一种磁性N-羧甲基壳聚糖造影剂的制备及性能研究

采用简单经济（与传统微乳法、热分解法等比较）的方法制备出一种磁性N-羧甲基壳聚糖造影剂。首先对壳聚糖的氨基进行羧甲基化制备N-羧甲基壳聚糖，然后在其链上采用原位生成Fe3O4纳米粒子的方法制备出磁性N-羧甲基壳聚糖，并对其进行了表征及性能的测试。热重分析结果表明：Fe3O4的生成量与N-羧甲基壳聚糖中羧甲基的含量有关，其生成量随着羧甲基含量的增加而增加，但当羧甲基的含量增加到一定程度时，Fe3O4的生成量达到某一峰值。透射电镜结果表明：生成的Fe3O4纳米粒子的粒径约为5-10 nm。磁共振成像结果显示：此磁性N-羧甲基壳聚糖的横向弛豫率为82.82 mmoL/L/s，高于超顺磁性氧化铁作为磁共振成像造影剂时R2需大于62 mmoL/L/s的最低标准，可作为潜在的磁共振成像阴性造影剂。

Preparation and Properties of Magnetic N-carboxymethy Chitosan as Contrast Agent

Magnetic N-carboxymethy chitosan as a kind of potential magnetic resonance imaging contrast agent was synthesized by a simple and economic route (compared with traditional Microemulsion and Thermal Decomposition). N-carboxymethyl chitosan was synthesized by the process of carboxymethylation of chitosan firstly. Then, Fe3O4 nanoparticles were obtained by in-situ reaction in the chains of N-carboxymethyl chitosan. The characterization and performance of magnetic N-carboxymethy chitosan were tested. The result of TGA showed that the generation amounts of Fe3O4 were related to the contents of catboxymethyl groups in N-carboxymethy chitosan. It increased unceasingly along with the increase of the contents of catboxymethyl groups. But the generation amounts of Fe3O4 reach a peak when the contents of catboxymethyl groups increased to some degree. The result of TEM presented that the average grain size of the Fe3O4 nanoparticles was about 5-10 nm. The MRI depicted that the magnetic N-carboxymethy chitosan provided high transversal relaxation rate with 82.82 mmoL/L/s. It was higher than the minimum standard of R2 being over 62 mmoL/L/s when superparamagnetic iron oxide as magnetic resonance imaging contrast agent. The magnetic N-carboxymethy chitosan could be used as a kind of potential magnetic resonance imaging negative contrast agent.