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Title: Exploration of the use of ESEM for the study of biological materials
Author: Guthrie, S. E.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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This study investigates the potential of environmental scanning electron microscopy (ESEM) for use in the biological sciences. The morphology observed in fixed, dried and coated specimens imaged in the SEM is compared with that observed in fixed and untreated samples in the ESEM, looking at human monocyte-derived macrophages (MDMs). Artefacts are observed as a result of sample preparation for SEM including volume loss and cracking. Samples viewed in the ESEM appear broadly similar and fixation is found to offer some protection against beam damage for delicate samples. Cell viability in ESEM is explored in 3T3 fibroblasts and human MDMs. It is found that while samples survive cooling and pumpdown, cells cannot be imaged live. This is due to damage sustained when the cells are exposed to evaporating conditions in order to remove surface liquid and uncover the cells for imaging. With the fibroblasts, a distinctive morphology is seen which suggests this process is via membrane collapse. E. coli, however, are found to be viable after imaging in ESEM under carefully controlled environmental conditions. Bacteria have a cell wall whilst mammalian cells only have a single membrane. This suggests that resistance to osmotic shock is key to viability of biological samples in ESEM and that environmental conditions are more significant than beam damage for such samples. Wet scanning transmission electron microscopy (STEM) is also investigated as a tool for biology, and the best imaging conditions for biological samples are established. Images are presented showing that a range of features can be imaged using this technique in mammalian cells and bacteria, revealing internal structure.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available