Thermodynamics and heat transfer analysis for isochoric cryopreservation

The long term preservation of biological material is one of the most challenging issues in medicine and biotechnology. In medicine, the current preservation technique consists of placing the organ in a preservation solution and keeping it at low temperature, normally around 2 to 6°C. This method achieves very short preservation times, resulting in a deficit of organs available for transplantation.;Longer periods of preservation time could be achieved by reducing the temperature of the biological material further. However, this is limited by the fact that the temperature of the preservation solution cannot be lower than the freezing temperature. Isochoric cryopreservation is an alternative technique presented in this work that can potentially overcome this limitation. During the isochoric freezing process, high pressures are developed, reducing the fluid temperature below freezing. Therefore, isochoric cryopreservation has great potential since it allows the preservation of biological materials at subzero temperature without the damaging effects of ice formation.;Chemical cryoprotectants and hyperbaric pressures have been previously developed to reduce the extent of chemical damages during freezing. Theoretical thermodynamic studies developed in this work show that in isochoric cryopreservation, the increase in solution concentration during freezing is lower at all temperatures by almost an order of magnitude as compared to isobaric cryopreservation.;The success of the preservation method is also function of the cooling ratio. In this work, a one dimensional isochoric freezing analysis has been developed. The results show that the isochoric freezing process is slower by an order of magnitude compared to the isobaric process. The analysis presented here helps to improve the performance of the isochoric cryopreservation technique by selecting the best process parameters.;Isochoric processes also find applications in the area of vitrification. The thermodynamic analysis developed in this work shows that the homogeneous freezing temperature of water can be significantly reduced, by around 100°C, when cooling in an isochoric environment. This shortens the gap between the freezing temperature and the glass transition temperature, facilitating vitrification.;There are several potential problems associated with the isochoric cryopreservation technique. These problems have been addressed in this work along with possible solutions to overcome them.