How Cryostats Work & How We Save You Time & Money

A cryostat’s primary functions include maintaining cryogenic temperatures for any device or sample placed inside it and cutting histological slides with a cryostat microtome blade. The difference between a standard microtome and a cryostat is that the microtome cuts tissue sections at room temperature. In contrast, a cryostat containing a microtome keeps the temperature at a cryogenic level.

Furthermore, to ensure a tissue sample is sliced accurately, it’s also essential that the tissue is embedded. This is accomplished by placing it face up on a tissue holder and covering the sample with an embedding medium. The specimen holder, or chuck, is then set upon a freezing temperature bar.

In addition to cryogenic temperatures and embedding, disposable blades are provided by manufacturers, such as Leica, that help researchers and physicians consistently produce high-quality sections/slides. However, the type of blade you choose for your cryostat depends on the microtome and the material you’re sectioning. For general applications, you can choose between fixed or disposable blades. The blade itself goes in the blade clamp, which is one part of the microtome’s blade holder, located at the device’s front.

While frozen sections produced by cryosectioning are not as physically stable as paraffin-embedded sections, they provide excellent tissue sample preservation.

The section thickness can be as thin as 1 micrometer, as the micrometer’s cutting is exact. To prevent any curling or rolling while a lab technician slices a section, an anti-roll plate, a square or rectangular glass plate held inside a metal frame, is used to keep the sections flat.

The tissue section is then mounted to a glass slide within the device and dried and stained as needed. A standard method of staining frozen sections is by utilizing immunohistochemistry (IHC) staining. While the utility the machine offers can seem simple, the convenience that it adds is undeniable. In terms of temperatures, cryostats can maintain a specific degree that the tissue requires, which is generally somewhere between 20 and 30°C.

That all said, there are many types of cryostats available, so it’s essential to know which will fit your specific needs and requirements.

The bath style is often similarly designed to vacuum flasks that utilize liquid helium. This includes having a cold plate placed in contact with the bath of liquid helium. The helium is replaced as it dissipates; this boil-off rate is determined by the size, style, frequency of use, and other factors.

The rapidity of the helium dissipating can be mitigated with the addition of vacuum shielding or the device having super-insulated walls. Most modern iterations are designed to include the super insulator materials as they are the most effective.

The continuous-flow models are cooled with liquid cryogens, almost exclusively liquid nitrogen or helium, from a storage dewar. Where the bath version has to refill the helium that dissipates manually, the boiled-off cryogen is continually replenished in a steady flow from the dewar.

The temperature controls of a continuous-flow cryostat system are done by controlling the rate at which the cryogen flows through the device, in addition to a heating wire that is part of a temperature control loop.

A closed-cycle type is differentiated by having a cryostat chamber through which cold helium vapor is pumped. This is attached to an external refrigerator that extracts the warmed helium exhaust vapor and then cools and recycles it. This type consumes a large amount of electricity to operate but never needs to be refilled with helium.

Sometimes it is necessary to have the cryostat be colder than liquid helium can accommodate.

This is done by adding additional cooler stages to the device, often a 1-K pot which allows the temperature to get as low as 1K. The only way to get below 1K with this device is to use magnetic refrigeration, which can be accomplished by adding another stage.

These devices offer a wide variety of applications and come in many different types. Most of their applications boil-down to two different types of users: clinicians and researchers.

• Clinical: If a surgeon needs a rapid intraoperative consultation, a cryostat can help get the immediate results needed by quickly, safely, and reliably slicing samples.
• Research: Delaying critical research eventually hurts your bottom line. The utility and speed that a trusted cryostat can bring allow you to section more tissue and thus analyze more specimens in a single day.