Current treatment for posterior segment ocular diseases requires intravitreal injections administered every 4-6 weeks. The potential for siRNA to be used to treat these diseases is extremely attractive due to the specificity of these molecules and their potential for making long term changes to the expression patterns of the cells. Due to physiological recognition, however siRNA undergoes rapid degradation upon application. The development of cationic nanogels using polymeric “smart” biomaterials with degradable components to transport siRNA is described. pH – sensitive N, N dimethylaminoethyl methacrylate (DMAEMA) was crosslinked with thermo-sensitive diethylene glycol methacrylate (DEGMA), by free radical emulsion-precipitation polymerization. Size, charge and morphology were analyzed to assess potential as a nanovehicle. Through modification of the particle composition, cationic nanogels, determined by zeta potential, with sizes of approximately 160 nm confirmed with dynamic light scattering (DLS), were synthesized. A composition of 55:45 (DEGMA:DMAEMA); a size and charge ideal for cellular uptake. These particles had minimal impact on cell proliferation and exhibited spherical morphology when imaged by TEM at physiological pH. The structure was maintained between pH 3.5-9. Sensitivity to pH was shown by DLS through swelling at physiological pH, which may be useful can be taken advantage of in future studies for loading and release. Degradation with a reducing agent was shown using gel permeation chromatography, DLS and turbidity analysis. The results suggest this formula will undergo degradation in the cell. Reducing environments mimicking intracellular conditions that promoted degradation of the crosslinker showed enhanced release of dexamethasone phosphate as a model drug. Ongoing work is focused on examining gene silencing using these formulations. / Thesis / Master of Applied Science (MASc)

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Orientador: Telma Teresinha Berchielli / Resumo: Objetivou-se a caracterização da comunidade bacteriana ruminal em novilhos Nelore alimentados com diferentes teores e fontes proteicas em dietas de alto concentrado, e a identificação de possíveis associações entre o perfil microbiano ruminal e as variações na eficiência de utilização de nitrogênio animal. Foram utilizados seis novilhos Nelore, castrados, canulados no rúmen e duodeno, distribuídos em um modelo de blocos incompletos, com seis dietas e quatro períodos experimentais. O volumoso usado foi à cana de açúcar e os concentrados possuíam xdois teores de inclusão de proteína bruta 10 e 13 % e três fontes proteicas: farelo de soja+ureia (FS), glúten de milho 60 (GLU) e grãos secos por destilação oriundo do processamento do milho (DDG). A fonte proteica DDG foi significativa na avalição dos índices de diversidade Shannon Wiener e Simpson (P<0,010). Avaliou-se a riqueza pelo índice Chao1 e os resultados demonstram um ambiente ruminal mais rico com o teor de 10% (P<0,010) e a fonte FS (P<0,010). Animais alimentados com 13% de PB apresentaram maior abundância dos filos Elusimicrobia e Spirochaetes (P>0,01) e menor abundância de Bacteriodetes e Synergistetes (P>0,01). A retenção de nitrogênio não foi influenciada pelo teor e a fonte utilizada, assim, os dados de retenção de nitrogênio foram distribuídos em três clusters: alta, média e baixa utilizando o NbClust package versão 2.0. Endomicrobium_Other_other (P =0,043) e Eubacterium (P=0,023) estiveram associados com a alta ret... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this study was to characterize the ruminal bacterial community in Nellore steers fed different levels and protein sources in high concentrate diets and to identify possible associations between the ruminal microbial profile and the variations in the efficiency of animal nitrogen utilization. Six Nellore steers were used, cannulated in the rumen and duodenum, distributed in a model of incomplete blocks, with six diets and four experimental periods. The soybean meal + urea (FS), corn gluten 60 (GLU) and dry grains were obtained by distillation from the sugar cane and the concentrates had two inclusion levels of crude protein 10 and 13% and three protein sources: of corn processing (DDG). The DDG protein source was significant in the evaluation of diversity indexes Shannon Wiener and Simpson (P <0.010). The richness was evaluated by the Chao1 index and the results showed a richer ruminal environment with 10% content (P <0.010) and FS source (P <0.010). Animals fed with 13% CP showed greater abundance of Elusimicrobia and Spirochaetes (P> 0.01) and lower abundance of Bacteriodetes and Synergistetes (P> 0.01). Nitrogen retention was not influenced by the content and the source used, so the nitrogen retention data were distributed in three clusters: high, medium and low using the NbClust package version 2.0. The low N retention was associated with Prevotella (P = 0.029), Weissella (P = 0.024), and Mogibacterium (P = .089) and Eubacterium. (P = 0.043). When we corre... (Complete abstract click electronic access below) / Mestre

