ABSTRACT
Cationic liposomes are the most widely used nonviral system for gene transfection. Simple incubation with anionic liposomes or micelles can reverse surface charge. Conventional liposomes are predominantly cleared by the cells of the immune system while sterically stabilizing coating reduces interactions with plasma components, resulting in their invisibility to macrophages. Cell entry may be by endocytosis or direct entry into the cytoplasm via membrane destabilization. DNA seems to be well protected in these complexes if they are prepared correctly. From a pharmaceutical point of view the disadvantages of cationic liposome-DNA complexes are toxicity of cationic lipids and lack of control over their interaction characteristics and stability upon application. Insertion of a variety of ligands does not present a problem. Although the encapsulated DNA is well protected, its efficient encapsulation presents the major drawback. Typical DNA is around 2 µm long, and it is difficult to entrap it into a small vesicle with inner diameter from 50 to 200 nm.
