Currently, most U.S. medical offices and hospitals use the ELISA (enzyme-linked immunosorbent assay) test to determine whether or not a person has a viral infection. It’s a common test but ELISA’s sensitivity is relatively low, so clinicians need a fairly high number of antibodies in a person’s blood to get a positive test result. It also often takes seven to 10 days after an infection for the test to register.
A technology was developed that can detect extremely small amounts of antibodies in a person’s blood. Antibodies develop to infect cells or kill pathogens, essentially fighting off a bacteria or virus. The levels of antibodies in the blood can tell whether that person is sick.
Using a small wire that is one-fourth the size of a human hair, the researchers developed a sensor that can detect as few as 10 antibody molecules within 20 minutes. Standard medical testing requires billions or trillions of antibody molecules for detection and can take up to a day to process. The new cost-effective instrument could help clinicians treat diseases sooner in people and could be used in low-resource settings.
Researchers chemically attached proteins related to Zika and chikungunya viruses to inexpensive, small gold wires. These particular viruses, along with West Nile and dengue, are transmitted by infected mosquitoes. Medical laboratories use these proteins in ELISA tests to look for antibodies that have developed to fight infections.
Next, they ran an electrical current through the wire, creating a charge on the wire similar to that of a battery. Antibodies were then added to bind to the viral proteins on the wire, which increased the mass on the outside of the wire. This also increased the ability of the wire to hold the charge. They then measured the change in mass to quantify the number of antibodies on the surface of the wire. The team did not see any reaction or reactivity from antibodies targeting other viruses, which can sometimes lead to false-positive test results.
The team is working to make the technology useful for point-of-care diagnostics and develop it into a compact handheld system that can be used in the clinic or in resource-limited areas. It could also be used in agricultural settings for livestock disease surveillance and environmental sensing.