PDMS as a Substrate for Lipid Bilayers

Area of Science:

• Biophysics
• Materials Science
• Surface Chemistry

Background:

• Polydimethylsiloxane (PDMS) is a widely used, cost-effective polymer for microfluidic and organ-on-chip applications.
• Its elasticity and ease of fabrication make it attractive for biophysical studies of cell membranes.
• However, the compatibility of PDMS as a substrate for supported lipid bilayers (SLBs) requires further investigation.

Purpose of the Study:

• To investigate the suitability of PDMS as a substrate for forming and studying supported lipid bilayers (SLBs).
• To characterize the effects of PDMS surface properties and plasma treatment on SLB formation, diffusion, and stability.
• To identify limitations and critical parameters for using PDMS in membrane biophysics experiments.

Main Methods:

• Atomic Force Microscopy (AFM) to analyze PDMS surface topography and roughness.
• Fluorescence optical microscopy to observe lipid bilayer formation, diffusion, and phase transitions.
• Contact angle measurements to quantify surface hydrophilicity and monitor hydrophobic recovery.

Main Results:

• Lipid bilayers successfully form on plasma-treated PDMS, exhibiting normal diffusion and phase transitions.
• PDMS surface roughness significantly restricts lipid phase separation and lateral hydrodynamic flow.
• Bilayer degradation occurs over time, correlated with PDMS hydrophobic recovery, with a critical water contact angle of 30° for stability.

Conclusions:

• PDMS is a suitable substrate for SLB formation and basic studies, but its inherent roughness limits more complex phenomena like lipid phase separation.
• Surface treatments like oxygen plasma improve hydrophilicity but do not fully eliminate roughness issues.
• Understanding PDMS hydrophobic recovery and its impact on bilayer integrity is crucial for reliable experimental design.