Although millions of individuals worldwide are affected by blinding retinal degenerative diseases, most have very few options for treatment and no hope for vision restoration. Induced pluripotent stem cell (iPSC) replacement therapies represent a promising treatment option, but their effectiveness is limited by an overall lack of physical support for injected cells. Stem cell scaffolds can be used to provide this support by serving as an attachment platform for cells before, during, and after implantation. Thus, the design of polymer scaffolds with appropriate biochemistry, mechanical properties, and morphology is a critical step toward developing feasible stem cell therapies for blinding eye diseases. In this work, we aim to design a regenerative scaffold for the retina and determine the interplay among these three key design parameters. First, the feasibility of using a synthetic scaffold to grow and differentiate iPSCs to neural progenitor cells is demonstrated. The porous and degradable poly(lactic-co-glycolic acid) scaffolds employed were able to support a greater density of differentiating iPSCS than traditional tissue culture plastic. Additionally, the power of chitosan, a naturally occurring polymer, to overcome the toxic effects of copper nanoparticles is described. For two different cell types, various doses, and several time points, chitosan coated copper nanoparticles were significantly less toxic than non-coated particles. The mechanical properties of the human retina and the effects of aging and disease were also estimated using measurements of compressive modulus in animal models. In order to reach a range similar to native tissue, polymer mechanical properties were controlled using cross-linking density and surfactant templating. The influence of morphology was studied by inducing polymer structure changes via surfactant templating. Morphology significantly influenced water uptake and compressive modulus for both cross-linked poly(ethylene glycol) (PEG) and cross-linked chitosan hydrogels. Surfactant templating did not negatively affect the biocompatibility of PEG hydrogels and slightly improved the ability of chitosan hydrogels to support the growth and differentiation of iPSCs. Overall we have demonstrated the ability to tune polymer structure, mechanical properties, and biochemistry. These results add to the growing body of research aimed to understand and control cell/material interactions for biomaterial optimization.

Although the presence of acrylamide in foods was detected a decade ago, public concern about this issue, and in general about food health, seems to have increased in recent years. Acrylamide is a toxic human carcinogen present mainly in foods from plant origin and subjected to transformation processes in which temperatures above 120 °C are reached, such as frying and baking. Foods that mostly contribute to the intake of acrylamide are: French fries and chips, coffee and coffee substitute, biscuits, bread, pastries, battered and breaded products, breakfast cereals ..., being children and adolescents the most exposed population. From a chemical point of view, acrylamide is formed mainly from the reaction, during thermal processing, between asparagine and reducing sugars, as an intermediate product of the Maillard reaction. In the last decade, both health authorities and the scientific community have made great efforts in scientifically establishing limits of toxicity as well as exploring strategies aimed at reducing acrylamide formation. The purpose of this doctoral thesis is framed in this last sense. On the one hand, our work has been focused on searching new strategies for acrylamide mitigation, in two different types of food: fried potatoes and battered products. The effect of an emerging frying technique, named hot air frying, as well as pre-frying treatments, were studied in fried potatoes. In the case of batters however, the strategy consisted in modifying their composition by adding a hydrocolloid, chitosan, after having tested its potential in model systems. Furthermore, the effect of chitosan addition on the physical properties of the batter formulations and on the quality of the final product was evaluated. Finally, acrylamide bioaccessibility of the food products with the highest acrylamide content was addressed. These food products were subjected to an in vitro gastrointestinal simulation in order to study how acrylamide content progressed throughout the digestion process. Results showed that air fried potatoes as well as chitosan addition to batter formulations reduced the formation of acrylamide by about 90 and 60 %, respectively. The modification of the characteristics of chitosan (molecular weight and deacetylation degree) conditioned its ability to reduce the formation of acrylamide. Furthermore, the incorporation of chitosan to batters reduced the absorption of fat during frying. Chitosan