A supramolecular polymerisation model for the structurisation of DNA–lipid complexes

Abstract

Complexes formed by DNA and lipid mixtures have great interest for the assessment of self-assembling mechanisms in open biological systems. X-ray diffraction has revealed that minor alterations of the cationic/neutral lipid composition produced major alterations to the liquid crystalline structure and the hydration of the complexes. We have extended to these systems by an approach based on the identification of a fundamental repeating unit that grows according to the general principles of supramolecular polymerisation and liquid crystallinity. Structural reorganisations that optimise the electrostatic and hydrophobic compensation are enhanced by competition between the rigidity of the polyelectrolyte and the cohesion of the lipid assembly. The non-hydrated hexagonal structure revealed by X-ray examination is represented by a dendritic-type supramolecular polymerisation of DNA units decorated by the aliphatic tails of dissociated liposomes. An increase in the cationic/neutral lipid component ratio enhances the stability of planar bilayers, favouring the formation of the partly hydrated lamellar structure revealed by X-ray diffraction.

Keywords:

• DNA–lipid complexes
• polyelectrolytes
• lipoplexes
• supramolecular polymerisation
• hexagonal phases
• lamellar phases

Acknowledgements

The author wishes to express his great appreciation to Giulio Caracciolo, Angelo Perico and Peter Walde for reading the manuscript and very useful comments, to Peggy Chan for clarifying information regarding the relevant literature, and to Luca Galbusera for analysis of the morphologies and elaboration of the figures.