Novos materiais obtidos a partir de polímeros biodegradáveis são uma alternativa para a redução do impacto ambiental causado pelo uso excessivo de polímeros derivados do petróleo. Atualmente, vários estudos têm sido realizados na busca de matéria-prima para o desenvolvimento de filmes biodegradáveis, com boa viabilidade técnica e econômica. Dentre estas matérias-primas, destacam-se as que são provenientes de fontes renováveis, de baixo custo e que tenham grande importância econômica e ambiental, como, por exemplo, o amido, as argilas, e a quitosana. Nos filmes que preparamos, adicionamos como plastificante a glicerina, um subproduto do biodiesel, e que contribui para maior estabilidade térmica dos filmes, em conjunto com o amido. O propósito deste trabalho foi o preparo de um biopolímero a base de quitosana e argila com propriedades de nanocompósitos, pois estes materiais costumam exibir propriedades físico-químicas diferenciadas em relação a outros materiais, devido à redução no seu tamanho. Sendo assim, através do estudo e comparação de duas argilas esmectíticas sódicas naturais, Bentogel e Corral, pôde-se observar o comportamento dos filmes formados em presença de amido e glicerina. Os filmes obtidos, através do método de dispersão em solução do polímero, foram caracterizados através das técnicas de DRX, MEV, IV, TG e DSC. Os resultados obtidos mostraram a formação de filmes nanocompósitos esfoliados de boa estabilidade térmica. / New materials made from biodegradable polymers are an alternative to reducing the environmental impact caused by excessive use of polymers derived from petroleum. Currently, several studies have been conducted in search of raw material for the development of biodegradable films, with good technical and economic feasibility. Among these materials, we highlight those that are from renewable resources, low cost and have great economic and environmental importance, such as, starch, clays, and chitosan. In preparing films, we added glycerol as a plasticizer, a byproduct of biodiesel, and contributes to better thermal stability of the films, together with starch. The purpose of this study was the preparation of a biopolymer based on chitosan and clay nanocomposites properties, because these materials tend to display different physico-chemical properties compared to other materials because of the reduction in size. Thus, through the study and comparison of two natural sodium smectite clays, Bentogel and Corral, it was observing the behavior of films formed in the presence of starch and glycerol. The films obtained by the method of dispersion in the polymer solution, were characterized by techniques of XRD, SEM, FTIR, TG and DSC. The results obtained showed the formation of exfoliated nanocomposites films and good thermal stability.

La lithographie est une étape clé de micro/nanotechnologie pour la fabrication de composants utilisés dans les domaines de la microéléctronique, de l’électronique flexible, de la photonique, du photovoltaïque, de la microfluidique... Cette étape de lithographie nécessite l’utilisation d’une résine inscriptible servant de masque temporaire permettant le transfert de motifs dans le matériau sous-jacent par gravure ou par déposition de nouveaux matériaux. La lithographie fait appel à des résines organiques mais aussi à des solvants organiques et des produits chimiques corrosifs et nocifs, ce qui va à l’encontre des problématiques environnementales et qui engendre des coûts supplémentaires liés à la gestion des risques et des déchets. De plus le contexte réglementaire (REACh ou US pollution act) évolue vers une plus grande protection de l’environnement et de la santé humaine et encourage l’utilisation de produits alternatifs. Dans ce contexte, mon projet de thèse visait à développer une résine biosourcée, non modifiée par des procédés de chimie de synthèse et développable dans l’eau. Cette résine devait être compatible avec les instruments de lithographies conventionnelles. Lors de ce travail, il a été démontré que le chitosane était une résine de tonalité positive permettant la réalisation d’un procédé complet de lithographie/gravure avec uniquement de l’eau comme solvant, sans modification du chitosane et sans l’utilisation de masque additionnel. Des motifs de 50 nm ont été obtenu dans la silice après lithographie électronique et gravure plasma et des motifs de 0.5 à 0.3 μm après photolithographie et gravure. / . Lithography is a key step in micro / nanotechnology with applications in the fields of microelectronics, flexible electronics, photonics, photovoltaics, microfluidics and biomedical. This lithography step requires the use of a writable resist to act as a temporary mask for transferring patterns in the underlying material by etching or deposition. Nowadays, lithography uses synthetic organic resin, organic solvents and hazardous chemicals which is contrary to environmental issues and generates additional costs associated with risk and waste management. Furthermore, regulation rules (REACh, US pollution act) tend to move toward the protection of human health and the environment from the risks that can be posed by chemicals and promote alternative chemicals. In this context, this PhD work aimed at replacing conventional synthetic organic resist with a biopolymer. This biopolymer will not be modified by synthetic organic chemistry, will be compatible with conventional lithography instruments and it should be developable in water. It was demonstrated that chitosan was a positive tone resist allowing accomplishing a complete lithography-etching process. The whole process was performed in aqueous solution without the use of hazardous chemicals. 50 nm features were obtained after ebeam lithography/plasma etching into a silica layer without the use of an additional masking layer. 0.3-0.5 μm feature were obtained using photolithography.

