No description available.

Silk fibroin is a widely studied material in the context of tissue engineering. Thanks to its versatility and impressive properties, the fields where silk fibroin is used have grown. In particular, silk fibroin has proved to be useful in all the cases when an interface with living tissues is needed (e.g. biophotonics, bioelectronics). As a consequence of this increasing interest, a wide range of protocols have been developed to prepare different materials starting from cocoons. The aim of this thesis is to investigate new strategies to fabricate silk fibroin-based materials, either improving previously developed protocols or proposing new methodologies both with the purpose to overcome certain limitations of current approaches and to propose new areas of application. We choose to work on three topics: the production of patterns using photolithography on a fibroin photoresist films (fibroin photocrosslinkable photoresist, FPP), the production of sponges made from a chemically modified version of the native protein (Methacrylated fibroin, Sil-MA), and the production of a solid bulk resin made starting from the regenerated protein. In the case of the FPP (and its counterpart made of sericine, SPP) the fabrication of films and pattern was restricted to the use of harsh chemicals. In addition, the resulting material had a roughness that limits its use in optical applications, making the determination of the refractive index (RI) not possible. The novelty of our work consisted in the modification of the original protocol to make it environmentally sustainable and to decrease the roughness in order to use ellipsometry to determine the RI dispersion. The broadly used silk-based sponges can be prepared by several protocols but they all suffer of the same limitations: the sponges are stabilized only by physical crosslinking (the change from the random to the crystalline secondary structure), and there are no clear models that correlate the sponge properties to their composition. We produced a new sponge, chemically crosslinked, whose stability was ensured by the creation, of chemical bonds between the protein chains during an UV curing. This task was accomplished using a simple protocol and a statistical method to model the composition-properties relations. The possibility to obtain a bulk, non-porous solid monolith from fibroin (solid-fibroin) has been received attention only in the last few years. This material is produced by a transition from solution to solid through solvent evaporation, a very slow process that takes weeks to be completed. The advantage of this transition is that it occurs at room temperature, allowing the addition of thermally degradable molecules (e.g. enzymes). We were able to optimize a procedure to produce the same material by compression of a silk sponge at high pressure and low temperature. The advantage of this method is the lower amount of time required to produce the material, minutes instead of days.

