Orientadora: Profa. Dra. Mariselma Ferreira / Tese (doutorado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2014. / O Brasil é um país com economia fundada na agroindústria, e por isso, é um grande produtor de celulose. Este estudo teve o objetivo de obter nanofibras de celulose proveniente de duas fontes vegetais: Curauá (Ananas erectifolius) e Fique (Furcraea andina). A escolha dessas plantas fibrosas justificou-se devido às suas características físico-químicas, alto teor de celulose, aspectos estratégicos de disponibilidade, e pioneirismo em aplicações biológicas. Duas metodologias de processamento foram utilizadas nas fibras, um puramente químico e outro químico-mecânico. O processo químico-mecânico consistiu de tratamentos de branqueamento, seguido de desfibrilação mecânica. Desses processos foram obtidas nanoestruturas celulósicas com morfologia de fibras e whiskers. A caracterização das nanofibras e nanowhiskers foi realizada através de ensaios físico-químicos (FTIR, DRX, TGA, número kappa, composição química e caracterização morfológica por MEV e MET). A biocompatibilidade foi testada através do comportamento citotóxico dos bionanomateriais em sistemas in vitro, pelos métodos diretos e indiretos de viabilidade celular por MTT, morfologia celular e adesão. As nanofibras assim como os nanowhiskers não apresentaram comportamento tóxico para as células do tipo Vero nas condições avaliadas. Os nanowhiskers de Curauá e Fique apresentaram maior teor de celulose em relação às nanofibras obtidas; todas as nanofibras apresentaram maior razão de aspecto que nanowhiskers; a maior resistência à tração máxima ocorreu com as nanofibras de Curauá, e foram necessários menor número de ciclos para ser desfibrilado; e uma etapa extra de branqueamento para obtenção de nanofibras e nanowhiskers a partir das fibras de Fique. Finalmente, foi comprovada a biocompatibilidade das nanofibras e nanowhiskers, possibilitando suas aplicações em vários setores biomédicos. / The Brazilian economy is funded on agribusiness and, therefore, is a big producer of cellulose. This study aimed to obtain cellulose nanofibers from two plants: Curauá (Ananas erectifolius) and Fique (Furcraea andina). The choice of these fibrous plants was justified due to its physical-chemistry characteristics, high cellulose content, strategic aspects of availability and the pioneering in biological applications. Two different methodologies to process the fibers were used, one strictly chemical and other chemicalmechanical. In that case, the chemical-mechanical process, consisted of bleaching treatments, followed by mechanical defibrillation. From those two processes, cellulosic nanostructures were obtained with morphology of fibers and whiskers. The characterization of nanofibers and nanowhiskers was performed by physical-chemical tests (FTIR, XRD, TGA, kappa number, chemical composition and morphological characterization by SEM and TEM). The biocompatibility was tested studying the cytotoxic behavior of the nanomateriais in in vitro systems, by the direct and indirect cell contact methods analyzed by cell viability using MTT, cell morphology and adhesion. The nanofibers as well as nanowhiskers did not exhibit citotoxicity behavior face to the Vero cells in the conditions studied. Nanowhiskers from Fique and Curaua showed higher cellulose content than all nanofibers obtained; nanofibers presented higher aspect ratio than nanowhiskers; nanofibers from Curauá got higher maximum tensile strength than nanofibers from Fique, besides requiring less number of cycles to be desfibrilated; one extra step of bleaching was needed to obtain nanofibers and nanowhisker from Fique fibers. Finally, it was proved the biocompatibility of nanofibers and nanowhiskers, enabling their applications in various biomedical sectors.

