Óxidos e hidróxidos de alumínio vêm sendo alvo de estudos no Laboratório de Matérias-Primas Particuladas Prof. Pérsio de Souza Santos (LPSS) nas últimas seis décadas. Várias rotas de síntese de mono- e tri-hidróxidos foram pesquisadas, bem como as transformações térmicas desses materiais em aluminas de transição e alumina-alfa. Mais recentemente, a síntese de boemita a partir do tratamento hidrotérmico de gibsita vem sendo o principal objeto dos estudos realizados no LPSS. Nesta Tese, a síntese hidrotérmica de boemita a partir de uma gibsita Bayer comercial foi estudada. Os cristais produzidos foram caracterizados por difração de raios X (DRX), por análises térmicas (TGA e DTA) e por microscopia eletrônica de varredura (MEV). Diferentes morfologias de cristais de boemita foram obtidas - cristais com dimensionalidade \"3D\" (cubos e paralelepípedos), \"2D\" (placas espessas, placas finas e placas alongadas) e \"1D\" (placas alongadas e ripas) por meio da variação da composição do meio reacional inicial. Reações conduzidas em meios com pH característico de suspensões de gibsita em água (pH alcalino) resultaram em cristais com morfologia \"3D\" ou \"2D espessa\", enquanto reações conduzidas em meio acidificado (pH = 2,0) resultaram em cristais com morfologia \"2D\". Reações conduzidas em meios acidificados contendo íon acetato levaram a cristais com morfologia \"2D fina e alongada\" ou morfologia \"1D\", dependendo da relação molar [Al : acetato] inicial de íon acetato (morfologia \"1D\" necessita de uma relação molar de no mínimo 1mol Al : 1mol acetato). Os cristais com morfologia \"1D\" e \"2D fina\" apresentaram espessuras nanométricas. A evolução térmica dos cristais de boemita produzidos foi estudada após aquecimentos entre 200ºC e 1200ºC. Todas as boemitas seguiram as transformações térmicas da chamada \"série ?\" , independentemente da sua morfologia, ou seja: boemita -> alumina-? -> alumina-? / alumina-? -> alumina-?. A temperatura de transformação da boemita em alumina-? é afetada pela morfologia dos cristais, ocorrendo em temperaturas mais baixas nos materiais com cristais de espessura nanométrica (morfologias \"1D\" e \"2D fina\"). Alumina-? com diferentes morfologias e diferentes áreas específicas (determinadas pelo método BET aplicado a isotermas de adsorção de nitrogênio gasoso a 77K) foram obtidas: 136 m2/g para alumina-? \"1D\"; 73,4 m2/g para alumina-? \"2D fina e alongada\"; 40,3 m2/g para alumina-? \"3D\". Foi possível, portanto, obter aluminas de transição potencialmente interessantes para aplicações industriais dadas as elevadas áreas específicas observadas. / Aluminum oxides and hydroxides have been the subject of studies in Laboratório de Matérias-Primas Particuladas Prof. Pérsio de Souza Santos (LPSS) in the last six decades. Several synthesis routes for mono- and tri-hydroxides were investigated as well as the thermal processing of these materials into transition aluminas and alpha-alumina. More recently, the synthesis of boehmite from the hydrothermal treatment of gibbsite has been the main object of studies in LPSS. In this Thesis, the hydrothermal synthesis of boehmite from a commercial Bayer gibbsite was studied. The crystals produced were characterized by X-ray diffraction (XRD), thermal analysis (TGA and DTA) and scanning electron microscopy (SEM). Different boehmite crystal morphologies were obtained - crystals \"3D\" (cubes and parallelepipeds), \"2D\" (thick plates, thin and elongated plates) and \"1D\" (elongated plates and strips) by varying the composition the initial reaction medium. Reactions conducted in media with characteristic pH of gibbsite suspension in water (alkaline pH) resulted in crystals with morphologies \"3D\" or \"thick 2D\" while reactions carried out in acidic medium (pH = 2.0) resulted in crystals with morphology \"2D\". Reactions carried out in acidic media containing acetate ion led to crystals with a \"thin and elongated 2D\" morphology or \"1D\" morphology, depending on the pristine [Al: acetate]. molar ratio (\"1D\" morphology requires a pristine molar ratio of at least 1mol Al: 1mol acetate). Crystals with \"1D\" or \"2D thin\" morphologies presented nanometric thickness. The thermal evolution of boehmite crystals produced was studied after heating between 200oC and 1200oC. All boehmites following thermal \"?-series\" transformation, regardless of their morphology, that is: boehmite -> ?-alumina -> ?-alumina /?-alumina -> ?-alumina. The transformation temperature of boehmite into ?-alumina is affected by crystal morphology, occurring at lower temperatures in the materials with nanometer thick crystals (\"1D\" and \"2D thin\" morphologies). ?-alumina with different morphologies and different specific surface areas (determined by BET method applied to adsorption isotherms of gaseous nitrogen at 77K) were obtained: 136 m2/g for ?-alumina \"1D\"; 73.4 m2/g for ?-alumina \"thin and elongated 2D\"; 40.3 m2/g for ?-alumina \"3D\". It was therefore possible to obtain transition aluminas potentially interesting for industrial applications given the high specific surface areas observed.

