[EN] Articular cartilage is a tissue that consists of chondrocytes surrounded by a dense extracellular matrix (ECM). The ECM is mainly composed of type II collagen and proteoglycans. The main function of articular cartilage is to provide a lubricated surface for articulation. Articular cartilage damage is common and may lead to osteoarthritis. Articular cartilage does not have blood vessels, nerves or lymphatic vessels and therefore has limited capacity for intrinsic healing and repair. Tissue engineering (TE) is a powerful approach for healing degenerated cartilage. TE uses three-dimensional (3D) scaffolds as cellular culture supports. The scaffold provides a structure that facilitates chondrocyte adhesion and expansion while maintaining a chondrocytic phenotype and limiting dedifferentiation, which is a problem in two-dimensional (2D) systems. Cell attachment to the scaffolds depends on the physical and chemical characteristics of their surface (morphology, rigidity, equilibrium water content, surface tension, hydrophilicity, presence of electric charges). The primary aim of this thesis was to study the influence of different kinds of biomaterials on the response of chondrocytes to in vitro culture. 3D scaffold constructs must have an interconnected porous structure in order to allow cell development through the network, to maintain their differentiated function, as well as to allow the entry and exit of nutrients and metabolic waste removal. Therefore, the effect of the hydrophilicity and pore architecture of the scaffolds was studied. A series of polymer and copolymer networks with varying hydrophilicity was synthesised and biologically tested in monolayer culture. Cell viability, proliferation and aggrecan expression were quantified. When human chondrocytes were cultured on polymer substrates in which the hydrophilic groups were homogeneously distributed, adhesion, proliferation and viability decreased with the content of hydrophilic groups. Nevertheless, copolymers in which hydrophilic and hydrophobic domains alternate showed better results than the corresponding homopolymers. Biostable and biodegradable scaffolds with different hydrophilicity and porosity were synthesised using a template of sintered microspheres of controlled size. This technique allows the interconnectivity between pores and their size to be controlled. Periodic and regular pore architectures and reproducible structures were obtained. The mechanical behaviour of the porous samples was significantly different from that of the bulk material of the same composition. Cells fully colonised the scaffolds when the pores' size and their interconnection were sufficiently large. Another objective was to assess the chondrogenic redifferentiation in a biodegradable 3D scaffold of polycaprolactone (PCL) of human autologous chondrocytes previously expanded in monolayer. This study demonstrated that chondrocytes cultured in PCL scaffolds without fetal bovine serum (FBS) efficiently redifferentiated, expressing a chondrocytic phenotype characterised by their ability to synthesise cartilage-specific ECM proteins. The influence that pore connectivity and hydrophilicity of caprolactone-based scaffolds has on the chondrocyte adhesion to the pore walls, proliferation and composition of the ECM produced was studied. The number of cells inside polycaprolactone scaffolds increased as porosity was increased. A minimum of around 70% porosity was necessary for this scaffold architecture to allow seeding and viability of the cells within. The results suggested that some of the cells inside the scaffold adhered to the pore walls and kept the dedifferentiated phenotype, while others redifferentiated. In conclusion, the findings of this thesis provide valuable insight into the field of cartilage regeneration using TE techniques. The studies carried out shed light on the right composition, porosity and hydrophilicity of the scaffolds to be used for optimal cartilage production. / [ES] El cartílago articular es un tejido compuesto por condrocitos rodeados por una densa matriz extracelular (MEC). La MEC se compone principalmente de colágeno tipo II y de proteoglicanos. La función principal del cartílago articular es proporcionar una superficie lubricada para las articulaciones. Las lesiones en el cartílago articular son comunes y pueden derivar a osteoartritis. El cartílago articular no tiene vasos sanguíneos, nervios o vasos linfáticos y, por tanto, tiene una capacidad limitada de auto-reparación. La ingeniería tisular (IT) es un área prometedora en la regeneración de cartílago. En la IT se utilizan "andamiajes" (scaffolds) tridimensionales (3D) como soportes para el cultivo celular y tisular. Los scaffolds proporcionan una estructura que facilita la adhesión y la expansión de los condrocitos, manteniendo un fenotipo condrocítico limitando su desdiferenciación; que es el mayor problema en los sistemas bidimensionales (2D). La adhesión celular a los scaffolds depende de las características físicas y químicas de su superficie (morfología, rigidez, contenido de agua en equilibrio, tensión superficial, hidrofilicidad, presencia de cargas eléctricas). El objetivo general de esta tesis fue estudiar la influencia de diferentes tipos de biomateriales en la respuesta de los condrocitos en cultivo in vitro. Los scaffolds deben tener una estructura porosa interconectada para permitir el desarrollo celular a través de toda la estructura 3D, potenciando que los condrocitos mantengan su fenotipo, así como permitiendo entrada de nutrientes y eliminación de desechos metabólicos. Se estudió el efecto de la hidrofilicidad y de la arquitectura de poro. Se cuantificó la viabilidad celular, la proliferación y la expresión de agrecano. Cuando los condrocitos humanos se cultivaron en sustratos poliméricos donde los grupos hidrófilos se distribuyeron de manera homogénea, la adhesión, la proliferación y la viabilidad disminuyó con el contenido de grupos hidrófilo. Sin embargo, los copolímeros en los que los dominios hidrófilos e hidrófobos se alternaban mostraron mejores resultados que los homopolímeros correspondientes. Se sintetizaron series de scaffolds bioestables y series biodegradables con diferente hidrofilicidad y porosidad utilizando plantillas de microesferas sinterizadas. Se obtuvieron arquitecturas de poros regulares y reproducibles. Las células colonizaron el scaffold en su totalidad cuando los poros y la interconexión entre ellos era lo suficientemente grande. Se evaluó la rediferenciación condrogénica de condrocitos autólogos humanos, previamente expandidos en monocapa, sembrados en un scaffold biodegradable de policaprolactona (PCL). Se demostró que los condrocitos cultivados en scaffolds de PCL con medio sin suero bovino fetal (FBS), se rediferenciaban de manera eficiente; expresando un fenotipo condrocítico, caracterizado por su capacidad de sintetizar proteínas de la MEC específicas de cartílago hialino. Se estudió la influencia de la hidrofilicidad y la conectividad de los poros de los scaffolds de caprolactona sobre la adhesión de los condrocitos a las paredes de los poros, su capacidad proliferativa y la composición de MEC sintetizada. Se observó que un mínimo de 70% de porosidad era necesario para permitir la siembra de los condrocitos en el scaffold y su posterior viabilidad. El número de células aumentaba a medida que aumentaba la porosidad del scaffold. Los resultados sugieren que parte de las células que se adherían a las paredes internas de los poros mantenían el fenotipo desdiferenciado de condrocitos cultivados en monocapa, mientras que otros se rediferenciaban. En conclusión, los resultados de esta tesis aportan un avance en el campo de la regeneración de cartílago articular utilizando técnicas de IT. Los estudios realizados proporcionan directrices sobre la composición, la porosidad y la hidrofilicidad más adecuada para l / [CA] El cartílag articular és un teixit format per condròcits envoltats per una densa matriu extracel·lular (MEC). La MEC es compon principalment de col·lagen tipus II i de proteoglicans. La funció principal del cartílag articular és proporcionar una superfície lubricada a les articulacions. Les lesions en el cartílag articular són comuns i poden derivar en osteoartritis. El cartílag articular no té vasos sanguinis, nervis ni vasos limfàtics i, per tant, té una capacitat limitada d'auto-reparació. L'enginyeria tissular (IT) és una àrea prometedora en la regeneració del cartílag. A la IT s'utilitzen "bastiments" (scaffolds) tridimensionals (3D) com a suports per al cultiu cel·lular i tissular. Els scaffolds proporcionen una estructura que facilita l'adhesió i l'expansió dels condròcits, mantenint un fenotip condrocític limitant la seua desdiferenciació; que és el major problema en els sistemes bidimensionals (2D). L'adhesió cel·lular als scaffolds depèn de les característiques físiques i químiques de la superfície (morfologia, rigidesa, contingut d'aigua en equilibri, tensió superficial, hidrofilicitat i presència de càrregues elèctriques). L'objectiu general d'aquesta tesi va ser estudiar la influència de diferents tipus de biomaterials en la resposta dels condròcits en cultiu in vitro. Els scaffolds han de tindre una estructura porosa interconnectada per a permetre el desenvolupament cel·lular a través de tota l'estructura 3D, potenciant que els condròcits mantinguen el seu fenotip així com permetent l'entrada de nutrients i l'eliminació de productes metabòlics. S'ha estudiat l'efecte de la hidrofilicitat i de l'arquitectura de porus dels scaffolds. Es va quantificar la viabilitat cel·lular, la proliferació i l'expressió de agrecà. Quan els condròcits humans es van cultivar en substrats polimèrics en els quals els grups hidròfils es van distribuir de manera homogènia, l'adhesió, la proliferació i la viabilitat van disminuir amb el contingut de grups hidròfils. No obstant això, els copolímers en els quals els dominis hidròfils i hidròfobs s'alternaven van mostrar millors resultats que els homopolímers corresponents. Es van sintetitzar sèries de scaffolds bioestables i sèries biodegradables