Fig. 4.

(a) The unit cell of the double-gyroid cubic phase (space group Ia3d) incorporating siRNA within its two water channels (green and orange). The structure was deduced by synchrotron x-ray scattering. For DOTAP/GMO–siRNA complexes the phase (labeled Q_II^{G, siRNA}) is observed for GMO (1-monooleoyl-glycerol) molar fractions (Φ_GMO) between 0.75 and 0.975. A lipid bilayer surface separates the two intertwined but independent water channels. The bilayer is represented by a surface (grey) corresponding to a thin layer in the center of the membrane as indicated in the enlarged inset. (b) Total (K_T, black lines and symbols) and nonspecific (K_NS, red lines and symbols) gene knockdown for DOTAP/GMO–siRNA complexes (squares) and DOTAP/DOPC–siRNA complexes (circles) as a function of mole fraction of neutral lipid (Φ_NL). DOTAP/GMO–siRNA complexes in the gyroid cubic phase (Q_II^{G, siRNA}) at low cationic lipid content (Φ_GMO ≥ 0.75) show remarkably improved sequence-specific gene silencing over complexes in the lamellar phase (L_α^siRNA). Reprinted with permission from reference 76. Copyright 2010, American Chemical Society.