Literatura académica sobre el tema "Interactions cellules/surfaces"
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Artículos de revistas sobre el tema "Interactions cellules/surfaces"
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Le, Huong, Hoang-Nghi Mai-Thi, Xuan Le, Ngoc Quyen Tran, Cam Tu Tran y Khon Huynh. "The concentration-independence cellular effects of fibronectin adsorbed on material surfaces with different hydrophobicities". Vietnam Journal of Biotechnology 20, n.º 3 (30 de septiembre de 2022): 435–44. http://dx.doi.org/10.15625/1811-4989/16585.
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In tissue engineering, coating biomaterial’s surface with extracellular matrix (ECM) proteins can promote many biological activities, including cellular responses, wound healing, and rejection reduction. Several interactions occur upon binding proteins onto the surfaces, leading to changes in the protein structural conformation, directly affecting the cell-host interactions. Therefore, this study investigates the impacts of surfaces’ wettability on protein conformation. In order to get the insights, organosilicate (OGS) was utilized to modify the tissue culture plate, resulting in surfaces with different wettability, followed by fibronectin (FN) immobilization. Then, the surfaces were used to study the fibrinogen interaction, cell attachment, and spreading. The results showed that OGS-modified surfaces produced four different wettability, ranging from super-hydrophilic (OGS150), hydrophilic (OGS100), hydrophobic (OGS60), to super-hydrophobic (OGS5). Each surface possessed particular nature, resulting in the variation of FN molecules' structural change. The amount of FN adsorbed on the OGS-coated surfaces was shown not to be perfectly proportional to the results of fibrinogen interaction, cell attachment, and spreading. The super-hydrophobic surfaces (OGS5) were highest in the amount of immobilized FN and the efficiency in subsequent experiments among the OGS-coated surfaces group. Notably, the hydrophobic surface adsorbed the lowest amount of FN but achieved remarkable results in the following experiments. Thus, this study holds a promising potential in producing biocompatible materials in tissue engineering.
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Noh, In Sup y Elazer R. Edelman. "Smooth Muscle Cell Ingrowth of a Surface-Modified ePTFE Vascular Graft". Key Engineering Materials 288-289 (junio de 2005): 367–72. http://dx.doi.org/10.4028/www.scientific.net/kem.288-289.367.
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A variety of attempts have been made to improve small diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts through cellular and tissue engineering. Some of these techniques have made their way into clinical trials. Coating of endothelial cells via surface modifications has increased graft patency in some hands but lack of firm adhesion of the seeded cells on the graft surface can lead to graft failures. We increased cell-graft and graft-tissue interactions by inducing smooth muscle cell growth into the pores of the graft wall through chemical modification of superficial surfaces, including those of the transmural pores. In contrast to non-modified surfaces seeded cells adhered on and proliferated into the modified pores and internodal surfaces. Cellular growth into these critical pores spaces seemed to arise from surface modification including defluorination and oxygenation incorporation leading to changes in chemical composition, surface tension, cell-surface interaction and modified surface fibril aggregation.
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Matsuoka, Satoshi, Hideaki Yukawa, Masayuki Inui y Roy H. Doi. "Synergistic Interaction of Clostridium cellulovorans Cellulosomal Cellulases and HbpA". Journal of Bacteriology 189, n.º 20 (10 de agosto de 2007): 7190–94. http://dx.doi.org/10.1128/jb.00842-07.
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ABSTRACT Clostridium cellulovorans, an anaerobic bacterium, produces a small nonenzymatic protein called HbpA, which has a surface layer homology domain and a type I cohesin domain similar to those found in the cellulosomal scaffolding protein CbpA. In this study, we demonstrated that HbpA could bind to cell wall fragments from C. cellulovorans and insoluble polysaccharides and form a complex with cellulosomal cellulases endoglucanase B (EngB) and endoglucanase L (EngL). Synergistic degradative action of the cellulosomal cellulase and HbpA complexes was demonstrated on acid-swollen cellulose, Avicel, and corn fiber. We propose that HbpA functions to bind dockerin-containing cellulosomal enzymes to the cell surface and complements the activity of cellulosomes.
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Vilaró, Pilar, Carina Sampl, Gundula Teichert, Werner Schlemmer, Mathias Hobisch, Michael Weissl, Luis Panizzolo, Fernando Ferreira y Stefan Spirk. "Interactions and Dissociation Constants of Galactomannan Rendered Cellulose Films with Concavalin A by SPR Spectroscopy". Polymers 12, n.º 12 (18 de diciembre de 2020): 3040. http://dx.doi.org/10.3390/polym12123040.
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Interactions of biomolecules at interfaces are important for a variety of physiological processes. Among these, interactions of lectins with monosaccharides have been investigated extensively in the past, while polysaccharide-lectin interactions have scarcely been investigated. Here, we explore the adsorption of galactomannans (GM) extracted from Prosopis affinis on cellulose thin films determined by a combination of multi-parameter surface plasmon resonance spectroscopy (MP-SPR) and atomic force microscopy (AFM). The galactomannan adsorbs spontaneously on the cellulose surfaces forming monolayer type coverage (0.60 ± 0.20 mg·m−2). The interaction of a lectin, Concavalin A (ConA), with these GM rendered cellulose surfaces using MP-SPR has been investigated and the dissociation constant KD (2.1 ± 0.8 × 10−8 M) was determined in a range from 3.4 to 27.3 nM. The experiments revealed that the galactose side chains as well as the mannose reducing end of the GM are weakly interacting with the active sites of the lectins, whereas these interactions are potentially amplified by hydrophobic effects between the non-ionic GM and the lectins, thereby leading to an irreversible adsorption.
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Munro, Thomas, Catherine M. Miller, Elsa Antunes y Dileep Sharma. "Interactions of Osteoprogenitor Cells with a Novel Zirconia Implant Surface". Journal of Functional Biomaterials 11, n.º 3 (16 de julio de 2020): 50. http://dx.doi.org/10.3390/jfb11030050.
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Background: This study compared the in vitro response of a mouse pre-osteoblast cell line on a novel sandblasted zirconia surface with that of titanium. Material and Methods: The MC3T3-E1 subclone 4 osteoblast precursor cell line was cultured on either sandblasted titanium (SBCpTi) or sandblasted zirconia (SBY-TZP). The surface topography was analysed by three-dimensional laser microscopy and scanning electron microscope. The wettability of the discs was also assessed. The cellular response was quantified by assessing the morphology (day 1), proliferation (day 1, 3, 5, 7, 9), viability (day 1, 9), and migration (0, 6, 24 h) assays. Results: The sandblasting surface treatment in both titanium and zirconia increased the surface roughness by rendering a defined surface topography with titanium showing more apparent nano-topography. The wettability of the two surfaces showed no significant difference. The zirconia surface resulted in improved cellular spreading and a significantly increased rate of migration compared to titanium. However, the cellular proliferation and viability noted in our experiments were not significantly different on the zirconia and titanium surfaces. Conclusions: The novel, roughened zirconia surface elicited cellular responses comparable to, or exceeding that, of titanium. Therefore, this novel zirconia surface may be an acceptable substitute for titanium as a dental implant material.
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Meyle, J., H. Wolburg y A. F. Von Recum. "Surface Micromorphology and Cellular Interactions". Journal of Biomaterials Applications 7, n.º 4 (abril de 1993): 362–74. http://dx.doi.org/10.1177/088532829300700404.
