendant" group with planar aryl groups. The combination of these two factors can help to harness, both nano-anisotropic properties and biological functions to the polymeric coating. Further, the drug, diclofenac (DIC) is immobilized to the polyvinyl alcohol (PVA), to develop the pendant polymer (PVA-DIC). The interaction of bound DIC with the albumin is a ligand-receptor based interaction, as per the studies by circular dichroism, differential scanning calorimetry, and SDS-PAGE. The non-polar π-π* interactions are regulating; the interactions between PVA bound DIC-DIC interactions, leading to "nano-anisotropic condensation" to form distinct "nano-anisotropic segments" inside the polymeric coating. This is evident from, the thermo-responsiveness and uniform size of nanoparticles, as well as regular roughness in the surface coating, with similar properties as that of nanoparticles. In addition, the hydrophobic DIC-polystyrene (PS) interactions, between the PVA-DIC coating and PS-substrate produce improved coating stability. Subsequently, the PVA-DIC coated substrate has the maximum capacity to suppress the macrophage (RAW 264.7 cell line) adhesion and spreading, which is partly due to wavy-surface topography of hydrophilic PVA and preferential albumin binding capacity of PVA bound DIC. Our result shows that, such surfaces suppress the macrophages, even under stimulation with lipopolysaccharide (LPS). The modified tissue culture plates can be used as an in vitro tool, to study the macrophage response under low spatial cues. Copyright © 2015 Elsevier B.V. All rights reserved.

Micropatterned arrays of porous silicon: toward sensory biointerfaces.

PubMed

Flavel, Benjamin S; Sweetman, Martin J; Shearer, Cameron J; Shapter, Joseph G; Voelcker, Nicolas H

2011-07-01

We describe the fabrication of arrays of porous silicon spots by means of photolithography where a positive photoresist serves as a mask during the anodization process. In particular, photoluminescent arrays and porous silicon spots suitable for further chemical modification and the attachment of human cells were created. The produced arrays of porous silicon were chemically modified by means of a thermal hydrosilylation reaction that facilitated immobilization of the fluorescent dye lissamine, and alternatively, the cell adhesion peptide arginine-glycine-aspartic acid-serine. The latter modification enabled the selective attachment of human lens epithelial cells on the peptide functionalized regions of the patterns. This type of surface patterning, using etched porous silicon arrays functionalized with biological recognition elements, presents a new format of interfacing porous silicon with mammalian cells. Porous silicon arrays with photoluminescent properties produced by this patterning strategy also have potential applications as platforms for in situ monitoring of cell behavior.

D-amino acids inhibit initial bacterial adhesion: thermodynamic evidence.

PubMed

Xing, Su-Fang; Sun, Xue-Fei; Taylor, Alicia A; Walker, Sharon L; Wang, Yi-Fu; Wang, Shu-Guang

2015-04-01

Bacterial biofilms are structured communities of cells enclosed in a self-produced hydrated polymeric matrix that can adhere to inert or living surfaces. D-Amino acids were previously identified as self-produced compounds that mediate biofilm disassembly by causing the release of the protein component of the polymeric matrix. However, whether exogenous D-amino acids could inhibit initial bacterial adhesion is still unknown. Here, the effect of the exogenous amino acid D-tyrosine on initial bacterial adhesion was determined by combined use of chemical analysis, force spectroscopic measurement, and theoretical predictions. The surface thermodynamic theory demonstrated that the total interaction energy increased with more D-tyrosine, and the contribution of Lewis acid-base interactions relative to the change in the total interaction energy was much greater than the overall nonspecific interactions. Finally, atomic force microscopy analysis implied that the hydrogen bond numbers and adhesion forces decreased with the increase in D-tyrosine concentrations. D-Tyrosine contributed to the repulsive nature of the cell and ultimately led to the inhibition of bacterial adhesion. This study provides a new way to regulate biofilm formation by manipulating the contents of D-amino acids in natural or engineered systems. © 2014 Wiley Periodicals, Inc.

On the stability of a rod adhering to a rigid surface: Shear-induced stable adhesion and the instability of peeling

NASA Astrophysics Data System (ADS)

Majidi, Carmel; O'Reilly, Oliver M.; Williams, John A.

2012-05-01

Using variational methods, we establish conditions for the nonlinear stability of adhesive states between an elastica and a rigid halfspace. The treatment produces coupled criteria for adhesion and buckling instabilities by exploiting classical techniques from Legendre and Jacobi. Three examples that arise in a broad range of engineered systems, from microelectronics to biologically inspired fiber array adhesion, are used to illuminate the stability criteria. The first example illustrates buckling instabilities in adhered rods, while the second shows the instability of a peeling process and the third illustrates the stability of a shear-induced adhesion. The latter examples can also be used to explain how microfiber array adhesives can be activated by shearing and deactivated by peeling. The nonlinear stability criteria developed in this paper are also compared to other treatments.

Assessing Chemical Transformation of Reactive, Interfacial Thin Films Made of End-Tethered Poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) Chains

DOE PAGES

Aden, Bethany; Kite, Camille M.; Hopkins, Benjamin W.; ...

2017-01-24

Designing thin films or surface scaffolds with an appropriate display of chemical functionality is useful for biomedical applications, sensing platforms, adhesives, and barrier coatings. Relationships between the structural characteristics of model thin films based on reactive poly(2-vinyl-4,4-dimethyl azlactone) (PVDMA) brushes and the amount and distribution of primary amines used to chemically functionalize these layers in situ are quantitatively detailed via neutron reflectometry and compared with results from ellipsometry. After functionalization, the PVDMA brush thickness increases as a result of the primary amines reacting with the azlactone rings. Both techniques show that the extent of functionalization by small-molecule amines depends onmore » the size of the amine, the grafting density of brush chains, and their molecular weight. However, constrained analysis of neutron reflectivity data predicated on that technique’s sensitivity to isotopic substitution and its ability to resolve structure at the nanoscale shows that the extent of functionalization is not accurately represented by the average extent of functionalization determined from ellipsometric thickness: reactive modification is not uniform, even in modestly dense brushes, except when the penetrant is small. In addition, there appears to be a loss of PVDMA chains during functionalization, attributed to chain scission resulting from additional stretching brought about by functionalization. In conclusion, these findings provide unprecedented insight into the alteration of surface properties by reactive modification and broadly support efforts to produce tailored surfaces in which properties such as friction, colloidal stability, adhesion, wettability, and biocompatibility can be modulated in situ by chemical modification.« less

Emergence of collective propulsion through cell-cell adhesion.

PubMed

Matsushita, Katsuyoshi

2018-04-01

The mechanisms driving the collective movement of cells remain poorly understood. To contribute toward resolving this mystery, a model was formulated to theoretically explore the possible functions of polarized cell-cell adhesion in collective cell migration. The model consists of an amoeba cell with polarized cell-cell adhesion, which is controlled by positive feedback with cell motion. This model cell has no persistent propulsion and therefore exhibits a simple random walk when in isolation. However, at high density, these cells acquire collective propulsion and form ordered movement. This result suggests that cell-cell adhesion has a potential function, which induces collective propulsion with persistence.

Emergence of collective propulsion through cell-cell adhesion

NASA Astrophysics Data System (ADS)

Matsushita, Katsuyoshi

2018-04-01

The mechanisms driving the collective movement of cells remain poorly understood. To contribute toward resolving this mystery, a model was formulated to theoretically explore the possible functions of polarized cell-cell adhesion in collective cell migration. The model consists of an amoeba cell with polarized cell-cell adhesion, which is controlled by positive feedback with cell motion. This model cell has no persistent propulsion and therefore exhibits a simple random walk when in isolation. However, at high density, these cells acquire collective propulsion and form ordered movement. This result suggests that cell-cell adhesion has a potential function, which induces collective propulsion with persistence.

Focal Adhesion Induction at the Tip of a Functionalized Nanoelectrode

PubMed Central

Fuentes, Daniela E.; Bae, Chilman; Butler, Peter J.

2012-01-01

Cells dynamically interact with their physical micro-environment through the assembly of nascent focal contacts and focal adhesions. The dynamics and mechanics of these contact points are controlled by transmembrane integrins and an array of intracellular adaptor proteins. In order to study the mechanics and dynamics of focal adhesion assembly, we have developed a technique for the timed induction of a nascent focal adhesion. Bovine aortic endothelial cells were approached at the apical surface by a nanoelectrode whose position was controlled with a resolution of 10s of nanometers using changes in electrode current to monitor distance from the cell surface. Since this probe was functionalized with fibronectin, a focal contact formed at the contact location. Nascent focal adhesion assembly was confirmed using time-lapse confocal fluorescent images of red fluorescent protein (RFP) – tagged talin, an adapter protein that binds to activated integrins. Binding to the cell was verified by noting a lack of change of electrode current upon retraction of the electrode. This study demonstrates that functionalized nanoelectrodes can enable precisely-timed induction and 3-D mechanical manipulation of focal adhesions and the assay of the detailed molecular kinetics of their assembly. PMID:22247742

Intraperitoneal adhesions--an ongoing challenge between biomedical engineering and the life sciences.

PubMed

Brochhausen, Christoph; Schmitt, Volker H; Rajab, Taufiek K; Planck, Constanze N E; Krämer, Bernhard; Wallwiener, Markus; Hierlemann, Helmut; Kirkpatrick, C James

2011-07-01

Peritoneal adhesions remain a relevant clinical problem despite the currently available prophylactic barrier materials. So far, the physical separation of traumatized serosa areas using barriers represents the most important clinical strategy for adhesion prevention. However, the optimal material has not yet been found. Further optimization or pharmacological functionalization of these barriers could give an innovative input for peritoneal adhesion prevention. Therefore, a more complete understanding of pathogenesis is required. On the basis of the pathophysiology of adhesion formation the main barriers currently in clinical practice as well as new innovations are discussed in the present review. Physiologically, mesothelial cells play a decisive role in providing a frictionless gliding surface on the serosa. Adhesion formation results from a cascade of events and is regulated by a variety of cellular and humoral factors. The main clinically applied strategy for adhesion prevention is based on the use of liquid or solid adhesion barriers to separate physically any denuded tissue. Both animal and human trials have not yet been able to identify the optimal barrier to prevent adhesion formation in a sustainable way. Therefore, further developments are required for effective prevention of postoperative adhesion formation. To reach this goal the combination of structural modification and pharmacological functionalization of barrier materials should be addressed. Achieving this aim requires the interaction between basic research, materials science and clinical expertise. Copyright © 2011 Wiley Periodicals, Inc.

Superhydrophobic gecko feet with high adhesive forces towards water and their bio-inspired materials.

PubMed

Liu, Kesong; Du, Jiexing; Wu, Juntao; Jiang, Lei

2012-02-07

Functional integration is an inherent characteristic for multiscale structures of biological materials. In this contribution, we first investigate the liquid-solid adhesive forces between water droplets and superhydrophobic gecko feet using a high-sensitivity micro-electromechanical balance system. It was found, in addition to the well-known solid-solid adhesion, the gecko foot, with a multiscale structure, possesses both superhydrophobic functionality and a high adhesive force towards water. The origin of the high adhesive forces of gecko feet to water could be attributed to the high density nanopillars that contact the water. Inspired by this, polyimide films with gecko-like multiscale structures were constructed by using anodic aluminum oxide templates, exhibiting superhydrophobicity and a strong adhesive force towards water. The static water contact angle is larger than 150° and the adhesive force to water is about 66 μN. The resultant gecko-inspired polyimide film can be used as a "mechanical hand" to snatch micro-liter liquids. We expect this work will provide the inspiration to reveal the mechanism of the high-adhesive superhydrophobic of geckos and extend the practical applications of polyimide materials. This journal is © The Royal Society of Chemistry 2012

Self-Assembling Multi-Component Nanofibers for Strong Bioinspired Underwater Adhesives

PubMed Central

Zhong, Chao; Gurry, Thomas; Cheng, Allen A; Downey, Jordan; Deng, Zhengtao; Stultz, Collin M.; Lu, Timothy K

2014-01-01

Many natural underwater adhesives harness hierarchically assembled amyloid nanostructures to achieve strong and robust interfacial adhesion under dynamic and turbulent environments. Despite recent advances, our understanding of the molecular design, self-assembly, and structure-function relationship of those natural amyloid fibers remains limited. Thus, designing biomimetic amyloid-based adhesives remains challenging. Here, we report strong and multi-functional underwater adhesives obtained from fusing mussel foot proteins (Mfps) of Mytilus galloprovincialis with CsgA proteins, the major subunit of Escherichia coli amyloid curli fibers. These hybrid molecular materials hierarchically self-assemble into higher-order structures, in which, according to molecular dynamics simulations, disordered adhesive Mfp domains are exposed on the exterior of amyloid cores formed by CsgA. Our fibers have an underwater adhesion energy approaching 20.9 mJ/m2, which is 1.5 times greater than the maximum of bio-inspired and bio-derived protein-based underwater adhesives reported thus far. Moreover, they outperform Mfps or curli fibers taken on their own at all pHs and exhibit better tolerance to auto-oxidation than Mfps at pH ≥7.0. This work establishes a platform for engineering multi-component self-assembling materials inspired by nature. PMID:25240674

Analysis of human articular chondrocyte CD44 isoform expression and function in health and disease.

PubMed

Salter, D M; Godolphin, J L; Gourlay, M S; Lawson, M F; Hughes, D E; Dunne, E

1996-08-01

Interactions between articular chondrocytes and components of the extracellular matrix are of potential importance in the normal function of cartilage and in the pathophysiology of arthritis. Little is known of the basis of these interactions, but cell adhesive molecules such as CD44 are likely to be involved. Immunohistology using six well-characterized anti-CD44 monoclonal antibodies demonstrated standard CD44 isoform (CD44H) expression by all chondrocytes in normal and osteoarthrotic (OA) cartilage but absence of the CD44E variant. Polymerase chain reaction (PCR) of reverse transcribed mRNA from monolayer cultures of normal and OA chondrocytes using primer sequences which span the region containing variably spliced exons produced a predominant band representing the standard form of CD44, which lacks the variable exons 6-15 (v1-v10). No product was seen at the expected size of the epithelial variant of CD44 (CD44v8-10). Use of exon-specific primers, however, showed expression of variant exons resulting in multiple minor isoforms. Standard CD44 was also shown to be the predominantly expressed isoform identified by immunoprecipitation, but human articular chondrocytes did not adhere to hyaluronan in vitro. Chondrocyte CD44 may function as an adhesion receptor for other matrix molecules such as fibronectin or collagen.

Neurotactin functions in concert with other identified CAMs in growth cone guidance in Drosophila.

PubMed

Speicher, S; García-Alonso, L; Carmena, A; Martín-Bermudo, M D; de la Escalera, S; Jiménez, F

1998-02-01

We have isolated and characterized mutations in Drosophila neurotactin, a gene that encodes a cell adhesion protein widely expressed during neural development. Analysis of both loss and gain of gene function conditions during embryonic and postembryonic development revealed specific requirements for neurotactin during axon outgrowth, fasciculation, and guidance. Furthermore, embryos of some double mutant combinations of neurotactin and other genes encoding adhesion/signaling molecules, including neuroglian, derailed, and kekkon1, displayed phenotypic synergy. This result provides evidence for functional cooperativity in vivo between the adhesion and signaling pathways controlled by neurotactin and the other three genes.

Effects of surface topography and vibrations on wetting: Superhydrophobicity, icephobicity and corrosion resistance

NASA Astrophysics Data System (ADS)

Ramachandran, Rahul

Concrete and metallic materials are widely used in construction and water industry. The interaction of both these materials with water and ice (or snow) produces undesirable results and is therefore of interest. Water that gets absorbed into the pores of dry concrete expands on freezing and can lead to crack formation. Also, the ice accretion on concrete surfaces such as roadways can have disastrous consequence. Metallic components used in the water industry undergo corrosion due to contact with aqueous corrosive solutions. Therefore, it is desirable to make concrete water/ice-repellent, and to make metallic surfaces corrosion-resistant. Recent advances in micro/nanotechnology have made it possible to design functional micro/nanostructured surfaces with micro/nanotopography providing low adhesion. Some examples of such surfaces are superhydrophobic surfaces, which are extremely water repellent, and icephobic surfaces, which have low ice adhesion, repel incoming water droplets before freezing, or delay ice nucleation. This dissertation investigates the effects of surface micro/nanotopography and small amplitude fast vibrations on the wetting and adhesion of concrete with the goal of producing hydrophobic and icephobic concrete, and on the wetting of metallic surfaces to prevent corrosion. The relationship between surface micro/nanotopography and small fast vibrations is established using the method of separation of motions. Both these small scale effects can be substituted by an effective force or energy. The structure-property relationships in materials and surfaces are established. Both vibrations as well as surface micro/nanopatterns can affect wetting properties such as contact angle and surface free energy. Hydrophobic engineered cementitious composite samples are produced by controlling their surface topography and surface free energy. The surface topography is controlled by varying the concrete mixture composition. The surface free energy of concrete is lowered using a hydrophobic emulsion. The hydrophobic concrete samples were able to repel incoming water droplets as well as resist droplet pinning. Corrosion resistance is achieved in cast iron samples by rendering them superhydrophobic. The corrosion resistance of superhydrophobic surfaces with micro/nanotopography may be explained by the low effective contact area with the electrolyte. The experimental results matched the theoretical predictions based on surface roughness and wettability. The icephobicity of engineered cementitious composite samples is achieved by hydrophobization, by using coatings containing dielectric material (such as polyvinyl alcohol fibers), and by controlling the surface topography. Two aspects of the icephobicity of concrete, namely, the repulsion of incoming water droplets before freezing and the ice adhesion strength, are investigated experimentally. It is found that icephobic performance of concrete depends on these parameters --- the hydrophobic emulsion concentration, the polyvinyl alcohol fiber content, the water to cement ratio, and the sand to cement ratio. The potential for biomimetic icephobicity of thermogenic skunk cabbage plant is investigated, and it is found that the surface topography of its leaves can affect the heat transfer from the plant to the surrounding snow. The hierarchical microstructure of the leaf surface coupled with its high adhesion to water suggests the presence of an impregnated wetting state, which can minimize the heat loss. Thus functional materials and surfaces, such as hydrophobic and icephobic engineered cementitious composites and corrosion resistant metallic surfaces, can be produced by controlling the surface micro/nanotopography.

Microarray expression profiling in adhesion and normal peritoneal tissues.

PubMed

Ambler, Dana R; Golden, Alicia M; Gell, Jennifer S; Saed, Ghassan M; Carey, David J; Diamond, Michael P

2012-05-01

To identify molecular markers associated with adhesion and normal peritoneal tissue using microarray expression profiling. Comparative study. University hospital. Five premenopausal women. Adhesion and normal peritoneal tissue samples were obtained from premenopausal women. Ribonucleic acid was extracted using standard protocols and processed for hybridization to Affymetrix Whole Transcript Human Gene Expression Chips. Microarray data were obtained from five different patients, each with adhesion tissue and normal peritoneal samples. Real-time polymerase chain reaction was performed for confirmation using standard protocols. Gene expression in postoperative adhesion and normal peritoneal tissues. A total of 1,263 genes were differentially expressed between adhesion and normal tissues. One hundred seventy-three genes were found to be up-regulated and 56 genes were down-regulated in the adhesion tissues compared with normal peritoneal tissues. The genes were sorted into functional categories according to Gene Ontology annotations. Twenty-six up-regulated genes and 11 down-regulated genes were identified with functions potentially relevant to the pathophysiology of postoperative adhesions. We evaluated and confirmed expression of 12 of these specific genes via polymerase chain reaction. The pathogenesis, natural history, and optimal treatment of postoperative adhesive disease remains unanswered. Microarray analysis of adhesions identified specific genes with increased and decreased expression when compared with normal peritoneum. Knowledge of these genes and ontologic pathways with altered expression provide targets for new therapies to treat patients who have or are at risk for postoperative adhesions. Copyright © 2012 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

Investigation of the influence of process parameters on adhesive wear under hot stamping conditions

NASA Astrophysics Data System (ADS)

Schwingenschlögl, P.; Weldi, M.; Merklein, M.

2017-09-01

Current challenges like increasing safety standards and reducing fuel consumption motivate lightweight construction in modern car bodies. Besides using lightweight workpiece materials like aluminum, hot stamping has been established as a key technology for producing safety relevant components. Producing hot stamped parts out of ultra-high strength steels offers the possibility to improve the crash performance. At the same time the weight of car structure is reduced by using thinner sheet thicknesses. In order to avoid oxide scale formation and ensure corrosion protection, AlSi coatings are commonly deposited on the sheet surfaces used for direct hot stamping. This workpiece coating has a critical impact on the tribological conditions within the forming process and, as a consequence, influences the quality of hot stamped parts as well as tool wear. AlSi coatings have been identified as major reason for adhesive wear, which represents the main wear mechanism in hot stamping. Within this study, the influence of the process parameters on adhesive wear are investigated in dependency of workpiece and tool temperatures, drawing velocities and contact pressures. The tribological behavior is analyzed based on strip drawing experiments under direct hot stamping conditions. The experiments are performed with AlSi coated 22MnB5 in contact with the hot working tool steel 1.2367. For analyzing the amount of adhesion on the friction jaws, the surfaces are characterized by optical measurements. The experiments indicate that higher workpiece temperatures cause severe adhesive wear on the tool surface, while an increase of drawing velocity or contact pressure led to reduced adhesion. The measured friction coefficients decreased with rising amount of adhesion and remained at a constant level after a certain adhesive layer was built up on the tool surface.

Adhesion and Interphase Properties of Reinforced Polymeric Composites

NASA Astrophysics Data System (ADS)

Caldwell, Kyle Bernd

Reinforced polymeric composites are an increasingly utilized material with a wide range of applications. Fiber reinforced polymeric composites, in particular, possess impressive mechanical properties at a fraction of the weight of many other building materials. There will always, however, be a demand for producing lighter, stiffer, and stronger materials. Understanding the mechanism of adhesion and ways to engineer the reinforcement-matrix interphase can lead to the development of new materials with improved mechanical properties, and even impart additional functionality such as electrical conductivity. The performance of reinforced polymeric composites is critically dependent upon the adhesion between the reinforcement and the surrounding polymer. The relative adhesion between a filler and a thermoplastic matrix can be predicted using calculable thermodynamic quantities such as the Gibbs free energy of mixing. A recent model, COSMO-SAC, is capable of predicting the adhesion between organo-silane treated glass surfaces and several thermoplastic materials. COSMO-SAC uses information based on the charge distribution of a molecule's surface to calculate many thermodynamic properties. Density functional theory calculations, which are relative inexpensive computations, generate the information necessary to perform the COSMO-SAC analysis and can be performed on any given molecule. The flexibility of the COSMO-SAC model is one of the main advantages it possesses over other methods for calculating thermodynamic quantities. In many cases the adhesion between a reinforcing fiber and the surrounding matrix may be improved by incorporating interphase modifiers in the vicinity of the fiber surface. The modifiers can improve the fracture toughness and modulus of the interphase, which may improve the stress transfer from the matrix to the fiber. In addition, the interphase modifiers may improve the mechanical interlock between the fiber surface and the bulk polymer, leading to improved adhesion. In recent years, the use of so called "migrating agents" have been used to self-assemble nanoparticle reinforced fiber-matrix interphases in thermosetting resin systems. The inclusion of a modest amount of thermoplastic migrating agent can lead to the formation of a self-assembled interphase, without causing aggregation of nanoparticles in the bulk phase. Formulations containing excess migrating agent, however, can induce aggregation in the bulk of increasing severity with increasing migrating agent concentration. Several techniques were used to study the mechanism by which the migrating agents operate including, scanning electron microscopy, and in situ fluorescence microscopy. The self-assembly mechanism by which migrating agents operate is described well by depletion forces, which are depend on the geometry of the approaching objects, as well as the migrating agent molecular weight and concentration.

Impact of x-Linkable Polymer Blends on Phase Morphology and Adhesion

NASA Astrophysics Data System (ADS)

Liu, Chun; Wan, Grace; Keene, Ellen; Harris, Joseph; Zhang, Sipei; Anderson, Stephanie; Li Pi Shan, Colin

Adhesion to dissimilar substrate is highly important to multiple industrial applications such as automotive adhesives, food packaging, transportation etc. Adhesive design has to include components that are affinity to both substrates, e.g. high surface energy polar and low surface non-polar substrates. Typically, these adhesive components are thermodynamically incompatible with each other, leading to macrophase separation and thus adhesive failure. By using functional adhesive components plus some additives, the adhesive can be in-situ cross-linked to prevent the macrophase separation with controlled phase morphology. Herein, we present the study on a cross-linkable adhesive formulation consisting of acrylic emulsion and polyolefin aqueous dispersion with additives for enhancing cross-linking and controlled phase morphologies. Contact angle measurement and ATR-IR spectroscopy are used to characterize the properties of adhesive surface. DMA is used to study the mechanical property of adhesive before and after cross-linking. The detailed phase morphologies are revealed by AFM, SEM and TEM. The resulting adhesive morphologies are correlated with the adhesive performance to establish structure-property relationship.

Predicting the reactivity of adhesive starting materials

Treesearch

Anthony H. Conner

1999-01-01

Phenolic compounds are important in the production of bonded-wood products. Phenolic compounds in addition to phenol and resorcinol are potential alternative feedstocks for producing adhesives. The reactivity of a wide variety of phenolic compounds with formaldehyde was investigated using semi-empirical and ab initio computational chemistry methods...

Flowmeter determines mix ratio for viscous adhesives

NASA Technical Reports Server (NTRS)

Lemons, C. R.

1967-01-01

Flowmeter determines mix ratio for continuous flow mixing machine used to produce an adhesive from a high viscosity resin and aliphatic amine hardener pumped through separate lines to a rotary blender. The flowmeter uses strain gages in the two flow paths and monitors their outputs with appropriate instrumentation.

Galaptin Mediates the Effect of Hypergravity on Vascular Smooth Muscle cell (SMC) Adhesion to Laminin Containing Matrices

NASA Technical Reports Server (NTRS)

Enahora, Fatisha T.; Bosah, Francis N.; Harris-Hooker, Sandra; Sanford, Gary L.

1997-01-01

Galaptin, an endogenous beta-galactoside specific lectin, has been reported to bind to laminin and subsequently decrease the binding of SMC. Cellular function depend on cell:matrix interactions. Hypergravity (HGrav) affect a number of cellular functions, yet little is known about its affect on cell adhesion. We examined the possibility that galaptin mediates the effects of hypergravity on SMC adherence. Confluent primate aorta SMC cultures were subjected to Hgrav (centrifuged at 6G) for 24 and 48 hr. Cells were non-enzymatically dispersed, pretreated with antisense (AS-oligo) or control sense (SS-oligo) oligonucleotides to galaptin mRNA (0.01 micro g/ml), then seeded in uncoated or ECL-matrix coated plates. Adhesion of cells were monitored after 6 hr. HGrav increased adhesion by 100-300% compared to controls. AS-oligo decreased adhesion for both HGrav and control cells. SS-oligo did not affect adhesion for either HGrav or control cells. These studies show that HGrav affects cell adhesion and that galaptin expression is required for this effect.

Lap Shear and Impact Testing of Ochre and Beeswax in Experimental Middle Stone Age Compound Adhesives.

PubMed

Kozowyk, P R B; Langejans, G H J; Poulis, J A

2016-01-01

The production of compound adhesives using disparate ingredients is seen as some of the best evidence of advanced cognition outside of the use of symbolism. Previous field and laboratory testing of adhesives has shown the complexities involved in creating an effective Middle Stone Age glue using Acacia gum. However, it is currently unclear how efficient different adhesive recipes are, how much specific ingredients influence their performance, and how difficult it may have been for those ingredients to be combined to maximum effect. We conducted a series of laboratory-based lap shear and impact tests, following modern adhesion testing standards, to determine the efficacy of compound adhesives, with particular regard to the ingredient ratios. We tested rosin (colophony) and gum adhesives, containing additives of beeswax and ochre in varying ratios. During both lap shear and impact tests compound rosin adhesives performed better than single component rosin adhesives, and pure acacia gum was the strongest. The large difference in performance between each base adhesive and the significant changes in performance that occur due to relatively small changes in ingredient ratios lend further support to the notion that high levels of skill and knowledge were required to consistently produce the most effective adhesives.

Lap Shear and Impact Testing of Ochre and Beeswax in Experimental Middle Stone Age Compound Adhesives

PubMed Central

2016-01-01

The production of compound adhesives using disparate ingredients is seen as some of the best evidence of advanced cognition outside of the use of symbolism. Previous field and laboratory testing of adhesives has shown the complexities involved in creating an effective Middle Stone Age glue using Acacia gum. However, it is currently unclear how efficient different adhesive recipes are, how much specific ingredients influence their performance, and how difficult it may have been for those ingredients to be combined to maximum effect. We conducted a series of laboratory-based lap shear and impact tests, following modern adhesion testing standards, to determine the efficacy of compound adhesives, with particular regard to the ingredient ratios. We tested rosin (colophony) and gum adhesives, containing additives of beeswax and ochre in varying ratios. During both lap shear and impact tests compound rosin adhesives performed better than single component rosin adhesives, and pure acacia gum was the strongest. The large difference in performance between each base adhesive and the significant changes in performance that occur due to relatively small changes in ingredient ratios lend further support to the notion that high levels of skill and knowledge were required to consistently produce the most effective adhesives. PMID:26983080

Mechanical Characterization of Polydopamine-Assisted Silver Deposition on Polymer Substrates

NASA Astrophysics Data System (ADS)

Cordes, Amanda Laurence

Inspired by the adhesive proteins in marine mussels, polydopamine has become a popular adhesive ad-layer for surface functionalization of a variety of substrates. Based on the chemistry of the dopamine monomer, amine and thiol functional groups are hypothesized to increase adhesion between polymer substrates and polydopamine thin films. This hypothesis was the central motivation for development of a tailorable thiol-ene system in order to study the effects of substrate chemistry on polydopamine adhesion. While polydopamine-adhered silver has been studied on a variety of substrates, no in depth mechanical characterization has been performed and to date, no research has been published on thiol-enes coated in polydopamine-adhered silver. The purpose of this study was to characterize the mechanical durability and adhesion properties of a polydopamine-adhered silver film on commercial substrates and a tailorable thiol-ene system. Polydopamine and silver coatings were deposited on a variety of polymer substrates through a simple dip-coat process. The polydopamine forms a thin uniform adhesive layer and the silver deposits in a discontinuous manner with a nanoparticle sized base layer covering the full surface and micron-sized clusters adhered sporadically on top. Mechanical tensile testing was performed to characterize the durability of the silver coating on commercial polymers. Coated nylon and HDPE showed no signs of degradation or delamination of the polydopamine-adhered silver coating up to 30% strain although both substrates showed large plastic deformation. Peel tests were performed on both commercial polymers as well as a tailorable thiol-ene system. Results support the hypothesis that polydopamine adhesion is increased with the presence of functional groups. Parts of the HDPE sample were cleanly peeled, but silver patches were left sporadically across the surface pointing to weaker adhesion between polyethylene and polydopamine. A high adhesive strength tape was used on nylon and the thiol-ene polymers and removed some of the large clusters but was ineffective at removing the particle base layer. The silver base layer remained firmly attached on the surface after multiple rounds of peel testing. With the addition of functional groups in the polymer makeup, the adhesion strength of polydopamine-adhered silver coatings can be increased to create a mechanically durable and adhesively robust silver coating.

Mechanical and Functional Properties of Nickel Titanium Adhesively Bonded Joints

NASA Astrophysics Data System (ADS)

Niccoli, F.; Alfano, M.; Bruno, L.; Furgiuele, F.; Maletta, C.

2014-07-01

In this study, adhesive joints made up of commercial NiTi sheets with shape memory capabilities are analyzed. Suitable surface pre-treatments, i.e., degreasing, sandblasting, and chemical etching, are preliminary compared in terms of surface roughness, surface energy, and substrate thinning. Results indicate that chemical etching induces marked substrate thinning without substantial gains in terms of surface roughness and free energy. Therefore, adhesive joints with degreased and sandblasted substrates are prepared and tested under both static and cyclic conditions, and damage development within the adhesive layer is monitored in situ using a CCD camera. Sandblasted specimens have a significantly higher mechanical static strength with respect to degreased ones, although they essentially fail in similar fashion, i.e., formation of microcracks followed by decohesion along the adhesive/substrate interface. In addition, the joints show a good functional response with almost complete shape memory recovery after thermo-mechanical cycling, i.e., a small accumulation of residual deformations occurs. The present results show that adhesive bonding is a viable joining technique for NiTi alloys.

Spectral force analysis using atomic force microscopy reveals the importance of surface heterogeneity in bacterial and colloid adhesion to engineered surfaces.

PubMed

Ma, Huilian; Winslow, Charles J; Logan, Bruce E

2008-04-01

Coatings developed to reduce biofouling of engineered surfaces do not always perform as expected based on their native properties. One reason is that a relatively small number of highly adhesive sites, or the heterogeneity of the coated surface, may control the overall response of the system to initial bacterial deposition. It is shown here using an approach we call spectral force analysis (SFA), based on force volume imaging of the surface with atomic force microscopy, that the behavior of surfaces and coatings can be better understood relative to bacterial adhesion. The application of vapor deposited TiO(2) metal oxide increased bacterial and colloid adhesion, but coating the surface with silica oxide reduced adhesion in a manner consistent with SFA based on analysis of the "stickiest" sites. Application of a TiO(2)-based paint to a surface produced a relatively non-fouling surface. Addition of a hydrophilic layer coating to this surface should have decreased fouling. However, it was observed that this coating actually increased fouling. Using SFA it was shown that the reason for the increased adhesion of bacteria and particles to the hydrophilic layer was that the surface produced by this coating was highly heterogeneous, resulting in a small number of sites that created a stickier surface. These results show that while it is important to manufacture surfaces with coatings that are relatively non-adhesive to bacteria, it is also essential that these coatings have a highly uniform surface chemistry.

Plasma treatment of polymers for improved adhesion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelber, J.A.

1988-01-01

A variety of plasma treatments of polymer surfaces for improved adhesion are reviewed: noble and reactive gas treatment of fluoropolymers; noble and reactive treatment of polyolefins, and plasma-induced amination of polymer fibers. The plasma induced surface chemical and morphological changes are discussed, as are the mechanisms of adhesion to polymeric adhesives, particularly epoxy. Noble gas plasma etching of flouropolymers produces a partially defluorinated, textured surface. The mechanical interlocking of this textured surface is the primary cause of improved adhesion to epoxy. Reactive gas plasmas also induce defluorination, but oxygen containing gases cause continual ablation of the fluoropolymer surface. Noble andmore » reactive gas (exept for hydrogen) etching of polyolefins results in surface oxidation and improved adhesion via hydrogen bonding of these oxygen containing groups across the interface. The introduction of amine groups to a polymer surface by amonia or amine plasma treatment generally results in improved adhesion to epoxy. However, amine-epoxy ring interactions can be severely effected by steric factors due to chemical groups surrounding the amine. 41 refs.« less

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

PubMed

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 < 0.0075), whole-capsule deformation confers the capsule a flattened bottom in contact with the functionalized surface, which hence promotes the rolling-to-firm-adhesion transition. It is consistent with the observations from previous studies that cell deformation promotes the adhesion of cells lying in the rolling regime. However, it is surprising to find that, at relatively high capillary numbers (e.g. 0.0075 < Ca < 0.0175), the effect of capsule deformability on its adhesion dynamics is far more complex than just promoting adhesion. High deformability of capsules makes their bottom take a concave shape with no adhesion bond formation in the middle. The appearance of this specific capsule shape inhibits the transitions of both rolling-to-firm-adhesion and detachment-to-rolling, and it means that capsule deformation no longer promotes the capsule adhesion. Besides, it is interesting to note that, when the capillary number exceeds a critical value (e.g. Ca = 0.0175), the rolling state no longer appears, since capsules exhibit large deviation from the spherical shape.

Enhancement of CNT/PET film adhesion by nano-scale modification for flexible all-solid-state supercapacitors

NASA Astrophysics Data System (ADS)

Kang, Yu Jin; Chung, Haegeun; Kim, Min-Seop; Kim, Woong

2015-11-01

We demonstrate the fabrication of high-integrity flexible supercapacitors using carbon nanotubes (CNTs), polyethylene terephthalate (PET) films, and ion gels. Although both CNTs and PET films are attractive materials for flexible electronics, they have poor adhesion properties. In this work, we significantly improve interfacial adhesion by introducing nanostructures at the interface of the CNT and PET layers. Simple reactive ion etching (RIE) of the PET substrates generates nano-scale roughness on the PET surface. RIE also induces hydrophilicity on the PET surface, which further enhances adhesive strength. The improved adhesion enables high integrity and excellent flexibility of the fabricated supercapacitors, demonstrated over hundreds of bending cycles. Furthermore, the supercapacitors show good cyclability with specific capacitance retention of 87.5% after 10,000 galvanostatic charge-discharge (GCD) cycles. Our demonstration may be important for understanding interfacial adhesion properties in nanoscale and for producing flexible, high-integrity, high-performance energy storage systems.

Frictional behavior and adhesion of Ag and Au films applied to aluminum oxide by oxygen-ion assisted Screen Cage Ion Plating (SCIP)

NASA Technical Reports Server (NTRS)

Spalvins, Talivaldis; Sliney, Harold E.

1994-01-01

A modified dc-diode ion plating system, by utilizing a metallic screen cage as a cathode, is introduced for coating nonconductors such as ceramics. Screen cage ion plating (SCIP) is used to apply Ag and Au lubricating films on aluminum oxide surfaces. This process has excellent ability to coat around corners to produce three-dimensional coverage of the substrate. A dramatic increase in adhesion is achieved when plating is performed in a reactive 50 percent O2 - 50 percent Ar glow discharge compared to the adhesion when plating is performed in 100 percent Ar. The presence of oxygen ion assistance contributes to the excellent adhesion as measured in a pull-type adhesion tester. The Ag and Au film adhesion is significantly increased (less than 70MPa) and generally exceeds the cohesion of the substrate such that portions of the alumina are pulled out.

Membrane tension controls adhesion positioning at the leading edge of cells

PubMed Central

Pontes, Bruno; Gole, Laurent; Kosmalska, Anita Joanna; Tam, Zhi Yang; Luo, Weiwei; Kan, Sophie; Viasnoff, Virgile; Roca-Cusachs, Pere; Tucker-Kellogg, Lisa

2017-01-01

Cell migration is dependent on adhesion dynamics and actin cytoskeleton remodeling at the leading edge. These events may be physically constrained by the plasma membrane. Here, we show that the mechanical signal produced by an increase in plasma membrane tension triggers the positioning of new rows of adhesions at the leading edge. During protrusion, as membrane tension increases, velocity slows, and the lamellipodium buckles upward in a myosin II–independent manner. The buckling occurs between the front of the lamellipodium, where nascent adhesions are positioned in rows, and the base of the lamellipodium, where a vinculin-dependent clutch couples actin to previously positioned adhesions. As membrane tension decreases, protrusion resumes and buckling disappears, until the next cycle. We propose that the mechanical signal of membrane tension exerts upstream control in mechanotransduction by periodically compressing and relaxing the lamellipodium, leading to the positioning of adhesions at the leading edge of cells. PMID:28687667

Emergence and subsequent functional specialization of kindlins during evolution of cell adhesiveness

PubMed Central

Meller, Julia; Rogozin, Igor B.; Poliakov, Eugenia; Meller, Nahum; Bedanov-Pack, Mark; Plow, Edward F.; Qin, Jun; Podrez, Eugene A.; Byzova, Tatiana V.

2015-01-01

Kindlins are integrin-interacting proteins essential for integrin-mediated cell adhesiveness. In this study, we focused on the evolutionary origin and functional specialization of kindlins as a part of the evolutionary adaptation of cell adhesive machinery. Database searches revealed that many members of the integrin machinery (including talin and integrins) existed before kindlin emergence in evolution. Among the analyzed species, all metazoan lineages—but none of the premetazoans—had at least one kindlin-encoding gene, whereas talin was present in several premetazoan lineages. Kindlin appears to originate from a duplication of the sequence encoding the N-terminal fragment of talin (the talin head domain) with a subsequent insertion of the PH domain of separate origin. Sequence analysis identified a member of the actin filament–associated protein 1 (AFAP1) superfamily as the most likely origin of the kindlin PH domain. The functional divergence between kindlin paralogues was assessed using the sequence swap (chimera) approach. Comparison of kindlin 2 (K2)/kindlin 3 (K3) chimeras revealed that the F2 subdomain, in particular its C-terminal part, is crucial for the differential functional properties of K2 and K3. The presence of this segment enables K2 but not K3 to localize to focal adhesions. Sequence analysis of the C-terminal part of the F2 subdomain of K3 suggests that insertion of a variable glycine-rich sequence in vertebrates contributed to the loss of constitutive K3 targeting to focal adhesions. Thus emergence and subsequent functional specialization of kindlins allowed multicellular organisms to develop additional tissue-specific adaptations of cell adhesiveness. PMID:25540429

Streptococcus mutans forms xylitol-resistant biofilm on excess adhesive flash in novel ex-vivo orthodontic bracket model.

PubMed

Ho, Cindy S F; Ming, Yue; Foong, Kelvin W C; Rosa, Vinicius; Thuyen, Truong; Seneviratne, Chaminda J

2017-04-01

During orthodontic bonding procedures, excess adhesive is invariably left on the tooth surface at the interface between the bracket and the enamel junction; it is called excess adhesive flash (EAF). We comparatively evaluated the biofilm formation of Streptococcus mutans on EAF produced by 2 adhesives and examined the therapeutic efficacy of xylitol on S mutans formed on EAF. First, we investigated the biofilm formation of S mutans on 3 orthodontic bracket types: stainless steel preadjusted edgewise, ceramic preadjusted edgewise, and stainless steel self-ligating. Subsequently, tooth-colored Transbond XT (3M Unitek, Monrovia, Calif) and green Grengloo (Ormco, Glendora, Calif) adhesives were used for bonding ceramic brackets to extracted teeth. S mutans biofilms on EAF produced by the adhesives were studied using the crystal violet assay and scanning electron microscopy. Surface roughness and surface energy of the EAF were examined. The therapeutic efficacies of different concentrations of xylitol were tested on S mutans biofilms. Significantly higher biofilms were formed on the ceramic preadjusted edgewise brackets (P = 0.003). Transbond XT had significantly higher S mutans biofilms compared with Grengloo surfaces (P = 0.007). There was no significant difference in surface roughness between Transbond XT and Grengloo surfaces (P >0.05). Surface energy of Transbond XT had a considerably smaller contact angle than did Grengloo, suggesting that Transbond XT is a more hydrophilic material. Xylitol at low concentrations had no significant effect on the reduction of S mutans biofilms on orthodontic adhesives (P = 0.016). Transbond XT orthodontic adhesive resulted in more S mutans biofilm compared with Grengloo adhesive on ceramic brackets. Surface energy seemed to play a more important role than surface roughness for the formation of S mutans biofilm on EAF. Xylitol does not appear to have a therapeutic effect on mature S mutans biofilm. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

Deciphering the molecular mechanisms underlying sea urchin reversible adhesion: A quantitative proteomics approach.

PubMed

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

2016-04-14

Marine bioadhesives have unmatched performances in wet environments, being an inspiration for biomedical applications. In sea urchins specialized adhesive organs, tube feet, mediate reversible adhesion, being composed by a disc, producing adhesive and de-adhesive secretions, and a motile stem. After tube foot detachment, the secreted adhesive remains bound to the substratum as a footprint. Sea urchin adhesive is composed by proteins and sugars, but so far only one protein, Nectin, was shown to be over-expressed as a transcript in tube feet discs, suggesting its involvement in sea urchin adhesion. Here we use high-resolution quantitative mass-spectrometry to perform the first study combining the analysis of the differential proteome of an adhesive organ, with the proteome of its secreted adhesive. This strategy allowed us to identify 163 highly over-expressed disc proteins, specifically involved in sea urchin reversible adhesion; to find that 70% of the secreted adhesive components fall within five protein groups, involved in exocytosis and microbial protection; and to provide evidences that Nectin is not only highly expressed in tube feet discs but is an actual component of the adhesive. These results give an unprecedented insight into the molecular mechanisms underlying sea urchin adhesion, and opening new doors to develop wet-reliable, reversible, and ecological biomimetic adhesives. Sea urchins attach strongly but in a reversible manner to substratum, being a valuable source of inspiration for industrial and biomedical applications. Yet, the molecular mechanisms governing reversible adhesion are still poorly studied delaying the engineering of biomimetic adhesives. We used the latest mass spectrometry techniques to analyze the differential proteome of an adhesive organ and the proteome of its secreted adhesive, allowing us to uncover the key players in sea urchin reversible adhesion. We demonstrate, that Nectin, a protein previously pointed out as potentially involved in sea urchin adhesion, is not only highly expressed in tube feet discs, but is a genuine component of the secreted adhesive. Copyright © 2016 Elsevier B.V. All rights reserved.

Chemical interaction of glycero-phosphate dimethacrylate (GPDM) with hydroxyapatite and dentin.

PubMed

Yoshihara, Kumiko; Nagaoka, Noriyuki; Hayakawa, Satoshi; Okihara, Takumi; Yoshida, Yasuhiro; Van Meerbeek, Bart

2018-04-28

Although the functional monomer glycero-phosphate dimethacrylate (GPDM) has since long been used in several dental adhesives and more recently in self-adhesive composite cements and restoratives, its mechanism of chemical adhesion to hydroxyapatite (HAp) is still unknown. We therefore investigated the chemical interaction of GPDM with HAp using diverse chemical analyzers and ultra-structurally characterized the interface of a GPDM-based primer formulation with dentin. HAp particles were added to a GPDM solution for various periods, upon which they were thoroughly washed with ethanol and water prior to being air-dried. As control, 10-methacryloyloxydecyl dihydrogen phosphate (MDP) was used. The molecular interaction of GPDM with HAp was analyzed using X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (NMR) spectroscopy. Crystal formation upon application of GPDM onto dentin was analyzed using thin-film XRD (TF-XRD). Its hydrophobicity was measured using contact-angle measurement. The interaction of GPDM with dentin was characterized using transmission electron microscopy (TEM). XRD revealed the deposition of dicalcium phosphate dihydrate (DCPD: CaHPO 4 ·2H 2 O) on HAp after 24h. NMR confirmed the adsorption of GPDM onto HAp. However, GPDM was easily removed after washing with water, unlike MDP that remained adhered to HAp. Dentin treated with GPDM appeared more hydrophilic compared to dentin treated with MDP. TEM disclosed exposed collagen in the hybrid layer produced by the GPDM-based primer formulation. Although GPDM adsorbed to HAp, it did not form a stable calcium salt. The bond between GPDM and HAp was weak, unlike the strong bond formed by MDP to HAp. Due to its high hydrophilicity, GPDM might be an adequate monomer for an etch-and-rinse adhesive, but appears less appropriate for a 'mild' self-etch adhesive that besides micro-retention ionically interacts with HAp, or for a self-adhesive restorative material. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Effect of surface topography and bioactive properties on early adhesion and growth behavior of mouse preosteoblast MC3T3-E1 cells.

PubMed

Li, Na; Chen, Gang; Liu, Jue; Xia, Yang; Chen, Hanbang; Tang, Hui; Zhang, Feimin; Gu, Ning

2014-10-08

The effects of bioactive properties and surface topography of biomaterials on the adhesion and spreading properties of mouse preosteoblast MC3T3-E1 cells was investigated by preparation of different surfaces. Poly lactic-co-glycolic acid (PLGA) electrospun fibers (ES) were produced as a porous rough surface. In our study, coverslips were used as a substrate for the immobilization of 3,4-dihydroxyphenylalanine (DOPA) and collagen type I (COL I) in the preparation of bioactive surfaces. In addition, COL I was immobilized onto porous electrospun fibers surfaces (E-COL) to investigate the combined effects of bioactive molecules and topography. Untreated coverslips were used as controls. Early adhesion and growth behavior of MC3T3-E1 cells cultured on the different surfaces were studied at 6, 12, and 24 h. Evaluation of cell adhesion and morphological changes showed that the all the surfaces were favorable for promoting the adhesion and spreading of cells. CCK-8 assays and flow cytometry revealed that both topography and bioactive properties were favorable for cell growth. Analysis of β1, α1, α2, α5, α10 and α11 integrin expression levels by immunofluorescence, real-time RT-PCR, and Western blot and indicated that surface topography plays an important role in the early stage of cell adhesion. However, the influence of topography and bioactive properties of surfaces on integrins is variable. Compared with any of the topographic or bioactive properties in isolation, the combined effect of both types of properties provided an advantage for the growth and spreading of MC3T3-E1 cells. This study provides a new insight into the functions and effects of topographic and bioactive modifications of surfaces at the interface between cells and biomaterials for tissue engineering.

Pulse-echo NDT of adhesively bonded joints in automotive assemblies.

PubMed

Titov, Sergey A; Maev, Roman Gr; Bogachenkov, Alexey N

2008-11-01

A new method for the detection of void-disbonds at the interfaces of adhesively bonded joins is considered. Based on a simple plane wave model, the output waveform is presented as a sum of two responses associated with the reflection of the ultrasonic wave at the first metal-adhesive interface and the second metal-adhesive interface, respectively. The strong response produced by the wave reverberating in the first metal sheet is eliminated through comparison between the pulse-echo signal measured at the area under the test and reference waveform recorded for the bare first metal sheet outside of the joint. The developed decomposition algorithm has been applied to the study of steel and aluminum samples having various adhesive layer thicknesses in a range of 0.1-1mm.

Durable anti-fogging effect and adhesion improvement on polymer surfaces

NASA Astrophysics Data System (ADS)

Moser, E. M.; Gilliéron, D.; Henrion, G.