amb diferent hidrofilicitat i porositat utilitzant plantilles de microesferes sinteritzades. Es van obtindre arquitectures de porus regulars i reproduïbles. Les cèl·lules van colonitzar el scaffold en la seua totalitat quan els porus i la interconnexió entre ells era suficientment gran. Es van avaluar la rediferenciació condrogènica de condròcits autòlegs humans, prèviament expandits en monocapa, en un scaffold biodegradable de policaprolactona (PCL). Es va demostrar que els condròcits cultivats en scaffolds de PCL sense sèrum boví fetal (FBS) es rediferenciaven de manera eficient, expressant un fenotip condrocític caracteritzat per la seua capacitat de sintetitzar proteïnes de la MEC específiques de cartílag hialí. També es va estudiar la influència de la hidrofilicitat i la connectivitat dels porus dels scaffolds de caprolactona sobre l'adhesió dels condròcits a les parets dels porus, la seua capacitat proliferativa i la composició de MEC sintetitzada. Es va observar que un mínim del 70% de porositat sembla ser necessari per permetre la sembra dels condròcits i la seua posterior viabilitat en el scaffold. El nombre de cèl·lules augmentava a mesura que augmentava la porositat del scaffold. Els resultats suggereixen que part de les cèl·lules que s'adherien a les parets internes dels porus mantenien el fenotip desdiferenciat de condròcits cultivats en monocapa, mentre que altres es rediferenciaven. En conclusió, els resultats d'aquesta tesi proporcionen informació valuosa en el camp de la regeneració de cartílag utilitzant tècniques d'IT. Els estudis realitzats proporcionen directrius sobre la composició, la porositat i la hidrofilicitat m / Pérez Olmedilla, M. (2015). Tissue engineering techniques to regenerate articular cartilage using polymeric scaffolds [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/58987

Grafenoxid (GO) ar en lovande kandidat som nano-tillsats i medicinska byggnadsstallningar for benregenerering. GO kan forbattra den biologiska kompatibiliteten och osteogena prestandan hos polymerbaserade byggstallningar, och ocksa vasentligt bidra till forbattringen av materialets mekaniska egenskaper. I detta arbete ympades nano-grafenoxid (nGO) kovalent pa ytan av poly (e-kaprolakton) (PCL) genom att fdrst modifiera polymerytan via aminolys. Med anvandning av 1,6-hexandiamin / isopropanol infordes fria amingrupper framgangsrikt pa PCL-ytan for efterfoljande immobilisering av nGO. En optimerad ympningsprocess utvecklades via en losningsmedelsassisterad metod med vatten som losningsmedel for att kovalent binda nGO pa ytan av PCL byggnadsstallningar. De initiala nGO koncentrationerna var 0,5 och 1 mg / ml. fourier-transform infrarodspektroskopi (FTIR) och termogravimetrisk analys (TGA) verifierade bindningen mellan de funktionella gruppema pa nGO och de fria aminema. Svepelektronmikroskopi (SEM) visade en homogen fordelning av nGO pa ytan av de porosa byggnadsstallningarna. De mekaniska testema som utfordes demonstrerade · en 50 och 21 % okning av kompressionsstyrkan :for byggnadsstallningarna ympade med de initiala nGO-koncentrationema pa 0,5 och 1 mg / ml. In vitro-mineraliseringstester visade bildandet av mineralfallningar pa ytan av byggnadsstallningama som okade i storlek med hogre nGO-halt. A ven nGO: s potential som nano-barare av ett antibiotikum studerades i detta arbete. Pa grund av sitt overflod av kemiska funktionaliteter kan nGO effektivt adsorbera foreningar genom olika sekundara interaktioner. I denna studie optimerades dessa sekundara interaktioner genom att reglera losningens pH for maximal adsorption av ciprofloxacin, ett bredspektrum antibiotikum som anvands vid behandling av osteomyelit. Ciprofloxacin befanns kunna adsorberas starkast i sin katjonform vid pH 5, dar 1t-1t elektron­donatoracceptor (EDA) -interaktioner dominerar. Sammanfattningsvis bekraftar de resultat som presenteras i detta arbete potentialen hos nGO som egenskapsforbattrare och lakemedelsbarare i applikationer inom vavnadsregenerering. / Graphene oxide (GO) is a promising candidate as nano-filler material in scaffolds for bone regeneration. It has been demonstrated to enhance the biological compatibility and osteogenic performance of polymer-based scaffolds, aside from its substantial contribution to the improvement of the material's mechanical properties. In this work, nano-graphene oxide (nGO) was covalently grafted to the surface of poly( e-caprolactone) (PCL) by first modifying the polymer surface via aminolysis. Using 1,6-hexanediamine/isopropanol, free amine groups were successfully introduced to the PCL surface for the subsequent immobilization of nGO. An optimized grafting pathway, which implements the solvent-assisted method and uses water as a solvent, was developed to covalently attach nGO using initial concentrations of 0.5 and 1 mg/mL. