Fig. 3: Analytical performance in presence of αvβ6.

a Optimization of the probe length to be immobilized onto the strip. For each experiment each probe at 100 nM concentration has been immobilized onto the strip; the impedimetric measurements have been carried out in presence of 5 ng/mL αvβ6. b Nyquist plots for the nanoengineered biosensor 3 challenged in absence (black dots) and in presence of different concentration of αvβ6, i.e., 1 (cyan dots), 2 (gray dots), 4 (orange dots), 5 (red dots), 10 (green dots) and 20 ng/mL (blue dots). The measurements were carried out as follows: the nanoengineered biosensor was covered with a solution containing the chosen level of αvβ6. After 30 min at room temperature, the biosensors were washed with phosphate buffer, and then covered with a solution containing 1 mM [Fe(CN)₆]^3−/4− dissolved in 0.1 M KCl. A potential of 0.2 V and a AC amplitude of 10 mV in a frequency range of 100 kHz to 0.1 Hz have been utilized. The X and Y axes represent, respectively, the real and imaginary components of impedance. The inset i shows the Randles equivalent electrical circuit that has been used to fit the spectra, comprising the electrolyte resistance, Re, in series with a parallel combination of Rct (charge transfer resistance), Zw (diffusion of the analytes in solution and corresponding to Warburg impedance straight line of the curves) and CPE (Constant Phase Element). c Linear range comprised between 1 and 20 ng/mL αvβ6. Inset shows the complete semi-log correlation in a wider range of αvβ6 concentrations, namely 0.01–50 ng/mL.