A typical day in any laboratory can involve a trip to a freezer or even a room full of them. These freezers, especially ultralow temperature (ULT) freezers, are crucial in any biological lab as they allow specimens to be preserved for a number of years without compromising on viability or quality.
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When running experiments, samples tend to be moved around. Some would be taken out of the ULT freezer and then put back in again after the experiment is over. This is acceptable in one laboratory, as the samples only cover short distances.
However, if samples are required to travel longer distances, like from one lab to another on the other side of a town or city or even from one state to another, then an appropriate method of transporting them while maintaining cold storage temperatures is crucial.
To transport heat-sensitive samples safely usually requires a cold chain. In effect, samples will remain in ultralow temperatures throughout transportation if an efficient cold chain is installed.
Freeze-thaw cycles
Cryopreservation is most effective when samples are consistently exposed to ultralow temperatures. If they are consistently stored inside a ULT freezer, they will remain viable for a number of years. However, if they are transported from place to place, they become susceptible to fluctuations in temperature which in turn could compromise sample viability.
Samples may thaw if ultralow temperatures are not maintained. For example, suppose a cell culture vial is transported from a ULT freezer set at -80 ºC to a styrofoam box filled with dry ice variations in temperature are possible.
The surface temperatures of dry ice range from -78 to -110 ºC, but the interior of the Styrofoam box may not be able to maintain that temperature. If the samples are exposed to even slight warming, viability could be compromised.
Thawing and freezing repeatedly can lead to irreversible damage, even when cryoprotectants are used. Thus, an effective cold chain is absolutely essential to ensure the samples are well-preserved during transport.
Keeping it cool
Keeping samples cool can be done in a number of ways. One frequently applied method is the storage of samples in tanks of liquid nitrogen during transport, as liquid nitrogen can maintain an ultralow temperature throughout the transportation of the samples.
Another method involves the use of portable ULT freezers. These can be readily transported anywhere and then plugged into regular power outlets. In some cases, compact freezers can be powered by 12-volt batteries. These can help sustain the ultralow temperatures required to preserve samples in transit.
Upon arrival
When samples arrive at their destination, they must be revived or immediately returned to a ULT freezer for storage. Thawing should be avoided at all costs, as it will have a detrimental impact on sample viability.
If an efficient cold chain has been instigated and maintained, the samples should remain intact and ready for use or storage once they arrive at their destination.
About inTEST Thermal Solutions
inTEST Thermal Solutions (iTS) specializes in the design and manufacture of precision temperature control systems. Our breadth of products and in-house engineering capabilities allow us to be a single-partner-solution for thermal test, process cooling, and cold storage applications. We are recognized globally for our expertise in precise temperature control and simulation of extreme thermal environments, from -185 to +500 °C, with rapid transitions or long dwell times. The iTS family includes four product brands: Temptronic, Sigma Systems, Thermonics, and North Sciences. inTEST Thermal Solutions is a wholly owned subsidiary of inTEST Corp, Mount Laurel, New Jersey, USA.
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