Around seventh grade, every child learns how sperm and egg meet to produce a human zygote, which will later grow into an embryo and baby. It may be a ubiquitous process, but up until now researchers have remained in the dark about the underlying mechanisms of fertilization. French biophysicists, however, have created a tool that provides highly- detailed images of what happens during the first moments of the fertilization proces.

Benjamin Ravaux, a physics graduate student at the Ecole Normale Superieure de Paris, is set to describe the new technique at the Biophysical Society’s 60th Annual Meeting, held Feb. 27-March 2 in Los Angeles. Ravaux and his colleagues worked with biologists and physicians to develop tools that could help elucidate mammalian fertilization. They designed a microfluidic chip compatible with imaging technologies, like confocal microscopy, too the team to choose and capture, precisely, the location where a sperm cell fuses with an egg.

The chip consists of a glass slide inside an egg cup. There is a tiny opening on the underside of the eggcup, through which the sperm cell can swim through to fuse and fertilize with fertilize the egg. Using the device, researchers were not only able to see hi-res images of the first contact between sperm and egg, but also the merging of their membranes and the moment when an egg completely engulfs the sperm. They were evn able to examine the incorporation of the sperm’s DNA inside the egg.

"This is a completely new approach," Ravaux said in a statement. "Our approach has the potential to provide new knowledge in a research field that remains largely unexplored because of a lack of adequate technologies. This 'IVF chip' is a unique tool to observe the cascade of molecular and membrane events occurring during the fertilization process."

Ravaux pointed out the conditions with the chip mimic the natural fertilization process —important since previous attempts to obtain information on the activity of sperm and egg have led to "non-physiological" situations such as multiple sperm in contact with the membrane of the egg.

"Combined with biological tools like fluorescent antibodies or genetically modified animals, the IVF chip can offer a new look at the membrane events during the interaction of gametes," Ravaux said. "An enhanced understanding of the molecular and physical mechanisms responsible for fertilization could ultimately lead to better methods to diagnose the causes of infertility, and improved personalized medicine treatments."

Source: Ravaux B, et al. Remodeling of Gamete Membrane During Mammalian Fertilization. Biophysical Society. Biophysical Society 60th Annual Meeting. 2016.