Current localised 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. However, a scientific group from the Nanyang Technological University, Singapore (NTU Singapore) has developed a ‘contact lens’ patch with microneedles that could provide a painless and efficient alternative to current methods of treating eye diseases (lat. Caecitudo) such as glaucoma and macular degeneration. 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% more effective in alleviating the condition than applying a single eye drop with 10 times more drug content. This novel approach, developed by a team led by NTU Professor Chen Peng from the School of Chemical and Biomedical Engineering (SCBE), with clinical insights from Singapore National Eye Centre’s Associate Professor Gemmy Cheung.

Professor Chen, the biotechnology expert who also developed the fat-burning microneedle patch, said this approach could realise the unmet medical need for a localised, long-lasting and efficient eye drug delivery with good patient compliance. He explained that microneedles are made of a substance found naturally in the body, and researchers have shown in lab tests on mice that they are painless and minimally invasive. If the team will 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. Prof Chen added that the patch could also help to tackle the rising disease burden of eye conditions. A local 2018 study projected that patients with eye diseases in Singapore will rise significantly by 2040, with glaucoma, diabetic retinopathy and age-related macular degeneration cases set to double.

A 2mm by 2mm patch has nine microneedles that can be loaded with drugs for lab tests. 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.

Dr Aung Than, NTU research fellow at SCBE, then planned and 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% 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.

Prof Chen said 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.