Carboxymethyl-chitin-hydroxyapatite

Sodium carboxymethyl chitin and phosphoryl chitin had most evident influences on the crystallization of calcium phosphate from supersaturated solutions. They potently inhibited the growth of hydroxyapatite and retarded the rate of spontaneous calcium phosphate precipitation. These chitin derivatives were incorporated into the precipitate and influenced both the phase and morphology of the calcium phosphate formed (flaky precipitate resembling octacalcium phosphate instead of spherical clusters in the absence of polysaccharide) [175]. 

There are several reports on the coating of bone-like hydroxyapatite onto natural polymer substrates. Kawashita et at. [57] reported that carboxymethylated chitin and gellan gum gels, which have carboxyl groups, can form hydroxyapatite on their surfaces in SBF if they are treated with a saturated Ca(OH)2 solution in advance, while curdlan gel, which has no carboxyl group, does not form hydroxyapatite in SBF, even if it is treated with Ca(OH)2 solution. These results support the hypothesis that carboxyl groups induce hydroxyapatite nucleation. Kokubo et at. [58,59] reported that non-woven fabrics of carboxymethylated chitin and alginate fibers also form hydroxyapatite on their surfaces in SBF if they are treated with Ca(OH)2 solution. 

There are several synthetic composite materials and their applications in tissue engineering are versatile. For instance, in one study a composite of carboxymethyl-chitin (CM-chitin) with hydroxyapatite (HAp) was examined for its ability to repair bone in animals. New bone formation of CM-chitin-HAp composite was superior to that of CM-chitin, HAp, and control (Tokura and Tamura, 2001). The porous CM-chitin-HAp composite was also a functional... 

Uda H., Sugawara Y., and Nakasu M. 2006. Experimental studies on hydroxyapatite powder-carboxymethyl chitin composite Injectable material for bone aagpaentarion.J PlastReconstrAesthet Surg 59 188-196. 

---