The thermodynamic principles of isochoric freezing pressure-aided supercooling

This study outlines a method for designing an isochoric (constant volume) system to reduce the supercooling preservation temperature without affecting the likelihood of ice nucleation and without the need for cryoprotective additives. The method involves a multiphase system wherein the biological material is separated from a second aqueous solution by a boundary that transfers pressure and heat but not mass. The pressure within the system is passively increased by the confined growth of ice within the secondary solution. This increased pressure in turn lowers the equilibrium freezing temperature of the biological matter, which may be utilized to lower the preservation temperature while maintaining the same degree of supercooling. For example, using this technique, the supercooling preservation temperature may be lowered from –2 °C to –5 °C without increasing the risk of ice nucleation, by ensuring the freezable phase makes up ∼17 % of the total system volume.