Figure 1.

Flow-through measurement chamber and measurement principle. (a) Flow-through measurement chamber with liquid inlet and outlet (arrows) and a 3-electrode setup including a golden working electrode (Au), a platinum counter electrode (Pt) and a reference electrode (Ref); (b) Working electrode modified with aptamer (violet) and 6-mercapto-1-hexanol (MCH) in a buffer containing the redox probe ferri-/ferrocyanide (red stars); (c) Upon binding of protein A (green) on the surface of S. aureus (yellow) to the immobilized aptamer (violet), the impedance increased due to the hindrance of electron transfer (curved arrow) between ferri-/ferrocyanide (red stars) in solution and gold electrode surface (orange); (d) Characteristic Nyquist-plot of impedance spectra before and after incubation with S. aureus (based on data from measurements); Z’: real part of impedance and Z’’: imaginary part of impedance.