ENHANCED HEAT TRANSFER FOR IMPROVED ICE-FREE CRYOPRESERVATION—INTERPLAY BETWEEN COOLING AND REWARMING

Among emerging approaches toward achieving long-term storage of biological systems within healthcare and in the pursuit of increasing biodiversity and sustainable global food production, ice-free cryopreservation, also known as vitrification-based cryopreservation, offers a significant promise. Recent success using a “cryomesh” approach can cryopreserve both organisms and organoids. Improving cooling and rewarming rates can increase biosystem viability and enable the ability to cryopreserve new biosystems at a larger scale, which have so far been unsuccessful because of biosystem sensitivity to cryoprotective agents (CPAs). We reviewed that improvements in the cooling process have enabled conductive cooling through the cryomesh based on heat transfer scaling. Conduction-dominated cryomesh can improve cooling rates from 2 to 10-fold (i.e., 0.24 to 1.2 × 10^5◦ C/min) in a variety of biosystems with a sample size > 5. Key parameters for improved vitrification include higher thermal conductivity, reduced thermal mass, and minimizing the nitrogen vapor barrier. For the rewarming process, we introduce a joule heating–based platform technology in which biological systems are rapidly rewarmed through contact with an electrical conductor that is supplied with a voltage pulse. Using tunable voltage pulse widths from 10 µs to 100 ms, numerical simulation predicts that warming rates from 5 × 10⁴ to 6 × 10^8◦ C/min can be achieved. This chapter reviews how to utilize the interplay between cooling and rewarming of cryomesh to improve the viability of ice-free cryopreservation. Altogether, cryomesh-based cryopreservation offers a comprehensive solution for cryopreserving a wide range of cellular, organismal, and tissue-based biosystems using low concentrations of a CPA in a scalable manner.