ABSTRACT
INTRODUCTION During the cryopreservation of cells, intracellular ice formation is the most common cause of cell death. To prevent this in oocytes/embryos, cytoplasm must be vitried using cell-permeating cryoprotectants, which can cause other major types of cell injury; for example, chemical toxicity of cryoprotectant during loading and osmotic swelling during removal of permeated cryoprotectant.1 Especially in vitrication, the potential toxicity of the nal vitrication solution is high, because of the high concentration of cryoprotectants needed to achieve the vitried state. erefore, the exposure time of oocytes/embryos to the vitrication solution has to be limited. However, short exposure times can cause insuf-cient permeation by the cryoprotectant and insucient dehydration/concentration of the cytoplasm, resulting in intracellular ice formation. To prevent these major injuries during vitrication, rapid movement of water and cryoprotectants is preferable.
