Neutrophils Activated by Nanoparticles and Formation of Neutrophil Extracellular Traps: Work Function Mapping and Element Specific Imaging.

Photoemission electron microscopy (PEEM) and imaging X-ray photoelectron spectroscopy (XPS) have over the years been powerful tools in classical surface physics and material sciences, and due to recent technological advances, their uses within other fields/disciplines are rapidly growing. Lately, the XPS/PEEM based elemental analysis and characterization in imaging mode, with exquisite spatial resolution and high sensitivity, has shown the potential to deliver new mechanistic insights in cell-biology/medicine. In this work, the aim was to visualize biological processes on the cellular level, with the additional dimension of topographical morphology and element specific information, mapping chemical composition and chemical states. This is hereby demonstrated by combined PEEM and imaging XPS investigation of neutrophils and their activation processes, where fluorescence microscopy commonly used in biology is used for benchmarking. Neutrophils are phagocytic cells and are vital components in the human immune system, with the fundamental role of fighting invading pathogens. They are capable of ingesting microorganisms or particles, and in order to capture and trap foreign objects, one of their strategies is to release nuclear DNA by the formation of extracellular web-like traps (NETs). Here, we report how neutrophils are triggered by controlled nanoparticle (NP) exposure. The neutrophils and NETs formation are imaged in the presence of NPs, and we report the elemental composition of single cells and the structure of NETs. Cellular uptake of nanoparticles is proven and the states just before and after NETs release are imaged, as well as visualization of the extraordinary capability for mass transport at distances 10 times or more than the size of the cell itself. This method paves the way for element specific imaging of biorelated cells on surfaces as well as nanoparticle tracking in the submicro- and nanoregions.

Novel material concepts of transducers for chemical and biosensors.

The objectives of this work are to contribute to the knowledge about physical and chemical properties of WBG semiconductors, such as ZnO and GaN towards development of advanced bio- and chemical sensors. For the semiconductors, growth techniques typically yielding single crystal material are applied. Thin epitaxial quality films of ZnO and GaN are fabricated on SiC or sapphire substrates. An emphasis is given to ZnO due to the interesting combination of the semiconductor and oxide properties. Surface bio-functionalization of ZnO is performed by APTES, MPA or MP-TMS molecules. We have compared some of the results to (hydroxylated) GaN surfaces functionalized by MP-TMS. The covalent attachment of the self-assembled biomolecular layers has been proven by XPS analysis. For complementary electrical characterization impedance spectroscopy measurements were performed. The results are intended to serve the realization of bioelectronic transducer devices based on SiC or GaN transistors with a ZnO gate layer. To take advantage of the catalytic properties of ZnO, initial prototypes of chemical sensors for gas sensing are processed on ZnO deposited either on SiC or on sapphire and they are further tested for the response to reducing or oxidizing gas ambient. The sensor devices show sensitivity to oxygen in the surface resistivity mode while a Pt Schottky contact ZnO/SiC device responds to reducing gases. These results are compared to published results on Pt/GaN Schottky diodes.