Abstract
AbstractCoupled with the ability of fast and quantitative response, electrochemical aptasensors (EA) have great potential in the application of early diagnosis of cancer biomarker. In order to determine the rare biomarkers in the complicate clinical samples, scientists are making unremitting efforts towards improving the sensitivity and selectivity of EA. Herein, a "sandwich"‐structure electrochemical aptasensor (SEA) is developed for analysis of cancer biomarker carcino‐embryonic antigen (CEA). Two DNA aptamers are employed, one of which is thiolated at 3′‐terminal and immobilized onto the gold electrode as a capture probe, while the other one is served as signal probe. The two aptamers could "sandwich" the target and signal probe is then subjected to the terminal deoxynucleotidyl transferase (TdT)‐catalyzed incorporation of biotin labeled dNTPs into its 3′‐terminal. Thus the as‐generated long DNA oligo tails allow specific binding of numerous avidin modified horseradish peroxidase (Av‐HRP), resulting in enhanced peroxidase catalyzed electrochemical signals. This signal amplification strategy is termed as surface initiated enzymatic polymerization (SIEP). This SIEP amplified SEA has a detection limit of 10 pg·mL−1, indicating the outstanding amplification efficiency.
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