Against the current

The female genital tract is not a favorable environment for male germ cells. Of the approximately 100 million sperm, only a few hundred enter the fallopian tubes. In them, the cells move against the fluid flow (rheotaxis) to reach the egg and fertilize it. Therefore, mobility and the ability to swim in the right direction are key characteristics of spermatozoa.

Using natural rheotaxis, researchers at Florida Atlantic University have developed a microfluidic sperm sorting chip that quickly, inexpensively, easily and efficiently extracts healthy sperm from sperm. It is important to note that the device collects sorted cells into a separate chamber, minimizing the clogging of deformed or dead sperm.

Assisted reproductive technologies such as in vitro fertilization (IVF), intrauterine fertilization and intracytoplasmic sperm injection (ICSI) require healthy sperm cells for a successful outcome. Modern methods of centrifugation for sperm sorting are carried out in several stages, each on different equipment, and take about two hours. These methods damage sperm cells during processing, cause significant DNA fragmentation and oxidative stress.

A study published in the journal Analyst of the Royal Society of Chemistry showed that spermatozoa isolated from the collection chamber in a new microfluidic chip showed significantly higher mobility (almost 2 times), a larger number of morphologically normal cells and significantly lower DNA fragmentation, which is a crucial parameter for the fertilization process. In addition, the chip provides a sufficient number of high-quality cells necessary for successful intracytoplasmic sperm injection.

Managing the new chip is simple: sperm is loaded into the sample entry chamber, high-quality sperm begin to move against the fluid flow to the collection chamber, from where they can be easily collected. Thus, sorting takes place in one stage within one hour, and an employee with minimal training can manage the process. The study also showed that selection based on rheotaxis allows you to isolate mostly healthy, mobile and fast spermatozoa.

The device consists of inexpensive materials, and the consumption of reagents used for sperm sorting is only a few milliliters, so the commercial cost of the chip will be less than $ 5.

The microfluidic chip consists of four cylindrical chambers interconnected by microchannels. The four chambers are a liquid intake chamber, a collection chamber, a sample entry chamber and a waste collection chamber. The channel between the collection chamber and the sample entry contains tracks for directing sperm. The shear stress inside the device is created by the fluid flow using a syringe pump. After the sperm is injected, functional spermatozoa swim to the collection chamber, effectively separating from dead and weakly mobile spermatozoa.

Worldwide, approximately 48.5 million couples suffer from infertility. According to the US Centers for Disease Control and Prevention, 12% of women of childbearing age have used infertility treatment services. The costs of infertility treatment can vary from 5 to 73 thousand dollars. On average, a patient undergoes two cycles of IVF, as a result of which the total cost of this procedure, including medications, ranges from 40 to 60 thousand dollars. It is estimated that 85% of IVF costs are often paid by the patients themselves.

Article by S.Sharma et al. Selection of healthy sperm based on positive rheotaxis using a microfluidic device is published in the journal Analyst.

Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru according to EurekAlert: Device directs sperm to 'go against the flow' to help infertility.