Determination of Thermal Conductivity of Cryoprotectant Solutions and Cell Suspensions

Abstract

Determination of thermal conductivity of cryoprotectant solutions is required in modeling and predicting cooling/warming conditions for optimal cryopreservation of cells and tissues. A needle-like "heat probe" was developed to measure the thermal conductivity in this study. The heat probe was inserted into a medium (e.g., a cryopreservation solution, a cell suspension, or a soft tissue) with unknown thermal conductivity. A constant voltage from an electrical power source was applied to the probe, while a digital Ampere meter was used to measure the change of electrical current in the probe as a function of ambient medium temperature change caused by heating (heat is generated in the probe when a current runs through the probe). The electrical current change was monitored and recorded by a computer. By analyzing/modeling the heat transfer between the probe and the surrounding medium, a relationship between the thermal conductivity of the medium and the measured current was derived and used to determine the thermal conductivity of the medium. Using this technique, thermal conductivity values of cryoprotectant solutions, human blood, and blood–glycerol mixture were determined as a function of temperature and cryoprotectant concentration. From this study, the "heat probe" method was shown to be accurate, minimally invasive and practical.