Cartilage regeneration is one of the most widely studied areas in tissue-engineering. Despite significant progress, most efforts to date have only focused on generating homogenous tissues whose bulk properties are similar to articular cartilage. However, anatomically and functionally, articular cartilage consists of four spatially distinct regions: the superficial, transitional, deep, and calcified zones. Each zone is characterized by unique extra-cellular matrix (ECM) compositions, mechanical properties, and cellular organization. The ECM is primarily composed of type II collagen and glycosaminoglycans (GAGs), whose relative concentrations vary between zones and therefore lead to distinctive mechanical properties. One of the major unsolved challenges in engineering cartilage has been the inability to regenerate tissue that mimics the zonal architecture of articular cartilage. Recent studies have attempted to imitate this spatial organization using zone-specific chondrocytes isolated from donor animal cartilage. Directed differentiation of a single stem population into zonally organized native-like articular cartilage has not yet been reported. This dissertation reports that hydrogels, incorporating both synthetic and natural polymers as well as cell-induced degradability, are suitable for generating zone-specific chondrogenic phenotypes from a single MSC population. Specifically, cues provided from the unique combinations of chondroitin sulfate (CS), hyaluronic acid (HA), and MMP-sensitive peptide (MMP-pep) within a PEG-based hydrogel, direct the chondrogenic differentiation of MSCs. The findings of this dissertation demonstrate the capability of creating native-like and mechanically relevant articular cartilage consisting of zone specific layers. This ability provides a new direction in cartilage tissue engineering and could be invaluable for cartilage repair if incorporated with current minimally invasive surgical techniques. / text

Polylactic acid (PLA) is one of the most promising bio-compostable and biodegradable thermoplastic made from renewable sources. PLA, is typically obtained by polymerising lactide monomer. The technique mainly used for ring opening polymerization (ROP) of Lactide is based on metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in suitable solvent. However, the PLA synthesized using such catalysts may contain trace elements of the catalyst, which may be toxic. In this work, reactive extrusion experiments using stannous octoate Sn(Oct)2 and tri-phenyl phosphine (PPh)3 were considered to perform ROP of lactide monomer using ultrasound as an alternative energy (AE) source for activating and/or boosting the polymerization. Mathematical model of ROP of lactide, was developed to estimate the impact of reaction kinetics and AE source on the polymerization process. Ludovic® software, a commercial code was used. It was adopted for the simulation of continuous reactive extrusion of PLA. Results from experiments and simulations were compared to validate the simulation methodology. Results indicate that the application of AE source in reaction process boost the PLA formation rate. Result obtained through Ludovic simulation and experiments were validated. It was shown that there is a case for reducing the residence time distribution (RTD) in Ludovic due to the ‘liquid’ monomer flow in the extruder. This change in the parameters resulted in validation of the simulation. However, it was concluded that the assumption would have to be established by doing further validations. The simulation model includes the details of kinetics of reactions involved with in the process and helps to upscale the reaction output. This work also estimates the usefulness and drawbacks of using different catalysts as well as effect of alternative energies and future aspects for PLA production.

