New polyphosphoramidate with a spermidine side chain as a gene carrier.


Journal Article

A new cationic polymer (PPA-SP), polyphosphoramidate bearing spermidine side chain, was prepared as a non-viral vector for gene delivery. PPA-SP was synthesized from poly(1,2-propylene H-phosphonate) by the Atherton-Todd reaction. The weight average molecular weight of PPA-SP was 3.44x10(4) with a number average degree of polymerization of 90, as determined by GPC/LS/RI method. The average net positive charge per polymer chain was 102. PPA-SP was able to condense plasmid DNA efficiently and formed complexes at an N/P ratio (free amino groups in polymer to phosphate groups in DNA) of 2 and above, as determined by agarose gel electrophoresis. This new gene carrier offered significant protection to DNA against nuclease degradation at N/P ratios above 2, and showed lower cytotoxicity than PLL and PEI in cell culture. The LD(50) of PPA-SP was 85 microg/ml in COS-7 cells, in contrast to 20 and 42 microg/ml for PLL and PEI, respectively. The complexes prepared in saline at N/P ratios of 5 approximately 10 had an average size of 250 nm and zeta-potential of 26 mV. PPA-SP mediated efficient gene transfection in a number of cell lines, and the transfection protocol was optimized in HEK293 cells using a luciferase plasmid as a marker gene. Gene expression mediated by PPA-SP was greatly enhanced when chloroquine was used in conjunction at a concentration of 100 microM. Under the optimized condition, PPA-SP/DNA complexes yield a luciferase expression level closed to PEI/DNA complexes or Transfast mediated transfection. In a non-invasive CNS gene delivery model, PPA-SP/DNA complexes yielded comparable bcl-2 expression as PEI/DNA complexes in mouse brain stem following injection of the complexes in the tongue.

Full Text

Cited Authors

  • Wang, J; Zhang, P-C; Lu, H-F; Ma, N; Wang, S; Mao, H-Q; Leong, KW

Published Date

  • September 2002

Published In

Volume / Issue

  • 83 / 1

Start / End Page

  • 157 - 168

PubMed ID

  • 12220847

Pubmed Central ID

  • 12220847

Electronic International Standard Serial Number (EISSN)

  • 1873-4995

International Standard Serial Number (ISSN)

  • 1873-4995

Digital Object Identifier (DOI)

  • 10.1016/s0168-3659(02)00180-3


  • eng