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Temperature quenched DODAB dispersions: Fluid and solid state coexistence and complex formation with oppositely charged surfactant

Cocquyt, J; Olsson, Ulf LU ; Olofsson, Gerd LU and Van der Meeren, P (2004) In Langmuir 20(10). p.3906-3912
Abstract
Dilute dispersions of the synthetic bilayer forming double-chained cationic lipid dioctadecyldimethylammonium bromide (DODAB) were investigated. In dispersions sonicated above the chain melting temperature T-m (approximate to45 degreesC) it was found by H NMR that about 50% of the surfactant chains remained fluid when the samples were cooled to room temperature, which is 20 degreesC below T-m. In contrast, there was no sign of a fluid fraction in unsonicated samples at room temperature. The addition of the anionic surfactant sodium dodecyl sulfate (SDS) to DODAB dispersions at room temperature resulted in the formation of an essentially stoichiometric DODA-DS complex with frozen chains, as seen by titration calorimetry and H NMR... (More)
Dilute dispersions of the synthetic bilayer forming double-chained cationic lipid dioctadecyldimethylammonium bromide (DODAB) were investigated. In dispersions sonicated above the chain melting temperature T-m (approximate to45 degreesC) it was found by H NMR that about 50% of the surfactant chains remained fluid when the samples were cooled to room temperature, which is 20 degreesC below T-m. In contrast, there was no sign of a fluid fraction in unsonicated samples at room temperature. The addition of the anionic surfactant sodium dodecyl sulfate (SDS) to DODAB dispersions at room temperature resulted in the formation of an essentially stoichiometric DODA-DS complex with frozen chains, as seen by titration calorimetry and H NMR experiments. For sonicated samples, turbidity experiments demonstrated that, after a fast complexation reaction, the system remains colloidally stable unless the SDS-to-DODAB mixing ratio is too close to unity. H NMR experiments also showed that in the unreacted DODAB the fraction of fluid chains remained close to 50%, indicating either that SDS reacts equally fast with fluid and frozen DODAB or that there is a relaxation of the fluid fraction after the complexation. The melting enthalpy and the melting temperature of the alkyl chains rise gradually as the mixing ratio increases. We observed with cryo-TEM that the fraction of large unilamellar vesicles was significantly larger after addition of SDS. This indicates vesicle fusion. Based on both wide- and small-angle X-ray scattering patterns, the structure of the equimolar SDS-DODAB complex at 25 degreesC was proposed to be lamellar. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
20
issue
10
pages
3906 - 3912
publisher
The American Chemical Society
external identifiers
  • pmid:15969378
  • wos:000221319400017
  • scopus:2542463852
ISSN
0743-7463
DOI
10.1021/la036080c
language
English
LU publication?
yes
id
14dd033f-1b7d-4238-9e39-de461f0fab4b (old id 153860)
date added to LUP
2007-07-11 09:00:14
date last changed
2017-11-05 03:29:10
@article{14dd033f-1b7d-4238-9e39-de461f0fab4b,
  abstract     = {Dilute dispersions of the synthetic bilayer forming double-chained cationic lipid dioctadecyldimethylammonium bromide (DODAB) were investigated. In dispersions sonicated above the chain melting temperature T-m (approximate to45 degreesC) it was found by H NMR that about 50% of the surfactant chains remained fluid when the samples were cooled to room temperature, which is 20 degreesC below T-m. In contrast, there was no sign of a fluid fraction in unsonicated samples at room temperature. The addition of the anionic surfactant sodium dodecyl sulfate (SDS) to DODAB dispersions at room temperature resulted in the formation of an essentially stoichiometric DODA-DS complex with frozen chains, as seen by titration calorimetry and H NMR experiments. For sonicated samples, turbidity experiments demonstrated that, after a fast complexation reaction, the system remains colloidally stable unless the SDS-to-DODAB mixing ratio is too close to unity. H NMR experiments also showed that in the unreacted DODAB the fraction of fluid chains remained close to 50%, indicating either that SDS reacts equally fast with fluid and frozen DODAB or that there is a relaxation of the fluid fraction after the complexation. The melting enthalpy and the melting temperature of the alkyl chains rise gradually as the mixing ratio increases. We observed with cryo-TEM that the fraction of large unilamellar vesicles was significantly larger after addition of SDS. This indicates vesicle fusion. Based on both wide- and small-angle X-ray scattering patterns, the structure of the equimolar SDS-DODAB complex at 25 degreesC was proposed to be lamellar.},
  author       = {Cocquyt, J and Olsson, Ulf and Olofsson, Gerd and Van der Meeren, P},
  issn         = {0743-7463},
  language     = {eng},
  number       = {10},
  pages        = {3906--3912},
  publisher    = {The American Chemical Society},
  series       = {Langmuir},
  title        = {Temperature quenched DODAB dispersions: Fluid and solid state coexistence and complex formation with oppositely charged surfactant},
  url          = {http://dx.doi.org/10.1021/la036080c},
  volume       = {20},
  year         = {2004},
}