**1. Introduction**

A tremendous effort has been and is currently being devoted to the research in the field of pharmaceutical nanotechnology. Several peculiar properties of gelled polymeric nanosize (<1μm) particulate systems have been reported, among which the ability to encapsulate either small molecular weight or macromolecular active principles in mild conditions and protect them from degradation by the harsh pH conditions or enzymes they may encounter in the organism, promote transport of actives across mucosal barriers, undergo internalization by cells thereby carrying actives into them. Chitosan, a copolymer of glucosamine and *N*acetylglucosamine, obtained by deacetylation of the naturally-occurring chitin, has been studied as a basic biomaterial for preparing pharmaceutical nanoparticles, because it is biodegradable and has a very low toxicity [1-5] besides an ability to promote transport of drugs, peptides and proteins across mucosal barriers [6-10]. The preparation procedures of chitosan nanoparticles, their characterization for drug encapsulation efficiency, physical and biophar‐ maceutical properties, and toxicity have been covered by recent reviews (11,12). Chitosan has been subjected to derivatization, taking advantage of the reactivity of the primary amino group in position 2, or the hydroxyl group in position 6 of its repeating unit, glucosamine. The derivatization changed the physicochemical, biopharmaceutical and biological properties of the parent chitosan and each derivative type lent itself to preparing nanoparticles with their own physical properties (size, shape, surface charge), drug encapsulation and release capa‐ bility, biopharmaceutical and biological properties (mucoadhesivity, ability to promote drug transport across biological barriers, aptitude for internalization within cells, citotoxicity).

In the following sections the nanoparticles obtained from chitosan derivatives will be surveyed in respect to preparation procedures, interactions with cells and tissues, factors influencing biological properties, pharmaceutical applications.

© 2013 Zambito; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
