Applying EIS (Electrochemical impedance spectroscopy) to determine the most appropriate oocyte fertilization time for ICSI (Intra cytoplasmic sperm injection) in rats

Current use of Assisted Reproductive Techniques in IVF centres are very time-consuming and often amount to a low success-rate or even failure of selecting appropriate gametes often. Electrochemical Impedance Spectroscopy (EIS) technique is a method that originated in biophysics and chemistry. Therefore, the rules of biophysics and biochemistry underlie how cells, the cytoplasm and organelles adapt. These (sub) cellular units have specific resistance and electrical behaviour potential, based on their biological structures. A total number of 55 Wistar albino rats (8-16 weeks, 220-250g) were obtained from Dokuz Eylul University department of Experimental Animals (15 males in groups A1, A2 and A3; and 40 female in groups B1, B2, B3). Vasectomy group (A2), comprised of 5 males that were vasectomized under ketasole anaesthesia 10 days before experimental onset. Remaining 10 males in the sperm aspiration groups (A1, A3) were undergoing Microsurgical Epididymis Sperm Aspiration (MESA) to produce sperm for ICSI. Oestrous phase of female rats of groups B1 and B3 was detected by Pap smear, after which these females where induced to super-ovulate. A microchip, suitable for the size of oocytes, was prepared for EIS measurement of electric potential. Half of all collected oocytes were evaluated by EIS, while the other half only benefited assisted reproductive techniques. ICSI was then performed on all selected oocytes. After successful ICSI, 4 to 14 third day staged embryos were transferred into previously prepared, anesthetized pseudo-pregnant rats. All data were evaluated by T-student and SPSS. 58 oocytes selected by the EIS appeared more successful in fertilization and embryo transfer as compared to 57 oocytes selected only by ART. We found, for the first time, that an EIS fertilization window of 118 to 132 mV defines suitable mature oocytes for fertilization in rats defined.