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Electrochemical-Signal-Amplification Strategy for an Electrochemiluminescence Immunoassay with g-C 3 N 4 as Tags

2018; American Chemical Society; Volume: 90; Issue: 21 Linguagem: Inglês

10.1021/acs.analchem.8b03554

1520-6882

Yuchen Jin, Qi Kang, Xinli Guo, Bin Zhang, Dazhong Shen, Guizheng Zou,

Electrochemical Analysis and Applications

Signal amplification for electrochemiluminescence (ECL) has conventionally been achieved by employing effective matrixes that can accelerate the electrochemical redox processes or carry more electrochemiluminophores. Herein, a convenient signal-amplification strategy was proposed for an ECL immunoassay with carboxylated g-C3N4 nanosheets (NSs) as tags and carcinoembryonic antigen (CEA) as the model target via electrochemically pretreating the substrate: a glassy-carbon electrode (GCE) modified with a polymerized 2-aminoterephthalic acid (ATA) film (GCE/ATA). Bioconjugates of g-C3N4 NSs and the signal CEA antibody (Ab2) (i.e., g-C3N4 NS–Ab2) were immobilized on GCE/ATA via a sandwich immunoreaction to form GCE/ATA–Ab1–Ag–Ab2–NSs. Electrochemical-impedance spectroscopy and potential-resolved ECL characterization proved that GCE/ATA plays an important role in the electron-transfer resistance (Ret) of the GCE/ATA–Ab1–Ag–Ab2–NSs for ECL and that successively scanning GCE/ATA–Ab1–Ag–Ab2–NSs from 0 to −1.6 V in K2S2O8- and H2O2-containing medium could reduce the Ret and bring out 3.3-times-enhanced ECL at the 10th scan cycle compared with that of the 1st scan cycle, which was about 10.2 times the ECL of the GCE/ATA–Ab1–Ag–Ab2–NSs in medium containing merely K2S2O8. Inspired by this, direct and successive scanning of GCE/ATA in K2S2O8- and H2O2-containing medium was employed during fabrication, which dramatically reduced the Ret of GCE/ATA–Ab1–Ag–Ab2–NSs and brought out obviously enhanced ECL responses for selectively determining CEA from 0.1 pg/mL to 1 ng/mL, with a detection limit of 3 fg/mL.