A pilot study of freeze drying of poly(epsilon-caprolactone) nanocapsules stabilized by poly(vinyl alcohol): Formulation and process optimization
A pilot study of freeze drying of poly(epsilon-caprolactone) nanocapsules stabilized by poly(vinyl alcohol): Formulation and process optimization
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DOI：
10.1016/j.ijpharm.2005.10.003
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发表时间：
2006-02-17
影响因子：
5.8
通讯作者：
Fessi, H
中科院分区：
文献类型：
--
作者：
Abdelwahed, W;Degobert, G;Fessi, H
在水性悬浮液中使用聚合物纳米颗粒的常见限制是由于它们在长时间保存时的差的化学和物理稳定性。因此，冷冻干燥这些胶体系统是实现长期稳定性的替代方法。纳米胶囊具有薄且易碎的壳结构，其可能无法抵抗这种过程的应力。为研究聚己内酯纳米胶囊（PCL NC）的冻干稳定性，采用乳化扩散法制备了聚己内酯纳米胶囊（PCL NC），并以聚乙烯醇（PVA）为稳定剂，对其冻干过程进行了研究。在整个冻融研究中测试了不同的参数，包括PVA和PCL浓度、冷却速率、冷冻保护剂浓度、包封油的性质和NC纯化。另一方面，纳米胶囊在纯化之前和之后都被冷冻干燥。通过粒度测定、崩解温度、T-g（'）测定、扫描电镜观察、环境扫描电镜成像和残留湿度定量等方法对冻干纯化PCL NC进行表征。结果表明，当PVA稳定剂浓度为5%时，PCL NC可以在不加保护剂的情况下进行冷冻干燥，而对于纯化NC，加入5%的保护剂对NC的稳定性是必要的。冷冻保护剂的类型几乎可以忽略不计的影响，冷冻干燥纳米胶囊的大小和再水化。退火过程可以加速升华，同时保持纳米胶囊尺寸不变。(c)2005年由Elsevier B. V.出版
A common limitation of using polymeric nanoparticles in aqueous suspension is due to their poor chemical and physical stability when conserved for a long time. Therefore, freeze drying of these colloidal systems is an alternative method to achieve long-term stability. Nanocapsules have thin and fragile shell structure, which may not resist to the stress of such process. The aim of this study is to investigate the formulation and process parameters in order to ensure the stability of polycaprolactone nanocapsules (PCL NC) by freeze drying.In this paper, we studied the freeze drying of PCL NC prepared by the emulsion-diffusion method and stabilized by poly(vinyl alcohol) (PVA). Different parameters have been tested throughout the freeze-thawing study including PVA and PCL concentration, cooling rate, cryoprotectant concentrations, nature of encapsulated oil and NC purification. On the other hand, nanocapsules have been freeze dried both before and after purification. Freeze dried purified PCL NC were characterized by particle size measurement, collapse temperature, T-g(') determination, scanning electron microscope observation, environmental scanning electron microscope imaging and residual humidity quantification. Finally, the effect of annealing on the NC stability and the sublimation rate has been well explored.The results suggest that PCL NC could be freeze dried without a cryoprotectant if the concentration of PVA stabilizer is sufficient (5%), while for the purified NC the addition of 5% of cryoprotectant seems to be necessary to ensure the stability of NC. The type of cryoprotectants had practically negligible effects on the size and the rehydration of freeze dried nanocapsules. The annealing process could accelerate the sublimation with the conservation of nanocapsules size. (c) 2005 Published by Elsevier B.V.