2010-01-01

The hydrophobic properties of polymeric surfaces may cause fogging in transparent packaging and poor adhesion to printing colours and coatings. Novel plasma processes for durable functionalization of polypropylene and polyethylene terephthalate substrates were developed and analysed using optical emission spectroscopy. A worm-like nano pattern was created on the polypropylene surface prior to the deposition of thin polar plasma polymerised layers. For both substrates, highly polar surfaces exhibiting a surface tension of up to 69 mN/m and a water contact angle of about 10° were produced - providing the anti-fogging effect. The deposition of thin plasma polymerised layers protects the increased surface areas and enables to tailoring the surface energy of the substrate in a wide range. Wetting characteristics were determined by dynamic contact angle measurements. Investigations of the chemical composition of several layers using X-ray photoelectron spectroscopy and FT-infrared spectroscopy were correlated with functional testing. The surface topography was investigated using atomic force microscopy. The weldability and peeling-off characteristics of the plasma treated polymer films could be adjusted by varying the process parameters. Global and specific migration analyses were undertaken in order to ensure the manufacturing of plasma treated polymer surfaces for direct food contact purposes.

Bone morphogenic protein 4 produced in endothelial cells by oscillatory shear stress stimulates an inflammatory response

NASA Technical Reports Server (NTRS)

Sorescu, George P.; Sykes, Michelle; Weiss, Daiana; Platt, Manu O.; Saha, Aniket; Hwang, Jinah; Boyd, Nolan; Boo, Yong C.; Vega, J. David; Taylor, W. Robert;

Flagellin based biomimetic coatings: From cell-repellent surfaces to highly adhesive coatings.

PubMed

Kovacs, Boglarka; Patko, Daniel; Szekacs, Inna; Orgovan, Norbert; Kurunczi, Sandor; Sulyok, Attila; Khanh, Nguyen Quoc; Toth, Balazs; Vonderviszt, Ferenc; Horvath, Robert

2016-09-15

Biomimetic coatings with cell-adhesion-regulating functionalities are intensively researched today. For example, cell-based biosensing for drug development, biomedical implants, and tissue engineering require that the surface adhesion of living cells is well controlled. Recently, we have shown that the bacterial flagellar protein, flagellin, adsorbs through its terminal segments to hydrophobic surfaces, forming an oriented monolayer and exposing its variable D3 domain to the solution. Here, we hypothesized that this nanostructured layer is highly cell-repellent since it mimics the surface of the flagellar filaments. Moreover, we proposed flagellin as a carrier molecule to display the cell-adhesive RGD (Arg-Gly-Asp) peptide sequence and induce cell adhesion on the coated surface. The D3 domain of flagellin was replaced with one or more RGD motifs linked by various oligopeptides modulating flexibility and accessibility of the inserted segment. The obtained flagellin variants were applied to create surface coatings inducing cell adhesion and spreading to different levels, while wild-type flagellin was shown to form a surface layer with strong anti-adhesive properties. As reference surfaces synthetic polymers were applied which have anti-adhesive (PLL-g-PEG poly(l-lysine)-graft-poly(ethylene glycol)) or adhesion inducing properties (RGD-functionalized PLL-g-PEG). Quantitative adhesion data was obtained by employing optical biochips and microscopy. Cell-adhesion-regulating coatings can be simply formed on hydrophobic surfaces by using the developed flagellin-based constructs. The developed novel RGD-displaying flagellin variants can be easily obtained by bacterial production and can serve as alternatives to create cell-adhesion-regulating biomimetic coatings. In the present work, we show for the first time that. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Intracellular targeting of annexin A2 inhibits tumor cell adhesion, migration, and in vivo grafting.

PubMed

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.

Effect of analgesic nerve block electrical stimulation in a patient with adhesive capsulitis.

PubMed

Gulick, Dawn T; Borger, Amy; McNamee, Lauren

2007-01-01

Although the pathophysiology of adhesive capsulitis is poorly understood, the primary goal of therapeutic intervention is to restore pain-free, functional range of motion (ROM) of the shoulder. Pain and muscle guarding, particularly of the subscapularis muscle, are common impairments that occur with adhesive capsulitis. The purpose of this case report is to describe a novel approach to help the pain-muscle guarding-pain cycle associated with pain and limited shoulder motion in a patient with a medical diagnosis of adhesive capsulitis. The patient was a 64-year-old female with adhesive capsulitis. Outcome variables were the Shoulder Pain and Disability Index (SPADI), internal rotation (IR) and external rotation (ER) ROM, and rotational lack. Twelve treatments of moist heat, analgesic nerve block electrical stimulation, contract/relax exercises for shoulder IR/ER, and Pendulum/Codman exercises were administered. After both 2 and 4 weeks of treatment, the patient demonstrated marked improvements in all areas. Overall, there was a 78-106% increase in ROM (IR and ER) and a 50-83% improvement in functional mobility (rotational lack & SPADI). It appears that analgesic electrical stimulation may have helped decrease the pain-muscle guarding cycle associated with adhesive capsulitis to enhance functional outcomes in a timely manner.

Indentation versus Rolling: Dependence of Adhesion on Contact Geometry for Biomimetic Structures.

PubMed

Moyle, Nichole; He, Zhenping; Wu, Haibin; Hui, Chung-Yuen; Jagota, Anand

2018-04-03

Numerous biomimetic structures made from elastomeric materials have been developed to produce enhancement in properties such as adhesion, static friction, and sliding friction. As a property, one expects adhesion to be represented by an energy per unit area that is usually sensitive to the combination of shear and normal stresses at the crack front but is otherwise dependent only on the two elastic materials that meet at the interface. More specifically, one would expect that adhesion measured by indentation (a popular and convenient technique) could be used to predict adhesion hysteresis in the more practically important rolling geometry. Previously, a structure with a film-terminated fibrillar geometry exhibited dramatic enhancement of adhesion by a crack-trapping mechanism during indentation with a rigid sphere. Roughly isotropic structures such as the fibrillar geometry show a strong correlation between adhesion enhancement in indentation versus adhesion hysteresis in rolling. However, anisotropic structures, such as a film-terminated ridge-channel geometry, surprisingly show a dramatic divergence between adhesion measured by indentation versus rolling. We study this experimentally and theoretically, first comparing the adhesion of the anisotropic ridge-channel structure to the roughly isotropic fibrillar structure during indentation with a rigid sphere, where only the isotropic structure shows adhesion enhancement. Second, we examine in more detail the anomalous anisotropic film-terminated ridge-channel structure during indentation with a rigid sphere versus rolling to show why these structures show a dramatic adhesion enhancement for the rolling case and no adhesion enhancement for indentation.

The Talin Head Domain Reinforces Integrin-Mediated Adhesion by Promoting Adhesion Complex Stability and Clustering

PubMed Central

Ellis, Stephanie J.; Lostchuck, Emily; Goult, Benjamin T.; Bouaouina, Mohamed; Fairchild, Michael J.; López-Ceballos, Pablo; Calderwood, David A.; Tanentzapf, Guy

2014-01-01

Talin serves an essential function during integrin-mediated adhesion in linking integrins to actin via the intracellular adhesion complex. In addition, the N-terminal head domain of talin regulates the affinity of integrins for their ECM-ligands, a process known as inside-out activation. We previously showed that in Drosophila, mutating the integrin binding site in the talin head domain resulted in weakened adhesion to the ECM. Intriguingly, subsequent studies showed that canonical inside-out activation of integrin might not take place in flies. Consistent with this, a mutation in talin that specifically blocks its ability to activate mammalian integrins does not significantly impinge on talin function during fly development. Here, we describe results suggesting that the talin head domain reinforces and stabilizes the integrin adhesion complex by promoting integrin clustering distinct from its ability to support inside-out activation. Specifically, we show that an allele of talin containing a mutation that disrupts intramolecular interactions within the talin head attenuates the assembly and reinforcement of the integrin adhesion complex. Importantly, we provide evidence that this mutation blocks integrin clustering in vivo. We propose that the talin head domain is essential for regulating integrin avidity in Drosophila and that this is crucial for integrin-mediated adhesion during animal development. PMID:25393120

Design rules for biomolecular adhesion: lessons from force measurements.

PubMed

Leckband, Deborah

2010-01-01

Cell adhesion to matrix, other cells, or pathogens plays a pivotal role in many processes in biomolecular engineering. Early macroscopic methods of quantifying adhesion led to the development of quantitative models of cell adhesion and migration. The more recent use of sensitive probes to quantify the forces that alter or manipulate adhesion proteins has revealed much greater functional diversity than was apparent from population average measurements of cell adhesion. This review highlights theoretical and experimental methods that identified force-dependent molecular properties that are central to the biological activity of adhesion proteins. Experimental and theoretical methods emphasized in this review include the surface force apparatus, atomic force microscopy, and vesicle-based probes. Specific examples given illustrate how these tools have revealed unique properties of adhesion proteins and their structural origins.

Flexible Circuits

NASA Technical Reports Server (NTRS)

1986-01-01

Adflex Solutions, Inc.'s flexible circuits may be molded to the shape of a chassis for bulk reduction. Particularly valuable when circuitry must be moved. They are produced by combining a plastic film, a metallic conductor and an adhesive. One adhesive, LARC-TPI, developed by the Langley Research Center, is a thermoplastic polyimide resin used to produce laminates by Rogers Corporation. It can be processed at a lower temperature, has good moisture resistance and excellent adherence. It is used to bond film to copper foil conductor materials in flexible circuits. The circuits have both aerospace and commercial applications.

Adjustment of surface chemical and physical properties with functionalized polymers to control cell adhesion

NASA Astrophysics Data System (ADS)

Zhou, Zhaoli

Cell-surface interaction is crucial in many cellular functions such as movement, growth, differentiation, proliferation and survival. In the present work, we have developed several strategies to design and prepare synthetic polymeric materials with selected cues to control cell attachment. To promote neuronal cell adhesion on the surfaces, biocompatible, non-adhesive PEG-based materials were modified with neurotransmitter acetylcholine functionalities to produce hydrogels with a range of porous structures, swollen states, and mechanical strengths. Mice hippocampal cells cultured on the hydrogels showed differences in number, length of processes and exhibited different survival rates, thereby highlighting the importance of chemical composition and structure in biomaterials. Similar strategies were used to prepare polymer brushes to assess how topographical cues influence neuronal cell behaviors. The brushes were prepared using the "grown from" method through surface-initiated atom transfer radical polymerization (SI-ATRP) reactions and further patterned via UV photolithography. Protein absorption tests and hippocampal neuronal cell culture of the brush patterns showed that both protein and neuronal cells can adhere to the patterns and therefore can be guided by the patterns at certain length scales. We also prepared functional polymers to discourage attachment of undesirable cells on the surfaces. For example, we synthesized PEG-perfluorinated alkyl amphiphilic surfactants to modify polystyrene-block-poly(ethylene-ran-butylene)- block-polyisoprene (SEBI or K3) triblock copolymers for marine antifouling/fouling release surface coatings. Initial results showed that the polymer coated surfaces can facilitate removal of Ulva sporelings on the surfaces. In addition, we prepared both bioactive and dual functional biopassive/bioactive antimicrobial coatings based on SEBI polymers. Incubating the polymer coated surfaces with gram-positive bacteria (S. aureus), gram-negative bacteria (E. coli) and marine bacteria (C. marina ) species demonstrated that, unlike biopassive surfaces, the dual functionality polymer coated surfaces can significantly reduce both live and dead cells, without killing the cells in the culture media. The knowledge gained from those studies offers opportunities for further modification and potential applications of those types of polymers in the future.

Human monocyte adhesion and activation on crystalline polymers with different morphology and wettability in vitro.

PubMed

Young, T H; Lin, D T; Chen, L Y

2000-06-15

This study evaluated the effects of crystalline polyamide (Nylon-66), poly(ethylene-co-vinyl alcohol) (PEVA), and poly(vinylidene fluoride) (PVDF) polymers with nonporous and porous morphologies on the ability of monocytes to adhere and subsequently activate to produce IL-1beta, IL-6, and tumor necrosis factor alpha. The results indicated monocyte adhesion and activation on a material might differ to a great extent, depending on the surface morphology and wettability. As the polymer wettability increases, the ability of monocytes to adhere increases but the ability to produce cytokines decreases. Similarly, these polymers, when prepared with porous surfaces, enhance monocyte adhesion but suppress monocyte release of cytokines. Therefore, the hydrophobic PVDF with a nonporous surface stimulates the most activity in adherent monocytes but shows the greatest inhibition of monocyte adhesion when compared with all of the other membranes. In contrast, the hydrophilic Nylon-66, which has a porous surface, is a relatively better substrate for this work. Therefore, monocyte behavior on a biomaterial may be influenced by a specific surface property. Based on this result, we propose that monocyte adhesion is regulated by a different mechanism than monocyte activation. Consequently, the generation of cytokines by monocytes is not proportional to the number of cells adherent to the surface. Copyright 2000 John Wiley & Sons, Inc.

Initial bioadhesion on dental materials as a function of contact time, pH, surface wettability, and isoelectric point.

PubMed

Müller, Christine; Lüders, Anne; Hoth-Hannig, Wiebke; Hannig, Matthias; Ziegler, Christiane

2010-03-16

The adsorption of bovine serum albumin (BSA) on surfaces of dental enamel and of dental materials was investigated by scanning force spectroscopy. This method provides adhesion forces which can be measured as a function of contact time between protein and surface, pH, wettability, and isoelectric point of the surface. Whereas the chosen ceramic and composite materials resemble very well the adhesion on natural enamel, a much stronger adhesion was found for the more hydrophobic surfaces, that is, gold, titanium, poly(methyl methacrylate) (PMMA), and poly(tetrafluoroethylene) (PTFE). On hydrophilic surfaces, adhesion is mainly influenced by the electrostatic forces between protein and surface. However, the conformational change of BSA at pH values above pH 8 has to be taken into account. On the very hydrophobic PTFE surface, the special interface structure between PTFE and water plays an important role which governs BSA adhesion.

Adhesion of liposomes: a quartz crystal microbalance study

NASA Astrophysics Data System (ADS)

Lüthgens, Eike; Herrig, Alexander; Kastl, Katja; Steinem, Claudia; Reiss, Björn; Wegener, Joachim; Pignataro, Bruno; Janshoff, Andreas

2003-11-01

Three different systems are presented, exploring the adhesion of liposomes mediated by electrostatic and lipid-protein interactions as well as molecular recognition of ligand receptor pairs. Liposomes are frequently used to gain insight into the complicated processes involving adhesion and subsequent events such as fusion and fission mainly triggered by specific proteins. We combined liposome technology with the quartz crystal microbalance (QCM) technique as a powerful tool to study the hidden interface between the membrane and functionalized surface. Electrostatic attraction and molecular recognition were employed to bind liposomes to the functionalized quartz crystal. The QCM was used to distinguish between adsorption of vesicles and rupture due to strong adhesive forces. Intact vesicles display viscoelastic behaviour, while planar lipid bilayers as a result of vesicle rupture can be modelled by a thin rigid film. Furthermore, the adhesion of cells was modelled successfully by receptor bearing liposomes. Scanning force microscopy was used to confirm the results obtained by QCM measurements.

Alpha-2 Heremans Schmid Glycoprotein (AHSG) Modulates Signaling Pathways in Head and Neck Squamous Cell Carcinoma Cell Line SQ20B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, Pamela D.; Sakwe, Amos; Koumangoye, Rainelli

2014-02-15

This study was performed to identify the potential role of Alpha-2 Heremans Schmid Glycoprotein (AHSG) in Head and Neck Squamous Cell Carcinoma (HNSCC) tumorigenesis using an HNSCC cell line model. HNSCC cell lines are unique among cancer cell lines, in that they produce endogenous AHSG and do not rely, solely, on AHSG derived from serum. To produce our model, we performed a stable transfection to down-regulate AHSG in the HNSCC cell line SQ20B, resulting in three SQ20B sublines, AH50 with 50% AHSG production, AH20 with 20% AHSG production and EV which is the empty vector control expressing wild-type levels ofmore » AHSG. Utilizing these sublines, we examined the effect of AHSG depletion on cellular adhesion, proliferation, migration and invasion in a serum-free environment. We demonstrated that sublines EV and AH50 adhered to plastic and laminin significantly faster than the AH20 cell line, supporting the previously reported role of exogenous AHSG in cell adhesion. As for proliferative potential, EV had the greatest amount of proliferation with AH50 proliferation significantly diminished. AH20 cells did not proliferate at all. Depletion of AHSG also diminished cellular migration and invasion. TGF-β was examined to determine whether levels of the TGF-β binding AHSG influenced the effect of TGF-β on cell signaling and proliferation. Whereas higher levels of AHSG blunted TGF-β influenced SMAD and ERK signaling, it did not clearly affect proliferation, suggesting that AHSG influences on adhesion, proliferation, invasion and migration are primarily due to its role in adhesion and cell spreading. The previously reported role of AHSG in potentiating metastasis via protecting MMP-9 from autolysis was also supported in this cell line based model system of endogenous AHSG production in HNSCC. Together, these data show that endogenously produced AHSG in an HNSCC cell line, promotes in vitro cellular properties identified as having a role in tumorigenesis. Highlights: • Head and neck squamous cell carcinoma cell lines synthesize and secret AHSG. • AHSG depleted cell lines are significantly inhibited in their ability to proliferate, adhere, migrate, invade and protect MMP-9. • Human AHSG and bovine fetuin-A are functionally equivalent in regards to growth promotion of cancer cell lines.« less

Complete genome sequence of bacteriocin-producing Lactobacillus plantarum KLDS1.0391, a probiotic strain with gastrointestinal tract resistance and adhesion to the intestinal epithelial cells.

PubMed

Jia, Fang-Fang; Zhang, Lu-Ji; Pang, Xue-Hui; Gu, Xin-Xi; Abdelazez, Amro; Liang, Yu; Sun, Si-Rui; Meng, Xiang-Chen

2017-10-01

Lactobacillus plantarum KLDS1.0391 is a probiotic strain isolated from the traditional fermented dairy products and identified to produce bacteriocin against Gram-positive and Gram-negative bacteria. Previous studies showed that the strain has a high resistance to gastrointestinal stress and has a high adhesion ability to the intestinal epithelial cells (Caco-2). We reported the entire genome sequence of this strain, which contains a circular 2,886,607-bp chromosome and three circular plasmids. Genes, which are related to the biosynthesis of bacteriocins, the stress resistance to gastrointestinal tract environment and adhesive performance, were identified. Whole genome sequence of Lactobacillus plantarum KLDS1.0391 will be helpful for its applications in food industry. Copyright © 2017 Elsevier Inc. All rights reserved.

Gas-driven ultrafast reversible switching of super-hydrophobic adhesion on palladium-coated silicon nanowires.

PubMed

Seo, Jungmok; Lee, Soonil; Han, Heetak; Jung, Hwae Bong; Hong, Juree; Song, Giyoung; Cho, Suk Man; Park, Cheolmin; Lee, Wooyoung; Lee, Taeyoon

2013-08-14

A gas-driven ultrafast adhesion switching of water droplets on palladium-coated Si nanowire arrays is demonstrated. By regulating the gas-ambient between the atmosphere and H2 , the super-hydrophobic adhesion is repeatedly switched between water-repellent and water-adhesive. The capability of modulating the super-hydrophobic adhesion on a super-hydrophobic surface with a non-contact mode could be applicable to novel functional lab-on-a-chip platforms. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PAK4 promotes kinase-independent stabilization of RhoU to modulate cell adhesion

PubMed Central

Dart, Anna E.; Box, Gary M.; Court, William; Gale, Madeline E.; Brown, John P.; Pinder, Sarah E.; Eccles, Suzanne A.

2015-01-01

P21-activated kinase 4 (PAK4) is a Cdc42 effector protein thought to regulate cell adhesion disassembly in a kinase-dependent manner. We found that PAK4 expression is significantly higher in high-grade human breast cancer patient samples, whereas depletion of PAK4 modifies cell adhesion dynamics of breast cancer cells. Surprisingly, systematic analysis of PAK4 functionality revealed that PAK4-driven adhesion turnover is neither dependent on Cdc42 binding nor kinase activity. Rather, reduced expression of PAK4 leads to a concomitant loss of RhoU expression. We report that RhoU is targeted for ubiquitination by the Rab40A–Cullin 5 complex and demonstrate that PAK4 protects RhoU from ubiquitination in a kinase-independent manner. Overexpression of RhoU rescues the PAK4 depletion phenotype, whereas loss of RhoU expression reduces cell adhesion turnover and migration. These data support a new kinase-independent mechanism for PAK4 function, where an important role of PAK4 in cellular adhesions is to stabilize RhoU protein levels. Thus, PAK4 and RhoU cooperate to drive adhesion turnover and promote cell migration. PMID:26598620

Glycan-functionalized diamond nanoparticles as potent E. coli anti-adhesives.

PubMed

Barras, Alexandre; Martin, Fernando Ariel; Bande, Omprakash; Baumann, Jean-Sébastien; Ghigo, Jean-Marc; Boukherroub, Rabah; Beloin, Christophe; Siriwardena, Aloysius; Szunerits, Sabine

2013-03-21

Bacterial attachment and subsequent biofilm formation on biotic surfaces or medical devices is an increasing source of infections in clinical settings. A large proportion of these biofilm-related infections are caused by Escherichia coli, a major nosocomial pathogen, in which the major adhesion factor is the FimH adhesin located at the tip of type 1 fimbriae. Inhibition of FimH-mediated adhesion has been identified as an efficient antibiotic-alternative strategy to potentially reduce E. coli-related infections. In this article we demonstrate that nanodiamond particles, covently modified with mannose moieties by a "click" chemistry approach, are able to efficiently inhibit E. coli type 1 fimbriae-mediated adhesion to eukaryotic cells with relative inhibitory potency (RIP) of as high as 9259 (bladder cell adhesion assay), which is unprecedented when compared with RIP values previously reported for alternate multivalent mannose-functionalized nanostructures designed to inhibit E. coli adhesion. Also remarkable is that these novel mannose-modified NDs reduce E. coli biofilm formation, a property previously not observed for multivalent glyco-nanoparticles and rarely demonstrated for other multivalent or monovalent mannose glycans. This work sets the stage for the further evaluation of these novel NDs as an anti-adhesive therapeutic strategy against E. coli-derived infections.

The effects of nanophase ceramic materials on select functions of human mesenchymal stem cells

NASA Astrophysics Data System (ADS)

Dulgar-Tulloch, Aaron Joseph

2005-11-01

Modification of the chemistry and surface topography of nanophase ceramics can provide biomaterial formulations capable of directing the functions of adherent cells. This effect relies on the type, amount, and conformation of adsorbed proteins that mediate the adhesion of mesenchymally-descended lineages. The mechanisms driving this response are not yet well-understood and have not been investigated for human mesenchymal stem cells (HMSCs), a progenitor-lineage critical to orthopaedic biomaterials. The present study addressed these needs by examining the in vitro adhesion, proliferation, and osteogenic differentiation of HMSCs as a function of substrate chemistry and grain size, with particular attention to the protein-mediated mechanisms of cell adhesion. Alumina, titania, and hydroxyapatite substrates were prepared with 1500, 200, 50, and 24 (alumina only) nm grain sizes, and characterized with respect to surface properties, porosity, composition, and phase. Adhesion of HMSCs was dependent upon both chemistry and grain size. Specifically, adhesion on alumina and hydroxyapatite was reduced on 50 and 24 (alumina only) nm surfaces, as compared to 1500 and 200 nm surfaces, while adhesion on titania substrates was independent of grain size. Investigation into the protein-mediated mechanisms of this response identified vitronectin as the dominant adhesive protein, demonstrated random protein distribution across the substrate surface without aggregation or segregation, and confirmed the importance of the type, amount, and conformation of adsorbed proteins in cell adhesion. Minimal cell proliferation was observed on 50 and 24 (alumina only) nm substrates of any chemistry. Furthermore, cell proliferation was up-regulated on 200 nm substrates after 7 days of culture. Osteogenic differentiation was not detected on 50 nm substrates throughout the 28 day culture period. In contrast, osteogenic differentiation was strongly enhanced on 200 nm substrates, occurring approximately 7 days earlier and in greater magnitude than that observed on 1500 nm substrates. In summary, the current study elucidated the chemical and topographical cues necessary to optimize the vitronectin-mediated adhesion, proliferation, and differentiation of human mesenchymal stem cells on ceramic surfaces. These results expand the understanding of surface-mediated cell functions and provide information pertinent to the design of next-generation orthopaedic and tissue engineering biomaterials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamawaki, Hideyuki, E-mail: yamawaki@vmas.kitasato-u.ac.jp; Kameshima, Satoshi; Usui, Tatsuya

Highlights: Black-Right-Pointing-Pointer Chemerin is a novel adipocytokine with almost unknown function in vasculature. Black-Right-Pointing-Pointer Chemerin activates Akt/eNOS/NO pathways in endothelial cells. Black-Right-Pointing-Pointer Chemerin inhibits TNF-{alpha}-induced monocyte adhesion to endothelial cells. Black-Right-Pointing-Pointer Chemerin inhibits TNF-induced VCAM-1 via suppressing NF-{kappa}B and p38 signal. Black-Right-Pointing-Pointer Chemerin is anti-inflammatory through producing NO in vascular endothelium. -- Abstract: Chemerin is a recently identified adipocytokine which plays a role on inflammation and adipocytes metabolism. However, its function in vasculature is largely unknown. We examined the effects of chemerin on vascular endothelial inflammatory states. Treatment of human umbilical vein endothelial cells with chemerin (300 ng/ml, 20 min)more » induced phosphorylation of Akt (Ser473) and endothelial nitric oxide (NO) synthase (eNOS) (Ser1177). Consistently, chemerin increased intracellular cyclic GMP content. Pretreatment with chemerin (1-300 ng/ml, 24 h) significantly inhibited phosphorylation of nuclear factor (NF)-{kappa}B p65 (Ser536) and p38 as well as vascular cell adhesion molecule (VCAM)-1 expression induced by tumor necrosis factor (TNF)-{alpha} (5 ng/ml, 20 min-6 h). Inhibitor of NF-{kappa}B or p38 significantly inhibited the TNF-{alpha}-induced VCAM-1 expression. Chemerin also inhibited TNF-{alpha}-induced VCAM-1 expression in rat isolated aorta. Moreover, chemerin significantly inhibited monocytes adhesion to TNF-{alpha}-stimulated endothelial cells. The inhibitory effect of chemerin on TNF-{alpha}-induced VCAM-1 was reversed by a NOS inhibitor. Conversely, an NO donor, sodium nitroprusside significantly inhibited TNF-{alpha}-induced VCAM-1. The present results for the first time demonstrate that chemerin plays anti-inflammatory roles by preventing TNF-{alpha}-induced VCAM-1 expression and monocytes adhesion in vascular endothelial cells. The effect is mediated via inhibiting activation of NF-{kappa}B and p38 through stimulation of Akt/eNOS signaling and NO production.« less

Uncovering a role for the tail of the Dictyostelium discoideum SadA protein in cell-substrate adhesion.

PubMed

Kowal, Anthony S; Chisholm, Rex L

2011-05-01

Previous work from our laboratory showed that the Dictyostelium discoideum SadA protein plays a central role in cell-substrate adhesion. SadA null cells exhibit a loss of adhesion, a disrupted actin cytoskeleton, and a cytokinesis defect. How SadA mediates these phenotypes is unknown. This work addresses the mechanism of SadA function, demonstrating an important role for the C-terminal cytoplasmic tail in SadA function. We found that a SadA tailless mutant was unable to rescue the sadA adhesion deficiency, and overexpression of the SadA tail domain reduced adhesion in wild-type cells. We also show that SadA is closely associated with the actin cytoskeleton. Mutagenesis studies suggested that four serine residues in the tail, S924/S925 and S940/S941, may regulate association of SadA with the actin cytoskeleton. Glutathione S-transferase pull-down assays identified at least one likely interaction partner of the SadA tail, cortexillin I, a known actin bundling protein. Thus, our data demonstrate an important role for the carboxy-terminal cytoplasmic tail in SadA function and strongly suggest that a phosphorylation event in this tail regulates an interaction with cortexillin I. Based on our data, we propose a model for the function of SadA.

Bio-inspired reversible underwater adhesive.

PubMed

Zhao, Yanhua; Wu, Yang; Wang, Liang; Zhang, Manman; Chen, Xuan; Liu, Minjie; Fan, Jun; Liu, Junqiu; Zhou, Feng; Wang, Zuankai

2017-12-20

The design of smart surfaces with switchable adhesive properties in a wet environment has remained a challenge in adhesion science and materials engineering. Despite intense demands in various industrial applications and exciting progress in mimicking the remarkable wet adhesion through the delicate control of catechol chemistry, polyelectrolyte complex, and supramolecular architectures, the full recapitulation of nature's dynamic function is limited. Here, we show a facile approach to synthesize bioinspired adhesive, which entails the reversible, tunable, and fast regulation of the wet adhesion on diverse surfaces. The smart wet adhesive takes advantage of the host-guest molecular interaction and the adhesive nature of catechol chemistry, as well as the responsive polymer, allowing for screening and activation of the interfacial interaction simply by a local temperature trigger in an on-demand manner. Our work opens up an avenue for the rational design of bioinspired adhesives with performances even beyond nature.

Membrane adhesion and the formation of heterogeneities: biology, biophysics, and biotechnology.

PubMed

Gordon, V D; O'Halloran, T J; Shindell, O

2015-06-28

Membrane adhesion is essential to many vital biological processes. Sites of membrane adhesion are often associated with heterogeneities in the lipid and protein composition of the membrane. These heterogeneities are thought to play functional roles by facilitating interactions between proteins. However, the causal links between membrane adhesion and membrane heterogeneities are not known. Here we survey the state of the field and indicate what we think are understudied areas ripe for development.

Nanotopographical Modulation of Cell Function through Nuclear Deformation

PubMed Central

Wang, Kai; Bruce, Allison; Mezan, Ryan; Kadiyala, Anand; Wang, Liying; Dawson, Jeremy; Rojanasakul, Yon; Yang, Yong

2016-01-01

Although nanotopography has been shown to be a potent modulator of cell behavior, it is unclear how the nanotopographical cue, through focal adhesions, affects the nucleus, eventually influencing cell phenotype and function. Thus, current methods to apply nanotopography to regulate cell behavior are basically empirical. We, herein, engineered nanotopographies of various shapes (gratings and pillars) and dimensions (feature size, spacing and height), and thoroughly investigated cell spreading, focal adhesion organization and nuclear deformation of human primary fibroblasts as the model cell grown on the nanotopographies. We examined the correlation between nuclear deformation and cell functions such as cell proliferation, transfection and extracellular matrix protein type I collagen production. It was found that the nanoscale gratings and pillars could facilitate focal adhesion elongation by providing anchoring sites, and the nanogratings could orient focal adhesions and nuclei along the nanograting direction, depending on not only the feature size but also the spacing of the nanogratings. Compared with continuous nanogratings, discrete nanopillars tended to disrupt the formation and growth of focal adhesions and thus had less profound effects on nuclear deformation. Notably, nuclear volume could be effectively modulated by the height of nanotopography. Further, we demonstrated that cell proliferation, transfection, and type I collagen production were strongly associated with the nuclear volume, indicating that the nucleus serves as a critical mechanosensor for cell regulation. Our study delineated the relationships between focal adhesions, nucleus and cell function and highlighted that the nanotopography could regulate cell phenotype and function by modulating nuclear deformation. This study provides insight into the rational design of nanotopography for new biomaterials and the cell–substrate interfaces of implants and medical devices. PMID:26844365

Materials from Mussel-Inspired Chemistry for Cell and Tissue Engineering Applications.

PubMed

Madhurakkat Perikamana, Sajeesh Kumar; Lee, Jinkyu; Lee, Yu Bin; Shin, Young Min; Lee, Esther J; Mikos, Antonios G; Shin, Heungsoo

2015-09-14

Current advances in biomaterial fabrication techniques have broadened their application in different realms of biomedical engineering, spanning from drug delivery to tissue engineering. The success of biomaterials depends highly on the ability to modulate cell and tissue responses, including cell adhesion, as well as induction of repair and immune processes. Thus, most recent approaches in the field have concentrated on functionalizing biomaterials with different biomolecules intended to evoke cell- and tissue-specific reactions. Marine mussels produce mussel adhesive proteins (MAPs), which help them strongly attach to different surfaces, even under wet conditions in the ocean. Inspired by mussel adhesiveness, scientists discovered that dopamine undergoes self-polymerization at alkaline conditions. This reaction provides a universal coating for metals, polymers, and ceramics, regardless of their chemical and physical properties. Furthermore, this polymerized layer is enriched with catechol groups that enable immobilization of primary amine or thiol-based biomolecules via a simple dipping process. Herein, this review explores the versatile surface modification techniques that have recently been exploited in tissue engineering and summarizes polydopamine polymerization mechanisms, coating process parameters, and effects on substrate properties. A brief discussion of polydopamine-based reactions in the context of engineering various tissue types, including bone, blood vessels, cartilage, nerves, and muscle, is also provided.

Interfacial friction and adhesion of cross-linked polymer thin films swollen with linear chains.

PubMed

Zhang, Qing; Archer, Lynden A

2007-07-03

The preparation and interfacial properties of a new type of tethered, thin-film lubricant coating are presented. These coatings are composed of three components: a dense self-assembled monolayer (SAM) underlayer that presents reactive vinyl groups at its surface; a cross-linked polydimethylsiloxane (PDMS) overlayer that is covalently tethered to the SAM; and free, mobile linear PDMS chains dispersed in the network. We investigate the influence of the molecular weight (Ms) and concentration of the free PDMS chains on the structure and equilibrium swelling properties of the cross-linked films. Using a bead-probe lateral force microscopy measurement technique, we also quantify the interfacial friction and adhesion characteristics of surfaces functionalized with these coatings. We find that both the volume fraction and the molecular weight of free PDMS molecules in the coatings influence their interfacial friction and adhesion properties. For example, the addition of short PDMS chains in dry, cross-linked PDMS thin films yields tethered surface coatings with ultralow friction coefficients (mu = 5.2 x 10(-3)). An analysis based on classical lubrication theory suggests that the reduction in friction force produced by free polymer is a consequence of the gradual separation of asperities on opposing surfaces and the consequent substitution of solid-solid friction by viscous drag of the free polymer chains in the network.

Thermal Alternating Polymer Nanocomposite (TAPNC) Coating Designed to Prevent Aerodynamic Insect Fouling

PubMed Central

Bayer, Ilker S.; Krishnan, K. Ghokulla; Robison, Robert; Loth, Eric; Berry, Douglas H.; Farrell, Thomas E.; Crouch, Jeffrey D.

2016-01-01

Insect residue adhesion to moving surfaces such as turbine blades and aircraft not only causes surface contamination problems but also increases drag on these surfaces. Insect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircraft with laminar-flow surfaces. Hence, certain topographical and chemical features of non-wettable surfaces need to be designed properly for preventing insect residue accumulation on surfaces. In this work, we developed a superhydrophobic coating that is able to maintain negligible levels of insect residue after 100 high speed (50 m/s) insect impact events produced in a wind tunnel. The coating comprises alternating layers of a hydrophobic, perfluorinated acrylic copolymer and hydrophobic surface functional silicon dioxide nanoparticles that are infused into one another by successive thermal treatments. The design of this coating was achieved as a result of various experiments conducted in the wind tunnel by using a series of superhydrophobic surfaces made by the combination of the same polymer and nanoparticles in the form of nanocomposites with varying surface texture and self-cleaning hydrophobicity properties. Moreover, the coating demonstrated acceptable levels of wear abrasion and substrate adhesion resistance against pencil hardness, dry/wet scribed tape peel adhesion and 17.5 kPa Taber linear abraser tests. PMID:27924913

Synergistic Effects of a Calcium Phosphate/Fibronectin Coating on the Adhesion of Periodontal Ligament Stem Cells Onto Decellularized Dental Root Surfaces.

PubMed

Lee, Jung-Seok; Kim, Hyun-Suk; Park, So-Yon; Kim, Tae-Wan; Jung, Jae-Suk; Lee, Jong-Bin; Kim, Chang-Sung

2015-01-01

This study aimed to enhance the attachment of periodontal ligament stem cells (PDLSCs) onto the decellularized dental root surface using surface coating with fibronectin and/or calcium phosphate (CaP) and to evaluate the activity of PDLSCs attached to a coated dental root surface following tooth replantation. PDLSCs were isolated from five dogs, and the other dental roots were used as a scaffold for carrying PDLSCs and then assigned to one of four groups according to whether their surface was coated with CaP, fibronectin, CaP/fibronectin, or left uncoated (control). Fibronectin increased the adhesion of PDLSCs onto dental root surfaces compared to both the control and CaP-coated groups, and simultaneous surface coating with CaP and fibronectin significantly accelerated and increased PDLSC adhesion compared to the fibronectin-only group. On in vivo tooth replantation, functionally oriented periodontal new attachment was observed on the CaP/fibronectin-coated dental roots to which autologous PDLSCs had adhered, while in the control condition, dental root replantation was associated only with root resorption and ankylosis along the entire root length. CaP and fibronectin synergistically enhanced the attachment of PDLSCs onto dental root surfaces, and autologous PDLSCs could produce de novo periodontal new attachment in an experimental in vivo model.

Thermal Alternating Polymer Nanocomposite (TAPNC) Coating Designed to Prevent Aerodynamic Insect Fouling.

PubMed

Bayer, Ilker S; Krishnan, K Ghokulla; Robison, Robert; Loth, Eric; Berry, Douglas H; Farrell, Thomas E; Crouch, Jeffrey D

2016-12-07

Insect residue adhesion to moving surfaces such as turbine blades and aircraft not only causes surface contamination problems but also increases drag on these surfaces. Insect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircraft with laminar-flow surfaces. Hence, certain topographical and chemical features of non-wettable surfaces need to be designed properly for preventing insect residue accumulation on surfaces. In this work, we developed a superhydrophobic coating that is able to maintain negligible levels of insect residue after 100 high speed (50 m/s) insect impact events produced in a wind tunnel. The coating comprises alternating layers of a hydrophobic, perfluorinated acrylic copolymer and hydrophobic surface functional silicon dioxide nanoparticles that are infused into one another by successive thermal treatments. The design of this coating was achieved as a result of various experiments conducted in the wind tunnel by using a series of superhydrophobic surfaces made by the combination of the same polymer and nanoparticles in the form of nanocomposites with varying surface texture and self-cleaning hydrophobicity properties. Moreover, the coating demonstrated acceptable levels of wear abrasion and substrate adhesion resistance against pencil hardness, dry/wet scribed tape peel adhesion and 17.5 kPa Taber linear abraser tests.

Thermal Alternating Polymer Nanocomposite (TAPNC) Coating Designed to Prevent Aerodynamic Insect Fouling

NASA Astrophysics Data System (ADS)

Bayer, Ilker S.; Krishnan, K. Ghokulla; Robison, Robert; Loth, Eric; Berry, Douglas H.; Farrell, Thomas E.; Crouch, Jeffrey D.

2016-12-01

Insect residue adhesion to moving surfaces such as turbine blades and aircraft not only causes surface contamination problems but also increases drag on these surfaces. Insect fouling during takeoff, climb and landing can result in increased drag and fuel consumption for aircraft with laminar-flow surfaces. Hence, certain topographical and chemical features of non-wettable surfaces need to be designed properly for preventing insect residue accumulation on surfaces. In this work, we developed a superhydrophobic coating that is able to maintain negligible levels of insect residue after 100 high speed (50 m/s) insect impact events produced in a wind tunnel. The coating comprises alternating layers of a hydrophobic, perfluorinated acrylic copolymer and hydrophobic surface functional silicon dioxide nanoparticles that are infused into one another by successive thermal treatments. The design of this coating was achieved as a result of various experiments conducted in the wind tunnel by using a series of superhydrophobic surfaces made by the combination of the same polymer and nanoparticles in the form of nanocomposites with varying surface texture and self-cleaning hydrophobicity properties. Moreover, the coating demonstrated acceptable levels of wear abrasion and substrate adhesion resistance against pencil hardness, dry/wet scribed tape peel adhesion and 17.5 kPa Taber linear abraser tests.

Influence of polymeric subcoats on the drug release properties of tablets powder-coated with pre-plasticized Eudragit L 100-55.

PubMed

Sauer, Dorothea; Watts, Alan B; Coots, Lonique B; Zheng, Weijia C; McGinity, James W

2009-02-09

The aim of the study was to investigate the properties of sodium valproate tablets that were dry powder-coated with pre-plasticized Eudragit L 100-55. Polyethylene glycol 3350 (PEG 3350) was used as primer to facilitate initial coating powder adhesion. Solubility parameters were employed to determine the wetting properties of the PEG 3350 primer. Additional PEG 3350 within the powder coating formulation was required to enable powder adhesion to the tablet cores. The application of a subcoat of either Eudragit E PO or Eudragit RL PO facilitated adhesion of the enteric polymer to the tablet cores and reduced the amount PEG 3350 required in the coating formulation. Since reduction of the PEG 3350 content produced less water-vapor permeable films, the enteric coating level necessary to control the drug release was decreased. PEG 3350 and Methocel K4M were incorporated in both Eudragit E PO and Eudragit RL PO subcoating formulations as pore forming agents. The influence of the pore forming excipients on physicochemical properties of free powder-cast films was investigated. The miscibility of the PEG 3350 and Methocel K4M in the film coating was correlated with their ability to function as pore forming agent.

Magnetic Beads Enhance Adhesion of NIH 3T3 Fibroblasts: A Proof-of-Principle In Vitro Study for Implant-Mediated Long-Term Drug Delivery to the Inner Ear

PubMed Central

Aliuos, Pooyan; Schulze, Jennifer; Schomaker, Markus; Reuter, Günter; Stolle, Stefan R. O.; Werner, Darja; Ripken, Tammo; Lenarz, Thomas; Warnecke, Athanasia

2016-01-01

Introduction Long-term drug delivery to the inner ear may be achieved by functionalizing cochlear implant (CI) electrodes with cells providing neuroprotective factors. However, effective strategies in order to coat implant surfaces with cells need to be developed. Our vision is to make benefit of electromagnetic field attracting forces generated by CI electrodes to bind BDNF-secreting cells that are labelled with magnetic beads (MB) onto the electrode surfaces. Thus, the effect of MB-labelling on cell viability and BDNF production were investigated. Materials and Methods Murine NIH 3T3 fibroblasts—genetically modified to produce BDNF—were labelled with MB. Results Atomic force and bright field microscopy illustrated the internalization of MB by fibroblasts after 24 h of cultivation. Labelling cells with MB did not expose cytotoxic effects on fibroblasts and allowed adhesion on magnetic surfaces with sufficient BDNF release. Discussion Our data demonstrate a novel approach for mediating enhanced long-term adhesion of BDNF-secreting fibroblasts on model electrode surfaces for cell-based drug delivery applications in vitro and in vivo. This therapeutic strategy, once transferred to cells suitable for clinical application, may allow the biological modifications of CI surfaces with cells releasing neurotrophic or other factors of interest. PMID:26918945

Are pelvic adhesions associated with pain, physical, emotional and functional characteristics of women presenting with chronic pelvic pain? A cluster analysis.

PubMed

Cheong, Ying; Saran, Mili; Hounslow, James William; Reading, Isabel Claire

2018-01-08

Chronic pelvic pain is a debilitating condition. It is unknown if there is a clinical phenotype for adhesive disorders. This study aimed to determine if the presence or absence, nature, severity and extent of adhesions correlated with demographic and patient reported clinical characteristics of women presenting with CPP. Women undergoing a laparoscopy for the investigation of chronic pelvic pain were recruited prospectively; their pain and phenotypic characteristics were entered into a hierarchical cluster analysis. The groups with differing baseline clinical and operative characteristics in terms of adhesions involvement were analyzed. Sixty two women were recruited where 37 had adhesions. A low correlation was found between women's reported current pain scores and that of most severe (r = 0.34) or average pain experienced (r = 0.44) in the last 6 months. Three main groups of women with CPP were identified: Cluster 1 (n = 35) had moderate severity of pain, with poor average and present pain intensity; Cluster 2 (n = 14) had a long duration of symptoms/diagnosis, the worst current pain and worst physical, emotional and social functions; Cluster 3 (n = 11) had the shortest duration of pain and showed the best evidence of coping with low (good) physical, social and emotional scores. This cluster also had the highest proportion of women with adhesions (82%) compared to 51% in Cluster 1 and 71% in Cluster 2. In this study, we found that there is little or no correlation between patient-reported pain, physical, emotional and functional characteristics scores with the presence or absence of intra-abdominal/pelvic adhesions found during investigative laparoscopy. Most women who had adhesions had the lowest reported current pain scores.

Placental Malaria Induces Variant-Specific Antibodies of the Cytophilic Subtypes Immunoglobulin G1 (IgG1) and IgG3 That Correlate with Adhesion Inhibitory Activity

PubMed Central

Elliott, Salenna R.; Brennan, Amy K.; Beeson, James G.; Tadesse, Eyob; Molyneux, Malcolm E.; Brown, Graham V.; Rogerson, Stephen J.

2005-01-01

Antibodies targeting variant antigens on the surfaces of chondroitin sulfate A (CSA)-binding malaria-infected erythrocytes have been linked to protection against the complications of malaria in pregnancy. We examined the isotype/subtype profiles of antibodies that bound to variant surface antigens expressed by CSA-adherent Plasmodium falciparum in pregnant Malawian women with and without histologically defined placental malaria. Women in their first pregnancy with placental malaria produced significantly greater amounts of immunoglobulin G1 (IgG1) and IgG3 reactive with surface antigens of malaria-infected erythrocytes than uninfected women of the same gravidity. IgG1 and IgG3 levels in infected and control women in later pregnancies were similar to those in infected women in their first pregnancy. Levels of IgG2 and IgG4 were similarly low in infected and uninfected women of all gravidities. IgM that bound to the surface of CSA-adherent P. falciparum occurred in all groups of women and malaria-naïve controls. There was a significant correlation between IgG1 and IgG3 levels, indicating that women usually produced both subtypes. Levels of IgG1 and IgG3 correlated with the ability of serum or plasma to inhibit parasite adhesion to CSA. Taken together, these data suggest that IgG1 and IgG3 dominate the IgG response to placental-type variant surface antigens. They may function by blocking parasite adhesion to placental CSA, but given their cytophilic nature, they might also opsonize malaria-infected erythrocytes for interaction with Fc receptors on phagocytic cells. PMID:16113309

Syndecan-2 is upregulated in colorectal cancer cells through interactions with extracellular matrix produced by stromal fibroblasts.

PubMed

Vicente, Carolina Meloni; Ricci, Ritchelli; Nader, Helena Bonciani; Toma, Leny

2013-05-25

The extracellular matrix (ECM) influences the structure, viability and functions of cells and tissues. Recent evidence indicates that tumor cells and stromal cells interact through direct cell-cell contact, the production of ECM components and the secretion of growth factors. Syndecans are a family of transmembrane heparan sulfate proteoglycans that are involved in cell adhesion, motility, proliferation and differentiation. Syndecan-2 has been found to be highly expressed in colorectal cancer cell lines and appears to be critical for cancer cell behavior. We have examined the effect of stromal fibroblast-produced ECM on the production of proteoglycans by colorectal cancer cell lines. Our results showed that in a highly metastatic colorectal cancer cell line, HCT-116, syndecan-2 expression is enhanced by fibroblast ECM, while the expression of other syndecans decreased. Of the various components of the stromal ECM, fibronectin was the most important in stimulating the increase in syndecan-2 expression. The co-localization of syndecan-2 and fibronectin suggests that these two molecules are involved in the adhesion of HCT-116 cells to the ECM. Additionally, we demonstrated an increase in the expression of integrins alpha-2 and beta-1, in addition to an increase in the expression of phospho-FAK in the presence of fibroblast ECM. Furthermore, blocking syndecan-2 with a specific antibody resulted in a decrease in cell adhesion, migration, and organization of actin filaments. Overall, these results show that interactions between cancer cells and stromal ECM proteins induce significant changes in the behavior of cancer cells. In particular, a shift from the expression of anti-tumorigenic syndecans to the tumorigenic syndecan-2 may have implications in the migratory behavior of highly metastatic tumor cells.

Development of high temperature service polyimide based adhesives for titanium and composite bonding applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayhew, R.T.; Kohli, D.K.

CYTEC Engineered Materials Inc. has developed several adhesives based on LaRC{trademark} PETI-5 Polyimide Resin for bonding titanium and composite substrates. These adhesives are intended for long term service at 177{degrees}C (350{degrees}F) and are processed at 350{degrees}C (660{degrees}F) in conventional autoclaves under 50 psi pressure. Titanium lap shears range from 48.3MPa (7000 psi) at room temperature to 31MPa (4500 psi) at 177{degrees}C (350{degrees}F). Excellent metal-to-metal peels and honeycomb bonding properties are reported for these products. In addition to film adhesive, primer and paste products have been described. Pilot line quantities of several hundred square feet of the film adhesive have beenmore » produced and sampled under the CYTEC designation FM{reg_sign} x5.« less

Bending energy penalty enhances the adhesive strength of functional amyloid curli to surfaces

NASA Astrophysics Data System (ADS)

Zhang, Yao; Wang, Ao; DeBenedictis, Elizabeth P.; Keten, Sinan

2017-11-01

The functional amyloid curli fiber, a major proteinaceous component of biofilm extracellular matrices, plays an important role in biofilm formation and enterobacteriaceae adhesion. Curli nanofibers exhibit exceptional underwater adhesion to various surfaces, have high rigidity and strong tensile mechanical properties, and thus hold great promise in biomaterials. The mechanisms of how curli fibers strongly attach to surfaces and detach under force remain elusive. To investigate curli fiber adhesion to surfaces, we developed a coarse-grained curli fiber model, in which the protein subunit CsgA (curli specific gene A) self-assembles into the fiber. The coarse-grained model yields physiologically relevant and tunable bending rigidity and persistence length. The force-induced desorption of a single curli fiber is examined using coarse-grained modeling and theoretical analysis. We find that the bending energy penalty arising from high persistence length enhances the resistance of the curli fiber against desorption and thus strengthens the adhesion of the curli fiber to surfaces. The CsgA-surface adhesion energy and the curli fiber bending rigidity both play crucial roles in the resistance of curli fiber against desorption from surfaces. To enable the desorption process, the applied peeling force must overcome both the interfacial adhesion energy and the energy barrier for bending the curli fiber at the peeling front. We show that the energy barrier to desorption increases with the interfacial adhesion energy, however, the bending induced failure of a single curli fiber limits the work of adhesion if the proportion of the CsgA-surface adhesion energy to the CsgA-CsgA cohesive energy becomes large. These results illustrate that the optimal adhesion performance of nanofibers is dictated by the interplay between bending, surface energy and cohesive energy. Our model provides timely insight into enterobacteriaceae adhesion mechanisms as well as future designs of engineered curli fiber based adhesives.

