ESR 1, Ana Filipa Mota, discusses below how advances in drug delivery research have changed the way the industry views contact lenses as a tool to treat posterior segment disease of the eye.
The use of contact lenses as platforms for controlled delivery of ophthalmic drugs was envisioned in 1961 by Otto Wichterle and co-workers. After 60 years, Johnson & Johnson Vision gained regulatory approval for the first commercial antihistamine-delivering contact lens in both Japan and Canada. The ACUVUE® Theravision™ daily disposable contact lens was approved for preventing itch associated with eye allergies.
It marks a significant milestone in the drug-eluting contact lens research.
Contact lenses are flexible, biocompatible and highly porous hydrogels with the ability to incorporate drugs and subsequently release them to the tear fluid located between the inner face of the lens and the cornea (post-lens tear film). This delivery system shows advantages of better corneal absorption, a greater maintenance of therapeutic levels for long periods of time, and vision correction at the same time.
The problem is that the materials used for the synthesis of contact lenses usually do not load the drugs and release them very quickly, so the major efforts on this field are being made on finding strategies to modify the composition of the contact lenses and improve the affinity for drugs, making them load higher amounts of drug and release them more slowly. This problem can be overcome by means of bioinspired strategies that rely on mimicking the human pharmacological receptor of the drug into the contact lens structure with the incorporation of functional monomers.
The major goal of my project is the design of hydrogel contact lenses suitable for loading and release of therapeutic amounts of drugs useful for the prevention or treatment of ocular pathologies associated with diabetes.
My work is being focused on designing contact lenses that have high affinity for statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors. Statins are one of the most commonly prescribed drugs in the world as they are widely orally used for the first line treatment of hypercholesterolemia and reduction of cardiovascular disease risks. Atorvastatin calcium was chosen as a model drug and a battery of functional monomers were screened regarding their interaction properties with the drug by computational modelling.
The incorporation of the N-(3-aminopropyl) methacrylamide (APMA) and 2-aminoethyl methacrylate (AEMA) monomers made it possible to provide the contact lenses with affinity for atorvastatin, without altering the swelling capacity, light transmission, mechanical properties and ocular compatibility typical of soft contact lenses. The prepared contact lenses also successfully sustained the release of atorvastatin for one week.
Ex vivo animal models revealed that atorvastatin mainly accumulates in the cornea and sclera, but does not diffuse into the receptor environment of the vertical diffusion cells.
In addition, since sterilization is a mandatory step in the conditioning of contact lenses, the effect of different methods of sterilization (steam heat, high hydrostatic pressure, and gamma radiation) on the loading and release capacity of the hydrogels was assessed during my secondment, in Instituto Superior Técnico, Lisbon under the supervision of Professor Ana Paula Serro. The ability to incorporate atorvastatin was maintained after high hydrostatic pressure sterilization, but decreased after autoclaving or radiation sterilization.
The design of contact lenses applying a bioinspired strategy allows the incorporation of atorvastatin without altering the properties required as a medical device. The new contact lens-statin combination product provides sustained levels of drug on the ocular surface.
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Pereira-da-Mota, A.F.; Vivero-Lopez, M.; Topete, A.; Serro, A.P.; Concheiro, A.; Alvarez- Lorenzo, C. Atorvastatin-Eluting Contact Lenses: Effects of Molecular Imprinting and Sterilization on Drug Loading and Release. Pharmaceutics 2021, 13, 606.