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Thesis advisor: Jeffery A. Byers / This dissertation discusses the development of a family of iron complexes and their role in the synthesis of degradable polymers. Chapter one will introduce the different areas of redox-switchable polymerization. In chapter two the synthesis of block copolymers containing a polyester and polyether block is presented. The application redox-switchable polymerization to form a copolymer with two fundamentally distinct backbone functionalities and their characterization is discussed. In chapter three the synthesis of a degradable cross-linked polymer through a novel redox-triggered cross linking event is summarized. In chapter four, a detailed mechanistic study of iron-complex catalyzed epoxide polymerization is examined and a unique mechanistic scheme is proposed. Lastly, in chapter five the synthesis and characterization of a formally iron(I) complex is presented. This complex shows remarkable catalytic activity towards ring-opening polymerization. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Résumé : Le poly(acide lactique) ou PLA est une famille de polyester thermoplastique linéaire qui a connu un essor commercial important durant la dernière décennie. L'enthousiasme pour le PLA vient de sa nature biosourcée, de ses bonnes propriétés mécaniques comme un module élastique élevé et de la possibilité de le biodégrader. Toutefois, certaines carences comme une faible résistance thermique et une faible élasticité à l’état fondu limitent son champ d’application. Fait à noter, le monomère d’acide lactique possède deux stéréo-isomères (L et D). Il est possible de polymériser les isomères L ou D pour former respectivement le PLLA ou le PDLA mais de façon surprenante, le mélange de PLLA et de PDLA permet la formation d’une structure cristalline distincte appelée le stéréocomplexe. Cette forme cristalline a un point de fusion 50[degré]C plus élevé par rapport aux formes cristallines du PLLA ou de PDLA d’où un premier intérêt pour augmenter la résistance thermique du matériau. Dans ce travail, l’usage de petites quantités (0-5 % massique) de PDLA comme additif dans une phase majeure de PLLA sera analysé. L’effet du stéréocomplexe formé à haute température sur la nucléation du PLLA et sur les propriétés rhéologiques du mélange sera plus particulièrement étudié. La présente thèse comprend une revue de littérature sur la cristallisation des PLA suivie de quatre parties expérimentales, conclusions et recommandations. La revue de littérature a pour objectif de réinterpréter l’ensemble des données disponibles sur la cristallisation du PLA afin d’en tirer des conclusions claires. La première partie expérimentale porte sur la cinétique de formation du stéréocomplexe à l'état fondu. Il a été constaté que la formation du stéréocomplexe est lente aux températures usuelles de mise en forme du PLLA ( 180[degré]C). De plus, la coexistence d’une morphologie baptisée dans ce travail « structure en réseau » et d’une morphologie sphérulitique a été révélée pour la première fois. Il a été démontré que la structure de réseau a une température de fusion moins élevée que la structure sphérulitique. Dans la seconde partie du travail, la cinétique de stéréocomplexation a été améliorée significativement pour adapter celle-ci aux cycles de refroidissement courts typiques des méthodes de mise en forme à l’état fondu. Ceci a été réalisé en ajoutant des agents nucléants qui initient la cristallisation à plus haute température et des agents plastifiants qui viennent augmenter la mobilité des polymères. Cette stratégie a permis de réduire le temps de cristallisation d’un ordre de grandeur. Dans un troisième temps, l'effet du stéréocomplexe sur les propriétés rhéologiques d’un mélange PDLA/PLLA a été investigué. En raison de son point de fusion élevé, le stéréocomplexe peut être préservé dans une matrice PLLA fondue et ainsi changer significativement les propriétés rhéologiques. La présence du stéréocomplexe a mené à une augmentation significative de la viscosité et de l'élasticité du PLA expliqué par la formation de points de « réticulation physique » dans la matrice amorphe. Enfin, dans la dernière partie expérimentale, le stéréocomplexe a été utilisé pour améliorer le comportement en moussage du PLA. Des expériences de visualisation et de moussage en mode discontinu ont montré que la présence de stéréocomplexe augmente la densité de nucléation de bulles et améliore significativement la morphologie de la mousse finale grâce à un effet de nucléation et à l’augmentation de l’élasticité du fluide. La revue de littérature et les trois premières parties expérimentales sont présentées sous forme d’articles scientifiques. La dernière partie expérimentale est à titre prospectif pour la suite du projet et ne sera pas soumise pour publication. // Abstract : Poly(lactic acid), or PLA, is a family of linear thermoplastic polyesters that has experienced strong market growth over the past decade. The enthusiasm for PLA originates from its bio-based nature, its good properties and its biodegradability. However, some of PLA deficiencies such as low thermal resistance and low melt elasticity have limited the development of this polymer. It is noteworthy that the lactic acid monomer has two stereo-isomers (L and D) that can be polymerized respectively into PLLA and PDLA but surprisingly, blending of PLLA and PDLA can lead to the formation of a “stereocomplex” which has a distinct crystalline structure from that of the homopolymers. This crystalline form has a melting point 50 oC greater than the crystalline PDLA or PLLA forms, thus it has by itself an interest in