Laser-assisted intracytoplasmic sperm injection in human oocytes

OBJECTIVE: To explore potential applications of a non-contact, 1,480-nm diode laser to intracytoplasmic sperm injection (ICSI) of human oocytes. STUDY DESIGN: Human oocytes obtained from in vitro fertilization (IVF) patients and failed to fertilize 24-48 hours after conventional IVF were used for ICSI along with discarded sperm. A noncontact, 1,480-nm diode laser was employed to immobilize sperm, to open a hole in the zona pellucida (ZP) and to perform ICSI through the hole. After ICSI and its simulation, oocytes were examined for formation of pronuclei, cleavage and normality of the cytoskeleton. RESULTS: The 1,480-nm diode laser permitted fast and easy sperm immobilization and microdrilling of ZP to facilitate microinjection. Of the 78 injected oocytes, 53 (68%) survived the procedure, and 13 (25%) of them formed two pronuclei by 18 hours. Further culture of two fertilized eggs resulted in cleavage up to the eight-cell stage before cease of culture. Four oocytes were fixed after simulation of the procedure without injecting sperm. None of them showed gross abnormalities in cytoskeletal organization. CONCLUSION: A noncontact, 1,480-nm diode laser can be used for the immobilization of sperm and for opening a hole in the ZP to facilitate ICSI, biopsy manipulation toward preimplantation genetic diagnosis and assisted hatching.