The objective of this paper is to emphasize the fact that while consistent interest has been
paid to the industrial use of chitosan, minor attention has been devoted to spread the knowledge
of a good characterization of its physico-chemical properties. Therefore, the paper attempts to
critically comment on the conflicting experimental results, highlighting the facts, the myths and the
controversies. The goal is to indicate how to take advantage of chitosan versatility, to learn how
to manage its variability and show how to properly tackle some unexpected undesirable features.
In the sections of the paper various issues that relate chitosan properties to some basic features and
to advanced solutions and applications are presented. The introduction outlines some historical
pioneering works, where the chemistry of chitosan was originally explored. Thereafter, particular
reference is made to analytical purity, characterization and chain modifications. The macromolecular
characterization is mostly related to molecular weight and to degree of acetylation, but also refers to
the conformational and rheological properties and solution stability. Then, the antimicrobial activity
of chitosan in relation with its solubility is reviewed. A section is dedicated to the formulation of
chitosan biomaterials, from gel to nanobeads, exploring their innovative application as active carrier
nanoparticles. Finally, the toxicity issue of chitosan as a polymer and as a constructed nanomaterial is
briefly commented in the conclusions.
