Target-aptamer binding triggered isothermal strand displacement polymerase reaction for prostate specific antigen detection

For the purpose of detecting prostate specific antigen (PSA), a ratiometric electrochemical aptasensor has been developed based on target-aptamer binding triggered isothermal strand displacement polymerase reaction (ISDPR). A ferrocene (Fc)-modified hairpin probe 2 (Fc-HP2) was self-assembled on the modified electrode surface. One terminus of hairpin probe 1 (HP1) bound to PSA and formed the HP1/PSA complex, and the other hybridized with Fc-HP2. Then, the S1 strand hybridized with the stem of Fc-HP2 and was extended with the aid of phi29 DNA polymerase (phi 29) and deoxyribonucleoside triphosphates (dNTPs), and the HP1/PSA complex could be displaced to trigger a new cycle of polymerization reaction. Finally, numerous double-stranded DNAs (dsDNAs) were produced for methylene blue (MB) intercalation. With the raising of PSA concentrations, the electrochemical responses of Fc (IFc) and MB (IMB) decreased and increased, respectively. When IMB/IFc was used as the response signal for quantitative determination of PSA, the proposed strategy possessed a wide linear range (10 pg mL−1–100 ng mL−1) and a low detection limit of 3.2 pg mL−1. Moreover, the proposed aptasensor displayed good performance for PSA determination in spiked human serum samples, showing great application prospects in bioanalysis.