terms of heat resistance. In this work, the use of small amounts of PDLA (0-5%) in a matrix of PLLA will be explored. Particular emphasis will be on the nucleating ability of the stereocomplex (formed at high temperature) on PLLA crystallization and on its effect on the blends rheological properties. The current thesis comprises a literature review on PLA crystallization followed by four experimental sections. The objective of the literature review was to reinterpret the large body of data available on PLA in order to draw clear conclusions on PLA crystallization. The first experimental part of the work focused on the kinetics and conditions of stereocomplex formation in the melt state. It was found that stereocomplex formation is slow in the melt processing temperature range of PLLA (180 oC). Co-existence of a so-called “network structure” with a spherulitic structure was revealed for the first time. It was shown that the network structure has a lower melting point than the spherulitic one. In the second part of the work, stereocomplexation kinetics was improved significantly to match it with the fast cooling cycles typical of melt processing techniques. This was achieved by adding nucleating agents that initiated crystallization at higher temperatures and plasticizers that enabled more polymer fluidity. This strategy enabled an order of magnitude decrease in crystallization time. The third part of the work was the investigation of rheological properties upon formation of the stereocomplex structure in 0-5% PDLA in PLLA blends. Due to its higher melting point, the stereocomplex can be preserved in molten PLLA and alter significantly the blend melt rheology. Stereocomplex formation was monitored through rheological measurements and compared to classical calorimetry data. The presence of the stereocomplex lead to a significant increase in viscosity and in melt elasticity explained through the presence of physical crosslink points in the amorphous matrix. Finally, in the last experimental part of the work, the stereocomplex was employed to enhance PLA foaming behavior. Foaming visualization experiments as well as batch foaming tests showed that the presence of the stereocomplex can increase bubble nucleation density and led to a finer and more uniform foam morphology due to its nucleating effect and to the increased melt elasticity. The literature review and the three first experimental sections are presented in Peer-reviewed journal format. The last experimental section is meant as an exploratory and prospective part for the project and will not be submitted for publication.

Thesis advisor: Jeffery A. Byers / This dissertation focuses on the development of iron-based polymerization catalysts for use in the production of high commodity polymers, polyethylene and poly(lactic acid). Chapter one establishes the current landscape of the plastic market and outlines the advantages to developing iron-based catalysts. Chapter two then explores the use of bis(pyridinylimino)isoindolate-ligated iron complexes as a family of ethylene polymerization catalysts possessing distinctive mechanistic behavior. Chapter three moves to focus on the polymerization of stereoregular poly(lactic acid) from an achiral bis(imino)pyridine-ligated iron precatalyst. The mechanism for the desymmetrization of the catalyst is further detailed, and new avenues for enhancing the behavior of the reaction are discussed. Chapter four details the development of conditions for the rapid chain transfer polymerization of lactide and cyclohexene oxide, offering another tool by which value and complexity may be added to polymerization reactions carried out by this family of bis(imino)pyridine-ligated iron complexes. Finally, chapter five leverages the known redox-switchable features of bis(imino)pyridine-ligated iron complexes to develop reaction conditions for the controlled branching of poly(lactic acid) in a one-pot polymerization reaction. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

The polymer materials industry is heavily dependent on the use of petroleum based plastics. This poses a problem, as the world is facing ongoing petroleum supply problems. A need exists for a bio-carbon based polymer material that has the performance and cost of currently used petroleum plastics. However, the overall performance of current bio-based plastics indicate that they must be somehow supplemented to achieve the properties of that of petroleum-based polymers. The low impact strength and thermal stability of poly(lactic acid), PLA are targets for improvement. One option is for development is through blending with acrylonitrile butadiene styrene (ABS). The viability and efficacy of using these two polymers as blending partners is investigated. The PLA used in these studies has unique and interesting crystallization properties. These have been examined and detailed in part 1. The second part of study includes neat polymer properties, miscibility analysis, and large scale process results. This results in an optimized blending ratio on which to go forward with development. The mechanical, thermal, and morphological properties are investigated in these studies. Significance of this research and development is widespread, as the material developed has the potential to reduce the use of petroleum-based carbon in plastics. / The financial support from the 2010 Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)/University of Guelph -Bioeconomy for Industrial Uses Research Program, Natural Sciences and Engineering Research Council (NSERC) AUTO21 NCE project and Grain Farmers of Ontario (GFO), to carry out this research is gratefully acknowledged.

