British researchers (University of Leeds and Hutchison/MRC Research Centre, Cambridge) have developed an electronic microchip that can test the presence of certain proteins, without the need for fluorescent tagging, while requiring only a small sample for testing. The idea is to build diagnostic medical devices based on this interesting new technology.
Dr Wälti 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.
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.
Press release: Microchip could aid in future disease diagnosis
Paper: Electrical protein detection in cell lysates using high-density peptide-aptamer microarrays Journal of Biology 2008, 7:3