Nanoscale materials have great applications in many areas. One of these applications is for manufacturing ultra-compact and efficient sensors for chemical and biological molecule detection. Noble metals, such as gold (Au) and silver (Ag), because of their distinguished optical property"localized surface plasmon resonances (LSPRs) that exhibit low loss, are ideal materials to fabricate these nanoscale plasmonic particles or structures. This work addresses the synthesis, characterization, and sensing applications of Au and Ag nanoparticles (NPs). The progress on certain subjects related to our work"NP synthesis, surface functionalization, Au sphere-film structure and two-photon fluorescence"are reviewed in Chapter 1. We also show the calculation results of LSPRs of Au nanosphere suspensions using Mie theory. The measured extinction spectra of Au nanosphere suspensions agree with the calculated results very well. Chapter 2 is a chapter describing the chemical synthesis of a variety of NPs, such as Ag prisms and cubes, Au spheres, rods, and bipyramids. These experiments involved different synthetic mechanisms and methods which enabled us to prepare NPs with desired shapes and optical properties. To put these NPs into application, it is desirable and sometimes necessary to functionalize their surfaces. In Chapter 3, we present the functionalization of Ag cubes with poly(allylamine hydrochloride) (PAH) and poly(allylamine hydrochloride)-dithiocarbamate (PAH-DTC), which follows our previous work on Au NPs. The purpose of studying Ag instead of Au is to use the stronger plasmonic enhancement in Ag when applied to two-photon imaging applications. However, we found that PAH-DTC shrank the Ag cubes. We also functionalized the cationic hexadecyltrimethylammonium bromide (CTAB)-stabilized Au NRs with anionic poly(sodium 4-styrenesulfonate) (PSS). Coated with the strong polyelectrolyte PSS, the NRs become more manageable and can be stable for over six months and are easily immobilized onto positively charged substrate. We put PSS-functionalized Au NPs into use and studied their adsorption process onto PAH-coated optical fiber tapers by monitoring the transmission light through the fiber. When the diameter of the fiber taper gets smaller, stronger coupling occurred between transmitted light inside the taper and the Au NPs on the taper surface (cylinder). This coupling resulted in a loss of the guided light at the plasmon resonance wavelength of the NPs. By monitoring this loss, we can study the adsorption rate of Au NPs onto the fiber. In Chapter 4, we used Au nanospheres to study the adsorption rate on substrates with different curvatures. We also established a theoretical model to explain this phenomenon for cylindrical surface as well as planar and spherical surfaces. Our results fit well with the theory, which predicts that particle adsorption rates depend strongly on surface geometry, and can exceed the planar surface deposition rate by over two orders of magnitude when the diffusion length of the particle is large compared to the surface curvature. In Chapter 5, we studied the optical properties of Au nanospheres separated from a thick Au film by a polyelectrolyte multilayer (PEM) film assembled from PAH and PSS under specific pH condition. The PEM film undergoes swelling and shrinking when the environmental pH is changed as a result of charging and discharging of the polyelectrolytes. Therefore, the PEM film provides an efficient means to tune the distance between Au spheres and Au film. The extinction peak blue-shifted as much as 100 nm when the pH of the water changed from pH 10 to pH 3 for 100 nm diameter Au spheres on a PEM film assembled at pH 9.5. Our preliminary estimates that the gap between sphere and surface can be as small as a few nm even though the film itself is tens of nm thick when it is not constrained by Au spheres. We studied two-photon excitation fluorescence (TPEF) from Ag triangles in Chapter 6. The triangles were fabricated by nanosphere lithography, which used convective self-assembly to make the nanosphere mask. The LSPRs of the nanotriangles were tuned to be in the 800--900 nm range to match with the Ti:Sapphire pulse laser at 880 nm. We found that certain spots on the fluorescence images gave rise to larger fluorescence intensity than rest of the area. SEM imaging reveals that the unusually bright spots seen on the surface were related to regions where the triangles transformed to spherical particles. The larger intensity is tentatively ascribed to the plasmon resonance of those spherical particles in ~400 nm range. / Ph. D.

