Serial block-face scanning electron microscopy

What is SBF-SEM?

Serial block-face scanning electron microscopy (SBF-SEM) is an imaging technique that generates 3D views of whole cells and tissue regions at higher resolutions than those achieved by light microscopy. It produces images of the internal ultrastructure of cells and tissues similar to those of transmission electron microscopy (albeit at slightly lower resolution), with the advantage of generating 3D datasets by serial imaging of the same area. 

The combination of electron microscopy resolution and serial imaging means that SBF-SEM allows us to see small details of the tissue/cell ultrastructure, while at the same time being able to place the ultrastructural detail in the broader 3D context of the cell and tissue architecture.

Given their 3D nature, SBF-SEM datasets can be used to produce 3D models of whole cells, organelles and other cellular structures.

How does SBF-SEM work?

In SBF-SEM, a piece of tissue or cell pellet embedded in plastic resin is placed inside a special imaging chamber called 3View (see video), which is fitted to a high-resolution scanning electron microscope. The face of the block is imaged by SEM, and then an ultrathin slice of the block face is removed while the block remains inside the microscope. The newly exposed block face is then imaged. This process is repeated hundreds of times to produce consecutive images of the sample, which are then combined into an image series referred to as a '3D volume'.

Although samples embedded in resin for transmission electron microscopy (TEM) can often be imaged by SBF-SEM, the best SBF-SEM datasets are produced using samples prepared especially for this technique, with protocols designed to enhance sample contrast before embedding. SBF-SEM is performed in very sensitive and complex equipment that is operated exclusively by highly trained staff and selected users with solid electron microscopy experience. 

What tissues or cells can be imaged by SBFSEM?

Most biological samples that can be fixed and then embedded in plastic resin can be imaged by SBF-SEM.

At the Centre for Bioimaging, we have produced SBF-SEM data from a variety of biological samples, including mammalian cells and tissues, worms, unicellular parasites (such as Plasmodium, trypanosomes and Leishmania), ctenophores, plant tissue and bacteria.