Convenient targeting of stealth siRNA-lipoplexes to cells with chelator lipid-anchored molecules

A major obstacle for the use of siRNAs as novel therapeutics is the requirement for functional delivery to specific cells in vivo. siRNA delivery by cationic agents is generally non-specific and a convenient targeting strategy has been lacking. This work explored the potential for using the chelator lipid 3(nitrilotriacetic acid)-ditetradecylamine (NTA₃-DTDA) with neutral stealth liposomes to target siRNA to cells. A novel method for incorporating siRNAs into lipoplexes was developed which utilised helper lipids and the ionisable lipid 1,2-dioleoyl-3-dimethylammonium-propane (DODAP). This approach results in an efficient (> 50%) incorporation of siRNA into lipoplexes, which when incorporated with Ni-NTA₃-DTDA and engrafted with a His-tagged form of murine CD4 can target siRNA to murine A20 B cells, in vitro. Also, siRNA-lipoplexes engrafted with His-tagged peptides that target receptors on HEK-293 cells, or the receptor for tumour necrosis factor alpha expressed on the murine dendritic cell line DC2.4, could target siRNA and silence the expression of enhanced green fluorescence protein (EGFP). siRNA-lipoplexes produced by this method are ~ 240 nm dia, exhibit low zeta-potential (- 1 mV), and target cells in serum-containing media. The results show that NTA₃-DTDA can be used to target siRNA-lipoplexes to cells, and could provide a convenient approach for targeting siRNA to cells in vivo for therapeutic applications.