Orientador: Prof. Dr. Jean Jacques Bonvent / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Biotecnociência, 2015. / Arcabouços são estruturas de inserção para suporte e regeneração de tecidos biológicos. Vários estudos mostraram que, quando constituídas por nanofibras de biopolímeros, essas estruturas tridimensionais apresentam características favoráveis, tais como biocompatibilidade, não-toxicidade e biodegrabilidade, para adesão e proliferação de componentes da matriz extra-celular. Este trabalho teve como objetivo desenvolver nanofibras poliméricas à base de Poli (álcool vinílico) (PVA) e quitosana, avaliar suas características morfológicas e atividade bactericida in vitro para possível aplicação como arcabouço para reparo tecidual. Filmes com nanofibras poliméricas foram obtidos pelo método de eletrofiação com diferentes parâmetros da solução polimérica, formada pela mistura de dois biopolímeros, o PVA (10%) e a Quitosana (1%). A morfologia dos filmes foi estudada por imagens de microscopia de força atômica (AFM) e microscopia eletrônica de varredura (MEV), comparando o diâmetro das estruturas das nanofibras obtidas de acordo com as mudanças dos parâmetros da solução polimérica. A análise da estrutura molecular dos filmes foi realizada por espectroscopia de infravermelho com transformada de Fourier (FTIR-ATR); a análise térmica e mecânica das amostras foi efetuada por análise termogravimétrica (TGA) e análise dinâmica mecânica (DMA), respectivamente. Como teste de bioatividade, as amostras foram postas em contato com bactérias Staphylococcus aureus (ATCC 6538) para análise de inibição de crescimento. As nanofibras foram obtidas com o diâmetro variando de acordo com a proporção de quitosana na solução polimérica, além de obter fibras mais uniformes e com menos contas com PVA. As blendas de PVA e Quitosana foram obtidas de forma homogênea com aumento da estabilidade térmica e menos resistente a deformação, além de preservar características intermoleculares de cada polímero em suas blendas. Nanofibras com diferentes frações de quitosana em solução polimérica não foram capazes de inibir o crescimento de bactérias, apresentando atividade bactericida somente quando misturadas ao cloridrato de tetraciclina (1%). Tais arcabouços necessitam de estudos mais aprofundados para a aplicação na engenharia de tecidos, para a promoção do reparo tecidual. / Scaffolds are materials applied for support and tissue regeneration. Nanofibers produced by polymeric matrix should attend some basics demands for scaffolds such as being biocompatible, nontoxic, biodegradable, allowing adhesion and growing of the matrix extra cellular components (fibroblast, collagens and integrins). The aims of this work was to develop polymeric nanofibers, with morphological characteristics and bactericidal activity for cell proliferation, as future scaffold candidate for skin wound repair. The polymeric nanofibers were obtained by electrospinning method with different solutions parameters of a mixture of Poly (vinyl alcohol) (PVA) (10 %) and Chitosan (1%). Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) was used in order to analyze the morphology of scaffold surface, in terms of fiber diameter and density, as well as surface layers porosity. Molecular analysis was performed with Fourier Transformed Infrared (FTIR-ATR mode); Thermal and mechanical properties of the scaffold were investigated by means of TGA and DMA, respectively. As bioactivity test, samples were placed in contact with Staphylococcus aureus bacteria (ATCC 6538) for growth inhibition analysis. The nanofibers were obtained with the diameter varying with the proportion of chitosan in the polymer solution, plus fibers uniform and less beads with PVA. The blends of PVA and chitosan were obtained homogeneously with increased thermal stability and less resistant to deformation, in addition to preserving intermolecular characteristics of each polymer in their blends. Nanofibers with different fractions of chitosan polymer solution were unable to inhibit the growth of bacteria, showing bactericidal activity only when mixed with tetracycline hydrochloride (1%). Such frameworks require further study for application in tissue engineering, to promote tissue repair.