We report the assembly of three-dimensional (3D) liver sinusoidal mimics comprised of primary rat hepatocytes, human or rat liver sinusoidal endothelial cells denoted as hLSECs and rLSECs respectively, and an intermediate chitosan-hyaluronic acid (HA) polyelectrolyte multilayer (PEM). The height of the PEMs ranged from 30-55nm and exhibited a shear modulus of ~ 100kPa. Primary rat hepatocytes coated with 5 and 15 PE layers exhibited stable urea and albumin production over a seven day period and these values were either comparable or superior to that in a collagen sandwich (CS). Hepatocyte-PEM-hLSEC liver mimics exhibited stable urea production and increasing albumin secretion over the culture period in comparison to hepatocyte-LSEC samples. In the 3D liver mimics, hLSEC phenotype was maintained and verified by the uptake of acetylated low-density lipoprotein (AcLDL). A sixteen-fold increase in CYP1A1/2 activity was observed for hepatocyte-PEM-10,000 hLSEC samples, thereby, suggesting that interactions between hepatocytes and hLSECs play a key role in enhancing hepatic phenotypes in in vitro cultures. As the first step towards elucidating key signaling pathways involved in cell-cell communications, global genome-wide transcriptional profiles of primary hepatocytes cultured in CS and hepatocyte monolayers (HMs) were performed over an eight-day period using DNA microarray measurements and Gene Set Enrichment Analysis (GSEA) in order to derive biologically meaningful information at the level of gene sets. The gene expression in CS cultures steadily diverged from that in HMs. Gene sets up-regulated in CS are those linked to liver metabolic and synthetic functions, such as lipid, fatty acid, alcohol and carbohydrate metabolism, urea production, and synthesis of bile acids. Monooxygenases such as CYP enzymes were significantly up-regulated starting on day 3 in CS cultures. These results serve as a baseline for further investigation into the systems biology of engineered liver tissues. 3D hepatic constructs were also assembled with primary rat hepatocytes and rLSECs, and a chitosan-HA PEM. In these hepatic models, the phenotype of hepatocytes and rLSECs were maintained. rLSEC phenotype was verified over a twelve-day period through immunostaining with the sinusoidal endothelial-1 (SE-1) antibody. In contrast, rLSECs cultured as monolayers lost their phenotype within 3 days. A two-fold increase in albumin production was observed only in the 3D liver models. rLSEC-PEM-hepatocyte cultures exhibited three- to six-fold increased CYP1A1/2 and CYP3A enzymatic activity. Well-defined bile canaliculi were observed in only 3D hepatic constructs. In summary, these results indicate that the layered rLSEC-PEM-hepatocyte constructs can be used as liver models for future studies. / Ph. D.

Le manque croissant en eau potable dans le monde est un problème d’envergure pour la population. La filtration par des membranes des eaux usées, insalubres ou la désalination apparaît comme une alternative viable pour le futur. La modification de membranes d’ultrafiltration par l’assemblage couche-par-couche permet d’obtenir des propriétés de nanofiltration en contrôlant avec une précision nanométrique l’épaisseur de la couche active de séparation déposée. Lors de cette thèse, nous avons étudié la construction de la couche de séparation ainsi que sa régénérabilité. Pour ce faire, nous avons développé des surfaces « membrane-like » pour étudier la construction sur des surfaces possédant des fonctions chimiques similaires à l’applicative. Par ailleurs, le temps de déposition a aussi été investigué afin de déterminer si les propriétés de séparation des membranes modifiées dépendaient du nombre de couches déposé ou du temps de dépôt. Les membranes ainsi développées présentent une couche de séparation régénérable et des propriétés de nanofiltration. / The increasing lack of drinking water in the world is of major concern for the population. Membrane filtration of brackish water, seawater appears to be a viable alternative for the future. Nanofiltration membranes can be obtained by modifying ultrafiltration membranes by the Layer-by-Layer (LbL) technique. This method also the deposition of an ultra-thin separation layer with a nanoscale precision and with tunable properties. During this PhD thesis, the build-up and the regenerability of the separation layer was investigated. For this purpose, mimicry surfaces were developed in order to study the LbL-assembly on surfaces presenting similar chemical functions as the applicative one. In addition, the deposition time was also investigated in order to determine if the separation properties of the membrane depend on the number of deposited layers or on the coating time. The developed membranes possessed a regenerable separation layer presenting nanofiltration properties.

