La nanochimie et l’auto-assemblage sont des voies prometteuses de fabrication de matériaux nanostructurés aux propriétés optiques innovantes dans le domaine visible. Dans cette étude, des nanocomposites plasmoniques anisotropes sont formulés en introduisant sélectivement des nanoparticules métalliques dans des phases ordonnées de copolymères diblocs symétriques selon différentes stratégies d’incorporation. Pour la stratégie de post-incorporation, des nanoparticules d’or présynthétisées en milieu aqueux sont introduites sélectivement dans des phases pré-ordonnées d’un copolymère dibloc amphiphile. L’incorporation directe consiste àmélanger des nanoparticules d’or présynthétisées et un copolymère dibloc dans un solvant commun.La synthèse in situ de nanoparticules consiste à réduire des précurseurs métalliques préalablement introduits dans un des deux blocs d’un copolymère via une étape de réduction. Nous étudions, en particulier, comment la taille des nanoparticules d’or et leur fraction volumique influencent la nanostructure et les propriétés optiques de ces films nanocomposites. La morphologie des films macroscopiques est étudiée par microscopie électronique à transmission et diffusion des rayons Xaux petits angles. Les films minces de nanocomposites sont caractérisés structurellement parmicroscopie à force atomique, microscopie électronique à transmission et réflectivité des rayons X. Les indices optiques déterminés par ellipsométrie spectroscopique peuvent être décrits par un modèle de Maxwell-Garnett, prenant éventuellement en compte de façon phénoménologique les effets de couplage entre nanoparticules d’or. / Nanochemistry and self-assembly are promising ways to fabricate nanostructuredmaterials with innovative optical properties for visible light. In this work, anisotropic plasmonicnanocomposites are formulated by selectively introducing metallic nanoparticles in ordered phasesof symmetric dibloc copolymers with different strategies. For the strategy of post-incorporation, presynthesizedgold nanoparticles in aqueous medium are selectively introduced in pre-ordered phasesof an amphiphilic dibloc copolymer. Direct incorporation consists in mixing pre-synthesized goldnanoparticles and dibloc copolymer in a common solvent. In situ synthesis of nanoparticles consistsin reducing metallic precursors previously introduced in one of two blocks of a copolymer via areduction step. The influence of the size and the volume fraction of gold nanoparticles on thenanostructure and the optical properties of the nanocomposite films have been particularly studied.Morphology of macroscopic films is studied by transmission electron microscopy and small angle Xrayscattering. The nanocomposite thin films are structurally characterized by force atomicmicroscopy, transmission electron microscopy and X-ray reflectivity. The optical indices obtained byspectroscopic ellipsometry can be described with Maxwell-Garnett models, which can take intoaccount phenomenologically the effects of coupling between gold nanoparticles.

La bêta lactoglobuline (βlg) est une protéine globulaire qui forme le constituant majoritaire du sérum du lait ou petit lait. Par chauffage la protéine se dénature irréversiblement, puis s’assemble pour former des agrégats ou gels présentant des structures très différentes selon les conditions environnementales, en particulier de pH et de force ionique. Des travaux récents ont montré la possibilité de créer des agrégats stables de βlg de forme sphérique, de 100 à 400 nm de diamètre dans une plage de pH bien spécifique. Ces particules sphériques que nous appelons microgels, sont potentiellement très intéressantes pour des applications dans l’agroalimentaire (blanchissement, stabilisation d’interfaces et encapsulation). L’objectif de la thèse est d’étudier le mécanisme de formation de ces microgels et leurs propriétés structurales dans différentes conditions environnementales afin de pouvoir créer de nouvelles fonctionnalités. La première partie de la thèse a consisté à étudier l’influence du pH sur la formation des microgels. Les suspensions stables de microgels sont formées par chauffage de la solution de βlg en absence de sel jusqu’à 50 g.L-1 de protéine si le pH est placé dans une gamme très étroite entre 5,75 et 6,1. La densité de ces particules sphériques est environ 150 g.L-1 et leur rayon hydrodynamique diminue de 200 nm à 75 nm en augmentant le pH. La formation de ces