(444c) Effects of Curvature on the Lung Surfactant Monolayer

For more than 40 years, Lung surfactant monolayers have been studied on flat interfaces. On a flat interface, lipid and fatty acid are known to phase separate into solid like domain in a liquid like disordered matrix. Unlike planar interface, curved interface exhibits connectivity of the solid phase domains coalescing into a mesh-like network under a confocal microscope. One way of describing this phenomenon of transitioning from circular liquid-condensed domain to discontinuous liquid-expanded phase is to measure the dramatic change in dilatational property within the limit of physiological relevance. We found that complex dilatational modulus is smaller for the larger bubbles than for the smaller bubbles (as it approaches alveolar size 100 micron); the LC phase mesh likely resists compression and expansion. The domains are not circular even immediately after adsorption and form extended linear structures as they age which is evident in both 200 and 300-micron size bubbles, suggesting equilibrium organization changes with curvature. In this study, we tried to dive deeper to understand the relation between morphology and rheology of clinical and model lung surfactant.