increased viscosity and consistency of batters but, the color and texture of the fried products were not significantly altered. The total replacement of wheat flour by rice flour allowed to obtain gluten-free batters with similar viscosity, when adding chitosan. This new formulation could be adjusted to gluten-free battered products. The simulation of in vitro digestion showed a significant increment of acrylamide after the gastric stage in a wide range of foods. However, acrylamide bioaccessibility (after the intestinal stage) was reduced until pre-digestion levels or even lower in chips and French fries. / Si bien es verdad que la presencia de acrilamida en alimentos se detectó hace más de una década, la preocupación por parte del consumidor, no sólo por este tema si en la alimentación saludable en general, parece haberse incrementado en los últimos años. La acrilamida es un tóxico posible carcinógeno humano presente principalmente en alimentos derivados de materias primas de origen vegetal y sometidos a procesos de transformación en los que se alcanzan temperaturas por encima de 120 ºC como la fritura y horneado. Los alimentos que contribuyen mayoritariamente a la ingesta de acrilamida son: patatas fritas (tipo French fries y chips), café y substituto de café, galletas, pan, bollería, rebozados y empanados, cereales de desayuno¿, siendo la exposición al tóxico superior por parte de población infantil y adolescente. Desde un punto de vista químico, la acrilamida se forma principalmente a partir de la reacción entre la asparagina y azúcares reductores durante el procesado térmico, como producto intermedio de las reacciones de Maillard. En la última década, tanto las autoridades sanitarias como la comunidad científica han puesto un gran empeño en establecer científicamente los límites de toxicidad y en la búsqueda de estrategias orientadas a reducir su formación. El cometido de esta tesis doctoral se enmarca en este último sentido. Por un lado, se ha trabajado en la búsqueda de nuevas estrategias para la reducción de acrilamida, en dos tipos de alimentos distintos: patatas fritas y masas de productos rebozados. En patatas fritas se estudió el efecto de una técnica emergente de fritura, concretamente la fritura por aire caliente, junto con tratamientos previos a la fritura. En masas de rebozados, en cambio, se optó por modificar la composición de estos, adicionando un hidrocoloide, el quitosano, después de haber ensayado su potencial en sistemas modelo. Además, se evaluó el efecto de la incorporación de quitosano sobre las propiedades físicas de la masa de rebozado y sobre la calidad del producto final. Por último y no por ello menos importante, se abordó la problemática de la acrilamida sobre la salud humana desde el punto de vista de su bioaccesibilidad. Para ello, se seleccionaron los productos con mayor contenido en acrilamida dietética y se sometieron a una simulación gastrointestinal in vitro con el fin de conocer los cambios experimentados por el tóxico durante este proceso y determinar su bioaccesibilidad. Los resultados mostraron que la fritura de patatas por aire caliente, así como la incorporación de quitosano a las masas de rebozado reducían la formación de acrilamida alrededor de un 90 y 60 %, respectivamente. La modificación de las características del quitosano (en cuanto a masa molecular y grado de desacetilación) condicionó su capacidad de reducir la formación de acrilamida. La incorporación de quitosano redujo la absorción de grasa durante la fritura de las masas. Si bien aumentó la viscosidad y consistencia de éstas, no se vio alterado significativamente el color y la textura del producto final frito. La substitución total de harina de trigo por harina de arroz permitió obtener masas de rebozado sin gluten con semejante viscosidad, al adicionar quitosano. Esta nueva formulación podría ser adaptada a productos rebozados sin gluten. La simulación de digestión in vitro mostró aumentos significativos de acrilamida tras la fase gástrica en una amplia gama de alimentos. Sin embargo, la bioaccesibildad de acrilamida (tras la fase intestinal) se redujo hasta niveles previos a la digestión o incluso menores, en patatas fritas tipo chips y tipo French fries. / Si bé és veritat que la presència d'acrilamida en aliments es va detectar fa més d'una dècada, la preocupació per part del consumidor, no només per aquest tema si no en l'alimentació saludable en general, sembla haver-se incrementat en els últims anys. L'acrilamida és un tòxic possible carcinogen per a l'èsser humà present principalment en aliments derivats de matèries primeres d'origen vegetal i sotmesos a processos de transformació en els quals s'assoleixen temperatures majors a 120 ºC, com el procés de fregida o al forn. Els aliments que contribueixen majoritàriament a la ingesta d'acrilamida són: creïlles fregides (tipus French fries i chips), cafè i substitut de