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Kunrath, Marcel F., André Correia, Eduardo R. Teixeira, Roberto Hubler y Christer Dahlin. "Superhydrophilic Nanotextured Surfaces for Dental Implants: Influence of Early Saliva Contamination and Wet Storage". Nanomaterials 12, n.º 15 (28 de julio de 2022): 2603. http://dx.doi.org/10.3390/nano12152603.
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Hydrophilic and nanotextured surfaces for dental implants have been reported as relevant properties for early osseointegration. However, these surface characteristics are quite sensitive to oral interactions. Therefore, this pilot study aimed to investigate the superficial alterations caused on hydrophilic nanotubular surfaces after early human saliva interaction. Titanium disks were treated using an anodization protocol followed by reactive plasma application in order to achieve nanotopography and hydrophilicity, additionally; surfaces were stored in normal atmospheric oxygen or wet conditioning. Following, samples were interacted with saliva for 10 min and analyzed regarding physical–chemical properties and cellular viability. Saliva interaction did not show any significant influence on morphological characteristics, roughness measurements and chemical composition; however, hydrophilicity was statistically altered compromising this feature when the samples were stored in common air. Cellular viability tested with pre-osteoblasts cell line (MC3T3-E1) reduced significantly at 48 h on the samples without wet storage after saliva contamination. The applied wet-storage methodology appears to be effective in maintaining properties such as hydrophilicity during saliva interaction. In conclusion, saliva contamination might impair important properties of hydrophilic nanotubular surfaces when not stored in wet conditions, suggesting the need of saliva-controlled sites for oral application of hydrophilic surfaces and/or the use of modified-package methods associated with their wet storage.
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Bucior, Iwona, Simon Scheuring, Andreas Engel y Max M. Burger. "Carbohydrate–carbohydrate interaction provides adhesion force and specificity for cellular recognition". Journal of Cell Biology 165, n.º 4 (17 de mayo de 2004): 529–37. http://dx.doi.org/10.1083/jcb.200309005.
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The adhesion force and specificity in the first experimental evidence for cell–cell recognition in the animal kingdom were assigned to marine sponge cell surface proteoglycans. However, the question whether the specificity resided in a protein or carbohydrate moiety could not yet be resolved. Here, the strength and species specificity of cell–cell recognition could be assigned to a direct carbohydrate–carbohydrate interaction. Atomic force microscopy measurements revealed equally strong adhesion forces between glycan molecules (190–310 piconewtons) as between proteins in antibody–antigen interactions (244 piconewtons). Quantitative measurements of adhesion forces between glycans from identical species versus glycans from different species confirmed the species specificity of the interaction. Glycan-coated beads aggregated according to their species of origin, i.e., the same way as live sponge cells did. Live cells also demonstrated species selective binding to glycans coated on surfaces. These findings confirm for the first time the existence of relatively strong and species-specific recognition between surface glycans, a process that may have significant implications in cellular recognition.
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Banci, Lucia, Ivano Bertini, Vito Calderone, Nunzia Della-Malva, Isabella C. Felli, Sara Neri, Anna Pavelkova y Antonio Rosato. "Copper(I)-mediated protein–protein interactions result from suboptimal interaction surfaces". Biochemical Journal 422, n.º 1 (29 de julio de 2009): 37–42. http://dx.doi.org/10.1042/bj20090422.
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The homoeostasis of metal ions in cells is the result of the contribution of several cellular pathways that involve transient, often weak, protein–protein interactions. Metal transfer typically implies the formation of adducts where the metal itself acts as a bridge between proteins, by co-ordinating residues of both interacting partners. In the present study we address the interaction between the human copper(I)-chaperone HAH1 (human ATX1 homologue) and a metal-binding domain in one of its partners, namely the P-type copper-transporting ATPase, ATP7A (ATPase, Cu+ transporting, α polypeptide). The adduct was structurally characterized in solution, in the presence of copper(I), and through X-ray crystallography, upon replacing copper(I) with cadmium(II). Further insight was obtained through molecular modelling techniques and site-directed mutagenesis. It was found that the interaction involves a relatively small interface (less than 1000 Å2, 1 Å=0.1 nm) with a low fraction of non-polar atoms. These observations provide a possible explanation for the low affinity of the two apoproteins. It appears that electrostatics is important in selecting which domain of the ATPase is able to form detectable amounts of the metal-mediated adduct with HAH1.
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De Wever, Pieter, Rodrigo de Oliveira-Silva, João Marreiros, Rob Ameloot, Dimitrios Sakellariou y Pedro Fardim. "Topochemical Engineering of Cellulose—Carboxymethyl Cellulose Beads: A Low-Field NMR Relaxometry Study". Molecules 26, n.º 1 (22 de diciembre de 2020): 14. http://dx.doi.org/10.3390/molecules26010014.
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The demand for more ecological, highly engineered hydrogel beads is driven by a multitude of applications such as enzyme immobilization, tissue engineering and superabsorbent materials. Despite great interest in hydrogel fabrication and utilization, the interaction of hydrogels with water is not fully understood. In this work, NMR relaxometry experiments were performed to study bead–water interactions, by probing the changes in bead morphology and surface energy resulting from the incorporation of carboxymethyl cellulose (CMC) into a cellulose matrix. The results show that CMC improves the swelling capacity of the beads, from 1.99 to 17.49, for pure cellulose beads and beads prepared with 30% CMC, respectively. Changes in water mobility and interaction energy were evaluated by NMR relaxometry. Our findings indicate a 2-fold effect arising from the CMC incorporation: bead/water interactions were enhanced by the addition of CMC, with minor additions having a greater effect on the surface energy parameter. At the same time, bead swelling was recorded, leading to a reduction in surface-bound water, enhancing water mobility inside the hydrogels. These findings suggest that topochemical engineering by adjusting the carboxymethyl cellulose content allows the tuning of water mobility and porosity in hybrid beads and potentially opens up new areas of application for this biomaterial.
Tesis sobre el tema "Interactions cellules/surfaces"
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Lavenus, Sandrine. "Études des interactions entre cellules souches et surfaces implantaires nanostructurées". Nantes, 2010. https://archive.bu.univ-nantes.fr/pollux/show/show?id=2d0946e5-0bbf-466c-a5b0-5c6e5d88f147.
