Lipoplex formation under equilibrium conditions reveals a three-step mechanism

[No Value] Oberle, U Bakowsky, IS Zuhorn, D Hoekstra*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

118 Citations (Scopus)

Abstract

Cellular transfection can be accomplished by the use of synthetic amphiphiles as gene carrier system. To understand the mechanism and hence to improve the efficiency of transfection, insight into the assembly and properties of the amphiphile/gene complex is crucial. Here, we have studied the interaction between a plasmid and cationic amphiphiles, using a monolayer technique, and have examined complex assembly by atomic force microscopy. The data reveal a three-step mechanism for complex formation. In a first step, the plasmids, interacting with the monolayer, display a strong tendency of orientational ordering. Subsequently, individual plasmids enwrap themselves with amphiphile molecules in a multilamellar fashion. The size of the complex formed is determined by the supercoiled size of the plasmid, and calculations reveal that the plasmid can be surrounded by 3 to 5 bilayers of the amphiphile. The eventual size of the transfecting complex is finally governed by fusion events between individually wrapped amphiphile/DNA complexes. In bulk phase, where complex assembly is triggered by mixing amphiphilic vesicles and plasmids, a similar wrapping process is observed. However, in this case, imperfections in this process may give rise to a partial exposure of plasmids, i.e., part of the plasmid is not covered with a layer of amphiphile. We suggest that these exposed sites may act as nucleation sites for massive lipoplex clustering, which in turn may affect transfection efficiency.

Original languageEnglish
Pages (from-to)1447-1454
Number of pages8
JournalBiophysical Journal
Volume79
Issue number3
Publication statusPublished - Sep-2000

Keywords

  • ATOMIC-FORCE MICROSCOPY
  • CATIONIC LIPOSOME COMPLEXES
  • GENE-TRANSFER
  • PLASMID DNA
  • CRYOELECTRON MICROSCOPY
  • CELLS
  • CONDENSATION
  • EFFICIENT
  • DELIVERY
  • LIPIDS

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