Die Diffusion durch Polyelektrolytschichten ist bei vielen biotechnologisch-pharmazeutischen Anwendungen im Nanometerbereich von Bedeutung. Bei Experimenten wurde gefunden, dass bei der Diffusion eines Quenchers in mit Fluoreszenzfarbstoff markierten Polyelektrolytmultischichten die Kinetik des Diffusionsprozesses Charakteristika einer anormalen Diffusion aufweist. In dieser Arbeit wird qualitativ und quantitativ gezeigt, dass die Diffusion des Quenchers mit Subdiffusion beschrieben werden kann. Der gemessene Diffusionsprozess kann durch eine Superposition von Markov‘schen Diffusionsprozessen dargestellt werden. Das wird mit einer Monte-Carlo-Simulation nachgewiesen, die auf der analytischen Lösung des vorliegenden Reaktions-Diffusionsgleichungssystems basiert. Die experimentellen Daten werden im Zusammenhang mit der strukturellen Basis der parallel ablaufenden Diffusionsprozesse diskutiert.

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Cette thèse concerne la fonctionnalisation des biomatériaux, le titane et l'alliage de titane Ti6Al4V ainsi que le PEEK (Poly-Éther-Éther-Ketone) pour l'application de ces biomatériaux dans les domaines de l'implantologie dentaire et de la reconstruction maxillo-faciale. Au cours de la première partie de ce travail nous avons synthétisé quatre peptides bi-fonctionnels avec une grande affinité pour la surface implantaire de Ti et de Ti6Al4V et également pour les kératinocytes oraux. La spectroscopie de force de la cellule unique (Single Cell Force Spectroscopy - AFM) a été utilisée pour étudier l'adhésion d'une cellule sur les surfaces fonctionnalisées par les quatre peptides bi-fonctionnels. A l'aide du test colorimétrique de para-nitrophenyl phosphate (pNPP) on a démontré l'adhésion des kératynocytes après 4 heures d'incubation sur les surfaces fonctionnalisées avec les peptides bi-fonctionnels. Les résultats de ces études ont démontré la présence d'un peptide bi-fonctionnel qui augmente l'adhésion cellulaire instantanée et l'adhésion 4h après incubation des kératinocytes oraux sur les métaux. Ce peptide résiste à l'influence de facteurs externes tels que l'adsorption d'albumine et représente une proposition prometteuse pour la fonctionnalisation de l'implant de Ti et de Ti6Al4V. La deuxième partie de notre mémoire de thèse décrit une méthode de dépôt par spray des films des multicouches de PLL/PGA (poly-l-lysine/acide polyglutamique), des protéines et des cellules souches pulpaires. Les outils de spray d'usage unique ont été adaptés aux exigences de la bonne pratique de fabrication (GMP - good manufacturing practice). Les premiers tests de prolifération cellulaire ont démontré qu'elle n'a pas été affectée par le spray. L'étude en AFM a démontré que la rugosité et l'épaisseur du film augmentaient exponentiellement avec l'augmentation du nombre des couches déposées. Le traitement physique par UV rayonnement ainsi que le traitement par la déshydratation et la réhydratation des films ont provoqué des changements dans l'épaisseur, l'élasticité et la dureté des films. Le dépôt des protéines sur les MPEs a aussi augmenté l'épaisseur et a influencé la dureté de la surface. Les changements chimiques de la structure des MPEs après le traitement physique et après le dépôt des protéines naturelles ont été étudiés par la spectroscopie Raman. La prolifération cellulaire au 1er, 3e et 8e jours après leur spray sur des films de MPEs et des protéines a été ensuite évaluée. Les MPEs traitées par UV combiné avec déshydratation/réhydratation ainsi que les PEMs couvertes par protéine - CaP ont entrainé une meilleure adhésion et prolifération cellulaires que les MPEs non-traitées. Finalement la méthode de dépôt par spray des MPEs, protéines et aussi des cellules souches pulpaires a été appliquée sur la surface de PEEK. La meilleure prolifération cellulaire au 8e jour après le spray était sur la surface couverte par le film de (PLL-PGA)5-protéine/CaP. Une étude in vitro sur le degré de minéralisation au 21e jour après l'incubation des cellules pulpaire dans un milieu ostéconductuer sur des différentes (MPEs couvertes-PEEK) surfaces a été effectuée. Les résultats de la microscopie électronique à balayage (MEB), microscopie