Medical researchers in the US have made a sensor device that can potentially be used to measure sugar levels in the blood. They hope it could help people suffering from diabetes and similar conditions monitor their blood glucose levels.

Ching-Hsuan Tung and colleagues from Massachusetts General Hospital based their system on an aqueous mix of a pH-sensitive dye and a boronic acid derivative.

The sensor depends on the change in the acid dissociation constant (pK_a) of the boronic acid when sugar molecules bind to it. This in effect raises the pH of the solution and causes a clear change in the colour of the dye. Almost uniquely, Tung's chemosensor operates in the near infrared range, where there is minimal background interference from biomolecules and blood.

'Despite the promising responses demonstrated by similar fluorescent probes in the past, their development is a complex process and optical responses are not easily predictable,' said Tung. 'In addition, those fluorophores frequently require an organic co-solvent to increase solubility in aqueous media.'

The group extended its approach to produce 'test strips' that were suitable for semi-quantitative sugar detection using the naked eye. The sensor solution was spotted onto filter paper and then dried. The initial colour of each spot immediately changed from reddish-pink at neutral pH to blue as the pH increased following addition of sugars. 'We hope the inexpensive test strip will find use for health care in developing countries,' said Tung. 'Although not as accurate as the glucose-meters widely used in developed countries, they could provide critical information,' he asserted.  

Duncan Graham of the Centre for Molecular Nanometrology at the University of Strathclyde, UK, commented: 'This work is interesting, and the team's approach is a significant advance on what's already out there. This offers promise, but there's a long way to go before it's an in vivo sensor!'

Michael Spencelayh