Survival of tissue culture cells frozen by a two-step procedure to -196 degrees C. II. Warming rate and concentration of dimethyl sulphoxide.

Abstract

Abstract Chinese hamster tissue culture cells in dimethyl sulphoxide (5%) required a lower holding temperature (−35 °C) for optimal survival on slow warming from −196 °C using a two-step cooling schedule, compared with that required (−25 °C) when warming was rapid. A lower concentration of dimethyl sulphoxide (1%) did not affect the “protection” against damage on cooling from the holding temperature to −196 °C and thawing. The results suggest that protective agents allow cells to be cooled initially to the holding temperature and minimize damage at the holding temperature. Damage following subsequent cooling and thawing may thus occur mainly as dilution shock on rewarming. This can be minimized by allowing the cells to shrink at the holding temperature.