Orientador: Prof. Dr. Everaldo Carlos Venancio. / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Nanociências e Materiais Avançados, 2015. / O processo de eletrofiação é conhecido por ser uma técnica eficiente para a fabricação de micro e nanofibras poliméricas. As fibras provenientes do processo de eletrofiação podem ser aplicadas em diversos setores tecnológicos, como engenharia de tecidos, sensores, liberação controlada de fármacos, catálise, compósitos entre outras. Este trabalho consiste na obtenção e caracterização de micro e nanofibras a partir de uma solução polimérica de um copolímero de Poli(acrilonitrila) (PAN), o Poli(acrilonitrila-co-acetato de vinila) (PANVA). A amostra de PANVA é composta de 94 % em massa do monômero acrilonitrila e 6% em massa do monômero acetato de vinila. Foi estudada a influência dos parâmetros de processamento como distância de trabalho entre a agulha e o coletor, concentração do polímero, vazão e potencial elétrico aplicado. Observou-se com esse estudo que ao diminuir a distância de trabalho, mantendo-se uma tensão constante de 20 kV, houve um aumento na quantidade de fibras de PANVA depositadas no coletor. Porém, quando a distância de trabalho foi mantida constante em 10 cm e variou-se a tensão aplicada (10-20 kV), ocorreu um aumento na quantidade de fibras formadas. Para valores de tensão inferiores a 20 kV foi observada a presença de uma grande quantidade de estruturas globulares de PANVA. O estudo do efeito da viscosidade da solução de PANVA foi realizado mantendo-se a tensão aplicada constante e igual a 20 kV e uma distância de trabalho constante e igual a 10 cm. Para baixos valores de viscosidade 7,34 mPa.s(2 % m/v) não foi observada a formação de fibras. Para valores de viscosidade entre 14,50 e 49,65 mPa.s (4 e 6 % m/v respectivamente) foi observada a formação de nanofibras. Para viscosidades acima de 111,30 mPa.s (8 % m/v) o processo de eletrofiação somente ocorre quando os valores de tensão aplicada forem maiores ou iguais a 25 kV. O diâmetro médio das fibras obtidas variou de 99,4 (±22,6) a 123,5 (±19,5) nm. Portanto, realizando-se um controle adequado da tensão aplicada, da distância de trabalho e da viscosidade da solução polimérica foi possível obter micro e nanofibras de PANVA. / The electrospinning process is known as being an efficient technique to produce polymer micro- and nano-fibers. The fibers obtained from electrospinning process are can be used in different technological áreas, as for example in tissue engineering, sensors, drug delivery, catalisis, composite materialas. In this work it was studied the production and characterization of micro- and nano-fibers by using a polyacrylonitrile (PAN) copolymer polymeric solution, poly(acrylonitrile-co-vinyl acetate) (PANVA). The PANVA used in this work is a copolymer containing 6 wt.% of polyvinylacetate. It was studied the electrospinning processing parameters effect, such as working distance from the needle and colector, polymer concentration and applied DC electric potential. When the working distance was increased from 10 to 20 cm (at constant applied electric potential, 20 kV) it was observed a decrease in the amount of fibers deposited on the colector. However, when the working distance was kept constant and the applied electric potential was increased from 10 to 20 kV, it was observed a increase in the amount of fibers deposited on the colector as well as a decrease in the amount of beads of PANVA in the sample. The study of the effect of the polymer solution viscosity was carried out at a constant applied eletric potential (20 kV) and working distance (10 cm). For low viscosity values, i.e. 7.34 mPa.s (2 wt.%) it was not observed the formation of fiber, i.e. only beads was formed. For viscosity values of 14.50 and 49.65 mPa.s (4 and 6 wt.%, respectively) it was observed the formation of nano-fibers. For viscosity values higher than 111.30 mPa.s (8 wt.%), the electrospinning process only occur for applied electric potential equal to (or higher than) 25 kV. The fibers mean diameter changed from 99.4 (±22.6) to 123.5 (±19.5) nm. Thereforte, by using the optimized electrospinning process conditions, i.e. applied DC electric potencial, working distance and PANVA solution viscosity it was possible to control the diameter of the PANVA fibers from microfibers to nanofibers.

