New portable gel could treat eye injuries

Scientists have developed an on-the-spot, temperature-sensitive gel that could seal eye injuries on the battlefield.
The reversible, temporary seal developed by researchers at University of Southern California (USC) in the US changes from a fluid to a super-strong semi-solid when applied to the eye.
When the patient is ready for surgery to permanently close the injury, doctors can remove the seal by adding cool water.
The material the group worked with for retinal implants is a hydrogel called PNIPAM, poly(N-isopropylacrylamide), which has a unique attribute that makes it a natural fit for this application.
When cooled, the hydrogel becomes a liquid for easy application, and when heated, it becomes a viscous semi-solid with strong adhesion, researchers said.

"Since the initial hydrogel's transition temperature was very close to the temperature of the human eye, we had to modify its properties to ensure that it would form a solid seal as soon as the gel was applied to the eye by a soldier or medic," said Niki Bayat, lead author of the study published in the journal Science Translational Medicine.

"Providing a perfect, yet reversible seal, the smart hydrogel shows promise for the next generation of tissue adhesives," Bayat said.
When an ophthalmologist is ready to repair the eye, the hydrogel can be extracted by applying cool water and converting it back to a less adhesive state.

The research team also developed a special syringe for the hydrogel that would be easy to use on the front lines and capable of quickly cooling the hydrogel before application.
The syringe has a cooling chamber filled with calcium ammonium nitrate crystals - the type used in instant ice cold packs.
By adding water to the chamber, the crystals activate and cool the hydrogel to operating temperatures within 30 seconds.
The customised seal and delivery device will also reduce the amount of time it takes to close penetrating eye injuries overall.
"We were able to optimise the delivery device so that it not only rapidly cools the hydrogel but also holds it at that temperature, giving users a 10-minute window to fill penetrations in the eye," said John Whalen, assistant professor at USC.