Influence of lipid bilayer phase behavior and substrate roughness on the pathways of intact vesicle deposition: A streaming potential study

Abstract

Deposition of vesicles on solid surfaces can in some cases result in the formation of assemblies of intact surface-bound vesicles known as supported vesicular layers (SVLs). Understanding the mechanism of SVL formation is thus important for effective utilization of vesicles in applications involving vesicle-substrate interactions such as drug delivery and fabric softening. In this work, we investigate SVL formation of two different types of cationic vesicles made up of lipid bilayers existing in the solid-gel and liquid-crystalline phases, respectively, on both smooth and rough anionic cellulose fibers. Deposition is studied quantitatively via spectrophotometric determination of bulk lipid concentrations, and characterization of fiber apparent zeta potentials via streaming potential measurements. Equilibrium deposition results, and profiles of variation of substrate apparent zeta potentials with deposition reveal that the deposition mechanisms of the two vesicle types are similar on rough surfaces (cotton) but significantly different on smooth surfaces (viscose). It is concluded that vesicle deposition mechanism is governed by the surface mobility of deposited vesicles which is dependent on substrate roughness and lipid bilayer phase behavior controlled vesicle properties. Results indicate that while both the vesicle types are immobile on rough surfaces, on smooth surfaces liquid-crystalline vesicles are preferentially mobile over solid-gel vesicles. Possible reasons underlying the vesicle surface mobility characteristics are discussed.