Beaming in on DNA detection

Extremely sensitive handheld devices capable of detecting tiny traces of drugs, DNA and explosives could be available for use by UK scenes of crime investigators within the next two years.

Researchers at Strathclyde University are developing an analytical technique known as surface-enhanced resonance Raman scattering (SERRS), which uses a laser beam to recognise different molecules, and is particularly effective at detecting white powders such as cocaine and amphetamines.

The system is so sensitive it is capable of detecting single molecules of a drug or explosive, although difficulties with collecting a single molecule from a surface would mean in reality the device would be used to measure a larger trace or group of molecules, said Prof Ewen Smith, deputy head of the department of pure and applied chemistry at the university.

Unlike other recent devices for detecting drugs or explosives, which consist of a handheld sampler and an analysis system about the size of a vacuum cleaner, SERRS equipment could all be fitted on to a handheld device, said Smith.

‘We are about to use micro-fluidics to develop a lab-on-a-chip system, so everything will be fitted on to a handheld device, including the computer.’

A single device could detect both drugs and DNA. In detecting DNA sequences, the technique produces much sharper results using simpler chemistry than existing systems, he said.

Raman spectroscopy has been under development for some time, and handheld devices are already being produced. The technique involves shining a beam of light on to a sample and measuring the light that comes back. The technique gives a sharp pattern of signals from which particular molecules can be identified. without anyphysical contact with the molecule itself.

But the conventional method is not very sensitive, so the research team has significantly enhanced the effect by attaching the molecule to a roughened surface such as a silver nanoparticle, said Smith. ‘The surface of the silver interacts with the molecule, and the signal is intensified.’

Unlike drugs and DNA, molecules of TNT explosives do not readily sit on the silver, so the molecules have to be put into a solution and converted into a dye before they can be made to grip to the nanoparticle. As a result, a separate handheld device would be needed to detect explosives.

The Strathclyde team has applied for an EPSRC grant as part of its £20m crime prevention and detection research programme, and is hoping to attract partners to help commercialise the technology. ‘The technique is now looking for commercialisation, and is ready to come out of the laboratory,’ said Smith.

The technology could also be used in pollution monitoring, DNA sequencing and the analysis and control of certain drugs within the pharmaceutical industry.