Researchers at Hokkaido University in Japan have developed a microfluidic test that can detect antibodies against a viral infection. So far, the test has been optimized to detect avian flu, but could be adapted to detect antibodies against the virus causing COVID-19. The device can provide a result in as little as 20 minutes and requires only 2 microliters of serum to run.

Antibody tests have been proposed as a way to determine how many people have been exposed to COVID-19, and may help us to understand how far the virus has spread. Given that many infected people are asymptomatic, they may never be recorded as infected, limiting our knowledge of infection levels and hampering the response to the pandemic.

However, testing random samples of people using antibody tests could help researchers to gain more knowledge in the fight against COVID-19. Such tests may also potentially be useful in determining who may have immunity against the virus, although it is not yet clear if the presence of antibodies against the virus causing COVID-19 indicates effective immunity.

Existing techniques to assess if an antibody is in the blood often rely on a visual assessment to determine whether a result is positive. This means that the accuracy is limited, as interpreting results is subject to human error. To address this, these researchers have developed a new type of microfluidic test, which is based on binding a fluorescently labelled protein to the antibody of interest in a serum sample.

The technique involves detecting the fluorescence polarization of the bound fluorescent molecules, and liquid crystal molecules are used to control the direction of this polarization. Once the sample is within the microfluidic device, it is then attached to a portable fluorescence polarization analyzer, weighing only 5.5 kg, which can measure the fluorescence signal and indicate if the antibody is present in the sample.

The researchers mix the serum sample with the fluorescent reagent and then allow it to rest for 15 minutes before loading it into the microfluidic device. They then attach the microfluidic device to the portable fluorescence polarization analyzer to obtain a reading. The entire process takes only 20 minutes, and such devices could help to speed up and streamline community testing for antibodies related to COVID-19, and allow for testing outside of medical labs.

“Our analyzer could be used to conduct other bio tests if suitable reagents are developed,” said Manabu Tokeshi, a researcher involved in the study. “By reproducing fragments of spike proteins expressed in the novel coronavirus, and using them as the reagent, the analyzer should be able to detect anti-coronavirus antibodies.”

Study in Sensors and Actuators B: Chemical: Rapid detection of anti-H5 avian influenza virus antibody by fluorescence polarization immunoassay using a portable fluorescence polarization analyzer

Via: Hokkaido University