Phosphorylated chitosan

Li QL, Wu MY, Tang LL et al (2008) Bioactivity of a novel nano-composite of hydroxyapatite and chitosan-phosphorylated chitosan polyelectrolyte complex. J Bioact Compat Polym... 

Superficially phosphorylated chitosan membranes prepared from the reaction of orthophosphoric acid and urea in DMF, showed ionic conductivity about one order of magnitude larger compared to the unmodified chitosan membranes. The crystallinity of the phosphorylated chitosan membranes and the corresponding swelling indices changed pronouncedly, but these membranes did not lose either tensile strength or thermal stability [234]. 

The biological significance of chitosan biomaterials in the hiunan body depends largely on the actions that certain hydrolases exert on them. The resulting chitoohgomers stimulate various cells, while the released monomers are phosphorylated and incorporated into hyaluronan, keratan sulphate and chondroitin sulphate, components of the intracellular matrix and connective tissue [348]. 

Gastrointestinal toxicity and myelotoxicity are caused by the 5-FU after its phosphorylation in the digestive tract and bone marrow tissue. To clarify whether chitosan enhances the antitumor activity of 5-FU and prevents the side effects induced by 5-FU, we examined the antitumor activity and side effects, such as myelotoxicity, immimocompetent organ toxicity, and gastrointestinal toxicity of combined treatment with chitosan and 5-FU in sarcoma 180-beaiing mice. 

Phosphorylated chitosan (P-C) was prepared and used as an additive for calcium phosphate cement (CPC) to improve its mechanical properties and particularly its compressive strength. The CPC/P-C system was proposed for use as a bone filler. 

Fernandez, C. Ausar, S.F. Badini, R.G. Castagna, L.F. Bianco, I.D. Beltramo, D.M. An FTIR spectroscopy study of the interaction between alpha s-casein-bound phosphoryl groups and chitosan. Int. Dairy J. 2003,13 (11), 897-901. 

Incorporation of chitosan as well as increasing its concentration in the finishing formulation improved the durability and flame retardancy property. -The enhancement in the aforementioned properties was attributed to its synergetic effects as well as to the enhancement in the extent of phosphorylation... 

Metal Ion Adsorption onto Chitin and Chitosan Grafted with Different Phosphorylated Groups... 

Beside kinetic and thermodynamic studies, equilibrium studies were done in order to determine the influence of the initial concentration of the metals ions upon the efficiency of the adsorption process and in order to determine the maximum adsorption capacities of the phosphorylated chitin and chitosan materials in the removal process of various metal ions from aqueous solutions. The experimental equilibrium data were fitted to the Langmuir and Freundlich isotherms. In all the cases the experimental results showed a better fit to the Langmuir than to the Freundlich equation. The maximum adsorption capacities obtained from the Langmuir isotherm plot in the... 

The maximum adsorption capacities of various phosphorylated chitins and chitosans in the removal process of different metal ions from aqueous solutions. 

Jayakumar, R., Reis, R.L., and J.F. Mano. 2006. Chemistry and applications of phosphorylated chitin and chitosan. E-Polymers 35 1-16. 

As stated above, the present biomedical products utilize only the base materials. Chanical derivatization is the way forward to realize the fuU potential of chitin and chitosan (Alves and Mano 2008). The well-known C6-earboxymethyl-chitin and ehitosan would be an ideal starting place (Raimunda and Campana-Filho 2008). However, this work again started with the alkali-chitin process that is known to be ineffieient and associated with inhomogeneity eoncems. Another recent work is the preparation of Af-hydroxyacryl-chitosan that utilizes ehitosan from a commercial source without further treatment (Maa et al. 2008). Phosphorylated chitins and ehitosans are another example of chemical derivatization that yields soluble compounds (Jayakumar et al. 2008). 

Direct phosphorylation of chitin and chitosan has been reported but the degree of phosphorylation is uncertain. Such products are polyelectrolytes and may have medical or cosmetic applications. 

Phosphorylated chitosans (12.255a) may be used for chelating alkaline earth cations or stabilising bleaching agents. Chitins of type (12.255b) are reported to improve the textile properties of co-spun alginate fibres [21]. 

Oxidized hyaluronic acid was coupled with chitosan to form porous scaffolds after freeze drying. The proportion of porosity of the freeze-dried chitosan-hyaluronic acid dialdehyde composite (CHDA) gels enhanced with augmentation in oxidation. Fibroblast cells seeded onto CHDA porous scaffold adhered, proliferated and offered extracellular matrix components on the scaffold [99]. Chondrocytes encapsulated in CHDA gels retained their viability and specific phenotypic features. The gel material is therefore projected as a scaffold and encapsulated material for tissue engineering applications. Films of hyaluronan (HA) and a phosphoryl choline-modified chitosan (PC-CH) were constructed by the electrolyte multilayer (PEM)... 

Varma H.K., Yokogawa Y., Espinosa F.F., Kawamoto Y., Nishizawa K., Nagata F., Kameyama T. Porous calcium phosphate coating over phosphorylated chitosan film by a biomimetic method. Biomaterials 1999 20 879-884... 

Figure 1. Some chemical reactions for the molecular design of chitin and chitosan. [1], chitin [2], chitosan [3], alkoxide (alkali chitin) [4] salt (carboxyl-ate) [5], chelation [6] Schiff s base [7], N-acylation [8], halogenation [9], N-alkylation [10], 0-alkylation [11], oxido-deaminative cleavage [12], 0-acylation [13], sulfonation [14], sulfation, phosphorylation and nitration.

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