Advanced Pharmaceutics and Drug Delivery Laboratory, Leslie L. Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, M5S 3M2, Canada.
Department of Biochemistry, Islamic Azad University, Sanandaj Branch, Sanandaj, Iran.
Drug Deliv Transl Res. 2017 Aug;7(4):529-543. doi: 10.1007/s13346-017-0381-8.
Development of highly concentrated formulations of protein and peptide drugs is a major challenge due to increased susceptibility to aggregation and precipitation. Numerous drug delivery systems including implantable and wearable controlled-release devices require thermally stable formulations with high concentrations due to limited device sizes and long-term use. Herein we report a highly concentrated insulin gel formulation (up to 80 mg/mL, corresponding to 2200 IU/mL), stabilized with a non-ionic amphiphilic triblock copolymer (i.e., Pluronic F-127 (PF-127)). Chemical and physical stability of insulin was found to be improved with increasing polymer concentration, as evidenced by reduced insulin fibrillation, formation of degradation products, and preserved secondary structure as measured by HPLC and circular dichroism spectroscopy, respectively. This formulation exhibits excellent insulin stability for up to 30 days in vitro under conditions of continuous shear at 37 °C, attributable to the amphiphilic properties of the copolymer and increased formulation viscosity. The mechanism of stabilizing insulin structure by PF-127 was investigated by coarse-grained molecular dynamics (CG-MD), all-atom MD, and molecular docking simulations. The computation results revealed that PF-127 could reduce fibrillation of insulin by stabilizing the secondary structure of unfolded insulin and forming hydrophobic interaction with native insulin. The gel formulations contained in microfabricated membrane-reservoir devices released insulin at a constant rate dependent on both membrane porosity and copolymer concentration. Subcutaneous implantation of the gel formulation-containing devices into diabetic rats resulted in normal blood glucose levels for the duration of drug release. These findings suggest that the thermally stable gel formulations are suitable for long-term and implantable drug delivery applications.
由于蛋白质和肽类药物更容易聚集和沉淀，因此开发高浓度的蛋白质和肽类药物制剂是一个主要挑战。由于装置尺寸有限和长期使用，许多药物输送系统，包括可植入和可穿戴的控释装置，都需要热稳定的高浓度制剂。在此，我们报告了一种高浓度胰岛素凝胶制剂（高达 80mg/mL，相当于 2200IU/mL），该制剂通过非离子两亲性三嵌段共聚物（即 Pluronic F-127（PF-127））稳定。随着聚合物浓度的增加，胰岛素的化学和物理稳定性得到了改善，这表现在胰岛素纤颤减少、降解产物形成减少以及通过 HPLC 和圆二色性光谱分别测量的二级结构得到保留。在 37°C 下连续剪切条件下，该制剂在体外长达 30 天表现出优异的胰岛素稳定性，这归因于共聚物的两亲性和增加的制剂粘度。通过粗粒度分子动力学（CG-MD）、全原子 MD 和分子对接模拟研究了 PF-127 稳定胰岛素结构的机制。计算结果表明，PF-127 可以通过稳定展开的胰岛素的二级结构并与天然胰岛素形成疏水相互作用来减少胰岛素的纤颤。微加工膜储库装置中包含的凝胶制剂以依赖于膜孔隙率和共聚物浓度的恒定速率释放胰岛素。将含有凝胶制剂的装置植入糖尿病大鼠的皮下，在药物释放期间使血糖水平保持正常。这些发现表明，热稳定的凝胶制剂适合于长期和可植入的药物输送应用。
