Getting drugs into the eye means getting past the body’s elaborate mechanisms for protecting and maintaining this vital organ. Eye drops are among the least invasive ways of achieving this goal but most of their contents are washed away by tears with just a few blinks. In order to get sufficient amounts of an active agent into the eye, such drops must be given often and in significant amounts, which increases the possibility of complications or even an overdose.
McMaster University chemical engineering professor Heather Sheardown maintains a research group that tackles the challenges of dealing with the eye’s intricate biochemical physiology. “The idea is really simple,” Sheardown says. “There’s a mucous layer on the surface of the cornea. If you can penetrate through it, then you can add a significant amount of residence time on the eye. If we can get something that sticks a little bit better, we can deliver lower doses, deliver for a longer period of time and deliver less frequently.”
Recently, Sheardown and her team developed a novel approach to do just that. Their work has focused on micelles, which are aggregates of molecules with a hydrophilic “head” and a hydrophobic “tail” that can effectively serve as containers for other compounds. Sheardown’s group has been forming micelles from phenylboronic acid, which adheres well to the eye’s mucous membranes and will stay put after insertion. These microscopic structures are then designed to break down once they are in place, making them suitable for the steady, long-term release of its contents.
Sheardown recently published these findings in the journal Biomacromolecules, where she and her colleagues described the micellization process in detail. They focused on the immunosuppressive drug cyclosporin A, which is widely used in the treatment of severe dry eye disease.
Micelles offered a much more efficient delivery mechanism for this agent than standard methods, such as adding the polysaccharide adhesive chitosan to help eyedrops remain longer in the eye.
Sheardown says that micellation can be applied to a number of different drugs, which could also be employed in other mucus environments, such as the sinuses or the vagina. Last year she helped launch a spin-off company to transform this innovation into the first phase of clinical trials that would ultimately lead to a commercial product.