Acylation, chitosan

Chitosan is the main structural component of crab and shrimp shells. Chitosan contains both reactive amino and hydroxyl groups, which can be used to chemically alter its properties under mild reaction conditions. Al-acyl chitosans were already reported as blood-compatible materials. UV irradiation grafting technique was utilized to introduce obutyrylchitosan (OBCS) onto the grafted SR film in the presence of the photosensitive heterobifunctional cross-linking agent. The platelet adhesion test revealed that films grafted on OBCS show excellent antiplatelet adhesion. 

Lee KY, Ha WS, Park WH (1995) Blood compatibility and biodegradability of partially N-acylated chitosan derivatives. Biomaterials 16(16) 1211—1216... 

A variety of acylation reactions of chitosan are possible by using different acyl-ating agents, such as aliphatic carboxylic acid chlorides (hexanoyl, dodecanoyl and tetradecanoyl chlorides), cyclic anhydrides and cyclic esters. The acylation reaction is not regioselective. When IV,0-acylated chitosans were prepared with acyl chlorides in methanesulfonic acid [62-63], the derivatives of 4-chlorobutyl and decanoyl chlorides showed higher fungidal activities than chitosan [64]. Selectively N-acylated chitosan have been obtained by Lee et al. [65-66] with butanoic, hexanoic and benzoic anhydride under homogeneous conditions... 

It has been reported that quaternary ammonium salt of chitosan exhibits good antibacterial activities, for example, diethylmethylchitosan chloride showed higher antibacterial activity than chitosan. Novel N,0-acyl chitosan... 

Hirano, S. and Noishiki, Y, The blood compatibility of chitosan and N-acyl-chitosans, /. Biomed. Mater. Res., 19, 413, 1984. 

KytoCel by Aspen, reported by Aspen (2014), is a highly absorbent dressing composed of natural, biodegradable acylated chitosan fibres, which bond with wound exudate to form a clear gel that locks in fluid, absorbs pathogens, and is conformable to the wound bed. 

Wu, Y, Seo, T., Maeda, S., Sasaki, T., Irie, S., and Sakurai, K. (2005). Circular dichroism induced by the helical conformations of acylated chitosan derivatives bearing cinnamate chromophores, /. Polym. Sci. Polym. Phys., 43,1354-1364. 

Zong, Z., Kimura, Y, Takahashi, M., and Yamane, H. (2000). Characterization of chemical and solid state structures of acylated chitosans. Polymer, 41, 899-906. 

Electrostatic polyelectrolyte complexes (PEC) are mentioned in the literature involving chitosan and synthetic or natural polymers such as PAA and CMC [155,156], xanthan, carrageenan, alginate [157-162], pectin [163,164], heparin, hyaluronan (HA) [165-169], sulfated cellulose, dextran sulfate, or N-acylated chitosan/chondroitin sulfate. Many systems were cited in the literature [2, 170]. The electrostatic interaction was discussed in relation with the stiffness of the backbone and the nature of the ionic groups involved. Especially, with alginate or HA, a pH-dependent complex is formed, whose stability depends on the ionic concentration. The complex formation was investigated in dilute solution by potentiometry (pH) and conductivity to determine the fraction of ion pairs (-COO + NH3 —) formed in dependence of the experimental conditions [164, 166]. 

A quaternized derivative, iV-(hydro)ypropyl)trimethylammonium chitosan chloride (HTCC), obtained by reacting chitosan with glycidyl-trimethylammonium chloride, has been found to be mucoadhesive and was successfully used for oral insulin delivery.For acylated chitosan, medium-chain fatty acids such as capiylate (C8), caprate (CIO) and laurate (C12) were able to enhance the paracellular permeability of hydrophilic drugs. 

Hirano S., Mizutani C., Yamaguchi R., Miura O., Formation of the polyelectrolyte complexes of some acidic gly-cosaminoglycans with partially V-acylated chitosans. Biopolymers, 17(3), 1978, 805-810. 

Tien, C. L., Lacroix, M., Szabo, P. I. et al. 2003. N-acylated chitosan Hydrophobic matrices for controlled dmg release. 7. Controlled Release 93 1-13. 

Acylated Chitosan Particles for Drug Delivery Applications An Overview... 

Acylated chitosan would reduce the hydration of the matrix and the network is stabilized because of its hydrophobic interaction. Acyl chitosan with longer acyl chain length ( ,< ) remains... 

In 1987, Hirano et al. prepared sulfated A-fatty acyl chitosan for improving the solubility of acy-lated chitosan. Derivatives with acyl chain length less than C14 were found to be soluble in water but that with palmitoyl group was slightly soluble due to the hydrophobic property of the acyl group. 

Hirano, S. and Kitagawa, S. 1987. Water soluble sulphated derivatives of N-fatty acyl chitosan. Agric. Biol. Chem. 51 1703-1704. 

Hirano, S., Yamaguchi, Y, and Kamiya, M. 2003. Water-soluble N-(n-Fatty acyl) chitosans. Macromol. Biosci. 3 629. 

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