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Ralph Tripp, Georgia Research Alliance Eminent Scholar in Vaccine Development in the UGA College of Veterinary Medicine
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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.”
Silver bullet: UGA researchers use laser, nanotechnology to rapidly detect viruses
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