Supramolecular assemblies of DNA delivery systems.

Gene delivery into cultured cells or in vivo is a promising approach to the treatment of diseases. Several gene delivery systems have been developed to promote gene expression either in vitro or in vivo. Concerns about viral-induced immune responses, the risk associated with replication-competent viruses, and production issues have stimulated efforts toward the development of alternative gene delivery systems such as cationic lipids and polymers. These positively charged molecules interact through electrostatic forces with DNA. This results in the formation of highly organized supramolecular structures where DNA molecules are condensed and protected against DNAses degradation. Association of DNA with cationic lipids under a micellar or liposomal form leads to lamellar organization with DNA molecules sandwiched between lipid bilayers. Although the lamellar phase is the common described structure, as evidenced by small-angle X-ray scattering and electron microscopy, monovalent cationic lipid combined with a hexagonal forming lipid resulted with DNA in an inverted hexagonal structure. Despite a lot of effort, the mechanism of gene transfer with cationic carrier is still ill-defined. Therefore, correlations need to be established between physicochemical properties of synthetic DNA delivery systems and in vitro and in vivo transfection efficiency.