Ultramicrotomy

Ultramicrotomy is a technique used in the field of microscopy to prepare ultra-thin sections of biological or material samples for examination under an electron microscope. This process involves cutting thin slices, typically around 50 to 100 nanometers thick, using an ultramicrotome. These sections are then mounted on grids and can be stained or coated for further analysis.

History

Ultramicrotomy was first developed in the 1950s as a method to overcome the limitations of conventional microtomy, which could only produce sections that were several micrometers thick. The need for thinner sections arose with the advent of electron microscopy, which required higher resolution imaging of samples. The technique was initially used in the field of biology to study cellular structures, but it has since found applications in various scientific disciplines.

Technique

Ultramicrotomy involves several steps to prepare the sample for sectioning. First, the sample is fixed and dehydrated to remove water content. This is followed by infiltration with a resin, such as epoxy or acrylic, which provides structural support to the sample during sectioning. The resin is then polymerized to form a solid block that can be easily handled.

The ultramicrotome is a specialized instrument used to cut thin sections from the resin-embedded sample. It consists of a knife holder, a specimen holder, and a mechanism to advance the sample for cutting. The knife used is typically made of glass or diamond and is extremely sharp to ensure precise sectioning.

During the cutting process, the sample block is trimmed to expose the region of interest. The ultramicrotome then advances the block, and the knife cuts a thin section from the surface. The section is collected on a water surface or a grid coated with a thin film of carbon or other materials. The water surface or grid helps support the fragile section during collection.

Applications

Ultramicrotomy has a wide range of applications in various scientific fields. In biology, it is used to study cellular structures, such as organelles and membranes, at high resolution. It is also used in materials science to examine the microstructure of materials, such as metals, polymers, and ceramics. Additionally, ultramicrotomy is employed in forensic science, pathology, and other disciplines where detailed analysis of thin sections is required.

See Also

• Electron microscopy
• Microtomy
• Resin embedding