Preparation Of Chitosan, Chitosan Derivative Microspheres And Basic Researches As Interventional Therapy Biomaterials

Chitosan, a linear macromolecular biomaterial composes ofβ-(1→4)-linked 2-amino-2-deoxy-D-glucose (GlcN) and 2-acetamido-2-deoxy- D-glucose (GlcNAc), is obtained on an industrial scale by the alkaline deacetylation of chitin. It is a biodegradablely cationic polysaccharide with good physicochemical properties and biocompatible properties. It has been widely used in the field of artifical skin, drug delivery, artifical vessel, gene therapy and cancer therapy. In this paper, the physicochemical properties of chitosan and the microspheres prepared by chitosan and its derivatives have been studied, in order to select an optical microsphere for the further in vivo and clinical researches.Chitosans with different molecular weight (MW) and degree of deacetylation(DD) are prepared using acid degradation and acetylation methods. The protonation constants of chitosans are demonstrated by the modified Henderson-Hasselbalch model (MHHM) and H?gfeldt's three-parameter model (HTPM). The protonation constants pKa of chitosan shows no significial change when the the MW changing from 1,370kDa to 60kDa. The degree of deacetylation shows a great effect on pKa values which is increased from 6.17 to 6.84 with the degree of deacetylation decreasing from 94.6% to 73.3%. Both MHHM and HTPM can fit the experimental data of potentiometric curves very well, but HTPM shows a better agreement.In this paper, a smooth-surface chitosan microsphere (CM) is prepared by emulsion and cross-linked method. ACM is prepared by directly surface acetylation of CM. CMCM is prepared also using emulsion and cross-linked method after carboxylating of chitosan. The morphology of the chitosan microspheres is determined by observation of the samples on an optical microscope or a scanning electron microscope. All microspheres are of well spherical shape with rather smooth...