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) both verified the successful attachment of nGO through the free amines. Scanning electron microscopy (SEM) depicts a homogeneous dispersion of nGO over the polymer matrix. Mechanical tests were performed and demonstrate a 50 and 21 % increase in compressive strength for the scaffolds grafted using initial nGO concentrations of 0.5 and 1 mglmL. In vitro mineralization tests showed the formation of mineral precipitates on the surface of the scaffolds that increased in size with higher nGO content. The potential of nGO as a nano-carrier of an antibiotic drug was also explored in this work. As it comprises of an abundance of chemical functionalities, nGO is able to efficiently adsorb compounds through various secondary interactions. In this study, these secondary interactions were optimized by controlling the solution pH for the maximum adsorption of ciprofloxacin, a broad-spectrum antibiotic used in the treatment of osteomyelitis. Ciprofloxacin was found to be adsorbed most strongly in its cationic form at pH 5, in which 1t-1t electron-donor acceptor (EDA) interactions predominate. Overall, the results presented in this work validate the potential of nGO as nano-enhancer and drug carrier in tissue engineering scaffold applications.

Avec plus de 2 millions d’interventions chirurgicales par an dans le monde, les actes de chirurgie osseuse sont les plus fréquents, ce qui pousse les entreprises du secteur des biomatériaux pour la régénération osseuse à investir massivement pour sans cesse améliorer leurs produits. Cette thèse est issue d’un contrat CIFRE effectué avec l’entreprise Kasios afin de l’aider dans le développement de céramiques et polymères poreux principalement pour des applications en chirurgie maxillo-faciale. Les travaux réalisés s’articulent autour du développement de biomatériaux biphasiques à base de phosphate tricalcique béta (β-TCP). En premier lieu, des microfibres de polycaprolactone (PCL) incorporant des particules élémentaires de β-TCP ont été fabriquées par électrospinning. Les principales applications des fibres concernent la régénération osseuse guidée pour la préservation alvéolaire ou les opérations de relevés de sinus. L’électrospinning des fibres a utilisé des solvants ne présentant pas de toxicité aiguë. Les fibres ont formé des membranes manipulables qui peuvent être facilement découpées et suturées même en environnement humide. Les études in vitro n’ont révélé aucune cytotoxicité et les membranes ont permis la prolifération de cellules ostéoblastiques. La seconde étude a permis la fabrication d’éponges de gélatine et d’acide hyaluronique saturées ou recouvertes en surface de granules de β-TCP pour le comblement alvéolaire. Les éponges étaient facilement façonnables pour correspondre à l’alvéole du patient. Le chirurgien pourrait alors bénéficier de la nature biphasique du dispositif médical afin de faciliter l’implantation et éviter la manipulation séparée des éponges et des granules. L’utilisation des éponges permettrait par ailleurs d’assurer un positionnement idéal des granules pour la cicatrisation alvéolaire. La troisième étude, plus fondamentale, porte sur l’interaction des cellules osseuses avec le β-TCP et sa résorption. Des études de biomécanique et de biodégradation ainsi que de biodissolution ont également été réalisées sur des biomatériaux produits par l’entreprise. / With more than 2 million surgeries per year, bone tissue is one of the most concerned tissues and biomaterial companies have developed massive investments to continually improve bone regeneration.This thesis was conducted during a CIFRE contract (a tripartite contract linking a student, a university and acompany) and was done in association with the company Kasios for the development of new porous polymers and ceramics. This thesis was specifically centered in the development of biphasic biomaterials based upon beta tricalcium phosphate (β-TCP). First, polycaprolacton (PCL) microfibers incorporating β-TCP elementary particles were produced using electrospinning. These fibers were developed to provide membranes for guided bone regeneration usable in alveolar preservation and sinus lifting. Electrospinning of the fibers did not require any high toxicity solvent. Our fibers formed membranes that could easily be handled, cut and sutured in dry and wet environment. In vitrocytotoxicity studies confirmed the non-toxic nature of the material and showed the ability of the membranes to encourage survival and proliferation of osteoblastic cells. Secondly, freeze-dried gelatin and hyaluronicacid sponges saturated or embedded with β-TCP granules were developed for alveolar filling. Theses ponges could easily be shaped to fit the patient’s dental socket. The biphasic nature of the sponges could make the implantation easier and faster by avoiding surgeons to handle separately the granules and the sponges. This medical device could also insure a correct and optimal positioning of the granules for the patient healing. Lastly, a fundamental study was conducted on resorption of β-TCP and the interaction between bone cells and the biomaterial. Biomechanical and biodegradation/biodissolution studies were also done on different types of biomaterials produced by the company.

