Protocol A8 by Ding et al. [105]: Adamantane as surface anchor for aptamers and signal amplification via amplification chain reaction Reagents 7-hydroxycarbonyl-2,4,9-trithiaadamantane was synthesized according to a previous report [179]. Adamantane solution consisting of 1 µM 7-hydroxycarbonyl-2,4,9-trithiaadamantane, 10 mM Tris-HCl, 1 mM EDTA, 10 mM TECP; Carboxyl group activation solution consisting of 200 mM EDC and 50 mM NHS; 1 µM capture probe solution; 4 µM mix of H1 probe and H2 probe; 10 mM phosphate buffer, pH 7.4; Analyte solution: PSA in phosphate buffer, containing 0.25 M NaCl. PSA concentrations ranging 0.1 pg/mL–0.1 µg/mL were investigated. Method Immerse the cleaned electrode in the adamantane solution for 4 h; Incubate with carboxyl group activation solution for 30 min; Rinse with double-distilled water; Incubate with capture probe solution for 1 h; Incubate with analyte solution for 1 h, followed by careful rinsing; Incubate with H1&H2 probe solution for 2 h.