Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Granada, Campus of Cartuja, s/n, 18071 Granada, Spain.
Int J Pharm. 2013 Sep 10;453(2):473-9. doi: 10.1016/j.ijpharm.2013.06.002. Epub 2013 Jun 10.
This work studied the influence of "maturation" conditions (time and agitation) on aggregation states, gel structure and rheological behaviour of a special kind of pharmaceutical semisolid products made of concentrated clay suspensions in mineral medicinal water. Maturation of the samples was carried out in distilled and sulphated mineral medicinal water, both in static conditions (without agitation) and with manual stirring once a week, during a maximum period of three months. At the measured pH interval (7.5-8.0), three-dimensional band-type networks resulting from face/face contacts were predominant in the laminar (disc-like) clay suspensions, whereas the fibrous (rod-like) particles formed micro-aggregates by van der Waals attractions. The high concentration of solids in the studied systems greatly determined their behaviour. Rod-like sepiolite particles tend to align the major axis in aggregates promoted by low shearing maturation, whereas aggregates of disc-like smectite particles did not have a preferential orientation and their complete swelling required long maturation time, being independent of stirring. Maturation of both kinds of suspensions resulted in improved rheological properties. Laminar clay suspensions became more structured with time, independently from static or dynamic maturation conditions, whereas for fibrous clay periodic agitation was also required. Rheological properties of the studied systems have been related to aggregation states and networking mechanisms, depending on the type of clay minerals constituents. Physical stability of the suspensions was not impaired by the specific composition of the Graena medicinal water.
本工作研究了“成熟”条件（时间和搅拌）对特殊类型的医药半固体产品聚集状态、凝胶结构和流变行为的影响，该产品由浓缩粘土悬浮液在矿物药水中制成。在测量的 pH 值范围内（7.5-8.0），在层流（盘状）粘土悬浮液中，主要由面-面接触形成的三维带状网络占主导地位，而纤维状（棒状）颗粒通过范德华吸引力形成微聚集体。在研究的系统中，高浓度的固体极大地决定了它们的行为。棒状海泡石颗粒在低剪切成熟的促进下倾向于将长轴排列在聚集体中，而片状蒙脱石颗粒的聚集体没有优先取向，它们的完全溶胀需要较长的成熟时间，且不受搅拌的影响。两种悬浮液的成熟都改善了流变性能。层流粘土悬浮液随着时间的推移变得更加结构化，与静态或动态成熟条件无关，而对于纤维状粘土，则需要周期性搅拌。研究系统的流变性能与聚集状态和网络形成机制有关，这取决于粘土矿物成分的类型。悬浮液的物理稳定性没有因 Graena 药用水中的特定成分而受到损害。
