High functionalization of dendrimer/cyclodextrin conjugate as a novel siRNA carrier

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We previously reported the potential use of starburst polyamidoamine dendrimer (dendrimer, generation 3, G3)conjugate with a-cyclodextrin (α-CDE) as a novel gene delivery carrier. In the present study, the potential of α-CDE and their sugar-appended α-CDEs as novel and cell-specific carriers of small interfering RNA(siRNA) and short hairpin RNA-expressing vector(shpDNA)was evaluated in vitro and in vivo. The RNAi effects of the siRNA complex with cc-CDE were preferable to those of the complexes with commercially-available siRNA carriers in NIH3T3 cells stably expressing pGL3 luciferase. In addition, the siRNA complex with a-CDE showed negligible cytotoxicity up to higher charge ratios. However, we found that a-CDE did not have the potential as shpDNA carriers because of low RNAi effect. When the solution containing the binary complex of siRNA with α-CDE was injected into tumor tissues of mice bearing Colon-26 cells stably expressing the GL3 luciferase gene, the sufficient RNAi effects were provided, although the complex of Lipofectamine^TM2000 with siRNA showed the off-target effect. Therefore, α-CDE was found to provide the sequence-specific gene silencing effect by the complexation with siRNA. On the other hand, we prepared mannosylated α-CDE(M-α-CDE)and lactosylated α-CDE(L-α-CDE)to delivery siRNA and shpDNA specifically to antigen-presenting cells and hepatocytes, respectively. However, we found that L-α-CDE was able to bind to asialoglycoprotein receptor expressing on hepatocytes, although M-a-CDE could not bind to mannose receptor expressing on antigen-presenting cells. Both L-α-CDE and M-α-CDE had negligible cytotoxicity. These results suggest that L-α-CDE has the potential for hepatocyte-specific siRNA and shpDNA carriers.