Liquidus tracking is a cryopreservation technique developed to cope with samples that are unsuitable for preservation by conventional means such as controlled-rate freezing and ultra-fast vitrification.
In tissues, for example, extra-cellular ice can form during conventional freezing. In contrast to cell suspensions, this extra-cellular ice can be damaging as it is contained within the system being preserved.
Conventional controlled-rate freezing only tackles the problem of inter-cellular ice, and although conventional vitrification inherently prevents the formation of ice, it typically relies on ultra-fast cooling rates of around 20 000 oC/min; these fast rates are unachievable with large samples.
By slowly increasing the concentration of cryoprotectant during the preservation process, the Liquidus Tracker prevents the formation of ice crystals within the samples, allowing vitrification without the necessity for fast cooling rates. This slow vitrification is achieved by increasing the concentration of cryoprotectant while the sample is cooled; the cytotoxicity of the cryoprotectant decreases with temperature and as such higher concentrations can be tolerated at the lower temperatures.
The Liquidus Tracker is a system designed to allow research into the use of liquidus tracking as a means of cryopreserving biological samples that are not suitable for conventional slow-rate freezing or ultra-fast vitrification.
The preservation of biological matter is medically extremely important. Human and animal tissue is stored for research and regenerative medical purposes – bone marrow for cancer treatment, blood products, embryos, skin, bone and cell lines etc are all frozen for later use. Whilst extra cold deep freezers (similar to domestic ones) can be used, generally the ultra cold of liquid nitrogen at -196°C is required for the greatest storage stability. Current Planer equipment allows some ‘difficult to freeze’ specimens to be cryopreserved with high post-thaw survival of living cells: cartilage is an example of a tissue that cannot currently be preserved with the survival of living cells.
Different tissues and systems will require the same basic approach but different perfusion chambers for each application: these will have to be engineered by the researcher to meet the necessary standards of safety and efficacy for any clinical use.
The advantage of the Liquidus Tracking method is that ice is not allowed to form at all. This is achieved by progressively raising the concentration of cryoprotectant as cooling proceeds such that the conditions of the solution that the cells or tissue experience are similar to those that they would experience during conventional cryopreservation but without the formation of any ice.
Cooling and warming rates are flexible, making the method worth trying for some tissues that could not be cooled or warmed rapidly. Cartilage, ova, hepatocytes being possible candidates.
Also see: Liquidus Tracking - a new cryopresevation method for mammalian cells in three dimensional culture - useful for a biomass in a Bioartificial Liver
Liquidus Tracking poster by Eva Puschmann - A new cryopreservation method for mammalian cells in three dimensional culture - useful for a biomass in a Bioartificial Liver
Vaccine and Large Quantity Freezer - Kryo 1060
Kryo 750 - Automated large quantity freezer
Further Information on the Liquidus Tracker is available - please contact us
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