Improvement of a Simple and Cost-Effective Passive Cooling Rate-Controlled Device for Cell/Tissue Cryopreservation

The currently used commercial cooling-rate control device is the liquid nitrogen controlled rate freezer (LNF), which has some shortcomings such as high cost, high liquid nitrogen consumption, and potential operational risks in quality control. Based on thermophysical properties of new materials, we improved, manufactured, and optimized a reliable yet simple device named the "passive cooling rate-controlled device (PCD)" with real-time temperature tracing. In this study, using the improved PCD we cryopreserved human umbilical vein endothelial cells (HUVECs) and compared the results with a standard commercial CryoMed LNF. The temperature profiles and cooling rates of the HUVEC samples in a cryopreservation solution (with dimethyl sulfoxide [DMSO] in 10% v/v concentration) were measured and automatically recorded by the PCD during the controlled cooling process. This study and experimental results showed that the HUVEC survival rates after cryopreservation using the PCD have no significant difference from those using the CryoMed LNF and that the improved PCD is a user-friendly, reliable, and low-cost device to ensure an optimal slow cooling rate ranging from -0.5 to -1°C/min for the cryopreservation. Considering the advantages of low cost, durability, reliability, and no liquid nitrogen consumption for the cooling process, it is concluded that the PCD is an excellent controlled cooling device to achieve a desired optimal cooling rate for cell/tissue cryopreservation.