Fig. 4.

Electrochemical SARS-CoV-2 aptasensor: (a) Differential pulse voltammogram (DPV) of aptamer modified electrode using ferrocenemethanol (1 mM in 0.1 M PBS, pH 7.4) as a redox meditor. Initial signal (black) and after addition 50 nM RBD for 10 min (grey line), washing and recording a new DPV in ferrocenemethanol. The decrease in current is due to RBD binding to the aptamer. DPV conditions: t_aquis = 3s, E_step = 0.01V, E_pulse = 0.06 V, t_pulse = 0.02 V, scan rate = 0.06 V s⁻¹. (b) Current response to increasing RBD concentrations using ferrocenemethanol (1 mM PBS, pH 7.4) as a redox probe. (c) Langmuir adsorption isotherm as extracted from Fig. 4b. (d) Dose-dependent response curve toward SARS-CoV-2 virus clade 20A.EU2 (black) as well as clade 20I/501Y.V1, “British variant” (green) and the clade 20H/501Y.V2, “South African variant” (blue) on aptamer-modified electrodes. (e) Selectivity of the aptamer sensors towards other real patient virus samples by comparison to SARS-CoV-2 positive samples. All the virus samples have Ct values between 22–25 and are nasal swab samples. All the values are displayed as means ± SEM (n = 5). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)