A label-free electrochemiluminescence immunosensor for carbohydrate antigen 153 based on polypyrrole-luminol-AuNPs...

Polypyrrole-luminol-AuNPs nanocomposites were prepared and used to develop a sensitive label-free electrochemiluminescence (ECL) immunosensor for carbohydrate antigen 153 (CA153) detection. Firstly, polypyrrole (PPY) nanoparticles were synthesized by a chemical oxidation method using FeCl₃ as an oxidizing agent, then luminol and gold nanoparticles (AuNPs) were combined with PPY nanoparticles through electrostatic interaction to form PPY-luminol-AuNPs nanocomposites. The nanocomposites were characterized by transmission electron microscopy (TEM), UV-Vis absorption spectra, atomic emission spectrometry (AES), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). Especially, iron element was also detected in the nanocomposites. The PPY-luminol-AuNPs nanocomposites showed excellent ECL activity due to the bi-catalysis of iron ion and gold nanoparticles on the ECL of luminol. Furthermore, the nanocomposites showed good film-forming property, and it can be fixed on electrode surface without the assistance of other film-forming materials. On this basis, an ECL immunosensor for CA153 was constructed by covalently immobilizing anti-CA153 on PPY-luminol-AuNPs modified indium-doped tin oxide (ITO) electrode. In the presence of CA153, a remarkable decrease in ECL signals was observed due to the formation of anti-CA153/CA153 complex. The immunosensor showed a good linear relationship in the concentration range of 0.001 to 700 U/mL for CA153, and the detection limit was 5.8 × 10^-4 U/mL (S/N = 3). Furthermore, the ECL immunosensor was applied to the determination of CA153 in practical human serum sample.