Chapter 9 - Chitosan and lipid composites as versatile biomedical material

Abstract

The development of biofunctional materials has had increasing scientific and technological interest over the years. Chitosan comprises a natural source polysaccharide of biodegradable, low-toxic, low-antigenic, biocompatible characteristics and detainer of mucoadhesive and antimicrobial activities. These properties render the polymer an interesting material in the development of micro- and nanostructures of broad applicability in advanced drug delivery and disease-preventing strategies. In this context, chitosan has found application trends in association with liposomes, especially considering improvements in stability, yield in encapsulating therapeutics and its controlled release, as well as an increase of the specificity of the application where bioadhesion is required. Therefore the association of chitosan with liposomes has been proposed in the development of carrier systems for drugs and vaccines. In recent years, the combination of chitosan with lipids was designed in the production of composites bearing multilamellar structure, where chitosan coats the outer and inner membrane surfaces of phospholipid bilayer. These composite nanoparticles have demonstrated applicability as carriers of antigens for vaccination, providing increased vaccine efficacy shown by in vivo experiments. The chemical modification of chitosan has further been considered in the development of composites with advantageous properties for specific applications. A strategy in order to enhance the functionality of chitosan is the chemical bonding of active ingredients from plant extracts. Among them, flavonoids have been used as effective antioxidants that neutralize free radicals, preventing the damage caused by diseases’ oxidative stress. Indeed, the chitosan composites containing chemically bonded flavonoids have shown potent oxidative stress reduction by inactivation of reactive oxygen species. The use of chitosan in liposomes designing composite systems hence improves the versatility of these materials considering the physicochemical properties and particularly the beneficial appeal of biocompatibility and biodegradability, which are important for biomedical applications.