Compositional sorting dynamics in coexisting lipid bilayer phases with variations in underlying e-beam formed...

Area of Science:

• Biophysics
• Materials Science
• Nanotechnology

Background:

• Lipid membranes exhibit distinct liquid ordered (Lo) and liquid disordered (Ld) phases.
• Controlling phase separation is crucial for understanding membrane function and developing separation techniques.
• Nanoscale substrate patterns can influence membrane behavior and lipid organization.

Purpose of the Study:

• To investigate how nanometer-scale substrate curvature patterns affect lipid phase separation dynamics.
• To explore mechanical energy-based separation strategies for analyzing biomembrane-associated species.
• To demonstrate control over lipid phase pixelation and sorting using patterned substrates.

Main Methods:

• Fabrication of silica substrates with patterned poly(methyl methacrylate) (PMMA) hemispherical features using electron beam lithography.
• Creation of square lattice patterns (100 nm radius) and variations including PMMA walls and gradients in feature spacing.
• Observation and analysis of lipid multibilayer behavior, phase pixelation, and dynamics (e.g., Ostwald ripening, vesiculation) under varying pattern conditions.

Main Results:

• Nanoscale curvature patterns imposed distinct sorting dynamics on metastable Lo-Ld lipid phases.
• PMMA walls altered the balance between Ostwald ripening and vesiculation, slowing the loss of the high line energy pixelated Lo phase.
• Gradient patterns induced Lo phase partitioning, and heating/cooling cycles regenerated and sharpened pixelation patterns.

Conclusions:

• Localized substrate curvature variations significantly impact lipid phase dynamics due to coupled mechanical energy optimization processes.
• Patterned substrates offer pathways for mechanical energy-based separations and analysis of biomembrane components.
• The study demonstrates tunable control over lipid phase behavior and organization at the nanoscale.