This new device detects anti-Covid antibodies in 5 minutes

With the onset of a new wave of Covid-19 in France, it is more necessary than ever to have effective serological tests. In France alone, nearly 70,000 new cases were diagnosed on Thursday 1is December 2022. A new very fast and cheap test has just been developed.

Effective serological screening is essential to control the epidemic and limit its spread. The evaluation of the level of anti-covid-19 antibodies in the serum of individuals allows to follow the disease. It is also very useful in evaluating screening campaigns to determine the population protection rate. It is in this context that a Brazilian team has just published the results of its serum antibody detection test against SARS-CoV-2 in the journal ACS Science and engineering of biomaterials.

An electrochemical method

The method is based on the use of an impedance-type electrochemical biosensor. The S protein of SARS-CoV-2 is immobilized on tin oxide substrates, doped with fluorine and modified by zinc oxide nanotubes, in turn associated with an electrode. Protein S acts as a bioreceptor: it is fixed on the support by physical adsorption, due to electrostatic interactions. This sensor is then placed in the presence of serum containing or not anti-SARS-CoV-2 antibodies. These have an affinity for protein S and will bind to it. This biological phenomenon is detected by the biosensor and displayed in the form of an electrochemical signal.

A sensitive and specific test

The method was tested using serum samples:

  • patients recovering from Covid-19 (n=47);
  • patients vaccinated with Sinovac’s CoronaVac vaccine after testing positive (n=20) or after testing negative for SARS-CoV-2 (n=25);
  • controls collected from healthy volunteers before the onset of the pandemic (n=15).
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For information, Sinovac’s CoronaVac vaccine is a Chinese-origin Covid-19 vaccine that has been validated by WHO. To evaluate the serum test’s capabilities for detecting SARS-CoV-2 antibodies, the authors used the Elisa reference diagnostic tests. Two tests were performed on each sample: the first to detect the presence or absence of anti-SARS-CoV-2 antibodies, the second to detect the presence or absence of seasonal anti-coronavirus antibodies.

The first test confirmed the sensitivity of the test of interest (88.7%), i.e. its ability to give a positive result in the presence of antibodies. The second Elisa test confirmed the detection specificity (100%) of the authors’ electrochemical test: no cross-reactivity was detected. For the record, the specificity of a test is its ability to give a negative result when there are no antibodies in the patient’s serum.

Moreover, the developed test was able to give a result in less than 5 minutes. It is also cheap, easy to produce and use. Good news in the current epidemic context.

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