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

Purdue University, West Lafayette IN

Investigators

Abstract

Franses / Purdue / 0651942 Intellectual Merit. The project examines how to understand and control the extent and rate of adsorption of surfactants, lipids, and proteins at air/water interfaces by focusing on the prevailing fundamental physicochemical, biophysical, and engineering phenomena and mechanisms. Such adsorption determines the equilibrium and dynamic surface tension, which affects free surface flows involving bubbles, drops, and liquid jets, and controls pressure and mass transfer in lung alveoli. Unique features include: (i) direct probing of the interfacial layers of aqueous solutions or dispersions of surfactants, lipids, proteins, and their mixtures, with quantitative infrared reflection absorption spectroscopy and ellipsometry; (ii) control of particulate or molecular adsorption of insoluble lipids by developing improved methods of lipid dispersion preparation; (iii) understanding of competitive adsorption of lipids and serum proteins (albumin or fibrinogen) which inhibit lung surfactant; (iii) studies of rates and mechanisms by which lipids produce very low dynamic surface tensions, less then 10 mN/m during surface compression; (iv) studies of mechanisms by which lipids can exclude or expel soluble proteins from the interfacial region; and (v) interactions of proteins with lipids in bulk solution and on surfaces, for developing biocompatible liposome formulations . The results are relevant to inkjet printing processes, agricultural sprays, DNA and protein microarrays, and processes affected by foam formation and stability. An important biomedical application, developing lipid formulations for long-term potential uses as lung surfactant replacement formulations, is an area of focus. The dynamic surface properties of lipid dispersions are related to the size and morphology of the dispersed particles, liposomes or vesicles. The scientific uniqueness of this project is the understanding of how to control lipid and protein adsorption at the air-water interface by controlling both their bulk and surface interactions. The unique aspect of the approach is the use of rigorous direct probes and quantitative engineering modeling principles in developing a rational understanding of lipid/protein interactions at fluid interfaces and in aqueous solution. Broader Impacts. Major societal benefits include: (i) understanding how to treat alveolar respiratory diseases of premature infants and adults with new formulations; and (ii) understanding how aggregation of liposomes or vesicles with serum proteins can be controlled by using a second lipid mixed with first so that aggregation with proteins is inhibited. The knowledge base for many of the above applications will be substantially expanded. The results may lead to partnerships with medical researchers or professionals, and with industrial and academic researchers dealing with such applications. This research aims at effective training of graduate and undergraduate students, who will be exposed to state-of-the-art experimentation and modeling. Certain results will be used in teaching of graduate and undergraduate courses. 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 under-represented groups over the past five years. He will recruit for minority students from the Purdue "Surf" program, in which minority seniors, from Purdue or other schools, are actively recruited, hired, mentored, and advised to pursue graduate or professional studies.