Gotowe bibliografie tematyczne / Interactions cellules/surfaces / Rozprawy doktorskie

Rozprawy doktorskie na temat „Interactions cellules/surfaces”

Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: Interactions cellules/surfaces.
Autor: Grafiati
Data publikacji: 20 lipca 2024

Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych

Wybierz rodzaj źródła:

Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „Interactions cellules/surfaces”.

Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.

Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.

Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.

1

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.

Pełny tekst źródła
Streszczenie:
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 titane
Metal 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
Style APA, Harvard, Vancouver, ISO itp.
2

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.

Pełny tekst źródła
Streszczenie:
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’ensemencement
In 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
Style APA, Harvard, Vancouver, ISO itp.
3

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.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
4

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.

Pełny tekst źródła
Streszczenie:
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-microbiennes
Microorganisms, 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
Style APA, Harvard, Vancouver, ISO itp.
5

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.

Pełny tekst źródła
Streszczenie:
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.
Style APA, Harvard, Vancouver, ISO itp.
6

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.

Pełny tekst źródła
Streszczenie:
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.
Style APA, Harvard, Vancouver, ISO itp.
7

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.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
8

Frazier, Richard Andrew. "Macromolecular interactions at polysaccharide surfaces". Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336946.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
9

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.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
10

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.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
11

Sharma, Sumana. "Genome-scale identification of cellular pathways required for cell surface recognition". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/271825.

Pełny tekst źródła
Streszczenie:
A range of biochemically diverse molecules located in the plasma membrane— such as proteins, glycans, and lipids—mediate cellular recognition events, initiation of signalling pathways, and the regulation of processes important for the normal development and function of multicellular organisms. Interactions mediated by cell surface receptors can be challenging to detect in biochemical assays, because they are often highly transient, and membrane-embedded receptors are difficult to solubilise in their native conformation. The biochemical features of low-affinity extracellular protein interactions have therefore necessitated the development of bespoke methods to detect them. Here, I develop a genome-scale cell-based genetic screening approach using CRISPR-Cas9 knockout technology that reveals cellular pathways required for specific cell surface recognition events. Using a panel of high-affinity monoclonal antibodies, I first establish a method from which I identify not only the direct receptor but also other required gene products, such as co-receptors, post-translational modi cations, and transcription factors contributing to antigen expression and subsequent antibody-antigen recognition on the surface of cells. I next adapt this method to identify cellular factors required for receptor interactions for a panel of recombinant proteins corresponding to the ectodomains of cell surface proteins to the endogenous surface receptors present on a range of cell lines. In addition to finding general cellular features recognised by many ectodomains, I also identify direct interaction partners of recombinant protein probes on cell surfaces together with intracellular genes required for such associations. Using this method, I identify IGF2R as a binding partner for the R2 subunit of GABAB receptors, providing a mechanism for the internalisation and regulation of GABAB receptor signalling. The results here demonstrate that this single approach can identify the molecular nature and cell biology of surface receptors without the need to make any prior assumptions regarding their biochemical properties.
Style APA, Harvard, Vancouver, ISO itp.
12

Österberg, Monika. "On the interactions in cellulose systems : surface forces and adsorption". Doctoral thesis, KTH, Chemistry, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3017.

Pełny tekst źródła
Streszczenie:

In this thesis the interactions in cellulose systems havebeen studied with emphasis on surface forces and adsorptionphenomenon. The study was limited to surfaces and polymers ofinterest for papermaking. During papermaking both therunability of the paper machine as well as the properties ofthe final paper will depend on the molecular interactionsbetween the components present in the suspension. The objectiveof this work was to gain a better understanding of theseinteraction forces and how they are affected by solutionconditions like pH and electrolyte concentration. The maintechniques employed for this purpose were direct surface forcemeasurements using both the interferometric surface forceapparatus (SFA) and the atomic force microscopy (AFM)colloidal-probe technique. In addition, both electronspectroscopy for chemical analysis (ESCA) and AFM imaging wereused for surface characterisation and to study adsorptionbehaviour. Since a smooth and transparent surface is needed forsurface force studies using SFA, Langmuir-Blodgett films ofcellulose were employed.

The interactions between cellulose surfacesand xylansurfaces were studied. Cellulose is the main constituent of thewood fibre. In close association with cellulose in the cellwall are the hemicelluloses, xylan being a commonhemicellulose. Steric forces were found to dominate theinteractions between these substances in aqueous solutions.Still factors like charge density, solution pH and electrolyteconcentration were important. The adhesion between cellulosesurfaces in air depended on the contact area. The effect of acationic polyelectrolyte on the forces between cellulosesurfaces and between cellulose and mineral surfaces wasinvestigated to obtain a better understanding of the effects ofcationic retention and strength additives. In the presence of acationic polyelectrolyte the forces at large distances weredominated by double-layer repulsion. Bridging attraction was insome cases observed, but the presence and magnitude of thisforce was dependent on the properties of the substratesurface.

Lignin on the fibre surface affects brightness, swelling andstrength of paper. In addition, dissolved lignin interfereswith added polymers during papermaking. For this reason theadsorption of lignin on cellulose fibre surfaces was explored.The adsorption of lignin was influenced by the concentration oflignin in solution and by the electrolyte composition of thesolution. The retention of lignin was affected by the presenceof a cationic polyelectrolyte and particularly by how thepolyelectrolyte was added. The AFM imaging revealed thestructure of the adsorbed lignin, which varied with the way ofadding the polyelectrolyte, and gave an idea about theadsorption mechanism. The effect of lignin on strengthproperties of paper sheets was also evaluated.

Keywords: cellulose, hemicellulose, xylan, lignin, surfaceforces, adsorption, polyelectrolyte, SFA, AFM, ESCA,Langmuir-Blodgett films, chitosan, steric forces,bridging,adhesion

Style APA, Harvard, Vancouver, ISO itp.
13

Lashkor, Minhaj. "Switchable surfaces for regulating biomolecular and cellular interactions under complex biological conditions". Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5902/.

Pełny tekst źródła
Streszczenie:
Stimuli-responsive surfaces that can regulate specific biomolecular interactions are enabling novel functionalities and new device designs for a variety of biological and medical applications. In this study two different mixed self-assembled monolayers (SAMs) were used to regulate biomolecular and cellular interactions under complex biological conditions. The first part of this study was based on a well-defined biotinylated mixed SAM with an ethylene glycol group that prevented non-specific binding and used an electrical stimulus to allow control over biomolecular interactions under complex biological matrixes. This SAM system, based on switchable oligopeptides, can be dynamically modulated by an electrical potential under different commonly used biological media, ranging from Dulbecco's Modified Eagle Medium (DMEM) to DMEM supplemented with fetal bovine serum (FBS) and zwitterionic buffering agents such as HEPES. The second study involved electrically switchable mixed SAMs that were shown to be capable of exposing and concealing the RGD cell adhesion motif, to dynamically regulate the adhesion of immune macrophage cells under complex biological conditions. Macrophage cell adhesion to biomaterial surfaces plays a key role in mediating immune response to foreign materials. This system is one of the first examples of a material surface system that can control macrophage cell adhesion on demand. Hence, this study will be useful in developing more realistic dynamic extracellular matrix models and is certainly applicable in a wide variety of biological and medical applications.
Style APA, Harvard, Vancouver, ISO itp.
14

Sergeeva, Yulia. "Complexes ADN/polycation en solution et aux interfaces en tant que vecteurs de transfection non viraux de pointe". Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-01064224.

Pełny tekst źródła
Streszczenie:
Ma thèse a porté sur des complexes de polyélectrolytes en solution et en films LbL pour la transfection de cellules et le contrôle des interactions cellule-surface. Il est possible de doser un agent de transfection et de l'ADN plasmidique dans des films LbL en ajustant le nombre de couches. Les efficacités de transfection avec différentes lignées cellulaires ont été au moins aussi bonnes que celles rapportées dans la littérature, mais sont restées globalement faibles. Différents nanobags ont également été systématiquement testés menant à un protocole de transfection très efficace avec une faible cytotoxicité pour des fibroblastes humains qui sont difficiles à transfecter. Nous avons pu identifier les architectures LbL qui permettent de contrôler l'adhésion cellulaire même en présence de sérum. Cela nous a permis d'introduire une nouvelle technique pour le suivi in situ de la transfection par QCM-D en suivant la mobilité du cytosquelette qui sera poursuivie dans un futur projet.
Style APA, Harvard, Vancouver, ISO itp.
15

Heintz, Eva Liang-Huang. "Surface Biological Modification and Cellular Interactions of Magnetic Spinel Ferrite Nanoparticles". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4944.

Pełny tekst źródła
Streszczenie:
Surface Biological Modification and Cellular Interactions of Magnetic Spinel Nanoparticles Eva Liang-Huang Heintz 191 Pages Directed by Dr. Z. John Zhang The interest in magnetic nanoparticles is multi-dimensional. Fundamentally, it is important to be able to control their magnetic properties and to correlate to specific applications. In biology, magnetic nanoparticles offer promising potential as magnetic carriers or chaperones for magnetic localization and manipulation of therapeutic reagents. The synthesis of superparamagnetic CoFe2-xSmxO4 nanoparticles and the tunability of their magnetic properties by size and composition variations are discussed. An increase in size of CoSm0.19Fe1.81O4 nanoparticles produced an increase in blocking temperature and saturation magnetization, but a non-linear coercitivity response was observed with change in size. By varying the composition, the saturation magnetization of CoFe2-xSmxO4 decreased dramatically while the coercitivity increased when compared to native cobalt spinel ferrite (CoFe2O4) nanoparticles. These results demonstrate how the magnetic properties of cobalt spinel ferrite nanoparticles can be tailored to specific applications. Surface modifications of cobalt spinel ferrite nanoparticles facilitated the conjugation of oligonucleotides. Using a transfection reagent, CoFe2O4 ??igonucleotide conjugates were delivered into mammalian cells. Post transfection, synchronized movement of cells in response to an external magnetic field was observed. This demonstrated the possibility of magnetic manipulation and localization of therapeutic reagents coupled to CoFe2O4 magnetic nanoparticles. Results from this thesis demonstrate the potential role of magnetic spinel nanoparticles in cell biology and will facilitate the progress towards in vivo testing.
Style APA, Harvard, Vancouver, ISO itp.
16

Utsel, Simon. "Surface Modification of Cellulose-based Materials for Tailoring of Interfacial Interactions". Doctoral thesis, KTH, Fiberteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-102368.

Pełny tekst źródła
Streszczenie:
The awareness of our need for a sustainable society has encouraged the search for renewable, high quality materials that can replace oil-based products. This, in combination with increased competition in the forest industry, has stimulated a lot of research into different types of wood-based materials where cellulose-rich fibers are combined with different types of polymers. There is hence a great need to develop efficient fiber modification techniques by which the fibers can be tailored to obtain specific properties. A significant change in properties can be achieved by modifying only the surface of fibers although only a relatively small amount of the total fiber material is modified. In this thesis, several surface modification techniques are presented as new tools to design the properties of different cellulose-based materials. In paper I, thermoresponsive nanocomposites have been assembled from specially designed thermoresponsive block copolymers and nanofibrillated cellulose. The block copolymers have one thermoresponsive block and one cationically charged block which can thus attach the polymer to an oppositely charged fiber/fibril surface. Multilayers were assembled with these block copolymers and nanofibrillated cellulose (NFC) utilizing the Layer-by-Layer (LbL) technique, resulting in thin films with a thermoresponsive behavior. In papers II and III, amphiphilic block copolymers with one less polar high molecular weight block and one cationic block were synthesized for use as a compatibilizer between fibers/fibrils and less polar polymer matrices in composites. The less polar block consisted of polystyrene (PS) in paper II and poly(ɛ-caprolactone) (PCL) in paper III. These polymers self-assemble into cationic micelles in water which can adsorb to oppositely charged surfaces, such as cellulose-based fibers/fibrils, in water under mild conditions and decrease the surface energy of the surface. Atomic force microscopy (AFM) was used to evaluate the adhesive properties of surfaces treated with these compatibilizers which clearly showed the formation of physical entanglements across the interfaces, which are essential for improved interfacial adhesion in the final composites. This modification technique could probably be utilized to make fiber-based composites with better mechanical properties. To be able to better compare this physical modification technique with a more traditional covalent grafting-from approach a method to measure attached amounts of grafted PCL onto cellulose model surfaces was developed in paper IV using a quartz crystal microbalance (QCM). In paper V, multilayers of poly(allylamine hydrochloride) (PAH) and hyaluronic acid (HA) were assembled using the LbL technique and surface structure, build-up and adhesive behavior of the multilayers were evaluated. AFM force measurements showed that a significant adhesion even at long separation distances between two surfaces treated with PAH/HA multilayers could be achieved due to extensive interdiffusion across the interface during contact, leading to significant disentanglement during separation. Fundamental parameters contributing to improved adhesion for this type of system have been evaluated and this knowledge could be used to improve cellulose-based fiber networks and possibly also other types of cellulose-based materials. In paper VI, click chemistry was used to covalently attach dendrons to cellulose surfaces and further modify them with mannose groups to obtain specific interactions with Concanavalin A. The protein interactions were studied at different protein concentrations with a QCM. The multivalent dendronized surface showed a 10-fold increase in sensitivity to the protein compared to a monovalent reference surface demonstrating greatly improved interfacial interactions. This approach could be used to improve interactions at different types of interfaces.

QC 20120918

Style APA, Harvard, Vancouver, ISO itp.
17

Chauve, Grégory. "Interactions de surface avec la cellulose en milieu dense et dilué". Université Joseph Fourier (Grenoble), 2003. http://www.theses.fr/2003GRE10188.

Pełny tekst źródła
Streszczenie:
Le premier volet décrit les expériences liées à de nouveaux matériaux composites à matrice polymère EVA renforcée par des whiskers de cellulose. Les propriétés mécaniques de ces nanocomposites sont augmentées et dépendent de la structure chimique du polymère. Il existe une interaction entre la matrice polymère et la cellulose. De nouveaux outils de modélisation ont été développés pour caractériser ces interactions à l'échelle moléclaire. Cette méthode a permis d'étudier les caractéristiques géométriques et énergétiques de ces phénomènes interfaciaux comme l'absorption d'une chaîne polymère d'EVA ainsi que l'adhésion d'un film mince d'EVA sur une surface de cellulose. Ce travail concerne aussi les expériences par RMN en solution aqueuse pour l'étude de l'absorption en milieu liquide de petites molécules ou des polymères, synthétiques ou biologiques. Cette technique est sensible pour de très faibles concentrations. La cellulose présente bien un caractère amphiphile.
Style APA, Harvard, Vancouver, ISO itp.
18

Coletti, Camilla. "Silicon Carbide Biocompatibility, Surface Control and Electronic Cellular Interaction for Biosensing Applications". [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002285.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
19

Foo, Guo Shiou. "Surface interactions of biomass derived oxygenates with heterogeneous catalysts". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54455.