Les nanotechnologies sont en train de révolutionner le domaine biomédical et plus particulièrement l’ingénierie tissulaire. Elles permettent aujourd’hui, non seulement de réparer mais aussi de régénérer les tissus. Cette nanomédecine régénérative est particulièrement adaptée pour répondre aux besoins importants liés aux maladies dégénératives, au vieillissement et aux traumatismes.Mon travail de thèse s’inscrit dans ce contexte et concerne l’élaboration de biomatériaux nanofibreux et microporeux actifs pour la régénération osseuse. Notre objectif essentiel est de réaliser un implant biodégradable nanostructuré permettant d’accélérer la réparation du tissu osseux. Notre stratégie innovante repose non seulement sur la mise en oeuvre de membranes par électrospinning mais aussi sur leur fonctionnalisation par des facteurs de croissance. Cette fonctionnalisation originale a consisté à enrober ces principes actifs dans des nanoréservoirs en utilisant la technique multicouche de polyélectrolytes. Des membranes de polycaprolactone (PCL) nanofibreuses et microporeuses ont été obtenues par électrospinning puis les fibres ont été enrobées de réservoirs contenant le facteur ostéoinducteur, la protéine morphogénique osseuse 2 (BMP-2). L’induction osseuse engendrée par ces réservoirs actifs a été mise en évidence in vitro après culture d’ostéoblastes humains primaires. Des expérimentations in vivo chez la souris ont permis de confirmer l’accélération de la régénération osseuse grâce à ces nanoréservoirs.Cette même stratégie a été validée in vivo, chez la souris, en utilisant des membranes de collagène d’origine animal commerciales utilisées en clinique. L’activité de ces membranes fonctionnalisées par des nanoréservoirs de BMP-2 est en cours d’analyse dans le cadre de tests précliniques pour une application maxillofaciale et parodontale. / Nanobiotechnology enables the emergence of entirely new classes of bioactive devices intended for targeted intracellular delivery for more efficiency and less toxicities. Tissue engineering is an interdisciplinary field that has attempted to implement a variety of processing methods for synthetic and natural polymers to fabricate tissue and organ regeneration scaffolds.We report here the first demonstration of bone regeneration by using a strategy based on a synthetic nanostructured membrane. This electrospun membrane is manufactured by using a FDA approved polymer, PCL, (polycaprolactone), and functionalized with nanoreservoirs of a growth factor (BMP-2). Our expected outcomes are the development of clinical applications in the field of tissue engineering and nanomedecine and particularly in bone regeneration.We propose the development of smart nanostructured active implants for regenerative medicine. Our strategycombines a synthetic biodegradable electrospun nanofibrous membrane based on PCL and a bioactive growth factor (BMP-2) entrapped into polymer nanoreservoirs built atop the nanofibers according to the layer-by-layer technology. In this study, by using primary osteoblasts, we have shown the capacity of these sophisticated implants to promote and accelerate not only in vitro bone induction; but also, in vivo, bone formation (mouse model).We have also validated our strategy, in vivo (mouse model), by using an already used in the clinic collagen membrane (animal origin) to accelerate bone regeneration. This unique strategy is used to entrap, protect and stabilize the therapeutic agent into polymer coating acting as nanoreservoirs enrobing fibers of membranes.

