Synthesis, characterization and evaluation of semi-IPN hydrogels consisted of poly(methacrylic acid) and guar gum for colon-specific drug delivery

The semi-IPN hydrogels consisting of poly(methacrylic acid) and guar gum (GG) are prepared at room temperature using water as solvent. 5-aminosalicylic acid (5-ASA) is entrapped in the hydrogel in the synthesis of hydrogel and all entrapment efficiencies are found above 85%. The hydrogel shows excellent pH-sensitivity. It exhibited minimum swelling in an acidic pH medium through the formation of a complex hydrogen-bonded structure and maximal swelling due to the electrostatic repulsion due to the ionization of the carboxylic groups in pH 7.4 medium. The degradation in vitro shows that the degree of degradation (R%) depended on the concentration of cross-linking agent and content of GG. The hydrogel shows a minimum release of 5-ASA due to the complex hydrogen bonded structure of the hydrogels in the medium of pH 2.2. The enzymatic degradation of hydrogels by cecal bacteria can accelerate the release of 5-ASA entrapped in the hydrogel in pH 7.4 medium. Copyright (c) 2007 John Wiley & Sons, Ltd.