Chitosan has garnered much interest due to its properties and possible applications. Every year the number of publications and patents based on this polymer increase. Chitosan exhibits poor solubility in neutral and basic media, limiting its use in such conditions. Another serious obstacle is directly related to its natural origin. Chitosan is not a single polymer with a defined structure but a family of molecules with differences in their composition, size, and monomer distribution. These properties have a fundamental effect on the biological and technological performance of the polymer. Moreover, some of the biological properties claimed are discrete. In this review, we discuss how chitosan chemistry can solve the problems related to its poor solubility and can boost the polymer properties. We focus on some of the main biological properties of chitosan and the relationship with the physicochemical properties of the polymer. Then, we review two polymer applications related to green processes: the use of chitosan in the green synthesis of metallic nanoparticles and its use as support for biocatalysts. Finally, we briefly describe how making use of the technological properties of chitosan makes it possible to develop a variety of systems for drug delivery.

Marine resources are well recognized for their biologically active substances with great potential applications in the cosmeceutical industry. Among the different compounds with a marine origin, chitin and its deacetylated derivative—chitosan—are of great interest to the cosmeceutical industry due to their unique biological and technological properties. In this review, we explore the different functional roles of chitosan as a skin care and hair care ingredient, as an oral hygiene agent and as a carrier for active compounds, among others. The importance of the physico-chemical properties of the polymer in its use in cosmetics are particularly highlighted. Moreover, we analyse the market perspectives of this polymer and the presence in the market of chitosan-based products.

Chitosan is a natural polymer composed of randomly distributed β-(1-4)-linked D-glucosamine (deacetylated unit) and Nacetyl- D-glucosamine (acetylated unit). It has been described as a non-toxic, biodegradable and biocompatible polymer with very interesting biological properties, such as permeation-enhancing and mucoadhesive properties, anticoagulant and antimicrobial activity and so on. Chitosan has been used in several areas such as biomedical, pharmaceutical and biotechnological fields as well as in the food industry. Recently, there has been a growing interest in the modification of chitosan to improve its solubility in physiological conditions, to introduce new applications or to improve chitosan biological properties. Research and development on a variety of amphiphilic copolymers containing hydrophobic and hydrophilic segments, have been very active due to their spontaneous self-assembly behaviour in aqueous media These smart transitions often lead to diverse functional compartment structures like micelles, vesicles and gels, which represent promising applications in the field of biotechnology and pharmaceutics. The aim of the present paper is to review the latest advances in the synthesis of chitosan amphiphilic derivatives with a special emphasis in their applications.