Made available in DSpace on 2016-12-08T17:19:26Z (GMT). No. of bitstreams: 1 Marindia Decol.pdf: 3575085 bytes, checksum: bed6c0ed662d3c76c64b6cfdac902d8b (MD5) Previous issue date: 2015-07-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Poly (lactic acid) (PLA) is a rigid and brittle thermoplastic polymer, and poly (ε-caprolactone) (PCL) is a thermoplastic polymer of lower rigidity and higher toughness than PLA. Combination of these properties through the blend PLA/PCL has been studied successfully to change the final properties of the PLA. The addition of multiwalled carbon nanotubes (MWCNT) in the blend PLA/PCL may induce peculiar orphologies depending on their location, resulting in the getting new properties or modifying the properties of the PLA matrix. This study aimed to evaluate the effect of adding the PCL, the compatibilizer Cesa-mix and MWCNT the final properties of the PLA. Mixtures were prepared in internal mixer chamber coupled to a torque rheometer and subjected to characterizations of morphological, thermal, mechanical and electrical properties. In the morphological analysis, there was a 37% reduction in the average size of the phases of the PCL blends PLA/PCL with the addition of compatibilizer Cesa®- mix, a heterogeneous distribution of MWCNT the PLA matrix and a selective location of MWCNT in phase PCL. With respect to thermal properties, the addition of the compatibilizing PCL and did not significantly affect the thermal degradation onset temperature (Tonset) of the PLA, but the addition of the MWCNT in PLA resulted in decreased Tonset nanocomposites. The melting temperature did not change significantly with the addition of PCL, the compatibilizer and MWCNT on the PLA matrix. Already cold crystallization temperature decreased and the degree of crystallinity of the PLA increased with the addition of PCL blends and MWCNT in nanocomposites. Decreases of 35% on elastic hardness and 29% in modulus of elasticity was observed with the addition of PCL and compatibilizer Cesa®-mix in the blends PLA/ PCL/AC/2,5%. With the addition of MWCNT was observed an increase of 6,8% on elastic hardness and 8% in the modulus of elasticity of PLA/CNT mixtures with 1,0% w/w. Blends of PLA/PCL with 0,5% and 1,0% w/w CNT with and without compatibilizer, had a decrease in modulus of elasticity and elastic hardness. No significant changes were observed in the electric resistance of the samples with the addition of the compatibilizer, the PCL and MWCNT with 0,5% and 1,0% w/w. Selective location of MWCNT the PCL phase had great influence on morphological, thermal, mechanical and electrical properties of nanocomposites. / O poli(ácido lático) (PLA) é um polímero termoplástico rígido e frágil, e a poli(ε-caprolactona) (PCL) é um polímero termoplástico de menor rigidez e maior tenacidade que o PLA. A combinação destas propriedades através da blenda PLA/PCL tem sido estudada com êxito no auxílio à alteração das propriedades finais do PLA. A adição de nanotubos de carbono de paredes múltiplas (NTCPM) na blenda PLA/PCL pode induzir a morfologias peculiares dependendo da sua localização, resultando na obtenção de novas propriedades ou na alteração das propriedades da matriz PLA. Este trabalho teve como objetivo avaliar o efeito da adição do PCL, do compatibilizante Cesa-mix e dos NTCPM nas propriedades finais do PLA. As misturas foram preparadas em misturador de câmara interna acoplado a reômetro de torque e submetidas à caraterizações das propriedades morfológicas, térmicas, mecânicas e elétricas. Na análise morfológica, observou-se uma redução de 37% no tamanho médio das fases de PCL nas blendas PLA/PCL com a adição do compatibilizante Cesa®- mix, uma distribuição heterogênea dos NTCPM na matriz PLA e uma localização seletiva dos NTCPM na fase PCL. Em relação às propriedades térmicas, a adição do PCL e do compatibilizante não afetaram significativamente na temperatura de início de degradação térmica (Tonset) do PLA, porém a adição de NTCPM no PLA resultou em decréscimo na Tonset dos nanocompósitos. A temperatura de fusão não apresentou variação significativa com a adição do PCL, do compatibilizante e dos NTCPM na matriz PLA. Já a temperatura de cristalização a frio diminuiu e o grau de cristalinidade do PLA aumentou com a adição de PCL nas blendas e dos NTCPM nos nanocompósitos. Diminuições de 35% na dureza elástica e de 29% no módulo de elasticidade foram observadas com a adição do PCL e do compatibilizante Cesa®-mix nas blendas PLA/PCL/AC 2,5%. Com a adição de NTCPM foi observado um aumento de 6,8% na dureza elástica e de 8% no módulo de elasticidade das misturas PLA/NTC com 1,0% m/m. As misturas de PLA/PCL com 0,5% e 1,0% m/m de NTC com e sem compatibilizante, tiveram um decréscimo no módulo de elasticidade e na dureza elástica. Não foram verificadas alterações significativas na resistência elétrica das amostras com a adição do compatibilizante, do PCL e dos NTCPM com 0,5% e 1,0% m/m. A localização seletiva dos NTCPM na fase PCL teve grande influência nas propriedades morfológicas, térmicas, mecânicas e elétricas dos nanocompósitos.

