Orientadores: Ângela Maria Moraes, José Alberto Fracassi da Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-19T03:16:00Z (GMT). No. of bitstreams: 1 RammazzinaFilho_WalterAnibal_M.pdf: 10957404 bytes, checksum: d23a9aea438343039da493db09603556 (MD5) Previous issue date: 2011 / Resumo: O uso de implantes em cirurgias de correção da parede abdominal é freqüentemente necessário. Telas de poli(propileno) podem ser empregadas com sucesso para essa finalidade, possuindo boa aceitação tecidual e baixo custo. O uso deste tipo de biomaterial pode, porém, ocasionar a aderência indesejada entre tecidos e/ou entre órgãos como o fígado e os intestinos e a tela, resultando em dores abdominais, obstrução intestinal e infertilidade. Neste contexto, o objetivo deste trabalho foi o de desenvolver uma estratégia de recobrimento de telas de poli(propileno) enfocando a deposição de soluções de quitosana de massa molar baixa e média e de polietilenoglicol (PEG) de massa molar igual a 1000 Da por electrospinning. Para fins de comparação, telas de poli(propileno) foram alternativamente recobertas por imersão com diferentes soluções combinando quitosana e PEG. Nos estudos de recobrimento via electrospinning, foram avaliadas as variáveis tipo de solvente para a dissolução da quitosana e do PEG, vazão de solução de recobrimento, proporção entre quitosana e PEG, diferença de potencial usada durante a deposição e distância entre a tela e o jato de injeção. As telas recobertas através da imersão em soluções de quitosana a 1% (tanto com a de baixa massa molar quanto a com massa molar média) e em soluções de quitosana misturada ao PEG também com concentração de sólidos total de 1% apresentaram-se satisfatórias para fins de barreira física em cirurgias de hérnia, considerando-se o aspecto, a uniformidade, os valores médios de espessura (de 1140 e 990 mm, respectivamente), a perda de massa em fluido corpóreo simulado (5,1 e 8,9%, respectivamente) e a capacidade de absorção do mesmo fluido (0,76 e 0,59 g/g, respectivamente). Já o recobrimento por electrospinning resultou no depósito de fibras emaranhadas na superfície das telas, que apresentaram, então espessuras finais variando entre 581 e 612 mm, perdas de massa entre 4,9 e 9,2% em fluido corpóreo simulado, capacidade de absorção de 0,17 a 0,36 g/g em fluido corpóreo simulado e diâmetros de fibras de 20,9 a 92,2 mm. O recobrimento via electrospinning resultou em biomateriais menos espessos e com menos massa associada, com bom potencial de uso na aplicação pretendida / Abstract: The use of implants in surgical correction of the abdominal wall is frequently required. Polypropylene meshes can be successfully employed for this purpose, having good tissue acceptance and low cost. The use of this biomaterial, however, can lead to undesired adhesion between tissues and/or between organs such as the liver and intestines and the mesh, resulting in abdominal pain, bowel obstruction and infertility. In this context, the objective of this work was to develop different coatings of polypropylene meshes, focusing on the deposition of solutions of chitosan of low and medium molecular weight and polyethylene glycol (PEG) of molecular weight equal to 1000 Da by electrospinning. For comparison, polypropylene meshes were alternatively coated by immersion in different solutions combining chitosan and PEG. In the studies of coating via electrospinning, the effect of the variables type of solvent for the dissolution of chitosan and PEG, coating solution flow rate, chitosan to PEG mass ratio, the potential difference used during the deposition and the distance between the mesh and the injection jet were evaluated. Meshes coated by immersion in chitosan (both with low and medium molar mass) and PEG solutions with total solids concentration of 1% were satisfactory for purposes of physical barrier in hernia surgery, considering aspect, uniformity, mean thickness (1140 and 990 mm, respectively), mass loss (5.1 and 8.9%, respectively) and the capacity of fluid absorption (0.76 and 0.59 g/g, respectively). Coating by electrospinning resulted in the deposition of entangled fibers on the surface of the meshes, which had final thickness ranging between 581 and 612 mm, losses of mass between 4.9 and 9.2% in simulated body fluid, absorption capacity of 0.17 to 0.36 g/g in the same fluid and fiber diameters from 20.9 to 92.2 mm. Coating the meshes via electrospinning resulted in thinner biomaterials and with less associated mass, with good potential for use in the intended application / Mestrado / Desenvolvimento de Processos Biotecnologicos / Mestre em Engenharia Química

