Mass transfer into biological matter using isochoric freezing.

This paper is a theoretical study of a protocol for transport of high concentrations of cryoprotectants into biological matter, using isochoric freezing. Unlike isobaric freezing, where the entire system freezes at temperatures lower than the freezing temperature, in isochoric freezing a substantial portion of the system remains unfrozen at temperatures below freezing. In isochoric freezing cryopreservation, the system is designed in such a way that the biological matter remains unfrozen and surrounded by an unfrozen solution. The protocol in this study involves the freezing of an isochoric systems along the "liquidus line" at which water and ice are in thermodynamic equilibrium. Rejection of solutes by ice increases the concentration of the solutes in the unfrozen solution surrounding the unfrozen biological matter, leading, thereby, to transport of increasingly higher concentrations of cryoprotectants into the biological matter, as the temperature of the system is lowered and the toxicity of the cryoprotectants is reduced.