Os nanomateriais, nanopartículas e nanocompósitos apresentam novas propriedades físicas e químicas, que combinam as do mundo clássico com as do mundo quântico, e despontam de maneira surpreendente na ciência e na vida cotidiana impulsionando a era da nanotecnologia. Os avanços tecnológicos nessa nova ciência estão atrelados à descoberta de materiais com características inovadoras e as moléculas atualmente são peças chaves de sistemas mais elaborados e projetados para maior desempenho. A presente dissertação teve como principal proposta levantar o estado da arte da utilização da nanotecnologia em diagnóstico e terapia no panorama nacional. O trabalho abordou pesquisa bibliográfica em bases de dados e pesquisa de campo com entrevistas semi estruturadas a profissionais locais atuantes na área biomédica. A coleta de dados evidenciou o progresso da nanotecnologia em função do tempo de acordo ao crescimento do número de publicações desde os primeiros artigos publicados até o presente e mostrou que ainda é incipiente o número de referências da nanotecnologia dentro da área nuclear: IAEA/INIS 25.948, frente a MEDLINE 90.627, PubMed 102.738 e Scopus 268.299 em maio 2015. A revisão bibliográfica contextualizou e embasou os conceitos, como interação da nanotecnologia nos sistemas biológicos e também a utilização e problemática da fiscalização e regulamentação nacional. Chegou-se à conclusão que a nanomedicina no Brasil está em processo de evolução e desenvolvimento tecnológico. O País se encontra atualmente em fase de testes pré clínicos de nanomedicamentos e ainda não possui produção em escala industrial, e está na criação e implantação legislativa. O conhecimento e a tecnologia estão sediados em pólos já desenvolvidos, fundamentalmente na região sudeste, e que mesmo nesta, a nanotecnologia encontram-se numa etapa muito inicial de aplicação no setor terapêutico e diagnóstico. / Nanomaterials, nanoparticles and nanocomposites exhibit new physical and chemical properties, matching those from the classic world with the ones from the quantum world: they emerge, surprisingly, in science and everyday life, boosting the era of nanotechnology. Technological advances in this new science are linked to the discovery of materials with innovative characteristics and molecules are, nowadays, key pieces of more complex systems designed for higher performance. This work was, mainly, proposed to improve the state of the art nanotechnology use for both diagnosis and therapy, in the national scene. This work covered bibliographic research in databases and field survey with semi-structured interviews with local professionals working in the biomedical field. Data collection showed the progress of nanotechnology, as a function of time, in agreement with the growing number of publications since the first articles published to date, demonstrating that the number of nanotechnology references is still deficient, within the nuclear area: IAEA / INIS 25 948 , compared to 90,627 MEDLINE, PubMed and Scopus 268 299 102 738, in May 2015. The literature review contextualized and comprised some concepts, such as the nanotechnology interaction with biological systems and, also, its use and problems concerning supervision and national regulation. We came to the conclusion that nanomedicine, in Brazil, is under an evolution process and technological development. The country is, currently, in a preclinical testing phase of nanodrugs, which are not produced in industrial scale yet. Also, we are working for creating and establishing a legislative policy. Our knowledge and technology are based on a geographical distribution already developed, mainly, in the southeastern region. Nevertheless, even there, nanotechnology is at an early stage as to its application for therapeutic and diagnostic purposes.

