Protocol A12 by Wang et al. [24]: Electrophoretic deposition of rGO/PEI nanocomposite and immobilization of azide-terminated aptamers onto rGO Reagents Graphite powder (< 20 micron); Polyethyleneimine (PEI); Tris buffer; 0.01 M phosphate buffer (PBS), pH 7.4; Diazonium reagent mixture: 0.5 mL 15 mM diazonium reagent, 0.5 mL 15 mM NaNO2, 0.5 mL 0.75 M HCl; Aptamer solution: 1 µM azide-terminated aptamer in 0.02 M Tris buffer, 1mM CuSo4, 1 mM sodium ascorbate, 2 mM tris(3-hydroxypropyl-triazolylmethyl)amine (THPTA). Method Prepare the diazonium reagent mixture and stir at 0 °C for 5 min; Add 2 mL of 0.5 mg/mL GO and 0.5 mL of 2 mg/mL PEI and apply a DC voltage of 15 V for 2 min; Rinse three times with deionized water and blow dry with nitrogen gas; Immerse the electrode in the aptamer solution at 4 °C overnight; Wash with PBS; Incubate in 5wt% BSA for 1 h; Rinse with Tris buffer.