title: Combining polyethylenimine and Fe(III) for mediating pDNA transfection.
abstract: BACKGROUND
  The potential use of Fe(III) ions in biomedical applications may predict the interest of its combination with pDNA-PEI polyplexes. The present work aims at assessing the impact of this metal on pDNA complex properties.
  
  
  METHODS
  Variations in the formation of complexes were imposed by using two types of biological buffers at different salt conditions. The incorporation of pDNA in complexes was characterised by gel electrophoresis and dynamic light scattering. Transfection efficiency and cytotoxicity were evaluated in HeLa and HUH-7 cell lines, supported by flow cytometry assays.
  
  
  RESULTS
  Fe(III) enhances pDNA incorporation in the complex, irrespective of the buffer used. Transfection studies reveal that the addition of Fe(III) to complexes at low ionic strength reduces gene transfection, while those prepared under high salt content do not affect or, in a specific case, increase gene transfection up to 5 times. This increase may be a consequence of a favoured interaction of polyplexes with cell membrane and uptake. At low salt conditions, results attained with chloroquine indicate that the metal may inhibit polyplex endosomal escape. A reduction on the amount of PEI (N/P 5) formed at intermediary ionic strength, complemented by Fe(III), reduces the size of complexes while maintaining a transfection efficiency similar to that obtained to N/P 6.
  
  
  CONCLUSIONS
  Fe(III) emerges as a good supporting condensing agent to modulate pDNA-PEI properties, including condensation, size and cytotoxicity, without a large penalty on gene transfection.
  
  
  CONCLUSIONS
  This study highlights important aspects that govern pDNA transfection and elucidates the benefits of incorporating the versatile Fe(III) in a gene delivery system.
authors.affiliation: Department of Chemistry, University of Coimbra, Rua Larga, Coimbra 3004-535, Portugal. Electronic address: andreiaj@qui.uc.pt.
authors.forename: Andreia F
authors.initials: AF
authors.lastname: Jorge
authors.affiliation: Pharmaceutical Biotechnology, Center for System-based Drug Research, and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München, Munich D-81377, Germany.
authors.forename: Ruth
authors.initials: R
authors.lastname: Röder
authors.affiliation: Pharmaceutical Biotechnology, Center for System-based Drug Research, and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München, Munich D-81377, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Kos
authors.affiliation: Biophysics and Medical Technology, Department of Physics, Norwegian University of Science and Technology, Trondheim 7491, Norway.
authors.forename: Rita S
authors.initials: RS
authors.lastname: Dias
authors.affiliation: Pharmaceutical Biotechnology, Center for System-based Drug Research, and Center for Nanoscience (CeNS), Ludwig-Maximilians-Universität München, Munich D-81377, Germany.
authors.forename: Ernst
authors.initials: E
authors.lastname: Wagner
authors.affiliation: Department of Chemistry, University of Coimbra, Rua Larga, Coimbra 3004-535, Portugal.
authors.forename: Alberto A C C
authors.initials: AA
authors.lastname: Pais
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002021:Buffers; D002712:Chlorides / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D024202:Electrophoretic Mobility Shift Assay; D004734:Energy Metabolism / Q000187:drug effects; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008027:Light; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration; D010957:Plasmids / Q000737:chemistry / Q000378:metabolism*; D011094:Polyethyleneimine / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D012542:Scattering, Radiation; D014162:Transfection / Q000379:methods*
chemical_list: D002021:Buffers; D002712:Chlorides; D005290:Ferric Compounds; D000255:Adenosine Triphosphate; D011094:Polyethyleneimine; D008156:Luciferases; C024555:ferric chloride
keywords: Fe(III); Polyethylenimine; Polyplexes; Transfection; pDNA