Selection of High Quality Sperm with Lower DNA Fragmentation

The first step of in-vitro fertilization is to sort out the motile sperm from the non-motile. Centrifugation based sperm swim-up and density gradient separation are common methods to sort sperm. However, these methods reduce sperm quality during the repetitive centrifugation steps and isolate sperm with high DNA fragmentation. In this work, we construct a microfluidic device based on the observation that motile sperm can swim against the flow within a specific range of flow rates. This sperm-sorting device consists of two chambers, top and bottom separated by a filter. After 45 minutes the sorted motile sperm is collected from the top retrieval chamber and placed on a glass slide for visual inspection with a light microscopy and data collection. The process is repeated for various flow rates. We find that 1) the most motile and functional sperm pass selectively through the micropores against the flow; 2) the optimum flow rate is the one that gives the highest concentration of motile sperm, the lowest DNA fragmentation and higher percentage of morphologically normal sperm. Our device provides an efficient, inexpensive way to sort sperm-out without the disadvantages of centrifugation.