Bea Perks/Washington DC, US

A lab-on-a-chip device that assays the protein and nucleic acid content of a clinical sample in one go could slash the time it takes to diagnose bacterial or viral infections, say US researchers. All the patient has to do is provide 0.3ml of saliva.

Prototype pocket-sized microfluidics device

'The idea is to take tests that are normally done with blood or urine and come up with a non-invasive alternative,' said Daniel Malamud, professor of biochemistry at the University of Pennsylvania. Malamud's team is developing an affordable technology that will diagnose viral or bacterial diseases in about an hour.

'The device we have uses microfluidics and divides into four channels,' Malamud told the American Association for the Advancement of Science annual meeting. 'One of them looks at proteins on the surface of the bacteria or virus, one looks at an antibody, and the other two are miniature PCR machines that can amplify RNA or DNA.' The sample, a drop of saliva, flows down through the channels in the credit card-sized device, which is then inserted into a reader. Data are read and the medic gets a diagnosis that currently takes days to deliver.

The team is developing the system with one virus, HIV and one bacteria, Bacillus cereus (a close relative of anthrax,

B. anthracis). 'We've been able to do all those four lanes, the DNA, the RNA, the antigen and the antibody, we haven't yet combined them into a single device, which we'll have to do in the next year or so,' said Malamud.

Saliva has several advantages over traditional clinical samples, says Edward Cone who runs ConeChem Research, Baltimore, US, a company that develops oral fluid testing systems for drugs of abuse. The sample more closely reflects the situation in the body and in the blood stream, he says. 'It gets a little closer than a urine test, which is more historical.'