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Les implants métalliques permettent des réhabilitations prothétiques présentant de fort taux de succès cliniques grâce leurs propriétés de surface. Différentes études ont montré que les propriétés de surfaces telles que la rugosité et la composition chimique modulent l'adhésion et la différenciation cellulaire et par conséquent, l'ostéointégration des implants. L'étude des intéractions entre les cellules et les surfaces implantaires est essentielle pour la compréhension de leur intégration tissulaire. Dans ce contexte, l'objectif de ce travail a été l'étude de l’adhésion et la différenciation de cellules souches mésenchymateuse (CSM) sur des surfaces en titane nanostructurées mimant la chimie de l’implant. Dans un premier temps, nous avons étudié l'adhésion et la différentiation des CSM sur des substrats ayant une composition différente et une rugosité similaire. Puis, des surfaces de titane nanostructurées ont été réalisées et caractérisées. Une évaporation de titane a été réalisée sur des membranes de polycarbonate percées par des pores de 50, 200 ou 400 nm de diamètre. Une méthode d’anodisation a permis d'obtenir une surface en nid d'abeille avec des pores de 30, 50 et 100 nm de diamètre. La dernière étape de ce travail a consisté à étudier les intéractiosn entre CSM et surfaces nanostructurées. L’adhésion et la différenciation ostéoblastique ont été étudiées par immunomarquage, analyse d’image et PCR arrays suivit de Q-PCR. Enfin, l'histomorphométrie après 1 et 3 semaine d'implantation de fil de titane anodisée dans des tibias de rats a permis de caractériser l'ostéointégration des implants et une corrélation avec les résultats obtenu in vitro. La caractérisation des propriétés de surfaces et l'étude biologique des différents types cellulaires sur ces surfaces permettront de mieux appréhender le comportement cellulaire et ces conséquences dans l'ostéointégration des implants en titaneMetal implants allow nowadays prosthetic rehabilitations with high clinical success due to their surface properties. Some studies have shown that surface properties such as roughness, wettability and chemistry changed the adhesion and differentiation of cells, and thereby, the integration of implant in tissues. Understanding of the interactions between cells and implant surfaces is essential in the field of tissue engineering and biomaterials. Attachment, adhesion and spreading of cells establish the first step of interaction between cells and surfaces and, so the quality of this step determined the cell capacity to proliferate and differentiate on implant surface. In this context, the aim of this study was to study the adhesion and differentiation of human mesenchymal stem cells (hMSC) on nanostructured surface. In the first part, the adhesion, proliferation and differentiation of hMSC, osteoblasts and gingival fibroblasts were compared on substrates with similar surface roughness and wettability, but different chemistries. Secondly, nanostructured titanium surface were realized and characterized. Titanium vapor deposition was performed on polycarbonate membranes with pores of 50, 200 or 400 nm of diameter. Anodisation also allowed obtaining a regular surface with pores of 30, 50 and 100 nm of diameter. In the last part of this work, the adhesion and osteoblastic differentiation of hMSC were studied on these nanostructured surfaces. Cell adhesion and differentiation have been investigated using staining, immunostaining, image analysis and gene expression. Finally, histomorphometric analysis of anodized implant after 1 and 3 weeks of implantation in rat tibia allowed the characterization of osteointegration. The characterization of surface properties and biological study of different cell type on nanostructured surface was necessary to understand the behaviour of cells and so, the consequence for the osteointegration
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Baujard-Lamotte, Lucie. "Interactions surfaces-protéines-cellules : Adsorption de la fibronectine sur supports modèles et influence sur le comportement cellulaire". Cergy-Pontoise, 2007. http://biblioweb.u-cergy.fr/theses/07CERG0390.pdf.
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In vivo, le comportement cellulaire dépend des interactions entre les cellules et leur environnement, la matrice extracellulaire (MEC). Classiquement, in vitro, une stratégie visant à améliorer la culture des cellules est de recouvrir le support de culture par une protéine de la MEC capable de favoriser l’adhérence cellulaire, comme la fibronectine. L’objectif de cette thèse est d’analyser la relation surfaces-protéinescellules, et en particulier les propriétés de la fibronectine adsorbée sur des surfaces modèles et leur influence sur le comportement cellulaire. Différents supports modèles (verre, OTS, polystyrène) sont générés et caractérisés. Puis, à partir de concentrations protéiques variées, les cinétiques d’adsorption sont suivies, et la quantité et les changements conformationnels de la fibronectine adsorbée sont déterminés de manière concomitante. Enfin, l’adhérence et la morphologie de deux types cellulaires sont étudiées, dans différentes conditions d’ensemencementIn living tissues, cell behaviors depend on close connections between cells and their environment, the extracellular matrix (ECM). For in vitro cell culture experiments, a classic strategy to improve cell culture is to coat cell culture supports by an ECM protein which is able to promote cell adhesion, like fibronectin. The aim of this thesis is to analyze the surfaces-proteins-cells relationship, and especially the properties of fibronectin adsorbed onto model surfaces and their influence on cell behavior. Different model supports (glass, OTS, polystyrene) are generated and characterized. Then, adsorption kinetics using various protein concentrations are followed, and the amount and the conformational changes of adsorbed fibronectin are concomitantly determined. Finally, cell adhesion and morphology are studied in different cell seeding conditions, and for two cell types
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Baujard-Lamotte, Lucie Pauthe Emmanuel. "Interactions surfaces-protéines-cellules Adsorption de la fibronectine sur supports modèles et influence sur le comportement cellulaire /". [s.l.] : [s.n.], 2009. http://biblioweb.u-cergy.fr/theses/07CERG0390.pdf.
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Stalet, Marion. "Protections antimicrobiennes : combinaison de la fonctionnalisation et de la nano-structuration pour explorer les interactions cellule/surface". Electronic Thesis or Diss., Université Grenoble Alpes, 2024. https://theses.hal.science/tel-04651199.
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Les micro-organismes, omniprésents et résilients, détiennent le titre incontestable d’organismes vivants les plus tenaces de notre planète. Présents sur Terre depuis environ 4 milliards d'années, leurs remarquables mécanismes d'adaptation leur ont permis de coloniser tous les environnements, même les plus extrêmes, et d’y jouer un rôle essentiel. Bien que leur prolifération remarquable et leur capacité de résistance aux antibiotiques soient établies depuis au moins un siècle, la fin de l'ère dorée des antibiotiques dans les années 1960 a ravivé les préoccupations en matière de santé publique. Afin de faire face au développement de cette résistance, de nouvelles solutions technologiques ont été explorées pour limiter la contamination d’environnements et de surfaces sensibles, notamment dans le domaine médical. Parmi elles, la fabrication de surfaces activement anti-microbiennes est particulièrement pertinente. Les approches de fonctionnalisation chimique de surface et de relargage d’agents anti-microbiens ont été extensivement explorées ces dernières années, mais souffrent encore de limites liées à la durabilité de leur activité. Des approches plus récentes dans le développement de matériaux dits « fonctionnels », comme la nano-fabrication de surfaces bio-inspirées, se révèlent également prometteuses et pourraient compléter les approches existantes. Cependant, les mécanismes d'interaction entre les micro-organismes et les matériaux sont complexes et, pour chaque approche, de nombreux paramètres peuvent influencer l'efficacité des surfaces. En outre, le manque de protocoles standards pour caractériser l'ensemble des propriétés anti-microbiennes des surfaces fonctionnelles complique la mise en commun des connaissances et la compréhension des mécanismes. En utilisant la fonctionnalisation chimique de matériaux avec des peptides antimicrobiens et la nano-structuration par électro-dépôt, cette thèse vise à mettre en évidence l'impact de certains paramètres de conception des surfaces et l'importance de les prendre en compte pour concevoir des solutions efficaces. En se basant sur l’étude d’Escherichia coli et Staphylococcus epidermidis, deux souches bactériennes pertinentes pour leur rôle sur la santé humaine et leurs différences morphologiques, un protocole exhaustif de caractérisation microbiologique des propriétés anti-microbiennes de matériaux fonctionnels, accompagné d'algorithmes semi-automatiques accélérant le traitement des données ainsi produites, a été développé. Ce protocole a été appliqué pour évaluer l’efficacité des approches, que ce soit individuellement ou en combinaison. Les résultats obtenus permettent de mieux comprendre l’impact des différents paramètres étudiés et mettent en avant les étapes clés dans la compréhension et l’évaluation des propriétés