title: Novel endosomolytic peptides for enhancing gene delivery in nanoparticles.
abstract: Trapping in the endosomes is currently believed to represent the main barrier for transfection. Peptides, which allow endosomal escape have been demonstrated to overcome this barrier, similarly to the entry of viruses. However, the design principles of such endosomolytic peptides remain unclear. We characterized three analogs derived from membrane disrupting antimicrobial peptides (AMP), viz. LL-37, melittin, and bombolitin V, with glutamic acid substituting for all basic residues. These analogs are pH-sensitive and cause negligible membrane permeabilization and insignificant cytotoxicity at pH7.4. However, at pH5.0, prevailing in endosomes, membrane binding and hemolysis of human erythrocytes become evident. We first condensed the emerald green fluorescent protein (emGFP) containing plasmid by protamine, yielding 115 nm diameter soluble nanoplexes. For coating of the nanoplex surface with a lipid bilayer we introduced a hydrophobic tether, stearyl-octa-arginine (SR8). The indicated peptides were dissolved in methanol and combined with lipid mixtures in chloroform, followed by drying at RT under a nitrogen flow. The dry residues were hydrated with nanoplexes in Hepes, pH7.4 yielding after a 30 min incubation at RT,rather monodisperse nanoparticles having an average diameter of 150-300 nm, measured by DLS and cryo-TEM. Studies with cell cultures showed the above peptides to yield expression levels comparable to those obtained using Lipofectamine 2000. However, unlike the polydisperse aggregates formed upon mixing Lipofectamine 2000 and plasmid, the procedure described yields soluble, and reasonably monodisperse nanoparticles, which can be expected to be suitable for gene delivery in vivo, using intravenous injection.
authors.affiliation: Helsinki Biophysics and Biomembrane Group, Department of Biomedical Engineering and Computational Science, Aalto University School of Science, Espoo, Finland.
authors.forename: Aqeel
authors.initials: A
authors.lastname: Ahmad
authors.affiliation: Helsinki Biophysics and Biomembrane Group, Department of Biomedical Engineering and Computational Science, Aalto University School of Science, Espoo, Finland.
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Ranjan
authors.affiliation: Department of Otolaryngology, University of Tampere, Medical School, Tampere, Finland.
authors.forename: Weikai
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Otolaryngology, University of Tampere, Medical School, Tampere, Finland.
authors.forename: Jing
authors.initials: J
authors.lastname: Zou
authors.affiliation: Department of Otolaryngology, University of Tampere, Medical School, Tampere, Finland.
authors.forename: Ilmari
authors.initials: I
authors.lastname: Pyykkö
authors.affiliation: Helsinki Biophysics and Biomembrane Group, Department of Biomedical Engineering and Computational Science, Aalto University School of Science, Espoo, Finland. Electronic address: Paavo.Kinnunen@aalto.fi.
authors.forename: Paavo K J
authors.initials: PK
authors.lastname: Kinnunen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry*; D011992:Endosomes / Q000378:metabolism*; D004912:Erythrocytes / Q000737:chemistry / Q000166:cytology; D015870:Gene Expression; D018698:Glutamic Acid / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006461:Hemolysis; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008055:Lipids / Q000737:chemistry; D008555:Melitten / Q000737:chemistry*; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D009842:Oligopeptides / Q000737:chemistry; D010316:Particle Size; D010455:Peptides / Q000737:chemistry*; D011479:Protamines / Q000737:chemistry; D013228:Stearates / Q000737:chemistry; D014162:Transfection / Q000379:methods*; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D008055:Lipids; C086724:Lipofectamine; D009842:Oligopeptides; D010455:Peptides; D011479:Protamines; D013228:Stearates; C044299:bombolitins; C487882:stearyl-octaarginine; D049452:Green Fluorescent Proteins; D008555:Melitten; D018698:Glutamic Acid; D054804:Cathelicidins
keywords: Endosomal escape; Endosomolytic peptides; Gene delivery; Gene expression; Nanoparticles; Transfection