ABSTRACT
Analytical, chemical, physicochemical, and rheological methods are required for the characterization and modification of chitin and chitosans and their derivatives. The chemical derivatization of chitosans aims to improve the solubility, hydrophilic character, gelling properties, and affinity toward bioactive molecules. Chitosans are modified under mild reaction conditions to alter their properties. Carboxymethyl chitosans are studied because of their ease of synthesis, ampholytic character, and wide variety of applications. In the solid state, chitosan chains form complexes of different nature with metal, surfactants, and oppositely charged polymers. One application, in the area of non-viral gene therapy, uses the ability of chitosans to compact DNA. The solubility of chitin and chitosans depends on such conditions as solution pH, molecular weight, ionic strength, and temperature. Both chitin and chitosans exhibit various biological properties: anticholesterolemic, wound-healing, anticancer, fungistatic, hemostatic, analgesic, antiacid, antiulcer, immunoadjuvant, and so on. In cosmetics, chitin and chitosans have been investigated as potential excipients and biologically active agents, thanks to their non-toxicity, biocompatibility, and biodegradability. Their antimicrobial, antioxidant, mucoadhesive, and penetration properties are important in the formulation of care products. Hemostatic agents derived from chitin and chitosans are developed because of their ability to bind with tissues.
