Chitosan is a non-toxic biopolymer that usually takes on the form of white powder. It is a linear polysaccharide composed of randomly distributed acetylated and deacetylated units of D-glucosamine. It is obtained by the deacetylation of chitin of natural origin which, in turn, becomes obtained from exoskeletons of marine organisms, such as crabs or shrimps, as well as from the cell walls of certain fungi. Due to its natural origin, great availability and the properties similar to those of cellulose, chitosan constitutes a valuable polymer that suits the applications in such fields as biomaterials, pharmaceuticals, cosmetics, chemical synthesis, agriculture or food processing.
The deacetylation of chitin makes such derived chitosan water-soluble, due to which it may take on the forms that are desirable from the point of view of certain applications (fibers, layers, etc.). Furthermore, thanks to simple production techniques, it is possible to obtain porous structures of chitosan which makes it an important biopolymer used in tissue engineering, particularly in orthopaedics and bone regeneration. Other forms of materials and medical products containing chitosan include gels, sponges, fibers or porous compositions of chitosan with ceramics, collagen and gelatine. Chitosan is used in combination with such materials as alginates, hydroxyapatite, hyaluronic acid, calcium phosphate, PMMA, poly-L-lactide acid and others.
The anti-bacterial properties of chitosan have also been recognised which explains the considerable interest in this biopolymer from the point of view of the targeted application of antibiotics or limiting the growth of bacterial films. The antibacterial properties, as combined with the haemostatic activity of chitosan, make it suitable for the application in medical dressings. The ability of chitosan to be combined with mucus is another interesting property, the same as its capacity of crossing epithelial barriers, due to which the application of chitosan as an adjuvant or supportive adjuvant in vaccines has also been considered.
Chitosan may be modified in order to increase its solubility, the compatibility of its mixtures with other compounds, as well as in order to obtain other desirable properties. The chemical modification of chitosan may lead to completely new applications, such as the deactivation of heparin or achieving an antiviral activity.