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In this article, we report the development of an electrochemical biosensor for the determination of the SARS-CoV-2 spike protein (rS). A gold disc electrode was electrochemically modified to form the nanocrystalline gold structure on the surface. Then, it was further altered by a self-assembling monolayer based on a mixture of two alkane thiols: 11-mercaptoundecanoic acid (11-MUA) and 6-mercapto-1-hexanol (6-MCOH) (SAMmix). After activating carboxyl groups using a N-(3-dimethylaminopropyl)-N'-ethyl-carbodiimide hydrochloride and N-hydroxysuccinimide mixture, the rS protein was covalently immobilized on the top of the SAMmix. This electrode was used to design an electrochemical sensor suitable for determining antibodies against the SARS-CoV-2 rS protein (anti-rS). We assessed the association between the immobilized rS protein and the anti-rS antibody present in the blood serum of a SARS-CoV-2 infected person using three electrochemical methods: cyclic voltammetry, differential pulse voltammetry, and potential pulsed amperometry. The results demonstrated that differential pulse voltammetry and potential pulsed amperometry measurements displayed similar sensitivity. In contrast, the measurements performed by cyclic voltammetry suggest that this method is the most sensitive out of the three methods applied in this research. [ABSTRACT FROM AUTHOR]

By the electrochemical protective efficiency of conversion coatings on an AZ31 alloy, it is shown that the corrosion stability of AZ31 alloy depends on the activating solution treated with magnetic field. Scanning electron microscopic studies demonstrate that the surface morphology of conversion coatings is identical irrespective of the magnetic field treatment. The cross-section composition of conversion coatings is determined by x-ray photoelectron spectroscopy (XPS). XPS data demonstrate that a conversion coating treated with magnetic field is thicker than coatings nonsubjected to this treatment. It is also shown that a conversion coating of AZ31 alloy mainly consists of oxides and hydroxides, namely, MgO, Mg(OH)2, MgF2 and γAl2O3, MgAl2O4. However, when magnetic field is applied, the aluminum concentration increases from 0.73 to 6.65 at. %, and the fluorine concentration decreases from 12.06 to 8.11 at. %. [ABSTRACT FROM AUTHOR]

The serologic diagnosis of coronavirus disease 2019 (COVID-19) and the evaluation of vaccination effectiveness are identified by the presence of antibodies specific to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this paper, we present the electrochemical-based biosensing technique for the detection of antibodies specific to the SARS-CoV-2 proteins. Recombinant SARS-CoV-2 spike proteins (rSpike) were immobilised on the surface of a gold electrode modified by a self-assembled monolayer (SAM). This modified electrode was used as a sensitive element for the detection of polyclonal mouse antibodies against the rSpike (anti-rSpike). Electrochemical impedance spectroscopy (EIS) was used to observe the formation of immunocomplexes while cyclic voltammetry (CV) was used for additional analysis of the surface modifications. It was revealed that the impedimetric method and the elaborate experimental conditions are appropriate for the further development of electrochemical biosensors for the serological diagnosis of COVID-19 and/or the confirmation of successful vaccination against SARS-CoV-2. [ABSTRACT FROM AUTHOR]