Chitin gels

One of the simplest ways to prepare a chitin gel is to treat chitosan acetate salt solution with carbodiimide to restore acetamido groups. Thermally not reversible gels are obtained by AT-acylation of chitosans N-acetyl-, N-propionyl- and N-butyryl-chitosan gels are prepared using 10% aqueous acefic, propionic and bufyric acid as solvents for treatment with appropriate acyl anhydride. Both N- and 0-acylation are found, but the gelation also occurs by selective AT-acylation in the presence of organic solvents. 

Reacetylated chitin gels were used to treat leg and decubitus ulcers in paraplegic subjects [309]. Selected preparative conditions permitted to obtain a self-sustaining gel useful for this use. The treatment periods were 63-182 days and complete healing was obtained. 

The c.d. spectra of chitin, both in HFIP solution and as a film cast from HFIP, are shown in Fig. 21. Chitin gels have a c.d. spectrum similar to... 

Specific examples using STEM include structural studies over chitin gels used to produce chitin films. The results of the tests performed revealed that shrinkage resulted in a coarser microstructure. This morphology affected the tensile properties. It was also observed that shrinkage was proportional to the ductility and roughness of the meterial [53]. 

Jayakumar, R., Tamura, T. Synthesis, characterization and thermal properties of chitin- -poly(6-cajnolactone) copolymers by using chitin gel. Int. J. Biol. Macromol. 43, 32—36 (2008)... 

Preparation of Nanofiber Films from the Chitin Gel with Ionic Liquid 373... 

PREPARATION OF NANOFIBER FILMS FROM THE CHITIN GEL WITH IONIC LIQUID... 

The ultrastructure of the solid-phase of chitin gel has been examined by scanning electron microscopy.The gel is considraed to be a polyphasic gel with small droplets of water suspended in micropoies. 

This paper describes a novel thermally reversible chitosan oxalate gel, a thermally irreversible chitosan gel, and a thermally irreversible chitin gel (N-acetylchitosan gel or regenerated chitin). An intramolecular conversion of the chitosan oxalate gel into the chitin gel via the chitosan gel is discussed. The chitin gel may play a role of the structural processing of crab and shrimp shells and insect cuticle. A sheet of transparent film has been prepared from the gel slice by air-drying, 2 and a sheet of non-transparent porous by freeze-drying. The gel may be usable as a digestible material for drug delivery systems and as media for the immobilization of enzymes and cells. 

The chitosan gel obtained above was treated with acetic anhydride (about 10 mols/GlcN) in 70% aqueous methanol solution at room temperature for 18 h, and a transparent chitin gel was obtained. A portion of the gel was homogenized, washed with distilled water, and dried to give amorphous powders. 1650 (C=0 for NAc), 1560 cm i (C=0 for NAc) CP/MAS-... 

The partially 0-acetylated chitin gel obtained above was suspended in aqueous 0.1% NaOH solution at room temperature overnight to give a chitin gel. The absence of 0-acetyl group in the product was confirmed by the disappearance of IR absorptions at 1760 and 1240 cm-, indicating that the 0-deacetylation effected little on the gel properties. 

Gelation of Chitosan Chitosan Oxalate Gel, Chitosan Gel and Chitin Gel... 

The opaque chitosan gel was treated with acetic anhydride in an aqueous methanol solution at room temperature overnight, and a transparent gel was obtained. The gel was indistinguishable from chitin gel prepared from chitosan by N-acetylation in aqueous acetic methanol on the basis of its IR and CP/MAS-NMR spectra, on the hydrolysis rate by lysozyme... 

As shown in Table 2, the xerogels prepared by these methods were hydrolyzed at almost the same rate by hen egg-white lysozyme, and the rate was about 6 times higher than that of crab shell chitin. The hydrolysis rate by lysozyme was slightly inhibited by the presence of 0-acetyl group in chitin xerogel, probably because of the steric hindrance of the 0-acetyl group at Ce for forming an enzyme substrate complex. The increase in the rate of enzymic hydrolysis also proves the formation of the same chitin gel by three independent methods. 

In conclusion, this is the first report dealing with a basic polysaccharide gel that is thermally reversible and dealing with an intramolecular conversion of one gel to another gel in the solid phase. The chitin gels, which were produced by N-acetylation of the chitosan gel via the chitosan oxalate gel, and by 0-deacetylation of the partial 0-acetylated... 

Partially 0-acetylated chitin gel Chitin gel from partially 0.20... 

It is also possible to prepare a chitin gel using a recently found calcium chloride dihydride saturated methanol [22]. If chitin powder is suspended in this solvent and stirred, it becomes a viscous solution. Upon casting this solution onto a glass plate and deforming, a gel-like chitin film is obtained by immersing the casting into a mixed solution of 20% sodium... 

A chitin gel can be prepared by methods other than those already described. While deacetylated chitin is chitosan, chitin can be obtained by acetylating chitosan. Chitosan is dissolved in an acetic acid solution and diluted to 50% concentration by methanol. If acetic anhydride is added to this solution at 3-1 Ox the number of moles of the amine groups present, the solution solidifies in several minutes and forms a transparent gel [23-26]. Time necessary to solidification depends on the concentration of chitosan, methanol, and acetic acid anhydride [27,28]. This gel can also be made into a thin film and the film permeates materials well [25, 26]. 

The micropowder of chitin is dispersed at room temperature using CaClj THjO saturated methanol solutions. When this is refluxed for several hours, a consistent and clear dope is obtained. After being degassed, the film is immersed in a 20% mixed sodium formic acid aqueous solution and ethylene glycol (1 1 v/v) overnight, resulting in a chitin gel after calcium is removed. 

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