离子凝胶反应法制备壳聚糖/N,O-羧甲基壳聚糖微球

Preparation of Chitosan/N,O-carboxymethyl Chitosan Microspheres by Ionically Cross-linking Method

以一氯乙酸与壳聚糖反应形成N,O-羧甲基壳聚糖两性聚电解质,分光光度法测定其等电点IEP=2.86。以此两性聚电解质与壳聚糖可以在一定条件下形成微球,光学显微镜和电子显微镜测试表明,控制两种聚电解质配比可以制备不同粒径大小的微球,而超声功率对微球粒径的影响较小。红外光谱测试表明微球中N,O-羧甲基壳聚糖羧基以羧酸根形式存在,分光光度与电导法联合测定表明两种聚电解质以离子凝胶作用形成微球,其最佳制备条件为IEP(CM-CHITOSAN)<pH<pKa(CS),在此较宽的pH值范围内微球可稳定存在。

Chitosan microspheres were prepared by ionically cross-linked chitosan with amphoteric N, O- carboxymethyl chitosan（ CM-chitosan）. CM-chitosan with a isoelectric point （IEP） 2.86 was synthesized by chemical reacting chitosan with monochloroacetic acid, and the chemical structure was analyzed by IR and ^13C NMR. By adding CM-chitosan into chitosan solution, microspheres were formed instantaneously, and the structure of microspheres was characterized by IR and microscopy. The observation of optical microscopy, scanning electron microscopy and transmission electron microscopy showed that the ratio of chitosan to CM-chitosan had more influence on morphology and size of the microspheres than ultrasonic power, indicating that the charge action between this two polyelectrolytes were the mechanism of microsphere formation. This mechanism was also confirmed by measurement the change of absorbance and conductivity with pH value of chitosan/CM-chitosan solution, the result also showed that the pH range for microsphere formation is IEP（CM-chitosan） 〈 pH 〈 pKa〈（chitosan）.