Non-contact Microdrilling of Mouse Zona Pellucida with an Objective-delivered 1.48-microns Diode Laser

Background And Objective: A non-touch laser-induced microdrilling procedure is studied on mouse zona pellucida (ZP).

Study Design/materials And Methods: A 1.48-microns diode laser beam is focused in a 8-microns spot through a 45x objective of an inverted microscope. Mouse zygotes, suspended in a culture medium, are microdrilled by exposing their ZP to a short laser irradiation and allowed to develop in vitro.

Results: Various sharp-edged holes can be generated in the ZP with a single laser irradiation. Sizes can be varied by changing irradiation time (3-100 ms) or laser power (22-55 mW). Drilled zygotes present no signs of thermal damage under light and scanning electron microscopy and develop as expected in vitro, except for a distinct eight-shaped hatching behavior.

Conclusion: The microdrilling procedure can generate standardized holes in mouse ZP, without any visible side effects. The hole formation can be explained by a local photothermolysis of the protein matrix.