Cross-linked chitin

Saravanan, D., Hemalatha, R., Sudha, P. N. Synthesis and characterization of cross-linked chitin/bentonite polymer blend and adsorption studies of Cu (It) and Cr (VI) on chitin. Der Pharma Chemica, 2011, 3,406-424. 

Cross-linking agents have been proposed for the improvement of chitin fibres in the wet state. Epichlorohydrin is a convenient base-catalysed crosslinker to be used in 0.067 M NaOH (pH 10) at 40 °C. The wet strength of the fibres was considerably improved, whereas cross-hnking had neghgible effect on the dry fibre properties. Of course, the more extended the chemical modification, the more unpredictable the biochemical characteristics and effects in vivo. Every modified chitin or modified chitosan fibre should be studied in terms of biocompatibiUty, biodegradabiUty and overall effects on the wounded tissues. 

Cross-linking of chitin Copper tyrosinase (animals)... 

From the results discussed so far it can be concluded that diflubenzuron interferes very rapidly with chitin deposition. The possible effects on the deposition of protein, the second important component of the endocuticular matrix, were studied by Hunter and Vincent with adult locusts (.44). It was concluded that protein deposition was completely unaffected as regards the quantity of protein found. Another conclusion was that cross-linking of the protein - as revealed by the differing solubilities of the protein fractions - was also unaffected. Deul et al. (45)... 

The murein-peptidoglycan gives rigidity and different specific shapes, such as rods, spheres, or spirals to bacterial ceUs. Because of the cross-linking of the murein chains, the peptidoglycan is considered one giant, bag-shaped macromolecule [91]. The stmctures of segments of chitin, chitosan, and murein are shown in O Fig. 6. 

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... 

Also it has been proposed that bonds exist between cuticular protein and chitin (38). Solid state l N-NMR analysis of chitin prepared by alkali extraction of 1, 3-[ 5 ]-histidine labeled M. sexta pupal exuviae revealed an N chemical shift expected for the substituted imidazole nitrogen cross-link structure depicted in Fig. 3 (24). Apparently, the chitin is not coupled directly to protein but, instead, to a diphenolic carbon, which serves as a part of the bridge between protein and chitin macromolecules. 

Figure 3 Proposed structure for diphenol mediated cross-link between protein and chitin in M. sexta pupal cuticle (from Schaefer et al. 24).

A very complicated exoskeleton is excreted by arthropods, consisting of many layers of proteins and lipids and a nitrogen-containing polysaccharide known as chitin. The more massive, rigid parts of arthropod exoskeletons are strengthened by the deposition of calcium carbonate in their middle layers or by the tanning of the proteins by cross-linking of the protein chains by orthoquinones. 

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