électronique à transmission (MET), combiné avec des études histologiques ont confirmé la formation d'une matrice extracellulaire minéralisée des autour des cellules pulpaires sur la surface de PEEK. Conclusions: Dans ce travail nous avons décrit une nouvelle approche de fonctionnalisation des surfaces de Ti and Ti6Al4V par des peptides bi-fonctionnels en proposant une séquence prometteuse qui augmente l'adhésion des kératinocytes oraux. Ensuite nous avons développé une méthode de fonctionnalisation de la surface de PEEK par des multicouches de polyeléctrolytes, des protéines naturelles et des cellules souches de la pulpe dentaire. La différentiation ostéoblastique in vitro a été finalement évaluée. / The objective of this thesis was to develop new techniques of surface functionalization of titanium; titanium alloy (Ti6Al4V) and PEEK (poly-ether-ether ketone) surfaces for their application on dental implantology and maxillofacial surgery. During the first part of the thesis we have synthesized four metal binding-cell specific peptides (MCSPs) with high affinity to titanium surface and to oral keratinocytes cells. Single Cell Force Spectroscopy (AFM) was used to study the instantaneous cell adhesion force of keratinicyte cell on MCSPs functionalized surfaces. The colorimetric para-nitrophenyl phosphate (pNPP) essay demonstrates the surface cell adhesion four hours after incubation. The results demonstrate the presence of one bi-functional peptide (MCSP-2) who increases both: the instantaneous and the 4 h cell adhesions. MCSP-2 resist to the influence of external factors like BSA adsorption and could be an interesting candidate for implant surface functionalisation. In the second part of the thesis we have developed a spray deposition method of polyelectrolyte multilayer (PEM) films build. PLL/PGA (poly-l-lysine/poly-glutamic acid) and proteins were used for surface coating. Consequently dental pulp stem cells (DPSC) are sprayed on the PEM films. The aims were to improve a spray -method for cells and the polyelectrolytes deposition on the PEEK implant. The entire spray device was designed for single use, which correspond to good manufacturing practice (GMP) conditions. Cell proliferation in 24 hours after spraying was not disturbed by the spray. Physicochemical properties of PEMs deposited by spray on glass surfaces were performed by Atomic Force Microscopy (AFM) and by contact angle measurements. The results have demonstrated the changes in films thickness and films roughness with increasing numbers of layers corresponding to exponential growth of the films. Physical treatment by UV irradiation and drying-wetting process affects the film thickness and the film elasticity and increases the stiffness of the film. The deposition of protein-CaP and collagen coatings on PEM films increased the layer thickness and influenced the hardness of the surface. Chemical changes in the polyelectrolyte structure during the physical treatment and after proteins deposition were studied by Raman spectroscopy. Cell proliferation of the pulp cells at 1st, 3th and 8th days after pulp cells deposition on PEMs coated glass surfaces, was then evaluated. The results demonstrated that 10 UV/ dray/wetted films and the natural proteins coated films enhanced cell adhesion and cell proliferation. The protein-CaP PEMs covered surface creates the best microenvironment to ensure the cell behavior. Finally PEM films coatings are applied on PEEK implant surface. The AFM study shows the changes of homogeneity and roughness of this surface after PEM film deposition. Contact angle measurement demonstrates decreases of surface hydrophobicity. Cell proliferation of dental pulp stem cells (DPSC) on (PLL-PGA)5-protein/CaP coated PEEK surface was highest compared to other functionalized surfaces. In vitro study of DPSCs osteogenic differentiation was evaluated by the degree of mineralization of the extracellular matrix on the PEEK surface at 21st day after cell incubation. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with histological studies improved the formation of mineralized extracellular matrix and confirmed the osteogenic differentiation of DPSCs on the PEMs coated PEEK surface. Conclusions: In this work we validated the method of Ti and Ti6Al4V functionalization with bi-functional peptides. One peptide that could increase the epithelial cell adhesion to the surface was proposed. Spray deposition technics of PEMs, protein and pulp stem cells were applied for PEEK implant functionalization. Finally we evaluated the differentiation of dental pulp stem cells on the PEEK surface in vitro.

