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

Purdue University, West Lafayette IN

Investigators

Abstract

ABSTRACT - 0457289 Purdue University Project Summary The health related project examines how to measure, characterize, and control the extent and rate of adsorption of surfactants, lipids, and proteins at air/water interfaces by understanding the fundamental phenomena and mechanisms. Such adsorption determines the equilibrium and dynamic surface tension, which affects free surface flows involving bubbles, drops, and liquid jets. The dynamic surface tension at constant and pulsating area condition is measured and modeled. Unique features include: (i) direct probing of the interfacial layers of aqueous solutions or dispersions of surfactants, lipids, proteins, and their mixtures with quantitative ellipsometry and infrared spectroscopy; (ii) control of adsorption of insoluble lipids by controlling the method of lipid dispersion preparation; (iii) understanding of competitive adsorption of lipids and serum proteins (albumin or fibrinogen); (iv) models of micellar dissolution and diffusion, and their effect on adsorption dynamics; and (v) studies of rates and mechanisms by which lipids reach the surface where they produce very low dynamic surface tensions (less then 10 mN/m during surface compression); and (vi) studies of rates and mechanisms by which lipids can exclude or expel soluble proteins from the interfacial region. The surface layer composition of lipid/soluble protein dispersions is probed for the first time by quantitative IR spectroscopy and ellipsometry. Thermodynamic and interfacial mass transfer principles are applied for the first time for predicting and controlling how lipids can adsorb and expel proteins from the interface. This could be important for processes affected by foam stability and breakup, such as bioreactors, washing machines, and foam-based separations, and in lung surfactants design and formulations. The results are important in processes involving drop deformation and breakup, as in DNA and protein microarrays, inkjet printing processes, and the design and uses of agricultural pesticide sprays. Since albumin and fibrinogen serum proteins can leak to the alveoli and inhibit the function of lung surfactant, understanding the factors which affect their displacement could lead in biomedical engineering applications of treatment of lungs injured by the acute respiratory distress syndrome (ARDS). This may have direct and indirect implications in effectively treating or alleviating infant and adult respiratory diseases. Other societal impacts could be improved and leaner pesticide formulations, for reducing environmental pollution. This research will also lead to effective training of graduate and undergraduate students, who will be exposed to state-of-the-art experimentation and modeling. The results will be used in part in a graduate course and an undergraduate course. Developing and refining surface layer characterization will improve the infrastructure of research and education in interfacial, biomedical, biochemical, and mineral engineering. The P.I. is committed to diversity in recruiting graduate and undergraduate students for this project, and has worked with several members of underrepresented groups over the past five years. The results may lead to partnerships with medical researchers or professionals and with industrial and academic researchers dealing with surfactant, lipid, and protein applications.