microgels entraine une augmentation de pH, qui est nécessaire pour obtenir une suspension stable. L’augmentation spontanée du pH pendant la formation des microgels entraine une augmentation de leur densité de charge à la surface qui a pour conséquence d'empêcher leur agrégation. Ce mécanisme d’auto-stabilisation n’est plus suffisant si le pH initial est inférieur à 5,75 et on observe alors la précipitation des microgels. Les microgels ne sont plus formés au-delà d’une valeur critique du pH initial. Dans ce cas, les agrégats fibrillaires sont formés avec un rayon hydrodynamique d’environ 15 à 20 nm. La seconde partie de ce travail traite de la formation des microgels induite par l’ajout des ions calcium. Nous avons montré que des suspensions stables de microgels peuvent être obtenues en chauffant les solutions de βlg en présence des ions calcium. Les conditions de formation des microgels ont été étudiées à différents pH entre 5.8 et 7.5 et différentes concentrations de protéine entre 5 et 100 g.L-1. Il existe un rapport molaire critique calcium/protéine (R) pour former des microgels qui est indépendant de la concentration de protéine. R diminue en diminuant le pH. Les microgels ont un rayon hydrodynamique qui varie entre 100 et 300 nm et leur densité est comprise entre 200 et 450 g.L-1. La détermination de quantité de calcium lié aux microgels indique que le paramètre crucial pour la formation des microgels est la densité des charges nettes des protéines natives. Les suspensions de microgels sont stables dans certaines gammes étroites de R mais s’agrègent et précipitent ou gélifient à des concentrations de calcium plus élevées. Dans la troisième partie, nous avons continué à étudier la formation des microgels dans les étapes initiales et observer leur croissance en présence des ions calcium. On a proposé un mécanisme de formation des microgels de βlg, qui commence par un processus de nucléation et croissance. Des nucléi de tailles bien définies sont formés à la première étape, puis ils continuent à grossir jusqu’à la taille finale des microgels. A des faibles concentrations de calcium les microgels sont stables. A des concentrations plus élevées, les microgels peuvent s’agréger pour former des agrégats plus grands et finalement un gel. La structure des gels de microgels est hétérogène à l’échelle de la microscopie confocale et similaire à celle formée en présence de NaCl 0.3M. Pourtant le processus de formation de ces gels n’est pas le même... / Beta lactoglobulin (βlg) is a major whey protein in the bovine milk. Upon heating above its denaturation temperature (which is pH-dependent), this globular protein undergoes molecular changes leading to the irreversible aggregation. Depending on the pH and ionic strength, either protein aggregates or gels exhibiting various structures and morphologies have been described. Very recently, it was found that in a narrow range of the pH close to iso-electric point, stable suspensions of rather monodisperse spherical particles with a radius of about a hundred nanometers were formed. These spherical particles which were called microgels might be of special interest for the production of liquid dispersions of β-lactoglobulin aggregates exhibiting various functionalities for food applications. The project on which I report here was a collaboration with the Nestlé Reseach Center (Lausanne, Switzerland) and its objective was to study the formation and structural properties of the microgels in different environmental conditions. The first part of the project is to study the influence of the pH on the formation of microgels. Stable suspensions of protein microgels are formed by heating salt free βlg solutions at concentrations up to about C = 50 g.L-1 if the pH is set within a narrow range between 5.75 and 6.1. The internal protein concentration of these spherical particles is about 150 g.L-1 and the average hydrodynamic radius decreases with increasing pH from 200 nm to 75 nm. The formation of the microgels leads to an increase of the pH, which is a necessary condition to obtain stable suspensions. The spontaneous increase of the pH during microgel formation leads to an increase of their surface charge density and inhibits secondary aggregation. This self-stabilization mechanism is not sufficient if the initial pH is below 5.75 in which case secondary aggregation leads to precipitation. Microgels are no longer formed above a critical initial