Physicians and health officials may no longer have to choose between flu tests that are either accurate yet time-consuming or rapid but error-prone, thanks to a new detection method that can identify influenza in minutes at only a fraction of a penny per exam. By coating gold nanoparticles with antibodies that bind to specific strains of the flu virus and then measuring how the particles scatter laser light using a commercially available device, this new technology can not only detect influenza in minutes, but it can also be done at the point of care. “We’ve known for a long time that you can use antibodies to capture viruses, and that nanoparticles have different traits based on their size,” said Ralph Tripp, Georgia Research Alliance Eminent Scholar in Vaccine Development in the University of Georgia’s College of Veterinary Medicine. “What we’ve done is combine the two to create a diagnostic test that is rapid and highly sensitive.” Tripp is co-author of the study, recently published in Analyst. Ralph Tripp, University of Georgia. (Image: UGA) Working in the UGA Nanoscale Science and Engineering Center, Tripp and co-author Jeremy Driskell linked immune system proteins known as antibodies with gold nanoparticles — the gold nanoparticle-antibody complex aggregates with any virus present in a sample. Driskell explained that gold nanoparticles, which are roughly one-tenth the width of a human hair, are extremely efficient at scattering light, while biological molecules such as viruses are intrinsically weak light scatterers. The clustering of the virus with the gold nanoparticles causes the scattered light to fluctuate in a predictable and measurable pattern. “The test is something that can be done literally at the point of care,” Driskell said. “You take your sample, put it in the instrument, hit a button and get your results.” Gold often is thought of as a costly metal, but the new diagnostic test uses such a small amount — less than what would fit on the head of the pin — that the cost is one-hundredth of a cent per test. The current standard for definitively diagnosing flu is a test known as PCR (polymerase chain reaction). PCR can be done only in highly specialized labs and requires that specially trained personnel incubate the sample for three days, extract the DNA and then amplify it many times, the researchers say. The entire process, from sample collection to result, takes about a week and is too costly for routine testing. The alternative is a rapid test known as a lateral flow assay. The test is cost-effective and can be used at the point of care, but it cannot identify the specific viral strain. It also misses up to 50 percent of infections and is especially error-prone when small quantities of virus are present. By overcoming the weaknesses of existing diagnostic tests, the researchers hope to enable more timely diagnoses that can help halt the spread of flu by accurately identifying infections and allowing physicians to begin treatment early, when antiviral drugs, such as Tamiflu, are most effective. Tripp and Driskell are planning to compare the new diagnostic test with another that Tripp and his colleagues developed. This one measures the change in frequency of a laser as it scatters off viral DNA or RNA. Tripp also is working to adapt the new technique so that poultry producers can rapidly detect levels of salmonella in bath water during processing. Poultry is the largest agricultural industry in Georgia, he pointed out, so the technology could have a significant impact on the state’s economy. “This test offers tremendous advantages for influenza, but we really don’t want to stop there,” Tripp said. “Theoretically, all we have to do is exchange our anti-influenza antibody out with an antibody for another pathogen that may be of interest, and we can do the same test for any number of infectious agents.” For more information, visit: www.nano.uga.edu