DNA compaction to multi-molecular DNA condensation induced by cationic imidazolium gemini surfactants

The compaction and condensation of DNA induced by cationic imidazolium gemini surfactants ([Cn-4-Cnim]Br2, n = 10, 12, 14) at different charge ratios have been investigated by dynamic light scattering (DLS), zeta potential, circular dichroism (CD), and ethidium bromide exclusion assay. Upon addition of [Cn-4-Cnim]Br2, DNA molecules undergo the process from compaction to multi-molecular condensation accompanied by conformation change, which could be proved by the DLS and CD results. The charge density changes in zeta potential measurements indicated the impact of the electrostatic interaction in DNA–surfactant complex. The comparison between DNA compaction and condensation by [Cn-4-Cnim]Br2 with different tail lengths demonstrated the important contribution of the hydrophobic interaction. The EtBr exclusion assay indicates the π–π interaction between imidazolium groups of [Cn-4-Cnim]Br2 and DNA aromatic rings also plays a role in the DNA/[Cn-4-Cnim]Br2 complex formation. The impact of the different interactions on the DNA compaction and condensation by gemini surfactants would shed light on their potential applications in gene delivery.

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► An evolution from DNA compaction to multi-molecular DNA condensation induced by [Cn-4-Cnim]Br2 is identified and its mechanism is discussed.
► [Cn-4-Cnim]Br2 as novel imidazolium gemini surfactants can interact with DNA via electrostatic, hydrophobic and π–π interaction.
► The stronger interaction between DNA and [Cn-4-Cnim]Br2 with longer tails demonstrates the important contribution of the hydrophobic interaction.