Antibacterial contact lenses take wing

Scientists are harnessing a physical trick used by cicadas and dragonflies on their wings to fight bacteria on contact lenses and artificial cornea.

These insects’ wings are coated with billions of tiny, pointed ‘pillars’ that skewer any bacteria that land on them. Yet these microscopic pillars leave human cells completely unharmed, researcher and University of California, Irvine graduate student, Mary Nora Dickson, told OT.

She explained: “This is because mammalian cells interact with surfaces through ‘feet’ called focal adhesions [so they] essentially have the ability to control their adhesion onto the surface.

“Bacteria, on the other hand, stick onto surfaces with their entire outer coating, and so, as they wrap their bodies around the pillars, they deform, often excessively, which is the likely cause of their death.”

However, in order to use this trick on a contact lens or artificial cornea, the University of California, Irvine, team needed a production process that could create these pillars on a polymer surface.

In research to be presented at the national meeting and exposition of the American Chemical Society today (15 March), the team has developed a robust, inexpensive method that can create polymer pillars capable of killing ‘gram-negative’ bacteria like E.coli.

The team expects that this potentially sight-saving technique could be used in artificial cornea, intraocular lenses and hard contact lenses.

“It can now be applied to medical devices that could improve people’s quality of life,” Ms Dickson said, emphasising: “The current cornea device, the Boston K-pro has a [significant] infection rate … and patients must take antibiotic eye-drops for the rest of their life. We are trying to create a new cornea device that has no, or a very minimal, risk of infection, even without eye drops.”

She added: “We plan to put the pillars on the front surface of the lens where bacteria are most likely to adhere.”

Ms Dickson said the team’s next goal was targeting ‘gram-positive’ bacteria such as MRSA, which has thicker cell walls that are tougher to skewer.

She explained that the taller, skinnier pillars on dragonfly wings are able to kill this type of bacteria. However, replicating these pillars on polymers proved tough – they broke apart when the mould was removed, much like cupcakes sticking to the inside of an ungreased tin.

The team have had some success using fluorinated silane coatings to help free the dragonfly-inspired pillars, Ms Dickson said. The team were also developing the technique so it worked on a curved surface.

It was still too early to estimate when the patented technology might be ready for market as part of artificial cornea and contact lenses, she stressed, adding: “We don’t have a date set yet for human patient trials. Currently we are optimising the prototypes in studies on cadaver eyes and we hope to begin animal trials soon.”