Contact lenses deliver medication

Scientists in Singapore have recently invented a simple method of making polymeric lens materials that can be loaded with eye medication for ophthalmic drug delivery applications.

Institute of Bioengineering and Nanotechnology (IBN) scientists Dr Edwin Chow and Dr Yi-Yan Yang have recently invented a simple method of making polymeric lens materials that can be loaded with eye medication for ophthalmic drug delivery applications.

The scientists’ challenge was to overcome problems inherent in the delivery of medication to the eyes. As much as 95% of the medication delivered by eye drops flows to where it is not needed. The drops usually mix with tears and drain into the nasal cavity, where they can flow through the blood stream to other organs and cause serious side effects. In addition, dosage through eye drops is inconsistent and difficult to regulate, as most of the drugs are released in an initial burst of concentration.

To counter these problems, researchers have been studying the use of contact lenses to deliver eye medication. One proposed method was to pre-soak the lenses in the drug solution, while another involved incorporating the drug solution in a hollow cavity made by bonding two separate pieces of lens material. However, neither of these methods proved very effective at delivering medication for extended periods of time.

Chow and Yang’s one-step process incorporates drugs within a bicontinuous nanostructured polymer matrix via an in situ microemulsion polymerisation process. Through this method, transparent and mechanically strong lens materials with a nanostructured polymer network can be easily and cost-effectively fabricated in the form of rods, sheets or ophthalmic moulds.

“The resulting material is compatible with human dermal cells, as well as human corneal epithelial cells,” said Chow. “It is also permeable to gases such as oxygen and carbon dioxide, water and components of the tear fluid. Thus, this material is suitable for use in biological and biomedical applications.”

Chow continued: “Our approach also allows great flexibility in designing controlled drug delivery vehicles that can be tailored to different drugs and remain effective for extended periods. Drugs may also be encapsulated in polymeric nanoparticles, which are then dispersed in the lens material precursor by polymerisation. By altering the size, concentration and structure of these polymeric nanoparticles, we can further control the drug delivery rate, while retaining the appropriate lens clarity.”

This new approach could be adapted to deliver glaucoma medication, as this eye disease is particularly hard to treat and existing medications are said to have numerous side effects. Contact lens wearers with dry eyes may also benefit from this invention, as the material can be modified to produce self-lubricating contact lenses.

Singapore-based IBN is currently looking for partners to help commercialise their idea.