Orientadores: Lucia Helena Innocentini Mei, Marcos Akira D'Ávila / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-20T02:05:21Z (GMT). No. of bitstreams: 1 Bizarria_MariaTrindadeMarques_D.pdf: 4483205 bytes, checksum: 44e9caae2b1e4e2bd5569681573ba911 (MD5) Previous issue date: 2012 / Resumo: A obtenção de nanofibras de polímeros biocompatíveis, baseadas em quitosana, bem como a montagem de equipamento capaz de produzi-las, foi o principal objeto deste trabalho. Com este propósito, buscou-se de início reunir os dispositivos eletrônicos e mecânicos indispensáveis à prática da eletrofiação e um equipamento básico, de baixo custo, mas funcional foi construído. Com base na literatura, o ácido acético glacial a 90% em água deionizada foi o solvente utilizado para preparo das soluções de quitosana. Para viabilizar o processo da produção das nanofibras pela técnica da eletrofiação utilizaram-se blendas de soluções de quitosana com soluções de outros polímeros biocompatíveis em vez de soluções de quitosana pura. Assim, blendas de soluções de quitosana com soluções aquosas do poli(óxido de etileno) - PEO , bem como, com soluções aquosas de Poli(álcool vinílico) - PVA, em diversas proporções, foram eletrofiadas. O Poli(óxido de etileno) mostrou superior desempenho, como auxiliar na fiação da quitosana, permitindo a obtenção de fibras com até 80% de quitosana, e com diâmetros inferiores àqueles obtidos com as blendas de soluções de quitosana/PVA. A adição de um eletrólito (NaCl) às soluções blendas de quitosana/PEO proporcionou um processo fácil ininterrupto, sendo assim, buscou-se um melhor entendimento sobre as propriedades das soluções da quitosana e do PEO que norteiam comportamentos mais ou menos favoráveis ao processo da eletrofiação, caracterizando-se essas soluções através de estudos de viscosidade, de medidas de tensão superficial e de condutividade elétrica. A morfologia das fibras obtidas foi caracterizada por microscopia eletrônica de varredura (MEV) e, as propriedades térmicas, das membranas nanoestruturadas resultantes da eletrofiação das soluções de Quitosana/PEO, foram avaliadas por análise termogravimétrica (TGA) e calorimetria diferencial exploratória (DSC). A biocompatibilidade das membranas com teor de quitosana mais elevado (80% quitosana/20% PEO) foi avaliada através de testes de citotoxicidade in vitro, biocompatibilidade in vivo e adesão e crescimento celular in vitro. Adicionalmente, foram conduzidos experimentos visando avaliar o desempenho destas mesmas membranas como carreadoras de fármacos sendo que, a incorporação de nanopartículas de prata (AgNPs), bem como de digluconato de clorexidina apresentaram resultados promissores / Abstract: The development of biocompatible polymer nanofibers based on chitosan and the design and assembly of equipment capable of producing them were the main objectives of this work. For this purpose, the basic electronic and mechanical devices were obtained and a low-cost functional electrospinning setup was built. Based on the literature, glacial acetic acid with concentration of 90% in deionized water was the solvent used to prepare the chitosan solutions. In order to enable the nanofiber production by electrospinning, blends of chitosan solutions with other biocompatible polymers were used instead of pure chitosan solutions. Thus, blends of chitosan solutions with aqueous solutions of poly (ethylene oxide) PEO as well as with aqueous solutions of poly (vinyl alcohol) PVA, in various proportions, were electrospun. The PEO presented superior performance as an aid to obtain chitosan fibers, resulting in fibers with up to 80% of chitosan, and with smaller diameters than those obtained with solutions of blends of chitosan / PVA. The addition of an electrolyte (NaCl) to the chitosan/PEO solution blends has provided an easy and uninterrupted process. Thus, to obtain a better understanding about the properties of chitosan and PEO solutions that lead to more or less favorable behaviors to the electrospinning process, these solutions were characterized by performing viscosity studies and measurements of surface tension and electrical conductivity. The morphology of the fibers was evaluated by scanning electron microscopy (SEM) and the thermal properties of nanostructured membranes resulting from electrospinning of chitosan/PEO solutions were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).The biocompatibility of the higher-content-chitosan membranes (80%chitosan /20% PEO) was evaluated by tests of in vitro cytotoxicity, in vivo biocompatibility and in vitro cell adhesion and growth. In addition, experiments were conducted to evaluate the performance of the same membrane as a carrier of drugs. In this way, the incorporation of silver nanoparticles (AgNPs) and chlorhexidine digluconate showed promising results / Doutorado / Ciencia e Tecnologia de Materiais / Doutor em Engenharia Química

