Dear Colleagues,

In the last few decades, chitosan and its derivatives have received considerable attention in the biomedical field.

Chitosan is a cationic polysaccharide that is obtained by the deacetylation of chitin, which represents the main component of the exoskeleton of arthropods, such as crustaceans, molluscs and insects, as well as the cell walls of bacteria and fungi. Its polycationic character determines its unique bioactive properties, which make chitosan a multifunctional excipient for the preparation of innovative drug delivery systems and scaffolds for tissue engineering purposes, comprising hydrogels, sponge-like dressings, films, and nanosystems (nanoparticles, nanocomposites, and nanofibers).

The Food and Drug Administration (FDA) approved the use of chitosan in several biomedical applications thanks to its well-known biocompatibility, nontoxicity, and biodegradability. Due to its mucoadhesive, hemostatic, and antimicrobial properties, chitosan has proven to be an effective healing enhancer, being involved in all stages of the wound-healing process. Moreover, it has been demonstrated that chitosan enhances drug penetration towards different biological membranes, such as intestinal, nasal, buccal, vaginal mucosae, and cornea, thus improving drug bioavailability.

A large family of chitosan derivatives has been produced in order to overcome some limitations of chitosan. Since chitosan is characterized by poor solubility in physiological media, the use of water-soluble derivatives, obtained through different chemical modifications, is preferable in the biomedical and pharmaceutical fields. In this perspective, chitosan chains can be modified at three reactive sites, which are two hydroxyl groups and one primary amino residue, producing CS derivatives with peculiar bulk properties. Among them, trimethyl–chitosan, carboxymethyl–chitosan, and carboxymethyl–trimethyl–chitosan have been investigated recently: They are characterized by an increased water solubility over a wide range of pH and maintain bioactive properties of pure chitosan. In an attempt to improve the antibacterial potential of chitosan, the functionalization of its backbone with chemotherapeutic agents, such as sulfonamides and derivatives, has been also proposed.

The present Special Issue on “Chitosan and Chitosan Derivatives in Biomedical Applications” serves as an overview of current research on this interesting topic, highlighting the progress in the design and development of novel drug delivery systems or tissue engineered products based on chitosan and chitosan derivatives.