Polyelectrolye complex formation between alginate and chitosan as a function of pH

Chitosan and alginate are two polyelectrolytes that can be used as thickening agents in the food industry, in drug-release systems in pharmaceutical applications as biomaterials in wound healing, and cell culture applications, or as ion exchange material for the removal of heavy metal ions from industrial wastewaters. These two polysaccharides can also be used together to form a polyelectrolyte complex, especially to encapsulate proteins, cells, and enzymes. Although there are many applications of these polyions, few publications explain the interaction between their functional groups. This is mostly because of the difficulty of following ionic interaction in an interface of macromolecules, especially since they alter much with the reaction conditions such as pH. The present study reveals the interaction between chitosan and alginate at different pH values by means-of a particular method for Fourier transform infrared (FTIR) studies. A previously reported disagreement between the yield of the complexes in weight and density of the interacting functional groups is explained through this method. The obtained results are supported with the morphological studies of the polyelectrolyte beads prepared at different pH values. Freeze-dried beads of both alginate and chitosan-coated alginate beads could be viewed after hexamethyl disilazane (HNIDS) treatment. (C) 2003 Wiley Periodicals, Inc.