Applying a nano-micelle based method for delivering atropine base from a contact lens

The world is facing a quiet epidemic of nearsightedness. Millions of people, particularly children, find themselves unable to see distant objects clearly, a condition known as myopia. While glasses and standard contact lenses correct the blur, they do not stop the eye from growing too long, which is the root cause of the problem. To halt this growth, doctors often prescribe eye drops containing a drug called atropine. However, these drops have a significant flaw: they wash away from the eye quickly, meaning most of the medicine never reaches its target, and patients must remember to put them in every single day. Researchers are constantly searching for a better way to deliver this medicine, hoping to find a method that keeps the drug stable, releases it slowly, and stays in the eye long enough to do its job without causing irritation.

In a recent study, a team of scientists at the University of New South Wales explored a new approach to solving this delivery problem. Instead of relying on simple liquid drops, they turned to tiny, microscopic structures called nano-micelles. Imagine a soap bubble, but instead of air inside, it has a core that can hold onto oily substances that water usually rejects. The researchers created these structures using a common, safe polymer and filled them with atropine in a form that does not dissolve easily in water. Their goal was to soak contact lenses in this special solution, allowing the lenses to act as a reservoir that holds the medicine and releases it steadily onto the eye over time. They tested two different types of contact lenses and measured how well the lenses absorbed the drug, how long the drug lasted in the solution, and whether the resulting lenses were safe for the cells that line the surface of the eye.

The researchers began by converting atropine sulfate, a common salt form of the drug, into atropine base, a version that is better suited for hiding inside the oily core of their nano-micelles. They mixed this drug with a polymer called poloxamer 407 in a salty water solution, creating the tiny micelles. They tested these mixtures at two different levels of acidity, one slightly acidic and one neutral, to see which environment kept the drug stable for the longest time. After letting the mixtures sit at room temperature for a full year, they found a clear difference. The mixture kept at the slightly acidic level retained almost 88 percent of its original drug, while the neutral mixture lost more than half of its drug to degradation. This suggested that keeping the solution slightly acidic was crucial for preserving the medicine over time.

Next, the team took two popular brands of contact lenses, one made of a material called etafilcon A and another called omafilcon A, and soaked them in these drug-filled micelle solutions for a day. They wanted to see if the lenses could act like sponges, pulling the medicine out of the solution and holding it inside their fibers. The lenses successfully absorbed the drug, with some taking in as much as 7.3 micrograms. When the researchers placed these loaded lenses into a fresh solution to mimic the environment of the eye, the lenses began to release the medicine. The release was not a sudden burst but a steady stream. For the lenses soaked in the most stable, acidic solution, about 81 percent of the drug was released within four hours. This slow, controlled release is exactly what is needed to keep the eye treated without the patient needing to constantly reapply drops.

The study also looked at whether these drug-loaded lenses would harm the delicate cells on the surface of the eye. The researchers grew human corneal cells in a dish and exposed them to the liquid that had been in contact with the loaded lenses. Most of the formulations were safe, with the cells surviving at high rates. However, one specific formulation, which had the highest drug stability, caused a slight drop in cell survival to 68 percent. While this was just below the safety threshold usually required for medical devices, it was close enough to suggest that the material itself is not toxic, but the amount of drug or the specific mixture might need fine-tuning. The lenses themselves did not change their physical properties; they remained clear and held the same amount of water as regular lenses, meaning they would likely feel and look the same to a wearer.

The findings point to a promising path forward for treating nearsightedness. The study demonstrated that it is possible to load contact lenses with a stable form of atropine using nano-micelles, and that these lenses can release the drug in a controlled manner. The slightly acidic solution proved to be the best environment for keeping the drug from breaking down over a year. While the lenses showed great potential for delivering the medicine, the researchers noted that the amount of drug released was higher than what is typically delivered by standard eye drops, suggesting that future versions might need to carry less medicine to avoid side effects like dilated pupils. The work also highlighted that while the drug stayed stable in the bottle, the lenses themselves were not tested for long-term stability after soaking, a step that will be necessary before this technology can be tested in people.

Ultimately, this research offers a concrete step toward a more effective way to manage myopia. By combining the stability of nano-micelles with the convenience of contact lenses, the team created a system that protects the drug from degrading and delivers it slowly to the eye. The study confirms that the lenses can hold the drug, release it over several hours, and remain largely safe for eye cells. However, the journey from the lab to the clinic is not finished. The researchers emphasize that further work is needed to optimize the exact amount of drug used, ensure the lenses remain safe for long-term wear, and verify that the medicine actually reaches the back of the eye where it is needed to stop the eye from growing too long. Until then, this nano-micelle approach stands as a compelling proof of concept that could one day replace the daily struggle of eye drops with a simple, effective lens.