The role of cholesterol in curvature and stripe width evolution in model lung surfactant monolayers.

Abstract

Lung surfactant (LS) is a lipid-protein monomolecular layer coating the alveolar air-liquid interface. A primary role of LS is to reduce the interfacial tension to facilitate breathing. Simple two and three component systems are used to model LS in studies to test the relationship between composition, morphology, rheological, and phase behavior. Failure of LS is associated with acute respiratory distress syndrome (ARDS). The primary lipid in LS is dipalmitoylphosphatidylcholine (DPPC) which accounts for 40-80 percent of native and replacement LS therapies. The addition of fatty acids, fatty alcohols, and cholesterol to replacement LS therapies is still an area of research. We utilize mixtures of DPPC and hexadecanol (HD) or palmitic acid (PA) with small mole fractions of dihydrocholesterol (DChol). The morphology of 2-dimensional self-assembled monolayers with coexisting crystalline-like domains (liquid-condensed phase) within a liquid-like matrix (liquid-expanded phase) is investigated. With the addition of DChol to the DPPC/HD or DPPC/PA system, a finger instability is seen during monolayer compression followed by a time dependent circle-to-stripe transition at a fixed interfacial tension. In this poster we will discuss recently published results on the equilibrium nature of these films (REF: Valtierrez et al., Sci. Adv. v:8:14, 2022) and extend this work to explore the role of cholesterol in determining morphology and curvature.