Study of thermal degradation of PLGA, PLGA nanospheres and PLGA/Maghemite superparamagnetic nanospheres

Poly(glycolide-co-lactide) (PLGA) nanospheres containing magnetic materials have been extensively studied because of its biomedical applications. Therefore, it is very important to know thermal properties of these materials in addition to other physical properties. Thermal degradation activation energy (Eα) of PLGA nanospheres with maghemite entrapment (PLGA-Mag), PLGA nanospheres (hollow spheres) (PLGA-H) obtained by an emulsion method and unprocessed PLGA (PLGA-R) were calculated by isoconversional Vyazovkin method based on data of TG analysis in order to evaluate modifications in thermal behavior caused by nanospheres obtainment process or by maghemite entrapment. Both hydrodynamic diameter in the range of 200-250 nm and polydispersity index lower than 0.3 are considered satisfactory. Thermal degradation of PLGA-R begins at higher temperatures than those of PLGA-H and PLGA-Mag, but processed samples presented increase in thermal stability, which was greater before processing by emulsion and in the presence of the magnetic materials. PLGA-Mag presents superparamagnetic behavior at room temperature

Nanofibras de ZnO produzidas por eletrofiação: síntese, caracterização e atividade fotocatalítica

Nanofibras de ZnO foram produzidas a partir de precursores à base de poli(álcool vinílico) (PVA) e acetato de zinco (AcZn) obtidos por eletrofiação, nas proporções mássicas de PVA/AcZn 1:1; 2:1 e 4:1, e posterior calcinação. Bandas características da ligação Zn-O e de transições eletrônicas do ZnO foram detectadas nos espectros de infravermelho (FTIR) e absorção fotoacústica (PAS) das nanofibras. Picos cristalinos característicos da estrutura wurtzita e fase hexagonal do ZnO foram detectados nos difratogramas de raios-X (DRX) das amostras produzidas. Os valores de energia de gap (Eg) estimados para as nanofibras de ZnO produzidas após calcinação dos precursores PVA/AcZn 1:1; 2:1 e 4:1 foram de 2,95; 3,15 e 3,02 eV, respectivamente, e a área específica (SBET) destas respectivas amostras foi de 25,26 m²/g; 20,95 m²/g e 23,79 m²/g. As imagens de MEV e MET das amostras de ZnO revelaram que após calcinação, a morfologia de fibra foi mantida apenas para aquelas produzidas a partir dos nanofios precursores de PVA/AcZn 1:1 e 4:1. Todas as amostras de ZnO exibiram excelente desempenho fotocatalítico, degradando cerca de 99% do corante Azul de Metileno, em ambos pH 7,0 e 9,0, e após 240 minutos de irradiação UV-visível

Optimization of maghemite-loaded PLGA nanospheres for biomedical applications

Magnetic nanoparticles have been proposed as interesting tools for biomedical purposes. One of their promising utilization is the MRI in which magnetic substances like maghemite are used in a nanometric size and encapsulated within locally biodegradable nanoparticles. In this work, maghemite has been obtained by a modified sol-gel method and encapsulated in polymer-based nanospheres. The nanospheres have been prepared by single emulsion evaporation method. The different parameters influencing the size, polydispersity index and zeta potential surface of nanospheres were investigated. The size of nanospheres was found to increase as the concentration of PLGA increases, but lower sizes were obtained for 3 min of sonication time and surfactant concentration of 1%. Zeta potential response of magnetic nanospheres towards pH variation was similar to that of maghemite-free nanospheres confirming the encapsulation of maghemite within PLGA nanospheres. The maghemite entrapment efficiency and maghemite content for nanospheres are 12% and 0.59% w/w respectively

Obtenção e uso de gradientes de densidade

Orientador : Fernando GalembeckTese (doutorado) - Universidade Estadual de Campinas, Instituto de QuimicaDoutorad

Phosphated guar gum: potential ingredient in the development of ethylcellulose isolated films

