INTEMA   05428
INSTITUTO DE INVESTIGACIONES EN CIENCIA Y TECNOLOGIA DE MATERIALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Model drugs release from 2-hydroxyethylmethacrylate / acrylamide hydrogels synthesized by photopolymerization: Influence of the ionic character of the drugs.
Autor/es:
MARÍA L. GÓMEZ (*); ROBERTO J. J. WILLIAMS; HERNÁN A. MONTEJANO; CARLOS M. PREVITALI
Lugar:
La Serena, Chile
Reunión:
Encuentro; X ENCUENTRO LATINOAMERICANO DE FOTOQUÍMICA Y FOTOBIOLOGÍA; 2010
Resumen:
In this work we report the synthesis of hydrogels employing visible-light photopolymerization. A silsesquioxane functionalized with methacrylate and amine groups (SFMA) was employed as crosslinker/co-initiator to obtain hydrogels, based on 2-hydroxyethylmethacrylate (HEMA) and acrylamide (AAm); safranine O (Saf) was employed as sensitizer. The source of light was provided by a photoreactor with eighth LEDs of 530 nm, hydrogels with a high swelling capability were synthesized. These hydrogels were loaded with different model drugs; the influence of the ionic character of a specific drug on its release rate from the hydrogel was analyzed. The following ionic or uncharged dyes were employed to mimic drugs: acridine orange (AO) as a neutral drug, safranine O (Saf) as a cationic drug, and resorufin (Rf) as an anionic drug. The release rates of the dyes were investigated by UV-Vis spectroscopy. A very high amount of the neutral dye could be loaded; the proportion was less but still significant for the cationic dye and almost negligible for the anionic dye. This means that the poly(HEMA-co-AAm) hydrogel is not suitable for the loading with anionic drugs (assuming that the behavior shown by the particular anionic dye used in this study can be extrapolated to other anionic drug). The significant loading observed for the cationic dye implies the existence of specific interactions between the cation and functional groups of the hydrogel. While the release rate of AO and Rf was relatively fast and followed a Fickian behavior, the release rate of Saf was slow and exhibited a non-Fickian behavior giving extra evidence of the presence of specific interactions with the hydrogel. Therefore, poly(HEMA-co-AAm) hydrogels are suitable for the high loading and fast release of neutral drugs and the intermediate loading and slow release of cationic drugs. Converting the amide into carboxylate groups by hydrolysis of the hydrogel at pH = 13, produced a significant increase of the loading capacity of the cationic dye and a significant decrease of its release rate. This was explained by the higher specific interactions of the cationic dye with carboxylate/carboxylic acid groups compared with amide groups. In conclusion, tuning the ionic character of a drug and the conversion of amide groups into carboxylate groups enables to control the loading capacity and the release rate from poly(HEMA-co-AAm) hydrogels used in drug-delivery applications.