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PREPARATION OF CARBOXYMETHYLCHITIN AND STUDIES ON ITS PROPERTIES

Objective To prepare carboxymethylchitin and study its properties. Methods Chitin was prepared from fresh shrimp shells and then carboxymethylchitin was prepared by the methods of alkalization and etherification as well as by the purification technique. The deacetylation degree of carboxymethylchitin was determined by the doublejump potentiometric titration method; the substitution degree was determined by the element analysis method; the carboxymethyl substitution position was analyzed by the Fourier transform infrared spectroscopy apparatus and the nuclear magnetic resonance spectroscopy apparatus; the relative molecular weight and its polydispersity were determined by the gel permeation chromatography with the multiple angle laser light scattering detection; the biological properties were tested according to the GB/T 16886 biological evaluation on medical devices. Results Carboxymethylchitin could be prepared by alkalization and etherification from chitin which was prepared from fresh shrimp shells by decalcification and deproteinization. The deacetylation degree of carboxymethylchitin was 13.76% according to the doublejump potentiometric titration; the degrees of deacetylation and substitution were 14.53% and 1.239 0 respectively according to the element analysis. The IR spectrum showed that the substitutive position was N,O-substitution, and the 13C-NMR spectrum showed that substitutive position of carboxymethylchitin was mostly primary substitution of 6-OH, and according to the substitutive proportion, the substitutive turns were in the following decreasing order: 6-OH, NH2, and 3-OH. The weightaveraged and the numberaveraged molecular weights and polydispersity were 6.25×105, 5.60×105 and 1.22, respectively. The results from the biological property test showed that carboxymethylchitin was a biomaterial that was sterile, pyrogen-free, acute toxicity-free, cytotoxicity-free, intracutaneous irritationfree, skin sensitization-free and biomaterial genotoxicity-free, with no side or adverse effects on the related tissues after implantation into the human body. Conclusion Carboxymethylchitin prepared from chitin by alkalization and etherification is amacromolecule biomaterial that has a low degree of deacetylation, a high degreeof substitution, and a good biocompatibility.