title: Cytoplasmic delivery of liposomal contents mediated by an acid-labile cholesterol-vinyl ether-PEG conjugate.
abstract: An acid-cleavable PEG lipid, 1'-(4'-cholesteryloxy-3'-butenyl)-omega-methoxy-polyethylene[112] glycolate (CVEP), has been developed that produces stable liposomes when dispersed as a minor component (0.5-5 mol %) in 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). Cleavage of CVEP at mildly acidic pHs results in dePEGylation of the latently fusogenic DOPE liposomes, thereby triggering the onset of content release. This paper describes the synthesis of CVEP via a six-step sequence starting from the readily available precursors 1,4-butanediol, cholesterol, and mPEG acid. The hydrolysis rates and release kinetics from CVEP/DOPE liposome dispersions as a function of CVEP loading, as well as the cryogenic transmission electron microscopy and pH-dependent monolayer properties of 9:91 CVEP/DOPE mixtures, also are reported. When folate receptor-positive KB cells were exposed to calcein-loaded 5:95 CVEP/DOPE liposomes containing 0.1 mol % folate-modified 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-polyethylene[76] glycolamide (folate-PEG-DSPE), delivery of the calcein cargo to the cytoplasm of the cells was observed as determined by fluorescence microscopy and flow cytometry. Fluorescence resonance energy transfer analysis of lipid mixing in these cells was consistent with membrane-membrane fusion between the liposome and endosomal membranes.
authors.affiliation: Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-1393, USA.
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Boomer
authors.forename: Marquita M
authors.initials: MM
authors.lastname: Qualls
authors.forename: H Dorota
authors.initials: HD
authors.lastname: Inerowicz
authors.forename: Robert H
authors.initials: RH
authors.lastname: Haynes
authors.forename: V Srilakshmi
authors.initials: VS
authors.lastname: Patri
authors.forename: Jong-Mok
authors.initials: JM
authors.lastname: Kim
authors.forename: David H
authors.initials: DH
authors.lastname: Thompson
mesh_terms: D002784:Cholesterol; D003593:Cytoplasm / Q000378:metabolism*; D005452:Fluoresceins / Q000008:administration & dosage*; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D007700:Kinetics; D008081:Liposomes / Q000493:pharmacokinetics*; D011092:Polyethylene Glycols; D014753:Vinyl Compounds
chemical_list: D005452:Fluoresceins; D008081:Liposomes; D014753:Vinyl Compounds; C100195:vinyl ether; D011092:Polyethylene Glycols; D002784:Cholesterol; C007740:fluorexon