pH, but instead short curved protein strands are obtained with a hydrodynamic radius of about 15-20 nm. The second part of the work is about the formation of microgels driven by the addition of calcium ions. We found that stable suspensions of spherical protein particles (microgels) can be formed by heating βlg solutions in the presence of calcium ions. The conditions for the calcium induced microgel formation were studied at different pH between 5.8 and 7.5 and different protein concentrations between 5 – 100 g.L-1. The results showed that a critical molar ratio of calcium to proteins (R) is needed to form microgels independent of the protein concentration. R decreases with decreasing pH. The microgels have a hydrodynamic radius ranging from 100 to 300 nm and their internal protein concentration ranges from 0.2 to 0.45 g.mL-1. The determination of calcium bound to the microgels suggests that the crucial parameter for microgel formation is the net charge density of the native proteins. The microgel suspensions are stable in a narrow range of R but aggregate at higher Ca2+ concentrations. In the third part, we continued to investigate the formation of microgels at initial step and how it is growing in the presence of calcium ions. We have proposed a mechanism of formation of blg microgels which follows a nucleation and growing process. The nucleus with define size are formed at the initial state and that is growing in size to reach final size of aggregates. At low calcium concentration it stabilizes and then we obtain a stable suspension of microgels. But at high concentrations, the microgels here can jump to form big aggregates and finally a gel. The structure of gel from microgels is heterogenous at the scale of confocal microscopy and similar to those formed in the presence of NaCl 0.3 M. However the process of formation of these gels is not the same...

Self-assembly of nanoparticles is a promising route to form complex, nanostructured materials with functional properties. Nanoparticle assemblies characterized by a crystallographic alignment of the nanoparticles on the atomic scale, i.e. mesocrystals, are commonly found in nature with outstanding functional and mechanical properties. This thesis aims to investigate and understand the formation mechanisms of mesocrystals formed by self-assembling iron oxide nanocubes. We have used the thermal decomposition method to synthesize monodisperse, oleate-capped iron oxide nanocubes with average edge lengths between 7 nm and 12 nm and studied the evaporation-induced self-assembly in dilute toluene-based nanocube dispersions. The influence of packing constraints on the alignment of the nanocubes in nanofluidic containers has been investigated with small and wide angle X-ray scattering (SAXS and WAXS, respectively). We found that the nanocubes preferentially orient one of their {100} faces with the confining channel wall and display mesocrystalline alignment irrespective of the channel widths.  We manipulated the solvent evaporation rate of drop-cast dispersions on fluorosilane-functionalized silica substrates in a custom-designed cell. The growth stages of the assembly process were investigated using light microscopy and quartz crystal microbalance with dissipation monitoring (QCM-D). We found that particle transport phenomena, e.g. the coffee ring effect and Marangoni flow, result in complex-shaped arrays near the three-phase contact line of a drying colloidal drop when the nitrogen flow rate is high. Diffusion-driven nanoparticle assembly into large mesocrystals with a well-defined morphology dominates at much lower nitrogen flow rates. Analysis of the time-resolved video microscopy data was used to quantify the mesocrystal growth and establish a particle diffusion-based, three-dimensional growth model. The dissipation obtained from the QCM-D signal reached its maximum value when the microscopy-observed lateral growth of the mesocrystals ceased, which we address to the fluid-like behavior of the mesocrystals and their weak binding to the substrate. Analysis of electron microscopy images and diffraction patterns showed that the formed arrays display significant nanoparticle ordering, regardless of the distinctive formation process.  We followed the two-stage formation mechanism of mesocrystals in levitating colloidal drops with real-time SAXS. Modelling of the SAXS data with the square-well potential together with calculations of van der Waals interactions suggests that the nanocubes initially form disordered clusters, which quickly transform into an ordered phase. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.</p>

