In-situ observation of the aggregated morphology and interaction of dialkyldimethylammonium bromide with DNA at air/water interface by Brewster angle microscopy

The effect of neutral helper lipids on the structure of cationic lipid monolayers

“…less than 5 mN m 21 while in the plateau region, very small circular domains were initially observed, these structures then changing into large flower-like domains (of diameter 30-50 mm) upon further compression, eventually fusing to form a more homogeneous film containing a very small number of small, circular domains in the surface pressure range 20-40 mN m 21 . These results are very similar to those of DODAB monolayers reported by Sun et al [12], although the lift-off area and location of the plateau occur at slightly different points on the isotherm owing to the differing experimental conditions. The mixed DODAB : cholesterol monolayer appeared homogeneous when visualized by BAM.…”

“…This lipid has been shown to be successful in delivering nucleic materials in vitro when used as sole lipid [6], although its effectiveness is increased in the presence of neutral helper lipids such as DOPE and the cholesterol derivative, PtdChol [7]. Previous studies have investigated the structure of a DODAB monolayer at the air -water interface [8 -11], sometimes in the presence of DNA [12,13] but (to the authors' knowledge) there have been no studies concerned with the effect of a helper lipid on the structure of the DODAB lipid monolayer.…”

The interaction between DNA and cationic lipid films at the air–water interface

“…Instead, the tilt angle of the lipid chains relative to the surface normal was found to increase upon coupling to the polyelectrolyte; meanwhile, the polymer conformation under the monolayer was found to be dependant on the polymer charge density. Sun et al [10] recently demonstrated by BAM that DNA interacted with different dialkyldimethylammonium bromides at the pure water-air interface. They found that the surface pressure of the mixed DNA-surfactant system was higher as compared to that of the pure surfactant system.…”

“…In the last decade, the potential use of DNA and cationic surfactants as vehicles for gene delivery and as biofunctional materials and biosensors have promoted the study of such systems not only in the bulk but also at the air-water interface [9][10][11][12][13]. Earlier Sun et al [10] investigated the effect of DNA on the morphology of the cationic monolayers from bromide dioctadecyldimethylammonium (DODAB) at the air-water interface by means of BAM. The authors found that the presence of DNA in the aqueous subphase changed the morphology of the monolayer at any given surface pressure.…”

Catanionic surfactant films at the air–water interface

“…The Langmuir-Blodgett film technique has been extensively used for the study inter alia of mixtures of neutral surfactants and of oppositely charged surfactants [18,19]. Previous investigations addressing catanionic monolayers, in particular, were based on mixtures with inorganic counterions [18,[20][21][22][23][24][25][26][27][28], but few on pure catanionic surfactants, where the oppositely charged surfactants are counterions to each other. In this work, we have measured π-A isotherm for a series of catanionic surfactants with variation of headgroups and lengths of hydrophobic chains.…”