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OSB archive

Glucose sensor science recognised

Pete Wilton

Research at Oxford University that led to a new type of sensor enabling people with diabetes to easily and accurately monitor their own blood sugar (glucose) levels has been celebrated with the unveiling of a special plaque.

The National Chemical Landmark plaque from the Royal Society of Chemistry [RSC] recognises work by Allen Hill, Tony Cass, and Graham Davis at Oxford's Department of Chemistry. In the 1980s they developed a new technique that enabled a range of proteins to be investigated electrochemically, paving the way for a new type of monitoring device.

Previously glucose monitoring had been done using 'colorimetric' methods in which a drop of blood was applied to a strip that changed colour to indicate the concentration of glucose in the blood. But these methods required a large droplet of blood and were not very accurate.

The new approach started with work into how proteins gain or lose electrons when linked in to an electrical circuit. Studying such electrochemical behaviour was tricky as the proteins tended to stick to the electrodes, creating a build up which prevented a current from flowing.

Allen and undergraduate student Mark Eddowes developed a way of protecting the electrodes by binding another molecule to them which did not interfere with the current. The protein could now pick up an electron from one electrode via the surface bound molecule and lose it at the other electrode: allowing a huge range of proteins to be investigated electrochemically for the first time.

In 1982 Allen, working with Tony Cass and Graham Davis, overcame a major drawback of the new method when applied to enzymes that used oxygen; the latter interfered with the electron transfer processes. They used ferrocene as a carrier of the electrons thereby creating a much more stable system. By using the enzyme which breaks down glucose (glucose oxidase) as the protein component in the device they were able to construct a new type of sensor.

Glucose oxidase reacts with any glucose in a sample, giving up electrons that are passed on to the electrode via the oxidised ferrocene: the larger the concentration of glucose the larger the current measured by the device.

Importantly, the new device needed just the tiniest pinprick of blood, would work with blood straight from the body, and could measure glucose levels much more accurately than colorimetric methods.

Attracting investors to commercialise the new sensor proved difficult until Ron Zwanziger provided financial backing and helped to secure the funds to found a new company, Medisense. The new glucose monitoring device finally went on sale in 1989.

Medisense was a great success, and was sold to Abbott Laboratories in the mid-1990s for around $800m. However, the greatest legacy of the work is that the many variants of the original Oxford-developed glucose monitor are used by people with diabetes around the world today.

Commenting on the original breakthrough, and how the technology has developed since, Allen told me:

'The initial reaction was a mixture of excitement and frustration. The former because we realised how useful the system we had discovered could be: frustration because it took a very long time parading our wares before one company after another before we were fortunate to meet Mr Zwanziger. Now the devices have developed enormously but they are still related to what we found in the '80s.'

Tony Cass is now Professor of Chemical Biology at Imperial College London.