Transfection properties of stabilized plasmid-lipid particles containing cationic PEG lipids

Recent work has shown that plasmid DNA can be efficiently encapsulated in well-defined stabilized plasmid-lipid particles (SPLP) that have potential as systemic gene therapy vehicles [Gene Ther. 6 (1999) 271]. In this work, we examine the influence of ligands that enhance cellular uptake on the transfection potency of SPLP. The ligand employed is a cationic poly(ethylene glycol) (PEG) lipid (CPL) consisting of a lipid anchor and a PEG(3400) spacer chain with four positive charges at the end of the PEG (CPL4). It is shown that up to 4 mol% CPL4 can be inserted into preformed SPLP, resulting in up to 50-fold enhancements in uptake into baby hamster kidney (BHK) cells. The addition of Ca2+ to SPLP-CPL4 (CPL4-incorporated SPLP) results in up to 10(6)-fold enhancements in transgene expression, as compared to SPLP in the absence of either CPL4 or Ca2+. These transfection levels are comparable to those observed for plasmid DNA-cationic lipid complexes (lipoplexes) but without the cytotoxic effects noted for lipoplex systems. It is concluded that in the presence of Ca2+ and appropriate ligands to stimulate uptake, SPLP are highly potent transfection agents. (C) 2003 Elsevier Science B.V. All fights reserved.