ABSTRACT
In this work that aims to synthesize and evaluate new cationic lipids as vectors for gene delivery, we report the synthesis of a series of cationic lipids in which a phosphate functional group acts as a linker to assemble on a molecular scale, two lipid chains and one cationic polar head. The mono or dicationic moiety is connected to the phosphate group by an aryl spacer. In this work, two synthesis strategies were evaluated. The first used the Atherton-Todd coupling reaction to introduce a phenolic derivative to dioleylphosphite. The second strategy used a sequential addition of lipid alcohol and a phenolic derivative on POCl3. The two methods are efficient, but the latter allows larger yields. Different polar head groups were introduced, thus producing amphiphilic compounds possessing either one permanent (N-methyl-imidazolium, pyridinium, trimethylammonium) or two permanent cationic charges. All these cationic lipids were formulated as liposomal solutions and characterized (size and zeta potential). They formed stable liposomal solutions both in water (at pH 7.0) and in a weakly acidic medium (at pH 5.5). Finally, this new generation of cationic lipids was used to deliver DNA into various human-derived epithelial cells cultured in vitro. Compared with Lipofectamine used as a reference commercial lipofection reagent, some cationic dialkylarylphosphates were able to demonstrate potent gene transfer abilities, and noteworthily, monocationic derivatives were much more efficient than dicationic analogues.
Subject(s)
Biomimetic Materials/chemistry , Drug Carriers/chemistry , Lipids/chemistry , Phosphates/chemistry , Transfection/methods , Biomimetic Materials/chemical synthesis , Biomimetic Materials/toxicity , Cell Line , DNA/chemistry , DNA/genetics , Drug Carriers/chemical synthesis , Drug Carriers/toxicity , Humans , Hydrophobic and Hydrophilic Interactions , Lipids/chemical synthesis , Lipids/toxicity , LiposomesABSTRACT
Initially, the Atherton-Todd (AT) reaction was applied for the synthesis of phosphoramidates by reacting dialkyl phosphite with a primary amine in the presence of carbon tetrachloride. These reaction conditions were subsequently modified with the aim to optimize them and the reaction was extended to different nucleophiles. The mechanism of this reaction led to controversial reports over the past years and is adequately discussed. We also present the scope of the AT reaction. Finally, we investigate the AT reaction by means of exemplary applications, which mainly concern three topics. First, we discuss the activation of a phenol group as a phosphate which allows for subsequent transformations such as cross coupling and reduction. Next, we examine the AT reaction applied to produce fire retardant compounds. In the last section, we investigate the use of the AT reaction for the production of compounds employed for biological applications. The selected examples to illustrate the applications of the Atherton-Todd reaction mainly cover the past 15 years.
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.