Pełny tekst źródła
Streszczenie:
Energy demand is projected to increase by 56% before 2040 and this will lead to the fast depletion of fossil fuels. Currently, biomass is the only sustainable source of organic carbon and liquid fuels. One major method of converting biomass involves the utilization of heterogeneous catalysts. However, there is still a lack of understanding in the reaction mechanisms and surface interactions between biomass-derived oxygenates and catalysts. Specifically, three important reactions are investigated: i) dehydration of glycerol, ii) hydrolysis of cellulose and cellobiose, and iii) hydrodeoxygenation of bio-oil. Some important concepts are gathered and provide insight into the most attractive conversion strategies. These concepts include the role of Lewis and Brønsted acid sites, synergistic effect between defect sites and functional groups, the advantage of weak acid sites, steric effect imposed by aromatic substituents, and the evolution of surface species in catalyst deactivation. These studies show that a deep understanding of surface chemistry can help to elucidate elementary reaction steps, and there is great potential in using heterogeneous catalysts for the conversion of biomass into targeted fuels and chemicals.
Style APA, Harvard, Vancouver, ISO itp.
20

Thakar, Dhruv. "Surfaces biomimétiques pour caractériser les interactions induites par les glycosaminoglycanes aux niveaux moléculaire, supramoléculaire et cellulaire". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAV005/document.

Pełny tekst źródła
Streszczenie:
L'adhésion contrôlée et la migration orientée des cellules est fondamentale pour plusieurs processus physiologiques et pathologiques. Une famille de polysaccharides linéaires, connus sous le nom de glycosaminoglycanes (GAG) est impliquée dans l'organisation et la présentation des protéines de signalisation, les chimiokines, à la surface des cellules et dans la matrice extracellulaire (ECM). Les travaux concernent le développement de surfaces biomimétiques bien définies aux niveaux moléculaires et supramoléculaires pour l‘étude des mécanismes d'intéractions protéines-GAG et l'analyse de la réponse cellulaire à des signaux biochimiques et biophysiques spécifiques. L'objectif de cette étude est de mieux comprendre les communications cellule-cellule et cellule-matrice induites par les GAGs.En utilisant la ligation oxime, les GAGs peuvent être fonctionnalisés de manière stable par la biotine à leur extrémité réductrice, ce mode de couplage s'est avéré déterminant pour préparer des surfaces fonctionnalisées par les GAGs de manière stable. Une monocouche de streptavidine est utilisée comme plateforme modulable pour assembler séquentiellement les molécules biotinylées, avec une orientation et des densités de surface contrôlées. Des GAGs (les héparane sulfate (HS), en particulier), des chimiokines et d'autres composants de l'ECM (par exemple un ligand d'adhésion cellulaire, RGD) ont été assemblés reconstituant certains aspects des surfaces in vivo (cellules ou de l'ECM). La microbalance à quartz (QCM-D) et l'ellipsométrie spectroscopique nous ont permis de caractériser et de contrôler la présentation supramoléculaire du HS et du RGD. Ces surfaces modèles ont été utilisées pour étudier les interactions supramoléculaires entre le HS et la chimiokine SDF-1α/CXCL12α facteur d'origine stromale et pour analyser les réponses cellulaires aux signaux extracellulaires. Nos données apportent la preuve que la chimiokine, CXCL12α rigidifie les assemblages de HS, et que cet effet est dû à la réticulation des chaînes de HS induite par la protéine. La cinétique des interactions HS-chimiokine a été quantifiée en utilisant la résonance plasmonique de surface (SPR). Nous avons également démontré que le mode de présentation de la chimiokine sur la surface, en particulier la présence des HS, influence le comportement des myoblastes. Nos données montrent que les récepteurs cellulaires CXCR4 (récepteur de la CXCL12α) et l'intégrine (récepteur du RGD) peuvent agir en synergie pour contrôler l'adhésion et la migration cellulaire. Ces surfaces modèles fournissent des indications précieuses qui pourront être appliquées au domaine de la glycobiologie, par exemple, pour étudier le rôle des GAGs dans la migration cellulaire induite par les chimiokines
The oriented migration and controlled adhesion of cells is fundamental to many physiological and pathological processes. A family of linear polysaccharides, known as glycosaminoglycans (GAGs), help organizing and presenting signaling proteins, so-called chemokines, on the cell surface and in the extracellular matrix thus regulating cellular behavior. The objective of this PhD thesis was to develop biomimetic surfaces that are highly defined and tunable, for mechanistic studies of GAG-protein interactions on the molecular and supramolecular levels, and to probe cellular responses to defined biochemical and biophysical cues to better understand GAG-mediated cell-cell and cell-matrix communications.Applying oxime ligation, GAGs could be stably functionalized with biotin at the reducing end, and these features proved crucial for the reliable preparation of GAG-functionalized surfaces. A streptavidin monolayer served as a ‘molecular breadboard' to sequentially assemble biotinylated molecules with controlled orientation and surface densities. GAGs (heparan sulfate (HS) in particular), chemokines and other ECM components (e.g. integrin ligands promoting cell adhesion, RGD) were assembled into multifunctional surfaces that recapitulate selected aspects of the in vivo situation. Quartz crystal microbalance (QCM-D) and spectroscopic ellipsometry permitted us to characterize and control the supramolecular presentation of HS and RGD. These model surfaces were used to study the supramolecular interactions between HS and the selected chemokine stromal derived factor SDF-1α/CXCL12α and to analyze cellular responses to extracellular cues. Our data provide evidence that CXCL12α binding rigidifies HS assemblies, and that this effect is due to protein-mediated cross-linking of HS chains. The kinetics of chemokine binding to HS was quantified using surface plasmon resonance (SPR). We also demonstrate that the way in which the chemokine is presented, and in particular the presence of HS, is important for regulating myoblast behavior. Our data shows that the cell surface receptors CXCR4 (the CXCL12α receptor) and integrins (the RGD receptor) can act synergistically in controlling cellular adhesion and migration. These surfaces can generate novel insights in the field of glycobiology, e.g. in dissecting the function of GAGs in chemokine-mediated cellular migration
Style APA, Harvard, Vancouver, ISO itp.
21

Forni, Luciana. "Recepteurs membrananires des lymphocytes b : interactions entre recepteurs et physiologie des cellules b". Paris 6, 1987. http://www.theses.fr/1987PA066375.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
22

Trent, Alexis Raven. "Fabrication, Characterization and Cellular Interactions of Keratin Nanomaterial Coatings for Implantable Percutaneous Prosthetics". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/94417.

Pełny tekst źródła
Streszczenie:
Implantable medical devices face numerous complications when interfacing with soft tissue, and are plagued by negative responses from host tissue. One such class devices are percutaneous osseointegrated prosthetics (POP). POP consist of a bone anchored titanium post that extrudes through the skin and attaches to an external prosthetic. Compared to the traditional socket interface, POPs offer better stability, limb functionality, and osseoperception for both upper and lower prosthetic limbs. Although the POP surgery technique is well established, the main disadvantage to this technology remains the titanium (Ti) - skin interface. Some of the complications that can arise include epithelial downgrowth, mechanical tearing, and infection. Various types of coatings, surface structure, and antibiotic release technologies have been used to coat Ti in an effort to mitigate POP's associated obstacles, but these methods have failed to translate into published clinical studies and mainstream medical use. One potential solution may be to mimic an interface already found in the human body, the fingernail-skin interface, which is infection-free and mechanically stable. The same keratins that make up the cortex of human hair fibers are found in the fingernail. These cortical human hair keratins can be extracted and purified, and fingernail-specific dimeric complexes coated onto Ti surfaces using silane coupling chemistry. Keratin has been used in other studies for its cell adhesion and differentiation properties, and it has been suggested that the Leu-Asp-Val (LDV) amino acid motif is the primary site responsible for cellular attachment. In the present work, keratins extracted from human hair fibers and recombinant keratin nanomaterials (KN) were used to create biomimetic coatings on silanized Ti surfaces. These coatings were characterized and investigated for surface topography, elemental composition, cell adhesion motifs, and cell adhesion. Both keratin substrates showed the ability to create uniform coatings that retain a protein conformation that exhibits cell adhesion motifs. The coatings exhibit the ability to support cell adhesion of both epithelial and connective tissue cells. Application of fluid shear stress was used to test the mechanical adhesion strength of cells on keratin coatings. The structure, biochemical stability and sustained cellular adhesion of these coatings support keratin's capacity to provide a stable interface between POPs and skin. Side-by-side studies of extracted and recombinant keratins reveals that the recombinant form of these materials may provide distinct advantages for their use in POP devices. Overall, this study confirmed that a uniform, silane-coupled keratin coating was feasible. We demonstrated the substrates contain a biological function in terms of cellular adhesion and phenotypic changes in skin-relevant cells. These results support the biomimetic function of keratin on silanized Ti, which may provide a suitable coating to translate percutaneous medical device coating applications toward clinical use.
Ph. D.
Style APA, Harvard, Vancouver, ISO itp.
23

Kirichuk, Oksana. "Avancées dans les études in vitro des interactions cellule-glycocalyx : développement d'une plateforme définie mécaniquement et biochimiquement". Electronic Thesis or Diss., Université Grenoble Alpes, 2023. http://www.theses.fr/2023GRALY084.

Pełny tekst źródła
Streszczenie:
L'adhésion des cellules à la paroi des vaisseaux sanguins est un processus complexe. Les globules rouges doivent s'éloigner de la paroi du vaisseau pour éviter la formation de caillots, tandis que les cellules immunitaires peuvent migrer dans les tissus. Ce processus repose sur le glycocalyx, une couche de macromolécules couvrant la paroi des vaisseaux. Cependant, nous ne comprenons pas complètement comment les propriétés du glycocalyx (souplesse, épaisseur, composition des récepteurs) affectent cette régulation. Notre hypothèse est que l'adhésion sélective des cellules fait intervenir des facteurs mécaniques et biochimiques. Il est difficile d'étudier ce phénomène dans de vrais vaisseaux sanguins, c'est pourquoi mon étude s'est concentrée sur le développement d'une plateforme in vitro. Cette plateforme combine un modèle de glycocalyx avec des modèles synthétiques de globules blancs sous flux, permettant un contrôle précis des paramètres physiques et biochimiques du modèle de glycocalyx et des modèles de cellules.Le modèle de glycocalyx nouvellement développé comprend plusieurs ingrédients clés dont les propriétés sont étroitement contrôlées : une brosse d’acide hyaluronique (HA, un composant essentiel du glycocalyx endothélial) est combinée à la sélectine P (une molécule d'adhésion à la surface des cellules endothéliales qui joue un rôle essentiel dans l'orientation des leucocytes). En m'appuyant sur l'expérience précédente de mon groupe de recherche, j'ai utilisé une bicouche lipidique supportée sur une lamelle de verre (SLB) portant une monocouche de streptavidine (SAv), qui peut lier des molécules biotinylées par l'intermédiaire de liaisons biotine-SAv. Je présente ici un contrôle de la mobilité dans le plan des molécules ancrées à la bicouche lipidique fluide en utilisant le glutaraldéhyde (GTA) comme agent de réticulation pour la SAv. Des densités de greffage contrôlées de chaînes d'HA biotinylées à une extrémité et de différentes longueurs permettent de créer des brosses aux propriétés mécaniques différentes. Je présente également une nouvelle méthodologie permettant d'ajuster quantitativement la densité de greffage de molécules biotinylées plus petites, qui est utilisée ici pour contrôler la densité de greffage d'une "protéine adaptatrice" pour l'ancrage de la P-sélectine. Le nouveau modèle in vitro du glycocalyx permet ainsi de contrôler la mobilité latérale, la densité de surface et l'orientation de deux molécules fonctionnelles distinctes.Le deuxième élément clé de la nouvelle plateforme consiste en des modèles de globules blancs, développés sur la base de microbilles disponibles dans le commerce ayant la taille d'une cellule et une fonctionalisation de surface avec de la SAv. Je présente une méthodologie pour le greffage simultané de deux types de protéines à la surface des billes : CD44 biotinylé (un ligand exprimé à la surface des leucocytes, interagissant spécifiquement avec l'HA) et PSGL-1 (un ligand de la P-sélectine). En outre, je présente une méthode permettant de contrôler la densité de surface de chacune de ces protéines.J'utilise une combinaison de méthodes comme outils de quantification et de contrôle de la qualité de la formation du modèle de glycocalyx et de la fonctionnalisation des billes : microbalance à quartz avec mesure de dissipation (QCM-D) ; ellipsométrie spectroscopique (SE), microscopie à contraste interférentiel par réflexion (RICM) ; microscopie confocale avec redistribution de fluorescence après photoblanchiment (FRAP), et cytométrie en flux.Cette plateforme nouvellement établie offre des conditions contrôlées pour l'étude de l'adhésion des cellules sanguines, reliant les interactions chimiques cellule-glycocalyx et les aspects mécaniques de la migration cellulaire sous flux. Elle est facilement complexifiable ou adaptable, permettant une compréhension de plus en plus fine de l'adhésion des cellules aux vaisseaux sanguins
Cell adhesion to the blood vessel wall is a complex, highly regulated physiological process. Red blood cells must repel from the blood vessel wall to prevent blood clotting while immune cells can be recruited from the vascular system to migrate into surrounding tissues. Cell adhesion hinges on the critical role played by the glycocalyx, a soft gel-like layer coating the vascular wall. However, how glycocalyx mechanical (softness, thickness) and biochemical (the composition and the density of surface receptors) properties affect this regulation is still poorly understood. Our hypothesis is that selective cell adhesion requires an intricate interplay of mechanical and biochemical cues. Elucidating the physical and molecular mechanisms that underpin selective adhesion directly in real blood vessels is challenging owing to the complexity and lack of control in in vivo systems. In my research, I aimed to construct an in vitro molecular interaction platform to facilitate mechanistic analyses. The platform combines a molecularly-defined model of the glycocalyx with mimetics of white blood cells under flow. While developing such a platform posed challenges, it offers the advantage of precise control over the physical and biochemical parameters of both the glycocalyx mimetic and cell mimetics.The newly developed glycocalyx model includes several key ingredients with tightly controlled properties: a brush of hyaluronan (HA, an essential component of the endothelial glycocalyx) is combined with P-selectin (an adhesion molecule on the endothelial cell surface critical for the homing of leukocytes). Building on previous experience in my research group, I employed a silica-supported lipid bilayer (SLB) bearing a monolayer of streptavidin (SAv), that can bind biotinylated molecules via biotin-SAv bonds. I introduce here a control of the in-plane mobility of molecules anchored to the fluid lipid bilayer using glutaraldehyde (GTA) as a cross-linking agent for SAv. Controlled grafting densities of one-end biotinylated HA chains of various lengths then create brushes of different mechanical properties. I also present a new methodology for quantitatively tuning the grafting density of smaller biotinylated molecules, which is deployed here to control the grafting density of an ‘adapter protein’ for anchoring P-selectin. The new in vitro model of the glycocalyx thus affords control over the lateral mobility, the surface density and the orientation of two distinct functional molecules.The second key component of the newly developed platform consists of white blood cell mimetics, developed based on commercially available microbeads with the size of a cell and a SAv coating. I introduce a methodology for simultaneous grafting of two types of proteins onto the bead surface: biotinylated CD44 (a ligand expressed on leukocyte surfaces, interacting specifically with HA) and PSGL-1 (a ligand of P-selectin). Additionally, I present a method for controlling the surface density of each of these proteins.I use a combination of methods as monitoring and quality control tools of glycocalyx model formation and bead functionalization: quartz crystal microbalance with dissipation monitoring (QCM-D); spectroscopic ellipsometry (SE), reflection interference contrast microscopy (RICM); confocal microscopy with fluorescence recovery after photobleaching (FRAP) capabilities, and flow cytometry.This newly established platform provides a controlled environment for studying blood cell adhesion, effectively bridging the divide between cell-glycocalyx chemical interactions and the mechanical aspects of cell migration under flow, including attachment and repulsion from the vascular wall. This platform holds the potential for expansion to encompass other surface adhesion molecules or to integrate multiple adhesion molecules, to gradually advance from the bottom up our understanding of the mechanisms governing cell adhesion to blood vessels
Style APA, Harvard, Vancouver, ISO itp.
24

Lipsker, Dan Michael. "Interactions de la protéine de stress hsp70 avec les cellules dendritiques humaines : Etude du trafic de certains antigènes de surface des cellules de Langerhans humaines". Université Louis Pasteur (Strasbourg) (1971-2008), 2002. http://www.theses.fr/2002STR13044.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
25

Kittle, Joshua Daniel. "Characterization of Cellulose and Chitin Thin Films and Their Interactions with Bio-based Polymers". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/26806.

