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The Cryopreservation Process
The Cryopreservation Process is where biological matter (cells, tissue, organs, etc) is preserved by cooling to a very low temperature. This process stops the normal cell functions and holds the sample in suspended animation. When the time comes to thaw the sample, normal biological function resumes.
Cryopreservation Process Steps
The cryopreservation process can be broken down into 5 steps:
Isolating material: When choosing material suitable for cryopreservation, certain properties must be considered including the volume, density, pH and degree of damage already sustained by the sample.
Use of cryoprotectant agent (CPA): Certain chemicals can be used to help the cryopreservation process. CPAs are added to the sample to reduce the freezing point of the sample and slow the cooling rate. This will reduce the risk of ice formation within the sample that can lead to damage.
Freezing: There are different methods of freezing that can be employed depending on the sample and CPAs. The vitrification process and freezing using liquid nitrogen are common methods used in the cryogenic freezing.
Cryogenic Storage: Some samples can be stored at -80 °C, however it is most common that samples would be stored at -196 °C in liquid nitrogen storage tanks.
Removal of CPA and Thawing: When samples are ready to be thawed, the material is slowly warmed, and CPAs are removed to allow normal function to resume.
Cryopreservation Methods for Cryogenic Freezing
There are several cryopreservation methods for cryogenic freezing. Two common methods are vitrification and slow freezing. Both methods have their advantages and disadvantages that should be taken into consideration.
The vitrification cryopreservation method is when a sample is preserved in a glass-like state. Vitrification is very quick, freezing the sample almost instantaneously to avoid the formation of ice crystals and it is low in cost. Vitrification does require some technical skill, and the sample is at risk of contamination due to poor technique and possible toxicity from the high concentrations of CPA used.
Slow freezing is much simpler than vitrification and does not require the same technical skills. A lower concentration of CPA is needed, lessening the risk of toxicity however there is a higher risk of damage to the cell from the formation of ice crystals within the sample. Slow freezing can also be more costly as specialist freezing equipment is needed.
There are several cryopreservation applications in the medical and research industries. Some of these applications are outlined below:
Fertility treatments: Oocytes, sperm samples and embryos can all by cryopreserved to aid fertility treatment. This can be for donations, to store reproductive samples to delay childbearing or for individuals undergoing gonadotoxic treatments who may wish to have children.
Biobanks: Biobanks are becoming more common in healthcare and pharmaceutical research. They are used to store human biological samples to aid research into genetics, biomarkers for diseases and personalized medicine.
Biodiversity Conservation: Non-human samples such as other animals, plants and bacteria can also be cryopreserved. The aim of this is for future research and to try and preserve biodiversity as thousands of species face extinction. Having cryopreserved samples means that in decades to come, and as technology improves, we may be able to revive species that have become extinct or are very close to it.
BIOBASE'S CRYOGENIC STORAGE AND CONSERVATION SOLUTIONS