Durability of adhesives in plywood

Treesearch

Robert H. Gillespie; Bryan H. River

1976-01-01

Seven different adhesives were evaluated for durability as plywood adhesives by exposing panels and shear-test specimens to weathering at the Madison exposure site for nearly 8 years. Wet-strength loss and wood-failure changes were measured as a function of exposure time. The method of exposure accelerated the degradation that would have resulted from exposure in most...

Poly(ester urea)-Based Adhesives: Improved Deployment and Adhesion by Incorporation of Poly(propylene glycol) Segments.

PubMed

Zhou, Jinjun; Bhagat, Vrushali; Becker, Matthew L

2016-12-14

The adhesive nature of mussels arises from the catechol moiety in the 3,4-dihydroxyphenylalanine (DOPA) amino acid, one of the many proteins that contribute to the unique adhesion properties of mussels. Inspired by these properties, many biomimetic adhesives have been developed over the past few years in an attempt to replace adhesives such as fibrin, cyanoacrylate, and epoxy glues. In the present work, we synthesized ethanol soluble but water insoluble catechol functionalized poly(ester urea) random copolymers that help facilitate delivery and adhesion in wet environments. Poly(propylene glycol) units incorporated into the polymer backbone impart ethanol solubility to these polymers, making them clinically relevant. A catechol to cross-linker ratio of 10:1 with a curing time of 4 h exceeded the performance of commercial fibrin glue (4.8 ± 1.4 kPa) with adhesion strength of 10.6 ± 2.1 kPa. These adhesion strengths are significant with the consideration that the adhesion studies were performed under wet conditions.

N-glycosylation at the SynCAM (synaptic cell adhesion molecule) immunoglobulin interface modulates synaptic adhesion.

PubMed

Fogel, Adam I; Li, Yue; Giza, Joanna; Wang, Qing; Lam, Tukiet T; Modis, Yorgo; Biederer, Thomas

2010-11-05

Select adhesion molecules connect pre- and postsynaptic membranes and organize developing synapses. The regulation of these trans-synaptic interactions is an important neurobiological question. We have previously shown that the synaptic cell adhesion molecules (SynCAMs) 1 and 2 engage in homo- and heterophilic interactions and bridge the synaptic cleft to induce presynaptic terminals. Here, we demonstrate that site-specific N-glycosylation impacts the structure and function of adhesive SynCAM interactions. Through crystallographic analysis of SynCAM 2, we identified within the adhesive interface of its Ig1 domain an N-glycan on residue Asn(60). Structural modeling of the corresponding SynCAM 1 Ig1 domain indicates that its glycosylation sites Asn(70)/Asn(104) flank the binding interface of this domain. Mass spectrometric and mutational studies confirm and characterize the modification of these three sites. These site-specific N-glycans affect SynCAM adhesion yet act in a differential manner. Although glycosylation of SynCAM 2 at Asn(60) reduces adhesion, N-glycans at Asn(70)/Asn(104) of SynCAM 1 increase its interactions. The modification of SynCAM 1 with sialic acids contributes to the glycan-dependent strengthening of its binding. Functionally, N-glycosylation promotes the trans-synaptic interactions of SynCAM 1 and is required for synapse induction. These results demonstrate that N-glycosylation of SynCAM proteins differentially affects their binding interface and implicate post-translational modification as a mechanism to regulate trans-synaptic adhesion.

A novel technique for performing a tongue-lip adhesion-the tongue suspension technique.

PubMed

Mann, Robert J; Neaman, Keith C; Hill, Brian; Bajnrauh, Robert; Martin, Matthew D

2012-01-01

The tongue-lip adhesion has undergone several modifications in an attempt to reduce surgical complications and failure rates. Current techniques rely on the use of a button at the tongue base for suspension, which raises concerns about possible aspiration and interference with oral motor function and bottle-feeding. A new technique for tongue-lip adhesion is proposed that adds a tongue suspension to the standard surgical adhesion. A total of 22 patients with Pierre Robin sequence who received a tongue-lip adhesion via a tongue suspension technique were reviewed. The surgical technique differs from the standard surgical approach by the use of a suture weave across the base of the tongue instead of a standard button to suspend the tongue anteriorly. Average age at the time of tongue-lip adhesion was 13.9 days, with a mean operative time of 88.8 minutes. A marked improvement in postoperative oxygenation was seen in the majority of patients. One dehiscence occurred secondary to a traumatic postoperative extubation, eventually requiring a tracheostomy for subglottic stenosis. A technical innovation for performing a tongue-lip adhesion using a tongue suspension in conjunction with a standard transverse adhesion of the lip is described. The advantage of the tongue-lip adhesion with suspension includes immediate postoperative extubation, as well as removal of concerns regarding button aspiration and possible interference in early developmental oral motor function and bottle-feeding. This technique is reproducible, expanding the craniofacial surgeon's armamentarium for the management of difficult airways in Pierre Robin sequence.

N-Glycosylation at the SynCAM (Synaptic Cell Adhesion Molecule) Immunoglobulin Interface Modulates Synaptic Adhesion*

PubMed Central

Fogel, Adam I.; Li, Yue; Giza, Joanna; Wang, Qing; Lam, TuKiet T.; Modis, Yorgo; Biederer, Thomas

2010-01-01

Select adhesion molecules connect pre- and postsynaptic membranes and organize developing synapses. The regulation of these trans-synaptic interactions is an important neurobiological question. We have previously shown that the synaptic cell adhesion molecules (SynCAMs) 1 and 2 engage in homo- and heterophilic interactions and bridge the synaptic cleft to induce presynaptic terminals. Here, we demonstrate that site-specific N-glycosylation impacts the structure and function of adhesive SynCAM interactions. Through crystallographic analysis of SynCAM 2, we identified within the adhesive interface of its Ig1 domain an N-glycan on residue Asn60. Structural modeling of the corresponding SynCAM 1 Ig1 domain indicates that its glycosylation sites Asn70/Asn104 flank the binding interface of this domain. Mass spectrometric and mutational studies confirm and characterize the modification of these three sites. These site-specific N-glycans affect SynCAM adhesion yet act in a differential manner. Although glycosylation of SynCAM 2 at Asn60 reduces adhesion, N-glycans at Asn70/Asn104 of SynCAM 1 increase its interactions. The modification of SynCAM 1 with sialic acids contributes to the glycan-dependent strengthening of its binding. Functionally, N-glycosylation promotes the trans-synaptic interactions of SynCAM 1 and is required for synapse induction. These results demonstrate that N-glycosylation of SynCAM proteins differentially affects their binding interface and implicate post-translational modification as a mechanism to regulate trans-synaptic adhesion. PMID:20739279

The vanishing limit of the square-well fluid: The adhesive hard-sphere model as a reference system

NASA Astrophysics Data System (ADS)

Largo, J.; Miller, M. A.; Sciortino, F.

2008-04-01

We report a simulation study of the gas-liquid critical point for the square-well potential, for values of well width δ as small as 0.005 times the particle diameter σ. For small δ, the reduced second virial coefficient at the critical point B2*c is found to depend linearly on δ. The observed weak linear dependence is not sufficient to produce any significant observable effect if the critical temperature Tc is estimated via a constant B2*c assumption, due to the highly nonlinear transformation between B2*c and Tc. This explains the previously observed validity of the law of corresponding states. The critical density ρc is also found to be constant when measured in units of the cube of the average distance between two bonded particles (1+0.5δ)σ. The possibility of describing the δ →0 dependence with precise functional forms provides improved accurate estimates of the critical parameters of the adhesive hard-sphere model.

The vanishing limit of the square-well fluid: the adhesive hard-sphere model as a reference system.

PubMed

Largo, J; Miller, M A; Sciortino, F

2008-04-07

We report a simulation study of the gas-liquid critical point for the square-well potential, for values of well width delta as small as 0.005 times the particle diameter sigma. For small delta, the reduced second virial coefficient at the critical point B2*c is found to depend linearly on delta. The observed weak linear dependence is not sufficient to produce any significant observable effect if the critical temperature Tc is estimated via a constant B2*c assumption, due to the highly nonlinear transformation between B2*c and Tc. This explains the previously observed validity of the law of corresponding states. The critical density rho c is also found to be constant when measured in units of the cube of the average distance between two bonded particles (1+0.5 delta)sigma. The possibility of describing the delta-->0 dependence with precise functional forms provides improved accurate estimates of the critical parameters of the adhesive hard-sphere model.

Insufficient cure under the condition of high irradiance and short irradiation time.

PubMed

Feng, Li; Carvalho, Ricardo; Suh, Byoung I

2009-03-01

To investigate if and why a plasma arc curing (PAC) light tends to undercure methacrylate-based resins or resin composites. Model dimethacrylate resins, commercial dental adhesives, and commercial resin composites were cured using a PAC light and a halogen light with the similar radiant exposures but different combinations of irradiance and irradiation time. The degree of double bond conversion (DC) was measured with FTIR spectroscopy and analyzed as a function of radiant exposure. The PAC light produced a lower DC than the halogen light for the model resin with the lowest viscosity and for three of the four adhesives. With a high irradiance, the PAC light could cure three of the four composites as thoroughly as its halogen counterpart. When the irradiance was reduced, however, three composites yielded a lower DC. Insufficient cure by PAC lights or any curing lights with very high irradiance is likely to happen when too short an irradiation time is used. It is because under higher irradiance, the lifetime of free radicals is shorter.

Laminated structures and methods and compositions for producing same

DOEpatents

Fumei, Giancarlo J.; Karabedian, James A.

1977-04-05

Methods for bonding two substrates, one of which is polymeric, which comprise coating the surface of at least one substrate with an adhesive composition comprising a major component which is an adhesive for the first substrate and a minor disperse phase which is a solution of a polymer in a solvent for the polymeric substrate and contacting the coated surface of the one substrate with the surface of the other substrate, together with adhesive compositions useful for joining such substrates, laminates so formed, and articles comprised of such laminates.

Evaluation of high temperature structural adhesives for extended service, phase 5

NASA Technical Reports Server (NTRS)

Hendricks, C. L.; Hill, S. G.; Hale, J. N.; Dumars, W. G.

1987-01-01

The evaluation of 3 experimental polymers from NASA-Langley and a commercially produced polymer from Mitsui Toatsu Chemicals as high temperature structural adhesives is presented. A polyphenylquinoxaline (PPQ), polyimide (STPI/LaRC-2), and a polyarylene ether (PAE-SO2) were evaluated as metal-to-metal adhesives. Lap shear, crack extension, and climbing drum peel specimens were fabricated from all three polymers and tested after thermal, combined thermal/humidity, and stressed hydraulic fluid (Skydrol) exposure. The fourth polymer, LARC-TPI was evaluated as an adhesive for titanium honeycomb sandwich structure. All three experimental polymers performed well as metal-to-metal adhesives from 219 K (-65 F) to 505 K (450 F), including humidity exposure. Structural adhesive strength was also maintained at 505 K for a minimum of 3000 hours. LaRC-TPI was evaluated as a high temperature (505 K) adhesive for titanium honeycomb sandwich structure. The LaRC-TPI bonding process development concentrated on improving the honeycomb core-to-skin bond. The most promising approach of those evaluated combined a LaRC-TPI polymer solution with a semi-crystalline LaRC-TPI powder for adhesive film fabrication and fillet formation.

Adsorption of phenanthrene on activated carbon increases mineralization rate by specific bacteria.

PubMed

Leglize, Pierre; Alain, Saada; Jacques, Berthelin; Corinne, Leyval

2008-03-01

Bioavailability of polycyclic aromatic hydrocarbons (PAH) in soil is affected by PAH sorption to solid phase. We studied the influence of activated carbon (AC) on phenanthrene (PHE) mineralization by five degrading bacterial strains isolated from contaminated soil. PHE adsorption on AC was important and reduced PHE aqueous concentration up to 90%. PHE degradation was improved in the presence of activated carbon with three of the bacterial strains, named NAH1, MATE3 and MATE7, which produced biofilms, whereas it was not improved with the two other ones, which did not produce biofilms, MATE10 and MATE12. Monitoring PHE distribution during incubation showed that aqueous PHE concentration was significantly higher with the biofilm-producing NAH1 than with MATE10. Bacterial adhesion on AC was also investigated. The precoating of AC with PHE increased NAH1 and MATE3 adhesion to the solid surface (>16 and >13%, respectively). Bacterial properties, such as biofilm production and adhesion to AC capacity seemed to be related to their ability to optimize PHE degradation by improving PHE diffusion and reducing diffusion path length.

PAR-2 mediates increased inflammatory cell adhesion and neointima formation following vascular injury in the mouse.

PubMed

Tennant, Gail M; Wadsworth, Roger M; Kennedy, Simon

2008-05-01

Activation of PAR-2 in the vasculature affects vascular tone and adhesion of leukocytes to the endothelium. Since adhesion of leukocytes is increased following vascular injury and is important in determining the extent of neointima formation, we hypothesised that mice lacking PAR-2 may have reduced neointima formation following vascular injury. PAR-2 activating peptides and trypsin induced endothelium-dependent relaxation of mouse carotid artery which was absent in the knockout mouse. Lack of a PAR-2 receptor did not affect lymphocyte adhesion under basal conditions, but reduced the contractile response produced by lymphocytes. Twenty-eight days after denuding injury, vessel contraction to lymphocytes was reduced in both strains while lymphocyte adhesion was significantly greater in PAR-2(+/+) mice compared to the PAR-2 knockout mice. Neointimal area was markedly reduced in the PAR-2 knockout mouse. Our data show that PAR-2 modulates inflammatory cell adhesion when stimulated and in mice lacking the PAR-2 receptor, adhesion to injured vessels is reduced with a consequent reduction in neointima formation.

Bonding Strength Properties of Adhesively-Timber Joint with Thixotropic and Room Temperature Cured Epoxy Based Adhesive Reinforced with Nano- and Micro-particles

NASA Astrophysics Data System (ADS)

Ahmad, Z.; Ansell, M. P.; Smedley, D.

2011-02-01

This research work is concerned with in situ bonded-in timber connection using pultruded rod; where the manufacturing of such joint requires adhesive which can produce thick glue-lines and does not allow any use of pressure and heat. Four types of thixotropic (for ease application) and room temperature cured epoxy based were used namely CB10TSS (regarded as standards adhesive), Nanopox (modification of CB10TSS with addition of nanosilica), Albipox (modification of CB10TSS with addition of liquid rubber) and Timberset (an epoxy-based adhesive with addition of micro-size ceramic particles). The quality of the adhesive bonds was accessed using block shear test in accordance with ASTM D905. The bond strength depends on how good the adhesive wet the timber surface. Therefore the viscosity and contact angle was also measured. The nano- and microfiller additions increased the bond strength significantly. The viscosity correlates well with contact angle measurements where lower viscosities are associated with lower contact angles. However contact angle contradicts with measured strength and wettability.

Hybrid joining of polyamide and hydrogenated acrylonitrile butadiene rubber through heat-resistant functional layer of silane coupling agent

NASA Astrophysics Data System (ADS)

Sang, Jing; Sato, Riku; Aisawa, Sumio; Hirahara, Hidetoshi; Mori, Kunio

2017-08-01

A simple, direct adhesion method was developed to join polyamide (PA6) to hydrogenated acrylonitrile butadiene rubber (HNBR) by grafting a functional layer of a silane coupling agent on plasma functionalized PA6 surfaces. The functional layer of the silane coupling agent was prepared using a self-assembly method, which greatly improved the heat resistance of PA6 from 153 °C up to 325 °C and the resulting PA6/HNBR joints showed excellent adhesion properties with cohesive failure between PA6 and HNBR. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and nanoscale infrared microscopy and chemical imaging (Nano-IR, AFM-IR) were employed to characterize the surfaces and interfaces. The Nano-IR analysis method was employed for the first time to analyze the chemical structures of the adhesion interfaces between different materials and to establish the interface formation mechanism. This study is of significant value for interface research and the study of adhesion between resins and rubbers. There is a promising future for heat-resistant functional layers on resin surfaces, with potential application in fuel hose composite materials for the automotive and aeronautical industries.

Novel dental adhesive with triple benefits of calcium phosphate recharge, protein-repellent and antibacterial functions.

PubMed

Xie, Xianju; Wang, Lin; Xing, Dan; Zhang, Ke; Weir, Michael D; Liu, Huaibing; Bai, Yuxing; Xu, Hockin H K

2017-05-01

A new adhesive containing nanoparticles of amorphous calcium phosphate (NACP) with calcium (Ca) and phosphate (P) ion rechargeability was recently developed; however, it was not antibacterial. The objectives of this study were to: (1) develop a novel adhesive with triple benefits of Ca and P ion recharge, protein-repellent and antibacterial functions via dimethylaminohexadecyl methacrylate (DMAHDM) and 2-methacryloyloxyethyl phosphorylcholine (MPC); and (2) investigate dentin bond strength, protein adsorption, Ca and P ion concentration, microcosm biofilm response and pH properties. MPC, DMAHDM and NACP were mixed into a resin consisting of ethoxylated bisphenol A dimethacrylate (EBPADMA), pyromellitic glycerol dimethacrylate (PMGDM), 2-hydroxyethyl methacrylate (HEMA) and bisphenol A glycidyl dimethacrylate (BisGMA). Protein adsorption was measured using a micro bicinchoninic acid method. A human saliva microcosm biofilm model was tested on resins. Colony-forming units (CFU), live/dead assay, metabolic activity, Ca and P ion concentration and biofilm culture medium pH were determined. The adhesive with 5% MPC+5% DMAHDM+30% NACP inhibited biofilm growth, reducing biofilm CFU by 4 log, compared to control (p<0.05). Dentin shear bond strengths were similar (p>0.1). Biofilm medium became a Ca and P ion reservoir having ion concentration increasing with NACP filler level. The adhesive with 5% MPC+5% DMAHDM+30% NACP maintained a safe pH>6, while commercial adhesive had a cariogenic pH of 4. The new adhesive with triple benefits of Ca and P ion recharge, protein-repellent and antibacterial functions substantially reduced biofilm growth, reducing biofilm CFU by 4 orders of magnitude, and yielding a much higher pH than commercial adhesive. This novel adhesive is promising to protect tooth structures from biofilm acids. The method of using NACP, MPC and DMAHDM is promising for application to other dental materials to combat caries. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Cell adhesion pattern created by OSTE polymers.

PubMed

Liu, Wenjia; Li, Yiyang; Ding, Xianting

2017-04-24

Engineering surfaces with functional polymers is a crucial issue in the field of micro/nanofabrication and cell-material interface studies. For many applications of surface patterning, it does not need cells to attach on the whole surface. Herein, we introduce a novel polymer fabrication protocol of off-stoichiometry thiol-ene (OSTE) polymers to create heterogeneity on the surface by utilizing 3D printing and soft-lithography. By choosing two OSTE polymers with different functional groups, we create a pattern where only parts of the surface can facilitate cell adhesion. We also study the hydrophilic property of OSTE polymers by mixing poly(ethylene glycol) (PEG) directly with pre-polymers and plasma treatments afterwards. Moreover, we investigate the effect of functional groups' excess ratio and hydrophilic property on the cell adhesion ability of OSTE polymers. The results show that the cell adhesion ability of OSTE materials can be tuned within a wide range by the coupling effect of functional groups' excess ratio and hydrophilic property. Meanwhile, by mixing PEG with pre-polymers and undergoing oxygen plasma treatment afterward can significantly improve the hydrophilic property of OSTE polymers.

Scalable and continuous fabrication of bio-inspired dry adhesives with a thermosetting polymer.

PubMed

Lee, Sung Ho; Kim, Sung Woo; Kang, Bong Su; Chang, Pahn-Shick; Kwak, Moon Kyu

2018-04-04

Many research groups have developed unique micro/nano-structured dry adhesives by mimicking the foot of the gecko with the use of molding methods. Through these previous works, polydimethylsiloxane (PDMS) has been developed and become the most commonly used material for making artificial dry adhesives. The material properties of PDMS are well suited for making dry adhesives, such as conformal contacts with almost zero preload, low elastic moduli for stickiness, and easy cleaning with low surface energy. From a performance point of view, dry adhesives made with PDMS can be highly advantageous but are limited by its low productivity, as production takes an average of approximately two hours. Given the low productivity of PDMS, some research groups have developed dry adhesives using UV-curable materials, which are capable of continuous roll-to-roll production processes. However, UV-curable materials were too rigid to produce good adhesion. Thus, we established a PDMS continuous-production system to achieve good productivity and adhesion performance. We designed a thermal roll-imprinting lithography (TRL) system for the continuous production of PDMS microstructures by shortening the curing time by controlling the curing temperature (the production speed is up to 150 mm min-1). Dry adhesives composed of PDMS were fabricated continuously via the TRL system.

Membrane adhesion and the formation of heterogeneities: biology, biophysics, and biotechnology

PubMed Central

Gordon, V. D.; O’Halloran, T.J.; Shindell, O.

2015-01-01

Membrane adhesion is essential to many vital biological processes. Sites of membrane adhesion are often associated with heterogeneities in the lipid and protein composition of the membrane. These heterogeneities are thought to play functional roles by facilitating interactions between proteins. However, the causal links between membrane adhesion and membrane heterogeneities are not known. Here we survey the state of the field and indicate what we think are understudied areas ripe for development. PMID:25866854

Vascular Cell Adhesion Molecule-1 Expression and Signaling During Disease: Regulation by Reactive Oxygen Species and Antioxidants

PubMed Central

Marchese, Michelle E.; Abdala-Valencia, Hiam

2011-01-01

Abstract The endothelium is immunoregulatory in that inhibiting the function of vascular adhesion molecules blocks leukocyte recruitment and thus tissue inflammation. The function of endothelial cells during leukocyte recruitment is regulated by reactive oxygen species (ROS) and antioxidants. In inflammatory sites and lymph nodes, the endothelium is stimulated to express adhesion molecules that mediate leukocyte binding. Upon leukocyte binding, these adhesion molecules activate endothelial cell signal transduction that then alters endothelial cell shape for the opening of passageways through which leukocytes can migrate. If the stimulation of this opening is blocked, inflammation is blocked. In this review, we focus on the endothelial cell adhesion molecule, vascular cell adhesion molecule-1 (VCAM-1). Expression of VCAM-1 is induced on endothelial cells during inflammatory diseases by several mediators, including ROS. Then, VCAM-1 on the endothelium functions as both a scaffold for leukocyte migration and a trigger of endothelial signaling through NADPH oxidase-generated ROS. These ROS induce signals for the opening of intercellular passageways through which leukocytes migrate. In several inflammatory diseases, inflammation is blocked by inhibition of leukocyte binding to VCAM-1 or by inhibition of VCAM-1 signal transduction. VCAM-1 signal transduction and VCAM-1-dependent inflammation are blocked by antioxidants. Thus, VCAM-1 signaling is a target for intervention by pharmacological agents and by antioxidants during inflammatory diseases. This review discusses ROS and antioxidant functions during activation of VCAM-1 expression and VCAM-1 signaling in inflammatory diseases. Antioxid. Redox Signal. 15, 1607–1638. PMID:21050132

On the use of SPM to probe the interplay between polymer surface chemistry and polymer surface mechanics

NASA Astrophysics Data System (ADS)

Brogly, Maurice; Noel, Olivier; Awada, Houssein; Castelein, Gilles

2007-03-01

Adhesive properties of a polymer surface results from the complex contribution of surface chemistry and activation of sliding and dissipating mechanisms within the polymer surface layer. The purpose of this study is to dissociate the different contributions (chemical and mechanical) included in an AFM force-distance curve in order to establish relationships between the surface viscoelastic properties of the polymer, the surface chemistry of functionalized polymer surfaces and the adhesive forces, as determined by C-AFM experiments. Indeed we are interested in the measurements of local attractive or adhesive forces in AFM contact mode, of controlled chemical and mechanical model substrates. In order to investigate the interplay between mechanical or viscoelastic mechanisms and surface chemistry during the tip - polymer contact, we achieved force measurements on model PDMS polymer networks, whose surfaces are chemically controlled with the same functional groups as before (silicon substrates). On the basis of AFM nano-indentation experiments, surface Young moduli have been determined. The results show that the viscoelastic contribution is dominating in the adhesion force measurement. We propose an original model, which express the local adhesion force to the energy dissipated within the contact and the surface properties of the material (thermodynamic work of adhesion). Moreover we show that the dissipation function is related to Mc, the mass between crosslinks of the network.

Wood adhesives : vital for producing most wood products

Treesearch

Charles R. Frihart

2011-01-01

A main route for the efficient utilization of wood resources is to reduce wood to small pieces and then bond them together (Frihart and Hunt 2010). Although humankind has been bonding wood since early Egyptian civilizations, the quality and quantity of bonded wood products has increased dramatically over the past 100 years with the development of new adhesives and...

"Greener" hybrid adhesives composed of urea formaldehyde resin and cottonseed meal for wood based composites

USDA-ARS?s Scientific Manuscript database

Urea formaldehyde (UF) resins are one of the most widely used adhesives in wood based composites. The major concerns of the resin utilization are free formaldehyde release and poor water resistance. As a renewable raw materials, water washed conttonseed meal can be used in wood bonding. To produce “...

The coffee diterpene kahweol inhibits tumor necrosis factor-{alpha}-induced expression of cell adhesion molecules in human endothelial cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Hyung Gyun; Kim, Ji Young; Hwang, Yong Pil

2006-12-15

Endothelial cells produce adhesion molecules after being stimulated with various inflammatory cytokines. These adhesion molecules play an important role in the development of atherogenesis. Recent studies have highlighted the chemoprotective and anti-inflammatory effects of kahweol, a coffee-specific diterpene. This study examined the effects of kahweol on the cytokine-induced monocyte/human endothelial cell interaction, which is a crucial early event in atherogenesis. Kahweol inhibited the adhesion of TNF{alpha}-induced monocytes to endothelial cells and suppressed the TNF{alpha}-induced protein and mRNA expression of the cell adhesion molecules, VCAM-1 and ICAM-1. Furthermore, kahweol inhibited the TNF{alpha}-induced JAK2-PI3K/Akt-NF-{kappa}B activation pathway in these cells. Overall, kahweol hasmore » anti-inflammatory and anti-atherosclerotic activities, which occurs partly by down-regulating the pathway that affects the expression and interaction of the cell adhesion molecules on endothelial cells.« less

Cell behavior on gallium nitride surfaces: peptide affinity attachment versus covalent functionalization.

PubMed

Foster, Corey M; Collazo, Ramon; Sitar, Zlatko; Ivanisevic, Albena

2013-07-02

Gallium nitride is a wide band gap semiconductor that demonstrates a unique set of optical and electrical properties as well as aqueous stability and biocompatibility. This combination of properties makes gallium nitride a strong candidate for use in chemical and biological applications such as sensors and neural interfaces. Molecular modification can be used to enhance the functionality and properties of the gallium nitride surface. Here, gallium nitride surfaces were functionalized with a PC12 cell adhesion promoting peptide using covalent and affinity driven attachment methods. The covalent scheme proceeded by Grignard reaction and olefin metathesis while the affinity driven scheme utilized the recognition peptide isolated through phage display. This study shows that the method of attaching the adhesion peptide influences PC12 cell adhesion and differentiation as measured by cell density and morphological analysis. Covalent attachment promoted monolayer and dispersed cell adhesion while affinity driven attachment promoted multilayer cell agglomeration. Higher cell density was observed on surfaces modified using the recognition peptide. The results suggest that the covalent and affinity driven attachment methods are both suitable for promoting PC12 cell adhesion to the gallium nitride surface, though each method may be preferentially suited for distinct applications.

Method for recovering and using lignin in adhesive resins by extracting demethylated lignin

DOEpatents

Schroeder, Herbert A.

1991-01-01

Lignin, or a lignin derived material, which has been significantly demethylated (e.g., the demethylated lignin found in the raffinate produced as a by-product of dimethyl sulfide production which can be carried out using the spent liquor from wood pulping operations) can be isolated by a process wherein an organic solvent is added to a lignin-containing aqueous solution. The organic solvent is typically a polar, and at least a partially water-immiscible substance such as, for example, ethyl acetate. The resulting lignin-containing aqueous solution/organic solvent mixture is acidified to produce a water layer which is discarded and an organic solvent layer which contains the demethylated lignin. Upon its recovery, the demethylated lignin is preferably dried and stored until it is used (along with an alkali, an aldehyde and an adhesive filler) in compounding an adhesive of the type generally used in the manufacture of plywood.

Characterization of Incorporation the Glass Waste in Adhesive Mortar

NASA Astrophysics Data System (ADS)

Santos, D. P.; Azevedo, A. R. G.; Hespanhol, R. L.; Alexandre, J.

Ehe search for reuse generated waste in urban centers, intending to preserve natural resources, has remained fairly constant, both in context of preventing exploitation of resources as the emplacement of waste on the environment. Glass waste glass created a serious environmental problem, mainly because of inconsistency of its flows. Ehe use of this product as a mineral additive, finely ground, cement replacement and aggregate is a promising direction for recycling. This work aims to study the influence of glass waste from cutting process in adhesive mortar, replacing part of cement. Ehe glass powder is used replacing Portland cement at 10, 15 and 20% by mass. Ehe produced mortars will be evaluated its performance in fresh and hardened states through tests performed in laboratory. Ehe selected feature is indicated by producers of additive and researchers to present good results when used as adhesive mortar.

An in vitro assessment of titanium functionalized with polysaccharides conjugated with vascular endothelial growth factor for enhanced osseointegration and inhibition of bacterial adhesion.

PubMed

Hu, Xuefeng; Neoh, Koon-Gee; Shi, Zhilong; Kang, En-Tang; Poh, Chyekhoon; Wang, Wilson

2010-12-01

The long-term success of orthopedic implants may be compromised by defective osseointegration and bacterial infection. An effective approach to minimize implant failure would be to modify the surface of the implant to make it habitable for bone-forming cells and anti-infective at the same time. In this in vitro study, the surfaces of titanium (Ti) substrates were functionalized by first covalently grafting either dopamine followed by carboxymethyl chitosan (CMCS) or hyaluronic acid-catechol (HAC). Vascular endothelial growth factor (VEGF) was then conjugated to the polysaccharide-grafted surface. Antibacterial assay with Staphylococcus aureus (S. aureus) showed that the polysaccharide-modified substrates significantly decrease bacterial adhesion. The CMCS-functionalized Ti demonstrated better antibacterial property than the HAC-functionalized Ti since CMCS is bactericidal while HA only inhibits the adhesion of bacteria without killing them. Osteoblast attachment, as well as alkaline phosphatase (ALP) activity and calcium deposition were enhanced by the immobilized VEGF on the polysaccharide-grafted Ti. Thus, Ti substrates modified with polysaccharides conjugated with VEGF can promote osteoblast functions and concurrently reduce bacterial adhesion. Since VEGF is also known to enhance angiogenesis, the VEGF-polysaccharide functionalized substrates will have promising applications in the orthopedic field. Copyright © 2010 Elsevier Ltd. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakwe, Amos M., E-mail: asakwe@mmc.edu; Koumangoye, Rainelli; Guillory, Bobby

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 collagenmore » 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.« less

Desmoglein 3 regulates membrane trafficking of cadherins, an implication in cell-cell adhesion.

PubMed

Moftah, Hanan; Dias, Kasuni; Apu, Ehsanul Hoque; Liu, Li; Uttagomol, Jutamas; Bergmeier, Lesley; Kermorgant, Stephanie; Wan, Hong

2017-05-04

E-cadherin mediated cell-cell adhesion plays a critical role in epithelial cell polarization and morphogenesis. Our recent studies suggest that the desmosomal cadherin, desmoglein 3 (Dsg3) cross talks with E-cadherin and regulates its adhesive function in differentiating keratinocytes. However, the underlying mechanism remains not fully elucidated. Since E-cadherin trafficking has been recognized to be a central determinant in cell-cell adhesion and homeostasis we hypothesize that Dsg3 may play a role in regulating E-cadherin trafficking and hence the cell-cell adhesion. Here we investigated this hypothesis in cells with loss of Dsg3 function through RNAi mediated Dsg3 knockdown or the stable expression of the truncated mutant Dsg3ΔC. Our results showed that loss of Dsg3 resulted in compromised cell-cell adhesion and reduction of adherens junction and desmosome protein expression as well as the cortical F-actin formation. As a consequence, cells failed to polarize but instead displayed aberrant cell flattening. Furthermore, retardation of E-cadherin internalization and recycling was consistently observed in these cells during the process of calcium induced junction assembling. In contrast, enhanced cadherin endocytosis was detected in cells with overexpression of Dsg3 compared to control cells. Importantly, this altered cadherin trafficking was found to be coincided with the reduced expression and activity of Rab proteins, including Rab5, Rab7 and Rab11 which are known to be involved in E-cadherin trafficking. Taken together, our findings suggest that Dsg3 functions as a key in cell-cell adhesion through at least a mechanism of regulating E-cadherin membrane trafficking.

Enhanced cell adhesion on bioinert ceramics mediated by the osteogenic cell membrane enzyme alkaline phosphatase.

PubMed

Aminian, Alieh; Shirzadi, Bahareh; Azizi, Zahra; Maedler, Kathrin; Volkmann, Eike; Hildebrand, Nils; Maas, Michael; Treccani, Laura; Rezwan, Kurosch

2016-12-01

Functional bone and dental implant materials are required to guide cell response, offering cues that provide specific instructions to cells at the implant/tissue interface while maintaining full biocompatibility as well as the desired structural requirements and functions. In this work we investigate the influence of covalently immobilized alkaline phosphatase (ALP), an enzyme involved in bone mineralization, on the first contact and initial cell adhesion. To this end, ALP is covalently immobilized by carbodiimide-mediated chemoligation on two highly bioinert ceramics, alpha-alumina (Al2O3) and yttria-stabilized zirconia (Y-TZP) that are well-established for load-bearing applications. The physicochemical surface properties are evaluated by profilometry, zeta potential and water contact angle measurements. The initial cell adhesion of human osteoblasts (HOBs), human osteoblast-like cells (MG-63) and mesenchymal stromal cells (hMSCs) was investigated. Cell adhesion was assessed at serum free condition via quantification of percentage of adherent cells, adhesion area and staining of the focal adhesion protein vinculin. Our findings show that after ALP immobilization, the Al2O3 and Y-TZP surfaces gained a negative charge and their hydrophilicity was increased. In the presence of surface-immobilized ALP, a higher cell adhesion, more pronounced cell spreading and a higher number of focal contact points were found. Thereby, this work gives evidence that surface functionalization with ALP can be utilized to modify inert materials for biological conversion and faster bone regeneration on inert and potentially load-bearing implant materials. Copyright © 2016 Elsevier B.V. All rights reserved.

Adhesion mechanisms of bituminous crack sealant to aggregate and laboratory test development

NASA Astrophysics Data System (ADS)

Hajialiakbari Fini, Elham

Crack sealing is a common pavement maintenance treatment because it extends pavement service life. However, crack sealant often fails prematurely due to a loss of adhesion. Since current test methods are mostly empirical and only provide a qualitative measure of bond strength, they cannot predict sealant adhesive failure accurately. Hence, there is an urgent need for test methods based on bituminous sealant rheology that can better predict sealant field performance. This study introduces three laboratory tests aimed to assess the bond property of hot-poured crack sealant to pavement crack walls. The three tests are designed to serve the respective needs of producers, engineers, and researchers. The first test implements the principle of surface energy to measure the thermodynamic work of adhesion, which is the energy spent in separating the two materials at the interface. The work of adhesion is reported as a measure of material compatibility at an interface. The second test is a direct adhesion test, a mechanical test which is designed to closely resemble both the installation process and the crack expansion due to thermal loading. This test uses the Direct Tension Test (DTT) device. The principle of the test is to apply a tensile force to detach the sealant from its aggregate counterpart. The maximum load, Pmax, and the energy to separation, E, are calculated and reported to indicate interface bonding. The third test implements the principles of fracture mechanics in a pressurized circular blister test. The apparatus is specifically designed to conduct the test for bituminous crack sealant, asphalt binder, or other bitumen-based materials. In this test, a fluid is injected at a constant rate at the interface between the substrate (aggregate or a standard material) and the adhesive (crack sealant) to create a blister. The fluid pressure and blister height are measured as functions of time; the data is used to calculate Interfacial Fracture Energy (IFE), which is a fundamental property that can be used to predict adhesion. The stable interface debonding process makes this test attractive. This test also may be used to estimate the optimum annealing time, and to quantify other interface characteristics, such as the moisture susceptibility of a bond. In addition, the elastic modulus of the sealant and its residual stresses can be determined analytically. While the direct adhesion test is proposed as part of newly-developed performance-based guidelines for the selection of hot-poured crack sealant, the blister test may be used to estimate the optimum annealing time, in addition to IFE determination.

Hyaluronic acid based hydrogel system for soft tissue regeneration and drug delivery

NASA Astrophysics Data System (ADS)

Jha, Amit Kumar

We have developed hyaluronic acid (HA)-based, biomimetic hydrogel matrices that are hierarchically structured, mechanically robust and biologically active. Specifically, HA-based hydrogel particles (HGPs) with controlled sizes, defined porosity, and improved stability were synthesized using different inverse emulsion systems and crosslinking chemistries. The resultant particles either contained residual functional groups or were rendered reactive by subsequent chemical modifications. HA-based doubly crosslinked networks (DXNs) were synthesized via covalent crosslinking of HA HGPs with soluble HA macromers carrying mutually reactive functional groups. These hybrid matrices are hierarchical in nature, consisting of densely crosslinked HGPs integrated in a loosely connected secondary matrix. Their mechanical properties and degradation kinetics can be readily tuned by varying the particle size, functional group density, intra- and interparticle crosslinking. To improve the biological functions of HA HGPs, perlecan domain I (PlnDI), a basement membrane proteoglycan that has strong affinity for various heparin binding growth factors (HBGFs), was successfully conjugated to the particles through the core protein via a flexible poly(ethylene glycol) (PEG) linker. The immobilized PlnDI maintains its ability to bind bone morphogenetic proteins (BMP-2) and modulates its in vitro release. A similar, sustained release of BMP-2 was achieved by encapsulating BMP-2-loaded HGPs within a photocrosslinked HA matrix. When encapsulated in HA DXNs, primary bovine chondrocytes were able to maintain their phenotype, proliferate readily and produce abundant glycosaminoglycan. Finally, cell-adhesive HA DXNs were fabricated by encapsulating gelatin-decorated HA HGPs in a secondary HA matrix. Human MSCs were shown to adhere to the composite matrix through the focal adhesion sites clustered on particle surface. The cell-adhesive composite matrices supported hMSC proliferation and migration into the gels. Human MSCs were undifferentiated during the early time points of culture, however differentiated into osteoblast phenotype after 28 days of culture. In summary, the HA-based hydrogel matrices are hierarchically structured, mechanically robust and enzymatically stable, capable of mediating cellular functions through the spatial and temporal presentation of defined biological cues. These hydrogel systems are promising candidates for soft tissue regeneration.

Co-immobilization of active antibiotics and cell adhesion peptides on calcium based biomaterials.

PubMed

Palchesko, Rachelle N; Buckholtz, Gavin A; Romeo, Jared D; Gawalt, Ellen S

2014-07-01

Two bioactive molecules with unrelated functions, vancomycin and a cell adhesion peptide, were immobilized on the surface of a potential bone scaffold material, calcium aluminum oxide. In order to accomplish immobilization and retain bioactivity three sequential surface functionalization strategies were compared: 1.) vancomycin was chemically immobilized before a cell adhesion peptide (KRSR), 2.) vancomycin was chemically immobilized after KRSR and 3.) vancomycin was adsorbed after binding the cell adhesion peptide. Both molecules remained on the surface and active using all three reaction sequences and after autoclave sterilization based on osteoblast attachment, bacterial turbidity and bacterial zone inhibition test results. However, the second strategy was superior at enhancing osteoblast attachment and significantly decreasing bacterial growth when compared to the other sequences. Copyright © 2014 Elsevier B.V. All rights reserved.

Sickle cell disease biochip: a functional red blood cell adhesion assay for monitoring sickle cell disease

PubMed Central

ALAPAN, YUNUS; KIM, CEONNE; ADHIKARI, ANIMA; GRAY, KAYLA E.; GURKAN-CAVUSOGLU, EVREN; LITTLE, JANE A.; GURKAN, UMUT A.

2016-01-01

Sickle cell disease (SCD) afflicts millions of people worldwide and is associated with considerable morbidity and mortality. Chronic and acute vaso-occlusion are the clinical hallmarks of SCD and can result in pain crisis, widespread organ damage, and early movtality. Even though the molecular underpinnings of SCD were identified more than 60 years ago, there are no molecular or biophysical markers of disease severity that are feasibly measured in the clinic. Abnormal cellular adhesion to vascular endothelium is at the root of vaso-occlusion. However, cellular adhesion is not currently evaluated clinically. Here, we present a clinically applicable microfluidic device (SCD biochip) that allows serial quantitative evaluation of red blood cell (RBC) adhesion to endothelium-associated protein-immobilized microchannels, in a closed and preprocessing-free system. With the SCD biochip, we have analyzed blood samples from more than 100 subjects and have shown associations between the measured RBC adhesion to endothelium-associated proteins (fibronectin and laminin) and individual RBC characteristics, including hemoglobin content, fetal hemoglobin concentration, plasma lactate dehydrogenase level, and reticulocyte count. The SCD biochip is a functional adhesion assay, reflecting quantitative evaluation of RBC adhesion, which could be used at baseline, during crises, relative to various long-term complications, and before and after therapeutic interventions. PMID:27063958

Interactions with nanoscale topography: adhesion quantification and signal transduction in cells of osteogenic and multipotent lineage.

PubMed

Biggs, Manus J P; Richards, R Geoff; Gadegaard, Nikolaj; McMurray, Rebecca J; Affrossman, Stanley; Wilkinson, Chris D W; Oreffo, Richard O C; Dalby, Mathew J

2009-10-01

Polymeric medical devices widely used in orthopedic surgery play key roles in fracture fixation and orthopedic implant design. Topographical modification and surface micro-roughness of these devices regulate cellular adhesion, a process fundamental in the initiation of osteoinduction and osteogenesis. Advances in fabrication techniques have evolved the field of surface modification; in particular, nanotechnology has allowed the development of nanoscale substrates for the investigation into cell-nanofeature interactions. In this study human osteoblasts (HOBs) were cultured on ordered nanoscale pits and random nano "craters" and "islands". Adhesion subtypes were quantified by immunofluorescent microscopy and cell-substrate interactions investigated via immuno-scanning electron microscopy. To investigate the effects of these substrates on cellular function 1.7 k microarray analysis was used to establish gene profiles of enriched STRO-1+ progenitor cell populations cultured on these nanotopographies. Nanotopographies affected the formation of adhesions on experimental substrates. Adhesion formation was prominent on planar control substrates and reduced on nanocrater and nanoisland topographies; nanopits, however, were shown to inhibit directly the formation of large adhesions. STRO-1+ progenitor cells cultured on experimental substrates revealed significant changes in genetic expression. This study implicates nanotopographical modification as a significant modulator of osteoblast adhesion and cellular function in mesenchymal populations.

Nanopatterning of steel by one-step anodization for anti-adhesion of bacteria.

PubMed

Chen, Shiqiang; Li, Yuan; Cheng, Y Frank

2017-07-13

Surface nanopatterning of metals has been an effective technique for improved performance and functionalization. However, it is of great challenge to fabricate nanostructure on carbon steels despite their extensive use and urgent needs to maintain the performance reliability and durability. Here, we report a one-step anodization technique to nanopattern a carbon steel in 50 wt.% NaOH solution for highly effective anti-adhesion by sulphate reducing bacteria (SRB), i.e., Desulfovibrio desulfuricans subsp. desulfuricans (Beijerinck) Kluyver and van Niel. We characterize the morphology, structure, composition, and surface roughness of the nanostructured film formed on the steel as a function of anodizing potential. We quantify the surface hydrophobicity by contact angle measurements, and the SRB adhesion by fluorescent analysis. The optimal anodization potential of 2.0 V is determined for the best performance of anti-adhesion of SRB to the steel, resulting in a 23.5 times of reduction of SRB adhesion compared to bare steel. We discuss the mechanisms for the film formation on the steel during anodization, and the high-performance anti-adhesion of bacteria to nanopatterned steels. Our technique is simple, cost-effective and environment-friendly, providing a promising alternative for industry-scale surface nanopatterning of carbon steels for effective controlling of bacterial adhesion.

Basal Lamina Mimetic Nanofibrous Peptide Networks for Skeletal Myogenesis

NASA Astrophysics Data System (ADS)

Yasa, I. Ceren; Gunduz, Nuray; Kilinc, Murat; Guler, Mustafa O.; Tekinay, Ayse B.

2015-11-01

Extracellular matrix (ECM) is crucial for the coordination and regulation of cell adhesion, recruitment, differentiation and death. Therefore, equilibrium between cell-cell and cell-matrix interactions and matrix-associated signals are important for the normal functioning of cells, as well as for regeneration. In this work, we describe importance of adhesive signals for myoblast cells’ growth and differentiation by generating a novel ECM mimetic peptide nanofiber scaffold system. We show that not only structure but also composition of bioactive signals are important for cell adhesion, growth and differentiation by mimicking the compositional and structural properties of native skeletal muscle basal lamina. We conjugated laminin-derived integrin binding peptide sequence, “IKVAV”, and fibronectin-derived well known adhesive sequence, “RGD”, into peptide nanostructures to provide adhesive and myogenic cues on a nanofibrous morphology. The myogenic and adhesive signals exhibited a synergistic effect on model myoblasts, C2C12 cells. Our results showed that self-assembled peptide nanofibers presenting laminin derived epitopes support adhesion, growth and proliferation of the cells and significantly promote the expression of skeletal muscle-specific marker genes. The functional peptide nanofibers used in this study present a biocompatible and biodegradable microenvironment, which is capable of supporting the growth and differentiation of C2C12 myoblasts into myotubes.

Effect of tetraethoxysilane coating on the improvement of plasma treated polypropylene adhesion

NASA Astrophysics Data System (ADS)

Pantoja, M.; Encinas, N.; Abenojar, J.; Martínez, M. A.

2013-09-01

Polypropylene is one of the most used polymers due to its lightweight and recyclability properties, among others. However, its poor characteristics regarding surface energy and lack of polar functional groups have to be overcome to perform adhesion processes. The main objective of this work is to improve the adhesion behavior of polypropylene by combining atmospheric pressure plasma surface activation and silane adhesion promoter. Tetraethoxysilane hydrolysis and condensation are followed through infrared spectroscopy by attenuated total reflectance in order to set the coating conditions. Contact angle measurements and surface energy calculations as well as infrared and X-ray photoelectron spectroscopy are used to evaluate polymer chemical modifications. Morphological changes are studied through scanning electron and atomic force microscopy. Results show the ability of plasma treatment to create active oxydised functional groups on the polypropylene surface. These groups lead to a proper wetting of the polymer by the silane. Shear strength of single-lap bonding of polypropylene with a polyurethane adhesive suffers a significant improvement when the silane coating is applied on previously plasma activated samples. It has been also demonstrated that the silane curing conditions play a decisive role on the adhesion response. Finally, the stability of the silane solution is tested up to 30 days, yielding diminished but still acceptable adhesion strength values.

Basal Lamina Mimetic Nanofibrous Peptide Networks for Skeletal Myogenesis

PubMed Central

Yasa, I. Ceren; Gunduz, Nuray; Kilinc, Murat; Guler, Mustafa O.; Tekinay, Ayse B.

2015-01-01

Extracellular matrix (ECM) is crucial for the coordination and regulation of cell adhesion, recruitment, differentiation and death. Therefore, equilibrium between cell-cell and cell-matrix interactions and matrix-associated signals are important for the normal functioning of cells, as well as for regeneration. In this work, we describe importance of adhesive signals for myoblast cells’ growth and differentiation by generating a novel ECM mimetic peptide nanofiber scaffold system. We show that not only structure but also composition of bioactive signals are important for cell adhesion, growth and differentiation by mimicking the compositional and structural properties of native skeletal muscle basal lamina. We conjugated laminin-derived integrin binding peptide sequence, “IKVAV”, and fibronectin-derived well known adhesive sequence, “RGD”, into peptide nanostructures to provide adhesive and myogenic cues on a nanofibrous morphology. The myogenic and adhesive signals exhibited a synergistic effect on model myoblasts, C2C12 cells. Our results showed that self-assembled peptide nanofibers presenting laminin derived epitopes support adhesion, growth and proliferation of the cells and significantly promote the expression of skeletal muscle-specific marker genes. The functional peptide nanofibers used in this study present a biocompatible and biodegradable microenvironment, which is capable of supporting the growth and differentiation of C2C12 myoblasts into myotubes. PMID:26555958

Carriage of adhesive Escherichia coli after restorative proctocolectomy and pouch anal anastomosis: relation with functional outcome and inflammation.

