Adsorption of DOPC vesicles on hydrophobic substrates in the presence of electrolytes: A QCM and reflectometry study

Abstract

The adsorption of lipid Dioleoylphosphatidylcholine (DOPC) vesicles on a hydrophobic substrate has been investigated in aqueous buffer solution by means of the quartz crystal microbalance (QCM) and reflectometry. DOPC vesicles were prepared by the injection method on a hydrophobic substrate using 1-octadecanethiol (ODT) self-assembled on a gold-coated AT-cut quartz. The reflection spectrometry measurements of the adsorbed vesicles showed nearly monolayer formation in few cases, while in most other experiments, the frequency changes measured suggested multilayer formation assuming the usual Sauerbrey equation to hold in the present system as well. Presence of NaCl, KCl, Na2SO4 and ethanol in the aqueous phase during the formation of vesicles suggest that the multilayer formation can be hastened in some cases. Atomic force microscopic study corroborate the thicknesses that range between 8 and 20 nm for high concentration of electrolytes or ethanol suggesting coalescence of vesicles leading to several bilayers possibly stacked over each other. © Indian Academy of Sciences.