Papers by Keyword: Pseudoboehmite

Abstract: Pseudoboehmite is a synthetic ceramic material obtained by the sol-gel process consisting of a network of inorganic oxides with high porosity and purity that can be used for drug delivery systems. This work studied the interaction between Metformin (Metformin Hydrochloride) and pseudoboehmite, which were treated with this ceramic material in the controlled drug release. The in vitro metformin release test was evaluated using UV-Vis spectrophotometry. X-ray diffraction data show that only the pseudoboehmite phase is present in the sample.

Abstract: Pseudoboehmite is an aluminium compound with a structure similar to that of boehmite. The unit cell of the pseudoboehmite is slightly larger than that of the boehmite because of the greater incorporation of water in the same structure [1]. It has particles of nanometric dimensions and can be synthesized with extremely high purity. Several papers published in the literature show the potential of using this material in the controlled release of drugs, including cancer treatment [2,3]. Using drugs in complexes incorporated into polymer matrices and ceramic gels can lead to adequate control of gastrointestinal absorption when administered orally. Consequently, there is the possibility of promoting a gradual action through the progressive release of the drug, thus increasing its efficiency and reducing dose and toxicity. Previous studies have shown that pseudoboehmite is non-toxic and can be used for drug delivery. During the tests to determine the toxicity of this material, it was observed that the blood glucose content was reduced in mice that took pseudoboehmite by gavage. Since pseudoboehmite is obtained via low-cost inorganic synthesis, different physicochemical characteristics can be incorporated into this high purity medium. The formed structure was evaluated as a drug delivery system to establish a profile of the influence of the physicochemical properties of a molecule in the process of interaction with pseudoboehmite, a drug with recognized pharmacological activity, simvastatin (IUPAC name (1S,3R,7S,8S,8aR)-8-{2-[(2R,4R)-4-hydroxy-6-oxooxan-2-yl]ethyl}-3,7-dimethyl-1,2,3,7,8,8a-hexahydronaphthalen-1-yl 2,2-dimethylbutanoate) was choose. It also emphasizes the importance of pseudoboehmite as a drug carrier, serving as a precursor to new therapeutic systems. The synthesis of pseudoboehmite from ammonium hydroxide and aluminium nitrate was optimized to release simvastatin in vitro. After absorption and hydrolysis in the liver to form the active β-hydroxy acid metabolite, simvastatin acts as a potent reversible, competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, an early and rate-limiting enzyme in the biosynthesis of cholesterol.

Abstract: The Pseudoboehmite is an aluminum compound used as an alumina precursor and it is produced by sol-gel process. The sol-gel process is a methodology to produce porous, vitreous or crystalline ceramics started by molecular precursors. Pseudoboehmite with high purity, high specific surface area and porous homogeneity was obtained by sol-gel process. The material was used to produce gamma-alumina with surface area ranging from 211.2-288.1m²/g. It was studied the effect of aging time, temperature of aging and poly (vinyl alcohol) addition in the synthesis.

Abstract: The development of ceramic matrix composites (CMCs) is currently of great importance in the field of ballistic protection. For that purpose, alumina, silicon carbide and boron carbide are usually used in civil and military armor. Combination of different materials results in increasingly lighter and tougher composite materials, which replace conventional materials in many applications, including aviation, aerospace, military, naval, and sports industry. The production of nanoparticle powders and nanostructured bodies may find many uses in CMCs. In this study, pseudoboehmite powders was synthesized through the sol-gel method. The main goal of this work was to obtain alpha-alumina from nanosized pseudoboehmite particles, aiming to improve the densification and reduction of sintering temperature of alumina. Both pseudoboehmite and alpha-alumina obtained might be used also as raw material for CMCs. The gel of pseudoboehmite, which was derived from aluminum nitrate and ammonium hydroxide, was calcined, thus originating the alpha-alumina used in this study. The powders were characterized by: X-ray diffraction (XRD), nitrogen adsorption isotherm, with specific surface area measured by BET method, thermogravimetric analysis (TG) and differential thermal analysis (DTA). The data show that the alpha-alumina obtained by burning the pseudoboehmite was highly pure.

Abstract: Polymeric nanocomposites are hybrid materials in which inorganic substances of nanometric dimensions are dispersed in a polymeric matrix. These inorganic substances have high surface area allowing a better interaction with the polymeric matrix and consequently promote changes in the physical properties of the final composite with small additions of the same. The preparation of nanocomposites with polymer matrix allows in many cases to find a relationship between a low cost due to the use of lower amount of charge, reaching high level of performance. In this work, it was obtained polystyrene nanocomposites with pseudoboehmite synthesized by the sol-gel process with different concentrations of pseudoboehmite using and not using octadecylamine as a coupling agent. The nanocomposites were prepared by the melt intercalation technique. The pseudoboehmite nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, differential thermal analysis and thermo gravimetric analysis. The nanocomposites were characterized by differential thermal analysis, thermogravimetric analysis, heat deflection temperature, Vicat softening point, mechanical and rheological tests. The results showed an increase in the thermal properties, hardness and tensile strength values and decrease in the melt index, impact resistance and tensile elongation, showing the interaction of the filler with the polymer matrix. Although in the samples with the presence of octadecylamine the data shows that the thermomechanical properties practically do not vary in relation with the samples without octadecylamine.