cafè, galetes, pa, brioixeria, arrebossats i empanats, cereals d'esmorzar ..., sent l'exposició al tòxic superior per part de població infantil i adolescent. Des d'un punt de vista químic, l'acrilamida es forma principalment a partir de la reacció entre l'asparagina i sucres reductors durant el processat tèrmic, com producte intermedi de les reaccions de Maillard. En l'última dècada, tant les autoritats sanitàries com la comunitat científica han posat un gran esforç a establir científicament els límits de toxicitat i en la recerca d'estratègies orientades a reduir la seva formació. La comesa d'aquesta tesi doctoral s'emmarca en aquest últim sentit. D'una banda, s'ha treballat en la recerca de noves estratègies per a la reducció d'acrilamida, en dos tipus d'aliments diferents: creïlles fregides i masses de productes arrebossats. En creïlles fregides es va estudiar l'efecte d'una tècnica emergent de fregit, concretament el fregit per aire calent, juntament amb tractaments previs al fregit. En masses d'arrebossats, en canvi, es va optar per modificar la composició d'aquests, addicionant un hidrocol·loide, el quitosà, després d'haver assajat el seu potencial en sistemes model. A més, es va avaluar l'efecte de la incorporació de quitosà sobre les propietats físiques de la massa d'arrebossat i sobre la qualitat del producte final. Finalment i no per això menys important, es va abordar la problemàtica de l'acrilamida sobre la salut humana des del punt de vista de la seva bioaccesibilidad. Per a això, es van seleccionar els productes amb major contingut en acrilamida dietètica i es van sotmetre a una simulació gastrointestinal in vitro per tal de conèixer els canvis experimentats pel tòxic durant aquest procés i determinar la seva bioaccesibilidad. Els resultats van mostrar que el fregit de creïlles per aire calent, així com la incorporació de quitosà a les masses d'arrebossat reduïen la formació d'acrilamida al voltant d'un 90 i 60%, respectivament. La modificació de les característiques del quitosà (quant a massa molecular i grau de desacetilación) va condicionar la seva capacitat de reduir la formació d'acrilamida. La incorporació de quitosà va reduir l'absorció de greix durant el fregit de les masses. Si bé va augmentar la viscositat i consistència d'aquestes, no es va veure alterat significativament el color i la textura del producte final fregit. La substitució total de farina de blat per farina d'arròs va permetre obtenir masses d'arrebossat sense gluten amb semblant viscositat, en addicionar quitosà. Aquesta nova formulació podria ser adaptada a productes arrebossats sense gluten. La simulació de digestió in vitro va mostrar augments significatius d'acrilamida després de la fase gàstrica en una àmplia gamma d'aliments. No obstant això, la bioaccesibildad d'acrilamida (després de la fase intestinal) es va reduir fins a nivells previs a la digestió o fins i tot menors, en creïlles fregides tipus chips i tipus French fries. / Sansano Tomás, M. (2017). Evaluation of acrylamide in foods and development of some strategies for its reduction [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86160 / TESIS

Le traitement de la corrosion constitue un enjeu économique, environnemental et de sécurité sanitaire. Plus largement utilisée à l’échelle industrielle, la protection par revêtements consiste à isoler le métal du milieu agressif par une couche adhérente, continue et imperméable. Ils doivent répondre à trois propriétés majeures : 1) être fortement adhérent au substrat métallique, 2) posséder de bonnes propriétés barrière pour limiter la pénétration de l’eau et des espèces agressives et 3) apporter un rôle d’inhibition de la corrosion. Cependant, la protection des surfaces métalliques par les techniques actuelles génère une pollution notable liée à l’usage de chromates. L’utilisation de polymères biosourcés et solubles en milieu aqueux serait un challenge et contribuerait à préserver l’environnement. Les polysaccharides comme le chitosane sont des macromolécules biodégradables et respectueuses de l'environnement possédant des propriétés d’anticorrosion et sont donc des alternatives envisageables. Ces travaux de thèse portent sur le développement de revêtements anticorrosion à base de chitosane. Le chitosane possède deux points faibles pour être utilisé comme revêtement contre la corrosion : 1) une adhésion insuffisante sur la surface des matériaux et 2) un caractère hydrophile. En conséquence, le chitosane a été modifié chimiquement afin d’augmenter son adhésion et ses propriétés barrières. Afin d’améliorer son adhésion sur des substrats métalliques, des groupements de type acide phosphonique ont été ajoutés via la réaction de Kabachnik-Fields sur le chitosane. L’élaboration d’un chitosane possédant des fonctions catéchol a été également discutée. Dans un premier temps, le chitosane modifié a été testé et caractérisé par spectroscopie d’impédance