Water is a simple molecule but is an essential part of life. One key aspect of the properties of water is the hydrophobic effect, and whilst there is an appreciation of this phenomenon at the macro-scale (raindrops falling off leaves) and the micro-scale (the structure of cellular systems), a complete understanding at the molecular level still eludes science. Addressing this issue, our studies involve synthetic supramolecular compounds that assemble in water via the hydrophobic effect. First of all, a novel water-soluble deep-cavity cavitand was synthesized. It possesses four endo methyl groups on top rim of the cavitand, eight water-solubilizing carboxylic acid groups coated on the cavitand exterior, and a relatively large hydrophobic interior. Compared to a previous well-studied water-soluble deep-cavity cavitand octa-acid (OA), this novel cavitand (TEMOA) possesses a non-monotonic assembly profile in the presence of a homologous series of straight-chain alkanes. Three supramolecular species were observed: 1:1, 2:2, and 2:2 and they are approximately isoenergetic. Second, we examined the guest-controlled self-sorting in assemblies. A mixture of OA and TEMOA formed hetero-capsular complex driven by the hydrophobic effect. The extent of homo- or hetero-dimerization is intimately tied to the size of the guest being encapsulated. TEMOA is less predisposed to dimerize than OA, thus TEMOA possesses the ability to form various self-assembled states, such as tetrameric and hexameric assemblies. Furthermore, we also discussed our observation of how external stimuli such as changing the nature or concentration of a co-solute salt influences a unique, unusual transition from one assembled state to another.

<p>A RET network consists of a network of photo-active molecules called chromophores that can participate in inter-molecular energy transfer called resonance energy transfer (RET). RET networks are used in a variety of applications including cryptographic devices, storage systems, light harvesting complexes, biological sensors, and molecular rulers. In this dissertation, we focus on creating a RET device called closed-diffusive exciton valve (C-DEV) in which the input to output transfer function is controlled by an external energy source, similar to a semiconductor transistor like the MOSFET. Due to their biocompatibility, molecular devices like the C-DEVs can be used to introduce computing power in biological, organic, and aqueous environments such as living cells. Furthermore, the underlying physics in RET devices are stochastic in nature, making them suitable for stochastic computing in which true random distribution generation is critical.</p><p>In order to determine a valid configuration of chromophores for the C-DEV, we developed a systematic process based on user-guided design space pruning techniques and built-in simulation tools. We show that our C-DEV is 15x better than C-DEVs designed using ad hoc methods that rely on limited data from prior experiments. We also show ways in which the C-DEV can be improved further and how different varieties of C-DEVs can be combined to form more complex logic circuits. Moreover, the systematic design process can be used to search for valid chromophore network configurations for a variety of RET applications.</p><p>We also describe a feasibility study for a technique used to control the orientation of chromophores attached to DNA. Being able to control the orientation can expand the design space for RET networks because it provides another parameter to tune their collective behavior. While results showed limited control over orientation, the analysis required the development of a mathematical model that can be used to determine the distribution of dipoles in a given sample of chromophore constructs. The model can be used to evaluate the feasibility of other potential orientation control techniques.</p> / Dissertation

