A 'contact lens' patch for efficient and controlled ocular drug delivery

Scientists have developed a 'contact lens' patch with microneedles that could provide a painless and efficient alternative to current methods of treating eye diseases such as glaucoma and macular degeneration.

Current localized treatment methods such as eye drops and ointments are hindered by the eye's natural defences, blinking and tears. Eye injections can be painful and carry a risk of infection and eye damage. As a result, some patients are unable to keep up with the prescribed regime for their eye ailments, many of which require long-term management.

The proof-of-concept patch, successfully tested in mice, is covered with biodegradable microneedles that deliver drugs into the eye in a controlled release. After pressing it onto the eye surface briefly and gently - much like putting on contact lenses - the drug-containing microneedles detach by themselves and stay in the cornea, releasing the drug over time as they dissolve.

When tested on mice with corneal vascularisation, a single application of the patch was 90 per cent more effective in alleviating the condition than applying a single eye drop with 10 times more drug content.

The senior author said, "The microneedles are made of a substance found naturally in the body, and we have shown in lab tests on mice that they are painless and minimally invasive. If we successfully replicate the same results in human trials, the patch could become a good option for eye diseases that require long-term management at home, such as glaucoma and diabetic retinopathy.

"Patients who find it hard to keep up with the regime of repeatedly applying eye drops and ointments would also find the patch useful as well, as it has the potential to achieve the same therapeutic effect with a smaller and less frequent dosage."

The team developed a 2mm by 2mm patch with nine microneedles that can be loaded with drugs for lab tests on mice.

Each needle, thinner than a strand of hair, is shaped like a pyramid for optimal tissue penetration. The needle is made of hyaluronic acid, a substance found in the eye and is used often in eye drops. A modified version of the hyaluronic acid is added to form a second layer of the needle to slow down the rate at which the needle degrades, ensuring a slower release of the drug.

The researchers conducted experiments over a week on mice with corneal vascularisation, a sight-threatening condition where new blood vessels grow into the corneal tissue due to oxygen deprivation. In this study, the researchers loaded the microneedles with DC101, an antibody that targets the growth factor that promotes blood vessel formation.

In mice with the patches applied, there was a 90 per cent reduction in the area of blood vessels with a single treatment dose of 1 microgram. In contrast, when a single drop of the same drug with a much higher dose of 10 micrograms was applied, there was no significant reduction.

There was also no puncture found on the cornea after a week, suggesting that the microneedles are strong enough to penetrate the cornea, but not too stiff to spear through the whole cornea.

The team has filed a patent, and is currently working on further improving the eye patch technology. They are also looking to partner clinician scientists to study the feasibility of conducting medical trials.

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