Made available in DSpace on 2016-12-08T17:19:29Z (GMT). No. of bitstreams: 1 Elementos pre-textuais.pdf: 89508 bytes, checksum: 6cbceb5e70da4a660d5066d97a20334f (MD5) Previous issue date: 2007-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In the past two decades, polyhydroxyalkanoates (PHAs) have been the focus of extensive research considering their potential application as biocompatible and biodegradable thermoplastics, due to their hydrolyzability in the human body as well as in natural circumstances. Aiming the development of new ductile and biodegradable materials, systems of poly(3-hydroxybutyrate), P(3HB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3HV-co-3HV) with poly(e-caprolactone) triol (PCL-T, 900 and 300 g.mol-1) with addition of 0 to 30 % of PCL-T (w/w), were obtained by casting or injection molding. The thermal behavior, the morphology and the crystallinity of these mixtures were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TG), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR). The rheology and the melt processing of P(3HB)/PCL-T systems were also studied. The crystallinity degree of casted P(3HB) decreased from 68 to 49% with addition of 5% of PCL-T 900, and from 68% to 54% with 5% of PCL-T 300 content. The TG analysis showed that the PCL-T did not change the thermal stability of P(3HB). It was also observed by DSC that the Tm of PCL-T did not change in all compositions, while the Tm of P(3HB) decreased when PCL-T content was increased. It was also noticed that the Tg of P(3HB) increased from 2.75 to -2ºC with the increase of PCL-T 900 content. The Tg of P(3HB) change from 2.75 to -10ºC with the PCL-T 300 content. Indeed, FTIR analyses did not show evidences of hydrogen bonds between the polymers, while SEM analysis revealed porous films. A similar behavior was observed for P(3HB-co-3HV)/PCL-T 900 systems, while no change in the cristallinity degree was observed for P(3HB-co-3HV)/PCL-T 300 systems. For blends with P(3HB-co-3HV), DSC analyses revealed that the Tg of P(3HB-co-3HV) decreased from 2ºC to ca. -10ºC with the addition of 15wt% of PCL-T 900 or PCL-T 300. It is also noticed that the Tm of P(3HB-co- 3HV) and PCL-T decreases gradually as the PCL-T content is increased. Rheological analyses showed a pseudoplastic behavior for all the samples and a very significant decrease in the viscosity when the PCL-T content was increased. The P(3HB-co-3HV)/PCL-T 300 systems with 20 and 30% of PCL-T 300 contents showed a behavior look likes a Newtonian. Tensile tests of injected specimens showed an increase of 67% in the elongation at break with 5% of PCL-T, while the Young modulus decreased 7.5%. A higher PCL-T content (10%), however, decreases the modulus more significantly (50% in relation to P(3HB)). The crystallinity degree of P(3HB), obtained from XRD analyses, decreases with the addition of PCL-T (from 59 to 50% with 10% of PCL-T) and is in agreement with tensile tests and SEM results, that presented a higher ductility for the mixtures with PCL-T. TG analyses showed that the onset temperature does not vary significantly with the PCL-T content. FTIR spectra present interesting changes with PCL-T addition that are possibly related to interactions between the polymers. The better processing behavior of the PHAs with the addition of PCL-T suggests that the latter acts both as a plasticizer and a flow auxiliary, providing new, more flexible biodegradable materials. / Nas últimas duas décadas, os polihidroxialcanoatos (PHAs) foram o foco de pesquisas extensivas considerando suas potenciais aplicações como termoplásticos biocompatíveis e biodegradáveis, devido a sua hidrolisidade no corpo humano bem como em circunstâncias naturais. Objetivando o desenvolvimento de novos materiais dúcteis e biodegradáveis, sistemas de poli(3-hidroxibutirato), P(3HB) e poli(3-hidroxibutirato-co-3-hidroxivalerato), P(3HB-co-3HV) com poli(å-caprolactona) triol, PCL-T (300 e 900g.mol-1) com adição de 0 a 30% de PCL-T (m/m), foram obtidos por casting ou moldagem por injeção. O comportamento térmico, a morfologia e a cristalinidade destas misturas foram estudados, para isso foram utilizadas as seguintes técnicas: calorimetria exploratória diferencial (DSC), análise termogravimétrica (TG), microscopia eletrônica de varredura (SEM), difração de raios-X (XRD) e espectroscopia no infravermelho por transformada de Fourier (FTIR). A reologia e o processamento dos sistemas de P(3HB) /PCL-T também foram estudados. O grau de cristalinidade do P(3HB) caiu de 68 para 49% com adição de 5% de PCL-T 900, e de 68 para 54% com adição de PCL-T 300. A análise de TG mostrou que a PCL-T não interfere na estabilidade térmica do P(3HB). Foi também observado por DSC que a Tm da PCL-T não mudou em todas as composições, enquanto que a Tm do P(3HB) decresceu quando o teor de PCL-T aumentou. Notou-se também que a Tg do