Claro Carmen, Muñoz José, de la Fuente Julia, Jiménez-Castellanos María Rosa, Lucero María Jesús
Departamento de Farmacia y Tecnología Farmacéutica, Facultad de Farmacia, Universidad de Sevilla, Spain.
Int J Pharm. 2008 Jan 22;347(1-2):45-53. doi: 10.1016/j.ijpharm.2007.06.027. Epub 2007 Jun 24.
This article reports data supporting that the hydroxypropyl cellulose-methyl methacrylate (HCMMA) hydrophobically modified polymer studied is surface-active at the air-water interface due to its amphiphilic nature. Surface tension measurements of diluted solutions point to the formation of a complex between this copolymer and a polyoxyethylene nonylphenyl ether non-ionic surfactant of high HLB. Conversely, no indications of specific interactions were found either with a polyoxyethylene nonylphenyl ether non-ionic surfactant of intermediate HLB or with an anionic surfactant such as sodium dodecyl sulfate (SDS). The physical stability of such dispersions depended on the surfactant used. The HCMMA/SDS systems studied showed phase separation shortly after preparation, while the dispersions with the non-ionic surfactant of higher HLB exhibited at least short-term stability and Newtonian behaviour. Foam-like dispersions of HCMMA-surfactant systems with intermediate HLB presented long-term stability, underlying the important role of hydrophobic interactions in these systems. One of the latter dispersions and the corresponding continuous phase were rheologically characterised by small amplitude oscillatory shear and flow curve experiments and exhibited a high Newtonian viscosity up to a critical shear stress followed by a shear thinning as well as weak-gel viscoelastic properties. The results obtained support that (a) the continuous phase presents a complex microstructure, which required the use of a serrated sensor system to avoid the occurrence of wall depletion phenomena, (b) it controls the rheology of the whole dispersion and (c) the latter showed both physical stability and rheological properties suitable for applications as controlled release systems in pharmacy or cosmetics.
本文报道的数据支持,所研究的羟丙基纤维素-甲基丙烯酸甲酯(HCMMA)疏水改性聚合物因其两亲性在气-水界面具有表面活性。稀释溶液的表面张力测量表明,该共聚物与高HLB值的聚氧乙烯壬基苯基醚非离子表面活性剂之间形成了复合物。相反,未发现与中等HLB值的聚氧乙烯壬基苯基醚非离子表面活性剂或阴离子表面活性剂(如十二烷基硫酸钠(SDS))有特定相互作用的迹象。此类分散体的物理稳定性取决于所使用的表面活性剂。所研究的HCMMA/SDS体系在制备后不久就出现了相分离,而含有较高HLB值非离子表面活性剂的分散体至少表现出短期稳定性和牛顿流体行为。具有中等HLB值的HCMMA-表面活性剂体系的泡沫状分散体具有长期稳定性,这突出了疏水相互作用在这些体系中的重要作用。对其中一种分散体及其相应的连续相进行了小振幅振荡剪切和流动曲线实验的流变学表征,结果显示,在临界剪切应力之前具有较高的牛顿粘度,随后出现剪切变稀以及弱凝胶粘弹性特性。所得结果支持:(a)连续相呈现出复杂的微观结构,这需要使用锯齿形传感器系统以避免壁面耗尽现象的发生;(b)它控制着整个分散体的流变学;(c)后者表现出适合作为药物或化妆品控释系统应用的物理稳定性和流变学性质。