RESUMEN
Chitosan microspheres were prepared and vitamin E (α-tocopherol) was anchored onto the polymer. The amount of α-tocopherol entrapped onto a gram of the microspheres based system was 13.4±0.4 mg. The microspheres modified with α-tocopherol were applied to vitamin E controlled release in a simulated gastrointestinal system. Characterizations were carried out by optical microscopy, FTIR and HPLC-UV techniques. For chitosan microspheres based system there was a 4.10% release, while for pure α-tocopherol the release was 25.53%. The percentage of α-tocopherol released at pH 6.8 was 13.10% for chitosan microspheres and 60.00% for free α-tocopherol. At pH 7.4, α-tocopherol release reached 51.30% and 92.88% for chitosan microspheres and pure α-tocopherol, respectively. α-tocopherol immobilized onto chitosan presented three distinct landings at each studied pH, whereas pure α-tocopherol presented only two established solubilization regions, one at pH 1.2, while between pH 6.8 and 7.4 it did not present any difference, establishing after 3.5h. Thus, the immobilization of α-tocopherol onto chitosan microspheres figures it as an efficient controlled release system.
Asunto(s)
Quitosano/química , Tracto Gastrointestinal/metabolismo , Microesferas , alfa-Tocoferol/farmacocinética , Antioxidantes/administración & dosificación , Antioxidantes/química , Antioxidantes/farmacocinética , Química Farmacéutica/métodos , Cromatografía Líquida de Alta Presión , Preparaciones de Acción Retardada , Sistemas de Liberación de Medicamentos/métodos , Humanos , Concentración de Iones de Hidrógeno , Estructura Molecular , Tamaño de la Partícula , Espectrofotometría Infrarroja , alfa-Tocoferol/administración & dosificación , alfa-Tocoferol/químicaRESUMEN
Hexagonal mesoporous silica modified with carboxylic acid (SiAc) has been obtained by reaction between chloroacetic acid and 3-aminopropyltrimethoxysilane, which was immobilized on porous material by a sol-gel process in the presence of an n-dodecylamine template. SiAc was characterized by TG, FT-IR, (29)Si NMR, (13)C NMR, SEM, surface charge density, surface area and porous diameter, which proved that the carboxylic group was chemically bonded to an inorganic structure, and the material presented a nanometric structure with spheres <50 nm and porous diameter of 10 nm. Herbicides 2,4-D and picloram were anchored on SiAc porous gel to produce the materials named SiD and SiPi, respectively. The controlled release of picloram from the SiAc was less than that of 2,4-D. After 26 days of releasing, 4.43 × 10(-5) mol L(-1) of picloram was delivered by SiPi, and 5.0 × 10(-5) L(-1) was released from the SiD in 30 days.