Ideal Freezing Curve Can Avoid the Damage by Latent Heat of Fusion During Freezing

Background:Liquid nitrogen freezing techniques have already met with widespread success in biology and medicine as a means of long-term storage for cells and tissues. The use of cryoprotectants such as glycerol and dimethylsulphoxide to prevent ice crystal formation, with carefully controlled rates of freezing and thawing, allows both structure and viability to be retained almost indefinitely. Cryopreservation of various tissues has various con-trolled rates of freezing. Material and Method: To find the optimal freezing curve and the chamber temperature, we approached the thermodynamic calculation of tissues in two ways. One is the direct calculation method. We should know the thermophysical characteristics of all components, latent heat of fusion, area, density and volume, etc. This kind of calculation is so sophisticated and some variables may not be determined. The other is the indirect calculation method. We performed the tissue freezing with already used freezing curve and we observed the actual freezing curve of that tissue. And we modified the freezing curve with several steps of calculation, polynomial regression analysis, time constant calculation, thermal response calculation and inverse calculation of chamber temperature. Result: We applied that freezing program on mesenchymal stem cell, chondrocyte, and osteoblast. The tissue temperature decreased according to the ideal freezing curve without temperature rising. We did not find any differences in survival. The reason is postulated to be that freezing material is too small and contains cellular components. We expect the significant difference in cellular viability if the freezing curve is applied on a large scale of tissues. Conclusion: This program would be helpful in finding the chamber temperature for the ideal freezing curie easily.ope