Orientador: Telma Teresinha Berchielli / Abstract: The use of rumen undegradable protein (RUP) sources in high-energy diets may be an alternative to increase the nitrogen use efficiency (NUE) in ruminants. In this study we had two main objectives: 1) to understand how the protein content of the diet and the rumen degradable protein (RDP) intake can affect urea recycling and its utilization. 2) how the protein content of the diet and the amino acid profile of the metabolizable protein (MP) can affect the efficiency of the use of amino acids (AA) in feedlot Nellore cattle receiving high-energy density diets. Thus, we evaluated the effects of different sources and protein levels in the diet of feedlot Nellore cattle receiving high-concentrate diets. We had two major hypotheses: 1) reducing dietary N associated with RUP sources can increase NUE by reducing ruminal NH3 concentration, urea production in the liver and urinary N excretion, while maintaining N available for microbial protein (MICP) synthesis through urea N recycling. 2) differences in AA use efficiency exists and the gross AA use efficiency is affected by dietary factors such as N sources and levels. These hypotheses were tested using six Nellore steers, cannulated in the rumen, duodenum and ileum with initial body weight (BW) of 354 ± 11.8 kg and 18 months of age. The animals were randomly assigned to receive each diet once over the 6 periods in a 6 × 6 Latin square design. Experimental diets consisted of 80% concentrate and 20% roughage (DM basis), where fresh chopp... (Complete abstract click electronic access below) / Resumo: O uso de fontes de proteína não degradável no rúmen (PNDR) em dietas de alta energia pode ser uma alternativa para aumentar a eficiência do uso de nitrogênio (ENU) em ruminantes. Neste estudo, tivemos dois objetivos principais: 1) compreender como o teor de proteína da dieta e a ingestão de proteína degradável no rúmen (PDR) podem afetar a reciclagem de uréia e sua utilização. 2) como o teor de proteína da dieta e o perfil de aminoácidos da proteína metabolizável (MP) podem afetar a eficiência do uso de aminoácidos (AA) em bovinos Nelore em confinamento recebendo dietas de alta densidade energética. Assim, avaliamos os efeitos de diferentes fontes e níveis proteína na dieta de bovinos Nelore confinados que recebendo dietas de alto concentrado. Tivemos duas hipóteses principais: 1) reduzir o teor de N na dieta associado às fontes de PNDR pode aumentar a ENU por uma redução na concentração de NH3 ruminal, produção de uréia no fígado e excreção urinária de N, enquanto mantém o N disponível para a síntese de proteína microbiana (MICP) através da reciclagem de ureia. 2) existem diferenças na eficiência do uso de AA e a eficiência bruta de uso de AA é afetada por fatores dietéticos, como fontes e níveis de N. Essas hipóteses foram testadas utilizando seis novilhos Nelore, canulados no rúmen, duodeno e íleo com peso corporal inicial (PC) de 354 ± 11,8 kg e 18 meses de idade. Os animais foram distribuídos aleatoriamente para receber cada dieta por uma vez ao longo dos 6 períodos, em ... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Natural compounds have been the primary resource used to produce polymeric materials by humankind since the mid-1900s. Yet, progress in bio-based polymers from renewable feedstock has encountered some obstacles, mainly due to the low prices of petroleum-based monomers, compared to natural and sustainable materials. However, most commodity plastics are non-degradable materials, and solid plastic waste accumulation adversely affects the environment. As the world population is growing and demanding chemicals, energy, and plastics materials, polymer research is focusing on synthesizing bio-based and degradable polymers. Thus, biomass, a sustainable and inexpensive feedstock, is highly appropriate for designing alternative thermoplastics that are degradable to reduce the current environmental issues. In this dissertation, three different approaches were used to afford alternative thermoplastics to petroleum‐based commodities: bio-based poly(ether-amide)s, random aromatic copolyesters, and copoly(acetal triazole)s. In our first approach, two new lignin‐derived poly(ether‐amide)s (PEA)s were prepared. Their thermal properties showed high degradation temperature (Td) ranging from 330 °C to 380 °C, and glass transition temperature (Tg) between 100 °C and 120 °C. The chemical degradation studies revealed that the PEAs were degradable in 4 M H2SO4, HNO3, and TFA in 3 days. The second polymer group synthesized were semicrystalline bio-based aromatic copolyesters with tunable thermal properties. The thermal analysis of these copolyesters revealed high Td (413 °C to 446 °C) and Tg and Tm ranging from –36 °C to 67 °C and 60 °C to 267 °C, respectively. Their crystallization behavior showed a dependence on the comonomer composition, exhibiting a pseudo-eutectic region. Finally, furfural- and benzaldehyde-based copoly(acetal triazole)s (Td range 280–340 °C) were prepared by click polymerization at room temperature. Preliminary results showed that furfural-based copoly(acetal triazole)s were susceptible to hydrolytic degradation under neutral conditions after only 8 days at 40 °C. Overall, degradable and bio-based polymers were successfully synthesized as a potential thermoplastic alternative for packaging applications.

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