To monitor and restrict the spread of SARS-CoV-2, epidemiological monitoring and healthcare services still require rapid, low-cost, and reliable diagnostics. Brazilian researchers have helped to the work in this sector by developing an electrochemical immunosensor that detects antibodies against the virus.
An publication in the journal ACS Biomaterials Science and Engineering describes the breakthrough. In quest of an unique diagnostic approach, the researchers chose zinc oxide, a common metallurgical substance, and coupled it for the first time with fluorine-doped tin oxide (FTO) glass, a conductive material used in solar electrodes and other advanced 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,” said 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 researchers’ electrode identified COVID-19 antibodies in serum in around five minutes with 88.7% sensitivity and 100% specificity, exceeding even the current gold-standard clinical diagnostic technique, the enzyme-linked immunosorbent assay (ELISA).
FAPESP funded the study through the National Science and Technology Institute for Bioanalysis and a Thematic Project. Prior understanding of chemical features such as the isoelectric point of the virus’s spike protein (S), according to Alves, who heads UFABC’s Electrochemistry and Nanostructured Materials Laboratory, enabled the researchers to design a platform for S to bond electrostatically to zinc oxide nanorods. Because of its flexibility and unique chemical, optical, and electrical characteristics, zinc oxide is increasingly being employed to manufacture biosensors.
The immunosensor is simple to build and operate, and it has a cheap production cost. “The group was able to construct the gadget due to its deep expertise of new materials and zinc oxide nanorod fabrication,” Alves explained.
The nanorods create a coating on the conductive surface of the FTO, establishing a suitable molecular milieu for S protein immobilisation and making the construct an easy approach to detect these antibodies.
The platform will now be modified to be portable and connectable to mobile devices for use in detecting COVID-19 and other infectious disorders, according to the researchers.
Analysis and potential applications
In all, 107 blood serum samples were examined. They were separated into four groups: pre-pandemic (15), COVID-19 convalescents (47), vaccinated without prior positive disease findings (25), and vaccinated after a positive result (20). CoronaVac was provided in two doses four weeks apart. CoronaVac is manufactured by the Chinese business SinoVac in collaboration with the Butantan Institute (Sao Paulo state).
The article’s authors, who are affiliated with UFABC and the Heart Institute (INCOR) at the University of Sao Paulo’s Medical School (FM-USP), note that the device detects antibodies produced in response to both virus infection and vaccination, and that it has excellent potential as a tool for monitoring seroconversion and seroprevalence.
Detecting vaccination responses is critical for public health officials to analyse the performance of various vaccinations as well as immunisation campaigns or programmes, they emphasise.
The technology has been verified for detecting immunity caused by CoronaVac, but the researchers want to use it to test for responses to Pfizer and AstraZeneca vaccines as well.
One of the electrode’s benefits is its flexible design, which allows it to be readily adapted for additional diagnostic and biomedical applications employing other biomolecules on the zinc oxide nanorods and other target 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