El-Gibaly I, Safwat S M, Ahmed M O
Pharmaceutics Department, Assiut University, Egypt.
J Microencapsul. 1996 Jan-Feb;13(1):67-87. doi: 10.3109/02652049609006804.
Sustained release cellulose acetate butyrate (CAB)-polystyrene (PS) microcapsules containing ketoprofen (a non-steroidal anti-inflammatory drug) were prepared adopting the modified W/O/W complex emulsion technique. The effect of polystyrene concentration and core/coat ratio on the yield, geometric mean particle diameter, dg, size distribution, drug loading as well as release and surface characteristics of the microcapsules was investigated. The results obtained revealed that polystyrene utilization as a wall material plays a dominant role in the manufacturing process. A particular composition of 92 center dot 5: 7 center dot 5 (%) of CAB to PS was found to improve greatly the microcapsule yield and maximize the drug loading. In most cases, the encapsulation efficiencies increased with increasing microcapsule size and theoretical drug loading. Kinetic analysis of the data shows that the drug release process from CAB microcapsules followed Higuchi model (a diffusion-controlled model for a planar matrix), whereas the release behaviour conforms with Baker and Lonsdale model (a diffusion-controlled model for a spherical matrix) for CAB-PS microcapsules. The preparation of free films of CAB and CAB-PS was described for comparison. The effect of processing parameters (polystyrene concentration, total polymers concentration and permeant concentration) on the permeation of ketoprofen through the polymeric films was discussed. The results demonstrated that ketoprofen permeation through the films and microcapsules could be controlled by modifying the CAB-PS ratio in the polymer matrices. The permeability constants lowered with increasing total polymers concentration up to 5% and were proportional to permeant concentration. To compare the kinetics of drug release from polymeric films with those of microcapsules, ketoprofen was incorporated at different concentrations within CAB-PS cast films. These films exhibited sustained release of the drug (t0 center dot 5; 58-146 h). Release rates were found to agree with the Baker and Lonsdale model, previously suggested for ketoprofen release from CAB-PS microcapsules.
采用改进的W/O/W复合乳液技术制备了含有酮洛芬（一种非甾体抗炎药）的缓释醋酸丁酸纤维素（CAB）-聚苯乙烯（PS）微胶囊。研究了聚苯乙烯浓度和核/壳比对微胶囊的产率、几何平均粒径、dg、粒径分布、载药量以及释放和表面特性的影响。所得结果表明，聚苯乙烯作为壁材在制备过程中起主导作用。发现CAB与PS的特定组成为92.5:7.5（%）时，可大大提高微胶囊产率并使载药量最大化。在大多数情况下，包封效率随微胶囊尺寸和理论载药量的增加而提高。数据的动力学分析表明，酮洛芬从CAB微胶囊中的释放过程遵循Higuchi模型（平面基质的扩散控制模型），而对于CAB-PS微胶囊，其释放行为符合Baker和Lonsdale模型（球形基质的扩散控制模型）。描述了制备CAB和CAB-PS的游离膜以作比较。讨论了加工参数（聚苯乙烯浓度、总聚合物浓度和渗透剂浓度）对酮洛芬透过聚合物膜的渗透的影响。结果表明，通过改变聚合物基质中CAB-PS的比例，可以控制酮洛芬透过膜和微胶囊的渗透。渗透率常数在总聚合物浓度增加至5%之前降低，并与渗透剂浓度成正比。为了比较聚合物膜和微胶囊的药物释放动力学，将不同浓度的酮洛芬掺入CAB-PS流延膜中。这些膜表现出药物的缓释（t0.5；58 - 146小时）。发现释放速率与先前提出的用于酮洛芬从CAB-PS微胶囊中释放的Baker和Lonsdale模型一致。
