N- chitosan

Sekar, N., Chitosan in textile processing-an update, Colourage, XLVII(7] (2000], 33-34. 

Giridev, V. R., Neelkandan, R., Sudha, N., Shamugasundaram, 0. L., and Nadaraj, R. N., Chitosan-A polymer with wider applications. Text Mag., July C2005], 83-86. 

Peniche, C., Monal, W. A, Peniche, H., and Acosta, N., Chitosan An attractive biocompatible polymer for microencapsulation,... 

Jayakumar R, Chennazhi KP, Muzzarelli RAA, Tamura H, Ntiir SV, Selveunurugan N. Chitosan conjugated DNA nanoparticles in gene therapy review ruticle. Carbohydr Polym. 

Ridolfi DM, Marcato PD, Justo GZ, Cordi L, Machado D, Duran N. Chitosan-solid lipid nanoparticles as carriers for topical delivery of tretinoin. Colloids Surf B Biointerfaces. 2012 93 36 0. 

It has been shown by IR-spectroscopic investigations which evidence on the appearance of new absorption bands after chitosan introducing, elementary analyses data. (N, occurrence in the samples, which quantity depends on chitosan nature and isolation conditions) It leads to significant increase of sorption capacity and specific surface of sorbents, which contain chitosan from silk waren chrysalises. Where as these parameters decrease for sorbents with chitosan from crabs. Evidently it is connected to more dense structure of the last one. It has been shown, that yield of sorbent on the base of PES and chitosan obtained by sol-gel method has depended significantly on such factors as components ratio, temperature, catalyst quantity etc. 

Reacetylation of chitosan under proper conditions leads to products having the same solubility. Experiments showed that the amount of acetic anhydride was the most important factor affecting the N-acetylation degree of the chitosan. The effect of the means of adding materials and the amount of solvent on the reaction could not be ignored [70]. 

Recent progress of basic and application studies in chitin chemistry was reviewed by Kurita (2001) with emphasis on the controlled modification reactions for the preparation of chitin derivatives. The reactions discussed include hydrolysis of main chain, deacetylation, acylation, M-phthaloylation, tosylation, alkylation, Schiff base formation, reductive alkylation, 0-carboxymethylation, N-carboxyalkylation, silylation, and graft copolymerization. For conducting modification reactions in a facile and controlled manner, some soluble chitin derivatives are convenient. Among soluble precursors, N-phthaloyl chitosan is particularly useful and made possible a series of regioselective and quantitative substitutions that was otherwise difficult. One of the important achievements based on this organosoluble precursor is the synthesis of nonnatural branched polysaccharides that have sugar branches at a specific site of the linear chitin or chitosan backbone [89]. 

The Schiff reaction between chitosan and aldehydes or ketones yields the corresponding aldimines and ketimines, which are converted to N-alkyl derivatives upon hydrogenation with borohydride. Chitosan acetate salt can be converted into chitin upon heating [130]. The following are important examples of modified chitosans that currently have niche markets or prominent places in advanced research. 

In general these derivatives are safe, their chemical functions being the glycine moiety the same holds for AT,0-carboxymethyl chitosan, as demonstrated for instance by studies intended to assess the efficacy of W,0-carboxymethyl chitosan to limit adhesion formation in a rabbit abdominal surgery model. The inability of fibroblasts to adhere to N,0-carboxymethyl chitosan-coated surfaces suggests that it may act as a biophysical barrier [135]. 

Reductive amination of AT-succinyl chitosan and lactose using sodium cyanoborohydride in a phosphate buffer (pH 6.0) for 6 days was suitable for the preparation of lactosaminated M-succinyl chitosan (Fig. 3). Over 10% of dose/g-tissue was distributed to the prostate and lymph nodes at 48 h postadministration in both chitosan and lactosaminated N-succinyl chitosan. The labeled lactosaminated M-succinyl chitosan was easily distributed into not only the liver but also prostate, intestine, preputial gland and lymph nodes [153]. 

Galactosylated chitosan prepared from lactobionic acid and chitosan with l-ethyl-3-(3-dimethylaminopropyl)-carbodiimideand N-hydroxysuccinimide was a good extracellular matrix for hepatocyte attachment [155] (Fig. 4). Furthermore, graft copolymers of galactosylated chitosan with poly(ethylene glycol) or poly(vinyl pyrrolidone) were useful for hepatocyte-targeting DNA carrier [156,157]. 

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. 

A novel fiber-reactive chitosan derivative was synthesized in two steps from a chitosan of low molecular weight and low degree of acetylation. First, a water-soluble chitosan derivative, N-[(2-hydroxy-3-trimethylammonium)-... 