PubMed Central

Lobo, A J; Sagar, P M; Rothwell, J; Quirke, P; Godwin, P; Johnston, D; Axon, A T

1993-01-01

Restorative proctocolectomy with pelvic ileal reservoir is a well accepted option for the surgical treatment of ulcerative colitis. Acute pouchitis is a common complication and resembles acute ulcerative colitis. Patients with ulcerative colitis carry Escherichia coli that adhere to epithelial cells and thus this study examined whether acute pouchitis is associated with the carriage of adhesive E coli. E coli isolated from stool samples from 24 patients (median age 34 years, range 16-64; 13 men, 11 women) who had had restorative proctocolectomy with pelvic ileal reservoir were examined by means of the buccal epithelial cell adhesion assay. Patients were studied at a median of 12 months (range 7-21) after operation. Eight of 24 patients had acute pouchitis at the time of study. Adhesive E coli were detected in nine of 24 patients with a pelvic ileal reservoir compared with none of 12 controls (p < 0.05). The buccal epithelial cell adhesion index was inversely related to the degree of acute pouchitis (rs = 0.46, p = 0.024) and to the functional outcome (rs = -0.49, p = 0.022). Carriage of adhesive E coli was not related to the design of the reservoir. By contrast with ulcerative colitis, acute pouchitis is not associated with the carriage of adhesive E coli. PMID:8244105

Functional characterization of human pluripotent stem cell-derived arterial endothelial cells.

PubMed

Zhang, Jue; Chu, Li-Fang; Hou, Zhonggang; Schwartz, Michael P; Hacker, Timothy; Vickerman, Vernella; Swanson, Scott; Leng, Ning; Nguyen, Bao Kim; Elwell, Angela; Bolin, Jennifer; Brown, Matthew E; Stewart, Ron; Burlingham, William J; Murphy, William L; Thomson, James A

2017-07-25

Here, we report the derivation of arterial endothelial cells from human pluripotent stem cells that exhibit arterial-specific functions in vitro and in vivo. We combine single-cell RNA sequencing of embryonic mouse endothelial cells with an EFNB2-tdTomato/EPHB4-EGFP dual reporter human embryonic stem cell line to identify factors that regulate arterial endothelial cell specification. The resulting xeno-free protocol produces cells with gene expression profiles, oxygen consumption rates, nitric oxide production levels, shear stress responses, and TNFα-induced leukocyte adhesion rates characteristic of arterial endothelial cells. Arterial endothelial cells were robustly generated from multiple human embryonic and induced pluripotent stem cell lines and have potential applications for both disease modeling and regenerative medicine.

Echinoderm adhesive secretions: from experimental characterization to biotechnological applications.

PubMed

Flammang, P; Santos, R; Haesaerts, D

2005-01-01

Adhesion is a way of life in echinoderms. Indeed, all the species belonging to this phylum use adhesive secretions extensively for various vital functions. According to the species or to the developmental stage considered, different adhesive systems may be recognized. (1) The tube feet or podia are organs involved in attachment to the substratum, locomotion, feeding or burrowing. Their temporary adhesion relies on a duo-gland adhesive system resorting to both adhesive and de-adhesive secretions. (2) The larval adhesive organs allow temporary attachment of larvae during settlement and strong fixation during metamorphosis. (3) The Cuvierian tubules are sticky defence organs occurring in some holothuroid species. Their efficacy is based on the instantaneous release of a quick-setting adhesive. All these systems rely on different types of adhesion and therefore differ in the way they operate, in their structure and in the composition of their adhesive. In addition to fundamental interests in echinoderm bioadhesives, a substantial impetus behind understanding these adhesives are the potential technological applications that can be derived from their knowledge. These applications cover two broad fields of applied research: design of water-resistant adhesives and development of new antifouling strategies. In this context, echinoderm adhesives could offer novel features or performance characteristics for biotechnological applications. For example, the rapidly attaching adhesive of Cuvierian tubules, the releasable adhesive of tube feet or the powerful adhesive of asteroid larvae could each be useful to address particular bioadhesion problems.

Uncovering a Role for the Tail of the Dictyostelium discoideum SadA Protein in Cell-Substrate Adhesion ▿ †

PubMed Central

Kowal, Anthony S.; Chisholm, Rex L.

2011-01-01

Previous work from our laboratory showed that the Dictyostelium discoideum SadA protein plays a central role in cell-substrate adhesion. SadA null cells exhibit a loss of adhesion, a disrupted actin cytoskeleton, and a cytokinesis defect. How SadA mediates these phenotypes is unknown. This work addresses the mechanism of SadA function, demonstrating an important role for the C-terminal cytoplasmic tail in SadA function. We found that a SadA tailless mutant was unable to rescue the sadA adhesion deficiency, and overexpression of the SadA tail domain reduced adhesion in wild-type cells. We also show that SadA is closely associated with the actin cytoskeleton. Mutagenesis studies suggested that four serine residues in the tail, S924/S925 and S940/S941, may regulate association of SadA with the actin cytoskeleton. Glutathione S-transferase pull-down assays identified at least one likely interaction partner of the SadA tail, cortexillin I, a known actin bundling protein. Thus, our data demonstrate an important role for the carboxy-terminal cytoplasmic tail in SadA function and strongly suggest that a phosphorylation event in this tail regulates an interaction with cortexillin I. Based on our data, we propose a model for the function of SadA. PMID:21441344

Bench to Bedside and Back Again: Molecular Mechanisms of α-Catenin Function and Roles in Tumorigenesis

PubMed Central

Benjamin, Jacqueline M.; Nelson, W. James

2009-01-01

The cadherin/catenin complex, comprised of E-cadherin, β-catenin and α-catenin, is essential for initiating cell-cell adhesion, establishing cellular polarity and maintaining tissue organization. Disruption or loss of the cadherin/catenin complex is common in cancer. As the primary cell-cell adhesion protein in epithelial cells, E-cadherin has long been studied in cancer progression. Similarly, additional roles for β-catenin in the Wnt signaling pathway has led to many studies of the role of β-catenin in cancer. Alpha-catenin, in contrast, has received less attention. However, recent data demonstrate novel functions for α-catenin in regulating the actin cytoskeleton and cell-cell adhesion, which when perturbed could contribute to cancer progression. In this review, we use cancer data to evaluate molecular models of α-catenin function, from the canonical role of α-catenin in cell-cell adhesion to non-canonical roles identified following conditional α-catenin deletion. This analysis identifies α-catenin as a prognostic factor in cancer progression. PMID:17945508

Structure, Function, and Assembly of Type 1 Fimbriae

NASA Astrophysics Data System (ADS)

Knight, Stefan D.; Bouckaert, Julie

Bacterial infections constitute a major global health problem, acutely accentuated by the rapid spread of antibiotic resistant bacterial strains. The widespread need for bacteria to attach - adhere - to target cells before they can initiate an infection may be used to advantage by targeting the bacterial adhesion tools such as pili and fimbriae for development of novel anti-bacterial vaccines and drugs. Type 1 fimbriae are widely expressed by Escherichia coli. and are used by uropathogenic strains to mediate attachment to specific niches in the urinary tract. These fimbriae belong to a class of fibrillar adhesion organelles assembled through the chaperone/usher pathway, one of the terminal branches of the general secretion pathway in Gram-negative bacteria. Our understanding of the assembly, structure and function of these structures has evolved significantly over the last decade. Here, we summarize current understanding of the function and biogenesis of fibrillar adhesion organelles, and provide some examples of recent progress towards interfering with bacterial adhesion as a means to prevent infection.

Plant-derived micronutrients suppress monocyte adhesion to cultured human aortic endothelial cell layer by modulating its extracellular matrix composition.

PubMed

Ivanov, Vadim; Ivanova, Svetlana; Kalinovsky, Tatiana; Niedzwiecki, Aleksandra; Rath, Matthias

2008-07-01

Monocyte adhesion to endothelium plays an important role in atherosclerosis. We investigated the effects of micronutrients on monocyte-binding properties of extracellular matrix (ECM) produced by human aortic endothelial cells (AoEC). Confluent cultures of AoEC were exposed to ascorbic acid, quercetin, gotu kola extract (10% asiatic acid), green tea extract (40% epigallocatechin gallate), or a mixture of these micronutrients for 48 hours. AoEC-produced ECM was exposed by differential treatment. U937 monocyte adhesion was assayed by fluorescence. ECM composition was assayed immunochemically and with radiolabeled metabolic precursors. AoEC exposure to micronutrients reduced ECM capacity to bind monocytes in a dose-dependent manner. This effect was accompanied by profound changes in the ECM composition. Correlation analysis revealed that changes in monocyte adhesion to ECM had the strongest positive correlation with ECM content for laminin (CC = 0.9681, P < 0.01), followed by fibronectin, collagens type III, I, and IV, biglycan, heparan sulfate, and elastin. The strongest negative correlation was with chondroitin sulfate (CC = -0.9623, P < 0.01), followed by perlecan and versican. Individual micronutrients had diverse effects on ECM composition and binding properties, and their mixture was the most effective treatment. In conclusion, micronutrient-dependent reduction of monocyte adhesion to endothelium is partly mediated through specific modulation of ECM composition and properties.

[Influence of slime production and adhesion of Candida sp. on biofilm formation].

PubMed

Ciok-Pater, Emilia; Smolak, Przemysław; Wróblewska, Joanna; Gospodarek, Eugenia

2011-01-01

The increase of fungal infections in recent years is connected with the progress in medicine. The vast usage of biomaterials is an inseparable element of contemporary medicine but it also leads to development of infections. Yeast-like fungi Candida albicans are still the main pathogen of candidiasis. The ability to slime production and adhesion to polystyrene of Candida sp. on different surfaces can cause to form biofilm on surfaces of biomaterials used in production of catheters, drains and prosthesis. The aim of the study was to evaluate the influence of slime production and adhesion to polystyrene, of Candida sp. on biofilm formation on different biomaterials. 50 strains of Candida sp. were examined. They isolated from ill to Clinics of Anesthesiology and Intensive Therapy University Hospital No 1 of dr. A. Jurasza in Bydgoszcz. The ability to slime production was evaluated by Christensen method in modification Davenport and Branchini methods. The adhesion to polystyrene was evaluated by Richards et el method. The ability to produce biofilm biomaterials by the studied fungi was measured after 72 hours of incubation at 37 degrees C on different biomaterials. Yeast-like fungi Candida sp. fabricating slime and adhesion forming frequently biofilm on surface researched of biomaterials. Influence of chosen biological specificity ascertain on the ability to produce biofilm on surfaces of siliconized latex and polyvinylchloride.

A pectin-honey hydrogel prevents postoperative intraperitoneal adhesions in a rat model.

PubMed

Giusto, Gessica; Vercelli, Cristina; Iussich, Selina; Audisio, Andrea; Morello, Emanuela; Odore, Rosangela; Gandini, Marco

2017-02-17

Adhesions are a common postoperative surgical complication. Liquid honey has been used intraperitoneally to reduce the incidence of these adhesions. However, solid barriers are considered more effective than liquids in decreasing postoperative intra-abdominal adhesion formation; therefore, a new pectin-honey hydrogel (PHH) was produced and its effectiveness was evaluated in a rat cecal abrasion model. Standardized cecal/peritoneal abrasion was performed through laparotomy in 48 adult Sprague-Dawley rats to induce peritoneal adhesion formation. Rats were randomly assigned to a control (C) and treatment (T) group. In group T, PHHs were placed between the injured peritoneum and cecum. Animals were euthanized on day 15 after surgery. Adhesions were evaluated macroscopically and adhesion scores were recorded and compared between the two groups. Inflammation, fibrosis, and neovascularization were histologically graded and compared between the groups. In group C, 17 of 24 (70.8%) animals developed adhesions between the cecum and peritoneum, while in group T only 5 of 24 (20.8%) did (p = 0.0012). In group C, one rat had an adhesion score of 3, sixteen had scores of 2, and seven rats had scores of 0. In group T, four rats had adhesion scores of 2, one rat had an adhesion score of 1 and nineteen have score 0 (p = 0.0003). Significantly lower grades of inflammation, fibrosis, and neovascularization were seen in group T (p = 0.006, p = 0.001, p = 0.002, respectively). PHH is a novel absorbable barrier that is effective in preventing intra-abdominal adhesions in a cecal abrasion model in rats.

Reelin promotes the adhesion and drug resistance of multiple myeloma cells via integrin β1 signaling and STAT3

PubMed Central

Lv, Meng; Liang, Xiaodong; Dai, Hui; Qin, Xiaodan; Zhang, Yan; Hao, Jie; Sun, Xiuyuan; Yin, Yanhui; Huang, Xiaojun; Zhang, Jun; Lu, Jin; Ge, Qing

2016-01-01

Reelin is an extracellular matrix (ECM) protein that is essential for neuron migration and positioning. The expression of reelin in multiple myeloma (MM) cells and its association with cell adhesion and survival were investigated. Overexpression, siRNA knockdown, and the addition of recombinant protein of reelin were used to examine the function of reelin in MM cells. Clinically, high expression of reelin was negatively associated with progression-free survival and overall survival. Functionally, reelin promoted the adhesion of MM cells to fibronectin via activation of α5β1 integrin. The resulting phosphorylation of Focal Adhesion Kinase (FAK) led to the activation of Src/Syk/STAT3 and Akt, crucial signaling molecules involved in enhancing cell adhesion and protecting cells from drug-induced cell apoptosis. These findings indicate reelin's important role in the activation of integrin-β1 and STAT3/Akt pathways in multiple myeloma and highlight the therapeutic potential of targeting reelin/integrin/FAK axis. PMID:26848618

Reelin promotes the adhesion and drug resistance of multiple myeloma cells via integrin β1 signaling and STAT3.

PubMed

Lin, Liang; Yan, Fan; Zhao, Dandan; Lv, Meng; Liang, Xiaodong; Dai, Hui; Qin, Xiaodan; Zhang, Yan; Hao, Jie; Sun, Xiuyuan; Yin, Yanhui; Huang, Xiaojun; Zhang, Jun; Lu, Jin; Ge, Qing

2016-03-01

Reelin is an extracellular matrix (ECM) protein that is essential for neuron migration and positioning. The expression of reelin in multiple myeloma (MM) cells and its association with cell adhesion and survival were investigated. Overexpression, siRNA knockdown, and the addition of recombinant protein of reelin were used to examine the function of reelin in MM cells. Clinically, high expression of reelin was negatively associated with progression-free survival and overall survival. Functionally, reelin promoted the adhesion of MM cells to fibronectin via activation of α5β1 integrin. The resulting phosphorylation of Focal Adhesion Kinase (FAK) led to the activation of Src/Syk/STAT3 and Akt, crucial signaling molecules involved in enhancing cell adhesion and protecting cells from drug-induced cell apoptosis. These findings indicate reelin's important role in the activation of integrin-β1 and STAT3/Akt pathways in multiple myeloma and highlight the therapeutic potential of targeting reelin/integrin/FAK axis.

Adhesion mechanisms in embryogenesis and in cancer invasion and metastasis.

PubMed

Thiery, J P; Boyer, B; Tucker, G; Gavrilovic, J; Valles, A M

1988-01-01

Cell-substratum and cell-cell adhesion mechanisms contribute to the development of animal form. The adhesive status of embryonic cells has been analysed during epithelial-mesenchymal cell interconversion and in cell migrations. Clear-cut examples of the modulation of cell adhesion molecules (CAMs) have been described at critical periods of morphogenesis. In chick embryos the three primary CAMs (N-CAM. L-CAM and N-cadherin) present early in embryogenesis are expressed later in a defined pattern during morphogenesis and histogenesis. The axial mesoderm derived from gastrulating cells expresses increasing amounts of N-cadherin and N-CAM. During metamerization these two adhesion molecules become abundant at somitic cell surfaces. Both CAMs are functional in an in vitro aggregation assay; however, the calcium-dependent adhesion molecule N-cadherin is more sensitive to perturbation by specific antibodies. Neural crest cells which separate from the neural epithelium lose their primary CAMs in a defined time-sequence. Adhesion to fibronectins via specific surface receptors becomes a predominant interaction during the migratory process, while some primary and secondary CAMs are expressed de novo during the ontogeny of the peripheral nervous system. In vitro, different fibronectin functional domains have been identified in the attachment, spreading and migration of neural crest cells. The fibronectin receptors which transduce the adhesive signals play a key role in the control of cell movement. All these results have prompted us to examine whether similar mechanisms operate in carcinoma cell invasion and metastasis. In vitro, rat bladder transitional carcinoma cells convert reversibly into invasive mesenchymal cells. A rapid modulation of adhesive properties is found during the epithelial-mesenchymal carcinoma cell interconversion. The different model systems analysed demonstrate that a limited repertoire of adhesion molecules, expressed in a well-defined spatiotemporal pattern, is involved in tissue formation and in key processes of tumour spread.

Adhesion, invasion and evasion: the many functions of the surface proteins of Staphylococcus aureus

PubMed Central

Foster, Timothy J.; Geoghegan, Joan A.; Ganesh, Vannakambadi K.; Höök, Magnus

2014-01-01

Staphylococcus aureus is an important opportunistic pathogen and persistently colonizes about 20% of the human population. Its surface is ‘decorated’ with proteins that are covalently anchored to the cell wall peptidoglycan. Structural and functional analysis has identified four distinct classes of surface proteins, of which microbial surface component recognizing adhesive matrix molecules (MSCRAMMs) are the largest class. These surface proteins have numerous functions, including adhesion to and invasion of host cells and tissues, evasion of immune responses and biofilm formation. Thus, cell wall-anchored proteins are essential virulence factors for the survival of S. aureus in the commensal state and during invasive infections, and targeting them with vaccines could combat S. aureus infections. PMID:24336184

Desmosomes in acquired disease

PubMed Central

Stahley, Sara N.; Kowalczyk, Andrew P.

2015-01-01

Desmosomes are cell-cell junctions that mediate adhesion and couple the intermediate filament cytoskeleton to sites of cell-cell contact. This architectural arrangement functions to integrate adhesion and cytoskeletal elements of adjacent cells. The importance of this robust adhesion system is evident in numerous human diseases, both inherited and acquired, that occur when desmosome function is compromised. This review focuses on autoimmune and infectious diseases that impair desmosome function. In addition, we discuss emerging evidence that desmosomal genes are often misregulated in cancer. The emphasis of our discussion is placed on how human diseases inform our understanding of basic desmosome biology, and in turn, how fundamental advances in the cell biology of desmosomes may lead to new treatments for acquired diseases of the desmosome. PMID:25795143

Evaluation of polyethylene glycol/polylactic acid films in the prevention of adhesions in the rabbit adhesion formation and reformation sidewall models.

PubMed

Rodgers, K; Cohn, D; Hotovely, A; Pines, E; Diamond, M P; diZerega, G

1998-03-01

To assess the efficacy of bioresorbable films consisting of various polyethylene glycol 6000 and polylactic acid block copolymers on the formation and reformation of adhesions in rabbit models of adhesion development between the sidewall to the adjacent cecum and bowel. The composition of the different polymers was expressed by the number of monomeric units in the block, namely, ethylene oxide (EO) and lactic acid (LA), respectively. Studies of the efficacy of EO/LA films were conducted in rabbit sidewall adhesion formation studies in the presence and absence of blood and in rabbit adhesion reformation studies. REPEL (Life Medical Sciences, Edison, NJ), a film of EO/LA ratio 3.0 manufactured under commercial conditions, was also tested in these animal models. University-based laboratory. New Zealand white rabbits. Placement of films of various EO/LA ratios at the site of injury to the parietal peritoneum. Adhesion formation and reformation. Films of various EO/LA ratios, Seprafilm (Genzyme, Cambridge, MA) and Interceed (Johnson and Johnson Medical, Arlington, TX) placed over an area of excised sidewall at the time of initial injury were highly efficacious in the prevention of adhesion formation. A film of EO/LA ratio 3.7, in contrast with Interceed, was also shown to maintain maximal efficacy in the reduction of adhesion formation in the presence of blood. Further, a film of EO/LA ratio 3.0 produced under commercial conditions, REPEL, was highly efficacious in reducing adhesion development in the rabbit models of adhesion and reformation. These studies suggest that bioresorbable EO/LA films reduced adhesion development in rabbit models of adhesion formation and reformation.

Formaldehyde emissions from ULEF- and NAF-bonded commercial hardwood plywood as influenced by temperature and relative humidity

Treesearch

Charles R. Frihart; James M. Wescott; Michael J. Birkeland; Kyle M. Gonner

2010-01-01

It is well documented in the literature that temperature and humidity can influence formaldehyde emissions from composite panels that are produced using urea-formaldehyde (UF) adhesives. This work investigates the effect of temperature and humidity on newer, ultra-low emitting formaldehyde urea formaldehyde (ULEF-UF) and no-added formaldehyde (NAF) adhesives. A...

Information Sources on Scientific Research Related to the Preservation of Books, Paper, and Adhesives. Directory.

ERIC Educational Resources Information Center

Commission on Preservation and Access, Washington, DC.

Produced as part of an effort by the Commission on Preservation and Access to assist with the formation of a preservation research agenda, this report contains: (1) a directory of laboratories and organizations working in the four specific areas of concern in preservation--books, paper, adhesives, and mold; (2) directories of indexes, abstracts,…

Preformed amide-containing biopolymer for improving the environmental performance of synthesized urea–formaldehyde in agro-fiber composites

Treesearch

Altaf H. Basta; Houssni El-Saied; Jerrold E. Winandy; Ronald Sabo

2011-01-01

Investigations have continued for production high performance agro-based composites using environmentally acceptable approaches. This study examines the role of adding amide-containing biopolymers during synthesis of urea–formaldehyde (UF) on properties of adhesive produced, especially its adhesion potential. The environmental performance of UF-resin synthesized in the...

Lap shear strength and healing capability of self-healing adhesive containing epoxy/mercaptan microcapsules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghazali, Habibah; Ye, Lin; Zhang, Ming-Qiu

The aim of this work is to develop a self-healing polymeric adhesive formulation with epoxy/mercaptan microcapsules. Epoxy/mercaptan microcapsules were dispersed into a commercialize two-part epoxy adhesive for developing self-healing epoxy adhesive. The influence of different content of microcapsules on the shear strength and healing capability of epoxy adhesive were investigated using single-lap-joints with average thickness of adhesive layer of about 180 µm. This self-healing adhesive was used in bonding of 5000 series aluminum alloys adherents after mechanical and alkaline cleaning surface treatment. The adhesion strength was measured and presented as function of microcapsules loading. The results indicated that the virgin lapmore » shear strength was increased by about 26% with addition of 3 wt% of self-healing microcapsules. 12% to 28% recovery of the shear strength is achieved after self-healing depending on the microcapsules content. Scanning electron microscopy was used to study fracture surface of the joints. The self-healing adhesives exhibit recovery of both cohesion and adhesion properties with room temperature healing.« less

Tuning cell adhesion by direct nanostructuring silicon into cell repulsive/adhesive patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Premnath, Priyatha, E-mail: priyatha.premnath@ryerson.ca; Tavangar, Amirhossein, E-mail: atavanga@ryerson.ca; Tan, Bo, E-mail: tanbo@ryerson.ca

2015-09-10

Developing platforms that allow tuning cell functionality through incorporating physical, chemical, or mechanical cues onto the material surfaces is one of the key challenges in research in the field of biomaterials. In this respect, various approaches have been proposed and numerous structures have been developed on a variety of materials. Most of these approaches, however, demand a multistep process or post-chemical treatment. Therefore, a simple approach would be desirable to develop bio-functionalized platforms for effectively modulating cell adhesion and consequently programming cell functionality without requiring any chemical or biological surface treatment. This study introduces a versatile yet simple laser approachmore » to structure silicon (Si) chips into cytophobic/cytophilic patterns in order to modulate cell adhesion and proliferation. These patterns are fabricated on platforms through direct laser processing of Si substrates, which renders a desired computer-generated configuration into patterns. We investigate the morphology, chemistry, and wettability of the platform surfaces. Subsequently, we study the functionality of the fabricated platforms on modulating cervical cancer cells (HeLa) behaviour. The results from in vitro studies suggest that the nanostructures efficiently repel HeLa cells and drive them to migrate onto untreated sites. The study of the morphology of the cells reveals that cells evade the cytophobic area by bending and changing direction. Additionally, cell patterning, cell directionality, cell channelling, and cell trapping are achieved by developing different platforms with specific patterns. The flexibility and controllability of this approach to effectively structure Si substrates to cell-repulsive and cell-adhesive patterns offer perceptible outlook for developing bio-functionalized platforms for a variety of biomedical devices. Moreover, this approach could pave the way for developing anti-cancer platforms that selectively repel cancer cells while favoring the adhesion of normal cells. - Highlights: • Si platforms with cytophobic/philic patterns were developed to program cell growth. • Both nanotopography and chemistry contributed to the cytophobic property. • Cytophobic zones efficiently repel and drive HeLa cells to migrate to adhesive sites. • The approach enables cell patterning, directionality, channelling, and trapping. • This approach paves the way for developing anti-cancer platforms.« less

The effects on tensile, shear, and adhesive mechanical properties when recycled epoxy/fiberglass is used as an alternative for glass microballoons in fiberglass foam core sandwiches

NASA Astrophysics Data System (ADS)

Wilson, Dru Matthew

The problem of this study was to determine whether fiberglass foam core sandwiches made with recycled epoxy/fiberglass have equal or better flatwise tension, shear, and peel (adhesion) mechanical properties when compared with composite sandwiches made with industry standard glass microballoons. Recycling epoxy/fiberglass could save money by: (1) reusing cured composite materials, (2) consuming less virgin composite materials, (3) spending less on transportation and disposing of unusable composites, and (4) possibly enabling companies to sell their recycled composite powder to other manufacturers. This study used three mechanical property tests, which included: flatwise tensile test, shear test, and peel (adhesion) test. Each test used 300 samples for a combined total of 900 sandwich test samples for this study. A factorial design with three independent variables was used. The first variable, filler type, had three levels: no filler, microballoon filler, and recycled epoxy/fiberglass filler. The second variable, foam density, had four levels: 3 lb/ft³, 4 lb/ft³, 5 lb/ft³, and 6 lb/ft³. The third variable, filler percentage ratio, had eight levels: 0%, 10%, 20%, 30%, 40%, 50%, 60%, and 70%. The results of this study revealed two primary conclusions. The first conclusion was that sandwich test panels produced with recycled epoxy/fiberglass powder were equal or significantly better in tensile, shear, and peel (adhesion) strength than sandwiches produced with hollow glass microballoons. The second conclusion was that sandwich test panels produced with recycled epoxy/fiberglass powder were equal or significantly lighter in weight than sandwiches produced with hollow glass microballoons.

Quantifying effects of cyclic stretch on cell-collagen substrate adhesiveness of vascular endothelial cells.

PubMed

Omidvar, Ramin; Tafazzoli-Shadpour, Mohammad; Mahmoodi-Nobar, Farbod; Azadi, Shohreh; Khani, Mohammad-Mehdi

2018-05-01

Vascular endothelium is continuously subjected to mechanical stimulation in the form of shear forces due to blood flow as well as tensile forces as a consequence of blood pressure. Such stimuli influence endothelial behavior and regulate cell-tissue interaction for an optimized functionality. This study aimed to quantify influence of cyclic stretch on the adhesive property and stiffness of endothelial cells. The 10% cyclic stretch with frequency of 1 Hz was applied to a layer of endothelial cells cultured on a polydimethylsiloxane substrate. Cell-substrate adhesion of endothelial cells was examined by the novel approach of atomic force microscope-based single-cell force spectroscopy and cell stiffness was measured by atomic force microscopy. Furthermore, the adhesive molecular bonds were evaluated using modified Hertz contact theory. Our results show that overall adhesion of endothelial cells with substrate decreased after cyclic stretch while they became stiffer. Based on the experimental results and theoretical modeling, the decrease in the number of molecular bonds after cyclic stretch was quantified. In conclusion, in vitro cyclic stretch caused alterations in both adhesive capacity and elastic modulus of endothelial cells through mechanotransductive pathways as two major determinants of the function of these cells within the cardiovascular system.

Time-temperature effect in adhesively bonded joints

NASA Technical Reports Server (NTRS)

Delale, F.; Erdogan, F.

1981-01-01

The viscoelastic analysis of an adhesively bonded lap joint was reconsidered. The adherends are approximated by essentially Reissner plates and the adhesive is linearly viscoelastic. The hereditary integrals are used to model the adhesive. A linear integral differential equations system for the shear and the tensile stress in the adhesive is applied. The equations have constant coefficients and are solved by using Laplace transforms. It is shown that if the temperature variation in time can be approximated by a piecewise constant function, then the method of Laplace transforms can be used to solve the problem. A numerical example is given for a single lap joint under various loading conditions.

An anti-let-7 sponge decoys and decays endogenous let-7 functions

PubMed Central

Yang, Xiangling; Rutnam, Zina Jeyapalan; Jiao, Chunwei; Wei, Duo; Xie, Yizhen; Du, Jun; Zhong, Ling; Yang, Burton B.

2012-01-01

The let-7 family contains 12 members, which share identical seed regions, suggesting that they may target the same mRNAs. It is essential to develop a means that can regulate the functions of all members. Using a DNA synthesis technique, we have generated an anti-let-7 sponge aiming to modulate the function of all members. We found that products of the anti-let-7 construct could bind and inactivate all members of the let-7 family, producing decoy and decay effects. To test the role of the anti-let-7 sponge, we stably expressed the anti-let-7 construct in two types of cells, the breast carcinoma cells MT-1 and the oldest and most commonly used human cervical cancer cell line, HeLa cells. We found that expression of anti-let-7 increased cell survival, invasion and adhesion, which corroborate with known functions of let-7 family members. We further identified a novel target site across all species of the let-7 family in hyaluronan synthase 2 (HAS2). HAS2 overexpression produced similar effects as the anti-let-7 sponge. Silencing HAS2 expression by siRNAs produced opposite effects to anti-let-7 on cell survival and invasion. The ability of anti-let-7 to regulate multiple members of the let-7 family allows us to observe their multiple functions using a single reagent. This approach can be applied to other family members with conserved sequences. PMID:22871741

Development of a biodegradable tissue adhesive based on functionalized 1,2-ethylene glycol bis(dilactic acid). II.

PubMed

Rohm, Henning W; Lurtz, Claudia; Wegmann, Juergen; Odermatt, Erich K; Behrend, Detlef; Schmitz, Klaus-Peter; Sternberg, Katrin

2011-04-01

In body regions where damage and bleeding must be avoided, a substitute for mechanical tissue fixation by sutures or staplers is needed. Since tissue adhesives provide easy and fast handling they are a promising alternative. The present study reports the development and analysis of a tissue adhesive that consists of two adhesive components: hexamethylene diisocyanate (HDI) functionalized 1,2-ethylene glycol bis(dilactic acid) (ELA-NCO) and chitosan chloride. This composition was chosen based on preliminary studies on several chain elongation agents. The present study evaluates this adhesive system by IR-spectroscopy, tensile tests, and gel point measurements in comparison to fibrin glue. The system's in vitro biocompatibility was tested with mouse fibroblasts (L929) according to ISO 10993-5. Furthermore, an implantation study was performed in SPF-Wistar rats. The adhesive strength of manually applied mixtures or mixtures applied by double chamber syringes with a mixing extruder was determined to be significantly higher than that of fibrin glue on bovine muscle tissue at 37°C. Tensile strength increased further when exposure time of the adhesive was increased from 10 min to 48 h. The rheological gel point determination showed that the mixture of ELA-NCO/DMSO and chitosan chloride offers a time window large enough to readjust the fused joint during surgery, as opposed to fibrin glue. Additionally, the in vitro and in vivo biocompatibility studies of the adhesive system revealed no toxic effects on the surrounding tissue. Copyright © 2010 Wiley Periodicals, Inc.

Cell adhesion molecules, the extracellular matrix and oral squamous carcinoma.

PubMed

Lyons, A J; Jones, J

2007-08-01

Carcinomas are characterized by invasion of malignant cells into the underlying connective tissue and migration of malignant cells to form metastases at distant sites. These processes require alterations in cell-cell and cell-extracellular matrix interactions. As cell adhesion molecules play a role in cell-cell and cell-extracellular matrix adhesion and interactions they are involved in the process of tumour invasion and metastases. In epithelial tissues, receptors of the integrin family mediate adhesion to the adjacent matrix whereas cadherins largely mediate intercellular adhesion. These and other cell adhesion molecules such as intercellular adhesion molecule-1, CD44, dystroglycans and selectins, are involved and undergo changes in carcinomas, which provide possible targets for anti-cancer drug treatments. In the extracellular matrix that is associated with tumours, laminin 5, oncofetal fibronectin and tenascin C appear. The degree of expression of some of these moieties indicates prognosis in oral cancer and offer targets for antibody-directed radiotherapy. Metalloproteases which degrade the extracellular matrix are increased in carcinomas, and their activity is necessary for tumour angiogenesis and consequent invasion and metastases. Metalloprotease inhibitors have begun to produce decreases in mortality in clinical trials. This report provides a brief overview of our current understanding of cell adhesion molecules, the extracellular matrix, tumour invasion and metastasis.

Patterning N-type and S-type Neuroblastoma Cells with Pluronic F108 and ECM Proteins

PubMed Central

Corey, Joseph M.; Gertz, Caitlyn C.; Sutton, Thomas J.; Chen, Qiaoran; Mycek, Katherine B.; Wang, Bor-Shuen; Martin, Abbey A.; Johnson, Sara L.; Feldman, Eva L.

2009-01-01

Influencing cell shape using micropatterned substrates affects cell behaviors, such as proliferation and apoptosis. Cell shape may also affect these behaviors in human neuroblastoma (NBL) cancer, but to date, no substrate design has effectively patterned multiple clinically important human NBL lines. In this study, we investigated whether Pluronic F108 was an effective anti-adhesive coating for human NBL cells and whether it would localize three NBL lines to adhesive regions of tissue culture plastic or collagen I on substrate patterns. The adhesion and patterning of an S-type line, SH-EP, and two N-type lines, SH-SY5Y and IMR-32, were tested. In adhesion assays, F108 deterred NBL adhesion equally as well as two anti-adhesive organofunctional silanes and far better than bovine serum albumin. Patterned stripes of F108 restricted all three human NBL lines to adhesive stripes of tissue culture plastic. We then investigated four schemes of applying collagen and F108 to different regions of a substrate. Contact with collagen obliterates the ability of F108 to deter NBL adhesion, limiting how both materials can be applied to substrates to produce high fidelity NBL patterning. This patterned substrate design should facilitate investigations of the role of cell shape in NBL cell behavior. PMID:19609877

"Self-Peel-Off" Transfer Produces Ultrathin Polyvinylidene-Fluoride-Based Flexible Nanodevices.

PubMed

Tai, Yanlong; Lubineau, Gilles

2017-04-01

Here, a new strategy, self-peel-off transfer, for the preparation of ultrathin flexible nanodevices made from polyvinylidene-fluoride (PVDF) is reported. In this process, a functional pattern of nanoparticles is transferred via peeling from a temporary substrate to the final PVDF film. This peeling process takes advantage of the differences in the work of adhesion between the various layers (the PVDF layer, the nanoparticle-pattern layer and the substrate layer) and of the high stresses generated by the differential thermal expansion of the layers. The work of adhesion is mainly guided by the basic physical/chemical properties of these layers and is highly sensitive to variations in temperature and moisture in the environment. The peeling technique is tested on a variety of PVDF-based functional films using gold/palladium nanoparticles, carbon nanotubes, graphene oxide, and lithium iron phosphate. Several PVDF-based flexible nanodevices are prepared, including a single-sided wireless flexible humidity sensor in which PVDF is used as the substrate and a double-sided flexible capacitor in which PVDF is used as the ferroelectric layer and the carrier layer. Results show that the nanodevices perform with high repeatability and stability. Self-peel-off transfer is a viable preparation strategy for the design and fabrication of flexible, ultrathin, and light-weight nanodevices.

Development of bioactive porous α-TCP/HAp beads for bone tissue engineering.

PubMed

Asaoka, Teruo; Ohtake, Shoji; Furukawa, Katsuko S; Tamura, Akito; Ushida, Takashi

2013-11-01

Porous beads of bioactive ceramics such as hydroxyapatite (HAp) and tribasic calcium phosphate (TCP) are considered a promising scaffold for cultivating bone cells. To realize this, α-TCP/HAp functionally graded porous beads are fabricated with two main purposes: to maintain the function of the scaffold with sufficient strength up to the growth of new bone, and is absorbed completely after the growth. HAp is a bioactive material that has both high strength and strong tissue-adhesive properties, but is not readily absorbed by the human body. On the contrary, α-TCP is highly bioabsorbable, resulting in a scaffold that is absorbed before it is completely replaced by bone. In this study, we produced porous, bead-shaped carriers as scaffolds for osteoblast culture. To control the solubility in vivo, the fabricated beads contained α-TCP at the center and HAp at the surface. Cell adaptability of these beads for bone tissue engineering was confirmed in vitro. It was found that α-TCP/HAp bead carriers exhibit low toxicity in the initial stages of cell seeding and cell adhesion. The presence of HAp in the composite bead form effectively increased ALP activity. In conclusion, it is suggested that these newly developed α-TCP/HAp beads are a promising tool for bone tissue engineering. Copyright © 2013 Wiley Periodicals, Inc.

Ethanol does not inhibit the adhesive activity of Drosophila neuroglian or human L1 in Drosophila S2 tissue culture cells.

PubMed

Vallejo, Y; Hortsch, M; Dubreuil, R R

1997-05-02

Members of the L1 family of homophilic neural cell adhesion molecules are thought to play an important role in nervous system development and function. It is also suggested that L1 is a direct target of ethanol in fetal alcohol syndrome, since ethanol inhibits the aggregation of cultured cells expressing L1 (Ramanathan, R., Wilkemeyer, M. F., Mittel, B., Perides, G., and Charness, M. E. (1996) J. Cell Biol. 133, 381-390). If ethanol acts directly on the homophilic adhesive function of the L1 molecule, then inhibition of aggregation by ethanol should be observed in any cell type that expresses L1. Here we examined the effect of physiologically relevant concentrations of ethanol on the aggregation of Drosophila S2 cells that expressed either neuroglian (the Drosophila homolog of L1) or human L1. The aggregation of these S2 cells is known to be solely dependent on the homophilic interactions between L1 or neuroglian molecules. Neither cell adhesion molecule was affected when cell aggregation assays were carried out in the presence of >/=38 mM ethanol. The recruitment of membrane skeleton assembly at sites of cell-cell contact (a transmembrane signaling function of human L1) was also unaffected by the presence of ethanol. Thus the previously described inhibition of cell adhesion by ethanol in L1-expressing cells cannot be explained by a simple direct effect on the adhesive activity of L1 family members.

Production of human vitronectin in Nicotiana benthamiana using the INPACT hyperexpression platform.

PubMed

Dugdale, Benjamin; Kato, Maiko; Deo, Pradeep; Plan, Manuel; Harrison, Mark; Lloyd, Robyn; Walsh, Terry; Harding, Robert; Dale, James

2018-02-01

Human vitronectin (hVN) is a glycoprotein that functions as a cell adhesion molecule and a regulator of coagulation in blood plasma and the extracellular matrix. In vitro, hVN is added to serum-free media in order to promote the adhesion of animal cells to tissue culture surfaces and the proliferation of undifferentiated stem cells. Here, we report the production of hVN in Nicotiana benthamiana using the inducible In Plant ACTivation (INPACT) hyperexpression platform. N. benthamiana plants were transformed with an INPACT expression cassette encoding hVN, and both the Tobacco yellow dwarf virus Rep/RepA activator and Tomato bushy stunt virus p19 gene under the transcriptional control of the ethanol-inducible AlcR:alcA gene switch. hVN expression was maximal 4-5 days postactivation of the INPACT platform with a dilute ethanol solution, and crude yields of the recombinant protein reached a maximum of 643 ± 78 mg/kg fresh weight. A three-stage purification protocol was developed using heparin and polyhistidine tag affinity binding and size exclusion filtration, resulting in a plant-made hVN product of >90% purity. Storage conditions for plant-made hVN were identified that maximized the capacity of the recombinant protein to promote cell adhesion. Critically, plant-made hVN was shown to be functionally equivalent to commercial, plasma-derived hVN at promoting one-half maximal attachment of murine fibroblast cells (BALB-C/3T3) in serum-free medium at <0.1 μg/cm 2 to tissue culture plasticware. The INPACT platform represents an attractive means of producing large quantities of functional, animal-free hVN for in vitro applications. © 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

In vivo quantitative analysis of Talin turnover in response to force

PubMed Central

Hákonardóttir, Guðlaug Katrín; López-Ceballos, Pablo; Herrera-Reyes, Alejandra Donají; Das, Raibatak; Coombs, Daniel; Tanentzapf, Guy

2015-01-01

Cell adhesion to the extracellular matrix (ECM) allows cells to form and maintain three-dimensional tissue architecture. Cell–ECM adhesions are stabilized upon exposure to mechanical force. In this study, we used quantitative imaging and mathematical modeling to gain mechanistic insight into how integrin-based adhesions respond to increased and decreased mechanical forces. A critical means of regulating integrin-based adhesion is provided by modulating the turnover of integrin and its adhesion complex (integrin adhesion complex [IAC]). The turnover of the IAC component Talin, a known mechanosensor, was analyzed using fluorescence recovery after photobleaching. Experiments were carried out in live, intact flies in genetic backgrounds that increased or decreased the force applied on sites of adhesion. This analysis showed that when force is elevated, the rate of assembly of new adhesions increases such that cell–ECM adhesion is stabilized. Moreover, under conditions of decreased force, the overall rate of turnover, but not the proportion of adhesion complex components undergoing turnover, increases. Using point mutations, we identify the key functional domains of Talin that mediate its response to force. Finally, by fitting a mathematical model to the data, we uncover the mechanisms that mediate the stabilization of ECM-based adhesion during development. PMID:26446844

Phenotypical Analysis of the Lactobacillus rhamnosus GG Fimbrial spaFED Operon: Surface Expression and Functional Characterization of Recombinant SpaFED Pili in Lactococcus lactis

PubMed Central

Kant, Ravi; Palva, Airi; von Ossowski, Ingemar

2014-01-01

A noticeable genomic feature of many piliated Gram-positive bacterial species is the presence of more than one pilus-encoding operon. Paradigmatically, the gut-adapted Lactobacillus rhamnosus GG strain contains two different fimbrial operons in its genome. However, whereas one of these operons (called spaCBA) is encoding for the functionally mucus-/collagen-binding SpaCBA pilus, for the other operon (called spaFED) any native expression of the SpaFED-called pili is still the subject of some uncertainty. Irrespective of such considerations, we decided it would be of relevance or interest to decipher the gross structure of this pilus type, and as well assess its functional capabilities for cellular adhesion and immunostimulation. For this, and by following the approach we had used previously to explicate the immuno-properties of SpaCBA pili, we constructed nisin-inducible expression clones producing either wild-type or SpaF pilin-deleted surface-assembled L. rhamnosus GG SpaFED pili on Lactococcus lactis cells. Using these piliated lactococcal constructs, we found that the pilin-polymerized architecture of a recombinant-produced SpaFED pilus coincides with sequence-based functional predictions of the related pilins, and in fact is prototypical of those other sortase-dependent pilus-like structures thus far characterized for piliated Gram-positive bacteria. Moreover, we confirmed that among the different pilin subunits encompassing spaFED operon-encoded pili, the SpaF pilin is a main adhesion determinant, and when present in the assembled structure can mediate pilus binding to mucus, certain extracellular matrix proteins, and different gut epithelial cell lines. However, somewhat unexpectedly, when recombinant SpaFED pili are surface-attached, we found that they could not potentiate the existing lactococcal cell-induced immune responses so elicited from intestinal- and immune-related cells, but rather instead, they could dampen them. Accordingly, we have now provided the first phenotypical description of a spaFED pilus operon, and with that furthered the functional understanding of surface piliation for a particular gut-commensalic genre of piliated Gram-positive bacteria. PMID:25415357

Phenotypical analysis of the Lactobacillus rhamnosus GG fimbrial spaFED operon: surface expression and functional characterization of recombinant SpaFED pili in Lactococcus lactis.

PubMed

Rintahaka, Johanna; Yu, Xia; Kant, Ravi; Palva, Airi; von Ossowski, Ingemar

2014-01-01

A noticeable genomic feature of many piliated Gram-positive bacterial species is the presence of more than one pilus-encoding operon. Paradigmatically, the gut-adapted Lactobacillus rhamnosus GG strain contains two different fimbrial operons in its genome. However, whereas one of these operons (called spaCBA) is encoding for the functionally mucus-/collagen-binding SpaCBA pilus, for the other operon (called spaFED) any native expression of the SpaFED-called pili is still the subject of some uncertainty. Irrespective of such considerations, we decided it would be of relevance or interest to decipher the gross structure of this pilus type, and as well assess its functional capabilities for cellular adhesion and immunostimulation. For this, and by following the approach we had used previously to explicate the immuno-properties of SpaCBA pili, we constructed nisin-inducible expression clones producing either wild-type or SpaF pilin-deleted surface-assembled L. rhamnosus GG SpaFED pili on Lactococcus lactis cells. Using these piliated lactococcal constructs, we found that the pilin-polymerized architecture of a recombinant-produced SpaFED pilus coincides with sequence-based functional predictions of the related pilins, and in fact is prototypical of those other sortase-dependent pilus-like structures thus far characterized for piliated Gram-positive bacteria. Moreover, we confirmed that among the different pilin subunits encompassing spaFED operon-encoded pili, the SpaF pilin is a main adhesion determinant, and when present in the assembled structure can mediate pilus binding to mucus, certain extracellular matrix proteins, and different gut epithelial cell lines. However, somewhat unexpectedly, when recombinant SpaFED pili are surface-attached, we found that they could not potentiate the existing lactococcal cell-induced immune responses so elicited from intestinal- and immune-related cells, but rather instead, they could dampen them. Accordingly, we have now provided the first phenotypical description of a spaFED pilus operon, and with that furthered the functional understanding of surface piliation for a particular gut-commensalic genre of piliated Gram-positive bacteria.

Control of Surface Chemistry, Substrate Stiffness, and Cell Function in a Novel Terpolymer Methacrylate Library

PubMed Central

Joy, Abraham; Cohen, Daniel M.; Luk, Arnold; Anim-Danso, Emmanuel; Chen, Christopher; Kohn, Joachim

2011-01-01

A focused library of methacrylate terpolymers was synthesized to explore the effects of varying surface chemistry and adhesive peptide ligands on cell function. The chemical diversity of methacrylate monomers enabled construction of a library of polymers in which one can systematically vary the chemical composition to achieve a wide range of contact angle, Young's modulus, and Tg values. Furthermore, the materials were designed to allow surface immobilization of bioactive peptides. We then examined the effects of these material compositions on protein adsorption and cell attachment, proliferation, and differentiation. We observed that chemical composition of the polymers was an important determinant for NIH 3T3 cell attachment and proliferation, as well as human mesenchymal stem cell differentiation, and correlated directly with the ability of the polymers to adsorb proteins that mediate cell adhesion. Importantly, functionalization of the methacrylate terpolymer library with an adhesive GRGDS peptide normalized cellular responses. RGD-functionalized polymers uniformly exhibited robust attachment, proliferation, and differentiation irrespective of the underlying substrate chemistry. These studies provide a library-based approach to rapidly explore the biological functionality of biomaterials with a wide range of compositions, and highlights the importance of cell and protein cell adhesion in predicting their performance. PMID:21226505

Intercellular adhesion molecule-1 expression by skeletal muscle cells augments myogenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goh, Qingnian; Dearth, Christopher L.; Corbett, Jacob T.

