Direct Probing and Modeling of Adsorbed Layers of Surfactant/Lipid/Protein Mixtures atT Air/Water Interfaces

Purdue University, West Lafayette IN

Investigators

Abstract

Abstract CTS-0135317 Franses, Elias I Purdue University "Direct Probing and Modeling of Adsorbed Layers of Surfactant/Lipid/Protein Mixtures at Air/Water Interfaces" The main objectives are to understand quantitatively and qualitatively how surfactants, lipids, and proteins adsorb at air/water interfaces. By adsorbing, alone or in competition, surface active molecules modify the equilibrium and dynamic surface tension, the surface charges, the foaming behavior, and the protein denaturation behavior. These phenomena have important applications in bioprocessing of biological and biochemical dispersions, spray drying of pharmaceutical solutions, spreading of agricultural chemical in leaves; also in foaming stability, and foam-based separations of dilute solutions of surfactants and proteins, mineral ore flotation, and detergency. A major focus is the area of replacement therapy of lung surfactant, which is a mixture of lipids and proteins responsible for stabilizing the lung alveoli and controlling breathing. The equilibrium and dynamic adsorption is probed not only with indirect surface tension methods but with direct optical (ellipsometry, EL) and infrared reflection absorption spectroscopy (IRRAS). IRRAS is used primarily to determine the extent, rates, and mechanisms of individual components. IRRAS, in combination with EL and surface tensiometry, has proven to be a valuable tool for quantitative probing of complex industrial or biological mixtures. The results are used to develop formulations which are technically effective, cost-effective, and biologically or environmentally friendly; and to develop new, potentially effective lung surfactant formulations. The systems examined are bovine serum albumin, fibrinogen, various lipids and soaps, and model ionic surfactants. The data are used to guide quantitative modeling of diffusion/adsorption processes of surfactants, lipids, and proteins from the bulk solution or dispersion to the interface. The models are used to help design new improved formulations, and to predict how formulations may function in different solutions and different geometries.