Viral detection: SERS sensitivity

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  • Published: Feb 1, 2013
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Viral detection: SERS sensitivity

SERS addresses antigens

Surface-enhanced Raman scattering (SERS) detection of multiple viral antigens using magnetic capture of SERS-active nanoparticles Credit: Johnson et al/Elsevier)

The surface envelope and antigens from the zoonotic pathogens West Nile virus (WNV) and Rift Valley fever virus (RVFV) can now be detected with high sensitivity thanks to the development of an immunoassay based on surface-enhanced Raman scattering (SERS) spectroscopy.

It is essential that we have simple and rapid diagnostic tests for lethal and fast-spreading pathogens so that treatment can be offered in a timely manner to stifle their spread. Unfortunately, current technology is somewhat limited in that it does not integrate multiple tests for pathogens where symptoms may be similar. Moreover, equipment is rarely portable, often requires specialist technicians to carry out the tests and interpret the results and is not always as rapid as healthcare workers would like. Surface-enhanced Raman scattering (SERS) spectroscopy is gradually emerging as a leading light in such diagnostics offering some hope of addressing almost all the problems that exist.

Multiplex detection of West Nile virus (WNV) and Rift Valley fever virus (RVFV) could be important and new research suggests that SERS could assist in the implementation of such diagnostics.

Viral spread

WNV is transmitted by mosquito bite and was originally found in the tropics with the first cases identified in the West Nile region of Uganda in 1937, hence the name. Until the middle of the 1990s, outbreaks were rare but an outbreak in Algeria in 1994 and large outbreak in Romania in 1996 raised the prominence of the disease. WNV is now present across the globe tropical and temperate regions. The first "Western" cases were seen in New York City in 1999 but it is now endemic across the Americas and has spread across Europe beyond the so-called Mediterranean Basin. It is widespread in Africa, Asia, Australia and in the Middle East. Among the symptoms of WNV are fever, headaches, fatigue, muscle pain, nausea, vomiting and rash. In less than 1% of cases there is severe neurological disease.

RVFV is spread by Aedes or Culex mosquitoes. It first detected in livestock in Kenya during World War I, but the virus can spread to humans. RVFV outbreaks occur across sub-Saharan Africa and in 1977-78 it afflicted several million people in Egypt leading to thousands of deaths. Usually, those infected either suffer no symptoms or have a mild illness with fever, headache, and muscle pain. But, it can lead to haemorrhagic fever syndrome or inflammation of the brain and in 1% of cases is lethal.

Jing Neng , Mark Harpster and Patrick Johnson of the University of Wyoming, Laramie, and William Wilson of the USDA/ARS, in Manhattan, Kansas, USA, developed their test using antibody-mediated recognition with Raman reporter-coated gold nanoparticles and paramagnetic nanoparticles. These were conjugated with polyclonal antibodies specific to each antigen target. A 785 nanometre laser causes the necessary excitation of the magnetically concentrated complexes. The team was able to demonstrate a conservative limit of detection of approximately 5 femtograms per millilitre when the assays were carried out in a phosphate buffered saline buffer and about 25 pg/ml for those undertaken in the same solution spiked with animal serum.

Inherently simple

"Based on the inherent simplicity of the assay, magnetic capture-based SERS assays afford promise as a biosensor platform that provides high-level multiplex detection sensitivity and can be adapted for portable diagnostic applications in limited resource settings," the team concludes in the current issue of the journal Biosensors and Bioelectronics. The team now addressing the various technical issues that remain with the adoption of SERS for multiplex detection of pathogens with a view to developing a portable Raman reader.

Related Links

Biosensors and Bioelectronics, 2013, 41, 316-324: "Surface-enhanced Raman scattering (SERS) detection of multiple viral antigens using magnetic capture of SERS-active nanoparticles"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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