Orientadores: Ana Rita Morales, Maria Aparecida Marin-Morales / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-22T13:30:08Z (GMT). No. of bitstreams: 1 Souza_PatriciaMoraesSinohara_M.pdf: 5897831 bytes, checksum: ff702db4dd4540ec41606b5fd8a007e3 (MD5) Previous issue date: 2013 / Resumo: Neste estudo, foram preparados nanocompósitos de PLA e argilas organofílicas Cloisite 20A e Cloisite 30B, pelo método de intercalação do fundido. Os materiais foram caracterizados mediante Difração de Raios-X (DRX), Microscopia Eletrônica de Transmissão (MET), Análise Termogravimétrica (TGA) e Calorimetria Diferencial Exploratória (DSC). A influência das argilas organofílicas no processo de biodegradação do PLA foi avaliada pela quantificação da taxa de mineralização do PLA e dos nanocompósitos pela norma ISO 14855-2, em condições simuladas de compostagem. Também foi avaliada a influência das argilas no processo de degradação hidrolítica do PLA, pela análise visual e monitoramento de peso molecular após os períodos de 15 e 30 dias de degradação em composto. Diante da falta de informação relacionada à ecotoxicidade de polímeros biodegradáveis, a avaliação de efeitos citotóxicos, genotóxicos e mutagênicos do composto orgânico após a degradação dos materiais foi realizada empregando o bioensaio com o organismo teste Allium cepa. Os nanocompósitos preparados apresentaram estrutura intercalada, evidenciada pela análise de DRX. As micrografias obtidas por MET permitiram a observação de diferentes níveis de dispersão, incluindo regiões esfoliadas. Foram verificadas, após a incorporação das argilas organofílicas, a redução da estabilidade térmica e o aumento do grau de cristalinidade do PLA, pelas análises de TGA e DSC, respectivamente. Com relação às medidas de mineralização, notou-se que a argila Cloisite 20A não apresentou influência significativa na biodegradação do PLA. Por outro lado, a argila Cloisite 30B levou à redução dos valores de mineralização comparados com o polímero puro, o que pode estar relacionado à atividade antimicrobiana de seu agente modificador. Na avaliação da degradação hidrolítica, notou-se que a presença de argilas organofílicas pode diminuir a taxa de degradação, possivelmente pela atuação de suas camadas como barreira. Ainda assim, mesmo no caso dos nanocompósitos, a redução do peso molecular foi significativa indicando que o processo de compostagem é favorável para a cisão de cadeia do polímero nos materiais em estudo. Na análise realizada por meio do bioensaio com o organismo teste Allium cepa, foi verificado que, após a degradação do PLA e dos nanocompósitos, o composto orgânico apresentou redução do índice mitótico e aumento da indução das alterações cromossômicas, de forma estatisticamente significativa em relação ao controle negativo do ensaio (água destilada). Pela comparação dos resultados obtidos para os nanocompósitos em relação ao polímero puro, não foram verificadas diferenças estatisticamente significativas. Os tipos de aberrações cromossômicas observadas indicam um efeito genotóxico dos materiais, possivelmente relacionado a uma ação aneugênica dos produtos de degradação do PLA / Resumo: Neste estudo, foram preparados nanocompósitos de PLA e argilas organofílicas Cloisite 20A e Cloisite 30B, pelo método de intercalação do fundido. Os materiais foram caracterizados mediante Difração de Raios-X (DRX), Microscopia Eletrônica de Transmissão (MET), Análise Termogravimétrica (TGA) e Calorimetria Diferencial Exploratória (DSC). A influência das argilas organofílicas no processo de biodegradação do PLA foi avaliada pela quantificação da taxa de mineralização do PLA e dos nanocompósitos pela norma ISO 14855-2, em condições simuladas de compostagem. Também foi avaliada a influência das argilas no processo de degradação hidrolítica do PLA, pela análise visual e monitoramento de peso molecular após os períodos de 15 e 30 dias de degradação em composto. Diante da falta de informação relacionada à ecotoxicidade de polímeros biodegradáveis, a avaliação de efeitos citotóxicos, genotóxicos e mutagênicos do composto orgânico após a degradação dos materiais foi realizada empregando o bioensaio com o organismo teste Allium cepa. Os nanocompósitos preparados apresentaram estrutura intercalada, evidenciada pela análise de DRX. As micrografias obtidas por MET permitiram a observação de diferentes níveis de dispersão, incluindo regiões esfoliadas. Foram verificadas, após a incorporação das