Pełny tekst źródła
Streszczenie:
As the two most abundant natural polymers on earth, cellulose and chitin have attracted increasing attention as a source of renewable energy and functional materials. Thin films of cellulose and chitin are useful for studying interactions of these materials with other natural and synthetic molecules via techniques such as quartz crystal microbalance with dissipation monitoring (QCM-D) and surface plasmon resonance (SPR). Because of the difficulty of extracting native cellulose, regenerated cellulose (RC), sulfated nanocrystalline cellulose (SNC), and desulfated nanocrystalline cellulose (DNC) thin films are often studied in its place. In this work, QCM-D solvent exchange studies showed that water contents of RC, SNC and DNC films were proportional to the film thickness (d). Accessibility and degradation of the films was further analyzed via substrate exposure to cellulase. Cellulase adsorption onto RC films was independent of d, whereas cellulase adsorption onto SNC and DNC films increased with d. Enhanced access to guest molecules for SNC and DNC films relative to RC films revealed they are more porous. The porosity of these cellulose films aided in understanding the observed differences of xyloglucan (XG) adsorption onto their surfaces. Xyloglucan adsorption onto RC, SNC, and DNC was studied by QCM-D and SPR. The amount of adsorbed XG increased in the order RC < SNC < DNC. XG adsorption onto RC films was independent of d, whereas XG adsorption was weakly dependent upon d for SNC films and strongly dependent upon d for DNC films. However, XG adsorbed onto "monolayer" thin films of RC, SNC, and DNC in approximately the same amount. These results suggested that the morphology and surface charge of the cellulose substrate had a limited effect upon XG adsorption and that accessible surface area of the cellulose film may be the factor leading to apparent differences in XG adsorption for different surfaces. The porosity and surface charge of SNC films presented a unique opportunity to examine polyelectrolyte adsorption and subsequent dewatering of the SNC substrate. The adsorption of a series of cationically derivatized dextran (cDex) polyelectrolytes with various degrees of substitution (DS) onto SNC was studied using QCM-D and SPR. As the hydrophobic character of the cDex samples increased, the water content of the adsorbed cDex layer decreased. For cDex with the greatest hydrophobic content, nearly 50% by mass of the initial water present in the porous SNC film was removed upon cDex adsorption. This study indicated that the water content of the film could be tailored by controlling the DS and hydrophobic character of the polyelectrolyte. This work also presents the first report of smooth, homogeneous, ultrathin chitin films, opening the door to surface studies of binding interactions, adsorption kinetics, and enzymatic degradation. The chitin films were formed by spincoating trimethylsilyl chitin onto gold or silica substrates, followed by regeneration to a chitin film. The utility of these chitin films as biosensors was evident from QCM-D and SPR studies that revealed bovine serum albumin adsorbed as a monolayer.
Ph. D.
Style APA, Harvard, Vancouver, ISO itp.
26

Jiang, Jian-Qiao. "Conception, préparation et évaluation des performances de dispositifs de capture de microvésicules à base de complexes polymétalliques : effet de la dendricité". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0376.

Pełny tekst źródła
Streszczenie:
Les microvésicules (MV) constituent un intérêt croissant pour la recherche en première ligne du diagnostic des maladies. Ils sont utilisés par presque tous les types de cellules du corps humain comme outil de communication intercellulaire. Ils peuvent donc être prélevés dans la plupart des liquides extracellulaires sans causer de dommages graves aux tissus environnants. Elles sont formées par le bourgeonnement de la membrane cellulaire, ainsi leurs protéines membranaires rappellent celles de leurs cellules mères, leur permettant ainsi de retrouver leur type de cellules mères. Ils contiennent de nombreuses variétés de biomolécules, notamment des lipides, des protéines et des acides nucléiques. Par conséquent, leur analyse fournira des informations physiologiques et pathologiques précieuses sur leurs cellules d'origine. Ils sont libérés lors d'un stress cellulaire, ils représentent donc la réponse cellulaire précoce aux stimuli correspondants. En d’autres termes, leur analyse est en mesure de fournir une approche pour la détection précoce de conditions pathologiques. Une caractérisation complète des MV inclut leur population par unité de volume du liquide échantillon, leur distribution en taille, leur morphologie, leur composition en lipides, protéines et acides nucléiques. Malheureusement, aucune plate-forme n’a été développée pour permettre tous les tests susmentionnés en même temps, alors que les protocoles de test existants sont sévèrement limités par les traitements pré-analytiques, en particulier les processus de purification. Ici, nous présentons la conception et la construction d'un dispositif sur lequel des microvésicules peuvent être capturées, permettant une analyse physique et chimique sur les MV dans un échantillon de fluide extracellulaire.Pour la construction du dispositif, nous avons d’abord synthétisé une série de dendrons de plus en plus dendriques capables de se lier spécifiquement à la phosphatidylsérine (PS), une molécule lipidique s’exposant uniquement sur le feuillet externe des vésicules extracellulaires. Les périphériques dendroniques sont fonctionnalisés avec des complexes dipicolylamine-Zn2 + (DPA-Zn) pour assurer l'interaction dendron-phosphatidylsérine. Les dendrons synthétisés de manière convergente sont adoptés comme support moléculaire des unités complexes, de sorte que la capacité de liaison des dendrons au PS puisse être contrôlée et améliorée grâce à la multivalence et à la synergie des unités DPA-Zn voisines. Le noyau de chaque dendron est attaché à un espaceur de n-hexylamine, permettant l’attachement à la surface du matériau
Microvesicles (MVs) have been a growing research interest at the front line of disease diagnosis. They are used by almost all types of cells in the human body as a tool of intercellular communication, thus can be sampled from most of the extracellular fluids without causing severe damage to the surrounding tissue. They are formed by budding of cell membrane, thus their membrane proteins are reminiscent to that of their parent cells, allowing them to be traced back to their parent cell types. They contain rich varieties of biomolecules including lipid, protein, and nucleic acids, thus the analysis of them will provide valuable physiological and pathological information on their cells of origin. They are released under cellular stress, thus they represent the early cellular response to corresponding stimuli. In other words, an analysis of them is able to provide an approach for the early detection of pathological conditions. A full characterization of the MVs includes their population per unit volume of the sample liquid, their size distribution, their morphology, their composition of lipid, protein, and nucleic acids. Unfortunately, there isn’t a platform developed allowing all the aforementioned tests at the same time, while existing test protocols are severely limited by the pre-analytical treatments, especially the purification processes. Herein, we present the design and construction of a device on which microvesicles can be captured, accommodating both physical and chemical analysis on the MVs within an extracellular fluid sample.For the device construction, we first synthesized a series of dendrons with increasing dendricity that are able to specifically bind to phosphatidylserine (PS), a lipid molecule exposing only on the outer leaflet of extracellular vesicles. The dendron peripherals are functionalized with dipicolylamine-Zn2+ (DPA-Zn) complexes to provide the dendron-phosphatidylserine interaction. The convergently synthesized dendrons are adopted as the molecular support for the complex units so that the binding ability of dendrons to PS can be controlled and improved through multivalency and synergy of neighboring DPA-Zn units. The core of each dendron is attached to an n-hexylamine spacer, allowing the attachment to the material surface
Style APA, Harvard, Vancouver, ISO itp.
27

Castellana, Donatello. "Tumor-derived microvesicles in cancer progression : In vitro study in a prostate cancer model". Université Louis Pasteur (Strasbourg) (1971-2008), 2008. http://www.theses.fr/2008STR13034.

Pełny tekst źródła
Streszczenie:
La membrane joue un rôle clé dans un large nombre de processus physiologiques. Lors d’une activation cellulaire, l’externalisation de PS sur la membrane plasmique est suivie par l’émission de microvésicules membranaires (MV). Les MV reflétant le profil antigénique de la cellule et de la stimulation dont elles sont originaires. Le microenvironnement tumoral est enrichi en MV libérées par les cellules qui constitue le tissu cancéreux. En nous focalisant sur l’implication des fibroblastes nous proposons un modèle in vitro dans lequel les cellules normales et cancéreuses communiquent entre elles via MV. Le but de cette étude est d’élucider un mécanisme, dans lequel les cellules du cancer de la prostate influencent le comportement de cellules normales du stroma, et ces dernières affectent l’agressivité des cellules de carcinome, Le tout via la libération mutuelle de MV pour promouvoir ou soutenir la création d’une niche favorable au développement de la tumeur
The plasma membrane plays a pivotal role in a large number of physiological processes. After cellular stimulation, externalization of PS in the exoplasmic leaflet of plasma membrane is followed by the shedding of membrane microvesicles (MV) in almost all cell types. MV composition reflect the antigenic profile of cells which they originate from, depending on the stimulus apply. Tumour microenvironment is highly enriched in MV shed from cells infiltrating the tumour tissue. Fibroblasts are associated with tumour cells at all stages of cancer progression. Focusing on fibroblasts implication in cancer, we propose an in vitro model in which cancer and normal cells communicate each other via MV. The aim of this study is to elucidate a mechanism, in which prostate cancer cells influence the behaviour of normal stromal cells that in turn affect the aggressiveness of carcinoma cells by mutual MV shedding, promoting or support the creation of a niche favourable for tumour development
Style APA, Harvard, Vancouver, ISO itp.
28

Bernier, Marie-Charlotte. "Étude des interactions de nanoparticules de dioxyde de titane manufacturées avec des cellules et des biomolécules". Compiègne, 2011. http://www.theses.fr/2011COMP1973.

Pełny tekst źródła
Streszczenie:
Les propriétés particulières des nanoparticules de dioxyde de titane (nTiO2) liées à leur petite taille (<100 nm) en font des matériaux utilisés dans de nombreuses applications de la vie quotidienne (cosmétiques, biomatériaux…). Cependant, leurs effets sur la santé humaine et sur l’environnement sont encore mal connus. Dans notre étude, des nTiO2 anatase et des nTiO2 rutile enrobées de silice ont été testées sur deux lignées cellulaires murines modèles : les pré-ostéoblastes MC-3T3 et les fibroblastes L929. Afin de comprendre les mécanismes de leur cytoxicité, l’état d’agrégation des nTiO2 dans les différents milieux de culture a été étudié, ainsi que leur interaction avec la protéine majoritaire de la matrice extracellulaire, la fibronectine (Fn). Les conséquences de ces interactions sur l’adhésion des cellules MC-3T3 à des revêtements de Fn ont également été évaluées. Nous avons pu mettre en évidence une cytotoxicité des nTiO2 dépendante du type cellulaire étudié, de la dose de nanoparticules, mais également de la nature chimique de la surface des nanoparticules. L’interaction des nTiO2 avec la Fn et la diminution de l’adhésion cellulaire dépendent aussi de la concentration et des propriétés de surface des nanoparticules. Par ailleurs, nos études de cytotoxicité concernant les pré-ostéoblastes ont montré une sécrétion de fortes doses de la cytokine pro-inflammatoire IL-6, connue pour induire l’ostéolyse via l’activation d’ostéoclastes. Ainsi notre étude met en évidence l’urgence de reconsidérer l’utilisation de biomatériaux nanostructurés qui pourraient inhiber la reconstruction osseuse
The small size (<100 nm) of titanium dioxide nanoparticles (nTiO2) gives them special properties that make them usefull for many everyday life applications (cosmetics, biomaterials. . . ). However, their effects on human health and the environment remain unkown or misunderstood. In this study, anatase nTiO2 and silica-coated rutile nTiO2 were tested on two murine cell lines: MC-3T3 pre-osteoblasts and L929 fibroblasts. In order to understand the cytotoxic mechanisms, TiO2 nanoparticles aggregation in different culture media and their interaction with fibronectin (Fn) –the major protein of the extracellular matrix– were studied. The consequences on MC-3T3 cell adhesion to Fn coatings were also evaluated. We have demonstrated that nTiO2 cytotoxicity depends on their concentration, the cell type, and the chemical nature of the nanoparticle surface. The interaction of nTiO2 with Fn and the decrease of cell adhesion also depend on the concentrations and surface’s nature of nanoparticles. Moreover, our cytoxicity studies concerning pre-osteoblasts have shown a secretion of high levels of the pro-inflammatory cytokine IL-6, known to mediate osteolysis by osteoclast activation. Thus, our study highlights the urgent need to reconsider the use of nanostructured biomaterials and to determine if they could inhibit bone reconstruction
Style APA, Harvard, Vancouver, ISO itp.
29

Bourouina, Nadia. "Colloïdes liquides pour la micro-actuation des interactions biologiques de surface : du système modèle à la cellule T". Paris 6, 2011. http://www.theses.fr/2011PA066238.

Pełny tekst źródła
Streszczenie:
Les interactions moléculaires spécifiques sont importantes dans de nombreux processus biologiques. Alors que les propriétés de formation et de stabilité des interactions spécifiques en solution sont bien connues, les interactions spécifiques entre molécules portées par des surfaces sont bien moins décrites. Dans ce projet, nous souhaitons comprendre les lois qui gouvernent les interactions moléculaires spécifiques entre deux surfaces liquides. Tout d’abord, nous avons étudié ces interactions 2D entre gouttes d’émulsion micrométriques complémentaires couvertes soit de streptavidines comme récepteur soit de biotines comme ligand. Ensuite, nous avons étudié la formation de liens spécifiques entre une cellule du système immunitaire, la cellule T et une goutte d’émulsion greffée avec un anticorps anti-CD3 qui cible le complexe TCR-CD3, responsable de l’activation de la cellule T. Nous avons montré que la formation des liens spécifiques entre surfaces liquides est efficace, mais que le contact doit être suffisamment long. L’engagement des premiers liens crée un gradient chimique qui conduit à la formation d’un contact concentré en molécules dans les deux systèmes étudiés. Nous avons trouvé que le contact goutte-goutte et goutte-cellule est composé de molécules de mobilité différente. Nous avons trouvé que l’engagement du complexe TCR-CD3 par l’anticorps anti-CD3 menait à l’activation de la cellule T ainsi qu’a une réponse mécanique de la cellule
Style APA, Harvard, Vancouver, ISO itp.
30

Sandrin, Ludivine. "Caractérisation des interactions biomoléculaires entre des ligands peptidiques immobilisés sur une surface et des récepteurs cellulaires". Phd thesis, Grenoble 1, 2009. http://tel.archives-ouvertes.fr/tel-00453636.

