Hydrogels chitin

Partially deacetylated chitin, a cellulose-like biopolymer consisting predominantly of N-acetyl-D-glucosamine chains, in the form of films or crosslinked hydrogels has been used for the delivery of drugs (28,29). The suitability of chitin as a vehicle for the sustained release of drugs was examined using indomethacin and papaverine hydrochloride as model drugs (30). In vitro studies showed that over 80% of the indomethacin was released within 7 hr, whereas papaverine hydrochloride dissolved almost immediately. 

Enzyme-Degradable Hydrogel. Because lysozyme is a well characterized enzyme, our first choice was a lysozyme-degradable hydrogel (11, 12). The natural substrate for lysozyme is chitin (13). but because chitin is a rigid, hydrophobic material, it is clearly not suitable for this work. The other natural substrates for lysozyme are certain bacterial cell-wall peptidoglycans (13. 

Chitin hydrogels, partially deacetylated, degradation, 182-184 Chloroformates, reaction with polysaccharides, 191,193-195... 

Chitin sheets are excellent for use in biomedical devices due to their biodegradability and lack of toxicity. These sheets can be prepared by simple procedures. A solution of a-chitin, in saturated calcium chloride dihydrate-methanol solvent system, is dropped into excess of distilled water with gentle mixing to desolubilize the ot-chitin the obtained chitin hydrogel is decanted several times with distilled water and filtered. ot-Chitin sheets are obtained after the evaporation of water. 

Due to the loose crystalline structure of p-chitin, it can be highly swollen in water by vigorous mixing using a suitable blender and forms a hydrogel. A suspension will be formed by the addition of excess water to the p-chitin hydrogel which is then filtered to form the p-chitm sheets. 

Zhao, X. Kato, K. Fukumoto, Y. Nakamae, K. Synthesis of bioadhesive hydrogels from chitin derivatives. 128. Int. J. Adhes. Adhes. 2001, 21, 227-232. 

Chitin is known to be biodegradable, biocompatible, and nontoxic. It is used in dmg delivery and bio medical applications. It also used in the purification of water especially for the absorption of toxic dyes. Chitin has limited solubility in solvents but chitosan is readily soluble in acidic aqueous solutions and has more tendency to be chemically modified. Chitosan can readily be spun into fibers, cast into films, or precipitated in a variety of micromorphologies from acidic solutions. Min and Kim have reported on the adsorption of acid dyes from wastewater using composites of PAN/chitosan [52]. Shin et al. has reported on copolymers composed of PVA and poly dimethyl siloxanes cross-linked with chitosan to prepare semi IPN hydrogels for application as biomedical materials... 

Chitin and chitosan Chitin hydrogel Lumber dorsal root Chitosan films Frier et al. 

Jayakumar R, Divyarani W, Shalumon KT et al (2009) Development of novel a- and P-chitin hydrogel membranes for tissue engineering applications. Asian Chitin J 5 63-70... 

Natural polymers have also been used as thermo-sensitive hydrogels, either on their own or in combination with other synthetic polymers. Popular natural polymers include chitosan, cellulose derivatives, dextran, xyloglucan and gelatin (Klouda and Mikos 2008). Chitosan is a polysaccharide derived from the shells of crustaceans and is produced by deacetylation of chitin, basically through the removal of the acetyl group using a concentrated NaOH solution (Fig. 11.5). The main advantage of chitosan for medical and pharmaceutical applications is its biocompatibility and inertness when in contact with human cells (Kumar et al. 

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