National Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, PR China.
Langmuir. 2012 Oct 2;28(39):13984-92. doi: 10.1021/la3017112. Epub 2012 Sep 17.
The microcosmic mechanisms of protein (recombinant human growth hormone, rhGH) incomplete release and stability from amphiphilic poly(monomethoxypolyethylene glycol-co-D,L-lactide) (mPEG-PLA, PELA) microspheres were investigated. PELA with different hydrophilicities (PELA-1, PELA-2, and PELA-3) based on various ratios of mPEG to PLA were employed to prepare microspheres exhibiting a narrow size distribution using a combined double emulsion and premix membrane emulsification method. The morphology, rhGH encapsulation efficiency, in vitro release profile, and rhGH stability of PELA microspheres during the release were characterized and compared in detail. It was found that increasing amounts of PLA enhanced the encapsulation efficiency of PELA microspheres but reduced both the release rate of rhGH and its stability. Contact angle, atomic force microscope (AFM), and quartz crystal microbalance with dissipation (QCM-D) techniques were first combined to elucidate the microcosmic mechanism of incomplete release by measuring the hydrophilicity of the PELA film and its interaction with rhGH. In addition, the pH change within the microsphere microenvironment was monitored by confocal laser scanning microscopy (CLSM) employing a pH-sensitive dye, which clarified the stability of rhGH during the release. These results suggested that PELA hydrophilicity played an important role in rhGH incomplete release and stability. Thus, the selection of suitable hydrophilic polymers with adequate PEG lengths is critical in the preparation of optimum protein drug sustained release systems. This present work is a first report elucidating the microcosmic mechanisms responsible for rhGH stability and its interaction with the microspheres. Importantly, this research demonstrated the application of promising new experimental methods in investigating the interaction between biomaterials and biomacromolecules, thus opening up a range of exciting potential applications in the biomedical field including drug delivery and tissue regeneration.
研究了两亲性聚（单甲氧基聚乙二醇-co-D,L-丙交酯）（mPEG-PLA，PELA）微球中蛋白质（重组人生长激素，rhGH）不完全释放和稳定性的微观机制。使用不同亲水比的 mPEG-PLA（PELA-1、PELA-2 和 PELA-3）制备微球，采用双重乳液和预混膜乳化法制备粒径分布较窄的微球。详细比较和描述了 PELA 微球的形态、rhGH 包封效率、体外释放曲线以及释放过程中 rhGH 的稳定性。结果表明，随着 PLA 含量的增加，PELA 微球的包封效率增加，但 rhGH 的释放速率和稳定性降低。首次结合接触角、原子力显微镜（AFM）和石英晶体微天平耗散（QCM-D）技术，通过测量 PELA 膜的亲水性及其与 rhGH 的相互作用，阐明了不完全释放的微观机制。此外，通过共聚焦激光扫描显微镜（CLSM）采用 pH 敏感染料监测微球微环境内的 pH 值变化，阐明了 rhGH 在释放过程中的稳定性。结果表明，PELA 的亲水性在 rhGH 的不完全释放和稳定性中起重要作用。因此，选择具有适当 PEG 长度的合适亲水聚合物在制备最佳蛋白质药物缓释系统中至关重要。本工作首次阐明了 rhGH 稳定性及其与微球相互作用的微观机制。重要的是，本研究展示了有前途的新实验方法在研究生物材料与生物大分子相互作用中的应用，从而为药物输送和组织再生等生物医学领域开辟了一系列令人兴奋的潜在应用。
