A simple device made from silicon and glass takes advantage of the natural behaviour of human sperm to separate healthy, swimming ones from defunct cells without harming them, which could boost the success of in vitro fertilisation (IVF) treatment.
Isolating the most active sperm from a sample is important for fertility treatments like IVF, but current clinical separation methods using centrifuges can harm the delicate cells.
The success rate of such assisted reproductive techniques is generally , so there is room for improvement.
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To see if they could divide sperm into groups without harming them, at Tarbiat Modares University in Tehran, Iran, and his colleagues have developed a method using microfluidics 鈥� the study of how liquids move through microscopic channels.
The idea was to take advantage of the characteristics of sperm: when there is no liquid flow, sperm tend to move in circular patterns, but when there is a current, this flow of liquid reorients them to face upstream because of their shape, so they swim in that direction. This mechanism seems to have evolved to direct sperm towards eggs after sex. Sperm are also known to move towards boundaries and swim along them.
Heydari and his colleagues have taken advantage of both these phenomena by designing a device made of silicon bonded onto glass into which a sperm sample is injected using a syringe, creating a direction of flow.
The circuit has four channels, each just 90 micrometres (渭m) across, containing hollow obstacles. These obstacles create local low-speed currents that make active sperm cells reorient around them and swim towards nearby reservoirs, each about 300渭m across, where they can be siphoned off, while dead cells and debris are washed away and through the device.
About 40 per cent of human sperm cells injected into the device in the fresh samples were mobile, but the researchers found that the proportion of those left in the reservoirs that were mobile was close to 100 per cent. They also discovered that it was possible to isolate only the fastest-swimming sperm by increasing the flow rate.
at the University of Sheffield, UK, says current sperm-separation techniques involving centrifuges are effective, but expensive and time intensive.
鈥淭his is a much simpler approach. Arguably it鈥檚 kind of tapping into the inherent properties of sperm. This is a much gentler, more natural way and, dare I say, might work better in low-income countries where you won鈥檛 need a centrifuge and you need less training,鈥� he says. 鈥淲ill it improve IVF success rates? I think the jury鈥檚 out. But as long as it鈥檚 equivalent and cheaper, it鈥檚 a good little piece of technology.鈥�
Scientific Reports