A aterosclerose é uma doença crônico-inflamatória multifatorial com o envolvimento do sistema imunológico, sendo o resultado da interação de diferentes elementos celulares. A lipoproteína de baixa densidade eletronegativa [LDL(-)], capaz de induzir o acúmulo de ésteres de colesterol em macrófagos e a subsequente formação de células espumosas, desempenha um papel-chave na doença. Anticorpos recombinantes têm sido gerados nas últimas décadas, como o scFv (single chain fragment variable), com o intuito de serem utilizados como uma novas alternativas de prevenção para o surgimento da lesão. Diante do papel da LDL(-) na aterosclerose, este projeto avaliou o efeito da imunização passiva de camundongos LDLr-/-- com scFv anti-LDL(-) em solução e scFv anti-LDL(-) conjugado a nanocápsulas, em relação ao desenvolvimento e progressão da aterosclerose. Após obtenção do scFv e sua conjugação à nanocápsulas (NC-scFv), ensaios in vitro determinaram a diminuição da captação de LDL(-) em macrófagos tratados com o scFv 2C7 anti-LDL(-) em solução. No entanto, o tratamento com NC-scFv promoveu o aumento da internalização de LDL(-) em relação ao controle, possivelmente por um mecanismo de endocitose mediada por receptor específico. Estudos in vivo determinaram que camundongos LDLr-/- com idade entre 2 e 3 meses tratados com o scFv em solução apresentaram menor área de lesão aterosclerótica (p<0,05) quando comparados ao controle e que animais com 3 a 4 meses de idade tratados com NC-scFv demonstraram uma tendência à diminuição do mesmo parâmetro. Na análise da expressão de proteínas por imunohistoquímica, ambos os grupos tratados com scFv 2C7 anti-LDL(-) em solução e NC-scFv demostraram redução significativa da expressão dos receptores CD14 e TLR-4 no local da lesão. Esse achado tem grande importância, uma vez que dados da literatura apresentam ambos os receptores como possíveis candidatos ao reconhecimento da LDL(-). Diante dos dados obtidos, o estudo evidenciou a eficácia do scFv 2C7 anti-LDL(-) em solução e da formulação NC-scFv no contexto da aterosclerose, possibilitando a sua utilização como estratégias terapêuticas na intervenção precoce para prevenir o desenvolvimento e a progressão da doença. / Atherosclerosis is a chronic inflammatory multifactorial disease related to the immune system and being the result of interaction of different cellular elements. The electronegative LDL, since the changes undergone by this particle are able to induce the accumulation of cholesterol esters in macrophages and the subsequent formation of foam cells, plays a key role in atherosclerosis. Recombinant antibodies have been generated in recent decades, such as scFv, (single chain fragment variable), and they may be used as a new alternative treatment for atherosclerosis treatment or prevention. Considering the role of LDL(-) in atherosclerosis, this project evaluated the effects of the treatment with anti-LDL(-) scFv 2C7 solution and anti-LDL(-) scFv conjugated to nanocapsules as a passive immunization strategy on atherosclerosis induced in LDL receptor knockout mice. After obtaining the anti-LDL(-) scFv 2C7 solution and its conjugation to nanocapsules (NC-scFv), in vitro tests led to the decrease in LDL(-) uptake in macrophages treated with anti-LDL(-) scFv 2C7. However, the treatment of macrophages with NC-scFv promoted increased internalization of LDL(-) as compared to control, possibly due to a mechanism of specific receptor-mediated endocytosis. In vivo studies have determined that LDLR-/- mice aged 2 and 3 months treated with anti-LDL(-) scFv 2C7 solution showed less atherosclerotic lesion area (p <0.05) compared to control and animals aged 3 to 4 months treated with NC-scFv showed a decreasing tendency of the same parameter. In the analysis of protein expression by immunohistochemistry, both groups treated with anti-LDL(-) scFv 2C7 solution and NC-scFv showed significant reduction of CD14 receptor expression and TLR-4 at the lesion site. This finding is of great importance, since the literature has both receptors as candidates for recognition of the LDL(-). From the data obtained, the study demonstrated the efficacy of treatments anti-LDL(-) scFv 2C7 in solution and NC-scFv in the context of atherosclerosis, enabling their use as therapeutic strategies in the early intervention to prevent the development and progression of the disease.

