title: Toward synthetic viruses: endosomal pH-triggered deshielding of targeted polyplexes greatly enhances gene transfer in vitro and in vivo.
abstract: Nonviral vectors should undergo "virus-like" changes compatible with the steps of gene delivery. Poly(ethylene) glycol (PEG) shielding of DNA/polycation polyplexes protects from nonspecific interactions with the extracellular environment. pH-triggered removal of the shield within the endosome may be advantageous. Polycation and PEG were linked via acylhydrazides or pyridylhydrazines. The pyridylhydrazone prepared from polylysine and propionaldehyde-PEG showed the greatest acid-dependent hydrolysis; at pH 5, 37 degrees C for 10 min, 90% hydrolyzed, while at pH 7.4 the half-life was 1.5 h. Particle size and zeta potential measurements of the polyplexes showed complete deshielding within 1 h at pH 5, while at pH 7.4 the shield remained at 4 h, 37 degrees C. For gene transfection a targeting conjugate was also included in the polyplex, transferrin as ligand for K562 and Neuro2A cells and epidermal growth factor for HUH-7 and Renca-EGFR cells. Marker gene expression showed that the reversibly shielded polyplexes exhibited up to 2 log orders of magnitude higher gene expression in vitro and 1 log magnitude higher gene expression in an in vivo mouse model, compared to the stably shielded control polyplexes. Engineering of polyplexes with more dynamic domains is an encouraging new direction in nonviral vector design.
authors.affiliation: Pharmaceutical Biology-Biotechnology, Department of Pharmacy, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, Room 3.023, D-81377 Munich, Germany. greg.walker@cup.uni-muenchen.de
authors.forename: Greg F
authors.initials: GF
authors.lastname: Walker
authors.forename: Carolin
authors.initials: C
authors.lastname: Fella
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Pelisek
authors.forename: Julia
authors.initials: J
authors.lastname: Fahrmeir
authors.forename: Sabine
authors.initials: S
authors.lastname: Boeckle
authors.forename: Manfred
authors.initials: M
authors.lastname: Ogris
authors.forename: Ernst
authors.initials: E
authors.lastname: Wagner
mesh_terms: D000818:Animals; D004247:DNA / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism*; D018014:Gene Transfer Techniques; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020014:K562 Cells; D051379:Mice; D011073:Polyamines; D000071228:Polyelectrolytes; D011092:Polyethylene Glycols; D013997:Time Factors
chemical_list: D004247:DNA; D011073:Polyamines; D000071228:Polyelectrolytes; D011092:Polyethylene Glycols