Electron tomography on latex particles suspended in water using environmental scanning electron microscopy

Abstract

Tilted image series are acquired on liquid suspensions of latex particles supported by a carbon membrane. To do so, a home-made stage fitting in an Environmental Scanning Electron Microscope (ESEM) is optimized in order to minimize cold losses and therefore improve both sample stability and spatial resolution in the images. As latex particles are electron-sensitive materials, sample degradation and stability are taken into account in the choice of the parameters for tilted image series acquisition. Despite the limited number of images, conventional algorithms are used to reconstruct the volume and study the three-dimensional arrangement of latex particles. The lattice types are in good agreement with what can be observed on frozen suspensions, although the domain sizes are smaller. Several quantitative parameters such as the latex particle size and the distance to the first neighbors are extracted from the 3D model. Finally, the spatial resolution in the tomograms is estimated using the Crowther's criterion and Fourier Shell Correlation analysis. It is also measured directly by analyzing a suspension containing latex particles and a surfactant of interest for composite formulation.

Three-dimensional SEM, TEM, and STEM for analysis of large-scale biological systems

“…Following this, the cells were fixed in 4% glutaraldehyde for 30 min and stored at 4 °C until image acquisition. Bekel et al designed a device to acquire images in tilt series for tomographic reconstructions (Jiao et al 2019;Masenelli-Varlot et al 2014). Bekel et al proceeded to record images by environmental scanning electron microscopy (ESEM) at 15 kV, maintaining humidity at or above 70% and a temperature of 4 °C, so that the cells did not dry out.…”

“…designed a device to acquire images in tilt series for tomographic reconstructions (Jiao et al. 2019 ; Masenelli-Varlot et al. 2014 ).…”

Liquid-Cell Electron Tomography of Biological Systems

“…Notable outcomes of this technology include structural studies that reveal intricate components of biological assemblies such as multiprotein secretion systems and flagellar motors. − Expanding upon these achievements, we have adapted a tomography workflow that can be used on a wide variety of electron microscopes to evaluate liquid specimens in 3-D. This work also complements recent efforts by other research teams to implement tomography methods for the environmental STEM community …”

“…This work also complements recent efforts by other research teams to implement tomography methods for the environmental STEM community. 20 To craft the LC-ET technique, we recorded an image series of a model system pertinent to host−pathogen interactions. We used the Agrobacterium sp.…”

New approach to electron microscopy imaging of gel nanocomposites in situ

“…In both cases, the information acquired during the imaging, will be equivalent to obtaining a series of two-dimensional projections of a non-rigid threedimensional spatial arrangement of nanoparticles. While obtaining of 3D structure of individual nanoparticles in liquid has been reported, analysis of spatial distribution of nanoparticles in liquid or gel matrix [44][45][46] would require optimization and commercialization of a new generation of fluid cell TEM holders. Until then, sample preparation protocols and imaging of hydrated viscous nanocomposite specimens, soft matter and biological specimens with nanoscale resolution with the fluid cell in situ in an unaltered state, can provide an alternative pathway to cryo-TEM 47 .…”