People who wear contact lenses may be familiar with the irritation that comes from dried-out eyes. Not only can this be an annoyance, it can also cause damage to ocular tissue. Scientists at the Technical University of Munich (TUM) say that they can better avert this danger, with a new type of lubricant based on molecules found in pig stomachs that keeps would-be dry eyes safe and sound.
Generally speaking, the surface of the human eye is kept well-lubricated (in part) by a molecule called mucin MUC5AC. Found in tears as well as the stomach and intestines, it keeps the eye surface nice and moist due to its ability to bind together lots of water. But for some people, the tear fluid simply doesn't contain enough mucin and can lead to dry eyes, which is a problem for people who wear contacts and then need a protective lubricant to avoid injury from the plastic lens.
This is where synthetic lubricants come in, but according to the TUM researchers, these have their share of drawbacks. Most are based on hyaluronic acid, something that doesn't occur naturally in the eye. They also need to be applied regularly in the form of eye drops, often several times throughout the day. The team says it has a better way of doing things, with a more natural lubricant that can be applied just once to the contact lens, to offer longer-term protection.
While not exactly the same as mucin MUC5AC, a similarly structured mucin molecule can be found in the stomach of pigs, and the team was able to isolate large quantities of it for the research. It says it did this in a way that did not cause chemical changes to the molecule and maintains its chief characteristics as a natural lubricant.
"Most of the commercially available mucins, which are already used for the treatment of oral dryness, have lost exactly this ability, we were able to demonstrate this in a series of experiments," TUM's Oliver Lieleg, who led the work, explains. "These commercial mucins are therefore not suitable for treating dry eyes."
The team then carried out tests on pig eyes, using their pig-derived mucins to lubricate contact lenses, and monitored their performance. It reports that the lenses caused no tissue damage, and believes that soaking the contact lens in the mucin solution overnight should be enough to avoid problems associated with dry eyes.
"We showed that the mucin passively adsorbs to the contact lens material and forms a lubricating layer between the contact lens and the cornea," explains Benjamin Winkeljann, first author of the study.
The researchers say the main benefits of their porcine-inspired approach are that the mucin is more closely associated with the natural molecule found in tear fluid, and that it won't require repeated applications throughout the day. Human trials are still a ways off, but the team is now looking to further test the technology on animals in the lab.
The research was published in the journal Advanced Materials Interfaces.
Source: Technical University of Munich
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