Thermal expansion of the cryoprotectant cocktail DP6 combined with synthetic ice modulators in presence and absence of biological tissues.

This study explores physical effects associated with the application of cryopreservation via vitrification using a class of compounds which are defined here as synthetic ice modulators (SIMs). The general classification of SIMs includes molecules that modulate ice nucleation and growth, or possess properties of stabilizing the amorphous state, by virtue of their chemical structure and at concentrations that are not explained on a purely colligative basis. A sub-category of SIMs, referred to in the literature as synthetic ice blockers (SIBs), are compounds that interact directly with ice nuclei or crystals to modify their structure and/or rate of growth. The current study is part of an ongoing effort to characterize thermo-mechanical effects during vitrification, with emphasis on measuring the physical property of thermal expansion-the driving mechanism to thermo-mechanical stress. Materials under investigation are the cryoprotective agent (CPA) cocktail DP6 in combination with one of the following SIMs: 12% polyethylene glycol 400, 6% 1,3 cyclohexanediol, and 6% 2,3 butanediol. Results are presented for the CPA-SIM cocktail in the absence and presence of bovine muscle and goat artery specimens. This study focuses on the upper part of the cryogenic temperature range, where the CPA behaves as a fluid for all practical applications. Results of this study indicate that the addition of SIMs to DP6 allows lower cooling rates to ensure vitrification and extends the range of measurements. It is demonstrated that the combination of SIM with DP6 increases the thermal expansion of the cocktail, with implications for the likelihood of fracture formation-the most dramatic outcome of thermo-mechanical stress.