Efficient in vitro siRNA delivery and intramuscular gene silencing using PEG-modified PAMAM dendrimers

Yin Tang, Yang-Bing Li, Bo Wang, Ri-Yuan Lin, Mallory van Dongen, Danielle M. Zurcher, Xiao-Yan Gu, Mark M. Banaszak Holl, George Liu, Rong Qi

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Although siRNA techniques have been broadly applied as a tool for gene knockdown, substantial challenges remain in achieving efficient delivery and in vivo efficacy. In particular, the low efficiency of target gene silencing in vivo is a critical limiting step to the clinical application of siRNA therapies. Poly(amidoamine) (PAMAM) dendrimers are widely used as carriers for drug and gene delivery; however, in vivo siRNA delivery by PAMAM dendrimers remains to be carefully investigated. In this study, the effectiveness of G5 and G6 PAMAM dendrimers with 8% of their surface amines conjugated to MPEG-5000 was studied for siRNA delivery in vitro and for intramuscular in vivo delivery in mice. The results from the PEG-modified dendrimers were compared to the results from the parent dendrimers as well as Lipofectamine 2000 and INTERFERin. Both PEG-modifed dendrimers protect the siRNA from being digested by RNase and gave high transfection efficiency for FITC-labeled siRNA in the primary vascular smooth muscle cells (VSMC) and mouse peritoneal macrophages. The PEG-modified dendrimers achieved knockdown of both plasmid (293A cells) and adenovirus-mediated green fluorescence protein (GFP) expression (Cos7 cells) in vitro with efficiency similar to that shown for Lipofectamine 2000. We further demonstrated in vivo that intramuscular delivery of GFP-siRNA using PEG-modified dendrimer significantly suppressed GFP expression in both transiently adenovirus infected C57BL/6 mice and GFP transgenic mice.

Original languageEnglish
Pages (from-to)1812-1821
Number of pages10
JournalMolecular Pharmaceutics
Issue number6
Publication statusPublished - 4 Jun 2012
Externally publishedYes


  • cytotoxicity
  • gene silencing effciency
  • in vitro and intramuscular siRNA delivery
  • PEG-conjugated PAMAM dendrimer
  • RNase stability

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