A Novel Biomarker for the Viability of Immotile Sperm Using Dielectrophoresis and the Potential for Automated Sperm Isolation from Samples with Low Concentrations of Sperm

Sholom Shuchat 1 shachar Libster 1 Ofer Fainaru 2 Gilad Yossifon 1,3
1Faculty of Mechanical Engineering, Technion Israel Institue of Technology, Israel
2IVF Unit, Rambam Health Care Campus, The Rappaport Faculty of Medicine, Israel
3School of Mechanical Engineering, Tel Aviv University, Israel

Introduction:
The electrical properties of live and dead sperm differ, allowing for their sorting using and alternating current (AC) electric field. The head and tail of live sperm also have differing properties allowing the head to be distanced from the electrodes during sorting.

Aims:
Automated, efficient sorting of sperm using dielectrophoresis (DEP) utilizing the electrical properties of the tail as a biomarker of the cell’s viability, even for immotile cells.

Methods & Materials:
A microchannel with curved transparent indium tin oxide (ITO) electrodes on the surface was used to manipulate the sperm. When exposed to an AC electric field the tail of viable sperm (as determined using CFDA staining) is attracted to the electrodes, while simultaneously the head is repelled.

Results:
We demonstrate a new biomarker for live sperm (even immotile ones). The tail of live sperm has a positive (attractive) DEP response while dead sperm react negatively and are repelled from field gradients. At the specific frequencies used, the head is simultaneously distanced from the electric fields helping prevent damage to the sperm DNA. Live sperm was sorted with over 90% efficiency from dead sperm and other debris.

Conclusion:
Since each cell passes the electrodes and is automatically sorted, the method could possibly be used for severely oligozoospermic and cryptozoospermic samples. Nowadays, such samples are searched manually and the small number of sperm present is often missed, leading to a mistaken azoospermic diagnosis and possibly unnecessary surgery. Relatively low cost of the disposable chips will allow wide implementation.