We previously demonstrated that the expression of intercellular adhesion molecule-1 (ICAM-1) by skeletal muscle cells after muscle overload contributes to ensuing regenerative and hypertrophic processes in skeletal muscle. The objective of the present study is to reveal mechanisms through which skeletal muscle cell expression of ICAM-1 augments regenerative and hypertrophic processes of myogenesis. This was accomplished by genetically engineering C2C12 myoblasts to stably express ICAM-1, and by inhibiting the adhesive and signaling functions of ICAM-1 through the use of a neutralizing antibody or cell penetrating peptide, respectively. Expression of ICAM-1 by cultured skeletal muscle cells augmented myoblast–myoblast adhesion, myotube formation,more » myonuclear number, myotube alignment, myotube–myotube fusion, and myotube size without influencing the ability of myoblasts to proliferate or differentiate. ICAM-1 augmented myotube formation, myonuclear accretion, and myotube alignment through a mechanism involving adhesion-induced activation of ICAM-1 signaling, as these dependent measures were reduced via antibody and peptide inhibition of ICAM-1. The adhesive and signaling functions of ICAM-1 also facilitated myotube hypertrophy through a mechanism involving myotube–myotube fusion, protein synthesis, and Akt/p70s6k signaling. Our findings demonstrate that ICAM-1 expression by skeletal muscle cells augments myogenesis, and establish a novel mechanism through which the inflammatory response facilitates growth processes in skeletal muscle. - Highlights: • We examined mechanisms through which skeletal muscle cell expression of ICAM-1 facilitates events of in vitro myogenesis. • Expression of ICAM-1 by cultured myoblasts did not influence their ability to proliferate or differentiate. • Skeletal muscle cell expression of ICAM-1 augmented myoblast fusion, myotube alignment, myotube–myotube fusion, and myotube size. • ICAM-1 augmented myogenic processes through mechanisms involving its adhesive and signaling functions.« less

Desmoglein 3 regulates membrane trafficking of cadherins, an implication in cell-cell adhesion

PubMed Central

Moftah, Hanan; Dias, Kasuni; Apu, Ehsanul Hoque; Liu, Li; Uttagomol, Jutamas; Bergmeier, Lesley; Kermorgant, Stephanie; Wan, Hong

2017-01-01

ABSTRACT E-cadherin mediated cell-cell adhesion plays a critical role in epithelial cell polarization and morphogenesis. Our recent studies suggest that the desmosomal cadherin, desmoglein 3 (Dsg3) cross talks with E-cadherin and regulates its adhesive function in differentiating keratinocytes. However, the underlying mechanism remains not fully elucidated. Since E-cadherin trafficking has been recognized to be a central determinant in cell-cell adhesion and homeostasis we hypothesize that Dsg3 may play a role in regulating E-cadherin trafficking and hence the cell-cell adhesion. Here we investigated this hypothesis in cells with loss of Dsg3 function through RNAi mediated Dsg3 knockdown or the stable expression of the truncated mutant Dsg3ΔC. Our results showed that loss of Dsg3 resulted in compromised cell-cell adhesion and reduction of adherens junction and desmosome protein expression as well as the cortical F-actin formation. As a consequence, cells failed to polarize but instead displayed aberrant cell flattening. Furthermore, retardation of E-cadherin internalization and recycling was consistently observed in these cells during the process of calcium induced junction assembling. In contrast, enhanced cadherin endocytosis was detected in cells with overexpression of Dsg3 compared to control cells. Importantly, this altered cadherin trafficking was found to be coincided with the reduced expression and activity of Rab proteins, including Rab5, Rab7 and Rab11 which are known to be involved in E-cadherin trafficking. Taken together, our findings suggest that Dsg3 functions as a key in cell-cell adhesion through at least a mechanism of regulating E-cadherin membrane trafficking. PMID:27254775

Impact of O-glycosylation on the molecular and cellular adhesion properties of the Escherichia coli autotransporter protein Ag43.

PubMed

Reidl, Sebastian; Lehmann, Annika; Schiller, Roswitha; Salam Khan, A; Dobrindt, Ulrich

2009-08-01

Antigen 43 (Ag43) represents an entire family of closely related autotransporter proteins in Escherichia coli and has been described to confer aggregation and fluffing of cells, to promote biofilm formation, uptake and survival in macrophages as well as long-term persistence of uropathogenic E. coli in the murine urinary tract. Furthermore, it has been reported that glycosylation of the Ag43 passenger domain (alpha(43)) stabilizes its conformation and increases adhesion to Hep-2 cells. We characterized the role of Ag43 as an adhesin and the impact of O-glycosylation on the function of Ag43. To analyze whether structural variations in the alpha(43) domain correlate with different functional properties, we cloned 5 different agn43 alleles from different E. coli subtypes and tested them for autoaggregation, biofilm formation, adhesion to different eukaryotic cell lines as well as to purified components of the extracellular matrix. These experiments were performed with nonglycosylated and O-glycosylated Ag43 variants. We show for the first time that Ag43 mediates bacterial adhesion in a cell line-specific manner and that structural variations of the alpha(43) domain correlate with increased adhesive properties to proteins of the extracellular matrix such as collagen and laminin. Whereas O-glycosylation of many alpha(43) domains led to impaired autoaggregation and a significantly reduced adhesion to eukaryotic cell lines, their interaction with collagen was significantly increased. These data demonstrate that O-glycosylation is not a prerequisite for Ag43 function and that the different traits mediated by Ag43, i.e., biofilm formation, autoaggregation, adhesion to eukaryotic cells and extracellular matrix proteins, rely on distinct mechanisms.

Differential effector responses by circulating/blood and tissue/peritoneal neutrophils following burn combined with Enterococcus faecalis infection.

PubMed

Fazal, Nadeem; Shelip, Alla; Siddiqui, Erum; Ali, Ashraf; Azim, Anser C; Al-Ghoul, Walid M

2012-03-01

Recently we found that superimposition of Enterococcus faecalis infection on burn injury caused an eruption of host mortality not seen with either individual challenge. We hypothesized that the Enterococcus bacteria, and/or factors related to these organisms, aggravate burn-induced modulations in host defense by neutrophils. Our study focuses on alterations in neutrophils' oxidative, proteolytic, and adhesive functions and transendothelial migration of neutrophils in burn rats inoculated with E. faecalis. Rats were subjected to burn (30% total body surface area) and then intra-abdominally inoculated with E. faecalis (10(4)CFU kg(-1) b.w). Polymorphonuclear neutrophils (PMNs) were harvested from circulating/blood and tissue/peritoneal cavity at day-2 post injury. Extracellular release of O(-)(2) anion production was determined by luminometry, and intracellular production of reactive oxygen species was measured by digital imaging technique. Fluoroscan analysis and confocal microscopy determined intracellular elastase production. The expression of adhesion molecule CD11b/CD18 was performed by flow cytometry. Calcein AM-labeled PMNs were co-cultured with TNF-α-stimulated rat lung microvascular endothelial cells, and their ability to adhere was assessed by fluorometry and digital imaging and finally, chemotaxis was measured by neutrophil transmigration assays. The results showed differential effector responses by circulatory and/or tissue PMNs. Tissue/peritoneal PMNs produced more O(-)(2), less intracellular elastase, and increased expression of CD11b/CD18 accompanied with increased adhesivity of MIP-2-stimulated PMNs to endothelial cells as compared to circulatory/blood PMNs. This differential effect was more pronounced following burn plus E. faecalis infection, indicating that the combined injury changed neutrophil functions. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Rectangle-capped and tilted micropillar array for enhanced anisotropic anti-shearing in biomimetic adhesion

PubMed Central

Wang, Yue; Li, Xiangming; Tian, Hongmiao; Hu, Hong; Tian, Yu; Shao, Jinyou; Ding, Yucheng

2015-01-01

Dry adhesion observed in the feet of various small creatures has attracted considerable attention owing to the unique advantages such as self-cleaning, adaptability to rough surfaces along with repeatable and reversible adhesiveness. Among these advantages, for practical applications, proper detachability is critical for dry adhesives with artificial microstructures. In this study, we present a microstructured array consisting of both asymmetric rectangle-capped tip and tilted shafts, which produce an orthogonal anisotropy of the shearing strength along the long and short dimensions of the tip, with a maximum anti-shearing in the two directions along the longer dimension. Meanwhile, the tilt feature can enhance anisotropic shearing adhesion by increasing shearing strength in the forward shearing direction and decreasing strength in the reverse shearing direction along the short dimension of the tip, leading to a minimum anti-shearing in only one of the two directions along the shorter dimension of the rectangular tip. Such a microstructured adhesive with only one weak shearing direction, leading to well-controlled attachment and detachment of the adhesive, is created in our experiment by conventional double-sided exposure of a photoresist followed by a moulding process. PMID:25808338

Inhibition of tumor necrosis factor-{alpha}-induced expression of adhesion molecules in human endothelial cells by the saponins derived from roots of Platycodon grandiflorum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Ji Young; Kim, Dong Hee; Kim, Hyung Gyun

2006-01-15

Adhesion molecules play an important role in the development of atherogenesis and are produced by endothelial cells after being stimulated with various inflammatory cytokines. This study examined the effect of saponins that were isolated from the roots of Platycodon grandiflorum A. DC (Campanulaceae), Changkil saponins (CKS), on the cytokine-induced monocyte/human endothelial cell interaction, which is a crucial early event in atherogenesis. CKS significantly inhibited the TNF{alpha}-induced increase in monocyte adhesion to endothelial cells as well as decreased the protein and mRNA expression levels of vascular adhesion molecule-1 and intercellular cell adhesion molecule-1 on endothelial cells. Furthermore, CKS significantly inhibited themore » TNF{alpha}-induced production of intracellular reactive oxygen species (ROS) and activation of NF-{kappa}B by preventing I{kappa}B degradation and inhibiting I{kappa}B kinase activity. Overall, CKS has anti-atherosclerotic and anti-inflammatory activity, which is least in part the result of it reducing the cytokine-induced endothelial adhesion to monocytes by inhibiting intracellular ROS production, NF-{kappa}B activation, and cell adhesion molecule expression in endothelial cells.« less

Structure and function of primitive immunoglobulin superfamily neural cell adhesion molecules: a lesson from studies on planarian.

PubMed

Fusaoka, Eri; Inoue, Takeshi; Mineta, Katsuhiko; Agata, Kiyokazu; Takeuchi, Kosei

2006-05-01

Precise wiring and proper remodeling of the neural network are essential for its normal function. The freshwater planarian is an attractive animal in which to study the formation and maintenance of the neural network due to its high regenerative capability and developmental plasticity. Although a recent study revealed that homologs of netrin and its receptors are required for regeneration and maintenance of the planarian central nervous system (CNS), the roles of cell adhesion in the formation and maintenance of the planarian neural network remain poorly understood. In the present study, we found primitive immunoglobulin superfamily cell adhesion molecules (IgCAMs) in a planarian that are homologous to vertebrate neural IgCAMs. We identified planarian orthologs of NCAM, L1CAM, contactin and DSCAM, and designated them DjCAM, DjLCAM, DjCTCAM and DjDSCAM, respectively. We further confirmed that they function as cell adhesion molecules using cell aggregation assays. DjCAM and DjDSCAM were found to be differentially expressed in the CNS. Functional analyses using RNA interference revealed that DjCAM is partly involved in axon formation, and that DjDSCAM plays crucial roles in neuronal cell migration, axon outgrowth, fasciculation and projection.

Enhanced Cellular Adhesion on Titanium by Silk Functionalized with titanium binding and RGD peptides

PubMed Central

Vidal, Guillaume; Blanchi, Thomas; Mieszawska, Aneta J.; Calabrese, Rossella; Rossi, Claire; Vigneron, Pascale; Duval, Jean-Luc; Kaplan, David L.; Egles, Christophe

2012-01-01

Soft tissue adhesion on titanium represents a challenge for implantable materials. In order to improve adhesion at the cell/material interface we used a new approach based on the molecular recognition of titanium by specific peptides. Silk fibroin protein was chemically grafted with titanium binding peptide (TiBP) to increase adsorption of these chimeric proteins to the metal surface. Quartz Crystal Microbalance was used to quantify the specific adsorption of TiBP-functionalized silk and an increase in protein deposition by more than 35% was demonstrated due to the presence of the binding peptide. A silk protein grafted with TiBP and fibronectin-derived RGD peptide was then prepared. The adherence of fibroblasts on the titanium surface modified with the multifunctional silk coating demonstrated an increase in the number of adhering cells by 60%. The improved adhesion was demonstrated by Scanning Electron Microscopy and immunocytochemical staining of focal contact points. Chick embryo organotypic culture also revealed strong adhesion of endothelial cells expanding on the multifunctional silk-peptide coating. These results demonstrated that silk functionalized with TiBP and RGD represents a promising approach to modify cell-biomaterial interfaces, opening new perspectives for implantable medical devices, especially when reendothelialization is required. PMID:22975628

Distinct Fcγ receptors mediate the effect of Serum Amyloid P on neutrophil adhesion and fibrocyte differentiation

PubMed Central

Cox, Nehemiah; Pilling, Darrell; Gomer, Richard H.

2014-01-01

The plasma protein Serum Amyloid P (SAP) reduces neutrophil adhesion, inhibits the differentiation of monocytes into fibroblast-like cells called fibrocytes, and promotes phagocytosis of cell debris by macrophages. Together, these effects of SAP reduce key aspects of inflammation and fibrosis, and SAP injections improve lung function in pulmonary fibrosis patients. SAP functions are mediated in part by Fcγ receptors, but the contribution of each Fcγ receptor is not fully understood. We found that amino acids Q55 and E126 in human SAP affect human fibrocyte differentiation and SAP binding to FcγRI. E126, K130 and Q128 affect neutrophil adhesion and SAP affinity for FcγRIIa. Q128 also affects phagocytosis by macrophages and SAP affinity for FcγRI. All the identified functionally significant amino acids in SAP form a binding site that is distinct from the previously described SAP-FcγRIIa binding site. Blocking FcγRI with an IgG blocking antibody reduces the SAP effect on fibrocyte differentiation, and ligating FcγRIIa with antibodies reduces neutrophil adhesion. Together, these results suggest that SAP binds to FcγRI on monocytes to inhibit fibrocyte differentiation, and binds to FcγRIIa on neutrophils to reduce neutrophil adhesion. PMID:25024390

Reduced endothelial activation after exercise is associated with improved HbA1c in patients with type 2 diabetes and coronary artery disease.

PubMed

Byrkjeland, Rune; Njerve, Ida U; Arnesen, Harald; Seljeflot, Ingebjørg; Solheim, Svein

2017-03-01

We have previously reported insignificant changes in HbA 1c after exercise in patients with both type 2 diabetes and coronary artery disease. In this study, we investigated the effect of exercise on endothelial function and possible associations between changes in endothelial function and HbA 1c . Patients with type 2 diabetes and coronary artery disease ( n = 137) were randomised to 12 months exercise or standard follow-up. Endothelial function was assessed by circulating biomarkers (E-selectin, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, von Willebrand factor, tissue plasminogen activator antigen, asymmetric dimethylarginine and L-arginine/asymmetric dimethylarginine ratio). Differences between the randomised groups were analysed by analysis of covariance and correlations by Spearman's rho or Pearson's correlation. No effect of exercise on endothelial function was demonstrated. The changes in HbA 1c in the exercise group correlated with changes in E-selectin ( r = 0.56, p < 0.001), intercellular adhesion molecule-1 ( r = 0.27, p = 0.052), vascular cell adhesion molecule-1 ( r = 0.32, p = 0.022) and tissue plasminogen activator antigen ( r = 0.35, p =  0.011). HbA 1c decreased significantly more in patients with versus without a concomitant reduction in E-selectin ( p =  0.002), intercellular adhesion molecule-1 ( p =  0.011), vascular cell adhesion molecule-1 ( p =  0.028) and tissue plasminogen activator antigen ( p =  0.009). Exercise did not affect biomarkers of endothelial function in patients with both type 2 diabetes and coronary artery disease. However, changes in biomarkers of endothelial activation correlated with changes in HbA 1c , and reduced endothelial activation was associated with improved HbA 1c after exercise.

Effect of evaporation of solvents from one-step, self-etching adhesives.

PubMed

Furuse, Adilson Yoshio; Peutzfeldt, Anne; Asmussen, Erik

2008-02-01

To investigate whether and to what extent the bonding capacity of one-step, self-etching adhesives is influenced by the degree to which solvent is evaporated. Seven one-step, self-etching adhesives were tested (Adper Prompt L-Pop, Clearfil S3 Bond, Futurabond NR, G-Bond, Hybrid Bond, iBond, Xeno III). The variation in degree of evaporation was obtained by varying the duration of the air-blowing step. The duration required to immobilize the adhesive layer, as established in a pilot study, was used as control. Two experimental air-blowing durations, shorter (half the control duration) and longer (double the control duration) than the control duration, were chosen. The resin composite Herculite XRV was bonded to flat human dentin surfaces treated with one of the adhesives following manufacturer's instructions, except for the air-blowing duration after application. After being stored in water at 37 degrees C for 1 week, the bonded specimens were broken in shear. Failure modes were evaluated under stereomicroscope. Air-blowing duration and brand of adhesive both had an effect on shear bond strength. An interaction was found between adhesive and air-blowing duration. Some adhesives were insensitive to variations in air-drying duration, but in general, air-blowing durations shorter than the control duration produced lower shear bond strengths. Significant effects of adhesive and air-blowing duration were also detected in relation to failure mode. More adhesive failures were observed with shorter air-blowing durations. A significant negative correlation between number of adhesive failures and bond strength was found. On the basis of this in vitro study, it may be concluded that the one-step, self-etching adhesives evaluated were sensitive to degree of evaporation of the solvents.

Cancer Cell Migration in 3D

NASA Astrophysics Data System (ADS)

Wirtz, Denis

2014-03-01

Two-dimensional (2D) in vitro culture systems have for a number of years provided a controlled and versatile environment for mechanistic studies of cell adhesion, polarization, and migration, three interrelated cell functions critical to cancer metastasis. However, the organization and functions of focal adhesion proteins, protrusion machinery, and microtubule-based polarization in cells embedded in physiologically more relevant 3D extracellular matrices is qualitatively different from their organization and functions on conventional 2D planar substrates. This talk will describe the implications of the dependence of focal adhesion protein-based cell migration on micro-environmental dimensionality (1D vs. 2D vs.. 3D), how cell micromechanics plays a critical role in promoting local cell invasion, and associated validation in mouse models. We will discuss the implications of this work in cancer metastasis.

Production and Characterization of TiO2 Nanofilms for Hemocompatible and Photocatalytic Applications

NASA Astrophysics Data System (ADS)

Schvezov, C. E.; Vera, M. L.; Schuster, J. M.; Rosenberger, M. R.

2017-10-01

Titanium dioxide (TiO2) coatings are currently produced for hemocompatible and photocatalytic applications by using two techniques: sol-gel and anodic oxidation. In this review, the research advances on TiO2 nanofilms produced with these techniques are presented, with a focus on different aspects such as process parameters, morphology, roughness, crystal structure, adhesion, wear and erosion resistance, corrosion resistance, hemocompatibility, toxicity, plaque and bacterial adhesion, and heterogeneous photocatalysis of immobilized porous material. This review was presented at the 3rd Pan American Materials Congress at the 2017 TMS Annual Meeting and Exhibition in San Diego, California, USA.

Effects of surface roughness and energy on ice adhesion strength

NASA Astrophysics Data System (ADS)

Zou, M.; Beckford, S.; Wei, R.; Ellis, C.; Hatton, G.; Miller, M. A.

2011-02-01

The aim of this study is to investigate the effects of surface roughness and surface energy on ice adhesion strength. Sandblasting technique was used to prepare samples with high roughness. Silicon-doped hydrocarbon and fluorinated-carbon thin films were employed to alter the surface energy of the samples. Silicon-doped hydrocarbon films were deposited by plasma-enhanced chemical vapor deposition, while fluorinated-carbon films were produced using deep reactive ion etching equipment by only activating the passivation step. Surface topographies were characterized using scanning electron microscopy and a stylus profilometer. The surface wetting properties were characterized by a video-based contact angle measurement system. The adhesion strength of ice formed from a water droplet on these surfaces was studied using a custom-built shear force test apparatus. It was found that the ice adhesion strength is correlated to the water contact angles of the samples only for surfaces with similar roughness: the ice adhesion strength decreases with the increase in water contact angle. The study also shows that smoother as-received sample surfaces have lower ice adhesion strength than the much rougher sandblasted surfaces.

Quick-release medical tape

PubMed Central

Laulicht, Bryan; Langer, Robert; Karp, Jeffrey M.

2012-01-01

Medical tape that provides secure fixation of life-sustaining and -monitoring devices with quick, easy, damage-free removal represents a longstanding unmet medical need in neonatal care. During removal of current medical tapes, crack propagation occurs at the adhesive–skin interface, which is also the interface responsible for device fixation. By designing quick-release medical tape to undergo crack propagation between the backing and adhesive layers, we decouple removal and device fixation, enabling dual functionality. We created an ordered adhesive/antiadhesive composite intermediary layer between the medical tape backing and adhesive for which we achieve tunable peel removal force, while maintaining high shear adhesion to secure medical devices. We elucidate the relationship between the spatial ordering of adhesive and antiadhesive regions to create a fully tunable system that achieves strong device fixation and quick, easy, damage-free device removal. We also described ways of neutralizing the residual adhesive on the skin and have observed that thick continuous films of adhesive are easier to remove than the thin islands associated with residual adhesive left by current medical tapes. PMID:23112196

Titania nanotube arrays as potential interfaces for neurological prostheses

NASA Astrophysics Data System (ADS)

Sorkin, Jonathan Andrew

Neural prostheses can make a dramatic improvement for those suffering from visual and auditory, cognitive, and motor control disabilities, allowing them regained functionality by the use of stimulating or recording electrical signaling. However, the longevity of these devices is limited due to the neural tissue response to the implanted device. In response to the implant penetrating the blood brain barrier and causing trauma to the tissue, the body forms a to scar to isolate the implant in order to protect the nearby tissue. The scar tissue is a result of reactive gliosis and produces an insulated sheath, encapsulating the implant. The glial sheath limits the stimulating or recording capabilities of the implant, reducing its effectiveness over the long term. A favorable interaction with this tissue would be the direct adhesion of neurons onto the contacts of the implant, and the prevention of glial encapsulation. With direct neuronal adhesion the effectiveness and longevity of the device would be significantly improved. Titania nanotube arrays, fabricated using electrochemical anodization, provide a conductive architecture capable of altering cellular response. This work focuses on the fabrication of different titania nanotube array architectures to determine how their structures and properties influence the response of neural tissue, modeled using the C17.2 murine neural stem cell subclone, and if glial encapsulation can be reduced while neuronal adhesion is promoted.

Relating the physical properties of Pseudomonas aeruginosa lipopolysaccharides to virulence by atomic force microscopy.

PubMed

Ivanov, Ivan E; Kintz, Erica N; Porter, Laura A; Goldberg, Joanna B; Burnham, Nancy A; Camesano, Terri A

2011-03-01

Lipopolysaccharides (LPS) are an important class of macromolecules that are components of the outer membrane of Gram-negative bacteria such as Pseudomonas aeruginosa. P. aeruginosa contains two different sugar chains, the homopolymer common antigen (A band) and the heteropolymer O antigen (B band), which impart serospecificity. The characteristics of LPS are generally assessed after isolation rather than in the context of whole bacteria. Here we used atomic force microscopy (AFM) to probe the physical properties of the LPS of P. aeruginosa strain PA103 (serogroup O11) in situ. This strain contains a mixture of long and very long polymers of O antigen, regulated by two different genes. For this analysis, we studied the wild-type strain and four mutants, ΔWzz1 (producing only very long LPS), ΔWzz2 (producing only long LPS), DΔM (with both the wzz1 and wzz2 genes deleted), and Wzy::GM (producing an LPS core oligosaccharide plus one unit of O antigen). Forces of adhesion between the LPS on these strains and the silicon nitride AFM tip were measured, and the Alexander and de Gennes model of steric repulsion between a flat surface and a polymer brush was used to calculate the LPS layer thickness (which we refer to as length), compressibility, and spacing between the individual molecules. LPS chains were longest for the wild-type strain and ΔWzz1, at 170.6 and 212.4 nm, respectively, and these values were not statistically significantly different from one another. Wzy::GM and DΔM have reduced LPS lengths, at 34.6 and 37.7 nm, respectively. Adhesion forces were not correlated with LPS length, but a relationship between adhesion force and bacterial pathogenicity was found in a mouse acute pneumonia model of infection. The adhesion forces with the AFM probe were lower for strains with LPS mutations, suggesting that the wild-type strain is optimized for maximal adhesion. Our research contributes to further understanding of the role of LPS in the adhesion and virulence of P. aeruginosa.

Adhesion and invasion to epithelial cells and motility of extended-spectrum β-lactamase-producing Escherichia coli reveal ST131 superiority: a comparative in vitro study of extraintestinal pathogenic E. coli lineages.

PubMed

Kondratyeva, Kira; Wollman, Ayala; Gerlitz, Gabi; Navon-Venezia, Shiri

2017-09-01

Extended-spectrum β-lactamase (ESBL)-producing extraintestinal pathogenic Escherichia coli (ExPEC) sequence type ST131 is pandemic, and it is the major contributor to antibiotic resistance in E. coli. Despite its epidemiological superiority, the physiological reasons that decipher its success remain elusive. We aimed to compare the adhesion, invasion and motility potential of ST131 versus other E. coli lineages. In this in vitro comparative study, 14 ESBL-producing ExPEC community-onset bacteremia isolates were chosen from a reported clinical collection (Karfunkel D, Carmeli Y, Chmelnitsky I, Kotlovsky T, Navon-Venezia S. Eur J Clin Microbiol Infect Dis 2013;32:513-521). Isolates were divided into two groups, ST131 (n=7) and 'non-ST131', sporadic sequence types (STs) (n=7). Virulence and adhesion genes were screened by PCR in all isolates. Virotyping and serotyping were performed for ST131 isolates. Adhesion and invasion to Caco-2 epithelial cells, and motility on semi-solid agar were quantified and compared between the two groups. Fluorescence microscopy using anti-LPS E. coli antibodies was used for visualization and confirmation of adhesion and invasion. ST131 isolates belonged to the O25b:H4-B2 subclone. Two ST131 virotypes were found, A (two blaCTX-M-15 H30-Rx) and C (two blaCTX-M-15 H30-Rx and three blaCTX-M-14 H30 isolates). The average number of adhesion and virulence genes carried by ExPEC ST131 isolates and non-ST131 isolates was 5.3 and 3.7, respectively (P<0.05). Group analysis showed that ST131 surpassed non-ST131 lineages in all three physiological properties: adherence (17.1 vs 13.1 %, P<0.001), invasion (0.4 vs 0.17 %, P<0.01), and swarming motility on all media tested (P<0.05). This study demonstrates ST131 superiority that may explain its improved gut-colonization and dissemination capabilities within the host. These insights are an important step in our understanding of ST131 epidemiological success.

The morphology and adhesion mechanism of Octopus vulgaris suckers.

PubMed

Tramacere, Francesca; Beccai, Lucia; Kuba, Michael; Gozzi, Alessandro; Bifone, Angelo; Mazzolai, Barbara

2013-01-01

The octopus sucker represents a fascinating natural system performing adhesion on different terrains and substrates. Octopuses use suckers to anchor the body to the substrate or to grasp, investigate and manipulate objects, just to mention a few of their functions. Our study focuses on the morphology and adhesion mechanism of suckers in Octopus vulgaris. We use three different techniques (MRI, ultrasonography, and histology) and a 3D reconstruction approach to contribute knowledge on both morphology and functionality of the sucker structure in O. vulgaris. The results of our investigation are two-fold. First, we observe some morphological differences with respect to the octopus species previously studied (i.e., Octopus joubini, Octopus maya, Octopus bimaculoides/bimaculatus and Eledone cirrosa). In particular, in O. vulgaris the acetabular chamber, that is a hollow spherical cavity in other octopuses, shows an ellipsoidal cavity which roof has an important protuberance with surface roughness. Second, based on our findings, we propose a hypothesis on the sucker adhesion mechanism in O. vulgaris. We hypothesize that the process of continuous adhesion is achieved by sealing the orifice between acetabulum and infundibulum portions via the acetabular protuberance. We suggest this to take place while the infundibular part achieves a completely flat shape; and, by sustaining adhesion through preservation of sucker configuration. In vivo ultrasonographic recordings support our proposed adhesion model by showing the sucker in action. Such an underlying physical mechanism offers innovative potential cues for developing bioinspired artificial adhesion systems. Furthermore, we think that it could possibly represent a useful approach in order to investigate any potential difference in the ecology and in the performance of adhesion by different species.

The Morphology and Adhesion Mechanism of Octopus vulgaris Suckers

PubMed Central

Tramacere, Francesca; Beccai, Lucia; Kuba, Michael; Gozzi, Alessandro; Bifone, Angelo; Mazzolai, Barbara

2013-01-01

The octopus sucker represents a fascinating natural system performing adhesion on different terrains and substrates. Octopuses use suckers to anchor the body to the substrate or to grasp, investigate and manipulate objects, just to mention a few of their functions. Our study focuses on the morphology and adhesion mechanism of suckers in Octopus vulgaris. We use three different techniques (MRI, ultrasonography, and histology) and a 3D reconstruction approach to contribute knowledge on both morphology and functionality of the sucker structure in O. vulgaris. The results of our investigation are two-fold. First, we observe some morphological differences with respect to the octopus species previously studied (i.e., Octopus joubini, Octopus maya, Octopus bimaculoides/bimaculatus and Eledone cirrosa). In particular, in O. vulgaris the acetabular chamber, that is a hollow spherical cavity in other octopuses, shows an ellipsoidal cavity which roof has an important protuberance with surface roughness. Second, based on our findings, we propose a hypothesis on the sucker adhesion mechanism in O. vulgaris. We hypothesize that the process of continuous adhesion is achieved by sealing the orifice between acetabulum and infundibulum portions via the acetabular protuberance. We suggest this to take place while the infundibular part achieves a completely flat shape; and, by sustaining adhesion through preservation of sucker configuration. In vivo ultrasonographic recordings support our proposed adhesion model by showing the sucker in action. Such an underlying physical mechanism offers innovative potential cues for developing bioinspired artificial adhesion systems. Furthermore, we think that it could possibly represent a useful approach in order to investigate any potential difference in the ecology and in the performance of adhesion by different species. PMID:23750233

The addition of nanostructured hydroxyapatite to an experimental adhesive resin.

PubMed

Leitune, Vicente Castelo Branco; Collares, Fabrício Mezzomo; Trommer, Rafael Mello; Andrioli, Daniela Guerra; Bergmann, Carlos Pérez; Samuel, Susana Maria Werner

2013-04-01

Was produced nanostructured hydroxyapatite (HAnano) and evaluated the influence of its incorporation in an adhesive resin. HAnano was produced by a flame-based process and was characterized by scanning electron microscopy. The surface area, particle size, micro-Raman and cytotoxicity were evaluated. The organic phase was formulated by mixing 50 wt.% Bis-GMA, 25 wt.% TEGDMA, and 25 wt.% HEMA. HAnano was added at seven different concentrations: 0; 0.5; 1; 2; 5; 10 and 20 wt.%. Adhesive resins with hydroxyapatite incorporation were evaluated for their radiopacity, degree of conversion, flexural strength, softening in solvent and microshear bond strength. The data were analyzed by one-way ANOVA and Tukey's post hoc test (α=0.05), except for softening in solvent (paired t-test) and cytotoxicity (two-way ANOVA and Bonferroni). HAnano presented 15.096 m(2)/g of specific surface area and a mean size of 26.7 nm. The radiopacity values were not different from those of 1-mm aluminium. The degree of conversion ranged from 52.2 to 63.8%. The incorporation of HAnano did not influence the flexural strength, which ranged from 123.3 to 143.4MPa. The percentage of reduction of the microhardness after immersion in the solvent became lower as the HAnano concentration increased. The addition of 2% nanostructured hydroxyapatite resulted in a higher value of microshear bond strength than the control group (p<0.05). The incorporation of 2% of nanostructured hydroxyapatite into an adhesive resin presented the best results. The incorporation of nanostructured hydroxyapatite increases the adhesive properties and may be a promising filler for adhesive resin. Copyright © 2013 Elsevier Ltd. All rights reserved.

CO2 adhesion on hydrated mineral surfaces.

PubMed

Wang, Shibo; Tao, Zhiyuan; Persily, Sara M; Clarens, Andres F

2013-10-15

Hydrated mineral surfaces in the environment are generally hydrophilic but in certain cases can strongly adhere CO2, which is largely nonpolar. This adhesion can significantly alter the wettability characteristics of the mineral surface and consequently influence capillary/residual trapping and other multiphase flow processes in porous media. Here, the conditions influencing adhesion between CO2 and homogeneous mineral surfaces were studied using static pendant contact angle measurements and captive advancing/receding tests. The prevalence of adhesion was sensitive to both surface roughness and aqueous chemistry. Adhesion was most widely observed on phlogopite mica, silica, and calcite surfaces with roughness on the order of ~10 nm. The incidence of adhesion increased with ionic strength and CO2 partial pressure. Adhesion was very rarely observed on surfaces equilibrated with brines containing strong acid or base. In advancing/receding contact angle measurements, adhesion could increase the contact angle by a factor of 3. These results support an emerging understanding of adhesion of, nonpolar nonaqueous phase fluids on mineral surfaces influenced by the properties of the electrical double layer in the aqueous phase film and surface functional groups between the mineral and CO2.

Bifurcations: Focal Points of Particle Adhesion in Microvascular Networks

PubMed Central

Prabhakarpandian, Balabhaskar; Wang, Yi; Rea-Ramsey, Angela; Sundaram, Shivshankar; Kiani, Mohammad F.; Pant, Kapil

2011-01-01

Objective Particle adhesion in vivo is dependent on microcirculation environment which features unique anatomical (bifurcations, tortuosity, cross-sectional changes) and physiological (complex hemodynamics) characteristics. The mechanisms behind these complex phenomena are not well understood. In this study, we used a recently developed in vitro model of microvascular networks, called Synthetic Microvascular Network, for characterizing particle adhesion patterns in the microcirculation. Methods Synthetic microvascular networks were fabricated using soft lithography processes followed by particle adhesion studies using avidin and biotin-conjugated microspheres. Particle adhesion patterns were subsequently analyzed using CFD based modeling. Results Experimental and modeling studies highlighted the complex and heterogeneous fluid flow patterns encountered by particles in microvascular networks resulting in significantly higher propensity of adhesion (>1.5X) near bifurcations compared to the branches of the microvascular networks. Conclusion Bifurcations are the focal points of particle adhesion in microvascular networks. Changing flow patterns and morphology near bifurcations are the primary factors controlling the preferential adhesion of functionalized particles in microvascular networks. Synthetic microvascular networks provide an in vitro framework for understanding particle adhesion. PMID:21418388

Characterization and complete genome sequences of L. rhamnosus DSM 14870 and L. gasseri DSM 14869 contained in the EcoVag® probiotic vaginal capsules.

PubMed

Marcotte, Harold; Krogh Andersen, Kasper; Lin, Yin; Zuo, Fanglei; Zeng, Zhu; Larsson, Per Göran; Brandsborg, Erik; Brønstad, Gunnar; Hammarström, Lennart

2017-12-01

Lactobacillus rhamnosus DSM 14870 and Lactobacillus gasseri DSM 14869 were previously isolated from the vaginal epithelial cells (VEC) of healthy women and selected for the development of the vaginal EcoVag ® probiotic capsules. EcoVag ® was subsequently shown to provide long-term cure and reduce relapse of bacterial vaginosis (BV) as an adjunct to antibiotic therapy. To identify genes potentially involved in probiotic activity, we performed genome sequencing and characterization of the two strains. The complete genome analysis of both strains revealed the presence of genes encoding functions related to adhesion, exopolysaccharide (EPS) biosynthesis, antimicrobial activity, and CRISPR adaptive immunity but absence of antibiotic resistance genes. Interesting features of L. rhamnosus DSM 14870 genome include the presence of the spaCBA-srtC gene encoding spaCBA pili and interruption of the gene cluster encoding long galactose-rich EPS by integrases. Unique to L. gasseri DSM 14869 genome was the presence of a gene encoding a putative (1456 amino acid) new adhesin containing two rib/alpha-like repeats. L. rhamnosus DSM 14870 and L. gasseri DSM 14869 showed acidification of the culture medium (to pH 3.8) and a strong adhesion capability to the Caco-2 cell line and VEC. L. gasseri DSM 14869 could produce a thick (40nm) EPS layer and hydrogen peroxide. L. rhamnosus DSM 14870 was shown to produce SpaCBA pili and a 20nm EPS layer, and could inhibit the growth of Gardnerella vaginalis, a bacterium commonly associated with BV. The genome sequences provide a basis for further elucidation of the molecular basis for their probiotic functions. Copyright © 2017 Elsevier GmbH. All rights reserved.

Production and in vitro evaluation of soy protein-based biofilms as a support for human keratinocyte and fibroblast culture.

PubMed

Curt, Sèverine; Subirade, Muriel; Rouabhia, Mahmoud

2009-06-01

This study presents results on soy protein isolate (SPI) biofilm production and the corresponding effect on the stability and toxicity of the derived films. SPI biofilms were prepared from SPI chemically treated with formaldehyde at various concentrations (0%, 1%, 2%, and 3%) as cross-linking agents. In vitro SPI biofilm degradation was evaluated as a function of water absorption leading to weight and size modifications. SPI biofilm toxicity was determined as a function of human keratinocyte and fibroblast adhesion, viability, and proliferation. Cytokine gene expression supported this using reverse transcriptase polymerase chain reaction techniques. Our results confirm that SPI can be used to produce biofilms. The resulting SPI biofilms without formaldehyde swell significantly, which leads to their physical instability. Formaldehyde treatment enhanced the mechanical properties of these biofilms by covalently cross-linking polypeptide chains. The decreased water absorption was dependent on the amount of formaldehyde present. SPI biofilms with 2% and 3% formaldehyde were highly stable and easier to manipulate than those with 0% and 1% formaldehyde. Tissue culture analyses revealed that the SPI biofilms without formaldehyde were non-toxic to human cells (keratinocytes and fibroblasts). The presence of formaldehyde in biofilms did not have any effects on cell viability, adhesion, or proliferation. This was supported by the high level of messenger RNA expression of interleukin-1 beta (IL-1beta) and tumor necrosis factor alpha by the keratinocytes and of IL-6 and IL-8 by the fibroblasts. Overall, we produced a stable, non-toxic soy protein support, which may be of potential interest in medical applications such as cell culture matrices and damaged tissue replacement.

Effect of Atmospheric Pressure Plasma Treatment on Surface Characteristics and Adhesive Bond Quality of Peel Ply Prepared Composites

NASA Astrophysics Data System (ADS)

Tracey, Ashley C.

The purpose of this research was to investigate if atmospheric pressure plasma treatment could modify peel ply prepared composite surfaces to create strong adhesive bonds. Two peel ply surface preparation composite systems previously shown to create weak bonds (low fracture energy and adhesion failure) that were potential candidates for plasma treatment were Toray T800/3900-2 carbon fiber reinforced polymer (CFRP) prepared with Precision Fabrics Group, Inc. (PFG) 52006 nylon peel ply and Hexcel T300/F155 CFRP prepared with PFG 60001 polyester peel ply. It was hypothesized that atmospheric pressure plasma treatment could functionalize and/or remove peel ply remnants left on the CFRP surfaces upon peel ply removal. Surface characterization measurements and double cantilever beam (DCB) testing were used to determine the effects of atmospheric pressure plasma treatment on surface characteristics and bond quality of peel ply prepared CFRP composites. Previous research showed that Toray T800/3900-2 carbon fiber reinforced epoxy composites prepared with PFG 52006 peel ply and bonded with Cytec MetlBond 1515-3M structural film adhesive failed in adhesion at low fracture energies when tested in the DCB configuration. Previous research also showed that DCB samples made of Hexcel T300/F155 carbon fiber reinforced epoxy composites prepared with PFG 60001 peel ply and bonded with Henkel Hysol EA 9696 structural film adhesive failed in adhesion at low fracture energies. Recent research suggested that plasma treatment could be able to activate these "un-bondable" surfaces and result in good adhesive bonds. Nylon peel ply prepared 177 °C cure and polyester peel ply prepared 127 °C cure CFRP laminates were treated with atmospheric pressure plasma after peel ply removal prior to bonding. Atmospheric pressure plasma treatment was capable of significantly increasing fracture energies and changing failure modes. For Toray T800/3900-2 laminates prepared with PFG 52006 and bonded with MetlBond 1515-3M, plasma treatment increased fracture energies from 460 J/m 2. Atmospheric pressure plasma treatment also increased fracture energies of Hexcel T300/F155 laminates prepared with PFG 60001 and bonded with EA 9696 from 1500 J/m2. It was demonstrated that atmospheric pressure plasma treatment was able to transform poor bonding surfaces into acceptable ones by reversing the negative effects of incorrect peel ply usage. To determine if the primary reason for adhesion was functionalization or removal, a number of experiments were performed. Surface characteristics of peel ply only and plasma treated samples were determined using contact angle (CA) measurements, FTIR spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). CA was used to assess solid surface energy that was useful to determine wetting of the adhesive on the adherend, one requirement of adhesion. FTIR and XPS were used to analyze composite surface chemistry, including the identification of functional groups that were a product of atmospheric pressure plasma treatment, as well as contaminants that can inhibit adhesive bonding. SEM was used to capture surface morphology to identify peel ply remnants and whether these remnants were physically removed or modified due to plasma treatment. This research supported that atmospheric pressure plasma treatment resulted in adhesion primarily due to functionalization of peel ply remnants, though a removal mechanism was not disproven. It was also shown that surface energy exhibited potential for predicting adhesion. Lastly, this research indicated that plasma treatment is a robust surface preparation, as strong bonds were observed up to 30 days after treatment.

Solvent composition of one-step self-etch adhesives and dentine wettability.

PubMed

Grégoire, Geneviève; Dabsie, Firas; Dieng-Sarr, Farimata; Akon, Bernadette; Sharrock, Patrick

2011-01-01

Our aim was to determine the wettability of dentine by four commercial self-etch adhesives and evaluate their spreading rate on the dentine surface. Any correlation with chemical composition was sought, particularly with the amount of solvent or HEMA present in the adhesive. The adhesives used were AdheSE One, Optibond All.In.One, Adper Easy Bond and XenoV. Chemical compositions were determined by proton nuclear magnetic resonance (NMR) spectroscopy of the adhesives dissolved in dimethylsulfoxide. Apparent contact angles for sessile drops of adhesives were measured on dentine slices as a function of time for up to 180s. The water contact angles were determined for fully polymerised adhesives. All adhesives were water-based with total solvent contents ranging from 27% to 73% for HEMA-free adhesives, and averaging 45% for HEMA containing adhesives. The contents in hydrophobic groups decreased as water contents increased. No differences were found in the adhesive contact angles after 180s even though the spreading rates were different for the products tested. Water contact angles differed significantly but were not correlated with HEMA or solvent presence. Manufacturers use different approaches to stabilise acid co-monomer ingredients in self-etch adhesives. Co-solvents, HEMA, or acrylamides without co-solvents are used to simultaneously etch and infiltrate dentine. A large proportion of water is necessary for decalcification action. Copyright © 2010 Elsevier Ltd. All rights reserved.

Corticotropin-Releasing Hormone Modulates Human Trophoblast Invasion through Carcinoembryonic Antigen-Related Cell Adhesion Molecule-1 Regulation

PubMed Central

Bamberger, Ana-Maria; Minas, Vassilis; Kalantaridou, Sophia N.; Radde, Jessica; Sadeghian, Helen; Löning, Thomas; Charalampopoulos, Ioannis; Brümmer, Jens; Wagener, Christoph; Bamberger, Christoph M.; Schulte, Heinrich M.; Chrousos, George P.; Makrigiannakis, Antonis

2006-01-01

Abnormalities in the process of trophoblast invasion may result in abnormal placentation. Both the embryonic trophoblast and maternal decidua produce corticotropin-releasing hormone (CRH), which promotes implantation. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), which is expressed in extravillous trophoblasts (EVTs) of normal human placenta, may also function in tro-phoblast/endometrial interactions. We investigated whether locally produced CRH plays a role in trophoblast invasion, primarily by regulating CEACAM1 expression. We examined cultures of freshly isolated human EVTs, which express CEACAM1, and an EVT-based hybridoma cell line, which is devoid of endogenous CEACAM1. CRH inhibited EVT invasion in Matrigel invasion assays, and this effect was blocked by the CRH receptor type 1 (CRHR1)-specific antagonist antalarmin. Additionally, CRH decreased CEACAM1 expression in EVTs in a dose-dependent manner. After transfection of the hybridoma cell line with a CEACAM1 expression vector, the invasiveness of these cells was strongly enhanced. This effect was inhibited by addition of blocking monoclonal antibody against CEACAM1. Furthermore, blocking of endogenous CEACAM1 in EVTs inhibited the invasive potential of these cells. Taken together these findings suggest that CRH inhibits trophoblast invasion by decreasing the expression of CEACAM1 through CRHR1, an effect that might be involved in the pathophysiology of clinical conditions, such as preeclampsia and placenta accreta. PMID:16400017

Super hydrophilic thin film nitinol demonstrates reduced platelet adhesion compared with commercially available endograft materials.

PubMed

Tulloch, Allan W; Chun, Youngjae; Levi, Daniel S; Mohanchandra, Kotekar P; Carman, Gregory P; Lawrence, Peter F; Rigberg, David A

2011-11-01

Thin film nitinol (TFN) is a novel material with which to cover stents for the treatment of a wide range of vascular disease processes. This study aimed to show that TFN, if treated to produce a super hydrophilic surface, significantly reduces platelet adhesion, potentially rendering covered stents more resistant to thrombosis compared to commercially available materials. TFN was fabricated using a sputter deposition process to produce a 5-μ thin film of uniform thickness. TFN then underwent a surface treatment process to create a super hydrophilic layer. Platelet adhesion studies compared surface treated TFN (S-TFN) to untreated TFN, polytetrafluoroethylene, Dacron, and bulk nitinol. In vivo swine studies examined the placement of an S-TFN covered stent in a 3.5 mm diameter external iliac artery. Angiography confirmed placement, and repeat angiography was performed at 2 wk followed by post mortem histopathology. S-TFN significantly reduced platelet adhesion without any evidence of aggregation compared with all materials studied (P < 0.05). Furthermore, in vivo swine studies demonstrated complete patency of the S-TFN covered stent at 2 wk. Post mortem histopathology showed rapid endothelialization of the S-TFN without excessive neointimal hyperplasia. These results demonstrate that S-TFN significantly reduces platelet adhesion and aggregation compared with commercially available endograft materials. Furthermore, the hydrophilic surface may confer thromboresistance in vivo, suggesting that S-TFN is a possible superior material for covering stents. Copyright © 2011 Elsevier Inc. All rights reserved.

Motility and Adhesiveness in Human Neutrophils

PubMed Central

Smith, C. Wayne; Hollers, James C.; Patrick, Richard A.; Hassett, Clare

1979-01-01

Human peripheral blood neutrophils (PMN) obtained from healthy adults were examined in vitro with techniques adapted to assess the effects of chemotactic factors (CF) on cellular configuration and adhesiveness. The results were compared with those that use certain conventional techniques for assessing chemotaxis and chemokinesis. Exposure of PMN to N-formyl-l-methionyl-l-phenylalanine (f-Met-Phe), zymosan-activated serum, bacterial chemotactic factor, or a low molecular weight chemotactic factor from activated serum (C5a) in the absence of a gradient resulted in a change in cellular shape from a spherical to a polarized configuration in a high percentage of cells. This occurred rapidly in suspension, under conditions designed to exclude a role for cell adhesiveness, and was reversible upon removal of the CF. Restimulation of cells with the CF resulted in reappearance of the polarized configuration to the same extent as on initial stimulation with one exception: f-Met-Phe pretreated cells failed to respond to f-Met-Phe, though they responded fully to the other CF. Each CF caused a significant increase in PMN attachment to protein-coated glass. This enhanced adhesiveness was not reversible upon removal of the CF when the cells were treated under conditions shown to produce chemotactic deactivation. Cells treated under these conditions also exhibited significantly reduced motility on glass and in micropore filters in the absence of a gradient of CF. Bacterial chemotactic factor, even at high concentrations, failed to produce deactivation and did not cause a sustained enhancement of adhesiveness. Images PMID:372238

Inhibition of bacterial adhesion on PVC endotracheal tubes by RF-oxygen glow discharge, sodium hydroxide and silver nitrate treatments.

PubMed

Balazs, D J; Triandafillu, K; Wood, P; Chevolot, Y; van Delden, C; Harms, H; Hollenstein, C; Mathieu, H J

2004-05-01

Medical-grade poly(vinyl chloride) (PVC) was chemically modified to study how the incorporation of monovalent silver influences Pseudomonas aeruginosa adhesion and colonization. The modification investigated consisted of a radio frequency-oxygen (RF-O(2)) glow discharge pre-functionalization, followed by a two-step wet-treatment in sodium hydroxide and silver nitrate solutions. X-ray photoelectron spectroscopy (XPS) analysis and contact angle measurements were used to investigate the chemical nature and surface wettability of the films following each step of the modification. XPS analysis proved that the RF-O(2) plasma pre-functionalization of native PVC reproducibly increased the amount of functional groups representative of PVC additives, including ether/alcohol, esters and carboxyl groups. More specifically, we demonstrated that the O-C=O groups representative of the phthalic ester and zinc carboxylate additives identified for native PVC increased by two-fold following the RF-O(2) plasma pre-functionalization step. Although RF-O(2) pre-functionalization did not have an effect on the silver content of the NaOH/AgNO(3) treated substrates, such a modification was necessary for biomaterial products that did not have reproducible surfaces amongst production lots. XPS analysis also demonstrated that saponification with sodium hydroxide (NaOH) of esters, like those of the phthalic ester additives of PVC is a simple, irreversible method of hydrolysis, which produced sodium carboxylate and sodium phthalate salts. Exposure of native PVC to NaOH resulted in an increased surface hydrophilicity (from ca 90 degrees to ca 60 degrees ) due to dechlorination. XPS analysis following further incubation in silver nitrate demonstrated that silver ions can be trapped when the sodium of sodium carboxylate is replaced by silver after performing a second treatment with a monovalent silver-containing solution. The creation of silver salt on native PVC resulted in an ultra-hydrophobic (>120 degrees ) surface. The chemical modifications using NaOH and AgNO(3) wet treatments completely inhibited bacterial adhesion of four strains of P. aeruginosa to both native and oxygen-pre-functionalized PVC, and efficiently prevented colonization over longer periods (72 h). Our results suggest that surface modifications that incorporate silver ions would be extremely effective at reducing bacterial colonization to medical devices.

Molecular Basis for Strain Variation in the Saccharomyces cerevisiae Adhesin Flo11p

PubMed Central

Li, Li; Lipke, Peter N.; Dranginis, Anne M.

