Folate-linked lipid-based nanoparticles for synthetic siRNA delivery in KB tumor xenografts

RNA interference (RNAi) is a sequence-specific gene-silencing mechanism triggered by synthetic small interfering RNA (siRNA), and is utilized in a wide range of fields including cancer gene therapy by down-regulating a specific target protein. In this study, for tumor-targeted siRNA delivery, we developed a folate-linked nanoparticle (NP-F), and evaluated the potential of NP-F-mediated tumor gene therapy in human nasopharyngeal KB cells, which overexpressed folate receptor (FR). NP-F was composed of cholesteryl-3β-carboxyamidoethylene-N-hydroxyethylamine (OH-Chol), Tween 80 and folate-poly(ethylene glycol)-distearoylphosphatidylethanolamine conjugate (f-PEG2000-DSPE), and NP-P was substituted f-PEG2000-DSPE in NP-F PEG2000-DSPE for a non-targeting nanoparticle. The NP-F and siRNA complex (nanoplex) formed at a charge ratio (+/−) of 2/1 in the presence of 5 mM NaCl was injectable size and increased transfection efficiency in the cells. NP-F showed a significantly higher intracellular amount of siRNA and stronger localization of siRNA in the cytoplasm than NP-P. When Her-2 siRNA was transfected into cells by NP-F and NP-P, NP-F significantly inhibited tumor growth, and selectively suppressed Her-2 protein expression more than NP-P. In in vivo gene therapy, a NP-F nanoplex of Her-2 siRNA by intratumoral injection significantly inhibited tumor growth of KB xenografts compared with control siRNA, but a NP-P nanoplex did not. These results of the experiments have provided optimal conditions to form folate-linked nanoparticle complexes with siRNA for folate-targeted gene therapy.