Barlow D J, Hollinshead C M, Harvey R D, Kudsiova L, Lawrence M J
Department of Pharmacy, Franklin Wilkins Building, King's College London, 150 Stamford Street, London SE1 9NH, UK.
J Colloid Interface Sci. 2007 Dec 15;316(2):741-50. doi: 10.1016/j.jcis.2007.08.014. Epub 2007 Aug 11.
The behaviour of monolayers and bilayers formed by the dialkyl chain non-ionic surfactant, 1,2-di-O-octadecyl-rac-glycerol-3-omega-methoxydodecaethylene glycol (2C(18)E(12)) in water at 297 K has been investigated. Using a surface film balance (or Langmuir trough) the compression-expansion cycle of the 2C(18)E(12) monolayer was found to be reversible when compressed to surface pressures (pi) less than 42 mN m(-1). Compression of 2C(18)E(12) monolayer to pi greater than 42 mN m(-1) above this resulted in a considerable hysteresis upon expansion with the pi remaining high relative to that obtained upon compression, suggesting a time/pressure dependent re-arrangement of 2C(18)E(12) molecules in the film. Morphology of the 2C(18)E(12) monolayer, investigated using Brewster angle microscopy, was also found to depend upon monolayer history. Bright, randomly dispersed domains of 2C(18)E(12) of approximately 5 mum in size were observed during compression of the monolayer to pi less than 42 mN m(-1). At pi of 42 mN m(-1) and above, the surfactant film appeared to be almost completely 'solid-like.' Regardless of the extent of compression of the monolayer film, expansion of the film caused formation of chains or 'necklaces' of individual surfactant domains, with the extent of chain formation dependent upon pressure of compression of the monolayer and the length of time held at that pressure. Irreversible effects on 2C(18)E(12) vesicle size were also seen upon temperature cycling the vesicles through their liquid-crystalline phase transition temperature with vesicles shrinking in size and not returning to their original size upon standing at 298 K for periods of more than 24 h. No comparable hysteresis, time, pressure or temperature effects were observed with the monolayer or vesicles formed by the corresponding phospholipid, disteaorylphosphatidylcholine, under identical conditions. The effects observed with 2C(18)E(12) are attributed to the ability of the polyoxyethylene head group to dehydrate and intrude into the hydrophobic chain region of the mono- and bilayers. These studies have important implications for the use of the vesicles formed by 2C(18)E(12) as drug delivery vehicles.
研究了二烷基链非离子表面活性剂1,2 - 二 - O - 十八烷基 - 外消旋甘油 - 3 - ω - 甲氧基十二乙二醇（2C(18)E(12)）在297 K水中形成的单层膜和双层膜的行为。使用表面膜天平（或朗缪尔槽）发现，当将2C(18)E(12)单层膜压缩至表面压力（π）小于42 mN m⁻¹时，其压缩 - 膨胀循环是可逆的。在此之上，将2C(18)E(12)单层膜压缩至π大于42 mN m⁻¹时，膨胀过程中会出现相当大的滞后现象，此时的π相对于压缩时获得的值仍然较高，这表明膜中2C(18)E(12)分子发生了时间/压力依赖性的重新排列。使用布鲁斯特角显微镜研究的2C(18)E(12)单层膜的形态也取决于单层膜的历史情况。在将单层膜压缩至π小于42 mN m⁻¹的过程中，观察到了尺寸约为5μm的2C(18)E(12)明亮、随机分散的区域。在π为42 mN m⁻¹及以上时，表面活性剂膜似乎几乎完全呈“固态”。无论单层膜的压缩程度如何，膜的膨胀都会导致单个表面活性剂区域形成链状或“项链”状结构，链状结构的形成程度取决于单层膜的压缩压力以及在该压力下保持的时间长度。当使2C(18)E(12)囊泡通过其液晶相转变温度进行温度循环时，囊泡尺寸也出现了不可逆的变化，囊泡尺寸缩小，在298 K下静置超过24小时后无法恢复到原来的尺寸。在相同条件下观察由相应的磷脂二硬脂酰磷脂酰胆碱形成的单层膜或囊泡时，未观察到类似的滞后、时间、压力或温度效应。观察到的2C(18)E(12)的效应归因于聚氧乙烯头部基团脱水并侵入单层膜和双层膜疏水链区域的能力。这些研究对于将2C(18)E(12)形成的囊泡用作药物递送载体具有重要意义。
