Characterization and modeling of lipid monolayer morphology and mechanical stability.

Abstract

Lipid monolayers at the air-water interface have been studied to better understand lipid response to mechanical forces and are biologically relevant in the ears, eyes, and especially lungs, where lateral compression of a lipid/protein monolayer at the air-water interface is common. Simpler lipid compositions can be utilized as models to characterize how lipid monolayers respond to compression and undergo loss of mechanical stability, known as collapse. By changing composition and temperature, one can also control the material properties of the monolayer such as fluidity, compressibility, and resistance to shear. Examples of common lipid monolayer collapse modes are folding, crumpling, shear banding, and vesiculation. Our work showcases a generality in monolayer collapse progression through these modes as a lipid system is softened. Utilizing fluorescence microscopy on a Langmuir trough, we distinguish unique collapse modes and study the morphological differences throughout the course of compression, mapping out how collapse modes relate to composition and temperature. Previous research within the field has modeled lipid monolayers as an elastic material and found the folding collapse mode to be an elastic response. We are working to extend this elastic model to previously uncharted collapse modes. Specifically, we model the previously uncharacterized shear banding instability with continuum mechanics by building finite element analysis simulations that model the compression of a monolayer on a Langmuir trough. In these simulations, we track the deformations and strain response of the monolayer undergoing collapse while tuning material properties. The long-term goal of this work is to better understand what material or structural characteristics of a monolayer cause it to exhibit a specific collapse mode and determine if this can be generalized and modeled independent of composition.