ABSTRACT
The synthetic vectors, mainly represented by cationic lipid/liposomes and cationic polymers, are an alternative to the viral vectors. The use of cationic liposomes has become popular because of their high transfection efficiency in vitro, reported their successful transfection results in vivo, their simplicity of use, and their ready availability from various commercial sources. Each individual structural domain seems to be important for the transfection activity of a cationic lipid. Recently, an elegant structure-activity study on a series of multivalent cationic lipids synthesized by a group from Genezyme Inc. revealed that while many multivalent cationic lipids could transfect cultured cells in vitro, only a few of these lipids showed significant in vivo transfection activity when delivered through airways to mouse lungs. A small fraction of the complexes managed to escape from endosomes before being degraded in lysosomes.
