Hormone gradient chip to assess male fertility

A chip designed to mimic the chemical trail from sperm to egg may offer a more comprehensive picture of male fertility. 

Current male fertility diagnostic tests include measuring the concentration and motility of sperm. Researchers at the University of Twente, the Netherlands have instead developed a chip to measure the sperm's movement toward increasing or decreasing concentrations of progesterone, a process called chemotaxis. 

Fully understanding the chemotactic ability of sperm could help diagnose male infertility with more accuracy as it would give a fuller picture of sperm function, the researchers reported in Analytic Chemistry.

Sperm use chemotaxis to navigate through the fallopian tube towards the egg. Progesterone is present at high concentrations in the fluid that surrounds the egg, and studies have indicated that the hormone can attract and activate the sperm of some mammalian species.

Sperm chemotaxis had previously been studied using microfluidic devices, which are plastic or hydrogel chips with tiny channels through which liquids flow in a highly controlled manner. However, these devices had various limitations, such as the need for pumps to drive the flow of fluid, which could affect sperm motility. 

The researchers at Twente wanted to develop an improved, pump-free microfluidic device that could quickly identify small differences in the chemotactic behaviour of sperm.

Their final design was made of agarose gelatine gel and contained various channels and side chambers. They created a concentration gradient of progesterone in the chip from left to right. The right side contained the highest progesterone level. 

They observed that when sperm were added to the device, more swam towards the right chamber, confirming the sperm's chemotactic movement towards a greater concentration of progesterone. 

In addition to fertility testing, the method could be used to investigate other substances that could also contribute to the sperm's guidance mechanism, the researchers said.