P(3HB) diminuiu de 2,75 para -2ºC com o aumento da PCL-T 900. A Tg do P(3HB) mudou de 2,75 para -10ºC com o aumento do teor de PCL-T 300. De fato, as análises de FTIR não mostraram evidencias de ligações de hidrogênio entre os polímeros, enquanto as análises de SEM revelaram filmes porosos. Um comportamento similar foi observado para o sistema de P(3HB-co-3HV)/PCL-T 900, enquanto nenhuma mudança no grau de cristalinidade do sistema de P(3HB-co-3HV)/PCL-T 300 foi observada. Para blendas com P(3HB-co-3HV), as análises de DSC revelaram que a Tg do P(3HB-co-3HV) diminuiu de 2ºC para ca. -10ºC com adição de 15% de PCL-T 900 PCL-T 300. Notou-se também que a Tm do P(3HB-co-3HV) e da PCL-T diminuíram ou gradualmente com o aumento do teor de PCL-T. A análise reologica mostrou um comportamento pseudoplastico para todas as amostras e um decréscimo muito significativo na viscosidade quando a PCL-T e adicionada. Os sistemas de P(3HB-co-3HV)/PCL-T 300 nas composições 80/20 e 85/15 mostraram um comportamento muito próximo do Newtoniano. Os testes de resistência à tração das espécies injetadas mostraram um aumento de 67% no alongamento com 5% de PCL-T, enquanto que o modulo de elasticidade diminuiu cerca de 7,5%. Uma alta quantidade de PCL-T (10%), entretanto, diminuiu o modulo mais significativamente (50% em relação ao P(3HB)). O grau de cristalinidade do P(3HB), obtido por XRD, diminuiu com adição de PCL-T 900 (de 58 para 51% com 10% de PCL-T 900) concordando com os testes de resistência a tração e resultados de SEM, que apresentaram uma alta ductilidade para as misturas contendo PCL-T. Análises de TG mostraram que a temperatura inicial de degradação não variou significativamente com a quantidade de PCL-T. Os espectros de FTIR apresentaram mudanças interessantes com adição de PCL-T que sugerem a existência de interações entre os polímeros. O melhor comportamento durante o processamento dos PHA com adição de PCL-T sugere que a PCL-Ts atuam como platificantes e auxiliares de fluxo, conferindo maior flexibilidade aos materiais biodegradáveis.

The master's thesis focuses on preparation of blown films from polylactid acid (PLA) which was blended with selected polyesteres – poly(butylene adipate-co-terephtalate) (PBAT), polycaprolactone (PCL) and polybutylene succinate (PBS) – and thermoplastic starch (TPS) in amount of 30% in order to soften PLA films. The influence of the aditives on static and mechanical tensile properties, on structure, morphology and thermal properties of the films was determined and the obtained parameters were compared to properties of films prepared from neat PLA and high density polyethylene (HDPE). The results showed that the additives increased crystalinity of PLA and thus significantly influenced the properties of the films. In contrast to the film from neat PLA, softening in terms of lowering glass transition temperature occured only by adding PBS and TPS, in terms of increasing ductility only by adding PBAT. All PLA films showed nearly constant elastic modulus up to the beginning of glass transition enabling their potential application till 50 °C. Preparation of the film with TPS was problematic and the film showed the worst mechanical properties. Preparation of other films was without any problems. The most promising additive from the tested ones was PBAT which showed comparable mechanical properties as the film from HDPE.

The diploma thesis deals with the treatment of polycaprolactone (PCL) nanofibers. PCL fibers were subjected to the deposition of plasma amine polymers in a low pressure pulsed radiofrequency capacitively coupled discharge using cyclopropylamine monomer (CPA). Collagen as an extracellular matrix (ECM) protein was immobilized and cell proliferation on the modified nanofiber surface was monitored. Untreated PCL fibers were also subjected to the deposition of an antibacterial copper layer, and the fibers were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDX).

This thesis deals with issues of the issue lead-acid batteries and their application in mode of hybrid electric vehicle. The experiment is focused on the production of electrodes to determine the effect five types of additives in negative active mass in PsoC(Partial State of Charge) mode. This simulates conditions occurring in the mode of hybrid electric vehicles (HEV).

The main aim of this paper is to contribute to the elucidation of electrochemical processes. These processes occur in the investigated experimental lead-acid cell. For this purpose, electrochemical impedance spectroscopy was used. There are two methods of measurement presented. First one is used to measure impedance between electrodes. Second one is used to measure impedance of collector ribs inside positive or negative electrode. The results are represented by electrical equivalent circuits, whose elements are described in detail in the theoretical part.