US chemists can now 'see' if patients have the flu. Identifying the virus in infected patients could become much quicker and easier if a test developed by Chris Bowman at the University of Colorado in Boulder and colleagues becomes commercially available. 

Bowman's antibody-coated biosensor detects flu virus proteins (red) using a detecting reagent containing antibodies and light-sensitive molecules

'Respiratory symptoms are very general,' says team member Hadley Sikes. 'So having a rapid, inexpensive way to rule out or confirm (and subtype) influenza is valuable, especially if the device is simple enough to be used anywhere and the results reliable,' she adds. 'Catching the spread of infections caused by particularly virulent flu strains early could help prevent a pandemic.'

Bowman's detector is a biosensor which has specific flu antibodies attached to part of its surface. When a mixture of flu virus lysate and a detecting reagent is placed on this surface and exposed to light, the antibody-coated areas become visible to the naked eye. The sensor works because virus proteins in the lysate attach to the antibodies on the surface. Since the detecting reagent contains both flu antibodies and light-sensitive molecules it also recognises and binds to the flu proteins if they are present and then, when exposed to light, forms hydrogel polymers which are visible. If no flu proteins are present, no reaction takes place and the test is negative.  

'We were particularly encouraged by the zero false positives obtained in our tests,' says Sikes. 'Of course, the real measure of whether the test has potential will come only after it is used successfully with real patient samples.'

Aaron Wheeler, whose team at the University of Toronto, Canada, works towards developing lab-on-a-chip devices for bioanalysis, describes the technology as 'really exciting' because results can be read unaided, by the human eye. 'Until now, many of the technologies being developed for point-of-care diagnostics required dedicated readers for analysis,' he says. 'This exciting new development could have a significant impact on this important problem.'   

'The usefulness of a diagnostic test which does not rely on instrumentation cannot be overstated,' agrees Sikes. 'In many parts of the world disease diagnosis is hindered both by the lack of equipment and staff trained to use it; so tests that are inexpensive and easy to perform without costly and high maintenance instruments offer a good solution.' 

Janet Crombie