COMPLEXES BETWEEN CATIONIC LIPOSOMES AND DNA VISUALIZED BY CRYO-TEM

The association structures formed by cationic liposomes and DNA-plasmi ds have been successfully employed as gene carriers in transfection as says. In the present study such complexes was studied by cryo-TEM (cry o-transmission electron microscopy). Cationic liposomes made up by DOP E (dioleoylphosphatidylethanolamine) and various amounts of three diff erent cationic surfactants were investigated. The cryo-TEM analysis su ggests that an excess of lipid in terms of charge, leads to entrapment of the DNA molecules between the lamellas in clusters of aggregated m ultilamellar structures. With increasing amounts of DNA free or loosel y bound plasmids were found in the vicinity of the complexes. The impo rtance of the choice of surfactant, as reported from many transfection assays, was not reflected in changes of the type of DNA-vesicle assoc iation. A tendency towards polymorphism of the lipid mixtures is repor ted and its possible implications are discussed.