Pełny tekst źródła
Streszczenie:
L'objectif visé dans cette étude consiste à développer une méthodologie de caractérisation des interactions ligands/récepteurs cellulaires à la surface d'un transducteur physique. Le ligand immobilisé est représenté par un cyclopentapeptide c(-RGDfK-) dont les propriétés de reconnaissance spécifique pour l'intégrine alphaV beta3 sont bien connues. Les travaux de thèse présentés dans ce manuscrit concernent la synthèse des ligands peptidiques, la mise au point des différentes techniques d'immobilisation de ces ligands et enfin la caractérisation des interactions biomoléculaires avec des cellules exprimant l'intégrine. Le ligand peptidique est présenté de façon multivalente sur un châssis moléculaire cyclodécapeptidique de séquence c(-Pro-Gly-Lys-Lys-Lys-)2. Le greffage des différents motifs se fait via la formation d'un lien éther d'oxime ou d'un lien amide sur les chaînes latérales des lysines orientées de part et d'autre du plan moyen du cyclopeptide. Trois approches ont été mises en œuvre pour fixer les ligands -RGD- sur une surface : le couplage affin, l'insertion dans une bicouche lipidique et le couplage covalent. Les surfaces fonctionnelles résultantes ont été caractérisées par des méthodes physico-chimiques d'analyse de surface et d'interface. Des tests d'adhésion cellulaire, suivis par QCM-D et par microscopie optique, ont ensuite permis de caractériser les propriétés de reconnaissance des ligands peptidiques. La comparaison des signaux de QCM-D et des images de la surface, obtenus à différents taux de greffage du ligand a permis d'identifier une densité de greffage minimale en ligand nécessaire à l'adhésion et à l'étalement des cellules.
Style APA, Harvard, Vancouver, ISO itp.
31

Desrousseaux, Camille. "Prévention de l'adhésion bactérienne et du développement du biofilm sur les dispositifs médicaux de la perfusion via les surfaces nanostructurées". Thesis, Clermont-Ferrand 1, 2015. http://www.theses.fr/2015CLF1PP03.

Pełny tekst źródła
Streszczenie:
Les infections nosocomiales liées aux dispositifs médicaux, et plus particulièrement ceux de la perfusion, sont un problème majeur dans le milieu hospitalier. Ces infections sont liées à la présence de biofilm. Pour lutter contre le biofilm, les mesures préventives en hygiène ne sont pas suffisantes. Les recherches se dirigent vers la modification des surfaces des matériaux des dispositifs médicaux: ajout de substances biocides, développement de surfaces antiadhésives par voie chimique ou topographique. L’objectif de cette thèse est de créer des polymères nanostructurés pouvant entrer dans la composition de dispositifs médicaux de la perfusion et de tester leur impact sur l’adhésion bactérienne et le développement du biofilm. Dans un premier temps, la technique de nanostructuration choisie repose sur la réplication d’un moule nanostructuré en alumine nanoporeuse qui se caractérise par des nanopores auto-organisés en nid d’abeille. Après avoir mis en place une station d’anodisation permettant la nanostructuration de ce moule, la reproductibilité du procédé de fabrication a été validée (diamètre des pores : 51 ± 6 nm, profondeur: 97 ± 9 nm, espace interpores: 102 ± 6 nm). Ensuite, les travaux de réplication ont été effectués avec le polymère ABS (acrylonitrile-butadiène-styrène). Plusieurs méthodes de réplication ont été testées à partir de dépôt de solutions de polymères ou de fonte du matériau sur le moule d’alumine. La méthode sélectionnée sur des critères de reproductibilité et de facilité de transposition industrielle donne des nanostructures de type nanopicots (diamètres des picots : 56 ± 7 nm, distances interpicots : 101 ± 16 nm, longueurs : 73 ± 33 nm). Les surfaces développées sont ensuite caractérisées (MEB, DSC analyse calorimétrique différentielle, spectrométrie Infra Rouge, angle de contact). La fabrication des nanostructures ne semble pas dégrader le matériau ABS et la modification topographique rend la surface plus hydrophile. Une étude de stabilité montre que les nanostructures résistent à plusieurs modes de stérilisation (oxyde d’éthylène, plasma H2O2 et rayon Beta) et sont conservés dans le temps, ce qui les rend applicables à la surface d’un dispositif médical. La seconde étape du travail consiste à évaluer l’adhésion bactérienne sur les surfaces témoins et nanostructurées. Différents tests de culture de biofilm ont été réalisés avec S. epidermidis en conditions statique ou dynamique. Après un temps de 3 à 48h, les bactéries sont décrochées de la surface puis dénombrées sur gélose. Il n’y a pas de différence significative d’adhésion bactérienne entre les deux types de surface. L’observation en microscopie électronique à balayage et confocale à 24h semble confirmer ce résultat. Des tests réalisés avec d’autres souches bactériennes (S. aureus, K. pneumoniae, P. aeruginosa) en condition statique montrent également que l’adhésion est également identique sur les deux surfaces. Par conséquent, nous pouvons conclure que nos surfaces ABS développées avec ces nanopicots spécifiques n’ont pas un effet anti-adhésion sur les bactéries testées. Des recherches récentes mettent en évidence que l’espacement entre les nanopciots est un facteur critique sur l’adhésion bactérienne. L’étape suivante de notre travail consiste à tester de nouvelles nanostructures réalisées avec un moule AAO ayant une distance interpore plus grande
Medical device-related infections are a public health concern and an economic burden. The role of biofilms in medical device-related infections is clearly established. Preventive hygiene measures are not often sufficient to prevent biofilms formation. One promising way of preventing device-related infections is the development of medical devices with surfaces or materials that reduce either microbial viability using biocidal substances or microbial adhesion with topographical modifications.Developing nanostructured polymeric surfaces, which could have applications in medical devices, and testing their impact on bacterial adhesion and biofilm development were the main goals of this thesis. First of all, the polymer was replicated on an aluminum anodized oxide nanostructured mold (AAO), characterized by highly ordered nanopores. An anodization station was made in order to create molds. Then, the reproducibility of the process fabrication was validated (pore diameter: 51 ± 6 nm, deepness 97 ± 9 nm, interpore espace: 102 ± 6 nm). Several replication techniques with ABS were tested including polymers solutions and melted polymers. The selected method was the one with the most reproducible results pillar diameter: 56 ± 7 nm, interpillar distance: 101 ± 16 nm, length: 73 ± 33 nm) and the most representative of industrial injection processes. The created surfaces were then characterized (MEB, DSC, ATR-FTIR, wettability). The fabrication process does not seem to degrade the ABS material and the topographical change increases the hydrophilicity of the surface. A stability study showed that the nanopillars were resistant to several sterilization processes (ethylene oxide, H2O2 plasma, Beta irradiation) and were maintained through time, which is an important element for applications in medical-devices.The second step of our work consisted of assessing bacterial adhesion on control and nanostructured ABS samples. Several biofilm tests were made with S. epidermis in static and dynamic conditions. Between 3 and 48 hours of culture, bacteria were removed from the surfaces and then viable plate counting was performed. No significant differences were observed between the samples. Microscopic observations (MEB, CSLM) seemed to confirm this result. Other bacteria with different morphologies were tested (S. aureus, K. pneumoniae, P. aeruginosa): bacterial adhesion was similar for the two surfaces. Therefore, we can conclude that our developed ABS surfaces with these specific nanopillars do not have an anti-adhesion effect on the tested bacteria. Recent researches showed that spacing between nanopillars is a critical factor on bacterial adhesion. The following step of our work would be to test new nanostructures using AAO molds with bigger interpore distance
Style APA, Harvard, Vancouver, ISO itp.
32

Hammache, Djilali. "Récepteurs glycolipidiques du VIH-1 à la surface des cellules CD4- (cellules épithéliales intestinales et spermatozoi͏̈des) et CD4+ (lymphocytes et macrophages) : analyse moléculaire des interactions virus-récepteurs au niveau des microdomaines de glycolipides reconstitués in vitro". Aix-Marseille 3, 1999. http://www.theses.fr/1999AIX30023.

Pełny tekst źródła
Streszczenie:
Les glycolipides sont des constituants du feuillet externe de la membrane plasmique des cellules procaryotes et eucaryotes. Ils interviennent dans de nombreux processus cellulaires, tels que la differenciation, la proliferation, la transduction du signal et la reconnaissance de differents ligands (hormones, champignons, virus, bacteries et toxines bacteriennes). Au cours de cette these, nous avons analyse l'interaction de la glycoproteine d'enveloppe de surface du vih-1 (gp120) et du vih-2 (gp105) avec differents glycolipides exprimes principalement par les cellules epitheliales intestinales, mais aussi par d'autres cibles cellulaires du virus : spermatozoides, lymphocytes cd4 + et macrophages. A l'aide d'analogues synthetiques de glycolipides, nous avons confirme l'implication de la boucle v3 de la gp120 dans la reconnaissance du galactosylceramide (galcer) par la gp120, et donc dans le mecanisme d'infection des cellules intestinales ht-29. L'interaction gp120-glycolipide a ete etudiee a l'aide des films monomoleculaires mimant les microdomaines membranaires de glycolipides. Cette etude a confirme le role du galcer -hydroxyle dans l'interaction du vih avec l'epithelium intestinal. Ce recepteur est implique dans la fusion du virus (vih-1 et vih-2) avec la membrane plasmique des cellules intestinales alors que le 3'sulfogalcer (ou sulfatide), bien que reconnaissant la gp120, n'est pas fonctionnel. Nous avons egalement identifie trois nouveaux recepteurs glycolipidiques du vih : le galactosyl-acyl-alkyl-glycerol des spermatozoides, le globotriaosylceramide (gb3) et le gm3 des cellules cd4 + (lymphocytes et macrophages). L'adhesion du virus aux microdomaines de gm3 ou de gb3 faciliterait la formation du complexe cd4-gp120-corecepteur (cxcr4 pour gb3, ccr5 pour gm3).
Style APA, Harvard, Vancouver, ISO itp.
33

Khokhlova, Mariya. "Interactions of cells with oxide thin films". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC241.

Pełny tekst źródła
Streszczenie:
Dans le présent travail, nous montrons comment des couches minces d'oxydes peuvent être utilisées comme surfaces bioactives, un domaine de recherche encore peu exploré. À cet effet, des couches minces de TiO2, Al2O3, VOx et quelques autres oxydes ont été déposés sur des substrats de verre par la technique d'ablation laser pulsé (PLD), et l'adhésion, la prolifération et la différenciation de cellules souches mésenchymateuses humaines dérivées de moelle osseuse ont été évaluées. Le comportement des cellules a été analysé par rapport aux principaux paramètres de surface tels que la chimie, la mouillabilité, la morphologie et l'épaisseur des films. Nos résultats indiquent que les couches minces de TiO2 et Al2O3 peuvent non seulement favoriser l'adhésion et la croissance des cellules souches mésenchymateuses, mais peuvent également être utilisées pour influencer la différenciation ostéogénique et chondrogénique. En outre, l'effet de films minces d'oxydes sur l'adhésion et la croissance de lignées de cellules cancéreuses a été examiné. Nous avons montré que la culture de ces lignées cellulaires sur des films minces affecte leur croissance et, par conséquent, pourrait être une méthode utile pour effectuer des tests de dépistage des drogues.Cette étude fournira une meilleure compréhension de la corrélation entre la chimie de surface et la réponse cellulaire, qui a un role important dans le domaine de la fabrication de biomatériaux
In the present work we demonstrate how oxide thin films can be used as bioactive surfaces, a field of research which is still underexplored. For this purpose, thin films of TiO2, Al2O3, VOx and some others were deposited on glass substrates using the Pulsed Laser Deposition (PLD) technique, and adhesion, proliferation and differentiation of human bone marrow-derived mesenchymal stem cells were evaluated. Cell behavior was analyzed with respect to the various key surface parameters such as chemistry, wettability, morphology and the thickness of films.Our results indicate that thin films of TiO2 and Al2O3 can not only support mesenchymal stem cells adhesion and growth, but also can be used to influence osteogenic and chondrogenic differentiation path. Additionally, effect of oxide thin films on adhesion and growth of cancer cell lines was studied. We showed that culturing these cell lines on thin films affects their growth and, therefore, could be a valuable method to perform screening tests with drugs.This work will provide a better understanding of correlation between surface chemistry and cellular response, which has a high significance in the field of biomaterials fabrication
Style APA, Harvard, Vancouver, ISO itp.
34

Dallanegra, Anne. "Étude de l'activation lymphocytaire dans l'environnement épidermique : régulation de l'expression de surface du complexe CD3/TCR et implications biologiques : rôle des cytokines dans les interactions entre les lymphocytes et les cellules épidermiques". Lyon 1, 1992. http://www.theses.fr/1992LYO1T182.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
35

Stanciuc, Ana-Maria. "In vitro evaluation of cell-material interactions on bioinert ceramics with novel surface modifications for enhanced osseointegration". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI053/document.