<p>The use of DNA as a polymeric building material transcends its function in biology and is exciting in bionanotechnology for applications ranging from biosensing, to diagnostics, and to targeted drug delivery. These applications are enabled by DNA’s unique structural and chemical properties, embodied as a directional polyanion that exhibits molecular recognition capabilities. Hence, the efficient and precise synthesis of high molecular weight DNA materials has become key to advance DNA bionanotechnology. Current synthesis methods largely rely on either solid phase chemical synthesis or template-dependent polymerase amplification. The inherent step-by-step fashion of solid phase synthesis limits the length of the resulting DNA to typically less than 150 nucleotides. In contrast, polymerase based enzymatic synthesis methods (e.g., polymerase chain reaction) are not limited by product length, but require a DNA template to guide the synthesis. Furthermore, advanced DNA bionanotechnology requires tailorable structural and self-assembly properties. Current synthesis methods, however, often involve multiple conjugating reactions and extensive purification steps.</p><p>The research described in this dissertation aims to develop a facile method to synthesize high molecular weight, single stranded DNA (or polynucleotide) with versatile functionalities. We exploit the ability of a template-independent DNA polymerase−terminal deoxynucleotidyl transferase (TdT) to catalyze the polymerization of 2’-deoxyribonucleoside 5’-triphosphates (dNTP, monomer) from the 3’-hydroxyl group of an oligodeoxyribonucleotide (initiator). We termed this enzymatic synthesis method: TdT catalyzed enzymatic polymerization, or TcEP.</p><p>Specifically, this dissertation is structured to address three specific research aims. With the objective to generate high molecular weight polynucleotides, Specific Aim 1 studies the reaction kinetics of TcEP by investigating the polymerization of 2’-deoxythymidine 5’-triphosphates (monomer) from the 3’-hydroxyl group of oligodeoxyribothymidine (initiator) using in situ 1H NMR and fluorescent gel electrophoresis. We found that TcEP kinetics follows the “living” chain-growth polycondensation mechanism, and like in “living” polymerizations, the molecular weight of the final product is determined by the starting molar ratio of monomer to initiator. The distribution of the molecular weight is crucially influenced by the molar ratio of initiator to TdT. We developed a reaction kinetics model that allows us to quantitatively describe the reaction and predict the molecular weight of the reaction products.</p><p>Specific Aim 2 further explores TcEP’s ability to transcend homo-polynucleotide synthesis by varying the choices of initiators and monomers. We investigated the effects of initiator length and sequence on TcEP, and found that the minimum length of an effective initiator should be 10 nucleotides and that the formation of secondary structures close to the 3’-hydroxyl group can impede the polymerization reaction. We also demonstrated TcEP’s capacity to incorporate a wide range of unnatural dNTPs into the growing chain, such as, hydrophobic fluorescent dNTP and fluoro modified dNTP. By harnessing the encoded nucleotide sequence of an initiator and the chemical diversity of monomers, TcEP enables us to introduce molecular recognition capabilities and chemical functionalities on the 5’-terminus and 3’-terminus, respectively.</p><p>Building on TcEP’s synthesis capacities, in Specific Aim 3 we invented a two-step strategy to synthesize diblock amphiphilic polynucleotides, in which the first, hydrophilic block serves as a macro-initiator for the growth of the second block, comprised of natural and/or unnatural nucleotides. By tuning the hydrophilic length, we synthesized the amphiphilic diblock polynucleotides that can self-assemble into micellar structures ranging from star-like to crew-cut morphologies. The observed self-assembly behaviors agree with predictions from dissipative particle dynamics simulations as well as scaling law for polyelectrolyte block copolymers.</p><p>In summary, we developed an enzymatic synthesis method (i.e., TcEP) that enables the facile synthesis of high molecular weight polynucleotides with low polydispersity. Although we can control the nucleotide sequence only to a limited extent, TcEP offers a method to integrate an oligodeoxyribonucleotide with specific sequence at the 5’-terminus and to incorporate functional groups along the growing chains simultaneously. Additionally, we used TcEP to synthesize amphiphilic polynucleotides that display self-assemble ability. We anticipate that our facile synthesis method will not only advance molecular biology, but also invigorate materials science and bionanotechnology.</p> / Dissertation

