Surface worker

A team at Imperial College, London is looking for a new method of detecting proteins in diagnostic tests such as those used to measure abnormal protein levels in the body. The researchers hope to find a way of using surface-enhanced Raman spectroscopy to give a test that is both more sensitive and more reproducible.

The project is a collaboration between biological chemist Robin Leatherbarrow in the chemistry department, Lesley Cohen in physics, who specialises in Raman spectroscopy, and electrical engineer Mino Green, whose expertise lies in surface fabrication. All three are involved in the EPSRC-funded Chemical Biology Centre at Imperial, which was set up to encourage the application of the physical sciences to biological problems.

‘The problem with Raman spectroscopy is that while it’s an information-rich technique, it’s relatively insensitive,’ Leatherbarrow explained. ‘The Raman effect is enhanced close to a rough silver or gold surface resulting in surface-enhanced Raman spectroscopy (SERS), which is far more sensitive. Without SERS the bound proteins would need to be tagged with a Raman active label, which is an expensive extra step.’

He added that they will be using microfabricated silicon surfaces. ‘These have what is, in effect, an immobilised colloidal silver surface on them, with silver toroids on the surface. The pores in these rings give the SERS effect.’ These microfabricated surfaces have already been applied to DNA-DNA interactions, and the next step is to test them with proteins, creating antibody-coated chips that will provide specificity for a variety of target molecules without a need for labelling.

He said that the big advantage of using these surfaces is the scale. ‘We could test for thousands — if not hundreds of thousands — of proteins on something the size of a silicon chip,’ he claimed. ‘Because the technique has the potential to be extremely sensitive, we should be able to miniaturise the chip. The limiting factor will be how hard it is to spot the proteins on to the chip, not their detection.’