New test for Zika uses nanorods for rapid diagnosis

Researchers from Washington University of St. Louis (MO, USA) have developed a proof-of-concept test that can rapidly detect the presence of Zika virus in blood, without the need for refrigeration.

Currently, diagnosis of Zika virus requires a blood sample from the patient, which must be shipped to a specialist laboratory or medical centre, potentially delaying diagnosis and treatment. Rapid testing for the virus is crucial as generic symptoms and delayed onset often mean those who are infected might go unnoticed.

Author, Evan D. Kharasch (Washington University of St. Louis), explained: “Zika infection is often either asymptomatic or mildly symptomatic. The most effective way to diagnose the disease is not to wait for people to develop symptoms but to do population screening.” However, population screening requires inexpensive, point-of-care tests that are both easy-to-use and easy-to-transport.

The novel diagnostic pioneered in this study uses gold nanorods mounted on paper to detect the presence of Zika virus. A Zika protein, NS1, is attached to the nanorods before they are mounted and the paper is then covered in protective nanocrystals, which allow the test to be shipped and stored without refrigeration.

Author, Jeremiah Morrisey (Washington University of St. Louis) commented: “We’re taking advantage of the fact that patients mount an immune attack against this viral protein. The immunoglobulins persist in the blood for a few months, and when they come into contact with the gold nanorods, the nanorods undergo a slight color change that can be detected with a hand-held spectrophotometer.

“With this test, results will be clear before the patient leaves the clinic, allowing immediate counseling and access to treatment.”

The researchers demonstrated the potential of their diagnostic by testing on nine blood samples – four from individuals with Zika virus, and five from individuals with no history of the disease. The test accurately diagnosed all patients, producing no false-positive results.

The team are hoping future iterations of the test will allow clinicians to view the crucial colour-change with the naked eye, reducing the need for further specialist equipment.

The test can produce results within a few minutes, in addition, it does not require cold chain storage. Although it has not yet been tested in medical situations this potential new diagnostic could prove useful for identifying Zika and other emerging infections.

Srikanth Singamaneni, an author from Washington University of St. Louis, concluded: “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. We wanted to make the test immune from variations in temperature and humidity.”

Sources: Morrisey J, Jiang Q, Chandar Y, Cai S, Kharasch E & Singamaneni S. Rapid, point-of-care, thermally stable paper-based plasmonic assay for Zika virus diagnosis. Advanced Photonics 2017, OSA Technical Digest, doi:10.1364/SENSORS.2017.SeTu1E.2 (2017) (Epub);


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