Pełny tekst źródła
Streszczenie:
Cette thèse porte sur l'évaluation de la réponse cellulaire in vitro vis-à-vis de différentes stratégies de modification de surface pour améliorer la capacité d’ostéointégration de céramiques bioinertes pour implants orthopédiques et dentaires. Premièrement des surfaces l'alumine-zircone avec différentes micro-rugosités obtenues par moulage par injection ont été étudiées. Le comportement d'ostéoblastes primaires humains (obtenus à partir de têtes de fémurs soumis à arthroplastie) a été étudié sur les surfaces telles quelles ou modifiées par traitement avec acide hydrofluorique. La micro-rugosité a eu seulement un effet mineur sur la réponse ostéoblastique tandis que la combinaison de micro- et nano-rugosité a eu un effet synergique sur la maturation ostéoblastique. Cette stratégie de modification de surface ouvre la voie vers des cupules acétabulaires céramiques monoblocs directement ostéo-intégrées. Deuxièmement, le robocasting (une technique d’impression 3D) a été exploré pour la production de structures macroporeuses en alumine-zircone avec une haute reproductibilité et contrôle architectural. Les structures imprimées ont présentées une topographie aux multiples niveaux grâce au design et les conditions de frittage. Les ostéoblastes ont pu s'attacher sur les structures 3D mais la préservation des cellules à l’intérieur des scaffolds sur le long terme reste à améliorer. Des techniques de sélection rapide de modifications de surface ont fait l'objet de la dernière partie de cette thèse. Deux différentes stratégies ont été utilisées sur la zircone: laser femtoseconde pour la production de multiples motifs sur un échantillon unique et échantillons avec un gradient de rugosité via le contrôle du temps d’attaque chimique. La morphologie des cellules souches humaines a permis d'avoir un indicateur précoce de la lignée de différentiation cellulaire. En conclusion, les différentes techniques de modification de surface de zircone et alumine-zircone utilisées à travers la thèse peuvent moduler l’interaction cellule-matériau en stimulant la différentiation ostéoblastique de cellules souches et la maturation des ostéoblastes
The focus of this PhD thesis is the in vitro evaluation of cell-material interactions on bioinert ceramics with novel surface modifications for enhanced osseointegration of orthopaedic and dental implants. Firstly, alumina-zirconia surfaces with different micro-roughnesses obtained by injection moulding were studied. The behaviour of human primary osteoblasts (hObs) obtained from patients undergoing total hip replacements was studied on the different micro-rough ZTA surfaces and on combined micro-/nano-rough surfaces modified by hydrofluoric acid treatment. Micro-roughness alone had minor effects on hOb response while the combination micro-/nano-roughness induced a synergic effect on hOb maturation. This latter surface modification technique opens the way to the fabrication of ceramic acetabular cups with direct implantation capabilities. Secondly, robocasting (a 3D printing technique) was explored for the fabrication of a alumina-zirconia macroporous structures with high reproducibility and control of the architecture. Roughness at different scales was observed for the 3D structures due to the scaffold design and to the low temperature sintering conditions. Osteoblasts were able to attach on the 3D structures but cell retention at long term needs further optimization. Rapid screening of cell-material interactions was the subject of the last part of the thesis. Two different strategies were tested on zirconia: femtosecond laser to produce multiple patterns on a single sample and samples with a roughness gradient by the control of chemical etching time. Stem cell morphology was used as an early marker of cell differentiation lineage. In conclusion, the different surface modification techniques of zirconia and alumina-zirconia surfaces used in the thesis allow the modulation of cell-material interactions by stimulating stem cells osteogenesis and osteoblast maturation
Style APA, Harvard, Vancouver, ISO itp.
36

Wang, Chao. "Renewable Natural Polymer Thin Films and Their Interactions with Biomacromolecules". Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64909.

Pełny tekst źródła
Streszczenie:
Natural polymers from renewable resources have attracted increasing interest as candidates for renewable energy and functional materials. In this work, the interactions between natural polymer thin films and biomacromolecules were studied via surface analysis techniques, such as a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM). Chitinase activity on regenerated chitin (RChitin) films was studied by QCM-D and AFM. The optimal temperature and pH for chitinase activity on surfaces determined by QCM-D and AFM were consistent with bulk solution studies in the literature. Results from QCM-D also indicated that chitinase showed higher activity on fully acetylated chitin than highly deacetylated chitosan. Nanocrystalline chitin (Chitin NC) thin films were prepared by spincoating a nanocrystalline chitin colloidal suspension onto solid surfaces. Solvent exchange experiments via QCM-D with H2O/D2O revealed that Chitin NC films had more water than RChitin films of similar thickness. Results from QCM-D demonstrated that Chitin NC films had high bovine serum albumin loading capacity, and chitinase not only degraded, but also caused swelling of the chitin nanocrystals. Adsorption of human serum albumin (HSA) and fibrinogen (HFN) onto bare gold, regenerated cellulose (RC) and RChitin thin films was studied by SPR and QCM-D. Studies by SPR indicated that HSA and HFN formed close-packed monolayers on gold surfaces and sub-monolayers on polysaccharide surfaces, and the adsorption affinity of HSA for polysaccharide surfaces was greater than that of HFN. Results from QCM-D and SPR showed that the protein layers on polysaccharide surfaces had more associated water than proteins on gold surfaces. The dehydrogenative polymerization of monolignols catalyzed by physically immobilized horseradish peroxidase was investigated using QCM-D and AFM. Results from QCM-D and AFM showed that coniferyl and p-coumaryl alcohol underwent polymerization directly, whereas sinapyl alcohol required the addition of a nucleophile for polymerization. Studies by QCM-D and AFM also indicated that the surface-initiated polymerization was greatly affected by the support surface, monolignol concentration, hydrogen peroxide concentration and temperature. Thin films of dehydrogenative polymer (DHP), kraft (KL), organosolv (OL) and milled wood (MWL) lignins were used to study the enzymatic degradation of lignin mediated by lignin peroxidase (LiP) and manganese peroxidase (MnP). Results from QCM-D showed that the initial rates for degradation catalyzed by LiP increased in the order: KL < OL < MWL < guaiacyl DHP (G-DHP) < p-hydroxyphenyl DHP (H-DHP). In contrast, manganese peroxidase only degraded DHP films with a faster initial rate for G-DHP than H-DHP. Adsorption of hemicelluloses onto KL, OL and MWL thin films was studied by QCM-D and SPR. Results from QCM-D showed that hemicelluloses with different structures displayed very different adsorption behavior. Adsorption isotherms from QCM-D and SPR indicated that xyloglucan possessed stronger affinity for KL and OL films than MWL films. Data from QCM-D and SPR revealed that xyloglucan formed less hydrated layers on lignin surfaces compared to RC surfaces, and the adsorbed xyloglucan layers on different lignin films had similar percentages of coupled water.
Ph. D.
Style APA, Harvard, Vancouver, ISO itp.
37

Biagi, Sofia. "A mesoscale investigation of the endothelial glycocalyx and its interaction with blood flow". Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY083/document.

Pełny tekst źródła
Streszczenie:
Une brosse de polymères est une matrice dense de macromolécules greffées à une surface donnée. Au-delà des brosses synthétiques réalisées en laboratoire, on trouve des exemples très variés dans la nature: un exemple emblématique est le glycocalyx endothélial, décorant la surface interne des vaisseaux sanguins des mammifères. L'interaction de cette structure avec le plasma et les cellules sous écoulement n'est encore que très partiellement explorée. La présente thèse propose, grâce à des simulations de "Dissipative Particle Dynamics", un modèle coarse-grained pour une analyse auto-cohérente d'une brosse polymérique dense sous écoulement parabolique. Cette étude mésoscopique met en évidence l'importance des effets collectifs entre molécules, entraînée par l'hydrodynamique, et propose des nouvelles interprétations à la phénoménologie du système brosse-écoulement. Des résultats préliminaires sont également produits pour l'interaction sous écoulement entre un objet mésoscopique déformable (prototype d'un globule rouge) et les polymères greffés
Polymer brushes are dense matrices of grafted macromolecules. In addition to brushes finely designed in laboratory, various examples are offered by Nature, as the endothelial glycocalyx, decorating the lumen of mammalian blood vessels. The interaction of such network with the flowing plasma and cells is still partially unknown.The present thesis, by mean of Dissipative Particle Dynamics simulations, proposes a coarse-grained model for the self-consistent analysis of a dense polymer brush under parabolic flow. Our mesoscale investigation highlights the relevance of collective effects, driven by hydrodynamics, and proposes novel interpretations regarding the rich phenomenology of the brush-flow system.Preliminary results are also provided for the interplay between a mesoscopic deformable flowing object (prototype of a red blood cell) and the grafted polymers
Style APA, Harvard, Vancouver, ISO itp.
38

Peyrot, Tom. "Dipole dipole interactions in dense alkali vapors confined in nano-scale cells". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLO012/document.

Pełny tekst źródła
Streszczenie:
Les vapeurs atomiques confinées dans des cellules nanométriques constituent une plateforme intéressante pour la réalisation de senseurs atomiques. Dans cette thèse, nous étudions l’interaction entre la lumière et un ensemble d’atomes d’alcalins dans une telle cellule. Nous nous concentrons sur les phénomènes qui pourraient modifier la réponse optique du système et ainsi affecter la sensibilité du senseur. Premièrement, nous étudions la réponse non locale à la lumière induite par le mouvement des atomes dans la vapeur thermique. Quand la distance de relaxation des atomes excède la taille de la cellule, la réponse optique dépend de la taille du système. En transmission, nous avons montré que cela entraine une modification des propriétés de la vapeur avec une période égale à la longueur d’onde de la transition optique. Nous avons ensuite montré que lorsque la densité augmente, la réponse redevient locale. De plus, dans ce régime dense, l’interaction dipôle-dipôle résonnante engendre des déplacements de fréquences collectifs pour des ensembles sub-longueur d’onde. Nous avons démontré que ces shifts sont induits par la cavité formée par la cellule, clarifiant ainsi un débat de plus de 40 ans. Pour ce faire, nous avons développé un modèle pour extraire les effets de la densité déconvolués de ceux de la cavité. Proche des surfaces, la réponse optique des atomes est aussi impactée par l’interaction de van der Waals. Nous avons introduit une nouvelle méthode pour extraire avec précision la force de cette interaction. Nous avons également construit une nouvelle génération de nano-cellules super-polies en verre et enfin comparé les propriétés spectrales en transmission et spectroscopie hors d’axe
Alkali vapors confined in nano-scale cells are promising tools for future integrated atom-based sensor. In this thesis, we investigate the interaction between light and an ensemble of atoms confined in a nano-geometry. We focus on the different processes that can modify the optical response of the atomic ensemble and possibly affect the sensitivity of a sensor based on that technology. First, we study the non-local response of atoms to a light excitation due the atomic motion in thermal vapors. When the distance over which the atoms relaxes is larger than the size of the cell, the optical response depends on the size of the system. We have observed that for transmission spectroscopy, this leads to a periodic modification of the optical response with a period equal to the wavelength of the optical transition. Subsequently we showed that when the density of atom increases, the atomic response becomes local again. In this dense regime, the resonant dipole-dipole interaction in a sub-wavelength geometry leads to collective frequency shifts of the spectral lines. We demonstrate that these shifts were induced by the cavity formed by the cell walls, hence clarifying a long-standing issue. We developed a model to extract the density shifts deconvolved from the cavity effects. Close to a surface, the optical response is also affected by the van der Waals atom-surface interaction. We introduced a new method to extract precisely the strength of this interaction. We also developed a new generation of super-polished glass nano-cells and we presented promising spectroscopic signals. Finally, using these cells, we have compared transmission and off-axis spectroscopic techniques
Style APA, Harvard, Vancouver, ISO itp.
39

DE, PARSEVAL AYMERIC. "Le virus de l'immunodeficience feline : regulation transcriptionnelle, role de la glycoproteine cd9 dans la replication virale, et interaction de la glycoproteine de surface (gp95) avec la cellule hote". Paris 7, 2001. http://www.theses.fr/2001PA077046.

Pełny tekst źródła
Streszczenie:
Le virus de l'immunodeficience feline (fiv) est un lentivirus lymphotrope d'hote non-primate considere comme un modele animal tres prometteur de l'infection par le virus de l'immunodeficience humaine (hiv). De nombreuses etapes de la replication du fiv sont encore mal connues. Par notre travail de these, nous avons tente d'elucider la regulation transcriptionnelle et le tropisme cellulaire de ce virus. Nous avons caracterise la proteine transactivatrice (ftat) du fiv. Ftat est similaire a la proteine tat des lentivirus des ongules, elle possede une activite tar-independante, et transactive faiblement le promoteur du fiv. Les sites impliques dans la transactivation par ftat ont des sequences consensus pour ap-1, c/ebp et atf. La glycoproteine cd9 a ete proposee comme un recepteur cellulaire putatif du fiv sur la base d'etudes d'inhibition de l'infection par un anticorps anti-cd9. Nous avons montre que cet anticorps agit a une etape post-entree du cycle de replication sans inhiber l'interaction du virus avec la cellule hote. Nous avons cibler l'activite anti-virale de cet anticorps a l'etape de l'assemblage et/ou du bourgeonnement des particules virales. Le chimiorecepteur cxcr4 est un (co)recepteur pour lefiv. Toutefois, certaines lignees cellulaires cxcr4+ sont refractaires a l'infection par des souches primaires de fiv. Pour mieux comprendre le role de cxcr4 comme recepteur principal ou corecepteur, nous avons produit la glycoproteine de surface (gp95) du fiv sous la forme d'une immunoadhesine (gp95-fc). L'attachement cellulaire de la gp95-fc a ete etudie par cytometrie de flux en utilisant differentes lignees cellulaires. Nos travaux ont montre que l'interaction de la gp95-fc avec la cellule hote fait intervenir le chimiorecepteur cxcr4, les heparanes sulfates et une proteine non-identifee de 40 kda, et depend de l'origine virale de la gp95 (souche primaire versus souche adaptee en laboratoire) mais egalement de la lignee cellulaire utilisee (lymphoide versus non-lymphoide).
Style APA, Harvard, Vancouver, ISO itp.
40

Shetty, Pramod. "Study on Supramolecular Gel Lubricants". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-76007.

Pełny tekst źródła
Streszczenie:
Most of the rolling element bearings are lubricated with Grease lubricant. Generally, the grease is expected to serve for life. The major causes of the bearing failure are due to the failure of the lubrication. The grease will experience creeping, oil permeation, oil separation etc. The separated oil will be lost permanently from the bearing. The widely used grease for general application is the lithium grease. The thickener of the grease consists covalent bond. When the grease is sheared, the breakage of the covalent bond will be permanent, resulting in the permanent loss of the rheological properties. The gels have unique properties such as thermal reversibility, viscoelasticity and thixotropy. They become mobile under shear stress and solidify again when the shear stress is removed. This property can be harnessed to avoid the base oil creeping, oil permeation, leakage in gears and bearings. Due to the presence of the polar group in the gels, they form a good tribo film and prevent the wear.  Under the shear stress, weak supramolecular interactions will be distorted, and this leads to the release of the oil and they re-form the structure after a certain period of rest. When the gel is in the solid-state, it will avoid creeping and evaporation. Many classes of gels are either derived from natural sources or from environmentally friendly materials. Thus, the lubricant formed out of gel would effectively solve both environmental as well as lubrication problems. In this work, supramolecular gel lubricants were prepared out of fully green, cellulose derivatives and starch hydrolysates. The non-ionic hydroxyethyl cellulose (HEC) and anionic sodium carboxymethyl cellulose (NaCMC) were chosen to understand the effect of ionic and non-ionic gelators on the rheological and the tribological parameters. Traditionally fat was used as a lubricant, now, in food industry various fat replacers are being used. To study whether the fat replacers can act as a thickener, Dextrin and maltodextrins were chosen.  Dextrin and maltodextrin with the different DE values were selected to understand the influence of molecular weight on gelation and tribological performance.  Inspired by the recent developments and advantages of aqueous lubrication, mixer of water and poly(ethylene glycol) 200 (PEG 200) is chosen as the base fluid. It was found that a very small amount of gelator can increase the viscosity of the PEG/water to several orders. The thermal stability of the gels was studied using thermogravimetric analysis (TGA) and found that gels can increase the thermal stability of the base fluid. FTIR results showed the formation of a non-covalent bond between the PEG molecules and water. It is shown that anionic gelator will result in producing low friction and wear in comparison to non-ionic gelator. The possible tribo-film formation due to the negative charge in the NaCMC molecules is attributed to these results. The very low friction and low wear was exhibited by the dextrin and maltodextrin gels. It is proposed that this could be due to the microspherical particles of gels which can act as nano bearings. It was found that choosing the optimum concentration of the gelator is important to reduce friction and wear. The higher gelator concentration will form the hard gel, which cannot flow and replenish the sliding contact, resulting in the starved lubrication. This will cause high wear and friction. These gel lubricants can be used in food, pharmaceutical and biomedical industries.
Style APA, Harvard, Vancouver, ISO itp.
41

Lintz, Michel. "MESURE DE LA VIOLATION DE LA PARITE SUR LA TRANSITION 6S-7S DU CESIUM PAREMISSION STIMULEE DANS UNE VAPEUR ATOMIQUE". Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00011127.

