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Groundbreaking Electrochemical Immunosensor for Rapid Detection of COVID-19

Fast, economical and precise tests continue to be indispensable for epidemiological investigation and for health services to track and control the escalation of SARS-CoV-2. Brazilian researchers have contributed to the tasks in this domain by creating an electrochemical immunosensor that is capable of detecting antibodies against the virus.

Illustration of the structure of zinc oxide modified with the spike protein and its interaction with antibodies in the sample. The novel method detects COVID-19 antibodies in 5 minutes. Image Credit: Karin Regina Leite de Oliveira/DK design.

The innovative immunosensor has been illustrated in a recently published article in ACS Biomaterials Science and Engineering.

Hunting for a unique diagnostic process, the team selected a material often used in metallurgy—zinc oxide—and integrated it for the first time with fluorine-doped tin oxide (FTO) glass, a conductive material employed in electrodes for photovoltaics and other modern applications.

With this unusual combination and the addition of a biomolecule, the viral spike protein, we developed a surface capable of detecting antibodies against SARS-CoV-2. The result is displayed as an electrochemical signal captured by this surface.

Wendel Alves, Study Lead Author and Professor, Center for Natural and Human Sciences Federal University of ABC

Alves is a chemist and heads the Electrochemistry and Nanostructured Materials Laboratory at UFABC.

The electrode created by the scientists identified COVID-19 antibodies in serum in approximately 5 minutes with 100% specificity and 88.7% sensitivity, outclassing even the enzyme-linked immunosorbent assay (ELISA) test, the prevalent gold-standard medical diagnostic tool.

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

According to Alves, who heads UFABC’s Electrochemistry and Nanostructured Materials Laboratory, prior insight into chemical properties, such as the isoelectric point of the virus’s spike protein (S), allowed the team to create a platform for S to adhere electrostatically to zinc oxide nanorods. Zinc oxide is progressively used to make biosensors due to its versatility and distinctive optical, electrical, and chemical properties.

The immunosensor is simple to create and use, and its production cost is comparatively low.

The group succeeded in developing the device thanks to its strong knowledge of novel materials and zinc oxide nanorod synthesis.

Wendel Alves, Study Lead Author and Professor, Center for Natural and Human Sciences Federal University of ABC

The nanorods develop a film on the FTO’s conductive surface, forming a suitable molecular microenvironment for immobilizing the S protein and making the construct to positively identify these antibodies.

The team will modify the platform to render it portable and connectable to mobile gadgets to identify COVID-19 and other contagious diseases.

Analysis and Future Uses

Nearly 107 blood serum samples were examined. They were separated into four groups: pre-pandemic (15), vaccinated without prior positive outcomes for the disease (25), vaccinated after a positive outcome (20), and COVID-19 convalescents (47).

Two doses of the vaccine CoronaVac were given four weeks apart. CoronaVac is made by SinoVac, a Chinese company in collaboration with Butantan Institute (São Paulo state).

The study authors—scientists affiliated with UFABC and the Heart Institute (INCOR), which is managed by the University of São Paulo’s Medical School (FM-USP)—observe that the device identifies antibodies made in reaction to infection by the virus as well as infection by vaccination, and demonstrates exceptional potential as a tool for tracking seroconversion and seroprevalence.

They emphasize that sensing the response to vaccination is vital to help public health authorities evaluate the efficacy of diverse vaccines and immunization programs or campaigns.

The device has been verified for identifying immunity prompted by CoronaVac, but the team plans to expand its use to testing for the reaction to AstraZeneca’s and Pfizer’s vaccines.

One of the benefits of the electrode they created is its versatile architecture. It can be tailored for other biomedical and diagnostic applications using various biomolecules on the zinc oxide nanorods and other crucial analytes.

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

Journal Reference:

Nunez, F.A., et al. (2022) Electrochemical Immunosensors Based on Zinc Oxide Nanorods for Detection of Antibodies Against SARS-CoV-2 Spike Protein in Convalescent and Vaccinated Individuals. ACS Biomaterials Science and Engineering.

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