Transformation of Lipid Vesicles into Micelles by Adding Nonionic Surfactants: Elucidating the Structural Pathway and...

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Biophysics

Background:

• Phospholipid lecithin and nonionic surfactant Tween 80 are utilized in critical applications like drug delivery and oil spill remediation.
• Understanding the nanostructure of lecithin-Tween 80 (LT) mixtures is crucial for optimizing these applications.

Purpose of the Study:

• To elucidate the nanostructures formed in lecithin-Tween 80 mixtures.
• To investigate the morphological transitions as a function of Tween 80 concentration.

Main Methods:

• Cryogenic transmission electron microscopy (cryo-TEM) for direct visualization.
• Dynamic light scattering (DLS) and small-angle neutron scattering (SANS) for structural characterization.

Main Results:

• Lecithin vesicles transform into spherical micelles with increasing Tween 80 concentration.
• Stable bicelles (disc-like micelles) and cylindrical micelles form at intermediate LT ratios.
• Bicelle size (∼13-26 nm) decreases with higher Tween 80 content; cylindrical micelles are short (<22 nm) and flexible.

Conclusions:

• Lecithin forms the body of bicelles, with Tween 80 occupying the rims, consistent with their molecular geometries.
• Direct visualization of LT mixture aggregates enhances understanding of morphological changes.
• The study provides fundamental insights into self-assembly in mixed amphiphile systems.