O uso de polissacarídeos tem atraído grande atenção no desenvolvimento de novos sistemas para liberação específica de fármacos. Esses polímeros estão disponíveis em abundância, a baixo custo, apresentando uma variedade de estruturas e propriedades, podendo ser facilmente modificados quimicamente, ademais são dotados de degradação específica. A modificação química representa uma alternativa ao inconveniente causado pela elevada hidrossolubilidade destes produtos, a qual poderá ocasionar liberação prematura do fármaco. No presente estudo, a goma guar foi fosfatada com trimetafosfato trisódico, sendo em seguida associada a etilcelulose, visando a formação de filmes isolados. Os produtos resultantes foram caracterizados físico-quimicamente (IV TF e DSC), sendo também avaliada a transmissão de vapor de água (TVA) e o grau de intumescimento (Ii%). Os resultados mostraram a fosfatação da goma guar, além da redução do intumescimento e permeabilidade após reticulação. Estes resultados caracterizam maior potencial de aplicação da goma guar fosfatada para sistemas reservatórios orais em relação a goma natural.The uses of polysaccharides are attracting a lot of attention for development of new specific drug delivery systems. These polymers are found in abundance, are inexpensive, are available in a variety of structure with varied properties and can be easily modified chemically; in addition, they are specific biodegradable. The cross linking of polysaccharides is an alternative for the inconvenience brought by it?s high water solubility, which can lead to early drug delivery. In the present study, guar gum was phosphated with trisodium trimetaphosphate and, than, associated with ethylcellulose on the purpose of forming isolated films. The resulting products were physicochemical characterized (with FT IR and DSC), the water vapour transmission (WVT) and the swelling index (Ii%) were also evaluated. The results confirmed the guar gum phosphatation and showed swelling and water permeability reduction due to the cross linking. Phosphated guar gum has therefore a greater application potential in oral drug delivery systems than native guar gum.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Phosphated guar gum: potential ingredient in the development of ethylcellulose isolated films

O uso de polissacarídeos tem atraído grande atenção no desenvolvimento de novos sistemas para liberação específica de fármacos. Esses polímeros estão disponíveis em abundância, a baixo custo, apresentando uma variedade de estruturas e propriedades, podendo ser facilmente modificados quimicamente, ademais são dotados de degradação específica. A modificação química representa uma alternativa ao inconveniente causado pela elevada hidrossolubilidade destes produtos, a qual poderá ocasionar liberação prematura do fármaco. No presente estudo, a goma guar foi fosfatada com trimetafosfato trisódico, sendo em seguida associada a etilcelulose, visando a formação de filmes isolados. Os produtos resultantes foram caracterizados físico-quimicamente (IV TF e DSC), sendo também avaliada a transmissão de vapor de água (TVA) e o grau de intumescimento (Ii%). Os resultados mostraram a fosfatação da goma guar, além da redução do intumescimento e permeabilidade após reticulação. Estes resultados caracterizam maior potencial de aplicação da goma guar fosfatada para sistemas reservatórios orais em relação a goma natural.The uses of polysaccharides are attracting a lot of attention for development of new specific drug delivery systems. These polymers are found in abundance, are inexpensive, are available in a variety of structure with varied properties and can be easily modified chemically; in addition, they are specific biodegradable. The cross linking of polysaccharides is an alternative for the inconvenience brought by it?s high water solubility, which can lead to early drug delivery. In the present study, guar gum was phosphated with trisodium trimetaphosphate and, than, associated with ethylcellulose on the purpose of forming isolated films. The resulting products were physicochemical characterized (with FT IR and DSC), the water vapour transmission (WVT) and the swelling index (Ii%) were also evaluated. The results confirmed the guar gum phosphatation and showed swelling and water permeability reduction due to the cross linking. Phosphated guar gum has therefore a greater application potential in oral drug delivery systems than native guar gum.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Synthesis and characterization of phosphated crosslinked chondroitin sulfate: potential ingredient for specific drug delivery

