Pharmaceutical Research

, Volume 23, Issue 8, pp 1868–1876

Biophysical and Structural Characterization of Polyethylenimine-Mediated siRNA Delivery in Vitro

  • Amy C. Richards Grayson
  • Anne M. Doody
  • David Putnam
Research Paper

DOI: 10.1007/s11095-006-9009-2

Cite this article as:
Richards Grayson, A.C., Doody, A.M. & Putnam, D. Pharm Res (2006) 23: 1868. doi:10.1007/s11095-006-9009-2


The goals of this study were as follows: 1) to evaluate the efficacy of different polyethylenimine (PEI) structures for siRNA delivery in a model system, and 2) to determine the biophysical and structural characteristics of PEI that relate to siRNA delivery.

Materials and Methods

Biophysical characterization (effective diameter and zeta potential), cytotoxicities, relative binding affinities and in vitro transfection efficiencies were determined using nanocomplexes formed from PEI's of 800, 25,000, (both branched) and 22,000 (linear) molecular weights at varying N:P ratios and siRNA concentrations. The HR5-CL11 cell line stably expressing luciferase was used as a model system in vitro.


Successful siRNA delivery was observed within a very narrow window of conditions, and only with the 25,000 branched PEI at an N:P ratio of 6:1 and 8:1 and with 200 nM siRNA. While the zeta potential and size of PEI:siRNA complexes correlated to transfection efficacy in some cases, complex stability may also affect transfection efficacy.


The ability of PEI to transfer functionally active siRNA to cells in culture is surprisingly dependent on its biophysical and structural characteristics when compared to its relative success and ease of use for DNA delivery.

Key Words

luciferasespolyethylenimineRNA interferencesmall interfering RNAtransfection



4-(2-hydroxyethyl) piperazine-1-ethanesulfonic acid




small interfering RNA

22 K L-PEI

22,000 molecular weight linear PEI

25 K B-PEI

25,000 molecular weight branched PEI

800 B-PEI

800 molecular weight branched PEI

Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • Amy C. Richards Grayson
    • 1
  • Anne M. Doody
    • 1
  • David Putnam
    • 1
  1. 1.Department of Biomedical Engineering and the School of Chemical and Biomolecular Engineering, 270 Olin HallCornell UniversityIthacaUSA