La régénération des défauts osseux de taille critique reste un défi majeur pour la santé. Les limitations des greffes de tissus communes nous ont incités à développer une alternative synthétique basée sur la construction d’un biomatériau, des facteurs ostéoinductifs et des cellules souches. Pour la construction du biomatériau, nous nous sommes concentrés sur les microporteurs polymères poreux, car ils supportent une expansion cellulaire à grande échelle et un assemblage modulaire des tissus, contournant deux goulots d'étranglement importants pour la traduction clinique. Pour assurer l'approvisionnement industriel et l'approbation réglementaire, nous avons conçu une méthode de fabrication sans solvant organique basée sur la cristallisation sphérulitique du poly(L-lactide) (PLLA) dans ses mélanges avec du polyéthylène glycol (PEG). Les sphérulites de PLLA ont été facilement récupérées sous forme de microporteurs en éliminant par rinçage le PEG soluble dans l'eau. Leur taille et leur porosité pourraient être contrôlées indépendamment en ajustant le rapport PLLA / PEG et la température de cristallisation. La biocompatibilité et l'ostéoconductivité des microporteurs à PLLA ont été confirmées par l'expansion et la différenciation ostéogénique des cellules souches adipeuses humaines (hASC). Comme cette dernière fonction hASC est sensible à différents paramètres de culture, nous avons ensuite utilisé l'approche de conception d'expériences pour leur dépistage rapide. En combinaison avec l'analyse à haut débit, nous avons identifié plusieurs paramètres ayant une influence marquée sur leur différenciation ostéogénique. Enfin, pour la délivrance de facteurs ostéoinducteurs, nous avons élaboré des multicouches de polyélectrolytes (PEM) à base de poly (L-ornithine) et d'acide hyaluronique biocompatibles. Ces PEM ont été caractérisées en termes de croissance, de morphologie, d'aptitude à incorporer des protéines morphogénétiques osseuses (BMP) et à fonctionner en tant que revêtements sur des microporteurs à PLLA. Nos résultats préliminaires ont montré que l’incorporation de BMP dans les PEM avait un effet important sur l’adhérence des hASC. Bien que des études supplémentaires soient nécessaires, les microporteurs à PLLA recouverts de PEM chargés de BMP et ensemencés avec hASC pourraient être un implant synthétique prometteur pour une régénération osseuse améliorée. / The regeneration of critical-sized bone defects remains a major healthcare challenge. The limitations of common tissue grafts prompted us to develop a synthetic alternative based on a biomaterial construct, osteoinductive factors and stem cells. For biomaterial construct, we focused on porous polymeric microcarriers as they support large-scale cell expansion and modular tissue assembly, circumventing two important bottlenecks for clinical translation. To insure industrial supply and regulatory approval, we designed an organic-solvent-free method for their fabrication based on the spherulitic crystallization of poly(L-lactide) (PLLA) in its blends with polyethylene glycol (PEG). The PLLA spherulites were easily recovered as microcarriers by rinsing away the water-soluble PEG. Their size and porosity could be independently controlled by tuning the PLLA/PEG ratio and crystallization temperature. The biocompatibility and osteoconductivity of PLLA microcarriers were confirmed through the expansion and osteogenic differentiation of human adipose stem cells (hASCs). Because the latter hASC function is sensitive to different culture parameters, we then used the Design of Experiments approach for their rapid screening. In combination with high-throughput analysis, we identified several parameters that had a pronounced influence on their osteogenic differentiation. Finally, for the delivery of osteoinductive factors, we elaborated polyelectrolyte multilayers (PEM) based on biocompatible poly(L-ornithine) and hyaluronic acid. These PEMs were characterized in terms of their growth, morphology, the ability to incorporate bone morphogenetic proteins (BMP) and to function as coatings on PLLA microcarriers. Our preliminary results showed that the incorporation of BMPs inside PEMs had a strong effect on hASC adhesion. While further studies are needed, hASC-seeded PLLA microcarriers coated with BMP-loaded PEMs could be a promising synthetic implant for improved bone regeneration.