anti-microbiennesMicroorganisms, ubiquitous and resilient, hold the undisputed title of the most persistent inhabitants of our planet. Present on Earth for approximately 4 billion years, their remarkable adaptive mechanisms have enabled them to colonize all environments, even the most extreme, and to play an essential role in them. Although their outstanding proliferation and antibiotic resistance capabilities have been established for at least a century, the end of the golden age of antibiotics in the 1960s has revived concerns. To address the resurgence of this resistance, new technological solutions have been explored to limit contamination in sensitive environments and surfaces, particularly in the medical field. Among these, the fabrication of actively antimicrobial surfaces is particularly relevant. Approaches involving chemical surface functionalization and the release of antimicrobial agents have been extensively explored in recent years but still suffer from disadvantages related to the durability of their activity. Newer approaches, such as the nanofabrication of bioinspired surfaces, also show promise and could complement existing methods. However, the interaction mechanisms between microorganisms and materials are complex, and for each approach, numerous parameters can influence surface effectiveness. Additionally, the lack of standardized protocols to characterize the full antimicrobial properties of surfaces complicates the sharing of knowledge and understanding of mechanisms. This thesis aims to highlight the impact of specific surface design parameters and the importance of taking them into account to design effective solutions, utilizing chemical functionalization with antimicrobial peptides and nanostructuring through electrodeposition. Drawing on the study of Escherichia coli and Staphylococcus epidermidis, two bacterial strains relevant for their impact on human health and their morphological differences, a comprehensive protocol for microbiological characterization of antimicrobial properties, accompanied by semi-automatic algorithms allowing faster data processing, has been developed. This protocol has been applied to assess the effectiveness of the approaches, whether individually or in combination. The obtained results contribute to a better understanding of the impact of the various studied parameters and emphasize key steps in comprehending and evaluating antimicrobial properties
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Balu, Balamurali. "Plasma processing of cellulose surfaces and their interactions with fluids". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31675.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Breedveld, Victor; Committee Chair: Hess, Dennis; Committee Member: Aidun, Cyrus; Committee Member: Deng, Yulin; Committee Member: Singh, Preet. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Lord, Megan Susan Graduate School of Biomedical Engineering Faculty of Engineering UNSW. "Biomolecular and cellular interactions with surfaces". Awarded by:University of New South Wales. Graduate School of Biomedical Engineering, 2006. http://handle.unsw.edu.au/1959.4/24213.
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The modulation of biological interactions with artificial surfaces is a vital aspect of biomaterials research. Protein adsorption is established as an early biological response to implanted materials that influences biocompatibility, hence an understanding of how to direct specific protein and cellular responses is critical for the development of future biomaterials. The effects of protein adsorption and subsequent cellular interactions on a variety of surfaces are investigated. Acrylic-based hydrogels are used as a model system in which to investigate both tear and serum protein adsorption from simple and complex solutions. The effect of surface topography, created by colloidal silica, on serum protein adsorption and conformation as well as cell adhesion is also investigated. Tantalum (Ta) and oxidised polystyrene (PSox) are investigated for their ability to support cell adhesion when precoated with various serum proteins. Protein interactions are examined using a combination of quartz crystal microbalance with dissipation (QCM-D), surface plasmon resonance (SPR), dual polarisation interferometry (DPI) and enzyme-linked immunosorbent assay (ELISA) while cellular interactions are analysed using QCM-D, microscopy and adhesion assays. The QCM-D technique was evaluated for its ability to provide new insight into cell-surface interactions. Most tear and serum proteins were found to adsorb onto the acrylic hydrogels, however, lysozyme was found to absorb into the hydrogel matrix and decrease the hydration, which may lead to an adverse biological response. Fibronectin adsorbed onto nanotextured colloidal silica surfaces was found to be conformationally changed compared to flat controls which is likely to correlate with the reduced endothelial cell adhesion observed on these textured surfaces. Ta and PSox precoated with either serum or fibronectin were shown to support cell adhesion and spreading, while surfaces precoated with albumin were not. QCM-D responses varied between underlying surfaces, protein precoating, ECM deposition, cytoskeletal activity and length of exposure indicating that alterations in cell-material responses are reflected in QCM-D measurements. QCM-D parameters were found to correlate with adhered cell numbers, cell contact area and cytoskeletal activity. The results highlight that characterisation of interfacial interactions with a wide range of analytical techniques is necessary to gain insight into cell-protein-material interactions which can then be utilised in the development of new generations of biomaterials with improved properties designed for specific applications.
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Stiernstedt, Johanna. "Interactions of cellulose and model surfaces". Doctoral thesis, Stockholm : Chemical Science and Engineering, KTH, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-619.
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Frazier, Richard Andrew. "Macromolecular interactions at polysaccharide surfaces". Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336946.
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Poptoshev, Evgeni. "Polyelectrolyte Moderated Interactions between Glass and Cellulose Surfaces". Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3247.
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Tze, William tai-Yin. "Effects of Fiberimatiux Interactions on the Interfacial Deformation Micromechanics of Cellulose-Fiberipolymer Composites". Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/TzeWT2003.pdf.
Texto completoLibros sobre el tema "Interactions cellules/surfaces"
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Cold Spring Harbor Symposia on Quantitative Biology (57th 1992). The cell surface. Plainview, N.Y: Cold Spring Harbor Laboratory Press, 1992.
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NATO, Advanced Research Workshop on the Cell Surface in Signal Transduction (1986 Besançon France). The cell surface in signal transduction. Berlin: Springer-Verlag, 1987.
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Laboratory, Cold Spring Harbor, ed. The Cell surface. Cold Spring Harbor, N.Y: Cold Spring Harbor Laboratory, 1992.
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R, George Susan y O'Dowd Brian Francis 1950-, eds. G protein-coupled receptor-protein interactions. Hoboken, N.J: Wiley-Liss, 2005.
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1945-, Fukuda Minoru, ed. Cell surface carbohydrates and cell development. Boca Raton: CRC Press, 1992.
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1954-, Parker Peter J. y Pawson T, eds. Cell signalling. Plainview, NY: Cold Spring Harbor Laboratory Press, 1996.
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Uehara Memorial Foundation Symposium on the Innate Immune System (2005 Tokyo, Japan). The innate immune system: Strategies for disease control : proceedings of the Uehara Memorial Foundation Symposium on the Innate Immune System ..., held in Tokyo, Japan between 11 and 13 July 2005. Editado por Taniguchi Masaru, Akira S y Nakayama Toshinori. Boston: Elsevier, 2005.
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1935-, Baszkin Adam y Norde Willem 1944-, eds. Physical chemistry of biological interfaces. New York: M. Dekker, 2000.
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Garrod, D. R. y C. M. Chadwick. Hormones, Receptors and Cellular Interactions in Plants. Cambridge University Press, 2009.
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Wagner, E. The Cell Surface in Signal Transduction. Springer, 2011.
Buscar texto completoCapítulos de libros sobre el tema "Interactions cellules/surfaces"
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Bauer, Robert y Franz Oberwinkler. "Cellular Ustilaginomycete–Plant Interactions". En Plant Surface Microbiology, 227–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-74051-3_14.
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Bauer, Robert y Franz Oberwinkler. "Cellular Basidiomycete–Fungus Interactions". En Plant Surface Microbiology, 267–79. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-74051-3_16.
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Lawford, Patricia. "Cellular Interactions in Extracorporeal Circuitry". En Interaction of Cells with Natural and Foreign Surfaces, 111–23. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4613-2229-0_10.
