POLYELECTROLYTE COMPLEXES OF SODIUM ALGINATE WITH CHITOSAN OR ITS DERIVATIVES FOR MICROCAPSULES

Chitosan, a cationic polysaccharide, was heterogeneously deacetylated with a 47% sodium hydroxide solution and followed by a homogeneous rea cetylation with acetic anhydrides to control the N-acetyl content of t he chitosan having a similar molecular weight. The chitosans having di fferent degrees of N-acetylation were complexed with sodium alginate, an anionic polysaccharide, and the formation behavior of polyelectroly te complexes (PECs) was examined by the viscometry in various pH range s. The maximum mixing ratio (R(max)) increased with a decrease in the degree of N-acetylation of the chitosan at the same pH, and with a dec rease in pH at the same degree of N-acetylation. Similarly, N-acylated chitosans were also prepared. The N-acyl chitosans scarcely affected the formation behavior of PECs with sodium alginates. For the applicat ion of the PECs produced, the microencapsulation of a drug was perform ed and the release property of drug was tested. The microcapsules were prepared in one step by the extrusion of a solution of guaifenesin an d sodium alginate into a solution containing calcium chloride and chit osan through interpolymeric ionic interactions. The drug release durin g the drug-loaded microcapsules storage in saline was found to depend on the pH where the microcapsules were formed and the kind of N-acyl g roups introduced to the chitosan. (C) 1997 John Wiley & Sons, Inc.