Cationic lipophosphoramidates with two different lipid chains: synthesis and evaluation as gene carriers

Abstract

Cationic lipids constitute a family of synthetic vectors commonly used for nucleic acids delivery. We herein report the results of a systematic study that aimed to compare the transfection efficacies of cationic lipophosphoramidates possessing either two identical lipid chains (termed symmetric cationic lipids) or two different lipid chains (non-symmetric cationic lipids). In addition, we also compared the transfection results of such a 'molecular approach' (the two different lipid chains being included in the same molecule) with those of a 'supramolecular approach' in which two types of symmetrical cationic lipids were mixed in one liposomal formulation. Thus, the present work allowed us first to optimize the methods used to synthesize non-symmetric cationic lipophosphoramidates. In addition, we could also identify two non-symmetric cationic lipids exhibiting high transfection efficiencies with a series of mammalian cell lines, both vectors being characterized by a single phytanyl chain and either an oleyl or a lauryl lipid chain.

Oxime Ether Lipids Containing Hydroxylated Head Groups are More Superior siRNA Delivery Agents than their Nonhydroxylated Counterparts

“…Hydrophobic domain asymmetry has been suggested as a structural factor that is beneficial for nucleic acid release, thus ultimately enhancing transfection activity [27,41]. Each of the OELs in our panel were used as a mixture of ( E , E )- and ( E , Z )-oxime ether isomers, meaning a nontrivial amount of nonsymmetric ( E , Z )-lipid was present.…”

“…Each of the OELs in our panel were used as a mixture of ( E , E )- and ( E , Z )-oxime ether isomers, meaning a nontrivial amount of nonsymmetric ( E , Z )-lipid was present. Nonsymmetric hydrophobic domains likely benefit transfection due to better nucleic acid release through looser lipid packing in the lipoplex formulation [27,42–44]. A second level of asymmetry was examined in this study in the use of lipid 2 having the mixed fatty acyl lengths, C 12 and C 14 chains in the hydrophobic domain.…”

“…This limitation has prompted investigators to explore monovalent cationic lipids as alternate transfection agents [21,9,20] Interestingly, the linking functionality, and to a lesser extent the nature of the cationic head group of the lipids have been demonstrated to contribute toward the observed nonspecific toxic effects [22]. Therefore, in addition to ether and ester linking domains in transfection lipids, such as in DOTMA and DOTAP, respectively, other linking functionalities, such as orthoester [23], carbamate [24], amide [25,26] and phosphoramidate [27] moieties have been studied. Besides the linking functionalities described above, lipid hydrocarbon chains lengths are also likely to contribute to the cytotoxicity of cationic lipids [14].…”

Synthesis of lipid-based unsymmetrical O,O-dialkylphosphites

“…This selection of lipid chains is explained by the excellent transfection results obtained with cationic lipids that possess these associations of lipid chains. 12 Once more, the unsymmetrical phosphite 3n and 3o were obtained in good yields (respectively, 85% and 80%).…”

“…10,11 On our side, we have recently published the synthesis of unsymmetrical lipophosphoramidates by an efficient 'one-pot' procedure starting from phosphorus oxychloride, a fatty alcohol, a primary amine and triethylamine as base. 12 Although this strategy was very efficient, we do not have isolated the unsymmetric lipophosphites which would be, by themselves, a very interesting lipid building block for the synthesis of other classes of amphiphilic compounds including lipophosphonates 13 or lipophosphates. 14 With respect to the synthesis of unsymmetrical O,O-dialkylphosphites, to the best of our knowledge, there is only one paper by Dal-Maso et al which reports the synthesis of unsymmetrical O,O-dialkylphosphites that include two lipid chains.…”