Maintenance of Existing Controlled Rate Freezers

NHSBT have requirements to cryopreserve haemopoietic stem cells for transplantation and Tissue Services cryopreserve processed tissue allografts (such as skin, arteries and heart valves). To ensure cell viability the stem cells/tissues have to be frozen at a controlled rate prior to storing in vapour phase nitrogen at a temperature below -135°C. Rapid freezing would cause cell/tissue damage and result in the loss of cell/tissue viability: as such the products must be slowed at a rate no quicker than -2°C /minute until they are below -40°C. A controlled rate freezer is the best way of achieving the slow rate of freeze required.