Pełny tekst źródła
Streszczenie:
Le travail présenté ici a pour but l'amélioration des tests de basse énergie des interactions faibles à courant neutre. Il a porté sur la mise au point d'une expérience à même de réaliser une mesure d'un dipôle de transition violant la parité dans une vapeur de césium en cellule avec une précision de 1% sur un montage de polarimétrie laser pompe-sonde. Son caractère original tient à la détection d'une transition interdite dans une vapeur, non plus par fluorescence comme l'ont fait toutes les expériences antérieures, mais par l'émission stimulée par le faisceau sonde, ce qui amplifie l'asymétrie à mesurer lorsque l'amplification du faisceau sonde est importante. De nombreux aspects expérimentaux ont nécessité de repousser les limites de l'expérimentation: amélioration des techniques de polarimétrie avec des lasers en impulsions, conception et préparation des cellules, maîtrise des effets de surface, maîtrise et réduction des effets liés aux dimères de césium, étude des champs parasites, puis de leur contrôle/réduction. Mais par-delà le développement de savoir-faire spécifiques, ce travail i) a permis d'amener l'expérience VPA à un stade où la précision de la mesure déjà effectuée est de 2,6%, et où le rapport signal/bruit atteint permet de se lancer dans une mesure à 1%; ii) a donné lieu à des expériences originales comme la photo-destruction des dimères d'une vapeur de césium, l'observation en champ nul et sans background de la transition 6S-7S en champ nul, la réalisation de cellules spectroscopiques "sans pertes par réflexion", la mise en évidence, par diffraction laser, des marches monoatomiques d'une surface vicinale ou encore des méthodes originales de détection homodyne du signal de réflexion sélective ou de mesure absolue de sections efficaces; iii) propose une méthode susceptible de permettre une mesure VPA à 0,1%, ainsi qu'une exploration de ce que permettrait le refroidissement laser pour l'étude des transitions interdites.
Style APA, Harvard, Vancouver, ISO itp.
42

Bai, Hongjuan. "Bio-colloidal transfer in saturated and unsaturated porous media : influence of the physical heterogeneity of the porous medium and cell properties on bacteria transport and deposition mechanisms". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2336/document.

Pełny tekst źródła
Streszczenie:
La compréhension du transport et du dépôt bio-colloïdal dans un milieu poreux présente un grand intérêt dans les applications environnementales, en particulier pour le contrôle de la bio-remédiation des sols et la protection des ressources en eau souterraine. Afin de mieux évaluer et prévenir les risques de contamination de la nappe phréatique et de proposer des solutions adéquates de remédiation, il est nécessaire d’avoir une bonne compréhension des mécanismes qui contrôlent le transport et le dépôt des bactéries dans les milieux poreux saturés et non saturés. L’objectif des ces travaux de thèse est d’étudier le rôle de l’hétérogénéité physique du milieu poreux (distribution granulométrique, porosité…) et de l’hydrodynamique du milieu sur les mécanismes de transport et de dépôt de particules bio-colloïdales, tout en prenant en compte l’impact des propriétés de cellules bactériennes sur ces mécanismes. Des expériences de traçage et d’injection de suspensions bactériennes ont été menées à l’échelle de colonnes de laboratoire dans trois milieux poreux avec une porosité et une distribution de taille de pore distincte. Afin de caractériser l’écoulement dans les milieux poreux, un soluté non-réactif a été utilisé comme traceur de l’eau. Trois souches bactériennes ont été utilisées pour préparer les suspensions bactériennes : une bactérie mobile (Escherichia coli), et deux non mobiles (Klebsiella sp. et R. rhodochrous). La caractérisation des propriétés cellulaires (telles que la taille et la forme des cellules, le potentiel zêta, la motilité et l'hydrophobicité) a été effectuée pour chaque souche. Des simulations numériques ont été réalisées en utilisant le code de calcul HYDRUS-1D afin de modéliser l’écoulement et d’estimer les paramètres de transport et de dépôt des bactéries. Ces derniers ont été explorés afin d'identifier le mode de transport bactérien et les mécanismes physico-chimiques ou physiques impliqués dans le dépôt des bactéries. Des expériences supplémentaires à l'échelle des pores ont été réalisées à l'aide de dispositifs microfluidiques conçus à cet effet. Un calcul théorique des différentes interactions entre les bactéries et le milieu poreux aux interfaces air/eau/solide a été effectué pour compléter les résultats expérimentaux ainsi que ceux issus de la modélisation numérique. Ainsi, les énergies d’interactions telles que les forces de van der Waals, électrostatiques de double couche, hydrophobes, stériques, capillaires et hydrodynamiques, impliquées dans le dépôt de bactéries ont été calculées pour décrire les interactions bactéries-interfaces afin d'identifier leur impact relatif sur le dépôt physico-chimique et physique des bactéries. Les résultats expérimentaux et la modélisation numérique ont mis en évidence un écoulement non uniforme, dépendant de la taille des grains ainsi que de la distribution de la taille des pores du milieu poreux. Pour un milieu poreux donné, l’écoulement devient plus dispersif quand la teneur en eau du milieu diminue. Ceci est dû à l’augmentation de la tortuosité du milieu, du fait de la présence de l’air dans les pores. Le transport des bactéries diffère de celui du traceur de l’eau. Le dépôt bactérien a été fortement influencé par la géométrie du réseau poral du milieu, les propriétés cellulaires et le degré de saturation en eau. Le piégeage physique et physico-chimique sont des mécanismes qui doivent être pris en compte pour bien décrire le dépôt bactérien, mais leur importance sur les mécanismes de dépôt est étroitement liée aux propriétés du milieu poreux et des cellules. Ces travaux mettent en évidence l’effet simultané des propriétés cellulaires, des propriétés physiques (granulométrie et distribution de taille de pores) et de l'hydrodynamique du milieu poreux sur les mécanismes de transport et de dépôt bactérien. Le calcul des différentes énergies d’interaction a permis d’identifier leur importance sur les mécanismes de dépôt bactérien
The investigation of the transport and retention of bacteria in porous media has a great practical importance in environmental applications, such as protection of the surface and groundwater supplies from contamination, risk assessment from microorganisms in groundwater, and soil bioremediation. The aim of this study is to gain a fundamental understanding of the mechanisms that control bacteria transport and deposition in saturated and unsaturated porous media. Laboratory tracer and bacteria transport experiments at Darcy scale were performed in three porous media with distinct pore size distribution in order to investigate and quantify water and bacteria transport process under steady state flow conditions. A conservative solute was used as water tracer to characterize water flow pathways through porous media. A gram negative, motile Escherichia coli, a gram negative, non-motile Klebsiella sp. and a gram positive, non-motile R. rhodochrous were selected for the transport experiments. Characterization of cell properties (such as cell size and shape, zeta potential, motility and hydrophobicity) was performed for each strain. Numerical simulations with HYDRUS-1D code were performed to characterize water flow and to estimate bacteria transport and deposition parameters. The later were explored to identify bacteria flow patterns and physicochemical or physical mechanisms involved in bacteria deposition. To provide a better understanding of the mechanisms involved on bacteria transport and deposition, pore scale experiments were carried out by using microfluidic devices, designed for this purpose. The information obtained from laboratory experiments and numerical modeling was improved by theoretical calculation of different interactions between bacteria and porous media at air/water/solid interfaces. DLVO and non-DLVO interactions such as hydrophobic, steric, capillary and hydrodynamic forces involved in bacteria deposition were considered to describe bacteria-interface interactions in order to identify their relative impact on physicochemical and physical deposition of bacteria. Results obtained through both laboratory experiments and numerical simulationsoutlined non-uniform flow pathways, which were dependent on both grain/pore size as well as pore size distribution of the porous media. For a given porous medium, water flow patterns became more non-uniform and dispersive with decreasing water saturation due to the presence of air phase, which lead to an increase of the tortuosity of the flow pathways under unsaturated conditions. Bacteria transport pathways were different from the tracer transport, due to size exclusion of bacteria from smaller pore spaces and bacteria motility. Bacteria deposition was greatly influenced by pore network geometry, cell properties and water saturation degree. Both physical straining and physicochemical attachment should be taken into account to well describe bacteria deposition, but their importance on bacteria deposition is closely linked to porous media and cell properties. The results obtained in this work highlighted the simultaneous role of cell properties, pore size distribution and hydrodynamics of the porous media on bacteria transport and deposition mechanisms. The calculation of DLVO and non-DLVO interactions showed that bacteria deposition in saturated and unsaturated porous media was influenced by both kinds of interactions
Style APA, Harvard, Vancouver, ISO itp.
43

Tavares, Lucas Alves. "O envolvimento da proteína adaptadora 1 (AP-1) no mecanismo de regulação negativa do receptor CD4 por Nef de HIV-1". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/17/17136/tde-06012017-113215/.

Pełny tekst źródła
Streszczenie:
O Vírus da Imunodeficiência Humana (HIV) é o agente etiológico da Síndrome da Imunodeficiência Adquirida (AIDS). A AIDS é uma doença de distribuição mundial, e estima-se que existam atualmente pelo menos 36,9 milhões de pessoas infectadas com o vírus. Durante o seu ciclo replicativo, o HIV promove diversas alterações na fisiologia da célula hospedeira a fim de promover sua sobrevivência e potencializar a replicação. A rápida progressão da infecção pelo HIV-1 em humanos e em modelos animais está intimamente ligada à função da proteína acessória Nef. Dentre as diversas ações de Nef está a regulação negativa de proteínas importantes na resposta imunológica, como o receptor CD4. Sabe-se que esta ação resulta da indução da degradação de CD4 em lisossomos, mas os mecanismos moleculares envolvidos ainda são totalmente elucidados. Nef forma um complexo tripartite com a cauda citosólica de CD4 e a proteína adaptadora 2 (AP-2), em vesículas revestidas por clatrina nascentes, induzindo a internalização e degradação lisossomal de CD4. Pesquisas anteriores demonstraram que o direcionamento de CD4 aos lisossomos por Nef envolve a entrada do receptor na via dos corpos multivesiculares (MVBs), por um mecanismo atípico, pois, embora não necessite da ubiquitinação de carga, depende da ação de proteínas que compõem os ESCRTs (Endosomal Sorting Complexes Required for Transport) e da ação de Alix, uma proteína acessória da maquinaria ESCRT. Já foi reportado que Nef interage com subunidades dos complexos AP-1, AP-2, AP-3 e Nef não parece interagir com subunidades de AP-4 e AP-5. Entretanto, o papel da interação de Nef com AP-1 e AP-3 na regulação negativa de CD4 ainda não está totalmente elucidado. Ademais, AP-1, AP-2 e AP-3 são potencialmente heterogêneos devido à existência de isoformas múltiplas das subunidades codificadas por diferentes genes. Todavia, existem poucos estudos para demonstrar se as diferentes combinações de isoformas dos APs são formadas e se possuem propriedades funcionais distintas. O presente trabalho procurou identificar e caracterizar fatores celulares envolvidos na regulação do tráfego intracelular de proteínas no processo de regulação negativa de CD4 induzido por Nef. Mais especificamente, este estudo buscou caracterizar a participação do complexo AP-1 na modulação negativa de CD4 por Nef de HIV-1, através do estudo funcional das duas isoformas de ?-adaptina, subunidades de AP-1. Utilizando a técnica de Pull-down demonstramos que Nef é capaz de interagir com ?2. Além disso, nossos dados de Imunoblot indicaram que a proteína ?2-adaptina, e não ?1-adaptina, é necessária no processo de degradação lisossomal de CD4 por Nef e que esta participação é conservada para degradação de CD4 por Nef de diferentes cepas virais. Ademais, por citometria de fluxo, o silenciamento de ?2, e não de ?1, compromete a diminuição dos níveis de CD4 por Nef da membrana plasmática. A análise por imunofluorêsncia indireta também revelou que a diminuição dos níveis de ?2 impede a redistribuição de CD4 por Nef para regiões perinucleares, acarretando no acúmulo de CD4, retirados por Nef da membrana plasmática, em endossomos primários. A depleção de ?1A, outra subunidade de AP-1, acarretou na diminuição dos níveis celulares de ?2 e ?1, bem como, no comprometimento da eficiente degradação de CD4 por Nef. Além disso, foi possível observar que, ao perturbar a maquinaria ESCRT via super-expressão de HRS (uma subunidade do complexo ESCRT-0), ocorreu um acumulo de ?2 em endossomos dilatados contendo HRS-GFP, nos quais também detectou-se CD4 que foi internalizado por Nef. Em conjunto, os resultados indicam que ?2-adaptina é uma importante molécula para o direcionamento de CD4 por Nef para a via ESCRT/MVB, mostrando ser uma proteína relevante no sistema endo-lisossomal. Ademais, os resultados indicaram que as isoformas ?-adaptinas não só possuem funções distintas, mas também parecem compor complexos AP-1 com diferentes funções celulares, já que apenas a variante AP-1 contendo ?2, mas não ?1, participa da regulação negativa de CD4 por Nef. Estes estudos contribuem para o melhor entendimento dos mecanismos moleculares envolvidos na atividade de Nef, que poderão também ajudar na melhor compreensão da patogênese do HIV e da síndrome relacionada. Em adição, este trabalho contribui para o entendimento de processos fundamentais da regulação do tráfego de proteínas transmembrana no sistema endo-lisossomal.
The Human Immunodeficiency Virus (HIV) is the etiologic agent of Acquired Immunodeficiency Syndrome (AIDS). AIDS is a disease which has a global distribution, and it is estimated that there are currently at least 36.9 million people infected with the virus. During the replication cycle, HIV promotes several changes in the physiology of the host cell to promote their survival and enhance replication. The fast progression of HIV-1 in humans and animal models is closely linked to the function of an accessory protein Nef. Among several actions of Nef, one is the most important is the down-regulation of proteins from the immune response, such as the CD4 receptor. It is known that this action causes CD4 degradation in lysosome, but the molecular mechanisms are still incompletely understood. Nef forms a tripartite complex with the cytosolic tail of the CD4 and adapter protein 2 (AP-2) in clathrin-coated vesicles, inducing CD4 internalization and lysosome degradation. Previous research has demonstrated that CD4 target to lysosomes by Nef involves targeting of this receptor to multivesicular bodies (MVBs) pathway by an atypical mechanism because, although not need charging ubiquitination, depends on the proteins from ESCRTs (Endosomal Sorting Complexes Required for Transport) machinery and the action of Alix, an accessory protein ESCRT machinery. It has been reported that Nef interacts with subunits of AP- 1, AP-2, AP-3 complexes and Nef does not appear to interact with AP-4 and AP-5 subunits. However, the role of Nef interaction with AP-1 or AP-3 in CD4 down-regulation is poorly understood. Furthermore, AP-1, AP-2 and AP-3 are potentially heterogeneous due to the existence of multiple subunits isoforms encoded by different genes. However, there are few studies to demonstrate if the different combinations of APs isoforms are form and if they have distinct functional properties. This study aim to identify and characterize cellular factors involved on CD4 down-modulation induced by Nef from HIV-1. More specifically, this study aimed to characterize the involvement of AP-1 complex in the down-regulation of CD4 by Nef HIV-1 through the functional study of the two isoforms of ?-adaptins, AP-1 subunits. By pull-down technique, we showed that Nef is able to interact with ?2. In addition, our data from immunoblots indicated that ?2- adaptin, not ?1-adaptin, is required in Nef-mediated targeting of CD4 to lysosomes and the ?2 participation in this process is conserved by Nef from different viral strains. Furthermore, by flow cytometry assay, ?2 depletion, but not ?1 depletion, compromises the reduction of surface CD4 levels induced by Nef. Immunofluorescence microscopy analysis also revealed that ?2 depletion impairs the redistribution of CD4 by Nef to juxtanuclear region, resulting in CD4 accumulation in primary endosomes. Knockdown of ?1A, another subunit of AP-1, resulted in decreased cellular levels of ?1 and ?2 and, compromising the efficient CD4 degradation by Nef. Moreover, upon artificially stabilizing ESCRT-I in early endosomes, via overexpression of HRS, internalized CD4 accumulates in enlarged HRS-GFP positive endosomes, where co-localize with ?2. Together, the results indicate that ?2-adaptin is a molecule that is essential for CD4 targeting by Nef to ESCRT/MVB pathway, being an important protein in the endo-lysosomal system. Furthermore, the results indicate that ?-adaptins isoforms not only have different functions, but also seem to compose AP-1 complex with distinct cell functions, and only the AP-1 variant comprising ?2, but not ?1, acts in the CD4 down-regulation induced by Nef. These studies contribute to a better understanding on the molecular mechanisms involved in Nef activities, which may also help to improve the understanding of the HIV pathogenesis and the related syndrome. In addition, this work contributes with the understanding of primordial process regulation on intracellular trafficking of transmembrane proteins.
Style APA, Harvard, Vancouver, ISO itp.
44