électrochimique (SIE) en tant qu’inhibiteur de corrosion puis des revêtements à partir de ce même chitosane ont été réalisés et leurs protections contre la corrosion ont été évaluées. Deux approches de mise en forme des revêtements ont été testées : par dip-coating et par la technique Layer-by-Layer (LbL). Différentes voies de fonctionnalisation du chitosane ont également été présenté afin d’augmenter les propriétés barrière du revêtement. La chimie de phthaloylation du chitosane a été décrite puis le greffage de chaînes hydrophobes a été étudié. / Corrosion treatment is an economic, environmental and health safety issue. More widely used on an industrial scale, coating protection consists in isolating the metal from the aggressive medium by an adherent, continuous and impermeable layer. They must have three major properties: 1) be strongly adherent to the metallic substrate, 2) have good barrier properties to limit the penetration of water and aggressive species and 3) provide a role in inhibiting corrosion. However, the protection of metal surfaces by current techniques generates significant pollution due to the use of chromates. The use of bio-based and soluble polymers in aqueous media would be a challenge and would contribute to preserving the environment. Polysaccharides such as chitosan are biodegradable and environmentally friendly macromolecules with anticorrosive properties and are therefore possible alternatives. These theses focus on the development of anticorrosion coatings based on chitosan. Chitosan has two weak points for use as a coating against corrosion: 1) insufficient adhesion on the surface of the materials and 2) hydrophilicity. As a result, chitosan has been chemically modified to increase its adhesion and barrier properties. In order to improve its adhesion on metal substrates, phosphonic acid groups have been added via the Kabachnik-Fields reaction on chitosan. The development of a chitosan with catechol functions was also discussed. Initially, the modified chitosan was tested and characterized by electrochemical impedance spectroscopy (EIS) as a corrosion inhibitor and coatings based on the same chitosan were made and their corrosion protection evaluated. Two approaches of coating elaborations were tested: dip-coating and Layer-by-Layer (LbL). Different ways of functionalizing chitosan have also been presented to increase the barrier properties of the coating. Phthaloylation chemistry of chitosan was described and hydrophobic chain grafting was studied.

The presented diploma thesis deals with a targeted modification of the structural properties of hydrogels, which is closely related to the application properties of these materials (eg transport). Due to the desired pharmacological applications of the use of these materials for targeted drug release, hydrogels based on chitosan and polyvinyl alcohol as substances with good biocompatibility were selected for the study. The combination of these polymers ensured swelling (controlled by the presence of chitosan) and viscoelastic (influenced by the presence of polyvinyl alcohol) properties, which were characterized by a wide range of analytical and physicochemical methods (swelling, tensile strength, rheology, atomic force microscopy or specific surface area, etc.). Information on structural properties played a crucial role not only for a detailed description of the studied materials in terms of whether the structural properties can be changed in a targeted manner, but also served as an explanation for the different release of the active substance diclofenac from the hydrogel matrix. With regard to the literature search, the effect of pH and crosslinking was chosen to modify the properties. From the measured results it was found that even a slight change in pH has an effect on the transport or release of the active substance. The results obtained in this work may be useful in the formation of hydrogel matrices with drugs depending on the intended medical applications.

This diploma thesis deals with application of microencapsulation techniques in development of hydrogel controlled-release systems in which the main role is played by humic acids, biopolymer chitosan, compound fertilizer NPK and 3-indoleacetic acid. This paper continues my bachelor thesis topic about utilization of polyelectrolyte complexes. The aim of this work was to develop a literature review focusing on the microencapsulation techniques and according to its results optimize the method. Microencapsulation was performed with a commercial encapsulator BUSCHI B-395 Pro and a release of individual components into a water was measured. An amout of released substances was measured by UV-VIS method and HPLC analysis. Practical part also included testing of repeated swelling and drying. It was found that suitable composition and combination of ingredients form hydrogels for further use in agriculture.