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Williams, D. F. "Cellular Interactions with Dental Materials". En Interaction of Cells with Natural and Foreign Surfaces, 293–301. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4613-2229-0_30.
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Capperauld, Ian. "Cellular Responses to Sutures". En Interaction of Cells with Natural and Foreign Surfaces, 243–57. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4613-2229-0_25.
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Rae, Trevor. "Cellular Aspects of Biotolerance". En Interaction of Cells with Natural and Foreign Surfaces, 71–81. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4613-2229-0_7.
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Preissner, Klaus T. y G. Singh Chhatwal. "Extracellular Matrix and Host Cell Surfaces: Potential Sites of Pathogen Interaction". En Cellular Microbiology, 87–104. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555817633.ch4.
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Etges, Robert, Jacques Bouvier y Clement Bordier. "The Promastigote Surface Protease of Leishmania". En Host-Parasite Cellular and Molecular Interactions in Protozoal Infections, 165–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-72840-2_18.
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Snary, David, Michael A. J. Ferguson, Anthony K. Allen, Michael A. Miles y Alan Sher. "Cell Surface Glycoproteins of Trypanosoma Cruzi". En Host-Parasite Cellular and Molecular Interactions in Protozoal Infections, 79–87. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-72840-2_9.
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Green, Kathleen J. y Jonathan C. R. Jones. "Interaction of Intermediate Filaments with the Cell Surface". En Cellular and Molecular Biology of Intermediate Filaments, 147–71. Boston, MA: Springer US, 1990. http://dx.doi.org/10.1007/978-1-4757-9604-9_6.
Texto completoActas de conferencias sobre el tema "Interactions cellules/surfaces"
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Forsström, Jennie, Malin Eriksson y Lars Wågberg. "Molecular Interactions between Model Cellulose Surfaces and Ink – Influence of Surface Energy and Surface Structure on Adhesion". En Advances in Paper Science and Technology, editado por S. J. I’Anson. Fundamental Research Committee (FRC), Manchester, 2005. http://dx.doi.org/10.15376/frc.2005.2.1379.
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The influence of surface roughness and surface hydrophobicity on ink detachment of water-based flexographic ink was studied. It was shown that increased surface roughness and an increased surface hydrophobicity both had a negative effect on ink detachment. The increased surface roughness was suggested to increase the molecular contact area between ink and cellulose and thereby also to decrease ink detachment. Ink cellulose interaction was evaluated from interfacial energies and contact angle measurements. A new technique in which the adhesion properties between ink and the model cellulose surface were directly measured using a Micro Adhesion Measurement Apparatus (MAMA) was also used. Upon increasing the hydrophobicity of the model cellulose surface it was shown that the work of adhesion between ink and model cellulose surfaces decreased. At the same time the interfacial energy between cellulose and ink increased, as did the interfacial energy between cellulose and water resulting in a lower degree of ink detachment.
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Neuman, Ronald D. "Surface Force Measurement in Papermaking Systems". En Products of Papermaking, editado por C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1993. http://dx.doi.org/10.15376/frc.1993.2.969.
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The surface force technique, whereby the forces acting between two solid surfaces immersed in liquids or in adhesive contact are directly measured, represents a novel approach for both fundamental and application-oriented studies of the surface and colloid science of papermaking. The nature and measurement of surface forces are briefly discussed, and some results reported for mica surfaces are reviewed in order to illustrate the surface chemical information obtainable using a conventional Israelachvili-type surface force apparatus. In the case of cellulose surfaces immersed in water and aqueous electrolyte solutions the measured force vs. distance profile is characterized by three regimes. Significantly, conventional DLVO theory cannot explain the interaction forces measured between cellulose surfaces. Electrostatic double-layer forces, as anticipated, dominate the long-range interactions. However, as the two cellulose surfaces begin to “contact” each other, there is an interplay of steric and electrostatic forces due to dangling tails of cellulose chains. The observed force curves, therefore, are interpreted in terms of a new model — the “dangling tail” model — of the cellulose surface, namely, the water-swollen cellulose surface has long and weakly charged cellulose chains or “molecularfibrils” which extend into the aqueous solution. In addition, the application of the surface force technique to basic problems in the adsorption of polymers, both cationic polyelectrolytes and hemicelluloses, and the colloidal stability of kaolin suspensions is illustrated. The advantages of using a new type of surface force apparatus in future studies of surface and physicochemical phenomena relevant to paper manufacturing, coating and recycling are also briefly discussed.
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Notley, Shannon M. y Lars Wågberg. "Direct Measurement of Attractive van der Waals Forces and Repulsive Electrostatic Forces between Regenerated Cellulose Surfaces in an Aqueous Environment". En Advances in Paper Science and Technology, editado por S. J. I’Anson. Fundamental Research Committee (FRC), Manchester, 2005. http://dx.doi.org/10.15376/frc.2005.2.1337.
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Using the colloidal probe technique, the interaction between carboxymethylated cellulose films and a cellulose sphere was studied. At low pH (pH 3.5), the interaction was dominated by dispersion forces. This was due to the low dissociation of carboxyl groups within the film at pH 3.5. However, at pH greater than 5, the interaction was dominated by an electrostatic repulsion. The increase in pH had the two-fold effect of completely dissociating the charged groups as well as causing appreciable swelling of the film leading to a decrease in the van der Waals component of the interaction. From these results it can be concluded that these cellulose films are suitable for a range of surface forces measurements including electrostatic, van der Waals’, steric and adhesion forces. Furthermore, the measurement of forces using the colloidal probe technique can be extended to inorganic particles as well as for interactions between surfaces in the presence of for example wet and dry strength agents and other materials relevant to the paper-making industry.
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Wagberg, Lars. "Invited Perspective: Fundamentals of Interactions Between Cellulose-Rich Surfaces". En Advances in Pulp and Paper Research. Pulp & Paper Fundamental Research Committee (FRC), Manchester, 2022. http://dx.doi.org/10.15376/frc.2022.1.87.
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The molecular mechanisms behind the interactions between fibres in fibrous networks, and their link to paper/network strength, have long been under intense scientific investigations and scientific debate (Wågberg and Annergren 1997, Lindström et al. 2005; Hirn and Schennach 2017) but still there is no unified view on how the strength of fibre/fibre joints and network strength can be linked to different molecular mechanisms (Wohlert et al. 2022). Historically the interaction between cellulose-rich fibre surfaces was ascribed to hydrogen bonding and elaborate models were developed for linking mechanical properties of fibrous networks to the H-bonding between the surfaces (Nissan and Batten Jr 1997). This is however an oversimplification for several reasons. First of all, the H-bonds are very specific, which means that they are short-ranged and not implicitly additive over the material volumes engaged in the contact region between the fibres. Secondly the molecular interactions in the fibre/fibre contact zones are actively participating in the formation of the fibre joints, i.e. in the making of the fibre/fibre joints. The interactions in the wet state will hence affect the dimensions of the wet and dry contact zones and they will also create built-in stresses in the zones of contact in the dried fibre/fibre joint. The dry mechanical properties of the fibrous networks, i.e. the breaking of the joints and the fibres, will then be controlled by the molecular contact zone, the interactions in the contact zone, and also outside the molecular contact zone but within the molecular interactions range, the number of molecular contacts/network volume and the individual fibre strength.
