The modification of siRNA with 3' cholesterol to increase nuclease protection and suppression of native mRNA by select siRNA polyplexes

Biomaterials. 2011 Feb;32(5):1404-11. doi: 10.1016/j.biomaterials.2010.10.019. Epub 2010 Nov 2.


Polymer-siRNA complexes (siRNA polyplexes) are being actively developed to improve the therapeutic application of siRNA. A major limitation for many siRNA polyplexes, however, is insufficient mRNA suppression. Given that modifying the sense strand of siRNA with 3' cholesterol (chol-siRNA) increases the activity of free nuclease-resistant siRNA in vitro and in vivo, we hypothesized that complexation of chol-siRNA can increase mRNA suppression by siRNA polyplexes. In this study, the characteristics and siRNA activity of self assembled polyplexes formed with chol-siRNA or unmodified siRNA were compared using three types of conventional, positively charged polymers: (i) biodegradable, cross-linked nanogels (BDNG) (ii) graft copolymers (PEI-PEG), and (iii) linear block copolymers (PLL10-PEG, and PLL50-PEG). Chol-siRNA did not alter complex formation or the resistance of polyplexes to siRNA displacement by heparin but increased nuclease protection by BDNG, PLL10-PEG, and PLL50-PEG polyplexes over polyplexes with unmodified siRNA. Chol-CYPB siRNA increased suppression of native CYPB mRNA in mammary microvascular endothelial cells (MVEC) by BDNG polyplexes (35%) and PLL10-PEG polyplexes (69%) over comparable CYPB siRNA polyplexes but had no effect on PEI-PEG or PLL50-PEG polyplexes. Overall, these results indicate that complexation of chol-siRNA increases nuclease protection and mRNA suppression by select siRNA polyplexes. These results also suggest that polycationic block length is an important factor in increasing mRNA suppression by PLL-PEG chol-siRNA polyplexes in mammary MVEC.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cells, Cultured
  • Cholesterol / analogs & derivatives
  • Cholesterol / chemistry*
  • Female
  • Mice
  • Nanogels
  • Polyethylene Glycols / chemistry
  • Polyethyleneimine / chemistry
  • Polymers / chemistry*
  • RNA, Messenger / metabolism*
  • RNA, Small Interfering / chemistry*
  • RNA, Small Interfering / metabolism*
  • Ribonucleases / metabolism*


  • Nanogels
  • Polymers
  • RNA, Messenger
  • RNA, Small Interfering
  • poly(oxyethylene) cholesteryl ether
  • polyethylene glycol polyethyleneimine nanogel
  • Polyethylene Glycols
  • Polyethyleneimine
  • Cholesterol
  • Ribonucleases