Surface modification techniques have played important roles in various aspects of modern technology. They have been employed to improve substrates by altering surface physicochemical properties. An ideal surface modifying technique would be a method that is applicable to any kind of materials prepared from a wide range of polymers and that can occur under mild reaction conditions. The work in this thesis has utilized four main concepts: I) the development of a ‘grafting-from’ technique by covalently growing polymer grafts from particle surfaces, II) the presence of steric and electrosteric forces due to long-range repulsive interactions between particles, III) a combined surface grafting and layer-by-layer approach to create polyelectrolyte multilayers (PEMs) on particle surfaces to fabricate strong and functional materials, and IV) the roles of hydrophilic polymer grafts and substrate geometry on surface degradation. A non-destructive surface grafting technique was developed and applied to polylactide (PLA) particle surfaces. Their successful modification was verified by observed changes to the surface chemistry, morphology and topography of the particles. To quantify the aggregation behavior of grafted and non-grafted particles, force interaction measurements were performed using colloidal probe atomic force microscopy (AFM). Long-range repulsive interactions were observed when symmetric systems, i.e., hydrophilic polymer grafts on two interacting surfaces, and asymmetric system were applied. Electrosteric forces were observed when the symmetric substrates interacted at pH 7.4. When PEMs were alternately assembled on the surface of poly(L-lactide) (PLLA) particles, the grafted surfaces played a dominated role in altering the surface chemistry and morphology of the particles. Three-dimensional scaffolds of surface grafted particle coated with PEMs demonstrated high mechanical performance that agreed well with the mechanical performance of cancellous bone. Nanomaterials were used to functionalize the scaffolds and further influence their physicochemical properties. For example, when magnetic nanoparticles were used to functionalize the scaffolds, a high electrical conductivity was imparted, which is important for bone tissue regeneration. Furthermore, the stability of the surface grafted particles was evaluated in phosphate buffered saline (PBS) solution. The nature of the hydrophilic polymer grafts and the geometry of the PLLA substrates played central roles in altering the surface properties of films and particles. After 10 days of PBS immersion, larger alterations in the surface morphology were observed on the film compared with microparticles grafted with poly(acrylic acid) (PAA). In contrast to the PAA-grafted substrates, the morphology of poly(acrylamide) (PAAm)-grafted substrates was not affected by PBS immersion. Additionally, PAAm-grafted microparticulate substrates encountered surface degradation more rapidly than PAAm-grafted film substrates. / <p>QC 20151002</p>

