Fig. 5.

Electrochemical detection. A) Schematic representation of the surface of a gold electrode functionalized with C7 aptamer by a sulfur-gold binding through thiol groups at the 5′-end (5′-thio-C7). The formation of the aptamer-S protein complex changes the aptamer conformation resulting in modification of the electrochemical signal, shortening the charge transfer distance of the redox molecules and thereby increasing the current as the concentration of the protein increases (inlet). B) Current signal I(Ipeak-I₀)/I₀I (%) of the differential potential voltammetry response versus increasing analyte concentration (1 fg/mL – 100 ng/mL). Inlet: same relation but in a semi-log representation. A linear fit was calculated over the linear dynamic detection range (Data points) by excluding the data points in saturation region (Excluded). The selectivity is demonstrated by the sensor signals obtained for Glycoprotein G of the RSV, the Hemagglutinin protein of the influenza (H1N1) virus, and the S protein of the MERS-CoV virus.