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Lack of scientific study on the effect of Transient Warming Event

Anthony Chun-Fung Chan, Ph.D. (Cantab)

Transient Warming Events (TWE) is unintentional exposures of samples transiently to room temperature. Multiple and longer duration of TWE has been proposed to correlate with viability loss and thus, number of times and duration that units subject to TWE should be kept in minimum. However, this claim has not been back by any scientific research, and none of international published articles can be found in PudMed and other search engines on this subject.

For a good practice of standpoint, the cryopreserved cord blood units must be stored at a temperature below glass transition point (Tg) which is in general regarded as being -132oC. Below this temperature no diffusion can take place and thus the biological clock stops. This means below this temperature the integrity of the cryopreserved cord blood units can be maintained, at least theoretically, for eternity. In fact -150oC will be quoted as critical temperature by many researchers, therefore storage of cryopreserved cord blood units under -196oC liquid phase or -180oC vapour phase of liquid-nitrogen (LN2) freezer allows large extent of safety margin for normal working operation during storage and sample retrieval.

The effect of TWE on cord blood units up-to-date still remains ambiguous. However, it is shocking that TWE has been boasted to be detrimental to the cryopreserved cord blood units. More scientific research should be performed to find if TWE has a significant effect on cells.