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Nano-encapsulated contact lenses could offer another means of delivering
ocular medications
Laszlo Dosa in New Orleans, US
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Anuj
Chauhan |
A NEW technique for encapsulating drugs within contact lenses could
some day offer an attractive alternative to conventional topical
delivery of ocular medications, say University of Florida bio-engineers.
The new technique involves first encapsulating drugs into microscopic
nanoparticles, which can then be incorporated into poly-2-hydroxyethyl
methacrylate (HEMA) soft contact lenses during the manufacturing
process, explained Anuj Chauhan PhD at the annual meeting of the
American Chemical Society.
The idea of using contact lenses to deliver drugs to the eyes is
not new. Other researchers have attempted soaking lenses in drug
solutions or entrapping the drugs inside a hollow cavity by bonding
two separate pieces of lens material. However, Dr Chauhan reports,
neither of these methods proved to be very effective in delivering
medications for extended periods of time.
“Our proposal is significantly different as we are entrapping
the drug molecules inside nanoparticles and incorporating them inside
the lens matrix during the polymerisation. This allows us greater
flexibility in designing controlled ophthalmic drug delivery vehicles
which can be tailored to various drug formulations and which are
effective for extended periods of time,” Dr Chauhan said.
The researchers believe that when contact lenses made in this way
are placed on the eye, the drug will diffuse from the nanoparticles,
travel through the lens matrix and enter the post-lens tear film
trapped between the cornea and the lens.
When administered via the lens in this way, drug molecules would
remain much longer in the post-lens tear film, compared with the
two-minute duration seen with topical drops.
Dr Chauhan explained that drugs administered over a longer time
result in higher drug flux through the cornea and reduce the drug
inflow into the mucous membranes, preventing drug absorption into
the blood stream.
Moreover, the new technology offers the potential of continuous
drug release for much longer periods of time for treatment of chronic
diseases such as glaucoma.
The research is still in the prototype design stage. Dr Chauhan
and his colleague Derya Gulsen PhD evaluated many different kinds
of microemulsions in which to entrap hydrophobic drugs. One of those
appears suitable for production of the required hydrogel matrix.
“The trapped particles in the hydrogel matrix are about 30nm
to 50nm in size, which is smaller than the wavelength of the visible
light, rendering the gel transparent. After synthesising the gel,
we measured the drug release rates of a model hydrophobic drug,
lidocaine, and showed that our proposed system can deliver therapeutic
levels of drug for about five days.
“The drug delivery rates can be controlled by tailoring the
microstructure of the hydrogel and manipulating the size, concentration
and structure of the nanoparticles,” Dr Chuahan said.
The researchers say the next step will be to develop ways of changing
and controlling the drug delivery rates by changing the properties
of the particles they are synthesising. They hope to begin animal
studies within two years, followed by clinical trials.
Dr Chauhan said the process could also be used to incorporate antibiotics
into the matrix of a lens, making an extended-wear lens that might
leave the wearer less vulnerable to bacterial infections.
The drug-encapsulated lenses might help minimise systemic side-effects
of some common topical agent such as timolol.
Anuj
Chauhan PhD
Chemical Engineering Department,
University of Florida, US
Email: chauhan@che.ufl.edu
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