Measurement of Specific Heat and Crystallization in VS55, DP6, and M22 Cryoprotectant Systems With and Without Sucrose

Cryopreservation represents one if not the only long-term option for tissue and perhaps future organ banking. In one particular approach, cryopreservation is achieved by completely avoiding ice formation (or crystallization) through a process called vitrification. This ice-free approach to tissue banking requires a combination of high-concentration cryoprotective additives such as M22 (9.4M), VS55 (8.4M), or DP6 (6M) and sufficiently fast rates of cooling and warming to avoid crystallization. In this article, we report the temperature-dependent specific heat capacity of the above-mentioned cryoprotective additives in small volumes (10mg sample pans) at rates of 5 degrees C/min and 10 degrees C/min using a commercially available differential scanning calorimetry (TA Instruments Q1000), in the temperature range of -150 degrees C to 30 degrees C. This data can be utilized in heat-transfer models to predict thermal histories in a cryopreservation protocol. More specifically, the effects of temperature dependence of specific heat due to the presence of three different phases (liquid, ice, and vitreous phase) can dramatically impact the thermal history and therefore the outcome of the cryopreservation procedure. The crystallization potential of these cryoprotectants was also investigated by studying cases of maximal and minimal crystallization in VS55 and DP6, where M22 did not crystallize under any rates tested. To further reduce crystallization in VS55 and DP6, a stabilizing sugar (sucrose) was added in varying concentrations (0.15M and 0.6M) and was shown to further reduce crystallization, particularly in VS55, at modest rates of cooling (1 degrees C/min, 5 degrees C/min, and 10 degrees C/min).