Comparison of two lipid/DNA complexes of equal composition and different morphology.

Two types of complexes were prepared from a cationic cholesterol derivative, dioleoylphos-phatidylcholine and DNA. Depending on the preparation procedure complexes were either dense snarls of lipid covered DNA (type A) or multilayer liposomes with DNA between layers (type B). The transfection efficiency of the snarl-shaped complexes was low but positive. The transfection efficiency of the liposome-shaped complexes was zero, while DNA release upon their interaction with anionic liposomes was 1.7 times higher. The differences in transfection efficacy and DNA release could not be ascribed to the difference in resistance of complexes to decomposition upon interaction with anionic liposomes or intracellular environment since the lipid composition of complexes is the same. Instead the complexes in which lipoplex phase is more continuous (type A) should require more anionic lipids or more time within a cell for complete decomposition. Prolonged life time should lead to the higher probability of DNA expression.