The Reporter
Issue 496, 23 February 2004
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New biosensors harness the power of antibodies

Dr Paul MillnerDr Paul Millner (left) has been defending our breakfast tables for years, working with Weetabix and Hovis to keep pesticides off the menu using biosensors – biochemical microchips the size of a fingernail that detect trace amounts of target chemicals. Now his team aims to transform the technology of testing by harnessing the body’s natural ability to recognise new molecules and stop their spread with antibodies.

Chemical testing is a multi-million pound business, and biosensors have many uses from food safety to forensics. In medicine, they can detect the chemical signals that many diseases leave in the blood, and can be used to diagnose and monitor the spread of disease. Millions of diabetics already use them to monitor their blood sugar.

Biosensors are cheap, versatile and sensitive and bring testing times down from days to minutes, though until now the technology has been limited. But a new breed of biosensors based on antibodies, under development at Leeds, could soon be seen in hospitals and GPs’ surgeries.

Dr Millner, of the department of biochemistry and molecular biology, said: “Most commercial biosensor technologies are based on enzymes, and have been limited to detecting just a few molecular targets. Our work will create a new generation of biosensors based on antibodies, which will be much more versatile. Over the next few years we will be able to design a biosensor to detect almost any molecule.”

The team’s work will harness the ability of immune cells to recognise invaders such as viruses, and stop their spread by producing antibodies – small molecules which attack the invader. Immune cells learn to produce a new type of antibody for each new intruder that comes along, so each antibody is like a molecular sniffer dog trained to respond to a particular molecule. By manipulating this recognition system, Dr Millner can create biosensors to order. The antibodies are attached to a biosensor microchip, which provides a reading when the target chemical is detected.

The Leeds researchers are leading a £1.7m EU project, which is unique in bringing together teams of biochemists, electrochemists, synthetic organic chemists, software designers, electronic engineers and micro-chip manufacturers – the whole production chain from lab to factory floor – to produce a prototype antibody biosensor within three years.

The work involves solving a specific problem in the way electrical signals produced when antibodies recognise a substance are generated and processed. With existing biosensors, enzymes either recognise the substance they are trying to sense or are inhibited by it – this changes the electrical current from the sensor in proportion to the amount of substance present. For such sensors supplies of specific enzymes are needed, which limits the range of substances that can be detected.
The next generation of sensors will move away from this approach, said Dr Millner, to one using antibody molecules which are plentiful and cheap, and can be produced to recognise almost any target molecule. This is because antibodies work by sticking to their targets very specifically and tightly.

However, the problem researchers have to solve, said Dr Millner, is recognising the electrochemical consequences of an antibody binding to a target molecule, which is a complex combination of electrical activity. If that can be discovered, and background electrical noise and non-specific interactions minimised, then antibodies could be used to quantify almost any molecule rapidly and cheaply.

Co-researcher Dr Tim Gibson said: “Our biosensors will be seen by hospital beds, as well as providing on-site, instant testing for pollution of food and water, or for GM contamination.”

It will be five years before we see the team’s antibody biosensors on the market, but we should expect them to become widespread soon after that. Although they represent the cutting edge of applied ‘bio-nanoscience’, when mass-produced, biosensor chips may be as cheap as, well, chips, costing only a few pounds each – not bad for a high-tech lab small enough to get lost in your wallet.


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