Is isochoric vitrification feasible?

Abstract

This study investigates the feasibility of ice-free isochoric vitrification for cryopreservation applications using mathematical modeling, computation tools, and the underlying principles of thermo-mechanics. This study is triggered by an increasing interest in the possibility of isochoric vitrification, following promising experimental results of isochoric cryopreservation. In general, isochoric cryopreservation is the preservation of biological materials in subzero temperatures in a rigid-sealed container, where some ice crystallization creates favorable pressure elevation due to the anomaly of water expansion upon ice Ih formation. Vitrification on the other hand is the transformation of liquid into an amorphous solid in the absence of any crystals, which is typically achieved by rapid cooling of a highly viscous solution. The current study presents a mathematical model for vitrification under variable pressure conditions, building upon a recently published thermo-mechanics modeling approach for isochoric cryopreservation. Using the physical properties of dimethyl sulfoxide (DMSO) as a representative cryoprotective agent (CPA), this study suggests that vitrification under isochoric conditions is not feasible, essentially since the CPA solution contracts more than the isochoric chamber by an order of magnitude. This differential contraction can lead to absolute zero pressure in the isochoric chamber, counteracting the premise of the isochoric cryopreservation process. It is concluded that the only alternative to prevent ice formation while benefiting from the potential advantages of higher pressures is to create the required pressures by external means, and not merely by passively enclosing the specimen in an isochoric chamber.