Toxicity potential of residual ethylene oxide on fresh or frozen embryos maintained in plastic straws

Abstract

The toxic effects of residual ethylene oxide (EtO), a frequently used gas-sterilant, on embryos either frozen for long-term purposes or stored acutely for 30 min to 9 hr in a fresh condition in 0.25-ml straw containers were evaluated. In Experiment 1, fresh embryos were frozen (using conventional technology) in straws previously aerated for 0 hr to 8 mo after EtO sterilization. With the exception of the 8-mo group in which survival and quality ratings were depressed, embryo viability was not affected significantly by short-term prefreeze and post-thaw exposure to EtO residues. Experiment 2 was conducted to analyze the influence of prefreeze exposure to EtO residues on embryo development in vitro for embryos temporarily stored in previously sterilized straws aerated for different intervals. Compared to non-EtO-sterilized control straws, the development, quality, and viability of embryos exposed to EtO-treated straws were compromised (p less than 0.05) as the aeration interval decreased and the exposure interval increased. The combined results of both experiments indicate that EtO-treated straws can be used to cryopreserve gametes efficiently, but only if the aeration interval is greater than or equal to 72 hr and the prefreeze duration of exposure is less than or equal to 3 hr.

Quality control measures in an embryo research program

“…Continental straws remain toxic to embryo development even afte 30 days aeration whereas 1 week aeration eliminates the toxicity of IMV straws (Takeda et al, 1987, Schiewe et al, 1988 We have held mouse embryo suspensions in manufacturer-sterilized or btU-treateo ^u, i and 3 days aeration) straws from 30 min to 9 hours at 20°C before washing and in vitro culmc ? Schiewe et al, 1988). The extent of toxicity is related inversely to the duration of aeration and dirccüy to the length of exposure (Table 1).…”

“…Gas stenhzation is a very effective method for sustaining quality control in the embryo laboratory, but the use of EtO mandates detailed knowledge and the routine practice of safety precautions. Schiewe et al, 1988. if w • ->>• t Based on a fluorescein diacetate fluorescence intensity assay rated on a scale of 0 = no tluoresence to 5 = very intense, uniform fluoresence (Schiewe et al 1985) DEV = development of embryos to the blastocyst stage. EDR = embryo degeneration rate.…”