Fig. 5

a Chronoamperometric curves for various concentrations of PSA antigen (ascending along the y-axis): 0, 0.001, 0.01, 0.1, 1, and 10 ng/mL in pH 7.4 PBS buffer containing 4.5 mM hydroquinone and 0.1 mM H₂O₂ solution in CASPE-MFD at − 2.0 mV vs silver pseudo-reference electrode. b The linear relationship between peak current and PSA antigen concentration in the CASPE-MFDs in pH 7.4 PBS buffer (blue line) and in human serum (red line). The linear regression equation of the blue line is Y = 14.87 + 3.927 × X (R² = 0.9985, n = 8), and the linear regression equation of the red line is Y = 14.15 + 3.622 × X (R² = 0.9986, n = 8). c Square wave voltammograms for various concentrations of PSA antigen in pH 7.4 PBS buffer containing 4.5 mM hydroquinone and 0.1 mM H₂O₂ solution in CASPE-MFD (ascending along the y-axis): 0, 0.001, 0.01, 0.1, 1, and 10 ng/mL, respectively. d The corresponding linear relationship of different concentrations of PSA antigen. The linear regression equation is Y = 34.53 + 9.246 × X (R² = 0.9884, n = 8)