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

Published

March 24, 2022

Author(s)

Igor K. Mkam Tsengam, Marzhana Omarova, Elizabeth Kelley, Alon V. McCormick, Geoffrey D. Bothun, Srinivasa R. Raghavan, Vijay T. John

Abstract

The phospholipid lecithin (L) and the nonionic surfactant Tween 80 (T) are used together in various contexts, including in drug delivery and oil spill remediation. There is hence a need to elucidate the nanostructures in L/T mixtures, which is the focus of this paper. We study these mixtures using cryogenic transmission electron microscopy (cryo-TEM), coupled with dynamic light scattering (DLS) and small angle neutron scattering (SANS). As the concentration of T is increased, the vesicles formed by L are transformed into spherical micelles. We identify bicelles (i.e., disc-like micelles) as well as cylindrical micelles as the key intermediate nanostructures. The bicelles have diameters 13 – 26 nm, and the bicelle size decreases as the T content increases. We propose that the L lipids form the body of the discs while the T surfactants occupy the rims. This hypothesis is consistent with geometric arguments since L is double-tailed and favors minimal curvature whereas the single-tailed T molecules prefer curved interfaces. In the case of the cylindrical micelles, cryo-TEM reveals that the micelles are short (length < 22 nm) and flexible. Collectively, we are able to directly visualize the path from vesicles to micelles, including structural details not previously established for lipid-surfactant mixtures.

Citation

Journal of Physical Chemistry B

Volume

126

Issue

11

Pub Type

Journals

Keywords

small angle neutron scattering, lecithin, nonionic surfactant, micelle, bicelle, vesicle

Citation

Mkam Tsengam, I. , Omarova, M. , Kelley, E. , McCormick, A. , Bothun, G. , Raghavan, S. and John, V. (2022), Transformation of Lipid Vesicles into Micelles by Adding Nonionic Surfactants: Elucidating the Structural Pathway and the Intermediate Structures, Journal of Physical Chemistry B (Accessed November 21, 2024)