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Ketola, Annika, Tuomo Hjelt, Timo Lappalainen, Heikki Pajari, Tekla Tammelin, Kristian Salminen, Koon-Yang Lee, Orlando Rojas y Jukka A. Ketoja. "The Relation Between Bubble-Fibre Interaction and Material Properties in Foam Forming". En Advances in Pulp and Paper Research. Pulp & Paper Fundamental Research Committee (FRC), Manchester, 2022. http://dx.doi.org/10.15376/frc.2022.1.65.
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Foam forming of cellulose fibre materials is based on an interaction between fibres and bubbles, which can take several material properties to new levels. To control the formed structure, the mechanisms of this interaction have been systematically investigated. This started with captive bubble studies where we analysed the interaction of a single bubble with various smooth cellulose and silica model surfaces. The bubbles adhered only to hydrophobic surfaces, and this attraction was sensitive to the surface tension. From this simplest case, the studied system gradually became more complex. We found that a bubble adheres weakly also to a submerged cellulose nanofibre (CNF) film, which could be explained by nanoscale surface roughness capturing nanobubbles. The interaction with real fibres was studied by pressing a single bubble against a fibre bed in water and sodium dodecyl sulphate (SDS) solution. Fibre type and surface tension had all apparent effects on the attachment. In the case of natural fibres, the presence of hydrophobic lignin clearly increased the fibre attachment on a bubble, while added SDS decreased the attachment with all fibre types. These findings agreed with the mechanisms found earlier using the model surfaces. Finally, when forming thick nonwoven materials using hydrophilic and hydrophobic viscose fibres, differences in fibre network structure and strength properties depended on the fibre hydrophobicity and surfactant type, as suggested by the results obtained in simpler systems.
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Eberhart, Robert C. "Reflections on Quantitative Gamma Imaging of Cell-Surface Interactions". En ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53388.
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Molecular and cellular interactions with foreign surfaces can be noninvasively measured by isotope imaging techniques. Long available for probing cell behavior, these techniques are now employed in molecular studies of disease progression, such as Alzheimer’s [1]. This paper reviews results obtained by noninvasive dual label gamma scintigraphy for the transient adhesion of platelets and neutrophils to pump-oxygenators during cardiopulmonary bypass (CPB). In this application, characteristic cell-foreign surface adhesion and release patterns are observed during CPB in the pig, as a function of oxygenator design and surface chemistry. Cell distributions in internal organs post-CPB are also affected by these processes. This method can be adapted to other settings where the understanding of protein-cell interactions with native and foreign surfaces is at issue, including fibrinogen-cell interactions, bacterial colonization, etc.
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Lindström, Tom. "Some Fundamental Chemical Aspects on Paper Forming". En Fundamentals of Papermaking, editado por C. F. Baker y V. Punton. Fundamental Research Committee (FRC), Manchester, 1989. http://dx.doi.org/10.15376/frc.1989.1.311.
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The fundamental physico-chemical aspects of retention chemistry are reviewed in the light of basic concepts in colloid chemistry. Special emphasis has been paid to the surface chemistry of cellulose and cellulosic materials, their origin of charge, dispersion force interactions as well as the implication of certain aspects of peculiar cellulosic surfaces, e.g. the influence of their porosity on polymer adsorption. Charge neutralization, patch flocculation, heterocoagulation, bridging and complex flocculation phenomena are discussed as well as polymer adsorption phenomena at the cellulose/water interface
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Tien, Joe, John L. Tan, Celeste M. Nelson y Christopher S. Chen. "Building Cellular Microenvironments to Control Capillary Endothelial Cell Proliferation, Death, and Differentiation". En ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/bed-23154.
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Abstract The dynamic binding interactions between cell surface receptors and local bioactive ligands serves as the principal mechanism by which cells survey their microenvironment and accordingly modulate their behaviors, such as proliferation, differentiation, migration, and suicide. Using conventional and non-conventional microfabrication approaches to engineer well-defined cellular microenvironments, we are examining how cells recognize and respond to adhesive interactions with the insoluble extracellular matrix (ECM). We will discuss our approaches to control the architecture and geometry of the adhesive interactions, as well as our resulting progress in identifying and elucidating the mechanisms by which cells sense the physical, chemical, and structural information carried within the ECM. By developing these approaches to engineering cell-surface interactions, we hope to improve the interconnect between artificial surfaces and living cells.
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"Effect of Surface Treated Biopolymer on Curing Behavior and Tensile Properties of Natural Rubber Composites". En Polymers/Composites/3Bs Materials 2023 International Joint Conference. SETCOR Conferences and Events, 2024. http://dx.doi.org/10.26799/cp-polymers-composites-3bsmaterials-2023/1.
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The growing demand for environmentally friendly materials has prompted several researchers to explore naturally occurring biopolymers for potential applications in a variety of fields. Cellulose is a biopolymer formed by the repeated joining of D-glucose building blocks and is characterized by its hydrophilicity, broad chemical modification capacity, biodegradability, and the formation of versatile morphologies of semicrystalline fibers; However, the interactions between the cellulose and the polymer matrix are limited due to the fact that the cellulose is hydrophilic while the matrix is hydrophobic. The surfaces are thus not sufficiently compatible, leading to a reduction in mechanical properties. In this study, cellulose was surface treated with two types of silanes. Modified cellulose was used as filler in natural rubber composites. The influence of treated and untreated cellulose on the curing characteristics, rheological properties, mechanical properties and crosslinking density of natural rubber composites was examined. The curing characteristics of the natural rubber composites, the scorch time and cure times, decreased for natural rubber composites filled with modified cellulose compared with natural rubber composite filled with unmodified cellulose. The measured values of tensile strength and crosslinking density showed higher values for natural rubber composites filled with modified cellulose compared with natural rubber composite filled with unmodified cellulose.
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Lundqvist, Asa y Lars Ödberg. "Surface Energy Characterization of Surface Modified Cellulosic Fibres by Inverse Gas Chromatography (IGC)". En The Fundamentals of Papermaking Materials, editado por C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1997. http://dx.doi.org/10.15376/frc.1997.2.751.
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In the present study, the surface properties of cellulosic fibres have been systematically varied and the dispersive and acid-base properties have been determined by inverse gas chromatography (IGC) at infinite dilution. Bleached kraft pulp fibres were carboxy methylated to different degrees. The results from the IGC measurements on the carboxymethylated fibres showed a linear relationship between the interaction energy with a basic probe (acidic properties) and the carboxylic acid group content. The extrapolation to zero degree of substitution ofcarboxylic acid groups indicates that,even in the absence of carboxylic groups, the fibres have acidic properties. The hydroxyl groups on the fibres obviously also contribute to the acidic properties. The interaction energy with an acidic probe (basic properties) was relatively constant with increasing carboxylic acid group content. An increase in the degree of carboxymethylation also seemed to slightly increase the dispersive part of the surface free energy. This could be a consequence of an increase in electron density, a more compact structure after drying the carboxymethylated fibres or removal of low molecular weight impurities. The dispersive as well as the acid-base properties are approximately the same for pulps in both their proton and sodium forms. The carboxymethylated fibres were peeled after the modification. The carboxylic group contents of the fibres and of the removed outer layers were determined by conductometric titration. The results showed that the carboxymethylation procedure is somewhat more effective in the outer layers of the fibres. IGC results for the peeled fibres pointed in the same direction. Diethylaminoethyl{DEAF}cellulose, which has a basic functional group was also characterised. The IGC results showed that the DEAE cellulose interacts more strongly with the acidic probe than the reference cellulose material.
