A sound approach for ova denudation

To introduce an innovative noncontact method for denudation process of cumulus-oocyte complexes (COCs) for intracytoplasmic sperm injection (ICSI).

We designed and fabricated novel acoustohydrodynamic tweezers (AHTs) to perform contactless denudation and tested them in a mouse model. Cumulus removal efficiency, preimplantation development, and live birth were assessed and compared with those in conventional manual pipetting (MP) denudation.

Fourteen female B6D2F1/J mice (approximately 4 weeks of age), nine male B6D2F1/J mice (6-12 weeks of age), and 28 CD-1 female mice (approximately 6 weeks of age) were used for experiment.

We designed a contactless platform for oocyte denudation on the basis of the principle of focalized acoustic waves. We first investigated the acoustic intensity and thermal variability by measuring the surface displacement and temperature with a thermal camera to ensure a safe operation. Cumulus-oocyte complexes were denuded by conventional MP with 40 IU/mL of hyaluronidase serving as control or by AHTs with a reduced amount of hyaluronidase (15 IU/mL). Piezo-ICSI was performed on both experimental and control groups. A triplicate of denudation and insemination experiments was performed. All embryos were monitored in a time-lapse incubator. Embryo developmental rates were compared by the chi-square test. Embryo morphokinetic timing as a continuous variable was compared by 1-way analysis of variance. Embryo transfers were performed on some blastocysts.

The procedural time for each denudation method was measured and compared. Fertilization, embryo development and morphokinetics, pregnancy, and live birth rate were compared between the control and experimental cohorts.

Facile noncontact denudation was achieved without any damage to oocyte. Acoustic induced fluidic shear was the main contributor to COC denudation. The average denudation time per oocyte decreased by 46% (15 seconds per oocyte for control vs. 8 seconds per oocyte for AHT) while using a lower concentration of hyaluronidase. Piezo-ICSI on oocytes processed by MP and AHTs resulted in comparable rates of survival (86.1% vs. 85.3%), fertilization (96.7% vs. 94.1%), and blastocyst (88.0% vs. 81.3%). Embryo morphokinetics for both experimental and control cohorts were comparable, showing no impact of sound waves on the embryo development. Eventual delivery rates were also comparable between the MP and AHT cohorts (51.3% vs. 55.4%).

Acoustohydrodynamic tweezers are used for contactless removal of the cumulus cells from the COCs before ICSI in an expedited, safe, and reliable manner. Embryo development outcomes confirm their safety and validate their potential for a comprehensive ICSI-on-chip device.