2016-01-01

ABSTRACT FLO11 encodes a yeast cell wall flocculin that mediates a variety of adhesive phenotypes in Saccharomyces cerevisiae. Flo11p is implicated in many developmental processes, including flocculation, formation of pseudohyphae, agar invasion, and formation of microbial mats and biofilms. However, Flo11p mediates different processes in different yeast strains. To investigate the mechanisms by which FLO11 determines these differences in colony morphology, flocculation, and invasion, we studied gene structure, function, and expression levels. Nonflocculent Saccharomyces cerevisiae Σ1278b cells exhibited significantly higher FLO11 mRNA expression, especially in the stationary phase, than highly flocculent S. cerevisiae var. diastaticus. The two strains varied in cell surface hydrophobicity, and Flo11p contributed significantly to surface hydrophobicity in S. cerevisiae var. diastaticus but not in strain Σ1278b. Sequencing of the FLO11 gene in S. cerevisiae var. diastaticus revealed strain-specific differences, including a 15-amino-acid insertion in the adhesion domain. Flo11p adhesion domains from strain Σ1278b and S. cerevisiae var. diastaticus were expressed and used to coat magnetic beads. The adhesion domain from each strain bound preferentially to homologous cells, and the preferences were independent of the cells in which the adhesion domains were produced. These results are consistent with the idea that strain-specific variations in the amino acid sequences in the adhesion domains cause different Flo11p flocculation activities. The results also imply that strain-specific differences in expression levels, posttranslational modifications, and allelic differences outside the adhesion domains have little effect on flocculation. IMPORTANCE As a nonmotile organism, Saccharomyces cerevisiae employs the cell surface flocculin Flo11/Muc1 as an important means of adapting to environmental change. However, there is a great deal of strain variation in the expression of Flo11-dependent phenotypes, including flocculation. In this study, we investigated the molecular basis of this strain-specific phenotypic variability. Our data indicate that strain-specific differences in the level of flocculation result from significant sequence differences in the FLO11 alleles and do not depend on quantitative differences in FLO11 expression or on surface hydrophobicity. We further have shown that beads coated with amino-terminal domain peptide bind preferentially to homologous cells. These data show that variability in the structure of the Flo11 adhesion domain may thus be an important determinant of membership in microbial communities and hence may drive selection and evolution. PMID:27547826

Switchable bio-inspired adhesives

NASA Astrophysics Data System (ADS)

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.

Glycoprotein Ibα receptor instability is associated with loss of quality in platelets produced in culture.

PubMed

Robert, Amélie; Boyer, Lucie; Pineault, Nicolas

2011-03-01

The development of culture processes for hematopoietic progenitors could lead to the development of a complementary source of platelets for therapeutic purposes. However, functional characterization of culture-derived platelets remains limited, which raises some uncertainties about the quality of platelets produced in vitro. The aim of this study was to define the proportion of functional platelets produced in cord blood CD34+ cell cultures. Toward this, the morphological and functional properties of culture-derived platelet-like particles (PLPs) were critically compared to that of blood platelets. Flow cytometry combined with transmission electron microscopy analyses revealed that PLPs formed a more heterogeneous population of platelets at a different stage of maturation than blood platelets. The majority of PLPs harbored the fibrinogen receptor αIIbβ3, but a significant proportion failed to maintain glycoprotein (GP)Ibα surface expression, a component of the vWF receptor essential for platelet functions. Importantly, GPIbα extracellular expression correlated closely with platelet function, as the GPIIb+ GPIbα+ PLP subfraction responded normally to agonist stimulation as evidenced by α-granule release, adhesion, spreading, and aggregation. In contrast, the GPIIb+ GPIbα⁻ subfraction was unresponsive in most functional assays and appeared to be metabolically inactive. The present study confirms that functional platelets can be generated in cord blood CD34+ cell cultures, though these are highly susceptible to ectodomain shedding of receptors associated with loss of function. Optimization of culture conditions to prevent these deleterious effects and to homogenize PLPs is necessary to improve the quality and yields of culture-derived platelets before they can be recognized as a suitable complementary source for therapeutic purposes.

Biomimetic approaches to modulate cellular adhesion in biomaterials: A review.

PubMed

Rahmany, Maria B; Van Dyke, Mark

2013-03-01

Natural extracellular matrix (ECM) proteins possess critical biological characteristics that provide a platform for cellular adhesion and activation of highly regulated signaling pathways. However, ECM-based biomaterials can have several limitations, including poor mechanical properties and risk of immunogenicity. Synthetic biomaterials alleviate the risks associated with natural biomaterials but often lack the robust biological activity necessary to direct cell function beyond initial adhesion. A thorough understanding of receptor-mediated cellular adhesion to the ECM and subsequent signaling activation has facilitated development of techniques that functionalize inert biomaterials to provide a biologically active surface. Here we review a range of approaches used to modify biomaterial surfaces for optimal receptor-mediated cell interactions, as well as provide insights into specific mechanisms of downstream signaling activation. In addition to a brief overview of integrin receptor-mediated cell function, so-called "biomimetic" techniques reviewed here include (i) surface modification of biomaterials with bioadhesive ECM macromolecules or specific binding motifs, (ii) nanoscale patterning of the materials and (iii) the use of "natural-like" biomaterials. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Nanowell-Trapped Charged Ligand-Bearing Nanoparticle Surfaces – A Novel Method of Enhancing Flow-Resistant Cell Adhesion

PubMed Central

Tran, Phat L.; Gamboa, Jessica R.; McCracken, Katherine E.; Riley, Mark R.

2014-01-01

Assuring cell adhesion to an underlying biomaterial surface is vital in implant device design and tissue engineering, particularly under circumstances where cells are subjected to potential detachment from overriding fluid flow. Cell-substrate adhesion is a highly regulated process involving the interplay of mechanical properties, surface topographic features, electrostatic charge, and biochemical mechanisms. At the nanoscale level the physical properties of the underlying substrate are of particular importance in cell adhesion. Conventionally, natural, pro-adhesive, and often thrombogenic, protein biomaterials are frequently utilized to facilitate adhesion. In the present study nanofabrication techniques are utilized to enhance the biological functionality of a synthetic polymer surface, polymethymethacrylate, with respect to cell adhesion. Specifically we examine the effect on cell adhesion of combining: 1. optimized surface texturing, 2. electrostatic charge and 3. cell adhesive ligands, uniquely assembled on the substrata surface, as an ensemble of nanoparticles trapped in nanowells. Our results reveal that the ensemble strategy leads to enhanced, more than simply additive, endothelial cell adhesion under both static and flow conditions. This strategy may be of particular utility for enhancing flow-resistant endothelialization of blood-contacting surfaces of cardiovascular devices subjected to flow-mediated shear. PMID:23225491

Cell Adhesion Molecules and Ubiquitination—Functions and Significance

PubMed Central

Homrich, Mirka; Gotthard, Ingo; Wobst, Hilke; Diestel, Simone

2015-01-01

Cell adhesion molecules of the immunoglobulin (Ig) superfamily represent the biggest group of cell adhesion molecules. They have been analyzed since approximately 40 years ago and most of them have been shown to play a role in tumor progression and in the nervous system. All members of the Ig superfamily are intensively posttranslationally modified. However, many aspects of their cellular functions are not yet known. Since a few years ago it is known that some of the Ig superfamily members are modified by ubiquitin. Ubiquitination has classically been described as a proteasomal degradation signal but during the last years it became obvious that it can regulate many other processes including internalization of cell surface molecules and lysosomal sorting. The purpose of this review is to summarize the current knowledge about the ubiquitination of cell adhesion molecules of the Ig superfamily and to discuss its potential physiological roles in tumorigenesis and in the nervous system. PMID:26703751

Numerical implementation of multiple peeling theory and its application to spider web anchorages.

PubMed

Brely, Lucas; Bosia, Federico; Pugno, Nicola M

2015-02-06

Adhesion of spider web anchorages has been studied in recent years, including the specific functionalities achieved through different architectures. To better understand the delamination mechanisms of these and other biological or artificial fibrillar adhesives, and how their adhesion can be optimized, we develop a novel numerical model to simulate the multiple peeling of structures with arbitrary branching and adhesion angles, including complex architectures. The numerical model is based on a recently developed multiple peeling theory, which extends the energy-based single peeling theory of Kendall, and can be applied to arbitrarily complex structures. In particular, we numerically show that a multiple peeling problem can be treated as the superposition of single peeling configurations even for complex structures. Finally, we apply the developed numerical approach to study spider web anchorages, showing how their function is achieved through optimal geometrical configurations.

Numerical implementation of multiple peeling theory and its application to spider web anchorages

PubMed Central

Brely, Lucas; Bosia, Federico; Pugno, Nicola M.

2015-01-01

Adhesion of spider web anchorages has been studied in recent years, including the specific functionalities achieved through different architectures. To better understand the delamination mechanisms of these and other biological or artificial fibrillar adhesives, and how their adhesion can be optimized, we develop a novel numerical model to simulate the multiple peeling of structures with arbitrary branching and adhesion angles, including complex architectures. The numerical model is based on a recently developed multiple peeling theory, which extends the energy-based single peeling theory of Kendall, and can be applied to arbitrarily complex structures. In particular, we numerically show that a multiple peeling problem can be treated as the superposition of single peeling configurations even for complex structures. Finally, we apply the developed numerical approach to study spider web anchorages, showing how their function is achieved through optimal geometrical configurations. PMID:25657835

Levels of Soluble Adhesion Molecules PECAM-1 and P-Selectin are Decreased in Children with Autism Spectrum Disorder

PubMed Central

Onore, Charity E.; Nordahl, Christine Wu; Young, Gregory S.; Van de Water, Judy A.; Rogers, Sally J.; Ashwood, Paul

2012-01-01

Background Although the etiopathology of Autism Spectrum Disorder (ASD) is not clear there is increasing evidence that dysfunction in the immune system affects many children with ASD. Findings of immune dysfunction in ASD include increases in inflammatory cytokines, chemokines and microglial activity in brain tissue and CSF, as well as abnormal peripheral immune cell function. Methods Adhesion molecules, such as platelet endothelial adhesion molecule-1 (PECAM-1), intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), P-Selectin, and L-Selectin, function to facilitate leukocyte transendothelial migration. We assessed concentrations of soluble adhesion molecules, sPECAM-1, sICAM-1, sVCAM-1, sP-Selectin, and sL-Selectin in the plasma of 49 participants with ASD, and 31 typically developing controls of the same age, all of whom were enrolled as part of the Autism Phenome Project (APP). Behavioral assessment, the levels of soluble adhesion molecules, head circumference and MRI measurements of brain volume were compared in the same subjects. Results Levels of sPECAM-1 and sP-Selectin were significantly reduced in the ASD group compared to typically developing controls (p < 0.02). Soluble PECAM-1 levels were negatively associated with repetitive behavior and abnormal brain growth in children with ASD (p=0.03). Conclusions As adhesion molecules modulate the permeability and signaling at the blood brain barrier as well as leukocyte infiltration into the CNS, current data suggests a role for these molecules in the complex pathophysiology of ASD. PMID:22717029

ATP release due to Thy-1–integrin binding induces P2X7-mediated calcium entry required for focal adhesion formation

PubMed Central

Henríquez, Mauricio; Herrera-Molina, Rodrigo; Valdivia, Alejandra; Alvarez, Alvaro; Kong, Milene; Muñoz, Nicolás; Eisner, Verónica; Jaimovich, Enrique; Schneider, Pascal; Quest, Andrew F. G.; Leyton, Lisette

2011-01-01

Thy-1, an abundant mammalian glycoprotein, interacts with αvβ3 integrin and syndecan-4 in astrocytes and thus triggers signaling events that involve RhoA and its effector p160ROCK, thereby increasing astrocyte adhesion to the extracellular matrix. The signaling cascade includes calcium-dependent activation of protein kinase Cα upstream of Rho; however, what causes the intracellular calcium transients required to promote adhesion remains unclear. Purinergic P2X7 receptors are important for astrocyte function and form large non-selective cation pores upon binding to their ligand, ATP. Thus, we evaluated whether the intracellular calcium required for Thy-1-induced cell adhesion stems from influx mediated by ATP-activated P2X7 receptors. Results show that adhesion induced by the fusion protein Thy-1-Fc was preceded by both ATP release and sustained intracellular calcium elevation. Elimination of extracellular ATP with Apyrase, chelation of extracellular calcium with EGTA, or inhibition of P2X7 with oxidized ATP, all individually blocked intracellular calcium increase and Thy-1-stimulated adhesion. Moreover, Thy-1 mutated in the integrin-binding site did not trigger ATP release, and silencing of P2X7 with specific siRNA blocked Thy-1-induced adhesion. This study is the first to demonstrate a functional link between αvβ3 integrin and P2X7 receptors, and to reveal an important, hitherto unanticipated, role for P2X7 in calcium-dependent signaling required for Thy-1-stimulated astrocyte adhesion. PMID:21502139

Glucosamine Treatment-mediated O-GlcNAc Modification of Paxillin Depends on Adhesion State of Rat Insulinoma INS-1 Cells*

PubMed Central

Kwak, Tae Kyoung; Kim, Hyeonjung; Jung, Oisun; Lee, Sin-Ae; Kang, Minkyung; Kim, Hyun Jeong; Park, Ji-Min; Kim, Sung-Hoon; Lee, Jung Weon

2010-01-01

Protein-protein interactions and/or signaling activities at focal adhesions, where integrin-mediated adhesion to extracellular matrix occurs, are critical for the regulation of adhesion-dependent cellular functions. Although the phosphorylation and activities of focal adhesion molecules have been intensively studied, the effects of the O-GlcNAc modification of their Ser/Thr residues on cellular functions have been largely unexplored. We investigated the effects of O-GlcNAc modification on actin reorganization and morphology of rat insulinoma INS-1 cells after glucosamine (GlcN) treatment. We found that paxillin, a key adaptor molecule in focal adhesions, could be modified by O-GlcNAc in INS-1 cells treated with GlcN and in pancreatic islets from mice treated with streptozotocin. Ser-84/85 in human paxillin appeared to be modified by O-GlcNAc, which was inversely correlated to Ser-85 phosphorylation (Ser-83 in rat paxillin). Integrin-mediated adhesion signaling inhibited the GlcN treatment-enhanced O-GlcNAc modification of paxillin. Adherent INS-1 cells treated with GlcN showed restricted protrusions, whereas untreated cells showed active protrusions for multiple-elongated morphologies. Upon GlcN treatment, expression of a triple mutation (S83A/S84A/S85A) resulted in no further restriction of protrusions. Together these observations suggest that murine pancreatic β cells may have restricted actin organization upon GlcN treatment by virtue of the O-GlcNAc modification of paxillin, which can be antagonized by a persistent cell adhesion process. PMID:20829364

Highly adhesive and high fatigue-resistant copper/PET flexible electronic substrates

NASA Astrophysics Data System (ADS)

Park, Sang Jin; Ko, Tae-Jun; Yoon, Juil; Moon, Myoung-Woon; Oh, Kyu Hwan; Han, Jun Hyun

2018-01-01

A voidless Cu/PET substrate is fabricated by producing a superhydrophilic PET surface comprised of nanostructures with large width and height and then by Cu electroless plating. Effect of PET surface nanostructure size on the failure mechanism of the Cu/PET substrate is studied. The fabricated Cu/PET substrate exhibits a maximum peel strength of 1300 N m-1 without using an interlayer, and virtually no increase in electrical resistivity under the extreme cyclic bending condition of 1 mm curvature radius after 300 k cycles. The authors find that there is an optimum nanostructure size for the highest Cu/PET adhesion strength, and the failure mechanism of the Cu/PET flexible substrate depends on the PET surface nanostructure size. Thus, this work presents the possibility to produce flexible metal/polymer electronic substrates that have excellent interfacial adhesion between the metal and polymer and high fatigue resistance against repeated bending. Such metal/polymer substrates provides new design opportunities for wearable electronic devices that can withstand harsh environments and have extended lifetimes.

Properties of Nanocomposite Nickel-Carbon Films Deposited by Magnetron Sputtering

NASA Astrophysics Data System (ADS)

Grenadyorov, A. S.; Oskomov, K. V.; Solov'ev, A. A.; Rabotkin, S. V.; Zakharov, A. N.; Semenov, V. A.; Oskirko, V. O.; Yelgin, Yu. I.; Korneva, O. S.

2017-12-01

The method of magnetron sputtering was used to produce a-C and a-C:Ni films on substrates of monocrystalline silicon and thermoelectric material of n-type ((Bi2Te3)0.94(Bi2Se3)0.06) and p-type ((Bi2Te3)0.20(Sb2Te3)0.80) conductivity. The authors studied the effect of Ni concentration on specific electric resistance, hardness and adhesion of the produced films. It was demonstrated that specific resistance of a-C films deposited by graphite target sputtering when supplying high bias voltage onto the substrate can be reduced by increasing the share of graphitized carbon. Adding Ni to such films allows additionally reducing their specific resistance. The increase in Ni content is accompanied with the decrease in hardness and adhesion of a-C:Ni films. The acquired values of specific electric resistance and adhesion of a-C:Ni films to thermoelectric materials allow using them as barrier anti-diffusion coatings of thermoelectric modules.

Tobacco smoke induces epithelial barrier dysfunction via receptor EphA2 signaling.

PubMed

Nasreen, Najmunnisa; Khodayari, Nazli; Sriram, Peruvemba S; Patel, Jawaharlal; Mohammed, Kamal A

2014-06-15

Erythropoietin-producing human hepatocellular carcinoma (Eph) receptors are the largest family of receptor tyrosine kinases (RTKs) that mediate various cellular and developmental processes. The degrees of expression of these key molecules control the cell-cell interactions. Although the role of Eph receptors and their ligand Ephrins is well studied in developmental processes, their function in tobacco smoke (TS)-induced epithelial barrier dysfunction is unknown. We hypothesized that TS may induce permeability in bronchial airway epithelial cell (BAEpC) monolayer by modulating receptor EphA2 expression, actin cytoskeleton, adherens junction, and focal adhesion proteins. Here we report that in BAEpCs, acute TS exposure significantly upregulated EphA2 and EphrinA1 expression, disrupted the actin filaments, decreased E-cadherin expression, and increased protein permeability, whereas the focal adhesion protein paxillin was unaffected. Silencing the receptor EphA2 expression with silencing interference RNA (siRNA) significantly attenuated TS-induced hyperpermeability in BAEpCs. In addition, when BAEpC monolayer was transfected with EphA2-expressing plasmid and treated with recombinant EphrinA1, the transepithelial electrical resistance decreased significantly. Furthermore, TS downregulated E-cadherin expression and induced hyperpermeability across BAEpC monolayer in a Erk1/Erk2, p38, and JNK MAPK-dependent manner. TS induced hyperpermeability in BAEpC monolayer by targeting cell-cell adhesions, and interestingly cell-matrix adhesions were unaffected. The present data suggest that TS causes significant damage to the BAEpCs via induction of EphA2 and downregulation of E-cadherin. Induction of EphA2 in the BAEpCs exposed to TS may be an important signaling event in the pathogenesis of TS-induced epithelial injury.

Surface chemistry from wettability and charge for the control of mesenchymal stem cell fate through self-assembled monolayers.

PubMed

Hao, Lijing; Fu, Xiaoling; Li, Tianjie; Zhao, Naru; Shi, Xuetao; Cui, Fuzhai; Du, Chang; Wang, Yingjun

2016-12-01

Self-assembled monolayers (SAMs) of alkanethiols on gold are highly controllable model substrates and have been employed to mimic the extracellular matrix for cell-related studies. This study aims to systematically explore how surface chemistry influences the adhesion, morphology, proliferation and osteogenic differentiation of mouse mesenchymal stem cells (mMSCs) using various functional groups (-OEG, -CH 3 , -PO 3 H 2 , -OH, -NH 2 and -COOH). Surface analysis demonstrated that these functional groups produced a wide range of wettability and charge: -OEG (hydrophilic and moderate iso-electric point (IEP)), -CH 3 (strongly hydrophobic and low IEP), -PO 3 H 2 (moderate wettability and low IEP), -OH (hydrophilic and moderate IEP), -NH 2 (moderate wettability and high IEP) and -COOH (hydrophilic and low IEP). In terms of cell responses, the effect of wettability may be more influential than charge for these groups. Moreover, compared to -OEG and -CH 3 groups, -PO 3 H 2 , -OH, -NH 2 and -COOH functionalities tended to promote not only cell adhesion, proliferation and osteogenic differentiation but also the expression of α v and β 1 integrins. This finding indicates that the surface chemistry may guide mMSC activities through α v and β 1 integrin signaling pathways. Model surfaces with controllable chemistry may provide insight into biological responses to substrate surfaces that would be useful for the design of biomaterial surfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

MAPLE fabrication of thin films based on kanamycin functionalized magnetite nanoparticles with anti-pathogenic properties

NASA Astrophysics Data System (ADS)

Grumezescu, Valentina; Andronescu, Ecaterina; Holban, Alina Maria; Mogoantă, Laurenţiu; Mogoşanu, George Dan; Grumezescu, Alexandru Mihai; Stănculescu, Anca; Socol, Gabriel; Iordache, Florin; Maniu, Horia; Chifiriuc, Mariana Carmen

2015-05-01

In this study we aimed to evaluate the biocompatibility and antimicrobial activity of kanamycin functionalized 5 nm-magnetite (Fe3O4@KAN) nanoparticles thin films deposited by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique. A laser deposition regime was established in order to stoichiometrically transfer Fe3O4@KAN thin films on silicone and glass substrates. Morphological and physico-chemical properties of powders and coatings were characterized by XRD, TEM, SEM, AFM and IR microscopy (IRM). Our nanostructured thin films have proved efficiency in the prevention of microbial adhesion and mature biofilms development as a result of antibiotic release in its active form. Furthermore, kanamycin functionalized nanostructures exhibit a good biocompatibility, both in vivo and in vitro, demonstrating their potential for implants application. This is the first study reporting the assessment of the in vivo biocompatibility of a magnetite-antimicrobial thin films produced by MAPLE technique.

Suppression of lysyl-tRNA synthetase, KRS, causes incomplete epithelial-mesenchymal transition and ineffective cell‑extracellular matrix adhesion for migration.

PubMed

Nam, Seo Hee; Kang, Minkyung; Ryu, Jihye; Kim, Hye-Jin; Kim, Doyeun; Kim, Dae Gyu; Kwon, Nam Hoon; Kim, Sunghoon; Lee, Jung Weon

2016-04-01

The cell-adhesion properties of cancer cells can be targeted to block cancer metastasis. Although cytosolic lysyl-tRNA synthetase (KRS) functions in protein synthesis, KRS on the plasma membrane is involved in cancer metastasis. We hypothesized that KRS is involved in cell adhesion-related signal transduction for cellular migration. To test this hypothesis, colon cancer cells with modulated KRS protein levels were analyzed for cell-cell contact and cell-substrate adhesion properties and cellular behavior. Although KRS suppression decreased expression of cell-cell adhesion molecules, cells still formed colonies without being scattered, supporting an incomplete epithelial mesenchymal transition. Noteworthy, KRS-suppressed cells still exhibited focal adhesions on laminin, with Tyr397-phopshorylated focal adhesion kinase (FAK), but they lacked laminin-adhesion-mediated extracellular signal-regulated kinase (ERK) and paxillin activation. KRS, p67LR and integrin α6β1 were found to interact, presumably to activate ERK for paxillin expression and Tyr118 phosphorylation even without involvement of FAK, so that specific inhibition of ERK or KRS in parental HCT116 cells blocked cell-cell adhesion and cell-substrate properties for focal adhesion formation and signaling activity. Together, these results indicate that KRS can promote cell-cell and cell-ECM adhesion for migration.

Bacterial Adhesion on the Titanium and Stainless-Steel Surfaces Undergone Two Different Treatment Methods: Polishing and Ultrafast Laser Treatment

NASA Astrophysics Data System (ADS)

Chik, N.; Zain, W. S. Wan Md; Mohamad, A. J.; Sidek, M. Z.; Ibrahim, W. H. Wan; Reif, A.; Rakebrandt, J. H.; Pfleging, W.; Liu, X.

2018-05-01

Bacterial adhesion has become a significant problem in many industries causing billions of dollars for its complicated removal treatment and maintenance. In this study, metal surfaces undergone treatment with ultrafast laser with varies power. The microstructure produced on its original surfaces were expected to prevent the adhesion of Escherichia coli (E. coli) ATCC 8739 and Staphylococcus aureus (S. aureus) ATCC 6838. The laser treatment was performed at 380 fs pulse duration, 515 µm central wavelength and a repetition rate of 200 kHz. Stainless steel AISI 316L was treated with an average laser power of 0.04 W (SS-0.04) and 0.11 W (SS-0.11), while Grade 5 titanium alloy was tested with high laser power 0.11 W (T-0.11). The adhesion was observed after 16 hours and the number of adhering bacteria was counted per cm2. The result achieved shows that, increasing the average laser power is leading to an enhanced S. aureus adhesion while E. coli adhesion is reduced which is due to the hydrophobicity interaction and difference in surface texture. Meanwhile, the laser treatment showed significant reduction of the bacterial adhesion on its surface compared to the polished surfaces. Thus, ultrafast laser texturing can be suggested as a promising method to reduce the bacterial adhesion, which reduced the adhesion of >80% for E. coli and >20% for S. aureus.

Modeling cell-substrate de-adhesion dynamics under fluid shear

NASA Astrophysics Data System (ADS)

Maan, Renu; Rani, Garima; Menon, Gautam I.; Pullarkat, Pramod A.

2018-07-01

Changes in cell-substrate adhesion are believed to signal the onset of cancer metastasis, but such changes must be quantified against background levels of intrinsic heterogeneity between cells. Variations in cell-substrate adhesion strengths can be probed through biophysical measurements of cell detachment from substrates upon the application of an external force. Here, we investigate, theoretically and experimentally, the detachment of cells adhered to substrates when these cells are subjected to fluid shear. We present a theoretical framework within which we calculate the fraction of detached cells as a function of shear stress for fast ramps as well as the decay in this fraction at fixed shear stress as a function of time. Using HEK and 3T3 fibroblast cells as experimental model systems, we extract characteristic force scales for cell adhesion as well as characteristic detachment times. We estimate force-scales of  ∼500 pN associated to a single focal contact, and characteristic time-scales of s representing cell-spread-area dependent mean first passage times to the detached state at intermediate values of the shear stress. Variations in adhesion across cell types are especially prominent when cell detachment is probed by applying a time-varying shear stress. These methods can be applied to characterizing changes in cell adhesion in a variety of contexts, including metastasis.

Substrate effect modulates adhesion and proliferation of fibroblast on graphene layer.

PubMed

Lin, Feng; Du, Feng; Huang, Jianyong; Chau, Alicia; Zhou, Yongsheng; Duan, Huiling; Wang, Jianxiang; Xiong, Chunyang

2016-10-01

Graphene is an emerging candidate for biomedical applications, including biosensor, drug delivery and scaffold biomaterials. Cellular functions and behaviors on different graphene-coated substrates, however, still remain elusive to a great extent. This paper explored the functional responses of cells such as adhesion and proliferation, to different kinds of substrates including coverslips, silicone, polydimethylsiloxane (PDMS) with different curing ratios, PDMS treated with oxygen plasma, and their counterparts coated with single layer graphene (SLG). Specifically, adherent cell number, spreading area and cytoskeleton configuration were exploited to characterize cell-substrate adhesion ability, while MTT assay was employed to test the proliferation capability of fibroblasts. Experimental outcome demonstrated graphene coating had excellent cytocompatibility, which could lead to an increase in early adhesion, spreading, proliferation, and remodeling of cytoskeletons of fibroblast cells. Notably, it was found that the underlying substrate effect, e.g., stiffness of substrate materials, could essentially regulate the adhesion and proliferation of cells cultured on graphene. The stiffer the substrates were, the stronger the abilities of adhesion and proliferation of fibroblasts were. This study not only deepens our understanding of substrate-modulated interfacial interactions between live cells and graphene, but also provides a valuable guidance for the design and application of graphene-based biomaterials in biomedical engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of Zirconia Nanoparticles in Epoxy-Silica Hybrid Adhesives to Join Aluminum Substrates.

PubMed

Figueroa-Lara, José de Jesús; Torres-Rodríguez, Miguel; Gutiérrez-Arzaluz, Mirella; Romero-Romo, Mario

2017-09-27

This research presents the interaction of the epoxy polymer diglicydil ether of bisphenol-A (DGEBA) with silica (SiO₂) nanoparticles plus zirconia (ZrO₂) nanoparticles obtained via the sol-gel method in the synthesis of an epoxy-silica-zirconia hybrid adhesive cured with polyamide. ZrO₂ nanoparticles were added to the epoxy-silica hybrid adhesive produced in situ to modify the apparent shear strength of two adhesively bonded aluminum specimens. The results showed that the addition of different amounts of ZrO₂ nanoparticles increased the shear strength of the adhesively bonded aluminum joint, previously treated by sandblasting, immersion in hot water and silanized with a solution of hydrolyzed 3-glycidoxipropyltrimethoxysilane (GPTMS). The morphology and microstructure of the nanoparticles and aluminum surfaces were examined by scanning electron microscopy (SEM), and elemental analysis was performed with the Energy-dispersive X-ray spectroscopy (EDS) detector; the chemical groups were investigated during the aluminum surface modification using Fourier transform infrared spectroscopy (FTIR).

Microfabricated adhesive mimicking gecko foot-hair.

PubMed

Geim, A K; Dubonos, S V; Grigorieva, I V; Novoselov, K S; Zhukov, A A; Shapoval, S Yu

2003-07-01

The amazing climbing ability of geckos has attracted the interest of philosophers and scientists alike for centuries. However, only in the past few years has progress been made in understanding the mechanism behind this ability, which relies on submicrometre keratin hairs covering the soles of geckos. Each hair produces a miniscule force approximately 10(-7) N (due to van der Waals and/or capillary interactions) but millions of hairs acting together create a formidable adhesion of approximately 10 N x cm(-2): sufficient to keep geckos firmly on their feet, even when upside down on a glass ceiling. It is very tempting to create a new type of adhesive by mimicking the gecko mechanism. Here we report on a prototype of such 'gecko tape' made by microfabrication of dense arrays of flexible plastic pillars, the geometry of which is optimized to ensure their collective adhesion. Our approach shows a way to manufacture self-cleaning, re-attachable dry adhesives, although problems related to their durability and mass production are yet to be resolved.

Influence of air-powder polishing on bond strength and surface-free energy of universal adhesive systems.

PubMed

Tamura, Yukie; Takamizawa, Toshiki; Shimamura, Yutaka; Akiba, Shunsuke; Yabuki, Chiaki; Imai, Arisa; Tsujimoto, Akimasa; Kurokawa, Hiroyasu; Miyazaki, Masashi

2017-11-29

The influences of air-powder polishing with glycine or sodium bicarbonate powders on shear bond strengths (SBS) and surface-free energies of universal adhesives were examined. Scotchbond Universal Adhesive (SU, 3M ESPE), G-Premio Bond (GP, GC), Adhese Universal (AU, Ivoclar Vivadent), and All-Bond Universal (AB, Bisco) were used in this study. Bovine dentin surfaces were air polished with glycine or sodium bicarbonate powders prior to the bonding procedure, and resin pastes were bonded to the dentin surface using universal adhesives. SBSs were determined after 24-h storage in distilled water at 37°C. Surface-free energy was then determined by measuring contact angles using three test liquids on dentin surfaces. Significantly lower SBSs were observed for dentin that was air-powder polished and surface-free energies were concomitantly lowered. This study indicated that air-powder polishing influences SBSs and surface-free energies. However, glycine powder produced smaller changes in these surface parameters than sodium bicarbonate.

Effect of Zirconia Nanoparticles in Epoxy-Silica Hybrid Adhesives to Join Aluminum Substrates

PubMed Central

Figueroa-Lara, José de Jesús; Torres-Rodríguez, Miguel

2017-01-01

This research presents the interaction of the epoxy polymer diglicydil ether of bisphenol-A (DGEBA) with silica (SiO2) nanoparticles plus zirconia (ZrO2) nanoparticles obtained via the sol-gel method in the synthesis of an epoxy-silica-zirconia hybrid adhesive cured with polyamide. ZrO2 nanoparticles were added to the epoxy-silica hybrid adhesive produced in situ to modify the apparent shear strength of two adhesively bonded aluminum specimens. The results showed that the addition of different amounts of ZrO2 nanoparticles increased the shear strength of the adhesively bonded aluminum joint, previously treated by sandblasting, immersion in hot water and silanized with a solution of hydrolyzed 3-glycidoxipropyltrimethoxysilane (GPTMS). The morphology and microstructure of the nanoparticles and aluminum surfaces were examined by scanning electron microscopy (SEM), and elemental analysis was performed with the Energy-dispersive X-ray spectroscopy (EDS) detector; the chemical groups were investigated during the aluminum surface modification using Fourier transform infrared spectroscopy (FTIR). PMID:28953243

Microfabricated adhesive mimicking gecko foot-hair

NASA Astrophysics Data System (ADS)

Geim, A. K.; Dubonos, S. V.; Grigorieva, I. V.; Novoselov, K. S.; Zhukov, A. A.; Shapoval, S. Yu.

2003-07-01

The amazing climbing ability of geckos has attracted the interest of philosophers and scientists alike for centuries. However, only in the past few years has progress been made in understanding the mechanism behind this ability, which relies on submicrometre keratin hairs covering the soles of geckos. Each hair produces a miniscule force ~10-7 N (due to van der Waals and/or capillary interactions) but millions of hairs acting together create a formidable adhesion of ~10 N cm-2: sufficient to keep geckos firmly on their feet, even when upside down on a glass ceiling. It is very tempting to create a new type of adhesive by mimicking the gecko mechanism. Here we report on a prototype of such 'gecko tape' made by microfabrication of dense arrays of flexible plastic pillars, the geometry of which is optimized to ensure their collective adhesion. Our approach shows a way to manufacture self-cleaning, re-attachable dry adhesives, although problems related to their durability and mass production are yet to be resolved.

Enzymatic Synthesis and Purification of Galactosylated Chitosan Oligosaccharides Reducing Adhesion of Enterotoxigenic Escherichia coli K88.

PubMed

Yan, Ya Lu; Hu, Ying; Simpson, David J; Gänzle, Michael G

2017-06-28

Enterotoxigenic Escherichia coli (ETEC) K88 causes diarrhea in weaned piglets and represent a suitable model system for ETEC causing childhood diarrhea. This study aimed to evaluate the effects of oligosaccharides against ETEC K88 adhesion to porcine erythrocytes with two bioassays. Galactosylated chitosan-oligosaccharides (Gal-COS) were synthesized through transgalactosylation by β-galactosidase. Fractions 2-5 of Gal-COS were obtained through cation exchange and size exclusion chromatography. Fractions 2-5 of acetylated Gal-COS were obtained through chemical acetylation followed by size exclusion chromatography. Gal-COS F2 containing the largest oligosaccharides had the highest antiadhesion activity with the minimum inhibitory concentration of 0.22 g/L, followed by F3 and F4. Acetylation of Gal-COS decreased their ability to reduce ETEC K88 adhesion. The composition of active oligosaccharides was determined with LC-MS. Galactosylation of COS produces oligosaccharides which reduce ETEC K88 adhesion; moreover, resulting oligosaccharides match the composition of human milk oligosaccharides, which prevent adhesion of multiple pathogens.

Nano-materials for adhesive-free adsorbers for bakable extreme high vacuum cryopump surfaces

DOEpatents

Stutzman, Marcy; Jordan, Kevin; Whitney, Roy R.

2016-10-11

A cryosorber panel having nanomaterials used for the cryosorption material, with nanomaterial either grown directly on the cryopanel or freestanding nanomaterials attached to the cryopanel mechanically without the use of adhesives. Such nanomaterial cryosorber materials can be used in place of conventional charcoals that are attached to cryosorber panels with special low outgassing, low temperature capable adhesives. Carbon nanotubes and other nanomaterials could serve the same purpose as conventional charcoal cryosorbers, providing a large surface area for cryosorption without the need for adhesive since the nanomaterials can be grown directly on a metallic substrate or mechanically attached. The nanomaterials would be capable of being fully baked by heating above 100.degree. C., thereby eliminating water vapor from the system, eliminating adhesives from the system, and allowing a full bake of the system to reduce hydrogen outgassing, with the goal of obtaining extreme high vacuum where the pump can produce pressures below 1.times.10.sup.-12 Torr.

A randomized controlled experimental study of the efficacy of platelet-rich plasma and hyaluronic acid for the prevention of adhesion formation in a rat uterine horn model.

PubMed

Oz, Murat; Cetinkaya, Nilufer; Bas, Sevda; Korkmaz, Elmas; Ozgu, Emre; Terzioglu, Gokay Serdar; Buyukkagnici, Umran; Akbay, Serap; Caydere, Muzaffer; Gungor, Tayfun

2016-09-01

Platelet-rich plasma (PRP) has been known to possess an efficacy in tissue regeneration. The aim of this study was to determine the role of PRP on post-operative adhesion formation in an experimental rat study. Thirty Sprague-Dawley rats were randomly divided into control, hyaluronic acid, and PRP treatment groups and operated on for uterine horn adhesion modeling. Blood was collected to produce a PRP with platelet counts of 688 × 10(3)/μL, and 1 ml of either hyaluronic acid gel or PRP was administered over the standard lesions, while the control group received no medication. The evaluation of post-operative adhesions was done on the 30th post-operative day. The location, extent, type, and tenacity of adhesions as well as total adhesion scores, tissue inflammation, fibrosis and transforming growth factor-1beta (TGF-1β) expressions were evaluated. The total adhesion score was significantly lower in the PRP group (3.2 ± 1.5) compared with the hyaluronic acid (5.0 ± 1.3) and control (8.1 ± 1.7) groups. The extent of the adhesions was significantly lower in the PRP group. There was no significant difference in the type and tenacity of adhesions between the hyaluronic acid and the PRP group. The level of inflammation was significantly higher in the control group than the others, while there was no difference between the PRP and hyaluronic acid groups. TGF-1β expression was significantly lesser in the PRP group than the control and hyaluronic acid groups. PRP is more effective than hyaluronic acid treatment in preventing post-operative adhesion formation in an experimental rat uterine horn adhesion model.

The effects of two soft drinks on bond strength, bracket microleakage, and adhesive remnant on intact and sealed enamel.

PubMed

Navarro, Raúl; Vicente, Ascensión; Ortiz, Antonio J; Bravo, Luis A

2011-02-01

The purpose of this study was to evaluate the effects of Coca-Cola and Schweppes Limón on bond strength, adhesive remnant, and microleakage beneath brackets. One hundred and twenty upper central incisor brackets were bonded to bovine incisors and divided into three groups: (1) Control, (2) Coca-Cola, and (3) Schweppes Limón. The teeth were submerged in the drinks three times a day for 15 minutes over a 15 day period. Shear bond strength (SBS) was measured with a universal testing machine, and adhesive remnant evaluated using image analysis equipment. Microleakage at the enamel-adhesive and adhesive-bracket interfaces was determined using methylene blue. One hundred and eight teeth were used for scanning electron microscopy to determine the effect of the drinks on intact and sealed enamel. SBS and adhesive remnant data were analysed using the Kruskal-Wallis test (P < 0.05) and microleakage using the Kruskal-Wallis and Mann-Whitney tests applying Bonferroni correction (P < 0.017). No significant differences were found in SBS and adhesive remnant between the groups (P > 0.05). Microleakage at the enamel-adhesive interface for groups 2 and 3 was significantly greater than for group 1 (P < 0.017). At the adhesive-bracket interface, microleakage was significantly greater in group 2 than in group 1 (P < 0.017) while microleakage in group 3 did not differ significantly from either group 1 or 2 (P < 0.017). The drinks produced enamel erosion, loss of adhesive and microleakage. Coca-Cola and Schweppes Limón did not affect the SBS of brackets or the adhesive remnant.

Bromelain: a natural proteolytic for intra-abdominal adhesion prevention.

PubMed

Sahbaz, Ahmet; Aynioglu, Oner; Isik, Hatice; Ozmen, Ulku; Cengil, Osman; Gun, Banu Dogan; Gungorduk, Kemal

2015-02-01

Peritoneal adhesions are pathological fibrous connections between peritoneal surfaces resulting from incomplete peritoneal repair. Adhesions cause various health problems ranging from pelvic pain and bowel obstruction to infertility. To date, no effective agent exists for intra-abdominal adhesion prevention. Bromelain is the crude extract of the pineapple and it has fibrinolytic, antithrombotic, and anti-inflammatory properties. Bromelain has been shown to be effective for removing necrotic tissues and has been found to be effective for treating various wounds, inflammatory conditions, and thrombotic pathologies. In the present study, we evaluated bromelain as a novel agent for preventing intra-abdominal adhesions. Group 1 (control group): Adhesions were produced by cecal abrasion method, and no treatment was applied. Group 2 (i.p. bromelain-treated group): After adhesion formation, 10 mg/kg/BW of bromelain dissolved in 1 mL saline solution was applied intraperitoneally for 10 days. Group 3 (i.p. saline-treated group): After adhesion formation, 1 mL saline solution was applied intraperitoneally for 10 days. On postoperative day 10, all animals were sacrificed. All 30 rats survived surgery. Throughout the follow-up period, no complications were observed. Statistically significant differences were found between the groups with regards to macroscopic adhesion scores, inflammation, fibrosis and neo-vascularization (p < 0.001, <0.001, p = 0.001, p = 0.002, respectively). Macroscopic and histopathologic (inflammation, fibrosis, neo-vascularization) adhesion scores were lowest in the bromelain-treated group. Bromelain, acting through its barrier, anti-inflammatory, antioxidant, and proteolytic effects and without increasing bleeding tendency or having any adverse effects on wound healing, may be a suitable agent for intra-abdominal adhesion prevention. Copyright © 2015 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.

Cloning and expression of recombinant adhesive protein MEFP-2 of the blue mussel, Mytilus edulis

DOEpatents

Silverman, Heather G.; Roberto, Francisco F.

2006-02-07

The present invention includes a Mytilus edulis cDNA having a nucleotide sequence that encodes for the Mytilus edulis foot protein-2 (Mefp-2), an example of a mollusk foot protein. Mefp-2 is an integral component of the blue mussels' adhesive protein complex, which allows the mussel to attach to objects underwater. The isolation, purification and sequencing of the Mefp-2 gene will allow researchers to produce Mefp-2 protein using genetic engineering techniques. The discovery of Mefp-2 gene sequences will also allow scientists to better understand how the blue mussel creates its waterproof adhesive protein complex.

Cloning and expression of recombinant adhesive protein Mefp-1 of the blue mussel, Mytilus edulis

DOEpatents

Silverman, Heather G.; Roberto, Francisco F.

2006-01-17

The present invention comprises a Mytilus edulis cDNA sequenc having a nucleotide sequence that encodes for the Mytilus edulis foot protein-1 (Mefp-1), an example of a mollusk foot protein. Mefp-1 is an integral component of the blue mussels' adhesive protein complex, which allows the mussel to attach to objects underwater. The isolation, purification and sequencing of the Mefp-1 gene will allow researchers to produce Mefp-1 protein using genetic engineering techniques. The discovery of Mefp-1 gene sequence will also allow scientists to better understand how the blue mussel creates its waterproof adhesive protein complex.

Adhesion in a Vacuum Environment and its Implications for Dust Mitigation Techniques on Airless Bodies

NASA Technical Reports Server (NTRS)

Berkebile, Stephen; Gaier, James R.

2012-01-01

During the Apollo missions, the adhesion of dust to critical spacecraft systems was a greater problem than anticipated and resulted in functional degradation of thermal control surfaces, spacesuit seals, and other spacecraft components. Notably, Earth-based simulation efforts did not predict the magnitude and effects of dust adhesion in the lunar environment. Forty years later, we understand that the ultrahigh vacuum (UHV) environment, coupled with micrometeorite impacts and constant ion and photon bombardment from the sun result in atomically clean and high surface energy dust particles and spacecraft surfaces. However, both the dominant mechanism of adhesion in airless environments and the conditions for high fidelity simulation tests have still to be determined. The experiments presented in here aim to aid in the development of dust mitigation techniques for airless bodies (e.g., lunar surface, asteroids, moons of outer planets). The approach taken consists of (a) quantifying the adhesion between common polymer and metallic spacecraft materials and a synthetic noritic volcanic glass, as a function of surface cleanliness and of triboelectric charge transfer in a UHV environment, and (b) determining parameters for high fidelity tests through investigation of adhesion dependence on vacuum environment and sample treatment. Adhesion force has been measured between pins of spacecraft materials and a plate of synthetic volcanic glass by determining the pull-off force with a torsion balance. Although no significant adhesion is generally observed directly as a result of high surface energies, the adhesion due to induced electrostatic charge is observed to increase with spacecraft material cleanliness, in some cases by over a factor of 10. Furthermore, electrostatically-induced adhesion is found to decrease rapidly above pressures of 10-6 torr. It is concluded that high-fidelity tests should be conducted in high to ultrahigh vacuum and include an ionized surface cleaning process.

Adhesion of bacterial pathogens to soil colloidal particles: influences of cell type, natural organic matter, and solution chemistry.

PubMed

Zhao, Wenqiang; Walker, Sharon L; Huang, Qiaoyun; Cai, Peng

2014-04-15

Bacterial adhesion to granular soil particles is well studied; however, pathogen interactions with naturally occurring colloidal particles (<2 μm) in soil has not been investigated. This study was developed to identify the interaction mechanisms between model bacterial pathogens and soil colloids as a function of cell type, natural organic matter (NOM), and solution chemistry. Specifically, batch adhesion experiments were conducted using NOM-present, NOM-stripped soil colloids, Streptococcus suis SC05 and Escherichia coli WH09 over a wide range of solution pH (4.0-9.0) and ionic strength (IS, 1-100 mM KCl). Cell characterization techniques, Freundlich isotherm, and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory (sphere-sphere model) were utilized to quantitatively determine the interactions between cells and colloids. The adhesion coefficients (Kf) of S. suis SC05 to NOM-present and NOM-stripped soil colloids were significantly higher than E. coli WH09, respectively. Similarly, Kf values of S. suis SC05 and E. coli WH09 adhesion to NOM-stripped soil colloids were greater than those colloids with NOM-present, respectively, suggesting NOM inhibits bacterial adhesion. Cell adhesion to soil colloids declined with increasing pH and enhanced with rising IS (1-50 mM). Interaction energy calculations indicate these adhesion trends can be explained by DLVO-type forces, with S. suis SC05 and E. coli WH09 being weakly adhered in shallow secondary energy minima via polymer bridging and charge heterogeneity. S. suis SC05 adhesion decreased at higher IS 100 mM, which is attributed to the change of hydrophobic effect and steric repulsion resulted from the greater presence of extracellular polymeric substances (EPS) on S. suis SC05 surface as compared to E. coli WH09. Hence, pathogen adhesion to the colloidal material is determined by a combination of DLVO, charge heterogeneity, hydrophobic and polymer interactions as a function of solution chemistry. Copyright © 2014 Elsevier Ltd. All rights reserved.

Soft material adhesion characterization for in vivo locomotion of robotic capsule endoscopes: Experimental and modeling results.

PubMed

Kern, Madalyn D; Ortega Alcaide, Joan; Rentschler, Mark E

2014-11-01

The objective of this work is to validate an experimental method and nondimensional model for characterizing the normal adhesive response between a polyvinyl chloride based synthetic biological tissue substrate and a flat, cylindrical probe with a smooth polydimethylsiloxane (PDMS) surface. The adhesion response is a critical mobility design parameter of a Robotic Capsule Endoscope (RCE) using PDMS treads to provide mobility to travel through the gastrointestinal tract for diagnostic purposes. Three RCE design characteristics were chosen as input parameters for the normal adhesion testing: pre-load, dwell time and separation rate. These parameters relate to the RCE׳s cross sectional dimension, tread length, and tread speed, respectively. An inscribed central composite design (CCD) prescribed 34 different parameter configurations to be tested. The experimental adhesion response curves were nondimensionalized by the maximum stress and total displacement values for each test configuration and a mean nondimensional curve was defined with a maximum relative error of 5.6%. A mathematical model describing the adhesion behavior as a function of the maximum stress and total displacement was developed and verified. A nonlinear regression analysis was done on the maximum stress and total displacement parameters and equations were defined as a function of the RCE design parameters. The nondimensional adhesion model is able to predict the adhesion curve response of any test configuration with a mean R(2) value of 0.995. Eight additional CCD studies were performed to obtain a qualitative understanding of the impact of tread contact area and synthetic material substrate stiffness on the adhesion response. These results suggest that the nondimensionalization technique for analyzing the adhesion data is sufficient for all values of probe radius and substrate stiffness within the bounds tested. This method can now be used for RCE tread design optimization given a set of environmental conditions for device operation. Copyright © 2014 Elsevier Ltd. All rights reserved.

A wet-tolerant adhesive patch inspired by protuberances in suction cups of octopi

NASA Astrophysics Data System (ADS)

Baik, Sangyul; Kim, Da Wan; Park, Youngjin; Lee, Tae-Jin; Ho Bhang, Suk; Pang, Changhyun

2017-06-01

Adhesion strategies that rely on mechanical interlocking or molecular attractions between surfaces can suffer when coming into contact with liquids. Thus far, artificial wet and dry adhesives have included hierarchical mushroom-shaped or porous structures that allow suction or capillarity, supramolecular structures comprising nanoparticles, and chemistry-based attractants that use various protein polyelectrolytes. However, it is challenging to develop adhesives that are simple to make and also perform well—and repeatedly—under both wet and dry conditions, while avoiding non-chemical contamination on the adhered surfaces. Here we present an artificial, biologically inspired, reversible wet/dry adhesion system that is based on the dome-like protuberances found in the suction cups of octopi. To mimic the architecture of these protuberances, we use a simple, solution-based, air-trap technique that involves fabricating a patterned structure as a polymeric master, and using it to produce a reversed architecture, without any sophisticated chemical syntheses or surface modifications. The micrometre-scale domes in our artificial adhesive enhance the suction stress. This octopus-inspired system exhibits strong, reversible, highly repeatable adhesion to silicon wafers, glass, and rough skin surfaces under various conditions (dry, moist, under water and under oil). To demonstrate a potential application, we also used our adhesive to transport a large silicon wafer in air and under water without any resulting surface contamination.