argilas organofílicas, a redução da estabilidade térmica e o aumento do grau de cristalinidade do PLA, pelas análises de TGA e DSC, respectivamente. Com relação às medidas de mineralização, notou-se que a argila Cloisite 20A não apresentou influência significativa na biodegradação do PLA. Por outro lado, a argila Cloisite 30B levou à redução dos valores de mineralização comparados com o polímero puro, o que pode estar relacionado à atividade antimicrobiana de seu agente modificador. Na avaliação da degradação hidrolítica, notou-se que a presença de argilas organofílicas pode diminuir a taxa de degradação, possivelmente pela atuação de suas camadas como barreira. Ainda assim, mesmo no caso dos nanocompósitos, a redução do peso molecular foi significativa indicando que o processo de compostagem é favorável para a cisão de cadeia do polímero nos materiais em estudo. Na análise realizada por meio do bioensaio com o organismo teste Allium cepa, foi verificado que, após a degradação do PLA e dos nanocompósitos, o composto orgânico apresentou redução do índice mitótico e aumento da indução das alterações cromossômicas, de forma estatisticamente significativa em relação ao controle negativo do ensaio (água destilada). Pela comparação dos resultados obtidos para os nanocompósitos em relação ao polímero puro, não foram verificadas diferenças estatisticamente significativas. Os tipos de aberrações cromossômicas observadas indicam um efeito genotóxico dos materiais, possivelmente relacionado a uma ação aneugênica dos produtos de degradação do PLA / Abstract: In this study, nanocomposites of PLA with organoclays Cloisite 20A and Cloisite 30B were prepared by the melt intercalation method. The materials were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). The influence of organoclays in the biodegradation process of PLA was assessed by quantifying the rate of mineralization according to ISO 14855-2, in simulated composting conditions. The influence of clays on the hydrolytic degradation process of PLA was also investigated by visual analysis and monitoring of molecular weight after periods of 15 and 30 days of degradation in organic compost. Given the lack of information related to ecotoxicity of biodegradable polymers, the assessment of citotoxic, genotoxic and mutagenic effects of the organic compost, after the materials degradation, was carried out using the bioassay with Allium cepa as test organism. The nanocomposites presented an intercalated structure, evidenced by XRD analysis. The TEM micrographs allowed the observation of different dispersion levels, including exfoliated regions. After incorporation of organoclays, a reduction of thermal stability and an increasing in the degree of crystallinity of the PLA were observed by TGA and DSC analysis, respectively. In respect to the mineralization, it was noted that the clay Cloisite 20A showed no significant influence on the biodegradation of PLA. On the other hand, the clay Cloisite 30B led to decreased levels of mineralization compared to the polymer, which may be related to an antimicrobial activity of its modifying agent. In the evaluation of hydrolytic degradation it was verified that the presence of organoclays can decrease the rate of degradation possibly by the action of its layers as a barrier. Nevertheless, even in the case of nanocomposites, the molecular weight reduction was significant, indicating that the composting process is favorable to the chain scission of the polymer in the studied materials. In the analysis performed by the bioassay using the test organism Allium cepa, it was verified that after degradation of PLA and the nanocomposites, the organic compost showed an reduction of the mitotic index and an increasing in the induction of chromosomal abnormalities. These results were statistically significant in relation to negative control (distilled water). By comparing the results obtained for the nanocomposites in relation to pure polymer, there were no statistically significant differences. The types of chromosomal aberrations observed indicate a possible genotoxic effect of materials, which may be related to an aneugenic action of the degradation products of PLA / Abstract: In this study, nanocomposites of PLA with organoclays Cloisite 20A and Cloisite 30B were prepared by the melt intercalation method. The materials were characterized by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). The influence of organoclays