Wednesday, November 7, 2007 - 3:30 PM
475a

Interactions And Transport Of Lipids And Proteins At Gas/liquid Interfaces

Sook Heun Kim1, Tze Lee Phang1, and Elias I. Franses2. (1) Purdue University, 480 Stadium Mall Drive, West Lafayette, IN 47907-2100, (2) School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, IN 47907-2100

Albumin and fibrinogen (FB) tend to inhibit lung surfactant's ability to produce low dynamic surface tensions (DSTs) in injured lungs. The adsorption behavior of lipids such as DLPC (dilauroylphosphatidylcholine) and DPPC (dipalmitoylphosphatidylcholine) and serum proteins such as bovine serum albumin (BSA) and FB at air/aqueous interfaces were studied with tensiometry, infrared reflection absorption spectroscopy (IRRAS), and ellipsometry. Dynamic surface tensions as low as 1 mN/m are observed for DLPC. Direct probing of the surface by IRRAS and ellipsometry indicates that DLPC adsorbs by a molecular adsorption mechanism. The surface layer is a monolayer with no particles attached to it. By having a molecular adsorption mechanism, DLPC lipid can expel BSA and FB from the air/aqueous interface. For DPPC with mostly vesicles, such low tensions, lower than 1 mN/m, are also observed when it is prepared with new protocols, involving extensive sonication above 50 °C. DPPC adsorbs by a particulate adsorption mechanism including two steps of diffusion of particles (vesicles or liposomes) form the bulk phase, followed by their partial disintegration to form an insoluble surface film and a surface associated reservoir. Apparently because of this adsorption mechanism, DPPC vesicles are unable to displace these serum proteins. However, when a DPPC dispersion is introduced with Trurnit's method, as an aqueous layer at the surface, or sprayed dropwise, onto an aqueous DPPC/protein surface, the DPPC layer formed on the surface prevents the adsorption of proteins and dominates the surface tension behavior. These results have implications in controlling the inhibition of lung surfactant tension behavior by serum proteins, when they leak at the alveolar lining layer, and in developing surfactant replacement therapies for alveolar respiratory diseases.