Department of Pharmacy, Faculty of Health and Medicinal Sciences, University of Copenhagen, Denmark.
Int J Pharm. 2012 May 10;427(2):345-53. doi: 10.1016/j.ijpharm.2012.02.034. Epub 2012 Mar 3.
The aim of the study was to visualize the behaviour of the hydroxypropyl methylcellulose (HPMC) in a buffer solution using UV imaging. The obtained results were related to rheological measurements in order to gain insight into critical polymer properties affecting drug release. Two viscosity grades of HPMC, 15cP and 50 cP, were used. The behaviour of the polymer at the surface of the compact was observed by UV-imaging at 214 nm for 90 min in a stagnant buffer solution and in presence of flow. Steady shear and oscillatory shear measurements were conducted to determine the rheological characteristics. Three distinctive phases could be detected by real-time UV-imaging of the HPMC; gel formation due to water penetration, further expansion of the gel into solution and finally steady conditions, where a critical polymer concentration that can withstand the shear forces without eroding was observed. The critical concentration corresponded to the rheologically determined gel point, which is the lowest concentration where a 3D-network is obtained. Higher viscosity grade HPMC swelled more rapidly and lead to a thicker gel layer, which was more resistant towards the shear forces due to the applied flow. The results showed that UV imaging is suitable for obtaining both qualitative and quantitative information on polymer behaviour.
本研究的目的是使用 UV 成像可视化羟丙基甲基纤维素 (HPMC) 在缓冲溶液中的行为。将所得结果与流变学测量相关联，以深入了解影响药物释放的关键聚合物性质。使用了两种粘度等级的 HPMC，即 15cP 和 50cP。在静止缓冲溶液中和存在流动的情况下，通过在 214nm 下进行 90 分钟的 UV 成像，观察了聚合物在致密表面的行为。进行了稳态剪切和振荡剪切测量，以确定流变特性。通过 HPMC 的实时 UV 成像，可以检测到三个明显的阶段；由于水渗透而形成凝胶，凝胶进一步扩展到溶液中，最后是稳定状态，观察到可以承受剪切力而不侵蚀的临界聚合物浓度。临界浓度对应于流变学确定的凝胶点，这是获得 3D 网络的最低浓度。较高粘度等级的 HPMC 膨胀更快，导致凝胶层更厚，由于施加的流动，凝胶层对剪切力的抵抗力更强。结果表明，UV 成像适用于获得有关聚合物行为的定性和定量信息。
