Evaluation of siRNA and cationic liposomes complexes as a model for in vitro siRNA delivery to cancer cells

Controlled release of genetic material such as small interfering RNA (siRNA) using lipid-based non-viral vectors has gained substantial importance in gene therapy applications. Therefore, the interaction between siRNA and these vectors must be well understood. This study aims to investigate the effect of different molar charge ratios (R+/-) between positive charges from microfluidics-produced cationic liposomes (CL) (egg phosphatidylcholine, 1,2-dioleoyl-3-trimethylammonium-propane and 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and negative charges from siRNA and on physico-chemical and morphological properties of the lipoplexes (CL/siRNA) as well as their in vitro luciferase silencing effect in HeLa cells. R+/- 3.27 was found to be the optimum point for complexation. This finding was confirmed by gel retardation and siRNA accessibility assays. According to Cryo-TEM analysis, the lipoplexes had multi-lamellarity. In vitro transfection efficiency of lipoplexes in HeLa cells was tested at three different siRNA concentrations (10, 25, and 35 nM). Significant knockdown of luciferase by siRNA lipoplexes was observed based on reduced luciferase activity of transfected HeLa cells. Our findings were comparable with the silencing effect of siRNA complexed with Lipofecamine (R). No cytotoxicity of lipoplexes was detected at the tested concentrations. This study was essential for further complexation studies which will be performed using microfluidic systems to formulate next-generation lipid-based controlled release systems. (AU)