Submitted by Franciele Grego Esteves null (francielegrego@gmail.com) on 2017-04-07T15:06:37Z No. of bitstreams: 1 Dissertação de Mestrado p biblioteca.pdf: 6918114 bytes, checksum: e45b8e0514dd2fe63b041ac88e0cd8f7 (MD5) / Rejected by Luiz Galeffi (luizgaleffi@gmail.com), reason: Solicitamos que realize uma nova submissão seguindo a orientação abaixo: Incluir o número do processo de financiamento nos agradecimentos da dissertação/tese. Corrija esta informação e realize uma nova submissão com o arquivo correto. Agradecemos a compreensão. on 2017-04-17T14:12:17Z (GMT) / Submitted by Franciele Grego Esteves (francielegrego@gmail.com) on 2017-04-20T20:14:39Z No. of bitstreams: 1 Dissertação Mestrado Franciele - Autoarquivamento UNESP.pdf: 6753928 bytes, checksum: 6e5332799980f808f7228f38b18d6a7c (MD5) / Rejected by Luiz Galeffi (luizgaleffi@gmail.com), reason: Solicitamos que realize uma nova submissão seguindo a orientação abaixo: O arquivo submetido não contém o certificado de aprovação. Corrija esta informação e realize uma nova submissão com o arquivo correto. Agradecemos a compreensão. on 2017-04-25T13:55:38Z (GMT) / Submitted by Franciele Grego Esteves (francielegrego@gmail.com) on 2017-04-25T15:04:46Z No. of bitstreams: 1 Dissertação Mestrado Franciele - Autoarquivamento UNESP.pdf: 6918354 bytes, checksum: 0ea68d3a1abeca7d8514c318aef0795e (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-04-25T16:05:41Z (GMT) No. of bitstreams: 1 esteves_fg_me_rcla.pdf: 6918354 bytes, checksum: 0ea68d3a1abeca7d8514c318aef0795e (MD5) / Made available in DSpace on 2017-04-25T16:05:41Z (GMT). No. of bitstreams: 1 esteves_fg_me_rcla.pdf: 6918354 bytes, checksum: 0ea68d3a1abeca7d8514c318aef0795e (MD5) Previous issue date: 2017-03-22 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A aranha Nephila clavipes pertence ao grupo das aranhas construtoras de teias orbitais, que desenvolveram a capacidade de sintetizar fios adesivos. Esses fios adesivos são encontrados nos círculos centrais destas teias, e apresentam gotículas oleosas contendo vesículas que aprisionam em seu interior soluções de proteínas, peptídeos e muitos compostos de baixa massa molecular. Estudos da análise química dessas gotículas identificaram toxinas, ácidos graxos saturados e até alcaloides. Especula-se que quando um inseto presa é aprisionado pela teia, os ácidos graxos dessas gotículas auxiliam no processo de desestabilização da cutícula do inseto, permitindo a difusão das toxinas para o interior do corpo da presa. Também são relatados alcaloides que atuam como repelentes a predadores em algumas teias, e como inseto-toxinas em outras. A presença dessas moléculas são evidências de que a teia não é uma simples ferramenta para captura mecânica e aprisionamento de presas, mas sim uma complexa estrutura, que parece desempenhar um papel estratégico “ativo” na captura de suas presas. Considerando isso, o objetivo deste estudo foi analisar a ultraestrutura, a disposição das gotículas sobre os fios de seda, e visualizar a presença de vesículas lipídicas extraídas das gotículas da teia orbital da aranha N. clavipes através de microscopia. Além disso explorou-se a riqueza do perfil químico dos compostos de baixas massas moleculares da seda da teia através da cromatografia gasosa bidimensional abrangente acoplada a um detector de massas; e por fim investigar a riqueza de proteínas presentes na seda da teia e nas glândulas produtoras de seda, através da digestão proteolítica em solução, cromatografia líquida, e espectrometria de massas, ressaltando as possíveis toxinas envolvidas na paralisia de presas. Primeiramente, foi realizado um estudo com microscopia eletrônica de varredura das gotículas depositadas sobre os fios de seda, e com microscopia de luz das vesículas lipídicas que se encontram em suspensão, retidas dentro do conteúdo aquoso das gotículas. Posteriormente na análise da perfilagem química foram encontrados 316 compostos, dentre esses 25 foram identificados a partir de padrões químicos, sendo a maioria hidrocarbonetos saturados e alguns ácidos graxos. Este estudo também demonstrou através de bioesaios de repelência, que alguns dos ácidos graxos e hidrocarbonetos identificados nas gotículas da teia apresentaram potencial como repelentes a formigas invasoras. Enquanto que o ácido palmítico apresentou ação potencial no processo de dissolução/desintegração da camada superficial da cutícula de abelhas, para permitir a passagem das toxinas ao interior do corpo das presas da aranha N. clavipes. Na análise proteômica foram indentificados um total de 2051 proteínas na seda da teia, sendo que 163 dessas proteínas são toxinas. Também foram identificadas um total de 927, 1961, 849, e 860 proteínas nas glândulas agregada, ampulada maior, flageliforme e ampulada menor, respectivamente; sendo que desses totais, 194, 78, 32 e 30 são toxinas pertencentes a cada glândula citada acima, respectivamente. Este estudo sugere que as glândulas de seda, principalmente a glândula agregada, podem sintetizar e depositar sobre a seda da teia toxinas importantes, que são comuns a alguns venenos animais, tornando dessa forma as teias como uma estrutura ativa na captura de presas. A partir dos resultados obtidos foi possível elaborar uma hipótese que relaciona o papel das gotículas, vesículas lipídicas e dos compostos identificados como parte da estratégia química da teia na pré digestão e paralisia da presa. Portanto, este estudo forneceu uma melhor compreensão da química-ecológica da captura de presas pela teia da aranha N. clavipes, além de informações que podem possibilitar o uso desses compostos no desenvolvimento de inseticida-seletivo, ou até mesmo em possíveis aplicações farmacológicas. / Nephila clavipes belongs to the group of orb-weavings spiders that have developed the ability to synthesize adhesive threads. Such adhesive threads are found in the core circles of the orb-webs, and present oily droplets which in turn contain many vesicles in suspension, entrapping solutions of proteins, peptides and many small-molecular mass compounds. Chemical analysis studies of these droplets identified toxins, saturated fatty acids and even alkaloids. It is speculated that when an insect-prey is trapped by the web, the fatty acids of these droplets aid in the process of destabilizing the insect cuticle allowing the diffusion of the toxins into the prey body. Some studies also reported alkaloids that act as repellents to predators in some webs, and as insect-toxins in others. The presence of these molecules is evidence that the web is not a simple tool for mechanical capture and imprisonment of prey; but rather a complex structure that seems to play a strategic "active" role in capturing its prey. Considering this, the aim of this study was to analyze the ultrastructure, the disposition of the droplets on the silk fibers, and to visualize the presence of lipid vesicles extracted from the web’s droplets of N. clavipes spider, by microscopy. In addition, the richness of the chemical profile of the small-molecular mass compounds in the web-silk was explored through comprehensive two-dimensional gas chromatography coupled to a mass detector; and finally to investigate the richness of proteins present in web-silk and silk-producing glands through in solution proteolytic digestion, liquid chromatography, and mass spectrometry, highlighting the possible toxins involved in the prey paralysis. First, was performed scanning electron microscopy study of the droplets deposited on the web-silk and light microscopy of the suspended lipid vesicles retained within the aqueous contents of the droplets. Posteriorly in the profiling chemical analysis were identified 316 compounds, among these 25 were identified from chemical standards, most of them are hydrocarbons saturated and some fatty acids. This study also demonstrated through repellence bioassays, that some of the fatty acids and hydrocarbons identified in the web's droplets presented potential as repellents to invasive ants. While the palmitic acid presented potential action in the process of dissolution / disintegration superficial layer of cuticle bees, to allow the difusion of toxins into the prey body. In the proteomic analysis a total of 2051 proteins were identified in the web-silk, of which 163 of these proteins are toxins. A total of 927, 1961, 849, and 860 proteins were also identified in the aggregate, major ampullate, flagelliform and minor ampullate glands, respectively; and of these totals, 194, 78, 32 and 30 are toxins belonging to each gland mentioned above, respectively. This study suggests that silkproducing glands, especially the aggregate gland, can synthesize and deposit on the silk-web important toxins, which are common to some animal venoms, thereby making the webs an active structure in the prey capture. From the obtained results it was possible to elaborate a hypothesis that relates the role of the droplets, lipid vesicles and the compounds identified as part of the chemical strategy of the web in the pre-digestion and prey paralysis. Thus, this study provided a better understanding of the chemical-ecological prey capture by N. clavipes spider web, in addition to information that may enable the use of these compounds in the development of insecticide-selective or even possible pharmacological applications. / FAPESP: 2011/51684-1 / FAPESP: 2015/14220-8

