International Journal of Biological Macromolecules 43 (2008) 221–225 Contents lists available at ScienceDirect International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac Review Preparative methods of phosphorylated chitin and chitosan—An overview R. Jayakumar a,* , N. Selvamurugan a , S.V. Nair a , S. Tokura b , H. Tamura b a Amrita Center for Nanosciences, Amrita Institute of Medical Sciences and Research Centre, Amrita Viswa Vidyapeetham University, Kochi 682026, India b Faculty of Chemistry, Materials and Bioengineering & High Technology Research Centre, Kansai University, Osaka 564-8680, Japan article info Article history: Received 21 May 2008 Received in revised form 24 June 2008 Accepted 1 July 2008 Available online 9 July 2008 Keywords: Chitin Chitosan Phosphorylated chitin and chitosan Biomaterials Polysaccharides abstract Biomaterials such as chitin, chitosan and their derivatives have a significant and rapid development in recent years. Chitin and chitosan have become cynosure of all party because of an unusual combination of biological activities plus mechanical and physical properties. However, the applications of chitin and chitosan are limited due to its insolubility in most of the solvents. The chemical modification of chitin and chitosan are keen interest because of these modifications would not change the fundamental skeleton of chitin and chitosan but would keep the original physicochemical and biochemical properties. They would also bring new or improved properties. The chemical modification of chitin and chitosan by phosphoryla- tion is expected to be biocompatible and is able to promote tissue regeneration. In view of rapidly growing interest in chitin and chitosan and their chemical modified derivatives, we are here focusing the recent developments on preparation of phosphorylated chitin and chitosan in different methods. © 2008 Elsevier B.V. All rights reserved. Contents 1. Introduction ......................................................................................................................................... 221 2. Preparative methods of phosphorylated chitin and chitosan ...................................................................................... 223 3. Conclusions ......................................................................................................................................... 225 References .......................................................................................................................................... 225 1. Introduction Chitin is the second most abundant natural biopolymer derived from exoskeletons of crustaceans and also from cell walls of fungi and insect [1]. Chitin is a linear cationic heteropolymer of ran- domly distributed GlcNAc and GlcN residues with -1,4-linkage. Chitobiose, 4-O-(2-amino-2-deoxy--d-glucopyranosyl)-(1 → 4)- 2-amino-2-deoxy-d-glucose, is the structural unit of native chitin [2]. Chitosan is the deacetylated derivative of chitin a natural polysaccharide found primarily in the exoskeletons of arthro- pods and some fungi. It is composed of residues of glucosamine and N-acetyl glucosamine connected via a–b (1–4) linkage. The ratio of glucosamine to N-acetyl glucosamine is referred to as the degree of deacetylation (DDA). The DDA is a factor of both the source of the chitosan (crab, shrimp, fungi, etc.) and the preparation methods, and may range from as low as 30% to * Corresponding author. Tel.: +91 484 280 1234; fax: +91 484 280 2020. E-mail addresses: rjayakumar@aims.amrita.edu, jayakumar77@yahoo.com (R. Jayakumar). almost 100%. Chitosan physical properties such as crystallinity, surface energy, and degradation also vary with the DDA of the polymer. These polysaccharides are renewable resources which are currently being explored intensively for their applications in pharmaceutical, cosmetics, biomedical, biotechnological, agri- cultural, food, and non-food industries (water treatment, paper, and textile) [3–8]. These unique polymers have emerged as a new class of physiological materials of highly sophisticated functions due to their versatile biological activity, excellent biocompatibility, and complete biodegradability in combina- tion with low toxicity [9–11]. To exploit the unique properties and to realize and obtain the full potential of these versatile polysaccharides, attempts are being made to chemically modify them. Chemical modifications of chitin and chitosan would bring new properties depending on the nature of the group introduced [12–15]. Recently, several methods have been reported to obtain phosphorylated derivatives of chitin and chitosan due to their interesting biological and chemical properties [14–19]. They could exhibit bactericidal [18], biocompatible [19–24], bioabsorbable [19–24], osteoinductive [19–24] and metal chelating properties 0141-8130/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.ijbiomac.2008.07.004