Researchers combined acoustic waves with fluid dynamics to envisage a new approach to human reproduction — isolating high-quality sperm from less desired ones to help infertile couples build families, according to a recent study published in the journal Lab on a Chip.
Researchers select high-quality sperm with acoustic waves, study says
This new rapid and automated acoustofluidic process comes from a team of Monash University's department of mechanical and aerospace engineering — and isolates sperm with normal head morphology and high quality "DNA integrity" from raw samples of semen.
The new device can process roughly 140 sperm per second and select more than 60,000 high-quality sperm in less than 50 minutes — a clinically-significant quantity of sperm to carry out IVF (In Vitro Fertilization) and ICSI (Intracytoplasmic Sperm Injection).
Acoustic forces push high-quality sperm out of mainstream flow
This new and life-enhancing research moved forward under the leadership of second-year doctoral student Junyang Gai, with supervision from Reza Nosrati and Professor Adrian Neild — both microfluidics experts from the mechanical and aerospace engineering department.
"The approach isolates sperm from raw semen by applying an acoustic field at a 30° angle to the flow direction," said Gai. "The acoustic forces direct and push high-quality sperm out of the mainstream, across the microchannel and isolates them in a sperate outlet, leaving the general population of sperm in the raw sample."
Isolated sperm group has 83 percent motility
In applying standing-surface acoustic waves (SSAW) at 19.28 MHz and 1 to 2 Watts, the team created an acoustic radiation force great enough to overcome the fluidic drag, and guide motile sperm across the microchannel width — leaving other sperm and debris to flow down the mainstream and be collected via a discard outlet.
This allowed a continuous, high-throughput, and size-variant selection process for isolating sperm deemed of high quality.
"Our results demonstrate that the selected sperm population exhibit a considerably higher percentage of progressively motile sperm (83%), than both the initial raw sample (52%) and the discarded subpopulation of sperm (36%)," added Gai.
'Acoustofluidic' sperm selection may remove negative stereotypes of infertility
Their results showed a successful selection of sperm with more than 60% improvement in progressive motility — which is the sperm's capacity to move on its own power) — while also offering a clinically-significant sample for IVF and ICSI procedures. Sperm chosen via this method shows an almost 40% improvement in DNA integrity, reports Phys.org.
Nosrati noted how the success rate depends on multiple parameters — but is ultimately at the mercy of the quality of not only the sperm, but also the egg.
"Our process aims to select better sperm within a faster time frame, so hopefully this can lead to improved outcomes in assisted reproduction," said Nosrati. "When fully tested and implemented, this method could open new windows and opportunities for infertile couples to have a baby."
"We hope that with further testing, our acoustofluidic sperm selection process can provide new opportunities and be of benefit to the assisted reproduction industry, and help remove the fear, anxiety and negative stereotypes associated with infertility."
Current sperm isolating process can harm sperm
In the last 50 years, infertility rates have increased — with one in six couples suffering infertility. Of these, male infertility counts for just under one-third (30%) of these cases — which means the combination of male and female causes contributes roughly half of the cases, globally.
"Sperm preparation or selection is a key step in assisted reproduction being performed right before fertilizing the egg," added Nosrati. "The current clinical process involves multiple washing and centrifugation steps and a manual selection step, and takes up to three hours to complete, which can also be harmful to sperm."
While it's too soon to say when this method of isolating sperm of greater preference for couples experiencing problems with infertility, it's incredible yet breathtaking to learn how scientific advancements in acoustics is pushing back the limits nature sometimes places on human reproduction.