Design and Evaluation of dendrimer/cyclodextrin conjugates as a novel siRNA carrier

RNA干扰(RNAi)是小干扰RNA(SiRNA)介导的基因沉默介导信使RNA降解的机制，是遗传分析和新型基因治疗的有力工具。然而，由于siRNA的亲水性和高相对分子质量，其传递的主要障碍之一是难以穿过生物膜。我们评估了平均取代度为2.4的α-环糊精(α-CDE偶联物)与星爆型聚酰胺胺树枝状大分子(第3代)作为小干扰RNA载体的潜在用途。由pGL2控制载体(PDNA)/pGL2siRNA/α-CDE结合物组成的三元复合体显示出比商业转染剂如Lipoect tamine2000(LP)、Transfast^&lt；TM&gt；(Tf)和Lipoect tin^&lt；TM&gt；(LF)具有更高的pGL2siRNA序列特异性基因沉默效应而没有脱靶效应。在二元络合物(小干扰RNA/载体)体系中，观察到α-CDE偶联物的抑制作用相似，且无细胞毒性。α-CDE偶联物与其他商品化转染剂相比具有更好的RNA干扰效果，这可能归因于稳定的复合体形成和细胞内小干扰RNA的分布。这些结果表明，α-CDE偶联物有可能成为一种新型的小干扰RNA载体。

RNA interference (RNAi) is the mechanism of gene silencing-mediated messenger RNA degradation by small interference RNA (siRNA), which becomes a powerful tool for genetic analysis and novel gene therapy. However, one of the major obstacles for siRNA delivery is the difficulty to cross the biological membrane due to its hydrophilicity and high molecular weight. We evaluated the potential use of the starburst polyamidoamine dendrimer (generation 3) conjugate with α-cyclodextrin having an average degree of substitution of 2.4 (α-CDE conjugate) as a siRNA carrier for RNAi. The ternary complex composed of pGL2 control vector (pDNA)/pGL2 siRNA/α-CDE conjugate showed higher pGL2 siRNA sequence-specific gene silencing effects without off-target effects than those of commercial transfection reagents such as Lipofectamine^<TM>2000 (LP), TransFast^<TM> (TF) and Lipofectin^<TM> (LF). In the binary complex (siRNA/carrier) system, the similar inhibitory effects of α-CDE conjugate were observed without cytotoxicity. These superior RNAi effects of α-CDE conjugate to the other commercial transfection reagents could be attributed to stable complex formation and cytoplasmic distribution of siRNA after transfection. These results suggest that α-CDE conjugate has the potential to be a novel carrier for siRNA.