Objective: To introduce the use of excimer lasers for penetration of the zona pellucida for micromanipulation purposes. Design: Cryopreserved two-cell mouse embryos were thawed and exposed to the 248-nm line of a krypton fluoride excimer laser (Lambda Physik EMG 202, Goettingen, Germany) creating a 2 to 4-μm opening in the zona pellucida. Setting: The Laser Ablation Laboratory at DuPont and the in Vitro Fertilization Laboratory at The Medical Center. Interventions: The embryos were exposed in either phosphate-buffered solution (PBS) or modified human tubal fluid (HTF) with the laser power varying from 1 to 2 J/cm2 and cultured in Ham's F-10 medium (GIBCO, Grand Island, NY) with 0.4% bovine serum albumin. Main Outcome Measures: The outcome of each experiment was measured by blastocyst formation of laser- exposed embryos as compared with a set of unexposed control embryos handled in a similar fashion. Results: Successful laser penetration of the zona pellucida was achieved using the 248-nm line of a krypton fluoride excimer laser. A higher blastocyst formation was found for embryos exposed in PBS. The higher optical absorption of the modified HTF partially inhibited embryo development. The blastocyst statistics increased 2.5-fold times by reducing the exposure of the embryos to ablation by-products. Conclusions: The use of a krypton fluoride excimer laser was introduced as a new method to open the zona pellucida of two-cell mouse embryos without interrupting blastocyst formation.
Blanchet, G. B., Russell, J. B., Fincher, C. R., & Portmann, M. (1992). Laser micromanipulation in the mouse embryo: A novel approach to zona drilling. Fertility and Sterility, 57(6), 1337–1341. https://doi.org/10.1016/S0015-0282(16)55097-3