Controlled drug delivery systems are becoming increasingly interesting with the contribution of nanotechnology. In the case of transdermal applications the greatest limitation is the highly impermeable outermost layer of the skin, the stratum corneum. One promising method of controlled transdermal drug delivery of the skin therapeutics is the use of nanoparticles as carriers. Encapsulation of the drug, as opposed to classical topical application of creams or emulsions, allows the drug to diffuse into hair follicles where drug release can occur in the deeper layers of the skin. The aim of this study was to develop micro and nano sized carriers as drug delivery systems to achieve treatment for skin conditions like psoriasis, aging or UV damage, caused by radiation or health problems. Two different types of bioactive agents, retinyl palmitate (RP) and Dead Sea Water (DSW), were used by encapsulating in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) carriers. In some tests MgCl2 was used as a substitute for DSW when quantification was needed. Bioactive agent loaded nanospheres and nanocapsules were prepared with o/w and w/o/w methods in low micron (1.9 &micro / m), mid nano (426 nm) and nano (166 nm) sizes. Loading, encapsulation efficiency and release kinetics were studied. The encapsulation efficiency and loading values are low especially for the water soluble agents, DSW and MgCl2. It was observed that the capsules loaded with hydrophilic agents released their content in the first 24 h in aqueous media. The encapsulation efficiency and loading values for RP were higher because of the insolubility of the agent in water. In the in vitro studies carried out with L929 mouse fibroblast cells, the nano sized PHBV capsules were detected in the cytoplasm of the cells. Cell viability assay (MTT) for L929 cells showed a growth trend indicating that the particles were not cytotoxic and the values were close to the controls. Hemolytic activity was examined using human erythrocytes and micro/nanoparticles of PHBV were found to be non hemolytic. In vivo testing with BALB/c mice, nanocapsule penetration revealed that a small amount of nano sized particles penetrated the mice skin, despite the highly impermeable outer skin layer. As a result, PHBV micro/nanoparticles have a significant potential for use as topical drug delivery systems in the treatment of skin diseases.

Coating of fine pthesiss to produce tailored surface properties is currently a key development for supercritical fluids applications, in different areas such as: pharmaceutical, nutraceutical, cosmetic, agrochemical, electronic and specialty chemistry industries. During the encapsulation process the pthesis surface can be designed with specific properties by spreading a thin film coating material over the surface of the pthesiss. Chitosan, a natural polymer, was used in this work as the encapsulant material. Chitosan is biocompatible, biodegradable to normal body constituents, safe, non-toxic, bacteriostatic, anticancerogen, and versatile polymer. These attributes are among the properties that make Chitosan an attractive component of pharmaceutical products. The main objective of this research was to encapsulate solid pthesiss under 5fÝm with a biopolymer, Chitosan, using supercritical CO2 as one of the solvents. In order to reach this goal, some the following initial tasks were completed: the cloud point for the system DMSO-CO2 was determined and compared with published data to validate the experimental system. Subsequently the cloud point experiments were extended to include the ternary system Chitosan-DMSO-CO2, and a dynamic solubility experimental set-up was constructed and used to obtain solubility data for the same ternary system. A novel SCF fluidized bed was used to micro encapsulate porous (TiO2) and non-porous pthesiss (CaO) through a temperature swing with a Chitosan thin layer. DMSO was used as an entrainer to enable solubilization of Chitosan and removed within the supercritical carbon dioxide. Several analytical methods were used to characterize these pthesiss; SEM-EDS analysis was used to evaluate a group of pthesiss, determining composition and pthesis diameter on samples up to 900 pthesiss. TEM and AFM confirmed pthesiss of one micron or less were encapsulated with a thickness of less than 5 nm. AFM shows pthesis roughness on the nanometer range, 46 nm or more for uncoated pthesiss and 2-4 nm for the encapsulated ones. FTIR, NMR and DSC-TGA analysis confirmed that the chemical structure of Chitosan remained constant before and after processing, and the changes observed were attributed to some DMSO and moisture adsorbed during the encapsulation process.

