Fig. 4.

Electrochemical antigenic COVID-19 sensors: a magnetic bead–based electrochemical immunosensors for S1 protein detection: change in DPV signal upon viral binding together with selectivity test (reprinted with permission from ref. [13]). b Electrochemical biosensors, eCoVSense, using glass slides coated with fluorine-doped tin oxide and modified with Au NPs serving for COVID-19 antibody conjugation by physisorption or electrostatic interactions; the same was performed on screen-printed carbon electrodes where antibodies were immobilized [36]. c Reagent-less sensing of COVID-19 viral particles based on the change in hydrodynamic diameter in the presence of the spike protein of the viral particle. Sensor architecture based on antibodies tethered to a stranded DNA bearing a ferrocene moiety. Application of a positive potential attracts the negatively charged DNA strand to the surface. Experimental time-dependent current transitions in the presence of the SARS-CoV-2 viral S1 protein (1 n mL⁻¹) and viral particles (10⁷ mL⁻¹) [37])