diseases such as glaucoma have been created by nano-engineers in
Singapore.
Most eye medications are delivered by drops. But most of the drug
quickly flows away from the eye, often draining into the nasal cavity
and then entering the bloodstream. "Eye drops are cumbersome, and
they lead to drug wastage and side effects," says Edwin Chow at the
Institute of Bioengineering and Nanotechnology.
The new technique involves mixing the drug with a pre-polymer liquid.
This mix is then polymerised, creating a transparent contact lens
material.
If the drug is water-soluble, it will be trapped within a network of
tiny inter-connected, water-filled channels in the material. If it's
water-insoluble, it will be trapped within nano-spaces in the polymer
matrix, and slowly leach out into the channels. In contact with fluid
on the eyeball, these channels open up and release the drug.
By varying the water content of the original mix, the team can vary the
size of the channels, and so control the rate at which the drug leaks
out onto the eye.
Not a dry eye
Previous attempts to create drug-releasing contact lenses have been
plagued with problems, including preventing sufficient oxygen through
to the eye - which can cause blood vessels to grow into the
oxygen-deprived cornea. The nanostructure of the new lenses, with the
inter-connected channels, allows gases, salts and nutrients to readily
diffuse across, says Chow.
So far, the team has tested the lenses in the lab using a water-soluble
glaucoma medication and a water-insoluble antibiotic. They found they
could precisely control the release of the drugs over a few hours or
even a few days.
Improved methods of administering medication to slow the progression of
glaucoma are badly needed, they say. The disease, which is caused by
damage to the optic nerve and leads to blindness, affects an estimated
60 million people worldwide.
The technique could also help contact lens wearers who suffer from dry
eyes, since the lens material could be modified to contain a
lubricating solution, suggests Chow.
lenses to deliver drugs. Their approach is to encapsulate drugs in
nanoparticles, and then to add these particles to their contact lens
material before polymerisation. But at high drug doses, this might
produce less lens clarity than is possible with the Singapore
technique, says Chow.
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