Dual-axis electron tomography of biological specimens: Extending the limits of specimen thickness with bright-field STEM imaging.

The absence of imaging lenses after the specimen in the scanning transmission electron microscope (STEM) enables electron tomography to be performed in the STEM mode on micrometer-thick plastic-embedded specimens without the deleterious effect of chromatic aberration, which limits spatial resolution and signal-to-noise ratio in conventional TEM. Using Monte Carlo calculations to simulate electron scattering from gold nanoparticles situated at the top and bottom surfaces of a plastic section, we assess the optimal acquisition strategy for axial bright-field STEM electron tomography at a beam-energy of 300keV. Dual tilt-axis STEM tomography with optimized axial bight-field detector geometry is demonstrated by application to micrometer-thick sections of beta cells from mouse pancreatic islet.

Imaging the distribution of individual platinum-based anticancer drug molecules attached to single-wall carbon nanotubes.

Aims: To image the distribution of drug molecules attached to single-wall carbon nanotubes (SWNTs).

Materials & Methods: Herein we report the use of scanning transmission electron microscopy (STEM) for atomic scale visualization and quantitation of single platinum-based drug molecules attached to SWNTs designed for targeted drug delivery. Fourier transform infrared spectroscopy and energy-dispersive x-ray spectroscopy were used for characterization of the SWNT drug conjugates.

Nanoscale 3D cellular imaging by axial scanning transmission electron tomography.

Electron tomography provides three-dimensional structural information about supramolecular assemblies and organelles in a cellular context, but image degradation, caused by scattering of transmitted electrons, limits applicability in specimens thicker than 300 nm. We found that scanning transmission electron tomography of 1,000-nm-thick samples using axial detection provided resolution comparable to that of conventional electron tomography. We demonstrated the method by reconstructing a human erythrocyte infected with the malaria parasite Plasmodium falciparum.