Fig. 2.

Fabrication and characterization of the electrochemical immunosensor. (a) A photograph of the screen-printed three-electrode immunosensor loaded with sample solution in the reaction zone. The reaction zone is defined by a wax-printed cycle and a thin PDMS line barrier printed at the “tail” of the electrode. (b) Cyclic voltammetry (CV) measurements, conducted at scan rates of 50 mV/s, 100 mV/s, 150 mV/s, 200 mV/s, and 300 mV/s. (c) The peak-peak current of the CV curve versus the square root of the scan rate (n = 5). (d) The oxidation current-voltage signals measured from two electrochemical immunosensors loaded with the electrochemical substrate pAPP and a mixture of pAPP and ALP-conjugated detection antibody, respectively, both with a hydrodynamic linear sweeping voltage in the range of −0.4 V and 0.4 V with a scanning speed of 100 mV/s.