The role of chitosan as a mucoadhesive agent in mucosal drug delivery

Mucoadhesive properties of chitosan are supported by an exceedingly high number of papers and have been studied using a number of different methods. Also, the myriad of chitosan derivatives that have been synthesized and proposed for pharmaceutical use have been studied for mucoadhesion, looking at the changes in mucoadhesivity induced by structure modifications. The review will briefly recall the possible mechanisms involved in chitosan mucoadhesivity, among which ionic interactions with mucin chains and hydration state are the prevailing ones. Furthermore, adhesion mechanism inevitably depends on the environmental conditions as well as on the type of physical and pharmaceutical form considered. Therefore, the testing methods used for mucoadhesivity should be carefully chosen. The present review will report on the experience acquired by the authors in the field. The focus will be on some examples of liquid, semisolid, solid and nanoparticulate formulations based on either chitosan or chitosan derivatives and on how it is possible to choose the most suitable testing method depending on the envisaged mucoadhesion mechanism and on the physical/pharmaceutical form under examination.