Painless Micro-Needle Drug Delivery For AMD

Those suffering with macular degeneration, or the majority dealing with age-related macular degeneration (AMD), sometimes need injections of medicine administered directly into their eye to slow disease progression and enable continued vision. These are called anti-VEGF (vascular endothelial growth factor) drugs which interfere with unwanted blood vessel formation macular degeneration needs to continue decimating the eye.

However, eye injections sound as bad as they feel. As a result, many patients choose to lose their sight rather than endure repeated eyeball injection treatments that are not only painful but carry the risk of infection and eye damage. 

Researchers know how uncomfortable injection therapy can be so continued studies have been underway to develop a less invasive application. Now, it looks like science is closer than ever before with the development of painless micro-needles to transport essential drugs to slow macular degeneration progression.

This new application just may enhance treatment for those formerly unwilling to undergo direct eye injections giving them more of a chance at elongated sight than ever before.

It Looks Scary, But It’s Not

Under a microscope, the new eye injection contact lens patch looks like it is covered in tiny, sharp, teeth-like spikes that would make anyone run out of the room rather than put it in their eye.

Yet, these “spikes,” coined “micro-drug reservoirs,” are part of a growing application of targeted pharmaceutical delivery systems. From dissolving medicine discs placed directly on top of tumors to drug filled contact lenses, these approaches will hopefully do away with invasive surgery and “heal from within” instead. 

The micro-needles are just that, “micro”, meaning that they are so small the patient doesn’t even feel them penetrate the cornea. It is also a huge shift from a doctor approaching your eye with a long needle. So even though these micro-needles may look scary, they have been proven to be painless and effective. 

Injections Work

If you have macular degeneration, although there is no cure, there are many treatment options to slow disease progression and maintain eyesight for as long as possible. One highly successful treatment is anti-VEGF injections which reduce new blood vessel growth and slows down any leakage or swelling these new blood vessels may cause.

This in turn can help to slow down or hold back any sight loss one may experience. 

According to the Bright Focus Foundation, 

“A recently published extension of the CATT [Comparison of AMD Treatments Trials] study showed that, after five years, 50 percent of patients receiving anti-VEGF injections had 20/40 vision or better in the treated eye; 20 percent had 20/200 or worse; and the remaining 30 percent had vision somewhere between these two figures.

Many patients did not require injections every month after the initial 2-year study period. In contrast, before wet AMD treatments were available, fewer than 10 percent of patients retained 20/40 vision after only two years.”

With these kind of stats attached to anti-VEGF injections, you would think more people suffering from AMD would be lining up to receive such treatment. Yet, it can be highly difficult to get people to endure this invasive medical care.

Vision care specialists hope that the newly developed, painless micro-needles will encourage an influx of patients for treatment, especially early into their diagnosis to get ahead of macular degeneration development. 

Using Human Acid

Researching a microscopic, spike-covered contact lens patch takes detailed, intensive trials to make sure it is safe for human application. Scientists at Nanyang Technological University in Singapore were able to develop and test a proof-to-concept patch on mice.

This patch contained biodegradable micro-needles made from hyaluronic acid, which is naturally found in the human eye. Also known as hyaluronan, hyaluronic acid is clear and viscous which is also found in skin and connective tissues acting as a lubrication that retains water to keep tissues moist. 

Hyaluronic acid supplements have been linked to: 

• Rapid wound healing
• Joint pain relief
• Reducing acid reflux
• Preserving bone strength
• Minimizing pelvic bladder pain
• Enhancing skin health
• Relieving dry eye

With all these benefits, it is no wonder that researchers made this the go-to material for a new micro-needle drug delivery system. Each “spike” of the micro-needles is shaped like a pyramid for optimal tissue penetration and is thinner than a human hair.

A second layer of hyaluronic acid known as methacrylated HA is then added to each spike which enables a slow, controlled degradation for prolonged release of the drug. Plus, because it is naturally found in the body, the eye does not reject the hyaluronic acid needles making it highly effective without pain or inflammation.

In The Lab

In the past, drug-coated solid stainless-steel MN (micro-needle) technology has been used for rapid release of drugs to the cornea. Also, hollow glass MN have been employed to infuse drug solutions directly into the sclera (the white outer layer of the eyeball continuous with the cornea). This is the first time hyaluronic acid needles have been used and lab testing of this lens showed some promising results. 

According to Asian Scientist,

“Testing their invention in mice, the researchers pressed the patch onto the eye surface briefly and gently. They found that the drug-containing micro-needles detached and stayed in the cornea, releasing the drug over time as they dissolved. In mice suffering from corneal vascularization, where blood vessels in the cornea obstruct vision, a single application of the patch was 90 percent more effective in alleviating the condition than applying a single eye drop containing ten times the drug content.”

The benefits of this micro-needle application continue after treatment inasmuch that after one week no punctures were found on the cornea. This indicated that the needles were strong enough to penetrate and dissolve into the cornea but not be so invasive that they penetrate and damage the entire cornea.

Also, the significance of a slow release of the anti-VEGF medicine is essential and with the specific design developed by these Singapore researchers, the micro-needles do just that. 

A report by Harvard University explains the process,

“The inner base layer can dissolve quickly in water, while the outer layer dissolves slowly. Both layers contain drugs. When the eye patch is pressed onto the wet surface of the cornea, the needles penetrate into the cornea and detach within 30 seconds as the inner layer dissolves, delivering a strong initial dosage.

After removing the eye patch, the outer layer of needles, which has remained embedded in the cornea, dissolves over several days, leading to a sustained release of the second dose.” 

Continued studies are underway to develop the ability for deeper penetration which will address macular degeneration progression.

Due to these current successful studies it shouldn’t be long before invasive anti-VEGF injections will become a thing of the past and dissolvable micro-needles will takeover future AMD treatment.