Improvement of cooling rate during cryopreservation of living cells

Cryopreservation is used in long term storage and transportation. Human ES / iPS cells could be useful in regenerative medicine. The problem of using cryopreservation for storing and transporting human ES / iPS cells is that the survival rate of these cells is low during the freezing and thawing process. Better cooling rates and cryoprotectants are needed for improvement of the cell survival rate. The growth of the ice crystals causes dehydration, deformation, contraction and increase of the electrolytic concentration. When cooled fast enough the cells freeze in the vitrification state and the ice crystals don't have time to form. Immersion in liquid nitrogen is necessary to achieve a high cooling rate. To achieve a higher cooling rate than the current state, it was reported in pur previous study that the effect of the surface condition on the cooling rate during cryopreservation was investigated. It was confirmed that the cooling rate is improved by covering the cooling subject with a stainless steel mesh. However, the difference in behavior of the vapor bubble during film boiling with surface condition has not been clarified yet. In order to investigate the boiling state with high cooling rate, visualization of film boiling on the surface of cooling object was performed using a high-speed camera. It was confirmed from the image analysis results that the size and frequency of the vapor bubble were changed with the surface condition.