A novel approach for long term protein delivery

描述(申请人提供)：聚丙交酯-乙交酯(PLGA)作为蛋白质传递载体广泛应用于微球(MS)中。然而，蛋白质在制造PLGA MS的过程中会经历物理和化学变性，并在体内释放。此外，这种制剂经常导致不希望的和不可预测的释放情况，其特征是突发效应和不完全释放。这使得PLGA MS Appraoch对大多数不稳定的蛋白质都不成功。我们的初步研究结果清楚地表明，聚乙二醇聚(聚(L-组氨酸))作为一种依赖于pH的“可逆分子屏障”在1)保存蛋白质结构和防止在水/有机界面聚集，2)在PLGA MS中发挥pH缓冲(蛋白质海绵效应)，3)增强蛋白质在溶液和MS中的物理稳定性，以及4)整体更好地控制蛋白质从PLGA MS中的释放(‘All-in-one’概念)中所扮演的角色的有效性。尽管我们的初步结果证明了可行性，但仍有许多变量可以改变，以优化或定制针对特定蛋白质(如胰岛素)的聚合物设计。这包括改变PolyHis的大小以及与其他氨基酸共聚以改变电荷间距或PolyHis构象。该提案远远超出了治疗性蛋白质的范畴，提出了酶和其他应用的潜在应用。该项目的长期目标是从PLGA MS中释放出的模型蛋白质--胰岛素--保持90%的生物活性，并在体外和体内试验中实现一个月以上的伪零级释放动力学。研究的具体目标包括1)实验验证优化的聚乙二醇聚His(或聚乙二醇改性聚His)/胰岛素复合物在水溶液中、在PLGA MS中和释放过程中具有最大的胰岛素稳定性，2)更好地控制释放曲线，3)结合生物相容性和两嵌段共聚物的命运进行体内性能测试。

DESCRIPTION (provided by applicant): Poly(lactide-co-glycolide) (PLGA) has been widely applied in microspheres (MS) as a protein delivery carrier. However, proteins undergo physical and chemical denaturation during the fabrication of PLGA MS and release in the body. In addition, such formulations often cause undesirable and unpredictable release profiles, characterized by a burst effect and incomplete release. This makes PLGA MS appraoch unsuccessful for most labile proteins. The results from our preliminary study are a clear pointer to the validity of the role played by PEG-polycation (poly(L-histidine)) as a pH-dependent 'reversible molecular shield' in 1) preserving protein structure and preventing aggregation at water/organic interface, 2) exerting a pH buffering (protein sponge effect) in PLGA MS, 3) enhancing protein's physical stability in solution and in MS, and 4) an overall better control over release of the proteins from the PLGA MS ('all-in-one' concept). Although our preliminary results demonstrate the feasibility, there are still a number of variables which can be altered to optimize or tailor this polymer design for specific proteins, such as insulin. This includes changing the size of polyHis and copolymerizing with other amino acids to alter charge spacing or polyHis conformation. The proposal goes well beyond therapeutic proteins in suggesting potential applications for enzymes and other applications. The long-term goal of this project is to preserve >90 % bioactivity of a model protein, insulin, when released from PLGA MS and to achieve pseudozero-order release kinetics for more than one month period in in vitro and in vivo tests. The research specific aims include 1) experimental verification of optimized PEG-polyHis (or PEG-modified polyHis)/insulin complex for maximum insulin stability in aqueous solutions, in PLGA MS and during release, 2) a better control over release profile and 3) in vivo performance tests combined with biocompatibility and the fate of the diblock copolymer.