Challenges in developing of chitosan – Based polyelectrolyte complexes as a platform for mucosal and skin drug delivery

Chitosan, a biocompatible positively charged polysaccharide from natural origin, is regarded as a promising compound in medical and pharmaceutical technology. However, despitehigh application potential of chitosan, its susceptibility to the presence of ions, pH – dependent solubility, insufficient rheological properties or poor mechanical characteristics, can be a serious limitation in the technology of modified release drug carriers. To date, different strategies have been applied to overcome too rapid disintegration of chitosan carriers and to improve theirphysical properties. Among modifications of chitosan backbone, particular attention has been paid toward polyelectrolyte complexes spontaneously formed by mixing chitosan with oppositely charged polymers from both natural or synthetic origin under mild conditions. The aim of this review is to highlight the most recent advances and current applications of chitosan – based polyelectrolyte complexes as potential drug delivery systems and medical devices for local (skin and mucosal) application. Regarding the fact that pharmaceutical processing appears particularly important in proper polyelectrolyte complexes formation, this review covers the influence of selected technological factors on final polyelectrolyte complexes characteristics. The influence of a type of an applied polyanion on the polyelectrolyte complexes properties including swelling capacity, bio – and mucoadhesiveness or biological activity was also briefly described.