(579c) Novel Cationic Lipids for Efficient siRNA Delivery to Liver Cancer

Safe and Efficient delivery of small interfering RNA (siRNA) is a critical challenge in clinical application of RNA interference (RNAi) technology. Cationic lipid-based nanocarriers are emerging as promising candidates for therapeutic siRNA delivery. In this study, we synthesized a series of novel cationic lipids by using Tris(2-aminoethyl)amine as a starting material. The key feature for these novel cationic lipids is the combination of multi-tertiary amines and unsaturated alkyl chains. 1H-NMR, pKa determination and differential scanning calorimetry (DSC) were applied to characterize these cationic lipids. Various liposomal siRNA nanoparticles were prepared through electrostatic interactions between negatively charged siRNA and empty cationic liposomes. The physicochemical properties of these liposomal siRNA nanoparticles were studied by gel electrophoresis, dynamic light scattering and cryogenic-temperature transmission electron microscopy (cryo-TEM). The gene silencing study in SK Hep-1 cell line showed that these cationic lipids can efficiently deliver luciferase siRNA in vitro. The transfection capabilities of these novel cationic lipids are much better than that of lipofectamine 2000, a commercial transfection reagent. It also showed good cell viabilities of these cationic lipids by MTT study. The siRNA delivery efficiency of these cationic lipids can be further enhanced by introducing fatty acids such as linoleic acid in the formulations. The significant accumulation of Cy3-siRNA in hepatocyte cells was observed in normal mice by tail vein injection of liposomal Cy3-siRNA based on these cationic lipids. The corresponding good down-regulation efficacy of factor VII siRNA was achieved in normal C57/BL mice. Furthermore, the preferential tumor cell localization of these cationic cy3-siRNA liposomal nanoparticles was examined in orthotopic liver cancer model. Taken together, the results show our novel cationic lipids can be used as effective and safe nanocarriers for systemic administration of siRNA in liver cancer.