Electrospinning is a fiber production method that has gained a special attention due to the simple setup and potential for the industry scale up to produce nanoregime polymer fibers. However, electrospun fibers have relatively poor mechanical properties, which could be improved by introducing reinforcing agents. Cellulose nanocrystals (CNCs) are a promising candidate for use as such fiber reinforcing phase due to nanoscale dimensions, excellent mechanical properties, abundance in nature, biocompatibility and renewability. The mechanical properties of reinforced fibers can be further improved by aligning them uniaxially. There are several reports available on aligning electrospun fibers and reinforcing them with CNCs. However, alignment of the reinforcing phase, such as CNCs, inside matrix is not studied extensively. The importance of aligning arises from different mechanical properties exhibited by the CNCs in longitudinal and transverse directions due to the high aspect ratio. This anisotropic nature of CNCs could be employed in nanocomposite fibers by aligning crystals along the fiber direction. In this study, the effect of the electric field modification on the alignment of CNCs in poly(vinyl) alcohol fibers was investigated. Fibers were collected using four different collector types, which also gave four different electric field configurations. Alignment of the reinforcing crystals in fibers with different degree of macroscopic orientation was studied using 2D XRD and polarized FT-IR. These studies confirm the alignment of both CNCs and PVA in uniaxially aligned fibers. Mechanical testing showed that improvement in alignment is directly related to the increase of the strength of the material. Aligned PVA-CNCs fibers had more than 100 times higher elastic modulus compared to non-aligned fibers. The rule of mixtures, Halpin-Tsai equation and orientation modified Cox’s equation were used to calculate theoretical values of elastic modulus and compare with experimental values. The comparison of between experimentally observed alignment of CNCs and theoretically predicted values shows that there is a potential for further improvement. The demonstrated improvements in the alignment of reinforcing phase could find applications, where well-aligned architectures are required, for example in uses as tissue engineering, scaffolds, membranes, microelectronic devices etc.

>Magister Scientiae - MSc / In recent times, the occurrence and presence of complex recalcitrant toxic contaminants in water and wastewater is increasing and consequently contributes to the non-availability of clean and safe drinking water. Water treatment is complex, time demanding and energy intensive due to the physico-chemical structural complexity and diversity of the pollutants. Non-availability of good drinking water has negatively affected human health and the ecosystem. Over the years, numerous conventional treatment techniques were used to degrade and remove these pollutants, but investigations indicated that some of the pollutants are not susceptible to conventional treatment. Advanced oxidation technology, among which heterogeneous photocatalysis (involving the use of a semiconductor) has emerged as one of the more promising techniques to remediate contaminated water. Titanium dioxide (TiO2) semiconductor photocatalysis is considered to be a good option due to its cost effectiveness, chemical and thermal stability, and inertness in the area of wastewater reclamation and re-use. However the post separation of the titania particles poses a threat to the wastewater remediation. Hence there is a need to develop a supported high surface area photocatalyst that will resolve the post separation challenge. This present study aimed to prepare high surface area TiO2 anatase nanocrystals supported on a stainless steel mesh. These new composite materials were used to remove methylene blue (MB) from aqueous solutions. The supporting procedure involved the thermal decomposition of a sol gel solution coated upon stainless steel mesh. The nanocrystalline anatase phase was formed by thermal decomposition on a stainless steel mesh coated with 8 % PAN/DMF/TiO2 sol gel formation calcined at varying temperatures of 300 °C, 400 °C, 500 °C and 600 °C. The heating rate of 50 °C/min and independent holding time of 1 h, 2 h, 3 h and 4 h were applied to find the optimum supporting conditions. The synthesised TiO2 nanocomposites materials were characterised using the following analytical techniques: XRD, HRSEM, EDS, HRTEM, SAED, FTIR and UV-Vis absorption spectroscopy materials were characterised, and the results indicate that synthesised TiO2 nanocrystals were in the anatase form, polycrystalline in nature, and contained additional carbon-carbon bonds from the polymer used during preparation with TiO2 particle sizes range from 13.6 nm to 2285 nm.

