Fig. 3.

Calibration for different anti-HRP immobilization strategies; (A) Example showing amperometric peaks with increasing concentrations of HRP using antibodies (Ab) passively adsorbed on bare carbon. Calibration graphs: (B) passively adsorbed Ab on bare electrodes; (C) covalently immobilized Ab on AuNP electrodes; (D) covalently immobilized Ab on rGO electrodes; (E) covalently immobilized on chitosan electrodes; (F) Ab oriented onto protein A passively adsorbed on bare electrodes; (G) Ab oriented onto protein A covalently immobilized on AuNP electrode. Logarithmic fits shown as blue dashed line; arrows indicate saturation points (Error bars = standard deviation, n=8)