Fast or accurate? Those are typically your choices for flu diagnosis. But a new biophotonics approach offers both speed and accuracy, and low cost as well—all things that are supremely helpful during outbreaks, especially because antiviral drugs are most effective in the early stages of disease.
Gold nanoparticles—coated with antibodies that bind to specific strains of flu virus—form the foundation of the approach. By measuring how the particles scatter laser light, University of Georgia researchers have been able to detect influenza in minutes at less than a penny per exam. “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 UGA College of Veterinary Medicine. “What we’ve done is combine the two.”
The nanoparticle-antibody complex aggregates with any virus present in a sample. This clustering causes the scattered light to fluctuate in a predictable and measurable pattern, and a commercially available device measures the intensity. “The test is something that can be done literally at the point-of-care,” said Jeremy Driskell, who co-authored the paper describing the work. “You take your sample, put it in the instrument, hit a button and get your results.”1
The approach competes with the current standard for definitively diagnosing flu, a test known as polymerase chain reaction (PCR), which requires specialized labs, trained personnel, multiple days, and numerous steps. Another alternative, lateral flow assay, is cost-effective and can be used at the point-of-care, but it’s error-prone and cannot identify specific viral strains.
Tripp and Driskell plan to compare the new test with another one Tripp and his colleagues developed, which 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. “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.”
1. J.D. Driskell et al., Analyst 136, 3083–3090 (2011).