Characterization of Oocytes For in vitro FertilizationUsing Electrical Impedance Spectroscopy

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Oocyte in vitro fertilization (IVF) is an established procedure in human and animal assisted reproduction. IVF is routinely employed when natural mating fails, or when livestock and research mammals must be preserved and propagated. IVF critically depends on the quality of oocytes, especially on the state of the zona pellucida (ZP) which comprises a gelatinous outer layer of extracellular matrix that spontaneously hardens and becomes impenetrable to sperm during oocyte isolation and culture. Oocyte quality is typically judged by optical inspection. This method is observer-biased. Here, we propose to employ electrical impedance spectroscopy (EIS) for mice oocyte characterization, because this technique is observer independent, as well as non-destructive thus allowing longitudinal live observation of maturing oocytes and developing embryos. The objective of the project is to develop a suitable measurement setup combining ease of use, miniaturization, integration, and portability. Ultimately, we will characterize time-resolved the hardening of the ZP of single mice oocytes by EIS. We will study the molecular basis of changes in impedance spectra of oocytes by using genetic strains of mice with known deficiencies in ZP structure and processing. Using EIS measurements over a wide frequency range, we will study impedance changes caused by changes in the ZP glycoprotein matrix, separate from electrophysiological changes in the oocyte cytoplasm. We will establish EIS as a non-destructive method to judge oocyte quality in an observer-independent manner to ultimately increase the fertilization rate in assisted reproductive technology.