Highly hydrated deformable polyethylene glycol-tethered lipid bilayers

Area of Science:

• Biophysics
• Materials Science
• Surface Chemistry

Background:

• Creating robust yet functional solid-supported lipid bilayers for membrane studies is challenging.
• Tethering to a substrate is necessary for robustness, but must not hinder lipid diffusion or membrane plasticity.
• A highly hydrated environment is essential for mimicking natural cell membranes.

Purpose of the Study:

• To develop a novel cushioned membrane system for studying membrane processes.
• To create a robust, hydrated, and deformable solid-supported lipid bilayer.
• To mimic the mechanical properties of natural cell membranes.

Main Methods:

• Grafting polyethylene glycol-lipid constructs (PEG2000-DSPE) to silicon oxide surfaces using silane chemistry.
• Depositing lipids onto the PEGylated surface via spin-coating.
• Utilizing neutron and X-ray reflectometry to analyze bilayer and PEG cushion properties.
• Employing Atomic Force Microscopy (AFM) indentation to assess membrane deformability and lipid diffusion measurements.

Main Results:

• A 55 Å thick PEG spacer with high hydration (90 ± 3%) was created between the lipid bilayer and silicon oxide surface.
• 11.5 ± 3% of lipids were grafted to the surface, with minimal impact on lipid diffusion (D = 2.1 ± 0.1 μm²/s, a 12% reduction).
• AFM indentation revealed significant plastic deformation (up to 40 Å) before bilayer rupture, mimicking natural cell membranes.

Conclusions:

• The PEG-tethered lipid bilayer system provides a robust and highly hydrated platform for membrane research.
• This biomimetic membrane exhibits excellent plastic deformability, closely resembling natural cell membranes.
• The developed system overcomes limitations of standard solid-supported lipid bilayers, offering enhanced functionality for studying membrane dynamics.