title: Triggered release of siRNA from poly(ethylene glycol)-protected, pH-dependent liposomes.
abstract: The ability of small interfering RNA (siRNA) to regulate gene expression has potential therapeutic applications, but its use is limited by inefficient delivery. Triggered release of adsorbed poly(ethylene glycol) (PEG)-b-polycation polymers from pH-dependent (PD) liposomes enables protection from immune recognition during circulation (pH 7.4) and subsequent intracellular delivery of siRNA within the endosome (pH ~5.5). Polycationic blocks, based on either poly[2-(dimethylamino)ethyl methacrylate] (31 or 62 DMA repeat units) or polylysine (21 K repeat units), act as anchors for a PEG (113 ethylene glycol repeat units) protective block. Incorporation of 1,2-dioleoyl-3-dimethylammonium-propane (DAP), a titratable lipid, increases the liposome's net cationic character within acidic environments, resulting in polymer desorption and membrane fusion. Liposomes encapsulating siRNA demonstrate green fluorescent protein (GFP) silencing in genetically-modified, GFP-expressing HeLa cells and glyceraldehyde-3-phosphate dehydrogenase (GAPD) knockdown in human umbilical vein endothelial cells (HUVEC). Bare and PD liposomes coated with PEG113-DMA31 exhibit a 0.16+/-0.2 and 0.32+/-0.3 fraction of GFP knockdown, respectively. In contrast, direct siRNA administration and Oligofectamine complexed siRNA reduce GFP expression by 0.06+/-0.02 and 0.14+/-0.02 fractions, respectively. Our in vitro data indicates that polymer desorption from PD liposomes enhances siRNA-mediated gene knockdown.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
authors.forename: Debra T
authors.initials: DT
authors.lastname: Auguste
authors.forename: Kay
authors.initials: K
authors.lastname: Furman
authors.forename: Andrew
authors.initials: A
authors.lastname: Wong
authors.forename: Jason
authors.initials: J
authors.lastname: Fuller
authors.forename: Steven P
authors.initials: SP
authors.lastname: Armes
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Deming
authors.forename: Robert
authors.initials: R
authors.lastname: Langer
mesh_terms: D000327:Adsorption; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D015870:Gene Expression; D018014:Gene Transfer Techniques; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000138:chemical synthesis / Q000737:chemistry*; D008689:Methacrylates / Q000737:chemistry; D010316:Particle Size; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000737:chemistry / Q000235:genetics; D012235:Rhodamines / Q000737:chemistry
chemical_list: D008055:Lipids; D008081:Liposomes; D008689:Methacrylates; C053685:N-(lissamine rhodamine B sulfonyl)-1,2-dioleoylphosphatidylethanolamine; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D034741:RNA, Small Interfering; D012235:Rhodamines; C484027:oligofectamine; C421283:poly(ethylene glycol)-dimethacrylate; D049452:Green Fluorescent Proteins; D011092:Polyethylene Glycols; C042077:N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidylethanolamine; C042511:1,2-dioleoylphosphatidylserine; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; C017251:1,2-oleoylphosphatidylcholine