Influence of frequency on shear fatigue strength of resin composite to enamel bonds using self-etch adhesives.

PubMed

Takamizawa, Toshiki; Scheidel, Donal D; Barkmeier, Wayne W; Erickson, Robert L; Tsujimoto, Akimasa; Latta, Mark A; Miyazaki, Masashi

2016-09-01

The purpose of this study was to determine the influence of different frequency rates on of bond durability of self-etch adhesives to enamel using shear fatigue strength (SFS) testing. A two-step self-etch adhesive (OX, OptiBond XTR), and two single step self-etch adhesives (GB, G-ӕnial Bond and SU, Scotchbond Universal) were used in this study. The shear fatigue strength (SFS) to enamel was obtained. A staircase method was used to determine the SFS values with 50,000 cycles or until failure occurred. Fatigue testing was performed at frequencies of 5Hz, 10Hz, and 20Hz. For each test condition, 30 specimens were prepared for the SFS testing. Regardless of the bond strength test method, OX showed significantly higher SFS values than the two single-step self-etch adhesives. For each of the three individual self-etch adhesives, there was no significant difference in SFS depending on the frequency rate, although 20Hz results tended to be higher. Regardless of the self-etch adhesive system, frequencies of 5Hz, 10Hz, and 20Hz produced similar results in fatigue strength of resin composite bonded to enamel using 50,000 cycles or until bond failure. Accelerated fatigue testing provides valuable information regarding the long term durability of resin composite to enamel bonding using self-etch adhesive system. Copyright © 2016 Elsevier Ltd. All rights reserved.

TES is a novel focal adhesion protein with a role in cell spreading.

PubMed

Coutts, Amanda S; MacKenzie, Elaine; Griffith, Elen; Black, Donald M

2003-03-01

Previously, we identified TES as a novel candidate tumour suppressor gene that mapped to human chromosome 7q31.1. In this report we demonstrate that the TES protein is localised at focal adhesions, actin stress fibres and areas of cell-cell contact. TES has three C-terminal LIM domains that appear to be important for focal adhesion targeting. Additionally, the N-terminal region is important for targeting TES to actin stress fibres. Yeast two-hybrid and biochemical analyses yielded interactions with several focal adhesion and/or cytoskeletal proteins including mena, zyxin and talin. The fact that TES localises to regions of cell adhesion suggests that it functions in events related to cell motility and adhesion. In support of this, we demonstrate that fibroblasts stably overexpressing TES have an increased ability to spread on fibronectin.

Clonal yeast biofilms can reap competitive advantages through cell differentiation without being obligatorily multicellular

PubMed Central

Hanghøj, Kristian Ebbesen; Andersen, Kaj Scherz; Boomsma, Jacobus J.

2016-01-01

How differentiation between cell types evolved is a fundamental question in biology, but few studies have explored single-gene phenotypes that mediate first steps towards division of labour with selective advantage for groups of cells. Here, we show that differential expression of the FLO11 gene produces stable fractions of Flo11+ and Flo11− cells in clonal Saccharomyces cerevisiae biofilm colonies on medium with intermediate viscosity. Differentiated Flo11+/− colonies, consisting of adhesive and non-adhesive cells, obtain a fourfold growth advantage over undifferentiated colonies by overgrowing glucose resources before depleting them, rather than depleting them while they grow as undifferentiated Flo11− colonies do. Flo11+/− colonies maintain their structure and differentiated state by switching non-adhesive cells to adhesive cells with predictable probability. Mixtures of Flo11+ and Flo11− cells from mutant strains that are unable to use this epigenetic switch mechanism produced neither integrated colonies nor growth advantages, so the condition-dependent selective advantages of differentiated FLO11 expression can only be reaped by clone-mate cells. Our results show that selection for cell differentiation in clonal eukaryotes can evolve before the establishment of obligate undifferentiated multicellularity, and without necessarily leading to more advanced organizational complexity. PMID:27807261

Influence of femtosecond laser produced nanostructures on biofilm growth on steel

NASA Astrophysics Data System (ADS)

Epperlein, Nadja; Menzel, Friederike; Schwibbert, Karin; Koter, Robert; Bonse, Jörn; Sameith, Janin; Krüger, Jörg; Toepel, Jörg

2017-10-01

Biofilm formation poses high risks in multiple industrial and medical settings. However, the robust nature of biofilms makes them also attractive for industrial applications where cell biocatalysts are increasingly in use. Since tailoring material properties that affect bacterial growth or its inhibition is gaining attention, here we focus on the effects of femtosecond laser produced nanostructures on bacterial adhesion. Large area periodic surface structures were generated on steel surfaces using 30-fs laser pulses at 790 nm wavelength. Two types of steel exhibiting a different corrosion resistance were used, i.e., a plain structural steel (corrodible) and a stainless steel (resistant to corrosion). Homogeneous fields of laser-induced periodic surface structures (LIPSS) were realized utilizing laser fluences close to the ablation threshold while scanning the sample under the focused laser beam in a multi-pulse regime. The nanostructures were characterized with optical and scanning electron microscopy. For each type of steel, more than ten identical samples were laser-processed. Subsequently, the samples were subjected to microbial adhesion tests. Bacteria of different shape and adhesion behavior (Escherichia coli and Staphylococcus aureus) were exposed to laser structures and to polished reference surfaces. Our results indicate that E. coli preferentially avoids adhesion to the LIPSS-covered areas, whereas S. aureus favors these areas for colonization.

Total internal reflection holographic microscopy (TIRHM) for quantitative phase characterization of cell-substrate adhesion

NASA Astrophysics Data System (ADS)

Ash, William Mason, III

Total Internal Reflection Holographic Microscopy (TIRHM) combines near-field microscopy with digital holography to produce a new form of near-field phase microscopy. Using a prism in TIR as a near-field imager, the presence of microscopic organisms, cell-substrate interfaces, and adhesions, causes relative refractive index (RRI) and frustrated TIR (f-TIR) to modulate the object beam's evanescent wave phase front. Quantitative phase images of test specimens such as Amoeba proteus, Dictyostelium Discoideum and cells such as SKOV-3 ovarian cancer and 3T3 fibroblasts are produced without the need to introduce stains or fluorophores. The angular spectrum method of digital holography to compensate for tilt anamorphism due to the inclined TIR plane is also discussed. The results of this work conclusively demonstrate, for the first time, the integration of near-field microscopy with digital holography. The cellular images presented show a correlation between the physical extent of the Amoeba proteus plasma membrane and the adhesions that are quantitatively profiled by phase cross-sectioning of the holographic images obtained by digital holography. With its ability to quantitatively characterise cellular adhesion and motility, it is anticipated that TIRHM can be a tool for characterizing and combating cancer metastasis, as well as improving our understanding of morphogenesis and embryogenesis itself.

Impact of the exopolysaccharide layer on biofilms, adhesion and resistance to stress in Lactobacillus johnsonii FI9785.

PubMed

Dertli, Enes; Mayer, Melinda J; Narbad, Arjan

2015-02-04

The bacterial cell surface is a crucial factor in cell-cell and cell-host interactions. Lactobacillus johnsonii FI9785 produces an exopolysaccharide (EPS) layer whose quantity and composition is altered in mutants that harbour genetic changes in their eps gene clusters. We have assessed the effect of changes in EPS production on cell surface characteristics that may affect the ability of L. johnsonii to colonise the poultry host and exclude pathogens. Analysis of physicochemical cell surface characteristics reflected by Zeta potential and adhesion to hexadecane showed that an increase in EPS gave a less negative, more hydrophilic surface and reduced autoaggregation. Autoaggregation was significantly higher in mutants that have reduced EPS, indicating that EPS can mask surface structures responsible for cell-cell interactions. EPS also affected biofilm formation, but here the quantity of EPS produced was not the only determinant. A reduction in EPS production increased bacterial adhesion to chicken gut explants, but made the bacteria less able to survive some stresses. This study showed that manipulation of EPS production in L. johnsonii FI9785 can affect properties which may improve its performance as a competitive exclusion agent, but that positive changes in adhesion may be compromised by a reduction in the ability to survive stress.

Various fates of neuronal progenitor cells observed on several different chemical functional groups

NASA Astrophysics Data System (ADS)

Liu, Xi; Wang, Ying; He, Jin; Wang, Xiu-Mei; Cui, Fu-Zhai; Xu, Quan-Yuan

2011-12-01

Neuronal progenitor cells cultured on gold-coated glass surfaces modified by different chemical functional groups, including hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), bromo (-Br), mercapto (-SH), - Phenyl and methyl (-CH3), were studied here to investigate the influence of surface chemistry on the cells' adhesion, morphology, proliferation and functional gene expression. Focal adhesion staining indicated in the initial culture stage cells exhibited morphological changes in response to different chemical functional groups. Cells cultured on -NH2 grafted surface displayed focal adhesion plaque and flattened morphology and had the largest contact area. However, their counter parts on -CH3 grafted surface displayed no focal adhesion and rounded morphology and had the smallest contact area. After 6 days culture, the proliferation trend was as follows: -NH2 > -SH> -COOH> - Phenyl > - Br > -OH> -CH3. To determine the neural functional properties of the cells affected by surface chemistry, the expression of glutamate decarboxylase (GAD67), nerve growth factor (NGF) and brainderived neurotrophic factor (BDNF) were characterized. An increase of GAD67 expression was observed on -NH2, -COOH and -SH grafted surfaces, while no increase in NGF and BDNF expression was observed on any chemical surfaces. These results highlight the importance of surface chemistry in the fate determination of neuronal progenitor cells, and suggest that surface chemistry must be considered in the design of biomaterials for neural tissue engineering.

Tumour-derived Interleukin 35 promotes pancreatic ductal adenocarcinoma cell extravasation and metastasis by inducing ICAM1 expression

PubMed Central

Huang, Chongbiao; Li, Na; Li, Zengxun; Chang, Antao; Chen, Yanan; Zhao, Tiansuo; Li, Yang; Wang, Xiuchao; Zhang, Wei; Wang, Zhimin; Luo, Lin; Shi, Jingjing; Yang, Shengyu; Ren, He; Hao, Jihui

2017-01-01

Interleukin 35 (IL-35) is a novel member of the IL-12 family, consisting of an EBV-induced gene 3 (EBI3) subunit and a P35 subunit. IL-35 is an immune-suppressive cytokine mainly produced by regulatory T cells. However, the role of IL-35 in cancer metastasis and progression is not well understood. Here we demonstrate that IL-35 is overexpressed in human pancreatic ductal adenocarcinoma (PDAC) tissues, and that IL-35 overexpression is associated with poor prognosis in PDAC patients. IL-35 has critical roles in PDAC cell extravasation and metastasis by facilitating the adhesion to endothelial cells and transendothelial extravasation. Mechanistically, IL-35 promotes ICAM1 overexpression through a GP130-STAT1 signalling pathway, which facilitates endothelial adhesion and transendothelial migration via an ICAM1–fibrinogen–ICAM1 bridge. In an orthotopic xenograft model, IL-35 promotes spontaneous pancreatic cancer metastasis in an ICAM1-dependent manner. Together, our results indicate additional functions of IL-35 in promoting PDAC metastasis through mediating ICAM1 expression. PMID:28102193

Spatial model of the gecko foot hair: functional significance of highly specialized non-uniform geometry.

PubMed

Filippov, Alexander E; Gorb, Stanislav N

2015-02-06

One of the important problems appearing in experimental realizations of artificial adhesives inspired by gecko foot hair is so-called clusterization. If an artificially produced structure is flexible enough to allow efficient contact with natural rough surfaces, after a few attachment-detachment cycles, the fibres of the structure tend to adhere one to another and form clusters. Normally, such clusters are much larger than original fibres and, because they are less flexible, form much worse adhesive contacts especially with the rough surfaces. Main problem here is that the forces responsible for the clusterization are the same intermolecular forces which attract fibres to fractal surface of the substrate. However, arrays of real gecko setae are much less susceptible to this problem. One of the possible reasons for this is that ends of the seta have more sophisticated non-uniformly distributed three-dimensional structure than that of existing artificial systems. In this paper, we simulated three-dimensional spatial geometry of non-uniformly distributed branches of nanofibres of the setal tip numerically, studied its attachment-detachment dynamics and discussed its advantages versus uniformly distributed geometry.

Fracture Simulation of Highly Crosslinked Polymer Networks: Triglyceride-Based Adhesives

NASA Astrophysics Data System (ADS)

Lorenz, Christian; Stevens, Mark; Wool, Richard

2003-03-01

The ACRES program at the U. of Delaware has shown that triglyceride oils derived from plants are a favorable alternative to the traditional adhesives. The triglyceride networks are formed from an initial mixture of styrene monomers, free-radical initiators and triglycerides. We have performed simulations to study the effect of physical composition and physical characteristics of the triglyceride network on the strength of triglyceride network. A coarse-grained, bead-spring model of the triglyceride system is used. The average triglyceride consists of 6 beads per chain, the styrenes are represented as a single bead and the initiators are two bead chains. The polymer network is formed using an off-lattice 3D Monte Carlo simulation, in which the initiators activate the styrene and triglyceride reactive sites and then bonds are randomly formed between the styrene and active triglyceride monomers producing a highly crosslinked polymer network. Molecular dynamics simulations of the network under tensile and shear strains were performed to determine the strength as a function of the network composition. The relationship between the network structure and its strength will also be discussed.

Real-time monitoring of ischemia inside stomach.

PubMed

Tahirbegi, Islam Bogachan; Mir, Mònica; Samitier, Josep

2013-02-15

The low pH in the gastric juice of the stomach makes it difficult to fabricate stable and functional all-solid-state pH ISE sensors to sense ischemia, mainly because of anion interference and adhesion problem between the ISE membrane and the electrode surface. In this work, the adhesion of ISE membrane on solid surface at low pH was improved by modifying the surface with a conductive substrate containing hydrophilic and hydrophobic groups. This creates a stable and robust candidate for low pH applications. Moreover, anion interference problem at low pH was solved by integration of all-solid-state ISE and internal reference electrodes on an array. So, the same tendencies of anion interferences for all-solid-state ISE and all-solid-state reference electrodes cancel each other in differential potentiometric detection. The developed sensor presents a novel all-solid-state potentiometric, miniaturized and mass producible pH ISE sensor for detecting ischemia on the stomach tissue on an array designed for endoscopic applications. Copyright © 2012 Elsevier B.V. All rights reserved.

Osteoblastlike cell adhesion on titanium surfaces modified by plasma nitriding.

PubMed

da Silva, Jose Sandro Pereira; Amico, Sandro Campos; Rodrigues, Almir Olegario Neves; Barboza, Carlos Augusto Galvao; Alves, Clodomiro; Croci, Alberto Tesconi

2011-01-01

The aim of this study was to evaluate the characteristics of various titanium surfaces modified by cold plasma nitriding in terms of adhesion and proliferation of rat osteoblastlike cells. Samples of grade 2 titanium were subjected to three different surface modification processes: polishing, nitriding by plasma direct current, and nitriding by cathodic cage discharge. To evaluate the effect of the surface treatment on the cellular response, the adhesion and proliferation of osteoblastlike cells (MC3T3) were quantified and the results were analyzed by Kruskal-Wallis and Friedman statistical tests. Cellular morphology was observed by scanning electron microscopy. There was more MC3T3 cell attachment on the rougher surfaces produced by cathodic cage discharge compared with polished samples (P < .05). Plasma nitriding improves titanium surface roughness and wettability, leading to osteoblastlike cell adhesion.

Thrombomodulin-mediated cell adhesion: involvement of its lectin-like domain.

PubMed

Huang, Huey-Chun; Shi, Guey-Yueh; Jiang, Shinn-Jong; Shi, Chung-Sheng; Wu, Chun-Mei; Yang, Hsi-Yuan; Wu, Hua-Lin

2003-11-21

Thrombomodulin (TM) is an integral membrane glycoprotein that is a potent anticoagulant factor. TM may also possess functions distinct from its anticoagulant activity. Here the influence of TM on cell adhesion was studied in TM-negative melanoma A2058 cells transfected with green fluorescent protein-tagged TM (TMG) or lectin domain-deleted TM (TMG(DeltaL)). Confocal microscopy demonstrated that both TMG and TMG(DeltaL) were distributed in the plasma membrane. TMG-expressed cells grew as closely clustered colonies, with TM localized prominently in the intercellular boundaries. TMG(DeltaL)-expressed cells grew singly. Overexpression of TMG, but not TMG(DeltaL), decreased monolayer permeability in vitro and tumor growth in vivo. The cell-to-cell adhesion in TMG-expressed cells was Ca2+-dependent and was inhibited by monoclonal antibody against the lectin-like domain of TM. The effects of TM-mediated cell adhesion were abolished by the addition of mannose, chondroitin sulfate A, or chondroitin sulfate C. In addition, anti-lectin-like domain antibody disrupted the close clustering of the endogenous TM-expressed keratinocyte HaCaT cell line derived from normal human epidermis. Double-labeling immunofluorescence staining revealed similar distributions of TM and actin filament in the cortex region of the TMG-expressed cells. Thus, TM can function as a Ca2+-dependent cell-to-cell adhesion molecule. Binding of specific carbohydrates to the lectin-like domain is essential for this specific function.

Evaluation of adhesion force between functionalized microbeads and protein-coated stainless steel using shear-flow-induced detachment.

PubMed

Mercier-Bonin, Muriel; Adoue, Mathieu; Zanna, Sandrine; Marcus, Philippe; Combes, Didier; Schmitz, Philippe

2009-10-01

Spherical microbeads functionalized with two types of chemical groups (NH(2), OH) were chosen as a simplified bacterial model, in order to elucidate the role of macromolecular interactions between specific biopolymers and 316 L stainless steel, in the frame of biofilm formation in the marine environment. NH(2) microbeads were used in their native form or after covalent binding to BSA or different representative poly-amino acids. OH microbeads were used in their native form. Adhesion force between microbeads and bare or BSA-coated stainless steel was quantified at nanoscale. Shear-flow-induced detachment experiments were combined with a simplified version of a theoretical model, based on the balance of hydrodynamic forces and torque exerted on microbeads. A maximal adhesion force of 27.6+/-8.5 nN was obtained for BSA-coated NH(2) microbeads. The high reactivity of OH functional groups was assessed (adhesion force of 15.6+/-4.8 nN for large microbeads). When charge-conducting stainless steel was coated with BSA, adhesion force was significantly lower than the one estimated with the bare surface, probably due to an increase in hydrophilic surface properties or suppression of charge transfer. The mechanism for microbead detachment was established (mainly rolling). The flow chamber and the associated theoretical modelling were demonstrated to be a relevant approach to quantify nanoscale forces between interacting surfaces.

Peptide-decorated chitosan derivatives enhance fibroblast adhesion and proliferation in wound healing.

PubMed

Patrulea, V; Hirt-Burri, N; Jeannerat, A; Applegate, L A; Ostafe, V; Jordan, O; Borchard, G

2016-05-20

RGD peptide sequences are known to regulate cellular activities by interacting with α5β1, αvβ5 and αvβ3 integrin, which contributes to the wound healing process. In this study, RGDC peptide was immobilized onto chitosan derivative 1,6-diaminohexane-O-carboxymethyl-N,N,N-trimethyl chitosan (DAH-CMTMC) to display RGDC-promoting adhesion for enhanced wound healing. The efficiency of N-methylation, O-carboxymethylation and spacer grafting was quantitatively and qualitatively analyzed by (1)H NMR and FTIR, yielding 0.38 degree of substitution for N-methylation and >0.85 for O-carboxymethylation. The glass transition temperatures for chitosan derivatives were also studied. Peptide immobilization was achieved through sulfhydryl groups using sulfosuccinimidyl (4-iodoacetyl)amino-benzoate (sulfo-SIAB method). RGDC immobilized peptide onto DAH-CMTMC was found to be about 15.3 μg/mg of chitosan derivative by amino acid analysis (AAA). The significant increase of human dermal fibroblast (HDF) viability in vitro over 7 days suggests that RGDC-functionalized chitosan may lead to enhanced wound healing (viability >140%). Moreover, bio-adhesion and proliferation assays confirmed that coatings of RGDC-functionalized chitosan derivatives exhibit in vitro wound healing properties by enhancing fibroblast proliferation and adhesion. These results showed that RGDC peptide-functionalized chitosan provides an optimal environment for fibroblast adhesion and proliferation. Copyright © 2016 Elsevier Ltd. All rights reserved.

A conserved role for L1 as a transmembrane link between neuronal adhesion and membrane cytoskeleton assembly.

PubMed

Hortsch, M; O'Shea, K S; Zhao, G; Kim, F; Vallejo, Y; Dubreuil, R R

1998-01-01

The L1-family of cell adhesion molecules is involved in many important aspects of nervous system development. Mutations in the human L1-CAM gene cause a complicated array of neurological phenotypes; however, the molecular basis of these effects cannot be explained by a simple loss of adhesive function. Human L1-CAM and its Drosophila homolog neuroglian are rather divergent in sequence, with the highest degree of amino acid sequence conservation between segments of their cytoplasmic domains. In an attempt to elucidate the fundamental functions shared between these distantly related members of the L1-family, we demonstrate here that the extracellular domains of mammalian L1-CAMs and Drosophila neuroglian are both able to induce the aggregation of transfected Drosophila S2 cells in vitro. To a limited degree they even interact with each other in cell adhesion and neurite outgrowth assays. The cytoplasmic domains of human L1-CAM and neuroglian are both able to interact with the Drosophila homolog of the cytoskeletal linker protein ankyrin. Moreover the recruitment of ankyrin to cell-cell contacts is completely dependent on L1-mediated cell adhesion. These findings support a model of L1 function in which the phenotypes of human L1-CAM mutations results from a disruption of the link between the extracellular environment and the neuronal cytoskeleton.

Comparison of tensile bond strengths of four one-bottle self-etching adhesive systems with Er:YAG laser-irradiated dentin.

PubMed

Jiang, Qianzhou; Chen, Minle; Ding, Jiangfeng

2013-12-01

This study aimed to investigate the interaction of current one-bottle self-etching adhesives and Er:YAG laser with dentin using a tensile bond strength (TBS) test and scanning electron microscopy (SEM) in vitro. Two hundred and thirteen dentin discs were randomly distributed to the Control Group using bur cutting and to the Laser Group using an Er:YAG laser (200 mJ, VSP, 20 Hz). The following adhesives were investigated: one two-step total-etch adhesive [Prime & Bond NT (Dentsply)] and four one-step self-etch adhesives [G-Bond plus (GC), XENO V (Dentsply), iBond Self Etch (Heraeus) and Adper Easy One (3 M ESPE)]. Samples were restored with composite resin, and after 24-hour storage in distilled water, subjected to the TBS test. For morphological analysis, 12 dentin specimens were prepared for SEM. No significant differences were found between the control group and laser group (p = 0.899); dentin subjected to Prime & Bond NT, XENOV and Adper Easy One produced higher TBS. In conclusion, this study indicates that Er:YAG laser-prepared dentin can perform as well as bur on TBS, and some of the one-step one-bottle adhesives are comparable to the total-etch adhesives in TBS on dentin.

High-throughput sequencing identification and characterization of potentially adhesion-related small RNAs in Streptococcus mutans.

PubMed

Zhu, Wenhui; Liu, Shanshan; Liu, Jia; Zhou, Yan; Lin, Huancai

2018-05-01

Adherence capacity is one of the principal virulence factors of Streptococcus mutans, and adhesion virulence factors are controlled by small RNAs (sRNAs) at the post-transcriptional level in various bacteria. Here, we aimed to identify and decipher putative adhesion-related sRNAs in clinical strains of S. mutans. RNA deep-sequencing was performed to identify potential sRNAs under different adhesion conditions. The expression of sRNAs was analysed by quantitative real-time PCR (qRT-PCR), and bioinformatic methods were used to predict the functional characteristics of sRNAs. A total of 736 differentially expressed candidate sRNAs were predicted, and these included 352 sRNAs located on the antisense to mRNA (AM) and 384 sRNAs in intergenic regions (IGRs). The top 7 differentially expressed sRNAs were successfully validated by qRT-PCR in UA159, and 2 of these were further confirmed in 100 clinical isolates. Moreover, the sequences of two sRNAs were conserved in other Streptococcus species, indicating a conserved role in such closely related species. A good correlation between the expression of sRNAs and the adhesion of 100 clinical strains was observed, which, combined with GO and KEGG, provides a perspective for the comprehension of sRNA function annotation. This study revealed a multitude of novel putative adhesion-related sRNAs in S. mutans and contributed to a better understanding of information concerning the transcriptional regulation of adhesion in S. mutans.

Medium-chain, triglyceride-containing lipid emulsions increase human neutrophil beta2 integrin expression, adhesion, and degranulation.

PubMed

Wanten, G J; Geijtenbeek, T B; Raymakers, R A; van Kooyk, Y; Roos, D; Jansen, J B; Naber, A H

2000-01-01

To test the hypothesis that lipid emulsions with different triglyceride structures have distinct immunomodulatory properties, we analyzed human neutrophil adhesion and degranulation after lipid incubation. Neutrophils, isolated from the blood of 10 healthy volunteers, were incubated in medium or physiologic (2.5 mmol/L) emulsions containing long-chain (LCT), medium-chain (MCT), mixed LCT/MCT, or structured (SL) triglycerides. Expression of adhesion molecules and degranulation markers was evaluated by flow cytometry. Also, functional adhesion was investigated by means of a flow cytometric assay using fluorescent beads coated with the integrin ligand intercellular adhesion molecule (ICAM)-1. Although LCT and SL had no effect, LCT/MCT significantly increased expression of the beta2 integrins lymphocyte-function-associated antigen 1 (+18%), macrophage antigen 1 (+387%), p150,95 (+82%), and (alphaDbeta2 (+230%). Degranulation marker expression for azurophilic (CD63, +210%) and specific granules (CD66b, +370%) also significantly increased, whereas L-selectin (CD62L, -70%) decreased. The effects of LCT/MCT were mimicked by the MCT emulsion. ICAM-1 adhesion (% beads bound) was increased by LCT/MCT (34% +/- 4%), whereas LCT (19% +/-3%) and SL (20% +/- 2%) had no effect compared with medium (17% +/- 3%). LCT/MCT and MCT, contrary to LCT and SL emulsions, increased neutrophil beta2 integrin expression, adhesion, and degranulation. Apart from other emulsion constituents, triglyceride chain length might therefore be a key feature in the interaction of lipid emulsions and the phagocyte immune system.

Growth and adhesion properties of monosodium urate monohydrate (MSU) crystals

NASA Astrophysics Data System (ADS)

Perrin, Clare M.

The presence of monosodium urate monohydrate (MSU) crystals in the synovial fluid has long been associated with the joint disease gout. To elucidate the molecular level growth mechanism and adhesive properties of MSU crystals, atomic force microscopy (AFM), scanning electron microscopy, and dynamic light scattering (DLS) techniques were employed in the characterization of the (010) and (1-10) faces of MSU, as well as physiologically relevant solutions supersaturated with urate. Topographical AFM imaging of both MSU (010) and (1-10) revealed the presence of crystalline layers of urate arranged into v-shaped features of varying height. Growth rates were measured for both monolayers (elementary steps) and multiple layers (macrosteps) on both crystal faces under a wide range of urate supersaturation in physiologically relevant solutions. Step velocities for monolayers and multiple layers displayed a second order polynomial dependence on urate supersaturation on MSU (010) and (1-10), with step velocities on (1-10) generally half of those measured on MSU (010) in corresponding growth conditions. Perpendicular step velocities on MSU (010) were obtained and also showed a second order polynomial dependence of step velocity with respect to urate supersaturation, which implies a 2D-island nucleation growth mechanism for MSU (010). Extensive topographical imaging of MSU (010) showed island adsorption from urate growth solutions under all urate solution concentrations investigated, lending further support for the determined growth mechanism. Island sizes derived from DLS experiments on growth solutions were in agreement with those measured on MSU (010) topographical images. Chemical force microscopy (CFM) was utilized to characterize the adhesive properties of MSU (010) and (1-10). AFM probes functionalized with amino acid derivatives and bio-macromolecules found in the synovial fluid were brought into contact with both crystal faces and adhesion forces were tabulated into histograms for comparison. AFM probes functionalized with -COO-, -CH3, and -OH functionalities displayed similar adhesion force with both crystal surfaces of MSU, while adhesion force on (1-10) was three times greater than (010) for -NH2+ probes. For AFM probes functionalized with bovine serum albumin, adhesion force was three times greater on MSU (1-10) than (010), most likely due to the more ionic nature of (1-10).

Distortion of the normal function of synaptic cell adhesion molecules by genetic variants as a risk for autism spectrum disorders.

PubMed

Baig, Deeba Noreen; Yanagawa, Toru; Tabuchi, Katsuhiko

2017-03-01

Synaptic cell adhesion molecules (SCAMs) are a functional category of cell adhesion molecules that connect pre- and postsynapses by the protein-protein interaction via their extracellular cell adhesion domains. Countless numbers of common genetic variants and rare mutations in SCAMs have been identified in the patients with autism spectrum disorders (ASDs). Among these, NRXN and NLGN family proteins cooperatively function at synaptic terminals both of which genes are strongly implicated as risk genes for ASDs. Knock-in mice carrying a single rare point mutation of NLGN3 (NLGN3 R451C) discovered in the patients with ASDs display a deficit in social interaction and an enhancement of spatial learning and memory ability reminiscent of the clinical phenotype of ASDs. NLGN4 knockout (KO) and NRXN2α KO mice also show a deficit in sociability as well as some specific neuropsychiatric behaviors. In this review, we selected NRXNs/NLGNs, CNTNAP2/CNTNAP4, CNTN4, ITGB3, and KIRREL3 as strong ASD risk genes based on SFARI score and summarize the protein structures, functions at synapses, representative discoveries in human genetic studies, and phenotypes of the mutant model mice in light of the pathophysiology of ASDs. Copyright © 2016 Elsevier Inc. All rights reserved.

Engineering of Surface Functionality onto Polystyrene Microcarriers for the Attachment and Growth of Human Endothelial Cells

NASA Astrophysics Data System (ADS)

Xiong, Gordon M.; Foord, John S.; Griffiths, Jon-Paul; Parker, Emily M.; Moloney, Mark G.; Choong, Cleo

2014-08-01

This work reports the effects of introducing diverse chemical functionalities onto the surface of polystyrene microcarrier beads on their ability to function as injectable cell carriers. Cellular adhesion and proliferation, as well as cellular outgrowths from microcarrier surfaces, using human umbilical vein endothelial cells (HUVECs), were examined in detail. It was observed that initial cell adhesion appeared to be most significantly decreased by hydrophobicity, whilst cell proliferation appeared to be improved in most chemical functional groups over unmodified polystyrene. Overall, our study highlights the importance of surface chemistry in directing the growth and function of human endothelial cells.

Polyesters from microorganisms.

PubMed

Kim, Y B; Lenz, R W

2001-01-01

Bacterial polyesters have been found to have useful properties for applications as thermoplastics, elastomers, and adhesives and are biodegradable and biocompatible. Poly(3-hydroxyalkanoates) (PHAs) and poly(beta-malate) are the most representative polyesters synthesized by microorganisms. PHAs containing a wide variety of repeating units can be produced by bacteria, including those containing many types of pendant functional groups which can be synthesized by microorganisms that are grown on unnatural organic substrates. Poly(beta-malate) is of interest primarily for medical applications, especially for drug delivery systems. In this chapter, the bacterial production and properties of poly(3-hydroxyalkanoates) and poly(beta-malate) are described with emphasis on the former.

Support and rehabilitation of patients with pulmonary expansion deficit by using game therapy.

PubMed

Chacon, P F S; Schon, C F; Furtado, V H L A; Signoretti, G L A M; Oliveira, J P P; Ribeiro, A G; Wanderley, C D V; Diniz, A A R; Soares, H B

2016-08-01

Patients suffering from hypoventilation and pulmonary expansion deficit are at increased risk of developing pulmonary complications such as atelectasis, pneumonia or pleural effusion. These complications can increase the length of stay and spending on health, and generate long-term functional impairment. This study aims to produce a therapeutic alternative to the traditional method of lung re-expansion through incentive spirometry (IS) using the game therapy to build an innovative system. This system makes use of infrared and Bluetooth communication technology to associate the game therapy to EI. At the end of the system implementation, we expect to obtain good adhesion of the patient and the physiotherapists.

Photon and radiowave emission from peeling pressure sensitive adhesives in air

NASA Technical Reports Server (NTRS)

Donaldson, E. E.; Shen, X. A.; Dickinson, J. T.

1985-01-01

During separation of an adhesive from a polymer substrate in air, intense bursts of photons ('phE', for photon emission) and long wavelength electromagnetic radiation ('RE', for radiowave emission), similar to those reported earlier by Deryagin, et al. (1978) have been observed. In this paper, careful measurements of the phE time distributions, as well as time correlations between bursts of phE and RE, are reported. These results support the view that patches of electrical charge produced by charge separation between dissimilar materials lead to microdischarges in and near the crack tip. The role of these discharges in producing sustained phE after the discharge has been extinguished is also discussed.

Identifying traction-separation behavior of self-adhesive polymeric films from in situ digital images under T-peeling

NASA Astrophysics Data System (ADS)

Nase, Michael; Rennert, Mirko; Naumenko, Konstantin; Eremeyev, Victor A.

2016-06-01

In this paper procedures are developed to identify traction-separation curves from digital images of the deformed flexible films during peeling. T-peel tests were performed for self-adhesive polymeric films. High quality photographs of the deformed shape within and outside the zone of adhesive interaction were made in situ by the digital light microscope. The deformed line is approximated by a power series with coefficients computed by minimizing a least squares functional. Two approaches to identify the traction-separation curve for the given deformation line are proposed. The first one is based on the energy integral of the non-linear theory of rods and allows the direct evaluation of the adhesion force potential. The second one utilizes the complementary energy type variational equation and the Ritz method to compute the adhesion force. The accuracy of both approaches is analyzed with respect to different approximations for the deformed line and the force of interaction. The obtained traction vs. axial coordinate and the traction-separation curves provide several properties of the adhesive system including the maximum adhesion force, the length of the adhesive zone and the equilibrium position, where the adhesive force is zero while the separation is positive.

Angiogenesis mediated by soluble forms of E-selectin and vascular cell adhesion molecule-1

NASA Astrophysics Data System (ADS)

Koch, Alisa E.; Halloran, Margaret M.; Haskell, Catherine J.; Shah, Manisha R.; Polverini, Peter J.

1995-08-01

ENDOTHELIAL adhesion molecules facilitate the entry of leukocytes into inflamed tissues. This in turn promotes neovascularization, a process central to the progression of rheumatoid arthritis, tumour growth and wound repair1. Here we test the hypothesis that soluble endothelial adhesion molecules promote angiogenesis2á¤-4. Human recombinant soluble E-selectin and soluble vascular cell adhesion molecule-1 induced chemotaxis of human endothelial cells in vitro and were angiogenic in rat cornea. Soluble E-selectin acted on endothelial cells in part through a sialyl Lewis-X-dependent mechanism, while soluble vascular cell adhesion molecule-1 acted on endothelial cells in part through a very late antigen (VLA)-4 dependent mechanism. The chemotactic activity of rheumatoid synovial fluid for endothelial cells, and also its angiogenic activity, were blocked by antibodies to either soluble E-selectin or soluble vascular cell adhesion molecule-1. These results suggest a novel function for soluble endothelial adhesion molecules as mediators of angiogenesis.

Regulation of epithelial and lymphocyte cell adhesion by adenosine deaminase-CD26 interaction.

PubMed Central

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:11772392

Epoxy Adhesives for Stator Magnet Assembly in Stirling Radioisotope Generators (SRG)

NASA Technical Reports Server (NTRS)

Cater, George M.

2004-01-01

As NASA seeks to fulfill its goals of exploration and understanding through missions planned to visit the moons of Saturn and beyond, a number of challenges arise from the idea of deep space flight. One of the first problems associated with deep space travel is electrical power production for systems on the spacecraft. Conventional methods such as solar power are not practical because efficiency decreases substantially as the craft moves away from the Sun. The criterion for power generation during deep space missions are very specific, the main points requiring high reliability, low mass, minimal vibration and a long lifespan. A Stirling generator, although fairly old in concept, is considered to be a potential solution for electrical power generation for deep space flight. A Stirling generator works on the same electromagnetic principles of a standard generator, using the linear motion of the alternator through the stationary stator which produces electric induction. The motion of the alternator, however, is produced by the heating and cooling dynamics of pressurized gases. Essentially heating one end and cooling another of a contained gas will cause a periodic expansion and compression of the gas from one side to the other, which a displacer translates into linear mechanical motion. NASA needs to confirm that the materials used in the generator will be able to withstand the rigors of space and the life expectancy of the mission. I am working on the verification of the epoxy adhesives used to bond magnets to the steel lamination stack to complete the stator; in terms of in-service performance and durability under various space environments. Understanding the proper curing conditions, high temperature properties, and degassing problems as well as production difficulties are crucial to the long term success of the generator. system and steel substrate used in the stator. To optimize the curing conditions of the epoxies, modulated differential scanning calorimetry analysis was done as a function of cure time and temperatures. Adhesion bond strength was tested at various temperatures with lap shear samples using Hiperco 50 substrate to ensure that the proper adhesive is being used. To try and solve the problem of bondline thickness, micro glass beads of 0.0017" in diameter were investigated to see if any other physical properties of the epoxy were affected. Efforts will be made to develop a standard, optimized, fabrication process/procedure of sub-scale magnet-stator assemblies for various adhesive performance evaluation studies under simulated generator conditions. Also, accelerated aging testing will be done in a pressurized canister with stator assembly samples for three years to verify if any degassing or thermal degradation of the epoxy occurs. The necessity of verifying the correct epoxy adhesive system for the stator magnet in the SRG is crucial because failure of the stator assembly would jeopardize the electrical system, and thereby the entire mission itself. My work involves specimen fabrications, testing, and data analyses of the epoxy adhesive system for the stator magnet in the SRG is crucial because failure of the stator assembly would jeopardize the electrical system, and thereby the entire mission itself.

Adhesive loose packings of small dry particles.

PubMed

Liu, Wenwei; Li, Shuiqing; Baule, Adrian; Makse, Hernán A

2015-08-28

We explore adhesive loose packings of small dry spherical particles of micrometer size using 3D discrete-element simulations with adhesive contact mechanics and statistical ensemble theory. A dimensionless adhesion parameter (Ad) successfully combines the effects of particle velocities, sizes and the work of adhesion, identifying a universal regime of adhesive packings for Ad > 1. The structural properties of the packings in this regime are well described by an ensemble approach based on a coarse-grained volume function that includes the correlation between bulk and contact spheres. Our theoretical and numerical results predict: (i) an equation of state for adhesive loose packings that appear as a continuation from the frictionless random close packing (RCP) point in the jamming phase diagram and (ii) the existence of an asymptotic adhesive loose packing point at a coordination number Z = 2 and a packing fraction ϕ = 1/2(3). Our results highlight that adhesion leads to a universal packing regime at packing fractions much smaller than the random loose packing (RLP), which can be described within a statistical mechanical framework. We present a general phase diagram of jammed matter comprising frictionless, frictional, adhesive as well as non-spherical particles, providing a classification of packings in terms of their continuation from the spherical frictionless RCP.

Construction of a multi-functional extracellular matrix protein that increases number of N1E-115 neuroblast cells having neurites.

PubMed

Nakamura, Makiko; Mie, Masayasu; Mihara, Hisakazu; Nakamura, Makoto; Kobatake, Eiry

2009-10-01

An artificially designed fusion protein, which was designed to have strong cell adhesive activity and an active functional unit that enhances neuronal differentiation of mouse N1E-115 neuroblast cells, was developed. In this study, a laminin-1-derived IKVAV sequence, which stimulates neurite outgrowth in conditions of serum deprivation, was engineered and incorporated into an elastin-derived structural unit. The designed fusion protein also had a cell-adhesive RGD sequence derived from fibronectin. The resultant fusion protein could adsorb efficiently onto hydrophobic culture surfaces and showed cell adhesion activity similar to laminin. N1E-115 cells grown on the fusion protein exhibited more cells with neurites than cells grown on laminin-1. These results indicated that the constructed protein could retain properties of incorporated functional peptides and could provide effective signal transport. The strategy of designing multi-functional fusion proteins has the possibility for supporting current tissue engineering techniques. (c) 2009 Wiley Periodicals, Inc.

Adhesion of protein residues to substituted (111) diamond surfaces: an insight from density functional theory and classical molecular dynamics simulations.

PubMed

Borisenko, Konstantin B; Reavy, Helen J; Zhao, Qi; Abel, Eric W

2008-09-15

Protein-repellent diamond coatings have great potential value for surface coatings on implants and surgical instruments. The design of these coatings relies on a fundamental understanding of the intermolecular interactions involved in the adhesion of proteins to surfaces. To get insight into these interactions, adhesion energies of glycine to pure and Si and N-doped (111) diamond surfaces represented as clusters were calculated in the gas phase, using density functional theory (DFT) at the B3LYP/6-31G* level. The computed adhesion energies indicated that adhesion of glycine to diamond surface may be modified by introducing additional elements into the surface. The adhesion was also found to induce considerable change in the conformation of glycine when compared with the lowest-energy conformer of the free molecule. In the Si and N-substituted diamond clusters, notable changes in the structures involving the substituents atoms when compared with smaller parent molecules, such as 1-methyl-1-silaadamantane and 1-azaadamantane, were detected. Adhesion free energy differences were estimated for a series of representative peptides (hydrophobic Phe-Gly-Phe, amphiphilic Arg-Gly-Phe, and hydrophilic Arg-Gly-Arg) to a (111) diamond surface substituted with different amounts of N, Si, or F, using molecular dynamics simulations in an explicit water environment employing a Dreiding force field. The calculations were in agreement with the DFT results in that adsorption of the studied peptides to diamond surface is influenced by introducing additional elements to the surface. It has been shown that, in general, substitution will enhance electrostatic interactions between a surface and surrounding water, leading to a weaker adhesion of the studied peptides.

Numerically bridging lamellipodial and filopodial activity during cell spreading reveals a potentially novel trigger of focal adhesion maturation.

PubMed

Loosli, Y; Vianay, B; Luginbuehl, R; Snedeker, J G

2012-05-01

We present a novel approach to modeling cell spreading, and use it to reveal a potentially central mechanism regulating focal adhesion maturation in various cell phenotypes. Actin bundles that span neighboring focal complexes at the lamellipodium-lamellum interface were assumed to be loaded by intracellular forces in proportion to bundle length. We hypothesized that the length of an actin bundle (with the corresponding accumulated force at its adhesions) may thus regulate adhesion maturation to ensure cell mechanical stability and morphological integrity. We developed a model to test this hypothesis, implementing a "top-down" approach to simplify certain cellular processes while explicitly incorporating complexity of other key subcellular mechanisms. Filopodial and lamellipodial activities were treated as modular processes with functional spatiotemporal interactions coordinated by rules regarding focal adhesion turnover and actin bundle dynamics. This theoretical framework was able to robustly predict temporal evolution of cell area and cytoskeletal organization as reported from a wide range of cell spreading experiments using micropatterned substrates. We conclude that a geometric/temporal modeling framework can capture the key functional aspects of the rapid spreading phase and resultant cytoskeletal complexity. Hence the model is used to reveal mechanistic insight into basic cell behavior essential for spreading. It demonstrates that actin bundles spanning nascent focal adhesions such that they are aligned to the leading edge may accumulate centripetal endogenous forces along their length, and could thus trigger focal adhesion maturation in a force-length dependent fashion. We suggest that this mechanism could be a central "integrating" factor that effectively coordinates force-mediated adhesion maturation at the lamellipodium-lamellum interface.

Biophysics of cadherin adhesion.

PubMed

Leckband, Deborah; Sivasankar, Sanjeevi

2012-01-01

Since the identification of cadherins and the publication of the first crystal structures, the mechanism of cadherin adhesion, and the underlying structural basis have been studied with a number of different experimental techniques, different classical cadherin subtypes, and cadherin fragments. Earlier studies based on biophysical measurements and structure determinations resulted in seemingly contradictory findings regarding cadherin adhesion. However, recent experimental data increasingly reveal parallels between structures, solution binding data, and adhesion-based biophysical measurements that are beginning to both reconcile apparent differences and generate a more comprehensive model of cadherin-mediated cell adhesion. This chapter summarizes the functional, structural, and biophysical findings relevant to cadherin junction assembly and adhesion. We emphasize emerging parallels between findings obtained with different experimental approaches. Although none of the current models accounts for all of the available experimental and structural data, this chapter discusses possible origins of apparent discrepancies, highlights remaining gaps in current knowledge, and proposes challenges for further study.

High Fidelity Tape Transfer Printing Based On Chemically Induced Adhesive Strength Modulation

NASA Astrophysics Data System (ADS)

Sim, Kyoseung; Chen, Song; Li, Yuhang; Kammoun, Mejdi; Peng, Yun; Xu, Minwei; Gao, Yang; Song, Jizhou; Zhang, Yingchun; Ardebili, Haleh; Yu, Cunjiang

2015-11-01

Transfer printing, a two-step process (i.e. picking up and printing) for heterogeneous integration, has been widely exploited for the fabrication of functional electronics system. To ensure a reliable process, strong adhesion for picking up and weak or no adhesion for printing are required. However, it is challenging to meet the requirements of switchable stamp adhesion. Here we introduce a simple, high fidelity process, namely tape transfer printing(TTP), enabled by chemically induced dramatic modulation in tape adhesive strength. We describe the working mechanism of the adhesion modulation that governs this process and demonstrate the method by high fidelity tape transfer printing several types of materials and devices, including Si pellets arrays, photodetector arrays, and electromyography (EMG) sensors, from their preparation substrates to various alien substrates. High fidelity tape transfer printing of components onto curvilinear surfaces is also illustrated.

Endothelial cell regulation of leukocyte infiltration in inflammatory tissues

PubMed Central

Mantovani, A.; Introna, M.; Dejana, E.

1995-01-01

Endothelial cells play an important, active role in the onset and regulation of inflammatory and immune reactions. Through the production of chemokines they attract leukocytes and activate their adhesive receptors. This leads to the anchorage of leukocytes to the adhesive molecules expressed on the endothelial surface. Leukocyte adhesion to endothelial cells is frequently followed by their extravasation. The mechanisms which regulate the passage of leukocytes through endothelial clefts remain to be clarified. Many indirect data suggest that leukocytes might transfer signals to endothelial cells both through the release of active agents and adhesion to the endothelial cell surface. Adhesive molecules (such as PECAM) on the endothelial cell surface might also ‘direct’ leukocytes through the intercellular junction by haptotaxis. The information available on the molecular structure and functional properties of endothelial chemokines, adhesive molecules or junction organization is still fragmentary. Further work is needed to clarify how they interplay in regulating leukocyte infiltration into tissues. PMID:18475659

N-cadherin prodomain processing regulates synaptogenesis.

PubMed

Reinés, Analía; Bernier, Louis-Philippe; McAdam, Robyn; Belkaid, Wiam; Shan, Weisong; Koch, Alexander W; Séguéla, Philippe; Colman, David R; Dhaunchak, Ajit S

2012-05-02

Classical cadherins, which are adhesion molecules functioning at the CNS synapse, are synthesized as adhesively inactive precursor proteins in the endoplasmic reticulum (ER). Signal sequence and prodomain cleavage in the ER and Golgi apparatus, respectively, activates their adhesive properties. Here, we provide the first evidence for sorting of nonadhesive precursor N-cadherin (ProN) to the neuronal surface, where it coexists with adhesively competent mature N-cadherin (N-cad), generating a spectrum of adhesive strengths. In cultured hippocampal neurons, a high ProN/N-cad ratio downregulates synapse formation. Neurons expressing genetically engineered uncleavable ProN make markedly fewer synapses. The synapse number can be rescued to normality by depleting surface ProN levels through prodomain cleavage by an exogenous protease. Finally, prodomain processing is developmentally regulated in the rat hippocampus. We conclude that it is the ProN/N-cad ratio and not mature N-cad alone that is critical for regulation of adhesion during synaptogenesis.

Geometric confinement influences cellular mechanical properties I -- adhesion area dependence.

PubMed

Su, Judith; Jiang, Xingyu; Welsch, Roy; Whitesides, George M; So, Peter T C

2007-06-01

Interactions between the cell and the extracellular matrix regulate a variety of cellular properties and functions, including cellular rheology. In the present study of cellular adhesion, area was controlled by confining NIH 3T3 fibroblast cells to circular micropatterned islands of defined size. The shear moduli of cells adhering to islands of well defined geometry, as measured by magnetic microrheometry, was found to have a significantly lower variance than those of cells allowed to spread on unpatterned surfaces. We observe that the area of cellular adhesion influences shear modulus. Rheological measurements further indicate that cellular shear modulus is a biphasic function of cellular adhesion area with stiffness decreasing to a minimum value for intermediate areas of adhesion, and then increasing for cells on larger patterns. We propose a simple hypothesis: that the area of adhesion affects cellular rheological properties by regulating the structure of the actin cytoskeleton. To test this hypothesis, we quantified the volume fraction of polymerized actin in the cytosol by staining with fluorescent phalloidin and imaging using quantitative 3D microscopy. The polymerized actin volume fraction exhibited a similar biphasic dependence on adhesion area. Within the limits of our simplifying hypothesis, our experimental results permit an evaluation of the ability of established, micromechanical models to predict the cellular shear modulus based on polymerized actin volume fraction. We investigated the "tensegrity", "cellular-solids", and "biopolymer physics" models that have, respectively, a linear, quadratic, and 5/2 dependence on polymerized actin volume fraction. All three models predict that a biphasic trend in polymerized actin volume fraction as a function of adhesion area will result in a biphasic behavior in shear modulus. Our data favors a higher-order dependence on polymerized actin volume fraction. Increasingly better experimental agreement is observed for the tensegrity, the cellular solids, and the biopolymer models respectively. Alternatively if we postulate the existence of a critical actin volume fraction below which the shear modulus vanishes, the experimental data can be equivalently described by a model with an almost linear dependence on polymerized actin volume fraction; this observation supports a tensegrity model with a critical actin volume fraction.

