Cornea-on-a-chip simulates blinking of the eye
While scientists have successfully produced various "organ-on-a-chip" models of body parts, the eye is particularly challenging, as a tear film is regularly moved across its surface as we blink. That action has recently been replicated, in a new device.
Developed by researchers at Japan's Kyoto University, the tool is specifically a cornea-on-a-chip – the cornea is the transparent front section of the eye, that covers the pupil, iris and anterior chamber.
The 3D-printed device consists of four upper and four lower channels, which are separated by a clear polyester porous membrane. Human corneal cells are incubated in each of the upper channels for a period of seven days, in which time they grow to form a solid barrier of cells on top of the membrane.
Fluid is then pumped through both the upper and lower chambers, placing pressure on both sides of the layer of corneal tissue. This simulates the manner in which a real cornea is subjected to pressure on one side by the blinking of the eyelid and the movement of tear fluid, and on the other side by the fluid contained within the eye.
When the cornea-on-a-chip was tested, it was found that the simulated blinking actually changed the shape of the corneal cells and increased their production of filaments, which help keep the cells flexible and stretchable.
"It was really interesting to find that an eye-blinking-like stimulus has a direct biological impact on these cells," says pharmaceutical scientist Rodi Abdalkader, who led the research along with micro-engineer Ken-ichiro Kamei. "We blink frequently and unconsciously all the time. With each blink, a shear stress is applied on the corneal barrier that causes the cornea counter-defence system to secrete fibrous filaments, like keratins, to overcome the effects of the stress."
Once developed further, it is hoped that the technology could be used to study eye disorders, and to evaluate experimental medications. A paper on the study was recently published in the journal Lab on a Chip.
And this isn't the first blinking eye-on-a-chip we've seen. Last year, a team from the University of Pennsylvania unveiled a model that actually incorporates a moving gelatin-slab "eyelid."