Large Thermal Conductivity Differences between the Crystalline and Vitrified States of DMSO with Applications to Cryopreservation

Abstract

Thermal conductivity of dimethyl-sulfoxide (DMSO) solution is measured in this study using a transient hot wire technique, where DMSO is a key ingredient in many cryoprotective agent (CPA) cocktails. Characterization of thermal properties of cryoprotective agents is essential to the analysis of cryopreservation processes, either when evaluating experimental data or for the design of new protocols. Also presented are reference measurements of thermal conductivity for pure water ice and glycerol. The thermal conductivity measurement setup is integrated into the experimentation stage of a scanning cryomacroscope apparatus, which facilitates the correlation of measured data with visualization of physical events. Thermal conductivity measurements were conducted for a DMSO concentration range of 2M and 10M, in a temperature range of -180°C and 25°C. Vitrified samples showed decreased thermal conductivity with decreasing temperature, while crystalline samples showed increased thermal conductivity with decreasing temperature. These different behaviors result in up to a tenfold difference in thermal conductivity at -180°C. Such dramatic differences can drastically impact heat transfer during cryopreservation and their quantification is therefore critical to cryobiology.

Thermal conductivity of the cryoprotective cocktail DP6 in cryogenic temperatures, in the presence and absence of synthetic ice modulators

“…The experimental setup used in this study has been presented previously [6] and is described here in brief only, for the completeness of presentation. The experimental setup consists of: (i) the scanning cryomacroscope [11], which enables visualization of vitrification, and (ii) a transient hot-wire set-up for simultaneously measuring thermal conductivity [12,15].…”

“…All details including modeling assumptions are described in [6]. The duration of each thermal conductivity measurement is 0.5 s, which is triggered every 40 s during the rewarming phase of the cryogenic protocol.…”

“…With a transient wire response obtained at a frequency of 60 Hz, each extracted thermal conductivity value represents curve fitting over 30 data points. The rewarming phase was selected as a choice of practice, where the quality of temperature control is higher and the resulting uncertainty in measurements is smaller [6]. …”

“…(2) during constant-rate rewarming of the bulk sample, the temperature variation of the bulk sample is subtracted from that measured during heating with the transient hot-wire [6]. Uncertainty in thermal conductivity measurements using the above setup and analysis method is estimated to be up to 0.03W/m-K [6].…”

“…Computer simulations of vitrification require knowledge on the thermophysical properties of the material, which represents a relatively uncharted area of research [5,6]. The current study focuses on the thermophysical property of thermal conductivity, which is a quantity indicating how well the material can transfer heat at steady-state.…”