Recent advances in the area of nanotechnology have led to interesting applications of nanomaterials in medicine, especially in the areas of imaging and treatment. This thesis presents the development of two molecularly imprinted polymers (MIPs) based on the same fluorescent functional monomer. One MIP, prepared in the bulk format, is investigated for its ability to detect tamoxifen and its metabolites. The other MIP synthesised in the nanogel format, holds the potential to be used as pH-responsive drug delivery system. Four objectives were identified within this project. The first was the design and synthesis of fluorescent functional monomer. Two coumarin derivatives carrying a polymerisable unit, for covalent bonding within the polymer, and a carboxylic moiety, for interaction site with the template, were synthesised and characterised. However, only one of them (the VCC: 6-vynilcoumarin-4-carboxylic acid) showed high fluorescent yield and was selected as functional monomer. The second objective involved the development of a detection system based on bulk MIP containing the VCC fluorescent monomer. This system proved effective in generating a detectable signal upon binding the analytes. The signal was observed as a quenching of the polymer fluorescence and it was proportional to the amount of target molecules detected. The third objective was the preparation of tamoxifen-imprinted nanogels for potential application in the drug delivery field. The optimisation of the procedure gave a set of NIP/MIP with the desired solubility, particle size and fluorescence emission. These nanogels were then employed in the last objective, which involved the toxicity study and evaluation of the drug loading on of transgenic line of zebrafish. The nanogels were non-toxic at the tested concentrations and the presence of tamoxifen was confirmed.

O licopeno é um composto bioativo que tem recebido atenção especial devido aos seus efeitos terapêuticos no combate e prevenção de doenças como câncer e doenças cardiovasculares. No entanto, por ser insolúvel em água, muito instável na presença de luz, oxigênio e calor, e altamente reativo, sua aplicação nos alimentos é limitada, o que prejudica o acesso do consumidor a produtos naturais como fontes de antioxidantes em substituição aos antioxidantes sintéticos. Assim, a utilização de nanocápsulas de compostos naturais, com ação antioxidante, pode ser considerada uma das tecnologias mais promissoras para disponibilizar compostos mais estáveis e disponíveis ao consumidor. Nesse contexto, nanocápsulas de licopeno extraído do tomate foram desenvolvidas e caracterizadas com o objetivo de conferir solubilidade aparente e estabilidade ao carotenoide em diferentes condições de armazenamento e processamento. O tipo de nanopartícula, a técnica de encapsulamento e o material de parede foram selecionados a partir de um levantamento na literatura, o qual originou os artigos de revisão apresentados. As nanocápsulas de licopeno (LYC-LNC) foram sintetizadas pela técnica de deposição interfacial do polímero pré-formado poli (Ɛcaprolactona) (PCL), mantidas em meio aquoso e caracterizadas com relação aos parâmetros de diâmetro médio, potencial zeta, índice de polidispersão, eficiência de encapsulação, morfologia, pH, cor, viscosidade e concentração de licopeno. Além disso, a estabilidade das nanocápsulas foi avaliada durante armazenamento a 5 °C e 25 °C, em experimentos de fotosensibilização a 5, 15 e 25°C em condições de saturação com ar e N2; e durante aquecimento a 60, 70 e 80 °C na ausência de luz. LYC-LNC apresentaram diâmetro médio de 193 ± 4,7 nm, índice de polidispersão de 0,069 ± 0,02, potencial zeta de -11,5 ± 0,4 mV, viscosidade de 1,09 ± 0,03 mPa.s e pH médio de 6,01 ± 0,04. Durante o armazenamento a 25°C, a suspensão LYC-LNC foi considerada estável pela ausência de alterações significativas no diâmetro, potencial zeta e apesar da redução significativa do pH, cor e concentração de licopeno, as nanocápsulas apresentaram estabilidade satisfatória com aproximadamente 50% do conteúdo total de licopeno após 14 dias de estocagem. Quando as amostras foram armazenadas a 5°C, LYC-LNC mostraram a mesma estabilidade para os parâmetros citados, exceto em relação à concentração do licopeno que teve uma melhora significativa com 40% do conteúdo total do carotenoide após 84 dias de estocagem. A degradação do licopeno durante a fotosensibilização e aquecimento seguiu uma cinética de degradação de primeira ordem e apresentaram energia de ativação de 67,0 kcal/mol e 24,9 kcal/mol respectivamente, valores superiores aos relatados pela literatura. Com base nos resultados obtidos, o presente estudo demonstrou que o nanoencapsulamento é uma técnica que pode, além de aumentar a solubilidade aparente do licopeno em meio aquoso, conferir