Abstract
Cryopreservation of cells is necessary for long periods of storage. However, some cell lines cannot be efficiently cryopreserved, even when optimized commercial cryoprotectants are employed. Previously, we found that a low-toxic synthetic zwitterion aqueous solution enabled good cryopreservation. However, this zwitterion solution could not cryopreserve some cells, such as human kidney BOSC cells, with good efficiency. Therefore, details of the cryoprotective effect of the zwitterions and optimization based on its mechanisms are required. Herein, we synthesized 18 zwitterion species and assessed the effects of the physical properties of water/zwitterion mixtures. Non-cell-permeable zwitterions can inhibit ice crystal formation extracellularly via direct interaction with water and intracellularly via dehydration of cells. However, cells that could not be cryopreserved by zwitterions were insufficiently dehydrated in the zwitterion solution. Dimethyl sulfoxide (DMSO) was combined as a cell-permeable cryoprotectant to compensate for the shortcomings of non-cell-permeable zwitterions. The water/zwitterion/DMSO (90/10/15, v/w/w) could cryopreserve different cells, for example freezing-vulnerable K562 and OVMANA cells; yielding ~1.8-fold cell viability compared to the case using a commercial cryoprotectant. Furthermore, molecular dynamics simulation indicated that the zwitterions protected the cell membrane from the collapse induced by DMSO.
Highlights
Cryopreservation of cells is necessary for long periods of storage
The cryoprotective effect was found to be significantly different depending on the cell line
HNF, mouse normal fibroblast (mNF), and BOSC were subjected to further studies as good, intermediate, and poor representatives, respectively
Summary
Cryopreservation of cells is necessary for long periods of storage. some cell lines cannot be efficiently cryopreserved, even when optimized commercial cryoprotectants are employed. Non-cell-permeable zwitterions can inhibit ice crystal formation extracellularly via direct interaction with water and intracellularly via dehydration of cells. DMSO is cell-permeable[9] and inhibits the formation of ice crystals intra- and extracellularly by interacting with water molecules[10]. Cryoprotectants have a long research history, and their optimization has been attempted for decades without success for freezing-vulnerable cells To break this unsuccessful cycle, the discovery of compounds that have not been applied to cryopreservation is needed. OE2imC3C has electric charges, as it is aprotic This charged molecule strongly interacts with water molecules and is expected to more strongly inhibit ice crystal formation than DMSO, possessing partial charges. Water/OE2imC3C (95/5, v/w) cryopreserved human normal fibroblasts (hNF) and five other cell lines, as well as a DMSO-containing commercial cryoprotectant. The mixtures of non-cell-permeable zwitterions and cell-permeable DMSO was found to cryopreserve freezingvulnerable cells
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