Exploring Biological Samples in 3D Beyond Classic Electron Tomography

Developments of electron tomography methods are of great importance to unravel the tridimensional organization and the interior detail of objects of nanometric scale. Here we describe two recently developed approaches to surpass some of the milestones of contemporary electron tomography: The low signal to noise ratio of tomograms and the detection of chemical elements in 3D. The techniques applied rely on STEM tomography and EFTEM tomography, capabilities of the 200kV electron microscope JEOL JEM-2200FS equipped with an in-column energy filter and STEM detectors. In the resin embedded samples tested, STEM-HAADF tomography was applied with success to improve the signal to noise ratio and determine cytoskeletal structures on mammalian kidney cells (LLC-PK1). For elemental detection, EFTEM tomography revealed the precise location and 3D arrangement of iron particles bound to cell wall of the pathogenic fungus Fonsecaea pedrosoi. Both techniques resulted in datasets clear enough for direct interpretation and thresholdbased segmentation.