Protocol A1 by Ciu et al. [77]: Mixed monolayer of aptamer and zwitterionic peptide Reagents 0.2 M PBS buffer pH 7.4; 0.5 µM thiolated aptamer in PBS buffer; 25 µM peptide in PBS buffer. Method Incubate clean electrode in aptamer solution for 12 h at RT; Incubate in peptide solution for 12 h at RT; Wash extensively with PBS buffer; Incubate in PBS buffer for 24 h at RT; For the bioassay, alpha-fetoprotein (AFP) was prepared in 10 mM PBS buffer pH 7.4. Linear concentration range: 10 fg/mL–100 pg/mL.

Protocol A2 by Peng et al. [110]: Signal amplification via graphene oxide and methylene blue binding Reagents PBS buffer; 2 mM mercaptohexanol (MCH) solution; 0.5 µM thiolated aptamer solution in 25 mM Tris-HCl buffer containing 20 mM NaCl; Bacteria solutions of differing concentrations (linear range: 2 × 101 to 2 × 106 CFU/mL) in PBS; 1 mg/mL graphene oxide (GO) solution in PBS; 120 µM methylene blue (MB) solution. Method Incubate the cleaned electrode in aptamer solution for 5 h at 24 °C; Rinse with PBS buffer; Incubate in MCH solution for 1 h. For the bioassay, incubate in bacteria solution for 1 h, followed by subsequent incubation in GO solution for 4 h and MB solution for another 1 h.