Fibrin is a biopolymer that assembles into a network during blood coagulation to become the structural scaffold of a blood clot. The precise mechanics of this network are crucial for a blood clot to properly stem the flow of blood at the site of vascular injury while still remaining pliable enough to avoid dislocation. A hallmark of fibrin's mechanical response is strain-stiffening: at small strains, its response is low and linear; while at high strains, its stiffness increases non-linearly with increasing strain. The physical origins of strain-stiffening have been studied for other biopolymer systems but have remained elusive for biopolymer networks composed of stiff filaments, such as fibrin. To understand the origins of this intriguing behavior, we directly observe and quantify the motion of all of the fibers in the fibrin networks as they undergo shear in 3D using confocal microscopy. We show that the strain-stiffening response of a clot is a result of the full network deformation rather than an intrinsic strain-stiffening response of the individual fibers. We observe a distinct transition from a linear, low-strain regime, where all fibers avoid any internal stretching, to a non-linear, high-strain regime, where an increasing number of fibers become stretched. This transition is characterized by a high degree of non-affine motion. Moreover, we are able to precisely calculate the non-linear stress-strain response of the network by using the strains on each fiber measured directly with confocal microscopy and by assuming the fibers behave like linearly elastic beams. This result confirms that it is the network deformation that causes the strain-stiffening behavior of fibrin clots. These data are consistent with predictions for low-connectivity networks with soft, bending, or floppy modes. Moreover, we show that the addition of small contractile cells, platelets, increases the low-strain stiffness of the network while the high-strain stiffness is independent of the presence of the platelets; this is also consistent with expectations for small contractile elements in a network with low connectivity. Our results elucidate the origins of strain-stiffening in fibrin networks as well as the mechanism underlying platelet-induced clot stiffening. / Physics

The first part of the thesis investigates the enhancement of fly ash-based geopolymer with alkali pretreated sweet sorghum fiber. The unconfined compression, splitting tensile and flexural tests were conducted to investigate the mechanical properties of geopolymer composite. The results indicate that the inclusion of sweet sorghum fiber slightly decreases the unconfined compressive strength (UCS), however, the splitting tensile and flexural strengths as well as the post-peak toughness increase with the fiber content up to 2% and then decrease thereafter. A durability test program containing 10 wet/dry cycles was performed to evaluate the long-term performance of the geopolymer composite related to wet/dry cycling. The results indicate that both the UCS and the splitting tensile strength of the geopolymer composite progressively decrease with the number of wet/dry cycles. The second part of the thesis investigates the utilization of biopolymers to stabilize MT for dust control. First, a fall cone method was adopted to evaluate the Atterberg limits and undrained shear strength of MT stabilized with biopolymers. The results indicate that the inclusion of biopolymers increases both the liquid limit and the undriained shear strength of MT. Two new equations are proposed for predicting the undrained shear strength of MT based on liquid limit and water content, and liquidity index. Second, an experimental program including moisture retention, wind tunnel and surface strength tests was performed to evaluate the effectiveness of biopolymer stabilization for dust control. The results indicate that biopolymers are effective in enhancing the moisture retention capacity, improving the dust resistance, and increasing the surface strength of MT. Third, a durability test program containing 10 wet/dry cycles was applied to MT samples treated with biopolymer solutions of different concentrations. The results show that the dust resistance of MT samples progressively decreases with the number of wet/dry cycles. Finally, experimental and numerical studies on the unconfined compressive strength (UCS) of MT stabilized with biopolymer were carried out. It is found that inclusion of biopolymer into MT favors the increase of adhesion between MT particles and thus the increase of the UCS of MT.

This thesis describes the development of a high-throughput approach towards the encapsulation of cancer cells in biopolymer microgels with tunable mechanical properties. In particular, this thesis is focused on: i) the high-throughput generation of biopolymer microgels with tunable mechanical properties ii) the measurement of the mechanical properties of the microgels, and iii) the high-throughput encapsulation of a cancer cell line within biopolymer gels. The microgels will be generated by (i) introducing in a microfluidic device two distinct streams of biopolymer solutions; (ii) mixing the streams; (iii) emulsifying the biopolymer and (iv) using thermosetting to transform the droplets in situ into microgels. By applying a compression force to the hydrogel microbead and measuring its deformation, the Young’s modulus and relaxation time of the microgel can be examined. The properties of cells were examined within the gels using various spectroscopic techniques such as absorption (UV-Vis) and fluorescence microscopy (fluorescent microscopy, confocal microscopy).

