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Fast, Simple Covid-19 Antibody Test Being Developed

Plasmonic fluor illustration

Plasmonic fluor, illustrated above, is the technology behind a point-of-care Covid-19 antibody test (Washington University in St. Louis)

20 Apr. 2020. An engineering lab is creating an easy-to-use test of immune-system antibodies to the SARS-Cov-2 virus responsible for Covid-19 infections. The project led by Washington University mechanical engineering and materials science professor Srikanth Singamaneni is funded by a one-year $100,000 grant from National Science Foundation.

The worldwide Covid-19 pandemic is now centered in the U.S., and a major factor affecting future public health and economic decisions will be the extent of immunity in the population to the SARS-Cov-2 virus. Testing for these antibodies, however, needs to be simple, fast, and easy to deploy across the population. The best solution in most cases is a point-of-care test, one that shows results quickly when administered, rather than sending a specimen sample to a separate lab for analysis.

Singamanen’s Soft Nanomaterials Lab studies nanoscale materials with plasmonic properties, where light waves excite electrons in characteristic patterns, such as when detecting the presence of certain biological molecules. In addition, the lab devises bio-sensors printed on inexpensive and readily available materials, such as filter paper, for point-of-care diagnostics, particularly in low-resource regions.

The NSF award funds development of a test that detects immunoglobulin G and M antibody proteins in blood that protect against Covid-19 infections. People who recovered from Covid-19 infections, including those who may not have shown characteristic symptoms, are likely to have those antibodies. The researchers say the test could also be used to detect current infections in people with mild or even no apparent symptoms.

The test will use what Singamanen and colleagues call plasmonic-fluors, nanoscale particles with high sensitivity that give off ultra-bright signals when detecting the target molecules, in this case antibodies protecting against the SARS-Cov-2 virus. The plasmonic-fluors will be printed on a paper-based medium enabling even low levels of antibodies to give off a bright fluorescent signal visible to the naked eye. In addition, the test will use different signaling methods to indicate high and low concentrations of antibodies.

A team from the WashU lab published a paper today in the journal Nature Biomedical Engineering (paid subscription required) demonstrating plasmonic-fluor bio-sensors. The sensors use gold nanoparticles to supercharge the intensity of fluorescent signals. As Singamanen explains in a university statement, “The problem in fluorescence is, in a lot of cases, it’s not sufficiently intense.”

The researchers say the gold nanoparticles absorb then scatter high concentrations of light, which causes surrounding fluorescent chemicals, called fluorophores, to emit much brighter signals. The gold nanoparticles also increase the speed of fluorophore chemical reactions, adding to the intense fluorescent emissions, and returning results in about 20 minutes..

Tests of the sensor with cellular fluids and urine from mice show the sensors, with 200 fluorophore points around each gold nanoparticle to emit signals equivalent to 6,700 fluorophores alone. The high intensity of the signals means fewer proteins are needed to generate the signals, a requirement for a highly sensitive Covid-19 antibody test.

The bio-sensor technology is licensed by the university to Auragent Bioscience LLC, also in St. Louis, a developer of fluorescence-based bio-detection materials. The company makes what it calls plasmonic patches that can be easily applied and give off fluorescent signals from low concentrations of biomarkers, such as antibodies.

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