In vitro cationic lipid-mediated gene delivery with fluorinated glycerophosphoethanolamine helper lipids

There is a need for the development of nonviral gene transfer systems with improved and original properties. "Fluorinated" lipoplexes are such candida tes, as supported by the remarkably higher in vitro and in vivo transfectio n potency found for such fluorinated lipoplexes as compared with convention al ones or even With PEI-based polyplexes (Boussif, O., Gaucheron, J., Boul anger, C., Santaella, C., Kolbe, H. V. J., Vierling, P. (2001) Enhanced in vitro and in vivo cationic lipid-mediated gene delivery with a fluorinated glycerophosphoethanolamine helper lipid. J. Gene Med. 3, 109-114). Here, we describe the synthesis of fluorinated glycerophosphoethanolamines (F-PEs), close analogues of dioleoylphosphatidylethanolamine (DOPE), and report on their lipid helper properties vs that of DOPE, as in vitro gene transfer co mponents of fluorinated lipoplexes based on pcTG90, DOGS (Transfectam), or DOTAP. To evaluate the contribution of the F-PEs to in vitro lipoplex-media ted gene transfer, we examined the effect of including the F-PEs in lipople xes formulated with these cationic lipids (CL) for various CL:DOPE:F-PE mol ar ratios [1:(l-x):x with x = 0, 0.5 and 1; 1:(2 - y):y with y = 0, 1, 1. 5 , and 2], and various N/P ratios (from 10 to 0.8, N = number of CL amines, P = number of DNA phosphates). Irrespective of the F-PE chemical structure, of the colipid F-PE:DOPE composition, and of the N/P ratio, comparable tra nsfection levels to those of their respective control DOPE lipoplexes were most frequently obtained when using one of the F-PEs as colipid of DOGS, pc TG90, or DOTAP in place of part of or of all DOPE. However, a large proport ion of DOGS-based lipoplexes were found to display a higher transfection ef ficiency when formulated with the F-PEs rather than with DOPE alone while t he opposite tendency was evidenced for the DOTAP-based lipoplexes. The pres ent work indicates that "fluorinated" lipoplexes formulated with fluorinate d helper lipids and conventional cationic lipids are very attractive candid ates for gene delivery. It confirms further that lipophobicity and restrict ed miscibility of the lipoplex lipids with the endogenous lipids does not p reclude efficient gene transfer and expression. Their transfection potency is rather attributable to their unique lipophobic and hydrophobic character (resulting from the formulation of DNA with fluorinated lipids), thus prev enting to some extent DNA from interactions with lipophilic and hydrophilic biocompounds, and from degradation.