A novel ratiometric electrochemical aptasensor for highly sensitive detection of carcinoembryonic antigen

A novel ratiometric electrochemical aptasensor was proposed for carcinoembryonic antigen (CEA) detection based on exonuclease III (Exo III)-assisted recycling and rolling circle amplification (RCA) strategies. A thiolated ferrocene-labeled hairpin probe 2 (Fc-HP2) was fixed on the gold nanoparticles (AuNPs)-modified gold electrode (AuE) surface through Au–S bonds. The presence of CEA led to the release of trigger, which hybridized with the 3′-protruding of hairpin probe 1 (HP1) and triggered the Exo III cleavage reaction, accompanied by the releasing of trigger and generation of new DNA fragment which was used for the successive hybridization with Fc-HP2. After the Exo III cleavage process, the remaining Fc-HP2 fragments hybridized as primers with the RCA template to initiate the RCA process, and long single-stranded polynucleotides were produced for methylene blue (MB) binding. Such changes resulted in the signal of Fc (I Fc ) decreased and that of MB (I MB ) increased, achieving a linear relationship between I MB /I Fc and logarithm of CEA concentrations ranging from 1.0 pg mL −1 to 100.0 ng mL −1 with a detection limit of 0.59 pg mL −1 . Additionally, the developed aptasensor had been successfully applied to detect CEA in human serum samples. Therefore, the proposed strategy might provide a new platform for clinical detections of CEA.