Fakhari, Tehrani Soudeh. "Propriétés de surface des nanoparticules et interactions avec les cellules endothéliales vasculaires". Thèse, 2019. http://hdl.handle.net/1866/23549.

Pełny tekst źródła
Streszczenie:
Les traitements et l’imagerie des tumeurs cérébrales malignes se sont avérés jusqu’à présent très peu efficaces, en raison de la présence de la barrière hémato-encéphalique (BHE) qui freine le passage des molécules thérapeutiques mais aussi diagnostiques vers les tissus du système nerveux central (SNC). Le développement de vecteurs nanométriques chargés en agents thérapeutiques et capables de traverser la BHE pourrait être une alternative pour améliorer la bio-distribution de principes actifs et d’agent d’imagerie au cerveau. Parmi les différents types de vecteurs proposés, les nanoparticules polymériques (NP) constituées de polymères dibloc comportant un bloc de poly (éthylène glycol) (PEG) pourrait présenter une solution prometteuse pour transporter des actifs à travers la BHE. La PEGylation de la surface des NPs améliore la stabilité colloïdale des NPs. De plus, elle diminue l'adsorption non spécifique des protéines à la surface de NPs (appelée aussi opsonisation). La vitesse de clairance des NPs est ainsi ralentie et les NPs circulent plus longtemps dans le sang. Malgré l’effet bénéfique de la couche de PEG à la surface des NPs, le rôle exact des propriétés de surface liées à la longueur de la chaîne PEG sur l'interaction des NPs avec les cellules endothéliales vasculaires est mal compris. Dans une première partie de ce travail, le rôle de la longueur de PEG sur l'endocytose et la transcytose des NPs a été étudié sur des monocouches de cellules bEnd.3, un modèle in vitro de BHE. Les mécanismes de transport des NPs ont été évalués en utilisant différents inhibiteurs de l'endocytose. La quantification du taux d'endocytose et de transcytose a révélé que l'endocytose et la transcytose des NPs augmentaient avec la longueur de la chaîne de PEG. Les taux d'endocytose et de transcytose les plus élevés ont été observés pour les NPs de PLA-PEG5000 et de PLA-PEG10000. Les résultats de l’étude mécanistique démontrent que la longueur de la chaîne de PEG influence la voie d'endocytose empruntée par les NPs PEGylées à travers un modèle in vitro de BHE. Dans une seconde partie de ce travail, l'effet de la longueur du PEG sur la toxicité des NPs et les processus inflammatoires a été étudié sur deux modèles de monocouche de cellules endothéliales vasculaires, soit les cellules bEnd.3 et HUVEC. L'effet de la longueur des chaînes de PEG sur l'expression des gènes impliqués dans la réponse inflammatoire aux NPs PEGylées a été évalué par qPCR. De plus, le potentiel de génération de dérivés réactifs de l'oxygène (DRO ou ROS) par les NPs a été évalué en utilisant le test cellulaire basé sur l'oxydation de la DCFH-DA. Les résultats démontrent que les NPs PEGylées induisent une augmentation légère et transitoire de l’expression des gènes des cytokines et des chimiokines inflammatoires. Cependant, la longueur des chaînes de PEG ne présente pas un effet significatif sur l'expression des gènes des cytokines et des chimiokines. De plus, nos résultats ne montrent pas l’induction de la génération de ROS par les NPs PEGylées. En résumé, la longueur de chaine de PEG influence le taux d’endocytose et de transcytose. La voie d’endocytose impliquée dans l’internalisation et la transcytose est influencée par la longueur des chaines de PEG. En revanche, les différences de longueur des chaines de PEG ne modulent pas significativement l’expression des cytokines et de chimiokines inflammatoires. Ces résultats devraient contribuer à développer des nanoformulations qui traversent plus efficacement la BHE, tout en minimisant les effets toxiques, notamment inflammatoires sur les cellules endothéliales vasculaires de la BHE. Ces perspectives devront toutefois être confirmées sur des modèles in vivo.
To date, imaging and treatment of brain tumors are proved to be very inefficient due to the presence of the blood-brain barrier (BBB). The (BBB) is a semipermeable barrier which prevents or restrains most therapeutic and diagnostic molecules reach the central nervous system (CNS). Polymeric nanoparticles (NPs) loaded by therapeutics molecules and diagnostic agents could represent a promising solution to help active ingredients to cross the BBB and as a consequence, their biodistribution to the brain could be improved. Polymeric NPs composed of di-block copolymers, such as poly (ethylene glycol) blocks (PEG) that bind to polyester hydrophobic chains, are considered one of the most versatile nanocarriers for transporting therapeutic molecules across the BBB. PEG on the surface of NPs improves the NPs colloidal stability. Furthermore, PEG surface coating decreases the non-specific adsorption of proteins on the surface of NPs (also called opsonization); therefore, the clearance rate of the NPs is slowed down and NPs circulation times in blood is extended. Despite the beneficial effect of the PEG coating on the surface of NPs, the exact role of the surface properties related to the PEG chain length on NPs interactions with the vascular endothelial cells is poorly understood. In first article, the role of PEG chain length on brain vascular endothelial cells endocytosis and transcytosis is investigated on monolayers of bend.3 cells as an in vitro BBB model. The NPs transport mechanisms were then investigated by using different endocytosis inhibitory processes. Our results revealed that NPs endocytosis and transcytosis rates increased with PEG chain length. Higher endocytosis and transcytosis rates were observed for PLA-PEG5000 and PLA-PEG10000 NPs. Moreover, the mechanistic studies demonstrated that the PEG chain length influenced the endocytosis pathway taken by PEGylated NPs through an in vitro model of BBB. In second article, the effect of PEG length on NPs cytotoxicity and inflammatory processes has been investigated in two vascular endothelial cell lines (bEnd.3 and HUVEC). The effect of PEG chain length coating on gene expression that are involved in the inflammation response was investigated by qPCR. Moreover, the potential Reactive Oxygen Species (ROS) generation was evaluated with DCFH-DA probe. The results showed that PEGylated NPs induce a mild and transient activation of inflammatory cytokine and chemokine genes. However, the length of the PEG chains did not modulate significantly gene expression of inflammatory cytokines and chemokines. Furthermore, our results showed that PEGylated NPs did not induce ROS generation. In summary, the chain length of PEG influences the endocytosis and transcytosis rate. The pathway of endocytosis involved in internalization and transcytosis is influenced by the length of PEG chains. In contrast, differences in the length of PEG chains did not significantly modulate the expression of cytokines and inflammatory chemokines. These results contribute to develop nanoformulations that cross the BBB more efficiently while keeping the toxic and inflammatory effects minimal, particularly on the vascular endothelial cells of the BBB. Nevertheless, these perspectives have to be confirmed on in vivo models.
Style APA, Harvard, Vancouver, ISO itp.
45

Pértile, Renata Aparecida Nedel. "Bacterial cellulose: studies on biocompatibility, surface modification and interaction with cells". Doctoral thesis, 2010. http://hdl.handle.net/1822/11194.

Pełny tekst źródła
Streszczenie:
Tese doutoramento em Engenharia Biomédica
A wide variety of biomaterials and bioactive molecules have been applied in tissue engineering as scaffolds in order to provide an appropriate environment to the growth and differentiation of cells. However, creating devices for biological substitutes that enhance the regeneration of neural tissues is still a challenge, because of the difficulty in providing an active stimulation of nerve regeneration. Biological scaffolds can be composed of natural polymers combined with extracellular matrix molecules and have been shown to facilitate the constructive remodeling of many tissues by the establishment of an environment necessary for the regulation of cell processes. In this context, different biomaterials have been used as scaffolds to improve interactions between material/cells and repair neurological damages. In recent years, bacterial cellulose (BC) emerged as a promising biomaterial in tissue engineering due its properties: high crystalinity, wettability, high tensile strength, pure nanofibers network, moldability in situ and simple production. BC has been modified to further enhance cell adhesion and biocompatibility; as an alternative to peptide chemical grafts, BC allow the use of recombinant proteins containing carbohydrates binding domains (CBMs), such as the CBM3, which has affinity by cellulose, representig a attractive way to specifically adsorb bioactive peptides on cellulose surface. The goal of this work was to modify the bacterial cellulose improving the neuronal cell affinity and producing a scaffold with potential to be used in neural tissue engineering. For this purpose, two strategies were used: 1) adhesive peptides fused to a carbohydrate binding domain with affinity to cellulose and; 2) surface modification by nitrogen plasma treatment. Also, in this work, we analized the biocompatibility in a longterm approach of two different types of BC grafts and the effect of BC nanofibers subcutaneously implanted in mice. The recombinant proteins IKVAV-CBM3, exIKVAV-CBM3 and KHIFSDDSSECBM3, were successfully expressed in E. coli, purified and stably adsorbed to the BC membranes. The in vitro results showed that the exIKVAV-CBM3 was able to improve the adhesion of both neuronal and mesenchymal cells (MSC), while IKVAV-CBM3 and KHIFSDDSSE-CBM3 presented only a slight effect on mesenchymal cell adhesion, and no effect on the other cells. The MSCs neurotrophin expression by cells grown on BC membranes modified with the recombinant proteins was also verified. NGF was expressed and released by cells adhered on the BC membranes, creating a microenvironment that promotes neuronal regeneration. The nitrogen plasma treatment did not increase the wettability of the material, but increased the porosity and changed the surface chemistry, as noticed by the presence of nitrogen. XPS analysis revealed the stability of the modified material along time and autoclave sterilization. The cell adhesion and proliferation of HMEC-1 and N1E-115 cells was significantly improved in the plasma treated BC, in contrast with the 3T3 cells, revealing a cell-specific effect. Regarding in vivo studies, the BC implants caused a low inflammatory reaction that decreased along time and did not elicit a foreign body reaction. A tendency for calcification, which may be related to the porosity of the BC implants, was observed. However, this tendency was different depending on the BC tested. Regarding nanofibers implants, after 2 and 4 months post implantation, mostly of injected nanofibers remained in aggregates in the subcutaneous tissue. There was infiltration of cells in these aggregates of nanofibers, mostly macrophages, and there is evidence of phagocytosis of the material by these cells. Moreover, no differences were observed between the controls and implanted animals in thymocyte populations, B lymphocyte precursors and myeloid cells in the bone marrow.BC is a good material to be used as scaffold in tissue engineering applications. However, is still necessary to improve the interaction of cells with the material to obtain a matrix that supports the growth, differentiation and selectivity of cells. In our attempt to enhance and select neuronal attachment to BC, the recombinant proteins produced were able to improve cell adhesion and viability on BC membranes. Also, nitrogen plasma treatment proved to be an effective and economical surface treatment technique, which was also capable to improve the adhesion of endothelial and neuroblast cells to the material. Therefore, the surface modification leads to a better cell affinity with BC, probably contributing for a better biocompatibility in vivo. In the in vivo results, our work points to the necessity to further investigation to verify the tendency to BC to calcify in long-term circumstances. Meanwhile, the BC nanofibers seem to be an innocuous material in mice subcutaneous tissue, and proved to be an eligible material to production of ECM-mimetic grafts.
Actualmente, um grande número de materiais poliméricos com diferentes propriedades estão disponíveis para aplicações biomédicas. Têm sido exploradas várias abordagens com o objetivo de melhorar a interação entre os polímeros e as células, que por ser geralmente inadequada, provoca reações in vivo como inflamações, perdas de tecido local e encapsulamento dos implantes. Entre estas abordagens, a modificação das superfícies, como por exemplo a funcionalização dos materiais com peptídeos imobilizados ou grupos químicos incorporados, mostra vantagens na obtenção de interações específicas das células com os materiais resultando em uma melhoria na sua biocompatibilidade. A celulose bacteriana (CB) tornou-se um biomaterial em foco para aplicações biomédicas devido a sua alta resistência mecânica, hidrofilicidade, alta cristalinidade e pureza, baixo custo de produção e sua característica rede de nanofibras. Além disso, o uso de domínios de ligação à celulose é uma alternativa simples e específica de enxertar peptídeos bioativos à estrutura da celulose possibilitando uma maior afinidade celular. O objectivo deste trabalho foi modificar a CB para aumentar a afinidade de células neuronais, produzindo um scaffold com potencial para ser utilizado em engenharia de tecidos neuronal. Com este propósito, duas estratégias foram utilizadas: 1) o uso de peptídeos de adesão conjugados a um domínio de ligação a carbohidratos (CBM), com afinidade para a celulose e, 2) modificação da CB através do tratamento com plasma de nitrogênio. Também, dentro do âmbito deste trabalho, avaliouse a biocompatibilidade a longo prazo da CB, tanto de implantes como de nanofibras implantados subcutaneamente em camundongos. As proteínas recombinantes IKVAV-CBM3, exIKVAV-CBM3 and KHIFSDDSSECBM3 foram expressas em E.coli, purificadas e adsorvidas de maneira estável nas membranes de CB. Os resultados in vitro mostraram que o exIKVAV-CBM3 aumentou a adesão de células neuronais e mesenquimais, enquanto que o IKVAV-CBM3 e KHIFSDDSSE-CBM3 apresentaram apenas um pequeno efeito na adesão das células mesenquimais, e nenhum efeito nas outras células testadas. Também, a expressão de neurotrofinas pelas células mesenquimais nas membranas de CB modificadas com as proteínas recombinantes foi verificada, e verificou-se que o NGF é expresso e libertado por estas células aderidas na CB, criando um ambiente promotor da regeneração neuronal. O tratamento com o plasma de nitrogênio não aumentou a molhabilidade da CB, mas foi capaz de aumentar a porosidade e a química de superfície, evidenciado pela presença do grupo nitrogênio. As análises de XPS mostraram a estabilidade do material modificado 180 dias após o tratamento, e após a esterilização por autoclave. A adesão e a proliferação celular das linhagens endotelial (HMEC-1) e neuronal (N1E-115) foi aumentada significativamente na celulose tratada com plasma, em contraste com os fibroblastos 3T3, o que revelou um efeito célula-específico. Quanto aos estudos in vivo, os implantes de CB causaram apenas uma reação inflamatória de baixa intensidade, que decresceu ao longo do tempo, e não estimulou reação de corpo estranho. Foi observada uma tendência para calcificar nas membranas de CB menos porosas, indicando uma relação com a porosidade dos implantes. Quanto aos implantes de nanofibras, após 2 e 4 meses de implantação, verificou-se que a maior parte das nanofibras permaneceram em agregados no tecido subcutâneo. Houve infiltração de células nesses agregados de nanofibras, sendo a maioria macrófagos, e evidências de fagocitose do material por estas células. Também, não foram encontradas diferenças entre os controles e os animais implantados nas populações de timócitos, precursores de linfócitos B e células mielóides na medula óssea. A CB é um bom material para ser utilizado em aplicações de engenharia de tecidos. Entretanto, ainda é necessário a modificação deste material para aumentar sua interação com as células, obtendo assim uma matriz capaz de manter o crescimento, a diferenciação e a seletividade de células. Na nossa tentativa de aumentar e selecionar a adesão de células neuronais à CB, as proteínas recombinantes produzidas foram capazes de aumentar a adesão e a viabilidade celular neste material. Também, o tratamento por plasma de nitrogênio provou ser um tratamento de superfície econômico e efetivo, sendo capaz de aumentar a afinidade das células com a CB, o que poderá contribuir para um melhoramento da sua biocompatibilidade in vivo. Quanto aos testes in vivo, este trabalho aponta para a necessidade de investigação futura para verificar a tendência da CB em calcificar em circunstâncias a longo prazo. Entretanto, as nanofibras de CB parecem ser inócuas quando implantadas no tecido subcutâneo, sendo um material elegível para a produção de enxertos que mimetizem a matriz extracelular.
Style APA, Harvard, Vancouver, ISO itp.
46

