A Neutron Reflectivity Study of Polymer-Modified Phospholipid Monolayers at the Solid-Solution Interface: Polyethylene Glycol-Lipids on Silane-Modified Substrates

Abstract

The structure of polymer-decorated phospholipid monolayers at the solid-solution interface was investigated using neutron reflectometry. The monolayers were composed of distearoylphosphatidylethanolamine (DSPE) matrixed with varying amounts of DSPE-PEG (DSPE with polyethylene glycol covalently grafted to its headgroup). Mixed lipid monolayers were Langmuir-Blodgett deposited onto hydrophobic quartz or silicon substrates, previously hydrophobized by chemically grafting a robust monolayer of octadecyltrichlorosilane (OTS). We show that this method results in homogeneous and continuous phospholipid monolayers on the silanated substrates and determine that the grafted PEG chains extend away from the monolayers into the solvent phase as a function of their density, as expected from scaling theories. In addition, ligands were coupled to the end of the PEG chains and selective binding was demonstrated using fluorescence microscopy. Our results demonstrate that these constructs are ideal for further characterization and studies with well-defined monomolecular films.

Chemisorption of thiolated poly(ethylene oxide) to gold: surface chain densities measured by ellipsometry and neutron reflectometry

“…Hydrophobic interactions among the alkane components near the gold surface in the systems studied by Tokumitsu et al may account for this difference. Previous neutron reflectivity measurements conducted by Kuhl et al [26] may be compared with our data. Their experiments were conducted with a Q z,max in the range of 0.05 to 0.15, compared to our chosen Q z,max of 0.1 (Fig.…”

Tethered polymer layers: phase transitions and reduction of protein adsorption

“…It is also important to emphasize that while the hydrophobic surfaces used in the experiments presented in Fig. 16 strongly attract the ethylene oxide segments of the PEO chains, there is a very large class of materials in which the PEO is not attracted to the surface, such as lipid surfaces 33,34) . There are two pronounced features that can be seen in Fig.…”

“…For example, it has been shown that for polyethylene oxide (PEO) in the regime of molecular weights used in biocompatible materials and drug carriers, there is a continuous change of structure from the mushroom to the brush 32) . It has been also found that PEO segments are attracted to hydrophobic surfaces and to the water-air interface but not to lipid surfaces 30,31,33,34) . Furthermore, many of the experimental studies are carried out in the intermediate region of surface coverage between the mushroom and the brush.…”

Generic Role of Polymer Supports in the Fine Adjustment of Interfacial Interactions between Solid Substrates and Model Cell Membranes

“…5 nm. However, in spite of numerous studies utilizing different polymers, including chemically immobilized or cross-linked hydrogels, 18,19 polymer brushes, 20,21 covalently grafted lipopolymers, 22, 23, 4 24 and polyelectrolyte multilayers, 25,26 there is no quantitative study that highlights how polymer supports would modulate the interfacial interactions.…”