Synthesis, self-assembly and lipoplex formulation of two novel cyclic phosphonate lipids

Background: Synthetic cationic lipids hold much potential as gene packaging and delivery agents for the treatment of inherited and acquired life threatening diseases, such as cancer, AIDS, cardiovascular diseases, and certain autoimmune disorders. Methods: We report the synthesis, self-assembly as characterized by critical micelle concentrations and plasmid DNA gel retardation using two novel cyclic, phosphonate cationic lipids 2a and 2b, which were synthesized by derivatizing two diastereomeric macrocyclic phosphonates 1a and 1b with a 2-carbon hydroxylamine linker, N, N-dimethylethanolamine (3). Results: The production of cyclic phosphonate lipids 2a and 2b in 73% and 60% yields, respectively, was achieved using classical synthetic methods involving nucleophilic substitution at the phosphorus centre. The characterization of these lipids with Mass Spectrometry, 1H, 13C and 31P Nuclear Magnetic Resonance supported the proposed stereochemistry and molecular structure of C17H36NO3P for these lipids. Critical micelle concentrations (CMC) for 2a and 2b were found to be 1.2 mM and 1.4 mM, respectively, at 25°C, providing evidence for the self-assembling ability of these novel cyclic lipids. Finally, lipid-DNA complexes (lipoplexes) formulated at various N/P (+/ − ) molar charge ratios and containing the co-lipid, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) were shown to retard DNA in an agarose gel retardation assay. Conclusions: The synthesis, aggregation and DNA binding properties of these novel cyclic phosphonate lipids suggest that they may have utility serving as gene packaging and delivery agents.