Cryostat Article #1: General Cryostat Information

Cryostat Article #1: General Cryostat Information

Some time in your research or clinical career, you may encounter a need to process tissue using a cryostat. Recently, our company Precisionary Instruments launched a brand new product called the CF-6100 cryostat. How did we develop this model? We interviewed dozens of customers and experienced cryostat users to gather direct feedback on what user needs are. We then designed and manufactured the Precisionary Cryostat CF-6100 based on those feedback comments (Figure 1).

For the next few weeks, we will be producing a cryostat information series. Here is the first article in our series!

Figure 1. Precisionary Cryostat CF-6100 model and new launch.

What is a cryostat?

Let’s break down the word: “cryo” means cold, and “stat” means stable. Taken together, a cryostat is a device that maintains stable cold (freezing) temperatures. There are many types of cryostats for engineering and medicine or biological research. Here, we specifically refer to a biological microtome type of freezing cryostat. Simply put, a research or clinical cryostat is used to prepare tissue samples at subzero temperatures so that they can be used in pathology, histology, immunohistochemistry, in-situ hybridization, and enzymatic detection. The tissue slices produced by cryostats are called “cryosections” or “frozen sections.”

Cryostat are stand-alone units much larger than a microtome (such as those for cutting paraffin-embedded tissues). Cryostats use cold temperatures to allow for tissue sectioning, and contain a freeze chamber that has a microtome and knife holder for sectioning frozen tissue (Figure 2). Tissue samples are embedded in freeze media, typically called OCT compound (optimal cutting temperature compound), and cut while they are in the freezing chamber. Once sectioned, the tissue slice is mounted onto a glass slide for staining and further examination. Overall, the process takes 10-20 minutes, but can vary greatly.

Figure 2. Cryostats in research and clinical settings may be operated by a histology technician (left) who makes very thin frozen tissue sections (right).

What are the advantages and disadvantages of cryostats?

There are many advantages to using a cryostat especially for producing slices for IHC (immunohistochemistry) and ISH (in-situ hybridization) experiments (Figure 3). They include:

  • It is easier to obtain slices after they are cut on a cryostat. For example, the slide can go directly onto the cut sample to easily collect the slice. This allows the user to easily obtain multiple slices onto one slide for staining.
  • The method to cut and obtain slices on a cryostat is very rapid (once one becomes a master at the hand-crank, many slices can be obtained very quickly).
  • There is minimal tissue shrinkage compared to paraffin embedded tissue sections; this results in healthier slices and improved results.
  • The procedure for freezing tissues for cryostat sectioning prevents certain substances (fat & enzymes) from degrading in the tissue while cutting, resulting in higher quality slices.
  • The tissue chucks as well as cutting blade can be moved/adjusted for optimal cutting angles, settings, and results.
  • Once the needed slices are obtained, the tissue sample/frozen block can go back in the freezer until it is needed again. This results in less individual tissue sample (frozen) prep, as well as preserving the rest of the sample for the future.
  • The cutting area/cryostat chamber is large enough to keep everything (such as tissue sample, slides, tissue handling tools, etc.) cold throughout cutting.
Figure 3. Top row of images show slicing technique on cryostats with a mounted sample. Bottom row contains stained tissue showing bronchiolo-alveolar carcinoma and kidney tubules.

There are also disadvantages to using a cryostat, ranging from the instrument itself, to the frozen preparation protocol, and the vitality of the tissue being cut. To be more specific:

  • Cryosections are not as stable as paraffin embedded sections but preparing these sections does not require dehydration of the tissue and these sections are ideal for visualizing antigenicity.
  • When preparing tissue samples to be frozen for cutting on a cryostat, the possibility of slight distortion of the tissues throughout this prep process can occur, including:

o   Ice crystal formation

o   Subcellular structures of the tissue cells are less preserved

o   Freeze-induced micro-cracks

o   Tissue may dry if not frozen properly

  • Cryostats are larger (they take up more space in the lab) and more expensive than vibratomes, as well as requiring more work to maintain, clean, and repair if they are damaged. At Precisionary Instruments, we make sure that our cryostats are the most affordable on the market.

What are key cryostat technical features?

When you are ready to purchase a cryostat and are gathering quotes and technical information on different brands and models, keep us in mind (Figure 4)! Here are key cryostat features you should consider when making an important decision:

  • Control panels: LED touchscreen panels allow for easy control of cryostat parameters, and are intuitive to use. Manual push buttons are found on older cryostat models, but may be more difficult to clean and fully disinfect.
  • Number of compressors: Dual compressors mean that a cryostat has two compressors. This is crucial because if one compressor fails, the second compressor acts as a backup. Be aware of cheaper cryostat models on the market that only have a single compressor system, which means they are not as robust. The Precisionary Cryostat CF-6100 comes with a dual compressor system.
  • Type of knife holder: Low profile and high profile blades are two options for disposable cryostat blades. Permanent tempered steel blades are also available. The cost over time between disposable and permanent blades are about the same.
  • Peltier cooling system: Having a Peltier cooling plate is ideal for rapid freezing of tissue samples being prepared for cutting. This is particularly desired for clinical cryostats.
  • UV disinfection: Having a built-in disinfection system with a UV lamp is highly desirable.
  • Customer service: Since a cryostat will likely be a high cost item in the lab and clinic, make sure you find a company and model that provides thorough, easy-to-access, and responsible support.
Figure 4. Precisionary Cryostat CF-6100 offers all of the key technical features above, included in one package on delivery.

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