Ce projet vise à proposer des nouveaux candidats médicaments pour lutter contre les infections parasitaires cutanéo-muqueuses qui représentent un problème de santé majeur. C’est notamment le cas de la Trichomonose urogénitale et la leishmaniose cutanée.Malheureusement, l’administration systémique de première intention par le métronidazole (MTZ) pour traiter la trichomonose urogéntitale occasionne des problèmes de résistances et des effets secondaires indésirables. Ainsi, nous avons développé de nouvelles stratégies thérapeutiques en ciblant à la fois les mécanismes pharmacologiques et physiques de l’infection par Trichomonas vaginalis. Après avoir réussi à augmenter la solubilité apparente du MTZ dans l’eau en utilisant une beta-cyclodextrine méthylée, nous l’avons formulé dans un hydrogel thermosensible et mucoadhésif composé de pluronic® F127 et d’un biopolymère cationique et mucoadhésif, le chitosane. Cette formulation est spécifiquement adaptée à une application topique tout en offrant un contrôle de la libération du MTZ et une réduction de son passage systémique à travers la muqueuse vaginale. La viscosité élevée de l’hydrogel à température corporelle nous a conduit à étudier son effet sur la mobilité du protozoaire Trichomonas vaginalis. Il s’agit d’une stratégie physique d’immobilisation du parasite en parallèle à la chimiothérapie par le MTZ. Le suivi des trajectoires des parasites par vidéo-microscopie a montré la capacité de l’hydrogel seul ou en association avec le chitosane à immobiliser complètement T. vaginalis et à inhiber son attachement à la muqueuse. Ces évaluations ont été réalisées chez la souris. Cependant, le chitosane seul n’a pas permis d’immobilier les parasites et n’a pas montré une activité anti-T. vaginalis propre. Dans ce contexte, nous nous sommes inspirés des travaux antérieurs menés par notre équipe sur le développement de formulations à base de chitosane, et plus particulièrement des nanoparticules (NPs) composées de poly(isobutylcyanoacrylates) recouvertes de chitosane. Ces NPs ont une activité trichomonacide propre, même sans rajouter des substances actives, alors que des NPs sans chitosane étaient inactives. Nous avons étudié le mécanisme d’action et nous avons montré une meilleure internalisation des NPs lorsqu’elles étaient recouvertes de chitosane. Ces NPs ont provoqué des altérations morphologiques drastiques de la membrane du parasite. Cette activité pourrait être due en partie à l’interaction électrostatique entre la surface de T. vaginalis chargée négativement et les NPs recouvertes de chitosane cationique.Dans le but d’élargir le champ des applications de ces NPs à d’autres parasites, nous nous sommes intéressés à l’évaluation de leur effet anti-leishmanien vis-à-vis de Leishmania major. En effet, le chitosane connu pour ces propriétés cicatrisantes nous a paru particulièrement adapté pour cette pathologie. Nous avons ainsi montré in vitro et in vivo que les NPs recouvertes de chitosane avaient une activité anti-L. major propre, sans ajouter de substances actives. Dans un deuxième temps, nous avons décidé de nous orienter vers des particules de formes allongées et d’évaluer leur activité anti-leishmanienne. Ces particules appelées « plaquettes » sont constituées d’assemblages de chitosane hydrophobisé avec l’acide oléique et l’alpha-cyclodextrine dans l’eau. Cette stratégie nous a paru intéressante pour améliorer l’interaction des plaquettes avec la membrane de L. major, vue que ces parasites sont également de morphologie non-sphérique. Les résultats histologiques et immunohistochimiques des lésions cutanées ont montré une diminution significative du granulome inflammatoire et une réduction de la charge parasitaire par rapport à l'amphotéricine B seule utilisée comme référence.En conclusion, au cours de cette thèse, plusieurs formulations ont été développées et ont montré des efficacités biologiques en agissant sur des mécanismes pharmacologiques et/ou physiques des parasites. / This project aims at developing new therapeutic strategies against parasitic muco-cutaneous infections such as urogenital trichomonosis and cutaneous leishmaniasis which still represents a major health problem worldwide.Unfortunately, metronidazole (MTZ) is a first-line systemic treatment for urogenital trichomoniasis that causes resistance and side effects. We have thus developed new strategies by acting on both the pharmacological and the physical mechanisms of Trichomonas vaginalis infection. After a successfull increase of the apparent solubility of MTZ in water using a methylated -cyclodextrin, we formulated it in a thermosensitive and mucoadhesive hydrogel composed of