Cryopreservation refers to the storage of a living organism, cell or tissue at ultra-low temperatures such that it can be restored to the same viable state as before it was frozen. Storage for an indefinite amount of time requires samples to be maintained below the glass transition temperature of aqueous solutions, approximately -130ºC, the temperature at which frozen water no longer sublimes and recrystallizes. Therefore -150°C mechanical freezers or liquid nitrogen storage tanks are required for long-term preservation.

In the late 19th century Sir James Dewar, a Scottish chemist and physicist, designed a vacuum jacketed vessel capable of effectively storing liquid gases, such as nitrogen, for long periods of time. This type of vessel is still being used today.

For years cryopreservation in liquid nitrogen at -196°C has been the standard for long term preservation. Over the years it became clear that cross contamination was a real risk with this kind of preservation. Not only can samples be contaminated by the nitrogen itself, but also by other samples. Evidence of cross contamination has been documented in the past, including a well known example of Hepatitis B transmission.
For this reason, storage in vapour phase became more popular. Valuable samples were no longer stored in liquid phase nitrogen to eliminate the risk of cross contamination.

There are also disadvantages of storage in vapour phase though:

• Loss of storage capacity; The bottom third of the vessel cannot be used as there is liquid phase nitrogen there.
• The temperature provided by vapour phase storage is highly dependent on the level of liquid nitrogen in the bottom of the vessel.
• Large vertical temperature gradients can put valuable samples at greater risk during long term storage.

Ultra-low -150ºC freezers - Dry storage

Due to the extended operation of compressors within ultra-low temperature freezers, lubricant oil is essential to reduce wear, prevent abrasions and seizure and therefore maintain the highest levels of freezer performance.

However, when lubricant oil circulates within the refrigeration circuit, it can cause piping to become clogged, resulting in compressor damage. Incorporating a high-efficiency oil separator, PHCbi -150ºC freezers effectively separate lubricant oil from refrigerant, increasing the durability of the compressors and offering a reliable ultra-low temperature environment.

Highly efficient compressors have been specially developed and incorporated our -150ºC freezers. The cascade refrigeration system incorporating Cool Safe® compressors offers enhanced reliability and increased sample security. These compressors achieve a 10% reduction in energy consumption and the aerodynamically designed and placed components in the refrigeration compartment provide superior airflow, significantly reducing the stress to the freezer and contributing to excellent durability.

With a powerful low noise design afforded by traditional ultra-low temperature technology, these freezers delivere durable, stable cooling. Securely store valuable and irreplaceable samples with the upmost confidence that they won’t be lost in the case of compressor failure.

The PHCbi patented VIP vacuum insulation panel thin-wall composite equipped with MDF-C2156VAN is a high-efficiency design that yields more interior storage volume in a conventional freezer footprint.