Photoemission and Characterization of Neutrophils and Nanoparticles : Energy Mapping and Elemental Composition with sub-µm Resolution

Sammanfattning: Imaging and visualization of cells and tissues are important when studying various biological phenomena. The ability to provide spatial information with molecular and chemical specificity may increase our insight and understanding of biological problems within life sciences. There is a need for well suited analytical imaging tools for addressing challenges that can increase our knowledge from the visualization on the cellular and subcellular level. In this thesis, we have focused on the use of surface analytical techniques based on the photoemission process. Synchrotron based surface analytical tools such as mirror electron microscopy, low energy electron microscopy, X-ray photoelectron spectroscopy, X-ray photoemission electron microscopy and near edge X-ray absorption fine structure spectroscopy were used to obtain highly resolved chemical information for both fundamental biological systems and technical innovations.A combined photoemission electron microscopy and imaging X-ray photoelectron spectroscopy instrument have been used for visualization and characterization of neutrophils attached to silicon and gold surfaces. Neutrophils are white blood cells and a major part of our innate immune system. In the body they circulate and scavenge for possible threats, such as pathogens. The neutrophils possess three main defense mechanisms to tackle any possible threat in the body. One of these mechanisms is the release and formation of extracellular traps used for entrapping and capturing. We have visualized the extracellular trap formation in presence of nanoparticles and images of the neutrophils have been obtained with threshold mapping and work function contrast from energy-filtering operations together with element specific imaging and chemical maps. We demonstrated work function variation in imaging mode for the cellular morphology and the characteristic polymorphonuclear morphology of the nucleus. These results demonstrate the potential and extend the use of photoemission electron microscopy and imaging X-ray photoelectron spectroscopy as analytical tools for visualization of biological materials and processes on the cellular level.The use of nanoparticles in recent years have significantly increased. Today, nanoparticles are being used in a wide range of applications, such as in electronics, energy, biology, and medicine. One hot topic in medicine is the development of contrast enhancement agents for magnetic resonance imaging. We report the development of two types of nanoparticles to be used as contrast enhancers for magnetic resonance imaging. The first type is water-dispersible and ultra-small Fe3O4 nanoparticles coated with polyacrylic acid. The Fe3O4 nanoparticles exhibit good magnetic properties, biocompatibility, excellent relaxivity properties and can be employed as a potential dual T1 and T2 weighted contrast agent. The second type is cerium oxide nanoparticles with the integration of gadolinium. Cerium oxide has unique redox properties due to the coexistence of Ce3+ and Ce4+ states making them suitable for scavenging reactive oxygen species. The integration of gadolinium makes these nanoparticles promising contrast agents with both therapeutic and diagnostic properties. We have designed a new technical innovative energy saving  process where a reduction in the annealing temperature for oxide removal is obtained, by the presence of europium doped gadolinium oxide nanoparticles in comparison to Eu3+ and Gd3+. A low coverage of nanoparticles and ions revealed a significant reduction in annealing temperature for the oxide removal. These results deliver a promising one step energy saving strategy of producing silicon-based contacts. In summary, this thesis work demonstrates the power of element specific imaging and chemical mapping of bio-related surfaces as well as nanoparticle tracking in the sub-micro and nano region.