Development of a Controlled Rate Cooling System for Cryopreservation

Cooling rate is one of the most critical factors affecting the survival of cells during cryopreservation. A novel box-in-box device has been developed for use in the cryopreservation of human hematopoietic stem cells (HSCs). This work presents the comparison of experimentally observed thermal profiles for two different setups and, in the near future, cryopreservation survival rates of live cells accordingly. In experiments, using a simple protocol with a −80°C freezer, the box-in-box device is used to: (1) achieve an average cooling rate of −1°C/min with polyethylene insulation layers on both sides, and (2) achieve an average cooling rate of −2°C/min with a polyethylene insulation layer on one side and by having the other side directly contacted to the outermost aluminum case, both from room temperature to −40°C. The concept that utilizes thermal inertia of materials may be readily adapted to other cooling rates to support cryopreservation of a wide array of tissues and cells. It is concluded that the box-in-box system can be developed into a cost-effective, durable and reliable device for the cryopreservation of HCSs.