Investigation of ionically crosslinked chitosan and chitosan–bovine serum albumin beads for novel gastrointestinal functionality

Abstract

AbstractThe objective of the work was to determine whether chitosan–tripolyphosphate (TPP) systems can be used to develop safe gel particles for in vivo applications. In particular, we are interested in the use of chitosan systems capable of swelling at low pH in vitro as potentially swellable, satiety‐enhancing ingredients. The formation of homogeneous chitosan‐TPP gel beads was improved by reducing the pH of the TPP gelling bath from 8.5 to 4.0 thus increasing the cationic nature of chitosan and the crosslink density. However, the mechanical strength of this system was reduced compared to the basic system. This has been related to tightening of the gel network by increased shrinking of this system. Although release studies have shown that decreasing the pore size of the gel, by increasing the crosslink density through increasing the TPP concentration, is a good way to trap our model release polymer (dextran), in simulated gastrointestinal conditions, these ionic gel beads showed marked shrinking. We propose that this is due to screening of the charge on the chitosan molecule in the presence of salt and/or an excess of TPP which encourages ionic interactions. We conclude that these ionic gels are an unfeasible alternative satiety‐enhancing ingredient to covalently crosslinked systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008