Les copolymères à blocs (BCP) sont des macromolécules capables de s’auto-assembler produisant des morphologies bien définies à l’échelle nanométrique. Un certain nombre de leurs propriétés macroscopiques peuvent être largement modifiées par des effets de confinement à l’échelle moléculaire, mais aussi par des effets de cisaillement (l’orientation des structures et donc un comportement mécanique fortement anisotrope). L’une des technologies permettant d’étudier ces effets sur la structuration des BCP est la coextrusion multinanocouches, qui permet de produire à grande échelle des matériaux sous forme de films possédant deux ou plusieurs constituants organisées en milliers de couches alternées ayant chacune une épaisseur nanométrique. À l’aide de ce procédé, des films constitués du tribloc poly(méthacrylate de méthyle-b-butyle acrylate-b-méthacrylate de méthyle) et des homopolymères polyméthacrylate de méthyle, polystyrène et polycarbonate (ayant donc différentes interfaces) ont été fabriqués en variant la composition du mélange et les conditions de coextrusion afin d’obtenir différentes épaisseurs du film (et donc différentes épaisseurs de couche). Une caractérisation multi-échelle a été effectuée en couplant différentes techniques, notamment AFM, MET (après une étape préalable de marquage) et SAXS. Elle a permis d’identifier les structures locales au sein des couches et de mieux comprendre la relation procédé-structure-propriétés suite à des essais en traction uni-axiale montrant de meilleures propriétés dans le cas de structures multicouches. Une faible stabilité thermique, à de temps comparables à ceux du procédé, a montré une influence sur la structuration de ce type de BCP. Nous avons mis en évidence un changement dans la morphologie du tribloc à partir d’une structure lamellaire, lorsque le matériau se trouve dans un état proche de l’équilibre thermodynamique, vers une structure cylindrique au sein du système multicouche et maintenue, quelle que soit l’épaisseur de couche, à grande distance. La maitrîse des procédés de transformation de matériaux à base de polymère à l’échelle micro ou nanométrique prend ainsi toute son importance afin de mieux contrôler, dans le cas des BCP, la structuration lors d’une production à grande échelle de matériaux hiérarchisés constitués de ces matériaux, ce qui influence fortement leurs propriétés macroscopiques. / Block copolymers (BCP) have proven to be of great interest, especially for their ability to spontaneously self-assemble in ordered and well-defined nanostructures. Some of their macroscopic properties can be altered by physical effects such as confinement (constraining domains at molecular scale) or shear (predominant orientation of domains with anisotropic mechanical response). Here, the study of these effects over the BCP structuration is achieved by using an industrially scalable technique, nanolayer coextrusion, which allows fabrication of macroscopic films made of thousands of alternating layers with individual thickness tuned down to a few tens of nanometers. Films are then coextruded using the triblock : poly(methyl methacrylate-b-butyl acrylate-b-methyl methacrylate) and the polymers : polymethyl methacrylate, polystyrene and polycarbonate (having different interfaces) by varying weight proportions and process parameters to target different layer thicknesses. A multi-scale characterization by coupling different technics as AFM, TEM (after samples staining) and SAXS allowed the local identification of nano-domains and the better understanding of process-structures-properties relation as a result of tensile tests showing improved mechanical behavior for these films. A low thermic stability for comparable process times showed a clear influence over structuration of this kind of BCP. We have observed a change in the triblock morphology from lamellar structures, when it is a close to thermodynamic equilibrium state, to cylindrical structures within the multilayer system which is maintained over long distances indistinct of layer thickness. The well understanding of the forming process parameters to create polymer-based materials at micro- or nanoscale scale is therefore an important factor in order to control nano-structures during a large-scale production of hierarchized materials consisting of BCP, which could strongly influence their macroscopic properties.

