(A) Nyquist plots for (i) bare and modified electrodes for detecting (ii) bio BSA/streptavidin, (iii) bio BSA/streptavidin/bio anti-HA, (iv) bio BSA/streptavidin/bio anti-HA/yeast-scFv, and (v) bio BSA/streptavidin/bio anti-HA/yeast-scFv/โ350โ complex in 10 mM phosphate buffer solution (pH 7.4) containing 2.5 mM K3[Fe(CN)6], 2.5 mM K4[Fe(CN)6]ยท3H2O, and 0.1 M KCl. (B) Corresponding DPV responses.