title: Uptake and transfection efficiency of PEGylated cationic liposome-DNA complexes with and without RGD-tagging.
abstract: Steric stabilization of cationic liposome-DNA (CL-DNA) complexes is required for in vivo applications such as gene therapy. PEGylation (PEG: poly(ethylene glycol)) of CL-DNA complexes by addition of PEG2000-lipids yields sterically stabilized nanoparticles but strongly reduces their gene delivery efficacy. PEGylation-induced weakening of the electrostatic binding of CL-DNA nanoparticles to cells (leading to reduced uptake) has been considered as a possible cause, but experimental results have been ambiguous. Using quantitative live-cell imaging in vitro, we have investigated cell attachment and uptake of PEGylated CL-DNA nanoparticles with and without a custom synthesized RGD-peptide grafted to the distal ends of PEG2000-lipids. The RGD-tagged nanoparticles exhibit strongly increased cellular attachment as well as uptake compared to nanoparticles without grafted peptide. Transfection efficiency of RGD-tagged PEGylated CL-DNA NPs increases by about an order of magnitude between NPs with low and high membrane charge density (σM; the average charge per unit area of the membrane; controlled by the molar ratio of cationic to neutral lipid), even though imaging data show that uptake of RGD-tagged particles is only slightly enhanced by high σM. This suggests that endosomal escape and, as a result, transfection efficiency of RGD-tagged NPs is facilitated by high σM. We present a model describing the interactions between PEGylated CL-DNA nanoparticles and the anionic cell membrane which shows how the PEG grafting density and membrane charge density affect adhesion of nanoparticles to the cell surface.
authors.affiliation: Department of Physics, University of California, Santa Barbara, CA 93106, USA; Department of Materials, University of California, Santa Barbara, CA 93106, USA; Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Ramsey N
authors.initials: RN
authors.lastname: Majzoub
authors.affiliation: Department of Physics, University of California, Santa Barbara, CA 93106, USA; Department of Materials, University of California, Santa Barbara, CA 93106, USA; Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, CA 93106, USA; Institute of Physics, Academica Sinica, Taipei 11529, Taiwan; National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
authors.forename: Chia-Ling
authors.initials: CL
authors.lastname: Chan
authors.affiliation: Department of Physics, University of California, Santa Barbara, CA 93106, USA; Department of Materials, University of California, Santa Barbara, CA 93106, USA; Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Kai K
authors.initials: KK
authors.lastname: Ewert
authors.affiliation: Department of Physics, University of California, Santa Barbara, CA 93106, USA; Department of Materials, University of California, Santa Barbara, CA 93106, USA; Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, CA 93106, USA; Division of Physical Chemistry, Centre for Chemistry and Chemical Engineering, Lund University, SE-221 00 Lund, Sweden.
authors.forename: Bruno F B
authors.initials: BF
authors.lastname: Silva
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan; Department of Electrophysics, National Chiao-Tung University, Hsinchu 30010, Taiwan.
authors.forename: Keng S
authors.initials: KS
authors.lastname: Liang
authors.affiliation: National Resource for Automated Molecular Microscopy, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Erica L
authors.initials: EL
authors.lastname: Jacovetty
authors.affiliation: National Resource for Automated Molecular Microscopy, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Bridget
authors.initials: B
authors.lastname: Carragher
authors.affiliation: National Resource for Automated Molecular Microscopy, Department of Integrative Structural and Computational Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Clinton S
authors.initials: CS
authors.lastname: Potter
authors.affiliation: Department of Physics, University of California, Santa Barbara, CA 93106, USA; Department of Materials, University of California, Santa Barbara, CA 93106, USA; Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, CA 93106, USA. Electronic address: safinya@mrl.ucsb.edu.
authors.forename: Cyrus R
authors.initials: CR
authors.lastname: Safinya
mesh_terms: D000818:Animals; D002412:Cations / Q000737:chemistry*; D002448:Cell Adhesion; D002460:Cell Line; D004247:DNA / Q000737:chemistry*; D015316:Genetic Therapy; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D051379:Mice; D008854:Microscopy, Electron; D053758:Nanoparticles / Q000737:chemistry; D009842:Oligopeptides / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D055672:Static Electricity; D014162:Transfection
chemical_list: D002412:Cations; D008055:Lipids; D008081:Liposomes; D009842:Oligopeptides; D011092:Polyethylene Glycols; C047981:arginyl-glycyl-aspartic acid; D004247:DNA
keywords: Gene therapy; Liposome; Live cell imaging; Nanoparticle; Polyethylene glycol; RGD peptide