pluronic® F127 and a cationic and mucoadhesive biopolymer, chitosan. This formulation is specifically adapted for topical application providing a control of MTZ release and reduction of its systemic passage through the vaginal mucosa.Then, the ability of the high viscosity hydrogel to immobilize T. vaginalis was investigated by video-microscopy. Monitoring the trajectories of each parasite by multiple particle tracking showed the ability of the hydrogel alone or in combination with chitosan to completely immobilize T. vaginalis and to inhibit parasite attachment to the mucosa. These evaluations were performed on mice experimental model. However, chitosan alone did not allow parasite immobilization and did not show any anti-T. vaginalis activity. In this context, we were inspired by previous works conducted by our team on the development of formulations based on chitosan, and more particularly nanoparticles (NPs) composed of poly(isobutylcyanoacrylates) coated with chitosan. These NPs have their own trichomonacidal activity, even without adding active substances, while NPs without chitosan were inactive. Investigated of the mechanism of the activity showed better internalization of NPs when coated with chitosan. These NPs caused drastic morphological alterations on the parasite membrane. This activity could be due to the electrostatic interaction between negatively charged T. vaginalis surface and cationic chitosan coated NPs.In order to broaden the applications of these NPs to other parasites, we were interested in evaluating the anti-L. major activity of NPs coated or not with chitosan. Indeed, chitosan known for its healing properties could be particularly adapted for this pathology. We thus showed in vitro and in vivo that NPs coated with chitosan had intrinsic anti-L. major activity without adding any drug. In a second step, we decided to design chitosan elongated particles and to evaluate their anti-leishmanial activity. These particles called "platelets" are composed of chitosan hydrophobically-modified with oleic acid and cyclodextrin in water. This strategy could be interesting to improve the interaction of platelets with the L. major membrane, as these parasites had also non-spherical morphology. The histological and immunohistochemical results of skin lesions showed a significant decrease in inflammatory granuloma and a reduction in parasitic load compared with amphotericin B alone, used as a reference.In conclusion, during this thesis, several formulations were developed and showed biological activities by acting on pharmacological and/or physical mechanisms of the parasites.

Orientador: Luiz Francisco Malmonge / Resumo: Os fertilizantes de liberação modificada têm conquistado âmbitos cada vez maiores nas pesquisas e em utilizações agrícolas devido a suas principais características de menores perdas de nutrientes e por seu menor custo, que envolve menos aplicações no campo e menores quantidades de fertilizantes utilizados, comparado aos fertilizantes convencionais. Este trabalho teve como objetivo elaborar fertilizantes com possível comportamento de liberação modificada, através da incorporação do fosfato de potássio monobásico (KH2PO4) no polímero quitosana, contribuindo, dessa forma, com as três fontes de nutrientes primários essenciais requeridos pelas plantas: nitrogênio, fósforo e potássio, por apenas dois recursos. Foram elaboradas duas amostras diferentes para posterior comparação, análise e aplicação. Os métodos utilizados no preparo das amostras foram: gotejamento em solução básica coagulante e casting. Foram feitas soluções de 8% de quitosana (m/v) dissolvidas em soluções de 5% de ácido acético, e subsequentemente foi adicionado o KH2PO4 (em diferentes concentrações para análise e para aplicação agrícola, foi usada a concentração de 60% (m/m) em relação à massa de quitosana). Foram feitas Microscopia eletrônica de varredura (MEV) para análise morfológica das amostras, Energia dispersiva de raios-X (EDX) para constatação dos elementos contidos nas amostras, o estudo da liberação dos nutrientes em solução aquosa (em pHs 5,4 e 6,7) e por fim, as amostras foram aplicadas em mudas de alf... