Navegando por Palavras-chave "Ordered Mesoporous Silicas"

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    Nanopartículas superparamagnéticas de óxido de ferro incorporadas em sílica mesoporosa ordenada SBA-15 com potencial aplicação biomédica
    (Universidade Federal de São Paulo (UNIFESP), 2020-03-23) Losito, Danilo Waismann [UNIFESP]; Martins, Tereza da Silva [UNIFESP]; Universidade Federal de São Paulo
    Iron oxide superparamagnetic nanoparticles (SPION) due to their intrinsic properties, as a single magnetic domain, are very promising for biomedical applications, both in diagnosis and therapy. However, their efficiency decreases due to agglomeration and its incorporation in ordered mesoporous silica, such as SBA-15, which has unique properties, such as high surface area (above 800 m2 g -1 ), mesoporous size around 8 nm, with narrow pore size distribution, can, besides to avoid SPION agglomeration, favor magnetically guided drug delivery system. Particle morphology, including size and shape, of SBA-15 may also favor the interaction between SPIONs and silica and in this context, the objective of this work was to prepare and characterize SBA-15 nanocomposites, with different morphologies, and SPIONs prepared by coprecipitation methods and thermo-composition, aiming at application in the biomedical area, as drug carriers, guided by magnetization. The SPIONs (10 and 30 wt%) were incorporated into the SBA-15 with different morphologies by wet impregnation in toluene and the composites formed were characterized by several physical-chemical techniques. The X-ray diffractometry (XRD) and low-angle X-ray scattering (SAXS) data of the composites showed that the crystalline (magnetite) phase of the SPIONs and the SBA-15 mesoporous structure did not undergo significant changes, when compared to pure materials. However, the data obtained from nitrogen physisorption showed significant changes in the textural properties of composites in relation to pure SBA-15, such as the decrease in the volume of adsorbed nitrogen and specific surface area, indicating the incorporation of SPIONs into the mesoporosity of SBA-15, mainly in composites prepared with nanoparticles obtained by thermal decomposition, which is probably a consequence of the smaller size of these nanoparticles. The presence of SPIONs in the mesoporosity and macroporosity of SBA-15 was observed in the images obtained by scanning electron microscopy (SEM) and transmission (TEM), and through dispersive energy spectroscopy (EDS). EDS and thermogravimetry (TG) data showed that the SPIONs content in the composites was lower than the nominal (10 and 30 wt%) due to the presence of oleic acid that was used in the synthesis of the nanoparticles, confirmed by Fourier transform infrared (FTIR) spectroscopy. SEM images showed a rod-like shape for SBA-15 particles with a uniform rod length, this morphology does not affect by the SPIONs incorporation. Magnetic curves profile of the composites also did not change in relation to the profile observed for pure SPIONs. However, the magnetization of the composites was lower due to weight percentage of SPIONs (10 and 30 wt%) in the composites, but with an increase in the magnetization for the composites obtained with the nanoparticles obtained by thermo-decomposition. Analysis of local structure by function of distribution of pairs (PDF) showed that the increase in SPION content in the composites and the reduction in the particle size of the SBA-15 cause significant changes in the local ordering. Toxicity tests have shown that both SPIONs and silicas, as well as composites, are safe for biological applications.