N-ACYL-(ALPHA,GAMMA DIAMINOBUTYRIC ACID)(N) HYDRAZIDE AS AN EFFICIENTGENE-TRANSFER VECTOR IN MAMMALIAN-CELLS IN CULTURE

Purpose. This study investigates the structure/activity relationship o f a series of N-acyl-peptides (lipopeptides) for the transfection of m ammalian cells. Methods. Lipopeptides comprising 1 to 3 basic amino-ac ids and a single fatty acid chain were synthesized. Transfecting compl exes between lipopeptide, plasmid DNA and dioleoyl phosphatidylethanol amine were prepared and applied on cells in culture. Transfection effi ciency was evaluated by measuring beta-galactosidase activity 48 h pos t-transfection. Lipopeptide-DNA binding was also investigated by physi cal means and molecular modelling. Results. Besides the length of the fatty acid chain, the nature of the basic amino-acid and the C-termina l group were crucial parameters for high transfection efficiency. The N-acyl-(diaminobutyric acid)n derivatives were the most potent transfe cting agents among those tested and induced a beta-galactosidase activ ity 2 to 20 times higher than the N-acyl-lysine, -ornithine or -diamin opropionic acid derivatives. Furthermore, a hydrazide C-terminal modif ication greatly enhanced transfection efficiency for all compounds tes ted. The reason why alpha, gamma-diaminobutyric acid hydrazide-based l ipopeptides were the most potent in transfection is not fully understo od but could be related to their high DNA binding. Conclusions. Poly- or oligo-diaminobutyric acid containing or not a hydrazide C-terminus could advantageously be used in peptide-based gene delivery systems.