Ultrasensitive Electrochemical Aptasensor Based on Surface‐Initiated Enzymatic Polymerization

Abstract

Coupled 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.

A joint action of aptamers and gold nanoparticles chemically trapped on a glassy carbon support for the electrochemical sensing of ofloxacin

“…The largest impedimetric signal change (ΔR=80 Ω) obtained at the concentration of 2.5×10 -6 M for aptamers. The impedimetric signal decreased to 40 Ω when the concentration increased to 5×10 -6 M. A steric hindrance or electrostatic repulsion between negatively charged DNA molecules at higher concentrations might explain the decrease in the impedimetric signal [83]. For this reason, the optimum DNA concentration was adopted for the 2.5×10 -6 M of aptamer.…”