melhoria na estabilidade em diferentes condições e por isso as LYC-LNC representam uma alternativa promissora para expandir o uso do licopeno em processos industriais, para melhorar a retenção deste composto em diferentes matrizes alimentares. / Lycopene is a bioactive compound that has received special attention due to their therapeutic effects in combating and preventing of diseases such as cancer and cardiovascular disease. However, lycopene is water insoluble, very unstable in presence of light, oxygen and heat and highly reactive, characteristics that can limit its application in food, affecting the access of consumer for natural products that can serve as sources of antioxidants, substituting synthetic antioxidants. Thus, the use of nanocapsules containing natural compounds with antioxidant action can be considered one of the most promising technologies to provide compounds more stable and available to the consumer. In this context, nanocapsules containing lycopene extracted from tomato have been characterized and developed with the objective of conferring apparent solubility and stability of this carotenoid in different storage and processing conditions. The type of nanoparticles, the encapsulation technique and the wall material were selected from a research in the literature, which resulted in review articles. The lycopene nanocapsules (LYC-LNC) were synthesized by the interfacial deposition of preformed poly(Ɛ-caprolactone) (PCL) maintained in an aqueous medium and characterized regarding to parameters such as mean diameter, zeta potential, polydispersity index, encapsulation efficiency, morphology, pH, color, viscosity and lycopene concentration. Furthermore, the stability of nanocapsules during storage was evaluated at 5 °C and 25 °C, in experiments of photosensitization at 5, 15 and 25 °C in saturated conditions with air and N2; and during heating at 60, 70 and 80 °C in the absence of light. LYC-LNC had an average diameter of 193 ± 4.7 nm, polydispersity of 0.069 ± 0.02, zeta potential of -11.5 ± 0.4 mV, viscosity of 1.09 ± 0.03 mPa.s and pH value of 6.01 ± 0.04. During storage at 25 °C, the LYC-LNC suspension remained stable and no significative changes in diameter and zeta potential were observed, and despite of significant reductions in pH, color and lycopene concentration, nanocapsules showed satisfactory stability containing approximately 50% the total content of lycopene after 14 days of storage. However, when the samples were stored at 5 °C, LYC-LNC showed the same stability for the mentioned parameters, except for the lycopene concentration that had a significant improvement, presenting approximately 40% of the total carotenoid content after 84 days of storage. The degradation of lycopene during photosensitization and heating followed a kinetic of first order and showed activation energy of 67.0 kcal/mol and 24.9 kcal/mol respectively, activation energy higher than those reported in the literature. Based on these results, this study demonstrated that the nanoencapsulation is a technique which can, in addition to increasing apparent solubility of lycopene in aqueous medium, confer better stability under different conditions and thus, LYC-LNC represent a promising alternative to expand the use of lycopene in industrial processes by improving the retention of this compound in different food matrices.

Fungos filamentosos com capacidade de produzir micotoxinas podem estar presentes em alimentos, desde o cultivo até o produto após industrialização. Devido a isso, estratégias para controlar o crescimento fúngico devem ser investigadas, a fim de evitar o desenvolvimento desses microrganismos, bem como a produção de suas toxinas nos alimentos. Neste trabalho, duas abordagens para o controle de fungos toxigênicos foram avaliadas. A primeira estratégia foi a utilização de bactérias provenientes de diferentes ambientes aquáticos, sendo que 10 linhagens de Bacillus spp. e a linhagem Pseudomonas sp. 4B foram testadas quanto à influência sobre os parâmetros de crescimento (taxas de crescimento micelial, esporulação e germinação de esporos) de fungos toxigênicos (Aspergillus e Penicillium) e formação de micotoxinas. Todas as bactérias foram capazes de inibir o crescimento dos fungos em meio de cultura, apresentando halos de inibição variando de 1,0 até 15,7 mm. Bacillus sp. P11 apresentou resultados mais expressivos em relação às demais linhagens do gênero Bacillus com maiores valores de redução na maioria dos parâmetros de crescimento. Além disso, Bacillus sp. P11 e Pseudomonas sp. 4B apresentaram efeito sobre as taxas de crescimento micelial, esporulação e germinação de esporos, com níveis de redução acima de 43,3, 32,1 e 84,1% respectivamente. Mesmo assim, as demais linhagens também apresentaram resultados