Gene Transfer Efficacies of Novel Cationic Amphiphiles with Alanine, β-Alanine, and Serine Headgroups: A Structure−Activity Investigation

Abstract

Herein, we report on the relative in vitro efficacies of nine novel nonglycerol based cationic amphiphiles with increasing hydrophobic tails and the amino acids serine, alanine and β-alanine as the headgroup functionalities (lipids 1 − 9, Scheme 1) in transfecting multiple cultured cells including CHO, COS-1, MCF-7, and HepG2. The gene transfer efficiencies of lipids 1 − 9 were evaluated using the reporter gene assays in all the four cell lines and the whole cell histochemical X-gal staining assays in representative CHO cells. In CHO, HepG2, and MCF-7 cells, cationic lipids with alanine (4 − 6) and β-alanine (7 − 9) headgroups were found to be remarkably more transfection efficient than their serine headgroup counterparts (1 − 3). Most notably, in CHO, HepG2, and MCF-7 cells, in combination with cholesterol as auxiliary lipid, the transfection efficiencies of the cationic lipids with alanine and β-alanine headgroups and myristyl and palmityl tails (lipids 4, 5, 7 and 8) were significantly higher (2−3-fold) than that of LipofectAmine-2000, a widely used commercially available liposomal tranfection vectors. Surprisingly, in COS-1 cells, although cationic lipids with β-alanine headgroups (7 − 9) were strikingly transfection efficient (3−4-fold more efficacious than LipofectAmine-2000), the gene transfer properties of both their structural isomers (4 − 6) and their serine headgroup counterparts (1 − 3) were adversely affected. In summary, the present structure−activity investigation demonstrate that high gene delivery efficacies of cationic amphiphiles containing alanine or β-alanine headgroups can get seriously compromised by substituting the alanine or β-alanine with serine presumably due to the enhanced sensitivity of DNA associated with such serine-head-containing cationic lipids.