| Many parents these days are choosing to have their | | | | take into account when deciding which method of |
| baby's umbilical cord blood frozen and stored as a | | | | storage to choose. The two main types of tank both |
| future source of stem cells. This article looks at the | | | | use liquid nitrogen for freezing, but use it in different |
| different ways in which blood and stem cell samples | | | | ways. The oldest method uses liquid nitrogen in its |
| are stored. | | | | liquid phase to freeze the sample and keep it at the |
| The process of having your baby's umbilical cord | | | | required temperature for storage. The important |
| blood collected, processed in a laboratory and kept in | | | | thing to remember is that there are usually also other |
| frozen storage is a relatively new one. The idea is | | | | samples from other individuals in the same storage |
| that the whole blood containing the stem cells or the | | | | tank. The liquid phase nature of the nitrogen in the |
| extracted stem cells themselves are available for | | | | tank means that there is a possible risk of |
| future use if the child needs any medical treatments | | | | contamination of samples by infectious disease |
| which require them. Although some treatments such | | | | particles if there was one or more infected samples |
| as those for sickle cell disease, leukemia and | | | | in the tank. The liquid nitrogen can carry infectious |
| Hodgkin's disease already use these cells, the idea is | | | | particles, such as viruses, between samples. There is |
| to also have a stock of compatible cells that can be | | | | evidence that transmission of Hepatitis B virus |
| used in treatments yet to be developed. Since the | | | | between samples has occurred while the samples |
| use of this type of cell for medical treatments is the | | | | were stored in liquid phase nitrogen.* |
| subject of much current research, the likelihood of | | | | Vapour Phase Nitrogen |
| new treatments becoming available in the future is | | | | The other design of storage tank also uses liquid |
| high. These future treatments have the potential to | | | | nitrogen, but it is used in a different way. The liquid |
| offer cures for diseases, injuries and conditions that | | | | nitrogen is confined to the walls of the storage |
| are incurable today. | | | | container, and only vapour phase nitrogen comes into |
| The collection and storage process starts just after | | | | contact with the samples. This means that any |
| birth when the umbilical cord blood collection kit | | | | infectious particles present in a sample could not be |
| supplied by the storage company is used by one of | | | | carried to other samples to cause contamination. In |
| the medical professionals to safely and painlessly | | | | the past, concerns were voiced about the vapour |
| collect the blood from the cord. This sample is then | | | | phase nitrogen's ability to maintain the correct |
| transported to the storage company's laboratory for | | | | storage temperature when the tank was opened for |
| processing. Some companies will extract the stem | | | | access. Design improvements now mean that a |
| cells from the cord blood before freezing the sample, | | | | constant temperature can be maintained in this design |
| whereas others freeze the whole blood. | | | | of storage tank. |
| Liquid Phase Nitrogen | | | | *Tedder R., M. Zuckerman, A. Goldstone, A. Hawkins, |
| The sample is frozen in a storage tank which is | | | | A. Fielding, E. Briggs, D. Irwin, S. Blair, A. Gorman, K. |
| cooled by liquid nitrogen at around minus 190 degrees | | | | Patterson, D. Linch, J. Heptonstall, and N. Brink. 1995. |
| Celsius. This extremely low temperature can preserve | | | | Hepatitis B transmission from contaminated |
| the quality of the sample for many years. There are, | | | | cryopreservation tank. Lancet 346: 137-140. |
| however, important storage tank design factors to | | | | |