The development of enhanced drug delivery methods to combat corneal blindness

By Dr Siân Morgan

I am extremely proud and honoured to have been awarded the Bronze prize in the category of ‘Biological and Biomedical Sciences’ at this year’s STEM for BRITAIN event, which is a major scientific poster competition normally held in Parliament. Prizes were awarded for the posters presented in each discipline which best communicated high level science, engineering, or mathematics to a lay audience. This year, due to Covid-19, the event was held online via Zoom and, despite the unusual circumstances, it was a fantastic experience, and I am very grateful to have been given the opportunity to share my research with both Houses of Parliament at this prestigious event. I highly recommend that early-career researchers in UK universities apply for future events as it really is an excellent platform to showcase your research. The poster that I presented at the event described my current research which centres around the development of more effective methods of delivering medications to the cornea of the eye in an attempt to combat corneal blindness.

The problem and its significance

Infectious disease of the cornea, which is the eye’s clear, protective outer layer (Image 1), represents a major health care problem worldwide, particularly in the developing world. Over 90% of people with corneal blindness live in low to middle income countries, particularly in communities with inadequate access to water and sanitation. Trachoma, for example, has been identified by the American Academy of Ophthalmology as the world’s leading cause of preventable blindness. It is referred to as preventable because it can be controlled by environmental measures and antibiotics. In its early stages, trachoma causes conjunctivitis (pink eye) accompanied by fairly mild symptoms of itching and irritation. However, if left untreated the patient experiences increasing degrees of pain and blurred vision and scarring inside the eyelid leads to the eyelashes turning inward, scratching the cornea resulting in corneal ulceration and vision loss (Image 2). Corneal infection and vision loss are not confined to the developing world, there are also many difficult-to-treat conditions in developed countries. For example, the potentially blinding condition Acanthamoeba keratitis, which is caused by water-borne microscopic organisms that are often found in heated swimming pools and hot tubs (Image 3). Drug delivery to the cornea is usually achieved via eye drops. The problem is that these are quickly washed out by tears and lost by blinking. It is estimated that around 75% of the dose is lost within the first few blinks. There is therefore a real need for new more efficient technologies to deliver corneal medications. The aim of my research is to investigate the potential of drug-loaded contact lenses as a novel alternative and more effective drug delivery method than standard care eye drops.

Experimental methods

In the lab, I test the drug-loaded contact lenses on pig eyes to ensure that they are both effective and safe before being used clinically. The drugs are loaded via a soaking method overnight before being applied to the eyes (Image 4a) and to mimic real-life conditions the eyes are kept at 37°C (normal body temperature) and artificial tear fluid is applied (Image 4b). The corneas are then removed from the eyes using surgical scissors (Image 4c) and the drug is separated from the cornea chemically using solvent extraction. I can then measure the amount of drug delivered using a separation method called High Performance Light Chromatography (HPLC), which can be used to identify and quantify substances. The drugs are also tested on corneal cells to ensure the delivered concentrations are not toxic (Image 4d).

Achievements so far

My early findings do suggest that drug-loaded contact lenses may represent a major advancement in drug delivery to the eye. To date, these lenses have been shown to be capable of delivering significantly higher levels of antimicrobial drugs to the cornea than standard eye drops, and importantly they are relatively safe, showing little impact on corneal cells1. The knowledge, skills and methods I have developed during this work are readily transferable to testing the efficacy of the contact lenses for the delivery of a wide range of drugs to treat a multitude of devastating eye conditions and show great potential for moving into the clinical setting.

Further reading:

Morgan, S.R., et al. (2020) Controlled in vitro delivery of Voriconazole and Diclofenac to the cornea using contact lenses for the treatment of Acanthamoeba Keratitis. Int J Pharm. 579:119102. DOI: https://doi.org/10.1016/j.ijpharm.2020.119102

About the author:

Dr Siân Morgan, Research Associate in the Schools of Optometry and Vision Sciences and Pharmacy and Pharmaceutical Sciences at Cardiff University. You can vie Siân’s Twitter page and LinkedIn page if you would like to know more about her work.

Twitter: @Spianeee

LinkedIn: https://www.linkedin.com/in/si%C3%A2n-morgan-643624a6/

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