Cationic Bilayers on Polymeric Particles: Effect of Low NaCl Concentration on Surface Coverage

Abstract

The interaction between dioctadecyldimethylammonium bromide (DODAB), chloride (DODAC), or acetate (DODAAc) cationic bilayer fragments (BF) and polystyrene sulfate (PSS) particles (2 × 1011 particles/mL) was evaluated at and above equivalence of total surface areas for bilayers and particles (Ab/Ap) over a range of low NaCl and lipid concentrations, by means of zeta-potential, ζ, and particle diameter, Dz, analysis. In pure water, lipid addition at and above Ab/Ap = 1 rapidly increased Dz and ζ, which reached stable plateau values above those expected at bilayer coverage. By addition of small NaCl concentrations (0.05−5.00 mM), Dz decreased with ζ still positive. Therefore, the effect of low salt concentration on the particle coverage with lipid bilayer fragments was surface rearrangement of bilayer fragments on the surface from uneven coverage with some bilayer fragments adsorbed vertically, to perfect bilayer coverage upon addition of small amounts of NaCl. This occurred over a broad range of lipid conce...