satisfatórios sobre esses parâmetros. Estas bactérias também reduziram a síntese de aflatoxina B1 e ocratoxina A em mais de 94 e 63%, respectivamente, quando cultivadas simultaneamente com os fungos produtores de cada micotoxina. Adicionalmente, a capacidade de Bacillus sp. P11 em produzir os lipopeptídeos iturina A (167,9 mg/mL de extrato butanólico) e surfactina (361,9 mg/mL de extrato butanólico) foi confirmada. Estes compostos podem ter contribuído para a atividade antifúngica desta bactéria. A segunda estratégia investigada neste estudo para controlar o desenvolvimento de fungos toxigênicos foi o emprego de nanofibras de poli-ɛ-caprolactona (PCL) incorporadas com cetoconazol e natamicina como material antimicrobiano. Nesta abordagem, as nanofibras foram produzidas pela técnica de eletrofiação e posteriormente caracterizadas e avaliadas quanto ao seu potencial antifúngico. Nanofibras funcionalizadas com cetoconazol ou natamicina apresentaram atividade antifúngica contra os isolados toxigênicos uma vez que zonas de inibição variando de 6 a 44 mm foram observadas. Além disso, as análises de microscopia eletrônica e espectroscopia demonstraram que a incorporação dos antifúngicos não altera de forma expressiva as principais características das nanofibras. Também foi possível verificar a capacidade de liberação controlada dos antifúngicos durante 72 h de contato das nanofibras com diferentes soluções simulantes. Valores próximos a 80 e 45 μg/mL de cetoconazol e natamicina, respectivamente, foram observados em solução de Tween 20 (5%). Portanto, o processo de eletrofiação foi capaz de agregar propriedades antifúngicas às nanofibras de PCL. Os resultados demonstraram que as bactérias e os nanomateriais investigados neste estudo são promissores para o controle de fungos toxigênicos e produção de micotoxinas. / Filamentous fungi that have the potential to produce mycotoxins may be present in food, from cultivation to after industrialization. Therefore, several strategies to control fungal growth must be investigated in order to avoid the development of these microorganisms and the production of their toxins in food. In this work, two approaches to toxigenic fungi control were evaluated. The first one was the use of bacteria from different aquatic environments as biocontrol agents in which 10 Bacillus spp. strains and the Pseudomonas sp. 4B strain were tested in relation to the effect on growth parameters (mycelial growth, sporulation and spore germination rates) of toxigenic fungi (Aspergillus and Penicillium) and mycotoxin formation. All bacteria were able to inhibit the fungal growth in culture medium with inhibition zones ranging from 1.0 to 15.7 mm. It was also observed that Bacillus sp. P11 had better results compared to other Bacillus strains with larger reduction values in most of growth parameters. Furthermore, Bacillus sp. P11 and Pseudomonas sp. 4B exhibited effect on mycelial growth, sporulation and spore germination rates with reduction values above of 43.3, 32.1 and 84.1%, respectively. Even so, the other strains also showed satisfactory results on these parameters. Finally, these bacteria reduced the synthesis of aflatoxin B1 and ochratoxin A at levels above 94 and 63%, respectively, when co-cultivated with each mycotoxin producing fungi. Additionally, the ability of Bacillus sp. P11 to produce lipopeptides such as iturin A (167.9 mg/ml of butanolic extract) and surfactin (361.9 mg/ml of butanolic extract) was confirmed. These compounds may have contributed to antifungal activity of this bacterium. The second investigation of this work in order to control the growth of toxigenic fungi was the use of poly-ε-caprolactone nanofibers incorporated with ketoconazole and natamycin as antimicrobial material. In this approach, nanofibers were produced by the electrospinning technique and subsequently characterized and evaluated for their antifungal potential. Both nanofibers functionalized with ketoconazole and natamycin showed antifungal activity against toxigenic isolates since inhibitory zones ranging from 6 to 44 mm were observed. In addition, scanning electron microscopy and infrared spectroscopy analysis showed that the antifungals incorporation does not change the characteristics of nanofibers. It was also possible to verify the ability of controlled drug release during 72 h of nanofibers contact with different simulants solutions. Values near 80 and 45 μg/ml of ketoconazole and natamycin, respectively, were observed in the solution containing 5% Tween 20. Therefore, the electrospinning process was able to provide antifungal properties to the nanofibers. The results showed that bacteria and nanomaterials investigated in this study are promising for developing control strategies of toxigenic fungi and mycotoxin production.

