537. Charge-Reversal Lipids for Gene Transfection

One of the critical steps limiting the efficiency of non-viral gene delivery is the intracellular release of DNA from the vector complex. The complex should be stable enough to prevent DNA degradation but also dissociate from the DNA once inside the cell for subsequent transcription. To facilitate the escape of DNA from the DNA-lipid complex in the cell, and thus improve transfection efficiency, we have developed esterase sensitive cationic lipids. These lipids form a strong complex with DNA. Once in the endosome, esterases hydrolyze the terminal ester linkage of the lipid affecting a change in overall lipid charge from cationic to anionic. This charge-reversal transition releases the DNA from the lipids. These charge-reversal lipids (Fig. 1) were synthesized and characterized. The complexation and dissociation of the lipid to the DNA was monitored using an ethidium bromide displacement assay. The supramolecular lipid/DNA complexes were also characterized by dynamic light scattering, TEM and X-ray diffraction. Successful gene transfection was observed with this new class of lipids with CHO, K562, and HEK293 cells.