Abstract
Conventional approaches for cell cryopreservation require the use of toxic membrane-penetrating cryoprotective agents (pCPA), which limits the clinical application of cryopreserved cells. Here, we show intentionally induced ice formation at a high subzero temperature (> -10 °C) during cryopreservation, which is often referred to as ice seeding, could result in significant cell injury in the absence of any pCPA. This issue can be mitigated by predehydrating cells using extracellular trehalose to their minimal volume with minimized osmotically active water before ice seeding. We further observe that ice seeding can minimize the interfacial free energy that drives the devastating ice recrystallization-induced cell injury during warming cryopreserved samples. Indeed, by combining predehydration using extracellular trehalose with ice seeding at high subzero temperatures, high cell viability or recovery is achieved for fibroblasts, adult stem cells, and red blood cells after cryopreservation without using any pCPA. The pCPA-free technology developed in this study may greatly facilitate the long-term storage and ready availability of living cells, tissues, and organs that are of high demand by modern cell-based medicine.