How Cord Blood Is Frozen

Not everyone will want the technical details about what becomes of the cord blood after you've given it to the cord blood bank. Some people, however, are very interested in these details. They will want to understand exactly what the lab is going to do with the cord blood, and how they will do it.

Separation and Storage

Most cord blood banks use a centrifuge to separate out the stem cells from the rest of the blood when it is brought in after retrieval. The stem cells are with the white blood cells and are stored either in bags or in small vials at the lab. These containers are frozen to preserve the stem cells in the event of their much later use.

Cryopreservation of Cord Blood

When the stem cells are frozen, they are first put into a solvent which will protect them from forming ice crystals. Ice crystals would rupture the cell membranes and render them useless. The solvent that is used the most is "DMSO" which stands for DiMethylSulfOxide. There are many researchers looking into alternative solvents at the moment, and time will tell which solvents companies will decide to use the most.

Slow Freezing

In order to further protect the cord blood cells against ice crystals, the cells need to freeze slowly. This is done with high-tech, controlled-rate freezers. Once the blood is frozen in these freezers, it is moved to long-term storage. The final storage temperature will be at -196 Celsius. It is essential that the cells stay below -130 C at all times while in storage. Should the temperature fluctuate and move above -130 C and then go back down below, the blood will have irreparable cell damage.

Types of Freezers

There are many types of freezers used on the market today for the storage of stem cells. Public banks often have different facilities than do private banks. A few public banks with large budgets and some private banks will use "BioArchive freezers which were originally developed at the New York Blood Center. The bag location and retrieval for each sample is completely computerized and the robotic arm in the freezer circulates and retrieves the samples to avoid any warming in the freezer when samples are added or removed.

Most of the public banks and some private banks, however, use "dewars" which are insulated tanks with lids. The problem with these units is that the temperature changes when they are opened to either add or retrieve samples. However, the temperatures are monitored closely and have been proven effective for long-term storage.


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