When obtaining three-dimensional images of cells using a scanning electron microscope, individual cells are scanned one section at a time and those images are then put together to form one complete 3D picture of that cell – the process often takes a long time to complete. When using a fluorescence microscope, cells must first by dyed so that they show up against their surroundings. Now, a team from Helmholtz-Zentrum Berlin (HZB) have demonstrated a process called X-ray nanotomography, that can instantly obtain 3D images of cells in their almost natural state.
Before they can be imaged by the X-ray microscope, living cells must first be flash frozen. Once in the viewing area, they are illuminated by partially coherent light – this means that the selected wavelengths are not completely in phase with one another, but not completely out of phase, either. Generated by a synchrotron, this type of light allows small details to show up better by providing a higher level of contrast than entirely coherent light.
The microscope also features a high-resolution lens, and allows for more open space around the sample. This means the sample can be turned by up to 158 degrees, and viewed from different angles.
Working with the National Cancer Institute in the U.S., the HZB researchers have created 3D images of mouse adenocarcinoma cells. The images were detailed enough to show the double membrane of the cell nucleus, membrane channels in the nucleus, inclusions in cell organelles such as lysosomes, and various other minutiae. The microscope was able to image down to 30 nanometers, which is a record for an X-ray-based device.
The team believe that their process could be particularly useful for studying how viruses or nanoparticles penetrate into cells or into the nucleus.
The research was recently published in the journal Nature Methods.