No description available.

This work presents the syntheses, photophysical and photochemical characterization of arylthio zinc phthalocyanines and their gold nanoparticle conjugates. Spectroscopic and microscopic studies confirmed the formation of the phthalocyanine-gold nanoparticle conjugates which exhibited enhanced photophysicochemical properties in comparison to the phthalocyanines. The studies showed that the presence of gold nanoparticles significantly lowered fluorescence quantum yields and lifetimes. However, this interaction did not restrict the formation of excited singlet and triplet states and hence the formation of singlet oxygen required for photocatalysis. The conjugates showed significantly higher singlet oxygen quantum yields and therefore enhanced photocatalytic activity compared to the phthalocyanines. The zinc phthalocyanines and their gold nanoparticle conjugates were successfully incorporated into electrospun polymer fibers. Spectral characteristics of the functionalized electrospun fibers indicated that the phthalocyanines and phthalocyanine-gold nanoparticle conjugates were bound and their integrity was maintained within the polymeric fiber matrices. The photophysical and photochemical properties of the complexes were equally maintained within the electrospun fibers. The functionalized fibers were applied for the photoconversion of 4-chlorophenol and Orange G as model organic pollutants. / Microsoft� Word 2010 / Adobe Acrobat 9.53 Paper Capture Plug-in

This thesis presents the development of chlorophyll, cholic acid, aflatoxin B1 molecularly imprinted polymer (MIP) particles and cholic acid MIP nanofibers for application as selective solid phase extraction (SPE) sorbents. The particles were prepared by bulk polymerization and the nanofibers by a novel approach combining molecular imprinting and electrospinning technology. The AFB1 MIP particles were compared with an aflatoxin specific immunoextraction sorbent in cleaning-up and pre-concentrating aflatoxins from nut extracts. They both recorded high extraction efficiencies (EEs) of > 97 % in selectively extracting the aflatoxins (AFB1, AFB2, AFG1 and AFG2). High reproducibility marked by the low %RSDs of < 1% and low LODs of ≤ 0.02 ng/g were calculated in all cases. The LODs were within the monitoring requirements of the European Commission. The results were validated with a peanut butter certified reference material. The chlorophyll MIP on the other hand selectively removed chlorophyll that would otherwise interfere during pesticide residue analysis (PRA) from > 0.6 to <0.09 Au in green plants extracts. The extracted chlorophyll was removed to far below the level of ≥ 0.399 Au that is usually associated with interference during PRA. Furthermore, the MIP demonstrated better selectivity by removing only chlorophyll (> 99%) in the presence of planar pesticides than the currently employed graphitized carbon black (GCB) that removed both the chlorophyll (> 88%) and planar pesticides (> 89%). For the interfering cholic acid during drug residue analysis, cholic acid MIP electrospun nanofibers demonstrated to be more sensitive and possessing higher loading capacity than the MIP particles. 100% cholic acid was removed by the nanofibers from standard solutions relative to 80% by the particles. This showed that the nanofibers have better performance than the micro particles and as such have potential to replace the particle based SPE sorbents that are currently in use. All the templates were optimally removed from the prepared MIPs by employing a novel pressurized hot water extraction template removal method that was used for the first time in this thesis. The method employed only water, an environmentally friendly solvent to remove templates to ≥ 99.6% with template residual bleeding of ≤ 0.02%.

