UGA researchers use gold nanoparticles to diagnose flu in minutes
Arriving at a rapid and accurate diagnosis is critical during flu
outbreaks, but until now, physicians and public health officials have
had to choose between a highly accurate yet time-consuming test or a
rapid but error-prone test.
A new detection method developed at the University of Georgia and
detailed in the August edition of the journal Analyst, however, offers
the best of both worlds. By coating gold nanoparticles with antibodies
that bind to specific strains of the flu virus and then measuring how
the particles scatter laser light, the technology can detect influenza
in minutes at a cost of only a fraction of 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 study co-author 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 to create a diagnostic
test that is rapid and highly sensitive.”
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, and a
commercially available device measures the intensity with which the
solution scatters light.
Driskell explained that gold nanoparticles, which are roughly a tenth of
the width of a human hair, are extremely efficient at scattering light.
Biological molecules such as viruses, on the other hand, 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,”
said Driskell, who worked on the technology as an assistant research
scientist in Tripp’s lab. “You take your sample, put it in the
instrument, hit a button and get your results.”
Gold is often 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 researchers noted that the current standard for definitively
diagnosing flu is a test known as PCR, for polymerase chain reaction.
PCR can only be done 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 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 can’t
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, Driskell added.
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 that 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.”
Source: University of Georgia News Release; August 3, 2011
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