- Zika virus
disease is a mosquito borne viral infection predominant in tropical and
subtropical parts of the world.
available Zika detection tests take days with added necessity of cold
storage and transport of blood.
- New study
proposes a 15 minute, low-cost, paper based plasmonic assay for Zika virus
Since Zika virus disease usually manifests in an asymptomatic manner, the
detection becomes difficult. Moreover, Zika virus infection in pregnant women
can cause fatal brain conditions in infants and other nerve damaging diseases
in adults. This calls for Zika virus screening in endemic regions. However, the
expense, time taken to obtain results and lower accessibility to testing
laboratories limit early detection of the virus. A study conducted at the
Washington University has reported a novel paper-based detection method that
uses nano-particles. This method claims to be a rapid and low-cost screening
technique that eliminates the need for cold storage, which is essential in most
other detection methods. The study is published in the journal Applied
What is Zika virus and why is it dangerous?
is a mosquito-borne flavivirus that has recently been reported
to spread, causing a global health problem. The Zika virus is carried by the
Aedes aegypti mosquito, a common carrier of dengue
and yellow fever. Zika virus infection in pregnant women has a
strong link to babies being born with microcephaly (small head circumference).
It also causes Guillain-Barre syndrome
; a nerve damaging disease
resulting in muscle weakness, in adults. Most adults affected with the disease
do not show any symptoms, which makes the infection difficult to detect and
hence harder to treat and contain the disease.
‘Novel Zika virus detection method gives result in 15 minutes and does not require cold storage.’
The infection spreads when an infected mosquito bites or when a mosquito
bites an infected person and further transmits the disease to unaffected
people. There have been cases of spreading through semen and also saliva. There
is presently no vaccine or cure available for Zika virus infections.
Current Zika virus detection tests
vaccination and cure are still far away, the ultimate approach to contain the
disease is early detection, which will facilitate early treatment, and early
counseling in case of infected expectant mothers. However, current tests for
Zika virus detection require that the blood is refrigerated and transported to
a central laboratory for testing. The test results are obtained days after
testing. This delays diagnosis and possible treatment.
The new, rapid, low-cost, plasmonic based assay
A research team at Washington University has developed a test that
quickly detects the presence of Zika virus in blood. Zika virus currently
flourishes in warm and humid regions like South and Central America, Asia and
Africa, all of which are resource limited in terms of refrigeration. This new
method was developed keeping in mind of these parts of the world that require
assays for detection that remain stable in both room and elevated temperatures.
"If an assay requires electricity and refrigeration, it defeats the
purpose of developing something to use in a
resource-limited setting, especially in tropical areas of the world," said
Singamaneni, the corresponding author of the study. "We wanted to make the
test immune from variations in temperature and humidity."
The test relies on a protein made by Zika virus called the Zika virus
non-structural protein 1 (NS1), which causes an immune response in infected
individuals. Infected individuals produce anti-NS1 antibodies upon recognizing
the viral NS1. These antibodies may be detected up to 1 month after the
infection, thus giving the detection process a one-month window.
The NS1 protein is attached to gold nanoparticles and uniformly mounted
on a piece of paper. The paper is then completely covered in nano-crystals,
which protect the nanoparticles and allow storage and shipping without refrigeration.
When the test needs to be conducted, the nano-crystals are removed by
rinsing the nano-particle mounted paper with an acidic solution. This exposes
the gold nanoparticles to react with the sample blood when dropped onto the
surface. If the person is infected with the virus, the blood will contain
anti-NS1 antibodies that will react with the NS1 protein attached to the gold
nanoparticles. If there is a reaction, a slight color change is observed using
a spectrophotometer, which indicates that the blood is infected with Zika
virus. The test results are obtained within 15 minutes.
- Facilitating the
reaction color change to be detected with the naked eye.
- Using saliva
samples instead of blood.
- Morrissey, J., Jiang, Q., Chandar, Y., Cao, S., Kharasch, E., & Singamaneni, S. (2017). Rapid, point-of-care, thermally stable paper-based plasmonic assay for Zika virus diagnosis. Advanced Photonics (2017 (IPR, NOMA, Sensors, Networks, SPPCom, PS). doi:10.1364/sensors.2017.setu1e.2