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After cord-blood collection has taken place, the blood is placed into bags or syringes and is usually taken by courier to the
cord blood bank. Once there, the sample is given a unique identification number. Then the stem cells are separated from the
rest of the blood and are stored cryogenically (frozen in liquid nitrogen) in a collection facility or a cord-blood bank.
Then, if needed, blood-forming stem cells can be unfreeze and used in either Autologous Procedures or Allogeneic Procedures.
While storing cord blood, each vial is clearly marked with: Cord Blood Number, Date of Birth, Baby's Name, Date of Processing,
and Contents, before it is sent to the first stage of the cryopreserving process. The vials are placed into two different
temperature cryo-tanks before being submerged into the liquid nitrogen tanks. This process is to ensure the safety of the
cells. The progression to lower and lower temperatures keeps the cells from going into shock from the extreme negative
temperature of -321° Fahrenheit.
Before the cells can go into the liquid nitrogen tanks where they will be stored at -321 degrees Fahrenheit, the cells go
throw a slow freeze process in the vapor tank. Your baby’s stem cells are stored in submerged liquid nitrogen tank. This
tank has 25 inches of liquid nitrogen to ensure that the temperature will remain at –321 degree Fahrenheit. All of these
tanks are located in the highly monitored and secured facility.
When living tissues are frozen, they are immersed in a solvent, which protects the cells against the formation of ice crystals,
because ice crystals would rupture cell membranes. The solvent most commonly used for cryopreservation of cord blood is
"DMSO" (DiMethylSulfOxide, usually in 10% solution) to act as a shield around the stem cells.
This solution is spun out of the stem cells in the removal and
usage by for a transplant. (Please note that it is not all-inclusive and concrete procedure, the actual procedure may
vary from one storage facility to another, as there is a massive research in the medical literature on alternate
chemical combinations).
Theoretically, stem cells should last forever, but cord-blood research has only been ongoing since the 1970s,
so the maximum time for storage and potential usage are still being determined. Blood-forming stem cells that
have been stored up to 14 years have been used successfully in transplants. So we can safely say that the shelf
life is good and if stored properly it can be used many years into the future.
Freezing Umbilical Cord Blood (UCB): To further protect cord blood cells against the formation of ice crystals, it is
important that the cells freeze slowly. This is done in a special controlled-rate freezer, and then the blood
is transferred to long-term storage. The final storage temperature should remain stable at -196 degree Celsius.
Freezers and handling procedures are designed to avoid "Transient Warming Events (TWEs)". In particular, the cells
must stay below -130 C while they are in storage. If the temperature fluctuates above -130 C and then below
again, the blood will suffer irreparable cell damage.
Freezer Types: A few public cord blood banks with big budgets use "BioArchive" freezers from Thermogenesis (Nasdaq: KOOL).
These freezers were originally developed at the New York Blood Center. This liquid nitrogen freezer uses a
proprietary, computer-driven robotic system to cryopreserve and archive up to 3,626 bag units.
The location and retrieval of each sample is computerized.
The goal of using a robotic arm to circulate and retrieve samples is to avoid "Transient Warming Events (TWEs)" when samples
are added or removed from storage. Most of the public cord blood banks in the USA are using "dewars", which are
basically insulated tanks with lids. The disadvantage of these units is the need to open the lid when adding or
removing samples. However, temperatures are monitored constantly and they have been proven effective for long-term
storage. All private cord blood banks in the USA are also using "dewars", like most of the public banks.
Freezer Contents: Blood is stored in either bags or vials. When the racks in the freezer are loaded with blood
containers, they should be spaced evenly to ensure temperature stability. A given freezer will have racks
designed to hold either bags or vials, you cannot mix containers in the same freezer. Hence, most banks build
their business around one type of storage container or the other. The cryogenic temperatures are maintained with
cold nitrogen. Some banks use the liquid phase of nitrogen and others use cold nitrogen vapor (gas). The pros and
cons of the nitrogen options are given in the table below.
| Liquid Nitrogen |
Vapor Nitrogen |
| Uses more nitrogen |
Cheaper (only fill the bottom of the tank) |
| Constant temperature |
Possible Transient Warming Events |
| Documented chance of infectious disease leaking from one bag onto the outside of another and infecting the recipient |
Safer for Quarantine Tank |
| Long-term viability confirmed Broxmeyer, H. E., et al. 2003 pnas.0237086100 |
Long-term viability not studied |
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