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Modified-release fertilizers have been increasingly used in research and in agricultural uses due to their main characteristics of lower nutrient losses and their lower cost, which involves fewer applications in the field and less quantities of utilized fertilizers, compared to the conventional ones. This work aimed to elaborate fertilizers with possible modified release behavior, through the incorporation of monobasic potassium phosphate (KH2PO4) in the chitosan polymer, thus contributing with the three sources of essential primary nutrients required by plants: nitrogen, phosphorus and potassium, from only two resources. Two different samples were prepared for later comparison, analysis and application. The methods used in preparing the samples were: dripping in a basic coagulant solution and casting. Solutions of 8% chitosan (w/v) were prepared dissolved in solutions of 5% acetic acid, and subsequently KH2PO4 was added (in different concentrations for analysis and for agricultural application, the concentration of 60% (w/w) in relation to the chitosan mass). Scanning electron microscopy (SEM) was performed for the morphological analysis of the samples, energy dispersive X ray (EDX) to verify the elements contained in the samples, the study of the release of nutrients in aqueous solution (at pH 5.4 and 6, 7) and finally, the samples were applied to lettuce seedlings for comparative effect and material efficiency. The results of the EDX spectra showed that in the samples made... (Complete abstract click electronic access below) / Mestre

>Magister Scientiae - MSc / Peptides are among the main drugs which attract much attention because of their great potential in treating sexually transmitted diseases and other chronic diseases. There has been a major challenge of delivering these drugs in mucosal sites with low pH environment. The aim of this study is to synthesize acidic pH stable peptide loaded chitosan nanoparticles gels that could penetrate mucus layers covering the epithelial cells and kill HIV virus. Chitosan nanoparticles were synthesized by crosslinking method called Ionic gelation with Sodium tripolyphosphateTPP. / 2023

Fibers are classified into two groups; natural fibers and man-made fibers (MMF). There are three kinds of MMF: those made by transformation of natural polymers, those made from synthetic polymers and those made from inorganic material. Chitosan is classified as a biobased polymer and can be spun into man-made fibers. Due to its various functions, including anti-microbial, biocompatibility, biodegradability, metal-chelating, metal ions-coupling properties and general high molecular affinity, much attention has been paid recently to include chitosan into various concepts. The overall aim of this master thesis was to investigate the possibilities to make an antibacterial paper. Because chitosan contain primary amino groups that are cationic under mildly acidic conditions, it has antibacterial properties. Lab scale spinning of chitosan filaments was attempted in order to produce chitosan staple fibers that could be mixed with pulp fibers to make paper with antibacterial properties. Spinning methods used for a particular polymer is determined by the characteristics of the polymer. In the development of chitosan spinning at laboratory scale three different spinning methods were tested. A successful filament was produced by dry wet spinning. The filament was superior to the others in terms of dope composition and weight ratio of chitosan/acetic acid for protonation of the amino groups. Furthermore, the addition of glycerol improved the swelling of the chitosan hydrogel (or dope). Moreover, the condition of the coagulation step resulted in a good solidified filament with satisfactory elasticity and strength to be able to be taken up by a drawing cylinder. However, too small amounts of chitosan were produced in the development of chitosan spinning at lab scale and for production of antibacterial paper of chitosan. A second option was melt spinning of polylactide (PLA) filaments containing various amounts of chitosan. In this case PLA act as a carrier of chitosan into the paper sheet. Continuous filaments were spun in a sufficient amount. The antibacterial activity of PLA/chitosan fibers on E. coli bacteria was tested both on PLA/chitosan fibers as well as on suspensions. Under nutrient free conditions weak antibacterial effects was observed both for fibers and suspensions. However, in a more nutrient rich environment no effect was observed. This suggests that the produced fibers only had a weak antibacterial activity. To my knowledge the use of PLA in fiber form to carry chitosan into paper has not been attempted previously although different approaches to use chitosan as e.g. wound dressing is well described. In conclusion, there is a possibility to produce man made biodegradable fibers using chitosan and PLA that potentially could be added to paper. This paper might exert antibacterial properties that could have an interest to the market, e.g. for cleaning, in hospitals, and in the food industry.

No description available.