Thermomechanical Stress in Cryopreservation Via Vitrification With Nanoparticle Heating as a Stress-Moderating Effect.
This study focuses on thermomechanical effects in cryopreservation associated with a novel approach of volumetric heating by means on nanoparticles in an alternating electromagnetic field. This approach is studied for the application of cryopreservation by vitrification, where the crystalline phase is completely avoided-the cornerstone of cryoinjury. Vitrification can be achieved by quickly cooling the material to cryogenic storage, where ice cannot form. Vitrification can be maintained at the end of the cryogenic protocol by quickly rewarming the material back to room temperature. The magnitude of the rewarming rates necessary to maintain vitrification is much higher than the magnitude of the cooling rates that are required to achieve it in the first place. The most common approach to achieve the required cooling and rewarming rates is by exposing the specimen's surface to a temperature-controlled environment. Due to the underlying principles of heat transfer, there is a size limit in the case of surface heating beyond which crystallization cannot be prevented at the center of the specimen. Furthermore, due to the underlying principles of solid mechanics, there is a size limit beyond which thermal expansion in the specimen can lead to structural damage and fractures. Volumetric heating during the rewarming phase of the cryogenic protocol can alleviate these size limitations. This study suggests that volumetric heating can reduce thermomechanical stress, when combined with an appropriate design of the thermal protocol. Without such design, this study suggests that the level of stress may still lead to structural damage even when volumetric heating is applied. This study proposes strategies to harness nanoparticles heating in order to reduce thermomechanical stress in cryopreservation by vitrification.