Chitosan-Based Hydrogels

Chitosan is a deacetylated derivative of chitin. This polysaccharide has received a great attention due to its biocompatibility, low toxicity, biodegradable, furthermore can be used into different shapes, such as beads, hydrogels, powders, films and membranes. Chitosan hydrogels may be formed by different mechanisms, as physical association or chemically cross-linked, thus can vary its geometries, formulations and shapes. Usually, hydrogels are prepared using a conventional sol-gel process, where polymer is dissolved in dilute acid to form an aqueous solution, after complete dissolution the cross-linking agents are subsequently incorporated, and the solution/gel transition depends on the number cross-links between the polymer chains and the cross-linking agents, and these should be enough until reaching the formation of a network. The chitosan hydrogels are formed from cross-linking of hydrogen bonds, hydrophilic interactions and crystalline groups of chitosan present in the sol-gel.Chitosan hydrogels have been largely used in drug delivery systems, wastewater and dye remediation, and tissue engineering supporting cell attachment and growth. In the food industry, chitosan hydrogels are used to maintain and/or improve the perception of flavor, release of fragrance compounds and increase shelf life. In the biomedical and biotechnological fields, these are used for controlled release formulations, for example, of compounds chemicals, volatiles, or proteins. Chitosan hydrogels can be used in dressing to adsorb the secretion of the injured area and release water on the wound surface, thus keeping it hydrated. Thus, the researches for employment of this material have been increasingly developed due to its favorable properties, such as durability, permeability, flexibility and its wide applicability.