Memory effects of monolayers and vesicles formed by the non-ionic surfactant, 2C18E12

Barlow, David and Hollinshead, Clare and Harvey, Richard and Kudsiova, Laila and Lawrence, M. Jayne (2007) Memory effects of monolayers and vesicles formed by the non-ionic surfactant, 2C18E12. Journal of Colloid and Interface Science, 316 (2). pp. 741-750. ISSN 0021-9797

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Official URL: http://dx.doi.org/10.1016/j.jcis.2007.08.014

Abstract

The behaviour of monolayers and bilayers formed by the dialkyl chain non-ionic surfactant, 1,2-di-O-octadecyl-rac-glycerol-3-ω-methoxydodecaethylene glycol (2C18E12) in water at 297 K has been investigated. Using a surface film balance (or Langmuir trough) the compression–expansion cycle of the 2C18E12 monolayer was found to be reversible when compressed to surface pressures (π) less than 42 mN m−1. Compression of 2C18E12 monolayer to π greater than 42 mN m−1 above this resulted in a considerable hysteresis upon expansion with the π remaining high relative to that obtained upon compression, suggesting a time/pressure dependent re-arrangement of 2C18E12 molecules in the film. Morphology of the 2C18E12 monolayer, investigated using Brewster angle microscopy, was also found to depend upon monolayer history. Bright, randomly dispersed domains of 2C18E12 of approximately 5 μm in size were observed during compression of the monolayer to π less than 42 mN m−1. At π 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 2C18E12 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 2C18E12 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 2C18E12 as drug delivery vehicles.

Item Type:Article
Additional Information:The behaviour of monolayers and bilayers formed by the dialkyl chain non-ionic surfactant, 1,2-di-O-octadecyl-rac-glycerol-3-ω-methoxydodecaethylene glycol (2C18E12) in water at 297 K has been investigated. Using a surface film balance (or Langmuir trough) the compression–expansion cycle of the 2C18E12 monolayer was found to be reversible when compressed to surface pressures (π) less than 42 mN m−1. Compression of 2C18E12 monolayer to π greater than 42 mN m−1 above this resulted in a considerable hysteresis upon expansion with the π remaining high relative to that obtained upon compression, suggesting a time/pressure dependent re-arrangement of 2C18E12 molecules in the film. Morphology of the 2C18E12 monolayer, investigated using Brewster angle microscopy, was also found to depend upon monolayer history. Bright, randomly dispersed domains of 2C18E12 of approximately 5 μm in size were observed during compression of the monolayer to π less than 42 mN m−1. At π 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 2C18E12 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 2C18E12 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 2C18E12 as drug delivery vehicles.
Keywords:non-ionic surfactant, monolayer, bilayer, Brewster angle microscopy, Langmuir trough
Subjects:C Biological Sciences > C770 Biophysical Science
C Biological Sciences > C790 Molecular Biology, Biophysics and Biochemistry not elsewhere classified
Divisions:College of Science > School of Life Sciences
ID Code:3044
Deposited By: Clare Miller
Deposited On:28 Jul 2010 14:07
Last Modified:19 Feb 2013 11:37

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