Chitosan synthesis

M. racemosus Rate of chitin and chitosan synthesis accelerated in mycelial cells 132... 

Davis LL, Bartnicki-Garcia S (1984) Chitosan synthesis by the tandem action of chitin synthetase and chitin deacetylase from Mucor rouxii. Biochemistry 23 1065-1073... 

Sashiwa, H., Norioki, K., Atsuyoshi, N., Einosuke, M., Noboru, Y., and Sei-ichi, A. (2002). Chemical modification of chitosan Synthesis of water-soluble chitosan derivatives by simple acetylation. Biomacromolecules, 3(5), 1126-1128. 

Crystallinity, DDA, the distribution of the acetyl groups, and molecular weight are among the main factors that influence the solubility of chitosan others include deacetylation conditions during chitosan synthesis such as the temperature, alkaline concentration, and ratio of chitin to alkali solution. Reducing the crystallinity by partial reacetylation or physical disruption by the addition of urea and guanidine hydrochloride improves the solubility of chitosan [65,66]. In addition, the solubility of chitosan in acidic solution increases with the decrease of the molecular weight [67]. 

Sakairi, N., Nishi, N. and Tokura, S. (1999) Cyclodextrin-linked chitosan synthesis and inclusion complexation ability, in Polysaccharide Applications Cosmetics and Pharmaceuticals (eds M.A. El-Nokaly and H.A. Soini), American Chemical Society, Washington, pp. 68-84. 

Tan Y, Liu CG. Self-aggregated nanoparticles from hnoleic acid modified carboxymethyl chitosan Synthesis, characterization and application in vitro. Colloids Surf B Biointerfaces. 2009 69(2) 178-82. 

Hayatsu, H. Pigment molecules linked to polymer support blue rayon, blue chitin, and green chitosan-synthesis and applications. Yakugaku Zasshi 2000, 120, 534-547 Chem. Abstr. 2000, 133, 160755. 

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]. 

Chitosan freeze-dried fleeces support chondrocyte attachment and synthesis of extracellular matrix [344]. Chitosan was used to assist the spontaneous tissue repair of the meniscus [345]. The repair of the cartilage and the prevention of its degradation in osteoarthritis is, however, possible with the association of glucosamine sulfate salt and chondroitine sulfate, the latter being particularly effective [346]. 

The NMR spectra have shown the formation of Schiff base as an intermediate product in the synthesis of the fully N-deacetylated oligomers from chitosan.32 The mechanism of the Schiff base reaction leading to chain cleavage and formation of 5-hydroxymethyl-2-furfural has been proposed. 

Besides the previously mentioned collagen, a wide variety of natural polymers have been involved in the synthesis of bio-nanohybrid materials with potential application in bone repair and dental prostheses. For instance, some recent examples refer to bionanocomposites based on the combination of HAP with alginate [96,97], chitosan [98,99], bovine serum albumin (BSA) [100], sodium caseinate [101], hyaluronic acid [102], silk fibroin [103,104], silk sericin [105], or polylactic add (PLA) [106,107]. These examples illustrate the increasing interest in the subject of HAP-based biohybrid materials, which has led to almost 400 articles appeared in scientific journals in 2006 alone. 

Chitosan gels are chemically stable in alkaline solutions and are thermally stable until 200°C [5], These conditions are compatible with the synthesis field of most aluminium-rich zeolites and allow to prepare composite materials by several methods. 

Preparation of chitosan-zeolite composites by in-situ zeolite synthesis... 

A preformed chitosan-silica composite with 60% weight inorganic part [7] is used as the source of silica for the zeolite synthesis. An alkaline solution of sodium aluminate (Na 2.1 M, Al 1 M) was used in three methods of preparation (A) beads of the chitosan-silica composite were stirred overnight in the aluminate solution, extracted and submitted to a hydrothermal treatment at 80 °C during 48h (B) beads of the chitosan-silica composite were immersed in the aluminate solution and the system underwent a hydrothermal treatment at 80 °C for 48h (C) beads of the chitosan-silica composite were stirred overnight in the aluminate solution, extracted, dried at 80 °C and exposed to water vapour at 80°C during 48h. 

Figure 3. (lefthand) X-ray powder diffraction pattern and (righthand) scanning electron micrograph of zeolite A-chitosan composite resulting from in-situ synthesis of the zeolite... 

Figure 4. (a) Adsorption-desorption isotherms of N2 at -196°C of 80°C-outgassed (empty squares) chitosan, (filled trangles) zeolite X-chitosan composite from in-situ zeolite synthesis and (empty triangles) zeolite Y-chitosan composite from encapsulation of the zeolite in the gelling chitosan. (b) Scanning electron micrographs of a calcined zeolite-chitosan bead prepared by zeolitisation of a silica-chitosan composite. 

Similar structures were later employed to create original dendronized polymers 485 and 486, based on a chitosan backbone and using such sialodendrons as 484 (Fig. 50).328 Chitosan itself is nontoxic, biodegradable, and has widespread biological activities, but major intrinsic drawbacks such as low solubility in both organic solvents and water have hampered its development as a bioactive polymer. Thus, the synthesis of water-soluble... 

SCHEME 56. Synthesis of dendronized chitosan-sialic acid hybrids.407-409... 

H. Sashiwa, Y. Shigemasa, and R. Roy, Chemical modification of chitosan. 10.1. Synthesis of dendronized chitosan-sialic acid acid hybrid using convergent grafting of preassembled dendrons built on gallic acid and tri(ethylene glycol) backbone, Macromolecules, 34 (2001) 3905-3909. 

PVA/chitosan blend membranes can be applied for the synthesis of monoglyceride, when used as a membrane enzyme reactor [277]. 

Monoglyceride (MG) is one of the most important emulsifiers in food and pharmaceutical industries [280], MG is industrially produced by trans-esterification of fats and oils at high temperature with alkaline catalyst. The synthesis of MG by hydrolysis or glycerolysis of triglyceride (TG) with immobilized lipase attracted attention recently, because it has mild reaction conditions and avoids formation of side products. Silica and celite are often used as immobilization carriers [281], But the immobilized lipase particles are difficult to reuse due to adsorption of glycerol on this carriers [282], PVA/chitosan composite membrane reactor can be used for enzymatic processing of fats and oils. The immobilized activity of lipase was 2.64 IU/cm2 with a recovery of 24%. The membrane reactor was used in a two-phase system reaction to synthesize monoglyceride (MG) by hydrolysis of palm oil, which was reused for at least nine batches with yield of 32-50%. 

Aiedeh, K., and Taha, M.O., Synthesis of chitosan succinate and chitosan phthalate and their evaluation as suggested matrices in orall administered, colon-specific drug delivery systems, Arch. Pharm (Weinheim), 332 103-107 (1999). 

Bernkop-Schnurch A., and Krajicek, M.E., Mucoadhesive polymers as platforms for peroral peptide delivery and absorption synthesis and evaluation of different chitosan-EDTA conjugates, J. Control. Rel., 50 215-223 (1998). 

Chitosan-stabilized Au NPs can be selectively synthesized on surfaces like poly (dimethylsiloxane) (PDMS) films using HAuC14 as precursor. The computation of surface plasmon bands (SPBs) based on Mie theory and experimental results indicates that the particles are partially coated by chitosan. The proposed mechanism implies that chitosan acts as a reducing/stabilizing agent. Furthermore, PDMS films patterned with chitosan could induce localized synthesis of gold nanoparticles in regions capped with chitosan only [110]. 

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