Lipid mixing upon deoxyribonucleic acid-induced liposomes fusion investigated by synchrotron small-angle x-ray scattering

Multipart cationic lipid/deoxyribonucleic acid (DNA) complexes (lipoplexes) were prepared, for the first time, by adding linear fragments of DNA to mixed lipid dispersions containing two distinct populations of cationic liposomes exhibiting different lipid headgroups and a number of systematic variations in relevant physical-chemical parameters. Upon DNA-induced fusion of liposomes, large lipid mixing at the molecular level occurs. As a result, highly organized mixed lipoplexes form spontaneously. By varying the composition of lipid dispersion, the physical properties of the emerging lipid carrier, i.e., the surface charge density and membrane thickness, can be modulated and distinct DNA packing densities can also be achieved. (C) 2005 American Institute of Physics.