The concentration of cationic lipid DODAB required to cover silica particles with a cationic lipid bilayer is 0.05 mM. Effect of DODAB concentration on zeta-average diameter (A, C) and zeta-potential (B, D) of SiO2 particles at 0.1 mg silica/ml, 25°C, in 1 mM NaCl, pH 6.3 (A, B) or 5 mM Tris.HCl, pH 7.4 (C, D). Cationic bilayer fragments were adsorbed onto 0.1 mg/ml silica particles (AEROSIL OX-50). Measurements were performed after 1 h interaction. The arrows indicate 0.05 mM DODAB as the concentration of cationic lipid that is required to attain maximal positive zeta-potential and minimal sizes for particles in dispersion.