Chitosan, derivatives degradability

The most common amino polysaccharide is chitosan, derived from chitin by N-deacetylation, and the N-deacetylation reaction can be conducted with little degradation of the polysaccharide chain. The depolymerization and sulfation of chitosan by sulfuric acid have been studied. Chitosan has several applications, for example, in the collection and separation of metal ions, and, in admixture with cellulose, for thin-layer, ion-exchange chromatography. - ... 

CM-chitosan is a kind of carboxymethylated derivative of chitosan, which is prepared by the chemical reactions of chitosan and monochloroacetic acid. It contains -COOH and -NH2 groups in the molecular structure. Being a soluble chitosan derivative in both acidic and basic physiological media, it might be a better candidate than chitosan for studying the mechanism of degradation reaction of chitosan derivatives. 

The radiation effect of chitosan derivatives can be summarized as follows solid state and lowconcentrated solution state result in degradation, while high-concentrated solution state is favorable for cross-linking. The irradiation effect of chitosan derivatives in different conditions are proposed in Scheme 31.4. 

SCHEME 31.4 Irradiation effect of chitosan derivatives in different conditions (the points represent radicals induced by irradiation). (From Zhao, L. and Mitomo, H., Polym. Degrad. Stabil., 93, 1607, 2008. With... 

Besides enzymatic degradation, the biodegradation behavior of chitosan derivatives hydrogels can also be evaluated by soil burial, microbial attack, and so on. The CM-chitin and CM-chitosan hydrogels before and after keeping for 10 weeks in soil is found to become smaller, revealing that... 

Carlos, R-C., Waldo, A.-M., Julio, S. R. 1993. A kinetic study of the thermal degradation of chitosan and a mercaptan derivative of chitosan. Polymer Degradation and Stability 39 21-28. 

L. Cui, C. Tang, and C. Yin, Effects of quaternization and PEGylation on the biocompatibility, enzymatic degradability and antioxidant activity of chitosan derivatives. Carbohydrate Polymers, 87 (4), 2505-2511,2012. 

Another polysaccharide system that has received considerable interest is the chitosans which are water soluble derivatives of chitin. These materials appear to be very biocompatible and degradable and so are potentially excellent candidates as polymeric drug systems (27). 

Chitosan has found many biomedical applications, including tissue engineering approaches. Enzymes such as chitosanase and lysozyme can degrade chitosan. However, chitosan is easily soluble in the presence of acid, and generally insoluble in neutral conditions as well as in most organic solvents due to the existence of amino groups and the high crystallinity. Therefore, many derivatives have been reported to enhance the solubility and processability of this polymer. 

The balance between the anabolism and catabolism of HA is maintained by the inhibitors of hyaluronidases. Heparin is a known and well-characterized inhibitor of hyaluronidase [132]. Chitosan inhibits HA degradation by venom and bovine testicular hyaluronidases [133]. Cis-unsaturated fatty acids can also inhibit the hyaluronidase activity [134]. Certain anti-inflammatory drugs including saly-cylates, indomethacin and dexamethasone are also known to exert anti-hyaluronidase activity [133, 135]. Ascorbic acid [136], as well as plant derived bioactive compounds, such as flavonoids, tannins, pectins, curcumins, cou-marins, gylcyrrhizin are used to block hyaluronidase activity [100]. 

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