Close up of woman's eye

Colour-changing contact lens shows distribution of eye drugs

Image credit: Pixabay

Scientists from China Pharmaceutical University and Southeast University in China have developed contact lenses that change colour after releasing drugs into the eye, a visual indicator that could help doctors determine whether a medication is being delivered to its intended treatment site.

According to the study, the lens could control and indicate the sustained release of many ophthalmic drugs, with the report saying, “As a prospective ophthalmic drug delivery device, contact lenses attract a lot of attention because of the improved drug residence time and bioavailability.”

Researchers Dawei Deng and Zhouying Xie fabricated a colour-sensitive contact lens using molecular imprinting, a technique that creates molecular cavities in a polymer structure that match the size and shape of a specific compound, such as a medicine.

In laboratory experiments, the molecular imprinted contact lenses were filled with timolol, a drug used to treat glaucoma, with the team exposing the lenses to a solution of artificial tears, which was used as a stand-in for the eye.

As the drug was released from the contacts, the architecture of the molecules near the drug changed, which also changed the colour in the iris area of the lenses.

“The specific recognition of target timolol by molecular imprinted sites can not only increase the loading amount and the residence time of the drug but also endow the structure colour of lens remarkable blue shift with the accumulative release of timolol,” the study said.

Researchers said that no dye was involved in the process, reducing possible side effects, and concluded that they could see this shift with the naked eye and with a fibre-optic spectrometer.

Ophthalmologists use eye drops and ointments to help treat eye diseases such as glaucoma. However, these methods have one disadvantage, with eye doctors unable to tell if the medication is getting into the eye.

Naturally, when something ventures into or toward an eye, the lids blink and tears start rapidly flowing to avoid infection and damage from foreign objects, which can hinder the uptake of much-needed medications for treatments in glaucoma and diabetes.

Studies suggest that less than 5 per cent of drugs in eye drops and ointments are absorbed, and much of the absorbed medication ends up in the bloodstream instead of the eye, causing side effects.

Researchers conclude that “the contact lens can be further used for controlling release of many ophthalmic drugs and has high potential to be a new generation of functional contact lenses.”

The contact lens study appears in ACS Applied Materials & Interfaces.

In related news, this Tuesday, researchers based at Northwestern University and Washington University demonstrated a bioelectronic device which stimulates faster nerve regeneration in a rat model, paving the way for ‘bioelectronic medicine’.

Also, at the end of August, bionic eyes were 3D-printed by researchers at the University of Minnesota that could one day restore the sight of blind people or help sighted people see better.

In July, bioengineers based at California Institute of Technology (Caltech) created an artificial neural network capable of identifying the molecular equivalent of handwritten numbers.

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