Made available in DSpace on 2015-03-03T15:11:25Z (GMT). No. of bitstreams: 1 JoseFernandoVN.pdf: 1709074 bytes, checksum: 0af621e6374e339196c6c65ecb0f15bc (MD5) Previous issue date: 2007-08-24 / O presente trabalho tem como objetivo investigar as caracter?sticas de filmes de SnO2 depositados em substrato de vidro borosilicato por um processo de silk-screen modificado para obten??o de espessura fina compat?vel com a aplica??o em c?lulas solares policristalinas de baixo custo. O filme de SnO2 ? um dos mais apropriados para obten??o de vidro TCO (transparent conductive oxide) para uso em c?lulas solares devido a sua baixa resistividade el?trica e alta transmit?ncia, sendo quimicamente inerte, mecanicamente duro e tem resist?ncia a altas temperaturas, o que facilita ent?o a calcina??o das amostras entre 500? C a 550? C. Os filmes foram obtidos a partir de uma solu??o precursora b?sica, preparada pela dissolu??o de SnCl2.2H2O em Etanol (99,5 %). Foi realizado um planejamento fatorial 2(3-1) para analisar a influ?ncia dos par?metros concentra??o da solu??o precursora (CETN), temperatura de calcina??o (TC) e taxa de aquecimento (tX) na calcina??o, sendo a concentra??o CETN o par?metro que apresentou maior efeito sobre os par?metros de respostas investigados: espessura do filme (?), resistividade de superf?cie (?) e a transmit?ncia relativa (?). Foi poss?vel obter com a metodologia utilizada, filmes com espessuras da ordem de 1 Nm com resistividade de superf?cie de 10 / e transmit?ncia relativa entre 70 e 80 %.

