Self-microencapsulation in polymer delivery systems without organic solvents

描述（由申请人提供）：我们的最终目标是开发一种新的简单方法，将药物和其他生物活性物质，特别是生物大分子，如蛋白质和肽，微胶囊化在可生物降解的控释聚合物中。目前的聚合物微胶囊化方法，如聚乳酸-羟基乙酸（PLGA），存在以下问题：a)蛋白质不稳定，包括使用蛋白质变性有机溶剂；b)昂贵的大规模无菌处理，用于每个感兴趣的肽/蛋白质的胶囊化；c)临床医生在护理点或其他非配方科学家在该领域无法有效地进行胶囊化。我们将利用我们自发闭合PLGA孔的新发现来微封装蛋白质和肽，方法是：创建具有定义孔网络的聚合物传递系统，将聚合物放置在感兴趣的药物水溶液中，然后通过简单加热到生理温度来关闭孔网络。与绝大多数在微胶囊化之前或期间将药物与溶解的聚合物接触的微胶囊化方法不同，这种方法创造了微胶囊化的新范例，即最初创建生物材料系统，然后在制备的最后进行微胶囊化。从某种意义上说，聚合物孔隙网络是自发地“自我”微胶囊化的，因此有了“自我微胶囊化”这个术语。此外，微胶囊化a)可以在非变性条件下进行，不需要有机溶剂，b)可以用最终灭菌的多孔PLGA微球廉价地完成，用于多种多肽和/或蛋白质，c)将适用于许多聚合物构型和几何形状，如微球，纳米球，组织工程支架，药物洗脱支架，d)可以由临床医生和研究人员在该领域进行。由于包封是通过简单的无菌混合蛋白质和聚合物。本课题将验证通过自微囊化可以制备高负载蛋白或多肽药物的聚乳酸微球，并且所得聚合物在体外和体内均具有优异的药物稳定性和释放性能。这一假设将在三个具体目标中得到验证：1)确定配方变量对模型蛋白自微胶囊化的影响；2)研究水介质中自发闭孔的机制；3)在体外和体内测试自微胶囊化稳定和控制治疗肽和蛋白释放的可行性。

DESCRIPTION (provided by applicant): Our ultimate goal is to develop a new and simple method to microencapsulate drugs and other bioactive substances, particularly biomacromolecules such as proteins and peptides, in biodegradable controlled-release polymers. Current methods of microencapsulation in polymers such as poly(lactic-co-glycolic acid) (PLGA) suffer from: a) protein instability including use of protein-denaturing organic solvents, b) expensive large-scale, aseptic processing for encapsulation of each peptide/protein of interest, and c) the inability of clinicians at the point-of-care or other non formulation scientists in the field to effectively perform encapsulation. We will exploit our novel finding of spontaneous PLGA pore closing to microencapsulate proteins and peptides by: creating polymer delivery systems with defined pore networks, placing the polymers in the presence of an aqueous drug solution of interest, and then causing the pore network to close, e.g., by simple heating to physiological temperature. Unlike the vast majority of microencapsulation methodologies, which place drug in contact with dissolved polymer before or during microencapsulation, this approach creates a new paradigm in microencapsulation, whereby the biomaterial system is initially created and then microencapsulation is performed at the very end of preparation. In a sense, the polymer pore network microencapsulates by "itself" spontaneously-hence the term, "self-microencapsulation." Moreover, microencapsulation a) takes place under nondenaturing conditions without the need for organic solvent, b) could be done inexpensively with terminally sterilized porous PLGA microspheres for multiple peptides and/or proteins, c) would be applicable to numerous polymer configurations and geometries such as microspheres, nanospheres, tissue engineering scaffolds, drug-eluting stents, and d) could be performed by clinicians and investigators in the field, since encapsulation is by simple aseptic mixing of protein and polymer. This proposal will test the hypothesis that PLGA microspheres entrapping high loading of protein or peptide drugs can be prepared reproducibly by self-microencapsulation, and the resulting polymer will exhibit excellent drug stability and release performance both in vitro and in vivo. This hypothesis will be tested in 3 specific aims: 1) determine the effect of formulation variables on self- microencapsulation of model proteins, 2) investigate the mechanism of spontaneous pore closing in aqueous media, and 3) test the feasibility of self-encapsulation to stabilize and control the release of therapeutic peptides and proteins in vitro and in vivo. PUBLIC HEALTH RELEVANCE: This project tests the feasibility of a brand new method of microencapsulation based on a recent finding from our group demonstrating how biodegradable polymers can heal their tiny holes and cracks spontaneously in water. The microencapsulation method does not use organic solvents and could have far reaching applications to the slow delivery of the important biomacromolecular class of drugs and vaccine antigens from injectable depots, tissue engineering scaffolds, and drug-eluting stents.