Antibody-Based Method Detects SARS-CoV-2 Without Blood Sample

A key challenge in limiting the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is identifying infected individuals. The ineffective identification of SARS-CoV-2-infected individuals has severely limited the global response to the COVID-19 pandemic, and the high rate of asymptomatic infections (16-38%) has exacerbated this situation. The predominant detection method to date collects samples by swabbing the nose and throat. However, the application of this method is limited by its long detection time (4-6 hours), high cost, and requirement for specialized equipment and medical personnel, particularly in resource-limited countries. Now, investigators have developed a new antibody-based method for the rapid and reliable detection of SARS-CoV-2 that does not require a blood sample.

An alternative and complementary method for the confirmation of COVID-19 infection involves the detection of SARS-CoV-2-specific antibodies. Testing strips based on gold nanoparticles are currently in widespread use for point-of-care testing in many countries. They produce sensitive and reliable results within 10-20 minutes, but they require blood samples collected via a finger prick using a lancing device. This is painful and increases the risk of infection or cross-contamination, and the used kit components present a potential biohazard risk. In order to avoid these drawbacks, researchers at the Institute of Industrial Science at the University of Tokyo (Tokyo, Japan) explored the idea of sampling and testing the interstitial fluid (ISF), which is located in the epidermis and dermis layers of human skin.

"To develop a minimally invasive detection assay that would avoid these drawbacks, we explored the idea of sampling and testing the interstitial fluid (ISF), which is located in the epidermis and dermis layers of human skin," explained Leilei Bao, lead author of the study. "Although the antibody levels in the ISF are approximately 15-25% of those in blood, it was still feasible that anti-SARS-CoV-2 IgM/IgG antibodies could be detected and that ISF could act as a direct substitute for blood sampling."

After demonstrating that ISF could be suitable for antibody detection, the researchers developed an innovative approach to both sample and test the ISF. "First, we developed biodegradable porous microneedles made of polylactic acid that draws up the ISF from human skin," said Beomjoon Kim, senior author of the study. "Then, we constructed a paper-based immunoassay biosensor for the detection of SARS-CoV-2-specific antibodies." By integrating these two elements, the researchers created a compact patch capable of on-site detection of the antibodies within three minutes (result from in vitro tests).

The novel detection device has great potential for the rapid screening of COVID-19 and many other infectious diseases that is safe and acceptable to patients. It holds promise for use in many countries regardless of their wealth, which is a key aim for the global management of infectious disease.

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