Informes sobre el tema "Interactions cellules/surfaces"
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Barnes, Eftihia, Jennifer Jefcoat, Erik Alberts, Hannah Peel, L. Mimum, J, Buchanan, Xin Guan et al. Synthesis and characterization of biological nanomaterial/poly(vinylidene fluoride) composites. Engineer Research and Development Center (U.S.), septiembre de 2021. http://dx.doi.org/10.21079/11681/42132.
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The properties of composite materials are strongly influenced by both the physical and chemical properties of their individual constituents, as well as the interactions between them. For nanocomposites, the incorporation of nano-sized dopants inside a host material matrix can lead to significant improvements in mechanical strength, toughness, thermal or electrical conductivity, etc. In this work, the effect of cellulose nanofibrils on the structure and mechanical properties of cellulose nanofibril poly(vinylidene fluoride) (PVDF) composite films was investigated. Cellulose is one of the most abundant organic polymers with superior mechanical properties and readily functionalized surfaces. Under the current processing conditions, cellulose nanofibrils, as-received and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized, alter the crystallinity and mechanical properties of the composite films while not inducing a crystalline phase transformation on the 𝛾 phase PVDF composites. Composite films obtained from hydrated cellulose nanofibrils remain in a majority 𝛾 phase, but also exhibit a small, yet detectable fraction of 𝛼 and ß PVDF phases.
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Eldar, Avigdor y Donald L. Evans. Streptococcus iniae Infections in Trout and Tilapia: Host-Pathogen Interactions, the Immune Response Toward the Pathogen and Vaccine Formulation. United States Department of Agriculture, diciembre de 2000. http://dx.doi.org/10.32747/2000.7575286.bard.
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In Israel and in the U.S., Streptococcus iniae is responsible for considerable losses in various fish species. Poor understanding of its virulence factors and limited know-how-to of vaccine formulation and administration are the main reasons for the limited efficacy of vaccines. Our strategy was that in order to Improve control measures, both aspects should be equally addressed. Our proposal included the following objectives: (i) construction of host-pathogen interaction models; (ii) characterization of virulence factors and immunodominant antigens, with assessment of their relative importance in terms of protection and (iii) genetic identification of virulence factors and genes, with evaluation of the protective effect of recombinant proteins. We have shown that two different serotypes are involved. Their capsular polysaccharides (CPS) were characterized, and proved to play an important role in immune evasion and in other consequences of the infection. This is an innovative finding in fish bacteriology and resembles what, in other fields, has become apparent in the recent years: S. iniae alters surface antigens. By so doing, the pathogen escapes immune destruction. Immunological assays (agar-gel immunodiffusion and antibody titers) confirmed that only limited cross recognition between the two types occurs and that capsular polysaccharides are immunodominant. Vaccination with purified CPS (as an acellular vaccine) results in protection. In vitro and ex-vivo models have allowed us to unravel additional insights of the host-pathogen interactions. S. iniae 173 (type II) produced DNA fragmentation of TMB-8 cells characteristic of cellular necrosis; the same isolate also prevented the development of apoptosis in NCC. This was determined by finding reduced expression of phosphotidylserine (PS) on the outer membrane leaflet of NCC. NCC treated with this isolate had very high levels of cellular necrosis compared to all other isolates. This cellular pathology was confirmed by observing reduced DNA laddering in these same treated cells. Transmission EM also showed characteristic necrotic cellular changes in treated cells. To determine if the (in vitro) PCD/apoptosis protective effects of #173 correlated with any in vivo activity, tilapia were injected IV with #173 and #164 (an Israeli type I strain). Following injection, purified NCC were tested (in vitro) for cytotoxicity against HL-60 target cells. Four significant observations were made : (i) fish injected with #173 had 100-400% increased cytotoxicity compared to #164 (ii) in vivo activation occurred within 5 minutes of injection; (iii) activation occurred only within the peripheral blood compartment; and (iv) the isolate that protected NCC from apoptosis in vitro caused in vivo activation of cytotoxicity. The levels of in vivo cytotoxicity responses are associated with certain pathogens (pathogen associated molecular patterns/PAMP) and with the tissue of origin of NCC. NCC from different tissue (i.e. PBL, anterior kidney, spleen) exist in different states of differentiation. Random amplified polymorphic DNA (RAPD) analysis revealed the "adaptation" of the bacterium to the vaccinated environment, suggesting a "Darwinian-like" evolution of any bacterium. Due to the selective pressure which has occurred in the vaccinated environment, type II strains, able to evade the protective response elicited by the vaccine, have evolved from type I strains. The increased virulence through the appropriation of a novel antigenic composition conforms with pathogenic mechanisms described for other streptococci. Vaccine efficacy was improved: water-in-oil formulations were found effective in inducing protection that lasted for a period of (at least) 6 months. Protection was evaluated by functional tests - the protective effect, and immunological parameters - elicitation of T- and B-cells proliferation. Vaccinated fish were found to be resistant to the disease for (at least) six months; protection was accompanied by activation of the cellular and the humoral branches.
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Droby, Samir, Michael Wisniewski, Ron Porat y Dumitru Macarisin. Role of Reactive Oxygen Species (ROS) in Tritrophic Interactions in Postharvest Biocontrol Systems. United States Department of Agriculture, diciembre de 2012. http://dx.doi.org/10.32747/2012.7594390.bard.
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To elucidate the role of ROS in the tri-trophic interactions in postharvest biocontrol systems a detailed molecular and biochemical investigation was undertaken. The application of the yeast biocontrol agent Metschnikowia fructicola, microarray analysis was performed on grapefruit surface wounds using an Affymetrix Citrus GeneChip. the data indicated that 1007 putative unigenes showed significant expression changes following wounding and yeast application relative to wounded controls. The expression of the genes encoding Respiratory burst oxidase (Rbo), mitogen-activated protein kinase (MAPK) and mitogen-activated protein kinase kinase (MAPKK), G-proteins, chitinase (CHI), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) and 4-coumarate-CoA ligase (4CL). In contrast, three genes, peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), were down-regulated in grapefruit peel tissue treated with yeast cells. The yeast antagonists, Metschnikowia fructicola (strain 277) and Candida oleophila (strain 182) generate relatively high levels of super oxide anion (O2−) following its interaction with wounded fruit surface. Using laser scanning confocal microscopy we observed that the application of M. fructicola and C. oleophila into citrus and apple fruit wounds correlated with an increase in H2O2 accumulation in host tissue. The present data, together with our earlier discovery of the importance of H₂O₂ production in the defense response of citrus flavedo to postharvest pathogens, indicate that the yeast-induced oxidative response in fruit exocarp may be associated with the ability of specific yeast species to serve as biocontrol agents for the management of postharvest diseases. Effect of ROS on yeast cells was also studied. Pretreatment of the yeast, Candida oleophila, with 5 mM H₂O₂ for 30 min (sublethal) increased yeast tolerance to subsequent lethal levels of oxidative stress (50 mM H₂O₂), high temperature (40 °C), and low pH (pH 4). Suppression subtractive hybridization analysis was used to identify genes expressed in yeast in response to sublethal oxidative stress. Transcript levels were confirmed using semi quantitative reverse transcription-PCR. Seven antioxidant genes were up regulated. Pretreatment of the yeast antagonist Candida oleophila with glycine betaine (GB) increases oxidative stress tolerance in the microenvironment of apple wounds. ROS production is greater when yeast antagonists used as biocontrol agents are applied in the wounds. Compared to untreated control yeast cells, GB-treated cells recovered from the oxidative stress environment of apple wounds exhibited less accumulation of ROS and lower levels of oxidative damage to cellular proteins and lipids. Additionally, GB-treated yeast exhibited greater biocontrol activity against Penicillium expansum and Botrytis cinerea, and faster growth in wounds of apple fruits compared to untreated yeast. The expression of major antioxidant genes, including peroxisomal catalase, peroxiredoxin TSA1, and glutathione peroxidase was elevated in the yeast by GB treatment. A mild heat shock (HS) pretreatment (30 min at 40 1C) improved the tolerance of M. fructicola to subsequent high temperature (45 1C, 20–30 min) and oxidative stress (0.4 mol-¹) hydrogen peroxide, 20–60 min). HS-treated yeast cells showed less accumulation of reactive oxygen species (ROS) than non-treated cells in response to both stresses. Additionally, HS-treated yeast exhibited significantly greater (P≥0.0001) biocontrol activity against Penicillium expansum and a significantly faster (Po0.0001) growth rate in wounds of apple fruits stored at 25 1C compared with the performance of untreated yeast cells. Transcription of a trehalose-6-phosphate synthase gene (TPS1) was up regulated in response to HS and trehalose content also increased.
