Microchip Could Aid In Future Disease Diagnosis

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A tiny, highly sensitive device that could give medics a head start in testing for a range of diseases is being developed by engineers at the University of Leeds.

Diagnostic devices work by identifying certain proteins in blood or urine that are associated with certain diseases. The Leeds device is more than ten times smaller than existing models while offering the accuracy and sensitivity required for clinical diagnostics - and the researchers believe the technology could allow them to reduce the size much further still.

"Size is as important as accuracy for these devices," explains Dr Christoph Walti. "With new born babies, for example, only small amounts of blood can be taken for tests, so any sensor has to be able to detect a large range of proteins with only a small test area to work from."

Dr Walti and Professor Giles Davies from the University's Faculty of Engineering used an array of electrodes as the base of their device rather than the conventional glass slide. The individual electrodes are created using the same technology used to produce modern microchips, so are very small and very closely spaced, currently about 10 micrometers apart - although this can be significantly reduced.

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Conventional techniques use antibodies as receptors on their sensors to bind to the target proteins - but these are not very stable when attached to a sensor and tend to lose their specificity.

So Dr Paul Ko Ferrigno, formerly from the MRC Cancer Cell Unit in Cambridge, and now at the Leeds Institute of Molecular Medicine, created an artificial robust antibody called a 'peptide aptamer' that is so stable that it can be attached to the electrodes and still bind to a specific target protein.

The Leeds researchers then devised a technique to attach different peptide aptamers to individual electrodes with very high precision. The electrodes are individually wired, so when the proteins of interest from samples such as blood bind to their associated peptide aptamer, an electronic signal is generated. This is far more informative than the conventional microarray system, which relies on labelling of the proteins in the sample with fluorescent tags, and using optical techniques to detect these tags.

Because the basic technology of the new device is similar to that used widely within the computer industry, the researchers believe that the number of sensors in their system could be scaled up for use commercially - with the device itself taken down to nanoscale size for use with very small samples.

"Using semiconductor technology provides huge advantages," said Professor Davies. "While conventional systems often use technology similar to that found in ink jet printers to pattern the arrays, they face problems when it comes to testing for large numbers of proteins from small sample volumes. Our invention overcomes these problems by providing a greater number of sensors within a smaller area, an effective electronic analysis, and a very robust sensor molecule to identify the target proteins."

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