A molecular mechanism of solvent cryoprotection in aqueous DMSO solutions

Abstract

Dimethyl sulfoxide (DMSO) in aqueous solution is widely used for the preservation of biological tissues under freezing conditions. DMSO and other agents are believed to act colligatively to depress the freezing point of water and, importantly, to promote the vitrification of water to prevent its crystallisation and the ensuing damage arising from the formation of intracellular ice. However, there has been no direct evidence of the precise effect of these agents on the vitrification properties of water. Here we report direct computational evidence, using molecular dynamics annealing simulations carried out within the experimentally inaccessible region in supercooled water, of a broadening of the glass transition of water, corresponding to the formation of a stronger glass in aqueous DMSO solutions. These findings provide insight at the molecular level into the mechanism of solvent cryoprotection by suggesting that the resulting thermodynamic stability of the glassy state of water reduces the probability of its nucleation and the subsequent formation of ice as the temperature is decreased.

Polarized light scanning cryomacroscopy, part II: Thermal modeling and analysis of experimental observations

“…Note that the specific heat of a liquid is expected to be between 10% (a strong material) to 80% (a fragile material) higher than that that of glass across the glass transition temperature range [1]. For 7.05M DMSO for example, 18% decrease in specific heat upon glass transition could be expected [20]. The Appendix to the current manuscript suggests that an uncertainty of 10% in the specific heat of 7.05M DMSO yields an uncertainty in temperature simulations of nearly 2°C.…”

The cryobiology of spermatozoa

“…As the concentration of media increases-whether in the form of permeating CPAs, such as DMSO or glycerol, or in the form of nonpermeating CPAs, such as sucrose, raffinose, or trehalose-the required cooling rate for amorphous glass formation is reduced. This cooling rate versus concentration relationship has been extensively explored in the literature [12][13][14][15].…”

Theoretical and experimental study of the antifreeze protein AFP752, trehalose and dimethyl sulfoxide cryoprotection mechanism: correlation with cryopreserved cell viability

“…A major drawback of cryopreservation is that ice crystallization during the freezing process can significantly damage the cells which then lose viability after thawing [1-4]. The freezing process is very complex, and the behaviour of water in both its liquid and frozen states is strongly affected by added substances [2-4]. …”

“…Cryoprotectants affect many processes which take place outside and inside frozen and thawed cells at various levels [1-4]. Recent studies have addressed cell survival after cryopreservation but have not correlated the effectiveness of cryoprotection with the freezing mechanism.…”