This thesis is focused on mixed systems of various copolymers (double hydrophilic block and gradient polyelectrolytes, hydrophobic graft copolymers) and low-molar-mass compounds (sodium dodecyl sulfate as a representative of a ionic surfactant or superparamagnetic iron oxides in the form of nanocrystals). The electrostatic and hydrophobic interactions in the studied systems in aqueous solutions leading to aggregation behavior and to the formation of co-assembled nanoparticles were investigated by combination of scattering and microscopy techniques, including light, X-ray and neutron scattering, electron microscopy and atomic force microscopy. Powered by TCPDF (www.tcpdf.org)

La vectorisation est une stratégie pharmaceutique qui consiste non seulement à réduire les quantités de principe actif administrées, mais aussi à améliorer le rapport bénéfice/risque pour le patient. La délivrance cellulaire spécifique est augmentée alors que les effets secondaires causés par la délivrance non spécifique sont diminués. Pour être le plus efficace possible, différents vecteurs ont été proposés, non seulement capables d’encapsuler des molécules thérapeutiques, mais aussi d’interagir efficacement avec les cellules cibles. De ce point de vue, les nanoparticules polymères sont des objets intéressants pour cibler de manière spécifique certaines cellules, grâce à la combinaison unique d’une taille nanométrique et de la possibilité de moduler considérablement leurs propriétés physico-chimiques.A ce jour, l’influence de la morphologie des micro- et nanoparticules sur leur biodistribution est quasiment inconnue. Cependant, les rares études sur ce sujet suggèrent que la forme des objets introduits dans le corps a une influence majeure sur leur devenir dans les fluides [1], in vitro [2], et in vivo. Ainsi, l’observation des micro-organismes a déjà démontré que leur forme influence non seulement leur déplacement, mais aussi leur capacité à interagir avec les cellules et à être capturés par les macrophages.Comprendre, au niveau micro- et nanométrique l’influence de la forme sur les interactions entre les particules et les cellules présente un intérêt scientifique et pharmaceutique indéniable. Dans ce cadre, l’objectif de notre projet était d’identifier les différents mécanismes ou phénomènes que la forme peut impacter, et d’essayer de quantifier leur importance respective. De plus en plus d’études sur la fabrication de micro- et nanoparticules de formes originales émergent, mais quasiment aucune donnée ne fournit d’indication sur l’influence de la forme sur le comportement de ces objets.Pour mener à bien ce travail, nous nous sommes concentrés sur la production de particules non sphériques de formes et surfaces contrôlées, soit par une méthode d’auto-assemblage de copolymères de poly(gamma-benzyle-L-glutamate), soit par la déformation de particules sphériques. Enfin nous avons étudié l’influence in vitro de la forme sur les interactions avec des surfaces caractérisées, par résonance plasmonique de surface, sur les interactions avec des cellules (Cellules endothéliales humaines du cordon ombilical, HUVEC), et l’influence de la forme sur le devenir in vivo de ces particules. Tous ces éléments ont permis de démontrer que la forme des micro- et nanoparticules doit être considérée comme un facteur majeur pour moduler leur devenir in vivo. / The drug targeting strategy aims not only to reduce the amount of administered drugs, but also to improve the benefit/risk ratio for the patient. Specific cellular delivery is raised while toxic effects caused by non specific delivery are weakened.To be fully efficient various vectors have been proposed, which are not only able to encapsulate the therapeutic molecules, but are also meant to interact efficiently with target cells. From this point of view, polymer nanoparticles are interesting objects for specifically targeting cells because of a unique combination of a nanometric size and the possibility to considerably modulate their physico-chemical properties.To this day the influence of the morphology of micro- and nanoparticles on their biodistribution is mostly unknown. However only a few studies suggest that the shapeof objects introduced in the body has a major influence on their fate in fluids[1], in vitro [2], and in vivo. Thus the observation of micro-organisms shows that shape not only influences their displacement, but also their capacity to interact with cells and the capture by macrophages.Understanding, at the micro- and nanometric levels the influence of shape on the interaction between particles and cells presents an undeniable scientific andpharmaceutical interest. Within this framework, the objective of our project is toidentify the different mechanisms or phenomena that the shape might impact, and to try to quantify their significance. More and more studies on the fabrication of micro and nanoparticles are emerging, but almost no data referred to the influence of shape on the behavior of these objects.To realize this study, we focused on producing non spherical particles of controlledshape and surface, either by auto-assembly of copolymers of poly(gamma-benzyl-Lglutamate)or by deformation of spherical nanoparticles. Then we studied the influence of shape on the in vitro interactions with characterized surfaces throughsurface plasmon resonance, on the interactions with cells (Human umbilical veinendothelial cells, HUVEC), and on the in vivo fate of the particles. All these elements demonstrated that the morphology of micro- and nanoparticles must be considered as a major factor to modulate their in vivo fate.