Economic development is a major concern to the majority of countries in the world today as they strive to catch up to the industrial West. Japan has been the most successful non-Western country in building an economy which qualifies it as developed. Most studies of economic development in Japan focus on macro-level issues, particularly on analysis of the role government played in the development process. It is generally recognized that Japan's central government played a major role in fostering industrial development. It is unfortunate that this fairly centralized political structure has somewhat obscured the role that local government may have had in helping local economies grow. In a sense, these local development efforts were at least as important as what was going on at the national level, because if peripheral areas had not developed at all, they would have become a liability for the central government and the core areas. This study examines one particular aspect of the development process in Japan; specifically, local government's role in fostering economic development throughout the Meiji (1868-1912) and Taisho (1912-1926) eras. The silk industry in Shimane prefecture provides the context of the case study approach used. The analysis focuses on two key issues: the mechanisms used by local government and the impact of growth on the local silk industry and on the standard of living.

No description available.

This thesis looks at the engineering aspects of silkworm cocoons as a structural biological composite system. A wide range of species of silk cocoons were studied for their morphologies, physical properties and mechanical behaviour. A silk cocoon can be described very broadly as a nonwoven fibre composite made of silk fibres bonded by sericin binder, although the a variety of species can show a diversity of structural features of the layers, porosity, degree of orientation, binding density and presence of crystals etc. These structural differences lead to diverse cocoon mechanical behaviour. Tensile and compressive properties of cocoons are tested and linked to their individual interfibre bonding, connectivity and density. Gas diffusion through the cocoon walls is controlled by the combination of thickness and density. In addition, a physically realistic quantitative model is developed, which links directly the structure and mechanical properties of silk cocoons. The gradual loss of connectivity of the interfibre bonding is the key mechanism for the deformation of cocoons. It can be quantified as a strain activated function of the bonding up to a failure criterion, where either a percolation threshold of 50% of these bonds or the failure stress of the binder arrives. For Bombyx mori cocoon, which has a graded-layer structure, the model was enhanced to include the contribution of interlayer and intralayer bonding in the system. This model can also be applied to other nonwoven fibre and particulate composites using a small number of physically realistic model parameters, and will be a valuable ‘bioinspired’ tool for the development of new composite systems. Based on the understanding of structure-mechanical property relationships in silkworm cocoons, an engineering approach was used for examining cocoon as an impact resistant structural material that provides mechanical protection from environmental threats. In addition, silk cocoons were used as a nonwoven reinforcement to develop an engineering composite by increasing the connectivity (more binder) in the cocoon. Using polyurethane or regenerated silk fibroin of medium concentration can increase the toughness of cocoons, and epoxy or regenerated silk fibroin of high concentration binding leads to a brittle system.

Silks are biomaterials made by spiders and silkworms, evolved for natural functions ranging from protection to predation. The research presented in this Thesis combines principles and methods from engineering, physics and biology to study the material properties of single silk fibres from a biological perspective. In particular, the factors that contribute to the variation in properties of single silk fibres are investigated. The first part of the Thesis focuses on silks made by silkworms. Whether naturally spun or forced reeled, the mechanical properties of these silks are sensitive to a range of environmental and processing conditions, such as humidity, stretching and reeling speed. The research presented in this section contributes to the understanding of how these applied conditions affect silk mechanical properties, which can be understood in terms of silk’s protein structure and biological context. The second section compares both silkworm and spider silk single fibres to other materials in terms of their sonic properties – how the materials propagate sound waves, whether following impact, or propagating vibrations. The results are discussed in the context of the silk’s natural function for impact resistance (silkworm cocoon or spider web) and vibrational signalling (spider silks). The Thesis ends with a discussion of how the presented techniques can be applied to help further our understanding of orb web function through studying spider silks. Overall, this interdisciplinary Thesis contributes to our understanding of the structure-property-function links of these fascinating biomaterials.

