Evidence of an inverted hexagonal phase in self-assembled phospholipid-$\chem{DNA}$-metal complexes

We report the first observation of an inverted hexagonal phase of phospholipid-DNA-metal complexes. These ternary complexes are formed in a self-assembled manner when water solutions of neutral lipid dioleoylphosphatidylethanolamine (DOPE), DNA and divalent metal cations ($\chem{Me^{2+}}$; $\chem{Me=Fe}$, $\chem{Co}$, $\chem{Mg}$, $\chem{Mn}$) are mixed, which represents a striking example of supramolecular chemistry. The structure, derived from synchrotron X-ray diffraction, consists of cylindrical DNA strands coated by neutral lipid monolayers and arranged on a two-dimensional hexagonal lattice ($H_{II}^{c}$). Besides the fundamental aspects, DOPE-DNA-$\chem{Me^{2+}}$ complexes may be of great interest as efficient nonviral delivery systems in gene therapy applications because of the low inherent cytotoxicity and the potential high transfection efficiency.