New gadget identifies COVID-19 antibodies in five minutes

Rapid, cost-effective, and accurate tests are still needed to monitor the epidemic and health care services to monitor and contain the spread of SARS-CoV-2. Brazilian researchers contributed to this field’s efforts by developing an electrochemical immunosensor that identifies antibodies against the virus.

The innovation is described in an article published in the journal ACS Biomaterials Science and Engineering.

In search of a novel diagnostic method, the team chose a material often used in metals – zinc oxide – and combined it for the first time with fluorine-doped tin oxide (FTO) glass, a portable material used in photovoltaics and other electrodes. advanced applications.

“With this unusual combination and the addition of a biomolecule, a viral spike protein, we create an area capable of recognizing antibodies against SARS-CoV-2. The result is shown as an electrochemical signal captured by this area,” said chemist Wendel Alves. , lead author of the article. Alves is a professor at the Center for Natural and Human Sciences, Federal University of ABC (UFABC), in the state of Sao Paulo.

The electrode developed by the researchers detected the antibodies of COVID-19 in the serum in about five minutes with a sensitivity of 88.7% and a specificity of 100%, even surpassing the enzyme-linked immunosorbent assay (ELISA), which is the current gold standard clinical diagnostic tool .

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The research was supported by FAPESP through the National Science and Technology Institute for Bioanalysis and Thematic Project.

According to Alves, who heads UFABC’s Electrochemistry and Nanostructured Materials Laboratory, prior knowledge of chemical properties such as the isoelectric point of the virus’s spike protein (S), enabled the group to develop a platform for S to bind electrostatically to zinc oxide nanorods. Zinc oxide is increasingly used to make biosensors because of its flexibility and unique chemical, physical and electrical properties.

Principle of Operation of the Immunosensor

How to directly connect an electronic device to a biological environment is challenging due to the inherent complexity of biosensor development. Nanomaterials enable the miniaturization of devices, improving their sensitivity due to their high surface area and long-range electron conductivity.

(72,73) ZnONRs create an ideal surface for the adsorption of biomolecules, maintaining their activity and converting biological events into a stable, selective, and sensitive measurable signal.

SARS-CoV-2 recombinant trimeric spike protein was the biomolecule that was used to develop an electrochemical biosensing platform for anti-spike antibodies as the S protein is the most antigenic target of all structural proteins of SARS-CoV-2. 2. (74) When working at physiological pH (7.4), the IEP of S protein (∼5) has a negative surface charge, and the ZnONR matrix with a high isoelectric point (∼9.5) assumes a positive charge density in the net.

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Therefore, the negatively charged protein can be immobilized by electrostatic interactions on the surface of the positively charged ZnONR matrix. This principle has been widely used in the development of many immunosensors.

Analysis and future use

A total of 107 blood serum samples were analyzed. They were divided into four groups: pre-pandemic (15), COVID-19 convalescents (47), vaccinated without previous positive results of the disease (25), and vaccinated after a positive result (20). The vaccine was two doses of CoronaVac given four weeks apart. CoronaVac is produced by the Chinese company SinoVac in collaboration with the Butantan Institute (Sao Paulo state).

The authors of this article – researchers affiliated with the UFABC and the Heart Institute (INCOR), run by the University of Sao Paulo’s Medical School (FM-USP) – note that the device detects antibodies produced in response to both viral infections. and vaccination, and shows great potential as a tool for monitoring seroconversion and seroprevalence. Finding vaccine response is important to help public health authorities evaluate the effectiveness of different vaccines and vaccination campaigns or programs, they emphasize.

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The device has been validated to detect immunity induced by CoronaVac, but the team plans to expand its use to testing the response to Pfizer and AstraZeneca vaccines.

One of the advantages of the electrode they developed is its flexible design, which means it can be easily adapted to other diagnostic and biomedical applications using different biomolecules on zinc oxide nanorods and other target analytes.

“The technology is a flexible biosensing platform. As it was developed by us, it can be adapted and customized for the serological detection of other diseases of public health interest,” said Alves.

Electrochemical Response Studies of ZnONRs/Spike Immunosensor

EIS, CV, and SWV were used to characterize the electrode at each manufacturing stage (Figure 4). It shows the redox Faradic impedance spectra of [Fe(CN)6]3–/4– is measured at each stage of production. The perceived impedance component (Z″) is shown as a function of the real impedance component (Z′), as shown in Figure 4A.

*with comments from ANI

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