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 ([C-n-4-C(n)im]Br-2. 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 [C-n-4-C(n)im]Br-2, 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 [C-n-4-C(n)im]Br-2 with different tail lengths demonstrated the important contribution of the hydrophobic interaction. The EtBr exclusion assay indicates the pi-pi interaction between imidazolium groups of [C-n-4-C(n)im]Br-2 and DNA aromatic rings also plays a role in the DNA/[C-n-4-C(n)im]Br-2 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. (C) 2012 Elsevier B.V. All rights reserved.