One of the objectives of nanotechnology is to develop ways to build functional nanoscale devices from nanostructures. Whether these nanodevices will constitute the basis for new technologies rests on the ability to precisely manipulate the nanostructures in such a way that large numbers of functional devices can be built in parallel, with each nanodevice precisely located and addressed. In this work nanostructures dispersed in solution are organized onto surfaces by means of molecular-scale directed assembly. This technique combines top down high resolution lithographic patterning to bottom up self-assembly: specific molecular interactions take place at locations precisely defined by lithography, resulting in the parallel assembly of an arbitrarily large number of devices into complex and precisely ordered arrangements. While different molecules are used in this study, DNA plays a key role throughout the work due to the specificity of its interactions, its programmability and outstanding chemical flexibility. Two approaches are developed to direct the assembly of nanostructures on a surface. The first involves the patterning and selective functionalization of metallic nanodots that are used as anchors for the attachment of DNA molecules, proteins, DNA nanostructures and single-wall carbon nanotube (SWCNT) segments wrapped by DNA. Different strategies are explored to maximize the yield of the desired assembly. This platform also allows the monitoring of DNA-protein interactions with single molecule resolution, which has many potential biomedical applications. In the second approach, lithographic patterning is used to define regions of high surface energy that promote the binding of DNA origami and SWCNT segments. The high patterning resolution again allows for single nanostructure manipulation. This method facilitates the assembly of SWCNT field effect transistors from DNA-wrapped SWCNT segments. The formation of multi-component nano-objects in solution, by directing the linkage of properly functionalized nanostructures, is also studied. The products of these reactions are suitable for surface placement with the developed directed assembly techniques, thereby resulting in a hierarchical directed assembly process. Among others, the synthesis of SWCNT-dsDNA heterostructures is described. These hybrid objects can be used to electrically probe dsDNA using the SWCNTs as electrodes, by assembling solid state devices by means of the directed assembly methods, and also by conductive AFM. The results of some electrical measurements of double stranded DNA are discussed. The techniques developed in this thesis are directly applicable to fundamental studies of electron transport in molecules and other nanostructures, but they also have utility in other fields, such as chemistry and biology, where single molecule resolution is required. In addition, the approaches developed in this work may facilitate the advancement of new electronics technologies, including, but not limited to, future circuits based on single-wall carbon nanotubes with specific electronic properties.

Biological systems are intricate self-assembled systems built from dynamic nanoscale components. These nanoscale components are responsible for many tasks, from subcellular (e.g. DNA replication, cytoplasmic streaming, intracellular transport) to organismal (e.g. intercellular signalling, blood circulation). At each level, biological materials demonstrate complex and dynamic behaviors which are still robust to many perturbations, requiring a balance of dynamism and stability. Being able to emulate biology by dynamically assembling complex systems and structures from nanoscale building blocks would greatly expand the types of materials and structures available, possibly leading to better smart, adaptive, self-healing materials in engineering. The overarching goal of this dissertation is to further the understanding of assembly in dynamic nanoscale systems. To this end, in vitro assays of kinesin motor proteins and microtubule cytoskeletal filaments are employed, providing a well-tested, minimalist, and convenient model system. In these assays, the kinesin motors are attached to the surface of the flow cell and the microtubule filaments are propelled over them. As the majority of past studies in active self-assembly of microtubules have been performed with biotin-labeled microtubules with streptavidin as a cross-linker (a "sticky" gliding assay), the first three parts of this dissertation focus on that system. In the first part, the adsorption kinetics of the streptavidin cross-linker onto the microtubule, which determines the interaction strength between microubule building blocks, is studied. The adsorption curve suggests that this is a negatively cooperative process, and here, the cause of the apparent negative cooperativity in the adsorption process is elucidated as a combination of steric and electrostatic interactions. In the second part, the difference between kinesin-propelled assembly and diffusion-driven assembly is investigated. While the kinesin-propelled microtubule assay has been used for over a decade, a control experiment comparing the active motor-driven system to a passive diffusion-driven system had never been performed. The control experiments showed conclusively that the passive system resulted in smaller and more disordered structures. Furthermore, these results fit well with existing models. The third part investigates the origins of microtubule spools observed in kinesin-propelled microtubule gliding assays, where the microtubules are allowed to cross-link via streptavidin and biotin. These microtubule spools have long been considered an example of a non-equilibrium structure which arises in motor-driven assembly. These spools exist in a dynamic state, having been observed to unwind in previous studies, and store large amounts of bending energy. Determining the origins of these spools is a first step towards understanding how to induce dynamically stable states. Finally, in the last part, a new dynamic system is engineered in which the microtubule assembles its own kinesin track as it moves along the surface while kinesin tracks which are not being used spontaneously disassemble. Thus, this system is stable enough to promote the motion of microtubules over the surface, but dynamic enough to allow for components to be recycled and assembled as needed. While such systems have been realized with mesoscopic to macroscopic components, such a system had not been realized in the nanoscale. As such, the realization of this system is the first step towards designing biomimetic active materials. Throughout this dissertation, the importance of short-range interactions on assembly kinetics is highlighted. The findings presented not only further the understanding and theory behind self-assembly in active nanoscale systems, but also further push the boundaries of experimentally realized systems.

