(Tookapic, Pexels)
7 December 2017. A medical engineering team created a gel material that safely closes injured eye tissue until surgical treatments can be given. Researchers at University of Southern California in Los Angeles describe the material and tests with lab animals in yesterday’s issue of the journal Science Translational Medicine (paid subscription required).
The team led by ophthalmology professor John Whalen, with associates from USC’s medical and engineering schools, are seeking stop-gap methods for treating traumatic eye injuries, particularly on today’s battlefields where soldiers encounter improvised explosive devices. Even among civilians, open-globe injuries that disrupt the cornea or sclera in the eye, account for 10 percent of the annual 2.5 million eye injuries in the U.S., according to data cited by the authors. The U.S. Department of Defense and National Institutes of Health funded the project.
Current treatments for open-globe injuries use sutures and adhesives that require professional care and surgical equipment, which in most cases are not available to military field medics nor civilian emergency medical technicians. Whalen and colleagues devised a temporary fix for emergency staff to safely close injured eye tissue until patients reach facilities providing more permanent treatment.
The researchers’ solution adapts a polymer material called PNIPAM, short for poly(N-isopropylacrylamide), a so-called smart polymer that changes its state from liquid to semi-solid in response to changes in temperature. This state-changing capability is important for an emergency treatment that needs to be easily and safely removed when reaching expert medical care facilities. The team added other biocompatible plastics to PNIPAM to produce a hydrogel form of the material that could temporarily fill the shape of the injury and seal the wound, yet still be easily removed.
Lab tests confirmed the gel material’s physical properties, notably its ability to maintain a gel state at body temperatures until washed away with cold water, which converts the gel to liquid. In addition, the gel retains its elasticity, viscosity, and durability in these tests. Further tests of the gel in eyes taken from pig cadavers with injured tissue show the gel fills the wounds, and in simulations enables the treated eyes to retain enough intraocular pressure to keep the eyes functioning and prevent retinal detachment.
The team devised an injector device to dispense the gel, contained in a chamber surrounded by calcium ammonium nitrate crystals, like those used in disposable cold packs. Adding water activates the crystals, cooling the gel into a liquid for about 10 minutes that can be applied to the injured eye.
The researchers then tested the gel using the injector system on lab rabbits induced with eye injuries. The results show the gel works as designed with the test rabbits, with only some immediate inflammation that subsides within a few hours. Intraocular pressure also is restored among test animals, while pressure in the eyes of untreated animals remains below safe levels. After 30 days, the test rabbits show no signs of nerve toxicity, degraded retinal tissue, or chronic inflammation.
The university applied for a patent on the technology with Whalen and 5 of the co-authors listed as inventors, including Niki Bayat, the lead author. Bayat, an engineering doctoral candidate at USC, is a co-founder of AesculaTech, a start-up company developing a thermo-responsive gel to treat glaucoma. The gel, says the company, is applied to the tear duct, which then hardens and dispenses medication for the disorder.
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