title: In vitro investigations of the efficacy of cyclodextrin-siRNA complexes modified with lipid-PEG-Octaarginine: towards a formulation strategy for non-viral neuronal siRNA delivery.
abstract: OBJECTIVE
  Development of RNA interference based therapeutics for neurological and neurodegenerative diseases is hindered by a lack of non-viral vectors with suitable properties for systemic administration. Amphiphilic and cationic cyclodextrins (CD) offer potential for neuronal siRNA delivery. We aimed to improve our CD-based siRNA formulation through incorporation of a polyethyleneglycol (PEG) shielding layer and a cell penetrating peptide, octaarginine (R8).
  
  
  METHODS
  CD.siRNA complexes were modified by addition of an R8-PEG-lipid conjugate. Physical properties including size, charge and stability were assessed. Flow cytometry was used to determine uptake levels in a neuronal cell model. Knockdown of an exogenous gene and an endogenous housekeeping gene were used to assess gene silencing abilities.
  
  
  RESULTS
  CD.siRNA complexes modified with R8-PEG-lipid exhibited a lower surface charge and greater stability to a salt-containing environment. Neuronal uptake was increased and significant reductions in the levels of two target genes were achieved with the new formulation. However, the PEG layer was not sufficient to protect against serum-induced aggregation.
  
  
  CONCLUSIONS
  The R8-PEG-lipid-CD.siRNA formulation displayed enhanced salt-stability due to the PEG component, while the R8 component facilitated transfection of neuronal cells and efficient gene silencing. Further improvements will be investigated in the future in order to optimise stability in serum and enhance neuronal specificity.
authors.affiliation: Pharmacodelivery Group, School of Pharmacy, University College Cork, Cavanagh Pharmacy Building College Rd., Cork, Ireland.
authors.forename: Aoife M
authors.initials: AM
authors.lastname: O'Mahony
authors.forename: Stephane
authors.initials: S
authors.lastname: Desgranges
authors.forename: Julien
authors.initials: J
authors.lastname: Ogier
authors.forename: Aoife
authors.initials: A
authors.lastname: Quinlan
authors.forename: Marc
authors.initials: M
authors.lastname: Devocelle
authors.forename: Raphael
authors.initials: R
authors.lastname: Darcy
authors.forename: John F
authors.initials: JF
authors.lastname: Cryan
authors.forename: Caitriona M
authors.initials: CM
authors.lastname: O'Driscoll
mesh_terms: D000818:Animals; D002460:Cell Line; D003505:Cyclodextrins / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009842:Oligopeptides / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000235:genetics / Q000493:pharmacokinetics; D014162:Transfection
chemical_list: D003505:Cyclodextrins; D008055:Lipids; D009842:Oligopeptides; D034741:RNA, Small Interfering; C448619:octaarginine; D011092:Polyethylene Glycols