Debido a su biodegradabilidad varios polímeros naturales, tales como los polisacáridos, han sido propuestos como excipientes adecuados para desarrollar sistemas de liberación controlada para la administración oral. El sulfato de condroitina (ChS), un mucopolisácarido altamente soluble en agua, fue reticulado con trimetafosfato de sodio (TMFS) para conseguir una reducción de su hidrosolubilidad. ChS fue tratado com TMFS en tres diferentes proporciones, en dispersión acuosa a pH 12 por 2 h a temperatura ambiente y en seguida secado. Los productos obtenidos fueron analizados por FTIR y DSC y comparados con los correspondientes análisis de ChS. Los resultados mostraron que (a) el TMFS efectivamente retícula al ChS y (b) los productos reticulados presentan una disminución de la absorción de agua, comparado con el polisacárido natural ChS. Estos resultados permiten concluir que el ChS modificado presenta buenas perspectivas para su uso en formulaciones farmacéuticas de liberación modificada.Because of its biodegradability several natural polymers, such as polysaccharides, have been proposed as appropriate excipients for the development of controlled drug delivery systems for oral administration. Chondroitin sulfate (ChS), a highly water-soluble mucopolysaccharide, was crosslinked with trisodium trimetaphosphate (TMFS) in order to achieve a reduction of its hydro-solubility. ChS was treated with TMFS in three different proportions, in aqueous dispersion at pH 12 for 2 h at room temperature, and then dried. The products obtained were analysed by their Fourier-transformed infrared (FTIR) spectra and differential scanning calorimetry (DSC) curves, which were compared with the analyses of a natural ChS control sample. The results showed that (a) TMFS has effective crosslinking action over ChS and (b) the crosslinked products have reduced water affinity, compared to the natural polysaccharide. These results lead to the conclusion that modified ChS presents good perspectives for its use on modified release pharmaceutical formulations.Colegio de Farmacéuticos de la Provincia de Buenos Aire

Synthesis and characterization of phosphated crosslinked chondroitin sulfate: potential ingredient for specific drug delivery

Debido a su biodegradabilidad varios polímeros naturales, tales como los polisacáridos, han sido propuestos como excipientes adecuados para desarrollar sistemas de liberación controlada para la administración oral. El sulfato de condroitina (ChS), un mucopolisácarido altamente soluble en agua, fue reticulado con trimetafosfato de sodio (TMFS) para conseguir una reducción de su hidrosolubilidad. ChS fue tratado com TMFS en tres diferentes proporciones, en dispersión acuosa a pH 12 por 2 h a temperatura ambiente y en seguida secado. Los productos obtenidos fueron analizados por FTIR y DSC y comparados con los correspondientes análisis de ChS. Los resultados mostraron que (a) el TMFS efectivamente retícula al ChS y (b) los productos reticulados presentan una disminución de la absorción de agua, comparado con el polisacárido natural ChS. Estos resultados permiten concluir que el ChS modificado presenta buenas perspectivas para su uso en formulaciones farmacéuticas de liberación modificada.Because of its biodegradability several natural polymers, such as polysaccharides, have been proposed as appropriate excipients for the development of controlled drug delivery systems for oral administration. Chondroitin sulfate (ChS), a highly water-soluble mucopolysaccharide, was crosslinked with trisodium trimetaphosphate (TMFS) in order to achieve a reduction of its hydro-solubility. ChS was treated with TMFS in three different proportions, in aqueous dispersion at pH 12 for 2 h at room temperature, and then dried. The products obtained were analysed by their Fourier-transformed infrared (FTIR) spectra and differential scanning calorimetry (DSC) curves, which were compared with the analyses of a natural ChS control sample. The results showed that (a) TMFS has effective crosslinking action over ChS and (b) the crosslinked products have reduced water affinity, compared to the natural polysaccharide. These results lead to the conclusion that modified ChS presents good perspectives for its use on modified release pharmaceutical formulations.Colegio de Farmacéuticos de la Provincia de Buenos Aire