Synthetic and biological macromolecules: protection of mouse embryos during cryopreservation by vitrification

The ability of macromolecules to protect 8-cell mouse embryos during a vitrification protocol was assessed by the comparison of a synthetic macromolecule, polyvinylpyrrolidone (in the form of Percoll), and a biological macromolecule, human serum albumin (HSA). Vitrification solutions, which included glycerol (50% v/v), sucrose (0.75 mol/l) and either macromolecule Percoll (50% v/v) or HSA (1.125% w/v), were found to provide similar rates of survival. Both compounds resulted in a significant reduction in the incidence of disruption to the zonae pellucidae of cryopreserved embryos, to 4.8 +/- 1.3% and 10.3 +/- 1.2% respectively, when compared to the outcome when neither was present in the vitrification solution (20.4 +/- 2.5%; P < 0.01). Polyvinylpyrrolidone in the form of Percoll offers advantages over HSA in this work: it provides a lower rate of zona disruption and avoids the need for screening for pathogenic contaminants such as human immunodeficiency virus and hepatitis B and C.