Issues with the dissolution and diffusion of polysulfides in liquid organic electrolytes hinder the advance of lithium–sulfur (Li-S) batteries for next generation energy storage. To trap and re-utilize the polysulfides, brush-like, zinc oxide (ZnO) nanowires based interlayers were prepared ex-situ using a wet chemistry method and were coupled with a sulfur/multi-walled carbon nanotube (S/MWCNT) composite cathode. The cell with this configuration showed a good cycle life at a high current rate ascribed to (a) a strong interaction between the polysulfides and ZnO nanowires grown on conductive substrates; (b) fast electron transfer and (c) an optimized ion diffusion path from a well-organized nanoarchitecture. A praline-like flexible interlayer consisting of titanium oxide (TiO2) nanoparticles and carbon (C) nanofiber was further prepared in-situ using an electrospinning method, which allows the chemical adsorption of polysulfides throughout a robust conductive film. A significant enhancement in cycle stability and rate capability was achieved by incorporating this interlayer with a composite cathode of S/MWCNT. These results herald a new approach to building functional interlayers by integrating metal oxides with conductive frameworks. The derivatives of the TiO2/C interlayer was synthesized by changing the precursor concentration and carbonization temperature. Finally, a dual-interlayer was fabricated by simply coating titanium nitride (TiN) nanoparticles onto an electro-spun carbon nanofiber mat, which was then sandwiched with a sulfur/assembled Ketjen Black (KB) composite cathode with an ultra-high sulfur loading. The conductive polar TiN nanoparticles not only have a strong chemical affinity to polysulfides through a specific sulfur-nitrogen bond but also improve the reaction kinetics of the cell by catalyzing the conversion of the long-chain polysulfides to lithium sulfide. Besides, carbon nanofiber mat ensures mechanical robustness to TiN layer and acts as a physical barrier to block polysulfides diffusion. The incorporation of dual interlayers with sulfur cathodes offers a commercially feasible approach to improving the performance of Li-S batteries.

Doctor of Philosophy / Department of Chemistry / Jun Li / Electrical energy storage (EES) is crucial in todays’ society owing to the advances in electric cars, microelectronics, portable electronics and grid storage backup for renewable energy utilization. Lithium ion batteries (LIBs) have dominated the EES market owing to their wide use in portable electronics. Despite the success, low specific capacity and low power rates still need to be addressed to meet the increasing demands. Particularly, the low specific capacity of cathode materials is currently limiting the energy storage capability of LIBs. Vanadium pentoxide (V₂O₅) has been an emerging cathode material owing to its low cost, high electrode potential in lithium-extracted state (up to 4.0 V), and high specific capacities of 294 mAh g⁻¹ (for a 2 Li⁺/V₂O₅ insertion process) and 441 mAh g⁻¹ (for a 3 Li⁺/V₂O₅ insertion process). However, the low electrical conductivities and slow Li⁺ ion diffusion still limit the power rate of V₂O₅. To enhance the power-rate capability we construct two core-shell structures that can achieve stable 2 and 3 Li⁺ insertion at high rates. In the first approach, uniform coaxial V₂O₅ shells are coated onto electrospun carbon nanofiber (CNF) cores via pulsed electrodeposition. The materials analyses confirm that the V₂O₅ shell after 4 hours of thermal annealing at 300 °C is a partially hydrated amorphous structure. SEM and TEM images indicate that the uniform 30 to 50 nm thick V₂O₅ shell forms an intimate interface with the CNF core. Lithium insertion capacities up to 291 and 429 mAh g⁻¹ are achieved in the voltage ranges of 4.0 – 2.0 V and 4.0 – 1.5 V, respectively, which are in good agreement with the theoretical values for 2 and 3 Li⁺/V₂O₅ insertion. Moreover, after 100 cycles, remarkable retention rates of 97% and 70% are obtained for 2 and 3 Li⁺/V₂O₅ insertion, respectively. In the second approach, we implement a three-dimensional (3D) core-shell structure consisting of coaxial V₂O₅ shells sputter-coated on vertically aligned carbon nanofiber (VACNF) cores. The hydrated amorphous microporous structure in the “as-deposited” V₂O₅ shells and the particulated nano-crystalline V₂O₅ structure formed by thermal annealing are compared. The former provides remarkably high capacity of 360 and 547 mAh g⁻¹ in the voltage range of 4.0 – 2.0 V and 4.0 – 1.5 V, respectively, far exceeding the theoretical values for 2 and 3 Li⁺/V₂O₅ insertion, respectively. After 100 cycles of 3 Li⁺/V₂O₅ insertion/extraction at 0.20 A g⁻¹ (~ C/3), ~ 84% of the initial capacity is retained. After thermal annealing, the core-shell structure presents a capacity of 294 and 390 mAh g⁻¹, matching well with the theoretical values for 2 and 3 Li⁺/V₂O₅ insertion. The annealed sample shows further improved stability, with remarkable capacity retention of ~100% and ~88% for 2 and 3 Li⁺/V₂O₅ insertion/extraction. However, due to the high cost of Li. alternative approaches are currently being pursued for large scale production. Sodium ion batteries (SIB) have been at the forefront of this endeavor. Here we investigate the sodium insertion in the hydrate amorphous V₂O₅ using the VACNF core-shell structure. Electrochemical characterization was carried out in the potential ranges of 3.5 – 1.0, 4.0 – 1.5, and 4.0 – 1.0 (vs Na/Na⁺). An insertion capacity of 196 mAh g-1 is achieved in the potential range of 3.5 – 1.0 V (vs Na/Na⁺) at a rate of 250 mA g⁻¹. When the potential window is shifted upwards to 4.0 – 1.5 V (vs Na/Na⁺) an insertion capacity of 145 mAh g⁻¹ is achieved. Moreover, a coulombic efficiency of ~98% is attained at a rate of 1500 mA g⁻¹. To enhance the energy density of the VACNF-V₂O₅ core-shell structures, the potential window is expanded to 4.0 – 1.0 V (vs Na/Na⁺) which achieved an initial insertion capacity of 277 mAh g⁻¹. The results demonstrate that amorphous V₂O₅ could serve as a cathode material in future SIBs.