This thesis describes the development of a high-throughput approach towards the encapsulation of cancer cells in biopolymer microgels with tunable mechanical properties. In particular, this thesis is focused on: i) the high-throughput generation of biopolymer microgels with tunable mechanical properties ii) the measurement of the mechanical properties of the microgels, and iii) the high-throughput encapsulation of a cancer cell line within biopolymer gels. The microgels will be generated by (i) introducing in a microfluidic device two distinct streams of biopolymer solutions; (ii) mixing the streams; (iii) emulsifying the biopolymer and (iv) using thermosetting to transform the droplets in situ into microgels. By applying a compression force to the hydrogel microbead and measuring its deformation, the Young’s modulus and relaxation time of the microgel can be examined. The properties of cells were examined within the gels using various spectroscopic techniques such as absorption (UV-Vis) and fluorescence microscopy (fluorescent microscopy, confocal microscopy).

Poly-γ-glutamic acid (γ-PGA) is a naturally occurring biopolymer made up of repeating units of glutamic acid and can be potentially used for multiple applications. This study compared the production of γ-PGA by eight bacteria (B. subtilis 23856, B. subtilis 23857, B. subtilis 23858 B. subtilis 23859, B. subtilis natto, B. licheniformis 1525, B. licheniformis 6816 and B. licheniformis 9945a) in GS and E media. B. subtilis natto and B. licheniformis 9945a have been investigated extensively for γ-PGA production, however, the remaining six have not previously been used. Using the eight bacteria, yields of up to 22.3 g/l were achieved in shake flasks. On characterization, it was observed that γ-PGA with different properties (crystallinity, acid/salt form and molecular weights ranging from 3,000 Da to 871,000 Da) was produced. Production of γ-PGA by B. subtilis natto in GS medium was scaled up using a fermenter and was tested for novel probiotic applications. The survival of probiotics during freeze drying, storage and ingestion was improved by combining them with a γ-PGA matrix. For L. paracasei, 10% γ-PGA protected the cells significantly better (P < 0.05) than 10% sucrose during freeze drying, whereas for B. longum and B. breve, it showed comparable cryoprotectant activity (P > 0.05) to 10% sucrose. This study also demonstrated the potential use of a non-dairy foodstuff (orange juice) for delivery of probiotics. Two Bifidobacteria strains protected with γ-PGA survived significantly better (P < 0.05) in orange juice for 39 days, with a log reduction in viability of less than 2.99 CFU/ml, when compared to unprotected cells, which showed complete loss in viability by day 20. In addition, γ-PGA protection improved survival of Bifidobacteria in a solution mimicking the environment of the stomach. γ-PGA-protected Bifidobacteria showed little (< 0.47 log CFU/ml) or no loss in viability when stored in simulated gastric juice (pH 2.0) for four hours, whereas unprotected cells died within two hours.

Nanopores (1 – 10 nm diameter) constructed in solid-state membranes, have shown promise as next-generation biopolymer analysis devices offering both high resolution and high throughput. One promising application of nanopores is in the analysis of nucleic acids, such as DNA. This involves translocation experiments in which DNA is placed in an ionic solution and is forced through a nanopore with the aid of an applied electric field. The modulation of ionic current through the pore during DNA translocation can then be correlated to various properties of the biopolymer such as the length. To optimally design and operate nanopore devices, it would be advantageous to develop an accurate computer simulation methodology to predict the physics of the translocation process. Hence, I have developed a physically accurate, computationally efficient simulation methodology to predict and analyze the physics of biopolymer translocation through solid-state (silicon nitride) nanopores. The overall theme of this thesis is to use this simulation methodology to thoroughly investigate important issues in the physics underlying translocation experiments and thereby determine the effects of key structural and operation parameters, such as nanopore dimensions, applied voltage, hydrodynamic interactions, solvent viscosity, and the polymer chain length. The results from these simulation studies can assist in not only proper nanopore design, but also help determine the proper experimental environments and parameters for nanopore operation.