A Biophysical Investigation on the Bindig and Controlled DNA release in a CTAB-SOS Cat-Anionic Vesicle System

The interactions between cat-anionic (an acronym indicating surfactant aggregates (micelles and vesicles) formed upon mixing cationic and anionic surfactants in nonstoichiometric amts.) vesicles and DNA have been the subject of intensive studies because of their potential applications in biomedicine. Here we report on the interactions between DNA and cetyltrimethylammonium bromide (CTAB)-sodium octyl sulfate (SOS) cat-anionic vesicles. The study was performed by combining dielec. relaxation spectroscopy, CD, dynamic light scattering, ion cond., and mol. biol. techniques. DNA is added to pos. charged vesicles until complete charge neutralization of the complex and formation of lipoplexes. This occurs when the mole ratio between the phosphate groups of DNA and pos. charges on the vesicle is about 1.8. Above this threshold the nucleic acid in excess remains free in soln. This very interesting new result shows that anionic surfactants are not expelled upon satn., and therefore, no formation of micelles occurs. Furthermore, vesicle-bound DNA can be released in its native form, as confirmed by dielec. spectroscopy and CD measurements. The nucleic acid is released upon addn. of SOS, which competes with the phosphate groups of the DNA: this results in the demolition of the CTAB-SOS cat-anionic vesicles. These results indicate the possibility of a controlled DNA release and might be of interest in biomedicine.