Probing the solid-liquid interface of synthetic biomaterials via x-ray scattering techniques

Understanding the process of protein and biomolecular adsorption onto solid surfaces is of great importance in a wide variety of applications including biomaterials, tissue engineering, biosensors, immunoassays, and protein arrays. As soon as a biomaterial is brought into contact with a biological fluid, synthetic and naturally occurring molecular adsorbates alter the surface properties of the biomaterial. The fact that protein adsorption takes place well before a cell will interact with the biomaterial offers strong incentive to study the protein-surface interface. However, direct investigation of adsorption processes and the hydrated conformation of a molecular adsorbate are difficult since the majority of surface analysis techniques require ultra-high vacuum conditions. In this work long period x-ray standing wave fluorescence spectroscopy coupled with x-ray reflectivity are developed as a spatial probes of molecular adsorption at the solid-liquid interface.; Specifically, the structural conformations of adsorbed peptides are probed at the aqueous-solid interface on several biomaterial surfaces, including amine-functionalized Si wafers and polymer films. X-ray photoelectron spectroscopy and atomic force microscopy are employed to study the chemistry and structure of the dry surface. The conformation of bromine labeled peptides adsorbed at liquid-solid interfaces is examined by long period x-ray standing wave fluorescence spectroscopy and x-ray reflectivity. Monitoring the bromine fluorescent yield profile as a function of incident angle provides information on the distance of the bromine layer with respect to the surface normal at an accuracy of several angstroms.; Microbial biofilms play an important role in the development of various human diseases. Biomedical devices fail frequently due to biofilm formation on the implants. Controlling the disease that is a result of biofilm growth requires an improved understanding of biofilm development. The biofilm-surface interaction is examined by monitoring the spatial migration of a peptide and small amino acid by x-ray stand wave fluorescence after a Bacillus subtilis biofilm is added to the surface.