Na safra de 2013/14 o Brasil produziu 751 mil toneladas de folhas de tabaco, que após beneficiamento pela indústria de cigarros são gerados resíduos constituídos basicamente pelas nervuras centrais dessas folhas. A produção de tabaco reconstituído com este material não consome a totalidade do montante gerado, sendo que até 4% do peso total do tabaco curado é descartado, pois seu maior teor de celulose comparativamente à lâmina, gosto desagradável durante a queima. A caracterização do material mostrou elevados teores de extrativos em água quente e baixos teores de lignina. Visando reaproveitamento, estes resíduos lignocelulósicos foram submetidos à polpação soda-antraquinona por explosão a vapor para obtenção de nanofibras de celulose. Empregou-se análise estatística para determinação das melhores condições para polpação variando-se o tempo e o álcali ativo, em função do rendimento bruto e do número kappa. Tempos de 6,8 minutos de reação a 175°C (expressos em termos de índice de severidade) combinados com 16,25 % de álcali ativo, foram definidas estatisticamente como as melhores condições para a polpação. As polpas obtidas nas condições ótimas mostraram boa fibrilação e remoção de aproximadamente 50% da lignina inicial. Após branqueamento, foram refinadas em moinho Masuko Sangyo MKCA6-2 com energia específica de refinação de até 5067 kWh/ton (equivalente a 4 horas de processamento nas condições utilizadas) para obtenção de nanoceluloses. Comparativamente, fibras de celulose branqueada de eucalipto foram processadas nas mesmas condições. A celulose de talos de fumo apresentou aspecto gelatinoso (indicativo de fibrilação a nível nanométrico) após 1,5 horas de refinação, em contraste com as 3 horas requeridas para a celulose de eucalipto. Para 2 horas de refinação, análises de Microscopia Eletrônica de Varredura por Emissão de Campo mostraram maior presença de nanofibras para celulose de talos de fumo do que para de eucalipto, além de algumas fibras intactas para ambas. Para 4 horas de refinação, a celulose de talos de fumo mostrou elevada fibrilação, sendo que a celulose de eucalipto ainda apresentava fibras incólumes. Análises térmicas (TGA), de infravermelho (FTIR) e de Raios-X (DRX) foram conduzidas para caracterização da matéria prima e do produto obtido. Pela análise dos dados obtidos no trabalho, conclui-se que a produção de nanofibras de celulose a partir de talos de fumo pode ser uma importante alternativa para reaproveitamento destes resíduos. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-02-25T17:03:10Z No. of bitstreams: 1 Dissertacao Glaiton Tuzzin.pdf: 3182992 bytes, checksum: fbea7678f05ee555735f6ee88c2d83a4 (MD5) / Made available in DSpace on 2016-02-25T17:03:10Z (GMT). No. of bitstreams: 1 Dissertacao Glaiton Tuzzin.pdf: 3182992 bytes, checksum: fbea7678f05ee555735f6ee88c2d83a4 (MD5) / In the 2013/14 harvest, Brazil produced 751,000 tons of tobacco leaves. Tobacco industry employs tobacco leaves for cigarette and cigar production. About 4% of the tobacco leaves processed become a waste, which is basically constituted of tobacco stems (leaves midribs) and dust from processing. Since cellulose confers an unpleasant taste when burnt, tobacco stems are not directly used in cigar and cigarette production. In order to allow tobacco stem use, it is laminated and turned into reconstituted tobacco. However, this process do not consumes all the waste produced. The characterization of tobacco stems showed high amounts of hot water extractives and low lignin contents. Aiming to reuse, tobacco stems were submitted to soda-anthraquinone pulping by steam explosion to obtain cellulose nanofibers. Statistical analysis was employed to determine the optimum conditions for pulping process. The independent variables tested were active alkali and severity index. Kappa number and raw yield were evaluated as dependent variables. Time of 6.8 minutes at 175 °C (expressed as severity index) combined with 16.25% of active alkali, was statistically defined as the optimum pulping condition. The pulps obtained in optimum condition had good fibrillation and extraction of about 50% of lignin. After bleaching, these pulps were refined in a Masuko Sangyo MKCA6-2 grinder using specific energy of up to 5067 kWh/ton for nanocelulose production. For comparative purposes, eucalyptus kraft pulp was refined in the same conditions. Tobacco stems pulp presented gel-like behavior after 1.5 hours of refining, while eucalyptus kraft pulp took 3 hours to present this behavior. For 2 hours of refining, FE-SEM analysis showed greater levels of nanofibers for tobacco stems pulp than for eucalyptus kraft pulp. In these conditions, some intact fibers were observed for both pulps. For 4 hours of refining tobacco stems pulp revealed high fibrillation and eucalyptus pulp still had undamaged fibers. Thermal analysis (TGA), infrared spectra (FTIR) and X-ray (XRD) were performed in order to characterize the raw material and the final product. After analisys of all data obtained in the study, it was concluded that production of cellulose nanofibers from tobacco stems may be an important alternative for the reuse of these residues.

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L’objectif de ce travail de thèse est de réaliser des substrats et des dispositifs de culture cellulaire pour des applications à grande échelle. En utilisant à la fois des techniques de lithographie conventionnelles et non conventionnelles, nous avons d'abord fabriqué des matrices denses de piliers élastomère avec un gradient de hauteur pour les études de migration cellulaire et nous avons observé un allongement cellulaire remarquable et une migration cellulaire dirigée, tout dépendant du gradient de rigidité. Les micropiliers élastomères pourraient également être organisés en gradient de hauteur oscillant, montrant des comportements cellulaire similaires. Sur la base d'une approche biomimétique, nous avons produit des nanofibres à deux côtés d'une membrane avec des trous traversants pour l’adhésion et la migration tridimensionnelles de cellules. Nos résultats ont montré qu'un tel substrat peut favoriser l'infiltration et la prolifération des cellules dans un environnement 3D. Enfin, nous avons utilisé des réseaux micropiliers de différentes hauteurs en tant que substrat de rigidité contrôlée pour la différenciation des cardiomyocytes à partir de cellules souches pluripotentes l'homme. À l'aide d'un stencil en élastomère, des embryons uniformes pourraient être obtenus et dérivés vers les cellules de ciblage sur le substrat de différentes rigidité, montrant clairement une dépendance de rigidité des substrats. / The purpose of this work is to develop manufacturable cell culture substrates and devices for large scale applications. By using both conventional and non-conventional lithography techniques, we firstly fabricated dense elastomer pillar arrays with height gradient for cell migration studies and we observed remarkable cell elongation and directed cell migration, all depending on the strength of the stiffness gradient. Elastomer micropillars could also be organized in ripple-like height gradient patterns, showing similar cell behaviors. Based on a biomimetic approach, we produced nanofibers on both side of a membrane with through holes for three-dimensional cell adhesion and migration. Our results showed that such a 3D scaffold can promote the cell infiltration and proliferation. Finally, we used micropillar arrays of different height as stiffness controlled substrate for cardiomyocytes differentiation from human induced pluripotent stem cells (hiPSCs). With the help of an elastomer stencil, uniform embryoids could be obtained and derived to the targeting cells on the substrate of different stiffness, showing a clear stiffness dependence of the substrates.