An Electrochemical Immunosensor Based on Carboxylated Graphene/SPCE for IgG-SARS-CoV-2 Nucleocapsid Determination

Abstract

The COVID-19 pandemic has emphasized the importance and urgent need for rapid and accurate diagnostic tests for detecting and screening this infection. Our proposal was to develop a biosensor based on an ELISA immunoassay for monitoring antibodies against SARS-CoV-2 in human serum samples. The nucleocapsid protein (N protein) from SARS-CoV-2 was employed as a specific receptor for the detection of SARS-CoV-2 nucleocapsid immunoglobulin G. N protein was immobilized on the surface of a screen-printed carbon electrode (SPCE) modified with carboxylated graphene (CG). The percentage of IgG-SARS-CoV-2 nucleocapsid present was quantified using a secondary antibody labeled with horseradish peroxidase (HRP) (anti-IgG-HRP) catalyzed using 3,3′,5,5′-tetramethylbenzidine (TMB) mediator by chronoamperometry. A linear response was obtained in the range of 1:1000–1:200 v/v in phosphate buffer solution (PBS), and the detection limit calculated was 1:4947 v/v. The chronoamperometric method showed electrical signals directly proportional to antibody concentrations due to antigen-antibody (Ag-Ab) specific and stable binding reaction.

Carboxylated graphene: A novel approach for enhanced IgA-SARS-CoV-2 electrochemical biosensing

“…These results were reported in the work published by Freire et al, [17]. concentration, what could be a consequence of the electrode passivation related to TMB precipitation [17], [31], [32]. The calibration curve was plotted using absolute values of stable current recorded at 20s against % human serum with IgG-SARS-CoV-2, and the performance was evaluated at 1:1000; 1:800; 1:600; 1:400; 1:200 v/v dilution factor.…”

“…These results were reported in the work published by Freire et al, [17]. concentration, what could be a consequence of the electrode passivation related to TMB precipitation [17], [31], [32].…”

“…Although graphene can be used to improve the electrical conductivity of composite materials, it also causes very high capacitive currents from SPEs (> 1 µA). To minimize these effects, a potential must be fixed during electrochemical measurements, and the capacitive current contribution is minimized, therefore, the analytical detection in biosensors suggested for SPCE modified with this material is chronoamperometry [28], [29] The EIS analysis (Figure 6 B) showed changes in resistance charge transfer represented in the Nyquist plot. The Nyquist diagrams can be simulated with an equivalent circuit (Figure 6 D), where RS is the resistance of the electrolyte solution, CPE is the constant phase element, Rct is the electron-transfer resistance, and ZW is the Warburg element due to diffusion of the redox couple ([Fe(CN)6] 4-/[Fe(CN)6] 3-) to the interface from the bulk interface from the bulk of the electrolyte.…”

Cost‐Effective Cholesterol Monitoring by Enzyme‐Based Electrochemical Assay

“…1B‐b). A possible reason for this phenomenon could be that the molecules’ insulating properties hinder the transfer of electrons from the substrate to the redox couple at the electrolyte interface similarly as reported by Freire et al [33] . As shown in Fig.…”

“…1B-b). A possible reason for this phenomenon could be that the molecules' insulating properties hinder the transfer of electrons from the substrate to the redox couple at the electrolyte interface similarly as reported by Freire et al [33] As shown in Fig. 1B-c, when the ChOx immobilized onto the surface of the electrode, the redox peaks decreased due to the redox active sites are deeply embedded in the ChOx enzyme macromolecular structure, which results in low response to the [Fe(CN) 6 ] 3À /4À solution.…”