壳聚糖微球/小牛松质骨支架复合缓释体系的制备及体外生物活性评价

目的：通过乳液交联法合成壳聚糖微球并负载骨形态发生蛋白（bone morphogenetic protein-2，BMP-2），再将其复合于脱细胞基质的小牛松质骨支架，制备壳聚糖微球/小牛松质骨支架复合缓释体系。方法： 使用红外光谱仪、扫描电镜对合成的复合缓释系统进行结构表征和形貌观察，并对微球的包封率和载药量进行检测。用动态浸泡的方法来检测BMP-2的体外释放特征，通过体外检测复合体系的细胞毒性和对细胞增殖的影响。结果： 壳聚糖发生了交联并成功包载了BMP-2，微球平均直径为5.982 μm，表面光滑，且成功负载于小牛松质骨支架，形成了新型的微球/支架药物缓释体系。缓释数据表明，5 mg微球在体外释放21 d，BMP-2逐渐释放，第21天时浓度仍达到（239.1±20.0） mg/L。体外测试表明，该缓释体系有利于小鼠前成骨细胞MC3T3-E1的生长，促进向成骨方向分化。结论： 壳聚糖微球/小牛松质骨支架复合缓释体系实现了BMP 2的生物学功能及其在骨修复部位的持续、缓慢释放，为骨组织缺损的修复治疗及骨组织工程支架材料的选择提供了依据。

Synthesis and in vitro characterization of chitosan microspheres/ceramic bovine bone composite scaffold

Objective：The chitosan microspheres encapsulated with bone morphogenetic protein-2 (BMP-2) were prepared by the emulsion cross-linking method. Then the chitosan microspheres were loaded in the ceramic bovine bone (CBB) to achieve the drug delivery system. Methods: The chemical structure and surface morphology of the drug delivery system were investigated by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) observation. Characterization preserved the loading capacity and encapsulation efficiency of the BMP-2. The dynamic immersion method was used to examine the in vitro release characteristic of BMP-2. Results: The chitosan microspheres were successfully encapsulated BMP-2 by cross-linking method. The microspheres were micron-sized (5.982 μm) and spherical in shape with smooth surface morphology. From the release experiments, it was found that 5 mg chitosan/BMP-2 soaked for 21 days with a gradual release of BMP-2. The concentration of BMP-2 was (239.1±20.0) mg/L on Day 21. The in vitro experiment showed that this novel drug delivery system could accelerate MC3T3-E1 cells proliferation and osteogenic differentiation. Conclusion: The drug delivery system achieves the biological function of BMP-2 and sustaining slow release in bone repair parts. Also it can provide the basis for repair of bone tissue defect treatment and the selection of bone tissue engineering scaffolds.