Canadian researchers develop eye drops that last longer

Canadian researchers have developed eye drops containing medicine that can be lodged in tears and slowly released. It's believed they could be administered just once a week, replacing conventional drops that are needed daily.

With conventional drops, 95% of medicine can be lost before it has a chance to work

The slow-release medicine, encased in an aggregate of molecules called a micelle, has been designed by a research team to be administered in a drop formulation. (Will Russell/Getty Images)

The eye does a good job of defending itself against foreign substances, and that includes important drops used to treat such conditions as dry eye or glaucoma.

Literally, in the blink of an eye, most of the medicine that goes in comes right back out.

With that in mind, researchers at McMaster University in Hamilton say they have developed a better way to deliver medicine to the surface of the eye.

Chemical engineer Heather Sheardown said one of her graduate students was developing micelle-based formulations in her lab and they discussed how they could adapt them to treat diseases of the eye.

The team came up with eye drops featuring a drug-carrying aggregate of fatty molecules called a micelle, which gradually releases medicine.

With conventional drops, 95 per cent of the medicine is typically lost before it has a chance to work.

'Lousy delivery system'

"It's a lousy delivery system," said Sheardown. "If you can deliver drops to the front of the eye at lower concentrations that work over a longer period, it could be huge."

Micelles are molecules similar to fatty liposomes, but smaller. They have a shell that is hydrophilic (tends to mix or dissolve in water) and a core that is hydrophobic (tends to repel water).

That structure gives the sphere-shaped micelles the ability to gradually dissolve after they lodge themselves in the eye's wet surface, releasing medicine through an aqueous medium over time.

Drug remains stable in tears

"The drug is enclosed inside the fatty layer, and on the outside, you've got a layer that likes water, so it allows it to remain stable in the water layer of the tears," Sheardown told CBC News. "But it keeps the drug inside, because drugs are, more often than not, hydrophobic. They like fat, they like the more hydrophobic layer."

It's hoped the microscopic packets of medicine could be administered just like regular eye drops once a week, replacing conventional drops that are needed daily.

The team is in the final stages of proving the safety and effectiveness of the new technology, which was described recently in the journal Biomacromolecules.

Sheardown is a Canada research chair in ophthalmic biomaterials and scientific director of the 20/20 NSERC Ophthalmic Materials Research Network. She's presenting the new technology to the Tear Film and Ocular Surface Society in France in September.

She said there has been interest in commercializing the technology, and she hopes it will be on the market in the near future.