Abstract
The suitability of porous materials to immobilize and release under control bioactive molecules prompted us to design and study delivery systems of Vitamin A (VitA). This molecule, relevant in several physiological functions, is easily oxidized. Commercial VitA was immobilized in two different clays, montmorillonite K-10 (MMT) and sepiolite (SEP), and in MCM-41, by impregnation. Characterization of the resulting hybrid materials by XRD, FTIR and 13C and 29Si (MAS) NMR spectroscopies revealed its presence. The photo-stability tests showed decreased degradation of VitA in the clays, compared to MCM-41 and the pure VitA, while thermostability is observed until ∼100 °C. The kinetics of the release depended on the structural features of the support material and the pH. Sepiolite originated a classic profile of increasing amount of VitA with time, indicating that no oxidation was taking place. In both montmorillonite and MCM-41 the amount of released VitA dropped after ∼2 hours, reflecting oxidation. Oxidation and degradation products obtained when VitA was immobilized in MCM-41, both under nitrogen and in air, were identified by mass spectrometry experiments. Sepiolite is therefore a suitable material to use in controlled release of VitA, since it appears to prevent oxidation.
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