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

AbstractRecent 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 PEG3400 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 106-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