in the biodegradation process of PLA was assessed by quantifying the rate of mineralization according to ISO 14855-2, in simulated composting conditions. The influence of clays on the hydrolytic degradation process of PLA was also investigated by visual analysis and monitoring of molecular weight after periods of 15 and 30 days of degradation in organic compost. Given the lack of information related to ecotoxicity of biodegradable polymers, the assessment of citotoxic, genotoxic and mutagenic effects of the organic compost, after the materials degradation, was carried out using the bioassay with Allium cepa as test organism. The nanocomposites presented an intercalated structure, evidenced by XRD analysis. The TEM micrographs allowed the observation of different dispersion levels, including exfoliated regions. After incorporation of organoclays, a reduction of thermal stability and an increasing in the degree of crystallinity of the PLA were observed by TGA and DSC analysis, respectively. In respect to the mineralization, it was noted that the clay Cloisite 20A showed no significant influence on the biodegradation of PLA. On the other hand, the clay Cloisite 30B led to decreased levels of mineralization compared to the polymer, which may be related to an antimicrobial activity of its modifying agent. In the evaluation of hydrolytic degradation it was verified that the presence of organoclays can decrease the rate of degradation possibly by the action of its layers as a barrier. Nevertheless, even in the case of nanocomposites, the molecular weight reduction was significant, indicating that the composting process is favorable to the chain scission of the polymer in the studied materials. In the analysis performed by the bioassay using the test organism Allium cepa, it was verified that after degradation of PLA and the nanocomposites, the organic compost showed an reduction of the mitotic index and an increasing in the induction of chromosomal abnormalities. These results were statistically significant in relation to negative control (distilled water). By comparing the results obtained for the nanocomposites in relation to pure polymer, there were no statistically significant differences. The types of chromosomal aberrations observed indicate a possible genotoxic effect of materials, which may be related to an aneugenic action of the degradation products of PLA / Mestrado / Ciencia e Tecnologia de Materiais / Mestra em Engenharia Química

Orientador: Eliana Aparecida de Rezende Duek / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T13:28:33Z (GMT). No. of bitstreams: 1 Cherutti_Giselle_M.pdf: 10018129 bytes, checksum: f1dee789d5fd5395442f06833f2c1fa7 (MD5) Previous issue date: 2012 / Resumo: Um dos desafios da Engenharia Tecidual é o de promover um melhor funcionamento de órgãos e tecidos danificados por doenças ou traumas. Com o objetivo de desenvolver um dispositivo bifásico para futura regeneração dérmica e aplicação na Engenharia Tecidual e Medicina Regenerativa, cultivou-se células fibroblásticas da linhagem VERO sobre uma matriz dérmica suína acelular associada a um polímero biorreabsorvível, poli (L-ácido láctico) (PLLA), com adição de um plastificante, o trietil citrato de sódio (TCS). Para a realização da pesquisa, membranas PLLA-TCS e PLLA puro foram preparadas e caracterizadas através de Microscopia Eletrônica de Varredura (MEV), Ensaio Dinâmico Mecânico pelo Módulo de Tração, Espectroscopia na região do Infravermelho com Transformada de Fourier (FTIR), Ressonância Magnética Nuclear (RMN 13C e 1H), Ângulo de Contato e Calorimetria Exploratória Diferencial (DSC). Os resultados mostraram que as membranas de PLLA- TCS, tornaram-se porosas e mais hidrofílicas em relação as membranas de PLLA puro, o que aumentou sua interação com as células fibroblásticas. Após a associação das membranas de PLLA-TCS à derme suína, as amostras foram analisadas por meio de Técnicas Histológicas e Microscopia Confocal para avaliar a presença de fibras colágenas e sua organização no arcabouço. Em seguida realizou-se cultura de células fibroblásticas sobre o dispositivo bifásico após 24 horas e 2 dias de cultivo para ensaios de Viabilidade Celular, e posteriormente Microscopia Eletrônica de Varredura (MEV). Os resultados obtidos pelos ensaios mecânicos e biológicos comprovaram que o material apresentou interação suporte-célula, principalmente devido a sua porosidade e afinidade celular apresentada