A Simple Ratiometric Electrochemical Aptasensor Based on Exonuclease III-Assisted Target Recycling for Ultrasensitive Detection of Prostate Specific Antigen

Prostate specific antigen (PSA) is considered as an important biomarker in prostate cancer diagnosis. Herein, an ultrasensitive ratiometric electrochemical aptasensor was constructed for analyzing PSA. The ferrocene (Fc)-labeled thiolated hairpin probe 2 (Fc-HP2) was conjugated to the gold nanoparticles (AuNPs)-modified gold electrode (AuE) surface by Au-S bonds. With the introduction of PSA, the aptamer region of hairpin probe 1 (HP1) preferred to bind with PSA, and the rest of HP1 could hybridize with Fc-HP2 to form Fc-HP2/HP1/PSA complex with a blunt 3 & PRIME; terminus, which triggered the exonuclease III (Exo III) cleavage process accompanied by Fc leaving from the electrode and recycling of HP1/PSA. The remaining Fc-HP2 fragments left on the electrode surface were then hybridized with methylene blue-labeled DNA (MB-DNA). This resulted in an enhancement of MB signal (I-MB) and a decrement of Fc signal (I-Fc). Under the optimal conditions, the proposed aptasensor showed good analytical performance for sensitive detection of PSA with a linear range from 100 fg & BULL;mL(-1) to 10 ng & BULL;mL(-1) and a detection limit of 34.7 fg & BULL;mL(-1). The fabricated aptasensor had been applied to detect PSA in diluted human serum samples and obtained satisfied results, suggesting it had great potential in clinical diagnosis.