Biocompatible and biodegradable porous materials based on silk fibroin (SF), a natural protein derived from the Bombyx mori silkworm, are being extensively investigated for use in biomedical applications including mammalian cell bioprocessing, tissue engineering, and drug delivery applications. In this work, low-pressure, gaseous CO2 is used as an acidifying agent to fabricate SF hydrogels. This low-pressure CO2 acidification method is compared to an acidification method using high-pressure CO2 to demonstrate the effect of CO2 mass transfer and pressure on SF sol-gel kinetics. The effect of SF molecular weight on the sol-gel kinetics is determined using the low-pressure CO2 method. The results from these studies demonstrate that low-pressure CO2 processing proves to be a facile method for synthesizing 3D SF hydrogels. We also determined the effect of SF solution concentration on the morphology and textural properties of SF aerogels. Changing the solution concentration from 2 wt% to 6 wt% yielded a higher surface area (260 to 308 m2/g) and different macro structure, but similar mesopore pore volume and size, and micro structure. Furthermore, we determined the effect of drying method on the morphology and textural properties of SF hydrogels gelled via CO2 acidification. Drying with supercritical carbon dioxide (scCO2) yielded an aerogel surface area five times larger than aerogels that were freeze dried. Moreover, a freeze dried hydrogel initially frozen at -20 °C had pores approximately 10 µm larger than a hydrogel initially frozen at -196 °C. The results presented here also demonstrate the potential of SF aerogels as drug delivery devices for the extended release of ibuprofen, a model drug compound. SF aerogels are loaded with ~21 wt% of ibuprofen using scCO2 at 40 °C and 100 bar. Differential scanning calorimetry of the ibuprofen-loaded SF aerogels indicates that the ibuprofen is amorphous. Scanning electron microscopy and nitrogen adsorption/desorption analysis are used to investigate the morphology and textural properties. Phosphate buffer solution (PBS) soaking studies at 37 °C and pH 7.4 reveal that the SF aerogels do not swell or degrade for up to six hours. In vitro ibuprofen release in PBS at 37 °C and pH 7.4 occurs over a six-hour period when the ibuprofen is loaded in SF aerogel discs with an aspect ratio of ~1.65 (diameter/thickness), whereas the dissolution of the same amount of pure ibuprofen occurs in 15 minutes. Furthermore, the release of ibuprofen from these SF aerogel discs are modeled using the Fu model which indicates that ibuprofen release follows Fickian diffusion for the first 65 wt% of ibuprofen release, and non-Fickian diffusion for the next 25 wt% of ibuprofen release. We also showed that SF aerogel scaffolds support in vitro human foreskin fibroblast cell attachment, proliferation, propagation, and cell seeding of different densities (10x103, 30x103, and 60x103). In summary, we created and characterized a tunable 3D SF aerogel scaffold with potential for applications in drug delivery and tissue engineering applications.

The resurgence, and eventual rise to prominence in the field of tissue engineering, that electrospinning has experienced over the last decade speaks to the simplicity and adaptability of the process. Electrospinning has been used for the fabrication of tissue engineering scaffolds intended for use in nearly every part of the human body: blood vessel, cartilage, bone, skin, nerve, connective tissue, etc. Diverse as the aforementioned tissues are in both form and function, electrospinning has found a niche in the repair of each due to its capacity to consistently create non-woven structures of fibers ranging from nano-to-micron size in diameter. These structures have had success in tissue engineering applications because of their ability to mimic the body’s natural structural framework, the extracellular matrix. In this study we examine a number of different techniques for altering scaffold properties (i.e. mechanical strength, degradation rate, permeability, and bioactivity) to create electrospun structures tailored to unique tissue specific applications; the end goal being the creation of a cellularized tissue engineering ligament analogue. To alter the mechanical properties of electrospun structures while maintaining high levels of bioactivity, synthetic polymers such as polydioxanone were blended in solution with naturally occurring proteins like elastin and fibrinogen prior to electrospinning. Cross-linking of electrospun structures, using glutaraldehyde, carbodiimide hydrochloride, and genipin, was also investigated as a means to both improve the mechanical stability and slow the rate of degradation of the structures. Fiber orientation and scaffold anisotropy were controlled through varying fabrication parameters, and proved effective in altering the mechanical properties of the structures. Finally, major changes in the structure of electrospun scaffolds were achieved through the implementation of air-gap electrospinning. Scaffolds created through air-gap electrospinning exhibited higher porosity’s than their traditionally fabricated counterparts, allowing for greater cell penetration into the scaffold. Overall, this collection of results provides insight into the diversity of electrospinning and reveals innumerous options, both pre and post fabrication, for the tissue engineer to create site-specific engineering scaffolds capable of mimicking both the form and function of native tissue.