X‐Ray Scattering Techniques Applied in the Development of Drug Delivery Systems

The advances in nanotechnology have found application in different fields, such as food, agriculture, materials, chemistry, and medicine. However, one of the most important approaches is the development of nanocarriers and, in order to understand their structural organization, different physicochemical techniques have been used. In particular, small angle X‐ray scattering (SAXS) and X‐ray diffraction (XRD) have given important contribution to the study of organization phase of nanocarriers such as organic/inorganic nanoparticles, micelles, liposomes, cyclodextrins, polymers, and their interaction with drugs and other bioactive molecules. In this chapter, we will present theoretical aspects, experimental design, and the applications of both techniques for the development of delivery systems for bioactive molecules

Growth kinetics and structure of a colloidal silica-based network: in situ RheoSAXS investigations

Silica gels have a multitude of applications ranging from cosmetics and food science to oil and gas recovery. For proper design and application, it is important to have a thorough understanding of the underlying mechanisms of gel formation under different circumstances. The growth and structure of colloidal silica gels has been investigated using RheoSAXS to study the effect of silica concentration, NaCl concentration, temperature and shear rate. Additionally, SAXS in combination with a strong magnetic field has been applied to investigate the effect of magnetic microparticles and magnetic field on the development of the gel structure. Results indicate that the strongest effect on the gel kinetics are achieved by altering the activator concentration, here in the form of NaCl, followed by silica concentration and temperature. Small structural effects were also observed, with larger cluster sizes being produced at lower silica concentration and at higher NaCl concentration. Applying shear caused major changes both in structure as well as the macroscopic behavior of the silica, preventing the gel from reaching an arrested state, instead forming a viscous liquid. Applying a magnetic field appears to suppress the formation of larger clusters. The same effect is observed for increasing magnetic microparticle concentrations.publishedVersio

CO2 Adsorption Enhanced by Tuning the Layer Charge in a Clay Mineral

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Intercalation of CO2 Selected by Type of Interlayer Cation in Dried Synthetic Hectorite

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Human N-acetyltransferase 2 (NAT2) gene variability in Brazilian populations from different geographical areas

Introduction: Several polymorphisms altering the NAT2 activity have already been identified. The geographical distribution of NAT2 variants has been extensively studied and has been demonstrated to vary significantly among different ethnic population. Here, we describe the genetic variability of human N-acetyltransferase 2 (NAT2) gene and the predominant genotype-deduced acetylation profiles of Brazilians.Methods: A total of 964 individuals, from five geographical different regions, were genotyped for NAT2 by sequencing the entire coding exon.Results: Twenty-three previously described NAT2 single nucleotide polymorphisms (SNPs) were identified, including the seven most common ones globally (c.191G>A, c.282C>T, c.341T>C, c.481C>T, c.590G>A, c.803A>G and c.857G>A). The main allelic groups were NAT2*5 (36%) and NAT2*6 (18.2%), followed to the reference allele NAT2*4 (20.4%). Combined into genotypes, the most prevalent allelic groups were NAT2*5/*5 (14.6%), NAT2*5/*6 (11.9%) and NAT2*6/*6 (6.2%). The genotype deduced NAT2 slow acetylation phenotype was predominant but showed significant variability between geographical regions. The prevalence of slow acetylation phenotype was higher in the Northeast, North and Midwest (51.3%, 45.5% and 41.5%, respectively) of the country. In the Southeast, the intermediate acetylation phenotype was the most prevalent (40.3%) and, in the South, the prevalence of rapid acetylation phenotype was significantly higher (36.7%), when compared to other Brazilian states (p < 0.0001). Comparison of the predicted acetylation profile among regions showed homogeneity among the North and Northeast but was significantly different when compared to the Southeast (p = 0.0396). The Southern region was significantly different from all other regions (p < 0.0001).Discussion: This study contributes not only to current knowledge of the NAT2 population genetic diversity in different geographical regions of Brazil, but also to the reconstruction of a more accurate phenotypic picture of NAT2 acetylator profiles in those regions

Caracterização de filmes finos por difração de raios-X com baixo ângulo de incidência

Orientador: Iris Concepcion Linares de TorrianiDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin"Resumo: Este trabalho apresenta um estudo de filmes finos e ultrafinos por difração de raios-X com reflexão as simétrica e baixo ângulo de incidência através da utilização do Goniômetro de Guinier. O objetivo principal deste trabalho foi estudar de maneira geral as propriedades da difração por reflexão as simétrica com o intuito de mostrar as possibilidades da técnica na aplicação ao estudo de filmes finos. São apresentados resultados da caracterização de filmes finos de Ge nanocristalino crescidos por sputtering sobre lâmina monocristalina do mesmo material. As análises permitem identificar um perfil de profundidade com relação à textura. Tanto nestas amostras como também em filmes de Au sobre Si monocristalino foi possível subtrair completamente as reflexões do substrato. Outro aspecto interessante desta técnica abordado neste estudo é mostrado com os resultados de uma amostra de GaAs não dopado crescido epitaxialmente sobre substrato de Si monocristalino. Foi obtida uma caracterização da epitaxia sob diferentes ângulos azimutais. Além de mostrar a aplicação desta geometria no estudo dos filmes mencionados, uma grande contribuição desta tese foi, sem dúvida, a implementação da técnica no Laboratório de Cristalografia Aplicada e Raios-X do IFGW onde será usado como importante instrumento de pesquisaAbstract: In this work we present a study of thin and ultrathin3 films by X-Ray diffraction with asymmetric ref1ection and small incidence angle using a Guinier goniometer. The main purpose of this work was to study, in general, the properties of the diffraction by asymmetric ref1ection showing alI the possibilities of this technique when applied to the study of thin films. We present results on characterization of nanocrystalline Germanium thin films deposited by sputtering on aGe substrate. The analyses allow us to identify a depth profile of the films texture. Both for these Germanium samples and for Gold thin films on monocrystalline Silicon it was possible to suppress the substrate ref1ection. Another interesting aspect of this technique is revealed by the results obtained in the study of an undoped GaAs epitaxial layer grown on a monocrystalline Silicon substrate. A characterization of the epitaxy under different azimuths was obtained. Besides showing the application of this geometry in the study of thin films, another contribution of this thesis as the implementation of the technique in the 'Laboratório de Cristalografia Aplicada e Raios-X' (IFGW) where it is going to be used as an important research toolMestradoFísicaMestre em Físic

Aggregate dependent electrochromic properties of amino acid appended naphthalene diimides in water

Naphthalene diimides can have electrochromic applications due to their highly stable dark reduced state along with a transparent colourless neutral state. We show here that the colouration and reversibility of water-dispersible amino acid appended NDIs are directly influenced by the aggregated state present at different pH using spectroelectrochemistry, small angle neutron scattering (SANS) and cyclic voltammetry (CV). We find the aggregation itself is influenced by both pH and the amino acid or dipeptide in the structure, with each NDI having a preferred morphology giving rise to a more intensely coloured state