Chitosan modification

The early works by Muzzarelh et al. [179] showed that tyrosinase converts a wide range of phenohc substrates into electrophihc o-quinones [180]. Tyrosinase was used to convert phenols into reactive o-quinones which then underwent chemical reactions leading to grafting onto chitosan. A review article showed that in general the tyrosinase-catalyzed chitosan modifications resulted in dramatic changes in functional properties [181]. 

Harish Prashanth, . V. and Tharanathan, R. N. (2007). Chitin/chitosan Modifications and their unlimited application potential. Trends Food Sci. Technol. 18,117-131. 

The obtained catalysts showed similar activity in cyclopentadiene hydrogenation. The selectivity data in cyclopentadiene hydrogenation are given in Table I. The selectivity of consecutive reaction was determined as a rate ratio of cyclopentene/cyclopentane formation. On the contrary, the chitosan modification influenced essentially the selectivity of the catalyst on it basis. 

Using succinate chitosan form very much improved the reaction selectivity the maximum of selectivity to cis-I,4-butenediol was achieved over catalyst N°2. But in this case, the reaction was not terminated at the stage of 1,4-butenediol formation. The rate of further hydrogenation of 1,4-butenediol (second stage) was rather high. Introducing Pb in chitosan completely suppressed the further 1,4-butenediol hydrogenation. The reaction was spontaneously finished over catalyst N°3 after consumption of 1 mole of Ha. Simultaneously, the selectivity with respect to cis-1,4-butenediol was improved by that chitosan modification. 

Keywords Chitosan, modification of chitosan, biomedical applications... 

Mourya VK, Inamdar NN (2008) Chitosan-modifications and applications opportunities galore. React Funct Polym 68 1013-1051... 

Zohuriaan-Mehr MJ (2005) Advances In chitin and chitosan modification through graft copolymerization a comprehensive review. Iran Polym J 14 235-265... 

Most of fhe early sfudies on chitosan addressed ifs N-acylafion with fatty acids to increase its hydrophobicity. Fewer studies were conducted on partial N-carboxylmethylation to produce materials for a variefy of industrial applications. On the other hand, the growing interest in chitosan as a biomaterial and source for a suifable carrier for bioacfive agents over the past 15 years led to a substantial increase in research activities relevant to chitosan modification as outlined below. 

Mourya, V. K., Inamdar, N. N. (2008). Chitosan-modifications andapplications Opportunities galore, 68,1013-1051. 

Chemiluminescence Detection, Fig. 9 Fabrication and assay procedure for the paper-based sandwich chemiluminescence ELISA in each microzone. (1) Paper zone surrounded by hydrophobic wax zone (2) chitosan modification (3) capture antibodies immobilized through glu-taraldehyde cross-linking (4) bovine serum albumin... 

In this chapter, we review the latest advances in chitosan modification, with a special focus on the synthesis and functional properties of chitosan/poly(ethylenimine) (CP/PEI) graft copolymers and their derivatives as pDNA carriers. We also address the prospects and challenges of the practical... 

Monal, W.A. andCovac, C.P. (1993) Chitosan modifications. Macromol. Chem. Rapid Commun., 14,735-740. 

Harish Prashanth KV, Tharanathan RN (2007) Chitin/chitosan modifications and their unlimited application potential—an overview. Trends Food Sci Tech 18 117-131... 

Tyrosinase-mediated chitosan modification is based on the activation of a phenolic substrate into a reactive o-quinone, and this in situ activation may offer safety advantages over modification methods that require the use of reactive reagents. AnothCT potential advantage is that the tyrosinase-catalyzed chitosan modification may have generic utility because these enzymes are robust, only require molecular oxygen as a co-substrate, catalyze reactions under mild conditions and have a broad substrate range for phenols [75, 111]. 

V. Mourya, and N.N. Inamdar, Chitosan-modifications and applications Opportunities galore. Reactive and Functional Polymers, 68 (6), 1013-1051, 2008. 

Zohuriaan-Mehr, M. J. (2005). Advanees in chitin and chitosan modification through graft copolymerization A eomprehensive review. Iranian Polymer Journal 14(3), 235-265. 

Chitosan films can also be readily functionalized with proteins, enzymes, antibodies, and DNA, for selective coatings for biosensors. Different methods have been demonstrated for chitosan modification physical interaction (eg, surface absorption, entrapment), chemical bonding, or covalent crosslink with each other (Koev et al., 2010). 

Progress in chitosan modification is quite rapid as evidenced by a sharp increase in the number of papers and patents in the past decade. However, there are also disadvantages which impeded the development of chitosan-based microspheres, such as friability, single function and tedious process of modification. So in the future, our work should focus on two main points On the one hand, the preparation process should be optimized and Improved to suit to industrial production and application. On the other hand, the modification should be easy and feasible. Moreover, it is necessary to expand the appUcation field further through controlled modification reactions. 

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