Co-administration of ofloxacin and chitosan in eyedrops increased the bioavailabUity of the antibiotic [290]. Trimethyl chitosan was more effective because of its solubility (plain chitosan precipitates at the pH of the tear fluid). On the other hand, N-carboxymethyl chitosan did not enhance the corneal permeability nevertheless it mediated zero-order ofloxacin absorption, leading to a time-constant effective antibiotic concentration [291]. Also W,0-carboxymethyl chitosan is suitable as an excipient in ophthalmic formulations to improve the retention and the bioavailability of drugs such as pilocarpine, timolol maleate, neomycin sulfate, and ephedrine. Most of the drugs are sensitive to pH, and the composition should have an acidic pH, to enhance stability of the drug. The delivery should be made through an anion exchange resin that adjusts the pH at around 7 [292]. Chitosan solutions do not lend themselves to thermal sterilization. A chitosan suspension, however. 

The semi-interpenetrating polymeric networks obtained by the radical-induced polymerization of N-isopropylacrylamide in the presence of chitosan using tetraethyleneglycoldiacrylate as the cross-linker were used as controlled release vehicles for pilocarpine hydrochloride [294]. 

TokuraS, Nishi N, Nishimura S, Ikeuchi Y (1984) In ZikakisJP (ed.) Chitin Chitosan and related Enzymes. Academic, New York, p. 303... 

A contrasting picture is seen for chitosans. Chitosans—as considered in detail in the following Chapter—are derivatives of chitin (after an alkali extraction procedure) and are available in large quantities from the shells of crabs, lobsters and other crustaceans. Pure chitin is poly-N-acetylglucoasmine. The N-acetyl groups are de-acetylated in chitosan to an extent represented by ei-... 

El Gueddari N.E. Rauchhaus U. Moerschbacher B.M. Deising H.B. (2002) Developmentally regulated conversion of surface-exposed chitin to chitosan in cell walls of plant pathogenic fimgi // New Phytologist. V. 156. P. 103-112. 

Khairullin R. M. Yusupova Z. R. Maksimov 1. V. (2000) Protective responses of wheat treated with fungal pathogens 1. Interaction of wheat anionic peroxidases s with chitin, chitosan, and thelyospores of Tilletia caries / / Rus. J of plant physiology. V. 47. N. 1. P. 97-102. 

Chitosan (Fig. 27) was deposited on sihca by precipitation. The palladium complex was shown to promote the enantioselective hydrogenation of ketones [80] with the results being highly dependent on the structure of the substrate. In the case of aromatic ketones, both yield and enantioselectiv-ity depend on the N/Pd molar ratio. Low palladium contents favored enan-tioselectivity but reduced the yield. Very high conversions were obtained with aliphatic ketones, although with modest enantioselectivities. More recently, the immobilized chitosan-Co complex was described as a catalyst for the enantioselective hydration of 1-octene [81]. Under optimal conditions, namely Co content 0.5 mmolg and 1-octene/Co molar ratio of 50, a 98% yield and 98% ee were obtained and the catalyst was reused five times without loss of activity or enantioselectivity. 

More recently chitosan polymers which are derivatives of chitin materials have evoked interest due to their bioactivity and biodegradability. For example, N-carboxybutyl chitosan has been show to effectively promote wound healing (9). Acetate, and butyrate derivatives of chitosan have decreased blood clotting time significantly (10). 

FU(1), chitosan-5FU(2), a-l,4-polygalactosamine-5FU(3), partially N-acetylated a-l,4-polygalactosamine-5FU(4), hyaluronic acid-5FU(5), dextran-5FU(6), and 6-0-carboxymethyl chitin(CM-chitin)-5FU(7). 

Moreover, chitin-5FU, chitosan-5FU, COS-5FU, a-1,4- polygalactosamine-5FU, partially N-acetylated a-1,4- polygalactosamine-5FU, GOS-5FU, hyaluronic... 

Numerous substituted derivatives of chitin and chitosan are known [67] some important examples are shown in Scheme 10.9. The possibility of forming either anionic (5,7,8,11) or cationic (9,12) derivatives should be noted. The O-carboxymethyl (5) and N-carboxymethyl (11) polymers are of particular interest as they have stronger complex-forming capabilities with metal ions than either unsubstituted chitosan or EDTA [65]. In practice, derivatives formed by substitution via the 2-amino group of chitosan are more common than those substituted via the 6-hydroxy position of the glucopyranose grouping [65]. 

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