微球中聚乳酸羟基乙酸共聚物浓度与微球结构、释药、降解的关系研究

Study on the Relationship among the PLGA Copolymers Concentration and the Structure,Release and Degradation of Microspheres

目的:研究微球中聚乳酸羟基乙酸共聚物(PLGA)浓度与微球结构、释药、降解的关系。方法:以牛血清白蛋白(BSA)为药物,采用复乳法制备PLGA浓度分别为10%、15%、20%的BSA-PLGA微球,以包封率、载药量、粒径为指标考察PLGA浓度对3种微球性质的影响;采用扫描电子显微镜观察3种微球和降解40 d内的外观和内部形态;使用荧光蛋白-异硫氰酸荧光素牛血清白蛋白代替BSA作为模型药物制备PLGA微球,并采用激光共聚焦显微镜观察荧光蛋白在微球骨架内的分布情况;采用BCA法考察3种微球的体外释药情况;采用压汞仪考察降解28 d内20%PLGA所制微球的孔径、孔隙率、截面孔隙率的变化;采用凝胶渗透色谱法检测10%、20%PLGA所制微球降解28 d内分子质量及其降解模型拟合。结果:与10%、15%PLGA所制微球比较,20%PLGA所制微球的包封率[(81.96±1.84)%]和粒径[(139.50±0.21)μm]最大,载药量[(7.28±0.45)%]最低,截面孔隙率[(32.35±1.98)%]和孔径[(12.43±0.14)μm]最小,释药突释率最低,40 d内的释放速率相对较慢,降解后截面孔隙率最大,降解均遵循假一级模式(r2=0.065 3)。结论:在考察范围内,随着PLGA浓度的增加,微球的结构更致密,释药更平稳,降解更易形成中空结构。

OBJECTIVE： To study the relationship among PLGA copolymers concentration and the structure, release and degra- dation of microspheres. METHODS： With bovine serum albumin （BSA） as model drug; W/O/W solvent evaporation method was conducted to prepare BSA-PLGA microspheres with the PLGA concentration of 10%, 15% and 20% ; encapsulation efficiency, drug-loading amount and particle size were used to investigate the effect of PLGA concentration on microspheres property; SEM was used to observe the external and internal forms of 3 microspheres and within 40 d degradation; The fluorescent protein the albu- min-fluorescein isothiocyanate conjugate was taken as model drug instead of BSA to prepare PLGA microspheres, and confocal la- ser scanning microscope was utilized to observe the fluorescent protein distribution within the microsphere skeleton. BCA was used to study the in vitro release; mercury porosimeter was used to study the changes of the pore size, porosity and surface porosity of microspheres prepared with 20% PLGA within 28 d degradation; gel permeation chromatography was used to detect the molecular mass and its degradation model fit of microspheres prepared with 10% and 20% PLGA within 28 d degradation. RESULTS： Com- pared with the microspheres prepared with 10% and 15% PLGA, microspheres prepared with 20% PLGA had the highest encapsu- lation efficiency [（81.96 ± 1.84）%] and particle size [（139.50 ± 0.21） μm], lowest drug-loading amount [（7.28 ± 0.45）%], surface porosity [（32.35 ± 1.98）%], pore size [（12.43 ± 0.14） μm] and release burst rate, which released more slowly within 40 d and had largest surface porosity after degradation; the degradation followed pseudo-first order kinetics （r^2=0.065 3）. CONCLUSIONS： Within the range of the investigation, with the increasing of PLGA concentration, the microspheres have closer structure and more stable release. The degradation is easier to form a hollow structure.