Dynamic release of riboflavin from a starch-based semi IPN via partial enzymatic degradation: part II

The dynamic release of riboflavin from the starch - cross-linked polyacrylic acid semi IPN has been studied at the physiological temperature 37 degreesC. The gel demonstrated nearly 39% drug in the amylase-free phosphate buffer of pH 7.4 while in the presence of 1.30 IU per ml enzyme activity in the release media, the gel underwent enzymatic degradation to release nearly 75% drug. The gel exhibited complex H-bonded structure in the lower pH thus demonstrating almost minimum release (i.e. 20%) in the release medium of pH 2.0. The amount of drug released was found to increase with the starch content in the gels. Similarly, with the increase in the initial water content, the quantity of drug released was also observed to increase. The degree of cross-linking was found to affect the release behavior. However, the gels demonstrated nearly 'zero-order release' for maximum as well as minimum concentration of cross-linker in the gels. A linear dependency between square of diameter of the gel and t(1/2) i.e. time required for 50% release was also observed. Finally, the gastrointestinal transit time and agitation speed also affected the release behavior. (C) 2004 Elsevier B.V. All rights reserved.