Due to the SARS-CoV-2 pandemic, there has been an increase in the search for affordable healthcare devices for mass testing and rapid diagnosis. In this context, this work described a new methodology for SARS-CoV-2 detection based on an impedimetric immunosensor developed using the advantageous immobilization of antibodies in the reduced graphene oxide (rGO). The rGO was obtained by chemical synthesis from the commercial graphene oxide (GO), and the materials were morphologically, electrochemically and visually characterized. The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were used to evaluate the fabrication steps of the immunosensor. The electrochemical immunoassay was considered for SARS-CoV-2 spike protein RBD detection using a impedimetric immunosensor and redox couple ([(Fe(CN)₆)]^3−/4−) as a probe. The immunosensor was effectively developed and applied in the detection of SARS-CoV-2 spike protein RBD in saliva samples.

A simple, cheap, and less aggressive immobilization procedure for biomolecules using reduced graphene oxide (rGO) was employed to prepare an impedimetric immunosensor for detection of staphylococcal enterotoxin A (SEA) from Staphylococcus aureus in milk samples. The scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS) were used to monitor the single steps of the electrode assembly process. The glassy carbon (GC)/rGO platform detected the antigen-antibody binding procedures of SEA with concentrations of 0.5 to 3.5 mg L⁻¹ via impedance changes in a low frequency range. The impedimetric immunosensor was successfully applied for the determination of SEA in milk samples.