Liao, Jinyu. "Probing Cellular Response to Heterogeneous Rigidity at the Micro- and Nanoscale". Thesis, 2017. https://doi.org/10.7916/D88K7H07.

Pełny tekst źródła
Streszczenie:
Physical factors in the environment of a cell regulate cell function and behavior and are involved in the formation and maintenance of tissue. There is strong evidence that substrate rigidity plays a key role in determining cell response in culture. Previous studies have demonstrated the importance of rigidity in numerous cellular processes including migration and adhesion and stem cell differentiation. Immune cells have been shown to respond differently to surfaces having different rigidities. Atypical response to rigidity is also a characteristic of cancerous cells. Understanding the mechanisms that support cellular rigidity sensing can lead to new tissue engineering strategies and potential new therapies based on rigidity modulation. A new technique was developed for the creation of biomimetic surfaces comprising regions of heterogeneous rigidity on the micro- and nanoscale. The surfaces are formed by exposing an elastomeric film of polydimethylsiloxane (PDMS) to a focused electron beam to form patterned regions of micro- and nanoscale spots. This thesis involves the formation of theses surfaces, characterization of their physical and chemical properties as a consequence of the electron beam exposure and investigation of how cells behave when plated on these surfaces. Cellular response to different patterns of heterogeneous rigidity is performed for several cell types. Human mesenchymal stem cells plated upon electron beam-exposed PDMS in a pattern of spots with diameters ranging from 2 µm to 100 nm display differential focal adhesion co-localization to the exposed features, depending on both rigidity and feature size. This behavior persists as the area of the exposed regions is reduced below ~1 µm. On spots with diameters of ~ 250 nm and smaller, focal adhesion co-localization is lost. This supports the notion that there is a length scale for cellular rigidity sensing, with the critical length in the range of a few hundred nanometers. When the heterogeneous rigidity surfaces are applied to CD4+ T cells, accumulations of proteins including TCR and pCasL on the exposed features are observed as a function of feature size. The pCasL appeared to significantly accumulate on 2 µm spots; For spots ~ 1 µm and below, cells appeared unable to identify the rigid regions. Further, Ca2+ release, a functional indicator of immunoresponse, is significantly enhanced on mixed-rigidity patterned PDMS relative to both soft and hard PDMS. Possible signaling pathways of TCR activation have been verified on e-beam exposed PDMS substrates with heterogeneous rigidity. These results are suggestive of possible new approaches to adoptive immunotherapy based on rigidity modulation. Studies on breast cancer cells indicate that on patterned substrates, sub-cellular processes are also significantly modulated. Integrin recruitment is enhanced on the rigid regions. Understanding the role of geometry in cellular rigidity response will point the way toward revealing its functional response and will shed light on the mechanistic underpinnings of this process.
Style APA, Harvard, Vancouver, ISO itp.
47

Kapsabelis, Susan. "Polymer-particle interactions : adsorption of ethyl(hydroxyethyl)cellulose (EHEC) onto modified silica and pharmaceutical particle surfaces". 2001. http://arrow.unisa.edu.au:8081/1959.8/50784.

Pełny tekst źródła
Style APA, Harvard, Vancouver, ISO itp.
48

Harrison, Nathan Daniel. "Nanoscale characterization of interactions between molecular specific plasmonic nanoparticles and living cells and its implications for optical imaging of protein-protein interactions". Thesis, 2009. http://hdl.handle.net/2152/ETD-UT-2009-12-556.

Pełny tekst źródła
Streszczenie:
Imaging of biomolecules on the nano-scale is a crucial developing technology with major implications for our understanding of biological systems and for detection and therapy of disease. Plasmonic nanoparticles are a key optical contrast agent whose signal is generated by the collective oscillation of electrons in the metal particle. The resonance behavior of the electrons depends strongly on the arrangement of neighboring nanoparticles in a structure. This property may be exploited in imaging applications to report information on nanoscale morphology of targeted biomolecules. While the effect of plasmon resonance coupling has been studied in dimers and linear arrays of nanoparticles, this phenomenon remains largely unexplored in the case of 2D and 3D assemblies which are important in molecular cell imaging. This dissertation demonstrates how the optical signal from assemblies of gold nanoparticles can be related to nanoscale morphology in cellular imaging systems. First, the scattering spectra from live cells labeled with gold nanoparticles were collected and compared to the nanoscale arrangement of the particles in the same cells as determined by electron micrograph. Then, trends in scattering spectra with respect to nanoparticle arrangement were analyzed using a model system that allowed precise control over arrangement of nanoparticles. Several approaches to creating these model systems are discussed including biochemical linking, capillary assembly of colloidal particles, and direct deposition of gold onto substrates patterned by electron beam lithography. Spectral properties of the assemblies including peak position, width, and intensity are gathered and related to model variables including interparticle gap and overall particle number. It is shown that the redshift in the scattering spectra from nanoparticle assemblies is derived from both the particle number and the gap and is due to near-field coupling of particles as well as phase retardation of the scattered wave. The redshift behavior saturates as the number of particles in the aggregate increases but the saturation point depends strongly on interparticle gap. The drastic dependence of the red-shift saturation on the gap between nanoparticles has not been previously described; this phenomenon can have significant impact on the development of nanoparticle contrast agents and plasmonic sensor arrays.
text
Style APA, Harvard, Vancouver, ISO itp.
49

Tham, YY. "Study of the interactions of softwood extractives and model compounds with different model surfaces". Thesis, 2016. https://eprints.utas.edu.au/23490/1/Tham_whole_thesis.pdf.

Pełny tekst źródła
Streszczenie:
Wood extractives released into the process water during the production of thermomechanical pulp from the softwood Pinus radiata can form colloidal dispersions that may deposit onto surfaces during paper manufacture and processing. The major components that make up wood extractives are fatty acids, resin acids, triglycerides, sterols and steryl esters. In this thesis, wood extractives were represented by three of the major components that are oleic acid (a typical fatty acid), abietic acid (a typical resin acid) and triolein (a typical triglyceride). The major aim of this thesis is to study the interaction between wood extractives and model surfaces to give an insight into the preferential desorption of largely resin acids, in preference to fatty acids and triglycerides, from paper onto metal surfaces. Adsorption isotherms established for interaction of wood extractives and model compounds onto pulp fibres and microcrystalline cellulose showed that multilayer adsorption would best explain the adsorption behaviour of these compounds. The effect of pH perturbations was also considered for adsorption onto pulp fibres. Multilayer adsorption behaviour was best described with the Freundlich isotherm model. The results suggest that reorganisation of the surface of wood extractive colloids most probably occurred after pH perturbations, and their behaviour was very similar to simple fatty acid colloids. This suggests the loss of abietic acid from the surface of wood extractive colloids. However, due to low solubility of abietic acid, the adsorption behaviour of abietic acid could not be determined accurately. Additionally, interactions of wood extractives and its individual components with model surfaces (cellulose and chromium) as well as the effects of different temperatures on adsorption behaviour (25°C and 50°C) were also studied using quartz crystal microbalance with dissipation monitoring (QCM-D). Different adsorption behaviour was observed to exist between the two surfaces as a function of temperature. At the lower temperature (25°C), two phases of adsorption occurred for adsorption onto cellulose surface, whereas a single adsorption phase occurred onto a chromium surface. At elevated temperature (50°C), only a single adsorption phase occurred on both cellulose and chromium surfaces. A greater amount of abietic acid was shown to adsorb on the chromium surface than the cellulose surface. Wood extractives were shown to adsorb less onto cellulose than onto chromium, which agrees with the practical observation that a greater amount of abietic acid adsorbed onto a chromium surface than onto a cellulose surface. A new technique of attaching soft colloids (model compounds and wood extractives colloids) onto hydrophobically functionalised tipless atomic force microscopy (AFM) cantilevers was developed to allow direct measurement of the forces of interaction between the colloid and a model surface. These measurements were carried out by atomic force microscopy (AFM). Similar to QCM-D results, it was observed that adhesion of abietic acid and wood extractives were comparable on both cellulose and chromium surfaces; whereas the adhesion of triolein and oleic acid onto a cellulose surface was much greater than onto a chromium surface. This would explain the preferential transfer of resin acids from a cellulose surface onto a chromium surface in preference to triolein or oleic acid from wood extractives. In addition to the experimental techniques, computational modelling was used to compliment the experimental data. Different levels of theories and basis sets were employed to model the interaction of the model compounds and model surfaces. However, computational modelling with ab initio theories was shown to be unsuitable for quantitative modelling of these interactions. Thus different modelling programs and methods may be needed to successfully model the interaction of model compounds with cellulose or chromium surfaces.
Style APA, Harvard, Vancouver, ISO itp.
50

Jay, Anthony. "Studies of CD36 interacting with fatty acids, oxidized low-density lipoprotein, and the cellular plasma membrane". Thesis, 2017. https://hdl.handle.net/2144/20779.

Pełny tekst źródła
Streszczenie:
The glycoprotein CD36 is expressed in the plasma membrane (PM) of many cell types that surround or contact arteries, including macrophages, myocytes, and endothelial cells. CD36 binds oxidized low density lipoprotein (oxLDL), which promotes atherosclerosis, and fatty acids (FA), which promotes their cellular uptake. To gain insights into the molecular mechanisms of uptake, HEK293 cells expressing CD36 were studied by cell biological and fluorescence methods. To test our hypothesis that the PM is not an impermeable barrier to FA and that FA move into cells by diffusion via their uncharged form, we first applied biophysical fluorescence spectroscopy to directly measure transmembrane FA movement and membrane fluidity. Expression of CD36 in HEK293 cells did not increase either transport across the PM or the fluidity of the PM compared to HEK293 cells without CD36; however, CD36 enhanced intracellular FA esterification. Furthermore, the widely used “inhibitors” of FA transport did not alter either the rapid FA transmembrane diffusion in HEK293 cells or diffusion in control experiments with protein-free phospholipid bilayers. To gain new insights into the physiological relevance of FA binding to CD36, we applied surface plasmon resonance (SPR) to quantify FA and oxLDL binding to the ectodomain of CD36. Structurally distinct FA [saturated, monounsaturated (cis and trans), polyunsaturated, ω-3, ω-6, and oxidized FA] were pulsed in a solubilized form (bound to methyl-β-cyclodextrin) across SPR channels, generating real-time association and dissociation binding curves. With the exception of the oxidized FA hydroxyoctadecadienoic acid (HODE), all FA tested bound to CD36 with rapid association and dissociation kinetics similar to human serum albumin. In addition, FA increased oxLDL binding to CD36. To investigate whether FA affect CD36-mediated oxLDL uptake in live cells, we monitored fluorescent oxLDL (Dii-oxLDL) uptake using confocal microscopy. Addition of exogenous FA to serum-free media enhanced dose-dependent oxLDL uptake. Exceptions were ω-3 FA, which bound to CD36, and HODE, which did not bind to CD36, demonstrating FA structure-specific effects on a major function of CD36 and a new mechanistic link between atherosclerosis and high levels of FA in obese and Type-II diabetic individuals.
Style APA, Harvard, Vancouver, ISO itp.
Możesz być także zainteresowany bibliografiami na temat „Interactions cellules/surfaces” dla innych typów źródeł:
Artykuły w czasopismach Książki
Oferujemy zniżki na wszystkie plany premium dla autorów, których prace zostały uwzględnione w tematycznych zestawieniach literatury. Skontaktuj się z nami, aby uzyskać unikalny kod promocyjny!

Do bibliografii