Fig. 5.

a Schematic representations of some engineered antibody fragments and their respective height dimension. b Influence of the COVID-19 surface ligand on the current of DPVs recorded on cysteine-modified gold electrodes (2 mM, 2 h) followed by covalent linkage of 10 μg mL⁻¹ VHH-72 (green), VHH-72-Fc (blue), or COVID-19 anti-spike IgG (Abcam, ab273074) via EDC/NHS coupling chemistry (15 mM/15 mM, 1 × PBS, 2 h): mediator: ferrocenemethanol (1 mM in 0.1 M PBS, pH 7.4). DPV parameters: E_step = 0.01 V, E_pulse = 0.06 V, t = 0.02 s, scan rate = 0.06 V/s. c Dose-dependent response curve toward SARS-CoV-2-cultured virus. d Concept of the distinction of infection state based on current difference. e DPVs acquired on VHH-72-modified electrodes before (black) and after immersion into nasal swab samples of PCR-categorized COVID-19-positive (red) or COVID-19-negative (green) patient samples. f Results of the preclinical trial on 25 PCR-categorized positive and 25 PCR-categorized negative patient samples [45]