Evaluation of polyamidoamine dendrimer/alpha-cyclodextrin conjugate (generation 3, G3) as a novel carrier for small interfering RNA (siRNA).

As the first step toward an evaluation of the potential use of the PAMAM dendrimer (G3) conjugate with alpha-cyclodextrin (alpha-CDE) for a small interfering RNA (siRNA) carrier, the ternary complexes of alpha-CDE or the transfection reagents such as Lipofactamine 2000 (L2), TransFast (TF) and Lipofectin (LF) with plasmid DNA (pDNA) and siRNA were prepared, and their RNAi effects, cytotoxicity, physicochemical properties and intracellular distribution were compared. Here the pGL2 control vector (pGL2) and pGL3 control vector (pGL3) encoding the firefly luciferase gene and the two corresponding siRNAs (siGL2 and siGL3) were used. The ternary complexes of pGL3/siGL3/alpha-CDE showed the potent RNAi effects with negligible cytotoxicity compared to those of the transfection reagents in various cells. alpha-CDE strongly interacted with both pDNA and siRNA, and suppressed siRNA degradation by serum, compared to those of the transfection reagents. alpha-CDE allowed fluorescent labeled siRNA to distribute in cytoplasm, whereas the transfection reagents resided in both nucleus and cytoplasm in NIH3T3 cells. Furthermore, the binary complex of siRNA/alpha-CDE provided the significant RNAi effect in NIH3T3 cells transiently and stably expressing luciferase gene. These results suggest that alpha-CDE may be utilized as a novel carrier for siRNA.