Phospholipid monolayers supported on spun cast polystyrene films

We investigated the use of spun cast polystyrene (PS) films as a hydrophobic solid support for phospholipid monolayers. Fluorescent microscopy indicated that a 1-palmitoyl-2-oleoyl-SN-glycero-3-phosphocholine (POPC) monolayer containing fluorescent lipid formed on similar to80 nm thick films of 2450 M-r PS exposed to phospholipid vesicle solutions. Qualitative fluorescence photobleaching experiments suggested that the phospholipid layer was continuous and the lipid diffusion rate was similar to those observed in glass-supported POPC bilayers. Examination of lipid diffusion by real-time, single-molecule fluorescence detection and fluorescence correlation spectroscopy (FCS) indicated that the lipid diffusion contained multiple components. We interpreted this as being caused by the presence of surface heterogeneities that confine lipid diffusion. In situ atomic force microscopy revealed the presence of 5-20 nm outgrowths on the PS film resulting from surface rearrangement upon exposure of the film to aqueous conditions. It is possible that such rearrangements play a role in determining the lipid translational dynamics. Our studies indicate that PS films can be suitable supports for phospholipid monolayers, but that immersion into an aqueous environment can significantly influence the film topography and the dynamics of the lipid in the supported monolayer.