Jalil R, Nixon J R
Chelsea Department of Pharmacy, Kings College London, University of London, UK.
J Microencapsul. 1990 Jan-Mar;7(1):41-52. doi: 10.3109/02652049009028422.
Poly (L-lactic acid) microcapsules were prepared using an emulsification and organic solvent evaporation technique (w/o system) with phenobarbitone as a reference core. Three polymers of different molecular weight (61,300; 43,200, 2400), were used to prepare different core loaded microcapsules. Microcapsule size increased with increase in polymer molecular weight. Microcapsule size was also found to increase with increase in core loading with the two high molecular weight polymers, whilst the low molecular weight polymer tended to aggregate to form larger microcapsules than expected. The calculated microcapsule density was found to decrease with an increase in the polymer molecular weight and core loading. 'Encapsulation efficiency' was reduced with the decrease in initial theoretical core loading. However, the phenobarbitone content of the microcapsules was not affected by the difference in polymer molecular weight. Significant morphological differences were observed due to variations in the polymer molecular weight. The two high molecular weight polymers were found to produce non-uniform, porous microcapsules, whilst low molecular weight polymer formed a uniform non-porous surface when core loading was low. With increasing core loading, an increasing number of phenobarbitone crystals were observed on the surface and microcapsules became increasingly porous. This was more evident after release of the drug. Differential scanning calorimetry of the microcapsules showed thermal events for both the polymer and phenobarbitone.
采用乳化和有机溶剂蒸发技术（水包油体系），以苯巴比妥为参比包芯物制备聚（L-乳酸）微胶囊。使用三种不同分子量（61300、43200、2400）的聚合物制备不同包芯量的微胶囊。微胶囊尺寸随聚合物分子量的增加而增大。还发现，对于两种高分子量聚合物，微胶囊尺寸随包芯量的增加而增大，而低分子量聚合物倾向于聚集形成比预期更大的微胶囊。计算得出微胶囊密度随聚合物分子量和包芯量的增加而降低。“包封率”随初始理论包芯量的降低而降低。然而，微胶囊中苯巴比妥的含量不受聚合物分子量差异的影响。由于聚合物分子量的变化，观察到显著的形态差异。发现两种高分子量聚合物产生不均匀的多孔微胶囊，而低分子量聚合物在包芯量较低时形成均匀的无孔表面。随着包芯量的增加，在表面观察到越来越多的苯巴比妥晶体，微胶囊的孔隙率也越来越高。药物释放后这种现象更加明显。微胶囊的差示扫描量热法显示了聚合物和苯巴比妥的热事件。
