(Nanowerk Spotlight) The surface of the eye is delicate and susceptible to damage from factors like aging, air pollution, and sun exposure. This can lead to painful eye conditions known as ocular surface diseases (OSDs) like dry eye syndrome and keratitis. Currently, eye drops containing antioxidants are used to try to prevent these conditions, but they are not very effective since the antioxidants get depleted quickly.
Now, researchers have developed specialized contact lenses containing nanoparticles that mimic antioxidant enzymes and continuously break down cell-damaging compounds called reactive oxygen species (ROS), harmful molecules that can damage our eyes. In animal studies, these “nanozyme” contact lenses protected the eye surface from ROS and inflammation better than regular lenses. The technology could provide a new way to prevent the onset of OSDs, especially in high-risk patients.
Schematics of a) multicolor PB family nanozyme-CCLs and b) their OSDs prevention applications. (Reprinted with permission by Wiley-VCH Verlag)
The nanozyme lenses contain tiny particles known as Prussian blue nanoparticles, which have protective properties against damage. The lenses also have Prussian blue analogs, similar particles that offer the same protection. These are like cousins to the Prussian blue nanoparticles, both working to shield the eyes.
These particles possess enzyme-like abilities to decompose ROS like hydrogen peroxide, hydroxyl radicals, and superoxide that are generated by factors like sunlight, pathogens, and aging. The particles were embedded into contact lenses made of hydroxyethyl methacrylate, a biocompatible material already used in commercial lenses. This allowed them to make nanozyme contact lenses in different colors.
Tests showed the colored nanozyme lenses quickly soaked up liquid and let oxygen through at levels comparable to normal lenses. The particles stayed firmly embedded in the lenses and did not leak out. Experiments culturing human corneal cells on the nanozyme lenses demonstrated they were not toxic to these eye cells.
Most importantly, the nanozyme lenses retained their ability to break down ROS. The researchers tested their performance in cells by adding hydrogen peroxide, which damages cells through oxidation. Lenses containing Prussian blue nanoparticles provided a 3-fold protective effect against cell death compared to normal lenses.
The researchers then tested the nanozyme lenses in animals. In rats, ultraviolet light exposure normally damages the cornea and causes inflammation. But rats wearing nanozyme contact lenses showed much less damage and inflammation than animals without lenses or with regular lenses.
Similar results were seen in animal experiments using eye drops containing hydrogen peroxide to simulate ROS-induced eye damage. Rats and rabbits wearing the nanozyme lenses were protected from corneal erosion compared to no lens or a normal lens. The colored lenses also reduced inflammation markers like TNF-alpha.
This demonstrates that the nanozyme contact lenses could act as an antioxidant shield on the eye surface to prevent oxidative damage from factors like sunlight and pollution. The technology provides continuous protection without the limitations of topical eye drops.
If the effects hold up in further studies, the researchers believe the nanozyme lenses could help prevent OSDs in patients at high risk due to their medications, environment or advancing age. Since the colored particles also act as pigments, the innovation could enhance cosmetic contact lenses. This “two birds with one stone” approach would make lenses more useful while also making them inherently therapeutic. With further development, the novel lenses may provide an easy way to protect our vulnerable eyes from debilitating diseases.
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