Abstract: The aim of this work was to synthesize eight samples of pseudoboehmite obtained by the sol-gel process under different conditions in a two level factorial experimental design consisting of three variables. It was observed how the properties of pseudoboehmites (crystallinity and morphology) were affected by the three analyzed variables, namely: aging temperature, aging time and addition of polyvinyl alcohol. The samples were characterized by x-ray diffraction, scanning electron microscopy with secondary electrons detector, differential thermal analysis, and thermogravimetric analysis. After being characterized, the pseudoboehmite powders were calcined in an electric furnace at 500°C. After calcination, the resultant powders were analyzed via x-ray diffraction. One of the most important results achieved in this work was the successful synthesis of gamma-alumina from pseudoboehmite, as well as high crystallinity in the pseudoboehmite samples aged at high temperatures.

Abstract: Polymeric nanocomposites are hybrid materials, where fillers with nanometric dimensions are dispersed in a polymeric matrix. The fillers have a high surface area, promoting better dispersion in the polymeric matrix and therefore an improvement in physical properties of the composite depending on the homogeneity of the material. In the present work, nanocomposites of polystyrene with different concentrations of pseudoboehmite obtained by a sol-gel process, and treated with octadecylamine were prepared. The nanocomposites were characterized by thermal and mechanical tests. The addition of pseudoboehmite caused a reduction of the melting flow during the production of the composites evidencing the interaction of pseudoboehmite with the polymeric matrix. The addition of pseudoboehmite promoted an increase in the melt flow index, in the the hardness of the nanocomposites obtained, practically does not affect the tensile strength and modulus and the impact strength decreases. The presence of pseudoboehmite causes increase in heat deflection temperature and Vicat softening point and the thermal decomposition occurred at a higher temperature than the pure PS.

Abstract: Polymer nanocomposites are formed by nanometrical particles embedded in a matrix. Additions of small amounts of nanoparticles of inorganic material in polymer matrixes can greatly improve mechanical properties when compared with the pure polymer. The high specific surface area of the inorganic nanoparticle materials promotes its dispersion in the polymeric matrix and the resulting properties are strongly related to the homogeneity of the dispersion. In the present work, nylon 6.12 nanocomposites with aged pseudoboehmite were obtained using octadecylamine to improve the union between the polymer and the pseudoboehmite. The nanocomposites were characterized by thermal and mechanical test. The pseudoboehmite was characterized by scanning electron microscopy and x-ray diffraction. The nanocomposite was characterized by tensile strength test, 3 points bending test and impact Izod resistance test. The addition of pseudoboehmite promote the increase of the elasticity modulus evidencing the interaction of the pseudoboehmite with the polymeric matrix, probably modifying its crystalline structure. The addition of pseudoboehmite promoted an increase in the HDT an Vicat temperatures of the nanocomposite.

Abstract: Recently, the incidence of American Cutaneous Leishmaniasis (ACL) has been grown in Latin America, especially in Brazil, where from 1980 to 2005, 605,062 cases were recorded. The drug glucantime®, whose active principle is the meglumine antimoniate (or meglumine antimonate) is used in the treatment of leishmaniasis. Its toxicity is due mainly to the presence of antimony in its structure. Therefore, it is crucial to determine the safe dose levels of this drug in the treatment. Drug delivery systems have been currently the focus of many studies due to its effectiveness in treating diseases proved to be superior compared to conventional methods. Drug delivery systems can avoid overdosing by decreasing the amount of drug intake, which results in a better therapeutic effect in addition to reducing the risks of plasma concentration reaching toxic levels. Synthetic nanomaterials have been receiving great attention due to their potential applications in pharmaceutical technology as well as the possibility of controlling their particle size and composition, which allows a better performance in drug release. Pseudoboehmite is a synthetic aluminum compound precursor of alumina [1] and a polymorph of boehmite, with active groups in its structure [2], making it an excellent adsorbent material. In this work, pseudoboehmite was prepared by using the sol-gel process for being used as an excipient. The incorporation of pseudoboehmite in glucantime® was performed in the processing of tablets. Both pseudoboehmite and the tablets were characterized via X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG), and scanning electron microscopy (SEM) using secondary electron detector and EDS detector. The release profile was obtained by UV/Vis spectroscopy for in vitro simulation. No reaction between the drug and the excipient was observed.

Abstract: Different samples of pseudoboehmite were synthesized through the sol-gel process, using aluminum nitrate as precursor. The influence of variables on the product of the synthesis of pseudoboehmite was studied. The variables were the ageing temperature (25 and 130°C), addition or not of polyvinyl alcohol to the precursor solution and the ageing time of the PB. The pH adjustment of the precursor solution was made by using ammonium carbonate. The pseudoboehmites, which were obtained on different conditions, were then characterized by X-ray diffraction, thermal analysis (Differential Thermal Analysis and Thermo Gravimetric Analysis) and the desorption-absorption curves were obtained as well, in order to measure the pore volume of the samples and the specific surface area measurements through the BET method. Finally, the results were analyzed through an experimental factorial planning, which showed that high specific surface area pseudoboehmite was obtained.