Phenotypic characterization and adhesive properties of vaginal Candida spp. strains provided by the CHU Farhat Hached (Sousse, Tunisia).

PubMed

Noumi, Emira; Snoussi, Mejdi; Noumi, Inès; Saghrouni, Fatma; Aouni, Mahjoub; Valentin, Eulogio

2015-01-01

Vulvovaginal candidiasis is a common infection among women worldwide, being Candida albicans the most commonly isolated species. Therefore, controlling this opportunistic yeast is one of the key factors for reducing nosocomial infection. We investigated several virulence properties of 28 vaginal strains of Candida isolated from Tunisian women suffering from vulvovaginitis. We also analyzed the virulence properties of a clinical Candida krusei strain and five Candida reference strains. Candida strains were subjected to microscopic analysis and culture in Candida ID2 chromogenic medium. The adhesive properties of these strains were estimated by the microtiter plate - the safranin-staining - and the Congo red agar (CRA) methods, for determining yeast ability to form biofilms on biomaterials used in urinary catheter manufacturing. Their potency to produce hydrolytic enzymes was also studied. Our results showed that nine out of the total studied strains produced phospholipase. In addition, very high protease activity was detected in 23 Candida strains. All Candida strains were beta-hemolytic and adhered to polystyrene microtiter plates in varying degrees. Two vaginal C. albicans strains were strongly adhesive to polystyrene and glass slides. Also, our results showed that vaginal Candida strains were more adhesive to the three tested materials than the reference strains. This study shows the presence of a range of virulence and adhesion factors in clinical isolates of vaginal Candida. Consequently, control and treatment of vaginal candidiasis as a means to prevent biofilm formation on urinary catheters is of crucial importance. Copyright © 2013 Revista Iberoamericana de Micología. Published by Elsevier Espana. All rights reserved.

Effects of membrane deformability and bond formation/dissociation rates on adhesion dynamics of a spherical capsule in shear flow.

PubMed

Zhang, Ziying; Du, Jun; Wei, Zhengying; Wang, Zhen; Li, Minghui

2018-02-01

Cellular adhesion plays a critical role in biological systems and biomedical applications. Cell deformation and biophysical properties of adhesion molecules are of significance for the adhesion behavior. In the present work, dynamic adhesion of a deformable capsule to a planar substrate, in a linear shear flow, is numerically simulated to investigate the combined influence of membrane deformability (quantified by the capillary number) and bond formation/dissociation rates on the adhesion behavior. The computational model is based on the immersed boundary-lattice Boltzmann method for the capsule-fluid interaction and a probabilistic adhesion model for the capsule-substrate interaction. Three distinct adhesion states, detachment, rolling adhesion and firm adhesion, are identified and presented in a state diagram as a function of capillary number and bond dissociation rate. The impact of bond formation rate on the state diagram is further investigated. Results show that the critical bond dissociation rate for the transition of rolling or firm adhesion to detachment is strongly related to the capsule deformability. At the rolling-adhesion state, smaller off rates are needed for larger capillary number to increase the rolling velocity and detach the capsule. In contrast, the critical off rate for firm-to-detach transition slightly increases with the capillary number. With smaller on rate, the effect of capsule deformability on the critical off rates is more pronounced and capsules with moderate deformability are prone to detach by the shear flow. Further increasing of on rate leads to large expansion of both rolling-adhesion and firm-adhesion regions. Even capsules with relatively large deformability can maintain stable rolling adhesion at certain off rate.

Hydroxyapatite nanobelt/polylactic acid Janus membrane with osteoinduction/barrier dual functions for precise bone defect repair.

PubMed

Ma, Baojin; Han, Jing; Zhang, Shan; Liu, Feng; Wang, Shicai; Duan, Jiazhi; Sang, Yuanhua; Jiang, Huaidong; Li, Dong; Ge, Shaohua; Yu, Jinghua; Liu, Hong

2018-04-15

Controllable osteoinduction maintained in the original defect area is the key to precise bone repair. To meet the requirement of precise bone regeneration, a hydroxyapatite (HAp) nanobelt/polylactic acid (PLA) (HAp/PLA) Janus membrane has been successfully prepared in this study by coating PLA on a paper-like HAp nanobelt film by a casting-pervaporation method. The Janus membrane possesses dual functions: excellent osteoinduction from the hydrophilic HAp nanobelt side and barrier function originating from the hydrophobic PLA film. The cell viability and osteogenic differentiation ability of human adipose-derived stem cells (hADSCs) on the Janus membrane were assessed. The in vitro experimental results prove that the HAp nanobelt side presents high cell viability and efficient osteoinduction without any growth factor and that the PLA side can prohibit cell attachment. The in vivo repair experiments on a rat mandible defect model prove that the PLA side can prevent postoperative adhesion between bone and adjacent soft tissues. Most importantly, the HAp side has a strong ability to promote defect repair and bone regeneration. Therefore, the HAp/PLA Janus membrane will have wide applications as a kind of tissue engineering material in precise bone repair because of its unique dual osteoinduction/barrier functions, biocompatibility, low cost, and its ability to be mass-produced. Precise bone defect repair to keeping tissue integrity and original outline shape is a very important issue for tissue engineering. Here, we have designed and prepared a novel HAp/PLA Janus membrane using a casting-pervaporation method to form a layer of PLA film on paper-like HAp nanobelt film. HAp nanobelt side of the Janus membrane can successfully promote osteogenic differentiation. PLA side of the Janus membrane exhibits good properties as a barrier for preventing the adhesion of cells in vitro. Mandible repair experiments in vivo have shown that the HAp/PLA Janus membrane can promote rat mandible repair on the HAp side and can successfully prevent postoperative adhesion on the PLA side at the same time. Therefore, the HAp/PLA Janus membrane with its osteoinduction/barrier dual functions can be applied to repair bone defect precisely. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

In-vitro transdentinal diffusion of monomers from adhesives.

PubMed

Putzeys, Eveline; Duca, Radu Corneliu; Coppens, Lieve; Vanoirbeek, Jeroen; Godderis, Lode; Van Meerbeek, Bart; Van Landuyt, Kirsten L

2018-06-01

Biocompatibility of adhesives is important since adhesives may be applied on dentin near the pulp. Accurate knowledge of the quantity of monomers reaching the pulp is important to determine potential side effects. The aim of this study was to assess the transdentinal diffusion of residual monomers from dental adhesive systems using an in-vitro pulp chamber model. Dentin disks with a thickness of 300 µm were produced from human third molars. These disks were fixed between two open-ended glass tubes, representing an in-vitro pulp chamber. The etch-and-rinse adhesive OptiBond FL and the self-etch adhesive Clearfil SE Bond were applied to the dentin side of the disks, while on in the pulpal side, the glass tube was filled with 600 µL water. The transdentinal diffusion of different monomers was quantified using ultra-performance liquid chromatography-tandem mass spectrometry. The monomers HEMA, CQ, BisGMA, GPDM, 10-MDP and UDMA eluted from the dental materials and were able to diffuse through the dentin disks to a certain extent. Compounds with a lower molecular weight (uncured group: HEMA 7850 nmol and CQ 78.2 nmol) were more likely to elute and diffuse compared to monomers with a higher molecular weight (uncured group: BisGMA 0.42 nmol). When the adhesives were left uncured, diffusion was up to 10 times higher compared to the cured conditions. This in-vitro research resulted in the quantification of various monomers able to diffuse through dentin and therefore contributes to a more detailed understanding about the potential exposure of the dental pulp to monomers from dental adhesives. Biocompatibility of adhesives is important since adhesives may be applied on dentin near the pulp, where tubular density and diameter are greatest. Copyright © 2018. Published by Elsevier Ltd.

The viscoelastic evaluation of transdermal adhesive systems and the influence of excipients

NASA Astrophysics Data System (ADS)

Wick, Steven Marshall

1998-12-01

The transdermal dosage form requires simultaneous consideration of both drug delivery and adhesion to skin in order to achieve the desired therapeutic effect. A transdermal system with inadequate adhesion performance will produce a variable and unpredictable systemic blood level profile. It is therefore of paramount importance that the adhesive performance be fully contemplated within the development of a total transdermal system. An experimental strategy was developed within this thesis which utilizes a sequential combination of a dynamic stress followed by a static shear stress evaluation Within the dynamic stress evaluation, a sinusoidal stress of constant frequency, over a frequency of 0.065 to 64 Hz was applied normal to the surface of an adhesive system. The static shear stress apparatus (CIRUSS) applies a constant shear stress for a defined time interval (three minutes) followed by an instantaneous removal of the applied shear stress. The mechanical behavior of two distinct adhesive polymers (silicone and acrylate) was modeled as a one-dimensional four-parameter solid and five-parameter solid respectively for the two adhesive systems. The effects of several additives were examined including ethyl oleate, glyceryl monolaurate, an amine oxide, Teflon and a macromer. In addition, the effect of branching and cross-linking was examined using the acrylate adhesive system. A physical interpretation of the mechanical behavior was proposed associating the deformation within an adhesive system with the disruption of the hydrogen bonding network as well as the covalent bonds within the polymer backbone. The collected data was consistent with the author's postulate. The presented results verify the utility of the aforementioned sequential evaluation strategy in characterizing adhesive viscoelastic performance.

Effect of blood contamination with 1-step self-etching adhesives on microtensile bond strength to dentin.

PubMed

Yoo, H M; Pereira, P N R

2006-01-01

This study evaluated the effect of blood contamination and decontamination methods on the microtensile bond strength of 1-step self-etching adhesive systems to dentin contaminated after adhesive application and light curing. Three commercially available "all-in-one" adhesives (One Up Bond F, Xeno III and Adper Prompt L-Pop) and 1 resin composite (Clearfil AP-X) were used. Third molars that had been stored in distilled water with 0.5% thymol at 4 degrees C were ground with #600 SiC paper under running water to produce a standardized smear layer. The specimens were randomly divided into groups according to the 3 adhesive systems. The adhesive systems were used under 3 conditions: no contamination, which was the control (C); contamination of the light-cured adhesive surface with blood and reapplication of adhesive (Contamination 1) and contamination of the light-cured adhesive surface with blood, then washing, drying and reapplication of the adhesive (Contamination 2). Following light curing of the adhesive, the resin composite was placed in 3 increments up to a 5-mm-thick layer on the bonded surface. All specimens were stored in distilled water at 37 degrees C for 24 hours. The microtensile bond strength was measured using a universal testing machine (EZ test), and data were analyzed by 1-way ANOVA followed by the Duncan test to make comparisons among the groups (p=0.05). After debonding, 5 specimens were selected from each group and examined in a scanning electron microscope to evaluate the modes of fracture. For all adhesives, contamination groups showed lower bond strength than the control (p<0.05). There was no statistically significant difference among the control groups (p>0.05). For Xeno III and Adper Prompt L-Pop, contamination group #2 showed the lowest bond strength among the groups (p<0.05). For One Up Bond F, contamination group #2 showed higher bond strength than contamination group #1 but showed no statistical significance between them (p>0.05).

Podocalyxin Is a Novel Polysialylated Neural Adhesion Protein with Multiple Roles in Neural Development and Synapse Formation

PubMed Central

Vitureira, Nathalia; Andrés, Rosa; Pérez-Martínez, Esther; Martínez, Albert; Bribián, Ana; Blasi, Juan; Chelliah, Shierley; López-Doménech, Guillermo; De Castro, Fernando; Burgaya, Ferran; McNagny, Kelly; Soriano, Eduardo

2010-01-01

Neural development and plasticity are regulated by neural adhesion proteins, including the polysialylated form of NCAM (PSA-NCAM). Podocalyxin (PC) is a renal PSA-containing protein that has been reported to function as an anti-adhesin in kidney podocytes. Here we show that PC is widely expressed in neurons during neural development. Neural PC interacts with the ERM protein family, and with NHERF1/2 and RhoA/G. Experiments in vitro and phenotypic analyses of podxl-deficient mice indicate that PC is involved in neurite growth, branching and axonal fasciculation, and that PC loss-of-function reduces the number of synapses in the CNS and in the neuromuscular system. We also show that whereas some of the brain PC functions require PSA, others depend on PC per se. Our results show that PC, the second highly sialylated neural adhesion protein, plays multiple roles in neural development. PMID:20706633

A novel diagnostic aid for intra-abdominal adhesion detection in cine-MR imaging: Pilot study and initial diagnostic impressions.

PubMed

Randall, David; Joosten, Frank; ten Broek, Richard; Gillott, Richard; Bardhan, Karna Dev; Strik, Chema; Prins, Wiesje; van Goor, Harry; Fenner, John

2017-07-14

A non-invasive diagnostic technique for abdominal adhesions is not currently available. Capture of abdominal motion due to respiration in cine-MRI has shown promise, but is difficult to interpret. This article explores the value of a complimentary diagnostic aid to facilitate the non-invasive detection of abdominal adhesions using cine-MRI. An image processing technique was developed to quantify the amount of sliding that occurs between the organs of the abdomen and the abdominal wall in sagittal cine-MRI slices. The technique produces a 'sheargram' which depicts the amount of sliding which has occurred over 1-3 respiratory cycles. A retrospective cohort of 52 patients, scanned for suspected adhesions, made 281 cine-MRI sagittal slices available for processing. The resulting sheargrams were reported by two operators and compared to expert clinical judgement of the cine-MRI scans. The sheargram matched clinical judgement in 84% of all sagittal slices and 93-96% of positive adhesions were identified on the sheargram. The sheargram displayed a slight skew towards sensitivity over specificity, with a high positive adhesion detection rate but at the expense of false positives. Good correlation between sheargram and absence/presence of inferred adhesions indicates quantification of sliding motion has potential to aid adhesion detection in cine-MRI. Advances in Knowledge: This is the first attempt to clinically evaluate a novel image processing technique quantifying the sliding motion of the abdominal contents against the abdominal wall. The results of this pilot study reveal its potential as a diagnostic aid for detection of abdominal adhesions.

Heterogeneity of Focal Adhesions and Focal Contacts in Motile Fibroblasts.

PubMed

Gladkikh, Aleena; Kovaleva, Anastasia; Tvorogova, Anna; Vorobjev, Ivan A

2018-01-01

Cell-extracellular matrix (ECM) adhesion is an important property of virtually all cells in multicellular organisms. Cell-ECM adhesion studies, therefore, are very significant both for biology and medicine. Over the last three decades, biomedical studies resulted in a tremendous advance in our understanding of the molecular basis and functions of cell-ECM adhesion. Based on morphological and molecular criteria, several different types of model cell-ECM adhesion structures including focal adhesions, focal complexes, fibrillar adhesions, podosomes, and three-dimensional matrix adhesions have been described. All the subcellular structures that mediate cell-ECM adhesion are quite heterogeneous, often varying in size, shape, distribution, dynamics, and, to a certain extent, molecular constituents. The morphological "plasticity" of cell-ECM adhesion perhaps reflects the needs of cells to sense, adapt, and respond to a variety of extracellular environments. In addition, cell type (e.g., differentiation status, oncogenic transformation, etc.) often exerts marked influence on the structure of cell-ECM adhesions. Although molecular, genetic, biochemical, and structural studies provide important maps or "snapshots" of cell-ECM adhesions, the area of research that is equally valuable is to study the heterogeneity of FA subpopulations within cells. Recently time-lapse observations on the FA dynamics become feasible, and behavior of individual FA gives additional information on cell-ECM interactions. Here we describe a robust method of labeling of FA using plasmids with fluorescent markers for paxillin and vinculin and quantifying the morphological and dynamical parameters of FA.

Cobra CRISP functions as an inflammatory modulator via a novel Zn2+- and heparan sulfate-dependent transcriptional regulation of endothelial cell adhesion molecules.

PubMed

Wang, Yu-Ling; Kuo, Je-Hung; Lee, Shao-Chen; Liu, Jai-Shin; Hsieh, Yin-Cheng; Shih, Yu-Tsung; Chen, Chun-Jung; Chiu, Jeng-Jiann; Wu, Wen-Guey

2010-11-26

Cysteine-rich secretory proteins (CRISPs) have been identified as a toxin family in most animal venoms with biological functions mainly associated with the ion channel activity of cysteine-rich domain (CRD). CRISPs also bind to Zn(2+) at their N-terminal pathogenesis-related (PR-1) domain, but their function remains unknown. Interestingly, similar the Zn(2+)-binding site exists in all CRISP family, including those identified in a wide range of organisms. Here, we report that the CRISP from Naja atra (natrin) could induce expression of vascular endothelial cell adhesion molecules, i.e. intercellular adhesion molecule-1, vascular adhesion molecule-1, and E-selectin, to promote monocytic cell adhesion in a heparan sulfate (HS)- and Zn(2+)-dependent manner. Using specific inhibitors and small interfering RNAs, the activation mechanisms are shown to involve both mitogen-activated protein kinases and nuclear factor-κB. Biophysical characterization of natrin by using fluorescence, circular dichroism, and x-ray crystallographic methods further reveals the presence of two Zn(2+)-binding sites for natrin. The strong binding site is located near the putative Ser-His-Glu catalytic triad of the N-terminal domain. The weak binding site remains to be characterized, but it may modulate HS binding by enhancing its interaction with long chain HS. Our results strongly suggest that natrin may serve as an inflammatory modulator that could perturb the wound-healing process of the bitten victim by regulating adhesion molecule expression in endothelial cells. Our finding uncovers a new aspect of the biological role of CRISP family in immune response and is expected to facilitate future development of new therapeutic strategy for the envenomed victims.

Characterization of four CD18 mutants in leucocyte adhesion deficient (LAD) patients with differential capacities to support expression and function of the CD11/CD18 integrins LFA-1, Mac-1 and p150,95

PubMed Central

Shaw, J M; Al-Shamkhani, A; Boxer, L A; Buckley, C D; Dodds, A W; Klein, N; Nolan, S M; Roberts, I; Roos, D; Scarth, S L; Simmons, D L; Tan, S M; Law, S K A

2001-01-01

Leucocyte adhesion deficiency (LAD) is a hereditary disorder caused by mutations in the CD18 (β2 integrin) gene. Four missense mutations have been identified in three patients. CD18(A270V) supports, at a diminished level, CD11b/CD18 (Mac-1, αMβ2 integrin) and CD11c/CD18 (p150,95, αXβ2 integrin) expression and function but not CD11a/CD18 (LFA-1, αLβ2 integrin) expression. Conversely, CD18(A341P) supports a limited level of expression and function of CD11a/CD18, but not of the other two CD11/CD18 antigens. CD18(C590R) and CD18(R593C) show a decreasing capacity to associate with the CD11a, CD11c and CD11b subunits. Transfectants expressing the CD11a/CD18 with the C590R and R593C mutations are more adhesive than transfectants expressing wild-type LFA-1, and express the reporter epitope of the monoclonal antibody 24 constitutively. Thus, the four mutations affect CD18 differently in its capacities to support CD11/CD18 expression and adhesion. These results not only provide a biochemical account for the clinical diversity of patients with leucocyte adhesion deficiency, but also offer novel insights into the structural basis of interaction between the α and β subunits, which is an integral component in our understanding of integrin-mediated adhesion and its regulation. PMID:11703376

Electrostatic adhesion for added functionality of composite structures

NASA Astrophysics Data System (ADS)

Heath, Callum J. C.; Bond, Ian P.; Potter, Kevin D.

2016-02-01

Electrostatic adhesion can be used as a means of reversible attachment. The incorporation of electrostatic adhesion into fibre reinforced polymer (FRP) composite structures could provide significant value added functionality. Imparting large potential differences (˜2 kV) across electrodes generates an attractive force, thus providing a means of attachment. This could be used as a reversible latching mechanism or as a means of controllable internal connectivity. Varying the connectivity for discrete elements of a substructure of a given design allows for control of internal load paths and moment of area of the cross section. This could facilitate variable stiffness (both in bending and torsion). Using a combination of existing fabrication techniques, functional electrodes have been integrated within a FRP. Copper polyimide thin film laminate material has been both co-cured with carbon fibre reinforced epoxy and bonded to PVC closed cell foam core material to provide a range of structural configurations with integrated electrodes. The ability of such integrated devices to confer variations in global bending stiffness of basic beam structures is investigated. Through the application of 4 kV across integrated electrostatic adhesive devices, a 112% increase in flexural stiffness has been demonstrated for a composite sandwich structure.

Preparation of an Arg-Glu-Asp-Val Peptide Density Gradient on Hyaluronic Acid-Coated Poly(ε-caprolactone) Film and Its Influence on the Selective Adhesion and Directional Migration of Endothelial Cells.

PubMed

Yu, Shan; Gao, Ying; Mei, Xu; Ren, Tanchen; Liang, Su; Mao, Zhengwei; Gao, Changyou

2016-11-02

Selective adhesion and migration of endothelial cells (ECs) over smooth muscle cells (SMCs) is very important in the rapid endothelialization of blood-contacting implants to prevent vascular restenosis. In this study, a uniform cell-resistant layer of methacrylate-functionalized hyaluronic acid (HA) was first immobilized on a poly(ε-caprolactone) (PCL) film via polydopamine coupling. Then, a density gradient of thiol-functionalized Arg-Glu-Asp-Val (REDV) peptide was prepared on the HA layer via thiol-ene click chemistry and the continuous injection method. The REDV gradient selectively enhanced EC adhesion and preferential directional migration toward the region of higher REDV density, reaching 86% directionality in the middle of the gradient. The migration rate of ECs was also significantly enhanced twofold compared with that on tissue culture polystyrene (TCPS). In contrast, the gradient significantly weakened the adhesion of SMCs to 25% of that on TCPS but had no obvious impact on the migration rate and directionality. Successful modulation of the selective adhesion and directional migration of ECs over SMCs on biodegradable polymers serves as an important step toward practical applications for guided tissue regeneration.

KHYG-1 and NK-92 represent different subtypes of LFA-1-mediated NK cell adhesiveness.

PubMed

Suck, Garnet; Tan, Suet-Mien; Chu, Sixian; Niam, Madelaine; Vararattanavech, Ardcharaporn; Lim, Tsyr Jong; Koh, Mickey B C

2011-01-01

Novel cancer cellular therapy approaches involving long-term ex vivo IL-2 stimulated highly cytotoxic natural killer (NK) cells are emerging. However, adhesion properties of such NK cells are not very well understood. Herein, we describe the novel observation of permanently activated alphaLbeta2 integrin leukocyte function-associated antigen (LFA)-1 adhesion receptor in long-term IL-2 activated NK cells and the permanent NK cell lines KHYG-1 and NK-92. We show that such cytokine activated NK effectors constitutively adhered to the LFA-1-ligand ICAM-1, whereas binding to the lower affinity ligand ICAM-3 required additional exogenous activating conditions. The results demonstrate an extended conformation and an intermediate affinity state for the LFA-1 population expressed by the NK cells. Interestingly, adhesion to ICAM-1 or K562 induced pronounced cell spreading in KHYG-1, but not in NK-92, and partially in long-term IL-2 stimulated primary NK cells. It is conceivable that such differential adhesion characteristics may impact motility potential of such NK effectors with relevance to clinical tumor targeting. KHYG-1 could be a useful model in planning future targeted therapeutic approaches involving NK effectors with augmented functions.

Micrometer scale spacings between fibronectin nanodots regulate cell morphology and focal adhesions

NASA Astrophysics Data System (ADS)

Horzum, Utku; Ozdil, Berrin; Pesen-Okvur, Devrim

2014-04-01

Cell adhesion to extracellular matrix is an important process for both health and disease states. Surface protein patterns that are topographically flat, and do not introduce other chemical, topographical or rigidity related functionality and, more importantly, that mimic the organization of the in vivo extracellular matrix are desired. Previous work showed that vinculin and cytoskeletal organization are modulated by size and shape of surface nanopatterns. However, quantitative analysis on cell morphology and focal adhesions as a function of micrometer scale spacings of FN nanopatterns was absent. Here, electron beam lithography was used to pattern fibronectin nanodots with micrometer scale spacings on a K-casein background on indium tin oxide coated glass which, unlike silicon, is transparent and thus suitable for many light microscopy techniques. Exposure times were significantly reduced using the line exposure mode with micrometer scale step sizes. Micrometer scale spacings of 2, 4 and 8 μm between fibronectin nanodots proved to modulate cell adhesion through modification of cell area, focal adhesion number, size and circularity. Overall, cell behavior was shown to shift at the apparent threshold of 4 μm spacing. The findings presented here offer exciting new opportunities for cell biology research.

Modeled Microgravity Disrupts Collagen I/Integrin Signaling During Osteoblastic Differentiation of Human Mesenchymal Stem Cells

NASA Technical Reports Server (NTRS)

Meyers, Valerie E.; Zayzafoon, Majd; Gonda, Steven R.; Gathings, William E.; McDonald, Jay M.

2004-01-01

Spaceflight leads to reduced bone mineral density in weight bearing bones that is primarily attributed to a reduction in bone formation. We have previously demonstrated severely reduced osteoblastogenesis of human mesenchymal stem cells (hMSC) following seven days culture in modeled microgravity. One potential mechanism for reduced osteoblastic differentiation is disruption of type I collagen-integrin interactions and reduced integrin signaling. Integrins are heterodimeric transmembrane receptors that bind extracellular matrix proteins and produce signals essential for proper cellular function, survival, and differentiation. Therefore, we investigated the effects of modeled microgravity on integrin expression and function in hMSC. We demonstrate that seven days of culture in modeled microgravity leads to reduced expression of the extracellular matrix protein, type I collagen (Col I). Conversely, modeled microgravity consistently increases Col I-specific alpha2 and beta1 integrin protein expression. Despite this increase in integrin sub-unit expression, autophosphorylation of adhesion-dependent kinases, focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (PYK2), is significantly reduced. Activation of Akt is unaffected by the reduction in FAK activation. However, reduced downstream signaling via the Ras-MAPK pathway is evidenced by a reduction in Ras and ERK activation. Taken together, our findings indicate that modeled microgravity decreases integrin/MAPK signaling, which likely contributes to the observed reduction in osteoblastogenesis.

Anionic deep cavitands enable the adhesion of unmodified proteins at a membrane bilayer.

PubMed

Ghang, Yoo-Jin; Perez, Lizeth; Morgan, Melissa A; Si, Fang; Hamdy, Omar M; Beecher, Consuelo N; Larive, Cynthia K; Julian, Ryan R; Zhong, Wenwan; Cheng, Quan; Hooley, Richard J

2014-12-28

An anionic self-folding deep cavitand is capable of immobilizing unmodified proteins and enzymes at a supported lipid bilayer interface, providing a simple, soft bioreactive surface that allows enzymatic function under mild conditions. The adhesion is based on complementary charge interactions, and the hosts are capable of binding enzymes such as trypsin at the bilayer interface: the catalytic activity is retained upon adhesion, allowing selective reactions to be performed at the membrane surface.

Adhesion Improvement between Polyethylene and Aluminum Using Eco-Friendly Plasma Treatment

NASA Astrophysics Data System (ADS)

Popelka, Anton; Krupa, Igor; Novák, Igor; Ouederni, Mabrouk; Abdulaqder, Fatima; Al-Yazedi, Shrooq; Al-Gunaid, Taghreed; Al-Senani, Thuraya

Polyethylene (PE) belongs among the most widely used polymers in many industrial applications, such as in building, packaging or transport industry. Qatar is one of the largest producers of PE in the world. Composite laminates consisting of PE and metal materials, such as aluminum (Al) lead to an improvement of various mechanical and physical properties necessary for special applications in building industry. Aluminum composite panel (ACP) represents type of flat panel that consists of two thin aluminum sheets bonded to a non-aluminum core, often made from PE. ACPs are frequently used for external cladding or facades of buildings. The main problem relates the adhesion between both materials. In this research work the improvement of adhesion properties of composite laminates prepared from PE and Al using plasma treatment was investigated. This surface treatment led to the significantly increase of peel strength of PE-Al adhesive joints.

HPK1 competes with ADAP for SLP-76 binding and via Rap1 negatively affects T-cell adhesion.

PubMed

Patzak, Irene M; Königsberger, Sebastian; Suzuki, Akira; Mak, Tak W; Kiefer, Friedemann

2010-11-01

The hematopoietic progenitor kinase 1 (HPK1) signals into MAPK and NFκB pathways downstream of immunoreceptors, but enigmatically is a negative regulator of leukocytes. Here, we report a novel role for HPK1 in regulating the activation of the adhesion molecule leukocyte function-associated antigen-1 (LFA-1). Upon TCR stimulation, mediated by binding of adhesion and degranulation promoting adaptor protein (ADAP) to SLP-76, a ternary complex composed of ADAP/55-kDa src kinase associated phosphoprotein (SKAP-55) and RIAM translocates to the membrane and causes membrane recruitment of the active small GTPase Ras-related protein 1 (Rap1). Active Rap1, via its binding to RapL (regulator for cell adhesion and polarization enriched in lymphoid tissues), mediates LFA-1 integrin activation. We show here that HPK1, which also binds SLP-76, compete with ADAP for SLP-76 binding. In addition, HPK1 dampens Rap1 activation, resulting in decreased LFA-1 activity. Analysis of HPK1-deficient T cells revealed increased ADAP recruitment to SLP-76 and elevated Rap1 activation in those cells, leading to increased adhesion to ICAM-1 and cell spreading. Altogether, these results describe a novel function for HPK1 in linking TCR signaling to cell adhesion regulation and provide a mechanistic explanation for the negative regulatory role of HPK1 in T-cell biology.

Intercellular adhesion molecule-1 expression by skeletal muscle cells augments myogenesis.

PubMed

Goh, Qingnian; Dearth, Christopher L; Corbett, Jacob T; Pierre, Philippe; Chadee, Deborah N; Pizza, Francis X

2015-02-15

We previously demonstrated that the expression of intercellular adhesion molecule-1 (ICAM-1) by skeletal muscle cells after muscle overload contributes to ensuing regenerative and hypertrophic processes in skeletal muscle. The objective of the present study is to reveal mechanisms through which skeletal muscle cell expression of ICAM-1 augments regenerative and hypertrophic processes of myogenesis. This was accomplished by genetically engineering C2C12 myoblasts to stably express ICAM-1, and by inhibiting the adhesive and signaling functions of ICAM-1 through the use of a neutralizing antibody or cell penetrating peptide, respectively. Expression of ICAM-1 by cultured skeletal muscle cells augmented myoblast-myoblast adhesion, myotube formation, myonuclear number, myotube alignment, myotube-myotube fusion, and myotube size without influencing the ability of myoblasts to proliferate or differentiate. ICAM-1 augmented myotube formation, myonuclear accretion, and myotube alignment through a mechanism involving adhesion-induced activation of ICAM-1 signaling, as these dependent measures were reduced via antibody and peptide inhibition of ICAM-1. The adhesive and signaling functions of ICAM-1 also facilitated myotube hypertrophy through a mechanism involving myotube-myotube fusion, protein synthesis, and Akt/p70s6k signaling. Our findings demonstrate that ICAM-1 expression by skeletal muscle cells augments myogenesis, and establish a novel mechanism through which the inflammatory response facilitates growth processes in skeletal muscle. Copyright © 2014 Elsevier Inc. All rights reserved.

Intercellular Adhesion Molecule-1 Expression by Skeletal Muscle Cells Augments Myogenesis

PubMed Central

Goh, Qingnian; Dearth, Christopher L.; Corbett, Jacob T.; Pierre, Philippe; Chadee, Deborah N.; Pizza, Francis X.

2014-01-01

We previously demonstrated that the expression of intercellular adhesion molecule-1 (ICAM-1) by skeletal muscle cells after muscle overload contributes to ensuing regenerative and hypertrophic processes in skeletal muscle. The objective of the present study is to reveal mechanisms through which skeletal muscle cell expression of ICAM-1 augments regenerative and hypertrophic processes of myogenesis. This was accomplished by genetically engineering C2C12 myoblasts to stably express ICAM-1, and by inhibiting the adhesive and signaling functions of ICAM-1 through the use of a neutralizing antibody or cell penetrating peptide, respectively. Expression of ICAM-1 by cultured skeletal muscle cells augmented myoblast-myoblast adhesion, myotube formation, myonuclear number, myotube alignment, myotube-myotube fusion, and myotube size without influencing the ability of myoblasts to proliferate or differentiate. ICAM-1 augmented myotube formation, myonuclear accretion, and myotube alignment through a mechanism involving adhesion-induced activation of ICAM-1 signaling, as these dependent measures were reduced via antibody and peptide inhibition of ICAM-1. The adhesive and signaling functions of ICAM-1 also facilitated myotube hypertrophy through a mechanism involving myotube-myotube fusion, protein synthesis, and Akt/p70s6k signaling. Our findings demonstrate that ICAM-1 expression by skeletal muscle cells augments myogenesis, and establish a novel mechanism through which the inflammatory response facilitates growth processes in skeletal muscle. PMID:25281303

Effect of Extreme Wettability on Platelet Adhesion on Metallic Implants: From Superhydrophilicity to Superhydrophobicity.

PubMed

Moradi, Sona; Hadjesfandiari, Narges; Toosi, Salma Fallah; Kizhakkedathu, Jayachandran N; Hatzikiriakos, Savvas G

2016-07-13

In order to design antithrombotic implants, the effect of extreme wettability (superhydrophilicity to superhydrophobicity) on the biocompatibility of the metallic substrates (stainless steel and titanium) was investigated. The wettability of the surface was altered by chemical treatments and laser ablation methods. The chemical treatments generated different functionality groups and chemical composition as evident from XPS analysis. The micro/nanopatterning by laser ablation resulted in three different pattern geometry and different surface roughness and consequently wettability. The patterned surface were further modified with chemical treatments to generate a wide range of surface wettability. The influence of chemical functional groups, pattern geometry, and surface wettability on protein adsorption and platelet adhesion was studied. On chemically treated flat surfaces, the type of hydrophilic treatment was shown to be a contributing factor that determines the platelet adhesion, since the hydrophilic oxidized substrates exhibit less platelet adhesion in comparison to the control untreated or acid treated surfaces. Also, the surface morphology, surface roughness, and superhydrophobic character of the surfaces are contributing factors to platelet adhesion on the surface. Our results show that superhydrophobic cauliflower-like patterns are highly resistant to platelet adhesion possibly due to the stability of Cassie-Baxter state for this pattern compared to others. Our results also show that simple surface treatments on metals offer a novel way to improve the hemocompatibility of metallic substrates.

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

PubMed

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 (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. 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.

Study of adhesion of vertically aligned carbon nanotubes to a substrate by atomic-force microscopy

NASA Astrophysics Data System (ADS)

Ageev, O. A.; Blinov, Yu. F.; Il'ina, M. V.; Il'in, O. I.; Smirnov, V. A.; Tsukanova, O. G.

2016-02-01

The adhesion to a substrate of vertically aligned carbon nanotubes (VA CNT) produced by plasmaenhanced chemical vapor deposition has been experimentally studied by atomic-force microscopy in the current spectroscopy mode. The longitudinal deformation of VA CNT by applying an external electric field has been simulated. Based on the results, a technique of determining VA CNT adhesion to a substrate has been developed that is used to measure the adhesion strength of connecting VA CNT to a substrate. The adhesion to a substrate of VA CNT 70-120 nm in diameter varies from 0.55 to 1.19 mJ/m2, and the adhesion force from 92.5 to 226.1 nN. When applying a mechanical load, the adhesion strength of the connecting VA CNT to a substrate is 714.1 ± 138.4 MPa, and the corresponding detachment force increases from 1.93 to 10.33 μN with an increase in the VA CNT diameter. As an external electric field is applied, the adhesion strength is almost doubled and is 1.43 ± 0.29 GPa, and the corresponding detachment force is changed from 3.83 to 20.02 μN. The results can be used in the design of technological processes of formation of emission structures, VA CNT-based elements for vacuum microelectronics and micro- and nanosystem engineering, and also the methods of probe nanodiagnostics of VA CNT.

Adhesion of resin composite core materials to dentin.

PubMed

O'Keefe, K L; Powers, J M

2001-01-01

This study determined (1) the effect of polymerization mode of resin composite core materials and dental adhesives on the bond strength to dentin, and (2) if dental adhesives perform as well to dentin etched with phosphoric acid as to dentin etched with self-etching primer. Human third molars were sectioned 2 mm from the highest pulp horn and polished. Three core materials (Fluorocore [dual cured], Core Paste [self-cured], and Clearfil Photo Core [light cured]) and two adhesives (Prime & Bond NT Dual Cure and Clearfil SE Bond [light cured]) were bonded to dentin using two dentin etching conditions. After storage, specimens were debonded in microtension and bond strengths were calculated. Scanning electron micrographs of representative bonding interfaces were analyzed. Analysis showed differences among core materials, adhesives, and etching conditions. Among core materials, dual-cured Fluorocore had the highest bond strengths. There were incompatibilities between self-cured Core Paste and Prime & Bond NT in both etched (0 MPa) and nonetched (3.0 MPa) dentin. Among adhesives, in most cases Clearfil SE Bond had higher bond strengths than Prime & Bond NT and bond strengths were higher to self-etched than to phosphoric acid-etched dentin. Scanning electron micrographs did not show a relationship between resin tags and bond strengths. There were incompatibilities between a self-cured core material and a dual-cured adhesive. All other combinations of core materials and adhesives produced strong in vitro bond strengths both in the self-etched and phosphoric acid-etched conditions.

Characterization of flexible ECoG electrode arrays for chronic recording in awake rats

PubMed Central

Yeager, John D.; Phillips, Derrick J.; Rector, David M.; Bahr, David F.

2008-01-01

We developed a 64 channel flexible polyimide ECoG electrode array and characterized its performance for long term implantation, chronic cortical recording and high resolution mapping of surface evoked potentials in awake rats. To achieve the longest possible recording periods, the flexibility of the electrode array, adhesion between the metals and carrier substrate, and biocompatibility was critical for maintaining the signal integrity. Experimental testing of thin film adhesion was applied to a gold – polyimide system in order to characterize relative interfacial fracture energies for several different adhesion layers, yielding an increase in overall device reliability. We tested several different adhesion techniques including: gold alone without an adhesion layer, titanium-tungsten, tantalum and chromium. We found the titanium-tungsten to be a suitable adhesion layer considering the biocompatibility requirements as well as stability and delamination resistance. While chromium and tantalum produced stronger gold adhesion, concerns over biocompatibility of these materials require further testing. We implanted the polyimide ECoG electrode arrays through a slit made in the skull of rats and recorded cortical surface evoked responses. The arrays performed reliably over a period of at least 100 days and signals compared well with traditional screw electrodes, with better high frequency response characteristics. Since the ultimate goal of chronically implanted electrode arrays is for neural prosthetic devices that need to last many decades, other adhesion layers that would prove safe for implantation may be tested in the same way in order to improve the device reliability. PMID:18640155

Evidence that activation of ASIC1a by acidosis increases osteoclast migration and adhesion by modulating integrin/Pyk2/Src signaling pathway.

PubMed

Li, X; Ye, J-X; Xu, M-H; Zhao, M-D; Yuan, F-L

2017-07-01

Activated acid-sensing ion channel 1a (ASIC1a) is involved in acid-induced osteoclastogenesis by regulating activation of the transcription factor NFATc1. These results indicated that ASIC1a activation by extracellular acid may cause osteoclast migration and adhesion through Ca 2+ -dependent integrin/Pyk2/Src signaling pathway. Osteoclast adhesion and migration are responsible for osteoporotic bone loss. Acidic conditions promote osteoclastogenesis. ASIC1a in osteoclasts is associated with acid-induced osteoclastogenesis through modulating transcription factor NFATc1 activation. However, the influence and the detailed mechanism of ASIC1a in regulating osteoclast adhesion and migration, in response to extracellular acid, are not well characterized. In this study, knockdown of ASIC1a was achieved in bone marrow macrophage cells using small interfering RNA (siRNA). The adhesion and migration abilities of osteoclast precursors and osteoclasts were determined by adhesion and migration assays, in vitro. Bone resorption was performed to measure osteoclast function. Cytoskeletal changes were assessed by F-actin ring formation. αvβ3 integrin expression in osteoclasts was measured by flow cytometry. Western blotting and co-immunoprecipitation were performed to measure alterations in integrin/Pyk2/Src signaling pathway. Our results showed that blockade of ASIC1a using ASIC1a-siRNA inhibited acid-induced osteoclast precursor migration and adhesion, as well as osteoclast adhesion and bone resorption; we also demonstrated that inhibition of ASIC1a decreased the cell surface αvβ3 integrin and β3 protein expression. Moreover, blocking of ASIC1a inhibited acidosis-induced actin ring formation and reduced Pyk2 and Src phosphorylation in osteoclasts and also inhibited the acid-induced association of the αvβ3 integrin/Src/Pyk2. Together, these results highlight a key functional role of ASIC1a/αvβ3 integrin/Pyk2/Src signaling pathway in migration and adhesion of osteoclasts.

Single Cell Force Spectroscopy for Quantification of Cellular Adhesion on Surfaces

NASA Astrophysics Data System (ADS)

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 quantitative insights.

Influence of biofilm lubricity on shear-induced transmission of staphylococcal biofilms from stainless steel to silicone rubber.

PubMed

Gusnaniar, Niar; Sjollema, Jelmer; Jong, Ed D; Woudstra, Willem; de Vries, Joop; Nuryastuti, Titik; van der Mei, Henny C; Busscher, Henk J

2017-11-01

In real-life situations, bacteria are often transmitted from biofilms growing on donor surfaces to receiver ones. Bacterial transmission is more complex than adhesion, involving bacterial detachment from donor and subsequent adhesion to receiver surfaces. Here, we describe a new device to study shear-induced bacterial transmission from a (stainless steel) pipe to a (silicone rubber) tube and compare transmission of EPS-producing and non-EPS-producing staphylococci. Transmission of an entire biofilm from the donor to the receiver tube did not occur, indicative of cohesive failure in the biofilm rather than of adhesive failure at the donor-biofilm interface. Biofilm was gradually transmitted over an increasing length of receiver tube, occurring mostly to the first 50 cm of the receiver tube. Under high-shearing velocity, transmission of non-EPS-producing bacteria to the second half decreased non-linearly, likely due to rapid thinning of the lowly lubricious biofilm. Oppositely, transmission of EPS-producing strains to the second tube half was not affected by higher shearing velocity due to the high lubricity and stress relaxation of the EPS-rich biofilms, ensuring continued contact with the receiver. The non-linear decrease of ongoing bacterial transmission under high-shearing velocity is new and of relevance in for instance, high-speed food slicers and food packaging. © 2017 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Micro/Nanostructured Films and Adhesives for Biomedical Applications.

PubMed

Lee, Jungkyu K; Kang, Sung Min; Yang, Sung Ho; Cho, Woo Kyung

2015-12-01

The advanced technologies available for micro/nanofabrication have opened new avenues for interdisciplinary approaches to solve the unmet medical needs of regenerative medicine and biomedical devices. This review highlights the recent developments in micro/nanostructured adhesives and films for biomedical applications, including waterproof seals for wounds or surgery sites, drug delivery, sensing human body signals, and optical imaging of human tissues. We describe in detail the fabrication processes required to prepare the adhesives and films, such as tape-based adhesives, nanofilms, and flexible and stretchable film-based electronic devices. We also discuss their biomedical functions, performance in vitro and in vivo, and the future research needed to improve the current systems.

Role of pressure-sensitive adhesives in transdermal drug delivery systems.

PubMed

Lobo, Shabbir; Sachdeva, Sameer; Goswami, Tarun

2016-01-01

Transdermal drug delivery systems (TDDS) are employed for the delivery of drugs across skin into the systemic circulation. Pressure-sensitive adhesive (PSA) is one of the most critical components used in a TDDS. The primary function of PSA is to help in adhesion of patch to skin, but more importantly it acts as a matrix for the drug and other excipients. Hence, apart from adhesion of the patch, PSA also affects other critical quality attributes of the TDDS such as drug delivery, flux through skin and physical and chemical stability of the finished product. This review article provides a summary of the adhesives used in various types of TDDS. In particular, this review will cover the design types of TDDS, categories of PSAs and their evaluation and regulatory aspects.

Mutation of the Conserved Calcium-Binding Motif in Neisseria gonorrhoeae PilC1 Impacts Adhesion but Not Piliation

PubMed Central

Cheng, Yuan; Johnson, Michael D. L.; Burillo-Kirch, Christine; Mocny, Jeffrey C.; Anderson, James E.; Garrett, Christopher K.; Redinbo, Matthew R.

2013-01-01

Neisseria gonorrhoeae PilC1 is a member of the PilC family of type IV pilus-associated adhesins found in Neisseria species and other type IV pilus-producing genera. Previously, a calcium-binding domain was described in the C-terminal domains of PilY1 of Pseudomonas aeruginosa and in PilC1 and PilC2 of Kingella kingae. Genetic analysis of N. gonorrhoeae revealed a similar calcium-binding motif in PilC1. To evaluate the potential significance of this calcium-binding region in N. gonorrhoeae, we produced recombinant full-length PilC1 and a PilC1 C-terminal domain fragment. We show that, while alterations of the calcium-binding motif disrupted the ability of PilC1 to bind calcium, they did not grossly affect the secondary structure of the protein. Furthermore, we demonstrate that both full-length wild-type PilC1 and full-length calcium-binding-deficient PilC1 inhibited gonococcal adherence to cultured human cervical epithelial cells, unlike the truncated PilC1 C-terminal domain. Similar to PilC1 in K. kingae, but in contrast to the calcium-binding mutant of P. aeruginosa PilY1, an equivalent mutation in N. gonorrhoeae PilC1 produced normal amounts of pili. However, the N. gonorrhoeae PilC1 calcium-binding mutant still had partial defects in gonococcal adhesion to ME180 cells and genetic transformation, which are both essential virulence factors in this human pathogen. Thus, we conclude that calcium binding to PilC1 plays a critical role in pilus function in N. gonorrhoeae. PMID:24002068

Effect of in vitro chewing and bruxism events on remineralization, at the resin-dentin interface.

PubMed

Toledano, Manuel; Cabello, Inmaculada; Aguilera, Fátima S; Osorio, Estrella; Osorio, Raquel

2015-01-02

The purpose of this study was to evaluate if different in vitro functional and parafunctional habits promote mineralization at the resin-dentin interface after bonding with three different adhesive approaches. Dentin surfaces were subjected to distinct treatments: demineralization by (1) 37% phosphoric acid (PA) followed by application of an etch-and-rinse dentin adhesive, Single Bond (SB) (PA+SB); (2) 0.5 M ethylenediaminetetraacetic acid (EDTA) followed by SB (EDTA+SB); (3) application of a self-etch dentin adhesive, Clearfil SE Bond (SEB). Different loading waveforms were applied: No cycling (I), cycled in sine (II) or square (III) waves, sustained loading hold for 24 h (IV) or sustained loading hold for 72 h (V). Remineralization at the bonded interfaces was assessed by AFM imaging/nano-indentation, Raman spectroscopy and Masson's trichrome staining. In general, in vitro chewing and parafunctional habits, promoted an increase of nano-mechanical properties at the resin-dentin interface. Raman spectroscopy through cluster analysis demonstrated an augmentation of the mineral-matrix ratio in loaded specimens. Trichrome staining reflected a narrow demineralized dentin matrix after loading in all groups except in PA+SB and EDTA+SB samples after sustained loading hold for 72 h, which exhibited a strong degree of mineralization. In vitro mechanical loading, produced during chewing and bruxism (square or hold 24 and 72 h waveforms), induced remineralization at the resin-dentin bonded interface. Copyright © 2014 Elsevier Ltd. All rights reserved.

Tunable denture adhesives using biomimetic principles for enhanced tissue adhesion in moist environments.

PubMed

Gill, Simrone K; Roohpour, Nima; Topham, Paul D; Tighe, Brian J

2017-11-01

Nature provides many interesting examples of adhesive strategies. Of particular note, the protein glue secreted by marine mussels delivers high adhesion in wet and dynamic environments owing to existence of catechol moieties. As such, this study focuses on denture fixatives, where a non-zinc-containing commercial-based formulation has been judiciously modified by a biomimetic catechol-inspired polymer, poly(3,4-dihydroxystyrene/styrene-alt-maleic acid) in a quest to modulate adhesive performance. In vitro studies, in a lap-shear configuration, revealed that the catechol-modified components were able to enhance adhesion to both the denture base and hydrated, functional oral tissue mimic, with the resulting mode of failure prominently being adhesive rather than cohesive. These characteristics are desirable in prosthodontic fixative applications, for which temporary adhesion must be maintained, with ultimately an adhesive failure from the mucosal tissue surface preferred. These insights provide an experimental platform in the design of future biomimetic adhesive systems. Mussel adhesive proteins have proven to be promising biomimetic adhesive candidates for soft tissues and here for the first time we have adapted marine adhesive technology into a denture fixative application. Importantly, we have incorporated a soft tissue mimic in our in vitro adhesion technique that more closely resembles the oral mucosa than previously studied substrates. The novel biomimetic-modified adhesives showed the ability to score the highest adhesive bonding out of all the formulations included in this study, across all moisture levels. This paper will be of major interest to the Acta Biomaterialia readership since the study has illustrated the potential of biomimetic principles in the design of effective prosthodontic tissue adhesives in a series of purpose-designed in vitro experiments in the context of the challenging features of the oral environment. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.