title: Biophysical and structural characterization of polyethylenimine-mediated siRNA delivery in vitro.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Biophysical characterization (effective diameter and zeta potential), cytotoxicities, relative binding affinities and in vitro transfection efficiencies were determined using nano-complexes 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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biomedical Engineering, The School of Chemical and Biomolecular Engineering, 270 Olin Hall, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Amy C Richards
authors.initials: AC
authors.lastname: Grayson
authors.forename: Anne M
authors.initials: AM
authors.lastname: Doody
authors.forename: David
authors.initials: D
authors.lastname: Putnam
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002850:Chromatography, Gel; D004563:Electrochemistry; D006801:Humans; D008156:Luciferases / Q000235:genetics; D008954:Models, Biological; D008970:Molecular Weight; D010957:Plasmids / Q000235:genetics; D011094:Polyethyleneimine / Q000737:chemistry*; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000737:chemistry; D014162:Transfection
chemical_list: D034741:RNA, Small Interfering; D011094:Polyethyleneimine; D008156:Luciferases