PEGylated Phospholipid Membrane on Polymer Cushion and Its Interaction with Cholesterol

Abstract

By employing poly(ethylene glycol) (PEG) shielding and a polymer cushion to achieve air stability of the lipid membrane, we have analyzed PEG influence on dried membranes and the interaction with cholesterol. Small unilamellar vesicles (SUVs) formed by the mixture of 1,2-dimyristoylphosphatidylcholine (DMPC) with different molar fraction of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000] (DSPE-PEG2000) adsorb and fuse into membranes on different polymer-modified silicon dioxide surfaces, including chitosan, poly(l-lysine) (PLL), and hyaluronic acid. Dried membranes are further examined by ellipsometer and atomic force microscopy (AFM). Only chitosan can support a visible and uniform lipid array. The thickness of dry PEGylated lipid membrane is reduced gradually as the molar fraction of PEG increases. AFM scanning confirms the lipid membrane stacking for vesicles containing low PEG, and only a proper amount of PEG can maintain a single lipid bilayer; however, the air stability of the membrane will be destroyed if overloading PEG. Cholesterol incorporation can greatly improve the structural stability of lipid membrane, especially for those containing high molar fraction of PEG. Different amounts of cholesterol influence the thickness and surface morphology of dried membrane.

Chitosan cushioned phospholipid membrane and its application in imaging ellipsometry based-biosensor

“…1A and B). This is an interesting phenomenon compared with our former discovery [24]. Spectroscopy ellipsometer (Woollam M2000DI) analysis indicates their thicknesses are within 4-5.5 nm range, in close agreement with the estimate thickness of model phospholipids bilayers, although the grayscales of lipid membrane formed by DMPC is only a bit higher than the others.…”

“…Recently, a few published research works have focused on creating air stable phospholipid membranes, nevertheless, there are still some problems, such as reduced fluidity [20], high density protein coverage [21] or the need for careful handling [22], which make these lipid membranes unsuitable for biosensor applications [23]. In our previous work chitosan cushion and PEG shielding could achieve air stability of the phospholipid membrane and the density of PEGylated lipids had influence on the final structure of dried lipid membrane [24]. However, during recent experiments, we have found model phospholipid bilayers, without PEG polymers protection, can also maintain air stability on chitosan modified silicon surface.…”

“…Phospholipid membrane was formed by small unilamellar vesicles (SUVs) adsorption and rupture on the chitosan modified silicon surface. Preparation of SUVs was carried out via the extrusion method [24]. Vesicles solution was stored at 4 • C until use.…”

“…3 shows an air stable phospholipid membrane microarray by imaging ellipsometry. Membranes with low PEG density or high cholesterol loading make higher signals, the possible reason for which have been discussed [24]. The terminal methoxy group on the PEGylated lipid is replaced by a carboxyl terminal group in order to immobilize proteins.…”

Serum tumor marker detection on PEGylated lipid membrane using biosensor based on total internal reflection imaging ellipsometry

“…Phospholipid membrane was formed by small unilamellar vesicles (SUVs) adsorption and rupture on the chitosan coated gold surface. Preparation of SUVs was carried out via the extrusion method [29]. Vesicles solution was stored at 4 • C until use.…”