Effects of DMSO treatment on cell viability for different freezing temperatures (n=3 for all cases). (a) When TL = −20 °C, the number of attached viable (i.e., non-PI stained) cells increases significantly over the range of 1 M to 2 M DMSO. This increase in the number of viable cells is due to the decrease in the number of detached cells, given that the number of attached damaged (i.e., PI stained) cells remains almost the same over the range of 1 M to 3 M DMSO. (b) For TL = −40 °C, when the DMSO concentration increases from 2 M to 3 M, the number of attached viable cells increases significantly. This increase is due to a smaller number of detached cells as the number of attached necrotic cells remains unchanged from 2 M to 3 M DMSO.