Advances in Biomedical Application of Chitosan and Its Functionalized Nano-derivatives

Abstract

The recent advances in nanotechnology open new avenues for the development of functionalized nanomaterials with wide potential application. Chitosan has become one of the most promising biopolymers with wide application in diagnostics and therapeutics. It is a linear copolymer of β-(1–4)-linked 2-acetamido-2-deoxy-β-d-glucopyranose and 2-amino-2-deoxy-β-d-glycopyranose, with a varying content of N-acetyl groups. It is obtained by deacetylation of parent polymer, chitin, and also occurs naturally in fungal species such as Absidia glauca, Absidia coerulea, Aspergillus niger, Mucor rouxii, Gongronella butleri, Phycomyces blakesleeanus, Absidia blakesleeanus, Rhizopus oryzae, Trichoderma reesei, and Lentinus edodes. Chitosan can also be directly extracted from fungi by alkaline/acid treatment and by use of microorganisms/proteolytic enzymes. Unlike chitin, chitosan is readily soluble in dilute acetic acid and widely used in preparation of gels, films, and fibers. The production of the biopolymer is generally influenced by parameters such as the nutritional factors, mode of cultivation, temperature, pH, and mineral salts. In therapeutics, chitosan and chitosan-based materials are used as antimicrobial, antitumor, antiulcer, antidiabetic, and a cholesterol-lowering agent. Being a naturally occurring polysaccharide, chitosan and its functionalized derivatives exhibit unique properties, such as biocompatibility, biodegradability, biological activity, and low toxicity. The conformational flexibility of chitosan is attributed to the presence of the free primary amino groups which makes chitosan an ideal candidate for biofabrication. Various methods, such as ionic gelation, desolvation, spray-drying, and covalent cross-linking, have been employed for functionalization of chitosan. Nanoparticles and its biofabrication impart desirable functional characteristics to chitosan. The molecular weight and the concentration of chitosan used along with an amount of cross-linking govern the physical properties of chitosan nanoparticles formed. Chitosan nanocomposites have shown to improve the dissolution rate of poorly soluble drugs and, thus, are exploited for enhancement of drug bioavailability and delivery. Various therapeutic agents, such as anticancer, anti-inflammatory, antibiotics, antithrombotic, steroids, proteins, amino acids, antidiabetic, and diuretics, have been incorporated in chitosan nanocomposites. The controlled release of therapeutic agents opened new windows in drug delivery and bio-imaging techniques using chitosan. Hence, chitosan and its nano-derivatives serve as one of the sustainable and ecofriendly alternative to synthetic polymers in biomedical applications.