People with a fear of eyes – or a fear of needles going into eyes, for that matter – look away now. A self-plugging microneedle, designed to deliver drugs to the retina while protecting against infections at the injection site, has been created by scientists.
The ultrathin needle is coated with a drug and topped with a hydrogel plug. Once inserted, it releases the drug and sticks around in the eye before biodegrading. The plug, meanwhile, can swell once injected to cover and seal off the hole made by the needle.
So far, it has performed well in preclinical tests, the results of which have been published in the journal Advanced Healthcare Materials.
“This novel improvement in drug delivery treatment can avoid problems associated with using needles to treat serious eye diseases,” said Dr Ali Khademhosseini, a co-author of the study, in a statement.
Treatment of various eye diseases – such as age-related macular degeneration and diabetic retinopathy – has provided a major therapeutic challenge for doctors over the years. Treatments often require injections of drugs into the jelly-like fluid of the eyeballs, from which they can diffuse to the retina – the thin layer of cells at the back of the eyeball. This is known as an intravitreal injection.
Typically, syringes and hypodermic needles are used, and multiple injections are often needed over a long period of time. Not only is this invasive and unpleasant for patients, but it can cause tissue damage and poses a risk of infection in the hole left by the needle. The creation of the hole also creates a risk of tumor cells escaping and spreading to other sites.
The best solution to this problem is a one-off injection with a needle that can remain in the eye and eventually biodegrade. Over the last decade, microneedles have been used in this capacity – and now, the current study has gone a step further, optimizing the teeny needles with a hydrogel plug on the blunt end.
Doctors can even play around with the needle length, allowing them to more precisely target drugs to the retina.
The researchers demonstrated the microneedles’ almost complete drug delivery over 24 hours in in vitro experiments. They then injected microneedles loaded with purple dye into cultured pig eyeballs, demonstrating there is no drop in pressure following injection, which suggests the plug is doing its job. The researchers were also able to track the spread of the drug (purple dye) through the eye.
Tests on live pigs revealed that the microneedles were still firmly in place, with no needle deformation, seven days after injection. Plus, there were no signs of leakage, inflammation, or tissue damage at the injection site.
While promising, these findings are still just in animal models, meaning we are a long way off the self-plugging microneedle being used in clinical practice. First, more animal studies are needed, and, eventually, clinical trials in humans.
Of course, clinical trials are famously slow, so eye disease patients shouldn’t be getting their hopes up any time soon. However, thanks to the self-plugging microneedle, perhaps at some point in the future, there might be a better treatment option out there for them.