pela composição estrutural da matriz dérmica, sendo atóxico às células VERO. O material atuou como substrato celular, sendo que a proliferação das células VERO foi maior em comparação com a placa de cultivo (controle), havendo infiltração celular. Concluí-se assim, que o dispositivo estudado apresenta potencial para ser utilizado como um substituto dérmico para implantes em áreas de queimaduras extensas, por ser altamente poroso, promovendo assim, maior migração, adesão e crescimento celular ao mesmo tempo em que o dispositivo é degradado pelo organismo. A capacidade de deformação apresentada pelo futuro substituto dérmico também auxilia em sua implantação, por facilitar o procedimento cirúrgico, que muitas vezes necessita distender um pouco o material para o total recobrimento da lesão; ou as movimentações naturais da pele após o implante. Além disso, o dispositivo minimiza as chances de contração do enxerto, por ser constituído por um componente dérmico / Abstract: One of the challenges of the Tissue Engineering is to promote a better functioning of organs and tissues damaged by diseases or traumas. With target for developing a biphasic device for future regeneration and dermal application in Tissue Engineering and Regenerative Medicine, fibroblasts from VERO cell line were cultivated on a porcine acellular dermal matrix associated to a bioresorbable polymer (PLLA) with the addition of a plasticizer (TCS). For this present study, PLLA-TCS membranes and pure PLLA were prepared and analyzed by means of characterization tests such as Scanning Electron Microscopy (SEM), Dynamical Mechanical Analysis (DMA), Spectroscopy of the Fourier Transform Infrared, Nuclear Magnetic Ressonance (NMR 13C e 1H), Contact Angle and Differential Scanning Calorimetry (DSC). The results showed that the PLLA-TCS, became porous and more hydrophilic compared to pure PLLA, which increased its interaction with the fibroblast cells. After the association of the PLLA-TCS to the porcine dermal matrix, the samples were analyzed by Histological Techniques and Confocal Microscopy to evaluate the presence of collagen fibers and their organization within scaffold. Afterwards, a culture of fibroblasts cell on the biphasic device was performed after 2 days and 24 hours of cultivation the Cellular Viability test was done and posteriorly Scanning Electron Microscopy (SEM). The results of the biphasic device in relation to mechanical and biological tests showed the cell-support interaction, through the analysis of viability, cell morphology and structural organization of collagen fibers and polymer structure, are nontoxic to VERO cells. The material behaves as a cell substrate where proliferation of VERO cells and their infiltration was higher compared to the cell culture plate. It can therefore be concluded that the studied device has the potential to be used as a substitute for dermal implants in areas of extensive burns, for being highly porous, thus promoting increased migration, adhesion and cell growth while the device is degraded by the body. The device deformation capacity also helps in the substitute implantation for facilitating the surgical procedure which often need to stretch the material for coverage of the injury completely or natural movements of the skin after implantation. Furthermore, the device minimizes the chances of skin graft contraction as the gadget consists of a dermal component / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Orientadores: Lucia Helena Innocentini Mei, Marcos Akira D'Avila / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-26T15:02:32Z (GMT). No. of bitstreams: 1 Santos_LarissaGiorgettidos_M.pdf: 23548686 bytes, checksum: e066ca702d1acefc2c3a72890d4456f5 (MD5) Previous issue date: 2014 / Resumo: Biomateriais nanofibrosos, obtidos com polímeros sintéticos biodegradáveis pela técnica de eletrofiação (electrospinning), com ou sem a presença de bioativos, são scaffolds promissores para aplicação na engenharia de tecidos devido a similaridade com matrizes extracelulares (ECM) naturais. O poli (ácido lático) (PLA) é um polímero de grande interesse tecnológico devido às suas propriedades para aplicação nessa área. Sedum dendroideum é um fitoterápico conhecido cientificamente por suas propriedades antiinflamatórias e cicatrizantes, e amplamente utilizado pela medicina popular. Neste trabalho, membranas de PLLA foram obtidas através do processo de eletrofiação, com variação da concentração