Mesomorphic Complexes of DNA with the Mixtures of a Cationic Surfactant and a Neutral Lipid

摘要

A complex system composing of polyanionic DNA bound to cationic lipid (CL) has appealed significant interests recently because of its use as a promising gene delivery carrier. Several studies has been done by Safinya’s group to investigate the relation between gene transfection efficiency and self-assembled structures of DNA-CL complex. Previous studies by means of X-ray scattering and electron microscopy have shown that these complexes self-assembled predominantly into a condensed multilamellar or inverted hexagonal mesophase controlled by spontaneous membrane curvature.Similar to CL, cationic surfactants (CS) are also amphiphilic molecules capable of forming complexes with DNA. Hence, considering the low cost and wide availability of CS, this type of complexes is worth studying for nanostructure template applications. In the present study, we investigated the self-assembly in the complexes of CS and NL. The CS and NL studied here are dodecyltrimethylammonium bromide (DTAB) and dioleoylphosphatidyl-ethanolamine (DOPE), respectively. We will show that the isoelectric ternary DNA-DTAB/DOPE complexes exhibit L_α~c or H_(II)~c phases at room temperature depending upon the DOPE-to-DTAB molar ratio (m). A thermotropic order-order transition between L_α~c and H_(II)~c phases will also be revealed and the driving force of the transition will be discussed here.