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

    Year: 2005

    Journal: Journal of Colloid and Interface Science 286 (2005) 166-175, 20111221

    Authors: Marite Cardenas , Tommy Nylander , Bengt Jönsson , Björn Lindman

    Organizations: a Physical Chemistry 1, Center for Chemistry and Chemical Engineering, University of Lund, P.O. Box 124, SE-221 00 Lund, Sweden b Theoretical Chemistry, Center for Chemistry and Chemical Engineering, University of Lund, P.O. Box 124,

    The interaction between DNA and positively charged dioctadecyldimethylammonium bromide (DODAB) and DODAB/disteroylphosphatidylcholine (DSPC) monolayers at the air-aqueous interface was studied by a combination of the surface film balance and Brewster angle microscopy. In presence of DNA, the π-A isotherm of the cationic monolayer shifts to larger mean molecular areas due to the electrostatic interaction with DNA while the typical liquid expanded-liquid condensed phase transition for DODAB monolayers disappear and the monolayer remains to be in the liquid expanded phase. Furthermore, the morphology of the film dramatically changes, where the large dendritic-like condensed aggregates observed for DODAB monolayers vanish. The charge density of the monolayer was varied by using mixed monolayers with the zwitterionic DSPC and no large effect was observed on the interaction with DNA. By modeling the electrostatic interactions with the linearized Poisson-Boltzmann equation using the finite-element method and taking into account the assumption in the dielectric constants of the system, it was possible to corroborate the expansion of the cationic monolayer upon interaction with DNA as well as the fact that DNA does not seem to penetrate into the monolayer.