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Nanomaterial-loaded contact lenses for treating anterior segment ophthalmic diseases

Liu, Zhen
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2021
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Abstract
Most eye diseases are treated by eye drops which are not efficient due to low bioavailability. Contact lenses are ideally suited to treat anterior segment diseases because of their proximity to cornea. Prior research has demonstrated that contact lenses are useful for increasing bioavailability and providing sustained drug release. Here we investigate gold nanoparticle-loaded contact lenses (GoldinLenses), which can be potentially useful for treating multiple ophthalmic diseases. Ocular cystinosis is a metabolic disease, which is characterized by an accumulation of cystine crystals in the cornea. Since cystine can bind to gold particles, when a GoldinLens is worn, cystine molecules in the tear film are expected to transport into the GoldinLens and attached to the surface of gold nanoparticles due to the high affinity of cystine molecules to the gold. Therefore, the concentration of cystine molecules in the tear film decreases, which result in the transport of cystine molecules from the cornea to the tear film, followed by a clearance (dissolution) of the cystine crystals in the cornea. Result shows that a maximum cystine uptake in vitro reaches 47 µg/lens within 5 hours, which may be therapeutic, but the permeability of cornea which may reduce the maximum amount that can be transport if the lens is worn for a few hours each day. We also explore the feasibility of utilizing GoldinLenses for laser protection (532 nm) due to the existence of gold nanoparticles. Gold nanoparticles absorb the radiation, which provide a superior laser protection efficacy, compared with the commercial laser safety glasses (around 50\%). Besides, the absorbed radiation by the gold nanoparticles results in a heat generation due to the electron clouds oscillation under the laser radiation, which can be utilized for meibomian gland dysfunction (MGD) dry eye treatment. MGD dry eye can be treated by warm compression treatment because warming the glands is expected to increase the lipid secretion. Therefore, GoldinLens will serve as an inner heating source to warm up the glands, which will be beneficial for increasing the lipid secretion from the glands. Since GoldinLenses may not be able to effectively treat cystinosis, we also explore designing contact lenses for sustained drug delivery. Prior research has shown that vitamin E aggregates in the contact lens behave as diffusion barriers to increase the diffusion pathway, which results in a more sustained drug delivery. Prior research was based on soaking lenses in vitamin E dissolved in ethanol which is effective but the process has challenges due to significant lens swelling. In our study, we increase the water content in the vitamin E loading solution up to 25\% (wt\%) to reduce the extent of swelling. Addition of water however reduces the solubility of vitamin E, but there is a concurrent increase in partition coefficient of vitamin E, which still allows loading of significant amount. This process does not affect the morphology of vitamin E barriers in the lens. Therefore, as for the contact lenses with similar vitamin E loading, the hydrophilic drug release profiles are similar, regardless the water content in the loading solution.
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