Jalil R, Nixon J R
Chelsea Department of Pharmacy, King's College London, University of London, UK.
J Microencapsul. 1990 Apr-Jun;7(2):229-44. doi: 10.3109/02652049009021836.
Poly(DL-lactic acid) (DL-PLA, molecular weight 20,500) microcapsules containing phenobarbitone (PB) as a reference core were prepared using a water/oil (W/O) emulsion system. Surface morphology, particle size and 'encapsulation efficiency' of the microcapsules prepared using different preparative variables have been investigated. Buffer pH 9 was used as a dissolution medium to determine the affect of preparative variables on the release rate from these microcapsules. With an increase in temperature of evaporation the microcapsule surface became increasingly irregular and porous, due to deposition of phenobarbitone crystals near the vicinity of the microcapsule surface leading to rapid release of the core. The normalized release rate was found to increase exponentially with an increase in the temperature of evaporation. Microcapsule morphology was also severely affected due to differences in polymer concentration in the disperse phase solvent. With the increase in polymer concentration, the microcapsule surface was found to be increasingly irregular and non-continuous, due to rapid precipitation of the polymer. Increased polymer concentrations also increased mean microcapsule diameter. The release rate increased with the increase in polymer concentration due to surface defects and did not exhibit a straight line correlation. When core loading was very high (e.g. C:P, 2:1 and 1:1), crystals of phenobarbitone appeared at the surface and these caused a very rapid burst effect. However, microcapsules containing a lower phenobarbitone content were found to follow t1/2 dependent release. The encapsulation efficiency was not seriously affected due to variations in temperature of preparation and polymer concentration. However, with the decrease in initial core loading the encapsulation efficiency of microcapsules was found to be reduced.
以苯巴比妥（PB）作为参比核心，采用水/油（W/O）乳液体系制备了聚（DL-乳酸）（DL-PLA，分子量20500）微胶囊。研究了使用不同制备变量制备的微胶囊的表面形态、粒径和“包封率”。使用pH 9的缓冲液作为溶解介质，以确定制备变量对这些微胶囊释放速率的影响。随着蒸发温度的升高，微胶囊表面变得越来越不规则且多孔，这是由于苯巴比妥晶体在微胶囊表面附近沉积，导致核心快速释放。发现归一化释放速率随蒸发温度的升高呈指数增加。由于分散相溶剂中聚合物浓度的差异，微胶囊形态也受到严重影响。随着聚合物浓度的增加，由于聚合物的快速沉淀，微胶囊表面变得越来越不规则且不连续。聚合物浓度的增加也增加了微胶囊的平均直径。由于表面缺陷，释放速率随聚合物浓度的增加而增加，且未呈现直线相关性。当核心载量非常高时（例如C:P为2:1和1:1），苯巴比妥晶体出现在表面，这些导致了非常快速的突释效应。然而，发现含有较低苯巴比妥含量的微胶囊遵循t1/2依赖性释放。制备温度和聚合物浓度的变化对包封率没有严重影响。然而，随着初始核心载量的降低，微胶囊的包封率被发现降低。