Van der Waals materials and inorganic nanoparticles are two categories of nanomaterials that have been widely investigated in the past two decades. Both of them have been considered to be promising as candidates for the next generation electrical, optical, and mechanical applications. However, both of them have a few limitations that greatly affect the performance of devices, e.g. zero bandgap for graphene; poor contact quality, low mobility and quantum efficiency for MoS2; and poor interparticle conductivity for nanoparticles. This thesis tries to explore a new way of combining these two categories of material into hybrids, so that the intrinsic limitations of materials from each category will be overcome by the other materials that are introduced into the hybrid. This thesis consists of five parts. The first part (Chapter 1) introduces the background and motivation of the thesis. The second part (Chapters 2, 3, 4, and 5) describes the detailed processes and methods, starting from preparing each element to the assembly of these element into a hybrid structure device. This part also includes understanding the mechanisms of 2D and 3D self-assembly of nanoparticles. The third part (Chapter 6 and 7) describes two examples of hybrid structures, including the investigation of electron or molecule transfer inside the hybrid. The fourth part (Chapter 8) introduces other findings and technical innovations, including alternative ways of thin film nanoparticle self-assembly/deposition, and fabrication methods for the band structure analysis of transition metal dichalcogenides by angle resolved photo-electron spectroscopy. The fifth part (Chapter 9) describes several possible future work directions that could be investigated to improve the understanding of the nanoparticle assembly and translating the conceptual device into real applications.

Single-molecule electronics is an emerging subfield of nanoelectronics where the ultimate goal is to use individual molecules as the active components in electronic circuitry. Over the past century, chemists have developed a rich understanding of how a molecule’s structure determines its electronic properties; transposing the paradigms of chemistry into the design and understanding of single-molecule electronic devices can thus provide a tremendous impetus for growth in the field. This dissertation describes how we can harness the principles of organosilicon and organogermanium chemistry to control charge transport and function in single-molecule devices. We use a scanning tunneling microscope-based break-junction (STM-BJ) technique to probe structure-conductivity relationships in silicon- and germanium-based wires. Our studies ultimately demonstrate that charge transport in these systems is dictated by the conformation, conjugation, and bond polarity of the σ-backbone. Furthermore, we exploit principles from reaction chemistry such as strain-induced Lewis acidity and σ-bond stereoelectronics to create new types of digital conductance switches. These studies highlight the vast opportunities that exist at the intersection between chemical principles and single-molecule electronics. Chapter 1 introduces the fields of single-molecule electronics, silicon microelectronics, and physical organosilane chemistry and our motivation for bridging these three worlds. Chapters 2-6 elaborate on the specific approach taken in this dissertation work, which is to deconstruct the molecular wire into three structural modules – the linker, backbone, and substituent – then synthetically manipulate each component to elucidate fundamental conductance properties and create new types of molecular conductance switches. Chapter 2 describes the first single-molecule switch that operates through a stereoelectronic effect. We demonstrate this behavior in permethyloligosilanes with methylthiomethyl electrode linkers; the strong σ-conjugation in the oligosilane backbone couples the stereoelectronic properties of the sulfur-methylene σ-bonds that terminate the molecule. Chapter 3 describes the electric field breakdown properties of C-C, Si-Si, Ge-Ge, Si-O, and Si-C bonds. The robust covalent linkage that the methylthiol endgroup forms with the electrodes enables us to study molecular junctions under high voltage biases. Chapter 4 unveils a new approach for synthesizing atomically discrete wires of germanium and presents the first conductance measurements of molecular germanium. Our findings show that germanium and silicon wires are nearly identical in conductivity at the molecular scale, and that both are much more conductive than aliphatic carbon. Chapter 5 describes a series of molecular wires with π–σ–π backbone structures, where the π–moiety is an electrode–binding thioanisole ring and the σ–moiety is a triatomic α–β–α chain composed of C, Si, or Ge atoms. We find that placing heavy atoms at the α–position decreases conductance, whereas placing them at the β–position increases conductance. Chapter 6 demonstrates that silanes with strained substituent groups can couple directly to gold electrodes. We can switch off the high conducting Au-silacycle interaction by altering the environment of the electrode surface. These chapters outline new molecular design concepts for tuning conductance and incorporating switching functions in single–molecule electrical devices.