Characterisation of membrane mimetics on a dual polarisation interferometer

Area of Science:

• Materials Science
• Surface Chemistry
• Biophysics

Background:

• Hybrid bilayer membranes (HBMs) are crucial in various applications, but their formation and structural properties require precise characterization.
• Understanding the real-time assembly of HBMs is essential for controlling their properties.

Purpose of the Study:

• To utilize dual polarisation interferometry (DPI) for real-time characterization of HBM formation on a silicon-oxynitride surface.
• To investigate the structural organization and physical properties of HBMs composed of different phospholipids.

Main Methods:

• Covalent attachment of decanoic acid to an amine-modified silicon-oxynitride surface via EDC condensation.
• Formation of HBMs by injecting phospholipid vesicles (DPPC or DMPC) onto the decanoic acid layer.
• Simultaneous measurement of mass, thickness, tilt angle, and refractive index using DPI during HBM formation.

Main Results:

• Decanoic acid layer exhibited a thickness of 0.92 nm, a tilt angle of 57 degrees, a mass of 1.05 ng/mm², and a refractive index of 1.450.
• DPPC-HBM showed a thickness of 4.32 nm, mass of 3.18 ng/mm², and refractive index of 1.404.
• DMPC-HBM displayed a thickness of 2.12 nm, mass of 2.25 ng/mm², and refractive index of 1.435.

Conclusions:

• DPI is a powerful technique for in-situ characterization of HBM formation, providing simultaneous multi-property analysis.
• Significant differences in structural organization and physical properties exist between DPPC- and DMPC-based HBMs.
• The study offers insights into the assembly and composition-dependent properties of hybrid bilayer membranes.