Fig. 5

A The ECL intensities of the proposed ECL immunosensor incubated with different concentrations of RBP4 (0.0001, 0.001, 0.01, 0.1, 1, 5, 10, 20, 50, 100 ng mL⁻¹); B correlation curve of ECL intensity as a function of RBP4; C calibration curve of the immunosensor; D the stability of the immunosensor for detecting 1 ng mL⁻¹ RBP4; E reproducibility of the immunosensor incubated with 5 ng mL⁻¹ RBP4 in PBS (pH = 8.0), F selectivity of the immunosensor against different interfering substances: AFP (10 ng mL⁻¹), Glu (10 ng mL⁻¹), BSA (10 ng mL⁻¹), FSH (10 ng mL⁻¹), PRL (10 ng mL⁻¹) and 1 ng mL⁻¹ RBP4 with 10 ng mL⁻¹ interfering substances (error bars, SD, n = 3)