Phase behavior, DNA ordering, and size instability of cationic lipoplexes: Relevance to optimal transfection activity

Dmitri Simberg, Dganit Danino, Yeshayahu Talmon, Abraham Minsky, Marilyn E. Ferrari, Carl J. Wheeler, Yechezkel Barenholz*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

176 Scopus citations


Mechanisms of cationic lipid-based nucleic acid delivery are receiving increasing attention, but despite this the factors that determine high or low activity of lipoplexes are poorly understood. This study is focused on the fine structure of cationic lipid-DNA complexes (lipoplexes) and its relevance to transfection efficiency. Monocationic (N-(1-(2,3-dioleoyloxy)propyl),N,N,N-trimethylammonium chloride, N-(1-(2,3-dimyristyloxypropyl)-N,N-dimethyl-(2-hydroxyethyl)ammonium bromide) and polycationic (2,3-dioleyloxy-N-[2(sperminecarboxamido)ethyl]-N,N-dimethyl-1-propanammonium trifluoroacetate) lipid-based assemblies, with or without neutral lipid (1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine, 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine, cholesterol) were used to prepare lipoplexes of different L+/DNA- charge ratios. Circular dichroism, cryogenic-transmission electron microscopy, and static light scattering were used for lipoplex characterization, whereas expression of human growth hormone or green fluorescent protein was used to quantify transfection efficiency. All monocationic lipids in the presence of inverted hexagonal phase-promoting helper lipids (1,2-dioleoyl-sn-glycero-3-phosphatidylethanolamine, cholesterol) induced appearance of Ψ- DNA, a chiral tertiary DNA structure. The formation of Ψ- DNA was also dependent on cationic lipid-DNA charge ratio. On the other hand, monocationic lipids either alone or with 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine as helper lipid, or polycationic 2,3-dioleyloxy-N-[2(sperminecarboxamido) ethyl]-N,N-dimethyl-1-propanammonium trifluoroacetate-based assemblies, neither of which promotes a lipid-DNA hexagonal phase, did not induce the formation of Ψ- DNA. Parallel transfection studies reveal that the size and phase instability of the lipoplexes, and not the formation of Ψ- DNA structure, correlate with optimal transfection.

Original languageEnglish
Pages (from-to)47453-47459
Number of pages7
JournalJournal of Biological Chemistry
Issue number50
StatePublished - 14 Dec 2001
Externally publishedYes


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