Chitosan

Reactive & Functional Polymers 46 (2000) 1–27 www.elsevier.com / locate / react

Review

A review of chitin and chitosan applications q
Majeti N.V. Ravi Kumar*
Department of Chemistry, University of Roorkee, Roorkee 247 667, India Received 24 January 2000; received in revised form 20 June 2000; accepted 25 June 2000

Abstract Chitin is the most abundant natural amino polysaccharide and isestimated to be produced annually almost as much as cellulose. It has become of great interest not only as an underutilized resource, but also as a new functional material of high potential in various fields, and recent progress in chitin chemistry is quite noteworthy. The purpose of this review is to take a closer look at chitin and chitosan applications. Based on current research and existingproducts, some new and futuristic approaches in this fascinating area are thoroughly discussed. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Beads; Biotechnology; Chitin; Chitosan; Controlled drug delivery; Fibers; Nanoparticles; Hydrogels; Tablets; Transdermal devices

1. Introduction Chitin, a naturally abundant mucopolysaccharide, and the supporting material of crustaceans,insects, etc., is well known to consist of 2-acetamido-2-deoxy-b-D-glucose through a b (1 → 4) linkage. Chitin can be degraded by chitinase. Its immunogenicity is exceptionally low, in spite of the presence of nitrogen. It is a highly insoluble material resembling cellulose in its solubility and low chemical reactivity. It may be regarded as cellulose with hydroxyl at
q This paper is dedicated toProfessor M.N.V. Prasad, Ph.D., FNIE (New Delhi), DSc. (hc Colombo), School of Life Sciences, University of Hyderabad, Hyderabad, India, who inspired me with his scientific approach, honesty and human warmth. *Post Bag No. 29, Roorkee 247 667, India. Fax: 191-133273560. E-mail address: mnvrkumar@mailcity.com (M.N.V. Ravi Kumar).

position C-2 replaced by an acetamido group. Like cellulose, itfunctions naturally as a structural polysaccharide. Chitin is a white, hard, inelastic, nitrogenous polysaccharide and the major source of surface pollution in coastal areas. Chitosan is the N-deacetylated derivative of chitin, although this N-deacetylation is almost never complete. A sharp nomenclature with respect to the degree of N-deacetylation has not been defined between chitin and chitosan [1,2].The structures of cellulose, chitin and chitosan are shown in Fig. 1. Chitin and chitosan are of commercial interest due to their high percentage of nitrogen (6.89%) compared to synthetically substituted cellulose (1.25%). This makes chitin a useful chelating agent [1]. As most of the present-day polymers are synthetic materials, their biocompatibility and biodegradability are much more limitedthan those of natural polymers such as cellulose,

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M.N.V. Ravi Kumar / Reactive & Functional Polymers 46 (2000) 1 – 27

radability, non-toxicity, adsorption properties, etc. Recently, much attention has been paid to chitosan as a potential polysaccharide resource [5].Although several efforts have been reported to prepare functional derivatives of chitosan by chemical modifications [6–8], very few attained solubility in general organic solvents [9,10] and some binary solvent systems [11–13]. Chemically modified chitin and chitosan structures resulting in improved solubility in general organic solvents have been reported by many workers [14–23]. The present review isan attempt to discuss the current applications and future prospects of chitin and chitosan.

2. Processing of chitin and chitosan Chitin is easily obtained from crab or shrimp shells and fungal mycelia. In the first case, chitin production is associated with food industries such as shrimp canning. In the second case, the production of chitosan–glucan complexes is associated with fermentation...