Full deacylation of polyethylenimine dramatically boosts its gene delivery efficiency and specificity to mouse lung

doi:10.1073/pnas.0502067102

Full deacylation of polyethylenimine dramatically boosts its gene delivery efficiency and specificity to mouse lung

^*Department of Chemistry and Division of Biological Engineering, ^†Center for Cancer Research and Department of Biology, ^‡Department of Chemical Engineering, and ^§Whitehead Institute of Biomedical Research, Massachusetts Institute of Technology, Cambridge, MA 02139

Contributed by Alexander M. Klibanov, March 12, 2005

Abstract

High-molecular-mass polyethylenimines (PEIs) are widely used vectors for nucleic acid delivery. We found that removal of the residual N-acyl moieties from commercial linear 25-kDa PEI enhanced its plasmid DNA delivery efficiency 21 times in vitro, as well as 10,000 times in mice with a concomitant 1,500-fold enhancement in lung specificity. Several additional linear PEIs were synthesized by acid-catalyzed hydrolysis of poly(2-ethyl-2-oxazoline), yielding the pure polycations. PEI87 and PEI217 exhibited the highest efficiency in vitro: 115-fold and 6-fold above those of the commercial and deacylated PEI25s, respectively; moreover, PEI87 delivered DNA to mouse lung as efficiently as the pure PEI25 but at a lower concentration and with a 200-fold lung specificity. These improvements stem from an increase in the number of protonatable nitrogens, which presumably results in a tighter condensation of plasmid DNA and a better endosomal escape of the PEI/DNA complexes. As a validation of the potential of such linear, fully deacylated PEIs in gene therapy for lung diseases, systemic delivery in mice of the complexes of a short interfering RNA (siRNA) against a model gene, firefly luciferase, and PEI25 or PEI87 afforded a 77% and 93% suppression of the gene expression in the lungs, respectively. Furthermore, a polyplex of a siRNA against the influenza viral nucleocapsid protein gene and PEI87 resulted in a 94% drop of virus titers in the lungs of influenza-infected animals.

Footnotes

↵ ¶ To whom correspondence should be addressed. E-mail: klibanov{at}mit.edu.
Author contributions: M.T., J.C., and A.M.K. designed research; M.T., J.J.L., Q.G., and C.Z. performed research; M.T. and Q.G. contributed new reagents/analytic tools; M.T. analyzed data; and M.T., J.C., and A.M.K. wrote the paper.
Abbreviations: PEI, polyethylenimine; PEIn, PEI with molecular mass n (in kDa); PEOZ, poly(2-ethyl-2-oxazoline); siRNA, short interfering RNA; NP, nucleocapsid protein; fLuc, firefly luciferase; EtdBr, ethidium bromide.