Self-enhanced PEI-Ru(II) complex with polyamino acid as booster to construct ultrasensitive electrochemiluminescence immunosensor for carcinoembryonic antigen detection

In this work, the luminophor tris (4,4′-dicarboxylicacid-2,2′-bipyridyl) ruthenium (II) dichloride (Ru(dcbpy)32+) was linked to coreactant polyethylenimine (PEI) with effectively shorted distance, forming a novel self-enhanced PEI-Ru(II) complex to fabricate ultrasensitive electrochemiluminescence immunosensor for carcinoembryonic antigen (CEA) detection by using polyamino acid l-cysteine (pL-Cys) as booster for further signal amplification. The light-emitting species (PEI-Ru(II)*) based on intramolecular electron transfer between PEI• and Ru(III) could efficiently amplify the ECL signal of Ru(dcbpy)32+ owing to its benefit for electron transmission. Secondly, the pL-Cys film was fabricated on the glassy carbon electrode by cyclic voltammogram. After that, the pL-Cys acted as a strongly reducing radical could react with PEI-Ru(III) to generate the excited state PEI-Ru(II)*, which further amplify the ECL signal. With the signal amplification factors, the prepared ECL immunosensor exhibited great advantages in simplification, rapidity, stability and selectivity. Furthermore, the linear range for the determination of CEA was from 0.10 pg/mL to 80 ng/mL with a correlation coefficient of 0.9942 and a detection limit of 0.045 pg/mL (S/N = 3).