Characterization of calcium alginate and chitosan-treated calcium alginate gel beads entrapping allyl isothiocyanate

Calcium alginate (CA), chitosan-coated calcium alginate (CCA-I), and chitosan-calcium alginate complex (CCA-II) gel beads, in which an oil-in-water emulsion containing allyl isothiocyanate (AITC) was entrapped, were prepared and characterized for efficient oral delivery of AITC. The AITC entrapment efficiency was 81% for CA gel beads, whereas about 30% lower values were determined for the chitosan-treated gel beads. Swelling studies showed that all the gel beads suddenly shrunk in simulated gastric fluid (pH 1.2). In simulated intestinal fluid (pH 7.4), CA and CCA-I gel beads rapidly disintegrated, whereas CCA-II gel beads highly swelled without degradation probably due to the strong chitosan-alginate complexation. Release studies revealed that most entrapped AITC was released during the shrinkage, degradation, or swelling of the gel beads, and the chitosan treatments, especially the chitosan-alginate complexation, were effective in suppressing the release. CCA-II gel beads showed the highest bead stability and AITC retention under simulated gastrointestinal pH conditions. (c) 2007 Elsevier Ltd. All rights reserved.