A Novel Microfluidic Method for Isolation of Rare Viable Sperm Based on Electrical Properties

Introduction:
Currently, sperm detection and separation in samples with low sperm concentrations (microTESE, oligozoospermic samples, etc.) is a time- and labor intensive process. Because only a minute portion of the sample is searched manually under a light microscope, high variability in sperm retrieval exists between clinics. As a result, there is a great need for innovative approaches to improve the speed and efficiency of the process.

Aims:
Developing a high throughput, microfluidic method for the isolation of rare vital sperm based on distinct electrical properties of sperm head and tail.

Materials and Methods:
We constructed a microchamber containing a quadripolar electrode array and PDMS-based microchannel (20 μm in height and 1 mm in width). Using a pressure gradient, human sperm cell samples were flowed across the electrodes at speeds between 25 to 35 μm/s, where they were exposed to non-uniform electric fields in which they were attracted or repelled based on their dielectric properties. CFDA and PI stainings were utilized to detect cell viability.

Results:
The distinct electrical properties of the head and tail enabled us to safely isolate sperm keeping the head (containing the DNA) far from the electrode. Importantly, we were able to isolate rare sperm including CFDA positive/PI negative viable immotile sperm.

Conclusion:
We hereby present a novel microfluidic method for intravital isolation of rare sperm based on its dielectric properties. This platform may serve as a high throughput automated process that can isolate rare immotile but vaible sperm, from patients that are diagnosed as cryptospermic/azoospermic and from TESE/Micro-TESE samples.