A supersandwich electrochemiluminescence immunosensor based on mimic-intramolecular interaction for sensitive detection of proteins

An electrochemiluminescence (ECL) immunoassay protocol was developed based on mimic-intramolecular interaction for sensitive detection of prostate specific antigen (PSA). It was constructed by integrating the ECL luminophore (tris(4,4′-dicarboxylicacid-2,2′-bipyridyl)-ruthenium(II)dichloride (Ru(dcbpy)32+)) and coreactant (histidine) into the supersandwich DNA structure. This strategy was more effective in amplifying the ECL signal by shortening the electronic transmission distance, improving the ECL luminous stability and enhancing the ECL luminous efficiency. The ECL matrices denoted as MWCNTs@PDA–AuNPs were fabricated through spontaneous oxidative polymerization of dopamine (DA) on multiwalled carbon nanotubes (MWCNTs) and reducing HAuCl4 to produce gold nanoparticles (AuNPs) by DA simultaneously. Then, the prepared matrices were applied to bind capture antibodies. Moreover, supersandwich Ab2 bioconjugate was designed using a PAMAM dendrimer to immobilize the detection antibody and supersandwich DNA structure. The PAMAM dendrimer, with a plurality of secondary and tertiary amine groups, not only facilitated high-density immobilization of the detection antibody and supersandwich DNA structure, but also greatly amplified the ECL signal of Ru(dcbpy)32+. The supersandwich DNA structure contained multiple Ru(dcbpy)32+ and histidine, further amplifying the ECL signal. The proposed supersandwich immunosensor showed high sensitivity with a detection limit of 4.2 fg mL−1 and a wide linear range of 0.01 pg mL−1–40.00 ng mL−1. With the excellent stability, satisfying precision and reproducibility, the proposed immunosensor indicates promising practicability for clinical diagnosis.