? For biomedical systems, determining the chemical state (composition, molecular structure, and orientation) and distribution of biological moieties present on a surface is critical. Many of the important functions of cells and tissue depend on the arrangement of molecules at their surfaces. Also, a central goal of modern bioengineering is the development of biomaterial surfaces that direct the biological healing response. These novel surfaces are envisioned to have a well-defined array of recognition sites designed to interact specifically with cells. Thus, it is essential to develop surface analysis techniques capable of providing detailed surface chemical state information at high spatial resolutions. The Kratos AXIS ULTRA imaging electron spectroscopy for chemical analysis (ESCA) system requested in this application will provide essential, new capabilities for NIH-funded biomedical research since our 12 and 18 year old ESCA systems do not have imaging capabilities. Also, in the past 10 years instrumentation manufacturers have made significant advances in all areas of ESCA performance, so all types of ESCA experiments (composition, high resolution spectra, angle dependent, multi-sample and imaging analyses) will benefit significantly from the purchase of a new imaging ESCA system. The specific improvements provided by the new imaging AXIS ULTRA ESCA system over our current ESCA systems are: 1) increase of the spatial resolution for spot analysis by an order of magnitude; 2) provide a new chemical state imaging modality; 3) improve energy resolution by 20% in the spectroscopy mode; 4) increased sensitivity (lower detection limits); 5) more efficient and easier to use charge neutralization system; 6) computer controlled, multi-sample analysis for angle dependent experiments; and 7) decreased instrument downtime. Imaging ESCA provides quantitative surface compositional information about the distribution of both elements and functional groups at a spatial resolution of less than 10 microns. This information is essential for determining the structure-function relationship of the biomaterial surface and its biological activity. Relevant applications for imaging ESCA include biocompatibility of implants, biomolecule separations, cell culture, biosensors, bacterial-induced corrosion, ELISA assays, and DNA manipulations. Combining the capabilities of the proposed imaging ESCA system with existing imaging time-of-flight secondary ion mass spectrometry (ToF SIMS) and scanning probe microscopy (SPM) systems will provide a powerful set of complementary biomedical surface analysis techniques that will make a significant contribution to NIH-funded biomedical research projects. ? ?