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Sharon, Amir y Maor Bar-Peled. Identification of new glycan metabolic pathways in the fungal pathogen Botrytis cinerea and their role in fungus-plant interactions. United States Department of Agriculture, 2012. http://dx.doi.org/10.32747/2012.7597916.bard.
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The involvement of glycans in microbial adherence, recognition and signaling is often a critical determinant of pathogenesis. Although the major glycan components of fungal cell walls have been identified there is limited information available on its ‘minor sugar components’ and how these change during different stages of fungal development. Our aim was to define the role of Rhacontaining-glycans in the gray mold disease caused by the necrotrophic fungus B. cinerea. The research was built on the discovery of two genes, Bcdhand bcer, that are involved in formation of UDP-KDG and UDP-Rha, two UDP- sugars that may serve as donors for the synthesis of cell surface glycans. Objectives of the proposed research included: 1) To determine the function of B. cinereaBcDh and BcEr in glycan biosynthesis and in pathogenesis, 2) To determine the expression pattern of BcDH and BcERand cellular localization of their encoded proteins, 3) Characterize the structure and distribution of Rha- containing glycans, 4) Characterization of the UDP-sugar enzymes and potential of GTs involved in glycanrhamnosylation. To address these objectives we generated a series of B. cinereamutants with modifications in the bchdhand bcergenes and the phenotype and sugar metabolism in the resulting strains were characterized. Analysis of sugar metabolites showed that changes in the genes caused changes in primary and secondary sugars, including abolishment of rhamnose, however abolishment of rhamnose synthesis did not cause changes in the fungal phenotype. In contrast, we found that deletion of the second gene, bcer, leads to accumulation of the intermediate sugar – UDP- KDG, and that such mutants suffer from a range of defects including reduced virulence. Further analyses confirmed that UDP-KDG is toxic to the fungus. Studies on mode of action suggested that UDP-KDG might affect integrity of the fungal cell wall, possibly by inhibiting UDP-sugars metabolic enzymes. Our results confirm that bcdhand bcerrepresent a single pathway of rhamnose synthesis in B. cinerea, that rhamnose does not affect in vitro development or virulence of the fungus. We also concluded that UDP-KDG is toxic to B. cinereaand hence UDP-KDG or compounds that inhibit Er enzymes and lead to accumulation of UDP-KDG might have antifungal activity. This toxicity is likely the case with other fungi, this became apparent in a collaborative work with Prof. Bart Thomma of Wageningen University, NETHERLANDS . We have shown the deletion of ER mutant in Verticillium dahlia gave plants resistance to the fungal infection.
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Morrison, Mark, Joshuah Miron, Edward A. Bayer y Raphael Lamed. Molecular Analysis of Cellulosome Organization in Ruminococcus Albus and Fibrobacter Intestinalis for Optimization of Fiber Digestibility in Ruminants. United States Department of Agriculture, marzo de 2004. http://dx.doi.org/10.32747/2004.7586475.bard.
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Improving plant cell wall (fiber) degradation remains one of the highest priority research goals for all ruminant enterprises dependent on forages, hay, silage, or other fibrous byproducts as energy sources, because it governs the provision of energy-yielding nutrients to the host animal. Although the predominant species of microbes responsible for ruminal fiber degradation are culturable, the enzymology and genetics underpinning the process are poorly defined. In that context, there were two broad objectives for this proposal. The first objective was to identify the key cellulosomal components in Ruminococcus albus and to characterize their structural features as well as regulation of their expression, in response to polysaccharides and (or) P AA/PPA. The second objective was to evaluate the similarities in the structure and architecture of cellulosomal components between R. albus and other ruminal and non-ruminal cellulolytic bacteria. The cooperation among the investigators resulted in the identification of two glycoside hydrolases rate-limiting to cellulose degradation by Ruminococcus albus (Cel48A and CeI9B) and our demonstration that these enzymes possess a novel modular architecture specific to this bacterium (Devillard et al. 2004). We have now shown that the novel X-domains in Cel48A and Cel9B represent a new type of carbohydrate binding module, and the enzymes are not part of a ceiluiosome-like complex (CBM37, Xu et al. 2004). Both Cel48A and Cel9B are conditionally expressed in response to P AA/PPA, explaining why cellulose degradation in this bacterium is affected by the availability of these compounds, but additional studies have shown for the first time that neither PAA nor PPA influence xylan degradation by R. albus (Reveneau et al. 2003). Additionally, the R. albus genome sequencing project, led by the PI. Morrison, has supported our identification of many dockerin containing proteins. However, the identification of gene(s) encoding a scaffoldin has been more elusive, and recombinant proteins encoding candidate cohesin modules are now being used in Israel to verify the existence of dockerin-cohesin interactions and cellulosome production by R. albus. The Israeli partners have also conducted virtually all of the studies specific to the second Objective of the proposal. Comparative blotting studies have been conducted using specific antibodies prepare against purified recombinant cohesins and X-domains, derived from cellulosomal scaffoldins of R. flavefaciens 17, a Clostridium thermocellum mutant-preabsorbed antibody preparation, or against CbpC (fimbrial protein) of R. albus 8. The data also suggest that additional cellulolytic bacteria including Fibrobacter succinogenes S85, F. intestinalis DR7 and Butyrivibrio fibrisolvens Dl may also employ cellulosomal modules similar to those of R. flavefaciens 17. Collectively, our work during the grant period has shown that R. albus and other ruminal bacteria employ several novel mechanisms for their adhesion to plant surfaces, and produce both cellulosomal and non-cellulosomal forms of glycoside hydrolases underpinning plant fiber degradation. These improvements in our mechanistic understanding of bacterial adhesion and enzyme regulation now offers the potential to: i) optimize ruminal and hindgut conditions by dietary additives to maximize fiber degradation (e.g. by the addition of select enzymes or PAA/PPA); ii) identify plant-borne influences on adhesion and fiber-degradation, which might be overcome (or improved) by conventional breeding or transgenic plant technologies and; iii) engineer or select microbes with improved adhesion capabilities, cellulosome assembly and fiber degradation. The potential benefits associated with this research proposal are likely to be realized in the medium term (5-10 years).