Dielectric properties of individual cryoprotective agents and cocktails VS55, M22, DP6 at subzero temperatures for cryopreservation

A range of electromagnetic (EM) rewarming approaches are being studied with the potential to enable organ cryopreservation. EM heating of materials, including cryoprotective agents (CPAs), is mainly governed by dielectric properties (dielectric constant ε'-polarization and dielectric loss ε″-energy dissipation). To design effective EM rewarming protocols for cryopreserved biomaterials, understanding the behavior of individual CPA components and their mixtures is essential. For instance, in dielectric rewarming CPA is the target for heating, while in nanowarming CPA is off target for heating. This study measured the dielectric properties as function of CPA mixture composition (mole fraction), frequency (0.2 to 3 GHz) and temperature (20° to - 40 °C). Dielectric properties were measured using an open-ended-coaxial-probe and vector analyzer inside a control-rate-freezer (CRF) producing subzero temperatures. Dielectric loss and constant were reported for common CPA mixtures (M22, DP6, VS55) at subzero temperatures and their components (DMSO, Formamide, EG, PG) and binary mixtures at room temperature. As temperature decreased below 0 °C, loss in M22, DP6, and VS55 decreased at higher frequencies (~ 3 GHz) and increased at lower frequencies (~ 200 MHz). We also found that dielectric loss of CPA mixtures can exceed that of individual components likely related to relaxation time and Hydrogen-bonding at the molecular level. This study aids in CPA development for EM rewarming approaches advancing organ cryopreservation.