Self-microencapsulation in polymer delivery systems without organic solvents

描述(申请人提供)：我们的最终目标是开发一种新的、简单的方法，将药物和其他生物活性物质，特别是生物大分子，如蛋白质和多肽，微胶囊到可生物降解的控释聚合物中。目前聚合物中微胶囊的方法，如聚(乳酸-乙醇酸)(PLGA)，存在以下问题：a)蛋白质不稳定，包括使用蛋白质变性的有机溶剂；b)昂贵的大规模、无菌工艺，用于包裹每个感兴趣的多肽/蛋白质；以及c)临床医生或该领域的其他非处方科学家无法有效地进行包裹。我们将通过以下方式利用我们的新发现：创建具有定义的孔网络的聚合物递送系统，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使孔网络关闭。与绝大多数微胶囊方法不同的是，在微胶囊之前或微胶囊期间，药物与溶解的聚合物接触，这种方法在微胶囊中创造了一种新的范式，即最初创建生物材料系统，然后在制备的最后进行微胶囊。从某种意义上说，聚合物孔网络通过“自身”自发地形成微胶囊--因此有了“自我微胶囊”这个术语。此外，a)在非变性条件下进行微胶囊化而不需要有机溶剂，b)可以廉价地使用末端灭菌的多肽和/或蛋白质的多孔PLGA微球，c)将适用于多种聚合物构型和几何形状，例如微球、纳米球、组织工程支架、药物洗脱支架，以及d)可以由临床医生和该领域的研究人员进行，因为包囊是通过蛋白质和聚合物的简单无菌混合来进行的。这项提议将验证这样的假设，即通过自微胶囊可以重复地制备高负载蛋白质或多肽药物的PLGA微球，所得到的聚合物在体内外都将表现出良好的药物稳定性和释放性能。这一假设将在3个方面得到验证：1)确定处方变量对模型蛋白质自微胶囊的影响，2)研究水介质中自发闭孔的机制，3)测试自胶囊在体内外稳定和控制治疗性多肽和蛋白质释放的可行性。 与公共健康相关：该项目测试了一种全新的微胶囊方法的可行性，该方法基于我们团队最近的一项发现，展示了可生物降解的聚合物如何能够自发修复水中的微小孔洞和裂缝。这种微胶囊化方法不使用有机溶剂，在从注射库、组织工程支架和药物洗脱支架缓慢输送重要的生物大分子类药物和疫苗抗原方面可能有广泛的应用。

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.