Preparation and characterization of hollow microcapsules for use as ultrasound contrast agents
Preparation and characterization of hollow microcapsules for use as ultrasound contrast agents
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DOI：
10.1002/pen.11612
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发表时间：
1999-11-01
影响因子：
3.2
通讯作者：
Wheatley, MA
中科院分区：
文献类型：
--
作者：
Narayan, P;Wheatley, MA
开发了一种实验室规模的可生物降解聚合物(如50/50聚(D，L-丙交酯-乙交酯共聚物))制备微米级中空微胶囊的方法，用于诊断超声造影剂。这项技术包括对挥发性固体核心材料进行微胶囊，然后将核心升华成中空的微球。核心材料，如碳酸铵，被研磨成合适的尺寸分布，并通过改进的溶剂挥发或凝聚技术进行包裹。本研究考察了用这两种包埋方法制备诊断可行的微胶囊的工艺参数，如聚合物相对分子质量(从10,000到50,000)、初始聚合物浓度、搅拌方法和稳定剂类型。聚合物溶液的粘度、多分散性和搅拌速度显著控制了微胶囊的平均尺寸。稳定剂在溶剂挥发过程中是必不可少的，但会破坏凝聚法制得的球体的形态。微球分散体的Zeta电位值表明两种包埋方法的表面特征不同。微囊与血清孵育可改善其在水介质中的分散性。利用彩色多普勒对新西兰白兔模型进行的初步体内超声研究表明，微囊在右肾具有显著的对比度。
A laboratory-scale method of producing micron-sized hollow microcapsules from a biodegradable polymer such as 50/50 poly(D,L-lactide-co-glycolide) (PLGA), for use as a diagnostic ultrasound contrast agent, was developed. The technique involved microencapsulation of a volatile solid core material, and subsequent sublimation of the core to leave a hollow microsphere. A core material, such as ammonium carbonate, was ground to a suitable size distribution and encapsulated by a modified solvent evaporation or coacervation technique. This study investigated process parameters to produce diagnostically viable microcapsules by these two encapsulation methods, such as polymer molecular weight (from 10,000 to 50,000), initial polymer concentration, agitation method, and stabilizer type. Polymer solution viscosity, polydispersity, and agitation rates significantly controlled the mean size of the microcapsules. Stabilizers were essential in solvent evaporation, but corrupted the morphology of spheres made by coacervation. Zeta potential values of microsphere dispersions revealed differences in surface characteristics between both encapsulation methods. Incubation of microcapsules with serum improved their dispersion in aqueous media. Preliminary in vivo ultrasound studies with the New Zealand white rabbit model, using color Doppler, showed that the microcapsules gave significant contrast in the right kidney.