Researchers from the Okinawa Institute of Science and Tech Graduate University (OIST) created a rapid, reliable and low-cost COVID-19 antibody test. A robust and widespread antibody test is key to fighting COVID. Current antibody testing is too inaccurate and too expensive to be widely used.

The new device uses a portable lab on a chip technology to accurately measure the concentration of antibodies present in diluted blood plasma. Antibodies are proteins produced by the immune system to neutralize a virus. COVID-19 antibodies are present in the body in later stages of infection and can linger in the blood after an infection has cleared, which allows individuals that had the virus to be identified.

Antibody tests are important to understand the full spread of COVID-19. Many countries have failed to employ large scale antibody testing. Existing antibody tests are accurate and reliable, but expensive and time-consuming. There are other tests that are easy to use, fast and portable, but they are not completely accurate. Accuracy is the most important factor in antibody testing.

The antibody testing platform, developed by researchers from the Micro/Bio/Nanofluidics Unit at OIST. Source: OISTThe antibody testing platform, developed by researchers from the Micro/Bio/Nanofluidics Unit at OIST. Source: OIST

The team created an alternative antibody testing platform that combines light-sensing technology with a microfluidic chip which gathers results in 30 minutes. The chip is can detect the lowest clinically relevant antibody concentration. It is inexpensive to manufacture and doesn't need lab operators. This test can be used for nationwide testing.

The testing platform is made of a microfluidic chip integrated with a fiber-optic light probe. The chip is has a gold-covered glass slide with an embedded microfluidic channel. An electric voltage is used to fabricate tens of thousands of tiny spiky gold structures on a glass slide. The gold spikes are modified by attaching a fragment of COVID-19 spike protein.

The team demonstrated the test using artificial human plasma sample spiked with COVID-19 antibodies. The sample was drawn through the chip with a syringe pump. As plasma flows past the protein-coated nano spikes, antibodies bind to the spike protein fragments. The binding was detected by a fiber-optic light probe.

The detection principle is based on the unique behavior of electrons on the surface of the nano spikes. The nano spikes oscillate together when hit by light. Resonating electronics are highly sensitive to changes, which causes a shift in the wavelength of light absorbed by nanospikes. The more antibodies that bind, the larger the shift in wavelength of absorbed light will be. A fiber-optic probe connected to the light detector measures the shift and determines the concentration of antibodies.

The device is still in the development phase. The team aims to reduce the chip size to cut manufacturing cost and improving overall reliability.

A paper on this technology was published in Biosensors and Bioelectronics.