do polímero (2,5%, 5%, 7,5% 10% e 12,5% m/v) e variação da taxa de vazão da solução no processo (2ml/h, 4ml/h e 6ml/h), buscando uma membrana com um menor diâmetro de fibra. A caracterização da massa molar, da isomeria, dos grupos químicos e do comportamento térmico do PLLA, foram feitas pelas técnicas de cromatografia de permeação (GPC), polarimetria, espectrometria no infravermelho (FT-IR), calorimetria diferencial de varredura (DSC) e Termogravimetria (TGA), respectivamente. O objetivo deste trabalho foi, além de obter membranas nanoestruturadas de PLLA por eletrofiação e caracterizá-la morfologicamente, foi incorporar extrato de S. dendroideum na membrana de menor diâmetro de fibra (7,5%) e investigar sua utilização no processo de cicatrização, com o intuito de otimizar as propriedades in vivo do material. Para tanto, foram realizados testes in vitro para análise do perfil de liberação do fitoterápico, no qual ficou constatado a libração do mesmo, e in vivo para verificar os efeitos da membrana como suporte na regeneração tecidual. Este estudo apresenta a eficácia das membranas de PLLA como suporte para liberação controlada do extrato de S. dendroideum e a sua capacidade em promover o reparo tecidual em lesões excisionais na pele do dorso de ratos Wistar. Os animais foram aleatoriamente divididos em cinco grupos: controle (C), animais tratados com membranas de PLLA (M), animais tratados com o extrato de S. dendroideum dissolvido em solução salina (F), animais tratados com membranas de PLLA com 10% de S . dendroideum (MF10), animais tratados com membranas de PLLA com 25% S. dendroideum (MF25). As amostras de tecidos foram colhidas no 2º, 6º e 10º dia após a cirurgia e foram submetidas a análise estrutural e morfológica. As observações experimentais mostraram a eficácia do fitoterápico incorporado na membrana, que promoveu um aumento significativo do número de células inflamatórias, a porcentagem de fibras colágenas maduras e birrefringentes e na espessura do epitélio em lesões cutâneas excisionais em ratos Wistar. Foi também demonstrado a aplicação das membranas de PLLA, sem o extrato, que promoveram respostas semelhantes no tecido lesionado, comprovando sua eficácia na aplicação como suporte para o crescimento de tecidos / Abstract: Nanofibrosos biomaterials, obtainde with biodegradable synthetic polymers through the electrospinning method, with or without bioactive molecules, are promising scaffolds in tissue engineering because of similarity to extracellular matrix (ECM) natural. Poly (lactic acid) (PLA) is a polymer of great interest due to its technological applications in this area. Sedum dendroideum is a herbal scientifically known for its anti-inflammatory and healing properties, and widely used in folk medicine. In this study, a PLLA membranes were obtained by electrospinning process, varying the polymer concentration (2.5%, 5%, 7.5% and 12.5% 10% w / v) and varying the flow rate solution in the process (2 ml / h, 4 ml / h and 6 ml / h) seeking a membrane with a smaller fiber diameter. The characterization of the molecular weight, of isomerism, chemical groups and the thermal behavior of PLLA were made by techniques permeation chromatography (GPC), polarimetry, infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and thermogravimetry (TGA), respectively. The aim of this work was in addition to getting nanostructured membranes of PLLA by electrospinning and morphologically characterize it, was incorporate S. dendroideum extract in the membrane of smaller fiber diameter (7.5%) and investigate their use in the healing process, in order to optimize the in vivo properties of the material. Therefore, in vitro tests were done to analyze the herbal release in which it was found the liberation of the same, and in vivo to check the effects of the membrane as support in tissue regeneration. This study shows the effectiveness of PLLA membranes as support for controlled release of the S. dendroideum extract and its ability to promote tissue repair in skin lesions excised from the back of Wistar rats. The animals were randomly divided into five groups: control (C) animals treated with PLLA membrane (M), animals treated with the extract of S. dendroideum dissolved in saline (F), animals treated with PLLA membranes with 10% S. dendroideum (MF10), animals treated with PLLA membranes with 25% S. dendroideum (MF25). Tissue samples were collected at 2nd, 6th and 10th days after surgery and underwent structural and morphological analysis. Experimental observations have shown the effectiveness of membrane embedded with herbal, which caused a significant increase in the number of inflammatory cells, the percentage of mature collagen fibers and birefringent and the thickness of epithelium in excising skin lesions in rats. It was also demonstrated the application of PLLA membranes without the extract, which promoted similar responses in the injured tissue, proving its effectiveness in application as support for tissue growth / Mestrado / Ciencia e Tecnologia de Materiais / Mestra em Engenharia Química