The thesis reports on fabricating alternative solid phase extraction (SPE) sorbents and colorimetric probes based on electrospun nanofibers for alkylphenols (APs). Hydroxyl methylated styrene [poly(co-styrene-CH₃OH)] and 3-oxobutanoate styrene [poly(co-styrene-OCOCH₃COCH₃)] copolymers were synthesized and fabricated into sorbent materials by electro-spinning/spraying. The fabricated morphologies consisting of bead free fibers, beaded fibers and particles were evaluated as SPE sorbents using batch experiments. Electropun fibers proved to be better sorbents as they exhibited extraction efficiency that exceeded 95% compared to 60% for beaded fibers and 40% for particles. In view to reduce sample and solvent volumes, smooth fibers were packed into pipette tips as SPE devices that yielded quantitative recoveries of APs from spiked wastewater samples. Recoveries ranged from 70% to 125% with LOD of 0.008, 0.01 and 0.1 μg mL⁻¹ for 4-tert octylphenol (4-t-OP), 4-octylphenol (4-OP) and 4-nonylphenol (4-NP) respectively, when using high performance liquid chromatography-fluorescence detector (HPLC-FLD). Furthermore, amino functionalised polydiacetylene polymers (PDAs), citrate capped gold (AuNPs) and silver nanoparticles (AgNPs) were evaluated as colorimetric probes for visual detection of APs. In colloidal studies, AuNPs probe showed a colour change from wine red to green upon introduction of analyte. UV-vis spectroscopy revealed the shifting of the surface plasmon resonance (SPR) peak from 525 nm to 729 nm induced by aggregation of AuNPs. For AgNPs probe, a colour change was observed from yellowish green to brown. Transmission electron microscopy (TEM) studies showed growth of AgNPs. A presumed oxidation of the analyte, forming an absorbing compound at 279 nm in both AgNPs and PDAs probes was also observed. For PDAs probe the colour change was from purple to pink. Concentrations as low as 30 μg mL⁻¹ were detectable in all colloidal based probes. Further colorimetric investigations were conducted with electrospun AuNPs-nylon 6 fiber mat. A colour change from purplish red to navy blue at concentrations of 1000 μg mL⁻¹ was observed. Electrospun AgNPs –nylon 6 fiber mat did not show a distinct colour change. High resolution scanning electron microscopy (HRSEM) revealed the analyte inducing the assembly of AuNPs and AgNPs as they covered the surface of the nanofiber mat. Electrospun nanofibers are a platform for analysis and thus tuning their chemistry will lead to sensitive and selective methods

Les biopiles microbiennes (PACB) sont un type de pile à combustible utilisant des bactéries comme catalyseurs. Par la métabolisation de matières organiques, les bactéries produisent et transfèrent des électrons à une matrice conductrice. Les matériaux carbonés, comme les feutres de carbone (fibres de 10 µm de diamètre) sont adaptés comme matériau anodique. L’objectif de cette thèse est d’évaluer l’effet des paramètres expérimentaux et structuraux sur la formation du biofilm et sur le comportement électrochimique d’une bactérie électro-active à la surface d’une électrode. Suite à l’optimisation de la croissance de Shewanella oneidensis en condition de semi-aérobie, l’effet de la présence d’oxygène, de l’état de croissance de la bactérie et de la nature de l’électrolyte sur le transfert électronique, ont été évalué. La polarisation de l’anode a des potentiels compris entre -0.3 et 0.5 V conduit à deux conclusions : (i) Les bactéries sont plus sensibles a des potentiels positifs élevés en réacteur mono-compartiment. (ii) En PACB à deux compartiments, les potentiels négatifs et positifs conduisent à deux structures de biofilm différentes. Un biofilm artificiel a été conçu en encapsulant des bactéries dans une gel de silice incorporé dans un feutre de carbone. Il apparait que le transfert électronique des bactéries encapsulées varie en fonction de la rigidité du réseau de silice. Finalement, par l’electrospinning d’une solution de PAN et le traitement thermique de la membrane obtenue, une électrode formée de fibres micrométriques a été conçue. Son utilisation en PACB conduit à une augmentation des performances de la biopile. Le courant anodique augmente d’un facteur 10 à 100. / Microbial fuel cells (MFC) are a type of fuel cells based on bacteria as biologic catalysts. By the metabolism of organic compounds, these micro-organisms produce and transfer electrons to a conductive matrix. The objective of this study is to evaluate the impact of working conditions and structural parameters on the biofilm formation and the electrochemical behaviour of electroactive bacteria. By optimising the bacterial growth of Shewanella oneidensis strain in semi-aerobic condition, various working condition was evaluated to better understand the interaction between a carbon felt (CF) electrode and the bacteria. It appears that the bacterial state of growth influences the electron transfer of the cells, as well as the electrolyte nature. The effect of the anodic polarization was evaluated by applying various poised potential between -0.3 V and 0.5 V in both single and dual-chamber MFC. This study leads to the conclusion that bacteria are more sensible to highly positive potential in membrane-less MFC. On the contrary, in dual-chamber reactors, both positive and negative potential leads to the formation of different biofilm architectures. Then, an artificial biofilm was created by incorporating bacteria encapsulated into a silica gel into a CF. The electrochemical behaviour of bacteria seems sensible to the tightness of the silica network. Finally, by the electrospinning of polyacrylonitrile solution and then the annealing of the fiber mat, an electrode with micro-scaled carbon fibers was produced. The use of this electrode as an anode in a MFC leads to an increase of the MFC performance and more specially of the anodic current density by a factor 10 to 100.

