Effect of complexation conditions on xanthan–chitosan polyelectrolyte complex gels

Polyelectrolyte hydrogels formed by xanthan gum and chitosan can be used for encapsulation and controlled release of food ingredients, cells, enzymes, and therapeutic agents. In this study, xanthan–chitosan microcapsules were formed by complex coacervation. The effects of initial polymer concentration and chitosan solution pH on the crosslinking density of xanthan–chitosan network were investigated by swelling studies and modulated differential scanning calorimetry (MDSC) analysis. The crosslinking density was found to be less dependent on chitosan solution concentration than xanthan solution concentration and chitosan pH. The capsules were completely crosslinked at all conditions studied when initial xanthan solution concentration was 1.5% (w/v). The changes in the conformation of chitosan chains as chitosan pH approaches 6.2 were found to be important in achieving capsule network structures with different crosslinking densities. These findings indicate that the parameters studied cannot be viewed as independent parameters, as their effects on the degree of swelling are interdependent. r 2008 Elsevier Ltd. All rights reserved.