Scientists develop low-cost chips to detect the presence and quantity of COVID-19 antibodies

Robust and extensive antibody testing is emerging as an important strategy in the fight against SARS-CoV-2, the virus responsible for the COVID-19 pandemic. However, current test methods are inaccurate or too expensive to run on a global scale. But now scientists at Okinawa Institute of Science and Technology (OIST) are developing rapid, reliable, and low-cost antibody tests.

of TerminalExplained in a proof-of-concept study published this week Biosensors and bioelectronics, Using portable lab on-chip technology, antibody Present diluted plasma..

Antibodies are proteins produced by the immune system to neutralize viruses. Studies have shown that the COVID-19 antibody is present late in the infection and remains in the blood after the infection is cleared, identifying previously infected individuals. Therefore, antibody testing is an important tool for determining the total spread of coronaviruses, and important information as a guide to public health policy.

Even so, many countries have so far failed to employ large-scale antibody tests.

“Many of the existing platforms for antibody testing are accurate and reliable, but they are expensive and require a trained operator to perform them in the lab, which means hours or even hours to get results. It could take a few days,” said Dr. Ricardo. Funari, first author and post-doctoral researcher of OIST’s Micro / Bio / Nanofluidics Unit. “Other tests are easy to use, portable and quick, but not accurate enough, which hinders testing efforts.”

Researchers have circumvented this tradeoff between accuracy and accessibility by developing an alternative antibody testing platform that combines powerful optical sensing technology with a microfluidic chip. The chip provides results in less than 30 minutes, is extremely sensitive and detects even the lowest clinically relevant antibody concentrations. Each chip is inexpensive to manufacture, eliminating the need for laboratories and trained operators and increasing the feasibility of national testing.

This newly developed platform also has another distinct advantage. ” test It not only detects the presence or absence of antibodies, but also provides information about the amount of antibodies produced by the immune system. In other words, it’s quantitative,” said Professor Amy Shen, who heads the Micro/Bio/Nanofluidics Unit. “This will greatly expand the potential applications of COVID-19, from treatment to use in vaccine development.”

Illuminate the antibody

The antibody testing platform is Microfluidic chip It is integrated with a fiber optic light probe. The chip itself is made from a glass slide covered with gold with embedded microfluidic channels. The team used voltage to build tens of thousands of small, spike-like gold structures on glass slides that were smaller than the wavelength of light.

Next, researchers modified these gold nanospikes by attaching fragments of the SARS-CoV-2 spike protein. This protein is important for helping coronaviruses infect cells and causes a strong reaction from the infected person’s immune system.

In this proof-of-concept study, scientists used artificial human plasma samples spiked with COVID-19 antibodies specific for spike proteins to show the principles behind how the test detects antibodies.

The sample is aspirated from the tip using a syringe pump. As plasma passes through the protein-coated gold nanospike, the antibody binds to the spike protein fragment. This binding event is detected by a fiber optic optical probe.

“The detection principle is simple but powerful,” said Funari. He explained that it was based on the unique behavior of electrons on the surface of gold nanospikes. These resonant electrons are very sensitive to changes in the environment, such as antibody binding, which shifts the wavelength of light absorbed by the nanospikes.

“The more antibody that binds, the greater the change in the wavelength of the light that is absorbed,” Dr. Funari added. “The fiber optic probe is connected to a photodetector that measures this shift, and that information can be used to determine the antibody concentration in plasma samples.”

bright future

Large scale deployments of quantitative tests can have a significant impact on how COVID-19 is processed.

For example, quantitative tests help doctors track how effectively a patient’s immune system fights the virus. It can also be used to identify suitable donors for a promising treatment called plasma transfusion therapy. In plasma transfusion therapy, the recovered patient’s antibody-rich blood is donated to currently infected patients to help fight the virus.

Being able to measure the level of the immune response also helps in the development of vaccines and allows researchers to determine how effectively a test vaccine induces the immune system.

However, researchers emphasized that the device is still under active development. The unit aims to reduce chip size and reduce manufacturing costs and is also committed to improving test reliability.

“We showed that this device works to detect different concentrations of spiked protein antibodies in artificial human plasma samples. Now we want to extend the test to allow the chip to detect multiple different antibodies simultaneously. I think,” said Dr. Funari. “Once the device is optimized, we will work with local hospitals and health care providers to test real patient samples.”