Diabetes hope on the wings of silver cicadas

Browsing the research posters at a scientific conference in 2002, Dr Paul Stoddart was taken aback. Before him was an electron micrograph of a cicada wing that showed line after line of microscopic pillars arrayed on the wing’s surface, a pattern that resembled just the nanostructure he was looking for to improve the sensitivity of a spectroscopy technique he was using.

That chance sighting led Stoddart, a research fellow at Swinburne University of Technology, to spend many days searching suburban scrub for cicadas, removing their wings and coating them with silver. This was no amateur nature experiment; it was a means of refining an optical fibre sensor that would allow the continuous monitoring of blood glucose levels in humans.

"When I saw these patterns of structure on the cicada wings I thought they could be of some interest to the sensor application. So I coated a wing with silver and found it produced excellent results," Stoddart said.

"The wings have an anti-reflection coating to prevent them reflecting sunlight and enhancing their camouflage. It turns out that this type of anti-reflective coating is exactly the kind of nanostructure suitable for the spectroscopy technique – Surface Enhanced Raman Scattering – that we use."

Stoddart and colleagues at Swinburne’s Centre for Atom Optics and Ultrafast Spectroscopy are using Surface Enhanced Raman Scattering in the development of a device that will constantly monitor blood glucose levels in people with diabetes.

The research team has developed and patented an optical fibre probe that could be used to monitor people’s blood glucose levels in real time, instead of the periodic tests diabetics must self-administer through the course of each day.

The probe fits inside a small-gauge needle and Stoddart envisages both would be incorporated into a wristwatch-style device. "The watch would contain the laser and the optics and the needle, with its fibre sensor, would be plugged in." With one end of the needle plugged in to the device the other would penetrate the skin.

Traditionally, optical fibre sensors have been used for industrial applications such as monitoring temperatures in oil wells, sensing strain in bridges or in optical fibre gyroscopes in aeroplanes. Their use in medical devices is only now being widely explored.

Stoddart hopes the optical fibre sensor would be used as an alternative to the existing finger-prick test for measuring blood glucose levels. "The problem with the finger-prick test is you get snapshots of your glucose level; there might be five or six measurements per day, but you don’t know what’s happening in between those measurements," he said.

"Our approach provides minimally invasive, continuous monitoring. If you want a controlled system you need to have continuous monitoring."

Such a novel application for optical fibre sensors started with the Diabetes Australia Research Trust providing seed funding for Swinburne’s research. Further funding over the past five years from the National Health and Medical Research Council (NHMRC) and ASX-listed company BioPharmica Ltd (BPH) has seen the research program make significant achievements.

Commercially available chemicals have been trialled and the research team has identified a treatment that allows detection of glucose at the lowest physiological levels in which they occur in humans. At current rates of progress Stoddart estimates the device would be available for trials in five years.

"By developing medical applications for optical fibre sensors we can find a way to make a difference to people’s lives," he said. "Whenever I talk about this diabetes work I ask for a show of hands from people with a family member or friend with diabetes; it’s amazing how many people put their hands up. You don’t get that when you’re working with oil wells."

(Source: Swinburne University of Technology: July 2009)