Freezing of mammalian embryos without the aid of a programmable freezer.

A simple, inexpensive and repeatable method of freezing/thawing (F/T) mammalian concepti was developed with the use of 2-cell mouse embryos. Cryoprotectants, length of exposure to protectants, and subzero holding times before liquid nitrogen (LN2) exposure were examined in an effort to obtain an effective freezing protocol. Sequential examination of these variables provided data suggesting that 3.5 M dimethyl sulfoxide (DMSO) plus 0.25 M sucrose exposure for 5 minutes at room temperature, followed by a -30 degrees C environment for 90 minutes, best prepared embryos for LN2 storage. After thawing and culture, 48 of the 93 (52%) embryos developed to the blastocyst stage.