Two-Dimensional Shear Viscosity of Model Lung Surfactant

The lung surfactant (LS) is a film (monolayer) that lines the lung alveoli, which is necessary for normal lung compliance and ease of breathing. The unique mixture of lipids and proteins reduces the surface tension at the air-alveoli interface, thus reducing the work of breathing and preventing the collapse of alveoli upon exhalation. A lack or dysfunction of LS induces respiratory problems such as Neonatal Respiratory Stress Disorder (NRDS) in infants. The current treatment for NRDS lies in replacement LS extracted from animals but quantities available are rather small and there is a risk of viral contamination. A synthetic LS should present the same physical properties as the natural LS, particularly it should present a rigid phase at high surface pressure. Our project focuses on the effect of the protein SP-B on the monolayer viscosity. Using a Magnetic Needle Viscometer, isotherm and viscosity measurements can be taken. Isotherms show the pressure of SP-B, as the molecular area increases with SP-B concentration. Viscosity measurements show an increase in the maximum viscosity with an increase in SP-B concentration. The results agree with the fact that SP-B interacts specifically with the lipid POPG by helping this relatively fluid lipid to build 3-D structures upon compression.