UK scientists have made a holographic sensor that could be used to continuously monitor blood glucose levels in people with diabetes.

Adrian Horgan, Kathryn Dean and colleagues at Smart Holograms, a start-up company based in Cambridge, UK, have developed a sensor that selectively measures glucose concentrations in the presence of other blood sugars, such as fructose.  

The sensor is a crosslinked polymer that contains phenylboronic acid groups, to which glucose binds differently than other sugars in the presence of amine functions, said Horgan.  

A hologram is imprinted into the polymer using a laser, leaving a regular arrangement of silver fringes, explained Dean.  When the polymer is placed in a glucose solution, it contracts, changing the spacing of the fringes and the colour of reflected light from green to blue.  For other sugars, the polymer expands giving a colour change of green to red.  A quantitative result, for diagnostic purposes, can be obtained by measuring the wavelength of the light, said Dean. 

Holographic sensors have many advantages over current methods used to monitor blood glucose levels, which rely on blood being drawn intermittently from the finger-tip of the patient, explained John Pritchard, Chief Technical Officer at Smart Holograms.  'The holographic sensors are flexible, making them easy to incorporate into contact lenses or catheters,' said Pritchard. 'Using this technology it may be possible to take measurements painlessly on an intermittent basis with a mobile phone or in a minimally-invasive manner on a continuous basis.' 

Andrew Mayes, an expert in holographic sensors at the University of East Anglia, said the work looked promising, 'the method looks like it should be very effective - it operates in the correct concentration range under physiological pH and salt concentrations,' he said. 'The results demonstrate an appropriate lack of cross-reactivity to sugars that might be present in physiological samples.'

The sensor can be sterilised and the different components are biocompatible, explained Horgan, but the next hurdle which faces the devices are toxicological tests and clinical trials in humans.  

'In three years, the holographic sensors could be available to people with diabetes as an easy and reliable way to monitor glucose concentrations in the blood,' said Pritchard. 

Alison Stoddart