A biomimetic nanovector-mediated targeted cholesterol-conjugated siRNA delivery for tumor gene therapy

RNA interference holds tremendous potential as a therapeutic approach of malignant tumors. However, safe and efficient nanovectors are extremely lack for systemic delivery of small interfering RNA (siRNA). The study aimed to develop a biomimetic nanovector, reconstituted high density lipoprotein (rHDL), mediating targeted cholesterol-conjugated siRNA (Chol-siRNA) delivery for Pokemon gene silencing therapy. Chol-siRNA-loaded rHDL nanoparticles (rHDL/Chol-siRNA complexes) were prepared using thin-film dispersion method and their characteristics were investigated in detail. RHDL/Chol-siRNA complexes at the optimal volume ratio (lipid: Chol-siRNA) exhibited high Chol-siRNA-loading efficiency (∼99%), desirable nanoparticle size and excellent stability in serum. In addition, by analyzing Chol-siRNA release profile, rHDL/Chol-siRNA complexes displayed sustained-release characteristic and storage stability. Observations from FACS and confocal microscopic analyses revealed that rHDL-mediated carboxyfluorescein tagged Chol-siRNA (FAM-Chol-siRNA) transfection resulted in highly efficient uptake and specific cytoplasmic delivery of FAM-Chol-siRNA into human hepatocellular carcinoma cell line HepG2 via HDL-receptor mediated mechanism. In vitro cytotoxicity, apoptosis and Western-blot analyses revealed significant cellular growth inhibition and decrease of Pokemon and Bcl-2 protein expression in HepG2 cells treated with Chol-siRNA-Pokemon-loaded rHDL nanoparticles (rHDL/Chol-siRNA-Pokemon complexes), respectively. In in vivo studies, the near-infrared (NIR) dye Cy5 labeled Chol-siRNA-loaded rHDL nanoparticles (rHDL/Cy5-Chol-siRNA complexes) obviously accumulated in tumor of nude mice after i.v. administration as compared with Cy5-Chol-siRNA-loaded lipoplexes (Lipos/Cy5-Chol-siRNA complexes). Morover, rHDL/Chol-siRNA-Pokemon complexes demonstrated great tumor growth inhibition and significant decrease of Pokemon and Bcl-2 protein expression in vivo. These results suggested that rHDL should be an ideal non-viral tumor-targeting vector for Chol-siRNA transfer, and rHDL-mediated Chol-siRNA-Pokemon delivery might be a promising new strategy for gene therapy in hepatocellular carcinoma.