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Abstract Bone tissue engineering has become a rapidly expanding research area because it offers a promising new approach for bone repair and regeneration. Compared to traditional autograft and allograft procedures, bone tissue engineering techniques based on the use of scaffolding materials in combination with autogenous stem cells can eliminate problems of donor site morbidity associated with the harvest of bone tissue, and its short supply. Clearly, the choices of material as well as a scaffold design that enhance bone regeneration are major challenges in the tissue engineering approach. Fibers in the micro-range in combination with textile-based technologies are consider as potential routes for the production of complex scaffolds since they can be used to generate a wide range of morphological structures and geometrically varied structures with high precision. Therefore in this thesis the specific objects were to: (i) develop a biocompatible composite fiber from poly(lactic acid) (PLA) and hydroxyapatite (HA) by melt spinning, (ii) design a 3D textile scaffold utilizing weaving and (iii) evaluate the scaffolds’ performance as a bone substitute material in vitro. In the present study PLA/HA composite fibers were successfully produced, and found to possess sufficient mechanical strength even at high loading concentrations (i.e. 20wt %), to be useful in a textile process. In addition, the material was shown to be biocompatible and the presence of HA in the PLA composite significantly enhanced the initial cell attachment. In a 3D woven scaffold, bone marrow derived human mesenchymal stem cells (hMSCs) differentiated into osteoblasts and mineralized bone formation in vitro was observed through-the-thickness of the scaffold. Taken together, these results indicate the potential feasibility of PLA/HA composite fiber in a 3D woven scaffold for use as a bone substitute material in tissue engineering applications. / Tiivistelmä Luupuutosten korvaaminen kudosteknologisesti on kehittynyt nopeasti ja tutkimustulokset tarjoavat lupaavia mahdollisuuksia tuottaa uutta luuta luupuutosalueelle. Perinteisiin potilaan omasta luusta tehtyihin luusiirteisiin ja pankkiluusiirteisiin verrattuna potilaan omat kantasolut voivat vähentää ongelmia, joita ovat siirremateriaalin rajallinen saatavuus ja vieraan kudoksen aiheuttamat reaktiot. On tärkeä etsiä hyviä materiaaleja, joista voidaan valmistaa sellaisia kolmiulotteisia (3D) rakenteita, joilla tehostetaan luun paranemista ja uuden luun muodostumista. Kutomalla tuotetut tukirakenteet mahdollistavat kantasolusiirteille kolmiulotteisuuden, jota voidaan säädellä monipuolisesti ja tarkasti. Tämän väitöstutkimuksen tarkoituksena oli: (i) kehittää bioyhteensopiva kuitu maitohappopolymeeristä poly lactic acid (PLA) ja hydroksiapatiitista (HA) kuituekstruusiolla, (ii) suunnitella ja kutoa tästä kuidusta 3D tekstiilirakenne, ja (iii) tutkia sen toimivuus ja ominaisuudet luunmuodostusta tukevana materiaalina soluviljelyolosuhteissa. Tämä tutkimus osoittaa, että PLA kuitua voidaan seostaa hydroksiapatiitilla, ja PLA/HA kuidut ovat mekaanisesti kestäviä sisältäessään jopa 20 painoprosenttia hydroksiapatiittia. Siten kuidut ovat tekstiilin valmistuksessa käyttökelpoisia. Lisäksi materiaali osoittautui bioyhteensopivaksi, ja hydroksiapatiitti paransi solujen tarttumista PLA kuituun viljelyn alkuvaiheessa. Ihmisen luuytimestä peräisin olevat sidekudoksen kantasolut (hMSCs) erilaistuivat soluviljelmässä luuta muodostaviksi soluiksi eli osteoblasteiksi, ja tuottivat mineralisoitunutta luun väliainetta kautta koko kudotun tukirakenteen. Johtopäätöksenä on, että PLA/HA yhdistelmäkuitua voidaan kutoa kolmiulotteiseksi tukirakenteeksi, ja sitä on mahdollista käyttää apuna korvattaessa luupuutoksia kudosteknologian keinoin.