Towards uniform and fast rewarming for cryopreservation with electromagnetic resonance cavity: numerical simulation and experimental investigation

The lack of effective rewarming techniques inhibits the development of organ or large tissue cryopreservation. This work aims to optimize the electromagnetic (EM) rewarming by developing a numerical model and experimentally testing a hybrid EM-conduction method. Fundamental properties of several cryoprotective agent (CPA) solutions including thermal conductivity, specific heat, and complex electric permittivity were experimentally determined. The impact of the sample shape on the rewarming and the selection of the optimum CPA for EM rewarming were performed by numerical simulation. DPVP (41% dimethyl sulfoxide and 6% polyvinylpyrrolidone) and cylindrical shape of sample were selected due to the higher warming rate. By inserting a rod in the cryopreserved sample, which absorbs EM energy more efficiently and acts as an auxiliary heat source, a combination of EM and conductive rewarming was proposed to improve the heating uniformity. This hybrid rewarming method achieved the rewarming rate of 43 °C min−1 for 20 mL DPVP using the current EM rewarming system configuration. More importantly, by using the auxiliary conduction rod, the temperature gradient was notably reduced by 50% (i.e., less than 1 °C mm−1). The results demonstrate a potentially feasible approach to rapid and uniform rewarming for successful cryopreservation of large biomaterials.