Two-step mechanism in cationic lipoplex formation as observed by dynamic light scattering, dielectric relaxation and circular dichroism methods

We employed dynamic light scattering, radiowave dielectric spectroscopy and circular dichroism measurements to reveal the structural features of complexes formed in the interaction between DNA and cationic liposomes. Two distinct types of complexes form in these systems, as the charge ratio increases. They are: (i) DNA-coated liposomes, where the DNA binds electrostatically to the outside of the cationic lipid vesicle, (ii) multilamellar complexes followed by rupture and reorganization of the bilayer structure or clusters of DNA-coated vesicles with alternating sheets of DNA and lipid bilayers. The knowledge of the complex morphology occurring in lipid-DNA lipoplex formation could provide insight for the development of efficient artificial delivery systems in genetic engineering and gene therapy.