Mechanism of cell transfection with plasmid/chitosan complexes

Tsuyoshi Ishii, Yoshio Okahata, Toshinori Sato

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325 Citations (Scopus)


Chitosan is useful as a non-viral vector for gene delivery. Although there are several reports supporting the use of chitosan for gene delivery, studies regarding effects on transfection and the chitosan-specific transfection mechanism remain insufficient. In this report, the level of expression with plasmid/chitosan was observed to be no less than that with plasmid/lipofectin complexes in SOJ cells. The transfection mechanism of plasmid/chitosan complexes as well as the relationship between transfection activity and cell uptake was analyzed by using fluorescein isothiocyanate-labeled plasmid and Texas Red-labeled chitosan. In regard to effects on transfection, there were several factors to affect transfection activity and cell uptake, for example: the molecular mass of chitosan, stoichiometry of complex, as well as serum concentration and pH of transfection medium. The level of transfection with plasmid/chitosan complexes was found to be highest when the molecular mass of chitosan was 40 or 84 kDa, ratio of chitosan nitrogen to DNA phosphate (N/P ratio) was 5, and transfection medium contained 10% serum at pH 7.0. We also investigated the transfection mechanism, and found that plasmid/chitosan complexes most likely condense to form large aggregates (5-8 μm), which absorb to the cell surface. After this, plasmid/chitosan complexes are endocytosed, and possibly released from endosomes due to swelling of lysosomal in addition to swelling of plasmid/chitosan complex, causing the endosome to rupture. Finally, complexes were also observed to accumulate in the nucleus using a confocal laser scanning microscope.

Original languageEnglish
Pages (from-to)51-64
Number of pages14
JournalBiochimica et Biophysica Acta - Biomembranes
Issue number1
Publication statusPublished - 2001 Sept 3


  • Chitosan
  • DNA complex
  • Plasmid
  • Subcellular distribution
  • Transfection

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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