title: Influence of lipoplex surface charge on siRNA delivery: application to the in vitro downregulation of CXCR4 HIV-1 co-receptor.
abstract: OBJECTIVE
  Cationic lipidic formulations have been successfully used to deliver small interfering RNA (siRNA) into cells but they show limitations for in vivo application due to their cytotoxicity and instability in the presence of serum. To overcome these limitations, the authors developed an anionic lipid-based carrier named Neutraplex (Nx). Here, they wanted to investigate the influence of the lipoplex (Lx) surface charge on cytotoxicity, delivery and silencing activity of siRNAs.
  
  
  METHODS
  The efficiency of three Nx formulations (cationic, close to neutrality and anionic) to deliver anti-CXCR4 siRNAs in MAGI cells was investigated and compared with the cationic commercial transfection reagent Lipofectamine RNAiMAX. Cellular uptake and intracellular localization of a fluorescent siRNA was monitored in live cells using fluorescence microscopy and silencing activity was measured by flow cytometry and RT-PCR analysis.
  
  
  RESULTS
  The authors found that the Lx surface charge influenced cellular uptake and silencing activity of siRNA in cell cultures. Although cationic Lx formulations were the most efficient carriers to deliver active silencing siRNAs, negatively charged lipoplexes were taken up by cells, delivered active siRNAs and presented low cytotoxicity.
  
  
  CONCLUSIONS
  Altogether, the findings support further investigation for in vivo delivery of therapeutic siRNAs using Nx. Furthermore, this study indicates that anionic delivery systems may have potential for in vivo RNAi therapeutics.
authors.affiliation: National HIV & Retrovirology Laboratories, National Microbiology Laboratory, Public Health Agency of Canada, 200 Tunney's Pasture Driveway, Ottawa, Ontario K1A 0K9, Canada. carole.lavigne@phac-aspc.gc.ca
authors.forename: Carole
authors.initials: C
authors.lastname: Lavigne
authors.forename: Kathryn
authors.initials: K
authors.lastname: Slater
authors.forename: Niranjala
authors.initials: N
authors.lastname: Gajanayaka
authors.forename: Christian
authors.initials: C
authors.lastname: Duguay
authors.forename: Erika
authors.initials: E
authors.lastname: Arnau Peyrotte
authors.forename: Germaine
authors.initials: G
authors.lastname: Fortier
authors.forename: Martin
authors.initials: M
authors.lastname: Simard
authors.forename: Arnold J
authors.initials: AJ
authors.lastname: Kell
authors.forename: Michael L
authors.initials: ML
authors.lastname: Barnes
authors.forename: Alain R
authors.initials: AR
authors.lastname: Thierry
mesh_terms: D015153:Blotting, Western; D049109:Cell Proliferation; D004337:Drug Carriers / Q000737:chemistry*; D016503:Drug Delivery Systems; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008055:Lipids / Q000737:chemistry*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000008:administration & dosage*; D060888:Real-Time Polymerase Chain Reaction; D019718:Receptors, CXCR4 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013499:Surface Properties
chemical_list: D004337:Drug Carriers; D008055:Lipids; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D019718:Receptors, CXCR4