The development of the layer-by-layer (LbL) technique has turned out to be an efficient way to physically modify the surface properties of different materials, for example to improve the adhesive interactions between fibers in paper. The main objective of the work described in this thesis was to obtain fundamental data concerning the adhesive properties of wood biopolymers and LbL films, including the mechanical properties of the thin films, in order to shed light on the molecular mechanisms responsible for the adhesion between these materials. LbLs constructed from poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA), starch containing LbL films, and LbL films containing nanofibrillated cellulose (NFC) were studied with respect to their adhesive and mechanical properties. The LbL formation was studied using a combination of stagnation point adsorption reflectometry (SPAR) and quartz crystal microbalance with dissipation (QCM-D) and the adhesive properties of the different LbL films were studied in water using atomic force microscopy (AFM) colloidal probe measurements and under ambient conditions using the Johnson-Kendall-Roberts (JKR) approach. Finally the mechanical properties were investigated by mechanical buckling and the recently developed SIEBIMM technique (strain-induced elastic buckling instability for mechanical measurements). From colloidal probe AFM measurements of the wet adhesive properties of surfaces treated with PAH/PAA it was concluded that the development of strong adhesive joints is very dependent on the mobility of the polyelectrolytes and interdiffusion across the interface between the LbL treated surfaces to allow for polymer entanglements. Starch is a renewable, cost-efficient biopolymer that is already widely used in papermaking which makes it an interesting candidate for the formation of LbL films in practical systems. It was shown, using SPAR and QCM-D, that LbL films can be successfully constructed from cationic and anionic starches on silicon dioxide and on polydimethylsiloxane (PDMS) substrates. Colloidal probe AFM measurements showed that starch LbL treatment have potential for increasing the adhesive interaction between solid substrates to levels beyond those that can be reached by a single layer of cationic starch. Furthermore, it was shown by SIEBIMM measurements that the elastic properties of starch-containing LbL films can be tailored using different nanoparticles in combination with starch. LbL films containing cellulose I nanofibrils were constructed using anionic NFC in combination with cationic NFC and poly(ethylene imine) (PEI) respectively. These NFC films were used as cellulose model surfaces and colloidal probe AFM was used to measure the adhesive interactions in water. Furthermore, PDMS caps were successfully coated by LbL films containing NFC which enabled the first known JKR adhesion measurements between cellulose/cellulose, cellulose/lignin and cellulose/glucomannan. The measured adhesion and adhesion hysteresis were similar for all three systems indicating that there are no profound differences in the interaction between different wood biopolymers. Finally, the elastic properties of PEI/NFC LbL films were investigated using SIEBIMM and it was shown that the stiffness of the films was highly dependent on the relative humidity. / <p>QC 20110923</p>

Layer-by-layer assembly of polyelectrolytes is a simple technique based on the self-assembly of polycations and polyanions mainly by electrostatic interactions, which has gained considerable scientific interest for its versatility of applications. Ease of fabrication process, inexpensive approach and use to coat surfaces with various geometries prompts the researchers to select this technique not only for the surface modification applications but also to study the processes which exploit the 3D matrix properties of polyelectrolyte multilayer films (PEMs). Recent advances have been made where PEMs coatings have been utilized for their bio-applications like drug delivery and in tissue engineering for modifying the biomaterial's surfaces. In the field of drug delivery and tissue engineering the location and availability of the constituent molecules is very important, which is defined by their ability to diffuse through the encapsulating material or reservoir. So the main objective of this thesis is to understand the transport of molecules in ultrathin Polyelectrolyte Multilayer Films in lateral as well as transverse direction to the substrate. To study this transport behaviour in PEMs, we have employed various strategies which can enhance or suppress the diffusivity across PEMs. Thus, understanding the diffusion at nanoscale resolution will lead us to design better host materials for loading of drugs and growth factors for various biomedical applications.