Stability of Poly(ethylene glycol) Modified Proteins

我们寻求通过提高生物相容的聚乳酸-羟基乙酸(PLGA)微球的稳定性来改善蛋白质的控制输送。这将进一步推动蛋白质药物在健康应用中的广泛使用，而这种应用仍然受到其固有结构不稳定性的限制。我们打算开展研究，以防止有害的蛋白质聚集和失活，当它们暴露在将其包裹到PLGA微球中时所涉及的严重压力下(例如，暴露在有机溶剂-水界面中)。我们假设这可以通过用聚乙二醇共价修饰蛋白质来实现。主要假设是将聚乙二醇共价连接到药物蛋白表面，可降低药物蛋白的聚集和失活敏感性(A)包裹在PLGA微球中，(B)在储存过程中处于固体状态，(C)在体外释放过程中。 此外，聚乙二醇化修饰也可能改善由非水(如油包固体)或半非水(即水包油)方法制备的PLGA微球中蛋白质的释放。 这是因为聚乙二醇化蛋白质可以溶于多种合适的有机溶剂。这应该会导致聚乙二醇化蛋白质在聚合物基质中更好的分布，并提供减少的突发释放。我们将使用不同的方法(例如，水包油、水包油固体和喷墨辅助封装)将聚乙二醇化修饰的蛋白质包裹到PLGA微球中。蛋白质的结构和稳定性数据将使用多种光谱技术(例如，FT-IR、FT-拉曼、圆二色谱和荧光光谱)和生物化学技术来获得。结构数据将与稳定性参数相关联，例如从设备中累积的蛋白质释放、特定的生物活性和蛋白质聚集。此外，稳定性 而结构数据将与表面修饰的化学性质和程度有关。这些数据将被用来开发针对压力的策略，以系统地消除蛋白质在封装和释放过程中的失活和聚集。

We seek to improve the controlled delivery of proteins from biocompatible poly(lactic-co-glycolic) acid (PLGA) microspheres by increasing their stability. This will further the widespread use of protein pharmaceuticals in health applications which is still limited by their inherent structural lability. We intend to carry out studies that will prevent detrimental protein aggregation and inactivation which occur when they are exposed to the severe stress involved during their encapsulation into PLGA microspheres (e.g., exposure to organic solvent-water interfaces). We hypothesize that this can be achieved by covalent modification of proteins with poly(ethylene glycol) (PEG). Main hypotheses are that covalently attaching PEG to the surface of pharmaceutical proteins will reduce their susceptibility towards aggregation and inactivation (a) upon encapsulation in PLGA microspheres, (b) in the solid state during storage, and (c) during in vitro release. Furthermore, PEG-modification will likely also improve the release of proteins from PLGA microspheres prepared by non-aqueous (e.g., solid-in-oil-in-oil) or semi non-aqueous (i.e., solid-in-oil-in-water) methods. The reason is that PEG-proteins are soluble in many suitable organic solvents. This should result in a better distribution of PEG-protein in the polymer matrix and afford a reduced burst release. We will encapsulate PEG-modified proteins in PLGA microspheres using various methodologies (e.g., water-in-oil-in-water, solid-in-oil-in-water, and ink jet assisted encapsulation). Protein structural and stability data will be obtained using a manifold of spectroscopic (e.g., FT-IR, FT-Raman, circular dichroism and fluorescence spectroscopy) and biochemical techniques. The structural data will be correlated with stability parameters, such as cumulative protein release from the devices, specific biological activity, and protein aggregation. Furthermore, stability and structural data will be related to the chemical nature and degree of surface modification. These data will be used to develop stress-specific strategies to systematically eradicate protein inactivation and aggregation during encapsulation and release.