A team of researchers hopes that in the not too distant future, millions of people who suffer from dry eyes will not have to apply eye drops three times a day. They are developing eye drops that use drug-infused nanoparticles – and feel no different to plain water – that will only have to be applied once a week.

Over 6% of people in the US suffer from dry eye syndrome, a result of an imbalance between tear production and tear drainage. It is more common in the over-50s and can eventually cause eye damage.

Drugs to treat the condition exist, but they have to be applied via drops three times a day because the eye is very efficient at washing them away.

Now a team from the University of Waterloo, ON, Canada, has developed a solution that only needs to be applied once a week. The solution contains drug-infused nanoparticles that stick to the surface of the eye, prolonging the time that the symptom-relieving drug stays in place.

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Over 6% of people in the US suffer from dry eye syndrome, a result of an imbalance between tear production and tear drainage.

In a study reported in the journal Nano Research, they describe how they treated mice with dry eyes with nanoparticles infused with the drug Cyclosporine A (CycA) and found they “sustained the release for up to 5 days at a clinically relevant dose.”

They then ran another series of tests where they only gave the mice a weekly dose of the drug-infused nanoparticles. Signs of inflammation were eliminated and the surface of the animals’ eyes “completely recovered,” they note.

The same once a week dosage also produced no signs of physical irritation or inflammation when tested in rabbits’ eyes.

The nanoparticles – which are about 1,000 times smaller than the width of a human hair – stick to the surface of the eyeball and use only 5% of the amount of drug normally required. The body eventually absorbs them harmlessly.

A challenge in the study was to find a way to make the nanoparticles stick to the eye surface. The team achieved this “by surface functionalizing the nanoparticles with phenylboronic acid,” and forming the nanoparticles “from self-assembly of block copolymers composed of poly(d, l-lactide) and Dextran.”

Lead author Shengyaen (Sandy) Liu, a PhD student at Waterloo’s Faculty of Engineering, explains:

I knew that if we focused on infusing biocompatible nanoparticles with Cyclosporine A, the drug in the eye drops, and make them stick to the eyeball without irritation for longer periods of time, it would also save patients time and reduce the possibility of toxic exposure due to excessive use of eye drops.”

He says, “You can’t tell the difference between these nanoparticle eye drops and water. There’s no irritation to the eye.”

The team is now working on setting up clinical trials to test the nanoparticle eye drops and foresees them being available in drugstores in the next 5 years.

The Natural Sciences and Engineering Research Council of Canada and 20/20: Ophthalmic Materials Network funded the study.

In August 2014, Medical News Today reported how another team – inspired by lubricants found in nature – is developing a new material that delivers long-lasting lubrication. One possible application is to make contact lenses more comfortable.