Microneedles for coronavirus
A sensor with microneedles will detect antibodies to the coronavirus without taking blood
Elina Stoyanova, PCR.news
Currently, immunochromatographic test strips are used to quickly determine antibodies to SARS-CoV-2. To perform the analysis, the patient must take a drop of blood from his finger. However, the puncture can be painful, in addition, there is a risk of infection.
Researchers from Japan have proposed an antibody test for coronavirus that does not require blood sampling. They have developed a sensor with porous microneedles that attaches to the skin and detects IgM and IgG immunoglobulins in the intercellular fluid. Previously, it was shown that the level of antibodies in the intercellular fluid is 15-25% of their levels in the blood. The concentration of antibodies should be equal to 1-6.4 micrograms /ml — such quantities are sufficient for detection.
Microneedles were made from a biodegradable polymer polylactide using a special technology. The structure and size of microneedles allow them to penetrate into the upper layers of the epidermis and dermis without stimulating nerve endings, which makes the process painless. The sensor size is 1.5×3.5 cm. Porous microneedles, due to the capillary effect, ensure the flow of intercellular fluid to the immunochromatographic sensor.
The sample first reaches the conjugation zone, which contains colloidal gold particles crosslinked with the receptor-binding domain of the SARS-CoV-2 S-protein. It then passes through lines carrying monoclonal mouse antibodies to human IgM and IgG. The test results are recorded visually.
The sensor is attached to the forearm. A section of skin without hair is selected so that the microneedles penetrate the skin more easily. The cellulose base made it possible to make the sensor flexible enough so that it could repeat the irregularities of the skin.
The strength of microneedles and their ability to extract intercellular fluid without damaging the surface capillaries of the skin were confirmed on pig skin, live rats, as well as on in vitro models of mouse skin. The diagnostic effectiveness of the biosensor was tested in vitro. The detection limit of the device is 3 ng/ml and 7 ng/ml for IgM and IgG, respectively.
The authors believe that the new biosensor will quickly and painlessly determine the presence of antibodies to the coronavirus, and its small size will make it a convenient tool for serological screening for COVID-19. Clinical validation of the biosensor in comparison with PCR testing is planned.
Bao et al. Anti-SARS-CoV-2 IgM/IgG antibodies detection using a patch sensor containing porous microneedles and a paper-based immunoassay is published in the journal Scientific Reports.
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