Rapid, inexpensive, and accurate testing is still required for epidemiological surveillance and health services to monitor and contain the spread of SARS-CoV-2. Brazilian researchers have contributed to efforts in this area by developing an electrochemical immune sensor that identifies antibodies to 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 group chose a material commonly used in metallurgy – zinc oxide – and combined it for the first time with fluorine-doped tin oxide glass (FTO), a conductive material used, among other things, in electrodes for photovoltaic advanced applications.
“With this unusual combination and the addition of a biomolecule, the viral spike protein, we have developed a surface that can detect antibodies against SARS-CoV-2. The result is displayed as an electrochemical signal captured by this surface,” says chemist Wendel Alves , lead author of the article. Alves is a professor at the Center for Natural and Human Sciences, Federal University of the ABC (UFABC), Sao Paulo State.
The electrode made by the researchers detected COVID-19 antibodies in serum in about five minutes with a sensitivity of 88.7% and a specificity of 100%, even surpassing the enzyme-linked immunosorbent assay (ELISA) test current gold standard tool for clinical diagnosis.
The research was supported by FAPESP through the National Science and Technology Institute for Bioanalysis and a thematic project.
According to Alves, head of the UFABC Laboratory of Electrochemistry and Nanostructured Materials, prior knowledge of chemical properties such as the isoelectric point of virus spike protein (S) enabled the group to develop a platform for S to electrostatically attach to zinc oxide nanorods tie. Zinc oxide is increasingly being used to fabricate biosensors due to its versatility and unique chemical, optical, and electrical properties.
The immune sensor is easy to manufacture and use, and its production cost is relatively low. “The group was able to develop the device thanks to their extensive knowledge of novel materials and the synthesis of zinc oxide nanorods,” said Alves. The nanorods form a film on the conductive surface of the FTO, creating a favorable molecular microenvironment for S-protein immobilization and making the construct an easy way to detect these antibodies.
Researchers will now adapt the platform to be wearable and connectable to mobile devices to be used to diagnose COVID-19 and other infectious diseases.
Analysis and Future Uses
A total of 107 blood serum samples were analyzed. They were divided into four groups: prepandemic (15), COVID-19 convalescents (47), vaccinated without prior positive results for the disease (25), and vaccinated after a positive result (20). The vaccine consisted of two doses of CoronaVac given four weeks apart. CoronaVac is manufactured by the Chinese company SinoVac in cooperation with the Butantan Institute (Sao Paulo state).
The authors of the article – researchers affiliated with UFABC and the Heart Institute (INCOR), operated by the University of Sao Paulo School of Medicine (FM-USP) – note that the device detects antibodies known as Response to both infections produced by the virus and vaccination and shows excellent potential as a tool for monitoring seroconversion and seroprevalence. Recognizing the response to vaccination is important to help public health officials assess the effectiveness of different vaccines and immunization campaigns or programs, they stress.
The device has been validated for detecting CoronaVac-induced immunity, but the group plans to extend its use to testing for response to the Pfizer and AstraZeneca vaccines.
One of the advantages of the electrode they developed is its flexible architecture, which means it can be easily adapted for other diagnostic and biomedical applications by using different biomolecules on the zinc oxide nanorods and other target analytes.
“The technology is a versatile biosensor platform. As developed by us, it can be modified and adapted for serological detection of other diseases of public interest,” said Alves.
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