Contact lenses that take longer to be foiled by proteins and other biological substances, UT PhD student Piet Driest sees the possibilities for the polymer Poly(Ethylene Glycol) Poly(Urethane-Isocyanurate), PEG PUI for short. In his dissertation, he describes the synthesis, properties and possible applications of the material.
Contact lenses are being worn more often and for longer periods of time, resulting in increasingly dirty lenses. Over time, proteins and bacteria attach to the surface. This is not only annoying for the vision - after all, the lens becomes increasingly cloudy - but also dangerous as it increases the risk of infections of the eye.
The material that Driest investigated, Poly(Ethylene Glycol) Poly(Urethane-Isocyanurate), PEG PUI in short, takes longer to be foiled than current materials. "The material is quite inert. This makes it difficult for bacteria and proteins to adhere", Driest explains. In his research, he compared the material with commercial contact lenses. After 24 hours in a solution of proteins, on average only half the amount of proteins had adhered to PEG PUI compared to the commercial lenses.
An additional advantage is that the new material has a higher refractive index than most contact lens materials. "This means you can make thinner contact lenses, which increases wearing comfort," Driest says. Other favourable properties for contact lenses such as flexibility, strength and transparency were similar to those of current materials.
To make PEG PUI, Driest combined materials for aeroplane coatings and hydrogels for burns. Driest says: "The hydrogels for burns already had the potential for contact lenses, but were not yet strong enough. By combining it with ingredients for aeroplane coatings, we have managed to make these hydrogels strong enough for use as contact lenses". In addition, the aeroplane coatings also contributed to the inert properties that are able to keep the lenses as clean as possible.
Before we can find contact lenses made from PEG PUI, more research is needed, according to Driest: "at the moment, the material does not yet allow enough oxygen to get through to the eye". According to Driest, this problem can be solved by combining the material with silicones, which are currently widely used in contact lenses and allow much more oxygen to pass through.
Piet Driest carried out his research in collaboration with Covestro, a German company that, among other things, produces polymers for the coating industry. In his thesis Poly(urethane-isocyanurate) Networks: Synthesis, Properties and Applications he describes the synthesis, properties and possible applications of PUI materials, including their use for contact lenses. He carried out his research within the Department of Biomaterials Science and Technology (faculty TNW) under the supervision of Prof. Dr. D.W. Grijpma and Prof. Dr. D. Stamatialis. The public defence of his thesis will take place on Friday 31 January 2020. A digital version of the dissertation is available on request.