The limited reparative capacity of the skin and the inadequacy of conventional treatments have necessitated the development of tissue engineered skin substitutes. Several substitutes, including Integra Dermal Regeneration Template, are finding increasingly widespread application in the treatment of acute and chronic wounds. To date, these substitutes are unable to fully recreate the functionality and aesthetics of skin prior to injury. This thesis applied an integrated approach combining solution preparation, material fabrication control and biological testing to investigate electrospun silk fibroin (SF) nano-microfibrous scaffolds as potential biomimetic skin substitutes. Further to this, the improvement of the existing Integra scaffold through the incorporation of hyaluronan (HA) was assessed. Through rheological analysis of regenerated SF solutions under shear and extensional deformation a concentration regime transition at 20 wt% SF was identified. Solutions with relaxation times under 0.001 seconds were found to be unsuitable for electrospinning. The incorporation of poly(ethylene oxide) (PEO) was found to significantly increase solution relaxation times and extensional viscosity, making them much more suitable for electrospinning. Solution viscoelastic properties were shown to directly influence electrospun fibre morphology, with increases in viscosity resulting in increases in fibre diameter under stable spinning conditions. The effects of electrospinning parameters on electrospun fibre morphologies were investigated using SF-PEO blended solutions. Increased electrical field, spinneret height and decreased flow rate were found to decrease fibre diameter. In vitro assessment of the attachment, spreading, proliferation, viability and gene expression of primary human dermal fibroblasts (PHDFs) and bone marrow-derived mesenchymal stem cells (BM-MSCs) was conducted. Both PHDFs and BM-MSCs attached and proliferated with greater rapidity on fibres of the smallest diameters (~250-300 nm) with proliferation decreasing as fibre size increased until fibre diameters reached ~1200 nm. Cells were observed to be spread, with multiple attachments between fibres in scaffolds composed of ~250-300 nm diameter fibres. Cells aligned themselves to single fibres in scaffolds composed of fibres greater than 1 micrometre. HA supplementation to Integra resulted in increased proliferation, viability and migration of PHDFs. In ex vivo cutaneous wound healing models, the invasion of Integra was enhanced when scaffolds were supplemented with HA, with increased matrix deposition observed. Optimal supplementation concentrations for in vitro and ex vivo increases in cell proliferation and migration were at 1.5 – 2 mg ml-1 HA. SF electrospun scaffolds facilitated epithelial migration in ex vivo artificial wounds, with the migratory epidermis more closely resembling the structures observed in vivo. Additional preliminary investigations into the efficacy of a paste-form of Integra, Integra Flowable Wound Matrix (IFWM) were performed ex vivo, with cell invasion comparable to the conventional scaffold format. The potential for the incorporation of viable PHDFs and BM-MSCs was also investigated and keratinocyte migration was enhanced in these scaffolds. The results in this thesis provide valuable optimisation information on the development of SF electrospun scaffolds for skin engineering. Additionally, the supplementation of Integra with HA may provide a simple and effective way to enhance the performance of the scaffold in vivo.