Modulation of Substrate–Membrane Interactions by Linear Poly(2‐methyl‐2‐oxazoline) Spacers Revealed by X‐ray Reflectivity and Ellipsometry

Abstract

Hydrated polymer interlayers between planar lipid membranes and solid substrates provide a water reservoir and thus maintain a finite membrane-substrate distance. Linear polymer spacers attached to lipid head groups (lipopolymer tethers) can be used as a defined model of oligo- and polysaccharides covalently anchored on cell surfaces (glycocalyx). They can offer a unique advantage over membranes physisorbed on polymer films (called polymer-cushioned membranes), owing to their ability to control both the length and density of polymer chains. In this study, a lipopolymer tether composed of a stable ether lipid moiety and a hydrophilic poly(2-methyl-2-oxazoline) spacer with a length of 60 monomer units is used to fabricate supported membranes by the successive deposition of proximal (lower) and distal (upper) leaflets. Using specular X-ray reflectivity and ellipsometry, we systematically investigate how the lateral density of polymer chains influences the membrane-substrate interactions. The combination of two types of reflectivity techniques under various conditions enables the calculation of quantitative force-distance relationships. Such artificial membrane systems can be considered as a half-model of cell-cell contacts mediated via the glycocalyx, which reveals the influence of polymer chain density on the interplay of interfacial forces at biological interfaces.

Cell Differentiation of Pluripotent Tissue Sheets Immobilized on Supported Membranes Displaying Cadherin-11

“…The other structural parameters, such as the thickness, the roughness and the scattering length densities of the proximal and distal head group regions as well as the thickness of water reservoir between the lipid bilayer and the substrate agree well with those reported in previous accounts [40], [56], [57].…”

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

“…One of the promising strategies to achieve high spatial resolution to higher q z , is given by specular X-ray reflectivity (XRR) with high energy X-rays (≥ 18 keV) that guarantee high transmittance of X-rays through bulk water. 30,31 In this work, we determined quantitatively the generic role of polymer supports in the modulation of interfacial interactions by the combination of NR and high energy XRR.…”

Tailored Poly(2‐oxazoline) Polymer Brushes to Control Protein Adsorption and Cell Adhesion

“…Especially the water‐soluble poly(2‐methyl‐2‐oxazoline) (PMeOx) and poly(2‐ethyl‐2‐oxazoline) (PEtOx) were found to prolong the blood circulation time of liposomes when incorporated as lipopolymers for stabilization 31–34. POx‐based lipopolymers35 are used successfully for the construction of biomimetic cell membranes on solids36–39 and the low interaction with proteins allows for transmembrane protein integration40 and quantitative studies of integrin‐mediated cell binding experiments 41–43. While PMeOx is highly hydrophilic, PEtOx is still well water soluble but shows a slight amphiphilicity, similar to PEG 44, 45.…”