Este trabalho tem como principal objetivo comparar as respostas de biossensores amperomé-tricos preparados a partir do uso de uma enzima, a tirosinase (polifenoloxidase, PFO), quando nas formas purificada e adquirida comercialmente e de extrato bruto enzimático do fruto do abacate (Persea Americana). As soluções de PFO apresentaram valores de atividades enzimá-ticas de 479 unidades de enzimas ativas por mililitro (UA mL-1) (purificada) e 259 UA mL-1 (extrato bruto). A enzima nas duas formas (pura e como extrato bruto) foi imobilizada quimi-camente em substratos de Au modificados com monocamadas automontadas (self-assembly monolayers, SAMs) de ácido mercaptopropiônico (MPA) pela técnica de impressão por mi-crocontato (CP). Os biossensores foram preparados sobre substratos de Au modificados por CP com um molde elastomérico de polidimetilsiloxano (PDMS), cujas trilhas paralelas de 100 m foram produzidas pela cura polimérica sobre um molde mestre de GaAs. A réplica de PDMS se mostrou fiel em relação ao molde mestre nos picos e vales, mas apresentou defeitos na borda dos moldes. Com o objetivo de otimizar o funcionamento dos biossensores, eles fo-ram caracterizados pelas técnicas de voltametria cíclica e cronoamperometria com um sistema de análise de injeção em fluxo (FIA) em meio de catecol a diferentes concentrações. Os po-tenciais de oxidação do catecol nos eletrodos de Au modificados foram observados em 418 e 365 mV, em pHs ótimos de funcionamento de 7,0 e 7,2, e com limites de detecção de 6,65 nmol L-1 e 4,65 nmol L-1 para os biossensores com a enzima purificada e com o extrato bruto, respectivamente. A saturação dos sensores teve início a uma concentração de catecol de 0,02 mol L-1. Com estes resultados, mostramos que é possível o preparo de biosensores com um baixo custo, eficientes e miniaturizadas a partir do uso da PFO na forma extrato bruto do fruto do abacate para a detecção de compostos fenólicos, tal como catecol, abrindo assim a possibi-lidade de uso destes biossensores na análise e no monitoramento de pesticidas presentes no solo e na água. / The main objective of this master thesis is to compare the performance of amperometric biosensors prepared using the purified tirosinase (PPO) enzyme, (commercially acquired) and the PPO present in the enzymatic crude extract from the avocado fruit (Persea Americana). The PPO solutions had 479 units of active enzyme per milliliter (UA mL-1) (purified) and 259 UA mL-1 (crude extract). Both forms of the enzyme (purified and crude extract) were chemically immobilized on gold substrates patterned with 3-mercaptopropionic acid (MPA) self assembled monolayers (SAMs), using the microcontact printing (CP) technique. The biosensors were prepared on gold subtracts patterned using CP with a polydimethylsiloxane (PDMS) elastomeric mold, that was shaped in the form as tracks using a gallium arsenate master mold. The PDMS mold was quite similar to the master mold in its peaks and valleys, but defects were found on the edges. In order to optimize the parameters of the biosensors , they were characterized using cyclic voltammetry and chronoamperometry techniques in a FIA system by cathecol injections at different concentrations. The oxidation potentials for the cathecol analysis using the patterned biosensors were observed at 418 and 365 mV, the optimum pH were 7,0 and 7,0, with detection limits of 6,65 nmol L-1 and 4,65 nmol L-1 for the purified enzyme and crude extract biosensors, respectively. The biosensors saturation point started at 0,02 mol L-1 of cathecol concentration. With this results, we demonstrate that it is possible to use miniaturized, efficient, low cost biosensors based on tyrosine from the avocado´s fruit crude extract to detect phenolic compounds, as the cathecol. This expands the possibility of using this biosensors in the analysis and monitoring pesticides in water and soil.