Castellanos I J, Carrasquillo K G, López J D, Alvarez M, Griebenow K
Department of Chemistry, University of Puerto Rico, San Juan 00931-3346, USA.
J Pharm Pharmacol. 2001 Feb;53(2):167-78. doi: 10.1211/0022357011775361.
Non-aqueous protocols to encapsulate pharmaceutical proteins into biocompatible polymers have gained much attention because they allow for the minimization of procedure-induced protein structural perturbations. The aim of this study was to determine if these advantages could be extended to a semi-aqueous encapsulation procedure, namely the solid-in-oil-in-water (s/o/w) technique. The model protein bovine serum albumin (BSA) was encapsulated into poly(lactide-co-glycolide) (PLG) microspheres by first suspending lyophilized BSA in methylene chloride containing PLG, followed by emulsification in a 1% aqueous solution of poly(vinyl alcohol). By variation of critical encapsulation parameters (homogenization intensity, BSA:PLG ratio, emulsifier concentration, ratio of organic to aqueous phase) an encapsulation efficiency of > 90% was achieved. The microspheres obtained showed an initial burst release of < 20%, a sustained release over a period of about 19 days, and a cumulative release of at least 90% of the encapsulated BSA. Different release profiles were observed when using different encapsulation protocols. These differences were related to differences in the microsphere erosion observed using scanning electron microscopy. Release of BSA was mainly due to simple diffusion or to both diffusion and microsphere erosion. Fourier-transform infrared studies were conducted to investigate the secondary structure of BSA during the encapsulation. Quantification of the alpha-helix and beta-sheet content as well as of overall structural changes showed that the secondary structure of encapsulated BSA was not more perturbed than in the lyophilized powder used initially. Thus, the encapsulation procedure did not cause detrimental structural perturbations in BSA. In summary, the results demonstrate that the s/o/w technique is an excellent alternative to the water-in-oil-in-water technique, which is still mainly used in the encapsulation of proteins in PLG microspheres.
将药物蛋白封装到生物相容性聚合物中的非水方法备受关注，因为它们能使程序诱导的蛋白质结构扰动降至最低。本研究的目的是确定这些优势是否可扩展至半水封装程序，即水包油包固体（s/o/w）技术。通过首先将冻干的牛血清白蛋白（BSA）悬浮于含聚乳酸-乙醇酸共聚物（PLG）的二氯甲烷中，随后在1%的聚乙烯醇水溶液中乳化，将模型蛋白牛血清白蛋白（BSA）封装到聚乳酸-乙醇酸共聚物（PLG）微球中。通过改变关键封装参数（均质强度、BSA:PLG比例、乳化剂浓度、有机相与水相比例），实现了>90%的封装效率。所得微球的初始突释<20%，在约19天的时间内持续释放，且封装的BSA累积释放至少90%。使用不同的封装方案时观察到不同的释放曲线。这些差异与使用扫描电子显微镜观察到的微球侵蚀差异有关。BSA的释放主要是由于简单扩散或扩散与微球侵蚀两者共同作用。进行了傅里叶变换红外研究以考察封装过程中BSA的二级结构。对α-螺旋和β-折叠含量以及整体结构变化的定量分析表明，封装的BSA的二级结构受到的扰动并不比最初使用的冻干粉更大。因此，封装程序未对BSA造成有害的结构扰动。总之，结果表明s/o/w技术是水包油包水技术的极佳替代方法，水包油包水技术目前仍是将蛋白质封装到PLG微球中时主要使用的方法。
