OBSERVATION OF INTERFACIAL PROCESSES SPM IV A biomaterial surface, when exposed to a protein-containing solution, becomes coated within seconds with proteins. The hierarchy of events: surface yields protein layer yields platelet and cell adhesion forms the basis of the generally accepted causality between the biomaterial surface property and the attempt of the host organism to isolate artificial material. In this revised competing continuation application, we propose to experimentally analyze the first step in this hierarchy by measuring the protein-biomaterial surface adsorption and to relate it to the two-dimensional variation of biomaterial's surface properties, such as surface energy and elasticity. We propose to perform this analysis on a size scale that is on the order of protein size (i.e. a few tens of nanometers), rather than in a macroscopic fashion. Our research ideal is to build a spatio-temporal picture of biomaterials-host interfaces on nanometers length and milliseconds time scales in terms of: - variation of surface properties, - related dynamics of protein- surface interactions, and surface - induced protein conformation, and to identify the critical parameters in these processes. A question that the proposed research will attempt to answer is: how much biomaterial surface heterogeneity is tolerated and at which length scales? Hence, we propose the four years research plan with the following specific research goals: Using the fast adhesion and elasticity mapping technique measure simultaneously the topography and two-dimensional distribution of adhesion """"""""pull-off"""""""" forces and elasticity on well-characterized model surfaces, and surface-modified and typical biomaterials on nanometers length scales. Use the adhesion forces measured in three liquids to spatially resolve non-polar and polar components of surface energy. Establish the rate by which the surface property changes upon a biomaterial's exposure from physiological to non-polar solutions. Study the two-dimensional and/or temporal distribution of major plasma proteins (albumin, fibrinogen, IgG and LDL) at model heterogeneous and selected set of biomaterial surfaces in situ using evanescent surface wave (TIRF) and near-field scanning optical (fluorescence) (NSOM) microscopies. Evaluate the combined information about the biomaterial surface-protein-solution interface obtained from the in situ SFM adhesion mapping and the in situ surface fluorescence spectroscopy techniques. Build a dynamic model of events based on the information that includes the two-dimensional map of biomaterial surface properties and the spatial-temporal distribution of individual plasma proteins.
