Objective: To validate the Cryo Bio System (CBS) straw in our current cryopreservation system before using it in clinical practice.
Design: A prospective comparison of blastocyst development rates in 278 murine embryos after refreezing and thawing at the two-cell stage against the standard Instruments-Medicine-Veterinarian (IMV) straw used in our cryopreservation program.
Setting: Private IVF laboratory.
Patient(s): No human subjects or material was used in this study.
Intervention(s): Frozen two-cell murine embryos were thawed and randomized into three treatments [1] refreezing in the CBS straws, [2] refreezing in IMV 0.25-mL straws, and [3] control embryos remaining in culture without refreezing. Embryos were refrozen using identical cryoprotectants and identical programmed controlled-rate freezers. After cryopreservation, straws were held in liquid nitrogen for a brief period before thawing and continued culture.
Main outcome measure(s): Postthaw murine blastocyst development rate.
Result(s): When the manufacturer's filling and loading protocol was used for the CBS straw there was no significant difference in the blastocyst development rate between CBS (75.0%) and IMV (76.4%) straws.
Conclusion(s): The CBS straw may be a viable and potentially safer alternative for cryopreservation of human embryos, particularly for patients with known infections.